Medium filter

Abstract

A water filter comprising a cylindrical pressure vessel for receiving a multi-layer particulate filter medium. The filter further comprises an inlet through which water to be filtered is introduced into the vessel. The inlet comprises a conduit which enters via the cylindrical side wall of the vessel and extends through the filter medium until it reaches the central axis of the vessel. At the central axis the conduit is bent and extends upwards as a central portion, and at a location above the filter medium the central portion branches into at least two spaced apart arms, each of which is provided at its free end with a jet outlet for introducing water in use into a body of water above the filter medium. Each jet outlet has a substantially different radial spacing from the inner surface of the cylindrical side wall.

Description

Technical Field

[0001] This invention relates to a media filter for water filtration. In particular, the invention is described with reference to a media filter having an improved inlet arrangement having a plurality of radially extending arms originating from a central tube portion. Background Technology

[0002] Media filters are used for a wide variety of water filtration applications, including industrial, commercial, drinking water, and wastewater treatment. They can be categorized into gravity filters and pressure filters. A typical pressure media filter has a cylindrical pressure vessel made of metal and contains layers of various granular filter media graded by size, with a fine layer at the top and a coarsest layer at the bottom. During normal use, the water to be filtered flows downwards from the top inlet through the pressure vessel to the bottom outlet. During a process called "backwashing," the water flow can be periodically reversed to fluidize the filter media, thereby cleaning and regenerating it. Air scouring is typically used after backwashing.

[0003] International Patent Publication WO2017 / 055794 (Cupples) describes and in its Figure 1 This document describes a known pressure-type media filter with multiple graded material layers, identified from bottom to top as pea gravel, coarse sand (coarse particles), fine particles, and fine sand. It also describes the use of a range of filter media, including heat-treated modified regenerated glass, and high-performance filter media with enhanced electrostatic charge to improve filtration efficiency. One such high-performance filter media that can replace fine sand is AFM® "Activated Filter Media," disclosed in GB 2521667 (Dryden Aqua Ltd). WO2017 / 055794 Figure 1 Known pressure-type media filters, as described in WO2017 / 055794, have a single inlet pipe that enters the pressure vessel through its cylindrical sidewall, but is typically curved upwards to provide an inlet above the top layer of filter media. As shown in WO2017 / 055794, such prior art pressure-type media filters can filter down to a level of 15-20 micrometers. When operating at this filtration level, the filter media tends to retain bacteria, fungal spores, and other microorganisms at the end of the operating cycle, shortly before backwashing occurs. Due to the low flow rate environment, these microorganisms can proliferate and colonize in both the filter media and the water. WO2017 / 055794 also describes various other prior art filters with different inlet arrangements and various attempts to improve them.

[0004] One disclosed improved form of filter is GB2461119 (Cupples), dating back to 2009, in which the main inlet is aligned tangent to the wall (see WO2017 / 055794). Figure 4 (Prior art), this causes the water above the filter media to move along a circular path in the vertical direction (vortex), as indicated by the arrow. The flowing water is used to continuously agitate and disperse the fine media forming the top layer of the filter, preventing bacterial colonization, thus enabling the filter to use much higher flow rates for fine filtration than earlier prior art could achieve. It also helps ensure that the flow through the filter bed is distributed throughout its entire area, thereby reducing contamination. The circulating movement of water tends to remove the filter media from the periphery of the pressure vessel and deposit it closer to the center of the vessel, where the water flow velocity is lower, thus forming a dome profile on the filter media. This is undesirable and can allow water to penetrate into the lower media layer, which can degrade the filter's performance. To avoid this effect, the media filters of GB2461119 employ a "vortex bed stabilizer" (in WO2017 / 055794). Figure 4 (Marked as 38). This vortex stabilizer is a distribution head arranged on the axis of a pressure vessel above the filter medium, supplied with water to be filtered, and has a discharge port oriented to horizontally spray water in the direction promoting the rotational movement of the water. See WO2017 / 055794. Figure 4 It can be understood that the discharge holes are circular, and each discharge hole sprays water in a corresponding direction tangent to the circle. In this way, the cone-shaped buildup of the filter media is reduced.

