Fluidized bed type biological treatment device and method of operating the same

Abstract

To sufficiently wash a screen in a fluidized bed type biological treatment device configured such that the screen is washed by air bubbles from air diffusing means and in the operating method thereof.SOLUTION: There are provided: a fluidized bed type biological treatment device comprising a tank body 2 containing a flowable carrier C, a screen 7 disposed in the tank body 2 to separate the carrier to guide treated water to a discharge port, a partition plate 8 partitioning the inside of the tank body 2 into a rectification region in which the screen 7 is disposed and a reaction region in which biological treatment is carried out, an air diffusion member 9 for allowing air bubbles to flow along a surface of the screen 7 on the rectification region side thereof, and an opening 11 disposed on the upper part of the partition plate 8 to allow the carrier to flow from the rectification region to the reaction region; and a method of operating the same.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a fluidized bed biological treatment device for treating wastewater, and more particularly to a fluidized bed biological treatment device having a tank body provided with a screen for separating the carriers from the treated water. The present invention also relates to a method for operating the fluidized bed biological treatment device. [Background technology]

[0002] A fluidized bed biological treatment device is known that uses a carrier on which microorganisms are attached at a high concentration in order to increase the load on the biological treatment device and improve the water quality. It is also known that a screen is used as a means for solid-liquid separation of the carrier (Patent Documents 1 and 2).

[0003] Patent Document 2 describes a method of cleaning the screen by inclining the screen so that it faces the treated water outlet of the tank body and diffusing air from below the screen with an air diffuser. Also, Fig. 3 of Patent Document 2 describes a method of providing a partition plate parallel to the screen. By providing the partition plate in this way, air bubbles from the air diffuser flow along the screen, improving the cleaning effect of the screen. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 7-47390 [Patent Document 2] JP 2020-138185 A Summary of the Invention [Problem to be solved by the invention]

[0005] In the case of a fluidized bed biological treatment device having a partition plate facing a screen as in Patent Document 2, if the stirring speed is increased to sufficiently diffuse the carriers within the tank in order to increase the treatment capacity of the device, the flow velocity and flow rate within the tank will increase, and the air bubbles diffused from the aeration means will be swept away by the swirling flow, resulting in insufficient cleaning of the screen.

[0006] An object of the present invention is to provide a fluidized bed biological treatment apparatus and an operating method thereof in which the screen is washed with air bubbles from an aeration means, so that the screen can be sufficiently washed. [Means for solving the problem]

[0007] The fluidized bed biological treatment device of the present invention comprises a tank body containing fluid carriers, a screen provided within the tank body for separating the carriers and directing treated water to an outlet, a partition plate which divides the inside of the tank body into a straightening area in which the screen is arranged and a reaction area in which biological treatment is carried out, an aeration member for causing air bubbles to flow along the surface of the screen facing the straightening area, and an opening provided in the upper part of the partition plate for transporting the carriers from the straightening area to the reaction area.

[0008] In one aspect of the present invention, the screen is provided facing the side wall surface of the tank body, the space between the screen and the side wall surface of the tank body forms a filtered water chamber, and the side wall surface of the tank body is provided with the outlet for filtered water overflow facing the filtered water chamber.

[0009] In one aspect of the present invention, the partition plate extends in the vertical direction along the screen, the lower end of the partition plate is located lower than the lower end of the screen, and the upper end of the partition plate is located higher than the water level in the reaction area and the water level in the straightening area within the tank body.

[0010] In one aspect of the present invention, the partition plate has a main plate facing the screen, the opening is provided in the upper part of the main plate, and the air diffusion member is arranged between the main plate and a downward extension surface of the front surface of the screen.

[0011] In one aspect of the present invention, the air diffusing member is disposed closer to the downward extension surface than a middle point between the main plate and the downward extension surface.

[0012] In one aspect of the present invention, the opening is provided with an opening / closing member.

[0013] The method for operating a fluidized bed biological treatment device of the present invention is a method for operating such a fluidized bed biological treatment device of the present invention, and comprises a steady cleaning step in which a steady amount of air is diffused from the aeration member, and a strong cleaning step in which the amount of air diffused from the aeration member is made greater than that in the steady cleaning step.

