Study On Effects Of Grease And Salt In Single-stage Anaerobic Digestion Of Food Waste

Anaerobic digestion is going to become the main treatment of kitchen and food waste, recently. However, grease and salt which is rich in kitchen and food waste can cumulate increasingly, in this way the activity of methane-producing bacteria and the stability of anaerobic system will be negatively affected. To find the cumulative disciplinarian and effects of grease and salt in anaerobic digestion, solve the inhibitory problem caused by excessive grease and salt, a single-stage anaerobic digestion process was adopt to treat the high content of grease and salt kitchen and food waste in this paper. The following aspects were concentrated on.①Research on single-stage anaerobic digestion of kitchen and food waste. The results show that the salt in anaerobic system cumulated continuously through the digestion. The content of salt in anaerobic system increased from 0.084% to 0.69% in 56d, and even continued to grow; the more feed-in quantity, the more grease and its'hydrolyzed outcomes cumulated in anaerobic system, because of the limited grease using capability of anaerobic bacteria; the single-stage anaerobic digestion process of kitchen and food waste worked well at the following conditions, 35℃, 3kgVS/m3·d (organic loading rate ). The COD and VFA maintained about 2620mg/L and 880mg/L separately, biogas yield was about 81L/d, methane content was 60%.②Research on effects of grease in single-stage anaerobic digestion of kitchen and food waste. The results indicated excessive grease can reduce the efficiency of biogas production in single-stage anaerobic digestion of kitchen and food waste. Methane production was inhibited obviously when grease content was 25%, methane cumulative yield was 1850mL, which accounts for 41% of 4557mL when grease content was 15%. The max methane cumulative yield obtained in 15% grease content was more than the 0% grease content by 85.7%; methane production was delayed by grease, which can lead to such problems as longer SRT and lower output of anaerobic process; the optimum pH was 7 at high grease content, the methane cumulative yield (pH was 8) was just 80.8% of that when pH value was 7, and compared to pH 7, methane production stopped about 5 days ahead when pH was 8; 55℃is preferd at high grease content, because it's methane cumulative yield just reduced by 9.4%, nevertheless, methane production period cut down by 57%.③Research on effects of salt (NaCl) in single stage anaerobic digestion of kitchen and food waste. Anaerobic digestion was inhibited badly by salt, the more salt content, the more toxicity to anaerobic bacteria. The methane cumulative yield of test 4g/L,8g/L and 12g/L accounted for 78%,72% and 61% of that in test 0g/L separately; the methane cumulative yield of test pH 8 reduced by 12% when salt content is 12g/L; the toxicity of salt was no difference when temperature was diverse.