WO2004031078A1

WO2004031078A1 - Apparatus for fluid treatment

Info

Publication number: WO2004031078A1
Application number: PCT/GB2003/004255
Authority: WO
Inventors: Ian A. Ramsay
Original assignee: Laser Installations Ltd.
Priority date: 2002-10-03
Filing date: 2003-10-03
Publication date: 2004-04-15
Also published as: AU2003271880A1; GB0222875D0

Abstract

The present invention relates to an apparatus suitable for use in the irradiation of a fluid having an UV absorbance not greater than 0.06cm-1 at an UV radiation wavelength of 254nm. The apparatus comprises a multiplicity of flow tubes 6 for conducting said fluid therethrough, a multiplicity of UV radiation source tubes (4), and a tube support structure formed and arranged so that said UV tubes and flow tubes extend substantially parallel to each other in a close-packed multicellular matrix array (1) made up of equilateral triangular cell units (14) having UV source tubes at their vertices and flow tubes midway between said vertices. The invention also provides a method of water treatment using an apparatus of the invention.

Description

Apparatus for Fluid Treatment

The present invention relates to the treatment of fluids using ultraviolet light.

Ultraviolet (UV) radiation systems have been used to disinfect aqueous fluids such as drinking water, waste water etc for many years, either alone or in conjunction with additional purification systems such as the use of filters or the addition of chlorine to the fluid. A drawback of currently employed UV treatment systems used to treat drinking water is their limited germicidal activity. While routinely used UV radiation dosages may inactivate many bacteria and virus strains, more resistant micro-organisms, such as Cryptosporidium, especially when the oocysts of Cryptosporidium are less than 6 weeks old, require a much higher dose to effect morbidity. Even supplementing the UV treatment by adding chlorine to the water is ineffective against Cryptosporidium when chlorine concentrations permissible in drinking water are used, leaving total barrier filtration with membrane filter installations as the most viable treatment option presently available. The necessary filters, though, are prohibitively expensive, and maintenance requirements are considerable to keep the filters working effectively.

A further disadvantage of existing UN systems is the use of submerged UV lamps which can enable micro-organisms to be shielded from the UV radiation emanating from the lamps. This can occur when a micro-organism, for example a Cryptosporidium oocyst, bacterium or virus, is eclipsed by particulate matter, debris or larger micro-organisms, for example, and hence escapes UV irradiation emanating from UV lamps proximal to the shielding matter. Providing the flow tube with a UV-reflective inner surface to reflect the UV radiation and increase the likelihood of a position within the flow tube receiving UV radiation from all angles, is one possible solution to the problem. This arrangement, however, is dependent not only on keeping the outer surfaces of the submerged lamps clean enough to emit adequately the UV radiation but also on keeping the inner flow tube surface clean enough to reflect the UV radiation sufficiently well to provide the required UV radiation to meet water treatment standards of various nations, for example no more than one oocyst per 10 litres prescribed by the UK Drinking Water

Inspectorate or a specified log scale reduction prescribed by other nations.

Shielding matter may be attached like a raft to the

Cryptosporidium oocyst, bacterium or virus. When using submerged UV lamps one can reduce the effect of such shielding by ensuring that the flow of water is turbulent because the attached shielding matter will lie between lamp and pathogen for only a portion of the duration of the rotating passage, caused by the turbulence, down the flow tube. However, in order to achieve the same level of kill in the presence of such shielding matter as is achieved at a given flow rate in clear water one would have to double or treble the number of modules of submerged lamps .

It is an object of the present invention to reduce or overcome one or more of the above disadvantages.

In one aspect the present invention provides an apparatus suitable for use in the irradiation of a fluid having a low UV absorbance, typically having an absorbance not greater than 0.06cm^"1 at an UV radiation wavelength of 254nm, which apparatus comprises a multiplicity of flow tubes for conducting said fluid therethrough in use of the apparatus, a multiplicity of UV radiation source tubes, and a tube support structure formed and arranged so that said UV tubes and flow tubes extend substantially parallel to each other in a close- packed multicellular matrix array made up of equilateral triangular cell units having UN source tubes at their vertices and flow tubes midway between said vertices.

Such a multicellular matrix or array of UV radiation source tubes and flow tubes provides an arrangement in which individual flow tubes receive UV radiation from different directions from a plurality of UV tubes, and in which maintenance of the apparatus including replacement of any expired UV tubes and cleaning of any deposits of material from the water being treated, are particularly easy and convenient, thereby ensuring maintenance of high levels of efficiency of the UN irradiation treatment . In particular it will be appreciated that any possible deposits will be restricted to the interior of the flow tubes, entirely remote from the UN tubes, thereby enabling cleaning of such deposits without interfering with the UV tubes. Moreover since the UV tubes are spaced apart and separate from the flow tubes and water being treated, they do not require to be individually encased or specially protected (i.e. apart from any external apparatus housing which may be provided) , thereby simplifying manufacture and reducing cost thereof. Also any cooling requirements which may arise (for protection of the UV tubes and/or water being treated, from overheating) are reduced and/or substantially simplified, by allowing cooling air to be vented (with or without assistance) from between the tubes in the matrix.

