Hybrid RED/ED system: Simultaneous osmotic energy recovery and desalination of high-salinity wastewater

Abstract

Reverse electro-dialysis (RED) is a potentially available technology to harvest salinity gradient power, which can be extracted from high-salinity wastewater in industrial processes. This study proposes a hybrid RED/ED system to simultaneous osmotic energy recovery and complete desalination in the phenol-containing wastewater treatment process. Experimental investigation on standalone ED system reveals that the high stack resistance, resulting from the salinity difference between both feed streams, accounts for the inefficient desalination performance in early stages, which implies potential implication of RED as a pre-desalination process with natural driving force to reduce the salinity difference. Pre-desalination rate is related to power generation in RED stage and energy saving in ED stage under optimal operation conditions. Compared with artificial seawater, greater power generation is produced by using phenol-containing wastewater as the high-salinity stream. Economic analysis suggests that average power generation and limiting wastewater treatment capacity can provide insightful guidelines for the design and improvement of the hybrid system. Control conditions are listed as a fundamental criterion to search for potentially applicable wastewater systems in the hybrid system. Therefore, hybrid RED/ED system can realize triplex advantages of salinity energy usage, high-valued resource reclamation, and low-energy desalination in high-salinity wastewater treatment processes.