Controlling biofouling and disinfection by-product formation during reverse osmosis treatment for seawater desalination

Abstract

Controlling membrane fouling and disinfection by-products (DBPs) is an ongoing challenge in achieving sustainable membrane-based seawater desalination. This study assessed the efficacy of a new disinfectant, stabilized hypobromite, for controlling biofouling and DBP formation during reverse osmosis (RO) membrane treatment of seawater. Accelerated chemical exposure tests revealed that stabilized hypobromite did not degrade a commercial polyamide RO membrane; thus, unlike other powerful oxidants, it is able to remain as a residual chemical on membrane surfaces. In our experiments, stabilized hypobromite also effectively inactivated bacteria in seawater and reduced potential organic foulants (e.g., humic acid-like and protein-like substances). Disinfection at a stabilized hypobromite dose of 5 mg-Cl2/L resulted in the formation of trihalomethanes (THMs), haloacetic acids (HAAs), and bromate at 55, 29, and <10 μg/L, respectively. Chlorine treatment resulted in higher formations of THMs, HAAs, and bromate (80, 74, and 50 μg/L, respectively), indicating stabilized hypobromite is superior to chlorine in this respect. Pilot-scale validation demonstrated that pre-disinfection with stabilized hypobromite enabled the RO membrane treatment to operate for half a year without significant fouling. The findings in this study indicate the great potential of stabilized hypobromite for controlling DBP formation and biofouling in seawater desalination.