WASTEWATER TREATMENT SYSTEM AND METHOD
A system, method and apparatus for treating wastewater containing biodegradable material wherein a submerged stand alone perforated cylinder reactor pod containing aerobic bacterial growth media and a draft tube with air pressure induced pumping action creates a spray or splash pattern so as to recirculated aerated liquor through the media and also to the area surrounding the cylinder pod. Free interchange of mixed and unmixed liquor is provided via the perforations in the cylindrical pod wall. Provision is also made for back flushing the media and returning mixed liquor to an area remote from the reactor pod.
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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 INVENTIONThe 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
Referring to
The structural details of the cylindrical reactor pod or unit 1 are shown in
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
The conduit 33 may comprise a PVC pipe in the order of ¼-2 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
As illustrated in
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
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
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.
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.
Claims
1. A wastewater treatment system comprising;
- a wastewater collection tank comprising a confined volume,
- said tank including a wastewater inlet for receiving wastewater containing biodegradable material and an outlet for outflow of treated effluent to a disposal site, said outlet defining the liquid level in the tank,
- said tank providing a first quiescent zone in the general area of said inlet for settling the major portion of solids from the wastewater to form a liquor in the confined volume of said tank and a second mixing zone in the general area of said outlet,
- a perforated wall open ended reactor pod located in said second zone and submerged in said liquor, said pod being provided with a quantity of buoyant aerobic bacterial growth media,
- an open ended draft tube supported in the central section of said reactor pod,
- an air pressure conduit extending from a source of air under pressure and connected to the lower portion of the draft tube for introducing an air pressure stream providing a pumping force to pull liquor upwardly therethrough and to expel liquor in an aerating splash pattern from the top of the tube,
- said pumping force being sufficient to form said splash pattern so as to return a first given portion of aerated liquor onto the media within the pod and a second substantial portion to the general area of said second zone adjacent the reactor pod for recirculation by said draft tube,
- said perforated wall of the pod permitting free exchange of mixed and unmixed liquor between the pod and media and the general volume of the tank,
- said treated recirculated liquor effluent being allowed to freely flow out of the tank through said outlet to maintain a constant liquid level in the tank.
2. The wastewater treatment system of claim 1 including;
- a return line extending from said splash pattern to the quiescent zone,
- a collector connected to the return line in the splash zone for collecting a third given portion of aerated liquor to the quiescent zone for gravity flow.
3. The wastewater treatment system of claim 1 including;
- a back flushing manifold located in the bottom portion of said reactor pod,
- air pressure source for selectively providing air under pressure to said manifold,
- said manifold introducing air streams upwardly through said media for scrubbing off organic build up and creating a turbulent zone to increase treatment and oxygen transfer.
4. The wastewater treatment system of claim 1 wherein said waste water tank comprises a septic tank including a lid with at least one access opening,
- said reactor pod comprising a cylinder having a plurality of perforations in the wall thereof and being sized for passing through the access opening, and
- support means for supporting said pod in the septic tank as a free standing unit,
- whereby the treatment capacity of the septic tank may be increased and decreased by inserting and withdrawing self contained reactor pods through the access opening.
5. A method for treatment of wastewater within a confined volume, comprising the steps of;
- settling out solids in a quiescent zone to form a liquor,
- pumping liquor from a mixing zone upwardly through an open draft tube so as to expel liquor in an aerating splash pattern,
- placing aerobic bacterial growth media in a submerged perforate walled reactor pod located about said draft tube,
- controlling the pumping action to form said splash pattern for returning a first given portion of the aerated liquor onto said media and a second substantial portion to the mixing zone beyond said pod,
- said perforate wall of the reactor pod permitting free exchange of mixed and unmixed liquor between the reactor pod and growth media and said confined volume.
6. The method according to claim 5 including the further steps of;
- collecting a third given portion of said aerated liquor, and
- channeling said third portion of aerated liquor to said quiescent zone.
7. The method according to claim 5 including the further step of;
- selectively introducing back flushing air streams upwardly through said media for scrubbing off organic build up and creating a turbulent zone to increase treatment and oxygen transfer.
8. A method for treatment of wastewater within a confined volume, comprising the steps of;
- directing wastewater into said confined volume,
- settling out the major portion of solids from the wastewater in a quiescent zone to form a liquor,
- pumping liquor from a mixing zone upwardly through an open draft tube by introduction of an air pressure stream within the draft tube so as to expel liquor in an aerating splash pattern,
- placing aerobic bacterial growth media in a submerged perforate walled reactor pod located about said draft tube,
- controlling the air pressure stream to create a pumping action sufficient to form said splash patter so as to return a first given portion of the aerated liquor onto said media and a second substantial portion to the mixing zone beyond the reactor pod,
- said perforate wall of the reactor pod permitting free exchange of mixed and unmixed liquor between the reactor pod and growth media and said confined volume, and
- allowing treated effluent to exit said contained volume to maintain a constant level of liquor.
