A filter unit and filtration method

Abstract

A filter unit and method is disclosed. The filter unit comprises a housing, a housing inlet which allows liquid effluent to enter the housing, a filter medium which can be removed from the housing, a first outlet which allows filtered liquid to exit the housing, an opening in the housing and a closure, which together have an unsealed and a sealed configuration, and when in the unsealed configuration the opening and closure are not water-tight, and when in the sealed configuration the opening and closure are water-tight, the opening and the closure also having an unsealed and open configuration which permits the filter medium to be removed from the filter unit, a filter chamber for accommodating the filter medium, a first valve, having an open configuration permitting liquid effluent to pass into the filter chamber, and which is opened when the opening and the closure are in the sealed configuration, and having a closed configuration preventing liquid effluent from entering into the filter chamber, and which is closed when the opening and the closure is in the unsealed configuration.

Description

A FILTER UNIT AND FILTRATION METHODField of the Invention

[0001] The present invention relates to a filter unit and to a method of using said filter unit. The filter unit is suitable for (partially or completely) removing microparticles from a liquid effluent and more especially for removing microplastics or microfibres from a liquid effluent.Background to the Invention

[0002] Filters for removing microparticles are disclosed in, for example, PCT patent publication WO2022 / 229646. Whilst this PCT patent publication does disclose valves which can be used to shut off the supply of the feed (effluent) liquid by means of stopping a pump or closing a valve this is disclosed to be a part of a method or series of intended steps. The effluent typically comprises microplastics in the form of microfibres originating from for example a washing machine.

[0003] Of course, if the user were to accidentally open the filter unit, for example to remove the filter medium, at the wrong time there remains the strong likelihood that effluent liquid would pour or spray undesirably through the filter unit out of the opening and towards the user.

[0004] Filter units also can suffer from difficulties depending on their location relative to the incoming liquid effluent. For example, if the flow of effluent is particularly speedy and / or if the incoming liquid effluent is at some pressure, then a secure and speedy means to shut off the incoming liquid effluent is all the more desirable, especially if the user were to open the filter unit at the wrong time. This is especially so when, for example, the filter unit is positioned lower than the incoming liquid effluent and / or lower than for example a sump in a textile treatment apparatus which supplies the incoming liquid effluent to the filter unit. This can result in a hydrostatic head of pressure which means that quickly and effectively shutting off the supply of the incoming liquid effluent is even more desirable. Furthermore, in some instances there can be a significant amount of effluent liquid located above and upstream of the filter unit which means there is also a propensity for effluent liquid to syphon into the filter unit especially if the user opens the filter unit at the wrong time. Thus, it is very possible for several litres of liquid effluent to exit the filter unit if the user opens it at the wrong time.

[0005] Filter units can be internal or external to the effluent producing apparatus such as a washing machine. For internal filter units a control unit in the washing machine can be used to actuate components within the filter unit. That said, another difficulty is encountered for external filter units in that they typically do not have any form of communication with the external effluent producing apparatus to determine when the incoming liquid effluent is being pumped actively towards the external filter unit. Thus, it is harder for external filter units to utilise valves whichrespond to the timing in say a wash cycle in a washing machine because the external filter unit would have no “information”” to decide when an inlet valve should be opened or closed.

[0006] The present invention seeks to solve at least in part one or more of the abovementioned technical problems.Summary of the Invention

[0007] According to a first aspect of the present invention there is provided a filter unit suitable for removing microparticles from a liquid effluent, the filter unit comprising: i. a housing; ii. a housing inlet which allows liquid effluent to enter the housing; iii. a filter medium which can be removed from the housing; iv. a first outlet which allows filtered liquid to exit the housing; v. an opening in the housing and a closure, which together have an unsealed and a sealed configuration, and when in the unsealed configuration the opening and closure are not water-tight, and when in the sealed configuration the opening and closure are water-tight; the opening and the closure also having an unsealed and open configuration which permits the filter medium to be removed from the filter unit; vi. a filter chamber for accommodating the filter medium; vii. a first valve, having an open configuration permitting liquid effluent to pass into the filter chamber, and which is opened when the opening and the closure are in the sealed configuration, and having a closed configuration preventing liquid effluent from entering into the filter chamber, and which is closed when the opening and the closure is in the unsealed configuration.Filter unit

[0008] The filter unit may be internal to a liquid effluent producing apparatus, more preferably the filter unit is external to a liquid effluent producing apparatus.

[0009] Liquid effluent producing apparatus includes any apparatus which uses a liquid and which tends to contaminate the liquid with microparticles, microplastics and especially microfibres. Liquid effluent producing apparatus which are especially suitable for providing liquid effluent for the present invention include textile treatment machines including: textile washing machines, textile finishing machines, textile dyeing machines, textile abrading and / or fading machines. These machines can be of any size from domestic machines (for example 1 Kg to 10Kgof dry textile load capacity), to commercial machines (for example 10Kg to 2000Kg of dry textile load capacity) to industrial machines (for example above 2000Kg of dry textile load capacity).

[0010] The liquid effluent producing apparatus may comprise a rotatable drum, a sump, a trap, a fresh liquid inlet and a liquid effluent outlet. The liquid effluent producing apparatus typically also comprises connections (typically tubes or pipes) between these components permitting fluid communication and transport of the liquid.

[0011] The liquid effluent producing apparatus may comprise a detergent drawer through which chemicals such as detergents and softeners can be added. The drawer can be located on a front face of the liquid effluent producing apparatus, this is an especially suitable location for the drawer when the effluent producing apparatus is a front loader apparatus. A front loader apparatus is one wherein the textile loading door is located on the front face of the effluent producing apparatus.

[0012] The liquid effluent producing apparatus preferably comprises a door or lid, preferably to permit the user to load and unload textile(s) into the apparatus and especially into the drum of the apparatus.

[0013] When the filter unit is internal to a liquid effluent producing apparatus it may be located below the sump, below the drum or more preferably above the drum and especially above the drum and behind the detergent drawer. When the filter unit is internal to a liquid effluent producing apparatus it is preferably accessible from the front face of said apparatus.

[0014] The filter unit can be external to the liquid effluent producing apparatus and in that case, the filter unit is preferably connected to the liquid effluent outlet via the exterior inlet of the filter unit. In some instances, an external filter unit can be connected to a storage vessel which contains liquid effluent comprising microparticles and which is connected to the filter unit via an exterior inlet of the filter unit.

[0015] When the filter unit is external to a liquid effluent producing apparatus it may be located below, above or at the same height as the liquid effluent producing apparatus.

[0016] When the filter unit is external to a liquid effluent producing apparatus it may be located below, above or at the same height as any of the detergent drawer, the drum, the sump, the trap, the outlet of the liquid effluent producing apparatus.

