GB2570818A

GB2570818A - UV reactor

Info

Publication number: GB2570818A
Application number: GB1905556.5A
Authority: GB
Inventors: Dragos Ciordas Ioan
Original assignee: Cathelco Ltd
Current assignee: Cathelco Ltd
Priority date: 2016-03-16
Filing date: 2016-03-16
Publication date: 2019-08-07
Anticipated expiration: 2036-03-16
Also published as: GB201905556D0; GB2570818B

Abstract

A UV reactor 102 for use in a water treatment system comprises a flow chamber 104 having a longitudinal axis, an input 106 for entry of water into the flow chamber and an output 108 for water to exit the flow chamber. The UV reactor comprises at least one UV lamp 110 comprising a length which is provided in the direction of the longitudinal axis of the flow chamber, wherein water flowing in the flow chamber can be exposed to UV radiation. The UV reactor also comprises at least one baffle 114 provided within the flow chamber and configured to impede water flowing along the flow path. The baffles are provided as a plurality of groups of baffles positioned along the longitudinal axis of the chamber, wherein each group comprises two or more baffles provided at the same distance along the longitudinal axis, and wherein axially adjacent groups are angularly offset from each other about the longitudinal axis. Suitably, the input comprises a tapered pipe 106a, such that the cross sectional area of the input pipe gradually reduces along the length of the pipe, the end of the pipe having the smallest cross-sectional area being coupled to the flow chamber.

Description

FIELD OF THE INVENTION

The present disclosure relates to a UV reactor for a water treatment system. More particularly, the present invention relates to a UV reactor for a ballast water treatment system.

BACKGROUND OF THE INVENTION

Cruise ships, large tankers, and bulk cargo carriers use marine water as a ballast to provide increased stability. Water is often taken on in one coastal region, for example after the unloading of cargo, and is then discharged in another coastal region, for example at the next port of call.

A large number of organisms and pathogens are present in sea water, and the transportation of this sea water in the ballast tank from location to location can introduce non-native species to new environments and cause the spread of harmful or invasive organisms. Due to this, it is of great importance to render organisms non-viable in the ballast water whilst it is stored on the ship prior to being discharged at a subsequent location.

According to the US Coast Guard Ballast Water Standard, for organisms having a size of 50 micrometers or greater, water containing less than 10 organisms per cubic meter can be discharged. Whereas for organisms having a size of 10 micrometers or greater, but less than 50 micrometers, water containing less than 10 organisms per milliliter may be discharged.

Water treatment systems using chemical treatments are known in the art. However, such methods are not desirable. Non-chemical treatment systems are beneficial as they ensure that no chemicals which could be harmful to the sea environment are released into the sea. Further to this, it is beneficial to remove chemical handling from taking place on board the ship.

Water treatment systems using filtration and ultraviolet (UV) radiation are generally known in the art. Such UV systems generally comprise a UV reactor for treating water.

Embodiments described herein are intended to provide an improved UV reactor for treatment of ballast water.

SUMMARY OF THE INVENTION

In a first aspect a UV reactor for use in a water treatment system is provided, the UV reactor comprising:

a flow chamber having a longitudinal axis;

an input for entry of water into the flow chamber and an output for water to exit the flow chamber, wherein the UV reactor is arranged such that water can flow along a flow path from the input to the output via the flow chamber;

at least one UV lamp, comprising a length which is provided in the direction of the longitudinal axis of the flow chamber, wherein water flowing along the flow path can be exposed to UV radiation as it flows from the input to the output; and at least one baffle provided within the flow chamber and configured to impede water flowing along the flow path.

UV reactors described herein are designed to treat ballast water by applying UV radiation to water passing through the reactor, thereby killing or rendering non-viable organisms present in the water. In order to achieve effective water treatment, an optimal distribution of UV dosage across water flowing through the UV reactor is required. It is an aim of the present invention to provide a more even distribution of UV radiation to water passing through the reactor, hence minimising the variation (e.g. the standard deviation) of UV radiation applied to organisms present in the water.

UV dosage within the reactor can be expressed as a function of UV power received by a given particle in the water and the duration of exposure to UV radiation. An even distribution may be achieved by controlling the flow velocity of water passing through the reactor. Water flowing through regions of the UV reactor that are exposed to a relatively low intensity of UV radiation may be slowed down. By slowing down the flow in these regions, the duration of exposure to UV radiation is increased, and so the UV dosage received is also increased. Conversely, water flow velocity in regions of the UV reactor that are exposed to a higher intensity of UV radiation may be increased to reduce over-exposure to UV i.e. exposure above that necessary to kill micro-organisms present in the water. By controlling the flow velocity through the UV reactor in this way, the application of an even UV dosage across the UV reactor is facilitated. This results in a UV reactor which is more efficient in treating water flowing through the reactor.

UV reactors described herein are arranged to impede water flow and preferably induce helical flow of the ballast water to optimise water carried organism exposure to UV radiation, thereby facilitating the application of an even UV dosage. This will now be described in more detail.

