Patent Publication Number: US-7713415-B2

Title: Method and apparatus for enhancing aquatic environments

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a divisional of and claims priority to U.S. patent application Ser. No. 11/383,708, filed May 16, 2006, now U.S. Pat. No. 7,544,286 which application is hereby incorporated by reference to the extent permitted by law. 
    
    
     FIELD OF THE INVENTION 
     This invention relates in general to the biological enhancement of aquatic systems and deals more particularly with a method and apparatus for enhancing aquatic environments in a manner to promote beneficial biogrowth. Typical applications of the invention are, for example, water and waste water treatment systems and aquaculture applications. 
     BACKGROUND OF THE INVENTION 
     Water and waste water are commonly treated using a variety of conventional techniques. For example, waste water can be treated by aerobic, anoxic, and/or anaerobic processes, depending upon the characteristics of the waste water and the intended result of the treatment. Each of these processes requires different types of bacteria and utilizes a different mechanism for removing contaminants. Consequently, it is desirable for a treatment system to be flexible such that it can effect anaerobic, anoxic or an aerobic environment, either at different times or in different parts of the treatment system at the same time, or by controlling system variables. 
     In activated sludge systems, the microbial organisms are free floating and are circulated in the basin or other treatment reactor so that they contact the soluble and particulate contaminants in the liquid. In other systems the microorganisms are fixed in place and the contaminants are circulated to them. In either case, the soluble waste and small particulate waste are the materials that are the primary focus of treatment and are most difficult to remove from the liquid. 
     Submerged media of various types have been used to provide a base for accumulating and growing microbial biomass in treatment basins. Rigid parallel plates and honeycomb structures allow the liquid to pass between them and contact the biomass that accumulates on the plate and the honeycomb cells. However, the rigidity of these structures allows essentially unlimited buildup of biomass, so they must be cleaned frequently or they clog unduly and disrupt the treatment operation when used as submerged media in a high organic loading or in a low water flow environment. The need for frequently cleaning results in significant maintenance costs and other problems such as down time of the treatment facility which limits the application of rigid systems of this type. 
     Other types of media have been proposed, including unusual media elements confined in a cage structure through which the liquid passes. Although media of this type function in a satisfactory manner in many respects, there are significant problems. Again, excessive biomass builds up on the media and must be removed frequently to prevent clogging. Further, the liquid must be pumped through the media using relatively complex and costly pumping systems. The media is costly and typically involves the use of baffles and other flow control devices to achieve the necessary flow pattern. Distributing the caged media properly throughout the reactor also presents problems. All of these factors detract from the viability of caged media systems for use in many applications. 
     Woven net structures have been used involving strands or other elements strung between support members in the reactor. These systems are disadvantaged in that they are costly, difficult to properly distribute throughout the basin, have inadequate surface to volume ratios, and have elements that are fixed at both ends and thus relatively inflexible so that excess biomass can accumulate and clog the media. 
     The foregoing systems were developed for use as packing in towers or for trickling filter applications where the liquid flows vertically across media surfaces and has a velocity sufficient to shear off excess biomass. However, when they are submerged in much lower velocity basins or lagoons with relatively slow horizontal flow and significant organic loading, the velocity is inadequate for biomass removal. Thus, the cleaning and maintenance requirements previously identified are inherent. The process control parameters in a basin or lagoon also differ markedly compared to a trickling filter, and there is a need to distribute the media horizontally and vertically in a very large reactor which is not present in a small volume trickling filter application. 
     U.S. Pat. Nos. 6,060,153; 6,171,686; 6,230,654 and 6,244,218 to McNeil disclose woven fabric in the form of thin sheets used primarily in aquaculture environments. The sheets may be split in their lower portions to form side by side strips. However, each strip is a thin planar structure having a thickness of only about ⅛ inch or less. The water can pass through the slits, but each strip is essentially two dimensional so that the liquid flows quickly past the media and at most contacts only one strip. The strips are flexible fabric and film surfaces which stick together when placed close to each other. There is no three dimensional flow through effect and no baffling effect that directs the liquid from one media element to another. Therefore, contact between the particles in the liquid and the biomass on the media is not effected in an optimal manner. 
