NZ572038A - Electrode having a cement coating that can serve as anode or cathode - Google Patents

Abstract

Disclosed is an apparatus for the electrolysis of water to promote the growth of aquatic organisms. The apparatus has at least two electrodes (100), each electrode having an electrically conductive interior (102) capable of serving alternately as an anode and as a cathode. Each electrode has a non-metallic exterior coat (103) made of from a chemical reaction between Portland cement and water, the coat having a surface and a controlled thickness. Each electrode also includes electrical connection means. The apparatus includes a reversible power supply, the supply capable of supplying a current at a controlled current density. The supply is also capable of reversing the polarity of the current at a rate so that any one electrode can serve alternately as a cathode and as an anode.

Description

Received at IPONZ on 1 April 2010 Patents Form no. 5 Patents Act 1953 Complete after Provisional Specification NZ 572038 cognated with NZ 577730 ELECTRODES FOR ELECTROLYSIS OF WATER I, Maurice James Robertson, of 13 Rewi St Torbay, North Shore City 0630, New Zealand, a citizen of New Zealand, do hereby declare this invention to be particularly described in the following statement: 1 Received at IPONZ on 1 April 2010 ELECTRODES FOR ELECTROLYSIS OF WATER FIELD This invention relates to apparatus for electrolysis of water; more particularly to stable and nontoxic electrodes for immersion in a body of water for the purpose of electrolysis of the water.

DEFINITIONS Ionic current means a current carried by ions in an ionisable liquid such as a body of water.

An electrode is a conducting body connected to a supply of electricity and immersed in a conducting medium, serving as a source or sink of charged ions in that medium.

Electrochemical disinfection refers to a process of passing an ionic current through water in 35 order to sterilise the water.

BOD - biological oxygen demand; used to describe a body of water or part thereof.

HOD (hydrogen-oxidising denitrifying organisms).

YcefSATi refers to the inevitable voltage drop across a transistor when saturated (turned fully on. Note that some other solid-state switching devices, or relays, do not exhibit this voltage drop. 40 BACKGROUND There is increasing interest in electrolysis of water for a number of purposes, including: - (a) sterilisation of bodies of water such as by adding dissolved oxygen or peroxide or halogen oxides. This can be used in waste water treatment, for swimming pools, or to ensure safety of drinking water. Waste water treatment includes storage in tanks or oxidation ponds, 45 optional filtration, and finally release, after adequate quality tests, into the environment, perhaps even as potable water. This is a lengthy process that may require holding vast amounts of water for an extended time. Electrolysis can enhance oxidation, and remove particulates in the final stages. In swimming pools a little sodium chloride or sodium bromide provides the halogen. (b) adding oxygen to water as a product of electrolysis. Oxygen depletion in the depths of 50 lakes is a well-publicised problem; leading in some cases to death of organisms. Adding oxygen encourages growth of certain types of desired aquatic micro-organisms.

Deaedt et al in Microbiological research 163, (2) 192-199 (2008) describe the disinfection of water containing Legionella pneumophila and Escherischia coli. If actually electrolysed, both 2 Received at IPONZ on 1 April 2010 types of organism were killed but if a residual concentration of 0.08 mg/1 free oxidant was used 55 instead, then the E.coli was killed but the L. pneumoniae was not completely killed.

For the final restoration of waste water as potable water, it is known that a process of electrolysis even in the absence of organisms can help dispose of undesirable contaminants by electrochemical reactions with free oxygen or hydrogen or chlorine or sodium - the latter being products of electrolysis of sodium chloride. Very small particles are broken apart. It is inefficient 60 to create actual bubbles of gas, because that gas is lost to the microbes. Both hydrogen and oxygen evolved during electrolysis of water maybe used in biological processes by microorganisms in the decomposition of organic waste matter, resulting in treated water with lower values of BOD, TSS, TN (total nitrogen), and FC. Hydrogen serves as an electron donor for hydrogen-oxidising denitrifying (HOD) bacteria. These micro-organisms are autotrophic. They 65 require carbon dioxide only as a carbon source, producing nitrogen and water from the nitrate and hydrogen. //, f NO, -> IIX) + A?, Removal of nitrates from effluent reduces the potential for eutrophication of lakes and rivers.

Green algae in a pond or tank add oxygen to the water in proportion to the amount of usable 70 light, as a by-product of photosynthesis. At night, when photosynthesis is halted, no oxygen is produced but continuing respiration of algae and bacteria removes oxygen from the water. Oxygen availability can be a limiting factor in ponds. When unicellular life forms such as algae and/or aerobic bacteria are farmed together, often in a symbiotic relationship, such as during remediation of waste water or if being farmed to make cell products such as edible materials or 75 bio fuels, enhanced growth has been noted when the water containing the unicellular life forms is subjected to electrolysis. The reasons for this observation seem to go beyond raising the dissolved oxygen. Perhaps the presence of calcium in the water together with an electrical field may encourage the metabolism of aquatic organisms . See Goldsworthy, N D. Effects of Externally Applied Electric Fields on Growth, retrieved from 80 http://www.bio.ic.ac.uk/research/agold/goldsworthv.htm.

It is known that electrodes having a working electrode surface composed of platinum or other noble metals (iridium, rhodium, rhenium, etc) have a long life when in use in bodies of water, since those materials seem to be immune from electrochemical reactions which cause attack of the electrodes, in particular electrodes used as anodes. Other advantages of platinum such as a 85 low over-voltage are known in the art of electrochemistry. Boron-doped diamond has been used as an electrode material. In contrast, electrodes of iron or stainless steel, particularly if used as the anode at a higher current density, do suffer attack, exhibit pitting and other forms of erosion, and so forth. Metal ions are released into the water. Many of these are toxic to algae, notably copper ions. An iron anode will form ferrous oxide, and it will therefore rust and degrade over Received at IPONZ on 1 April 2010 90 time, although small amounts of ferrous iron may enhance algal growth, and have been used to combine with phosphate ions (see JP2000051894). Attempts to use carbon electrodes have not been promising. Even electrodes comprised of woven carbon fibre are attacked when used as anodes; turning into a brown slime. Aluminium anodes will readily oxidise and the resulting oxides and hydroxides will dissolve over time, resulting in degradation of the anode. Titanium 95 anodes do not degrade substantially over time, however their cost may be prohibitive.

