BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to on-site wastewater (sewage) treatment systems and processes, and more particularly to a stand-alone aerobic treatment unit or pod system for promoting oxygen transfer and aerobic bacterial activity in conjunction with conventional septic tank systems for family residences and commercial establishments.

2. Description of the Prior Art

At present, many single and multiple family dwelling units as well as small commercial installations rely upon the well known process of wastewater (sewage) disposal involving a septic tank and drain field installation. In these installations the biodegradable wastewater contains a wide variety of solid and liquid materials which are introduced directly from the source into a septic tank for primary treatment. The septic tank itself functions as a settling chamber in which the solids are allowed to settle out in a quiescent zone with both liquids and solids being subjected to digestion exclusively by anaerobic micro organisms. The anaerobic liquor or effluent, free of most solids, is then discharged directly into a drain field for final disposal. One common form of septic tank system includes at least two chambers with the primary chamber receiving the raw wastewater where the solids are allowed to settle to the bottom. The liquor then transfers to a second chamber where further settling and anaerobic digestion is allowed to proceed. The effluent then drains off to a drain field. The anaerobic treatment system is extremely slow compared to aerobic processes whereby oxygen is introduced and absorbed into the wastewater so that aerobic micro organisms are relied upon to provide aerobic metabolism of sewage organics. The aerobic system of sewage treatment is not only more rapid than anaerobic treatment but also eliminates offensive odors and oft times pollution of the environment caused by odiferous insufficiently treated wastewater from aging or overloaded septic tank systems. A multitude of systems have been proposed in the prior art for increasing the efficiency and effectiveness of septic tank systems in the nature of chemical treatment plants, filter systems and secondary sewage treatment systems for aeration of the liquids discharged, either from the septic tank or directly from the source. Filter systems and/or chemical treatment processes have been used for both large and smaller installations, however, such systems tend to be complex, expensive to install, unreliable and difficult to maintain. Examples of prior art secondary sewage treatment systems using aeration and aerobic bacterial growth media are disclosed in U.S. Pat. Nos. 5,030,353; 5,200,081; 5,202,027; and 5,609,754.

In some instances, reactors containing microbial growth media and/or filtering devices incorporating aeration features to treat the liquid effluent have been proposed for use in conjunction with septic tanks. One example of this type of device may be found in U.S. Pat. No. 5,554,996. In this type of device, air is diffused into a reactor chamber so as to cause liquor to recirculate within the reactor chamber in the presence of microbial growth media with the reactor chamber being connected directly to outflow of the treatment tank. Thus, only the liquor-effluent within the reactor chamber is being aerated and mixed leaving the balance of the volume within the settlement tank untreated. The major part of the septic tank thus remains anaerobic with the usual inefficient and slow odor producing decomposition attendant standard septic tank systems. In addition, all wastewater entering the septic tank must pass through the reactor chamber on its way to the outlet of the tank. The volume of liquor treated is thus limited and frequent clogging of the media and/or filter system may occur with ultimate failure of the tank system during overload periods or after long use. Systems of this type may also employ pumping devices which must be regulated in such a manner as to accommodate variations in flow volume and timed dosing, resulting in frequent failures and a fluctuating liquid depth within the septic tank. Since all sewage is not created equal and may vary widely over any given time period in terms of strength, volume and composition, these shortcomings are of great concern.

In view of the foregoing, there remains a continuing need for a system with greater efficiency and reliability for the treatment of wastewater and sewage in primary treatment systems such as standard septic tanks of all configurations as well as other traditional anaerobic digestion systems. To be successful, the system must be of a nature that is adaptable for retrofitting existing septic tank systems of all sizes and have the ability to increase the dissolved oxygen content of the otherwise anaerobic liquor so as to promote aerobic microbial digestion processes in the entire tank volume. Expensive pumping systems and dosing mechanisms which require constant maintenance must be avoided. There is also a need for the ability to back-flush and clear the microbial growth medium of organic build up to prevent clogging and to increase effectiveness without extensive reworking or modification of the system. Back flushing may also be used in situations where the unit is organically overloaded and additional air entrainment points are required to increase the available oxygen necessary for treatment. In order to provide for increased usage or loading of the septic system, provision must also be made for increasing or decreasing the treatment units within an existing septic system without major overhaul or reworking of the existing septic system.

