Application of chlorine dioxide (ClO₂) to reverse osmosis (RO) membrane for seawater desalination

There are justifiable concerns about reverse osmosis (RO) performance deterioration and carcinogenic by-products from disinfection in water treatment facilities. Traditional disinfectant chlorine (Cl₂) has been replaced with stable and safe disinfection processes. Chlorine dioxide (ClO₂) as an alternative disinfectant has been increasingly adopted in various water treatment facilities. To identify the applicability of ClO₂ to RO desalination process, lab-scale experiments were designed by simulating actual oxidant exposure circumstances. In the experiment, Cl₂ or ClO₂ solution was injected separately into a working RO system. Our results showed that Cl₂ dosage greatly decreased permeate flux slope. However, instant flux increase of approximately 5% was observed when ClO₂ was injected. ATR FT-IR and EDX analysis for exposed membranes showed that Cl₂ deformed amide peaks and attached Cl atom onto the membrane, indicating chlorination. However, none of these results was observed in ClO₂ exposure cases. In addition, immediate sodium bisulfite application alleviated flux decrease under Cl₂ chlorination.