A filter for reducing and preventing biofilm formation

Abstract

A filter unit comprising a housing, or casing, a power source, and a filter element, wherein the housing houses, or encapsulates, the filter element and has at least one inlet arranged to receive a feed, and at least one outlet, arranged to discharge, or release, filtrate, wherein the filter is arranged to form the filtrate from the feed, and wherein the power source is arranged to apply an electric current to the filter element for reducing biofilm formation.

Description

[0001] A FILTER FOR REDUCING AND PREVENTING BIOFILM FORMATION

[0002] Technical field

[0003] The technology proposed herein relates generally to filtration of liquid fluid or filters .

[0004] Background

[0005] In the production process of dairy products , or in the food industry in general , municipal water or well water is commonly used . Contaminants such as rust and dirt in the water will reduce the service li fe of components of a food processing system . Accordingly, it is necessary to filter and puri fy the water used by using filters to improve the service li fe of systems .

[0006] Microbiological growth in filters , such as bacterial growth forming biofilms , is a recogni zed problem . Such growth can negatively af fect the performance of the filters , for example with respect to flow rates and filtration ef ficiency . Microbiological growth is particularly a problem in dairy, or food, production since such products are high in nutrients favorable for microbiological growth .

[0007] Filters used in the processing of such food products typically have high rates of microbiological growth and require frequent cleaning to prevent a drop in quality of the product or rendering the products unfit for use or consumption . Typically, production must be interrupted for cleaning and chemicals are commonly used in cleaning, which contributes to a decreased ef ficiency and increased production costs . The microbiological growth is particularly a problem in filters that cannot be easily disassembled for manual cleaning . Such filters typically require extensive flushing with anti-microbial chemicals for cleaning . Accordingly, there is a need to reduce downtime for filter cleaning . In addition, there is a need to reduce the need for chemicals for cleaning filters .

[0008] The proposed technology aims at preventing or reducing microbiological growth, such as bacterial growth forming biofilms , in filter membranes and particularly in pores of filter membranes . It is also an obj ect to reduce microbiological growth in filters comprising filter membranes , used in the processing of liquid food products , and speci fically in reverse osmosis filters in dairy production .

[0009] Summary

[0010] According to a first aspect of the proposed technology, a filter element , or filter media, is provided, wherein the filter element comprises a first filter membrane that has , or forms , pores arranged to filter a feed, wherein the first filter membrane is electrically conductive .

[0011] It is further speci fied that the filter element , or filter media, is configured to be positioned in a filter housing, and that and to form a filtrate from a feed, the filter element comprising a first filter membrane that has , or forms , pores arranged to filter the feed, wherein the first filter membrane is electrically conductive , and a filter support configured to be positioned in the housing, and support the filter element in the housing, wherein the first filter membrane is electrically coupled to the filter support .

[0012] According to a second aspect , a filter unit , or filter system, is provided, the filter unit comprising a filter element , a housing or casing, a power source , wherein the filter element is arranged to form a filtrate from a feed, and wherein the power source is arranged to apply an electric current to the filter element for reducing biofilm formation .

[0013] It is speci fied above that the filter element comprises at least a first filter membrane that is electrically conductive . This means that the filter element is electrically conductive when at least the first filter membrane is electrically conductive .

[0014] The filter element and the electric power source may be operationally coupled, or connected, in an electric circuit arranged to lead the current from the power source to establish an electrical potential over the filter element . The electric current , and / or the electric potential , is configured to inhibit , reduce , or prevent , microbiological growth within, or in, the filter element . This means that microbial growth may be inhibited in a portion of , or the complete , filter element .

[0015] As speci fied above , the filter element , or filter media, is configured to be positioned in a filter housing . Worded di f ferently, the filter element , or filter media, may be housed, or arranged, or installed, in a housing .

[0016] The filter element and the housing may be electrically coupled in an electric network . It is understood that the electric network forms part of the abovementioned electric circuit . This means that the electric current , and / or the electric potential , provided by the power source may be configured to inhibit , reduce , or prevent , microbiological growth within, or in, the filter element as well as the housing . In addition, this also means that microbiological growth is inhibited, reduced, or prevented, on or in, any further elements that forms components , or parts , of the electric network and conducts current from the power source and are in contact with feed or filtrate .

[0017] The electric network may be arranged to distribute the current between the housing and the filter element . For example , the housing and the filter element may be arranged in parallel in the electric network . This means that in the electric network, a first portion of the current is conducted through, or via, the housing and a second portion of the current is conducted through, or via, the filter element .

[0018] The electric circuit may be connected to ground . Worded di f ferently, the filter element may be electrically coupled to the power source via ground, or the electric circuit may incorporate ground . Ground may be a signal ground or earth ground . For example , ground may incorporate an electrically conductive structure connected to and supporting the filter element . In one example , this structure may be the housing .

[0019] It is understood that the filter support discussed above may be conductive and that the filter support may be electrically coupled, or connected, to the housing . The filter support may thus form part of the electric network . This means that microbial growth is inhibited, reduced, or prevented also in the filter support . In one example , the filter support may contact and fixate the filter element relative to the housing . This means that the filter support , or at least a portion of the filter support , may directly contact , or be in contact with, the housing .

[0020] According to the second aspect , the power source and the filter unit as such may j ointly form part of a closed electric circuit , arranged to supply electric current from the power source to the filter element . It is understood that this is in the absence of the feed or filtrate .

[0021] Worded di f ferently, the filter element and the power source may be coupled in a closed electric circuit arranged to supply electric current to the filter element . It is understood that this is in the absence of the feed or filtrate . It is understood that in a closed electric circuit there are no gaps , or clearances , between the components . For example , there are no gaps in the electric circuit . This contributes to reduce electrolytic ef fects in the circuit within the filter element . In other words , the electric circuit is non-electrolytic . This means that the electric circuit does not generate an electrolysis within in the feed, or within the filter element , or its components . Worded di f ferently, the feed as such does not form part of the electric circuit and the filter element forms a continuous , or non-interrupted, electric conductor in the electric circuit .

[0022] It is understood that in a closed electric circuit , the filter element constitutes a resistive connection or element in the electric circuit . The first filter membrane may be configured to form part of the closed electric circuit .

[0023] According to a third aspect , a method for filtering a liquid fluid using the filter assembly is provided, the method comprising :

[0024] - flowing a liquid fluid through filter membrane as speci fied above , while

[0025] -applying a voltage potential over the filter membrane to generate an electrical current flow in the filter membrane , wherein the voltage is an alternating current having a frequency in the range of 1- 100 Hz , a voltage in the range of 40- 120 V, and a duty cycle of about 50% .

[0026] Throughout these speci fications , i f a first element is electrically coupled to a second element there may be further conductive elements between them, and i f a first element is electrically connected to a second element there are no conductive elements between them .

[0027] Feed is understood to refer to the liquid fluid that is to be filtered, or the unfiltered liquid fluid, or the liquid fluid prior to filtration . Filtrate is understood to refer to the filtered liquid fluid, or the liquid fluid after filtration, or post filtration . Worded di f ferently, feed refers to liquid fluid upstream filter elements of a filter, and filtrate refers to liquid fluid downstream filter elements of a filter . In other words , the first filter membrane may be arranged to form a filtrate from the feed .

[0028] The feed and / or filtrate may thereby be a fluid, such as a liquid fluid . The fluid may be susceptible to microbiological growth . The fluid may contain water . The fluid may be a liquid, such as water, raw milk or raw j uice . It is understood that the fluid may contain solid particles . The fluid may be a paste , or a minced or pureed product .

[0029] It is speci fied above that the first filter membrane has pores . It is understood that in a filter membrane , pores allow liquid of the feed to pass through the filter membrane and prevent passage of particles and microorganisms through the filter membrane . For example , pores encompasses openings , or perforations , in the first filter membrane . It is understood that pores extend through the filter membrane and that the pores form a barrier that prevents passage of particles and microorganisms through the pores and the filter membrane .

[0030] Microorganisms are here understood to encompass unicellular organisms that may exist in single-celled forms or in colonies of cells , and microscopic multicellular organisms . For example , the microorganisms may be bacteria forming biofilms . It is speci fied that the first filter membrane is electrically conductive . I f a current is applied to the first filter membrane , for example by applying an electric potential over the first filter membrane or the filter element , bacterial growth and biofilm formation is reduced . Thus , the proposed filter element allows for reduced biofilm formation, and in extension blocking of pores is reduced and the resulting pressure increase in the filtrate is reduced . This in turn reduces pumping losses when a higher pressure is needed to maintain filtering capacity . Wording the first filter membrane being electrically conductive di f ferently, the applied current from the power source may prevent biofilm formation on both the feed and the filtrate side of the first filter membrane as well as in the pores . This reduces the risk of filtrate being contaminated by microorganisms releasing from a biofilm formed on the filter membrane feed side . It is understood that biofilm formation is more prevalent on the feed side of the first filter membrane since microorganism and particle buildup is higher on the feed side . Thus , applying current on the feed side of the first filter membrane will also reduce the risk of biofilm formation and growth in the pores and the filtrate side of the first filter membrane .

