Abstract:
A system and method for wastewater treatment using ultraviolet (UV) irradiation of wastewater flowing in a treatment chamber. Wastewater to be treated flows into the first UV exposure chamber where it is exposed to UV illumination. Wastewater exposure time is lengthened by channeling the wastewater to first flow down a first UV exposure chamber and then back up through a second UV exposure chamber both of which are in a single structure. The first and second UV exposure chambers are separated by the UV illumination source so that wastewater on the two sides of the UV illumination source (i.e. both UV exposure chambers) cannot mix, and so that UV illumination time is dictated by the flow rate of the wastewater and the length of the UV illumination source. Thus the UV illumination path is roughly twice the length of the UV illumination source.

Description:
BACKGROUND 
       [0001]    For years, chlorine has been used extensively as a disinfectant in water and wastewater treatment processes. While chlorine is an effective disinfectant, the treated water is not potable, and must be dechlorinated using a precise dechlorination process. This additional step of dechlorination is not efficient and results in its own effluent that must be mitigated. 
       SUMMARY 
       [0002]    Exposing wastewater to concentrate ultraviolet radiation under controlled conditions can accomplish the same disinfecting effect as can be obtained using chlorine disinfection without the additional step of dechlorination. Ultraviolet radiation offers several advantages over traditional chlorine treatment of wastewater. UV is effective against all microorganisms. It is economical, purifying hundreds of gallons per kilowatt hour. UV is safe, not requiring dangerous chemicals with the corresponding risk of overdose or danger to the environment. UV provides continuous germicidal action without special attention or measurement, and without leaving a chlorine taste in recycling systems and without corrosion problems affecting the plumbing. It is known that irradiation of water with ultraviolet light within the range from about 150 nanometers through about 300 nanometers is effective in destroying microorganisms. 
         [0003]    The effectiveness of UV disinfection is a product of UV radiation intensity, wavelength and exposure time. In various embodiments illustrated herein, a first and second UV exposure chamber are provided. The first and second UV exposure chambers are separated by a UV illumination source. The UV illumination source could be UV fluorescent tubes, UV LEDs, UV xenon lamps, UV mercury-xenon lamps, UV argon lamps, UV deuterium lamps or any other suitable source of UVC radiation. This list is merely for purposes of example and is not intended as a limitation as to the potential sources of UV illumination. 
         [0004]    Wastewater to be treated flows into the first UV exposure chamber where it is exposed to UV illumination. Wastewater exposure time is lengthened by channeling the wastewater to first flow down a first UV exposure chamber and then back up through a second UV exposure chamber. The first and second UV exposure chambers are separated by the UV illumination source so that wastewater on the two sides of the UV illumination source (i.e. both UV exposure chambers) cannot mix, and so that UV illumination time is dictated by the flow rate of the wastewater and the length of the UV illumination source. Thus the UV illumination path is roughly twice the length of the UV illumination source. 
         [0005]    A mechanism for cleaning and/or replacing the UV illumination source is also provided. To this end, a system in which the UV illumination source and related assembly can be removed without the need to disassemble any major portion of the system is also provided. This allows a system operator to deal with a potential problem with UV sanitation units, that is, the collection of contaminants on the surface of the UV illumination source, which reduces the output of the UV illumination source. 
         [0006]    Embodiments illustrated herein may also enclose the UV illumination source within a quartz tube, thereby preventing contaminants from building up on the UV illumination source itself. Quartz is transparent to UV radiation at the wavelengths used in disinfection of wastewater, having a high transmittance and allowing the passage of UV radiation with little loss in power. The quartz tube also protects the UV illumination source from direct contact with the wastewater being disinfected. A small air chamber between the UV illumination source and the quartz tube helps to regulate the temperature of the UV illumination source. While quartz is illustrated herein, other types of material may be used so long as they transmit a substantial portion of the UV energy from the UV illumination source. 
