Performance of a waste stabilization pond system treating domestic and hospital wastewater and its implications to the aquatic environment - a case study in Dar es Salaam, Tanzania

The reported study herein aimed at investigating the performance of the Lugalo Waste Stabilization Ponds (WSP) system in treating combined domestic and hospital wastewater. The studied parameters include antibiotic residues (AR), salmonella bacteria (SB), heavy metals (HM), pH, coliform bacteria (CB), temperature, chemical oxygen demand (COD) and biochemical oxygen demand (BOD). Results of this study confirmed the presence of antibiotics (amoxicillin and ampicyillin) at varying concentrations in the wastewater. Fecal coliform (FC) and total coliform (TC) count in the WSP effluent were 8 x106 and 25 x 106 count/100 mL, respectively. This represents removal efficiency of 65% (for FC) and 63% (for TC). Salmomella removal efficiency in the WSP was 62%. On the other hand, the concentration of cadmium and chromium as observed in the domestic and hospital effluents ranged from 0.02-0.03 ppm, while in the WSP effluent it was observed to be less than 0.01 ppm. Wastewater effluent had an average lead concentration of 1.05 ppm. The influent and effluent BOD5 concentrations were 124.33 mg/L and 51.07 mg/L, respectively. The removal efficiency in the facultative ponds was observed to be 48.5% while overall removal in the WSP was 59%. Findings of this study generally suggest that the effluent that is discharged from the WSP does not meet the required standards. Its poor performance is probably attributed to addition or inclusion of hospital wastewater. This can have a negative effect on the survival of microbial communities in WSP which may consequently curtail biological processes responsible for degrading pollutantsKeywords: Antibiotics; Heavy metals; Fecal coliform; Waste stabilization Ponds, Wastewater treatmen