Tratamento de efluente têxtil empregando o processo fotocatalítico combinado com o biológico

Abstract

The textile industry demands high water consumption in its activities and uses dyes, surfactants and additives that are usually organic compounds of complex structures. As a consequence, the effluent generated throughout the production process has a high polluting and toxic loading, which is difficult to degrade by conventional treatments. Therefore, this study aims to investigate the degradation of an industrial textile effluent through the combination of an Advanced Oxidative Process (AOP) and aerobic biological treatment. Two real textile effluents, from different industries, were used in this study. The chosen OAP was the heterogeneous photocatalysis performed with Fe/TiO2 under visible radiation. The Fe/TiO2 catalyst was prepared by impregnation of the commercial TiO2 P25 using Fe (NO3)3.9H2O salt, and the material obtained was dried at 100 ° C. The reaction conditions, such as reaction time, catalyst concentration and air flow used in the heterogeneous photocatalysis were defined by an experiment planning study, employing a central composite rotational design 23 (CCRD), aiming at the most favourable conditions for the degradation of the textile effluent. The decolourization of the effluent was evaluated through the UV-VIS spectrophotometer scan, between 400 and 700 nm , while the organic matter degradation were determined by Total Organic Carbon (TOC) and chemical oxygen demand (COD) analysis. In the photocatalytic tests, the best condition reached 45% decolourization after 150 min of reaction and TOC and COD removals weres 25%. However, after the photocatalytic treatment, the effluent was extremely toxic. In the biological process, which lasted 72 h, acclimated sludge was used, and at the end of the combined treatment a textile effluent was produced with 72% of colour removal and 78% and 86% of TOC and COD removals, respectively, in addition to the total removal of the toxicity obtained in the photocatalytic stage. In order to compare the efficiency of the isolated biological treatment with the combined treatment, the raw industrial effluent was treated only by bioprocess. The isolated biological assay was conducted for 48 h, since it was found that both color and organic matter removals remained practically unchanged after this treatment time. The decolourization achieved for the crude effluent was 56% and the removal of TOC and COD were 65% and 79%, respectively. So, the combined process achieved superior results, being more effective in the degradation of the textile effluent than the biological treatment alone, indicating the feasibility of the continuation of the study and a promising route in the treatment of industrial textile effluents.