Abstract:
A method and apparatus for removing hydrocarbon contaminants from groundwater. The apparatus preferably removes contaminants from groundwater by heating the groundwater to a temperature at which the contaminant vaporizes and separates from the liquid groundwater. Sparge air may be passed through the groundwater to assist in separating the vaporized contaminant. Further, a vacuum may be applied to lower the vaporization temperature of the contaminant. The extracted hydrocarbons are preferably destroyed in a thermal or catalytic oxidizer while the groundwater with the vaporized contaminant removed is preferably pumped through activated carbon filters to further reduce the amount of contaminants to governmental standards.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This application is a continuation of and claims priority to U.S. patent application Ser. No. 09/797,287, filed Feb. 27, 2001 by Noel A. Shenoi, the respective disclosure of which is incorporated herein by reference in its entirety, for all purposes. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The invention relates to a method and apparatus for removing hydrocarbon (“HC”) contaminants, including methyl tert-butyl ether (“MTBE”) and benzene, from contaminated groundwater. 
       BACKGROUND OF THE INVENTION 
       [0003]    In various industrial and commercial environments, including sites having gasoline service stations, dry cleaners or other industrial sites where hydrocarbons have been stored and used, the soil and underlying groundwater may become contaminated with spilled or leaked hydrocarbons. The contaminants typically may include petroleum or chlorinated hydrocarbons, with MTBE, benzene, toluene, ethylbenzenes, xylenes, tert-butyl alcohol, perchloroethane, and tetrachloroethane being some of the most common. It is desirable, therefore, to extract contaminates from groundwater to meet regulatory standards. The extraction system and method should preferably be adaptable for use at various sites and capable of removing various contaminants. 
         [0004]    In a known treatment method, a vehicle, such as a truck, or a trailer, on which extraction and filtering equipment is mounted, is brought to a site to be cleaned. Among the equipment are a groundwater holding tank, carbon filter tanks, and a groundwater extraction device. The groundwater extraction device is generally a series of connected pipes attached at one end to the holding tank. The end opposite the holding tank is perforated and is inserted into the ground. A vacuum is applied to the pipes to draw contaminated water into the perforated end, through the pipes and into the holding tank. The groundwater is then transferred from the holding tank through a series of carbon filter tanks to remove contaminant thereby cleaning the water to an acceptable standard, which is normally determined by a government agency. When too much contaminant accumulates in the carbon filter tank “break through” occurs. Break through means that the quantity of contaminant in the water exiting the carbon filter tanks is above the acceptable threshold. At that point the system is shut down and one or more of the carbon filter tanks is replaced with a new tank, wherein each tank costs about $500. The cost of new tanks and the lost operational time to change the tanks adds to the cost of cleaning the groundwater. 
         [0005]    Another problem is that certain contaminants, such as MTBE, are highly soluble in water. If one of these contaminants leaks into the ground it can quickly disperse throughout the groundwater. Such a contaminant can only be removed by extraction of the groundwater and separation of the contaminant. The contaminant is often separated by passing the groundwater through a carbon filter as described above. 
       SUMMARY OF THE INVENTION 
       [0006]    As used herein, the following terms have the following meanings: (1) “contaminant” means any chemical or chemicals having a boiling point lower than water and includes hydrocarbons, such as MTBE (methyl tert-butyl ether), ETBE (ethyl tert-butyl methyl ether, TAME, (tert-Amyl Methyl Ether), DIPE (diisopropyl ether), TBA (tert-butyl alcohol), BTEX (which refers to one or more of benzene, toluene, ethylbenzene and xylenes), gasoline and diesel fuel; (2) “contaminated water” means water containing a contaminant; (3) “groundwater” means water extracted from the ground regardless of the method by which it is extracted; (4) “vaporize” means to transform into a vapor; (5) “applying a vacuum” means using an external source to lower pressure; (6) “cleaned water” means groundwater separated from vaporized contaminant; and (7) “on site” means a fixed location or portable facility that is proximate water or groundwater being treated. 
         [0007]    The invention is a method for removing contaminant from groundwater by vaporizing contaminant present in the groundwater, the vaporized contaminant separating from the liquid groundwater, thus creating cleaned water. The contaminant is preferably vaporized by heating the groundwater in a tank to a temperature at which the contaminant vaporizes and separates from the liquid groundwater. Optionally, the tank has a vacuum applied to reduce the vaporization temperature of the contaminant. Further, the groundwater may be agitated, preferably by passing a gas such as air through the groundwater, to assist in separating the vaporized contaminant from the groundwater. 
         [0008]    The method may also include, among other things, one or more of the following steps: (1) extracting the groundwater from the ground and transferring it to the tank, the groundwater preferably being extracted using a vacuum process, (2) removing the vaporized contaminant from the tank and disposing of it, preferably by burning it, (3) removing the cleaned water from the tank, and (4) passing the cleaned water through a filter, such as one or more carbon filter tanks, to remove additional contaminant. 
