Current and aeration system for wastewater plant

Abstract

A defined current and aeration system for the aeration chamber of an aerobic wastewater treatment plant is disclosed. It includes the release of oxygenation gas or air into the aeration chamber through a diffuser or the like at a position such that the air injected into the tank provides the necessary amount of oxygen for aerobic bacterial digestion of the waste while creating a current or circulation pattern in the chamber that forces every portion of the fluid within the aeration chamber into circulation thus preventing the accumulation of solids as sludge in the wastewater treatment plant.

Description

BACKGROUND OF THE INVENTION

This invention relates to an improved system for supplying air to the aeration chamber of an aerobic wastewater treatment plant.

In remote areas, newly developed subdivisions, or other locations where a municipal sewer system is not available, small anaerobic or aerobic wastewater treatment plants are used to handle the wastewater produced. Septic tanks use anaerobic bacteria to convert the organic solid waste in the wastewater stream. Usually, however, most of the organic solids settle as sludge to the bottom of the septic tank and must be pumped out periodically.

Aerobic wastewater treatment plants use “extended aeration” to efficiently encourage aerobic bacteria growth. Extended aeration includes contacting the wastewater with a large number of small bubbles of oxygen-carrying gas, thus maximizing the surface area for oxygen transfer. Air or oxygen is generally pumped into the tank through diffusers that break up the air into thousands of tiny air bubbles. Aerobic bacteria in the water convert waste products to water and CO₂, thus purifying the water and reducing the wastewater to a clear odorless liquid. Through extended aeration, the home wastewater treatment plants accelerates the reduction of waste substantially beyond the rate of reduction which can be accomplished with an anaerobic septic tank or even the rate of reduction observed in nature.

One problem associated with aerobic wastewater treatment plants is the failure of the flow of air in the aeration chamber to keep some of the solids from continuously settling to the bottom, where they build up a layer of sludge in the aeration and clarifier chamber, requiring periodic removal. It is desirable that a minimum of sludge removal be required since, in addition to the high maintenance requirement, disposal of the sludge presents an ecological problem. An accumulation of sludge within the unit further results in a deterioration of the wastewater treatment process because the high concentration of bacteria in the sludge rapidly consumes the available oxygen in the immediately surrounding water, whereupon, the bacteria begins to break down nitrogen compounds in the sludge to release bonded oxygen. This results in a release of nitrogen gas, which rises to the surface producing scum and disrupting the bacterial conversion. Thus, bacteria and waste need be maintained in solution for optimum conversion.

The basic aerobic wastewater treatment plant for home use includes a tank which is buried in the ground except for the top opening which provides access to the inside of the tank. The tank is divided into an aeration chamber into which the wastewater flows, where oxygen is supplied to cause aerobic bacteria to digest the solids in the wastewater, and a clarifier chamber from which the treated wastewater exits the treatment plant. An external oxygen source is generally connected to a PVC line which drops through the top portion of the tank to the bottom of the tank in the aeration chamber.

There are two basic designs of these treatment plants known in the art which are devised to retain solids in the aeration chamber until they can be broken down by bacteria. The first design includes two substantially rectangular chambers separated by a baffle or partition extending from the top of the plant a substantial length down through the plant. Wastewater must flow under this baffle to reach the clarifier chamber. A deflector directing errant solids out of the clarifier chamber back into the aeration chamber is a frequent element in this type of plant.

The second basic design of treatment plants includes a partition that is shaped like an inverted, truncated cone. This partition divides the tank into the two chambers, an outer aeration chamber and an inner clarifier chamber. This design may also incorporate a pyramid shaped deflector placed beneath the truncated conical partition to deflect solids settling out of the clarifier chamber back into the aeration chamber for further bacterial digestion.

Any solids remaining in the wastewater entering the clarifier chamber are expected to be converted by the bacteria in the clarifier chamber before the water reaches the outlet. Since this does not always happen, it is best to minimize the amount of solids reaching the clarifier chamber by efficiently exposing all solids in the aeration chamber to bacterial digestion and avoiding solid accumulation in the form of sludge.

