METHOD AND APPARATUS FOR EFFECTING A CHEMICAL REACTION

Related Application

This application claims priority from Australian Provisional Patent Application No. 2006904284, filed 4 August 2006, the content of which is herein incorporated by reference.

Field of the Invention

The present invention relates to a method and apparatus for effecting a chemical reaction. More specifically, it relates to means for the treatment of secondary effluent or contaminated water bearing an organic load.

The invention has been developed primarily as a means of remediating wastewater containing a load of small organic molecules such as the carcinogen 1,4- dioxane and/or the endocrine-disruptive N-nitrosodimethylamine (NDMA), and/or non- aesthetic compounds such as those emitting undesirable odour and/or colour, and/or pathogens/organisms such as bacteria, viruses and protozoa. Although the present invention will be described herein with reference to such applications, it will be appreciated that the invention is not limited to this particular field of use.

Background of the Invention

Any discussion of the prior art throughout the specification should in no way be considered as an admission that such prior art is widely known or forms part of common general knowledge in the field.

In recent years, the treatment and remediation of secondary effluent for the purposes of re-use has become increasingly important. Factors such as generally increasing population pressures, urbanisation, global warming with the attendant changes in weather patterns, and the continuing industrial pollution of natural sources of fresh water serve to place often severe limitations on the per capita availability of fresh drinking water. Accordingly, liquid-based effluent is becoming increasingly treated and re-used to both potable and non-potable standards.

The past 2-3 decades has seen a significant number of changes in how such secondary effluent is treated. Specifically, new filter and membrane technologies have supplemented and even replaced more traditional effluent treatments. In addition, new disinfection technologies have also evolved and been applied to supplement the

improved membrane technologies.

The present state of the art in the treatment of secondary effluent to potable and non-potable standards typically includes a first-pass microfiltration or ultrafiltration process, thereby to remove physical or granular contaminants such as dirt. Such processes generally go some way toward the removal of certain pathogens from the effluent.

The first-pass microfiltration or ultrafiltration process is typically followed by a Reverse Osmosis (RO) membrane treatment that was once widely thought to remove dissolved organic and inorganic molecules. Relatively recently, however, it has been shown that low concentrations of certain small organic molecules such as 1,4-dioxane and NDMA have the ability to pass through an RO treatment process or even form as by-products (e.g. trihalomethanes) from chemical disinfection treatments. Such molecules pose a significant health risk in that they are known carcinogens and endocrine-disrupting compounds, respectively. Finally, a disinfection step or advanced treatment step may be present so as to remove any residual pathogens. Such a step typically utilises chlorine, ozone or UV light as the disinfectant.

As related above, in photogenerated catalysis the photocatalytic activity (PCA) depends upon the ability of the catalyst to create electron hole pairs, which generate free radicals able to undergo secondary reactions. The resulting free radicals are very efficient oxidisers of organic matter. The photocatalytic activity of UV light in TiO ₂ and indeed other photocatalytic materials such as ZnO, CdS and WO ₃ has been studied extensively because of its potential use in sterilisation, sanitation, and remediation applications. TiO ₂ , when irradiated by UV ₅ reacts with water and oxygen to form reactive species such as hydroxyl and superoxide free radical molecules. The photocatalytic activity of TiO ₂ results in thin coatings of the material exhibiting self-cleansing and disinfecting properties under exposure to UV radiation.

TiO ₂ is desirous as an agent in the remediation of contaminated water due to several factors, including, but not limited to: the process occurring under ambient conditions; TiO ₂ not being consumed or degraded; the oxidation of organic molecule contaminants to water and CO ₂ can be effected to completion; the photocatalyst is inexpensive and has a high turnover; TiO ₂ can be supported or immobilised on suitable reactor substrates; and the process offers great potential as an industrial technology to

detoxify contaminated waters.

In order to remove organic contaminants, some treatment plants have installed UV-peroxide or UV-ozone AOP treatment facilities. In such facilities, peroxide is typically injected into the treated effluent stemming from the initial RO procedure, and this mix is then passed through a high flux of UV light. Appreciably, such facilities suffer from significant problems, primarily associated with cost and chemical exposure. Where a raw secondary effluent contains no organic load, the UV light required to disinfect such a stream is typically 40 mJ/cm ² /s or higher. Where such effluent does contain an organic load, peroxide is required to be added, and the peroxidised effluent is then passed through UV light with a flux of typically 150-500 mJ/cm ² /s. To achieve such UV intensity, a typical 100 ML/day treatment plant may require 200-250 UV lamps, each costing around US$2,000, and each needing to be replaced annually. In addition, the cost of electricity need to run such a UV source is relatively vast.

A photocatalyst being irradiated by light rays of short wavelength displays a high propensity to decompose water to activated oxygen (O) and hydrogen gas (H ₂ ). Moreover, a photocatalyst, as means of eliminating or decreasing environmental pollution, contributes to the decomposition of pollutants such as those described above.

A summary of the available literature representing the state of the art may include an article by A. Danion, et al. in Applied Catalysis B: Environmental 52 (2004) 213-223, entitled "Characterisation and study of a single TiO ₂ coated optical fiber reactor". In this study, a TiO ₂ coated optical fiber photoreactor was built in order to optimise different parameters before the development of a multi-optical fiber reactor. The physicochemical properties of the TiO ₂ film prepared by a sol-gel method on an optical fiber were determined. A thickness of about 30 nm per layer and a roughness of 2 nm were estimated by ESEM and AFM, respectively. The refractive index of the TiO ₂ coating was determined by a simulation method. Then, the influences of the film thickness, coating length and coating volume on the light transmission within the fiber were investigated.

The intensity of transmitted light was found to decrease exponentially as the volume of TiO ₂ increased. Afterward, the dependence of the photocatalytic degradation of hydroxy butanedioic acid on the incident light intensity, the TiO ₂ coating thickness and the coating volume were studied and modelled. The photocatalytic degradation was stabilised above a TiO ₂ volume of 200 μm ³ for a fiber of 1 mm and 100 μm ³ for a fiber of 0.6 mm. Finally, a multi-fiber reactor was built and its degradation rate of

hydroxybutanedioic acid was compared to that obtained in a single-optical-fiber reactor. An article by W. Choi, et ah, in Applied Catalysis B: Environmental 31 (2001) 209-220, entitled "Investigation on TiO ₂ coated optical fibers for gas-phase photocatalytic oxidation of acetone" concerns a preliminary optical fiber reactor that employs bare quartz fibers as a light-transmitting support of TiO ₂ . This was tested for gas treatment by investigating photocatalytic oxidation of acetone in air (50-750 ppmv). Using one or four TiO ₂ coated fibers in a continuous flow photoreactor, a steady-state conversion up to 80% was achieved at ambient temperature and pressure.