Concrete is a conductive, insoluble meshwork of fibrous crystals and embedded inert material, formed by the re-crystallisation of a mineral or in particular of a manufactured product following a chemical reaction with water. One "manufactured product" is Portland cement (see below). Concrete is widely used for pipes and tanks for water. The tanks maybe above the ground or 100 buried. Typically concrete is made with included metal reinforcing bars or mesh since concrete has a poor tensile strength property on its own.

Cement or "ordinary Portland cement" is a finely ground form of Portland cement clinker which is a hydraulic material consisting of at least two-thirds by mass of calcium silicates OCaO.SiO? and 2CaO.SiQ7), the remainder consisting of aluminium- and iron-containing clinker phases and 105 other compounds. The ratio of CaO to SiO? should not be less than 2.0. The magnesium content (MgO) should not exceed 5.0% by mass. Cement is used to make concrete, stucco, or mortar or grout by addition of gravel, sand, and water and a reaction between the cement and water produces a rigid solid material which, of relevance in this invention, is inherently porous and conductive. Either Type II or Type V cement types as defined in the US standard "ASTM C150" 110 maybe best suited for the present application. Others have used cements based on magnesium.

PRIOR ART Published patents include the following: W02008/098298 to Iogenyx describes a "half-electrode" in which one electrode, preferably the anode, is buried in soil beside a tank of algae, or the tank wall itself is used as one electrode. The 115 organisms are protected from materials released from the anode. A cathode is immersed in the liquid. This is asymmetrical, does not lend itself to polarity reversal, and either relies on soil conductivity or places the tank wall at some risk of deterioration. For waste water treatment, AU2005201638 uses a large surface area cathode and encourages bacterial growth upon it, using what is said to be an electrostatic voltage. NZ 534551 from the same inventor makes the cathode 120 into a conduit shape and encourages growth within a non-woven felt layer. Likewise, US 7404905 Musson describes cathodes used "in electrostatic mode" to attract a mat of algae. For waste water treatment, JP2000051894 usees two iron plate electrodes adapted to trap microorganisms and their polarity is periodically reversed. Denitrification is promoted, and phosphate ions are removed by flocculation with iron ions. For waste water treatment, 125 JP2003071453 usees porous electrodes adapted to trap microorganisms by flocculation and by a Received at IPONZ on 1 April 2010 container shape. Oxygen is generated at an anode for consumption by aerobic bacteria. Denitrification is promoted at the cathode. For waste water treatment, US 3562137 Gehring cleans up the water in a series of electrolysis cells including electrodialysis membranes to separate the electrodes from the water to be purified; the peri-electrode area generating useful 130 amounts of, for example, caustic soda.

US 3725236 Johnson uses "exhaustive electrochemical oxidation" to oxidise organic samples and derive a measure of the BOD. That test method could be used on a process scale. US 3914164 Clark makes use of electrolytically generated gas bubbles in order to gently mix aquatic life forms while processing waste water, carried out in a "septic tank extender unit". The reason 135 for doing this includes removing materials likely to clog the soil in a drain field taking waste water from the septic tank. US 3925176 Okert uses electrolysis of waste water to produce oxidising agents effective in killing pathogenic bacteria and fungi. US 4382866 Johnson uses a reversible 12V 50A power source to supply current to a cylinder comprising conductive perforated material separated by non-conductive perforated material wound together; connected 140 as a first electrode or second electrode alternately. Waste water is forced radially though the cylinder. No prior art has been identified in which a vulnerable metal electrode (such as a carbon or an iron anode) is protected by being cloaked in cement.

OBJECT An object of this invention is to provide a substantially inert yet conductive electrode as a 145 replacement for conventional metal electrodes for use in electrolysis of water, or at least to provide the public with a useful choice.

STATEMENT OF INVENTION In a first broad aspect the invention provides a novel electrode suitable for use as either an anode or a cathode during an aqueous electrolysis procedure, wherein the electrode has an electrically 150 conductive interior connected to elongated electrical connection means; the interior being completely covered by a rigid, conductive, non-toxic and non-metallic exterior coat such that only the non-metallic exterior is exposed to the aqueous liquid; the electrode not being included in a wall of a containing means holding the aqueous liquid.

Preferably the coat is comprised of a concrete material comprised of a settable cement optionally 155 including further materials selected from a range including carbon and manganese dioxide.

Preferably the non-metallic exterior coat is at least 10 mm thick over any part of the electrically conductive interior.

More preferably the non-metallic exterior coat is at least 20 mm thick over any part of the electrically conductive interior.

Received at IPONZ on 1 April 2010 160 In another aspect the electrically conductive interior of the or each electrode is comprised of a substance selected from a range including iron, steel, stainless steel, aluminium, titanium, and carbon fibre.

In one option the electrode resembles a flattened cube, having as an interior a common metal in the form of an open mesh, thereby resembling a flat slab having an electrically conductive centre 165 to which an electrical connection is made.

Optionally the electrode is provided with one or more suspending means so that it may be suspended at a working height from an inextensible cord while immersed in the aqueous liquid.

