WO2011020142A1

WO2011020142A1 - Aeration device

Info

Publication number: WO2011020142A1
Application number: PCT/AU2010/001051
Authority: WO
Inventors: Man Heng Soo
Original assignee: Active Bio-Culture International Pty Ltd; Active Bio-Culture Pty Ltd
Priority date: 2009-08-18
Filing date: 2010-08-17
Publication date: 2011-02-24
Also published as: IN2012DN02248A; AU2010212397B2; AU2010212397A1

Abstract

An aeration device (100) comprises a conduit (101) having a conduit outlet end portion (105) terminating in an outlet (103) at one end of the conduit (101), a conduit inlet end portion (104) terminating in an inlet (102) at an opposing end of the conduit (101) and a conduit riser portion (106) located between the conduit outlet end portion (105) and the conduit inlet end portion (104). The gas delivery port (107) delivers a gas into the conduit riser portion (106). A gas delivery device (108) communicates with the gas delivery port (107). A float (110) maintains the conduit outlet end portion (105) in a position extending at least partially along, or at least partially generally parallel and adjacent to, the surface (3) of a body (2) of liquid with the conduit inlet portion (104) disposed in the body (2) of liquid at a level below the conduit outlet end portion (105).

Description

AERATION DEVICE

Technical Field

The present invention relates to the field of aeration devices for aerating liquids in applications including, but not limited to, sewage aeration treatment, fresh waterbody aeration treatment, industrial/commercial waste water treatment, aquaculture aeration, agriculture waste water aeration treatment and the aeration, de-stagnation and de- stratification of deep ponds, lakes and reservoirs. Background of the Invention

Various forms of aeration device are known for infusing and mixing oxygen into liquids for waste water treatment or biological cultivation.

One such form of aeration device is a mechanical aeration device which uses centrifugal or centripedal forces to move liquids with intense turbulence to thereby induce aeration. Such mechanical aeration devices, however, have high energy usage and are subject to corrosion and unreliability. Additional problems are encountered in

aquaculture applications where damage to crops or animals by rotating mechanisms of the mechanical aeration devices can be substantial. Further, in ponds that are naturally saturated with dissolved oxygen on the surface by phytoplankton blooms during the day, the centrifugal or centripedal effect of the mechanical aeration devices tends to shear the oxygen molecules from their attachment to water molecules. Centripedal or centrifugal actions are vortiginous and act within only a limited sphere of influence. These activities are counter-productive, leading to hydraulic short circuits and "dead zones" in the liquid, besides resulting in a less than satisfactory infusion of oxygen.

Another form of aeration device is a fine bubble diffuser. Whilst these types of aeration devices generally perform better than mechanical aeration devices, they are typically designed for very expensive deep tanks with numerous static bottom diffusers which can only be seen, replaced or maintained by draining the entire tank. Each maintenance check requires potentially expensive operation downtime and bypass.

Blockage and damage to diffusers are also common, especially in "stop-start" sequencing batch reactors in sewage treatment applications.

Although fine bubble diffuser types of aeration devices generally have lower energy consumption than mechanical aeration devices, they still typically use large amounts of energy because of the intensive air delivery back-pressure and frictional losses in the conduit feeding the diffuser. This is due to the large operating depths and also employment of very large numbers of diffusers and pipe fittings.

Water stratification in dams is a problem which is typically dealt with by using equipment designed to circulate water within the dam. This equipment can be very expensive to operate and difficult to service because of the heavy solid pipes and other components such as diffusers which are installed in the bottom of the dam.

Object of the Invention

It is an object of the present invention to substantially overcome or at least ameliorate at least one of the above disadvantages.

Summary of the Invention

In a first aspect, the present invention provides an aeration device comprising: a conduit having a conduit outlet end portion terminating in an outlet at one end of said conduit, a conduit inlet end portion terminating in an inlet at an opposing end of said conduit and a conduit riser portion located between said conduit outlet end portion and said conduit inlet end portion;

a gas delivery port for delivering a gas into said conduit riser portion;

a gas delivery device communicating with said gas delivery port; and

a float for maintaining said conduit outlet end portion in a position extending at least partially along, or at least partially generally parallel and adjacent to, the surface of a. body of liquid with said conduit inlet portion disposed in said body of liquid at a level below said conduit outlet end portion.

