Abstract:
The invention is a non-metallic, preferably, plastic container for delivering oxygen generating materials (OGMs) into wells. By constructing the canister of a plastic and sealing the ends, the canister can be disposable or reusable.

Description:
BACKGROUND 
       [0001]    1. Field of the Invention 
         [0002]    The invention is a canister for releasing oxygen into water, such as groundwater, for example in wells, wastewater, drinking water, and swimming pools, and other natural and man-made bodies of water. By providing a non-metallic canister, such as a plastic and disposable canister for the oxygen-releasing material, significant advantages can be realized over conventional systems. 
         [0003]    2. Background of the Invention 
         [0004]    Groundwater is often contaminated with petroleum or other volatile organic carbons (VOCs), often as result of leaking underground storage tanks (LUSTs). Many of these LUSTs were removed since the 1970&#39;s. However, in many of these former sites, VOCs are still detected at significant levels. 
         [0005]    Oxygen can be used to clean up many types of VOCs. Native microorganisms utilize, often dissolved, oxygen as an electron acceptor, and the targeted contaminant can serve as the electron donor, resulting in its destruction. Accordingly, oxygen can be used for organic constituents amenable to aerobic biodegradation processes to clean up a variety of contaminants, including: (1) petroleum hydrocarbons; (2) polycyclic aromatic hydrocarbons (PAHs); and (3) benzenes, toluenes and xylenes (BTEX). Oxygen is also used to stimulate aerobic biodegradation through nutrient delivery to the microorganisms. 
         [0006]    Typically, oxygen is delivered into groundwater systems by introducing an oxygen-generating material (OGM) into the groundwater. Suitable OGMs include mixtures of peroxides (e.g., calcium peroxide), hydroxides (e.g., calcium hydroxide) and hydrated aluminosilicates (e.g., sodium, calcium aluminosilicates), optionally mixed in a weight ratio, respectively, of 45-70:10-20:20-30. Such a material is a white solid (optionally in powder form), having a bulk density of 500-650 g/L, and is insoluble in water. The OGM can be mixed with water, e.g., to form a slurry (approximately 10-60%, typically 10-20% and preferably approximately 20% solids), before being introduced to the groundwater. Many of such OGM are provided with nutrients, such that the microorganisms can feed and grow on the nutrients, as well as pH buffers, to help to ensure a desirable environment for the microorganisms. 
         [0007]    In many of such systems, the OGM is not mixed with water before being added to the groundwater, but is contained in a metal canister for introducing the OGM to the groundwater in its solid state. Thus, the mixing occurs inside the well (“downhole”), whereby the groundwater comes into contact with the solid OGM, as opposed to a slurry. Often, the OGM is contained in a reusable metal canister, having a diameter slightly less than the wellhole, e.g., approximately 2″ or approximately 4″ and a length of between 12″ and 48″, typically approximately 36″. 
         [0008]    These reusable metal canisters can damage the well and associated apparatii. Often, electrical and electronic devices are located downhole in the vicinity of the OGM-containing canisters and are powered or otherwise connected to components outside the well. Thus, the metal canisters often come into contact with the wires connecting the downhole devices to the outside components. Because metals can be corrosive and/or abrasive, the contact between the canister and the wires can result in abrading of any insulation on the wires and eventual shorting of the devices and/or components, as many of the metals used to form the canisters are electrically conductive. 
         [0009]    Moreover, the devices are often suspended downhole by ropes or cables, and if such cables are not specifically constructed of an abrasion resistant material, the same action which can result in damage to the wires can also cause degradation of the suspension cable and possible loss of the device. 
         [0010]    Many metals are also chemically reactive to chemicals used downhole, significantly limiting the types of metals which can suitably be used to form the canisters. 
         [0011]    Finally, should one desire to re-use the metal canisters, it would be necessary to decontaminate the canister to ensure that no cross-contamination of other wells occurs. 
       SUMMARY OF THE INVENTION 
       [0012]    In order to address the drawbacks of other systems for oxygenating groundwater, the present invention includes a disposable non-metallic plastic canister for delivering an OGM to the groundwater. The invention is described for use with groundwater. However, it is understood that the invention can be used with any type of water or more generally any fluid, for example, described herein. 
         [0013]    The canister can be of any type of plastic, but is preferably of a relatively inexpensive non-reactive or inert material, such as polyvinyl chloride (PVC), flouropolymers, such as polytetraflouroethylene (PTFE) or an olefin (e.g., polypropylene or polyethylene) and copolymers and blends thereof. The canister can have a multi-layer structure, such as a main structural part of a first plastic, and a coating of a second plastic. The canister  10  can be of a rigid shape or can be flexible. 
         [0014]    The canister  10  preferably has an inner space for receiving the OGM, and is designed to allow the OGM to contact the groundwater. This can be accomplished by providing the canister with one or more apertures (e.g., holes, slits, or irregularly shaped openings) permitting the water to enter the canister. In such a configuration, the canister is largely closed, with, optionally, only the spaced holes penetrating the canister and the large holes on the top and bottom of the canister. Alternatively, the canister can be more open, e.g., almost as a mesh, permitting the water to flow therethrough. The particular size/shape of the holes/mesh should be dependent upon the specific condition of the OGM, e.g., solid mass, powder, flakes, etc. 
         [0015]    In some embodiments, it is desirable to have the OGM in a liner or sleeve of woven, felted or non-woven fabric which is placed inside the canister. The requirements for the liner or sleeve is that it permits water to contact the OGM contained therein and has openings of such a size as to retain the OGM therein, especially where the OGM is in a powder or flake form. 
         [0016]    Other objects, features and advantages of the present invention will become apparent from the following detailed description. It should be understood, however, that the detailed description and the specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]      FIG. 1  is a schematic representation of a canister in accordance with the invention; 
           [0018]      FIG. 2  is a schematic representation of a second canister in accordance with the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0019]    Initially, it is to be understood that like numbers in different drawings indicate similar structures. In the interests of brevity and in order to focus on the distinctions between the different drawings/embodiment, unless specifically discussed, when a particular feature is described as being used or usable in one embodiment, such a feature can be used or useable in other embodiments. 