The characteristics of coated-optical fibers were quantitatively analysed and their use in photocatalytic gas treatment was discussed in detail. The acetone molecules degraded were quantitatively converted to CO ₂ with no intermediates detected. No noticeable deactivation was observed within a few hours of operation under the experimental conditions. The conversion of acetone linearly increased with the incident light intensity without showing any sign of saturation. The transmitted light intensity through a TiO ₂ coated optical fiber exponentially decreased along the fiber, showing 90% extinction within 30 cm.

The photocatalytic conversion measured as a function of the coated-fiber length showed a similar trend. An optimal coating thickness was found at around 1.5 μm, above which the photocatalytic efficiency was reduced. The presence of water vapor reduced the reactivity due to the competitive adsorption on active surface site with acetone. While a measurable conversion of acetone was observed in the absence of O ₂ , increasing O ₂ concentration up to 15% effectively enhanced the conversion.

United States Patent No. 6,108,476, to Iimura, relates to a photocatalyst optical fiber and a method for activating the photocatalyst optical fiber. The photocatalyst optical fiber comprises at least an optical fiber having a core and a light input end, a photocatalyst layer including photocatalyst disposed partially or entirely on the core, wherein light is introduced from the light input end into the core and the light reflects repeatedly inside of the core, wherein said light leaks gradually from the core to the photocatalyst layer, and wherein the photocatalyst layer is activated by irradiation of the light.

The method for activating the photocatalyst optical fiber comprises: (a) providing at least an optical fiber, each having a photocatalyst layer, i.e. photocatalyst film including photocatalyst, in which the photocatalyst layer is partially or entirely disposed on the optical fiber; (b) introducing light into the optical fiber; (c) letting the

light to reflect repeatedly inside of the optical fiber; and (d) letting the light to leak gradually from the optical fiber to the photocatalyst layer, whereby the photocatalyst layer is activated by irradiation of the light. Therefore, US 6,108,476 can efficiently activate the photocatalyst on the optical fiber by irradiating directly light leaked from the optical fiber. Unfortunately, the invention described in US 6,108,476 is unsuitable for application in scale-up flow-through industrial processes for the remediation of wastewater to potable or non-potable standards.

United States Patent No. 6,238,630, also to Iimura, relates to a photocatalyst device including a light guide member composed of a substantially transparent member having a first surface and/or a second surface, a plurality of diffusing areas and a plurality of non-diffusing areas disposed alternately on the first surface and/or the second surface, and photocatalyst member including photocatalyst material, being disposed adjacent to the transparent member, or being disposed on the transparent member. Further, a photocatalyst reactor includes the photocatalyst device as described above and one or more light sources generating light directed toward the transparent member. The transparent member may be composed of a transparent panel having a substantially uniform thickness or a substantially variable thickness. A density of the diffusing areas and/or the non-diffusing areas may be variably distributed on the first surface and/or the second surface. The diffusing areas may be rough surface areas and/or the non-diffusing areas may be smooth surface areas. The invention described in US 6,238,630 is again unsuitable for efficient application in scale-up flow-through industrial processes.

United States Patent No. 6,258,736, to Massholder, discloses a device with at least one surface layer made from a semiconductor material having an inner side, which rests on a support, and a disinfectable and/or oxidising outer side, and with a UV radiation source, in which device the support conducts light, UV radiation from the UV radiation source is input directly on to the inner side of the semiconductor material via the light-conducting support. The light-conducting support and the surface layer of the semiconductor material lying thereon can be applied to the surface of a piece of equipment which is to be disinfected or may even form this piece of equipment. Although one may envisage such a device being amenable to a scale-up flow-through water treatment facility, the use of semiconductors render it undesirably complex and therefore, relatively expensive and undesirable.

United States Patent No. 6,764,655, to Nishii, relates to a light-leakage type photocatalyst in which fibers are bundled together to form a filter assembly having an enormous number of minute gaps which provide fluid communication paths in a longitudinal direction of the photocatalyst fibers. Light is incident to each of the photocatalyst fibers constituting the filter assembly while an object fluid to be processed is introduced through an end face of the filter assembly to pass through the gaps among the photocatalyst fibers in the longitudinal direction. However, the invention disclosed in US 6,764,655 is adapted for a single-pass flow through, which requires either a larger cell size, or successive cells arranged in series, in order to provide the sought UV exposure to the incident wastewater.

United States Patent Nos. 5,875,384 and 6,051,194, both to Peill, et al, each relate to a photochemical reactor system employing optical fibers in the form of a cable to transmit light to solid-supported TiO ₂ containing photocatalyst. Light energy is transmitted to TiO ₂ containing particles, chemically anchored onto one or more quartz fiber cores, via radial refraction of light out of each fiber. TiO ₂ containing coating layer minimises the interfacial surface area of the quartz core and TiO ₂ containing particles and operation with incident irradiation angles near 90 degrees enhance light propagation along the fibers. A maximum quantum efficiency of φ =1.1% for the oxidation of 4- chlorophenol was achieved. Fiber efficiency permits the light source to be separated from the photocatalyst. Neither system is suitable for a scale-up flow-through industrial process aimed at treating organics-bearing secondary effluent.

United States Patent No. 6,555,011, to Tribelski, et al., relates to a method for disinfecting and purifying liquids and gasses comprising: a) passing said liquids or gasses through a reactor or a combination of reactors, having a truncated compounded concentrator geometry; and b) simultaneously delivering and concentrating diversified electromagnetic and acoustic energies into a specific predetermined inner space of said compounded concentrator reactor, forming a high energy density zone in said reactor or reactors over a predetermined period of time. The reactor is preferably a compounded parabolic concentrator or a compounded ellipsoidal concentrator. The electromagnetic energy delivered and concentrated into and inside the reactor can be of any range of the electromagnetic spectrum, such as ultra-violet, visible, infra-red, microwave, etc., or combination thereof. The acoustic energy is of any suitable frequency. The radiation source delivering the electromagnetic radiation can be enclosed within the reactor or can

be external to the reactor. The invention disclosed by US 6,555,011 is relatively complex, and thereby relatively expensive to build, operate and maintain.

United States Patent No. 6,773,609, to Hashizume, discloses a method for water treatment which comprises subjecting water containing a hazardous material such as a dioxin or polychlorinated biphenyls (PCBs) to an ozone treatment, contacting the water with fine bubbles of ozone having an average diameter of 0.5 to 3 microns, a combination of the ozone treatment with one or more of a hydrogen peroxide treatment, a UV radiation treatment, an electrolysis treatment and a treatment with a carbonaceous filter material. The above ozone treatment or combination of treatments can be used for surer realisation on of an intended effect of a water treatment, which is difficult to achieve by the use of a conventional method wherein ozone or hydrogen peroxide is simply mixed with a water to be treated. Electrolysis and ozonation techniques are relatively expensive, and the inventive method defined in Hashizume is therefore undesirable. United States Patent No. 6,409,928, to Gonzalez, et ah, discloses a method and apparatus for mineralising organic contaminants in water or air. The invention provides photochemical oxidation in a two-phase or three-phase boundary system formed in the pores of a TiO ₂ membrane in a photocatalytic reactor, hi the three-phase system, gaseous (liquid) oxidant, liquid (gaseous) contaminant, and solid semiconductor photocatalyst meet and engage in an efficient oxidation reaction.

