Research On Processing Technic Of Circulating Cooling Sewage In Refining And Chemical Industry

The water shortages and pollution are becoming more and more serious.With the intensity of environmental protection,the circulating cooling sewage（CCS）that used to be"clean water"is now included in the scope of sewage treatment.However,the existing sewage treatment systems of most enterprises are difficult to load the CCS which has a huge volume.Targeted treatment to reuse the CCS would be helpful,as it could reduce the cost and pressure of the enterprises’sewage treatment systems and make contributions to the water-saving and emission reduction.At present,the treatment methods of the CCS include coagulation filtration,electric adsorption and membrane treatment,which show some limitations and have low water recovery rate.Compared with the above technologies,electrodialysis technology has the advantages of low energy consumption,high water recovery rate and simple operation,and is widely used in wastewater treatment.The electrolysis method uses the redox reaction to remove the pollutants,which has the advantages of low cost and high efficiency.The main contents of this paper are as follows:（1）Exploring the feasibility of electrodialysis technology in the treatment of the CCS and selecting the best operating condition to calculate the reuse rate and energy consumption of sewage;（2）Exploring the law of nitrate nitrogen removal in simulated water by electrolysis,mainly investigating the influence of cathode materials,electrolysis conditions and water quality conditions,and to analyze the reaction kinetics of nitrate nitrogen removal;（3）Applying the electrolysis technology to electrodialysis concentrated water,and analyzing the change of water quality,the effect of hardness on degradation,and the effect of electrocoagulation on hardness reduction.The results show that:（1）When the operating voltage was 14V,the inflow flow was200 mL/min,the volume ratio of concentrated and fresh water was 4:1,the electrodialysis ran for 80 minutes,the water quality of the fresh water chamber reached the reuse standard,the desalination rate was 90%,the power required to treat 1 ton of water was1.36 degrees,and the sewage reuse rate was 73.6%;（2）When the operating anode was Ti/Ti-Ru O₂-Ir O₂plate,the cathode was Ti plate,the current density was 30mA/cm²,the initial concentration of nitrate nitrogen was 100 mg/L,the concentration of chloride ion was 1500 mg/L,the distance between plates was 1cm,and the pH was 5.5,after 4 hours’electrolyzed the removal rate of nitrate nitrogen was 88%.The reaction of removing nitrate nitrogen from water by electrolysis accords with the first-order kinetics.（3）Using electrolysis technology to treat the electrodialysis concentrated water,the removal rate of COD and chloride ions reached 80%and 72%,but the removal rate of nitrate nitrogen was relatively low.Because the calcium and magnesium ions were scaling on the plate,which affected the efficiency of nitrate nitrogen removal by cathodic reduction.The electrocoagulation technology was used to treat the concentrated water of electrodialysis,and the hardness removal rate was 89.9%.