Application of backwashing with demineralized water for UF fouling control in UF-RO desalination

The effectiveness of demineralized water backwash on ultrafiltration (UF) fouling control of seawater is investigated in this study. Fouling experiments for two different backwashes (UF permeate and demineralized water) were conducted at three fluxes: 120, 180 and 240 L/(h m²) to compare their fouling control efficiency on UF membranes. Results show that backwashing with demineralized water improved the fouling control of UF membranes. When the UF membranes were backwashed with demineralized water, probably because more foulants were flushed away from the UF membrane than UF permeate backwashes, the increase in trans membrane pressure (TMP) for backwashing with demineralized water was less than that with UF permeate. Furthermore, the fluxes of experiments also played a role on the fouling control. When the flux was 120 L/(h m²), the difference between two different backwashes was small. However, at the flux of 240 L/(h m²), the TMP for backwashing with UF permeate increased faster than that with demineralized water, although the TMP for backwashing with demineralized water increased as well.