Mechanisms linking triclocarban biotransformation to functional response in sulfur-metabolism biofilm

Triclocarban (TCC), a persistent antimicrobial compound widely present in municipal wastewater, poses potential risks to biological nitrogen removal processes. However, the potential risks posed by TCC to advanced treatment processes-particularly sulfur-metabolism biofilm reactor-remain poorly understood and require further elucidation. This study investigated the impact of TCC on sulfur-metabolism biofilm base on sulfur-metabolism biofilm reactor, focusing on nitrogen removal performance, TCC transformation pathways, and microbial community dynamics. The results showed that sulfur-metabolism biofilm maintained stable nitrogen removal efficiency under trace TCC (≤ 25 μg/L) stress with nitrate removal improved from 93 % to 98 %, whereas performance declined significantly at 100 μg/L, reducing nitrate removal to 81.8 ± 3.9 % and increasing effluent NO₂⁻-N and N₂O-N by 6.0- and 28.0-fold, respectively. Functional predictions via FAPROTAX suggested TCC-induced alterations in sulfur and nitrogen metabolic pathways. In addition, TCC and its transformation intermediates (MCC, DCC, NCC, 3,4-DCA, 4-CA) accumulated in the biofilm. Network analysis revealed syntrophic interactions between sulfur-oxidizing bacteria (e.g., Sulfurisoma and Sulfuritalea) and hydrogenase-rich TCC degraders (e.g., Unclassified Chloroflexi). These findings highlight the potential of sulfur-metabolism biofilm to achieve simultaneous nitrogen removal and micropollutant transformation in low-carbon, sulfur-rich wastewater environments, offering a sustainable solution for advanced wastewater treatment systems.