Selection Of Pharmaceutical Treatment For High Concentration Automobile Coating Wastewater And Economic Evaluation

Coating process is widely used on automobile surface treatment. In China, the wastewater produced from automobile coating process is mainly treated by phosphating, which will result in high content of phosphate in wastewater and polluting the environment heavily.Along with people’s increasing production and living requirements and the prosperous development of automobile industry, automobile enterprises are discharging more and more wastewater every year, causing more and more pollution to the environment. In particular, the wastewater discharged during automobile production has various contaminants and high concentration, which makes it hard to dispose. As a result, automobile wastewater treatment has become an important task in today’s sewage treatment engineering. Years of exploration and engineering practice reveal that the physicochemical treatment and biochemical treatment to process the automobile coating wastewater is economical and effective, but it is still problematic in practice. Therefore, it is necessary to optimize and improve the process to be more stable and efficient.This subject carries out the research mainly based on the selection of chemicals for treatment on high-concentration coating wastewater produced from the manufacturing process of one automobile manufacturer. Determining the optimal reaction pH condition is 11 for the wastewater treatment, and choosing mixture of calcium chloride and sodium hydroxide which has better effect on removing the Ni and phosphate from the wastewater. Then the optimal addition dosage for calcium chloride is 0.4kg/t (0.4kg per ton wastewater),0.8kg/t for sodium hydroxide, and the cost is 3.72 RMB/t.Adding the mixture of NaOH and Ca(OH)2 to phosphating wastewater for treatment is practical in principle and works good. The optimal reaction dosing ratio is 1:4, and the optimal addition dosage for NaOH is 0.048 kg/t,0.48kg/t for Ca(OH)2, the cost is 1.57RMB/t. Besides, the optimal addition dosage on this basis for PAC is 0.15kg/t, and 2.5×10-3kg/t for PAM.In conclusion, the best option for chemicals selection on high-concentration coating wastewater treatment is dosing the mixture of NaOH and Ca(OH)2 with the help of PAC and PAM on flocculation. The phosphate content in processed water is lower or equal to 0.5mg/L, which meets the first class standard of Integrated Wastewater Discharge Standard in China. The cost is 1.49 RMB/t,0.84 RMB/t lower than the original chemical selection for treatment which costs 2.33RMB/t. This provides reference for manufacturers on reducing the cost of wastewater treatment and selection of chemicals for similar wastewater treatments.