UV APPARATUS

Abstract

UV apparatus comprises a tube (1) of UV transparent material, at least one UV lamp (5) provided externally of the tube so as to emit UV light towards the tube, and a core (3) extending in an axial direction within the tube and configured to create turbulent flow in a liquid passing through the tube. A photocatalyst is provided on at least one surface of the core and is responsive to UV light emitted by the lamp to generate free radicals in liquid passing through the tube.

Claims

1. UV apparatus comprising: a tube (1) of UV transparent material; at least one UV lamp (5) provided externally of the tube so as to emit UV light towards the tube; and a core (3) extending in an axial direction within the tube and configured to create turbulent flow in a liquid passing through the tube, a photocatalyst being provided on at least one surface of the core and responsive to UV light emitted by the lamp to generate free radicals in liquid passing through the tube.

2-43. (canceled)

Description

[0022] FIG. 1 is a diagrammatic cross-sectional view through one embodiment of a UV apparatus according to the present invention;

[0023] FIG. 2 is a diagrammatic elevational view of the UV apparatus shown in FIG. 1 together with ancillary equipment;

[0024] FIG. 3 is a cross-sectional view through a UV apparatus according to the present invention and incorporating a plurality of tubes operating in parallel;

[0025] FIG. 4 illustrates a modification of the apparatus of FIG. 3, in which two tubes are arranged in parallel and operated sequentially; and

[0026] FIGS. 5, 6 and 7 illustrate a modification of the apparatus of FIG. 2 by providing means for introducing and removing photocatalytic beads into and from liquid being treated in the apparatus.

[0027] The UV apparatus shown in FIG. 1 comprises a tube 1 of UV transparent material, such as quartz or a UV transparent polymer, which typically has a length of about 600 to 1200 mm and a diameter of about 20 to 100 mm, although other dimensions are possible. A liquid to be treated passes through the tube 1. In practice, the liquid is pumped from a source of contaminated liquid, through a coarse filter (not shown), through the tube 1 and is then returned to the source, although other arrangements may be employed, such as passing the treated liquid to an alternative destination. A core 3 is provided within the tube 1, the core extending in the axial direction of the tube, and is configured to create turbulent flow in liquid passing through the tube as will be explained in more detail hereinafter. The core 3 is typically made of a ceramic, plastics or metal material and is configured to create a vortex in the liquid flowing through the tube 1 such that, in use of the apparatus, different portions of the liquid are continually presented at the inner surface of the tube. UV light is provided by a plurality of UV lamps 5 and reflectors 7 are provided where necessary to reflect UV light emitted from the lamps in a direction other than towards the tube 1 back towards the tube 1. Alternatively, reflectors may be incorporated into the lamps 5 to create a directional profile to the emitted UV light. The lamps 5 are spaced around the circumference of the tube 1 (for example, four lamps may be provided spaced substantially equally around the circumference of the tube) and extend in the axial direction of the tube 1, substantially along the length thereof and each lamp as illustrated may be a single lamp extending substantially the entire operative length of the tube or may be in the form of a plurality of lamps in an axial configuration. Clearly, other arrangements are possible for the lamps.

[0028] Ideally, the lamps 5 emit substantially monochromatic radiation at a frequency of 254 nm. This eliminates as far as possible, contamination with infrared radiation so minimising the generation of heat and avoiding the need for a cooling fan (although a cooling fan may be provided if required). The substantial elimination of infrared radiation also increases the effectiveness of the lamps by increasing the overall output of UV light.

[0029] The reflectors 7 are ideally configured to focus light onto the inner surface of the tube 1.

[0030] The tube 1 and the core 3 are dimensioned in the illustrated embodiment such that the surface of the core is some 3 to 15 mm from the inner surface of the tube, for a 50 mm internal diameter tube.

