GB2380120A

GB2380120A - Equipment for cleaning settlement tanks

Info

Publication number: GB2380120A
Application number: GB0123573A
Authority: GB
Inventors: Simon Charles Anderson; Bernard Andrew Bate
Original assignee: QUATROSERVE Ltd
Current assignee: QUATROSERVE Ltd
Priority date: 2001-10-01
Filing date: 2001-10-01
Publication date: 2003-04-02
Anticipated expiration: 2021-10-01
Also published as: GB0123573D0; GB2380120B

Abstract

The invention comprises equipment for cleaning the walls of a settlement tank of the type having a main reservoir [not shown] and a peripheral channel defined by an outer wall 4 and an inner, dam wall 3 forming a weir over which liquid from the main reservoir may flow into the channel. The equipment includes brushes 15,16 for cleaning the inner surfaces of the channel and a further brush 25 for cleaning the upper edge of the inner wall 3. This brush is mounted resiliently via a leaf spring 23. All the brushes are mounted on a moving girder 9 which is part of a bridge assembly extending across the settlement tank and revolving around it's central point, the tank usually being circular.

Description

SEWAGE TREATMENT The invention relates to the treatment of sewage, in particular, to settlement or sedimentation tanks.

Typically the invention is applicable to primary, humus or final settlement tanks of the type having a main chamber containing a rotary arm arranged to scrape solids settled out from the liquid to a draw-off point and a bridge provided with a girder to which the arm is attached, the bridge girder being arranged to rotate in concert with the arm and to provide support therefor at a distal edge thereof. Typically, the tank is cast of concrete and the arm and bridge girder rotate about a support located at the centre of the tank.

Because there is a flow of water and the tank is open to the environment, the conditions for the growth of algae can be ideal. It is desirable to brush the exposed surfaces regularly to remove the algae. The brushes can be mounted on the bridge girder or arm. This system can work well but the concrete of which the tank is made is cast to crude tolerances. As a result, a brush at the end of a centrally located bridge girder will not reach all the surfaces where algae can grow. If the algae are allowed to grow, the quality of the water may fall below the prescribed standard. This is especially true if the algae are fibrous because they grow to a size at which lengths thereof may break off, these are plainly seen as unacceptable solids

in a water sample. It is one object of this invention to provide means to remove such algae, and/or to prevent its'build-up on the surfaces.

In one aspect the invention provides a sewage settlement tank comprising at least two generally parallel, generally circular walls, the innermost of the walls defining a chamber for receiving mixtures of solids and liquids and for settling solids from liquids held therein, the chamber having an outlet for discharging settled solids therefrom; the upper edge of the inner wall providing a weir over which liquids may flow, into the generally annular space between the two walls, the inner wall further comprising a ledge portion extending toward the outer wall; an agitator arm and bridge girder mounted at or at least proximate the centre of the chamber for rotation, the bridge girder having mounted at, or towards, its distal end first brush means for cleaning opposing faces of the walls and second brush means resiliently mounted to the girder by leaf spring means for substantially continuous contact with the upper edge of the inner wall.

The second brush means preferably comprises a first brush part for substantially continuous contact with the upper edge of the inner wall and a second brush for continuous contact with the ledge portion.

The first brush part, in use, may be arranged to trail the girder in its'rotation and the second brush part, in use, may be arranged to precede the girder in its' rotation or vice versa.

The upper edge of the inner wall of the settlement tank may have a weir board mounted thereon, preferably the weir board will comprise spaced-apart notches.

In a preferred embodiment, the second brush means may be arranged to clean matter and/or inhibit deposition of matter on the upper edge of the inner wall, in use.

There is further provided, by a second aspect of the invention, cleaning equipment for a settlement tank comprising first brush means for cleaning opposing faces of at least generally circular, generally parallel walls and second brush means and leaf spring means, said second brush means being arranged to be resiliently mounted to a bridge girder by said leaf spring means for continuous contact with an upper edge of the inner wall of the settlement tank.

