| Since reform and opening, China's steel industry has developed rapidly, which also has promoted the production technology of cold-strip steel to improve constantly and the types of cold-rolled products also have been diverse accordingly. This not only creates a huge economic benefit for the iron and steel companies, but also brings serious environmental pollution problems. Because the components of the wastewater discharged from cold rolling mills are very complex and the species are quite diverse, it poses more challenges to the development of wastewater treatment and reuse technology. Especially the the oil-containing emulsion waste water is very difficult to treat. As the cost of processing is rising and environmental protection standard is becoming more and more strict, the disposal of the oil-containing emulsion wastewater has been regarded as one of the most difficult wastewater in iron and steel industry. It's urgent to research the wastewater treatment technology of cold rolling mill. This is both a necessary requirement for healthy and sustainable development of iron and steel industry and a need to take a new road to industrialization.According to the varied sources and compositions, the waste water from cold rolling mills generally can be divided into three types:acid wastewater, oil-containing emulsion wastewater and chromium-containing wastewater. With the increasingly improvement of water treatment technology, various wastewater treatment methods are applied:acid wastewater commonly dealed with neutralization; oil and emulsion wastewater treatment is difficult, it usually combines several methods to implement, such as gravitational separation, flotation, chemical method, biological method, membrane, adsorption, and etc; chromium-containing wastewater is widely adapted chemical reducing method.This paper analyzes the domestic and overseas treatment means for wastewater from cold rolling mill firstly, comprehensively describes the water quality conditions and treatment processes and technical parameters of the wastewater treatment plant of Baosteel's No.5 cold rolling mill. Then the paper set Baosteel's No.5 cold rolling mill as study object to validate the feasibility and validity of each system and process for cold-rolling wastewater treatment. Water quality test results shows:it is very effective to utilize the process of "flotation and biological contact oxidation" to treate dilute alkali oily wastewater, the total removal of CODcr after treating is more than 97%, the average of petroleum content is 1.8mg/L, the average of animal and plant oil content is 4.5mg/L, and SS average is 21.4mg/L; Acid wastewater treatment system adopts the measure of two-stage neutralization. CODcr in filtered water is 18-47 mg/L, the petroleum content is 0.1-2.8mg/L, animal and plant oil content is 2.1-3.9 mg/L, and SS average is 14.5 mg/L; Oily wastewater passes through the core process "ultrafiltration with ceramic membranes and Membrane Bio-Reactor (MBR) system", CODcr average in outlet water is 32.8mg/L, the average of petroleum content is 1.2mg/L, the average of animal and plant oil is 3.6mg/L; Use chemical reducing with sodium bisulfite and neutralization with lime cream to treate chromium-containing wastewater, this system is stable and reliable and the average removal efficiency of total chrome and Cr(VI) is 5.91% and 83.45%. The quality of all the processed water meet Baosteel's reuse water standard, which has laid a good foundation for recycle use of Baosteel's water resource.This paper also compares tricks of the cold-rolling wastewater treatments between Baosteel's No.5 cold rolling mill and others, and on this basis, it bring forward improvements of wastewater station. Through the course of this research, which provide with a new idea for domestic's wastewater from cold rolling mill.
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