As water flows through the flow chamber it will tend towards laminar flow. In other words, water flowing through the centre of the chamber will tend to remain substantially at the centre, and water flowing in the region of an outer wall of the chamber will tend to remain substantially adjacent the outer wall. UV power from the lamp decreases exponentially with distance, therefore water flowing adjacent the UV lamp will be exposed to a much higher amount of radiation compared to water flowing through areas of the reactor away from the UV lamp. Consequently, it may be that not all water flowing through the reactor will receive the same UV dosage, resulting in uneven treatment of the water.

By impeding the flow of water along the flow path, exposure of the water carried organisms to UV radiation in these impeded regions can be increased. Therefore, water flowing through the reactor as a whole can receive a more even UV dosage.

It will be understood that the term 'flow path' is understood to mean a route through the flow chamber along which water can flow as it travels from the input to the output.

In some embodiments, the at least one baffle is provided adjacent a side wall of the flow chamber, for example an outer wall of the flow chamber. In some embodiments, the at least one baffle extends from a side wall, for example an outer wall, of the flow chamber.

Depending on the precise placement of the UV lamp, water flowing along the side wall or outer wall of the chamber is more likely to be at the greatest distance from the lamp compared with other locations in the chamber, therefore water in this region is more likely to receive a lower UV dosage. By providing at least one baffle adjacent the side wall or outer wall of the flow chamber, water flowing from the inlet to the outlet via the region of this baffle is slowed down and preferably encouraged to follow a longer, helical, trajectory through the flow chamber. This increases the duration for which particles in water flowing close to the side wall or outer wall are exposed to UV radiation and hence increases the UV dosage in these regions, whilst not impeding the flow of water in regions exposed to a relatively high UV intensity e.g. close to the or each lamp. This facilitates the provision of a more even UV dosage across the body of water flowing through the flow chamber. This provides more reliable and efficient water treatment. This also enables the use of a shorter length of UV reactor since water exposed to a lower amount of UV radiation is slowed down as it travels through the reactor, therefore increasing the UV dosage received in a shorter length of reactor.

The flow velocity of water travelling in regions of high UV exposure, e.g. those regions in which flow is not impeded, can be increased, provided that a minimum UV dosage is achieved. This ensures that only the required UV dosage is applied i.e. reducing the application of an unnecessarily high dose, and hence results in a more efficient water treatment.

In some embodiments, the UV reactor comprises a plurality of UV lamps.

By increasing the number of lamps in the UV reactor, the UV power transmitted to the water passing through the reactor is increased. Consequently, the required UV dosage is more likely to be achieved. In addition, by increasing the UV power transmitted, a shorter exposure time to the radiation is required in order to achieve the necessary UV dosage. Consequently a flow chamber having a shorter length may be used.

The required UV dosage will depend on the type and number of organisms present in the water. For example, for Bacilosubtilis, a dose of 400 J/m² would be desirable to kill 99% of organisms. Other organisms may require a different UV dosage, as will be understood by those skilled in the art.

A shorter flow chamber is advantageous for maintaining a helical flow of water, since it is easier to maintain a helical flow over a shorter distance.

In addition, a shorter UV reactor means that shorter UV lamps may be used. These have lower individual power requirements which require simpler, more commonly available power electronics systems to drive them. The electrical power systems required to drive these shorter lamps are easier to cool and so do not require additional air conditioned cooling units, but rather can simply be air cooled. Shorter UV lamps are also more easily replaced since less space is required to do so.

A shorter flow chamber has the advantage of occupying a smaller length of space, which is particularly important on a ship where space is at a premium. A shorter UV reactor can also be mounted vertically which can be preferable in order to align with existing pipework.

Additional UV lamps in the flow chamber may require the flow chamber to have a larger cross sectional area. Increasing the cross sectional area of the chamber has the effect of decreasing the flow velocity through the reactor. Water flowing through the reactor is therefore exposed to UV radiation for a longer duration, cancelling out the loss in exposure time due to lower exposure trajectory length again resulting in the advantage that a shorter reactor can be used whilst maintaining the desired UV dosage.

In some embodiments, the UV reactor comprises four UV lamps.

In some embodiments 2-6 lamps may be used, for example, 2, 3, or 5 lamps may be used.

In some embodiments, the UV reactor comprises six UV lamps.

The use of six lamps may be preferable where a higher UV dosage is required. For example, the use of six lamps instead of 4 lamps may result in an approximately 50% increase in the average UV dosage applied to water carried organisms.

In some embodiments more than six lamps may be used.

For example 2-10 lamps, for example 4-8 lamps may be used. For example, 7, 8, 9 or 10 lamps may be used.

In some embodiments a series of baffles is provided.

In some embodiments a single baffle may be provided, for example, the single baffle may be helical in shape.

In some embodiments, the or each baffle comprises a respective surface extending in a direction transverse to the longitudinal axis of the chamber.

