Abstract:
A magnetic separation filtering and cleaning apparatus for adding flocculant and magnetic powder to raw water containing pollutant particles to form magnetic floc in treated fluid and separating and removing the magnetic floc from the treated fluid, comprising: a magnetic field generation device being provided in a rotating body for suctioning the magnetic floc on a surface of the rotating body from the treated fluid containing the magnetic floc, a magnetic field rotating device for rotating the magnetic field generation device, a sludge recovery device for separating sludge including the magnetic floc mechanically from the surface of the rotating body of the magnetic field generation device; and a filtering device having a rotating net for filtering out the magnetic floc from the treated fluid including the magnetic floc and flowing down the treated fluid filtered through the rotating net.

Description:
CLAIM OF PRIORITY 
     The present application claims priority from Japanese application serial No. 2007-082323, filed on Mar. 27, 2007, the content of which is hereby incorporated by reference into this application. 
     BACKGROUND OF THE INVENTION 
     1. Field of Technology 
     The present invention relates to a sewage cleaning apparatus intended for water clarification and solid-liquid separation, and in particular, relates to a magnetic separation filtering and cleaning apparatus for trapping magnetic materials by a membrane and magnetically separating trapped materials. 
     2. Prior Art 
     There is a well-known magnetic separation sewage cleaning apparatus (for example, see Japanese Application Patent Laid-open Publication No. 2002-273261) in which a net woven out of thin wires or polymeric fibers is used as a water separation membrane for the purpose of solid-liquid separation, flocculant and magnetic powder are added to raw water containing pollutant particles to form  magnetic floc, the magnetic floc is separated by the membrane, and the magnetic floc trapped by the membrane is magnetically removed by a magnetic field generation means, thereby recovering highly concentrated sludge. 
     The above-mentioned membrane separation cleaning apparatus is equipped with a net woven out of stainless-steel thin wires or polyester fibers, and has, for example, a membrane molecular portion having a several tens of micron-meter mesh opening. In order to separate microscopic pollutants smaller than the projected area or a projected diameter of the opening, for example, aluminum sulfate, polyaluminum chloride, iron polysulfate, and magnetic powder are beforehand added to raw water as flocculant and stirred so that microscopic suspended solids, algae, fungi, and microorganisms contained in raw water are flocculated by a flocculant to form several hundred micron meter magnetic floc. The magnetic floc cannot pass through the opening of a several tens of micron meter mesh and is trapped and separated at a high elimination ratio, and the water filtered through the membrane becomes high-quality clarified water. 
     Magnetic floc trapped on the membrane is washed off from the membrane by cleaning water. Then, magnetic floc which remains on and around the surface of the water is suctioned by a magnetic force of a magnet immobilized near the water surface, magnetically separated, and transferred  by a sludge transfer device to a sludge recovery tank and eliminated. Eventually, sludge is normally carried by a truck to a repository site or an incineration site or made into compost. 
     SUMMARY OF THE INVENTION 
     In a conventional magnetic separation sewage cleaning apparatus, when microscopic suspended solids in raw water are highly concentrated, a large amount of magnetic floc is generated. When the magnetic floc reaches a membrane, the magnetic floc is filtered and trapped on the entire surface of the membrane thereby significantly decreasing the membrane&#39;s ability to flow water. Accordingly, when treating a large amount of raw water, there is a problem in that a large filtering area is necessary, which increases the size of the components of the filtering device, increasing the size of the cleaning apparatus; consequently, the apparatus manufacturing costs increase. Furthermore, if the size of the components of the filtering device increases, the filtering device has to be divided into a plurality of devices in some cases. In that case, the number of installed magnetic components, which magnetically suction magnetic floc cleaned and separated from the  filtering device increases; consequently there is a problem in that the size of the magnetic components increases thereby increasing the apparatus manufacturing costs. 
     The object of the present invention is to provide a magnetic separation filtering and cleaning apparatus with compact size. 
