Batch Experiment Study Of Emulsified Oil Carbon Source In-situ Remediation Of Cr(Ⅵ) In Groundwater

In recent years,Cr（Ⅵ） pollution incidents in groundwater has been occurred frequently.In situ treatment of Cr（Ⅵ） in groundwater by adding carbon source has been more and more weidely applied.The choice of carbon source is an important factor of treatment effect.Emulsified oil,as a new type of carbon source,has been widely used in the treatment of groundwater contamination.In this experiment emulsified oil was used as carbon source,the effect of Cr（Ⅵ） reduction by microbial,which can utilization of emulsified oil as carbon source,was studied.The effects of temperature,NO₃^-,SO₄^2- and different initial pH on microbial reduction of Cr（Ⅵ） has been discussed,detection of microbial community changes by using macro genome sequencing,this paper mainly obtains the following conclusions.（1）The activated sludge acclimation experimental results showed that the reduction process of Cr（Ⅵ） in accord with the zero order reaction kinetics.Under the 350 C condition,the 2ml emulsified oil can support Microbial reduction of Cr（Ⅵ）,the concentration was 10mg/L,for 6 cycles.The total reduction amounts of Cr（Ⅵ） was 18.2mg,and the total reduction rate of Cr（Ⅵ） was 89.04%,1L emulsified oil can treat 0.91m3 concentration of 10mg/L Cr（Ⅵ） solution.（2）The results of in situ soil experiment showed that the reduction rate of Cr（Ⅵ） in each cycle was 100%.The reduction rules of Cr（Ⅵ） in accord with the first order reaction kinetics,the first order reaction kinetic constant k is roughly between 0.6891 and 0.7769d-1.Under the 250 C condition,0.5ml emulsified oil support the microbial reduction of 5mg/L Cr（Ⅵ） solution for 7 cycles.The total reduction amounts of Cr（Ⅵ） was 0.581 mg,At the end of the experiment,the reduction ability of microorganisms to Cr（Ⅵ） was not diminished.Therefore, the volume of 1L emulsified oil support microbial reduction of 5mg/L Cr（Ⅵ） solution should be much larger than 0.232m3.Emulsified oil significantly promoted the growth and reproduction of Azospirillum and Natranaerovirg,But it reduced the microbial diversity in each group.（3）The results of in situ soil experiment show that,both NO₃^- and SO₄^2- can promote microbial reduction of Cr（Ⅵ）,the total average reduction rate of Cr（Ⅵ） was 2.2 and 1.4 times of the control group,the promoting effect of SO₄^2- was weaker than NO₃^-.pH value of 8.7⁹.1 is more conducive to the reduction of Cr（Ⅵ） than 8.3⁸.7.The addition of NO₃^- and SO₄^2- can enable Pseudomona that can adsorption and reduction of Cr（Ⅵ） and Desulfosporosinus,which can reduced the SO₄^2-,became the dominant genera,respectively,this is the main reason for the microbial reduction of Cr（Ⅵ）.