Long-term performance and life cycle assessment of integrated Hydroponics-Microbial Electrochemical Technology for managing domestic wastewater resources

This study aimed at assessing the practical applicability and environmental sustainability of the emerging integrated Hydroponics-Microbial Electrochemical Technology (iHydroMET) for managing domestic wastewater resources through a year-long field study. The tower-design iHydroMET system, comprised of seven modular reactors containing leafy greens such as lettuce/sweet basil/peppermint, coconut husk, and a granular activated carbon-electrode assembly, achieved robust wastewater treatment (90.1±2.7% at 405.5±34.1 mg/L.d COD, 45.2±5.2% at 32.9±3.8 mg/L.d total nitrogen, and 98.3±0.6% turbidity removal), without showing clogging signs at 11.7 h hydraulic retention time. It produced reclaimed water (∼20 mg/L TN and ∼5 mg/L TP) suitable for gardening, substantial leafy greens (∼312 g/m 3 wastewater ), and electric power output (75.7±4.8 mW/m 2 ) for on-site use. The "cradle-to-gate" life cycle analysis revealed plastic framework and electricity consumption as the major contributors to environmental burdens (e.g., 0.34 kg CO2-eq global warming potential), while plant cultivation avoided the impacts (6.5 to 23.2%). The land footprint of the demonstrated system (1.6 m 2 /PE) is higher than that of aeration-based technologies but lower than constructed wetlands. The findings suggest that low-cost iHydroMET is suitable for managing domestic wastewater, thereby promoting circular resource utilization paradigms at point sources such as households. • iHydroMET achieves robust sewage treatment and resource recovery in field conditions • It produces leafy greens (312 g/m 3 ww ) and N & P-rich reclaimed water for gardening • Negligible sign of clogging (∼5% void volume reduction) over a year-long operation • Electricity usage and plant cultivation are crucial to the environmental impact • GWP of iHydroMET (0.34 kgCO 2 -eq) is low compared to conventional technologies