[0014] In one embodiment of the operating method of the present invention, the opening is closed in the steady cleaning step, and the opening is opened in the strong cleaning step, and the carrier is returned from the flow straightening region through the opening to the reaction region. Effect of the Invention

[0015] According to the fluidized bed biological treatment device and the operating method thereof of the present invention, the diffusion of air bubbles into the tank body can be prevented, the screen can be efficiently washed, and clogging of the screen by the carriers or biofilms attached to the carriers can be suppressed, thereby enabling stable biological treatment.

[0016] In one embodiment of the present invention, the partition plate has a main plate facing the screen, the opening is provided in the upper part of the main plate, and the air diffuser is disposed between the main plate and the downward extension of the front surface of the screen. This reduces the horizontal cross-sectional area of ​​the flow straightening region, and enhances the cleaning effect of the screen by the diffused air bubbles. In addition, the carriers that have entered the flow straightening region gather at the opening and are easily transported to the reaction region.

[0017] In one embodiment of the present invention, an opening and closing member is provided at the opening in the upper part of the partition plate. In this embodiment, when the water level in the reaction region or the flow straightening region changes due to the operating conditions, the opening can be opened or closed or the opening degree can be adjusted appropriately according to the situation.

[0018] In the method of operating a fluidized bed biological treatment device according to the present invention, steady cleaning is performed with a predetermined amount of aeration during biological treatment of wastewater, and strong cleaning is performed by temporarily spraying an amount of aeration that is greater than that during steady cleaning. During this strong cleaning, the transfer of carriers from the flow straightening area to the reaction area is promoted through the openings in the upper part of the partition plate.

[0019] In one embodiment of the method of the present invention, the biological treatment is anaerobic biological treatment, and aeration is performed so that the total of the dissolved oxygen (DO) weight in the inflow raw water and the dissolved oxygen weight by the water surface or aeration does not exceed 10% of the total weight including the oxygen weight of the components to be treated contained in the inflow raw water. As a result, even when aeration is performed with oxygen-containing gas, the DO contained in the water transferred from the rectification region to the reaction region is quickly consumed, so that the anaerobic nature of the reaction region can be maintained. [Brief description of the drawings]

[0020] [Figure 1] 1 is a vertical cross-sectional view of a fluidized bed biological treatment device according to an embodiment. [Diagram 2] FIG. 2 is a vertical cross-sectional view taken along line II-II in FIG. [Diagram 3] FIG. 2 is a horizontal cross-sectional view taken along line III-III in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] BEST MODE FOR CARRYING OUT THE DISCLOSURE Hereinafter, a fluidized bed biological treatment device and an operating method thereof according to an embodiment will be described with reference to Figs.

[0022] This fluidized bed biological treatment device 1 includes a tank body 2, a drive shaft 3 disposed at the axial center position of the tank body 2, and a rotor (mixing blade) 4 fixed to the drive shaft 3. In this embodiment, a bearing portion (not shown) is provided on the bottom surface of the tank body 2, and the lower end of the drive shaft 3 is supported by this bearing portion, but the drive shaft 3 may also be suspended from above. The drive shaft 3 is driven to rotate by a drive unit M.

[0023] In this embodiment, the tank body 2 is a rectangular tank having a square horizontal cross section as shown in FIG. 3, but the tank body 2 may have other shapes, such as a cylindrical tank.

[0024] An inlet 5 for raw water (water to be treated) is provided at the top of one wall surface 2a of the tank body 2, and an outlet (overflow port) 10 for treated water is provided at the top of the other wall surface 2b on the opposite side. The inlet 5 is disposed higher than the outlet 10. Note that a raw water inlet pipe may be provided instead of the inlet 5. In this embodiment, the fluidized bed biological treatment device 1 is an anaerobic biological treatment tank, and the top surface of the tank body 2 is closed by a top plate (not shown).

[0025] A screen 7 extending in the vertical direction is provided so as to face the other wall surface 2b. In this embodiment, since the other wall surface 2b is flat, the screen 7 is also flat. The screen 7 is preferably made of a bar screen, a mesh, a wedge wire, a punched metal, or the like.

