Fluid treatment system and process

Abstract

A fluid treatment system includes one or more radiation sources arranged in an irradiation zone with a treatment zone through which fluid to be treated passes and is irradiated. The radiation zone has a closed cross section to maintain the fluid within a predetermined maximum distance form he radiation source. Preferably, the irradiation zone comprises a reduced cross-sectional area perpendicular to the direction of fluid flow and thus the fluid flow velocity is increased through the irradiation zone.

What is claimed is: 
     
       1. A gravity fed fluid treatment system comprising a fluid inlet, a fluid outlet, an irradiation zone disposed between the fluid inlet and fluid outlet, and at least one radiation source assembly comprising at least one radiation source and a support therefor, the at least one radiation source being elongate and having a longitudinal axis substantially parallel to the direction of fluid flow through the irradiation zone and being fully submersed in fluid flow through the irradiation zone, the support being disposed upstream or downstream of the irradiation zone, the irradiation zone having a closed cross-section to confine fluid to be treated within a predefined maximum distance from the at least one radiation source, said closed cross-section being less than a cross-section of said fluid inlet. 
     
     
       2. A system according to claim 1, wherein said support has a longitudinal axis which is disposed in the fluid inlet substantially perpendicular to the fluid flow. 
     
     
       3. A fluid treatment system according to claim 1 wherein the cross-sectional area of said irradiation zone is less than the cross-sectional area of said fluid inlet and the cross-sectional area of said fluid outlet. 
     
     
       4. A fluid treatment system according to claim 3 wherein the cross-sectional area of said irradiation zone is less than the cross-sectional area of the fluid inlet and said irradiation zone is disposed in a treatment zone including a transition region connecting said fluid inlet to said irradiation zone, said transition region reducing pressure loss in said fluid between said inlet and said irradiation zone. 
     
     
       5. A fluid treatment system according to claim 3 wherein the cross-sectional area of said irradiation zone is less than the cross-sectional area of the fluid outlet and said irradiation zone is disposed in a treatment zone including a transition region connecting said fluid outlet to said irradiation zone, said transition region reducing pressure loss in said fluid between said outlet and said irradiation zone. 
     
     
       6. A fluid treatment system according to claim 2 wherein the cross-sectional area of said irradiation zone is less than the cross-sectional areas of said fluid inlet and said fluid outlet, said irradiation zone being disposed in a treatment zone including first and second transition regions, said first transition region connecting said fluid inlet to said irradiation zone and said second transition region connecting said irradiation zone to said fluid outlet, said first and second transition regions reducing pressure loss in said fluid between said fluid inlet and said irradiation zone and between said irradiation zone and said fluid outlet, respectively. 
     
     
       7. A fluid treatment system according to claim 6 wherein said at least one radiation source assembly comprises at least one ultraviolet lamp and a support therefor. 
     
     
       8. A fluid treatment system according to claim 7 wherein said .Iadd.at least one .Iaddend.radiation source assembly includes a sleeve about a portion of the exterior of each .[.of.]. said at least one ultraviolet lamp. 
     
     
       9. A fluid treatment system according to claim .[.6.]. .Iadd.1 .Iaddend.wherein said longitudinal axis is substantially vertical and said .[.first transition region.]. .Iadd.system .Iaddend.alters a substantially horizontal fluid flow through said fluid inlet to a substantially vertical fluid flow through said irradiation zone. 
     
     
       10. A fluid treatment system according to claim 9 wherein said .[.second transition region.]. .Iadd.system .Iaddend.alters said substantially vertical fluid flow through said .[.first.]. irradiation zone to a substantially horizontal fluid flow through said fluid outlet. 
     
     
       11. A fluid treatment system according to claim 7, wherein said longitudinal axis .Iadd.of said at least one radiation source .Iaddend.is substantially horizontal. 
     
     
       12. A fluid treatment system according to claim 1 further including cleaning means to remove undesired materials from the exterior of said at least one radiation source assembly. 
     
