REDUCTION OF CR(6(-BED BIOREACTOR()) TO CR(3(+)) IN A PACKED)

Hexavalent chromium, Cr(6+), is a common and toxic pollutant in soils and waters. Reduction of the mobile Cr(6+) to the less mobile and less toxic trivalent chromium, Cr(3(+)), can be achieved with conventional chemical reduction technologies. Alternatively, Cr(6(+)) can be bioch emically reduced to Cr(3(+)) by anaerobic microbial consortia which ap pear to use Cr(6(+)) as a terminal electron acceptor. A bioprocess for Cr(6(+)) reduction has been demonstrated using a packed-bed bioreacto r containing ceramic packing, and then compared to a similar bioreacto r containing DuPont Bio-Sep beads. An increase in volumetric productiv ity (from 4 mg Cr(6(+))/L/h to 260 mg Cr(6(+))/L/h, probably due to an increase in biomass density, was obtained using Bio-Sep beads. The be ads contain internal macropores which were shown by scanning electron microscopy to house dense concentrations of bacteria. Comparisons to c onventional Cr(6(+)) treatment technologies indicate that a bioprocess has several economic and operational advantages.