Hydrodynamically-enhanced UV photo-oxidation of contaminated liquids

Abstract

The present disclosure relates to a fluid treatment system. The system comprises a vessel, comprising a peripheral wall and two end walls at a distance from each other along a longitudinal axis of the vessel, where the distance defines an axial length of the vessel. Further a plurality of UV lamps is arranged in the vessel for treatment of fluid. Also a fluid input and a fluid discharge are provided, configured to generate a flow of fluid through the interior of the vessel. According to the present disclosure, at least one of the input and the discharge extends over a substantial portion of the axial length of the vessel on the peripheral wall between the end walls and is oriented tangentially to an inside of the peripheral wall, wherein a spiraling flow of fluid extending to or from the tangential fluid input and / or discharge is generated inside the vessel.

Description

[0001] HYDRODYNAMICALLY-ENHANCED UV PHOTO-OXIDATION OF CONTAMINATED LIQUIDS

[0002] FIELD

[0003] The present disclosure relates to the field of fluid treatment and more in particular hydrodynamically-enhanced photo-oxidation of contaminated liquids, and, in particular, though not exclusively, to a system for hydrodynamically-enhanced UV photo-oxidation of contaminated fluids.

[0004] BACKGROUND

[0005] Nowadays contaminated water or other fluid originating from domestic residences and / or industry (e.g. the pharmaceutical industry, hospitals, farming, etc.) requires removal of the contaminants before it can be re-used or released to open water. Typically, the contaminants are organic and / or inorganic micro-pollutants and the removal of these pollutants from the fluid (water) is based on an oxidation reaction wherein an oxidation agent, e.g. Hydrogen peroxide is homolytically cleaved into OH-radicals and these are used to oxidize pollutants in the stream. Other reagents like Ozone can also be used. This process is commonly referred to as advanced oxidation in the industry and is used by many, in different ways, mainly for fluid (water) treatment. Preferably fast and efficient full oxidation of the (micro)pollutants is desired.

[0006] Radicals typically react orders of magnitudes faster with contaminants than chemical oxidants such as ozone and hydrogen peroxides alone, without UV activation. These radicals may be generated by a catalyst like titanium oxide or combining UV light with hydrogen peroxide or ozone. In some cases these reactions may be improved using a suitable catalyst such as in the -Fenton reaction wherein OH radicals may be generated on the basis of hydrogen peroxide in combination with iron II / III ions.

[0007] The OH radical reacts non-selectively with every impurity that can be oxidized it encounters and its lifetime is therefore very short. Known systems for UV photo-oxidation solve this problem by using relatively high concentrations of hydrogen peroxide in combination with high doses of UV light, to create as many radicals as quickly as possible in the fluid (water) stream. Typically these high UV doses are achieved by high- power, medium, low or high-pressure UV sources.

[0008] For example, US-2011 / 318237 describes an UV photo- oxidation reactor wherein the contaminated influent and hydrogen peroxide are led into a reaction chamber that comprises one or more UV lamps for generating OH radicals so that contaminants in the reaction chamber are oxidized. The reactor volume is divided in a plurality of segmented baffles in order to increase radial mixing. Despite the claims in this document, the baffles inevitably create dead spaces where the liquid does not flow thereby reducing the total effective volume of the reactor. Further, the baffles will cause shadowing effects reducing the UV exposure of the liquid. Hence, although some improvement in mixing of the oxidation agent in the liquid will be achieved, the baffles will also have a significant effect on the oxidation efficiency. Additionally, the baffles will form substantial flow impedance for the pumping system so that substantially more pumping power is required in order to maintain a certain flow through the reactor when compared with the situation without baffles. A further photo-oxidation system is closed in US 2004 / 045886 Al. Merely as an example, further reference is made here to EP-3.166.889, in the same name as the present disclosure.

