Chromium remediation

Mohan, D., et al., 2011. Modeling and evaluation of chromium remediation from water using low cost bio-char, a green adsorbent. Journal of Hazardous Materials 188 (1), 319—333. 

FIGURE 1.9 Five-step batch process for chromium recycling. (From Wang, L.K. et al. Case Studies of Cleaner Production and Site Remediation, Training Manual DTT-5-4-95, United Nations Industrial Development Organization, Industrial Sectors and Environment Division, Vienna, Austria, April 1995.)... 

Biological activity can be used in two ways for the bioremediation of metal-contaminated soils to immobilize the contaminants in situ or to remove them permanently from the soil matrix, depending on the properties of the reduced elements. Chromium and uranium are typical candidates for in situ immobilization processes. The bioreduction of Cr(VI) and Ur(VI) transforms highly soluble ions such as CrO and UO + to insoluble solid compounds, such as Cr(OH)3 and U02. The selenate anions SeO are also reduced to insoluble elemental selenium Se°. Bioprecipitation of heavy metals, such as Pb, Cd, and Zn, in the form of sulfides, is another in situ immobilization option that exploits the metabolic activity of sulfate-reducing bacteria without altering the valence state of metals. The removal of contaminants from the soil matrix is the most appropriate remediation strategy when bioreduction results in species that are more soluble compared to the initial oxidized element. This is the case for As(V) and Pu(IV), which are transformed to the more soluble As(III) and Pu(III) forms. This treatment option presupposes an installation for the efficient recovery and treatment of the aqueous phase containing the solubilized contaminants. 

U.S. EPA, Permeable Reactive Subsurface Barriers for the Interception and Remediation of Chlorinated Hydrocarbon and Chromium (VI) Plumes in Ground Water, Technical Report EPA-600-F-97-008, U.S. EPA, Washington, 1997. 

Srinath T, Verma T, Ramteke PW, Garg SK (2002) Chromium biosorption and bioaccumulation by chromate resistant bacteria. Chemosphere 48 427-435 Stephen JR, Macnaughton SJ (1999) Developments in terrestrial bacterial remediation of metals. Curr Opinion Biotechnol 10 230-233 Tabak HH, Lens P, van Hullebusch ED, Dejonghe W (2005) Developments in bioremediation of soils and sediments polluted with metals and radionuclides 1. Microbial processes and mechanisms affecting bioremediation of metal contamination and influencing metal toxicity and transport. Rev Environ Sci Bio/Technol. 4 115-156... 

Davis A, Olsen RL (1995) The geochemistry of chromium migration and remediation in the subsurface. Ground Water 33 759-768... 

Bacteria indigenous to Cr(VI)-polluted areas are Cr(VI) tolerant and/or resistant and have been considered as potential candidates for bioremediation of Cr(VI)-contaminated sites.16 However, the ability of bacteria to reduce Cr(VI) to the less-toxic Cr(III) compounds may produce reactive intermediates (such as Cr(V), Cr(IV), radicals), which are known to be active genotoxins and are likely to be carcinogenic.17 Therefore, the formation and lifetimes of Cr(V) intermediates, produced via bacterial reduction of Cr(VI), need to be evaluated carefully if microorganisms are to be employed as a means for remediation of chromium-polluted subsurface environments. Similarly, Cr(V) accumulation should first be monitored when considering plants and algae as biosorption materials for the bioremediation in the event of chromium pollution.18... 

Laboratory studies indicate that aquathermolysis can be used to aid in the remediation of waste oils, chromium (Cr VI) and volatile organic compounds (VOCs) in contaminated soils and aquifers. Aquathermolysis is particularly useful in lowering the viscosity of oil and increasing its mobility to facilitate further treatment. Potential applications range from treating household and industrial refuse to destruction of chemical warfare agents. 

The groundwater at the 2-acre Avco Lycoming Superfund site in Williamsport, Pennsylvania, was contaminated with chlorinated solvents, cadmium, and hexavalent chromium. Following a successful pilot-scale demonstration that lasted from 1995 through 1996, the technology was applied on a fuU-scale. The cost of the pilot-scale demonstration was approximately 145,000. The full-scale remediation system cost about 220,000 to construct. Operation and maintenance costs have been approximately 50,000 per year (D210571, p. 93 D213376, p. A-47). 

The ARS Technologies, Inc., Ferox process is an in situ remediation technology for the treatment of chlorinated hydrocarbons, leachable heavy metals, and other contaminants. The process involves the subsurface injection and dispersion of reactive zero-valence iron powder into the saturated or unsaturated zones of a contaminated area. ARS Technologies claims that Ferox is applicable for treating the following chemicals trichloroethene (TCE), 1,1,1-trichloroethane (TCA), carbon tetrachloride, 1,1,2,2-tetrachloroethane, lindane, aromatic azo compounds, 1,2,3-trichloropropane, tetrachloroethene (PCE), nitro aromatic compounds, 1,2-dichloroethene (DCE), vinyl chloride, 4-chlorophenol, hexachloroethane, tribromomethane, ethylene dibromide (EDB), polychlorinated biphenyls (PCBs), Freon-113, unexploded ordinances (UXO), and soluble metals (copper, nickel, lead, cadmium, arsenic, and chromium). 