         [0009]    Also disclosed herein is a system used to practice the method and a tank used in practicing the method. 
         [0010]    Thus, the function of the method of the invention is to remove contaminant from groundwater. The way in which it accomplishes this function is to vaporize at least some of the contaminant, which separates from the liquid groundwater. The result is cleaned water, which can then have additional contaminants removed. Among the benefits of the invention are: (1) cost effectiveness as compared to known methods for site clean up, (2) quick mobilization to a clean-up site by being installed on a mobile unit, such as a truck or trailer, and (3) faster site cleaning than known methods. 
         [0011]    The cost effectiveness and faster cleaning are attributable in part to the fact that the method of the invention does not rely exclusively on filters to remove contaminant. Much of the contaminant is removed when it is vaporized and separates from the liquid groundwater. Therefore, if filters, such as carbon filters, are used, they filter a smaller amount of contaminant and last longer. This either eliminates the need for filters or greatly reduces the number of filters used to filter a given amount of groundwater, which reduces material costs and maintenance time. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         [0012]      FIG. 1  is a partial schematic diagram illustrating the process and apparatus of the preferred embodiment of the invention. 
           [0013]      FIG. 2  is an enlarged view of the partial schematic diagram of  FIG. 1 , illustrating the process and apparatus of the preferred embodiment of the invention. 
           [0014]      FIG. 3  generally illustrates the preferred method of extracting groundwater according to the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0015]    The invention is preferably used to remove hydrocarbon contaminants from water, but can be used to remove any contaminant from any liquid. Most preferably, the invention is used to remove hydrocarbon oxygenates such as MTBE, ETBE, TAME, DIPE, aromatic hydrocarbons, such as BTEX, or fuels such as gasoline or diesel fuel. 
         [0016]    Turning now to the drawing wherein the purpose is for describing a preferred embodiment and not to limit same,  FIG. 1  illustrates a situation in which fuel has leaked from two tanks, A and B, into ground G. The fuel itself is a contaminant C that contains other contaminant C, such as MTBE. 
         [0017]    Vacuum pipes  1 ,  1 A, and  1 B each have respective first ends  2 ,  2 A and  2 B, second ends  3 ,  3 A and  3 B and perforations  4 . Perforations  4  may be disposed along an entire length of vacuum pipes  1 ,  1 A and  1 B (as shown in  FIGS. 1 and 3 ), or alternatively, perforations  4  may only be disposed proximate ends of the vacuum pipes  1 ,  1 A and  1 B to be submerged in the ground water. 
         [0018]    Flexible hoses  5  each have a first end  5 A and a second end  5 B. First ends  2 ,  2 A and  2 B are connected respectively to a first end  5 A of a hose  5 . The purpose of each vacuum pipe  1 ,  1 A and  1 B is to be inserted into the ground and extract contaminated groundwater therefrom (preferably by the application of vacuum). Any device or devices capable of performing this function may be used. The hoses transfer the extracted groundwater to system  10 , described below. Any device or devices, including submersible pumps, may be used to transfer groundwater to system  10 , and any number of pipes and hoses may be used to extract contaminated groundwater and transfer it to system  10 . 
         [0019]    A system  10  for treating extracted groundwater is preferably mounted on a vehicle V. In a preferred embodiment, the portions of system  10  located on vehicle V are obtained from and assembled onto vehicle V by SOLLECO LLC. Turning now to  FIG. 2 , system  10  preferably includes an inlet knockout (or holding) tank  12 . Contaminated groundwater is transferred from each of hoses  5  into inlet knockout tank  12 . Tank  12  temporarily retains, or holds, extracted liquids and any structure capable of performing this function may be used. Alternatively, tank  12 , or similar structure, may not be included as part of system  10 . Tank  12  is preferably supplied by SOLLECO LLC, has approximately a 28″ inside diameter, an approximate height of 5′, is manufactured from ¼″ thick steel, and has a capacity of approximately 200 gallons. However, it should be noted that the size and materials of tank  12  may be selected based on the desired characteristics taking into consideration performance and logistics requirements of system  10 . 
         [0020]    A conduit  14  connects tank  12  to a process tank  16 . The function of each of the conduits herein is to transfer liquid and/or vapor, depending upon the conduit, and any structure capable of performing the function of a respective conduit may be used. Each of the conduits described herein is manufactured of ¼″ thick steel and has an inner diameter of 4″. Tank  16  preferably has an agitator [not shown], which is preferably a tube connected to a valve  18  on tank  16  to introduce compressed air at a preferred pressure of below 1 pound per square inch (psi) or atmospheric air, which is introduced into process tank  16  under vacuum. Tank  16  also includes a heating element [not shown]. The heating element is preferably positioned on or near the inner annular wall of tank  16  and transfers heat to the groundwater in the tank in order to vaporize at least some of contaminant C. Tank  16  is where, in the preferred embodiment, contaminant is separated from groundwater, in the method discussed below. Any device or devices capable of performing this function may be used to practice the invention. A preferred embodiment for vacuum pipes  1 , hoses  5 , vehicle V, inlet tank  16 , conduit  14 , agitator  18 , and the heating element are set forth in the following chart. 
         [0000]    
       
