Abstract:
Filter assemblies and fluid flow inhibitors that are particularly well suited for use in centrifugal separation enhanced filtration devices are described. Moreover extensible filter assemblies are described. In one aspect of the invention, extensible filtration assemblies can be used to operate in circulating fluid filtration devices. Such extensible filter elements can use fluid manifold to reduce the effects of fluid circulation inside filter elements and to reduce reverse flow problems in such filters. Additionally, indexable filter elements and invertable filtration elements can be used to extend filter life in filtration in filtration devices.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority of U.S. Provisional Patent Application No. 61/421,095 filed Dec. 8, 2010, which is incorporated herein by reference in its entirety. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention generally relates to hydroclone filter cleaning assemblies and chamber manifolds for use in centrifugal separation enhanced filtration. In one aspect, extensible filter assemblies are discussed. The described devices may be used in a variety of water treatment, fluid filtering and particle separation applications. 
       BACKGROUND OF THE INVENTION 
       [0003]    The present invention generally relates to hydroclone filter systems, methods and apparatus. The described devices may be used in a variety of water treatment, fluid filtering and particle separation applications. 
         [0004]    A wide range of technologies are currently used to treat, purify and/or filter water. Many such technologies require a relatively large amount of physical space and/or require the use of consumable filters that add to operational costs. For example, many drinking water treatment applications utilize settling ponds in combination with a series of screens and filters of progressively decreasing pore size to remove suspended solid particles from water. 
         [0005]    In other applications cyclonic separators or hydroclones have been used to separate suspended particles from water and other fluid mediums. Hydroclones operate by introducing water into a conically shaped chamber to create a vortex within the chamber. Generally, the influent water is introduced near the top of a conical chamber and an effluent stream is discharged near the bottom of the chamber. Centrifugal force tends to cause heavier particles to move towards the periphery of the vortex. As a result the water near the center of the vortex tends to be cleaner than water at the periphery of the vortex. Thus, relatively cleaner water can be drawn from a central region of the hydroclone. By way of example, U.S. Pat. Nos. 3,529,724; 5,407,584, 5,478,484, and 5,879,545 all describe various hydroclone designs. 
         [0006]    Although hydroclones have been used to remove suspended particles from water in a variety of applications, existing hydroclones are generally not well suited for filtering applications that require the removal of relatively small sized particles from large volumes of water. Therefore, hydroclones are typically not used to pre-filter drinking water or in a wide variety of other applications due to limitations in their filtering ability. 
         [0007]    Although existing water filtering systems and existing hydroclones work well for their intended uses, there are continuing efforts to provide improved and/or more cost effective purification and/or filtering devices that can meet the needs of various specific applications. 
       SUMMARY OF THE INVENTION 
       [0008]    Filter assemblies that are flexible in use and adaptable to a wide range of contamination environments are desirable and well suited to aspects of centrifugal separation enhanced filtration devices which are described as follows. 
         [0009]    In one aspect of the invention, a centrifugal separation enhanced filtration device is described. Such devices include a hydroclone tank having a number of fluid inlets and outlets that provide an inlet for fluid requiring filtration, a filtered fluid outlet arranged to extract filtered fluid from a filter assembly, an effluent outlet and an internal chamber having arranged to enable a circulating fluid. The device also includes a cleaning assembly that rotates around the filter to assist cleaning of the filter. In one particularly advantageous implementation, the device further includes a plurality of filter stages including a first and supplementary stage arranged such that the filtered fluid outlet can extract filtered fluid from the filtered fluid chamber of the first stage. Moreover, the staged filter is arranged such that each supplementary stage is in communication with the filtered fluid chamber of the first stage but not with other supplementary stages. 
         [0010]    In one aspect, the supplementary stages include associated manifolds that prevent direct fluid circulation from a supplementary stage to an adjacent stage comprises a connector enabling filtered fluid communication between the first stage and the filtered fluid chamber of each supplementary stage. 
         [0011]    In another aspect, the filter assembly comprises an extensible filter assembly that can be adjusted in its filter capacity. Additional stages can be added to the assembly or stages can be removed at need. Thus, the staged filter assembly comprises an extensible filter assembly configured to enable additional supplementary filter stages to be added or removed from the staged filter assembly. It is pointed out that each of these added stages can include manifolds to control fluid flow in the system. 
         [0012]    In another aspect, centrifugal separation enhanced filtration devices comprise pressure management systems used to balance and/or optimize pressure in the filtration device to enhance filter efficiency. 
         [0013]    In another aspect, centrifugal separation enhanced filtration devices comprise rotation control systems that manage the rotation rate of the rotating cleaning assembly to adjust rotation rate to optimize filtration and/or cleaning performance. 
         [0014]    In another aspect, centrifugal separation enhanced filtration devices systems and filter assemblies comprise flexible and reorientable filter assemblies that can enable reduced filter wear by rotation and readjustment of filter orientation are also disclosed in the patent. 
         [0015]    In another aspect a staged filter assembly is disclosed. The assembly can include a plurality of filter stages including a first stage and at least one supplementary stage. Each filter stage can include a frame element and an associated filter membrane defining therein a filtered fluid chamber. The assembly configured such that the filter stages are stacked concentrically one upon another. And such that each supplementary stage is in fluid communication with the first stage and configured such that fluid from one supplementary stage cannot communicate with fluid from another supplementary stage. In one aspect, this can be facilitated using manifolds associated with the stages. Such that a manifold prevents direct fluid circulation from a supplementary stage to an adjacent stage. In one approach, a manifold comprises a connector enabling filtered fluid communication between the filtered fluid chamber of the first stage and the filtered fluid chamber of each supplementary stage. Additionally an isolation member can work cooperatively with a connector to enable the inhibition of direct chamber to chamber filtered fluid flow while enabling filtered fluid flow from all chambers to the filtered fluid chamber of the first stage. 
         [0016]    In another aspect, such filter assemblies are extensible as needed, by adding or removing supplementary filter stages with or without associated manifolds. 
