Study of treatment of high-strength industrial waste water by a recycled Biomass anaerobic process: A case study of Thika brewery

Abstract

Performance and effectiveness of anaerobic process with biomass recycle, analogous to activated sludge process, in the treatment of high-strength brewery wastewater was investigated. Using laboratory bench scale anaerobic digester, at organic loading rate in the range of 0.29 to 10 kg COD m-3d-1 which was much higher than the theoretical values in the conventional anaerobic process (completely stirred tank reactor),' that ranges between 0.25 to 3.00 kg COD m-3d-l. The experimental results showed the recycled process achieved a percentage COD removal of between 86% and 95% while the conventional anaerobic process achieved between 66% and 84.2% for the' same range of volumetric loading rate. 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 rn3/kg COD removed for the recycled process while it was between 0.19 and 0.30 m3/kg COD removed for the conventional process. Comparing the experimental results most of the COD removed was converted to methane as opposed to biomass synthesis. This also resulted in 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 waste water like brewery effluent. However, a pilot plant study would be necessary in order to obtain operational and design parameters for a full-scale operation.