     
       13. A fluid treatment system according to claim 12, wherein said cleaning means comprises a cleaning sleeve surrounding said at least one radiation source assembly, said cleaning sleeve being movable between a retracted position wherein a first portion of said at least one radiation source assembly is exposed to said fluid flow and an extended position wherein said first portion of said at least one radiation source .Iadd.assembly .Iaddend.is covered by said cleaning sleeve. 
     
     
       14. A fluid treatment system according to claim 13 wherein said cleaning sleeve includes a chamber surrounding and in contact with the exterior of said at least one radiation source assembly, said chamber being supplied with a cleaning solution suitable to remove undesired materials from the exterior of said at least one radiation source assembly. 
     
     
       15. A fluid treatment system according to claim 14 wherein said cleaning sleeve includes a seal between the exterior surface of said at least one radiation source assembly and said cleaning sleeve, said seal removing a portion of said undesired materials from the exterior of said at least one radiation source assembly when said cleaning sleeve is moved between said retracted and extended positions. 
     
     
       16. A fluid treatment system according to claim 14 wherein said supply of said cleaning solution is pressurized to said cleaning sleeve and said cleaning sleeve is extended to said extended position by said pressure. 
     
     
       17. A fluid treatment system according to claim 16 wherein said cleaning sleeve is retracted to said retracted position by the removal of said pressurized cleaning solution from said cleaning sleeve. 
     
     
       18. A fluid treatment system according to claim 6 including a first radiation source assembly located upstream of and extending into said irradiation zone and a second radiation source assembly located downstream of and extending into said irradiation zone. 
     
     
       19. A radiation source module for use in a fluid treatment system comprising: a first support member;   at least one radiation source assembly extending from said first support member; and   a second support member extending from said first support member,   wherein said at least one radiation source assembly extends from said first support member substantially parallel to said second member, said second support member extending from said first support member and having a free end to affix the radiation source module in the fluid treatment system.   
     
     
       20. A radiation source module according to claim 19 wherein said second support member extends from said first support member to a greater extent than said at least one radiation source assembly. 
     
     
       21. A radiation source module according to claim 19 wherein said at least one radiation source assembly comprises an ultraviolet source. 
     
     
       22. A radiation source module according to claim .[.20.]. .Iadd.21 .Iaddend.wherein said radiation source assembly further comprises a sleeve about said ultraviolet source to provide an insulating gap between said ultraviolet source and fluid passing therearound. 
     
     
       23. A radiation source module according to claim 19 wherein said .Iadd.first .Iaddend.support member includes conduit means through which an electrical power supply is provided to said radiation source assembly. 
     
     
       24. A radiation source module according to claim 21 wherein at least two of said ultraviolet sources are connected to each first support member. 
     
     
       25. A cleaning apparatus for a radiation source assembly in a fluid treatment system, comprising: a cleaning sleeve engaging a portion of the exterior said radiation source assembly and movable between a retracted position wherein a first portion of said radiation source is exposed to a flow of fluid to be treated and an extended position wherein said first portion of said radiation source assembly is completely or partially covered by said cleaning sleeve, said cleaning sleeve including a chamber in contact with said first portion of said radiation source assembly and being supplied with a cleaning solution suitable to remove undesired materials from said first portion.   
     
     
       26. A cleaning apparatus according to claim 25 further comprising at least one seal between the exterior surface of said radiation source assembly and said cleaning sleeve, said at least one seal removing a portion of said undesired materials from the exterior of said radiation source assembly when said cleaning sleeve is moved between said retracted and extended positions. 
     
     
       27. A cleaning apparatus according to claim 25 wherein said supply of said cleaning solution is pressurized to said cleaning sleeve. 
     
     
       28. A cleaning apparatus according to claim 27 wherein said cleaning sleeve is retracted to said retracted position by the removal of said pressurized cleaning solution from said cleaning sleeve. 
     
     
       29. A cleaning apparatus according to claim 25 wherein said cleaning sleeve engages a portion the exterior of at least two radiation source assemblies. 
     
     
       30. A cleaning apparatus according to claim 29 wherein said cleaning sleeve is connected to at least one means to move said cleaning sleeve between said retracted and extended positions. 
     
