GB2419590A

GB2419590A - Water disinfection apparatus and method

Info

Publication number: GB2419590A
Application number: GB0520939A
Authority: GB
Inventors: Nigel Paston
Original assignee: TANYA YVONNE PASTON
Current assignee: TANYA YVONNE PASTON
Priority date: 2004-10-14
Filing date: 2005-10-14
Publication date: 2006-05-03
Anticipated expiration: 2025-10-14
Also published as: GB2419590B; GB0422773D0; GB0520939D0

Abstract

The apparatus is adapted for eliminating or inhibiting the growth of microorganisms within a body of water. A first electrode 6 comprising silver and a second electrode 8 , preferably containing copper, are each mounted in contact with the body of water. The first electrode means may comprise a first copper electrode body 7 adjacent a silver electrode body 6. Alternatively, the first electrode means may comprise silver wire (17, Fig. 4) wound around and spaced from a second copper electrode comprising a copper plate (15. Fig. 4). Also claimed is an apparatus adapted for eliminating or inhibiting the growth of microorganisms within a body of water contained in reservoir means, comprising an apertured body containing metallic silver. The body is a woven mesh and may comprise clay balls (20, Fig. 5) containing a plurality of silver strands (22, Fig 5).

Description

WATER DISINFECTION APPARATUS AND METHOD * S S * *5

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The present invention relates to apparatus and a method for killing harmful bacteria present I...., in water. More particularly, but not exclusively, it relates to apparatus and a method for. I...

killing or preventing the growth of bacteria such as legionella, salmonella and E. coli in water **U tanks, lagoons, ponds and the like. : : Many potentially lethal bacteria and other microorganisms may grow in bodies of stored water, such as storage tanks, header tanks, feeder tanks, lagoons, reservoirs and ponds, which for simplicity will collectively be referred to herein as "reservoir means". Organisms such as legionella notoriously build up in water tanks of air conditioning systems. Bacteria that can cause food poisoning, such as salmonella and E. coli, may incubate in ponds, water troughs and the like, being picked up by livestock and poultry as they drink. Many other microorganisms will multiply in stored water to the extent that they may harm humans or animals that subsequently come into contact therewith.

It is believed that many of these microorganisms grow preferentially at or near the surface of the water, particularly within the meniscus itself.

Silver, copper and their ions known to have a bactericidal effect, but appear not to have been applied to water purification and disinfection with any significant degree of success.

It is hence an object of the present invention to provide an apparatus to eliminate and/or inhibit the growth of microorganisms in bodies of water. It is also an object of the present to provide a method for eliminating and/or inhibiting the growth of microorganisms in bodies of * water. :... :. * S

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According to a first aspect of the present invention, there is provided an apparatus for * * SS* eliminating or inhibiting the growth of microorganisms within a body of water contained in....* *.SS reservoir means, comprising first electrode means comprising silver and a second electrode ** : means, each mounted in contact with the body of water.

In one embodiment, the apparatus comprising first electrode means mountable to the reservoir means to extend through or adjacent a surface of water therein and comprising a silver electrode body, and second electrode means mountable to the reservoir means remotely from the first to extend through or adjacent said water surface and electrically connected to the first electrode means.

Preferably, the first electrode means additionally comprises a first copper electrode body adjacent the silver electrode body.

Advantageously, the second electrode means comprises a second copper electrode body.

The silver electrode body may be cotmected to the first copper electrode body.

The silver electrode body may be in direct contact with the first copper electrode body.

Alternatively, the silver electrode body and the first copper electrode body may be spaced apart, each from the other, optionally by a distance substantially less than a maximum dimension of each.

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Preferably, the silver electrode body is substantially planar. :...:. *SSS * S

* S* * Advantageously, the first copper electrode body is substantially planar. * * S... * ... * S S S. S

One or each of the electrode bodies, optionally the silver electrode body, may comprise an apertured body, such as a woven mesh.

The silver electrode body and the first copper electrode body are preferably of generally equal dimensions.

