Fluorescence analysis of NOM degradation by photocatalytic oxidation and its potential to mitigate membrane fouling in drinking water treatment

• Fluorescence-based monitoring of the photocatalytic oxidation of natural water.
• Photocatalytic oxidation of NOM as a method to mitigate membrane fouling.
• ZnO displayed higher extent of NOM degradation when compared to TiO2.
• Photocatalytic oxidation treatment of river water considerably reduced UF membrane fouling.

This study examined the photocatalytic oxidation of natural organic matter (NOM) as a method to mitigate membrane fouling in drinking water treatment. ZnO and TiO2 photocatalysts were tested in concentrations ranging from 0.05 g L−1 to 0.5 g L−1. Fluorescence peaks were used as the primary method to characterize the degradation of three specific NOM components – fulvic acid-like humic substances, humic acid-like humic substances, and protein-like substances during photocatalytic oxidation. Fluorescence peaks and Liquid Chromatography–Organic Carbon Detection (LC–OCD) analysis indicated that higher NOM degradation was obtained by photocatalytic oxidation with ZnO than with TiO2. Treatment of the feed water by ZnO photocatalytic oxidation was successful in reducing considerably the extent of hydraulically reversible and irreversible membrane fouling during ultrafiltration (UF) compared to feed water treatment with TiO2. Fouling during UF of water subjected to photocatalytic oxidation appeared to be caused by low molecular weight constituents of NOM generated during photocatalytic oxidation.