An Assessment of the quality of liquid effluents from opaque beer-brewing plants in Bulawayo, Zimbabwe

Abstract

The quality of liquid effluents from two opaque sorghum beer-brewing plants in Bulawayo, Zimbabwe were studied by analysing snap and composite samples collected manually from the plants' effluent discharge points over a period of six months. Both plants generate effluents that could negatively impact on the municipal treatment system if no efforts are made to significantly reduce their pollution load in terms of both quality and quantity. The results from both plants for the main pollution indicators showed high values of chemical oxygen demand (COD) (in excess of 30 000 mg/l in some instances), biological oxygen demand (BOD) and suspended solids (SS), indicating high organic load. Analysis of BOD values indicates that the effluents are biologically degradable. No significant heavy metals were found in the effluents, as these are food-processing plants. The effluent treatment plants in both plants were not only inadequate but also poorly operated thereby rendering them ineffective in reducing the pollution loads of the effluents. Simple good housekeeping and operational practices and well as design modifications are suggested to reduce the pollution load of the effluents.

Key words: industrial effluents, opaque beer-brewery, pollution load, quality, quantity

Water SA Vol.31(1) 2005: 141-150