GB2422793A

GB2422793A - A liquid filtration system

Info

Publication number: GB2422793A
Application number: GB0602415A
Authority: GB
Inventors: Nicholas Jackson; Jasper Hendericus Mari Kuijper
Original assignee: Evolution Aqua Ltd
Current assignee: Evolution Aqua Ltd
Priority date: 2005-02-07
Filing date: 2006-02-07
Publication date: 2006-08-09
Also published as: GB0502529D0; WO2006082447A2; WO2006082447A3; GB0510674D0; GB0602415D0; EP1850939A2

Abstract

A liquid filtration system comprises a first chamber and a second chamber, the first chamber defined by a receptacle containing a particulate media. The receptacle is located in the second chamber and has an aperture to facilitate fluid communication between the first and second chamber. The system further comprises at least one fluid inlet for introducing a fluid to agitate media in the receptacle. Advantageously the system prevents over time, the displacement of the particulate media along a given flow path thus channelling is prevented and filtration of the liquid is maintained.

Description

APPARATUS AND METHODS FOR FILTERING LIQUID

The present application relates to methods and apparatus for filtering a liquid. More particularly, the present application relates to methods and apparatus for mechanically filtering a liquid utilising a particulate media.

It is known to use a media, such as the KI moving bed particulate media produced by AnoxKaldnes AS of P.O. Box 2011, N.-3103 T nsberg, Norway and supplied worldwide by the Applicant, to perform biological filtration of a liquid. It has also been recognised that particulate media is suitable for performing mechanical filtration of a liquid by passing the liquid through the particulate media. Subsequent cleaning of the particulate media may be performed by agitating the particulate media to dislodge debris trapped therein.

It is known from International patent application number PCT/US98/07732 to provide an inlet screen to remove large debris as the liquid is introduced into a filter chamber in which the particulate media is located. Air is stored in a charge chamber and periodically introduced into the filter chamber to agitate the particulate media and dislodge debris trapped therein. The introduction of air into the filter chamber causes liquid to be expelled from the filter chamber back through the screen. Thus, the screen is backflushed and debris trapped therein dislodged into a settlement chamber prior to disposal.

There remain a number of problems with existing filtration systems employing particulate media to perform mechanical filtration of a liquid.

Significantly, the flow of liquid through the pack of particulate media tends to be along a set path, typically the shortest route between the inlet and outlet. Over a period of time, the liquid displaces the particulate media along this flow path into the surrounding pack of particulate media. The displacement of the particulate media along this flow path causes a channel to be formed through the pack of particulate media. The liquid may flow through this channel relatively unobstructed by the particulate media. Thus, liquid may pass through the pack of particulate media without being properly filtered and the efficiency of the filter is reduced. The formation of these channels is known as channelling or tracking and presents a considerable problem.

The present invention, at least in preferred embodiments, sets out to overcome or ameliorate some of the problems associated with known filtration systems.

Viewed from a first aspect, the present application relates to a liquid filtration system comprising a first chamber and a second chamber, the first chamber being defined by a receptacle containing a particulate media, the receptacle being located in the second chamber; wherein at least one aperture is provided in the receptacle to facilitate fluid communication between the second chamber and the first chamber.

The location of the receptacle inside the second chamber at least in preferred embodiments can help to establish a uniform flow of liquid through the particulate media when the filtration system is operating. The inventors in the present case have recognised that the creation of a uniform flow through the particulate media is desirable insofar as is it reduces the likelihood of channelling or tracking occurring. The filtration system may therefore operate efficiently over prolonged periods of time. The velocity of the liquid flowing through the particulate media may also be reduced, further promoting the deposit of debris from the liquid.

The receptacle may have a single aperture which, for example, defines a serpentine path in the receptacle. Preferably, however, the receptacle is provided with a plurality of apertures and the location of the apertures is arranged to promote a uniform flow of liquid through the particulate media. The positioning of the apertures may be varied depending on the type of media contained in the receptacle. The desired positioning of the apertures could be determined by experimentation or computational modelling of the fluid flow through the first chamber.

The receptacle preferably has a sidewall and said at least one aperture is provided in said sidewall. The receptacle is preferably open at the top to facilitate visual inspection of the particulate media and to provide access to the particulate media, if required.

The receptacle preferably has a base. The at least one aperture may be formed in said base to facilitate fluid communication between the first and second chambers. The receptacle preferably also has a sidewall and said sidewall may be substantially impervious.

The second chamber is preferably defined by a vessel.

Viewed from a further aspect, the present application relates to a liquid filtration system comprising a first chamber and a second chamber, the first chamber being defined by a receptacle containing a particulate media for filtering liquid; wherein the receptacle has a base and a sidewall and at least one aperture is provided in said sidewall to allow liquid to enter the first chamber from said second chamber.

The introduction of the liquid into the first chamber through the sidewall helps establish a uniform flow of liquid through the particulate media. Therefore, the filtration is performed more evenly by the particulate media and it may operate for longer periods of time before becoming clogged. The velocity of the liquid through the particulate media may also be relatively low, encouraging debris to be deposited in the first chamber and thereby improving the efficiency of the system.

The first chamber and the second chamber are preferably provided adjacent to each other. Preferably they are provided side by side (rather than one above the other). The first chamber and the second chamber are preferably separated from each other by the sidewall of said receptacle.

It is particularly desirable to locate the first chamber inside the second chamber. This is achieved by locating the receptacle inside the second chamber. This arrangement effectively creates a vessel within a vessel and may expose a larger proportion of the surface area of the receptacle to the liquid in the second chamber.

The second chamber preferably extends around at least a portion of the first chamber. The first chamber and the second chamber are preferably arranged concentrically.

The receptacle is preferably tubular, cylindrical or conical. The receptacle may alternatively be substantially spherical. The receptacle may have a circular, oval or polygonal cross-section. These arrangements at least in preferred embodiments allow the liquid to enter the first chamber from different directions and pass through the particulate media in a radially inwards direction.

If a single aperture is provided it preferably extends around at least a portion of the circumference of the receptacle. The aperture may, for example, form a helix in the sidewall of the receptacle. Preferably, however, a plurality of apertures is provided and the apertures are located around the circumference of the sidewall of the receptacle to allow uniform liquid flow into the first chamber.

