Water purification apparatus and process for purifying water

A water purification apparatus is provided. The apparatus includes a casing and an electrode array. The casing has an outer surface, a substantially annular inner surface, and a water flow passage chamber surrounded by the substantially annular inner surface, the water flow passage chamber providing an outer annulus region and an inner central region. The electrode array features at least four electrodes in adjacent relationship to one another and circumferentially spaced apart from another about the outer annulus region, each electrode having a respective first planar surface and a respective second planar surface facing and substantially parallel to the respective second planar surface and the respective first planar surface of the adjacent electrodes on opposite sides thereof.

FIELD OF THE INVENTION

The present invention relates to purification or disinfection of water and, more particularly, to the electrolytic purification or disinfection of water.

BACKGROUND OF THE INVENTION

A conventional electrode arrangement found in water purification apparatus is shown inFIG. 9, in which a positive electrode91and a negative electrode93are cylindrical with circular cross sections extending continuously along their lengths. The highest current density92between the electrodes is found in a common plane that intersects the diameters of both of the electrodes91,93. The respective outer surfaces of the electrodes91,93are closest to one another in the common plane, that is, along narrow, substantially linear peripheral surface areas of the cylindrical electrodes intersected by the common plane.

Because the current density is greatest over such a narrow and relatively small surface area of the cylindrical electrodes91,93, cylindrical electrodes are not efficient in electrolyzing salts such as bromides. Additionally, certain cylindrical electrodes such as graphite can experience erosion along these narrow surface areas, releasing graphite particles into the electrolyte where the particles may accumulate. Further, the erosion causes the distance between the “closest” peripheral surface areas of the electrodes to increase. As the distance between electrodes increases, greater voltage is required to maintain current flux.

FIG. 10is another example of a conventional electrode arrangement in which a positive electrode101and a negative electrode103each have a square cross section extending continuously along their lengths. The parallel plane surfaces of the electrodes101,103facing one another provide a greater total surface area for quasi equal paths of greatest current flow102than the narrow, substantially linear areas of the cylindrical electrodes91,93ofFIG. 9. However, a problem with this conventional arrangement shown inFIG. 10is that the opposite side surfaces of the electrodes make relatively insignificant contributions to overall current flow because they are coplanar with one another and farther from one another than the facing surfaces of the electrodes101,103. Also, sufficient uniform electrolyte fluid flow and fluid flow distribution across the electrode surface, in the parallel plane geometry ofFIG. 10, is difficult to achieve. To the extent that direct flow of sufficient velocity may be achieved between the electrodes101,103, another problem arises in that the fluid flow can lead to premature failure of the graphite lattice. Still another problem is that dislodge graphite particles may become an aesthetic issue if the electrolyte is transparent.

Another drawback of conventional electrode geometry arrangements is compliance with industry standards. For example, UL Standard 1081 requires that the inlet to outlet voltage differential of the electrode assembly be essentially zero volts. UL Standard 1081 28.4 provides that there shall be no voltage drop in the water in the cell of an electrolytic chlorinator as measured between the water inlet and outlet, nor shall there be a flow of current, either alternating or direct, in excess of 1 milliampere from the water to ground. When using conventional parallel plane geometry, the zero volt differential between inlet and outlet is difficult to achieve because the geometrical orientation of the graphite electrodes in relation to the fluid flow inlet and the outlet will vary the differential voltage between the inlet and outlet.

SUMMARY OF THE INVENTION

A first aspect of the invention provides a water purification apparatus including a casing and an electrode array. The casing has an outer surface, an inner surface with a substantially annular cross section, and a water flow passage chamber surrounded by the inner surface, the water flow passage chamber providing an annulus region and a central region. The electrode array includes at least four electrodes in adjacent relationship to one another and circumferentially spaced apart from another about the annulus region. Each electrode has a respective first facet and a respective second facet facing and substantially parallel to the respective second facet and the respective first facet of the adjacent electrodes on opposite sides thereof.