     (1) In order to achieve the above object, the present invention of a magnetic separation filtering and cleaning apparatus for adding flocculant and magnetic powder to raw water containing pollutant particles to form magnetic floc in treated fluid and separating and removing the magnetic floc from the treated fluid, comprising: a magnetic field generation device being provided in a rotating body for suctioning the magnetic floc on a surface of the rotating body from the treated fluid containing the magnetic floc, 
     a magnetic field rotating device for rotating the magnetic field generation device, a sludge recovery device for separating sludge including the magnetic floc mechanically from the surface of the rotating body of the magnetic field generation device; and a filtering device having a rotating net for filtering out the magnetic floc from the treated fluid including the magnetic floc and flowing down the treated fluid filtered through the rotating net. 
     (2) In the above first aspect of the present invention,  it is preferable that the magnetic field generation device comprising a plurality of permanent magnets being provided in the rotating body, and a protection body for protecting the plurality of permanent magnets to keep them watertight. 
     (3) In the above second aspect of the present invention, it is preferable that the magnetic field generation device comprising a plurality of permanent magnets being provided in the rotating body, a protection body for protecting the plurality of permanent magnets to keep them watertight, and a clamping device for fixing the rotating body onto the protection body. 
     (4) In the above first aspect of the present invention, it is preferable that further comprising a control device for controlling a rotation speed of the magnetic field rotating device to rotate the magnetic field generation device in synchronization with the flow velocity of the treated fluid containing the magnetic material. 
     According to the present invention, it is possible to provide a magnetic separation filtering and cleaning apparatus with compact size. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an entire configuration drawing of a magnetic separation filtering and cleaning apparatus to show an embodiment of the present invention.  
         FIG. 2  is an enlarged cross-sectional view of a membrane separation device used for the embodiment of the magnetic separation filtering and cleaning apparatus shown in  FIG. 1 . 
         FIG. 3  is a cross-sectional view taken substantially along the line A-A of  FIG. 2 . 
         FIG. 4  is an enlarged cross-sectional view of another membrane separation device used for the embodiment of magnetic separation filtering and cleaning apparatus shown in  FIG. 1 . 
         FIG. 5  is a cross-sectional view taken substantially along the line A-A of  FIG. 4 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     First Embodiment 
     Hereafter, configuration of a magnetic separation filtering and cleaning apparatus according to an embodiment of the present invention will be described with reference to  FIGS. 1 through 3 . 
       FIG. 1  is an entire configuration drawing of a magnetic separation filtering and cleaning apparatus to show an embodiment of the present invention.  FIG. 2  is an enlarged cross-sectional view of a membrane separation device used for the embodiment of the magnetic separation filtering and cleaning apparatus shown in  FIG. 1 .  FIG. 3  is a cross-sectional  view taken substantially along the line A-A of  FIG. 2 . 
     As shown in  FIG. 1 , raw water  2  that is treated water from which several millimeter foreign particles have been removed is stored in a raw water storage tank  1 . A prescribed amount of the stored raw water  2  is pumped by a pump  3  and sent to the piping  4 . Through a conduit  6  into the piping  4 , a seeding agent adjusting device  5  adds magnetic powder including ferrous-ferric oxide or the like, pH adjuster, flocculant such as aqueous solution of polyaluminum chloride, ferric chloride, or ferric sulfate which provides aluminum ion and iron ion, and polymer strengthening agent. In an agitation tank  7 , an agitation blade  9  driven and rotated by a motor  8  stirs the mixture at a high speed to generate several hundred micron meter magnetic micro floc. 
     After that, a polymer agent adjusting device  11  adds a polymer strengthening agent or the like into the piping  10  through a conduit  12 . In an agitation tank  13 , an agitation blade  15  driven and rotated by a motor  14  stirs the mixture at a low speed to generate pretreatment water  17  that contains several millimeter magnetic floc (magnetic floc  16  shown in  FIG. 2 ). 
