AU705424B2 - A sewage treatment plant - Google Patents

Description

1 A SEWAGE TREATMENT PLANT Technical Field The present invention relates to sewage treatment plants, and more particularly but not exclusively to secondary sewage treatment plants.

Background of the Invention The development of on-site sewage treatment plants for households was in response to health authorities conclusion that septic tanks and effluent disposal trenches were not satisfactory in many areas, particularly where soil absorption limited the ability of the primary treated effluent to either escape to the sub-strata and/or to be taken up by o evaporation and transportation through plants.

More recently, health authorities have realised porous soils which allow effluent to soak away is also undesirable as the effluent finds its way to streams and rivers and causes algae blooms and other broad environmental problems.

On-site sewage treatment plants such as those used for households suffer several disadvantages including cost of running and unreliability, particularly where fans or blowers were used to deliver air to the material being treated.

.0 0 00.. Object of the Invention It is the object of the present invention to overcome or substantially ameliorate the above disadvantages.

0:00 Summary of the Invention S°There is disclosed herein a device to mix two fluids, said device comprising: an outer member providing a passage extending in a predetermined direction; a divider extending along a portion of said first passage and having a terminal end located therein, said divider dividing said passage into a first sub-passage and a second sub-passage extending in said direction, the sub-passages extending to outlet openings at 00 said terminal end; and pump means to deliver one of said fluids to one of said sub-passages so that in use a 0 region of low pressure is located at said terminal end to cause the other fluid to pass through the other sub-passage so that the two fluids are mixed downstream of said S 30 terminal end in said passage.

00There is further disclosed herein a sewage treatment plant including a tank providing a space to receive effluent, and aeration means to deliver the air into the effluent to treat the effluent, said aeration means comprising: a pump located within the tank, to be submerged in the effluent; a first duct, said first duct extending from said pump to receive effluent therefrom, said first duct having a longitudinally extending portion; [N:\LIBT3100574:KEH a second duct having an end to receive air, and including a longitudinally extending portion located within the portion of said first duct to deliver air thereto; and the first duct portion and the second duct portion cooperating to define a space therebetween through which effluent passes to provide a region of low pressure adjacent said second duct to move air therethrough.

Preferably, the above sewage treatment plant has the portion of said second duct terminating with an opening through which the air enters the first duct, and said first duct expands in cross sectional area downstream of said opening so that said first duct provides a mixing chamber for said air and effluent.

Brief Description of the Drawings A preferred form of the present invention will now be described by way of example only with reference to the accompanying drawings wherein: Figure 1 is a schematic sectioned side elevation of a sewage treatment plant; Figure 2 is a schematic top plan view of the plant of Figure 1; Figure 3 is a schematic side elevation of a further sewage treatment plant; and Figure 4 is a schematic side elevation of a still further sewage treatment plant.

Detailed Description of the Preferred Embodiment :In the accompanying drawing there is schematically depicted a sewage treatment plant 10 which includes a generally circular tank 11 providing a space 12 to receive 20 primary treated effluent via an inlet 13. Located within the space 12 is a submerged 00•.

electrically driven pump 14, which draws effluent in via pump inlets 15. Effluent under pressure is delivered to an upwardly extending tube 16 which terminates at its upper end at a junction assembly 17. Effluent under pressure is delivered to the interior of the assembly 17.

The assembly 17 has a first hollow arm 18 through which there extends an air inlet S° tube 19 through which air passes. The tube 19 effectively closes the end of the arm 18.

e• [N:\LIBTT]00574:KEH The junction 17 has a second arm 20 from which there extends an outer tube 21 and through which the tube 19 extends. The tube 21 effectively closes the end of the arm The third arm 38 is effectively closed by a tube 37.

The outer diameter of the tube 19 is smaller than the inner diameter of the tube 21 so that there is an annular longitudinally extending space between the tubes 19 and 21.

That space extends to the interior of the junction assembly 17, so that effluent under pressure passes along the space between the tubes 19 and 21 until it reaches a space 22 just beyond the extremity 47 of the tube 19. The tube 19 has an open end (extremity 47) facing the space 22.

