Enhanced anaerobic fermentation of waste activated sludge by NaCl assistant hydrolysis strategy: Improved bio-production of short-chain fatty acids and feasibility of NaCl reuse

Effect of NaCl Concentration on Microbiological Properties in NaCl Assistant Anaerobic Fermentation: Hydrolase Activity and Microbial Community Distribution

“…The fermentation period (4 days) was selected according to our previous study, in which the sludge samples and experimental conditions were the same. In our previous study, the optimal period of NaCl assistant anaerobic fermentation was found to be 4 days ( Pang et al, 2020e ). The experimental results are averaged in triplicates.…”

“…Despite the sludge solubilization, EPS disruption, SCFA yield, and relevant mechanism were explored in our previous study ( Pang et al, 2020e ); the effects of NaCl concentration on enzyme activity and microbial community structure are still unfathomed. Actually, the tolerance of bacteria for high salinity condition is different.…”

“…It has been reported that high NaCl concentration could induce sludge solubilization and deteriorate floc structure ( Reid et al, 2006 ; Cui et al, 2015 ; Su et al, 2016 ; Lu et al, 2019 ). In our previous research, a novel and efficient NaCl assistant anaerobic fermentation strategy was developed for bio-production of SCFAs ( Pang et al, 2020e ). In the process of NaCl assistant anaerobic fermentation, the addition of NaCl resulted in significant osmotic pressure difference between the sludge phase and the liquid phase, which caused the decomposition of WAS flocs and the breakdown of extracellular polymeric substances (EPS).…”

“…Thereby, the efficiencies of sludge hydrolysis and the subsequent SCFAs production were improved. It was reported that numerous soluble chemical oxygen demand (SCOD) of 4,092 mg/L was released into the supernatant at the optimal NaCl concentration of 20 g/L, meanwhile considerable SCFAs of 288.2 mg COD/g VSS was produced through a 4-day anaerobic fermentation ( Pang et al, 2020e ). Such performances on sludge solubilization and SCFAs yield in NaCl assistant anaerobic fermentation were comparable to the anaerobic fermentation with chemical pretreatments (e.g., surfactants, enzymes, cation-exchange resin, etc.…”

“…After NaCl assistant anaerobic fermentation, the fermentative liquid with numerous SCFAs could be used as external carbon source, e.g., the substrate for biological electricity production through microbial fuel cell (MFC) or the external carbon source for supplementing the carbon gap in municipal wastewater. The feasibility of these utilization approaches were discussed in our previous study ( Pang et al, 2020e ). After utilization of the soluble organic matters, the fermentative liquid could be reused for NaCl assistant anaerobic fermentation since there is numerous NaCl existed in the fermentative liquid.…”