Evaluation of contaminants removal by waste stabilization ponds: A case study of Siloam WSPs in Vhembe District, South Africa

Abstract

Waste stabilization ponds (WSPs) are widely used for wastewater management owing to the simplicity of their design, low cost and the use of low-skilled operators. This study was carried out to assess the efficiency of a WSP system in reducing the levels of contaminants in hospital wastewater in a rural area of South Africa and to evaluate the current management of the WSP system. Sampling was conducted monthly from January to June 2014. Physicochemical and microbiological parameters were monitored using standard methods. The microbiological parameters (Escherichia coli and enterococci) in the effluent were higher than those in the influent in some sampling months. Also, low pathogen removal efficiency (<1 log reduction) was recorded. The chemical oxygen demand (COD) in the effluent (82–200 mg/L) exceeded the South African Department of Water Affairs for wastewater discharge guideline value of 75 mg/L although reduction efficiencies of 7.7%, 49.1% and 31.1% were observed for the months of February, April and June, respectively. The WSP system did not show a general trend of contaminant reduction except for Zn (5.5–94.8%). The Siloam WSP is not functioning properly and is releasing effluent of poor quality into the receiving river. It is recommended that the WSP system be expanded to cater for the extra load of wastewater it receives, also desludging should be performed as recommended for such systems. Continuous monitoring of the system for compliance to regulatory guideline should be routinely performed.

Keywords

• E. coli
• Enterococci
• Hydraulic retention time
• Waste stabilization ponds
• Wastewater treatment