The extremity 47 can be located at a desired location along the length of the tube 21. For example the extremity 47 may be located adjacent the junction 47 or adjacent the member 23.

Attached to the tube 21 adjacent the space 22 is an expansion member 23 which then leads to tubing 24 which extends to distribution pipes In operation, effluent pumped to the junction assembly 17, passes along the space between the tubes 19 and 21 and enters the space 22 from where it flows to expansion member 23 and tubing 24. The tubes 19 and 21, and the space 22 as well as the Sexpansion member 23 act to create a low pressure region at the opening 47 so that air is moved through the tube 19 to distribute bubbles through the effluent passing through the tubing 24 and then distributed via the pipes The expanded cross-sectional area of 24 allows the effluent flowing from the gap between 19 and 21, and the air from 19 to mix, without increasing the back pressure on, and thus lowering the flow rate from, pump 14.

The tube 24 allows bubbles of air to come into close contact with the effluent which enables the oxygen in the air to oxidize the organics in the effluent which is the purpose of the treatment process. The tube 24 thus provides a mixing chamber.

Attached to one of the distribution pipes 25 is an upwardly extending hollow member 26, which collects some of the air bubbles and directs air and effluent up the tube 27. The tube 27 extends to the top of an air/water separation member 28. The member 28 encloses a chamber 29 which collects air. As the air collects, the pressure in the Schamber 29 builds up and forces air along the tube 30. The lower end of the member 28 is open to the space 12.

Surrounded by the space 12 is a clarifier 31 which has an internal conical wall 32 which concentrates the sludge in the apex area defined by the conical wall 32.

Operatively associated with the clarifier 31 is a sludge return line 33, which has a lower end 34 which collects sludge from the apex area defined by the wall 32. A duct extends from the lower end 34 to a sludge return pipe 36. Connected to the duct 35 is the air tube 30 which causes sludge in the duct 35 to rise and exit via the pipe 36 into a primary tank.

[N:\L1BTr100574:hiw The tube 37 extends, via a flow control valve 39 to the upper end of the chamber 29, so that the tube 37 is charged with effluent whenever the pump 14 is operating.

When the pump 14 is turned off, air pressure within the chamber 29 forces the effluent back along the pipe 37 so that the air under pressure can escape via the tube 19.

Accordingly, when the pump 14 is not turned on, the pressure within the chamber 29 is "atmospheric" pressure.

Attached to the tube 30 is a pressure sensitive switch 40 which indicates when the pump 14 is not operative. When there is no pressure in the chamber 29, the switch activates an alarm, such as a light, to show that the pump 14 is not operative. In this regard it should be appreciated when the pump 14 is first activated, it takes a small period of time to build up pressure in the chamber 29 to activate the switch Flow through the tube 27 is controlled by a flow control valve 41.

Extending from the clarifier 31, is a tube 42 which extends to the pump tank 43.

Located in the pump tank 43 is a pump 44 which pumps water out through the pipe Operatively associated with the pump 44 is a float valve 46 so that when water in the pump tank 43 reaches a predetermined level, the pump 44 is activated to pump a predetermined amount of water from the tank 43. Once a minimum level is reached, the pump 44 is turned off. A safety switch is provided together with a float 48 to activate a warning device when the maximum liquid level in the tank 43 is reached or exceeded.

*0o0 20 Located in the space 12 are two baffle assemblies 49 upon which bacteria grow.

The baffle assemblies 49 consist of a plurality of plates of "growth media" such as plates or sheets of plastics material. The sheets or plates are closely spaced and arranged in "packs" so as to act as a "biological filter" through which passes effluent containing organic material not treated in the aerated liquid of the tank, or in the mixing which takes 25 place in expansion member 23, tubing 24 and pipes In Figure 3 there is schematically depicted a sewage treatment plant 60. The plant includes a tank 61 having a water level 62. Located within tank 61 is a pump 63 which delivers effluent under pressure to the tube 64. The tube 64 delivers the effluent to a junction 65. Extending to the junction 65 is a tube 66 which extends to atmosphere so o that the junction 65 receives effluent as well as air. The junction 65 includes an outer housing 68 which is connected to a tube 67. The housing 68 provides an internal passage extending to the tube 67. Located in the passage is a divider, having a terminal end and dividing the passage into two sub-passages. The sub-passages extend to outlet openings at the terminal end of the divider. One sub-passage communicates with the tube 64, and the other sub-passage communicates with the tube 66. The sub-passages extend in the same direction as the passage of the housing 68.

