Microscopic Evaluation of Activated Sludge 
from Eleven Wastewater Treatment Plants in 
Cape Town, South Africa 
Pamela Welz 
Student number: 20161794 
Dissertation submitted in partial fulfillment of the 
requirements for the degree Master of Environmental 
Science and Managements the Potchefstroom 
campus of the North-West University 
Supervisor: Dr HA Esterhuysen 
November 2008 
ACKNOWLEDGEMENTS 
I would like to acknowledge the help and input of the staff of the Scientific 
Services Department of the City of Cape Town, as well as staff from the 
Wastewater department of the City of Cape Town. 
Thanks especially to Mjikisile Vulindlu, the head of Microbiology at Scientific 
services for backing my project and allowing me the use of the excellent facilities 
in his department. Thanks also to Heidi Richards, the head of the Wastewater 
laboratory at Scientific Services for providing me with the process data from her 
laboratory and for her assistance and technical expertise in this regard. In 
addition, Roland Moollan kindly assisted with setting aside time to impart 
valuable technical input. 
From NWU, my supervisor, Dr Andre Esterhuysen spent many hours poring over 
my volumes of text at a busy time in his academic schedule. 
II 
ABSTRACT 
From June to November 2007, a microscopic analysis was conducted on the activated 
sludge from eleven selected wastewater treatment plants (WWTP's) belonging to the 
City of Cape Town. The primary objective was the identification of the dominant and 
secondary filamentous organisms. Other important criteria included were the floe 
character, diversity, filament index (Fl) and identification of the protozoan and metazoan 
communities. The operational data determined from routine analyses of the sludge, 
influent and effluent were used to assess the relationship of the filamentous population to 
wastewater characteristics and to compare this with previous findings. Fl values of >3 
and dissolved sludge volume indices (DSVI's) of >150 were chosen as representing the 
possibility of bulking conditions being present. The five most prevalent dominant 
filaments were Type 0092, Type 1851, actinomycetes, Microthrix parvicella and Type 
021N, being present in 74%, 31%, 22%, 17% and 14% of samples respectively. Type 
0092 did not appear to be associated with bulking in any of the WWTP's, although it was 
often incidentally present as a co-dominant species when bulking conditions existed. All 
three WWTP's with the Modified Ludzack-Ettinger configuration harboured Type 1851 as 
the major dominant species, irrespective of whether the plants treated domestic or 
industrial effluent. Conditions suggestive of bulking were present in two of these 
WWTP's. Contrary to expectations, Type 1851 was often found as a dominant species 
where domestic waste was the primary influent. Type 021N and actinomycetes were 
strongly implicated when bulking occurred. The overgrowth of these filaments appeared 
to be related to factors such as nutrient deficiency (Type 021N) or the presence of large 
amounts of low molecular weight substances in the influent. Microthrix parvicella did not 
cause major bulking problems. There was a strong association between low levels of 
nitrates/nitrites in the clarifier supernatant and good phosphorous removal, irrespective 
of the configuration of the WWTP. The converse was also true. 
Keywords. Microscopic analysis, Activated sludge, Filamentous organisms, Operational 
data, Bulking 
HI 
OPSOMMING 
Gedurende Junie tot November 2007, is mikroskopiese analises op die geaktiveerde 
slyk van elf geselekteerde afvalwaterbehandeiingsisteme van die Stad van Kaapstap 
uitgevoer. Die primere doel was die identifisering van die dominante en sekondere 
filamentagtige organismes. Ander belangrike kriteria het ingesluit die vlokkarakter, 
diversiteit, filamentindeks (Fl) en die identifikasie van die protosoe en metasoe 
populasies. Die bedryfs data van roetine analises van die slyk, invloei en uitvloei was 
gebruik in die assessering van die verwantskap tussen die filamentpopulasie tot 
afvalwatereienskappe en om te vergelyk met vorige bevindings. Fl-waardes van > 3 en 
opgeloste slyk volume indekse van > 150 was gekies om die moontlikheid van 
uitdiuende slyk toestande te verteenwoordig. Die vyf mees oorwegend dominante 
filamente was Tipe 0092, Tipe 1851, Actinomycetes, Microthrixparvicella en Tipe 021N, 
teenwoordig as 74%, 31%, 22%, 17% en 14% in die monsters, respektiewelik. Tipe 0092 
was nie geassosieer met uitduiende slyk in enige van die afvalwaterbehandeiingsisteme 
nie, alhoewel dit dikwels as mede-dominante spesie, indien toestande vir uitduiende slyk 
voorkom, teenwoordig was. In al die afvalwaterbehandeiingsisteme met die Modified 
Ludzack-Ettinger konfigurasie was Tipe 1851 die hoof dominante spesie, ongeag of die 
sisteem huishoudelike of industriele uitvloeisel behandel. Toestande wat aanduidend is 
vir uitduiende slyk was teenwoordig in twee van hierdie afvalwaterbehandeiingsisteme. 
In teenstelling met die verwagtings, was Tipe 1851 dikwels as die dominante spesie in 
sisteme wat huishoudelike afval as primere invloei het, gevind. Die teenwoordigheid van 
Tipe 021N en Actinomycetes word sterk geassosieer met uitduiende slyk. Die oorgroei 
van hierdie filamente is biykbaar verwant aan faktore soos voedingstoftekorte (Tipe 
021N) of die teenwoordigheid van groot hoeveelhede lae molekulere gewig bestanddele 
in die invloei. Microthrix parvicella veroorsaak nie groot uitduiende slyk probleme nie. 
Daar is 'n sterk assosiasie tussen lae vlakke van nitrate/nitriete in die supernatant van 
die besinkingsdam en goeie fosfaatverwydering, ongeag die konfigurasie van die 
geaktiveerde slykbehandlingsisteem. Die teenoorgestelde is ook waar. 
Sleutelwoorde. Mikroskopiese analises, Geaktiveerde slyk, Filamentagtige organismes, 
Bedryfs data, Uitduiende 
IV 
ABBREVIATIONS 
AA: Anaerobic/aerobic 
AMF: Aerobic mass fraction 
ATP: Adenosine triphosphate 
AOO: Ammonium oxidizing organism 
AS: Activated sludge 
BNR: Biological nitrogen removal 
BPR: Biological phosphorous removal 
BOD: Biological oxygen demand 
BODL: Ultimate biological oxygen demand 
BOD5: Five day biological oxygen demand 
COD: Chemical oxygen demand 
COD/N: Chemical oxygen demand to nitrogen ratio 
COD/P: Chemical oxygen demand to phosphorous ratio 
DO: Dissolved oxygen 
DPOA: Denitrifying phosphorous accumulating organism 
DSVI: Dissolved sludge volume index 
EFF: Effluent 
EPBR: Enhanced biological phosphate removal 
Fl: Filament index 
F/M: Food/microorganism ratio 
GAO: Glycogen accumulating organism 
HMW: High molecular weight 
IAND: Intermittently aerated nitrification-denitrification 
IN: Influent 
LMW: Low molecular weight 
MCRT: Mean cell residence time 
MLE: Modified Ludzack-Ettinger 
MLR: Mixed liquor recycle 
MLSS: Mixed liquor suspended solids 
MLVSS: Mixed liquor volatile suspended solids 
MUCT: Modified UCT 
NDBEPR: Nitrification-denitrification biological excess phosphorous removal 
NOO: Nitrite oxidizing organism 
OUR: Oxygen utilization rate 
P: Phosphorous 
PAO: Phosphorous accumulating organism 
PHA: Polyhydroxyalkanoate 
PHB: Polyhydroxybutyrate 
PST: Primary settling tank 
RAS: Return activated sludge 
RASSS: Return activated sludge suspended solids 
RBCOD: Readily biodegradable COD 
SBCOD: Slowly biodegradable COD 
SR: Sludge recycle 
SRT: Solids retention time 
SS: Suspended solids 
SUR: Substrate utilization rate 
SVI: Sludge volume index 
TKN: Total Kjeldahl nitrogen 
v 
Hmax: Maximum specific growth rate 
UCT: University of Cape Town 
VFA: Volatile fatty acid 
VFA/N: Volatile fatty acid to nitrogen 
VSS: Volatile suspended solids 
WAS: Waste activated sludge 
WF: Waste flow 
WWTP: Wastewater treatment plant 
2RMD: 2-reactor nitrification-denitrification 
TABLE OF CONTENTS 
Acknowledgements i 
Abstract ii 
Opsomming ii
Abbreviations v 
Table of contents v
CHAPTER 1 
INTRODUCTION 
1.1 Reasons for study 2 
1.2 Data sources 3 
1.2.1 Plant configuration and operating parameters 3 
1.2.2 Microscopic analysis
1.2.3 Historical data
1.3 Data analysis 4 
1.3.1 Individual plant analyses 4 
1.3.2 Meta-analysis
CHAPTER 2 
LITERATURE REVIEW 
2.1 Bacterial metabolism and wastewater treatment 6 
2.2 Nutrient removal and bulking 6 
2.1.1 Nitrification/denitrification
2.2.2 Phosphorous removal 8 
2.3 Bulking 10 
2.4 Microorganism population in mixed liquor 15 
2.5 Scum formation 8 
CHAPTER 3 
METHODS 
3.1 Sample collection 20 
3.2 Operational data 1 
3.3 Microscopic analysis
3.3.1 Wet mounts 2 
22 
22 
22 
22 
22 
23 
32 
32 
32 
3.3.1 (a) Morphological characteristics of the floes 
3.3.1 (b) Filament index 
3.3.1 (c) Filament characteristics 
3.3.1 (d) Diversity 
3.3.1 (e) Monocolonies 
3.3.1 (f) Identification of protozoa and metazoa 
3.3.2 Sulphur storage test 
3.3.3 Gram stain 
3.3.4 Neisser stain 
VII 
3.3.5 Calculations 32 
TABLE OF CONTENTS (cont.) 
CHAPTER 4 
INDIVIDUAL PLANT ANALYSES 
4.1 AthloneWWTP 25 
4.1.1 Plant configuration and operating parameters 2
4.1.2 Results 6 
4.1.2(a) Operational data 2
4.1.2(b) Microscopic sludge analysis 32 
4.1.3 Discussion 35 
4.2 Bellville WWTP 41 
4.2.1 Plant configuration and operating parameters 4
4.2.2 Results
4.2.2 (a) Operational data 42 
4.2.2 (b) Microscopic sludge analysis 44 
4.2.3 Discussion 47 
4.3 Borcherds Quarry WWTP 50 
4.3.1 Plant configuration and operating parameters 5
4.3.2 Results 51 
4.3.2 (a) Operational data
4.3.2 (b) Microscopic sludge analysis 53 
4.3.3 Discussion 7 
4.4 Cape Flats WWTP 60 
4.4.1 Plant configuration and operating parameters 6
4.4.2 Results
4.4.2 (a) Operational data
4.4.2 (b) Microscopic sludge analysis 62 
4.4.3 Discussion 65 
4.5 Kraaifontein WWTP 8 
4.5.1 Plant configuration and operating parameters 6
4.5.2 Results
4.5.2 (a) Operational data 6
4.5.2 (b) Microscopic sludge analysis 70 
4.5.3 Discussion 72 
4.6 Macassar WWTP 4 
4.6.1 Plant configuration and operating parameters 7
4.6.2 Results
4.6.2 (a) Operational data 7
4.6.2 (b) Microscopic sludge analysis 76 
4.6.3 Discussion 81 
4.7 Mitchells Plain WWTP 3 
4.7.1 Plant configuration and operating parameters 8
4.7.2 Results
4.7.2 (a) Operational data 8
4.7.2 (b) Microscopic sludge analysis 87 
4.7.3 Discussion 90 
4.8 Parow WWTP 2 
4.8.1 Plant configuration and operating parameters 9
4.8.2 Results
4.8.2(a) Operational data 9
4.8.2(b) Microscopic sludge analysis 94 
4.8.3 Discussion 96 
VIM 
TABLE OF CONTENTS (cont.) 
4.9 Potsdam WWTP 98 
4.9.1 Plant configuration and operating parameters 9
4.9.2 Results
4.9.2(a) Operational data 9
4.9.2(b) Microscopic sludge analysis 100 
4.9.3 Discussion 103 
4.10 Wesfleur WWTP 5 
4.10.1 Plant configuration and operating parameters 10
4.10.2 Results
4.10.2(a) Operational data 10
4.10.2(b) Microscopic sludge analysis 107 
4.10.3 Discussion 109 
4.11 Wildevoelvlei WWTP 111 
4.11.1 Plant configuration and operating parameters 11
4.11.2 Results 112 
4.11.2(a) Operational data 11
4.11.2(b) Microscopic sludge analysis 114 
4.11.3 Discussion 7 
CHAPTER 5 
META-ANALYSIS OF COMBINED RESULTS FROM WASTEWATER 
TREATMENT PLANTS 
5.1 Population dynamics of filamentous organisms from June-Nov 2007 121 
5.1.1 Results 12
121 
123 
124 
125 
125 
127 
127 
128 
129 
130 
131 
132 
133 
134 
135 
136 
136 
136 
138 
138 
138 
141 
141 
141 
144 
144 
5.1.1 (a) Prevalence and comparison with similar South African studies 
5.1.1 (b) Correlation with DSVI and Fl 
5.1.1.2 (bi) DSVI results 
5.1.1.2 (bii) Fl results 
5.1.1.2 (biii) Combined Fl and DSVI results 
5.1.2 Discussion 
5.1.2(a) Type 0092 
5.1.2(b) Type 1851 
5.1.2(c) Type 0041 
5.1.2(d) Microthrix parvicella 
5.1.2(e) Type 021N 
5.1.2(f) Actinomycetes 
5.1.2(g) Haliscomenobacter hydrosis 
5.1.2(h) Nostocoida limicola 111 
5.1.2(i) Type 1701 
5.1.2 (j) Flexibacterspp. 
5.1.2 (k) Type 0581 
5.1.2(1) Thiothrixspp. 
5.2 Population dynamics of protozoa/metazoa from June-Nov 2007 
5.2.1 Results 
5.2.1 (a) Protozoa 
5.2.1 (b) Metazoa 
5.2.2 Discussion 
5.2.2 (a) Protozoa 
5.2.2 (b) Metazoa 
5.2.3 Additional observations 
IX 
TABLE OF CONTENTS (cont.) 
5.3 Population dynamics of spirochaetes and free-living cells from 
June-November 2007 145 
5.3.1 Results 14
5.3.2 Discussion 6 
5.3.3 Additional observations 147 
CHAPTER 6 
SUMMATION 
6.1 WWTP configuration, nutrient removal, bulking and filamentous 
growth 148 
6.2 Identification of microorganisms 153 
6.3 Other important study findings 4 
? References 155 
? Annexures 
Annexure 1 
Raw operational data from WWTP's 160 
? Illustrations 
List of figures 
Figure 4.1.1 Key for WWTP configurations 
Figure 4.1.2 UCT process configuration 
Figure 4.1.3 Graph depicting the raw flow into Athlone WWTP and the design capacity of the 
Figure 4.1.4 Graph depicting the increasing influent chemical oxygen demand (ICOD) at Athlone 
Figure 4.1.5 Graph depicting the percentage removal of chemical oxygen demand at Athlone 
Figure 4.1.6 Graph depicting the chemical oxygen demand of the leachate from Wastetech, Cape 
Metropolitan Council and Vissershoek processed at the Athlone WWTP during the study 
period 
Figure 4.1.7 Graph depicting the effluent ammonia levels and effluent nitrate and nitrite levels at 
Athlone 
Figure 4.1.8 Graph depicting the influent levels of Total Kjeldahl nitrogen and ammonia at Athlone 
Figure 4.1.9 Graph depicting the ratio of the influent COD to Total Kjeldahl nitrogen at Athlone 
Figure 4.1.10 Graph depicting the influent and the effluent alkalinity levels at Athlone 
Figure 4.1.11 Graph depicting the influent total phosphate, influent o-phosphate and effluent o-
phosphate levels at Athlone 
Figure 4.1.12 Graph depicting the influent levels of suspended solids at Athlone 
Figure 4.1.13 Graph depicting the sludge volume index and dissolved sludge volume index in bioreactor 
A of Athlone 
Figure 4.1.14 Graph depicting the sludge wasting rate from the bioreactors at Athlone 
Figure 4.1.15 Graph depicting the calculated sludge age of bioreactor A at Athlone 
Figure 4.1.16 Graph depicting the suspended solids in the return activated sludge at Athlone 
Figure 4.1.17 Micrographs of wet mounts of mixed liquor from Athlone reactor A 
Figure 4.1.18 Graph of the filament index at Athlone 
Figure 4.1.19 Micrographs of various filamentous prokaryotic microorganisms detected in mixed liquor 
from Athlone 
Figure 4.1.20 Wet mount of TMothrixspp. from mixed liquor from bioreactor A at Athlone 
Figure 4.2.1 Key for WWTP configurations 
Figure 4.2.2 Diagram of MLE configuration 
X 
Figure 4.2.3 Graph depicting the influent COD at Bellville 
Figure 4.2.4 Graph depicting the %COD removal at Bellville 
Figure 4.2.5 Graph depicting the influent total phosphate, influent o-phosphate and effluent o-
phosphate levels at Bellville 
Figure 4.2.6 Graph depicting the influent Total Kjeldahl nitrogen, influent ammonia, effluent ammonia 
and effluent nitrates and nitrites at Bellville 
Figure 4.2.7 Graph depicting the influent mixed liquor suspended solids and mixed liquor volatile 
suspended solids from the North reactor at Bellville 
Figure 4.2.8 Graph depicting the sludge volume index and dissolved sludge volume index from the 
mixed liquor from the North reactor at Bellville 
Figure 4.2.9 Graph depicting the influent alkalinity and effluent alkalinity at Bellville 
Figure 4.2.10 Graph depicting the effluent suspended solids at Bellville 
Figure 4.2.11 Graph depicting the influent return activated sludge suspended solids at Bellville 
Figure 4.2.12 Graph depicting the calculated sludge age of mixed liquor at Bellville 
Figure 4.2.13 Micrographs of wet mounts of the floes structure of the mixed liquor from Bellville 
Figure 4.2.14 Graph depicting the filament index of mixed liquor from at Bellville 
Figure 4.2.15 Wet mount of mixed liquor showing unidentified worm-like organism at Bellville 
Figure 4.3.1 Key for WWTP configurations 
Figure 4.3.2 Diagram of 5-stage Bardenpho (Phoredox) configuration 
Figure 4.3.3 Graph depicting the influent COD at Borcherds quarry 
Figure 4.3.4 Graph depicting the COD removal efficiency at Borcherds quarry 
Figure 4.3.5 Graph depicting the effluent ammonia levels at Borcherds quarry 
Figure 4.3.6 Graph depicting the influent Total Kjeldahl ammonia and ammonia at Borcherds quarry 
Figure 4.3.7 Graph showing the effluent suspended solids at Borcherds quarry 
Figure 4.3.8 Graph showing the influent suspended solids volatile suspended solids at Borcherds 
quarry 
Figure 4.3.9 Graph showing the influent total phosphates, o-phosphates and effluent o-phosphates at 
Borcherds quarry 
Figure 4.3.10 Graph depicting the mixed liquor suspended solids and mixed liquor volatile suspended 
solids at Borcherds quarry 
Figure 4.3.12 Micrograph of Wet mount of mixed liquor at Borcherds quarry showing numerous Type 
021N rosettes and filaments protruding from pin floes 
Figure 4.3.13 Graph of the filament index at Borcherds quarry 
Figure 4.3.14 Micrograph of Neisser stain of Type 021N and Type 0092 from mixed liquor at Borcherds 
quarry 
Figure 4.4.1 Graph depicting the flow rate at Cape Flats 
Figure 4.4.2 Graph depicting the influent and effluent COD levels at Cape Flats 
Figure 4.4.3 Graph depicting the removal efficiency of COD at Cape Flats 
Figure 4.4.4 Graph depicting the influent TKN and ammonia as well as the effluent ammonia and 
nitrates/nitrites at Cape Flats 
Figure 4.4.5 Graph depicting the levels of influent total phosphates o-phosphates as well as the effluent 
levels of o-phosphates at Cape Flats 
Figure 4.4.6 Graph depicting the values for the SVI and DSVI at Cape 
Figure 4.4.7 Graph showing the relationship between the influent COD and TKN ratio and the effluent 
levels in nitrates/nitrites at Cape Flats 
Figure 4.4.8 Micrograph of wet mounts of mixed liquor from Cape Flats WWTP in showing the floe 
structure 
Figure 4.4.9 Graph depicting the filament index values at Cape Flats 
Figure 4.4.10 Micrographs of Neisser stain of Type 0092 from mixed liquor at Cape Flats 
Figure 4.5.1 Graph depicting the influent COD levels at Kraaifontein 
Figure 4.5.2 Graph depicting the COD removal efficiency at Kraaifontein 
Figure 4.5.3 Graph depicting the influent TKN influent ammonia, effluent nitrates/nitrites and effluent 
ammonia levels at Kraaifontein 
Figure 4.5.4 Graph depicting the influent total phophates, o-phosphate and effluent o-phosphate levels 
at Kraaifontein 
Figure 4.5.5 Graph depicting the SVI and DSVI values at Kraaifontein 
Figure 4.5.6 Micrograph of wet mount of mixed liquor showing floe structure at Kraaifontein 
Figure 4.5.7 Graph showing the Fl values from the mixed liquor at Kraaifontein 
Figure 4.5.8 Micrograph of Neisser stain of Microthrix parvicella from mixed liquor sample taken at 
Kraaifontein 
Figure 4.5.9 Micrograph of Gram stain and Neisser stain of GAO's from mixed liquor from Kraaifontein 
Figure 4.6.1 Graph depicting the design capacity and the flow rate at Macassar 
Figure 4.6.2 Graph depicting the influent COD at Macassar 
XI 
Figure 4.6.3 Graph depicting the COD removal efficiency at Macassar 
Figure 4.6.4 Graph depicting the influent TKN and ammonia at Macassar 
Figure 4.6.5 Graph depicting the effluent ammonia and nitrates/nitrites at Macassar 
Figure 4.6.6 Graph depicting the influent o-phosphates and total phosphates and the effluent o-
phosphates at Macassar 
Figure 4.6.7 Graph of the mixed liquor suspended solids and mixed liquor volatile suspended at 
Macassar 
Figure 4.6.8 Graph of the Sludge volume index and dissolved sludge volume index from at Macassar 
Figure 4.6.9 Micrograph of Wet mount of mixed liquor showing floe structure at Macassar 
Figure 4.6.10 Graph depicting the filament index at Macassar 
Figure 4.6.11 Micrograph of Wet mount of mixed liquor from at Macassar WWTP showing Spirostomum 
spp., apparently mating 
Figure 4.7.1 Graph of Influent COD levels from Mitchells plain 
Figure 4.7.2 Graph showing removal efficiency of COD at Mitchells plain 
Figure 4.7.3 Graph depicting the influent suspended solids at Mitchells plain 
Figure 4.7.4 Graph showing the at Mitchells plain 
Figure 4.7.5 Graph depicting the influent TKN and ammonia at Mitchells plain 
Figure 4.7.6 Graph showing the effluent nitrates/nitrites and ammonia at Mitchells plain 
Figure 4.7.7 Graph giving the influent total phosphates and influent o-phosphates at Mitchells plain 
Figure 4.7.8 Graph depicting the effluent o-phosphates at Mitchells plain 
Figure 4.7.9 Graph of the influent and effluent alkalinity at Mitchells plain 
Figure 4.7.10 Graph of mixed liquor suspended solids and volatile suspended solids at Mitchells plain 
Figure 4.7.11 Graph giving values of sludge volume index and dissolved sludge volume index at 
Mitchells plain 
Figure 4.7.12 Graph showing the ratio of influent COD/TKN plotted against the effluent levels of 
nitrates/nitrites in reactor C at Mitchells plain 
Figure 4.7.13 Graph showing the ratio of influent COD/TKN plotted against the effluent levels of 
nitrates/nitrites in reactor G at Mitchells plain 
Figure 4.7.14 Micrograph of Wet mount showing the floe structure at Mitchells plain 
Figure 4.7.15 Graph of Filament index at Mitchells plain 
Figure 4.8.1 Graph of inflow of raw wastewater into Parow WWTP 
Figure 4.8.2 Graph depicting the removal of COD at Parow 
Figure 4.8.3 Graph depicting the effluent ammonia nitrates/nitrites from Parow 
Figure 4.8.4 Graph depicting the influent alkalinity and effluent alkalinity values at Parow 
Figure 4.8.5 Graph showing the influent total phosphates o-phosphates as well as the effluent 
o-phosphates at Parow 
Figure 4.8.6 Graph showing the SVI and DSVI values from the mixed liquor at Parow 
Figure 4.8.7 Micrographs of Wet mounts of mixed liquor samples taken from Parow WWTP showing 
the structure of the floes that has been disturbed by voracious feeding of the large 
nematode population as well as examples of two of these nematodes. 
Figure 4.8.8 Graph depicting the filament index at Parow 
Figure 4.9.1 Graphs showing the raw flow into Potsdam 
Figure 4.9.2 Graph depicting the levels of influent total phoshaptes and o-phosphates as well as the 
effluent levels of o-phosphates at Potsdam 
Figure 4.9.3 Graph depicting the influent COD at Potsdam 
Figure 4.9.4 Graph showing the COD removal efficiency at Potsdam 
Figure 4.9.5 Graph depicting the influent ammonia and influent TKN at Potsdam 
Figure 4.9.6 Graph depicting the effluent ammonia and nitrates/nitrites at Potsdam 
Figure 4.9.7 Graph depicting the SVI and DSVI values at Potsdam 
Figure 4.9.8 Micrographs of Wet mount of mixed liquor sample taken from Potsdam showing floe 
structure and Neisser stain showing monocolonies 
Figure 4.9.9 Graph representing the Fl values obtained at Potsdam 
Figure 4.10.1 Graph depicting the influent COD values at Wesfleur 
Figure 4.10.2 Graph depicting the COD removal efficiency at Wesfleur 
Figure 4.10.3 Graph depicting the influent levels of ammonia and TKN at Wesfleur 
Figure 4.10.4 Graph depicting the effluent levels of ammonia and nitrates/nitrites at Wesfleur 
Figure 4.10.5 Graph depicting the influent total phosphates, a-phosphates as well as the effluent a-
phosphates at Wesfleur 
Figure 4.10.6 Graph depicting the influent and effluent conductivity values conductivity values at 
Wesfleur 
Figure 4.10.7 Graph showing the values for the sludge volume index and the dissolved sludge volume 
index at Wesfleur 
Figure 4.10.8 Graph showing the Filament index values at Wesfleur 
XII 
Figure 4.10.9 Micrographs of a Gram stain of Type 1851 and a wet mount showing a Tardigrade and an 
Oligocheaete worm from Wesfleur 
Figure 4.11.1 Key for WWTP configurations 
Figure 4.11.2 Diagram of 3-stage Phoredox configuration 
Figure 4.11.3 Graph showing the influent COD at Wildevoelvlei 
Figure 4.11.4 Graph showing COD removal efficiency at Wildevoelvlei 
Figure 4.11.5 Graph showing the influent TKN ammonia levels at Wildevoelvlei 
Figure 4.11.6 Graph showing the effluent ammonia levels at Wildevoelvlei 
Figure 4.11.7 Graph depicting the influent and effluent alkalinity at Wildevoelvlei 
Figure 4.11.8 Graph showing the sludge age of the mixed liquor at Wildevoelvlei 
Figure 4.11.9 Graph showing the influent total phosphates, a-phosphates as well as the effluent a-
phosphates at Wildevoelvlei 
Figure 4.11.10 Graph showing the SVI and the DSVI values from the mixed liquor at Wildevoelvlei 
Figure 4.11.11 Graphs depicting the Fl values at Wildevoelvlei 
Figure 4.11.12 Micrographs of Gram stain of Type 0092 and actinomycetes from mixed liquor sample of 
Wildevoelvlei 
Figure 5.1.1 Bar chart depicting the percentage prevalence of dominant and secondary filamentous 
microorganisms 
Figure 5.1.2 Bar chart depicting the percentage prevalence of secondary filamentous microorganisms 
Figure 5.1.3 Bar chart showing the relationship between elevated Fl and/or DSVI and filament type 
Figure 5.1.4 Micrograph of Gram stain of type 1851 from Bellville WWTP. 
Figure 5.1.5 Micrographs of Gram stain of Type 021N from Parow WWTP 
Figure 5.1.6 Micrographs of Gram and Neisser stains of N. limicola III and Type 0092 
Figure 5.1.7 Bar chart showing the monthly distribution of sessile ciliates from the mixed liquor of the 
study WWTPs 
Figure 5.1.8 Bar chart showing the monthly distribution of crawling cilates present in >20% of mixed 
liquor samples examined during the study 
Figure 5.1.9 Bar chart showing the monthly distribution of free-living cilates present in >20% of mixed 
liquor samples examined during the study 
Figure 5.1.10 Bar chart showing the monthly distribution of flagellates present in >20% of mixed liquor 
samples examined during the study 
Figure 5.1.11 Bar chart showing the monthly distribution of amoebae (present in >20% of mixed liquor 
samples examined during the study) 
Figure 5.1.12 Bar chart showing the monthly distribution of rotifera (present in >20% of mixed liquor 
samples examined during the study) 
Figure 5.1.13 Bar chart depicting the abundance of spirchaetes in mixed liquor samples during random 
timing and after the introduction of comparative timed analysis 
Figure 5.1.14 Bar chart depicting the abundance of free-living cells in mixed liquor samples during 
random timing and after the introduction of comparative timed analysis 
Figure 5.1.14 Bar chart depicting the abundance of free-living cells in mixed liquor samples during 
random timing and after the introduction of comparative timed analysis 
List of tables 
Table 2.1 The reactions and the catalyzing enzymes for dissimilatory nitrate reduction 
Table 4.1.1 Oxygen utilization rate (OUR) test results on mixed liquor at Athlone 
Table 4.1.2 Metal analysis on raw influent 
Table 4.1.3 Phenol index on raw influent and leachate 
Table 4.1.4 Food to microorganism (F/M) ratio in reactor at Athlone 
Table 4.1.5 Dominant and secondary filamentous organisms identified at Athlone 
Table 4.1.6 Protozoa/metazoa identified at Athlone 
Table 4.2.1 F/M ratio at Bellville 
Table 4.2.2 Dominant and secondary filamentous organisms identified at Bellville 
Table 4.2.3 Protozoa/metazoa identified at Bellville 
Table 4.3.1 F/M ratio at Borcherds quarry 
Table 4.3.2 Dominant and secondary filamentous organisms identified at Borcherds quarry 
Table 4.3.3 Protozoa/metazoa identified at Borcherds quarry 
Table 4.4.1 F/M ratio at Cape Flats 
Table 4.4.2 Dominant and secondary filamentous organisms identified at Cape Flats 
Table 4.4.3 Protozoa/metazoa identified at Cape flats 
XIII 
Table 4.5.1 F/M ratio at Kraaifontein 
Table 4.5.2 Dominant and secondary filamentous organisms identified at Kraaifontein 
Table 4.5.3 Protozoa/metazoa identified at Kraaifontein 
Table 4.6.1 F/M ratio at Macassar 
Table 4.6.2 Dominant and secondary filamentous organisms identified at Macassar 
Table 4.7.1 F/M ratio at Mitchells plain 
Table 4.7.2 Dominant and secondary filamentous organisms identified at Mitchells plain 
Table 4.7.3 Protozoa/metazoa identified at Mitchells plain 
Table 4.8.1 F/M ratio at Parow 
Table 4.8.2 Dominant and secondary filamentous organisms identified at Parow 
Table 4.8.3 Protozoa/metazoa identified at Parow 
Table 4.9.1 F/M ratio at Potsdam 
Table 4.9.2 Dominant and secondary filamentous organisms identified at Potsdam 
Table 4.9.3 Protozoa/metazoa identified at Potsdam 
Table 4.10.1 F/M ratio at Wesfleur 
Table 4.10.2 Dominant and secondary filamentous organisms identified at Wesfleur 
Table 4.10.3 Protozoa/metazoa identified at Wesfleur 
Table 4.11.1 F/M ratio at Wildevoelvlei 
Table 4.11.2 Dominant and secondary filamentous organisms identified at Wildevoelvlei 
Table 4.11.3 Protozoa/metazoa identified at Wildevoelvlei 
Table 5.1.1 Comparison of the prevalence of filamentous organisms from three South African surveys 
Table 5.1.2 Effect of filamentous organism type on SVI 
Table 5.1.3 Reactors with DSVI > 150 
Table 5.1.4 Dominant filaments with DSVI >150 ml/g 
Table 5.1.5 Reactors with Fl > 3 
Table 5.1.6 Dominant filaments with Fl >3 
Table 5.1.7 Dominant filaments with DSVI >150 ml/g and Fl > 3 
Table 5.1.8 Dominant filaments with DSVI >150 ml/g or Fl >3 
Table 6.1 Comparison of nutrient removal efficiency in study WWTPs 
Table 6.2 Comparison of bulking conditions and filamentous microorganisms in study WWTPs 
Table 6.3 Summary of advantages and disadvantages of conventional microscopic investigation, 
DGGE and FISH for the microbiological characterization of activated sludge 
XIV 
CHAPTER 1 
INTRODUCTION 
1.1 REASONS FOR STUDY 
The primary practical objective of the study was to conduct a microscopic analysis over a 
period of six months on the activated sludge from eleven selected wastewater treatment 
plants (WWTP's) belonging to the City of Cape Town. This took place from June to 
November 2007. 
Literature research has revealed only two publications on filamentous organism surveys 
conducted in South Africa: Blackbeard et al. (1988) and Lacko et al. (1999). In the first 
study, 33 WWTP's from over South Africa were included. At this time, biological nutrient 
removal was in its infancy and knowledge on the control of bulking was limited. This 
resulted in the situation where filamentous bulking sludges were found in approximately 
three quarters of the study WWTP's. It stands to reason that with a more modern 
approach, the microbial composition may have changed. In the survey by Lacko et al. 
(1999) the frequency, dominance and seasonal variation of filamentous organisms from 
six WWTP's from the KwaZulu-Natal were determined. In both of these surveys, the 
filamentous population was identified primarily by morphology ascertained by light 
microscopy. 
The proposed study was more extensive than either of the above and some of the 
objectives were: 
> To microscopically determine the current composition of the filamentous 
population in the activated sludge in the Cape Town geographical area. (Routine 
microscopic analysis is not performed on activated sludge samples from WWTP's 
in this city). 
> To perform a more extensive microscopic analysis, not only limited to the 
frequency and dominance of the filamentous organism population. 
> To compare the microbial composition so determined to that obtained from other 
geographical locations, both local and global, where available. 
> To assess the relationship of the filamentous population to wastewater 
characteristics and to compare these with expected findings, chiefly those 
reported by the leading authors in this field, namely Eikelboom (2000) and 
Jenkins eta/. (2004). 
> To assess any changes from winter to summer in both the prokaryotic and 
eukaryotic microbiota and to compare these with expected findings in a similar 
manner. 
> To obtain operational data from the WWTP's included in the study. 
> To expand the analysis of the microscopic results to encompass the use of the 
operational data as a marker of plant efficiency, especially in terms of bulking and 
nutrient removal. 
> To extrapolate mechanisms obtained using bench-scale experimentation to full-
scale operation on a number of WWTP's and to assess the functional validity 
thereof. The bulking hypothesis of Casey et al. (1999) was taken as a particular 
point of interest as there is to date no literature proving or refuting this hypothesis 
as a common cause of bulking in full-scale wastewater treatment plants. 
2 
1.2 DATA SOURCES 
The investigation consisted of three parts that were dealt with individually and in an 
integrated manner, namely the plant configuration and operating parameters, the 
microscopic analysis and the operational data. 
1.2.1 PLANT CONFIGURATION AND OPERATING PARAMETERS 
This information was supplied by the individual WWTP managers and the Scientific 
Services department of the City of Cape Town and included: flow rates, design dissolved 
oxygen (DO) levels and reactor volumes. Loading rates, important in filament analysis 
and measured in the amount of chemical oxygen (mgCOD) to mixed liquor suspended 
solids ratio (mgMLVSS) per day (mgCOD/mgMLVSS.day), were calculated using this 
information, together with the operational data. 
1.2.2 MICROSCOPIC ANALYSIS 
This was performed exclusively by the masters' student, using the methods of Eikelboom 
(2000) and supplemented by those of Jenkins eta/. (2004). The analysis was performed 
on grab samples of mixed liquor from the weir overflow site exiting the bioreactor. The 
results included: 
> Floe characterization 
> Analysis of bacterial diversity 
> The presence and quantitation of moncolonies, spirochaetes and spirils 
> The determination of filament index 
> Filament identification and quantitation 
> Identification and quantitation of protozoa and metazoa 
Although a variety of molecular methods have been developed or are in the process of 
being developed for microbial sludge analysis, there is still a place for classical direct 
microscopy in assessing the functional efficiency of WWTP's. A holistic approach 
incorporating all the available methodology is ideal, but not always practically feasible. 
This fact is elucidated upon in chapter 2. 
1.2.3 OPERATIONAL DATA 
These results were included retrospectively. This was to prevent any influence that the 
knowledge of plant parameters may have had on the microscopic results - if results were 
known prior to the microscopic analysis, it may have inadvertently influenced the 
outcome. The influent values used were either from results obtained from the 
supernatant of the primary settling tanks (PST's), or in the absence of PST's, the raw 
influent into the bioreactor. Mixed liquor samples were as per the microscopic analysis 
and effluent samples were those obtained from the clarifier supernatant. Routine weekly 
testing is performed on samples from the WWTP's belonging to the City of Cape Town. 
The data below were included in the study. Additional data was included at a later date if 
deemed necessary to explain pertinent features of the analysis. 
> Influent and effluent chemical oxygen demand (mgCOD/L) 
> Influent, effluent and mixed liquor suspended solids (105°Cmg/L) 
> Influent total Kjeldahl nitrogen and ammonia (Nmg/L) 
> Effluent ammonia and nitrates/nitrites (Nmg/L) 
3 
> Influent total phosphates, influent and effluent ortho-phosphates (Pmg/L) 
> Influent and effluent chloride (Cl"mg/L) 
> Influent and effluent alkalinity (CaC03mg/L) 
> Influent and effluent conductivity (mS/m) 
> Mixed liquor volatile suspended solids (mg/L) 
> Mixed liquor settleable solids (30min ml/L) 
> Mixed liquor sludge volume index and dissolved sludge volume index (mL/g) 
> Sludge age (days) 
1.3 DATA ANALYSIS 
As mentioned previously, the analysis was divided into two sections, namely the 
individual plant analyses and the meta-analysis. 
1.3.1 INDIVIDUAL PLANT ANALYSES 
Each WWTP was assessed as a single entity, with some inter-plant comparisons being 
made. The content included analysis of the efficiency of the WWTP, especially in terms 
of bulking and nutrient removal. The presence of bulking conditions was assessed using 
the dissolved sludge volume index (DSVI) and the filament index (Fl) as indicators. 
Nutrient removal was assessed by analysis of the available operational data. The 
reason/s for any loss of efficiency was/were speculated upon according to literature 
findings. This was tied in with an analysis of the microbial community, according to 
prevailing conditions. The similarities and differences to the associations reported in the 
literature were elucidated upon. 
1.3.2 META-ANALYSIS 
This included combined data from all eleven WWTP's and was structured according to: 
• Population dynamics of the filamentous organism population 
> Prevalence and comparison with similar South African studies 
> Changes from winter to summer over a six month period 
> Correlation with DSVI and comparison to findings of Eikelboom (2000) 
> Discussion of the most prevalent filament types regarding the documented 
organism characteristics, and comparison with study findings 
• Population dynamics of the protozoa and metazoa 
> Changes from winter to summer over a six month period 
> Discussion of the documented organism characteristics and comparison with the 
findings of the study 
4 
CHAPTER 2 
BACKGROUND LITERATURE 
2.1 BACTERIAL METABOLISM AND WASTEWATER TREATMENT 
In a functional activated sludge system under aerobic conditions the synthesis of 
biomass (C5H7N02) from organic matter (COHNS) takes place according to the equation: 
COHNS + 02 + nutrients -> C02 + NH3 + C5H7N02 + other end products. 
(Tchobanglous and Burton, 1991) 
Decompostion of the biomass takes place by a process of endogenous respiration. This 
is enhanced when nutrients have been expended and is related to the equation: 
C5H7NO2 + 502 -> 5C02 + 2H20 + NH3 + energy 
(Tchobanglous and Burton, 1991) 
At the beginning of aeration, the nutrient concentration, or food (F) is at its highest, 
allowing aerobic bacteria to grow quickly, increasing the biomass (M). Thus, during 
aeration the food/microorganism (F/M) ratio decreases logarithmically until if and when 
the supply of nutrients is expended. At low F/M ratios, the cells of many strains of 
bacteria stick together forming floes, which can be separated from the water by settling in 
a clarifier (Eikelboom, 2000). 
For optimal settling results in the clarifier, microbial growth in the mixed liquor should be 
in the endogenous phase and excess sludge should be wasted to maintain the correct 
F/M ratio, desired MLSS and sludge age (Veissman and Hammer, 1998). 
For process stability, the aim is to create conditions that allow for culture of the desired 
bacterial strains. These strains should consume the largest part of the influent nutrients. 
Due to ongoing competition for available nutrients, the population is constantly changing 
due to differences in a variety of factors. The operational parameters and physical 
conditions that have the largest effect are: sludge load, influent composition, DO and 
temperature (Eikelboom, 2000). 
The configuration of the plant has an effect on the nutrient concentration and loading rate 
of the activated sludge (Eikelboom, 2000) 
2.2 NUTRIENT REMOVAL AND BULKING 
2.2.1 N itrif ication/denitrif ication 
The bulk of nitrogen removal takes place by assimilation and nitrification/denitrification. 
In the former, ammonia is incorporated into cell mass that may be released when the cell 
lyses and dies. The nitrifiers are sensitive to a variety of inhibitors, temperature, pH and 
oxygen concentration. By nitrification, the oxygen demand of ammonia is reduced and a 
large amount of alkalinity is consumed (Metcalf and Eddy, 1991). 
The nitrifiers are chemolithotrophs that obtain their energy from the oxidation of either 
ammonia or nitrite (or both) that serve as electron donors for the chemiosmotic 
generation of adenosine triphosphate (ATP). They do not need preformed organic 
substances, but use inorganic C02 as the source of carbon for the synthesis of organic 
cellular compounds (Atlas, 1997). 
6 
In contrast, the heterotrophs are chemoorganotrophs that use organic molecules as their 
source of energy, electrons and carbon. A relatively low amount of energy is produced 
by nitrification, and about 35 moles of ammonia or 100 moles of nitrite are needed to fix 
one mole of carbon dioxide. This leads to a situation where the nitrification process is 
very high, but the growth of the bacteria very slow, especially in comparison to the 
heterotrophic population (Atlas, 1997). 
Low oxygen conditions give many heterotrophic bacteria a competitive advantage over 
nitrifiers. Nitrifiers conserve less electrons in biomass and have a maximum yield co 
efficient that is about one quarter that of heterotrophs. The maximum specific growth rate 
is so small that large mean cell residence times (MCRT's), especially at low 
temperatures, in conjuction with adequate dissolved oxygen (DO), stable pH, and low 
inhibitor levels are needed to prevent washout (Rittman and McCarty, 2001). 
Metcalf and Eddy (1991) have published a ratio of BOD5/TKN of 1-3 to be expected in 
separate stage nitrification. They have determined that this will yield an estimated 
fraction of nitrifiers in the biomass of 0.21 (at 1), to 0.083 (at 3). Furthermore, they state 
that a ratio of approximately >5 would be expected in combined carbon oxidation and 
nitrification processes. 
Denitrification is employed when complete nitrogen removal from wastewater is required. 
Most wastewater contains reduced nitrogen that must be oxidized to nitrate or nitrite to 
allow for denitrification - this is performed chiefly by facultatively aerobic heterotrophs. In 
oxygen-limited conditions, these organisms use nitrate and/or nitrite as a final electron 
acceptor during anaerobic respiration, thereby reducing nitrate or nitrite. Some 
denitrifiers are autotrophs that denitrify using hydrogen or reduced sulphur instead of 
organic carbon as electron donors. In contrast to nitrification, denitrification produces 
alkalinity (Rittman and McCarty, 2001). 
TABLE 2.1 THE REACTIONS AND" 
DISSIMILATORY Nil 
THE CATALYZING ENZYMES FOR 
rRATE REDUCTION 
Equation Enzyme 
NO3" + 2e + 2H" -> N02" + H20 nitrite reductase 
N02" + e" + 2H" -> NO + H20 nitrate reductase 
2IMO + 2e_+2H'-> NzO + H20 nitric oxide reductase 
N20 + 2e_ + 2H"-> N2(g) + H20 nitrous oxide reductase 
(Rittman and McCarty, 2001) 
According to Rittman and McCarty (2001), oxygen controls denitrification in two ways: by 
repression of the reductase genes and by inhibiting the activity of the enzymes 
themselves. The latter takes place at a much higher level of DO than the former, so that 
denitrification can still take place in the presence of oxygen, especially within floes where 
the concentration is lower than in the bulk liquid. Nitrate reductase is repressed less than 
the other reductases at high DO, so the intermediates, which are greenhouse gases, 
may accumulate. This can also happen when the concentration of electron donor that 
drives the half-reactions is low. 
7 
Komorowska-Kaufman eta/. (2006), employed batch testing that mimicked a Bardenpho 
configuration to demonstrate the effects of various factors on denitrification. These 
included the effect of additional carbon source, the effect of the volatile fatty acid to 
nitrate (VFA/N) ratio and the effect of the primary nitrate concentration in the anoxic 
zone. The authors found that with additional carbon, intensive denitrification took place in 
the first hour of anoxic conditions being established. If the VFA concentration was low 
and there was no additional carbon added, the intensive period was only thirty minutes 
and the overall process took double the time. An increase in the initial nitrate 
concentration caused enhanced denitrification efficiency, but not enough to prevent a 
lengthening of time required for denitrification. They also showed that intensive 
denitrification was optimal at a ratio of acetate to initial nitrate concentration of 1.67 mg 
CH3COOH/mg N. From a lower value, as the ratio increased towards the optimum, the 
intensive denitrification time shortened and the intensive denitrification rate and 
efficiency increased. They determined that an increase over this optimum caused a 
decrease in denitrification rate. 
2.2.2 Phosphorous removal 
Orthophosphate, polyphosphate and organically bound phosphate occur in wastewater. 
After primary sedimentation, most is in the soluble form. Conventional secondary 
activated sludge (AS) processes reduce phosphorous to around 6 mg/L, but for 
protected watersheds a maximum value of around 1mg/L should be found. This is 
because it is the primary limiting nutrient in most natural water systems and the presence 
of this element is thus strongly related to eutrophication. Phosphorus may be removed 
by precipitation before, during or after biological treatment, or solely by biological means. 
If the removal of nitrogenous waste is also a requisite, then the longer solids retention 
times (SRT's) necessary for nitrification will lead to lower phosphorus removal rates 
(Rittman and McCarty, 2001). 
A recent review article by Oehman eta/. (2007) exhaustively details all elements of the 
enhanced biological phosphorous removal (EBPR) process in order to endeavour to 
explain why disturbances and prolonged periods of poor removal have been seen in full-
scale plants under seemingly favourable conditions. In the absence of external forces 
such as high rainfall causing over-aeration in the anaerobic zone, excessive nitrate 
loading to the anaerobic zone or nutrient limitation, the chief reason for failure of 
phosphorus removal seems to be an increased ratio of glycogen accumulating 
organisms (GAO's) to phosphorous accumulating organisms (PAO's). There is plausible 
evidence that Accumulibacter spp. is a common PAO as this organism has been 
identified by molecular techniques in many efficient EBPR pilot-scale and full-scale 
plants (Oehman eta/. 2007). The review article points out that these findings have been 
substantiated by metabolic studies, such as those conducted by McMahon eta/. (2002), 
where they detected the gene sequence for polyphosphate kinase as well as the gene 
products of this enzyme in Accumulibacter spp. Competibacter spp. has likewise been 
found to belong to the GAO organism group and studies often use these two organisms 
as indicator species. Both GAO's and PAO's compete for substrate, mainly VFA's 
formed by fermentation of influent slowly biodegradeaable chemical oxygen demand 
(SBCOD) and paniculate organics. In a domestic WWTP setting, VFA's consist chiefly of 
acetate and to a lesser extent propionate. Concentrations of the latter can be increased 
by pre-fermentation of the influent. Amino acids and sugars as substrate may be relevant 
in an industrial setting. Oehman et al. (2007) also cite strong evidence that when 
conditions favour the growth of PAO's over GAO's, phosphorous removal is enhanced 
and vice versa. 
8 
Cech and Hartman (1993) found that acetate supported the growth of both organism 
types, but when used as the sole substrate, the PAO's grew preferentially and for the 
most part phosphorous removal was good. There were short periods when performance 
deteriorated, which the researchers ascribed to predation of the PAO's by a flagellate 
bloom. When glucose was used as a carbon source in addition to acetate, GAO's 
dominated the population. 
Liu et al. (1997) determined that the ratio of phorphorous to carbon was an important 
factor influencing dominance of either PAO's or GAO's. Ratios of less than 2:100 
favoured the growth of GAO's, while higher concentrations of 10:100 or more favoured 
the growth of PAO's. According to the authors, a chemical oxygen demand to 
phosphorous concentration ratio (COD:P) of 10-20mgCOD/mgP should favour the 
PAO's. Their theory is: PAO's take up acetate at a faster rate than GAO's anaerobically 
(substantiated experimentally). They proposed that because the uptake mechanism is 
energy dependent and relies on the stores of polyphosphate that have accumulated 
under aerobic conditions that if the supply of phosphorous is below the threshold level, 
the GAO's with their glycogen energy source can out-compete the PAO's for substrate. 
Furthermore, providing there is sufficient acetate, GAO's will still be present when 
phosphorous levels are high and the ratio of PAO's to GAO's is dependent on the 
concentration of substrate and phosphorous. 
In their article, Oehman et al. (2007) also elucidated on the organisms dubbed as 
denitrifying phosphate accumulating organisms (DPAO's). These PAO's are capable of 
using nitrate/nitrite as terminal electron acceptors and can take up phosphate and 
denitrify simultaneously under anoxic conditions. They point out the not only a low 
COD:P ratio, but sufficient VFA's need to be present for EBPR. Propionate has proven to 
be a better substrate than acetate for EBPR ostensibly because Accumulibacter spp. 
seem to be able to switch between propionate and acetate while Competibacter spp. 
much prefer acetate. However, other GAO's show a preference for propionate. Oehman 
et al. (2007) postulate that GAO's prefer only one substrate, be it propionate or acetate 
and that by manipulating pre-fermentation conditions to enhance substrate switches it 
would lead to a preferential growth of PAO's. The authors refer to studies incorporating 
both substrates when alternation of substrate eliminated GAO's almost entirely. 
The physical parameters of pH and temperature are also factors to be taken into 
consideration. A pH over about 7.25 leads to a better substrate uptake by PAO's in 
comparison to GAO's with EBPR. The converse also holds true (Oehman et al. 2007). 
This is because the energy consumption by the former for the uptake of acetate is higher 
at increased pH, leading to increased anaerobic polyphosphate degradation and release. 
Lower temperatures favour the growth of PAO's and higher temperatures that of GAO's. 
EBPR is still satisfactory at 20°C, but is retarded at 30°C. Saito et al. (2004) found that 
accumulation of nitrite in the anoxic zone inhibits the growth rate of PAO's. 
In terms of the process conditions, the presence of nitrate in the anaerobic zone allows 
the ordinary heterotrophic population to compete for VFA's as substrate. Pre-
denitrification demands high mixed liquor recycle from the aerobic to the anoxic zone to 
provide polyhydroxyalkanoate (PHA) rich PAO sludge with nitrates for denitrifying 
phosphorous removal and for denitrification of ammonia from the aerobic zone. The 
mixed liquor recycle from the anoxic to the anaerobic zone should be at the end of the 
anoxic zone and contain little nitrates and nitrites (Oehman eta/., 2007). 
9 
2.3 BULKING 
Some bacteria, fungi or algae do not become detached from one another on cell division 
and grow into filaments. Certain bacteria form filaments under almost all conditions and 
there are around 30 species that are observed in activated sludge, with 10 being 
frequently found. Filamentous organisms are normally present in activated sludge. When 
conditions are created that allow them to out-compete the other bacteria to such an 
extent that they grow en masse, problems may be encountered: bulking sludge, 
deterioration of settling and dewatering properties and sometimes scum formation. The 
number of filaments present is not the only parameter determining sludge settling and 
the SVI or DSVI does not always correlate directly with the filament index (Eikelboom 
2000). 
Jenkins et al. (2004) advocates the following approach to correct solids separation 
problems: 
> Perform a microscopic examination. 
> Determine the probable cause of the problem using the information from the 
microscopic examination, coupled with knowledge of plant operating 
conditions and wastewater characteristics. 
> Make appropriate operating changes. These may be minor or major. 
Problems needing minor changes include septic wastewater and nutrient 
deficiency. Major changes would include design or operating changes such 
as installing additional aeration capacity or changing the aeration basin 
configuration. 
If clarifier capacity is sufficient, even sludges with high DSVI's may settle sufficiently. The 
following equation gives a basic understanding of this: 
Ga = X (Q+Qr)/A, where 
Ga is the allowable applied suspended solids (SS) loading rate 
X is the mixed liquor suspended solids (MLSS) concentration 
Q is the influent flow rate 
Qr is the return activated sludge (RAS) flow rate 
A is the clarifier surface area 
Q,/A is the underflow RAS rate 
This equation is simplified and does not take into account factors such as the settling 
characteristics of the AS itself. More complicated calculation techniques exist, that relate 
Ga, RASSS, Qr/A and a range of sludge volume indices (SVI's) in a diagrammatic form. 
These Clarifier Operating Diagrams are used to empirically determine loading rates by 
correlation of settling tests with points on the diagrams. Ideally, empirical values should 
be compared with actual performance as a method of calibration (Jenkins eta/., 2004). 
Under growth limiting conditions, the growth rate of floc-forming organisms generally 
decreases more than that of filamentous organisms. Only at very high nutrient (loading) 
levels, can the faster growing floc-formers out-compete the filaments. Some filamentous 
organisms also have competitive nutrient requirements. If certain elements or 
compounds are present in large enough quantities, these filaments have an advantage. 
For example, Thiothrixspp. and Type 021N, amongst others, can utilize reduced sulpur 
for growth. Most filamentous organisms are aerobic, so the creation of anoxic or 
anaerobic conditions will generally allow the growth of anaerobic or facultative floc-
formers, but not filaments (Jenkins et al., 2000). Eikelboom (2000) postulates that this is 
10 
because most filaments can absorb free higher fatty acids from the water phase under 
anaerobic and anoxic conditions, whereas most floc-formers can only absorb and 
process them aerobically. 
Prolific growth of so-called "low F/M filaments" cannot be controlled by the selector effect 
in intermittently aerated systems used for biological nitrogen removal (BNR) such as 
Carrousel® and Orbal plants. This is also the case for multi-reactor anaerobic-anoxic-
aerobic nitrification-denitrification enhanced biological phosphorous removal (NDBEPR) 
plants such as the modified University of Cape Town (MUCT) or Bardenpho 
configurations. True "low F/M filaments" are classified by Jenkins et al. (2004) as being 
selected when loading rates are in the range of 0.05-0.2 kg BOD5/kgMLSS.day. 
They are as follows: 
> Type 0675, Typel 851, Type 0803 
> Type 0041 (may also be selected if there is pre-mixing of influent with RAS). 
> Type 0092, Type 0581, Type 0914 (These may also be selected in conditions of 
high concentrations of low molecular weight (LMW) organic acids. In addition, the 
presence of H2S favours the growth of Type 0914). 
> Microthrix parvicella (there are many other conditions that favour the growth of 
this problem species such as abundant fatty acids, low temperatures (<15°C), 
reduced nitrogenous and sulphurous waste). 
