Hybrid ion exchange - Pressure driven membrane processes in water treatment: A review

Over the last decades, the tightening of water quality regulations and the increased attention given to trace contaminants in water has been favouring the emergence of novel treatment technologies in order to upgrade or improve conventional water treatment processes. This review surveys recent studies on using combined ion exchange (IX) and pressure driven membrane processes (microfiltration (MF), ultrafiltration (UF), nanofiltration (NF) and reverse osmosis (RO)) in water treatment. It was shown that interest on these hybrid processes has increased substantially in the last years from both industry and academia due to need for higher efficiency, optimization and cost reduction of water treatment processes. The studies on using of hybrid IX-pressure driven membrane processes for prevention of membrane fouling, selective removal of targeted pollutants, treatment of waste waters and desalination of brackish/sea water have been critically analysed. It was shown that in some cases the combination of ion exchange resins (IXR) with MF, UF, NF and RO has a pronounced synergetic effect in creation of efficient and cost-effective technologies for water treatment. For example, RO-IXR treatment may be regarded as a standard technology for boron removal from RO permeate during seawater desalination. Hybrid IX-membrane processes also seem as promising solutions for prevention of membrane scaling/fouling, reduction of desalination costs, treatment of new types of waste waters such as produced waters from unconventional gas resources. However, further research including long-term operability, feed-specific and economical life-cycle analysis should be conducted to evaluate the feasibility of these hybrid processes for various potential applications in water treatment.