In one form, said inlet and said outlet are directed in generally opposing directions.

Typically, said gas delivery port is positioned such that, in use, said gas delivery port is located at less than half the depth of the body of liquid.

Typically, said gas delivery port is in the form of a gas injector. The gas injector may be directed into and along said conduit towards said outlet.

In one form, said device further comprises a weight for weighing down said conduit inlet end portion towards a bottom of the body of liquid.

In an alternate form, said device further comprises a frame secured to said float and said conduit riser portion to direct said conduit riser portion towards a bottom of the body of liquid. In a preferred form, said conduit outlet portion is formed of a corrugated hose. Typically, said corrugated hose is flexible.

In one form, said conduit inlet portion and said conduit riser portion are also formed of a flexible corrugated hose. Typically, in this case, said conduit is integrally formed of a single flexible corrugated hose. The conduit riser portion may have a length selected such that, in use, said conduit inlet portion is located adjacent a bottom of the body of liquid.

The conduit may be encased in a fabric stocking.

The aeration device may further comprise a heating device operatively associated with said gas delivery device for heating the gas.

In one or more embodiments, said aeration device comprises an array of said conduits, each being provided with a said gas delivery port.

In a second aspect, the present invention provides a method of aerating a liquid body comprising:

arranging an aeration device as defined above in said body of liquid with said conduit outlet end portion in a position extending at least partially along, or at least partially generally parallel and adjacent to, the surface of said body of liquid and said conduit inlet portion disposed in said body of liquid at a level below said conduit outlet end portion;

delivering a gas into said conduit riser portion through said gas delivery port, said gas drawing liquid from said body of liquid through said inlet, mixing said liquid with said gas in said conduit and ejecting said gas and liquid from said outlet along and adjacent to said surface of said body of liquid. Brief Description of the Drawings

Preferred embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings wherein:

Figure 1 is a cross-sectional side elevation view of a body of water housing an aeration device according to a first embodiment;

Figure 2 is a perspective view of an aeration device according to a second embodiment;

Figure 3 is a cross-sectional view of a body of water housing an aeration device according to a third embodiment;

Figure 4 is a cross-sectional front elevation view of the aeration device depicted in Figure 3; and Figure 5 is a fragmentary perspective view of an aeration device according to a fourth embodiment.

Detailed Description of the Preferred Embodiments Referring to Figure 1 of the accompanying drawings, a body of liquid is shown in the form of a reservoir 1 filled with liquid in the form of water 2. The water 2 will typically embody suspended or settled sediment or other impurities, but may be free from such impurities. The reservoir 1 may be a natural reservoir such as a lake or sea or a man-made structure such as a dam or man-made pond. The water 2 may be an aquatic medium used in aquaculture, waste water used in sewage treatment or any other body of water, either pure or containing impurities, which is desired to be aerated. Liquids other than water may also be aerated as desired.

Within the water 2 is located an aeration device 100 according to a first embodiment. The aeration device 100 comprises a conduit 101 that extends from an inlet 102 at one end of the conduit 101 to an outlet 103 at the opposing end of the conduit 101. A conduit inlet end portion 104 terminates at the inlet 102 whilst the conduit outlet end portion 105 terminates at the outlet 103. A conduit riser portion 106 is located between the conduit inlet end portion 104 and the conduit outlet end portion 105 and here rises generally vertically.

A gas delivery port 107 is provided in the conduit riser portion 106. The gas delivery port 107 is in the form of a gas injector which is directed into and along the conduit 101 towards the outlet 103, such that gas injected into the conduit riser portion 106 from the gas delivery port 107 is injected in a direction aimed up the conduit riser portion 106 towards the outlet 103. It is also envisaged that the gas injector forming the gas delivery port 107 may be directed into the conduit riser portion 106 perpendicular (or any other angle) to the wall of the conduit riser portion 106, allowing the gas to naturally rise toward the outlet 103.

The gas delivery port 107 need not be located towards the bottom 4 of the reservoir 1 but may be positioned in the conduit riser portion 106 at only a relatively shallow depth from the water surface 3. For example, for a 2 metre deep reservoir with gas delivered at 1 psi (7kPa), positioning the gas delivery port at a depth of about 700 mm would be suitable. Depending upon the application and gas delivery pressure, the gas delivery port will typically be located at a depth less than half the water depth.

