The pilot-scale horizontal reactor was investigated in this research for the anaerobic digestion of excess sludge. The reactor with the solar thermal insulation was operated under conditions of 20% solid content and continuous feeding mode. Results showed that the biogas yield reached 274 mL/g VS with methane content of 58% after 3 months' operation. The VS conversion rate was 46%, in which protein and polysaccharide were 36.7% and 30.1% respectively. Moreover, the maximum VFA content with the value of 2 395 mg/kg was appeared on the 42nd day during the whole process. The ammonia concentration increased slowly, then reached the maximum value of ~ 124.3 mg/kg during the digestion process. The degradation rate of VS, protein and polysaccharide in four sampling port of the reactor showed obvious difference, indicating that the sludge degradation rate in the reactor was positively collated with the distance along the reactor. After 73 days' anaerobic digestion, the methane producing potential of sludge could reach 273 mL/g VS, which showed that the system had a good potential for methane generation, and the residual municipal in the reactor had been successfully transformed into anaerobic activated sludge.
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