JP2006205076A - Filtering method, filtering unit used for the filtering method and filter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To efficiently and inexpensively filter raw water stored in a water storing vessel and to effectively suppress generation of trihalomethane even when adding a halogen based chemical liquid such as hypochlorite to the raw water to be filtered. <P>SOLUTION: A filtering unit 1 having a membrane module housed in a cylindrical casing with a bottom 2 is immersed and installed in the water storing vessel 11 storing the raw water W. The raw water W in the water storing vessel 11 is introduced into the casing 2 and a chemical liquid is added to the raw water introduced into the casing 2, and thereafter the raw water W is filtered by the membrane module. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a filtration method for filtering raw water in a water storage tank or a reservoir (hereinafter referred to as a water storage tank or the like) such as a sedimentation basin of a water purification plant, a filtration unit used in the filtration method, and this filtration unit. The present invention relates to a filtration device installed in the above-mentioned reservoir or the like.

As a filtration device for filtering raw water held in a water storage tank such as a sedimentation basin such as a water purification plant in this way, for example, in Patent Document 1, a membrane module is disposed in the upper part of the filtration tank. In addition, an immersion-type membrane filtration device provided with a sludge scraper at the bottom of the filtration tank is described. That is, in the filtration device described in Patent Document 1, a cylindrical partition is attached to the center of the upper portion of the cylindrical filtration tank, and is divided into a columnar section and a donut-shaped section. The raw water is introduced into the filter tank and flows into the filtration tank from below, and a membrane module incorporating a hollow fiber membrane is disposed in the donut-shaped compartment, and a diffuser tube is concentrically disposed below the membrane module. Several are arranged. On the other hand, the bottom of the filtration tank is provided with the sludge scraping machine having a rake disposed close to the bottom of the filtration tank and a rotating shaft to which the rake is attached, and is attached to the rake. In addition, sludge accumulated at the bottom of the filtration layer is scraped by a large number of gathering plates.
JP-A-10-230261

  However, in the filtration device described in Patent Document 1, when air is blown from the diffuser tube and the membrane module is washed by air scrubbing, the raw water in the filtration tank is agitated by blowing air. The sludge accumulated on the bottom of the filtration tank may be rolled up. However, since the sludge thus wound up further rises to the upper part of the filtration tank by the air blown from the air diffuser, the filtration operation is resumed until the sludge settles together with the deposits peeled off from the membrane module. Then, sludge and the like adhere to the membrane, resulting in a loss of filtration efficiency. In addition, in order to install the membrane module in the tank, a long-term and large-scale construction is required, which is expensive.

  Furthermore, in such a filtering device, for example, a chlorine-based chemical solution such as hypochlorite is added to the raw water in order to sterilize and prevent the membrane water from being filtered as purified water. In a filtration apparatus like patent document 1, this chlorinated chemical | medical solution must be added directly to the raw | natural water in a filtration tank. However, if a chlorinated chemical solution is added to the raw water in the filtration tank in which sludge is accumulated at the bottom of the filtration layer as described above, or the sludge is wound up by aeration by the air diffuser, the chemical solution and the sludge are added. There is a high possibility that trihalomethane, which has been pointed out as carcinogenic in recent years, is produced from organic substances in the inside. Furthermore, to wash the membrane module with a chemical solution such as hypochlorite, either drain the raw water in the filtration tank and then fill the entire filtration tank with the chemical solution, or remove each membrane module and wash it individually. There are only methods, and these require a lot of labor and cost.

  The present invention has been made under such a background, and enables efficient and low-cost filtration of raw water held in a water storage tank and the like, and chlorine-based materials such as hypochlorite in the raw water to be filtered. An object of the present invention is to provide a filtration method capable of effectively suppressing generation of trihalomethane, a filtration unit used in the filtration method, and a filtration device even when a chemical solution is added.

