IL255057A - Liquid maintenance system and method - Google Patents

Description

1 LIQUID MAINTENANCE SYSTEM AND METHOD FIELD AND BACKGROUND OF THE INVENTION The present invention, in some embodiments thereof, relates to a liquid maintenance system and method, more particularly, but not exclusively, to a liquid maintenance system and method for processing a liquid in a reservoir.

Maintenance of liquid level in a reservoir, such as a swimming pool, requires response to various parameters, including, response to variations in liquid level, circulation of liquid back to the reservoir and control of contaminants concentration in the reservoir.

The contaminants concentration may be controlled by using a filter, which separates the contaminants from the liquid. A balance tank may be used to control the liquid level in the reservoir, which is operated to receive overflow liquid from the reservoir when overflow in the reservoir occurs and to withdraw liquid back to the reservoir when liquid level in the reservoir is beneath a predetermined level.

It is highly desired to provide a liquid maintenance system and method for various applications, which will result in recycling of purified liquid in an efficient, easy and cost effective manner.

SUMMARY OF THE INVENTION According to an aspect of some embodiments of the present invention, there is provided a liquid maintenance system for processing a recycled liquid in a reservoir. The system comprising a balance tank having at least one inlet for receiving liquid from an overflow line of the reservoir and at least one outlet, the balance tank comprises: an integrally disposed filter adapted to separate contaminants from the liquid within the balance tank while the liquid flows from the at least one inlet towards the at least one outlet; and a liquid level control mechanism adapted to operate at least one valve to vary liquid level in the balance tank; wherein the balance tank comprises a plurality of directional nozzles mounted in a bottom portion of the balance tank for directing flow of the liquid to a flow line connected to the reservoir. 2 According to some embodiments of the invention, the system wherein the filter is a sand filter.

According to some embodiments of the invention, the filter comprises a material selected from: sand, glass, stones, gravel, diatomic earth, activated carbon, depth, metallic alloy, ceramic, block carbon resin, microfiltration membrane and ultrafiltration membrane.

According to some embodiments of the invention, the system wherein the balance tank does not contain a filter after the outlet.

According to some embodiments of the invention, the system wherein the inlet comprises a valve, which when open allows liquid from the reservoir to flow towards the balance tank, and when closed stops such flow.

According to some embodiments of the invention, the system further comprises a liquid block valve before the inlet.

According to some embodiments of the invention, the system wherein the valve is adapted to be operated when overflowed liquid from a peripheral top edge gutter of the reservoir exceeds a predetermined level.

According to some embodiments of the invention, the system wherein the outlet is connected to flow line via a recirculating pump.

According to some embodiments of the invention, the system wherein the recirculating pump is connected to the balance tank via a float switch.

According to some embodiments of the invention, the system wherein the filter is configured to remove contaminants between about 10 and about 1000 µm size.

According to some embodiments of the invention, the system wherein the balance tank has a volume respective to between about 2-10% of area of the liquid reservoir.

According to some embodiments of the invention, the system wherein the plurality of directional nozzles having a diameter between about 20 mm and about 200 mm.

According to some embodiments of the invention, the system wherein the plurality of directional nozzles are distributed laterally about a plane of the balance tank 2 and have an inter-nozzle spacing of at least about 10 mm and about 40 mm per 1 cm filter area. 3 According to some embodiments of the invention, the system wherein the liquid flow conduit is connected to nozzles having a length of between about 1m and about 5m 2 per 1 m filter area.

According to some embodiments of the invention, the system wherein the conduit has a diameter of at least 90 mm.

According to some embodiments of the invention, the system wherein the at least one liquid level control mechanism further comprises a plurality of liquid level floats.

According to some embodiments of the invention, the system wherein the at least one liquid level control mechanism comprises a liquid level safety switch adapted to operate the recirculating pump to vary liquid level in the balance tank.

According to some embodiments of the invention, the system wherein the flow of the purified liquid back to the reservoir via the return flow line is carried out after the liquid level is beneath a predetermined amount.

According to some embodiments of the invention, the system wherein the reservoir is at least one of: a swimming pool, a hot tub, a liquid purification system and a water fountain.

According to an aspect of some embodiments of the present invention, there is provided a method of recycling liquid in a reservoir via a balance tank. The method comprising: flowing liquid from an overflow line of the reservoir to an inlet of the balance tank; flowing the liquid in the balance tank via a filter towards an outlet while separating contaminants from the liquid; and withdrawing the liquid from the outlet to the reservoir via flow line in accordance with liquid level in the balance tank.

According to some embodiments of the invention, the method wherein the withdrawing liquid is carried out by pumping the liquid to the reservoir.

According to some embodiments of the invention, the method wherein the pumping is controlled by a valve and/or a recirculating pump.

According to some embodiments of the invention, the method wherein the recirculating purified liquid into the reservoir is controlled by a liquid-level control mechanism. 4 According to some embodiments of the invention, the method further comprises supplying liquid to the balance tank via withdrawing liquid from a bottom drain line of the reservoir.

According to some embodiments of the invention, the method further comprises supplying an amount of disinfecting material to the liquid withdrawn from the outlet.

According to some embodiments of the invention, the method wherein the liquid is withdrawn from the outlet is essentially free of contaminants prior to entering a conduit and/or pump.

According to some embodiments of the invention, the method wherein the liquid from the overflow line is distributed throughout the balance tank via a liquid distributor prior to reaching the filter.

According to some embodiments of the invention, the method wherein the liquid withdrawn from the outlet having a turbidity level of at most 0.19 NTU.

According to some embodiments of the invention, the method wherein the withdrawing liquid from the outlet after one cycle is at a filtering efficiency of between about 20% and about 30%.

According to some embodiments of the invention, the filtering efficiency after n cycles is between about 60% and about 99%, wherein n is between 1 and 5.

Unless otherwise defined, all technical and/or scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art of liquid maintenance systems and in the art to which the invention pertains. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of embodiments of the invention, exemplary methods and/or materials are described below. In case of conflict, the patent specification, including definitions, will control. In addition, the materials, methods, and examples are illustrative only and are not intended to be necessarily limiting.

BRIEF DESCRIPTION OF THE DRAWINGS Some embodiments of the invention are herein described, by way of example only, with reference to the accompanying drawings and images. With specific reference now to the drawings in detail, it is stressed that the particulars shown are by way of example and for purposes of illustrative discussion of embodiments of the invention. In this regard, the description taken with the drawings makes apparent to those skilled in the art how embodiments of the invention may be practiced.

