Design of advanced oxidation process for decolorization of reactive dye waste stream using Fenton's reagent

Reactive dyes, used for cotton dyeing, hydrolyze and discharged into wastewater. Strong nitrogen bond and ring structure of these dyes make biological oxidation difficult and sometimes incomplete. Although there are no toxicity issues, color discharge to the stream can become a compliance issue. This paper details Laboratory analysis of the use of the Fenton's reagent to decolorize reactive dyes waste stream. Experiments were performed on individual dyes as well as on the wastestream at variable pH, different ratios and concentrations of ferrous sulfate and hydrogen peroxide. The analysis is based on initial and final readings of color, absorbance, time and toxicity. Also cost analysis for a system to treat 20,000 gallons/week is performed. It was observed that initial reaction period for breaking up the dye molecule is almost instantaneous. The final color solution was observed to be tight yellow, which is suitable to discharge to further treatment. Toxicity analysis was performed using HACH PolyTox test which measures respiration of bacteria in the medium. Successful experiments were conducted using carbon dioxide injection for pH adjustment. Fenton's reagent is an economical and promising advanced oxidation technology for decolorization and destruction of reactive dyes and dyeing auxiliaries.