Research On Pretreatment Process For Complex Electroplating Wastewater

Electroplating industry is developing very rapidly. Not only the scale is becoming larger, but also electroplating species is increased. The complication of electroplating wastewater quality is prominent. Especially heavy metal complexes add considerable difficulties to the electroplating wastewater treatment. Because of the variety of mixed wastewater, Existing treatment processes and equipments can not be run efficiently. The treatment effect has been affected seriously. Therefore, the way in which the electroplating wastewater is respectively discharged and treated from the source is imperative.According to the actual situation of the treatment process of a electroplating park of all workshops in Shenzhen, complex wastewater and pre-treatment wastewater isolated from comprehensive electroplating wastewater have been individually treated. As the complicated composition, complex wastewater is treated difficultly. Under the new water quality classification, the article has determined the optimum operating parameters as the basis for guiding the project commissioning by theoretical study of complex wastewater treatment process.Acidification-oxidation de-complexation+chemical precipitation has been utilized widely in electroplating wastewater treatment process which has selected acidic oxidant NaClO. Acidification-oxidation de-complexation is rarely applied from pH6 to 8. By comparing the oxidant NaClO with H2O2, the article has investigated feasibility of H2O2 de-complexation+chemical precipitation process and determined the operating parameters to complex wastewater treatment process from pH6 to 8. The results showed that from pH6 to 8, oxidation de-complexation effect of H2O2 was better. The best combination of treatment processes conditions: H2O2 dosage: 0.34ml/L, de-complexation times: 40min, pH: 10.5, Na2S dosage: 250mg/L, FeSO4 dosage: 50mg/L, PAC dosage: 7.5mg/L, PAM dosage: 4.5mg/L.Specific processes: raw water pH6 to 8 using H2O2 de-complexation, using NaOH to adjust to pH to 10.5, dosing Na2S, next dosing FeSO4,coagulant PAC,flocculant PAM, flowing to inclined tube sedimentation tanks, ammonia stripping, into the subsequent biological treatment process. The process is anaerobic tank, flowing to sedimentation tank, anoxic tank, contact oxidation tank, MBR, flowing out. The debugging results show that using the process above can meet the discharge standard stably.