[0005] To improve upon this known prior art, WO2017 / 055794 describes an improved pressure filter, as shown in Figures 6 and 7, in which a first inlet is arranged above the horizontal plane of the filter media and oriented in a manner that causes the water above the filter media to rotate. This rotational motion helps reduce biofouling. It also has a secondary inlet at the center of the pressure vessel above or below the top surface of the filter media to resist unwanted build-up and its "cone". The prior art also describes how the velocity of the water entering the pressure vessel and the rotational speed of the eddies within the pressure vessel significantly affect the overall filter performance. To enable tuning and optimization of this aspect of filter performance, it suggests the use of interchangeable velocity regulators suitable for a variety of applications from low to high flow rates. The prior art describes a pressure filter with a diameter of approximately 1200 mm, and its design is not suitable for larger sizes in the diameter range of 1600-3000 mm. Furthermore, during backwashing, typical diffusers tend to allow water to pass through the center first, which causes the central core of the media bed to bulge, while surface debris is driven downwards, bypassing the periphery and entering the media bed.

[0006] Another issue with WO2017 / 055794 (Cupples) is that the effectiveness and efficiency of the filter media are significantly affected by the flow rate, which in turn is influenced by the radial velocity required to maintain the vortex. This prior art media filter, with a diameter of 1200 mm, allows you to rotate the filter media at a radial velocity of up to approximately 10,000 rpm. However, this prior art still performs poorly at higher rotational speeds, particularly in terms of filter media effectiveness and efficiency, and is not suitable for larger filters, especially when biofouling can still occur in the “dead zone,” such as biofouling that may occur above the inlet.

[0007] The present invention provides a water filter that overcomes at least one problem associated with the prior art. Summary of the Invention

[0008] In a first aspect, the present invention comprises a water filter comprising: a cylindrical pressure vessel for receiving a multilayer particulate filter medium; an inlet through which water to be filtered is introduced into the vessel, the inlet comprising a conduit that enters through a cylindrical sidewall of the vessel and extends through the filter medium until it reaches the central axis of the vessel, characterized in that, at the central axis, the conduit bends and extends upward as its central portion, and at a position above the filter medium, the central portion branches into at least two spaced-apart arms, each arm having a jet outlet at its free end for introducing water into a body of water above the filter medium during use, each of the jet outlets having a substantially different radial distance from the inner surface of the cylindrical sidewall.

[0009] Preferably, the injection outlet of the spaced-out arm closest to the cylindrical sidewall is spaced from the cylindrical sidewall at a distance ranging from 5 to 20% of the diameter of the pressure vessel, and another injection outlet on the other spaced-out arm is spaced from the cylindrical sidewall at a distance ranging from approximately 15 to 40% of the diameter of the pressure vessel.

[0010] Preferably, the water flow from the jet outlet causes the water contained in the container to rotate at high speed along a generally circular path around the central axis, thereby causing a portion of the upper layer of the fluid medium to rotate and remain in a vortex.

[0011] Preferably, the uppermost layer of the filter medium is a level 0 activated filter medium, and the particles in the uppermost layer rotate at a speed of about 20,000 rpm in the vortex.

[0012] Preferably, the vortex stabilizer is disposed on the central portion of the conduit, the vortex stabilizer having a plurality of spaced-apart tangential grooves, and in use, when a portion of the upper layer of the fluid medium rotates and remains in the vortex, the vortex stabilizer is flush with or nearly flush with the flat bed of the filter medium below the vortex, and water flowing out of the conduit leaves the grooves of the vortex stabilizer, maintaining the substantially flat surface of the filter medium below.

[0013] Preferably, each of the jet outlets is oriented upwards at least a few degrees from the horizontal axis passing through the corresponding arm. Preferably, the at least a few degrees is two or three degrees.

[0014] Preferably, the substrate is disposed below the filter medium in the container, and the substrate includes a plurality of diffusers that allow water to pass through in both downward and upward directions during filtration and backwashing.

[0015] Preferably, in one embodiment, the at least two arms are two arms oriented in substantially opposite directions. Preferably, the diameter of the container is in the range of 1200 mm to 2000 mm.

[0016] Preferably, in another embodiment, the at least two arms are three arms that are substantially equidistant from each other. Preferably, the diameter of the container is in the range of 2000 mm to 3000 mm.

