Abstract:
A bioremediation method and system for destroying of reducing the level of contaminants in a contaminated subterranean body of water includes a plurality of spaced injection sites. The injection sites extend below ground and intersect a body of groundwater. Each of the plurality of injection sites are in communication with a supply of concentrated oxygen. The oxygen is conveyed by a delivery mechanism from the supply of oxygen to the injection points to naturally reduce the contaminants in the groundwater.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present invention claims priority from U.S. Provisional Application No. 60/296,540, entitled “Direct Oxygen Injection Technology Systems”, filed Jun. 6, 2001 and U.S. Provisional App. Ser. No. 60/296,528, entitled “Enhanced Dissolved Oxygen Technology Systems”, filed Jun. 6, 2001. 
    
    
     TECHNICAL FIELD 
     The present invention relates generally to a method and system for reducing the level of contaminants in a body of groundwater and more particularly to a bioremediation method and system for groundwater treatment. 
     BACKGROUND ART 
     Groundwater contamination, typically arising from petroleum storage tank spills or from intentional or accidental discharge of liquid hydrocarbons or compositions containing same, has become a problem of increasing concern. This type of contamination occurs not only at industrial complexes, but also in suburban neighborhoods, which would appear to be havens from such phenomena. The source of contamination in suburban neighborhoods or areas is very commonly automobile service station sites at which antiquated or abandoned storage tanks have released gasoline, fuel oils, lubricants, and the like into the local groundwater. Other common sources of such noxious materials can include dry cleaning establishments and/or manufacturers or distributors of the tetrachloroethane which is used in the dry cleaning process. 
     Various remediation techniques have been utilized in the past for the treatment of contaminated groundwater in order to reduce or eliminate the contaminants. One of the most widely used systems is one based on so-called “pump and treat” technology. These systems withdraw the contaminated groundwater and a phase-separated product from a recovery well located in the groundwater and pump it to an above ground treatment facility. Thereafter, various treatment techniques, as are well known, are used to remove contaminants from the displaced groundwater. These “pump and treat” systems are relatively expensive to install and require that the remaining contaminants, which have been separated from the groundwater, be disposed in an environmentally friendly manner. These processes further increase the cost of the techniques. 
     One example of a known remediation system is disclosed in U.S. Pat. No. 5,286,141. The &#39;141 patent teaches oxidizing the source of groundwater contamination to harmless constituents by locating a plurality of mutually spaced wells into a groundwater region. A treating flow of hydrogen peroxide solution is provided into the groundwater from one or more wells. The treating flow typically contains reaction surface enhancing reagents, which provide increased surfaces at which the reaction between the hydrogen peroxide and the hydrocarbon contaminants may occur. Further, a catalytic agent is also preferably incorporated into the treating solution or as a pre-injection into the groundwater region to promote the desired reaction between the hydrogen peroxide and hydrocarbons. 
     Recently, there has also been increasing interest in bioremediation technology. However, its use in treating groundwater has been relatively ineffective due to the complexity of the procedures and equipment required, including expensive and complex reactors. Moreover, current bioremediation techniques can cause adverse geochemical reactions and can introduce new toxic compounds into the groundwater. Additionally, current bioremediation systems, still require the use of non-organic catalysts or additives to cause the process to be completed in a reasonable period of time. These catalysts or additives raise other contaminant issues with respect to the groundwater. 
     It is known that naturally growing bacteria in the groundwater can break down groundwater contaminants. However, these bacteria feed off oxygen and the lack of oxygen is the single biggest limiting factor on the growth of the bacterial population and therefore contaminant decrease. Ambient air, which is comprised of about 21% percent oxygen, only results in approximately 10-12 ppm of dissolved oxygen in the groundwater and thus is not sufficient to adequately destroy or reduce contaminants. Various attempts to increase the amount of oxygen by utilizing oxygen releasing compounds have been tried, but these oxygen releasing compounds, such as magnesium peroxide or calcium peroxide are expensive. Further, these oxygen releasing compounds only produce a small amount of usable oxygen and therefore do not significantly increase the bacterial population. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the present invention to provide a bioremediation method and system for groundwater treatment that is more effective than prior bioremediation systems. 
     It is another object of the present invention to provide a bioremediation method and system for groundwater treatment that is less expensive than prior bioremediation systems. 
     It is still another object of the present invention to provide a bioremediation method and system for groundwater treatment that treats contamination naturally and effectively. 
     It is still another object of the present invention to provide a bioremediation system that is relatively easy and inexpensive to install and operate. 
     It is a related object of the present invention to provide a bioremediation system that can be installed with minimal site disturbance. 
     In accordance with the above and other objects of the present invention a bioremediation method and system is provided. The method includes providing a plurality of injection points extending from above ground to a subterranean body of groundwater. Substantially pure oxygen is delivered to the plurality of injection points and into the subterranean body of groundwater until the level of contaminants in the groundwater is reduced or eliminated. 
