Enhancing Volatile Fatty Acid By Anaerobic Digestion Using Municipal Sludge Combined With Multiple Organics

Anaerobic fermentation is the most environmental and high-resource utilization rate method for sludge treatment method. However, the solo sludge anaerobic fermentation is inefficient, and the methane liquid is difficult to deal with because of high COD. Anaerobic fermentation intermediates — volatile fatty acid(VFA) has much more economic performance than methane, and can be the most suitable carbon sources for nitrogen and phosphorus removal process, which is already used in practical engineering applications by many researchers.In order to overcome the low-efficiency of single sewage sludge anaerobic fermentation, and fermentation reaction termination phenomenon caused by high organic load of city organic waste, our research use the sludge combined with protein, carbohydrate and fat, which are the three main kinds of organic ingredients in city garbage for acid producing. Build acid production and rate as the main index. Analysing influencing factors of acid production through the factors of substrate degradation rate, anaerobic fermentation environment change to get the most suitable organic ingredients combined with sludge for anaerobic acid production. Finally, discussing the feasibility of using acid production as carbon sources for nitrogen and phosphorus removal process.The experiment uses laboratory test device, the sludge respectively mixed with peptone, glucose and stearic acid glycerol ester solution according to 1:1 rate and the reaction period is 20 days. Combined anaerobic fermentation proceed in three different conditions: non-pretreatment, alkali pretreatment and alkaline fermentation. Test conclution shows as follows:(1) In the test group without pretreatment, the protein group produces the most VFA yield, 14.52g/L, and Productivity rate reaches 43.47%, which is 218% and 59% higher than the single sludge group respectively. It is mainly due to the high ammonia anaerobic environment which buffers acid production and has some inhibition effect on the producting process of methane.(2) In the test group with alkaline pretreatment, acid production all declined except polysaccharide group, indicating that alkaline pretreatment processing more significant effects on methane production, which is harmful to the accumulation of volatile acids.(3) In the test group with alkaline fermentation, the acidity and acid production rate were increased significantly. The acid production of protein group is the highest, about 19.2 g/L; while the acid production of polysaccharide group and lipid group increased 324% and 361% respectively. The results indicate that alkaline fermentation environment is most suitable for VFA generation and accumulation.(4) According to the feasibility analysis, we conclude that the most suitable matrix for acid producing is protein, and the most suitable anaerobic digestion environment is alkaline fermentation.