Liquid purification or separation – Processes – Treatment by living organism
Patent
1996-10-03
1998-11-24
Woo, Jay H.
Liquid purification or separation
Processes
Treatment by living organism
210610, 210631, 210717, 210719, 210724, 210747, 210909, 210912, 405128, 4352625, C02F 330
Patent
active
058401911
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a process for the treatment of contaminated material, in particular a process for the treatment of organic and metal, especially heavy metal, contaminants in bulk particulate material such as land or soil using biochemical processes.
BACKGROUND OF THE INVENTION
World-wide, substantial amounts of land have been contaminated with both organic and inorganic substances as a result of industrial, waste disposal and other activities. Examples of such contaminants include: toxic heavy metals including mercury, cadmium, barium and lead, radionuclides such as actinides and fission products and organic pollutants such as btex (benzene, toluene, ethylbenzene and xylene), PAHs (polyaromatic hydrocarbons), polychlorinated biphenyls (PCBs) and dioxins. Such contaminants can pose a significant threat to ground water and therefore drinking water supplies and in many cases either limit, or prevent land re-use. Additionally, as a result of recent legislation in the United States of America and likely similar legislation within the European Community and elsewhere, waste producers are becoming increasingly liable to prosecution and to meet the costs of recovery and clean up if they do not act responsibly towards their wastes. Consequently there is a growing need for technologies which can solve the problem of contaminated land.
To date, a number of techniques have been developed to remediate contaminated land. Examples include: soil stabilization, electromigration, vitrification, volatilization, incineration, soil washing, pump and treat systems, land farming, slurry phase bioremediation etc. Many of these known techniques possess several limitations including: material to a toxic landfill, or entrapment within matrixes possessing a limited life; contaminated land in the case of current biological processes; e.g. soil stabilization and incineration; particular site, e.g. as in the case of incineration or soil washing; when applied to metals.
SUMMARY OF THE PRESENT INVENTION
The present invention seeks to address these problems by enabling biological systems to remediate metal and organic contaminated media such as land non-specifically.
According to the present invention a process for the decontamination of a medium comprising a material contaminated with one or more organic species and one or more metal species comprises the steps of treating a body of the said medium by a process which breaks down the organic contaminant(s) by or through the action of microbial agents followed by treating the same body with microbially produced sulfuric acid so as to solubilize and leach the metal species as a metal sulfate; and treating the leached metal sulfate by a bioprecipitation process which converts the said sulfate to one or more insoluble metal sulfides. Desirably, the process also includes the following steps: reusable source of sulfur containing ingredient.
In the said process organic contaminants may also be broken down by the action of microbially produced sulfuric acid in the second (metal species removal) stage of the process.
In the first or organic degradation stage of the process the pH of the medium being treated is desirably in the range 4 to 9. The micro-organisms which break down the organic compounds may be present in the said medium as naturally occurring species, e.g. as bacteria present in soil, or cultures of them may be added to the said medium. In either case, nutrients are desirably fed to promote the activity of the appropriate species. The microbial consortia employed will depend upon the type of organic contaminant present, which may be determined by prior analysis of the said medium, and the nutrients will be selected accordingly. The enrichment of the medium by addition of different types of micro-organism to break down the organic contaminants present is described further below.
The organic contaminants may comprise, for example, benzene, toluene, other aromatic compounds, PAHs or any of the other common organic contaminants referred to abov
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British Nuclear Fuels PLC
Morrison Betsey J.
Woo Jay H.
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