Accordingly, only low power is required to drive the air into the conduit riser portion 106 compared to aeration devices that deliver air to greater depths. The gas delivery port 107 communicates with a gas delivery device, here in the form of an air blower 108 or compressor via an air hose 109. The air hose 109 will typically be flexible so as to allow for displacement of the delivery port 107 with changing water levels. The air blower 108 takes air from the atmosphere at ambient temperature and delivers it to the delivery port 107 through the air hose 109 at pressure. Under cold conditions it is envisaged that the ambient air may be replaced by heated air from a heater 108a or other heating device, operatively associated with the gas delivery device, providing hot air to prevent frost or ice damage or to promote micro-organism growth in the water. It is also envisaged that gases other than air might be utilised for specific applications. In the arrangement depicted, the air blower 108 is located on land adjacent the reservoir 1.

A float 110 is used to maintain the conduit outlet end portion 105 in a position at least partially extending along, or at least partially generally parallel and adjacent to, the surface 3 of the water 2. In the arrangement depicted, the float 110 is attached to the conduit 101 by way of ties 111 of any other suitable fastening devices. The conduit inlet end portion 104 is disposed in the water 2 at a level below the conduit outlet portion 105. In the arrangement depicted, the conduit inlet end portion 104 is weighed down by a weight 112 that rests on the bottom 4 of the reservoir 1. Alternatively, the weight could be configured to retain the conduit inlet end portion spaced from the bottom 4.

The conduit 101 is here integrally formed of a single flexible corrugated hose, typically having a diameter of 50 to 150 mm. The conduit 101 could, however, be formed of multiple lengths of hose or tubing, which may or may not be flexible or corrugated. A flexible hose is preferred, providing the advantage of automatically adjusting the position of the outlet end portion 105 as the water level within the reservoir 1 fluctuates, with the float 110 maintaining the conduit outlet end portion 105 at or adjacent the water surface 3. The length of the conduit 101 should thus be selected to allow for anticipated fluctuations in water level and maintaining at least part of the conduit outlet end portion

105 in the roughly horizontal orientation extending along or adjacent to the water surface 3. The roughly horizontal section of the conduit outlet end portion 105 will typically have a length of at least 1 m and more typically at least 2 m. The conduit riser portion

106 will typically have a length selected such that the conduit inlet end portion 104 is located adjacent to the bottom 4 of the reservoir 1, particularly when any fluctuating water level is at its highest. The corrugated conduit riser portion 106 is then able to rise or fall with fluctuations in the water level whilst keeping the conduit inlet end portion 104 at the bottom 4. The typical dimensions set out above are typical for applications in larger bodies of water, such as ponds, lakes and reservoirs. The dimensions may be readily scaled for different applications, such as in home aquariums where significantly smaller dimensions would be appropriate.

In the arrangement depicted, the outlet 103 and inlet 102 are directed in generally opposing directions so as to reduce the possibility of any hydraulic short circuit, circulating water directly from the outlet 103 back into the inlet 102. Accordingly, the inlet end portion 104 is also arranged to extend in a generally horizontal manner adjacent to the bottom 4 of the reservoir 1. The generally horizontal orientation may be achieved by securing the weight 112 to the conduit 101 at a distance from the inlet 102.

The conduit 101 may be encased in a fabric stocking 101a so as to provide additional substrata for intensifying growth and attachment of useful bacteria, such as nitrifying bacteria in the water if so desired.

In use, the air delivered to the conduit riser portion 106 by the air blower 108 will mix the water in the conduit riser portion 106 adjacent to and above the gas delivery port 107. This air/water mixture, having a density less than that of the remaining water, will rise through the conduit riser portion 106 and conduit outlet end portion 105, exiting the conduit at the outlet 103 at or adjacent to the water surface 3. This generates a pressure reduction which draws replacement water from adjacent the bottom 4 of the reservoir 2 into the inlet 102, upwelling through the conduit inlet end portion 104 and up through the conduit riser portion 106. The conduit 101 thus acts as an air-lift pump. The corrugations in the extended generally horizontal section of the conduit outlet end portion 105 provide for pockets of air bubbles to be retained within the conduit 101, increasing the air/water interface available for drawing further air bubbles into the water. Such bubbles drawn into the water may be referred to as "cavitations". The extended length of the conduit outlet end portion 105 acts as a retention chamber allowing more time for air- water mixing to take place.