Wastewater treatment plants of all shapes suffer from an accumulation of sludge in the tank. Sludge accumulates due to circulatory “dead spots” in the tank where the fluid does not flow. Dead spots may occur in corners of vessels due to the circulation pattern achieved in the vessel. Dead spots may also occur with the use of diffusers in two or more locations due to the interference pattern produced in the circulation or currents by the diffusers. It has been determined, that sludge tends to accumulate at the base of deflectors and, even worse, directly below the clarifier chamber. As discussed previously, sludge build-up results in the release of nitrogen gas. When the sludge is below the clarifier chamber, the nitrogen bubbles up into the clarifier chamber producing scum and interfering with the operation of the clarifier.

While the use of diffusers in multiple locations necessarily creates the problem of circulatory dead spots where sludge accumulates, this problem is accentuated since air entering into multiple lines is not emitted evenly. The air tends to come out more from one diffuser that the other, particularly if the tank is slightly tilted.

Current U.S. Pat. Nos. 4,664,795 and 4,834,879 by William A. Stegall et al issued May 12, 1987 and May 30, 1989 respectively, disclose the use of a diffuser in the rectangular-shaped treatment plant such that the placement of the diffuser opposite of the baffle and deflector set up a circular pattern in the aeration chamber specifically to avoid the migration of solids into the clarifier chamber. The drop line delivering air to the diffuser is placed directly below the inlet to the wastewater treatment plant and close to the bottom of the plant. The position of the diffuser creates a rolling pattern such that fluid carrying solids moves away from the opening of the clarifier chamber. Sludge build-up in low- or no-circulation zones is not addressed, but the circulation pattern as demonstrated in the drawing, while sweeping the bulk of the fluids into motion, does not sweep into the corners of the chamber. Presumably, this is where sludge build-up occurs.

U.S. Pat. No. 5,266,239 issued to T. Gig Drewery on Nov. 30, 1993, discusses the use of a wastewater treatment plant with an truncated, inverted conical partition having three drop lines for air, as shown in the drawings. The drop lines with diffusers for releasing air are spaced circumferentially and placed near the bottom of the plant. The diffusers create a current including three rolling patterns. The patent drawings show downwardly sweeping necessitated by the interference pattern of the neighboring diffusers. This creates multiple dead zones on the bottom of the aeration chamber. With the use of multiple diffusers, one such dead zone is created directly beneath the clarifier chamber.

U.S. Pat. No. 5,221,470 from the current Applicant, Jerry L. McKinney, issued Jun. 22, 1993, discloses a treatment plant having an inverted truncated conical partition and a pyramidshaped deflector below. One of the inventions of this patent is the use of rigid conduits through which flexible air hoses extend to discharge air adjacent to the bottom of the aeration chamber. These rigid conduits are attached to the plant wall and extend vertically towards the bottom of the plant. The use of two diffusers creates interference patterns similar to those exhibited in the Drewery patent.

It is a feature of this invention to minimize or eliminate sludge build up in a wastewater treatment plant.

It is a further feature of this invention to create an improved current in a wastewater treatment plant that sweeps all solids into circulation to prevent solids from accumulating in a wastewater treatment plant.

It is a further feature of this invention to position an air diffuser in a single location in the aeration chamber of a wastewater treatment plant to create currents in the wastewater in the tank that will maintain all solids in circulation with the wastewater.

These and other objects, advantages, and features of this invention will be apparent to those skilled in the art from a consideration of this specification including the attached drawings and appended claims.

