TOTAL MINERALIZATION OF AQUEOUS ATRAZINE IN THE PRESENCE OF AMMONIUM-NITRATE USING OZONE AND KLEBSIELLA-TERRAGENA (STRAIN DRS-I) - MECHANISTIC CONSIDERATIONS FOR PILOT-SCALE DISPOSAL

s-Triazines have been found to be somewhat recalcitrant to enhanced biomineralization (preoxidation prior to microbial degradation). Atrazine ozonation studies provided evidence for a hydroxy radical process in which kinetics are sterically rather than electronically controlled. These results enabled the optimization of the ozonation procedures and the isolation of an organism better adapted for pesticide waste streams. Klebsiella terragena (strain DRS-I) was shown to effectively utilize chlorodiamino-s-triazine (CAAT), the final oxidation product of atrazine, as a nitrogen source in the presence of NH4NO3, a fertilizer often found in pesticide waste. Evidence for the metabolic pathway is provided, which was shown to proceed via aminochlorohydroxy-s-triazine (COAT) followed by dechlorination and total mineralization. Formulated atrazine was successfully mineralized in a pilot scale system (ca. 200 L) with and without NH4NO3 present. Ozonation efficiencies were nearly identical in both cases; degradation of CAAT and COAT was readily achieved after ca. 1 day of incubation.