Abstract:
The invention described herein provides a novel modification of an aerobic bacterial generator, typically used for sewage wastewater treatment. By providing a pre-filter one creates the equivalent of a “sub-gravel filter” known to the aquarium trade. In such fashion the device is portable and can be placed at the bottom of any pond, lake or other body of water to act as an aeration and biological filtration device. Further the unit incorporates a means of inoculation and maintenance of cultures of beneficial bacteria within the device to improve digestion of organic residues as well as to compete with algae for mineral nutrients, thereby preventing noxious blooms of plant material.

Description:
RELATED APPLICATIONS  
       [0001]     This application claims benefit of Provisional Patent Application No. 60/615,394, filed Oct. 4, 2004 and Provisional Patent application 60/709,906 filed Aug. 22, 2005. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates to pond aerators and, in particular, to a type of aerator that enhances the growth of bacterial cultures beneficial to the maintenance of water quality in ponds or fish culture facilities.  
         [0004]     2. Description of the Related Art  
         [0005]     Ponds used for landscaping purposes or for the culture of aquatic plants or animals represent artificial environments that need to be managed in order to maintain water quality.  
         [0006]     One of the most significant problems relating to water quality in such ponds is the buildup of mineral nutrients that stimulate the growth of plant materials such as algae. Such plants take advantage of these nutrients to foster the process of photosynthesis, through which the plants fix carbon from the atmosphere to form living cellular biomass.  
         [0007]     As such living plant material accumulates, a byproduct of gaseous O 2  is released, increasing the dissolved oxygen in the water during periods of illumination. However, during non-illuminated periods these same organisms must consume oxygen for normal aerobic metabolism.  
         [0008]     A problem in the aquatic environment is that water has a limited ability to absorb and hold dissolved O 2 . Water at typical ambient temperatures is saturated with oxygen tensions ranging from only 7-10 mg/L. As algal cells accumulate, densities can be high enough to produce transient O 2  tensions during active photosynthesis in excess of 20 mg/L.  
         [0009]     These plants utilize oxygen for the various non-photosynthetic metabolic processes as they produce oxygen through photosynthesis. During sunlight the amount of oxygen produced is more than sufficient to meet the needs of their aerobic metabolism. However, any oxygen produced beyond a tension of 7-10 mg/L escapes into the atmosphere and therefore will not be available to the algae during periods of darkness when no more O 2  is being released through photosynthesis.  
         [0010]     Where nutrients stimulate the growth of sufficient biomass to require uptake of greater than the 7-10 mg/L available over the course of a nightly dark period, such plants can draw the dissolved oxygen concentration down effectively to zero. At such times aquatic animals, such as fish or crustaceans, being totally dependent on dissolved oxygen for survival, will die.  
         [0011]     One means to deal with loss of dissolved O 2  in ponds or fish culture facilities is to actively aerate the ponds. A wide variety of means of delivering air exist. One such means involves pumping of the water so that it is exposed to air such that it takes up oxygen in dissolved form. This can be done by spraying the water into the air or allowing it to flow over complex surfaces that mix the water or allowing it to splash back into the pond as a waterfall.  
         [0012]     Another means is to send air directly into the water via air pumps or compressors. This air can be delivered through pipes or hoses as coarse bubbles or it can be delivered through diffusers such as air stones or membrane diffusers that reduce bubble size, thereby increasing the transfer of O 2  to the water.  
         [0013]     Another means of improving water quality beyond supplementing with O 2  is to use either biological, mechanical or chemical means to remove plant material that cause the oxygen depletion in the first place. One way to do this is to pass the water through porous media, either within the pond or aquarium, or outside the system. Such filtration will strain algal cells from the water but will not typically remove dissolved nutrients. These nutrients will allow regrowth of algae and plants in the system.  
         [0014]     Such filtration, however, can be enhanced by allowing the filter media to build up a colony of bacteria. These bacteria provide several benefits. They consume all forms of organic wastes in the pond, converting it to CO2 gas that can then escaped from the pond. They also compete with the algae for the mineral nutrients, preventing excess photosynthesis. They also can convert nutrients, especially nitrogenous compounds to less toxic forms, as well as to N2 gas, thus allowing excess nitrogen to dissipate from the liquid.  
