Abstract:
A filtration apparatus including a tubular element ( 17 ) for purifying wastewater that flows from outside to inside, and a spray tube ( 21 ) for spraying cleaning water onto the external peripheral surface of the tubular element. In the first step, the external peripheral surface of the tubular element is cleaned and most of solid matter is removed. In the second step, compressed air is fed to the tubular element, and fine solid matter that is embedded in the filter is removed by backwashing.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to a technique for filtering wastewater in which solid components are mixed. 
       BACKGROUND OF THE INVENTION 
       [0002]    A filtering apparatus is an important tool in making effective use of water resources. This is because wastewater can be converted to purified water by a filtering apparatus. An essential component of a filtering apparatus is an element for removing impurities that include solid matter from wastewater. The amount of solid matter that accumulates in the element is proportional to the time elapsed in filtering. Flow resistance increases when the amount of sediment increases, and the amount of water that can be treated is reduced. In order to restore the amount of water that can be treated, the element must be replaced with a new element or the element must be regenerated. 
         [0003]    Considering the effective use of earth resources, regeneration is more preferable to replacing elements. A technique for regenerating elements is described in, e.g., Japanese Patent Application Laid-Open Publication No. 2001-108790 (JP 2001-108790 A). The filtering and regenerating technique described in JP 2001-108790 A is described with reference to  FIGS. 8A to 8C  hereof. 
         [0004]    Solid matter in the wastewater flows (arrow B) from an outer surface  101  of an element  100  toward an inner surface  102  when the wastewater flows in the manner indicated by arrow A parallel to the element  100 , which is composed of a ceramic filter, as shown in  FIG. 8A . In this case, solid matter  103  accumulates on the outer surface  101  of the element  100 . Wastewater is purified in this manner. 
         [0005]    Water pressure P 1  is applied from the inner surface of  102  toward the outer surface  101  when a fixed amount of wastewater is treated, as shown in  FIG. 8B . On the other hand, a water pressure P 2 , which is a lower pressure than water pressure P 1 , is applied from the outer surface  101  toward the inner surface  102 . 
         [0006]    Next, the water pressure P 2  is rapidly reduced. At this point, the solid matter  103  that is deposited on the outer surface  101  is removed by the effect of the water pressure P 1 , as described in  FIG. 8C . The element  100  is thereby regenerated. 
         [0007]    Regeneration is smoothly carried out because sludge is soft when the solid matter  103  is principally composed of sludge. 
         [0008]    However, in the case that sand and fine metals are mixed in large quantities in the solid matter  103 , a substance is formed in which the sand or the like in the sludge is embedded as an aggregate and becomes hard overall, and the removal of the solid matter  103  becomes difficult. The difficulty particularly increases when the thickness of the sediments increases. The regeneration described above is not suitable for wastewater that contains large amounts of sand and the like. 
         [0009]    In view of the above, there is a need for a filtration technology that is advantageous for treating wastewater containing large amounts of sand and the like. 
       SUMMARY OF THE INVENTION 
       [0010]    In the discussion below, the term “backwashing” is short for “backflow washing.” Backflow washing refers to washing by sending a fluid in an opposite direction of the filtration flow. Also, the term “regeneration” refers to removal of impurities from an element and the regeneration of the element. 
         [0011]    According to the present invention, there is provided a wastewater filtering apparatus for filtering wastewater in which solid matter is mixed, the apparatus comprising a container for storing the wastewater; a wastewater inlet tube that is connected to the container and that directs wastewater into the container; a tubular element that is disposed inside the container and that removes impurities containing the solid matter from wastewater that flows from an outside to an inside; a purified water transport tube for drawing out filtered purified water to the exterior of the container; a cleaning water spray tube that is disposed inside the container and that sprays cleaning water to an outside surface of the tubular element; a rotation mechanism for rotating the tubular element when the cleaning water is sprayed, and causing the outside surface of the tubular element to be uniformly aligned facing the cleaning water spray tube; a backflow supply tube for supplying fluid to the inside of the tubular element after the rotation by the rotation mechanism has been stopped, and washing the tubular element using the backflow; and a deposit transport tube which extends from a bottom of the container and whereby the impurities containing the solid matter that has been removed by the cleaning water and the fluid are discharged from the container. 
         [0012]    There is an advantage in that the external peripheral surface of the tubular element is cleaned and most of the solid matter is removed in the first step, even fine solid matter that has been embedded on the filter in the second step can be removed by backwashing, and highly precise regeneration can be achieved. As a result, wastewater that contains large amounts of sand and the like can be treated. 