[0031] The core 3 is provided, at least on the surface thereof, with a catalyst. The catalyst may be in the form of a coating or may be incorporated into the material of the core. The catalyst is in the form of a photocatalyst, such a titanium dioxide, which has the effect of splitting water in the liquid to form active oxidising radicals, the radicals in turn killing the bacteria or the like. It has been found that the UV light dose required to activate the catalyst is much lower than the dose required to kill the bacteria, so that UV penetration in a cloudy liquid is sufficient to activate the catalyst and to kill bacteria or the like in the body of the liquid even where the dose of UV is insufficient to do so alone. For example, it has been found that a titanium dioxide catalyst requires only 0.001 Watts per square metre for the catalyst to generate DNA-disrupting hydroxyl free radicals. This is a factor of 10.sup.5 less than that required at the inner surface of the tube 1 for killing the bacteria or the like. Moreover, individual portions of the liquid are only exposed to a sufficient direct dose of UV light on a transient basis during its turbulent flow through the tube, while the catalyst on the core 3 is permanently exposed to the UV light and is therefore receiving UV radiation and generating free radicals at all times the UV lights are energised. Thus, the combination of direct UV radiation and UV activation of the catalyst is particularly effective in cloudy liquids and allows purification at substantially higher throughput rates compared with only direct UV radiation. If the liquid is especially optically dense and therefore significantly reduces penetration of UV light, means may be provided such that the flow of liquid through the tube is intermittent, for example pulsed, so that the photocatalyst is intermittently uncovered and therefore exposed directly to the UV light. The burst of energy received by the photocatalyst is sufficient that it remains active for several seconds, until the flow is again interrupted. Overall, it has been found that the use of a photocatalyst increases the rate at which the DNA of bacteria is disrupted by more than 50% compared with the use of direct UV alone.

[0032] In more detail, the photocatalyst may be nano-crystalline titanium dioxide, although other photocatalysts, such as zinc oxide, may be employed, either alone or in combination. Where titanium dioxide is used, this is generally in the form of nano-crystalline titanium dioxide in its anatase form which is either added to the material of the core as a powder or formed into a coating by the addition of a binder and applied, for example by spraying or dipping, onto the outer surface of the core.

[0033] In general, the larger the internal diameter of the tube 1 the greater the volume of liquid that may be disinfected in a certain time. Moreover, subject to maintaining the required turbulence, the larger the diameter of the tube the greater the surface area of the core 3 that can be accommodated within the tube. This increases the surface area of the catalyst with a corresponding increase in the performance of the apparatus.

[0034] Where the tube 1 is of relatively small diameter, say about 25 mm or less, the core 3 may be in the form of an open coil with reversals to disturb liquid flow without restricting flow. In larger diameter tubes the core 3 may be a solid helical coil with reversals while still allowing sufficient free cross-sectional area for high flow rates of liquid. The solid helical coil may be a simple helical spring or a solid coil of plastics, concrete or metal. In at least one embodiment, at each complete revolution the flow of liquid in the coil is reversed and turbulence is created. This creates an ever changing thin film of liquid at the inner surface of the tube, and also helps to maintain the inner surface of the tube clean and free of patches of grime.

[0035] FIG. 2 shows the UV apparatus, including the tube 1, core 3 and lamps 5 together with a source 9 of contaminated liquid and a pump 11 for circulating the liquid. A non-return valve 13 is provided to prevent liquid returning from an inlet of the tube 1 to the pump 11 or source 9. A valve 15, such as a solenoid valve, may be provided to direct liquid exiting the tube 1 either to the source 9 or to an optional part of the additional apparatus including a source 17 of cleaning liquid for receiving treated liquid, and a further pump 19 for circulating the cleaning liquid to the tube 1.

[0036] The configuration of the core 3 in the illustrated embodiments is such that the liquid passing through the tube alternately rotates in an anti-clockwise direction for about a centimetre and then rotates in a clockwise direction for a similar axial distance. Clearly the distance between alternate directions may be altered, especially in dependence upon the scale of the apparatus. The alternating flow directions create a series of vortices with massive turbulence thereby continually presenting different portions of the liquid at the inner surface of the tube. It has been found in practice that it is preferred to provide at least six flow reversals along the length of the tube 1. The core has been found to create fluid forces which keep the surface of the tube 1 clean and therefore free of adherent materials which would normally form an impervious filter for the UV light. This either eliminates or substantially reduces the need for chemical flushing of the tube to remove adherent materials.