[0031] It is speci fied above that at least the first filter membrane is electrically conductive . In addition, the complete filter element , or all its components , may be electrically conductive .

[0032] The first filter membrane may comprise a first filter material . The first filter material may be electrically conductive . The first filter material may be a singlecomponent material . For example , the first filter material may be an electrically conductive polymer . It is understood that an electrically conductive polymer, sometimes referred to as intrinsically conducting polymers ( ICPs ) , are polymers that conduct electricity . This is advantageous in that an applied current on the first filter membrane will reduce biofilm formation on the feed side , in and on the pores and the filtrate side of the first filter membrane . It is understood that an electrically conductive polymer encompasses both inorganic or organic polymers and that the polymer as such is electrically conductive . The first filter membrane may be a polymer film .

[0033] Alternatively, the first filter material may be a composite material . The first filter material may comprise , or be composed of , an electrically insulating material and an electrically conductive additive . The electrically insulating material may be polypropylene ( PP ) , aromatic polyamide ( PA) , cellulose acetate ( CA) or polyvinylidene fluoride ( PVDF) . Alternatively, the electrically insulating material may be polyethylene ( PE ) or polyester or polyethylene terephthalate ( PET ) . The electrically conductive additive may be carbon or a metal , for example in the form of particles or fibers . Carbon black is a preferred additive in combinations with electrically insulating polymers . In this configuration, the first filter membrane may be a fleece , or a resin bonded filter or a spun filter . Alternatively, in this configuration, the first filter membrane may be in the form of a composite polymer film .

[0034] The first filter membrane may be composed of the first filter material , which means that there are no other materials in the first filter membrane . Alternatively, the first filter membrane may be a composite structure comprising the first filter material and a second filter material . It is understood that the two materials are separate , or noncomposite . The second filter material may be electrically insulating . In another example , the second filter material may be polypropylene ( PP ) , cellulose acetate , cellulose nitrate ( collodion) , polyamide (nylon) , polycarbonate , polypropylene , and polytetrafluoroethylene ( Teflon) . In this configuration, the first filter membrane may be a weave of the first filter material and the second filter material .

[0035] The filter element may be a mono-membrane , or single membrane , filter . Worded di f ferently, the feed is filtered through a single membrane that forms the filtrate . Alternatively, the filter element may comprise a second filter membrane arranged to filter the feed . In other words , the filter element may be a multi-membrane filter element . It is understood that the filter element may have additional filter membranes , for example positioned between the first filter membrane and the second filter membrane .

[0036] The first filter membrane and the second filter membrane may be j uxtaposed or j ointly form a layered, or sandwiched, structure . Worded di f ferently, the second filter membrane may be aligned with and contact the first filter membrane . The second filter membrane may cover, or contact , the complete first filter membrane . The second filter membrane may be laminated to the first filter membrane . It is understood that the second filter membrane may contribute to form the filtrate . In other words , the second filter membrane may be arranged to form, or at least in part form, the filtrate from the feed .

[0037] The second filter membrane may be electrically conductive . This means an applied current will prevent biofilm formation on both the feed and the filtrate side of the second filter membrane The second filter membrane may be of a third filter material . The third filter material may be electrically conductive . The third filter material may have any of the features of first filter material . The third filter material may be of the same material as the first filter material .

[0038] The second filter membrane may be composed of the third filter material , which means that there are no other materials in the second filter membrane . Alternatively, the second filter membrane may be a composite structure comprising the third filter material and a fourth filter material . The fourth filter material may have any of the features of second filter material . The fourth filter material may be the same material as the second filter material .

[0039] Alternatively, to the second filter membrane being electrically conductive , the second filter membrane may be electrically insulating . The third filter material may be electrically insulating . This means that the above-described inhibition of microbiological growth may not be present in the second filter membrane , which may lead to a reduced flow rate of the feed through the second filter membrane .

[0040] The second filter membrane may be positioned, or intended to be positioned, upstream of the first filter membrane in relation to the feed . The second filter membrane may have greater pores than the first filter membrane . This contributes to lessen the ef fect of the microbiological growth on the flow rate . The second filter membrane may have the same pore si ze as the first filter membrane .

[0041] The filter element may further comprise a first backing layer that supports the first filter membrane . It is understood that a backing layer does not form, or lacks , or is devoid of , pores intended for filtering the feed . The first filter membrane and the first backing layer may be j uxtaposed or j ointly form a layered, or sandwiched, structure . Worded di f ferently, the first backing layer may be aligned with and contact the first filter membrane . The first backing layer may cover, or contact , the complete first filter membrane . The first filter membrane may be attached to the first backing layer .

[0042] In one example , the first filter membrane is a film membrane j uxtaposed, or laminated, to the first backing layer to form the layered, or sandwiched, structure .

[0043] The first backing layer may form passages , or channels . The passages , or channels , may be arranged to allow the feed or the filtrate to pass through the first backing layer . For example , the passages may have an averages si ze that is at least an of order of magnitude greater in si ze then the average si ze of the pores of the first filter membrane and / or the second filter membrane . For example , the passages may have a si ze at least 50- 1000 times that of the openings of the first filter membrane . The first backing layer may be a mesh, web or grid . The first backing layer may be positioned, or intended to be positioned, upstream of the first filter membrane , or the second filter membrane i f present , in relation to the feed . The first backing layer may be arranged to form an internal space for holding filtrated particles or microorganisms from the feed . Worded di f ferently, the first backing layer may be a collector layer to collect filtrated particles or microorganisms .

[0044] The first backing layer may be electrically conductive . This may prevent bacterial growth and biofilm formation of collected filtrated particles or microorganisms . The first backing layer may be of a backing layer material . The first backing layer may share properties with the first filter material or the second filter material . The backing layer material may be the same as the first material or the second material . The backing layer material may be of the same material as the first filter material or the second filter material .

[0045] In one example , the backing layer material may be a single-component material . The backing layer material may be an electrically conductive polymer . The electrically conductive polymer may be an inorganic or organic polymer . In another example , the backing layer material may be polyethylene , polypropylene , polyamide , or polyester .

[0046] Alternatively, the backing layer material may be a composite material . The backing layer material may comprise , or be composed of , an electrically insulating material and an electrically conductive additive . The electrically conductive additive may be carbon or a metal , for example in the form of particles or fibers .

[0047] When the filter element comprises a backing layer of an electrically conductive backing layer material arranged downstream the first filter membrane , the formation of biofilm on the backing layer and the release of microorganisms into the filtrate is further reduced .

[0048] Alternatively, to the first backing layer being electrically conductive , the first backing layer may be electrically insulating . This means that the above-described inhibition of microbiological growth may not be present in the backing layer material , which may lead to a reduced flow rate of the feed and to the release of microorganisms from the backing layer to the filtrate .

[0049] In one example , the backing layer may be made from a metal mesh, or metal grid . It is understood that when the backing layer is made from a metal mesh, or metal grid, the backing layer is electrically conductive .

[0050] It is understood that the first filter membrane may form a continuous structure . More speci fically the filter element may form a sel f-supporting structure . Worded di f ferently, the first filter membrane may form a sel f-supporting continuous structure . The filter element may be sel f-supporting, comprising no further layers besides the first filter membrane . More speci fically the filter element may form a sel f-supporting structure . This means that the first filter membrane lacks any backing layer or any further membrane ( s ) . In one example , the filter element may be a melt blown or spun filer . A melt blown or spun filter is understood to be formed from polymer fibers that are pressed and sintered, and then melt-blown onto a rotating spindle to create cylindrical filter elements . The resulting structure may thereby be made sel f-supporting . In one example , the polymer fibers are mixed with electrically conductive additive in the form of carbon or a metal , in the form of particles or fibers , prior to being sintered and melt-blown onto the rotating spindle .

[0051] The filter element may further comprise a second backing layer that supports the first filter membrane . I f the second filter membrane is present , the second backing layer may also support the second filter membrane. The first filter membrane, or the first filter membrane and the second filter membrane, may be positioned between the first backing layer and the second backing layer.

[0052] The first filter membrane, or the second filter membrane if present, and the first backing layer may be juxtaposed. Worded differently, the second backing layer may be aligned with and contact the first filter membrane, or the second filter membrane if present. The second backing layer may cover, or contact, the complete first filter membrane or second filter membrane. The first backing layer may be laminated to the first filter membrane or the second filter membrane. Worded differently, the first filter membrane and the second filter membrane if present, may be laminated to the first backing layer.

[0053] The first backing layer, the first filter membrane, and the second backing layer may jointly form, or form part of, a layered, or sandwiched structure. If the second filter membrane is present, the first backing layer, the first filter membrane, the second filter membrane and the second backing layer may jointly form, or form part of, a layered, or sandwiched, structure. It is understood that the membranes and backing layers are arranged in said order in the structures .

[0054] The second backing layer may comprise any of the features of the first backing layer. For example, the first backing layer and the second backing layer may be a metal mesh. The second backing layer may be electrically conductive or electrically insulating.