         [0013]    Preferably, a plurality of the tubular elements is disposed about a periphery of the cleaning water spray tube. There is an advantage in that a plurality of the tubular elements can be cleaned by using a single purified water spray tube. 
         [0014]    Desirably, the purified water transport tube is provided with an activated charcoal filter that further filters the filtered purified water. Very fine sand and the like that cannot be filtered by the tubular element can be reliably filtered. Filtration precision increases. 
         [0015]    In a preferred form, the fluid for the backwashing be compressed air. The cleaning of the first step is performed using water, and most of the impurities are removed. The cleaning of the second step is adequately performed using compressed air. In accordance with the present invention, water can be conserved in comparison with the case in which water is used in the first and second steps. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0016]    A preferred embodiment of the present invention will be described in detail below, by way of example only, with reference to the accompanying drawings, in which: 
           [0017]      FIG. 1  is a cross-sectional view of a wastewater filtering apparatus according to the present invention; 
           [0018]      FIG. 2  is a cross-sectional view taken along line  2 - 2  of  FIG. 1 ; 
           [0019]      FIG. 3  is a schematic view illustrating an ordinary filtrating operation; 
           [0020]      FIG. 4  is a schematic view illustrating a first step of a regeneration operation; 
           [0021]      FIG. 5  is a schematic view illustrating a second step of the regeneration operation; 
           [0022]      FIG. 6  is a flowchart of the filtration operation and regeneration operation; 
           [0023]      FIG. 7  is a diagrammatical view illustrating a basic theory of a workpiece cleaning machine provided with the filtering apparatus; and 
           [0024]      FIGS. 8A to 8C  are diagrammatical views illustrating conventional filtration and regeneration operations. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0025]    As shown in  FIG. 1 , the filtering apparatus  10  is comprised of a container  11  that is opens at the top, an intermediate plate  12  that is disposed in an upper portion of the container  11  so as to close off the container  11 , a cylinder  13  that is superimposed on the intermediate plate  12 , a cover  14  that is superimposed on the cylinder  13  and acts as a cover of the cylinder  13 , a hollow body  15  that passes completely through the intermediate plate  12  in the vertical direction and that is rotatably supported by the intermediate plate  12  via a bearing  16 , a sprocket  24  provided to the top end of the hollow body  15 , a tubular element  17  that is supported at the lower end of the hollow body  15  and that extends in the perpendicular direction into the container  11 , a passage  18  that is disposed inside the hollow body  15  and that connects the inner part of the tubular element  17  and the inner part of the cylinder  13 , a cleaning water spray tube  21  that is disposed in the container  11  and that is vertically placed between a plurality of tubular elements  17 , a rotation mechanism  25  that rotates the sprocket  24 , a wastewater inlet tube  27  that is provided to the side surface of the lower portion of the container  11  and that introduces wastewater into the container  11 , a wastewater discharge tube  28  that is provided to the outer surface of the lower portion of container  11  and that is used for discharging wastewater from inside the container  11 , a deposit transport tube  29  that is provided to the bottom surface of container  11  and that is used for transporting to the exterior solid matter that has been removed by cleaning, a purified water tank  32  that is connected to the cleaning water spray tube  21  via a cleaning water inlet tube  31 , an activated charcoal filter  34  that is provided to the exterior of the cylinder  13  and that is used for further filtering the filtered water, a flowmeter  35  that is disposed in the vicinity of the activated charcoal filter  34  and that is used for measuring the flow rate of the filtered water, a purified water transport tube  36  in which the distal end is connected to the cylinder  13  and which contains the activated charcoal filter  34  and the flowmeter  35 , and a backflow supply tube  37  in which the distal end is connected to the cylinder  13  separately from the purified water transport tube  36  and which supplies compressed air inside the cylinder  13 . 
         [0026]    The rotation mechanism  25  has a rotating shaft  38  that extends in the front/rear direction of the diagram, a rotating shaft sprocket  39  provided to the rotating shaft  38 , and a chain  41  that is disposed so as to make contact with rotating shaft sprocket  39  and the sprocket  24  and that drives the sprocket  24 , as shown in  FIG. 2 . 
