共存离子对硫酸盐还原菌(SRB)还原U(Ⅵ)的影响

采用硫酸盐还原菌(SRB)生物(还原)沉淀法消除地浸含铀废水中的放射性U污染,研究了pH值、SO42-和NO3-对混合SRB菌群对地浸废水中U生物沉淀过程的影响.厌氧序批式实验结果表明,溶液pH值对U生物沉淀存在显著影响,在pH=6.0时U的沉淀率最高达99.4%,随pH值的降低其U的沉淀率也不断降低.SO42-质量浓度低于4 000 mg/L时对U生物沉淀没有影响,但超过5 000 mg/L时会产生明显的抑制作用,且抑制作用随着初始SO42-浓度的上升而加强.NO3-的存在会严重抑制SRB还原沉淀U,只有先彻底去除NO3-才能利用SRB还原沉淀U.因此,寻找分离或驯化培养出嗜酸性SRB菌群以及应用SRB和反硝化细菌(DNB)的混合菌群协同作用对酸法地浸采铀地下水进行原位生物修复具有重要意义.

Influence of coexistent ions on microbial reduction of hexavalent uranium by sulfate reducing bacteria

Microbial reduction(bioprecipitation) technology by sulfate reducing bacteria were employed to treat radionuclide-bearing wastewater from acid in situ leach uranium mining.Anaerobic batch experiments were conducted to evaluate the influence of pH,sulfate,and nitrate on the process of U(VI) bioprecipitation.Laboratory incubation tests demonstrated that the precipitation yield was significantly affected by the initial pH and reduced with decreasing pH.A maximum yield(99.4%) was achieved when the initial pH was adjusted to 6.0.No inhibition of U(VI) reduction was found with the initial concentration of sulfate less than 4 000 mg/L,however,anion levels above 5000mg/L slowed (U(VI)) bioprecipitation and the inhibitory effect was enhanced with increasing sulfate concentration.The U(VI) reductive precipitation will not commence until nitrate(1 000 mg/L) was completely eliminated.Therefore,the isolation of acidophilic SRB as well as synergism of mixed cultures of SRB and denitrifying bacteria(DNB) can be of great significance to bioremediate contaminated groundwater from acid in situ leach uranium mining.