This may further reduce channelling in the pack of media and further reduce the velocity of the liquid in the first chamber.

A plurality of openings is preferably formed in the base of the receptacle to allow filtered debris to exit the first chamber as it settles. The debris preferably exits the first chamber into the second chamber. The second chamber is preferably provided with a discharge outlet to allow filtered debris and debris which has settled out of suspension to be expelled from the system.

The system preferably comprises means for agitating particulate media in the first chamber. Mechanical means, such as a rotatable member or a rotatable blade may be provided. The mechanical means may be manually driven or they may be driven by a motor. The receptacle may itself be rotatable to agitate the particulate media contained therein.

Alternatively, at least one fluid inlet may be provided for introducing fluid into the first chamber to agitate the particulate media. The at least one fluid inlet is preferably separate from the liquid inlet through which liquid to be filtered enters the second chamber. The fluid may be a gas, such as air. Alternatively, the fluid may be a liquid, from a dedicated source, such as a tap, or liquid which has previously been filtered by the particulate media. A dedicated pump may be provided to pump the fluid through the at least one fluid inlet.

The introduction of fluid, either liquid or gas, into the first chamber raises the level of the liquid in this chamber. The increased liquid level creates a pressure difference between the liquid in the first chamber and the liquid in the second chamber and this encourages the liquid to flow from the first chamber to the second chamber. This flow of liquid backwashes the at least one aperture provided in the sidewall of the receptacle and can help to dislodge trapped debris.

The at least one fluid inlet may be located inside the receptacle and introduce fluid directly into the first chamber. Alternatively, the at least one fluid inlet may be provided in the second chamber. The at least one fluid inlet is preferably provided below the base of the receptacle, the fluid being introduced into the first chamber, in use, through at least one opening formed in the base.

The at least one fluid inlet may comprise one or more nozzles or it may comprise a conduit having a plurality of holes provided therein. The conduit is preferably flexible so that it may readily be arranged in a variety of configurations.

The conduit is preferably ring-shaped. The at least one fluid inlet may introduce fluid at the centre of the receptacle or towards the outside thereof.

The fluid inlet is preferably provided at the base of the receptacle. The at least one fluid inlet is preferably arranged so as to displace the particulate media and cause circulation within the receptacle. The fluid preferably forces the particulate media upwardly in the centre of the first chamber. The particulate media is then displaced outwardly at the top of the first chamber before being forced down the inside of the sidewall of the receptacle. This circulation of the particulate media is preferably sustained by the introduction of fluid at a substantially uniform rate. The first chamber may be open at the top to allow this circulating process to continue freely. Alternatively, a guide member may be provided at the top and/or bottom of the receptacle to guide the movement of the particulate media.

Alternatively, the fluid may force the particulate media upwardly at the outside of the first chamber. The particulate media is then displaced inwardly at the top of the first chamber before being forced down in the centre thereof.

Again, the circulation of the particulate media is preferably sustained by the introduction of fluid at a substantially uniform rate.

It will be appreciated that the at least one fluid inlet may be arranged to displace the particulate media downwardly. Again, the continued action of the fluid preferably causes circulation of the particulate media within the first chamber. This arrangement is more suitable for media which is negatively buoyant.

The introduction of fluid may continue for a period of time equal to or greater than 5, 10, 15,20,30 or6O seconds. The period of time may be predetermined, for example by a control device.

The at least one aperture formed in the sidewall of the receptacle is preferably a slot. The at least one slot preferably has a width less than or equal to 7mm. The at least one slot preferably has rounded ends to help prevent the particulate media becoming trapped.

Alternatively the at least one aperture may be a hole. Preferably a plurality of holes is provided. The holes preferably have a diameter less than or equal to 7mm.

A further alternative is to form at least a portion of the sidewall from a mesh, a grill or a screen. The at least one aperture in the receptacle is formed between the elements making up the grill, mesh or screen. It will be appreciated that at least a portion of the sidewall may be formed by a perforated member.

The size of the at least one aperture in the sidewall determines the size of particulate material or debris which may enter the first chamber. For example, a very fine mesh or screen could be used to allow only very small particles to enter the first chamber. The sidewall may alternatively be a permeable membrane.

The sidewall may alternatively be formed from a sheet material, such as a sheet of stainless steel, having at least one aperture formed therein.

It will be appreciated that the aperture or apertures could extend over substantially all of the sidewall of the receptacle. For example, the sidewall could be formed from a mesh, a grill or a screen.

In preferred embodiments, substantially all of the at least one aperture is provided in a region making up only a portion of the sidewall of the receptacle.

The region may make up less than or equal to 10%, 20%, 30%, 40%, 50%, 60%, 70% or 80% by area of the sidewall of the receptacle. The region may make up 5% to 15%; 15% to 25%; 35% to 45%; 45% to 55%; 55% to 65%; or 65% to 80% by area of the sidewall. A plurality of apertures are preferably distributed evenly throughout said region.

The region is preferably rectangular, circular, or elliptical in shape. The region is preferably offset vertically from the outlet through which filtered liquid exits the first chamber to increase the length of the pathway taken by the fluid through the particulate media in the first chamber. The region is preferably provided at the top or bottom of the receptacle. In arrangements whereby the receptacle is tubular or cylindrical, the region preferably extends circumferentially around the receptacle. For example, the region may form a band in which the majority or all of the at least one aperture is located. The band may be located at the top or bottom of the sidewall. The remainder of the sidewall is preferably substantially impervious.

In preferred embodiments, substantially all of the at least one aperture is/are located in less than or equal to 20%, 30%, 40%, 50%, 60%, 70%, or 80% by height of the sidewall of the receptacle. When the receptacle is to contain positively buoyant media, substantially all of the at least one aperture is preferably provided towards the bottom of the sidewall of the receptacle to increase the path which must be taken by the liquid to pass through the particulate media. If the particulate media is negatively buoyant, substantially all of the at least one aperture is preferably provided at the top of the sidewall of the receptacle.

A movable sleeve may be provided to allow the height of the receptacle to be adjusted. The sleeve is preferably movable to cover at least some of the at least one aperture formed in the receptacle.

