Performance Evaluation of Oke-Afa Wastewater Treatment Plant in Isolo, Lagos State, Nigeria

Abstract

For three months, the Oke-Afa wastewater treatment plant (O-AWWTP) located in Oke-Afa was studied. Data was collected from both the raw influent, which enters the WWTP, and the treated wastewater (effluent) from the plant. The parameters indicators, including pH, dissolved oxygen (DO), biochemical oxygen demand (BOD₅), chemical oxygen demand (COD), total suspended solids (TSS), Ammonia (NH₃), electrical conductivity (EC), fecal coliform (FC), and Phosphate concentration (PO4) were tested for both samples to evaluate the performance of O-AWWTP. The removal efficiency of the plant in treating these parameter indicators was estimated, and the treatment plant reliability factor (RF) of each parameter indicator was calculated based on the NESREA-approved acceptable limit for discharge. Based on the study conducted, the effluent's average concentration of parameter indicators was determined. BOD₅ had a concentration of 18.242mg/l, pH had a concentration of 7.186, DO had a concentration of 7.499mg/l, COD had a concentration of 44.458mg/l, TSS had a concentration of 10.586mg/l, NH₃ had a concentration of 4.392mg/l, EC had a concentration of 237.917µS/cm, FC had a concentration of 31.250 MPN/100ml, and PO₄ had a concentration of 1.903mg/l. The plant's removal efficiency for these pollutants: BOD_5, COD, TSS, NH_3, FC_, and PO₄   was 85.5%, 78%, 93%, 67.5%, 97%, and 71.2%, respectively. However, the plant's performance was deemed unsatisfactory in terms of COD, TSS, and FC removal as their average pollutant concentration in the effluent still exceeded the maximum permissible discharge limit set by the NESREA. Specifically, the limits for COD, TSS, and FC are ≤20mg/l, ≤0.75mg/L, and ≤1.0MPN/100ml, respectively. Based on the indicators tested, most of the estimated RF values were less than 1.0. However, the RF values for COD, TSS, and FC were above 1.0, with values of 2.20, 14.11, and 31.25, respectively