     Pretreatment water  17  thus generated is sent to a magnetic separation and membrane separation device  19   through a conduit  18 . The magnetic separation and membrane separation device  19  comprises a rotating drum  20  for filtering and a magnet  29 . 
     Herein, the structure of a magnetic separation and membrane magnetic separation apparatus  19  will be described with reference to  FIGS. 2 and 3 . 
     As shown in  FIG. 2 , a net  21  is disposed on the outer circumferential surface of the rotating drum  20  shown in  FIG. 1 . The net  21  is made of thin stainless-steel wires, thin copper wires, or polyester fibers to form a membrane having an opening with a mesh of between several micron meters and several tens of micron meters. 
     On the other hand, a rotary magnet  29 , shown in  FIG. 1 , used as a magnetic field generation device to execute magnetic separation is structured, as shown in  FIG. 2 , such that a plurality of permanent magnetic bodies  31  are immobilized by an adhesive onto a plurality of grooves located on the outer surface of the rotating body  30  made of nonmagnetic material and the structure is covered by a protection tube  32  to ensure the watertight. The rotating body  30  rotates while the motor  72 , shown in  FIG. 3 , controls the number of revolutions. The rotational axis  70  of the rotating body  30  is supported by a watertight bearing  71 . 
     In  FIG. 1 , pretreatment water  17  flown into the tank  22   flows inside the flow channel  34  ( FIG. 2 ) constructed by a partition wall  33  and flows into the flow channel  36  which is separated from the inside of the tank  22  by a partition wall  35 , as shown in  FIG. 2 . The flow channel  36  is disposed close to the permanent magnet body  31  which rotates in the same direction as pretreatment water flows and at almost the same velocity. Most of magnetic floc  16  contained in the pretreatment water that has flown into the flow channel  36  is magnetically suctioned therein, trapped on the surface of the watertight protection tube  32 , and magnetically separated from the pretreatment water. 
     In  FIG. 2 , pretreatment water from which most of magnetic floc  16  has been magnetically separated is discharged from an outlet of the flow channel  36  into the tank  22 . Herein, pretreatment water passes through the net  21  of the rotating drum  20  from outside to the inside, and at that point in time, magnetic floc  16  that remains in the pretreatment water is trapped on the outer surface of the net  21 . The water that has passed through the net  21  and been removed from magnetic floc  16  becomes clarified water, is then discharged from the opening  23 , shown in  FIG. 1 , passes through the piping  24 , stored in the clarified tank  25 , and then discharged outside the system through the piping  80 . 
     Herein, as shown in  FIG. 2 , motive energy that enables  pretreatment water  17  to pass through the net  21  is a water level difference between the pretreatment water  17  and the clarified water in the drum  20 . Since magnetic floc that has not reached the net  21  tends to deposit toward the bottom of the tank  22 , magnetic floc is moved close to the net  21  by a stirred flow generated by an agitation blade  38  mounted to the rotational axis  37  (the rotary drive is not shown) located in the tank  22 , filtered and trapped by the filtering water flow. In  FIG. 2 , magnetic floc  16  which has been filtered and attached to the outer surface of the net  21  that rotates counter-clockwise becomes sediment and is exposed to the air above the water level. 
     In  FIG. 1 , clarified water in the clarified tank  25  is pressurized by a pump  26  and sent to a shower pipe  28  through a conduit  27 . As shown in  FIG. 2 , shower water sprays through a hole of the shower pipe  28  from the inner surface of the net  21  toward the outer surface side. Magnetic floc  16  accumulated on the outer surface of the net  21  is removed by shower water sprayed from the shower pipe  28 , and the surface of the net  21  is cleaned for the next use. Washed out magnetic floc  16  remains on the surface of the pretreatment water  17  in the tank  22 . 
