US EPA

1232158 

Journal Article 

Iron promoted reduction of chromate by dissimilatory iron-reducing bacteria 

Wielinga, B; Mizuba, MM; Hansel, CM; Fendorf, S 

2001 

1 

Environmental Science & Technology
ISSN: 0013-936X
EISSN: 1520-5851 

35 

3 

522-527 

English 

11351723 

10.1021/es001457b 

WOS:000166727700024 

Chromate is a priority pollutant within the U.S. and many other countries, the hazard of which can be mitigated by reduction to the trivalent form of chromium. Here we elucidate the reduction of Cr(VI) to Cr(III) via a closely coupled, biotic-abiotic reductive pathway under iron-reducing conditions. Injection of chromate into stirred-flow reactors containing Shewanella alga strain BrY and iron (hydr)oxides of varying stabilities results in complete reduction to Cr(III). The maximum sustainable Cr(VI) reduction rate was 5.5 micrograms CrVI.mg-cell-1.h-1 within ferric (hydr)oxide suspensions (surface area 10 m2). In iron limited systems (having HEPES as a buffer), iron was cycled suggesting it acts in a catalytic-type manner for the bacterial reduction of Cr(VI). BrY also reduced Cr(VI) directly; however, the rate of direct (enzymatic) reduction is considerably slower than by Fe(II)(aq) and is inhibited within 20 h due to chromate toxicity. Thus, dissimilatory iron reduction may provide a primary pathway for the sequestration and detoxification of chromate in anaerobic soils and water.