[0009] Here, it is noted and acknowledged that the prior art publication CH-580037 discloses vessels with in- and outputs that are arranged at and limited to longitudinally opposing ends of the longitudinal vessel. The fluid input of this know vessel configuration is oriented tangentially on an interior wall of the vessel at one end wall only of the vessel, thus generating a helical fluid flow through the interior of the vessel, with a helical flow having an essentially constant diameter along an inside of the outer wall of the vessel, wherein fluid (water) and in more detail particles or molecules thereof travel axially away from the input, at an essentially constant flow speed. Such vessels need to be embodied impractically long in order to even approximate a desired level of removal of contaminants, the more so because a helical fluid flow will only propagate along an interior wall of the vessel in the helical path. As a consequence, a central volume of fluid in the vessel may remain stagnant inside the vessel, reducing the effectiveness and efficiency of this prior art configuration. This is emphasized and exacerbated by the provision in the prior art vessel of an air filled container 15, in which Ozon may be generated using an air input, an air outlet and at least one UV lamp extending in or through the air filled container.

[0010] Hence, there is a need in the art for improved systems for UV photo-oxidation of contaminated liquids. In particular, there is a need in the art for systems for UV photo-oxidation of contaminated liquids that allow more efficient oxidation of contaminants in the fluid such as water using UV- generated radicals, while at the same time reducing dimensions, and in particular axial as well as radial dimensions, of a vessel relative to prior art configurations, needed to achieve a same or even higher degree of fluid treatment, such as in particular fluid sanitation or sterilization or contaminant oxidization.

[0011] SUMMARY

[0012] The system according to the present disclosure provides improvements over the prior art in terms of efficiency of oxidation of contaminants in the fluid such as water using UV-generated radicals and / or of size and / or dimensions of a system required therefore.

[0013] To this end the present disclosure presents a fluid treatment system, comprising:

[0014] - a vessel, comprising a peripheral wall and two end walls at a distance from each other along a longitudinal axis of the vessel, where the distance defines an axial length of the vessel;

[0015] - a plurality of UV lamps arranged in the vessel for treatment of fluid; - a fluid input and a fluid discharge, configured to generate a flow of fluid through the interior of the vessel.

[0016] According to the present disclosure, at least one of the input and the discharge extends over a width corresponding with and parallel to a substantial portion of the axial length of the vessel between the end walls and is oriented tangentially to an inside of the peripheral wall, wherein a spiraling flow of fluid extending to or from the tangential fluid input and / or fluid discharge is generated inside the vessel. The spiraling fluid flow and the means of achieving the same distinguish the present disclosure over the prior art and the helical fluid flow thereof, wherein fluid (water) and in more detail particles or molecules thereof flow around the longitudinal axis at increasing or decreasing distances and correspondingly decreasing or increasing fluid flow speeds, but essentially not along and only around the axis, in order to be considered spiraling (in instead of helical).

[0017] In a particular embodiment, the fluid discharge may be arranged in line with the longitudinal axis. Then, the axial fluid discharge may comprise an output conduit which is centrally arranged inside the vessel, and in this embodiment the conduit of the axial fluid discharge may comprise a central tube with though flow openings at positions on the inside the vessel and a output end outside the vessel.

[0018] In an alternative or additional embodiment, at least one of the plurality of UV lamps may be arranged in the interior of the fluid discharge.

[0019] In an alternative or additional embodiment, the fluid input may comprise a tangentially oriented manifold.

[0020] In an alternative or additional embodiment, the fluid input may comprise an input conduit extending parallel to the longitudinal axis of the vessel on the outside of the peripheral wall.

[0021] In an embodiment with a tangentially oriented manifold and an input conduit parallel to the longitudinal axis an input of the tangentially oriented manifold may be formed by the input conduit.

[0022] In an embodiment with at least a tangentially oriented manifold, the manifold may comprise a plurality of branch conduits oriented tangentially to an inside of the peripheral wall.

[0023] In an alternative or additional embodiment, the tangentially oriented fluid input may be arranged tangentially oblique to the peripheral wall. Alternatively, the fluid input may extend essentially perpendicularly into the vessel and comprises at least a bend inside the peripheral wall for tangential injection of the fluid.

[0024] In an alternative or additional embodiment, the spiraling flow of fluid defines an axially extending front of flow of fluid propagating over time at decreasing or increasing distances from the longitudinal axis of the vessel.

[0025] In an alternative or additional embodiment, the UV-lamps may be, in cross sectional view perpendicular to the longitudinal axis, arranged in coaxial rings having different diameters. Then, each ring may comprise the same number of UV lamps, distributed evenly over the circumference of each ring. Alternatively or additionally, at least one UV lamp may be omitted in an outer ring at a position immediately downstream from the fluid input. In an alternative or additional embodiment, the UV lamps may be elongate and extend in parallel with the longitudinal axis over the axial length of the vessel.

