Water Science & Technology Vol 64 No 2 pp 460–468 © IWA Publishing 2011 doi:10.2166/wst.2011.661

Treatment of wastewater from a cotton dyeing process with UV/H₂O₂ using a photoreactor covered with reflective material

Claudinei Fernandes de Melo, Flavio T. da Silva and Teresa C. B. de Paiva

Wastewater containing several dyes, including sulfur black from the dyeing process in a textile mill, was treated using a UV/H₂O₂ process. The wastewater was characterized by a low BOD/COD ratio, intense color and high acute toxicity to the algae species Pseudokirchneriella subcaptata. The influence of the pH and H₂O₂ concentration on the treatment process was evaluated by a full factorial design 2² with three replicates of the central experiment. The removal of aromatic compounds and color was improved by an increase in the H₂O₂ concentration and a decrease in pH. The best results were obtained at pH 5.0 and 6 g L^-1. With these conditions and 120 min of UV irradiation, the removal of the color, aromatic compounds and COD were 74.1, 55.1 and 44.8%, respectively. Under the same conditions, but using a photoreactor covered with aluminum foil, the removal of the color, aromatic compounds and COD were 92.0, 77.6 and 59.4%, respectively. Moreover, the use of aluminum foil reduced the cost of the treatment by 40.8%. These results suggest the potential application of reflective materials as a photoreactor accessory to reduce electric energy consumption during the UV/H₂O₂ process.

Keywords: acute toxicity; degradation rate; first-order kinetics; photolysis; reflective material; UV irradiation

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