9. The method according to claim 8 including the further steps of;
- collecting a third given portion of said aerated liquor, and
- channeling said third portion of aerated liquor to said quiescent zone.
10. The method according to claim 8 including the further steps of;
- selectively introducing back flushing air streams upwardly through said media for scrubbing off organic build up and creating a turbulent zone to increase treatment and oxygen transfer.
11. A method for treatment of wastewater containing biodegradable material within a septic tank having a confined volume, a wastewater source inlet and a drain field disposal outlet, comprising the steps of;
- directing wastewater from said source into said tank through said inlet,
- settling out the major portion of contained biodegradable solids from the wastewater in a quiescent zone in the general area of said inlet to form a liquor in the confined volume of the septic tank,
- pumping liquor from a second adjacent mixing zone in the general area of said outlet upwardly through an open draft tube by introduction of an air pressure stream within the draft tube so as to expel liquor outwardly in an aerating splash pattern from the top end of the tube,
- surrounding the draft tube with aerobic bacterial growth media contained in a perforate walled reactor pod submerged in said second zone,
- controlling said air pressure stream to create a pumping action sufficient to form said splash pattern so as to return a first given portion of said aerated liquor onto said media within said pod and a second substantial portion to the general area of said second zone adjacent said pod,
- said perforate wall of said reactor pod permitting free exchange of mixed and unmixed liquor between the reactor pod and growth media and the general volume of the tank, and
- allowing free flow of oxygen rich aerobic effluent to exit said tank through said disposal outlet to maintain a constant level of treated liquor in said tank.
12. The method according to claim 11 including the further steps of;
- collecting a third given portion of said aerated liquor from said splash pattern, and
- channeling said third portion of aerated liquor to said quiescent zone.
13. The method according to claim 1 1 including the further step of;
- selectively introducing back flushing air streams upwardly through said media for scrubbing off organic build up and creating a turbulent zone to increase treatment and oxygen transfer.
14. The method according to claim 11 wherein said septic tank includes a lid with at least one access opening, said reactor pod comprises a cylinder having a plurality of perforations in the wall thereof, said pod being a free standing unit supported within the septic tank and having a diameter sized for passing through the access opening, the method further including the step of;
- selectively increasing and decreasing the treatment capacity of the septic tank by inserting and withdrawing self contained reactor pods through the access opening.
15. Apparatus for oxygen enrichment of the wastewater in a septic tank to provide aerobic microbial digestion of biological material, said tank including a wastewater inlet and a disposal outlet defining the liquid level of the wastewater liquor in the tank, said apparatus comprising;
- a perforated wall reactor pod submerged in said liquor,
- said pod being open at the top and bottom ends provided with aerobic bacterial growth media,
- an open ended draft tube supported in the reactor pod, and
- an air pressure conduit providing air under pressure to the lower end of said draft tube creating a pumping force to expel aerated liquor from the top of the tube in a splash pattern,
- said pumping force being sufficient to form said splash pattern so as to return a first given portion of aerated liquor onto the media within the pod and a second substantial portion to the general area surrounding the pod for recirculation by said draft tube,
- said perforated wall permitting free interchange of mixed and unmixed liquor between the pod and media and the area surrounding the pod.
16. The apparatus according to claim 15, wherein;
- said reactor pod comprises an open ended cylinder having a top rim and plurality of perforations in the wall thereof for free exchange of mixed and unmixed liquor between the pod and media and the area surrounding the cylinder.
17. The apparatus according to claim 16 wherein said septic tank includes a bottom wall, said apparatus including;
- support structure for supporting said cylinder on the bottom wall of the tank with the top rim thereof below the water line.
18. The apparatus according to claim 17 wherein said media comprises buoyant spheres adapted for collecting aerobic bacterial growth on the surface thereof.
19. The apparatus according to claim 18 including;
- support structure for supporting said draft tube vertically within the central portion of said cylinder with the top end thereof above the water lie and the lower end adjacent the bottom end of the cylinder,
- said media surrounding said draft tube.
20. The apparatus according to claim 15 including;
- a return line conduit having one end supported on said cylinder and extending to a location remote from the general area surrounding said cylinder pod, and
- collector means on said one end of the return line conduit located within the splash pattern for collecting a third portion of aerated liquor and conducting the same by gravity flow said to remote position.
21. The apparatus according to claim 16 including;
- a back flushing manifold having openings therein for producing airjets,
- means for introducing air under pressure into said manifold, and
- support structure for supporting said manifold adjacent the bottom end of said cylinder pod for producing air jets directed upwardly through said media.
22. The apparatus according to claim 17 wherein said septic tank includes a lid with at least one access opening,
- said cylinder and support structure therefor being sized for passing through the access opening for inserting and withdrawing the reactor pod into and out of the septic tank.
Type: Application
Filed: Feb 15, 2005
Publication Date: Aug 17, 2006
Applicant:
Inventors: William Stuth (Kent, WA), Matthew Lee (Kent, WA)
Application Number: 11/059,187
International Classification: C02F 3/06 (20060101);