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BACTERIALLY-MEDIATED DEGRADATION OF A CHIRAL DISINFECTION BYPRODUCT
Citation:
Wommack, E., B A. Shira, J Avants, AND A W. Garrison. BACTERIALLY-MEDIATED DEGRADATION OF A CHIRAL DISINFECTION BYPRODUCT. Presented at American Society for Microbiology Annual Meeting, Orlando, FL, May 20-24, 2001.
Impact/Purpose:
Extend existing model technologies to accommodate the full range of transport, fate and food chain contamination pathways, and their biogeographical variants, present in agricultural landscapes and watersheds. Assemble the range of datasets needed to execute risk assessments with appropriate geographic specificity in support of pesticide safety evaluations. Develop software integration technologies, user interfaces, and reporting capabilities for direct application to the EPA risk assessment paradigm in a statistical and probabilistic decision framework.
Description:
Disinfection of drinking and waste waters, through chlorination, can result in the production of chlorinated organic compounds, many of which are regulated by the U.S. Environmental Protection Agency. Among these regulated compounds are the haloacetic acids, which exhibit toxic effects in aquatic plants and algae and are believed to be carcinogenic. In waters containing trace levels of bromine, the chiral disinfection byproduct bromochloroacetic acid (BCAA) is commonly formed. Often times the enantiomers (stereoisomers) of chiral pollutant compounds exhibit dramatically different fates in the environment. That is, one enantiomer degrades quickly, while the other is recalcitrant to degradation. To examine the contribution of natural bacterial populations to BCAA degradation, a mesocosm study was performed using river water or mineral media amended with riverine bacterioplankton. BCAA enantiomers were separated and quantitated using capillary electrophoresis. Virio- and bacterioplankton abundance was determined by epifluorescence microscopy and bacterial community structure was assertained using terminal restriction fragment analysis (T-RFLP) of 16S rDNA. The Microtox bacterial toxicity assay, which uses the luminescent marine bacterium Photobacterium phosphoreum, as well as direct counts, revealed the bacteriocidal character of BCAA. In mesocosms, BCAA degradation was almost entirely bacterially-mediated as sterile controls exhibited little degradation over the time course of the experiment. In general, BCAA degradation proceeded rapidly after an initial lag of 3 to 5 days. The fastest degradation was observed in bacterioplankton-amended mineral media in which BCAA was the sole carbon source. T-RFLP analysis of community 16S rDNA revealed significant shifts in bacterioplankton community structure after the addition of BCAA racemates. Overall, observations of BCAA degradation indicate that autochthonous bacterioplankton are critical in determining the fate of this chiral pollutant in aquatic environments.