[0055] It is specified above, that the filter element may have a first filter membrane and a second filter membrane. If the second filter membrane is present, an intermediate spacer may be arranged between the first filter membrane and the second filter membrane. The intermediate spacer may space the first filter membrane and the second filter membrane apart. The intermediate spacer may form a channel to transport filtrate to a filter element outlet. The intermediate spacer may be electrically conductive. The intermediate spacer may be of an intermediate spacer material. The intermediate spacer material may share properties with the backing layer material, the first filter material or the second filter material. In one example, the intermediate spacer material may be a single-component material. For example, the intermediate spacer material may be an electrically conductive polymer.

[0056] Alternatively, the intermediate spacer material may be a composite material. The intermediate spacer material may comprise, or be composed of, an electrically insulating material and an electrically conductive additive. The intermediate spacer material may be made from a first backing material or a second backing material. Alternatively, the intermediate spacer material may be a metal material. The intermediate spacer may be a mesh, or grid, or weave.

[0057] The filter element may further comprise a filter support, or frame, or frame arrangement. The filter support may be attached, or joined, to a first filter membrane, and if present, a further filter membrane, a filter backing layer, and / or an intermediate spacer. Worded differently, the filter membrane, a filter backing layer and / or an intermediate spacer may be attached to the filter support. It is understood that the filter support maintains the filter membrane, and if present, filter backing layers, and intermediate spacer in position during filtration. The filter support may thus prevent the collapse of the first filter membrane, and any further present layers, due to the pressure and flow of the feed. When the filter membrane is a self- supporting filter membrane, the filter element may not have, or lack, a filter support. The filter support may be a unitary body, or the filter support may be formed by two or more separate filter frames such as a first filter frame a second filter frame . For example , the first filter frame and the second filter frame may each attach to a filter membrane , a filter backing layer, and / or an intermediate spacer at separate locations . The first filter frame and the second filter frame may attach, or j oin, to a filter membrane , filter backing layer, and / or intermediate spacer at a first end and a second end of the filter element . The first end and the second end of the filter element may be a longitudinal , or axial , end of the filter element . The first end and the second end may be opposite longitudinal ends of the first filter membrane . Alternatively, the first end and the second end may be a first radially inner end and a second radially outer end of the filter element .

[0058] The filter support may comprise a third filter frame . The third filter frame may j oin, or connect , to the first filter frame and the second filter frame . For example , the third filter frame may extend longitudinally, between the first and second longitudinal , or axial , first end and second end of the filter element . Alternatively, the third filter frame may extend radially, between the first radially inner end, or first filter frame , and the second radially outer end, or second filter frame .

[0059] The filter support may be electrically conductive . The filter support may be of a filter support material . The filter support material may share properties with the first filter material or the second filter material . The filter support material may be the same material as the first filter material or the second filter material . The filter support material may share properties with the first backing material or the second backing material . The filter support material may be of the same material as the first backing material or the second backing material . In one example , the filter support material may be a single-component material . For example , the filter support material may be an electrically conductive polymer . It is understood that an electrically conductive polymer encompasses both inorganic or organic polymers and that the polymer as such is electrically conductive .

[0060] Alternatively, the filter support material may be a composite material . The filter support material may comprise , or be composed of , an electrically insulating material and an electrically conductive additive .

[0061] In a further alternative , the filter support material may be made of metal , such as stainless steel .

[0062] Alternatively to the filter support material being electrically conductive , the filter support material may be electrically insulating . This means that the above-described inhibition of microbiological growth may not be present in the filter support material , which may lead to biofilm formation on the filter support .

[0063] The filter element and the at least one first filter membrane may be arranged for dead-end filtration of the feed . Alternatively, the filter element and the least one first filter membrane may be arranged for cross- flow filtration of the feed .

[0064] It is understood that in dead-end filtration, the flow of feed is transverse , perpendicular, or vertical , to the filter membrane surface . In dead-end filtration the retained particles may rapidly solidi fy on the surface of the filter to form a so-called filter cake . Reducing biofilm formation in dead-end filtration thus prevents filter cake build up . It is understood that in dead-end filtration the formation and buildup of a biofilm will lead to particles and microorganisms being caught by the biofilm leading to blockage of the membrane pores resulting in a decrease in filtering ef ficiency . By reducing biofilm formation and growth, a dead-end filtration filter may operate for longer durations of time before the need for cleaning or replacing the filter .

[0065] It is understood that in cross- flow filtration the filter membrane surfaces are arranged tangential , or parallel , to the flow direction of the feed . The feed is thus pushed through the pores of the filter membrane by pressure . By the feed being tangential , or transverse , to the filter membrane surfaces , buildup of filter cake is reduced . However, in cross- flow filtration there is a risk of biofilm buildup that may impede the filter ef ficiency and service li fe .

[0066] By reducing biofilm formation and growth, a cross- flow filtration filter may operate for longer durations of time before the need for cleaning or replacing the filter .

[0067] It is speci fied above that the first filter membrane is electrically conductive . In addition, to the first filter membrane being electrically conductive , the second filter membrane , the second filter membrane , the backing layer and / or the intermediate spacer, when present in the filter element , may be conductive .

[0068] According to the second aspect , the filter element may be connected, or coupled, to a power source . The power source is thereby arranged to supply an electric current , and / or an electric potential to at least the filter element , and to at least the first filter membrane of the filter element .

[0069] According to the first aspect , the filter element may comprise an electrical connection interface that connects , or couples , the filter element to the power supply, or power source . This may allow for current to be applied to the filter element . The applied current prevents biofilm formation on at least the filter membrane or membranes of the filter element . The electrical connection interface may be formed by an electrical first connector and an electrical second connector . The electrical first connector and the electrical second connector may be arranged directly on a filter membrane or a backing layer .

[0070] The electrical first connector may be coupled, or connected, to ground and the second connector may be coupled, or connected, to positive power of the power source .

[0071] In one example , the electrical connection interface is formed by an electrical first connector coupled to positive power, an electrical second connector coupled to positive power, and an electrical third connector coupled to ground . For example , the first filter frame may form the electrical first connector, the second filter frame may form the electrical second connector, and the third frame may form the electrical third connector . The electrical connection interface , and the first connector, the second connector and / or the third connector, may thus form part of the electric network, discussed above .

[0072] Alternatively, when the filter element comprises a filter support , the electrical connection interface may be formed by the filter support itsel f .

[0073] According to the second aspect , the filter support , may be electrically coupled, or connected, to the housing . In this example , at least a portion of the filter support , such as a portion of the first filter frame , a portion of the second filter frame and / or a portion of the third filter frame , directly contacts the housing, to form an electric connection, between the housing and the filter support , or the respective filter frame or frames . The filter support may thus form part of the electric network discussed above .

[0074] It is speci fied above that the filter support may be configured to be positioned in the housing, and support the filter element in the housing . Worded di f ferently, the filter support may locate , or fixate , or mount , the filter element in the housing . In addition to the contact , between the filter support and the housing, the contact between the filter support and the housing may form an electrical connection between the filter support and the housing . This means that the filter support may fixate , or locate , the filter element relative to the housing and, in addition, form an electric connection between the filter element and the housing .

[0075] It is understood that the contact between the filter support and the housing may be a fluid tight , or fluid sealing contact , that forms a seal between the housing and the filter support . This prevents feed to bypass the filter element , and thus prevents feed to not be filtered .

[0076] It is speci fied above that the filter support may directly contact the housing, to form an electric connection, between the housing and the filter support .

[0077] Alternatively, the filter support may contact the housing via a sealing element , or gasket , or 0-ring . The sealing element itsel f may be electrically conductive and form part of the electric network discussed above . This means that a current may pass between the housing and the filter support , such as filter frame or frames , of the filter element via the sealing element . The sealing element may thus match the outline of the filter support , or the outer border, or edge , of the filter support . The sealing element may thus be an annular-shaped, or ring-shaped seal , or sealing collar .

[0078] It is further understood that the filter support may, simultaneously, contact the housing via both the sealing element , as discussed above , and via a portion of the filter support , itsel f . For example , the filter support may comprise a protrusion, or tab, that protrudes from the filter support , wherein the protrusion contacts the housing, when the filter element is arranged, or mounted, in the housing . Worded di f ferently, the protrusion may be arranged to contact and fixate the filter support relative to the housing . It is understood that the protrusion may be electrically conductive .

[0079] In a further example , the above discussed protrusion may form a separate part , that contacts both the housing and the filter support , and that the separate part is electrically conductive . In one example , the separate part is a clamping, or fixing, member, that fixates , or holds , the filter support in position, relative to the housing .

[0080] According to the first or second aspect , in one example , the first connector and the second connector may be arranged on the filter support . Worded di f ferently, the filter support may have , or comprise , the first connector and the second connector . This has the ef fect to , in addition to the filter membrane , reduce biofilm formation and growth on the filter support as well as the first filter membrane . The filter support may comprise the electrical connection interface . When the filter support comprises the electrical connection interface , the filter membrane may be electrically coupled, or connected, to the electrical connection interface of the filter support . At least the first filter membrane may be electrically coupled, or connected, to the filter support , as discussed above . For example , both the filter support and filter membrane may be conductive , and j oined by an electrically conductive j oint , such as by conductive adhesive , and an applied current may flow through both the filter support and the filter membrane .