         [0015]     One common means of implementing media based biological treatment is through the use of a “sub sand” or “sub gravel” filter. This involves creation of a space beneath a porous “false” bottom consisting of sand, gravel or other granular material. A pump can then pump water out of that space with replacement water thereby being drawn slowly through the bottom granular medium such that it contacts the bacterial film that typically colonizes such medium.  
         [0016]     One method of pumping water from a sub sand filter is through the use of an “air lift” pump. This consists of a tube that passes through the false bottom into the space below. An air hose is placed inside the tube and air is pumped and released as a bubble stream at the base of the tube. As the bubbles rise through the tube they expand in size as the pressure reduces with depth. This pushes water in front of the expanding bubbles and generates a current. As above, such water is replaced with water that diffuses slowly through the false bottom granular medium. Not only does such a device generate a water flow through the biological medium, it aerates the water as it does so.  
         [0017]     The bacterial component of such systems can be allowed to develop in haphazard fashion through colonization with wild bacteria or it can be established using commercial strains as inoculants. One group of bacteria with beneficial properties is that of the “facultative bacteria”. These are predominantly aerobic species of bacteria but they also possess metabolic pathways that allow them to live in the absence of free O 2 .  
         [0018]     Certain species in the group  Bacillus  are spore formers so they can readily be obtained as stable commercial cultures. Other groups such as  Pseudomonas  are not spore formers but can be stabilized as vegetative cells making them also commercially available.  
         [0019]     A device is described in U.S. Pat. No. 6,780,318 that encourages growth of such facultative bacteria in wastewater treatment applications. It is commercially marketed as an ABG or Aerobic Bacterial Generator. This device uses the airlift principle described above to aerate and pass wastewater over a matrix within the column on which bacteria can grow. The device further describes a means through which commercial cultures of desirable bacteria can be introduced.  
         [0020]     An advantage of this device is that it is scalable such that small versions can be used in small treatment vessels while larger, more powerful versions can be used in larger applications.  
         [0021]     A second advantage is that the unit is portable. It can be incorporated as an integral component of a wastewater treatment vessel or it can be added as a completely transportable retrofit into any form of liquid vessel.  
         [0022]     A specialized use of an ABG is described in Non-Provisional Patent Application #f10/984,009, filed on Nov. 8, 2004 for the purpose of carrying out the biological denitrification of nitrogenous compounds typically found in wastewater. Further a method to enhance this reaction is described in Provisional Patent Application No. 60/616,961 and Provisional Patent Application No. 60/709,906.  
         [0023]     There exists a need to combine the above described processes such that a simple device can provide the benefits of aeration, mechanical filtration, biological media filtration and bacterial supplementation in a single, portable system that can be economically installed in ponds or other fish culture applications.  
       SUMMARY OF THE INVENTION  
       [0024]     The present invention provides a method to treat water in a pond or fish culture facility so to improve clarity, preserve dissolved oxygen and prevent excessive blooms of noxious plant materials. The method includes the step of adding facultative bacteria to the pond or fish culture facility. The step of adding facultative bacteria includes the step of aerating and circulating the liquid in the pond or fish culture facility over a medium capable of supporting the growth of such bacteria.  
         [0025]     The present invention also includes a method to enhance growth of a second group of bacteria that oxidizes ammonia compounds and acts in concert with the facultative bacteria to convert such oxidized nitrogen compounds to nitrogen gas so it can dissipate from the liquid.  
         [0026]     The method also includes a means of delivering cultures of bacteria as well as specific nutrients to the system to supplement and control the bacterial colony existing in the system.  
         [0027]     The present invention also includes an aerator and filtration device. The aerator/filtration device consists of a fine bubble diffuser at the base of a column which, when aerated, generates a water current through the column.  
         [0028]     The column of the aerator/filtration device is filled with a matrix on which heterotrophic, facultative bacteria can attach and form a colony. Aerated water passing over this column exposes bacteria to nutrients and organic material contained in the pond or fish culture facility liquid.  
         [0029]     The present invention also includes a method for introducing calcium carbonate material in the form of oyster shells, or other similar materials, within the column to act as a surface that stimulates growth and attachment of ammonia oxidizing autotrophic bacteria.  
