Study On Remediation Of Arsenic-Contaminated Soil By Microbial And Electrokinetic Technology

Arsenic is a kind of harmful metal to the human body.It often enters the food chain through water or soil to threaten human health.The problem of soil arsenic pollution in China is serious.It is particularly important to study the repair of soil arsenic pollution.The current electrokinetic remediation technology for arsenic has the advantages of short repair time,good effect,low cost,and can be repaired in situ.It is suitable for arsenic-contaminated paddy soil.The effect of electrokinetic remediation technology needs to be combined with other technologies.Among them,the microorganism combined electrokinetic remediation technology has the advantages of green environmental protection,and is most suitable for arsenic repair in paddy soil.In view of this,this article separate electrokinetic remediation experiment group is used as a control group,combines the addition of nutrient elements to promote the growth of reducing microorganisms and electric power technology,adding 2%,5%,and 10% sucrose and 10%,25%,and 50% biogas slurry as soil mass percentages,respectively.Nutrients are designed to promote the reduction of iron/arsenic in soil through reducing microorganisms,thereby improving the efficiency of arsenic removal.Taking rice paddy soil,which has been contaminated with high arsenic coal mine wastewater,as the research object,the soil p H,Eh,water content,high-throughput sequencing of reducing microorganisms,Fe(II)concentration,arsenic species,and the determination and analysis of arsenic residues,explored the effects of sucrose and biogas slurry on eelectrokinetic remediation technology and the efficiency of arsenic removal,and provided a scientific basis for the application of microbial-electric technology in aged arsenic-contaminated soil.Through data analysis and comparison,the main conclusions are as follows:(1)The soil p H value of the control group is 3.81,the soil p H value of the sucrose group is 0.2?0.3 lower than that of the control group,the addition of biogasslurry increases the soil p H value by 0.29?0.31;the control group Eh is 480.8m V,the addition of sucrose is significant The soil Eh was reduced by 167.61 m V?236.51 m V.The Eh value of the soil added with biogas slurry was slightly lower than that of the control group,and the soil moisture content decreased the most.The proportion of soil reducing microorganisms in the different treatment groups was more than 70%.Clostridium sensu stricto,Bacillus,Desulfosporosinus,Tumebacillus,and Desulfitobacterium and Gp3 are the main reducing bacteria.The addition of sucrose significantly promotes the growth of Clostridium sensu stricto;the addition of biogas slurry increases the soil microbial diversity and promotes the growth of Bacillus and Desulfosporosinus.(2)The concentration of Fe(II)in the soil of the sucrose group is higher than that of the control group and the biogas slurry group,and the addition of biogas slurry cannot promote iron reduction and release of arsenic.The total iron migration amount is low,the amorphous iron content increases,and the increase in the later stage of the experiment is higher than that in the early stage of the experiment.There is no significant difference between the initial and the end of the crystalline iron content experiment.The form of arsenic in the soil is mainly in the form of residue and crystalline iron-bound state.When the Eh is low,the content of amorphous iron-bound arsenic increases.When the Eh increases,the amorphous iron-bound arsenic is converted into crystalline iron-bound arsenic..The addition of sucrose promotes the conversion of crystalline iron-bound arsenic to exclusive adsorbed arsenic and amorphous iron-bound arsenic,while the residual arsenic decreases,while the addition of biogas slurry residual arsenic decreases significantly,and the crystalline iron-bound arsenic increases.(3)The arsenic removal rate of the control group on aging arsenic-contaminated soil is only 4.81%.Adding appropriate amounts of sucrose and biogas slurry as nutrients significantly enhances the arsenic removal effect.Among the sucrose group,5% sucrose group has the highest arsenic removal rate,and the average arsenic removal rate 14.27%;the 25% biogas slurry group has the highest arsenic removal rate,and the average arsenic removal rate can reach 13.30%.The mechanism ofincreasing the arsenic removal rate in the sucrose group is mainly dissimilated iron reducing bacteria Clostridium sensu stricto and Bacillus reducing iron to promote the release of arsenic;the mechanism for increasing the arsenic removal rate in the biogas slurry group is mainly the function of iron/arsenic reducing bacteria Bacillus and Desulfosporosinus reducing and release of arsenic;the main removal mechanism of the 5% sucrose group and the 25% biogas slurry group is electrodialysis and electrophoresis,and the remaining treatment groups are mainly electrodialysis.(4)Except for the sucrose group,the other currents of the different treatment groups all rise first,then fall,and finally fall to about 40 m A.The total energy consumption of the device for 15 days of operation is 0.77 k W·h?0.92 k W·h,which is used per unit weight of dry soil The energy consumption is 0.9?0.12 k W·h/kg,the overall energy consumption of the biogas slurry group is higher,and the energy consumption of the other sucrose groups is lower than the 2% sucrose group;the sucrose group and the biogas slurry group have low removal efficiency and high energy in the later stage of the experiment consume.