Surfactant-assisted thermal hydrolysis off waste activated sludge for improved dewaterability, organic release, and volatile fatty acid production

Abstract

The surfactant-assisted thermal hydrolysis pretreatment (THP) of waste activated sludge (WAS) was investigated, focusing on the effect of the surfactant addition on the results of sludge disintegration, dewaterability, organic release, and production of volatile fatty acids (VFAs) via fermentation. Typical anionic surfactant sodium dodecyl sulfate (SDS) and cationic surfactant cetyl trimethyl ammonium bromide (CTAB) were used for the THP experiments. The supernatant of the THP-treated sludge was anaerobically fermented to determine its potential VFAs yield. The results showed that the surfactant addition, particularly CTAB, enhanced the hydrolysis and organic solubilization of the sludge during THP. CTAB addition led to a 36% increase of dissolved organic and a 27% increase of VFAs production. For the THP-treated sludge with the surfactant addition, its dewaterability was also greatly improved. When the CTAB dosage increased from 0 to 0.10 g/g VSS, the minimum capillary suction time (CST) of the sludge decreased from 205 to 50 s/g TSS, and the sludge particles became smaller and less negative with the zeta potential changing from −12.4 to −8.2 mV. Analysis of extracellular polymeric substances (EPS) of the sludge revealed that the surfactant addition increased the sludge disintegration and organic dissolution during the THP process. The surfactant-assisted THP is shown to be a promising technology to enhance the WAS treatment for improved sludge dewaterability, waste reduction, and resource recovery.