A vertical region of the sidewall by height is preferably substantially impervious. Preferably, the region extends over less than or equal to 10%, 20%, 30%, 40%, 50%, 60%, 70%, or 80% by height of the sidewall. The region is preferably located distal from the at least one fluid inlet through which fluid is introduced to agitate the particulate media. This is advantageous since it prevents liquid exiting the first chamber and helps establish and maintain circulation of the particulate media within the first chamber. The substantially impervious region may be provided at the top or bottom of the sidewall of the receptacle.

The system preferably comprises a system outlet for allowing filtered liquid to exit the first chamber. The outlet is preferably provided in the centre of the first chamber. Most preferably, the outlet and the receptacle are arranged concentrically to ensure uniform liquid flow throughout the particulate media provided in the first chamber.

A guard device is preferably provided to act as a cover to allow filtered water to exit the first chamber but to prevent media exiting through the system outlet. The guard device preferably comprises a tubular member. The guard device and the receptacle are preferably arranged concentrically. The guard device preferably has a plurality of openings formed therein.

The system preferably also includes a discharge outlet for expelling filtered debris from the system. The discharge outlet is preferably provided in the second chamber. The filtered debris may enter the second chamber from the first chamber through holes in the base of the receptacle or through the at least one aperture in the sidewall thereof.

In use, 15-30%; 30-45%; 45-55%; 55-60%; 60%-65%; 60-80%; or 80-90% by volume of the receptacle is preferably filled with said particulate media. Most preferably, approximately 55%, 60% or 65% by volume of the receptacle is filled with the particulate media. This helps to ensure that sufficient space is retained to allow the particulate media to circulate within the first chamber.

The particulate media are preferably positively buoyant. The apertures in the sidewall are preferably provided towards the base of the sidewall to increase the length of the path which must be taken by the liquid as it passes through the first chamber. In this arrangement, there are preferably no apertures provided in the top portion of the sidewall.

The particulate media may alternatively be negatively buoyant. In this case, the apertures in the sidewall are preferably provided towards the top of the sidewall of the receptacle. In this arrangement, there are preferably no apertures provided in the bottom portion of the sidewall.

Alternatively, the particulate media may be neutrally buoyant. In this case, the flow of liquid through the first chamber will displace the particulate media away from the apertures in the sidewall and therefore increase the flow path through the particulate media. The outlet from the first chamber should accordingly be displaced vertically from the apertures to increase the length of the path followed by the liquid.

The particulate media may be closed cell (for example, beads or cubes).

Preferably, however, the particulate media are open-cell.

The particulate media are preferably substantially cylindrical; substantially elliptical; or substantially spherical in shape.

The particulate media are preferably made of a plastics material.

The receptacle is preferably made of stainless steel or a plastics material.

Liquid to be filtered may be supplied to the second chamber under the action of gravity or under pressure.

The filtration system may be pressurised or unpressurised.

If the filtration system is to be pressurised, the second chamber is preferably defined by a vessel capable of sustaining a pressure greater than atmospheric pressure.

The ability of the filtration system to be unpressurised advantageously allows air to be introduced into the first chamber while the system operates. If air was introduced into a pressurised system while it was under pressure, nitrogen may be introduced into the water which may poison fish or wildlife in a body of water being filtered.

A pump may be provided to pump liquid into the filtration system under pressure. The pump may be provided upstream of the system inlet.

Alternatively, a pump may be provided downstream of the second chamber to draw water through the first chamber. The pump may be provided downstream of the system outlet.

Viewed from a further aspect, the present application relates to a kit of parts for a filtration system as described herein, the kit comprising a receptacle for defining a first chamber for containing particulate media for filtering liquid, and a guard device for preventing said media exiting the chamber through an outlet.

The kit may also include media for filtering liquid.

The present application also relates to a method of installing a kit of parts as described herein. The method comprises the steps of: (a) locating the - 10- receptacle in a vessel to form said first and second chambers; and (b) locating the guard device partially to obstruct an outlet. The method may also include the step of removing an existing filter prior to completing steps (a) and (b).

Viewed from a further aspect, the present application relates to a method of filtering a liquid, the method comprising the steps of: (a) introducing the liquid to be filtered into a first chamber defined by a receptacle located in a second chamber; and (b) passing the liquid through a particulate media contained in the receptacle to filter the liquid.

The method may further include the step of removing filtered debris form the first chamber.

The method may also include the step of agitating the particulate media in said first chamber to dislodge debris trapped in the particulate media. The particulate media may be agitated using a mechanical device, such as a rotatable member or a rotatable blade. The method may comprise the step of rotating the receptacle to agitate the particulate media. Alternatively, fluid may be introduced into the first chamber to agitate said media. The fluid may be introduced though an inlet provided in the first chamber. Although a liquid, such as liquid already filtered by the system, may be used to agitate the particulate media, the fluid is preferably a gas. Most preferably, the fluid is air.

The introduction of liquid into the first chamber is preferably halted whilst the particulate media is agitated.

The particulate media may be open or closed cell.

The receptacle may be tubular, cylindrical or conical. The receptacle may have a circular, oval or polygonal cross-section.

The first chamber and the second chamber are preferably arranged concentrically.

The liquid may be introduced into the second chamber under pressure or it may be gravity fed.

Viewed from a further aspect, the present application relates to a receptacle mountable in a vessel to form a first chamber inside a second chamber, the receptacle being suitable for containing a particulate media for filtering liquid; wherein at least one aperture is provided in the receptacle to allow -11 - liquid to enter the first chamber from the second chamber. The receptacle may be retro-fitted to an existing filter.

The receptacle preferably has a sidewall. The at least one aperture is preferably provided in the sidewall of the receptacle.

The region may make up less than or equal 10%, 20%, 30%, 40%, 50%, 60%, 70% or 80% by area of the sidewall of the receptacle. The region may make up 5% to 15%; 15% to 25%; 35% to 45%; 45% to 55%; 55% to 65%; or 65% to 80% by area of the sidewall. A plurality of apertures is preferably distributed evenly throughout said region.

