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 mg/l. Ozonation was able to remove DBP precursors selectively. After application of an absorbed ozone mass of 1.5 mg/mg 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 mg/mg DOC. In the hydrogen peroxide/UV 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 1,050 min and a hydrogen peroxide consumption of 5.6 mg/l, 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 1,050 min of irradiation.
Kleiser
G
G
Engler-Bunte-lnstitut, Unitersität Karlsruhe, Germany.
Frimmel
F H
FH
D004202:Disinfectants / Q000378:metabolism*; D005609:Free Radicals; D006861:Hydrogen Peroxide; D009930:Organic Chemicals / Q000378:metabolism; D010083:Oxidants, Photochemical / Q000378:metabolism*; D010084:Oxidation-Reduction; D010126:Ozone / Q000378:metabolism*; D014865:Waste Disposal, Fluid / Q000379:methods
D004202:Disinfectants; D005609:Free Radicals; D009930:Organic Chemicals; D010083:Oxidants, Photochemical; D010126:Ozone; D006861:Hydrogen Peroxide