Microbiological and bioengineering process development for the large-scale production of an immobilized biosorbent for treatment of uranium-contaminated wastewaters

Pseudomonas aeruginosa CSU, a nongenetically-engineered strain shown to bind dissolved U(VI) and to reduce it to U(IV), is the foundation of an experimental process for removal of uranium from wastewater. Several polymers (including alginate, polyacrylamide, polysulfone, and polyurethane) were tested as possible immobilization matrices for the biomass. Initial screening was based on material cost, mechanical and chemical stability, case of manufacture, and effect of immobilization on sorptive behavior of the biomass. Polyurethane was thus identified as the superior candidate. Several polyurethane formulations, including a hydrogel, a solid, a pure foam, and two unique foam composites formed by blending polyurethane with other polymers, were tested further. The hydrogel and the foam composites were selected for further characterization. A novel biosorbent bead fabrication technique was developed. Immobilized biomass was evaluated via measurement of sorption isotherms within a batch, stirred-tank reactor and via study of elution behavior within a continuous, expanded-bed columnar reactor. Sorption equilibrium and dynamics were described using a pore-diffusion mass transfer model. Results indicate that polyurethane-immobilized P. aeruginosa CSU is competitive with both commercial and experimental resins for removal of uranium from dilute, acidic, aqueous solutions