[0017] When the filter unit is external to a liquid effluent producing apparatus it may be located below, above or at the same height as the uppermost height of any drain outlet which can be connected to an exterior outlet of the filter unit.

[0018] One advantage of the filter unit of the present invention is that it can be located in a wide variety of locations relative to a liquid effluent producing apparatus or the various components.Microparticles

[0019] In order of increasing preference, at least some of the microparticles preferably have a size of less than 5mm, less than 1 mm, less than 900pm, less than 800pm, less than 700pm, lessthan 600pm, less than 500pm, less than 400pm, less than 300pm, less than 200pm. A lower limit is often that wherein the microparticles have a particle size of 1 micron. Thus, as an example preferred microparticles are those wherein at least some of the microparticles have a size of from 1 mm to 1 micron. Typically, at least 1wt%, 5wt%, 10wt%, 20wt%, or 50wt% of the total amount of microparticles are within this size region.

[0020] The microparticles may be microplastics or more preferably microfibres.

[0021] Microparticles can include particles of ceramic, metal, mineral, polymeric or organic materials.

[0022] Microparticles can have any shape including spherical, disc, ellipsoidal, irregular, cuboid, prismatic and filament. Of these microparticles having the shape of filaments, and especially in the form of fibres are especially suited to the present invention.

[0023] The microparticles may be present in the liquid effluent at a concentration of from 0.001wt% to 30wt%, more preferably from 0.001 wt% to 15wt% and especially from 0.001wt% to 5wt%.

[0024] The microplastics may be thermoset or thermoplastics. The microplastics may be or comprise of any kind of polymer including without limitation polyolefins, polyamides, polyacrylics, polyesters, polyurethanes, polystyrenics and polyacrylonitriles.

[0025] The microfibres may be or comprise a synthetic fibre, a natural fibre, a semi-synthetic fibre or a combination thereof.

[0026] Microfibres which are synthetic can be or comprise any of the aforementioned kinds of polymers.

[0027] Microfibres which are natural can be or comprise cellulosic fibres, keratin fibres, silk fibres. Examples of cellulosic fibres include: cotton, jute, hemp and flax fibres. Examples of keratin fibres include animal hair, especially mammal animal hair and more especially wool.Liquid Effluent

[0028] The liquid in the liquid effluent may be an organic liquid or more preferably an aqueous liquid. Preferably, the liquid effluent comprises water. Preferably, the liquid effluent comprises water and optionally an organic liquid which is water miscible.

[0029] Suitable water miscible organic liquids include alcohols, ethers, ketones, aldehydes, amides, sulfones, pyrrolidones and the like. Preferably, the liquid effluent comprises at least 70wt%, at least 80wt% at least 90wt% and at least 95wt% of water relative to all of the liquids present in the liquid effluent.Housing

[0030] The housing can be or comprise any suitable material including metal, alloy, wood, ceramic, and especially polymeric materials.

[0031] The housing can be of any shape although a preferred shape is a prism, or more preferably a substantially cylindrical shape.

[0032] Preferably, the housing provides the filter chamber, more preferably the filter chamber is located within the housing.

[0033] The housing may be manufactured by additive manufacture such as 3D printing, laser sintering, lithography or more preferably by injection moulding.

[0034] The housing may be one single (integral) component, more preferably the housing is comprised of two or more sections. These sections are preferably detachable, preferably so as to provide a means to service and / or repair components of the filter unit.

[0035] The housing can be unitary, or it may comprise two or more separable portions which seal together to form the housing.Housing Inlet

[0036] The housing inlet allows liquid to enter the housing. The housing inlet can be located at any position on the housing, but it is preferably located further away from the opening more preferably towards the rear of the housing, especially furthest from the opening. The housing inlet preferably enters the housing from beneath the housing. The housing inlet preferably enters the housing behind and upstream of the first valve. The housing inlet preferably enters the housing in a direction perpendicular to the housing walls, especially when the housing is substantially cylindrical.

[0037] Preferably, the housing is substantially cylindrical and the one end of the cylinder has the opening, the first valve is typically located towards the end of the cylinder away from the opening, the housing inlet is located behind and upstream of the first valve further away from the opening, the inlet is typically located on a curved wall of the cylinder entering from below the housing and entering in a direction substantially perpendicular to the length of the cylinder.

[0038] The housing inlet can be in the form of a pipe or tube. The housing inlet may be readily connected to the bypass flow path and / or to an exterior inlet.Filter Medium

[0039] The filter medium can be located on a filter cage. The location on the filter cage can be by means of attachments such as clips, screws, bolts or the like. Preferably, the filter medium is located on a filter cage by permanently affixing the filter medium to the filter cage. Examples ofpermanently affixing include: over moulding, bonding, gluing, welding, co-forming, fusing and sintering. Preferably, the filter cage is manufactured in the presence of the filter medium so that the two become bonded together. The filter cage can be manufactured by additive manufacture (as described above in relation to the housing) or more preferably by injection moulding.

[0040] The filter medium can be a single filter medium or a plurality of filter media.

[0041] The filter medium can take the shape of a flat panel, a pleated surface, or more preferably a shape which provides a cavity, preferably a cavity in part bounded by and internal to the filter medium. Preferably, the filter medium optionally together with the filter cage forms a prismatic or more preferably a substantially cylindrical shape and provide a cavity which is also substantially cylindrical in shape.

[0042] The filter medium can be disposable for example the filter medium can be or comprise a biodegradable material including for example paper, cotton, wood, wool and the like.

[0043] Preferably, the filter medium can be re-used two or more times, more especially the filter medium can be used for at least 10, at least 100 or at least 1 ,000 filtration cycles. Preferably the filter medium is not biodegradable. Preferably the filter medium is or comprises a polyamide, more preferably a Nylon.

[0044] The filter medium can be fibrous for example a felt material.

[0045] Preferably, the filter medium is a mesh or a net.

[0046] In order of increasing preference, the pores in the filter medium preferably have a pore size of 500pm or less, 400pm of less, 300pm or less, 200pm of less, 100pm or less or 80pm or less. The filter medium preferably has a pore size of at least 1 pm, at least 5pm or at least 10pm in size. The size of the pores in the filter medium can be established by for example optical microscopy using an appropriate scale optionally utilising image analysis software. The size is preferably an average size and more preferably an arithmetic average size.

[0047] Preferably, the filter unit is suitable for removing microparticles, especially microplastics and more especially microfibres having a size of 500pm, 400pm, 300pm, 200pm or 100pm.

[0048] Preferably, the filter medium forms a cavity in its interior space. Preferably, the housing inlet directs liquid effluent towards the cavity. Preferably, the liquid effluent flows from the interior to the exterior surface of the filter medium. Preferably, the filtered liquid exits via the first outlet. Preferably, microparticles having a size larger than the pore size of the filter medium are deposited on the interior surface of the filter medium. Preferably, microparticles accumulate within the cavity.

