Comparison of photocatalytic degradation of natural organic matter in two Australian surface waters using multiple analytical techniques

Natural organic matter (NOM) is a heterogeneous mixture of organic compounds that is ubiquitous in surface waters. The character of NOM varies according to source, age and season. This variability can have an impact on the NOM reactivity during water treatment. In the present study, NOM removal efficiencies by TiO2 photocatalysis from two Australian surface water samples were assessed by monitoring the concentration, absorbance in the ultraviolet range (200–350 nm), molecular weight distribution and the chemical polarity of the source and treated water. In addition, the potential of the treated waters to form trihalomethanes (THM) after chlorination were evaluated. From the two surface waters after photocatalysis, similar product distributions were observed, which indicates that the degradation process can be described in terms of a similar reaction pathway. The organics remaining in the treated water consist mostly of low molecular weight hydrophilic compounds with weak UV absorbance at wavelength of 254–260 nm, and little reactivity with chlorine to form THM. Most importantly, use of multiple complementary analytical approaches resulted in a better understanding of the photocatalytic degradation process and its products.