Effect of Temperature and Organic Loading Rate on the Methane Yield in Anaerobic Digestion of Municipal Sewage Sludge

Abstract

Anaerobic digestion has been considered as the most suitable stabilization process for sewage sludge due to conversion to methane (energy) and useful biosolid as the end products. This study was conducted to evaluate the effect of different organic loading rates (OLR) and operational temperatures on the methane yield of the sewage sludge digestion in a municipal wastewater treatment plant (WWTP). The mesophilic temperatures of 35 and 38°C and three levels of OLR (0.72, 0.94 and 1.3 kg VS/m3 /d) were applied to a laboratory-scale semi-continuously fed anaerobic digester. The duration of the digestion was approximately 90 days for each level of OLR. The methane yield and volatile solids removal (VSr) increased with increasing OLR and temperature. Methane yields at 0.72, 0.94 and 1.3 kg VS/m3 /day OLRs, respectively, were obtained as 0.32, 0.42 and 0.44 L/(gVSfed.d) at 35°C and 0.42, 0.48 and 0.52 L/(gVSfed.d) at 38°C. VSr increased from 42 to 55% with increasing temperature and OLR. As the result, 38°C and 1.3 kg VS/m3 /day OLR proved to be beneficial for the anaerobic digestion of sewage sludge.