In some embodiments, the respective surface of the or each baffle is orthogonal to the longitudinal axis.

In some embodiments, the respective surface of the or each baffle is at an angle of between 0° and 90° to the longitudinal axis.

In some embodiments, the surface of a first baffle is provided at a different angle to the longitudinal axis compared to the surface of a second baffle. The first and second baffles may comprise a pair of baffles or may comprise axially adjacent baffles, for example.

In some embodiments, baffles are offset in the direction of the longitudinal axis of the flow chamber. In some embodiments, baffles are angularly offset about the longitudinal axis.

In some embodiments, adjacent baffles which are axially offset are also angularly offset about the longitudinal axis.

Offsetting the baffles in this manner facilitates impedance of the flow of water in regions of relatively low UV exposure and encourages a helical flow in these regions, whilst not impeding flow in the regions exposed to a relatively high UV intensity, thereby providing more even UV exposure. A helical flow is induced by obstructing the flow of water in the regions of the baffles, thereby preventing laminar flow in these regions and forcing the water to change direction to follow a more helical trajectory. Water flowing in regions of high UV intensity is not slowed down but may flow at an increased velocity to compensate for the slower, impeded flow and maintain the same overall flow rate, provided that a minimum UV dosage is achieved.

In some embodiments, adjacent baffles which are axially offset along the longitudinal axis are angularly offset 90° or by 60°.

For example, in reactors having four lamps, a 90° offset may be sufficient to provide adequate turbulence in the water flow to achieve the required UV dosage, whereas where six lamps are used, a 60° offset may be required. In some embodiments, the baffles may be offset by 30°, 45°, 60°, 90° or multiples thereof.

In some embodiments, the baffles are angularly offset by multiples of 360° divided by the number of lamps. For example, for 6 lamps the baffles may be offset by 360% = 60°, or multiples thereof. For example, for 8 lamps the baffles may be offset by 360°/8 = 45°, or multiples thereof. In some embodiments, where the lamps are provided in a regular arrangement about the longitudinal axis such that they are spaced at the same angle about the longitudinal axis, the baffles may be spaced apart by the same angle as the lamp offset angle, or multiples thereof.

In some embodiments, the baffles are provided in pairs, such that the or each pair of baffles is provided at the same distance along the longitudinal axis.

In other words, each baffle in a pair of baffles is provided at the same point along the longitudinal axis of the chamber. By providing pairs of baffles in this manner, a pair of gaps is defined between each pair of baffles. This pair of gaps defines a pair of flow trajectories along which water may flow from one pair of baffles to the next. In embodiments where adjacent pairs of baffles are axially and angularly offset with respect to the longitudinal axis, the pairs of gaps define a pair of helical flow trajectories. Accordingly, water flowing in this region is encouraged to adopt a helical flow. In some embodiments, having two helical flow trajectories has been found to be an optimal arrangement to ensure sufficient mixing of water and a reliable UV exposure.

In alternative embodiments, instead of pairs, groups of three or four baffles are provided such that the or each group is provided at a predetermined location or point along the longitudinal axis. In such embodiments, correspondingly more helical flow trajectories are defined between adjacent groups of baffles.

In some embodiments, baffles are provided at 2, 3 or more locations in a direction along the longitudinal axis. For example, between 4 and 10 locations, between 6 and 8 locations, at 7 or 8 locations. For example, pairs or groups of baffles may be provided at 7 or 8 points along the longitudinal axis, so to provide sufficient flow control.

In some embodiments, the or each baffle is shaped to correspond to at least a portion of an area of chamber which is greater than a predetermined distance away from the or each UV lamp.

In this way, the or each baffle occupies a space in which UV exposure is likely to be below a given amount in which, were baffles not provided, water flowing through this region would be unlikely to receive the required UV dosage. By impeding the flow of water in this region and inducing helical flow, UV exposure in these regions can be maximised. Shaping the or each baffle to correspond to an area of the chamber which is above a predetermined distance away from the or each lamp maximises the impedance of water in these low exposure areas of the chamber, whilst not impeding the flow of water in regions exposed to relatively high UV intensity. This provides more even UV exposure of water flowing through the reactor.

In some embodiments, the or each UV lamp comprises a tube and the or each baffle comprises an arcuate edge complementary to the surface of the or each tube.

Such complementary shaping of the baffle to the surface of the lamp encourages water flow towards the lamp, and hence into areas of high exposure. The arcuate edge of the baffle provides a parallel surface to the lamp for the flow to attach to once near the baffle edge, encouraging flow towards the lamps. This is due to the Coanda effect, as will be understood by those skilled in the art, where a fluid flow attaches itself to a nearby surface and remains attached even when the surface directs away from the initial flow direction.

Alternatively, the edges of the or each baffle adjacent the lamps may comprise a straight edge.

In some embodiments, at least one of the or each baffle is provided with an aperture.

In some embodiments, the aperture is provided adjacent the side wall or outer wall of the flow chamber.

