Real-Time Control of Redox Dynamics in Stormwater Biofilters Enhances Organic Chemical Removal

Real-time control (RTC) strategies in stormwater biofilters can enhance the removal of trace-level organic chemicals (TrOCs), yet performance depends on compound properties and rainfall conditions. This study investigated system dynamics, soil moisture, and redox potential (oxidation-reduction potential, ORP) in RTC and conventional biofilters (Non-RTC) under different antecedent dry weather periods (ADWP) to clarify mechanisms influencing TrOC removal. Mesocosm-scale vegetated columns operated for 1 year were sampled over 8 months under Non-RTC and three RTC configurations, with embedded sensors continuously monitoring moisture and the ORP in the unsubmerged and submerged zones. RTC-induced system operations significantly altered moisture and ORP conditions within the biofilters (p-value <0.001). RTC extended aerobic-anoxic conditions compared with predominantly anaerobic Non-RTC systems, significantly improving removal of TrOCs favoring aerobic biodegradation (p-value <0.001), with mean improvements of 37.2-45.5%. RTC accommodated ADWP-driven variability in system dynamics and treatment, except during 17-day ADWP when sustained anaerobic conditions in Non-RTC increased sulfamethoxazole and atrazine removal by up to 20.1%. Microbial profiling revealed modest increases in the diversity and abundance of TrOC-degrading genera under RTC (up to 4-fold). These findings demonstrate RTC's potential to optimize TrOC removal via active control of system dynamics, supporting broader and more sustainable operation of stormwater biofilters.