     The system includes a plurality of injection points extending below ground such that they intersect a body of groundwater. The plurality of injection points are in communication with a supply of concentrated oxygen. The concentrated oxygen is conveyed to each of the plurality of injection points and into the groundwater. The system includes at least one monitoring well for evaluating the level of contaminants in the groundwater. 
    
    
     The above objects and other objects, features and advantages of the present invention will be apparent from the following detailed description of best made for carrying out the invention to be taken in connection with the accompanying drawings and appended claims. 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic illustration of a direct oxygen injection bioremediation system in accordance with a preferred embodiment of the present invention; 
     FIG. 2 is an illustration of a flow meter of the system of FIG. 1 in accordance with a preferred embodiment of the present invention; and 
     FIG. 3 is a schematic illustration of an exemplary direct oxygen injection bioremediation system installation in accordance with a preferred embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to FIG. 1 which illustrates a bioremediation system  10  in accordance with the present invention. The preferred bioremediation system  10  is preferably used to clean up biodegradable petroleum constituents that are present in contaminated groundwater. However, it should be understood, that the system  10  can be used to clean up other contaminates or constituents in groundwater and that the system may be used for a variety of other purposes. 
     The preferred bioremediation system  10  preferably includes a source of oxygen  12 , such as a liquid oxygen tank. However, the oxygen can be provided in a variety of other forms. While the source of oxygen is preferably pure, it can also be of sufficient purity to accomplish the objectives of the present invention. For example, a source of oxygen that has over 50% oxygen may also be sufficient. The source of oxygen  12  is preferably in communication with a control panel  14  to regulate the flow of oxygen from the oxygen source  12 . The oxygen that flows to the control panel  14  is then conveyed to a plurality of injection sites  16  in a subterranean body of groundwater, generally indicated by reference number  18 . The location of the injection sites  16  can be determined in a variety of ways, as discussed below. 
     The source of oxygen  12  is preferably coupled to the control panel  14  by a pressure hose  20  in order to convey the oxygen thereto. The pressure hose  20  has a first end  22  that is connected to the source of oxygen  12  and a second end  24  that is connected to the control panel  14 . The source of oxygen  12  has a shut off valve  26  associated therewith and located between the source of oxygen  12  and the first end  22  of the pressure hose  20 . The shut off valve  26  allows the flow of oxygen from the source of oxygen  12  to the pressure hose  20  to be manually closed as desired. It should be understood that the valve can also be electronically controlled. The second end  24  is preferably connected to a pressure regulator  28  which allows the pressure of oxygen exiting the source of oxygen  12  to be controlled. In the preferred embodiment, the pressure regulator  28  is set such that the pressure of oxygen exiting the oxygen source  12  is set for example, at 100 psi. It should be understood that the pressure regulator  28  can be adjusted to regulate the flow of oxygen to a variety of different pressures. 
     The oxygen that exits the pressure regulator  28  enters a first conduit  30 , which conveys the pressure regulated oxygen to an oxygen header pipe  32 . The oxygen header pipe  32  has a plurality of flow meters  34  connected thereto and in fluid communication therewith. The pressure regulator  28 , the first conduit  30 , the oxygen header pipe  32  and the plurality of flow meters  34  are all preferably disposed within the control panel  14  and the control panel  14  is preferably mounted to a fence, wall or other structure  35 . However, more or less items may be included in the control panel  14 . The flow meters  34  regulate the flow of oxygen from the header pipe  32  to a respective outlet tube  36 . Each outlet tube  36  is in communication with an injection tube  38  that terminates at a respective one of the plurality of injection sites or points  16 . Accordingly, the number of flow meters  34  that are utilized in a particular system will depend upon the number of injection sites that are determined to be necessary to clean up the groundwater at a given location. The conduits, pipes, tubes, and injection points are preferably constructed of PVC piping. The outlet tube  36  is preferably ¼ inch tubing and the injection tubes  38  are preferably ½ inch tubing. The size and material of the pipes and tubes can obviously vary. 
     As shown in more detail in FIG. 2, each flow meter  34  is preferably connected to the oxygen header pipe  32  by a compression fitting  40  that allows oxygen at the regulated pressure to be delivered thereto. Each flow meter  32  is preferably mounted to a mounting board  42  or other structure in the control panel  14  and includes a pressure indicator  44  that provides a visual indication of the pressure of fluid flowing therethrough. The outlet tubes  36  that are in communication with the outlet of the flow meters  34  preferably extend through a protective conduit  46  (FIG. 1) which extends from the control panel  14  into the ground. The protective conduit  46  acts to shield and protect the outlet tubing  36 . The outlet tubing  36  is preferably located at least one foot below the ground and runs generally parallel thereto. The injection tubing  38  in communication with the outlet tubing  36  extends generally perpendicularly downward from the outlet tubing  36 . As shown, the outlet tubing  36  intersects the groundwater  18  below the water table at designated injection sites  16  in order to deliver the pure oxygen thereto. 