         [0027]    A motor  43  for driving the rotation mechanism  25  is provided to the upper portion of the cover  14 , as shown in  FIG. 1 . The upper surface of the container  11 , the lower surface of the intermediate plate  12 , and the cylinder  13  are connected by a long bolt  45 , and the cylinder  13  and the cover  14  are connected by a short bolt  46 . Reference numerals  47 ,  48 ,  49 ,  51 ,  52 , and  53  are valves that open and close the tubes, and  54  is a sealing material, preferably an O-ring. 
         [0028]    The effect of the filtering apparatus having the configuration described above will be described next. In other words, an ordinary filtration operation will be described with reference to  FIG. 3 , the operation of the first step of regeneration will be described with reference to  FIG. 4 , the operation of the second step of regeneration will be described with reference to  FIG. 5 , and the overall flow of the operation will be described with reference to  FIG. 6 . Furthermore, the dark arrows in  FIGS. 3 to 5  indicate the flow of water, and white arrows indicate the flow of air. 
         [0029]    The wastewater introduced from the wastewater inlet tube  27  into the container  11  flows from the external peripheral surface toward the internal peripheral surface of the tubular element  17 , and the filtration of the first step is performed by the tubular element  17 , as described in  FIG. 3 . Purified water thus filtered flows from a purified water outlet  22  to the cylinder  13  and passes through the purified water transport tube  36 , and the filtration of the second step is performed by the activated charcoal filter  34 . 
         [0030]    Very fine sand and the like that could not be filtered by the tubular element  17  can be reliably filtered. Filtration precision increases. 
         [0031]    Purified water that has been purified by the tubular element  17  and the activated charcoal filter  34  in the second step can thereby be obtained in a continuous fashion. However, sand and other solid matter that was contained in wastewater accumulates on the external peripheral surface of the tubular element  17  when the purification operation progresses, and filtration capacity is reduced. In view of the above, the regenerating operation is suitably carried out in the following manner. 
         [0032]    First, the wastewater inlet valve  47  is closed in the first step of regeneration, and the introduction of wastewater to the container  11  is stopped, as shown in  FIG. 4 . Next, the wastewater discharge valve  49  is opened. Wastewater collected in the container  11  can thereby be discharged to the exterior as indicated by the white arrow at bottom right of the diagram. 
         [0033]    When the discharge of wastewater is completed, the wastewater discharge valve  49  is closed, the motor  43  is actuated as indicated by the arrows, and the tubular element  17  is rotated. The cleaning water inlet valve  51  is opened at the same time. At this point, the cleaning water can be sent from the purified water tank  32  to the cleaning water spray tube  21  as indicated by the black arrows. The cleaning water is sprayed from the cleaning water spray tube  21  toward the external peripheral surface of the tubular element  17 , and the deposits of tubular element  17  are cleaned in the manner indicated by the imaginary lines. 
         [0034]    The large portion of solid matter accumulated on the external peripheral surface of the tubular element  17  can be removed by the cleaning water. The sediments in which sand and fine metals have become mixed in the sludge and hardened can be particularly effectively removed by the water pressure of the cleaning water. 
         [0035]    Furthermore, since the tubular element  17  is rotated at a fixed speed by the motor  43 , the cleaning water indicated by the imaginary lines uniformly makes contact with the entire periphery of the tubular element  17 , and unclean areas do not occur. In other words, a plurality (e.g., six) of the tubular elements  17  can be cleaned in a single process by using a single cleaning water tube  21 . 
         [0036]    The cleaning water inlet valve  51  closes and cleaning by the purified water is ended when the cleaning is performed by the cleaning water spray tube  21  for a fixed length of time. 
         [0037]    Next, in the second step of regeneration, the cleaning water inlet valve  51  is first closed, as shown in  FIG. 5 . Next, the backflow inlet valve  52  is opened and compressed air is sent from the backflow supply tube  37  to the cylinder  13  as indicated by the black arrows. The compressed air sent into the cylinder  13  passes through the purified water outlet  22  and flows from the internal peripheral surface of the tubular element  17  towards the external peripheral surface. 
         [0038]    The solid matter that is deposited on the external peripheral surface of the tubular element  17  is blown to the exterior by compressed air as indicated by the white arrows. The cleaning capacity is low because the density of air is less than that of water. However, in the present invention, the quantity of remaining deposits is low and the thickness of the layer is also low because a large portion of the sediments has been cleaned away in the first step of the regeneration operation. For this reason, cleaning is possible even using compressed air in the second step. 
