Laboratory Study On The Remediation Of The Chromium Contaminated Groundwater By The Chemical—Biological Permeable Reactive Barrier(PRB) Technology

With the quick development of the economic and the industrialization, the water resource has been polluted more and more seriously today, and the pollution of the groundwater also has been polluted more and more widely. At the same time, the research about the effective treatment methods and technologies to remediate the heavy metal pollution of the hexavalent chromium gradually attracted the attention of the experts and scholars, one of the most popular in situ remediation technology to remediate the groundwater polluted by the chromium was the permeable reactive barrier (PRB). But, there were also some defects for this technique such as the very high cost and its frequent replacement of the conventional zero-valent iron filling medium. As well as its secondary pollution, at the same time, this technique required replacing the filling and chemical reaction medium to treat the polluted groundwater which would lead to the secondary pollution and so on. In order to make up the disadvantages of this medium, different mediums(Iron powder, nano composite materials, and scrap iron etc.) experiments were designed to investigated their remediation effects for the groundwater polluted by the chromium to confirm the optimum filling medium of the PRB and its reaction conditions, meanwhile,the microorganism which has the characteristic of degradation for the hexavalent chromium also has been acclimated and screened and the characteristics of the microorganismgot preliminary analysis in these experiments,based on the experiments above, a double medium Permeable Reactive Barrier that made up of chemicalµbial mediums was structured to investigate the effect and the optimum reaction conditions of its in situ remediation effect for the chromium contaminated groundwater.The research results showed that:the scrap iron,the nanocomposite and the iron powder all had perfect remediation effectsfor the remiadation of the the chromium contaminated groundwater, but along them, the scrap iron has the advantages of the lowest cost and the same remediation effect so, it was selected to be the optimal medium of the PRB, The optimal reaction conditions when it was used as the filling medium in the experiment process were:the dosage was0.5g, the pH value was5,the reaction time was60minutes,and the temperature was25℃.Then, the scrap iron was selected as the filling medium of the PRB applied to the remediation simulation experiments of the hexavalent chromium contaminated groundwater, the simulation analysis showed the test results were:Under different flow rate.the hexavalent chromium removal rates changed with the initial concentration of the best regression model is the cubic polynomial regression analysis model; the hexavalent chromium removal rate has a strong correlation with the initial concentration and the velocity, and the correlation degree between the hexavalent chromium removal rates with the initial concentrations was higher than the correlation degree between the hexavalent chromium removal rates with the velocities; the Binary nonlinear regression model could be better to simulate the trend of the hexavalent chromium removal rates along with the change of the initial concentration and velocity than the binary linear regression one.Through comparing the effects of usages of the dry soil,wet soil and the chromium contaminated groundwater which near some chromium slag treatment plant in Xining of Qing Hai province to domesticate makings to degrading the hexavalent chromium showed that:the wet soil has a better degradation ability; the optimum dosage both of the glucose and nitrogen source is5g/1when microorganism remediated the chromium contaminated groundwater applied. The results of the chemicalµbial permeable reactive barrier remediated the chromium contaminated groundwater showed that:the hexavalent chromium concentration of the effluent was0.04mg/1, the effluent ionic concentration of the bivalent iron was0.2mg/1, and the quality of the effluent met the requirements of the national groundwater quality standard Ⅲ.