The porous membrane has pores that have a region wherein the meniscus of the liquid varies from the molecular diameter of water to that of a capillary tube resulting in a diffusion layer that is several orders of magnitude smaller than the closest known reactors. The photocatalytic reactor operates effectively at ambient temperature and low pressures. A packed-bed photoreactor using photocatalyst-coated particles is also provided. The process defined in Gonzalez would be relatively expensive to operate, and labour-intensive to maintain.

United States Patent No. 6,932,947, to Leung, et ah, discloses a fluid purification and disinfection system, which includes a housing, an ultraviolet lamp and a photocatalytic oxidation device. The housing is an enclosed case that is fitted with an inlet and an outlet; the ultraviolet lamp is mounted inside the housing; the photocatalytic oxidation device is a disinfection core coated with photocatalyst; the disinfection core is installed around the ultraviolet lamp, and is fixed onto said housing; the photocatalyst therein is titanium dioxide.

The working principle of the invention is to utilise ultraviolet light to irradiate the titanium dioxide-coated surface of the photocatalytic oxidation device to generate the photocatalytic oxidation process. As a result, Escherichia coli, Vibriocholerae and pathogenic organisms that contact the surface of photocatalytic oxidation device can be relatively quickly killed, and contaminants in the fluid can be eliminated. By such means, water or fluid that flows through said disinfection device is disinfected and purified.

United States Patent No. US 6,285,816, to Anderson, et al., relates to a waveguide comprising a transparent substrate and a metal oxide coating. The substrate can propagate light in an attenuated total reflection mode. The claims define a waveguide for propagating light of a selected wavelength in an attenuated total reflection mode, the waveguide comprising: a transparent internal reflection element (IRE); and a particulate transition metal oxide coating on one or more surfaces of the internal reflection element, the coating having a boundary parallel to the at least one IRE surface, wherein the coating does not scatter light of the selected wavelength and has a refractive index greater than that of the internal reflection element.

Japanese Patent No. 10-337579, to Kubota Corporation, relates to a process to remove by degradation trace poisonous materials such as polychlorinated dibenzodioxins (PCDDs), wherein water is passed through an ultraviolet ray reaction tower holding a photocatalyst which accelerates an oxidation reaction of the wastewater. The trace poisonous elements in the wastewater are removed by degradation with the photocatalyst and ultraviolet rays. In an ultraviolet and ozone reactor, wastewater containing poisonous materials flows into a reaction tower and flows upward together with a photocatalyst. An ultraviolet ray is radiated from an ultraviolet lamp, and ozone is supplied from an ozone generator. The treated water near an outlet permeates a net, is conducted as ultraviolet and ozone treated water out to a pH-adjusting tank.

The photocatalyst remaining with the net is circulated together with the surrounding treated water near to a flow inlet. During this time, it comes in contact with a powder photocatalyst in the reaction tower. Accordingly, the trace poisonous substances such are efficiently removed by degradation with synergism of the ultraviolet ray and the photocatalyst.

Japanese Patent No. 2003-144939, to Titanium Kogyo KK, relates to a substrate body for a photocatalyst having high photocatalytic activity and excellent fixing property to the substrate, and capable of being applied to both of gas and an aqueous

solution. The substrate has effective separation/workability with a liquid to be treated such as contaminated water and capable of being borne for a practical use. The photocatalyst particle is fixed onto a surface of a granulation type artificial light weighted aggregate covered with a glass-based shell making an inorganic substance as a binder.

Japanese Patent No. 2003-190908, to Mitsubishi Jukogyo KK, relates to a treatment method and an apparatus capable of oxidising and decomposing sparingly decomposable substances existing in fly ashes. The treatment apparatus is intended for oxidising and decomposing sparingly decomposable substances contained in solid matter such as fly ashes discharged out of an incinerator. The apparatus comprises a mixing tank for mixing the solid matter with water and producing a slurry; and a decomposition tank where the sparingly decomposable substances contained in the slurry are oxidised and decomposed in the presence of hydroxy radicals by intensely stiπing the slurry. The decomposition tank is provided with pulverisation means for pulverising the solid matter, a plurality of catalyst-bearing beads that carry a photocatalyst or have photocatalytic function by themselves and are fluidised by contact with the slurry, and a UV lamp disposed in a position where UV rays are radiated to the catalyst-bearing beads. The hydroxy radical is generated by the catalyst-bearing beads in combination with the UV lamp.

Japanese Patent No. 2001-327961, to Fujishima, relates to a water treating device capable of effectively treating dioxins in water and water to be treated containing organic substances such as endocrine disrupting chemical materials, agricultural chemicals and organic colouring materials; the device uses an optical catalyst. A basket frame in which optical catalyst carrying reticulated sheets are horizontally placed is installed in a water tank into which the water to be treated flows. The whole of the basket frame is connected to the disk of a motor with a disk by a central shaft to be reciprocated vertically. Black light which is inserted into a glass tube is lit to make the optical catalyst generate hydroxy radicals, and the amount of water coming into contact with the optical catalyst per unit time is relatively increased, thereby effectively decomposing the organic substances in the water to be treated at relatively high speed.

Japanese Patent No. 2002-018429, to Okada, relates to a water purifier in which dioxins, a chlorine compound, a nitric compound, a nitrogen oxide and an organic compound contained in drinking water such as tap water are subjected to oxidative

decomposition treatment by a photocatalyst. Bacteria contained in drinking water are sterilised and more purified drinking water can be obtained.

In a water purifier equipped with a cartridge removing dirt and chlorine contained in drinking water and an electrolytic water producer for changing drinking water into alkali ion water, a photocatalyst device for causing a catalytic action by irradiating ultraviolet rays on titanium dioxide is provided between the cartridge and the electrolytic water producer. Drinking water is passed through the photocatalyst device and bacteria contained in drinking water are sterilised by generated ozone. The ozone is then decomposed by the electrolytic water producer. It is an object of the present invention to overcome or ameliorate at least one of the disadvantages of the prior art, or to provide a useful alternative.

It is an object of the present invention in a particularly preferred form to provide a means of effecting a chemical transformation in a modular apparatus, that is relatively cheap to construct, maintain and operate. It is an object of a particularly preferred form of the present invention to provide means for remediating secondary effluent initially containing an organic load such as 1,4-dioxane and/or JV-nitrosodimethylamine (NDMA), preferably to a potable standard. It is a further object of the present invention, in a further preferred form, to provide a relatively cost effective means of achieving same. Although preferred embodiments of the present invention will been described with reference to specific examples and/or aspects of the invention, it will be appreciated by those skilled in the art that the invention may be embodied in many other forms. In particular, features of any one of the various described examples may be provided in any combination in any of the other described examples.

