A novel strategy to promote sludge solubilization and short-chain fatty acid production by coupling thermal hydrolysis and sodium thiosulfate pretreatment.

Thermal hydrolysis (TH) technology is promising for sludge pretreatment, but the high cost and the generation of refractory substances limit its application. In this study, sodium thiosulfate (STS) was innovatively combined with TH pretreatment to improve the anaerobic fermentation efficiency of sludge. TH-STS pretreatment (140 °C, 0.132 g/g TSS) increased sludge solubility by 33.4 % and increased short-chain fatty acid (SCFA) production to 1.86 times that of the control group. TH effectively stripped the extracellular polymeric substances, and STS subsequently lysed the cells through its reducing power. TH-STS pretreatment promoted SCFA accumulation by increasing the activity of key enzymes and enriching hydrolyzing and acidifying bacteria. In addition, TH-STS pretreatment increased the activity of the electron transport system, which positively promoted the biotransformation of SCFAs. This study reveals that STS and TH pretreatment have a synergistic effect, providing an effective method for improving sludge pretreatment and resource recycling.