Bioproduction of Short Chain Fatty Acids in Primary and Excess Sludge Fermentation: Performance and Microbial Community Structures Comparison

The fermentation characteristics of activated biomass from two types of sludge, namely primary sludge (PS) and excess sludge (ES) were compared under three pH conditions (uncontrolled, 4, 10) over a period of 8 days. Results show the highest production of short-chain fatty acids (SCFAs) in PS and ES of 352 ± 7 and 324 ± 13 mg COD/g VSS, respectively at pH 10, on the 2 day in PS fermentation, and the 5 day in ES. Consequently, MiSeq high-throughput sequencing was applied to analyze the succession of microbial community structures in an alkaline condition, since SCFAs production was higher at the pH 10 than the other two pH conditions. For bacteria at the genus level, Bacillus and Anaerobacillus were only detected in the fermented sludge. The relative abundance of Bacillus and Anaerobacillus showed a big difference in the two types of sludge fermentation systems. Bacillus accounted for 62.4% and 33.1%, in PS and ES, respectively, while Anaerobacillus was 18.5% and 40.3%. More acidogenesis bacteria were found in PS than in ES fermentation. Thus, PS under alkaline fermentation could provide a promising carbon source for WWTPs.