ANAEROBIC SLUDGE DIGESTER PERFORMANCE IMPROVEMENT BY ADDING ORGANIC MUNICIPAL SOLID WASTES

Abstract

The technical feasibility of the co-digestion of primary sewage sludge (PS) and food wastes as an organic fraction of municipal solid waste (OFMSW), in the context of typical Egyptian solid waste, was evaluated through this study. A pilot unit with 1.5 m3 net volume, simulates dynamically and geometrically full scale digester, was erected in El-Berka wastewater treatment plant, Cairo, Egypt. The digester worked under routine natural operating conditions and was daily fed through pulsing feeding. The study was operated in four stages each with different mixing ratio of PS to OFMSW 95:5, 90:10, 80:20, and 70:30 by volume, respectively. The unit was operated in mesophilic temperature, under minimal mixing conditions, and at retention time of 30 days, and the functioning of the digester was assessed by calculating the efficiencies of solids destruction and chemical oxygen demand (COD) removal. The digester was capable to work optimally under the mesophilic temperatures, without using any temperature adjustment devices. The results showed increase in solids destruction and COD removal efficiencies with increasing the portion of the food wastes in the influent mixtures. The TS, TSS and VSS destruction efficiencies reached 76.4 %, 82.1 %, 93.4 %, respectively, and the total and soluble COD removal efficiencies reached 70.1 % and 85.3 %, respectively. The optimum mixing ratio was of 80 % PS to 20 % OFMSW. It was also noticed that there was a need for pH adjustment through the process.