WO2003024873A1

WO2003024873A1 - Ultraviolet water treatment apparatus with dome-shaped baffle

Info

Publication number: WO2003024873A1
Application number: PCT/CA2002/001420
Authority: WO
Inventors: Demao Wang
Original assignee: Photoscience Japan Corporation
Priority date: 2001-09-18
Filing date: 2002-09-17
Publication date: 2003-03-27

Abstract

Pipe apparatus for the treatment of water with ultraviolet radiation. The apparatus (1) has a radiation chamber (4) with an inlet (2) and an outlet (5), the inlet (2) being connected to a source of water to be treated. The radiation chamber (4) has at least one elongated radiation source (14). The inlet to the radiation chamber (4) has a dome-shaped baffle (12) oriented with the dome being axial with respect to the inlet and concave with respect to flow of water through the inlet (2) into the radiation chamber (4). The dome (12) has a plurality of apertures therein. In preferred embodiments, the apertures have a total cross-sectional area that is at least as great as the inlet cross-sectional area. The outlet may also have a dome-shaped baffle (13).

Description

ULTRAVIOLET WATER TREATMENT APPARATUS WITH DOME-SHAPED BAFFLE

Field of the Invention

The present invention relates to apparatus for the treatment of water, and especially apparatus for the treatment of water with ultraviolet radiation in which a baffle is used as a flow control device and is placed in-line with a radiation treatment zone in a pipe system. In the present invention, the baffle is a dome-shaped baffle, with the dome aligned with and concavely located with respect to the inlet flow of water into the radiation treatment zone. The apparatus may additionally have a dome- shaped baffle located at the outlet to the radiation treatment zone.

Background to the Invention

It is known to treat water with ultraviolet light to destroy undesirable bacteria and other microorganisms. To effect treatment, water is passed through a radiation chamber containing a plurality of radiation sources. The radiation chamber may be a channel in which an array of radiation sources is located or in-line in a pipe reactor.

In a pipe reactor, also known as a tube reactor, water is passed through a fluid-flow passageway, typically an annular passageway, in which there is at least one radiation source. The radiation source is normally in the form of elongated ultraviolet lamps enclosed in quartz sleeves, and is located in a radiation chamber. The radiation source may be aligned with the direction of flow of water i.e. aligned longitudinally, through the radiation chamber or extend lateral to the direction of flow of water i.e. extend across a diameter of the radiation chamber.

To be effective, a water treatment system must provide the minimum UV fluence to effect treatment of all of the water passing through the radiation chamber, and preferably does so by providing substantially equal fluence to all water passing through the radiation chamber. UV fluence is the product of the fluence rate and time of exposure, and fluence rate decreases with the square of the distance from the radiation source. The ability of ultraviolet light to treat water is affected by several factors, including the age of the lamp and the associated reduction in output, the degree of fouling of the quartz sleeve around the lamp and the clarity of the water i.e. the transmission of the ultraviolet light through the water. While steps may be taken to replace the lamp when the ultraviolet output of the lamp falls below a predetermined level and to clean the quartz sleeve around the lamp, the clarity of the water may be difficult or impossible to control. Consequently, the design of the radiation chamber of the water treatment system is important.

In any design, the fluence rate varies within the radiation chamber, and steps are required to ensure that all microorganisms in the water being treated are treated effectively. Poorly designed radiation chambers allow microorganisms in the water to pass through the radiation chamber without being subjected to minimum fluence to effect treatment of the microorganism.

If the fluid flow is parallel to the axis of the radiation source i.e. the radiation sources are oriented parallel to the longitudinal axis of the radiation chamber in the pipe treatment system, it is important to maximize turbulence or mixing in a direction lateral to the radiation source. In water with low transmission characteristics, the ultraviolet light is only transmitted for a short distance, and insufficient fluence is provided to regions in the radiation chamber that are distant from the lamp. The amount of fluence in such regions even after long treatment times would be insufficient to adequately treat the water. Turbulence effects movement of microorganisms in regions of low fluence into regions of higher fluence where treatment is more effective. In other treatment systems, the radiation lamps are oriented perpendicular to the flow of water. In such systems, control of flow rates of water in each section of the radiation chamber is more important than creation of turbulence, as the fluence is more uniform in all cross- sectional regions of the reactor. For water with high transmission of ultraviolet transmission, light is able to penetrate to regions distant from the lamp and there may be little or no need for water to be brought closer to the lamp. Retention time of water in the radiation chamber and flow rate for each volume of water entering the radiation chamber become more important factors. Prevention of regions of relatively high flow rate is important. In an ideal situation, the design of the radiation chamber would reduce the flow of water and allow for a greater retention or hold-up time in regions of the radiation chamber that have lower fluence, and increase flow rate and lower retention time in regions of the radiation chamber with higher fluence. As the fluence decreases with distance from the lamp, the retention time of the water should increase proportionately, in order to maintain the product of fluence rate and retention time i.e. fluence, at a substantially constant value.

