WO2009052831A1

WO2009052831A1 - A fluid treatment unit comprising a radiation source

Info

Publication number: WO2009052831A1
Application number: PCT/DK2008/050257
Authority: WO
Inventors: Christian Rasmussen; Finn Beldring; Ebbe Kruse Vestergaard
Original assignee: Grundfos Management A/S
Priority date: 2007-10-26
Filing date: 2008-10-22
Publication date: 2009-04-30

Abstract

In order e.g. to provide consistent fluid treatment, there is disclosed a fluid treatment unit comprising a radiation source and a flow passage being connected to an inlet and an outlet of the fluid treatment unit through which the fluid flows into and out of, and comprising: a direct exposure channel guiding the fluid past a radiation source so that the radiation source emits radiation directly into the fluid, an indirect exposure channel comprising one or more wall elements being penetrable to radiation emitted from said radiation source and arranged so that radiation emitted into the direct exposure channel is also emitted into the indirect exposure channel, one or more total pressure increasing means for increasing the total pressure of the fluid at least locally in the fluid treatment unit, and a casing encapsulating the direct and indirect exposure channels and the one or more total pressure increasing means.

Description

A FLUID TREATMENT UNIT COMPRISING A RADIATION SOURCE

The present invention relates to a unit and method for exposing fluid, typically being a liquid, to treatment in the form of exposing the fluid to radiation emitted from one or more radiation sources. The invention relates in particular to a fluid treatment unit through which fluid may flow while being exposed to treatment, the unit comprising a radiation source arranged to emit radiation into fluid being present in the treatment unit. The unit may further comprise a flow passage being connected to an inlet and an outlet of the fluid treatment unit through which the fluid flows into and out of the fluid treatment unit. The fluid treatment unit preferably further comprises one or more total pressure increasing means for increasing the total pressure of fluid at least locally in the fluid treatment unit and a casing.

In a preferred embodiment, the treatment is performed is by electromagnetic radiation, preferably in the form of ultra-violet light.

BACKGROUND OF THE INVENTION

Although the present invention finds use in many applications not involving exposing fluid to L)V radiation (ultra violet radiation), the background of the invention may advantageously be presented with reference to L)V radiation treatment of a fluid.

Fluids, and in particular water, are often treated with L)V radiation in order to destroy micro organisms such as bacteria. In many industrial applications, such water treatment is often a preliminary, intermediate, or final step of a process involving many other processes wherein the fluid is used for e.g. cleaning, cooling or heating. The fluid is exposed to L)V radiation in a unit where the fluid typically flows past a radiation source, and this flow causes a pressure drop in the water treatment process. The pressure drop must be balanced by pressurisation means, such as a pump. Today this pressure drop is balanced by a pump arranged upstream or downstream of the treatment unit, as the combination of L)V radiation and pump is provided by stand-alone units connected with each other by piping. This piping often results in a complex construction being vulnerable to e.g. leakage. Furthermore, pipes and other connections often result in pressure losses.

Furthermore, water to be treated often flows in a tube in a regular flow pattern, such as parallel flow in a tube before it is led to the radiation source. In connection with the present invention, it has been found that this regular flow pattern often needs to be changed to bring the fluid close to the radiation source to ensure that the fluid is sufficiently exposed to the L)V radiation. Whether or not a change is necessary typically depends on the condition of the fluid, such as how penetrable it is to rays of L)V radiation. When the fluid is less transparent, e.g. muddy, turbid, or the like, damping of the radiation occurs in the fluid resulting in that fluid flowing at a distance from the source of L)V radiation will not be sufficiently exposed to radiation. This problem is particularly difficult to handle when the transparency of the fluid varies over time.

One particular problem occurring when exposing fluid to L)V radiation is that it must often be guaranteed that the fluid is exposed to a minimum dose of L)V radiation when the fluid passes through a fluid treatment unit. This dose may depend on the actual condition of the fluid, and this condition is often varying. Additionally, fouling occurs at surfaces for instance on a source shield shielding the source of L)V radiation from the fluid which fouling may result in the fluid not being sufficiently exposed to radiation. A particular problem may occur when the radiation source becomes warm during use and the flow of fluid past the source is insufficient to cool the radiation source. In such cases, the radiation source may become so warm that it breaks down.

A further problem occurs in situations where the radiation source needs some warm-up time in order for it to radiate, this being particularly severe if the source during such warm-up period needs cooling as the flow used for cooling the source will not be exposed to the radiation during the warm-up period.

Thus, an aim of the present invention is to solve or at least mitigate one or more of the above disclosed problems or disadvantages of fluid treatment systems known today.

DISCLOSURE OF THE INVENTION

Thus, in a first aspect the present invention relates to a fluid treatment unit through which fluid may flow while being exposed to treatment, the unit preferably comprising a radiation source arranged to emit radiation into fluid being present in the treatment unit, a flow passage being connected to an inlet and an outlet of the fluid treatment unit through which the fluid flows into and out of the fluid treatment unit, and comprising: - a direct exposure channel guiding the fluid past a radiation source so that the radiation source emits radiation directly into the fluid

- an indirect exposure channel comprising one or more wall elements being penetrable to radiation emitted from said radiation source and arranged so that radiation emitted into the direct exposure channel is also emitted into the indirect exposure channel at least when no fluid is present in the unit, one or more total pressure increasing means for increasing the total pressure of the fluid at least locally in the fluid treatment unit, and a casing encapsulating the direct and indirect exposure channels and the one or more total pressure increasing means.

The radiation is preferably electromagnetic radiation, such as L)V radiation, but other types of radiation may also be used alone or in combination.

Whether or not radiation is emitted into the indirect exposure channel when a fluid is present in the unit depends on how penetrable the fluid is to the radiation; i.e. how far away from the radiation source the radiation can penetrate. An important feature to consider when a fluid is to be exposed to radiation, in particular being L)V radiation, typically with the purpose of destroying bacteria, is the dose of radiation the fluid receives while flowing through a treatment unit. Dose is typically expressed in a flux-like manner as dose (J/m²) = intensity (W/m²) * time (s) where m² relates to the area through which the radiation is emitted. This relation shows that although the intensity in a given region of the fluid is low, the fluid may receive a considerable dose if the exposure time is sufficiently long to e.g. influence bacteria present in the fluid. In the present invention, this has been utilised by the combination of indirect exposure channels and direct exposure channels so that the contribution from the radiation source in an indirect treatment channel is utilised.

The direct and indirect exposure channels are preferably arranged in the treatment unit so that fluid with particles, such as bacteria, to be exposed to radiation receives a more uniform radiation dose as compared to e.g. systems in which a longitudinal radiation source is arranged co-axially in a pipe through which fluid to be exposed to radiation flows. In such pipe based systems, some fluid will flow along the outer wall boundary of the pipe, and some fluid will flow along the outer wall boundary of the radiation sources whereby the fluid and particles will be exposed to a dose depending on its distance to the source and the turbidity of the fluid. This often result in that such units are dimensioned based on a worst case scenario including that the highest turbidity and farther distance from the source set the lower limit for the effect emitted by the radiation source, so that fluid with particles flowing farthest away from the radiation source receives a minimum dose. This design criterion often results in that fluid with particles flowing along the boundary of the radiation source receives a dose being larger than what is required. Thus, by applying the concept of direct and indirect exposure channels, a good utilisation of the radiation emitted to the fluid may be obtained.