[0026] The gap between both sides of the flat screen 7 extending in the vertical direction and the wall surface 2b is closed by side plates 7a (Fig. 3), and the gap between the lower side of the screen 7 and the wall surface 2b is closed by a bottom plate 7b (Fig. 1).

[0027] The upper end of the screen 7 extends above the lower edge of the outlet 10, and preferably extends to the upper edge of the outlet 10 or above it.

[0028] Between the screen 7 and the wall surface 2b of the tank body 2, a filtrate chamber 6 is formed, which is surrounded by the screen 7, the side plate 7a, and the bottom plate 7b. The outlet 10 is disposed so as to face the inside of the filtrate chamber 6. The level of the lower edge of the outlet 10 is the water level WL2 of the flow straightening area of ​​the tank body 2.

[0029] In this embodiment, the screen 7 extends in a substantially vertical direction, but the screen 7 can also extend in an oblique direction so that the distance between the screen 7 and the wall surface 2b of the tank body 2 is shorter at the lower end than at the upper end, and if the lower end of the screen 7 is positioned so as to contact the wall surface 2b of the tank body 2, the bottom plate 7b can be omitted.

[0030] A partition plate 8 is provided extending in the vertical direction so as to surround the screen 7. The upper end of the partition plate 8 extends above the upper end of the screen 7. The inner region of the partition plate 8 (the region on the screen 7 side from the partition plate 8) is a flow straightening region, and the outer region of the partition plate 8 (the region on the rotor 4 side) is a reaction region.

[0031] The partition plate 8 has a U-shaped horizontal cross section and includes a main plate 8a facing the screen 7 and a pair of side plates 8b (FIG. 3) that close the gap between both sides of the main plate 8 and the wall surface 2b.

[0032] It is desirable that the main plate 8a and the side plate 8b of the partition plate 8 extend in a substantially vertical direction, but there is no problem if they are within ±5° of the vertical direction.

[0033] The horizontal width of the main plate 8a is slightly larger than the horizontal width of the screen 7.

[0034] The lower end of the partition plate 8 is located below the lower end of the screen 7 and above the bottom surface of the tank body 2. An opening is formed between the lower edge of the partition plate 8 and the wall surface 2b, and water containing the carrier C can flow from the reaction region to the flow straightening region through this opening.

[0035] An air diffusing member 9 such as an air diffusing tube is provided to make air bubbles flow along the surface of the screen 7 on the main plate 8a side (hereinafter sometimes referred to as the front surface of the screen). The air diffusing tube preferably extends in a direction parallel to the width direction of the screen 7 and has a length equal to or less than the width of the screen 7.

[0036] In this embodiment, the air diffusing member 9 is disposed above the lower end of the partition plate 8 and below the lower end of the screen 7. The air diffusing member 9 is preferably disposed on the downward extension side of the front surface of the screen 7 rather than midway between the downward extension surface and the main plate 8a. This allows air bubbles diffused from the air diffusing member 9 to rise along the front surface of the screen 7, and deposits on the front surface of the screen 7 are efficiently peeled off and removed. When the screen 7 is extended in an oblique direction rather than vertically as described above, it is preferable to dispose the air diffusing member 9 as close as possible to the wall surface 2b of the tank body 2.

[0037] An opening 11 is provided at the upper part of the main plate 8a for transferring water and carriers from the straightening region to the reaction region when the water level WL2 in the straightening region inside the partition plate 8 is higher than the lower end of the opening 11.

[0038] The width of the opening 11 is desirably 50% or more of the width of the screen 7. In addition, the width of the opening 11 is desirably 150 cm or less. This allows the carriers remaining near the water surface in the flow straightening area to be efficiently returned to the reaction area through the opening 11.

[0039] The lower edge of opening 11 is located lower than the lower end of inlet 5. The difference in height between the lower edge of opening 11 and the lower end of inlet 5 is preferably 40 cm or less, particularly 10 to 30 cm. The upper edge of opening 11 is located higher than the lower end of inlet 5. The difference in height between the upper edge of opening 11 and the lower end of inlet 5 is preferably 40 cm or less, particularly 10 to 30 cm. The vertical width of opening 11 is preferably about 20 to 60 cm.

