This study investigates the effectiveness of different backwash waters on ultrafiltration (UF) fouling control on a pilot-scale setup. Surface water and ion exchange (IEX) pretreated surface water were used as feed water. Three backwash waters were tested: demineralized water, UF permeate and nanofiltration (NF) permeate. Results show that backwashing with demineralized water substantially improves fouling control efficiency. It is supposed that both the reduction of charge screening and Ca-bridging effect cause this improvement on fouling control. Furthermore, backwashing with NF permeate also negatively influences the fouling control efficiency, indicating the impact of monovalent ions in backwash water on the ultrafiltration fouling. Findings from such a pilot scale setup also show that it is possible to apply backwashing with demineralized water on the operation of UF plants.
Keywords: backwash, demineralized water, fouling, ultrafiltration