Enhanced volatile fatty acid production from anaerobic fermentation of waste activated sludge by combined sodium citrate and heat pretreatment

In this study the combination pretreatment of sodium citrate (SC) and heating was investigated to enhance the volatile fatty acid (VFA) production during anaerobic fermentation of waste activated sludge (WAS). The results showed that the combined pretreatment (0.3 g-SC/g-TSS + at 121 degrees C for 30 min) resulted to the maximum VFA yield of 354.5 mg-COD/g-VS, which was 16.4, 6.0 and 2.0-fold of that of control, with sole SC and sole heat pretreatment, respectively. Meanwhile, the combined pretreatment greatly improved the proportion of acetate and butyrate, while the production of propionate significantly decreased. Mechanism analysis indicated that the combined pretreatment effectively promoted WAS disintegration and solubilization. Moreover, the heat pre-treatment exhibited superior performances to the SC pretreatment on release of organic matters and enhance-ment of VFA production in the combined pretreatment. The microbial analysis revealed that with the combined pretreatment the microbial community shifted toward hydrolysis-acidification, such as Enterobacter and Macellibacteroides.