Status and progress of coking wastewater advanced treatment technology

Coking wastewater is a kind of typical high concentration refractory organic wastewater, which has the characteristics of complex pollutant composition, high pollutant concentration, poor biodegradability, high toxicity, high chroma and great fluctuation of water quality. Due to the high concentration of COD in coking wastewater and the large amount of refractory organic pollutants such as phenol, ester, cyanogen, indole, pyridine and long-chain alkane, the traditional combined process of “pretreatment+biochemical treatment” can not meet the new coking wastewater discharge standard GB 16171—2012 Emission Standard of Pollutants for Coking Chemical Industry. Therefore, it is urgent to find a stable, economic and resource-based advanced treatment process to meet the emission standards. Based on this, the authors summarize the research results of water quality characteristics, discharge standards and unit treatment technology of coking wastewater at home and abroad in recent years, summarize the current advanced treatment technology of coking wastewater, such as MBBR, BAF, coagulation, advanced oxidation technology and membrane separation technology, and point out the single biochemical technology or the physicochemical treatment technology is difficult to meet the discharge or wastewater reuse requirements.Three new combined processes of high-efficiency and economic coking wastewater advanced treatment, namely “oxidation pretreatment + MBBR + (magnetic) coagulation”,“magnetic/coagulation/filtration+ozone catalytic oxidation” and “magnetic/coagulation+advanced oxidation+double membrane treatment”, are proposed and successfully applied in practical projects. According to the water quality conditions of coking wastewater, it is the development trend of coking wastewater advanced treatment technology in the future to select or develop the combined process with advantages of good treatment effect, advanced technology and simple operation according to local conditions.