With the rapid development of economy in our country, the demand of cold rolled steel plate products is increased continuously and wastewater containing thin oil has become one of the main types of wastewater in iron and steel enterprises. It is crucial for reaching the standard of environmental protection and recycle of water resource in enterprises to efficiently and stably treat the wastewater containing thin oil. In the paper, the removal effect and operating characteristics of chemical oxygen demand (COD) in each process section are systematically analyzed through the data of over 700 water quality tests in one year based on the combination process of neutralization-coagulation flocculation-air flotation-bioactive sludge by taking the treatment system of wastewater containing thin oil in Cold Rolled Rare Earth Steel Plate Plant of Baotou Steel as research object. The results showed that the average removal rate of COD in pretreatment unit of flocculation-air flotation could reach 75.24% so that degradable organics could be efficiently removed; recalcitrant wastewater was further degraded with biological system and the COD of final effluent was stably lower than 70 mg/L. The study could provide data supports and practical references for stable operations, process optimization as well as operation and maintenance control of system of wastewater containing thin oil in cold rolling.

cold rolling  /  wastewater treatment  /  wastewater containing thin oil  /  bioactive sludge