The aperture provides an additional helical flow trajectory, further encouraging this flow pattern in impeded areas. This aperture also provides an additional route by which water is directed back towards the UV lamps. Again, this is as a result of the Coanda effect, as will be understood by those skilled in the art. Consequently, additional turbulence is provided in the region of the side wall or outer wall of the chamber.

As water flows through the chamber it will tend to flow along the length of the lamps due to the Coanda effect. As the number of lamps is increased, there are consequently more surfaces for water to flow along, thereby increasing laminar flow in the chamber. The or each baffle is therefore particularly important to introduce turbulence in reactors having a larger number of lamps. Similarly, apertures in the or each baffle which encourage additional turbulence are also beneficial.

In some embodiments the flow chamber is cylindrical.

A cylindrical chamber is advantageous since helical flow of water is easier to control in a cylindrical chamber. A cylindrical chamber is also a structurally strong shape, able to withstand higher pressures and flow rates. In a preferred embodiment the flow chamber has an internal diameter of 250mm.

Alternatively, the flow chamber may have any other cross section, for example, a symmetrical cross section. In some instances the chamber may have a hexagonal or octagonal cross section.

In some embodiments, each of the UV lamps is provided at the same distance from the longitudinal axis. The UV lamps may be provided in a regular arrangement within the chamber, for example, the lamps may be arranged in a ring coaxial with the longitudinal axis of the chamber. Where a large number of UV lamps are used, the lamps may be arranged in two rings of different diameters, coaxial with the longitudinal axis of the chamber.

Increasing the symmetry of the chamber about the longitudinal axis has the advantage of supporting helical flow.

In some embodiments the input and output are provided at opposite ends of the UV reactor. This can be beneficial in connecting the UV reactor to existing pipework.

Alternatively, the input and output may be provided at the same end of the UV reactor. In such arrangements the flow chamber may comprise a substantially U-shaped flow chamber. In some embodiments, the flow chamber may have a first arm and a second arm wherein the arms are joined by a turning portion. The first arm is coupled to the inlet and the second arm is coupled to the outlet, such that water may enter at the input, flow along the first arm, turn through approximately 180° at the turning portion to enter the second arm, flow along the second arm and leave the flow chamber through the output. Such an arrangement may be desirable where a longer length of flow chamber is required to achieve the necessary UV dosage, whilst maintaining an overall shorter length of reactor.

In some embodiments the input is off-centre to the cross sectional width of the flow chamber.

In this way an eccentric input is provided to the flow chamber. Offsetting the input in this manner, directs water entering the flow chamber towards the side wall or outer wall of the chamber to encourage helical flow.

In some examples, the input comprises a longitudinal axis and the input is arranged such that the longitudinal axis of the input and the longitudinal axis of the chamber offset from the flow chamber are spaced apart (i.e. they do not intersect). In this manner, the input is off centre to the cross-sectional width of the flow chamber. For example, the input may comprise a pipe.

In some embodiments the input comprises a tapered pipe, such that the cross-sectional area of the input pipe gradually reduces along the length of the pipe, the end of the pipe having the smallest cross-sectional area being coupled to the flow chamber.

In some embodiments the input pipe comprises a stepped reduction in the cross-sectional area of the input pipe.

In embodiments with a tapered input pipe, water enters the input pipe at the end having the largest cross-sectional area, and water leaves the input pipe at the end having the smallest cross-sectional area, at which point the pipe is coupled to the flow chamber. The end of the input pipe which is coupled to the flow chamber may be attached directly to the flow chamber. Alternatively, the end of the input pipe which is coupled to the flow chamber may be attached to the flow chamber via additional pipework.

Tapering of the input pipe results in a constricted entry point for water entering the flow chamber. This has the advantage of increasing the velocity flow entering the flow chamber and hence assists in maintaining the desired flow trajectory through the flow chamber.

In some embodiments, the input pipe comprises a tapered section and untapered section, the untapered section defining a longitudinal axis of the input pipe, wherein the longitudinal axis of the input pipe intersects the longitudinal axis of the flow chamber. For example, the longitudinal axis of the input pipe is orthogonal to the longitudinal axis of the flow chamber.

In some embodiments the input pipe comprises an asymmetric taper such that the end of the input pipe having the smallest cross-sectional area is off-centre to the longitudinal axis of the input pipe. The longitudinal axis of the input pipe is provided in relation to the end of the input pipe having the largest cross-sectional area (i.e. the untapered section). In such embodiments, the input pipe may be coupled to the flow chamber such that the longitudinal axis of the input pipe intersects the longitudinal axis of the flow chamber, however, due to the asymmetric taper of the input pipe, the input pipe is coupled to the flow chamber such that the entry point into the flow chamber off-centre to the cross sectional width of the flow chamber.

By tapering and/or offsetting the input in relation to the flow chamber, helical flow in the flow chamber is encouraged. Accordingly, the distribution of UV exposure is optimised and hence a shorter UV reactor may be used to achieve the required dose.

