Abstract: Based on the actual case of a medium temperature dry anaerobic fermentation system for kitchen waste in Chongqing， the changes of solid content, alkalinity, volatile fatty acids, ammonia nitrogen, pH and methane concentration in the debugging stage were studied. The operation results showed that methane content could reach more than 55% in about two weeks after starting anaerobic fermentation with biogas residue and cow manure. The system could run stably when the pH was maintained between 8.0-8.2, the alkalinity was between 12 000-14 000 mg/L, the volatile fatty acids was between 2 500-3 000 mg/L, and the ammonia nitrogen was about 2 500 mg/L. With the material moved to the back end of the fermenter, the solid content and volatile fatty acids gradually decreased, the total alkalinity and pH gradually increased, and the ammonia nitrogen had no obvious change trend. After stable operation of the system, the gas production per unit feed volume of the anaerobic fermenter was about 140 m3/t, and the methane content was maintained between 55%-65%. The three-stage dewatering system operated stably and had good dewatering effect.

Key words: kitchen waste, medium temperature dry anaerobic fermentation, solid content, volatile fatty acids