In another broad aspect the invention provides a reversible power supply for an electrolysis device using at least two electrodes each as previously described in this section; the power 170 supply having a facility of reversing the polarity of a direct current supply connected through the elongated electrical connection means to a first set of one or more electrodes serving for the time being as one or more cathodes and to a second set of one or more electrodes serving for the time being as one or more anodes, at a selected rate.

Preferably the selected rate is between 400 alternations per second to once a month. 175 More preferably the selected rate is at about one Hz.

In a related aspect the invention provides a reversible power supply for an electrolysis device using at least two electrodes each as previously described in this section, wherein the least positive voltage applied to any electrode is maintained at a more positive voltage than that of any other conductive material in contact with the aqueous liquid by means of a further elongated 180 electrical connection means connected from the power supply to said other conductive material, so that said other conductive material acquires cathodic protection.

Preferably the power supply includes means capable of maintaining an ionic current density of about 0.1 mA per square centimetre of electrode surface.

Alternatively the power supply includes means capable of maintaining an ionic current density 185 between the electrodes of between 1 mA and 500 mA per cubic metre of aqueous medium.

Alternatively the power supply includes means capable of maintaining a potential gradient between the electrodes of between 1 V and 24 V per metre of aqueous medium.

In a third broad aspect the invention provides a method of using at least one electrode as previously described in this section with a reversible power supply as previously described in 190 this section, the method being applied to promote of growth of aquatic organisms in an aqueous medium, wherein said aquatic organisms include aerobic bacteria and algae.

In a related aspect the invention provides a method for promotion of growth of selected aquatic organisms in an aqueous medium in a container in a waste water treatment facility, so that 6 Received at IPONZ on 1 April 2010 biological oxidation proceeds more rapidly. 195 Preferably a current density sufficient to evolve oxygen as dissolved oxygen into the waste water is used, but not sufficient to generate visible bubbles of oxygen at or near the anode, so that the metabolism of aerobic micro-organisms contained within the waste water is supported.

In a further related aspect the invention provides a method for sterilisation of water in a container in a waste water treatment facility. 200 In a yet further related aspect the invention provides waste water processing apparatus employing production of oxygen within the waste water by an electrolytic process, wherein the oxygen is made upon the surface of a conductive non-metallic surface serving as an anode electrode.

In yet another related aspect the invention provides a method for promotion of growth of HOD 205 (hydrogen-oxidising denitrifying) organisms by dissolved hydrogen so that the nitrate content of the waste water is reduced.

In an even further aspect the invention provides a method for maintaining the pH of a body of water in a range between 8.5 and 11.0. 210 DETAILED DESCRIPTION OF THE INVENTION The description of the invention to be provided herein is given purely by way of example and is not to be taken in any way as limiting the scope or extent of the invention. Throughout this specification unless the text requires otherwise, the word "comprise" and variations such as "comprising" or "comprises" will be understood to imply the inclusion of a stated integer or step 215 or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.

DRAWINGS Fig 1; shows an "X-ray diagram" of a typical electrode according to the invention.

Fig 2; shows a transverse section of a typical electrode according to the invention. 220 Fig 3: is a top view of a water treatment tank containing two electrodes according to the invention.

Fig 4: shows a woven material made of carbon fibre wired and ready for inclusion within a concrete electrode.

Fig 5: shows a circuit diagram for switching between electrodes and maintaining fixed 225 equipment at a lightly more negative voltage. 7 Received at IPONZ on 1 April 2010 Fig 6: shows a floating barge or frame holding suspended electrodes in a "dead" body of water.

Fig 7: is a graph comparing biological oxygen demand in a test tank, as compared to a control tank not including any electrodes, over time.

Fig 8: is a graph showing increased growth of aquatic organisms in a test tank, as compared to 230 a control tank not including any electrodes.

DESCRIPTION OF PREFERRED EMBODIMENTS In summary the specification will describe the preferred composite electrode made of concrete with a conductive inner mass, then illustrate use of this type of electrode with a power supply, preferably a reversible power supply. Two or more of the invention may be used inside man-235 made containers such as tanks and conduits, or used in natural environments such as in dams, streams and lakes.

EXAMPLE 1 See Figs 1-3. Fig 1 is a "surface X-ray" diagram. The electrode 100 of this invention has an inner core comprised of a conductive material such as a metal mesh 102 having at least one 240 conducting lead 101 brought to the exterior. A non-metallic conductor 102 such as an array or a mesh of carbon fibres may also be used. Optional lugs or handles 104, 105 or other lifting means maybe provided so that the electrode can be totally immersed in a body of water with only the insulated conductor 101 brought out to an external source of electricity. Preferably the lugs or handles will not, even if cracked, expose the inner core to the aqueous medium. The inner core 245 may also have a reinforcing function for the concrete once it has set. The outer coating 103 is made of a porous conductive settable material preferably though not essentially one based on Portland cement which has been described in the Background. The final mixture of cement, sand and water might be called "grout" or "mortar" or "stucco" in the absence of added gravel. For simplicity we shall refer to it as "concrete" in this specification. Certain kinds of cement make a 250 concrete that is better adapted to tolerate exposure to ground water. Concrete is known to be conductive, especially when wet. Concrete is porous and includes some free cations including sodium and calcium. The calcium may assist in the growth or metabolism of the microorganisms.