     
       31. A cleaning apparatus according to claim 30 wherein said at least one means to move is hydraulically operated. 
     
     
       32. A cleaning apparatus according to claim 30 wherein said at least one means to move is pneumatically operated. 
     
     
       33. A method of treating a fluid with at least one radiation source assembly comprising at least one radiation source and a support therefor, the method comprising the steps of: (i) providing a gravity fed flow of fluid from a fluid inlet to a fluid outlet, and irradiation zone being disposed between said inlet and said outlet;   (ii) disposing the at least one radiation source assembly within said irradiation zone such that the at least one radiation source has a longitudinal axis which is substantially parallel to the flow of fluid and the support is upstream or downstream of the irradiation zone;   (iii) confining the flow of fluid such that it is within a predefined maximum distance from and fully submerses the at least one radiation source, said confining .[.source.]. .Iadd.step .Iaddend.including the step of confining the flow of fluid in a closed cross-section which is smaller than a cross-section of the fluid inlet;   (iv) exposing the flow of fluid to radiation from the radiation source; and   (v) feeding the flow of fluid from step (iv) to a fluid outlet.   
     
     
       34. A method according to claim 33, wherein said disposing step includes the step of disposing the radiation source assembly support such that its longitudinal axis is disposed in the fluid inlet and is substantially perpendicular to the fluid flow. 
     
     
       35. A method according to claim 33 wherein the flow of fluid is at a first velocity in said fluid inlet, a second velocity in said irradiation zone and a third velocity in said fluid outlet. 
     
     
       36. A method according to claim 35 wherein said second velocity is greater than at least one of said first velocity and said third velocity. 
     
     
       37. A method according to claim 35 wherein said second velocity is greater than both of said first velocity and said third velocity. 
     
     
       38. A method according to claim 37 wherein said third velocity is substantially equal to said first velocity. 
     
     
       39. A method according to claim 37 wherein prior to step (ii), the fluid flow is .[.admired.]. .Iadd.admitted .Iaddend.to a transition zone which increases the velocity thereof. 
     
     
       40. A method according to claim 37 wherein prior to step (v), the fluid flow is admitted to a transition zone which decreases the velocity thereof. 
     
     
       41. A method of removal of fouling materials from a radiation source in situ in a fluid treatment system using a cleaning apparatus comprising a cleaning sleeve engaging a portion of the exterior said radiation source assembly and movable between a retracted position wherein a first portion of said radiation source is exposed to a flow of fluid to be treated and an extended position wherein said first portion of said radiation source assembly is completely or partially covered by said cleaning sleeve, said cleaning sleeve including a chamber in contact with said first portion of said radiation source assembly, comprising the steps of: (i) providing a supply of a cleaning fluid to a cleaning chamber;   (ii) moving said cleaning chamber to said extended position;   (iii) maintaining said cleaning fluid in contact with said portion;   (iv) allowing said cleaning fluid to facilitate removal of fouling materials from the radiation source; and   (v) moving said cleaning chamber to said retracted position.   
     
     
       42. A method according to claim 41 wherein said cleaning chamber includes a seal member in slidable engagement with said portion and sweeping said portion to further remove fouling materials when said cleaning chamber is moved to at least one of said extended position and said retracted position. 
     
     
       43. A method according to claim 41 wherein said cleaning chamber simultaneously contacts a like portion of at least two radiation sources. 
     
     
       44. A method according to claim 41 wherein said cleaning chamber is substantially continuously pressurized by said cleaning fluid and contains inward spray means to remove the fouling materials from the radiation source. 
     
     
       45. A method according to claim 41 wherein said cleaning chamber is kept stationary and the radiation source is moved relative thereto to remove the fouling materials from the radiation source. 
     
     
       46. A method according to claim 41 wherein said cleaning chamber further comprises scouring means to increase rubbing against said radiation source while in contact with the cleaning chamber. .Iadd. 
     
     
       47.  A gravity fed fluid treatment system suitable for installation in an open fluid canal, said system comprising a fluid inlet, a fluid outlet, an irradiation zone disposed between the fluid inlet and the fluid outlet, and at least one radiation source assembly comprising at least one radiation source and a support therefor, the at least one radiation source being elongate and having a longitudinal axis substantially parallel to the direction of fluid flow through the irradiation zone and being fully submersed in fluid flow through the irradiation zone, the support being disposed upstream or downstream of the irradiation zone, the irradiation zone having a closed cross-section to confine fluid to be treated within a predefined maximum distance from the at least one radiation source, said closed cross-section being less than a cross-section of the open fluid canal upstream of said irradiation zone..Iaddend..Iadd. 
     
