US20030196803A1

US20030196803A1 - Well evacuator

Info

Publication number: US20030196803A1
Application number: US10/125,812
Authority: US
Inventors: Gordon Kingsley
Original assignee: Individual
Current assignee: Individual
Priority date: 2002-04-18
Filing date: 2002-04-18
Publication date: 2003-10-23

Abstract

The nature of the invention is the use of WELL-EVACUATOR™ to extract and convey polluted liquid and vapor from wells to the surface for separation and treatment. This technology is an alternative to use of conventional well pumps alone or in combination with soil vapor extraction or two phase extraction. Three applications are presented; circulated water supplied as prime mover to eductor(s), compressed air prime mover, and soil vapor extraction blower in combination with WELL-EVACUATOR™. All three rely on use of a prime mover such as water or air supplied to a jet to create a vacuum capable of extracting and conveying water and soil vapor under pressure from a well to separation and treatment equipment at the surface. If the well head is sealed, a vacuum is created in the subsurface enhancing removal of contaminants. These novel applications allow use of commercially available equipment.

Description

BACKGROUND OF THE INVENTION

A method and apparatus for removal of soil gas and groundwater in the subsurface and separation and treatment facilities are disclosed. This invention, WELL-EVACUATOR™, relates generally to a process and apparatus for extraction of liquid and vapor from below surface using an ejector or jet powered by air, steam or water or other prime movers, to entrain and convey vapor and liquid to the surface for separation and treatment. System designs will vary depending on application. As an example, tests were conducted at a gas station in Sebastopol, Calif. In the first test contaminated groundwater was extracted under vacuum from a single and multiple wells using a surface mounted centrifugal pump and eductor. In a second test, an eductor was positioned near the bottom of a well and compressed air was used to extract and convey well water and soil vapor to a separator activated carbon treatment system at the surface.

Removal of liquids and gases from the subsurface has been a continuing problem throughout human history. In the last century a considerable amount of pollutants including gasoline, oil, chlorinated solvents, and volatile organic compounds have found their way into the subsurface at numerous sites. Often these sites are difficult and expensive to remove by conventional means such as excavation of contaminated soil or extraction of groundwater using underground well pumps, followed by treatment (pump and treat). Contaminated sites using pump and treat, such as those found in Santa Clara, Calif. can require over one hundred years to restore at a cost of hundreds of millions of dollars. More reliable and/or robust technologies such as WELL-EVACUATOR™ offer promise for reducing costs and time for restoration of these environmentally distressed properties.

Centrifugal and reciprocating subsurface, well pumps have been successfully used to convey water from the subsurface for centuries. In permeable formations they remain the equipment of choice for many applications. In low permeability formations, low water flows, sediment inclusion and corrosion, often make these pumps expensive to maintain and operate. These problems are compounded by the need to remove soil vapor and groundwater under negative pressure (vacuum) at contaminated sites. Low flows of liquid in combination with low pressure can cause cavitation, overheating, and eventual failure of pumps. Small volume, air operated, reciprocating pumps help reduce these problems however, maintenance and operating costs are still high. Recent advancements such as 2-Phase® Extraction (2PE), and air sparging eliminate the need for subsurface pumps. In 2PE a tube is inserted into the formation and water and soil gas are aspirated to the surface under high vacuum, where it is separated and treated. This technology has been demonstrated to be effective for removal of contaminants in low permeability soils formations such as clays and fine silts. However, due to the complexity and costs for equipment, licensing, operation and maintenance, 2PE is often not selected. Also, energy costs for aspiration of water under vacuum is high, as compared to transport of soil gas and groundwater utilizing WELL-EVACUATOR™ technology. Air injection has also been used successfully at sites. Air is sparged into a well and the air bubbles carry water and soils vapor to the surface where they are separated and treated. High volumes of compressed air are needed and the treatment system costs are proportional to these high volumes. This technology does not provide the higher vacuums possible using SVE or WELL-EVACUATOR™. Therefore application of this technology is limited.

To minimize the deficiencies of conventional technologies the invention, utilizes unique technologies to remove and convey contaminated liquid or vapor or combination thereof to separation and treatment equipment at the surface.

