Effect of continuous 3,5-dichlorophenol dosing on excess sludge reduction in activated sludge systems

This study investigated the impact of introducing 3,5-dichlorophenol (3,5-DCP) via influent water on excess sludge reduction and microbial community dynamics in wastewater treatment. Continuous exposure to 3,5-DCP maintained high chemical oxygen demand (CODCr) removal efficiency and significantly reduced sludge yield, compared to conventional methods. Microbial analysis revealed a significant abundance of the obligate aerobe Leadbetterella and the obligate anaerobe Clostridium sensu stricto 13. These findings suggest that both genera adapted to 3,5-DCP, with Clostridium likely utilizing anaerobic pathways, such as substrate-level phosphorylation (SLP), in response to the inhibitory effect of 3,5-DCP on oxidative phosphorylation. This study demonstrates the potential of influent-based 3,5-DCP application as an effective strategy for modulating microbial community structure and optimizing sludge management in wastewater treatment processes. • We investigated the effects of 3,5-dichlorophenol (3,5-DCP) on excess sludge reduction and microbial dynamics in wastewater treatment. • Long-term exposure to 3,5-DCP, compared to short-term exposure, led to more efficient sludge reduction and high CODCr removal efficiency. • Significant adaptation and resilience were observed in Clostridium and Leadbetterella . • Our results suggest that long-term 3,5-DCP application is a promising strategy for sludge management.