Case Application of a Combined Treating Process on Azo Dye Wastewater

In this study, a combined treating process (neutralization, electrolysis, ozone oxidization, coagulation and cinder adsorption) was introduced to investigate the possibility of degradation of concentrated azo dye wastewater. The optimum operation parameters were obtained through small-scale bench tests and pilot-scale tests, and then were put into operation. The experimental results showed that the removal rates of chemical oxygen demand (COD) and chroma were all above 99.5%. After treatment, the COD of the outflow was lowered less than 100 mg/L, the chroma was reduced 50 times, and the pH was 6-9, with the outflow under the national standards for the wastewater discharge. The application of the combined treating process would be a good demonstration for the concentrated organic wastewater in dyestuff industry. Meanwhile, the sludge and the residue generated from each unit of the combined treating process could be processed for further resource utilization based on economic analysis; the treatment cost is 1.08 Yuan (RMB)/m³, so this application also captured considerable benefits in terms of environments and economics for protection of water resources effectively.