[0049] More preferably, the filter medium is substantially cylindrical, the cylindrical filter medium forms a cavity in its interior space. Preferably, the housing inlet directs liquid effluent towards the cavity. Preferably, the liquid effluent flows from the interior to the exterior surface of the filter medium. Preferably, the filtered liquid exits via the first outlet during the operation of the filter unit. Optionally, (typically smaller amounts of) filtered liquid may exit via the optional second outlet.Preferably, microparticles having a size larger than the pore size of the filter medium are deposited on the interior surface of the filter medium. Preferably, microparticles accumulate within the cavity.Filter Cage

[0050] The filter cage can have a flat, a corrugated shape or more preferably a shape which forms a cavity within its interior space. The filter cage can be prismatic or more preferably substantially cylindrical in shape.

[0051] Preferably, both the filter cage and the filter medium are cylindrical. The filter cage preferably comprises a rigid body and a plurality of open areas around the circular wall of the cylindrical shape. The open areas are preferably covered with the filter medium or with a plurality of filter media. Preferably, the combination of the filter cage and the filter medium form a cylindrical shape.

[0052] Preferably, the shape of the cavity within the filter cage is itself substantially cylindrical.

[0053] The filter cage may be or comprise a metal, alloy, ceramic, wood or more preferably a plastic. The plastic may be a thermoset or more preferably a thermoplastic. The filter cage may be formed by additive manufacture for example 3D printing or more preferably by injection moulding.

[0054] The filter cage may be unitary, or it may comprise two or more portions which are optionally detachable or separable. Optionally a portion of the filter cage furthest from the cap is detachable or separable and this portion may comprise the engagement surfaces.Engagement surfaces

[0055] The filter cage preferably has one or more engagement surfaces. These engagement surfaces are preferably configured to engage with a drive connector. The one or more engagement surfaces on the filter cage are preferably located at one end of the filter cage. For example, when the filter cage is substantially cylindrical the one or more engagement surfaces are preferably located at one end. As mentioned before the filter medium is preferably located on the filter cage.

[0056] The one or more engagement surfaces on the filter cage may be in the form of blades, typically 2 to 10, preferably from 3 to 6 and especially 4 blades. The blades are preferably equally spaced in a radial direction from an axis of rotation of the filter cage and filter medium. These blades work especially well when the drive connector has slots for the engagement surface.

[0057] The one or more engagement surfaces of the filter cage may be in the form of slots, these slots may open out wider closer to the drive connector and narrow closer to the opening.These slots work especially well when the drive connector has blades for the engagement surface.

[0058] A filter cage end piece and especially a lid is preferably attached to the filter cage at one end, especially at the other end of the substantially cylindrical filter cage opposite the one or more engagement surfaces. The filter cage end piece (e.g. lid) has the function of sealing off one end of the filter cage.

[0059] The filter medium may be located on the exterior surface of the filter cage, on the interior surface of the filter cage or it may be laminated or bonded within the structure of the filter cage.

[0060] Thus it is preferred that the filter unit comprises: a substantially cylindrical filter cage having at one end of the cylinder one or more engagement surfaces to engage with a drive connector, and wherein the filter medium is located on the filter cage; a closure which is preferably a cap, attached to the filter cage at the other end of the substantially cylindrical filter cage opposite the one or more engagement surfaces.

[0061] The filter cage may be unitary, or it can comprise a plurality of parts which connect together forming the filter cage. When the filter cage is substantially cylindrical, the cylinder may be split into two or more parts, as an example one part of the filter cage might carry the filter medium and one might carry the engagement surfaces to engage with a drive connector. Having a filter cage which splits into parts can be helpful in recycling, servicing, cleaning or repairing. Having a filter cage which is unitary (comprising one single part) can help reduce costly part counts and it can add rigidity to the filter cage. When the filter cage comprises two or more parts one or more seals may be used in the connections between the parts.Rotating filter medium

[0062] Preferably the filter medium is rotatable about an axis.

[0063] Preferably, the filter medium is located on a filter cage, wherein the filter cage and the filter medium are rotatable about an axis. Preferably, the filter cage and filter medium form a substantially cylindrical shape and the rotatable axis runs down the centre of the cylinder.First Outlet

[0064] The first outlet allows the filtered liquid effluent to exit the housing. The first outlet may take the form of a pipe projecting from the housing outer surface. When the housing is substantially cylindrical the outlet is typically located towards one end of the cylinder more typically towards an end furthest from the opening in the housing. The outlet is preferably connectable to hoses, pipes and the like. When the housing is substantially cylindrical the first outlet preferably exits the housing in a direction which is tangential to the cylindrical surface of the housing.Second Outlet

[0065] Preferably, the filter unit comprises a second outlet in the housing, which is preferably located at a lowermost point in the housing.

[0066] The second outlet is especially suitable for draining the last residues of filtered liquid from the housing and the filter chamber.

[0067] Preferably, the filter medium and optionally the filter cage are rotatable, a motor drives the rotation and any remaining liquid is spun off the filter medium. This rotation can be performed whilst liquid effluent is not entering the filter chamber and such that the filter medium is dewatered or spin dried thereby removing much of the remaining liquid on the filter medium. The dewatered or “spun off” remaining liquid is preferably able to exit the housing via the second outlet.Pump

[0068] The filter unit preferably comprises a pump, which is preferably located at or downstream of the second outlet and which when actuated can pump filtered liquid out of the filter unit. Preferably, the pump is a liquid pump.

[0069] Preferably, the pump can prevent filtered liquid from flowing back into the housing and the filter chamber, preferably from any point downstream of the pump especially from the exterior outlet. Preferably, the pump also itself acts as a non-return valve.

[0070] Preferably, the pump is a diaphragm pump or a displacement pump.The opening in the housing

[0071] The opening in the housing and the closure have a configuration which permits the filter medium and optionally the filter cage to be removed from the filter unit. This configuration is also an unsealed configuration as it requires the closure to be in the open position.

[0072] The opening in the housing can be of any suitable shape including a triangle, a square, a rectangle, an oval but more preferably the opening is substantially circular.Closure

[0073] The closure as described herein has the same meaning as a closing member, or a closing means. Functionally speaking the closure together with the opening in the housing are able to form a sealed and unsealed configuration.

[0074] There are several types of closure which are suitable for the present invention. The closure may be a door, which is preferably located on a hinge. The closure may be a shutterwhich may be a lateral shutter or a diaphragm shutter. The closure may be a cover which is removable from the opening.

[0075] Preferably, the closure is substantially circular and even more preferably a (circular) cap.