It will be appreciated that whilst the inner flow tubes of the array are each immediately surrounded by four UV radiation sources, the outer flow tubes at the perimeter of the matrix array will be in the direct path of UV radiation emanating from only three UV radiation sources in immediate proximity thereto. The reduced UV radiation flux may however be augmented by providing the apparatus with a reflector at the outside of the matrix array to reflect UV radiation exiting the outside of the array back in towards the outer flow tubes of the matrix array. Conveniently UV source tubes at the outside edge of the matrix array have an arcuate shaped reflector formed and arranged for directing UV radiation received thereon, back onto such outside edge flow tubes . Some suitable reflector geometries are illustrated in the detailed description hereinbelow. Any suitable form of reflector for use with UV radiation may be used including for example, silvered glass, and polished metal, for example, polished aluminium, available under the trade name "Lorin lighting sheet".

It will be appreciated that the UV radiation flux levels inside the flow tubes will depend on the geometry of the cellular units, and in particular on the relative sizes of the UV tubes, flow tubes and the spacing thereof i.e. the size of the triangular cells. More particularly it will be appreciated that in order to maximize fluid flow it is preferred that the diameter of the flow tubes is larger than that of the UV tubes. On the other hand it is also preferred that the flow tube diameter should not be so great that UV radiation from the remote vertex of the cellular unit is substantially occluded. Another disadvantage of using excessively large flow tube diameters is that the air flow between the tubes of the multicellular matrix becomes restricted thereby increasing the risk of overheating. Preferably therefore the flow tube diameter is from 1.5 to 3 times the UV tube diameter. Advantageously the length of the triangular cell side is from 4 to 8 times the UV tube's outer diameter.

Particularly preferred dimensions of the triangular cell unit can be determined on the basis of the chosen UV tube and flow tube diameter sizes using suitable trigonometrical calculations. It is preferable for each flow tube in the matrix array to receive UV radiation from the UV tubes most proximal to the flow tube around the entire circumference of the flow tube. If the triangular cell unit is too small the path of a UV radiation beam emanating from a UV tube at a vertex of the triangular cell unit that is directed towards a target flow tube at the midpoint of the opposite side of the triangular cell unit to the UV tube, will be obstructed by the other two flow tubes in the cell unit. Therefore, the smaller the cell unit, the narrower will be the UV beam which is incident on the target flow tube without being interrupted. If the uninterrupted beams are too narrow, UV radiation of sufficient intensity to kill Cryptosporidium will not be received around the entire circumference of the flow tube. If the triangular cell unit is made too large, the intensity of the UV radiation incident on the flow tubes may be too low for sufficient killing activity.

The most preferred length of the side of the equilateral cell unit for maximising close packing obstruction of UV radiation beams can be determined using suitable calculations as described below, a range of from 80% to 150% of the most preferred length of side is also generally acceptable.

Suitable UV tubes are generally available in a limited number of standard diameters, notably 15mm and 19mm outer diameter. As the effective diameter of the discharge in the UV tubes is closer to the internal diameter of the UV tube it is more appropriate and convenient to dimension the other features of the cellular unit relative to this measurement. A 15mm outer diameter UV tube typically has an internal diameter of about 12mm and a 19mm outer diameter UV tube typically has an internal diameter of about 16mm.

Preferably the multicellular matrix array of the present invention is of hexagonal form. Advantageously the sides of said hexagonal matrix would be of equal lengths. However, it is also acceptable to provide a hexagonal matrix array which has some difference in length between different sides, whilst still achieving a reasonably efficient ratio of flow tubes to UN tubes in terms of power consumption relative to UV radiation flux in the flow tubes . Where the lengths of the sides of the hexagonal matrix are of unequal length it is preferable for the longest sides of the hexagon to be not more than twice the length of the shortest side of the hexagon, and further preferable for the majority of sides to be longer than the minority of sides. The hexagonal matrix arrays of the present invention have two principal orthogonal axes referred to herein as "h" and "v". A first axis of symmetry passes through opposing vertices of the matrix array with an inter-vertices separation of "h". A second axis of symmetry orthogonal to said first axis of symmetry, bisects opposing sides of the matrix with an inter-side separation of "v". Where the matrix is of hexagonal shape of different lengthened sides the second axis of symmetry bisects the most closely spaced opposing pair of sides of the matrix with an inter-side separation of "v". The most economical and efficient forms of matrix array have a v:h ratio in the range from 0.866 to 1.155, most preferably in the range from 0.866 to 1.01.