     Aquacultural systems have need for waste removal as well as other needs. For example, fish and other aquatic life must be protected against ammonia contamination. The ammonia that makes its way into the water must be converted to nitrate in a nitrification process involving one type of biogrowth, and the nitrate may then be converted to nitrogen gas in a de-nitrification (removal) process involving different types of microbes. Additionally, an environment can be provided where small fish and hatchlings are protected from predators, and the fish can utilize much of the biogrowth such as snails and other lower level organisms to feed on. Proper application of submerged media allows soil or floor erosion to be stabilized where it has been allowed to occur. The aquacultural systems proposed in the past have not adequately addressed all of these concerns. 
     SUMMARY OF THE INVENTION 
     A need remains to provide a media system that enhances the biological growth environment in various aquatic applications such as water and waste water treatment and aquaculture systems. At the same time, the media system must have the flexibility and adaptability in a system to allow management of the environment and the treatment process. 
     It is an object of the invention to provide a biogrowth media system and method wherein the media are arranged to present a large surface area in a controlled volume to support large biomass colonies and the accumulation of sufficient biomass to effect the desired end result. The type and amount of biomass can be controlled in the system by the proper control of media area volume, mixing energy, aeration energy, and media distribution. 
     Another object of the invention is to provide a system and method of the character described which is adapted to effect economical distribution of the media in the basin or other receptacle. 
     Still another object of the invention is to provide a method and system of the character described wherein excess biomass is removed automatically and naturally without the need to shut down the system and clean the media. This feature is achieved by providing media in the form of individual flexible elements that are free at one end so that natural flexing of the elements causes excessive biomass to detach from the media and drop to the bottom of the reactor. 
     A further object of the invention is to provide a method and system of the character described wherein aerobic, anoxic or anaerobic processes can be designed and operated with both low intensity lagoon waste treatment processes and high intensity complete mix processes carried out. Mixing with or without aeration can be selectively effected in one or more zones to allow aerobic or anoxic or anaerobic treatment. At the same time, the aeration/mixing can be carried out at high intensity in a complete mix zone with clarification and/or solids return capabilities, or mixing with or without aeration can be carried out at lower intensity in lagoon systems. Also, the environment can be selected or adjusted to obtain the desired effect by changing the physical area and volume characteristics or the location of the media or its density, changing the aeration location or intensity, changing the intensity of mixing, or any combination of these variables. An alternative arrangement of the media can involve arranging the media parallel to the flow direction so that one or more treatment channels are formed that may be beneficial for long sludgeage applications or other special or unique applications. This flexibility sets the present invention apart from other systems and methods and is of great practical advantage. 
     A still further object of the invention is to provide a method and system of the character described wherein the flexible media are arranged in one or more clusters with the elements collectively occupying a thickness dimension to create flow through the media volume that is substantial. Preferably this media will incorporate a thickness of at least one inch to more than three feet in some applications. This three dimensional flow through configuration is a highly important feature of the invention in that the particulates and solubles in the liquid are exposed to the biomass on a large number of the individual elements in each cluster, thereby maximizing the contact with the biomass. Also, the individual elements across the thickness dimension provide a baffling effect causing the liquid to be directed from element to element for further increased exposure to the biogrowth. The liquid passes through this thickness creating concurrent oxic, anoxic, and anaerobic zones in the media volume. These zones can be controlled by aeration, mixing and proper sizing or distribution of the media. 
     Yet another object of the invention is to provide a method and system of the character described wherein the different media elements within a cluster media can have different properties such as different lengths, specific gravities or other variables. For example, some elements can essentially float to provide sunlight protection, and loose or tight compaction of the elements or long and short elements within the same cluster can be provided, thereby enhancing the versatility of the system to meet different treatment goals. 
