Unveiling the different faces of chlortetracycline in fermentative volatile fatty acid production from waste activated sludge.

[Display omitted] • CTC promotes volatile fatty acid production from waste activated sludge. • 10 mg/kg TSS CTC induces the highest volatile fatty acid accumulation. • CTC stimulates the secretion of extracellular polymeric substances. • CTC enhances acidification and inhibits methanation by regulating enzyme activity. One of the key challenges of wastewater treatment today is to understand the potential effect of residual pollutants on the management of waste activated sludge (WAS). This study aims to clarify the effect of chlortetracycline (CTC) as a residual antibiotic on the anaerobic fermentation of WAS to produce volatile fatty acids (VFAs). The results show that CTC with a concentration of 10 mg/kg total suspended solids enhances the VFA production by 21.1%. Mechanistically, CTC was found to prompt the secretion of extracellular polymeric substances to provide more substrates for anaerobic fermentation. Meanwhile, CTC stimulates acidification by increasing the activity of acetate kinase, and inhibits methanogenesis by reducing F 420 activity, thereby increasing the accumulation of VFAs. This article provides new insights into the behavior of CTC in WAS fermentation, which is essential for resource recovery from WAS containing CTC. [ABSTRACT FROM AUTHOR]