| Electroplating industry was known as one of three most heavily-polluted industries in the world due to the properties of high quantity, intricate species of pollutant and high toxicity in electroplating wastewater. Based on nickel-containing electroplating wastewater of a metalsfinishing company in Zhongshan City, Guangdong province and for the situation that the main pollutants of Ni2+ and CODCr in the electroplating wastewater of this company could not meet the standard of pollutions for electroplating( GB21900—2008), this paper mainly used tubular micro-filtration(TMF) and reverse osmosis(RO) as ways to treat electroplating wastewater of the company for the purpose of meeting the discharge standard or being recycled.The process of coagulating sedimentation pretreatment, TMF and RO was mainly studied in the paper. In the process of coagulating sedimentation pretreatment, the effects of p H and the dosage of PAM on effluent quality were discussed. The results showed that the best precipitation p H of Ni2 and Cu2+ in nickel-containing electroplating wastewater was 9. Under the same p H condition, the coagulating effect of nickel-containing electroplating wastewater was best when the dosage of PAM was 15mg/L. Under the optimum conditions for coagulation pretreatment, concentrations of Ni2+, Cu2+ and COD were 7.3mg/L, 2.6mg/L, 154mg/L respectively, removal rates of them were 98.3%, 84.1%, 36.1%, respectively, removal efficiency of Ni2+ was best and that of COD was worst among them.In the process of TMF on the treatment of coagulating sedimentation water, effect of membrane pore size, ratio of freshwater to concentrate and operating pressure on effluent quality and flux is discussed respectively, research indicated removal rates of COD, Ni2+ and Cu2+ using TMF membrane pore size of 0.05μm were 10% higher than that of 0.05μm under the same running time of TMF, therefore, TMF with 0.05μm pore size be used for follow-up experiment in the situation of having no big difference in flux of the two membranes. Lowering the ratio of freshwater to concentrate was beneficial to the increase of contaminants removal rate in wastewater in the case of maintaining appropriate flux and recovery rate, therefore, 1:34 is the optimum ratio of freshwater to concentrate. In order to enhance the stable flux of TMF, the pressure range of 0.1 to 0.15 Mpa is optimum.In the process of RO on the treatment of coagulating sedimentation water, effect of ratio of freshwater to concentrate, feed water conductivity, temperature and p H of feed on the separating performance of RO is discussed respectively, and the sequence of every factor for membrane properties was analyzed through designing orthogonal experimental. Finally, the results were verified to evaluate the feasibility of RO permeate reusing and study the relationship between effluent quality and reuse rate under the optimum conditions of each factor. Research showed that removal of Ni2+ imposed by RO is the best and removal rate is between 96.7% and 100%, the permeate concentration of Ni2+ was 0.07mg/L or less which have meet emission standards and reuse requirement. For purpose of making other indicators to achieve reuse requirements, the ratio of freshwater to concentrate should be controlled in the region of 1:10 to 1:8, feed temperature ranged from 19℃ to 25℃ and feed p H ranged 8 to 9. The effect of recycling rate on the quality of permeate is studied under the optimum level of the above factors, the indicators of RO permeate meet the standards of reusing water when reuse rate is 53.2%. Flux increased with the operating pressure and the water temperature rising and decreased with feed water conductivity increasing. It drawn conclusions by orthogonal experiment that the factor of affecting system desalination rate most is feed conductivity which is followed by the ratio of freshwater to concentrate; and the factor of affecting Ni2+ removal rate most is the ratio of freshwater to concentrate which is followed by feed temperature; and the factor of affecting flux most is the ratio of freshwater to concentrate and other factors had little effect on the ratio of freshwater to concentrate, the optimum level of the ratio of freshwater to concentrate, feed temperature, feed p H is 1:10, 19℃, 8, respectively. Finally, under the optimal conditions of each factor, the results were verified as follows: permeate conductivity is 124μS/cm, concentration of COD, Ni2+, Cu2+, is 25mg/L, 0.01mg/L, 0.23mg/L, respectively, it can be seen that the indicators of RO permeate are lower than the standards of drainage water and reuse water. In the study on the relationship between RO effluent quality and reuse rate, it is found that the indicators of RO permeate meet the standards of reuse water when reuse rate is 53.2%. |
PDF Full Text Request