         [0017]    The described filtration devices and filter assemblies are particularly well suited for use in operating centrifugal separation enhanced filtration devices including hydroclone filtration devices, cylindrical centrifugal enhanced filtration device, and other cross-flow filtration applications. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]    The invention, together with further objects and advantages thereof, may best be understood by reference to the following description taken in conjunction with the accompanying drawings in which: 
           [0019]      FIG. 1  is a diagrammatic external perspective view of a closed hydroclone based filtering system in accordance with an embodiment of the invention; 
           [0020]      FIG. 2  is a diagrammatic cross-section view of a closed hydroclone based filtering system in accordance with an embodiment of the invention; 
           [0021]      FIG. 3  is an exploded view of an example filter assembly and an associated cleaning assembly separated into conveniently described components in accordance with an embodiment of the invention; 
           [0022]      FIG. 4(   a ) is a diagrammatic perspective view of a cleaning assembly including a set of drive paddles as described herein; 
           [0023]      FIG. 4(   b ) is a diagrammatic cross-section view of an embodiment of a cleaning assembly paddle and cleaning element arranged in an operative arrangement with a filter element in accordance with an aspect of the present invention; 
           [0024]      FIG. 4(   c ) is a diagrammatic plan view of a fluid bearing suitable for supporting a cleaning assembly as it is rotated about a filter assembly in accordance with an embodiment of the present invention; 
           [0025]      FIG. 5(   a ) is a perspective view of a filter assembly nested inside a cleaning assembly as it would be in one embodiment of an operating arrangement of the hydroclone; 
           [0026]      FIG. 5(   b ) is a top down view of the nested filter assembly and cleaning assembly showing how a vortex flow can rotate the cleaning assembly around a filter assembly in one embodiment of the hydroclone; 
           [0027]      FIG. 5(   c ) is a top down view of a portion of a cleaning assembly and one embodiment of an associated particulate tolerant fluid bearing illustrating an angled orientation for the paddles and magnetic marker; 
           [0028]      FIGS. 5(   d )- 5 ( e ) are diagrammatic side section views of filter and associated rotating cleaning assemblies illustrating certain types of uneven wear patterns that can occur in some embodiments of the invention; 
           [0029]      FIG. 6(   a ) is an exploded diagrammatic view illustrating one embodiment of a filter assembly with removable and re-attachable lid and bottom in accordance with an embodiment of the invention; 
           [0030]      FIGS. 6(   b )- 6 ( d ) are various diagrammatic top views illustrating various wear patterns and the effect of filter rotation to compensate for the wear in accordance with some embodiments of the invention; 
           [0031]      FIG. 7(   a ) is a diagrammatic side section view of a portion of a hydroclone based filtering system arranged in a hydroclone chamber and illustrating the extensible filter stages and connectors in one embodiment of an upper influent inlet: 
           [0032]      FIG. 7(   b ) is an exploded view of the hydroclone embodiment shown in  FIG. 7(   a ); 
           [0033]      FIG. 7(   c ) is a simplified top down view of the hydroclone embodiment with manifold in an operative arrangement such as shown in  FIG. 7(   a ); and 
           [0034]      FIG. 7(   d ) is a diagrammatic side section view of a filter frame and bottom portion showing an embodiment of an engagement feature of a hydroclone embodiment in accordance with the principles of the present invention. 
       
    
    
       [0035]    The depictions in the figures are diagrammatic and not to scale. Additionally, the drawings depicted are illustrative examples and are not intended to limit the invention. 
       DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0036]    The present invention generally relates to fluid filtration systems and to mechanisms for improving the filtration of such systems. A variety of methods and systems for providing extensible filter systems and filter cleaning approaches are also described. Also, extensible filter elements are described that can be added to and staged within a hydroclone chamber. 
         [0037]    The assignee of the present invention has developed a hydroclone filter system that is well adapted for a wide variety of liquid filtering and particle separation applications. Various aspects and modifications of such a system are described in some detail in U.S. Pat. Nos. 7,632,416, 7,896,169 and pending U.S. application Ser No. 13/163,537, U.S. Application Nos. 61/421,095, and 61/483,221, each of which are incorporated herein by reference. 
       General Explanation of Hydroclone Operation 
       [0038]    Hydroclone based filtration systems in accordance with selected embodiments of the present invention are diagrammatically illustrated in  FIGS. 1-3 . As seen in  FIG. 1 , the hydroclone based filtration system  100  includes a housing  103  having chamber walls  105  and a lid  109 . The chamber walls  105  define a tapered (frusto-conically shaped) fluid compartment  106  with the lid  109  arranged to cover the fluid compartment  106 . The housing  103  can be supported by a stand  111  that can take any suitable form. In some embodiments, the hydroclone may not require a stand at all. 
         [0039]    A filter assembly  120  is positioned within the fluid compartment  106 . The filter assembly  120  includes filter element  122  generally comprising a cross flow filtration membrane although not limited to such. In the embodiment illustrated in  FIG. 2 , the filter element  122  has a substantially cylindrical shape. However, in other embodiments, the filter may incorporate any of a variety of geometries. By way of example, the filter element  122  may be generally conical, frusto-conical, stepped, cylindrical, or any of a variety of other suitable shapes. The filter assembly is positioned centrally within the fluid compartment  106  so that the filter is spaced apart from the peripheral chamber walls  105 . The region between the chamber walls  105  and the filter element  122  is defined as a hydroclone chamber  110  and the region in the central region of the filter is defined as a filtered fluid chamber  112 . 
         [0040]    The filter assembly  120  includes a surface filter membrane  121  configured to serve as a cross-flow surface filter. The filter membrane  121  may take the form of a micro-filter having a multiplicity of fine elongate filtration apertures suitable for filtering very minute particulate from a fluid. One such filter element is discussed in more detail in the &#39;416 patent (which is incorporated herein by reference). 
         [0041]    Referring to  FIG. 3 , functionally the hydroclone  100  has four main openings. As shown here a fluid inlet  101  located at the wide (upper) end of the hydroclone chamber  110 , an effluent outlet  133  located at the narrow (bottom) end of the hydroclone chamber  110 , a reflow outlet  137  also located at a lower portion of the hydroclone chamber  110 , reflow outlet  137  being configured to recirculate unfiltered fluid from the chamber  110  (e.g., unfiltered influent), and a filtered fluid outlet  136  arranged to remove filtered fluid from filtered fluid chamber  112 . In this embodiment, the filtered fluid outlet  136  is arranged near an upper end (commonly the lid  109 ) of the housing  103 . The fluid inlet  101  is preferably arranged to impel a tangential flow to the incoming fluid  131 . In one example (such as shown by inlet  101  of  FIG. 1 ) an offset inlet  101  provides a suitable approach. Thus, fluid entering  131  the hydroclone chamber  110  flows substantially tangentially into a region at the wide (top) end of the fluid compartment  106  between the chamber wall  105  and the filter  120  and generally moves through the hydroclone chamber  110  in a swirling vortex towards a bottom portion of the chamber  110  such that it can drain into an outlet portion  102  of the hydroclone  100 . This portion of the chamber  110  which defines a region where the circulating vortex of fluid is operative can also be referred to as a fluid circulating region. Some of the fluid entering the hydroclone chamber will pass through the filter assembly  120  into the filtered fluid chamber  112 . Filtered fluid (e.g., clean water) exits the filtered fluid chamber through the filtered fluid outlet  107 . Any fluid in the hydroclone that does not pass through the filter  120  exits the hydroclone chamber  110  through the effluent outlet  102  or the reflow outlet  104 . 
