Research On The Bioremediation Capability And Mechanism Of Mercury Pollution By Rheinonia In Tangshan

RTS-4,a bacterial strain of Rheinheimera tangshanensis with strong tolerance to Hg²⁺was screened from sewage.In solid and liquid medium,the maximum Hg²⁺tolerance concentration of RTS-4 were 120 mg/L and 60 mg/L,respectively.Under the optimum culture conditions(30?,pH 7,150 r/min and 5%inoculation quantity),the maximum Hg²⁺removal rate by RTS-4 was 86.72%in 48 h.This results showed there were three mechanisms of Hg²⁺removal by RTS-4,including the reduction of Hg²⁺by meroperon,the adsorption of Hg²⁺by producing extra-cellular polymeric substances(EPS),and adsorption of Hg²⁺by the dead bacterial biomass.In the presence of low concentrations of Hg²⁺(Hg²⁺?10 mg/L),there existed two mercury removal mechanisms:the reduction by meroperon and the adsorption by dead bacterial biomass,their percentage in the total removal process were 54.57%and45.43%,respectively;In the presence of higher concentrations of Hg²⁺(10 mg/L<Hg²⁺?50mg/L),all three mechanisms mentioned above existed,their percentage in the total removal process were 0.26%,81.7%and 18.04%,respectively,and the adsorption by EPS was dominant;Under the high concentration of Hg²⁺(Hg²⁺>50 mg/L),the two mechanisms of adsorption by EPS and dead bacterial biomass of Hg²⁺existed,and the percentage in the total removal process were 19.09%and 80.91%,respectively.When all the three mechanisms exist,the reduction of Hg²⁺by meroperon occurred in the early stage of treatment(0-8 h),the adsorption of Hg²⁺by EPS and dead bacterial biomass occurred together in the middle stage of treatment(8-20 h),and the adsorption of Hg²⁺by dead bacterial biomass occurred after 8 h of treatment.In this study,Chlorella was used as a bio-indicator to examine the effect of RTS-4 on the removal of Hg²⁺.This study provides a solid theoretical basis and valuable strain resources for the microbial remediation of mercury-contaminated waste water.On the basis of this study,the RTS-4 strain was studied to verify the tolerance concentrations of other common four metal ions Cr⁶⁺,Cd²⁺,As³⁺,and Pb²⁺,and found that the tolerance concentrations were 10 mg/L,30 mg/L,60 mg/L,60 mg/L,The strain is embedded in immobilized pellets with sodium alginate-activated carbon-calcium chloride and put into artificial sewage.The removal rate of the five metal ions of Cr⁶⁺,As³⁺,Cd²⁺,Pb²⁺and Hg²⁺after 180 min at the highest tolerable concentration of the strain Respectively:100%,93.4%,96%,92.6%,99.5%,the adsorption capacity is 29.9 mg/g,169.8 mg/g,86.4 mg/g,134.8 mg/g,30.121 mg/g;the removal rates of As³⁺,Cd²⁺,Hg²⁺three metal ions after 180 min of immobilized strains in actual sewage are 95.17%and 97.12%,respectively,100%,the adsorption capacity is 0.32 mg/g,1.03 mg/g,0.37 mg/g,respectively.The above results show that the RTS-4 strain can effectively remove Hg²⁺by using different mechanisms,and the immobilized pellets can be made to remove metal ions in water more effectively,and the adsorption capacity is low,which realizes the reuse of immobilized pellets.This research provides a solid theoretical foundation and precious bacteria resources for the microbial remediation of mercury-contaminated wastewater.