[Mechanism of acetate accumulation during sludge anaerobic digestion]

To investigate the organic carbon metabolism during sludge anaerobic digestion and to clarify the mechanism of acetate accumulation.

We Used inhibitors 2-bromoethanesulfonate (BES) and chloroform (CHCl3) to block the methanogesis to investigate the accumulation of various fermentation intermediates. We determined the bacterial number of homoacetogen and syntrophic acetogen and calculated the thermodynamics of the acetogenesis reaction to identify the directions of organic carbon metabolism and acetate accumulation during sludge anaerobic digestion.

With the addition of BES, the acetate concentration was 27 mmol/L, the gene copy number of fhs was 2-3 folds of the control group and the number of sytroph acetogen was slightly decreased. In the group of chloroform addition, the acetate was 22 mmol/L, while the copy number of fhs gene was one order of magnitude lower than that in the BES model.

The two inhibitors lead to acetate accumulation from the anaerobic digestion of sludge. BES inhibited the methanogen and had no effect on other anaerobic acetogens. The accumulation of the acetate came from the hydrolysis acidogenesis, homoacetogenesis and syntrophic acetogenesis. Chloroform inhibited not only methanogen but also the homoacetogen and syntrophic acetogen severely. The acetate accumulation mainly came from the hydrolysis acidogenesis fermentation.