Low-dose trichloroisocyanuric acid pretreatment improves anaerobic fermentation performance of waste activated sludge

Chemical oxidation pretreatments are potent facilitators of short-chain fatty acids (SCFAs) production, yet the high dosages typically required escalate operational expenses. This study demonstrates that trichloroisocyanuric acid (TCCA) acts as a highly effective oxidative pretreatment, delivering a maximum SCFAs concentration of 1454.4 mg COD/L (4.3-fold higher than the control) at a low dosage of 20 mg/g TS, less than 1/4 of the rate commonly needed for conventional oxidants. Mechanism investigation revealed that TCCA addition markedly enhanced waste activated sludge (WAS) disintegration by disrupting extracellular polymeric substances (EPS) and the cell envelope. This enhancement was most likely driven by the combined effects of radical oxidation, free chlorine species, and a decrease in pH. Assays using model compounds further showed that 20 mg/g TS TCCA stimulated the activity of SCFAs producers while suppressing the microbial activity associated with SCFAs consumption, thereby favoring SCFAs accumulation. Microbial community profiling unveiled that TCCA enriched hydrolytic and acidogenic bacteria (e.g., norank_f__JG30-KF-CM45). Functional gene analysis further highlighted the upregulation of glycolysis, amino acid metabolism and acetate metabolism within acidogenic metabolism in the 20 mg/g TS TCCA group. These findings not only extend the applicability of TCCA but also offer new insights into advancing low-dose oxidant strategies for WAS treatment and resource recovery.