Desalination of concentrated wastewater from reverse osmosis by bipolar membrane electrodialysis

摘要

The present study focused on the feasibility of bipolar membrane electrodialysis (BMED) for desalination of concentrated wastewater from reverse osmosis, including the reduction of total dissolved solids (TDS) and the generation of mixed acid/base. The effects of parameters such as current density, electrolyte concentration, and initial acid/base concentration were explored and discussed. The optimal current density was 10 mA/cm(2), the suitable electrolyte concentration was 0.25 mol/L, and the appropriate initial acid/base concentration was 0.05 mol/L. Experimental results indicated that 89.05% TDS could be removed, and the generated acid and base concentrations could reach to 0.12 mol/L and 0.18 mol/L respectively. The energy consumption for removing per kilogram TDS was 2.33 kWh. Besides, the energy consumption for acid generation was 2.55 kWh/kg, with a current efficiency of 67.7%; and for base production was 1.80 kWh/kg, with a current efficiency of 87.5%. All the results indicated that the BMED process was technical and environmental feasible for desalination of concentrated wastewater from RO. The generated mixed acid/base solution and fresh water (TDS less than 1.45 g/L) after treatment could be reused as resource.