Profiles of heavy metals in Ilupeju, Ikeja and Isolo industrial wastewaters and seasonal impacts on quality of water downstream and upstream in Lagos metropolis were determined. Wastewater samples from industrial estate were collected at the point of discharge of effluents into the streams and at spatial interval of 50 to 200 meters upstream and downstream of the discharge point over a two- year period (2005-2007) .The effluents were analyzed for heavy metals using standard methods. At the point of wastewater discharge into water bodies, during dry and rainy seasons, only Manganese showed significant difference (p < 0.05) in the first year in Ikeja. In dry and rainy seasons, the level of iron fluctuated from 8.95 ± 0.18 mg/L upstream to 8.96 ± 0.88 mg/L downstream in Ikeja; 1.40 ± 0.17 mg/L to 15.94 ± 1.56 mg/L in Ilupeju and 9.10 ± 0.64 mg/L to 4.98 ± 0.76 mg/L in Isolo industrial zones. In all the industrial areas considered, all the heavy metals have high accumulation factor at one season or the other except chromium and zinc. Accumulation factor for manganese increases in order of 2.38<4.10<4.70 in Ilupeju, Ikeja, Isolo respectively and in the order of 2.21<3.91<4.04 for copper in Isolo, Ilupeju, Ikeja respectively. However, iron had highest accumulation factor of 11.38 in the rainy season for Ilupeju. The upstream and downstream levels of chromium, manganese, iron and lead were higher than permissible level with traces of cadmium. The upstream and downstream water quality was poor and not suitable for drinking and routine purposes hence control of industrial wastewater is necessary to asswage its impact on proximate river bodies.
: industrial wastewaters, effluents, discharge point, upstream, downstream, accumulation factor, heavy metals, seasonal variation