Study On The Treatment Process And Improvement Scheme Of Cold Rolling Wastewater In Iron And Steel Enterprises

The complexity and diversity of wastewater components in cold rolling process bring more challenges to the development of wastewater treatment and reuse technology.Especially the oil-bearing and emulsion wastewater is the most difficult wastewater to be treated in the steel industry because of the difficulty of treatment,the increasing cost of treatment and the increasingly strict requirements of environmental protection This is not only the need of healthy and sustainable development of iron and steel enterprises,but also the inevitable requirement of taking the new industrialization road.With the continuous progress of water treatment technology,various wastewater treatment methods are also applied:acid and alkali wastewater is generally treated by neutralization method;the treatment of oil-bearing and emulsion wastewater is difficult,which often requires a combination of several methods,such as gravity separation,air flotation,chemical method,biological method,membrane method,adsorption method,etc.;chromium containing wastewater treatment is widely used by reduction precipitation methodThis paper first analyzes the treatment methods of cold rolling wastewater at home and abroad,focusing on the water quality and quantity of cold rolling wastewater station,as well as the treatment process and technical parameters of each system.Then,the feasibility and effectiveness of each system process in the actual production of cold rolling wastewater treatment are verified by taking the five cold rolling as the research object.The results of water quality test show that the process of "air flotation and contact biological oxidation" is very effective for the treatment of dilute alkali oil-bearing wastewater,and the total removal rate of COD in the effluent of the system can also be maintained above 97%;the average content of petroleum in the effluent is 1.8 mg/L,the average content of animal and vegetable oil is 4.5mg/L,and the average value of solid suspension is 21.4mg/L;the acid wastewater treatment system adopts two-stage neutralization treatment The chemical oxygen demand of the effluent is 18～47mg/L,the petroleum content is 0.1-2.8 mg/L,the animal and vegetable oil content is 2.1～3.9mg/l,and the average value of the solid suspension is 14.5 mg/L;the average value of the chemical oxygen demand of the effluent of the system is 32.8 mg/L and the average value of the petroleum content of the effluent is 1.2 mg/L after the core process of "inorganic ceramic membrane ultrafiltration and membrane bioreactor(MBR)",The average content of animal and vegetable oil is 3.6 mg/L.The treatment of chromium containing wastewater by sodium bisulfite reduction and lime neutralization process is stable and reliable.The average removal rates of total chromium and hexavalent chromium are 94%and 98.6%,respectively.After treatment,the water quality indexes of the oil-bearing waste water of the cold rolling mill all reach the reuse standard of the iron and steel enterprises,which lays a good foundation for the recycling of the water resources of the iron and steel enterprises.The paper also compares the technological processes of other cold rolling wastewater treatment stations,and on this basis,puts forward the improvement scheme of five cold rolling wastewater treatment stations.The research results of this paper provide a new idea for cold rolling wastewater treatment in China.