IL182973A - Method and apparatus for reducing metal concentration in water - Google Patents

Description

182973 'Ώ I 453562 τηχ METHOD AND APPARATUS FOR REDUCING METAL CONCENTRATION IN WATER Field of the Invention The present invention relates to a device and method for adjusting the concentration of metal components in water, particularly for adjusting pH 5 or hardness. Provided is a system comprising an electrolytic cell and a lowered pressure element for purifying said cell, that efficiently reduces metal compounds in water, removing, for example, calcium carbonate from water for cooling towers. i o Background of the Invention Water used in households and industry contains dissolved minerals rendering it "hard". Problems associated with unwanted precipitation of solids or with corrosion of metallic parts arise during industrial usage of water. System parts become encrusted, the deposits usually comprising calcium and magnesium carbonates and sulfates. Removing at least a part of said dissolved materials from water before its use is called water softening, and may be achieved by several methods, comprising ion exchange, conditioning water by lowering availability of insoluble salt by the addition of softening agents such as polyphosphates, or by various 0 electro-treatments.

WO 02/079098 describes a household apparatus for removing substances from water, employing an electrodialysis cell, comprising ion exchange elements. US 5,240,579 describes a water softening process, comprising precipitation of calcium carbonate after electrolytic alkalization of water, comprising doublets of cation-exchange and anion-exchange layers. US 6,139,714 relates to an electrochemical adjustment of pH in aqueous fluids. The existing methods employing electro-treatments are rather complex, they include ion exchangers, complicated circulation regimens, or they are designed for small scale purifications only. It is therefore an object of this invention to provide a system for large scale water softening, without using ion exchangers.

It is another object of this invention to provide softened water, at least partially purified.

It is still another object of this invention to provide a generally applicable, environmentally friendly system for water softening, without using chemicals.

It is a further object of this invention to provide a cost effective method and device for adjusting the concentration of metal components in water, particularly for adjusting pH or hardness.

It is a still further object of this invention to provide a cost effective device and method for water softening.

It is a still another object of this invention to provide a system for large scale water purification, particularly for use in removing calcium carbonate from water for cooling towers.

Other objects and advantages of present invention will appear as description proceeds.

Summary of the Invention The present invention provides a device for modifying the concentration of metallic components in water, comprising i) at least one electrolyzing cell in which two electrodes and an ion selective membrane placed between the electrodes divide the cell into four chambers - two inner ones (inner cathode and inner anode chambers) and two outer ones (outer cathode and outer anode chambers); ii) an aqueous fluid stream forming closed flow-circuits in which the mass of the fluid is essentially conserved; and iii) opened flow-branches through which the mass enters and exits the system, comprising an injecting pipe creating vacuum, through which water enters the system. When relating to metallic components, the term includes cations, except for cations of alkali metals or ammonium, as well as complex ions comprising heavy metals. Usually, the term will include hydrogen cations and heavy metals. Said device preferably comprises i) at least one electrolyzing cell in which two electrodes and an ion selective membrane placed between the electrodes divide the cell into four chambers - two inner ones (inner cathode and inner anode chambers) and two outer ones (outer cathode and outer anode chambers); ii) a regulator chamber; iii) a sedimentation tank; iv) an aqueous fluid stream forming three closed flow-circuits in which the mass of the fluid is essentially conserved, wherein the first of said flow-circuits comprises said two inner and two outer chambers and said sedimentation tank, the second of said flow-circuits comprises said two inner chambers and said regulator chamber, and the third of said flow-circuits comprises said two inner and two outer chambers and said cooling tower, and v) three opened flow-branches through which the mass enters and exits the system, the first of said flow-branches comprises an inlet of tap water and said regulator chamber, and the second of said flow-branches comprises flow of a suspension of precipitated salts from said regulator chamber via said sedimentation tank out of the system, and the third of said flow-branches comprises water being lost from the system by evaporation or leakage and/or pumped out of the system. Said first circuit provides for removal of precipitated metal components from said cell to said tank; said second circuit provides for equalizing the difference in component pressures, as well as electrical potentials, shortly between the fugacities in said two inner chambers, and further the circuit enables transferring precipitated salts from the cell to the regulator chamber; and the third circuit provides for supplying softened water to said cooling tower. The first of said flow-branches provides for entering tap water to the system through a water pump making vacuum; the second of said flow-branches provides for removing the precipitated calcium carbonate, or other salts such as magnesium carbonate, etc., out of the system; and the third of the flow-branches provides for both desired or incidental losses of water in the system. The precipitation is initiated and seeded in the proximity of said cathode, and wherein said precipitation causes removal of at least a part of said metal components from said aqueous fluid stream into said sedimentation tank. Elemental chlorine is created by the electrode processes and the disinfecting element spreads in said aqueous fluid through the whole system. Said metallic components, in a preferred device according to the invention, comprise heavy metals. In a preferred embodiment of the invention, said metallic component comprises calcium carbonate. Further, a strong stable source of direct current is included in the device, and filters, pumps, regulation elements, valves, pressure sensors, pH electrodes, electronic regulation of the flow-rates and the pressures, and microprocessors.