A third aspect of the invention provides a method of cleaning surfaces of a settlement tank comprising at least two generally parallel, generally circular walls, the innermost of the walls defining a chamber for receiving mixtures of solids and liquids and for settling solids from liquids held therein, the chamber having an outlet for discharging settled solids therefrom; the upper edge of the inner wall providing a weir over which liquids may flow, into the generally annular space between the two walls, the inner wall further comprising a ledge portion extending toward the outer wall; the tank further comprising an agitator arm and bridge girder mounted at or at least proximate the centre of the chamber for rotation; the method

comprising mounting at or at least towards the distal end of the bridge girder first brush means for cleaning the opposing faces of the walls and second brush means via a leaf spring, urging said second brush means into substantially continuous contact with the upper edge of the inner wall and rotating the bridge girder, thereby cleaning the surfaces of any matter deposited thereon and inhibiting further deposition.

In order that the aspects of the invention may be well understood, it will now be described by way of example with reference to the accompanying diagrammatic drawings, in which: Figure 1 is a section through a prior art settlement tank; Figure 2 is a side elevation in section of part of a settlement tank according to the invention; Figure 3 is a plan view of part of the tank of Figure 2; Figure 4A and 4B are plan views of the cleaning devices of the tank of Figure 2; Figure 5 is a sectional elevation through the channel of the tank of Figure 2; and Figure 6 is an elevation along the channel of the tank of Figure 2.

Referring firstly to Figure 1, a known settlement tank 100 having a main chamber 102, defined by a generally circular peripheral wall 103 outside of which is a generally parallel, generally circular wall 104, the space therebetween providing a

drainage channel 107. A central feed pipe 110 provides access for a mixture of solids and liquids to be separated and a sludge discharge pipe 105 provides egress means for separated solids.

The tank 100 is provided with a main beam or girder G'. from which is suspended an agitator arm 106. A drive unit 111 is provided at the distal edge of the girder G'for rotation of the girder G'about a central pivot 108, the drive unit 111 running along the top of the outside wall 104.

In use, a slurry or mixture of solids and liquids is fed through the feed pipe 110 where it is emitted into a diffusion box 112. Solids settle out from the liquids and are scraped by the rotating arm 106 toward the centre of the tank 100 where they are drawn off through pipe 105. Separated liquid flows over the top edge of the wall 103, acting as a weir, and into the drainage channel 107. A scum hopper 113 may be provided to collect scum removed by a scum trap (not shown).

Referring now to Figures 2 and 3, a circular settlement tank 1 of the invention is cast of concrete and has a main chamber 2 surrounded by generally parallel inner and outer walls 3,4. The main chamber 2 has a sloping floor leading to an outlet 5. A sludge or slurry feed pipe is also provided but is not shown for reasons of clarity. The upper edge of the inner wall 3 has V-shaped notches 6 to act as a weir and is provided with a sloping ledge L whereas the outer wall 4 has a plain, horizontal upper surface. A solids-free liquid drainage channel 7 is present between the walls. A shaft 8 is present at the centre of the tank 2 about which a

girder g may rotate so that an arm 9 will encourage the solids entrained in the liquid to exit the chamber 2. The settled solids leave via the outlet 5, whereas the relatively solid-free liquid overflows the weir notches 6 into the channel 7 to exit separately. Mounted at the distal end of the girder g are cleaning brush or scraper devices, generally indicated at S.

Referring to Figures 4A, 4B, 5 and 6, a first brush device 10 is present at the end of the girder g to clean facing vertical surfaces 11,12 of the walls 4,3 as well as the floor 13 of the channel 7 of algae and the like. The device 10 depends from the free end of the girder g through a parallelogram linkage P and trails the girder g as it rotates. As shown, the device 10 comprises a bracket 14, through which it is attached to the girder g, and has outwardly facing side brushes 15 to clean the facing vertical surfaces 11,12 and downwardly facing brushes 16 to clean the floor 13. The weight of brushes 16 holds them against the floor 13 and the tension in leaf spring means 17 holds the brushes 15 against the vertical surfaces 11,12. Note that there is no power to rotate the brushes which simply follow the girder g. A cord or rope C is provided to enable the device 10 to be lifted from the channel 7 for its' maintenance, such as cleaning, repair or the like.

A second brush device 20 is also connected to the girder g by a bracket 21.

Connected to the bracket are two leaf springs 22 and 23, each having a brush 24,25 attached to its respective distal end. Each leaf spring 22,23 is arcuate and biases each brush 24,25 in to contact with the vertical surfaces of the V notch weir 6 and the top surface of the ledge L respectively.

The brushes 15,16, 24,25 have bristles to clean the respective surfaces with which they are in contact.

