Application of Fenton's Reagent for Acrylic Dyeing Wastewater Decolorization, Organic Matter Reduction and Biodegradability Improvement

Abstract

Fenton's reagent oxidation was employed for organic matter and color removal, along with biodegradability improvement, of a synthetic acrylic dyeing wastewater, previously treated by coagulation/flocculation. The initial iron load in the Fenton's stage varied from the residual soluble iron concentration resulting from the coagulation/flocculation process (which was 275 mg Fe/L) up to 400 mg/L, by adding increasing amounts of ferrous sulfate. The combination of the two treatments led to overall removals of 99.8, 84.2 and 78.6% for color, dissolved organic carbon (DOC) and chemical oxygen demand (COD), respectively, complying with maximum allowable discharge values. The Fenton process was also directly applied to the effluent. Under the optimum conditions, the color removal (99.5%) was similar to that obtained in the combined process, but DOC and COD removals were lower (66.5 and 65.1%, respectively). An improvement of the wastewater biodegradability was observed in such condition: the specific oxygen uptake rate and BOD:COD ratio increased from <0.2 to 17.9 mgO(2)/(g(VSS).h)) and from similar to 0 to 0.40, respectively. The effluent toxicity also decreased, from 97 to 29% (30 min contact time), allowing the subsequent integration of a biological process.