Lakay et al. (1999) conducted a number of laboratory-scale experiments in order to 
determine factors contributing to the growth of "low F/M filaments". The authors mention 
the classification system of Jenkins et al. (2004) and refer to "low F/M filaments" in this 
context. In reality, many of the filaments identified at increased DSVI values were not 
classical "low F/M" filaments according to Jenkins et al. (2004). Haliscomenobacter 
hydrosis (H. hydrosis) in particular was referred to repeatedly as being "low F/M". 
(Perhaps using terminology such as "possible bulking conditions" or "filamentous 
overgrowth" in the article would have been more accurate). 
The substrates employed in the experiments by Lakay etal. (1999) were: 
> Municipal sewage 
> Municipal sewage subjected to ultrafiltration to give both readily 
biodegradeable chemical oxygen demand (RBCOD) and slowly 
biodegradeable chemical oxygen demand SBCOD) 
> Defined substrate. The reason for the defined substrate was to eliminate 
variation in composition that may have affected low F/M filament growth. 
Nitrate dosing was employed in all experiments in order to maintain the anoxic conditions 
and compare nitrate utilization in some instances. Filament identification for dominant, 
secondary and tertiary organisms was performed approximately every thirty days, or 
more randomly in some cases, according to requirements. 
Evidence from the feeding regimes and filament identification led Lakay et al. (1999) to 
suggest that bulking can occur with either municipal or defined substrate (RBCOD and 
SBCOD). However, two of the three dominant filaments, namely H. hydrosis and Type 
021N are not classified by Jenkins etal. (2004) as "low F/M". 
Lakay et al. (1999) found an increase in DSVI associated with anoxic conditions and 
concluded that RBCOD supplied under anoxic conditions resulted in "low F/M" 
proliferation. A similar experiment by the same authors employing defined substrate 
11 
yielded substantially higher DSVI values associated with H. hydrosis and type 1851. 
H. hydrosis was also the dominant species during protracted anoxic conditions, where it 
was associated with low DSVI values in this occasion. DSVI values increased during 
periods of intermittent aeration compared to either aerobic or anoxic conditions. The 
results of Lakay et al. (1999) with the unfiltered sewage and alternating continual and 
intermittent aeration concurred with those of Ketley et al. (1991) who found that 
intermittent aeration caused an increased DSVI associated with Microthrixparvicella (M. 
parvicella) dominance. The highest DSVI values were obtained with a 30-40% aerobic 
mass fraction for both intermittently aerated nitrification-denitrification (IAND) and two 
modified UCT (MUCT) systems. With the MUCT systems, type 0092 was the dominant 
species for the duration of the experiment. 
Warburton etal. (1991) showed that there was little effect on DSVI, filament proliferation 
or filament species when the sludge age was decreased from 20 to 10 days. When 
sludge age was further decreased, filament population remained similar, but the 
organisms were less proliferative. However, such sludge ages are not appropriate in 
nutrient removal plants. 
Casey et al. (1994a) demonstrated that lower DSVI values were obtained for 2 reactor 
nitrification-denitrification systems (2RND) operated at the same aerobic mass fraction 
as an IAND system. Further to this, the author compared differences between both 
systems and sought to establish clarity on the facets discussed in the following 
paragraphs: 
> The frequency of exposure of IAND and 2RND systems to alternating anoxic-
aerobic cycles. For IAND systems this is usually high (>30/day), while that of 
2RND systems is low (<5/day) due to the low aerobic-anoxic and sludge 
recycle ratios. Lakay et al. (1999) refer to studies by Ketley etal. (1991) and 
Hulsman et al. (1992) who determined that the frequency did not affect "low 
F/M" proliferation under the influent composition and operating conditions 
they used. 
> RBCOD concentration differences between the two systems. The rationale for 
these experiments by Lakay etal. (1999) was that both RBCOD and SBCOD 
are fed to an IAND system in proportion to the respective aerobic/anoxic 
mass fractions. In 2RND systems, the RBCOD will be utilized either 
aerobically (Wuhrman plant configuration) or anaerobically (Modified 
Ludzack-Ettinger plant configuration). In a typical domestic WWTP, operating 
at an aerobic mass fraction of 30%, all the RBCOD is utilized in the first 
reactor. The second reactor thus only has SBCOD as substrate. A 2RND 
system was operated in Modified Ludzack-Ettinger (MLE) configuration with a 
steady-state DSVI of approximately 130 ml/g. Influent sewage (approximately 
20% RBCOD) was then diverted into both the aerobic and anoxic reactors to 
simulate an IAND system. There was no significant change in DSVI, 
demonstrating that the system configuration and thus environmental 
conditions does not affect "low F/M" growth. 
> The DO concentration in the aerobic period or reactor. In IAND systems, 
there is a high DO concentration at the start of aeration and then a 
decreasing gradient until oxygen is expended by biological action. With a 
2RND system, oxygen is either present at a high concentration in the aerobic 
reactor, or entirely absent in the anoxic reactor. Results of the experiments by 
Lakay et al. (1999) provided evidence that "low F/M" proliferation in IAND 
configurations is not due to decreasing DO gradient. 
12 
> Nitrate concentrations in the anoxic period of IAND and 2RND systems. The 
findings of these experiments by Lakay eta/. (1999) were novel and form the 
basis for an important model on the causes of filamentous bulking, so the 
discussion is more protracted and detailed: 
Nitrate concentration in an IAND system is high at the end of the aerobic period due to 
nitrification. The nitrate concentration then decreases during the anoxic period due to 
denitrification and may be completely expended if the anoxic period is long enough. 
However, there is little variation in nitrate concentration with short anoxic periods. In an 
IAND system, there is a large gradual change in redox potential chiefly due to the 
varying concentrations of the electron acceptors nitrate, nitrite and oxygen. Oxygen 
levels are high at the beginning of the aeration cycle, and this element is used as the 
preferential electron acceptor, until depletion. At this stage, nitrates and then nitrites 
assume this role, until they too are depleted and anaerobic conditions ensue. In contrast, 
the anoxic zone of a 2RND system will have a constant (usually low to zero) nitrate 
concentration depending on the nitrate load from the recycle and the denitrification 
potential of the system. A different but constant redox potential is established in the 
aerobic and anoxic zones. This means that biota being transferred from one reactor to 
another will be subjected to large and sudden changes in redox potential (Lakay et a/., 
1999). 
Lakay et a/. (1999) measured the redox potential for over a month in a 2RND system 
(MLE) and found an average value of -81 mV in the anaerobic zone and +48mV in the 
aerobic zone. When the same system was changed to an IAND configuration, the DSVI 
values increased substantially. In one complete 8-hour cycle, the redox potential 
increased during the aeration cycle to a maximum of +40mV and declined to a minimum 
of -80mV during the anoxic cycle. These are almost identical to the figures obtained from 
the 2RND system. The authors deduced experimentally that the presence of nitrites and 
nitrates present throughout the cycle created a propensity for overgrowth of "low F/M" 
filaments. 
Musvoto eta/. (1999) conducted further experimentation in order to ascertain the relative 
implication of nitrate and/or nitrite as the causative agent of bulking in nutrient removal 
plants. At this point, it was recognized that what they had termed "low F/M bulking" was 
perhaps a misleading label, because their research had shown that the most probable 
cause of filamentous bulking in nutrient removal WWTP's was alternating anoxic/aerobic 
conditions. They thus termed this group of organisms "AA filaments". MUCT systems 
were dosed separately with excess nitrate and nitrite. Dissolved sludge volume index 
(DSVI) values were determined and nitrate and nitrite levels were measured. It was 
found that the rate of DSVI increase for nitrate dosing (with subsequent high nitrate and 
low nitrite levels in the second anoxic reactor) was 1.0 ml/g/day. The rate of DSVI 
increase for nitrite dosing (with high nitrite and low nitrate levels in the second anoxic 
tank) was 1.5ml/g/day. Filaments identified during nitrate dosing included dominant 
filaments Type 0092 and Type 0914 and secondary filaments Type 0092, Type 0041, M. 
parvicella and Beggiatoa spp. During nitrite dosing, filaments were identified only once 
with Type 0092 being dominant and type 021N and Type 0675 secondary. All of the 
dominant filaments fall into the "low F/M" category of Jenkins eta/. (2004). 
Musvoto et a/. (1999) concluded that in MUCT nitrogen and phosphorous removal 
systems, filament proliferation takes place when the sludge is subjected to sequential 
anoxic-aerobic conditions. In addition, nitrate and or nitrite levels of >2.0 and >1.0mgN/L 
respectively must be present in the anoxic zone immediately preceding the aerobic zone. 
13 
Furthermore, Musvoto eta/. (1999) made the assumption that denitrification is mediated 
predominantly by facultative heterotrophs (filaments and floe formers). In this case, they 
pointed out that alternating anoxic and aerobic conditions would force these organisms 
to switch between the nitrates/nitrites and oxygen as the terminal electron acceptor and 
hypothesized that bulking occurs due to the efficiency of this switching mechanism by 
some filamentous organisms. 
Casey eta/. (1999c) proposed a biochemical model to explain AA bulking using those 
assumptions. Initially, a literature review of the biochemistry of heterotrophic respiratory 
metabolism was conducted Casey et a/. (1999a). This was followed firstly by the 
formulation of a conceptual biochemical model of the behaviour of heterotrophic 
facultative aerobic organisms when subjected to aerated and unaerated conditions and 
secondly by a series of experiments to test this model (Casey et a/., 1999b). His theory is 
that, assuming both filaments and floc-formers are facultative aerobes, under completely 
aerobic or anoxic conditions, floc-forming heterotrophs out-compete filaments for 
substrate because they have higher substrate utilization rates (SUR's). However, when 
configurations are such that there are alternating aerobic and anoxic conditions, RBCOD 
levels are low or absent and the SUR of floc-formers is inhibited under aerobic 
conditions. The mechanisms proposed by Casey eta/. (1999c) for the proliferation of AA 
filaments are summarized simplistically in the ensuing paragraph: 
Cytochrome d is integral to aerobic respiration. It is inhibited by nitric oxide. When there 
is insufficient RBCOD, the intermediate nitric oxide is formed intracellularly in floc-
formers, resulting in the inhibition of cytochrome d. When cytochrome d is inhibited, 
aerobic respiration is inhibited and electrons are directed to the reductase enzymes. 
Oxygen changes the permeability of the membrane so that nitrate cannot diffuse across 
the membrane to reach nitrate reductase. The pathway for aerobic denitrification of nitrite 
to nitric oxide (and further) is thus followed. When the supply of electrons is restricted, 
there is a preferential electron flow to nitrite reductase over nitric oxide reductase, 
leading to accumulation of nitric oxide. This obviously occurs when the levels of nitrite 
are high enough (as is the case with alternating aerobic anoxic conditions) for two 
reasons - firstly, the denitrifying bacteria are inhibited under aerobic conditions, so in 
subsequent anoxic periods, there is an accumulation of nitrite. Secondly, the inhibition of 
NOO's (and to a lesser extent other nitrifiers) under oxygen limitation also leads to nitrite 
accumulation. If there are sufficient electrons (as is the case with RBCOD) however, the 
supply of electrons from NADH is not restricted. The intracellular concentration of nitric 
oxide is kept low enough by its reductase to prevent inhibition of aerobic respiration. In 
contrast, the AA filaments only produce the enzyme for the reduction of nitrate to nitrite 
(nitrate reductase). The reductases responsible for the conversion of nitrite to nitric oxide 
and further are not manufactured. Therefore, under anoxic conditions the cytochrome d 
inhibitor, nitric oxide does not accumulate. Under ensuing aerobic conditions, aerobic 
respiration in not inhibited. This gives the AA filaments a competitive advantage. 
The results of a variety of batch tests on AS were reported by Casey eta/. (1999c) and 
these substantiated the theoretical model. For example it was determined that when 
nitrite was added to a system following an anoxic phase the inhibition of the OUR during 
the aerobic phase increased with increased nitrite concentration (at the start of the 
aerobic phase). There was no inhibition of aerobic respiration when nitrite was absent. 
When RBCOD in the form of sewage was added, inhibition was relieved. 
Casey eta/. (1999c) also determined that sludge with a high DSVI was assumed to have 
a high proportion of filamentous organisms and that with a low DSVI, a high proportion of 
14 
floc-formers. In 8/10 tests, sludge from an anoxic system with a high DSVI accumulated 
nitrite, but did not accumulate dinitrogen when subjected to nitrogen reduction tests. The 
converse was true of the sludge with low DSVI. Casey et al. (1999c) took this as 
supportive of the hypothesis that the enzyme system of AA filaments does not allow for 
the conversion of nitrite to dinitrogen - denitrification of nitrate to nitrite only occurs. 
In light of the above, Casey et al. (1999c) proposed some control measures to prevent 
bulking in nutrient removal plants, including: 
> Aerobic mass fraction: avoid ranges between 30-40% 
> Reduce nitrite levels: reduce to near zero prior to sludge entering the aerobic 
zone. This can be achieved by reducing the a-recycle or increasing the 
unaerated mass fraction to ensure complete denitrification in the anoxic zone. 
> Reduce nitric oxide: reduce intracellular nitric oxide significantly if the above 
is impractical due to inflexible plant configuration or inherent wastewater 
characteristics. This can be achieved by the inclusion of a small aerobic or 
anoxic reactor upstream of the main aerobic reactor to which RBCOD 
(sewage wastewater) is fed. 
Note: 
There are many causes of bulking and means of correcting this phenomenon. An in-
depth analysis of every possibility is beyond the scope of this study. Only factors playing 
a role in many sections of chapters 3-6 have been discussed. Other more specific facts 
are elucidated upon in chapters 3-6 if pertinent to a particular WWTP or microorganism. 
Similarly, although scum formation is an important cause of poor plant performance, it 
was not a major focus of the study, so is not discussed in detail. 
2.4 MICROORGANISM POPULATION IN MIXED LIQUOR 
Microscopic analysis enables the evaluation of conditions over a longer period of time 
than chemical data (Jenkins et al. 2004). Within the last decade, there has been a move 
to identify the microbial population from WWTP's by molecular methods. There are 
advantages and disadvantages to each approach, and although microscopic 
identification of filaments is out of vogue in academic research, it still has many positive 
attributes that should not be disregarded. The main reasons for the ineffectiveness of the 
traditional method is that it does not allow distinction of different organisms that are 
morphologically the same, nor does it allow for identification of the same organisms 
exhibiting variable morphology (Hug eta/., 2005). 
The most popular molecular methods employed are Fluoresecent in situ hydridization 
(FISH) and Denaturing Gradient Gel Electrophorsis (DGGE). 16S rRNA DGGE analysis 
has excellent sensitivity and allows the identification of minority constituents. Muyzer et 
al. (1992) found the method able to identify organisms representing only 1% of the 
population. Drawbacks are that the method is time-consuming and requires 
establishment of extensive clone libraries. In addition, the clone frequencies in the clone 
libraries do not reflect the in situ quantities of the organisms thus identified 
(Eschenhagen et al., 2003). Sekiguchi et al. (2001) discovered that when DGGE 
methodology, several phylogenetic species formed part of a single band, and that in 
order to differentiate these organisms, it was necessary to repeat the procedure in 
triplicate. 
15 
FISH allows for the definitive identification of a range of microorganisms and is 
particularly useful in detecting non-filamentous organisms such as the species that form 
the PAO and GAO population (Eschenhagen et ai, 2003). Using FISH, it has been 
discovered that some Eikelboom morphotypes such as M. parvicella appear to represent 
single species (Liu etai, 2001b). However, this is not always the case. The microscopic 
identification of Nostoicoida limicola (A/, limicola) has proven to be problematic. Liu etai 
(2001b) designed oligonucleotide probes for this group of filaments and discovered that 
N. limicola II can consist of a number of phylogenetically unrelated filaments and that N. 
limicola I and N. limicola II are probably the same organism that changes 
morphologically according to culture conditions. However, the technique they used 
required numerous probes and mismatches (a common problem) did occur. 
FISH can be used successfully to quantitate species or groups in the sludge. Hug etai, 
(2005) have devised a rapid system based on mathematical principles to quantitate 
organisms using FISH. However, this method is limited to those filaments that are not 
part of the floes. Eschenhagen et al. (2003) performed a comparative study employing 
FISH and 16S rDNA analysis using DGGE and T-RFLP. They found the latter were far 
superior to FISH for the detection of community diversity. Due to the nature of the 
methodology employed by FISH, the identification can only be as reliable as the 
oligonucleotides probes employed. Mismatches are bound to occur, especially while the 
technology is still relatively new. As new probes are designed, this phenomenon should 
decrease (Muyzer atal. 1992). 
Apart from the difficulties with the traditional microscopic identification of N. limicola, 
there are reported inconsistencies in the identification of Eikelboom Type 021N. 
Kanagawa etai (2000) performed a variety of morphological, biochemical and molecular 
tests to definitively identify 15 strains of this morphological type isolated from bulking 
sludges. The molecular methods employed were the sequencing of 16S rDNA 
(employing PCR and automated sequencing) and FISH to allow differentiation of the so-
called 021N- Thiothrix cluster. They used the results to differentiate the 021N 
morphotypes into three distinct groups (I, II and III). The FISH technique required the use 
of three probes and the authors discovered mismatches with type II. 
Molecular methods, especially FISH have also been used successfully to differentiate 
between bacteria that are loosely attached to floes with a propensity to become free-
swimming and those bacteria that tend to form an integral part of the floe (Morgan-
Sagastume et al., 2007). The population was classified broadly, for example as Beta-, 
Alpha- and Deltaproteobacteria with 10 different group specific probes. The results 
obtained by Wilen et al. (2007) employing shear testing and FISH identification 
concurred that the population prone to shear is different from that which is strongly 
associated with floe formation. 
A drawback of conventional microscopic filament identification is that the filaments inside 
the floes are not visible. Liao etai (2003) has used this as argument to promote the use 
of FISH. This was a drawback also reported by Gulez etai (2008), who employed pilot-
scale reactors and used conventional microscopy, FISH and DGGE in an effort to 
compare the methods for filament identification in activated sludge. Only three filaments 
were identified in the study - Sphaerotilus natans (S. natans), Thiothrix spp. and N. 
limicola. Even with this limited number of species, they discovered anomalies with each 
method and advocated multiple approaches to filament identification. They pointed out 
the problems inherent in each methodology: FISH has been biased by poor permeability 
of the cell walls of certain species. Indeed, in their study, N. limicola was not detected 
16 
from all samples using this method, possibly due to impermeability despite treatment 
with lysozyme and mutanolysin (supposed to prevent this occurrence). This strain was 
also not detected by DGGE, ostensibly due to the cell wall composition affecting DNA 
extraction. Besides these problems with FISH, Gulez eta/. (2008) cite literature findings 
of bias due to low ribosome content, lack of specificity of probes, a higher order structure 
of either the target or the probe and fluoresence either causing background interference 
or being bleached (FISH). DGGE may give artefactual bands, single bands may 
represent more than one organism or there may be more than one band per organism. 
DGGE is a time-consuming procedure relying on nucleic acid extraction, PCR 
amplification, visualization of PCR products on a gel, excision of these products and 
subsequent sequencing Gulez et al. (2008). The advantages and disadvantages of the 
three methods are summed up in chapter 6. 
Microscopic evaluation also allows a rapid assessment of floe quality and the 
composition of the protozoan and metazoan communities (Jenkins et al., 2004). 
Microscopic analysis can be used effectively to qualitatively assess the sludge and to aid 
in troubleshooting WWTP's that are not functioning to expectation. The characteristics of 
the floes formed in the mixed liquor play a large role in determining the settling 
characteristics of the sludge in the clarifier. Robust, compact floes settle best. The more 
diverse the range of microorganisms encountered in the sludge, the more robust and 
flexible the degradation process. Low diversity usually only occurs when there is a lack 
of nutrients, such as would be encountered in a high-loaded industrial treatment plant 
(Eikelboom, 2000). 
Floe characteristics from plants with similar process conditions closely resemble one 
another and have similar protozoa and metazoa. Eikelboom (2000) has established that 
90% of floes in Dutch WWTP's fall into three groups based on loading rates and type of 
aeration employed. Surface aeration tends to break up floes, so they will be smaller than 
those from plants employing diffuse aeration. Floes from industrial treatment plants often 
differ considerably from plant to plant and are often small and fragmented, especially in 
plants where chemical waste is being treated and surface aeration is used. The floes 
may be irregular because of the growth of masses of filamentous organisms. With 
industrial plants, he advocates that sludge should be examined over a period of time and 
the individual floe characteristics established. Further samples can then be compared to 
this norm (Eikelboom, 2000). 
Protozoa and metazoa may utilize bacteria and particulate organic matter as a source of 
energy, thereby performing a polishing function of the treatment process. The 
protozoan/metazoan population is indicative of the process conditions in the WWTP, with 
some species being used as indicator organisms. The contribution of bacteria to the 
overall treatment process is far greater than that of these organisms (Eikelboom, 2000). 
Salvado et al. (1995) determined that ciliates are best used as indicator organisms for 
seven different physico-chemical parameters when the population density in a sample is 
high. The parameters used in the study were: effluent and settled sewage BOD5, 
retention time in aeration tank, organic loading rate, mixed liquor volatile suspended 
solids (MLVSS), mean cell retention time (MCRT) and dissolved oxygen (DO) in the 
aeration tank. They concluded that an increase in the abundance of ciliate species 
reflects the optimal range conditions for growth of that species. This allows for the 
assessment of the quality of effluent. 
17 
On start-up of a new plant, there is a distinct species succession with time. By recycling 
all sludge in the initial phases (large solids retention time), the resident population can be 
established. At first the nutrient supply is abundant and the bacteria that are present are 
not capable of fully processing this. Large numbers of flagellates and amoebae develop. 
Later, free-swimming ciliates appear and the numbers of flagellates and amoebae 
decline. With the increase in biomass, the loading levels decrease and so does the 
growth rate of the free-living ciliates due to nutrient deficiency. As the solids retention 
time (SRT) is decreased, many species are washed out. This is when the crawling and 
sessile ciliates appear, as they are not vulnerable in this way. Metazoa are established 
when the plant has been in operation for sufficient time. This gives an indication of the 
different conditions needed for the growth of the protozoa and metazoa. For example, at 
moderate loading levels many ciliates, testate amoebae and some metazoa are usually 
present. If the DO levels are too low, there is a decline in the removal of COD and this 
favours the growth of flagellates and amoebae. The presence of toxins results in the 
disappearance of the protozoan and metazoan population, followed by an explosion in 
the numbers of protozoa after a few days. This is because of the large number of free-
living bacteria available for consumption after the absence of their predators (Eikelboom, 
2000). 
The higher bacterial prey densities found in high loaded plants favours the growth of 
flagellates, amoebae and small, free-swimming ciliates - these three groups all exhibit 
inefficient chase and capture feeding mechanisms. Attached ciliates, rotifers and other 
invertebrates are selected at lower loading levels - they are attached to the floes and 
feed by more efficient mechanisms. A balance between free-swimming and attached 
ciliates and rotifers is likely to be encountered in sludge when AS performance is good. 
Generally speaking, an overabundance of flagellates, amoebae or free-swimming ciliates 
indicates high F/M. Conversely, an overabundance of attached ciliates, rotifers and other 
life forms indicates low load. Low DO, high temperatures, unfavourable pH (<6.6 or > 
8.5), as well as toxicity can lead to floe stress with resultant release of numerous bacteria 
as a food source. Blooms of flagellates and/or small free-swimming ciliates ensue 
Jenkins eta/. (2004). 
2.5 SCUM FORMATION 
Eikelboom (2000), has observed that filamentous scum reaches a peak in winter months 
in The Netherlands and that there is a direct correlation with filament index of the scum. 
By comparing the population of filaments found in the mixed liquor and scum of problem 
WWTP's, he deduced that M. parvicella, actinomycetes and N. limicola (to a lesser 
extent), flotate selectively. These organisms have Gram positive and thus hydrophobic 
cell walls. Together with their morphology of flexible, bowed filaments, their 
hydrophobicity confers a predilection for forming networks over the hydrophobic surfaces 
of gas bubbles. Both M. parvicella and the actinomycetes compete for the hydrophobic 
fat fraction of the wastewater, with higher temperature and sludge load favouring the 
latter. Most of the other Gram-positive filaments found in low loaded plants are straight 
and have sheaths, so the hydrophobic cell wall is not in contact with the mixed liquor 
directly. When scum formation is not excessive, control measures such as skimming, 
removal and destruction of scum or spraying effluent on the scum can be employed. 
However, if scum formation is excessive, controlling the growth of the responsible 
filamentous organisms is necessary (Eikelboom, 2000). 
Wastewater with high concentrations of oil or grease may lead to a high population of 
actinomycetes, while there is anecdotal evidence that wastewaters such as those found 
18 
from paper and pulp processing with no oil or grease rarely harbour these organisms 
(Jenkins eta/., 2004). 
Under anoxic and anaerobic conditions, M. parvicella can take up and store long chain 
fatty acids, possibly because of the presence of surface-associated lipases. It is thought 
that when no oxygen is present, hydrolysis rates of particulate organics by the sludge 
population is decreased. Under these circumstances, the floc-formers are unable to 
metabolize lipid substrates, leading to a competitive advantage for M. parvicella (Jenkins 
etai, 2004). 
*Additional literature is incorporated into the body of the text, where discussion on a 
particular feature of the study takes place. There is no duplication of this content is in this 
chapter (chapter 2). This was due to the wide-ranging content of the study and to obviate 
the need for constant cross-referencing between the body of the text and chapter 2. 
19 
CHAPTER 3 
METHODS 
3.1 SAMPLE COLLECTION 
This task is ordinarily performed on a weekly basis by the operational staff at each of the 
WWTP's of the City of Cape Town. Grab samples are taken in plastic bottles from the 
weir overflow site exiting the bioreactor. The site of collection is clearly marked at each 
WWTP. Samples are transported to the Scientific Services Department of the City of 
Cape Town and routinely analyzed on the day of collection. During the study period, the 
microscopic analysis was conducted on the same day as sample collection in most 
circumstances. On the rare occasion when this was not possible, the delay was never 
greater that 24 hours post collection. 
3.2 OPERATIONAL DATA 
The staff employed by the Scientific Services Department of the City of Cape Town 
conducted all of the tests listed in this section. 
COD 
VSS 
Settleable solids 
SVI 
DSVI 
Conductivity 
According to the methods described by Clesceri eta/. (2005) 
Seven of the parameters were conducted using an automated system. A Lachat flow 
injection analysis (FIA) analyzer was employed to quantitate the amounts of ions present 
according to QuickChem methods. The parameters are given below together with the 
relevant QuickChem method number: 
TKN 10-107-06-2-D 
Ammonia 10-107-06-1-A 
Nitrates/nitrites 10-107-04-1-A 
Total Phosphates 10-115-01-1-E 
Ortho-phosphates 10-115-01-1-A 
Chloride 10-117-07-1-A 
Alkalinity 10-303-31-1-A 
3.3 MICROSCOPIC ANALYSIS 
The microscopic analysis was performed on samples without prior knowledge of the 
parameters given in section 3.2 so as to not inadvertently skew any results. The 
methodology given by Eikelboom, (2000) in his manual and accompanying CD was used 
as the basis for the analysis. Wherever possible, comparisons were made with 
micrographs from the manual and accompanying CD of Eikelboom (2000), 
supplemented with the text and micrographs from the manual of Jenkins eta/. (2004). All 
parameters were recorded on a separate chart for each mixed liquor sample. 
21 
3.3.1 Wet mounts 
Three wet mounts were prepared from each mixed liquor sample. The edges of the 
coverslips were sealed with Vaseline to prevent desiccation during examination. The 
slides were examined using 10X, 20X and 40X phase contrast objective lenses to give 
final magnifications of 100X, 200X and 400X respectively. If there was a need to observe 
further detail, a 100X lens was employed using oil immersion to give a final magnification 
of 1000X. The wet mounts were used to determine: 
3.3.1 (a) Morphological characteristics of the floes 
• Size (diameter): small <25um, medium 25-250um, large >250um 
• Shape: round or irregular 
• Structure: compact or open 
• Strength: firm or weak 
3.3.1 (b) Filament index 
The filament index is a semi-quantitative assessment of the number of filaments between 
the floes. Sample micrographs of sludges with different indices are located on the CD 
accompanying the manual by Eikelboom, (2000) as comparative measures. These were 
used extensively in order to maintain consistency of results throughout the study. 
Filament index was classed on a scale of 0-5, incorporating half measures where 
appropriate (for example 1.5). 
3.3.1 (c) Filament characteristics 
Certain characteristics pertaining to the filaments were noted, including motility, the 
presence or absence of sheaths, cell shape, the presence or absence of septa, filament 
shape, filament diameter and attached growth. At times, some of these characteristics 
were better visualized on the stained preparations. This was especially apparent when 
different filaments shared similar features. Thus, the unstained and stained slides were 
used in conjunction with one another to determine the characteristics of the filaments 
necessary for reliable identification. 
3.3.1 (d) Diversity 
The diversity of the bacterial population was noted as being low (1), moderate (2) or high 
(3). 
3.3.1 (e) Monocolonies 
The presence of monocolonies was quantified as absent (0) or present in either scanty 
(1), moderate (2) or numerous (3) amounts. 
3.3.1 (f) Free-living cells, spirochaetes and spirils 
The presence of free-living cells, spirochaetes and spirils was quantified as absent (0) or 
present in either scanty (1), moderate (2) or numerous (3) amounts. 
Initially a number of wet mounts were prepared simultaneously, sealed and then 
examined. Midway into the study, this was changed as it was noted that numbers of free-
living cells and spirochaetes appeared to be greater in slides that had been left standing 
for longer periods. At this point, it was decided to prepare the wet mounts and examine 
immediately for free-living cells and spirochaetes. After 10 minutes, the mounts were re-
examined. This was referred to as "comparative timed analysis" and the results are 
divided into those obtained before and after the introduction of this "comparative timed 
analysis". 
22 
3.3.1 (g) Identification of protozoa and metazoa 
These organisms were identified exclusively from the text of Eikelboom's (2000) manual 
and accompanying CD. Due to the lack of any prior experience, no attempt to speciate 
within any of the genera was made. When there was any uncertainty, the microbes were 
merely classed as unidentified protozoa, unidentified free-living ciliates or unidentified 
crawling ciliates. There were no unidentified microbes in any of the other categories. 
Numbers were enumerated semi-quantitatively as scanty, moderate or numerous. 
3.3.2 Sulphur storage test 
This was performed on all mixed liquor samples according to the method described in 
the manual of Eikelboom, (2000). 
3.3.3 Gram stain 
One slide was prepared from each of the undiluted mixed liquor samples and stained 
according to the method reference number BSOP TP 39i1 described in the manual of the 
Standard Operating Procedures of the Health Protection Agency (HPA) of the United 
Kingdom. The initial stain employed was 0.5% crystal violet. The decolouriser used was 
acetone and the counterstain was diluted carbol fuschin. The choice of Gram stain was 
due to the personal preference and experience of the microscopist. 
(source: /7flp;//www.evaluations-standards.orq.uk.) 
The slides were examined at 1000X magnification under oil-immersion. The staining 
characteristics as well and the apparent morphological characteristics of the filaments 
were noted. The latter were compared to the results observed in the wet mounts, after 
staining with the Neisser technique and after the sulphur storage test, to give a holistic 
picture of each filament type. 
3.3.4 Neisser stain 
One slide was prepared from each of the undiluted mixed liquor samples and stained 
according to the method described in the manual of Eikelboom, (2000). 
The slides were examined at 1000X magnification under an oil-immersion lens. The 
staining characteristics as well and the apparent morphological characteristics of the 
filaments were noted. The latter were compared to the results observed in the wet 
mounts, after staining with the Gram technique and after the sulphur storage test, to give 
a holistic picture of each filament type. 
3.3.5 Calculations 
3.3.5 (a) Sludge age 
This value is a measure of the age of the microbial population inherent in the sludge. 
Reactor volume (m3) X mixed liquor volatile suspended solids (MLVSS) (g/L) 
Sludge wasted (kg/day) 
3.3.5 (b) F/M ratio 
This value is a measure of the amount of nutrients supplied to the biomass within the 
reactor. 
Influent flow rate into bioreactor (ML/dav) X Chemical oxygen demand (COD) (mqCOD/U 
Bioreactor volume (ML) X MLVSS (mg/L) 
23 
4.1 ATHLONE WWTP 
4.1.1 PLANT CONFIGURATION AND OPERATING PARAMETERS 
Athlone WWTP is a nitrification-denitrification biological excess phosphorous removal 
(NDBEPR) plant with a design capacity to treat approximately 120ML effluent per day. 
The plant houses six identical bioreactors named from A to F, which operate in a 
University of Cape Town (UCT) configuration with diffuse aeration. The raw influent 
consists of approximately 70% industrial effluent and 30% domestic effluent. Influent to 
the primary settling tank (PST) consists of raw influent as well as the liquid component 
from the digesters and thickeners. The plant operates at a dissolved oxygen (DO) 
concentration of 2.5 to 3mg/L, anaerobic mass fraction of 15%, anoxic mass fraction of 
29% and aerobic mass fraction of 56%. 
o 
ANOXIC REACTOR 
AEROBIC REACTOR 
ANAEROBIC REACTOR 
MLR: MIXED LIQUOR RECYCLE 
SR: SLUDGE RECYCLE 
WF: WASTE FLOW 
IN: INFLUENT 
EFF: EFFLUENT 
CLARIFIER 
Figure 4.1.1 Key for WWTP configurations 
MLR MLR 
WF 
SR 
Figure 4.1.2 UCT process configuration 
(Metcalf and Eddy, 1991) 
25 
4.1.2 RESULTS 
4.1.2 (a) Operational data 
The influent (I) that flows into the reactors A-F is supernatant from the PST as well as the 
liquid component from the digesters and thickeners. 
The mixed liquor (ML) from reactor A flows into the appropriate clarifier. 
The effluent (E) is the clarifier supernatant. 
*Note: breaks in the graph lines occur when no data was available 
Figure 4.1.3 Graph depicting the raw flow into Athlone WWTP and the design capacity of 
the WWTP (2007). 
900 
750 
S 600 
450 
300 
150 
-ICOD 
IT™ i—i "|"''"T-I i—i—i—i'"Tf"i"" i—r°""i i'"""f"-r-r—r'"i-"T" 
5/6 3/7 31/7 28/8 25/9 23/10 20/11 
Date 
95 
70 
-RCOD 
5/6 3/7 31/7 28/8 25/9 23/10 20/11 
Date 
Figure 4.1.4 Graph depicting the 
increasing influent chemical oxygen 
demand (ICOD) at Athlone WWTP in 
2007. 
Figure 4.1.5 Graph depicting the 
percentage removal of chemical 
oxygen demand (RCOD) at Athlone 
WWTP in 2007 
26 
—?—WT —•—CMC —*—FFS 
o ^ / 
g 15000 r^ / \ / "k M
0> / NA \ 
^ 10000 - —A y "v -^ 
5000 ? ^ A- r-^ ^r-^ , -/T V / +S* \—^^^. ^+-XC^A>^~*~1&&+ *-? V-** -*--»--* ?-"* 
«^rr=i »-« 
4/6/2007 
—"I—i' -i—i— 
2/7/2007 30/7/07 3/9/2007 1/10/2007 29/10/07 
Date 
26/11/2007 
Figure 4.1.6 Graph depicting the chemical oxygen demand (COD) of the leachate 
from Wastetech (WT), Cape Metropolitan Council (CMC) and Vissershoek (FFS) 
processed at the Athlone WWTP during the study period 
Figure 4.1.7 Graph depicting the effluent ammonia levels (EAMM) from June 2007 to 
June 2008 and effluent nitrate and nitrite levels (ENN) from June to November 2007 
at Athlone WWTP 
27 
?ITKN -IAMM 
70 
60 
50 
d 40 
30 
20 
10 
yz 
?^yy-
-r-T—i 'i I i v i v T" i "i "r 'i' i i i i—i—i 'i" r 'i' 
5/6 3/7 31/7 28/8 25/9 23/10 20/11 
Date 
16 
15 
14 
1 13 
I 12 
§ 11 
8 10 
E 9 
-ICOD/TKN 
5/6 3/7 31/7 28/8 25/9 23/10 20/11 
Date 
Figure 4.1.8 Graph depicting the 
influent levels of Total Kjeldahl nitrogen 
(ITKN) and ammonia (IAMM) at 
Athlone WWTP in 2007 
Figure 4.1.9 Graph depicting the ratio 
of the influent COD (ICOD) to Total 
Kjeldahl nitrogen (TKN) at Athlone 
WWTP in 2007 
-IALK -EALK 
350 
150 -
100 i r r 'i i 'i r i i' i' i' i ' i 
5/6 3/7 31/7 28/8 25/9 23/10 20/11 
Date 
-ITP -IOP -EOP 
28/8 25/9 23/10 20/11 
Date 
Figure 4.1.10 Graph depicting the 
influent alkalinity levels (IALK) and the 
effluent alkalinity levels (EALK) at 
Athlone WWTP in 2007 
Figure 4.1.11 Graph depicting the 
influent total phosphate (ITP), influent 
o-phosphate (IOP) and effluent o-
phosphate levels at Athlone WWTP in 
2007 
28 
-ISS 
400 
350 
300 
d 250 
o 200 
g 150 
100 
50 
?^%^% 
"i i "T"i i i r-r'"i i r"TT"T—"i r"r"]""i i i n-i" 
5/6 3/7 31/7 28/8 25/9 23/10 20/11 
Date 
-SVI -DSVI 
5/6 3/7 31/7 28/8 25/9 23/10 20/11 
Date 
Figure 4.1.12 Graph depicting the 
influent levels of suspended solids 
(ISS) at Athlone WWTP in 2007 
Figure 4.1.13 Graph depicting the 
rising sludge volume index (SVI) and 
dissolved sludge volume index (DSVI) 
in bioreactor A of Athlone WWTP in 
2007 
-SWR 
4000 
3000 "t y i" r'r r'r"i i i r"t i 'i r 'i' r i i i i r i i 
5/6 3/7 31/7 28/8 25/9 23/10 20/11 
Date 
-AGE 
15 
14 
ID >. 
IS 
?o 
11 
10 
:.,N "\„Jv i 
"T—1—i—r—I—r—i—I—r—r-1—n—1—1—r—r-l—I—I—I—r—r-
5/6 3/7 31/7 28/8 25/9 23/10 20/11 
Date 
Figure 4.1.14 Graph depicting the 
sludge wasting rate (SWR) from the 
bioreactors at Athlone WWTP in 2007 
Figure 4.1.15 Graph depicting the 
calculated sludge age of bioreactor A 
at Athlone WWTP in 2007 
29 
—?— RASSS 
13000 - ? 
A 
11000 -A/*w 
o) 10000 -
8000 V \ 
5/6 3/7 31/7 28/8 25/9 23/10 20/11 
Date 
Figure 4.1.16 Graph depicting the 
decreasing amount of suspended solids 
(SS) in the return activated sludge (RAS) 
at Athlone WWTP in 2007 
TABLE 4.1.1 OXYGEN UTILIZATION RATE (OUR) TEST RESULTS FOR MIXED 
LIQUOR AT ATHLONE WWTP ON 8/11/2007 
Time after start of test (min) Ave OUR (mg O/l/hr) 
0:15-0:30 57 
0:30-1:00 39 
1:00-1:30 27 
1:30-2:00 22 
2:00-2:30 19 
2:30-3:00 16 
3:00 - 3:30 15 
The OUR was measured as the amount of oxygen consumed per liter of composite 
sample in one hour (mg O/l/hr). The composite sample consisted of equal parts of mixed 
liquor and raw influent. 
TABLE 4.1.2 METAL ANALYSIS ON RAW INFLUENT 
Parameter Units 25/10/2007 26/10/2007 27/10/2007 28/10/2007 
Aluminium ugAI/l 2090 1910 1760 811 
Arsenic ugAs/l 2.0 2.0 <1.0 3.2 
Cadmium ugCd/l 1.0 <1.0 <1.0 <1.0 
Chromium ugCr/l 104 40 24 16 
Copper ugCu/l 144 78 71 48 
Iron ugFe/l 1800 1370 1400 1060 
Manganese ugMn/l 77 74 72 53 
Nickel unNi/l 48 22 14 11 
Lead ugPb/l 20 7.6 8.6 11 
Zinc ugZn/l 405 249 221 210 
30 
TABLE 4.1.3 PHENOL INDEX ON RAW INFLUENT AND LEACHATE 
Sample Phenol Index (mg/l) 
Raw Influent 
25/10/2007 0.33 
26/10/2007 0.28 
27/10/2007 0.32 
Vissershoek leachate 
22/10/2007 30.97 
29/10/2007 27.40 
Cape Metropolitan Council leachate 
22/10/2007 12.92 
29/10/2007 8.13 
Wastetech leachate 
29/10/2007 23.59 
TABLE 4.1.4 FOOD TO MICROORGANISM (F/M) RATIO IN REACTOR A OF 
ATHLONE WWTP IN 2007 
June 0.22 mgCOD/mgVSS.day 
July 0.22 mgCOD/mgVSS.day 
August 0.26 mgCOD/mgVSS.day 
September 0.32 mgCOD/mgVSS.day 
October 0.26 mgCOD/mgVSS.day 
November 0.41 mgCOD/mgVSS.day 
31 
4.1.2 (b) Microscopic sludge analysis 
This was performed monthly on the following dates: 26/6/07, 23/7/07, 28/8/07, 24/9/07, 
22/10/07 and 26/11/07. 
• Floe structure 
In June, July and August, the floes were round, compact, firm and medium in size, 
conforming to Eikelboom (2000) floe type 2. In September, the floes were more open 
with bridging and filaments protruding from the floes and between floes. Many gonidia 
and rosettes were apparent. In October and November, there was an abundance of 
filamentous organisms both bridging the floes and free between the floes. Many gonidia 
and rosettes were once again present. Filamentous growth was so abundant that it was 
not possible to discern the floe shape and structure accurately, although the floes 
appeared as small and round and joined by filamentous growth. 
Figure 4.1.17: Micrographs of wet mounts of mixed liquor from Athlone reactor A 
showing the deterioration in floe character from June 2007 (left) to November 2007 
(right). The floes are smaller in November with more inter-floe bridging 
• Diversity 
In October, there was low diversity in both the prokaryotic and eukaryotic organisms 
present, with overwhelming numbers of Aspidisca spp. present and very scanty numbers 
of other protozoa/metazoa. 
Filament index 
—?—Filament index 
4 
a 2 
1 ? 
n -
^ 
June July Aug Sept Oct Nov 
Month 
Figure 4.1.18 Graph showing the increasing 
filament index from June to November 2007 
32 
TABLE 4.1.5 DOMINANT AND SECONDARY FILAMENTOUS ORGANISMS IDENTIFIED IN THE MIXED 
LIQUOR OF ATHLONE WWTP REACTOR A IN 2007 
AS DOMINANT F LAMENTS 
June July Aug Sept Oct Nov % Prevalence 
(dominant) 
% Prevalence 
(overall) 
Type 0092 X X X X 66 100 
Type 021N X X X 50 83 
Type 0041 X 17 66 
Actinomycetes X 17 50 
N. limicola\\\ X 17 50 
AS SECONDARY FILAMENTS 
Type 0092 X X 
1 Also dominant 
f filaments 
Type 021N X X 
Type 0041 X X X 
Actinomycetes X X 
N. limicola\\\ X X 
M. parvicella X X X X X 0 83 
Type 1851 X X X 0 50 
Thiothrixspp. X X 0 33 
Flexibacter spp. X 0 17 
H. hydrosis X 0 17 
Type 0914 X 0 17 
Figure 4.1.19 Micrographs of various filamentous prokaryotic microorganisms 
detected in mixed liquor from Athlone WWTP in November 2007 
(a) Gram stain of type 021N (b) Neisser stain of N. limicola III and 
Type 021N 
(c) Gram stain of N. limicola III (d) Neisser stain of N. limicola 111 
33 
TABLE 4.1.6 PROTOZOA/METAZOA IDENTIFIED IN THE MIXED LIQUOR OF ATHLONE WWTP 
REACTOR A IN 2007 
SCANTY 
June July Aug Sept Oct Nov 
Sessile ciliates Carchesium spp. X 
Epistylis spp. X X 
Suctorean X 
Vorticella spp. X X X 
Crawling ciliates Aspidisca spp. X X X X 
Chilodonella spp. X 
Trachelophyllum spp. X X X 
Free-living ciliates Colpidium spp. X 
Euplotes spp. X X 
Litonotus spp. X X 
unidentified X 
Flagellates Bodospp. X X X X 
Peranema spp. X X X X 
Monsiga spp. X 
Trepomonas spp. X 
Amoebae 
Heliozoa 
Rotifers 
Nematodes 
MODERATE 
Sessile ciliates Vorticella spp. X 
Crawling ciliates Aspidisca spp. X 
Flagellates Peranema spp. X 
NUMEROL s 
Crawling ciliates Aspidisca spp. X 
34 
4.1.3 DISCUSSION 
Figures 4.1.3 to 4.1.6 and 4.1.12 show that Athlone WWTP was overloaded for almost 
the entire winter of 2007 and that although there was an increase in both chemical 
oxygen demand (COD) and suspended solids (SS) in September, October and 
November, the COD removal remained relatively efficient throughout the trial period. The 
increased COD corresponded to a high COD in the leachate that originated from the 
Cape Metropolitan Council source, but this may be circumstantial. Table 4.1.4 gives the 
figures for the food to microorganism ratio (F/M), which also show an increase in 
September and November. The return activated sludge suspended solids (RASSS) 
levels decreased (figure 4.1.16). 
Regarding nutrient removal, the removal of phosphorous was satisfactory (figure 4.1.11), 
but the plant experienced problems with the removal of nitrogenous waste. Towards the 
end of September, the performance of the plant deteriorated considerably. This was 
chiefly reflected by the substantial increase in effluent ammonia levels, despite only a 
small increase in influent ammonia and TKN. These results are reflected in figures 4.1.7 
and 4.1.8. The effluent nitrate and nitrite levels decreased to zero when nitrification was 
poor. 
At the same time, the dissolved sludge volume index (DSVI) and filament index (Fl) 
values increased to those predictive of bulking conditions as depicted by figures 4.1.13 
and 4.1.18. In addition, there was a considerable change in the protozoan and metazoan 
community. In September, there was a sharp decrease in the diversity and quantity of 
these organisms, such as would be encountered with a toxic event. In October, there 
was still a lack of diversity, but there were overwhelming numbers of Aspidisca spp. with 
numerically few other protozoa and metazoa. By November, Aspidisca spp. and 
Peranema spp. were both moderately abundant. There was a slight recovery in the 
numbers of other protozoa and metazoa. Although only semi-quantitative results are 
given in the results section, special notes were made on the results sheet regarding the 
protozoan and metazoan communities at Athlone WWTP. This was due to the striking 
difference in the diversity and abundance in comparison with the other study samples. 
Sludge was imported from another WWTP in December, and nitrification performance 
improved. Unfortunately, it was not possible to obtain worthwhile information on this 
retrospectively. The nitrification results as given by effluent ammonia levels for the study 
period plus a further six months have been given in figure 4.1.7. Here it can be seen that 
after the initial improvement, the situation once again deteriorated. The pattern at this 
stage was somewhat different with nitrification being more erratic, but never entirely 
satisfactory. Over the problem period in 2007, the aerators experienced some periods 
with mechanical failure, but the exact dates could not be established. 
There are a number of likely explanations for the sudden loss of nitrification - insufficient 
DO in the aerobic zone or an influx of toxic substances being the most obvious according 
to the results of the OUR testing and the loss of diversity. These are expanded on and 
discussed in the following pages as far as possible with the data available. Causes such 
as the increased influent COD to Total Kjeldahl nitrogen (ICOD/TKN) ratio (shown in 
graph 4.1.9), increased F/M ratio (table 4.1.4), septic conditions, decreased DO, sludge 
age (figure 4.1.15) and possible nitrifier washout are also taken into account as 
contributing factors. It was unfortunately not possible to obtain the operational DO results 
for the study period, which would have made the ensuing discussion less speculative. 
35 
The reasons for postulating that toxicity and not lack of DO was the determining factor 
are: 
> Species of the genera Nitrosomonas and Nitrobacter are the main organisms 
responsible for the conversion of ammonia to nitrite and nitrite to nitrate 
respectively. The nitrifiers are sensitive to a variety of inhibitors, temperature, pH 
and oxygen concentration. Re-establishment of an effective nitrifier population 
may take weeks after an adverse event due to their show specific growth rate. 
During nitrification, a large amount of alkalinity is consumed (Metcalf and Eddy 
1991). Figure 4.1.10 shows that despite and relatively stable influent alkalinity, 
there is a rise in effluent levels during the problem period, coinciding with the loss 
of nitrification. 
> The nitrifying population is more sensitive to toxins than the heterophiles and the 
first step in the nitrification sequence shows the most sensitivity (Gerhaey eta/., 
1997). Many decades back, Tomlinson et a/. (1966) tested a wide range of 
substances for toxicity to nitrifiers. By 1977, this was still considered to be the 
most complete analysis of nitrification toxicity (Hockenbury, 1977). A literature 
search in 2008 did not reveal anything more complete. The chemicals analysed 
by Tomlinson et a/. (1966) included those likely to be produced by industry and 
thus found in WWTP's treating a component of industrial effluent. For instance, a 
wide range of sulphur compounds that were used in the vulcanization of rubber 
were tested and found to be toxic. The concentration of phenol found to reduce 
ammonium oxidation by 75% was determined at 5.6 mg/L. By referring to at table 
4.1.3, it can be seen that the leachate phenol concentrations were substantially 
higher than this value before dilution. Heavy metals have also been implicated in 
nitrifier toxicity in wastewater, but the concentrations of cadmium, chromium, lead 
and zinc shown in table 4.1.2 that were found in the raw influent were not 
sufficient to cause loss of nitrification as determined by Madoni et a/. (1999). 
Aluminium and lead levels appear high, but no literature could be found to assess 
the impact of these metals on the nitrifier population. Hockenbury et a/. (1977) 
determined toxicity levels of a number of organic compounds by nitrifier toxicity 
testing. These researchers also found that ammonia exerted substrate inhibition 
on its own oxidation by Nitrosomonas spp. and that by increasing the levels of 
ammonia this increased the toxic effects of some organic compounds such as 
aniline. It is not conceivable to test for levels of every possible toxin, and the 
results given in table 4.1.2 and 4.1.3 and figure 4.1.6 are all that were available 
retrospectively. It is possible that the treatment of leachate at Athlone WWTP 
affected the nitrifying population, but this practice was abandoned at the end of 
2007 and only resumed in June 2008. During this period, nitrification only 
improved slightly, albeit the pattern was more erratic than previously. The weekly 
leachate samples do differ from batch to batch, but limited information is routinely 
provided on the content of these. Athlone also has a high industrial waste 
component (70%), so the possibility of toxic substances from this source is also 
valid. Also, the influent to the PST's includes the liquid component from the 
digesters and thickeners that increases the likelihood of septic conditions being 
present (with resultant chemicals such as sulphides). 
> Nitrification improved when sludge was imported and deteriorated again later 
even although at this stage the mechanical problems (and thus presumably any 
problems with DO levels) had been rectified. The results of the OUR tests 
conducted on the sludge from Athlone WWTP (shown in table 4.1.1) suggest that 
there were insufficient nitrifiers present. Oxygen utilization is a function of both 
the heterotrophic and the autotrophic nitrifying population, so this test is not 
36 
specific. The results of the OUR tests were interpreted by the laboratory 
(Scientific Services Wastewater laboratory) in a comment accompanying the test 
results: 
"After an initial high, there was a rapid rate of decline of the OUR in a 
short period of time. This would seem to indicate that the biodegradable 
COD does get consumed, but there are insufficient nitrifiers present to 
convert most of the ammonia to nitrites and nitrates and hence much less 
oxygen is required after the biodegradable COD is depleted". 
To explain this more fully - the degradation of readily biodegradeable COD 
(RBCOD) by the heterotrophic population is rapid in the presence of sufficient 
oxygen (Casey et a/., 1999b). This source of nutrition on its own is expended 
quickly resulting in an accompanying rapid drop in the OUR. If the nitrifier 
population was intact at this point, in the presence of ammonia, the OUR rate 
would be maintained at a moderate level due to the process of nitrification and 
the ammonia would be converted to nitrates and nitrites (Metcalf and Eddy, 
1991). Thus, the interpretation that there were insufficient nitrifiers is plausible, in 
that the OUR rate declined precipitously and nitrification itself was grossly 
retarded for a NDBEPR WWTP. There are a number of specific tests designed to 
detect the loss of nitrification such as those described by Gerhaey et a/. (1997). 
The test developed by these authors is based on the principle that the nitrification 
potential of known cultures of nitrifying organisms will be inhibited when 
subjected to sludge containing substances toxic to this population (measured 
against a control population). The results of this type of test would have been 
more conclusive in determining the cause of poor nitrification at Athlone WWTP, 
but was too specialized for the laboratory in question. Furthermore, the test has 
to be performed when the toxins are present in the sludge, which will not be the 
case if nitrifier loss is due to a single toxic event, unless monitoring is continuous. 
Such testing as a routine may be considered as an option in WWTP's that are 
known to experience problems with nitrification (either ongoing or intermittent). 
> COD removal remained satisfactory throughout. The ICOD/TKN ratio shown in 
figure 4.1.9 increased at the beginning of the period when nitrification initially 
deteriorated. This, together with the concurrent increase in F/M may have 
exacerbated the condition. According to Metcalf eta/. (1991), a BOD5/TKN ratio 
of 1-3 would be expected in separate stage nitrification. The lower the ratio, the 
greater the fraction of nitrifiers. Most work on ratios of carbon to nitrogen has 
been performed at low temperatures, when nitrification is considerably reduced, 
or using BOD, not COD values. It is not possible to extrapolate BOD from COD 
values from a WWTP with such a high component of industrial effluent. In 
addition, the values given in figure 4.1.9 used influent COD values. With the UCT 
configuration, much COD removal takes place in the anoxic zone preceding the 
aerobic zone, so figures would realistically fall somewhere between the influent 
and effluent values. It is therefore difficult to assess whether the increase in COD 
played a role in the nitrification problem. 
> The microorganism population is a good reflection of the prevailing conditions 
(Jenkins eta/., 2004). There was a loss of diversity amongst both the prokaryotic 
and eukaryotic organisms. Spirochaetes, spirils and filaments associated with low 
DO (Eikelboom, 2000), were not prevalent. Ciliates outnumbered flagellates, also 
pointing to lack of oxygen not being excessive (Eikelboom, 2000). Some 
Aspidisca species have been shown to be tolerant of high metal concentrations. 
(Abraham et a/. 1998). Nostocoida limicola III appeared in September and was 
dominant by December. This organism is known to be strictly aerobic (Eikelboom, 
2000). The lack of diversity can also be caused by lack of nutrients (Jenkins et 
37 
a/., 2004). Besides COD, nitrites/nitrates and phosphates, no routine monitoring 
of other micronutrients or macronutrients is performed on the sludge from Athlone 
WWTP. However, due to the loss of nitrification, there were little nitrates and 
nitrites present in the latter months of the study. Type 021N, that was dominant in 
September, October and November is amongst other factors, associated with 
nitrogen deficiency (Jenkins eta/., 2004). 
> The sludge wasting rate and sludge age shown in figures 4.1.14 and 4.1.15 
respectively did not change substantially during the course of events, although 
there was a downward trend in the RASSS (figure 4.1.16). The latter may be due 
to the steady increase in the filamentous population that was associated with a 
high DSVI and thus poor settling. A substantial increase in the filaments would 
still allow COD removal to take place, and there may well have been a decrease 
in the ordinary heterotrophic population. It is possible that some washout of the 
nitrifying population contributed to the loss of nitrification, as the mean cell 
residence time (MCRT) needed for the growth of these organisms would increase 
under adverse conditions. Rittman and McCarty, (2001) calls for a solids 
retention time (SRT) of >15 days, with even longer times being implemented 
under conditions where toxins are present, or DO and/or temperature is low. 