BRIEF SUMMARY OF THE INVENTION

The introduction of diffused oxygenation gas or air in a single location close to the direction directions, as indicated by the numbers 102 and 104. As these currents meet on the opposite side of the partition, the intersection of the outer currents cause causes a downwardly flowing current 106 which flows to the bottom of the aeration chamber which creates main currents 108, 110, and 112 that sweep across the bottom in all directions. The water sweeping generally in a straight line across the bottom of the vessel in direction 108 moves with the greatest speed and serves to move any solid falling out of the clarifier chamber back into circulation in the aeration chamber, thus preventing any accumulation of solids in the bottom of the aeration chamber. The water moving generally around the outer perimeter of the vessel in directions 110 and 112 moves at a slower speed but with enough speed to scour the edges of the vessel and to sweep the solids into circulation. All areas of the bottom of the vessel are forced into circulation. Those areas intermediate between the path straight across the bottom of the vessel and the path around the outer perimeter travel at respectively intermediate speeds. While FIG. 1 shows the entire circulation pattern, FIG. 5-7 show different views of parts of this pattern. As depicted in FIGS. 1 and 6, the injection system generates an area of aerating bubbles adjacent the intersection of the side wall and the bottom wall that induces the current flow shown in FIGS. 1 and 6. Thus, assuming that direction 100 in FIG. 1 depicts the current flow of the wastewater induced at an injection area adjacent the intersection of the side wall and the bottom wall of the aeration chamber, a branched current having runs indicated by 102 and 104 is produced. Accordingly, if multiple diffusers are used, they must be positioned in sufficient proximity to one another such that the current or circulation pattern depicted in FIG. 5 is achieved.

While the wastewater in the aeration chamber is thus forced into circulation, the clarifier chamber remains largely undisturbed. Fluid rises in the clarifier chamber in direction 114 as a result of hydrostatic head. The defined current produced by the introduction of oxygenated gas, flows across the opening of the inverted, truncated cone defining the clarifier chamber in direction 116 but does not flow into the clarifier chamber. Thus the clarifier chamber has reduced turbulence, while the aeration chamber bacteria effectively digest the solid particles from the wastewater. Treated wastewater rises through the clarifier chamber and exits the plant through an outlet pipe.

The diffuser is located close to the bottom of the plant, preferably within 3 to 4 inches from the bottom, and close to the side wall of the tank in order to produce the desired current. Placing the diffuser closer to the center causes the air to hit the conical partition, thus changing the pattern. Such placement also causes the tiny bubble to coalesce into larger bubbles along the partition, thus reducing the aeration effect. If the diffuser is placed too far above the bottom of the tank, then sludge will accumulate beneath the diffuser on the bottom of the tank.

Experimentation was conducted on a base case of a 850 gallon tank using one air diffuser at [x] psig and [y] flow rate. The current pattern described above was observed. The current sweeps up the side wall above the diffuser in direction 100, around the partition in directions 102 and 104, down the opposite side wall in direction 106, and across the bottom in directions 108, 110, and 112. It can be observed that the flow turns below the truncated conical partition creating slight suction which pulls solids out of the bottom of the clarifier chamber by this action. Thus, the defined current not only mixes the solids and water for maximum digestion of the waste such that fewer particles are available to enter the clarifier chamber, but the current also serves to pull solids out of the bottom of the clarifier chamber for further digestion in the aeration chamber.

When a diffuser plugs up or for whatever reason a drop line needs to be removed for repair or replacement, the drop line is discovered disconnected from the external oxygenation gas source, such as an air compressor, and simply pulled out of the rigid conduit in which it is located and out of the tank through opening 14. The new or repaired hose and diffuser can then be threaded back through the rigid conduit and reconnected to the air compressor.

Another preferred embodiment includes the use of multiple diffusers all of which are placed generally below the inlet to the wastewater tank close to the bottom. This allows the introduction of a higher volume of oxygenation gas while creating the circulation or current pattern of the invention. To equalize the pressure between the multiple diffusers, a pressure regulator such as a choke valve can be utilized. This assures an equal amount of oxygenation gas flowing to each diffuser.

Another preferred embodiment includes releasing the oxygenation gas through a diffuser located close to the bottom and close to the side wall of the wastewater treatment plant by delivering oxygenation gas directly through the bottom or side of the wastewater treatment plant into the aeration chamber.

