Variation in organic matter characteristics and mitigation of ultrafiltration membrane fouling by chlorine and UV/chlorine pre-oxidation in secondary effluent treatment

Abstract

Membrane fouling caused by effluent organic matter (EfOM) limits its further application in wastewater reuse. In this study, the effect of UV/chlorine pretreatment on membrane fouling was investigated in treating secondary effluent by ultrafiltration (UF) process. The relation between organic matter changes and fouling alleviation after UV/chlorine pretreatment was also studied according to the molecular weight (MW) changes in various resin fractions derived from EfOM. Results showed that UV/chlorine pretreatment effectively alleviated irreversible fouling, whereas chlorine pre-oxidation primarily mitigated reversible fouling. UV/chlorine pre-oxidation reduced 18% of reversible membrane fouling and 38% of irreversible membrane fouling at a chlorine dosage of 8 mg/L, indicating better performance in membrane fouling mitigation than chlorine pre-oxidation. UV/chlorine pre-oxidation also decreased dissolved organic matter in the UF permeate. The hydrophobic acidic (HPO-A) fraction caused dominant membrane fouling, while the hydrophilic (HPI) fraction contained most of high MW organic matter. Pre-oxidation changed the polarity of organic matter in the HPO-A fraction and decomposed the organics of high MW in the HPI fraction, which alleviated membrane fouling. These results showed that UV/chlorine pre-oxidation was a prospective pretreatment process prior to UF in wastewater reclamation.