         [0020]      FIG. 1  shows a first canister  10  in accordance with the invention. The canister is typically substantially cylindrical in shape, having a top  11  and a bottom  12 , separated by a middle section or body  13 . Although shown as being a perfect cylinder, i.e., with the top  11  and bottom  12  being flat, planar structures defining parallel planes and the canister having a completely circular cross-section of a constant diameter across its length, the canister  10  of the present invention is not so limited. For example, the canister  10  can have a cross-section (either at a single location or uniform along the length of the canister  10 ) in the shape of any closed, regular or irregular polygon, e.g., square, hexagon, rectangle, triangle, and pentagon. 
         [0021]    For example, the canister  10  can have any shape sufficient to hold OGM disposed therein. While the shape of the canister  10  is preferably a closed three-dimensional structure, it is considered within the scope of the invention to provide the canister  10  with other, e.g., non-uniform shapes, allowing for greater flow of groundwater through the canister  10 . In such an embodiment, the diameter of the circular cross-section could increase or decrease across the height of the canister  10 . 
         [0022]    In order to oxygenate groundwater into which the canister  10  is placed, the top  11 , bottom  12  and body  13  define an interior space into which material is placed. Typically, such material is an oxygen-generating material (OGM) which can be mixed with other materials, such as nutrients, pH buffers or other chemicals (e.g., surfactants, salts—such as salts of sodium, chlorine, and potassium, and halogens, chlorinators, bleaches, softeners, and ozone-generating materials) designed to interact with the water, microorganisms and other downhole materials. 
         [0023]    In the embodiment shown in  FIG. 1 , the body  13  is provided with apertures  14 . Although shown as being regularly spaced and substantially circular, the invention is certainly not so limited, as any repeating or non-repeating pattern is suitable. The body  13  can include any number of apertures  14 , e.g., from one to thousands. The apertures  14  need also not be circular. For example, the apertures  14  can be of any regular or irregular polygonal shape, e.g., square and hexagonal. The apertures  14  may also consist of an elongated slit which extends, preferably only part-way, horizontally between the top  11  and the bottom  12 , vertically between the top  11  and the bottom  12  or at any angle therebetween. The size, shape, number and position of the one or more apertures  14  largely depends upon the physical form of the OGM, as will be described below. 
         [0024]    In order to achieve the advantages of the present invention, at least the body  13  of the canister is formed from a non-metallic, preferably plastic, material. Typically, the plastic is a thermoplastic material, such as polyvinyl chloride (PVC), an olefin (such as polyethylene, polypropylene, and polybutylene), copolymers thereof and blends thereof. The plastic material can also be of any density, e.g., HDPE, LDPP, etc., as the material can be foamed (open cell or closed cell), extruded, or molded. The canister  10  may also be produced from more than one type of plastic (either as a blend, or as separate pieces joined together), and one or more different types of materials (in combination with a plastic material). 
         [0025]    In a most preferred embodiment, the top  11  and bottom  12  of the canister  10  are fixedly attached to the body  13 . Such is preferably accomplished by welding, e.g., spot, sonic, or solvent welding. 
         [0026]    Because many of the plastics to be used as the material for the canister  10  have a low density compared to that of the groundwater, preferably, the canister  10  is weighted. In a preferred embodiment, the bottom  12  is provided with an increased weight. This can be accomplished in any number of manners. For example, the density of the plastic material forming the bottom  12  may be greater. However, in a preferred embodiment, the bottom  12  has an area for receiving a weight (which can be as simple as a rock, a fishing weight, or a bag of ordinary sand). In one embodiment, the weight is integral with the canister  10  and in a most preferred embodiment, the weight is unitary with the canister. By providing the canister  10  with a weighted bottom  12 , it can be assured that the OGM contained within the canister  10  is properly contacted, i.e., partially or completely submerged under the groundwater. In one embodiment, the weight added to the bottom  12  is calculated such that only a portion of the canister  10  is submerged when placed downhole. As the OGM inside the canister  10  is used up, the level to which the canister  10  is submerged will be closer to the bottom of the canister  10 . If the density/mass of the groundwater on the one hand and the canister  10  on the other hand, as well as the density/mass (as well as the rate of consumption) of the OGM, the canister  10  can be advantageously weighted such that the submersion level moves up the height of the canister  10  at a controlled rate. In a preferred embodiment, the OGM includes a water-absorbing material, such that the OGM increases in mass to become water-logged during operation thereof. 
         [0027]    In one embodiment, the OGM is in a powdered form, having an average particle size between 1μ and 10 cm. In other embodiments, however, the OGM is in a compacted solid form, which will react with the groundwater only at the outer surface thereof. Accordingly, the size of the apertures  14  is specifically selected such that the groundwater is permitted to wash into the canister  10  in order to contact the OGM, while hindering, if not completely preventing the OGM (in whatever form) from exiting the canister. 
         [0028]    In order to assist in placing the canister  10  downhole and removing it when the OGM has been expended, the canister typically is provided with a loop  17 , preferably attached to the top  11 . This loop  17  can be attached to a rope or cable to raise and/or lower the canister  10 . In one embodiment, the canister is provided with a second loop  17 ′, attached to the bottom  11 . In such a configuration, multiple canisters  10  can be connected in series, with the loops  17  interconnected with a connector, such as a short rope or cable, connecting a loop  17 ′ of a first canister  10  to a loop  17  of a second canister  10 . 
         [0029]    The size, shape and position of the apertures  14  are particularly selected as to achieve a desired result with respect to contacting the groundwater with the OGM. For example, should it be desired that the OGM only contact a small volume of groundwater at any time, the apertures  14  can be small in both number and size. If for example, it is desired that the OGM react with the groundwater for an extended time before the treated groundwater/OGM combination exit the canister  10 , there may be a number of larger apertures  14  positioned along the circumference of the body  13 , however only near the top  11 . As a result, the untreated groundwater can enter the canister  10  at the top, flow to the bottom  12  of the canister  10  where it reacts to the OGM contained therein, and slowly come back to the top  11  before being allowed to exit the canister  10 . 
         [0030]    Depending upon the condition and physical state of the OGM, the body  13  of the canister  10  can be open from 0.05% to 99.95% (where the open % is calculated as follows: 
         [0000]    
       
