Electron accelerator to reduce toxicity of textile effluent and chemicals applied during cotton dyeing

The textile processing uses an important amount of water during their production, while generating effluents that have various types of chemicals, such as surfactants, peroxides, acids, salts and dyes. Considering their complexity, these effluents commonly have high toxic load and coloration. Advanced Oxidative Processes have been used to improve the treatment of this type of effluent, complementing the biological treatment. Electron beam irradiation has been proposed as a technology for treatment of textile effluents, in order to reduce toxicity, coloration, chemical oxygen demand, and other parameters. The objectives of this work were to evaluate the toxicity of chemical compounds used in the cotton fibers, and the textile effluent (containing red reactive dye 239) to aquatic organisms; and to evaluate the efficiency of electron beam irradiation in treatment of these contaminants. Acute toxicity assays were performed with aquatic organisms Vibrio fischeri bacteria and Daphnia similis crustacean. For chronic effect, D. similis crustacean was used, being evaluated the reproduction, sublethal effects and body length after 21 days exposure to textile effluent containing reactive dye Red 239. The effluent as well as organic compounds were irradiated in electron beam accelerator, with dose range between 0.5 and 15 kGy. The irradiation treatment improved the toxicity, color, chemical oxygen demand and total organic carbon of the effluent. Regarding acute toxicity for raw effluent, the mean EC 50% was between 2.93 ± 0.13 and 9.28 ± 0.32 for D. similis and 5.65 ± 0.16 and 8.40 ± 1.45 for V. fischeri. The electron beam treatment was effective in reducing the toxicity of the samples, 5 kGy: EC 50% = 16.36 ± 5.37, representing 61.43% toxicity removal for D. similis and 15.05 ± 2.93, 50.73% toxicity removal for V. fischeri. While 10 kGy resulted in over 70% of acute effects removal for both organisms. Regarding color reduction, 5 kGy resulted in > 95% efficiency. Among the surfactants analyzed, the nonionic alkylene oxide and the ethoxylate were more toxic to both organisms, with mean EC 50 values below 4.5 mg L^-1. For the chronic measurements, D. similis exposed to raw textile effluent (concentration 3%), sublethal effects were observed, such as dye deposition in the filtering system and eggs malformation. (author)