[Co-digestion of waste activated sludge and kitchen garbage]

The effects of mixture ratio and hydraulic retention time on mesophilic co-digestion of waste activated sludge and kitchen garbage were investigated, and the mixtures having the ratios of 75%:25%, 50%:50% and 25%:75% on a TS basis, operated at the HRTs of 10d, 15d and 20d. In all the digesters, with an OLR 1.53-5.63 g/(L x d), there were no indication of failure, such as low pH, insufficient alkalinity, ammonia inhibition and accumulation of VFAs. The optimum operating conditions of all the digesters were found to be a mixture of 50%:50% in terms of the stability and performance, buffer capacity was the highest. The volatile solid removal efficiency, specific methane production and methane content in this condition achieved 51.1%-56.4%, 0.353-0.373 L/g and 61.8%-67.4%.