Determination of optimum coagulant dosage in the treatment of abattoir wastewater, using calcium hydroxide as coagulant

Abstract

This research was carried out to evaluate the effective and efficient treatment of abattoir wastewater using calcium hydroxide coagulant. Samples were collected from an abattoir unit in Ikpoba-Okha Local Government Area, Benin City, Edo State. The raw samples were characterized to determine: Dissolved oxygen (DO), chemical oxygen demand (COD), biochemical oxygen demand (BOD), temperature (T), pH, electrical conductivity (EC), turbidity, total dissolved solids (TDS), total suspended solids (TSS), total alkalinity (Alk), chloride, total Kjeldhal nitrogen (TN), hardness, potassium, phosphorous and total bacteria count (TBC). Thereafter, the samples were treated with several doses of calcium hydroxide coagulant (2g, 4g, 6g, 8g, 10g, 12g, 14g, and 16g). Results obtained were used to determine the optimum coagulant dosage in a plot of percentage COD against masses of coagulants used. From the optimum dose obtained (12g Ca(OH)2), a batch treatment was carried out. The treated wastewater was further characterized to ascertain compositional changes. Result revealed increase in oxygen and substantial reduction in chemical oxygen demand, total nitrogen, phosphorus and turbidity. Biochemical oxygen demand and total solids were also reduced. The treated effluent could be discharged into the environment without fear of pollution and may be reused for agricultural purposes.