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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. [ABSTRACT FROM AUTHOR]

Abstract: Because of the demand for acid solutions in seawater desalination pretreatment and the difficulty of transporting sulfuric acid or hydrochloric acid, seawater concentrate from an RO system was used as the feed for the production of mixed acid by bipolar membrane electrodialysis (BMED) after the removal of calcium ions and magnesium ions. In this experiment, the feasibility of the process was tested using a laboratory ED-cell with an effective area of 88cm2. Based on the configuration of the BP-C-A-BP, the mixed acid solution was produced in the acid compartment, and the base solution was produced in the base compartment. The results showed that 1mol/L mixed acid and sodium hydroxide could be produced continuously at a constant current density of 57mA/cm2 and a flow rate of 0.30L/h in the continuous-mode BMED. After the production of the acid and base solution, membrane fouling was inspected by measuring the stack resistance and using electron microscopy and surface elemental analysis. No visible fouling deposits on the surface of the CEMs (AEMs) were observed, and there was an increased stack resistance, thus proving that the BMED process for mixed acid production with pretreated RO concentrate is suitable for a long-term run. [Copyright &y& Elsevier]