WO1997000833A1

WO1997000833A1 - Sewage tank improvement

Info

Publication number: WO1997000833A1
Application number: PCT/AU1996/000380
Authority: WO
Inventors: Grant Andrew Wride; Ronald Hubert Wride
Original assignee: Individual
Current assignee: Individual
Priority date: 1995-06-23
Filing date: 1996-06-21
Publication date: 1997-01-09
Anticipated expiration: 1997-12-23
Also published as: AUPN374395A0

Abstract

A sewerage treatment tank for providing both anaerobic and aerobic treatment of sewerage the tank being integrally moulded from concrete and having an inner and an outer cylindrical wall coaxially aligned and a bottom extending below both walls and having a place of the anaerobic treatment which is around the walls between the inner and outer walls and where the length of the chamber provididng a passageway for anaerobic treatment defined by cross walls is at least seven times longer than the width of the chamber throughout that passage length, and there are means to provide aerobic treatment within the chamber.

Description

SEWAGE TANK IMPROVEMENT

This invention relates to a reinforced concrete tank system that can be used as a sewerage station particularly incorporating both septic or anaerobic treatment of sewerage and aerobic treatment in the same tank system and to a method of use of such a tank.

It is also known to use a conventional septic tank and have the outflow connected to an aerobic treatment tank so as to provide for both forms of treatment for best results.

The problem with the separate tanks is that there is a difficulty in connecting the two together. The problem is that with rigid connectors these are extremely vulnerable to being fractured with differential ground movement.

There is therefore value in putting together a system that is internally connected but this is not so easy.

It is known to use a tank system that has an outermost cylindrical wall made from concrete and an inner cylindrical container made from a different material such as fibre reinforced plastics materials that is located fully within the outer wall. Differential pressures that result from a joint use approach mean that the inner container is very vulnerable to fracture unless significant thickness's of fibreglass are used which becomes very costly.

For an application where the sewerage is to be treated anaerobically as in a septic tank type treatment then there are different problems from the aerobic treatment.

Firstly, the shape of inner and outer cylindrical shapes do not at first appear to be appropriate for this type of application. For instance the handling capacity of any unit is considered to depend on the magnitude of contained volumes and these are not obviously economically achieved with this described configuration.

The problem has been to find a material that will not corrode in the expected very harsh environment, be as light as possible to ensure that the tank can be economically transported, while at the same time have sufficient strength to resist damage during transport as well as resist fracture under hydraulic pressures during use and be able to be made at a competitive price.

The problem has been one that has not been able to be solved hitherto by those specialising in the manufacture of these units.

Accordingly an object of this invention is to provide a unit for use as a sewerage station for both anaerobic and subsequent aerobic treatment which can be economic in manufacture, light enough for economic transport while providing a size appropriate for the purposes.

Accordingly this invention can be said to reside in a reinforced concrete tank system for use as an anaerobic treatment sewerage station comprising an outer tubular wall, an inner tubular wall extending so as to be at least approximately parallel to and within the outer tubular wall, at least two cross walls extending across from the inner wall to the outer wall so as to provide a long narrow settlement path to effect anaerobic handling of influent the path extending between the inner and outer tubular wall, and a bottom extending across an end of both the outer and inner tubular walls and the cross walls.

In preference the settlement path which provides a primary treatment chamber extends more than half way around the peripheral shape of the respective inner and outer walls.

Further in preference the distance apart of the walls defining that path on average is such that the length of the path is more than seven times greater than the said average distance apart.

Put another way in preference there are provided the proportions of the passageway providing a primary separation which has a settlement path which include both a primary and secondary part which is such that this has a length which is at least seven times longer than an average width of the passage along which the length is measured.

In preference, the tubular shape of each of the inner wall and the outer wall is cylindrical. In preference, the inner cylindrical wall is coaxial with the outer cylindrical wall.

One specific problem is that with a joint usage, that is, both aerobic and anaerobic some chambers can be full while adjacent chambers may be empty. This creates the problem that the walls in each case must be able to withstand very high hydrostatic pressures particularly; at the bottom of a respective chamber. If reinforced concrete is to be used (and this is an appropriate material for general cost and life reasons) then the thickness needed to withstand the forces becomes very high and may be expected to either make the whole construction so heavy as to be uneconomic for transport or from a total cost point of view.

Accordingly in preference, the bottom, the outer wall and the inner wall are together integrally moulded in reinforced concrete.

Also in preference, each of the cross walls is integral with the bottom, the outer wall and the inner wall. Such integral moulding has the significant advantage of providing such greater strength with not so much material and is also saving in costs.