         [0042]    The filter assembly  120  includes a surface filter  121  that is designed to prevent the entry of particles into the filtered fluid chamber  112 . In one implementation, the filter can comprise a cross-flow filtration membrane. To continue, a circulating fluid flow is arranged to flow tangentially across the filter surface to help prevent particulate matter from entering the internal filtered fluid chamber. Such tangential flow of the feed stream across the filter surface is referred to as cross flow filtration. 
         [0043]    By way of general description, the filtering characteristics of the described system can be varied significantly by controlling, among other things, the relative flow rates of the effluent  102  and filtered fluid  107  outlets as well as differential pressures between chamber  110  and  112 . Additionally, system efficiencies and the concentrating characteristics of the system can be varied significantly by recirculating at least some of the effluent stream back into the hydroclone (e.g., using reflow line  104 ) and by controlling the relative rates and nature of such feedback. 
         [0044]    There are a number of aspects of the illustrated hydroclone that make it work particularly well for fluid filtration applications. Generally, the device creates a fluid vortex causing heavier particles to migrate towards the exterior of the vortex, while lighter materials (e.g. cleaner liquids) tend to move towards the center of the vortex. With this arrangement, an effluent outlet near the bottom of the separator can be used to remove the particles, while an outlet that draws from a central region of the separator can be used to remove a more particle free liquid. In this implementation of a hydroclone based separator, the process is enhanced by using a filter assembly  120  to further separate the particles and other contaminants from the center region  112  of the hydroclone. Thus, the introduction of a central filter can be quite effective at improving the cleanliness of the discharged clean water. 
         [0045]    A wide variety of filters  120  can be used within the hydroclone and their physical size, geometry and pore size may all be widely varied. Although a wide variety of different filter designs may be used within the hydroclone a few specific filter designs that are particularly well adapted for use in the hydroclone are briefly described below. 
         [0046]    Generally, it is preferable to use a surface filter that blocks particles at the surface of the filter rather than a standard depth filter that collects particulates within the filter itself. As will be described in more detail below, the use of a surface filter facilitates self-cleaning and thus reduces the overall maintenance of the device since the surface filters do not need to be replaced as frequently as depth filters would typically need to be replaced. Such a surface filter can comprise many types. However, in one embodiment a surface filter comprises a plurality of elongate apertures. In a particular embodiment the elongate filter apertures are arranged such that a long axis of the apertures is vertically arranged. Thus, the narrow dimension of the apertures extends horizontally thus the tangential inflowing fluid  131  flows perpendicular to the long axis of the apertures. It is also possible that the pattern of apertures is slanted instead of vertical. By way of example, electroformed surface filters work well. Aperture dimensions can be widely varied. Embodiments having openings in the range of about 1-500 microns have been found to work well in a number of applications. For example, elongated (slot-like) apertures having a surface width in the range of 5 to 50 microns and a length in the range of 100 to 500 microns tend to work well. In one specific application, slots having a width of about 20 microns and a length of about 400 micron are used. Of course, these particular dimensions can be widely varied to meet the filtering requirements of any particular application. By way of example, some specific electroformed filter membranes that are well suited for use in hydroclone applications are described in the &#39;416 patent. As will be appreciated by those of familiar with the art, other configurations and dimensions can be used as well. It is important to point out that the invention is not limited by type or capabilities of filtration elements or membranes. 
       The Filter Assembly 
       [0047]      FIG. 2  is a cross sectional view of a hydroclone cleaning apparatus constructed in accordance with one embodiment of the invention. In particular, the cleaning apparatus includes a single stage cylindrical filter assembly  120 . Further,  FIG. 3  is an exploded view of a filter assembly  120  and an associated cleaning assembly  300  suitable for use within the hydroclone  100 . The filter assembly  120  and cleaning systems are designed to be easily assembled and disassembled. Additionally, they are designed to be modular so that the filtering capacity of the hydroclone may readily be adjusted to meet the needs of any particular application. 
         [0048]    The illustrated filter assembly  120  generally includes a surface filter membrane  121  that extends circumferentially around a frame  311 . In some embodiments, a cylindrical surface filter membrane  121  is positioned about an outer surface of cylindrical frame  311  of the filter assembly  120  to form a cylindrical surface filter. Alternatively, a rectangular strip of filter material can be wrapped around the frame  311  and adhered or otherwise attached to form the filter. Additionally, a cylindrical filter membrane  121  can be arranged near an outer portion of the cylindrical frame  311  in any manner such that it provides a seal between the inner filter chamber and the outside of the filter assembly  120 . 
         [0049]    An end plate  124  is attached to one end (i.e., the bottom face) of the frame and an attachment ring  310  is secured to the other end of the frame. Thus, the bottom plate  124  seals the bottom of the frame  311 . A seal  126  is provided on the upper surface of the attachment ring  310 . In the one stage filter that is shown, the seal  126  engages with the lid  109  at the top surface  125  of the filter  120  to seal the top of the filter. An opening in the center of the attachment ring enables connection with the filtered fluid outlet  107 . 
         [0050]    Surface filters are arranged to block particulates contained in a feed stream at the surface of a filter membrane rather than trapping the particulates within a filter bed. During use, the filter pores will sometimes become blocked by particulates in the feed stream that are caught at the surface filter. The amount of blockage tends to increase the longer the filter is used so that over time, the filter throughput tends to degrade. Therefore, it is typically necessary to at least periodically clean the surface filter. 
         [0051]    During operation of the hydroclone filter, the filter pores will sometimes become blocked by particulates in the feed stream within the hydroclone. U.S. Pat. No. 7,632,416 (which is incorporated herein by reference) describes the use of a circulating cleaning assembly positioned within the hydroclone region to help continually clean the exterior (feed side) surface of the filter membrane during operation of the hydroclone. The circulating cleaning assembly has been found to be very useful in extending the operational span of the filter before the filter becomes blocked. The described embodiments also incorporate a circulating cleaning assembly  300 . 
         [0052]    In the illustrated embodiments, the cleaning unit is integrated with the filter assembly such that the combined filter assembly/cleaning assembly can readily be inserted into and removed from the fluid chamber  106  as a single unit. In other embodiments, the components can be installed separately. The combined assembly  120 / 300  can be mounted on the lid  109  such that the whole filter unit is inserted into and removed from the fluid chamber  106  as a single unit with the opening and closing of the lid  109 . One such arrangement is illustrated in  FIG. 2 . Preferably, the filter assembly is sealed relative to the lid  109  so that fluid within the hydroclone chamber  110  can not enter the filtered fluid chamber  112  without passing through the filter membrane. In one approach an upper support surface of the filter assembly has a seal  126  configured to engage with a mated portion of the lid  109 . Thus, fluid cannot flow into chamber  112  unless it flows through the filter assembly  120  first. 