SUMMARY OF THE INVENTION

The present invention provides a system and method for oxygen enrichment of wastewater within a wastewater tank of the type that is normally subjected to anaerobic decomposition of biodegradable materials. The wastewater tank will normally be provided with inlet and outlet fittings for providing a constant level of wastewater within the tank, the effluent being disposed of in the drain field or the like. The septic tank may or may not be divided into separate compartments but, in any event, will have a settling zone where solids are settled out from the wastewater forming the liquor within the tank. According to the present system and method, oxygen is introduced into the liquor in a mixing zone with the introduction of air under pressure to create and aerating spray or splash zone with aerated liquor being mixed with the untreated liquor in the tank to convert the anaerobic liquor to an aerobic condition before exiting the tank.

The aerobic microbial digestion process is accomplished by a reactor pod located preferably in a mixing zone in the general area adjacent the outlet of the tank. In the preferred embodiment, the reactor pod comprises a cylinder having a multitude of perforations in the wall thereof which is submerged in the liquor. A draft tube is located within the cylindrical pod and an air pressure source introduces an air stream which pumps liquid vertically upwardly through the draft tube and creates a splash or spray pattern above the surface of the water level, serving to aerate the expelled liquor. Aerobic microbial media is contained in the cylindrical pod and a portion of the aerated liquor in the spray pattern is returned and allowed to pass downwardly through the media and to be recirculated through the draft tube and spray pattern. In addition, the spray pattern is configured to deliver a substantial portion of the aerated liquor outside of the perimeter of the reactor pod and returned to the unmixed liquor in the general volume of the tank. Since the walls of the pod are perforated, there is a free exchange of mixed and unmixed liquor between the general volume of the tank and microbial growth media in the pod. The reactor pod is not connected nor does it deliver treated effluent to the outlet of the tank, thus not only providing treatment for liquor within the pod but also treating of the liquor in the general volume of the tank.

In order to increase the effectiveness of the treatment of the liquid in the tank, a return line may be installed for the purpose of collecting a predetermined volume of oxygen rich aerated liquor from the spray pattern and returning it to the quiescent or settling zone of the tank in the general area of the inlet. In this manner, the entire volume of the tank may be converted from an anaerobic to an aerobic digestion processes. A buoyant microbial growth media is preferred for containment in the cylindrical reactor pod. Although this media does not tend to incur flocculent build up during normal operation, a back flushing feature for scrubbing off organic build up and preventing the process from becoming anaerobic is provided. A back flushing air pressure manifold is located in the bottom end of the cylindrical pod which may release air jets upwardly from a manifold in order to scrub off organic build up and to create a turbulent zone to increase treatment and oxygen transfer if desired.

The features of the present invention include the ability to add or withdraw self contained stand alone reactor pods to accommodate the actual organic waste load at a given site or under given conditions of loading. The pod as described is preferably a cylindrical open ended cylinder supported on the bottom of the septic tank. When used in the normal septic tank environment, the tank will be fitted with access openings and the diameter of the cylindrical pods may be chosen so as to allow for easy insertion and withdrawal of pod units as the situation dictates. This is also made possible by the fact that the reactor pods can be made as a stand alone self contained unit not connected in any way to the structure of the septic tank.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is perspective view of a septic tank installation embodying the wastewater treatment system of the present invention;

FIG. 2 is a perspective view of the reactor cylinder pod or mixing unit;

FIG. 3 is a partially sectioned view of the cylindrical pod in the aeration mode;

FIG. 3A is a cross sectional view of the cylindrical pod in the back flush mode;

FIG. 4 is a perspective view of the back flush manifold;

FIGS. 5-7 are diagrammatic illustrations of installations utilizing 1, 2 and 3 cylindrical pods respectively in an optionally divided chamber septic tank system;

