Effluents from the paint industry have been a major source of environmental pollution. There is a need to investigate the compliance of wastewater discharged from paint industries with regulatory standards. In response, this study evaluates the physicochemical parameters of both raw and treated wastewater, the wastewater treatment plants (WWTPs) efficiencies as well as the compliance level of five selected paint manufacturing companies in Lagos, Nigeria with some regulatory standards: Federal Ministry of Environment (FME) in Nigeria, World Health Organization (WHO) and Department of Water Affairs (DWA) in South Africa. All parameters investigated were analysed using standard methods. The values of pH, electrical conductivity (EC) and total dissolved solids (TDS) levels were in the range of 4⁻12.2, 149.1⁻881.3 mS/m and 1100⁻6510 mg/L, respectively. The range of other parameters include total suspended solids (TSS); 0⁻2470 mg/L, TS; 1920⁻6510 mg/L, chloride; 63.8⁻733.8 mg/L, dissolved oxygen (DO); 0⁻6.7 mg/L, oil and grease (O & G); 44⁻100 mg/L, biochemical oxygen demand (BOD); 162.8⁻974.7 mg/L, chemical oxygen demand (COD); 543⁻1231 mg/L, nitrates;12.89⁻211.2 mg/L, phosphate; below detection limit (bdl)⁻0.02 mg/L, sulphate; 195⁻1434 mg/L, nickel; bdl⁻1.9 mg/L while copper, lead and chromium were below detection limits. The results indicated that the WWTPs of the studied paint companies were ineffective in reducing the TS, TSS, BOD, COD and (O & G) to acceptable limits. Routine monitoring of wastewater from paint industries is therefore recommended to prevent the risk of contamination to the receiving watershed which many communities rely on as source for domestic water.
Keywords: biochemical oxygen demand; paint industries; percentage efficiency; wastewater treatment.