In general we have found that suitable matrix array geometries of the invention can be defined by the general formulae:

F = n (3n+2) -s (3s+l) and L = (n+1) ²-s (s+1) , provided that 2s<n<3s,

where F is the number of flow tubes, L is the number of UV tubes, n is the length of the maximum width of the matrix array for a hexagonal array and is equal to the inter- vetrices separation "h" (in terms of triangular cell units) , and s is the length of the shortest side of the matrix array (again in terms of triangular cell units) . It may be seen that s = o corresponds to a triangular matrix array i.e. a hexagonal matrix array in which the shortest sides have zero length. It may also be noted that s+1 corresponds to the number of cell matrix variants for any given values of n and s which have the preferred v:h ratio in the range from 0.866 to 1.155.

In principle there is no upper limit on the size of the multicellular matrix array. In practice, though, if particularly large numbers of UV tubes and flow tubes are used then the risk of overheating and/or cooling needs become too high. Accordingly it is preferred that s is not greater than 4, and advantageously is not greater than 3. It will be appreciated that the size and form of the matrix will determine the preferred form of the reflector. Where the apparatus comprises a hexagonal matrix array, the reflector preferably takes the form of a reflector tube of circular cross section, coaxial with the matrix array of UN tubes and flow tubes, and positioned around the array and concentric with the central longitudinal axis of the array.

The diameter of the reflector tube is preferably chosen so the reflector tube is close enough to the flow tubes and UV tubes for the cumulative intensities of the reflected beams incident on the outer flow tubes to be substantially maximised. The farther away that the reflector tube is from the outer flow tubes the less intense the reflected UV beam is. If the reflector tube is too close to the UV tubes and outer flow tubes the extent of the reflected beams of UV radiation directed onto the outer flow tubes will be restricted. It is the cumulative effect of the coincident reflected radiation from the different outer UV tubes that compensates for the reduced intensity of each individual outer UN tube's beam as it travels to and from the reflector. It has been found that the preferred diameter of the reflector tube is in the range of 1.2 "v" to 2.0 "v", more preferably 1.4 "v" to 1.8 "v" advantageously about 1.6 "v".

It will be appreciated that the walls of the flow tubes should be of material which is substantially transparent to electromagnetic radiation in the UV radiation wavelength region of the chosen lamp. Typically the wavelength of radiation may be from 150nm to 350nm, and preferably from 220nm to 280nm, with substantial UV-transparency at a wavelength of 254mm being particularly preferred. The UV transparent walls of the flow tubes may be made from an inorganic material such as a fused quartz, for example those sold under the trade names of Spectrosil and Vitreosil. Where transmission below the wavelength of 220nm is required it is preferable to use Spectrosil fused quartz. Alternatively the flow tube walls may be formed from plastics such as organic polymers, co-polymers and the like such as, but not limited to, cellulose products (sold under the trade name Cellophane) PTFE, FEP, PVC and PE, although these generally have lower UV transmission and are therefore less preferred. A suitable flow tube wall thickness is generally of the order of 1.5mm to 3mm and has a UV transmission at 254mm of 80% to 95%. Preferably the flow tube wall material and thickness thereof is selected to have a UV transmission at 254mm of at least 80%, preferably at least 85%.

The flow tubes preferably have a circular cross-sectional shape although tubes of other cross-sectional shapes may be used, for example oval section tubes.

The diameter of the flow tubes is preferably chosen to permit UV radiation to penetrate and pass through to the centre region of said flow tubes such that all the fluid within the flow tubes receives a substantial dosage of UV radiation from the surrounding UV radiation source tubes . Typically the flow tubes have an internal diameter of from 20 to 60 mm preferably from 25 to 40 mm, for example, 32mm. In the case of a 32mm tube, with a radial dimension of 16mm, when the fluid flowing in the flow tubes has an absorbance of approximately 0.06cm^"1, the drop in intensity of the radiation will not be more than 20%. It will be appreciated that larger diameter flow tubes could be used in conjunction with effective fluid mixing means, such as for example static flow mixers mounted inside the flow tubes. This is however generally less preferred as on the one hand it would increase the cost and complexity of the apparatus, and on the other hand it would interfere with any cleaning of the interior of the flow tubes .

