Performance of Copolymerized Organo-Selenium RO Feed Spacers during Fouling

Abstract

Fouling of reverse osmosis (RO) systems to produce clean drinking water is a major problem. Organo-selenium inhibition is an attractive solution for this application because biofilm prevention has been shown in medical devices, water filtration systems, and plastics. This study examined whether selenium-coated polymers would have positive effects in controlling RO fouling. This study included an analysis of modified feed spacers’ performance on reduction of total biomass concentration, average biofilm thickness on the surface of RO membranes versus real wastewater sources, the impact of selenium catalytic activity on the reduction of RO membrane chemical scaling, and the performance of fouling and biofilm formation. A 1.5% organo-selenium was copolymerized into spacer elements used in an RO system. These systems were then tested with both city and industrial wastewater with different total dissolved solids (TDS) concentrations for effects on (1) flux, (2) biofilm formation, and (3) inorganic binding. The comparison of an organo-selenium spacer with a control spacer yielded the following for RO membranes: (1) lower calcium and magnesium binding; (2) better flux at high TDS concentrations in both city and industrial water; (3) lower biofilm thickness and volume; and (4) a decrease in both dead and viable bacteria. Testing of varying solids concentrations resulted in greater log inhibition of fouling as a result of operating the RO system with selenium copolymerized feed spacer. The impact of selenium catalytic activity versus divalent foulants (magnesium and calcium) is important because of their ability to create bridges between biological cells and membrane surface, leading to increased possibility of biofouling.