Enhanced short-chain fatty acid production from sludge anaerobic fermentation by combined pretreatment with sodium pyrophosphate and thermal hydrolysis.

[Display omitted] • Sodium pyrophosphate and thermal hydrolysis had synergistic effects. • Proposed combined pretreatment doubled short-chain fatty acid yield. • Hydrolysis and acidification were enhanced while methanation was inhibited. • Macellibacteroides sp. and Romboutsia sp. were enriched. The slow breakdown of sludge is the primary obstacle hindering the conversion of waste-activated sludge to short-chain fatty acids (SCFAs) by anaerobic fermentation. This study proposed a novel method incorporating sodium pyrophosphate and thermal hydrolysis (SP-TH) for sludge pretreatment and evaluated its effectiveness regarding SCFA production. The combined pretreatment of SP at 0.4 g/g of total suspended solids and TH at 140 °C enhanced SCFA production from 2,169 ± 208 to 4,388 ± 184 mg chemical oxygen demand/L. SP strips extracellular polymeric substances, and the subsequent TH decomposes cells in the sludge, thus promoting sludge hydrolysis. SP-TH pretreatment promoted SCFA accumulation by enhancing enzyme activity and enriching acidifying bacteria. This study demonstrated that SP-TH pretreatment can effectively promote acid production from sludge, providing a new avenue for organic matter recovery through sludge anaerobic fermentation pretreatment. [ABSTRACT FROM AUTHOR]