Salinity gradient power production from underground seawater and municipal wastewater using reverse electrodialysis: comprehensive understanding of fouling mechanisms of pore-filling ion-exchange membranes

Abstract

Reverse electrodialysis (RED), an emerging technology harnessing salinity gradient power (SGP), has garnered significant attention in recent years due to its high yield and environmentally friendly attributes. Utilizing treated municipal wastewater as a low-concentration feed solution alternative for RED holds promise for mitigating environmental concerns and reducing energy consumption in municipal wastewater treatment plants. In this study, A lab-scale RED stack equipped with pore-filling ion-exchange membranes (PF-IEMs) was developed to generate SGP. This system utilized site-specific underground seawater and treated municipal wastewater in Jeju Island, South Korea. The findings revealed that the RED stack with PF-IEMs achieved a net specific energy consumption of 0.04 kWh/m3, equivalent to 5–20 % of the energy consumption in conventional wastewater treatment plants. During the continuous operation of RED, the constant voltage mode exhibited superior stability compared to the constant current mode. Based on these findings, a unique fouling development mechanism is proposed that considers the environment surrounding the foulant. This mechanism sheds light on the formation of organic-inorganic complexes involving organic foulants and multi-valent cations within both anion-exchange and cation-exchange membranes. The outcomes of this study hold the potential to significantly enhance RED systems for clean energy production by utilizing natural water resources and municipal wastewater.