         [0030]     In the present invention the base of the column is surrounded and encompassed by a containment apparatus that acts as a pre-filter. This pre-filter contains a porous, fibrous matrix that mechanically filters incoming liquid and also supports the growth of attached facultative heterotrophic bacteria.  
         [0031]     The method of the invention also includes a material consisting of calcium carbonate, in the form of crushed oyster shells or other similar materials, which stimulate colonization and growth of ammonia oxidizing bacteria in the external pre-filter.  
         [0032]     In the present invention the diffuser within the aerator/filtration device is supplied with air from a remote air pump or compressor delivered through a pipe or hose connected from the pump to the diffuser.  
         [0033]     The method also includes a hose passing from the surface down and into the pre-filter matrix portion of the device through which liquid cultures of facultative heterotrophic bacteria and/or ammonia oxidizing bacteria can be added as needed.  
         [0034]     The method also provides a central tube within the column of the device that allows a porous packet of bacterial cultures to be added and held within the aerated water column generated by the airlift action. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0035]      FIG. 1  is a flow chart illustrating method  100  in accordance with the present invention.  
         [0036]      FIG. 2  is a flow chart illustrating method  200  in accordance with the present invention.  
         [0037]      FIG. 3  is a flow chart illustrating method  300  in accordance with the present invention.  
         [0038]      FIG. 4  is a flow chart illustrating method  400  in accordance with the present invention.  
         [0039]      FIG. 5  is a flow chart illustrating method  500  in accordance with the present invention.  
         [0040]      FIG. 6  is a cross-sectional view illustrating an aeration/filtration device  600  in accordance with the present invention.  
         [0041]      FIG. 7  is a cross-sectional view illustrating an aeration/filtration device  700  in accordance with the present invention.  
         [0042]      FIG. 8  is a cross-sectional view illustrating an aeration/filtration device  800  in accordance with the present invention.  
         [0043]      FIG. 9  is a cross-sectional view illustrating an aeration/filtration device  900  in accordance with the present invention.  
         [0044]      FIG. 10  is a cross-sectional view illustrating an aeration/filtration device  1000  in accordance with the present invention. 
     
    
     DETAILED DESCRIPTION  
       [0045]      FIG. 1  shows a flow chart that illustrates a method  100  in accordance with the present invention. As shown in  FIG. 1 , method  100  has a single step  110  of adding facultative, heterotrophic bacteria and ammonia oxidizing bacteria to a pond or fish culture facility containing organic waste.  
         [0046]     The liquid in the pond or fish culture facility contains nutrients that stimulate blooms of photosynthetic algae that can degrade water quality and depress the level of dissolved oxygen.  
         [0047]     The facultative bacteria added to the pond or fish culture facility compete for nutrients and supplant the algal community and prevent the deterioration of water quality due to excessive photosynthetic loading to the pond or fish culture facility while the ammonia oxidizing bacteria can initiate conversion of ammonia to nitrogen gas in concert with the facultative heterotrophic bacteria.  
         [0048]      FIG. 2  shows a flow chart that illustrates a method  200  in accordance with the present invention. Method  200  is an example of one way of implementing method  100 . As shown in  FIG. 2 , method  200  begins at step  210  by aerating and circulating the liquid in a pond or fish culture facility that contains organic and mineral nutrients within the liquid.  
         [0049]     Following this, method  200  moves to step  212  to add facultative bacteria such that the growth of the facultative bacteria is enhanced by the aeration and circulation of the liquid in the pond or fish culture facility. As a result of the aeration and circulation of the liquid the added bacteria will flourish and colonize surfaces within the pond or fish culture facility, thereby enhancing the bacteria&#39;s ability to digest organic and mineral nutrients within the liquid.  
         [0050]      FIG. 3  shows a flow chart that illustrates a method  300  in accordance with the present invention. Method  300  is an example of implementing method  100 . As shown in  FIG. 3 , method  300  begins at step  310  by aerating and circulating the liquid in a pond or fish culture facility that contains organic and mineral nutrients within the liquid.  
