Roles of Sulfites in Reverse Osmosis (RO) Plants and Adverse Effects in RO Operation

Abstract

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.

Recovery of the Properties of Spent Commercial Reverse Osmosis Membrane Elements and Ways of their Reuse

“…After washing, the elements were kept in a stabilization solution [Tyvonenko et al, 2023a]. To stabilize the modified membrane elements, solutions of sodium metabisulfite (1%) and glycerol (5%) were used [Maeda 2022].…”

Production of physiologically complete drinking water using modified reverse osmosis membrane elements

“…To modify the RO elements, a 4 % sodium hypochlorite solution was used (Milam, Ukraine). To stabilize the modified membrane elements, solutions of sodium metabisulfite (1 %) (CHEMICO GROUP, China) and glycerol (5 %) (Miranda-S, Ukraine) were used [17]. Reverse osmosis water was used to prepare solutions.…”

“…After modification, membrane elements were washed from the active chlorine solution by passing reverse osmosis water through membrane elements for at least 30 minutes until no reaction to active chlorine in permeate and concentrate was achieved. After washing, the elements were kept in a stabilization solution containing 1 % metabisulfite and 5 % glycerol [17].…”

Demineralisasi Kalsium (Ca) dan Besi (Fe) pada Air Minum Soft Water Berteknologi Reverse Osmosis (RO)

“…Metode ini membuat air mendekati murni, sehingga air tersebut bisa menghasilkan output sesuai spesifikasi air yang dibutuhkan, contohnya bisa untuk air langsung konsumsi, dan air untuk scalling mesin [11]. RO banyak digunakan dalam pengolahan air, desalinasi air laut, pengolahan air limbah, produksi ultra-pure water (UPW), dan air untuk proses industri [12].…”