However, the presence of rotifers and nematodes points to a long sludge age 
(Eikelboom, 2000). 
In light of the above, the ongoing problems with nitrification were most likely 
caused initially by lack of DO and poisoning of the nitrifying population coupled 
with increased ICOD/TKN and F/M. After "recovery" and the cessation of 
leachate addition, there were again problems in 2008. However, at this stage 
periods of good nitrification punctuated the poor periods. If a decrease in the 
nitrifying population was to blame in 2008, the effluent ammonia levels would not 
show such repeated rapid recovery. Figure 4.1.7 shows that in 2008, nitrification 
performance varied constantly. This is in contrast to 2007, where performance 
was consistently poor for a protracted period. No mixed liquor samples were 
examined during 2008 (out of study period) and the cause of poor nitrification in 
2008 may very well have been entirely different from that experienced in the latter 
stages of 2007. 
In summary, on a practical level: it is not possible to continuously monitor influent 
for all possible toxins. Further microscopic analysis, in conjunction with detailed 
DO, ICOD/TKN and F/M ratios and ideally nitrifier toxin testing would help to 
pinpoint the problem. During the study period, plant-operating parameters in 
terms of the historical data and physical functioning of the WWTP's were 
unknown. This was purposeful, so as not to inadvertently skew microscopic 
results to fit known parameters (blind). Unfortunately, this led to the situation 
where the microscopic analysis could not reach its full potential as a 
troubleshooting aid. If microscopic analysis was part of the routine testing 
protocol, this situation could very well have been rectified. For example, when the 
change in the protozoan and metazoan population was noted, levels of possible 
toxins in the influent could have been determined in an endeavour to source the 
toxic waste and prevent future loss of nitrification. 
38 
Table 4.1.4 shows the results regarding the identification of the filamentous 
population: there was a distinct change in the dominant population after the onset 
of decreased nitrification. The true low F/M species of Type 0041 and Type 0092 
were present in June, together with actinomycetes. Type 0092 continued to co-
dominate until September, after which it became secondary. Type 021N became 
co-dominant in September and continued to dominate for the remainder of the 
study period, together with N. limicola\\\ in November. 
Type 021N is not restricted to low F/M environments and is associated with the 
presence of easily biodegradable compounds and/or sulphur compounds such as 
would occur under septic conditions (Eikelboom, 2000). Of the four organism 
types associated with the presence of hydrogen sulphide and/or the presence of 
easily biodegradable compounds and/or nutrient deficient conditions (Jenkins et 
a/., 2004), three were found as either dominant or secondary species in the 
Athlone plant, both before and after the "problem" period: Thiothrix spp. in July 
and August, Type 021N from July to November and Type 0914 in August. For the 
first three months of the study, the most likely reasons for the growth of these 
filaments are: the inherent composition of the industrial raw influent and/or septic 
influent either raw from the sewers or from the returned influent from the 
digesters and thickeners. 
Figure 4.1.20 Wet mount of Thiothrix 
spp. from mixed liquor from bioreactor A 
at Athlone WWTP in July 2007 after 
application of the sulphur storage test 
Nutrient deficiency would be unlikely to be associated with the growth of all of 
these species before the loss of nitrification potential led to a lack of nitrates and 
nitrites. Type 021N and N. iimico/awere the major dominant species at the stage 
when the DSVI was increasing. Neither of these organisms are associated with 
low DO (Jenkins eta/., 2004). Furthermore, the filaments that are associated with 
low DO by this author, namely S. natans, Type 1701 and H. hydrosis, were 
absent (except for one occasion when H. hydrosis was present as a secondary 
species). According to Jenkins et a/. (2004), under nutrient deficient conditions, 
Type 021N forms gonidia and rosettes. These were seen abundantly in the mixed 
liquor samples from Athlone reactor A during the "problem" period. This lends 
credence to the hypothesis that due to impaired nitrification, there was a lack of 
nutrition in the form of nitrates and nitrites. This would be exacerbated with an 
increased influent COD. Both Jenkins et al. (2004) and Eikelboom (2000) have 
associated N. HmicolaWtih nutrient deficiency. 
39 
In terms of bacterial composition, it seems likely that the conditions encountered 
over the first three months of the project allowed the growth of a variety of mainly 
low F/M filaments prevalent in most of the Cape Town plants. At this stage 
competition between these filaments and the heterotrophic population did not 
allow filamentous overgrowth and bulking conditions were absent. Due to lack of 
nitrification over the latter three months, a nutrient deficiency (nitrates and 
nitrites) ensued. This allowed the filaments suited to these conditions to out-
compete the heterotrophic population and bulking conditions arose. This is 
entirely different to the bulking hypothesis postulated by Casey eta/. (1999), as in 
this case the bulking was probably caused by the absence and not the presence 
of nitrates and nitrites. 
40 
4.2 BELLVILLE WWTP 
4.2.1 PLANT CONFIGURATION AND OPERATING PARAMETERS 
The three industrial bioreactors (named North, Center and South), at Bellville have the 
capacity to treat approximately 60ML effluent per day. The configuration is the Modified 
Ludzack-Ettinger (MLE) and the method of aeration is diffuse. The influent consists of 
raw, unsettled influent of industrial origin that is supplemented by the primary sludge 
from the PST of the nearby domestic WWTP. The plant operates at a DO of 1-2 mg/L, an 
anoxic mass fraction of 20% and an aerobic mass fraction of 80%. 
ANOXIC REACTOR 
O [ AEROBIC REACTOR 
ANAEROBIC REACTOR 
MLR: MIXED LIQUOR RECYCLE 
SR: SLUDGE RECYCLE 
WF: WASTE FLOW 
IN: INFLUENT 
EFF: EFFLUENT 
? CLARIFIER 
Figure 4.2.1 Key for WWTP configurations 
SR 
Figure 4.2.2 MLE configuration 
(Metcalf and Eddy, 1991) 
41 
4.2.2 RESULTS 
4.2.2 (a) Operational data 
The influent (I) flows into 3 reactors. The North reactor was used for the study. 
The mixed liquor (ML) from the North reactor flows into the clarifier. 
The effluent (E) is the supernatant from the appropriate clarifier. 
"Note: breaks in the graph lines occur when no data was available 
•ICOD 
29/8 26/9 24/10 21/11 
Date 
I 
Q O 
O 
95 
90 
85 
B 80 
75 
70 
65 
60 
•COD removal 
100 i 
—i—i—i—i—m—i—f 'i" I—r i' 'f 'i" i—i" r 'i' i i—i—r 
6/6 4/7 1/8 29/8 26/9 24/10 21/11 
Date 
Figure 4.2.3 Graph depicting the influent 
COD (ICOD) at Bellville WWTP in 2007 
Figure 4.2.4 Graph depicting the %COD 
removal at Bellville WWTP in 2007 
-ITP -IOP -EOP 
1/8 29/8 26/9 24/10 21/11 
Date 
-ITKN -IAMM -EAMM -Hk— ENN 
160 
6/6 4/7 1/8 29/8 26/9 24/10 21/11 
Date 
Figure 4.2.5 Graph depicting the influent 
total phosphate (ITP), influent a-phosphate 
(IOP) and effluent a-phosphate (EOP) 
levels at Bellville WWTP in 2007 
Figure 4.2.6 Graph depicting the influent 
Total Kjeldahl nitrogen (ITKN) influent 
ammonia (IAMM), effluent ammonia 
(EAMM) and effluent nitrates and nitrites 
(ENN) at Bellville WWTP in 2007 
42 
-MLSS -?—MLVSS 
9000 
E 8000 
7000 
CD E 
o 
u> 
o 
6000 
5000 
4000 
3000 
6/6 4/7 1/8 29/8 26/9 24/10 21/11 
Date 
•SVI -DSVI 
200 
60 
6/6 4/7 1/8 29/8 26/9 24/10 21/11 
Date 
Figure 4.2.7 Graph depicting the influent 
mixed liquor suspended solids (MLSS) and 
mixed liquor volatile suspended solids 
(MLVSS) from the North reactor at Bellville 
WWTP in 2007 
Figure 4.2.8 Graph depicting the sludge 
volume index (SVI) and dissolved sludge 
volume index (DSVI) from the mixed 
liquor from the North reactor at Bellville 
WWTP in 2007 
?IALK -EALK 
29/8 26/9 24/10 21/11 
Date 
80 
70 I 
! 
I. 
*± 20 
<D 
3 E 
u 
60 
50 
40 
30 
1
•ESS 
^»~V» 
"f'f" 1" I1"1!" 
6/6 4/7 1/8 29/8 26/9 24/10 21/11 
Date 
Figure 4.2.9 Graph depicting the influent 
alkalinity (IALK) and effluent alkalinity 
(EALK) at Bellville WWTP in 2007 
Figure 4.2.10 Graph depicting the effluent 
suspended solids (ESS) at Bellville WWTP 
in 2007 
43 
-RASSS 
I' I 'I 'I' 1(11 l'"l I' 'I'"!"1! I" 
6/6 4/7 1/8 29/8 26/9 24/10 21/11 
Date 
-AGE 
28 
26 
24 
22 
» 20 
f 18 
16 
14 
12 
10 
V^ ? ? 
1 
\ r'rr'i—i—i—r—r-i—m—i i i i i i i—i—m—i—r—r 
6/6 4/7 1/8 29/8 26/9 24/10 21/11 
Date 
Figure 4.2.11 Graph depicting the influent Figure 4.2.12 Graph depicting the 
return activated sludge suspended solids calculated sludge age of mixed liquor (age) 
(RASSS) at Bellville WWTP in 2007 of the North reactor at Bellville WWTP in 
2007 
TABLE 4.2.1 FOOD TO MICROORGANISM (F/M) RATIO IN NORTH REACTOR OF 
BELLVILLE WWTP IN 2007 
June 0.46 mgCOD/mgVSS.day 
July 0.57 mgCOD/mgVSS.day 
August 0.59 mgCOD/mgVSS.day 
September 0.65 mgCOD/mgVSS.day 
October 0.70 mgCOD/mgVSS.day 
4.2.2 (b) Microscopic sludge analysis 
This was performed monthly on the following dates: 28/6/07, 26/7/07, 23/8/07, 29/9/07, 
25/10/07 and 22/11/07. 
• Floe structure 
In June and July, the floes were irregular in shape, open in structure and firm in strength. 
In August and September, the floes were irregular in shape, compact in structure and 
firm in strength. In October, the floes were irregular in shape, open in structure and firm 
in strength. In November, the floes were irregular in shape, open in structure and weak in 
strength. 
The average floes were large in size over the duration, until November, when the floe 
structure was divided between pin floes or large open floes (seemingly many small floes 
joined by filaments). 
There was bridging between filaments in July and August and from September there 
were also increasing numbers of tangled masses of filaments between floes. There was 
an overall deterioration of the floe character over the period of the study. 
44 
Figure 4.2.13 Micrographs of wet mounts of mixed liquor from the north reactor at 
Bellville WWTP taken in June 2007 (left) showing the large, open floe structure and 
September 2007 (right), showing the tangled masses of filaments 
• Diversity 
There was a medium amount of diversity over the duration. 
Scanty monocolonies were present in all samples. 
• Filament index 
Figure 4.2.14 Graph depicting the filament 
index of mixed liquor from the north reactor at 
Bellville WWTP in 2007 
45 
TABLE 4.2.2 DOMINANT AND SECONDARY FILAMENTOUS ORGANISMS IDENTIFIED IN THE MIXED 
LIQUOR OF ATHLONE WWTP REACTOR A IN 2007 
AS DOMINANT F LAMENTS 
June July Aug Sept Oct Nov % Prevalence 
(dominant) 
% Prevalence 
(overall) 
Type 1851 X X X X X X 100 100 
Type 021N X X X X 67 100 
AS SECONDARY FILAMENTS 
Type 021N X X } Also dominant 
Actinomycetes X X X X X 0 83 
Type 0092 X X X X 0 67 
Type 0041 X X X X 0 67 
Beggiatoa spp. X 0 17 
TABLE 4.2.3 PROTOZOA/METAZOA IDENTIFIED IN THE MIXED LIQUOR OF ATHLONE WWTP 
REACTOR A IN 2007 
SCANTY 
June July Aug Sept Oct Nov 
Sessile ciliates Carchesium spp. X X 
Epistylis spp. X 
Opercularia spp. X 
Suctorean X 
Vorticella spp. X X X 
Crawling ciliates Aspidisca spp. X X 
Trachelophyllum spp. X X 
Unidentified X 
Free-living ciliates Blespharisma spp. X X X X 
Euplotes spp. X 
Litonotus spp. X 
Spirostomum spp. X X X 
Unidentified X X 
Flagellates Bodo spp. X X 
Peranema spp. X X X 
Pleuromonas spp. X 
Trepomonas spp. X 
Amoebae X X X X X 
Rotifers X X X X X 
Unidentified "worms" X X 
MODERATE 
Free-living ciliates Spirostomum spp. X 
Crawling ciliates Trachelophyllum spp. X 
Flagellates Bodo spp. X X X 
Trepomonas spp. X 
Unidentified "worms" X X X 
46 
Figure 4.2.15 Wet mount of mixed liquor 
showing unidentified worm-like organism. It 
is possible to compare the size to the 
surrounding spirochaetes 
4.2.3 DISCUSSION 
By examining figures 4.2.3 and 4.2.4, it can be ascertained that although influent COD 
was comparatively high (albeit erratic), removal was satisfactory until October. At this 
stage there was a marked deterioration in COD removal that coincided with increased 
levels of effluent suspended solids (figure 4.2.10). 
Phosphate removal is not part of the MLE design process as there is no anaerobic zone, 
but surprisingly this function was good in most samples until September. From October 
there was also deterioration of this process, as reflected in figure 4.2.5. In an exhaustive 
literature review, Oehman et al. (2007) implicated the COD/P ratio, the presence of 
adequate volatile fatty acids (VFA's) and the lack of nitrate in the anaerobic zone as 
being the most important parameters for efficient phosphorous removal. Such conditions 
allow the phosphorous accumulating organisms (PAO's) to successfully out-compete the 
glycogen accumulating organisms (GAO's). (The latter is discussed in more detail in 
chapter 2). It can be assumed that the level of VFA's would be adequate in a plant 
treating mixed industrial effluent. The COD/P values at Bellville ranged from 66.0-
121.8mgCOD/mgP with a mean of 89.9mgCOD/mgP. According to Liu et al. (1997), a 
ratio of 10-20mgCOD/mgP should favour the growth of PAO's, while levels greater than 
50mgCOD/mgP should enhance the growth of GAO's. This fact would lead to 
decreased, not enhanced phosphorous removal. 
The explanation for the unexpected results is probably due to the fact that nitrification, 
and thus nitrification products were almost entirely lacking at Bellville WWTP. This would 
render the anoxic reactor a de facto anaerobic reactor with the result that the plant 
became capable of functioning as an enhanced biological phosphorous removal (EBPR) 
WWTP. Another mechanism for phosphorous removal could very well have been 
precipitation with ionic components (such as iron or aluminium), or absorption with 
components that were inherent in the industrial waste. 
By examining figure 4.2.6, it can be seen that influent ammonia levels were not high and 
removal of this chemical was consistently poor. Nitrates and nitrites in the clarifier 
effluent were absent for almost the entire six months of the study. In the only sample 
where nitrates/nitrites were present, ammonia levels were zero. Alkalinity, reflected in 
figure 4.2.9, was high. From these observations, it can clearly be deduced that 
47 
nitrification was poor, and that the denitrification potential of the plant was sufficient to 
remove any nitrification products. It thus stands to reason that in the MLE system, with 
an anoxic zone preceding the aerobic zone, no nitrates/nitrites were present as the 
sludge passed into the aerobic zone. Therefore, the bulking conditions encountered 
could not be linked to the conditions required in the AA bulking hypothesis of Casey eta/. 
(1999). 
The two most likely causes of the poor nitrification achieved at Bellville are the high F/M 
(Eikelboom, 2000) or the presence of substances toxic to the nitrifier population 
(Gerhaey et al., 1997), or a combination of these factors. Adequate overall sludge age, 
shown in graph 4.2.12 that is backed up by the presence of slow-growing metazoa such 
as rotifers, make the possibility of nitrifier washout unlikely. The population of protozoa 
and metazoa point to a plant with a high load and/or low DO (Eikelboom, 2000) - over the 
study period, there was a gradual increase in the flagellate to ciliate ratio that indicates 
these conditions. In fact, there were no ciliates present in the samples from either 
October or November. 
A healthy ciliate population is indicative of sufficient oxygen and/or a low floe load 
(Eikelboom, 2000). The fact that the food to microorganisms (F/M) ratio (given in table 
4.2.1) exhibits an increasing trend points to the loading rates being the "culprit". The 
increased effluent COD substantiates the likelihood that COD overloading lead to poor 
plant performance. 
With an increase in F/M, the oxygen requirements are elevated. Unless the DO was 
increased to cater for the higher loading, lack of oxygen for both COD removal and 
nitrification would play a role in poor plant performance. 
The presence of moderate numbers of Bodo spp. in September, October and November 
and Trepomonas spp. in November is further evidence - both of these flagellates are 
associated with high sludge load and/or lack of oxygen according to Eikelboom (2000). 
The fact that none of the filaments exclusively associated with low DO by Jenkins et al. 
(2004), namely Sphaerotilus natans, Type 1701 and Ha/iscomenobacter hydrosis were 
found in any of the samples tends to implicate F/M rather than D/O as being more 
plausible. It is impossible to accurately speculate on whether toxins such as heavy 
metals were responsible for a diminished nitrifier population, as no additional results are 
available (as in the case of Athlone WWTP). However, if there were large quantities of 
heavy metals in the influent, this could explain both the lack of nitrification (due to 
toxicity) and the good phosphorus removal (due to precipitation). 
Figure 4.2.7 depicts the gradual decrease in MLVSS, figure 4.2.8 the increase in DSVI 
and SVI and figure 4.2.14 the increase in Fl. Musvoto et al. (1999) demonstrated a link 
between decreasing VSS and increasing DSVI that is borne out by these results. The 
high filament index pointed to the existence of filamentous bulking conditions from July, 
but although there was a steady increase in the DSVI, the value did not exceed 150mg/L 
until October. The deteriorating sludge quality in terms of Fl, DSVI, floe character and the 
increase in numbers of tangled filament masses, was accompanied by a gradual 
decrease in RASSS. The link between poor sludge quality and decreasing RASSS was a 
phenomenon also noted at the Athlone WWTP. 
The dominant filaments were Type 1851, (for the duration of the study period), and Type 
021N (in all months bar September and October). In chapter 5, the association of both of 
these organism types with bulking conditions in the study WWTP's was established. 
According to Eikelboom (2000), Type 1851 is supposedly associated with industrial 
48 
WWTP's such as Bellville. It is classed as a low F/M filament by Jenkins eta/. (2004) and 
Eikelboom (2000). However, Eikelboom (2000) does concede that there is limited 
knowledge about this organism. In this case the F/M values (given in table 4.2.1) were 
not low, and showed an increasing trend from June to October. 
Dominant growth of Type 1851 must therefore be linked to other factors besides low F/M 
conditions in this instance. Both type 1851 and type 021N are associated with low 
molecular weight (LMW) compounds (Eikelboom, 2000), and the latter is not considered 
low F/M. It can be speculated that the numerical abundance of these two filament types 
was associated with increased availability of LMW compounds that is in turn reflected by 
the increasing F/M. In addition, a lack of nutrients (nitrates/nitrites) may be implicated for 
reasons outlined in 4.1.3 (Athlone WWTP discussion). The continual presence of 
actinomycetes, albeit as secondary filaments, supports the fact that there was a large 
LMW component (Eikelboom, 2000). 
Type 0092, so prevalent in the study as a dominant species was found as a secondary 
species in four of the six samples. Although this filament and Type 0041 are classed as 
low F/M by both Jenkins eta/. (2004) and Eikelboom (2000), Noutsopolous eta/. (2006) 
determined the preferred range for growth of Type 0092 to be between 0.19 and 0.45 
mgCOD/mgVSS.day. This organism was found at much higher F/M ratios in this study. 
By November, when the F/M ratio was highest, Type 0092 was no longer apparent, but 
Type 0041 was. These findings question the validity of classifying both of these filaments 
as low F/M. 
In summary, then, the evidence points to an overloaded industrial WWTP, with an 
increasing F/M ratio that lead to inadequate nitrification and increasingly poor COD 
removal. The presence of toxic substances may or may not have played a role in poor 
nitrification. The high F/M also had a negative effect on floe formation, the high level of 
LMW compounds provided a competitive advantage for certain filaments over their 
heterotrophic rivals, leading to the presence of bulking conditions. This may have been 
exacerbated by nutrient (nitrate) deficiency. In addition, although phosphous removal is 
not an inherent feature of WWTP's with the MLE configuration, this function did indeed 
take place. This was probably due to the fact that the anoxic zone became an effective 
anaerobic zone, allowing for functional EBPR. 
49 
4.3 BORCHERDS QUARRY WWTP 
4.3.1 PLANT CONFIGURATION AND OPERATING PARAMETERS 
Borcherd's Quarry WWTP has a design capacity of 32ML/day with an influent of 
approximately 40% industrial and 60% domestic effluent. The plant processes the night 
soil from the entire black bucket system of the mega city. Landfill leachate is processed 
on weekends only, so the influent is highly variable from day to day. The Influent that 
flows into the two bioreactors (named B and C) in equal volumes is the supernatant from 
the PST. The configuration is the same as that of the Cape Flats WWTP, namely the 5-
stage Bardenpho (Phoredox). The DO concentration in the primary aerobic reactor is 
2.3mg/L and the method of aeration is diffuse. The plant experiences intermittent 
problems with scum formation. 
| ANOXIC REACTOR | 
O 
| AEROBIC REACTOR | 
| ANAEROBIC REACTORJ 
MLR: MIXED LIQUOR RECYCLE 
SR: SLUDGE RECYCLE 
WF: WASTE FLOW 
IN: INFLUENT 
EFF: EFFLUENT 
? [ CLARIFIER ] 
Figure 4.3.1 Key for WWTP configurations 
MLR 
SR 
Figure 4.3.2 5-stage Bardenpho (Phoredox) configuration 
(Metcalf and Eddy, 1991) 
50 
4.3.2 RESULTS 
4.3.2.1 (a) Operational data 
The influent (I) into is supernatant from the primary settling tank (PST) that flows into 
bioreactor B and bioreactor C. 
The mixed liquor (ML) from reactor B and reactor C flows into clarifier B and clarifier C 
respectively. 
The effluent (E) is the supernatant from the clarifier B and C. 
*Note: breaks in the graph lines occur when no data was available  
-ICOD 
-] ) ! i—)—!—)—]—)—i—i—]—j—]—i—]—j—]—)—]—]—)—)—r 
5/6 3/7 31/7 28/8 25/9 23/10 20/11 
Date 
-B RCOD -#— C RCOD 
co > 
o E 
S a 
o o 
105 
100 
95 
90 
85 
80 
75 
70 
65 
60 
S****^**f-' 
5/6 3/7 31/7 28/8 25/9 23/10 20/11 
Date 
Figure 4.3.3 Influent COD (ICOD) into Figure 4.3.4 % removal of COD by 
bioreactors of Borcherds quarry WWTP in bioreactor B (B RCOD) C (C RCOD) at 
2007 Borcherds quarry WWTP in 2007 
-B EAMM 
-BENN 
-C EAMM 
?CENN 
5/6 3/7 31/7 28/8 25/9 23/10 20/11 
Date 
160 
40 
20 
?ITKN -IAMM 
:^3p^ 
5/6 3/7 31/7 28/8 25/9 23/10 20/11 
Date 
Figure 4.3.5 Effluent ammonia from 
clarifier B (B EAMM) and C (C EAMM) and 
effluent nitrates/nitrites from clarifer B (B 
ENN) and C (C ENN) at Borcherds quarry 
WWTP in 2007 
Figure 4.3.6 Influent Total Kjeldahl 
ammonia (ITKN) and influent ammonia 
(IAMM) into bioreactors of Borcherds 
quarry WWTP in 2007 
?BESS -CESS 
300 
250 
_j 200 
o 150 
in 
o 
*" 100 
50 .in,, n iMi. . I...,,,,, ?- iiTTYm.i.i 
=A ^*kiJQ-^vM-^-' 
5/6 3/7 31/7 28/8 25/9 23/10 20/11 
Date 
900 
800 
700 
O) 
E 
w 
£ 600 
•a 
E o 
in 
500 
400 
300 
200 
100 
-ISS -IVSS 
5/6 3/7 31/7 28/8 25/9 23/10 20/11 
Date 
Figure 4.3.7 Eflluent suspended solids 
from clarifier B (B ESS) and C (C ESS) at 
Borcherds quarry WWTP in 2007 
Figure 4.3.8 Influent suspended solids (ISS) 
and influent volatile suspended solids 
(IVSS) from the primary settling tank at 
Borcherds quarry WWTP in 2007 
-ITP -IOP -BEOP -CEOP 
E 
Q. 
45 
40 
35 
30 
25 
20 
15 
10 
5 
0 
lf\ I it l\ A L\ 
- i, rrinV^ M 11 
5/6 3/7 31/7 28/8 25/9 23/10 20/11 
Date 
-B MLSS 
-B MLVSS 
-C MLSS 
-C MLVSS 
i I'i'i'ri i i i i i"i i i i i i i i i i i 
5/6 3/7 31/7 28/8 25/9 23/1020/11 
Date 
Figure 4.3.9 Influent total phosphates (ITP), 
influent a-phosphates (IOP), and effluent a-
phosphates from clarifier B (B EOP) and C 
(C EOP) at Borcherds quarry WWTP in 
2007 
Figure 4.3.10 Mixed liquor suspended 
solids from reactor B (B MLSS) and C (C 
MLSS) and mixed liquor volatile suspended 
solids from reactor B (B MLVSS) and 
reactor C (C MLVSS) at Borcherds quarry 
WWTP in 2007 
52 
Figure 4.3.11 Sludge volume index from reactor B (B SVI) and reactor C (C SVI) and 
dissolved sludge volume index from reactor B (B DSVI) and reactor C (C DSVI) at 
Borcherds quarry WWTP in 2007 
TABLE 4.3.1 FOOD TO MICROORGANISM (F/M) RATIO IN REACTOR B AND 
REACTOR C OF BORCHERDS QUARRY WWTP IN 2007 
REACTOR B REACTOR C 
June 0.26 mgCOD/mgVSS.day 0.20 mgCOD/mgVSS.day 
July 0.13 mgCOD/mgVSS.day 0.12 mgCOD/mgVSS.day 
September 0.23 mgCOD/mgVSS.day 0.15 mgCOD/mgVSS.day 
October 0.42 mgCOD/mgVSS.day 0.31 mgCOD/mgVSS.day 
November 0.31 mgCOD/mgVSS.day 0.20 mgCOD/mgVSS.day 
4.3.2 (b) Microscopic sludge analysis 
This was performed monthly on samples from reactor B and reactor C on the following 
dates: 20/6/07, 18/7/07, 29/8/07, 19/9/07, 24/10/07 and 21/11/07. In addition, filament 
identification was performed on scum from reactor B on 3/10/07. 
• Floe Structure 
Reactor B 
The floes were round in shape and firm in strength for the duration of the study, except 
for September, when floes were both round and irregular in shape. With regard to the 
structure of the floes, they were compact in June and October and open in July, August, 
September and November. The floes were moderate in size from June to August. In 
September, the floes were dispersed between being small, medium and large in size, 
while in October and November the floes were predominantly small. In September, there 
was much bridging between floes and in October and November there were numerous 
rosettes present with filaments protruding from the floes and free in the sludge (see 
figure 4.3.11). 
Reactor C 
The floes were round in shape, open in structure and firm in strength for the duration of 
the study, with the exception of October and November, when they were both round and 
irregular in shape. 
53 
Figure 4.3.12 Wet mount of mixed liquor from 
reactor B at Borcherds quarry WWTP in October 
2007, showing numerous Type 021N rosettes 
and filaments protruding from pin floes 
• Diversity 
Reactor B and reactor C 
There was a moderate amount of microbial diversity for the duration of the study in both 
reactors. There were scanty monocolonies in all samples, except those from reactor B in 
October and reactor C in August, when there was a moderate number of monocolonies. 
• Filament index 
5-1 
4 -
? Reactor B * Reactor C 
_ 3 
? 
o 
w 2 
S^^* 
n -
June July Aug Sept Oct Nov 
Month 
Figure 4.3.13 Filament index from mixed liquor 
of reactor B and reactor C at Borcherds quarry 
WWTP in 2007 
54 
TABLE 4.3.2 DOMINANT AND SECONDARY FILAMENTOUS ORGANISMS IDENTIFIED FROM THE 
MIXED LIQUOR OF REACTOR B AND REACTOR C AT BORCHERDS QUARRY WWTP IN 2007 
AS DOMINANT F LAMENTS 
June July Aug Sept Oct Nov % Prevalence 
BandC 
(dominant) 
% Prevalence 
BandC 
(overall) 
Type 0092 X 
(B,C) 
X 
(B,C) 
X 
(B,C) 
X 
(B,C) 
X 
(B,C) 
X 
(B,C) 
100 100 
Type 02 IN X 
(B) 
X 
(B) 
X 
(B) 
X 
(B,C) 
42 92 
Actinomycetes X 
(C) 
8 17 
AS SECONDARY FILAMENTS 
Type 021N X 
(C) 
X 
(B.O 
X 
(C) 
X 
(C) 
X 
(C) > Also dominant 
V filaments Actinomycetes X 
(C) 
M. Parvicella X 
(B,C) 
X 
(B,C) 
X 
(B,C) 
X 
(B) 
0 58 
Type 0041 X 
(C) 
X 
(B,C) 
X 
(B) 
0 33 
N. limicola III X 
(B,C) 
X 
(C) 
0 25 
Type 0803 X 
(B) 
0 8 
Figure 4.3.14 Neisser stain of Type 021N 
(Neisser negative) and Type 0092 (Neisser 
positive - blue) from reactor B Of Borcherds 
quarry WWTP in November 2007 
55 
TABLE 4.3.3 PROTOZOA/METAZOA IDENTIFIED IN THE MIXED LIQUOR FROM REACTOR B AND 
REACTOR C AT BORCHERDS QUARRY WWTP IN 2007 
SCANTY 
June July Aug Sept Oct Nov 
Sessile ciliates Carchesium spp. X 
(C) 
X 
(B.C) 
X 
(B) 
X 
(B) 
X 
(B) 
Epistylis spp. X 
(B) 
X 
(B.C) 
X 
(B) 
X 
(B.C) 
X 
(C) 
Vaginicola spp. X 
(C) 
Vorticella spp. X 
(B,C) 
X 
(B.C) 
X 
(B.C) 
X 
(C) 
X 
(C) 
Crawling ciliates Aspidisca spp. X 
(B.C) 
X 
(B.C) 
X 
(B.C) 
X 
(B) 
X 
(B.C) 
X 
(B.C) 
Chilodonella spp. X 
(C) 
X 
(C) 
Paramecium spp. X 
. (B> Trachelophyllum spp. X 
(C) 
X 
(B.C) 
X 
(B.C) 
X 
(C) 
X 
(B) 
Blepharisma spp. X 
(C) 
X 
(C) 
X 
(C) 
X 
(C) 
X 
(C) 
Free-living ciliates Colpidium spp. X 
(B.C) 
X 
(B.C) 
X 
(B.C) 
X 
(B.C) 
X 
(B.C) 
X 
(B.C) 
Euplotes spp. X 
(B) 
£/to/7oft/sspp. X 
(B.C) 
X 
(B) 
Colpidium spp. X 
(B) 
X 
(B) 
X 
(B) 
Spirostomum spp. X 
(C) 
X 
(C) 
X 
(C) 
X 
(C) 
X 
(C) 
unidentified X 
(C) 
Flagellates £fc>ob spp. X 
(B) 
X 
(B.C) 
X 
(C) 
X 
(C) 
X 
(B) 
Pe/a/7e/77aspp. X 
(B.C) 
X 
(B.C) 
X 
(B.C) 
X 
(B.C) 
X 
(B.C) 
X 
(B.C) 
Unidentified X 
(B.C) 
X 
(B) 
X 
(B.C) 
X 
(B.C) 
X 
(B.C) 
X 
(C) 
Amoebae X 
(B.C) 
X 
(B) 
X 
(B.C) 
X 
(C) 
X 
(B) 
X 
(B) 
Testate amoebae Arcella spp. X 
(C) 
Heliozoa X 
(C) 
X 
(B) 
Rotifers X 
(B.C) 
X 
(B.C) 
X 
(B.C) 
X 
(B) 
Tardigrades X 
(C) 
Oligochaeta X 
(C) 
X 
(C) 
56 
TABLE 4.3.3 (CONTINUED) PROTOZOA/METAZOA IDENTIFIED FROM THE MIXED LIQUOR OF 
REACTOR B AND REACTOR C AT BORCHERDS QUARRY WWTP IN 2007 
MODERATE 
Sessile ciliates Ep/sty//sspp. X 
(C) 
Crawling ciliates Aspidisca spp. X 
(C) 
Oligochaeta X 
(C) 
Rotifera X 
(B) 
NUMEROUS 
Flagellates Trepomonasspp. X 
(C) 
4.3.3 DISCUSSION 
Borcherds Quarry experienced a comparatively high influent COD and SS. Apart from 
one anomalous result in each case, removal of both COD and SS was efficient (refer to 
figures 4.3.3, 4.3.4, 4.3.7 and 4.3.8). 
Regarding the removal of nitrogen reflected in figures 4.3.5 and 4.3.6, nitrification 
efficiency was excellent, despite the sometimes relatively short calculated sludge age 
and high influent TKN. There was also one unexplained anomalous result in the case of 
effluent ammonia, where it seems that almost no nitrification took place. In this instance, 
there was complete denitrification, perhaps because there was insufficient nitrification 
product to denitrify. As with Cape Flats (also 5-stage Bardenpho), complete 
denitrification did not take place. Residual nitrate/nitrite levels in the clarifier supernatant 
were higher from reactor C than reactor B. The influent COD/TKN ratio ranged from 8.4 
to 20.3 mgCOD/mgTKN with a mean of 13.1 mgCOD/mgTKN. These values were 
substantially higher than the values found at Cape Flats WWTP (mean of 
7.8mgCOD/mgTKN). Even the lowest value of 8.4 mgCOD/mgN that was obtained at 
Borcherds quarry equaled that reported by Kujawa et al. (1996) as necessary for 
complete denitrification. There was no correlation between the influent COD/TKN ratio 
and effluent nitrates/nitrites as was the case with Cape Flats WWTP (see section 4.4.3). 
At Borcherds Quarry, it is highly unlikely that lack of electron donor was the reason for 
incomplete denitrification. The most probable reasons for the presence of residual 
nitrates/nitrites would thus be plant operating conditions, for example, insufficient mixed 
liquor recycle from the aerobic to the first anoxic zone or insufficient retention time in the 
anoxic zone. 
Regarding the removal of phosphorous, shown in figure 4.3.9, results were inconsistent, 
but poor for this type of configuration. The COD/P ratio ranged between 46.5-
91 JmgCOD/mgP with a mean of 69.4mgCOD/mgP. According to Liu et al. (1997), a 
ratio of 10-20mgCOD/mgP should favour the growth of PAO's, while levels greater than 
50mgCOD/mgP should enhance the growth of GAO's. Theoretically, then according to 
this ratio, the growth of GAO's should have been favoured with a resultant negative 
effect on phosphorous removal. In addition, the likely presence of nitrates in the 
anaerobic zone probably also played a role and is substantiated by the fact that reactor 
C, with the highest levels of nitrates/nitrites in the clarifier effluent, also showed higher 
effluent phosphorous levels (poor removal). Both reactors receive the same influent, but 
57 
there is a link between denitrification efficiency that seemingly translates into 
phosphorous removal efficiency. In addition to the fact that the presence of nitrates in the 
anaerobic zone allows the ordinary heterotrophs to compete for substrate, there is 
another is a biological link - some PAO's are capable of denitrification in the anoxic 
zone. The polyhydroxybutyrate (PHB) formed when phosphate is released serves as a 
carbon source under anoxic conditions. Nitrate serves as the electron acceptor and 
phosphorous is taken up simultaneously. In a situation where the growth of heterotrophs 
and GAO's is favoured over the growth of PAO's, this will also then negatively affect 
denitrification (Kuba eta/., 1996). 
An interesting result was that reactor C, which exhibited the worst performance in terms 
of nutrient removal, gave consistently better results with both of the bulking indicators 
DSVI and Fl, as depicted by graphs 4.3.11 and 4.3.13 respectively. None of the mixed 
liquor samples taken from reactor C gave values indicating the presence of bulking 
conditions for either of these parameters. In fact, the DSVI values never rose much over 
100ml/g for the duration of the study. In contrast, both parameters for the mixed liquor 
samples from reactor B indicated bulking conditions from September to November. 
The presence of higher levels of nitrates/nitrites in reactor B and bulking conditions being 
present only in reactor C would seem to refute the AA bulking hypothesis of Casey eta/. 
(1999) as being pertinent in this case. Importantly, in the Cape Flats WWTP with similar 
levels of nitrates/nitrites in the effluent, bulking was not apparent. There are no results for 
the concentrations of these nitrogenous substances in the reactors themselves, so this is 
merely an assumption. 
Type 021N was never dominant at Cape Flats and was only dominant for one month in 
reactor C at Borcherds Quarry. However, this filament was co-dominant for four of the six 
months of the study period in reactor B. This may give a clue as to the reason for bulking 
conditions being present only in reactor B. If Type 021N was indeed the filament 
responsible for bulking conditions, the AA bulking hypothesis of Casey eta/. (1999) is 
again implausible as according to Eikelboom (2000), this filament is aerobic, and not 
facultative in nature. 
The reported calculated sludge age was low at times, but nitrification that requires long 
MCRT's was good throughout. There was an absence of metazoa towards the end of the 
study. These organisms grow slowly (Eikelboom, 2000) and are also reliant upon long 
retention times. There was a healthy and diverse ciliate population in both reactors 
throughout, reflecting good oxygenation and probable lack of toxic substances (Jenkins 
eta/., 2004). 
From September, the MLVSS was lower in reactor B. Once again, a link is established 
between increasing DSVI and decreasing MLVSS (Casey eta/., 1999b). In this case a 
clear comparison can be seen between both reactors. It is not clear which comes first -
increasing DSVI or decreasing MLVSS (see figure 4.3.10). 
The microscopic quality of the sludge mirrored the DSVI results obtained from reactor B. 
There was a steady deterioration and by November the floes were predominantly pin 
forms and numerous filaments were seen both protruding from the floes and between the 
floes. Many rosettes were seen. This is shown in figure 4.3.12. 
By examining table 4.3.2, it can be ascertained that the dominant filaments consisted of 
Type 0092 in all samples from both reactors and Type 021N which co-dominated in 
reactor B from August to the end of the study. Type 021N was constantly present as a 
58 
secondary species in reactor C, and also became co-dominant by November. Microthrix 
parvicella was prevalent in 58% of samples albeit as a secondary species. The only 
noticeable difference in the filament composition between the two reactors was the 
abundant numbers of Type 021N found in the mixed liquor samples from reactor B. It is 
not clear whether the overgrowth of this filament caused a decrease in the MLVSS with a 
resultant increase in F/M of reactor B (in comparison to reactor C), or whether an 
increased F/M resulted In the overgrowth of Type 021N, which in turn lead to a 
decreased MLVSS. The F/M values are given in table 4.3.1. Type 021N also became 
dominant in the Athlone WWTP at a time when the plant exhibited bulking tendencies. 
M. parvicella is also associated with LMW compounds, as is N. limicola III (Eikelboom, 
2000). 
Unfortunately, samples from Borcherds Quarry WWTP are only taken on a particular day 
of the week, so influent composition only mirrors the circumstances on those days, 
complicating analysis of results. 
The growth of Type 021N is enhanced by the presence of easily biodegradable 
compounds and/or sulphides. Such substances could be found from either the night soil 
(septic sewage) or the industrial effluent. Under nutrient removal conditions, the easily 
biodegradable fraction is usually expended in the anaerobic and anoxic zones, so the 
aerobic Type 021N does not have access to nutrients in the oxic zone (Eikelboom, 
2000). It is thus a possibility that with an increase in F/M due to decreased VSS or vice 
versa, there was more substrate still available for this organism under aerobic conditions. 
The decrease in VSS presupposes that there was a decrease in the ordinary 
heterotrophic population. Thus, there would also have been less competition for 
substrate. Jenkins etal. (2004) associates the presence of rosettes and gonidia of Type 
021N with nutrient deficiency, but this is unlikely as neither total denitrification nor 
phosphorous removal took place, and sufficient amounts of these should by inference 
have been available. 
In summary, both reactors exhibited sub-optimal performance in terms of expected 
nutrient removal. Poor phosphorous removal was probably due to the high COD/P ratio 
coupled to the presence of nitrate in the anaerobic zone. The reactor with superior 
performance in terms of nutrient removal developed poor settling that was associated 
with decreased VSS, increased F/M, overgrowth of filament Type 021N and poor floe 
formation. The latter was most likely due to an increased availability of easily 
biodegradable compounds and possibly sulphides in the aerobic zone. 
59 
4.4 CAPE FLATS WWTP 
4.4.1 PLANT CONFIGURATON AND OPERATING PARAMETERS 
Cape Flats is a NDBEPR WWTP with a design capacity to treat approximately 200ML 
effluent per day. The plant has six identical bioreactors that operate in a 5-stage 
Bardenpho configuration with diffuse aeration. The raw influent consists of approximately 
25% industrial effluent and 75% domestic effluent. The configuration is the same as that 
at Borcherds quarry WWTP and is depicted by figure 4.3.1 in the previous section. The 
plant operates at a DO concentration of 2.5 mg/L in the first aerobic zone and 1 to 1.5 
mg/L in the second aerobic zone and an aerobic mass fraction of 35%. The plant was 
often volumetrically overloaded in winter 2007 (see figure 4.4.1) 
4.4.2 RESULTS 
4.4.2 (a) Operational data 
The influent (I) into the bioreactor G and bioreactor H is supernatant from the PST. 
The mixed liquor (ML) from both reactor G and reactor H flows into the clarifier. 
The effluent (E) is the supernatant from the clarifier. 
*Note: breaks in the graph lines occur when no data was available 
100 
50 
0 
?Flow -Capacity 
—?»??? 
i "r i" i i i i' i i 'i' i i T'I r "i i"'i r i i ii i 
6/6 2/7 30/7 27/8 24/9 22/10 19/11 
Date 
I COD -ECOD 
600 
"*?••»?*? 
i" i i i i' i i i i i i i' i i i "i i i i i i i1 i 
6/6 2/7 30/7 27/8 24/9 22/10 19/11 
Date 
Figure 4.4.1 Graph depicting the 
overloading of Cape Flats WWTP in the 
winter of 2007 
Figure 4.4.2 Graph depicting the influent 
(ICOD) and effluent COD (ECOD) levels 
at Cape Flats WWTP in 2007 
60 
-RCOD 
20 
10 
fV 
"i i "i i'"i'' i""!1" i T""'T T"T r-r r r i '1 t""'t r-r r r 
6/6 2/7 30/7 27/8 24/9 22/10 19/11 
Date 
-ITKN -IAMM -ENN —?—EAMM 
80 
70 
60 
50 
40 
30 
20 
10 
6/6 2/7 30/7 27/8 24/9 22/10 19/11 
Date 
Figure 4.4.3 Graph depicting the removal 
efficiency of COD (RCOD) at Cape Flats 
WWTP in 2007. 
Figure 4.4.4 Graph depicting the influent 
TKN (ITKN) and ammonia (IAMM) as 
well as the effluent ammonia (EAMM) 
and nitrates/nitrites (ENN) at Cape Flats 
WWTP in 2007 
-ITP —»-IOP -EOP 
i i'"i i i i' i' i' i 'i i'"i i i i' i' 
6/6 2/7 30/7 27/8 24/9 22/10 19/11 
Date 
-GSVI -HSVI -Hfc-GDSVI -H DSVI 
6/6 2/7 30/7 27/8 24/9 22/10 19/11 
Date 
Figure 4.4.5 Graph depicting the levels of 
influent total phosphates (ITP) and 
influent a-phosphates (IOP) as well as 
the effluent levels of a-phosphates at 
Cape Flats WWTP in 2007 
Figure 4.4.6 Graph depicting the values 
for the SVI (G SVI) and (H SVI) and 
DSVI (G DSVI and H CSVI) of the mixed 
liquor in reactor G and H respectively at 
the Cape Flats WWTP in 2007 
61 
—??—ICOD/ITKN -*--ENN 
z 16 
z z 
UJ 
14 
12 
g»_i t-s. 10 
Q fc O 
O 8 
Ol F 
ts a 
o o 4 
6/6 2/7 30/7 27/6 24/9 22/10 19/11 
Date 
Figure 4.4.7 Relationship between the influent COD and TKN ratio (ICOD/TKN) and the 
effluent levels in nitrates/nitrites at the Cape Flats WWTP in 2007 
TABLE 4.4.1 FOOD TO MICROORGANISM (F/M) RATIO IN REACTOR G AND 
REACTOR H OF CAPE FLATS WWTP IN 2007 
REACTOR G REACTOR H 
June 0.1 ImgCOD/mgVSS.day 0.11 mgCOD/mgVSS.day 
July 0.12mgCOD/mgVSS.day 0.12mgCOD/mgVSS.dav 
August 0.31 mgCOD/mgVSS.day 0.28mgCOD/mgVSS.dav 
October 0.16mgCOD/mgVSS.day 0.15mgCOD/mgVSS.day 
November 0.15mgCOD/mgVSS.day 0.13mgCOD/mgVSS.day 
4.4.2 (b) Microscopic sludge analysis 
Figure 4.4.8 Wet mounts of mixed liquor from reactor H on the left and reactor G on the 
right from the Cape Flats WWTP in June 2007, showing the type of structure found in 
both reactors throughout the study 
62 
• Filament index 
Figure 4.4.9 Graph depicting the low filament 
index values in both reactor G and H in 2007 
TABLE 4.4.2 DOMINANT AND SECONDARY FILAMENTOUS ORGANISMS IDENTIFIED IN THE MIXED 
LIQUOR OF REACTOR G (G) AND REACTOR H (H) AT BORCHERDS QUARRY WWTP IN 2007 
AS DON INANT F LAMENTS 
June July Aug Sept Oct Nov % Prevalence 
BandC 
(dominant) 
% Prevalence 
BandC 
(overall) 
Type 0092 X 
(G,H) 
X 
(G,H) 
X 
(G,H) 
X 
(G,H) 
X 
(G,H) 
X 
(G,H) 
100 100 
H. hydrosis X 
(G) 
X 
(G) 
17 50 
N. limicola X 
(G) 
X 
(G) 
17 33 
AS SECONDARY FILAMENTS 
H. hydrosis X 
(G.H) 
X 
(H) 
X 
(H) I Also dominant 
J filaments N. limicola'III X 
(H) 
X 
(H) 
M. parvicella X 
(G,H) 
X 
(G,H) 
X 
(G,H) 
X 
(G,H) 
0 67 
Type 0041 X 
(H) 
X 
(G,H) 
X 
(G,H) 
X 
(G,H) 
0 58 
Type 1701 X 
(G,H) 
X 
(G,H) 
X 
(G,H) 
0 50 
Type 1851 X 
(G) 
X 
(G,H) 
X 
(H) 
X 
(H) 
X 
(H) 
0 50 
Type 021N X 
(G) 
X 
(G,H) 
X 
(G,H) 
X 
(H) 
0 50 
Type 0581 X 
(G,H) 
X 
(G,H) 
X 
(G) 
0 42 
Flexibacterspp. X 
(G,H) 
X 
(G,H) 
0 33 
63 
TABLE 4.4.3 PROTOZOA/METAZOA IDENTIFIED IN THE MIXED LIQUOR FROM REACTOR G AND 
REACTOR H AT CAPE FLATS WWTP IN 2007 
SCANTY 
June July Aug Sept Oct Nov 
Sessile ciliates Carchesium spp. X 
(G,H) 
X 
(G) 
Epistylis spp. X 
(G,H) 
X 
(G) 
X 
(G) 
X 
(G,H) 
X 
(G) 
Opercularia spp. X 
(G) 
Vaginicola spp. X 
(G) 
X 
(G,H) 
X 
(G,H) 
X 
(G,H) 
Vorticella spp. X 
(G,H) 
X 
(G,H) 
X 
(G,H) 
X 
(G,H) 
X 
(G) 
Crawling dilates Aspidisca spp. X 
(H) 
X 
(G) 
X 
(G,H) 
X 
(G,H) 
X 
(G,H) 
X 
(G,H) 
Chilodonella spp. X 
(G,H) 
X 
(G) 
X 
(H) 
Trachelophyllum spp. X 
(G,H) 
X 
(G,H) 
X 
(H) 
X 
(G,H) 
Unidentified X 
(H) 
Free-living ciliates Blepharisma spp. X 
(H) 
X 
(G) 
X 
(H) 
Et//?/otesspp. X 
(H) 
Z./ito/70ft/sspp. X 
(H) 
X 
(G,H) 
X 
(G,H) 
X 
(H) 
X 
(G,H) 
Paramec/itymspp. X 
(G) 
Spirostomum spp. X(G,H) X 
(G) 
X 
(G) 
X 
(G,H) 
Unidentified X 
(G) 
Flagellates ftooto spp. X 
(H) 
X 
(G.H) 
X 
(G) 
X 
(G) 
X 
(H) 
X 
(G,H) 
Peranema spp. X 
(G.H) 
X 
(G,H) 
X 
(G,H) 
X 
(H) 
Monsiga spp. X 
(G) 
Amoebae X 
(G,H) 
X 
(G,H) 
X 
(G,H) 
X 
(G,H) 
X 
(H) 
X 
(H) 
Testate amoebae X 
(H) 
Heliozoa X 
(H) 
X 
(H) 
X 
(G) 
Rotifers X 
(G,H) 
X 
(G,H) 
X 
(G,H) 
X 
(G,H) 
X 
(G,H) 
X 
(G,H) 
Nematodes X 
(H) 
Tardigrades X 
(G) 
X 
(H) 
X 
(G,H) 
X 
(G) 
64 
TABLE 4.4.3 (CONTINUED) PROTOZOA/METAZOA IDENTIFIED IN THE MIXED LIQUOR FROM 
REACTOR G AND REACTOR H AT CAPE FLATS WWTP IN 2007 
Oligochaeta X 
(G) 
X 
<G1_ 
MODERATE 
Sessile ciliates Epistylis spp. X 
(H) 
X 
(H) 
X 
(H) 
Figure 4.4.10 Neisser stain of Type 0092 from 
mixed liquor from reactor G at Cape Flats WWTP 
in June 2007. 
4.4.3 DISCUSSION 
Both reactor G and H of the Cape Flats WWTP showed good results for COD and 
ammonia removal for the entire study period, as can be seen from figures 4.4.2 and 
4.4.3. 
Figure 4.4.4 shows the presence of residual nitrate/nitrite, presumably due to incomplete 
denitrification in the anoxic zones. (The level of nitrate/nitrite in the clarifier supernatant 
was continuously around the 10mgN/L mark). Unfortunately, routine testing 
understandably does not include more detailed results on the nitrogenous compounds in 
various stages of the bioreactor. A plant of this configuration with two anoxic zones 
should achieve complete denitrification. The presence of readily available electron donor 
in the form of COD in the anoxic zone is necessary for this function (Tchobanglous and 
Burton, 1991). 
An article by Komorowska-Kaufman et al. (2006), describes evidence of the effects of 
wastewater characteristics and biological process conditions on nitrogen removal 
effectiveness in Bardenpho mode reactors. They found that denitrification was enhanced 
by the addition of extra carbon source in the form of acetate until the VFA/N ratio was 
equal to 1.67 mg acetate/mg N, after which no extra benefit was derived. 
The authors refer to a study by Kujawa eta/. (1996), who determined that a COD/N ratio 
of 8.4mgCOD/mgN was required for complete denitrification of wastewater. The ratio in 
65 
the influent at Cape Flats over the six-month study period ranged between 6.1 and 13.7, 
with a mean of 7.8mgCOD/mgTKN in the influent. Obviously requirements will differ from 
plant to plant because of substrate differences and the amount of utilization or absorption 
of COD taking place in the anaerobic zone preceding the first anoxic zone. In the second 
anoxic reactor in the Bardenpho system, denitrification takes place by the slower 
mechanism of endogenous respiration, and is significantly retarded by even low levels of 
DO. The effect of DO on nitrification is not significantly affected at high COD levels (Jeill 
eta/., 1999). 
To ascertain whether lack of electron donor was the reason for incomplete denitrification, 
graph 4.4.7 was plotted comparing the influent COD/TKN ratio to effluent levels of 
nitrates and nitrites. There appears to be a link in that on most occasions, an increased 
trend on the influent COD/TKN ratio is followed by a decreased trend in the effluent 
nitrate/nitrite levels. It merits further work to ascertain whether this is indeed the case, as 
not only is the level of nitrates/nitrites in the effluent affected, but also possibly the 
phosphorous levels (see below). The other most obvious causes are: 
> insufficient mixed liquor recycle from the aerobic to the first anoxic zone 
> insufficient retention time in the anoxic zones 
> carry over of DO in the mixed liquor recycle and/or from the aerobic to the second 
anoxic zone 
> insufficient retention time in the anoxic zone 
Phosphorous removal, graphically depicted in graph 4.4.5, was less that ideal for a 
system designed for this purpose. The presence of nitrates/nitrites in the clarifier effluent 
indicates that these nitrogenous compounds were probably also present in the RAS that 
enters the anaerobic zone. 
Assuming this was the case, the anaerobic zone would become a de facto anoxic zone. 
This can be compared to exactly the opposite scenario experienced at the Bellville plant 
(MLE) that possibly resulted in unexpectedly good phosphorous removal. There is also a 
link between denitrification and phosphorous removal that was alluded to in the previous 
section (4.3, Borcherds Quarry). 
Carlsson et a/. (1995), found that the concentration of VFA's was the most important 
parameter associated with the removal of phosphorous and that the relationship between 
the VFA/P ratio and removal of this nutrient was linear. The most important source of 
VFA's is the influent and this is supplemented by the formation of these fatty acids in the 
anaerobic zone by fermentation and hydrolysis. An important parameter to be 
considered is the retention time in the sewer - the longer the retention time, the higher 
the concentration of VFA's. 
Under anoxic conditions, the ordinary heterotrophic population can compete with PAO's 
for VFA substrate. If sufficient VFA substrate and anaerobic conditions are present, 
biological phosphorous removal is chiefly dependent on conditions that result in PAO's 
having a competitive advantage over GAO's. This is described extensively in chapter 2. 
Both organism types compete for VFA's in the influent although substrate preferences in 
terms of acetate and propionate do differ. A ratio of P/COD of 10-20mgCOD/mgP 
favours the growth of PAO's. A ratio of 50mgCOD/mgP enhances the growth of GAO's 
(Liu et a/., 1997). The ratio encountered at Cape Flats ranged from 28.5-
45.3mgCOD/mgP with a mean value of 35.8mgCOD/mgP. The assumption can thus be 
made that conditions did not favour either PAO's or GAO's. Thus the first steps to 
ascertain why phosphorous removal is inefficient would be to determine the levels of 
nitrates, nitrites and VFA's in the anaerobic zone. 
66 
The F/M ratio (shown in table 4.4.1), measured in mgCOD/mgMLVSS.day, was low in 
June, July, October and November and was slightly higher in August in both reactors. 
From table 4.4.2, it can be seen that Type 0092, classed as low F/M by Jenkins et al. 
(2004), was dominant throughout the study in both reactors, which correlates well with 
the F/M results obtained. Co-dominant N. limicola III and H. hydros/swere only found in 
2 of the 12 samples, but their presence in terms of F/M was not unexpected as they can 
both occur over a wide range of F/M values. 