From the foregoing it will be seen that this invention is one well adapted to attain all of the ends and objects hereinabove set forth, together with other advantages which are obvious and which are inherent to the apparatus and structure.

Because 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.

For example, oxygenation gas can be delivered in many ways to the diffuser location close to the bottom and the side wall of the aeration chamber of the wastewater treatment plant. In addition to the drop lines, aeration pipes or the like can be used. The release of the oxygenation gas to create the circulation pattern of this invention encompasses all such deliveries.

Likewise, while a diffuser is used to release the oxygenation gas or air so as to encourage bacteria growth and to force the circulation, other emitters or components can be used to produce this desired effect. By releasing the oxygenation gas in such an amount and at such a location as to create the circulation pattern of this invention, such substitute components are encompassed within this invention.

The above examples are illustrative and are to be understood as non-limiting as to the scope of the invention.

Claims

1. In an aerobic wastewater treatment plant comprising:

a vessel defining an aeration chamber and having a substantially flat bottom wall and a substantially cylindrical side wall,

said aeration chamber containing aerobic bacteria into which wastewater containing organic solids flows to be exposed to aerobic bacteria to convert aerobically digest the organic solids in the wastewater to water and CO₂, said aeration chamber having a bottom and side walls ,

means for injecting an oxygenation gas into the wastewater

an aeration system in the aeration chamber to support growth of the aerobic bacteria, and

a clarifier chamber formed in said vessel and into which wastewater from the aeration chamber flows upwardly toward an outlet pipe through which the wastewater flows from the wastewater treatment plant, said clarifier chamber being defined by a partition in the form of an inverted, truncated cone into the bottom of which the wastewater flows from the aeration chamber,

the improvement comprising a diffuser for releasing the oxygenation gas as bubbles into the wherein said aeration chamber of the wastewater treatment plant, said diffuser providing system forms an aeration area adjacent the intersection of the bottom and side wall of the vessel and provides sufficient flow such that all solids suspended within the plant are forced into circulation, said diffuser being placed close to the bottom of the aeration chamber of the wastewater treatment plant and close to the side wall of the aeration chamber, said diffuser aeration system providing sufficient oxygenation gas to allow the aerobic bacteria to convert digest the organic solids in the wastewater into CO₂ and water and a current pattern having at least one first component flowing upwardly in a direction perpendicular to the bottom wall of the vessel and adjacent to the side wall of the vessel, second and third components that flow in opposite directions around the partition which defines the clarifier chamber, a fourth component that flows along said side wall opposite said first component to the bottom, a fifth component that flows across the bottom under the opening to the clarifier chamber, and sixth and seventh components that flow in opposite directions adjacent the bottom wall of the vessel, said current pattern being such that wastewater in said clarifier chamber remains largely undisturbed.

2. The wastewater treatment plant of claim 1, wherein the wastewater treatment plant has a substantially flat bottom.

3. The wastewater treatment plant of claim 2, wherein the released oxygenation gas produces a current in the aeration chamber, the current flowing upwardly from a position of the diffuser in a direction perpendicular to the bottom of the aeration chamber and parallel to the side wall of the aeration chamber, then around the partition which defines the clarifier chamber, then downwardly along the opposite side wall to the bottom and then across the bottom under the opening to the clarifier chamber and around the side wall of the aeration chamber adjacent the bottom of the chamber to keep solids from settling on the bottom of the aeration chamber.

4. The wastewater treatment plant of claim 3 3 wherein said oxygenation gas injecting means aeration system further comprises:

a drop line having a first end attached to an external oxygenation source and a second end open to dispense oxygenation gas received from the an external oxygenation gas source, said second end being attached to said diffuser into said aeration area.

5. The wastewater treatment plant of claim 4 wherein said oxygenation gas injecting means aeration system further comprises

a rigid conduit mounted to the inside of the wastewater treatment plant vessel for receiving and firmly securing the drop line such that the drop line extends from the external oxygenation gas source towards the bottom wall of the plant vessel.

