DBP formation and speciation in a central anatolian dam water depending on pH, TOC level, fraction and chlorine dose

Abstract

The effects of pH, NOM concentration, fractions and the chlorine dose on the formation and speciation of THMs and HAAs were determined in Altinapa Dam water (Konya/Turkey). Water sample was isolated and chlorinated at different TOC levels and pH's. The isolate was fractioned; THM and HAA species were measured after chlorination. THM increased with increasing pH (6 to 8) whereas a consistent pH tendency could not be inferred from the HAA changes. CF is the dominant THM specie which exerts up to 91% of the total THM. The majority of total HAAs composed of MCAA, DCAA and TCAA. The hydrophobic fraction was the main THM precursor under the studied conditions although their percentage was lower than hydrophilics, whereas, hydrophilic fraction had significant contribution to HAA formation, in contrast to the general tendency for HAA. High correlation (0.97) was calculated between total THMs and HAAs.KEYWORDS: Natural organic matter, fractionation, trihalomethanes, haloacetic acids, chlorination. INTRODUCTIONNatural organic matter (NOM) exists in all surface waters and groundwaters as a result of complex biotic and abiotic reactions. The application of disinfectants to drinking water reduces the microbial risk but possess chemical risk in the form of disinfection by-products (DBPs) by reactions between dissolved portion of NOM and disinfectant. Applied chlorine rapidly hydrolyses and so formed hypochlorous acid (HOCl) undergoes subsequent reactions resulting in the formation of DBPs. There has been an increasing concern about DBPs since Rook (1974) and Bellar and Lichtenberg (1974). Although there are various identified halogenated DBPs, trihalomethanes (THMs) and haloacetic acids (HAAs) are the most common DBPs which are carcinogenic and potentially hazardous to human health. There are a lot of limitations imposed by EPA, EU and WHO for DBPs. Maximum limits has been decreased in recent revisions.