         [0000]    Integration of Cleaning Structure with Filter Element 
         [0053]    In the embodiment illustrated in  FIG. 3 , the cleaning assembly  300  comprises a generally circular structure encompassing a robust bearing support  315 , a plurality of cleaning structures  312 , a plurality of paddles  313 , and a support ring  314 . The bearing comprises a substantially rigid particulate tolerant fluid bearing  315  that provides a robust cleaning assembly. In general, several cleaning structures and paddles  312 / 313  are supported by the bearing  315  and the support ring  314  to enable rotation of the cleaning assembly  300  around the filter  120  during use of the hydroclone. The paddles are arranged to extend out into the circular fluid flow path within the hydroclone chamber so that during use, the fluid vortex drives the cleaning assembly about the filter. Although a particular cleaning assembly is shown, it should be appreciated that a wide variety of different cleaning assembly and paddle structures can be employed in alternative embodiments. It is pointed out that this structure  300  is more ruggedly built than prior art technologies providing more a tight fit and improved alignment with an associated journal surface or race such a the prior art embodiments which have a more flexible counting configuration. 
         [0054]    In one embodiment, the paddles  313  can be configured to support cleaning structures  312  such that a cleaning surface of the cleaning structure is in contact with or is positioned an operative distance from the filter  121 . The operative distance is variable depending on the nature of the cleaning structure  312  (e.g., brushes, squeegees, and other such surface cleaning apparatus). In some embodiments, a direct contact between the cleaning surface  312  and the filter  121  provides an optimal operational distance. However, in other approaches, a small separation distance between the filter  121  and the cleaning surface  312  can be preferred. 
         [0055]    Although single piece paddle assemblies can be used. However, in the depicted embodiment, a mated pair of paddle sub-assemblies  313   a  are used together to secure an associated cleaning structure  312  in place. The paddle sub-assemblies can be adhered or otherwise coupled together by a number of fasteners or fastening devices (screws, mounting pins, rivets, and so on). Such fastening can be used to secure the cleaning structures in place although many alternative arrangements of supporting the cleaning structures will be apparent to those of ordinary skill. It is specifically pointed out that other embodiments can employ single piece paddle structures or other suitable paddle and cleaning element structures. 
         [0056]      FIG. 4(   a ) shows an assembled cleaning assembly in more detail. As shown, a plurality of paddles  313  support a plurality of cleaning surfaces  312 . The paddles  313  engage with a support ring  314  and also engage with a bearing  315 . The bearing  315  facilitates rotation of the cleaning assembly  300  about the filter assembly. The support ring  314  provides stability to the cleaning assembly  300 . It should be pointed out that although depicted here ( FIG. 4(   a )) as twelve ( 12 ) paddles  313  arranged about a robust bearing  315 , each paddle associated with an associated cleaning element  312  of the configurations are contemplated. For example, embodiments where there are more paddles  313  than cleaning elements  312  can be used. In fact one advantageous implementation uses 24 paddles while using only 12 cleaning elements. 
         [0057]      FIG. 4(   b ) is a more detailed side view of an assembled paddle  313  which shows the arrangement of the cleaning structure  312  as it is journaled about a bearing  310  of the cleaning filter assembly  120  and the filter membrane  121  and further depicts the attachment of a paddle  313  to the bearing  315 . In this embodiment, the paddle  313  is engaged with a mated slot in the bearing  315  to secure the paddle with the bearing. Thus, an inner facing surface  315   a  of the bearing  315  is arranged in a journaled position enabling rotation about a support surface  310   a  of attachment ring  310  of the filter assembly enabling the cleaning structure  312  to remain operative to clean the surface filter  121  as it rotates about the filter assembly. Thus, the attachment ring support surface serves as a race for the bearing  315 . 
         [0058]    Returning to a discussion of  FIG. 4(   a ), the cleaning assembly  300  includes a plurality of assembled paddles  313 , each having a cleaning structure  312  arranged in a generally circular configuration. The paddles  313  are engaged with a support ring  314  and also engaged with a bearing  315  that will enable rotation of the cleaning assembly  300  about the filter assembly  120 . The engagement features  318  of the paddles  313  are coupled with receiving slots  317  of the bearing to form a stable support structure. 
         [0059]      FIG. 4(   c ) provides a view of the bearing  315  as viewed from the top. The bearing  315  includes a number of receiving slots  317  arranged about its circumference to engage with associated paddles  313  as shown and described previously. The inner surface  315   a  of the bearing is a substantially circular surface sized to match diameter with an attachment ring  310  of the filter assembly  120  or alternatively an upper mounting portion  140  of the inside of lid  109  depending on the particular embodiment used. 
         [0060]    In this embodiment the bearing  315  is somewhat rigid and includes a plurality of cutouts  331  arranged about the inner circumference of the bearing. As mentioned above, the bearing is preferably sufficiently rigid to insure that the cleaning surfaces can be held in their desired orientation relative to the filter surface  121  during rotation even in high vortex speeds and very viscous fluids. 
         [0061]    Moreover, to deal with feed fluids  131  having a high concentration of particulate matter the bearing  315  can include particulate removal features. In one embodiment, the features can include cutout features  331 . The cutouts  331  enable the particulates to move through and around the bearing  315  and not excessively bind up the cleaning assembly as it rotates around the filter assembly  120 . Alternative bearing structures are discussed, for example, in provisional patent application 61/355,989 filed Jun. 17, 2010 “Particulate Tolerant Fluid Bearings for Use in Hydroclone Based Fluid Filtration Systems” which is incorporated herein by reference for all purposes. 
         [0062]      FIG. 5(   a ) illustrates a cleaning assembly  300  assembled in a mounted arrangement with a filter assembly  120  (akin to the exploded view of  FIG. 3)  to form a “nested” assembly  500  as it would be in one example of an operating arrangement of the hydroclone. Here, the filter  120  is nested inside the cleaning assembly  300  and is secured in place using a particulate tolerant fluid bearing  315 . The cleaning structures  312  are carried by a set of paddles  313  which in turn are carried by the bearing  315  and supported by a toroid support ring  314 . Here, the support ring  314  is arranged as a toroid band that engages an external groove of each paddle. Accordingly, the support ring  314  is easily installed and due to its extended width in a radial direction provides improved radial support for the paddles  313 . Although such a toroid support ring is advantageous, it is not a required aspect of the invention. 