The invention is directed to a device for providing softened and purified water for a cooling tower, comprising i) an electrolytic cell comprising a planar anode, a planar cathode, and a planar ion-selective membrane placed between said anode and cathode, the three planes dividing the internal space of said cell into a cathode outer chamber, cathode inner chamber, anode inner chamber, and anode outer chamber; ii) a regulatory chamber through which tap water is brought to the device via narrowed inlet, while creating vacuum; iii) a sedimentation tank in which precipitated calcium carbonate is collected; iv) a circulation means ensuring water flow from said tower through said cathode outer chamber, cathode inner chamber, anode inner chamber, and anode outer chamber back to the tower; v) a circulation means ensuring mass flow from said cathode inner chamber via said regulatory chamber to said anode inner chamber; vi) a circulation means ensuring mass flow from said cathode outer chamber via said sedimentation tank to said anode outer chamber; and a circulation means ensuring water flow from said cooling tower and the cell via said four chambers. The device according to the invention preferably comprises circuitry through which an aqueous fluid passes, including a narrowed injecting pipe through which tap water enters the system, filling said regulatory chamber and creating vacuum therein; and a first passage and a second passage connecting said regulatory chamber with said cathode inner chamber and said anode inner chamber, respectively; wherein said cathode and said anode comprise a plurality of parallel channels, and wherein direct electrical voltage is supplied to said electrodes, alkalizing water near said cathode and causing the precipitation of calcium carbonate which is collected in said sediment chamber. The device comprise a power supplier providing direct current between the electrodes. Said selective membrane may be chosen from materials known in the art. In a preferred embodiment of the invention, said electrical current causes the conversion of at least a part of chlorides in said aqueous stream to elemental chlorine. Said vacuum assists in removing gases out of the system.

A device for softening water for cooling tower is provided, essentially as described in Fig. 1, comprising at least one electrolytic cell (7); a regulatory chamber (5); sedimentation tank (6); the cell comprising planar anode (8) and planar cathode (9) being provided with a plurality of parallel channels, and planar ion-selective membrane (10); the three planes dividing the internal space of said cell into a cathode outer chamber (1), cathode inner chamber (2), anode inner chamber (3), and anode outer chamber (4); chambers (2) and (3) being connected with chamber (5); chambers (1) and (4) being connected with tank (6); chambers (1) and (4) being further connected with tower (11); and a narrowed inlet (12) bringing tap water into chamber (5) and creating the vacuum.

The invention also provides a method of softening a water stream, comprising i) alkalization of water in an electrolytic cell consisting of anode and cathode provided by a plurality of parallel channels, and an ion selective membrane, resulting to the precipitation of calcium carbonate being removed into a sedimentation tank; ii) injecting said water stream through a narrowed inlet to a regulatory chamber connected with said electrolytic cell and with said sedimentation tank, thereby creating vacuum and sucking gases out of said cell; iii) circulating said water between said sedimentation tank and said cell; and iv) circulating said water between said regulatory chamber and said cell; thereby providing softened and purified water. Said softened water has a lowered concentration of calcium carbonate, and is disinfected by elemental chlorine created during the electrode reactions. Usually, said softened water has lower corrosive power in view of lowered concentration of salts.