[0081] The first connector and the second connector may be positioned, or located, at opposite sides of the filter element . For example , the first connector and the second connector may be positioned, or located, at opposite sides of the first filter membrane . The first connector may be arranged on the first filter frame and the second connector may be arranged on the second filter frame . This contributes to distribute the applied current over the first filter membrane . For example , the filter membrane may be a disc filter and the first connector may be arranged at , or about , a radial center of the disc, and the second connector may be arranged at , or about , a radial outer border of the disc . In a further example , the filter membrane may be an axial filter, having a longitudinal extension along a filter axis , and the first connector may be arranged at , or about , a first axial end of the filter membrane and the second connector may be arranged at , or about , a second axial end of the filter membrane .

[0082] It is speci fied above that the filter support material may be a composite material . It is understood that portions of the filter may be electrically conductive . It is understood that the portions of the filter support that are not electrically conductive , may be electrically insulating . For example , during moulding, or forming, of the filter support , electrically conductive additive may be added to portions of the structure forming the filter support .

[0083] The current may flow in the filter membrane transverse relative to the feed . For example , the element may be a disc filter arranged transverse to the feed, arranged for dead-end filtration . The current may flow parallel relative to the feed . For example , the filter element may be an axial filter, or a cross- flow filter, and the current may flow in the filter membrane of the filter in a direction parallel to the feed .

[0084] It is speci fied above that the filter element may have a first filter membrane and a second filter membrane . According to the second aspect , each filter membrane may be individually coupled, or connected, to the power source , by a respective electrical connection interface . The first filter membrane may be coupled, or connected, to a first electrical connection interface . The second filter membrane may be coupled, or connected, to a second electrical connection interface . This allows the power source to control the currents applied to the first filter membrane and the second filter membrane . For example , the second filter membrane may be arranged upstream the first filter membrane and thus more susceptible to biofilm formation and growth . The power source may apply a di f ferent and / or higher current to the first filter membrane to counter this ef fect .

[0085] Alternatively, the first filter membrane and the second filter membrane may share an electrical connection interface . For example , the first filter membrane and the second filter membrane may be j oined to the filter support discussed above , and the filter support may comprise the connection interface . The first filter membrane and the second filter membrane may be coupled, or connected, to the power source in parallel . The current applied over a membrane may thus depend on the overall resistance of a filter membrane . The first filter membrane and the second filter membrane may be coupled, or connected, to the power source in series . This allows the current applied to both the first filter membrane and the second filter membrane to be controlled by the power source .

[0086] In a further example according to the second aspect , the first connector and the second connector may each form part of a snap connector, or snap mount . For example , the first connector may be formed by a male or female connector, arranged on the filter membrane or the filter support , arranged to connect to a female or male connector arranged on the filter housing or filter element support . A snap connector is understood as a connector for which a pushing force must be overcome for mating the first connector part to a matching connector and a pulling force must be overcome for detaching the first connector from the matching connector part .

[0087] Alternatively, the first and second connector may each form part of a bayonet connector, or bayonet mount . The first connector and the second connector may be metal connectors laminated, or attached, to the support frame or the filter membrane. For example, the first connector and the second connector may form part of the fixings, or mounts, for fixating the filter membrane to a filter unit housing, or housing .

[0088] The first connector and the second connector may be fixed, or non-detachable, connectors. For example, the first connector and the second connector may be formed by a lead, or electric cable, soldered, or fixedly attached to the filter membrane or filter support. It is understood that the lead, or electric cable, may form part of the electric network discussed above.

[0089] According to the first aspect, the filter element may outline a cylinder or a cylindrical tube. The filter element may outline a cube, or cuboid. The filter element may outline a prism, such as a hexagonal prism. The filter element may outline a cone. The filter element may outline a circular disc or a square disk. The filter element may be rotational symmetric around a central axis. The filter element may be non-rotational symmetric around a central axis. In one example, the filter element is a cylindrical filter cartridge. In an alternative example, the filter element is a disc filter.

[0090] It is specified above that a first filter membrane has, or forms, pores arranged to filter a feed. The filter membrane may comprise pores of a size adapted, or arranged, to filter out particles or micro- or bio-organisms of a predetermined size.

[0091] The filter membrane may be a particle filter membrane, that has a pore size or diameter of the pores, or perforations, in the range of 0.01 mm to 1 mm. The filter membrane may be a microfiltration membrane, that has a pore size or diameter of the pores, or perforations, in the range of 0.1 pm to 10 pm.

[0092] The filter membrane may be an ultrafiltration membrane, that has a pore size or diameter of the pores, or perforations, in the range of 0.02 pm to 0.09 pm, or in the range of 0.02 pm to 0.05 pm.

[0093] The filter membrane may be a nanofiltration membrane, that has a pore size or diameter of the pores, or perforations, in the range of 1 nm, or 0.001 pm, to 10 nm, or 0.01 pm.

[0094] The filter membrane may be a reverse osmosis membrane, that has a pore size or diameter of the pores, or perforations, in the range of 0.0001 pm to 0.001 pm.

[0095] With decreasing pore size, the risk of blockage due to biofilm formation and growth may be increased. Thus, reducing biofilm formation and growth is particularly beneficial with pore sizes below 0.01 pm as blockage of pores with a decrease in flow rate of the filter is prevented. This reduces pumping losses and improves filtering efficiency. The electric current applied to the filter membranes may be low compared to the increased electric current needed to overcome pumping losses .

[0096] According to the third aspect, the current applied to the filter membranes may be adjusted depending on filter membrane pore size. For example, a lower current may be applied when the pore size corresponds to particle filtration microfiltration relative to nanofiltration or reverse osmosis filtration. This means that the power source may adapt the current depending on the pore size of the filter membrane of a filter element forming part of the electric network.

[0097] It is specified above that the filter element may have an electrical connection interface for applying an electrical current to the at least the first filter membrane, and that the electrical connection interface may be formed by a first connector and a second connector . According to the second aspect , the electrical connection interface may couple , or connect , to the power source . The power source may be configured, or arranged, to supply an electric current or electric potential for reducing, inhibiting, or preventing growth of microorganisms in at least the first filter membrane .

[0098] The power source may convert electric power of a first type , or form, to an output electric power . It is understood that the output electric power may be provided to the filter element .

[0099] The power source may have a first terminal and a second terminal . The first terminal may supply the current or the potential and the second terminal may be , coupled, or connected, to ground . In this context , it is understood that the potential is relative to ground . The power source may be a single-phase power source . This means that it has a single terminal supplying the current or the potential , for example by the first terminal .

[0100] The electric current may be an alternating current . It is understood that an alternating current periodically changes direction, or polarity . The alternating current may have a square wave form . This means that the peak voltage is approximately equal to the root-mean square voltage . It has been found that this type of current inhibits microbiological growth . The alternating current may be below 10 mA, below 1 mA, between 0 . 1 mA and 1 mA, or between 0 . 3 mA and 0 . 7 mA. It has been found that this current is suf ficient for inhibiting microbiological growth . The alternating current may have a frequency below 100 Hz , below 10 Hz , or below 1 Hz . The alternating current may be supplied at a peak voltage below 120 V, in the range 40 V to 100 V, or in the range 70 to 90 V. Additionally or alternatively, the alternating current may have a duty cycle of about 50 % .

[0101] In one example , the power source may be arranged, or configured, to output an electrical alternating current having a frequency in the range of 1- 100 Hz , a voltage in the range of 40- 120 V, and a duty cycle of about 50% .

[0102] Alternatively, to the current being an alternating current , the current may be a direct current . A direct current is understood to have a constant direction . The direct current may be a pulsed current . It is understood that no current is supplied between pulses . It is understood that this may prevent electrolysis in the feed or filtrate . The pulsed current may have a regular pulse frequency . The pulse frequency may be below 100 Hz , below 10 Hz , or below 1 Hz . The pulse frequency may be greater than 0 . 1 Hz . The direct current may have a duty cycle in the range 60% to 40% , or about 50% . For example , the current may be supplied with a pulse length of 500 ms with a pulse separation of 500 ms . The pulsed current may be supplied at a peak voltage below 120 V, in the range 10 V to 100 V, or in the range 20 V to 90 V, or in the range 30 V to 70 V .

[0103] The power source may be a trans former that trans forms a mains power to the above output voltage and current . Alternatively, the power source may be an inverter that converts a DC power, such as provided by a battery, to the above speci fied output voltage and current and frequency .

[0104] The output of the power source may be adj usted based on input from a sensor such as a microorganism detecting sensor arranged downstream a filter element . A microorganism detecting sensor may thus form part of the filter unit , or filter system, discussed below .

[0105] It is speci fied above that the filter element may be arranged, or housed, or encapsulated, in a filter housing, or filter casing . According to the second aspect , the housing and the filter element may thus form a filter unit , or filter system . The filter element may thereby be configured to be positioned in the filter housing . It is understood that the filter element of the filter unit may have any of the features discussed above for the filter element according to the first aspect . The housing may match the shape , or dimensions , of a filter element to allow the housing to hold a filter element . The housing may thereby form, or enclose , an inner space for holding, or retaining, the filter element , or filter elements . The housing may have a wall forming the inner space for holding the filter element , or elements . It is understood that the wall may be exposed to the feed and / or filtrate . The wall may be electrically conductive . For example , the wall may be of metal . It is understood that the housing, or wall , may be composed of several components that are connected, or j oined, together .

