Decontamination of synthetic textile wastewater by electrochemical processes: energetic and toxicological evaluation

The treatment of a synthetic textile wastewater, prepared with several compounds used in the finishing of textile materials, was comparatively studied by electrochemical methods such as electrooxidation (EO) (titanium electrode) and electrocoagulation (EC) (with aluminum and iron electrodes). The influence of pH, current density and operating time on the treatment was assessed by the parameters used to measure the level of organic contaminants in the wastewater; i.e. color, toxicity and chemical oxygen demand (COD). The experimental results showed that an effective electrochemical oxidation was achieved in which the wastewater was decolorized and 92% of COD was completely eliminated. In particular, the mineralization took place by indirect oxidation, mediated by active chlorine, and the treatment efficiency was enhanced by the addition of NaCl to the wastewater and by increasing the applied current density. The toxicity, still higher than the toxicity of the raw effluent, indicated a presence of toxic products after EO. Good results were obtained with the Al and Fe electrodes, mainly with respect to the removal of color and toxicity. EC is more economical than EO and the toxicity evaluation with the Daphnia magna test shows a significant reduction after EC.