[0076] Preferably, the cap can be closed (and sealed) into the opening in the housing by means of a twist lock or screw thread mechanism.Unsealed Configuration

[0077] The unsealed configuration is preferably obtained, as or when, the closure is opened. The closure need not be completely opened from the opening to have an unsealed configuration. Even a partial opening of the closure may provide an unsealed configuration. Of course, when the opening is completely open then there is an unsealed configuration. The closure may be opened in several ways, for example, opening a door, opening a shutter, opening or removing a cover or more preferably turning and optionally removing a cap.Sealed Configuration

[0078] The sealed configuration is preferably obtained when the closure is in the closed position.

[0079] The closure can be closed in several ways for example closing a door, closing a shutter, closing or securing a cover, or more preferably turning and optionally securing a cap.

[0080] Preferably, the filter unit provides an indication to the user that the closure together with the opening is in the sealed configuration. The sealed configuration can also be regarded as a “locked” or “fully closed” configuration. The indication can be in the form of a visual indication, for example, an LED, an alignment between the closure and the opening. The indicator can separately or additionally be in the form of a haptic indicator, for example a vibration or difference in resistance to the action of closing which can be felt by for example the user’s hand. The indication can be a sound, for example a buzz, a ping, a click, a bell sound or the like.End-stop

[0081] Preferably, the filter unit, more preferably the housing and especially the opening of the housing and / or the closure comprise an end-stop.

[0082] The sealed configuration is preferably obtained when the closing action is terminated by an end-stop, especially an end-stop providing a predetermined position. By predetermined position it is preferably meant that when in the sealed configuration the closure is in a predetermined position relative to the opening. Thus, preferably the closure can be sealed into a predetermined position (which is fully closed) by means of an end-stop.

[0083] The end-stop may be in the form of an end-stop surface on the closure and / or on a surface of the opening which prevents, for example the user, from closing the closure any further.

[0084] When the closure is a cap the end-stop may comprise, for example, one or more lugs on the cap which as the cap is turned and closed in the opening will eventually abut an end-stop surface on the opening.

[0085] A preferred filter unit is one wherein the closure is a cap, the opening in the housing is substantially circular, and wherein the cap can be sealed into a predetermined position via an end-stop so that the cap and the opening in the housing provide the sealed configuration of the housing; and the cap can be unsealed from the housing by moving the cap away from the end-stop, to provide the unsealed configuration of the housing.Filter Chamber

[0086] The filter chamber may be of a number of shapes such as a prism, cone, cuboid though preferably the filter chamber is substantially cylindrical in shape.First Valve

[0087] The wording “which is opened when” in the first aspect of the present invention item vii preferably means “which is configured to open when”. Equally, the wording “which is closed when” in the first aspect of the present invention item vii preferably means “which is configured to close when”. Preferably, the idea being that the first valve is configured to respond to these two options, preferably without necessitating further user intervention.

[0088] Preferably, once the end user opens or closes the closure to provide an unsealed or sealed configuration all subsequent steps to open or close the first valve are fully automatic. By fully automatic it is preferably meant that the filter unit itself actuates the opening and closing of the first valve, preferably without any further end user intervention or decision. The actuation can comprise an electrical or mechanical means and especially the actuation of the first valve is exclusively mechanical. Preferably, the mechanical actuation is directly or indirectly caused by the act of the user closing the closure and forming the sealed configuration. Preferably, there is a mechanical connection as between the closing of the closure and the first valve. Preferably, the mechanical connection allows the transfer of a mechanical force from the user closing the closure which opens the first valve.

[0089] The first valve may be electronic or more preferably mechanical. Even more preferably the first valve is exclusively mechanical, that is to say that it comprises no electronic or electrical components. Preferably, the first valve is not opened and / or closed by an electrical device.

[0090] Accordingly, a preferred item vii. in the first aspect of the present invention is:a first valve, having an open configuration permitting liquid effluent to pass into the filter chamber, and which is mechanically opened by the filter unit when the opening and the closure are in the sealed configuration, and having a closed configuration preventing liquid effluent from entering into the filter chamber, and which is mechanically closed by the filter unit when the opening and the closure in the housing is in the unsealed configuration.

[0091] The mechanical valve is preferably a biased valve. By a biased valve it is preferably meant that the valve has a bias to return to either a closed or an open configuration if there is no mechanical actuation of the valve. Preferably, the biased valve is biased towards a closed configuration. This desirably provides a useful safety feature as it means that if the actuation of the first mechanical valve for some reason fails the valve remains in a closed, and thereby a safer position with respect to the user.

[0092] Preferably, the filter unit is one wherein when the opening in the housing and the closure are in the unsealed configuration the bias in the biased valve results in a closed configuration of the first valve, and when the opening in the housing and the closure are in the sealed configuration the bias is overcome by a mechanical force acting on the first valve resulting in an open configuration of the first valve.

[0093] The bias in the biased valve is preferably provided by means of a spring, an elastomer, a magnetic device or a pneumatic device, more preferably by means of a spring or an elastomer and especially by means of a spring.

[0094] Preferably, the spring is a compressible spring.

[0095] Preferably, the bias in the biased valve can be overcome by a mechanical force acting on the first valve which results in an open configuration of the first valve.

[0096] The mechanical force is preferably transmitted from the closure, more preferably as the closure is closed to provide the sealed configuration the closing of the closure itself provides a mechanical force. The mechanical force can be transmitted by any means without particular limitation. The mechanical force can be transmitted to the first valve via one or more transmitting components. The transmitting component can be a rod, for example a rod running exterior or interior to the filter chamber.

[0097] More preferably, the mechanical force is transmitted from the closure via the filter cage, filter medium, the engagement surfaces and a drive connector to the biased valve. This arrangement has the advantage that in addition to the sealed configuration, the filter cage and the filter medium must be placed in the filter chamber in order for the closing of the closure to open the first biased valve. Accordingly, the filter unit will not permit effluent liquid to enter thefilter chamber unless the closure is closed, the opening and the closure form a sealed configuration, and the filter cage and filter medium is present in the filter chamber.

[0098] Preferably, the closure (e.g cap), the filter cage and the filter medium are all attached to each other such that the opening of the biased valve cannot be accomplished without the filter cage and the filter medium being correctly within the filter chamber, the closure being closed and the opening in the housing and the closure being in the sealed configuration.

[0099] Preferably, opening of the first valve additionally requires that the filter cage and filter medium are present in the filter chamber.