US Patent 4 601 822 of Zamburro describes a water treatment apparatus in which fins are located in the radiation chamber to re-direct the water being treated so that the water is treated four times by the radiation source in a single pass through the apparatus. US Patent 5 503 800 of Free describes the use of projections located in the channel of the radiation chamber to induce turbulence. US Patent 5 846 437 of Whitby et al describes the use of ring-shaped devices e.g. washers, on the lamps to increase turbulence. US Patent 5 696 380 of Cooke et al describes the use of mechanically static, fluid dynamic elements to induce turbulent flow. US Patent 5 545 335 of Sween et al describes the use of guide baffles to induce turbulent flow. US Patent 5 352 359 of Nagai et al describes the use of mixing baffles plates to effect flow at right angles to the radiation sources. Published application WO 01/25154 of Taghipour et al describes a water treatment device with a fluid inlet having a cross- sectional area less than the cross-sectional area of the treatment zone and a longest diameter substantially parallel to the longitudinal axis of the treatment zone. The treatment zone is transverse to the direction of flow of water. Baffles may be inserted between radiation sources in the treatment zone.

In an article entitled "Experiences with UV Disinfection at Helsinki Water" IUVA (International Ultraviolet Association) Vol. 2 No. 6 pp 4-7,29, E. Toivanen describes commercial pipe water treatment systems with a flow rate of >1000 m³/hr. Flow straighteners in the form of baffle plates with small holes were installed at both ends of the UV treatment units but caused noise problems. Larger holes were drilled, and were subsequently replaced with thicker baffles with large holes. The ultraviolet lamps are susceptible to breakage, during installation and especially if struck by a solid object during use. Screens may be placed in-line, especially at the inlet, to remove any solid objects (debris) that may be in the water passing through the system. Radiation chambers must be designed to permit replacement of lamps as required. Moreover, ultraviolet lamps tend to have a length that is greater than the diameter of the pipe system attached to the inlet and outlet to the radiation chamber, resulting in the need to for the radiation chamber to have a greater diameter than the pipe system. The flow of water must be equilibrated in such a chamber in order to obtain uniform fluence. One of the problems encountered in pipe treatment systems is that devices inserted to effect turbulence or to improve uniformity of flow and to remove any solid objects, cause a loss of pressure or create a headloss in the flow of water. In particular, devices that reduce the cross- sectional area at any point in the flow of water cause significant headloss e.g. the baffles and turbulence increasing devices described above. Uniformity of flow may also be improved by increasing the length of piping or radiation chamber, but this leads to problems in installation into existing piping systems due to space restrictions. Compact devices that are intended to remove solid objects and provide proportional treatment of water with reduced or minimal headloss would be useful.

Summary of the Invention

One aspect of the present invention provides pipe apparatus for the treatment of water with ultraviolet radiation, said apparatus comprising a radiation chamber with an inlet and an outlet, said inlet being adapted to be connected to a source of water to be treated, said radiation chamber having at least one elongated radiation source, said inlet to the radiation chamber having a dome-shaped baffle oriented with the dome being axial with respect to the inlet and concave with respect to flow of water through the inlet into the radiation chamber, the dome having a plurality of apertures therein.

In a further aspect of the apparatus of the present invention, the total cross-sectional area of the apertures is at least as great as and preferably greater than the inlet cross-sectional area. In another aspect of the invention, the apertures of the dome are of a plurality of shapes and sizes.

In a further aspect of the invention, the radiation chamber additionally has a dome-shaped baffle at the outlet to the radiation chamber, especially a dome-shaped baffle oriented with the dome being axial with respect to the outlet and convex with respect to flow of water through the outlet from the radiation chamber i.e. concave with respect to the radiation chamber.

In yet a further aspect of the present invention there are a plurality of radiation sources. Brief Description of the Drawings

The present invention is illustrated by the embodiments shown in the drawings, in which:

Fig. 1 is a schematic representation of a cross-section of a plan view of a pipe water treatment system with two dome-shaped baffles in the radiation chamber;

Fig. 2 is a schematic representation of the pipe water treatment system of Fig. 1 , through A-A;

Fig. 3 is a schematic representation of the pipe water treatment system of Fig. 1 , through C-C;

Fig. 4 is a schematic representation of an end view of a dome- shaped baffle; and

Fig. 5 is a schematic representation of a cross-section of the dome- shaped baffle of Fig. 4, through B-B.

