Indian Journal of Science and Technology

Abstract

Objectives: Utilization and minimization of premature washout of active microbes from the bioreactor and providing better microbe-substrate contact through suitable modification in existing bioreactor models for enhancing biogas production. Methods / Statistical Analysis: A large bioreactor (15000ml) used as control was compared for gas production and pH with two sets3 smaller bioreactors each with capacity 1/3rd of the larger one. One set of three bioreactors were arranged in parallel fashion and the other set was connected in series. This experiment was repeated twice keeping all the considerable aspects same. The gas production patterns obtained were quite similar thus their mean is presented in the results. Findings: Gas production both from the set up in series as well as parallel was found to be 11 to 15% higher in comparison to larger bioreactor used as control. Reactors in series were producing highest biogas during first 7 days but 8th day onwards there was rapid decrement in production due to low pH of the leading tank in the series connection. On the other hand parallel set-up was stable throughout and its gas production pattern was although higher but similar to control. The subdivision method used here for the bioreactor design with arrangement of the sub units in series and parallel has enhanced biogas production, which has made good case for bioreactor optimization in terms of minimizing microbial loss and stabilization of influential parameters like pH, organic loading rate, hydraulic retention time etc. through proper combinations of series-parallel arrangements. Application / Improvements: If series parallel combination is properly chosen as per feed substrate, such a design can properly utilize washed out microbes and undigested organic material in the effluent thus increasing biogas yield.

Keywords: Active Microbial Washout, Anaerobic Digestion, Biogas, Microbe-substrate contact, Parallel, Series