Preferably, the first and second electrode means are mounted adjacent generally diametrically opposite sides of the reservoir means.

The apparatus may comprise or be connectable to electrical power supply means.

An electrical current may then be passable between the first and second electrode means.

Alternatively or additionally, the apparatus may comprise third electrode means mountable to the reservoir means to extend into the water therein.

An electrical current may then be passable between the third electrode means and either or each of the first and second electrode means.

The first electrode means may be provided with means to oxygenate water in contact *. :* therewith. * *

Preferably, said aeration means is adapted to deliver air or other gas comprising oxygen to a * : :::* submerged portion of the silver electrode body. S... * ..* * S S

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The first electrode means may be provided with surface abrasion means.

Preferably, said surface abrasion means is adapted to act on all or part of a submerged surface of the silver electrode body.

The surface abrasion means may comprise a plurality of abrasive bodies and means to move said abrasive bodies across a surface of the silver electrode body.

The apparatus may be provided with earthing means.

The earthing means may optionally be linked to the first electrode means, the second electrode means, or to each.

The apparatus is preferably adapted to be mountable to reservoir means containing slow moving or substantially stationary water.

According to a second aspect of the present invention, there is provided An apparatus for eliminating or inhibiting the growth of microorganisms within a body of water contained in reservoir means, comprising an apertured body containing metallic silver. : * ** * S S.....

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Preferably the body is a woven mesh. :. *.:. S... * *SSS

Alternatively, the body comprises clay and silver wire so heat treated as to render it * S...

permeabletogas. *:.: In this case, the apparatus may further comprising means adapted to deliver air or other oxygen containing gas to a submerged portion of the silver containing body.

According to a third aspect of the present invention there is provided reservoir means, as herein defined, provided with apparatus as described in the first aspect above for eliminating or inhibiting the growth of micro-organisms in water held within the reservoir means.

According to a fourth aspect of the present invention there is provided a method for eliminating or inhibiting the growth of micro-organisms in a body of water, comprising the steps of providing first electrode means comprising a silver electrode body and second electrode means connected to the first by means to conduct electricity, and disposing each electrode means remotely from the other in the water, extending through or adjacent a surface thereof.

Advantageously, the second electrode means comprises a second copper electrode body. S. S * S * * ..

The silver electrode body may be disposed in direct contact with the first copper electrode:...:. body.

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Alternatively, the silver electrode body and the first copper electrode body may be spaced.. S...

apart, each from the other, optionally by a distance substantially less than a maximum * *: : dimension of each.

Each or any of the electrode bodies may be substantially planar, and may optionally comprise a mesh.

Preferably, the method comprises the step of disposing the first and second electrode means adjacent generally diametrically opposite sides of the reservoir means.

The method may comprise the steps of providing third electrode means extending into the body of water and passing a current between the third electrode means and either or each of the first and second electrode means.

The method may comprise the step of oxygenating the water in contact with the first electrode means.

The method may comprise the step of abrading a submerged surface of the first electrode means, particularly a submerged surface of the silver electrode body.

The method may comprise the step of earthing the reservoir means, optionally of earthing any one or more of the electrode means. : ** * * ***** The method may comprise the step of providing apparatus as described in the first aspect:...:. ****

above. S... * *.*

Embodiments of the present invention will now be more particularly described by way of *:. : example and with reference to the accompanying drawings, in which: Figure 1 shows a schematic cross-section of a tank of water with first disinfection apparatus embodying the invention mounted thereto; Figure 2 is a scrap perspective view of a bimetallic electrode unit of the first disinfection apparatus shown in Figure 1, isolated therefrom; Figure 3 is a schematic cross-section of an agricultural pond with first disinfection apparatus embodying the invention in position therein; Figure 4 is a schematic perspective view of a second disinfection apparatus embodying the present invention; and Figure 5 is a schematic elevation of a plurality of disinfecting spheres embodying the present invention, one of which is shown in cross-section..