FIG. 8 is a diagrammatic illustration of the free standing cylindrical pod and optional return line arrangement.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIG. 1, a typical installation of the treatment system includes the cylindrical pod reactor unit 1 and a typical septic tank 2 having an inlet end wall 3 and an outlet end wall 4. The tank 2 defines a confined volume and is usually located below ground level and will have a suitable removable lid (not shown) completely covering the tank. This relationship is shown more clearly in FIG. 8 wherein the lid 6 will also include suitable manhole or access covers 7 and 8 and may include suitable venting means (not shown). Although the typical underground septic tank will be referred to in the description of the preferred embodiment of the present invention, it will be understood that the invention may be utilized in conjunction with any type or configuration of anaerobic wastewater septic system. In the system shown, the tank 2 will be connected to the source of wastewater or sewage through the wastewater disposal line 9 emanating from a single or multiple family dwelling unit or a commercial establishment. The terminal end of the line 9 is normally mounted in the end wall 3 and includes a baffle 11 having a vent 12 extending above the liquid level line 13 as shown in FIG. 1. The end wall 4 is fitted with an effluent outlet line 14 also provided with a baffle 16 and air vent 17 in a well known manner. As is well known in the art, in the standard installation, wastewater will enter the tank 2 from the house or other source via the line 9, solids are settled out and collect at the bottom of the tank in a quiescent zone and the liquid effluent exits the tank via the outlet line 14 and flows to a suitable drain field or mound for final disposal. In the normal situation, the wastewater and biodegradable solids in the tank 2 undergo an anaerobic process whereby the biodegradable solids are digested by anaerobic microbes. This process is an extremely long and highly inefficient process, also producing noxious gasses during the process. The wastewater enters the tank undergoes the anaerobic digestion process and, hopefully absent the settled solids, exits the tank through the line 14 in an anaerobic condition in which it remains until settled out in a drain field or is otherwise treated in some secondary system. It will be noted that the cylindrical pod is located near the outlet end of the tank 2 as illustrated in FIG. 1 and an optional return line 18 extends away from the pod toward the inlet end of the tank for a purpose presently to be described.

The structural details of the cylindrical reactor pod or unit 1 are shown in FIGS. 2-4. Referring to FIG. 2, the unit 1 is a stand alone unit comprising the cylindrical reactor pod 19 supported by four leg members 21 preferably connected at their bottom ends by means of the cross bracing members 22 for stability. The upper extent of the legs 21 may be attached by any convenient means such as welding or fastener means to the internal framework of the cylinder 19. The upper ends of the leg members 21 may be connected and held in position by means of cross bracing 23-24 and 26-27. The legs 21 will extend upwardly through the cylinder 19 to the position adjacent to or shortly above the upper rim of the cylinder 19 which has been cut away in FIG. 2 to better illustrate the structural details. It will also be noted that the upper and lower ends of the cylinder are open to allow free liquid flow therethrough. As seen most clearly in FIG. 8, the bottom ends of the legs 21 are designed to be supported on the tank bottom and are of such an extent as to support the upper rim of the cylinder 19 preferably a distance of approximately 2 inches below the liquid level 13 of the tank when installed in the preferred embodiment. This relationship is shown in FIGS. 3 and 3A. In a typical 1000-2000 gallon tank, the cylinder 19 may have a height in the neighborhood of 2 feet and typical diameter of approximately 18 inches. In practice, the cylinder 19 may be formed from a tubular plastic material such as PVC and the leg members 21 and cross bracing members described may also be made from PVC tubing. The legs, the cylinder and the cross bracing may be conveniently connected by standard pipe fittings, plastic welding or fastener members as desired. It will also be noted that the cylinder 19 in addition to being open at top and bottom is provided with perforations 28 to allow for free passage of liquid effluent through its wall surface. The size, number and spacings of these perforations may be varied as a matter of design depending upon the degree of circulation of liquor desired.

A centrally located draft tube is supported within the cylindrical reactor pod 19 by any convenient means such as the upper and lower connectors 31 and 32 respectively extending from one or more of the cross bracing 23-24 and 26-27. Any suitable alternative means for supporting the draft tube 29 within the cylinder pod 19, of course, is possible. Air under pressure is introduced into the draft tube 29 by means of the air pressure conduit 33 as seen in FIGS. 3 and 3A. The conduit 33 extends downwardly into the cylinder 19 exterior of the draft tube and is connected to the tube 29 through a free opening via fitting 34. The conduit 33 directs a stream of air under pressure from a pressure source such as the blower 36. As seen in FIG. 3, air under pressure introduced through the conduit 33 creates a pumping action which causes a flow of liquor vertically upwardly in the draft tube 29, pulling liquid from the area surrounding the pod 19 into the tube 29 and upwardly toward the open upper end of the tube.

The conduit 33 may comprise a PVC pipe in the order of Â¼-2 inches in diameter and will be connected at the lower portion of the draft tube 29 to provide a clear unobstructed air stream into the draft tube, enhancing the pumping and mixing of the effluent as it flows upwardly through the draft tube. The draft tube 29 may have a diameter of approximately 3 inches in order to maximize the blower energy. As illustrated in FIGS. 1 and 3, sufficient pumping force will be developed so as to create an aerating spray or splash of aerated effluent from the upper open end of the tube with the splash area of the expelled aerated effluent being sufficient to reach beyond the upper peripheral edge of the cylinder pod 19. In this manner, the recirculating pattern of the liquor promotes oxygen transfer and treatment to the surrounding liquid in the tank. The upper end of the tube 29 may be maintained at or somewhat above the water level 13 of the tank in order to create the aerated spray or splash.

