title: Effects of Sludge Kind, Size and Structure on Sludge Anaerobic Fermentation
design: Seven experimental groups were carried out using identical 300 mL serum bottles, which contained 250 mL of AFS, AGS200-500, AGS500-1600, AGS>1600, CAGS200-500, CAGS500-1600, and CAGS>1600, respectively. Each group was purged with nitrogen gas for 2 min to remove oxygen, then tightly sealed and placed in an air-bath shaker (200 rpm, 35  1 C) for anaerobic fermentation. The pH values in each group varied arbitrarily without any control during anaerobic fermentation. The mixed liquor samples were centrifuged at 10000 rpm for 10 min, after which the supernatant was filtered through a 0.45m cellulose membrane and used for chemical analysis. Each group was performed in triplicate.