A second aspect of the invention relates to a water purification apparatus including a casing and an electrode array. The casing has an outer surface, an inner surface with a substantially annular cross section, and a water flow passage chamber surrounded by the inner surface, the water flow passage chamber providing an annulus region and a central region. The electrode array includes at least four electrodes in adjacent relationship to one another and circumferentially spaced apart from one another about the annulus region. Each electrode has a respective first facet and a respective second facet facing and substantially parallel to the respective second facet and the respective first facet of the adjacent electrodes on opposite sides thereof. The electrodes of the electrode array include a first set of common polarity electrodes and a second set of common polarity electrodes, the electrodes of the first set in alternating arrangement with the electrodes of the second set. The electrode array is operable to simultaneously provide the first set of common polarity electrodes with a negative charge and the second set of common polarity electrodes with a positive charge.

Third and fourth aspects of the invention relate methods of purifying water utilizing the water purification apparatus of the first and second aspects of the invention, respectively.

Fifth and sixth aspects of the invention relates to a water purification system including the water purification apparatus of the first and second aspects of the invention, respectively.

Other aspects of the invention, including apparatus, systems, sub-assemblies (e.g., an electrolyzer unit), methods, and the like which constitute part of the invention, will become more apparent upon reading the following detailed description of the exemplary embodiments and viewing the drawings.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS AND EXEMPLARY METHODS

Reference will now be made in detail to exemplary embodiments and methods of the invention as illustrated in the accompanying drawings, in which like reference characters designate like or corresponding parts throughout the drawings. It should be noted, however, that the invention in its broader aspects is not limited to the specific details, representative devices and methods, and illustrative examples shown and described in connection with the exemplary embodiments and methods.

FIGS. 1-4illustrate an exemplary embodiment of an electrolyzer apparatus for water purification. The apparatus, generally designated by reference number10, includes a central electrolyzer unit11featuring a substantially cylindrical casing12having an outer surface14and an inner surface16. A water flow passage chamber18(FIG. 2) is surrounded by the inner surface16. Any suitable material may be selected as the casing12. It is preferred that the casing12material be electrically non-conductive. Plastics and ceramics, for example, PVC, may be selected as the casing12.

An electrode array including six electrodes21,22,23,24,25, and26is positioned inside the chamber18of the casing12. Each electrode21-26is elongated so as to be substantially coextensive with the length of the cylindrical casing12. The electrodes21-26are arranged in adjacent relationship to one another so that electrodes are positioned on opposite sides of each electrode, e.g., electrode21is adjacent to electrodes22and26; electrode22is adjacent to electrodes21and23; etc. The electrodes21-26are circumferentially spaced apart from another to establish an outer annulus region of the chamber18. The circumferential spacing of the electrodes21-26as shown is substantially uniform. An inner central region of the chamber18within this annulus region is essentially empty of any structural component for allowing the flow of water through the casing12. Water is also able to flow through the annulus region in the spacing between the electrodes21-26.

In the illustrated embodiment the electrodes21-26are essentially identical. In the interest of brevity, only electrode21will be described in greater detail in connection withFIG. 3. Electrode21has a radially outer surface (facet)21afacing the casing12, a radially inner surface (facet)21bfacing the inner central region (and diametrically opposing another electrode24on the opposite side of the central region), and opposite side surfaces (facets)21cand21din substantially parallel planes to one another arranged generally perpendicular to the radially inner and outer surfaces21a,21b. Oblique planar surfaces (facets)21eand21fare set at an oblique angle relative to surfaces21b,21c, and21d. The electrode21as shown inFIG. 3is six sided21a-21f, i.e., hexagonal, in cross section. Although the electrodes21-26are substantially identical to one another in the embodiment ofFIGS. 1-4, it should be understood that the electrodes21-26may possess different shapes and may be made of different materials from one another. Further, the electrodes21-26are not necessarily coextensive with the length of the casing12.

As best shown inFIG. 2, the oblique planar surfaces21eand21fface and are substantially parallel to the oblique planar surface26fof electrode26and the oblique planar surface22eof the electrode22, respectively. (Conversely, the side surfaces21cand21dare not substantially parallel to the side surface26dof electrode26and the side surface22cof the electrode22, respectively.) The other electrodes22-26likewise have similar relationships with respect to their respective adjacent electrodes.

