IL272438B2

IL272438B2 - Self-cleaning filtering system and method

Info

Publication number: IL272438B2
Application number: IL272438A
Authority: IL
Inventors: Ben-Dosa Haim
Original assignee: Liquid Automation Ltd; Kessler Ilan Man And Developmen 2001 Ltd; Haim Ben Dosa
Priority date: 2020-02-03
Filing date: 2020-02-03
Publication date: 2023-02-01
Also published as: IL272438B; IL272438A; WO2021156853A1

Description

SELF-CLEANING FILTERING SYSTEM AND METHOD FIELD OF THE INVENTION: The present invention relates to the field of liquid filtering. More particularly, the present invention relates to a system with a self-cleaning filtering vessel and a related method for filtering liquid.

BACKGROUND OF THE INVENTION: Several filtration systems are used in the treatment of raw water (e.g., sewage, industrial effluents) for removing insoluble solids, floating particles, heavy particles, and the like suspended in the raw water. Typically, a backwash or pressure wash process is applied to a system filtering element simultaneously to the filtering process in order to open blockages that accumulate on the filter element and keep the filtering element unclogged and functional (not foul) and thus improving system filtration efficiency. The backwash or pressure wash consumes great amounts of fresh water.

US20040112846 relates to a filter unit for filtering particulates and other foreign matter from a fluid supply, comprising a filtering chamber. At least a portion of an exterior of the filtering chamber being provided with a mesh through which fluid may enter the filtering chamber in use. The mesh being sized to filter particulates and other foreign matter from the fluid. The filter unit further comprising an outlet through which filtered fluid exits the filter unit, and a rotatable member located within the filtering chamber, the rotatable member having at least one outlet spaced from an internal face of a mesh. The axis of - 2 - rotation of the rotatable member being such that the at least one outlet traverses at least a substantial portion of the internal face of a mesh. The filter unit further comprising a dedicated pump having an inlet communicating with the filtering chamber and an outlet communicating solely with the rotatable member such that operation of the pump causes filtered fluid from within the filtering chamber to be pumped through the rotatable member to exit the at least one outlet and impinge on the internal face of the mesh so as to cause particulates and other foreign matter located on an external face of the mesh to be dislodged.

Other publications teach of filtration systems with self cleaning filter element techniques, such as US 9,901,850, US 9,061,226, EP 2027905, US 8,857,452, WO 2012/046240, US7,055,699, EP 2125146, US 2016/0310876, US 5,855,794 US5,268,095, WO 2006/080653, JP 2004-141785, GB 2504120 and AU 2012203034.

US 9,789,423 relates to a filtration apparatus whose interior is divided into a filtrate zone and a filtering zone. The filtering zone is adapted to receive a stream of raw-water and a lower portion of its volume is filled with filtering grains, and the filtrate zone is adapted to receive a filtrate obtained from passage of said stream of raw-water via the filtering grains and a perforated member.

The apparatus further includes a pressure reducing device in fluid communication with the lower portion of the filtering zone and with an upper portion thereof. The pressure reducing device is adapted to receive a stream of water and responsively to continuously remove filtering - 3 - grains from said filtering zone and separate filtration residues therefrom by the reduction of pressure conditions thereinside, and direct a stream comprising the stream of water and the separated filtering grains and filtration residues to the upper portion of said filtering zone.

The current filtering systems and methods e.g., the systems and methods described in the publications above, have not yet provided satisfactory solutions for rapidly and efficiently filtering raw water using a relatively small amount of clean water in the process.

It is therefore an object of the present invention to provide a water filtration system and method for efficiently filtering raw water.

It is a further object of the present invention to provide a filtration system and method less susceptible to filter blockages.

Other objects and advantages of the present invention will become apparent as the description proceeds.

SUMMARY OF THE INVENTION: The present invention relates to a filtration system having a vessel which its interior comprises a flow splitter placed above a hollow perforated member. The vessel is capable of receiving a stream of raw-water filling its interior and the hollow perforated member is adapted to receive a filtrate obtained from passage of a stream of raw-water from its outside to its interior via its perforations (e.g. pores, mesh holes).- 4 - The raw water is discharged into the filtration vessel from the top of the vessel such that the raw water flows vertically downwards. The flow splitter member is placed beneath the inlet and above the perforated member splitting the raw water flow such that the raw water flow entering the vessel does not directly flow and engage the perforated member, but instead a large portion of the flow flows diagonally downwards around the hollow perforated member (along the splitter member and thereafter along skating surfaces explained hereinafter). The vessel has two skating surfaces that slant diagonally downwards from the sides of the interior of the vessel until a gap is formed therebetween. The two skating surfaces are configured to enclose a majority of floating particles that have passed downwards through the gap (typically by the inertial force of the raw water entering the vessel), such that the floating particles are maintained under the two skating surfaces. This assists in keeping the floating particles away from the perforated member and lessens the perforated member blockages that may occur on the outer surface of the hollow perforated member during filtration. This contributes to the efficiency of the entire filtering process.