[0106] At least one filter element may be mounted, or installed into the filter housing, and a portion of each filter element , such as the filter support , may directly contact the housing, or the inner wall of the housing, as discussed above . Alternatively, the filter support may contact the housing via sealing element , or 0-ring, as discussed above .

[0107] The housing may form, or define , a cylinder . The housing may be rotation symmetric around a cylinder axis . The housing may have a first end wall , or first base , and a second end wall , or second base . The first end wall and / or the second end wall may be convex, or hal f-spherical . The first end wall and / or the second end wall may be transverse to the body cylinder mantle surface .

[0108] The housing may further comprise a housing support structure that fixedly supports the housing relative to a plane , such as a floor . The housing may be electrically connected to , or coupled to , the support structure . Alternatively, the housing may be electrically insulated from the support structure , or from the surroundings . This may contribute to an improved control of the electric current in the housing, and in extension to an improved reduction of microbiological growth .

[0109] The housing may have at least one inlet and at least one outlet . The inlet may be arranged to receive the feed, or liquid to be filtered . The inlet may be connected to a pipe or other fluid transport means , such as a hose , or other source of feed . The outlet may be connected to a pipe or other fluid transport means , such as a hose , and provide filtrate . Worded di f ferently, the feed may enter the inlet , be filtered by the filter element ( s ) to form filtrate and subsequently may be discharged from the housing from the outlet .

[0110] The outlet may be arranged in downstream fluid communication with, or downstream, the inlet . This means that the liquid fluid flows from the inlet to the outlet . It is understood that the outlet may be arranged downstream the inlet . This means that the outlet is arranged after the inlet relative to the flow direction of the feed, or liquid fluid . It is understood that the inlet may be arranged upstream the outlet . This means that the inlet is arranged before the outlet relative to the flow direction of feed, or liquid fluid . The inlet and the outlet may be located at opposite sides , or ends , of the housing . In one example , the inlet may be arranged at the first end wall , or first base , of the housing and the outlet may be arranged at the second end wall , or second base , of the housing . Alternatively, the inlet and the outlet may be located at the same side , or end, of the housing .

[0111] The housing may hold at least one filter element . Alternatively, the housing may hold a plurality of filter elements . Each filter element may be identical and share the same mechanical or structural properties as the other filter elements . This means that the plurality of filter elements may have filter membranes with pores of a matching, or identical si ze or diameter . It is understood that the plurality of filter elements may be electrically coupled, or connected, in series . Alternatively, the plurality of filter elements may be electrically coupled, or connected, in parallel .

[0112] Alternatively, each filter element may be di f ferent from other filter elements , in relation to mechanical or structural properties . For example , a second filter element may be arranged upstream a first filter element . The first filter membrane of the first filter element may have pores of a smaller si ze , or diameter, compared to a first filter membrane of the second filter element . The current applied to the first filter element and the second filter element may then be tuned depending on biofilm formation and growth .

[0113] The housing may further hold filter elements that do not , or lacks , electrically conductive filter membranes .

[0114] It is understood that the housing may be made of an electrically conductive material . The housing may be made of a housing material . In one example , the housing may be made from metal , such as stainless steel . The housing material may be an electrically conductive polymer . Alternatively, the housing material may be a composite material . For example , the housing may be carbon fiber comprising carbon fibers and a resin . The first filter material may comprise , or be composed of , an electrically insulating material and an electrically conductive additive . Alternatively, the first housing material may be a composite structure comprising the housing material and an electrically conductive coating material applied on the housing material . It is understood that the two materials are separate , or non-composite . In one example , the housing material may be a fiber composite material that has been coated on a housing internal surface , or inner wall , with an electrically conductive material , such as a polymer . The inner wall of the housing may thus be coated with an electrically conductive coating .

[0115] It is speci fied above that the filter element may be housed, or arranged, or installed in a housing and the filter element and the housing may be electrically coupled in an electric network .

[0116] It is speci fied above that the filter element may have an electrical connection interface for applying an electrical current to the at least the first filter membrane , and that the electrical connection interface may be formed by a first connector and a second connector . It is also speci fied above , that the filter element may be arranged in, or installed, or mounted to , the housing and the filter element may directly contact the housing, or the housing inner wall , and that the contact between the filter element and the housing inner wall may be an electrically conductive contact .

[0117] It is understood that for the above embodiment , the filter element is coupled, or connected, to the power source via the housing, and that this embodiment does not use the electrical connection interface , or connectors , discussed above . This removes the need to configure , or arrange , the filter element with a first connector and a second connector .

[0118] It is speci fied above that the housing inlet and the housing outlet may be located at opposite sides , or ends , of the housing . The electric circuit may be connected to the housing at the inlet and at the outlet . This contributes to inhibit microbiological growth on the housing between the inlet and the outlet . I f the inlet and the outlet are located at opposite sides of the housing, microbiological growth in the complete housing may be inhibited .

[0119] In one embodiment the housing may hold, or encase , at least one filter element and the filter element , or filter support , may be arranged to contact the housing, or housing inner wall , at the inlet and the outlet . Microbiological growth in the complete housing as well as the complete filter element may thereby be inhibited .

[0120] The filter system may further comprise a feed pipe connected to the inlet of the housing and arranged to lead the fluid to the inlet . It is understood that the feed pipe may be configured to provide a feed to the inlet of the housing . Similarly, the system may further comprise a discharge pipe connected to the outlet of the housing . It is understood that the discharge pipe may be configured to receive a filtrate from the housing outlet .

[0121] The feed pipe and / or the discharge pipe may be electrically conductive . For example , they may be of metal , such as steel . The feed pipe may be connected to the housing inlet via a pipe connection, and the discharge pipe may be connected to the housing outlet via a pipe connection . The pipe connection may be formed as a flange connection .

[0122] The feed pipe and / or the discharge pipe may be electrically connected to the housing, for example by directly contacting the housing . The feed pipe and / or the discharge pipe may form part of the abovementioned electric circuit . The electric circuit may be arranged to lead the current through, or via, the feed pipe and / or the discharge pipe , and / or to establish the potential over the housing via the feed pipe and / or the discharge pipe .

[0123] The electric circuit may be arranged to lead the current through and / or to establish the potential over at least a portion of the feed pipe and / or over at least a portion of the discharge pipe . This means that there may be parts of the feed pipe and / or discharge pipe through which the current does not run . The electric circuit may be arranged to lead the current through and / or to establish the potential over the complete feed pipe and / or the discharge pipe . It is speci fied above that the electrical connection interface may be formed by an electrical first connector and an electrical second connector . It is further understood that the housing may be arranged with an electrical third connector and an electrical fourth connector, arranged to be coupled, or connected, to the power source . This has the ef fect that biofilm formation, or growth, on the housing internal walls , or surfaces , may be prevented and reduced . It further has the ef fect that the electric current and / or electric potential over the housing may be di f ferent from that of the filter element , or filter elements .

[0124] It is speci fied above that the housing may hold one or a plurality of filter elements . The filter element may be a disc shaped filter element , or disc filter . The disc filter may have a diameter that matches , or conforms , to the inner diameter of a filter housing . The disc filter may be arranged for dead-end filtration . The discs are thus arranged transverse to the housing geometrical axis . The disc filters may seal against the housing and form a liquid fluid seal against the inner surface of the housing . A plurality of disc filters may be arranged in the housing in a stacked formation to form a multi filter element filter unit . The housing may house at least three disc filters , at least five disc filters , at least ten disc filters such as between ten and fi fteen disc filters .

[0125] The disc filters may be arranged, or mounted, to a central support beam, or axial fixing rod . The support beam may be aligned with the housing central axis , or longitudinally extending axis . The support beam may be supported at a first end and / or a second end of the housing . The central support beam may be connected to the first end wall and / or second end wall of the housing . The support may be electrically insulated from the housing . The disc filters may comprise a central opening matching the diameter or shape of the support beam . The disc filters may be arranged to slide onto , and along, the support beam and be fixated to the support beam . A first disc filter may be arranged at an axial distance , along the support beam, from a second disc filter by a sleeve , or a shim . The stack of a plurality of disc filters may comprises at least one sleeve , or shim, arranged between two adj acent disc filters . The central opening in a disc filter received, or placed onto , the support beam may be matched with the support beam to form a fluid tight fit and seal . This means that fluid may be prevented from flowing between the support beam and the central opening of a disc filter, and that liquid fluid is forced to flow through the plurality of pores of the filter membranes . The support beam may be made from metal , or other electrically conductive material . In one example , the support beam may be made from stainless steel . Alternatively, the support beam may be non- conductive and comprises a conductive lead arranged on or inside the support beam, arranged to be connected, or coupled to disc filters .

[0126] It is speci fied above that the housing may be made from an electrically conductive material such as stainless steel . The central support beam may form a first part of the electrical first connection interface between a disc filter and the central support beam . The housing may form a second part of the electrical first connection interface between a disc filter and the housing . This means that a voltage potential may be formed between the housing and the support beam, and an electric current is generated through the disc filters when a voltage potential between the housing and support beam is applied . This may reduce and prevent buildup of a biofilm on the disc filters .

