TiO₂/UV: Single stage drinking water treatment for NOM removal?

Problems arise at water treatment works due to the reaction of natural organic matter with chlorine to produce disinfection by-products (DBP). Trihalomethanes (THMs) are the main DBP regulated in various countries. The UK THM standard is 100 μg L^–1 while in the USA it is 80 μg L^–1. At certain times of the year the efficiency of conventional treatment processes is compromised due to seasonal increases in the concentration of natural organic matter (NOM). During these periods water treatment works generally increase the coagulant dose but this subsequently increases the volume of potable sludge generated. Advanced oxidation processes have the potential to remove NOM and thereby reduce the DBP formation. Here the adsorption of NOM onto pelletised titanium dioxide (TiO₂) and the oxidation of the surface of the pellets by UV light have been shown to reduce the dissolved organic carbon (DOC) concentration of source water by 70%. Key words: photocatalysis, titanium dioxide, natural organic matter (NOM), trihalomethanes, sludge reduction.