The effect of salinity on waste activated sludge alkaline fermentation and kinetic analysis

The effect of salinity on sludge alkaline fermentation at low temperature (20°C) was investigated, and a kinetic analysis was performed. Different doses of sodium chloride (NaCl, 0-25g/L) were added into the fermentation system. The batch-mode results showed that the soluble chemical oxygen demand (SCOD) increased with salinity. The hydrolysate (soluble protein, polysaccharide) and the acidification products (short chain fatty acids (SCFAs), NH4(+)-N, and PO4(3-)-P) increased with salinity initially, but slightly declined respectively at higher level salinity (20g/L or 20-25g/L). However, the hydrolytic acidification performance increased in the presence of salt compared to that without salt. Furthermore, the results of Haldane inhibition kinetics analysis showed that the salt enhanced the hydrolysis rate of particulate organic matter from sludge particulate and the specific utilization of hydrolysate, and decreased the specific utilization of SCFAs. Pearson correlation coefficient analysis indicated that the importance of polysaccharide on the accumulation of SCFAs was reduced with salt addition, but the importance of protein and NH4(+)-N on SCFA accumulation was increased.