The flow of aerated water through the flexible outlet end portion 105 is turbulent as a result of the mixing action between air and water through the extended outlet end portion 105. This turbulent flow causes the flexible outlet end portion 105 to undulate and the outlet 103 to bob up and down thereby agitating the water adjacent the water surface 3 outside the conduit 101. This generates ripples and waves 5 at the water surface 3 to increase the overall aeration and mixing of the water 2. After the water leaves the outlet 103, it generates laminar mixing at the air water interface as it generally flows towards the wall 6 of the reservoir at which the outlet 103 is directed and then down the wall 6, along the bottom 4 of the reservoir 1 and back towards the inlet 102. Full inversion and circulation of the water 2 is thus achieved.

Forming the conduit 101 as a single piece, only having a single bend between the generally horizontal inlet end portion 104 and vertically extending conduit riser portion 106 and a gentle curve joining the conduit riser portion 106 and the conduit outlet end portion 105, reduces the likelihood of any flow blockages which may otherwise result from sediment suspended in the water.

Figure 2 depicts an aeration device 200 according to a second embodiment. In the following discussion of the second embodiment, features of the aeration device 200 that are the same or equivalent to those of the aeration device 100 of the first embodiment are represented with reference numerals equivalent to those used in relation to the first embodiment, increased by 100. Similarly, for the third and fourth embodiments discussed further below, equivalent reference numerals are utilised increased by 200 and 300 respectively.

The aeration device 200 of the second embodiment utilises the same principles as those of the aeration device 100 of the first embodiment discussed above, however rather than utilising a single conduit, the aeration device 200 utilises an array of conduits 201, with the array here comprising six separate conduits 201. The use of an array of conduits increases the aeration capacity of the aeration device, thus making it suitable for larger bodies of water. The number and size of the conduits 201 may be adjusted to suit the specific size and type of application.

Each conduit 201 again extends from an inlet 202 to an outlet 203 and is in the form of a conduit inlet end portion 204 that is weighed down by a weight 212, a conduit riser portion 206 and a conduit outlet end portion 205. Again, the conduit 201 is formed of a flexible corrugated hose. The conduit outlet end portion 205 of each of the conduits 201 is secured beneath, and extends along, a float in the form of a floating platform 210 by way of stainless steel straps 211. The section 205a of each conduit end portion 205 that extends along the underside of the floating platform 210 will thus, in use, extend along generally parallel and slightly below the water surface, with a kink being formed in the section 205b of the conduit end portion 205 that projects beyond the end of the floating platform 210 so as to bring the outlet 203 to a position at the water surface.

Again, a fabric stocking may encase each of the conduits 201 as desired.

A separate air hose 209 communicates the gas delivery port 207 of each conduit 201 with a gas distribution manifold 215 that is integrally formed with, or attached to the top of, the floating platform 210. hi one specific integral form, the floating platform 210 is hollow and acts as the gas distribution manifold 215. Air control valves 216 are provided in each air hose 209 for regulating the volume and pressure of air supplied to each conduit 201. The gas distribution manifold 215 communicates with the gas delivery device that is again in the form of an air blower 208 which is here mounted on the floating platform 210 (and specifically on the manifold 215). A pressure gauge 217 is mounted on the manifold 215 to enable monitoring of correct functioning of the air blower 208. Rather than utilising a single air blower 208 and associated distribution manifold 215, it is envisaged, although less preferred, that a separate gas delivery device might be associated with each conduit 201.

The air blower 208 may be powered by a self-contained power source mounted on the floating platform 210 such as a battery, solar panel or generator. Alternatively, power could be supplied from an alternate power source located on land adjacent the reservoir and connected to the gas delivery device 208 by a power cable 218.

Figures 3 and 4 depict an aeration device 300 according to a third embodiment. In this embodiment, a single conduit 301 formed of separate distinct sections is employed. The conduit 301 comprises a rigid section 320 that incorporates the conduit riser portion 306 and has a T-junction 321 in the conduit riser portion from which extends an intermediate length 322. The intermediate length 322 together with a flexible corrugated hose 323 that extends from an elbow 324 at the conduit outlet 303 form the conduit outlet end portion 305.