         
               
               
               
             
           
               
                   
                   
               
               
                   
                 Item 
                 Make/Manufacturer/Model # 
               
               
                   
                   
               
             
             
               
                   
                 Vacuum Pipes 1 
                 1″ or 1¼″ ID made of ¼″ thick steel 
               
               
                   
                   
                 having perforations ¼″ in diameter 
               
               
                   
                 Flexible Hoses 5 
                 1″ or 1¼″ Series BW Water Hose from 
               
               
                   
                   
                 Kuriyama 
               
               
                   
                 Vehicle V 
                 GMC 2001 truck with 17′ flatbed. 
               
               
                   
                 Inlet Tank 16 
                 ¼″ steel, internally braced to withstand 
               
               
                   
                   
                 high vacuums to 29″ Hg. Approximate 60″ 
               
               
                   
                   
                 height, 28″ diameter with a mist pad on 
               
               
                   
                   
                 top. Connections and fittings are in the 
               
               
                   
                   
                 side of the tank. Manufacturer - 
               
               
                   
                   
                 SOLLECO LLC, Anaheim, CA. 
               
               
                   
                 Conduit 14 
                 4″ ID steel pipe made from ¼″ thick steel. 
               
               
                   
                   
                 Manufacturer - SOLLECO LLC, Anaheim, 
               
               
                   
                   
                 CA. 
               
               
                   
                 Agitator 18 
                 ½″ ID PVC (polyvinyl chloride) pipe with 
               
               
                   
                   
                 ⅛″ holes (minimum 20 holes) to let air or 
               
               
                   
                   
                 gas enter inlet tank 16. Valve 19 is a ½″ 
               
               
                   
                   
                 ball valve, made by Apollo. 
               