The region is preferably rectangular, circular, or elliptical in shape. The region is preferably provided at the top or bottom of the receptacle. In arrangements whereby the receptacle is tubular or cylindrical, the region preferably extends circumferentially around the receptacle. For example, the region may form a band in which the majority or all of the at least one aperture is located. The band may be located at the top or bottom of the sidewall. The remainder of the sidewall is preferably substantially impervious.

In preferred embodiments, substantially all of the at least one aperture is located in less than or equal to 10%, 20%, 30%, 40%, 50%, 60%, 70%, or 80% by height of the sidewall of the receptacle.

A vertical region of the sidewall by height is preferably substantially impervious. Preferably, the region extends over less than or equal to 10%, 20%, 30%, 40%, 50%, 60%, 70% or 80% by height of the sidewall. The substantially impervious region may be provided at the top or bottom of the sidewall of the receptacle.

The at least one aperture is preferably a slot. The at least one slot preferably has a width of 4.5mm; or a width less than or equal to 7mm; less than or equal to 5mm; or less than or equal to 3mm. The at least one slot preferably has a length of 35mm or 60mm inclusive; or a length in the range 25mm to 70mm inclusive. - 12-

The at least one aperture may alternatively be a hole. In this case, the at least one hole preferably has a diameter less than or equal to 7mm.

The receptacle preferably has a diameter of 400mm. In alternative embodiments, the receptacle may have a diameter in the range 150mm to 250mm inclusive; 250mm to 350mm inclusive; 350mm to 450mm inclusive; 450mm to 550mm inclusive; or 550mm to 600mm inclusive.

The receptacle preferably has a length of 475mm or 620mm. Again, in alternative embodiments, the receptacle may have a length in the range 350mm to 450mm inclusive; 450mm to 550mm inclusive; or 550mm to 650mm inclusive.

The receptacle may rest on its base in use. Preferably, however, the receptacle has at least one supporting member, such as at least one leg, for supporting it above the base of the vessel. This is desirable as it creates a region of liquid under the receptacle which is relatively stagnant. Debris is therefore more likely to be deposited in this region.

The at least one supporting member preferably has a length of 90mm or 130mm; a length in the range 80mm to 140mm inclusive; or 140mm to 180mm inclusive.

The top of the receptacle is preferably open.

The receptacle preferably has a base. The base preferably has at least one opening provided therein. The at least one opening may be holes. The holes preferably have a diameter less than 7mm.

Alternatively, the openings may be slots. The slots preferably have a width less than 7mm.

The width of the at least one aperture in the sidewall of the receptacle is preferably equal to or less that the width of the at least one opening in the base of the receptacle. Thus, in use, any particulate material or debris which is small enough to pass through the at least one aperture in the sidewall of the receptacle will be able to escape through the at least one opening in the base. Thus, the likelihood of a build-up of debris in the receptacle is reduced.

The present application also relates to a filtration system incorporating a receptacle as described herein.

Viewed from a yet further aspect, the present application relates to a guard device for mounting in a liquid filtration system to prevent particulate media escaping through a system outlet, the guard device having at least one opening formed therein to allow liquid to exit through said outlet.

The guard device is preferably tubular or cylindrical. The guard device preferably has a diameter of 110mm. Alternatively, the member may have a diameter between 30mm and 60mm inclusive; between 60mm and 90mm inclusive; between 90mm and 120mm inclusive; or between 120mm and 150mm.

The guard device is preferably mountable in a conduit forming the system outlet. The internal diameter of the conduit is, for example, 104mm.

Alternatively, the guard device may be mounted around a conduit forming the system outlet. The external diameter of the conduit is, for example, 130mm.

The at least one opening is preferably formed in a sidewall of the guard device. The at least one opening is preferably provided towards the top of the sidewall. The at least one opening is preferably provided in the upper or lower 20%, 30%, 40% or 50% of the sidewall by height.

The bottom 20%, 30%, 40%, or 50% of the sidewall of the guard device by height is preferably substantially impervious.

The at least one opening is preferably a slot.

The at least one slot preferably has a width of 4.5mm. Alternatively, the slot may have a width less than or equal to 7mm; less than or equal to 5mm; or less than or equal to 3mm.

The at least one slot may have a length of 35mm or 60mm. Alternatively the at least one slot may have a length in the range 30mm to 70mm inclusive;70mm to 115mm inclusive; or 115mm to 150mm inclusive.

It will be appreciated that the arrangements of the receptacle and the guard device described herein, such as the dimensions thereof, are equally applicable to the corresponding components of the filtration system described herein.

The present application further relates to a kit of parts comprising a receptacle as described herein; and a guard device as described herein.

The kit of parts may further comprise particulate media for filtering liquid. - 14-

Viewed from a still further aspect, the present application relates to a liquid filtration system comprising a receptacle for containing media for filtering liquid, the receptacle having a base and a sidewall and forming a first chamber; wherein at least one aperture is provided in the sidewall of the receptacle to allow liquid to enter the first chamber from a second chamber.

Viewed from a yet still further aspect, the present application relates to a liquid filtration system comprising a first chamber and a second chamber, the first chamber being defined by a receptacle for containing a media for filtering liquid, the receptacle being located in said second chamber; wherein the receptacle has at least one aperture to allow liquid to enter the first chamber from said second chamber.

The receptacle may have a base and a sidewall; said at least one aperture being provided in the base of the receptacle. The sidewall of the receptacle may be substantially impervious.

Alternatively, the receptacle may have a base and a sidewall; said at least one aperture being provided in the sidewall of the receptacle.

Viewed from a further aspect, the present application relates to a liquid filtration system comprising a first chamber and a second chamber, the first chamber being defined by a receptacle containing a media for filtering liquid; wherein the receptacle has an inlet for allowing fluid to enter the first chamber to be filtered and an outlet for allowing filtered debris to exit the first chamber, said inlet being separate from said outlet.

Viewed from a still further aspect, the present application relates to a method of filtering a liquid, the method comprising the steps of: (a) introducing the liquid to be filtered into a first chamber through an inlet; (b) passing the liquid through media provided in the first chamber to filter the liquid; and (C) removing filtered debris from the first chamber through an outlet separate from said inlet.