  In order to solve the above problems and achieve such an object, the filtration method of the present invention includes a filtration unit in which a membrane module is housed in a bottomed cylindrical casing in a water storage tank or the like holding raw water. The raw water in the water storage tank or the like is introduced into the casing, a chemical solution is added to the raw water introduced into the casing, and the raw water is filtered through the membrane module. And

  The filtration unit of the present invention used in such a filtration method adds a chemical solution to the bottomed cylindrical casing, a membrane module accommodated in the casing, and the raw water introduced into the casing. Further, the filtration device of the present invention is characterized in that such a filtration unit is immersed and installed in a water storage tank or the like holding raw water.

  Therefore, for example, in the above filtration method using such a filtration unit, and in the filtration apparatus provided with the filtration unit, first, in the bottomed cylindrical casing of the filtration unit installed by being immersed in a water storage tank or the like Since the membrane module is accommodated, relatively clear raw water after the sludge settles and accumulates in the water tank can be introduced into the casing for filtration. Even when cleaning is performed by scrubbing cleaning means, this cleaning means is installed in the casing and the inside and outside of the casing are shut off by closing the inlet for introducing the raw water, so that only the raw water in the casing is stirred during cleaning. The sludge accumulated on the bottom of the water storage tank or the like is not rolled up. Further, the membrane module can be installed in a water storage tank or the like together with the filtration unit, and the construction is easy, and even when the membrane module is cleaned with a chemical solution, the casing is filled with the chemical solution, Since it is sufficient to discharge the fuel, it takes less time and can reduce the installation cost and the running cost.

  Further, in the filtration method, the chemical water or the like is added to the raw water thus introduced into the casing, and the raw water is filtered by the membrane module. In the filtration unit and the filtration device, Since the chemical solution adding means for adding the chemical solution to the raw water introduced into the casing of the filtration unit is provided, the relatively clear raw water in which the sludge is settled in the water storage tank as described above, that is, the content of organic matter is The chemical solution is added to a small amount of raw water. Therefore, according to the present invention, it is possible to suppress the generation of trihalomethane as much as possible when a chlorinated chemical solution is used for such organic matter while ensuring sterilization and membrane fouling prevention of raw water. Become.

  Here, in order to disinfect and sterilize raw water more reliably and quickly with this chemical solution, it is desirable to introduce the raw water into the casing while stirring, and to add the chemical solution when introducing the raw water into the casing. Thus, by adding the chemical solution to the raw water introduced into the casing while being stirred, the chemical solution can be uniformly and rapidly dispersed in the raw water to ensure sterilization. In addition, in order to introduce the raw water into the casing while stirring in this way, the filtration unit is provided with an inlet for introducing the raw water into the casing at the upper part of the casing, and inside the casing. Is provided with a descending pipe line extending downward from the opening on the inner side of the inlet, and the chemical solution adding means may add the chemical solution to the raw water in the down pipe line. The raw water is stirred together with the added chemical solution while flowing down the descending pipe line extending from the inlet to the bottom, and the chemical solution can be reliably and quickly dispersed. Furthermore, in order to disperse this chemical solution more reliably and quickly, it is only necessary to provide a stirring means such as a baffle plate for stirring the raw water introduced by flowing down the descending conduit in the descending conduit.

  1 and 2 show an embodiment of the filtration unit of the present invention, and FIG. 3 shows an embodiment of the filtration apparatus of the present invention in which the filtration unit of this embodiment is installed. The filtration unit 1 of this embodiment is installed in the water tank 11 in which the raw water W is hold | maintained as shown in FIG. 3, The bottomed cylindrical shape into which the raw water W in this water tank 11 can be introduce | transduced inside The casing 2 is provided with a membrane module 3A. The casing 2 is provided with cleaning means 4 for cleaning the membrane module 3A, and the casing 2 includes raw water W in the casing 2 after cleaning. The discharge means 5 which discharges is provided.

