AWWA ACE62947

This research examined the influence of natural organic matter (NOM) and bromide on the loss of chlorpyrifos (CP) in the presence of free chlorine. The effect of bromide on CP degradation was examined at two different free chlorine concentrations ([FC]_T = 10 and 50 µM), bromide concentrations from 0-10 mM, over the pH range 7-9. A model NOM source, Suwannee River fulvic acid (SRFA), was used to provide a potential sink for active oxidants in the aqueous system. Results are presented as observed first order rate coefficients (k_obs). Experiments were conducted at 25 ¿¿¿¿ 1ºC in 128 mL amber batch reactors. Free chlorine was added to the aqueous system containing 0.5 µM CP, 10 mM carbonate buffer, and with or without the presence of bromide and/or NOM. Details of the experimental procedures have been discussed elsewhere. A stock solution of NOM was prepared from lyophilized Suwannee River fulvic acid (SRFA). The SRFA (50 mg) was dissolved in 500 mL of de-ionized water for 24 hours, filtered through a 0.45 micron filter to remove lyophilized SRFA that did not reconstitute, and the pH was adjusted to 9.0 with NaOH. UV/Vis spectra were obtained on a Perkin Elmer Lambda 900 spectrophotometer. Total organic carbon (TOC) concentration was analyzed with a Shimadzu TOC 5050A analyzer with normal sensitivity platinum catalyst. Includes 8 references, table, figures.