Referring now to the Figures and to Figure 1 in particular, a water tank 1 contains a volume of stored water 2. The water 2 may be piped into the tank 1, for example as part of a water supply arrangement, or may have collected there, for example as part of an air conditioning system. In each case, water 2 is usually tapped off from such a tank 1 via an outlet 3 located adjacent its base, as and when required; water 2 in such a tank 1 normally has a relatively long residence time and is only occasionally disturbed or mixed. : . :* * S S.....

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It has been found that potentially harmful or even lethal micro organisms may proliferate in:...:.

such tanks 1. These include bacteria such as Legionella, a particular hazard in air- "...

conditioning systems, and Salmonella and E. coli, which are responsible for many outbreaks of food poisoning. These bacteria and others grow preferentially in upper layers of the water: , : 2, and are particularly associated with the meniscus 4 at the surface of the water 2. Thus, although some bacteria will diffuse to lower portions of the tank 1 and be tapped off through the outlet 3, a main concentration thereof may reside and grow at or near the meniscus 4 for considerable periods. Once infected, such a tank I may become a long-term source of dangerous micro-organisms.

The tank I shown is provided with apparatus to eliminate or at least to inhibit the growth of such micro-organisms (henceforth, for simplicity, referred to as "disinfection" apparatus).

This comprises a first, bimetallic electrode unit 5, comprising a silver electrode 6 in close proximity to a first copper electrode 7, and a second electrode unit comprising a second copper electrode 8. The first and second electrode units are linked by an electrically conductive cable 9.

Each of the silver electrode 6 and the copper electrodes 7, 8 is immersed in the water 2, close to or extending through the meniscus 4. In a currently preferred version, the first electrode unit 5 comprises a flat sheet of silver mesh forming the silver electrode 6 and a flat copper plate of substantially the same size and shape forming the first copper electrode 7, as shown in Figure 2. These are aligned substantially parallelly, each to the other, spaced by a distance substantially less than a width of either. In an alternative version (not shown) the silver.

electrode 6 and first copper electrode 7 are in direct contact rather than being spaced apart. :*..:. * S

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In a simplest embodiment of the disinfection apparatus, the electrodes 6, 7, 8 form an *....* electrochemical cell with the water 2 as electrolyte, which results in the gradual formation of * copper and/or silver ions in the water 2 generally between the electrodes 6, 7, 8. Both copper *: * : : and silver ions are known to have a bactericidal effect, including against bacteria such as Legionella, Salmonella and E. coli. The arrangement described thus generates bactericidal metal ions in exactly the region of the water 2 in which these bacteria grow preferentially, which should act to eliminate or at least severely inhibit bacterial propagation at source.

In a preferred embodiment, as shown, an electrical power supply 10 is linked to the cable 9 and hence to the electrodes 6, 7, 8. A small electric current is then passed between the electrodes 6, 7, 8, encouraging the formation of dissolved copper and/or silver ions.

Optionally, a third copper electrode 11 is provided, extending into the water 2 substantially beneath the meniscus 4. In embodiments in which the power supply 10 is present, the third copper electrode 11 is also connected thereto.

In some embodiments, the tank 1 is provided with an earth connection 12.

In several embodiments, the water 2 adjacent the bimetallic electrode unit 5, and particularly adjacent the silver electrode 6, is oxygenated, for example by bubbling air across the bimetallic electrode unit 5 from below, for example by means of a directed nozzle (not *, shown) linked to an air compressor or compressed air supply. This is believed to enhance the oxidation process by which metallic silver forms Ag ions. *.:. **** * *

* ** * **.* In some embodiments, the silver electrode 6 is provided with an arrangement to abrade its i.., . * S..

surface. For example, a plurality of balls or pellets of stone or ceramic materials (not.

shown), held in a cage around the silver electrode 6, may be agitated gently so that they move across the surface of the silver electrode 6. This may maintain a clean, fresh silver surface andlor may remove trace amounts of metallic silver to increase the dissolution rate. It is believed that this feature may act synergistically with the oxygenation arrangement referred to above.

