Abstract:
A water disinfection system includes a housing having a plurality of risers  207  therein for directing independent columns of water from a manifold at the bottom of the housing. An ultraviolet light source  214  is disposed above the risers to treat the water flowing therein. The UV light source may also be in the form of a fiber optic system (FIG.  4 ) or a mercury arc lamp including a parabolic reflector  64 . Each of the risers can also include notches  304  (FIG.  9 ) for inducing turbulence to the water flowing thereover in order to ensure that all of the microorganisms receive ultraviolet light. The water flow rate and the light intensity may be adjusted to accommodate different levels of water contamination.

Description:
This application is a continuation under 35 U.S.C. 120 of PCT Application Ser. No. PCT/US99/07874 , filed Sep. 4, 1999 the contents of which are expressly incorporated herein by reference, which application in turn claims the benefit under 35 U.S.C. 119(e) of the filing date of U.S. Provisional Patent Application Ser. No. 60/081,154, filed Apr. 9, 1998, the contents of which are herein also expressly incorporated by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to water disinfection, and, more particularly, to water disinfection using ultraviolet light. 
     2. Description of the Related Art 
     Water is an important resource that is used in many commercial purposes, such as agriculture and aquaculture, as well as for household use. Furthermore, clean water that is free from unhealthy chemicals and microorganisms is becoming a more precious resource as populations increase. 
     Water is often treated prior to it being used for commercial purposes or household use. Disinfection of the water to remove microorganisms is a common treatment. The use of ultraviolet (“UV”) light as a disinfecting agent is not a new idea. Downs and Blunt discovered that sunlight destroyed some bacteria in 1878. Since their discovery, scientists have performed experiments to determine the conditions when UV radiation can be used as a disinfecting agent, and have determined the doses required to kill many microorganisms. Disinfection is generally accomplished using heat, chemicals, or UV light. UV light is particularly desirable since it leaves no toxic residue in the water. 
     The prior art has many applications of treating water with UV light to kill microorganisms. These applications involve flowing water going past a UV light source. In some applications, water flows past a bank of light sources. This application is problematic as the light sources may be extremely heavy, making them difficult to replace. In another application, a UV light source is suspending axially in a pipe and water flows past it. The maintenance of this type of light source may also be difficult. Some problems are common to both applications. The light sources become fouled with use from being in continual contact with the water flow, thereby reducing the efficiency of the light sources. Further, the UV light is often not efficiently absorbed by the water. Instead, the UV light is absorbed by the walls of the vessels in which the UV lights are disposed Therefore, a water disinfection system using UV light that does not incur fouling of the light source and has efficient absorption of the UV light by water is needed. It is further needed a system that permits quick and simple maintenance of the UV light source. 
     SUMMARY OF THE INVENTION 
     In an aspect of the invention, a water disinfection system comprises a vertical water column directing channel and an ultraviolet light beam generator system. The vertical water column directing channel has an open top end and a channel interior space extending from the open top end. The ultraviolet light beam generator system has an ultraviolet light beam exit. The ultraviolet light beam generator system is arranged such that an ultraviolet light beam generated therein exits through the ultraviolet light beam exit, passes through the channel top open end, and enters the channel interior space. 
     In a further aspect of the invention, the channel open top end comprises a top end interior cross-section. Additionally, the ultraviolet light beam produced by the ultraviolet light beam generator system has a light beam cross section that is the substantially the same as the top end interior cross-section or eclipses the top end interior cross-section. 
     In a further aspect of the invention, the ultraviolet light beam produced by the ultraviolet light beam generator system comprises ultraviolet light in a spectral band of approximately 242 nm to 270 nm. 