In some embodiments more than one radiation source is present each being arranged to emit radiation into a direct exposure channel and into indirect exposure channels. Thus, a direct exposure channel may constitute an indirect exposure channel for another radiation source.

By use of fluid treatment units according to the present invention, the fluid leaving the unit via outlets has been exposed to treatment, and inside the fluid treatment unit the total pressure of fluid being treated is increased at least locally by total pressure increasing means. While the description of the invention presented herein focuses on treating one fluid, the invention is well suited for treating more than one fluid.

In accordance with the present invention, a fluid treatment unit has a casing which preferably may be considered as a container like structure inside which the one or more radiation sources and one or more total pressure increasing means are arranged. Thereby the need for connecting standalone units by pipes to provide a fluid treatment device may be avoided, and a compact unit providing a good possibility to meet a given treatment demand may be provided. The casing is preferably made from or coated with a material not allowing radiation from the radiation source(s) to be emitted out from the unit.

The fluid treatment will typically result in a pressure loss e.g. due to a flow path including bends and the like, and the total pressure increasing means is/are preferably used to overcome at least the pressure loss resulting from the fluid flowing through the fluid treatment unit.

Thus, while the known fluid treatment units are assembled by connecting a number of stand-alone units via pipes, the present invention is designed so that it preferably comprises a pressure carrying casing inside which the radiation source(s) and total pressure increasing means are arranged, whereby the unit may be made more compact and efficient. It should be mentioned that the radiation source may comprise one or more connections (electrical, fluid connections or the like), one or more handles or the like extending outside the unit. However, the interaction between the radiation source and the fluid preferably takes place inside the unit.

The efficiency of the unit may furthermore be increased as the number of treatments stages may be chosen so that a given demand may be matched more accurately than by building a fluid treatment unit from a number of stand-alone units.

An advantageous aspect of the present invention relates to photo catalytic conversion of e.g. H₂O into OH^", and in preferred embodiments of the present invention one or more surface sections of the interior of the treatment unit are coated with TiO₂. In many of the preferred embodiments of the present invention, surfaces facing the fluid to be treated and receiving L)V radiation from behind are present, and these surfaces may advantageously be coated with TiO₂.

In the present context a number of terms are used. Although these terms are used in a manner ordinary to a person skilled in the art, a brief explanation will be presented below on some of these terms.

Treatment stage is preferably used to designate a segment of the unit. A treatment stage may preferably be in the form of a cassette (see below).

Source channel is preferably used to designate a part of the direct exposure channel where the source or a shield for the radiation source constitutes a part of the wall of the direct exposure channel. In other embodiments, the source channel is a part of the direct exposure channel guiding the fluid to flow in close vicinity of the radiation source.

Radiation source is preferably used to designate an element emitting radiation, such as electromagnetic radiation, e.g. L)V radiation, laser radiation, microwave radiation, radioactive radiation, sound waves. It should be mentioned that waves are preferably considered to be radiation.

Casing is preferably used to designate the wall of the fluid treatment unit which wall confines fluid in the fluid treatment unit so that fluid may flow into / out of the processing unit through one or more inlets and outlets provided in the casing. The casing may preferably comprise a number of wall elements. Cassette is preferably used to designate a treatment stage which either contains one or more radiation sources and/or is adapted to receive one or more radiation sources. A cassette typically comprises an outer housing arranged so as to form at least part of the casing, one or more inlets and one or more outlets. The outer housing may preferably be pressure carrying in the sense that no further casing is needed to withstand the pressure difference between the interior and exterior of the cassette. A cassette is shaped so that it comprises one or more flow passages through the cassette from its inlet to its outlet, which one or more flow passages form part of the flow passage through the unit. The inlet(s) and outlet(s) of cassettes are openings in the cassettes in which fluid may flow into and out of the cassettes. The inlets and outlets are preferable provided so that when two cassettes are combined, the outlet(s) of one cassette are directly connected to the inlet(s) of the other cassette and vice versa. "Directly connected" is preferably used to designate a situation where the velocity and pressure of the fluid flowing out of the outlet is the same as the velocity and pressure of the fluid flowing into the inlet. This may e.g. be provided by connecting the outlet and inlet with each other with no intermediate piping in between. Furthermore, when two or more cassettes are combined, the outer casings of the cassettes are preferably combined to form at least part of the pressuring carrying casing of the processing unit. Furthermore, as a cassette often comprises total pressure increasing means overcoming the pressure loss due to fluid flowing though the cassette, the assembled unit may often be pressure neutral to the process in which it is to operate. A Cassette therefore preferably comprises total pressure increasing means and at least one fluid interaction component. Thereby, a cassette can in many cases be considered as a fluid processing unit for which, if the total pressure increasing means is selected appropriately, no further means is/are needed to pump the fluid through the cassette. This makes the design of a given fluid processing unit very easy while providing a build in security that treatment of the fluid is consistent. This may e.g. be due to the build in pressure increasing means.

Velocity inducer is preferably used to designate an element inducing velocity to the fluid so that its direction and/or total pressure is changed. Fluid is used to designate at least liquid, gas, a fluidized medium or combinations thereof. Thus, fluid preferably also includes bacteria or other substances carried by the fluid.

Inlet/outlet is preferably used to designate a cross section or a region where fluid flows into or out of an element. The inlet/out may preferably be an end cross section or a region of a pipe, channel or the like. Inlet and outlet may preferably also be considered as the sections of a control volume through which fluid flows into /out of the element which control volume encircles the element in question. Although the description of the present invention focuses on exposing fluid to L)V radiation, it should be mentioned that the invention is not limited to L)V radiation or electromagnetic radiation in general.

Further embodiments of the present invention are presented in below and in the claims. The present invention and in particular preferred embodiments thereof will now be disclosed in connection with the accompanying drawings in which:

Fig. 1 shows schematically a preferred embodiment of fluid treatment unit according to the present invention,

Fig. 2 shows schematically a longitudinal cross sectional view of a treatment stage of the embodiment shown in fig. 1,

Fig. 3 shows schematically the configuration of the floor elements of the embodiment of fig. 1.

Fig. 4 shows schematically the rotational motion of the fluid through a unit according to the present invention in which the radiation source is arranged above a floor element,

Figure 5 shows schematically a further embodiment of the present invention in which a penetration is provided in a floor element,

Fig. 6a and b each shows a three dimensional view of a part of a fluid treatment unit according to the present invention; fig. 6a shows the inlet side and fig. 6b shows the outlet side of the unit (inlet and outlet elements are removed for clarity).

Fig.7 shows schematically a longitudinal cross sectional view along line A-A of the fluid treatment unit disclosed in fig. 6,

Fig. 8 shows a horizontal cross sectional view taken along line B-B of the embodiment shown in fig. 7,

Fig. 9 shows schematically a further preferred embodiment of a stage of a fluid treatment unit according to the present invention wherein the radiation source is arranged radially,

Fig. 10. a and 10. b show schematically further preferred embodiments of a stage according to the present invention wherein the source channel is a penetration provided in the wall element, Fig. 11 shows schematically a treatment stage of a fluid treatment device comprising an ultrasound source; fig. 11a shows the treatment stage in a partly exploded view and fig. lib shows a segment of a cross sectional view taken along a radius of the stage. Fig. 12 shows schematically a fluid treatment unit according to the present invention; the unit comprises six stages, an inlet element, an outlet element and a motor for rotating impellers arranged in the fluid treatment unit,

Fig. 13 shows schematically a longitudinal cross section of a fluid treatment unit according to the present invention. The unit comprises seven stages, an inlet element, an outlet element and a motor for rotating impellers arranged in the fluid treatment unit. Fig. 13 shows in particular an embodiment of assembling the unit shown in fig. 12; radiation sources as well as the flow passages are not shown in the figure,

Fig. 14 shows schematically a longitudinal cross section of three stages according to the present invention assembled by threads being provided on a part of the stages' housing rings,

Fig. 15 shows schematically a longitudinal cross section of a fluid treatment unit according to the present invention comprising six stages, an inlet element, an outlet element, a motor for rotating impellers (not shown) arranged in the fluid treatment unit. Radiation sources as well as the flow passages are not shown in the figure.