The electrodes may be made of any suitable material, many of which are known and conventional in the art. Metallic materials such as copper, silver, and alloys and combinations thereof may be selected, as may mixed metal oxides (MMO's) such as titanium plated with RuO2. Graphite electrodes are particularly useful with bromine salt electrolytes. The graphite may include metals and/or mixed metal oxides. Graphite may be vacuum impregnated with copper to strengthen the graphite lattice and produce copper ions in the electrolyte. Copper ions aid in the reduction of algae in the electrolyte. Epoxy, silicone adhesives (e.g., Dow Corning 737), or other bonding substances may be vacuum impregnated in the graphite electrodes to help stabilize the graphite lattice. A semipermeable membrane may be used to cover the graphite, and thus lengthen the electrodes useful life. Exemplary electrode materials are disclosed in U.S. Pat. Nos. 7,452,456 and 7,351,331.

Referring back toFIG. 1, each electrode21-26is mounted to the easing12with a respective conductive fastener30received in a countersunk through hole of the casing12. As discussed in greater detail below, the conductive fasteners30serve the additional function of electrically connecting the electrodes21-26with their respective voltage source. Additional countersunk through holes32are longitudinally spaced apart from the countersunk through holes in which the conductive fasteners30are received. The additional fasteners (not shown), which may be made of a conductive or non-conductive material, may be received in the countersunk through holes32to further secure the electrodes21-26to the casing12. As best shown inFIG. 3, the electrodes, e.g.,21, have threaded holes29for receiving the fasteners. A bonding agent (e.g., Dow Corning 737) may be inserted in the holes29and/or applied to facet21ato secure the electrodes21-26to the casing12. The bonding agent may also serve to prevent oxidation of exposed surface areas of the fasteners. The fasteners may be, for example, screws, bolts, pins, rivets, etc.

The casing12of the electrolyzer11is provided with a first groove36and a second groove38encircling the outer surface14of the casing12. A first conductive wire is primarily situated in the first groove, and a separate second conductive wire is primarily situated in the second groove. The first conductive wire is electrically connected to the conductive fasteners30positioned that mount electrodes21,23, and25to the casing12. The second conductive wire is electrically connected to the conductive fasteners30positioned that mount electrodes22,24, and26to the casing12. Thus, alternating electrodes21,23,25are commonly electrically connected to one another via the first conductive wire, and alternative electrodes22,24, and26are electrically connected to one another (but not to electrodes21,23, and25) by the second conductive wire. A portion of the first and second wires may protrude from the grooves36,38to facilitate their electrical connection to a controller and power source, such as with use of an adapter (discussed below). It should be understood that alternative wiring arrangements may be employed. For example, each electrode21,23,25of the first set of common polarity electrodes may be directly connected to an identical or different controller or voltage source so long as the electrodes21,23,25share the same (common) polarity (i.e.,21,23,25are all positive or all negative). The same holds for electrodes22,24,26of the second set.

Returning toFIG. 1, the apparatus10further includes end caps40and42situated on the opposite ends of the electrolyzer unit11. The end caps40and42may be pressure fitted to the casing12, or may be secured using conventional fasteners and/or bonding. As best shown in the cross-sectional view ofFIG. 4, the end cap42is defined by an inner cylindrical portion46that receives and is pressure fitted or otherwise connected to the casing12. The end cap42further includes an inner shoulder47against which the end of the casing12may abut. An inner cylindrical portion49is connected to the shoulder47by a tapering portion48. Finally, an outlet opening45is present at the distal end of the end cap42. The inner cylindrical portion49and opening45may be sized to cooperate with (e.g., receive or be received by) inlet and outlet water flow conduits, such as flow pipe116discussed below in connection withFIG. 11.

End cap42has an attachment boss44for allowing access to the first and second wires of the electrolyzer11. An adapter (not shown) is shaped so that it may be received by the attachment boss44for electrically connecting terminals of the adapter to the first and second wires, and hence to the electrodes. A crimp may be used to secure the electrical connection. Adhesive bonding and/or other fasteners also may be used.

End cap40has a substantially identical construction in the illustrated embodiment, except that end cap40does not include the attachment boss44(although it may).