[0017] Preferably, in a further embodiment, the at least two arms are four arms, and each arm is spaced substantially 90 degrees from the adjacent arm. Preferably, the diameter of the container is approximately 3000 μm.

[0018] In a second aspect, the invention comprises a water filter comprising: a cylindrical container for receiving multiple layers of particulate filter media, the diameter of the cylindrical container being in the range of 1200 mm to 3000 mm; an inlet through which water to be filtered is introduced into the container, the inlet comprising a conduit that enters through a cylindrical sidewall of the container and extends through the filter media until it reaches the central axis of the container, characterized in that, at the central axis, the conduit bends and extends upward as its central portion, and at a position above the filter media, the central portion branches into a plurality of spaced-apart arms, each arm having a jet outlet at its free end for introducing water into a body of water above the filter media in use, each of the jet outlets having a substantially different radial distance from the inner surface of the cylindrical sidewall, wherein the water flow from the jet outlet causes the water contained in the pressure vessel to rotate at high speed in a generally circular path substantially around the central axis, thereby causing a portion of the upper layer of the fluid medium to rotate and remain in a vortex.

[0019] Preferably, the uppermost layer of the filter medium is a level 0 activated filter medium, and the particles in the uppermost layer rotate at a speed of about 20,000 rpm in the vortex. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of a vertical plane cross-section of a media filter for water filtration according to a first embodiment of the present invention.

[0021] Figure 2 Through Figure 1 A schematic diagram of the horizontal cross-section of II.

[0022] Figure 3 yes Figure 1 The diagram depicts the tangential flow emitted by the eddy current stabilizer of the media filter.

[0023] Figure 4 yes Figure 1 A schematic plan view of the diffuser substrate of the water filter depicted.

[0024] Figure 5 yes Figure 4 A cross-sectional schematic diagram of the diffuser substrate arrangement. Detailed Implementation

[0025] This invention describes an embodiment of a media filter for water filtration. However, this media filter is applicable to liquids other than water. Therefore, throughout this specification, any reference to "water" should be understood to include the meaning of "liquids other than water".

[0026] Figures 1 to 5 A first embodiment of a pressure-type media filter 100 suitable for filtering water or other liquids is described. Although water will be mentioned in this specification, the filter can also be used with another liquid.

[0027] It has a pressure vessel 102, which is generally cylindrical but has a dome-shaped upper end wall 104 and a lower end wall 106, with an inlet cover 108 in the upper dome-shaped end wall 104. In this embodiment, the pressure vessel 102 has a diameter of approximately 2000 mm. The pressure vessel 102 contains a filter medium 118, which may comprise layers, with a fine layer at the top and a coarsest layer at the bottom. In this preferred embodiment, the finest layer is a Class 0 activated filter medium, such as that sold under the name AFM®. Water to be filtered enters the pressure vessel 102 through inlet 114. The upper medium level is indicated by line 20.

[0028] Inlet 114 includes a conduit (duct) that enters through the cylindrical sidewall 129 of pressure vessel 102 and extends through the filter medium 118 until it reaches the central longitudinal axis L of pressure vessel 102, where it bends and extends upward as a central conduit portion 114a. At a position above the filter medium 118 (when the filter is not in use), the central conduit portion 114a of inlet 114 branches into two spaced-apart arms 112, 113, each extending horizontally toward the cylindrical sidewall 129 in substantially opposite directions. Thus, at point 25 on axis L, arms 112, 113 branch, forming a 180-degree angle with each other. Each arm 112, 113 provides a jet outlet 116, 117 at its free end for introducing water into the body of water above the filter medium. Figure 2 As shown, arms 112 and 113 are curved as they extend away from the central axis L, and their jet outlets 116 and 117 are not equidistant from the central axis L. This ensures that the inlet jets 116 and 117 are positioned (spaced apart) at a radial distance different from the inner surface of the cylindrical wall 129, and are oriented in substantially opposite directions, and that the size and shape of the inlet jets are different from each other.

[0029] The nozzles of the inlet spray 116 and 117 are oriented in a manner that minimizes the water being guided to the cylindrical wall 129.

