Study On The Remediation Of Cadmium Contaminated Soil By Cadmium-tolerant Strains Combined With Electrokinetic Technology

Cadmium(Cd)pollution in the soil has become increasingly prominent in recent years,electrokinetic technology(EK)is considered to be a method of remediation of cadmium contaminated soil.The traditional electrokinetic(EK)has the disadvantages of high energy consumption and heavy metals easily precipitate in the cathode region,to improve the efficiency and economy of traditional electrokinetic(EK),this study used Cd-tolerant strains combined with EK to remove Cd from the contaminated soil.The impacts of different Cd-tolerant strains on Cd removal and soil microecological environment were evaluated by inoculating Escherichia coli strain,Bacillus sp.and Bacillus cereus strain in soil with 10 days under a 1V·cm-1.Design of the response surface was designed by the Design principle of Box-Benken(BBD).The main results are follows:(1)Three Cd-tolerant strains isolated from cadmium-contaminated soils after EK,the strains were identified as Escherichia coli strain,Bacillus sp.and Bacillus cereus strain based on the morphological,physiological-biochemical characteristics and molecular identification,and the strains was noted as strain A-1,B-1,C-1,respectively.(2)The optimal growth conditions are pH=7.0?7.2,28?,NaCl%=0.125%,100 mL of medium capacity by combined with the suitable growth conditions of three strains.Strain A-1,B-1,C-1 tolerated Cd2+ up to 400,600,700 mg·kg-1 in LB solid medium and 150,200,200 mg·L-1 in LB liquid medium,the adsorption rate has reached 19.40%,30.55%,37.36%,respectively.(3)Compared with the traditional EK treatment,electro-bioremediation can improve the Cd removal effeciency and reduce the energy consumption(P<0.05).The Cd removal effeciency with Bacillus cereus strain,Bacillus sp.,Escherichia coli strain was 173.75%,153.11%and 67.88%respectively,which were higher than the traditional EK treatment.In addition,the energy consumption with Bacillus cereus strain,Bacillus sp.,Escherichia coli strain was 70.34%,66.18%and 39.15%respectively,which were lower than the traditional EK treatment.(The Cd removal efficiency of EK was 11.24%,the energy consumption of EK was 165.48 kW·min·mg-1)(4)Electro-bioremediation can improve the S-ACP,S-UE,S-?-GC activities and culturable microorganisms in soil compared with the traditional EK treatment,the soil enzyme activity was EBR-Bcs>EBR-Bs>EBR-Ecs>Control,and the abundance of soil culturable microorganisms in the anode region was higher than those in the cathode region(P<0.05)because electrophoresis was greater than electroosmosis in soil.(5)Bacillus cereus strain combined with EK was achieved the highest Cd removal effeciency and the lowest energy consumption,the response surface exepriments was designed by Bacillus cereus strain combined with EK,and the best solution for electro-bioremediation on cadmium contaminated soil was obtained:processing time was 10.05d,the voltage gradient was 1.09 V·cm-1,bacterial suspensions was 100 mL.