AWWA ACE63220

The objective of this study was to increase the understanding of dihalogenated haloacetic acid (DXAA) formation duringchloramination in the presence of bromide. This research proposes that the variability inDXAA formation and speciation is associated with the relative concentrations of thedifferent haloamine species and their varying reactivities. Therefore, a betterunderstanding of haloamine speciation in the presence of bromide under the range ofconditions encountered in drinking water treatment, as well as the reactivity of thevarious haloamine species in forming DXAA, will allow development of betterapproaches for minimizing DXAA formation. The experiments conducted to characterize the reactivity of the bromamines in formingHAAs are summarized in the paper. The natural waters were dosed with preformedbromamine stock solutions. Simultaneously, the concentrations of the individualbromamine species in the stock solutions were measured spectrophotometrically. The pHof the water matched that of the dosing solution to ensure that the bromamine speciationdid not change upon dosing. The dose was selected to provide a target residualconcentration between 0.5 and 1 mg/L as Cl₂ at 24 hours. Samples were incubated inbrown glass bottles and capped headspace free with Teflon-lined septa. HAA9 sampleswere taken at 5 minutes and again at 0.5, 1, 4, 24, 48, and 72 hours and extractedimmediately to avoid complications that may arise due to sample preservation. Totalcombined oxidant concentrations were measured alongside the HAA samples todetermine total oxidant demand. To study the influence natural waters may have onbromamine demand, control experiments were run with carbonate buffered Milliporewater under the same experimental conditions as the bromamine reactivity experimentsoutlined in the paper. The carbonate concentrations were added to match the concentrationfound in the natural waters. In addition, several controls were also run with chloraminesinstead of bromamines to determine relative differences in reactivity. These experimentswere conducted at the same pH, buffer concentration, and initial haloamine dose as thebromamine reactivity experiments, but were dosed with preformed chloramines insteadof bromamines. Includes 8 references, tables, figures.

Product Details

Edition:

Vol. - No.

Published:

06/01/2006

Number of Pages:

11

File Size:

1 file , 320 KB