[0127] It is understood that the filter element may be a spiral wound filter element , or spiral filter . The spiral filter may comprise at least one membrane , wound around a permeate spacer or permeate pipe . The permeate pipe may be in fluid feed connection with the inlet and may distribute the fluid received at the inlet to the membrane or membranes . The fluid may flow from the openings in the permeate pipe , radially outwards and be filtered by the membrane or membranes , to form filtrate . The filtrate may exit the spiral filter at the outermost surface , or radially outer surface , of the spiral filter . Alternatively, the filtrate may be collected in at least one intermediate spacer layer and exit the spiral filter at an axial end of the filter . The permeate pipe may be open at an axial first end and closed at an axial second, opposite , end . The permeate pipe may form, or form part of , the filter support . The permeate pipe may be made from an electrically conductive material sharing properties of the filter support material disclosed above . The permeate pipe may thus form part of the electric network discussed above . The permeate pipe may be made of the same material as the filter support . The permeate pipe may be metal such as stainless steel .

[0128] In one example , the permeate pipe may form part of the electrical connection interface of a spiral filter that is connected, or coupled, to a power supply .

[0129] The housing may house a plurality of spiral filters , arranged in parallel with the housing central axis and spaced apart at a radius from the housing axis . The housing may then comprise a wall divider, that divides the housing into an inlet space , or inlet mani fold, and an outlet space , or outlet mani fold . The wall divider may comprise a plurality of openings matching the outer circumference of the plurality of spiral filters . The wall divider may form the first connector, and may couple , or connect , to the longitudinal end first filter frame of the spiral filter . It is understood that the wall divider may form a first support to support the plurality of spiral filters at a first axial end of the spiral filters. The housing may be arranged comprising a second support for supporting the opposite second axial end of the spiral filters.

[0130] Brief description of the drawings

[0131] A more complete understanding of the abovementioned and other features and advantages of the technology proposed herein will be apparent from the following detailed description of preferred embodiments in conjunction with the appended drawings, wherein:

[0132] Fig. 1A shows a filter comprising a plurality of disc filters;

[0133] Fig. IB shows a plane view of a disc filter;

[0134] Fig. 1C shows a plane view of an alternative disc filter;

[0135] Fig. ID shows an enlarged view of the structure of the filter element of Fig. IB

[0136] Fig. 2A shows a filter comprising a single spiral wound filter;

[0137] Fig. 2B shows a cross sectional plane view along A-A of the spiral filter of Fig. 2A.

[0138] Fig. 2C a multi-layered membrane structure of the filter of Fig. 2A and 2B;

[0139] Fig. 2D shows an alternative membrane structure of the filter of Fig. 2A-2C;

[0140] Figs. 3A shows a filter with a spiral wound multi-layered membrane reverse osmosis filter element;

[0141] Fig. 3B shows a multi-layered membrane structure of the filter of Fig. 3A;

[0142] Fig. 4A shows a filter comprising a plurality of spiral filters housed in a filter housing; Fig . 4B shows a first cross sectional view along B-B of the filter assembly of Fig . 4A;

[0143] Fig . 5A shows a reverse osmosis filter arranged in a housing;

[0144] Fig . 5B shows an alternative example of the reverse osmosis filter of Fig . 5A;

[0145] Fig . 5C shows a further alternative example of the reverse osmosis filter of Fig . 5A.

[0146] Detailed description of the drawings

[0147] Fig . 1A shows a filter unit 1 comprising a power source 70 and a housing 20 that houses filter elements 30 . The filter 1 is shown housing, or encapsulating, a plurality of filter elements 30 in the form of disc filters 30 . The housing 20 is shown having an inlet 22 and an outlet 24 . The inlet 22 is connected and arranged to receive a source of feed, or liquid fluid to be filtered . The outlet 24 is connected to provide , or arranged to discharge , a filtrate , or filtered liquid fluid, from the housing 20 . The filter unit 1 is arranged to filter feed that flows from the inlet 22 , through the disc filters 30 , wherein the disc filters 30 form the filtrate from the feed . The filtrate is discharged from the filter housing 20 via the outlet 24 . The inlet 22 is arranged upstream the disc filters 30 and the outlet 24 . The outlet 24 is arranged downstream the inlet 22 and the disc filters 30 . The inlet 22 is shown as a radial , or transverse to a central housing axis A, inlet 22 . The outlet 24 is shown as a radial , or transverse to the housing axis A, outlet 24 .

[0148] The disc filters 30 are disc shaped and has a central opening arranged, or adapted, to be secured to an axial fixing rod 60 . The fixing rod 60 is shown aligned and coaxial to the housing axis A. The disc filters 30 are shown having a central first frame 32 that matches the diameter of the fixing rod 60 ( see Fig . IB ) . This allows the disc filters to be slid, or axially moved, onto the fixing rod 60 , or the first frame 32 to be received on the fixing rod 60 . The first frame 32 thereby defines an opening to receive the fixing rod 60 . The first frame 32 seals against the fixing rod 60 , to prevent flow of feed, or liquid fluid, from bypassing the disc filters 30 . In addition, the disc filters 30 have a second filter frame 34 ( See Fig . IB ) arranged at a radially outer edge 36 , or border 36 , of the disc filter 30 . The second filter frame 34 is thus arranged at a radial outer from the first filter frame 32 . The second frame 34 matches the inner diameter, and cross-sectional shape , of the housing 20 . The second filter frame 34 seals against the housing 20 and prevents feed, or liquid fluid, from bypassing the disc filters 30 . The feed is thereby forced to pass through the pores of the filter membranes 40 of the plurality of disc filters 30 .

[0149] Between disc filters 30 , a spacer 38 , or sleeve 38 , is arranged on the fixing rod 60 . The spacers 38 separate and maintains a disc filter 30 at a predetermined distance from an adj oining disc filter 30 , or a further disc filter 30 that a disc filter 30 faces . The spacer 38 is slid, or axially moved, onto the fixing rod 60 and engages an axial surface of the disc filter 30 . Thereby a stack, or row, of disc filters 30 is formed and fixed on the fixing rod 60 . In addition, a first and a second end clamp 64 , or end stop 64 , are fixed on the fixing rod 60 arranged to clamp, and hold the stack, or row, of disc filters 30 , together . The stack of disc filters thus forms part of a multi disc filter, filter unit 1 . The fixing rod is shown supported at the housing axial ends by two axial rod fixings 62 . The fixing rod 60 is electrically insulated from the housing 20 . The rod fixings 62 are non- conductive and insulates the fixing rod 60 in relation to the housing 20 . The fixing rod 60 is connected, or coupled, to the power source 70 by an electrical first cable 72 , or first lead 72 . In addition, the power source 70 is coupled, or connected, to the housing by an electrical second cable 74 , or second lead 74 . The housing 20 shown is electrically conductive and couples , or connects , to the second frame 34 of the plurality of disc filters by the housing inner mantle surface . The second frame 34 is electrically conductive and couples , or connects , to the filter membrane 40 of a respective disc filter 30 . The first frame 32 of the plurality of disc filters 30 is electrically coupled, or connected, to the fixing rod 60 . The fixing rod 60 is electrically conductive . The first frame 32 is electrically conductive . The first frame 32 of the plurality of disc filters 30 forms the first part of the electrical connection interface . The second frame 34 of the plurality of disc filters forms the second part of the electrical connection interface . When the power source applies a current and voltage to the first cable 72 , and the second cable 74 , a current is generated, and flows , through the filter membranes of the plurality of disc filters that reduces , prevents , or inhibits biofilm formation on the filter membranes . In addition, the current reduces , prevents , or inhibits biofilm formation on the filter frames 32 , 34 . A current will flow from the power source 70 , through the first cable 72 , to the fixing rod 60 . From the fixing rod 60 the current will be divided into a plurality of parallel currents that flow through each of the first filter frames 32 , through the filter membranes 40 to the second filter frames 34 of the plurality of disc filters 30 . From the second filter frames 34 of the plurality of disc filters 40 , the current will flow into the housing 20 and to the second cable 74 and back to the power source 70 . When the polarity of the applied voltage potential provided by the power source 70 is altered, the current will flow in the opposite direction in relation to what is described above .

[0150] Fig . IB shows an axial view, of one disc filter 30 of the filter 1 shown in Fig . 1A. The disc filter 30 outlines a disc . The disc filter 30 is shown having a plurality of pores 42 distributed over the filter membrane 40 . Arranged centrally at a central geometric axis of the filter membrane 40 , is the first filter frame 32 . Arranged radially outwards from the central geometric axis , along the border, or edge , of the filter membrane 40 , the second filter frame 34 is arranged . The filter frames 32 , 34 are shown manufactured by the same material as the filter membrane , and the filter frames 32 , 34 are j oined together with the membrane 40 to form an electrical connection between the frames 32 , 34 and the filter membrane 40 .

