A method for removal of toxic chromium using dialysis-sac cultures of a chromate-reducing strain of Enterobacter cloacae.

A method for removal of toxic hexavalent chromium (chromate: CrO2-4) was developed by use of dialysis-sac cultures of a chromate-reducing strain of Enterobacter cloacae (HO1). E. cloacae strain HO1 cells were put in dialysis (semipermeable membrane) sacs, and the sacs were submerged in water containing toxic CrO2-4. The dialysis sacs allowed CrO2-4 to diffuse into the culture, and CrO2-4 was reduced anaerobically in the dialysis sacs by the E. cloacae cells. Because reduced chromium readily formed insoluble chromium hydroxides in the dialysis sacs, the greater part of reduced chromium was unable to diffuse out through the semipermeable membrane. Thus the dialysis culture of E. cloacae strain HO1 could successfully remove toxic chromium from the surrounding water. If the initial concentration of CrO2-4 was less than 4 mM (208 ppm as chromium), about 90% of the total chromium could be removed from water by the described method.