In some embodiments the flow chamber comprises an internal rod provided along the length of the chamber, coaxial with longitudinal axis.

The internal rod may be solid or may be a hollow pipe.

The internal rod acts as an additional baffle, directing the flow of water away from low exposure areas of the chamber and towards high exposure areas. The internal rod itself may occupy a low exposure area of the chamber. For example, the UV lamps are provided in a ring and the internal rod is provided in the centre of the ring.

In some embodiments the internal rod is arranged to carry cleaner unit for cleaning the or each UV lamp.

For example, the internal rod may be threaded to carry the cleaner unit. Cleaning of the or each UV lamp is important to ensure UV radiation emitted to the chamber is maximised.

In some embodiments, the distance between the edges of the or each baffle and the or each lamp is sufficient to permit the cleaning unit to pass between the baffles and the lamps.

In some embodiments the or each UV lamp extends the length of the flow chamber.

In some embodiments, the or each UV lamp is a low pressure UV lamp.

In some embodiments the or each UV lamp is a medium pressure UV lamp.

Medium pressure UV lamps have a higher UV power output as compared with low pressure UV lamps. Accordingly, using medium pressure UV lamps rather than low pressure UV lamps means that fewer lamps are necessary to achieve the required UV dosage.

The UV emission spectrum from medium pressure UV lamps comprises output peaks at additional wavelengths compared with the emission spectrum of low pressure UV lamps. Whilst both low and medium pressure have a peak output at a frequency which is effective at killing or rendering non-viable organisms typically present in salt water, medium pressure UV lamps emit radiation at an additional frequency which is effective against fresh water organisms. Accordingly the UV reactor described herein can be used to treat both fresh and salt water.

In some embodiments a UV sensor is provided and is arranged to obtain feedback with regard to the intensity of radiation emitted into the flow chamber by the or each UV lamp at the position of the sensor. The expected output of the lamps is known from the power electronics system of the or each lamp, and expected UV transmission through the water passing through the UV reactor is also known from a UV transmission sensor upstream of the reactor. A flow rate of the water is measured by a flow meter. From these measurements, an expected UV intensity at the location of the sensor can be calculated. If the measured intensity is less than the calculated intensity, this may indicate that the UV lamps require cleaning or replacing.

In some embodiments, the side wall is an outer wall of the flow chamber.

In a second aspect a UV reactor for use in a water treatment system is provided, the UV reactor comprising:

a flow chamber having a longitudinal axis;

at least one fitting for at least one UV lamp arranged such that, in use, a length of the at least one UV lamp is provided in the direction of the longitudinal axis of the flow chamber, such that water flowing along the flow path can be exposed to UV radiation as it flows from the input to the output; and at least one baffle provided within the flow chamber and configured to impede water flowing along the flow path.

In some embodiments the UV reactor comprises a plurality of fittings for UV lamps.

In some embodiments, the or each fitting is arranged for a plurality of UV lamps.

In some embodiments, a plurality of fittings is provided, each of which being arranged for a single UV lamp.

In some embodiments 2-6 lamps may be used, for example, 2, 3, or 5 lamps may be used. In some embodiments, six UV lamps may be used.

In some embodiments more than six lamps may be used lamps may be used, for example 210 lamps, for example 4-8 lamps may be used. For example, 7, 8, 9 or 10 lamps may be used.

As will be understood, optional features described in relation to the first aspect also apply to the second aspect of the invention.

DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will now be described with reference to the accompanying drawings, in which:

Figures la, lb and lc illustrate schematic views of a UV reactor according to a first embodiment of the invention;

Figures 2a and 2b show schematic plan views of the UV reactor of Figures la to lc;

Figures 3a-d illustrate water flow trajectories through the UV reactor of Figures la-lc;

Figures 4 and 4b show a graph illustrating the UV dose distribution achieved by the reactor of Figures la-lc in a simulation carried out at a flow rate of 250m³/h, 45% UVT@10mm, 30kW total lamp power;

Figures 5a, 5b and 5c illustrate schematic views of a UV reactor according to a second embodiment of the invention;

Figures 6a and 6b show schematic plan views of the UV reactor of Figures 5a-5c;

Figures 7a-d illustrate water flow trajectories through the UV reactor of Figures 5a to 5c; and Figures 8a and 8b show a graph illustrating the UV dose distribution achieved by the reactor of Figures 5a to 5c in a simulation carried out at a flow rate of 250m³/h, 45% UVT@10mm, 45kW total lamp power.

DETAILED DESCRIPTION OF EMBODIMENTS

Referring firstly to Figures la, lb and lc, a UV reactor 2 comprises a cylindrical flow chamber 4 through which ballast water can flow. An input pipe 6 and an output pipe 8 are coupled to the chamber 4 such that water can enter the flow chamber 4 through the input pipe 6 and leave the chamber 4 through the output pipe 8. The input and output pipes 6, 8 are provided at opposite ends of the flow chamber 4.