         
           
             
               
                 
                   BSA 
                   - 
                   
                     ∑ 
                     MSA 
                   
                 
                 BSA 
               
               × 
               100 
             
             , 
           
         
       
     
         [0000]    where BSA is the total surface area of the body, and MSA is the minimum cross-sectional area of each aperture  14 ). The embodiment shown in  FIG. 1  has a relatively low open percent, e.g., less than about 10%, preferably less than about 8%, most preferably less than about 5%. 
         [0031]      FIG. 2  shows a second embodiment for the body  13 , where the apertures  14  are replaced with a grid  16 , such that the body has a high open %. Essentially, the grid  16  is a material formed by intersecting plastic pieces to form a pattern of openings therein. As shown in  FIG. 2 , the grid  16  includes a series of repeating spaces in the grid  16  of substantially the same size and shape. However, it is within the scope of the invention to have the number and size of the spaces be less homogeneous, i.e., either changing in a gradient across the body  13 , or randomly. In the embodiment of  FIG. 2 , the body  13  has an open percent greater than about 50%, preferably greater than about 60% and most preferably greater than about 70%. 
         [0032]    In order to assist in lowering the canister  10  into the well, and to aid in positioning and lifting the canister  10  from the well, the canister  10  is typically provided with a lifting hook  17 , at the top  11 . 
         [0033]    In a preferred embodiment, the OGM is contained in a sleeve or liner  18 . The liner  18  is designed to allow for ingress of ground water and is typically formed from cotton or other water permeable material. By providing the OGM inside a liner  18 , the canister  10  is more easily constructed than if the OGM were simply placed into the interior chamber of the canister  10 . When such a liner  18  is used, the particular size/shape/position of the apertures  14  becomes less important. 
         [0034]    The liner  18  is preferably a material having holes therein, allowing groundwater to pass through while limiting or preventing the OGM from passing through. The liner  18  can be used when the OGM is in a slurry, powder or solid form as described above. This liner  18  may be in the form of a woven or non-woven, flexible or rigid, cellulosic or plastic structure, which can allow groundwater to pass through, while substantially preventing escape of the OGM and permitting escape of the generated oxygen. 
         [0035]    The canister  10  of the invention can also be used as a groundwater sampling device, such as a passive diffusion sampler. In this embodiment, the OGM includes or is replaced with a material which will absorb groundwater when the canister  10  is placed downhole. Once the OGM absorbs a groundwater sample, the canister  10  can be lifted out of the well and the absorbed groundwater removed from the OGM, by e.g., chemical processes, or physical squeezing. 
         [0036]    It should be apparent that embodiments other than those specifically described above may come within the spirit and scope of the present invention. Hence, the present invention is not limited by the above description.