[0030] In this embodiment where the diameter of filter 100 is approximately 2000 mm, the spray outlet 116 on arm 112 is positioned substantially closer to the inner surface of the cylindrical sidewall 29 than the spray outlet 117 on the opposite side arm 113. In this embodiment, the radial distance (pitch) D1 from the center of spray outlet 116 to the inner surface of cylindrical wall 129 is approximately 100 mm, while on the opposite side, the radial distance (pitch) D2 from the center of spray outlet 117 to the inner surface of cylindrical wall 129 is approximately 300 mm. These radial distances (pitches) D1 and D2 can vary, but they must be substantially different from each other. In this embodiment, 100 mm of D1 is 5% of the diameter of filter 100, and 300 mm of D2 is 15% of the diameter of filter 100. It should be understood that these radial distances (spacings) D1 and D2 can vary within a certain range, for example, D1 is about 5-20% of the diameter of filter 100 and D2 is about 15-40% of the diameter of filter 100, and filter 100 will still operate fairly effectively as long as there is a substantial difference between the spacings D1 and D2.

[0031] During operation, the water flow from the jet outlets 116 and 117 causes the water in the pressure vessel 102 to rotate approximately in a circular path around the central axis L, such as... Figure 2As shown, it rotates counterclockwise. This high-speed flow causes the "upper layer," the AFM® fine layer media, of the filter media 118 to rotate and remain in a vortex. Internally arranged dual distribution arms 112, 113 and their respective jet outlets 116, 117 ensure uniform fluidization of the Class 0 AFM® media while maintaining a flat bed within the media 118 to provide a homogeneous bed. When the Class 0 surface is fluidized and rotated at a constant speed, most of the removed suspended solids remain on the inner cylindrical wall 129 above the media bed (media 118), regardless of the volumetric inflow rate. This constant-speed rotation, regardless of the volumetric inflow rate, does not occur in any of the aforementioned prior art filters.

[0032] In this embodiment, the Class 0 AFM® media rotates at a preferred constant high standard radial velocity of 20,000 rpm. This constant velocity is achieved through different positioning (spacing) relative to the inner surface of the cylindrical wall 129, different sized nozzles at the jet outlets 116 and 117, and the orientation of the inlet jets 116 and 117 relative to each other. This significantly improves the generation of electrostatics (negative zeta potential) on the surface of the AFM® media particles, resulting in greater efficacy and efficiency. Due to the increased filtration efficiency, most solid waste and biological waste, as well as oxidized organic and inorganic dissolved solids, such as iron, are trapped in the upper part of the pressure vessel 102, rather than on or above the surface (upper layer) of the media bed 118, thereby inhibiting water flow and reducing volumetric efficiency. Therefore, this also significantly reduces the amount of backwash water required compared to the prior art, as only contaminated water in the top area of ​​the container above the media flat bed needs to be removed.

[0033] For any nozzle size, the radial velocity of the vortex will vary depending on the flow rate of water passing through the media filter 100. Since the preferred constant high standard radial velocity is approximately 20,000 m / h, the nozzle sizes of the jet outlets 116 and 117 can be selected for a range of flow rates to maintain a constant high standard radial velocity of approximately 20,000 rpm. This will be discussed later, as nozzle sizes will differ for different filter sizes.

[0034] The central conduit section 114a includes a vortex stabilizer 130 through which water is discharged and maintains a substantially flat bed surface of the medium 118, ensuring the formation of stable vortices. The vortex stabilizer 130 has four or more tangential grooves with a depth of approximately 1 to 5 mm, which allow water to exit tangentially, such as... Figure 3As depicted by the arrows in the diagram. Calculate or adjust the tank dimensions to accommodate the density of the incoming water to ensure sufficient distribution to maintain vortex stability. When the media filter 100 is not in use, with the media 118 having settled and essentially stationary, the vortex stabilizer 30 is located approximately 10-30 mm below the upper surface of the bed of filter media 118 (media level). However, when the filter 100 is in use, a portion of the uppermost Class 0 AFM® media is suspended and moves within the vortex, causing the vortex stabilizer 130 to be flush with or nearly flush with the bed of filter media 118 below the vortex.

[0035] In this embodiment with a diameter of 2000 mm, the media filter 100, having two radial inlet jets 116 and 117 of different lengths, branches off from each other at an angle of approximately 180 degrees, at a distance of 25 to 60 m. 3 / hr / m 2 At the aforementioned high constant standard radial velocity of 20,000 rpm, at the flux rate, demonstrable and measurable improvements in filter performance are achieved: consistent electrostatic charge levels, uniform fluidization of the bed, maintained eddy current stability, and no need for scouring of the media in the bed.

