Increased biodegradability of the fungicide Imazalil after photo-Fenton treatment

E. LOPEZ LOVEIRA; G. CURUTCHET; CANDAL, R.

Environmental Biotechnology and Engineering 2014

CINVESTAV

Año: 2015; p. 771 - 779

Imazalil (C14H14Cl2N2O) is a widely used fungicide for the post-harvest treatment of citric fruits. This fungicide is usually commercialized in the form of emulsions containing 50% of the active compound and coadjutants that help to stabilize the emulsion and disperse the product. The presence of Imazalil and the coadjutants in waste waters, produced by washing the fruits before packing, is a potential risk for the living organisms present in the receptor water courses. The treatment of the waste waters containing pesticide is mandatory to preserve environment quality. Imazalil is not easily biodegradable; however, a resistant microbial consortium was isolated from sludge containing the fungicide that was not able to degrade the pollutant in culture with planktonic biomass.  Photo-Fenton is an advanced oxidation process that was successfully used to degrade pesticides in water using light, Fe(III) and H2O2, as energy source, catalyst and oxidant respectively. Frequently, it is not possible to completely mineralize the pollutant and only a partial reduction of total organic carbon (TOC) can be accomplished. However, the partial oxidation of the recalcitrant compound may lead to byproducts with a higher biodegradability than the former pollutant. In this work, water solutions containing 500 mg/L Imazalil and 500 mg/L TOC were partially oxidized by photo-Fenton process (FeCl3.6H2O (0,15 mM), pH = 3.0, 25 ºC and H2O2 doses (9 mM)). The reaction was carried out in a batch reactor (250 mL) with top lighting (UVA, 20 W). After 6 h illumination, Imazalil was completely degraded. There was no change in the TOC with 1 and 2 doses of H2O2, which means that mineralization was negligible under these conditions, but with 3 doses, TOC mildly decreased. The three remaining solutions were adjusted for biological treatment. The pH was raised to 7.0 and the solution was supplemented with inorganic nutrients (SO4(NH4)2, K2HPO4, MgSO4 and CaCl2). The solutions (100 mL) were inoculated with a consortium previously adapted to Imazalil, and incubated at 25 ºC. After 5 days of incubation, the TOC decreased by 38%, 53% and 59% in solutions 1, 2 and 3 respectively, indicating that the oxidation treatment produces byproducts with higher biodegradability than the former fungicide. This coupled process shows to have great potential for treatment of Imazalil for waste water from fruit industry.