Enhancement of anaerobic digestion of cellulosic fraction in wastewater by microaeration

Abstract

Effects of micro aeration on the anaerobic digestion of cassava wastewater with added cassava residue in the continuous stirred tank reactor (CSTR) system without temperature and pH control were studied. The results indicated that with the optimum COD loading rate of 1.710 kg/m3 d, the generated gas was mainly composed of CH4 (74.42 %) and CO2 (18.43 %). The addition of 1,000 ppm of cassava residue resulted in a total optimum COD loading rate of 1.884 kg/m3 d. The produced gas had higher CH4 and CO2, 80.09 % and 12.84 %, respectively. The oxygen supply increased the CH4 composition to 82.25 %. Therefore, it may be explained that the addition of cassava residue resulted in the increase in the organic compounds available for the anaerobic bacteria to degrade consistence with increase the methane production rate. Besides, the oxygen supply rate of 3.0 mL O2/LR d was considered to be the optimum micro aerobic condition that was suitable for the anaerobic bacteria growth. The micro aeration not only provided the high methane yield but also resulted in the high efficiency of desulphurization of the produced biogas including the high hydrolysis efficiency in accordance with the high degradation of cassava residue.