Referring now more particularly toFIG. 11, a water treatment system110according to an exemplary embodiment includes a reservoir112, such as a spa or swimming pool, connected to a recirculation system. A recirculation flow pipe116communicates at its opposite ends with an outlet112aand an inlet112bof the reservoir112. The system110further includes a pump118for displacing water114in the reservoir112through the recirculation flow pipe116, and optionally includes a filter120, such as a mechanical filter, situated along the recirculation flow pipe116, for removing solid particles and debris from the system110. In certain systems, such as for a hot tub, the recirculation system may further include a heater122for heating the water114to a selected temperature.

A water purification apparatus124, e.g., such as apparatus10(or50,60,70, or80, discussed below) is also incorporated into the recirculation system. For example, the water purification apparatus124may be located near the outlet112abefore the pump118, between the pump118and the filter120, between the filter120and the heater122, or near the inlet112b. Electrical connectors128, e.g., wires, electrically connect the water purification apparatus124to a controller126that supplies electrical current to the system. Any suitable power source can be used to power the controller126. For example, the controller126may be supplied with power from a DC source or an AC source, and/or may include an appropriate AC/DC converter. Alternative power sources, such as combustible gas or natural power (e.g., wind, solar), may be used. The controller126may further provide on/off capability, and polarity reversal capability for reducing scale buildup at the electrode surfaces. A timer (not shown) may be used for automatically reversing polarity of the electrodes and/or automatically turning the system on and off. The controller126also may include sensors (not shown) for controlling operation of the system, for example, turning the system on and off based on a pH, water quality, or biological-based readings of the water114.

Appropriate voltage and current levels and polarity reversal cycles depend on the intended use of the apparatus, and selection of suitable operation parameters and equipment is within the purview of those skilled in the art. In exemplary embodiments the voltage and current are designed to maintain the efficiency of electrolyzer unit11operation at some variable of distance between the conducting surfaces of the electrodes21-26. A PWM (pulse with modulation) circuit may be used to control the rate of ion production while maintaining a suitable current and voltage for a given electrode element material geometry. For example, voltages of about 5 to about 7.5 and electrical currents between electrodes of about 50 milliamps to 2.00 amps have been found to be suitable for use of the apparatus10in connection with a recreational spa. Selection of polarity reversal time and technique for minimizing scale build up on the surfaces of the electrodes21-26is application dependent.

The length, width, depth, individual geometry, and number electrodes utilized in the assembly10are not limited to the six elements shown in the embodiment ofFIGS. 1-4. Further, the casing12is not limited to a cylindrical shape. For example,FIG. 5illustrates an alternative embodiment50in which the substantially annular casing is polygonal annular.FIG. 6illustrates an alternative embodiment of an apparatus60possessing eight electrodes and a polygonal annular casing, wherein the electrodes have a trapezoidal cross section with greater interfacing surface areas between adjacent electrodes.FIGS. 7 and 8illustrate still additional embodiments of apparatus70and apparatus80having four electrodes. Still other arrangements, shapes, and relationships may be practiced. The cross sections of the casing and the electrodes, while shown uniform, may vary over their length. The electrodes of an apparatus are not necessarily identical to one another.

Similarly, the purification system is not necessarily limited to the embodiment shown inFIG. 11. For example, instead of treating and recycling water in a reservoir112, the system may be operated to purify drinking water, ground water, rainwater, or waste water.

Operation of the apparatus10in accordance with an exemplary embodiment will now be described.

It is desirable but not required that the apparatus10be oriented in a vertical position, perpendicular to the earth, with the inlet end cap40at the bottom and the outlet end cap42at the top. However, the apparatus10may be operated at various angles from perpendicular or in a horizontal orientation. Although the electrodes21-26are shown extending in length substantially parallel to water flow through the apparatus10, it should be understood that the electrodes21-26may be obliquely or perpendicularly arranged relative to water flow.

The apparatus10may be used to purify water for recreational, residential, commercial and industrial uses. For example, recreational systems that the apparatus10may be used with include spas, hot tubs, swimming pools, saunas, etc. The apparatus also may be used in connection with the purification of drinking water, water storage tanks, well tanks, home water systems, etc. Depending on its desired application, the apparatus10may be operated as part of a chemical-based system, a copper ionization system, or a chemical-free system.