     
       48.  A gravity fed fluid treatment system suitable for installation in an open fluid canal, said system comprising: a fluid inlet;   a fluid outlet;   an irradiation zone disposed between the fluid inlet and the fluid outlet; and   at least one radiation source assembly comprising at least one radiation source and a support therefor, the at least one radiation source being elongate and having a longitudinal axis substantially parallel to the direction of fluid flow through the irradiation zone and being fully submersed in fluid flow through the irradiation zone,   the support being disposed upstream or downstream of the irradiation zone,   the irradiation zone having a closed cross-section to confine fluid to be treated within a predefined maximum distance from the at least one radiation source,   wherein said closed cross-section causes the velocity of fluid flow therein to be higher than a velocity of fluid flow in the open fluid canal upstream of said irradiation zone..Iaddend..Iadd.49. A system according to claim 48, wherein said support comprises a vertically-extending member partially submersed in a fluid flow area having a fluid flow velocity which is less than the fluid flow velocity of the closed cross-section..Iaddend..Iadd.50. A system according to claim 49, wherein the vertically-extending member is movable to remove the at least one   
     
     
        radiation source from the irradiation zone..Iaddend..Iadd.51.  A system according to claim 49, wherein the at least one radiation source is supported by a single vertically-extending member..Iaddend..Iadd.52. A system according to claim 48, wherein said closed cross-section has inner walls which are configured to follow contours of the at least one radiation source..Iaddend..Iadd.53. Apparatus for irradiating fluid in an open fluid canal of a gravity-fed fluid treatment system, comprising: an irradiation zone disposed in the open fluid canal and having a closed cross-section for confining the fluid flow, such that a fluid flow velocity in the irradiation zone is higher than a fluid flow velocity upstream of the irradiation zone in the open fluid canal;   a plurality of elongate ultraviolet lamps disposed in the irradiation zone with their longest axes substantially parallel to the direction of fluid flow therethrough;   a plurality of supports for holding said plurality of ultraviolet lamps in the closed cross-section irradiation zone, said plurality of supports being positioned upstream of the irradiation zone in the open fluid canal, each support being movable with respect to the irradiation zone so that the ultraviolet lamps may be removed from the irradiation zone;   a plurality of protective sleeves respectively disposed to cover the plurality of ultraviolet lamps;   a plurality of sleeve cleaners, each disposed around an outer surface of a corresponding sleeve; and   driving apparatus which drives the plurality of sleeve cleaners along the   
     
     
        plurality of sleeves to clean the sleeves..Iaddend..Iadd.54.  Apparatus for irradiating fluid in a gravity-fed fluid treatment system, comprising: an enclosed flow zone which physically restricts the flow of fluid therethrough as compared to a relatively less restricted flow zone upstream of said enclosed flow zone;   a plurality of elongate radiation sources disposed within the enclosed flow zone so that a longitudinal axis of each radiation source is substantially parallel to a direction of the fluid flow through said enclosed flow zone; and   a support member for holding one or more of said plurality of radiation sources in the enclosed flow zone, at least a portion of said support member being disposed outside of said enclosed flow zone,   said enclosed flow zone having inner walls which are configured to follow contours of portions of said plurality of radiation   
     