Four medium pressure UV lamps 10 are located within the chamber 4. The UV lamps 10 are tubular and are positioned such that the length of the tube is substantially parallel to a longitudinal axis A of the cylindrical chamber 4. The four UV lamps 10 are each positioned at an equal distance from the longitudinal axis and are also equidistant from each other. Each UV lamp 10 comprises quartz tube and the tube extends the length of the flow chamber 4 and is of tubular shape.

Also within the chamber 4 is located a rod 12 extending from one end of the chamber 4 to the other and which is coaxial with the longitudinal axis. The rod 12 is threaded such that a cleaning unit 13, for example a wiper, is carried by the rod 12 and configured to clean the outer surface of each UV tube 10.

The flow chamber 4 has an outer wall 16 and a series of baffles 14 extending from this outer wall 16 into the interior of the flow chamber 4. The baffles are arranged as a series of opposing pairs, wherein each pair is axially offset from the next pair along the longitudinal axis. Adjacent pairs are also angularly offset by 90° about the longitudinal axis.

A UV sensor 17 is provided at the outer wall 16 of the reactor and is arranged to obtain feedback from the flow chamber 4 relating to the intensity of radiation emitted by the UV lamps 10 at the position of the sensor 17. The expected output of the lamps 10 is known from the power electronics system of the lamps 10, and expected UV transmission through the water passing through the UV reactor 2 is also known from a UV transmission sensor (not shown) upstream of the reactor 2. A flow rate of the water is measured by a flow meter (not shown). From these measurements, an expected UV intensity at the location of the sensor 17 can be calculated. If the measured intensity is less than the calculated intensity, this may indicate that the UV lamps 10 require cleaning or replacing.

With reference also to Figures 2a and 2b, input pipe 6 comprises a tapered wall 6a. The input pipe 6 tapers such that the end of the input pipe 6 having the largest cross-sectional area is provided furthest away from the flow chamber 4, and the end of the input pipe 6 having the smallest cross-sectional area is coupled directly to the flow chamber 4.

The input pipe 6 has a longitudinal axis which is provided central to the end of the input pipe having the largest cross-sectional area (i.e. the untapered section). The tapering of the input pipe 6 is asymmetric to this longitudinal axis such that the end of the input pipe 6 having the smallest cross-sectional area is off-centre to the longitudinal axis of the input pipe.

The input pipe 6 is coupled to the flow chamber 4 such that the longitudinal axis of the input pipe 6 intersects the longitudinal axis of the flow chamber 4. Due to the asymmetric taper in the input pipe 6, the input pipe 6 is coupled to the flow chamber 4 off-centre to the cross sectional width of the flow chamber.

The untapered section of the input pipe 6 is arranged to align with the output pipe 8 when the reactor is viewed along the longitudinal axis of the flow chamber. This assists in connecting the UV reactor to the existing pipework on-board a ship.

The flow chamber 4 has an internal diameter of 250mm and the quartz tubes of the UV lamps 10 have a diameter of 45mm. The untapered section of the input pipe 6 and the output pipe 8 are of a standard diameter to facilitate connecting the UV reactor to the existing pipework onboard a ship.

With particular reference to Figure 2a, each baffle 14 extends from the outer wall 16 of the chamber 4 along an arc of 90° of the circumference of the outer wall, although it will be understood that alternative arc lengths may be used provided the water flow in these regions is sufficiently controlled to ensure a desired UV dosage is achieved. In some embodiments, the baffles may extend along a longer arc. The baffles 14 each have a surface 18, the plane of which is orthogonal to the longitudinal axis. The edge 20 of the surface 18 of the baffle includes scalloped portions 22, 24 shaped such that a constant distance is provided between the edge of the scalloped portion 22, 24 and the nearest UV lamps 10. The distance between the scalloped portion 22, 24 and the nearest UV lamps 10 is sufficient to enable the cleaning unit 13 to pass between the baffles and the UV lamps. It will be understood that the shape of the each baffle 14 corresponds to a portion of an area of the chamber 4 which would typically receive a relatively low UV exposure.

With reference to Figure 3a-d, which illustrates flow trajectories and the respective velocities of water travelling through the reactor, in use, ballast water enters the flow chamber 4 via the input pipe 6. Since the input pipe 6 is positioned off-centre to the flow chamber 4, water entering the chamber 4 is directed to flow around the outer wall 16 of the chamber 4 following a helical trajectory (see Figure 3d, for example). The tapered shape of the input pipe 6 constricts water flow into the chamber 4 thereby increasing the flow rate of water entering the chamber 4. Consequently, the helical flow is more easily maintained.