[0100] The first valve may be located up-stream of the housing inlet, at the housing inlet or more preferably within an interior of the housing and down-stream of the housing inlet. The first valve is preferably located or partially located on a peripheral wall of, or forms or partially forms the ending of a peripheral wall of the filter chamber when the valve is in the closed configuration. Preferably, this peripheral wall is towards the rear end of the filter chamber furthest from the opening. The positioning of first valve within the interior of the housing and down-stream of the housing inlet has the advantage that when it closes there are no or negligible amounts of liquid effluent which can enter the filter chamber. This is to be contrasted with the valve being located at the housing inlet or upstream of the housing inlet which will by necessity mean that even when the first valve is closed an amount of effluent liquid within the housing inlet or upstream of the housing inlet can still enter the filter chamber and potentially be released from the opening in the housing.

[0101] When the filter medium and optionally the filter cage are rotatable about an axis the spring in the biased first valve is preferably located substantially parallel to the axis of rotation. Preferably, the axis of rotation runs though the spring.

[0102] The first valve preferably comprises a sealing surface which acts to permit or prevent the liquid effluent from entering the filter chamber. The sealing surface is preferably in the form of an annulus. The sealing surface is preferably located towards the rear of the filter chamber, more preferably forming, or partially forming a peripheral wall of the filter chamber when in the closed configuration.

[0103] The first valve is preferably configured so that liquid pressure from the housing inlet or exterior inlet acts to urge the sealing surface into a stronger contact thereby providing a better seal. To do this the configuration is preferably such that the direction of closing the first valve follows the same direction as the positive pressure from the effluent liquid in the housing inlet which allows liquid to enter the housing. In a preferred configuration the first valve closes as it moves closer towards the opening in the housing and further from the housing inlet. Preferably, the opening and closing of the first valve runs in a direction parallel to the axis of rotation of the filter cage.Second Valve

[0104] Preferably, the filter unit comprises a second valve, preferably this is located at or downstream of the first outlet. Preferably, the second valve is one which permits the flow of the filtered liquid exiting the housing from the first outlet to exit the filter unit but it prevents filtered liquid from flowing back into the housing. Such valves are often referred to as non-return valves. This is particularly advantageous when the filter unit is external and is located at a height lower than the highest point on the inlet to a drainpipe. Such a location is very susceptible to back-flow of the filtered liquid into the filter unit, into the housing and potentially into the filter chamber. Preferably, the second valve is mechanical. Preferably, the second valve has no electrical or electronic components. Preferably, the second valve is opened and closed mechanically by the direction of the flow of the filtered liquid.Bypass

[0105] Preferably, the filter unit comprises a bypass flow path to selectively permit liquid effluent flowing towards the housing inlet (which allows liquid effluent to enter the housing) to flow to an outlet without passing through the housing or the filter chamber.

[0106] The bypass flow path can be selectively permitted when the first valve is closed. Alternatively, or in addition, the bypass flow path can be selectively permitted when the filter medium becomes blocked and / or when a pressure sensor or plurality of pressure sensors in the filter unit detect a back pressure as between an inlet (especially the housing inlet) and an outlet, for example the first outlet. In normal operation of the filter unit when the first valve opens and the filter medium is not blocked the bypass flow path is not permitted or utilised.

[0107] The bypass flow path preferably permits fluid connection between the exterior inlet and the exterior outlet. Preferably the bypass comprises a bypass valve and especially a bypass valve which can be actuated electrically or even more especially a bypass valve which opens mechanically in response to a predetermined pressure. Optionally, the control unit can actuate this bypass valve in response to for example signals from one or more pressure sensors.Pressure sensor(s)

[0108] Preferably, the filter unit comprises one or more pressure sensors, preferably to establish the pressure as between an inlet (especially the housing inlet which allows liquid effluent to enter the housing) and an outlet. By an outlet, this can mean the first outlet, the second outlet or the exterior outlet of filter unit which for example can be connected to the drain.

[0109] By “an inlet” this preferably means the housing inlet (which allows liquid effluent to enter the housing) or the exterior inlet or any of the connections between these inlets.

[0110] The pressure sensed by the pressure sensor(s) can be used to perform any one or more of the follow tasks: i. Provide a status indicator on a display device; ii. Illuminate a light visible to the user; iii. Generate sound from a speaker; iv. Open a valve in the bypass flow path. v. Shut off for example a motor used to rotate the filter medium and optional filter cage; vi. Activate a motor used to rotate the filter medium and optional filter cage.

[0111] Of these vi. is especially preferred. Thus, preferably the pressure sensor(s) are used to activate a motor used to rotate the filter medium and optional filter cage. This is especially useful for an external filter unit. In one embodiment the pressure sensed by the pressure sensor(s) can be used to determine that liquid effluent is entering an inlet and a control unit can be used to activate a motor to rotate the filter medium and optional filter cage. Thus, the external filter unit can sense the flow of effluent liquid from the effluent producing apparatus and can respond by rotating the filter medium and optional filter cage.

[0112] The pressure sensor(s) can be used to inform the user of the status of the filter unit and / or to direct the user to remove filtered microparticles from the filter medium. The pressure sensor(s) may also be utilised to estimate or calculate the remaining number of filtration cycles before the filter medium and optional filter cage will require emptying.

[0113] Optionally a certain pressure as between an inlet (especially the housing inlet) and an outlet could indicate that the filter medium is blocked and / or that the filter medium has collected all the microparticles it can. In either case the user can then empty and clean the filter medium.

[0114] The pressure sensor(s) can be located upstream and / or downstream of the filter chamber, more preferably the pressure sensor(s) can be located on an inlet (especially the housing inlet) and / or on an outlet.

[0115] Alternatively, the pressure sensor(s) can be located on a control unit with the pressure being transferred via a pressure connector, for example a tube, beginning from upstream and / or downstream of the filter chamber, more preferably transferred via a tube beginning from an inlet and / or an outlet, in either case the tube ending by connecting to the pressure sensor(s) on the control unit.Control Unit

[0116] Preferably the filter unit comprises a control unit to control various components within the filter unit. The control unit is preferably electronic.

[0117] The control unit preferably controls one or more of the following:i. The rotation of an electrical motor which is able to rotate the filter medium and optionally the filter cage; ii. The opening of a bypass valve; iii. The actuation of a pump; iv. A speaker, a light or a display device to indicate for example whether the pressure sensor(s) indicate that the filter medium needs emptying.

[0118] Preferably, the control unit receives signals from the pressure sensor(s), preferably the control unit is able to control the actuation of a valve to open the bypass flow path between the housing inlet (which allows liquid effluent to enter the housing) and an outlet. The control unit could equally well receive signals from other sorts of sensor(s) to actuate the opening of a valve to open the bypass flow path between the housing inlet (which allows liquid effluent to enter the housing) and an outlet.

