Of ¦Á-amylase Pretreatment On The Anaerobic Digestion Of Municipal Solid Waste

A large quantity of municipal solid waste (MSW) was produced in China, with mainly disposed by landfill. It brings in environmental hazards and land occupation. MSW contains a significant fraction of organics, so anaerobic digestion is an effective technology for MSW's resource utilization. But the degradation of solid substances is the rate-limiting step for anaerobic digestion. In this paper, a-amylase was applied to hydrolyze MSW before anaerobic digestion to raise hydrolysis rate, utilization ratio of substrate, biogas yield and shorten digestion period. It is possible to provide the basic data for optimization of anaerobic digestion technology.Firstly, the component of MSW was analyzed. It is found that starch and cellulose are the highest material,5.94% and 7.16% respectively. The degree of hydrolysis which is influenced by the hydrolysis temperature, hydrolysis time, a-amylase dosage and the concentration of substrate were studied by the method of single factor. The result show that the optimum condition is a-amylase dosage 80u/gVS, hydrolysis time 60min, hydrolysis temperature 80℃and substrate concentration 10% (VS concentration). However, the maximum degree of hydrolysis 10.24% is in the condition of a-amylase dosage 80u/gVS, hydrolysis time 60min, hydrolysis temperature 80℃and substrate concentration 6%.Secondly, the effects of substrate to inoculum ratio (SIR) (1:1,1.5:1,2:1,3:1,3.5:1) and fermentation concentration (2%,4%,6%,8%,10% and 12%(VS concentration) respectively) on anaerobic digestion were studied by the method of single factor. It is shown that 3.5:1 emerges acidification in 8%,3:1 and 3.5:1 in 10% and 2:1,3:1 and 3.5:1 in 12%. In the SIR of 1:1,1.5:1 and 2:1,2:1 which reaches the maximum cumulative biogas production (2290mL) is the best choice for SIR. In the fermentation concentration of 2%,4% and 6%,6% which reaches the maximum cumulative biogas production (1524mL) is the best choice for fermentation concentration.Finally, the effects of pretreatment on the anaerobic digestion of MSW with a-amylase were studied. Each index of anaerobic digestion such as cumulative biogas production, biogas production potential of substrate and cumulative methane production etc are higher than that of control group. It achieves a certain improvement in anaerobic digestion to pretreat MSW with a-amylase. The result indicate that the optimum condition of strengthening the anaerobic digestion is a-amylase dosage 100u/gVS, hydrolysis time 60min, hydrolysis temperature 50℃and substrate concentration 10% (VS concentration). However, the maximum cumulative biogas production, biogas production potential of substrate and relative increment(1104.97mL,460.40mL/gVS and 9.67% respectively) are in the condition of a-amylase dosage 100u/gVS, hydrolysis time 60min, hydrolysis temperature 60℃and substrate concentration 8%(VS).