     A key characteristic of the media is the use of thin strips less than two inches wide to create the media cluster. These strips are specially designed to minimize or eliminate any biological bonding of media and maintain the media strips as discrete surface areas in the cluster. This avoids the loss of area and efficiency of flat fabric strips if placed in similar proximity to one another. 
     An additional object of the invention is to provide a method and apparatus of the character described which is suited to enhance aquaculture environments. In this regard nitrification and de-nitrification can be employed alone or with other waste treatment processes, and the media serves both as a support for biogrowth and multiple life forms such as snails and other nourishment for fish and as a protected area to harbor small fish and hatchlings against predators. The system also provides stabilization where erosion in an aquaculture system may be a problem. 
     Other and further objects of the invention, together with the features of novelty appurtenant thereto, will appear in the course of the following description. 
    
    
     
       DESCRIPTION OF THE DRAWING 
       In the accompanying drawing which forms a part of the specification and is to be read in conjunction therewith: 
         FIG. 1  is the front elevational view of a submerged media arranged in a cluster in accordance with a preferred embodiment of the present invention. 
         FIG. 2  is a side elevational view of the media shown in  FIG. 1 ; 
         FIG. 3  is a view similar to  FIG. 2  but showing the modified submerged media in which the individual media elements have varying lengths in accordance with a modified embodiment of the invention; 
         FIG. 4  is an elevational view similar to  FIG. 2 , but showing still another modified media in which the individual elements have varying densities (specific gravities) in accordance with another modified embodiment of the invention; 
         FIG. 5  is a diagrammatic elevational view showing a variety of clusters of submerged media arranged in a basin at different locations and having different characteristics; 
         FIG. 6  is a diagrammatic plan view of a basin or lagoon equipped with submerged media and other components arranged to provide different types of treatment zones in accordance with the present invention; 
         FIG. 7  is a diagrammatic plan view of a basin or lagoon equipped with clusters of media that are separated by gaps in accordance with one aspect of the present invention; 
         FIG. 8  is a diagrammatic plan view of a lagoon or basin equipped with submerged media arranged in strings or curtains extending essentially parallel to the direction of liquid flow of a basin or lagoon in accordance with one aspect of the present invention; 
         FIG. 9  is a diagrammatic plan view of a basin or lagoon equipped with submerged media and other components arranged to provide complete mix aeration for combined suspended growth and media fixed film or attached growth treatment in accordance with one aspect of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention is directed to the use of uniquely arranged submerged media to enhance the environment in an aquatic system such as a water or waste water treatment system or an aquaculture system. The details of the submerged media as used in an aquatic system will be described in connection with waste water treatment facilities. However, it is to be understood that the submerged media has equal applicability in other types of aquatic systems, including water treatment systems and aquaculture applications. 
     As one example of the type of aquatic environment in which the submerged media may be employed,  FIG. 5  depicts a reactor  10  containing a liquid such as waste water. The reactor  10  may be a basin, lagoon or other containment vessel. The reactor  10  may contain a generally flat bottom  12  and opposite sides  14 . The liquid level of the basin  10  is identified by numeral  16 . In accordance with the present invention, one or more clusters  18  of submerged media may be installed in the basin  10  at submerged locations. 
       FIG. 1  depicts a cluster  18  constructed according to one embodiment of the present invention. The cluster  18  is constructed of a plurality of individual ribbons or strips  20  preferably less than two inches wide which are bunched together to form the cluster  18 . The strips  20  may be supported from a support structure that includes a cable or rope  22  stretched across the basin  10  near the water line  16  and anchored to the opposite sides  14  by suitable anchors  24  (see  FIG. 5 ). Referring again to  FIG. 1  in particular, the upper ends of the ribbons  20  may be secured to a pipe or other support  26  (or to the cable  22  or a rope or other structure) and secured in place by clamps  28 . 