Summary of the Invention

According to a first aspect of the present invention there is provided a method for effecting a chemical transformation, said method comprising the steps of: providing a catalytic substrate; providing a feed comprising one or more reactants; providing an energy source wherein energy derived therefrom is contactable via a transport medium with said catalytic substrate, thereby to provide a species active against said one or more reactants; and contacting said active species with said feed, thereby to actively

effect said chemical transformation.

Preferably, said chemical transformation takes place within a modular apparatus. Preferably, said energy source is spaced from or proximal with said catalytic substrate. Alternatively, said energy source is directly coupled with said catalytic substrate. Preferably, said transport medium is a waveguide. More preferably, said waveguide is a planar optical waveguide.

Preferably, said waveguide acts both as said transport medium and as a substrate for catalytic material applied to the surface thereof. Preferably, said waveguide comprises a single material. Alternatively, said waveguide comprises a plurality of materials. Preferably, said plurality of materials are of differing refractive indices, thereby to relatively enhance the waveguiding efficiency of said waveguide.

Preferably, said waveguide may comprise scattering centres, reflective elements, diffractive elements, or a combination thereof, thereby to facilitate incident light being shifted out of the plane of said waveguide and contacting with said catalyst.

Preferably, said catalytic material is applied to one or more surfaces of said catalytic substrate. Preferably, said catalytic material is illuminated substantially perpendicular to the axis thereof. Alternatively, said catalytic material is illuminated substantially parallel to the axis thereof. The inventive method preferably further includes provision of an outlet port remote from an inlet port, thereby to facilitate flow of said feed therebetween. Alternatively, the inventive method includes provision of an outlet port integral with an inlet port, thereby to facilitate said method to operate on a batch basis.

Preferably, said feed is a fluid. Preferably, said fluid is a liquid, gas, or a combination thereof. More preferably, said fluid is a fluid effluent, said method thereby operative to remediate at least a portion of said fluid effluent. Preferably, said fluid effluent is a contaminated or polluted liquid, gas and/or steam.

Preferably, said liquid, gas and/or steam comprises said one or more reactants in solution and/or undissolved state. More preferably, said liquid is water. Preferably, said solution comprises said one or more reactants in aqueous phase.

Preferably, said contaminated or polluted liquid comprises one or more organic contaminants. More preferably, said one or more organic contaminants comprise organic molecules and organisms. More preferably still, said organic molecules comprise 1,4-dioxane and/or N-nitrosodimethylamine (NDMA). Alternatively, said one

or more organisms comprise bacteria, protozoa and/or viruses.

Preferably, said catalytic substrate is a photocatalytic substrate. More preferably, said photocatalytic substrate is TiO ₂ .

Preferably, said energy is light. More preferably, said light comprises one or more wavelengths within the range of approximately 200-400 nm.

Preferably, said active species is an excited species. More preferably, said excited species are free radicals.

Preferably, said catalytic material is provided as a coating over one or more surfaces of said waveguide. More preferably, said coating is adhered to said waveguide via solid phase, gas phase and/or liquid phase deposition techniques.

Preferably, said deposition techniques comprise annealing, adhesive, etching, extrusion, moulding, dip coating, sputter coating, slot coating, lamination, or a combination thereof .

Preferably, said coating may be on a substantially smooth or complex surface. Preferably, said waveguide has a complex surface. More preferably, said complex surface is applied upon said waveguide by etching, extrusion moulding, stamping, or a combination thereof.

In an embodiment, said waveguide has a complex surface, said coating applied thereupon by etching, extrusion moulding, stamping, or a combination thereof. Preferably, said complex surface is formed in the same material and is integral with said waveguide. Alternatively, said complex surface is formed separately from said waveguide. Preferably, said complex surface is formed in a different material to said waveguide.

Preferably, said complex surface facilitates enhanced fluid dynamics. Preferably, said enhanced fluid dynamics are relatively enhanced flow rate and/or relatively enhanced mixing. More preferably, said complex surface increases the effective surface area of said catalytic substrate.

Preferably, said waveguide comprises one or more stacked sheets. More preferably, said one or more stacked sheets are spaced by one or more discrete spacer units and/or said complex surface.

Preferably, said one or more stacked sheets are arranged to provide optimal contact time of said feed with said active species. Preferably, said one or more stacked sheets are arranged to provide a relatively increased surface area per unit volume.

Preferably, said one or more stacked sheets are arranged to provide a serpentine

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flow of said feed between said sheets.

In a preferred embodiment, said relatively increased surface area is enabled by way of a plate-and-frame type configuration. Preferably, said plate-and-frame type configuration comprises a plurality of said sheets stacked substantially horizontally. In another preferred embodiment, said relatively increased surface area is enabled by way of a Swiss-roll type arrangement.

In another preferred embodiment, said relatively increased surface area is enabled by way of a vane type arrangement.

According to a second aspect of the present invention there is provided an apparatus for effecting a chemical transformation, said apparatus comprising: a catalytic substrate; means for providing a feed comprising one or more reactants; an energy source; a transport medium through which energy derived from said energy source is contactable with said catalytic substrate, thereby to provide a species active against said one or more reactants; and means for contacting said active species with said feed, thereby to actively effect said chemical transformation.

Preferably, said chemical transformation takes place within a modular apparatus. Preferably, said energy source is spaced from or proximal with said catalytic substrate. Alternatively, said energy source is directly coupled with said catalytic substrate.

Preferably, said transport medium is a waveguide. More preferably, said waveguide is a planar optical waveguide.

Preferably, said waveguide acts both as said transport medium and as a substrate for catalytic material applied to the surface thereof. Preferably, said waveguide comprises a single material.

Alternatively, said waveguide comprises a plurality of materials. Preferably, said plurality of materials are of differing refractive indices, thereby to relatively enhance the waveguiding efficiency of said waveguide. Preferably, said waveguide may comprise scattering centres, reflective elements, diffractive elements, or a combination thereof, thereby to facilitate incident light being shifted out of the plane of said waveguide and contacting with said catalyst.

Preferably, said catalytic material is applied to one or more surfaces of said catalytic substrate. Preferably, said catalytic material is illuminated substantially

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perpendicular to the axis thereof. Alternatively, said catalytic material is illuminated substantially parallel to the axis thereof.

The inventive apparatus preferably further includes provision of an outlet port remote from an inlet port, thereby to facilitate flow of said feed therebetween. Alternatively, the inventive apparatus includes provision of an outlet port integral with an inlet port, thereby to facilitate said method to operate on a batch basis.

Preferably, said feed is a fluid. Preferably, said fluid is a liquid, gas, or a combination thereof. More preferably, said fluid is a fluid effluent, said method thereby operative to remediate at least a portion of said fluid effluent. Preferably, said fluid effluent is a contaminated or polluted liquid, gas and/or steam.

Preferably, said liquid, gas and/or steam comprises said one or more reactants in solution and/or undissolved state. More preferably, said liquid is water.