  Here, in the present embodiment, the casing 2 is made of a metal material having high corrosion resistance such as stainless steel and has a rectangular shape in plan view, and the height thereof is longer than the length of the rectangle. The vertically elongated bottomed rectangular cylinder, that is, the bottom of the rectangular cylinder is closed, and is installed with the bottom facing downward and the height direction oriented vertically. Further, the bottom portion of the casing 2 has a downward convex convex shape as the cross section gradually decreases, and in this embodiment, in particular, has a convex curved surface shape. Specifically, as shown in FIG. 1, among the four side wall surfaces extending in the height direction of the casing 2, the lower ends of the pair of first side wall surfaces 2 </ b> A and 2 </ b> A facing each other are the height of the casing 2. A pair of remaining second side wall surfaces 2B facing each other, the lower end edge of which extends in the direction and has a convex curved shape that protrudes downward in a side view facing the first side wall surface 2A. The lower end portion of 2B is formed in a convex curved surface shape that gradually approaches each other as it goes downward along the lower end edge of the first side wall surface 2A, and the first and second side wall surfaces 2A, 2B. The lower end portion of the casing 2 defines the bottom portion of the casing 2.

  In the present embodiment, the upper end edge of the first side wall surface 2A defines a short side, and the upper end edge of the second side wall surface 2B defines a long side in the rectangle that the casing 2 is in plan view. It has become. Further, the lower end edges of the first side wall surfaces 2A and 2A of the present embodiment are a single arc, and particularly in the present embodiment, a semicircular arc. Therefore, the lower end portions of the second side wall surfaces 2B and 2B are It will be smoothly connected to each other to form a semi-cylindrical shape. Further, a drain port 2C is disposed at the lower end of the casing 2 as shown in FIG. However, the bottom portion of the casing 2 is not limited to the convex curved shape of the present embodiment. For example, the other pair of second side wall surfaces 2B and 2B are inclined flat surfaces that approach each other as they move downward at a constant inclination angle. Or the pair of first side wall surfaces 2A, 2A is also formed into a convex curved surface shape or an inclined flat surface shape that gradually approaches each other as it goes downward, and the bottom portion of the casing 2 is formed into a convex curved surface shape over the whole. Alternatively, a truncated pyramid shape or a gable roof shape that protrudes downward may be used.

  On the other hand, an inlet 2D for introducing the raw water W into the casing 2 is provided in the upper part of the casing 2, and the raw water W flows through the inlet 2D to the inlet 2D. Control means (not shown) for controlling the above is provided. Here, in this embodiment, the inflow port 2D is the upper part of one first side wall surface 2A of the pair of first side wall surfaces 2A, 2A along the rectangular short side of the casing 2 in plan view. It is comprised by the internal peripheral surface of one tubular member protrudingly provided so that it might penetrate this wall surface 2A in the center part of the width direction. Thus, by using one inflow port 2D, a decrease in strength of the first side wall surface 2A on which the inflow port 2D is disposed can be minimized.

  Further, the control means is constituted by an opening / closing valve such as a butterfly valve provided at the base portion of the tubular member, and by opening the inlet 2D by driving the opening / closing valve by a driving means (not shown), The raw water W can be introduced into the casing 2 through the inflow port 2D, and the casing 2 is isolated from the outside raw water W by closing the inflow port 2D, so that the raw water through the inflow port 2D is separated. The inflow of W and the outflow of raw water W from the casing 2 are prevented, that is, the flow of the raw water W is controlled. As shown in FIG. 1, the inflow port 2D is submerged below the height of the water surface H of the raw water W held in the water storage tank or the like, more specifically, slightly below the water surface H. It is possible to open to the height to be. However, the inflow control method is not limited.

  Further, a partition plate 2E is provided on the outer periphery of the casing 2 so as to surround the periphery of the inflow port 2D. In the present embodiment, as shown in FIG. 1, the partition plate 2E includes the second side from both ends in the width direction of the upper surface of the first side wall surface 2A on which the inlet 2D is disposed. Two plate members extending so as to protrude in parallel with the side wall surfaces 2B and 2B, and a rectangular plate material extending in parallel with the surface of the first side wall surface 2A between the protruding ends of these plate materials, The upper and lower sides of the partition plate 2E are open.