A self-cleaning "backflush" spray from a plurality of nozzles/sprinklers in fluid communication with clean water is applied from the interior of the hollow perforated member outwards, in order to disconnect floating particles that become attached to the outer surface of the hollow perforated member, contributing to the efficiency of the filtering process. An advantageous feature is that clean - 5 - water causing the "backflush" spray is taken from a portion of the filtrate obtained by the present invention system.

The present invention relates to a filtration system comprising: a filtration vessel; a filtration vessel inlet at the top of said filtration vessel; a filtration vessel outlet at the bottom of said filtration vessel; a hollow perforated member comprising a plurality of pores, mounted within said filtration vessel; a filtrate outlet for streaming filtrate obtained within the hollow perforated member to a filtrate reservoir; and a flow splitter member placed above said hollow perforated member.

Preferably, the filtration vessel inlet comprises an inlet valve and wherein the filtration vessel outlet comprises an outlet valve.

Preferably, the filtration vessel comprises an upper portion in the form of a cylindrical body and a lower portion that tapers downwards; and wherein the filtration vessel comprises two skating surfaces that slant downwards from the sides of the interior of said vessel until a gap is formed therebetween.

Preferably, the hollow perforated member is cylindrical.

Preferably, the hollow perforated member is mounted from one side of the interior of the vessel to the other.- 6 - Preferably, the longitudinal axis of the hollow perforated member is substantially perpendicular to the longitudinal axis of the filtration vessel.

Preferably, said system comprises a raw water tank coupled to the filtration vessel inlet; and wherein the filtrate reservoir is coupled to the filtrate outlet.

Preferably, the splitter member comprises two elongated surfaces attached to one another.

Preferably, the elongated surfaces are two rectangular surfaces where one side of one surface is attached to one side of the second surface thereby forming an attachment line therebetween and an angle therebetween.

Preferably, the attachment line faces the top of the filtration vessel.

Preferably, the filtration vessel comprises an upper portion in the form of a cylindrical body and a lower portion that tapers downwards; and wherein the filtration vessel comprises two skating surfaces that slant (diagonally) downwards from the sides of the interior of said vessel until a gap is formed therebetween; and wherein the length of the splitter member is substantially parallel to the length of the gap.- 7 - Preferably, the system comprises a bypass flow pipeline coupled to the filtrate outlet, and coupled to a pressure pump; wherein said pressure pump is coupled to a pressure chamber; wherein said system further comprises a tube having a portion placed along the central axis of the hollow perforated member and having a portion placed along the pressure chamber; wherein the tube portion placed along the central axis of the hollow perforated member comprises a plurality of sprinklers attached thereon and the tube portion placed along the pressure chamber comprises an aperture; and wherein the system further comprises a motor configured to rotate the tube.

Preferably, a sealed partition is placed between the hollow perforated member and the pressure chamber.

The present invention relates to a method for filtering a liquid comprising: discharging a stream of liquid vertically downwards into a filtering vessel thereby causing a vertically downwards flow; splitting the vertically downwards flow such that most of the vertically downwards flow does not initially directly engage a hollow perforated member within said filtering vessel; passing liquid within the filtering vessel to the interior of the hollow perforated member via the perforations, while periodically sprinkling portions of the inner surface of the hollow perforated member;- 8 - extracting filtrate from the interior of the hollow perforated member.

Preferably, the method comprises one or more of the following (steps): preventing particles from passing into the hollow perforated member; entrapping floating particles from the stream of liquid in a lower portion of the filtering vessel; bringing heavy particles to a lower portion of the filtering vessel by means of the inertial force of the discharged liquid and the force of gravity.

Preferably, the method step of periodically sprinkling portions of the inner surface of the hollow perforated member comprises: directing a stream of filtrate from the interior of the hollow perforated member into a pressure chamber; passing filtrate from the pressure chamber to the interior of a first portion of a tube that is placed within said pressure chamber, via an aperture in said first portion of a tube; extracting the filtrate from a second portion of the tube that is placed within the hollow perforated member, via sprinklers disposed on the second portion of the tube; rotating the tube.

Preferably, the method further comprises: periodically carrying out a flushing stage, said flushing stage comprises: discharging the liquid content of the filtering vessel;- 9 - directing a stream of clean liquid into the pressure chamber; passing clean liquid from the pressure chamber to the interior of a first portion of a tube that is placed within said pressure chamber, via the aperture in the first portion of the tube; extracting the clean liquid from the second portion of the tube that is placed within the hollow perforated member, via the sprinklers disposed on the second portion of the tube; rotating the tube.

Preferably, periodically carrying out the flushing stage is actually carried out when the flow rate of the filtrate extracted from the interior of the hollow perforated member is below a predefined threshold.