The assumption that denitrification was incomplete can be coupled to the hypothesis on 
AA bulking by Casey et al. (1999c) and lead to the possibility that conditions conducive 
to the overgrowth of AA filaments were present (the presence of sufficient levels of 
nitrates/nitrites in the mixed liquor entering the aerobic zones). However the DSVI values 
depicted in graph 4.4.6 and Fl values depicted in graph 4.4.9 did not reflect the presence 
of bulking conditions at any time over the study period. 
The floe character was as expected from a low loaded WWTP treating predominantly 
domestic effluent and with diffuse aeration (Eikelboom, 2000). The even spread of 
protozoa and metazoa in the sludge samples reflected the prevailing conditions of 
aerobic (ciliates) and anaerobic/anoxic (flagellates, amoeba). The presence of 
bacteriovorous free-living ciliates reflected the finding of free-living cells in many 
samples. The presence of rotifers, nematodes, tardigrades and oligochaete worms 
similarly reflected the generally long sludge ages (Eikelboom, 2000). 
In summary, the reactors used in the study did not exhibit bulking tendencies in terms of 
elevated DSVI and/or Fl from June to September 2007. This was despite the probability 
that there were nitrates/nitrites present in the anoxic zone preceding the aerobic zone. 
Nutrient removal was poor, most likely due to insufficient VFA's in the anaerobic zone, 
and/or too much nitrate in the anaerobic zone and/or lack of electron donor in the first 
anoxic zone. 
67 
4.5 KRAAIFONTEIN WWTP 
4.5.1 PLANT CONFIGURATION AND OPERATING PARAMETERS 
Kraaifontein is a relatively small NDEBPR WWTP for the treatment of domestic 
wastewater. The configuration of the plant is classic UCT (see figure 4.1.2) and surface 
aeration is employed. There is only one bioreactor and the aerobic, anoxic and 
anaerobic mass fractions are 59%, 30% and 11% respectively and the average DO 
concentration is 2.8mg/L. Influent is first settled in PST's before entering the bioreactor. 
4.5.2 RESULTS 
4.5.2 (a) Operational data 
The influent (I) is the supernatant from the PST's combined. 
The mixed liquor (ML) results are from the bioreactor. 
The effluent (E) is the averaged results from the supernatant of three clarifiers. 
*Note: breaks in the graph lines occur when no data was available 
-ICOD 
i 'i "i i" i i i i i i i i'' V" i" r "r" i i i 'i i i i 
6/6 4/7 1/8 29/8 26/9 24/10 21/11 
Date 
O O 
o 
> o 
E 
8. 
100 
95 
90 
85 
80 
75 
70 
65 
60 
55 
50 
-RCOD 
g£ 
-y-r i ? I-'T"1 'i "?ii"""r"r 'i '"i—i r r i r i i"11 "r" I i' T 
6/6 4/7 1/8 29/8 26/9 24/10 21/11 
Date 
Figure 4.5.1 Graph depicting the influent 
COD levels at Kraaifontein WWTP in 2007 
Figure 4.5.2 Graph depicting the COD 
removal efficiency (RCOD) at 
Kraaifontein WWTP in 2007 
68 
•ITKN -IAMM -ENN -EAMM 
100 
t 
6/6 
'r'iii¥wii 
4/7 1/8 29/8 26/9 24/10 21/11 
Date 
-ITP -IOP -EOP 
16 
T—J—r—r 
6/6 4/7 1/8 29/8 26/9 24/10 21/11 
Data 
Figure 4.5.3 Graph depicting the influent 
TKN (ITKN), influent ammonia (IAMM), 
effluent nitrates/nitrites (ENN) and effluent 
ammonia (EAMM) levels at Kraaifontein 
WWTP in 2007 
Figure 4.5.4 Graph depicting the influent 
total phophate (ITP), influent o-
phosphate and effluent o-phosphate 
levels at Kraaifontein WWTP in 2007 
Figure 4.5.5 Graph depicting the SVI and DSVI values obtained at Kraaifontein WWTP in 
2007 
TABLE 4.5.1 FOOD TO MICROORGANISM (F/M) RATIO IN BIOREACTOR OF 
KRAAIFONTEIN IN 2007 
June 0.08 mgCOD/mgVSS.day 
July 0.31 mgCOD/mgVSS.day 
September 0.19 mgCOD/mgVSS.day 
October 0.16 mgCOD/mgVSS.day 
November 0.14 mgCOD/mgVSS.day 
69 
4.5.2(b) Microscopic sludge analysis 
This was performed monthly on the following dates: 28/6/07, 26/7/07, 23/8/07, 20/9/07, 
25/10/07 and 22/11/07. 
• Floe structure 
The floes were open in structure and firm in strength for the duration of the study. The 
shape of the floes differed from round, in June, August and November, irregular in July 
and both irregular and round in September and November. The size of the floes was 
medium in June, small (pin floes) and medium in July, medium and large in August, 
September and October and medium again in November. 
Figure 4.5.6 Micrograph of wet mount of mixed 
liquor showing irregular floe structure at Kraaifontein 
WWTP in September 2007 
• Diversity 
Diversity was moderate to low for the duration of the study, and there were a moderate 
number of monocolonies, staining principally as GAO bacteria (see section 4.5.3 and 
figure 4.5.9). 
• Filament index 
? Filament index 
5-, 
4 
-. 3 -in 
i 
1 -
n -
June July Aug Sept Oct Nov 
Month 
Figure 4.5.7 Graph showing the Fl values obtained 
from the mixed liquor at Kraaifontein WWTP in 2007 
70 
TABLE 4.5.2 DOMINANT AND SECONDARY FILAMENTOUS ORGANISMS IDENTIFIED FROM THE 
MIXED LIQUOR AT KRAAIFONTEIN WWTP IN 2007 
AS DOMINANT F LAMENTS 
June July Aug Sept Oct Nov % Prevalence 
(dominant) 
% Prevalence 
(overall) 
Type 0092 X X X X X X 100 100 
M. parvicella X X X 50 100 
AS SECONDARY ^LAMENTS 
M. parvicella X X X \ Also dominant 
* filaments 
Type 1851 X X X X X X 0 100 
Type 0041 X X X X 0 67 
Type 021N X 0 17 
Type 1863 X 0 17 
Figure 4.5.8 Neisser stain of Microthrix parvicella 
from mixed liquor sample taken at Kraaifontein 
WWTP in October 2007. 
TABLE 4.5.3 PROTOZOA/METAZOA IDENTIFIED IN THE MIXED LIQUOR FROM KRAAIFONTEIN WWTP 
IN 2007 
SCANTY 
June July Aug Sept Oct Nov 
Sessile ciliates Carchesium spp. X X X X 
Epistylis spp. X X X X 
Vorticella spp. X X X X 
Crawling ciliates Aspidisca spp. X X X X X 
Chilodonella spp. X X X 
Trachelophyllum spp. X X 
Free-living ciliates Colpidium spp. X 
Unidentified X X 
Flagellates Bodo spp. X X X 
Peranema spp. X X X 
Unidentified X X 
Amoebae X X X 
Testate amoebae Arcella spp. 
Heliozoa X 
71 
TABLE 4.5.3 (CONTINUED) PROTOZOA/METAZOA IDENTIFIED IN THE MIXED LIQUOR FROM 
KRAAIFONTEIN WWTP IN 2007 
June July Aug Sept Oct Nov 
Rotifers X 
Nematodes X X X 
MODERATE 
Sessile ciliates Ep/sty/isspp. X 
Crawling ciliates Aspidisca spp. X 
Trachelophyllum spp. X 
Free-living ciliates Euplotes spp. X 
Flagellates Peranema spp. X 
Amoebae X 
4.5.3 DISCUSSION 
By studying figures 4.5.1, 4.5.2 and 4.5.3, it can be seen that the removal of ammonia 
and COD at Kraaifontein WWTP was relatively efficient over the study period, except for 
at the end of October, when there were some high aberrant results for COD and 
suspended solids in the clarifier effluent. The problem may have been linked to the 
clarifier and not the bioreactor. 
There was residual nitrate/nitrite in the clarifier effluent for most of the trial period. On the 
odd occasion when nitrates/nitrites were absent, there was a link to an increase in 
ammonia levels, which is demonstrated by figure 4.5.3. This infers that nitrification of 
ammonia is usually complete, but the amount of nitrates/nitrites thus formed exceed 
denitrification potential of this system, resulting in the presence of residual nitrate/nitrites. 
However, when nitrification is incomplete, the conversion of ammonia into nitrates/nitrites 
is not achieved to the same degree and the biological denitrification system can fully 
cope with the lower levels of nitrate/nitrite. 
The possible reasons for lack of denitrification have already been elucidated upon in the 
previous sections of this chapter (4.2.3 and 4.3.3). Regarding the lack of electron donor, 
the influent COD/TKN ratio ranged from 5.0-10.2mgCOD/mgTKN, with a mean of 
7.2mgCOD/mgTKN. The mean was thus below the value of 8.4mgCOD/mgTKN reported 
by Kujawa et al. (1996) as being necessary for complete denitrification. There was no 
obvious correlation between this ratio and effluent nitrate/nitrite values, but this does not 
necessarily rule out the lack of electron acceptor as being the major cause of complete 
denitrification. The nitrate/nitrite levels in the clarifier effluent only serve as a guideline 
under these circumstances and do not necessarily reflect the true daily reactor 
conditions. 
The erratic nature of phosphorus removal efficiency is reflected in figure 4.5.4. There 
were periods of almost complete or complete removal interspersed with poor removal, 
especially around the end of August. Ekama et al. (1984) found that with a TKN/COD 
ratio of <0.08, no external energy source was necessary for complete denitrification to 
occur. In a UCT system, a TKN/COD ratio of >0.14 usually results in a nitrate being 
carried over from the primary anoxic reactor to the anaerobic reactor with a resultant 
negative effect on phosphorous removal. In fact, at this level, Ekama eta/. (1984) found 
it unlikely that BPR would be achieved with any consistency because of insufficient 
denitrification. The TKN/COD range at Kraaifontein from June to November 2007 was 
0.098-0.201 mgN/mgCOD, with a mean value of 0.14mgN/mgCOD. 
72 
To prevent carry over of nitrates, the practice is to increase the mixed liquor recycle from 
the aerobic zone and effectively increase the anoxic retention time. The presence of 
varying amounts of nitrate in the mixed liquor recycle to the anaerobic zone may explain 
the erratic nature of phosphorous removal, but the fact that a moderate number of GAO's 
were seen in the mixed liquor presupposes that conditions were created that allowed 
these organisms to compete with the PAO's. 
The COD/P ratio ranged between 27.6-48.6mgCOD/mgP with a mean of 
39.8mgCOD/mgP. At this level, the growth of neither the GAO's nor the PAO's should be 
enhanced over the other (Liu eta/., 1997). 
However, there were moderate numbers of monocolonies in all samples. These stained 
principally as GAO bacteria (see figure 4.5.9 below) and the phenomenon is discussed in 
more detail later in this chapter under section 4.9. 
Figure 4.5.9 Gram stain of GAO's from mixed liquor from Kraaifontein WWTP in 
August 2007 (left) and Neisser stain of GAO's from mixed liquor from Kraaifontein 
WWTP in August 2007 (right). 
The floe structure of the mixed liquor was open, which is a characteristic of surface 
aeration (Eikelboom, 2000). Apart from the floes occasionally being irregular in shape, 
and the presence of pin floes June, the overall floe character was fair. 
Both dominant filaments, namely Type 0092 and M. parvicella are classified by Jenkins 
et a/. (2004) as "low F/M". This correlates well with the calculated values given in table 
4.5.1. The value in July was higher than the other months of the study, and in this month, 
there was a concomitant increase in the number of sessile and crawling ciliates. This can 
be seen by examining figure 4.5.3. Epistylis spp., Aspidisca spp. and Trachelophyllum 
spp. were all found in moderate amounts in this month. However, on the whole, the even 
spread of ciliates and the presence of amoeba, rotifers and nematodes reflect the varied 
DO levels, lack of high levels of toxic substances and long sludge age (Eikelboom, 
2000). 
It can be speculated that the presence of residual amounts of nitrate/nitrite would be 
conducive to AA bulking using the metabolic hypothesis of Casey etal. (1999). In fact, 
the indicator Fl and the DSVI values shown in figure 4.5.7 and 4.5.5 respectively were 
never a cause for concern. 
73 
4.6 MACASSAR WWTP 
4.6.1 PLANT CONFIGURATION AND OPERATING PARAMETERS 
Macassar WWTP has a design capacity of 34ML/day. The plant is equipped with two 
Carousel® systems operating in UCT mode (figures 4.1.1 and 4.1.2). The influent is 
primarily of domestic origin. DO concentrations in the reactors should range from 0.2-
0.9mg/L. The plant experiences intermittent problems with scum formation. 
4.6.2 RESULTS 
4.6.2 (a) Operational data 
The influent (I) is the raw wastewater. 
The mixed liquor (ML) results are from the two bioreactors differentiated as reactor 1 and 
reactor 2. The mixed liquor from these reactors flows into separate the clarifiers, also 
named 1 and 2. 
The effluent (E) is the supernatant from clarifiers. 
*Note: breaks in the graph lines occur when no data was available 
?Flow rate -Capacity 
'I I 'I I ''I' l""V "I""!" I''"l'rlr 'VT'T"!'"'!""!'"'!""!""!'"!""!" 
3/6 1/7 29/7 26/8 24/9 21/10 18/11 
Date 
-ICOD 
3/6 1/7 29/7 26/8 24/9 21/1018/11 
Date 
Figure 4.6.1 Graph depicting the design 
capacity and the actual flow rate into the 
Macassar WWTP, showing the 
theoretical gross volumetric overloading 
in 2007 
Figure 4.6.2 Graph depicting the influent 
COD (ICOD) levels at Macassar WWTP 
in 2007 
74 
100 
8 I 
65 
60 
?1 RCOD -2 RCOD 
i i i \ i1 i i ii i i i I r r i i" i—i i i i i 
3/6 1/7 29/7 26/8 24/9 21/10 18/11 
Date 
?ITKN -IAMM 
?i i ' i' i i i f i'"i—i—f'T-i—r-rm"i"r""i—i rn—i—i—r-T 
3/6 1/7 29/7 26/8 24/9 21/10 18/11 
Date 
Figure 4.6.3 Graph depicting the COD 
removal efficiency of reactor 1 (1 RCOD) 
and reactor 2 (2 RCOD) at Macassar 
WWTP in 2007 
Figure 4.6.4 Graph depicting the influent 
TKN (ITKN) and influent ammonia (IAMM) 
levels at Macassar WWTP in 2007 
-1 EAMM 
?1 ENN 
-2 EAMM 
-2 ENN 
26/8 24/9 21/10 18/11 
Date 
-IOP -1 EOP -2 EOP ?ITP 
—,—p-,—,—i' |.T.M|—rn—,—!—r 
3/6 1/7 29/7 26/8 24/9 21/10 18/11 
Date 
Figure 4.6.5 Graph depicting the effluent 
ammonia levels from clarifier 1 (1 EAMM) 
and clarifier 2 (2 EAMM) and the effluent 
nitrates/nitrites from clarifier 1 (1 ENN) and 
clarifier 2 (2 ENN) at Macassar WWTP in 
2007 
Figure 4.6.6 Graph depicting the influent a-
phosphates (IOP) and total phosphates (ITP) 
and the effluent a-phosphates from clarifier 1 
(1 EOP) and clarifier 2 (2 EOP) at Macassar 
WWTP in 2007 
75 
?1 MLSS —•— 2 MLSS 
?1 MLVSS -•— 2MLVSS 
O) 
E 
in 2 
7000 
6500 
6000 
5500 
5000 
=d 4500 
E o 
in 
V) 
E 
4000 
3500 jif^-3 
3000 
2500 
2000 r"<' f"r i i i ' i' T i 'i'"i" 
3/6 1/7 29/7 26/8 24/9 21/10 18/11 
Date 
-1 SVI -2 SVI ? 1 DSVI -2 DSVI 
i""i'"i ill r II T i 
3/6 1/7 29/7 26/8 24/9 21/10 18/11 
Date 
Figure 4.6.7 Mixed liquor suspended solids 
from reactor 1 (1 MLSS) and reactor 2 
(2 MLSS) and mixed liquor volatile 
suspended solids from reactor 1 
(1 MLVSS) and reactor 2 (2 MLVSS) at 
Macassar WWTP in 2007 
Figure 4.6.8 Sludge volume index from 
reactor 1 (1 SVI) and reactor 2 (2 SVI) and 
dissolved sludge volume index from reactor 
1 (1 DSVI) and reactor 2 (2 DSVI) at 
Macassar WWTP in 2007 
TABLE 4.6.1 FOOD TO MICROORGANISM (F/M) RATIO IN REACTOR 1 AND 
REACTOR 2 OF MACASSAR WWTP IN 2007 
REACTOR 1 REACTOR 2 
July 0.14 mgCOD/mgVSS.day 0.14 mgCOD/mgVSS.day 
September 0.09 mgCOD/mgVSS.day 0.08 mgCOD/mgVSS.day 
October 0.10 mgCOD/mgVSS.day 0.08 mgCOD/mgVSS.day 
November 0.09 mgCOD/mgVSS.day 0.08 mgCOD/mgVSS.day 
4.6.2 (b) Microscopic sludge analysis 
This was performed monthly on the following dates: 26/6/07, 23/7/07, 28/8/07, 24/9/07, 
22/10/07 and 26/11/07. 
• Floe structure 
Reactor 1 
In June, the floes were irregular in shape, open in structure and firm in strength. In July, 
October and November, the floes were round in shape, open in structure and firm in 
strength. In August and September the floes were round in shape, compact in structure 
and firm in strength. The floes were medium-sized for the duration of the study. 
Reactor 2 
In June, July, September, October and November the floes were round in shape, open in 
structure and firm in strength. In August, the floes were round in shape, compact in 
structure and firm in strength. The floes were medium-sized for the duration of the study. 
76 
Figure 4.6.9 Wet mount of mixed liquor from 
reactor 2 at Macassar WWTP in July showing 
round, open and firm floe structure 
• Diversity 
Microscopic examination revealed moderate diversity in all samples from both reactors. 
Scanty monocolonies were present in all samples except those from reactor 1 in June, 
August, and October and reactor 2 in June, October and November, when no 
monocolonies were observed. 
• Filament index 
Figure 4.6.10 Graph depicting the filament index 
of reactor 1 and reactor 2 at Macassar WWTP in 
2007. In August and September the Fl for both 
reactors was the same. 
77 
TABLE 4.6.2 DOMINANT AND SECONDARY FILAMENTOUS ORGANISMS IDENTIFIED FROM THE 
MIXED LIQUOR OF REACTOR 1 AND REACTOR 2 AT MACASSAR WWTP IN 2007 
AS DOMINANT F LAMENTS 
June July Aug Sept Oct Nov % Prevalence 
land 2 
(dominant) 
% Prevalence 
land 2 
(overall) 
M. parvicella X 
(1,2) 
X 
(1,2) 
X 
(1,2) 
X 
(D 
X 
(1,2) 
75 83 
Actinomycetes X 
(2) 
X 
(1,2) 
X 
(1,2) 
X 
(2) 
50 92 
Type 0092 X 
(2) 
X 
(2) 
X 
(2) 
X 
(D 
33 100 
Type 1851 X 
(D 
X 
(1,2) 
25 67 
H. hydrosis X 
(2) 
X 
(2) 
17 75 
Type 0041 X 
(2) 
8 83 
AS SECONDARY FILAMENTS 
M. parvicella X 
(2) 
V Also dominant 
J filaments 
Actinomycetes X 
(1) 
X 
(1) 
X 
(1,2) 
X 
(D 
Type 0092 X 
(1) 
X 
(1) 
X 
(1,2) 
X 
(D 
X 
(1,2) 
X 
(2) 
Type 1851 X 
(1,2) 
X 
(1,2) 
X 
(2) 
H. hydrosis X 
(1,2) 
X 
(D 
X 
(1,2) 
X 
(1,2) 
Type 0041 X 
(2) 
X 
(1,2) 
X 
(1,2) 
X 
(1,2) 
X 
(1,2) 
Type 021N X 
(2) 
X 
(1,2) 
X 
(D 
X 
(D 
X 
(1,2) 
0 58 
Type 0581 X 
(1) 
0 8 
Type 0914 X 
(1) 
0 8 
Type 1701 X 
(D 
0 8 
78 
Figure 4.6.11 Wet mount of mixed liquor from 
reactor 1 at Macassar WWTP in November 2007 
showing Spirostomumspp., apparently mating. 
TABLE 4.6.3 PROTOZOA/METAZOA IDENTIFIED IN THE MIXED LIQUOR FROM REACTOR 1 AND 
REACTOR 2 AT MACASSAR WWTP IN 2007 
SCANTY 
June July Aug Sept Oct Nov 
Sessile ciliates Epistylis spp. X 
(2) 
X 
(1,2) 
X 
(1) 
Opercularia spp. X 
(1) 
X 
(1) 
Vaginicola spp. X 
(1) 
Vorticella spp. X 
(1) 
X 
(1,2) 
X 
(1,2) 
X 
(1,2) 
X 
(1,2) 
Crawling ciliates Aspidisca spp. X 
(1) 
X 
(1,2) 
X 
(1) 
X 
(1) 
X 
(2) 
Chilodonella spp. X 
(2) 
X 
(1,2) 
Trachelophyllum spp. X 
(1) 
X 
(1) 
X 
(2) 
Free-living ciliates Blepharisma spp. X 
(1) 
Colpidium spp. X 
(1) 
X 
(1,2) 
X 
(1,2) 
X 
(1,2) 
£l£y/7/otesspp. X 
(2) 
Z./to/70/itysspp. X 
(2) 
X 
(2) 
X 
(1) 
X 
(2) 
Paramecium spp. X 
(1,2) 
Spirostomum spp. X 
(1,2) 
X 
(1) 
X 
(2) 
79 
TABLE 4.6.3 (CONTINUED) PROTOZOA/METAZOA IDENTIFIED IN THE MIXED LIQUOR FROM 
REACTOR 1 AND REACTOR 2 AT MACASSAR WWTP N 2007 
June July Aug Sept Oct Nov 
Unidentified X 
(2) 
X 
(2) 
X 
(2) 
Flagellates Bodo spp. X 
(1,2) 
X 
(1,2) 
X 
(2) 
Peranema spp. X 
(D 
Trepomonas spp. X 
(1) 
Amoebae X 
(1,2) 
X 
(1,2) 
X 
(1) 
X 
(D 
X 
(D 
X 
(1,2) 
Rotifera X 
(1,2) 
X 
(1,2) 
X 
(1) 
X 
(1,2) 
Nematodes X 
(1,2) 
X 
(1) 
X 
(1) 
X 
(1,2) 
MODERATE 
Attached ciliates Vaginicola spp. X 
(2) 
Vorticella spp. X 
(1,2) 
Crawling ciliates Aspidisca spp, X 
(D 
X 
(1) 
Free-living ciliates Euplotes spp. X 
(1) 
Spirostomum spp. X 
(1) 
Flagellates Bodo spp. X 
(1) 
Amoebae X 
(2) 
Rotifera X 
(1,2) 
X 
(1) 
NUMEROL IS 
Crawling ciliates Aspidisca spp. X 
(2) 
Flagellates Pleuromonas spp. X 
(1) 
80 
4.6.3 DISCUSSION 
Macassar WWTP was severely overloaded in terms of design capacity, which is clearly 
depicted in figure 4.6.1 However, due to the low influent COD, the removal of this 
substrate was efficient (figures 4.6.2 and 4.6.3) The influent COD was consistently lower 
than that of most other WWTP's included in the study, perhaps due to the lack of 
industrial component. 
Nitrification was satisfactory but denitrification was often poor, with erratic results that 
can be seen by perusing figures 4.6.4 and 4.6.5. The levels of residual nitrates/nitrites 
were extremely erratic (0-15mg/L). There was no obvious correlation between influent 
COD/TKN ratios and effluent nitrate/nitrite levels. This fact does not preclude the 
possibility of electron donor deficiency in the anoxic zone being the reason for poor 
denitrification, as from the values in table 4.6.1, it can be seen that the F/M ratio 
(mgCOD/mgMLVSS.day) was constantly low in both reactors: 
High levels of nitrates/nitrites were often, but not exclusively found when total nitrification 
(zero ammonia) had taken place. Again, the inference in these circumstances is that 
when nitrification is incomplete, for whatever reason, the biological denitrification system 
can fully cope with the lower levels of nitrate/nitrite produced. The influent COD/TKN 
ratio ranged from 5.5-17.9mgCOD/mgTKN with a mean value of 8.3mgCOD/mgTKN. 
The latter is close to the value of 8.4mgCOD/mgTKN reported by Liu et al. (1996) as 
being necessary for complete denitrification. In some instances neither complete 
nitrification nor complete denitrification was achieved. Although nitrification was similar in 
both reactors, denitrification was usually markedly better in reactor 2. 
The phosphorous removal efficiency of the WWTP was extremely poor, despite the 
relatively low levels in the influent. This can be seen in figure 4.6.6. Possible reasons 
have been outlined in previous sections of chapter 4 and are applicable here, especially 
lack of VFA's or increased COD/P ratio in the influent and/or the presence of nitrate in 
the anaerobic zone. The fact that reactor 2, with consistently less nitrates/nitrites 
measured in the effluent also showed consistently better phosphorous removal leads to 
the assumption that the presence of nitrates in the anaerobic zone played at least a 
partial role. The COD/P ratio ranged from 33.2-77.6mgCOD/mgP with a mean of 
50.9mgCOD/mgP. According to Liu et al. (1997), this figure suggests that the GAO's 
would have a competitive advantage over the PAO's, adversely affecting phosphorous 
removal. 
The DSVI values reflected in figure 4.6.8 were consistently higher in reactor 2 than in 
reactor 1 and were above 150mg/L on a number of occasions. The values for reactor 1 
ranged between 100 and 150mg/L. However, the Fl, shown in figure 4.6.10 was similar 
for both reactors throughout. As with Borcherds Quarry (section 4.3), the reactor that 
performed better in terms of nutrient removal, seemed to exhibit a propensity, albeit 
small in this case, for bulking. However, at Macassar there was no significant difference 
in F/M between the reactors. In this case the reactor with the lower DSVI values (reactor 
1) also had the lower VSS concentrations in the mixed liquor (figure 4.6.7), except for 
one month, when levels were equal in the two reactors. 
A point of interest is that filament composition in the two reactors differed slightly from 
month to month, even although the influent was the same. In addition, although the Fl 
was considered normal for both reactors, the DSVI was "raised" in reactor 2. Perhaps the 
link between Fl and MLVSS would be better than that between DSVI and MLVSS, 
because the Fl is a more quantitative measurement of filament abundance, whereas 
DSVI reflects settling, and can thus be influenced by a host of other factors. 
81 
It can once again be speculated that the presence of residual amounts of nitrate/nitrite 
would be conducive to AA bulking using the metabolic hypothesis of Casey eta/. (1999). 
Once again, the reactor with the higher levels of nitrates/nitrites in the effluent, performed 
better in terms of DSVI, making this unlikely. 
By referring to table 4.6.2 it can be seen that M. parvicella and actinomycetes were the 
most prevalent dominant filaments, and the problem with scum formation is thus not 
surprising. It can be speculated that the cause was the presence of large amounts of 
dietary fats in the influent, with other process conditions playing a contributory role. Four 
of the six dominant filaments encountered fall into the "low F/M" category according to 
Jenkins et al. (2004). These are: M. parvicella, actinomycetes, Type 0041, and Type 
1851. The other two, namely H. hydros/sand actinomycetes can be found at a wide 
range of loading levels (Jenkins et al, 2004). M. parvicella did not show any variation 
from winter to summer, and was still a dominant filament in November. 
Notable was the presence of Type 1851 in high numbers and the fact that this organism, 
according to Eikelboom (2004), is commonly found, but almost never dominates in 
domestic WWTP's, and is more likely to prevail in large numbers in industrial plants. In 
such WWTP's there is an abundance of LMW compounds. It would be interesting to 
analyse the composition of the influent to Macassar, and other domestic WWTP's in 
Cape Town with Type 1851 as a dominant filament, to ascertain whether influent 
composition is the reason for it's abundance or whether there are other factors at play. 
For example, the plant manager was worried that incomplete mixing and the creation of 
septic conditions was taking place in some areas within the Carousel system. If this is 
true, these septic conditions could be a contributory factor. 
M. parvicella, actinomycetes and Type 0041 were dominant in random scum samples 
from both reactors. The implication of the former two filaments with scum formation is 
well documented and there is further discussion on this topic in Chapter 5 under sections 
5.1.2.4 and 5.1.2.6. The presence of Type 0041 is not so clear-cut. The organism has a 
hydrophobic Gram-positive cell wall, but it usually has a sheath. However, if the sheath 
became damaged, the organism would presumably also have a propensity to float. Also, 
the filaments were so intertwined that it is possible M. parvicella and actinomycetes 
provided the means of flotation for the entire mass. 
The protozoan and metazoan composition given in table 4.6.3, was such that it reflected 
the presence of varying concentrations of dissolved oxygen, low F/M ratio and a long 
sludge age. The presence of high numbers of P/euromonasspp., such as encountered in 
reactor 2 usually indicates a lack of oxygen or a high sludge load (Eikelboom, 2000). The 
latter can be ruled out, so lack of oxygen is the more likely cause. However, nitrification 
and COD removal were not dramatically affected during this period. Perhaps there was a 
toxic event that led to the demise of most of the ciliate population and to the abundance 
of flagellates thereafter. However, without further data and online DO readings, it is 
difficult to definitively speculate whether the bloom was due to such an occurrence, 
insufficient oxygen or another reason entirely. 
In summary, Macassar WWTP performed poorly in terms of the removal of 
nitrates/nitrites and phosphorous. Lack of phosphorous removal was likely due to the 
high COD/P ratio and the presence of nitrates in the anaerobic zone. The filaments 
encountered were indicative of low F/M conditions, supported by actual values obtained. 
The presence of M. parvicella and actinomycetes points to high levels of dietary fat in the 
influent and explains the problems with intermittent scum formation. The presence of 
bulking conditions was marginal for one of the reactors. 
82 
4.7 MITCHELLS PLAIN WWTP 
4.7.1 PLANT CONFIGURATION AND OPERATING PARAMETERS 
Mitchells plain WWTP is a NDBEPR plant with a UCT configuration (figure 4.1.1 and 
4.1.2). The design capacity is 37 ML/day and there are eight bioreactors named 
alphabetically from A to H, that treat wastewater primarily of domestic origin. Thirty five 
percent of the flow is channeled into 4 of the reactors (C, D, E and F) and the other 65% 
into the larger reactors (G and H). One reactor from each of these groups, namely 
reactor C and reactor G were chosen for the study. The DO in the aerobic zone is 
maintained in the range of 2.0 to 2.5mg/L by means of diffuse aeration. The plant does 
experience intermittent problems with scum formation, particularly in the anoxic zone. 
The scum tends to break up before the weir overflow site and there is no carry over. 
Scum samples from the plant were not analyzed. 
4.7.2 RESULTS 
4.7.2 (a) Operational data 
The influent (I) is the supernatant from the alphabetically named PST's supplying reactor 
G (PST C-F) and reactor H (PST GH). 
The mixed liquor (ML) results are from reactor C and reactor G, the former being fed 
from PST (C-F) and the latter from PST (GH). The mixed liquor from the reactors flows 
into the clarifiers also alphabetically named. Clarifier CD is supplied by reactor C and 
clarifier GH is supplied by reactor G. 
The effluent (E) is the supernatant from clarifiers CD and GH. 
*Note: breaks in the graph lines occur when no data was available 
-C-F ICOD -GH ICOD 
400 
4/6 2/7 30/7 27/8 24/9 22/10 19/11 
Date 
99 
90 
-CD RCOD -GH RCOD 
4/6 2/7 30/7 27/8 24/9 22/10 19/11 
Date 
Figure 4.7.1 Influent COD levels from PST 
C-F (C-F ICOD) and PST GH (GH ICOD) 
at Mitchells plain WWTP in 2007 
Figure 4.7.2 Removal efficiency of COD by 
bioreactors CD (CD RCOD) and GH (GH 
RCOD at Mitchells plain WWTP in 2007 
83 
-C-F ISS -GH ISS 
100 
^M 
4/6 2/7 30/7 27/8 24/9 22/10 19/11 
Date 
-CD ESS -GH ESS 
i i i' i i i ? I"11 
24/9 22/10 19/11 
Figure 4.7.3 Influent suspended solids Figure 4.7.4 Effluent suspended solids 
from PST C-F (C-F ISS) and PST GH (GH from clarifier CD (CD ESS) and clarifier GH 
ISS) at Mitchells plain WWTP in 2007 (GH ESS) at Mitchells plain WWTP in 2007 
-C-F ITKN 
-GH ITKN 
-C-F I AMM 
-C-F IAMM 
27/8 24/9 22/10 19/11 
Date 
-CD ENN 
-GH ENN 
-CD EAMM 
-GH EAMM 
4/6 2/7 30/7 27/8 24/9 22/10 19/11 
Date 
Figure 4.7.5 Influent TKN from PST C-F 
(C-F ITKN) and PST GH (GH ITKN) and 
influent ammonia from PST C-F (C-F 
IAMM) and PST GH (GH IAMM) at 
Mitchells plain WWTP in 2007 
Figure 4.7.6 Effluent nitrates/nitrites from 
clarifier CD (CD ENN) and clarifier GH (GH 
ENN) and effluent ammonia from clarifier 
CD (CD EAMM) and clarifier GH (GH 
EAMM) at Mitchells plain WWTP in 2007 
84 
-C-F ITP 
-GH ITP 
-C-F IOP 
•GHIOP 
-T—m—i—r-r-i—r r i T"i 'i—r-r-i—r-m—r-r-i—r 
4/6 2/7 30/7 27/8 24/9 22/10 19/11 
Date 
?CD EOP -GH EOP 
-l—l—i—i "i II)II—i—i—r-l—m—r 
4/6 2/7 30/7 27/8 24/9 22/10 19/11 
Date 
Figure 4.7.7 Influent total phosphates from 
PST C-F (C-F ITP) and PST GH (GH ITP) 
and influent o-phosphates from PST C-F 
(C-F IOP) and PST GH (GH IOP) at 
Mitchells plain WWTP in 2007 
Figure 4.7.8 Effluent cr-phosphates from 
clarifier CD (CD EOP) and clarifier GH (GH 
EOP) at Mitchells plain WWTP in 2007 
-C-F I ALK 
-CD EALK 
-GH IALK 
-GHALK 
450 
400 
350 
-300 
E 250 
O 200 
O 150 
100 
50 
jpffiP^ 
wjVWSp *&*& 
4/6 2/7 30/7 27/8 24/9 22/10 19/11 
Date 
-C MLSS 
-C MLVSS 
-G MLSS 
-G MLVSS 
10000 
o) 8000 
6000 
4000 
2000 
th\#^Y*i 
111111111 
4/6 2/7 30/7 27/8 24/9 22/10 19/11 
Date 
Figure 4.7.9 Influent alkalinity from PST C-
F (C-F IALK) and PST GH (GH IALK) and 
effluent alkalinity from clarifier CD (CD 
EALK) and clarifier GH (GH ALK) at 
Mitchells plain WWTP in 2007 
Figure 4.7.10 Values for mixed liquor 
suspended solids in reactor C (C MLSS) 
and reactor G (G MLSS) and and mixed 
liquor volatile suspended solids in reactor 
C (C MLVSS) and reactor G (G MLVSS) at 
Mitchells plain WWTP in 2007 
85 
250 
-C SVI -*-G SVI —*r-C DSVI -•—G DSVI 
0 4 
<p <p <p to DOfiOCOCO^ffiQP ^?*-coujcMO>f«-«©<oc«>©f«-co©f«-^-^C^^^^^^^ 
*- T- CM t-CMtO i- N N t-t-CMt-0OlfiCNCnifiNO5<O •«- CM CM
 T- T- CM 
date 
Figure 4.7.11 Values of sludge volume index for reactor C (C SVI) and reactor G (G SVI) 
and dissolved sludge volume index for reactor C (C DSVI) and reactor G (G DSVI) at 
Mitchells plain WWTP in 2007 
—?—COD/TKN -ENN 
4/6 2/7 30/7 27/8 24/9 22/10 19/11 
Date 
-ITKN/COD -ENN 
4/6 2/7 30/7 27/8 24/9 22/10 19/11 
Date 
Figure 4.7.12 Ratio of influent COD/TKN 
plotted against the effluent levels of 
nitrates/nitrites from reactor C at Mitchells 
plain WWTP in 2007 
Figure 4.7.13 Ratio of influent COD/TKN 
plotted against the effluent levels of 
nitrates/nitrites from reactor G at Mitchells 
plain WWTP in 2007 
86 
TABLE 4.7.1 FOOD TO MICROORGANISM (F/M) RATIO IN REACTOR C AND 
REACTOR G OF MITCHELLS PLAIN WWTP IN 2007 
REACTOR C REACTOR G 
June 0.19 mgCOD/mgVSS.day 0.18 mgCOD/mgVSS.day 
July 0.17 mgCOD/mgVSS.day 0.10 mgCOD/mgVSS.day 
August 0.23 mgCOD/mgVSS.day 0.27 mgCOD/mgVSS.day 
October 0.21 mgCOD/mgVSS.day 0.17 mgCOD/mgVSS.day 
November 0.19 mgCOD/mgVSS.day 0.14 mgCOD/mgVSS.day 
4.7.2 (b) Microscopic sludge analysis 
This was performed monthly on the following dates: 18/6/07, 16/7/07, 20/8/07, 24/9/07, 
22/10/07 and 26/11/07. 
• Floe structure 
Reactor C 
The floes were round in shape, compact in structure and firm in strength for the duration 
of the study except for the structure in October, which was open. The floe size was 
predominantly large (>250nm) in August, but medium-sized for the balance. 
Reactor G 
The floes were round in shape, compact in structure and firm in strength for the duration 
of the study (see figure 4.7.14). The floe size was medium in June and July, but 
predominantly large from August to November. 
• Diversity 
There was a moderate amount of diversity with scanty monocolonies in all samples, 
except the sample from reactor C in October, which had a moderate number of 
monocolonies, probably G-bacteria. 
Figure 4.7.14 Micrograph of Wet mount showing the 
floe structure encountered at Mitchells plain reactor 
G in August 2007, namely large, compact and firm 
87 
• Filament index 
—?—Reactor C —•— Reactor G 
~ 3-u> 
? 
2. 2- Hf— HI -Hi ?— ?— 
?\ . 
?^ "*^**"-^»_ » 
June July Aug Sept Oct 
Month 
Nov 
Figure 4.7.15 Filament index of reactor C and 
reactor G at Mitchells plain WWTP in 2007. The 
results were the same in June, July and August 
TABLE 4.7.2 DOMINANT AND SECONDARY FILAMENTOUS ORGANISMS IDENTIFIED FROM THE 
MIXED LIQUOR OF REACTOR C AND REACTOR G AT MITCHELLS PLAIN WWTP IN 2007 
AS DOW INANT F LAMENTS 
June July Aug Sept Oct Nov % Prevalence 
CandG 
(dominant) 
% Prevalence 
CandG 
(overall) 
Type 0092 X 
(CG) 
X 
(C,G) 
X 
(C,G) 
X 
(C,G) 
X 
(C) 
X 
(C,G) 
92 100 
Type 1851 X 
(G) 
X 
(G) 
X 
(G) 
25 92 
M. parvicella X 
(C) 
8 25 
AS SECONDARY FILAMENTS 
Type 0092 X 
(G) 
> Also dominant 
J filaments 
Type 1851 X 
(G) 
X 
(C,G) 
X 
(C,G) 
X 
(C) 
X 
(C) 
X 
(C) 
M. parvicella X 
(C) 
X 
(C) 
Type 0041 X 
(C) 
X 
(C,G) 
X 
(C,G) 
X 
(C.G) 
X 
(C,G) 
X 
(C,G) 
0 92 
Type 1701 X 
(G) 
X 
(G) 
0 17 
Flexibacter spp. X 
(C,G) 
0 17 
Type 021N X 
(G) 
X 
(G) 
0 17 
Type 0803 X 
(C) 
0 8 
Thiothrixspp. X 
(G) 
0 8 
88 
TABLE 4.7.3 PROTOZOA/METAZOA IDENTIFIED IN THE MIXED LIQUOR FROM REACTOR C AND 
REACTOR G AT MITCHELLS PLAIN WWTP IN 2007 
SCANTY 
June July Aug Sept Oct Nov 
Sessile ciliates Carchesium spp. X 
(C,G) 
X 
(C.G) 
X 
(G) 
X 
(G) 
Epistylis spp. X 
(C) 
X 
(C.G) 
X 
(C) 
X 
(C.G) 
X 
(C.G) 
Suctorean X 
(G) 
Vaginicola spp. X 
(C.G) 
Vorticellaspp. X 
(G) 
X 
(C,G) 
X 
(C) 
X 
(C.G) 
X 
(C.G) 
X 
(C.G) 
Crawling ciliates Aspidisca spp. X 
(C.G) 
X 
(C) 
X 
(C.G) 
X 
(C.G) 
Chilodonella spp. X 
(C) 
X 
(G) 
X 
(C.G) 
X 
(C.G) 
Trachelophyllum spp. X 
(G) 
X 
(G) 
X 
(G) 
X 
(G) 
Free-living ciliates Blepharisma spp. X 
(G) 
X 
(G) 
X 
(G) 
Colpidium spp. X 
(C.G) 
X 
(C) 
X 
(C) 
Euplotesspp. X 
(G) 
X 
(C,G) 
L/tonotusspp. X 
(G) 
X 
(C) 
X 
(C,G) 
Spirostomum spp X 
(C) 
Unidentified X 
(C) 
X 
(G) 
Flagellates Bodo spp. X 
(C) 
X 
(G) 
X 
(C.G) 
X 
(G) 
X 
(C.G) 
Peranema spp. X 
(C) 
X 
(C) 
X 
(C.G) 
Unidentified X 
(C) 
X 
(G) 
Amoebae X 
(C) 
X 
(C) 
X 
(C.G) 
X 
(G) 
X 
(C,G) 
Testate amoebae X 
(C,G) 
Heliozoa X 
(C) 
X 
(C) 
Oligochaeta X 
(C) 
X 
(G) 
X 
(C.G) 
X 
(G) 
Rotifera X 
(G) 
X 
(C.G) 
X 
(C.G) 
X 
(C.G) 
X 
(C.G) 
X 
(C.G) 
Tardigrades X 
(G) 
X 
(C) 
89 
TABLE 4.7.3 (CONTINUED) PROTOZOA/METAZOA IDENTIFIED IN THE MIXED LIQUOR FROM 
REACTOR C AND REACTOR G AT MITCHELLS PLAIN WWTP IN 2007 
MODERATE 
June July Aug Sept Oct Nov 
Attached ciliates Vorticella spp. X 
(G) 
Crawling ciliates Aspidisca spp. X 
(G) 
X 
(C) 
X 
(CG) 
Tardigrades X 
(C) 
4.7.3 DISCUSSION 
The influent into each of the two reactors was not from the same PST source. Therefore 
influent levels of certain substrates differed considerably during the trial period, notably 
the influent COD, SS, and TKN. Levels of these were usually higher from the PST 
supplying reactor G. Influent ammonia levels also differed, but neither PST was prone to 
supplying consistently higher levels than its counterpart. 
Both reactor C and G performed well in terms of the removal of COD (figure 4.7.2), SS 
(figure 4.7.3 and 4.7.4) and ammonia (figure 4.7.7 and 4.7.8). There was a large drop in 
alkalinity, depicted in figure 4.7.9, from PST effluent to clarifier effluent, due to the high 
degree of nitrification taking place. 
Although nitrification was efficient in both reactors for most of the study period, residual 
nitrates and nitrites were constantly present, shown in figure 4.7.8. Denitrification took 
place to a larger extent in reactor C, with satisfactory levels of nitrates/nitrites in the 
clarifier effluent being achieved at times. Complete denitrification is not expected in a 
WWTP with the UCT configuration as there is no second anoxic zone to enable 
denitrification of all nitrification products formed in the aerobic zone. Although there 
should be a high mixed liquor re-circulation from the aerobic to the anoxic zone, there 
will still be some nitrification products that exit the aerobic zone. However, values 
obtained were high, especially from reactor G. As described for other WWTPs in 
previous sections of this chapter, on the occasions that ammonia levels increased, there 
was an accompanying decrease in nitrates/nitrites. 
Operating conditions leading to poor denitrification were discussed in section 4.4.3. 
Regarding the lack of electron donor as having an adverse effect on denitrification: the 
influent COD/TKN ratio for reactor C ranged between 6.2-13.3mgCOD/mgTKN (mean 
8.3mgCOD/mgTKN). The mean for reactor G was 9.9mgCOD/mgTKN. Thus, the mean 
from reactor C was much closer to the value of 8.4mgCOD/mgTKN reported by Kujawa 
eta/. (1996), as being necessary for complete denitrification. If this figure is correct, and 
if lack of electron donor did play a role in poor denitrification in reactor C, it would explain 
the more erratic nature of denitrification from this reactor - there would have been 
periods where electron donor was insufficient interspersed with periods of sufficiency. 
This is substantiated by the fact that when the COD/TKN ratio was plotted against 
effluent nitrates/nitrites, there was a correlation between increased influent COD/TKN 
and more efficient denitrification in reactor C. This is especially apparent around the 
beginning of September 2007. There was no such correlation in reactor G. These 
relationships can be seen in figures 4.7.12 and 4.7.13. This suggests that denitrification 
90 
in reactor C, with a smaller COD/TKN ratio, was adversely affected by lack of electron 
donor to some extent. The mechanism for poor denitrification in the case of reactor G, 
with a higher COD/TKN ratio, overshadowed any effect that a lack of electron donor may 
have had (if any). 
The efficiency of phosphorous removal shown in graphs 4.7.7 and 4.7.8, was erratic in 
reactor C, but was constantly poor in reactor G. In all cases where more than one reactor 
per WWTP was included, there was a comparative correlation between denitrification 
efficiency and phosphorous removal. Reactors C and G at Mitchells plain are not 
identical and receive influent from different PST's. Even so, reactor C, with lower levels 
of nitrates and nitrites in the clarifier effluent generally performed better regarding 
phosphorous removal than reactor G. Values for reactor G were constantly poor, while 
those from reactor C were more erratic. 
Once again, it can be inferred that the presence of nitrates in the anaerobic zone 
interfered with the biological process of phosphorous removal. The influent COD/P ratio 
in reactor C was also lower than that of reactor G: 42.6-69.9mgCOD/mgP (mean 
53.6mgCOD/mgP) and 66.9-83.5 (mean 66.9mgCOD/mgP). These levels should 
enhance the growth of GAO's over PAO's according to Liu et al. (1997), but would be 
more pronounced for reactor G. 
The other consistent comparison that was a feature of the study was that the reactor that 
performed better in terms of nitrate/nitrite removal showed consistently higher DSVI 
values. These are reflected in figure 4.7.11. This phenomenon also occurred at Mitchells 
plain WWTP and is elucidated upon in chapter 6. However, in this case neither the DSVI 
values nor the Fl values were ever high enough to indicate the presence of bulking 
conditions at Mitchells Plain WWTP. 
There was a large difference in the MLSS and MLVSS values of reactor C and G, seen 
in figure 4.7.10, but the operation of the reactors was such that loading rates, given in 
table 4.7.1 remained similar. The incomplete denitrification could theoretically lead to AA 
bulking according to the hypothesis of Casey eta/. (1999). However, the chosen bulking 
indicators of Fl and DSVI were never raised, and the DSVI was in fact lower for the 
reactor with the most residual nitrates/nitrites. In addition, as already noted, the reactor 
with the lower values of nitrates/nitrites in the clarifier effluent exhibited the higher DSVI 
values. 
Referring to table 4.7.2, it can be seen that Type 0092 was the major dominant filament 
encountered in both reactors. M parvicella was present as a dominant species on one 
occasion in reactor C. In reactor G, Type 1851 was co-dominant from September, 
possibly being linked to the higher settling values from this reactor. Once again, this 
filament was unexpectedly found as a dominant species in a domestic wastewater 
removal plant (Eikelboom, 2000). All three dominant filaments are classed as low F/M by 
Jenkins et al. (2004). This correlates well with the calculated loading rates. The 
association of the ubiquitous Type 0092 with non-bulking conditions was established in 
the meta-analysis, and conditions leading to the competitive growth of this organism 
should be encouraged. 
In summary, both reactors from the Mitchells Plain WWTP gave sub-optimal results in 
terms of nutrient removal (phosphorous and nitrates/nitrites). The reactor that showed 
the worst nutrient removal record exhibited the lowest DSVI. The dominant filaments 
were all classed as low F/M and bulking conditions were not encountered at any stage. 
91 
4.8 PAROW WWTP 
4.8.1 PLANT CONFIGURATION AND OPERATING PARAMETERS 
Parow WWTP is a small plant treating designed to treat 1ML effluent/day. There is no 
primary settling and the configuration of the bioreactor is MLE with surface aeration 
(refer to figure 4.2.1 and 4.2.2). The theoretical operational DO is 2.3 mg/L. The plant is 
generally overloaded in terms of capacity and is due to be upgraded in the near future. 
There are often operational problems with wasting leading to MLSS values above the 
ideal range. 
4.8.2 RESULTS 
4.8.2 (a) Operational data 
The influent (I) is raw influent. There are no PST's. 
The mixed liquor (ML) results are from the bioreactor. 
The effluent (E) is the supernatant from the clarifier. 
*Note: breaks in the graph lines occur when no data was available 
-Raw flow —•—Capacity 
1.3 
1.2 
3 1.1 r 
!? »»»???«?»»»» 
0.9 i" i T i'"i 'i i" i i "r 'i i-i i 'i- I'T i -I i i "'i""i i" 
6/6 4/7 1/8 29/8 3/10 1/11 28/11 
Date 
99 
98 
97 
91 
90 
89 
-RCOD 
? »? 
i' i"'i—i—i"r i" i r i' i i 'i i—i—r-i—m—i r"i—r 
6/6 4/7 1/8 29/8 3/10 1/11 28/11 
Date 
Figure 4.8.1 Graph of inflow of raw 
wastewater into Parow WWTP plotted 
against the design capacity of the plant in 
2007 
Figure 4.8.2 Graph depicting the removal 
of COD (RCOD) from Parow WWTP in 
2007 
92 
•EAMM -«—ENN 
6/6 4/7 1/8 29/8 3/10 1/11 28/11 
Date 
•IALK -EALK 
400 
350 
300 
S.250 
E 2 200 
O o 
3 150 
100 
50 
/wy\/A/V 
I I "I—I "I' I I—I V'l 'I "I1 I— I 'I" I")"1 I—r~1—r 
6/6 4/7 1/8 29/8 3/10 1/11 28/11 
Date 
Figure 4.8.3 Graph depicting the effluent Figure 4.8.4 Graph depicting the influent 
ammonia (EAMM) and effluent alkalinity (IALK) and effluent alkalinity 
nitrates/nitrites (ENN) from Parow WWTP (EALK) values at Parow WWTP in 2007 
in 2007 
-ITP -«—IOP —A— EOP 
25 
vi 'i—i—r r r i—p-n—i—i ' IMI 'i i' i 
6/6 4/7 1/8 29/8 3/10 1/11 28/11 
Date 
•SVI -DSVI 
-T—i )' i" i—r-i—i—i—i—i—r-i—r—i—i—r-i—\—i—i—r 
6/6 4/7 1/8 29/8 3/10 1/11 28/11 
Date 
Figure 4.8.5 Graph showing the influent Figure 4.8.6 Graph showing the SVI and 
total phosphates (ITP) and influent a- DSVI values from the mixed liquor at 
phosphates (IOP) as well as the effluent a- Parow WWTP during 2007 
phosphates (EOP) at Parow WWTP in 
2007 
93 
TABLE 4.8.1 FOOD TO MICROORGANISM (F/M) RATIO IN REACTOR OF PAROW 
WWTP IN 2007 
June 0.19 mgCOD/mgVSS.day 
July 0.15 mgCOD/mgVSS.day 
September 016 mgCOD/mgVSS.day 
October 0.23 mgCOD/mgVSS.day 
November 0.20 mgCOD/mgVSS.day 
4.8.2.1 Microscopic sludge analysis 
This was performed monthly on the following dates: 28/6/07, 26/7/07, 23/8/07, 24/9/07, 
25/10/07 and 22/11/07. 
• Floe structure 
The floes were round in shape, open in structure and firm in strength from June to 
September. In October and November, the shape changed from round to irregular. The 
floes were medium-sized from June to August, became large in September and 
remained large in October. In these latter months, the floes exhibited extensive bridging, 
the large floes appearing to be smaller floes joined together by bridging. In November, 
this phenomenon was so extensive, that it was impossible to accurately determine floe 
size. In this month the floes appeared as large open matts. In September and October, 
the large number of nematodes that were voraciously feeding on the floes disturbed the 
floe structure, leaving holes in the floes (see figure 4.8.7). 
Figure 4.8.7 Wet mounts of mixed liquor samples taken from Parow WWTP in September 
2007. Micrograph A shows the structure of the floes that has been disturbed by voracious 
feeding of the large nematode population. Micrograph B shows an example of two of 
these nematodes. 
94 
• Diversity 
There was a moderate amount of diversity with scanty monocolonies in all samples, 
except for November, when there were no monocolonies seen. 
• Filament index 
5-, 
? Filament index 
4 -
— 3-
IA 
^^"~* '" *-*--~^.— 
82-
June July Aug Sept Oct 
Month 
Nov 
Figure 4.8.8 Graph depicting the rising filament 
index from the activated sludge at Parow WWTP 
from June to October 2007 
TABLE 4.8.2 DOMINANT AND SECONDARY FILAMENTOUS ORGANISMS IDENTIFIED IN THE MIXED 
LIQUOR OF PAROW WWTP IN 2007 
AS DON INANT F LAMENTS 
June July Aug Sept Oct Nov % Prevalence 
(dominant) 
% Prevalence 
(overall) 
Actinomycetes X X X X X 83 100 
Type 1851 X X X X X 83 100 
Type 0092 X X X 50 100 
Type 0041 X X 33 50 
Actinomycetes X 
L Also dominant 
f filaments 
Type 1851 X 
Type 0092 X X X 
Type 0041 X 
Type 021N X X X X 0 67 
M. parvicella X X X 0 50 
H. hydrosis 0 17 
95 
TABLE 4.8.3 PROTOZOA/METAZOA IDENTIFIED IN THE MIXED LIQUOR OF PAROW WWTP IN 2007 
SCANTY 
June July Aug Sept Oct Nov 
Sessile ciliates Epistylis spp. X X X X 
Opercularia spp. X X 
Crawling ciliates Aspidisca spp. X X X 
Chilodonella spp. X 
Unidentified X 
Free-living ciliates Euplotes spp. X 
Flagellates Bodo spp. X X 
Peranema spp. 
Pleuromonas spp. 
Trepomonas spp. 
Rotifers X X X X X 
Nematodes X X 
MODERATE 
Sessile ciliates Epistylis spp. X 
Crawling ciliates Aspidisca spp. X 
Nematodes X X 
NUMEROL S 
Crawling ciliates Aspidisca spp. X 
Flagellates Monsiga spp. X 
4.8.3 DISCUSSION 
Removal of COD was good throughout (figures 4.8.1 and 4.8.2). From graph 4.8.8, it can 
be seen that nitrification and denitrification was extremely unstable. At times effluent 
ammonia levels were high, and effluent nitrate/nitrites were low to absent. At other times 
the converse was true. The other WWTP's discussed in this chapter generally exhibited 
either poor nitrification or poor denitrification, but none gave such aberrant results with 
both. As expected, enhanced consumption of alkalinity mirrored periods of good 
nitrification and vice versa, graphically depicted in figures 4.8.3 and 4.8.4. 
