Biomineralization of atrazine ozonation products. Application to the development of a pesticide waste disposal system

Development of remediation techniques for unusable pesticide wastes has led to a binary scheme involving ozonation followed by biomineralization of the resultant oxidized pesticides. Preliminary field tests of this technique indicated that the s-triazines were somewhat more recalcitrant than the other pesticides present. Further experiments identified the final ozonation products of atrazine, the most widely used s-triazine, as 4-acetamido-6-amino-2-chloro-s-triazine (CDAT) and chlorodiamino-s-triazine (CAAT). These compounds can be utilized by microorganisms only as nitrogen sources; however, 1% concentrations of ammonia fertilizers are not uncommon in pesticide waste. Therefore, the organism should prefer an organic nitrogen source and tolerate high ammonia concentrations. A Klebsiella terragena (strain DRS-I) was observed to degrade CAAT in the presence of high ammonia concentrations (0.8 M) with the addition of a carbon source (corn syrup), in contrast to a known s-triazine-degrading organism which could not. Nearly complete mineralization of CAAT to CO2 by DRS-I was demonstrated using CAAT-U-ring-14C. Bench-scale reactors indicated that continuous-flow or fixed-film reactors would support growth of DRS-I cultures and CAAT degradation