Anaerobic Co-digestion Of Food Waste And Dewatered Sludge For Methane Generation

Food waste and dewatered sludge are two major component of the municipal solid waste, and the generation has been increasing year by year. Food waste was characterized by high organic matter content, rich in nitrogen, phosphorus and other nutritional elements, and resource recycling and reuse value was desirable strategy. On the other hand, high moisture content (75%to95%), fat content (crude fat accounted for21.82%of the dry matter of the food waste) and perishable, smelly and breeding ground for pathogens resulting in the spread of the disease. Thus, the food waste collection, transportation and processing are troublesome, and also polluted the surrounding environment and groundwater. Municipal dewatered sludge has a high moisture content (about85%), perishable odor, a large number of pathogenic bacteria and parasite eggs, chromium, mercury and other heavy metals. Improper disposal will cause secondary pollution of groundwater and soil, then pollute the environment and endanger the health of people.Therefore, food waste not only has a great resource utilization value, but also will cause environmental pollution. Settlement of sludge treatment and disposal, effectively prevent the formation of secondary pollution, increase sludge recycling technology promotion efforts, there is an urgent need to complete the task.In this thesis, semi-continuous anaerobic co-digestion with the food waste (FW) and dewatered sludge (DS) at the temperature of37℃(the FW:DS based on VS mass was1:0,3:1,1:1,1:3and0:1, respectively) was earned out. The following conclusions were drawn.(1) With larger proportion of FW in the co-substrate, higher methane productivity and methane yield were obtained. The addition of FW significantly improved the methane productivity.(2) Reactor system with more FW favored higher VS removal. The VS reductions were76.47%,58.63%,47.96%,31.25%and19.49%, respectively, FW:DS based on VS mass were1:0,3:1,1:1,1:3and0:1.(3) With more FW in the co-substrate, total ammonia nitrogen (TAN) and volatile fatty acids (VFA) showed decreasing trend. The ammonia and VFA were potential inhibitory substances that threatened the stability of the system when DS and FW was digested alone. In comparison with the mono-system of DS or FW, the co-digestion system showed higher stability due to diluting toxicant like ammonia or VFA to much lower levels. (4) TG and DTG curves of pyrolysis and combustion characteristics were significant different for different samples. Addition of FW to the sludge anaerobic digestion system, improved the pyrolysis rate of digested sludge and reduced the amount of combustion residues.