Preferably, said solution comprises said one or more reactants in aqueous phase. Preferably, said contaminated or polluted liquid comprises one or more organic contaminants. More preferably, said one or more organic contaminants comprise organic molecules and organisms. More preferably still, said organic molecules comprise 1,4-dioxane and/or iV-nitrosodimethylamine (NDMA). Alternatively, said one or more organisms comprise bacteria, protozoa and/or viruses.

Preferably, said catalytic substrate is a photocatalytic substrate. More preferably, said photocatalytic substrate is TiO ₂ .

Preferably, said energy is light. More preferably, said light comprises one or more wavelengths within the range of approximately 200-400 ran.

Preferably, said active species is an excited species. More preferably, said excited species are free radicals. Preferably, said catalytic material is provided as a coating over one or more surfaces of said waveguide. More preferably, said coating is adhered to said waveguide via solid phase, gas phase and/or liquid phase deposition techniques.

Preferably, said deposition techniques comprise annealing, adhesive, etching, extrusion, moulding, dip coating, sputter coating, slot coating, lamination, or a combination thereof .

Preferably, said coating may be on a substantially smooth or complex surface. Preferably, said waveguide has a complex surface. More preferably, said complex surface is applied upon said waveguide by etching, extrusion moulding, stamping, or a combination thereof.

Preferably, said complex surface is formed in the same material and is integral with said waveguide. Alternatively, said complex surface is formed separately from said waveguide. Preferably, said complex surface is formed in a different material to said waveguide. Preferably, said complex surface facilitates enhanced fluid dynamics.

Preferably, said enhanced fluid dynamics are relatively enhanced flow rate and/or relatively enhanced mixing. More preferably, said complex surface increases the effective surface area of said catalytic substrate.

Preferably, said waveguide comprises one or more stacked sheets. More preferably, said one or more stacked sheets are spaced by one or more discrete spacer units and/or said complex surface.

Preferably, said one or more stacked sheets are arranged to provide optimal contact time of said feed with said active species. Preferably, said one or more stacked sheets are arranged to provide a relatively increased surface area per unit volume. Preferably, said one or more stacked sheets are arranged to provide a serpentine flow of said feed between said sheets.

In a preferred embodiment, said relatively increased surface area is enabled by way of a plate-and-frame type configuration. Preferably, said plate-and-frame type configuration comprises a plurality of said sheets stacked substantially horizontally. hi another preferred embodiment, said relatively increased surface area is enabled by way of a Swiss-roll type arrangement.

In another preferred embodiment, said relatively increased surface area is enabled by way of a vane type arrangement.

According to a third aspect of the present invention there is provided the product of a chemical transformation, when said chemical transformation is so-effected by a method according to the first aspect of the present invention.

In general terms, the present invention provides means suitable for the treatment of organics-containing Reverse Osmosis effluent, such that the organics are able to be removed with relatively high efficiency. The inventive process is scalable to an industrial, or a modular system for individual or household use.

The first part of the process is to use photocatalytic processes to create free radicals in effluent water. It is known that UV light, when interacting with certain materials (such as TiO ₂ , ZnO, CdS and WO ₃ ) causes a photoreaction that initiates the decomposition of water into free radicals such as hydroxy radicals ('OH). These

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radicals are the active agent that reacts with the organic molecules in the effluent to initiate their decomposition into harmless products (most advantageously carbon dioxide and water).

Whilst other inventors have sought to use such TiO ₂ /UV-derived photocatalysts in the treatment of water, it has proved difficult to develop a system where the light required to initiate the sought photochemistry is brought efficiently to the reaction vessel. To this end, the principal limitations include:

Firstly, since contaminated water itself absorbs and scatters UV light, it is preferable that the light itself comes into contact the photocatalyst without first travelling through the contaminated water. Most of the available literature appears to teach away from such an arrangement in proposing the use of TiO ₂ sols suspended in water, or even a TiO ₂ carrier system. However, one embodiment of the present invention does require the energy to travel through water. In this embodiment, the catalytic substrate is applied to one or more auxiliary surfaces spaced from the transport medium to define a reactor volume comprising the one or more reactant species, the incident energy is thereby able to perform a pliotolytic transformation prior to contacting with said photocatalytic surface following which a photocatalytic transformation may be effected. The one or more auxiliary surfaces may be substantially reflective such that energy passing through the catalytic surface is reflected back toward the reactor volume.

, Secondly, it has proven difficult to place the TiO ₂ optimally within a photochemical system. Known techniques include placing the TiO ₂ in a suspension, with the appreciably negative impact that the suspension itself limits the path-length of UV light through the solution due to light absorption and scattering. Further, a TiO ₂ suspension is difficult to manage and maintain in a flow-through system. . One alternative, as proposed according to the present invention, is to affix any TiO ₂ on a surface accessible to the UV, and whereby the UV light does not have to travel through water in order to arrive at the TiO ₂ .

Thirdly, the reactive species produced by TiO ₂ induced photocatalysis have a limited distance from where they are generated at the photocatalytic surface into the water, as these species have a high propensity to recombine to form non-reactive species. Hence, there is an optimum volume of water, or reactor fluid, around the photooxidation site that ensures chemical oxidation of the effluent organic and/or pathogen species is effected. The present invention seeks to optimise the balance

between pliotocatalytic surface area and reactor volume such that the resultant method and apparatus are relatively efficient with respect to known systems.

Fourthly, it is problematic as to precisely how to get UV into a water flow system. For example, if water passes through an optically clear pipe, the water can be irradiated with UV. However, because UV is absorbed by water and also because radicals can recombine, there is an optimum pathlength for the UV light applicable to the present invention. Any macro-scale pipe is far from the optimum in terms of the ratio of irradiated surface area to water flow volume.

From the above discussion, it is clear that the three key features in any such system of remediating organics-containing effluent are: water, light and photocatalytic material. The present invention seeks to combine these in a manner which provides for a relatively simple and efficient remediation of such secondary effluent to both potable and non-potable standards.

Such a system is designed to relatively maximise the efficiency of UV light utilisation, surface area of photocatalyst, and the ability to tailor the volume and flow rate of the contaminated water, such that the maximum efficiency of reaction is achieved. To this end, the flow rate of the contaminated water may be altered according to the concentration of the organic load it bears. When each of these elements is optimised, the cost of removing such organic molecules from contaminated RO effluent is relatively reduced.

The basic components of the present invention include: An optical transporter comprising an optical fiber or an optical sheet. These can be made of any optically clear materials, most usefully comprising an optically clear path in the UV (where UV light is preferred). Typically, such optical transporters are made of inorganic glasses, quartz, or polymeric materials.