As water flows through the chamber 4 it is exposed to UV radiation from the UV lamps 10. Water flowing in close proximity to the lamps will receive a higher intensity of radiation compared to water flowing near the outer wall of the chamber 4, i.e. further away from the lamps 10. As the water flows through the chamber 4 laminar flow along the length of the chamber 4 is impeded in regions adjacent the outer walls by the baffles 14. As the water hits the baffles 14 it is slowed down and the direction of flow is rotated to encourage helical flow (see in particular Figures 3a-c). This slowing and change of direction increases the duration for which the water is exposed the UV radiation, thereby increasing the UV dosage received by the water. Since the baffles 12 are provided in pairs, a pair of gaps 26 is defined between the two baffles making up each pair of baffles 12. Further, since adjacent pairs of baffles not just axially offset but are angularly offset by 90°, the gaps 26 are also offset by 90°. This arrangement of gaps defines a pair of helical flow trajectories around the outer wall 16 of the chamber. Accordingly, water flowing in this region is encouraged to adopt a helical flow. Water flowing through the chamber is also deflected towards the UV lamps by the rod 12.

In contrast, water flowing in close proximity to the lamps 10 (i.e. not in the region of the baffles 14) is not impeded and so flows at a higher velocity compared to water flowing in the region of the baffles 14 (see Figure 3a and 3b, for example).

Figure 3a illustrates a simulation of 200 flow trajectories which are followed as water flows through the UV reactor 2 and the velocity of flow associated with each trajectory. An enlarged view of flow trajectories in the flow chamber 4 is provided by Figure 3b. A further enlarged view of flow trajectories in the flow chamber 4 is provided by Figure 3c, which illustrates a simulation of 100 flow trajectories. These figures illustrate the effect of the baffles 14 in encouraging helical flow through the flow chamber and slowing down flow in these regions. Figure 3d shows a top down view of the flow of water into the flow chamber 4. This image is generated from a simulation of 200 flow trajectories and illustrates the effect of the tapered, offset inlet on encouraging helical flow.

By directing the water flow in the manner described above, a more even UV dosage is applied water passing through the UV reactor. This is illustrated in Figures 4a and b which show the results of a simulation carried out at a flow rate of 250m³/h, 45% UVT@10mm, 30kW total lamp power. In the figure, the x-axis shows the dosage applied and the y-axis shows the exposure time. The mean dosage was found to be 698 J/m² and the mean exposure time was found to be 0.37s.Figure 4b shows the bottom left portion of the graph shown in Figure 4a.

With reference to Figures 5a, 5b and 5c a second embodiment of the invention is illustrated. In this embodiment like features are indicated by the same reference numbers increased by 100. This embodiment is similar to the first embodiment described above, however differs in that the UV reactor 102 comprises six UV lamps 110. As can be seen most clearly in Figures 6a and 6b, the UV lamps are positioned at an equal distance from the longitudinal axis and are also equidistant from each other.

Since more UV lamps 110 are present, the water will have a greater tendency to adopt a laminar flow along the length of the lamps. Accordingly a series of baffles that more strongly directs the flow to follow a helical trajectory is required.

The baffles 112 are arranged as a series of opposing pairs, wherein each pair is axially offset from the next pair along the longitudinal axis. Adjacent pairs are also angularly offset by 60°. As with the first embodiment, a pair of gaps 126 is therefore formed by each pair of baffles 112, the gaps 126 defined by the series of baffles themselves defining a pair of helical trajectories around the outer wall of the chamber along which water is encouraged to flow.

The baffles 112 extend from the outer wall 116 of the chamber 104 along an arc of 145°. Again, it will be understood that alternative arc lengths are possible provided that water flowing in these regions is sufficiently controlled to ensure a desired UV dosage is achieved. The baffles also comprise an aperture 128 adjacent the outer wall 116 of the chamber 104 through which water may flow. As water flows through this aperture 128 it is directed back towards the UV lamps 110 and hence to a region of higher UV exposure. This provides an additional flow path for water to follow and encourages water flow towards regions of relatively high UV intensity.

With reference to Figures 7a-d, when in use, ballast water flows through the chamber 104 in a similar manner to that described in relation to the first embodiment. The helical flow and turbulence induced by the UV reactor of this embodiment ensures that an even UV dosage is applied to water passing through the UV reactor and hence improved overall power efficiency of the reactor is obtained. Figure 7a illustrates a simulation of 200 trajectories which are followed as water passes through the UV reactor 102 and the velocity associated with each trajectory. An enlarged view of flow trajectories in the flow chamber 104 is provided by Figure 7b. A further enlarged view of flow trajectories in the flow chamber 104 is provided by Figure 7c, which illustrates a simulation of 100 flow trajectories. These figures illustrate the effect of the baffles in encouraging helical flow through the flow chamber and slowing down flow in these regions. Figure 7d shows a top down view of the flow of water into the flow chamber 104. This image is generated from a simulation of 200 flow trajectories and illustrates the effect of the tapered, offset inlet on encouraging helical flow.

Figures 8a and 8b illustrate that a more even dosage is applied to water flowing through the reactor 102. These figures show the results of a simulation carried out at a flow rate of 250m³/h, 45% UVT @ 10mm, 30kW total lamp power. The mean dosage was found to be 1139J/m² and the mean exposure time was found to be 0.36s. Figure 8b shows the bottom left portion of the graph shown in Figure 8a.

