The impact of wastewater quality on receiving water bodies and public health in buffalo city and Nkonkobe municipalities

Abstract

The Eastern Cape Province of South Africa is composed mainly of rural areas where the communities still rely heavily on surface water sources for their domestic, irrigation and recreational water needs. This fact places major importance on effluents discharged from wastewater treatment plants into the surrounding surface water bodies to adhere to stringent water quality standards. The chemical and microbiological quality of the effluents must therefore be closely controlled and diligently monitored so that these needs can be met without the communities in the region being put at risk of contracting waterborne diseases. This study evaluated the efficiency of the various wastewater treatment plants for the removal of chemical and microbiological contaminants in order to establish the relationship between the quality of the final effluents and that of the receiving water bodies. To this end, four wastewater treatment plants in the region, i.e. Alice and Fort Beaufort (which both serve the Nkonkobe municipal region), Dimbaza and East London (which both serve the Buffalo City municipal region) were investigated. Wastewater samples were taken monthly from the individual plants analysed from the 6th August 2003 to the 24th March 2004. Wastewater samples were physicochemically characterised according to biological oxygen demand (BOD), chemical oxygen demand (COD), dissolved oxygen (DO), pH, phosphate, residual chlorine, temperature, total nitrogen and total suspended solids (TSS). Student’s t-test was used to compare the physicochemical parameters in the effluent and receiving water body samples. The targeted pathogenic microorganisms under investigation in this study were Salmonella typhimurium, Shigella dysenteriae and Vibrio cholera. Standard methods were applied in all aspects of the analyses for the isolation and detection of these microorganisms and also for the identification of the general microbiological quality of the effluent and the receiving water bodies. Polymerase chain reaction (PCR) was used to confirm the presence of the target microorganisms. The risk assessment was conducted based on the outcome of molecular characterisation of isolates to study the impact of target microorganisms on the health of the communities.