When referring to Fig. 1, a method for softening an aqueous fluid is provided, comprising i) circulating an aqueous fluid between a sedimentation tank (6) and an electrolytic cell (7), the cell comprising planar anode (8), planar cathode (9), and planar ion-selective membrane (10), the three planes dividing the internal space of said cell into a cathode outer chamber (1), cathode inner chamber (2), anode inner chamber (3), and anode outer chamber (4); ii) providing a direct current between said anode and cathode, thereby increasing the pH of said fluid near the cathode, while starting the precipitation of calcium carbonate, followed by its removal into said sedimentation tank, and thereby forming elemental chlorine, while disinfecting the fluid; iii) circulating said fluid from said anode inner chamber via said cathode inner chamber to an outer regulatory chamber (5); iv) injecting untreated aqueous fluid to said regulatory chamber through a narrowed inlet (12), thereby ensuring the required volume of the fluid in the system, while creating vacuum and sucking gases out of said cell; and v) circulating said fluid between said cell via said four chambers to a device where softened and disinfected water is needed.

In a preferred embodiment of the invention, a device for adjusting water, comprising lowering hardness, eventually adjusting pH, lowering microbial growth, and removing debris and other solids, comprises a plurality of electrolyzing units, each one comprising anode and cathode provided with parallel channels and separated by ion-selective membranes.

The invention relates to a water purification system, comprising i) at least one electrolyzing cell in which two electrodes are provided with parallel channels and are separated with an ion selective membrane, the membrane dividing the cell into four chambers - two inner ones (inner cathode and inner anode chambers) and two outer ones (outer cathode and outer anode chambers); ii) a regulator chamber connected with said inner cathode and said inner anode via two connectors enabling the passage of water; iii) a sedimentation tank connected with said outer cathode and said outers anode chambers via two connectors enabling the passage of water; and iv) a circuitry comprising three closed flow-circuits and three opened flow-branches through which water can move, wherein the mass of the fluid is essentially conserved in said flow-circuits, and wherein the mass enters or exits the system through said flow-branches. The first of said flow-circuits comprises said two inner and two outer chambers and said sedimentation tank, the second of said flow-circuits comprises said two inner chambers and said regulator chamber, and the third of said flow-circuits comprises said two inner and two outer chambers and a device in which the purified water is used. The first of said flow-branches comprises an inlet of tap water and said regulator chamber, and the second of said flow-branches comprises flow of a suspension of precipitated salts from said regulator chamber via said sedimentation tank out of the system, and the third of said flow-branches comprises water being lost from the system by evaporation or leakage and/or pumped out of the system. The system of the invention, preferably comprises the regulation of pH. The water purification system according to the invention may be used in providing drinking water, water for producing beverages or cosmetic products, water for industry, water for agricultural needs, etc. In a preferred embodiment, the system of the invention is used for providing softened and purified water for cooling towers. A cost effective system is provided, for water processing, without using chemicals.

Brief Description of the Drawings The above and other characteristics and advantages of the invention will be more readily apparent through the following examples, and with reference to the appended drawings, wherein: Fig. 1. is a scheme showing a softening system according to the invention, comprising three closed flow-circuits (in grey) and three opened flow-branches (in black).

Detailed Description of the Invention An arrangement has now been found for surprisingly efficient water softening, comprising water circulation system, wherein water enters the system as a jet through a narrowed pipe so creating vacuum, and further passes through an electrolytic unit with cathode and anode being separated by a ion selective membrane. Both cathode and anode comprise a plurality of parallel channels for increasing the electrode surface. A power supplier provides direct current between the electrodes. The cathodic reactions increase the pH, thereby precipitating calcium carbonate which is collected and removed from the system. In parallel, the chloride ions are converted to elemental chlorine by the electrode reactions, thereby introducing a disinfection agent into the system. Said vacuum, created by the fluid jet, assists in cleaning the whole system of gases and debris. Thus, the arrangement of the elements along the fluid circuit in the system according to the invention attains simultaneously several tasks associated with softening and purifying an aqueous fluid. The device and method were found to be generally effective in adjusting the concentration of metal components in water, including reducing the concentrations of heavy metals other than calcium, and adjusting the hydrogen cation concentration. Particular use of the device of the invention comprises adjusting pH and lowering hardness. Provided is a system comprising an electrolytic cell and a lowered pressure element for purifying said cell, that efficiently reduces metal compounds in water, removing, for example, calcium carbonate from water for cooling towers In one aspect, the invention relates to a device for softening water. An example of a device according to the invention is presented schematically in Figure 1 to which the following description refers. The device comprises an electrolytic cell, having cathode, anode, ion selective membrane and an adjacent cleaning chamber (5). Both cathode and anode of the electrode have parallel holes serving as stalling elements for increasing the contact surface between the electrodes and the aqueous fluid. The electrode receives its electric current from a powerful stabilized power supplier (stabilized 100 AMPS 50 VT power supplier). Three plains of anode, cathode, and membrane define four electrode chambers (1) to (4). Several processes occur simultaneously in the device.

