Assessment of the impact of wastewater from an abattoir in Oyo state on groundwater in Onidundu community, Nigeria

Abstract. This study aimed to assess the composition of wastewater from the Oyo Central Abattoir and its possible impact on the surrounding groundwater (wells) in Onidundu community as users use them for economic and recreational purposes without being fully aware of the hazard the water can cause. For this purpose, wastewater and groundwater were analyzed for seven physicochemical parameters, verified by standard methods and compared with World Health Organization (WHO) standards. All physicochemical parameters evaluated were within acceptable limits, except for biochemical oxygen demand (BOD), dissolved oxygen (DO), total dissolved solids (TDS), total dry matter (TS) and hardness in some of the water sources. Three microorganisms (Escherichia coli, Citrobacter sp. and Klebsiella sp.) were isolated and identified by standard procedures. Water Quality Index (WQI) and Comprehensive Pollution Index (CPI) were applied to assess water quality. The WQI values ranged from 1.06 to 2.30, while the CPI score ranged from 1.02 to 1.82 among the sampled water sources. Those indices classify the waters as moderately polluted and excellent, respectively, but also due to the high numbers (0.86 × 105 CFU/mL to 4.84 × 105 CFU/mL) of pathogenic microorganisms due to microbial pollution, the analyzed water samples are not suitable for drinking, aquaculture and other household activities. Waste treatment in slaughterhouses, well water intended for domestic use, dug deep and away from waste disposal sites, are recommended to prevent possible hazards to the environment and public health.