Improvements on the Performance of a Microbial Fuel Cell for Biological Treatment of Hexavalent Chromium

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Chromium in the natural environment


A great variety of chemical compounds can be found in water, not all of them of the same concentration or significance. Even with respect to the same chemical element, different aquatic conditions like reduction/ oxidation potential and pH may bring out a variety of different properties with varying importance. Among other inorganic contaminants, chromium can be found in water as a result of anthropogenic processes like electroplating, leather tanning, textile and pigment manufacturing and wood preserving (U.S.E.P.A., 2000). In the U.S.A., chromium is considered to be the second most abundant pollutant found at hazardous waste sites, (Blowes, 2002), mainly as a result of the disposal of waste produced by the above mentioned processes.

The main oxidation states that chromium can be found in nature are Cr(III) and Cr(VI) (Palmer and Puls, 1994), with chromium being significantly more toxic when in the hexavalent state. Genetic studies on the effect of Cr(VI) in animal cells in vivo and animal and human cells in vitro, revealed various effects “including DNA damage, gene mutation, sister chromatid exchange, chromosomal aberrations, cell transformation and dominant lethal mutation” (W.H.O., 1997). For the above reasons, Cr(VI) has been evaluated by the World Health Organisation as “carcinogenic to humans (Group 1)” (W.H.O., 1997), while insufficient proof for similar impacts on humans by Cr(III) compounds has categorized them as “not classifiable as to their carcinogenicity to humans (Group 3)” (W.H.O., 1997). Furthermore, Cr(III) is considered as a micronutrient and safe for human health at the concentrations found in ambient water environments (Brandhuber et al., 2004).

As a result of...

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...of water intended for human consumption. Brussels.

MOLOKWANE, P. E. & NKHALAMBAYAUSI-CHIRWA, E. M. 2009. Microbial culture dynamics and chromium (VI) removal in packed-column microcosm reactors. Water Science & Technology, 60, 381-388.

PALMER, C. D. & PULS, R. W. 1994. Natural Attenuation of Hexavalent Chromium in Groundwater and Soils. In: U.S.E.P.A. (ed.) EPA Ground Water Issue. U.S. Environmental Protection Agency.

U.S.E.P.A. 2000. In Situ Treatment of Soil and Groundwater Contaminated with Chromium- Technical Resource Guide. Washington DC: U.S. Environmental Protection Agency, Office of Research and Development.

W.H.O. 1997. Chromium, Nickel and Welding. IARC Monographs on the Evaluation of Carcinogenic Risks to Humans. International Agency for Research on Cancer.

W.H.O. 2004. Guidelines for Drinking-water Quality. 3rd ed. Geneva: World Health Organization.
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