| The components of coking wastewater are very complex, which contains refractory organic compounds such as tar, benzene, phenol, cyanide, quinoline and pyridine etc,and it has fluctuation characteristic of the water quality and water flow.It is a typical industrial wastewater, which contains a number of toxic and nocuous compounds.Coking tailrace is the effluent of the coking wastewater treated by A2/O, and it contains high concentration of COD and poor biodegradability. Based on the"4×104 m3/d Steelworks Wastewater Treatment and Reclamation Project"of a steelworks in Jiangsu province, The removal of COD and SS in the wastewater, as well as the application prospect of air-floatation + BAF used for coking tailrace treatment was studied. Sewage water and steelworks wastewater are introduced to improve the biodegradability. The actual project application indicates that treatment effect of this technology is good, and COD and SS of the effluent are less than 60 mg/L and 10 mg/L, respectively, which can meet the recycle standard.Researching on the mechanism of air-floatation and BAF and the engineering application of the technology, the obtained results are as follows:(1)The pretreatment of air-floatation is effective to remove SS, at the same time it can remove some COD, which meets our expectation. The process featured stable system and easy operation ensures the subsequent biochemical treatment of BAF.(2)The running of BAF shows that the process is effective to remove COD and SS, and the COD of effluent can keep less than 60 mg/L if COD of influent is within the designed value.(3)The feasibility and usability of air-floatation + BAF process to treat coking tailrace are confirmed through a year's debugging and running experience. The running results show that the technology has many advantages, such as good effluent quality, small volume, low cost and strong endurance to load variation. It has been an economical and practical process for the wastewater treatment and reuse.
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