Reduction of soil contamination

Details Reduction of soil contamination Reduction of soil contamination

2001-07-02

2002-12-24

Shackelford, Heather (Department: 3673)

Hydraulic and earth engineering

Soil remediation

In situ contaminant removal or stabilization

C405S128150, C405S128450, C172S146000, C172S151000

Reexamination Certificate

active

06497534

ABSTRACT:

BACKGROUND OF THE INVENTION
This invention relates generally to clean up of hydrocarbon polluted soil and more particularly to dispersing of microbes into hydrocarbon pollutant-containing soil to reduce pollutant levels.
Hydrocarbon pollution occurs in many ways, and areas, among which are the following:
1) spillage into the ground as at gasoline service stations (i.e. from rusted tanks, etc.); and
2) leakage into the ground, i.e. formation, at or near oil wells.
Cleanup of such hydrocarbon pollutants is difficult, time consuming and expensive. While microbes have been employed to consume hydrocarbons, it is difficult to deploy the microbes, accurately and in sufficiently quantity into polluted in situ soil.
There is need for improved methods and apparatus to rapidly and effectively treat soil so as to overcome hydrocarbon pollution in soil.
SUMMARY OF THE INVENTION
It is a major object of the invention to provide improved methods and apparatus to meet the above need. Basically, the improved method of treating hydrocarbon contamination in soil includes the steps:
a) providing and operating a rotary tiller having tilling spaces or elements that rotate into and out of the soil to till and loosen the soil, and to elevate or impel soil upwardly so that loosened elevated soil than drops downwardly, and becomes aerated,
b) and dispersing into the soil aqueous streams that contain microbes characterized as reacting with hydrocarbons in the loosened soil to produce CO
2
and water, thereby to decontaminate the soil.
Typically, soil to be treated extends generally horizontally, and the rotating tiller is traveled generally horizontally or parallel to the exposed soil surface to progressively till the soil, and also throwing it upwardly for aeration, while the aqueous streams of microbes are dispersed into the loosened and rising or falling soil. The contaminated soil may have originated underground, as for example at a gasoline or hydrocarbon fuel filling station, and such soil is removed and spread out for treatment.
Dispersing of the aqueous streams of microbes may be effected in the path of tiller travel, or at the successive locations of the tiller; and ducting may be provided at tiller rotary arms to be ejected up and down, forwardly and rearwardly, into soil being tilled and rising and falling; and other ducting may be provided in closely spaced relation to the traveling tiller, and from which such aqueous streams of microbes are ejected onto soil to soak the soil being tilled or to be tilled as referred to.
Ducting at the rotating arms typically communicates with the rotary backsides of the arms from which said streams are ejected into the soil being tilled and aerated.
The tiller arms preferably have terminals which extend sidewise or laterally to act as knives or spades and elevators to cut into and elevate soil, aqueous streams being ejected at locations on the arms at spaced locations from such terminals.
A further object includes allowing said microbes to consume the hydrocarbon in the aerated soil, thereby to de-contaminate the soil.
An additional object includes returning the de-contaminated soil to underground locations from which contaminated soil has been removed.
Another object includes rotating the tiller at speeds above 300 to 1000 revolutions per minute, to obtain rapid lifting of the soil, for aeration; and ejecting the microbe streams at pressures above about 100 psi, to obtain sufficient penetration into the soil being tilled and elevated, and added displacement of such soil.
These and other objects and advantages of the invention, as well as the details of an illustrative embodiment, will be more fully understood from the following specification and drawings, in which:


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