Pollution effects of brewery wastes: Ruaraka River

This paper reports the results of a two-year study on the pollutional effects of brewery wastewater on the Ruaraka River. As a preliminary investigation to an extensive river pollution study, samples were taken twice weekly between August 1988 and June 1990 from two sampling points immediately upstream and downstream of the point of discharge of the Tusker Brewery wastewater into the river. The samples were analysed for BOD and COD as well as other parameters. The results of this preliminary investigation showed that whilst the average BOD of the river water was about 6.9 mg/1 at the section just above the wastewater outfall, the average BOD of the river water at the sampling point immediately below the outfall was about 115.6 mg/1. Similarly, the average COD concentrations for the upstream and downstream sections were 34.7 mg/1 and 240.4 mg/1 respectively. If the brewery wastewater was treated in an anaerobic pond having only 45 per cent BOD reduction efficiency before discharge, it is estimated that the average BOD concentration of the river water at the downstream section would only be about 65mg/l. Treatability studies carried out on the wastewater showed that it would be possible to achieve a BOD reduction of 45 per cent or more in laboratory scale anaerobic pond units.