The fluid may be passed through the flow tubes by a pump, usually a pump located upstream of an inlet to the flow tubes. Alternatively the fluid may be supplied to the flow tube by gravity feed. The rate of flow of fluid through flow tubes may be controlled by any suitable fluid flow regulator such as a flow restriction valve, or a pump flow rate controller. The rate of flow of fluid through each flow tube will of course depend on the flow tube diameter, and the residence time required for effective treatment, which will in turn depend on the total amount of UV radiation received, its frequency etc. Generally the flow rate is of the order 0.25 Is^"1. It will be appreciated that to achieve an increased net flow rate it is possible to connect a plurality of apparatuses of the present invention in series and/or parallel in order to increase the effective treatment time. Preferably such an arrangement would utilise multicellular matrix arrays of the present invention of the largest sizes for which cooling and maintenance can be practically achieved. For example where 42 flow tubes each with a flow rate of the order of 0.25 Is^"1 are connected in parallel a net flow rate of the order of 10 Is^"1 can be achieved. In general the flow rate is chosen so as to provide a fluid residence time within an irradiation zone i.e. part of the flow tubes receiving UV radiation from the UV tubes, which results in the fluid receiving a UV radiation dosage sufficient to achieve a log kill or inactivation rate which reduces the viable micro-organism concentration to a level less than 1 oocyst per 20 litres, preferably less than 1 oocyst per 100 litres, and desirably avoiding damage to any useful radiation and/or heat sensitive components that may be present in the fluid.

It will of course be appreciated that the fluid residence time in the irradiation zone required for effective treatment in order to ensure an adequate level of micro-organisms inactivation etc, will depend on many different factors such as the degree of contamination of the fluid, the absorbance of the fluid at the wavelength of the UV radiation being used, the diameter of the flow tubes, the thickness and absorbance at said wavelength of the flow tube walls, and the UV radiation flux through the flow tubes which will depend on the energy of the UN tubes used and their separation from the flow tubes, as well as the susceptibility of the microorganism concerned to the particular UV radiation used. In general appropriate fluid residence times for any given apparatus can most conveniently be determined by simple trial and error on fluid samples containing contamination loadings corresponding to or exceeding those in the fluids to be treated. Actinometry can also be used to determine UV radiation dosage levels for given fluid flow residence times.

The UV radiation source tubes may be selected from low pressure UV lamps or medium pressure UV lamps. Suitable UV lamps include low pressure and medium pressure mercury lamps, for example those manufactured by Heraeus Noblelight Ltd of Bromborough, Wirral, UK (Models NNI 120/84, NNI 200/107) . In general we prefer to use low pressure lamps due to their lower cooling requirements. It will be appreciated that, particularly where lamps of higher pressure are used, it is desirable to provide the apparatus of the present invention with a cooling system to prevent over heating of the apparatus . Most conveniently there is used a forced airflow cooling system, circulating air through the matrix array. Nevertheless other cooling systems may be used in addition thereto or instead thereof, such as, for example water cooling systems. It will be appreciated, however, that where a water cooling system is used and the lamps are provided with a water jacket there will be a loss in intensity of the UN radiation that reaches the fluid to be disinfected due to the passage of the radiation through the cooling water and jacket.

Typically a plurality of fans would be provided positioned around the exterior of the multicellular matrix array preferably in the middle and near both ends thereof, in order to induce a forced air flow. Apertures may be provided in the reflector to vent warm air outwards from the apparatus and introduce cooling air into the apparatus . Preferably both fans which blow cooling air towards the apparatus, and fans which expel hot air from the apparatus, would be provided.

Desirably also the cooling system is formed and arranged to help maintain the UV radiation sources at a generally uniform temperature along their length, so as to reduce the likelihood of a temperature differential of the gas within the UN source at different positions along the length of the

UV tubes as such differentials could lead to variations in the magnitude and uniformity of the output intensity along the length of the UV radiation source.

Preferably the rotation speed of the fans is adjustable in response to a feedback system which monitors the temperature within the matrix array, in order to maintain an optimal temperature therein, typically an air temperature of around 30 to 60 °C, thereby helping to maintain optimum UV source efficiency and UN radiation intensity.

Cooling of the apparatus can be assisted by coating or painting the outer surface of the reflector in a dark colour, typically black, which has a high capacity to radiate heat energy away from the apparatus .

It will be appreciated that the hereinabove described cooling systems are an optional addition to the apparatus according to the present invention and it has been found that in practice sufficient cooling of said apparatus can be achieved by the fluid which is to be treated. As said fluid flows through the flow tubes it extracts heat energy away from the apparatus .

It is particularly advantageous to provide the apparatus with UV lamps which can be operated with a range of different currents passing therethrough. Preferably the current passing through the individual UV lamps can be adjusted. Typically the current in commercially available UV lamps can be adjusted in the range from 1A to 2A or from 2A to 3A. By incorporating such lamps in the apparatus, the current of the outer lamps of the array may be set towards the higher end of the range and the current of the inner lamps set at lower values, decreasing inwardly towards the innermost lamps of the array which would be set at the lowest current used in the array. Such an arrangement would mean that the inner regions of the matrix array least accessible to cooling would tend to generate less heat while those outer regions more readily cooled could have their UV radiation intensity maximised.

