Characterization of haloacetic acid precursors in source water

Abstract

Raw water from the Bangkok (Thailand) main municipal water supply canal was examined for its natural organic composition by fractionation with adsorption resins. DAX-8 resin was the first resin employed to fractionate the hydrophobic fractions. Fractionation at neutral pH resulted in the separation of the hydrophobic neutral components; at a high pH level (approx. 10) separation of the hydrophobic base components occurred; and at a low pH level (approx. 2) the hydrophobic acid components were separated. AG-MP-50 cationic resin was then used to separate the hydrophilic base components, and WA-10, a weak anionic resin, was applied finally to fractionate the hydrophilic acid and neutral components. Subsequently, each fraction was tested for its chlorine disinfection by-product (DBP) formation potential. The HAA formation tests demonstrated that the various organic fractions had different reactivity levels for the formation of haloacetic acids (HAAs). For this source water, the hydrophilic neutral fraction dominated over the other five fractions in being the main organic component and the most significant precursor of HAAs formation. On the other hand, in terms of specific HAA formation potential (FP), the hydrophobic and hydrophilic base fractions were the most reactive precursors to the formation of HAAs. In all cases, the quantity of HAAs formed depended linearly upon the amount of organic constituents in the water sample.