[0040] This allows the carriers to be efficiently transported from the flow straightening area to the reaction area. In particular, the water level in the flow straightening area may rise due to the air lift effect of the aeration, and become higher than the water level in the reaction area, but even in such a case, the carriers can be efficiently transported to the reaction area.

[0041] In Fig. 1, the water level WL1 in the reaction area and the water level WL2 in the rectification area are drawn to be at the same height, but as mentioned above, the water level WL1 in the reaction area and the water level WL2 in the rectification area can change depending on the operating conditions. For example, when the raw water flow rate is high, the water level WL1 in the reaction area rises, and when the amount of aeration from the aeration member 9 is high, the water level WL2 in the rectification area rises. In addition, the water level WL2 in the rectification area also fluctuates depending on the water level in the downstream reaction tank.

[0042] Although not shown in the figure, an opening / closing member is provided at the opening 11. The opening / closing member is preferably one that can adjust the opening degree of the opening 11, and for example, one that is composed of a plate that can move up and down along the opening 11 and a guide rail that guides the up and down movement of the plate, etc., is used, but is not limited to this.

[0043] The rotor 4 is disposed near the vertical center of the drive shaft 3. The height H2 of the upper edge of the rotor 4 (height from the bottom surface of the tank body; the same applies below) is preferably about 20 to 80%, and more preferably about 50 to 70%, of the water depth H1 of the tank body 2. The vertical width H3 of the rotor 4 is preferably about 5 to 60%, and more preferably about 10 to 40%, of the water depth H1 of the tank body 2. The height H4 of the lower edge of the rotor 4 is preferably about 20 to 80%, and more preferably about 30 to 50%, of the water depth H1 of the tank body.

[0044] In this embodiment, the rotor 4 is provided in only one stage in the vertical direction, but it may be provided in two or more stages. When the rotors are provided in two or more stages, the height of the upper edge of the uppermost rotor should be in the range of H3+H4, the height of the lower edge of the lowermost rotor should be in the range of H4, and the sum of the vertical widths of the rotors should be in the range of H3.

[0045] The tank body 2 is filled with a carrier C. The carrier may be made of any material, but a granular polymer crosslinked gel that is resistant to wear is preferable.

[0046] Examples of the resin material for the gel carrier include polyolefin, PVA, PEG, (poly)acrylamide, N-substituted acrylamide, (poly / meth)acrylic acid or its alkali metal salt, alginic acid, polyalkylene oxide, dimethylaminoethyl (meth)acrylate (DAM), diacetone alcohol (DAA), polyalkylene oxide, etc. More specifically, examples include sodium polyacrylate, copolymers of sodium acrylate and acrylamide, copolymers of sodium acrylate and sodium acrylamido 2-methylpropanesulfonate, terpolymers of sodium acrylate, acrylamide, and sodium acrylamido 2-methylpropanesulfonate, and homopolymers or copolymers of tertiary salts or quaternary ammonium salts of dimethylaminoethyl (meth)acrylate with acrylamide, etc.

[0047] The average particle size of the carrier C is preferably 1 to 10 mm, and particularly preferably 3 to 5 mm. If it is smaller than this, it becomes difficult to separate the carrier C from the water, and if it is larger, it impedes flow. It is preferable that the carrier C settles when stirring is stopped, and the true specific gravity is 1.0 to 1.3 g / cm. 3 It is preferable that the density is 1.1 to 1.2 g / cm. 3 It is desirable that:

[0048] The amount of carrier packed is preferably an amount such that the bulk volume of the carrier is 5 to 50% of the volume of the reaction zone below the water level WL1 in the reaction zone. If the amount of carrier is less than this amount, the treatment efficiency will be low, and if it is more than 50%, the stirring power will be excessive.

[0049] In the fluidized bed biological treatment device 1 configured as above, raw water (organic matter-containing wastewater) is supplied into the tank body 2 from the raw water inlet 5 while the rotor 4 is rotated by the drive device M, and biological treatment is performed. In this embodiment, the organic matter in the raw water is anaerobic biologically treated by microorganisms supported on the carrier C. In this embodiment, the aeration member 9 is disposed in a location surrounded by the partition plate 8, so that the air bubbles diffused from the aeration member 9 rise along the screen 7 without being affected by the swirling flow caused by the rotor 4.