At the very least, the core of the optical transporter requires a higher refractive index material, optionally surrounded by a cladding of lower refractive index material. Such optical transporters are well known in the telecommunications, data- communications and aesthetic lighting industries. Potentially useful additional elements include light scattering functionality in the optical transporter in order to distribute the UV light substantially orthogonal to the incident light path, and thereby into the reaction vessel itself. Such scattering ability may be achieved via the inclusion of small particles or physical defects, and will be elaborated upon, below. hi a preferred embodiment, the optical transporter is a waveguide that propagates

light from the light source to the photocatalytic sheet. In a particularly preferred embodiment, the optical transporter and the waveguide are unitary. The waveguide advantageously uses common fibre optics techniques to ensure that a maximum amount of the light is propagated to the sheet, {e.g. using a lower refractive index surface layer). In other embodiments, the waveguide may facilitate the light source being remote from the photocatalytic sheets that are in the reactor.

The present invention also includes a photocatalytic material placed upon the surface of the optical transporter. For example, TiO ₂ (or other photocatalytic materials such as ZnO, CdS and WO ₃ ) may be coated on to one or more exterior surfaces of a polymeric optical sheet. Such a coating may be imparted upon the optical transporter by a variety of means, including solvent-based coating techniques similar to processes currently used to place protective coatings on optical fibers. Alternatively, such a coating can be achieved during production of the optical fibers or optical sheets by bringing a cooling fiber/sheet into contact with TiO ₂ powder. Many other means of achieving a functional coating of a photocatalytic material upon an optical transporter may be envisaged.

In a preferred embodiment, photocatalytic sheets comprising a non- photocatalytic, optical substrate, and having a surface layer of photocatalytic material (e.g. TiO ₂ ), comes into contact with the aqueous gas or fluid that is to be remediated or processed. This surface layer is coated/immobilised on to one or more external surfaces of the substrate. The substrate is made of a material such as an inorganic glass, or plastic, that is substantially optically clear, thereby allowing light of a wavelength of about 200 nm to about 400 nm to pass through its entirety. Using fibre optics and/or commercial light propagation techniques (e.g. scattering, notching, particles, layers of different refractive indices, layers such as optical cladding, etc.) allows the light to reach substantially all the exterior photocatalytic surface material. hi another preferred embodiment, 'potting' of one or more of the optical transporters into a cartridge allows separation of the optical path from the water transport path. Typical examples include a fiber filter cartridge directly analogous to hollow fiber membrane cartridges, with the exception that such fibers are solid optical fibers. Yet another important example is a rolled-sheet filter cartridge, which is akin to a Reverse Osmosis membrane cartridge, except that an optical sheet replaces the membrane. The potting is achieved as in most membrane and filter cartridges, by the use of a polymeric system to seal the ends of the cartridge around the fibers or sheets.

_ _{χ g} _

The present invention further comprises a UV light source at one or more ends of the optical transporter that allows the distribution of light from the light source lamp down the optical transporter, thereby to scatter substantially orthogonally from the TiO ₂ coating and produce the sought radicals in water. In a preferred embodiment, the UV light source is in the form of UV light from a light-emitting device, such as a diode, UV lamp, LED, or groups/banks thereof. The light energy source is able to produce light within the wavelength spectrum of around 200-400 nm, most preferably, a tight beam of 350 nm, thereby to utilise a maximum amount of the light energy. The optimum wavelength is below 380 nm, which corresponds to the maximum effective wavelength for undoped TiO ₂ photocatalysis. The light source may be part of the photocatalytic sheet, or remote therefrom, in which case it is adjoined thereto by a waveguide.

The present invention may also comprise a reactor vessel preferably having an inlet and an outlet, to allow an aqueous gas or liquid feed to enter the vessel, and then once treated, exit the vessel. Alternatively, the inlet is integral with the outlet, thereby to facilitate a batch treatment process if desirous. The inside of the vessel allows for an advantageous configuration of photocatalytic sheets/fibres to be attached, allowing the raw feed optimum contact time with the photocatalytic surface of the sheets/fibres. The vessel also has a port that allows the waveguide, or energy source for the light {e.g. UV lamp) to enter the vessel and affix to the sheets. This may be in a plate-and-frame arrangement shown in the accompanying drawings, a "Swiss roll" arrangement as used in the Reverse Osmosis module, or a plurality of vanes.

Brief Description of the Drawings A preferred embodiment of the present invention will now be described by way of example and only with reference to the accompanying drawings and examples in which:

Figure 1 is a side elevation of an optical fiber cartridge according to one embodiment of the present invention; Figure 2 is a cross section taken on the line II-II of Figure 1, showing longitudinally-extending optical fibers potted within the cartridge;

Figure 3 is relatively magnified view of a single optical fiber as depicted in Figures 1 and 2, showing a preferred embodiment in which the three principal components of the fiber are a relatively high refractive index core, TiO ₂ surface coating,

_ _

and a relatively low refractive index cladding;

Figure 4 is a side schematic view of a cartridge/module and filter housing adaptable to accommodate certain preferred embodiments of the present invention;

Figure 5 is an elevation of a single flat sheet, showing a relatively high refractive index optical core, optional relatively low refractive index cladding and surface coating of catalytic material;

Figure 6 is a side schematic representation of a "plate-and-frame" embodiment according to the present invention, employing a plurality of stacked optical sheets, and showing a tortuous or serpentine path along which the feed flows; and Figure 7 is a side view of a wound spiral Reverse Osmosis cartridge, again adaptable to certain preferred embodiments of the present invention.

Preferred Embodiment of the Invention

A preferred form of the apparatus according to one aspect of the present invention comprises a catalytic substrate, which is preferably a photocatalytic substrate, most preferably being TiO ₂ , in the form of anatase, rutile, titania or a combination thereof.

The apparatus also comprises means for providing a feed comprising one or more reactants. The feed is a fluid, most preferably being a liquid, gas, or a combination thereof. More preferably, the fluid is a fluid effluent, with the apparatus thereby operative to remediate at least a portion of the fluid effluent. In a particularly preferred embodiment, the fluid effluent is a contaminated or polluted liquid, gas and/or steam.

The liquid, gas and/or steam comprises one or more reactants in solution and/or undissolved state. Most preferably, the liquid is water. The means for providing a feed includes provision of an outlet port remote from an inlet port, thereby to facilitate flow of said feed therebetween. Alternatively, the inventive apparatus includes provision of an outlet port integral with an inlet port, thereby to facilitate the method to operate on a batch basis.

The apparatus also comprises an energy source spaced from the catalytic substrate. Alternatively, the energy source may be proximal with the catalytic substrate.

More preferably, the energy source is directly coupled with the catalytic substrate. The energy is preferably UV light, most preferably comprising one or more wavelengths within the range of approximately 200-400 nm.

The apparatus also comprises a transport medium through which energy

derived from the energy source is contactable with the catalytic substrate, thereby to provide a species active against said one or more reactants. In a preferred embodiment, the transport medium is a waveguide. More preferably, the waveguide is a planar optical waveguide. The waveguide may act both as the transport medium and as a substrate for catalytic material applied to the surface thereof. Preferably, the waveguide comprises a single material. Alternatively, the waveguide comprises a plurality of materials. Preferably, the plurality of materials are of differing refractive indices, thereby to relatively enhance the waveguiding efficiency of the waveguide.