         [0051]     Following this, method  300  moves to step  312  to add ammonia-oxidizing bacteria to the pond or fish culture facility. The ammonia oxidizing bacteria convert ammonia to nitrite and the facultative heterotrophic bacteria convert nitrite to gaseous nitrogen, which can dissipate from the liquid to the atmosphere.  
         [0052]      FIG. 4  shows a flow chart that illustrates a method  400  in accordance with the present invention. Method  400  is similar to method  200  and, as a result, utilizes the same reference numbers to designate the steps that are in common to both methods. As shown in  FIG. 4 , method  400  differs from method  200  in that method  400  includes step  410 , which adds a host material for facultative heterotrophic bacteria to the pond or fish culture facility.  
         [0053]     The host material for the facultative heterotrophic bacteria provides a surface for the bacteria to grow on that increases the number of facultative heterotrophic bacteria that are present in the pond or fish culture facility. In the preferred embodiment, the bacterial host material is placed adjacent to the aeration source so that the bacterial host material is bathed in air and waste material when the aeration source is in operation.  
         [0054]      FIG. 5  shows a flow chart that illustrates a method  500  in accordance with the present invention. Method  500  is similar to method  300  and, as a result, utilizes the same reference numbers to designate the steps that are in common to both methods. As shown in  FIG. 5 , method  500  differs from method  300  in that method  500  includes step  510 , which adds a host material for ammonia oxidizing bacteria to the pond or fish culture facility.  
         [0055]     The host material for the ammonia oxidizing bacteria provides a surface for the bacteria to grow on that increases the number of ammonia oxidizing bacteria that are present in the pond or fish culture facility. In the preferred embodiment, the bacterial host material is placed adjacent to the aeration source so that the bacterial host material is bathed in air and waste material when the aeration source is in operation.  
         [0056]     Further the host material for the ammonia oxidizing bacteria is placed adjacent to the host material for the facultative heterotrophic host material so that as ammonia is oxidized by the ammonia oxidizing bacteria to nitrite, the nitrite is readily available to the facultative heterotrophic bacteria so that they can convert the nitrite to nitrogen gas. In such fashion the nitrogen can readily dissipate from the liquid.  
         [0057]      FIG. 6 . shows a cross sectional view that illustrates an aerator/filtration device  600  in accordance with the present invention. Aerator/filtration device  600  is an example of a device that can be used to implement the methods of the present invention.  
         [0058]     As shown in  FIG. 6 , aerator/filtration device  600  includes and air diffuser  610  that aerates and circulates the liquid in a pond or fish culture facility. Diffuser  610  has an air input side and a bubble output side. In addition, diffuser  610  provides bubbles of air  612  evenly across the diameter of a column  614  that extends away from the bubble output side of the diffuser  610 . Diffuser  610  can provide micro-fine, fine, medium, or course bubble sizes.  
         [0059]     Aerator/filtration device  600  also includes a compressed air line  616  that is connected to the air input side of air diffuser  610 , and an air compressor (or blower)  618  that is connected to the compressed air line  616 . Compressor  618 , which is located a distance away from diffuser  610 , can be implemented with, for example an 80-watt compressed air pump. Line  616  provides diffuser  610  with pressurized air pumped from compressor  618 .  
         [0060]     In the example shown in  FIG. 6 , line  616  extends around from the input side to the bubble side of air diffuser  610 , and then extends away from the bubble side in column  614  that extends away from diffuser  610 . Diffuser  610  is preferably implemented with a micro-fine bubble diffuser because a micro-fine diffuser can inject more oxygen into a stream of liquid at a lower air pressure, which, in turn, lowers the operating requirements of compressor  618 .  
         [0061]     Aerator/filtration device  600  optionally includes a bacterial host material  620  that is positioned within the column  614  that extends away from diffuser  610 . Material  720  is positioned a predetermined distance away from the bubble output side of the diffuser  610 , measured normal to the surface of the bubble output side. Material  620  can be any material that provides a surface area for bacteria to grow and that water can pass through without clogging.  
         [0062]     Material  620  is preferably manufactured from a material that is resistant to decay, and configured and placed within the column in a fashion that provides the maximum possible film forming surface area with the volume of the column. Material  620  is placed to allow for the free flow of both liquid and air through material  620 . For example, material  620  can be implemented with a sheet of cuspated plastic material manufactured similar to the method described in U.S. Pat. No. 4,449,072, which is hereby incorporated by reference.  
