Technical Field f The present invention relates to the purification I of contaminated water, and in particular an improved method 5 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

10 removal) of water borne chemical species has been the 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 a suspension of powdered catalytic material contained in a

15 closed system through which the contaminated water 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

20 which may be sunlight or an artificial source of ultraviolet light. Disclosure of the Invention

We have found that the destruction and removal of chemical species contaminants in water can be improved

25 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

30 purifying water to destroy and remove chemical species, wherein the water is passed down an inclined surface formed by a metallic catalyst, whilst being exposed to ultraviolet light.

The invention also envisages an apparatus for

35 purifying water to destroy and remove chemical species, said apparatus comprising means to provide an inclined surface of metallic catalyst, and a source of ultraviolet

light.

Brief Description of the Drawings

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

Referring to the drawings, the apparatus, 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. 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 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 the flow of water down the trough which assists the photocatalytic oxidation of the chemical species in the 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 system as many times as are necessary to achieve the desired result.

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.

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.