Plant husbandry – Process
Reexamination Certificate
1998-11-17
2001-03-27
Campell, Bruce R. (Department: 1661)
Plant husbandry
Process
C111S200000, C210S668000
Reexamination Certificate
active
06205708
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention is directed to phytoremediation in general, and more specifically to incorporating the use of a remediation-assisting or treatment material within a vegetation remediation system in order to enhance the remediation of contaminated soil and groundwater in the vicinity of the vegetation.
Phytoremediation refers to the use of vegetation in the remediation of contaminated soil and groundwater. It is emerging as the remediation technology of choice when it is feasible to use as a primary or secondary system. The natural ability of vegetation to clean contaminants from soil and groundwater is of great benefit to the environment and society. It is effective and relatively inexpensive to use and the natural setting created by it renders this technology highly desirable.
U.S. Pat. Nos. 5,829,191 and 5,829,192 to the inventor herein disclose unique phytoremediation techniques, as does U.S. Provisional Application Ser. No. 60/066,678, filed Nov. 26, 1997 and Ser. No. 60/075,473, filed Feb. 20, 1998. These techniques improve the remediation of contaminants by vegetation by increasing effectiveness and/or decreasing expense. These patents and applications are incorporated herein by reference as if fully set forth.
Of course, remediation technologies and techniques other than phytoremediation must also be considered as well. Many other technologies and techniques remain effective, inexpensive and in some applications necessary.
By way of example, U.S. Pat. No. 5,266,213 to Gillham describes a technique for treating contaminated groundwater in an aquifer, i.e, water from deep underground, by excavating a trench with a trench-cutting machine and placing a homogeneous mixture of sand and iron filings in the trench. The permeability of the iron-sand mixture should not be lower than that of the aquifer itself so that the flow of water is not impeded by the mixture. The iron must be placed in the trench so that no oxygen can reach it, thus the iron must be buried within the trench. Otherwise, accessibility to oxygen will rust the iron and it will become ineffective to promote the breakdown of contaminants. The iron must be exposed to the groundwater for a “residence time,” about one to two days. Alternatively, a tank or pond is provided at the surface of the remediation site, and contaminated groundwater is drawn out of the soil by means of a pump and fed into the pond which contains a body of iron filings or a mixture of iron fillings and sand. In either arrangement, the water slowly percolates through the iron fillings of the mixture for the residence time, and certain contaminants-halogenated-are broken down chemically.
The techniques in the Gillham patent require considerable labor, and the results and applications are limited. By way of example, it may be difficult to match the aquifer flow characteristics to prevent blockage or to channel for possible redirection of the groundwater flow. Also, there is a potential for the iron to transform and cause secondary reactions in the barrier wall or downgradient from the barrier wall that may cause the aquifer to become clogged, become contaminated with elevated levels of iron in solution or cause other reactions to occur that might prove deleterious. Moreover, there may be incomplete contaminant degradation. The Gillham system relies on the need to provide an adequate residence time for total degradation of the halogenated compounds. If that residence time changes because of changes in the groundwater flow or the physical or chemical dynamics of the iron barrier, an incomplete reaction could occur that would allow derivative contaminants to escape the iron barrier. Such derivative contaminants (e.g., vinyl chloride) could be more toxic than the contaminants which were to be treated.
The present invention marries the phytoremediation technology with other technologies for remediating contamination in soil and groundwater. In doing so, a single system can be more effective in remediating at least particular contaminants. Those contaminants not necessarily removed by any of the discrete technologies can through the use of the techniques in accordance with the present invention be removed or at least substantially removed.
SUMMARY OF THE INVENTION
The present invention relates to a method for using a tree to pump contaminated groundwater to a treatment area at which a treatment material, structure or device (broadly, “a treatment expedient”) is provided to treat a contaminant, and apparatus therefor. The treatment area is at least in the area directly below or around the base of a tree, typically in or around the location of the hydraulic gradients created by the root system of a tree. The treatment expedient is disposed in and around the treatment area.
The treatment expedient used is any material or structure or device useful for the treatment of contaminants or target contaminants or for preparing contaminated water for remediation by a tree. Of course, any combination of materials, structures or devices can also be used as a treatment expedient. Treatment materials can remediate by microbial reaction, or chemical or physical reaction (including a catalytic or bonding action). Examples of treatment materials include zero valence iron, iron or other metal filings, powder or the like, ceramics impregnated with microbes, iron sesquioxide, organic compost materials (such as sphagnum peat) or a reed sedge peat, activated carbon and ion exchange resins. The treatment material could be a combination of different materials, such as sand and iron filings. A zero valence iron can treat chlorinated hydrocarbons, and other materials can be used to treat petroleum hydrocarbons, uranium and many other contaminants.
Treatment structures and devices could include the physical manipulation of the treatment area and the contaminated water therein, for instance air sparging which would remove volatile compounds (that would have to be vented out perhaps at the top of the hole) and/or oxygenate the water for improved root adsorption. Electro-osmosis or electro-ultra-filtration or other known means for electrically moving and/or separating polar compounds in solution might be used in extracting or moving specific molecules in the groundwater. These include any electrolysis type of treatment, such as those which separate H
2
O into H and O
2
gases. For example, soluble lead could be drawn to the area of the roots by such a method.
Other contaminants that might prove phytotoxic could be drawn to a collection vessel (e.g., ultrafiltration) for selective removal. Such contaminants would thus be kept from the tree at least substantially so that the health of the tree could be maintained for the remediation of other contaminants. A small pump might also be used to assist in moving water through a packed resin column or column-like structure, or otherwise assist in moving water. Water from a deep aquifer might be moved to a location closer to the root system so that the root system could effectively or more effectively use the water. In such a situation, a cost-effective pump could be used since pumping will not be required for a great distance. In other applications, pumps might be used to take water away from an aquifer or tree-created reservoir, perhaps because the tree is not eliminating enough water or in order to bring that water for other processing.
Each of these treatment expedients provide a means of some treatment of contaminants or target contaminants. Of course, any type of expedient which facilitates the remediation of contaminants, whether the same contaminants to be remediated by the vegetation or other contaminants, can be used together with the vegetation in accordance with the present invention.
In a preferred embodiment, the treatment expedient is a treatment material. In a further preferred embodiment, the material is a zero valence iron. It is disposed in and/or around the treatment area which is in the vicinity of the root system of a tree. The root system of the tree increases the hydraulic gradient at
Campell Bruce R.
Grunberg Anne Marie
Lerner David Littenberg Krumholz & Mentlik LLP
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