Study of heavy metals pollution and physico-chemical assessment of water quality of River Owo, Agbara, Nigeria

Abstract

The various selected physicochemical and biological condition of freshwater bodies which receive varying number of outfalls of industrial and domestic effluents containing heavy metals of River Owo, Agbara Industrial Estate, a boundary town between Lagos and Ogun state, along Badagry Expressway in Nigeria, was assessed for five consecutive months. Four sampling points were chosen from the water body to reflect the effect of industrial effluent, domestic effluent and lotic habitats. Temperature, pH, salinity, total alkalinity, total hardness (TH), total settle-able solids (TSS), dissolved oxygen (DO), turbidity, biochemical oxygen demand (BOD), ammonia, phosphate, chloride level, sulphate, nitrate, cadmium, chromium, copper, iron, lead, manganese zinc, colour were analyzed monthly between November 2007 and March 2008 using standard methods and procedures. The ranges of these factors were found to be comparable to the recommended limit of the Lagos State Environment Protection Agency (LASEPA) 2001 and the Federal Environmental Protection Agency (FEPA) except for biochemical oxygen demand (BOD), ammonia, phosphate, cadmium, chromium, lead, copper and Iron which were found in higher concentrations at sampling point B (effluent discharge point) above LASEPA, FEPA and Freshwater limit. DO of the three sampling points A, C and D were between recommended limit but slightly low at point B (effluent discharge point), which is less than the recommended limit. The level of pollution is more pronounced at sampling point B due to the greater amount of BOD and the release of some heavy metals like cadmium, chromium and lead which greatly affect the water quality of the river. The study concludes that River Owo is slightly polluted while the pollution is as a result from the discharge of effluents by the companies, factory and materials from other anthropogenic sources. Key words: Industrial and domestic effluent, biochemical physicochemical condition oxygen demand (BOD), heavy metals, monitoring, anthropogenic sources.