  As shown in FIG. 2, the partition plate 2E is spaced from the inflow port 2D and is positioned at the height of the water surface portion H of the raw water W held in a water storage tank or the like. Therefore, the raw water W enters between the partition plate 2E and the casing 2 through the lower opening of the partition plate 2E, and enters the casing 2 through the inlet 2D. Will be introduced. Accordingly, it is possible to prevent floating matters such as dust floating on the water surface portion H from being introduced into the casing 2 as they are, and by surrounding the periphery of the inflow port 2D with the plate material, the partition plate The increase in the occupied volume in the water storage tank or the like of the filtration unit 1 due to the provision of 2E is minimized.

  On the other hand, the membrane module 3A accommodated in the casing 2 is formed by laminating a large number of elements having a hollow fiber membrane stretched in a screen shape or a flat membrane-like separation membrane, or a large number of tubular ceramic membrane elements. The membrane modules 3A are bundled and combined into a module by a header (not shown) or the like, and each membrane module 3A has a substantially horizontally long rectangular parallelepiped shape in the present embodiment. In this embodiment, there are a plurality (four in the figure) of such membrane modules 3A having the same shape and the same size, and a pair of side surfaces extending in the longitudinal direction are horizontal and the long side of the side surfaces is in a plan view. The membrane module set 3 is formed in parallel with the long side of the rectangle (the upper end edge of the second side wall surface 2B) formed in parallel, so that the membrane modules 3A face each other and are aligned vertically. And disposed in the casing 2.

  The plurality of membrane modules 3A stacked in this manner are such that the uppermost membrane module 3A is positioned below the inlet 2D of the casing 2 as shown in FIG. Further, the membrane modules 3A that are vertically adjacent to each other may be in close contact with each other or may be spaced at an appropriate interval. The header is connected to a suction pump (not shown) via a membrane filtration water pipe 3B, and the filtered water filtered from the raw water W by the plurality of membrane modules 3A of the membrane module set 3 is passed through the membrane filtration water pipe 3B by this suction pump. Discharged through.

  Further, the cleaning means 4 diffuses air into the casing 2 when an adhering matter adheres to the surface of the membrane module 3A of the membrane module set 3 to cause clogging, etc., and air scrubbing with the bubbles is performed. The deposits are peeled off and the membrane module 3A (membrane module set 3) is washed. That is, the cleaning means 4 includes, for example, an air pipe 4B having a plurality of pipes or sintered pipes provided with a plurality of downwardly opened air holes and disposed under the membrane module set 3. Is connected to an air supply source such as a blower (not shown), and the air supplied from the air supply source passes through the air pipe 4B and is connected to an air hole or a fire provided in the pipe of the air diffuser 4A. Each of the membrane modules 3A of the membrane module set 3 located above the membrane module set 3 is washed by being ejected from fine pores formed in the tube. For example, when activated carbon is added to the raw water W in the casing 2 in order to adsorb organic matter or the like in the raw water W, the raw water W is stirred using the air diffuser 4A of the cleaning means 4. The activated carbon may be uniformly dispersed.

  Further, in the present embodiment, the casing 2 is provided with the descending pipeline 6 extending so as to descend downward from the inlet 2D, and the lower end opening 6A of the descending pipeline 6 is provided with cleaning means. 4 is positioned below the diffuser 4A. Here, in the descending pipeline 6 of the present embodiment, the angle-shaped strip material having a "U" shape with a flat cross section is provided below the air diffuser 4A from the opening inside the casing 2 of the inlet 2D. The opening of this cross section extends directly above the bottom of the casing 2 of the casing 2 and the portion corresponding to the inlet 2D (the center in the width direction) of the back surface of the first side wall surface 2A of the casing 2 provided with the inlet 2D. The upper end portion of the casing 2 is opened at a height substantially equal to the upper end portion of the casing 2 beyond the height of the inflow port 2D.

