Abiotic Degradation of Disinfection Byproducts (Co-PI with Prof. W.A. Arnold, Funding from the National Science Foundation and AWWA Research Foundation).

Disinfection by-products (DBPs) are formed upon addition of chlorine to water and consist of a wide variety of compound classes including trihalomethanes (THMs), haloacetic acids (HAAs), halonitromethanes (HNMs) and others. Many DBPs are known or suspected carcinogens and therefore, the Disinfectants and Disinfection By-Products Rule was promulgated to limit exposure to these compounds via drinking water. In the negotiated Stage 2 DBP Rule, the spatial variability of DBP levels in the distribution system must be considered as new sample sites will need to be utilized that have maximum THM and maximum HAA occurrence. Unfortunately, little is known about the fate of DBPs in distribution systems. Decreases in HAA concentrations in water distribution systems have been reported by several researchers, but the mechanisms for these losses are unclear. Because "unlined" cast and ductile iron pipe are present in many distribution systems, this research was performed to evaluate the abiotic degradation of DBPs by iron metal (Fe0), synthetic iron minerals, and iron corrosion propipe photoducts. The experimental approach involves batch experiments performed in glass serum bottles and in reactors comprised of 6 inch ID x 12 inch iron pipe sections. An investigation of the kinetics and pathways of the degradation of the nine chlorinated and brominated HAAs and the three chlorinated HNMs by Fe0 has been completed. All compounds were completely dehalogenatd via hydrogenolysis, except  for chloropicrin (trichloronitromethane), which was degraded via a combination of hydrogenolysis and alpha-elimination. The end products of the degradation of HAAs and HNMs were acetate and methylamine, respectively. Most experiments were performed in the absence of competing oxidants such as dissolved oxygen or chlorine, but we have also investigated the kinetics of DBP degradation in the presence of these oxidants. The degradation of additional classes of DBPs (e.g., haloacetonitriles, haloketones) by Fe0, and the degradation of DBPs by iron minerals (e.g., green rust, magnetite) and iron corrosion products obtained from water distribution systems (see photo of pipe to the right) has also been investigated. This research has important implications for understanding and predicting the fate of DBPs in water distribution systems and may be useful for designing new water treatment systems for DBP removal from water supplies.


Publications:

  1. Lee, Jeong-Yub, Hozalski, R.M., and Arnold , W.A. Effects of Dissolved Oxygen and Iron Aging on the Reduction of Trichloronitromethane, Trichloracetonitrile, and Trichloropropanone. Chemosphere (submitted).

  2. Chun, C., Hozalski, R.M., and Arnold , W.A. Degradation of Disinfection Byproducts by Carbonate Green Rust. Environmental Science and Technology (submitted).

  3. Chun, C., Hozalski, R.M., and Arnold , W.A. (2005). Degradation of Disinfection Byproducts by Synthetic Goethite and Magnetite. Environmental Science and Technology, 39:8525-8532.

  4. Pearson, C.R., Hozalski, R.M., and Arnold , W.A. (2005). Degradation of Chloropicrin in the Presence of Fe(0). Environmental Toxicology and Chemistry, 24:12: 48-53.

  5. Zhang, L., Arnold , W.A., and Hozalski, R.M. (2004). Kinetics of Haloacetic Acid Reactions with Fe(0) . Environmental Science and Technology, 38:6881-6889.

  6. Hozalski, R.M., Zhang, L., and Arnold, W.A. (2001). Reduction of Haloacetic Acids by Fe(0): Implications for Treatment and Fate. Environmental Science and Technology, 35:11:2258-2263.



Photo of batch bottles on rotator

Photograph of batch bottles mixing on a rotator (note: bottles would be covered with aluminum foil for experiments)

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