OPERATION AND DESIGN IMPACTS ON EFFICIENCY AND TOXICITY DURING ELECTROCHEMICAL TREATMENT OF AZO DYE-CONTAINING WASTEWATER
Wastewaters from textile dyeing operations often contain organics compounds with strong color accompanied by a high concentration of sodium chloride (NaCl), and electrochemical treatment is a promising way to treat the waste. The objective of this investigation was to evaluate the impact of design and operational parameters on decolorization efficiency and effluent toxicity during electrochemical treatment of wastewater containing the dye Acid Alizarin Violet N (AAVN; 14.65 mg/L) and NaCl (0.35 M). Cell configuration (split and undivided) and electrical current density (4 and 8 mA/cm ^2 ) were the chosen reactor design parameters and pH (4, 7 and 10) and applied current (72 and 144 mA) were the chosen operational parameters. Extent of removal, power consumption, and effluent toxicity were the design criteria signifying efficiency, cost effectiveness, and environmental impact of the process. The split cell configuration provided the highest color removal, consuming significantly lower power than the undivided cell. Extent of decolorization was higher at pH 4 than that at pH 10 and pH 7. Increasing applied current increased the extent of color removal in the split cell whereas performance was unaffected in the undivided cell. Microtox ® toxicity test showed that effluents collected from more efficient conditions (split cell at pH 4) revealed the highest toxicity. In contrast, negligible toxicity was found in the effluent from the least efficient undivided cell - pH 10 conditions. A design strategy that maximizes the efficiency is in direct conflict with the goal of minimizing effluent toxicity. This study demonstrates the importance of considering end product toxicity in addition to more traditional criteria in making suitable decisions for electrochemical reactor design.
School:University of Cincinnati
School Location:USA - Ohio
Source Type:Master's Thesis
Keywords:azo dyes color removal electrochemical wastewater treatment cell configuration surface to volume ratio effluent toxicity
Date of Publication:01/01/2005