The media or particulate media is preferably KI media produced by AnoxKaldnes AS or an equivalent filter media. Alternatively K3 media, also produced by AnoxKaldnes AS, or Biochip media may be used.

The liquid may be introduced into the second chamber under pressure.

Alternatively, the liquid may be introduced into the second chamber under the action of gravity.

Viewed from a still further aspect, the present application relates to a liquid filtration system comprising a first chamber and a second chamber, the first chamber being defined by a receptacle containing a media for filtering liquid, the system further comprising a first inlet for allowing liquid to be filtered to enter the second chamber, and a second inlet for allowing a fluid to be introduced into the first chamber at a substantially uniform rate to agitate said media. The introduction of fluid, such as air or water, into the chamber agitates the media and dislodges particulate material or debris trapped therein. The fluid is introduced at a uniform rate for a period of time. The period of time may be predetermined. The length of the period of time over which the fluid is introduced may be tailored for particular applications to ensure that the media is adequately cleaned. The fluid may be introduced for a period of time equal to or longer than 5, 10, 20, 30 or 60 seconds, or even equal to or longer than 1 minute, 5 minutes or 10 minutes.

Viewed from a still further aspect, the present application relates to a method of filtering a liquid, the method comprising the steps of: (a) introducing the liquid to be filtered into a first chamber through an inlet; (c) passing the liquid through a media provided in the first chamber to filter the liquid; and (c) periodically introducing a fluid into said first chamber at a substantially uniform rate to agitate the media. The introduction of fluid, such as air or water, into the chamber agitates the media and dislodges particulate material or debris trapped therein. The length of the period of time over which the fluid is introduced may be tailored for particular applications to ensure that the media is adequately cleaned. The fluid may be introduced for a period of time equal to or longer than 5, 10, 20, 30 or 60 seconds, or even equal to or longer than 1 minute, 5 minutes or 10 minutes.

The first chamber described herein is typically a filtration chamber for containing liquid to be filtered. The second chamber is typically a settlement chamber for allowing debris to settle out of suspension. However, the velocity of - 16- the fluid flow in the second chamber may in certain embodiments be too great to allow substantial quantities of debris to settle in this chamber.

The term particulate media used throughout the present application is to be understood as relating to any media suitable for filtering a liquid. The term covers, for example, granular media, filter media or filtration media. The skilled person will appreciate that different types of media can be employed in the apparatus and processes described herein without departing from the scope of the present invention.

Preferred embodiments of the present invention will now be described by way of example only and with reference to the accompanying drawings, in which: Figure 1 shows a cross-sectional view of a filtration system in accordance with a first embodiment of the present invention; Figure 2 illustrates the circulation of particulate media when air is introduced into the filtration chamber of the system shown in Figure 1; Figure 3 illustrates the discharge of debris from the filtration chamber of the embodiment shown in Figures 1 and 2; Figure 4 shows a perspective view of the receptacle shown in Figures 1, 2 and 3; Figure 5 shows a plan view of the base of the receptacle shown in Figure 4; and Figure 6 shows a perspective view of an alternative embodiment of the present invention.

A liquid filtration system 1 for filtering water from a pond (not shown) in accordance with the present invention is shown in Figure 1. The system 1 comprises a housing 3 having a central container 5 and an outer annular container 7.

A receptacle 9 is provided in the central container 5 to divide the container into a first filtration chamber 11 and a second settlement chamber 13. A pack 15 of particulate media, such as the Ki media produced by AnoxKaldnes AS, is provided inside the filtration chamber 13 for mechanically filtering the water. The KI media is cylindrical in shape and typically has a diameter of 7mm and a length of 10mm. Ki media has an open cell structure. The particulate media is positively buoyant and forms a pack at the surface of the water being filtered, as shown in Figure 1.

The receptacle 9 is cylindrical in shape and has a circular cross-section.

The top of the receptacle 9 is open to allow visual inspection of the pack 15 of particulate media. A base 14 closes the bottom of the receptacle 9. The receptacle 9 is made of stainless steel, and has a diameter of 400mm and a height of 620mm.

The filtration chamber 11 and the settlement chamber 13 are arranged concentrically. The settlement chamber extends around the outside of filtration chamber.

A guard device 17 is provided over an outlet 19 in the filtration chamber 11. A first series of vertical slots 20 are provided over the upper portion of the guard device 17 to allow the mechanically filtered water to exit through the outlet 19 but to retain the particulate media in the filtration chamber 11. The first slots 20 are 4.5mm wide and 130mm long.

The outlet 19 is in fluid communication with the outer annular container 7.

A moving bed 18 of particulate media, such as the KI media, is provided in the annular container 7. The moving bed 18 performs biological filtration on the water before it exits through a system outlet 21. Air is introduced into the annular container 7 through a ring-shaped conduit 22 to agitate the particulate media in the moving bed 18. Advantageously, the particulate media within the moving bed 18 may circulate within the annular container 7, as illustrated by the arrows A in Figure 3.

A second series of vertical slots 23 are formed in the bottom half of the sidewall of the receptacle 9. The second slots 23 are sized to allow water to enter the filtration chamber 11 but to prevent the particulate media in this chamber escaping into the settlement chamber 13. In the present case, the second slots 23 are 4.5mm wide and 60mm long. The upper and lower ends of the second slots 23 are radiused to help prevent the particulate media in the pack 15 becoming trapped. The second slots 23 are arranged in three rows which collectively form a band extending around the receptacle 9. The pack 15 of particulate media partially covers some of the upper second slots 23. - 18-

The receptacle 9 is supported on four legs 25, 26, 27, 28, as shown in Figure 4. The legs 25, 26, 27, 28 raise the receptacle 9 above the base of the settlement chamber 13 and, in use, create a region of stagnant water which encourages debris to fall out of suspension.

A ring-shaped conduit 31 is provided around the base of the outlet 19 below the receptacle 9. The ring-shaped conduit 31 has a series of outlets formed along its length. Air pumped into the conduit 31 exits through the outlets formed therein. In use, air passes through a plurality of openings 33 formed in the base 14 of the receptacle 9, as shown in Figures, and enters the filtration chamber 11.