Desirably the apparatus is also provided with UV radiation monitoring means . Various forms may be used including on the one hand solid state detector devices and on the other hand actinometric techniques. Advantageously any such devices are formed and arranged for monitoring UV radiation transmitted through flow tubes, whereby there may be simultaneously detected any reduction in UV radiation source output and any formation of deposits inside the flow tubes. Preferably the devices should be formed and arranged for monitoring all of the UV radiation source tubes and all of the flow tubes, in order to ensure the proper treatment of the whole fluid flow through the apparatus .

The apparatus of the present invention can be used in a fluid treatment system in conjunction with various other water treatments, including for example membrane filters which are routinely used in fluid treatment plants and well known in the art .

In a further aspect the present invention provides a method of treating a fluid, especially water, comprising the steps of: a) providing an apparatus according to the present invention; and b) passing said fluid through said flow tubes and irradiating it with UN irradiation from the UV radiation source tubes of said apparatus .

The present invention also extends to water which has been treated using an apparatus of the present invention.

Since the UN tubes are essentially independent of the flow tubes, the tube support structure may be formed and arranged so that the flow tubes may be withdrawn from the multicellular matrix array, either individually or as greater or lesser matrix sub-arrays, for the purposes of cleaning the flow tubes and removing any deposits therefrom. (It should of course be appreciated that although the arrangement of the flow tube and UV tube matrix array has been defined in terms of cellular units each containing a plurality of UV tubes and flow tubes, the actual construction does not need to be built up on a cellular basis) . Alternatively the flow tubes may be provided at each end with one or more releasably connected manifold units for connecting respective ends of the flow tubes to an untreated fluid supply conduit (s) and to a treated fluid delivery conduit (s), so that disconnection of the manifold (s) at one or both ends will provide access to the tube interior for cleaning purposes. In a preferred arrangement the input and output manifolds may be moved outwards away from the flow tubes and, conveniently, the flow tubes therebetween and disconnected manifolds may be moved transversely relatively to one another to provide access to the flow tubes . Various cleaning methods may be employed but mechanical cleaning devices such as one or more of scrapers, brushes, wire brushes or brushes with tips of steel wool, are generally preferred. Most conveniently there is used a multiple cleaning device matrix array having a geometry corresponding to that of the flow tubes so that several or all of the flow tubes can be cleaned simultaneously. It will also be appreciated that whilst cleaning may generally be most simply and conveniently effected by axial displacement of cleaning devices along the length of the flow tubes, there may also be used rotational displacement, conveniently helical displacement, of the cleaning devices inside the flow tubes, for cleaning thereof. Preferably there are used substantially porous cleaning devices in order to avoid excessive pressure build-up inside the flow tubes when they are displaced along the length of the flow tubes. It may also in any event be advantageous to provide the flow tubes with pressure relief valves - especially where the flow tubes are of a material such as quartz which has a limited capability for resisting explosive pressure. Further details of suitable cleaning arrangements are illustrated below in the detailed description of preferred embodiments.

Further preferred features and advantages of the present invention will appear from the following detailed description given by way of example of some preferred embodiments illustrated with reference to the accompanying drawings in which:

Fig. 1 is a cross sectional view of a hexagonal shaped matrix array of UV tubes and flow tubes for an apparatus according to one embodiment of the present invention; Fig. 2 shows an equilateral triangular cell unit which is used to determine the length of the sides of equilateral triangular cell units of the hexagonal shaped matrix of Fig.

1;

Fig. 3 shows a reflector and cooling system for the matrix array shown in Fig. 1;

Fig. 4 is a perspective view of a multimodular apparatus according to the present invention;

Fig. 5 is a partial perspective view (with some parts omitted for clarity) of an alternative multimodular apparatus according to the present invention provided with a cleaning unit; Fig. 6 is a longitudinal cross section of an apparatus module provided with a cleaning unit according to another embodiment of the present invention; and

Fig. 7 is an end view of one module of the apparatus of Fig. 5 with the cleaning rod matrix array removed for clarity.

In Fig. 1 a cross sectional view of a close-packed multicellular matrix array, generally indicated by reference number 1, of parallel UV tubes 4 and flow tubes 6 of an apparatus for irradiating water to be supplied as mains waters is shown. The outer UN tubes 8 and outer flow tubes 10 define a hexagonally shaped form of the matrix array 1. The array 1 comprises nineteen UV tubes 4, each one of which is positioned at one of the vertices 12 of an equilateral triangle shaped cell unit, indicated by the dashed triangle 14 and shown in Fig 2. The array 1 has forty-two flow tubes

10, each one of which is positioned midway between two of the UV tubes 4 at the vertices 12 of the triangular cell units 14. Water 15 to be disinfected by UV radiation, flows through the flow tubes 6.