Detailed Description of the Invention

The present invention relates to water treatment apparatus with at least one dome-shaped baffle. In particular, the present invention relates to a water treatment apparatus in the form of a pipe water treatment system with at least one radiation source, in which at least the inlet to the zone with the radiation source has a dome-shaped baffle. The dome- shaped baffle is in-line with the radiation source. The apparatus may have dome-shaped baffles at both the inlet and outlet to the zone with the radiation source. The baffle at the inlet will collect debris in the water system, and prevent the debris from reaching the radiation source where the debris could cause damage to the radiation source. However, the dome-shaped baffles of the apparatus of the invention are intended to effect turbulence in the flow of water and/or control flow of water and facilitate treatment of all microorganisms in the water. Fig. 1 shows one embodiment of pipe water treatment apparatus of the present invention, generally indicated by 1. Pipe water treatment apparatus 1 has inlet pipe 2 connected to housing 3 of radiation chamber 4, in which water is treated. Housing 3 is also connected to outlet pipe 5. In the embodiment shown, housing 3 has a greater diameter than inlet pipe 2 and outlet pipe 5, which is the preferred embodiment because of the physical requirements to house the radiation source and any associated cleaning apparatus, but housing 3 could be of the same or smaller diameter than inlet pipe 2 and outlet pipe 5. Bolts 8 attach inlet pipe 2 and outlet pipe 5 to housing 3 at inlet flange 6 and outlet flange 7, respectively. Housing 3 is formed of three parts, for convenience in use and in insertion and removal of the radiation sources, being inlet section 9, intermediate section 10 and outlet section 11 , which are held in position by flanges. Inlet dome-shaped baffle 12 is attached at inlet flange 6, with the dome being concave with respect to radiation chamber 4. Similarly, outlet dome-shaped baffle 13 is attached at outlet flange 7, with the dome being concave with respect to radiation chamber 4. Thus, both inlet dome- shaped baffle 12 and outlet dome-shaped baffle 13 are oriented with their domes facing into the radiation chamber i.e. the dome-shaped baffles are both concave with respect to the radiation chamber, and consequently in . opposite orientations with respect to each other. The dome-shaped baffles are further described below.

It is understood that the apparatus of the invention may have only one dome-shaped baffle, being inlet dome-shaped baffle 12, although it is preferred that the apparatus have both inlet dome-shaped baffle 12 and outlet dome-shaped baffle 13.

Intermediate section 10 of radiation chamber 4 of pipe water treatment apparatus 1 has radiation source 14. In the embodiment illustrated, the radiation source is oriented lateral to the direction of flow of water through the radiation chamber. Radiation source 14 has an ultraviolet lamp 15 with quartz sleeve 16, as is known for such radiation sources. In the embodiment shown, radiation source 14 has cleaning device 17 attached to drive motor 18. Cleaning device 17 is adapted to traverse radiation source 14 using guide 19 located on guide bar 20. It is understood that a variety of cleaning devices could be used to clean the radiation source. Although only one radiation source is apparent in Fig. 1 , a plurality of radiation sources would normally be used, for example as seen in the view of Fig. 2. Fig. 2 shows an end view of pipe water treatment apparatus 1 , at

A-A. Apparatus 1 has four radiation sources, 14A-D, that extend across radiation chamber 4 and terminate at each end in a lamp housing. Radiation chamber 4 is shown as having a square cross-section, which is convenient, but other cross-sectional shapes may be used. Dome- shaped baffle 12 is shown as having baffle flange 21 and inner section 22. Drive motor 18 of cleaning device 17 is connected to shaft 23, which connects at guide 19 to cleaning units 24 located on each quartz sleeve 16 of radiation sources 14A-D. Guide bars 20A and 20B guide the movement of cleaning units 24, to reduce the possibility of damage to the radiation sources during cleaning. The use of cleaning systems for radiation sources in pipe water treatment systems, and elsewhere, is known.

Fig. 3 shows a view of pipe treatment apparatus 1 , at C-C. Fig. 3 also shows the presence of deflector vanes 25A and 25B, which are optional but if used aid in the turbulence generated within radiation chamber 4.

Each of the dome-shaped baffles has a plurality of holes, and in preferred embodiments has holes with a total cross-sectional area that is at least equal to and especially greater than the cross-sectional area of inlet pipe 2 and outlet pipe 5, respectively. Moreover, the holes may be of different sizes so as to direct the flow of water throughout radiation chamber 4 in a manner to facilitate treatment of all microorganisms by equalizing the fluence. The holes sizes, variation and distribution of holes and hole sizes and location of holes of different sizes are all factors in directing the flow of water towards the lamps and the generation of turbulence. Such factors would be expected to vary depending on the particular piping system and radiation chamber, and the rate of flow of water.