The concrete-covered electrode according to this invention is preferably made with a large 255 surface area to volume ratio so that the resulting current density is nowhere high. The physical form may be a horizontally flattened cube to lie on a tank floor, or a vertically disposed flattened cube (rather like an oil-filled panel heater), as shown in vertical cross-section in Fig 2. This cross-section also shows that the inner core is preferably covered to an approximately even thickness with concrete. For example, 20 mm is a suggested coating thickness although 10 mm 260 has been used. It maybe preferable to use 40 or 50 mm of concrete if that will ensure reliability 8 Received at IPONZ on 1 April 2010 over a service life time. A base 106 may be attached, or simply placed on the tank floor to receive the electrode, so that the electrode is held in place in a vertical alignment, and with respect to other electrodes (see Fig 3) placed side by side on a base of a tank as shown in Fig 3, which is a plan view (from above) of a tank. A power supply 301 is shown. 303 represents the 265 body of water, and 302 represents the wall of the container or tank. Compatible tanks might be made to include an array of grooves that match the electrode dimensions, perhaps down the walls or in the floor, so that the electrodes are held in place. More than one electrode pair may be placed in a tank. Preferably the electrode surfaces face each other, rather than face the walls, so that the tank wall is involved in current flow as little as possible. 270 In some arrangements the tank wall 302 itself may serve as one electrode, since repeated current reversal seems to help overcome degradation that is otherwise a problem in whichever electrode is used as an anode, although for long life the tank wall is not included in any significant flow of ions and only the concrete electrodes are included in a powered circuit. The electrodes should be installed in a way that allows them to be lifted and their physical condition checked at intervals 275 of six months to one year, so it may be convenient to tie polypropylene ropes to the handles 104/105 of each one and leave the ropes trailing outside a manhole cover or retrievable from just inside the cover (if the tank is enclosed), so that electrodes can easily be retrieved. Inspection maybe synchronised with tank cleaning operations. It seems inadvisable to lift the electrodes by means of their electric connecting wires 101 since the stress might break the wire or open a crack 280 into the interior. Preferably more than one lead is included in each concrete electrode in case any one lead breaks or becomes separated from the conductive core. Since a typical current per typical electrode is under 1 A (ampere) the wire does not need to be heavy.

Slab-like electrodes maybe made as follows. A mould of suitable size, like the outline of 100 in Fig 1 and for example, 42 mm in depth is placed flat upon the ground. First an optional dusting 285 of manganese dioxide powder (to serve as a catalyst for reduction of hydrogen peroxide), or a release agent, or other surface treatment is placed on the bottom of the mould. Then an about 20 mm thick layer of wet concrete (as herein defined) is placed over the coating. (Other thicknesses have previously been discussed). The wet concrete may include conductive material such as granules of carbon, but extra conductive solids are not necessary. Then a piece of metal mesh 290 102, for example "338 reinforcing mesh" which is fabricated from 4 mm diameter mild steel rods spot welded at 50 mm spacing, which already has the insulated conductor 101 bonded to it (such as by brazing and then painting the brazed bead at 101A just in case unwanted copper ions escape into the tank) is placed upon the wet concrete. Then a further layer of wet concrete is poured over the mesh, and the two concrete layers are merged by puddling the wet concrete such 295 as with a rod, so that the concrete layers merge and the mesh becomes sealed within the concrete. Another layer of manganese dioxide or other surface treatment may be dusted over the top surface at the end. A rough external surface gives more surface area than a smooth finish. The electrode can be used once the concrete has hardened sufficiently for the electrode to be Received at IPONZ on 1 April 2010 removed from the mould and allowed to set further. The above description of manufacture may 300 be modified as is well known to those skilled in the art, for mass production.

These concrete electrodes are useful in the production of dissolved hydrogen and dissolved oxygen in a body of water, such as for the benefit of aerobic decomposing micro-organisms which are processing waste water, or for encouraging growth of algae, or for the later stages of rendering waste water re-usable. The outer surface of the concrete, not the conductive core 305 within, serves as the effective electrode surface and the inner core is not degraded - at least much more slowly than an exposed metal or carbon-fibre anode electrode. Meanwhile metal ions do not reach the body of water so potentially cytotoxic or polluting materials do not arise. This approach to the provision of an electrode is a preferred way to overcome the tendency of metal anode surfaces to become oxidised and to then deteriorate and add heavy metals to the issuant 310 waste water. In this version the effective anode is not a metal. The concrete could be regarded as a form of "half-cell" or "semi-permeable coating". Operation of this type of electrode over extended periods of months shows no significant deterioration. Migration of metal ions from the core has not been observed. Microbial coverings that may form during use have not as yet been studied, but do not appear to be important in the specific example applications for which the 315 electrodes have been tested. It is important to note that this invention does not describe "electrostatic" processes, because (a) a significant current flow is created and (b) the polarity of the electrodes is preferably interchanged on a regular basis. Any ions arising from the concrete are either non-toxic or beneficial to life, such as calcium, (which also has pH control attributes) or silicon which is a necessary element for algal skeletal structure. Calcium hydroxide usually 320 forms at or within the anode. This compound has the effect of stabilising the pH at a relatively high level within the aquatic environment. At night the calcium hydroxide reacts with the extra carbon dioxide produced by respiration of the aquatic organisms to produce calcium carbonate, which also serves to stabilise the pH of the aquatic environment at relatively high levels. For an aquatic environment that contains aerobic bacteria and/or algae, a preferred pH range is between 325 7.5 and 12, with an optimum range for wild algae being between 8.5 and 11.0. So long as there are sufficient calcium ions within the aquatic environment, the electrical field will serve to maintain the pH of the aquatic environment within these preferred ranges. Some sodium hydroxide might be added to the wet cement.

Fig 4 shows how a woven sheet 102 made of carbon fibres maybe attached to an insulated wire 330 101. First about 100 mm ofinsulation is stripped from one end of the wire, exposing the multi-stranded copper wires 401. The wires are laid over an edge of the sheet - preferably midway along one edge, then the sheet is bunched together along its edge (403) and the copper strands are brought away from the sheet and then wrapped around and around the bunch (terminating at 401), so as to form a contact with all of the carbon filaments extending from the bunch towards 335 the far side of the sheet (beyond 404). The exposed copper might optionally be dipped in wax or epoxy or the like, or left alone.