Fig. 16 shows schematically a cross sectional view of a segment of an embodiment in which radiation guide means in the form of a lens for focusing the radiation into the source channel is arranged. Fig. 17 shows schematically a cross sectional view of a segment of an embodiment in which radiation guide means in the form of a mirror for focusing radiation into the source channel is arranged.

Fig. 18 shows schematically a cross sectional view of an embodiment of a fluid treatment unit according to the present invention, Fig. 19 shows a further cross sectional view of the embodiment shown in fig. 18, and

Fig. 20 shows schematically a further embodiment of a treatment stage of a preferred embodiment of a treatment unit according to the present invention. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE PRESENT INVENTION

Fig. 1 shows schematically a preferred embodiment of a fluid treatment unit according to the present invention. The treatment performed by the unit shown in fig. 1 comprises exposing fluid to L)V radiation. The unit 1 comprises a treatment section 2 assembled with an inlet element 5 and an outlet element 4. Fluid to be exposed to L)V radiation flows into the unit 1 via an inlet 6 provided in the inlet element 5 and leaves the unit 1 after being exposed to L)V radiation during its passage through the treatment section 2 via an outlet 7 provided in the outlet element 4. The assembly of the treatment section 2 and the inlet and outlet elements 5,4 is provided so the unit 1 is fluid tight.

The unit further comprises an electric motor 8 arranged on a motor fixture 9. The motor rotates a shaft 35 which extends into the unit 1 and is sealed against the outlet element 4 to avoid fluid from leaking out of the unit 1.

The treatment section 2 comprises a tubular source shield 10 made of a material being transparent to L)V radiation, such as made of quarts. The source shield 10 extends into the interior of the treatment section 2 (as will be explained in greater details below) and is adapted to house a radiation source, preferably an L)V source, such as a L)V lamp, so that the fluid present in the treatment section 2 may be exposed to radiation preferably being L)V radiation.

The unit 1 is cylindrical along its length axis (vertical with respect the orientation of fig. 1), and a longitudinal cross sectional view of the treatment section 2 is shown in fig. 2. The treatment section comprises a tubular and cylindrical outer casing 11 inside which a number of elements are arranged. Inside in the treatment section 2 three impellers 12 are arranged on the shaft 35. Floor elements 13, 14 are also arranged in the unit 1 which floor elements 13, 14 in combination with e.g. the impellers 12 define a flow passage through the treatment section 2. The flow path through the flow passage is indicated by the dotted line in the figure. The source shield 10 is also shown in the figure.

The floor elements 13, 14 are of two different shapes. The floor element 13 leaves a passage open between its rim and the outer casing 11, and the floor element 14 is sealed at its rim to the casing 11 and comprises a central penetration to allow fluid to flow towards and into an impeller 12. Thus, when the shaft 35 rotates, the impellers 12 pump fluid through the unit 1 in a flow pattern where the fluid flows from the inlet 6 of the inlet element 5 and into the first impellerl2 being the impeller located most upstream in the treatment section 2 towards the inlet 6. The fluid leaves the first impeller 12 and flows towards and over the rim of the first floor element 13 where after the fluid flows towards the second impeller 12 located downstream of the first impeller 12. This pattern is repeated until the fluid leaves the treatment section 2 and flows into the outlet element 4 to flow to the outlet 7.

During the fluid's passage through the treatment section 2, the fluid flows in close vicinity of the L)V source located in the tube 10. Furthermore, the floor elements 13, 14 are made of a material being penetrable to L)V radiation, e.g. made of quarts, so that the radiation may penetrate - depending on the damping characteristics of the fluid - to regions of the treatment section 2 not located in direct proximity of the source shield 10. The treatment section 2 is designed so that a number of connected channels are defined by the floor elements 13, 14 where the channels 15 are direct exposure channels into which the source emit radiation directly, and where the channels 16 are indirect exposure channels into which the source emits radiation indirectly as the radiation has passed through one or more floor elements 13, 14. In this respect, the source is considered to emit directly into the channels 15 although the source is shielded by the source shield 10.

Some regions of the flow passage through the unit 1 are not exposed to radiation from the source located in the tube 10 e.g. as they are shielded by impellers 12 through which e.g. L)V radiation cannot penetrate. Such regions are referred to as no exposure channels. It should be noted that whether or not an indirect exposure channel receives radiation depends inter alia on the damping characteristics of the fluid. If, e.g. the fluid damps the radiation to a high degree, the radiation may not penetrate the fluid and into an indirect exposure channel. However, the treatment section 2 is designed so that when the damping from the fluid is insignificant, the radiation from the L)V source will extend into the indirect exposure channels 16.

Fig. 3 shows schematically the configuration of the floor elements of the embodiment of fig. 1. The rotational motion of the fluid flow induced by the impeller is shown. As shown in fig. 3, the floor elements 13, 14 are circular and disc shaped elements. The floor elements 13, 14 are also transparent to radiation emitted from the source preferably being L)V radiation; they may be made of e.g. quarts. Fig. 4 shows schematically the rotational motion of the fluid through a unit in which the radiation source is arranged above a floor element 14. This rotational flow is indicated by the arrow drawn as a spiral in the figure. The source may be arranged in a number of ways including in the outlet element 4 above a stack of floor elements 13, 14 and/or in one or more of the floor elements 13, 14 as disclosed in connection with figs. 1-3. This will be disclosed in connection with fig. 5. An impeller (not shown) is arranged at the penetration centrally arranged in the floor element 14. The radiation is in fig. 4 shown by the arrows labeled L)V. The floor element 14 defines a channel above and a channel below the floor element 14 which is penetrable to the radiation emitted by the source. Thus, due to the damping of the fluid, the fluid present in the channel above the floor element 14 is exposed to a stronger radiation than the fluid present in the channel below the floor element 14. Fouling on the surfaces of the floor elements 13, 14 may occur during use of a unit, and such fouling may, if not being removed, result in a damping of the radiation. This damping may become so large that no radiation goes through the floor elements 13,14. The rotational motion of the flow include a shear stress acting on the surface of the floor elements 13,14 which shear stress tends to remove the fouling. If this is not sufficient cleaning, a specific cleaning process may need to be carried out. Such cleaning process could comprise an increase of the fluid velocity inside the treatment unit accomplished by increasing the rotational speed of the impellers. However, during the cleaning process the fluid may receive too low a dose, and a recirculation of the fluid may be performed to increase the dose emitted to the fluid during a cleaning process. Alternatively or in combination thereto, a cleaning fluid may used to clean the unit.