     In a further aspect of the invention, the vertical water column directing channel comprises a riser having a length from the open top end to a bottom end and a substantially constant interior cross-section through the riser length. The top end interior cross-section is generally equal to the riser interior cross-section. In a still further aspect of the invention, the riser is generally cylindrical in shape. 
     In a further aspect of the invention, a water column turbulating feature located at the channel top open end. In a still further aspect of the invention, the water column turbulating feature is one or more notches in the vertical water column directing channel at the open top end. 
     In a further aspect of the invention, the vertical water column directing channel comprises an untreated water entrance into the channel&#39;s interior space. The channel&#39;s interior space also comprises a channel interior space portion being defined by the top open end and the untreated water entrance. The channel interior space portion has a continuous volume therein with a constant latitudinal cross-section and an axial length extending from the open top end and through the channel interior space portion. Further, the ultraviolet light beam generator system is arranged such that the ultraviolet light beam is directed through the open top end along the channel interior space portion continuous volume. 
     In a still further aspect of the invention, the ultraviolet light beam has a water absorption distance that is less than the continuous volume axial length. As a result, the ultraviolet light beam is substantially absorbed by water flowing through the vertical water column directing channel and not by the vertical water column directing channel. 
     In a further embodiment of the invention, the ultraviolet light beam generator system comprises a lamp and a reflector. The lamp produces dispersed light to be used to form the ultraviolet light beam. The reflector may be parabolic or elliptical and positioned to direct the dispersed light from the lamp. In a still further aspect of the invention, the lamp is a medium pressure mercury arc lamp. In an aspect of the invention, the ultraviolet light beam generator system comprises a fiber optic system. 
     In a further aspect of the invention, there may be a plurality of vertical water column directing channels. The ultraviolet light beam generator system comprises a plurality of ultraviolet light beam exits. The ultraviolet light beam generator system is arranged such that ultraviolet light beams generated therein exit through the ultraviolet light beam exits, pass through the channels top open ends and enter the channels interior spaces. A lamp in ultraviolet light beam generator system may generate the ultraviolet light beams for more than one exit and/or riser. 
     In a further aspect of the invention, an uninterrupted air space is disposed between the channel open top end and the ultraviolet light beam exit of the ultraviolet light beam generator system. In this case, the water has limited, if substantially non-existent, opportunities to contact the surface of the exit and start fouling it. 
     In an aspect of the invention, a process of disinfecting water comprises the steps of forming a vertically oriented column of flowing water to be disinfected and directing an ultraviolet beam into the column. The flowing water moves from a bottom of the column to a top of the column, at which point the flowing water flows in a general radial direction away from the column top. The ultraviolet light beam is directed through an uninterrupted air space, the flowing water column top and into the column of water. The ultraviolet light beam disinfects the flowing water prior to the flowing water flowing away from the flowing water column top 
     In a further aspect of the invention, the column of flowing water is formed by directing the flowing water through a vertically oriented channel. In a still further aspect of the invention, the vertically oriented channel is a cylindrical riser. 
     In a further embodiment of the invention, the light beam is collimated and has a latitudinal cross-section generally the same as, or bigger than, a latitudinal cross-section of the flowing water column top. Further, the collimated ultraviolet light beam is aligned with the column of flowing water such that the collimated ultraviolet light beam is generally coincident with the column of flowing water after the collimated ultraviolet light beam passes through the flowing water column top. 
     In a further aspect of the invention, the light beam. is substantially absorbed by the column of flowing water. 
     In a further aspect of the invention, a volumetric flow rate of the column of flowing water and an intensity of the ultraviolet light beam is chosen to achieve a predetermined microorganism survival rate. In a still further aspect of the invention, the using a microorganism survival equation, the microorganism survival equation is: 
     