Received at IPONZ on 1 April 2010 During operation, it has been found that oxidation of the component elements of the concrete at the surface is minimal and that oxygen generated at the anode becomes dissolved in the water, becoming available for microbial respiration and enhancing aerobic decomposition activity. In a 340 trial, four electrodes of the concrete-coated carbon fibre type have been running continuously for 4 months when supplied with a potential difference of 10.5 volts, alternating at an 0.5 Hz rate. The current flow is 50 mA through each electrode. There has been no visible sign of deterioration, nor any change in the current consumption over that time.

Here are details of measurements of a typical carbon-fibre concrete electrode pair immersed in 345 slightly salty pond water. Electrode area, for both sides of one electrode: about 0.2 square metres. A constant supply voltage is maintained between wires 101 of each electrode at 10.5 V. Current passing though loop = 75 mA. Voltage drop across each electrode - to its outer surface = 2.1 V. Therefore 5.3 volts is dropped across the water. Equivalent electrode resistance = 35 ohms each. Equivalent water resistance = 70 ohms. Average current density = 0.375 A.m"2' As 350 compared to a simple steel rod used as a cathode, an electrode made of concrete as herein described has a much larger surface area, allowing for greater overall conductivity between two electrodes with water between, thus allowing more ionic current at a fixed voltage. Conductivity tests in pure water in the dark comparing the same amount of metal mesh alone compared with mesh buried within a concrete electrode revealed: Mesh alone: V = 10.9 V , I = 25.7 mA; Mesh 355 in concrete: V = 10.3 V, I = 111 mA. Or, if the current was regulated at 18.8 mA, the voltage dropped from around 10V to around 8V when a concrete cathode was substituted for a metal mesh.

The relatively bulky concrete provides a large surface area for the supplied current to pass through so that the current density per unit area is quite low. It is known that algae can be killed 360 if too high a voltage is applied to a cell. This effect may be related to high spot current densities. Another effect relied on in this invention is that the relatively resistive concrete, in series with and between the metal portion of the electrode and the electrolyte, is partially self-regulating. It may be considered as an infinite number of resistances in parallel that collectively tend to reduce any effect for current density to become concentrated at any one point because a tendency for a 365 higher current to pass through any point leads to a greater voltage drop at that point on account of Ohm's law, and so less current will flow at that point. That is why incorporation of extra conductive materials such as carbon, or steel wool, are not particularly useful at least in the trials carried out to date. The internal metal structure is used to shorten the conductive path of current through the concrete, so that the series resistance of the concrete does not unduly affect 370 efficiency. This approach to the provision of an electrode is a preferred way to overcome the tendency of metal anode surfaces to become oxidised and to then deteriorate and add heavy metals to the issuant waste water. In this version the effective anode surface is not a metal. 11 Received at IPONZ on 1 April 2010 Both anodes and cathode type concrete electrodes are made in the same way, so that the resulting installation is inherently symmetrical and electrode polarity can be reversed from time to time if 375 required - see below. The tank wall and any immersed conductive items such as propellers, pumps or pipes should not be included in any significant flow of ions. Significant ionic current should be restricted to flows between the concrete electrodes. The other parts maybe given some cathodic protection by being maintained at a slightly lower voltage than any active concrete electrode (see below). If polarity reversal is not used over a long period of some days, the 380 concrete anode electrode may split open because of accumulation of electrolysis products at the metal/concrete interface. If this does occur, it tends to heal again if that electrode is then used as a cathode for a similar period, by accretion of calcium-rich insoluble salts in the crack.

Fig 5 shows a preferred reversible power supply 301 including in particular a switching circuit 301 and a separate connection to the walls of a tank or other immersed conductive items. Since 385 this is a constant-voltage circuit it may easily be connected in parallel to separate tanks or to more than one pair of electrodes 103 in any one tank 302. For example two cathodes are usable with an anode in between - as CAC/ACA, or four electrodes CACA/ACAC, where "C" = cathode and "A" = anode. A 12-volt battery 501 is connected through suitable fuses and a switch (not shown) to a positive bus 503 and a negative bus 504. A mains-drive "plugpack" may be 390 substituted for the battery, or a solar panel, either used alone or in a battery charger configuration, for which circuits are well-known to those skilled in the art. This has the advantage of not requiring that a sewage farm or the like be possibly unsafely wired for mains electricity, and that each tank can be electrically an isolated unit with no current flowing through pipes or the tank walls. 395 Four transistors - where 505 and 507 are PNP types and 506 and 508 are NPN types, are connected across the busses as shown, and the electrodes 103 in the tank 302 are connected to the interconnections between the pairs of transistors. This comprises a standard "H-bridge" switch which, if the transistors are driven in an opposite, complementary way as shown by the "A" and "NOT-A" symbols adjacent their bases by driving means 502 constructed according to 400 standard electronics practice, will connect each electrode alternately to the positive bus then to the negative bus; one out of phase with the other. Driving means 502 should provide symmetrical square wave drives to the transistor bases and preferably at least one binary divider stage is used internally, following an oscillator, to assure symmetry so that there is not a trend for one electrode to be an anode more often than it is a cathode. Because of the inherent VCe(sat) 405 drops across the transistors the voltage applied to the electrodes is about 10.7 volts. Because of the inherent Vce (sat) drops across the lower two transistors the cathode electrode at any time is 1 x Vce (sat) above the potential at which the reinforcing 509 of the concrete tank 302 (or any other immersed equipment) is held, so that some cathodic protection is always given. The bonding wire 510 carries about 5 mA in the inventor's experimental prototype. The bonding wire is not 410 essential, but is advantageous for cathodic protection. In one alternative, such as where 12 Received at IPONZ on 1 April 2010 conductive tanks placed in conducting soil are present, the bonding wire is connected to an earth peg; a conductor firmly placed within the conducting soil, not to the tanks themselves.

