Biobeds are used to collect and decontaminate liquids with high concentration of pesticide residues. It consists on a biomixture of three components: soil, lignocellulosic and wetting materials which are mixed at different volume ratios. Straw and peat ar

COLL, ANDREA; LESCANO, MAIA; LÓPEZ, ALEJANDRO; CRISTINA S. ZALAZAR

Simposio; The fifth International Symposium of Enviromental Biotechnology and Engineering, 50 ISEBE; 2016

Advanced oxidation processes (AOPs), a special kind of wastewater treatment technologies, have been successfully applied for recalcitrant pollutants degradation as herbicides. The studies are generally performed employing single compounds at higher concentrations than the values that can be found in the environment. There are few researches that report mixtures degradation. The application of aqueous commercial herbicide mixtures is nowadays a common practice in agriculture-intensive South American countries. Glyphosate is combined, for example, with other herbicides such as 2,4-dichlorophenoxyacetic acid (2,4-D) and atrazine. The disposal of aqueous herbicide wastewaters is still an unresolved environmental issue in many of these countries. An advanced oxidation technology as the UV/H2O2 process is an effective and attractive alternative to treat this kind of contamination. The UV/H2O2 process has certain advantages in comparison with the most renowned AOPs: relatively low capital and operating costs as well as simplicity in its operation.In this study, the suitability of the UV/H2O2 process for commercial herbicide mixtures degradation (glyphosate, 2,4-D and atrazine) is studied. Optimization of specific operating conditions as H2O2 to Total Organic Carbon molar ratio (R) and pH is also evaluated. Experimental runs were carried out in a batch photo-reactor, samples were taken each one hour, reaction temperature was set at 25 ºC and radiation was supplied by two low pressure mercury vapor lamps (λ = 253.7 nm). Optimization of the selected operating conditions was assessed by the response surface methodology (RSM) technique. Employing this kind of method, a minimum set of assays adequately distributed in the experimental region was tested (1≤R≤18, 3≤pH≤10). A 3-level full factorial design with two factors (R, pH) was selected. The Total Organic Carbon (TOC) conversion (%) at 8 hours was defined as the response.Results have shown that second-order polynomial regression model could well describe and predict the system behavior within the tested experimental region. The model satisfies the assumptions of the analysis of variance (ANOVA). According to the probability value for calculated Fisher F-test (p0.9), it can be observed that the model is statistically significant. Under the optimum conditions (R close to 5 and neutral pH; TOC conversion>60%) experimental values agreed with the simulated ones confirming the significance of the model and highlighting the success of RSM for UV/H2O2 process optimization.The UV/H2O2 process could be suitable for aqueous commercial herbicide mixtures degradation. The optimum operating conditions found could be useful for real field applications.