As well as discrete water tanks 1 as shown in Figure 1, the disinfection apparatus shown is also usable in bodies of water such as ponds or even swimming pools. Figure 3 shows (schematically) similar disinfection apparatus in place in a farm pond 13. Such ponds may be a primary source of drinking water for livestock or poultry 14, but are likely to be contaminated with faecal matter, leading to growth therein of micro-organisms such as Salmonella and E. coli. These can then be picked up by the livestock or poultry 14, in some cases even being passed to eggs, and potentially leading to food poisoning when the livestock, poultry or eggs are eaten. Similar problems may apply to artificial drinking troughs unless they are regularly scoured out.

Therefore, the bimetallic electrode unit 5 of the disinfection apparatus is inserted into the pond 13, etc, adjacent a first bank thereof, and the second electrode unit 8 is placed adjacent a generally opposite bank. The cable 9 (not shown) may be run around the banks of the pond 13, and a low-voltage electrical supply 10 maybe provided if desired. A low concentration..

* S S*S p of silver andlor copper ions will thus be generated in the water of the pond 13, near to its surface where the harmful bacteria would grow preferentially. The concentration of these: * bacteria will be significantly restricted or even reduced to zero, removing the causes of food a a...

poisoning at source. In this case, depending on the size of the pond 13, the second electrode:; : unit 8 may beneficially comprise several copper electrodes spaced apart along the banks of the pond 13, or even a horizontally-elongated single electrode.

Figure 4 shows a variant on the above 4isinfection apparatus. A copper plate 15, roughly twenty-five millimetres square, has an elongate insulating body 16 extending along two opposite edges. The insulating bodies 16 conveniently comprise a malleable non-conductive material, such as a putty, ideally slightly tacky to hold it to the copper plate 15. Each insulating body 16 is thicker than the copper plate 15, and extends to either side of the plane thereof.

An elongate silver wire 17 is wound several times around the copper plate 15, extending transversely to the insulating bodies 16 and in contact therewith. The silver wire 17 thus extends several times across each face of the copper plate 15, but slightly spaced therefrom.

The copper plate 15 is connected to a first terminal of an electrical power supply 18 (here a conventional 1.5V dry cell) while the silver wire 17 is connected to a second terminal of the power supply 18. When the apparatus is immersed in water or other electrolyte, a current will therefore flow between the silver wire 17 as a first electrode and the copper plate 15 as a second electrode.

A region surrounding the apparatus is oxygenated, here by means of a porous fired clay air block 19, disposed beneath the copper plate 15 and supplied with air or oxygen. This bubbles! ..

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out of fine pores in an upper surface of the air block 19, producing a stream of fine bubbles a *a *.e.

flowing upwardly around and across the surfaces of the copper plate 15 and the silver wire * * a... 17. a... p..' * .*. a a *

This disinfection arrangement has been tested on a heavily-contaminated water sample, having an initial concentration of coliform bacteria of 7. 5x103 (units of MPN/lOOml used throughout), of which the count of E coli came to 2.0x103. After four hours with only a very low current passing between the silver and copper electrodes, the count of coliform bacteria dropped by almost three-quarters to 2.0x103, of which E coli comprised 1. 45x103. Normally, one would expect the bacterial count to have grown slightly over this period. It is believed that a significant bacterial kill had been achieved after no more than one hour of this treatment.

Figure 5 shows, schematically, another, allied approach to carrying out effective disinfection of water using silver. This approach involves the use of a plurality of fired clay balls 20.

Each clay ball 20 is produced by kneading together a conventional clay with short strands of silver wire and strips of paper, then rolling the mixture into small spheres (typically ten to twenty millimetres in diameter). These spheres are then baked in a kiln, firing the clay and burning out the paper to leave a plurality of pores 21 extending through the balls 20, as shown schematically in the sectioned clay ball 20 shown in Figure 5. The clay balls 20 also contain a plurality of silver strands 22, some of which probably extend through the clay itself, while others probably extend into and along an interior of the pores 21. The pores 21 are accessible to water and other aqueous electrolytes in which the balls 20 are immersed. I. - * I * lb

A test was carried out on a heavily contaminated water sample, containing an initial concentration of coliform bacteria of 7.5x 10, of which the count of E coli amounted to 2.0x103. A small number of silver-impregnated clay balls 20 were placed in the sample and allowed to form a bed resting on a floor of its container. After four hours, the total count of t coliform bacteria had almost halved, to 4.2x I 0, with E coli representing only 1.Ox 1 0. As * above, without the clay balls 20 present, a slight rise in the bacterial count might be expected.

