Study On Technology And Process Of Comprehensive Electroplating Wastewater Treatment

Electroplating is now one of the three major industrial pollutions, Electroplating wastewater accounts for about 10 percent of the total industrial wastewater emissions, of which only less than 50 percent of the wastewater are treated effectively before discharged. At present, the size of the electroplating business are growing bigger and bigger, which makes the wastewater constituents become increasingly complex, and the difficulty of treatment becomes harder and harder, wastewater pollution problems have seriously restricted the survival and development of electroplating enterprises in our country, therefore, the study on technology and process of comprehensive electroplating wastewater treatment is particularly necessary, ingredients of the wastewater are extremely complex, and the concentration of complex is high.This paper relied on analysis of the comprehensive electroplating wastewater produced by a large electroplating industrial park in Shenzhen, testes are conducted on exploration of the treating process flow, studies are also conducted on the optimization of process conditions to deal with wastewater containing chromium and acid-base integrated wastewater; according to the actual characteristics of the wastewater, the process flow and controlling conditions are identified and verified.The method of chemical reduction precipitation was used to treated electroplating wastewater which contains chromium ions,and sodium bisulfite is used as reducing agent, the optimum conditions of hexavalent chromium reduction process included: the addition dosage of reducing agent sodium bisulfite is 1.4 times that of theory, the pH value is 1.8, the reaction time is 15 minutes; the precipitation effect of trivalent chromium is obviously better when adjusting the pH value using lime than sodium hydroxide, because the neutralisation ability of lime is weak, and it can not adjust pH value quickly and accurately, so the optimum condition of trivalent chromium precipitation process is adjusting the pH value to about 9.0 in the way of rough tuning by lime and fine tuning by lye.Copper and nickel metal ions in acid-base integrated wastewater form very stable complex, treatment using the traditional hydroxide and sulfide precipitation method can not reach the discharge standards, studies are conducted on exploration of the acidification-oxidation de-complexation process, bleaching liquid NaOCl is choosed as oxidant, which opens the coordination bonds to make the complexed forms of metal ions change into free state by its strong oxidation, and then remove them by the combining of sulfide and hydroxide precipitation process. The optimum conditions of acidification-oxidation de-complexation process included: the addition dosage of oxidant bleaching liquid is 1.2mL/L wastewater, the reaction pH value is 2.3, the reaction time is about 2.0 hours; the optimum condition of precipitation process is adjusting the pH value to about 10.0 in the way of rough tuning by lime and fine tuning by lye, the addition dosage of sodium sulfide is 600 mg/L. According to the actual characteristics of the wastewater, the pretreating air floatation process is added to remove the oil, and the addition dosage of sodium sulfide can be reduced to 200 mg/L.Based on the test, and according to the possibility of production operation, a set of process flow of comprehensive electroplating wastewater treatment and reuse is designed to realize industrial practical application, which is reasonable and feasible in both technical and economic aspects.