Abstract:
A bioremediation method and system for destroying or reducing the level of contaminants in a contaminated subterranean body of water includes a plurality of 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. Each of the plurality of injection sites are also in communication with a supply of microbials. The oxygen is conveyed by a delivery mechanism from the supply of oxygen to the injection points. The microbials are also conveyed 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 Application Serial 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 that utilizes biodegraders. 
     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, such as COCs. 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 are not always present in large enough quantities to be effective and can also be absent altogether. Moreover, 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. A source of substantially pure oxygen is provided. A supply of microbials is also provided. The oxygen and an amount of microbials are each 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 system includes a supply of concentrated oxygen and a supply of microbials. The oxygen and microbials are each delivered to the plurality of injection points and into 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 an enhanced dissolved oxygen groundwater bioremediation system in accordance with a preferred embodiment of the present invention; 
     FIG. 2 is a schematic illustration of the breakdown of contaminants in accordance with a preferred embodiment of the present invention; and 
     FIG. 3 is an illustration of a flow meter of the system of FIG. 1 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 plurality of injection sites  16  are also in communication with a supply of microbials  20 . 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  22  in order to convey the oxygen thereto. The pressure hose  22  has a first end  24  that is connected to the source of oxygen  12  and a second end  26  that is connected to the control panel  14 . The source of oxygen  12  has a shut off valve  28  associated therewith which is located between the source of oxygen  12  and the first end  24  of the pressure hose  22 . The shut off valve  28  allows the flow of oxygen from the source of oxygen  12  to the pressure hose  22  to be manually closed as desired. It should be understood that the valve  28  can also be electronically controlled. The second end  26  is preferably connected to a pressure regulator  30  which allows the pressure of oxygen exiting the source of oxygen  12  to be controlled. In the preferred embodiment, the pressure regulator  30  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  30  can be adjusted to regulate the flow of oxygen to a variety of different pressures. 
     The oxygen that exits the pressure regulator  30  enters a first conduit  32 , which conveys the pressure regulated oxygen to an oxygen header pipe  34 . The oxygen header pipe  34  has a plurality of flow meters  36  connected thereto and in fluid communication therewith. The pressure regulator  30 , the first conduit  32 , the oxygen header pipe  34 , and the plurality of flow meters  36  are all preferably disposed within the control panel  14  and the control panel  14  is preferably mounted to a fence, wall or other structure  38 . However, more or less items may be included in the control panel  14 . The flow meters  36  regulate the flow of oxygen from the header pipe  34  to a respective outlet tube  40 . The outlet tube  40  is also in communication with a source of microbials  42  through a microbial outlet tube  44 . The microbials  42  exit the source  42  and pass through the microbial outlet tube  44  and enter the outlet tubes  40 . Preferably, the microbials  42  are injected initially prior to injection of the oxygen. The amount of microbials is preferably determined based on the size of the contaminated area. Thereafter, the microbials will reproduce to ensure that an appropriate amount of food for the oxygen is present in the groundwater. 
     The outlet tube  40  is in communication with an injection tube  46  that terminates at a respective one of the plurality of injection sites or points  16 . Accordingly, the number of flow meters  36  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  40  is preferably ¼ inch tubing and the injection tubes  46  are preferably ½ inch tubing. The size and material of the pipes and tubes can obviously vary. 
     Referring now to FIG. 2, which illustrates the desired chemical reaction induced by the preferred bioremediation system  10 . As shown, a contaminant is present in the groundwater  18 , as generally indicated by reference number  48 . Oxygen molecules, as generally indicated by reference number  50 , are fed to a microbial, which is generally indicated by reference number  52 . The microbial  52  feeds off the oxygen molecules  50  and breaks down the contaminants  48  into a combination of water, as generally indicated by reference number  54 , and carbon dioxide, as generally indicated by reference number  58 . It will be understood that the contaminants are typically a COC chain, but could be a variety of other contaminants that require removal. 
     The system  10  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). 
     A plurality of monitoring wells  66  are preferably utilized to determine the extent and location of any contaminants so that the system usage can be maximized. 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  46 , which are connected to the source of liquid oxygen  12  and the control panel  14  and also the source of microbials  42  are installed to inject the pure oxygen into the groundwater at the injection sites  16 . 
     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. Additionally, if the source of microbials  12  becomes depleted, it can also be easily replaced without disrupting the remediation 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. 
     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. However, if the bacterial population is too small or nonexistent, it needs to be enhanced for the pure oxygen to work effectively. The issue thus becomes how to deliver the pure oxygen and the microbials 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 and microbials to the injection sites may also be utilized. 
     However, in the preferred embodiment, a plurality of injection tubes  46  are utilized to convey the pure oxygen from the source  12  and microbials from the source  42  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 and reacts with the microbials. The injection points  16  and the injection tubes  46  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 using other direct push and auger drilling techniques known in the art, such as those provided by GEOPROBE® Systems (GEOPROBE is a registered trademark of KEJR Engineering, Inc. of Kansas). GEOPROBE® Systems provide hydraulically-powered machines that use both static force and percussion to advance sampling and logging tools into 
     Preferably, the injection tubes  46  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  46  via a hose. The air flow and pressure from the compressor act as a cutting tool and the injection tube  46  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. 
     As shown in more detail in FIG. 3, each flow meter  36  is preferably connected to the oxygen header pipe  34  by a compression fitting  60  that allows oxygen at the regulated pressure to be delivered thereto. Each flow meter  36  is preferably mounted to a mounting board  62  or other structure in the control panel  14  and includes a pressure indicator  64  that provides a visual indication of the pressure of fluid flowing therethrough. The outlet tubes  40  that are in communication with the outlet of the flow meters  36  preferably extend through a protective conduit  64  (FIG. 1) which extends from the control panel  14  into the ground. The protective conduit  64  acts to shield and protect the outlet piping  40 . The outlet piping  40  is preferably located at least one foot below the ground and runs generally parallel thereto. The injection tubes  46  are in communication with the outlet piping  40  and extend generally perpendicularly downward from the outlet piping  40 . As shown, the outlet piping  40  intersects the groundwater  18  below the water table at designated injection sites  16  in order to deliver the pure oxygen and the microbials thereto. 
     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.