In the drawings: FIG. 1 is a schematic illustration of a reservoir provided with an exemplary liquid maintenance system, according to some embodiments of the present invention; FIG. 2 is a flow chart illustrating an exemplary method of recycling liquid in a reservoir via a balance tank, according to some embodiments of the present invention.

DETAILED DESCRIPTION OF THE INVENTION The present invention, in some embodiments thereof, relates to a liquid maintenance system and method, more particularly, but not exclusively, to a liquid maintenance system and method for processing liquid in a reservoir.

Before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not necessarily limited in its application to the details of construction and the arrangement of the components and/or methods set forth in the following description and/or illustrated in the drawings and/or the Examples. The invention is capable of other embodiments or of being practiced or carried out in various ways.

Liquid reservoirs, such as swimming pools and water treatment plants, require routine liquid management, inter alia, maintenance of liquid level in the reservoir (e.g., controlling liquid height in the reservoir to be at a predefined level) and maintaining liquid purity (e.g., controlling amount/concentration of contaminants below a predefined amount). Liquid management mechanisms may be utilized for such liquid maintenance, and typically contain a unit comprising a balance tank for regulating the liquid level in the reservoir; and a filter unit for removing contaminants in the liquid. The filter unit is typically installed as a separate unit from the balance tank. Liquid, which may typically 6 include contaminants, such as, particulate solids including dirt, sediment, hair, leaves and/or other foreign matter; may be extracted from distinct locations in the reservoir (e.g., bottom and sidewalls of a swimming pool), and then provided to a filter for separating the contaminants from the liquid to recirculate clean liquid back to the reservoir.

A filter typically contains particles (e.g., sand, diatomic earth and/or the like), having particles size sufficient to trap the contaminants, but fine enough to allow liquid (e.g., water) to flow through filter grains having a diameter size of between, e.g., about 0.01 mm and about 2 mm. Optionally, smaller grains diameter may be utilized to provide higher surface area, e.g., when higher decontamination of inlet liquid is required.

Typically, a filter unit operates by receiving liquid (e.g., by receiving liquid withdrawn from a reservoir, for example, when liquid overflow in a reservoir exceeds a predefined level), which is then drawn down by gravity through the filter particles layer, referred to at times as a filter bed (e.g., sand filter bed), to cause contaminants in the liquid to be captured in the particles layer and to pass freely clean liquid downwards to the bottom of the filter unit.

Typically, a balance tank may be utilized to control the amount (e.g., height) of liquid in a reservoir and/or for equalizing flows from liquid sources when object(s) enter the reservoir and liquid level rises over a predetermined level. When the object(s) exit the reservoir, the liquid from the balancing tank flows back to the reservoir. For example, a balance tank may be utilized in various applications, including: in industrial applications to control flow and load downstream processes (e.g., combined foul and surface water sewers), in liquid treatment plants, in public swimming pools when occupancy in the pool reaches a maximum level and water overflow is detected, etc.

A balance tank may utilize liquid control devices, which measure liquid level within the tank to determine the optimum flow the reservoir will receive, which may in turn, allow to potentially reduce the amount of new liquid entering the reservoir, and/or size of a treatment system in treatment plants. When required (e.g., if liquid level is below a predetermined level), liquid may be added to the reservoir from the balance tank, optionally, via a pump.

A balance tank should be typically large enough to contain the liquid displaced by object(s), which, in turn, dictates the maximum overflow in the pool. For example, when 7 the reservoir is a swimming pool, a required size of the balance tank may be determined by the maximum amount of swimmers allowed to enter the pool times the amount of water per swimmer entering the pool.

When required, liquid may be recirculated back to the reservoir. As appreciated, in order to efficiently recirculate a liquid in a reservoir, a liquid circulation system should be operated at a relatively low volume flow rate, e.g., contaminated liquid may be withdrawn from the reservoir and then filtered to efficiently separate contaminants from the liquid for providing filtered liquid back to the reservoir.

The inventor has found that the system and method of the present invention can efficiently improve liquid recirculation by operation at a relatively low volume flow rate (filtering rate) and/or by utilizing increased filter area so as to provide high-purity grade liquid (e.g., providing substantially contaminant-free liquid back to the reservoir).

Some aspects of the present invention aim at providing a liquid maintenance system for processing a recycled liquid in a reservoir utilizing a balance tank for managing liquid level in the reservoir and having an integrally disposed filter therewithin for separating contaminants from the liquid.

Treatment of liquids contaminated with suspended particles, hair, debris, and/or the like; may be handled by utilizing a filter. Filtering systems may include filtering materials such as: sand filters, diatomic filters and/or the like, which may be utilized for treating various types of liquids, for example, waste water with high solid and suspended material component such as industrial waste water, for treating water in industrial use taken from ground water and surface water, for recirculating water, cooling water, and also for swimming pool water as well as treatment of potable water.

Some embodiments of the present invention utilize a filter material that comprises a material selected from: sand, glass, stones, gravel, diatomic earth, activated carbon, depth, metallic alloy, ceramic, block carbon resin, microfiltration membrane and ultrafiltration membrane.

Some embodiments of the present invention utilize a filter material that comprises sand and/or diatomic earth, and/or is sand /or diatomic earth.

A further aim of the present invention is to provide quick and easy handling of a filter unit and/or reduce time required to service a filter unit as problems typically 8 associated with filter maintenance (e.g., clogging of filter with contaminant particles, leakage from filter unit, formation of contaminant lumps in upper layer of filter bed, etc) are to be handled promptly to prevent disoperation of such a system, and to continuously circulate cleansed liquid to the reservoir.

This is achieved according to some embodiments of some aspects of the system and/or method of the invention, by utilizing a balance tank comprising an integrally disposed filter. The reservoir liquid enters the balance tank (optionally through at least one diffuser/sprinkler), for drawing the liquid downwards to the filter material layer. The contaminant particles may be captured in the filter bed, and the liquid may exit from the bottom of the filter to return clean liquid (filtered liquid) to the reservoir.

