AU709825B2 - Water Purification - Google Patents

Description

2 WATER PURIFICATION TECHNICAL FIELD The present invention relates to the purification of contaminated water, and in particular an improved method and apparatus for photocatalytic oxidation of water borne chemical species, for example, microtoxins, phenolic compounds, and pesticide and insecticide compounds.

BACKGROUND ART Photocatalytic oxidation (destruction and removal) of water borne chemical species has been the 15 subject of considerable research in recent years, and has involved oxidisation of a wide range of water borne chemical species where catalytic surfaces, represented by g**i a suspension of powdered catalytic material contained in a closed system through which the contaminated water 20 circulates, is exposed to a photoactivating light source, or alternatively a stationery catalytic surface is provided over which the contaminated water passes whilst "being exposed to a source of photoactivating ultraviolet light which may be sunlight or an artificial source of 25 ultraviolet light. Closed systems have a disadvantage in that there can be limited oxidation and they have limited pollutant stripping capabilities. This is because any air in the closed system will soon become saturated with pollutants. Thus, in a poorly aerated system such as an enclosed system, there is a reduced capability of stripping certain organic pollutants from the water (i.e.

a reduced capability of causing dissolved organic species to come out of the water).

DISCLOSURE OF THE INVENTION SWe have found that the destruction and removal of H:\MCooper\Keep\Speci\27797.95-markup.doc 13/07/99 -3 chemical species contaminants in water can be improved markedly if a stationary catalytic surface formed by a metallic catalyst, and inclined at an angle down which the contaminated water flows, is exposed to sunlight or artificially generated ultraviolet light.

The invention therefore envisages a method of purifying water to destroy and remove chemical species contaminants in water, wherein the water is passed down an inclined surface formed by a metallic catalyst whilst being exposed to ultraviolet light, said inclined surface also being such as to provide turbulence in the water, and said inclined surface not being enclosed.

The invention also envisages an apparatus for purifying water for destroying and removing chemical 15 species contaminants in water, said apparatus comprising means to provide an inclined surface of metallic catalyst, and exposed to a source of ultraviolet light, said inclined surface also being such as to provide turbulence in the water, and said inclined surface not being 20 enclosed.

BRIEF DESCRIPTION OF THE DRAWINGS o One preferred embodiment of the invention will now be described with reference to the accompanying drawings, in which: Figure 1 is a schematic plan view of the apparatus of the preferred embodiment and to carry out the method of the preferred embodiment; Figure 2 is a schematic side elevational view of the apparatus of Figure 1; and Figure 3 is an enlarged view of the catalytic surface of the embodiment of Figures 1 and 2.

BEST MODE FOR CARRYING OUT THE INVENTION SReferring to the drawings, the apparatus, H:\MCooper\Keep\Speci\27797.95-markup.doc 13/07/99 4 generally indicated as 10, comprises an inclined trough 11 which contains an undulating member 12 providing a series of transverse ridges, and consisting of an outer layer 13 of a metallic catalyst supported as a thin film on a backing 14 of glass fibre matting or glass fibre weave, or any other material which provides a suitable backing. As can be seen from Figures 1 and 2 the undulating member 12 is not enclosed. The trough 11 terminates at its lower end above an open topped tank 15 into which water gravitating down the trough on the metallic catalyst surface is delivered. Water in the tank 15 is drawn through a transfer pipe 16 by a pump 17 which pumps the water up through a supply pipe 18, containing a flow control valve 19, to a header manifold 20 from which the 15 water flows to the top of the trough 11 and down the -trough to the tank 15. The ridges provided by the undulating member 12 assisting generating turbulence in :o the flow of water down the trough which assists the photocatalytic oxidation of the chemical species in the 20 contaminated water, whilst if a single pass down the trough is not sufficient to destroy and remove the chemical species, the water can be circulated around the o system as many times as are necessary to achieve the desired result.

It will be understood that the turbulence in the water will break the surface of the water causing the water to be aerated, thus allowing the water to be oxygenated provided the water is exposed to sufficient air. This ensures that air surrounding does not become saturated with pollutants.

In this preferred embodiment of the invention a lamp 21 providing a source of ultraviolet light is positioned above and parallel to the trough, and extends along substantially the full length of the trough.

Alternatively, or in addition, sunlight may be used to provide a natural source of ultraviolet light when water purification during daylight hours is acceptable.

H.\MCooper\Keep\Speci\27797.95-markup.doc 13/07/99 In the preferred embodiment a metallic catalyst of titanium dioxide antaese has been found to be an effective metallic catalyst, although other metallic catalysts may be effective to the same or lesser extent.

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Claims (10)

1. A method of purifying water to destroy and remove chemical species contaminants in water, wherein the water is passed down an inclined surface formed by a metallic catalyst whilst being exposed to ultraviolet light, said inclined surface also being such as to provide turbulence in the water, and said inclined surface not being enclosed.

2. A method as claimed in Claim 1, wherein the water is pumped from a tank at the bottom of the inclined surface to the top of the inclined surface, and gravitates down the surface to the tank.

3. A method as claimed in Claim 1 or 2, wherein the source of ultraviolet light is an artificial source, or the sun, or both. 20

4. A method as claimed in any one of the preceding claims, wherein the flow of water to the top of the inclined surface is regulated.

An apparatus for purifying water for destroying and removing chemical species contaminants in water, said :'"apparatus comprising means to provide an inclined surface of metallic catalyst, and exposed to a source of ultraviolet light, said inclined surface also being such as to provide turbulence in the water, and said inclined surface not being enclosed.

6. An apparatus as claimed in Claim 5, further including a tank positioned at the bottom of said inclined surface, and a pump to pump water from said tank to the top of said surface.

7. An apparatus as claimed in Claim 5 or 6, wherein H:\MCooper\Keep\Speci\27797.95-narkup.doc 13/07/99 7 the source of ultraviolet light is an artificial source, or the sun, or both.

8. An apparatus as claimed in any one of Claims 5 to 7, wherein the means to provide said surface is a backing member to which a layer of metallic catalyst is applied, and said backing member with the metallic catalyst applied thereto is positioned within a trough.

9. An apparatus as claimed in any one of Claims 5 to 8, wherein the means to provide said surface is undulated along its length to provide a series of transverse ridges.

10. An apparatus as claimed in any one of Claims 5 to 15 9, wherein means are provided to regulate the flow of 0* water to the top of said surface. V Dated this 13th day of July 1999 RONALD WILLIAM ARTHUR AND 20 BRACE HARVEY BOYDEN By their Patent Attorneys GRIFFITH HACK Fellows Institute of Patent and Trade Mark Attorneys of Australia S H:\MCooper\Keep\Speci\27797 .95-markup.doc 13/07/99