Haloacetic acids: A new method for detection in drinking water and reactions with iron

Haloacetic acids (HAAs) are an important class of disinfection byproducts formed during the chlorination of water and wastewater. HAAs in drinking water are currently regulated by the United States Environmental Protection Agency (USEPA). Thus, HAAs are routinely monitored by water utilities. The current USEPA-approved HAA analysis methods require tedious and time-consuming extraction and derivatization steps and the use of hazardous chemicals. Thus, a safe and rapid method is needed. In addition, to predict the fate of HAAs in natural or engineered systems and to design treatment processes for removing HAAs, information is needed regarding the reactivity and kinetics of these compounds.; A method involving solid phase extraction (SPE) followed by capillary electrophoresis (CE) analysis was developed to analyze HAAs in drinking water. The SPE-CE method can be used to analyze all nine chlorinated and brominated HAAs except chlorodibromoacetic acid (CDBAA) (co-migrated with a contamination peak) and tribromoacetic acid (TBAA) (used as the surrogate). The estimated method detection limits ranged from 1.5--3.5 mug/L.; Batch experiments were conducted to investigate the pathways and detailed kinetics of the reactions of HAAs with Fe(0) and the effects of dissolved oxygen on HAA reaction rates. All nine chlorinated and brominated HAAs reacted with Fe(0) via sequential hydrogenolysis with bromine preferentially removed over chlorine. Acetate was the final product of the reactions.; The reactions of TBAA, CDBAA, and bromodichloroacetic acid were mass transfer limited. Intraspecies and interspecies competition effects were observed for the reactions of trichloroacetic acid, dichloroacetic acid, chloroacetic acid, bromoacetic acid (BAA), bromochloroacetic acid, and dibromoacetic acid. A Langmuir-Hinshelwood-Hougen-Watson (LHHW) kinetic model incorporating a mass transfer term provided a good fit of the experimental data. Oxygen inhibition was observed for BAA (a reaction limited species) while no inhibition was observed for TBAA (a mass transfer limited species).; The information regarding the reaction pathways and kinetics will be helpful for the development of a mathematical model for predicting the fate of HAAs in water distribution systems comprised of unlined cast iron or ductile iron pipes. It will aid in the development of treatment processes to remove HAAs from water or wastewater.