D.M.Migwi, B.N.K.Njoroge and D.M.Wanjau

N.K. PROFNJOROGEBERNARD. "D.M.Migwi, B.N.K.Njoroge and D.M.Wanjau .". In: University of Nairobi. Boniface Kavoi, Andrew Makanya, Jameela Hassanali, Hans-Erik Carlsson, Stephen Kiama; 2001.


Performance and effectiveness of anaerobic process with biomass recycle, analogous to activated sludge process, in the treatment of high-strength brewery wastewater was investigated. This was achieved by using laboratory bench scale anaerobic digester, at organic loading rate in the range of 0.29 to 10kg Chemical Oxygen Demand (COD) m-3d-1 which was much higher than the theoretical values in the conventional anaerobic process (continuous stirred tank reactor), that ranges between 0.25 to 3.00 kg COD m-3d-1. The study was undertaken using brewery wastewater collected from Thika Brewery Limited in Kenya. The experimental results showered that the recycled process achieved a percentage COD removal of between 86% and 95% while the conventional anaerobic process achieved between 66% and 84% for the same range of volumetric loading rate at a hydraulic retention time (HRT) of 10 days. The recycled process had a shorter start-up time and responded much better to changes in both hydraulic and organic loading rates. Gas production was higher in the recycled process than in the conventional process. The methane yield at standard temperature (20 C) ranged between 0.25 and 0.32 m3/kg COD removed foe the recycled process while it was between 0.19 and 0.30m-3kg COD for conventional process. The experimental result showed that most of the COD removed was converted to methane as opposed to biomass synthesis. This has an added advantage in that there is less sludge production for the recycled process. The results of the study show that anaerobic process with biomass recycle holds potential for treatment of high-strength industrial wastewater, like brewery effluent. Such a process could result in savings, in reduced sludge to be disposed and better effluent than is possible with the conventional anaerobic digestion process.




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