Enhancing treatment performance in electroactive wetlands via innovative conductive channeling: A multi-phase, pilot-scale study

Abstract

This study introduces the innovative designing of electroactive wetlands (EAW) and explores its potential for real wastewater treatment at pilot scale. The design incorporates conductive channeling pathways strategically positioned between thin layers of anode and cathode to facilitate direct electron shuttling, circumventing necessity of saturating the entire wetland substrate with cost-prohibitive conductive materials. The system was evaluated over four operational phases using two electrode/substrate materials: granular activated charcoal (GAC) channeled electroactive wetland (GAC-C-EAW); a conductive substrate and low-cost barbecue charcoal (LCBC) channeled electroactive wetland (LCBC-C-EAW); a non-conductive substrate compared to a conventional constructed wetland (CW). GAC-C-EAW consistently outperformed COD, ammonium, and phosphate removal, generating an average voltage of 631 f 33 mV. Average influent COD was 319 f 65 mg/L, reduced to 44 f 26 mg/L at an overall average loading rate of 12.2 f 3.1 g/m2 center dot d. Ammonium decreased from 114 f 16 mg/L to 54 f 30 mg/L (overall average loading rate 4.5 f 1.7 g/m2 center dot d), and phosphate dropped from 29 f 6 mg/L to 12 f 7 mg/L (overall average loading rate 1.1 f 0.3 g/m2 center dot d). Higher nutrient removal was observed in GAC-C-EAW despite lowest Phragmites australis biomass accumulation of 4.665 kg/m2 (GAC-C-EAW) compared to 10.925 kg/m2 (CW) and 8.945 kg/m2 (LCBC-C-EAW). Since biomass primarily contributes to nutrient accumulation, this indicates that conductive substrate and enhanced electron transfer mechanisms play a significant role in nutrient removal independent of plant biomass. Conclusively, this highlights the potential of the innovative EAW design to enhance wastewater treatment efficiency, offering a robust and scalable solution for real-world applications.