6. The wastewater treatment plant of claim 5 wherein said rigid conduit extends generally parallel to the partition and from there generally to the bottom wall of the wastewater treatment plant vessel such that the rigid conduit is intimately connected to the partition.

7. In an aerobic wastewater treatment plant comprising:

vessel having a substantially flat, bottom wall and a substantially cylindrical side wall and defining an aeration chamber into which the wastewater flows to be exposed to aerobic bacteria to convert aerobically digest the organic solids in the wastewater to water and CO₂, said aeration chamber having a bottom and side walls,

means for injecting an oxygenation gas into the wastewater in the aeration chamber to support growth of the aerobic bacteria , and

a clarifier chamber in which wastewater from the aeration chamber flows upwardly toward an outlet pipe through which the wastewater flows from the wastewater treatment plant, said clarifier chamber being defined by a partition disposed in said vessel, said partition being in the form of an inverted, truncated cone into the bottom of which the wastewater flows from the aeration chamber,

the improvement comprising means for injecting an oxygenation gas and generating a wastewater current pattern in the aeration chamber, the current flowing upwardly from a position from an aeration area close to the bottom and the side wall of the aeration chamber vessel, the current pattern having at least one first component flowing upwardly in a direction perpendicular to the bottom wall of the aeration chamber vessel and parallel to adjacent the side wall of the aeration chamber vessel, then second and third components that flow in opposite directions around the partition which defines the clarifier chamber, then downwardly a fourth component that flows along the said side wall opposite side wall said first component to the bottom and then of the aeration chamber, a fifth component that flows across the bottom under the opening to the clarifier chamber and and sixth and seventh components that flow in opposite directions around the side wall of the aeration chamber vessel adjacent the bottom wall of the chamber vessel to keep solids from settling on the bottom of the aeration chamber.

8. The method of creating a current pattern inside an aeration chamber of a wastewater treatment plant, said aeration chamber having a bottom and side walls, comprising the step of

injecting an oxygenation gas such that a current pattern is produced in the aeration chamber, the current pattern having a first component flowing upwardly from a position close to the bottom and side wall of the aeration chamber in a direction perpendicular to the bottom of the aeration chamber and parallel to the side wall of the aeration chamber, then first and second components flowing in opposite directions around the partition which defines a clarifier chamber, then a third component flowing downwardly along the opposite side wall to the bottom and then , a fourth component flowing across the bottom under an opening to the clarifier chamber, and fifth and sixth components flowing in opposite directions around the side wall of the aeration chamber adjacent the bottom of the aeration chamber to keep solids from settling on the bottom of the aeration chamber.

9. An aerobic wastewater treatment plant comprising:

an aeration chamber containing aerobic bacteria into which wastewater containing organic solids flows to be exposed to aerobic bacteria to convert digest the organic solids in the wastewater to water and CO₂ , said aeration chamber having a substantially flat, bottom wall and a substantially cylindrical side walls wall,

means for injecting an oxygenation gas into the wastewater in the aeration chamber to support growth of the aerobic bacteria,

a clarifier chamber into which wastewater from the aeration chamber flows upwardly toward an outlet pipe through which the wastewater flows from the wastewater treatment plant, said clarifier chamber being defined by a partition in the form of an inverted, truncated cone into the bottom of which the wastewater flows from the aeration chamber, said bottom wall providing a substantially planar surface under said partition,

a diffuser an aeration system for releasing the an oxygenation gas as bubbles into the aeration chamber of the wastewater treatment plant, said diffuser aeration system providing an aeration area and sufficient flow such that all solids suspended within the plant are forced into circulation a circulation pattern, said diffuser aeration system being placed close to the bottom of the aeration chamber of the wastewater treatment plant and close to the side wall of the aeration chamber, said diffuser aeration system providing sufficient oxygenation gas to allow the aerobic bacteria to convert digest the solids in the wastewater into CO₂ and water and a current pattern having at least one first component flowing upwardly in a direction perpendicular to the bottom wall of the vessel and adjacent the side wall of the vessel, second and third components that flow in opposite directions around the partition which defines the clarifier chamber, a fourth component that flows along said side wall opposite said first component to the bottom, a fifth component that flows across the bottom under the opening to the clarifier chamber, and sixth and seventh components that flow in opposite directions adjacent the bottom wall of the vessel.