       Cleaning Assembly Modes of Operation 
       [0063]      FIG. 5(   b ) is a schematic representation of a section view of a simplified depiction of the assembly  300  such as shown in  FIG. 5(   a ) and taken along A-A. In this depiction, a simplified view of the assembly  300  is diagrammatically depicted in a hydroclone induced circulating fluid flow  131 . Here, the fluid flow  131  is that generated by the presence of the vortex. The cleaning assembly  300  is shown with the cleaning structures  312  having cleaning surfaces in close proximity to, or in contact with, the filter surface  121 . The fluid flow around the filter (the vortex  131 ) impels a rotational motion  135  to the cleaning assembly  300  enabling the assembly to spin around the filter  120 . The rotation aids the cleaning structures  312  used to clean the filter  120 . The rotational effect of the vortex can be enhanced when paddles  313  are interposed into the flow  131  of fluid. 
         [0064]    The paddles  313  can be added as separate elements or can be part of existing components. Here, the paddles  313  extend radially away from the center of the filter  120  and are generally coplanar with the depicted cleaning structures. In some embodiments, the paddles  313  are merely extensions of the cleaning structures  312 . 
         [0065]    With reference to  FIG. 5(   c ) is a top plan view of a portion of the cleaning assembly  300 . This view specifically illustrates an embodiment having cleaning paddles  313  that are arranged at an angle other than radially disposed on the bearing  310 . Here the paddle  313  is angled away from perpendicular to the vortex flow  131 . This angle  320  can be at any angle directed away from the tangential flow  131  of the vortex fluid and other than radially disposed on the bearing  315 . Angles  320  ranging from about 5°-45° have been particularly useful with an angle  320  of about 12.5° being preferred. Such an angle is optimized to be perpendicular to a fluid flow directly from the inlet  101  (see, for example  FIG. 1)  just a bit sooner than went the flow from the inlet  101  is tangential to the cleaning assembly. Surprisingly, this has been found to generate higher rotational speed in the cleaning assembly and superior cleaning of the filter  120 . It should be pointed out that the paddle geometry should in no way be limited to the specific examples provided here. 
         [0066]    Additionally, in some situations the inflowing fluid  131  through inlet  101  can exert an uneven force on the cleaning assembly  300  which results in uneven wear on the surface  121  of the filter  120 . One example of such an uneven wear condition is illustrated and described using the exaggerated diagrammatic depiction of  FIG. 5(   d ). For example, the cleaning structure  312  on the side closest to the inlet  101  is pressed against the associated portion  121   a  of the filter surface  121  by, for example, the inflowing fluid stream  131 . Not surprisingly, this causes more wear to be incurred at upper portion  121   a ′ of filter surface  121  on the side facing the inlet  101  and lesser wear can occur on opposing side  121   b  of the filter surface  121 . Thus,  FIG. 5(   e ) illustrates this increased wear on one side ( 121   a ′) of the filter relative to other portions of the filter ( 121   b ). 
         [0067]    An advantage of the filter design described below and usable in the system above is that the filter assembly  120  can readily be disassembled, the filter frame  311  can be simply and easily be flipped over and the filter reassembled with a top portion of the filter now being on the bottom. By flipping the filter upside down, the worn portion  121   a ′ of the filter assembly is, moved to the bottom and thus away from the upper region of heavy wear. Thus, the useable life of the surface filter can readily be extended. This is sometimes desirable because fine filter membranes can be relatively expensive. 
         [0068]    Referring next to  FIG. 6(   a ), both the attachment ring  310  and the bottom plate  124  of the filter assembly  120  are reversibly attachable to and detachable from the filter frame  311  thereby facilitating reversal of the filter. The specific devices used to secure the attachment ring  310  and the bottom plate  124  to the filter assembly may be widely varied. For example, the components (top attachment ring  310  and bottom plate  124 ) can be attached to the filter frame  311  using almost any type of reversible mechanical fastener. For example, attached using screws or other reversible fasteners, clasps, clamps, clips, mated threaded features enabling the components to be screwed or unscrewed. Of particular utility is a pin and groove “bayonet” type attachment device. In one example, one component (bottom plate  124  or filter frame  311 ) is configured with pin features with the other component (the other of filter frame  311  or bottom plate  124 ) having complementary groove or pin receiving features. Although described using a simple pin and groove lock “bayonet” type attachment feature, the invention is not intended to be limited to just the enumerated features but is intended to cover numerous possible alternatives such that a sufficient fluid seal is provided and that the attachment is reversible. The idea being that the bottom plate  124  can be removed from a first side  311   t  of the filter frame  311  and reattached to a second side  311   b  of the filter frame  311 . 
         [0069]    In a similar fashion, upper attachment ring  310  can be reversibly attachable with the frame  311 . For example, the frame  311  and attachment ring  310  can also be attached using almost any type of reversible mechanical fastener. As before, of particular utility are pin and groove “bayonet” type attachment features with one component having pin features with the other component having complementary groove locking features. As shown here, a top side  311   b  (of frame  311 ) is configured with pins (not shown in this view) having a mated set of associated retention slots  310   s  on the attachment ring  310 . The pins are engaged with the slots  310   s  and then the frame  311  can be twisted to engage the pin and slot fastener in a locking position. It is intended that the process also be reversible. Many versions of such pin and slot “bayonet” fasteners can be used. 
         [0070]    In one implementation, after a certain degree of wear occurs on a portion of the filter assembly  120 , bottom plate  124  and top attachment ring  310  are removed from the frame  311 . The frame  311  (and surface filter  121  mounted thereon) is then flipped over and the bottom plate  124  and top attachment ring  310  are remounted on the frame  311  in the reverse order such that the bottom plate  124  is mounted on side a top and the attachment ring  310  is mounted on side  311   b.    
         [0071]    As described above with respect to  FIG. 5(   d ), another uneven wear situation occurs when the wear is more substantial on one side of the filter than the others (e.g., when greater wear is occurring at side  121   a  as compared to side  121   b  To mitigate this problem, the filter can periodically be disassembled and indexed (i.e. rotated) relative to its present position. One mechanism for facilitating such rotation will be described with reference to  FIGS. 6(   a )- 6 ( d ). As mentioned above, the attachment ring  310  may be fixed onto the lid  109  of hydroclone  100 , for example using screws (or other fasteners). To facilitate rotation of the filter, the frame may have a multiplicity of pins  311   p  located on its top and bottom surfaces (pins located on side  311   b , are not shown in the view of  FIG. 6(   a )). The pins are arranged to engage with complementary features  310   s  of the attachment ring  310 . It should be appreciated that the filter frame  311  can be engaged with the features  310   s  in a number of orientations to selectively position the frame  311  to extend the filter life. The views in  FIGS. 6(   b )- 6 ( d ) illustrate how selective engagement and partial rotation of the filter can extend filter life. In one such embodiment, at least three features  310   s  are configured to engage at least three pins  311   p  (sets can be on either side  311   t  or  311   b ). In some embodiments, many more than three pins  311   p  and features  310   s  are used and such pins and features are symmetrically disposed around the frame  311  and equidistant from each adjacent feature. 
