WO1999037391A1

WO1999037391A1 - Self-inducting aerator

Info

Publication number: WO1999037391A1
Application number: PCT/US1999/001263
Authority: WO
Inventors: Paul R. Goudy
Original assignee: Goudy Paul R
Priority date: 1998-01-21
Filing date: 1999-01-21
Publication date: 1999-07-29
Also published as: AU2331699A

Abstract

A fluid aerator includes an upright tube (10) that contains a spiral motionless mixer, such as a spiral-wound bristle brush (30, 32). Fluid is pumped into the top of the tube (10) and mixes with air drawn through the open bottom of the tube (10). The tube (10) may be mounted in a housing (12) with air inlets (24) and fluid inlets (18) and outlets (26). A plurality of the aerators may be mounted on a central standard (42) and floated in a body of fluid to be aerated.

Description

SELF-INDUCTING AERATOR

BACKGROUND OF THE INVENTION

This invention relates to aerators, and particularly to an aerator in which the fluid

to be aerated descends through a spiral, motionless mixer while air moves upwardly

through the mixer.

Conventional aeration technology, as employed in the typical municipal

wastewater treatment system, uses high horsepower air blowers. The blowers are

connected through hard plumbed distribution piping systems to fine bubble ceramic air

diffusers or other forms of air diffusers. Such systems provide a low ratio of oxygen per

horsepower per hour.

The present invention is directed to an aerator whose only power requirements are

that necessary to lift the water or other fluid to be aerated to a level above a motionless

mixer. The invention is also directed to a method of aerating a fluid in which air is

induced to rise upwardly against the flow of the fluid.

SUMMARY OF THE INVENTION

In accordance with the invention, a spirally-wound bristle brush or other spiral,

motionless mixer fills a portion of the length of an upright tube. Water or other fluid is

introduced into the top of the tube. The bottom of the tube is open to air.

As water flows from the top of the tube to the bottom through the mixer, layered

plug flow through the upper spirals of the mixer creates a low pressure area in the tube

above the mixer. Air is drawn through the bottom of the tube into the low pressure area. When a spirally-wound brush is used, the brush preferably has a normal diameter

which is greater than the inner diameter of the tube. The brush is inserted through the top

of the tube with the result that the bristles extend partially upwardly as well as

horizontally. The bristles are spaced sufficiently close to each other that the surface

tension of the water or other fluid spans adjacent bristles. A cup is formed at the topmost

bristles and this cup generates an elliptical flow pattern of fluid and air above the level

of the brush to promote frothing.

Preferably, the tube is mounted within an outer housing having a fluid inlet and

an air inlet. The housing may be mounted to the side of a fluid reservoir with the bottom

of the tube above the fluid surface, while the bottom of the housing is below the fluid

surface and contains openings for the discharge of aerated fluid.

The tubes may also be mounted about a central standard containing connections

for fluid and air. A fluid pump may be mounted at the base of the standard and the

standard and pump may be mounted on a float structure for floating in a body of fluid to

be aerated.

The bubbles of air created by the aerator are very small, resulting in highly

desirable increased surface area as compared with prior aerators.

The foregoing and other objects and advantages of the invention will appear in

the detailed description that follows. In the description, reference is made to the

accompanying drawings which illustrate preferred embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a view in vertical section through an aerator in accordance with the

invention;

-2- Fig. 2 is a view in horizontal section taken in the plane of the line 2-2 of Fig. 1;

Fig. 3 is a top plan view of another embodiment of the invention; and

Fig. 4 is a side view of the embodiment of Fig. 3 with portions broken away for

illustration purposes.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to Figs. 1 and 2, an aeration tube 10 is disposed concentric to an outer

shell 12. A top cap 14 and a bottom cap 16 are joined to the shell 12 by solvent or heat

welding, or other known methods to form a housing. The top cap 14 mounts a central

plug 18 which may be internally threaded to receive a fluid pipe connection and which

may be externally threaded to receive a tube cap 20. The open center of the plug 18 leads

to the interior of the aerator tube 10 through the tube cap 20. The aerator tube 10 is

spaced from the shell 12 by foam blocks 22. The shell 12 contains an air opening 24 near

its upper end and the bottom cap 16 has a series of fluid openings 26. As shown in Fig.

1, the housing formed by the shell 12 and caps 14 and 16 is mounted within a pool of

fluid to be aerated with the fluid level being between the bottom of the aerator tube 10

and the bottom cap 16.

A spirally- wound brush is mounted within the aerator tube 10. The brush

includes a twisted wire stem 30 and bristles 32 mounted between the twisted wires at the

lower end of the stem 30. At the top of the stem 30, the two wires 34 and 36 which form

the brush are bent laterally to rest upon the top edges of the aeration tube 10.

The bristles 32 on the brush before being mounted in the tube 10 occupy a volume

that has a diameter that is greater than the inner diameter of the aerator tube 10. The

brush is inserted from the top of the aerator tube 10 so that the bristles are bent slightly

-3- upwardly, as shown in Fig. 1. This forces the bristles closer together and also forms a

cup 38 at the upper end of the bristles. In a typical installation, the aerator tube 10 may

have a diameter of two inches and the brush may have a diameter of three inches.