The prototype is preferably run at 0.5 Hz, so that each electrode is alternately held for 1 second as a cathode and then for 1 second as an anode, over time. Other switching devices such as 415 manually operated switches, automatically driven relays, a dual power supply arrangement, or other active solid-state devices may be used. The use described above of the inherent VCe (sat) drop across a power transistor may be simulated if other switching means are used (such as a relay, a physical switch or connectors, or a different form of solid-state switching device) by including one or more suitably rated silicon or other diode in forward conduction mode between 420 the ground and the least positive contact of each other switching means, as will be apparent to one skilled in the art. This uses the inherent diode voltage drop effect, not dependent on current.

More complex versions may include a microprocessor which may be also attached to monitoring means appropriate for the process in use, optionally also communicating the data to a remote site or storing it for downloading from time to time, and optionally also programmed so as to control 425 taps or valves or other process-control devices so that the process under control is optimised.

The current density considered to be appropriate for most purposes is described as "a level slightly under that at which formation of bubbles of dissolved oxygen gas is observed". That density is about 0.1 milliamperes per square centimetre of anode electrode surface - or about 320 mA for a 0.4 x 0.4 m two-sided panel shape. Another expression of current density is that it may 430 be set at between 1 mA and 500 mA per cubic metre of water. A constant-current form of DC supply may be used instead of a constant-voltage supply (see Example 3 discussion). Alternatively output from a transducer sampling the dissolved oxygen may be used as input to a voltage or current control means. Water conductivity, reflecting ion concentration, is usually "sufficient" for this invention. Clear water in lakes and rivers typically has specific conductivity 435 of the order of 1000 uS/cm. Waste water typically has higher specific conductivity owing largely to ions in solution, which provides an effective conducting liquid for the electrolysis process. Typical electrochemical reactions during the electrolysis of water are; Cathode (reduction); 4H+ + 4e~ 2H2 440 Anode (oxidation): 2H20 —> (32 + 4H+ + 4e~ The cathode reaction is straight-forward and in water produces hydrogen, which does not react with the cathode material. The hydrogen produced becomes available for HOD bacterial activity (see below), if bacteria are present. Because oxygen is more soluble in water than hydrogen, as 445 current density increase bubbles of hydrogen will occur on the cathode surface before bubbles of 13 Received at IPONZ on 1 April 2010 oxygen appear at the anode. The anode reaction is more complex and the oxygen produced is readily available to oxidise the material of the anode. If this is a metal, lacking a coating of concrete or the like, the end product is typically a combination of oxides and hydroxides of the metal, which dissolve and contaminate the water. 450 The solubility of hydrogen in water at 25 deg C is 1.5 mg/litre of water. Using Faraday's law of electrolysis, 1 mA of current will produce about 0.01 \ig of hydrogen per second which will need to move away from the cathode surface before bubbles can form. It has been found that bubbles of hydrogen are produced at the surface of the cathode if there is a current density greater than the order of 1 mA/cm2. The solubility of oxygen in water at 25 deg C is 40 mg/litre. 1 mA will 455 produce about 0.08 \ig of oxygen per second which will need to move away from the anode surface to remain dissolved. For a total effective electrode area of 1 m2, 1 A will produce a current density of 0.1 mA /cm2, which is below the threshold for bubble formation of both hydrogen and oxygen. The amount of oxygen produced over time by 1 A current is about 7 g per day, from Faraday's law of electrolysis. In a 1,000 litre pond, assuming no oxygen-consuming 460 organisms or chemicals, this would increase the dissolved oxygen by 7 ppm per day.

EXAMPLE 2 APPLICATION IN WASTE WATER.

Construction of the preferred concrete electrodes has been described in Example 1.

This Example describes a process involving continuous low-level electrolysis for facilitating the secondary or tertiary treatment of wastewater. The experiment was carried out on a waste water 465 system servicing a household of 7 adults. It is believed that the electrolysis acts to treat the water in several ways, including supplementing the dissolved oxygen concentration, and may also provide some gentle stirring.

Fig 3 is a top view of an active region- a pond in a wastewater plant - wherein two electrodes each labelled 103 are suspended within the tank 302, filled with water to be processed 303. A 470 wire 101 connects between each electrode and a terminal on a preferably alternating power supply 301. The installation may operate in darkness or in light. Here, aerobic micro-organisms are encouraged to proliferate in order to decompose of wastewater, in order to effect a tertiary treatment. Preferably each electrode, if vertically mounted, is high enough to reach from near the upper surface of the wastewater down close to the base. 475 The operation of the system may be monitored and regulated on a basis including one or more of: (a) measuring the biological oxygen demand of the water, (b) measuring the coliform content of the outlet water, (c) turbidity or like measurements sensitive to the existence of bubbles in a liquid, around the anode, or (d) a simple ammeter and "rule of thumb" concerning treatment duration. 480 The prototype used a simple DC "plugpack" run from the mains. 14 Received at IPONZ on 1 April 2010 Test Results A series of tests have been made with a waste water system using electrodes and low-level electrolysis according to the invention as previously described in this document. Samples were taken over a 38 day period with the same waste water system servicing a household of 7 adults. 485 Samples were delivered to NZLabs Ltd, 303 Eastbourne St East, Hastings, NZ, for testing according to approved relevant methods. The results showed a time course of results as per the following table: Date 11/3/09 18/3/09 2/4/09 17/4/09 Biochemical Oxygen Demand (mg/L) 33 31 <1 Total Suspended Solids (mg/L) 78 34 9 Faecal Coliforms (cfu/100ml) 72,000 ,700 7,000 97 Dissolved Oxygen (mg/L) 0.47 1.9 2.9 4.5 490 The operating temperature was in the range of 10 to 20° C. This may be compared with a recent trial of commercial, aerated waste water disposal plants conducted at Rotorua. Of course the above results are not obtained from an "production" system so they can't be compared with that trial which was intended to replicate ordinary operating conditions. The average results obtained 495 from a variety of On-Site Effluent Treatment (OSET) systems in the Rotorua trial, using city sewage give the following average results: Biochemical Oxygen Demand (mg/L) = 4.7 Total Suspended Solids (mg/L) = 10 Faecal Coliforms (cfu/lOOml) = 9.8 x 104 500 Only 3 of the 7 systems in the trial showed Total Suspended Solids counts of less than 9 and none came close to the inventor's other figures.

