AWWA ACE62968

This slide presentation outlines a study on conducting a systematic investigation for gaining insight into the formation and speciation of haloacetic acids (HAA9) during chloramination. Specifically, the study examined: HAAs formation pathways; HAA formation kinetics; and, the role of natural organic matter (NOM) characteristics in HAA formation in chloramination. Summary of important findings included: major amount (80%) of HAA is formed from the direct reaction of NH₂Cl with DOM at pH 6. HOCl, the hydrolysis product of NH₂Cl, only contributes about 20% to HAA formation, the influence of HOCl decreases with increasing pH; in the presence of bromide, the relative significance of direct reactions and decomposition reactions are the same as in the absence of bromide; the extent of HAA formation decreased with increasing pH for both pathways; Dichloramine (NHCl₂) did not form HAA under typical drinking water conditions; selection of a quenching agent is important in order to obtain reliable results in kinetics experiments, the use of NH₄Cl, the quenching agent recommended by US Environmental Protection Agency Method 552.3 for DBP samples, may create an artifact on the HAA results, especially at short contact or reaction times; and, lag period between Cl₂ and NH₃ addition needs to be carefully optimized to comply with HAA regulations. Includes tables, figures.