         [0007]    Yet other embodiments illustrated herein allow the entire UV subassembly to be easily removed for cleaning without the need to open the UV exposure chambers or empty the wastewater treatment system. The UV subassembly is held in place during normal operation by a top plate. Once the top plate is removed, the entire UV subassembly easily slides out of the UV exposure chambers for cleaning. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]      FIG. 1  illustrates a front cross section elevation view of an embodiment of the present invention; 
           [0009]      FIG. 2  illustrates a side cross section elevation view of an embodiment of the present invention; 
           [0010]      FIG. 3  illustrates a top view cross section of an embodiment of the present invention; 
           [0011]      FIGS. 4   a  and  4   b  illustrate a side cross section elevation view of a joint between components in an embodiment of the present invention; 
           [0012]      FIG. 5  illustrates a top view of a keyway in an embodiment of the present invention; 
       
    
    
     DETAILED DESCRIPTION 
       [0013]    Referring to  FIG. 1 , the UV disinfecting apparatus is illustrated. An embodiment of the apparatus is shown in cross section. The influent wastewater to be treated may be derived from a variety of sources and may be, for example, wastewater treatment plant effluent or filter effluent. 
         [0014]    The apparatus comprises an influent line  2  connected to an inlet opening  4  on a double sanitary tee  16 , and an effluent line  10  connected to an outlet opening  8  on the double sanitary tee  16 . The top end of a vertically descending tube  6  is connected to the lower opening on the double sanitary tee  16 . The lower end of the vertically descending tube  6  is sealed. 
         [0015]    The upper opening of the double sanitary tee  16  is connected to a riser pipe  18 . A UV subassembly  20  (described below) is removably fixed within the vertically descending tube  6  and divides the vertically descending tube  6  into a first UV exposure chamber  62  and a second UV exposure chamber  64 . The UV subassembly  20  rests on a bottom plate  12  which centers the UV subassembly  20  within the vertically descending tube  6  and offsets the UV subassembly  20  from the bottom of the vertically descending tube  6 . The UV subassembly  20  is secured within the vertically descending tube  6  by a top plate  14 . The top plate  14  removably holds the UV subassembly  20  in position and covers the top end of the vertically descending tube  6 . A handle  36  is attached to the upper surface of the top plate  14  and is used for inserting and removing the UV subassembly  20 . In an embodiment, the handle  36  is hollow so as to permit electrical and control wires  72  for a UV illumination source  22  to pass through the handle  36 , up the riser pipe  18  and out of the system, where it is connected to a suitable power supply. The UV illumination source  22  could be UV fluorescent tubes, UV LEDs, UV xenon lamps, UV mercury-xenon lamps, UV argon lamps, UV deuterium lamps or any other suitable source of UVC radiation. 
         [0016]    In an embodiment, the vertically descending tube  6 , the influent line  2  and effluent line  10  are formed with standard 4-inch ABS pipe and fittings. In an embodiment, the outer structure of the UV disinfecting device is made primarily of preformed ABS plastic pipe, although this is not intended as a limitation. Other suitable materials with sufficient structural rigidity and interconnectability would be acceptable. The influent line  2  and the effluent line  10  are connected to the vertically descending tube  6  by use of a double sanitary tee  16 . The connections between the double sanitary tee  16  and the influent line  2  and the effluent line  10  are made by inserting the influent line  2  and effluent line  10  into corresponding flanges on the sanitary tee  16 . Likewise, the vertically descending tube  6  is connected to the sanitary tee  16  by inserting the top end of the vertically descending tube  6  into a corresponding flange on the bottom of the sanitary tee  16 . 
         [0017]    Referring to  FIGS. 2 and 3 , an embodiment of the UV subassembly  20  is illustrated in side view and top view. The UV subassembly  20  comprises a UV illumination source  22  positioned inside a surrounding quartz tube  24 . The quartz tube  24  protects the UV illumination source  22  from damage and provides an air chamber  28  surrounding the UV illumination source  22 . The air chamber  28  helps to regulate the temperature of the UV illumination source  22 . A silicon rubber gasket  26  extends laterally away from both sides of the quartz tube  24 . In an embodiment, a silicon rubber seal is preferred because it will create a seal yet not damage the quartz tube. The use of silicon rubber is not meant as a limitation. Other suitable materials that will provide a seal yet not damage the quartz tube are suitable for this function. The proximate edge of the silicon rubber gasket  26  presses snugly against the quartz tube  24  forming a liquid-tight seal. The amount of pressure between the seal and the quartz tube is the amount necessary to create a seal that will prevent wastewater from the first and second UV exposure chambers from mixing. The distal end of the silicon rubber gasket  26  is connected to one side of aluminum H-channel  30 . The H-channel  30  provides structural integrity to the UV subassembly  20 . Aluminum is preferred because it is light weight yet structurally rigid, but this is not meant as a limitation, as any suitable material that provides the structural integrity of the UV subassembly  20  may be used for the H-channel  30 . 