       
         
           N 
           1 
           /N 
           0 
           =e 
           −k(It) 
         
       
     
     where 
     N 1 =Final number of living organisms 
     N 0 =Initial number of living organisms 
     −k=rate constant 
     I=Intensity of the ultraviolet light beam (mW/cm 2 ) 
     t=time required to achieve the desired kill percentage 
     and the volumetric flow rate of the column of flowing water is a light absorbance volume divided by t, wherein the light absorbance volume is a volume of the column of flowing water in which substantially all of the ultraviolet light beam is absorbed. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows an axial cross-section of a vertical riser with a water column moving upwardly therethrough and a UV light beam directed downwardly through the water column. 
     FIG. 2 shows the cross-section  2 — 2  of FIG. 1, which is a downward view of the vertical riser. 
     FIG. 3 show the cross-section  3 — 3  of FIG. 1, which is an upward view of the UV light beam. 
     FIG. 4 shows a schematic view of an optical fiber system for providing UV light to disinfect water. 
     FIG. 5 shows a schematic view of a parabolic reflector system for providing UV light to disinfect water. 
     FIG. 6 shows a schematic view of an elliptical reflector system for providing UV light to disinfect water. 
     FIG. 7 shows a UV light reactor. 
     FIG. 8 shows an isometric view of a reactor interface with nipples from a UV light reactor. 
     FIG. 9 shows a detailed view of a nipple having a notched rim. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Now referring to the figures, wherein like reference numbers refer to like elements throughout the figures, and specifically to FIGS. 1,  2 , and  3 , a water column  10  is shown being disinfected by an UV light beam  12 . The water column  10  originates from a stream of water  14  that enters a vertical riser  16  at a riser entrance  18 . The riser  16  extends vertically from the riser entrance  18  and terminates at a riser end  20 . The riser also has an axis  34  that defines an upwards axial direction  36  and a downwards axial direction  38 . In a preferred embodiment of the invention, the riser  10  has a circular riser inner perimeter  22  which defines a riser circular internal cross-section  24  that is substantially constant throughout the riser  10  as the riser is cylindrical in shape. Other embodiments of the invention may have risers of other cross-sections, varying cross-sections, or have other vertical water column directing channels. 
     The water column  10  flows through the riser  16  in the upwards vertical direction  36 . Since the riser  16  forms the water column  10 , the column has a column circular cross-section  32  that is equivalent to the riser internal cross-section  24 . Other embodiments of the invention may have differently shaped cross-sections and perimeters. The water column  10  terminates at the water column end  40  that is shown to be substantially co-existent with the riser end  20 . Other embodiments of the invention may have the water column end  40  located above the riser end  20 . At the water column end  40 , the disinfected water  42  is shown flowing in a general radial direction away from the column top and down a riser exterior surface  44  in the downward axially direction  38 . Other embodiments of the invention may have the disinfected water  42  flow in other directions. 
     The UV light beam  12  is generated by a light source  28  and directed in the downwards axial direction  38  through the water column end  40  and into the water column  10 . The light source  28  is not in direct contact with the water column end  40 , resulting in reducing, if not eliminating, inefficiencies due to fouling of the light source. Embodiments of the invention comprises an uninterrupted air space adjacent to the water column  10  that the light beam  12  passes through prior to entering the water column. 
     The UV light beam  12  has a circular cross-section  30 . In the preferred embodiment of the invention, the UV beam cross-section  30  is substantially the same as the riser cross-section  24 . By being substantially the same, all of the UV light beam  12  enters the water column  10  and efficiently functions as a disinfecting agent. Other embodiments of the invention may have a UV light beam that substantially eclipses the riser cross-section  24  or have a UV light beam of other cross-sections. 
     In a preferred embodiment of the invention, the UV light beam  12  is substantially absorbed by the water column  10  within a water absorption distance  48  of the riser end  20 . The beam  12  is substantially absorbed because the water absorption distance  48  is shorter than a riser length  46 , which is the distance between the riser entrance  18  and the riser end  20 . By having the riser length  46  longer than the water absorption distance  48 , the UV light beam  12  is absorbed by the water column  10 , and not by a wall, plate, or some other structure (not shown) at the riser entrance  18 . 
     The portion of the water column  10  in which the UV light beam  12  is substantially absorbed into is a light absorbance volume  49 . The light absorbance volume  49  in the shown embodiment of the invention is the water absorption distance  48  times the riser cross-section  24 . In an embodiment of the invention, the ultraviolet light beam  12  is collimated and aligned with the riser  16  such that the collimated ultraviolet light beam is generally coincident with the column of flowing water in the riser. In other embodiments of the invention have the UV light beam  12  may have the light absorbance volume be only a portion of the channel through which the water flows. The channel portion is of a continuous volume with a constant latitudinal cross-section such that the light beam  12  is absorbed by the water in the channel portion and not by the channel itself. 
     The intensity of the UV light beam  12  and the residence time of the vertical riser are predetermined based on the type and concentration of the micro-organisms in the stream of water  14 . Different exposures to UV light is required to kill different micro-organisms. For a 90% kill, with the UV light moving through air, the exposures are: 
     
       
         
               
               
               
             
           
               
                   
                   
               
               
                   
                   
                 Exposure 
               
               
                   
                 Organism 
                 (μWs/cm 2 ) 
               
               
                   
                   
               
             
             
               
                   
                 Bacteria 
                  1,500-20,000 
               
               
                   
                 Virus 
               
               
                   
                   E. Coli  (dry) 
                   ˜250 
               
               
                   
                   E. Coli  (wet) 
                 ˜5,000 
               
               
                   
                 Yeast 
                 3,000-6,000 
               
               
                   
                 Mold Spores 
                 15,000-45,000 
               
               
                   
                   
               
             
          
         
       
     
     Although some disagreement of opinion exists, it is thought that the disinfection of water requires exposure of five to fifty times greater that in air. Other factors affect the amount of exposure, such as water turbidity, water depth, and water clarity. 
     Different water streams requires different exposure to be treated based on the above listed factors, and others, each stream of water need to be tested to determine required exposure to UV light. The microorganism survival equation is: 
     
       
         
           N 
           1 
           /N 
           0 
           =e 
           −k(It) 
         