The UV tubes 4 have an inner radius of 8mm and the dimensions of the matrix array 1 are based on this measurement and that of the chosen diameter of the flow tube 6. It will be appreciated that different dimensions will be appropriate for different flow tube 6 and UV tube 4 diameters. The flow tubes 6 in the illustrated embodiment have an outer radius of 17.5mm. An inner flow tube 16 is shown receiving UV radiation emanating from the four UV tubes 18 immediately surrounding it. The widest beams of UV radiation falling on the inner flow tube 16 whose paths are not interrupted by other flow tubes in the array, are indicated by lines with an arrowhead. It will be appreciated that UV radiation will be emanating from the UV tubes 4 in all directions and other radiation paths which are not specifically shown will also be present . It can be seen that the entire circumference of flow tube 16 has directly incident UV radiation falling on it, thus the water 15 flowing through the flow tube is irradiated from all directions with UV radiation. This is achieved by positioning the centres 20 of the UV tubes 4 at the vertices 12 of the equilateral cell unit 14, which vertices are spaced apart by 103.5mm, this separation (indicated at a in Fig. 2) being determined on the basis of standard trigonometrical calculations.

Fig. 3 shows a cross-sectional view of a multi-cellular matrix array 1, as described in Fig. 1 and indicated in outline by the hexagon, which is provided with a cylindrical reflector 26 of circular cross section and fans 28 positioned around the circumference of the reflector 26.

The hexagonal matrix array 1 in which nineteen UV tubes 4 and forty-two flow tubes 6 are arranged in this way has a first axis of symmetry h passing through opposing vertices 30^a, 30° of the matrix array 1 which is equal in length to four of the sides of the equilateral triangular cell unit 14, i.e. 414.00mm, and a second axis of symmetry v, orthogonal to axis of symmetry h, which bisects opposing sides 32^a, 32^b of the matrix array 1, the length of which is equal to four times

^3/2 times the length of the side of the equilateral cell unit 14, i.e. 358.53mm. The ratio of y:h is equal to 0.866.

The reflector 26 has a diameter D equal to 574mm. The inner surface 34 of the reflector 26 is of polished aluminium and reflects UV radiation (not shown) emanating outwardly of the hexagonal matrix array, from the outer UN tubes 8, back towards the outer flow tubes 10, to provide the outermost portion 36 of the outer flow tubes 10 with UN radiation. In this way the outer flow tubes 10 receive UV radiation incident around their entire circumference, of intensity sufficient to. disinfect water 15 flowing through them.

The fans 28 are spaced circumferentially, an equal distance apart, around the outside of reflector 26. Three fans 28 are positioned along the length of each of the six longitudinally extending, faces of the hexagonal matrix array 1. The fans 28 positioned along adjacent longitudinally extending faces of the hexagonal matrix array 1 are staggered with respect to those of the adjacent longitudinally extending faces such that the fans 28 along one face are positioned at different distances along the length of the reflector 26 and matrix array 1 from those along the adjacent faces.

Fans 28^a, 28°, 28^e positioned along alternate faces of the hexagonal matrix array 1 blow cooling air towards the reflector 26, which is provided with holes 38 to allow the air to penetrate through and cool the matrix array 1. The remaining fans 28°, 28^d, 28^f expel hot air from the matrix array 1 by drawing it outwardly of the matrix array 1.

Various other arrangements of cooling fans are also possible. In an alternative preferred arrangement the matrix array 1 and fans 28 shown in Fig. 3 are mounted in the apparatus so that the longitudinally extending faces 32a, 32b at opposite sides of matrix array 1 face directly downwards and upwards, respectively. The fans 28 positioned along the directly upwards facing face 32a and the upwardly inclined adjacent faces 28a, 28c are arranged to blow cooling air through the reflector 26 downwardly into the matrix array 1 and the fans at the opposite downwardly directed faces 28d, 28e, 28f at the lower half of the apparatus, are arranged to draw air outwardly from the matrix array 1. This arrangement is designed to counteract the effect of hot air rising through the matrix array 1.