In use, as the girder g rotates, the brushes 24,25 of the second device 20 are urged by the springs 22,23 into contact with the respective surfaces to clean them of algal growth. The leaf springs 22,23 are made of stainless steel and the bristles of plastics materials. The brushes 24 and 25 are arranged to precede or follow the girder g as it rotates, depending on the direction of rotation, one following, one preceding.

As shown, the inner wall 3 has been cast of concrete to crude tolerances forming the ledge L on the side of the wall 3 facing the channel 7. The ledge L is not usually of uniform width. The ledge L may vary in width from 150 to 300 mm.

As a result, rotation of the arm in a true circle from the centre of the chamber 2, will not follow the true contour of the ledge L. Moreover, the ledge L may be noncircular, for example it may be oval, or it may not be concentric with the weir 6, or outer wall 4 or it may not be level. In any case, the use of leaf springs 17,22, 23 which resiliently urge the brushes 15,24, 25 into contact with respective surfaces L, 6,11, 12 ensures that each surface L, 6,11, 12 is cleaned of algae, scum and the like.

The weir 6 need not comprise notches, it may be a flat topped weir board.

Claims

CLAIMS 1. A settlement tank comprising at least two generally parallel, generally circular walls, the innermost of the walls defining a chamber for receiving mixtures of solids and liquids and for settling solids from liquids held therein, the chamber having an outlet for discharging settled solids therefrom; the upper edge of the inner wall providing a weir over which liquids may flow. into the generally annular space between the two walls, the inner wall further comprising a ledge portion extending toward the outer wall; an agitator arm and bridge girder mounted at or at least proximate the centre of the chamber for rotation, the bridge girder having mounted at, or towards, its distal end first brush means for cleaning opposing faces of the walls and second brush means resiliently mounted to the girder by leaf spring means for substantially continuous contact with the upper edge of the inner wall.
2. A settlement tank according to Claim 1, wherein said second brush means comprises a first brush part for substantially continuous contact with the upper edge of the inner wall and a second brush part for continuous contact with the ledge portion.
3. A settlement tank according to Claim 2, wherein one of the first and second brush parts, in use, is arranged to trail the girder in its'rotation.

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4. A settlement tank according to Claim 3, wherein the other of the first and second brush parts, in use, is arranged to precede the girder in its'rotation.
5. A settlement tank according to any preceding Claim, wherein the upper edge of the inner wall comprises spaced-apart notches.
6. A settlement tank according to Claim 5, wherein said second brush means is arranged to clean matter and/or inhibit deposition of matter on the upper edge of the inner wall, in use.
7. Cleaning equipment for a settlement tank comprising first brush means for cleaning opposing faces of at least generally circular, generally parallel walls and second brush means and leaf spring means, said second brush means being arranged to be resiliently mounted to a bridge girder by said leaf spring means for continuous contact with an upper edge of the inner wall of the settlement tank.
8. A method of cleaning surfaces of a settlement tank comprising at least two generally parallel, generally circular walls, the innermost of the walls defining a chamber for receiving mixtures of solids and liquids and for settling solids from liquids held therein, the chamber having an outlet for discharging settled solids therefrom; the upper edge of the inner wall providing a weir over which liquids may flow, into the generally annular space between the two walls, the inner wall further comprising a ledge portion extending toward the outer wall ; the tank

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further comprising an agitator arm and bridge girder mounted at or at least proximate the centre of the chamber for rotation; the method comprising mounting at or at least towards the distal end of the bridge girder first brush means for cleaning the opposing faces of the walls and second brush means via a leaf spring, urging said second brush means into substantially continuous contact with the upper edge of the inner wall and rotating the bridge girder, thereby cleaning the surfaces of any matter deposited thereon and inhibiting further deposition.
9. A method according to Claim 8, wherein said second brush means comprises a first brush part for continuous contact with the upper edge of the inner wall and a second brush part for continuous contact with the ledge portion.
10. A method according to Claim 9 comprising mounting one of the first and second brush parts such that one thereof trails the girder during rotation.
11. A method according to Claim 10 further comprising mounting the other of the first and second brush parts such it precedes the girder during rotation.
12. A settlement tank substantially as hereinbefore described and with reference to Figures 2 to 6 of the accompanying drawings.
13. Cleaning apparatus for a settlement tank substantially as hereinbefore described and with reference to Figures 2 and 6 of the accompanying drawings.

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14. A method of cleaning a settlement tank substantially as hereinbefore described.