Chromium (VI) reduction in activated sludge bacteria exposed to high chromium loading: Brits culture (South Africa)

Abstract

BiocatalysisBacillus sp. IntroductionHexavalent chromium [Cr(VI)] compounds are used in a wide variety of commercial processes and unregulated disposal of chromium containing effluents has led to the contamination of soil, aquatic sediments, and surface and groundwater environments. Chromium, a steel-grey, lustrous, hard and brittle metal, occurs in nature in the bound form that constitutes 0.1-0.3 mg/kg of the Earth's crust. It has several oxidation states ranging from (ÀII) to (þVI), the trivalent and hexavalent states being the most stable. A maximum acceptable concentration of 50 mg/L for Cr(VI) in drinking water has been established on the basis of health considerations (Kiilunen, 1994). In some American states, the exposure limit for Cr(VI) is as low as 15 mg/L for humans and 10 mg/L for aquatic organisms (Levitskaia et al., 2008) which is below the detection limit for most low cost colorimetric methods. Cr(VI) concentrations above the allowable limit cause cancer in humans and aquatic fauna, and is acutely toxic at much higher concentrations (U.S. EPA, 1978; Federal Register, 2004 A v a i l a b l e a t w w w . s c i e n c e d i r e c t . c o m j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / w a t r e s ARTICLE IN PRESS0043-1354/$ -see front matter ª

Finite difference simulation of biological chromium (VI) reduction in aquifer media columns

“…Cr(VI) has also been known to hinder seed germination and cause morphological changes in plants (James et al, 1984;Towill, 1978). So far, contamination of groundwater resources around mining areas has been shown to exceed the internationally acceptable exposure limit of 0.05 mg•ℓ −1 in a significant number of groundwater resources (Molokwane et al, 2008;Kobya, 2004;Baral and Engelken, 2002).…”

Occurrence and Evaluation of Chromium Reducing Bacteria in Seepage Water from Chromite Mine Quarries of Orissa, India

“…So the correlation appeared to be highly significant. The chromite mine seepage water microflora was dominated by Gram-negative bacteria (nearly 55%) contradictory to the high presence of Grampositive bacteria in areas polluted with metal [25][26][27].…”

“…The identity of which was further confirmed by the Institute of Microbial Technology, Chandigarh, India and was deposited to the Microbial Type Culture Collection as Corynebacterium paurometabolum SKPD 1204 with an accession number MTCC 8730. Further the strain could reduce about 94% of initial 60 µM Cr(VI) in mine seepage water supplemented with VB concentrate (Figure 3 Trehalose + -+ -----+ + Rhamnose -+ + + -+ -+ --Raffinose ----------Mannose --------+ + Arabinose -+ -+ + + -+ + + Cellobiose --------+ + Xylose --------+ + Salicin -------- [27,29]. Thus the combined ability of chromate resistance as well as bioreduction of Cr(VI) to its nontoxic form by C. paurometabolum SKPD 1204 could be useful for detoxification of chromium in chromite mining sites in general and Orissa, India in particular.…”

Aqueous solubility of Cr(VI) compounds in ferrochrome bag filter dust and the implications thereof

“…Treatment of BFD (and indeed any Cr(VI) containing FeCr waste) usually involve the aqueous reduction of Cr(VI) with an appropriate inorganic reducing agent such as Fe(II) (Beukes et al, 2012;Seaman et al, 1999;Buerge and Hug, 1997) and S(IV) (Beukes et al, 2001 and1999), or bacterial reduction (Dhal et al, 2013;Molokwane et al, 2008). Although Cr(VI) can also be reduced with numerous organic compounds (Kassem, 2010;March, 1992), this is usually avoided due to the potential solubilisation of Cr(III) (Beukes et al, 2012;Apte et al, 2006).…”