Assessment of Dissolved Oxygen and Biochemical Oxygen Demand in Waterways Receiving Abattoir Effluents in Jos, Plateau State

Abattoir operations generate large quantities of organic-rich wastewater containing blood, offal, and fat residues that impose high oxygen demands on receiving water bodies. This study assesses dissolved oxygen and biochemical oxygen demand in waterways receiving abattoir effluents in Jos, Plateau State, North Central Nigeria. Sampling was conducted at the abattoir effluent outlet, and at distances of 50, 200, and 500 metres downstream over a six-week period. Standard Winkler titration was used to determine dissolved oxygen, while biochemical oxygen demand was measured by the five-day dilution method at 20 degrees Celsius. Additional parameters including temperature, pH, total suspended solids, ammonia, and nitrate were also determined. Results indicate that dissolved oxygen at the effluent outlet fell below 1 milligram per litre, far below the minimum of 5 milligrams per litre recommended for sustaining fish and invertebrate life. Biochemical oxygen demand values at the outlet reached 1,800 milligrams per litre, decreasing to 45 milligrams per litre at 500 metres downstream but still well above the acceptable discharge limit of 30 milligrams per litre. Strong correlations between total suspended solids and biochemical oxygen demand were observed. Benthic macroinvertebrate diversity indices confirmed severe ecological degradation proximate to discharge points. Recommendations include mandatory installation of anaerobic and aerobic pre-treatment systems at the abattoir and enforcement of effluent quality standards by the Plateau State Environmental Protection Agency. Keywords: dissolved oxygen, biochemical oxygen demand, abattoir effluent, Jos, water pollution