[0037] Although the turbulent flow of the liquid effects cleaning of the inner surface of the tube 1, this is not always sufficient, especially when the heat produced by the UV lamps tends to char constituents of the liquid. To help maintain the inner surface of the tube 1 clean, the cleaning fluid may be circulated periodically, for example for a short period each day or more frequently (such as hourly) if required. The cleaning fluid may incorporate abrasive particles if desired.

[0038] In practice the flow rate of the liquid through the tube is such that the liquid is exposed to the UV light for a time in the range of 1 to 10 seconds.

[0039] The intensity of UV light at the point of the tube 1 where it can be effective is in the range of 140 to 300 Watts per square metre for each lamp 5. The cross-over of light from the four lamps 5 shown in FIG. 2 will increase the intensity. The dose range (powertime) to kill with UV only is in the range of 10 to 100 Watts per square metre per second for most bacteria in clear water, while moulds may require 100 to 600 Watts per square metre per second.

[0040] FIG. 3 shows an arrangement in which the UV apparatus includes a plurality of tubes 1. As illustrated, the tubes 1 are arranged in parallel in a substantially straight line array, but other configurations are possible. Each tube is provided with a core 3 and a plurality of lamps 5 are arranged around the array of tubes (although, if desired the lamps could also be arranged within the array of tubes). The lamps 5 are surrounded by a single reflector 7 in the form of a reflective inner surface of a container for the apparatus, although again a different reflector arrangement can be used if desired. Although arranged in parallel, the tubes 1 may be connected either in series or in parallel, either to maximise the disinfecting effect or to maximise throughput.

[0041] FIG. 4 shows an apparatus which is particularly useful where the liquid is especially optically dense. In this case, two tubes 1 are arranged in parallel (although more than two tubes may be so arranged of desired) and are provided with valves 21, 23 at each end. Valves 21 provided at the inlet of the tubes 1 may be solenoid valves and operate to allow liquid to enter one of the tubes at a time. Valves 23 provided at the outlet of each of the tubes 1 are non-return valves and serve to prevent treated liquid flowing back through either of the tubes. The two tubes are operated sequentially, with each tube emptying in turn to reveal the catalyst to the UV light. Once the core 3 has been exposed to the required dose of UV light, the valves 21 are switched so that the liquid flows through the tube with the active catalyst. The cycle time may be, for example, from 1 to 15 minutes.

[0042] FIGS. 5, 6 and 7 show an apparatus in which photocatalytic beads may additionally be introduced into, and removed from, the liquid being treated. As shown in FIG. 5, the apparatus includes a valve 25 for introducing beads into a bead flow circuit and a pump 27 for circulating the beads through the tube 1. The beads may be of ceramic, plastics or metal and may incorporate or be coated with the same or a different photocatalyst as that used in conjunction with the core 3. The beads provide additional sites for the generation of free radicals and assist in maintaining the inner surface of the tube 1 clean, while preferably circulating only in a limited part of the apparatus. As shown in more detail in FIGS. 6 and 7, the beads 29 may be introduced upstream of the inlet to the tube 1 by way of a Venturi arrangement 31 and may be removed from the liquid downstream of the outlet of the tube, by way of a slanting grid 33 which is dimensioned to restrain and divert the beads back to the pump 27.

[0043] Alternatively or additionally, means may be provided for injecting a chemical, such as hydrogen peroxide, into the fluid stream. The chemical, under the influence of the UV lamps, increases the density of aggressive chemical radicals in the fluid stream. This can be of particular use in the treatment of waste water to reduce Carbon Oxygen Demand (COD) and Biological Oxygen Demand (BOD).

[0044] It has been found that the apparatus according to the present invention is particularly useful in the control of bacteria in metalworking fluids, cloudy water, and in sensitive environmental areas such as open sea drilling.