BRIEF DESCRIPTION OF THE DRAWINGS: The present invention is illustrated by way of example in the accompanying drawings, in which similar references consistently indicate similar elements and in which: - Fig. 1 illustrates the present invention system according to an embodiment of the present invention.

- Fig. 2A illustrates a cross-section at one angle of the present invention vessel according to an embodiment of the present invention.

- Fig. 2B illustrates a cross-section at another angle of the present invention vessel according to an embodiment of the present invention.- 10 - - Fig. 2C illustrates a visual aspect of the splitter member, the hollow perforated member, and the skating surfaces, according to an embodiment of the present invention.

- Figs. 3A-3B show a first state of operation according to an embodiment of the present invention.

- Figs 4A-4B show a second state of operation according to an embodiment of the present invention.

- Figs 5A-5B show a third state of operation according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION: The present invention relates to a filtration system having a vessel which its interior is divided into a filtrate zone and a filtering zone. The filtering zone is capable of receiving a stream of raw-water filling the entire filtering zone of the vessel, and the filtrate zone is adapted to receive a filtrate obtained from passage of said stream of raw-water via a hollow perforated member, wherein the filtrate zone is within the interior of the hollow perforated member.

The present invention is especially useful for being a Pre filter for fine filtration systems.

The raw water is discharged into the filtration vessel (preferably via a vertical inlet pipe) from the top of the vessel such that the raw water flows vertically downwards.

A flow splitter member is placed above the perforated member splitting the raw water flow such that the raw water flow entering the vessel does not directly flow and engage - 11 - the perforated member, but instead a large portion of the flow flows diagonally downwards around the hollow perforated member. The vessel has two skating surfaces that slant diagonally downwards from the sides of the interior of the vessel until a gap is formed therebetween. The two skating surfaces are configured to enclose a majority of floating particles that have passed downwards through the gap, such that the floating particles are maintained under the two skating surfaces. This assists in keeping the floating particles away from the perforated member and lessens the perforated member blockages that may occur on the outer surface of the hollow perforated member during filtration. This contributes to the efficiency of the entire filtering process.

A self-cleaning "backflush" spray from a plurality of nozzles in fluid communication with clean water is applied from the interior of the hollow perforated member outwards, in order to disconnect floating particles that become attached to the outer surface of the hollow perforated member, contributing to the efficiency of the filtering process. An advantageous feature is that clean water causing the "backflush" spray is taken from a portion of the filtrate obtained by the present invention system.

According to an embodiment of the present invention, the present invention relates to a system 10 comprising a filtration vessel 20, shown in Fig. 1. The upper part 20a of the filtration vessel 20 is preferably in the form of a cylindrical body and the lower part 20b of the filtration vessel 20 tappers downwards (having a tapering shape (e.g.,- 12 - conical, funnel-shape) which tapers downwardly towards the base of the filtration vessel 20.

The system 10 may comprise a raw water tank 5 that holds raw water 3 to be filtered. The raw water tank 5 comprises an outlet 6 having a valve 7. The outlet 6 is coupled via a flow pipeline to a pump 8 which is configured to pump raw water 3 from the raw water tank 5 and deliver a stream of raw water via a flow pipeline 9 to the filtration vessel . The filtration vessel comprises an inlet 11 at its top, such that the raw water discharged into the filtration vessel 20 is discharged vertically downwards. System 10 may comprise an inlet valve 11v for opening/closing inlet 11.

According to an embodiment of the present invention, the filtration vessel 20 has two skating surfaces 15a and 15b that slant (e.g. diagonally) downwards from the sides of the interior of vessel 20 (shown in Fig 2A). The skating surfaces 15a and 15b actually slant from the upper part 20a of the filtration vessel 20. Fig. 2a is a cross-section at one angle of vessel 20. The skating surfaces 15a and 15b outer edges have an oval shape and their outer edges engage and are sealably attached to the interior round side of vessel 20. The skating surfaces 15a and 15b slant diagonally downwards from the sides of the interior of the vessel 20 (preferably from two corresponding points below the hollow perforated member) until a gap 16 is formed therebetween such that the interior of the vessel 20 is divided by an upper portion above the surfaces 15a and 15b and a lower portion beneath the surfaces 15a and 15b, with the gap 16 at the border between the two. The content of the upper portion may travel to the lower potion only via - 13 - gap 16, thereby gap 16 is actually a passage between the upper portion and lower portion of the vessel 20. Each of the surfaces 15a and 15b is actually in the form of a portion (e.g. half) of an ellipse, where their inner edges are straight lines placed across the inner interior of the vessel 20 forming gap 16. Optionally, each surface 15a, 15b inner straight-line edge (forming one side of gap 16) is attached to a corresponding rectangular surface 17a, 17b respectively, that extends downwards therefrom.