     
        sources..Iaddend..Iadd.5.  Apparatus according to claim 54, wherein said support member comprises a vertically-extending member disposed in a fluid flow area which has a fluid flow velocity which is less than a fluid flow velocity of the enclosed flow zone..Iaddend..Iadd.56. Apparatus according to claim 55, wherein the vertically-extending member is movable to remove the one or more of said plurality of radiation sources from the enclosed flow zone..Iaddend..Iadd.57. Apparatus according to claim 55, wherein each of said one or more of said plurality of radiation sources is supported by a single vertically-extending member..Iaddend..Iadd.58. A system for treating fluid in an open fluid canal of a gravity fed fluid system, comprising: a closed cross-section irradiation zone in which the velocity of fluid flowing therethrough is higher than the velocity of fluid flowing in a zone upstream of said irradiation zone in the open fluid canal;   a plurality of ultraviolet lamps disposed in said irradiation zone parallel to a direction of fluid flow therethrough, said ultraviolet lamps for treating the fluid flowing through the closed cross-section irradiation zone; and   at least one support which holds one or more of the plurality of ultraviolet lamps in the irradiation zone, the at least one support being disposed upstream of the irradiation zone in the open fluid canal,   wherein said closed cross-section irradiation zone is defined at least in   
     
     
        part by a main body restricting fluid flow..Iaddend..Iadd.59.  A system according to claim 58, wherein said at least one support comprises a vertically-extending member disposed in a fluid flow area having a fluid flow velocity which is less than a fluid flow velocity of the closed cross-section irradiation zone..Iaddend..Iadd.60. A system according to claim 59, wherein the vertically-extending member is movable to remove the one or more of the plurality of ultraviolet lamps from the closed cross-section irradiation zone..Iaddend..Iadd.61. A system according to claim 59, wherein each of said one or more of the plurality of ultraviolet lamps is supported by a single vertically-extending member. .Iadd.62. A system according to claim 58, wherein said closed cross-section irradiation zone has inner walls which are configured to follow contours of the plurality of ultraviolet lamps disposed in the irradiation zone..Iaddend..Iadd.63. A radiation module for an open-canal gravity-fed fluid treatment system having an irradiation zone, comprising: a plurality of radiation sources for disposal in the irradiation zone and having longitudinal axes which are substantially parallel to a direction of fluid flow through the irradiation zone;   a vertically-extending support member coupled to said plurality of radiation sources such that each radiation source is supported by a single vertically-extending support member, said support member holding the plurality of radiation sources in the irradiation zone, said support member being movable with respect to the irradiation zone so that said plurality of radiation sources may be removed from the irradiation zone; and   cleaning means, movable in the direction of the longitudinal axes of the radiation sources, for cleaning outer surfaces of the radiation sources while said radiation sources are in the irradiation zone..Iaddend..Iadd.64. A module according to claim 63, further comprising an additional support member for coupling said support member to the fluid   
     
     
        treatment system..Iaddend..Iadd.65.  A module according to claim 63, wherein said plurality of radiation sources are horizontally-disposed, and wherein said vertically-extending support member comprises a vertical member..Iaddend..Iadd.66. A fluid treatment system for a gravity fed fluid canal through which fluid to be treated flows, comprising: a main body installed across the fluid canal such that the main body is at least partly immersed in the fluid of said canal so as to direct the fluid to an irradiation zone;   an irradiation zone through which the fluid flows before returning to the fluid canal; and   at least one radiation source disposed in said irradiation zone to treat fluid with radiation, said at least one radiation source having its longest axis parallel to said fluid flow,   said irradiation zone having a closed cross-section to confine fluid within a predefined maximum distance from the at least one radiation source,   said irradiation zone having a cross-sectional area that is less than that   
     
