| China is a developing country with a lack supply of water resources and seriouswater pollution, current situation worsens the limited water resources supply.Currently, approximate2.1×109m3metal smelting wastewater is discharged everyyear in China. This kind of wastewater is characterized as high total dissolved solids,high suspended solids, high acidity, high hardness and high content of heavy metalions. The direct discharge of metal smelting wastewater without treatment will badlydeteriorate and jeopardize the environment. Therefore, it is extremely urgent to takeappropriate measures to deal with the wastewater for detoxification. In the presentstudy, one reasonable and efficient resolution for the reclamation of metal smeltingwastewater is proposed and investigated.The target wastewater was originated from a well-known nonferrous metalscompany in Hubei province in this study. It is mainly composed of the domesticwastewater from the smelting plant, and industrial drainage being treated withlime-ferric salts from the smelting and rare and precious metal plants. The wastewaterwas characteristic as high total dissolved solids, high hardness, complex composition,and greatly varied water quality. Because the high concentration of Ca2+and totaldissolved solids restricted the reuse of the wastewater, electrodialysis and ionexchange technologies were employed to treat the target water, respectively. Thetreatment efficiency and economic cost of these two methods were studied andcompared. It was found that electrodialysis technology could significantly improvethe reuse rate of wastewater, but the yield of water with low content of pollutants wasnot satisfactory. The water with relatively high concentration of pollutants is neededto be further disposed, this will sacrifice the processing cost. Ion exchange technologyis supposed to be the more appropriate method compared with electrolysis due to thehigh concentration of heavy metal ions presenting in the target water. It was foundthis technology could significantly enhance the reuse rate of wastewater withrelatively low running costs. However, the current employed ion exchange proceduresare time-consuming and laborious; a new technological process has been proposed. Inbrief, it contains a deep desalination and hardness removal processing withcoagulating sedimentation and ion exchange. The feasibility for the proposed newtechnical process were evaluated and verified in the following investigation. The results suggested that this new technical process could significantly shorten the wholetreatment process, the quality of effluent has satisfied with the standard of circulatedcooling make-up water. Except for above tests, because corrosion and foulingphenomena are always accompany with the operation of circulated cooling watersystem. Appropriate agents for corrosion and fouling inhibition were selected, and theappropriate dosages were evaluated for achieving the optimized inhibition efficiency.Pilot tests was further verified the feasibility of our proposed technology forachieving the predicted purpose. In detail, the TDS in the final effluent wasdetermined to be less than300.0mg/L; hardness was less than20.00mg/L. Theseparameters are far lower than the specified criteria of circulated cooling make-upwater. In addition, the content of arsenic was less than0.35mg/L, which is satisfiedwith the specified criteria of wastewater discharge.The application of the present project will provide technological supports for thewastewater quality in wastewater treatment station, making it achieve therequirements of circulated cooling make-up water to supply for production, flushingdevices and cooling facilities in some workshops. Most importantly, it will furtherimprove the reuse rate of wastewater, thus contributing to the economic benefits,environmental benefits and social results for enterprise in all-round way. |
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