S. Hapuarachchi and T. G. Chasteen

Department of Chemistry
Sam Houston State University
Huntsville, Texas 77341-2117

Presented at the 225^th ACS National Meeting in New Orleans, Louisiana, USA, March 23-27, 2003.

Talk ENVR 112, presented in the second session of "ACS Award for Creative Advances in Environmental Science and Technology, Honoring Dr. John Birks"; T. G. Chasteen presiding.

This talk's PowerPoint presentation. (3.2 MB)

Experiments were carried out to determine the mass balance of selenium biologically processed by an Se-resistant bacterium, Pseudomonas fluorescens, isolated by Ray Fall, CU Boulder. The bioprocessing of this toxicant in a growing liquid culture resulted in reduction and, in some part, methylation that yielded Se distributed between the solid, liquid, and gas phases. Initial anaerobic experiments with different amended selenium concentrations were carried out and the Se mass balance determined using inductively coupled plasma and fluorine-induced chemiluminescence-based GC analysis. Finally, bioreactor experiments were carried out under sequential anaerobic/aerobic culture growth conditions again the mass balance determined. As a percentage of amended selenium, selenite was more effectively reduced to metallic Se by P. fluorescens than selenate. When low amounts of selenite were present in the solution, reducing efficiency as a percentage of added Se was higher as measured by the production of Se zero. Sequential anaerobic/aerobic growth conditions did not have a big effect in this detoxification process as carried out under these conditions. A fast motion movie of the bioremediation process will be used to visualize the culture's action on added Se.