[0119] Other sorts of sensors include float valves, capacitance sensors, flow sensors and the like. These can be present in the filter unit and located in place of or in addition to the pressure sensors. The other sorts of sensors are preferably located at or upstream of the housing inlet and at or downstream of the first and / or second outlet.Flow of Effluent from the interior to the exterior of the filter medium

[0120] Preferably, the filter medium optionally together with the filter cage form a cavity within their interior surface. More preferably, the housing inlet directs effluent liquid towards the interior of said cavity. Preferably, the flow of the effluent liquid is from the interior of the cavity through the filter medium in a direction from its interior to its exterior surface. The filtered liquid then preferably flows towards the first outlet and / or optionally the second outlet. Any microparticles having a size larger than the pore size of the filter medium are preferably deposited on the interior surface of the filter medium.Motor

[0121] The filter unit preferably comprises a motor. The motor is preferably an electric motor. The motor is preferably activated by an electrical connection to a control unit.

[0122] The motor is preferably able to drive rotation at a speed of from 100rpm to 5,000rpm, more preferably from 500rpm to 2,500rpm and especially from 800 rpm to 2,000 rpm.

[0123] The electric motor can be a DC motor or an AC motor. The motor can be brushless or brushed. The motor preferably comprises a drive shaft.

[0124] The drive shaft is preferably connected directly or indirectly to a drive connector. The drive connector preferably engages with the filter cage and the filter cage has a filter medium located on it.

[0125] Preferably, the motor is connected to the filter cage and which when said motor is activated is able to rotate the filter cage and filter medium.Drive connector

[0126] The drive connector is preferably attached to the motor, preferably this is via a drive shaft of the motor.

[0127] The drive connector preferably has an engagement surface in the shape of a plurality of blades, typically from 2 to 10, preferably from 3 to 6 and especially 4 blades. The blades are preferably equally spaced in a radial direction from an axis of rotation of the filter cage and filter medium.

[0128] The drive connector may comprise an engagement surface in the form of slots, especially slots which narrow moving further away from the opening in the housing.

[0129]

[0130] Preferably, the drive connector has an engagement surface (which is complementary to and) which engages with the one or more engagement surfaces on the filter cage, especially a substantially cylindrical filter cage.Exterior Inlets / Outlets and fluid connections

[0131] Preferably, the filter unit comprises an exterior inlet and an exterior outlet. These represent the inlet and outlet accessible to the end-user for connection and installation when the filter unit is an external filter unit.

[0132] The exterior inlet is preferably fluidly connected to the housing inlet (which allows liquid effluent to enter the housing). The fluid connection can be by means of pipes, hoses, channels, ducts and the like. The exterior inlet preferably is connected to a bypass flow path and to the housing inlet or to the first valve.

[0133] The exterior outlet is preferably fluidly connected to the first and optionally the second outlet. The fluid connection can be by any of the aforementioned means for the exterior inlet. A valve and especially a non-return valve is preferably positioned between the external outlet and the first and / or second outlet, especially the second outlet. A pump which also acts as a valve such as a displacement pump or diaphragm pump can be positioned between the external outlet and the first and / or second outlet, especially the second outlet.

[0134] The exterior inlet provides a means to externally connect the filter unit to an effluent producing apparatus such as a washing machine or a textile treatment machine. Typically an exterior inlet will be connected to an effluent producing apparatus by means of a pipe or hose.

[0135] The exterior outlet provides a means to externally connect the filter unit to a drain. Typically, a pipe or hose will connect the exterior outlet to the drain.Power supply

[0136] The filter unit preferably comprises a power supply, especially a power supply to supply power to any one or more of a motor, a control unit, pressure sensor(s), valves, a pump, lights, speakers or displays.Preferred Configurations

[0137] Preferably, the filter medium is substantially cylindrical, the cylindrical filter medium forms a cavity in its interior space, the housing inlet directs the liquid effluent towards the cavity, the liquid effluent flows from the interior to an exterior of the filter medium, and the filtered liquid exits via the first outlet, such that microparticles having a size larger than the pore size of the filter medium are deposited on the interior surface of the filter medium.

[0138] Preferably, the filter unit comprises: a substantially cylindrical filter cage having at one end of the cylinder one or more engagement surfaces to engage with a drive connector, and wherein the filter medium is located on the filter cage; the closure is a cap attached to the filter cage at the other end of the substantially cylindrical filter cage opposite the one or more engagement surfaces; a motor which is connected to the filter cage via a drive connector and which when the motor is activated is able to rotate the filter cage and filter medium; wherein the drive connector has one or more engagement surfaces to engage with the one or more engagement surfaces on the filter cage; wherein the first valve is a mechanical, biased valve; when the opening in the housing and the closure are in the unsealed configuration the bias in the biased valve results in a closed configuration of the first valve, and when the opening in the housing and the closure are in the sealed configuration the bias is overcome by a mechanical force acting on the first valve resulting in an open configuration of the first valve;wherein the opening in the housing and the closure are in the sealed configuration when the filter cage, filter medium and cap are located within the housing and the cap has been closed to the housing to a predetermined end-stop, and wherein the action of closing the cap to the housing to the predetermined end-stop causes the mechanical force to be transmitted via the cap, the filter cage and the drive connector to act on the first valve resulting in an open configuration of the first valve; and the opening in the housing and the closure are in the unsealed configuration when the cap is withdrawn from the end-stop.Method

[0139] According to a second aspect of the present invention there is provided a method of filtering a liquid effluent comprising microparticles using a filter unit according to the first aspect of the present invention.

[0140] Preferably, the microparticles are microplastics and especially microfibres.

[0141] Preferably, the method comprises rotating the filter medium and optionally the filter cage and the filter medium during the filtration.Summary of the Figures

[0142] Embodiments of the present invention will be described hereinafter, by way of example only, with reference to the accompanying drawings in which:

[0143] Figure 1 shows an external isometric view of a filter unit according to the present invention.

[0144] Figure 2 shows an exploded view of the same filter unit as Figure 1 according to the present invention.

[0145] Figure 3 shows an isometric view of the same filter unit as Figure 1 but with the outer cover removed and all the components other than the outer cover assembled.

[0146] Figure 4 shows a plan (overhead) view of the same filter unit as Figure 1 and indicates a cross-section A-A.

[0147] Figure 5 shows the cross-section view of the same filter unit as Figure 1 as taken through A-A in Figure 4.

[0148] Figure 6 shows an exploded view of the filter cage and closure present in the filter unit of Figure 1 .

[0149] Figure 7 shows an isometric view of the filter cage and closure of Figure 6 fully assembled.

[0150] Figure 8 shows an exploded view of the first valve and drive connector present in the filter unit of Figure 1 .