[0036] like Figure 2 As shown, the inlet jets are displayed with a curved, elbow-shaped shape. Furthermore, the orientation of the inlet jets 116 and 117 a few degrees above the horizontal plane, such as five degrees or less, preferably two to three degrees above the horizontal plane, helps stabilize the vortex and minimize the dead zone above the inlet jets 116 and 117, thereby minimizing the risk of biocontamination in the upper region of container 102. It should be noted that in Figure 1 In the diagram, for ease of reference, the curved elbow nozzle 116 appears to be aligned with the horizontal line, but it is actually at a 2-degree angle above the horizontal plane, pointing slightly upwards. A height exceeding 5 degrees would cause flushing of the flat media bed, which is detrimental to filtration efficiency.

[0037] A high constant radial velocity helps determine the fluidization of the top medium of the bed of fluid medium 118 and minimizes the risk of biocontamination within the media filter 100.

[0038] In primary mode, the aforementioned media filter 100 operates as a suspended solids removal filter, inducing disinfection and oxidation to remove bacteria, pathogens, and other dissolved contaminants and biological materials. This can: • Removes twice the mass of existing technology sand filters of similar size.

[0039] • Removes 4-24% of total dissolved solids (TDS).

[0040] • Removes particles smaller than 0.45 microns with an efficiency greater than 92% in the absence of flocculants or coagulants.

[0041] • Remove pathogens and bacteria to a level that essentially prevents recolonization.

[0042] • Produces 1-2 NTU of output water clarity.

[0043] • Produces output water with an SDI of <5, which is suitable for flowing into a reverse osmosis filter in most cases.

[0044] • The filtration speed is three to five times that of a sand filter of the same size, while using less energy than a sand filter with the same volume of processing capacity.

[0045] Compared to existing sand filters of similar size, it can reduce backwash water loss by more than 75%.

[0046] If needed, the above implementation allows for the recycling of water and the centralized management of resources.

[0047] A diffuser substrate (filter plate) 140 is positioned approximately 50 mm above the vertical element of the cylindrical portion of the pressure vessel 102. The substrate 140 includes multiple diffusers 150 to allow water to flow uniformly in both directions: downwards during filtration and upwards during backwashing. The diffuser 150 is designed to allow for uniform vertical flow, ensuring that the medium does not shift due to internal circulation. This allows for flow in the 20-25m range. 3 / hr / m 2 At high throughput, faster backwashing is performed on the media 118 bed with a bed expansion rate of less than 22.5% to prevent loss of tunneling effect in other larger, heavier media below the top layer of Class 0 AFM® media during backwashing. A funnel 141 positioned above arms 116, 117 allows water to exit the media filter 100 via outlet conduit 142 during backwashing, minimizing the removal of media 118.

[0048] It should be noted that in existing sand filters, the backwash flux is 30 to 60 m³ / s. 3 / hr / m 2You cannot use Class 0 AFM® media, as it will wash the media away. Class 1 is the finest that other media filters can use, and it can filter up to 3 microns. This is why Media Filter 100 allows the use of Class 0 AFM® and achieves filtration of less than 0.45 microns. Because Media Filter 100 keeps most of the removed material at the top of pressure vessel 102, 85-90% of the removed waste can be washed away during the first two to four minutes of backwashing. Sand filters and sand filters using AFM® media instead of sand must have the entire vessel flushed, which takes 5 to 15 minutes, resulting in considerable water loss (Media Filter 100 at a flux of 22 m³ / s). 3 / hr / m 2 The time was 4 minutes, which is significantly less than the 45 minutes of existing sand filter technology. 3 / hr / m 2 (10 minutes at the flux).

[0049] Due to the reduced backwashing frequency and the lower required backwashing flux, the arrangement of the media filter 100 requires less energy for backwashing. The backwashing flux of the sand filter is 30 to 60 m³ / s. 3 / hr / m 2 The backwashing rate of media filter 100 is 20 to 25 m. 3 / hr / m 2 This is important because backwash water loss means significant energy and water loss that would preclude demanding a high water recovery capacity from the media filter 100. Furthermore, the media filter 100 has a significantly smaller "green footprint" than a row of sand filters. The smaller volume of centralized backwashing makes it easier to handle and reduces transportation costs associated with treatment. In an increasing number of cases, the inflow water is separated or distributed to the water output and centralized removal of backwash material, generating recyclable resources from the backwash. For example, oil separated from the water can be used as a resource. In other words, the media filter 100 acts as a distributor.

