Electrowetland Pilot of 50 m2: Operation and Characterization Under Real Conditions for 1 Year

ABSTRACT Traditional wastewater treatment plants (WWTPs) consume a significant amount of energy to clean wastewater. However, for medium‐ and small‐scale WWTPs, it is crucial to have an energetically self‐sustained treatment. In this regard, novel low‐energy demand treatment systems, such as nature‐based solutions (NBS), are highly suitable alternatives. Constructed wetlands coupled with microbial fuel cells (MFC), referred to as electrowetlands (EWs), are NBS able to treat wastewater while recovering electricity. In this study, initially, various granular carbon materials were tested as anode materials in laboratory‐scale MFCs, and anthracite was selected due to its higher electrochemical activity. Then, pre‐pilot scale tests were conducted, evaluating different EW configurations. The one consisting in a horizontal anode yielded the best wastewater treatment efficiencies (chemical oxygen demand [COD] degradation greater than 90%) and electricity production (11 mW m−2; 260 mWh day−1 m−2). Finally, a 50 m2 pilot was constructed in Valladolid, studying its performance under real conditions for 1 year. The pilot showed robust and stable performance, achieving high wastewater treatment efficiencies (COD degradation >85%, outflow COD of 100 ppm) and generating 115 Wh in 1 year (power density of 0.4 mW m−2).