AWWA ACE70782

This powerpoint presentation begins by providing a brief overview of tastes and odors (T&O) in developed countries. A flavor profile analysis of Boussy St Antoine raw and chlorinated water (Dec 1985) is presented, along with THM's identified by SDE-GC-MS (Boussy St Antoine, Dec 1985). Topics presented include: Weber-Fechner curve for Iodoform and Bromoform (medicinal descriptor); literature review of odor thresholds for various THM (FPA method: 45ºC); Vernouillet case study of chlorination of groundwater containing ammonia; role of ammonia in iodinated THM formation (Gittelman and Yohe, 1989); Cassan Treatment Plant (December 1996); taste intensity as a function of chlorine dose; Cassan case study conclusion; compared formation of iodoforms (µg/L) with chlorine and chlorine dioxide (La Falaise groundwater); formation mechanism of iodinated THM Bichsel et al., 1999 HOI/OII-I; iodides in the environment; analytical methods for iodides and iodo THMs and I-HAAs; and, identification of iodoacetic acid in methylated acidic extract (Bordeaux area, July 1994) during medicinal odor episode. Conclusions indicate that: medicinal taste and odor episodes caused by iodinated DBP's have been observed at dozens of sites scattered throughout France; all of them were observed in groundwaters containing 20-100 µg/L of iodides and disinfected with chlorine only (chloramines are not allowed in France); iodoacids not investigated but detected on one occasion; most iodoform problems were solved by switching from chlorine to chlorine dioxide; chloramination where ammonia is added before chlorine or at the same time encourages formation of iodinated species; larger contact times (> 5 minutes) with chlorine before ammoniation reduces formation of iodinated species; and, removing the iodide precursors with a strong oxidant prior to disinfection may be the best option. Includes tables, figures.