Chemical oxygen demand reduction kinetics in co-digestion of municipal solid wastes with cow dung

Abstract

This work investigated the use of laboratory batch anaerobic digester to derive chemical oxygen demand (COD)reduction kinetic parameters for anaerobic co-digestion of the organic fraction of municipal solid waste (OFMSW) with cow dung (CD) by mixing the substrates to achieve optimum carbon to nitrogen ratio (C/N) of 30:1 for a hydraulic retention time of 18 days at ambient mesophilic temperature of 37^oC and pH of 6.9.A consortium of Staphylococcus aureus Bacillus species, Micrococcus, Pseudomonas aureus, Streptococcus and Escheria coli isolated from the OFMSW and Coliform, Staphylococcus aureus, salmonella, Streptococcus, Bacillus species and Escheria coli isolated from CD were employed in the COD reduction. Codigestion of OFMSW and CD reduce COD by 86.47% while OFMSW reduced it by 61.3%. The COD reduction process is described by Michaelis-Menten kinetics. The rate constants for the COD reduction by Co-digestion of OFMSW and CD were – 239.21 mg/L.day and 0.1315/day for the zero order and first order regions respectively, whereas the reduction by OFMSW alone had constants -36.01 mg/L.day and 0.0567day-1 for the zero order and first order regions respectively. This work showed that the two bacteria used have the potential to be utilized in COD reduction processes.