Experimental study on the treatment of printing and dyeing wastewater by supercritical water oxidation based on response surface methodology

Abstract

With the continuous growth of global printing and dyeing production, the volume of wastewater generated by these processes is also increasing. Dyes are classified into categories such as azo, anthraquinone, and aromatic compounds based on their chemical structure. Traditional methods for treating printing and dyeing wastewater primarily involve chemical and physical approaches. However, the effluents produced after these treatments often require secondary processing to meet environmental standards. Supercritical water oxidation (SCWO) has emerged as an efficient and environmentally friendly technology for the advanced treatment of organic pollutants. In this study, a batch reactor was employed to conduct supercritical water oxidation experiments. The response surface methodology (RSM) was utilized to evaluate the degradation of chemical oxygen demand (COD) and ammonia nitrogen (NH₃-N) in printing and dyeing wastewater under various process parameters. Additionally, the interactions between different reaction parameters were examined. The optimal reaction conditions were identified as 520°C, a reaction time of 6.74 min, an oxidation coefficient of 1.84, a raw material concentration of 30 wt.%, and a pH of 12. Under these conditions, the removal efficiencies for COD and NH₃-N reached 96.89% and 62.42%, respectively. These results demonstrate that supercritical water oxidation is a highly effective method for removing organic matter and ammonia nitrogen from printing and dyeing wastewater.