Deciphering the mechanism of microbial metabolic function shift and dissolved organic matter variation in acidogenic fermentation of waste activated sludge induced by antiviral drugs.

Antiviral drugs (ATVs), as emerging contaminants enriched in wastewater activated sludge (WAS) in wastewater treatment plants, affect subsequent treatment. ATVs have been shown to have negative influences on anaerobic digestion of WAS, but it is unclear how ATVs affect functional microbial metabolic activity and changes in intermediates. Thus, the effect of the anti-HIV drug ritonavir (RIT) on the period of anaerobic fermentation (AF) and the response of microbial community structure were examined in this study. Results indicated that the production of total volatile fatty acids (VFAs) decreased from 2010.21 mg/L to 372.03 mg/L under 125-1000 μg RIT/kg TSS treatment. Characterization of organic matters revealed that dissolved organic matter in the high-dose RIT groups was less biodegradable, with lower protein content and higher humus content. Mechanistic analyses indicated that RIT exposure reduced the abundance of hydrolyzers and inhibited carbohydrate metabolism, resulting in an increased humification index in the RIT groups. In addition, the expression of genes associated with the synthesis of VFAs was also significantly reduced in the RIT groups, leading to a decrease in both the amount and type of VFAs. This study provides a novel perspective on the effects of emerging contaminants on WAS treatment processes and pollution prevention.