Assessment of the Efficiency of Wastewater Treatment Plant in Oil and Gas Firm in Eleme Rivers State, Nigeria

The study aimed to determine the efficiency of a wastewater treatment plant and the quality of effluent discharged by the plant into the receiving water body (Okochiri River) in Eleme, Rivers State. The study lasted for four months. Wastewater samples were collected at various stages of the treatment unit and tested for major water quality parameter such as Biological Oxygen Demand (BOD), oil/grease, phenol, Dissolved Oxygen (DO), Total Suspended Solids (TSS), and sulphide. In general, the composite wastewater treatment system (comprising dissolve air floatation, Rotary Bio-Disk, and sedimentation unit) was effective in pollutant removal, except for sulphide, which had a negative efficiency (-238%). In line with Pearson Correlation, there are strong positive relationships between several parameters, such as pH and Sulphide (0.93), Phenol and Oil/grease (1.00), and Phosphate and Sulphide (0.91). The Principal Component Analysis yielded four principal components (PC1-4): PC1 parameters with the highest loadings on the first factor (D1) were sulphates and phenols, whereas Chemical Oxygen Demand and Biological Oxygen Demand had the highest loadings on the second factor (D2). Dissolved oxygen was most strongly associated with the third factor (D3), and pH was the parameter with the highest loading on the fourth factor (D4). It is recommended that the wastewater treatment system's overall efficiency be improved for the system to consistently meet regulatory limits for pollutant control. Recommendations for improving system efficiency include (1) ensuring regular maintenance of individual units in the treatment plant; and (2) maintaining optimal operating conditions for the rotary bio-disk unit.