STUDY ON STRATEGIES TO REDUCE MEMBRANE SCALING AND FOULING IN DRINKING WATER AND WATER REUSE MEMBRANE SYSTEMS

Abstract

Central Arizona Project (CAP) water was treated using the process of slowsand filtration, chemical pretreatment and RO membrane. Both bench scale plate and frame reactor and pilot scale tests suggested RO membrane fouling by clay and organic matter with minor scaling by CaCO3 and BaSO4. Several strategies were studied to reduce RO membrane fouling and scaling. The first is choosing optimized operation conditions through bench scale tests. The second is to modify the traditional concentration polarization model for a better fouling/scaling prediction. This modified model was also used to optimize concentrate spacer design, which leads to reduced concentration polarization index. The third is to develop a method for anti-scalant test and comparison, which can be used for anti-scalant selection and dose optimization.Additional to these strategies, pre-oxidation pretreatment for RO membrane in water reuse application was investigated at bench and pilot scale. In the MBR-Ozone-RO train study, ozone showed certain impact on RO membrane fouling, but no significant difference was made on membrane cleaning frequency. UV and UV/AOP impacts on RO membrane fouling tests were done on plate and frame reactor. UV did not show any competency to reduce membrane fouling, while UV/AOP tests showed promising results by reducing RO membrane fouling rate by 50%.