               
                   
                 Heating Element 
                 ½″ ID copper coil is 100′ long and is 
               
               
                   
                   
                 placed in inlet tank 16 to carry heated water 
               
               
                   
                   
                 (preferably over 100° F.) to heat 
               
               
                   
                   
                 groundwater in inlet tank 16, and is 
               
               
                   
                   
                 assembled in tank 16 by SOLLECO. The 
               
               
                   
                   
                 heating element could also be a heating 
               
               
                   
                   
                 immersion strip, such as 5000 watt copper 
               
               
                   
                   
                 thermostatically controlled brushing 
               
               
                   
                   
                 immersion heater manufactured by 
               
               
                   
                   
                 Grainger, #2E932. 
               
               
                   
                   
               
             
          
         
       
     
         [0021]    A conduit  20  connects process tank  16  to a high vacuum pump  22 . A conduit  24  connects pump  22  to an orifice flow tube  26 . A conduit  28  connects tube  26  to a thermal/catalytic oxidizer  30 . Oxidizer  30  is used to burn, or oxidize, contaminant, releasing the exhaust into the atmosphere. Any device, however, capable of performing this function may be used. 
         [0022]    A conduit  32  connects process tank  16  to temporary storage tank  34 . Pump  33  is disposed in conduit  32  to pump liquid from tank  16  to tank  34 . A water sample port  36  is connected to conduit  32  and enables an operator to sample water exiting process tank  16 . Temporary storage tank  34  temporarily stores cleaned groundwater that has exited process tank  16 . Any device capable of performing this function may be utilized. Alternatively, system  10  may not include a temporary storage tank or similar structure. Temporary storage tank  34  is preferably a 550-gallon PVC storage tank to temporarily hold groundwater. A conduit  38  connects temporary storage tank  34  to one or more filters. Preferably the one or more filters are granular activated carbon filters  40 A,  40 B and  40 C. As shown in  FIG. 2 , filters  40 A and  40 B, and  40 C are connected by, respectively, conduits  42  and  46 . An exit conduit  50  extends from tank  40 C. A canister  40 A sample port  44  is used to sample water exiting carbon filter  40 A. A canister  40 B sample port  48  is used to sample water exiting carbon filter  40 B. A canister  40 C sample port  52  is used to sample water exiting carbon filter  40 C. 
         [0023]    Following is a description of preferred embodiments of conduit  20 , pump  22 , conduit  24 , orifice tube  26 , conduit  28 , oxidizer  30 , conduit  32 , storage tank  34 , Sample Port  36 , conduit  38 , conduit  42 , conduit  46 , conduit  50 , carbon filters  40 , and pump  33 . 
         [0000]    
       
         
               
               
               
             
           
               
                   
                   
               
               
                   
                 Item 
                 Description 
               
               
                   
                   
               
             
             
               
                   
                 Conduit 20 
                 4″ ID steel of ¼″ thickness manufactured 
               
               
                   
                   
                 by SOLLECO LLC. 
               
               
                   
                 Pump 22 
                 25 HP liquid ring blower, such as that 
               
               
                   
                   
                 manufactured by STERLING, Model 
               
               
                   
                   
                 #560AB8310A0, powered by a direct- 
               
               
                   
                   
                 driven electric motor 25 HP, such as that 
               
               
                   
                   
                 manufactured by U.S. Electric Motors, 
               
               
                   
                   
                 Model #T811A, 240 V, 3 phase LRP, in 
               
               
                   
                   
                 order to create vacuum up to 29″ Hg. 
               
               
                   
                 Conduit 24 
                 4″ ID steel of ¼″ thickness manufactured 
               
               
                   
                   
                 by SOLLECO LLC. 
               
               
                   
                 Orifice Tube 26 
                 4″ ID stainless steel tube with a 2.75″ ID 
               
               
                   
                   
                 Orifice to measure vapor flow rate in cubic 
               
               
                   
                   
                 feet per minute. Manufactured by DICK 
               
               
                   
                   
                 MUNNS COMPANY, Los Alamitos, CA. 
               
               
                   
                 Conduit 28 
                 Preferably the same as conduit 20 and 24. 
               