Figure 5 shows schematically a further embodiment of the present invention in which a penetration 18 is provided in a floor element 19 made of e.g. quarts. A unit according to the present invention with the floor element of fig. 5 may be embodied as disclosed in connection with fig. 1-3 in which a number of floor elements 19 as disclosed in fig. 5 are stacked as in fig. 2 instead of the floor elements 13, 14 in fig. 5, and impellers 12 are arranged as disclosed in connection with fig. 2. In this case, the floor elements 19 extend radially to the outer casing 11 so that fluid will not flow past the rim of the floor elements 19 but only through the penetrations 18.

Fig. 6a and b each shows a three dimensional view of a part of a fluid treatment unit 1 according to a preferred embodiment of the present invention. The part shown embodies a treatment section with three stages, 2a, 2b, 2c. Fig. 6a shows side where the fluid flows into the part of the fluid treatment unit 1 with an inlet element 5 (see fig. 1) removed to unveil the inter alia the impeller 12c and the inlet to a source channel 20c. Similarly fig. 6b shows the outlet side of the part of the unit 1 with an outlet element 4 (see fig. 1) removed to unveil at least an element 31a with a passage forming an outlet 7a.

Fluid to be treated flows via an inlet 6 to the impeller 12c in which the pressure of the fluid is increased. The fluid flows out of the impeller 12c in a spiraling motion towards and into source channel 20c, being part of direct exposure channel, where the fluid flow past a source shield 10 preferably made of e.g. quarts as indicated by the arrows on fig. 6a. The fluid flows out through the outlet 7a shown in fig. 6b and into the outlet element 4 (see fig. I)-

The treatment section 2 may further comprises sockets 21 adapted to receive or comprises a radiation source 22. Although the sockets 21 may comprise a fixture (not shown) for fixating the radiation source 22, such fixation may be provided by other means not necessarily being a part of the socket 21. The socket 21 is preferably fluid-tightly sealed off from the source channel 20. With reference to fig. 7 showing a cross sectional view of the preferred embodiment of a treatment section 2 shown in fig. 6, further details will be given. Please not that the flow direction in figure 7 differs from the one in fig. 1. Fig. 7 shows the parts of the treatment section 2 with three treatment stages 2a, 2b, 2c which in the embodiment shown in fig. 7 are similar to each other; however the actual number of stages may be varied and the stages may not always be similar to each other, a, b and c in the following refer to these three stages.

Each treatment stage 2 comprises a fluid velocity inducer 12, a stage connecting passage 23, and a source channel 20. In the embodiment shown in fig. 7, the fluid velocity inducers 12 are in the form of rotating impellers receiving fluid in an axial direction through a stage connecting passage 23 (or through the inlet for stage c) and delivering fluid at a higher velocity in radial direction as indicated by arrows in fig. 2.

Each treatment stage 2 further comprises two cavities 25, 26 divided from each other by a floor element 19 and being in fluid communication with each other through the source channel 20. The source channel 20 is formed as a passage leading fluid from cavity 25 to 26.

A part of the wall of the source channel 20 is formed by a source shield 10 behind which a radiation source 22 is arranged. In the preferred embodiment shown in fig. 6 and 7, the radiation source 22 is an L)V radiation source, such as an L)V lamp. The source shield 10 is transparent for the radiation to allow the fluid to be exposed to the radiation emitted from the source 22. When the radiation source is an L)V lamp, the source shield 10 is typically a protecting tube made from quartz.

The floor elements 19 and the elements 31 and 24 are preferably made of a material, e.g. quarts, being penetrable to the radiation emitted by the source 22. Thereby the cavities 26a, 25a, 26c and 25c are indirect exposure channels for the source 22b, and the cavities 25b and 26b are direct exposure channels for the source 22b. Similarly, the cavities 25c, 26c, 25b and 26b are indirect exposure channels for the source 22a, and the cavities 25a and 26a are direct exposure channels for the source 22a. The source channel 20b is direct exposure channel for radiation source 22b.

Typically, the elements 27 defining wall elements of the source channels 20 are made from a material not being penetrable to the radiation emitted from the sources 22, and the source channels 20 are therefore not indirect exposure channels for any of the sources 22 when the configuration shown in fig. 7 as the elements 27 shadow for radiation. However, the stages 2 may be configured either by rotating the stages relatively to each other so that the radiation sources are not aligned as in fig. 7, and/or the elements 27 may be made from a material being penetrable to radiation emitted from the radiation source whereby the source channels 20 may form part of indirect exposure channels.

An impeller shaft 35 is provided for rotating all impellers 12 in common, and the impeller shaft 35 is connected to a motor (not shown; 8 in fig. 1). Thus, when activating the motor, the impellers 12 are rotating whereby fluid is drawn into the treatment section 1 through the inlet 6. Starting from above (with reference to the orientation of the figure) fluid flows through the impeller 12c into the cavity 25c and through the source channel 20c. During the fluid's passage of the treatment section 2, the fluid is exposed to the radiation in the direct exposure channels from the sources exposing radiation into these channels and in the indirect exposure channels from the source exposing radiation indirectly into these channels. Thus, fluid flowing through the treatment section 2 is exposed to radiation with different intensity, and while flowing through the source channels 20, the fluid flows in close vicinity of the source 22 so as to provide a high intensity for a short period of time to the fluid.

As illustrated in figs. 6 and 7, the treatment section 2 may be modular e.g. by each stage 2 being a cassette so that a number of treatment stages 2a, 2b, 2c can be stacked. As the treatment stages can be stacked, a particular treatment section 2 may easily be configured to meet a specific demand or reconfigured to meet an altered demand. The assembly of the unit 1 may be accomplished by assembling rings 28 arranged in grooves provided in housing rings 29 of the treatment section 2. The assembling rings 28 furthermore provide sealing of the unit by the O-rings 30.

Fig. 8 shows a horizontal cross sectional view taken along line B-B in fig. 7. Fig. 8 shows in particular, the radiation source 22, the source shield 10 and a cross section of the source channel 20. All the fluid passing through the treatment section 2 is passing through the source channel 20 and, as indicated in fig. 7, the dimensioning of the source channel 20 is so that the fluid flows in close vicinity of the source of radiation.

Fig. 8 also indicates that the source shield 10 is sealed to the section 2 by seals 32 and secured to the section 2 by a screwed cap 33 so that fluid cannot flow to the interior of the source shield 10. Thereby the radiation source 22 can be replaceably arranged within the source shield 10 so that replacement of the radiation source 22 can be provided without dismantling the whole treatment section 2.

Cooling of the radiation source 22 may be accomplished by transporting a cooling fluid through the inside of the source shield 10. Another option, particularly relevant during start-up, would be to cool the radiation source 22 by maintaining a flow of fluid inside the treatment unit without having any (new) fluid flowing into and out of the treatment unit.

Fig. 9 shows schematically a further embodiment of a stage 2 of a fluid treatment unit according to the present invention. In this embodiment, the source channel 20 is arranged parallel to a radius of the floor element 19. Similar to the embodiment shown in fig. 6, the stage 2 comprises a socket (not shown) for receiving a radiation source; the source is not shown in the figure. Fig. 10a and 10b show further embodiments of stages of fluid treatment units according to the present invention. The source channel is in these embodiments defined by a penetration 34 provided in the floor element 19 wherein the stream wise extension of the source channel is the thickness of the floor element 19. In this embodiment the wall of the direct exposure channel is defined by the floor element 19 and floor elements 19 above and below. Also in this embodiment, the floor element 19 is made of a material, e.g. quarts, being transparent to the radiation emitted from the radiation source. The figures show configurations where a source shield 10 in the form of a tube is provided for housing e.g. a L)V source similar to the source shield shown in fig 7. The penetration 34 is a part of the direct exposure channel and guides the fluid to flow in close vicinity of the radiation source 22 located in the source shield 10. In fig. 10b an impeller source shield 36 is arranged in which an impeller 12 is to be arranged as disclosed in connected with fig. 11. b.

