SUMMARY
The performance of the Abesan wastewater treatment plant situated at the Abesan Low Cost Housing Estate, Abesan, Lagos had been evaluated. The treatment plant operates on biological treatment method (Activated Sludge Process) with an average wastewater inflow of 6 MLD has been considered for the case study. Thirty – six (36) grab samples of wastewater influent and effluent were collected over a period of six weeks during the dry and rainy seasons. The samples were analyzed for different wastewater quality variables. Average removal efficiencies of the measured parameters from the treated effluents were 96.3% for Chemical Oxygen Demand (COD), 93.3% for Biological Oxygen Demand (BOD), 92.4% for Total Suspended Solids (TSS), and 41.6% for Total Dissolved Solids (TDS) for the dry season. The rainy season average removal efficiency of the measured parameters were 96.8% for COD, 94.6% for BOD, 95.9% for TSS, and 38.6% for TDS. The values obtained for the dry season are lower than that obtained in the rainy season except for TDS. Most of the values of the effluent parameters exceeded the regulatory requirement of the Federal Environmental Protection Agency guideline for effluent limitation. The results obtained from this research conclude that regular routine de-silting and maintenance works of the plant be carried out to allow effective running of the plant.