[0151] Figure 9 shows an exploded view of the fluid connections to the housing inlet, and to the first outlet, Figure 9 also shows the exterior inlet and exterior outlet to the filter unit itself. Figure 9 shows a bypass flow path.Detailed Description

[0152] Figure 1 shows an isometric external view of a preferred filter unit (100) according to the present invention. Figure 1 shows the outside of the closure (101 ), the outer cover (102) and a part of the exterior outlet (103).

[0153] Figure 2 shows an exploded view of the filter unit (200) of Figure 1 . The figure shows the closure (201 ) in the form of a cap fitted with a screw thread to engage into the opening of the housing, the outer cover (202) and the exterior outlet (203) and exterior inlet (204). Figure 2 shows a housing (205), a housing inlet (not visible) which allows liquid effluent to enter the housing, a filter cage (207) having a filter medium (208). The housing (205) is cylindrical and has an opening(209) at one end and at the other end a valve assembly (210) comprising the first valve (not fully visible) and the drive connector (211 ). A part of the filter chamber (212) is just visible inside the opening (209). An electric motor (213) is fitted to the rear of the filter unit via the valve assembly(210).

[0154] A bypass assembly (214) comprises the fluid connections for the filter unit as well as the bypass subsystem. The bypass assembly provides fluid connections as between the exterior outlet (203) and the first outlet (215a) and second outlet of the housing. (not quite visible). The bypass assembly (214) also provides the fluid connections as between the exterior inlet (204) and the housing inlet which allows liquid effluent to enter the housing (not visible). The bypass assembly also comprises two pressure connectors (not labelled). The bypass assembly also comprises a bypass valve which can selectively open or close a fluid flow path as between the exterior inlet (204) and (eventually) the exterior outlet (203).

[0155] The bypass assembly also comprises a second valve situated downstream of the first outlet, between the first outlet and the exterior outlet. This second valve has the function of preventing filtered effluent from re-entering the housing from the exterior outlet.

[0156] The filter unit of Figure 2 has a base plate (215) onto which many of the filter unit components are secured. The filter unit in Figure 2 also has a circuit board (216) which comprises a control unit and pressure sensors which receive pressure from the pressure connectors (in the form of pipes), the control unit controls the rotation of the motor (213). The circuit board may be covered with a cover-plate (not shown) so as to protect the circuit board from any drips or spills of liquids in the unlikely event of a seal or connection failing.

[0157] Figure 3 shows an isometric view of the same filter unit (300) as Figure 1 and 2, here the outer cover has been removed. The closure (301 ) is in place in the housing (305). The circuit board (316) is secured to the base plate (315). The first outlet (315a) is visible. The valve assembly (310) connects between the housing (305) and the motor (313).

[0158] Figure 4 shows a plan view of the same filter unit (400) as figures 1 to 3. A cross-section A-A is shown which runs through the centre of the housing and bisects the axis of rotation of the filter cage and filter medium. The closure (401 ), the housing (405), the first outlet (415a) and the motor (413) are all visible from this perspective.

[0159] Figure 5 shows the cross-section A-A (500) as from figure 4. Figure 5 shows, the closure (501 ), the housing (505) and the motor (513). The housing inlet (516) which allows liquid effluent to enter the housing is fluidly connected to the exterior inlet (504). The valve assembly (510) can be seen including the first valve (517) itself comprising the mechanical valve with a bias in the form of a spring (518) which runs through the axis of rotation of the filter cage (507). The first valve has a sealing surface (519) in the form of an annulus. In figure 5 the second outlet (515b) can be seen located at the lowermost point in the housing. A pump (520) is located downstream of the second outlet (515b). This pump can be used to pump filtered liquid out of the filter unit even if the filter unit is placed at a low point relative to an effluent producing apparatus such as a washing machine and / or relative to a drain. The drive connector (511 ) has engagement surfaces designed to engage with the engagement surfaces on the filter cage (507).

[0160] Figure 6 shows an exploded view of a filter cage and closure assembly (600). The closure (601 ) is in the form of a cap fitted with a screw thread. The closure also comprises a circlip (621 ), a shoulder screw (622), an O-ring (623), a seal carrier (624), a washer (625), a flange bearing (626) and a larger O-ring (627). The filter cage (607) has a filter medium (608). The filter cage further comprises a lid (628) attached to which are several impellor blades (629b). When fully assembled, the scraper blades (629a) are attached to the impellor blades (629b). The lid (628) and one end of the filter cage have a securing mechanism which is shown here as a twist-lock mechanism. The filter cage has at the other end furthest from the cap, engagement surfaces to engage with the drive connector. In this filter unit the filter cage has a removable portion (631 ) furthest from the cap which comprises the engagement surfaces (not visible).

[0161] Figure 7 shows an assembled filter cage and closure assembly (700) identical to that in figure 6. The closure (701 ) in the form a cap is able to rotate relative to the lid (728) and the other components of the filter cage (707) including the filter medium (708) and the removable portion (731 ).

[0162] Figure 8 shows the valve assembly (800) as shown in other figures above. The valve assembly comprises a bolt (832), a washer (833), a drive connector (811 ) having four engagement surfaces (834) to engage with the engagement surfaces of the filter cage (located in the removable portion of the filter cage). The valve assembly also comprises a rotary seal (835)in the form of a v-seal, a sealing tube (836). The valve assembly has attachment surfaces (837) to securely attach and lock the valve assembly to the housing. The valve assembly has attachment surfaces (838) to securely attach and lock the valve assembly to the motor. A seal ring (839) is located on a first outer valve shaft (840) within which is located a bias in the form of a spring (818), the spring being secured in part by a shaft adapter (841 ).

[0163] Figure 9 shows the bypass assembly (900) which has an exterior inlet (904) and an exterior outlet (903). A bypass valve (942) is located between the exterior inlet and the exterior outlet. A second valve (943) is located downstream of the first outlet and before the exterior outlet (903). Pressure connectors are attached to the inlet at (944a) and outlet at (944b) locations of the bypass assembly. Pressure connectors in the form of pipes (945a and 945b) permit the pressure to pass to the circuit board where it is converted into electrical signals by pressure sensors within the circuit board. O-rings (946a, 946b and 946c) are used to ensure the connections of the pipes in the bypass assembly are water-tight. The second outlet via the outlet from the pump connects to an opening (947) in the bypass assembly via a pipe. Fasteners in the form of hex socket caps such as the one labelled (948) are used to secure the bypass assembly to the base plate (315) shown in figure 3.

[0164] Also described herein is a filter unit suitable for removing microparticles from a liquid effluent, the filter unit comprising: a housing comprising a housing inlet which allows liquid effluent to enter the housing, a first outlet which allows filtered liquid to exit the housing, a filter chamber for accommodating a removable filter medium, and an opening through which the removeable filter medium can be removed from the housing; a closure configured to selectively seal the opening, wherein in an unsealed configuration the opening and the closure are not water-tight, and in a sealed configuration the opening and the closure are water-tight; and a first valve that is configured to open when the opening and the closure are in the sealed configuration such that liquid effluent can pass into the filter chamber, and that is configured to close when the opening and the closure are in the unsealed configuration such that liquid effluent is prevented from entering into the filter chamber.General

[0165] In the present invention items in the singular also include items in the plural unless stated to the contrary. Thus, by example, a filter medium means one or more filter media.