The filter may be an opened filter and/or a closed filter. Some embodiments of the present invention may require increased flow pressure and/or flow rate to drive the liquid through the bed. For example, smaller filter grains size may provide more surface area and therefore a higher decontamination of inlet liquid, however, may also require more pumping energy to drive the fluid through the bed. At times, the filter may comprise grains size (e.g., diameter) between about 0.6 mm to about 1.2 mm. Some embodiments of the invention may utilize larger grain sizes (>100 µm diameter) in accordance with application type, which may tend to block pores of the filter bed.

Some embodiments of the invention provide a filter for removing contaminants having particle size (e.g., diameter) between about 10 µm and about 1000 µm.

The system and/or method may efficiently improve liquid recirculation (e.g., liquid filtering) by operation at a relatively low volume flow rate (e.g., filtering rate) and/or by utilizing increased filter area so as to provide high-purity grade liquid (e.g., providing substantially contaminant-free liquid back to the reservoir). Some embodiments of the invention utilize a flow rate (e.g., filtering rate) of between about 10 and 50 cubic m/h, or at times at a flow rate of between about 20 and 30 cubic m/h, or even further at times at a flow rate of at most about 25 cubic m/h, where the filtering is carried out for a predetermined time, e.g., 1 hour, or at times two hours, or three hours, or four hours, or even five hours. Some examples of such embodiments may provide a filtering efficiency of between about 22% to 30%, optionally determined by, e.g., measuring the one or more optical property level/grade (such as turbidity) of liquid 9 withdrawn from the balance tank after n cycles of liquid from the reservoir (e.g., after n filtering cycle), wherein n is between 1 and 8, or at times between 1 and 7, or between 1 and 6, or between 1 and 5, or between 1 and 4, or between 1 and 3, or between 1 and 2, or even at times, a single cycle.

The one or more optical property measurements/tests, such as turbidity, may be determined by, e.g., measuring light scattered and/or absorbed in a sample of liquid rather than transmitted through the sample before and after filtering according to the process of the invention, optionally at a predetermined filtering rate (e.g., at a flow rate of between about 10 and 50 cubic m/h, or at times between about 20 and 30 cubic m/h, or at most 25 cubic m/h); where the filtering is carried out for a predetermined time, e.g., 1 hour, or at times two hours, or three hours, or four hours, or even five hours. Turbidity level/grade (also referred herein: Turbidity) is typically a measure of relative sample clarity, e.g., corresponding to the level of contaminants in the liquid, and may be measured by a Turbidimeter device (e.g., EMEC sensor probe; Orbeco Hellige USA TB200-10 - white light field portable; etc.) to measure light in a sample of liquid as above said. The units of turbidity level/grade may be typically arbitrary (e.g., in NTU units - Nephelometric Turbidity Units), and as such, a Turbidimeter may be optionally calibrated against standards with known scattering properties, e.g., by using at least one test tube having an initial turbidity of 0 NTU, and/or 40 NTU and/or 100 NTU, followed by a step of filling a cube having a volume of about 1000 L liquid having turbidity of 100 NTU and measuring the turbidity before filtering and after one cycle of filtering and/or after a plurality of filtering cycles at the predetermined filtering rates and filtering times, as above said. In one such exemplary test of determining filtering efficiency of a liquid (e.g., water) processed according to the invention, after the first filtering cycle the turbidity decreased by between about 20% to about 35%, at times between about 22% and about 30%, or at times, between about 26 and about 29% was measured (e.g., by Orbeco Hellige USA TB200-10 - white light field portable turbidimeter), or further at times, between about 22% and about 28.5%. Optionally, the Turbidimeter may be calibrated before one or more test measurements against standards with known scattering properties of e.g., 0 NTU, and/or 40 NTU and/or 100 NTU.

In another exemplary turbidity test (e.g., measured by Orbeco Hellige USA TB200-10 - white light field portable turbidimeter), after a single filtering cycle, and/or 2 and/or 3 and/or 4 and/or 5 and/or 6 and/or 7 and/or 8 and/or 9 filtering cycles, the liquid exhibited a turbidity of between about 0.01 NTU and about 0.5 NTU, at times, between about 0.01 NTU and about 0.2 NTU, at times between about 0.01 NTU and about 0.1 NTU, at times between about 0.01 NTU and about 0.08 NTU, at times, at most about 0.07 NTU, and even further at times, at most about 0.06 NTU. In another such exemplary test of determining filtering efficiency of a liquid (e.g., water) processed according to the invention, the turbidity (e.g., measured by Orbeco Hellige USA TB200-10 - white light field portable turbidimeter) decreased from an initial purity grade of about 100 NTU to about 0.3 NTU after a single filtering cycle, and/or 2 and/or 3 and/or 4 and/or 5 and/or 6 and/or 7 and/or 8 and/or 9 filtering cycles. In yet another such exemplary test of determining filtering efficiency of a liquid (e.g., water) processed according to the invention, the turbidity (e.g., measured by Orbeco Hellige USA TB200-10 - white light field portable turbidimeter) decreased from about 25.2 NTU to about 0.25 NTU, or at times to about 0.2 NTU, or to about 0.18 NTU, or 0.16 NTU, or 0.14 NTU, or 0.12 NTU, or 0.10 NTU, or 0.08 NTU, or 0.07 NTU, or 0.06 NTU, or even to about 0.05 NTU; after a single filtering cycle, and/or 2 and/or 3 and/or 4 and/or 5 and/or 6 and/or 7 and/or 8 and/or 9 filtering cycles. The filtering efficiency may be determined by, e.g., measuring the turbidity level/grade (e.g., measured by Orbeco Hellige USA TB200-10 - white light field portable turbidimeter) of liquid withdrawn from the balance tank after n cycles of liquid from the reservoir (e.g., after n filtering cycle), wherein n is between 1 and 8 cycles, or at times between 1 and 7 cycles, or between 1 and 6, or between 1 and 5, or between 1 and 4, or between 1 and 3, or between 1 and 2, or even at times, a single cycle; optionally at a predetermined filtering rate (e.g., at a flow rate of between about 10 and 50 cubic m/h, or at times between about 20 and 30 cubic m/h, or at most 25 cubic m/h); where the filtering is carried out for a predetermined time, e.g., 1 hour, or at times two hours, or three hours, or four hours, or even five hours.

A linear relationship may exist between the turbidity in NTU and the filtering cycle number according to the method of the invention, e.g., before filtering (cycle 0) the turbidity may be 100 NTU, after 1 filtering cycle the turbidity level/grade may be 71.8 11 NTU, after two filtering cycles the turbidity may be 46.8 NTU, and after three filtering cycles the turbidity may be 18.8 NTU.