[0151] Fig . 1C shows an alternative disc filter 30 . The membrane 40 is shown divided by an electrically insulated continuous and gradually widening spiral border 82 that extends from the first frame 32 to the second frame 34 . The membrane is thus formed from a membrane strip 80 that is continuous and gradually widening spiral strip 80 that j oins the first frame 32 at a first end and j oins the second frame 34 at a second end . Since the border 82 is electrically insulated, when a voltage potential is applied between the first frame 32 and the second frame 34 , the current will flow in and along the spiral membrane strip 80 from the first end to the second end .

[0152] Fig . ID shows the membrane layer structure of the disc filter of Fig . IB . The first filter membrane 44 is j uxtaposed, or layered, or sandwiched, to a first backing layer 46 . The second filter membrane 48 is j uxtaposed, or layered, or sandwiched, to a second backing layer 50 . The second backing layer 50 is in turn j uxtaposed, or layered, or sandwiched, to the first filter membrane 44 . The feed will first be filtered by the second filter membrane 48, and subsequently by the first filter membrane 44. As shown in Fig. ID, the pores 42 of the second filter membrane 48 is a magnitude larger than the pores 42 of the first filter membrane 44. The filter element of Fig. ID is a multimembrane laminated layer filter element.

[0153] Fig. 2A shows a housing 20, that houses, or encapsulates a filter element 30' in the form of a spiral wound axial filter 30', or spiral filter 30' . The housing 20 is a cylindrical housing 20 and has a first end 26 and an axially opposite second end 28 and a mantle surface connecting the first end 26 to the second end 28. The first end 26 is defined by a first end wall 26. The second end 28 is defined by a second end wall 28. The first end wall 26 has an axial opening 22, aligned and arranged centrally around the central geometric axis A of the housing 20. The axial opening 22 forms the inlet 22 of the housing 20. The second end wall 28 comprises a further axial opening 24, arranged centrally around the central geometric axis A of the housing 20. The further axial opening 24 forms the outlet 24 of the housing 20. The inlet 22 and the outlet 24 are axial openings arranged parallel to the geometric axis of the housing 20. In addition, the inlet 22 and outlet 24 are shown being coaxial to the geometric axis A of the housing 20. The spiral filter 30' has a first end facing towards the first end wall 26 of the housing 20. The spiral filter 30' has a second end facing towards the second end wall 28 of the housing 20. The first end of the spiral filter 30' is formed by the spiral filter first frame 32' . The second end of the spiral filter is formed by the second frame 34' of the spiral filter 30' . The first frame 32' has a filter inlet 54, or opening, matching, or conforming to, the diameter of the housing inlet 22. The second frame 34' forms a filter end. A filter inlet 54 seals against the housing inlet 22 by a sleeve 76. Feed entering the housing inlet 22 is thereby guided to the filter inlet 54 and is prevented from flowing, or escaping, past the filter 30 " . The filter inlet 54 and the first frame 32 ' is positioned, or arranged, onto , or around a sleeve 76 . The filter 30 ' is shown comprising a permeate tube 66 , or pipe 66 . The membrane 40 is wound around the permeate pipe 66 . The permeate tube 66 is a rigid tube that supports the spiral wound filter 30 ' . The permeate tube 66 comprises radial openings that distribute the feed to the filter membrane 40 to improve filtration ef ficiency . The permeate tube 66 is connected to the first frame 32 ' and the second frame 34 ' . The second frame 34 ' blocks the end of the permeate tube 66 .

[0154] Fig . 2B shows a cross-sectional view along A-A of the spiral filter shown in Fig . 2A having a membrane 40 wound around the permeate tube 66 . The membrane 40 of the spiral filter 30 ' is a multi- membrane filter 40 and is shown in Fig . 2C . The multi-membrane filter 40 is formed by a plurality of layers layered, or sandwiched, together to form the multi-layered filter membrane 40 . A first membrane layer 44 is j oined at a first surface to a first surface of a first backing layer 46 facing the first surface of the first membrane layer 44 . The first membrane layer 44 is electrically conductive . The first backing layer 46 is electrically conductive . The first backing layer 46 is on an opposite surface , relative to the surface facing the first membrane layer 44 j oined to a second membrane layer 48 . The first backing layer 46 is thus layered, or sandwiched, between, and j oined to both, the first membrane layer 44 and the second membrane layer 48 . The second membrane layer 48 is electrically conductive . The second membrane layer 48 is further j oined to a second backing layer 50 . The second backing layer 50 is arranged on an opposite surface of the first backing layer 46 . Thus , the second membrane layer 48 is layered, or sandwiched, between the first backing layer 46 and the second backing layer 50. The second backing layer 50 is electrically conductive. Fig. 2C further shows a third membrane layer 52 joined to the second backing layer 50. The third membrane layer 52 is arranged on an opposite surface relative to the second membrane layer 48. The third membrane layer 52 is electrically conductive. In order the membrane layers are arranged: first membrane layer 44, first backing layer 46, second membrane layer 48, second backing layer 50 and third membrane layer 52 that together form the multilayered membrane 40.

[0155] Fig. 2D shows an alternative multi-membrane filter to the filter of Fig. 2C. The filter membrane of Fig. 2D differs by comprising a plurality of electrically insulated axial borders 82' that extend in parallel from the first frame 32' to the second frame 34' . The borders divide the filter membrane into sub-membranes 78 that are electrically insulated from each other. This means that the current in the sub-membranes 78 flows from the first frame 32' to the second frame 34' in a sub-membrane 78 and is prevented from transitioning to a neighboring, or adjacent sub-membrane 78.

[0156] Fig. 3A shows an alternative filter comprising a filter housing 20 and a filter element 30' ' housed, or encapsulated, in the housing 20. The housing 20 has the outline of a cylinder. The housing 20 comprises an inlet 22, in the form of an axial inlet 22 arranged in a first end wall 26 of the housing 20. The housing 20 further comprises an axial outlet 24, arranged on an opposite, second end wall 28 of the housing 20. The filter element 30' ' is in the form of a reverse osmosis filter 30' ' . The filter 30' ' is a multilayered membrane filter comprising a plurality of filter membranes layered, or sandwiched, together to form the filter 30' ' . The filter element 30' ' comprises an axial permeate outlet 58 coupled to, or forming part of, a permeate tube 66.

[0157] A filter inlet 32', a first outlet 34' and the permeate outlet 58 are axial outlets , parallel and aligned with a central axis A of the housing 20 . The filter element 30 " ' is arranged downstream the housing inlet 22 , and upstream the housing outlet 24 . Feed enters the inlet 22 and flow into the filter inlet 54 and flows from the filter inlet 54 to the filter outlet 56 through channels in the filter . The pressure di f ference between the filter channels and the permeate tube 66 results in that small particles pass through the membrane layers to reach the permeate tube 66 as filtrate . The filtrate is discharged from the permeate outlet 58 . The permeate outlet 58 and the feed outlet 56 are separate . Fig . 3A further shows that the filter membrane comprises an outer wrap 90 that is impermeable to the feed, such as liquid fluid . The outer wrap 90 seals the filter and prevents feed from passing past the filter element 30 " ' .

[0158] Fig . 3B shows the filter membrane of the filter of Fig . 3A, wherein the filter membrane 30 ' is formed by a plurality of layered, or sandwiched, layers . A first feed channel spacer 92 is arranged and layered onto an outer wrap (not shown) . The feed channel spacer may also be a first backing layer . The first feed channel spacer 92 allows feed to flow from the filter inlet to the filter outlet . The feed channel spacer 92 provides structural strength to the filter element and prevents filter element collapse . Arranged and layered on the first feed channel spacer 92 is a first membrane layer 94 . Arranged and layered on the first membrane layer 94 is a permeate collection layer 96 , or intermediate spacer 96 . Arranged and layered on the permeate collection layer 96 is a second membrane layer 98 . The permeate collection layer 96 is thus layered, or sandwiched, between the first membrane layer 94 and the second membrane layer 98 . Arranged and layered on the second membrane layer 98 is a second feed channel spacer 100 , or second backing layer 100 . The filter membrane is wound around the permeate tube 66 . Feed enters the first feed channel spacer 92 and the second feed channel spacer 100 and is filtered by the first membrane layer 94 and the second membrane layer 98 and the filtrate is collected by the permeate collection layer 96 and flow to the permeate tube 66. From the permeate tube 66 the filtrate transported to and discharged from the permeate outlet 58. The unfiltered feed is discharged from the spiral filter by the filter outlet 56.