Circulating water to be treated is pumped into Chamber 1 (1) where a strong electrical current causes oxidation in the vicinity of the cathode and creates an alkaline environment, with elevated pH levels. By means of gravitation the fluid descends from Chamber 1 (1) into Sedimentation Tank (6); there calcium carbonate (CaCOa) affected by the cathodic reactions precipitates. The softened fluid is pumped into Chamber 4 (4), where the anode reactions lower the pH levels, which has in average a mean value in the system of about 7.8 - 8.2. During the process, a part of chlorides are converted into chlorine which acts as an antiseptic agent, preventing the growth of bacteria, fungi, and algae. The lowered level of chlorides contributes to the decrease of the fluid corrosiveness. Two inner electrode chambers of the electrode space, Chambers 2 and 3, are connected with an external chamber, Chamber 5 (5), enabling free electron and material flow, thereby equalizing the pressure in Chambers 2 and 3. Chamber 5, beside being equalizing means for chambers 2&3, also serves as a cleaning unit for those chambers relieving them from gases and debris. The cleaning process is achieved by creating a vacuum in the chamber that "sucks in" the contaminants and disposes them into the Sedimentation Tank (6). The term vacuum, used herein for the sake of brevity, relates in fact to a pressure relatively lower than the external pressure. The vacuum is created by injecting tap water into the chamber and from there to a smaller diameter pipe.

In a preferred embodiment, said water to be treated is water for cooling towers. The system comprises three flow circuits; the first circuit includes the fluid flow from cooling tower (7) via Chambers 1, 2, 3, and 4 back to the tower; the second circuit comprises the fluid flow from Chamber 2 via Chamber 5 to Chamber 3; and the third circuit includes the material transport from Chamber 1 via Sedimentation Tank to Chambers 4, 3, and 2 back to Chamber 1. Beside the three closed circuits, the system comprises a half-opened circuit corresponding to the inlet bringing fresh tap water to the system, making up for water losses in the system, and further also creating said vacuum. The fluid flow in all circuits is regulated by pumps, electronic valves, and relevant software, taking into consideration the total volume of the system, quantities of the material removed from the system, including water and salts, and the pressure. The circuits comprise filters.

The invention, thus, provides a method of softening tap water, comprising i) alkalization of said water in an electrolytic cell consisting of anode, cathode, and an ion selective membrane, leading to the precipitation of calcium carbonate to be removed into a sedimentation tank; ii) injecting tap water to a regulatory chamber connected with said electrolytic cell and with said sedimentation tank, thereby creating vacuum and sucking gases out of said cell; iii) circulating said water between said sedimentation tank and said cell; and iv) circulating said water between said regulatory chamber and said cell. In a preferred embodiment, the invention provides a method of softening water for cooling towers, while also lowering its corrosivity and its microbial contamination, comprising i) circulating an aqueous fluid between a sedimentation tank (6) and an electrolytic cell (7), the cell comprising planar anode (8), planar cathode (9), and planar ion-selective membrane (10), the three planes dividing the internal space of said cell into a cathode outer chamber (1), cathode inner chamber (2), anode inner chamber (3), and anode outer chamber (4); ii) providing a direct current between said anode and cathode, thereby increasing the pH of said fluid near the cathode, while starting the precipitation of calcium carbonate, followed by its removal into said sedimentation tank, and thereby forming elemental chlorine, while disinfecting the fluid; iii) circulating said fluid from said anode inner chamber via said cathode inner chamber to an outer regulatory chamber (5); iv) injecting tap water to said regulatory chamber through a narrowed inlet (12), thereby ensuring the required volume of the fluid in the system, while creating vacuum and sucking gases out of said cell; v) circulating said fluid between said cooling tower and the cell via said four chambers; thereby supplying to said tower softened and disinfected water.