Received at IPONZ on 1 April 2010 EXAMPLE 3 APPLICATION IN ANOXIC WATERS.

Construction of the preferred concrete electrodes has been described in Example 1. In relation to 505 an as yet un-tested example device for remediation of anoxic lower layers of a lake, Fig 6 shows a barge 600 or other floating frame preferably moored in place on a lake surface 600A over a deep layer of anoxic water 601. A power supply 301 provides preferably switched DC current to an array of electrodes 103, supported by supports 602. Optionally the power supply is provided with 12V DC from a standard lead-acid battery or the like, and optionally this battery may be 510 continually replenished with electricity from an array of solar cells or the like, for continuous oxygenation. In this diagram we have not shown ropes and conducting leads to the electrodes separately. These may be of considerable length.

When in use, the apparatus is left to run by itself. Since there are no moving parts and the concrete electrodes have been shown to be unaffected by long periods of use, this device may be 515 left in place, which saves on labour costs. As one option the supply might be run at a higher voltage in order to boost the ionic current density, since the effect of bubbles on mixing of the layers of water maybe beneficial. On the other hand, it is dissolved oxygen in particular that counts in this kind of problem, so the doubled voltage may not be any more effective than a supply that does not produce free bubbles. While the act of blowing air under pressure through a 520 pipe into such a layer in order to oxygenate it is well known, this approach to overcoming the problem does not use moving parts and there is no energy required to force a gas downwards, against a head of water. Therefore the example device could be used in quite deep waters, such as in a dammed lake used for a municipal water supply. Further, the theoretical maximum saturation of dissolved oxygen arising from contact with pure oxygen is known, from published 525 articles, to be about 40 ppm (at standard temperature and pressure; STP) whereas the theoretical maximum saturation of dissolved oxygen arising from contact with air is about 10 ppm.

EXAMPLE 4 APPLICATION: PROMOTING ALGAL GROWTH.

Construction of the preferred concrete electrodes has been described in Example 1. A pilot study for enhancing the growth of aquatic organisms; for instance of a type which may be used to 530 produce a useful biomass such as for use in animal feeds, human feeds, production of lipid material and the like, or for instance as part of a disposal process, was done in a dual-pond concrete tank, lined with a polythene lining in order to render both ponds separately watertight. Pond A has a 320 x 320 x 20 mm concrete-encased anode electrode made using a 300 x 300 mm section of 338 reinforcing mesh encased in concrete, according to Example 1 and connected to a 535 DC power supply. In this trial it was a DC current-regulated supply. The concrete anode electrode rests on the bottom of the north end of Pond A. In the early part of this DC (non-reversing) Example, a simple cathode electrode which was a 200 mm length of 16 mm diameter steel reinforcing rod, suspended at the south end of Pond A is used. Pond B is the control. It has 16 Received at IPONZ on 1 April 2010 identical size, shape and treatment, but no electrodes are placed in it, nor is there any other 540 connection to the DC supply. Ponds A and B received identical treatment.

The power supply was set at 11.00 V. The initial current at 1800h on 1 September 2008 was 7.6 mA. The current was regulated to approximately this value and settled at 8.5 mA, at which current it was regulated up to 1800h 16 September. The voltage varied diurnally according to aqueous conductivity. The current was then regulated to be 18.8 mA from 1800h 16 September 545 2008. The voltage again varied diurnally. A current density a little under that which generates visible bubbles was used. On 20 September, the steel cathode electrode 4 (of Fig 4) was replaced by another electrode, like the existing anode, consisting of steel mesh encased in concrete. The current was regulated at 18.8 mA, and the voltage dropped from around 10V to around 8V with the concrete cathode, indicating better conductivity of the concrete cathode. 550 The ponds were placed outdoors in a New Zealand spring, for about 2 months, and their top surfaces were open to the air. The water was inoculated with a supply of aerobic bacteria and algae. Initial treatment was 1.5 litres of a liquid made from horse manure in a barrel of water added to each pond. This served as a supply of aerobic bacteria. A 750ml stirred sample of fish pond water known to contain species of green algae including Scenedesmus quadricauda was 555 also added. As a result of the electrolysis, providing more oxygen and possibly also providing other benefits to the aquatic organisms including pH control but otherwise beyond the scope of this document, yet without the disadvantages of exposed metal electrodes, growth of the aerobic bacteria and algae is enhanced as shown in Figs 7 and 8. Fig 7 is a graph comparing biological oxygen demand in a test pond "A", as compared to a control pond "B" not including any 560 electrodes, over 45 days. Fig 8 is a graph showing increased growth of aquatic organisms in a test pond, as compared to a control pond that did not include any electrodes.

In Fig 7, the diurnal change in dissolved oxygen readings, presumed to indicate changes in the supply over the consumption of oxygen, is plotted. The treated pond had greater swings in dissolved oxygen. 565 In Fig 8, the percentage increase in the daily swing in dissolved oxygen in pond A, as compared to pond B, is plotted as an indication of the biomass present. The inventor did not have means to measure the actual biomass. It can be seen that on average there is 2.55 times as great a biomass in the treated pond as in the pond without electrodes.

