Study On Repairing Heavy Metal Pollution Of Groundwater By Infiltration Reaction Wall Of Natural Mineral Composite Material

Permeable reactive barrier (PRB) is fast emerging as an alternative to traditionalpump-and-treat and dig-and-treat methods for in-situ remediation of inorganic andorganic groundwater contaminants. This paper provide degradation basis to controlthe pollution of heavy metals in the groundwater, which choose cadmium(Cd)pollution in the groundwater for example, combined with the process and themechanism which remove cadmium by PRB technology and combination material oflimestone, bentonite and sepiolite. The main original conclusions of this work are asfollows:1.Chose3materials from the14habitats which had the best removal effects ofCd as medium material of PRB. Under the test condition the treated water containingcadmium is disposed of by bentonite that the remove rate of Cd can reach70%, whileusing the other materials were higher than41%. Through the dynamic experiment andthe effects of initial Cd concentration and initial pH of the materials, it is found thatthe processing efficiency of Cd from high to low is bentonite>sepiolite>manganeseore>limestone, the adsorption capacity of the material is limestone>bentonite>sepiolite>manganese ore, the removal rate of Cd under the weak-acid condition islimestone>bentonite> sepiolite>manganese ore. Compared these results with theorigins and types, while considering material leaching of heavy metals, and ultimatelyselected limestone, sepiolite and bentonite as PRB effective reaction medium.2. Selected the optimal composition of filling materials for PRB from16kinds ofpermeable reactor with orthogonal test method. It is found that the Cd removal ratesof the applied combination materials were above99.8%. The dosage of limestone wasthe main influence factor to the treatment effect of Cd, which was obviously improvedby increasing the amount of limestone. When the limestone content reached10%, theCd concentration of simulated Cd-polluted ground-water after treatment was less than0.7μg/L, meeting the class II water quality standard according to Groundwater qualitycriteria (GB/T14848-93). By increasing the amount of limestone, it had little effecton the permeability of barrier but caused the effluent to be weakly alkaline (7<pH<9).The pH of the effluent slowly decreased to about8. To increase the dosage ofsepiolite and bentonite, it had a little effect on improving the treatment effect, butsignificantly decreased the permeability of barrier. The optimal composition of fillingmaterials for PRB obtained with the orthogonal design-direct analysis method was20%of limestone,10%of Sepiolite and2%of bentonite in mass. 3. Developed a simulation device which is applicable to PRB simulation runs. Itis found that the PRB simulation devices can effectively remove Cd in simulatedCd-polluted ground water, simulated contaminated groundwater and wastewater inXiawan port as well as remove Zn,Cu,Pb,Ni,Mn. The device always had a highremoval rate of heavy metals during the64days running wastewater in Xiawan port,and the concentration of Mg, Ca, Na increased in the water after the treatment, but thetotal hardness meet the standards.