Phosphorous removal too was extremely unstable (figure 4.8.5). There was a very strong 
link between poor denitrification and poor phosphorous removal. This is evidence that 
the presence of nitrates/nitrites in the anoxic zone was responsible for deterioration in 
phosphorous removal. Conversely, when there were no residual nitrates/nitrites in the 
effluent, and by association, none in the anoxic zone, phosphorous removal was 
enhanced. The latter also occurred in Bellville WWTP, which has the same configuration. 
It thus lends credence to the speculation that lack of nitrates/nitrites due to poor 
nitrification, did indeed convert the anoxic zone into a de facto anaerobic zone with 
resulting EBPR. This occurred intermittently at Parow WWTP and on a continual basis 
at Bellville WWTP. 
The DSVI values reflected in figure 4.8.6 indicated the presence of bulking conditions for 
most of the study period, with especially high values during the latter stages of the study. 
The Fl values depicted in figure 4.88 also indicated the presence of bulking conditions 
from August to November. 
96 
Table 4.8.2 reflects the dominant and secondary filaments identified. No noticeable 
change in species dominance occurred with an increase in DSVI. In fact, Type 0092, not 
strongly associated with bulking conditions by the meta-analysis, was one of the 
dominant filaments at this stage. There was an increase in loading rates, given in table 
4.8.1 at this stage that may have played a role in filament abundance. 
All of the dominant species except the actinomycetes are classed as low F/M by Jenkins 
et a/. (2004). Actinomycetes are able to grow over a range of loading rates. Type 1851 
was also found as a dominant in other WWTP's, notably at Bellville, another MLE 
configured plant, where there was an increased DSVI and Fl but also a high F/M. It is 
unlikely that Type 0092 had any effect on the advent of bulking conditions, as this 
filament tends to hide in the floes. The increased DSVI and Fl may have been due to a 
relative change in the ratio of heterotrophs to filaments induced by predation of 
nematodes that allowed the existing filamentous population to flourish. 
The diversity of the protozoa and metazoa was low. This was probably due to the 
continual change in environmental conditions that must have been present to create 
such erratic nutrient removal results. Only the species able to adapt to changing 
conditions would prevail. There were interesting blooms of particular species at times: 
> The flagellate Monsiga spp. an indicator organism for high sludge load and or 
shortage of oxygen (Eikelboom, 2000) was present in large numbers in June. 
Concurrent with this was a poor rate of nitrification. As the calculated F/M values 
were low, loss of nitrification was probably associated with low DO. 
> Large numbers of nematodes were feeding on the floes. These worms were 
present from July, but increased in number until October. The physical 
disturbance of the floes as well as consumption of heterotrophs possibly played a 
role in the increased DSVI. The nematodes were not capable of feeding on the 
filamentous population, giving the latter a competitive advantage. 
In summary, Parow WWTP functioned in a particularly unstable manner in terms of 
nutrient removal and was prone to bulking. There was excellent evidence of a link 
between the absence of nitrates/nitrites in the anoxic zone and phosphorous removal 
efficiency that can be extrapolated to other MLE WWTP's such as Bellville. Changes in 
nitrification/denitrification patterns were most likely associated with changes in DO. 
Unfortunately, the DO results could not be obtained to substantiate this fact 
unequivocally. 
97 
4.9 POTSDAM WWTP 
4.9.1 PLANT CONFIGURATION AND OPERATING PARAMETERS 
Potsdam WWTP uses both activated sludge bioreactors and fixed medium (stone) 
trickling filter systems to treat the influent. This influent consists of primarily domestic 
waste with an industrial component. The trickling filter system is ageing and function is 
poor. The plant is presently being upgraded to increase both capacity and efficiency. 
Approximately half of the influent is treated in the two identical bioreactors after 
undergoing primary settling. The plant operates in the UCT configuration with surface 
aeration. Potsdam WWTP experiences intermittent scum problems, mainly in winter and 
during periods of overloading. 
4.9.2 RESULTS 
4.9.2 (a) Operational data 
Influent (I) is the supernatant from the PST. 
The mixed liquor (ML) results are from combined samples from both bioreactors. 
The effluent (E) is the supernatant from the appropriate clarifier. 
*Note: breaks in the graph lines occur when no data was available 
?Raw Flow ? PSTAFlow * Capacity 
45 
40 
35 
f3„ 
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20 
15 
10 
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T I I I I I | ''I ' |f ?T-",|'"r|' l"T I Vi|ifirTTmri,| IMJ ,r„ 
5/6 3/7 31/7 28/8 25/9 23/10 20/11 
Date 
E 
o. 
?ITP -IOP -EOP 
5/6 3/7 31/7 28/8 25/9 23/10 20/11 
Date 
Figure 4.9.1 Graphs showing the raw flow 
into Potsdam WWTP in 2007 as well as 
the design capacity. In addition, the flow 
into the PST feeding the bioreactors is 
given (PSTA). 
Figure 4.9.2 Graph depicting the levels of 
influent total phosphates (ITP) and a-
phosphates as well as the effluent levels of 
a-phosphates at Potsdam WWTP in 2007 
98 
•ICOD 
l 'i r i \—I1" l rill"—l T i 'I""I' i' i i "i i' 
6/6 4/7 1/8 29/8 3/10 1/11 28/11 
Date 
•RCOD 
Q O 
U 
1 
o 
£ 
100 
95 
90 -
85 
80 
75 
70 
65 
60 i i i i i i i i i i—i 'i 'i i i—i i ' i" i "i'""i—r-r 
5/6 3/7 31/7 28/8 25/9 23/10 20/11 
Date 
Figure 4.9.3 Influent COD (ICOD) from the Figure 4.9.4 COD removal efficiency 
PST at Potsdam WWTP in 2007 (RCOD) by the bioreactor at Potsdam 
WWTP in 2007 
•ITKN -IAMM 
«—*^ 
i"i i"1 i' r i'" i"'i i "i" 'I111 i""i"T'"r"i i'"i i' ?[?" |"'|'"|—rr 
5/6 3/7 31/7 28/8 25/9 23/10 20/11 
Date 
•EAMM -ENN 
5/6 3/7 31/7 28/8 25/9 23/10 20/11 
Date 
Figure 4.9.5 Graph depicting the influent Figure 4.9.6 Graph depicting the effluent 
ammonia (IAMM) and influent TKN (ITKN) ammonia (EAMM) and nitrates/nitrites 
at Potsdam WWTP in 2007 (ENN) at Potsdam WWTP in 2007 
99 
Figure 4.9.7 Graph depicting the SVI and DSVI values experienced from the mixed liquor 
at Potsdam WWTP in 2997 
TABLE 4.9.1 FOOD TO MICROORGANISM (F/M) RATIO IN BIOREACTOR OF 
POTSDAM IN 2007 
June 0.12 mgCOD/mgVSS.day 
July 0.09 mgCOD/mgVSS.day 
September 0.13 mgCOD/mgVSS.day 
October 0.08 mqCOD/mgVSS.day 
November 0.06 mgCOD/mgVSS.day 
4.9.2 (b) Microscopic sludge analysis 
This was performed monthly on the following dates: 20/6/07, 18/7/07, 29/8/07, 19/9/07, 
24/10/07 and 21/11/07. 
• Floe structure 
The floes were round in shape, open in structure and firm in strength in all samples. The 
floes were medium in size in June and September. In June, there was bridging between 
the floes. In July and August, there were numerous pin floes as well as large open floes 
with extensive bridging. In October and November, the floes were large and open with 
extensive bridging (see figure 4.9.8A). 
• Diversity 
Diversity was low in June, July, August and November, medium-low in September and 
medium in October. Notable was the abundance of monocolonies from June to October 
(see figure 4.9.8B). However, by November the numbers were low. On staining, the 
majority appeared to be GAO's (see section 4.9.3 for further details). 
100 
Figure 4.9.8 Wet mount (A) of mixed liquor sample taken from Potsdam WWTP in 
July 2007 showing floe structure with numerous filaments and bridging between the 
floes and Neisser stain (B) of mixed liquor taken from Potsdam WWTP in August 2007 
showing monocolonies staining as GAO's. 
• Filament index 
—?—Filament index 
^ -, 
4 -
_ 3 -
«9 
2-2-
1 -
n -
*\ t^-^* 
^Sssv//' 
June July Aug Sept Oct Nov 
Month 
Figure 4.9.9 Graph representing the Fl values 
obtained at Potsdam WWTP in 2007 
101 
TABLE 4.9.2 DOMINANT AND SECONDARY FILAMENTOUS ORGANISMS IDENTIFIED FROM THE 
MIXED LIQUOR AT POTSDAM WWTP IN 2007 
AS DOMINANT F LAMENTS 
June July Aug Sept Oct Nov % Prevalence 
(dominant) 
% Prevalence 
(overall) 
Type 0092 X X X X X X 100 100 
M. parvicella X 16 100 
AS SECONDARY FILAMENTS 
M. parvicella X X X X X l Also dominant 
?> filaments 
Type 1851 X X X X 0 67 
Actinomycetes X X X X 0 67 
Type 021N X X X 0 50 
Type 0041 X X X 0 50 
N. limicola\\\ X 0 16 
TABLE 4.9.3 PROTOZOA/METAZOA IDENTIFIED IN THE MIXED LIQUOR FROM KRAAIFONTEIN WWTP 
IN 2007 
SCANTY 
June July Aug Sept Oct Nov 
Sessile ciliates Carchesium spp. X 
Epistylis spp. X X 
Vorticella spp. X X X X 
Crawling ciliates Asp/d/sca spp. X X X X 
Chilodonella spp. X X 
Trachelophyllum spp. X X X X 
Free-living ciliates Colpidium spp. X X X 
Litonotus spp. X X X 
Unidentified X X X 
Flagellates Bodo spp. X 
Peranema spp. X X X 
Unidentified X 
Amoebae X X 
Rotifera X X X X X X 
MODERATE 
Crawling ciliates Aspidisca spp. X 
Flagellates Peranema spp. X 
Rotifera X 
102 
4.3 DISCUSSION 
Potsdam WWTP was overloaded in terms of volume for the entire study period as shown 
in figure 4.9.1. Despite this, the removal of COD was generally efficient, albeit erratic 
during a period in July (unexplained). The influent COD and COD removal values are 
reflected in figures 4.9.3 and 4.9.4. 
Nitrification was efficient for most of the study period, but residual nitrates/nitrites were 
present in the clarifier effluent (figures 4.9.5 and 4.9.6). The values were never very high 
and not unexpected for a WWTP with a UCT configuration. 
Most of the study WWTP's that exhibited residual nitrates/nitrites in the clarifier effluent 
showed poor phosphorous removal. This was not the case for Potsdam WWTP, and 
removal of this nutrient was generally excellent, except for a period in November, when 
both influent and effluent values increased slightly (refer to figure 4.9.3). In the earlier 
months, moderate numbers of monocolonies were observed in the mixed liquor samples. 
These numbers were far greater than those from any of the other WWTP's (barring some 
samples from Kraaifontein). In November, there was both a decrease in monocolonies 
and phosphorous removal. The majority of the monocolonies stained as GAO's (or G-
bacteria). The cell wall, but not the contents of G-bacteria stain with the Neisser stain, 
but genuses may be either Gram positive or Gram negative. The microbial composition 
in terms the presence of large numbers of GAO organisms as well as the filamentous 
and protozoan/metazoan population was remarkably similar to that found at Kraaifontein 
WWTP. By comparing the relevant tables from each of these WWTPs (table 4.5.2 with 
4.9.2 and 4.5.3 with 4.9.3), this can be clearly seen. Both WWTPs have the same 
configuration (UCT) and mode of aeration (surface). Both experienced similar low 
loading rates and influent COD values (figures 4.5.1 and 4.9.3 and tables 4.5.1 and 
4.9.1). 
The COD/P ratio at Potsdam WWTP ranged from 51.6-65.9mgCOD/mgP with a mean 
value of 57.1mgCOD/mgP. These values, according to Liu et al. (1997), should favour 
the growth of GAO's over PAO's. However, WWTP's with lower COD/P values than 
those obtained at Potsdam were far less efficient for the removal of phosphorous. The 
amount of VFA's and nitrates in the anaerobic zone were unfortunately unknown. In 
terms of nutrient removal, the performance at Potsdam WWTP was also similar to that 
experienced at Kraaifontein WWTP. 
Conditions in terms of the COD/P ratio encountered at Potsdam WWTP would appear to 
support the growth of GAO's in preference to PAO's, according to Liu et al. (1997). In 
addition, many GAO's were seen in the mixed liquor samples. Despite these findings, 
phosphorous removal was efficient. This seemingly presents an anomaly. To enhance 
the understanding of the dynamics of phosphorous removal at the Cape Town WWTP's 
there is a need to perform comparative measurements of VFA's, nitrates and oxygen in 
the anaerobic zones of the bioreactors. 
In chapter 2, the hypothesis of Liu et al. (1997), outlining the metabolic mechanism and 
operating conditions responsible for competition between the GAO's and PAO's is 
described in detail. However, it seems that not all representatives of the phylogenetically 
diverse group of GAO's are capable of anaerobic synthesis of intracellular 
polysaccharides. Seviour etal. (2000) examined pure cultures of Amaricoccus spp. and 
ascertained that although some stains can synthesize intracellular polysaccharides in 
large amounts under aerobic conditions using either glucose or acetate as substrate, 
they were not capable of doing so under anaerobic conditions. Thus, with this organism, 
103 
there is no direct evidence to support the theory of Liu et al. (1997). In the case of 
Potsdam, with large numbers of GAO's and high COD/P ratios concurrent with efficient 
phosphorous removal, the supposition is that the resident G-bacteria (of unknown 
phylogeny) did not compete against the PAO's under anaerobic conditions. Without 
further details on the composition of nutrients in the various reactor zones, it is not 
possible to speculate further on the relative abundance of these organisms. All of the 
above assumes that the Potsdam organisms were indeed GAO's and not PAO's. 
Identification by one of the molecular techniques would be necessary to definitively 
identify these bacteria. It must be pointed out that organisms staining as classic PAO's 
were also observed in the mixed liquor, but were considerably outnumbered by the 
GAO's. 
The DSVI values shown in graph 4.9.7 were only higher than 150ml/g in July and 
August. This was the indicator value chosen to represent the presence of bulking 
conditions. The Fl however, was less than the similarly chosen indicator value only in 
August. Thus, both the appearance of the floes and the filament index point to the 
presence of possible bulking, but this was not reflected in the DSVI values. The 
dominating filament throughout the study was Type 0092. In the meta-analysis, this 
organism was not highly associated with bulking in terms of DSVI and Fl. This filament is 
known for growing inside the floes and not affecting settling (Eikelboom, 2000). The 
secondary filaments that grew outside and between the floes, such as M. parvicella, 
Type 1851 and actinomycetes, were probably responsible for the high Fl values. Both 
Type 1851 and actinomycetes were linked to bulking in the meta-analysis, so other 
factors, such as the large number of monocolonies in the mixed liquor may have played 
a role in the enhanced settling. 
The dominant filament, Type 0092 is classed as low F/M by Jenkins eta/. (2004), which 
substantiates this finding. The constant presence of M. parvicella and actinomycetes 
may possibly be related to dietary fats in the influent. It is also highly likely that these 
organisms are responsible for the intermittent problems with scum formation 
experienced by Potsdam WWTP. There was no variation in the prevalence of Micorthrix 
parvicella from winter to summer. This phenomenon was not unique to Potsdam. 
Apart from the similarity of the protozoan and metazoan community to that at 
Kraaifontein WWTP, there was nothing notable in the range of these organisms 
encountered at Potsdam WWTP. The presence of a number of ciliates, flagellates, 
amoeba and rotifera throughout the study period adequately reflect the alternating 
anaerobic and aerobic conditions, lack of toxic substances and adequate sludge age. 
Neither the presence of Peranema spp. or rotifera in moderate numbers in September is 
a cause for concern at this point as no literature was found linking either of these 
organisms with specific process conditions. 
In summary, the bioreactors at Potsdam WWTP performed well in terms of nutrient 
removal. The removal of phosphorous was especially efficient in comparison to most of 
the other WWTP's with residual nitrates/nitrites in the clarifier effluent. The presence of a 
high COD/P ratio and large numbers of GAO's should, in theory, result in decreased 
phosphorous removal due to the competitive advantage of GAO's over PAO's. The 
results obtained were thus anomalous, and further identification of the monocolonies, as 
well as comparative values for nitrates and VFA's in the anaerobic zones would be 
necessary to endeavour to explain this phenomenon. 
104 
4.10 WESFLEUR WWTP 
4.10.1 PLANT CONFIGURATION AND OPERATING PARAMETERS 
Wesfleur WWTP treats effluent from a variety of industrial sources in the Atlantis area. 
The plant also houses a reactor that treats domestic waste. Only the industrial reactor 
was included in the study, in order to enable comparisons between the filaments found in 
this type of WWTP and those treating either mixed industrial and domestic effluent or 
those treating effluent entirely of a domestic nature. The configuration of the reactor is 
the Modified Ludzack-Ettinger with an operational DO of 2.8mg/L created by diffuse 
aeration (refers to figures 4.2.1 and 4.2.2). The influent is not subjected to primary 
settling and is thus of a raw nature. 
4.10.2 RESULTS 
4.10.2 (a) Operational data 
The influent (I) is raw industrial influent. There are no PST's. 
The mixed liquor (ML) results are from the single industrial bioreactor. 
The effluent (E) is the supernatant from the clarifier. 
*Note: breaks in the graph lines occur when no data was available 
-ICOD 
'I "T"T" i"11 'i i i I"I i i "r"i r i1 'i i i' 
5/6 3/7 31/7 28/8 25/9 23/10 20/11 
Date 
a O 
o 
« 
5 
98 
96 
94 
92 
90 
88 
86 
84 
82 
80 
78 
-RCOD 
5/6 3/7 31/7 
T ')'" i' 'i i—i—i i i r i ) "') i 
28/8 25/9 23/10 20/11 
Date 
Figure 4.10.1 Graph depicting the influent 
COD values at Wesfleur WWTP in 2007 
Figure 4.10.2 Graph depicting the COD 
removal efficiency (RCOD) at Wesfleur 
WWTP in 2007 
105 
?ITKN -IAMM 
"\ I"""!1" V'f l"|--r-T~T-T"'V" T'1 1 1"'V"T'-r','l"'"-'l",,T r""V"T" 
5/6 3/7 31/7 28/8 25/9 23/10 20/11 
Date 
-EAMM -ENN 
5/6 3/7 31/7 28/8 25/9 23/10 20/11 
Date 
Figure 4.10.3 Graph depicting the influent Figure 4.10.4 Graph depicting the effluent 
levels of ammonia (IAMM) and TKN (ITKN) levels of ammonia (EAMM) and 
at Wesfleur WWTP in 2007 nitrates/nitrites (ENN) at Wesfleur WWTP 
in 2007 
-ITP -IOP -EOP 
5/6 3/7 31/7 28/8 25/9 23/10 20/11 
Date 
-ICON -ECON 
550 
500 
450 
400 
350 I 
300 
250 
200 
100 
::s^r^^ 
'i" i ""i i—i1 r i 'i—r-i—r—T—r~i—i—i—i—i—i—i—i—i—i—rr 
5/6 3/7 31/7 28/8 25/9 23/10 20/11 
Date 
Figure 4.10.5 Graph depicting the influent Figure 4.10.6 Graph depicting the influent 
total phosphates (ITP) and influent o- conductivity values (ICON) and effluent 
phosphates (IOP) as well as the effluent a- conductivity values at Wesfleur WWTP in 
phosphates at Wesfleur WWTP in 2007 2007 
106 
Figure 4.10.7 Graph showing the values for the sludge volume index (SVI) and the 
dissolved sludge volume index for the mixed liquor at Wesfleur WWTP in 2007 
TABLE 4.10.1 FOOD TO MICROORGANISM (F/M) RATIO IN INDUSTRIAL 
BIOREACTOR OF WESFLEUR IN 2007 
June 0.09 mgCOD/mgVSS.day 
July 0.11 mgCOD/mgVSS.day 
September 0.11 mgCOD/mgVSS.day 
October 0.10 mgCOD/mgVSS.day 
November 0.19 mgCOD/mgVSS.day 
4.10.2 (b) Microscopic sludge analysis 
This was performed monthly on the following dates: 20/6/07, 18/7/07, 29/8/07, 19/9/07, 
24/10/07 and 21/11/07. 
• Floe structure 
The shape of the floes was round from June to October, but in November there were also 
irregularly shaped floes present. The floes were compact in structure in all samples. The 
floes were medium-sized in June, July and November, whilst in August, September and 
October they were small and large, the large floes appeared as small floes bound by 
bridging. 
• Diversity 
There was a moderate amount of diversity in all samples. 
107 
5 -I 
4 -
—?—Filament Index 
3-
25" i 
o —' 2 -
?\ . 
n J 
June July Aug Sept 
Month 
Oct Nov 
Figure 4.10.8 Graph showing the Filament index 
values obtained from the mixed liquor at Wesfleur 
WWTP in 2007 
TABLE 4.10.2 DOMINANT AND SECONDARY FILAMENTOUS ORGANISMS IDENTIFIED FROM THE 
MIXED LIQUOR AT WESFLEUR WWTP IN 2007 
AS DOM INANT F LAMENTS 
June July Aug Sept Oct Nov % Prevalence 
(dominant) 
% Prevalence 
(overall) 
Type 1851 X X X X X X 100 100 
Type 0092 X X X 50 100 
Type 0041 X X X 50 83 
AS SECONDARY FILAMENTS 
Type 0092 X X X } Also dominant filaments 
Type 0041 X X 
N. limicola\\\ X X 0 33 
H. Hydrosis X X 0 
Figure 4.10.9 A, Gram stain of Type 1851 from mixed liquor sample showing "clean" 
filaments associated with industrial wastewater from Wesfleur WWTP and B, wet 
mount of mixed liquor from Wesfleur WWTP taken in October 2007 showing a 
Tardigrade (above) and an Oligocheaete worm (below). 
TABLE 4.10.3 PROTOZOA/METAZOA IDENTIFIED IN THE MIXED LIQUOR FROM WESFLUER WWTP IN 
2007 
SCANTY 
June July Aug Sept Oct Nov 
Sessile ciliates Carchesium spp. X 
Vbrtice/ia spp. X X X 
Vaginicola spp. X 
Crawling ciliates Aspidisca spp. X X X X X 
Trachelophyllum spp. X X 
Free-living ciliates Colpidium spp. X 
Euplotes spp. X 
Litonotus spp. X 
Spirostomum spp. X X X X 
Flagellates £o<?ospp. X X X 
Amoebae X X X 
Heliozoa X X 
Rotifers X X X X 
Oligochaeta X X X X X 
Tardigrades X X 
MODERATE 
Crawling ciliates Aspidiscaspp. 
Chilodonella spp. 
Free-living ciliates Spirostomum spp. 
4.10.3 DISCUSSION 
The Wesfleur industrial bioreactor received effluent with a high COD content, but 
removal was good as can be seen by the removal efficiency reflected in figures 4.10.1 
and 4.10.2. 
Nitrification was satisfactory for most of the study period as shown by the influent and 
effluent levels of ammonia in figures 4.10.3 and 4.10.4. The latter graph also shows the 
erratic results of effluent nitrates/nitrites. The levels of these nitrogenous compounds 
decreased with an increase in ammonia, but also randomly at other times. Complete 
denitrification is not expected with the MLE configuration, but nitrate/nitrite levels were 
often high. Lack of electron donor can almost certainly be ruled out as a cause - the 
COD/TKN ratio was extremely high with a range between 12.6-24.1mgCOD/mgTKN and 
a mean of 18.5mgCOD/mgTKN. Not surprisingly, there was no correlation between this 
result and the residual levels of nitrates/nitrites. Operational conditions probably led to 
poor denitrification. 
When nitrification was poor, especially during the peak level at the end of September, 
the cause of low nitrates/nitrites was most likely due to aeration problems. Lack of DO 
would lead to the dual effects of reduced nitrification (and thus less substrate for 
denitrification) as well as possible continuation of denitrification within the aerobic 
reactor. The latter could occur in severe cases, such as with mechanical breakdown of 
aerators. 
The presence of high residual nitrates/nitrites at times when nitrification was adequate 
was probably due to either insufficient mixed liquor recycle between the aerobic and 
109 
anoxic zone (so that nitrates/nitrites formed in the aerobic zone could not be denitrified 
and were present in the clarifier effluent), or too high DO in the anoxic zone. 
No biological phosphorus removal is expected with the MLE configuration, but removal 
did occur - this was erratic but substantial at times as seen by figure 4.10.5. By 
examining figure 4.10.6, it can be seen that the conductivity of the influent was high. The 
industrial nature of this influent would result in the presence of a range of chemicals. It 
can be speculated that phosphorus removal took place was by chemical co-precipitation. 
However, in the two other MLE configured WWTP's, namely Bellville WWTP and Parow 
WWTP, there was also substantial phosphorous removal that coincided with increased 
levels of effluent ammonia and decreased nitrates/nitrites. Lack of nitrates and nitrites 
(and presumably also oxygen) in the anoxic zone probably turned this section of the 
bioreactor into a de facto anaerobic zone with resultant EBPR. The high COD/P ratio 
would make conditions unsuitable for a large PAO population to flourish. (The COD/P 
ratio was 91.6-125.3mgCOD/mgP with a mean of 112.4mgCOD/mgP - double that of 
Parow WWTP). 
The parameters for the presence of bulking conditions used in the study, namely Fl and 
DSVI, shown in graph 4.10.8 and 4.10.7 respectively were both within the defined limits 
for the duration of the study period. 
The calculated monthly F/M ratios shown in table 4.10.1 were low. This supports the fact 
that the three dominant filaments, namely Type 1851, Type 0041 and Type 0092 are 
classed as low F/M by Jenkins et a/. (2004). The association of Type 1851, with 
industrial waste by Eikelboom, (2000) holds true in this instance (but is not the case with 
some of the domestic WWTP's included in the study). The filaments found at Wesfleur 
were often without a sheath and attached growth, a phenomenon also noted by 
Eikelboom, (2000) as being more typical for industrial waste. 
The mixed liquor supported a healthy population of protozoa and metazoa adapted to the 
prevailing conditions. This, coupled with the presence of healthy nitrifier population, 
points to the fact that toxicity levels were never a problem. All these populations are 
extremely sensitive to a range of toxins (discussed in section 4.1.3) 
In summary, the operation and microbial population and dynamics of this industrial 
WWTP were satisfactorily stable for the entire six months. The high COD levels were 
considerably reduced throughout the study and there were no obvious signs of poisoning 
at any stage. The filament population reflected the low F/M conditions that prevailed. 
110 
4.11 WILDEVOELVLEI WWTP 
4.11.1 PLANT CONFIGURATION AND OPERATING PARAMETERS 
Wildevoelvlei WWTP is designed to treat approximately 14.5ML of domestic effluent per 
day. The plant houses two different bioreactors: reactor A is a carousel-type system that 
operates in a 3-stage Phoredox mode from the anaerobic zone. This reactor operates 
with a DO of 2.0ppm and receives 54% of the daily influent while reactor B receives 46%. 
Reactor B is configured and operated in the UCT (see figure 4.1.1) mode with an 
operational DO of 2.2 ppm. Both reactors have an aerobic mass fraction of 50%, an 
anaerobic mass fraction of 19% and an anoxic mass fraction of 31%. 
o 
| ANOXIC REACTOR | 
AEROBIC REACTOR 
| ANAEROBIC REACTOR | 
MLR: MIXED LIQUOR RECYCLE 
SR: SLUDGE RECYCLE 
WF: WASTE FLOW 
IN: INFLUENT 
EFF: EFFLUENT 
[ CLARIFIER 
Figure 4.11.1 Key for WWTP configurations 
MLR WF 
SR 
Figure 4.11.2 3-stage Phoredox configuration 
(Metcalf and Eddy, 1991) 
111 
4.11.2 RESULTS 
4.11.2 (a) Operational data 
The raw influent (I) is distributed to bioreactor A and reactor B. There is no PST. 
The mixed liquor (ML) from bioreactor A and B flows into the clarifiers A and 
respectively. 
The effluent (E) is the supernatant from the plant clarifiers A and B. 
*Note: breaks in the graph lines occur when no data was available 
B 
-ICOD 
l ' l' "I' l '-i—r i i 'l I l i i1 i 1 i l l—l I l i i 
4/6 2/7 30/7 27/8 24/9 22/10 19/11 
Date 
-A ROOD -B ROOD 
84 
82 
60 -1—1—l—i—r-T—l—i—r-1—r—l—r-|—I—I—i—rn—I—r~r 
4/6 2/7 30/7 27/8 24/9 22/10 19/11 
Date 
Figure 4.11.3 Graph showing the influent 
COD (ICOD) at Wildevoelvlei WWTP in 
2007 
Figure 4.11.4 Graph showing COD 
removal efficiency from clarifier A (A 
RCOD) and clarifier B (B RCOD) at 
Wildevoelvlei WWTP in 2007 
-ITKN -IAMM 
i i i II II i i i f '? 
4/6 2/7 30/7 27/8 24/9 22/10 19/11 
Date 
35 
30 
25 
z 15 
10 
5 
- A EAMM 
-A ENN 
-B EAMM 
-BENN 
4/6 2/7 30/7 27/8 24/9 22/10 19/11 
Date 
Figure 4.11.5 Graph showing the influent 
TKN (ITKN) and influent ammonia (IAMM) 
levels at Wildevoelvlei WWTP in 2007 
Figure 4.11.6 Graph showing the effluent 
ammonia levels from clarifier A (A EAMM) 
and B (B EAMM) and the effluent 
nitrates/nitrites from clarifier A (A ENN) 
112 and B (B ENN) at Wildevoelvlei WWTP 
-IALK -A EALK -B EALK 
350 
300 
250 
_j 
f200 
8 150 
O 
100 
50 
-W^I^V: 
-T—i i r r i i r i i"i r'l i—i i"i i i "i" i"i ; i 
4/6 2/7 30/7 27/8 24/9 22/10 19/11 
Date 
-A AGE -BAGE 
180 
160 
140 
120 
(A 100 
I 80 
60 
40 
20 
\ 
A-t^L 
I ) ) ) f ) I ) I I I I ) ) I ) ) ) ) I i "7" ) ) 
4/6 2/7 30/7 27/8 24/9 22/10 19/11 
Date 
Figure 4.11.7 Graph depicting the 
influent alkalinity (IALK) and the effluent 
alkalinity from clarifier A (A EALK) and B 
(B EALK) at Wildevoelvlei WWTP in 
2007 
Figure 4.11.8 Graph showing the sludge 
age of the mixed liquor in reactor A (A 
AGE) and reactor G (B AGE) at 
Wildevoelvlei WWTP in 2007 
-ITP -IOP -A EOP -BEOP 
"T-n i i I ' 'i' i i i i i i i r i i i 
4/6 2/7 30/7 27/8 24/9 22/10 19/11 
Date 
-A SVI -BSVI -A DSVI -B DSVI 
300 
50 ? I I I . I I I . . I I ' . I I I ! 
4/6 2/7 30/7 27/8 24/9 22/10 19/11 
Date 
Figure 4.11.9 Graph showing the influent 
total phosphates (ITP) and influent a-
phosphates (IOP) as well as the effluent a-
phosphates from clarifier A (A EOP) and 
clarifier B (B EOP) at Wildevoelvlei WWTP 
in 2007 
Figure 4.11.10 Graph showing the SVI 
from the mixed liquor of reactor A (A SVI) 
and B (B SVI) as well as the DSVI values 
from the mixed liquor of reactor A (A DSVI) 
and reactor B (B DSVI) at Wildevoelvlei 
WWTP in 2007 
113 
TABLE 4.11.1 FOOD TO MICROORGANISM (F/M) RATIO IN REACTOR A AND 
REACTOR B OF WILDEVOELVLEI WWTP IN 2007 
REACTORA REACTOR B 
June 0.10 mgCOD/mgVSS.day 0.10 mgCOD/mgVSS.day 
July 0.18 mgCOD/rngVSS.day 0.13 mgCOD/mgVSS.day 
Auqust 0.12 mgCOD/mgVSS.day 0.09 mgCOD/mgVSS.day 
September 0.12 mgCOD/mgVSS.day 0.13 mgCOD/mgVSS.day 
October 0.32 mgCOD/mgVSS.day 0.14 mgCOD/mgVSS.day 
November 0.32 mgCOD/mgVSS.day 0.09 mgCOD/mgVSS.day 
4.11.2 (b) Microscopic sludge analysis 
This was performed monthly on samples from reactor A and reactor B on the following 
dates: 26/6/07, 25/7/07, 21/8/07,19/9/07, 24/10/07 and 27/11/07. 
• Floe Structure 
Reactor A 
The floes were round in shape, open in structure, firm in strength and medium in size 
from June to August. Although other parameters remained the same for the last three 
months, the shape of the floes was both irregular and round. There was bridging 
between floes from July to November and in October there were tangled masses of 
filaments. 
Reactor B 
In June, July, October and November the floes were round in shape, open in structure 
firm in strength and medium in size. In August, the shape was irregular and in 
September, both irregular and round. Many filaments were in tangled masses from June 
to October and there was bridging in all samples. 
• Diversity 
Reactor A and reactor B 
There was moderate diversity and scanty monocolonies were present in all samples. 
Filament index 
•9 
o 
-Reactor A -Reactor B 
June July Aug Sept 
Month 
Oct Nov 
Figure 4.11.11 Graphs depicting the Fl values 
obtained from the mixed liquor of reactor A and 
reactor B at Wildevoelvlei WWTP in 2007 
TABLE 4.11.2 DOMINANT AND SECONDARY FILAMENTOUS ORGANISMS IDENTIFIED FROM THE 
MIXED LIQUOR OF REACTOR A AND REACTOR B AT WILDEVOELVLEI WWTP IN 2007 
AS DOMINANT F LAMENTS 
June July Aug Sept Oct Nov % Prevalence 
AandB 
(dominant) 
% Prevalence 
BandC 
(overall) 
Type 0092 X 
(A,B) 
X 
(A,B) 
X 
(A,B) 
X 
(A,B) 
X 
(B) 
X 
(B) 
83 100 
Actinomycetes X 
(B) 
X 
(A,B) 
X 
(A) 
X 
(A,B) 
X 
(B) 
58 100 
Type 1851 X 
(A) 
X 
(A,B) 
X 
(A,B) 
X 
(A,B) 
58 83 
M. parvicella X 
(B) 
X 
(B) 
17 67 
Type 021N X 
CA) 
8 92 
AS SECONDARY FILAMENTS 
Type 0092 X 
(A) 
X 
(A) 
| Also dominant 
> filaments 
Actinomycetes X 
(A) 
X 
(B) 
X 
(A) 
X 
(A,B) 
Type 1851 X 
(B) 
X 
(A,B) 
M. parvicella X 
(A,B) 
X 
(B) 
X 
(A) 
X 
(B) 
X 
(A) 
Type 021N X 
(B) 
X 
(A,B) 
X 
(B) 
X 
(A,B) 
X 
(A,B) 
X 
(A,B) 
Type 0041 X 
(B) 
X 
(A) 
X 
(A,B) 
X 
(B) 
X 
(A,B) 
X 
(A,B) 
0 75 
H. hydrosis X 
(B) 
X 
(A) 
0 17 
Type 1701 X 
(A) 
0 8 
F/ex/bacter spp. X 
(B) 
0 8 
TABLE 4.11.3 PROTOZOA/METAZOA IDENTIFIED IN THE MIXED LIQUOR FROM REACTOR B AND 
REACTOR C AT BORCHERDS QUARRY WWTP IN 2007 
SCANTY 
June July Aug Sept Oct Nov 
Sessile ciliates Carchesium spp. X 
(B) 
Epistylis spp. X 
(A,B) 
X 
(B) 
X 
(B) 
X 
(B) 
X 
(B) 
Opercularia spp. X 
(B) 
X 
(B) 
Vaginicola spp. X 
(A) 
X 
(A,B) 
X 
(A) 
Vorticella spp. X 
(B) 
X 
(A,B) 
X 
(A,B) 
X 
(B) 
X 
(A,B) 
115 
TABLE 4.11.3 (CONTINUED) PROTOZOA/N 
REACTOR A AND REACTOR 
IETAZOA IDENTIFIED FROM THE MIXED LIQUOR OF 
k B AT WILDEVOELVLEI WWTP IN 2007 
June July Aug Sept Oct Nov 
Crawling ciliates Aspidisca spp. X 
(B) 
X 
(A,B) 
X 
(B) 
X 
(A,B) 
X 
(A.B) 
X 
(A,B) 
Trachelophyllum spp. X 
(A) 
X 
(A) 
X 
(A) 
X 
(A) 
Free-living ciliates Blepharismsa spp. X 
(A) 
X 
(A) 
Euplotes spp. X 
(B) 
X 
(A) 
Litonotus spp. X 
(A) 
Colpidium spp. X 
(A) 
Spirostomum spp. X 
(A) 
X 
(A) 
X 
(A) 
X 
(A) 
Unidentified X 
(B) 
X 
(A) 
Flagellates Zfoctospp. X 
(A,B) 
X 
(A) 
X 
(A) 
X 
(A,B) 
X 
(B) 
Hexamitus spp. X 
(A) 
Pe/ane/waspp. X 
(A) 
X 
(A) 
X 
(B) 
X 
(B) 
X 
(A) 
Pleuromonas spp. X 
(A) 
7?e/70/770/7asspp. X 
(B) 
X 
(A) 
Unidentified X 
(B) 
X 
(A) 
Amoebae X 
(A) 
X 
(A,B) 
X 
(B) 
X 
(B) 
Testate amoebae X 
Nematodes X 
(A) 
X 
(B) 
Rotifers X 
CA.B) 
X 
(A.B) 
X 
(A,B) 
X 
(A,B) 
X 
(A,B) 
Tardigrades X 
(A) 
X 
(B) 
X 
(A,B) 
X 
(A) 
Oligochaeta X 
(A) 
116 
TABLE 4.11.3 (CONTINUED) PROTOZOA/METAZOA IDENTIFIED FROM THE MIXED LIQUOR OF 
REACTOR A AND REACTOR B AT WILDEVOELVLEIWWTP IN 2007 
MODERATE 
June July Aug Sept Oct Nov 
Attached ciliates Vaginicola spp. X 
(A) 
Crawling ciliates Aspidisca spp. X 
(A) 
X 
(A) 
Free-living cilates Paramecium spp. X 
(A) 
Flagellates Bodo spp. X 
(B) 
X 
(B) 
Peranema spp. X 
(B) 
3.11.3 DISCUSSION 
Removal of COD at Wildevoelvlei WWTP was good (figure 4.11.3 and 4.11.4), with 
results from reactor A being more consistent. Figure 4.11.6 and graph 4.11.7 show that 
nitrification and denitrification efficiency also differed between the two reactors. Reactor 
A produced mostly excellent results for nitrification, while the results from reactor B were 
inconsistent, being particularly poor from October. Loss of nitrification in this reactor was 
accompanied by increased effluent alkalinity as reflected in figure 4.11.7. Toxic 
poisoning of the nitrifier population can be ruled out, as reactor A was unaffected. 
Overloading is also ruled out, as the F/M (table 4.11.1) remained low throughout in 
reactor B (in fact, reactor A showed an increased F/M in October and November). 
Unfortunately, no MLVSS results were available for the calculation of F/M ratios in 
August and September, but results were extrapolated using the percentage of MLVSS to 
MLSS in other months. This figure was very consistent with a range of between 82 and 
85%, with a mean of 83% for reactor A, and a range of 81 to 83%, with a mean of 82% 
for reactor B. The sludge age, depicted in graph 4.11.8 was also long enough to support 
the growth of sufficient numbers of nitrifiers. The most likely cause then of poor 
nitrification in reactor B would be insufficient DO. 
The levels of residual nitrates/nitrites were also consistent in reactor A, (mostly between 
5-10mgN/L) and erratic in reactor B. There were no residual nitrates/nitrites in the 
clarifier effluent from reactor B when there was loss of nitrification. This type of result 
was common in the WWTP's included in the study. The influent COD/TKN ratio ranged 
from 6.1-14.4mgCOD/mgTKN with a mean of 10.9mgCOD/mgTKN. The mean is thus 
higher than the value of 8.4mgCOD/TKN reported by Kujawa et a/. (1996) as being 
necessary for complete denitrification, but the range fell on either side of this value. 
However, there was no correlation between the levels of effluent nitrates/nitrites and the 
COD/TKN ratio. In addition, complete denitrification is not expected in either of these 
types of reactors with only one anoxic zone. The most probable reasons for the 
intermittent presence of high levels of residual nitrates/nitrites would thus be plant 
operating conditions for example, insufficient mixed liquor recycle from the aerobic to the 
anoxic zone or insufficient retention time in the anoxic zone. 
117 
Phosphorous removal, shown in figure 4.11.9 from reactor A was almost consistently 
poor, while that from reactor B was generally better, but not entirely adequate. The 
reactor with the higher levels of nitrates/nitrites in the clarifier effluent was the worst 
performer in terms of phosphorous removal. Notwithstanding the fact that the recycle for 
the two reactors is different, it can be speculated once again that the phosphorous 
removal function was retarded, at least to some degree by the presence of nitrates in the 
anaerobic reactor. The influent COD/P ratio was in the range of 46.2 to 
70.8mgCOD/mgP with a mean of 56.6mgCOD/mgP. At this level, according to Liu etal. 
(1996), the growth of GAO's over PAO's would be favoured. 
The DSVI values shown in figure 4.11.10 were only slightly above 150mg/L mark during 
periods of August and November in reactor A. In reactor B, the values were above this 
level from June until August and subsequently decreased. The filament index was raised 
to a level suggestive of bulking for periods in both reactors - from August to October in 
reactor A and from June to October in reactor B. The Fl, given in graph 4.11.11 was 
always higher in reactor B. There was often substantial bridging between the floes and 
the filaments formed tangled masses. In this WWTP sludge settling was better than the 
amount of filamentous growth and the floe characteristics would suggest. 
Regarding the filament species given in table 4.11.2, the presence of Type 0092 as a 
dominant filament does not affect settling as it tends to form the backbone of floes and 
grows within the floes. However, it would also not be included in the filament index 
evaluations for the same reason. Type 1851 was found as a dominant species in both 
reactors in more than half of the samples. The association of this filament as a dominant 
species not only with industrial effluent (as expected), but also with domestic effluent 
was a feature of the study. The presence of Type 1851 correlated with the presence of 
bulking conditions according to the meta-analysis, but only to a moderate degree. The 
correlation of actinomycetes with bulking conditions in the meta-analysis was significant. 
This organism was also present as a dominant species in more than half of the samples 
from Wildevoelvlei WWTP. The presence of large number of filaments associated with 
bulking conditions with only moderately increased DSVI values presents an anomaly. It 
can be speculated that there were other unknown factors present in the wastewater that 
enhanced settling even under these circumstances. 
Although the F/M values were similar in June and July, there was a marked difference in 
October and November. The presence of M. parvicella and actinomycetes suggests high 
levels of dietary fats in the influent. Type 0092 and Type 1851 are considered as low F/M 
by Jenkins etal. (2004). Type 1851 was present as a dominant species in both reactors 
in October and November. Type 0092 was present in both reactors as a dominant 
species until September, after which it only present as a dominant species in reactor B. 
This establishes an excellent correlation between type 0092 and low F/M conditions. 
Filament composition was similar for both reactors, reflecting that in this case, influent 
composition was more important than plant configuration for species succession. 
118 
Figure 4.11.12 Gram stain of Gram negative (pink) 
Type 0092 and Gram positive Blue) branching 
actinomycetes from mixed liquor sample of 
Wildevoelvlei WWTP taken from reactor A in 
November 2007. 
Regarding the protozoa and metazoa - there were substantial differences between 
ciliates and flagellates. The identification results are given in table 4.11.3. Reactor B 
harboured a greater variety of sessile ciliates and reactor A a greater variety of free-living 
ciliates. In reactor B in July and August, the flagellates outnumbered the ciliate 
population. This usually indicates a high sludge load and/or a lack of DO. The most 
abundant flagellate was Bodo spp., which is an indicator organism for the same 
conditions (Eikelboom, 2000). 
The calculated F/M for reactor B was low throughout the study period, so lack of DO 
must be considered. However, nitrification and COD removal remained satisfactory 
during this period and only deteriorated at a later date. One speculative explanation is 
that there was a chronic lack of DO that was not initially apparent by analysis of the 
chemical results but was reflected in the protozoan and metazoan population. 
Furthermore, there may have been was just sufficient DO to achieve satisfactory COD 
removal and nitrification until the influent COD increased from the end of September. At 
this stage, the amount of available DO became insufficient to achieve both COD removal 
and nitrification and the nitrifier population was adversely affected, leading to high 
effluent ammonia. 
In summary, reactor A functioned in a more stable manner than reactor B in terms of 
nutrient removal. There was a period of high effluent ammonia in reactor B, probably due 
to lack of DO resulting in a retarded nitrifier population. Phosphorous removal was 
adversely affected, ostensibly by a high COD/P ratio and the presence of nitrates in the 
anaerobic zone. The microscopic sludge quality relating to floe character and filament 
index suggested bulking conditions to a greater extent than the DSVI values would imply. 
The filament population was similar in both reactors but the protozoan population in 
reactor B pointed to low DO in this reactor. 
119 
CHAPTER 5 
META-ANALYSIS OF COMBINED RESULTS 
FROM WASTEWATER TREATMENT PLANTS 
120 
5.1 POPULATION DYNAMICS OF FILAMENTOUS ORGANISMS FROM JUNE 
TO NOVEMBER 2007 
5.1.1 Results 
5.1.1 (a) Prevalence and comparison with similar South African studies 
• Sample distribution 
Number of samples: 96 
Number or reactors: 16 
Number of WWTP's: 11 
16 Filament species found as dominant or secondary species. 
Prevalence 
I Dominant H Secondary 
O) 
2 
MpwviceUa Type021N 
Filament type 
Figure 5.1.1 This bar chart depicts the percentage prevalence of dominant filamentous 
microorganisms in the 96 samples examined during the course of the study. The 
prevalence of these organisms as secondary species is also represented. 
H Secondary 
20 
15 
Filament type 
Figure 5.1.2 Percentage prevalence of filamentous microorganisms that were identified 
only as secondary species during the study period 
121 
• Comparison with other filamentous surveys conducted in South Africa 
Two surveys for filamentous organisms in South Africa were found in the literature, one 
from KwaZulu-Natal (KZN), conducted in 1999 (Lacko eta/., 1999) and the other from 
nutrient removal plants distributed over the country (SA), conducted in 1986 (Blackbeard 
eta/., 1988). In the KZN study, mixed liquor samples were taken from 5 nutrient removal 
plants in the KwaZulu-Natal (KZN) area every fortnight from May-October in the late 
1990's. Filaments were identified and data was analyzed according to frequency of 
occurrence (prevalence) and abundance (Lacko et a/., 1999). A decade earlier, 
Blackbeard eta/. (1988), examined the mixed liquor of 33 nutrient removal plants from 
over South Africa. At the time, nutrient removal was in its infancy, and the scope of the 
study represented three quarters of these plants operating in the country at the time. In 
addition, the presence of bulking sludge was extremely common compared to the 
situation today. The reason is that adjustments to operating parameters to deter bulking 
in nutrient removal plants have been instituted over the years - evidence of the causes of 
the bulking phenomenon have been uncovered using data from pilot scale laboratory 
observations and empirical data from functioning WWTP's. Unfortunately, the 
geographical distribution of the plants is not given, so comparisons in terms of filament 
abundance and location cannot be made. 
TABLE 5.1.1 PEF 
DOMINANCE (D) F 
ICENTAGE P 
ROM 3 FILAM 
REVALENCE: 
ENTOUS OR< 
OVERALL PREVALANCE | 
3ANISM SURVEYS IN SOL 
[OP) AND 
TH AFRICA 
FILAMENT KZN (OP) 
1999 
SA (OP) 
1986 
SA(D) 
1986 
CT (OP) 
2007 
CT(D) 
2007 
Type 0092 0 94 82 98 74 
Type 1851 100 58 21 69 31 
M. parvicella 100 76 33 58 17 
Type 0041 67 85 39 67 7 
Type 021N 50 0 0 58 14 
Actinomycetes/ 
Nocardia spp * 
67 24 15 45 22 
H. hydrosis 33 21 12 23 4 
N. limicola \\\l\\** 83 21 6 14 3 
Type 1701 50 0 0 10 0 
Flexibacter spp. 0 0 0 8 0 
Type 0581 0 0 0 5 0 
Thiothrix spp.*** 50 6 3 3 0 
Type 0914 50 70 33 2 0 
Type 0803 0 27 17 2 0 
Beggiatoa spp. 33 0 0 1 0 
Type 1863 0 9 6 1 0 
Type 1702 0 3 0 0 0 
Type 0675 **** 67 73 45 Type 0041 Type 0041 
Type 0961 0 3 0 0 0 
S. natans 33 0 0 0 0 
*Eikelboom (2000) prefers the term Actinomycetes, Jenkins eta/. (2004) use the term Nocardia spp. for this 
group of organisms with similar morphological characteristics. 
**Eikelboom (2000) no longer classifies N. limicola II as a separate entity. Both N. limicola II and N. limicola 
III are now classed as N. limicola III that includes all strains with similar morphological characteristics. 
Blackbeard eta/. (1986) do not separate N. limicola\, II or III, merely naming N. limicola perse. 
***Lacko et al. (1999) separate Thiothrix I (17% occurrence and dominance) and Thiothrix II (33% 
occurrence and dominance). As they were found in different plants, the percentages have been added in the 
above table. 
""Eikelboom (2000) now classifies Type 0675 as part of Type 0041. 
122 
Table 5.1.1 shows that the results for certain filaments differed markedly from those in 
the Cape Town 2007 study and some of the more notable discrepancies are discussed 
more fully in section 5.1.2. that deals with filamentous microorganisms that were found in 
more than 2% of the study. However, there were four filaments that were found in 
significant numbers in one or both of the previous studies (Lacko et a/., 1999 and 
Blackbeard eta/., 1988) and were scanty or absent in this study: 
• Type 0914 was prevalent in 50% of the samples examined by Lacko eta/. (1999) 
and 33% of samples examined by Blackbeard eta/. (1988). This organism occurs 
in low loaded plants with H2S in the influent (Eikelboom, 2000). 
• Type 0803 was prevalent only in the study conducted by Blackbeard eta/. (1988). 
It is a filament commonly found in industrial wastewater (Eikelboom, 2000). 
• Beggiatoaspp. was prevalent in the study by Lacko eta/. (1999). This filament is 
an indicator species for the presence of many reduced sulphides and/or low DO 
conditions (Eikelboom, 2000). The 3 organisms, namely Type 0914, Type 0803 
and Beggiatoa spp. have similar requirements. Conditions in the Cape Town 
WWTPs that were examined were probably not conducive to the growth of these 
filaments. 
• Sphaerotilus natans was found in 33% of the samples examined by Lacko et at. 
(1999), but only from one of the WWTPs included in their study. According to 
Eikelboom (2000), this previously problematic filament is rare in modern nutrient 
removal plants. The filament enjoys moderate loading conditions. It is associated 
with nutrient deficiency (including oxygen) and complete mixing in the aerobic 
zone (Eikelboom, 2000). In addition, the filament enjoys the presence of high 
amounts of LMW substances. Lacko eta/. (1999) postulate that the presence of 
large amounts of complex carbohydrates in the wastewater from a nearby 
brewery may have led to the proliferation of this organism. 
This highlights that different populations occur in WWTPs in different geographical 
locations and that results from one area cannot necessarily be extrapolated to another. 
For example, the mining and industry in Gauteng will necessitate a larger industrial 
component in the WWTPs in comparison to the Western Cape. 
5.1.1 (b) Correlation with DSVI and Fl 
Eikelboom, (2000) deduced the effect of different filament types on SVI by data analysis, 
as outlined in table 5.1.2. 
TABLE 5.1.2 EFFECT OF FILAMENTOUS ORGANISM TYPE ON SVI (EIKELBOOM) 
SIGNIFICANT EFFECT MODERATE EFFECT MINIMAL EFFECT 
M. parvicella 
S. natans 
Th/othr/x spp. 
Type 02 IN 
Type 1851 
Actinomycetes 
H. hydrosis 
Type 0041 
Type 0092 
Type 0803/0914 
Type 1701 
N. limicola 
Type 1863 
The effect may be enhanced for Type 0092 and Type 0041 in industrial WWTP's. 
Eikelboom (2000) uses the wording "large, medium and small" not significant, moderate and 
minimal for the effect on filament type. 
123 
For this study DSVI was chosen over the SVI as it is deemed to be a better indicator of 
bulking conditions (Jenkins eta/., 2004). Deterioration of settling is often seen with an Fl 
of 3 or above. Although the Fl is a measure of the number of filaments present, it does 
not take into account filaments that are within the floes (Eikelboom, 2000). Correlation 
between SVI/DSVI and Fl is not always consistent because settling is also affected by 
other factors besides the number of filaments (Eikelboom, 2000). A figure of >150 ml/g 
for DSVI and Fl of >3 was deemed to be indicative of bulking conditions being present. 
Eight out of 16 reactors (50%) in 7 of the 11 WWTP's (64%) had DSVI's that were >150 
ml/g for at least one month during the study period. Seven of the 16 reactors (44%) in 6 
of the 11 WWTP's (54%) had Fl's that were >3 for at least one month during the same 
period. Although DSVI's were performed on a weekly basis, the Fl's were only performed 
monthly. If the DSVI was >150 ml/g at any time during a given month, it was included. In 
order that the two parameters could be compared, each of the six months constituted 
one "sample" for each WWTP, giving a total of 96 samples for both the Fl and the DSVI. 
5.1.1 (bi) DSVI results 
The results when the DSVI was >150 ml/g are given below. This was the case for 24% of 
the samples. 
TABLE 5.1.3 REACTORS WITH DSVI :> 150 
June July Aug Sept Oct Nov 
Athlone A X X 
Bellville N X X 
Borcherds quarry B X X X 
Macassar 2 X X X X 
Pa row X X X X X X 
Potsdam X X 
Wildevoelvlei A X 
Wildevoelvlei B X X X 
*The figures in red denote the samples where the Fl results were not £3 (30%) 
TABLE 5.1.4 DOMINANT FILAM ENTS WITH DSVI £150 ml/g 
Filament type % Prevalence 
DSVI >150 
ml/g 
% Overall 
Dominance 
Monthly distribution 
June July Aug Sept Oct Nov 
Type 0092 61 74 2 3 4 2 1 2 
Actinomycete 43 22 2 2 2 1 1 2 
Type 1851 35 31 1 1 1 1 2 1 
Type 021N 26 14 1 2 3 
M. parvicella 13 17 1 1 1 
Type 0041 9 7 1 1 
H. Hydrosis 4 4 1 
N. limicola\\\ 4 3 1 
*For overall dominance refer to figure 5.1.1 
124 
5.1.1 (bii) Fl results 
The results when the Fl >3 are given below. This was the case for 28% of the samples. 
TABLE 5.1.5 REACTORS WITH Fl£3 
June July Aug Sept Oct Nov 
Athlone A X X X X X 
Bellville N X X 
Borcherds quarry B X X X 
Pa row X X X X 
Postdam X X X X X 
Wildevoelvlei A X X X 
Wildevoelvlei B X X X X X 
*The figures in red denote the samples where the DSVI results were not >150ml/g (41%) 
TABLE 5.1.6 DOMINANT FILAMENTS WITH Fl of £3 
Filament type % Prevalence 
Fl>3 
% Overall 
Dominance 
Monthly distribution 
June July Aug Sept Oct Nov 
Type 0092 63 74 2 2 3 4 3 3 
Type 1851 44 31 1 2 4 4 1 
Actinomycete 33 22 1 1 2 2 2 1 
Type 021N 30 14 1 1 1 2 3 
M. parvicella 7 17 1 1 
N. limicola\\\ 4 3 1 
*For overall dominance refer to figure 5.1.1 
5.1.1.2 (bii) Combined Fl and DSVI results 
The results of the dominant filaments encountered when the DSVI values where >150 
ml/g and the Fl values were >3 are given in the table below (5.1.7). This occurred in 17% 
of samples. 