It should be mentioned that although the embodiments shown in fig.s 6-11 are shown to comprise one source channel 20, more than one source channel 20 may be provided in a stage 2. Furthermore, the mutual orientation of the source channels 20 may be varied, e.g. two or more source channels may be orientated similar to each other or different to each other.

In some embodiments, the radiation source 22 - or one or more radiation sources in general - of a stage 2 is an integral part of the stage 2 in the sense that it is non-removable, and in other embodiments the stages 2 are provided with a socket 21 that enables removal of the radiation source 22. The latter embodiments are particularly useful in situations where for instance the radiation source deteriorate during use, and/or in cases where the type of processing of the fluid is to be changed. This may be then be performed by only changing the radiation source.

Fig. 11 shows schematically a treatment stage 2 of a fluid treatment device according to a preferred embodiment of the invention wherein the radiation source is an ultrasound source. Fig. 11a shows the treatment stage 2 in a partly exploded view, and fig. lib shows a segment of a cross sectional view taken along a radius of the treatment stage 2 with the shaft 35 removed. Arrows labeled F in the figure indicate the flow of the fluid through the stage 2.

As shown in fig 11a, the treatment stage 2 is similar to one of the treatment stages 2 shown in fig. 6 and 7 although the treatment stage 2 in fig. 11 does not comprise the source shield 10 and the L)V radiation source 22. Instead, an ultrasound generator 37 with an ultrasound horn 38 is arranged to emit ultrasound to the source channel 20. A flow guide 39 is also arranged within the source channel 20. The flow guide 39 leaves a passage open between the ultrasound horn 38 and the end of the flow guide 39 whereby the flow guide assists in guiding the fluid towards the ultrasound horn 38. The flow guide 39 may further more be excited by the sound waves emitted from the ultrasound horn 38. Also in this case a number of treatment stages 2 may be stacked similarly to what is shown in fig. 7, and the stack may be incorporated in the embodiments shown in fig. 12 and 13. Furthermore, such a stack of treatment stages may comprise different radiation sources to provide different treatment technologies, for instance a combination of the L)V treatment and the ultrasound treatment. Also in this embodiment, the floor element 19 may be made of a material, e.g. quarts, being transparent to L)V radiation so that when one ore more stages of fig. 11 are combined with e.g. one or more stages of fig. 7, the L)V radiation may penetrate the floor element 19.

An impeller 12 is arranged within the impeller shield 36 which shield 36 guides the fluid through the impeller 12.

It should be noted that while the stages shown in figs. 6-11 are disclosed as being stacked, each stage may be used alone. In such embodiments, a stage is equipped with an inlet element and outlet element e.g. as shown in fig. 1 inside which suitable flow guides are arranged so that direct exposure channels are defined above and below the floor element.

Fig. 12 shows schematically a fluid treatment unit 1 according to the present invention. The unit shown in fig. 12 is formed as an elongated unit having cylindrical outer shape and comprising six stages 2, an inlet element 5, an outlet element 4 and a motor 8. The motor 8 is arranged on a fixture 9. The sockets 21 are also indicated in the figure.

Within the stages 2 a number of impellers 12 (see fig. 7) are arranged which impellers 12 are arranged on a common shaft 35 extending from the motor 8 to a bearing 40 (see fig. 13) arranged in the inlet element 5 so that when the motor 8 rotates, it rotates all the impellers 19.

Fluid enters into the fluid treatment unit 1 through the inlet 6 provided in the inlet element 5, flows through the treatment stages 2 an leaves the fluid treatment unit 1 through the outlet 7 provided in the outlet element 4. A pressure increasing step may be provided in the inlet element 5 or the outlet element 4 by arranging a number of impellers 12 to form a pressure increasing stack of impellers 12 which impellers are arranged on the common shaft 35. The pressure increase provided by the stack of impellers 12 may be larger than the pressure drop resulting from the flow and processing of the fluid in the stages 2, and the fluid thereby leaves the fluid treatment unit 1 at an increased pressure level relatively to the pressure of the fluid at the inlet 6. The number of stages 2 may be selected according to a specific need for treatment. For instance, the three stages 2 shown in fig. 7 may be three of the stages 2 shown in fig. 12 and the remaining three stages being omitted. Alternatively, only one of the stages 2 shown in fig. 7 may be one of the stages shown in fig. 12 and the remaining five stages 2 being omitted.

Fig. 13 shows schematically a longitudinal cross section of a fluid treatment unit 1 according to the present invention, and shows in particular one way of assembling the unit shown in fig. 12. The unit is formed as an elongated unit having a cylindrical casing 41 and comprises seven stages 2, an inlet element 5, an outlet element 4 and a motor 8 arranged on a fixture 9 with a shaft 35 for rotating impellers (not shown) arranged in the fluid treatment unit 1. Radiation sources as well as the flow passages are not shown in the figure. The stages 2 may be in the form shown in the previous figures with corresponding descriptions. The inlet element 5 and the outlet element 4 are considered as part of the casing.

In the embodiment illustrated in fig. 13, the stages 2 and elements 4,5 are assembled by a fluid treatment unit assembling fixture 42 comprising a number of stay bolts 43 extending along the longitudinal direction of fluid treatment unit 1 and penetrating clamps 44. Nuts 45 are provided on the ends of the stay bolts 43 so that when the nuts 45 are tightened, the clamps 44 will provide a longitudinal force to the fluid treatment unit 1 so that the elements 4,5 and stages 2 are held together in the longitudinal direction.

Securing of the elements 4,5 and stages 2 in a direction perpendicular to the longitudinal direction of the fluid treatment unit 1 is shown as being provided by ring shaped guides 46 into which the elements 4,5 and stages 2 fit snugly. Sealing of the fluid treatment unit is provided by applying o-rings (not shown) e.g. in grooves (not shown) provided in the ring shaped guides 46. Alternatively, or in combination thereto, the ring shaped guides 46 may be formed as assembling rings 28 arranged inside the fluid treatment unit as shown in fig. 7.

Fig. 14 shows schematically a longitudinal cross section of three stages 2 according to the present invention assembled in an alternative manner. The stages 2 may e.g. be three of the stages shown in fig. 12, but the method of assembling the stages may be used in other embodiments. Again, flow passages and radiation sources are not shown in the figure. The housing rings 29 of the stages 2 are provided with a recess 47 at one end and a projection 48 at the opposite end. In the recess 47 and on the projection 48 threads are provided, which projection and recess with threads are corresponding so that stages can be assembled by turning the stages relatively to each other. It should be mentioned that this way of assembling may also be applied to the assembling of the inlet and outlet elements 4,5 with the stages 2.