The operation of the first embodiment of the present invention will now be described with reference to Figure 3.

Water to be filtered is introduced into the central container 5 through a system inlet (not shown). The inlet introduces the water in a tangential direction to establish a rotational flow within the settlement chamber 5.

Larger pieces of debris suspended in the water may be deposited on the base of the settlement chamber 13. The water then passes through the second slots 23 in the sidewall of the receptacle 9 and enters the filtration chamber 11.

Debris larger than the second slots 23 is trapped on the outside of the receptacle 9 and cannot enter the filtration chamber to contaminate the pack 15 of particulate media.

Particulate material and other debris which passes through the second slots 23 becomes trapped between the particulate media forming the pack 15 in the filtration chamber 11. Thus, the water is mechanically filtered as it travels through the filtration chamber 11. The filtered water passes through the guard device 17 and exits the filtration chamber 11 through the outlet 19. The mechanically filtered water then enters the annular vessel 7. The particulate media in the moving bed 18 biologically filters the water before it exits the system through the system outlet 21.

The pack 15 of particulate media is periodically cleaned by introducing air into the filtration chamber 11 through the conduit 31. The air causes the particulate media in the centre of the pack 15 to rise. The particulate media - 19- travels upwards and is then forced radially outwardly before contacting the receptacle 9 and being displaced downwardly. This cycle repeats itself as the air is introduced at a uniform rate over a predetermined period of time and the particulate media in the pack 15 circulates within the filtration chamber, as represented by arrows B in Figures 2 and 3. The circulation of the particulate media dislodges trapped debris to affect cleaning of the particulate media. Some of the dislodged debris settles to the bottom of the filtration chamber 11 and escapes through the openings 33 formed in the base 14.

As shown in Figure 3, the introduction of air into the filtration chamber 11 also raises the water level in filtration chamber above that of the water in the settlement chamber 13 (illustrated by height h). A pressure differential is therefore created between the filtration chamber 11 and the settlement chamber 13. Accordingly, water flows from the filtration chamber 11, through the second slots 23 and into the settlement chamber 13. This reversal in the flow direction through the receptacle 9 backwashes the second slots 23 and dislodges trapped debris, as illustrated by the arrows C in Figure 3.

The filtration chamber 11 may periodically be drained to wash debris collected therein through the openings 33 in the base 14 and into the settlement chamber 13. The openings 33 in the base 14 are 4.5mm in width to prevent the particulate media making up the pack 15 escaping into the settlement chamber when the filtration chamber is drained. A waste outlet 35 is provided at the base of the settlement chamber 13 to allow debris to be expelled from the system 1.

An alternative embodiment of the present invention is shown in Figure 6.

Like reference numerals have been used for like components. The filtration chamber 11 and the settlement chamber 13 are arranged side by side in this embodiment. A pack 15 of particulate media (not shown) is contained in the filtration chamber 13 between a first screen 37 and a second screen 39.

The first screen 37 is provided with a first series of slots 41 provided in the lower half thereof. The second screen 39 is provided with a second series of slots 43 provided in the upper half thereof. The length of the flow path through the filtration chamber is thereby increased. The particulate media in the pack 15 is preferably positively buoyant and covers substantially all of the second series - 20 - of slots 43. Alternatively, if the particulate media is negatively buoyant, it preferably covers the first series of slots 41.

The location of the first and second series of slots 41, 43 may be reversed (i.e. the first series of slots provided in the upper half of the first screen 37, and the second series of slots provided in the lower half of the second screen 39), for example if a negatively buoyant media is employed.

It will be appreciated that the first and second screens 37, 39, together with the base and sidewalls of the housing 3 collectively form a receptacle equivalent to the receptacle 9 according to the first embodiment of the present invention.

Water is introduced through a system inlet 39 into the settlement chamber 13. The water then passes through the receptacle 9 and enters the filtration chamber 11. Debris collected in the filtration chamber 11 is expelled through a discharge outlet 35 provided in the base thereof. A mesh or screen guard device (not shown) is provided over the outlet 35 to prevent the particulate media being flushed out of the filtration chamber 11. A separate outlet may be provided in the settlement chamber 13 to remove debris which has settled in this chamber.

A conduit 45 having a plurality of holes formed therein extends transversely across the filtration chamber 13. Air is periodically introduced into the filtration chamber 11 through the conduit 45 to agitate the particulate media located in the filtration chamber. The conduit 45 is preferably located midway between the first and second screens 37, 39 to help circulate the pack 15 of particulate media throughout the filtration chamber. The air is introduced into the filtration chamber 13 at a uniform rate. A dedicated pump may be provided to pump air along said conduit 45.

The filtered water enters an optional third chamber 41 prior to exiting through a system outlet 21. A moving bed 18 of particulate media may be provided in the third chamber 41 to perform biological filtration of the water.

Alternatively, UV treatment may be performed on the water in the third chamber 41.

The systems and processes described herein are particularly suitable for aquatics applications, such as filtration of water for a pond or aquarium. The - 21 - systems may also be used for filtering swimming pools. In alternative embodiments, the systems may equally be employed for industrial liquid filtration, for example in a sewage works.

It will be appreciated that various alternative arrangements are possible without departing from the scope of the present invention.

Claims

- 22 - CLAIMS: 1. A liquid filtration system comprising a first chamber

and a second chamber, the first chamber being defined by a receptacle containing a particulate media, the receptacle being located in the second chamber; wherein at least one aperture is provided in the receptacle to facilitate fluid communication between the second chamber and the first chamber, the liquid filtration system further comprising at least one fluid inlet for introducing fluid to agitate media in said receptacle.
2. A liquid filtration system as claimed in claim 1, wherein the receptacle has a base and said at least one aperture is provided in said base.
3. A liquid filtration system as claimed in claim 2, wherein the receptacle has a sidewall and said sidewall is substantially impervious.
4. A liquid filtration system as claimed in claim 1, wherein the receptacle has a sidewall and said at least one aperture is provided in said sidewall.
5. A liquid filtration system as claimed in claim 1 or claim 4, wherein the receptacle has a base.
6. A liquid filtration system comprising a first chamber and a second chamber, the first chamber being defined by a receptacle containing a particulate media for filtering liquid; wherein the receptacle has a base and a sidewall and at least one aperture is provided in said sidewall to allow liquid to enter the first chamber from said second chamber.
7. A liquid filtration system as claimed in claim 6, wherein the first chamber and the second chamber are provided adjacent to each other.