The conduit inlet portion 304 is also formed of a flexible corrugated hose, so as to allow for variations in the water depth, and extends from one end of the conduit riser portion 306 to the conduit inlet 302. A weight 312 weighs down the conduit inlet end portion 304.

The conduit riser portion 306 has a projecting section 325 located above the T- junction 321 and which projects above the water surface 3, defining an air-filled cavity 326 that provides an additional air/water interface 327 within the conduit 301 for drawing air bubbles into the water.

A diffuser leg 328 extends from the conduit riser portion 306, with the junction therebetween defining the gas delivery port 307. The diffuser leg 328 extends from the conduit riser portion 306 at an acute angle, extending downwardly, such that gas delivered through the gas delivery port 307 is directed upwardly towards the conduit outlet 303. A cap 329 is provided on the end of the diffuser leg 328. A gas diffuser 330 is located within the diffuser arm 328 and communicates with a gas delivery device, again in the form of an air blower 308 or a compressor via an air hose 309 that extends through a cap 331 at the end of the projecting section 325 of the conduit riser portion 306. The gas diffuser 330 delivers gas bubbles to the diffuser leg 328. Locating the gas diffuser 330 in the diffuser leg 328, out of the main flowpath in the conduit riser portion 306 reduces the possibility of flow blockages. An air valve 316 and pressure gauge 317 are provided on the air hose 309.

The air blower 308 is again here mounted on a float 310 that is also secured to the intermediate length 322 of the conduit outlet end portion 305 by way of a frame 311 so as to maintain the conduit outlet end portion 305 in a position extending along, or generally parallel and adjacent to, the water surface 3. In this particular arrangement, a downwardly projecting elbow 324 is formed at the end of the conduit outlet end portion 305, with a small weight 332 being mounted on the conduit outlet end portion 305 adjacent the elbow 324. This arrangement allows larger air bubbles to amass adjacent the outlet 303, which will be released from the outlet 303 intermittently, causing further undulation of the flexible corrugated hose 323 of the conduit outlet end portion 305, creating further disturbances in the water surface 3. Whilst in the arrangement depicted in the third embodiment, the outlet 303 and inlet 302 extend in the same general direction away from the conduit riser portion 306, it is preferred that the conduit inlet end portion 304 extends in an opposing direction from the conduit riser portion 306 such that the inlet 302 and outlet 303 extend in generally opposing directions.

Figure 5 depicts part of an aeration device 400 according to a fourth

embodiment. The aeration device 400 of the fourth embodiment is equivalent to the aeration device 200 of the second embodiment described above, with the primary distinction being that, rather than utilising weights to weigh down the conduit inlet end portions, a frame 440 is secured to the underside of the float 410 and to the riser portion 406 of each of the conduits 401. The frame 440 secures each of the riser portions 406 such that they are directed towards the bottom of the body of liquid. As a result, the conduit inlet end portions extend along the bottom of the body of liquid in a similar manner to that of the first and second embodiments. The frame 440 may be formed of any suitable material such as stainless steel, plastic or the like. In the fourth embodiment, the float 410 is fabricated from PVC piping, although it may be fabricated from any of various materials including other plastics, stainless steel or fibreglass. A stainless steel float encasing foam or other buoyant material could be used to assist flotation. The air blower 408 is covered and mounted on the float 410. A separate gas distribution manifold 415 is attached to the float 410 and communicates with the air blower 408 by way of a tube 415a. Separate hoses 409 communicate the gas delivery port of each conduit 401 with the gas distribution manifold 415.

The embodiments of the aeration device described above thus act to effectively aerate a body of water relatively efficiently, aerating the water through an air-lift mechanism, mixing the air and water as it passes through the conduit and further mixing the water through agitation of the water at the water surface.

Aeration of the water results in any organic sediment or micro-organisms becoming more homogenously dispersed in an "animated suspension" within the water, acting like a moving bio-film to increase the surfaces for the attachment and growth of the micro-organisms on the organic sediment. Micro-organisms in the water are thus vitalised to feed and grow profusely instead of settling to the bottom. The aeration device described may be used in agriculture, aquaculture and industrial, commercial and sewage waste water treatment to facilitate aeration and recovery of purer water. The aeration device is also suitable to alleviate the stratification of water in reservoirs, dams and other bodies of water as desired.