       
     
     where 
     N 1 =Final number of living organisms 
     N 0 =Initial number of living organisms 
     −k=rate constant 
     I=Intensity of the UV light (mW/cm 2 ) 
     t=time required to achieve the desired kill percentage 
     Upon determining I and t, the volumetric flow rate of the column of water is the light absorbance volume  49  divided by t for any I. Embodiments of the invention may have means for adjusting the residence time and/or the light intensity based on input concerning changes in the characteristics of the water being treated. Further discussions concerning treating water with ultraviolet light are disclosed in U.S. Pat. Nos. 5,208,461 and 5,675,153, which are incorporated by reference herein in their entireties. 
     Different embodiments of the invention may have different light sources for generating the UV beam of light. In general, a lamp, or light pump, generates dispersed light comprising UV spectrum light and non-UV spectrum light. A UV light beam forming means for filtering a substantial amount of the non-UV spectrum light from the dispersed light, and for focusing the remaining light into the UV light beam  12  is used to provide the UV light beam  12 . 
     Referring to FIG. 4, one embodiment of the invention uses a light source  50  comprised of a light pump  52  with an optical fiber  54  connected thereto to provide the UV light beam  12 . The optical fiber  54  has an end  56  through which the UV light beam  12  emerges. Light sources  50  that produce an UV light beam are known in the art. 
     Referring now to FIG. 5, one embodiment of the invention uses a light source  60  comprised of a mercury lamp  62 , a parabolic reflector  64 , and a cold mirror  66 . In an embodiment of the invention, the mercury lamp  62  may be a low pressure mercury lamp. A low pressure mercury lamp is of relatively low cost and 95% of the light it emits is in a narrow band centered on approximately 254 nm −260 nm, making it very effective. In another embodiment of the invention, the mercury lamp  62  may be a medium pressure lamp. Other embodiments of the invention may use other lamps. 
     During operation, the mercury lamp  62  emits a dispersed light  68  which is reflected and directed by the parabolic reflector  64  as a prefiltered beam  70  to the cold mirror  66 . In one embodiment of the invention, the cold mirror  66  filters out the non-UV spectrum in the prefiltered beam  70  by reflecting only UV spectrum light to form the UV light beam  12 . In other embodiments of the invention, the UV light beam  12  has an UV spectrum of substantially approximately 242 to 270 nm or approximately 240 to 320 nm. Other embodiments of the invention may use other filtering means which will result in other UV spectrum ranges for the UV light beam  12 . The non-UV spectrum light passes through the cold mirror  66  and forms a non-UV spectrum light beam  72 . Additionally, by filtering out the non-UV spectrum light, the “hotter” non-UV light does not enter the water column  12 , thereby heating it up and promoting algae growth. 
     Other embodiments of the invention may use other types of UV light generation systems, such as those disclosed in U.S. Pat. Nos. 5,661,828; 5,682,448; 5,706,376; 5,708,737; 5,790,723; 5,790,725; 5,862,277; and 5,892,867, the contents of which are expressly incorporated herein by reference. 
     Now referring to FIG. 6, one embodiment of the invention uses a light source  80  comprised of a mercury lamp  82 , an elliptical reflector  84 , a first cold mirror  86 , a lens array  88 , a second cold mirror  90  and a collimating lens  92  to produce the UV light beam  12 . The mercury lamp  82  has similar characteristics as the previously described mercury lamp  62  and produces a dispersed light  94 . The elliptical reflector  84  focusses and directs the dispersed light  94  as a first prefiltered light beam  94  to the first cold mirror  86 . The first cold mirror  86  operates in a similar fashion as the cold mirror  66  previously described, with a first non-UV spectrum light beam  102  extending from the mirror, and a second prefiltered light beam  96  reflecting off of the mirror. The second prefiltered light beam  96  is directed through the lens array  88  to form a third prefiltered beam  98 . The third prefiltered beam  98  is directed to the second cold mirror  90 , with a precollimated UV light beam  100  reflecting off of the mirror, and a second non-UV spectrum light  104  extending from the mirror. The first and second cold mirrors  86  and  90  may be the same, or have different filtering characteristics. The precollimated UV light beam  100  is directed through collimating lenses  92  to produce the UV light beam  12 . Other embodiments of the invention may not provide a collimated UV light beam  12  and, therefore, not have the collimating lenses  92 . 
     Other embodiments of the invention may use other lamps, reflectors, spectrum filters, lenses, and arrangements thereof to produce the UV light beam  12 . 
     Referring now to FIG. 7, a UV light reactor  200  for disinfecting an influent stream  220  is comprised of an inlet  202 , a manifold  204 , an array of risers  206 , a reactor interface plate  208 , an air spacer  210 , a holding plate  212 , UV light pumps  214 , and an outlet  216 . The manifold  204 , array of risers  206 , the reactor interface plate  208 , the air spacer  210 , and the holding plate  212  are contained in a reactor wall  218  which is shown in ghost lines. The reactor wall  218  is shown to be cylindrical and vertical. Other embodiments of the invention may have reactor walls of other shapes. 