A number of factors were not controlled in this pilot study such as the ecological balance of 570 organisms, an accidental spill, and apparent depletion of some raw materials which on one occasion was overcome with application of a plant food (Yates' "Thrive"). The electrode polarities were not reversed at all in this study. 17 Received at IPONZ on 1 April 2010 575 COMMERCIAL ADVANTAGES 1. The invention provides cheap, long-lasting electrodes at least for relatively low-intensity electrolysis of water. 2. Encasing the electrodes (especially when used as the anode) within concrete protects the metal part of the electrode from degradation. 580 3. Use of symmetrical anode and cathode electrodes facilitates reversal of electrochemical reactions (simply by reversing polarity) from time to time, at least doubling the life time of the electrodes. 4. Encasing the electrodes in concrete provides for a greater surface area for the electrochemical reaction to occur than if mesh alone was used; allowing the current density to be 585 low and the resistive nature of the concrete allows the surface potential over the concrete surface to be relatively even.

. Conductivity of the circuit is significantly improved over simple metal electrodes. 6. Concrete electrodes tend to sink to the bottom of a natural aquatic environment, where the water will generally have less oxygen. 590 7. The electric field and hence the ionic current flow is substantially horizontal within a tank, for upright electrodes, facilitating a substantially even current density within a tank or the like. 8. The invention enhances the growth of aquatic organisms such as aerobic bacteria and/or algae in a body of water, by increasing the dissolved oxygen content within the aquatic 595 environment using electrical means. 9. Concrete electrodes may release a useful amount of calcium ions into the water, possibly beneficial to the aquatic organisms, or silicon as silicates or the like, by maintaining the pH between optimum pH ranges.

. The invention increases the rate at which an algae/bacteria process can remediate 600 nutrient-contaminated water, and allows control over that process at a low cost. 11. A substantial reduction of faecal coliform bacteria per ml is noted. Further tests may be useful since there are likely to be many associated factors.

Finally, it will be understood that the scope of this invention as described by way of example and/or illustrated herein is not limited to the specified embodiments. Where in the foregoing 605 description, reference has been made to specific components or integers of the invention having known equivalents, then such equivalents are included as if individually set forth. Those of skill will appreciate that various modifications, additions, known equivalents, and substitutions are possible without departing from the scope and spirit of the invention as set forth. 18 RECEIVED at IPONZon 16 November 2010

Claims (12)

1) Apparatus for the electrolysis of water characterised in that the apparatus includes (a) at least two electrodes; each electrode having an electrically conductive interior selected from a range of: iron, steel, stainless steel, aluminium, titanium, and carbon fibre and capable of serving alternately as an anode and as a cathode; (b) each electrode having a non-metallic exterior coat having a surface and a controlled thickness; the coat comprising a concrete made using a chemical reaction between Portland cement and water; (c)each electrode also including electrical connection means; (e) the apparatus also including a reversible power supply having at least one first terminal and at least one second terminal capable of being connected in a circuit including the electrodes, (f) the power supply being capable of supplying a current at a controlled current density in a range of between 0.01 milliamperes and 1 milliampere per square centimetre of electrode surface, and (g) the power supply further being capable when in use of regularly reversing the polarity of said current at a rate; thereby allowing any one electrode to serve alternately as a cathode and as an anode.

2) An apparatus as claimed in claim 1, characterised in that the power supply includes at least one third terminal capable of being electrically connected to any electrically conductive object or objects, not being an electrode, also in contact with the water and the power supply includes means capable of ensuring that the least positive voltage provided to any electrode is maintained at a more positive voltage than the voltage provided at the third terminal, so that said electrically conductive object or objects are provided with cathodic protection.

3) An apparatus as claimed in claim 1, characterised in that the rate of reversal of the power supply occurs at a selected rate of between 400 Hz to direct current.

4) An apparatus as claimed in claim 3, characterised in that the selected rate is 0.5 Hz.

5) An electrode for an apparatus as claimed in claim 1, characterised in that the thickness of the non-metallic exterior coat is in a range of between 2 mm and 50 mm. 19 RECEIVED at IPONZon 16 November 2010

6) An electrode as claimed in claim 5, characterised in that the electrode is provided with one or more suspending means so that, when in use, it may be suspended at a working height while immersed in the water.

7) A pair of electrodes, each as claimed in claim 5, characterised in that a first rodlike coated electrode is mounted concentrically within a second cylindrical electrode having a coat on at least the inside surface; the combination serving as a means capable of performing electrolysis on water held or carried between the pair of electrodes.

8) An electrode as claimed in claim 5, characterised in that the electrically conductive interior is provided in the form of an open mesh having apertures passing therethrough, and the exterior coat is sufficiently thin to maintain the presence of said apertures passing therethrough.

9) An apparatus as claimed in claim 1, characterised in that the apparatus includes a series of at least two open-mesh concrete-coated electrodes each as claimed in claim 8, alternately connected as an anode and a cathode; the series of electrodes being confined in a container such that a flow of water to be treated passes between the meshes of all of the electrodes.

10) A method of use of an apparatus as claimed in claim 1, characterised in that the method comprises operating the apparatus so as to cause promotion of growth of aquatic organisms selected from a range including aerobic bacteria and algae in an aqueous medium.

11) A method of use of an apparatus as claimed in claim 1, characterised in that the method comprises operating the apparatus so as to cause sterilisation of water in a container in a waste water treatment facility.

12) A method of use of an apparatus as claimed in claim 1, characterised in that the method comprises operating the apparatus so as to cause promotion of growth of hydrogen-oxidising denitrifying organisms by dissolved hydrogen so that a nitrate content of the water is reduced. 20