Sustainable energy harvesting and on-site disinfection of natural seawater using reverse electrodialysis

Abstract

Seawater is a cost-effective and abundant electrolyte used as an electrode rinse solution to enable optimum utilization of reverse electrodialysis (RED). However, it is associated with several limitations, including the use of precious electrode materials, and its long-term stability must be addressed prior to its application in the field of seawater technology. In this context, a novel RED based on carbon electrodes was designed, and the experimental conditions were optimized for maximizing the harvesting of energy with aquaculture wastewater disinfection and recycling. The power obtained by RED, with a current density of 30 A/m2 and a flow rate of 424 mL/min, designed by response surface methodology, was in good agreement with the predicted maximum power density (0.64 W/m2). The treatment was sustainable, mainly due to an anodic reaction of electro-generated sodium hypochlorite (NaOCl) under natural conditions, which afforded a high disinfection efficiency (above 99.5 ± 0.2% within 1 min under continuous flow (pH 8)), even under real seawater conditions and in aquaculture wastewater. Simultaneously, a stable power of 0.1 ± 0.03 W (0.25 ± 0.07 W/m2) generated a reasonable specific energy (within 0.02 kWh/m3). Inorganic fouling was efficiently suppressed using a surface-modified carbon cathode for 680 h. Thus, the on-site seawater disinfection by RED described herein is practically feasible and could offer a sustainable and energy-efficient alternative to seawater recycling.