         [0063]     Aerator/filtration device  600  additionally includes a bacteria container/applicator  622  that is positioned within column  614  that extends away from diffuser  610 . Container  622  is positioned a predetermined distance away from the bubble output side of diffuser  610 , measured normal to the surface of the bubble output side. Bacteria container/applicator  622  includes a porous sack, or any other similar packaging, which can contain a bacterial starter culture allowing timed release of viable bacteria over a prolonged period or the outlet end of a tube or other means to deliver bacteria from an external source.  
         [0064]     To maintain the position of bacterial host material  620  and bacterial container/applicator  622  within the column that extends away from diffuser  610 , material  620  and container/applicator  622  can be connected to airline  616 . Alternately, device  600  can include a frame or structure to provide the necessary positional relationships.  
         [0065]      FIG. 7  shows a perspective view that illustrates an aerator/filtration device  700  in accordance with the present invention. Device  700  is similar to device  600  and, as a result, utilizes reference numerals to designate the structures, which are common to both devices.  
         [0066]     As shown in  FIG. 7 , aerator/filtration device  700  differs from device  600  in that the base of the column  714  is surrounded by an external pre-filter device  724  through which liquid must pass to enter the aerator/filtration device  700 . In the preferred embodiment pre-filter device  724  is filled with a material  726  similar to that used for furnace or air conditioner filters, or any material that provides porosity while at the same time being sufficiently dense to provide mechanical filtration and act as a matrix for bacterial colonization.  
         [0067]     Pre-filter  724  is a closed unit that is perforated with openings  728  to allow liquid to enter into the device through the majority of the filter material  726  as it passes into the zone of the air diffuser  610  and into the column  614  which extends away from diffuser  610  and over the material  620  within the column that acts as a matrix for bacterial settlement and past container  622  that contains a bacterial culture.  
         [0068]      FIG. 8  shows a perspective view that illustrates an aerator/filtration device  800  in accordance with the present invention. Device  800  is similar to device  700  and, as a result, utilizes reference numerals to designate the structures, which are common to both devices.  
         [0069]     As shown in  FIG. 8 , aerator/filtration device  800  differs from device  700  in that a second material  830  is added to the filter material  726 , either loosely or as a separate container, that consists of calcium carbonate derived from crushed oyster shells or similar material that stimulates the settlement and growth of autotrophic ammonia oxidizing bacteria to act in concert with facultative heterotrophic bacteria introduced to the aeration/filtration device  800  via the container  622  containing such culture.  
         [0070]      FIG. 9  shows a perspective view that illustrates an aerator/filtration device  900  in accordance with the present invention. Device  900  is similar to device  800  and, as a result, utilizes reference numerals to designate the structures, which are common to both devices.  
         [0071]     As shown in  FIG. 9 , aerator/filtration device  900  differs from device  800  in that a second material  932  is placed adjacent to material  820  within the column  614  which extends away from diffuser  610 , either loosely or as a separate container, that consists of calcium carbonate derived from intact or crushed oyster shells or similar material that stimulates the settlement and growth of autotrophic ammonia oxidizing bacteria to act in concert with facultative heterotrophic bacteria introduced to the aeration/filtration device  900  via the container  622  containing such culture.  
         [0072]      FIG. 10  shows a perspective view that illustrates an aerator/filtration device  1000  in accordance with the present invention. Device  1000  is similar to device  900  and, as a result, utilizes reference numerals to designate the structures, which are common to both devices.  
         [0073]     As shown in  FIG. 10 , aerator/filtration device  1000  differs from device  900  in that a second means of introducing both heterotrophic facultative bacteria and autotrophic ammonia oxidizing bacteria is provide by a hose  1032  that passes from any place outside the pond or fish culture facility and terminates either within the filter material  726  and  1028  within the pre-filter  1024  or adjacent to container  1022  inside column  1014  which extends away from diffuser  1010  or at both locations such that a liquid bacterial culture consisting of either facultative heterotrophic bacteria or autotrophic ammonia oxidizing bacteria, or both, can be passed through hose  1032  from a remote location.