     With additional reference to  FIG. 2 , the strips  20  are folded over the support cable or rope at  20   a  and secured to the rope or cable or to pipe  26  in any suitable manner. The strips have free lower ends  20   b  which are submerged well below the water level  16  and which are unattached so that the strips  20  are free to flex or flutter. As shown in  FIGS. 1 and 2 , the strips are preferably arranged closely together along a length dimension L ( FIG. 1 ) of the cluster  18 . The length dimension L may occupy the entire width of the basin or some distance less than the basin width. Each cluster  18  has a thickness dimension T ( FIG. 2 ) that may vary to match process needs. The thickness dimension T is occupied by a plurality of the individual strips  20  and preferably is at least one inch thick and may be up to three feet thick or more in some applications. In any event, the thickness dimension T should be substantial so that the liquid that is being treated will be exposed to a relatively large number of strips  20  as the liquid passes through the thickness T. The media clusters allow the design of systems with oxic, anoxic and anaerobic environments as waste passes through the clusters. The bunching of the strips  20  throughout the thickness dimension T also arranges the strips such that they have a baffling effect to increase the distribution and exposure of the liquid to the surfaces of the discrete strips  20  as the liquid passes through the thickness dimension T. The strips  20  are constructed and arranged to prevent them from sticking together, even when biomass builds up on them. This maintains each strip as an individual discrete element for enhanced effectiveness. By way of example, the strips  18  can be curved, heated and twisted, or otherwise constructed in a manner to resist lying flatly against one another, although the invention contemplates flat as well as other configurations. 
       FIG. 3  depicts a cluster  18  in which the strips include relatively long strips having their lower ends  20   b  located well below the ends  21   b  of shorter strips  21 . It should be understood that the strips in any media cluster  18  may have various lengths and may be compacted to provide each cluster with different densities or compactions and thickness dimensions. 
     The arrangement shown in  FIG. 4  depicts a somewhat modified cluster  18  in which some shorter strips  21  have a lower specific gravity or more buoyant than the higher density strips  20 . Consequently, the strips  21  may float on or near the liquid surface  16  and thus act to block sunlight from reaching the underlying cluster  18  and the strips  20  contained therein. 
     Referring again to  FIG. 5 , some or all of the clusters  18  may be supported on a cable  30  or other submerged support located well below the liquid level  16 . The cable  30  may be connected at its opposite end with submerged anchors  32  located on the sides  14  at a location spaced above the bottom  12  but below the water line  16 . Some of the clusters  18  supported on the cable  30  may have a specific gravity greater than 1.0 such that the ribbons  20  hang downwardly from the cable  30 . Other clusters  18  may include individual ribbons  23  having specific gravities equal to or less than 1.0 such that the free ends  23   b  of strips  23  are at the upper ends of the clusters as the buoyant media ribbons  23  tend to rise in the reactor  10 . Combinations of long and short ribbons can be used in any of the clusters  18 . Likewise, ribbons having various specific gravities can be used in any of the clusters  18 . The ribbons in any of the clusters  18  may be installed densely or loosely or anywhere in between. 
     With continued reference to  FIG. 5 , the submerged media clusters  18  may be used with an aeration system. The aeration system may include a floating air lateral (pipe)  34  which is located at the water level  16  and secured in place at its opposite ends. One end of the air lateral  16  receives air under pressure from a blower  36 . Aeration devices which may take the form of submerged tubular diffusers  38  may be suspended from the air lateral  34  on flexible hoses  40 . The diffusers  38  are preferably located slightly above the bottom  12  of the reactor  10  and function in a well known manner to diffuse air into the liquid in the reactor vessel in the form of fine bubbles which provide aeration and circulation of the liquid. It should be understood that other types of aeration devices can be employed in connection with the submerged media, including floor mounted or surface mounted aerators. The diffusers  38  may be selectively operated (supplied with air) in order to aerate the liquid at such times and such intensities and durations as is appropriate for the particular result that is desired. 
