Microbial and physico-chemical quality of groundwater in the North-West Province, South Africa
Ferreira, Simoné Lynn
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More than 80% of the North West Province's (NWP's) rural community solely depend on groundwater for their water needs (Kalule-Sabiti & Heath, 2008). Aquifers are exposed to pollution from anthropogenic activities, yet comprehensive data about the microbial and physico-chemical quality of this water source in the NWP is lacking. The aim of this study was to generate data indicating the microbial and physico-chemical quality of groundwater in the North West Province. Detection of faecal indicator bacteria indicates the possible presence of disease causing pathogens such as viruses (enterovirus, adenovirus and hepatitis A & B) and bacteria (Vibrio cholerae, Shigella spp. Yersina spp. and Enterocolitica spp.). Results may facilitate in predicting possible health risks to exposed communities. Methods included membrane filtration, culture-based methods, biochemical tests, Kirby-Bauer disk diffusion for antibiotic profiles and multiplex PCR for E. coli detection. Physico-chemical variables were measured with calibrated multi-meters and probes. Sampling took place during two sampling periods of 2009 and 2010. A total of 114 boreholes were tested in this study. Of the 76 boreholes tested in 2009, 49% were positive for faecal coliforms, 67% for faecal streptococci, 47% for presumptive P. aeruginosa and 7% for S. aureus. Thirty-three percent of boreholes had heterotrophic plate counts exceeding 1 OOOcfu/ml, increasing the risk of infectious disease transmission. Detection of faecal indicators was higher in the warm, wet seasons than the cold and dry season. Members of the Enterobacteriaceae family were identified with the API 20E system, including E. coli and K pneumonia. In 2010, 38 boreholes were sampled, of which 55% were positive for faecal coliforms, 63% for faecal streptococci, and 55% for P. aeruginosa. Based on the results obtained from MLGA medium, 34% of the 2010 sampled boreholes had E. coli present, whereas multiplex PCR indicated E. coli in 47% of boreholes. Of the 114 boreholes tested over the two sampling periods, 31 % had a FC/FS ratio <O. 7, indicating possible non-human source faecal contamination. Fourteen percent of these had FC/FS ratio >2, indicating human source faecal contamination. Twenty-three percent of the total boreholes tested negative for both faecal coliforms and faecal streptococci. Several of the faecal coliform isolates tested were resistant to multiple antibiotics, especially beta-lactam antibiotics. The average MAR index for 2009 was 0.213 and 0.126 for 2010. Percentage resistance of faecal coliforms to AMOX and AMP decreased significantly in 2010 (21 % and 15% respectively) compared to that of 2009 (54% and 41 %). Resistance to CEP remained consistent throughout both sampling periods. Intermediate resistance to KAN increased from 4% in 2009 to 37% in 2010. The pH, EC and TDS levels were at acceptable ranges for both sampling periods. Only 28% of the total boreholes tested complied with the Department of water affairs target water quality range for nitrate (6mg/L N03-N), and 43% of the boreholes had nitrate levels >20mg/L N03-N. This study demonstrated that groundwater from the North West Province is vulnerable to faecal and nitrate contamination. Antibiotic resistance of indicator bacteria, and subsequently pathogens, further increase the risk to water users. Therefore, this water source should be used with care. Communities should be educated on the risks involved from using this water source for domestic purposes as well as how to minimise these risks. In conclusion, groundwater is the fibre of the socio-economics of the Province and should be managed accordingly.