         [0072]    Again referring to  FIGS. 6(   b )- 6 ( d ) when wear at a selected portion  121   a  reaches a certain point, the frame  311  can be disengaged from the lid  310  by twisting the frame  311  such that the pins disengage from the locking features  310   s . The frame is then rotated to another locking position and then re-engaged using the pins and locking features. For example, upon disconnection, rotation, and reattachment,  FIG. 6(   c ) the filter is oriented so that the most worn portion  121   a  is rotated away from the most wear vulnerable position. Thus, by way of continued example, upon further disconnection, rotation, and reattachment,  FIG. 6(   d ) the filter is again re-oriented so that the most worn portion  121   c  is also rotated away from the most wear vulnerable position. In an example embodiment, an indexed partial rotation of about 60 degrees per partial rotation can be used. Of course partial rotations of other magnitudes can be used. Thus, although portion  121   c  is subject to increased wear it can be index away from the high wear location by using partial rotation. Accordingly, a relatively unworn portion  121   d  is now moved into the position of increased wear. It is to be noted that the features of rotating the filter and flipping it over can be combined if necessary or if desired. 
       Extensible Filter Assembly 
       [0073]    In some embodiments, such as the embodiment shown in  FIG. 2 , a single filter assembly  120  is placed inside the hydroclone chamber  106 . Such an approach provides excellent filtering capacity. However, if it becomes desirable to expand the filtering capacity of a given hydroclone device, the invention as described below, can achieve this goal with great flexibility and utility. 
         [0074]    With reference to  FIGS. 7(   a )- 7 ( c ), a simplified extensible filter embodiment is described. A stacked filter assembly  700  can replace the single stage assembly depicted, for example, in  FIG. 1 . In this embodiment a plurality of filter stages (here,  701 ,  702 ,  703 ) can be used to replace the single stage filter of the previously described embodiments. 
         [0075]    In the depicted embodiment a first stage filter element  701  can be substantially the same as filter  120  described with respect to  FIG. 2  with some differing features. Instead of a single cylindrical filter, the extensible filter assembly  700  can be used instead. As shown here the extensible filter assembly  700  comprises a number of stages. Any approach using two or more stages can be used. In this embodiment, three stages ( 701 ,  702 ,  703 ) are used, with each stage  701 ,  702 ,  703  including a filter frame and surface filter. The stages are arranged such that filter frames have decreasing diameter as the stages extend downward toward the bottom of the hydroclone chamber  106 . The frames having progressively smaller diameter in general relation to the angle of the chamber wall  105 . It is pointed out that in some embodiments, the filter elements can be the same size. 
         [0076]    A number of co-assigned patents and patent applications have described the use of stepped and/or frusto-conically shaped filter assemblies within the hydroclone chamber. Although such filter assemblies work very well in many applications, under certain operational conditions the pressure gradients in the hydroclone chamber  106  and the filtered fluid chamber respectively may be such that some reverse fluid flow (i.e., filtered fluid flowing out of the filter through the membrane into the regions containing unfiltered fluid) occurs through certain portions of the filter, which reduces the filtration efficiency. In filter chambers that drain filtered fluid out the top of the filtered fluid chamber, the reverse fluid flow is most likely to occur near the bottom of the filter. 
         [0077]    The risk of reverse flow can be mitigated by effectively separating the filter assembly into several smaller chambers that are each in communication with the outlet  107  and upper chamber  112  but substantially isolated from direct communication with each other. This can be facilitated by using specialized isolation manifolds with fluid connectors described as follows. 
         [0078]    The stacked filter assembly  700  of  FIG. 7(   a ) includes a first filter stage  701  and a plurality of supplementary stages (here  702 ,  703 ). The top filter assembly (first stage)  701  can be substantially similar to the filter assembly  120  described above. An important difference is illustrated using  FIGS. 7(   a )- 7 ( b ). The bottom plate of filter  120  is removable and can be replaced with an isolation manifold  710  arranged at the lower portion of the first filter stage  701 . As shown in this embodiment, the isolation manifold  710  includes a flow connector  712  and an isolation member  711 . The connector  712  passes through the isolation member  711 . When reattached and secured to a bottom portion of filter  701  the isolation manifold  710  (via connector  712 ) enables fluid communication between chamber  112  and chamber  723  (defined by an underlying second (supplementary) filter stage  702 ). Thus, the connector  712  enables an equalization of fluid pressure between chamber  112  and chamber  723 . Thus, the member  711  operates as a fluid barrier confining fluid flow between the two adjacent chambers. Accordingly, it minimizes free fluid movement within the filter assembly as would be the case in the absence of the isolation manifold. In this way, the outflow of filtered fluid from the filter assembly to the main chamber  106  is substantially reduced thereby enhancing the filtration efficiency of the system. 
         [0079]    In continuing explanation of this embodiment, and as described in the exploded view of  FIG. 7(   b ), in one embodiment the connector  712  of the isolation manifold is centrally located to enable the addition of further filter stages as explained below. However, it is to be noted that in other embodiments the connector  712  can be offset from the center location depicted here. Additionally, in other embodiments several such connectors  712  can be arranged in the member  711 . 
         [0080]    As shown in this example, a third (supplementary) filter stage  703  can be arranged under the second filter  702  which can be similar to the filters above excepting that it has a lesser diameter. As with the filter stages described above and illustrated in  FIGS. 7(   a )- 7 ( b ), another isolation manifold  720  (for the second filter stage  702 ) includes a connector  722  that passes through the isolation member  721  enabling fluid communication between chamber  112  and chamber  733  defined by a third filter stage  703 . In this embodiment and as shown in  FIG. 7(   b ), the isolation manifold  720  has a connector  722  that is also centrally located which enables the centrally located connector  722  to pass through the inside of connector  712 . The diameters of connectors  712 ,  722  are such connector  722  can fit inside connector  712 . This enabled direct fluid communication between chamber  112  and both chambers  723 ,  733  without enabling flow between the second chamber  723  and the third chamber  733 . Also, in other embodiments, the connectors  722 ,  712  can be offset from the center locations depicted here. 