In yet a further exemplary test of determining filtering efficiency of a liquid (e.g., water) processed according to the invention, the turbidity level/grade (e.g., measured by Orbeco Hellige USA TB200-10 - white light field portable turbidimeter) decreased from an initial purity grade of about 40 NTU to about 10.0 NTU, or even at times from about 40 NTU to about 0.06 NTU, after a single filtering cycle, and/or 2 and/or 3 and/or 4 and/or 5 and/or 6 and/or 7 and/or 8 and/or 9 filtering cycles.

Some other exemplary tests of determining filtering efficiency in a liquid (e.g., 3 water in a swimming pool of 100 m ) processed according to the invention, at a filtering 3 rate of about 40 m /h for 2 hours, the turbidity level/grade decreased from about 3 NTU to about 0.4 NTU (e.g., measured by Orbeco Hellige USA TB200-10 - white light field portable turbidimeter).

Some embodiments of the method of the invention provide liquid withdrawn from the outlet having a turbidity level/grade of at most 0.2 NTU, or at times, at most 0.19 NTU, or 0.18 NTU, or 0.17 NTU, or 0.16 NTU, or 0.15 NTU, or 0.14 NTU, or 0.13 NTU, or 0.12 NTU, or 0.11 NTU, or 0.10 NTU, or 0.09 NTU, or 0.08 NTU, or 0.07 NTU, or 0.07 NTU, or 0.06 NTU, or even at times at most 0.05 NTU; the turbidity level/grade being optionally determined as above said (e.g., by Orbeco Hellige USA TB200-10 - white light field portable turbidimeter).

Some embodiments of the method of the invention provide a filtering efficiency after one cycle of between about 20% and about 30%. Some embodiments of the method of the invention provide a filtering efficiency after n cycles of between about 60% and about 99%, wherein n is between 1 and 8 cycles, or at times between 1 and 7 cycles, or between 1 and 6, or between 1 and 5, or between 1 and 4, or between 1 and 3, or between 1 and 2, or even at times, a single cycle; optionally at a predetermined filtering rate (e.g., at a flow rate of between about 10 and 50 cubic m/h, or at times between about 20 and 30 cubic m/h, or at most 25 cubic m/h); where the filtering is carried out for a predetermined time, e.g., 1 hour, or at times two hours, or three hours, or four hours, or even five hours.

The inventor has found that the system and/or method of the present invention can efficiently improve energy efficiency when heating a reservoir in comparison to 12 conventional systems (e.g., closed filter). This is achieved by the present invention by utilizing pipes (conduits) having a decreased length of about 50-70%. Some embodiments of the invention utilize one or more pipes having a length of between about 5 m and about 10 m, optionally below about 8 m, optionally below about 6m (according to position of the reservoir respective to position of equipment in the equipment room, e.g., for maintaining one or more of a balance tank, filter, chemicals, control system, pumps, electric panel, etc).

The depth of the filter bed (e.g., height of the filter material within the balance tank) may be between about 45 cm and about 1.8 m, at times between about 45 cm and about 1.4 m, further at times between about 80 cm and about 1.1 m. The depth of the filter bed may be calculated in accordance with operating parameters to allow desired filtering of the liquid, such as, liquid flow rate. For example, some embodiments which require a relatively slow liquid flow rate (filtering rate) between about 20 and about 30 cubic meter per hour, utilize a filter bed depth of between 45 cm and about 1 m is utilized.

Reference is now made to FIG. 1, which presents a schematic illustration of a reservoir 101 provided with an exemplary liquid maintenance system 100, according to some embodiments of the present invention. Reference is also made to FIG. 2, which presents a flow chart of a method 200 for maintaining liquid in a reservoir 101 (e.g., recycling liquid in a reservoir), according to some embodiments of the present invention.

Some embodiments of the present invention may utilize a reservoir 101, e.g., a swimming pool, a hot tub, a liquid purification system, a water fountain, and/or any system that may requires liquid-level adjusting and/or liquid cleaning/purification.

System 100 generally comprises a balance tank 104. Balance tank 104 integrally comprises a filter 108, adapted to separate contaminants in the liquid arriving from the reservoir 101 when liquid level increases therein 201 (e.g., via line 120 and/or overflow line 121 connected to drain 102 and/or gutter 103, respectively) at the balance tank 104.

As the liquid level increases in the reservoir 101, 201, overflow may be detected (e.g., excess liquid in the reservoir). Excess liquid may be withdrawn from overflow line 121, 203, optionally via one or more liquid distributors 109 (e.g., sprinklers) placed in a top portion of the balance tank 104, for distributing the withdrawn liquid homogeneously 13 and for preventing voids in the filter material layer 108. Optionally, liquid of a purity grade that is different from purity grade of the excess liquid coming from the surface of the reservoir 101 may flow via drain line 120, 202, optionally to a block valve 106 for preventing wash back liquid to flow back to the reservoir 101. At least the excess liquid from the overflow line 121, 205, and optionally, the liquid from the drain line 120, 204, reach the balance tank 104. The excess liquid drained liquid, optionally mixed with one or more of the drained liquid and/or other liquid, may be reach the balance tank 104 and then filtered to provide contaminant-free liquid, optionally while the liquid flows from the reservoir 101 towards one or more outlets 117 of the balance tank 104, 206.

A downstream of cleansed liquid is provided to a bottom surface of the balance tank 104, 206, cleansed liquid may be recirculated back to the reservoir 101 via return line 122, 207 optionally via one or more bifurcated lines 112, which may be connected to a bottom surface of the reservoir 101, and which may distribute return line 122 to prevent development of pathogens (e.g., microorganisms, bacteria) due to still liquid. As such, the system 100 and/or method 200 of the present invention utilize a balance tank 104 having an integrally disposed filter 108 adapted to separate contaminants from the liquid within the balance tank 104 while the liquid flows from the reservoir 101 (e.g., via at least one inlet, e.g., 116) towards at least one outlet 117, 206 connected to the balance tank 104 (e.g., via line 122). Thus, continuous flow 122 of cleansed liquid back to the reservoir 101 is provided simultaneously to withdrawing liquid from one or more of line 120 and/or overflow line 121, 207.