     It has been determined that pure oxygen works to clean up contaminants in a body of groundwater more efficiently than ambient air and more efficiently and at less cost than various oxygen releasing compounds. By increasing the amount of dissolved oxygen, it has been found that the bacterial population increases by over a magnitude of a thousand. The issue thus becomes how to deliver the pure oxygen into the ground and into communication with the groundwater. In accordance with the present invention, the preferred way is through the delivery system described above. Moreover, other delivery systems for conveying the oxygen to the injection sites may also be utilized. 
     However, in the preferred embodiment, a plurality of injection tubes  38  are utilized to convey the pure oxygen from the source  12  to the injection sites  16 . While the source of oxygen  12  is preferably initially in liquid form, the pressure in the source  12  causes the liquid to turn to vapor. It is the pure oxygen vapor that is captured and then delivered through the delivery system. The injection points  16  and the injection tubes  38  can be installed by any of a variety of methods, including typical hollow stem auger with sand backfill. This is primarily for sites interbedded with clays and sites. Alternatively, the injection tubes  38  may be installed by known GeoProbe® (GeoProbe is a registered trademark of KEJR Engineering, Inc. of Kansas) installation techniques. 
     Preferably, the injection tubes  38  are installed by airjet injection. Airjet injection is a novel installation technique that is part of the present invention. In accordance with the present invention, airjet injection utilizes a compressor that is connected to an injection tube  38  via a hose. The air flow and pressure from the compressor act as a cutting tool and the injection tube  38  can be “injected” or inserted into the ground with minimal site description and minimal time and capital expense. It has been determined that up to eighty (80) or more injection points can be installed in a single day. This is significantly higher than the number of points that could be installed under prior installation methods. 
     Referring now to FIG. 3 which illustrates an exemplary installation of the system  10  in accordance with the present invention. The system shown in FIG. 3 is preferably installed at a site that was formerly a service station and has been determined to have groundwater that is contaminated with petroleum, whether through accidental or intentional spillage. As is known, the groundwater can be tested through the use of a monitoring well to determine whether or not the groundwater has been contaminated. In accordance with the present invention, one way for determining the existence of contaminants is the absence or depletion of oxygen which indicates that naturally existing bacteria are feeding on the oxygen in an effort to breakdown the contaminants. It can be assumed that a body of groundwater has unacceptable levels of contamination when the percentage of oxygen in and around the groundwater is in the order of 0%-1%. 
     Once it has been determined that the groundwater is contaminated, in accordance with the present invention, the location of the injection points can be determined. The location of the injection points can be determined in a variety of different methods. Preferably, however, the injection points are located in a grid that takes into account the direction and flow rate of groundwater flow. By taking into account the groundwater flow, injection sites will be positioned to prevent contaminants from spreading. Typical grid determination is based on site specifics, but generally, a grid is based on two months of groundwater flow (e.g. if the groundwater flows 120 feet per year, the grid would be a 20 foot grid). 
     Accordingly, as shown in FIG. 3, the exemplary system  10  is installed at a gas station  50  having a plurality of dispenser islands  52 . The dispenser islands  52  were provided with petroleum from a plurality of storage tanks  54 . A plurality of monitoring wells  56  are utilized to determine the extent and location of any contaminants so that the system usage can be maximized. In FIG. 3, five (5) monitoring wells  56  are illustrated. Obviously, any number of wells can be created. The injection sites  16  are preferably located in a grid pattern as shown (i.e. columns and rows), and then the injection tubes  38 , which are connected to the source of liquid oxygen  12  and the control panel  14  are installed to inject pure oxygen into the groundwater at the injection sites  16 . The arrow  60  designates the direction of groundwater flow. 
     Once the system is installed, the oxygen vapor will be regulated and metered to be delivered into the groundwater at a predetermined rate. The rate is preferably adjusted over time. The dissolved oxygen in the groundwater and the amount of oxygen in the soil gas are monitored to assure a sufficient flow of oxygen to the injection sites  16 . Similarly, the oxygen is monitored to determine if too much oxygen is being added in order to prevent undue waste. Obviously, the rate and pressure of the oxygen vapor can be varied as needed. The effect of the system on the contaminants can be monitored periodically through the monitoring wells. Further, if the source of oxygen  12  becomes depleted, it can be easily replaced without disrupting the clean up process. 
     The preferred system is relatively inexpensive to install as it costs significantly less than prior systems. Moreover, the system operates twenty-four hours a day and requires no electricity or maintenance to operate. Further, as there are no moving parts, there is nothing to lube, oil or grease. The system is also less susceptible to break down. 
     While particular embodiments of the invention have been shown and described, numerous variations and alternate embodiments will occur to those skilled in the art. Accordingly, it is intended that the invention be limited only in terms of the appended claims.