[0166] Throughout the description and claims of this specification, the words “comprise” and “contain” and variations of them mean “including but not limited to” and they are not intended to (and do not) exclude other moieties, additives, components, integers or steps.

[0167] Features, integers, characteristics or groups described in conjunction with a particular aspect, embodiment or example of the invention are to be understood to be applicable to any other aspect, embodiment or example described herein unless incompatible therewith. All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and / or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of the features and / or steps are mutually exclusive. The invention is not restricted to any details of any foregoing embodiments. The invention extends to any novel single, or novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel single, or any novel combination, of the steps of any method or process so disclosed.

[0168] The reader’s attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

Claims

Claims:

1. A filter unit suitable for removing microparticles from a liquid effluent, the filter unit comprising: i. a housing; ii. a housing inlet which allows liquid effluent to enter the housing; iii. a filter medium which can be removed from the housing; iv. a first outlet which allows filtered liquid to exit the housing; v. an opening in the housing and a closure, which together have an unsealed and a sealed configuration, and when in the unsealed configuration the opening and closure are not water-tight, and when in the sealed configuration the opening and closure are water-tight; the opening and the closure also having an unsealed and open configuration which permits the filter medium to be removed from the filter unit; vi. a filter chamber for accommodating the filter medium; vii. a first valve, having an open configuration permitting liquid effluent to pass into the filter chamber, and which is opened when the opening and the closure are in the sealed configuration, and having a closed configuration preventing liquid effluent from entering into the filter chamber, and which is closed when the opening and the closure is in the unsealed configuration.

2. A filter unit according to claim 1 wherein the first valve is a mechanical valve.

3. A filter unit according to claim 2 wherein the mechanical valve is a biased valve.

4. A filter unit according to claim 3 wherein the bias in the biased valve is provided by means of a spring, an elastomer, a magnetic device or a pneumatic device.

5. A filter unit according to any one of claims 3 or 4 wherein: when the opening in the housing and the closure is in the unsealed configuration the bias in the biased valve results in a closed configuration of the first valve, and when the opening in the housing and the closure is in the sealed configuration the bias is overcome by a mechanical force acting on the first valve resulting in an open configuration of the first valve.

6. A filter unit according to any one of the preceding claims which is external to a liquid effluent producing apparatus.

7. A filter unit according to any one of the preceding claims wherein the filter medium is located on a filter cage, and wherein the filter cage and filter medium are rotatable about an axis.

8. A filter unit according to claim 7 comprising a motor which is connected to the filter cage and which when said motor is activated is able to rotate the filter cage and filter medium.

9. A filter unit according to any one of the preceding claims wherein the filter cage is substantially cylindrical.

10. A filter unit according to any one of the preceding claims wherein the filter chamber is substantially cylindrical.

11. A filter unit according to any one of the preceding claims wherein the closure is a cap, the opening in the housing is substantially circular, and wherein the cap can be sealed into a predetermined position via an end-stop so that the cap and the opening in the housing provide the sealed configuration of the housing; and the cap can be unsealed from the housing by moving the cap away from the end-stop, to provide the unsealed configuration of the housing.

12. A filter unit according to claim 11 wherein the cap can be closed into the opening in the housing by means of a twist lock or screw thread mechanism.

13. A filter unit according to any one of the preceding claims comprising a second valve located at or downstream of the first outlet.

14. A filter unit according to any one of the preceding claims which comprises a bypass flow path to selectively permit liquid effluent flowing towards the housing inlet to flow to an outlet without passing through the housing or the filter chamber.

15. A filter unit according to any one of the preceding claims comprising a second outlet in the housing located at a lowermost point in the housing.

16. A filter unit according to claim 15 which comprises a pump located at or downstream of the second outlet and which when actuated can pump filtered liquid out of the filter unit.

17. A filter unit according to claim 16 wherein the pump can prevent filtered liquid from flowing back into the housing and the filter chamber.

18. A filter unit according to claim 17 wherein the pump is a diaphragm pump or a displacement pump.

19. A filter unit according to any one of the preceding claims which comprises one or more pressure sensors to establish the pressure as between an inlet and an outlet.

20. A filter unit according to any one of the preceding claims wherein the filter medium has a pore size of 500pm or less.

21. A filter unit according to any one of the preceding claims wherein the filter medium has a pore size of 100pm or less.

22. A filter unit according to any one of the preceding claims wherein the filter medium is substantially cylindrical, the cylindrical filter medium forms a cavity in its interior space, the housing inlet directs the liquid effluent towards the cavity, the liquid effluent flows from the interior to an exterior of the filter medium, and the filtered liquid exits via the first outlet, such that microparticles having a size larger than the pore size of the filter medium are deposited on the interior surface of the filter medium.

23. A filter unit according to claim 1 comprising a substantially cylindrical filter cage having at one end of the cylinder one or more engagement surfaces to engage with a drive connector, and wherein the filter medium is located on the filter cage; the closure is a cap attached to the filter cage at the other end of the substantially cylindrical filter cage opposite the one or more engagement surfaces; a motor which is connected to the filter cage via a drive connector and which when the motor is activated is able to rotate the filter cage and filter medium; wherein the drive connector has one or more engagement surfaces to engage with the one or more engagement surfaces on the filter cage; wherein the first valve is a mechanical, biased valve; when the opening in the housing and the closure are in the unsealed configuration the bias in the biased valve results in a closed configuration of the first valve, andwhen the opening in the housing and the closure are in the sealed configuration the bias is overcome by a mechanical force acting on the first valve resulting in an open configuration of the first valve; wherein the opening in the housing and the closure are in the sealed configuration when the filter cage, filter medium and cap are located within the housing and the cap has been closed to the housing to a predetermined end-stop, and wherein the action of closing the cap to the housing to the predetermined end-stop causes the mechanical force to be transmitted via the cap, the filter cage and the drive connector to act on the first valve resulting in an open configuration of the first valve; and the opening in the housing and the closure are in the unsealed configuration when the cap is withdrawn from the end-stop.

24. A filter unit according to any one of the preceding claims which is suitable for removing microparticles having a size of 100 microns.

25. A method of filtering a liquid effluent comprising microparticles using a filter unit according to any one of the preceding claims.

26. A method of filtering a liquid effluent comprising microfibres using a filter unit according to any one of the preceding claims.

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