Bacteriological assessment of the impact of untreated abattoir effluents on the Okokpon Stream and Surrounding Groundwater, Edo State, Nigeria

The discharge of untreated abattoir waste into rivers and streams can adversely affect environmental and public health by increasing microbial contamination of receiving waters. This study assessed the spatial trend in the bacteriological quality of Okokpon Stream receiving raw abattoir waste. Water samples were collected over a period of four weeks from four points: upstream, the effluent discharge point, downstream, and a well servicing the abattoir. Samples were transported to the laboratory within three hours of collection for bacteriological analysis. Total aerobic viable count (TAVC), total coliform count (TCC), and Escherichia coli count (ECC) were determined using nutrient agar, MacConkey broth, and eosin methylene blue agar, respectively. TAVC and ECC were determined by the pour plate method, while TCC was determined by the Most Probable Number (MPN) presumptive test. Mean counts in the abattoir effluent were 7.45×10³ cfu/mL for TAVC, 72.5 MPN/mL for TCC, and 9.25×10¹ cfu/mL for ECC. Corresponding downstream mean values were 4.67×10⁴ cfu/mL, 18.3 MPN/mL, and 1.44×10¹ cfu/mL, compared with upstream values of 2.12×10³ cfu/mL, 1.95 MPN/mL, and 3.75 cfu/mL, respectively. The abattoir well water also showed microbial contamination, with mean TCC and ECC values of 23MPN/mL and 5.38 cfu/mL. These findings indicate contamination associated with abattoir discharge and show that the microbiological status of Okokpon Stream poses environmental and health risks to residents who use the stream for domestic, recreational, and food-production purposes. To reduce contamination, it is recommended that to construct a simple sedimentation pond or vegetated buffer strip between the abattoir and the stream; Divert all liquid waste through a small biogas digester before discharge; Provide an alternative water source (borehole) for abattoir operations, separate from the well-used for washing; Enforce monthly microbial monitoring of the stream by the local government environmental health department. If possible, the stream water should be adequately treated before use and that regulatory agencies enforce strict control of abattoir waste disposal into surrounding water bodies.