Avaliação da possibilidade de reúso de efluentes têxteis após tratamento complementar por processos oxidativos avançados

Abstract

The purpose of this study is to verify the possibility of reusing textile wastewater treated by conventional activated sludge process and submitted to further treatment by advanced oxidative processes. Three alternative processes are discussed: Fenton, photo-Fenton andUV/H2O2 process. The evaluation of the treatments effects is based on factorial experiment design in which the response variables are the maximum reduction in chemical oxygen demand and the minimum concentration of residual hydrogen peroxide in the wastewatertreated by these different processes. Results indicate Fenton's reagent in COD/[H2O2]/[Fe2+] mass ratio of 1:2:2 as the best alternative among the tested options. The selected technique is applied to a real effluent from the conventional treatment station of a textile mill. The qualityof the wastewater before and after the additional treatment is monitored in terms of 16 physical-chemical parameters defined as suitable for the characterization of waters subject to industrial textile use. The degradation of the wastewater is also evaluated by determining thedistribution of its molecular weight, along with the organic matter fractionation by ultrafiltration, measured in terms of chemical oxygen demand. Finally, a sample of the wastewater after additional treatment is fed to the textile mill, where testing for reuse in a pilot scale is conducted in order to evaluate the impact on the quality of dyed fabrics. Resultsshow partial compliance of the treated wastewater with the physical-chemical quality guidelines for reuse. Most of the parameters meet the proposed limits or achieve significant reduction. Removal and conversion of high and medium molecular weight substances intolow molecular weight substances are observed, as well as degradation of most of the organic matter in the wastewater. The reuse tests show positive results in comparison with the waters regularly used in industry, indicating the possibility of wastewater reuse after the suggestedadditional treatment. The implementation of the practice on an industrial scale depends on a technical and economic evaluation, considering the reuse benefits, the inconvenience of generating a solid waste at the end of the process and the costs associated with reagents andfacilities. A treatment optimization study is recommended.