     Preferably, the individual strips  20  take the form of thin members less than two inches wide that may be constructed of a flexible plastic such as polyethylene or other synthetic material, as well as a wide variety of other materials. The material used should be characterized by the ability to effectively promote the growth of microbes and to allow the biogrowth to accumulate on the strips in sufficient quantity to effectively treat the wastewater or other liquid that is undergoing treatment. At the same time, the flexibility of the strips  20  and maintaining one end  20   b  (or  21   b  or  23   b ) free allows the strips  20  to naturally flex when wastewater flows through the clusters  18 , with the flexing of the strips acting to dislodge excessive biomass that may accumulate on them. In this manner, undue buildup of biomass that could clog the clusters  18  is avoided. The strips may also be shaped to prevent bio-bonding in order to maintain full function when partially or fully loaded with biomass. 
     Alternatively, the strips may be constructed of a variety of materials and may have configurations other than flat strips. By way of example, human or animal hair, synthetic fibers, suspended ropes, woven strings, woven fabrics or sheets or ribbons of various materials may be used, as may other elements that are suitably flexible and capable of being supported adequately in an aquatic environment without bio-bonding. Whatever exact type of flexible element is used, the elements should be arranged in clusters having a significant thickness dimension T to provide a three dimensional flow through effect of the treatment, as previously described. 
       FIGS. 6-9  depict various wastewater treatment applications in which the submerged media may be used in accordance with the present invention. Referring first to  FIG. 6 , a basin or lagoon  110  is provided with a plurality of clusters  18  of the submerged media. The clusters  18  may each extend in a substantially continuous curtain across the entire width of the basin or lagoon  110 . The wastewater flow is longitudinally through the length of the basin  110 , as indicated by the directional arrows  112  at the inlet end of the basin or lagoon. Flows along and through the media are typically assisted by operation of an aeration system. 
     The basin or lagoon  110  may be provided adjacent to its inlet end with a zone  114  which may be anoxic or anaerobic. The zone  114  may be provided with a mixing device  116  that is non-aerating. The zone  114  may be provided with one or more of the media clusters  18  (or no submerged media in some cases). The basin or lagoon  110  may be provided with another zone  120  downstream from zone  114  which may include one or more of the submerged media clusters  18  and/or one or more aeration chains  122 . The clusters  18  may be arranged in a continuous curtain extending transversely across the basin or lagoon  110 . The aeration strings  122  may each take a form similar to what is shown in  FIG. 5  and may include submerged tubular diffusers  38  or other suitable aeration devices. An optional recirculation line  124  may be provided to extend from the outlet end of the basin  110  back to the inlet end. 
     In operation of the system shown in  FIG. 6 , the incoming wastewater enters the basin or lagoon in the first zone  114  which may be an anoxic or anaerobic zone for anoxic or anaerobic treatment of the wastewater at the inlet end portion of the basin. The wastewater then flows into the second zone  120  which may be operated as an anoxic zone (with little or no aeration) or as a low or high level aerobic zone if the aeration chains  122  are operated with high intensity aeration. A third zone is sometimes employed for maximum process control. 
     In the system of  FIG. 6  or any other system employing the submerged media, the wastewater or other liquid that is being treated flows through the cluster  18  at a relatively slow rate. The wastewater is exposed to the microbial biomass that grows and accumulates on the individual strips  20  or other flexible elements in the cluster  18  such that the microbes are able to remove suspended and soluble solids. The provision of a substantial thickness dimension T in each cluster  18  results in significant exposure of the liquid to the biomass because the liquid is directed in intimate contact with a number of different strips  20  as it flows through the thickness dimension T. In addition, the strips  20  have a baffling effect which directs the wastewater from strip to strip to increase the exposure and contact time of the liquid with the biomass. 
     It is a particular feature of the invention that the flexibility of the individual flexible elements in each cluster  18  results in the elements being naturally flexed by aeration/mixing or the wastewater flowing through the clusters  18 , with the flexure being allowed due to the free ends of the flexible elements in the cluster and the special non-stick (non bio-bond) construction thereby automatically dislodging any excess biomass build up that may occur on the elements in the cluster. This automatic dislodging of excessive biomass prevents the clusters  18  from clogging unduly and inhibiting the flow of wastewater through the clusters to lose treatment efficiency and the maintenance problems that plague other types of submerged media are thus avoided, along with the costs and downtime associated with such maintenance requirements. 