[0026] BRIEF DESCRIPTION OF THE DRAWING

[0027] In the appended drawing, embodiments of fluid heating systems and components thereof are shown in non-limiting embodiments, wherein the same or similar elements, components and functional aspects may be designated throughout the drawing, also for mutually differing embodiments, with the same or similar reference signs and wherein:

[0028] FIG. 1 exhibits a schematic configuration of an embodiment of a fluid treatment system according to the present disclosure;

[0029] FIG. 2 exhibits a cross sectional view of the embodiment in FIG. 1 ;

[0030] FIG. 3 exhibits a similar view as FIG. 2 of an alternative embodiment;

[0031] FIG. 4 exhibits variations on common features of the embodiments in FIG’s. 2 and 3;

[0032] FIG. 5 exhibits yet another alternative embodiment; and

[0033] FIG. 6 exhibits an embodiment of a fluid discharge.

[0034] DETAILED DESCRIPTION OF EMBODIMENTS

[0035] In FIG. 1, an embodiment of a fluid treatment system 1 according to the present disclosure is shown. System 1 may be used for treatment of contaminated water or other fluid originating from domestic residences, natural sources and / or industry (e.g. the pharmaceutical industry, hospitals, farming, etc.), which may require removal of contaminants before it can be re-used or released to open water.

[0036] To this end, system 1 comprises a cylindrical vessel 2 with a cylindrical peripheral wall 3 and two end walls 4 at a distance from each other along a cylinder axis 5 of vessel 2. The distance between end walls 4 (of which only one is visible in FIG. 1) along axis 5 defines an axial length of the vessel 2.

[0037] In vessel 2, a number of elongate and preferably slim UV lamps 6 is arranged for treatment of the fluid. Lamps 6 are preferably slim to minimize turbulence caused thereby, and may extend axially between end walls 4. However, lamps 6 may extend through (one of the) end walls 4, if appropriate sealing is provided, for example for connecting lamps 6 to a power supply (not shown). The present disclosure is not restricted to axial lamps 6, and in another (not-shown) embodiment, lamps 6 may have any orientation and / or position.

[0038] Lamps 6 are arranged, in the shown embodiment, in vessel 2 in a pattern of - in this embodiment - two rings of lamps 6 in cross sectional view concentrically positioned around cylinder axis 5. This is expected to suffice for a system 1 for processing relatively small amount of fluid or water per unit of time, depending on the capacity of lamps 6. Numerous patterns of lamps 6 are possible within the scope of the present disclosure, and some exemplary, non-limiting possible patterns will be discussed herein below. In an embodiment in which end walls 4 function to hold or suspend lamps 6, end walls 4 need to be sufficiently sturdy to withstand water pressure from the interior during treatment of the water. To allow a uniform length of lamps 6 between end walls 4, preferably, end walls 4 are flat and / or straight, in addition to sufficiently sturdy. However, flexing end walls 4 and / or non-uniform length lamps 6 may be employed in another embodiment (not shown).

[0039] To provide fluid for treatment, such as water containing contamination, to the interior of vessel 2, a fluid input 7 is provided. In an embodiment, an UV-activatable oxidation agent (or at least part there of oxidations) such as ozone and / or hydrogen peroxide may be mixed in with the contaminated fluid or water before it enters vessel 2 via fluid input 7. Fluid input 7 extends over a substantial portion of the axial length of the cylindrical vessel 2 and is oriented tangentially to an inside of the cylindrical peripheral wall 3. More in detail, input 7 extends over a substantial portion of the axial length of the vessel on the peripheral wall between the end walls. In contrast, the above referenced prior art configuration has a local input at one end wall and a local discharge at an opposing end wall to yield a helical fluid flow along interior wall of a cylindrical vessel. The configuration according to the present disclosure allows an inward spiralling flow of fluid to be generated, extending from the tangential fluid input inside the vessel. More in detail, wide sheets of fluid extending over the axial length of vessel 2 at the fluid input 7 define the inward spiralling flow starting from the tangentially oriented fluid input 7. At any cross section along the cylinder axis, an at least approximately identical inward spiralling flow is generated, which is desired and achievable to attain the advantages / benefits of the present disclosure in terms of a more compact and more efficient configuration. This spiralling flow forms a laminar flow, where subsequent turns of the inward spiral are adjacent to one another (laminar), and remain be so positioned at ever decreasing distance from the axis 5, with a surprisingly low levels of turbulence occurring there between. In other words, according to the present disclosure, a fluid flow front is generated which extends parallel to axis 5, and progress along a spiralling inward path, at - in time - decreasing distance from axis 5 to arrive at discharge 10. Thereby, the present disclosure makes it possible to generate an advantageous flow pattern for photooxidation on the basis of for example hydrogen peroxide within vessel 2 without the use of baffles or the like, wherein a key difference with the above referenced prior art is the generating of the inward spiralling fluid flow instead of the known helical fluid flow.