         [0018]    The opposite side of the H-channel  30  is connected to a strip of flexible polyimide film  32  such as Kapton® brand film. The flexible polyimide film  32  presses snugly against the inner surface of the vertically descending tube  6  to create a substantially fluid-tight seal. Again, the amount of pressure between the flexible polyimide film  32  and the inside wall of vertically descending tube  6  is the amount necessary to create a seal that will prevent wastewater from the first and second UV exposure chambers from mixing. The flexible polyimide film  32  creates a defined flow path within the vertically descending tube  6 . The combination of the quartz tube  24 , the silicon rubber gasket  26 , the H-channel  30  and the flexible polyimide film  32  serve to divide the vertically descending tube  6  into two sections, namely the first UV exposure chamber  62  and the second UV exposure chamber  64 . Wastewater enters the first UV exposure chamber  62  at the top, travels down the length of the UV subassembly  20 , flows around the bottom plate  12  and flows up the second UV exposure chamber  64 . Thus the waste water is exposed to UV radiation on both sides of the UV illumination source  22 , first while flowing down the first UV exposure chamber  62  and again while flowing up the second UV exposure chamber  64 . In this way, the exposure time of the waste water to UV radiation is doubled without the need to increase the length of the UV illumination source or the need to use additional UV illumination sources. 
         [0019]    The bottom plate  12  has a vertical standoff at its base to create a space that allows influent to flow between the first UV exposure chamber  62  and the second UV exposure chamber  64 . The bottom plate  12  supports the UV subassembly  20 . A vertical standoff of the bottom plate  12  ensures adequate flow of influent between the first UV exposure chamber  62  and the second UV exposure chamber  64 . The influent flows through the influent line  2  and enters the first UV exposure chamber  62  through the inlet opening  4 . Inside the first UV exposure chamber  62  the influent is exposed to UV radiation produced by the UV illumination source  22  as the influent flows down the first UV exposure chamber  62 , around the bottom plate  12 , and into the second UV exposure chamber  64 . While in the second UV exposure chamber  64  the influent is exposed to UV radiation produced by the UV illumination source  22 . The influent flows up the second UV exposure chamber  64  through the outlet opening  8  and out the effluent line  10 . 
         [0020]    Referring to  FIGS. 4   a  and  4   b , a cross section of one side of the joint between the sanitary tee  16  and the vertically descending tube  6  is shown. The interior of the resulting joint includes a small triangular void  40  around the entire interior circumference of the joint. The presence of the void  40  can prevent the flexible polyimide film  32  from forming a fluid-tight seal against the inside of the vertically descending tube  6  where the vertically descending tube  6  meets the sanitary tee  16 . Having a uniform snug seal will prevent wastewater from the first UV exposure chamber  62  mixing with wastewater from the second UV exposure chamber  64 . This void  40  is eliminated by use of a spacer  70  which fits tightly into the void  40  and creates a smooth inner surface around the entire inner circumference of the joint. In an embodiment, the spacer  70  is made of ABS plastic, although this is not intended as a limitation. Other suitable materials with sufficient structural rigidity and interconnectability would be acceptable. 
         [0021]    Referring to  FIG. 5 , an embodiment of a keyway is illustrated in top view. A keyway  34  is installed in the sanitary tee  16  above the inlet opening  4  and outlet opening  8 . The keyway  34  incorporates a UV subassembly guide  38  to ensure proper positioning of the UV subassembly  20  as it is inserted into the sanitary tee  16 . The keyway  34  incorporates film guides  36  to ensure the flexible polyimide film  32  is positioned correctly and imparts a curl to the flexible polyimide film  32  which causes the flexible polyimide film  32  to spring into a position snugly against the inner surface of the vertically descending tube  6 , thereby creating a fluid-tight seal and dividing the vertically descending tube  6  into the first UV exposure chamber  62  and the second UV exposure chamber  64 . 
         [0022]    A system and method for providing wastewater disinfection have been described. It will be understood by those skilled in the art that the present invention may be embodied in other specific forms without departing from the scope of the invention disclosed and that the examples and embodiments described herein are in all respects illustrative and not restrictive. Those skilled in the art of the present invention will recognize that other embodiments using the concepts described herein are also possible. Further, any reference to claim elements in the singular, for example, using the articles “a,” “an,” or “the,” is not to be construed as limiting the element to the singular.