  Further, a baffle plate 7A is projected on the inner wall surface of the descending pipeline 6 below the inlet 2D, and the baffle plate 7A serves as the stirring means 7 in the present embodiment. Here, in the present embodiment, the plurality of baffle plates 7A are alternately directed downward on the back surface of the first side wall surface 2A constituting the descending pipeline 6 and the inner surface of the angle-shaped strip material facing the first side wall surface 2A. In addition, each of the baffle plates 7A is a baffle plate 7A which is horizontally provided with a protruding amount that does not hinder the introduction of the raw water W and flows into the casing 2 after flowing down in the descending pipe 6. It stirs in the down pipe 6 by flowing down while colliding with the pipe.

  However, the descending pipe line 6 is not limited to the above-mentioned form. For example, the strip material has a semicircular cross-sectional shape opened to the inlet 2D side in a plan view, or the first side wall surface on the inner side of the casing 2. Another wall surface is newly disposed so as to be parallel to and spaced from the back surface of 2A, and the internal space of the casing 2 is partitioned, so that a gap between the wall surface and the back surface is used as a descending pipeline 6 or the like. The cross-sectional shape is not limited. Moreover, it is good also as the descending pipeline 6 by arrange | positioning pipes, such as a circular tube and a rectangular tube, so that it may extend in the downward direction in the casing 2 from inflow port 2D. Further, the stirrer 7 may also be provided with a baffle plate 7A on the other inner surface of the angle-shaped strip, and provided that the raw water W can be stirred by protruding from the descending pipe 6. It does not have to be plate-shaped. The descending pipeline 6 also functions as membrane module protection means for suppressing the raw water W introduced into the casing 2 from directly colliding with the membrane module 3A.

  Further, the discharge means 5 in the present embodiment is provided with a discharge pipe 5A having one end opened at the bottom of the casing 2 and the other end connected to a suction pump (not shown) disposed outside the casing 2. ing. The discharge pipe 5A extends from the suction pump side directly above the casing 2 of the filtration unit 1 and is passed through the casing 2 in the height direction from an opening at the top of the casing 2, and the one end thereof is connected to the bottom of the casing 2 Moreover, one end of the discharge pipe 5A is arranged so as to open downward in the vicinity of the lower end of the inner bottom portion of the casing 2 which is convexly curved and protrudes downward as described above. It is installed.

  In the present embodiment, the membrane filtration water pipe 3B of the membrane module set 3 and the air pipe 4B of the cleaning means 4 are also passed through the casing 2 from the upper opening to the header and scattering of each membrane module 3A, like the discharge pipe 5A. It is connected to the air device 4A. In the present embodiment, a plate-like casing cover 2F is detachably covered on the upper opening of the casing 2 as shown in FIG. 2, and the upper opening of the casing 2 is opened by the casing cover 2F. It can be blocked. However, the casing cover 2F is provided with an insertion hole portion through which the membrane filtration water pipe 3B, the air pipe 4B, and the discharge pipe 5A are inserted. Moreover, you may make it provide a cover also in the upper opening part of the said partition plate 2C.

  Further, as the discharge means 5, a drain discharge pipe (not shown) connected to a suction pump from the outside of the casing 2 may be connected to the drain port 2 </ b> C provided at the bottom of the casing 2. This drain discharge pipe is constituted by, for example, a flexible flexible pipe, and the suction pump extends outside the casing 2 in the height direction of the casing 2 and has one end disposed outside the water storage tank or the like. Connected to. However, the drain discharge pipe is not limited to a flexible pipe but may be a rigid pipe such as a steel pipe.

  Furthermore, a support member 8 made of a rigid material is attached to the casing 2 so as to suspend and support the casing 2 in raw water W in a water storage tank or the like. Here, in the present embodiment, the support member 8 is formed of a metal material such as a steel material such as stainless steel like the casing 2 and has a cylindrical shape or a tubular shape (square pipe shape) having a rectangular cross section as shown in FIG. In addition, a pair of such support members 8 having the same shape and the same size are parallel to each other in the longitudinal direction at the upper outer edges of the pair of second side wall surfaces 2B, 2B of the casing 2 and the second The side wall surface 2B is parallel to the upper edge of the side wall 2B and is positioned on one plane perpendicular to the height direction of the casing 2 oriented in the vertical vertical direction, that is, on one horizontal plane, and both ends thereof are paired with the pair of The first side wall surfaces 2A and 2A protrude from each other by an equal length, and are fixedly attached by fastening with bolts or the like or joining by welding or the like.