For a better understanding of this invention it will now be described in relation to a preferred embodiment which shall be described with the assistance of drawings wherein:

FIG 1 is a plan view of the tank according to a first embodiment this being illustrated as it would be manufactured as a blank prior to installation of weirs, inlets and outlets and any cover or source of aeration,

FIG 2 is a perspective view from a top of the tank blank of the first embodiment,

FIG 3 is the same view essentially as in FIG 2 except that the tank is rotated,

FIG 4 is a plan view of the same tank as in FIG 1 except that the interconnecting elements showing the way the tank can be used as a sewage station are now added and more explicitly detailed, FIG 5 is a cross sectional view along the Iines 5-5 of the first embodiment shown in earlier FIG 1-3,

FIG 6 is a perspective view of a second embodiment again this being shown as a blank from which the tank system will be manufactured,

FIG 7 is a cross sectional view along the Iines 7-7 in FIG 6, and

FIG 8 is an enlarged view in cross section of a bottom corner in accord with the first embodiment.

Referring in detail to the drawings there is a reinforced concrete tank 1 which is moulded in one piece according to existing known techniques.

The tank is moulded for use as a sewerage station using an anaerobic treatment and aerobic treatment in the same integral tank system.

The problem has been to find a shape having both an appropriate number of stages of appropriate size and to provide for these to be able to be provided so that they are effective for the treatment purpose, compact, economical and of light weight for commercial effectiveness.

This is achieved by having a first outer wall 2 of cylindrical shape and an inner wall 3 of cylindrical shape and having the two walls coaxial so as to leave therebetween a deep and narrow passage 4 which because of the incorporation of a weir extends to provide for septic treatment through from the wall 6 to the wall 8 and which in this case has a length which is more than seven times the width which is to be measured by taking the distance apart throughout the passage length and applying a simple mathematical average to this. It is assumed that the width will be approximately constant throughout the passage length.

There is a bottom or floor 5.

There are also cross walls 6, 7 and 8 each being integrally moulded with the two cylindrical walls 2 and 3 and the bottom 5.

In use the tank is conventionally embedded within the ground so that both the bottom 5 and the outer wall 2 have earth surrounding their outer side.

The central chamber within the wall 3 is used for aeration and there are conduits connecting the various other chambers.

One of the first substantial advantages of the arrangement is that there can be provided with this arrangement in an efficient and economic manner, a length and depth of path of sewage from a first inlet to a first transfer which is very effective to assist in settlement of materials within the liquor and to thereby promote anaerobic (that is septic) treatment of the liquor.

It has been found for instance that if a length of travel for the septic treatment part is seven times more than the average width of the passage through which the travel passes, on the presumption that the width is approximately constant along that length, then this provides very good settlement.

As will be seen, if the passageway 9 is used so that an inlet 10 provides sewage into this passageway 9 then there is a substantial distance from this inlet to the transfer overflow at 11 which acts as a baffle which then extends to the wall 8 to provide for the overall length of the septic treatment part.

The chamber 9 provides a primary septic separation chamber as a long narrow pathway which minimises subsequent disturbance at the end by the introduction of the sewage or influent at the beginning.

This is assisted by having the very deep narrow shape as well.

The part 12 extends the primary separation chamber 9 for ongoing septic or anaerobic treatment with the transfer weir 11 in between so that this also provides an advantageous settlement . The length of the passageway for assessment of the ration of length to width is taken from the wall 6 fully around the periphery, through baffle at 11 to wall 8, and the width through this is the average distance apart through this path.

The outlet from the second part of the primary chamber is by a weir at 13 which then allows the liquor into a central chamber 14 and it is here that aeration is introduced. Once again because of the advantageous shape overall, the centre being substantially circular in cross-sectional shape and being of deep cylindrical shape, ensures that by use of aeration into the now confined body of liquor, allows a best result from such aeration after a preliminary septic treatment. Aeration is typically provided in the liquor by a pump drawing air from above the liquor level.

An outlet from this aeration chamber 14 is provided by weir 15 into a chamber 16.

A weir and baffle at 17 allow overflow into the pump out chamber 18.

There is a pump out arrangement schematically shown at 19.

What we now have with the pump out chamber 18 is a chamber that will be variously emptied or filled so that there will be hydrostatic pressure from the surrounding filled chambers.

In order to adequately resist these, it is both the thickness and shape of the walls that assist and it is here therefore that the appropriate shapes are chosen for this purpose to provide a minimum concrete thickness for purposes of economy and all up weight for transport.

The sewage station would be conventionally covered with a concrete top with an access aperture aUowing for sludge return into the primary separation chamber or channel 9 from the central chamber 14 and otherwise there is access to the pump out pump 19 for inspection and maintenance purposes.