               
                   
                 Thermal/Catalytic 
                 24″ ID made of 3/16″ thick steel stock with 
               
               
                   
                 Oxidizer 30 
                 a 5″ thick fiber insulation inside to protect 
               
               
                   
                   
                 the outer metal. Manufacturer - 
               
               
                   
                   
                 SOLLECO LLC. It thermally incinerates 
               
               
                   
                   
                 hydrocarbons in the vapor and greatly 
               
               
                   
                   
                 reduces emissions to atmosphere. 
               
               
                   
                 Conduit 32 
                 1″ ID steel pipe Sch 40 Manufactured by 
               
               
                   
                   
                 SOLLECO LLC. 
               
               
                   
                 Storage Tank 34 
                 550 gallon PVC storage tank to temporarily 
               
               
                   
                   
                 hold groundwater. 
               
               
                   
                 Sample Port 36 
                 ¼″ brass ball valve with ¼″ opening 
               
               
                   
                 Conduit 38 
                 1″ ID PVC or plastic base Manufactured by 
               
               
                   
                 Conduit 42 
                 Kuriyama. 
               
               
                   
                 Conduit 46 
               
               
                   
                 Conduit 50 
               
               
                   
                 Carbon Filters 40 
                 200 Series carbon absorber with virgin 
               
               
                   
                   
                 coconut carbon from U.S. Filter Westates. 
               
               
                   
                   
                 Model #200SCA/CC602BB 
               
               
                   
                 Pump 33 
                 1 HP Goulds Model 3656 centrifugal pump 
               
               
                   
                   
                 powered by a Balder JMM 35461 1 h.p. 
               
               
                   
                   
                 electric motor (pumps liquid conduit 32 
               
               
                   
                   
                 from tank 16 to tank 34). 
               
               
                   
                   
               
             
          
         
       
     
         [0024]    In practice, groundwater is extracted by pipes  1  and is transferred via hoses  5  into holding tank  12 . The groundwater is then transferred to tank  16  where enough heat is supplied by the heating element to vaporize at least some of the contaminant, but not vaporize any significant amount of groundwater. The vaporized contaminant separates from the liquid groundwater. 
         [0025]    Preferably, vacuum is applied to tank  16  by pump  22  through conduit  20 . The vacuum lowers the temperature at which contaminant C vaporizes, and if enough vacuum is applied no heat need be applied by the heating element to vaporize contaminant C. 
         [0026]    The groundwater is also preferably agitated to assist in separating vaporized contaminant. The groundwater is preferably agitated by introducing gas (preferably air) through valve  18 . Other agitation devices, such as an impeller, may be used. 
         [0027]    After the vaporized contaminant separates from the liquid groundwater it passes through conduit  20 , pump  22 , conduit  24 , orifice flow tube  26 , conduit  28  and into oxidizer  30  where it is burned, preferably to governmental emission standards. Cleaned water exits tank  16  and passes through conduit  32  to temporary storage tank  34 . It passes out of tank  34  through conduit  38  and preferably into one or more filters  40 A,  40 B and  40 C. The filter(s) remove additional contaminant, preferably lowering the amount in the cleaned water to an acceptable government standard. The water is then expelled through conduit  50 , preferably onto the ground at the site. 
         [0028]      FIG. 3  illustrates the groundwater extraction process. Pipe or stinger tube  1  is inserted into the ground and over a period of time, or specifically depicted, the cone of depression for the groundwater around the well is increased, thereby allowing additional soil to be affected by vapor extraction to remove hydrocarbons from the exposed soil. 
         [0029]    The system used to practice the invention can have any throughput, but preferably has the capacity of extracting a minimum of about 10 gallons per minute from the ground. The technical specification of the preferred system is as follows:
       (1) 450 cubic feet per minute (CFM) maximum air flow for the vacuum pump;   (2) 29″ of mercury (Hg) maximum vacuum applied by the vacuum pump;   (3) 50 gallons per minute (gal/min) maximum water extraction from the ground;   (4) 600,000 to a maximum of 1,000,000 BTU/hr catalytic oxidizer; and   (5) a minimum 99% or greater DRE (destination removal efficiency), which is the total amount of contaminate removed from the groundwater by system  10 .       
 
