Effects of UV/H2O2 on NOM fractionation and corresponding DBPs formation

In this study, UV/H2O2 treatment was used to evaluate its efficacy for control of natural organic matter (NOM) in different water sources in Taiwan and the results were compared with the conventional water treatment process. The NOM fractions analysis showed that compositions of NOM could be very different between the various water sources, and the raw water quality in Kin-Men (an off shore island of Taiwan) was characteristic when compared to other water sources. Raw water taken from Kin-Men generally had high dissolved organic carbon (DOC) concentrations and ~ 50% of the NOM in the raw water was hydrophilic. After UV/H2O2 treatment, a portion of the hydrophobic fractions of NOM in raw waters were transformed into hydrophilic ones. In conventional water treatment process, coagulation and slow filtration treatments have better efficiency to reduce the NOM in water especially for the hydrophobic portion. However, the pre-chlorination treatment for raw water increased the DOC concentration due to the lysis of algae cells. This study concluded that hydrophobic acids portion is the most sensitive portion of NOM to UV/H2O2 and conventional treatment processes. Trihalomethanes formation potential (THMFP) tests showed that hydrophobic acids portion is also the main contributor to THMs formation after chlorination process.

Research Highlights
► UV/H2O2 treatment efficiency for NOM from different water sources was assessed.
► The very hydrophobic acid (VHoA) fraction of NOM is sensitive to the UV/H2O2 process.
► The VHoA fraction was the main contributor to THM formation in chlorination process.
► Part of the hydrophobic NOM is transformed into hydrophilic ones after UV photolysis.
► The THMFP decreases with increase of UV photolysis time after UV/H2O2 treatment.