10. An aerobic wastewater treatment plant comprising:

an aeration chamber into which the wastewater flows to be exposed to aerobic bacteria to convert aerobically digest the organic solids in the wastewater to water and CO₂ , said aeration chamber having a substantially flat, bottom wall and a substantially cylindrical side walls wall,

means for injecting an oxygenation gas into the wastewater in the aeration chamber to support growth of the aerobic bacteria,

a clarifier chamber in which wastewater from the aeration chamber flows upwardly toward an outlet pipe through which the wastewater flows from the wastewater treatment plant, said clarifier chamber being defined by a partition in the form of an inverted, truncated cone into the bottom of which the wastewater flows from the aeration chamber, and

a current in the aeration chamber, the current flowing upwardly from a position close to the bottom and the side wall of the aeration chamber in a direction perpendicular to the bottom of the aeration chamber and parallel to the side wall of the aeration chamber, then around the partition which defines the clarifier chamber, then downwardly along the opposite side wall to the bottom and then across the bottom under the opening to the clarifier chamber and around the side wall of the aeration chamber adjacent the bottom of the chamber to keep solids from settling on the bottom of the aeration chamber

means for injecting an oxygenation gas and generating a wastewater current pattern in the aeration chamber, the current pattern having at least one first component flowing upwardly in a direction perpendicular to the bottom of the aeration chamber and adjacent the side wall of the aeration chamber, second and third components that flow in opposite directions around the partition which defines the clarifier chamber, a fourth component that flows downwardly along the opposite side wall to the bottom, a fifth component that flows across the bottom under the opening to the clarifier chamber, and sixth and seventh components that flow in opposite directions around the side wall of the aeration chamber adjacent the bottom of the chamber to keep solids from settling on the bottom of the aeration chamber.

11. The wastewater treatment plant of claim 1 wherein said aeration system comprises multiple diffusers.

12. The method of claim 8 wherein injection of said oxygenation gas is through a diffuser system.

13. The method of claim 12 wherein injection of said oxygenation gas is through multiple diffusers.

14. The wastewater treatment plant of claim 9 wherein said aeration system comprises multiple diffusers.

15. The wastewater treatment plant of claim 10 wherein said means for generating said current pattern comprises a diffuser system.

16. The wastewater treatment plant of claim 15 wherein said diffuser system comprises multiple diffusers.

17. In an aerobic wastewater treatment plant comprising:

an aeration chamber containing aerobic bacteria into which wastewater containing organic solids flow to be exposed to aerobic bacteria to digest the organic solids in the wastewater, said aeration chamber having a substantially flat bottom and side walls,

means for injecting an oxygenation gas into the wastewater in the aeration chamber to support growth of the aerobic bacteria, and

a clarifier chamber into which wastewater from the aeration chamber flows upwardly toward an outlet pipe through which the wastewater flows from the wastewater treatment plant, said clarifier chamber being defined by a partition in the form of an inverted, truncated cone into the bottom of which the wastewater flows from the aeration chamber,

the improvement comprising a diffuser for releasing the oxygenation gas as bubbles into the aeration chamber of the wastewater treatment plant, said diffuser providing sufficient flow such that all solids suspended within the plant are forced into circulation, said diffuser being placed close to the bottom of the aeration chamber of the wastewater treatment plant and close to the side wall of the aeration chamber, said diffuser providing sufficient oxygenation gas to aerobically digest the organic solids in the wastewater, the released oxygenation gas producing a current pattern in the aeration chamber, the current pattern flowing upwardly from a position of the diffuser in a direction perpendicular to the bottom of the aeration chamber and parallel to the side wall of the aeration chamber, then around the partition which defines the clarifier chamber, then downwardly along the opposite side wall to the bottom and then across the bottom under the opening to the clarifier chamber and around the side wall of the aeration chamber adjacent the bottom of the chamber to keep solids from settling on the bottom of the aeration chamber.