Fig. 15 shows schematically a longitudinal cross section of a fluid treatment unit 1 according to the present invention. The fluid treatment unit 1 is formed as an elongated unit having a cylindrical shape and comprises six stages 2, an inlet element 5, an outlet element 4 and a motor 8 with a shaft 35 for rotating impellers (not shown) arranged in the fluid treatment unit 1; radiation sources as well as the flow passages are not shown in the figure. The part of the unit's casing extending along the stages 2 is a composite casing composed by a tubular part 49 and the housing rings 29 of the stages 2. Other structures may be included in the composite casing, such as sealing elements, further tubular elements, securing elements guides etc. The internal diameter of the tubular part 49 is chosen in respect to the outer diameter of the stages 2, so that a snug fit between the wall of the tubular part 49 and the housing rings 29 of the stages 2 is provided. Thus, as the housing rings 29 abut the tubular part 49 and thereby provide a composite casing, the housing rings 29 of the stages 2 form a part of casing. It should be mentioned that although the housing rings 29 of the stages 2 are shown as abutting the tubular part 49 along the entire longitudinal extension of stages 2, this may not always be the situation. For instance, some or all of the housing rings 29 may be recessed along the side of the housing rings 29 facing towards the interior surface of the tubular part 49 so that only a part of the housing rings 29 abuts the tubular part 49. Assembly of the fluid treatment unit disclosed in connection with fig. 15 may be provided in the manner disclosed in connection with figs. 13 and 14. However, the fluid treatment unit 1 according to fig. 15 may preferably be assembled by providing threads in a recess 47 of the inlet element 5, the outlet element 4 and on the outer wall of the tubular part 49 so that the fluid treatment unit 1 is assembled by turning the inlet and outlet elements 4,5 relatively to the tubular part 49.

Although the description of the present invention presented herein focus on impellers for driving the fluid through the fluid treatment unit, other types of pressurisation means may be used. However, in connection with the present invention it has been found that impellers are advantageous, as the impellers provide a flow which includes a swirling velocity component in the fluid flowing through the one or more of the stages or the whole fluid treatment unit. Such a swirling velocity component may be used to increase the interaction with the radiation source in the unit which may be utilised to process the fluid more intensively while keeping the overall outer dimensions of the fluid treatment unit low and the velocity in the unit high.

Fig. 16 shows schematically a cross sectional view of a segment of an embodiment in which radiation guide means in the form of a lens for focusing the radiation into the source channel is arranged. Fig. 16 shows in particular, a source shield 10 in the form of an elongated tube similar to the source shield disclosed in connection with e.g. fig. 3. Inside the source shield 10 a radiation source 22, preferably being an L)V radiation source is arranged together with a lens 50. Arrow 51 indicates the flow of the fluid flowing through the source channel 20. The lens 50 focuses the radiation emitted from the source 22 preferably on a wall part 52 of the source channel 20 as indicated by the lines. The wall part 52 may also be made as a radiation direction part, typically embodied by making the wall part 52 reflective to reflect radiation back into the source channel 20. Fig. 17 shows schematically a cross sectional view of a segment of an embodiment in which radiation guide means in the form of a mirror for focusing radiation into the source channel is arranged. Fig. 17 shows an embodiment similar to the embodiment shown in fig. 16 except that the radiation guide means is in the form a mirror 53 re-directing radiation emitted in a direction facing away from the source channel 20 into the channel as indicated by the lines in the figure. Also in this embodiment, the wall part 52 may be made as a radiation direction part, typically embodied by making the wall part 52 reflective to reflect radiation back into the source channel 20. It should be noted that combinations of the radiation guide means may be used, e.g. a combination of the mirror 53 and the lens 50, which combination may be combined with the reflective wall part 52.

By employing such guide means, the intensity of the radiation may be increased by focusing radiation locally whereby a more efficient exposure may be applied to the fluid.

In many practical implementations it has been found valuable to measure the intensity of the radiation emitted into the fluid flowing through the source channel 20 - typically in order establish whether the fluid has been exposed to radiation sufficiently strong to e.g. destroy bacteria or the like. In preferred embodiments, a radiation sensor is arranged in the wall of the source channel 20 e.g. at the position indicated by numeral 54 in fig. 16 and 17. The use of sensors is not restricted to applications with a radiation source emitting L)V radiation; other type of sensors may be implemented in the unit. Such other sensor may be used for measuring e.g. the radiation emitted from the treatment unit and/or the effect of emitting radiation to the fluid.

A photo catalytic coating such as TiO₂ may advantageously be provided to the surface of the wall part 52 facing towards the radiation source 22.

Fig. 18 shows schematically a cross sectional view of preferred embodiment of a fluid treatment unit according to the present invention. Fig. 18 shows in particular a fluid treatment unit from which the segments shown in fig. 16 and 17 are taken. The radiation guide means 50,53 are not shown in fig. 18. Reference is furthermore made to fig. 7 which shows a similar configuration although fig. 18 comprises an inlet element 55 being different from the inlet element 5 (see fig. 12) applied in connection with the embodiment of fig. 7 and although the layout of the treatment is different.

In situations where the radiation is L)V radiation, the L)V radiation may be used to generate ozone which may be led into the fluid present in the fluid treatment unit. In one particularly preferred embodiment, generation of ozone is provide by air flowing past the radiation source 22 arranged in the source shield 10 (see e.g. fig. 18) whereby ozone is generated in the air inside the source shield 10. Such a flow past the radiation source has furthermore the effect of cooling the radiation source. This mixture of ozone and air is fed into the fluid treatment unit 1, preferably at a location upstream of the radiation source 22, for instance by a nozzle (not shown) arranged upstream of the source channel. This is particularly useful in connection with destruction of legionella bacteria as the ozone punctures host cells for the legionella bacteria so that the host cells become ready for L)V radiation. Destruction of e.g. legionella may be additionally or alternatively be further assisted by exposing the fluid to ultrasound. Fig. 19 shows a cross sectional view of the embodiment shown in fig. 18.

In some situations recirculation of fluid may be advantageous. For instance, some radiation sources need some warm-up time before the radiation level of the source reaches an appropriate level when considering the amount of radiation needed for a given purpose. In such an many other situations in general, fluid having flown through one or more source channels has not been sufficiently exposed to the radiation and in order to treat this fluid further, the fluid is re-circulated to flow through one or more source channels. The recirculation may be performed internally in the unit by e.g. arranging a closeable connection in the floor element 19 of the embodiment shown in fig. 7 and/or fluid may be re-directed from the outlet 7 to the inlet 6 by a suitable valve system.

An alternative or additional method of providing a kind of recirculation, such as in order to increase the exposure to radiation may be to provide a more or less spiralling flow pattern by the one or more impellers. This may be provided by increasing or decreasing a tangential velocity of the flow of the fluid around the impeller without affecting a radial velocity component. This may be provided by increasing a speed of the one or more impellers. The increase of the impeller speed will have a tendency to increase the total pressure of the fluid during its passage through the impellers. This increase in total pressure may, if no other measures are incorporated in the device, result in a higher flow rate giving a lower residence time. In order to take this into account, throttling of the flow of the fluid to be treated may be applied e.g. by a throttling valve arranged in the flow path. Furthermore, one or more flow sensors are typically arranged in connection with the throttling valve(s) for determining the actual flow rate through the device so that if e.g. an increase in rotational speed of the impellers give rise to an unwanted increase in flow rate, the device may be throttled so as to decrease the flow rate.