TABLE 5.1.7 DOMINANT FILAMENTS WITH DSVI £150 ml/g AND Fl >3 
Filament type % Prevalence 
DSVI >150 
ml/g and Fl £3 
% Overall 
Dominance 
Monthly distribution 
June July Aug Sept Oct Nov 
Type 0092 63 74 1 2 3 1 1 2 
Actinomycete 38 22 1 1 2 1 1 
Type 021N 38 14 1 2 3 
Type 1851 31 31 1 1 2 1 
M. parvicella 6 17 1 
N. limlcola\\\ 6 3 1 
125 
The results of the dominant filaments encountered when the DSVI values were >150 
ml/g or the Fl values were >3 are given in the table below (5.1.8). This occurred in 35% 
of samples. 
TABL E 5.1.8 DOMINA NT FILAMENTS WITH DSVI £150 ml/g OR Fl >3 
Filament type % Prevalence 
DSVI >150 
ml/g 
or Fl >3 
% Overall 
Dominance 
Monthly distribution 
June July Aug Sept Oct Nov 
Type 0092 62 74 3 3 4 5 3 3 
Actinomycete 38 22 2 2 2 3 2 2 
Type 1851 44 31 1 2 2 4 4 2 
Type 021N 24 14 1 1 1 2 3 
M. parvicella 15 17 1 1 2 1 
Type 0041 6 7 1 1 
H. Hydrosis 3 4 1 
N. limicola\\\ 3 3 1 
Figure 5.1.3 Bar chart showing the relationship between elevated Fl and/or DSVI and 
filament type 
The association depicted by figure 5.1.3 was made in an attempt to ascertain whether 
certain filament types were more likely to be involved in the advent of bulking conditions 
in the Cape Town WWTPs. For example, the overall percentage of samples containing 
Type 0092 as a dominant species was less than those samples with an elevated DSVI 
and/or Fl by more than 10% in each case, so the association of Type 0092 with bulking 
tendencies is low. In contrast, using the same logic, the association of Type 021N with 
bulking conditions is high. 
126 
5.1.2 Discussion 
Twelve of the sixteen filament types found are discussed, in order of prevalence. Four 
filaments that were prevalent in 2% or less of samples and never dominant have been 
are omitted. These are Type 0914, Type 0803, Beggiatoa spp. and Type 1863 and are 
mentioned in section 5.1.1 and chapter 4 if significant. Filaments are discussed in light of 
the overall findings in this chapter, and together with plant configuration and operating 
parameters under the individual plant analyses in chapter 4. 
The discussion will take place for each filament under three headings, namely: 
• Documented organism characteristics 
• Occurrence in selected WWTP's in Cape Town from June-November 2007 
• Analysis of findings 
5.1.2 (a) Type 0092 
• Documented organism characteristics 
Very little is known about the physiology of this organism. The bacterium grows within 
the floes, so it does not have a profound effect on the DSVI (Eikelboom, 2000). Logically, 
this would then also hold true for filament index. Type 0092 is associated with low sludge 
loading levels and has been termed as a "low F/M" filament. In his manual, Jenkins eta/. 
(2004) gives growth parameters of MCRT's of between 8 and 50 days and a F/M of 
between 0.05 and <0.2 kgBODs/kgMLSS/day, the latter being similar to the loading rates 
documented by Eikelboom, (2000). 
Evidence points to that fact that it has the ability to utilize slowly biodegradeable 
chemical oxygen demand (SBCOD) for growth and metabolism. Particulates and slowly 
metabolizable substrates are not readily degraded in the anaerobic or anoxic zones. In 
the aerobic zones of biological nutrient removal (BNR) WWTPs, they are hydrolyzed to 
produce low concentrations of soluble organics. It is thought that this source of nutrient 
supply favours the growth of Type 0092 (amongst other filaments). 
Eikelboom, (2000) suggests that M. parvicella and Type 0092 have similar substrate 
requirements, but different temperature requirements - at very high MCRT's, the latter 
will predominate at temperatures over 15°C and the latter at lower temperatures. He also 
reports an association between raw influent and the growth of this organism. 
In a study by Noutsopoulos et al. (2006) it was found that although the reduction in 
sludge age below six days at <18°C suppressed the growth of M. parvicella, it did not 
affect the growth of Type 0092. The organic loading range used in these experiments 
was 0.19-0.45 kgCOD/kgVSS.day, thus conflicting with the categorization of this filament 
as strictly low F/M. 
• Occurrence in selected WWTP's in Cape Town from June-November 2007 
Percentages given are from monthly analyses and are given in sequential chronological 
order from June to November 2007. Type 0092 was the most frequently encountered as 
well as the most frequently dominant species. 
Type 0092 was ubiquitous, being found in between 94% (June and October) and 100% 
(July, August, September, November) of samples. From June to November 2007, it was 
dominant or co-dominant in 75%, 81%, 75%, 81%, 56% and 75% of samples. However, 
127 
as can be seen from figure 5.1.3, in samples that were deemed to be prone to bulking by 
virtue of elevated DSVI and/or Fl, this filament was only found in 61-63% of the samples. 
• Analysis of findings 
Figure 5.1.3 shows that Type 0092 was in terms of frequency overwhelmingly the most 
common filament both in the elevated DSVI and/or Fl (bulking) and overall categories. 
However, this was not strongly related to elevated DSVI or Fl, as the figures derived for 
these conditions were consistently more than 10% less for those of overall dominance of 
this filament. Thus, in this study it can be said that the effect of Type 0092 on DSVI is 
minimal and not in agreement with Eikelboom (2000). (Refer to table 5.1.2). However, as 
previously stated and generally accepted, DSVI is a more reliable indicator of bulking 
than SVI. In addition, no conditions are given for the derived data found in table 5.1.2. 
Furthermore, it can be deduced that there is no obvious change in the prevalence of this 
organism from winter to summer in Cape Town. All of the WWTP's included in the study 
were nutrient removal plants with high mean cells residence times (MCRT's) and low 
loading levels. This supports the theory that this filament enjoys conditions of low F/M 
and can utilize SBCOD for growth and metabolism. Given the Mediterranean climatic 
conditions in Cape Town, the temperature of the activated sludge is unlikely to decrease 
to the point where growth of Type 0092 is inhibited. This is borne out by the fact that 
growth was prodigious throughout the duration of the study from mid-winter to summer. It 
is not known what the situation would be when conditions had been warmer for extended 
periods as the study did not continue into midsummer. Thus, the seasonal variation with 
temperature variation seen in other parts of the world can neither be categorically proven 
nor refuted, although evidence does suggest that Cape Town WWTP's will not 
experience the same patterns as those found in colder climates. 
This filament was found in the study by Blackbeard et al. (1988) as the most common 
organism, but was not found at all in the study conducted in KwaZulu-Natal. Some 
possibilities for this finding are outlined in the paragraphs below. 
The influent characteristics and/or climatic conditions experienced in KwaZulu-Natal are 
sufficiently different to those experienced in Cape Town to allow for the ubiquitous 
growth only in the latter area. This is unlikely to occur for the entire year, especially as 
Type 0092 is deemed to prefer warmer conditions. 
There are discrepancies with the differentiation of N. limicola and Type 0092. This is the 
idea forwarded by Lacko etal. (1999) in their paper on the topic, and is discussed further 
under the section on N. l/m/co/a'm section 5.2.1.8. 
5.1.2(b) Type 1851 
• Documented organism characteristics 
This filament is also present in low loaded plants. Eikelboom, (2000) gives a preferential 
sludge load of <0.15 kgBODg/kgMLSS/day. According to Jenkins etal. (2004), growth of 
Type 1851 may be suppressed by the use of a selector. Anoxic or anaerobic conditions 
and compartmentalization of the selector enhance this phenomenon. Intermittent feeding 
has also been shown to suppress the growth of this filament. According to Eikelboom 
(2000), Type 1851 is commonly found, but almost never dominates in domestic WWTP's 
and he also states that it can be present in large numbers in industrial plants especially 
from the agro industry, where there is an abundance of low molecular weight (LMW) 
compounds. 
128 
Figure 5.1.4 Gram stain of type 1851 from Bellville 
WWTP. 
• Occurrence in selected WWTP's in Cape Town from June-November 2007 
This filament was the second most common and the second most dominant filament 
encountered. From June to November 2007, it was found in 31%, 62%, 88%, 81%, 81% 
and 69% of samples and was dominant in 19%, 25%, 19%, 38%, 44% and 44% 
respectively. 
• Analysis of findings 
There was an upward trend in the occurrence of this organism from June to August. 
There is no obvious reason for this occurrence. 
Type 1851 was found to be dominant in a number of domestic WWTP's in Cape Town. 
This is discussed under the pertinent individual plant analyses in chapter 4. It was also a 
common isolate in the study by Lacko eta/. (1999) and Blackbeard eta/. (1988) and was 
dominant in about one third of the samples that were positive for the presence of Type 
1851. 
From figure 5.1.3 it can be deduced that this organism is slightly more likely to be found 
in samples that are associated with bulking conditions in terms of elevated DSVI and/or 
Fl as the prevalence in these samples is higher than the overall dominance in most 
categories. However, the effect can be classed as moderate, which conflicts with that of 
Eikelboom, (2000) relected in table 5.1.2, namely a large effect on SVI. It must be re 
iterated that DSVI is a better indicator of bulking conditions than SVI and that conditions 
for the data in table B are unknown. 
5.1.2(c) Type 0041 
• Documented organism characteristics 
Like Type 0092, 0041 can grow on SBCOD substrate and can thus be problematic in 
nutrient removal plants. Pre-mixing of influent and RAS before aeration allows this 
organism to grow on the paniculate fraction. It is classed by both Jenkins et a/. (2004) 
and Eikelboom (2000) as preferring conditions of low F/M. 
• Occurrence in selected WWTP's in Cape Town from June-November 2007 
Type 0041 was the third most commonly encountered and the sixth most dominant 
filament. From June to November 2007, this organism was found in 31%, 43%, 88%, 
129 
75%, 88% and 75% of samples, and was dominant in 13%, 13%, 6%, 6%, 0% and 6% 
respectively. 
• Analysis of findings 
This filament was commonly encountered in all three South African studies (see table 
5.1.1). There appeared to be a spring maximum in the prevalence of this organism, but 
levels of dominance did not vary considerably. Values of overall dominance are slightly 
greater than those for elevated DSVI and/or Fl in the Cape Town plants, agreeing with 
Eikelboom's (2000) categorization of this organism as having a moderate effect on SVI. 
However, these results must be taken with caution, as numbers were low. 
5.1.2 (d) Mkxothrix parvicella 
• Documented organism characteristics 
M. parvicella is found commonly in domestic low F/M WWTP's and is the most common 
cause of bulking sludge and scum formation in nutrient removal plants in many countries. 
In colder climates, there is a winter growth maximum, as this filament prefers 
temperatures of <15°C for optimal growth. Domestic wastewater, and other wastewaters 
containing higher fatty acids e.g. oleic acid provide selective nutrition. Nielsen et al. 
(2002) have postulated that surface lipases allow M. parvicella to take up and store long 
chain fatty acids under anoxic as well as anaerobic conditions. Under these conditions, 
the organism thus has an advantage because of the slow hydrolysis rates of paniculate 
organics by the rest of the biota. 
Growth can also be supported by simple carbon substrates such as glucose, acetate and 
ethanol. Long retention times in sewers, PST's or anaerobic zones allow for hydrolysis of 
fats into fatty acids, therefore creating conditions where this organism can proliferate. 
Conditions of low DO in the aerobic reactor or a large anoxic mass fraction also 
contribute to overgrowth of this problem species. The presence of reduced sulphur and 
nitrogen, as may be found when recycling water from dewatering units, is another factor 
that has been implicated (Jenkins etal. 2004). 
In 2006, Noutsopoulos etal. conducted a study to determine the effect of solids retention 
time on the growth of M. parvicella. They used a series of bench-scale continuous-flow 
experiments and growth kinetic studies. The inoculum consisted of mixed liquor from 
plants experiencing bulking and foaming problems supplemented with oleic acid in the 
form of Tween 80. The latter was employed to enhance the proliferation of M. parvicella. 
The experiments were only conducted in the temperature range of 14°C to 18°C. The 
authors deduced that the maximum sludge age to avoid foaming caused by M. parvicella 
at these temperatures was 6 days. The filaments were shorter and did not stain uniformly 
with the Gram method under these conditions. The loss of hydrophobicity alleviated the 
foaming problems, but significant growth suppression was only achieved at sludge ages 
of less than 5.7 days. 
The kinetic studies were conducted according to the experimental protocol of Ekama et 
al. (1986). They found that the biomass with a high proportion of M. parvicella gave low 
but stable nmax values. With a decreasing M. parvicella to floc-former ratio, there was a 
concurrent increase in nmax. Thus the results of kinetic studies of biomass with a large 
M. parvicella count were deemed to be attributable to this filament as opposed to the 
floc-formers that were chiefly responsible for results at low M. parvicella counts. The low 
ixmax values for M. parvicella of 0.67 l/d and 0.53 l/d for aerobic and anoxic conditions 
respectively were determined. The maintenance co-efficient for M. parvicella was 30% 
lower than that of the floc-formers, reflecting the fact that this filament needs significantly 
less energy to perform its basic biochemical processes. This gives the former an 
130 
advantage under the starvation conditions encountered in nutrient removal systems. In 
practice, there is a major problem with decreasing MCRT to control bulking and foaming 
and that is the adverse affect on nitrification. 
• Occurrence in selected WWTP's in Cape Town from June-November 2007 
Together with Type 021N, this classically problem filament was the fourth most abundant 
organism encountered. It was also the fourth most dominant organism identified in the 
samples. From June to November 2007, it was present in 13%, 56%, 75%, 81%, 69% 
and 56% of samples and was dominant in 13%, 19%, 19%, 25%, 13% and 25% 
respectively. 
• Analysis of findings 
Apart from the low frequency in June there was no obvious change in the occurrence of 
this organism from winter to summer in Cape Town. Given the Mediterranean climatic 
conditions in Cape Town, the temperature of the activated sludge is unlikely to decrease 
to the point where growth of M. parvicella is enhanced. This is assuming that other 
criteria for the growth of this organism are met and is borne out by the fact that M. 
parvicella was present throughout the duration of the study from mid-winter to summer. It 
is not known whether there would be less growth during extended warmer periods, as 
the study did not continue into midsummer. Thus, the seasonal variation with 
temperature variation seen in other parts of the world can neither be categorically proven 
nor refuted, although evidence does suggest that Cape Town WWTP's will not 
experience the same patterns as those found in colder climates. 
In the KZN study (Lacko et al, 1999), the organism was found in 100% of mixed liquor 
samples, but was never dominant. In the foam samples, it was found in 3 of the five 
WWTP's and exhibited a preference for the winter months in two of these. The climate in 
that region is sub-tropical and the temperatures are warmer throughout the year than 
those experienced in the Western Cape. In KZN, this filament was never dominant, 
probably because temperatures were never low enough to allow abundant growth, and in 
summer it is possible that temperatures were too high to allow for any growth at all in 
foam samples. It can be postulated that the Cape Town temperatures are not cold 
enough to allow for prolific growth in winter, neither are they warm enough to prevent 
growth in early summer. 
The findings in the 1986 survey by Blackbeard et al. (1988) mirror those of the latest 
Cape Town survey in terms of the percentage of dominance from "positive" samples. 
The expected bulking problems associated with this organism were not apparent. From 
figure 5.3, it can be seen that the prevalence in samples with elevated DSVI's and Fl's, 
was less than the overall prevalence. Thus, in the Cape Town WWTP's, association can 
be classed as minimal, and not as significant (Table 5.1.2). If, as postulated, prevailing 
temperatures prevented mass overgrowth, it would explain this phenomenon. 
5.1.2(e) Type 021N 
• Documented organism characteristics 
This strict aerobe can grow over a broad range of loading levels. According to Eikelboom 
(2000) it is more likely to grow in massive amounts if the load is >0.1 
kgBOD/kgMLSS.day. Growth is promoted if the influent contains easily biodegradable 
compounds (such as fatty acids) that can arise in the sewer or in industrial effluent. Type 
021N can utilize hydrogen sulphide as a source of energy, so together with the 
predilection for biodegradable compounds abundant growth under septic conditions can 
occur. 
131 
Other factors that are deemed to favour its growth are nutrient (nitrogen, phosphorous, 
oxygen) shortages (Eikelboom, 2000). Substrate is removed from biological nutrient 
removal plants with initial anaerobic and anoxic zones, and because this filament is 
aerobic, it is thought to only cause bulking problems in industrial treatment plants and 
domestic plants without nutrient removal. Configurations with complete mixing in the 
aeration tank and continuous feeding can also promote the growth of Type 021N 
(Jenkins etal. 2004). According to Jenkins, (2004), they form gonidia and rosettes under 
nutrient deficient conditions. 
Figure 5.1.5 Gram stain of Type 021N from Parow 
WWTP, showing rosette formation. 
• Occurrence in selected WWTP's in Cape Town from June-November 2007 
Together with M. parvicella, this filament was the fourth most abundant organism 
encountered. It was the fifth most dominant filament. From June to November 2007, it 
was found in 25%, 50%, 63%, 69%, 75% and 69% of samples and was dominant in 
13%, 16%, 13%, 13%, 13% and 25% respectively. 
• Analysis of findings 
This filament had a moderate prevalence, supporting the fact that it has specific growth 
requirements. However, if conditions were such to allow for the presence of Type 021N, 
it can be seen from figure 5.1.3, that is was significantly more likely to cause bulking as 
determined by elevated DSVI and/or Fl. From table 5.1.2, it can be seen that this 
concurs with the findings of Eikelboom, (2000). Blackbeard etal. (1988) did not identify 
this organism in any samples, but numbers in the KwaZula-Natal study were also 
moderately high. Perhaps this can be attributed to changes in wastewater composition or 
other parameters since the 1980's, but it is difficult to make any assumptions with the 
available details. 
5.1.2 (f) Actinomycetes 
• Documented organism characteristics 
Jenkins et at. (2004) refers to this group of filaments as nocardioform organisms and 
includes many genera. Whichever term is used (actinomycetes or nocardioforms), for 
this dissertation, the filaments included are all Gram positive branching bacilli, albeit of 
mixed genera and growth requirements. 
132 
The combined results of Richard eta/. (1982) and Strom and Jenkins (1984), cited by 
Jenkins et at. (2004), show that this group of organisms were the most common 
filaments in 270 bulking and foaming plants in the US. 
They are not considered low F/M filaments, but can grow over a broad range of MCRT's 
including long sludge ages associated with low F/M conditions. According to Eikelboom 
(2000), however, the actinomycetes prefer higher sludge loads to M. parvicella. Both of 
these organisms can grow on the fat fraction of the wastewater. Like M. parvicella, the 
actinomycetes have a Gram positive cell wall that is not covered by a sheath or attached 
growth. They are thus hydrophobic and lipophilic so they tend to float and become 
attached to the fat fraction of the wastewater (Eikelboom, 2000). There is thus a strong 
association between the presence of actinomycetes and scum formation. Due to the fact 
that they float preferentially, the numbers are often greater that those in the mixed liquor. 
Conditions that are known to favour the growth of the actinomycetes are the presence of 
fats or other hydrophobic compounds, the presence of surface-active materials, recycling 
of floating material and temperatures > 15°C (Jenkins eta/., 2004). 
• Occurrence in selected WWTP's in Cape Town from June-November 2007 
This group of organisms was the sixth most common filament, but the third most 
dominant. In almost half the samples where it was encountered, it occurred as a 
dominant species group. From June to November 2007, it was found in 37%, 56%, 50%, 
37%, 44% and 44% of samples and was dominant in 19%, 25%, 19%, 25%, 25% and 
13% respectively. 
• Analysis of findings 
The there was no obvious change in the occurrence of this organism from winter to 
summer in Cape Town. This ties in well with the results obtained for Type 0092, which 
has similar temperature preferences. 
When present, there was a significant likelihood of this filament being dominant. From 
figure 5.1.3, it can also be assumed that the actinomycetes are closely associated with 
bulking conditions in terms of elevated DSVI and/or Fl. In this category, dominance was 
10-20% higher than the overall dominance (depending on the FI/DSVI category). Once 
again, there is conflict with Table 5.1.2, which denotes a moderate affect of this organism 
on SVI. It must be re-iterated that DSVI is a better indicator of bulking conditions than 
SVI and that conditions for the data in table 5.1.2 are unknown. 
5.1.2 (g) HaliscomenobacterhydrosJs 
• Documented organism characteristics 
According to Jenkins eta/. (2004), H. hydrosis \s associated with low DO and/or nutrient 
(phosphorous and/or nitrogen) deficiency. The preferential sludge loads he cites are 
between >0.05 and <0.8 kgBOD/kgMLSS.day, while Eikelboom (2000) gives a value of 
>0.2kgBOD.kgMLSS.day. He also associates this filament with low DO and a phosphate 
deficiency and he links the growth of H. hydrosis to the presence of LMW compounds 
and/or high nitrogen concentration in the influent, and/or complete mixing in the aeration 
tank. 
• Occurrence in selected WWTP's in Cape Town from June-November 2007 
H. hydrosis was the seventh most prevalent and the seventh most dominant species. It 
was not present in any of the samples in June, but from July to November 2007, it 
occurred in 6%, 38%, 25%, 38% and 31% of samples and was dominant in 6%, 0%, 6%, 
6%, and 6% respectively. 
133 
• Analysis of findings 
The organism was not detected in any samples in June and only 6% of samples in July. 
Thereafter, H. hydrosis was present in similar numbers for the rest of the study period. 
Referring to figure 5.1.3, it appears that the filament can be associated with elevated 
DSVI, but not elevated Fl. However, when dominant, H. hydrosis was not the only 
dominant species and numbers are too small to make any assumptions. It is interesting 
to note that studies by Lakay et al. (1999) at UCT also found an association between 
high DSVI and H. hydrosis, except during protracted anoxic conditions. 
5.1.2 (h) Nostacoida limkx)ta\\\ 
• Documented organism characteristics 
Eikelboom (2000) includes the organism species previously named N. limicola II into this 
group of species. He cites the F/M range favourable for growth as being a load of 0.1-0.3 
kgBOD/kgMLSS.day, whereas Jenkins et al. (2004) gives the range for N. limicola II as 
>0.05-0.6 kgBOD/kgMLSS/day. Other conditions Eikelboom (2000) cites are: pre-
settlement of influent, low water temperature, complete mixing in the aeration tank and 
the presence of easily metabolizable compounds (such as found in industrial waste). He 
also alludes to the possibility of nutrient shortages being a factor. 
Jenkins etai (2004) concurs that easily degraded compounds (specifically LMW organic 
acids) and nutrient deficiency play a role. 
• Occurrence in selected WWTP's in Cape Town from June-November 2007 
N. limicola III was the eighth most prevalent and dominant filament. It was not found in 
June, July or August, but from September, October and November was identified in 6%, 
44% and 13% of samples and was dominant in 0%, 6% and 13% respectively. 
• Analysis of findings 
N. limicola was found to a much larger extent in the KwaZulu-Natal study, supporting the 
hypothesis by Lacko et al. (1999) that there may be errors with identification between 
Type 0092 and this filament. 
According to the literature source, the identification methods used by this group of 
researchers was based on the 1984 Manual by Jenkins et al. and differentiated the two 
filaments mainly on cell shape (the assumption is thus made that the majority of the 
filaments were Gram negative), and by the presence of PHB granules. In the 2007 study 
in Cape Town, the filaments were differentiated according to Eikelboom (2000) and 
supported by Jenkins (2004). Both filaments can be Gram negative and blue-grey after 
Neisser staining, although N. limicola III is most often Gram positive. It is difficult to 
assess unstained preparations microscopically as both of these filaments tend to grow 
within the floes. 
Notable differences were: 
• Gram stain: the majority of the Cape Town N. limicola III were Gram positive. 
• Septa: Individual cells could be clearly discerned for N. limicola III after either a 
Gram or Neisser stain had been performed, whereas no septa could be seen, 
even at 1000X magnification for Type 0092. 
• Filament shape: Filaments of N. limicola III were more coiled by comparison with 
Type 0092. 
• Comparisons with micrographs: Eikelboom provides a number of micrographs in 
a CD that accompanies his 2000 Manual that allows more accurate identification. 
134 
No PHB granules were noted in either of these filaments. It would be interesting to 
perform cross-identification to determine whether identification methodology was indeed 
the reason for the discrepant results. Newer methodologies such as fluorescent in-situ 
hybridization (FISH) should minimize such occurrences. 
Without further details, there is no plausible argument for the large increase in the 
presence of this filament in late spring and the phenomenon can merely be noted at this 
stage. Any findings of dominance on an individual plant basis are discussed in chapter 4. 
Figure 5.1.6 
A Micrograph of a Gram stain of a Gram 
positive (blue) strain of N. limicola III 
typically found in the study 
C Micrographs of a Neisser stain (blue-
positive) of Type 0092 found in the study 
B Micrographs of a Neisser stain of a 
Neisser positive (grey-blue) strain of N. 
limicola III typically found in the study 
D Micrograph of a Gram stain of Gram 
negative (pink) Type 0092 from the study 
(The Gram positive organisms are 
actinomycetes) 
5.1.2 (i) Type 1701 
• Documented organism characteristics 
The sludge load that Jenkins etal. (2004) cites for optimal growth of this filament is >0.1 
to <0.8 kgBOD/kgMLSS/day, which is very similar to the value of 
>0.2kgBOD.kgMLSS.day, given by Eikelboom (2000). Both authors agree that low DO 
also encourages growth of Type 1701. In addition, Eikelboom (2000) ties high levels of 
carbohydrates, complete mixing and temperature of >15°C as contributory factors to the 
135 
prevalence of this filament. He also states that Type 1701 "almost never" grows in 
domestic nutrient removal plants, but can cause high SVI in plants treating effluent from 
the agro industry. 
• Occurrence in selected WWTP's in Cape Town from June-November 2007 
This was the 8th most prevalent filament, but was never present as a dominant species. It 
did not occur in October and November, but was present from June to September in 6%, 
19%, 25% and 13% of samples respectively. It occurred in 50% of samples from the 
Kwazulu-Natal study (refer to table 5.1.1). 
• Analysis of findings 
The filament was only found as a secondary species and numbers were too small to 
make any overall assumptions. 
5.1.2 (j) Flexibacter spp. 
• Documented organism characteristics 
There is little known about the occurrence of this filament except that it has no effect on 
settling (Eikelboom, 2000). 
• Occurrence in selected WWTP's in Cape Town from June-November 2007 
This group comprised the 9th most prevalent filaments, but they were never dominant. 
They were absent in August and October, but were present in June, July, September and 
November in 6%, 6%, 13% and 25% of samples respectively. 
• Analysis of findings 
Numbers were too limited and knowledge of this organism too scanty to perform any 
analysis on its presence. 
5.1.2 (k) Type 0581 
• Documented organism characteristics 
Jenkins eta/. (2004) links the growth of this organism to elevated LMW compounds and 
classes it as low F/M. Little is known about this filament. 
• Occurrence in selected WWTP's in Cape Town from June-November 2007 
Type 0581 was the 10th most common filament, but was never dominant. It was not 
present from September to November, but in June, July and August was found in 13%, 
13% and 6% of samples respectively. 
• Analysis of findings 
There appears to be a winter maximum in the growth of this filament, but numbers were 
too low to make any definite assumptions. This filament was not identified in the other 
studies quoted in table 5.1.1. 
5.1.2(1) Thiothrix spp. 
• Documented organism characteristics 
Both Eikelboom, (2000) and Jenkins et al. (2004) agree that this filament has a broad 
range of growth requirements in terms of sludge load and is associated with elevated 
LMW carbon compounds and/or reduced sulphur and/or nutrient deficiency 
(nitrogen/phosphorous). In addition, Eikelboom (2000) links the growth of this organism 
to lack of oxygen and complete mixing in the aeration tank. He also found that Thiothrix 
spp. are only found in nutrient removal plants where there are high levels of sulphide, 
such as encountered with stale sewage. 
136 
• Occurrence in selected WWTP's in Cape Town from June-November 2007 
This filament was only found in 2 WWTP's and was never present as a dominant 
species. It was found in 6% of the samples from July and 13% of the samples from 
August. 
• Analysis of findings 
It is not possible to make any overall assumptions about this filament, as it is only 
encountered under very specific conditions in nutrient removal plants. This is discussed 
under the pertinent plants in the individual analyses in chapter 4. In the KwaZulu Natal 
study, Thiothrix spp. occurred in 50% of samples, the authors postulating that the 
increase in industrialization in the region was responsible for this high figure. 
137 
5.2 POPULATION DYNAMICS OF PROTOZOA/METAZOA FROM JUNE TO 
NOVEMBER 2007 
5.2.1 Results 
Number of samples: 96 
Number or reactors: 16 
Number of WWTP's: 11 
The prevalence was calculated using the number of samples. The abundance (scanty, 
moderate or numerous) was not taken into account in this calculation. The object of this 
chapter is to elucidate on the extent of these life forms in the Cape Town WWTP's over 
the study period. If the abundance of a particular organism is deemed to be significant, it 
is discussed under the analysis of individual plant in which it is found in chapter 4. 
Figures are given in the same manner as for filamentous organisms - in descending 
order of prevalence with the number of samples in which the organism was found and 
the percentage of samples in which that organism was found in parenthesis. 
5.2.1 (a) Protozoa 
• Ciliates 
• Sessile ciliates 
Prevalence from all samples (n=96) 
Vorticella spp. (64/66%), Epistylis spp. (48/50%), Carchesium spp. (29/30%), Vaginicola 
spp. (18/19%), Opercularia spp. (8/8%), Sucroreans (3/3%). At the top of the following 
page is the monthly distribution graph (figure 5.2.1) for the three genera of sessile 
ciliates present in > 20% of samples 
ridJjJj 
Figure 5.1.7 Bar chart showing the monthly distribution of sessile ciliates from the 
mixed liquor of the study WWTPs 
• Crawling ciliates 
Prevalence from all samples (n=96) 
Aspidisca spp. (84/88%), Trachelophyllum spp. (39/41%), Chilodonella spp. (23/24%), 
unidentified crawling ciliates (3/3%). 
138 
LLLULL 
Figure 5.1.9 Bar chart showing the monthly distribution of crawling ciliates present in 
>20% of mixed liquor samples examined during the study 
• Free-living ciliates 
Prevalence from all samples (n=96): 
Spirostomum spp. (33/35%), Litonotus spp. (26/27%), Colpidium spp. (21/22%), 
Unidentified free-living ciliates (16/17%), Euplotes spp. (15/16%), Blepharisma spp. 
(15/16%), Parameciumspp. (5/5%). 
Figure 5.1.10 Bar chart showing the monthly distribution of free-living ciliates present in 
>20% of mixed liquor samples examined during the study 
139 
• Flagellates 
Prevalence from all samples (n=96): 
Bodo spp. (53/55%), Peranema spp. (47/49%), unidentified flagellates (10/10%), 
Trepomonas spp. (7/7%), Monsiga spp. (3/3%), Pleuromonas spp. (3/3%), Hexamitus 
spp. (1/1%). 
B Bodo spp. a Peranema spp. 
16 j 
C T^ "" O 
£ in --
<1> 
E 
to b --
(O 
¥ 4 -
*~ 2 --
0 --
h 
June July Aug Sept Oct Nov 
Month 
Figure 5.1.11 Bar chart showing the monthly distribution of flagellates present in >20% of 
mixed liquor samples examined during the study 
• Amoebae, testate amoebae and heliozoa 
Prevalence from all samples (n=96) 
Amoebae (55/57%), heliozoa (11/11%) and testate amoebae (5/5%). 
B Amoebae 
16 i 
14 -.c 
c 12-o 1Z 
E 10 
4) 
Q. 8 E 
3 6 
5 4-II 
c — 2 
0 -
= 1 
June July Aug Sept Oct Nov 
Month 
Figure 5.1.12 Bar chart showing the monthly distribution of amoebae (present in >20% of 
mixed liquor samples examined during the study) 
mid 
=i= 
140 
5.2.1 (b) Metazoa 
• Rotifers, Nematodes, Tardigrades and Oligochaete worms 
Rotifers (83/86%), Tardigrades (18/19%), Nematodes (16/17%), Oligochaete worms 
(16/17%). 
Figure 5.1.13 Bar chart showing the monthly distribution of rotifera (present in >20% of 
mixed liquor samples examined during the study) 
5.2.2 Discussion 
Only the ciliates and flagellates that were present in >20% of samples are discussed 
further in this chapter. If any of the others are relevant in the context of the individual 
WWTP in which they were found, they will be elucidated upon in the relevant section in 
chapter 4. The organisms were only identified to genus level (ciliates and flagellates), so 
any changes from winter to summer does not take into account that there may have 
been species succession within genera. 
5.2.2 (a) Protozoa 
• Ciliates 
• Documented organism characteristics 
Unless otherwise stated, the facts contained in this section are taken from Eikelboom, 
(2000). 
• Sessile ciliates 
> Carcheskim spp. 
This genus predates mainly on bacteria. It is a common ciliate and is associated 
with sludge loads of <0.2kgBOD/kgMLSS.day. In a pilot plant study to assess the 
use of ciliates as bio-indicators, Lee et a/. (2002) found significant statistical 
correlation between the presence of Carchesium spp. and low DO, evaluating it 
to be a good bio-indicator of these conditions. 
> Epistylls spp. 
This commonly found organism has similar food and loading (0.1 to 
0.2kgBOD/kgMLSS.day) requirements to Carchesium spp. 
141 
> Vottice/la spp. 
As with the other stalked ciliates, Vorticella spp. is ubiquitous and predates on 
bacteria. It can tolerate higher loading rates (<0.4kgBOD/kgMLSS.day) than the 
other two sessile ciliates discussed above. Lee et al. (2002), found Vorticella 
campanula, to be an indicator of good quality effluent and good settling by 
association with low BOD and SVI respectively. Other species within this genus 
did not show significant correlation with low BOD, but were not deemed to be 
indicators of high BOD as determined in previous studies by Madoni etal. (1994) 
and Salvado et al. (1995). The findings of Lee et al. (2002) are backed up by 
those of Zhou et al. (2006), who found high numbers of Voriticella convallaria 
during periods of good plant performance and a strong negative correlation 
coefficient with BOD (the study was conducted over the period of a year at a 
sewage treatment plant in China). 
> Opercularia spp. 
Although this stalked ciliate was only found in 8% of samples, it is mentioned in 
this text because of the correlation of Opercularia microdiscusvtWh high wasting 
rates as determined by Lee et al. (2002), and its resistance to the presence of 
heavy metals as determined by Madoni etal. (1996). Zhou et al. (2006) found a 
significant positive correlation of Opercularia coarctata with BOD and SS that 
suggested its use as an indicator of low quality effluent. 
• Crawling ciliates 
> Aspkffsca spp. 
This ciliate preys on bacteria. It is frequently found providing the sludge load is 
<0.2kgBOD/kgMLSS.day. As with Chilononella spp. (below), Lee et al. (2002) 
found a significant association of Aspidisca spp. with low F/M and of Aspidisca 
cicada with old sludge age. 
> Chilodonelb spp. 
Chilodonella spp. are also bacteriovores and are common in plants with the same 
sludge load as for Aspidisca spp. In a study toxicological conducted by Puigagut 
et al. (2005), Chilodonella uncinata (together with Acineria uncinata), were the 
most tolerant to raised levels of ammonia, where they became the dominant 
species. Lee etal. (2002) suggested that Chilodonella spp. could be used as bio-
indicators of high organic loading and poor effluent quality as determined by 
factor analysis with high SVI and MLSS. There was a similar relationship 
between the abundance of this organism and long SRT, so they also deduced 
this genus to be indicative of old sludge. In addition, they found that there was a 
relationship between these (and other) crawling ciliates and low F/M and 
postulated a possible metabolic advantage in competition for substrate. 
> Trachehphylhjm spp. 
These prey mainly on other ciliates as are thus deemed to be carnivorous. It 
occurs commonly at sludge loads of <0.4kgBOD/kgMLSS.day. 
• Free-living ciliates 
> Colpkllum spp. 
This ciliate is a bacteriovore with a propensity for sludge loads of 0.1 to 0.4 
kgBOD/kgMLSS.day. It is not frequently encountered. 
> Utonotus spp. 
Litonotus spp. is a carnivore and is encountered in plants with sludge loads of 
<0.4kgBOD/kgMLSS.day. Lee etal. (2002) determined that statistically Litonotus 
lamella and other carnivorous protozoa were associated with poorly settling 
sludge and that this relationship was opposite to that of the stalked Vorticella spp. 
Zhou et al. (2006), found a correlation between poor settling conditions and 
142 
Litonotus obtusus. (This was the only species in the genus that was frequently 
present). 
> Spimstomum spp. 
These are the largest ciliates found in mixed liquor and occur as common 
protozoans in WWTP's with sludge loads of <0.2 kgBOD/kgMLSS.day. 
• Occurrence in selected WWTP's in Cape Town from June-November 2007 
• Sessile ciliates 
By examining figure 5.1.7, it can be seen that Vorticella spp. was the most frequently 
found sessile ciliate with a maximum in August. Epistylis spp. was the second most 
frequent, being found in similar numbers to Carchesium spp. in winter, but was much 
more common in spring (maximum) and summer, where it competed numerically with 
Vorticella spp. 
• Crawling ciliates 
The results depicted by figure 5.1.8 show that Aspidisca spp. were the most commonly 
encountered crawling ciliates. Indeed, they were the most frequently found protozoan. 
There was little fluctuation in numbers over the study period, but Trachellophyllum spp., 
the second most common crawling ciliate, did show a distinct maximum frequency in 
August and September. 
• Free-living ciliates 
From figure 5.1.9, it can be seen that although Spirostomum spp. was the most common 
ciliate in this group overall, Litonotus spp. was found more frequently in July and August, 
after which numbers declined from September to November. Conversely, the numbers of 
Colpidium spp. increased toward the end of the study period, when they were greater 
than those of Litonotus spp. and similar to those of Spirostomum spp. 
• Analysis of findings 
The common sessile and free-living ciliates exhibited a succession. In addition, so did 
Trachelophyllum spp. and to a lesser extent Chilodonella spp. Of the crawling ciliates. 
Aspicisca spp. did not exhibit much fluctuation in numbers over the duration of the study. 
The latter is the most commonly encountered protozoan in most WWTP's, so the 
findings in terms of frequency for the Cape Town plants, is expected. The common 
occurrence of all the ciliates, barring Colpidium spp. concurs with Eikelboom's 
descriptions. The latter was a common isolate in the Cape Town WWTP's. The fact that 
Vorticella spp. was a common isolate suggests many reactors had low BOD and/or good 
settling according to literature findings. 
• Flagellates 
• Documented organism characteristics 
> Boob spp. 
The presence of this organism is indicative of either a high sludge load and/or a 
lack of oxygen. 
> Peranema spp. 
No specific process conditions are linked to this organism and as such it plays no 
indicator role. 
• Occurrence in selected WWTP's in Cape Town from June-November 2007 
Looking at figure 5.1.11, it can be seen that Bodo and Peranema spp. increased in 
numbers from June to August, where after the number of Bodo spp. declined, so that 
they were less than those of Peranema spp. by November. The frequency of the latter 
remained at similar figures from August to November. 
143 
• Analysis of findings 
The commonly encountered flagellates exhibited succession. 
• Amoebae, testate amoebae and heliozoa 
• Documented organism characteristics 
According to Eikelboom, (2000), amoebae are seldom observed in low loaded plants and 
are usually associated with loads of 0.1 to 0.4 kgBOD/kgMLSS.day. and/or oxygen 
shortages. 
• Occurrence in selected WWTP's in Cape Town from June-November 2007 
Amoebae were found in a large number of samples and increased in number towards 
spring, after which they declined. 
• Analysis of findings 
Low sludge loads as found in nutrient removal plants should are not normally associated 
with the presence of amoebae, so the fact that this was a commonly observed organism 
may be explained by the low oxygen conditions encountered in the anaerobic and/or 
anoxic zones. 
5.2.2 (b) Metazoa 
• Rotifers, Nematodes, Tardigrades and Oligochaete worms 
The metazoa are usually seen at loading levels of <0.15kgBOD/kgMLSS.day. Although 
they are larger than the bacteria and protozoa, they generally only play a minor in the 
treatment of AS. 
• Documented organism characteristics 
Due to the size of their feeding apparatus, rotifers and nematodes cannot consume large 
particles. The major portion of their diet is thus restricted to free-living bacteria and small 
floe particles. Rotifers usually only reach large numbers of plants that treat waste from 
the agro-industry. Tardigrades graze on the surface of the floes. Worms such as the 
oligocheaeta can consume floes and floe particles. At times they may bloom to large 
numbers in low loaded plants with pre-settled influent. In such circumstances there may 
be a concomitant decrease in sludge production. 
• Occurrence in selected WWTP's in Cape Town from June-November 2007 and 
analysis of findings 
There was little unexpected about the occurrence of the metazoa in the Cape Town 
WWTP's. The rotifers were the most abundant and exhibited a spring maximum. The 
exceptions are discussed further under the individual plants in chapter 4. 
5.2.3 Additional observations 
Due to the lack of technical expertise, the protozoa and metazoa were not speciated in 
this study. Most literature findings on the use of protozoa as bio-indicators point to 
different species being associated with certain operational parameters. Assumptions to 
genus level can often be made, but in many cases, there is not enough evidence to state 
that these findings would hold true for every species within a genus. For the analysis of 
protozoa in sludge, maximum benefit would be derived from linking the abundance of 
individual species with operating conditions for individual plants and then using these as 
bio-indicators in later samples. The problem with this is that it is extremely time-
consuming and requires experienced personnel, which cannot be justified for routine 
monitoring of plant operation for the amount of benefit derived from such investigations. 
Thus, this type of work is likely to remain academic until such time as more data 
becomes available from research work to use a number of protozoa to make categorical 
144 
links between a genus and a variety of operating parameters. In this text and in the 
individual plant analyses in chapter 4, postulates are made according to previous 
research findings. 
5.3 POPULATION DYNAMICS OF SPIROCHAETES AND FREE-LIVING CELLS 
FROM JUNE TO NOVEMBER 2007 
5.3.1 Results 
A total of 61 samples had been processed with random timing before comparative timed 
analysis was instituted (see methods, chapter 2). A further 35 samples were examined at 
0 minutes and again at 10 min. 
• Spirochaetes 
After the introduction of comparative timed analysis, 80% of samples showed an 
increase in the number of spirochaetes detected between 0 and 10 minutes. Of the 
remaining 20%, all but 1 sample had no spirochaetes at both 0 and 10 minutes. 
Figure 5.1.14 Abundance of spirochaetes in mixed liquor samples during random timing 
and after the introduction of comparative timed analysis 
• Free-living cells 
After the introduction of comparative timed analysis, 69% of samples showed an 
increase in the number of free-living cells detected between 0 and 10 minutes. Of the 
remaining 31%, all but 2 samples had no free-living cells at both 0 and 10 minutes. 
145 
Figure 5.1.15 Abundance of free-living cells in mixed liquor samples during random timing 
and after the introduction of comparative timed analysis 
5.3.2 Discussion 
• Documented organism characteristics 
Jenkins et al. (2004), associates the finding of spirochaetes with high organic acid and 
low DO concentrations, as may be found in septic wastewater. Eikelboom, (2000) 
equates their presence with anoxic conditions. 
• Occurrence in selected WWTP's in Cape Town from June-November 2007 
The data outlined in this section is mirrored in figures 5.1.14 and 5.1.15. In the samples 
where there were no free-living cells or spirochaetes, the figures were similar when the 
samples were viewed randomly or after 10 minutes: 21% and 26% of samples with free-
living cells and 18% and 17% of samples with spirochaetes observed at random timing 
and 10 minutes respectively. 
Although it may be assumed that some of the random samples were viewed immediately 
and thus should have higher numbers with no organisms, this was not the case. This can 
be attributed to the fact that the microscopic analysis is a lengthy process, and 
organisms that emerged from the floes during the examination were included. Indeed, 
the common occurrence of this phenomenon led to the introduction of comparative timed 
analysis to prove this observed effect. 
The presence of both of these organisms was ubiquitous in the Cape Town WWTP's 
tested, being found in close to approximately 80% of samples with both random timing 
and after 10 minutes of making a wet mount. However, figures taken from when the wet 
mount was examined immediately for spirochaetes and free-living cells they were found 
in only 11% and 26% of samples respectively. With regard to the spirochaetes, not only 
was there a 71% increase in the observation (absent to present) of this bacterium 
between 0 and 10 minutes, in all save 1 sample, there was an increase in abundance in 
the samples that were already positive. With the free-living cells, there was a 48% 
increase in the observation and only 2 samples did not show an increase in abundance. 
146 
Most of the samples with free-living cells did not have a large diversity of these 
organisms, with most seeming to have only one morphological type. Very few were 
immobile and a large number exhibited a tumbling type of motility reminiscent of that 
exhibited by Listeria monocytogenes. 
• Analysis of findings 
From the results, the following deductions can be made: 
> Even in fresh samples, there was a high prevalence of spirochaetes and free-
living cells in mixed liquor from the Cape Town WWTP's included in the study. 
> These organisms live chiefly within the floes and emerge under the cover slip of a 
wet mount (wet mounts were sealed with Vaseline). 
> The conditions that cause this phenomenon are unknown. It can be speculated 
that lack of oxygen is responsible. However, spirochaetes are associated with 
anoxic conditions, the fact that they reside within floes supports this fact. 
> Although Eikelboom, (2000) notes for spirochaetes that "their number can 
increase during microscopic investigation" because spirochaetes are often 
"hidden in the floes" and that "spirochaetes disappear if the sludge sample is 
stored for a few days in a refrigerator", he gives no guidance as to whether these 
emerging bacteria should be included in the analysis or not. For instance, if the 
microscopic examination is brief and the slide is prepared immediately before 
examination, they may easily be missed, or at the very least underestimated. 
5.3.3 Additional observations 
Work to ascertain more about the nature of these organisms in the Cape Town WWTP's 
could include sampling from different stages in the reactor cycles. These samples could 
be observed microscopically for the comparative abundance of spirochaetes and free-
living cells. Perhaps these organisms grow in the free liquid phase during anaerobic and 
anoxic cycles and enter the floes when the DO levels increase during the aerobic cycle. 
The spirochaetes and most of the free-living cells were highly motile, which would allow 
them to move in and out of floes according to prevailing conditions. 
No additional supporting literature could be found on this topic. 
147 
CHAPTER 6 
SUMMATION 
6.1 WWTP CONFIGURATION, NUTRIENT REMOVAL, BULKING AND 
FILAMENTOUS GROWTH 
The tables below briefly summarize the nutrient removal results (table 6.1) and the 
bulking and notable filamentous characteristics (table 6.2) of the study WWTP's. 
TABLE 6.1 COMPARISON OF NUTRIENT REMOVAL EFFICIENCY IN STUDY 
WWTP'S 
WWTP CONFIG. NUTRIENT 
REMOVAL 
MOST PROBABLE REASON/S 
FOR GOOD OR POOR 
REMOVAL 
Bellville MLE Ammonia - poor Nitrates/nitrites - good 
Phosphorous - good 
Overloading 
Decreased supply of substrate due to poor 
nitrification 
Favourable influent composition. Lack of 
nitrates/nitrites creating anaerobic 
conditions in anoxic zone 
Pa row MLE Ammonia - erratic Nitrates/nitrites - erratic 
Phosphorous - erratic 
Low DO 
Plant operation 
Intermittent nitrates/nitrites in anoxic zone 
creating alternating anaerobic and anoxic 
conditions. 
Wesfleur MLE Ammonia - erratic Nitrates/nitrites - erratic 
Phosphorous - erratic 
Low DO 
Plant operation 
Intermittent nitrates/nitrites in anoxic zone 
creating alternating anaerobic and anoxic 
conditions. 
Athlone UCT Ammonia - poor Nitrates/nitrites - good 
Phosphorous - good 
Demise of nitrifier population due to toxins 
Favourable plant operation. Reduced 
supply of substrate when nitrification poor 
Favourable influent composition. Lack of 
nitrates/nitrites in anaerobic zone 
Kraaifontein UCT Ammonia - good 
Nitrates/nitrites -
moderately poor 
Phosphorous - erratic 
Favourable plant operation. Sufficient DO. 
Healthy nitrifier population 
Unfavourable plant operation. Possible 
lack of electron donor 
Intermittent nitrates/nitrites in anaerobic 
zone 
Mitchells 
Plain 
UCT Reactor C: Ammonia - good 
Nitrates/nitrites -
moderate, erratic 
Phosphorous -
moderate 
Reactor G: 
Ammonia - good 
Nitrates/nitrites - poor 
Phosphorous - poor 
Favourable plant operation. Sufficient DO. 
Healthy nitrifier population 
Intermittent lack of electron donor. Plant 
operation. 
Intermittent presence of nitrates/nitrites in 
anaerobic zone. Competition for substrate 
by GAO's. 
Same as for reactor C 
Unfavourable Plant operation 
Nitrates/nitrites in anaerobic zone. 
Competition for substrate by GAO's 
Potsdam UCT Ammonia - good 
Nitrates/nitrites - good 
Phosphorous - good 
Favourable plant operation. Sufficient DO. 
Healthy nitrifier population 
Favourable plant operation. Sufficient 
electron donor 
Favourable influent composition. Lack of 
nitrates/nitrites in anaerobic zone 
149 
TABLE 6.1 CONTIN UED 
WWTP CONFIG. NUTRIENT 
REMOVAL 
MOST PROBABLE REASON/S 
FOR GOOD OR POOR 
REMOVAL 
Macassar UCT 
(carousel) 
Reactor 1/reactor 2: 
Ammonia - good 
Nitrates/nitrites - erratic 
(poor to good) 
Phosphorous - erratic 
(moderate to poor) 
Favourable plant operation. Sufficient DO. 
Healthy nitrifier population 
Insufficient electron donor. 
Nitrates/nitrites in anaerobic zone. 
Borcherds 
quarry 
5-stage 
Bardenpho 
Reactor B/reactor C: 
Ammonia - good 
Nitrates/nitrites - poor 
Phosphorous - poor 
Favourable plant operation. Sufficient DO. 
Healthy nitrifier population 
Unfavourable plant operation 
Nitrates/nitrites in anaerobic zone. 
Competition for substrate by GAO's. 
Cape Flats 5-stage 
Bardenpho 
Reactor G/reactor H: 
Ammonia - good 
Nitrates/nitrites - poor 
Phosphorous - poor 
Favourable plant operation. Sufficient DO. 
Healthy nitrifier population 
Lack of electron donor 
Nitrates/nitrites in anaerobic zone. 
Possible lack of VFA's in anaerobic zone. 
Wildevoelvlei 3-stage 
Phoredox 
Reactor A: 
Ammonia - erratic 
Nitrates/nitrites - poor 
Phosphorous - poor 
Reactor B: 
Ammonia - good 
Nitrates/nitrites - erratic 
Phosphorous -
moderately poor 
Changes in DO 
Unfavourable plant operation 
Nitrates/nitrites in anaerobic zone. 
Competition for substrate by GAO's 
Favourable plant operation. Sufficient DO. 
Healthy nitrifier population 
Unfavourable plant operation 
Nitrates/nitrites in the anaerobic zone. 
Competition for substrate by GAO's 
In order to fully understand the nature of the unexpectedly poor phosphorous removal in 
some of the Cape Town WWTP's a study incorporating all of the NDBEPR WWTP's in 
the area would be prudent. Testing should include separate quantitation of nitrates in the 
various sections of the bioreactors as well as influent levels of acetic and propionic acid. 
The above measures are uncomplicated and inexpensive. The additional use of 
molecular methods to assess the microbial population in terms of GAO's and PAO's 
would add useful information. Such research would be beneficial and applied. Results 
would allow the implementation of substrate switches by changing operating conditions 
to improve nutrient removal. 
In addition, the use of microscopy to aid in troubleshooting when confronted with loss of 
WWTP performance, such as occurred at Athlone WWTP is recommended. Regular 
assessment, especially regarding the protozoan and metazoan succession at the time 
would have been valuable. The use of FISH or DGGE to assess the nitrifier population at 
the time would have been definitive. 
150 
TABLE 6.2 COMPARISON OF BULKING COr 
MICROORGANISMS IN ST 
sIDITIONS AND FILAMENTOUS 
UDY WWTP'S 
WWTP BULKING 
CONDITIONS 
MAJOR 
DOMINANT 
SPECIES 
CASEY'S 
HYPOTHESIS 
SUPPORTED 
FURTHER 
COMMENTS 
Bellville Yes Type 1851 
(Type 021N)* 
No Filamentous population probably 
associated with 
increased LMW 
compounds in 
influent. Frequency of 
type 021N less than 
that of Type 1851 
Pa row Yes Actinomycetes 
Type 1851 
No Type 1851 dominant in domestic WWTP 
Wesfleur No Type 1851 No "Clean" Type 1851 filaments 
Athlone Yes Type 0092 
(Type 021N)* 
No Type 0092 decreasing and Type 
021N (with gonidia 
and rosettes) 
increasing in 
dominance with 
bulking conditions. 
Bulking may be 
associated with 
nitrogen deficiency. 
Kraaifontein No Type 0092 No Large similarities with Potsdam WWTP 
Mitchells 
Plain 
C-no 
G-no 
Type 0092 
Type 0092 
No Reactor with better nutrient removal had 
higher DSVI values. 
Type 1851 also 
dominant (domestic 
WWTP). 
Potsdam Yes Type 0092 No Secondary organisms responsible for high 
Fl. Enhanced settling, 
possibly by large 
number of 
moncolonies 
Macassar 1 -no 
2-yes 
(marginal) 
M. parvicella 
M. parvicella 
Actinomycetes 
No Reactor with better nutrient removal had 
higher DSVI values. 
Type 1851 also 
dominant (domestic 
WWTP). 
Borcherds 
quarry 
B-yes 
C-no 
Type 0092 
(Type 021N)* 
Type 0092 
No Reactor with better nutrient removal had 
higher DSVI values. 
Type 0092 
decreasing and Type 
021N (with gonidia 
and rosettes) 
increasing in 
dominance with 
bulking conditions in 
reactor B. 
151 
TABLE 6.2 (CONTINUED) 
WWTP BULKING 
CONDITIONS 
MAJOR 
DOMINANT 
SPECIES 
CASEY'S 
HYPOTHESIS 
SUPPORTED 
FURTHER 
COMMENTS 
Cape Flats G-no 
H-no 
Type 0092 
Type 0092 
No 
Wildevoelvlei A-yes 
(marginal) 
B -yes 
Type 0092 
Type 1851 
Type 0092 
No Type 1851 found as a major dominant 
filament in a domestic 
WWTP. 
*The major dominant filaments in table 6.2 are those with the highest frequency as dominant filaments. 
Although some of the dominant filaments did not have the highest frequency over the study period, their 
occurrence was equally high or higher during times of bulking. These filaments have been included in 
brackets. 
By examining table 6.1 in conjunction with table 6.2, some strong associations can be 
determined. In terms of the WWTP configurations, the following was noted: 
MLE configuration 
All three plants with this configuration harboured Type 1851 as the major dominant 
species, irrespective of whether the plants treated domestic or industrial effluent. Type 
021N at Bellville and actinomycetes at Parow were also present as major dominant 
species and in these two WWTP's, bulking conditions existed during the study period. At 
Wesfleur, Type 1851 was the sole major dominant species, and there was no indication 
of bulking. 
Phosphorous removal was unexpectedly good at Bellville, for a WWTP of the MLE 
configuration. There was a strong relationship between the presence or absence of 
nitrates/nitrites in the effluent (and thus presumably the anaerobic zone) and 
phosphorous removal in the three plants. 