  Such a support member 8 is passed over the water storage tank 11 into which the raw water W is introduced in the state where the bottom portion of the casing 2 is faced downward and the height direction is directed in the vertical vertical direction as described above. The lower surfaces of both end portions projecting from the first side wall surfaces 2A and 2A are mounted on the support portions such as a frame and a rail (not shown) or the opening end surfaces on both sides of the upper opening portion of the water storage tank 11 therebetween. By placing or fixing, the load of the filtration unit 1 including the casing 2 and the membrane module set 3 is supported substantially without bending, and the casing 2 is suspended in the raw water W in the water storage tank 11 as described above. So that it is immersed. Further, the support member 8 is such that the casing 2 is suspended and immersed in the raw water W, and the inlet 2D of the casing 2 and the partition plate 2E are at the height of the surface H of the raw water W as described above. Membrane modules accommodated in the inlet 2D and the partition plate 2E and the casing so that all the membrane modules 3A of the membrane module set 3 are immersed in the raw water W introduced from the inlet 2D. The plurality of membrane modules 3A in the set 3 are attached so as to be positioned above the position where the uppermost membrane module 3A is disposed.

  And the filtration unit 1 of this embodiment comprised in this way is further equipped with the chemical | medical solution addition means 9 which adds chlorine-type chemical | medical solutions, such as hypochlorite, to the raw | natural water W introduce | transduced in the said casing 2. FIG. In the present embodiment, the chemical solution adding means 9 includes a chemical solution injection pipe 9A extending from a chemical solution tank (not shown) that holds the chemical solution into the casing 2 via a pump or the like. Further, in the present embodiment, the chemical liquid injection pipe 9A extends from the insertion hole of the casing cover 2F into the upper opening of the descending pipeline 6 and is introduced into the casing 2 above the inlet 2D. It arrange | positions so that it may open upwards rather than the water surface part of the raw | natural water W. FIG.

  In one embodiment of the filtration device of the present invention in which such a filtration unit 1 is installed, the water storage tank 11 is, for example, a settling tank provided in an existing water purification plant, and in FIG. In a plan view having a rectangular shape, a pool shape is formed so that the rectangular shape can be dug down. And the said filtration unit 1 is supported by the said supporting member 8, is installed in the said longitudinal direction one end side (right side in FIG. 3) in this water tank 11, and is immersed in the raw water W introduce | transduced into the said water tank 11 Is done.

  A flock formation tank 12 to which raw water W introduced into the water storage tank 11 is supplied to the other end side in the longitudinal direction of the water storage tank 11 (left side in FIG. 3) is a wall on the other end side of the water storage tank 11. It is attached so that it may adjoin via part 11A. The floc-forming tank 12 is supplied with raw water W rapidly added with a flocculant and rapidly stirred with a flocculator (not shown). The raw water W adjusted so as to be sufficiently formed is introduced into the water storage tank 11 through a plurality of introduction holes 11B formed in the wall portion 11A.

  Further, as shown in FIG. 3, the water storage tank 11 has a substantially rectangular shape with an open upper portion having a long side in the longitudinal direction as shown in FIG. 3, except that the other end side of the bottom portion 11 </ b> C is lowered by one step. The sludge pit 13 is connected to a sludge pipe (not shown) that discharges the sludge M through a sludge valve (not shown).

  Further, a sludge scraping means 14 is provided at the bottom 11C of the water tank 11. However, the sludge scraping means 14 is not limited to that shown in FIG.