[0040] To generate this spiralling flow in the shown embodiment, fluid input 7 comprises an input conduit 8 extending in parallel to cylinder axis 5 on the outside of and through peripheral wall 3 of vessel 2 and supplies the fluid in the direction of arrow A, to yield a relatively compact design. A manifold is formed by conduit 8 and branch tubes 9, which extend from and fluidly connect input conduit 8 to the interior of cylindrical peripheral wall 3 of vessel 2. Input conduit 8 defines an input chamber of the thus formed manifold 8, 9, and manifold tubes 9 connect input conduit 8 with the inside of vessel 2. Manifold tubes 9 are oriented along arrow C to inject flows of fluid, i,e, water to be treated, in a direction tangential relative to inner surface of cylindrical peripheral wall 3, as is shown clearly in the cross sectional view of FIG. 2. The number of manifold tubes 9 that is provided together spans essentially the (axial) length of vessel 2, to ensure essentially identical spiralling flow paths with - in distance and / or time - diminishing diameter at practically any cross section through vessel 2, perpendicular to cylinder axis 5.

[0041] In a direction of flow from a supply end of input conduit 8 to the closer end in the representation of FIG. 1, subsequent manifold tubes 9 may have variable, for example decreasing, diameters to ensure uniform amounts of fluid being injected into vessel 2 by each of the manifold tubes 9 per unit of time, to achieve laminar sheets flowing in inward spirals or to benefit the vortex inside in other ways. More and / or other features may be included to ensure uniform injection amounts per unit of time along the axial length of vessel 2 at each manifold tube 9 of the fluid input 7.

[0042] As an alternative for a plurality of manifold tubes 9 could be formed by a single (for instance oval or rectangular) fluid input, where measures may need to be taken to ensure that influx of fluid into vessel 2 is practically identical at any part of a width of such an oval port which corresponds with the axial length of vessel 2. Likewise, manifold tubes 9 may be provided in a higher or lower number than the five manifold tubes 9 shown in FIG. 1 and input conduit 8 could be oriented in any other direction than axial relative to vessel 2, for example perpendicular to the axis 5 and in-line with manifold tubes 9. Such a configuration would be less compact, but may exhibit advantages in terms of equality of spiralling flows along the axial direction of the fluid input. Relative to the configuration of FIG. 1, input conduit 8 could be supplied with fluid to be treated from the opposite direction than arrow A or in both directions, also yielding more homogeneity of spiralling flows starting at different point along the axial length of the fluid input. In the shown embodiment, conduit 8 could be closed at two ends and be connected to a single central supply tube and / or multiple off-centre supply tubes, for instance at the ends of such an axially closed off version of conduit 8.

[0043] Manifold tubes 9 of fluid input 7 are arranged tangentially oblique to the cylindrical peripheral wall 3 and still perpendicular to the central cylinder axis 5, which may pose a challenge for proper welding where oval, three-dimensionally curved welds are required. One of multiple possible alternative configurations is discussed below in relation to FIG. 5, where this issue may be mitigated, but not completely prevented, at the expense of a less optimal flow, i.e. more turbulence.