The liquid level in the balance tank 104 may be maintained between about 25 mm to about 30 cm over the filter material 108. Excess liquid required to maintain such a liquid level in the balance tank 104, may be provided by one or more of drain line 120 and/or overflow line 121.

The filter material layer 108 within the balance tank 104 may have a height between about 0.5 m and about 2 m, e.g., between about 0.75 m and about 1.25 m.

The balance tank 104 may have a volume respective to between about 2% and about 10% of reservoir 101 area, optionally, between about 4% and about 8% of reservoir area, further optionally between about 4% and about 6% of reservoir area, yet further 14 optionally, about 5%. For example, for a swimming pool having 25 m length and 12.5 m width, the respective volume 5% is about 15.624.

The balance tank 104 may have at least one inlet 116, for receiving liquid from the overflow line 121, which may extend from one end of the reservoir 101 to one end of the balance tank 104, via a suitable valve connected to the reservoir 101, optionally via a pump 115, which may be driven via a suitable electric motor so as to withdraw overflowed liquid from the reservoir 101 towards the balance tank 104. The overflowed liquid may enter the reservoir 101, optionally through gutter 103, which may be optionally disposed at a top portion around the reservoir periphery (e.g., top edge and/or sidewalls on the surface around the reservoir). One or more valves may be connected to the overflow line 121 connecting the balance tank 104 to the reservoir 101 (e.g., connected via a conduit) for controlling flow rate of the liquid flowing from the reservoir 101 into the balance tank 104. The valves may be operated by one or more sensors actuating operation and determining flow rate of the liquid from the reservoir 101, as discussed further below.

Some embodiments of the invention may utilize, optionally via one or more inlets (e.g., 116) connected to the reservoir 101 at one or more of its ends, at least one valve 105 and/or 115, which when open may allow liquid from the reservoir 101 to flow towards the balance tank 104, and when closed may stop such liquid flow.

Some embodiments may utilize a liquid block valve 106 before one or more inlets (e.g., 116) connected to the reservoir 101, for preventing liquid in flow line 120, which has yet to be filtered, from returning back to the reservoir 101 and contaminating it.

Additionally and/or alternatively, the balance tank 104 may withdraw liquid from one or more lines, e.g., line 120 connected to the reservoir 101 via a bottom drain 102, e.g., through inlet 106 so as to withdraw liquid of a higher purification grade than the purification grade of overflow liquid from the overflow line 121, which may typically include an increased amount of suspended contaminants floating in the reservoir surface.

Optionally, liquid from line 120 is withdrawn via pump 106, which may be driven via a suitable electric motor. Operation of one or more of the valves for withdrawing liquid from the reservoir 101 towards the balance tank 104, optionally via pump 115 and/or pump 106, may be actuated by liquid-level sensor(s) for detecting variation in liquid- level (e.g., liquid overflow) in the reservoir 101, to operate liquid withdrawing valves in overflow line 121 and/or bottom drain line 120. The one or more valves may be located in each of the liquid lines 120 and 121, and may be adjusted to regulate the amount of liquid required for the balance tank 104 and/or for filter 108.

For example, when one or more swimmer(s) occupy a swimming pool, the water level in the pool may exceed a predetermined level to generate an overflow of water exceeding a certain level. The overflowed water may then be withdrawn from the pool, such as from a bottom drain and/or a surface skimmer, and/or may trigger operation of a valve and/or pump for directing an overflow water line from the pool to the balance tank via suitable inlet.

The balance tank 104 may have at least one inlet 116 for receiving liquid from an overflow line 121. The liquid from the reservoir 101 optionally enters the balance tank 104 through at least one liquid distributor (e.g., sprinkler) 109, for drawing the liquid downwards to the filter material 108. The contaminant particles may be captured in the filter bed 108, and the liquid may exit from the bottom of the filter 108 to return clean liquid (filtered) to the reservoir 101, via flow return line 122, optionally via recirculating pump 110.

One or more sensors may be positioned throughout the system 100 for detecting liquid level and/or height (liquid overflow and/or deficit) in the reservoir 101, and/or in the balance tank 104. Some embodiments of the invention utilize a liquid level control mechanism 113 adapted to operate at least one valve for varying liquid level in the reservoir 101 and/or in the balance tank 104. The liquid level control mechanism 113 may be disposed in one or more suitable regions in the balance tank 104. Some exemplary embodiments utilize liquid level control mechanism 113, which may further comprise a plurality of liquid level floats 113a, 113b and 113c, disposed in the top portion of the balance tank 104, for detecting liquid overflow and/or deficit in the balance tank 104, which may indicate liquid overflow and/or deficit in the reservoir 101. Some embodiments utilize one or more liquid level control mechanisms 113 and or devices, comprising liquid level sensors, ultrasonic distance detectors, capacitive sensors, etc.

Examples of liquid level floats that may be utilized according to some embodiments may be, emergency liquid level floats for signalling deficiency of liquid in the balance tank 16 and disoperation of pump (e.g., 110); liquid level height float; liquid level signalling flooding in the balance tank, etc.

Some embodiments utilize one or more liquid level control mechanisms 113 of the kind described above, and/or devices that may comprise a liquid level safety switch for controlling operation of the liquid overflow withdrawal pump 115 for signalling when additional liquid is required to be added to the reservoir 101, optionally via at least one liquid distributor and/or sprinkler 109 for distributing the liquid to prevent flooding in gutter 103 and/or to prevent creation of voids in the filter bed 108. When required, liquid may be added to the balance tank 104 via one or more additional inlets, for compensating liquid deficit in the balance tank 104.

Some embodiments of the invention utilize one or more float switches for detecting the level of the liquid within the balance tank 104 and/or reservoir 101. Float switches may be used to control and/or activate one or more pumps (e.g., recirculating pump 110) and/or valves, as an indicator and/or signal trigger, and/or to control other devices, by determining a trigger liquid level point within the balance tank 104 and/or reservoir 101, for activating one or more pumps and/or valves. For example, as water may evaporate in a swimming pool, the water level may decrease and a float switch may detect the level of the water. When the water decreases below a certain level, the pool may be filled, optionally, via activating an auto-fill pump and flowing water to fill the pool to a proper level.