Although the invention has been described above with reference to one or more embodiments, it will be appreciated that various changes or modifications may be made without departing from the scope of the invention as defined in the appended claims.

Claims

1. A UV reactor for use in a water treatment system, the UV reactor comprising:

a flow chamber having a longitudinal axis;

at least one UV lamp comprising a length which is provided in the direction of the longitudinal axis of the flow chamber, wherein water flowing along the flow path can be exposed to UV radiation as it flows from the input to the output; and a series of baffles provided within the flow chamber and configured to impede water flowing along the flow path;

wherein the series of baffles is provided as a plurality of groups of baffles positioned along the longitudinal axis of the chamber, wherein each group comprises two or more baffles provided at the same distance along the longitudinal axis, and wherein axially adjacent groups are angularly offset from each other about the longitudinal axis.

2. A UV reactor according to claim 1, where the UV reactor comprises a plurality of UV lamps.

3. A UV reactor according to claim 2, wherein the UV reactor comprises four or six UV lamps.

4. A UV reactor according to any preceding claim, wherein each baffle is adjacent a side wall of the flow chamber.

5. A UV reactor according to any preceding claim, wherein each baffle extends from a side wall of the flow chamber.

6. A UV reactor according to any preceding claim, wherein each baffle comprises a respective surface extending in a direction transverse to the longitudinal axis.

7. A UV reactor according to claim 6, wherein the respective surface of each baffle extends in a direction orthogonal to the longitudinal axis.

8. A UV reactor according to any preceding claim, wherein axially adjacent groups of baffles are angularly offset by 90° or by 60°.

9. A UV reactor according to any preceding claim, wherein each group of baffles comprises a pair of baffles.

10. A UV reactor according to any preceding claim, wherein each baffle comprises a shape corresponding to at least a portion of an area of chamber which is greater than a predetermined distance away from the or each UV lamp.

11. A UV reactor according to claim 10, wherein the or each UV lamp comprises a tube and each baffle comprises an arcuate edge complementary to the surface of the or each tube.

12. A UV reactor according to any preceding claim, wherein at least one of the baffles is provided with an aperture.

13. A UV reactor according to claim 12, wherein the aperture is provided adjacent a side wall of the flow chamber.

14. A UV reactor according to any preceding claim, wherein the input is off-centre to the cross sectional width of the flow chamber.

15. A UV reactor according to any preceding claim, wherein the input comprises a tapered pipe, such that the cross sectional area of the input pipe gradually reduces along the length of the pipe, the end of the pipe having the smallest cross-sectional area being coupled to the flow chamber

16. A UV reactor according to claim 15, wherein the input comprises a tapered section and untapered section, the untapered section defining a longitudinal axis of the input pipe, wherein the longitudinal axis of the input pipe intersects the longitudinal axis of the flow chamber.

17. A UV reactor according to claim 16, wherein the longitudinal axis of the input pipe is orthogonal to the longitudinal axis of the flow chamber.

18. A UV reactor according to claim 16 or 17, wherein the input pipe comprises an asymmetric taper such that the end of the input pipe having the smallest crosssectional is off-centre to the longitudinal axis of the input pipe.

19. A UV reactor according to any preceding claim, wherein the flow chamber is cylindrical.

20. A UV reactor according to any preceding claim, wherein the input and output are provided at opposite ends of the UV reactor.

21. A UV reactor according to any preceding claim, further comprising an internal rod provided along the length of the chamber, coaxial with longitudinal axis.

22. A UV reactor according to claim 21, wherein the internal rod is arranged to carry a cleaning unit for cleaning the or each UV lamp.

23. A UV reactor according to any preceding claim, wherein the or each UV lamp is a medium pressure UV lamp.

24. A UV reactor according to any preceding claim, further comprising a UV sensor arranged to obtain feedback with regard to the intensity of radiation emitted into the flow chamber by the or each UV lamp.

25. A UV reactor for use in a water treatment system is provided, the UV reactor comprising:

a flow chamber having a longitudinal axis;

an input for entry of water into the flow chamber and an output for water to

5 exit the flow chamber, wherein the UV reactor is arranged such that water can flow along a flow path from the input to the output via the flow chamber;

at least one fitting for a UV lamp arranged such that, in use, a length of the UV lamp is provided in the direction of the longitudinal axis of the flow chamber, wherein water flowing along the flow path can be exposed to UV radiation as it flows 10 from the input to the output; and a series of baffles provided within the flow chamber and configured to impede water flowing along the flow path;

wherein the series of baffles is provided as a plurality of groups of baffles positioned along the longitudinal axis of the chamber, wherein each group comprises 15 two or more baffles provided at the same distance along the longitudinal axis, and wherein axially adjacent groups are angularly offset from each other about the longitudinal axis.