Mineralization and biodegradability improvement of textile wastewater using persulfate/dithionite process

The present study evaluates the color wastewater treatment in the textile industry by the persulfate/ dithionite (PS/DTN) process. This study was performed on a laboratory scale in a reactor with a batch system. The wastewater was taken from the textile industry, and the efficiency of the PS/DTN process in the treatment and removal of COD of this wastewater was optimized by the operational parameters of pH, PS, DTN, and reaction time. Optimal values of these parameters were obtained at pH = 3, PS = DTN = 1.5 g/L, and reaction time = 90 min. Although in optimal condition, the removal efficiency of COD and TOC reached 64.9 and 54.5%; it does not meet the required discharge conditions and standards. On the other hand, it was observed that this process has a good ability to improve the biodegradability properties of textile wastewater, and the results showed a good increase in BOD₅/COD and average oxidation state (AOS) and carbon oxidation state (COS) indexes to 0.47, 0.7, and by 2.4. Dominant radical contributed to the system for oxidation was found to be \({\mathrm{SO}}_{4}^{\bullet -}\) based on the scavenger radical test. According to the findings, it can be suggested that this system can be proposed as a pre-treatment step to reduce the toxicity of wastewater and reduce the input COD load to the biological system.