- 23 -
8. A liquid filtration system as claimed in claim 6 or claim 7, wherein the receptacle is located in the second chamber.
9. A liquid filtration system as claimed in any one of claims 4 to 8, wherein the first chamber and the second chamber are separated from each other by the sidewall of said receptacle.
10. A liquid filtration system as claimed in any one of claims 4 to 9, wherein the at least one aperture extends over an area less than or equal to 20%, 30%, 40%, 50%, 60% or 70% of the total area of the sidewall.
11. A liquid filtration system as claimed in claim 10, wherein all of, or the majority of said at least one aperture is provided in a region extending over only part of the sidewall.
12. A liquid filtration system as claimed in any one of the preceding claims, wherein the second chamber extends around at least a portion of the first chamber.
13. A liquid filtration system as claimed in any one of the preceding claims, wherein the first chamber and the second chamber are arranged concentrically.
14. A liquid filtration system as claimed in any one of the preceding claims, wherein the receptacle is tubular, cylindrical or conical.
15. A liquid filtration system as claimed in any one of the preceding claims, wherein the receptacle has a circular, oval or polygonal crosssection.
16. A liquid filtration system as claimed in any one of the preceding claims, wherein the at least one fluid inlet is located inside the receptacle.

- 24 -
17. A liquid filtration system as claimed in claim 16, wherein the at least one fluid inlet is provided at the centre of the receptacle.
18. A liquid filtration system as claimed in any one of the preceding claims, wherein the at least one fluid inlet is provided below the receptacle.
19. A liquid filtration system as claimed in any one of the preceding claims, wherein the at least one fluid inlet is ring-shaped.
20. A liquid filtration system as claimed in any one of the preceding claims, wherein the at least one aperture is a slot.
21. A liquid filtration system as claimed in claim 20, wherein the at least one slot has a width less than or equal to 7mm.
22. A liquid filtration system as claimed in claim 20 or claim 21, wherein the at least one slot has rounded ends.
23. A liquid filtration system as claimed in any one of the claims I to 19, wherein at least a portion of the sidewall is formed from a mesh, a grill or a screen.
24. A liquid filtration system as claimed in any one of the preceding claims further comprising a system outlet for allowing filtered liquid to exit the first chamber.
25. A liquid filtration system as claimed in claim 24, wherein the system outlet and the first chamber are concentric.
26. A liquid filtration system as claimed in claim 24 or claim 25 further comprising a guard device for preventing media exiting the first chamber through the system outlet.

- 25 -
27. A liquid filtration system as claimed in claim 26, wherein the guard device has a plurality of openings formed therein.
28. A liquid filtration system as claimed in any one of the preceding claims further comprising a discharge outlet for expelling filtered debris from the system.
29. A liquid filtration system as claimed in any one of the preceding claims, wherein 15-30%; 30-45%; 45-55%; 55-60%; 60%-65%; 60-80%; or 8090% by volume of the receptacle is filled with said particulate media.
30. A liquid filtration system as claimed in any one of the preceding claims, wherein said particulate media are positively buoyant; neutrally buoyant; or negatively buoyant.
31. A liquid filtration system as claimed in any one of the preceding claims, wherein said particulate media are open-cell.
32. A liquid filtration system as claimed in any one of the preceding claims, wherein said particulate media are substantially cylindrical or substantially spherical.
33. A liquid filtration system as claimed in any one of the preceding claims, wherein said particulate media are made of a plastics material.
34. A liquid filtration system as claimed in any one of the preceding claims, wherein the receptacle is made of stainless steel or a plastics material.
35. A liquid filtration system as claimed in any one of claims 5 to 34, wherein a plurality of openings are formed in the base of the receptacle to allow filtered debris to exit the first chamber.

- 26 -
36. A liquid filtration system as claimed in any one of the preceding claims, wherein, in use, liquid to be filtered is supplied to the second chamber under the action of gravity.
37. A liquid filtration system as claimed in any one of claims 1 to 35, wherein, in use, liquid to be filtered is supplied to the second chamber under pressure.
38. A liquid filtration system as claimed in claim 37, wherein, in use, the system is pressurised.
39. A liquid filtration system as claimed in any one of the preceding claims, wherein the second chamber is defined by a vessel.
40. A kit of parts for a filtration system as claimed in any one of the preceding claims, the kit comprising a receptacle for defining a first chamber for containing particulate media for filtering liquid, and a guard device for preventing said media exiting the chamber through an outlet.
41. A kit as claimed in claim 40 further comprising media for filtering liquid.
42. A method of installing a kit of parts as claimed in claim 40 or claim 41, the method comprising the steps of: (a) locating the receptacle in a vessel to form said first and second chambers; and (b) locating the guard device partially to obstruct an outlet.
43 A method as claimed in claim 42 further comprising the step of removing an existing filter prior to completing steps (a) and (b).
44. A method of filtering a liquid, the method comprising the steps of: 27 - (a) introducing the liquid to be filtered into a first chamber defined by a receptacle located in a second chamber; (b) passing the liquid through a particulate media contained in said receptacle to filter the liquid; and (c) periodically introducing fluid to agitate the particulate media in said first chamber to dislodge debris trapped in the particulate media.
45. A method as claimed in claim 44, further comprising the step of removing filtered debris from the first chamber.
46. A method as claimed in claim 44 or claim 45, wherein fluid is introduced though at least one inlet provided in said first chamber.
47. A method as claimed in claim 44, 45 or 46, wherein said fluid is air; or liquid filtered by the particulate media.
48. A method as claimed in any one of claims 44 to 47, wherein the introduction of liquid into the first chamber is halted whilst the particulate media is agitated.
49. A method as claimed in any one of claims 44 to 48, wherein said media is open-cell.
50. A method as claimed in any one of claims 44 to 49, wherein the receptacle is tubular, cylindrical or conical.
51. A method as claimed in claim 50, wherein the receptacle has a circular, oval or polygonal cross-section.
52. A method as claimed in any one of claims 44 to 51, wherein the first chamber and the second chamber are arranged concentrically.
53. A method as claimed in any one of claims 44 to 52 further comprising the step of removing the filtered liquid through an outlet.
54. A method as claimed in claim 53, wherein said outlet and the first chamber are concentric.
55. A method as claimed in any one of claims 44 to 54, wherein the liquid is introduced into the second chamber under the action of gravity.
56. A method as claimed in any one of claims 44 to 55, wherein the liquid is introduced into the second chamber under pressure.
57. A method as claimed in claim 56, wherein the liquid in the first and second chambers is pressurised.
58. A receptacle mountable in a vessel to form a first chamber inside a second chamber, the receptacle being suitable for containing a particulate media for filtering liquid; wherein at least one aperture is provided in the receptacle to allow liquid to enter the first chamber from the second chamber in use.
59. A receptacle as claimed in claim 58, wherein the receptacle has a sidewall.
60. A receptacle as claimed in claim 59, wherein said at least one aperture is provided in the sidewall of the receptacle.
61. A receptacle as claimed in claim 60, wherein said at least one aperture is provided towards the bottom of the sidewall.
62. A receptacle as claimed in any one of claims 58 to 61, wherein the at least one aperture is a slot.