Discharge of electrical energy between the electrodes21-26, more particularly between the substantially parallel planar surfaces of adjacent electrodes, during operation creates a reactive species in the water that can kill or render harmless pathogens,E coli, algae, viruses, and other microorganisms and contaminants. The reactive species may also prevent organic material from becoming a nutrient for algae and other microorganisms. For example, in chemical-free systems with the appropriate electrode material, the system may utilize a hydrolysis reaction to generate free radical forms of oxygen, such as hydroxyl radicals, atomic oxygen, hydrogen peroxide, and hydroxide ions. In chemical based systems, e.g., bromide and chloride salt solutions, the apparatus is operated to generate free bromine and chlorine. One particularly suitable electrolyte is an aqueous solution containing a bromide salt concentration of, for example, 50 to 4000 ppm.

The aforementioned improved design characteristics of the electrolyzer unit geometry may increase bromine production efficiency per unit area of the electrode surface. The higher bromine production efficiency improvement can be utilized to reduce the required surface area of the electrodes, reduce the volume of material (e.g., graphite) used in the individual electrodes, increase the MTBF (mean time between failures) through lower current density, and/or reduce the required bromide concentration. Reduction in electrode size allows for the production of more compact, smaller apparatus with lower material costs.

The electrolyte flow between the electrodes (in the annulus of the casing12) is offset from the main electrolyte flow (in the central region of the casing12); allowing for sufficient purging of the electrolyzed molecules from the surface of the electrodes, while reducing deterioration of the electrodes (e.g., the graphite lattice). In the horizontal orientation, gases produced by the electrolysis event have been observed flowing in the direction toward the inlet. In the illustrated embodiment, the orifice of the inlet end cap40is smaller in diameter than the inner diameter of the casing12. The inlet orifice causes the hydrodynamics to produce a flow at the inner surface of the electrolyzer chamber opposite to the inlet flow, improving the circulation in the electrolyzer chamber. Thusly, a balance between the necessary circulation of the electrolyte on the surface of the electrodes is achieved, without unnecessary reduction of the electrodes useful life. The improved method of electrode flow control, by reducing the electrode (e.g., graphite lattice) deterioration, reduces the amount of unsightly particles contained in the electrolyte.

In operation, current flow between the electrodes21-26of the array in the above-discussed exemplary embodiment is evenly distributed. Evenly distributed current flow results in longer term stability of the distance between erodible electrode materials such as graphite. Thus, the electronic control of the current between the graphite electrodes is simpler to attain. The substantially annular array of electrodes provides a geometry that more efficiently utilizes the electrode element surface areas, facilitating a more efficient utilization of electrode material, particularly those made of graphite. Thus, commercialization potential is improved because a very small amount of graphite is lost in the fabrication process.

The electrolyzer apparatus10geometry also reduces and preferably eliminates the electrode fluid flow inlet to outlet differential voltage. The annular array geometry of the electrodes with alternating polarities successfully integrates the fluid flow inlet to outlet voltage differential. Also, the substantially annular array geometry is not sensitive to the geometrical relationship of the elements to the input and output of flow. Therefore, the orientation of the fluid flow input to output is an insignificant variable.

In accordance with an embodiment, graphite is typically produced in rectangular bars that are cut into shape as dictated by the desired design. The implementation of non-planar and non-perpendicular cuts to form, for example, the electrode shapes described above reduces production material losses. More exotic shapes for the graphite electrodes may be fabricated by using, for example, vapor deposition.

The foregoing detailed description of the certain exemplary embodiments of the invention has been provided for the purpose of explaining the principles of the invention and its practical application, thereby enabling others skilled in the art to understand the invention for various embodiments and with various modifications as are suited to the particular use contemplated. This description is not intended to be exhaustive or to limit the invention to the precise embodiments disclosed. Although only a few embodiments have been disclosed in detail above, other embodiments are possible and the inventors intend these to be encompassed within this specification and the scope of the appended claims. The specification describes specific examples to accomplish a more general goal that may be accomplished in another way. Modifications and equivalents will be apparent to practitioners skilled in this art and are encompassed within the spirit and scope of the appended claims and their appropriate equivalents. This disclosure is intended to be exemplary, and the claims are intended to cover any modification or alternative which might be predictable to a person having ordinary skill in the art.

Only those claims which use the words “means for” are to be interpreted under 35 U.S.C. §112, sixth paragraph. Moreover, no limitations from the specification are to be read into any claims, unless those limitations are expressly included in the claims.