In a preferred aspect of the invention, a device for softening water for cooling towers is provided, comprising i) electrolytic cell comprising a planar anode, a planar cathode, and a planar ion-selective membrane, the three planes dividing the internal space of said cell into a cathode outer chamber, cathode inner chamber, anode inner chamber, and anode outer chamber; ii) a regulatory chamber through which tap water is brought to the device via narrowed inlet, while creating vacuum; iii) sedimentation tank in which precipitated calcium carbonate is collected; iv) circulation means ensuring water flow from said tower through said cathode outer chamber, cathode inner chamber, anode inner chamber, and anode outer chamber back to the tower; v) circulation means ensuring mass flow from said cathode inner chamber via said regulatory chamber to said anode inner chamber; vi) circulation means ensuring mass flow from said cathode outer chamber via said sedimentation tank to said anode outer chamber; vii) circulation means ensuring water flow from said cooling tower and the cell via said four chambers; thereby supplying to said tower softened and disinfected water.

In a preferred embodiment of the invention, the device for softening water comprises more than one electrolyzing unit comprising anode and cathode separated by a ion-selective membrane, wherein closed units may be connected in series or in parallel. In other preferred embodiment, a larger unit comprises a plurality of parallel triplets of elements, namely anode/membrane/cathode. The invention relates to a water purification system comprising pH regulation along the water flow, enabling to affect the pH in the circulating water in a broad range of values. The method according to the invention may be used in providing drinking water, water for producing beverages or cosmetic products, water for industry, water for agricultural needs, and in recycling water. Further, the method may be used when processing water streams, including streams containing heavy metals, or streams comprising municipal waste water or other industrial waters. Particularly, the method is useful in softening and purifying water for cooling towers. The method, doing without added chemical agents, enables low-cost, as well as environmentally friendly processing of water continual or circulating streams.

In one aspect, the invention is directed to a water softening system for a cooling tower comprising i) at least one electrolyzing cell in which two electrodes and an ion selective membrane placed between the electrodes divide the cell into four chambers - two inner ones (inner cathode and inner anode chambers) and two outer ones (outer cathode and outer anode chambers); ii) a regulator chamber; iii) a sedimentation tank; and iv) an aqueous fluid stream forming three closed flow-circuits in which the mass of the fluid is essentially conserved, and three opened flow-branches through which the mass enters and exits the system; wherein the first of said flow-circuits comprises said two inner and two outer chambers and said sedimentation tank, the second of said flow-circuits comprises said two inner chambers and said regulator chamber, and the third of said flow-circuits comprises said two inner and two outer chambers and said tower, and the first of said flow-branches comprises an inlet of tap water and said regulator chamber, and the second of said flow-branches comprises flow of a suspension of precipitated salts from said regulator chamber via said sedimentation tank out of the system; and the third of said flow-branches comprises water being either lost from the system by evaporation or leakage and/or pumped out of the system. Said first circuit provides for removal of precipitated calcium carbonate from the cell to the tank; said second circuit provides for equalizing pressures between said two inner chambers and further for transfer of precipitated salts from the cell to the regulator chamber; the third circuit provides for circulating softened and purified water between the cell and the tower; the first of said flow-branches provides for entering tap water through a water pump making vacuum to the system; the second of said flow-branches provides for removing the precipitated calcium carbonate out of the system; and the third of the flow-branches provides for both desired or incidental losses of water in the system. The simple, but unique, topology of the mass streams, including moving precipitation seeds from the proximity of the cathode toward the sedimentation tank, and spreading the elemental chlorine along the whole system, results in unexpectedly efficient system for providing soft and disinfected water to cooling towers. Of course, the softened water may be utilized also otherwise. The above described system comprises regulation elements, known in the art, including valves, pressure sensors, pH electrodes, electronic regulation of the flow-rates, and of the pressures, supported with microprocessors and relevant software. Said fluid stream goes through filters which remove particles of desired size, comprising salt precipitates and microorganisms. Said first flow-branch, provides not only for entering tap water, but also for the vacuum that sucks undesired gases out from the system. Purging the system off the gases further contributes to reducing the corrosion due to lowered activity of oxygen. Said electrolyzing cell comprises a strong stable source of direct current programmable to be reversed according to the need, and to provide pulses of any needed shape and frequency. Said fluid steam is kept moving by pumps strong enough to provide required flow-rates and pressures, while employing all required filters, the pumps being capable of flow reversal. The occasional reversal of the fluid flow and of the electrical current increase the stability of the system, and improve the purification efficiency. In a preferred arrangement, the flow rate is regularly reversed, as well as the electric current. The system of the invention enables to use both sides of the electrodes. When using the term planar for the electrodes, what is intended is that the electrodes have two sides which are essentially planar, but without any limitation regarding the volume between the to sides. In a preferred embodiment, the electrodes are thick metal blocks with parallel channels shaped as a network of slots going through and increasing the contact surface. The membranes separate the anode and the cathode, but its precise position is not limited to be equidistant.