         [0081]    Although depicted here as three filter stages  701 ,  702 ,  703  (each configured similarly to filter stage  120 ) the invention contemplates embodiments having more or fewer filter stages. As with the above described stages, each stage can have an isolation manifold that is in communication with the upper chamber  112  but not in direct communication with the other chambers. This structure is freely extensible to accommodate as many filter stages as desired. At the lowest filter stage (here stage  703 ) a bottom cap  731  is installed to cap off the bottom of the filter assembly  700  preventing the intrusion of unfiltered fluids. 
         [0082]      FIG. 7(   c ) is a diagrammatic top down view of a portion of a filter assembly  700 . In this depicted embodiment, stages  701  and  702  are engaged with each other and filter stage  702  is engaged with stage  703 . Also depicted are isolation manifolds  710 ,  720 , associated members  711 ,  721  and the associated connectors  712  and  722 . It is to be noted that in this particular embodiment, the connectors  712  and  722  are coaxially arranged one inside the other. Although the invention contemplates non-concentric implementations the depicted embodiment is preferred. Accordingly, connector  712  is positioned inside the inner diameter of connector  722  thereby enabling fluid to flow up into chamber  112  from chamber  733  and likewise from chamber  723  to chamber  122 . Importantly, the fluid flow is accomplished without free fluid flow between chambers  723  and  733  (these being isolated from direct communication between each other). In this manner the fluid pressure is substantially the same in all of the chambers  112 ,  723 , and  733 . 
         [0083]    Additionally,  FIG. 7(   d ) illustrates one approach for attaching a manifold at a filter stage to enable flexible extensibility of the filter assembly  700  per the needs of the system. Instead of a standard bottom (e.g., like  731 ) another bottom (like isolation manifold  721 ) can be employed. One example of such an isolation manifold  721  is described. A filter frame (e.g.,  702 ) is provided. An isolation manifold (e.g.,  721 ) replaces the standard bottom. In this depiction the bottoms and isolation manifolds are configured to be easily replaceable and interchangeable. In one example, the filter frame  702  can include a bayonet-type locking feature (e.g., slot  702   s ) into which a locking pin  721   p  of isolation manifold  721  can be fitted. For example, the pin, or a set of pins  721   p  is aligned with a complementary locking feature  702   s  (features) that (in this embodiment) are arranged at an inner diameter of the frame  702 . The pin(s)  721   p  are aligned feature(s)  702   s  and engaged by moving the pins upward  741  and then twisting  742  the pin  721   p  and locking feature  721   s  to fully engage. This can affect a solid lock between the two components. Further, seals can prevent fluid leakage into or out of the chamber  723 . As can be readily appreciated, many other reversible engagement features can be employed to extensibly attach a series of filter frames together to form a stepped filter. In some embodiments the isolation manifold  721  can include locking features  721   s  that can enable further extensibility of the attachment of a standard bottom piece (i.e., a bottom piece without a connector, e.g.,  722 ). 
         [0084]    To enable cleaning, added fluid bearings and cleaning assemblies can be added independently at each stage. Alternatively, one large integrated cleaning assembly can be employed that includes cleaning elements at each stage arranged to help clean the filters of each stage while rotating around the stacked filter assembly. In one embodiment, such an assembly can use a bearing at the upper filter stage ( 120 ,  701 ) and another bearing at the lowest one (e.g.,  703 ). Additionally, further intermediate bearings can be included to engage mounting surfaces on one or more of the supplementary filters if added stability is desired. It is readily apparent that other arrangements can be employed with similar results. 
       Pressure Equalization 
       [0085]    In some operating conditions, the filter clogging can become serious enough such that before the cleaning assemblies cannot clean the filter surfaces effectively. This clogging can also impair the effectiveness of the filters themselves thereby reducing the rate of filtration substantially, and thereby reducing the throughput of filtered fluid by the system. Again referring, to  FIG. 2  it is believed that a pressure differential between the unfiltered fluid in the hydroclone chamber  106  and a filtered fluid chamber within the filter assembly (e.g.,  112 ) can aggravate this clogging problem. For example, a pressure differential between the higher pressure in the fluid circulating region  106  and a low pressure inside the filtered fluid chamber(s) (e.g.,  112 ,  723 ,  733 ) can push particles and other contaminants against the side the filtered fluid chamber(s) blocking filtration pores and making it difficult to clean the filters elements/membranes of the various stages ( 120 ,  701 ,  702 ,  703 , etc.). The effect of this build up is to degrade cleaning effectiveness of the filtration device. 
         [0086]    One approach for increasing the cleaning effectiveness of the cleaning assemblies is to control the pressure differential between the inside and outside of the filter assembly. For example, an inventive pressure management system can be used to operate hydroclone devices such that the aforementioned pressure differential is maintained within a specified operational range. In one example, the pressure management system can be used to equalize the pressures between the inside of the filtered fluid chamber(s) and the outer fluid the fluid compartment  110 / 106 . The filtration management system can include pressure detectors  132 ,  134  arranged to detect a pressure differential between the filtered fluid chamber(s) ( 112 ,  723 ,  733 , etc.) and the external fluid compartment  110 / 106 . This information can be received by a regulator system  133  that can operate to equalize the pressure differential. A wide range of pressure detection systems can be used. For example, the invention can include, but are not limited to pressure sensors including one or more of mechanical and hydraulic pressure sensors, electrical pressure sensors in general, piezoelectric transducers, resistive strain gauge transducers, capacitive transducers, electromagnetic transducers, optical transducers, potentiometric transducers, resonant frequency transducers, MEMS technologies, thermal transducers, as well as many others. The regulator  133  can equalize the pressure using a number of approaches including, but not limited to reducing or shutting off the influent flow  131  through the inlet  101 , reducing or shutting off the outflow  107  of filtered fluid from the inside (e.g.,  112 ) of the filter element(s) (e.g.,  120 ), introducing air or gas into the filtered fluid chamber(s)(e.g.,  112 ). The invention contemplates that many other approaches can be used as well. 
         [0087]    In one particular embodiment, a differential pressure threshold is set in a desired cutoff range (in one example, between about 1 psi. to about 3 psi). Once set, the hydroclone undergoes normal operation with each pressure sensor  132 ,  134  measuring the pressure in the respective chamber. Pressure information is received by a regulatory system  133  which is configured to take the appropriate action. For example, in one embodiment piezoelectric pressure sensors  132 ,  134  measure the pressures in the associated chambers and provide pressure information to a microprocessor  133 . The microprocessor  133  can generate differential pressure information and when said differential pressure varies outside the desired range, the microprocessor can initiate a predetermined remedial action. For example, in one embodiment, where the measured differential pressure exceeds the predetermined threshold (for example, where the pressure in chamber  106  is significantly greater than the pressure inside chamber  112 ) remedial action is taken. In one case, the influent flow  131  can be reduced or stopped, allowing the two pressures to equilibrate. Once equilibrium is reached, the inlet  101  flow can be returned to normal operating conditions. 
