HEAVY METAL CONCENTRATIONS IN SEDIMENT AND SURFACE WATER IN THE VICINITY OF A BREWERY IN ALAKIA – ADEGBAYI INDUSTRIAL AREA OF IBADAN, SOUTHWESTERN NIGERIA

Heavy metal concentrations (Cr, Pb, Cd, Zn, Mn, Cu, and Ni) and physicochemical parameters were analyzed in sediment, stream water, and shallow well water, in areas around a brewery in Alakia-Adegbayi industrial sector of Ibadan, southwestern Nigeria. The objective was to evaluate the impact of the brewery effluent on sediment and water quality. In relation to public health, heavy metals are known for their toxic effect. Water and sediment samples were collected at ten locations along an effluent receiving stream down the water course adjacent to the effluent carriage system. Also, water samples were collected from shallow wells, in nearby residential area adjacent to river courses. Results show elevated concentrations of Cr (0.372 ppm), Pb (0.287 ppm), and Ni (0.700 ppm) in stream water and well water, which are higher than the WHO recommended guideline, though concentrations of Cd (0.002 ppm), Zn (0.133 ppm), Cu (0.002 ppm), Mn (0.078 ppm) in stream water, and Cd (0.002 ppm), Zn (0.130 ppm), Cu (0.002 ppm), Mn (0.038 ppm) in well water are lower. The average concentrations of Cr (33.13 ppm), Pb (32.76 ppm), Cd (33.40 ppm), Zn (10.50 ppm), Mn (41.63 ppm), Cu (4.15 ppm) and Ni (17.40 ppm) in stream sediment are higher than the concentrations in stream and shallow water wells, which indicates that most metals are absorbed to the sediment. The physicochemistry of stream and well water shows a positive trend, with parameters within permissible level, except for the high turbidity, color unit, and fluoride concentration, which are observed in stream water. This could be direct effect of effluent discharge into the stream without prior treatment. Hardness observed in well water could be traced to the dissolution of granite gneiss, which constitutes the bedrock. Correlation of results obtained in stream and well water shows a positive progression, indicating that the shallow groundwater in the locality is subjected to pollution from anthropogenic sources. In summary, results show that water and sediment in the area are susceptible to pollution. There is need for strict regulation on disposal of industrial effluents to prevent further contamination and to reduce risk to public health.