Liquid purification or separation – Processes – Including geographic feature
Patent
1992-05-26
1993-11-30
Silverman, Stanley S.
Liquid purification or separation
Processes
Including geographic feature
210757, 210763, 210908, 210909, 210170, C02F 170
Patent
active
052662136
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a procedure for cleaning groundwater, being groundwater which is permeating through an aquifer, that has been contaminated with chlorinated or halogenated organic compounds such as solvents, or pesticides.
The invention is concerned with groundwater in its native aquifer, the term aquifer being used herein in its broad sense to signify any in-ground geological formation containing water, including sand and gravel, broken rock, etc, and is not intended to be limited only to those formations which yield a water supply.
Industrial solvents such as carbon tetrachloride, trichloroethane, tetrachloroethylene, and also PCB, and chloroform, can be highly toxic and carcinogenic, in groundwater. In drinking water, only tiny concentrations, as measured in the parts-per-billion range, of such contaminants are permitted.
BACKGROUND TO THE INVENTION
The conventional procedures for cleaning groundwater that has been contaminated with such chlorinated solvents have generally not involved the chemical breakdown of the contaminant, but have merely removed the contaminant from the water. For example, it is known to pass the water over activated carbon, whereby the contaminants are adsorbed onto the carbon. Whilst this is effective to clean the water, the contaminants remain on the carbon: this creates in turn another disposal problem.
Since, as a general rule, the contaminants are volatile, they may also be removed by air-stripping. The water is aerated, which cleans the water, but the problem again remains that the contaminants still exist. It is becoming increasingly unacceptable simply to discharge the contaminated air into the atmosphere, so that the contaminants once again have to be removed, for example by sorbtion onto activated carbon.
An alternative conventional procedure does break down chlorinated contaminants. This procedure involves catalytic oxidation at an elevated temperature; though very expensive, the procedure breaks the contaminants down into carbon dioxide and an appropriate chloride, which is harmless in small concentrations. The procedure is usually out of the question on cost grounds, for a drinking water supply.
In U.S. Pat. No. 4,382,865 (SWEENY, May 10, 1983) there is disclosed a system for treating the effluent created during the manufacture of halogenated pesticides. Here, the effluent water stream, containing the waste material from the pesticide manufactory is passed over a combination of metals, and it is the fact of the combination which is instrumental in causing the breakdown of the halogenated contaminant.
The present invention is concerned, like Sweeny, with removing halogenated contaminants from water; unlike Sweeny, the invention is concerned with removing halogenated contaminants, particularly solvents, from groundwater that is permeating through its native aquifer. It is recognised, in the invention, that a key aspect of such groundwater is that, unlike a factory effluent, groundwater can be expected, as a general rule, to be substantially oxygen-free.
It is recognised, in the invention, that the chemical break-down of halogenated contaminants in in-ground groundwater can be effected much more cheaply than is suggested by the prior art, by using, for example, materials that can be obtained, in the quantities needed, as a discarded by-product from metal-cutting processing.
GENERAL FEATURES OF THE INVENTION
In the invention, the water containing the halogenated organic contaminants is placed under, and held for a substantial period under, or remains under, highly reducing conditions, and the groundwater is brought into intimate contact, during the said period, with a metal. It is thought that under those conditions the chlorine (or it may be another halogen) ion in the organic material can be replaced by a hydroxide ion, whilst the released chloride ion remains in solution. The chloride remains in the water, or it may be precipitated out, at concentrations that usually are well below the permitted limits for inorganic chlorides.
Thus, the organic molecule
REFERENCES:
patent: 2758084 (1956-08-01), Deyrup et al.
patent: 3640821 (1972-02-01), Sweeney
patent: 3737384 (1973-06-01), Sweeney
patent: 4219419 (1980-08-01), Sweeney
patent: 4382865 (1983-05-01), Sweeney
patent: 4401569 (1983-08-01), Shaveri et al.
patent: 4417977 (1983-11-01), Pytlewski
patent: 4430208 (1984-02-01), Pytlewski
patent: 4460797 (1984-07-01), Pytlewski
patent: 4471143 (1984-09-01), Pytlewski
patent: 4523043 (1985-06-01), Pytlewski
patent: 4591443 (1986-05-01), Brown et al.
patent: 4664809 (1987-05-01), Fenton et al.
patent: 4789486 (1988-12-01), Ritter
patent: 5057227 (1991-10-01), Cohen
Chemical Abstracts, vol. 103, No. 22, 2 Dec. 1985 (Dombush Treatment of Leachate . . . ).
Asquith Anthony
Nessler Cynthia L.
Silverman Stanley S.
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