[0159] Fig. 4A shows a filter 1 comprising a housing 20' that houses a plurality of axial filters 30' . The housing 20' is shown having a central axial inlet 22 arranged in a first side wall 26 of the filter housing 20' . In addition, the housing comprises an axial outlet 24 arranged in the second end wall 28 of the filter housing 20' . The second end wall 28 is arranged on an opposite side of the housing 20' from the first end wall 26. In addition, the housing 20' has a divider 84, or dividing wall 84, dividing the housing 20' into an inlet section 102, or inlet manifold 102, and an outlet section 104, or outlet manifold 104. The divider 84 has a plurality of divider sleeves 86 arranged around the central axis of the housing 20. The plurality of sleeves 86 are each in fluid communication with the housing inlet 22 and with a filter inlet 54 of a respective filter 30' . The feed, after entering the housing inlet 22, is collected in the inlet section 102 and divided into a plurality of feeds by the divider wall 84. Each divided feed subsequently flows through a sleeve 86 and enters a respective filter element 30' inlet 54. The divided feeds are filtered through the filter elements 30' and forms filtrate. Downstream the filters 30' the filtrate is collected in the outlet section 104, or outlet manifold 104, and is provided to the housing outlet 24, wherein the filtrate is discharged from the filter housing 20 and filter 1. The filter elements are axial multilayered filter elements 30', sharing structure with the axial filter disclosed in relation to Fig. 2A. The power source 70 is coupled, or connected, to the divider wall 84 by a first cable 72, or lead 72. The divider wall 84 is electrically conductive and in electrical contact with the first filter frame of the plurality of filter elements 30" . The second filter frame of the plurality of filter elements 30' is coupled, or connected, to the power source 70 by a second cable 74, or lead.

[0160] Fig. 4B shows a cross-sectional view along B-B showing the divider wall 84 and the plurality of sleeves 86 arranged around the central axis of the housing 20' . Each sleeve 86 is in fluid connection with the filter inlet 54 of a respective filter element 30' .

[0161] Fig. 5A shows a further example of a filter 1, or filter unit 1, wherein the filter 1 is a reverse osmosis filter. The filter 1 comprises a housing 20, that holds a reverse osmosis filter element 30' ' . The housing has an inlet 22 and two outlets 24, 24' . One of the inlets 24 is arranged to discharge filtrate, or permeate, and the other of the inlets 24' is arranged to discharge concentrate, or the fluid containing undesirable content of the feed that has not passed through the membranes within the reverse osmosis filter element 30' ' .

[0162] The reverse osmosis filter element 30' ' is cylindrical shaped and matches the shape of the housing 20. The housing 20 is thereby also cylindrical shaped. The reverse osmosis filter element 30' ' has a first filter frame 32' and a second filter frame 34' arranged, or positioned, at two opposite ends of the reverse osmosis filter element 30' ' . The first filter frame 32' is at least partially electrically conductive and electrically coupled, or connected, to the reverse osmosis filter element membranes. The first filter frame 32' and the second filter frame 34' contacts, and seals, against the inner wall 112 of the housing 20 via a filter seal 106. The seal 106 thereby prevents feed to bypass the reverse osmosis filter element 30" ' . The seal 106 is an annular seal, that seals between the perimeter of the first filter frame 32' and the inner wall 112 of the housing 20 and between the second filter frame 34' and the inner wall 112 of the housing 20. The seal 106 is a conductive seal, that is electrically conducting, or adapted to conduct an electric current .

[0163] The housing 20 is coupled, or connected, to the power source 70 by a first cable 72, or lead 72, and a second cable 74, or lead 74. The first cable 72, and the second cable 74, connect to the housing via housing power connectors 106, 108.

[0164] Fig. 5B shows a further example of the filter unit, or filter 1, of Fig. 5A. In Fig. 5B the housing is coupled, or connected, to the power source 70 by the first cable 72, or lead 72, and the second cable 74, or lead 74. In addition, the housing is coupled, or connected, to ground via a housing ground connector 110. The power source is arranged to provide an alternating current or a direct current via the first cable 72, or lead 72, and the second cable 74, or lead 74. The housing 20 itself is grounded by the housing ground connector 112. For example, the housing ground connector 112 can be a separate ground connector, or the housing ground connector 112 can be formed via a housing support element, such as a housing stand (not shown) .

[0165] Figs. 5A-5B shows the power source coupled, or connected, to the housing and not directly to the filter element. In the examples, the filter element is coupled, or connected, to the housing via a seal. The reverse osmosis filter element 30' ' shown in Fig. 5A-5B may be replaced with any of the other filter element exampled discussed above, wherein electrical connection between the housing element and the filter element is made via a seal 106.

[0166] Fig. 5C shows another example of the filter 1 of Fig. 5A wherein the filter housing inlet 24 is fluidly coupled to a feed pipe 114 . The feed pipe 114 provides feed for the filter to filtrate . The housing outlet 24 ' is fluidly coupled to a discharge pipe 116 . The feed pipe 114 is coupled, or connected, to the power source 70 via a first the first cable 72 , or lead 72 , and the discharge pipe is coupled, or connected, to the power source via the second cable 74 , or lead 74 .

[0167] Item list

[0168] 1 filter unit , filter

[0169] 20 housing

[0170] 22 inlet

[0171] 24 , 24 ' outlets

[0172] 26 housing first end

[0173] 28 housing second end

[0174] 30 disc filter element

[0175] 30 ' spiral filter element

[0176] 30 ' ' reverse osmosis filter element

[0177] 32 , 32 ' first filter frame

[0178] 34 , 34 ' second filter frame

[0179] 36 outer edge , or border

[0180] 38 spacer, or sleeve

[0181] 40 filter membrane

[0182] 42 pores

[0183] 44 first filter membrane

[0184] 46 first backing layer

[0185] 48 second filter membrane

[0186] 50 second backing layer

[0187] 52 third membrane layer 54 filter element inlet 56 filter element outlet 58 filter element permeate outlet 60 fixing rod, support beam 62 rod fixings 64 end clamps , end stop

[0188] 66 permeate tube

[0189] 68 feed channel

[0190] 70 power source

[0191] 72 first cable , or lead

[0192] 74 second cable , or lead

[0193] 76 sleeve

[0194] 78 sub-membrane

[0195] 80 spiral membrane

[0196] 82 spiral border

[0197] 84 divider

[0198] 86 divider sleeve

[0199] 88 wrap

[0200] 90 multi-layered reverse osmosis membrane

[0201] 92 feed channel spacer, first backing layer

[0202] 94 first filter membrane

[0203] 96 permeate collection layer, intermediate spacer

[0204] 98 second filter membrane

[0205] 100 feed channel spacer, second backing layer

[0206] 102 inlet mani fold

[0207] 104 outlet mani fold

[0208] 106 filter seal

[0209] 108 , 110 housing power connector

[0210] 110 housing ground connector

[0211] 112 housing inner wall

[0212] 114 feed pipe

[0213] 116 discharge pipe

[0214] 118 pipe coupling

Claims

CLAIMS1. A filter element, or filter media, configured to be positioned in a filter housing, and to form a filtrate from a feed, the filter element comprising a first filter membrane that has, or forms, pores arranged to filter the feed, wherein the first filter membrane is electrically conductive, and a filter support configured to be positioned in the housing, and support the filter element in the housing, wherein the first filter membrane is electrically coupled to the filter support.

2. The filter element of claim 1, wherein the filter support comprises an electrical connection interface configured to connect, or couple, the filter element to a power supply.

3. The filter element of claim 2, wherein the filter support forms, or has, the electrical connection interface.

4. The filter element of claim 1-3, wherein the filter membrane is a mono-membrane, or single membrane, filter.

5. The filter element of any of claims 1-4, wherein the first filter membrane forms a self-supporting continuous structure.

6. The filter element of claims 1-4, wherein the filter element further comprises a second filter membrane, and the first filter membrane and the second filter membrane are, layered, or sandwiched, together to form a multi-layered filter membrane, wherein the second filter membrane contacts the first filter.

7. The filter element of claim 6, wherein the first filter membrane and the second filter membrane are both electrically coupled, or connected, to the filter support.

8. The filter element of any of claims 1-7, wherein the filter element comprises a first backing layer that is juxtaposed, or jointly forms, a layered, or sandwiched, structure together with the first filter membrane.

9. The filter element of any of claims 1-8 when dependent on claims 2-3, wherein the filter support is formed by a first filter frame and a second filter frame that forms the electrical connection interface.

10. The filter element of claims 9, wherein the filter element is a spiral wound filter element, or spiral filter, comprising the first filter frame arranged at a first axial end of the filter element and the second filter frame arranged at a second axial end of the filter element.

11. The filter element of claim 9-10, wherein the first filter frame has, or forms, an electrical first connector and the second filter frame has, or forms, an electrical second connector .

12. A filter unit, or filter system, comprising: a housing, or casing, a power source, and a filter element according to any of claims 1-11, wherein the housing houses, or encapsulates, the filter element and has at least one inlet arranged to receive a feed, and at least one outlet, arranged to discharge, or release, filtrate, wherein the filter is arranged to form the filtrate from the feed, and wherein the power source is arranged to apply an electric current to the filter element for reducing biofilm formation .

13. The filter unit of claim 12, wherein the housing is electrically conductive and the power source is coupled, or connected, to the housing.

14. The filter unit of claim 12-13, wherein the power source is directly coupled, or connected, to the filter support of the filter element.

15. The filter unit of claim 12-13, wherein the filter support is coupled, or connected, to the power source via the housing .

16. The filter unit of claim 15, wherein the filter support comprises a sealing element that is electrically conductive and the filter support is coupled, or connected, to the housing via the sealing element.

17. The filter unit of claims 12-16, wherein the housing defines, or outlines, a cylinder having a first axial end and a second axial end, wherein the filter support is electrically coupled, or connected, to the housing, at the first axial end and the second axial end of the housing.

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