It should be mentioned that when throttling is applied, the control method may comprise a step of increasing/decreasing throttling while maintaining the rotational speed of the impellers. Thus, the fluid past the radiation source and past elements made of a radiation penetrable material - flows also in a spiralling flow pattern comprising a radial velocity component V_r and a tangential velocity component V_t - for which the velocity components may be optimised and regulated, along with the throttling, in order to provide an amount of spiralling flow to obtain an exposure to radiation which fulfils the requirements. The method may comprise use of information on the relationship between the rotational velocity of the impellers and the transferral of e.g. radiation. This information may include quantitative or qualitative information on the correlations with the tangential velocity of the fluids, which correlation may depend on the physical properties of the fluids. The information may e.g. be gained from experiments or from computer simulations or even via feedback from a radiation sensor and/or from a sensor measuring the effect of emitting radiation to the fluid. Information from experiments or from computer simulations is typically stored in a database or other computer readable medium from where it can be retrieved by the control system used in the application of the method.

Furthermore, fouling of the unit and in particular of the source shield may be removed by increasing the velocity of the fluid flowing past the surfaces. This results in an exposure time being relatively smaller than if the velocity was lower, and it may therefore be necessary to re-circulate the fluid through the unit.

When recirculating the fluid in one or more of the ways described herein the increased performance of the system is also due to the increased turbulence created by the recirculation which again increases the certainty that all of the fluid is treated.

Fig. 20 shows schematically a further embodiment of a treatment stage of a preferred embodiment of a treatment unit according to the present invention. Fig. 20 shows a treatment stage 2 comprising an outer casing 56 and an inner tube 57. Inside the inner tube 57 a radiation source 22 is arranged in a source shield 10 similarly to what is disclosed in connection with e.g. fig. 2 and 3. The inner tube 57 is penetrable to the radiation emitted from the radiation source, and the channel 58 defined between the outer casing 56 and the inner tube 57 thereby constitutes an indirect exposure channel, and the channel 59 defined between the inner tube 57 and the source shield 10 constitutes a direct exposure channel. The flow path through the treatment stage is indicated by the arrows. The fluid is pumped through the treatment stage by an impeller 12 driven by a motor 8.

The above description has focussed on radiation of electromagnetic radiation in form of L)V radiation. However, the invention is also applicable in connection with other radiation sources, such as radioactive radiation, ultrasound, mechanical wave radiation, and pressure wave radiation (e.g. ultrasound). Implementation of these other types of radiation may e.g. be accomplished arranging a desired source inside the source shield 10 similarly to the source 22 in fig. 8 or arranging the desired source in the source channel 20 in general. If no shielding is needed or preferred, the source shield 10 may of course be omitted.

An advantageous feature of the present invention is coating of some of some of the surfaces in the unit with a photo catalytic substance such as TiO₂, since exposure of such coated surface with e.g. L)V light when water is contacting the coated and exposed surfaces result in generation of OH^". This has shown to have advantageous effect in cleaning e.g. water. In the present invention, such coating may very advantageously be applied to surfaces behind which the source is arranged. Thus, the coating may preferably be arranged on the surface of the source shield 10 facing the fluid flow. Other surfaces may also advantageously be coated e.g. the surface of the floor elements 19. Furthermore, the wall part 52 of fig. 16 and 17 may also advantageously be coated with TiO₂. Alternatively TiO₂ particles can be added to the fluid, e.g. before the fluid is led into the fluid treatment unit 1.

One aspect of the invention relates to exposing fluid to L)V radiation. Conventional L)V sources may be applied in connection with the present invention, such as L)V bulbs and L)V light emitting diodes. The L)V light radiation may be introduced to the fluid as indicated in the above disclosed embodiments. In addition or in combination thereto, L)V radiation - or radiation in general - may e.g. be introduced by directing L)V radiation into the floor elements 19 for instance at the rim of the floor elements, or by embedding a number of L)V sources e.g. L)V light emitting diodes into the floor elements 19.

Furthermore, optical fibres may be used to guide L)V radiation into the treatment unit. In one embodiment, optical fibres are arranged as a bundle of fibres arranged in the source channel 20, so that each fibre in the bundle is arranged with a distance to neighboring fibres to allow fluid to flow through the source channel 20. Furthermore, the source shield 10 is left out and the fibre bundles also occupy the space of the source shield. The surface of the optical fibres may be coated with a photo catalytic substance such as TiO₂. As indicated above, the embodiments of the present invention may be made modular e.g. by a stack comprising a number of treatment stages 2. One or more of the treatment stages are preferably a cassette which comprises one or more radiation sources 22, impellers 12 and the like - or is adapted to receive such feature - so that a cassette is preferably a ready to use element which can be arranged in a stack to form a complete treatment unit such as the unit shown in fig. 12. In other embodiments, one or more cassettes disclosed herein are combined with cassettes comprising other means for interacting with the fluid.

It should be noted that the casing of the units according to the present invention preferably are made of a material which is not penetrable to radiation so that the radiation emitted from one or more sources emitting preferably electromagnetic radiation does not leave the unit. Utilisation of cassettes is very convenient where treatment units need to be tailored to a specific need - for instance various treatment technologies may be combined by combining cassettes with the various treatment technologies and a given treatment capacity may be matched by stacking a number of cassettes.

Another aspect of the present invention relates to controlling the amount of radiation emitted to the fluid flowing through devices according to the present invention. In many of the devices according to the present the total pressure increasing means comprising one or more impellers and such impellers generate a spiralling flow pattern inside the device. Such a spiralling flow pattern comprises a radial velocity component V_r and a tangential velocity component V_t where V_r is considered correlated with the flow rate through the device and V_t is considered non-correlated with the flow rate but correlated with the rotational speed of the impellers. Typically, the radial component may be estimated based on the flow rate divided by a flow channel area. The flow rate may be slightly correlated with the rotational speed of the impellers due to a change in pressure increase resulting from a change in rotational speed of the impellers. However, the correlation may be removed by arranging one or more throttling valves in the flow path for the fluid so as to control the flow rate.

Thus, the flow through the device may be controlled by controlling the rotational speed of the impellers which may advantageously be applied to control the radial and tangential velocities. This control method has the advantage that the magnitude of the radial and tangential velocity components may be controlled independently of each. By using this control method the flow rate through the device may e.g. be increased or decreased while maintaining the magnitude of the tangential velocity component or the magnitude of the tangential velocity component may be increased without changing the flow rate. By utilising the control method the advantages that fouling on the source may be removed and tailing effects (where particles shadow for each other) may be made smaller by increasing the tangential velocity component.

Claims

1. A fluid treatment unit through which fluid may flow while being exposed to treatment, the unit comprising - a radiation source arranged to emit radiation into fluid being present in the treatment unit, a flow passage being connected to an inlet and an outlet of the fluid treatment unit through which the fluid flows into and out of the fluid treatment unit, and comprising: - a direct exposure channel guiding the fluid past a radiation source so that the radiation source emits radiation directly into the fluid

2. A fluid treatment unit according to claim 1, wherein the casing furthermore encapsulates one, more or all of the one or more radiation sources.

3. A fluid treatment unit according to claim 1 or 2, wherein the flow passage through the unit further comprises one or more source channels.

4. A fluid treatment unit according to any of the preceding claims, wherein the unit comprises one or more treatment stages each comprising a flow passage forming part of the flow passage through the unit.

5. A fluid treatment unit according to claim 4 when dependent on claim 3, wherein some or all of the flow passages of one or more of the treatment stages comprises two cavities being in fluid communication with each other via the source channel.

6. A fluid treatment unit according to any of the preceding claims, wherein the total pressure increasing means comprise(s) one or more velocity inducers.

7. A fluid treatment unit according to any of the preceding claims, wherein at least one of the one or more total pressure increasing means comprises one or more impellers.

