Waste activated sludge hydrolysis and short-chain fatty acids accumulation in the presence of SDBS in semi-continuous flow reactors: Effect of solids retention time and temperature

In the presence of surfactant sodium dodecylbenzene sulfonate (SDBS), the effects of sludge retention time (SRT) and temperature on the hydrolysis and short-chain fatty acids (SCFA) accumulation during waste activated sludge (WAS) anaerobic fermentation were investigated in semi-continuous flow reactors. Results showed that the presence of SDBS remarkably increased WAS hydrolysis and SCFA accumulation. A longer SRT or higher temperature accelerated WAS hydrolysis. The SCFA accumulation was increased as SRT increased from 3 to 12 d, but decreased as SRT further increased to 18 d. The presence of SDBS increased the total SCFA concentration remarkably, but did not change the SCFA composition significantly. The SCFA production was improved with the enhancement of temperature from 10 to 35 °C. During WAS fermentation in the presence of SDBS, the concentration of released NH4+-N increased linearly with SRT or temperature, but that of PO43-P remained relatively stable. Further investigation revealed that the presence of SDBS caused not only more total SCFA accumulation than the blank (1149.8 against 246.9 mgCOD/L), but also more volatile suspended solids reduction (33.8% versus 17.9%).