       RPM Monitoring 
       [0088]    In some embodiments, it is important to maintain the rotation rate of the cleaning assembly  300  within a desired operational range. Numerous factors can play into this, including, but not limited to fluid viscosity, optimized rotation rates for filter cleaning, desired vortex speeds, and so on. 
         [0089]    Therefore, it can be advantageous to have a method of measuring cleaning assembly rotation rates. In some embodiments it can serve as an accurate measure of vortex velocity in the fluid circulating region  110  as well as a measure of the rotation rate of the cleaning assembly  300 . 
         [0090]    Although many different approached can be taken, such approaches must be sensitive to the sometimes difficult environment of contaminated viscous fluids. Although, simple optical or electrical methods can be used. The invention includes a particularly robust and serviceable embodiment using simple magnetic measurement of rotation rate for the rotating cleaning assembly  300 . In the depicted embodiment  300  as shown in  FIGS. 2 and 5(   c ) a rotation rate measurement system is briefly described. A very basic embodiment comprises a marker  141  arranged on some rotating location on the cleaning assembly  300  and a transducer  142  arranged to detect the rotational rate and controller element  143  arranged to receive data from the transducer  142 . The controller element  143  can be used to monitor and/or regulate the rotation rate of the cleaning assembly  300 . Such regulation can be accomplished, for example, by reducing the inflow rate through inlet  101  as well as other approaches. 
         [0091]    In the depicted embodiment, the marker  141  can be a magnet arranged on the assembly  300 . For example, a magnet  141  can be arranged on one of the paddles  313  and a magnetic transducer  142  can be arranged to detect the magnet  141  as it passes near the transducer. This information can be received from the transducer  141  at the controller element  143 . Depending on the fluid viscosity, optimized cleaning rpm, and other factors, the controller element  143  can then adjust the rotation rate of the cleaning assembly to optimize or otherwise regulate the cleaning assembly rpm. In this implementation, a magnet and associated magnetic transducer are desirable because they are relatively simple components and function well even in highly viscous and very low visibility environments. The invention specifically contemplates that a wide variety of other sensing technologies can be used to detect the rotational speed of the cleaning assembly. 
         [0092]    The described hydroclones can be used in a wide variety of water filtering, pre-filtering and water treatment applications. By way of example, many drinking water treatment facilities use a series of screens and consumable filters that have progressively finer filtering meshes. The described hydroclone can be used in place of one or more staged filter devices. The hydroclone is particularly well suited for applications that require low maintenance; applications that begin with relatively dirty water; and applications that require a relatively small filter footprint while handling a relatively large volume of water through the filter. 
         [0093]    The described hydroclones are well suited for use in relatively small scale drinking water filtering applications. In drinking water applications that require very high levels of filtering, the hydroclone is very well adapted for use as a pre-filter (as for example a 5-20 micron prefilter). Since the hydroclone utilizes a surface filter as opposed to a consumable depth filter, fewer filter stages are typically required to pre-filter the drinking water. In water filtration applications that permit larger (e.g. 2-10 micron) particles, the hydroclone can be used as the final filter. 
         [0094]    The described hydroclones are also very well suited for ballast water filtering applications. As will be appreciated by those familiar with international shipping, many cargo (and other) ships utilize ballast water for load balancing. Environmental concerns have caused some countries to require (or contemplate requiring) ships to filter their ballast water before dumping it back into the sea. Since the described hydroclones require little maintenance and are very compact for the volume of water they can handle, they are well suited for ballast water treatment applications. 
         [0095]    Such hydroclones can be used in produced water applications in the petrochemical industry where large amounts of water are to be returned to subsurface formations. 
         [0096]    In various filtering applications, multiple hydroclones can be plumbed together in parallel or in series. Typically hydroclones having the same filter mesh size would be plumbed in parallel to facilitate handling a greater volume of water. Graduated filtering can be accomplished by plumbing hydroclones having progressively smaller meshes together in series. 
         [0097]    In general, a representative hydroclone-based water filtration system that includes a hydroclone is described herein. The system draws a fluid to be filtered (water, petroleum, etc.) from a source. In the case of water, any suitable water source can be used, including river water, well water, collected water, bilge water or any other suitable source. The source water is delivered to the hydroclone which can act as a final filter, or more commonly, acts as a prefilter. Filtered water that exits the hydroclone can be directed to further fine filters that filter particles down to a further level (e.g. 1 micron or less) that is desired in the particular application (e.g. for drinking water). By way of example, fine filters having mesh sizes of 5 and 1 micron respectively work well with a hydroclone having a filter pore size of 10 microns. Of course, in other applications, fewer or more or no fine filters could be used downstream of the hydroclone. In still other applications a pair of hydroclones having different opening sizes may be used as the prefilters. Such an arrangement is particularly appropriate when the source water is considered quite dirty (i.e., has a high concentration of suspended particles). 
         [0098]    After passing through the filters, the clean water can be directed to a bacterial control unit for further treatment. Any of a variety of conventional bacterial control units may be used in the water treatment system. By way of example, germicidal ultraviolet light and ozone are the two most common non-chemical bacterial control mechanisms used in water treatment systems. 
         [0099]    After passing through the bacterial control unit, the water may be stored in a clean water storage tank or drawn as clean water. Water that is intended for drinking may optionally be passed through an activated carbon filter, reverse osmosis filtration units, or other enhanced filtration devices if desired, before it is delivered to a final downstream location (e.g., a tap, a storage tank, and so on). As will be appreciated by those familiar with the art, carbon filters are well suited for removing a variety of contaminants that may remain even in highly filtered water. 
         [0100]    Although only a few embodiments of the invention have been described in detail, it should be appreciated that the invention may be implemented in many other forms without departing from the spirit or scope of the invention. For example, although a few specific applications have been described, the hydroclones may be used in a wide variety of other filtering applications. Additionally, there are some applications where it is desirable to concentrate particles that are suspended within water (or other fluids) in order to recover the particles. A hydroclone that has been plumbed for recirculation of the effluent stream is particularly well adapted for use in such concentrating applications, particularly when the hydroclone is operated in the periodic purge mode. In these applications, it may be the concentrated purged fluids that contain the effluent of interest. 
         [0101]    Although specific components of the hydroclone such as specific filters, cleaning assemblies, and intake structures have been described, it should be appreciated that the various devices may be used in combination or together with other suitable components without departing from the spirit of the present inventions. Therefore, the present embodiments are to be considered as illustrative and not restrictive and the invention is not to be limited to the details given herein, but may be modified within the scope and equivalents of the appended claims.