More than 60 years have passed since UCLA first announced the development of an innovative asymmetric cellulose acetate reverse osmosis (RO) membrane in 1960. This innovation opened a gate to use RO for commercial use. RO is now ubiquitous in water treatment and has been used for various applications, including seawater desalination, municipal water treatment, wastewater reuse, ultra-pure water (UPW) production, and industrial process waters, etc. RO is a highly integrated system consisting of a series of unit processes: (1) intake system, (2) pretreatment, (3) RO system, (4) post-treatment, and (5) effluent treatment and discharge system. In each step, a variety of chemicals are used. Among those, sulfites (sodium bisulfite and sodium metabisulfite) have played significant roles in RO, such as dechlorination, preservatives, shock treatment, and sanitization, etc. Sulfites especially became necessary as dechlorinating agents because polyamide hollow-fiber and aromatic thin-film composite RO membranes developed in the late 1960s and 1970s were less tolerable with residual chlorine. In this review, key applications of sulfites are explained in detail. Furthermore, as it is reported that sulfites have some adverse effects on RO membranes and processes, such phenomena will be clarified. In particular, the following two are significant concerns using sulfites: RO membrane oxidation catalyzed by heavy metals and a trigger of biofouling. This review sheds light on the mechanism of membrane oxidation and triggering biofouling by sulfites. Some countermeasures are also introduced to alleviate such problems.

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As a part of Dow's 2015 Sustainability Goals, Dow Water & Process Solutions have been involved in developing solutions for economically viable desalination. The integrated membrane system (IMS) is an integral part of solutions to lower desalination costs and to make an RO process more affordable.In order to enhance the IMS, the larger membrane area SFP-2880 UF module was developed. This module is an ideal choice for IMS with capacities greater than 50 m 3 /h. Larger and longer, 8 inch diameter and 80 inch in length, together with an increase in packing density of 10,000 fibers, this module offers the highest effective membrane area of the DOW TM Ultrafiltration modules. The SFP-2880 contributes to a more economical membrane system design.TM ® Trademark of The Dow Chemical Company ("Dow") or an affiliated company of Dow