Some embodiments provide a system and/or method in which one or more lines 112 are bifurcated and may connect the liquid return flow line 122 to the reservoir 101 (optionally, to the bottom surface of the reservoir 101) by one or more nozzles and/or conduits having a suitable diameter in accordance with filter material surface area. For example, for each square meter of filter area between about 1 m and about 3 m nozzles and/or conduits should be installed having a diameter of between about 50 mm and about 100 mm, optionally between about 55 mm and about 90 mm, further optionally between about 60 mm and about 75 mm, further optionally between about 60 mm and about 65 mm, yet further optionally about 63 mm.

Balance tank 104 may comprise a plurality of directional nozzles 107 mounted in a bottom portion of the balance tank 104 for directing flow of the liquid to flow line 122 17 connected to the reservoir 101, and/or for preventing filter material 108 to enter recirculating pump 110, when liquid flows from the balance tank 104 to flow line 122.

Some embodiments provide a system and/or method in which one or more nozzles and/or conduits 107 may be optionally uniformly distributed throughout the bottom portion of the balance tank 104, e.g., having a suitable diameter in accordance with filter material surface area. For example, for each square meter of filter area between about 1 m and about 3 m nozzles and/or conduits should be installed in the bottom portion of the balance tank 104, and having a diameter of between about 20 mm and about 200 mm, optionally, having a diameter of between about 50 mm and about 100 mm, optionally between about 55 mm and about 90 mm, further optionally between about 60 mm and about 75 mm, further optionally between about 60 mm and about 65 mm, yet further optionally about 63 mm.

Some embodiments of the method and/or system of the invention further provide one or more nozzles and/or conduits 107 distributed laterally about a plane of the balance tank 104 and have an inter-nozzle spacing of between about 10 mm and about 40 mm per 2 2 1 cm filter area, e.g., between about 15 mm and about 30 mm per 1 cm filter area, e.g., 2 between about 20 mm and about 30 mm per 1 cm filter area, even between about 20 cm 2 and about 30 cm per 1 cm filter area.

The one or more nozzles and/or conduits 107 may be directional nozzles and/or conduits for directing flow of the liquid (e.g., filtered liquid) to the flow line 122 connected to the reservoir 101, via outlet 117. The one or more nozzles and/or conduits 2 107 may have a length of between about 1 m and about 5 m per 1 m filter area. Some embodiments utilize one or more conduits having a diameter of between about 70 mm and about 500 mm, e.g., between about 80 mm and about 300 mm, e.g., at least about 90 mm.

Some embodiments of the method and/or system of the invention further provide one or more directional nozzles and/or conduits 107 having a diameter of between about mm and about 200 mm, e.g., between about 20 mm and about 180 mm, e.g., between about 50 mm and about 150 mm, e.g., between about 50 mm and about 120 mm.

Some embodiments of the method and/or system of the invention further provide withdrawing filtered liquid from the outlet 117 of the balance tank 104, which is 18 essentially free of contaminants prior to entering of the filtered liquid into a conduit and/or pipeline and/or pump (e.g., 110), which is typical for conventional methods and/or systems, which utilize a balance tank which is installed as a separate unit from a filter, and thus require an additional flow passageway (e.g., flow line, conduit) between the balance tank and filter unit, which may result in contaminants (e.g., hair) clogging a flow passageway and/or pump and/or flow line. As such, the balance tank 104 utilized herein does not contain a filter unit after the balance tank outlet 122. The contaminant particles may be captured in the filter bed 108, and the liquid may exit 122 from the bottom of the filter 108, via balance tank outlet 122, to return clean liquid (filtered) to the reservoir 101.

The liquid withdrawn from the balance tank outlet 122 may be essentially free of contaminants prior to entering a conduit and/or pump 110, for recirculating filtered liquid back to the reservoir 101. As such, utilizing a further contaminant filter (e.g., hair filter and/or the like) may no longer be necessary as a result of the liquid being filtered before reaching a rotary pump, such as recirculating pump 110.

To sufficiently mitigate pathogens that may be present in the recirculated liquid, such as bacteria and mildew; some embodiments utilize supplying an amount of chemicals to the liquid withdrawn from the outlet 117, to disinfect the filtered liquid returning back into the reservoir 101. Chemicals may be added to the filtered liquid, such as disinfecting materials (e.g., chlorine), optionally via one or more conduits and/or flow lines positioned before and/or after one or more of the distribution lines 112. As such, one or more disinfecting material lines may be added to one or more of the filtered liquid distribution lines 112 and/or return line 122, to provide disinfected filtered liquid back to the reservoir 101 (recirculation of cleansed and disinfected liquid back to the reservoir).

The amount of chemicals required for supplying liquid back to the reservoir via one or more distribution lines 112, may be detected by one or more sensors positioned in the reservoir 101 for detecting the purity grade of the liquid (e.g., concentration of disinfecting material in the liquid currently in the reservoir and the amount required to be added to provide a predetermined concentration).

In addition, the system and/or method of the invention may enable providing a large amount of disinfecting material (such as, chlorine) only to the filter bed, without opening the filter unit as typically done in conventional filter units. 19 Additionally, a further advantage of the present invention is in that disinfecting systems, such as UV and ozone devices, may be installed in the body of the balancing tank, and as such disinfecting process is facilitated to provide recirculation of liquid having an increased purity grade in comparison to conventional liquid treatment systems and methods.

Some embodiments of the invention provide a system and/or method in which an amount of filtered liquid with and/or without addition of disinfecting material that may be recirculated back into the reservoir 101 may be optionally controlled by a liquid-level control mechanism 113 adapted to operate at least one valve for varying liquid level in the reservoir 101 and/or in the balance tank 104. The liquid level control mechanism 113 may be disposed in one or more suitable regions in the balance tank 104. Some exemplary embodiments utilize liquid level control mechanism 113, which may further comprise a plurality of liquid level floats 113a, 113b and 113c, disposed in the top portion of the balance tank 104, for detecting liquid overflow and/or deficit in the balance tank 104, which may indicate liquid overflow and/or deficit in the reservoir 101. Some embodiments utilize one or more liquid level control mechanisms 113 and or devices, comprising liquid level sensors, ultrasonic distance detectors, capacitive sensors, etc.

Some embodiments utilize one or more liquid level control mechanisms 113 and/or devices that may include a liquid level safety switch for controlling operation of one or more of the liquid withdrawal overflow pump 115 and/or drain flow pump 105, for signalling when additional liquid is required to be added to the reservoir 101 (which is determined by the amount of liquid required to be added in the balance tank 104). When required, the filtered liquid may be recirculated back to the reservoir 101, for compensating liquid deficit in the reservoir 101.