P H 2 0 WATER TECHNOLOGIES LTD 182973/2

Claims (18)

1. CLAIMS 1. A device for decreasing the concentration of metallic components in water contained in a reservoir, comprising i) at least one electrolytic cell with water inlets, comprising of three electrodes (two cathodes and one anode or two anodes and one cathode) and two ion selective membranes placed between said electrodes, providing a divided cell containing four units; ii) an aqueous fluid stream forming closed flow-circuits in which the mass of the fluid is essentially conserved; iii) opened flow-branches through which the mass enters and exits the system; iv) a vacuum cleaning unit, for cleaning said electrolytic cell; and v) a sedimentation tank connected to said vacuum unit and said electrolytic cell and a collecting tank for collecting and removing the sediment.

2. A device according to claim 1, wherein the aqueous fluid stream forms three closed flow-circuits in which the mass of the fluid is essentially conserved, wherein the first of said flow-circuits comprises said four units and said sedimentation tank, the second of said flow-circuits comprises said four units, said vacuum unit and said tank, and the third of said flow-circuits comprises said four units, said tank and said reservoir, and wherein in the three opened flow-branches through which the mass enters or exits the system, the first of said flow-branches comprises an inlet of water or air and said vacuum unit, the second of said flow-branches comprises flow of a suspension of precipitated salts from said vacuum unit via said sedimentation tank out of the system, and the third of said flow- branches comprises water being lost from the system by evaporation or leakage and/or pumping out of the system. P H 2 0 WATER TECHNOLOGIES LTD 182973/2

3. A device according to claim 2, wherein said first circuit provides for removing precipitated metal components from said cell through said tank; said second circuit provides for transferring precipitants from the cell via said vacuum unit and to said tank; and the third circuit provides for supplying at least partially purified water back to the system.

4. A device according to claim 3, wherein the first of said flow-branches provides for entering water or air through a pump making vacuum to the system; the second of said flow-branches provides for removing the precipitated metal components out of the system; and the third of the flow-branches provides for both desired or incidental losses of water in the system.

5. A device according to claim 4, wherein the precipitation is initiated and seeded in the proximity of said cathode, and wherein said precipitation causes the removal of at least a part of said metal components from said aqueous fluid stream into said sedimentation tank.

6. A device according to claim 5, wherein elemental chlorine is created by the electrode process and spreads through by said aqueous fluid through the whole system.

7. A device according to claim 1, wherein said metallic components are heavy metals.

8. A device according to claim 1, wherein said metallic components are calcium and magnesium.

9. A device according to claim 1, further comprising a strong stable source of direct electrical current, filters, pumps, regulation elements, valves, pressure sensors,, pH electrodes, devices for electronic regulation of the flow-rates and the pressures, and microprocessors.

10. A device for reducing alkaline earth and heavy metals in water contained in a reservoir, comprising: P H 2 0 WATER TECHNOLOGIES LTD 182973/2 i) an electrolytic cell comprising an odd number of planar electrodes (e.g. two cathodes and one anode or two anodes and one cathode), and planar ion-selective membranes placed between said electrodes, dividing the internal space of said cell into at least four units; ii) a vacuum cleaning unit, for cleaning said electrolytic cell; iii) a sedimentation tank in which precipitated materials are collected, which is connected to said vacuum unit, to said electrolytic cell and to a collecting tank, for collecting and removing the sediment, iv) a circulation means ensuring water flow from said reservoir through said units back to the system; v) a circulation means ensuring mass flow from said cathode unit via said vacuum unit to said tank and to said anode unit; vi) a circulation means ensuring mass flow from said cathode unit via said sedimentation tank to said anode unit; and vii) a circulation means ensuring water flow from said reservoir to said cell, through said sedimentation tank, back to the cell and optionally back to the system.