     
        of the fluid canal..Iaddend..Iadd.67.  A system according to claim 66, further comprising a support member for supporting the at least one radiation source in the irradiation zone..Iaddend..Iadd.68. A system according to claim 67, wherein said support member comprises a vertically-extending member partially submersed in a fluid flow area having a fluid flow velocity which is less than a fluid flow velocity of the irradiation zone..Iaddend..Iadd.69. A system according to claim 68, wherein the vertically-extending member is movable to remove the at least one radiation source from the irradiation zone..Iaddend..Iadd.70. A system according to claim 68, wherein said at least one radiation source is supported by a single vertically-extending member..Iaddend..Iadd.71. A system according to claim 66, wherein said irradiation zone closed cross-section has inner walls which are configured to follow contours of the at least one radiation source disposed in the irradiation zone..Iaddend..Iadd.72. A system according to claim 66, wherein said at least one radiation source is mounted on a support therefor with the support being disposed in an area upstream or downstream of said irradiation zone..Iaddend..Iadd.73. A fluid treatment system for irradiating fluid flowing in an open fluid canal, comprising: an irradiation zone disposed in said open fluid canal to receive the fluid flow from the open fluid canal;   said irradiation zone having a closed cross-sectional area that is smaller than the cross-sectional area of the fluid flowing in the open fluid canal;   a plurality of elongate ultraviolet lamps disposed in said irradiation zone with the longest axis of each lamp being substantially parallel to the direction of fluid flow; and   at least one vertically-extending support member for supporting said plurality of ultraviolet lamps in the irradiation zone;   each of said plurality of ultraviolet lamps being supported by a single vertically-extending support member;   said at least one vertically-extending support member being disposed in an area upstream or downstream of said irradiation zone..Iaddend..Iadd.74. A system according to claim 73, wherein the closed cross-section causes a fluid flow velocity in the irradiation zone to be higher than a fluid flow velocity in the open fluid canal..Iaddend..Iadd.75. A system according to claim 73, wherein said support member comprises a vertically-extending member partly submersed in a fluid flow area having a fluid flow velocity which is less than a fluid flow velocity in the irradiation zone closed cross-section..Iaddend..Iadd.76. A system according to claim 75, wherein the vertically-extending member is movable to remove the plurality of ultraviolet lamps from the irradiation zone..Iaddend..Iadd.77. A system according to claim 73, wherein the irradiation zone closed cross-section has inner walls configured to follow contours of the plurality of ultraviolet lamps..Iaddend..Iadd.78. A system according to claim 73, wherein said vertically-extending support member is movably mounted with respect to said fluid treatment system so that said ultraviolet lamps may be moved into and out of said irradiation zone..Iaddend..Iadd.79. A system according to claim 73, wherein each said ultraviolet lamp is located within a sleeve, and wherein said system further includes a cleaning member disposed about said sleeve and which is reciprocally movable from a retracted position to an extended position to clean the surface of said sleeve..Iaddend..Iadd.80. A radiation source module for an open fluid treatment system which includes a fluid inlet, and a fluid outlet, comprising:   a vertically-extending support member for disposal in the fluid;   a plurality of elongated radiation source assemblies extending from said support member,   each of said radiation source assemblies being supported by a single vertically-extending support member; and   another support member disposed outside of the fluid and extending from said vertically-extending support member to movably position said radiation source module in an irradiation zone in said fluid treatment system..Iaddend..Iadd.81. A module according to claim 80, wherein each elongated radiation source assembly includes an ultraviolet lamp, and further comprises cleaning means for cleaning each ultraviolet   
     
     
        lamp..Iaddend..Iadd.82.  A module according to claim 80, wherein said another support member is coupled to the fluid treatment system..Iaddend..Iadd.83. A module according to claim 80, wherein said vertically-extending support member comprises a vertical member..Iaddend..Iadd.84. A module according to claim 80, wherein said vertically-extending support member is movable with respect to the irradiation zone so as to extract said plurality of radiation source assemblies from the irradiation zone..Iaddend..Iadd.85. A method of treating a fluid in an open canal system, comprising the steps of: (i) providing a gravity fed flow of fluid at a first velocity in the open canal;   (ii) feeding the flow of fluid from the open canal through an elongate irradiation zone at a second velocity which is greater than the first velocity, the elongate irradiation zone having a closed cross-section and having disposed therein an elongate radiation source having a longitudinal axis substantially parallel to the flow of fluid, the elongate radiation source being connected to a support disposed in an area upstream or downstream of the irradiation zone;   (iii) confining the flow of fluid at the second velocity within a redefined maximum distance from the at least one radiation source;   (iv) exposing the flow of fluid at the second velocity to radiation from the radiation source; and   (v) feeding the flow of fluid from step (iv) to the open canal downstream   
     
     
        of the irradiation zone..Iaddend..Iadd.86.  A fluid treatment method for a gravity fed fluid flow, comprising the steps of: disposing a main body across an open fluid canal such that the main body is at least partly immersed in the fluid of said canal;   directing fluid flow to an irradiation zone through which the fluid flows before returning to the fluid canal;   disposing at least one radiation source in said irradiation zone, said at least one radiation source having its longest axis parallel to said fluid flow;   irradiating the fluid flow with the at least one radiation source in the irradiation zone;   providing said irradiation zone with a closed cross-section to confine fluid within a predefined maximum distance from the at least one radiation source; and   providing said irradiation zone with a cross-sectional area that is less   
     