8. A fluid treatment unit according to claim 7, wherein some or all the impellers are arranged on a common shaft connected to a motor.

9. A fluid treatment unit according to any of claims 4-8 when dependent on claim 4, wherein each treatment stage comprises at least one total pressure increasing means.

10. A fluid treatment unit according to any of the preceding claims, wherein at least one of the at least one radiation sources is arranged in a channel being shielded from the flow passage and being transparent to radiation emitted from the radiation source, the unit being adapted to transport fluid through the channel and subsequently transport the fluid into the flow passage of the fluid treatment unit.

11. A fluid treatment unit according to claim 10, wherein the radiation source is an L)V source and the fluid transported through the channel is atmospheric air.

12. A fluid treatment unit according to claim 10 or 11, wherein the fluid transported into the fluid passage is transported into the flow passage upstream of one of the at least one radiation sources.

13. A fluid treatment unit according to any of the preceding claims, wherein the at least one radiation source is/are one or more emitting sources emitting radiation.

14. A fluid treatment unit according to claim 13, wherein the one or more of the one or more emitting sources is/are one or more electromagnetic radiation source(s) emitting electromagnetic radiation into the at least one source channel.

15. A fluid treatment unit according to claim 14, wherein the one or more electromagnetic radiation sources is/are L)V radiation source, a laser light emitting source, light emitting diodes and/or a microwave emitting source.

16. A fluid treatment unit according to claim 15, wherein one or more of the L)V radiation sources is/are placed inside a source shield such as a protecting tube.

17. A fluid treatment unit according to claim 16, wherein the source shield is made from quartz.

18. A fluid treatment unit according to claim 13, wherein one or more of the one or more emitting sources is/are one or more sources emitting

5 radioactive radiation.

19. A fluid treatment unit according to claim 13, wherein one or more the one or more emitting sources is/are one or more sources emitting sound waves, such as ultrasound waves.

20. A fluid treatment unit according to any of the claims 13-19, wherein one 10 or more of the at least one emitting sources is/are elongated and has a length axis.

21. A fluid treatment unit according to any of the claims 13-20, the unit comprising a plurality of radiation sources of at least two different types.

22. A fluid treatment unit according to any of the preceding claims, the unit 15 further comprising radiation guide means for directing radiation emitted from one or more of the least one radiation source.

23. A fluid treatment unit according claim 22, wherein the radiation guide means is/are adapted to direct radiation emitted from a radiation source into a direction being different from the direction it was emitted from the

20 radiation source.

24. A fluid treatment unit according to claim 22 or 23, wherein the radiation guide means comprises one or more lenses.

25. A fluid treatment unit according to any of the claims 22-24, wherein the radiation guide means comprises one or more mirrors.

25 26. A fluid treatment unit according to any of the claim 22-25, wherein the radiation guide means focus radiation emitted from a radiation source.

27. A fluid treatment unit according to any of the preceding claims, the treatment unit comprising a pressure sensor, a temperature sensor, a fluid velocity sensor, a mass flow sensor, a volumetric flow sensor, a pH-sensor,

30 a conductivity sensor, an organic content sensor, a capacitance sensor, a turbidity sensor, a radiation sensor, a spectrometric sensor or combinations thereof.

28. A fluid treatment unit according to any of the preceding claims, further comprising means for recirculating fluid that has flown through one or more

35 source channels to flow through one or more source channels again.

29. A fluid treatment unit according to claim 28, wherein the recirculation is performed inside the casing.

30. A fluid treatment unit according to claim 28, wherein the recirculation is performed by transporting fluid from the outlet to the inlet of the fluid treatment unit.

31. A fluid treatment unit according to any of the preceding claims, wherein one or more sections of surfaces of the flow passage through the unit being exposed to radiation emitted from the one or more radiation source(s) is/are coated with or being made from a photo catalytic substance.

32. A fluid treatment unit according to claim 31, wherein the photo catalytic substance is TiO₂.

33. A fluid treatment unit according to claim 31 or 32, wherein the section of the surface being coated with or made from a photo catalytic substance comprises the surface of a shield shielding the radiation source from direct contact with the fluid flowing through the unit.

34. A fluid treatment unit according to any of the clams 31-33, wherein the section of the surface being coated with a photo catalytic substance comprises at least one or more sections of the wall elements of the indirect exposure channel being penetrable to radiation emitted from the radiation source and arranged so that radiation emitted into the direct exposure channel is also emitted into the indirect exposure channel.

35. A fluid treatment unit according to any of the claims 31-34 when dependant on claim 22, wherein the section of the surface being coated with a photo catalytic substance comprises one or more surface section of the radiation guide means.

36. A fluid treatment unit according to any of the preceding claims, wherein the radiation source is a source emitting L)V radiation with a wave length in the order of 250 nm.

37. A fluid treatment unit according to any of the preceding claims, the unit comprising one or more cassettes.

38. A fluid treatment unit according to 37, wherein an outer housing of one or more of the cassettes forming at least a part of the casing forms at least a part of an outer surface of the casing.

39. A fluid treatment unit according to claim 37 or 38, wherein an outer housing of one or more of the cassettes forming at least a part of the casing abuts an interior surface of the casing.

40. A fluid treatment unit according to any of the claims 37-39, wherein one or more of the cassettes comprises total pressure increasing means.

41. A fluid treatment unit according to any of the claims 37-40, wherein one or more of the cassettes is adapted to receive or comprises a velocity

5 inducer, preferably being an impeller, the velocity inducer constituting at least a part the flow passage(s).

42. A fluid treatment unit according to any of the claims 37-41, wherein one, some or all of the cassettes comprises a treatment stage.

43. A fluid treatment unit according to any of the preceding claims, wherein 10 the one or more total pressure increasing means for increasing the total pressure of the fluid at least locally in the fluid treatment unit comprises a pump.

44. A fluid treatment unit according to any of the preceding claims, wherein one or more throttling valves are arranged in the flow path of the fluid.

15 45. A cassette comprising one or more radiation sources or being adapted to receive one or more radiation sources, one or more total pressure increasing means or being adapted to receive one or more total pressure increasing means for increasing 20 the total pressure of fluid at least locally in the cassette.

46. A cassette comprising one or more of the features according to claim 1-

44.

47. A method of treating a fluid, the method comprising letting fluid flow through a fluid treatment unit according to any of claims 1-44.

25 48. A method of treating a fluid according to claim 47, wherein photo catalytic particles, such as TiO₂ particles, are present in the fluid.

49. A method of controlling a fluid treatment unit according to any of the preceding claims 7-44, the method comprising controlling the rotational speed of the impellers so that a pre-determined flow rate is obtained or

30 maintained.

50. A method of controlling a fluid treatment unit according to claim 49, further comprising controlling a radial velocity component V_r and a tangential velocity component V_t of one or more impellers, and hereby generating a spiralling flow pattern inside the device.

35 51. A method of controlling a fluid treatment unit according to any of the preceding claims 49 or 50, the method further comprising throttling one or more throttling valves in the flow path of the fluid and hereby controlling the radial velocity component V_r and the tangential velocity component V_t of the one or more impellers.

52. A method of controlling a fluid treatment unit according to any of the preceding claims 49, 50 or 51, the method further comprising increasing the tangential velocity component of the one or more impellers.

53. A method of controlling a fluid treatment unit according to any of the preceding claims 49-52, wherein the spiralling flow pattern inside the device is provided at least partly around the one or more impellers and is provided as a way of at least partly recirculating the fluid inside the device.