[0050] The media filter 100 can generate its own backwash water from the filtrate because the water is of suitable quality, disinfected, and free of bacteria and organic matter. This means that almost no external water supply is needed for the "backwash" water.

[0051] The embodiments described above, employing two branch arms 112, 113, are suitable for filters with diameters ranging from 1600 mm to 2000 mm. However, for larger diameter filters, it is preferable to use a greater number of branch arms and associated inlet jets. For example, in a further embodiment (not shown) of a filter with a diameter ranging from 2000 mm to 3000 mm, three branch arms and their three corresponding inlet jets are equidistantly branched (spaced apart), i.e., substantially 120 degrees (120°) apart from each other. In an even further embodiment (not shown) of a filter with a diameter of 3000 mm, four branch arms and their four corresponding inlet jets are branched (spaced apart) substantially 90 degrees (90°) apart from each other. Similar to the first embodiment described above, these embodiments (not shown) have three or four branch arms with inlet jets arranged (spaced apart) at a radial distance different from the inner surface of the cylindrical wall and oriented in substantially opposite directions, and the size and shape of the inlet jets differ from each other. Furthermore, as in the first embodiment, these inlet jets are preferably oriented upwards a few degrees above the horizontal plane.

[0052] The Media Filter 100 is designed to combine the advantages of light-medium centrifugal fluidization and a static flat bed of media. Centrifugal action fluidizes light (Class 0 AFM®) media and enhances the electrostatic charge and surface area of ​​the media interacting with the inflow fluid. This results in surface interactions that are three hundred times greater than those achievable in sand-based media. The high-speed fluidization and circulation result in the generation of hydroxyl radicals, which oxidize and disinfect the inflow liquid.

[0053] The above-described embodiments of the present invention have the following advantages: • Allows the removal of suspended solids smaller than 0.45 microns and produces chemical transformations that allow the removal of certain dissolved solids, including some salts.

[0054] • Effectively removes or significantly reduces: - Hydrophobic contaminants, such as hydrocarbons (oils and fats) and organic matter.

[0055] - Microplastics in both hard and soft water.

[0056] - Positively charged particles, such as heavy metals (e.g., iron, manganese, and arsenic), do not require coagulation and / or flocculation.

[0057] - Cryptosporidium oocyst.

[0058] - Escherichia coli: Legionella; • Filtration does not rely on bioburden accumulation to improve filtration efficiency; • It can achieve consistently high filtration performance; and • No air rinsing is required after backwashing.

[0059] Regardless of the diameter of the media filter of this invention, it has been found that optimal efficiency and effectiveness can be achieved when the high constant radial velocity of the vortex is maintained at approximately 20,000 rpm at various inflow rates. Optimal electrostatic charge is reached after three hours of continuous operation. Table 1 below shows how the nozzle size will vary to maintain a high constant radial velocity of approximately 20,000 rpm across the range of water inflow rates and filter diameters.

[0060] Table 1. Filter diameter and nozzle size for maintaining a radial velocity of 20,000 rpm If the density of the fluid differs from that of water, such as when water contains a large amount of solids or oil, it is also necessary to change the optimal size of the nozzle to maintain the vortex at a constant radial velocity of approximately 20,000 rpm.

[0061] Because the above-described embodiments of the present invention can be used more effectively in larger diameters than those in the prior art, they are suitable for potential primary processes of separating and recovering light oils from water, as well as for concentrating and collecting salts from seawater, or as a first step in seawater desalination prior to reverse osmosis.

[0062] When filtered water requires enhanced removal of larger heavy metals, injecting an oxidant containing "micro" or "nano" bubbles, such as oxygen, hydrogen peroxide, or ozone, into the water entering the filter will improve the efficiency of removing heavy metals that are insoluble oxides from the feed water. The addition of this oxidant in the form of "micro" or "nano" bubbles can reduce reliance on water treatment chemical additives and remove tannins from the water. Similarly, reducing agents can be injected into the influent to meet specific requirements.

