title: Optimization of a bioremediation system of soluble uranium based on the biostimulation of an indigenous bacterial community.
abstract: High concentrations of uranium(VI) in the Witwatersrand Basin, South Africa from mining leachate is a serious environmental concern. Treatment systems are often ineffective. Therefore, optimization of a bioremediation system that facilitates the bioreduction of U(VI) based on biostimulation of indigenous bacterial communities can be a viable alternative. Tolerance of the indigenous bacteria to high concentrations of U and the amount of citric acid required for U removal was optimized. Two bioreactor studies which showed effective U(VI) removal more than 99 % from low (0.0037 mg L(-1)) and high (10 mg L(-1)) concentrations of U to below the limit allowed by South African National Standards for drinking water (0.0015 mg L(-1)). The second bioreactor was able to successfully adapt even with increasing levels of U(VI) feed water up to 10 mg L(-1), provided that enough electron donor was available. Molecular biology analyses identified Desulfovibrio sp. and Geobacter sp. among known species, which are known to reduce U(VI). The mineralogical analysis determined that part of the uranium precipitated intracellularly, which meant that the remaining U(VI) was precipitated as U(IV) oxides and TEM-EDS also confirmed this analysis. This was predicted with the geochemical model from the chemical data, which demonstrated that the treated drainage was supersaturated with respect to uraninite > U4O9 > U3O8 > UO2(am). Therefore, the tolerance of the indigenous bacterial community could be optimized to remediate up to 10 mg L(-1), and the system can thus be upscaled and employed for remediation of U(VI) impacted sites.
authors.affiliation: TIA/UFS Metagenomics Platform, Department of Microbial, Biochemical and Food Biotechnology, University of the Free State, PO Box 339, Bloemfontein, 9300, South Africa.
authors.forename: Maleke
authors.initials: M
authors.lastname: Maleke
authors.forename: Peter
authors.initials: P
authors.lastname: Williams
authors.forename: Julio
authors.initials: J
authors.lastname: Castillo
authors.forename: Elsabe
authors.initials: E
authors.lastname: Botes
authors.forename: Abidemi
authors.initials: A
authors.lastname: Ojo
authors.forename: Mary
authors.initials: M
authors.lastname: DeFlaun
authors.forename: Esta
authors.initials: E
authors.lastname: van Heerden
mesh_terms: D001673:Biodegradation, Environmental; D019149:Bioreactors; D058645:Denaturing Gradient Gel Electrophoresis; D003901:Desulfovibrio / Q000378:metabolism; D045302:Geobacter / Q000378:metabolism; D006089:Gram-Negative Anaerobic Bacteria / Q000378:metabolism*; D046529:Microscopy, Electron, Transmission; D008906:Mining; D008956:Models, Chemical; D010084:Oxidation-Reduction; D016133:Polymerase Chain Reaction; D013019:South Africa; D014501:Uranium / Q000032:analysis / Q000378:metabolism*; D017974:Uranium Compounds / Q000032:analysis; D014875:Water Pollutants, Radioactive / Q000032:analysis / Q000378:metabolism*; D018508:Water Purification / Q000379:methods*
chemical_list: D017974:Uranium Compounds; D014875:Water Pollutants, Radioactive; D014501:Uranium; C047385:uranium oxide