     The influent stream  220  flows into the reactor  200 , where it is treated with the UV light pumps  214 , and flows out of the reactor  200  as an effluent stream  234 . The influent stream  220  flows through the inlet  202 , past the reactor wall  218  and into the manifold  204 . The manifold is round and fits against the interior of the reactor wall  218  at the reactor bottom  219 . The manifold  204  distributes the influent stream  220  to the array of risers  206 , where a column of vertically moving water is created in each riser (not shown). The array of risers  206  comprises seven risers  207  arranged in a circular formation. Other embodiments of the invention may have more or less risers, and the risers may be arranged in other suitable formations. The array of risers  206  extends vertically from the manifold  204  to the reactor interface plate  208 . The reactor interface plate  208  is round and has a diameter less than the inner diameter of the reactor wall  218 . The now disinfected water  221  emerges from the array of risers  206  through the plate  208 , flows over the plate, and descends downwardly either by flowing over an outside edge  222  of the plate or by flowing through internal holes  224  in the plate. The disinfected water  221  descends to the bottom of the reactor  200  and exits through the outlet  216  as the effluent stream  234 . 
     The UV light pumps  214 , which disinfect the influent stream  220 , are located at the top  232  of the reactor  200 . The reactor  200  has seven UV light pumps  214  (two shown) mounted on light pump supports  236 . The light pump supports  236  are cylindrical in shape and are disposed on the holding plate  212  over holes (not shown). The holding plate  212  is round and fits against the top  232  of the reactor wall  218 . The supports  236  are aligned with the risers  207  such that each riser has a light pump  214 . The holes enable an UV light beam (not shown) to travel from the light pumps  214  to its respective riser  207  to disinfect the column of water therein. With one light pump  214  per riser  206 , the light pump is relatively light, compact, and readily replaceable if needed. Other embodiments of the invention may have one light pump providing UV light to more than one riser. 
     To inhibit fouling of the light pumps  214 , an air space  228  separates the flow of water through the reactor  200  from the UV light pumps  214 . The air space  228  is formed by air spacers  210  vertically separating the reactor interface plate  208  and the holding plate  212 . The air spacer  210  is a stainless steel cylinder that is slotted to permit the disinfected water to flow therethrough. A bottom end  230  of the air spacer  210  rests at the edge  222  of the interface plate  208 . The holding plate  212  is disposed on top of the air spacer  210 . Other embodiments of the invention may use other means to inhibit or prevent water from fouling the light sources. Other embodiments may omit the air spacer and use other suitable means for creating the air space  228 . 
     Now referring to FIG. 8, in one embodiment of the invention, a reactor interface plate  250  is annularly shaped and has six risers  252  connected to it. The risers  252  enter the underside of the plate  250  at holes  254 . On the top surface  258  of the plate  250 , nipples  256  extend from the holes  254 . The nipples  256  encourage turbulence at the top of the column of water (not shown) in the risers  252 . By having turbulence at the top of the column, the microorganisms are more effectively radiated by the UV light beam (not shown). Without the turbulence, some microorganisms in the water may be shielded from the UV light by other microorganisms or debris in the water and not killed. Other embodiments of the invention may have other means of creating turbulence at the top of the column of water. 
     Now referring to FIG. 9, an embodiment of the invention is shown with a riser  207  terminating at a nipple  300  having a notched rim  302 . The notched rim  302  has a plurality of notches  304  around its circumference. The column of vertically moving water (not shown) exits the riser at the nipple  300  as disinfected water  221 . The volumeric flow rate of the column of vertically moving water is such that a majority, if not substantially all, of the water flows out of the riser through the notches  304  in the rim  302 . By having the disinfected water  221  flowing through the notches  304 , the top of the water column has turbulent flow. Embodiments of the invention may have the nipple  300  mounted to the plate  208 , mounted to the terminating end of the riser, removable mounted to either one, or mounted in some other suitable fashion. Other embodiments of the invention may have other turbulating features to create turbulence flow at the top of the water column. 
     Although presently preferred embodiments of the present invention have been described in detail hereinabove, it should be clearly understood that many variations and/or modifications of the basic inventive concepts herein taught, which may appear to those skilled in the pertinent art, will still fall within the spirit and scope of the present invention, as defined in the appended claims.