Performance Evaluation And Redesign Of Waste Stabilization Ponds For The Treatment Of Wastewater In Ongwediva

ABSTRACT

The existing Ongwediva Waste Stabilization Ponds have had several problems in their operations over the past years. Thus, the treatment performance of the waste stabilization ponds was assessed in terms of the reduction efficiency of some physical, chemical and biological pollutants of importance. Data were collected daily from May to June 2017 and analyzed for both raw and treated wastewater. Results of these investigation showed that the average effluent concentrations of BOD, DO, TSS FC, nitrate, nitrite, ammonia, pH, EC and turbidity taken at the secondary facultative pond were 22.07mg/l, 1.91 mg/l, 21.73 mg/l, 2×105 counts/100 ml, 2.33 mg/l, 0.39 mg/l, 0.74 mg/l, 7.64, 16.67 NTU and 98.52 mS/m respectively. The results also indicated that the average effluent concentrations of BOD, nitrate, nitrite, ammonia, TSS and pH complied with the Namibian treated wastewater standards for disposal. However, FC, EC, TDS and turbidity exceeded their maximum permissible limits. The lowest overall efficiencies were for EC, TDS and FC of 5.05%, 5.12% and 20% respectively. Hence the addition of two maturation ponds of size 5408m2 as a final stage of OWSPs. The design of facultative ponds can also be modified by adding additional entrances of wastewater to the ponds to make complete mix in the ponds.