[0044] Turning back to the embodiment of FIG. 1, a fluid discharge 10 is provided to expel treated fluid in the direction of arrow B, which is parallel to and in line with cylinder axis 5 of vessel 2. An output conduit 11 is visible in FIG. 1 behind vessel 2, and forms with an interior central tube 12 an exemplary, non-limiting embodiment of fluid discharge 10. The combination of output conduit 11 outside vessel 2 and interior central tube 12 is shown in FIG. 6. Output conduit 11 is arranged in line and coaxially with cylinder axis 5 and interior central tube 12 extends between end walls 4. Thereby, output conduit 11 passes the treated fluid from central tube 12 out of vessel 2 through one or both of the end walls 4. Central tube 12 is able to capture spiralling fluid by an intake formed by though optimised flow openings 13 in the form of slits, ovals or other optimised orifices and discharge the same in the direction of arrow B to the output conduit 11. Fluid discharge 10 therefore comprises output conduit 11, of which an exemplary and non-limiting embodiment is shown in FIG. 6, but other embodiments are equally possible. Output conduit 11 is centrally arranged outside cylindrical vessel 2, and in another embodiment the conduit of the axial fluid discharge may comprise only central tube 12 with though flow openings 13 at positions on the inside of vessel 2 and an output end outside vessel 2 without a separate output conduit 11. The position of the one of the end walls 4, through which fluid discharge 10 extends, is shown in FIG. 6. The central tube 12 with slits-shaped openings 13 is clearly visible to be limited to the interior of vessel 2.

[0045] In the embodiment shown in FIG’s. 2 and 3, some of the plurality of UV lamps 6 are arranged in the interior of the central tube 12 of the fluid discharge 10, while lamps 6 inside central tube 12 are omitted in the embodiments of FIG’s. 4 and 5.

[0046] In the embodiment of FIG. 1, two rings with UV-lamps 6 are accommodated; an outer ring with ten UV lamps 6, and an inner ring of six UV lamps 6. The outer and inner rings are concentric around cylinder axis 5 in cross sectional view, with the cross section being perpendicular to cylinder axis 5. The rings of UV lamps 6 have different diameters. In the embodiment of FIG’s. 2 and 3, five rings of UV lamps are provided at radii R1 - R5, with each ring having nine UV lamps 6. Thus, according to the present disclosure, each ring may have the same or a different number of UV lamps. UV lamps 6 are preferably distributed evenly over the circumference of each ring. As a very local exception to equal lamp numbers and even distribution, outer ring at radius R5 in FIG. 3 as well as the outer ring in the embodiment of FIG. 4 may have one or more lamp 6 omitted at the position indicated by arrow D, relative to other more inward positioned rings (with smaller diameters at R1 - R4), to better accommodate the influx of fluid from manifold tubes 9.

[0047] FIG. 4 illustrates variations in intermediate distances between five rings of UV lamps 6, to adapt system 1 to an expected size, and related throughput capacity and situation of use. For example, at low volumes of water to be treated per unit of time, a small diameter vessel 2 and low number of rings of UV lamps 6 may suffice. For relative high volumes, larger vessels 2 and higher numbers of rings of UV lamps 6 may be required. However, in a practical and economically viable embodiment, which has been simulated and tested under confidentiality, it has been proven that a system of an appropriately sized vessel 2 of for example 2 up to 3 meter and preferably approximately 2,5 meter in diameter and three to eleven (preferably five) rings of UV lamps 6 is capable of processing by UV treatment volumes of contaminated water of between 500 and 800 m3 / hr, while achieving more than adequate decontamination, at least by current and foreseeable standards. To minimize turbulence, not only numbers of rings of lamps 6, (relative) positions thereof and numbers of lamps per ring may be varied, but also the distance between the rings, which may be made to coincide with laminar flow sheets of the inward spiralling flow that is generated in accordance with the present disclosure. Even a spiralling arrangement of lamps 6 (instead of rings of lamps 6) may be contemplated for this purpose, so that not even the rings with UV lamps 6 form a limitation on the scope according to the present disclosure. FIG. 4 illustrates that even UV lamps 6 belonging to any one ring may have variations in distance to cylinder axis 5, or that a common diameter of (potentially: all) lamps 6 in one ring may be varied in an optimization process for minimizing turbulence caused by lamps 6 extending in inward spiralling flows, generated from the input 7.