     In  FIG. 2 , a flock of magnetic floc  16  that has washed out and remains on and around the water surface is suctioned and moved toward the magnet due to a magnetic  field of the permanent magnet body  31  that rotates clockwise while trapping magnetic floc  16  that has been magnetically suctioned in the flow channel  36 . The flock of magnetic floc  16  is then trapped and attached to the outer surface of the protection tube  32  which rotates together with the permanent magnet body  31  and is exposed to the air as the permanent magnet body  31  rotates. In the air, excess water contained in the flock of magnetic floc  16  flows down by gravity, returned to the tank  22 , and the flock of magnetic floc  16  is further concentrated. Herein, the water content of magnetic floc  16  decreases to approximately 97%. The flock of magnetic floc  16  concentrated on the surface of the protection tube  32  is moved as the protection tube  32  rotates. 
     Therefore, according to the structure of this embodiment, it is possible to significantly reduce the filtering load of the filtering device by magnetically separating most of magnetic floc  16  in the filtering and clarifying pretreatment process; therefore, it is possible to clarify a large amount of raw water without increasing the size of the filtering device in the post-process. Furthermore, because the filtered magnetic floc  16  can be removed from the filtering membrane  21  by cleaning water and magnetically separated by the magnet, it is possible to discharge magnetic floc  16  to the outside at a high speed.  As a result, the size of the apparatus can be reduced. Moreover, the same magnet  29  (permanent magnet body  31 ) can magnetically separate both magnetic floc  16  in the flow channel  36  and magnetic floc  16  washed out by the cleaning water from outer surface of the membrane  21  at the same time without providing different magnets; therefore, it is possible to reduce the size of the apparatus and decrease apparatus manufacturing costs. 
     As shown in  FIG. 2 , a flock of magnetic floc  16  is mechanically broked and removed from the surface of the protection tube  32  by a rotating brush  87  and a spatula  88  supported by a part of the tank  22 , drops into a sludge recovery tank  39  by gravity, and separated and collected as sludge. 
     In  FIG. 1 , sludge discharged to a sludge recovery tank  39  is directed to a dewatering apparatus  41 , such as a centrifuge or beltpress dewatering apparatus, through the piping  40 , and the water content is reduced to approximately 85% or less so that water will not leak from the sludge during transportation. Furthermore, highly concentrated sludge whose water content is approximately 75% so as to activate microorganisms that break down organic matter during composting is stored in the sludge tank site  43  through the piping  42 . Sludge is transported by truck to a repository site, incineration site and a  compost treatment site. Treated sewage dewatered by a dewatering apparatus is sent to a treated sewage tank  45  through the piping  44 , passes through the piping  47 , is pressurized by a pump  46 , then, returned to a raw water tank  1  through the piping  48 , and directed to the pretreatment process again. 
     In  FIG. 1 , a sensor  49  measures the water level, turbidity, temperature, pHm value of raw water  2 , and sends the measured information to a drive control device  48  via a signal line  50 . Based on the measured information, the drive control device  48  calculates the additive amount of chemical agents (pH adjuster, magnetic powder, flocculant) most suitable for the generation of good magnetic floc by using an optimal amount calculation program that has been inputted beforehand, then sends the control information to a chemical agent tank  5  via a signal line  51 , and then optimal amount of chemical agents are added. 
     Furthermore, simultaneously, the drive control device  48  calculates the number of revolutions of the agitation motor  8 , sends the control information to the motor  8  via a signal line  52 , and then rotates the agitation blade  9  by the motor  8  at the optimal number of revolutions. Moreover, the drive control device  48  calculates residence time in the agitation tank  7  and sends the data via a signal line  53 , thereby controlling the discharge rate of the pump  3   that determines the residence time in the agitation tank  7 . 
     Furthermore, the drive control device  48  calculates the additive amount of chemical agents (polymer) most suitable for the generation of good magnetic floc by using an optimal amount calculation program that has been inputted beforehand, then sends the control information to a chemical agent tank  11  via a signal line  54 , and then the optimal amount of chemical agents are added. 
