Treatment Of Secondary Electroplating Wasterwater By UV-Fenton Oxidation Combine Power Activated Carbon -sequencing Batch Reactor- Coagulation

Chemical Oxygen Demand of the effluent wasterwater from HuaMao electroplate plating set goes far beyond national emission standard,which was treated by sodium metabisulphite reduction-ozone removing cyanogen-sodium hydroxide precipitation polyacrylamide flocculation process.This paper studied the treatment on secondary electroplating wastewater by UV-Fenton combine PAC-SBR-coagulation, and results showed that effluent COD_cr reached the national electroplating standards for pollutants discharge (GB21900-2008).First, the results of the PAC static adsorption COD_cr of secondary electroplating wastewater indciated that the adsorption effect of PAC is better than that of granular activated carbon, and removal efficiency could reach 14.3%. The optimum conditions of adsorption process were 25℃, pH value of 8, activated carbon dosage quantity of 200 mg, adsorption time of 2 h. The result fitted by the Ferundlich isotherm showed that the COD_cr adsorption efficiency from electroplating wastewater by powder activated carbon is not ideal.Second, the results of PAC-SBR and SBR treatment on high concentrations secondary electroplating wastewater comparative experimental study showed that, PAC-SBR process was superior to the SBR process with regard to COD_cr and TN removal efficiency. Third, the result of PAC-SBR treatment on low concentration secondary electroplating wastewater showed that the optimal preprecipitation all sorts of heavy metal by NaOH was 11, the COD_cr scope of effluent water was from 530 to 590 mg/L drop to from 250 to 300 mg/L and TN removal efficiency decreased from 85% to 28% and effluent index could achieve 110 mg/L in supreme cases. As to Zn²⁺,Cu²⁺, Ni²⁺ these three heavy metal removal efficiency, Cu²⁺ removal efficiency was best and could be as high as 70%, at the same time these three heavy metal concentration of effluent can reach national emission standard.Fourth, when the treatment on secondary electroplating wastewater by Fenton reagents, the result of an orthogonal tests showed that initial conditions were pH value of 3, reaction time of 120 min, Fe²⁺dosage quantity of 160 mg/L, H2O2 dosage quantity of 1,200 mg/L. Then using the single factor experiment for further optimizing the react condition,it came to the result that the optimal condition were initial pH value of 3, the reaction time 60 min, Fe²⁺ dosage quantity of 160 mg/L, H2O2 dosage quantity of 900 mg/L.Finally, the results of UV-Fenton method combined PAC-SBR-coagulation treatment on secondary electroplating wastewater with NaOH preprecipitation showed the most optimum reaction time of UV-Fenton was 60 min, and the final COD_cr of effluent of UV-Fenton reagent combined PAC-SBR treatment was 113 mg/L.Then following the coagu-flocculation process that was optimum polymerization aluminium chloride dosage quantity of 100 mg/L and optimum pH of 8 later, the effluent indexes achieved emission standard of pollutants for electroplating except TN.