An end view of a dome-shaped baffle is shown in Fig. 4. It will be noted that in the embodiment shown the holes form a plurality of concentric circles and moreover the holes are aligned. For instance, the holes 26 are substantially annular, extending around the baffle. Holes 27 form a second annular alignment. Moreover, the holes indicated by 28 are aligned towards the centre of the baffle. Such an array of holes is convenient, but other arrangements may be used. It is preferred to have a substantially close-packed array or holes, or other arrangement, especially tc maximize the surface area of the holes, whereby the surface of the dome is substantially covered in holes while maintaining structural integrity of the dome. Such an array minimizes the head loss on water flowing through the dome-shaped baffle.

Fig. 5 shows a cross-section of a dome-shaped baffle. The baffle has a flange, 21 , for attachment of the baffle to the pipe system. The baffle is also shown with a cylindrical section 30 and a curved section 31. The relative amounts of the cylindrical section and curved section may be varied, primarily depending on the dimensions of the radiation chamber and the provision of a surface area of holes that is greater than the surface area of inlet pipe 2.

In order to provide a dome with holes having an area that is at least as great as the cross-sectional area of the pipe, and maintain structural integrity of the dome-shaped baffle, it is expected that the dome would need to extend into the radiation chamber by a distance that is at least 0.5 times the diameter of the pipe. In embodiments of the invention, the dome extends into the radiation chamber by 0.5-1.5 times the diameter of the pipe inlet. The sizes of the holes may vary with the type of radiation source, especially the orientation of the lamps in the radiation chamber. For instance, if the radiation source is a single radiation source oriented longitudinally i.e. in the direction of flow of water, the dome-shaped baffle may have larger holes towards the longitudinal axis and smaller holes away from the axis. If the radiation source is in the form of a pair of lamps oriented at right angles to each other and lateral to the flow of water, the holes could be larger in planes corresponding to the planes of the crossed lamps and smaller out of the planes of the lamps. However, other variations of hole patterns could be used. The holes would normally be circular, for ease of manufacture, but other shapes could be used.

As noted above, in embodiments of the invention, the radiation chamber additionally has a dome-shaped baffle at the outlet to the radiation chamber. It is preferred that the outlet dome-shaped baffle be oriented with the dome being axial with respect to the outlet and convex with respect to flow of water through the outlet from the radiation chamber i.e. concave with respect to the radiation chamber.

The present invention provides improvements in the flow of water through the radiation chamber of a pipe water treatment system, to improve uniformity of fluence and/or to control flow of water through the radiation chamber, and does so with reduced loss of pressure or reduced headloss in the system. The dome-shaped baffles will not require maintenance or will require minimal maintenance. In addition, the dome- shaped baffles are compact and are readily installed, including in existing pipe water treatment systems. Uniformity of fluence and turbulence in the flow may be obtained. The improvements in flow of water make the water treatment apparatus more effective in the ability of the apparatus to effect treatment of all microorganisms entering the radiation chamber.

Claims

CLAIMS:

1. Pipe apparatus for the treatment of water with ultraviolet radiation, said apparatus comprising a radiation chamber with an inlet and an outlet, said inlet being adapted to be connected to a source of water to be treated, said radiation chamber having at least one elongated radiation source, said inlet to the radiation chamber having a dome-shaped baffle oriented with the dome being axial with respect to the inlet and concave with respect to flow of water through the inlet into the radiation chamber, the dome having a plurality of apertures therein.

2. The pipe apparatus of Claim 1 in which said apertures have a total cross-sectional area that is at least as great as the inlet cross-sectional area.

3. The pipe apparatus of Claim 1 in which the total cross-sectional area of the apertures is greater than the inlet cross-sectional area.

4. The pipe apparatus of Claim 1 in which the apertures of the dome are of a plurality of shapes and sizes.

5. The pipe apparatus of Claim 1 in which the radiation chamber additionally has a dome-shaped baffle at the outlet to the radiation chamber.

6. The pipe apparatus of Claim 5 in which the dome-shaped baffle at the outlet to the radiation chamber is oriented with the dome being axial with respect to the outlet and concave with respect to the radiation chamber.

7. The pipe apparatus of Claim 6 in which said apertures have a total cross-sectional area that is at least as great as the inlet cross-sectional area.

8. The pipe apparatus of Claim 6 in which the total cross-sectional area of the apertures is greater than the inlet cross-sectional area.

9. The pipe apparatus of Claim 6 in which the apertures of the dome are of a plurality of shapes and sizes.

10. The pipe apparatus of Claim 1 in which there are a plurality of radiation sources.