As illustrated in FIGS. 3 and 3A, the cylindrical reactor pod 19 will be filled with a multiplicity of buoyant media such as the spheres 37 which freely float within the pod. The media 37 are preferably composed of buoyant hollow plastic spheres that provide a high surface area to volume ratio in the order of 48 square feet per cubic foot or more with a 93.5% void space to promote oxygen transfer and circulation within the pod. This type of buoyant media and its function of providing maximum microbial growth surfaces is well known in the art and, although subject to modification, is the preferred media for the present system. The buoyant media does not tend to incur flocculent buildup during operation and avoids the consequent clogging typical of fixed or packed media treatment systems. As indicated by the arrows in FIG. 3, the cylinder pod 29 provides a mixing zone for the liquid effluent in the septic tank as the aerated oxygen rich liquor is pumped upwardly through the draft tube 29 and is caused to spill back down into the media 37 as well as into the general body of the liquor surrounding the cylinder pod. Additionally, the perforations 28 in the wall of the cylinder 19 provide a constant mixing and interchange of aerated and non-aerated liquid. Because of the available voids, aerobic biological growth takes place in the mixing zone with the buoyant media, which has a low resistance to liquid flow, providing a non turbulent zone with low oxygen loading rates, creating surface conditions receptive to aerobic microbial growth. Since the cylinder pod 19 is a free standing unit within the body of the liquid in the tank, it is not necessary to connect it structurally to the outlet of the tank either for support or liquid delivery, thus allowing the liquid level in the septic tank to remain constant. Because the cylindrical pod of the present invention is not attached to the outlet of the tank and does not have a lift feature intended for discharge, the mixed liquor within the tank remains at a constant volume. This constant volume relates to a constant volume of sewage treated to a specific level. In the present configuration, the sewage enters the septic tank of the inlet conduit 9, is mixed with oxygen rich liquor treated by the cylinder pod 19 and immediately flows out of the tank through the exit line 14. Under normal operating conditions this results in a specific detention time for sewage within the tank. Because of the perforations 28 in the cylinder 19, liquor is allowed to flow into and out of the treatment unit, as shown by the arrows in FIG. 3, creating a recirculating pattern which enhances oxygen transfer and treatment to the surrounding body of liquid. The cylinder pod 19 is thus not directly processing effluent and discharging it into the drain field but rather is treating the entire tank volume.

Although the buoyant media 37 of the type under consideration is not normally subjected to clogging because of microbial build up, causing the process to become anaerobic, in the case of constant organic overload, the present system incorporates a back flushing feature for scrubbing off organic build up and creating a turbulent zone to increase treatment and oxygen transfer if desired. Referring specifically to FIGS. 3A and 4, a back flush air pressure manifold, indicated generally at 38 in FIG. 4, is suspended in the cylinder pod 19 and includes air pressure supply conduit 39 supplied with air under pressure from the blower unit 41 as shown in FIG. 8. The pressure conduit 39 is connected to an air pressure manifold which is in the shape of a loop comprising the downwardly directed conduits 42 and 43 connected to a diffuser 44 surrounding the bottom end of the draft tube 29. The manifold is provided with orifices 46 for releasing air jets upwardly, as shown by the arrows in FIG. 3A, through media 37. In the event of clogging or undue organic buildup on the media 37, the pumping air stream from conduit 33 is halted and the blower 41 is actuated to produce reverse air streams through the media 37 to flush the media 37. Although separate blowers 36 and 41 have been illustrated and discussed relative to the present embodiment, it will be understood, of course, that a single blower or compressor and appropriate valving and controls could be utilized as a source of air pressure for both of the lines 33 and 39 well within the skill of an artisan.