18. The wastewater treatment plant of claim 17 wherein said oxygenation gas injecting means further comprises

a drop line having a first end attached to an external oxygenation source and a second end open to dispense oxygenation gas received from the external oxygenation gas source, said second end being attached to said diffuser.

19. The wastewater treatment plant of claim 18 wherein said oxygenation gas injecting means further comprises

a rigid conduit mounted to the inside of the wastewater treatment plant for receiving and firmly securing the drop line such that the drop line extends from the oxygenation source towards the bottom of the plant.

20. The wastewater treatment plant of claim 19 wherein said rigid conduit extends generally parallel to the partition and from there generally to the bottom of the wastewater treatment plant such that the rigid conduit is intimately connected to the partition.

21. In an aerobic wastewater treatment plant comprising:

an aeration chamber into which the wastewater flows to be exposed to aerobic bacteria to digest the organic solids in the wastewater, said aeration chamber having a bottom and side walls,

means for injecting an oxygenation gas into the wastewater in the aeration chamber to support growth of the aerobic bacteria, and

a clarifier chamber in which wastewater from the aeration chamber flows upwardly toward an outlet pipe through which the wastewater flows from the wastewater treatment plant, said clarifier chamber being defined by a partition in the form of an inverted, truncated cone into the bottom of which the wastewater flows from the aeration chamber,

the improvement comprising a current pattern produced in the aeration chamber, the current pattern flowing upwardly from a position close to the bottom and the side wall of the aeration chamber in a direction perpendicular to the bottom of the aeration chamber and parallel to the side wall of the aeration chamber, the around the partition which defines the clarifier chamber, then downwardly along the opposite side wall to the bottom and then across the bottom under the opening to the clarifier chamber and around the side wall of the aeration chamber adjacent the bottom of the chamber to keep solids from settling on the bottom of the aeration chamber.

22. The method of creating a current inside an aeration chamber of a wastewater treatment plant, said aeration chamber having a bottom and side walls, comprising

injecting an oxygenation gas such that a current pattern is produced in the aeration chamber, the current pattern flowing upwardly from a position close to the bottom and side wall of the aeration chamber in a direction perpendicular to the bottom of the aeration chamber and parallel to the side wall of the aeration chamber, then around the partition which defines a clarifier chamber, then downwardly along the opposite side wall to the bottom and then across the bottom under an opening to the clarifier chamber and around the side wall of the aeration chamber adjacent the bottom of the aeration chamber to keep solids from settling on the bottom of the aeration chamber.

23. An aerobic wastewater treatment plant comprising:

an aeration chamber into which the wastewater flows to be exposed to aerobic bacteria to digest the organic solids in the wastewater, said aeration chamber having a bottom and side walls,

means for injecting an oxygenation gas into the wastewater in the aeration chamber to support growth of the aerobic bacteria,

a clarifier chamber in which wastewater from the aeration chamber flows upwardly toward an outlet pipe through which the wastewater flows from the wastewater treatment plant, said clarifier chamber being defined by a partition in the form of an inverted, truncated cone into the bottom of which the wastewater flows from the aeration chamber, and

a current pattern in the aeration chamber, the current pattern flowing upwardly from a position close to the bottom and the side wall of the aeration chamber in a direction perpendicular to the bottom of the aeration chamber and parallel to the side wall of the aeration chamber, then around the partition which defines the clarifier chamber, then downwardly along the opposite side wall to the bottom and then across the bottom under the opening to the clarifier chamber and around the side wall of the aeration chamber adjacent the bottom of the chamber to keep solids from settling on the bottom of the aeration chamber.

24. The wastewater treatment plant of claim 7 wherein said means for injecting comprises an injection system for creating an injection area adjacent to the intersection of said side wall and said bottom wall.

25. The wastewater treatment plant of claim 24 wherein said injection system comprises multiple diffusers.