In operation, water or other fluid to be aerated is pumped through the plug 18 into

the top of the aerator tube 10. Layered plug flow defined by the spiraling layers of the

bristles 32 descend down the aerator tube 10. This creates a reduced pressure area in the

space above the bristles 32. Air entering the opening 24 passes from the bottom of the

tube 10 upwardly into the area of reduced pressure. The surface tension of the water

allows the water to span the bristles and flow in a spiral path. The air is not so

constrained and can flow up between bristles. As the air and water pass each other,

bubbles of air form in the water. A froth develops in the space above the bristles 32 in

the tube 10. The bristle cup 38 generates an elliptical flow pattern which promotes the

frothing. Fluid exiting the bottom of the tube 10 will be aerated with very fine bubbles.

The only power needed for the aerator is that required to pump the fluid up to the

top of the housing. Using a two-inch diameter aerator tube, a water flow rate of from five

to 20 gallons per minute has been achieved. At least five gallons per minute is necessary

to initiate the self-induction of the air upwardly through the aerator tube. Equal amounts

of air appear to be inducted for each gallon per minute of fluid flow. The velocity of the

fluid and air movements over the bristles 32 is sufficient to keep the bristles from

plugging. Although bacteria may form on the surface of the bristles 32, it is desirable

aerobic bacteria which can aid in the treatment of the fluid.

A formed screw could be used instead of the spirally- wound brush, but it would

be more expensive. The oversized brush forms an inexpensive spiral and can be mounted

-4- in the tube by the simple expedient of hanging the brush from the lateral extending ends

of the wires that form the stem.

Figs. 3 and 4 illustrate an embodiment in which four housings 40 containing

aerator tubes as in Fig. 1 are mounted about a central standard 42. The standard 42 is

hollow and contains fittings 44 for the introduction of fluid and other fittings 46 for the

introduction of air into each of the housings 40. A pump 48 is suspended at the bottom

of the standard 42 and has a manifold that connected to hoses 50 extending to the fluid

fitting 44 for each housing 40. The standard 42 has several air openings 52 at its upper

end which lead to the hollow interior of the standard 42 and therefore to each of the air

fittings 46 leading to the four aerator housings 40.

The standard 42 is mounted on a buoyant structure that includes a hollow beam

54 with hollow cross-members 56 at each end. The buoyant structure will support the

standard 42 and its aerator housings 40 at a level within a pool of water such that angled

discharge portions 58 on each aerator housing 40 discharge beneath the surface (see Fig.

4). The embodiment of Figs. 3 and 4 can be floated in a reservoir and pipe extensions

can be mounted to the end of a discharge portion 58 to distribute the aerated water

throughout the bottom surface of the reservoir.

Claims

I claim:

1. An aerator for fluids, comprising:

an upright tube having an upper end and a lower end;

the tube having an air opening adjacent the lower end and a fluid inlet adjacent

the upper end; and

a spiral motionless mixer disposed in the tube between the inlets.

2. An aerator according to claim 1 wherein the motionless mixer is a spirally-

wound bristle brush.

3. An aerator according to claim 2 wherein the bristles of the brush when not

within the tube occupy a volume that has a diameter that is greater than the inner

diameter of the tube.

4. An aerator according to claim 3 wherein the brush is inserted into the tube

through the upper end.

5. An aerator according to claim 2 wherein adjacent bristles of the brush are

closely spaced such that the surface tension of the fluid spans adjacent bristles.

6. An aerator according to claim 1 wherein the mixer has a top that is cupped

and confronts the fluid inlet.

7. An aerator for fluids, comprising:

an upright tube having an open upper end and an open lower end;

a housing surrounding and spaced from the tube, the housing having a fluid inlet

in air-tight communication with the upper end of the tube and an air inlet in

communication with the lower end of the tube; and

a spiral motionless mixer filling a length of the tube between the upper and lower

ends.

8. An aerator according to claim 7 wherein the housing includes a base at a

level beneath the lower end of the tube and the base has outlets for aerated fluid.

9. An aerator according to claim 8 wherein the housing has a top cap with

a plug that supports the tube, the plug including the fluid inlet.

10. An aerator according to claim 7 wherein the mixer is a brush with bristles

that are spirally mounted on a twisted wire stem, the stem being supported at the open

end of the tube.

-7-

11. An aerator assembly comprising a plurality of aerators according to

claim 7 mounted about a hollow central standard, the standard having fluid fittings

connected to the fluid inlet of each aerator housing and air fittings connected to the air

inlet of each aerator housing, the standard having air openings adjacent a top of the

standard, a fluid pump in the standard, and hoses connected between the pump and each

fluid fitting.

12. An aerator assembly according to claim 11 together with a buoyant

support mounted to the standard.

13. A method of aerating a fluid, comprising:

introducing the fluid into the upper end of a tube containing a spiral motionless

mixer, the lower end of the tube being open to air, thereby inducing layered plug flow of

the fluid downwardly through the tube to create a reduced pressure above the mixer in

the tube to draw air upwardly in the tube against the flow of fluid in the tube.

-8-