Additionally and/or alternatively, excess filtered liquid in the balance tank 104 may overflow into a drain (sewage system) 114.

The system 100 of the kind described herein provides a solution to liquid leakage from the filter 108. In addition, such a system provides a filter that does not need to discharge air, and thus may provide a solution for intake of air in one or more of the liquid flow lines 120 and/or 121 (suction lines) and to prevent air from entering the liquid treatment engines.

Some embodiments of the invention are directed to large-scale applications, such as a public swimming pool, and may utilize a filter bed depth of between about 90 cm and about 1.1 m to provide a liquid flow rate between about 20 and about 30 cubic meter per hour.

As such, the system and/or method of the invention may provide significant liquid (e.g., water) savings due to utilizing increased filtration surface area, which may also reduce the need for frequent rinsing of the filter.

Additionally, current liquid treating systems require utilization of transparent pipes when tightening of a filter material is carried out. However, after a short time the pipes may become insufficiently transparent, thus resulting in operation difficulty as estimation of rinsing and tightening durations become inaccurate. Nonetheless, in the method and/or system of the invention, utilization of a transparent pipe is not required, as the transparency of the liquid may be seen since the balance tank and/or filter components may be visible continuously (observable) throughout the filtration process according to some embodiments of the invention (e.g., by installing a window in the balance tank).

The system of the invention 100 utilizes a balance tank 104 provided with a filter material 108 (e.g., balance tank filled with filter material, such as sand). Liquid may be provided to the balance tank 104 (e.g., from a reservoir 101) for capturing contaminants.

During filtration of the liquid, the filter material 108 (e.g., filter height and quality) may be observed at any given time.

As such, clogging of contaminants from the liquid in the upper surface of the filter bed may be easily identified, and disposal of such clogged material may be handled conveniently.

In addition, it is not necessary to remove the entire filter bed to a contaminated place as typically done (e.g., the floor of an engine facility) when maintenance of the system components is required (e.g., broken nozzle, etc), which in turn, may result in returning the filter bed with contaminants. As such, maintenance and handling of the system components of the invention (e.g., replacing a broken nozzle, etc) may be executed without removing the filter bed. 21 In a conventional process of replacing components (e.g., nozzles, filter bed, etc) in large-scale and/or industrial liquid treatment systems, a technician is required to enter the filter unit and replace an old filter layer with a new filter layer and return the new filter layer back to the filter unit, which is dangerous and challenging to perform.

The rinsing and tightening processes of the system 100 components (e.g., of the filter 108) may be carried out by reversing the direction of the flow of the liquid, e.g., by flowing liquid through the filtration bed to the nozzles 107 and from the nozzles back to the balancing tank 104 and/or to the drain 114. The liquid may reach the nozzles 107 at a pressure of between 1.5 to 2 atm, at times, up to 2 atm. During the tightening process, the filter height and/or liquid height in the balance tank 104 may be easily observed, as required for quick and easy handling and maintenance of various liquid treatment systems.

Thus, the present invention may be utilized in various applications and uses.

Some embodiments of some aspects of the invention are directed to applications and uses of a system 100 for processing a recycled liquid in a reservoir 101, and/or method 200 for recycling liquid in a reservoir 101. According to some embodiments, the reservoir 101 may be a swimming pool, a hot tub, a liquid purification system, and/or a water fountain. According to some embodiments, the system may be used in industrial applications and/or the liquid may be supplied to the reservoir and/or a tank via liquid supply source. Some non-limiting examples include, waste water treatment with high solid and suspended material component such as industrial waste water, public swimming pool, etc.

It is appreciated that certain features of the invention, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the invention, which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable sub-combination or as suitable in any other described embodiment of the invention. Certain features described in the context of various embodiments are not to be considered essential features of those embodiments, unless the embodiment is inoperative without those elements. 22 Various embodiments and aspects of the present invention as delineated hereinabove and as claimed in the claims section below find experimental support in the following examples.

As used herein the term “about” refers to ?10%.

The word "exemplary" is used herein to mean "serving as an example, instance or illustration." Any embodiment described as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments and/or to exclude the incorporation of features from other embodiments.

The word "optionally" is used herein to mean "is provided in some embodiments and not provided in other embodiments." Any particular embodiment of the invention may include a plurality of "optional" features unless such features conflict.

The terms "comprises", "comprising", "includes", "including", “having” and their conjugates mean "including but not limited to".

The term “consisting of” means “including and limited to”.

The term "consisting essentially of" means that the composition, method or structure may include additional ingredients, steps and/or parts, but only if the additional ingredients, steps and/or parts do not materially alter the basic and novel characteristics of the claimed composition, method or structure.

As used herein, the singular form "a", "an" and "the" include plural references unless the context clearly dictates otherwise. For example, the term "a compound" or "at least one compound" may include a plurality of compounds, including mixtures thereof.

Throughout this application, various embodiments of this invention may be presented in a range format. It should be understood that the description in range format is merely for convenience and brevity and should not be construed as an inflexible limitation on the scope of the invention. Accordingly, the description of a range should be considered to have specifically disclosed all the possible subranges as well as individual numerical values within that range. For example, description of a range such as from 1 to 6 should be considered to have specifically disclosed subranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6 etc., as well as individual numbers within that range, for example, 1, 2, 3, 4, 5, and 6. This applies regardless of the breadth of the range. 23 Whenever a numerical range is indicated herein, it is meant to include any cited numeral (fractional or integral) within the indicated range. The phrases “ranging/ranges between” a first indicate number and a second indicate number and “ranging/ranges from” a first indicate number “to” a second indicate number are used herein interchangeably and are meant to include the first and second indicated numbers and all the fractional and integral numerals therebetween.

It is appreciated that certain features of the invention, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the invention, which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable sub-combination or as suitable in any other described embodiment of the invention. Certain features described in the context of various embodiments are not to be considered essential features of those embodiments, unless the embodiment is inoperative without those elements.

Various embodiments and aspects of the present invention as delineated hereinabove and as claimed in the claims section below find experimental support in the following examples.

Although the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, it is intended to embrace all such alternatives, modifications and variations that fall within the spirit and broad scope of the appended claims.