         [0035]    System  10  is preferably fully mobile and functions without hookup to site utilities, such as water or sewer. System  10  is preferably rendered mobile by placing it on vehicle V. 
       EXAMPLE 1  
       [0036]    The invention was used in a 24-hour dual phase (i.e., vapor and groundwater) extraction pilot test. The subject site had elevated concentrations of petroleum hydrocarbons, including the oxygenated gasoline additives MTBE and TAME, in the soil and groundwater. 
         [0037]    The lithology of the site generally consisted of sand/silty sand 0-15 feet below ground surface (“bgs”), clay and silt/silty clay at 15-55 feet bgs, and sand/gravelly sand at &gt;55 feet bgs. Shallow groundwater was located in a thin saturated zone at approximately 24 feet bgs. 
         [0038]    The results of the extraction pilot test indicated an effective radius of influence of the extraction device of approximately 29 feet. Extracted groundwater was treated utilizing the system and method according to the invention on site to treat groundwater and expel water meeting applicable governmental standards. Approximately 495 pounds of hydrocarbons were burned during the 24-hour test. The results of the groundwater samples are presented in Table 1. 
         [0000]    
       
         
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
             
           
               
                 TABLE 1 
               
               
                   
               
               
                   
                 Prior To 
                 After 
                   
                 Carbon 
                   
               
               
                   
                 Extraction 
                 Treatment 
                 Percent 
                 Polishing Post 
                 Percent 
               
               
                 Parameter 
                 (14) 
                 Process (36) 
                 Reduction 
                 Treatment (52) 
                 Reduction 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 MtBE 
                 360,000 
                 μg/L 
                 6,740 
                 μg/L 
                 98% 
                 ND (&lt;0.5 μg/L) 
                 100% 
               
               
                 TPHg 
                 228,000 
                 μg/L 
                 11,300 
                 μg/L 
                 95% 
                 ND (&lt;50 μg/L) 
                 100% 
               
               
                 TAME 
                 2,590 
                 μg/L 
                 25.3 
                 μg/L 
                 99% 
                 ND (&lt;0.5 μg/L) 
                 100% 
               
               
                 Benzene 
                 33,700 
                 μg/L 
                 267 
                 μg/L 
                 99% 
                 ND (&lt;0.5 μg/L) 
                 100% 
               
               
                 Toluene 
                 52,700 
                 μg/L 
                 987 
                 μg/L 
                 99% 
                 ND (&lt;0.5 μg/L) 
                 100% 
               
               
                 Ethylbenzene 
                 6,580 
                 μg/L 
                 162 
                 μg/L 
                 98% 
                 ND (&lt;0.5 μg/L) 
                 100% 
               
               
                 Xylenes 
                 40,900 
                 μg/L 
                 1,497 
                 μg/L 
                 96% 
                 ND (&lt;1.0 μg/L) 
                 100% 
               
               
                 Napthalene 
                 10,200 
                 μg/L 
                 147 
                 μg/L 
                 98% 
                 ND (&lt;0.5 μg/L) 
                 100% 
               
               
                   
               
               
                 TPHg—Total Petroleum Hydrocarbons - Gasoline Range 
               
               
                 ND (&lt;0.5 μg/L)—Not Detected Above the Laboratory Reporting Limit of 0.5 μg/L 
               
             
          
         
       
     
         [0039]    Having now described a preferred embodiment, modifications or alterations that do not depart from the spirit of the invention may occur to others. For example, while the present invention has been described in reference to treatment of ground water, the invention may be equally implemented to clean water from any source in addition to groundwater (e.g., rivers, lakes, ponds, swimming pools, and reservoirs). The invention is thus not limited to the preferred embodiment, but is instead set forth in the appended claims and legal equivalents thereof. Unless specifically stated otherwise, the method steps of any of the following claims may be performed in any order capable of vaporizing contaminate and having it separate from liquid groundwater.