The bottom portion of the lower part 20b of the filtration vessel 20 comprises an outlet 21 coupled to a valve 23.

When the valve 23 is in an open state the content of vessel (including the residues and particles) is discharged.

The filtration vessel 20 comprises an air release valve 26 to be in an open state when the content of vessel 20 is flushed/discharged (wherein the content of vessel 20 is flushed/discharged by the force of gravity).

The vessel 20 comprises a hollow perforated member 50 mounted thereinside, thereby defining a filtrate zone inside the hollow perforated member 50 (having perforations, e.g. a plurality of pores) and a filtering zone in the volume of the filtrating vessel 20 external to the hollow perforated member 50. The filtrate zone is adapted to receive a filtrate obtained from passage of a stream of raw-water (that has been discharged into the vessel 20 e.g. from raw water tank 5) that passes via the pores of the hollow perforated member 50 into its interior.

The hydraulic pressure within the filtrating vessel 20 is greater than the pressure within the hollow perforated member 50. For example, the operational pressure - 14 - differences may be e.g. pressure drops of about 0.2 to 2 Bar.

The hollow perforated member 50 comprises at least one outlet 58 suitable for streaming filtrate obtained in the filtrate zone to a filtrate reservoir 60 (via flow pipeline 55). System 10 may comprise an outlet valve 58v for opening/closing outlet 58. The filtrate is delivered to the filtrate reservoir 60 by the force of the pressure differences and/or a dedicated pump (not shown) for this purpose. Flow pipeline 55 may comprise a sensor 57 for measuring the flow rate within flow pipeline 55. For example, the flushing stage explained herein may be carried out when the sensor 57 senses a flow rate within pipeline 55 that is below a predefined threshold.

Optionally, the hollow perforated member 50 may further comprise an inlet suitable for streaming fresh water into the filtrate zone for carrying out backwash operations. The hollow perforated member 50 acts as a main strainer.

According to one embodiment of the present invention, the hollow perforated member 50 may be in the form of a mesh, (e.g. the outer surface may be in the form of a mesh, lattice, net, grid and the like.

According to an embodiment of the present invention, the hollow perforated member 50 is cylindrical and preferably mounted from one side of the interior of the vessel 20 to the other. The length of hollow perforated member 50 is substantially parallel to the length of gap 16. The hollow perforated member 50 is substantially perpendicular to the longitudinal axis (i.e. vertical central axis 22) of - 15 - filtration vessel 20. Fig. 2B shows a cross-section of vessel 20 at an angle where a cross-section of the length of the cylindrical hollow perforated member 50 is shown (where the horizontal central axis 51 of hollow perforated member 50 intersects with the vertical central axis 22 of vessel 20). Fig. 2A shows a cross-section of vessel 20 at an angle where the cross-sectional area of the cylindrical hollow perforated member 50 is shown (at a 90 degrees rotation from Fig. 2B).

Hollow perforated member 50 is mounted within filtration vessel 20, preferably between two opposing inner sides of filtration vessel 20. Hollow perforated member 50 is preferably fixated inside filtration vessel 20 through two lateral openings formed in opposing sides of filtration vessel 20, and optionally configured to allow easy and fast removal and replacement of hollow perforated member 50 therethrough. Optionally, the hollow perforated member 50 is fixated by means of lateral mounting ports provided over the two lateral openings. The outlet 58 is coupled to one side of perforated member 50. A pressure chamber 70 (explained hereinafter) is attached to the other side of hollow perforated member 50.

According to an embodiment of the present invention, the system 10 utilizes a portion of the filtered water (preferably taken from outlet 58) prior to its delivery to filtered water tank reservoir 60, to backwash spray the inner surface of the hollow perforated member 50, thereby pushing away blockages formed on the outer surface of the hollow perforated member 50. Such materials that form the blockages may be particles (e.g. floating particles 95) - 16 - that have been sucked and attached to the outer surface of hollow perforated member 50 (attached to one or more of the pores of hollow perforated member 50).

System 10 comprises a bypass flow pipeline 64 coupled to outlet 58 capable of directing a portion of the filtrate exiting hollow perforated member 50 (via outlet 58), for the backwash spray. The flow pipeline 64 is coupled to a pressure pump 62 which is capable of sucking (i.e. causing negative pressure conditions) filtrate from outlet 58 and directing the filtrate (e.g. therethrough) to the pressure chamber 70 via a flow pipeline 61 (where the filtrate is passed through flow pipeline 61 typically at an increased fluid velocity. Flow pipeline 61 comprises a regulating valve 65 such that a desired stream may enter the pressure chamber 70 (and thus a desired pressure may be obtained in pressure chamber 70 by the pressure force of pressure pump 62 applied and the position of regulating valve 65). The bypass flow pipeline 64 may comprise a one way valve 67.

