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Water Science & Technology Vol 52 No 7 pp 49–55 © IWA Publishing 2005

Uranium removal by sulfate reducing biofilms in the presence of carbonates

E. Marsili*, H. Beyenal**, L.Di Palma***, C. Merli****, A. Dohnalkova*****, J.E. Amonette****** and Z. Lewandowski*******

* Center for Biofilm Engineering, Department of Civil Engineering, Montana State University, Bozeman, MT 59717, USA (E-mail: emarsili@erc.montana.edu; beyenal@erc.montana.edu; zl@erc.montana.edu); Department of Chemical Engineering, University “La Sapienza”, Via Eudossiana, 18 00184 Rome, Italy, (E-mail: luca.di.palma@ingchim.ing.uniroma1.it; carlo.merli@ingchim.ing.uniroma1.it)
** Center for Biofilm Engineering, Department of Civil Engineering, Montana State University, Bozeman, MT 59717, USA (E-mail: emarsili@erc.montana.edu; beyenal@erc.montana.edu; zl@erc.montana.edu)
*** Department of Chemical Engineering, University “La Sapienza”, Via Eudossiana, 18 00184 Rome, Italy, (E-mail: luca.di.palma@ingchim.ing.uniroma1.it; carlo.merli@ingchim.ing.uniroma1.it)
**** Department of Chemical Engineering, University “La Sapienza”, Via Eudossiana, 18 00184 Rome, Italy, (E-mail: luca.di.palma@ingchim.ing.uniroma1.it; carlo.merli@ingchim.ing.uniroma1.it)
***** Fundamental Sciences Directorate, Pacific Northwest National Laboratory, 790 6 St, Richland, WA 99352, USA, (E-mail: alice.dohnalkova@pnl.gov; jim.amonette@pnl.gov)
****** Fundamental Sciences Directorate, Pacific Northwest National Laboratory, 790 6 St, Richland, WA 99352, USA, (E-mail: alice.dohnalkova@pnl.gov; jim.amonette@pnl.gov)
******* Center for Biofilm Engineering, Department of Civil Engineering, Montana State University, Bozeman, MT 59717, USA (E-mail: emarsili@erc.montana.edu; beyenal@erc.montana.edu; zl@erc.montana.edu)


ABSTRACT
Hexavalent uranium [U(VI)] was immobilized in biofilms composed of the sulfate reducing bacteria (SRB), Desulfovibrio desulfuricans G20. The biofilms were grown in two flat-plate, continuous-flow reactors using lactate as the electron donor and sulfate as the electron acceptor. The growth medium contained uranium U(VI) and the pH was maintained constant using bicarbonate buffer. The reactors were operated for 5 months, and during that time biofilm activity and uranium removal were evaluated. The efficiency of uranium removal strongly depended on the concentration of uranium in the influent, and was estimated to be 30.4% in the reactor supplied with 3 mg/L of U(VI) and 73.9% in the reactor supplied with 30 mg/L of U(VI). TEM and SAED analysis showed that uranium in both reactors accumulated mostly on microbial cell membranes and in the periplasmic space. The deposits had amorphous or poor nanocrystalline structures. Keywords Biofilm; D. desulfuricans; uranium immobilization; uranium reduction

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