[0048] It is noted here that a configuration according to the present disclosure may have a design for a specific high flow rate, for example 800 m3 / hr, which doesn’t need to be processed always. For example, at some times a lower flow rate will need to be processed, for instance 400 m3 / hr, that can progress through the spiralling path at lower velocities. Then a number of rings of lamps 6 or parts thereof, or turns of a spiralling configuration of lamps or parts thereof may be turned off to impart a same dose of illumination for processing the fluid with UV radiation as for the higher flow rates, and achieve the same processing results. Since lamps at inner rings (or inner turns of a spiral) are arranged at smaller circumferential intervals for higher fluid flow velocities than at the outside rings or turns of the lamp configuration, it has been shown not to matter if lamps on inner rings or turns are turned off, or at outer rings or turns. The same total dose of illumination may be generated for passing fluid to be properly decontaminated. Such switching on and / or off of (a selection of) lamps 6 may be achieved by a controller, based on prior knowledge of the flow per time unit to be processed, or on measurement results from a flow meter providing instantaneous insight into the flow per time and configured to determine how many of the lamps need to be switched on to impart a desired UV dose to the fluid to be processed. This allows for achieving energy savings for situations when less fluid per time unit needs to be decontaminated or otherwise processed.

[0049] In FIG. 1, a controller 21 is shown to be connected to a flow meter 20, to determine an instantaneous flow of fluid through input conduit 8 or through manifold tubes 9 into vessel 2. A result from the flow meter indicating the instantaneous flow of fluid - absent prior knowledge thereof or in addition thereto for verification - is forwarded to controller 21. Controller 21 is configured to determine a desired combined dose of UV illumination from selected lamps 6 to effectively process (decontaminated) the amount of fluid flowing into vessel 2 per unit of time. To effectively accommodate the flow of fluid in this sense, a number of the lamps may always be switched on and connected to a power source 22. However, a selection of lamps 6 may be connected to power source 22 via an array of switches 23. One of the switches in the array of switches 23 may drive a ring or turn of lamps 6 in unison, where such a ring or turn of lamps may be at an in- or outside of vessel 2. Additionally or alternatively, each one of lamps 6 may be connected to power source 23 via one of the switches in the array 23. The switches in the array of switches 23 are controlled by control 21.

[0050] Further, reference is made to the configuration in FIG. 5, which provides an alternative for the tangential and straight arrangement of the manifold tubes 9, that may need to be welded into a large oval and three dimensionally curved through hole. In this embodiment, manifold tubes 9 are directed straight at cylinder axis 5 and into vessel 2 for greater ease of welding the manifold tubes 9 in through holes in vessel wall 3. Here manifold tubes 9 extend through vessel wall 3 and debouch at a turned down or bent end portion 15 in the direction of tangential arrow C, to generate a similar tangential fluid flow as the preceding embodiments. However, even though the presence of the manifold tubes 9 and bent end portions 15 on an inside of vessel 2 is expected to cause more disturbance of a desired laminar flow for high volume flows than the preceding embodiments, it is still a compliant embodiment and resides within the scope of the present disclosure. Alternatively a wide rectangular orifice may be welded into the tank combining the multitude of pipes and bends into a single downward slit shaped orifice.

[0051] From the above example of FIG. 5, it is evident that the scope of protection under the appended claim is not bound by features of any specific embodiment disclosed herein. With appropriate adaptation, the working of a system within the scope of claim 1 could even be reversed, using central tube 12 as an alternative embodiment of the fluid input and tubes 9 of the manifold as an alternative embodiment of the fluid discharge. In the above disclosed embodiments, the UV lamps are parallel to each other and the axis 5. However, within the scope of below appended claim 1, lamps 6 may in fact cross each other and / or may cross axis 5, and / or may be arranged to form a pattern like spokes of a wheel, which may exhibit certain advantages in terms of fluid dynamics, which enhances the notion that lamps 6 may be arranged in any (other) configuration. Some other modifications have been identified in the above disclosure, where aspects for which the modifications provide alternatives are discussed.