         [0039]    The cleaning of the second step can be performed using cleaning water, but the quantity of cleaning water that is used can be reduced when compressed air is used as in the present invention. 
         [0040]    The backflow inlet valve  52  is closed and the backflow produced by the compressed air is ended after the backflow produced by the compressed air is carried out for a fixed length of time. 
         [0041]    Next, the deposit transport valve  53  is opened. Solid matter collected in the bottom portion of the container  11  and the cleaning water used in the first step are thereby sent from the deposit transport tube  29  to the exterior as indicated by the white arrow in the lower portion of the diagram, and the cleaning of the tubular element  17  is ended. 
         [0042]    Next, the overall operation of  FIGS. 3 to 5  described above will be described with reference to  FIG. 6 . 
         [0043]    A treatment flow rate Q 1  is set in step (hereinafter abbreviated as ST)  01  in the manner shown in  FIG. 6 . The wastewater is introduced into the wastewater tank and filtered by the tubular element (ST 02 ). The cumulative flow rate Q 2  is measured in this interval (ST 03 ). Specifically, the flow rate of filtered water is measured by the flowmeter  35  shown in  FIG. 1 . 
         [0044]    The cumulative flow rate Q 2  is examined as to whether the treatment flow rate Q 1  has been reached (ST 04 ). If the cumulative flow rate is less than Q 1 , the filtration of wastewater (ST 02 ) continues, and the filtration stops when Q 1  is reached (ST 05 ). Specifically, the wastewater inlet valve  47  shown in  FIG. 1  is closed. 
         [0045]    Wastewater inside the wastewater tank is discharged from the wastewater discharge outlet (ST 06 ). 
         [0046]    The tubular element is rotated (ST 07 ), purified water is sprayed onto the external peripheral surface of the tubular element that is being rotated, and the tubular element is washed (ST 08 ). 
         [0047]    The tubular element is backwashed by compressed air (ST 09 ). 
         [0048]    The deposits collected in the lower portion of the wastewater tank and the purified water sprayed in ST 08  are discharged to the exterior of the wastewater tank (ST 10 ). 
         [0049]    The filtration apparatus  10  described above can be provided to a variety of applications. An example in which the filtration apparatus is applied to a workpiece washing apparatus will be described below. 
         [0050]    A workpiece washing apparatus  60  includes a reticulated workpiece mount  62  on which a workpiece  61  to be washed is mounted, and a wastewater tank  63  for receiving the wastewater generated when the workpiece  61  is washed, as shown in  FIG. 7 . 
         [0051]    One opening of a three-way valve  55  is connected to the flowmeter  35 , one of the remaining openings of the three-way valve  55  is connected to the purified water tank  32 , and the remaining opening is connected to the workpiece cleaning apparatus  60 . 
         [0052]    The purified water filtered through the filtration apparatus  10  is allowed to flow to the purified water tank  32  until a prescribed quantity is collected in the manner indicated by arrow ( 1 ). The three-way valve  55  is switched when the prescribed quantity of purified water is collected in the purified water tank  32 . The purified water is then sent to the workpiece cleaning apparatus  60  when the three-way valve  55  switches in the manner indicated by arrow ( 2 ). 
         [0053]    The workpiece  61  is cleaned in the manner indicated by the arrow ( 4 ) by purified water sent to the workpiece cleaning apparatus  60 , and purified water is introduced from a workpiece cleaning water inlet tube  64  in the manner indicated by arrow ( 3 ). Sand and the like that have been deposited on the workpiece  61  by cleaning the workpiece  61  is made to fall into the wastewater tank  63  together with water in the manner indicated by arrow ( 5 ). 
         [0054]    The wastewater collected in the wastewater tank  63  passes through the wastewater inlet tube  27  in the manner indicated by arrow ( 6 ), and is introduced into the filtration apparatus  10 . The wastewater thus introduced is filtered inside the filtration apparatus  10 , and steps ( 1 ) through ( 6 ) are repeated. 
         [0055]    Wastewater is not required to be discarded and a contribution is made to environmental conservation because purified water that has been filtered is used to wash the workpiece  61 . The quantity of purified water introduced from the workpiece cleaning inlet tube  64  can be reduced. In addition, purified water obtained by filtration is made to flow into the purified water tank, and the element is regenerated using purified water. The quantity of purified water introduced from the exterior can be reduced, as can running costs of using the filtration apparatus. 
         [0056]    Obviously, various minor changes and modifications of the present invention are possible in light of the above teaching. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.