Fig. 4 shows a multimodular apparatus 50 according to the present invention for disinfecting water. The multimodular apparatus 50 comprises ten apparatus modules 52 each of which comprises a hexagonal matrix array 1 of UN tubes 4 and flow tubes 6 as described in Figs . 1 and 2 in a rectangular housing 54 of polycarbonate to block transmission of UV light therethrough while still allowing transmission of the visible region of the spectrum. Where transmission of visible light is not deemed to be of benefit standard opaque structural materials can be used. The apparatus modules 52 are arranged in two parallel rows 56,58, each having five apparatus modules 52. The ends of the hexagonal matrix arrays 60,61 connect via an inlet and outlet chamber 62,63, respectively, to an inlet and outlet manifold 64,66, respectively.

Water is fed into the multimodular apparatus 50 via a multimodular apparatus inlet pipe 68 and flows in the direction shown by the arrows through a first inlet manifold 64^a with first multiple inlet tubes 65 leading into respective inlet chambers 62 from where it enters the flow tubes 6 of the apparatus modules of the first 56 of the two rows 56,58 of apparatus modules 52 where it is subjected to UV radiation from the UV tubes 4. The UV irradiated water flows out of the apparatus modules 52 of the first row 56 of modules 52 into the outlet chambers 63 and first outlet manifold 66^a (via respective first multiple outlet tubes 67^a) , and then into a second inlet manifold 64^b from where it enters, via second multiple inlet tubes 65°, respective inlet chambers 62 and flow tubes 6 of the apparatus modules 52 of the second row 58 of apparatus modules. The UV irradiation treatment is repeated and the treated water flows into the outlet chambers 63 and out of the apparatus modules 52 of the second row 58 into a second outlet manifold 66^b .

When the multimodular apparatus is to be cleaned or maintained, a series of valves 70 can be operated to stop water flowing through the modules 52 and the water therein drained from the modules 52. The ends of the flow tubes 6 can be disconnected from the inlet and outlet manifold chambers 62,63 and the chambers 62,63 can be slid outwards from the flow tubes along a first set of runners 72. The apparatus modules 52 can then be slid out from between the chambers 62,63 along a second set of runners 74 running along the length of the rows of modules 56,58. The ends of the flow tubes 6 can then be accessed for cleaning of their interiors, and the UV tubes 4 or flow tubes 6 can be replaced or serviced etc as required.

Fig. 5 shows an alternative embodiment of a multimodular apparatus 80 provided with a cleaning unit 82 which may be operated while water continues to flow through the apparatus modules 84. The apparatus modules are generally similar to those of Fig. 4 but for clarity the connections of the manifold pipes have been omitted.

The cleaning unit 82 comprises a matrix array 86 of longitudinal cleaning rods 88 which has a geometry corresponding to that of the flow tubes 6 of the hexagonal matrix array 1. The cleaning rods 88 have a cleaning head tip of steel wool 90 as shown in Fig. 6. For clarity only two cleaning rods 88, two flow tubes 6 and a single UV tube 4, are shown in Fig. 6. The cleaning rods 88 of the cleaning unit 82 are supported by an apertured support plate 92 within respective ones 94,97 of the inlet and outlet manifold chambers 94,95,96 and 97 of the upstream and downstream sets of apparatus modules 84^a, 84° and via sliding seal furnished openings 89 in the outermost wall 91 of the inlet manifold chamber 94, so that the geometry of the matrix array 86 of the cleaning rods 88 is aligned with that of the matrix array 1 of the flow tubes 6. The cleaning rods 88 are sized so that they can be slid into and out of the flow tubes 6 while the steel wool cleaning head 90 frictionally contacts and scrapes away accumulated residue or dirt that has collected on the interior surface 98 of the flow tubes 6, to clean the tubes.

The cleaning unit 82 shown in Fig. 5 has the cleaning rods 88 connected at the outer ends 100 thereof, so that all the cleaning rods 88 can be moved together as a single unit, to clean each flow tube 6 of the module 84 simultaneously. Alternatively as shown in Fig. 6 the individual cleaning rods 88 could be arranged to be operated independently of one another. In order to protect the flow tubes 6 against possible damage due to possible pressure increases therein during displacement of the cleaning rods 88, the outlet manifold 95 is desirably provided with a pressure relief valve 99.

Fig. 7 is an upstream end view of an upstream treatment apparatus module 84^a together with part of an associated cleaning module 94 with the cleaning rod matrix array 86 removed, whereby the flow tubes 6 may be seen via the openings 89 in the outermost wall 91 of the inlet manifold chamber 94. In the corresponding outermost end wall 102 of the apparatus module 84, there may be seen an annular series of ^{^}bowler-hat ' shaped apertures 104 with radially inwardly extending slots 106, which provide access to and mountings for a cylindrical reflector 26 made up of a series of 6 partly overlapping part-cylindrical (64° sector) segments.