[0063] Throughout this specification and claims, unless the context otherwise requires, the word "comprise" and variations such as "comprises" and "comprising" shall be understood to imply inclusion of the said integer or step or group of integers or steps, but not to exclude any other integer or step or group of integers or steps.

Claims

1. A water filter comprising: Cylindrical pressure vessel used to receive multi-layer particulate filter media; An inlet is provided through which water to be filtered is introduced into the container. The inlet includes a conduit that enters through the cylindrical sidewall of the container and extends through the filter media until it reaches the central axis of the container. Its features At the central axis, the conduit bends and extends upward as its central portion, and at a position above the filter medium, the central portion branches into at least two spaced arms, each arm having a jet outlet at its free end for introducing water into the water body above the filter medium during use, each of the jet outlets having a substantially different radial distance from the inner surface of the cylindrical sidewall.

2. The water filter of claim 1, wherein the jet outlet of the spaced-out arm closest to the cylindrical sidewall is spaced from the cylindrical sidewall by a distance in the range of 5-20% of the diameter of the pressure vessel, and another jet outlet on the other spaced-out arm is spaced from the cylindrical sidewall by a distance in the range of about 15-40% of the diameter of the pressure vessel.

3. The water filter of claim 1, wherein the water flow from the jet outlet causes the water contained in the container to rotate at high speed along a generally circular path substantially around the central axis, thereby causing a portion of the upper layer of the fluid medium to rotate and remain in a vortex.

4. The water filter of claim 3, wherein the uppermost layer of the filter medium is a level 0 activated filter medium, and the particles of the uppermost layer rotate at approximately 20,000 rpm in the vortex.

5. The water filter of claim 3, wherein a vortex stabilizer is disposed on the central portion of the conduit, the vortex stabilizer having a plurality of spaced-apart tangential grooves, and in use, when a portion of the upper layer of the fluid medium rotates and remains in the vortex, the vortex stabilizer is flush with or nearly flush with the flat bed of the filter medium below the vortex, and water from the conduit exits the grooves of the vortex stabilizer, maintaining a substantially flat surface of the filter medium below.

6. The water filter of claim 1, wherein each of the jet outlets is oriented upward from a horizontal axis passing through the respective arm by at least a few degrees.

7. The water filter according to claim 6, wherein the at least several degrees is 2 degrees or 3 degrees.

8. The water filter of claim 1, wherein a substrate is disposed below the filter medium in the container, the substrate comprising a plurality of diffusers that allow water to pass through it in both downward and upward directions during filtration and backwashing.

9. The water filter of claim 1, wherein the at least two arms are two arms oriented in substantially opposite directions.

10. The water filter of claim 9, wherein the diameter of the pressure vessel is in the range of 1200 mm to 2000 mm.

11. The water filter of claim 1, wherein the at least two arms are three arms spaced substantially equidistant from each other.

12. The water filter of claim 11, wherein the diameter of the container is in the range of 2000 mm to 3000 mm.

13. The water filter of claim 1, wherein the at least two arms are four arms, and each arm is spaced substantially 90 degrees apart from the adjacent arm.

14. The water filter of claim 13, wherein the diameter of the container is about 3000 μm.

15. A water filter comprising: A cylindrical container for receiving multilayer particulate filter media, the diameter of the cylindrical container being in the range of 1200 mm to 3000 mm; An inlet is provided through which water to be filtered is introduced into the container. The inlet includes a conduit that enters through the cylindrical sidewall of the container and extends through the filter media until it reaches the central axis of the container. Its features At the central axis, the conduit bends and extends upward as its central portion, and at a position above the filter medium, the central portion branches into a plurality of spaced arms, each arm having a jet outlet at its free end for introducing water into the body of water above the filter medium during use. Each of the jet outlets has a substantially different radial distance from the inner surface of the cylindrical sidewall, wherein the water flow from the jet outlet causes the water contained in the pressure vessel to rotate at high speed in a generally circular path about the central axis, thereby causing a portion of the upper layer of the fluid medium to rotate and remain in a vortex.

16. The water filter of claim 15, wherein the uppermost layer of the filter medium is a level 0 activated filter medium, and the particles of the uppermost layer rotate at approximately 20,000 rpm in the vortex.

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