The effect of illegal dumping on surface water quality using diatoms as a bioindicator
Abstract
Aquatic ecosystems are vital for all life on earth as, without water, there would be no life. It is
therefore important that this vital resource is protected, properly managed and that all
measures are taken to ensure that it is used in a sustainable manner. As water moves
through towns and cities of a region, the water resources are impacted by the anthropogenic
activities within these regions. Poor waste management is one such example of an impact
that pollutes water resources all over the world. The poor municipal waste management
services and the challenges and gaps identified within the waste management legislation,
has led to events of illegal dumping.
Illegal dumping has been identified as a global problem and not only a local environmental
problem in South Africa. The effects caused by illegal dumping are not only limited to where
the location of the dumping site is but extends rather to a much greater footprint. Some of
the effects caused by illegal dumping include health, social, environmental and economic
impacts. Studies have indicated that illegal dumping is more common in the rural
communities where there is very limited access to basic services such as potable water,
sanitation services and municipal waste collection.
This study aimed to assess the impact that illegal dumping has on water quality, through the
use of diatoms as a bioindicator of the health of the aquatic ecosystem. Diatoms are known
as primary producers that play a significant ecological role in the aquatic ecosystems with
their dynamic position at the bottom of the trophic food web. Their specific environmental
requirements make them sensitive to any changes within their environment and therefore
they are regularly used in aquatic ecosystem studies to assess the anthropogenic impacts
and the ecosystem health of aquatic ecosystems.
The study was conducted at several surface water bodies within the Ikageng and Promosa
suburbs of Potchefstroom in the North-West Province of South Africa. These water bodies
form part of a larger drainage system which drains into the Mooi River. The Mooi River is a
very important water resource as it is the only source supplying water to the Potchefstroom
city. Eight sampling sites were selected for the study at which once-off water and diatom
samples were collected during the late summer rainfall month between 15 to 16 February
2019. These sites are located along the drainage lines/streams and dams which all
eventually feed into the Mooi River system. The sites were selected as they were
representative of the area and the water resources of the area during the time of sampling.
Site 8 was used as a reference site to determine the anthropogenic impacts at the other
sites and the effect of the illegal dumping on the water quality of those sites. In situ water
quality variables were measured at each sampling site and water samples were collected to
The effect of illegal dumping on surface water quality using diatoms as a bioindicator
measure the physicochemical variables of the water at each site. The samples were
analysed for nitrites, nitrates, ammonium, phosphate, sulphate and chloride. The water
quality results determined for each site was then compared to the South African water
quality guidelines volume 7 specified for aquatic ecosystems to determine if the
anthropogenic impacts such as illegal dumping affected the water quality at the different
sites. During the diatom sampling, two sets of diatom samples were collected for the live and
fixed diatom analysis. Diatoms were sampled from submerged aquatic vegetation stems at
each site and prepared and analysed according to the prescribed method of Taylor et al.
(2004).
The water quality results analysed for the sites raised concern as some of the variables far
exceeded the specified concentration range within the water quality guidelines specified for
aquatic ecosystems. The inorganic nitrogen (nitrate, ammonium and phosphate)
concentrations measured for the sites were very high and indicated the sites to be of a
eutrophic/hypertrophic ecological state. These eutrophic conditions at the sites are
problematic as it can cause excessive growth of aquatic plants and blue-green algae blooms
of which some species could be toxic and harmful to the livestock, humans and wildlife
within the area. The chloride concentrations for all sites far exceeded the chronic and the
acute effect value. The pH level measured at Site 3 was extremely low and indicated that the
system was very acidic, with pH values within the recommended range measured for all the
other sites.
From the diatom results analysed for the study area, a total of 56 diatom species were
identified over the eight sampling sites. The dominant species identified at the sampling sites
indicated that all the sites (except sites 1 and 8) are eutrophic as these are species that
prefer nutrient-enriched waters and are commonly identified in waters known to be eutrophic
and heavily to extremely polluted. The diatom results corresponded with the measured
physicochemical water variables which also indicated these sites as nutrients enriched and
affected by some sort of pollution. The diatom indices calculated (Specific Pollution
sensitivity Index and Generic Diatom Index) also indicated that the sites had poor to bad
water quality and was classified as eutrophic ecological state. The Percentage Pollutant
Tolerant Valves scores for sites 2 and 3 (fixed) indicated that these sites were heavily
contaminated with organic pollution which could be as a result of wastewater discharge from
the surrounding areas causing organic pollution. The fixed and live diatom samples had a
similar trend for some of the index scores for most of the sites while Site 3 had little
resemblance in the index trend for the live and fixed samples.
The effect of illegal dumping on surface water quality using diatoms as a bioindicator
These results, therefore, indicate that the ecosystem is enriched with nutrients which
correlates with the water quality and dominant diatom species. The presence of the illegal
dumping at these sites definitely contributed to the elevated nutrient concentrations as
previous studies have indicated illegal dumping to be a contributing factor in certain elevated
water quality variables such as nutrients. The hypothesis of the study is therefore supported
as it can be concluded that the illegal dumping of waste near water sources does negatively
influence the water quality of these water resources by altering the water quality parameters
which has led to eutrophic polluted conditions. It was concluded that illegal dumping together
with various other sources (such as waste water and agricultural runoff) does have an
impact on the quality of the selected water resources within the Ikangeng and Promosa area.