As discussed above, one of the objects of the present method, system and apparatus is to provide aerated and oxygen rich mixed liquor to the general area of the septic tank which may be accomplished in the main by (1) providing a free recirculation pattern and mixing zone between the pod and the surrounding effluent and (2) by creating a splash area of the outflow from the upper end of draft tube 29 in the mixing zone beyond the periphery of the cylinder reactor pod 19. With the perforations 28 a constant recirculation pattern is created with the surrounding tank volume providing increased dissolved oxygen within the tank to promote aerobic decomposition. In order to further enhance this process if required, a return line 18 may be mounted on the wall of the cylinder pod 19 for collecting aerated liquid expelled from the draft tube 29 and transporting it to the area preferably adjacent the inlet area of the tank as shown in FIGS. 1 and 5-8. Referring to the detail in FIG. 3, the return line 18 may be a plastic pipe supported by the bracket 47 and passing through a suitable retainer or collar 48 carried by the bracket. The bracket 47 is fixed to the wall of the cylindrical pod 19 and may be attached by such means as adhesives, plastic welding or fasteners of any suitable design. The line 18 is open at its distal end adjacent the inlet area of the tank to allow for discharge of mixed liquor and has its opposite end at the pod configured to collect outfall from the draft tube 29 as illustrated. The collector configuration on the end of the return line 18 can be conveniently formed by removing a top portion of the conduit as illustrated at 49 in FIG. 2. The conduit or return line 18 will be positioned above the water line 13 in the tank so as to provide an incline to accommodate gravity flow. The distance of the end of the conduit 18 above the water line 13 may be adjusted to accommodate any particular installation and will normally be in the range of 2-4 inches to ensure gravity flow. For this purpose, the bracket 47 may be made adjustable or, in the alternative, the position of the collar 48 in the bracket 47 may be made adjustable (not shown). It will also be noted that any form of collector apparatus may be substituted for the collector configuration 49 without departure from the spirit and scope of the invention. In a typical 1000-2000 gallon septic tank, the pumping rate through the draft tube 29 may be adjusted to deliver in the range 0-3500 gallons per day through the return line 18, providing good results in converting the septic tank volume to aerobic condition.

In practice it is often difficult to predict the actual organic waste load at a given site or the conditions may simply change and the organic waste load may increase for one reason or another. The present configuration of stand alone cylinder pod is not connected to, nor does it deliver liquid directly to the outlet of the tank and, in fact, is not in any way required to be structurally connected to the tank itself. This configuration lends flexibility, allowing additional pods or treatment cells to be added to the same tank compartment, thus enlarging the mixing zone without disturbing or modifying the existing septic tank. Since the present unit or pod 19 may have a nominal diameter of 18 inches, additional pods may be inserted through a standard 24 inch access opening usually provided in the tank lid. FIGS. 5-7 illustrate progressively a single, a double and a triple pod installation in a typical septic tank. Although subject to modifications, these pods are preferably located in an area adjacent the outlet of the tank. As illustrated in FIGS. 5-7, the tank may also include a compartment wall 51, shown in dotted lines creating a primary or inlet settling compartment 52 and a larger mixing and settling compartment 53. If such a configuration is utilized, it is recommended that the cylinder pod or pods be located in the larger area compartment of the tank. In this instance, of course, the return line will extend past the compartment wall 51 so as to deliver aerated liquor into the primary compartment 52. As shown in FIG. 5, a first access opening 7 may be located so as to access the distal end of the return line 18 and may also be sized and positioned to overlie the inlet baffle. A second access opening 8 is provided for the insertion, removal and manipulation of the pod 19. In the event of multiple pods, suitable collector units 49a and collector lines 18a will be utilized to deliver the liquor from the pods to return line 18. Additional pods may be arranged with suitable collector devices and return lines to channel the flow of aerated liquor from the pods to a suitable return line.

Although the preferred embodiment has been described and illustrated utilizing a free standing cylindrical pod unit in order to gain the advantage of easy addition and removal of the units, it would of course be possible to support the units via connection to the tank structure. In such a case, however, the ability of free removal, replacement and/or addition of pod units without disturbing the tank structure may be forfeited.

While the present invention has been illustrated and described according to a preferred embodiment and certain alternatives, it is to be understood that further modifications and variations in the apparatus and treatment method may occur to those skilled in the art which are considered to be well within the intended scope and spirit of the present invention. For example, the apparatus and method may be combined with other sewage treatment apparatus and the present apparatus and method may be applied to a wide variety of septic tank capacities and configurations. In this connection, the dimensions and exact configuration details of the various parts of the apparatus may be modified as well as the choice of materials and assembly methods used in constructing the apparatus. The exact air pressure controls utilized is deemed well within the skill of those conversant in the art as are the flow rates and air pressure values required to provide any design result. The scope of the invention, therefor, is only to be limited by the claims appended hereto.