Physicochemical Parameters and Heavy Metals Assessment of Effluent Discharges from Some Industries in Benin City, Nigeria

In Nigeria, the continuous discharge of industrial wastewater with non-complaint quality parameters as stipulated by the National Environmental Standards and Regulation Enforcement Agency (NESREA) is a daunting challenge. This precarious situation has led to the continuous decline in our freshwater quality, with adverse environmental and health implications. Consequently, monitoring of wastewater discharged from industries is of utmost importance in order to check them and raise awareness, where necessary. In this study, wastewater samples were collected from four processing facilities around Benin City and environs, namely: a carbonated soft drink company, a brewery, glass manufacturing company and a meat processing outfit (abattoir). Physicochemical parameters and heavy metal concentrations were evaluated in the samples. Results obtained were compared with set standards for effluent discharge by the National Environmental Standards and Regulations Enforcement Agency (NESREA) and the United States Environmental Protection Agency (USEPA) to determine the effluent quality and compliance level of the concerned industries. Data obtained from physicochemical analyses of the effluents from the industries revealed that some parameters, namely: PO4 3- (90.60-311.55 mg/L), SO4 2- (605.9-765.0 mg/L), Cl- (590.14-765.0 mg/L), calcium hardness (283.35-370.0 mg/L), and a heavy metal [Zn (1.90-2.11 mg/L)] had values higher than the maximum permissible limits of NESREA and USEPA while effluents from the carbonated drink and abattoir recorded Pb levels of 0.03 mg/L which was above the permissible limit stipulated by both regulating bodies. The study shows non-compliance of these industrial outfits with standards/guidelines set by the regulatory bodies and calls for appropriate action to stem the present trend whereby poor quality effluents are indiscriminately discharged into receiving water bodies.