  Furthermore, an inclined plate 15 inclined with respect to the horizontal plane is spaced apart from the upper portion of the water storage tank 11 provided with the sludge scraping means 14 at the bottom 11C in order to efficiently precipitate flock. A large number of layers are stacked. That is, the inclined plate 15 is preferably formed of a flat plate material such as a resin plate on which reinforcing ribs are formed. A large number of such inclined plates 15 are in the same direction and at the same angle with respect to the horizontal plane as described above. Inclined and attached to a frame-like support frame made of stainless steel or the like at equal intervals so as to form a substantially rectangular parallelepiped shape extending in the longitudinal direction of the water storage tank 11 as a whole. However, each side of the rectangle formed in a plan view is accommodated in parallel with each side of the rectangle formed by the water storage tank 11. However, it is not limited to the inclined plate 15 as long as it is a means for increasing the sedimentation efficiency, and for example, an inclined tube may be used. Furthermore, if the area of the water storage tank 11 is large and sufficient precipitation can be performed, the inclined plate 15 and the like may be omitted.

  And in this embodiment, the said filtration unit 1 makes the said bottom part of the casing 2 face down, and makes the said height direction into the vertical vertical direction as mentioned above, and the water storage tank 11 which makes a rectangular shape in this way planar view in this way It is installed on one end side of the inclined plate 15, that is, on the opposite side to the side where the raw water W is introduced into the water storage tank 11. Here, the filtration unit 1 is configured so that the casing 2, which is also rectangular in plan view, has a rectangular shape parallel to each other with respect to the rectangular shape of the water storage tank 11 in plan view. It is installed so as to be spaced from the inner wall of the tank 11. Although only one filtration unit 1 is shown in FIG. 3, a plurality of filtration units 1 may be installed.

  Thus, in the filtration apparatus in which the filtration unit 1 is installed in the water storage tank 11, the raw water W is transferred from the flock formation tank 12 into the water storage tank 11 of the filtration apparatus as described above, and the wall on the other end side. Most of the flocs such as sludge M are settled and deposited on the bottom 11C while being introduced through the introduction hole 12B of the portion 12A toward the one end side of the rectangular longitudinal direction of the water storage tank 11 in plan view. The water is relatively clear. The sludge M thus deposited on the bottom portion 11C is scraped and discharged by the sludge scraping means 14 to the drainage pit 13 on the other end side in the longitudinal direction.

  Furthermore, the clarified raw water W is filtered by the filtration unit 1 of the above embodiment disposed on one end side of the water storage tank 11. That is, at the time of filtration work in the filtration unit 1, the opening / closing valve as the control means is opened to open the inlet 2D, and the inlet 2D can be opened to the water surface portion H of the raw water W. The raw water W in the water storage tank 11 flows down from the inlet 2D through the descending pipeline 6 as described above, and is introduced into the casing 2 from the bottom. In the filtration unit 1, the introduced raw water W is filtered by the membrane module 3A of the membrane module set 3, and the filtered water T thus filtered is discharged through the membrane filtration water pipe 3B.

  Therefore, in the filtration method according to an embodiment of the present invention using such a filtration device, first, relatively clean raw water W after the sludge M is substantially settled and deposited in the water storage tank 11 as described above is formed in a bottomed cylindrical shape. Since it can introduce into the casing 2 and can perform filtration, there is little burden on the membrane module 3A, and efficient filtration can be performed. Further, even when the membrane module 3A is cleaned by air scrubbing by the cleaning means 4, the sludge M deposited on the bottom 11C of the water storage tank 11 is wound up by installing the cleaning means 4 in the casing 2. The raw water W from which the adhered matter after cleaning has been peeled is discharged by the discharge means 5 and newly introduced into the casing 2 so that the filtration operation can be resumed promptly. Furthermore, even in the case of configuring such a filtration device, the membrane module set 3 together with the filtration unit 1 may be installed in the water tank 11, the construction is simple, and the cost for installation can be reduced. Even when the module 3A is cleaned with the chemical solution, it is only necessary to fill and clean the casing 2 with the chemical solution, so that it is possible to reduce the running cost without taking time and effort.

