Abstract

Preliminary studies highlight the positive effect of coupling photocatalysis and biological processes for the treatment of biorecalcitrant compounds. Before biological treatment, photocatalysis can be used as a pre-treatment process to increase pesticide biodegradability. Kinetics of amitrole biodegradation during cultures of Pseudomonas fluorescens was examined to ensure that the target compound was biorecalcitrant; its inhibitory effect justified a pre-oxidation. The biodegradation of cyanuric acid, one of the by-products resulting from photocatalyis of amitrole was confirmed. Pseudomonas fluorescens could metabolize this compound as a nitrogen source when a supplementary carbon source was added. The addition of supplementary carbon and nitrogen sources favoured growth and accordingly cyanuric acid degradation. Degradation yields (with TiO₂ coated on cellulose fibers, 25 g.m-2) in the range 47% to 55% were obtained after 50h of irradiation for solutions of amitrole in the range concentrations between 70 to 6000 ppm. Between 10% and 34% of amitrole was mineralized to carbon dioxide. The production of ammonium and nitrate ions was negligible. An inhibition of TiO₂ active sites was assumed to account for the weak mineralization. Identification of some of the intermediate by-products by LC-MS/MS shows negligible quantity of cyanuric acid. This work demonstrates that the hybrid process photocatalysis/bioremediation is a cost-effective promising solution for the treatment of wastewater containing biorecalcitrant compounds.

Recommended Citation

de la Rochebrochard d'Auzay, Samuel; Brosillon, Stephan; Fourcade, Florence; and Amrane, Abdeltif (2007) "Integrated Process for Degradation of Amitrole in Wastewaters: Photocatalysis/Biodegradation," International Journal of Chemical Reactor Engineering: Vol. 5: A51.
Available at: http://www.bepress.com/ijcre/vol5/A51