All publications, patents and patent applications mentioned in this specification are herein incorporated in their entirety by reference into the specification, to the same extent as if each individual publication, patent or patent application was specifically and individually indicated to be incorporated herein by reference. In addition, citation or identification of any reference in this application shall not be construed as an admission that such reference is available as prior art to the present invention. To the extent that section headings are used, they should not be construed as necessarily limiting.

Claims (30)

:

1. A liquid maintenance system (100) for processing a recycled liquid in a reservoir (101), comprising: a balance tank (104) having at least one inlet (116) for receiving liquid from an overflow line (121) of the reservoir (101) and at least one outlet (117), said balance tank (104) comprises: a filter (108) comprising filter material disposed within the balance tank (104) and adapted to separate contaminants from said liquid within the balance tank (104) while said liquid flows from said at least one inlet (116) towards said at least one outlet (117); and a liquid level control mechanism (113) adapted to operate at least one valve to vary liquid level in said balance tank (104) and at least one liquid distributor (109) configured to distribute liquid above the filter material; wherein said balance tank (104) comprises a plurality of directional nozzles (107) mounted and distributed below the filter material in a bottom portion of said balance tank (104) for directing flow of the liquid from the filter material to a flow line (122) connected to said reservoir (101).

2. The system according to claim 1, wherein said filter (108) is a sand filter.

3. The system according to claim 1 or 2, wherein said filter (108) comprises a material selected from: sand, glass, stones, gravel, diatomic earth, activated carbon, metallic alloy, ceramic, block carbon resin, microfiltration membrane and ultrafiltration membrane.

4. The system according to any of claims 1-3, wherein said filter (108) consists of a filter (108) disposed between said at least one inlet (116) and said at least one outlet (117). 25 255057/2

5. The system according to any of claims 1-4, wherein said inlet comprises a valve (105), (115), which when open allows liquid from the reservoir (101) to flow towards the balance tank (104), and when closed stops such flow.

6. The system according to any of claims 1-5, further comprising a liquid block valve (106) before said inlet.

7. The system according to any of claims 1-6, wherein said valve is adapted to be operated when overflowed liquid from a peripheral top edge gutter (103) of the reservoir (101) exceeds a predetermined level.

8. The system according to any of claims 1-7, wherein said outlet is connected to flow line (111) via a recirculating pump (110).

9. The system according to claim 8, wherein said recirculating pump (110) is connected to said balance tank (104) via a float switch.

10. The system according to any of claims 1-9, wherein said filter (108) is configured to remove contaminants between about 10 and about 1000 µm size.

11. The system according to any of claims 1-10, wherein said balance tank (104) has a volume respective to between about 4-8% of area of the liquid reservoir (101).

12. The system according to any of claims 1-11, wherein the plurality of directional nozzles (107) have a diameter between about 20 mm and about 200 mm.

13. The system according to any of claims 1-12, wherein the plurality of directional nozzles (107) are distributed laterally about a plane of the balance tank (104) 2 and have an inter-nozzle spacing of at least about 20 mm and about 30 mm per 1cm filter area. 26 255057/2

14. The system according to any of claims 1-13, comprising a liquid flow conduit connected to the plurality of nozzles (107) having a length of between about 1 m 2 and about 5 m per 1 m filter area.

15. The system according to claim 14, wherein the conduit has a diameter of at least 90 mm.

16. The system according to any of claims 1-15, wherein the at least one liquid level control mechanism (113) comprises a plurality of liquid level floats (113a, 113b, 113c).

17. The system according to any of claims 1-16, wherein said at least one liquid level control mechanism (113) comprises a liquid level safety switch adapted to operate said recirculating pump (110) to vary liquid level in said balance tank (104).

18. The system according to any of claims 1-17, wherein the flow of the purified liquid back to the reservoir via the flow return line (122) is carried out after the liquid level is beneath a predetermined amount.

19. The system according to any of claims 1-18, wherein the reservoir (101) is a swimming pool, a hot tub, a liquid purification system and/or a water fountain.

20. A method of recycling liquid in a reservoir (101) via a balance tank (104) comprising: flowing liquid from an overflow line (121) of the reservoir (101) to an inlet of a balance tank (104) comprising a filter (108) disposed within said balance tank (104) and comprising filter material; flowing said liquid in said balance tank (104) via a liquid level control mechanism (113) toward the filter (108), and distributing the liquid above the filter material with at least one liquid distributor (109); separating contaminants from said liquid with the filter (108); 27 255057/2 directing flow of the liquid from the filter material towards at least one outlet (117) of a flow return line (122) connected to said reservoir (101) via a plurality of nozzles (107) mounted below the filter material and distributed uniformly in a bottom portion of said balance tank (104; and withdrawing said liquid from the outlet (117) to said reservoir (101) via flow return line (122) in accordance with the liquid level in said balance tank (104).

21. The method according to claim 20, wherein the withdrawing said liquid is carried out by pumping the liquid to the reservoir (101).

22. The method according to claim 20 or 21, wherein the pumping is controlled by a valve or a recirculating pump.

23. The method according to any of claims 20-22, wherein the recirculating purified liquid into the reservoir is controlled by a liquid-level control mechanism (113).

24. The method according to any of claims 20-23, further comprising supplying liquid to the balance tank (104) via withdrawing liquid from a bottom drain line (120) of the reservoir (101).

25. The method according to any of claims 20-24, further comprising supplying an amount of disinfecting material to the liquid withdrawn from said outlet.

26. The method according to any of claims 20-25, wherein the liquid withdrawn from said outlet is essentially free of contaminants prior to entering a conduit or pump (110).

27. The method according to any of claims 20-26, wherein the liquid from the overflow line (121) is distributed throughout the balance tank (104) via the at least one liquid distributor (109) prior to reaching the filter (108).

28. The method according to any of claims 20-27, wherein the liquid withdrawn from the outlet having a turbidity level of at most 0.19 NTU. 28 255057/2

29. The method according to any of claims 20-28, wherein said withdrawing liquid from said outlet after one cycle is at a filtering efficiency of between about 20% and about 30%.

30. The method according to claim 29, wherein the filtering efficiency after n cycles is between about 60% and about 99%, wherein n is between 1 and 5. Roy S. Melzer, Adv. Patent Attorney G.E. Ehrlich (1995) Ltd. 11 Menachem Begin Road 5268104 Ramat Gan