Optionally, the pressure pump 62 may also be coupled to another water source, e.g. a city water valve 69 coupled to a city water faucet (not shown), for an enhanced amount of clean water to be entered into the pressure chamber during the process of cleaning/flushing system 10 (i.e. when the content of vessel 10 is flushed via outlet 21, etc.).

System 10 comprises a tube 73 along the central axis of the hollow perforated member 50, such that the central axis of tube 73 is actually the horizontal central axis 51 of hollow perforated member 50. The tube 73 is hollow and sealed at both of its ends. The pressure chamber 70 is - 17 - preferably in the form of a cylinder (preferably in the form of a continuation of hollow perforated member 50). A sealed partition 71 is placed between the hollow perforated member 50 and the pressure chamber 70. The sealed partition 71 (e.g. a bearing element) comprises an aperture such that the tube 73 passes tightly therethrough in a sealable manner such that water from the pressure chamber 70 does not pass to the interior of hollow perforated member 50 and vice versa. However, tube 73 may rotate within the aperture. One end of tube 73 is mounted on an appropriate bearing 76 placed near the outlet 58.

The tube 73 extends beyond the perforated member 50 and terminates at the end of the pressure chamber 70. The portion of tube 73 within the pressure chamber 70 comprises an aperture 75.

According to one embodiment the present invention system 10 comprises a motor 80 configured to rotate tube 73 around its central axis 51. According to one embodiment, the end of tube 73 that terminates at the end of the pressure chamber 70 has a sealing surface 72, and the motor 80 is configured to rotate a rotatable axle (not shown) extending therefrom wherein the sealing surface 72 is mounted on and fixed to the axle (at sealing surface 72 center). The motor 80 is configured to cause rotation of the axle (and thus of the sealing surface 72 mounted thereon and fixed thereto).

Typically, the axle is aligned along the axis 51.

The portion of tube 73 within hollow perforated member 50 comprises a plurality of apertures. A plurality of sprinklers 74 are attached to tube 73, each sprinkler at a - 18 - location of a corresponding aperture. The sprinklers 74 are configured to spray the pressured filtrate within tube 73 (passing through the apertures and through the sprinklers 74) on the interior surface of hollow perforated member 50, thereby disconnecting blockages (e.g. residues, particles, floating particles) attached to the external surface of hollow perforated member 50. This contributes to the efficiency of the filtering process. It should be noted that according to one embodiment the sprinklers may be the apertures themselves, i.e. simple apertures/pores within tube 73.

The sprinklers 74 preferably spray the filtrate at an angle such that when tube 73 fully rotates (and the sprinklers 74 continuously sprinkle) an internal portion of hollow perforated member 50 having an elongated ring shape (a cylindrical portion) is fully sprinkled. Each sprinkler 74 covers a certain portion adjacent to its adjacent sprinkler's 74 portion. Preferably, the sprinklers 74 are spaced apart such that each sprinkler 74 covers a corresponding elongated ring portion such that every spot of the interior surface of hollow perforated member 50 is covered by at least one rotating sprinkler (after a full rotation cycle of tube 73). Preferably, the sprinklers 74 are evenly spaced apart. Preferably, a first group of sprinklers 74 are aligned and evenly spaced apart on one side of tube 73 and a second group of sprinklers 74 are aligned and evenly spaced apart on the opposing side of tube 73, wherein all of the sprinklers are evenly spaced apart one from each other (as shown in Fig. 2B).- 19 - The pump 62 and regulating valve 65 cause the pressure in the pressure chamber 70. This configuration enables a constant sprinkle of the sprinklers 74. On one hand the tube 73 constantly rotates. On the other hand, the pressure in the pressure chamber 70 enables the filtrate to constantly enter the tube 73 via aperture 75 at any rotation position that aperture 75 is in. Thus tube 73 is constantly fully filled with filtrate and the sprinkling pressure is dependent on the pressure chamber pressure (which is dependent on the pumping force of pump 62 and regulating valve 65).

An advantageous feature of the present invention is flow splitter member 90 (a cross section of it is shown in Fig. 2A). The raw water 3 is discharged into the filtration apparatus via a flow pipeline 9 from the top of the vessel such that the raw water 3 flows vertically downwards. A flow splitter member 90 is placed above the perforated member 50 splitting the raw water flow such that the raw water flow entering the vessel does not directly flow and engage the perforated member 50, but instead a large portion of the flow flows diagonally downwards around the hollow perforated member 50.

The split raw water flow containing floating particles 95 continues with the inertial force downwards and around the perforated member 50 and then downwards diagonally along the skating surfaces 15a and 15b and through the gap 16.

The inertial force causes the particles (both heavy particles 96 and floating particles 95) do travel downwards past the gap 16, where the heavy particles 96 tend to go downwards towards outlet 21 (by the inertial force and - 20 - gravity), and the floating particles 95 tend to go sideways (and optionally also a bit upwards) under skating surfaces 15a and 15b.

