AWWA ACE63220

The objective of this study was to increase the understanding of dihalogenated haloacetic acid (DXAA) formation during chloramination in the presence of bromide. This research proposes that the variability in DXAA formation and speciation is associated with the relative concentrations of the different haloamine species and their varying reactivities. Therefore, a better understanding of haloamine speciation in the presence of bromide under the range of conditions encountered in drinking water treatment, as well as the reactivity of the various haloamine species in forming DXAA, will allow development of better approaches for minimizing DXAA formation. The experiments conducted to characterize the reactivity of the bromamines in forming HAAs are summarized in the paper. The natural waters were dosed with preformed bromamine stock solutions. Simultaneously, the concentrations of the individual bromamine species in the stock solutions were measured spectrophotometrically. The pH of the water matched that of the dosing solution to ensure that the bromamine speciation did not change upon dosing. The dose was selected to provide a target residual concentration between 0.5 and 1 mg/L as Cl₂ at 24 hours. Samples were incubated in brown glass bottles and capped headspace free with Teflon-lined septa. HAA9 samples were taken at 5 minutes and again at 0.5, 1, 4, 24, 48, and 72 hours and extracted immediately to avoid complications that may arise due to sample preservation. Total combined oxidant concentrations were measured alongside the HAA samples to determine total oxidant demand. To study the influence natural waters may have on bromamine demand, control experiments were run with carbonate buffered Millipore water under the same experimental conditions as the bromamine reactivity experiments outlined in the paper. The carbonate concentrations were added to match the concentration found in the natural waters. In addition, several controls were also run with chloramines instead of bromamines to determine relative differences in reactivity. These experiments were conducted at the same pH, buffer concentration, and initial haloamine dose as the bromamine reactivity experiments, but were dosed with preformed chloramines instead of bromamines. Includes 8 references, tables, figures.