UCT configuration 
Four of the five WWTP's with this configuration harboured Type 0092 as the major 
dominant species. The structure and operating parameters of Macassar is considerably 
different to the other four and M. parvicella was the major dominant species in both 
reactors from this plant, along with actinomycetes in reactor 2. In this reactor, bulking 
conditions existed during the study period. Of the other four WWTP's, bulking conditions 
only existed at Athlone and Potsdam. At Athlone, the bulking was related to Type 021N 
rather than Type 0092, and at Potsdam, the secondary organisms may have been 
responsible for the high Fl. The microbial populations (filaments, GAOs and 
protozoa/metazoa) at Kraaifontein WWTP and Potsdam WWTP showed remarkable 
similarities. 
Ammonia removal was good in all of these plants, barring Athlone. The levels of 
nitrates/nitrites in the clarifier supernatant were absent to low only at Potsdam and 
Athlone WWTP's, and these were the only plants that showed good phosphorous 
removal. As with the MLE plants, there was a strong association between the presence 
or absence of nitrates/nitrites in the effluent and phosphorous removal. This must lead to 
the conclusion that the major cause of poor phosphorous removal in the Cape Town 
WWTP's is the presence of nitrates in the anaerobic zone. 
152 
5-stage Bardenpho configuration 
There were only two WWTP's with this configuration. Due to the fact that the 
configuration includes two anoxic and aerobic zones, the removal of nitrates/nitrites 
should be complete or nearly complete. This was not the case for either WWTP. Once 
again, the presence of nitrates/nitrites in the effluent and poor phosphorous removal 
occurred concurrently. 
3-stage Phoredox configuration 
There was only one WWTP with this configuration. Type 0092 was the major dominant 
species, along with Type 1851 in reactor A. In the latter, bulking conditions did exist 
during the study period, but were borderline. 
Thus, there were many similarities between the WWTPs in each configuration type, 
seemingly more strongly associated with configuration types than with influent 
composition. A recommendation that a larger survey including more WWTP's in each 
group to further establish or refute this link would be plausible. The perceived benefit of 
this is that corrective procedures applied to one WWTP with similar configuration and 
microbial dynamics would have application for other WWTPs in the same "category". 
6.2 IDENTIFICATION OF MICROORGANISMS 
The study results would have been more complete if molecular methodology was 
employed concurrently to assess the prokaryotic population. However, the City of Cape 
Town does not (or have the intention of introducing) the identification of microorganisms 
as a routine measure in the WWTP's in the area. As such, the study has provided 
valuable information that otherwise would not have been available. 
In addition, there are advantages and disadvantages to all the commonly used 
methodologies (FISH and DGGE and conventional microscopic morphological 
identification, that have been discussed in chapter 1). A summarized comparison of the 
advantages and disadvantages of FISH and conventional microscopy is presented in 
table 6.3. (In reality DGGE only has an academic function due to the protracted nature of 
the test, the expertise required and the need for expensive and specialized equipment). 
TABLE 6.3 SUMMARY OF ADVANTAGES AND DISADVANTAGES OF 
CONVENTIONAL MICROSCOPIC INVESTIGATION, DGGE AND FISH FOR 
THE MICROBIOLOGICAL CHARACTERIZATION OF ACTIVATED SLUDGE 
CONVENTIONA L MICROSCOPY 
Advantages Disadvantages 
It allows semi-quantitative analysis of the 
microbial population 
It does not allow for accurate identification 
of non-filamentous bacteria, for example 
GAOs, PAOs, nitrifiers 
It is simple to use once trained It does not allow for identification of 
different species within the same 
morphotype 
It requires minimal equipment It does not always allow for identification of 
different morphotypes of the same species 
It allows for assessment of floe character •Problems may be experienced in 
identifying Gram negative filaments within 
the floes 
It allows assessment of filaments, protozoa 
and metazoa 
153 
TABLE 6.3 (CONTINUED) SUMMARY OF ADVANTAGES AND 
DISADVANTAGES OF CONVENTIONAL MICROSCOPIC INVESTIGATION, 
DGGE AND FISH FOR THE MICROBIOLOGICAL CHARACTERIZATION OF 
ACTIVATED SLUDGE 
CONVENTIONA L MICROSCOPY 
Advantages Disadvantages 
It is inexpensive 
There is well-established data linking 
various microorganisms identified in this 
manner to operational conditions 
For the above reasons, it is widely used in 
Routine wastewater laboratories. Thus 
academic results obtained by this method 
are still of practical value 
FISH 
Advantages Disadvantages 
Theoretically allows for identification of the 
entire microbial population, for example 
filaments, PAOs, GAOs, nitrifiers 
A number of probes need to be used and 
are not yet standardized 
Allows tiered identification from group to 
species level 
Mismatches occur 
Methods have been described for 
quantitation of organisms 
Permeability problems may occur 
High level of specificity with correct probes Autofluorescence or quenching of 
fluorescence may occur 
Does not allow for floe characterization and 
identification of protozoa and metazoa (yet) 
*Regarding the identification of Gram negative filaments within floes, during this study no 
problems were experienced and this may have been due to the different staining 
techniques employed. 
6.3 OTHER IMPORTANT STUDY FINDINGS 
M. parvicella did not cause major bulking problems in the Cape Town WWTP's. Little 
work was performed on scum formation. At Macassar, both M. parvicella and 
actinomycetes and were found in the scum samples. However, these two filaments were 
also present as major dominant species at that WWTP. It is possible that these 
organisms are implicated in the intermittent scum problems experienced at WWTP's 
such as Potsdam, where this phenomenon mainly occurs during the winter months. 
Having said that, there was no variation in the occurrence of either M. parvicella or Type 
0092 during the course of the study. 
Regarding the spirochaetes and free-living cells, very little could be deduced as these 
organisms move out of the floes due to their motility, even in fresh samples. Unless 
standard methods are developed, it is difficult to interpret inter-laboratory results. 
154 
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159 
ANNEXURE 1.1 RAW DATA FROM ATHLONE WWTP 
INFLU ENT 
Date: Flow SS SETS COD TKN AMM TP OP CL PH CON ALK 
5/6 113.6 132 <0.1 492 39.9 27.2 7.0 3.9 200 7.1 129 262 
12/6 113.6 130 0.5 407 38.3 24.7 6.9 3.7 196 7.5 128 250 
19/6 144.3 128 1.0 542 49.9 27.3 8.6 4.4 209 7.5 135 282 
26/6 129.7 140 2.0 372 41.1 22.6 4.4 1.8 170 7.4 112 222 
3/7 143.0 127 <0.1 410 35.8 23.2 6.2 3.7 196 7.7 126 252 
10/7 135.1 114 <0.1 453 40.8 27.0 6.8 4.2 235 7.4 145 244 
17/7 ND 130 ND 434 42.1 29.2 6.2 3.8 231 7.3 142 261 
24/7 126.6 134 ND 410 34.2 20.9 4.3 2.2 211 7.3 124 218 
31/7 183.2 114 2.0 325 32.3 22.6 6.0 3.2 199 7.8 131 263 
7/8 175.6 ND ND ND ND ND ND ND ND ND ND ND 
14/8 169.6 86 1.0 342 30.1 20.3 4.4 2.0 155 7.5 108 256 
21/8 161.5 116 1.0 338 36.4 23.9 4.8 2.3 185 7.7 122 215 
28/8 156.1 130 1.0 378 34.5 21.3 5.5 2.5 158 7.7 118 248 
4/9 162.8 128 <0.1 434 42.0 29.0 6.5 3.8 198 7.6 133 269 
10/9 156.3 146 <0.1 424 41.5 35.3 5.1 2.6 181 7.7 125 260 
18/9 145.1 120 <0.1 456 43.1 29.9 7.3 5.3 215 7.7 137 260 
25/9 134.2 156 0.1 460 50.4 35.6 9.1 6.3 188 7.7 130 256 
2/10 127.4 156 0.1 460 50.4 35.6 9.1 6.3 188 7.7 130 256 
9/10 130.1 258 1.0 688 60.1 36.2 8.7 5.6 200 7.5 134 288 
16/10 127.5 258 8.0 600 44.6 25.3 8.0 4.8 208 7.5 131 260 
23/10 121.1 256 4.0 534 45.5 31.1 6.2 3.7 205 7.1 126 247 
30/10 122.1 268 5.0 739 54.2 36.1 9.2 6.6 236 7.2 146 334 
6/11 118.9 311 8.0 756 58.3 35.1 8.7 5.6 181 7.4 126 254 
13/11 122.2 345 10.0 794 51.7 34.8 9.2 6.5 194 7.2 127 276 
20/11 117.2 282 4.0 638 49.5 33.1 8.2 6.0 188 7.1 126 273 
27/11 121.0 246 6.0 660 48.9 28.3 8.7 5.7 188 7.3 125 294 
MIXED LIQUOR REACTOR A SLUDGE (ALL REACTORS) 
Date SS SETS VSS SVI DSVI PH SWR AGE RASSS 
5/6 6490 720 5185 111 62 6.7 3648 12 11280 
12/6 5575 650 116 47 6.4 3648 12 12695 
19/6 6100 750 123 72 6.8 3520 13 11480 
26/6 3610 900 249 155 6.6 3533 12 10620 
3/7 6800 950 5490 140 94 6.8 3445 13 11750 
10/7 6530 910 139 98 6.8 3576 13 11650 
17/7 7240 970 134 99 6.6 3576 ND 11600 
24/7 7620 980 129 94 6.6 3485 13 12130 
31/7 4630 550 119 104 6.8 3672 13 10490 
7/8 5810 860 4740 148 103 6.7 3582 13 11450 
14/8 5650 950 168 106 6.6 3561 13 10920 
21/8 5770 870 151 104 6.8 3544 13 10910 
28/8 4550 700 154 105 6.9 3516 13 10190 
4/9 5550 940 4570 169 115 7.0 3606 13 10700 
10/9 5440 960 176 110 7.0 3610 12 10430 
18/9 5580 980 176 129 7.0 3688 12 9670 
25/9 5530 930 168 123 7.0 3837 11 ND 
2/10 5750 1000 4680 174 160 6.9 3658 12 10000 
9/10 5330 980 184 150 7.1 3633 12 9200 
16/10 5590 1000 179 179 7.0 3594 12 8630 
23/10 5820 980 168 172 7.1 3694 12 8380 
30/10 5720 1000 175 175 6.9 3500 13 8620 
6/11 5040 1000 4350 198 198 6.8 3694 12 9220 
13/11 7190 1000 139 223 6.9 3061 14 9250 
20/11 5950 1000 168 202 6.9 3340 13 8520 
27/11 6660 1000 150 300 6.9 3541 13 7500 
160 
EFFLUENT 
Date SS DS COD CODF AMM NN OP CL PH CON ALK 
5/6 26 ND 94 ND 2.7 6.2 0.2 182 7.2 104 154 
12/6 13 586 65 ND 0.5 4.5 0.2 159 7.4 97 154 
19/6 2 ND 52 ND 4.9 1.1 1.0 193 7.1 110 205 
26/6 17 ND 83 51 1.0 3.9 0.2 155 7.1 93 145 
3/7 15 ND 66 ND 3.5 2.8 0.5 184 7.4 111 186 
10/7 7 598 53 49 2.8 2.9 0.4 200 7.1 116 169 
17/7 5 ND 51 51 5.7 2.5 1.5 231 7.0 118 189 
24/7 14 ND 55 ND 2.9 3.2 0.4 201 7.0 111 163 
31/7 4 ND 51 ND 2.8 3.1 0.2 169 7.1 108 197 
7/8 5 ND 48 ND 2.4 2.3 0.3 163 7.0 97 174 
14/8 8 ND 69 ND 4.5 1.7 0.6 158 7.0 94 194 
21/8 6 ND 65 ND 5.4 0.4 1.2 165 7.2 106 182 
28/8 10 ND 54 ND 7.6 1.1 1.4 163 7.2 110 201 
4/9 7 ND 66 ND 6.5 0.6 1.5 166 7.3 105 201 
10/9 9 619 69 ND 10.9 0.9 1.2 172 7.4 113 222 
18/9 8 ND 65 ND 24.7 0.1 3.2 184 7.4 127 260 
25/9 16 ND 71 ND 13.2 0.5 0.9 179 7.3 111 215 
2/10 16 ND 71 ND 13.2 0.5 0.9 179 7.3 111 215 
9/10 13 ND 65 ND 23.8 <0.1 1.9 181 7.4 122 256 
16/10 17 ND 55 ND 24.8 0.9 2.0 181 7.9 121 252 
23/10 24 ND 91 ND 25.3 0.1 1.8 190 7.4 125 249 
30/10 13 ND 73 ND 27.0 <0.1 2.3 188 7.4 125 295 
6/11 14 ND 81 ND 25.3 <0.1 2.0 170 7.3 117 239 
13/11 20 595 82 ND 26.3 0.1 1.8 185 7.4 120 250 
20/11 17 ND 80 ND 29.5 0.5 3.4 183 7.3 121 254 
27/11 12 ND 55 ND 19.5 <0.1 1.5 182 7.5 115 247 
AGE: Sludge age (days) 
ALK: Alkalinity (CaC03 mg/L) 
AMM: Ammonia (N mg/L) 
CL: Chloride (Cr mg/L) 
COD: Chemical oxygen demand (mg COD/L) 
CODF: Chemical oxygen demand (filtered) 
CON: Conductivity (mS/m) 
DS: Dissolved solids (mg/L) 
DSVI: Dissolved sludge volume index (ml/g) 
Flow: Raw flow (ML/day) for entire plant 
ND: Not determined 
NN: Nitrate and nitrite (N mg/L) 
OP: ortho-phosphate (P mg/L) 
RASF: RAS flow rate (s) (kUday) 
RASSS: RAS suspended solids (mg/L) 
SETS: Settleabale solids (30 min ml/L) 
SS: Suspended solids (105°C mg/L) 
SVI: Sludge volume index (ml/g) 
SWR: Sludge wasting rate (kL/day) 
TKN: Total Keldjahl nitrogen (N mg/L) 
TP: Total phosphorus (P mg/L) 
VSS: Volatile suspended solids (mg/L) 
Figures in red are anomalies and not transcription errors from the laboratory printouts. These results do not fit the general 
trend and have been left out of the graphs in the results and discussion section. 
161 
ANNEXURE 1.2 RAW DATA FROM BELLVILLE WWTP 
RAW INDUSTRIAL WASTEWATER INTO REACTORS (INFLUENT) 
Date: Flow SS vss SETS COD TKN AMM TP OP PH CL ALK CON 
6/6 50.7 504 434 18.0 978 58.5 39 10.4 6.0 7.1 99 259 97 
13/6 ND 835 ND 37.0 1172 62.9 37 17.4 9.9 7.2 97 268 105 
20/6 55.0 1650 ND 120.0 6010 150 39 33.5 15.6 6.9 115 307 111 
27/6 54.6 634 ND 30.0 921 69.4 42 13.3 8.5 7.3 101 273 99 
4/7 ND 592 ND 17.0 987 53.5 33 10.6 6.8 7.1 122 273 112 
11/7 54.5 560 ND 30.0 1223 60.8 28 13.4 7.3 6.9 135 260 115 
18/7 48.5 535 ND 22.0 1285 65.6 34 15.6 9.4 6.5 110 257 108 
25/7 58.5 297 ND 10.0 683 ND 24 ND 5.1 7.2 112 227 96 
1/8 78.9 568 ND 25.0 1003 54.7 36 11.9 7.2 7.1 124 272 104 
8/8 ND 498 ND 20.0 788 ND 32 ND 4.9 7.4 108 264 95 
15/8 63.6 488 ND 27.0 834 58.9 33 9.9 5.5 7.3 100 268 100 
22/8 58.0 907 ND 50.0 2119 85.6 36 17.4 8.5 7.2 103 275 102 
29/8 61.6 828 ND 26.0 1339 67.5 37 20.3 10.7 7.2 124 258 111 
5/9 70.0 276 219 11.0 748 44.9 26 6.8 4.0 7.4 112 256 100 
12/9 ND 535 ND 26.0 927 49.3 27 12.1 7.0 7.4 150 244 108 
19/9 ND 158 ND <0.1 679 43.4 29 9.4 7.2 7.3 116 260 105 
26/9 48.2 840 ND 38.0 1290 59.3 32 11.9 7.8 7.2 115 279 109 
3/10 ND 844 ND 27.0 1178 64.9 34 13.4 8.2 7.1 110 284 104 
10/10 ND 1260 ND 58.0 1672 88.7 44 17.1 9.3 6.8 101 300 107 
17/10 47.7 498 ND 16.0 1016 62.8 36 ND 7.8 7.1 112 278 109 
24/10 ND 792 ND 3.0 1326 64.5 41 13.7 10.4 7.0 114 303 108 
1/11 49.6 624 ND 28.0 1145 79.3 51 ND 6.6 7.3 98 264 101 
8/11 48.4 670 495 25.0 1092 58.1 32 11.3 7.6 7.3 102 258 97 
14/11 ND 987 ND 54.0 1387 83.7 34 15.0 7.9 7.4 97 257 99 
21/11 52.9 890 ND 42.0 1492 64.7 34 13.4 7.2 7.2 92 227 88 
28/11 51.5 560 ND 28.0 1211 65.1 46 14.4 10.6 7.2 102 311 104 
MIXED LIQUOR REACTOR N 
Date SS SETS VSS SVI DSVI PH SWR RASF AGE RASSS 
6/6 7870 820 6225 104 76 6.9 508 ND 19 14300 
13/6 5950 580 ND 98 74 7.2 ND ND ND 12970 
20/6 6980 840 ND 120 80 6.7 432 ND 22 12810 
27/6 6360 750 ND 118 82 6.7 659 ND 12 14070 
4/7 6900 910 5350 132 99 6.4 ND ND ND 10240 
11/7 6840 870 ND 127 88 6.6 467 ND 22 11350 
18/7 6970 800 ND 115 80 6.7 467 ND 21 12440 
25/7 5900 700 ND 119 81 6.6 433 ND ND ND 
1/8 5590 750 ND 134 86 6.6 400 ND 22 10320 
8/8 3970 500 ND 126 91 6.6 ND ND ND ND 
15/8 4770 600 ND 126 84 6.6 428 1284 27 6820 
22/8 5960 820 ND 138 94 6.8 500 1500 26 8030 
29/8 7210 880 ND 122 78 6.7 561 ND 19 11850 
5/9 6630 900 5055 136 90 6.9 667 ND 15 11740 
12/9 6840 950 ND 139 117 6.7 ND ND ND 11140 
19/9 6860 970 ND 141 140 7.0 ND ND ND 10640 
26/9 6950 970 ND 140 138 6.9 567 ND 20 10500 
3/10 6510 970 5020 149 135 6.9 ND ND ND 9740 
10/10 6250 960 ND 154 141 6.8 ND ND ND 9690 
17/10 5750 930 ND 162 118 7.0 1067 ND 23 4060 
24/10 6400 970 ND 152 163 6.9 ND ND ND 10980 
1/11 5680 970 ND 171 155 7.1 ND ND ND 8820 
8/11 5790 990 4300 171 173 7.1 600 ND 23 7270 
14/11 5490 980 ND 179 182 6.9 ND ND ND 7430 
21/11 5595 1000 ND 179 179 6.9 833 ND 14 7205 
28/11 5450 980 ND 180 183 6.9 700 ND 18 6760 
162 
CLARIFI ER N (EF FLUENT) 
Date: SS COD AMM NN OP PH CL ALK CON 
6/6 6 37 12 0.4 0.6 7.1 102 232 89 
13/6 14 40 1.9 8.8 0.3 7.7 108 191 86 
20/6 11 73 24 <0.1 10.3 7.4 115 307 111 
27/6 12 76 17 <0.1 0.6 7.4 106 252 93 
4/7 12 63 26 0.2 1.8 7.4 119 261 103 
11/7 10 51 18 <0.1 1.1 7.6 120 259 105 
18/7 12 48 22 <0.1 0.8 7.4 110 261 100 
25/7 ND ND 16 <0.1 0.4 7.6 112 227 96 
1/8 19 59 8.5 0.2 0.4 7.4 117 247 98 
8/8 ND ND ND ND ND ND ND ND ND 
15/8 14 48 9.4 1.0 0.2 7.3 98 238 90 
22/8 4 55 15 <0.1 0.5 7.6 93 232 86 
29/8 8 48 17 <0.1 0.9 7.4 118 257 99 
5/9 10 62 24 <0.1 7.9 7.7 111 259 102 
12/9 6 44 24 <0.1 1.6 7.8 106 262 98 
19/9 11 55 23 <0.1 1.4 7.8 100 264 98 
26/9 10 55 22 <0.1 2.7 7.7 104 257 98 
3/10 13 75 24 0.1 5.7 7.5 102 255 95 
10/10 5 44 20 <0.1 0.6 7.7 104 252 93 
17/10 12 55 28 <0.1 1.4 7..8 101 264 98 
24/10 22 99 25 0.2 4.2 7.5 100 247 93 
1/11 14 105 25 <0.1 11.3 7.9 111 251 97 
8/11 15 90 23 <0.1 6.0 7.6 112 272 99 
14/11 35 114 31 0.1 12.0 7.6 109 274 102 
21/11 68 279 32 0.4 10.2 7.5 103 298 97 
28/11 39 163 28 <0.1 9.5 7.6 101 297 95 
AGE: Sludge age (days) 
ALK: Alkalinity (CaC03 mg/L) 
AMM: Ammonia (N mg/L) 
CL: Chloride (Cl" mg/L) 
COD: Chemical oxygen demand (mg COD/L) 
CON: Conductivity (mS/m) 
DSVI: Dissolved sludge volume index (ml/g) 
Flow: Raw Flow (ML/day) for entire industrial plant (into north, central and south reactors) 
ND: Not determined 
NN: Nitrate and nitrite (N mg/L) 
OP: ortho-phosphate (P mg/L) 
RASF: RAS flow rate (s) (kL/day) 
RASSS: RAS suspended solids (mg/L) 
SETS: Settleabale solids (30 min ml/L) 
SS: Suspended solids (105°C mg/L) 
SVI: Sludge volume index (ml/g) 
SWR: Sludge wasting rate (kL/day) 
TKN: Total Keldjahl nitrogen (N mg/L) 
TP: Total phosphorus (P mg/L) 
VSS: Volatile suspended solids (mg/L) 
Figures in red are anomalies and not transcription errors from the laboratory printouts. 
163 
ANNEXURE 1.3 RAW DATA FROM BORCHERDS QUARRY WWTP 
INFLUENT FROM PST 
Date: Flow SS VSS SETS COD TKN AMM TP OP PH CL ALK CON 
5/6 33 700 613 28.0 1464 95.0 51 16.8 10.2 7.0 113 346 117 
12/6 33 247 ND 2.0 745 71.4 44 15.3 11.6 7.1 108 333 117 
19/6 33 236 ND 4.0 690 70.1 44 16.2 12.5 7.4 116 311 106 
26/6 33 202 ND 20.0 873 74.4 33 13.1 7.6 7.0 95 243 92 
3/7 33 238 ND <1.0 790 94.3 73 17.0 13.5 7.8 124 370 128 
10/7 33 840 ND 130.0 2584 148 52 34.9 20.5 7.1 121 321 124 
17/7 32 500 ND 3.0 1133 88.0 54 16.9 12.7 6.6 117 336 126 
24/7 33 209 ND 5.0 705 67.2 34 10.9 7.9 7.1 94 255 94 
31/7 34 344 ND 12.0 869 42.9 28 15.1 9.9 7.4 110 290 112 
7/8 ND ND ND ND ND ND ND ND ND ND ND ND ND 
14/8 ND 496 ND 15.0 1020 87.0 48 12.6 7.9 7.5 158 394 110 
21/8 ND 360 ND 12.0 981 70.3 41 10.7 7.0 7.5 117 312 114 
28/8 32 260 ND 2.0 775 66.4 39 14.0 9.7 7.6 110 317 115 
4/9 33 264 ND 2.0 851 85.8 59 16.4 12.7 7.7 112 328 123 
11/9 33 229 ND 2.0 674 56.9 31 9.9 6.6 7.5 108 286 105 
18/9 32 240 ND 2.0 1015 67.3 46 14.7 11.9 7.6 113 310 113 
25/9 ND 633 ND 23.0 1235 92.4 49 15.6 10.7 7.6 114 334 118 
2/10 33 792 ND 30.0 1798 86.9 49 20.8 16.6 6.9 110 330 111 
9/10 32 288 ND 3.0 892 72.9 48 12.3 9.0 7.5 107 304 110 
16/10 32 278 ND 2.0 1006 76.3 43 12.7 10.5 7.1 117 321 114 
23/10 32 200 ND <1.0 808 89.8 64 15.2 11.9 7.1 111 352 122 
30/10 30 ND ND 100.0 2731 152 51 30.4 16.8 6.7 105 429 122 
6/11 32 810 ND 25.0 1437 107 61 20.5 15.2 7.3 105 335 116 
13/11 32 630 ND 28.0 1467 92.9 54 17.3 13.3 6.9 114 324 119 
20/11 32 474 ND 18.0 945 73.5 55 11.9 8.7 7.3 104 312 107 
27/11 32 277 ND 1.0 970 88.5 56 14.2 11.0 7.0 118 391 122 
MIXED LIC JUOR REACTOR B 
Date SS SETS VSS SVI DSVI PH SWR AGE RASS 
5/6 7350 980 6225 133 114 6.7 1150 13 13090 
12/6 7630 970 ND 127 100 6.9 1250 12 12850 
19/6 7370 970 ND 132 119 6.9 990 15 10730 
26/6 6470 960 ND 148 105 6.7 990 14 12860 
3/7 8100 990 6750 122 114 7.1 ND ND 12640 
10/7 6600 980 ND 148 133 6.7 ND ND 12820 
17/7 6750 960 ND 142 101 6.4 ND ND 9430 
24/7 6380 980 ND 154 125 6.7 1190 12 12320 
31/7 6060 980 ND 162 132 6.8 1090 13 11400 
7/8 5790 810 ND 157 124 6.8 ND ND ND 
14/8 6380 960 ND 150 125 6.6 ND ND 12090 
21/8 4020 600 ND 149 119 6.6 ND ND 8110 
28/8 4140 850 ND 205 126 7.0 ND ND 9580 
4/9 4750 960 4080 202 126 7.0 2100 7 16230 
11/9 4410 900 ND 204 123 7.2 1340 11 11100 
18/9 5780 990 ND 171 152 6.7 1270 11 11510 
25/9 3860 860 ND 223 124 7.1 ND ND 5420 
2/10 5630 980 4680 174 156 6.6 ND ND 11810 
9/10 6160 1000 ND 162 162 6.8 2423 6 9990 
16/10 5510 1000 ND 181 181 6.7 824 17 9600 
23/10 5660 980 ND 173 163 7.0 1150 12 9500 
30/10 6020 1000 ND 166 140 6.8 1080 14 12270 
6/11 5980 980 4940 164 154 6.9 1050 13 4960 
13/11 5340 970 ND 182 150 7.0 1180 12 9230 
20/11 7365 980 ND 133 130 6.9 1190 12 9675 
27/11 5200 930 ND 179 92 6.9 1160 12 11640 
164 
MIXED LIQUOR REACTOR C 
Date SS SETS VSS SVI DSVI PH RASS 
5/6 9540 980 7955 103 92 6.8 13200 
12/6 8840 980 ND 111 91 6.9 11350 
19/6 9900 980 ND 99 89 6.9 13920 
26/6 9170 960 ND 105 79 6.7 17990 
3/7 8700 960 7190 110 97 7.0 13840 
10/7 9340 990 ND 106 107 6.7 13690 
17/7 9080 960 ND 106 79 6.5 12220 
24/7 8650 970 ND 112 97 6.8 13200 
31/7 7640 950 ND 124 89 6.9 11780 
7/8 6930 800 ND 115 81 6.9 ND 
14/8 7920 850 ND 107 70 6.7 11830 
21/8 8890 840 ND 94 72 6.7 13100 
28/8 8640 920 ND 106 69 7.0 13010 
4/9 7050 860 5880 122 74 7.0 11340 
11/9 9730 960 ND 99 82 7.0 14400 
18/9 8800 960 ND 109 91 6.7 12410 
25/9 8340 930 ND 112 77 7.0 10410 
2/10 7320 950 6080 130 98 6.5 12330 
9/10 6370 890 ND 140 88 6.9 8930 
16/10 7760 980 ND 126 88 6.7 10090 
23/10 7690 900 ND 117 68 7.0 11730 
30/10 8350 900 ND 108 62 6.8 12540 
6/11 9270 950 7550 101 73 6.9 6510 
13/11 8520 940 ND 110 80 7.0 12070 
20/11 7775 920 ND 118 77 7.0 13845 
27/11 8290 970 ND 117 101 6.9 12240 
CLARIFI ER B (EF CLUENT) 
Date: SS COD AMM NN OP PH CL Alk CON 
5/6 13 55 <0.4 1.5 3.6 7.1 118 166 78 
12/6 8 33 <0.4 2.7 2.7 7.4 103 163 76 
19/6 5 41 <0.4 3.3 5.2 7.2 114 173 80 
26/6 13 47 <0.4 6.6 2.5 6.9 100 122 71 
3/7 9 51 <0.4 4.0 2.5 7.4 122 169 84 
10/7 32 77 <0.4 3.3 3.1 7.1 118 160 84 
17/7 10 48 0.7 3.2 1.7 7.0 123 165 83 
24/7 6 44 0.6 4.5 2.9 7.0 111 156 82 
31/7 4 41 <0.4 5.5 3.3 7.3 112 193 91 
7/8 ND ND ND ND ND ND ND ND ND 
14/8 272 392 1.4 6.3 0.4 7.1 122 168 80 
21/8 9 55 <0.4 6.2 0.3 7.5 112 163 89 
28/8 5 49 <0.4 4.5 4.5 7.5 106 174 86 
4/9 25 95 6.8 4.6 39.9 7.1 112 211 99 
11/9 10 58 0.1 4.5 3.2 7.3 116 167 85 
18/9 8 62 <0.4 2.0 2.7 7.5 124 175 88 
25/9 24 83 1.2 10.1 5.4 7.2 131 149 91 
2/10 9 44 <0.4 3.5 2.5 7.1 111 147 76 
9/10 21 55 <0.5 4.7 6.0 7.4 113 149 80 
16/10 8 37 0.5 3.9 4.2 7.5 116 163 82 
23/10 18 73 <0.4 9.0 7.1 7.4 106 138 80 
30/10 6 46 0.4 0.9 3.6 7.3 102 182 76 
6/11 29 66 <0.4 1.6 2.0 7.4 102 174 77 
13/11 23 60 <0.4 4.9 4.4 7.4 112 157 77 
20/11 16 58 1.3 1.1 10.3 7.5 110 163 79 
27/11 22 66 <0.4 5.3 5.6 7.4 121 174 83 
165 
CLARIFI ER C (EFFLUENT) 
Date: SS COD AMM NN OP PH CL ALK CON 
5/6 9 47 2.9 4.5 7.3 7.0 114 169 81 
12/6 10 40 <0.4 7.5 5.2 7.3 104 144 77 
19/6 15 45 0.4 7.1 10.1 7.1 112 162 82 
26/6 14 47 <0.4 12.3 8.2 7.0 103 115 74 
3/7 12 47 <0.4 4.0 2.5 7.4 122 169 84 
10/7 42 74 <0.4 3.3 3.1 7.1 118 160 84 
17/7 19 58 <0.4 5.0 4.7 7.1 118 152 87 
24/7 51 91 0.5 9.9 6.4 6.9 109 139 82 
31/7 10 48 <0.4 10.2 5.8 7.2 110 175 92 
7/8 ND ND ND ND ND ND ND ND ND 
14/8 11 51 0.8 10.4 4.7 7.0 121 153 84 
21/8 9 51 <0.4 9.1 3.5 7.4 116 155 89 
28/8 28 61 <0.4 9.9 6.3 7.2 105 149 87 
4/9 7 44 <0.4 10.3 13.6 7.3 111 144 89 
11/9 22 76 2.3 6.4 3.5 7.1 112 170 86 
18/9 21 76 <0.4 9.3 5.7 7.3 122 151 90 
25/9 60 108 <0.4 10.2 7.1 7.1 123 146 90 
2/10 84 129 <0.4 10.6 11.1 6.8 107 127 80 
9/10 7 44 <0.4 13.1 8.2 7.2 114 122 74 
16/10 13 58 <0.4 13.9 5.8 7.2 118 128 84 
23/10 23 73 <0.4 15.0 9.8 7.2 108 116 83 
30/10 22 62 1.1 12.5 4.0 7.1 101 141 79 
6/11 18 59 <0.4 8.8 0.9 7.3 105 148 77 
13/11 11 45 <0.4 14.9 5.6 7.3 111 121 80 
20/11 31 116 49 0.1 7.2 7.5 102 307 106 
27/11 11 48 <0.4 9.8 0.1 7.5 122 163 83 
AGE: Sludge age (days) 
ALK: Alkalinity (CaC03 mg/L) 
AMM: Ammonia (N mg/L) 
CL: Chloride (Cl" mg/L) 
COD: Chemical oxygen demand (mg COD/L) 
CON: Conductivity (mS/m) 
DSVI: Dissolved sludge volume index (ml/g) 
Flow: Raw flow for entire plant (ML/day) 
ND: Not determined 
NN: Nitrate and nitrite (N mg/L) 
OP: ortho-phosphate (P mg/L) 
RASSS: RAS suspended solids (mg/L) 
SETS: Settleabale solids (30 min ml/L) 
SS: Suspended solids (105°C mg/L) 
SVI: Sludge volume index (ml/g) 
SWR: Sludge wasting rate (kL/day) 
TKN: Total Keldjahl nitrogen (N mg/L) 
TP: Total phosphorus (P mg/L) 
VSS: Volatile suspended solids (mg/L) 
Figures in red are anomalies and not transcription errors from the laboratory printouts. 
166 
ANNEXURE 1.4 RAW DATA FROM CAPE FLATS WWTP 
INFLU ENT FROM PST EFGH 
Date: Flow SS COD TKN AMM TP OP PH CL ALK CON 
6/6 170 142 353 47.0 37.0 12.2 10.1 7.0 130 239 100 
11/6 222 196 340 36.5 22.0 9.8 6.3 6.9 98 194 86 
18/6 258 138 328 42.3 30.2 9.4 7.0 7.1 112 231 92 
25/6 201 128 286 42.9 28.8 8.2 5.7 7.1 97 212 89 
2/7 222 108 281 35.8 25.6 9.0 7.3 7.3 114 221 94 
9/7 226 152 375 47.4 30.9 13.3 10.6 7.2 104 223 97 
17/7 167 164 404 46.6 32.7 12.4 9.5 7.2 98 218 99 
23/7 191 100 268 43.6 33.9 9.4 7.5 7.0 117 229 102 
30/7 318 98 217 22.2 17.6 6.7 4.2 7.2 93 207 88 
6/8 318 233 397 32.2 15.7 7.7 4.4 6.8 77 159 65 
13/8 350 88 228 32.9 19.5 6.5 4.0 7.2 82 197 88 
20/8 328 102 223 33.9 21.8 6.7 4.9 7.5 109 206 92 
27/8 281 114 259 33.8 22.9 7.4 5.4 7.5 117 215 98 
3/9 315 124 318 34.7 24.1 8.8 6.1 7.4 95 220 92 
10/9 284 136 305 39.2 26.4 10.6 7.9 7.4 93 220 90 
17/9 204 134 339 40.7 32.4 7.5 6.1 7.4 100 236 96 
24/9 184 ND ND ND ND ND ND ND ND ND ND 
1/10 184 148 395 45.9 40.2 10.8 9.2 7.4 109 257 113 
8/10 174 144 398 53.3 38.5 10.0 7.4 7.4 99 250 93 
15/10 178 128 306 54.9 42.8 10.4 9.1 7.4 106 260 98 
22/10 155 164 397 54.9 44.8 9.8 7.9 7.3 99 255 94 
29/10 162 136 397 55.5 43.8 11.5 9.3 7.3 115 255 101 
5/11 154 260 516 56.6 38.2 11.4 8.6 7.4 96 242 95 
12/11 166 106 374 60.2 49.7 9.4 8.3 7.5 119 278 106 
19/11 ND 124 376 62.3 52.8 10.6 9.3 7.5 114 286 107 
26/11 157 242 541 73.3 52.6 12.4 7.5 7.5 118 289 109 
MIXED LIQUOR F tEACTOR G 
Date SETS SS vss SVI DSVI RASSS SWR RASF AGE 
6/6 800 5400 4305 148 82 7930 690 ND 26 
11/6 260 2965 ND 66 71 8485 690 ND 22 
18/6 440 4140 ND 106 68 6210 690 ND 19 
25/6 500 4280 ND 109 84 8850 690 ND 20 
2/7 510 5190 4180 98 77 8900 690 ND 40 
9/7 780 5740 ND 136 77 9760 690 ND 47 
17/7 830 6760 ND 123 71 9990 ND ND ND 
23/7 860 6590 ND 131 79 11600 ND ND ND 
30/7 270 3550 ND 76 68 10980 690 0 35 
6/8 380 4220 3290 90 66 8640 690 0 7 
13/8 270 3130 ND 86 77 7600 690 ND 62 
20/8 320 3630 ND 88 66 6620 690 ND 27 
27/8 300 3110 ND 96 90 6710 690 ND ND 
3/9 150 2050 ND 73 ND 4610 690 ND 16 
10/9 230 3280 ND 70 ND 6300 690 ND 29 
17/9 240 3270 ND 73 ND 5610 690 ND 35 
24/9 250 4270 ND 59 ND ND 690 ND ND 
1/10 340 4560 3750 75 53 ND 690 ND 34 
8/10 320 4600 ND 70 52 6800 691 ND 25 
15/10 360 4930 ND 73 57 7530 691 ND 27 
22/10 500 6470 ND 77 56 8680 691 ND 37 
29/10 780 8030 ND 97 60 11720 691 ND 22 
5/11 670 5960 4730 112 67 9070 691 ND 32 
12/11 300 4150 ND 72 58 9610 691 ND 46 
19/11 480 5950 ND 81 54 7510 ND ND ND 
26/11 530 5800 ND 91 62 7560 691 ND 31 
167 
MIXED LIQUOR REACTOR H 
Date SETS ss vss SVI DSVI RASSS SWR AGE 
6/6 620 5530 4425 112 72 7930 690 26 
11/6 350 4135 ND 85 68 8485 690 22 
18/6 370 3950 ND 94 71 6210 690 19 
25/6 590 5010 NO 118 72 8850 690 20 
2/7 520 5230 4230 99 76 8900 690 40 
9/7 800 5810 ND 138 76 9760 690 47 
17/7 820 6540 ND 125 73 9990 ND ND 
23/7 850 6820 ND 125 70 11600 ND ND 
30/7 260 3670 ND 71 65 10980 690 35 
6/8 460 4260 3710 108 66 8640 690 7 
13/8 270 3080 ND 88 78 7600 690 62 
20/8 360 3770 ND 95 74 6620 690 27 
27/8 320 3390 ND 94 83 6710 690 ND 
3/9 150 2040 ND 74 ND 4610 690 16 
10/9 230 3300 ND 70 ND 6300 690 29 
17/9 230 3230 ND 71 ND 5610 690 35 
24/9 270 5380 ND 50 52 ND 690 ND 
1/10 360 4720 3820 76 59 ND 690 34 
8/10 300 4400 ND 68 45 6800 691 25 
15/10 390 4680 ND 83 68 7530 691 27 
22/10 620 3930 ND 158 102 8680 691 37 
29/10 770 8080 ND 95 59 11720 691 22 
5/11 720 6390 5150 113 63 9070 691 32 
12/11 480 5330 ND 90 60 9610 691 46 
19/11 500 6120 ND 82 52 7510 ND ND 
26/11 590 5840 ND 101 62 7560 691 31 
CLARIFI ERGH (EFFLUEN1 D 
Date: SS COD AMM NN OP PH CL ALK CON 
6/6 9 44 <0.4 10.0 7.4 6.9 115 82 74 
11/6 4 30 <0.4 7.3 4.3 6.6 106 98 75 
18/6 6 37 <0.4 13.7 6.5 7.0 109 78 74 
25/6 8 41 <0.4 9.7 5.1 6.7 102 89 71 
2/7 10 51 <0.4 10.5 4.9 6.9 108 86 75 
9/7 6 37 <0.4 14.4 7.1 7.0 105 81 76 
17/7 5 33 <0.4 9.2 5.6 6.9 110 90 75 
23/7 5 30 <0.4 8.4 4.7 6.9 111 94 76 
30/7 17 51 0.4 8.6 2.3 7.0 87 113 75 
6/8 173 263 <0.4 9.7 3.5 6.6 105 110 75 
13/8 4 33 <0.4 8.4 3.4 7.0 117 114 71 
20/8 5 41 <0.4 11.1 4.8 7.4 103 99 78 
27/8 3 26 <0.4 11.6 3.5 7.2 89 88 71 
3/9 58 118 <0.4 6.2 2.2 7.3 90 125 73 
10/9 4 34 <0.4 8.9 5.2 7.3 96 92 73 
17/9 4 37 0.5 6.2 4.9 7.4 97 112 73 
24/9 ND ND ND ND ND ND ND ND ND 
1/10 18 55 <0.4 13.7 6.8 7.2 105 83 81 
8/10 10 44 <0.4 10.2 5.0 7.3 103 90 72 
15/10 8 35 <0.4 9.7 4.7 7.4 102 89 73 
22/10 8 37 <0.4 9.4 6.3 7.2 104 98 73 
29/10 9 34 1.5 7.2 8.8 7.1 111 108 77 
5/11 7 34 <0.4 5.5 4.4 7.3 95 104 68 
12/11 11 45 <0.4 5.0 6.3 7.3 111 116 75 
19/11 9 48 <0.4 11.6 12.2 7.2 108 99 74 
26/11 8 33 <0.4 11.5 9.4 7.0 107 95 73 
168 
AGE: Sludge age (days) 
ALK: Alkalinity (CaC03 mg/L) 
AMM: Ammonia (N mg/L) 
CL: Chloride (Cl' mg/L) 
COD: Chemical oxygen demand (mg COD/L) 
CON: Conductivity (mS/m) 
DSVI: Dissolved sludge volume index (ml/g) 
Flow: Flow (ML/day) for entire plant into PST ABCD and EFGH 
ND: Not determined 
NN: Nitrate and nitrite (N mg/L) 
OP: ortho-phosphate (P mg/L) 
RASF: RAS flow rate(s) (kL/day) 
RASSS: RAS suspended solids (mg/L) 
SETS: Settleabale solids (30 min ml/L) 
SS: Suspended solids (105°C mg/L) 
SVI: Sludge volume index (ml/g) 
SWR: Sludge wasting rate (kL/day) 
TKN: Total Keldjahl nitrogen (N mg/L) 
TP: Total phosphorus (P mg/L) 
VSS: Volatile suspended solids (mg/L) 
Figures in red are anomalies and not transcription errors from the laboratory printouts. It was not in the scope of this study 
to speculate on reasons for anomalies. 
169 
ANNEXURE 1.5 RAW DATE FROM KRAAIFONTEIN WWTP 
PST (INFLUENT) 
Date: FLOW SS COD TKN AMM TP OP PH CON CL ALK 
6/6 12.8 242 460 65.5 48 10.5 6.9 7.2 95 104 247 
13/6 30.8 215 544 57.5 44 13.5 9.3 7.5 113 140 283 
20/6 26.0 156 507 75.2 57 12.6 9.8 7.3 109 122 290 
27/6 21.6 206 550 53.9 33 12.6 7.6 7.3 107 131 254 
4/7 18.0 236 566 81.2 61 13.7 10.1 7.4 122 130 315 
11/7 16.6 190 470 69.8 52 11.5 8.9 7.2 125 55 294 
18/7 23.2 240 599 78.7 56 13.5 10.7 7.3 113 125 281 
25/7 23.9 ND ND ND ND ND ND ND ND ND ND 
1/8 32.3 162 400 41.2 29 10.7 6.9 7.1 107 128 251 
8/8 29.2 ND ND ND ND ND ND ND ND ND ND 
15/8 32.1 132 403 40.2 28 8.3 5.7 7.1 98 123 253 
22/8 25.8 140 417 68.5 55 11.4 8.9 7.8 118 125 323 
29/8 24.6 137 368 51.3 41 10.4 7.8 7.6 102 141 279 
5/9 24.5 151 311 45.5 33 7.2 5.0 7.6 87 93 235 
12/9 25.2 180 520 52.3 43 12.0 9.2 7.3 109 128 272 
19/9 23.6 140 385 64.2 52 10.4 7.8 7.7 106 113 282 
26/9 21.1 176 467 ND 65 12.3 9.8 7.7 112 107 308 
3/10 21.2 124 412 69.5 62 9.7 7.6 7.7 100 92 288 
10/10 20.6 148 401 80.7 67 13.2 9.4 7.8 115 125 309 
17/10 19.3 148 488 70.1 54 12.6 10.7 7.6 100 100 270 
24/10 19.6 240 512 71.9 58 13.1 9.9 7.6 109 112 295 
1/11 20.1 ND ND ND ND ND ND ND ND ND ND 
8/11 19.6 178 571 89.9 72 13.0 10.0 7.6 117 130 309 
14/11 19.8 152 463 86.7 74 12.0 9.4 7.9 111 115 311 
21/11 19.2 151 400 55.3 48 9.7 7.3 7.5 81 80 226 
28/11 20.2 177 400 73.5 63 14.5 10.7 7.7 105 111 303 
MIXED LIQUOR 
Date SETS SS vss SVI DSVI PH RASSS SWR 
6/6 970 6120 4715 158 111 6.8 12430 ND 
13/6 ND ND ND ND ND ND ND ND 
20/6 980 5740 ND 171 118 6.9 9060 ND 
27/6 970 6550 ND 148 110 6.8 9910 ND 
4/7 970 6760 5050 144 130 6.5 10420 ND 
11/7 960 5330 ND 180 128 6.7 10590 797 
18/7 970 5950 ND 163 114 6.3 10600 752 
25/7 960 5300 ND 181 113 6.8 ND 564 
1/8 610 4260 ND 143 122 6.9 7630 890 
8/8 800 3450 ND 232 128 7.1 ND 958 
15/8 450 3830 ND 117 104 6.7 7990 1076 
22/8 500 3820 ND 131 105 7.0 5570 866 
29/8 520 3720 ND 140 97 7.1 4510 ND 
5/9 440 3600 2765 122 89 7.0 7590 730 
12/9 470 3180 ND 148 101 6.9 5570 900 
19/9 310 2680 ND 116 90 7.0 2670 807 
26/9 450 3830 ND 118 84 6.9 7000 616 
3/10 770 4570 3590 169 105 6.9 9330 686 
10/10 700 4830 ND 145 91 6.9 7160 ND 
17/10 940 5360 ND 175 90 7.0 7710 558 
24/10 750 4860 ND 154 99 6.8 10360 ND 
1/11 50 700 ND 71 118 7.6 1040 ND 
8/11 950 5780 4610 164 111 7.6 12850 ND 
14/11 360 2440 ND 148 115 6.9 3250 ND 
21/11 930 4175 ND 223 125 6.9 10865 ND 
28/11 980 4600 ND 213 148 6.9 6140 ND 
170 
AVERAGE FOR FOR CLAR FIER 1, 2 AND 3 (EFFLUENT) 
Date: SS COD AMM NN OP PH CON CL ALK 
6/6 65 92 <0.4 17.2 2.7 6.4 69 114 27 
13/6 24 52 1.4 7.9 0.3 7.2 88 146 125 
20/6 26 66 0.4 15.3 0.5 6.9 75 124 76 
27/6 9 55 <0.4 8.7 0.2 7.2 83 132 106 
4/7 49 91 1.1 5.9 0.1 7.1 81 132 109 
11/7 34 62 1.9 15.5 3.5 6.9 89 138 83 
18/7 14 56 2.1 10.4 0.1 7.0 81 127 92 
25/7 ND ND <0.4 12.3 0.2 7.4 84 134 102 
1/8 a) 13/37 c) 43/109 <0.4 11.8 1.4 7.2 89 135 113 
8/8 ND ND ND ND ND ND ND ND ND 
15/8 7 35 <0.4 16.3 0.7 7.2 81 118 110 
22/8 6 48 <0.4 22.3 0.3 7.2 83 119 62 
29/8 10 50 <0.4 16.3 0.3 7.2 88 137 87 
5/9 9 35 3.1 13.4 0.9 7.2 75 103 97 
12/9 10 46 0.2 21.5 6.0 6.9 77 111 43 
19/9 6 45 <0.4 21.9 7.0 6.9 77 109 39 
26/9 31 73 2.2 12.5 1.4 7.2 72 103 85 
3/10 12 52 2.9 3.8 0.2 7.3 69 106 118 
10/10 20 49 9.3 0.9 0.2 7.5 78 117 153 
17/10 47 52 0.4 13.7 0.2 7.1 66 98 72 
24/10 b) 79/150 d) 112/187 <0.4 25.3 0.1 6.5 69 104 16 
1/11 65 143 42 0.2 e) 2.3/3.8 7.6 99 116 243 
8/11 12 47 <0.4 11.5 0.1 7.2 71 112 78 
14/11 5 30 <0.4 8.4 0.2 7.2 68 109 79 
21/11 18 53 0.4 12.4 0.1 7.2 66 104 77 
28/11 18 38 <0.4 16.0 5.9 7.1 66 107 51 
Note: The results in most cases for all three clarifiers are very close. In the case where there are anomalous results, 2 
results are given in red. The first figures are those excluding the anomalous result and the second includes the anomalous 
result. The latter are the figures used for the graphs in the "Results and Discussion". 
The anomalous results are as follows: 
SS: (a)1s'Aug-STE1-187 
COD: (c)1s,Aug-STE 1-240 
OP: (e)1s,Nov-STE3-7.0 
No results were given for STE 3 on the 14th Nov. 
(b)24thAug-
(d)24thAug-
STE1 
STE1 
292 
337 
ALK: Alkalinity (CaC03 mg/L) 
AMM: Ammonia (N mg/L) 
CL: Chloride (CI" mg/L) 
COD: Chemical oxygen demand (mg COD/L) 
CON: Conductivity (mS/m) 
DSVI: Dissolved sludge volume index (ml/g) 
Flow: Flow (ML/day) raw flow for entire plant 
ND: Not determined 
NN: Nitrate and nitrite (N mg/L) 
OP: ortho-phosphate (P mg/L) 
RASSS: RAS suspended solids (mg/L) 
SETS: Settleabale solids (30 min ml/L) 
SS: Suspended solids (105°C mg/L) 
SVI: Sludge volume index (ml/g) 
SWR: Sludge wasting rate (kL/day) 
TKN: Total Keldjahl nitrogen (N mg/L) 
TP: Total phosphorus (P mg/L) 
VSS: Volatile suspended solids (mg/L) 
Figures in red are anomalies and not transcription errors from the laboratory printouts. 
