Modular stacked bioelectrocatalytic-triphasic constructed wetland for continuous wastewater treatment

A modular stacked SS316L electrode assembly integrated into a continuous-flow Bioelectrocatalytic Treatment (BET) reactor as a plug-and-play intensification module, enabling in-situ redox regulation without structural modification of conventional sewage treatment plants (STPs) or effluent treatment plants (ETPs) is reported. Self-generated electrochemical potentials formed distinct anodic and cathodic microenvironments, facilitating microbial electron transfer and enhancing bioelectrocatalytic activity at the electrode-biofilm interface. Electrochemical characterization demonstrated progressive bioelectrode maturation and enhanced electron-transfer activity, with peak currents reaching 3.8 mA and maximum current and power densities of 10.33 mA m^-2 and 11.78 mW m^-2, respectively. Over 108 h of continuous operation, the BET reactor achieved significantly higher pollutant removal than the unelectrified control, with Chemical Oxygen Demand (COD), Biochemical Oxygen Demand (BOD₅), and Total Organic Carbon (TOC) removal efficiencies of 88%, 89%, and 88%, respectively. Nitrate, sulfate, and phosphate removals reached 84%, 73%, and 81%, respectively. GC-MS profiling revealed substantial reductions in environmentally relevant compounds, including phthalate esters, siloxanes, long-chain hydrocarbons, and phenolic antioxidants, with 80-90% lower peak area signals relative to the influent. 16S rRNA amplicon sequencing revealed distinct shifts in microbial community structure, diversity, and predicted functional potential following electrode integration, indicating electrode-driven microbial adaptation within the BET system. Downstream integration with a triphasic constructed wetland supporting Eichhornia crassipes, Hydrilla verticillata, and Lemna minor facilitated tertiary polishing through rhizospheric plant-microbe interactions and redox stratification. The proposed electro-biogenic intensification strategy offers a scalable and energy-efficient solution for upgrading conventional wastewater treatment infrastructure.