There is a need to improve our understanding of how disinfectants used to control biofouling of reverse osmosis (RO) membranes react with active layer polymers and affect membrane performance over time with specific emphasis on the role of water quality. This work investigates structural and performance changes to the SW30HR RO membrane exposed to seawater disinfected with monochloramine. Batch experiments with RO membranes were conducted to determine the effect of secondary oxidizing agents, formed from the reaction between monochloramine, iodide, and bromide, on membrane structure. Membrane coupons were exposed to varying concentrations of monochloramine (2, 20 and 200 mg/L as Cl2) in synthetic seawater containing proportional levels of bromide (65, 650 and 6,500 mg/L) and iodide (0.06, 0.6 and 6 mg/L) and various contact times to achieve target exposures. Batch experiments also exposed membranes to real seawater treated with monochloramine (2 mg/L as Cl2) for 68 days. Rutherford back-scattering spectrometry (RBS) and ATR-FTIR analyses reveal structural changes corresponding to transformation of reverse osmosis membrane polymers including halogenation of the polyamide active layer. RBS analyses of membrane samples equilibrated with heavy ions also reveal changes in membrane structure as a result of disinfectant exposure. Complementary permeation experiments with membrane samples reveal a correlation between physic-chemical transformation of the active layer and changes in RO membrane performance.

Effects of chloraminated seawater on a reverse osmosis membrane

246th National Meeting (2013)

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