171 
ANNEXURE 1.6 RAW DATA FROM MACASSAR WWTP 
RAW INFLUENT (NO PST) 
Date: Flow SS vss SETS COD TKN AMM TP OP PH CON CL ALK 
3/6 32.7 ERR ND 60 ERR ERR 55.5 ERR 9.7 6.9 126 165 327 
10/6 44.9 162 ND 4 282 34.8 25.5 5.8 3.8 7.0 106 146 249 
17/6 51.6 84 ND <1 339 52.7 39.1 9.0 6.3 7.2 115 151 290 
24/6 36.9 119 ND 0 384 61.0 44.9 8.1 6.3 7.4 117 154 271 
1/7 49.5 202 168 4 479 48.0 32.1 8.2 5.7 7.5 123 163 292 
8/7 41.7 208 ND 8 440 50.3 34.3 8.1 5.4 7.5 117 159 269 
15/7 37.5 262 ND 7 583 ND 43.3 ND 7.4 7.2 129 185 282 
22/7 38.8 98 ND <1 365 56.9 41.2 8.8 6.7 7.2 123 161 282 
29/7 54.7 30 ND 0 95 16.4 11.3 2.8 1.6 7.5 102 146 215 
5/8 57.9 118 106 <1 295 ND 27.3 7.0 5.1 7.1 125 181 269 
12/8 59.9 125 ND <1 276 38.9 25.4 6.3 4.5 7.3 122 175 271 
19/8 55.9 178 ND 8 813 45.5 28.6 6.7 4.9 7.6 128 176 270 
26/8 45.4 242 ND 5 452 43.4 37.6 7.2 5.4 7.4 108 133 255 
2/9 44.8 88 74 <1 303 44.4 29.1 7.5 5.7 7.7 121 165 257 
9/9 38.0 54 ND <1 259 43.9 37.3 7.8 6.7 7.7 123 168 262 
16/9 36.2 111 ND 1 398 55.7 43.0 9.3 7.6 7.7 130 173 288 
24/9 32.3 268 ND 4 491 61.4 35.7 10.7 7.4 7.6 118 155 177 
30/9 32.4 238 218 8 502 59.3 41.7 10.0 6.6 7.5 132 164 266 
7/10 34.1 300 ND 6 508 49.5 31.7 7.5 4.8 7.5 111 154 247 
14/10 34.7 112 ND <1 353 64.1 44.6 9.1 7.4 7.5 134 208 281 
21/10 31.8 122 ND <1 365 57.9 44.2 9.7 8.0 7.5 124 184 267 
28/10 36.8 120 ND <1 311 51.6 37.5 8.2 6.5 7.6 205 439 257 
4/11 32.3 214 190 0 408 57.9 46.9 9.2 7.6 7.5 127 196 268 
11/11 30.8 492 ND 19 947 75.5 46.6 12.2 8.0 7.5 140 223 270 
18/11 29.6 480 ND 12 886 71.4 51.4 12.6 9.1 7.5 128 191 282 
25/11 32.8 190 ND 4 506 60.7 47.6 11.6 8.8 7.5 130 184 281 
MIXED LIQUOR R EACTOR 1 
Date SETS SS VSS SVI DSVI PH SWR AGE RASF RASSS 
3/6 740 4400 3505 168 109 6.9 909 36 ND 6310 
10/6 610 4265 ND 143 94 6.8 893 37 ND 7595 
17/6 750 5010 ND 150 96 7.0 955 39 32.0 6910 
24/6 920 4730 ND 195 135 6.9 660 52 37.0 8330 
1/7 700 4340 3400 162 120 7.0 826 43 35.0 7550 
8/7 650 4000 ND 162 120 6.9 1002 34 ND 6510 
15/7 730 4570 ND 160 114 6.8 1002 36 ND 7850 
22/7 900 4820 ND 187 124 6.7 600 62 ND 7500 
29/7 400 3040 ND 132 92 6.7 615 58 ND 8720 
5/8 530 3160 ND 168 127 6.9 526 48 ND 7210 
12/8 600 4090 ND 147 108 6.9 711 38 33.0 7440 
19/8 870 4320 ND 201 148 7.1 739 47 33.0 7780 
26/8 620 3830 ND 162 125 7.1 739 46 32.0 6590 
2/9 690 3950 3050 175 122 7.2 681 54 30.0 7100 
9/9 730 4510 ND 162 115 7.2 813 46 30.0 5140 
16/9 620 3440 ND 180 140 7.1 1022 34 31.0 4710 
24/9 740 3540 ND 209 136 7.1 1022 ND 31.0 ND 
30/9 700 4030 3320 174 119 7.1 826 44 33.0 5150 
7/10 430 2860 ND 150 84 5.9 835 42 28.0 5770 
14/10 540 3690 ND 146 87 7.2 522 69 18.0 6370 
21/10 650 4320 ND 150 93 7.1 114 268 18.0 6840 
28/10 630 4830 ND 130 83 6.9 ND ND 18.0 7830 
4/11 600 3940 3170 152 102 7.1 914 37 18.0 7390 
11/11 570 4200 ND 136 86 7.0 392 93 19.0 7750 
18/11 420 4940 ND 85 65 7.2 715 50 18.0 6660 
25/11 500 3350 ND 149 108 7.1 531 59 18.0 7600 
172 
MIXED LIQUOR REACTOR 2 
Date SETS SS VSS SVI DSVI PH SWR AGE RASF RASSS 
3/6 980 4220 3445 232 190 6.8 1020 34 ND 5350 
10/6 780 3645 ND 214 154 6.9 990 32 ND 6625 
17/6 910 4470 ND 204 152 6.5 962 38 28.0 6190 
24/6 980 4950 ND 198 154 6.8 586 63 35.0 5410 
1/7 870 4280 3440 199 137 6.9 1007 34 37.0 6730 
8/7 850 4160 ND 204 144 6.8 1037 35 ND 6300 
15/7 860 4250 ND 190 124 6.7 1037 34 ND 6920 
22/7 930 4540 ND 205 141 6.7 604 61 ND 6860 
29/7 870 4670 ND 186 120 6.6 595 61 ND 8550 
5/8 720 4300 ND 167 121 6.8 646 47 ND 7490 
12/8 700 4480 ND 156 125 6.9 818 44 31.0 6830 
19/8 820 3570 ND 230 168 7.0 747 43 36.0 5880 
26/8 800 4390 ND 182 137 7.0 747 49 36.0 6250 
2/9 840 4430 3350 189 126 7.1 696 54 35.0 6340 
9/9 950 4090 ND 232 176 7.2 777 48 33.0 6020 
16/9 780 3730 ND 209 161 7.1 1043 35 34.0 5280 
24/9 800 4200 ND 191 143 7.1 1043 - 34.0 ND 
30/9 820 2670 4000 223 174 7.0 856 43 35.0 5160 
7/10 700 3760 ND 186 117 7.1 861 42 31.0 6350 
14/10 610 3290 ND 185 122 7.1 887 42 35.0 4840 
21/10 830 4170 ND 199 125 7.1 618 59 32.0 5060 
28/10 730 3550 ND 206 124 6.9 1079 34 35.0 13870 
4/11 720 4030 3280 179 119 7.1 573 61 33.0 6080 
11/11 830 4360 ND 190 128 7.0 492 75 32.0 6140 
18/11 940 3800 ND 247 168 7.0 900 42 30.0 7180 
25/11 970 6980 ND 139 138 7.0 696 52 30.0 7180 
CLARIFI ER 1 (EFFLUENT) 
Date: SS COD AMM NN OP PH CON CL ALK 
3/6 23 76 <0.4 16.4 8.8 7.2 92 144 69 
10/6 13 38 <0.4 11.8 3.8 7.3 85 129 102 
17/6 2 41 0.4 5.6 7.3 7.8 90 143 131 
24/6 10 58 0.5 7.4 7.1 7.5 90 149 102 
1/7 6 37 0.7 12.0 4.1 7.7 89 146 108 
8/7 11 44 0.8 17.3 5.4 7.4 94 149 84 
15/7 10 33 3.2 2.1 3.0 7.5 100 174 145 
22/7 2 47 2.6 4.0 5.3 7.5 97 161 139 
29/7 3 30 <0.4 13.4 1.3 7.7 92 136 137 
5/8 15 40 <0.4 18.4 2.8 7.4 108 177 124 
12/8 21 58 <0.4 12.8 3.1 7.7 101 161 136 
19/8 6 51 2.4 0.3 3.9 7.7 105 160 171 
26/8 9 44 0.6 15.4 5.7 7.7 104 162 97 
2/9 3 34 <0.4 13.8 5.2 7.9 102 166 110 
9/9 3 55 <0.4 14.0 6.5 7.8 101 159 104 
16/9 12 52 0.4 9.7 6.6 7.7 101 167 114 
24/9 ND ND 1.8 6.5 6.2 7.9 101 171 121 
30/9 6 40 <0.4 3.1 6.8 7.5 124 208 57 
7/10 6 37 <0.4 17.8 5.9 7.1 111 224 56 
14/10 4 54 1.2 9.9 7.7 7.8 106 203 108 
21/10 4 45 <0.4 5.9 8.0 7.9 98 181 108 
28/10 6 30 <0.4 3.3 5.0 8.0 178 416 122 
4/11 16 58 <0.4 16.7 6.8 7.7 108 203 75 
11/11 3 42 <0.4 17.6 8.5 7.6 127 253 86 
18/11 9 56 2.2 16.9 9.0 7.5 104 200 84 
25/11 12 47 0.4 17.9 8.5 7.5 97 178 75 
173 
CLARIFI ER 2 (EFFLUENT) 
Date: ss COD AMM NN OP PH CON CL ALK 
3/6 13 58 1.1 0.8 7.6 7.5 88 155 122 
10/6 16 38 <0.4 6.1 3.5 7.3 82 129 125 
17/6 4 33 0.7 0.7 7.1 7.6 89 143 185 
24/6 3 40 0.9 0.7 5.9 7.6 88 149 126 
1/7 10 41 <0.4 6.9 4.1 7.8 89 139 129 
8/7 7 44 0.8 6.0 5.3 7.6 90 150 119 
15/7 12 33 3.2 0.3 1.1 7.6 100 173 154 
22/7 3 44 3.1 0.9 4.8 7.6 97 164 148 
29/7 3 30 <0.4 14.8 0.2 7.7 100 153 142 
5/8 13 40 <0.4 13.3 0.2 7.5 108 177 145 
12/8 5 48 <0.4 7.5 3.0 7.8 97 157 154 
19/8 10 47 <0.4 9.9 5.4 7.8 105 166 129 
26/8 4 29 <0.4 7.2 3.8 7.3 93 146 124 
2/9 2 34 1.5 0.3 5.3 8.0 100 171 155 
9/9 2 37 <0.4 10.7 5.7 7.9 100 159 114 
16/9 7 37 0.4 4.3 6.2 8.0 100 171 130 
24/9 ND ND 1.6 0.3 4.9 7.9 100 177 133 
30/9 4 36 0.5 1.4 4.8 7.9 118 205 128 
7/10 7 26 <0.4 10.9 5.2 7.7 110 223 80 
14/10 3 43 0.6 7.9 7.2 7.9 106 206 109 
21/10 4 41 <0.4 1.5 7.9 7.8 97 182 119 
28/10 6 37 <0.4 6.1 6.2 8.0 174 401 109 
4/11 7 40 0.4 3.6 6.8 7.9 108 214 119 
11/11 3 45 0.9 8.4 7.6 7.9 123 246 110 
18/11 2 45 0.7 2.0 6.4 7.8 100 204 126 
25/11 10 37 0.8 1.0 7.3 7.9 95 177 127 
AGE: Sludge age (days) 
ALK: Alkalinity (CaC03mg/L) 
AMM: Ammonia (N mg/L) 
CL: Chloride (Cr mg/L) 
COD: Chemical oxygen demand (mg COD/L) 
CON: Conductivity (mS/m) 
DSVI: Dissolved sludge volume index (ml/g) 
ERR: Result error 
Flow: Flow (ML/day) for entire plant 
ND: Not determined 
NN: Nitrate and nitrite (N mg/L) 
OP: ortho-phosphate (P mg/L) 
RASF: RAS flow rate (s) (kL/day) 
RASSS: RAS suspended solids (mg/L) 
SETS: Settleabale solids (30 min ml/L) 
SS: Suspended solids (105°C mg/L) 
SVI: Sludge volume index (ml/g) 
SWR: Sludge wasting rate (kL/day) 
TKN: Total Keldjahl nitrogen (N mg/L) 
TP: Total phosphorus (P mg/L) 
VSS: Volatile suspended solids (mg/L) 
Figures in red are anomalies and not transcription errors from the laboratory printouts. 
174 
ANNEXURE 4.1.7 RAW DATE FROM MITCHELLS PLAIN WWTP 
PSTC-F (INFLL IENT) 
Date: Flow SS COD TKN AMM TP OP PH CL ALK CON 
4/6 40 254 577 93.1 81 13.0 10.7 7.2 78 357 109 
11/6 29 148 542 72.8 54 11.2 8.8 7.1 71 263 90 
18/6 34 262 768 101 85 16.2 13.1 7.3 92 363 114 
25/6 34 168 1307 74.1 66 13.9 11.4 7.1 78 281 100 
2/7 28 235 748 93.0 90 14.3 12.3 6.9 90 377 115 
9/7 ND 268 892 105 83 17.5 14.7 7.0 89 371 122 
17/7 34 244 867 99.3 92 12.5 11.0 6.8 91 394 118 
23/7 34 243 870 99.2 72 16.6 13.5 6.8 100 337 121 
30/7 39 235 707 98.4 88 14.3 11.5 7.1 94 399 134 
6/8 40 254 778 76.5 49 12.4 9.8 6.6 85 305 100 
13/8 42 220 791 101 78 16.9 13.5 6.9 84 378 122 
20/8 37 373 824 102 74 12.5 10.1 7.0 94 373 120 
27/8 ND 338 853 96.2 77 13.7 11.2 7.0 71 348 114 
3/9 38 300 990 74.6 50 19.2 15.4 7.0 85 308 107 
10/9 ND 272 871 77.6 55 12.6 9.7 6.8 83 293 104 
17/9 ND 206 638 ND 84 11.7 10.6 7.1 81 366 110 
24/9 34 ND ND ND ND ND ND ND ND ND ND 
1/10 34 175 602 74.6 70 12.2 10.3 7.3 86 318 119 
8/10 33 216 679 86.9 72 11.2 9.6 7.3 87 326 107 
15/10 34 140 604 94.0 78 13.5 12.0 7.3 91 351 113 
22/10 ND 164 540 80.6 70 10.7 9.2 7.4 88 320 106 
29/10 ND 184 662 101 83 14.2 12.2 7.2 88 357 116 
5/11 31 267 669 79.9 58 10.8 9.2 6.9 75 287 95 
12/11 ND 204 830 91.0 71 14.7 13.4 7.1 90 324 111 
19/11 ND 240 873 80.9 63 18.0 15.5 6.8 84 308 106 
26/11 ND 172 634 104 90 14.9 12.6 7.5 87 361 117 
PSTGH (INFLUENT) 
Date: Flow SS COD TKN AMM TP OP PH CL ALK CON 
4/6 40 264 747 119 98 14.8 11.7 7.1 85 408 124 
11/6 29 360 945 79.9 53 13.6 10.2 6.6 80 274 91 
18/6 34 874 1684 91.6 61 18.1 12.8 6.7 87 299 97 
25/6 34 474 1178 66.8 48 12.1 9.4 6.4 73 239 82 
2/7 28 255 719 111 98 14.4 12.2 7.1 90 394 129 
9/7 ND 384 1158 85.9 56 19.6 15.3 6.7 77 296 104 
17/7 34 356 888 112 83 12.5 10.5 6.6 94 375 122 
23/7 34 392 1199 103 63 16.7 12.7 6.5 108 311 115 
30/7 39 227 662 - 89 14.6 12.0 7.2 94 411 136 
6/8 40 338 876 72.0 46 11.5 8.9 6.4 84 283 95 
13/8 42 192 727 105 83 16.1 13.3 7.0 86 402 126 
20/8 37 416 874 120 92 13.8 11.3 7.1 88 406 131 
27/8 ND 290 754 106 79 14.2 11.4 7.2 77 352 119 
3/9 38 228 1025 71.6 49 18.9 14.7 6.9 81 290 105 
10/9 ND 449 864 117 91 13.6 6.3 7.0 85 352 127 
17/9 ND 645 1437 111 91 14.9 11.6 7.1 82 381 128 
24/9 34 ND- ND ND ND ND ND ND ND ND ND 
1/10 34 352 952 97.7 80 12.8 10.7 6.8 85 361 128 
8/10 33 472 1002 107 80 12.7 10.2 6.9 85 355 113 
15/10 34 534 1295 110 80 15.5 12.7 6.7 86 362 116 
22/10 ND 688 1028 113 94 13.5 11.5 6.8 89 388 123 
29/10 ND 416 1122 139 110 17.1 13.6 7.0 91 396 127 
5/11 31 357 945 102 77 12.0 10.1 6.9 77 322 108 
12/11 ND 500 1123 96.5 74 15.0 12.8 6.9 84 323 109 
19/11 ND 368 1039 74.8 64 17.4 15.3 6.9 91 306 106 
26/11 ND 705 1371 119 89 17.9 14.0 7.0 88 358 118 
175 
MIXED LIQUOR REACTOR C 
Date SETS SS VSS SVI DSVI PH SWR AGE 
4/6 870 4070 3445 214 138 6.7 105 21 
11/6 870 4335 ND 201 120 6.5 99 29 
18/6 770 3780 ND 204 116 6.6 100 29 
25/6 900 5490 ND 164 102 6.4 100 23 
2/7 650 4100 3500 159 98 6.7 100 26 
9/7 580 4280 ND 136 94 6.7 ND ND 
17/7 660 4890 ND 135 82 6.6 ND ND 
23/7 540 3720 ND 145 86 6.5 ND ND 
30/7 530 4250 ND 125 85 6.8 ND ND 
6/8 700 4710 3860 149 85 6.7 ND ND 
13/8 750 4520 ND 162 87 6.6 ND ND 
20/8 650 4900 ND 133 90 6.8 ND ND 
27/8 670 4910 ND 136 90 6.8 ND ND 
3/9 720 5900 ND 122 75 6.8 100 28 
10/9 810 5590 ND 145 86 6.8 ND ND 
17/9 770 5150 ND 150 93 6.9 ND ND 
24/9 550 4900 ND 112 90 6.8 100 ND 
1/10 430 3300 2830 130 97 6.9 100 26 
8/10 420 4180 ND 100 96 6.9 100 28 
15/10 700 4840 ND 145 83 6.9 100 28 
22/10 650 4160 ND 156 87 6.8 ND ND 
29/10 1000 4210 ND 238 86 6.9 ND ND 
5/11 300 3570 3080 84 78 6.8 ND ND 
12/11 520 4910 ND 106 65 6.8 ND ND 
19/11 760 5780 ND 131 76 6.7 ND ND 
26/11 740 7570 ND 98 58 6.8 ND ND 
MIXED LIQUOR REACTOR G 
Date SETS SS VSS SVI DSVI PH SWR AGE 
4/6 760 9920 8535 77 52 6.5 65 70 
11/6 870 11395 ND 76 49 6.5 23 ND 
18/6 870 11770 ND 74 51 6.5 200 30 
25/6 820 8970 ND 91 67 6.4 200 30 
2/7 910 12660 10960 72 54 6.7 200 30 
9/7 890 12900 ND 69 46 6.6 ND ND 
17/7 960 13300 ND 72 51 6.4 ND ND 
23/7 750 9990 ND 75 52 6.5 ND ND 
30/7 690 9510 ND 73 50 6.7 400 15 
6/8 520 8130 6690 64 54 6.6 400 15 
13/8 680 9730 ND 70 45 6.6 ND ND 
20/8 610 9770 ND 62 45 6.8 ND ND 
27/8 490 8330 ND 59 48 6.8 ND ND 
3/9 640 7990 ND 80 50 6.9 300 20 
10/9 650 9490 ND 69 46 6.8 ND ND 
17/9 570 9510 ND 60 50 6.8 ND ND 
24/9 740 11610 ND 64 45 6.7 200 ND 
1/10 840 11590 9900 73 52 6.6 200 30 
8/10 600 9370 ND 64 47 6.9 200 30 
15/10 860 9790 ND 88 65 6.9 100 59 
22/10 890 12930 ND 69 46 6.7 ND ND 
29/10 780 12950 ND 60 43 6.7 ND ND 
5/11 780 12380 10630 63 45 6.7 ND ND 
12/11 660 11040 ND 60 40 6.7 ND ND 
19/11 720 11920 ND 60 37 6.7 ND ND 
26/11 740 10510 ND 71 46 6.7 ND ND 
176 
CLARIFI ER CD (E FFLUENT) 
Date: SS COD AMM NN OP PH CL Alk CON 
4/6 23 51 <0.4 8.4 11.7 6.7 82 82 62 
11/6 7 23 <0.4 8.1 12.0 6.4 76 55 55 
18/6 3 30 <0.4 16.7 9.0 6.6 88 48 63 
25/6 29 55 6.6 6.9 4.6 6.6 79 93 60 
2/7 15 41 <0.4 9.6 6.6 6.7 87 69 66 
9/7 7 37 <0.4 9.1 0.5 6.8 86 85 64 
17/7 9 33 <0.4 6.6 0.1 6.8 91 87 68 
23/7 8 30 0.4 11.7 2.9 6.6 94 64 72 
30/7 9 44 <0.4 8.5 1.0 6.8 90 99 71 
6/8 10 43 <0.4 8.6 2.3 6.5 93 107 72 
13/8 6 36 <0.4 7.0 1.5 6.7 84 109 67 
20/8 7 40 <0.4 6.7 3.7 7.1 88 102 71 
27/8 9 37 <0.4 7.4 6.1 6.9 73 88 65 
3/9 8 22 1.0 6.5 4.1 7.1 76 109 67 
10/9 11 51 0.2 3.1 1.6 7.0 80 108 64 
17/9 9 48 0.6 5.8 5.8 7.1 81 100 67 
24/9 ND ND ND ND ND ND ND ND ND 
1/10 10 30 <0.4 11.5 9.7 6.9 84 72 75 
8/10 8 44 0.4 12.1 9.1 6.9 93 71 67 
15/10 8 25 <0.4 13.5 9.9 7.0 85 61 65 
22/10 13 37 <0.4 7.9 6.2 6.9 84 82 64 
29/10 6 30 <0.4 9.4 10.3 7.1 82 79 64 
5/11 8 34 <0.4 8.4 7.0 7.2 85 92 65 
12/11 12 49 0.5 8.9 11.8 7.0 86 85 66 
19/11 8 37 3.2 6.1 8.2 6.8 85 113 68 
26/11 6 30 0.8 11.0 9.9 7.0 81 81 64 
CLARIFI ER GH (E FFLUENT) 
Date: SS COD AMM NN OP PH CL Alk CON 
4/6 29 61 0.4 11.8 6.6 6.7 80 81 63 
11/6 7 37 0.4 10.0 3.7 6.6 76 64 55 
18/6 11 51 0.4 14.4 9.0 6.8 89 72 65 
25/6 12 50 <0.4 14.5 4.9 6.6 84 80 64 
2/7 20 55 <0.4 10.9 5.8 6.7 86 76 66 
9/7 45 104 0.6 10.0 3.1 6.9 85 98 67 
17/7 14 44 0.3 7.6 6.5 6.8 91 82 69 
23/7 34 62 <0.4 14.5 8.9 6.5 96 59 74 
30/7 9 37 <0.4 13.0 5.5 6.8 90 76 72 
6/8 12 47 <0.4 15.5 6.1 6.5 93 83 74 
13/8 2 47 <0.4 13.1 4.5 6.7 86 83 71 
20/8 8 51 0.4 17.0 7.4 7.0 87 70 75 
27/8 6 44 <0.4 16.6 6.9 6.9 75 50 67 
3/9 7 40 <0.4 20.7 8.7 6.9 77 61 71 
10/9 11 58 <0.4 12.7 4.4 7.0 78 61 69 
17/9 15 51 <0.4 13.4 3.4 7.1 82 78 70 
24/9 ND ND ND ND ND ND ND ND ND 
1/10 14 44 <0.4 14.4 2.8 7.0 83 85 77 
8/10 8 48 <0.4 18.9 6.9 7.2 90 59 70 
15/10 7 46 29 0.1 4.8 7.5 84 224 86 
22/10 22 48 0.8 3.0 5.8 7.1 84 122 67 
29/10 26 52 0.4 15.2 9.0 7.0 83 75 67 
5/11 15 45 0.4 14.5 12.1 7.1 84 72 68 
12/11 30 67 0.5 15.1 13.1 6.8 86 69 71 
19/11 14 52 0.4 23.0 12.0 6.7 87 56 70 
26/11 22 65 0.4 13.9 9.4 7.0 81 88 66 
177 
AGE: Sludge age (days) 
ALK: Alkalinity (CaC03 mg/L) 
AMM: Ammonia (N mg/L) 
CL: Chloride (Cr mg/L) 
COD: Chemical oxygen demand (mg COD/L) 
CON: Conductivity (mS/m) 
DSVI: Dissolved sludge volume index (ml/g) 
Flow: Flow (ML/day) for entire plant 
ND: Not determined 
NN: Nitrate and nitrite (N mg/L) 
OP: ortho-phosphate (P mg/L) 
SETS: Settleabale solids (30 min ml/L) 
SS: Suspended solids (105°C mg/L) 
SVI: Sludge volume index (ml/g) 
SWR: Sludge wasting rate (kL/day) 
TKN: Total Keldjahl nitrogen (N mg/L) 
TP: Total phosphorus (P mg/L) 
VSS: Volatile suspended solids (mg/L) 
Figures in red are anomalies and not transcription errors from the laboratory printouts. 
178 
ANNEXURE 4.1.8 RAW DATA FROM PAROW WWTP 
RAW INFLUEN-r (NO PST) 
Date: Flow ss SETS COD TKN AMM TP OP PH CON CL ALK 
6/6 1.0 336 14.0 754 65.9 58 16.1 9.2 7.5 75 134 271 
13/6 1.0 453 27.0 793 83.2 73 16.3 7.8 8.2 120 147 309 
20/6 1.0 708 27.0 1180 118 70 18.6 7.9 7.7 120 151 286 
27/6 ND 360 22.0 778 87.8 59 16.1 7.3 8.2 121 149 274 
4/7 ND 353 17.0 688 81.7 58 12.9 6.8 8.2 132 177 274 
11/7 ND 400 22.0 704 84.2 61 13.0 6.8 7.9 143 209 285 
18/7 ND 384 20.0 707 95.4 70 12.4 7.1 8.2 118 140 275 
25/7 1.1 473 21.0 855 ND 67 ND 7.2 8.2 132 169 287 
1/8 1.2 408 27.0 699 80.7 62 12.1 6.8 8.1 136 178 285 
8/8 ND 324 15.0 695 ND 29 ND 5.8 7.5 107 164 216 
15/8 ND 252 18.0 557 75.1 47 10.1 6.0 7.9 123 164 274 
22/8 ND 423 23.0 760 96.4 69 12.4 7.2 8.4 129 164 309 
29/8 1.1 484 20.0 669 76.8 57 12.4 6.5 8.3 129 183 281 
5/9 1.1 360 22.0 698 71.2 50 13.4 6.3 7.8 115 151 259 
12/9 1.2 297 22.0 584 54.3 39 11.9 5.7 8.0 115 158 238 
26/9 ND 452 22.0 838 95.6 69 12.7 7.5 8.1 140 204 299 
3/10 1.1 456 22.0 893 96.2 64 13.7 7.3 8.3 120 164 281 
10/10 1.0 440 20.0 872 104 74 ND 8.3 8.4 123 154 309 
17/10 1.0 296 20.0 802 83.2 56 15.0 8.0 8.2 107 132 254 
24/10 1.0 380 18.0 679 86.5 66 13.5 7.3 8.2 116 152 262 
1/11 1.0 620 29.0 1008 97.6 69 17.1 9.5 7.7 118 137 335 
8/11 1.0 504 24.0 940 112 82 14.8 9.0 8.3 123 149 311 
14/11 1.0 523 23.0 862 102 73 14.6 8.3 7.9 114 134 294 
21/11 1.1 925 24.0 1969 125 66 21.3 7.7 8.2 117 152 268 
28/11 1.0 503 25.0 938 96.2 73 15.2 9.1 8.1 117 149 305 
MIXED LIQUOR 
Date SETS ss vss SVI DSVI PH RASSS 
6/6 970 4510 3885 215 151 7.0 6560 
13/6 1000 5740 ND 174 160 7.1 7790 
20/6 990 5620 ND 176 ND 7.0 11310 
27/6 1000 6420 ND 156 156 6.7 7180 
4/7 1000 5620 4570 178 164 6.5 7500 
11/7 970 4850 ND 200 173 6.7 5620 
18/7 980 4650 ND 211 163 6.3 5860 
25/7 920 4300 ND 214 149 6.4 ND 
1/8 920 3870 ND 238 165 6.7 5330 
8/8 960 3410 ND 282 223 6.8 ND 
15/8 970 4230 ND 229 189 6.6 4600 
22/8 980 5050 ND 194 198 6.9 7400 
29/8 990 5920 ND 167 135 7.0 6200 
5/9 1000 5780 4835 173 104 7.0 9280 
12/9 1000 5690 ND 176 225 7.1 8710 
26/9 980 4630 ND 212 216 7.1 6570 
3/10 1000 5190 4250 193 247 7.1 5930 
10/10 1000 5290 ND 189 ND 6.9 7680 
17/10 1000 4560 ND 219 228 7.0 7280 
24/10 1000 4740 ND 211 253 6.9 6060 
1/11 1000 4500 ND 222 222 6.8 6980 
8/11 1000 5420 4530 185 236 7.0 6180 
14/11 1000 5200 ND 192 292 6.9 6640 
21/11 1000 5555 ND 180 360 6.9 5635 
28/11 1000 4820 ND 208 332 6.9 5400 
179 
CLARIFI ER (EFFLUENT) 
Date: ss COD AMM NN OP PH CON CL ALK 
6/6 6 40 1.5 7.0 6.6 7.0 99 204 84 
13/6 5 33 15 <0.1 7.1 7.5 123 240 179 
20/6 1 48 12 0.7 0.5 7.4 112 219 171 
27/6 2 58 0.4 1.9 1.8 7.2 110 229 112 
4/7 4 45 <0.4 17.6 8.3 7.1 126 238 66 
11/7 5 29 <0.4 23.3 6.9 6.9 133 270 50 
18/7 3 34 <0.4 20.6 6.7 6.8 118 240 60 
25/7 ND ND 0.4 16.3 7.4 7.1 102 194 52 
1/8 8 55 <0.4 16.6 5.9 7.0 139 276 90 
8/8 ND ND ND ND ND ND ND ND ND 
15/8 5 44 0.6 21.5 6.4 6.6 125 239 70 
22/8 5 62 <0.4 19.6 6.1 7.1 129 262 80 
29/8 3 55 7.0 0.8 1.1 7.4 132 267 180 
5/9 4 33 9.2 0.3 0.9 7.5 130 254 183 
12/9 6 40 17 0.1 0.7 7.6 130 246 196 
26/9 6 48 17 0.5 2.7 7.5 124 234 184 
3/10 5 40 5.0 2.5 0.4 7.4 105 214 134 
10/10 2 41 14 0.1 4.2 7.4 114 219 174 
17/10 4 33 11 1.5 1.9 7.4 111 210 152 
24/10 4 45 5.2 1.6 7.3 7.3 104 201 126 
1/11 6 55 23 0.1 4.5 7.6 116 200 191 
8/11 2 57 12 0.4 0.8 7.5 107 206 162 
14/11 2 30 0.5 3.3 8.2 7.4 98 202 109 
21/11 3 41 <0.4 5.9 10.1 7.3 92 183 95 
28/11 6 44 <0.4 9.4 10.1 7.2 97 199 88 
AGE: Sludge age (days) 
ALK: Alkalinity (CaC03 mg/L) 
AMM: Ammonia (N mg/L) 
CL: Chloride (CP mg/L) 
COD: Chemical oxygen demand (mg COD/L) 
CON: Conductivity (mS/m) 
DSVI: Dissolved sludge volume index (ml/g) 
Flow: Flow (ML/day) for entire plant 
ND: Not determined 
NN: Nitrate and nitrite (N mg/L) 
OP: ortho-phosphate (P mg/L) 
RASSS: RAS suspended solids (mg/L) 
SETS: Settleabale solids (30 min ml/L) 
SS: Suspended solids (105°C mg/L) 
SVI: Sludge volume index (ml/g) 
TKN: Total Keldjahl nitrogen (N mg/L) 
TP: Total phosphorus (P mg/L) 
VSS: Volatile suspended solids (mg/L) 
Figures in red are anomalies and not transcription errors from the laboratory printouts. 
180 
ANNEXURE 1.9 RAW DATE FROM POTSDAM WWTP 
PSTA( NFLUEN1 D 
Date: RAW 
FLOW 
PSTA 
FLOW 
SS COD TKN AMM TP OP PH CL ALK CON 
5/6 36.9 17.2 192 676 60.8 40 11.8 8.5 6.6 161 288 124 
12/6 37.5 16.8 156 610 50.7 38 11.2 8.4 6.7 168 272 121 
19/6 36.8 16.4 164 599 57.7 40 10.8 8.5 6.8 166 291 120 
26/6 34.3 21.9 152 475 47.3 31 9.2 6.4 6.7 135 215 99 
3/7 36.5 17.9 121 579 53.5 38 10.0 8.2 7.1 171 285 125 
10/7 34.1 19.4 142 588 56.6 41 10.4 8.6 6.7 192 275 135 
17/7 32.5 19.3 162 616 61.9 43 10.9 8.6 6.7 184 262 132 
24/7 32.7 19.0 122 540 55.3 35 8.8 6.3 6.8 163 271 119 
31/7 36.4 21.0 126 519 45.6 32 10.3 8.1 6.7 198 258 132 
7/8 33.7 20.1 ND ND ND ND ND ND ND ND ND ND 
14/8 33.6 20.4 80 460 45.8 29 7.9 5.1 6.8 184 235 121 
21/8 33.2 19.4 120 545 44.9 31 8.1 6.4 6.8 177 228 124 
28/8 37.4 22.6 132 577 51.1 33 10.4 8.0 6.9 182 278 136 
4/9 35.3 19.8 172 692 57.2 39 10.5 8.3 7.0 177 294 132 
11/9 ND ND 174 612 58.2 39 11.3 9.1 6.9 205 267 140 
18/9 40.0 16.6 128 609 50.0 38 10.4 8.2 6.9 187 255 133 
25/9 30.0 15.6 140 531 59.7 43 9.9 8.3 7.0 170 280 128 
2/10 30.6 17.7 114 536 51.9 43 10.3 9.5 6.8 170 285 122 
9/10 31.3 18.0 140 677 65.2 44 10.8 8.4 6.9 162 292 104 
16/10 36.5 18.0 150 700 63.2 45 12.2 9.5 7.0 187 296 130 
23/10 32.5 16.5 172 556 56.2 44 8.8 6.9 6.9 182 264 124 
30/10 35.7 14.4 142 604 60.0 44 11.6 9.4 7.0 163 309 122 
6/11 37.3 12.8 154 646 60.5 45 11.3 9.5 7.0 163 275 123 
13/11 ND ND 186 823 61.3 47 15.1 13.1 6.7 156 306 121 
20/11 ND ND 226 710 61.7 46 12.6 10.6 6.9 161 283 118 
27/11 31.4 16.2 152 621 ND 47 ND 9.8 6.9 157 286 120 
MIXED LIQUOR COMBINED E AND W REACTORS 
Date SETS SS VSS SVI DSVI PH SWR RASF AGE RASSS 
5/6 980 6180 5005 159 136 6.6 994 ND 8 9410 
12/6 980 6900 ND 142 139 6.7 ND ND ND 7630 
19/6 990 6830 ND 145 146 6.8 ND ND ND 10210 
26/6 1000 6840 ND 146 146 6.6 ND ND ND 10280 
3/7 1000 7960 6270 126 75 6.8 ND ND ND 10900 
10/7 1000 7980 ND 125 160 6.8 1126 ND 8 11210 
17/7 1000 7070 ND 141 141 6.6 1061 ND 8 10330 
24/7 1000 7210 ND 139 ND 6.6 991 ND 9 10850 
31/7 1000 6800 ND 147 153 6.9 1148 ND 8 10590 
7/8 970 6490 ND 150 150 6.9 1262 ND ND ND 
14/8 1000 6660 ND 150 150 6.6 676 ND 11 11170 
21/8 1000 6410 ND 156 156 6.7 1219 ND 7 10510 
28/8 1000 6960 ND 144 ND 6.9 855 ND 9 10230 
4/9 1000 6790 5510 147 ND 7.0 1547 ND 6 10340 
11/9 1000 6380 ND 157 144 6.9 ND ND ND 8990 
18/9 970 6660 ND 146 138 6.7 1437 ND 6 10630 
25/9 970 7600 ND 128 116 6.7 1081 ND 8 9660 
2/10 990 8050 6500 123 109 6.5 1186 ND 8 10190 
9/10 980 7930 ND 124 106 6.8 1596 ND 6 12630 
16/10 990 8390 ND 118 105 6.8 1556 ND 6 14990 
23/10 970 8390 ND 116 105 6.8 638 ND 13 13430 
30/10 1000 9860 ND 101 101 6.8 656 ND 13 12250 
6/11 980 9040 7100 108 93 6.9 1483 ND 6 12240 
13/11 970 8610 ND 113 102 6.9 ND ND ND 12840 
20/11 970 8615 ND 113 98 6.8 ND ND ND 11315 
27/11 960 8680 ND 111 101 6.8 1515 ND 6 11220 
181 
CLARIFI ER A (EFFLUENT) 
Date: SS COD AMM NN OP PH CL Alk CON 
5/6 25 69 <0.4 6.0 0.2 7.3 143 143 88 
12/6 15 44 <0.4 2.7 0.2 7.3 140 119 85 
19/6 23 52 <0.4 3.5 0.3 7.2 158 153 91 
26/6 19 55 <0.4 2.4 0.4 7.1 147 128 88 
3/7 9 41 <0.4 3.0 0.4 7.5 168 159 100 
10/7 37 92 <0.4 1.2 1.5 7.2 167 181 107 
17/7 15 76 0.5 4.6 0.5 7.2 163 121 102 
24/7 42 76 0.5 2.9 1.4 7.3 156 129 91 
31/7 34 180 <0.4 3.6 0.6 7.1 182 148 106 
7/8 ND ND ND ND ND ND ND ND ND 
14/8 16 55 0.6 3.6 1.2 7.2 186 125 106 
21/8 12 55 <0.4 4.1 1.2 7.9 170 115 104 
28/8 12 54 <0.4 2.7 0.8 7.8 171 154 106 
4/9 22 55 <0.4 3.3 0.4 7.9 183 158 106 
11/9 59 123 <0.4 6.0 0.2 7.7 177 110 106 
18/9 30 97 <0.4 4.6 0.5 7.9 171 122 101 
25/9 10 62 <0.4 6.4 0.7 7.8 167 123 97 
2/10 11 51 <0.4 2.9 1.2 7.4 170 149 96 
9/10 5 44 1.0 2.6 3.5 7.9 153 160 95 
16/10 7 40 <0.4 2.0 0.4 7.9 170 151 98 
23/10 10 69 1.4 2.0 1.3 7.8 182 139 99 
30/10 6 51 <0.4 1.3 1.0 7.9 167 139 96 
6/11 8 41 <0.4 3.7 0.4 7.9 159 145 93 
13/11 6 42 <0.4 1.7 4.6 7.9 160 161 93 
20/11 10 66 0.4 3.1 3.9 8.1 156 142 92 
27/11 9 55 0.6 1.2 5.4 8.2 158 157 92 
AGE: Sludge age (days) 
ALK: Alkalinity (CaC03 mg/L) 
AMM: Ammonia (N mg/L) 
CL: Chloride (Cl" mg/L) 
COD: Chemical oxygen demand (mg COD/L) 
CON: Conductivity (mS/m) 
DSVI: Dissolved sludge volume index (ml/g) 
Flow: Flow (ML/day) for entire plant 
ND: Not determined 
NN: Nitrate and nitrite (N mg/L) 
OP: ortho-phosphate (P mg/L) 
RASF: RAS flow rate (s) (kL/day) 
RASSS: RAS suspended solids (mg/L) 
SETS: Settleabale solids (30 min ml/L) 
SS: Suspended solids (105°C mg/L) 
SVI: Sludge volume index (ml/g) 
SWR: Sludge wasting rate (kL/day) 
TKN: Total Keldjahl nitrogen (N mg/L) 
TP: Total phosphorus (P mg/L) 
VSS: Volatile suspended solids (mg/L) 
Figures in red are anomalies and not transcription errors from the laboratory printouts. 
182 
ANNEXURE 1.10 RAW DATE FROM WESFLEUR INDUSTRIAL WWTP 
RAW INFLOW (NO PST) 
Date: Flow SS vss SETS COD TKN AMM TP OP PH CON CL ALK 
5/6 4.3 206 ND 6.0 814 48.6 26 8.5 5.7 7.2 171 307 279 
12/6 3.9 627 ND 8.0 1417 73.5 27 10.5 4.3 7.7 243 295 353 
19/6 4.2 284 ND 12.0 1062 59.9 34 10.9 6.8 7.3 170 306 277 
26/6 4.0 366 ND 12.0 1013 53.5 32 6.3 3.9 7.4 187 313 233 
3/7 4.1 322 ND 8.0 981 51.9 30 10.0 6.5 7.5 194 402 280 
10/7 4.1 356 ND 13.0 849 52.8 29 10.5 5.9 7.4 198 354 265 
17/7 6.0 248 ND ND 767 57.5 42 8.7 7.1 7.0 168 270 244 
24/7 ND 324 ND 9.0 940 54.2 29 7.5 4.5 7.2 165 125 249 
31/7 4.3 334 ND 12.0 1037 46.5 28 8.9 5.4 7.5 178 299 267 
7/8 4.2 303 ND 10.0 952 ND 28 ND 4.9 7.4 193 355 265 
14/8 3.9 192 ND 5.0 1070 44.8 30 6.7 4.4 7.5 213 264 516 
21/8 4.3 273 ND 4.0 1138 54.2 24 9.3 5.0 7.7 267 324 331 
28/8 4.4 216 ND 6.0 811 48.7 30 8.3 6.2 7.5 181 279 248 
4/9 4.2 294 290 12.0 1002 56.3 29 8.9 5.5 7.2 179 317 267 
11/9 4.0 284 ND 2.0 984 56.9 28 8.5 4.1 7.9 236 401 310 
18/9 4.3 230 ND 5.0 733 44.3 26 8.0 5.8 7.4 212 397 290 
25/9 3.7 148 ND 2.0 990 48.8 36 7.1 5.8 7.1 212 304 439 
2/10 3.8 204 188 3.0 885 42.2 26 7.8 5.5 7.0 195 371 279 
9/10 3.9 308 ND 10.0 1074 51.2 30 9.2 6.2 7.2 191 344 277 
16/10 4.2 442 ND 12.0 949 76.2 47 9.1 5.8 7.5 192 313 260 
23/10 4.1 500 ND 15.0 1368 70.9 46 9.5 5.4 7.3 161 254 247 
30/10 4.2 576 ND 18.0 1438 59.5 27 12.2 7.1 7.1 154 264 298 
6/11 4.1 664 556 25.0 1539 69.1 33 12.2 7.2 7.2 185 325 270 
13/11 4.2 384 ND 7.0 896 46.4 30 8.1 5.3 7.1 196 406 343 
20/11 4.1 178 ND 2.0 691 42.4 35 7.3 6.7 7.2 178 319 233 
27/11 4.2 420 ND 12.0 1129 89.8 65 11.0 6.9 7.4 160 400 212 
MIXED LIG IUOR INDUSTRIAL BIO REACTOR 
Date SETS SS VSS SVI DSVI PH SWR AGE RASS 
5/6 960 7080 6115 136 107 7.1 91 59 11960 
12/6 960 6410 ND 150 112 7.1 179 32 14510 
19/6 900 6360 ND 142 88 7.0 241 25 10970 
26/6 890 5780 ND 154 90 7.0 102 52 12310 
3/7 880 6060 5190 143 91 7.1 127 46 10100 
10/7 920 6730 ND 137 95 7.2 98 58 9730 
17/7 890 6860 ND 130 76 6.5 139 38 12620 
24/7 880 6860 ND 128 93 6.7 ND ND 10920 
31/7 850 6950 ND 122 104 7.0 132 45 10400 
7/8 940 6770 ND 139 100 6.9 87 ND ND 
14/8 920 7270 ND 127 77 6.9 113 52 12240 
21/8 940 7020 ND 134 80 6.9 122 46 14110 
28/8 900 7050 ND 128 85 7.0 112 49 10930 
4/9 860 6100 5600 141 85 7.2 217 28 10340 
11/9 860 5850 ND 147 89 7.1 175 34 10170 
18/9 780 6010 ND 130 73 7.0 134 43 10940 
25/9 470 6440 ND 73 50 6.9 165 34 8450 
2/10 640 6100 5240 105 59 7.1 119 47 9860 
9/10 670 6850 ND 98 58 7.0 81 68 10790 
16/10 600 6090 ND 99 59 6.9 266 23 8810 
23/10 490 5440 ND 90 59 7.1 279 22 6540 
30/10 430 5400 ND 80 52 6.9 144 42 8480 
6/11 500 5970 5010 84 60 7.1 120 50 8100 
13/11 650 5660 ND 115 71 7.3 128 43 8960 
20/11 650 6425 ND 101 69 6.9 172 36 9365 
27/11 810 6210 ND 130 77 7.0 105 56 9940 
183 
CLARIFI ER I (INFLI JENT) 
Date: SS COD FCOD AMM NN OP PH CON CL ALK 
5/6 28 104 ND 9.5 0.2 4.4 7.6 182 277 278 
12/6 39 112 ND <0.4 30.7 0.2 7.3 160 264 136 
19/6 25 67 ND <0.4 14.7 0.2 7.3 156 297 163 
26/6 32 100 66 <0.4 14.7 1.7 7.4 185 345 162 
3/7 20 70 ND <0.4 14.4 2.2 7.4 175 375 111 
10/7 21 98 ND 0.5 2.7 3.9 7.7 210 324 374 
17/7 32 88 ND 3.3 11.9 1.0 7.0 128 232 92 
24/7 15 66 48 0.4 14.2 4.8 7.1 151 284 99 
31/7 15 73 ND <0.4 11.7 0.2 7.1 166 316 142 
7/8 ND ND ND ND ND ND ND ND ND ND 
14/8 17 69 ND 0.5 19.0 0.2 7.4 169 351 140 
21/8 27 78 49 <0.4 15.0 0.2 7.1 147 259 77 
28/8 29 79 ND <0.4 15.7 2.4 7.3 167 281 90 
4/9 16 69 51 <0.4 2.5 3.6 7.6 181 354 153 
11/9 18 70 ND <0.4 12.2 0.9 7.5 194 407 140 
18/9 19 99 ND <0.4 13.5 1.2 7.6 222 434 142 
25/9 40 98 ND <0.4 18.2 8.7 7.1 144 270 67 
2/10 28 122 ND 26 0.7 5.5 7.7 199 332 279 
9/10 23 86 ND <0.4 14.7 0.2 7.5 189 361 126 
16/10 14 76 ND <0.4 12.8 0.5 7.5 167 345 105 
23/10 12 98 ND <0.4 10.3 0.4 7.5 171 350 126 
30/10 12 63 ND 0.4 12.1 0.2 7.4 155 306 108 
6/11 12 78 ND 0.4 12.8 0.2 7.4 184 382 102 
13/11 26 133 ND 1.2 1.4 8.9 7.8 199 383 296 
20/11 12 62 55 0.4 17.1 0.4 7.4 156 301 106 
27/11 13 73 ND <0.4 13.7 0.1 7.4 162 335 122 
AGE: Sludge age (days) 
ALK: Alkalinity (CaC03 mg/L) 
AMM: Ammonia (N mg/L) 
CL: Chloride (Cr mg/L) 
COD: Chemical oxygen demand (mg COD/L) 
CON: Conductivity (mS/m) 
DSVI: Dissolved sludge volume index (ml/g) 
FCOD: Filtered chemical oxygen demand 
Flow: Flow (ML/day) for entire plant 
ND: Not determined 
NN: Nitrate and nitrite (N mg/L) 
OP: ortho-phosphate (P mg/L) 
RASF: RAS flow rate (s) (kL/day) 
RASSS: RAS suspended solids (mg/L) 
SETS: Settleabale solids (30 min ml/L) 
SS: Suspended solids (105°C mg/L) 
SVI: Sludge volume index (ml/g) 
SWR: Sludge wasting rate (kL/day) 
TKN: Total Keldjahl nitrogen (N mg/L) 
TP: Total phosphorus (P mg/L) 
VSS: Volatile suspended solids (mg/L) 
Figures in red are anomalies and not transcription errors from the laboratory printouts. 
184 
ANNEXURE 4.11 RAW DATE FROM WILDEVOELVLEI WWIP 
RAW IN FLUENT (NO PS1 0 
Date: Flow SS vss SETS COD TKN AMM TP OP CL PH CON ALK 
4/6 10.2 400 328 27.0 790 67.9 47 12.8 8.6 103 7.3 101 260 
11/6 15.8 228 ND 11.0 355 42.2 26 7.0 4.2 124 7.3 93 20 
18/6 ND 250 ND 11.0 554 72.1 39 11.0 8.4 135 7.4 106 247 
25/6 ND 406 ND 15.0 732 55.2 31 10.4 7.1 112 7.3 95 218 
2/7 19.0 220 192 9.0 533 46,3 30 10.8 7.9 138 7.4 108 229 
9/7 15.3 312 ND 14.0 679 60.7 37 12.2 9.0 135 7.4 113 249 
17/7 ND 350 ND 12.0 595 57.8 43 8.4 9.8 135 7.3 99 296 
23/7 ND 303 ND 14.0 712 63.2 38 12.7 10.0 125 7.2 100 245 
30/7 22.7 175 ND 9.0 411 32.5 21 8.9 5.7 150 7.4 106 220 
6/8 19/6 210 167 7.0 369 36.4 20 5.7 3.4 102 7.4 79 175 
13/8 ND 160 ND 10.0 520 45.9 28 9.2 6.7 135 7.3 106 258 
20/8 18.5 211 ND 10.0 566 50.0 28 11.1 8.1 131 7.6 108 231 
27/8 17.1 280 ND 9.0 636 53.4 30 8.7 6.8 131 7.5 109 247 
3/9 17.1 178 ND 7.0 421 36.4 24 8.0 6.1 91 7.6 83 192 
10/9 16.2 344 ND 13.0 679 62.1 44 14.1 10.6 120 7.4 113 273 
17/9 ND 325 ND 8.0 576 46.8 32 10.7 8.3 98 7.5 94 217 
24/9 ND 296 ND 11.0 547 88.9 60 9.0 6.3 163 8.2 135 206 
1/10 12.9 456 376 14.0 823 60.1 40 14.3 11.2 116 7.3 116 260 
8/10 ND 364 ND 12.0 679 64.4 45 12.5 9.7 127 7.5 110 275 
15/10 ND 277 ND 13.0 688 ND 40 14.1 11.3 117 7.4 101 250 
22/10 ND 300 ND 15.0 684 59.3 43 11.5 9.2 130 7.3 106 263 
29/10 ND 384 ND 19.0 713 76.6 55 14.1 10.9 129 7.5 113 286 
5/11 ND 297 187 11.0 804 61.9 40 11.8 9.8 114 7.4 104 249 
12/11 ND 192 ND 7.0 564 59.1 42 12.2 10.8 130 7.5 110 254 
19/11 ND 328 ND 16.0 787 54.6 36 14.5 12.9 107 7.3 96 249 
26/11 10.9 367 ND 14.0 747 98.6 74 11.7 7.6 146 7.9 129 330 
MIXED LIC IUOR BIOR EACTOR A 
Date SETS SS VSS SVI DSVI PH SWR AGE RASSS RASF 
4/6 920 6200 5140 148 116 6.6 ND ND 10840 ND 
11/6 930 5450 ND 171 110 6.7 ND ND 15690 ND 
18/6 910 4925 ND 185 114 6.8 ND ND 10215 ND 
25/6 760 3660 ND 208 109 6.6 ND ND 18410 ND 
2/7 770 4240 3490 182 113 6.8 63 63 10760 ND 
9/7 970 6250 ND 155 122 6.7 133 51 7100 ND 
17/7 950 5630 ND 169 121 6.5 ND ND 8340 ND 
23/7 970 6560 ND 148 122 6.6 ND ND 10290 ND 
30/7 900 5525 ND 163 145 6.8 131 51 11555 ND 
6/8 810 4500 ND 180 142 6.9 236 27 12440 ND 
13/8 970 5400 ND 180 141 6.9 ND ND 11730 ND 
20/8 960 5700 ND 168 147 6.6 275 26 8920 ND 
27/8 1000 5340 ND 187 157 6.9 333 21 6520 ND 
3/9 950 4630 ND 205 147 7.1 182 37 7820 10MI/d 
10/9 950 5070 ND 187 142 6.9 278 25 6060 13 
17/9 760 3330 ND 228 144 7.1 ND ND 6180 ND 
24/9 940 5110 ND 184 141 7.0 ND ND ND ND 
1/10 550 2600 2130 212 139 7.0 151 39 8340 182 
8/10 940 4880 ND 193 148 6.9 ND ND 6530 ND 
15/10 950 4930 ND 193 138 6.9 ND ND 7800 ND 
22/10 820 3570 ND 230 123 6.9 ND ND 7900 ND 
29/10 920 4980 ND 185 120 7.0 ND ND 7310 ND 
5/11 380 2200 1860 173 127 7.1 ND ND 6910 ND 
12/11 880 3660 ND 240 142 6.9 ND ND 8080 ND 
19/11 930 4480 ND 208 134 6.9 ND ND 5540 ND 
26/11 930 4230 ND 220 151 7.0 339 21 5240 ND 
185 
MIXED LIQUOR BIOREACTOR B 
Date SETS SS VSS SVI DSVI PH SWR AGE RASSS RASF 
4/6 1000 6110 4990 164 164 6.6 ND ND 7630 ND 
11/6 390 2050 ND 190 137 6.7 ND ND 5470 ND 
18/6 950 4105 ND 231 156 6.8 ND ND 4535 ND 
25/6 770 2990 ND 258 160 6.7 ND ND 4110 ND 
2/7 1000 5680 4610 176 176 6.7 65 74 7230 ND 
9/7 1000 6530 ND 153 153 6.6 151 46 7900 ND 
17/7 1000 7480 ND 134 171 6.4 ND ND 8740 ND 
23/7 460 2490 ND 185 161 6.9 ND ND 11850 ND 
30/7 970 5215 ND 186 161 6.7 221 30 9605 ND 
6/8 970 5880 ND 165 156 6.7 286 21 7260 ND 
13/8 800 4310 ND 186 ND 6.8 ND ND 19770 ND 
20/8 940 3970 ND 237 161 6.6 360 20 8420 ND 
27/8 950 3960 ND 240 182 6.8 377 19 6200 11 
3/9 930 3990 ND 233 170 7.0 225 30 5940 ND 
10/9 970 6200 ND 156 142 6.7 225 30 8910 ND 
17/9 770 5960 ND 129 121 6.8 ND ND 15000 ND 
24/9 940 5450 ND 172 125 7.0 ND ND ND ND 
1/10 940 5570 4490 169 129 6.8 13 169 6060 36 
8/10 950 5480 ND 173 124 6.8 ND ND 10070 ND 
15/10 980 6670 ND 147 132 6.6 ND ND 9710 ND 
22/10 970 6760 ND 143 118 6.7 ND ND 9740 ND 
29/10 820 4930 ND 166 97 6.9 ND ND 10350 ND 
5/11 980 7230 6020 135 121 6.9 ND ND 7190 ND 
12/11 730 3360 ND 217 119 6.8 ND ND 6480 ND 
19/11 1000 8230 ND 122 107 6.8 ND ND 12140 ND 
26/11 960 6570 ND 146 116 7.0 ND ND 12950 ND 
CLARIFIER A (EFFLUENT) 
Date: SS COD AMM NN OP CL PH CON ALK 
4/6 8 33 11 <0.1 1.7 117 7.3 80 160 
11/6 6 30 <0.4 7.9 1.8 136 6.9 81 95 
18/6 4 41 <0.4 3.3 8.5 142 7.1 75 113 
25/6 10 47 <0.4 1.3 6.8 130 7.0 79 114 
2/7 12 41 <0.4 12.4 5.8 151 6.9 91 86 
9/7 4 33 1.3 8.8 5.9 147 7.2 91 99 
17/7 5 33 0.7 8.5 7.3 143 7.1 88 96 
23/7 6 37 <0.4 8.4 8.2 144 6.9 90 88 
30/7 3 51 <0.4 8.9 4.6 161 7.1 98 121 
6/8 9 33 <0.4 10.4 5.1 158 7.2 94 110 
13/8 2 36 0.4 9.6 4.5 149 7.2 93 127 
20/8 2 51 <0.4 9.5 4.8 151 7.3 96 110 
27/8 4 30 <0.4 9.5 4.2 140 7.3 92 102 
3/9 4 30 <0.4 10.7 4.6 137 7.4 91 106 
10/9 4 51 0.1 9.4 5.5 136 7.3 88 102 
17/9 3 30 <0.4 11.5 6.1 132 7.3 88 87 
24/9 ND ND ND ND ND ND ND ND ND 
1/10 7 33 <0.4 4.9 5.4 125 7.3 91 103 
8/10 3 41 <0.4 8.1 5.8 126 7.3 79 91 
15/10J 15 35 <0.4 7.0 7.2 127 7.3 81 94 
22/10 3 34 <0.4 6.7 8.3 120 7.2 77 90 
29/10 3 19 <0.4 8.1 8.7 129 7.3 79 84 
5/11 4 30 <0.4 2.3 4.3 114 7.5 73 108 
12/11 4 38 0.7 6.2 7.2 123 7.2 76 97 
19/11 4 37 <0.4 13.6 9.8 121 7.3 79 67 
26/11 6 30 <0.4 13.2 10.3 116 7.2 76 71 
186 
CLARIFIER B (EFFLUENT) 
Date: SS [ COD AMM NN OP CL PH CON ALK 
4/6 7 30 0.6 4.2 5.9 115 7.1 74 107 
11/6 10 34 0.4 5.8 2.4 143 7.0 84 111 
18/6 5 34 1.8 2.7 1.0 142 7.2 83 128 
25/6 21 70 1.2 2.3 1.4 125 7.0 77 117 
2/7 10 44 ND 4.0 2.7 150 7.1 89 124 
9/7 4 40 0.5 3.3 2.6 149 7.3 89 126 
17/7 5 37 1.1 1.5 4.0 146 7.2 86 125 
23/7 10 44 0.7 9.2 2.4 133 7.0 83 91 
30/7 5 50 ND 7.9 2.7 160 7.2 97 128 
6/8 18 47 ND 6.4 2.9 156 7.3 93 128 
13/8 14 75 9.8 5.6 5.5 148 7.2 98 168 
20/8 3 51 ND 8.5 1.0 151 6.9 91 114 
27/8 4 40 ND 5.7 2.6 134 7.4 89 117 
3/9 5 37 ND 7.2 3.5 136 7.6 89 118 
10/9 6 44 0.1 6.7 3.7 135 7.4 87 116 
17/9 6 33 ND 12.8 4.9 133 7.5 88 89 
24/9 ND ND ND ND ND ND ND ND ND 
1/10 13 40 ND 9.4 3.7 127 7.4 90 91 
8/10 1 37 ND 10.4 4.8 129 7.3 78 86 
15/10 6 32 1.0 0.6 3.3 120 7.4 79 114 
22/10 5 37 3.6 1.8 7.0 120 7.3 79 126 
29/10 6 30 5.4 0.2 9.1 128 7.5 80 136 
5/11 8 37 12 <0.4 4.3 114 7.5 73 108 
12/11 17 60 24 0.5 8.4 122 7.4 95 201 
19/11 23 70 33 0.4 7.4 120 7.5 99 229 
26/11 22 61 14 0.4 0.6 112 7.4 79 174 
AGE: Sludge age (days) 
ALK: Alkalinity (CaC03 mg/L) 
AMM: Ammonia (N mg/L) 
CL: Chloride (Cr mg/L) 
COD: Chemical oxygen demand (mg COD/L) 
CON: Conductivity (mS/m) 
DSVI: Dissolved sludge volume index (ml/g) 
Flow: Flow (ML/day) for entire plant 
ND: Not determined 
NN: Nitrate and nitrite (N mg/L) 
OP: ortho-phosphate (P mg/L) 
RASF: RAS flow rate (s) (ML/day) 
RASSS: RAS suspended solids (mg/L) 
SETS: Settleabale solids (30 min ml/L) 
SS: Suspended solids (105°C mg/L) 
SVI: Sludge volume index (ml/g) 
SWR: Sludge wasting rate (kL/day) 
TKN: Total Keldjahl nitrogen (N mg/L) 
TP: Total phosphorus (P mg/L) 
VSS: Volatile suspended solids (mg/L) 
Figures in red are anomalies and not transcription errors from the laboratory printouts. 
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