  Further, the filtration unit 1 of the above embodiment is further provided with a chemical solution adding means 9 for adding a chemical solution to the raw water W introduced into the casing 2. Therefore, a filtration method and a filtration using the filtration unit 1 are provided. In the apparatus, the chemical solution can be added to the relatively clear raw water W in which the content of organic matter is reduced by the sludge M settling in the water storage tank 11 as described above. For this reason, according to the filtration method and the filtration apparatus having the above-described configuration, even when a chlorine-based chemical solution is used when the raw water W is surely sterilized and disinfected by the addition of the chemical solution to prevent the membrane from being soiled, It is possible to suppress the generation of trihalomethane by the chemical solution and the organic matter in the raw water W as much as possible, and it is possible to provide safer purified water.

  Further, in the filtration unit 1 of the above-described embodiment, an inlet 2D for introducing the raw water W into the casing 2 is provided at the upper part of the casing 2, and the inside of the casing 2 includes the inlet 2D. A descending pipe 6 extending downward from the opening on the inner side is provided, so that the raw water W is introduced into the casing 2 while being stirred while flowing down in the descending pipe 6. The chemical solution adding means 9 is configured such that the injection pipe 9 </ b> A opens to the upper part in the descending pipeline 6 and adds the chemical solution to the raw water W. Therefore, in the filtration method of the present embodiment, this chemical solution is introduced into the casing 2 while being stirred together with the raw water. Therefore, the chemical solution is reliably and quickly dispersed in the raw water W, so that more efficient sterilization can be performed. It is possible to prompt.

  Moreover, in the filtration unit 1 of the present embodiment, the baffle plate 7A is provided as the stirring means 7 in the descending pipeline 6, and the raw water W flowing down the descending pipeline 6 and the added chemical solution are It will be further stirred by colliding with the baffle plate 7A. Therefore, according to the filtration method having the above-described configuration using such a filtration unit 1, the chemical liquid can be dispersed more reliably and quickly in the raw water W, thereby achieving more efficient sterilization of the raw water W. It becomes possible. In place of such a baffle plate 7A, for example, a bar-like member may protrude, and the stirring means 7 is not limited.

It is a perspective view which shows one Embodiment of the filtration unit of this invention (however, illustration is abbreviate | omitted in the casing cover 2F and the stirring means 7 (baffle plate 7A)). It is a longitudinal cross-sectional view of embodiment shown in FIG. It is a longitudinal cross-sectional view of one Embodiment of the filtration apparatus of this invention which installed the filtration unit 1 of embodiment shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Filtration unit 2 Casing 2D Inlet 3A Membrane module 4 Washing means 5 Discharge means 6 Falling pipe 7 Stirring means 7A Baffle plate 9 Chemical solution addition means 9A Chemical solution injection pipe 11 Water storage tank W Raw water

Claims (7)

  A filtration unit in which a membrane module is housed in a bottomed cylindrical casing is immersed in a water tank or reservoir holding raw water, and the raw water in the water tank or reservoir is introduced into the casing. A filtration method characterized by adding a chemical solution to the raw water introduced into the casing and filtering the raw water through the membrane module.   The filtration method according to claim 1, wherein the raw water is introduced into the casing while stirring, and the chemical solution is added when the raw water is introduced into the casing.   The filtration method according to claim 1 or 2, wherein the chemical solution is a chlorine-based chemical solution.   A filtration unit used in the filtration method according to any one of claims 1 to 3, wherein the bottomed cylindrical casing, a membrane module accommodated in the casing, and the casing are introduced into the casing. A filtration unit comprising chemical solution adding means for adding a chemical solution to the raw water.   The upper part of the casing is provided with an inflow port for introducing the raw water into the casing, and the inside of the casing has a descending pipe line extending downward from the opening on the inner side of the inflow port. The filtration unit according to claim 4, wherein the chemical solution adding means adds the chemical solution to the raw water in the descending pipeline.   6. The filtration unit according to claim 5, wherein a stirring means for stirring the raw water introduced by flowing down the down pipe is provided in the down pipe. A filtration apparatus comprising the filtration unit according to any one of claims 4 to 6 soaked in a water tank or a reservoir for holding raw water.

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