Embodiments of the aeration device described above enhance the biological process of aeration in wastewater treatment by air-lifting the wastewater from the bottom of the water body through the enclosed conduit/conduits to the surface. This air- water mixture, whose total volume flow rate through the conduit(s) is determined by the input volume flow rate of air from the air blower, is released from the conduit outlet to the surface as laminar flow and wave movements, which eventually invert at a distance from the conduit inlet. This gentle water current is conducive to the growth and prolific reproduction of the micro-organisms in the wastewater. There is no shear force or strong turbulence as associated with other mechanical aerators. Organic and inorganic particles (sludge) in the wastewater may be kept in continuous suspension by the aeration devices described to enable the micro-organisms to attach to the particles to feed, grow and reproduce prolifically in an aerobic habitat and facilitate organic digestion of sludge. The aeration device when turned off creates an anaerobic habitat for biological nitrate and phosphorous removal.

Embodiments of the aeration device described may also be utilised to relatively homogenously distribute enzymes, probiotics, chemicals or other material throughout a liquid body.

A person skilled in the art will appreciate that various other applications of the aeration device may be made, and that the aeration device itself may be modified in various manners without departing from the nature of the aeration device described.

Claims

CLAIMS:

1. An aeration device comprising:

a conduit having a conduit outlet end portion terminating in an outlet at one end of said conduit, a conduit inlet end portion terminating in an inlet at an opposing end of said conduit and a conduit riser portion located between said conduit outlet end portion and said conduit inlet end portion;

a gas delivery port for delivering a gas into said conduit riser portion;

a gas delivery device communicating with said gas delivery port; and

a float for maintaining said conduit outlet end portion in a position extending at least partially along, or at least partially generally parallel and adjacent to, the surface of a body of liquid with said conduit inlet portion disposed in said body of liquid at a level below said conduit outlet end portion.

2. The aeration device of claim 1, wherein said inlet and said outlet are directed in generally opposing directions.

3. The aeration device of claim 1 , wherein said gas delivery port is positioned such that, in use, said gas delivery port is located at less than half the depth of the body of liquid.

4. The aeration device of claim 1, wherein said gas delivery port is in the form of a gas injector.

5. The aeration device of claim 4, wherein said gas injector is directed into and along said conduit towards said outlet.

6. The aeration device of claim 1 , wherein said device further comprises a weight for weighing down said conduit inlet end portion towards a bottom of the body of liquid.

7. The aeration device of claim 1 , wherein said conduit outlet portion is formed of a corrugated hose.

8. The aeration device of claim 7, wherein said corrugated hose is flexible.

9. The aeration device of claim 8, wherein said conduit inlet portion and said conduit riser portion are formed of a flexible corrugated hose.

10. The aeration device of claim 9, wherein said conduit riser portion has a length selected such that in use, said conduit inlet end portion is located adjacent a bottom of the body of liquid.

11. The aeration device of claim 9, wherein said conduit is integrally formed of a single flexible corrugated hose.

12. The aeration device of claim 1, wherein said conduit is encased in a fabric stocking.

13. The aeration device of claim 1 , further comprising a heating device operatively associated with said gas delivery device for heating the gas.

14. The aeration device of claim 1, wherein said aeration device comprises an array of said conduits, each being provided with a said gas delivery port.

15. The aeration device of claim 1 , wherein said device further comprises a frame secured to said float and said conduit riser portion to direct said conduit riser portion towards a bottom of the body of liquid.

16. A method of aerating a body of liquid comprising:

arranging an aeration device according to claim 1 in said body of liquid with said conduit outlet end portion in a position extending at least partially along, or at least partially generally parallel and adjacent to, the surface of said body of liquid and said conduit inlet portion disposed in said body of liquid at a level below said conduit outlet end portion;

delivering a gas into said conduit riser portion through said gas delivery port, said gas drawing liquid from said body of liquid through said inlet, mixing said liquid with said gas in said conduit and ejecting said gas and liquid from said outlet along and adjacent to said surface of said body of liquid.

17. The method of claim 16, wherein said method generates a circulatory flow in said body of liquid.

18. The method of claim 16, wherein said body of liquid comprises wastewater.