The effect of DOM on floc formation and membrane fouling in coagulation/ultrafiltration process for treating TiO2 nanoparticles in various aquatic media

Dissolved organic matter (DOM) would absorb on nanoparticle (NP) surface and affect their fate, transport, bioavailability, toxicity and control. The study explored the removal of TiO 2 NPs as a function of DOM composition in coagulation/ultrafiltration membrane (UF) process by comparing the flocs properties and membrane fouling in different water samples (e.g. HA synthetic water (WATER SN ), surface water (WATER XQ ) and municipal wastewater (WATER MW ). The results showed that floc size of WATER SN increased with higher dosage and lower pH conditions. In contrast, the floc size of WATER MW decreased with increasing dosages while the floc size of WATER XQ was not affected by Polyaluminum Chloride (PAC) dosage and pH. TiO 2 NPs in WATER MW and WATER XQ aggregated to larger and looser flocs than those in WATER SN , probably due to the higher protein and larger molecules DOM fractions in WATER MW and WATER XQ . The floc properties in different water samples affected fouling behavior in ultrafiltration membrane following pre-coagulation. PAC (2   mg   L −1 ) could reduce 67% of external fouling resistance for WATER SN but only 20% for WATER MW . In addition, lower restricting internal fouling for WATER MW and WATER XQ was achieved by a pre-coagulation process.