- 29 -
63. A receptacle as claimed in any one of claims 58 to 62, wherein said at least one slot is provided in the upper or lower 20%, 30%, 40%, 50%, 60% or 70% of the sidewall by height.
64 A receptacle as claimed in any one of claims 58 to 63, wherein the at least one aperture is a hole.
A receptacle as claimed in claim 59 or in any one of claims 60 to 64 when dependent directly or indirectly on claim 59, wherein the upper or lower 20%, 30%, 40%, 50%, 60%, 70% or 80% of the sidewall by height is substantially impervious.
66. A receptacle as claimed in any one of claims 58 to 65, wherein the receptacle has at least one leg for mounting the receptacle in the vessel.
67. A receptacle as claimed in any one of claims 58 to 66 further comprising a base.
68. A receptacle as claimed in claim 67, wherein the base has at least one opening.
69. A receptacle as claimed in claim 68, wherein the at least one opening is at least one hole.
70. A receptacle as claimed in claim 68, wherein the at least one opening is at least one slot.
71. A receptacle as claimed in claim 58, wherein said receptacle has a base and said at least one aperture is provided in said base.
72. A receptacle as claimed in claim 59, wherein the receptacle has a sidewall and said sidewall is substantially impervious.

- 30 -
73. A guard device for mounting in a liquid filtration system to prevent particulate media escaping through a system outlet, the guard device having at least one opening to allow liquid to exit through said outlet.
74. A guard device as claimed in claim 73, wherein the guard device is mountable in a conduit forming the system outlet.
75. A guard device as claimed in claim 73, wherein the guard device is mountable around a conduit forming the system outlet.
76. A guard device as claimed in any one of claims 73, 74 or 75, wherein said at least one opening is formed in a sidewall of the guard device.
77. A guard device as claimed in claim 76, wherein said at least one opening is provided towards the top of the sidewall.
78. A guard device as claimed in claim 77, wherein said at least one opening is provided in the upper or lower 20%, 30%, 40%, 50% or 60% of the sidewall by height.
79. A guard device as claimed in any one of claims 76, 77 or 78, wherein the top or bottom 20%; 30%, 40%; or 50% of the sidewall by height is substantially impervious.
A guard device as claimed in any one of claims 73 to 80, wherein said at least one opening is a slot.
81. A kit of parts comprising a receptacle as claimed in any one of claims 58 to 72; and a guard device as claimed in any one of claims 73 to 80.

- 31 -
82. A kit of parts as claimed in claim 81 further comprising particulate media for filtering liquid.
83. A liquid filtration system comprising a receptacle for containing media for filtering liquid, the receptacle having a base and a sidewall and forming a first chamber; wherein at least one aperture is provided in the sidewall of the receptacle to allow liquid to enter the first chamber from a second chamber.
84. A liquid filtration system comprising a first chamber and a second chamber, the first chamber being defined by a receptacle for containing media for filtering liquid, the receptacle being located in said second chamber; wherein the receptacle has at least one aperture to allow liquid to enter the first chamber from said second chamber.
85. A liquid filtration system as claimed in claim 84, wherein the receptacle has a base and a sidewall; said at least one aperture being provided in the base of the receptacle.
86. A liquid filtration system as claimed in claim 85, wherein the sidewall is substantially impervious.
87. A liquid filtration system as claimed in claim 84, wherein the receptacle has a base and a sidewall; said at least one aperture being provided in the sidewall of the receptacle.
88. A liquid filtration system comprising a first chamber and a second chamber, the first chamber being defined by a receptacle containing media for filtering liquid; wherein the receptacle has an inlet for allowing fluid to enter the first chamber to be filtered and an outlet for allowing filtered debris to exit the first chamber, said inlet being separate from said outlet.
89. A method of filtering a liquid, the method comprising the steps of: 32 - (a) introducing the liquid to be filtered into a first chamber through an inlet; (b) passing the liquid through media provided in the first chamber to filter the liquid; and (c) removing filtered debris from the first chamber through an outlet separate from said inlet.
90. A liquid filtration system comprising a first chamber and a second chamber, the first chamber being defined by a receptacle containing media for filtering liquid, the system further comprising a first inlet for allowing liquid to be filtered to enter the second chamber, and a second inlet for allowing a fluid to be introduced into the first chamber at a substantially uniform rate to agitate said media.
91. A method of filtering a liquid, the method comprising the steps of: (a) introducing the liquid to be filtered into a first chamber through an inlet; (c) passing the liquid through media provided in the first chamber to filter the liquid; and (c) periodically introducing a fluid into said first chamber at a substantially uniform rate to agitate said media.
92. A liquid filtration system substantially as herein described with reference to Figures 1 to 5; or Figure 6.
93. A method of filtering a liquid substantially as herein described with reference to Figures 1 to 5; or Figure 6.