The waveguide may comprise scattering centres, reflective elements, diffractive elements, or a combination thereof, thereby to facilitate incident light being shifted out of the plane of the waveguide and contacting with the photocatalyst. The active species is an excited species, most preferably, the excited species are free radicals.

The apparatus also comprises means for contacting said active species with said feed, thereby to actively effect said chemical transformation. As such, the catalytic material is applied to one or more surfaces of the catalytic substrate. Preferably, the catalytic material is illuminated substantially perpendicular to the axis thereof. Alternatively, the catalytic material may be illuminated substantially parallel to the axis thereof.

The catalytic material is provided as a coating over one or more surfaces of the waveguide. Foreseeably, the coating is adhered to the waveguide via solid phase, gas phase and/or liquid phase deposition techniques. Such deposition techniques comprise annealing, adhesive, etching, extrusion, moulding, dip coating, sputter coating, slot coating, lamination, or a combination thereof .

The coating may be on a substantially smooth or complex surface. Most preferably, the waveguide has a complex surface. The complex surface is applied upon the waveguide by etching, extrusion moulding, stamping, or a combination thereof.

In one embodiment, the complex surface is formed in the same material and is integral with the waveguide. Alternatively, the complex surface is formed separately from the waveguide. Preferably, the complex surface is formed in a different material to the waveguide. The complex surface føcilitates enhanced fluid dynamics, such as relatively enhanced flow rate and/or relatively enhanced mixing. The complex surface also increases the effective surface area of the catalytic substrate.

The solution comprises said one or more reactants in aqueous phase. The contaminated or polluted liquid comprises one or more organic contaminants. More

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preferably, the one or more organic contaminants comprise organic molecules and organisms. More preferably still, the organic molecules comprise 1,4-dioxane and/or N- nitrosodimethylamine (NDMA). Alternatively, the one or more reactants comprise non- aesthetic compounds such as those emitting undesirable odour and/or colour, and/or pathogens/organisms such as bacteria, viruses and protozoa.

The waveguide ideally comprises one or more stacked sheets. Each of the arrangement of one or more stacked sheets is spaced by one or more discrete spacer units and/or the complex surface. The one or more stacked sheets are arranged to provide optimal contact time of the feed with the active species. Ideally, the one or more stacked sheets are arranged to provide a relatively increased surface area per unit volume. The arrangement of one or more stacked sheets is adaptable to provide a serpentine flow of the feed between the sheets.

In a preferred embodiment, the relatively increased surface area is enabled by way of a plate-and-frame type configuration. Preferably, the plate-and-frame type configuration comprises a plurality of sheets stacked substantially horizontally, with the fluid flow able to function 'up-hill' or 'downhill', as desired. In another preferred embodiment, the relatively increased surface area is enabled by way of a Swiss-roll type arrangement. In a further preferred embodiment, the relatively increased surface area is enabled by way of a vane-type arrangement. According to a preferred embodiment, a chemical transformation takes place within a modular apparatus, as exemplified in Figure 6.

This preferred embodiment of the present invention provides a chemical reactor (filter) vessel that enables dissolved small organic compounds, e.g. N- nitrosodimethyleamine (NDMA) or 1,4-dioxane, in an aqueous gas or aqueous liquid feed to be destroyed or broken down by an advanced oxidation process (AOP), undertaken in a photocatalytic reaction.

The reactor vessel enables UV light to be transmitted from a light source, to one or more of a configuration of sheets, each said sheet having a photocatalytic surface that enables the photocatalytic portion thereof to undergo photocatalysis, which in turn produces an AOP to destroy the organics present in the gaseous or fluid feed, as it passes over the surface of the sheets.

In the following description, a preferred embodiment of a hollow fiber optical transporter according to the present invention is exemplified in Figures 1 to 3. In this example, the optical transport medium is a plurality of optical fibers 1, which are

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' potted' into a cartridge 2, the cartridge being analogous to a kidney dialysis or microfiltration cartridge.

The optical fibers 1 extend longitudinally down the cartridge 2, and are affixed at the respective ends 3 and 4 by a potting compound 5. The potting compound 5 serves both to fix the optical fibers 1, and also to seal the ends of the cartridge 2 such that water cannot pass through the ends thereof. The cartridge 2 optionally includes a screen 6 to support the outermost optical fibers and maintain the mechanical rigidity of the cartridge 2 for transport and installation.

Referring specifically to Figure 2, in which an end-view of the cartridge 2 is depicted, wherein the exposed ends of the optical fibers 1 can be seen. It is through these ends that the UV light is propagated down the fibers.

Referring specifically to Figure 3, in which a close-up of an optical fiber 1 in the cartridge 2 is shown, the optical fiber is typical inasmuch as that there is a core 7 of relatively high refractive index and an optical cladding 8 of relatively low refractive index. Accordingly, the optical fiber will guide light. Optionally, the fiber 1 may have a exterior coating, hi this preferred embodiment, the optical fiber has a coating of TiO ₂ on its outermost surface 9, the TiO ₂ coating being in contact with the water or other flowable material bearing the chemical reactant(s).

Optionally, the optical fiber 1 may be manufactured from polymeric materials such as polycarbonate or acrylics. Fluorinated polymers can be used if enhanced oxidation resistance of the polymer is required. Polymeric optical fibers have the advantage that they are readily available, relatively low cost, available in any specified diameter, and are insensitive to water exposure.

An enhancement in the optical fiber 1 according to the present invention is the use of scattering to ensure that relatively more of the light that enters the ends of the optical fibers is usefully, and evenly scattered into the cladding 8 of the fiber, and thus efficiently converted into radicals after interaction with TiO ₂ at the outer surface 9 of the optical fiber 1. It should be remembered that the outer surface 9 of the optical fiber is in contact with the water, or effluent feed. Such scattering may be achieved by the addition of scattering particles into the core and/or cladding of the optical fiber, or by the inclusion of physical notches in the cladding of the optical fiber. Such techniques are well known in the application of optical fibers for aesthetic "side-lighting" purposes, and can be tailored such that light is scattered relatively evenly along the length of the optical fiber, despite one end of the

optical fiber being closer to the light source.

Referring now to Figure 4, in which a schematic of the filter cartridge 2 and housing 10 is provided, two UV lamps 11 and 12 illuminate the respective ends 3 and 4 of the optical fibers 1 at each end of the cartridge 2. The UV light passes along the optical fibers, and is scattered onto the surface of the optical fibers, where it interacts with the surface coating of TiO ₂ and the water to create radicals. The water flows in to and out of the cartridge via the ports 13 and 14, as illustrated, and follows a tortuous or serpentine path between these ports. Accordingly, there is a relatively increased contact of water with the surface of the optical fibers. Along this path, the organic molecules in the feed water react with radicals produced at the surface of the optical fibers to produce relatively harmless decomposition products, preferably, carbon dioxide and water. The optical fiber diameter and density, together with the water flow rate is optimised so as to relatively minimise the overall cost of treating the water. The end-pots, as shown, seal the water from the UV lamps. The housing and other engineering used for such a cartridge is advantageously adapted from microfiltration, ultrafiltration or Reverse Osmosis membrane cartridges.