In the first application, an ejector is mounted near the bottom of a well with provision of a conduit for introducing compressed air (or other prime mover) from equipment at the surface. The well is sealed at the top to prevent leakage of outside air into the well. Introduction of compressed air into the ejector creates a vacuum at the inlet initially entraining water that is conveyed to the surface under pressure. In sites having low permeability, such as soils with clay or fine silt, water depth eventually decreases to below the extraction jet inlet allowing both soil vapor and groundwater in combination to be aspirated to the surface. Displacement of the water and vapor creates a vacuum in the well and the surrounding area (area of influence). Air at the surface is drawn into the formation causing volatile contaminants such as gasoline to evaporate and be swept into the well and conveyed to the surface for treatment. Removal of volatile contaminants in the vapor phase is commonly referred to as soil vapor extraction (SVE). This technology is highly effective in removing gasoline from the subsurface especially in combination with groundwater removal.

In a second application, a surface mounted jet pump is utilized to extract contaminated liquid, vapor or combination thereof and convey to separation and treatment equipment. The jet pump is connected to single of multiple wells. A single jet eductor is connected directly to the pump for shallow wells (liquid depth less than 25 feet). Deep wells require a separate eductor for each well be connected to the bottom of each extraction tube with provisions for supplying circulated water. Air separators are installed at the surface to prevent vapor locking the jet pump when the liquid level drops below the extraction tip(s) of any of the wells, allowing the entrance of soil gas.

In a third application, a surface mounted jet pump or compressed air is utilized to remove and convey liquid and small quantities of vapor from the subsurface as described above. A blower or vacuum pump is connected to the top of the well to remove relatively large volumes of vapor.

Each site is unique. Pilot testing is often conducted to determine which application will result in the least cost and health risk required to remove contaminants.

This invention has several advantages. Ejectors have no moving parts. Maintenance is therefore minimal. Air, water and steam are often either existing, on-site or equipment is commercially available. A simple liquid/gas separator followed by activated carbon for is often the only equipment needed for treatment of soil vapor and groundwater prior to discharge. No exotic vacuum pumps, coolers, and related oil separation equipment are needed. No subsurface moving parts to maintain. Controls and maintenance are minimized. Operation is simplified, minimizing labor and training. The combined capital, operating and maintenance savings are often significant in comparison with other available technologies. This invention provides a much needed technology for economic, energy efficient, simplified subsurface dewatering and cleanup of volatile organic compound (VOC) contaminated groundwater and soils.

BRIEF SUMMARY OF THE INVENTION

This invention relates to a vacuum ejector designed to entrain liquid, vapor or liquid and vapor combined from the subsurface and transmit through a conduit to above ground where it can be separated, treated, and discharged as appropriate. The simplicity of an ejector overcomes problems with conventional pumps and vapor extraction systems commonly employed in remediation of contaminated sites or pumps used for dewatering excavations.

An ejector is connected to a source of compressed air (or other prime mover source). The unit is mounted in a conduit allowing enough room for air and gas to flow to the surface in the annular space created between pipes. At the well head, the lines are separated; the compressed air is connected to a compressor, and the liquid vapor line is routed to an air/water separator followed by activated carbon beds. The well head is sealed using a slip connector that allows insertion and positioning of the ejector in the bottom of the well and prevents short-circuiting of atmospheric air.

BRIEF DESCRIPTION OF THE DRAWINGS

To clarify the concept of the invention a brief description of the attached drawings follows. [0012]
FIG. 1 is an elevation section view of an assembled ejector unit constructed in accordance with this invention and inserted into a screened well designed for removal of both contaminated soil gas and groundwater. [0013]
FIG. 2 is an elevation section view of an assembled ejector unit constructed in accordance with this invention and inserted into a screened well designed for removal of groundwater. Soil vapor is removed through a separate conduit at the top of the well and connected to SVE equipment or a separate eductor. [0014]
FIG. 3 is a conceptual drawing of the optional liquid/gas separator and carbon adsorption treatment system. [0015]
FIG. 1A is a prior art section view drawing a 2PE extraction pipe in the bottom portion of a well. [0016]
FIG. 1B is a prior art section view drawing of air sparge pipe in the bottom portion of a well.[0017]

