Development and long-term field test of electrodeionization for decentralized desalination facility

Abstract

Conventional desalination methods, such as distillation and reverse osmosis, are primarily utilized in large-scale plants. However, these techniques face challenges when implemented in decentralized facilities, such as in remote or underdeveloped areas, due to their high cost and complex systems requiring elevated temperature and pressure operations. With the advantages of relatively low operating pressure and temperature, electrodeionization (EDI) can be an alternative to conventional desalination methods. This study explores the potential application of EDI for small-scale decentralized desalination facilities. This study examines the performance of EDI under various operating conditions, including spacer thickness, applied voltage, water recovery, and feed flow rate. Based on the Porous Plug model analysis, the majority of the electric current circulates through the solid phase, possibly due to the high conductivity of the ion-exchange resins. EDI with 4 mm spacer thickness can achieve >99% salt removal at 20 V applied voltage, 75% water recovery, and 2 mL/s circulation flow rate. In addition, a thinner spacer thickness can enhance the desalination rate while lowering the final solution temperature. Furthermore, two-stage EDI can effectively maintain the salt-removal rate, suppress reverse salt diffusion, and reduce the desalination time. The long-term performance test indicates that EDI exhibits excellent performance stability.