Isolation And Identification Of A Sulfate-reducing Bacteria And Its Application In Acid Wastewater Treatment

In situ leaching of uranium ore has become an important method of uranium mining in the world.The injection of high concentration sulfuric acid leaching agent into the production solution leads to the dissolution of toxic and harmful heavy metals and other elements into the ore bearing aquifer,resulting in the problems of low p H value of groundwater and excessive content of sulfate,uranium and other components in the ore bearing aquifer,which poses a potential threat to the in-situ leaching mining area and the surrounding ore bearing aquifer after mining is stopped.Sulfate Reducing bacteria（SRB）is widely used in the treatment of sulfate containing wastewater due to its high desulfurization efficiency and low cost.However,the action conditions of sulfate reducing bacteria are generally neutral or alkaline,and the application under acidic or acidic conditions is relatively rare.Aiming at the problems of low p H and high sulfate content in acid mine groundwater,this paper used Postgate medium to enrich and domesticate the leachate from the leachate collection pipeline of a landfill in Nanchang,and purified an acid resistant sulfate reducing bacteria by limit dilution method combined with three-layer plate anaerobic method.The obtained strain（N19D-S）was identified by morphology and 16Sr DNA gene sequence analysis.The effects of different initial p H value,temperature,carbon source and carbon sulfur ratio(COD/SO₄^2-)on the growth and sulfate reduction characteristics of the strain were studied,and the sulfate reduction culture conditions were optimized.Finally,under the optimized conditions,the optimal inoculation amount of the strain n19d-s in the bioleaching uranium leaching solution and the removal effect of U（VI）and SO₄^2-in the leaching solution were studied.The main conclusions of this study are as follows:An acid-resistant sulfate-reducing bacteria strain N19D-S was obtained through enrichment,isolation and domestication.And the strain N19D-S was a Gram-negative bacteria,belonging to a strain（D.M.-N19D-S）of Desulfovibrio marrakechensis（D.M.）through the morphological and 16S r DNA gene sequence analysis and identification.The study of growth characteristics showed that,the strain N19D-S had higher sulfate reduction ability with p H of 5.0,and the sulfate reduction primarily occurred in the logarithmic growth phase after 48h.The optimized culture conditions of sulfate-reducing bacteria were:sodium lactate for the optimal carbon source,COD/SO₄^2-=2.0,35℃for the temperature,Growth p H of 7.0.Under these conditions,the sulfate reduction rate within 96h reached 83.20%..Under the optimized culture conditions,with the microbial leaching solution of uranium ore as the remediation solution,the optimum inoculation amount of strain N19D-S was 10%,and the removal rates of SO₄^2-and U（VI）were 80.05%and 90.36%respectively after 7 days;the strain N19D-S has good tolerance when the U（Ⅵ）concentration was within 25mg/L,and the strain N19D-S had a good remediation efficiency on the removal of uranium and sulfate in the aqueous solution.When the initial concentration of U（VI）was 5 mg/L and the inoculation amount of bacterial solution was10%,the removal rates of U（VI）and SO₄^2-reached the maximum at 7 days,which were84.57%and 95.02%respectively..In summary,A desulfurizing arc genus Desulfovibrio marrakechensis,N19D-S,isolated and bred in this study,has good remediation effect on the removal of SO₄^2-and U（VI）in acid uranium sulfate wastewater with p H of 5.0.The results can provide a theoretical basis for the application of strain N19D-S in the remediation of acid uranium mine wastewater in the future.