DETAILED DESCRIPTION OF THE INVENTION

Reference FIG. 1: [0018]
An [0019] ejector 26 is mounted inside a conduit 6 with provision for compressed gas or liquid 20. The unit 10 is inserted in screened well 4 with the ejector at or below the water table 18. Slip joint seals 22 prevent outside air from entering well and provide means for adjusting ejector elevation in combination with flexible conduits (such as hose or tubing) 20 and 28. As compressed air flows through the ejector 26 throat, a vacuum is created at the inlet 8 entraining soil gas 14 and groundwater 16 that is discharged from ejector outlet 30 into conduit 6. Gas and liquid travel up conduit 6 to the surface and enter conduit 2 wherein they are routed to gas/liquid separator 40. A mesh pad 50 within the gas/liquid separator 40 entrains and coalesces liquid in the gas stream before exiting the unit. Liquid 54 exits the bottom. Pump 56 circulates portion of water, where applicable, to well eductor. Vapor 52 exits from the top. Activated carbon units 42 adsorb volatile organic compounds (VOC) from liquid and gas streams. Treated ground water 44 and soil gas 46 are discharged to sewer and atmosphere respectively. Dehumidified air 50, produced by expanding compressed air, is blended with soil vapor to enhance adsorption capacity of carbon where applicable.
Reference FIG. 2: [0020]
An [0021] ejector 92 is mounted inside a conduit 95 with provision for compressed gas or liquid 80. The unit 90 is inserted in screened well 86 with the ejector at or below the water table 18. Slip joint seals 88 prevent outside air from entering well and provide means for adjusting ejector elevation in combination with flexible conduits (such as hose or tubing) 94 and 96. As compressed air flows through the ejector throat 92, a vacuum is created at the inlet 98 entraining soil gas 14 and groundwater 16 that is discharged from ejector outlet 93 into conduit 96. Gas and liquid travel up conduit 95 to the surface and enter conduit 84 wherein they are routed to gas/liquid separator 40 and subsequent carbon adsorption system described above.
Reference FIG. 1A: [0022]
In prior art design for air sparging, [0023] compressed air 64 enters conduit 60 and is discharged 62 near bottom of well 66. Gas bubbles rise to the surface in the well and entrain soil gas 14 and groundwater 16. At the surface the soil gas and groundwater travel out the well 70, are collected, separated and treated as appropriate to meet environmental requirements.
Reference FIG. 1B: [0024]
In prior art design for 2PE, [0025] soil gas 14 and groundwater 16 enter well 4 and are aspirated under high vacuum into conduit 30. Conduit 30 is connected to a vacuum system at the surface. Liquid and gas are treated as appropriate to meet environmental requirements.
Groundwater and soils vapor extraction using a down-hole ejector, is a simple solution to an age-old problem. Centrifugal and reciprocating pumps are costly to install, operate and maintain especially in ‘tight’ low permeability formations. An ejector has no moving parts and can run long periods without maintenance or operating over-site. Commercially available, off the shelf, air compressors and ejectors in a variety of sizes are readily available for purchase or lease. Above ground equipment can operate at or above atmospheric pressure eliminating the need for additional pumps. Simple activated carbon systems can often be used to remove many volatile organic contaminants prior to disposal. [0026]
Other possible variations include surface mounted ejector for groundwater extraction. A perfect vacuum is the equivalent of approximately 30′ water column. Therefore for shallow aquifers, ejectors can be mounted directly to a centrifugal or similar pump. Multiple wells can be manifolded to the suction line to the pump to simplify installation, operation and maintenance of an extraction system. [0027]
Another variation is to have two separate ejectors—one for groundwater and a second sized for soil vapor. The groundwater ejector is considerably smaller and mounted near the bottom of the well. The soil vapor ejector is installed at ground level thereby simplifying and reducing piping, costs and energy required. [0028]
Another variation is to connect a blower for removing vapor from the top of the well and using a groundwater ejector mounted near the bottom of the well. [0029]
Another variation is to orient the eductor vacuum inlet along the same axis as the discharge. [0030]
Still another variation is to provide separate piping for prime mover and discharge lines connected to eductor. [0031]
One skilled in the art may appreciate that additional embodiments may be contemplated, including alternative piping and treatment arrangements. [0032]
In the foregoing description, certain terms have been used for brevity, clarity, and understanding, but no unnecessary limitations are to be implied there from beyond the requirements of the prior art, because such words are used for description purposes herein and are intended to be broadly construed. Moreover, the embodiments of the apparatus illustrated and described herein are by way of example, and the scope of the invention is not limited to the exact details of construction. [0033]