Particular advantages of apparatuses according to the present invention include a capability of effectively treating water with significantly higher turbidity levels (typically up to lOx higher) than that which can be treated with existing immersed lamp systems, as well as reduced electrical power consumption - especially where low pressure UV source lamps are used.

Claims

CLAI S

1. An apparatus suitable or use in the irradiation of a fluid having an UN absorbance not greater than 0.06cm^"1 at an UV radiation wavelength of 254nm, which apparatus comprises a multiplicity of flow tubes for conducting said fluid therethrough in use of the apparatus, a multiplicity of UV radiation source tubes, and a tube support structure formed and arranged so that said UV tubes and flow tubes extend substantially parallel to each other in a close-packed multicellular matrix array made up of equilateral triangular cell units having UV source tubes at their vertices and flow tubes midway between said vertices .

2. An apparatus as claimed in claim 1 wherein UV source tubes at the outside edge of the matrix array have an arcuate shaped reflector formed and arranged for directing UN radiation received thereon, back onto such outside edge flow tubes .

3. An apparatus as claimed in claim 1 or claim 2 wherein the diameter of the flow tubes is larger than that of the UV tubes .

4. An apparatus as claimed in claim 3 wherein the flow tube diameter is from 1.5 to 3 times the UV tube diameter.

5. An apparatus as claimed in any one of claims 1 to 4 wherein the length of the triangular cell side is from 4 to 8 times the UN tube's outer diameter.

6. An apparatus as claimed in any one of claims 1 to 5 wherein the multicellular matrix array has a geometry defined by the general formulae :

F = n (3n+2) -s (3s+l) and L = (n+1) -s (s+1) , provided that 2s<n≤3s, and wherein F is the number of flow tubes, L is the number of UV tubes, n is the length of the maximum width of the matrix array for a hexagonal array and is equal to the inter-vertices separation "h" (in terms of triangular cell units) , and s is the length of the shortest side of the matrix array (again in terms of triangular cell units) .

7. An apparatus as claimed in claim 6 wherein s has a value of from 0 to 4.

8. An apparatus as claimed in claim 7 wherein s has a value of from 1 to 3.

9. An apparatus as claimed in any one of claims 6 to 8 wherein the matrix array has a v:h ratio in the range from 0.866 to 1.155, where v and h are inter-side and inter- vertices separations as defined hereinbefore.

10. An apparatus as claimed in claim 9 wherein said ratio is in the range from 0.866 to 1.01.

11. An apparatus as claimed in any one of claims 6 to 9 wherein s has a value of from 0 to 4.

12. An apparatus as claimed in claim 11 wherein s has a value of from 1 to 3.

13. An apparatus as claimed in any one of claims 6 to 12 when dependent on claim 2 wherein is provided a reflector having a diameter of from 1.2 to 2.0 v, where v has the same meaning as before.

14. An apparatus as claimed in any one of claims 1 to 13 wherein said flow tubes have walls, which have a UV transmission at 254 nm of at least 80%.

15. An apparatus as claimed in any one of claims 1 to 14 wherein said flow tubes have an internal diameter of from 20 to 60 mm.

16. An apparatus as claimed in any one of claims 1 to 15 wherein said UV radiation source tubes are selected from low pressure UN lamps and medium pressure UV lamps.

17. An apparatus as claimed in any one of claims 1 to 16 wherein is provided a forced airflow cooling system, for circulating air through the matrix array.

18. An apparatus as claimed in claim 17 wherein said cooling system is provided with a temperature control device formed and arranged for controlling operation of said cooling system so as to maintain an air temperature in said matrix array in the range from 30 to 60 °C.

19. An apparatus as claimed in any one of claims 1 to 18 wherein the tube support structure comprises input and output manifolds connected to respective ends of the flow tubes.

20. An apparatus as claimed in any one of claims 1 to 19 wherein is provided a multiple mechanical cleaning device matrix array reciprocably displaceable inside said flow tubes for cleaning thereof.

21. An apparatus as claimed in any one of claims 1 to 20 wherein the inner UV radiation source tubes are operated at a lower current than the outer ones in the matrix array.

22. An apparatus as claimed in any one of claims 1 to 21 which apparatus is coupled to another water treatment apparatus for use in combination therewith to provide a multifactorial fluid treatment.

23. An apparatus as claimed in any one of claims 1 to 22 which apparatus is provided with an UV radiation monitoring system formed and arranged for monitoring UV radiation transmitted through flow tubes, whereby there may be simultaneously detected any reduction in UV radiation source output and any formation of deposits inside the flow tubes.

24. A method of treating a fluid comprising the steps of: a) providing an apparatus according to claim 1; and b) passing said fluid through said flow tubes and irradiating it with UN irradiation from the UV radiation source tubes of said apparatus .

25. Water which has been treated using an apparatus according to claim 1.