     
        than that of the fluid canal..Iaddend..Iadd.87.  A radiation source module for use in a fluid treatment system comprising: a single vertically-extending support member;   a plurality of radiation source assemblies extending from the support member, the plurality of radiation source assemblies each comprising at least one radiation source, the at least one radiation source being elongate with its longitudinal axis substantially parallel to a direction of fluid flow, the plurality of radiation source assemblies being supported by the single vertically-extending support member; and   fastening means to affix the radiation source module in the fluid treatment system..Iaddend..Iadd.88. A gravity fed fluid treatment system for an open canal, comprising:   an array of radiation sources disposed in an elongate irradiation zone having a closed cross-section which provides a fixed geometry to restrict fluid flow through the irradiation zone as compared to a flow in the open canal, the array of radiation sources being disposed substantially parallel to the fluid flow;   a fluid inlet upstream of the irradiation zone;   a fluid outlet downstream of the irradiation zone; and   at least one vertically-extending support for the array of radiation sources, the at least one vertically-extending support being partly submersed in the fluid flow upstream or downstream of the irradiation   
     
     
        zone..Iaddend..Iadd.89.  A gravity fed fluid treatment system comprising: an open canal for receiving a fluid flow;   an array of elongate radiation sources disposed substantially parallel to the fluid flow;   an elongate irradiation zone surrounding the array of radiation sources and having a closed cross-section to (i) restrict the fluid flow within a predetermined maximum distance from the array of radiation sources and (ii) to increase a fluid flow velocity in the irradiation zone with respect to a fluid flow velocity in the open canal; and   at least one support for the array of radiation sources disposed in the open canal upstream or downstream of the irradiation   
     
     
        zone..Iaddend..Iadd.  .  A system according to claim 1 wherein said at least one radiation source comprises a high intensity ultraviolet lamp..Iaddend..Iadd.91. A module according to claim 19, wherein said at least one radiation source assembly comprises a high intensity ultraviolet lamp..Iaddend..Iadd.92. A method according to claim 33, wherein said disposing step includes the step of disposing a radiation source which 
     
     
        comprises a high intensity ultraviolet lamp..Iaddend..Iadd.93.  A system according to claim 47, wherein said at least one radiation source comprises a high intensity ultraviolet lamp..Iaddend..Iadd.94. A system according to claim 48, wherein said at least one radiation source comprises a high intensity ultraviolet lamp..Iaddend..Iadd.95. Apparatus according to claim 53, wherein each of said plurality of ultraviolet lamps comprises a high intensity ultraviolet lamp..Iaddend..Iadd.96. Apparatus according to claim 54, wherein each of said plurality of elongated radiation sources comprises a high intensity ultraviolet lamp..Iaddend..Iadd.97. A system according to claim 58, wherein each of said plurality of ultraviolet lamps comprises a high intensity ultraviolet lamp..Iaddend..Iadd.98. A module according to claim 63, wherein each of said plurality of radiation sources comprises a high intensity ultraviolet 
     
     
        lamp..Iaddend..Iadd.99.  A system according to claim 66, wherein said at least one radiation source comprises a high intensity ultraviolet lamp..Iaddend..Iadd.100. A system according to claim 73, wherein each of said plurality of elongated ultraviolet lamps comprises a high intensity ultraviolet lamp..Iaddend..Iadd.101. A module according to claim 80, wherein each of said plurality of elongated radiation source assemblies comprises a high intensity ultraviolet lamp..Iaddend..Iadd.102. A module according to claim 87, wherein said at least one radiation source comprises a high intensity ultraviolet lamp..Iaddend..Iadd.103. A system according to claim 88, wherein each of the radiation sources comprises a high intensity ultraviolet lamp..Iaddend..Iadd.104. A system according to claim 89, wherein each elongate radiation source comprises a high intensity ultraviolet lamp..Iaddend.