In general, the floating particles 95 have a specific gravity smaller than that of the water (or liquid being filtered). The heavy particles 96 have a specific gravity greater than that of the water (or liquid being filtered).

The two skating surfaces 15a and 15b are configured to enclose a majority of floating particles 95 that have passed downwards through the gap 16, such that the floating particles 95 are maintained under the two skating surfaces 15a and 15b. This assists in keeping the floating particles 95 away from the perforated member 50 and lessens the perforated member 50 blockages (i.e. the load on the perforated member 50) that may occur on the outer surface of the hollow perforated member 50. This contributes to the efficiency of the filtering process.

The splitter member 90 comprises two elongated surfaces attached to one another with an angle therebetween.

Preferably, the splitter member 90 comprises two adjacent rectangular surfaces 90a and 90b where one side of surface 90a is attached to one side of surface 90b with an angle therebetween, wherein the attachment line is the peak 91 of splitter member 90. The peak 91 faces the top of the vessel . The angle between rectangular surfaces 90a and 90b may vary according to different embodiments, e.g. the angle is usually between 90 and 120 degrees.- 21 - The splitter member 90 is placed horizontally and mounted from one side of the interior of the vessel 20 to the other. The length of splitter member 90 is substantially parallel to the length of hollow perforated member 50 (and is substantially parallel to the length of gap 16; and is substantially perpendicular to the longitudinal axis - vertical central axis 22). Fig. 2B shows a cross-section of vessel 20 at an angle where peak 91 is shown. Fig. 2A shows a cross-section of vessel 20 at an angle where the cross section of splitter member 90 is shown (at a 90 degrees rotation from Fig. 2B).

Fig. 2A further shows a plurality of heavy particles 96 which mainly pass the splitter member 90 and fall downwards (e.g. along skating surfaces 15a and 15b) towards outlet 21 and accumulate there. When the valve 23 is in an open state the liquid content of vessel 20 (including the residues, heavy particles 96, floating particles 95) is discharged and flushed e.g. into an open drain 25. Fig. 2A further shows two lateral service openings 29a and 29b formed in opposing sides of filtration vessel 20. Typically, the imaginary line connecting service openings 29a and 29b is substantially perpendicular to the cylindrical hollow perforated member 50.

Fig. 2C shows a visual aspect of the splitter member 90 above the hollow perforated member 50, and the skating surfaces 15a and 15b, within the filtering vessel 20 according to an embodiment of the present invention. The splitter member 90 is shown in the form of a roof element above the cylindrical hollow perforated member 50.- 22 - Preferably, filtration vessel 20 may be made from any material suitable for holding high pressures, e.g. steel.

Hollow perforated member 50 may comprise material such as steel, stainless steel, e.g. stainless steel 316.

Pipelines 9, 55, 64, 61 may comprise steel.

Tube 73 may comprise stainless steel.

Pressure chamber 70 may comprise steel.

Skating surfaces 15a and 15b may comprise steel.

The splitter member 90 may be comprise steel.

A commercial example of the valves 26, 67, 58v, 11v, 23, 7, 65, is e.g. Belimo butterfly valves. A commercial example of the pump 62 and the motor 80 may be e.g. a Pedrollo pump and motor CM32-160a.

The vertical length of the filtration vessel 20 is usually between 100 and 200 cm. Its diameter (of the upper portion 20a) is usually between 40 and 170 cm. Its thickness is usually between 6 and 10 mm.

The length of the hollow perforated member 50 is usually between 20 and 170 cm. Its diameter is usually between 20 and 300 mm. According to one embodiment, the pores are usually between 100 and 500 microns. According to one embodiment, the distance between two adjacent pores is usually between 200 and 300 microns.- 23 - Pipelines 9, 55, 64, 61 lengths are usually between 40 and 100 cm. Their diameters are usually between 40 and 50 mm.

Their thickness are usually between 4 and 5 mm.

The length of tube 73 is usually between 60 and 150 cm. Its diameter is usually between 4 and 5 cm.

The length of pressure chamber 70 is usually between 20 and cm. Its diameter is usually between 16 and 20cm.

The length (diagonal) of each of the skating surfaces 15a and 15b is usually between 40 and 80 cm. Their width is usually between 40 and 150 cm. Their thickness is usually between 6 and 10 mm.

The diameter of aperture 75 is usually between 3 and 4 cm.

The length of the splitter member 90 is usually between 20 and 170 cm. Its thickness (i.e. the thickness of each surface 90a and 90b) is usually between 6 and 10 mm.

Optionally, system 10 comprises a control unit (comprising a memory and a processor) that is connected to the system valves, pumps 8, 62, sensor 57 and motor 80, and configured to control these elements thus controlling the filtering process manner. For example, the valves, pumps 8, 62, and motor 80 may be controlled according to the readings of e.g. sensor 57.