     Furthermore, simultaneously, the drive control device  48  calculates the number of revolutions of the agitation motor  14 , sends the control information to the motor  14  via a signal line  55 , and then rotates the agitation blade  15  by the motor  14  at the optimal number of revolutions. 
     On the other hand, the membrane separation device  19  measures the level of pretreatment water  17  in the tank  22  by using a sensor  56  and sends the measured information to the drive control device  48  via a signal line  57 . Based on the measured information, the drive control device  48  calculates the optimal number of revolutions of the rotating drum  20  and appropriate recovery speed of a flock of magnetic floc  16  by using an optimal amount calculation program that has been inputted beforehand so that the level of the pretreatment water is located almost in the middle of the installation position of the magnet  29 , that is, the location at which an average value of the magnetic field  generated by a magnet  29  is maximum. Then, the drive control device  48  sends the control signal to a rotation motor (not shown) of the rotating drum  20  via a signal line  58 , and subsequently sends the signal to the motor  72  for the rotary magnet ( FIG. 3 ) via a signal line  59 , thereby controlling the optimal number of revolutions. 
     Furthermore, in the case in which the level of pretreatment water in the tank  22  increases when the amount of water filtered by the net  21  becomes less than the amount of inflow due to the insufficient number of revolutions of the net  21  or other reasons, overflow of the pretreatment water from the tank  22  into the sludge recovery tank  39  over the wall  60  must be inhibited; therefore, an overflow water recovery tank  61  is provided. Overflow water flown in the overflow water recovery tank  61  is sent to the treated sewage tank  45  through the piping  62 , pressurized by a pump  46 , and then returned to the raw water tank  1  through the piping  47 . 
     This structure allows the level of pretreatment water in the tank  22  to increase and the pretreatment water  17  that has flown over the wall  60 , as shown in  FIG. 2 , is flown into the overflow water recovery tank  61  instead of flowing into the sludge tank  39 . Therefore, the water content of highly concentrated sludge recovered in the sludge tank  39  increases due to the inflow of the  pretreatment water, and the concentration decreases increasing the volume of the sludge; consequently, increase of sludge treatment cost can be prevented. 
     As stated above, according to this embodiment, since approximately 90% of magnetic floc  16  contained in the pretreatment water in the flow channel  36  is magnetically separated by a rotary magnet  29 , only approximately 10% of magnetic floc  16  is filtered by a rotating drum  20 , which device that the load is significantly small; therefore, the area of the membrane  21  of the rotating drum  20  can be small and it is possible to reduce the size of the filtering device. Furthermore, because the filtered magnetic floc  16  is removed from the filtering membrane  21  by using cleaning water and magnetically separated by a magnet, it is possible to discharge magnetic floc  16  to the outside the apparatus at a high speed. As a result, the size of the apparatus can be small. Moreover, magnetic floc  16  in the flow channel  36  and magnetic floc  16  in the cleaning water washed out from the membrane  21  can be magnetically separated simultaneously by the same magnet  29  without providing different magnets to execute magnetic separation individually; therefore, the size of the apparatus can be small and the apparatus manufacturing cost can be reduced. 
     Second Embodiment   
     Next, the configuration of a magnetic separation filtering and cleaning apparatus according to another embodiment of the present invention will be described by referring to  FIGS. 4 and 5 . The entire configuration of the magnetic separation filtering and cleaning apparatus according to this embodiment is the same as that shown in  FIG. 1 . 
       FIG. 4  is an enlarged cross-sectional view of another membrane separation device used for the embodiment of magnetic separation filtering and cleaning apparatus shown in  FIG. 1 .  FIG. 5  is a cross-sectional view taken substantially along the line A-A of  FIG. 4 . Moreover, the same numbers and alphanumeric characters as those shown in  FIGS. 1 through 3  indicate the same portions. 
