Response of extracellular polymeric substances and enzymatic activity to salinity for the waste activated sludge anaerobic fermentation process

Salinity (NaCl) was used in waste activated sludge (WAS) anaerobic fermentation system which had been presented to greatly enhance the extracellular polymeric substance (EPS) production including protein and polysaccharide and short-chain fatty acids (SCFAs). Salinity enhanced soluble protein and polysaccharide (SB-EPS) release which was 4.04 times (protein) and 1.83 times (polysaccharide) compared to 0 g/L NaCl level. More important, salinity restrained the coenzyme 420 activity ( F420 ), but increased the hydrolase activity. Abundant hydrolysis of substrate and highly active hydrolase led to abundant SCFA production. Pearson correlation coefficient showed that the protein became the main reaction substrate for SCFA generation. Graphic abstract