Air and effluent is then mixed in the mixing tubes 67 and 69.

The tube 69 extends to a coupling 70 to which there is attached a distribution tube 71, through which the effluent and air entrapped therein is returned to the main body of effluent contained in the tank 61. However, air also enters the tubular member 72 which IN:\LIBT1]00574: w extends to the tube 73. Air collects and forms bubbles and pass up the tube 73 and takes with it effluent, so that effluent bubbles out the upper extremity of the tube 73 for other process usage.

The device 80 of Figure 4, is basically a rearrangement of the device 60 of Figure 3. Accordingly, items of Figure 4 have been allocated the same reference numerals as the corresponding items of Figure 3. In Figure 4, the mixing device 65 is located above water level 62, and the tube 69 is vertically extending as opposed to being horizontal.

The above described preferred embodiments describe the invention as being incorporated in a sewage treatment plant. However, the plant could also be used to treat 1 o any body of water, such as water in dams. It also could be used to treat any body of liquid.

*o *o [N:\L1BTrfiJ574:hrw The claims defining the invention are as follows: 1. A device to mix two fluids, said device comprising: an outer member providing a passage extending in a predetermined direction; a divider extending along a portion of said first passage and having a terminal end located therein, said divider dividing said passage into a first sub-passage and a second sub-passage extending in said direction, the sub-passages extending to outlet openings at said terminal end; and pump means to deliver one of said fluids to one of said sub-passages so that in use a region of low pressure is located at said terminal end to cause the other fluid to pass through the other sub-passage so that the two fluids are mixed downstream of said terminal end in said passage.

2. The device of claim 1, further including a mixing chamber to which said passage extends.

3. The device of claim 1 or 2, wherein said divider is tubular so that said first sub-passage is located between a housing and said divider and surrounds said divider, and said second sub-passage is provided internally of said divider.

4. The device of claim 3, wherein said passage is generally cylindrical, and said S• o tube is cylindrical so that said first passage is generally annular in configuration.

A sewage treatment plant including a tank providing a space to receive 20 effluent, and aeration means to deliver air into the effluent to treat the effluent, said aeration means comprising: pump located within the tank, to be submerged in the effluent; :.oo-a first duct, said first duct extending from said pump to receive effluent therefrom, said first duct having a longitudinally extending portion; a second duct having an end to receive air, and including a longitudinally extending portion located within the portion of said first duct to deliver air thereto; and the first duct portion and the second duct portion cooperating to define a space therebetween through which effluent passes to provide a region of low pressure adjacent said second duct to move air therethrough.

S 30 6. The sewage treatment plant of claim 5, further including an expansion member at a downstream end of said first duct, and a mixing chamber downstream of said expansion member.

7. The sewage treatment plant of claim 5 or 6 further including a hollow upwardly extending air collection means downstream of said first duct to receive effluent and air therefrom; a clarifier located in said tank to receive effluent; a sludge extraction duct extending through and from said clarifier and having a lower end to be submerged in the effluent in the clarifier, and an upwardly extending portion; and 7 [N:\IBTT]00574:KEH [N:\LIBTTOO574:KEH ~Vr7 n,

Claims (1)

1. 8. A sewage treatment plant substantially as hereinbefore described with reference to Figures 1 and 2, Figure 3 or Figure 4. Dated 12 March, 1999 Commercial Waste Treatment Pty Ltd Patent Attorneys for the Applicant/Nominated Person SPRUSON FERGUSON *e 0 *0 *0 00 000*0 0* S S *0 [N:\LIBTT]00574:KEH A SEWAGE TREATMENT PLANT Abstract A sewage treatment plant (60) including a pump (63) which delivers effluent to a tube The tube (64) extends to a housing (68) to which air is also delivered. The housing (68) extends to a tube (67) within which the effluent and air are mixed. .e ee [N:\LBTrO]574:hrw