Figs. 3A-3B show a first state of operation according to an embodiment of the present invention. In this state the raw - 24 - water enters the filtering vessel 20 (from raw water tank ) and is filtered, and the filtrate is delivered to the filtered water tank 60. The following table 1 shows the modes of the operating elements. With relation to the system valves, the "ON" state indicates an open (or partially open) valve, and the "OFF" state indicates a closed valve.

Table 1 ELEMENT MODE Valve 11v ON Valve 58v ON Valve 23 OFF Valve 65 ON Valve 26 OFF Valve 69 OFF Pump 62 ON Motor 80 ON Figs. 4A-4B show a second state of operation according to an embodiment of the present invention. In this state the raw water does not enter the filtering vessel 20, and the filtrate is not delivered to the filtered water tank 60.

The content of filtering vessel 20 is flushed/discharged.

The following table 2 shows the modes of the operating elements.- 25 - Table 2 ELEMENT MODE Valve 11v OFF Valve 58v OFF Valve 23 ON Valve 65 ON Valve 26 ON Valve 69 OFF Pump 62 OFF Motor 80 OFF Figs. 5A-5B show a third state of operation according to an embodiment of the present invention. In this state an enhanced cleansing and flushing of the system is carried out. The city water valve 69 is turned on and water from a city water faucet is provided to pump 62 (optionally along with filtrate via pipeline 64). The motor 80 is activated and the sprinklers 74 cleanse the cylindrical hollow perforated member 50 from the inside to the outside, thus cleansing the outer surface of the cylindrical hollow perforated member 50 (e.g. from blockages formed thereon) including opening the pores. The following table 3 shows the modes of the operating elements.- 26 - Table 3 ELEMENT MODE Valve 11v OFF Valve 58v OFF Valve 23 ON Valve 65 ON Valve 26 ON Valve 69 ON Pump 62 ON Motor 80 ON For the sake of simplicity, most reference numbers have not been added to Figs 3A-3B, 4A-4B and 5A-5B, wherein the reference numbers of Figs. 2A-2B may be applied to Figs 3A- 3B respectively, to Figs. 4A-4B respectively and to Figs. 5A-5B respectively. The differences between each stage may be seen by the positions of the particles in each stage and the open/close position of the valves 11v, 58v and 23 in each stage (wherein these valves and particles' reference numbers have been added to these figures). The valves in each stage in Figs. 3A-3b, 4A-4B, 5A-5B, are shown as being open or closed according to the tables above.

For the sake of simplicity, the present invention system has been explained herein in relation to filtering water.

However, the present invention system may be used for filtering other liquids.- 27 - The present invention relates to a method (explained herein also with reference to the system 10) for filtering liquid (e.g. raw water). The method comprises: discharging a stream of liquid vertically downwards into a filtering vessel thereby causing a vertically downwards flow; splitting the vertically downwards flow such that most of the vertically downwards flow does not initially directly engage a hollow perforated member within said filtering vessel (of course, after the initial entrance, when the liquid fills the vessel, the liquid is filtered by passing into the interior of the hollow perforated member); passing liquid within the filtering vessel to the interior of the hollow perforated member via the perforations/pores, while periodically sprinkling portions of the inner surface of the hollow perforated member (e.g. with clean water); extracting filtrate from the interior of the hollow perforated member.

Preferably, the method comprises one or more of the following: preventing particles from passing into the hollow perforated member; entrapping floating particles from the stream of liquid in a lower portion of the filtering vessel; bringing heavy particles to a lower portion of the filtering vessel by means of the inertial force of the discharged liquid and the force of gravity.

According to one embodiment, the method step of periodically sprinkling portions of the inner surface of the hollow perforated member comprises: - 28 - directing a stream of filtrate from the interior of the hollow perforated member into a pressure chamber; passing filtrate from the pressure chamber to the interior of a first portion of a tube that is placed within said pressure chamber, via an aperture in said first portion of a tube; extracting the filtrate from a second portion of the tube that is placed within the hollow perforated member, via sprinklers disposed on the second portion of the tube; rotating the tube.

Preferably, the method further comprises: periodically carrying out a flushing stage, said flushing stage comprises: discharging the liquid content of the filtering vessel; directing a stream of clean liquid into the pressure chamber; passing clean liquid (e.g. clean water) from the pressure chamber to the interior of a first portion of a tube that is placed within said pressure chamber, via the aperture in the first portion of the tube; extracting the clean liquid from the second portion of the tube that is placed within the hollow perforated member, via the sprinklers disposed on the second portion of the tube; rotating the tube.

Preferably, periodically carrying out the flushing stage is carried out when the flow rate of the filtrate extracted from the interior of the hollow perforated member is below a predefined threshold (e.g. according to sensor 57).- 29 - While some of the embodiments of the invention have been described by way of illustration, it will be apparent that the invention can be carried into practice with many modifications, variations and adaptations, and with the use of numerous equivalents or alternative solutions that are within the scope of a person skilled in the art, without departing from the spirit of the invention, or the scope of the claims.

