Study On Treatment Of Wastewater Of Zinc Smelting From Industrial Zinc Oxide Through Coagulating Sedimentation And SBR Technology

Zinc smelting industry is an important part of metallurgy industry in China. Zinc smeltingprocess will produce large amounts of wastewater, which is high content of heavy metals.Current zinc smelting wastewater treatment process is complex, high cost, recycling limitedand easy to produce secondary pollution. So it is necessary to develop a new treatmentprocess which is suit for enterprise applications, and will economic and efficient disposeheavy metals of the wastewater and realize the recycling of water resources at the same time.The research according to the content characteristic of heavy metals and COD andammonia nitrogen in wastewater of zinc smelting from industrial zinc oxide, synthesizeddomestic and foreign research process of zinc smelting wastewater treatment, adoptedcoagulating sedimentation and SBR （sequencing batch reactor activated sludge process） toexperimental study. It explored the best process parameters through analyzing the removaleffect of heavy metals and COD and ammonia nitrogen, and the variation followed thecondition such as pH and temperature and so on. The results are as follows:In the stage of coagulation precipitation, the composite flocculating agent was made ofanionic polyacrylamide （APAM） and polyaluminium chloride （PAC）. Result of single factorexperiment showed that best technology parameters for coagulating sedimentation wereAPAM: PAC mass ratio for4:3, composite flocculants dosage for12mg·L^-1, pH for8⁹,temperature for20℃³5℃, mixing speed for60r·min^-1and mixing time for20min. Aftertreated through best technology of coagulating sedimentation, Zn was0.48mg·L^-1, Cd was0.05mg·L^-1, Cr was0.21mg·L^-1, COD为310mg·L^-1in the wastewater.After12days test and operation, activated sludge of SBR color gradually changed fromblack to brown, which settling performance was favorable. And the quality of SBR effluentwas stable.In the stage of SBR operation, the wastewater （effluent water of coagulating sedimentation:sanitary sewage=5:1） was continuous feed15cycles. Result of single factor experimentshowed that best technology parameters for SBR were MLSS for3800mg·L^-1, HRT for10h,volume loading for0.6kgCOD/m3·d^-1. After treated through best technology of SBR operation,COD was67mg·L^-1, ammonia nitrogen was8mg·L^-1in the wastewater. After obtained the optimum technology parameters for coagulating sedimentation and SBRthrough experiment, the wastewater was treated through coagulating sedimentation and SBRon the condition of best technology parameters. The result showed that the removal rate of Zn,Cd, Cr, COD, ammonia nitrogen were93.6%,94.1%,88.7%,86.7%,92.5%. Zn was0.40mg·L^-1, Cd was0.04mg·L^-1, Cr was0.19mg·L^-1, COD was67mg·L^-1and ammonianitrogen was8mg·L^-1in final effluent water, which could achieve the first level standard ofthe “integrated wastewater discharge standard”(GB8978^-1996).The treatment effect of this technology was favorable on industrial zinc oxide zinc smeltingwastewater. The technology was easy operation and maintenance, economic and energysaving compared with the traditional technology, which was suitable for enterprise automaticoperation, and had reference value for design and operation of practical engineering.