     The difference between this embodiment and the embodiment shown in  FIGS. 2 and 3  is that the rotating body  67  and the protection tube  69  of the rotary magnet  68  in this embodiment are separated from each other and the rotating body  67  can be mounted and removed from the air side. Moreover, the rotary magnet  68  comprises a rotary body  67  and a permanent magnet  66  fixed onto the rotating body  67 . 
     The protection tube  69  is made as large as possible to fit the inside and rotates by a motor  72  in a prescribed direction. The rotational axis  70  is supported by a  watertight bearing  71 , and the protection tube  69  is supported by a watertight bearing  75 . The rotary magnet  68  is immobilized to the protection tube  69  by a clamping device such as a bolt  76  and operates as one body with the protection tube  69 . 
     According to this structure, in the case in which, for example, microscopic iron dust in raw water is magnetically suctioned during operation and trapped on the outer surface of the protection tube  69 , comes in contact with the membrane  21  while rotating, it is possible to remove the bolt  76  and remove the rotary magnet  68  from the apparatus, and thus a magnetic force is eliminated, making it possible to remove microscopic iron dust from the outer surface of the protection tube  69 . Furthermore, the rotation function can be obtained by integrating the rotary magnet  68  by a bolt into one unit without providing a rotary drive system on the rotary magnet  68 ; therefore, apparatus manufacturing costs can be further reduced when compared to the case in which rotary drive device are separately provided. 
     Furthermore, in this embodiment, by eliminating a difference between the flow velocity inside the flow channel  36  and the circumferential velocity of the permanent magnet  31  provided in the rotary magnet  68 , efficiency is increased in the magnetic suction of magnetic floc  16  that flows almost as fast as water flows in the  flow channel  36 . Flow velocity in the flow channel  36  fluctuates according to the flow rate of raw water. Therefore, the drive control device  48  obtains a flow rate in the flow channel  36  from the operating conditions of the operating pump  3 , shown in  FIG. 1 , or from a flowmeter (not shown); obtains an average flow velocity based on the cross-sectional area calculated by the dimensions of the flow channel  36 ; calculates the number of revolutions that can obtain circumferential velocity almost identical to the above-mentioned average flow velocity according to the outer diameter of the protection tube  32  or  69  of the rotary magnet  29  or  68 ; and controls the number of revolutions of the motor  72  via a signal line  59 ; consequently, it is possible to eliminate the velocity difference, increasing the efficiency in the magnetic suction of magnetic floc  16 . Accordingly, the filtering load of the filtering device can be further reduced by increasing the efficiency in the magnetic separation of magnetic floc  16  in the filtering and clarifying pretreatment process; therefore, the size of the post-process filtering device can be further reduced. 
     In the embodiment stated above, a permanent magnet is used as a magnetic field generation device; however, the same effects can be obtained by using a normal conduction electromagnet or a superconducting electromagnet cooled by  the freezer or the like. 
     Moreover, although a drum-type net  21  has been described in the above embodiments, the net  21  can be a disk, and a plurality of disks can be vertically disposed to configure an apparatus so as to obtain the same effects. 
     Moreover, in the above embodiments, the drum-type rotating body  30  or  67  is made of nonmagnetic material, a plurality of permanent magnets  31  are immobilized on the circumferential surface thereof by an adhesive or the like, and the entire configuration is covered by the protection tube  32  or  69 . However, the same effects can be obtained in the case in which a structure is made such that a plurality of permanent magnets  31  are bonded with an adhesive onto the circumferential surface and both sides of a disk-type rotating body  30  and the entire structure is covered by a roof-shaped protector instead of using a protection tube  32 ; and a plurality of the disk-type rotating body  30  or  67  are arranged in a row at prescribed intervals to form a group of disks and disposed in the flow channel  36 ; then the magnetic floc  16  in the flow channel  36  is trapped by a magnetic force of the permanent magnets immobilized on the circumferential surface and both sides of the rotating disk group; and then the trapped the magnetic floc  16  on the rotating disk group is scraped and removed by a specified spatula disposed along the protector covering over the  circumferential surface and both sides of the group of disks.