Referring specifically to Figure 5, a preferred format for the optical transporter 1 is a flat sheet optical transporter 15, as shown. The optical transporter sheet may be comprised of plastic, inorganic glasses or other suitable materials. The optical transporter sheet can be constructed of one or more optical layers. Optionally, the optical transporter sheet comprises a photocatalyst layer, e.g. TiO ₂ , upon one or more of its exterior surfaces 16. The photocatalyst layer 17 is applied by any suitable means (e.g. liquid coating, powder coating, lamination, etc.). The essential theory behind the use of the flat sheet is that the incident UV light is sent through the ends 18 of the flat sheet 15, and emitted through the surface of the sheet, whereupon the UV light interacts with water and the photocatalyst to create the radicals by which the organic reactants are decomposed.

A flat sheet optical transporter can be integrated within the inventive remediation system in many ways. Two preferred examples are provided in Figures 6 and 7. Specifically, the arrangement depicted in Figure 6 could be termed the "plate-and- frame" configuration. In this arrangement, successive flat sheets of optical transporter material 15 are layered on top of each other, spanned by supporting spacer material 19, thereby allowing the fluid/gas feed to pass between, and to ensure that fluid/gas flow is evenly distributed across the surface, optimally crating a mixing action.

In a particularly preferred embodiment, the photocatalytic surface is formed by etching, extruding, moulding, or any other known or applicable means. The photocatalytic surface may comprise a complex surface to allow an increase in effective surface area, whilst at once helping the fluid dynamics (i.e. flow, mixing) of the system. The complex surface may even function as the spacer, in which case the photocatalytic sheets may be substantially self-stacking. In employing the method provided by the present invention, the photocatalytic surface is self-cleansing.

The entire stack is then edge-glued in such a fashion as to seal the edges, thereby to stop water from leaking out at the edges. However, this operation is performed in such a manner as to still allow UV light to be illuminated into the optical transporters/waveguides. One perceived water flow regime is depicted in Figure 6, wherein it should be appreciated that the water flows right through the module 20 from inlet 21 to outlet 22 in a controllable and advantageous fashion.

The second such example, as depicted in Figure 7, is the "spiral wound"-type configuration often used for Reverse Osmosis membranes. In a hollow pipe cartridge housing 23 is a flat sheet 24 (not shown) having a space both above and below it. Prior to placement in the cartridge 23, the stack is wound into a spiral or helix, and the spiral is then edge-glued in such a fashion as to allow light to be illuminated into an optical transporter/waveguide. This configuration is directly analogous to the "plate-and- frame"-type configuration disclosed above. However, it has been found that the spiral configuration is relatively cheaper to fabricate.

In terms of the comparative advantages of flat sheet and hollow fiber configurations, the most important consideration is cost per unit volume of water treated. Overall cost comprises initial capital expenditure plus operating and maintenance costs. Also important is the time and expenditure required to develop new water treatment technologies, which directly takes account of the degree to which earlier non-patented engineering technologies may be incorporated, both from photonics and membrane water treatment processes.

Optical fibers are now readily available at relatively low cost, whereas a flexible flat optical sheet is a boutique specialty product used for aesthetic lighting. However, almost any optically clear extruded polymer sheet could be used. Since this application does not require high definition optics, a simple three-sheet polymer laminate could be used. One such example is that of relatively low cost everyday plastic films, such as PET or acrylics, laminated together with heat, and with optional glues. In certain

circumstances, the optics may be forgiving enough such that a single polymer film layer is sufficient.

Compared with the optical fibers, flat sheet technology is relatively easy to handle, easier to make into a module, and even relatively easy coat with ηO ₂ . Also, flat sheet technology offers the advantage of a defined liquid flow path, whereas in using fibers, the flow path is never optimal. Essentially, using fibers, a preferred path is created by the water flow pushing the fibers aside, and optimal contact time is seldom achievable. hi water treatment using microfiltration, hollow fibers are generally preferred over a flat sheet. This is because the feed water is generally relatively dirty, thus leading to fouling, in addition to backwashing requirements. However, in the present invention the feed is envisaged to be relatively clean, and accordingly, fouling is much less of an issue. Further, the present invention utilises cross-flow systems with no pressure across the 'filter'. In Reverse Osmosis membrane treatment, a flat sheet is preferred over hollow fiber systems. Those active in the relevant industry have in the past employed hollow fiber Reverse Osmosis. However, the overwhelming trend has been toward the flat sheet. This is because it is inherently cheaper, and there is no special requirement for a hollow fiber, namely solids-loaded feed water.

Accordingly, the most preferred embodiment of the present invention is directed toward using an optical sheet. This could be as a rigid flat sheet in a plate-and-frame set-up, or in rolled-sheet (e.g. "Swiss-roll") format. The principal advantages of such a system include optimising the energy efficiency in removing organic species by generating peroxide, in situ, ensuring relatively more of the light is converted to radicals, and ensuring that the radicals are most efficiently used to react with the small organic molecules, as opposed to recombining with each other.

A further advantage of the present invention resides in the use of existing filter and membrane cartridge technologies. This results in lower development and unit costs. It also allows a single or low count of UV lamp to illuminate a relativelylarge effective volume of water. Further, it allows the development of small area footprint treatment plants, which is a major factor in terms of cost and adoption of new treatment technologies.

Yet a further advantage of the present invention resides in it using existing cartridge designs, the ancillary engineering (pipes, pumps, valves, control systems, management software and hardware) will also be familiar and have relatively low cost.

This engineering has a direct effect upon the volume-cost curve. Familiar engineering also lowers the barrier to adoption of this new technology within the marketplace.

In summary, a system according to the present invention may have significant cost advantages. - For a specific required removal rate of small organic molecules in Reverse Osmosis effluent, lower capex should be achieved, together with relatively reduced operating and maintenance costs.

In general terms, the present invention is advantageous in that it creates an efficient means to bring a reaction system together with activating light in a low cost cartridge, with the ability to adjust the relative surface areas and volumes with relative ease, in order to maximise the efficiency of the process.

One foreseeable application of the inventive system is for water treatment to remove dissolved organics. However, it would be readily apparent to one skilled in the relevant art that the system may have efficacy for any fluid reaction system where photocatalysis is required. Moreover, the means in which the photocatalyst is employed is optional; it can be placed on the surface of the optical transporter, as described, or even in suspension. The effluent phase can be a liquid or a gas. The light source can be any wavelength of light that is suitable to induce photocatalysis.

Unless the context clearly requires otherwise, throughout the description and the claims, the words 'comprise', 'comprising', and the like are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense; that is to say, in the sense of "including, but not limited to".

Although the invention has been described with reference to specific examples it will be appreciated by those skilled in the art that the invention may be embodied in many other forms.