[0052] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and / or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0053] The corresponding structures, materials, acts, and equivalents of all means or step plus function elements in the claims below are intended to include any structure, material, or act for performing the function in combination with other claimed elements as specifically claimed. The description of embodiments of the present invention has been presented for purposes of illustration, but is not intended to be exhaustive or limited to the implementations in the form disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the present invention. The embodiments were chosen and described in order to best explain the principles and some practical applications of the present invention, and to enable others of ordinary skill in the art to understand the present invention for various embodiments with various modifications as are suited to the particular use contemplated.

Claims

CLAIMS1. A fluid treatment system, comprising:- a vessel, comprising a peripheral wall and two end walls at a distance from each other along a longitudinal axis of the vessel, where the distance defines an axial length of the vessel;- a plurality of UV lamps arranged in the vessel for treatment of fluid; and- a fluid input and a fluid discharge configured to generate a flow of fluid through the interior of the vessel,CHARA CTERSIED IN THAT at least one of the input and the discharge extends over a width corresponding with and parallel to a substantial portion of the axial length of the vessel between the end walls and is oriented tangentially to an inside of the peripheral wall, wherein a spiraling flow of fluid extending to or from the tangential fluid input and / or fluid discharge is generated inside the vessel.

2. The fluid treatment system as claimed in claim 1, wherein the fluid discharge is arranged in line with the longitudinal axis.

3. The fluid treatment system as claimed in claim 2, wherein the axial fluid discharge comprises an output conduit which is centrally arranged inside the vessel.

4. The fluid treatment system as claimed in claim 3, wherein the output conduit of the axial fluid discharge comprises a central tube with though flow openings at positions on the inside the vessel and a output end outside the vessel.

5. The fluid treatment system as claimed in any of the preceding claims, wherein at least one of the plurality of UV lamps is arranged in the interior of the fluid discharge.

6. The fluid treatment system as claimed in any one of the preceding claims, wherein the fluid input comprises a tangentially oriented manifold.

7. The fluid treatment system as claimed in any one of the preceding claims, wherein the fluid input comprises an input conduit extending parallel to the longitudinal axis of the vessel on the outside of the peripheral wall.

8. The fluid treatment system as claimed in claims 6 and 7, wherein an input of the tangentially oriented manifold is formed by the input conduit.

9. The fluid treatment system as claimed in claim 6 or 8, wherein the manifold comprises a plurality of branch conduits oriented tangentially to an inside of the peripheral wall.

10. The fluid treatment system as claimed in any one of the preceding claims, wherein the tangentially oriented fluid input is arranged tangentially oblique to the peripheral wall.

11. The fluid treatment system as claimed in any one of the preceding claims 1 - 9, wherein the fluid input extends essentially perpendicularly into the vessel and comprises at least a bend inside the peripheral wall for tangential injection of the fluid.

12. The fluid treatment system as claimed in any one of the preceding claims, wherein the spiraling flow of fluid defines an axially extending front of flow of fluid propagating overtime at decreasing or increasing distances from the longitudinal axis of the vessel.

13. The fluid treatment system as claimed in any one of the preceding claims, wherein the UV-lamps are, in cross sectional view perpendicular to the longitudinal axis, arranged in coaxial rings having different diameters.

14. The fluid treatment system as claimed in any one of the preceding claims, wherein the UV-lamps are, in cross sectional view perpendicular to the longitudinal axis, arranged in a spiraling configuration having an increasing or decreasing diameter from the longitudinal axis of the vessel, when following along a path defined by the spiraling configuration.

15. The fluid treatment system as claimed in claim 13 or 14, wherein each ring comprises the same number of UV lamps, distributed evenly over the circumference of each ring.

16. The fluid treatment system as claimed in claim 13 or 14 or 15, wherein at least one UV lamp is omitted in an outer ring at a position immediately downstream from the fluid input.

17. The fluid treatment system as claimed in any of the preceding claims, wherein the UV lamps are elongate and extend in parallel with the longitudinal axis over the axial length of the vessel.

18. The fluid treatment system as claimed in any of the preceding claims, wherein at least some of the UV lamps are selectively switched off at a fluid flow less than a maximum flow.

19. The fluid treatment system as claimed in claim 18, wherein a controller is connected to drive at least one switch for selectively switching the at least some of the lamps on or off, depending on the fluid flow.20 The fluid treatment system according to claim 18 or 19, further comprising a flow meter at or in at least one of the fluid input and the fluid discharge.

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