Claims

- 30 - CLAIMS:

1. A filtration system comprising: a filtration vessel; a filtration vessel inlet at the top of said filtration vessel; a filtration vessel outlet at the bottom of said filtration vessel; a hollow perforated member comprising a plurality of pores, mounted within said filtration vessel; a filtrate outlet for streaming filtrate obtained within the hollow perforated member to a filtrate reservoir; and a flow splitter member placed above said hollow perforated member; wherein the filtration vessel comprises an upper portion in the form of a cylindrical body and a lower portion that tapers downwards; and wherein the filtration vessel comprises two skating surfaces that slant downwards from the sides of the interior of said vessel until a gap is formed therebetween.

2. The filtration system according to claim 1, wherein the filtration vessel inlet comprises an inlet valve and wherein the filtration vessel outlet comprises an outlet valve.

3. The filtration system according to claim 1, wherein the hollow perforated member is cylindrical.

4. The filtration system according to claim 3, wherein the hollow perforated member is mounted from one side of the interior of the vessel to the other.- 31 -

5. The filtration system according to claim 3, wherein the longitudinal axis of the hollow perforated member is substantially perpendicular to the longitudinal axis of the filtration vessel.

6. The filtration system according to claim 1, wherein said system comprises a raw water tank coupled to the filtration vessel inlet; and wherein the filtrate reservoir is coupled to the filtrate outlet.

7. The filtration system according to claim 1, wherein the splitter member comprises two elongated surfaces attached to one another.

8. The filtration system according to claim 7, wherein the elongated surfaces are two rectangular surfaces where one side of one surface is attached to one side of the second surface thereby forming an attachment line therebetween and an angle therebetween.

9. The filtration system according to claim 8, wherein the attachment line faces the top of the filtration vessel.

10. The filtration system according to claim 9, wherein the filtration vessel comprises an upper portion in the form of a cylindrical body and a lower portion that tapers downwards; and wherein the filtration vessel comprises two skating surfaces that slant downwards from the sides of the - 32 - interior of said vessel until a gap is formed therebetween; and wherein the length of the splitter member is substantially parallel to the length of the gap.

11. The filtration system according to claim 5, wherein the system comprises a bypass flow pipeline coupled to the filtrate outlet, and coupled to a pressure pump; wherein said pressure pump is coupled to a pressure chamber; wherein said system further comprises a tube having a portion placed along the central axis of the hollow perforated member and having a portion placed within the pressure chamber; wherein the tube portion placed along the central axis of the hollow perforated member comprises a plurality of sprinklers attached thereon and the tube portion placed within the pressure chamber comprises an aperture; and wherein the system further comprises a motor configured to rotate the tube.

12. The filtration system according to claim 11, wherein a sealed partition is placed between the hollow perforated member and the pressure chamber.

13. A method for filtering a liquid comprising: discharging a stream of liquid vertically downwards into a filtering vessel thereby causing a vertically downwards flow; splitting the vertically downwards flow such that most of the vertically downwards flow does not initially directly - 33 - engage a hollow perforated member within said filtering vessel; entrapping floating particles from the stream of liquid in a lower portion of the filtering vessel; passing liquid within the filtering vessel to the interior of the hollow perforated member via the perforations, while periodically sprinkling portions of the inner surface of the hollow perforated member; extracting filtrate from the interior of the hollow perforated member.

14. The method according to claim 13, comprising one or more of the following: preventing particles from passing into the hollow perforated member; bringing heavy particles to a lower portion of the filtering vessel by means of the inertial force of the discharged liquid and the force of gravity.

15. The method according to claim 13, wherein the method step of periodically sprinkling portions of the inner surface of the hollow perforated member comprises: directing a stream of filtrate from the interior of the hollow perforated member into a pressure chamber; passing filtrate from the pressure chamber to the interior of a first portion of a tube that is placed within said pressure chamber, via an aperture in said first portion of a tube; extracting the filtrate from a second portion of the tube that is placed within the hollow perforated member, via sprinklers disposed on the second portion of the tube; rotating the tube.- 34 -

16. The method according to claim 15, further comprising: periodically carrying out a flushing stage, said flushing stage comprises: discharging the liquid content of the filtering vessel; directing a stream of clean liquid into the pressure chamber; passing clean liquid from the pressure chamber to the interior of a first portion of a tube that is placed within said pressure chamber, via the aperture in the first portion of the tube; extracting the clean liquid from the second portion of the tube that is placed within the hollow perforated member, via the sprinklers disposed on the second portion of the tube; rotating the tube.

17. The method according to claim 16, wherein periodically carrying out the flushing stage is carried out when the flow rate of the filtrate extracted from the interior of the hollow perforated member is below a predefined threshold.