Application of oxidative removal of NOM to drinking water and formation of disinfection by-products

Water samples of different origins (Buyukcekmece and Omerli, Istanbul, Turkey, and Alento, Salerno, Italy) were treated by coagulation, ozonation, and coagulation followed by ozonation and photocatalysis. Disinfection by-products (DBPs) formation potential of raw and treated water samples was compared in relation to removal efficiencies by the respective treatment methods. The major DBPs, namely trihalomethanes (THMs) and haloacetic acids (HAAs), and other DBPs were identified and quantified. Besides major THMs and HAAs, the presence of bromoform in high amounts was also detected due to the high levels of bromide ions in raw Buyukcekmece and Omerli water samples. Depending on the natural organic matter (NOM) removal efficiencies of each treatment process, the distribution of individual THMs and HAAs was found to be NOM-site specific. Other DBPs were also detected and chloral hydrate (C2H3Cl3O2) was found in significant amounts. The responsible precursor sites could only be reduced by photocatalytic treatment of NOM.

An effective NOM control program relies upon a good understanding of the origin, occurrence, and fluctuation of the organic matter in surface water. The results presented here display the effects of treatment methods on the removal of organic matter taken from different regions of Istanbul, Turkey, and Salerno, Italy. The effects of ozonation, coagulation, ozonation followed by coagulation and photocatalysis were investigated in terms of SUVA254 and DBP formation potentials in relation to D. magna immobilization. The related removal efficiencies were found to be site specific. All of the THMs were formed, and the presence of high levels of bromide ions in the Buyukcekmece and Omerli water samples resulted in considerable amounts of bromoform. The distribution of HAAs was not significantly affected by the treatment methods except for the fact that trichloroacetic acid formation was [1] P.C. Singer, Water Sci. Tech., 40(9) (1999) 25–30. [2] M.A. McGeehin, J.S. Reif, J.C. Becher and E.J. Mangione, Am. J. Epidemiol., 138(7) (1993) 492– 501. [3] C.Y. Yang, Toxicology, 198 (2004) 249–254. [4] US Environmental Protection Agency (USEPA), Disinfectants and disinfection by products: final rule. Federal Register, 63(24) (1998) 69478. [5] U. Von Gunten, Water Res., 37(7) (2003) 1469– 1487. [6] V. Camel and A. Bermond, Water Res., 32(11) (1999) 3208–3222. [7] US EPA, Enhanced Coagulation and Enhanced Precipitative Softening Guidance Manual, EPA 815-R99-012, Washington, DC, 1999. [8] L. Rizzo, H. Selcuk, A. Nikolaou, V. Belgiorno, M. Bekbolet and S. Meric, submitted for publication. [9] A. Kerc, M. Bekbolet and A.M. Saatci, Water Sci. Tech., 49(2) (2004) 7–12. [10] M. Bekbolet, A.S. Suphandag and C.S. Uyguner, J. Photochem. Photobiol. A: Chem., 148 (2002) 121– 128.