In the second embodiment the tank shown as a blank at 20 in Figure 6 has a further wall 21 across a central chamber 22 thereby providing two separate chambers of equal size and shape at 23 and 24 into each of which there will be substrate for supporting bioactive material and means to effect a supply of air into the biomass.

The orientation of the wall 21 also assists the rigidity and provides support for the extended wall part of the inner wall.

The other features that is that the blank is integrally moulded and has a passageway shown here to extend from wall 25 through primary separation chamber 26 and by reason of a weir at 27 extending into the chamber 28 up to the wall 29. This then provides a very long and narrow passageway to effect septic action for influent and where the length of the passageway is substantially greater than the approximately constant width of the passageway through this length.

In order to gain an idea of the size of the tank being considered the tank has in one example an outside diameter of 1.2 meters, and a height of 2.3 meters.

What is shown therefore provides a substantial advantage in terms of the art this arising from the selected shape of the tank and it is also useful as applied when specifically specified as a sewage station as shown.

Claims

1 A reinforced concrete tank system for use as a sewerage station comprising an outer tubular wall, an inner tubular wall extending so as to be at least approximately parallel to and within the outer tubular wall, at least two cross walls extending across from the inner wall to the outer wall, and a bottom extending across an end of both the outer and inner tubular walls and the cross walls.

2 A reinforced concrete tank system for use as an anaerobic treatment sewerage station comprising an outer tubular wall, an inner tubular wall extending so as to be at least approximately parallel to and within the outer tubular wall, at least two cross walls extending across from the inner wall to the outer wall so as to provide a long narrow settlement path to effect anaerobic handling of influent the path extending between the inner and outer tubular wall, and a bottom extending across an end of both the outer and inner tubular walls and the cross walls.

3 A reinforced concrete tank system as in any one of the preceding claims further characterised in that the settlement path which provides a primary treatment chamber extends more than half way around the peripheral shape of the respective inner and outer walls.

4 A reinforced concrete tank system as in any one of the preceding claims further characterised in that the distance apart of the walls defining that path on average is such that the length of the path is more than seven times greater than the said distance apart.

5 A reinforced concrete tank system as in any one of the preceding claims further characterised in that the tubular shape of each of the inner wall and the outer wall is cylindrical.

6 A reinforced concrete tank system as in any one of the preceding claims further characterised in that the inner cylindrical wall is coaxial with the outer cylindrical wall.

7 A reinforced concrete tank system as in any one of the preceding claims further characterised in that the bottom, the outer wall and the inner wall are together integrally moulded in reinforced concrete.

8 A reinforced concrete tank system as in any one of the preceding claims further characterised in that each cross wall is integral with the bottom, the outer wall and the inner wall.

9 A reinforced concrete tank system as in any one of the preceding claims further characterised in that the proportions of the passageway providing a primary separation has a settlement path which is such that this has a length which is seven times longer than the width of the passage through which the length is measured.

10 A reinforced concrete tank system as in any one of the preceding claims further characterised in that there is a second separation chamber of less length than the primary separation chamber and of between one and one half to two times smaller in volume.

11 A reinforced concrete tank system as in any one of the preceding claims further characterised in that the outlet from the second chamber is by a weir which then allows liquor to pass from this into a central chamber being within the inner tubular wall.

12 A reinforced concrete tank system as in any one of the preceding claims further characterised in that there are aeration means within the central chamber.

13 A reinforced concrete tank system as in any one of the preceding claims further characterised in that the central chamber is divided into two separate chambers both of which have aeration means and both of which have means to hold biologically active materials on substrates to assist in the aerobic treatment.

14 A reinforced concrete tank system as in the immediately preceding claim further characterised in that there is an outlet from the secondary chamber provided by a weir into a central chamber .

15 A reinforced concrete tank system as in any one of the preceding claims further characterised in that there is a weir and baffle to allow overflow into a pump out chamber.

16 A reinforced concrete tank system as in any one of the preceding claims further characterised in that there is a pump out arrangement in the pump out chamber.

17 A reinforced concrete tank system as in any one of the preceding claims further characterised in that the tank system has a concrete top with an access aperture allowing for sludge return into the primary separation chamber from the central chamber.

18 A method of treatment of sewerage which comprises introducing sewerage into a reinforced concrete tank system as in any one of the preceding claims and wherein the said primary chamber is such as to effect a septic anaerobic action on the influent and the effluent from the primary chamber is treated aerobically in a further chamber within the tank system.

19 A reinforced concrete tank system substantially as described in the specification with reference to and as illustrated by Figures 1 -5 of the accompanying illustrations.

20 A method of treatment of sewerage substantially as described in the specification with reference to and as illustrated by Figures 1 -5 of the accompanying illustrations.