The process can be used to treat dissolved metals and is commonly used in groundwater treatment for the reduction and precipitation of hexavalent chromium, as well as in the oxidation of cyanide wastes (at concentrations up to 10%). Other potential applications of electrochemical treatment include remediation of arsenic, cadmium, molybdenum, aluminum, zinc,... 

At the Coast Wood Preserving, Inc., Superfund site (Ukiah, California), the technology was used to remove metal contamination to comply with both state and federal cleanup standards [50 parts per billion (ppb) arsenic, 50 ppb chromium, and 1 ppm copper]. The estimated total cost for the source control component of the remedy was 1,000,000, and the estimated total operational and maintenance costs was estimated to be 19,500 for a 20-year period (D16888B, p. 3, Report Documentation p. 2). 

In 1991, an EXXFLOW/EXXPRESS system was combined with an air stripper to remediate groundwater contaminated with chromium and trichloroethene (TCE) beneath an abandoned manufacturing plant in Newbury Park, California. System equipment cost approximately... 

Fluor Daniel GTl, Inc. (now part of the IT Corporation), has developed in situ geochemical fixation technology to immobilize metallic contaminants in soil, sediment, sludge, and groundwater. The technology uses a site- and contaminant-specific combination of reagents to convert ionic contaminants to less soluble forms. In situ geochemical fixation has been used to remediate sites contaminated with chromium, uranium, molybdenum, and copper. 

In 1997, it was reported that the vendor was using in situ geochemical fixation to remediate a Midwestern wood treatment site contaminated with chromium. The cleanup is expected to last for 2 years and cost approximately 600,000. The vendor states that treating the site by conventional pump-and-treat technology would have taken more than a decade to complete and would have cost far more (D16925Z, p. 1). 

Remediation of groundwater containing soluble metals such as chromium,... 

Reductive biotransformation of a contaminant can occur when the contaminant serves as the terminal electron acceptor. Many contaminants that are recalcitrant to bio-oxidation will undergo reductive biotransformations. These biotransformations can lead to detoxification, mineralization, or changes in the mobility of the targeted contaminant. Hexavalent chromium and tetra-chloroethene (PCE) have been investigated as candidates for reductive biotransformation. This technology may be most applicable for in situ remediation for the following scenarios PCE contamination, low-yield aquifers, areas contaminated by both alkylbenzenes and chlorinated ethenes, and deep aquifer contamination. 

Versar, Inc., has developed a method for the ex situ remediation of soils contaminated with hexavalent chromium. In this process, soil is mixed with a sodium bisulfite solution to chemically reduce the chromium to the less toxic trivalent form. 

Mohan, D. and Ch. U. Pittman. 2006. Activated carbons and low cost adsorbents for remediation of tri- and hexavalent chromium from water. J. Hazard. Mater. B 137 762-811. 

James BR. The challenge of remediating chromium-containing soil. Environ Sci Technol 1996 30 248A-251A. 

The microbial reduction of chromium(VI) to chromium(ni) has been discussed as a possible remediation technique in heavily contaminated environmental media or wastes (Chen and Hao 1998). Factors... 

Remedial investigations and feasibility studies conducted at the NPL sites contaminated with chromium will add to the available database on exposure levels in environmental media, exposure levels in humans, and exposure registries, and will increase current knowledge regarding the transport and transformation of chromium in the environment. No other long-term research studies regarding the environmental fate and transport of chromium, or occupational or general population exposures to chromium were identified. 

EPA. 1984c. Health effects assessment for hexavalent chromium. Report to Office of Emergency and Remedial Response, U.S. Environmental Protection Agency by Environmental Criteria and Assessment Office, U.S. Environmental Protection Agency, Cincinnati, OH. ECA0-CIN-H019. 

James BR, Petura JC, Vitale RJ, et al. 1997. Oxidation-reduction chemistry of chromium Relevance to the regulation and remediation of chromate-contaminated soils. Journal of Soil Contamination 6(6) 569-580. 

Palmer CD, Wittbrodt PR. 1991. Processes affecting the remediation of chromium-contaminated sites. Environ Health Perspect 92 25-40. 

Remediation options for the treatment of electroplating and leather tanning effluent containing chromium -A review. Miner. Proc. Extractive Metall. Rev., 2, 99-130. 

Quantitative chromium solid-state speciation in chromite ore processing residue (COPR) has defined the mineral species and the processes controlling the retention and release of Cr(VI) from CO PR-contaminated sites (Hillier et al, 2003). Information that, used within a process-based modelling framework, has helped to predict the impact of changes in physicochemical conditions on the COPR, to test the extent to which the system may be considered at equilibrium and that, therefore, need to be considered within the context of informed remediation (Geelhoed et al, 2001). 

Johnson, C.R. et al., Colloid mobilization in the field using citrate to remediate chromium, Ground Water, 39, 895, 2001. 

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