11. A device for providing softened and purified water for a cooling tower, comprising i) an electrolytic cell comprising an odd number of planar electrodes (e.g. two cathodes and one anode or two anodes and one cathode), and planar ion- selective membranes placed between said electrodes, thus dividing the internal space of said cell into at least four units; ii) a vacuum cleaning unit, for cleaning said electrolytic cell; iii) a sedimentation tank in which precipitated calcium and magnesium are collected; P H 2 0 WATER TECHNOLOGIES LTD 182973/2 iv) a circulation means ensuring water flow from said tower through said units and said tank, and back to the tower; v) a circulation means ensuring mass flow from said cathode unit via said vacuum unit to said tank and to said anode unit; vi) a circulation means ensuring mass flow from said cathode unit via said sedimentation tank to said anode unit; and vii) a circulation means ensuring water flow from said cooling tower to said cell and said tank, and back to said tower.

12. A device according to claim 10, comprising closed flow-circuits through which an aqueous fluid passes, comprising i) a vacuum cleaning unit; and ii) passages connecting said vacuum unit with said units; wherein said electrodes comprise a plurality of parallel cathode and anode channels, and wherein direct electrical voltage is supplied to said electrodes, alkalizing the water near said cathode and causing the precipitation of metal salts, for example as metal hydroxides, which are collected in said sediment tank.

13. A device according to claim 12, comprising a power supplier providing direct electrical current between the electrodes.

14. A device according to claim 10, wherein said electrical current causes the conversion of at least a part of chlorides in said aqueous stream to elemental chlorine.

15. A device according to claim 4, wherein said vacuum assists in removing gases and debris out of the system. P H 2 0 WATER TECHNOLOGIES LTD 182973/2

16. A method of reducing alkaline earth and heavy metals in water stream, comprising: i) alkalization of water in an electrolytic cell consisting of an odd number of planar electrodes provided by a plurality of parallel channels, and ion selective membranes placed between said electrodes, resulting in the precipitation of said metals and removal thereof into a sedimentation tank; ii) creating a vacuum for sucking gases and debris out of said cell into said sedimentation tank; and Mi) circulating said water between said sedimentation tank and said cell; thereby providing softened and purified water.

17. A method according to claim 16, wherein said softened and purified water has a lowered concentration of calcium and magnesium, and is disinfected by elemental chlorine created during the electrode reactions.

18. A method according to claim 16, wherein said softened and purified water is less corrosive. 20. A device according to claim 1, comprising a plurality of electrolytic units, each one comprising an odd number of electrodes provided with parallel channels and separated by ion-selective membranes. 21. A water purification system, comprising i) at least one electrolytic cell comprising three electrodes separated with ion selective membranes, thus dividing said cell into four units; ii) a vacuum unit connected with said units enabling the removal of gases and debris from cell; iii) a sedimentation tank connected with said units via two connectors enabling the passage of water; and P H 2 0 WATER TECHNOLOGIES LTD 182973/2 iv) flow-circuits comprising three closed flow-circuits and three opened flow- branches through which water can move, wherein the mass of the fluid is essentially conserved in said flow- circuits, and wherein the mass enters or exits the system through said flow-branches. 22. A water purification system according to claim 21, wherein the first of said flow- circuits comprises said four units and said sedimentation tank, and wherein the second of said flow-circuits comprises said units and said vacuum unit, and that the third of said flow-circuits comprises said four units and a device in which the purified water is used. 23. A water purification system according to claim 21, wherein the first of said flow- branches comprises an inlet of water or air and said vacuum unit, and that the second of said flow-branches comprises flow of a suspension of precipitated salts out of said vacuum unit via said sedimentation tank out of the system, and that the third of said flow-branches comprises water being lost from the system by evaporation or leakage and/or pumped out of the system. 24. A water purification system according to claim 21, including pH regulation and stabilization. 25. A water purification system according to claim 21, providing drinking water, water for producing beverages or cosmetic products, water for industry, water for agricultural needs, and water meeting environmental standards to drain or open water reservoirs (e.g. sea, lakes and rivers). 26. A water purification system according to claim 21, providing softened and purified water for cooling towers. 27. A water purification system according to claim 21, providing softened and purified water without using chemical agents. P H 2 0 WATER TECHNOLOGIES LTD 182973/2 28. A water purification system according to claim 21, providing purified water from industrial process or municipal sewage containing heavy metals in a concentration lower than the maximal allowed concentration for discharging to a sewage system. 29. A water purification system according to claim 21, providing purified water with a values stabilized at a value of from 2.0 to 13.0, according to need.