Removal of precursors for disinfection by-products DBPs/ } differences between ozone- and OH-radical-induced oxidation

Pre-oxidation is often applied to reduce the formation of disinfection by-products DBPs.. The aim of pre- oxidation is to remove the centers of natural organic matter NOM. which are responsible for the formation of DBPs. In this paper, the differences between ozone- and OH-radical-induced oxidation to remove DBP-precursors are compared. The experiments were done with water of the River Ruhr Germany. with a concentration of dissolved organic carbon DOC. of 2 mgrl. Ozonation was able to remove DBP precursors selectively. After application of an absorbed ozone mass of 1.5 mgrmg DOC, a reduction in the formation potential for THM-FP. and in the formation potential for organic halogen adsorbable on activated carbon AOX-FP. down to 68 and 73% of the initial concentration was achieved, respectively. A removal of NOM was not achieved using absorbed ozone masses between 0.5 and 1.5 mgrmg DOC. In the hydrogen peroxiderUV process, in which OH-radicals are the reactive species, an increase in the THM concentration was measured after application of this process with short irradiation times. The maximum value of the THM-FP was 20% higher than the initial THM-FP. After an irradiation time of 1050 min and a hydrogen peroxide consumption of 5.6 mgrl, the THM-FP and AOX-FP decreased to 75 and 71% of the initial formation potential, respectively. There was no selective removal of DBP precursors because the DOC concentration decreased also to 75% of the initial DOC-concentration after 1050 min of irradiation