Claims

What I claim is:

1) A process for extracting, conveying, separating and treatment of contaminated liquid and vapor from the subsurface which comprises:

a) providing extraction tube(s) in well(s) with jet eductor(s) positioned below or above ground to remove liquid, vapor or a combination thereof, over a portion or the entire length of the well(s);

b) piping, or fittings, and manifolds for supplying prime mover including but not limited to water, air, or steam to eductor(s) within well(s) and collection of liquid and vapor discharged from wells;

c)foot check valve(s) at the end of extraction tube(s) to prevent reversed flow;

d) strainers to prevent check valves from plugging;

e) piping to convey vapor and liquid from eductor to above ground equipment;

f) vessel for liquid/vapor separation;

g) vapor treatment equipment including but not limited to activated carbon, aluminum oxide, molecular sieves, biofilters, catalytic oxidation, combustion;

h) pump(s) for conveying liquid to equipment for storage and treatment;

i) tank for storage of liquid;

j) liquid treatment equipment including but not limited to activated carbon, aluminum oxide, air stripping, combustion, activated sludge, molecular sieves;

k) instrumentation for control and monitoring of process parameters;

l) pumps, boilers, air compressors for supplying prime mover(s);

m) seal(s) at well head(s), boring(s) or opening(s) with provisions for facilitating piping or tubing, so that a vacuum applied within the extraction tube will extract gases and liquids from the subsurface but not above the seal.

2) A process for extracting, conveying, separating and treatment of contaminated liquid and vapor from the subsurface which comprises:

a) providing extraction tube(s) in well(s) with eductor(s) positioned below ground to remove liquid over a portion or the entire length of the well(s). Vapor blower(s), fan(s), eductors or other vacuum devices attached to well head to convey vapor to surface mounted separation and treatment units.

b) piping, or fittings, and manifolds for supplying prime mover including but not limited to water, air, or steam to eductor(s) within well(s);

d) strainers to prevent check valves from plugging;

d) piping to convey vapor and liquid from eductor to above ground equipment;

e) vessel for liquid/vapor separation;

f) vapor treatment equipment including but not limited to activated carbon, aluminum oxide, molecular sieves, biofilters, catalytic oxidation, combustion;

g) pump(s) for conveying liquid to equipment for storage and treatment;

h) tank for storage of liquid;

i) liquid treatment equipment including but not limited to activated carbon, aluminum oxide, air stripping, combustion, activated sludge, molecular sieves;

j) instumentation for control and monitoring of process parameters;

k) pumps, boilers, air compressors for supplying prime mover(s);

l) seal(s) at well head(s), boring(s) or opening(s) with provisions for facilitating piping or tubing, so that a vacuum applied within the extraction tube will extract gases and liquids from the subsurface but not above the seal.

3) A process for extracting, conveying, separating and treatment of contaminated liquid from multiple wells or openings from the subsurface which comprises:

a) providing extraction tubes in wells with jet eductors positioned above ground and manifolded to remove liquid, over a portion or the entire length of multiple wells

b) piping, or fittings, and manifolds for supplying liquid to eductors within wells and collection of liquid and vapor discharged from wells;

d) strainers to prevent check valves from plugging;

e) piping to convey vapor and liquid from eductor to above ground equipment;

f) vessel for liquid/vapor separation to prevent cavitation, loss of prime and/or air locking pump;

g) liquid treatment equipment including but not limited to activated carbon, aluminum oxide, air stripping, combustion, activated sludge, molecular sieves;