WP2 Wastewater Treatment: Analysis, Fate and Removal of Emerging Contaminants
Wednesday, 16 November 2005: 8:00 AM - 6:30 PM in Exhibit Hall

(AGA-1117-446345) Identification of biotransformation products of trimethoprim antibiotic in nitrifying activated sludge.

Aga, D¹, Eichhorn, P¹, ¹ Department of Chemistry, University at Buffalo, Buffalo, NY, USA

ABSTRACT- Concern surrounding the detection of pharmaceuticals in the natural environment has increased recently as improvements in analytical methods coupled with larger scale surveys revealed the broad range of persistent pharmaceuticals present in soil and water. Many of these reported surveys, however, do not monitor the byproducts generated during the biotic and abiotic transformations of these pharmaceuticals. This presentation will focus on the use of ion-trap mass spectrometry and accurate mass measurements employing time-of-flight mass spectrometry, to identify novel degradates of trimethoprim produced by nitrifying activated sludge bacteria in a small-scale laboratory batch-reactor. The structural elucidation of the metabolites was accomplished by conducting consecutive fragmentation steps (MSⁿ) combined with H/D-exchange experiments using electrospray ionization. One metabolite corresponded to alpha -hydroxy trimethoprim, while oxidation of the aromatic ring within the diaminopyrimidine substructure was determined for the second degradate. The study emphasized the potential of nitrifying activated sludge bacteria for breaking down a persistent antibiotic that is otherwise poorly degradable by a bacterial community encountered in a conventional activated sludge process. Results from our studies indicate that the absence of pharmaceutical compounds in treated water does not necessarily imply the complete removal of these chemicals. Although the toxicity of these metabolites has not been determined, results from this study underscores the importance of identifying metabolites because it is possible that some of them may still have biological activity similar to their parent compounds as the chemical structures show only very minor modification after microbial degradation.

Key words: antibiotic, ion-trap, nitrifiers, activated sludge