Photocatalytic oxidation of natural organic matter surrogates and the impact on trihalomethane formation potential

Natural organic matter (NOM) consists of a complex mixture of organics and acts as precursors for a range of disinfection by-products (DBPs) including trihalomethanes (THMs). The characteristics of these precursors are still not well identified and here we have used a range of NOM surrogates that allows us to investigate how the characteristics of NOM relate to treatability with photocatalytical oxidation. Nine surrogates of NOM (five amino acids, two carbohydrates, two phenolic compounds) were evaluated and the impact of retention time on dissolved organic carbon (DOC) and trihalomethane formation potential (THMFP) measured. Adsorption of the compounds onto TiO2 was evaluated and electrostatic forces played a significant role in their removal although photocatalytic oxidation was found to be unselective. DOC and THMFP decreased significantly with retention time except for l-leucine where the by-products formed during photocatalytic oxidation were significantly more reactive with chlorine than the parent compound.