[New ways to improve volatile fatty acids accumulation in sludge alkaline fermentation system]

To improve the hydrolysis and acidification of activated sludge, two new ways, which were adding fermented sludge or sterilized fermented sludge to batch-mode activated sludge alkaline fermentation system, were investigated in this study. Temperature effect was also studied (10 degrees C and 35 degrees C). Result showed that mesophilic condition greatly enhanced sludge hydrolysis and acidification, which resulted in an obvious volatile fatty acids (VFAs) accumulation in the system. These two new ways could improve both sludge hydrolysis and acidification. The hydrolysis and acidification efficiencies of adding sterilized fermented sludge system were 2 and 1.5 times higher than those of adding fermented sludge system, respectively. In addition, VFAs content was nearly constant in a long time in sterilized fermented sludge addition system while it greatly consumed in fermented sludge addition system. The reason for this enhancement of two new ways were different, fermented sludge addition increased the amount of hydrolytic enzyme and acid-forming bacteria, while sterilized fermented sludge addition increased the amount of degradable substances, and the result also demonstrated that strengthen hydrolysis was more important than acidification. Therefore, mesophilic condition together with sterilized fermented sludge addition was a more effective way to enhance VFAs accumulation in alkaline sludge fermentation process.