It is believed that even better results would be achieved is the bed of balls 20 had been aerated, thus oxygenating the water penetrating the pores 21 and contacting the silver 22. No quantitative results are yet available, however. An agitated or fluidised bed might also improve the effectiveness of the balls 20, as might forcing a stream of water through a stationary bed.

It should be borne in mind that E coli is one of the most difficult bacteria to kill. The results achieved above against E coli imply that this approach would kill more susceptible bacteria, such as Legionella, even more effectively.

The silver-impregnated clay balls 20 would therefore be of particular utility in air- conditioning systems, where growth of Legionella in water in cooling ducts, water sprays and so forth is a major public health concern. Legionella grows preferentially in well oxygenated conditions at the air- water interface. Silver-impregnated porous clay balls 20 introduced into the air-conditioning system would be in a highly oxygenated aqueous environment, so should have a greatly-enhanced disinfectant effect. They would also target this effect on precisely the areas where Legionella is most likely to grow.

It is therefore believed that the silver-impregnated clay balls 20 would be an effective * * * SI I S S disinfecting medium for air conditioning systems, even without the beneficial effect of a current being passed through the silver and adjacent water as in the systems of Figures 1 to 4. :5..:. *5*S * I *.S. S... * . I... * S.. * . I I. *

Claims

CLAIMS.

1. An apparatus for eliminating or inhibiting the growth of microorganisms within a body of water contained in reservoir means, comprising first electrode means comprising silver and a second electrode means, each mounted in contact with the body of water.

2. An apparatus as claimed in claim 1, further comprising a source of electrical power adapted to be connected across said first and second electrode means. : . :* * S *SSSSS

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3. An apparatus as claimed in claim 2, wherein said first electrode means comprise ** S...

silver wire wound around and spaced from the second electrode means. S... * S S... * S..

4. An apparatus as claimed in claim 3, wherein the second electrode means comprises a: body of copper or a material containing copper.

5. An apparatus as claimed in any one of the preceding claims, wherein the first electrode means comprises a first copper electrode body adjacent the silver electrode body, and the second electrode means comprises a second copper electrode body

6. An apparatus as claimed in any one of the preceding claims, further comprising means to introduce an oxygen containing gas into the body of water.

7. An apparatus as claimed in any one of the preceding claims, wherein the first and second electrode means mountable to the reservoir means remotely from the first to extend through or adjacent said water surface.

8. An apparatus for eliminating or inhibiting the growth of microorganisms within a body of water contained in reservoir means, comprising an apertured body containing metallic silver.

9. An apparatus as claimed in claim 8, wherein the body is a woven mesh. : ..* I.....

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10. An apparatus as claimed in claim 8, wherein the body comprises clay and silver wire:*..:. *5S* * * ****

so heat treated as to render it permeable to gas. S... * S *... * S..

11. An apparatus as claimed in any one of claims 8 to 10, further comprising means.. : adapted to deliver air or other oxygen containing gas to a submerged portion of the' silver containing body.

12. A reservoir means, as herein defined, provided with apparatus as claimed in any one of the preceding claims, for eliminating or inhibiting the growth of micro-organisms in water held within the reservoir means.

13. A method for eliminating or inhibiting the growth of micro-organisms in a body of water, comprising the steps of providing first electrode means comprising a silver electrode body and second electrode means connected to the first by means to conduct electricity, and disposing each electrode means to extend through or adjacent a surface thereof.

14. A method as claimed in claim 13, further comprising the step of oxygenating the water in contact with the electrode means. * . * * ** * S

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