     With reference to  FIG. 7 , a basin or lagoon  210  receives wastewater at its inlet end, as indicated by the directional arrow  212 . The basin  210  is equipped with a plurality of clusters  18  of submerged media which are arranged in strings extending transversely across the width of the basin or lagoon  210  perpendicular to the flow direction. In each string of media, one or more gaps  214  may be presented between adjacent clusters. Optional aerators  216  may be located to provide aeration in some or all of the gaps  214  if desired. The gaps in adjacent strings of submerged media clusters  18  may be staggered or offset from one another, as indicated for the gaps  214   a  and  214   b . The submerged media may be arranged with gaps in an application of the type shown in  FIG. 6  or any other configuration, depending upon the desired treatment. 
       FIG. 8  depicts a basin or lagoon  310  which receives incoming wastewater at its inlet end as indicated by the directional arrows  312  which indicate the direction of flow longitudinally in the basin  310 . One or more strings of submerged media clusters  18  are installed in the basin or lagoon  310  to extend longitudinally in a direction substantially parallel to the direction of flow indicated by the directional arrow  312 . The clusters  18  may be arranged to extend continuously in a curtain extending the entire length of the basin or lagoon  310 , or the clusters may be arranged with gaps in each string of submerged media. Between each adjacent pair of strings of submerged media  18 , a channel  314  is formed for the flow of wastewater from the inlet and to the outlet end of the basin or lagoon  310 . One or more of the channels  314  may be equipped with an aeration chain  316  arranged with the aerators  38  spaced apart in a direction longitudinally of the basin along the length of the channel  314 . The aeration devices of the aeration chain  316  may be tubular diffusers such as those identified by numeral  38  in  FIG. 5 , or other types of aeration devices. The arrangement of  FIG. 8  may find use in some long sludgeage applications or in other special applications involving the treatment of wastewater or other liquids. 
       FIG. 9  depicts a lagoon  410  that is equipped with submerged media in combination with a suspended biogrowth system. Wastewater enters the basin or lagoon  410  at its inlet end and flows longitudinally through the basin in the direction indicated by the directional arrow  412 . The inlet end portion of the basin or lagoon  410  may be arranged to provide a complete mix zone  414 . In zone  414 , one or more strings of submerged media clusters  18  may be provided. The submerged media clusters  18  may be oriented to extend either longitudinally in the complete mix zone  414  or transversely in zone  414 . Preferably, an aeration chain  416  is provided between each adjacent pair of strings of clusters  18 . The aeration chains  416  may extend parallel to the clusters  18  and may include tubular diffusers  38  or other suitable aeration devices. 
     A clarifier  418  or other solids separation device may be provided to effect settling of sludge from the liquid in the basin  410 . Selected quantities of sludge  420  may be returned to the head end of the basin  410  along a sludge return line  420 . 
     Downstream from the complete mix zone  414 , the basin may be equipped with additional strings of clusters  18  and/or additional aeration chains  416 . The strings of clusters  18  may be arranged and oriented in virtually any manner, as may the aeration chains  416 . 
     The aeration in the complete mix zone  414  is carried out with sufficient intensity to maintain a complete mix condition in zone  414 . Downstream zones are typically operated under partial mix conditions. 
     From the foregoing it will be seen that this invention is one well adapted to attain all ends and objects hereinabove set forth together with the other advantages which are obvious and which are inherent to the structure. 
     It will be understood that certain features and subcombinations are of utility and may be employed without reference to other features and subcombinations. This is contemplated by and is within the scope of the claims. 
     Since many possible embodiments may be made of the invention without departing from the scope thereof, it is to be understood that all matter herein set forth or shown in the accompanying drawings is to be interpreted as illustrative, and not in a limiting sense.