[0050] The rotation speed of the drive shaft 3 of the rotor 4 is preferably adjusted so that the G value is 100 to 200, and is preferably about 5 to 20 rpm.

[0051] A part of the water being stirred in the reaction region in the tank body 2 flows around the underside of the partition plate 8 and enters the space (flow straightening region) between the partition plate 8 and the screen 7. Then, the filtrate that permeates the screen 7 and flows into the filtrate chamber 6 overflows from the outlet 10 and is taken out as treated water.

[0052] Since deposits adhere to the front surface of the screen 7, air is diffused from the air diffusing member 9, and the air bubbles are caused to rise along the front surface of the screen 7, thereby removing the deposits from the front surface of the screen 7. Note that hereinafter, this operation may be referred to as cleaning of the screen 7.

[0053] In this embodiment, the straightening area is surrounded by the partition plate 8, so that the diffusion of air bubbles into the reaction area in the tank body 2 can be prevented, the screen 7 can be efficiently cleaned, and clogging of the screen 7 by the carrier C or a biofilm attached to the carrier C can be suppressed.

[0054] Methods for cleaning the screen 7 include regular cleaning, in which a specified flow rate of gas is continuously sprayed from the aeration member 9 to continuously clean the surface of the screen 7 while the fluidized bed biological treatment device 1 is in operation, and strong cleaning, which is performed when blockage of the screen 7 is suspected, when accumulated deposits need to be removed, or when carriers have accumulated between the screen 7 and the partition plate 8.

[0055] In steady cleaning, it is preferable to constantly spray a predetermined flow rate of gas from the aeration member 9 during operation of the fluidized bed biological treatment device 1, but spraying may be stopped intermittently.

[0056] Strong cleaning is preferably performed for a period of several to several tens of seconds (e.g., 5 to 70 seconds) by temporarily increasing the amount of aeration to at least twice that during normal cleaning, particularly about 3 to 5 times. During this strong cleaning, the amount of air bubbles in the water increases on the front side of the screen 7, so the fluid density as a mixed fluid of liquid and gas decreases, and the flow rate of filtrate passing through the screen 7 increases due to the same principle as an air lift pump. Therefore, during strong cleaning, it is preferable to open the opening 11 and transfer the water inside the partition plate 8 to the reaction area through the opening 11, so that the flow rate of filtrate does not become excessive.

[0057] The gas diffused from the diffuser 9 is preferably a gas with a low oxygen content in order to maintain the anaerobic condition inside the tank body 2, but there is no problem in using an oxygen-containing gas such as air. When using an oxygen-containing gas, it is desirable to operate the system so that the total weight of dissolved oxygen in the inflow raw water and the weight of dissolved oxygen on the water surface or due to diffusion does not exceed 10% of the total weight including the oxygen weight of the components to be treated contained in the inflow raw water. Under these conditions, even when oxygen-containing gas is diffused, the DO contained in the water transferred from the rectification region to the reaction region is quickly consumed by the microorganisms in the reaction region, so the anaerobic condition of the reaction region can be maintained.

[0058] It is also desirable to add organic matter, such as methanol and IPA (isopropanol), which are consumed by the microorganisms in the tank body 2 during respiration, in an amount appropriate for the treatment load, in addition to the amount added in excess.

[0059] Tank volume load is 0.3kgN / m 3 / d or more, e.g. 0.3-10kgN / m 3 / d is desirable. If the load is above a certain level, even if a small amount of oxygen gas is mixed into the reaction zone, the microorganisms in the reaction zone will immediately consume DO, and anaerobic conditions can be maintained. On the other hand, if the load is too high, the amount of suspended sludge will increase in addition to the sludge attached to the carrier, increasing the risk of clogging the screen with sludge.

[0060] According to the fluidized bed biological treatment device and the operating method thereof of this embodiment described above, the diffusion of air bubbles from the straightening area to the reaction area in the tank body 2 is prevented, the screen is efficiently washed, and clogging of the screen by the carriers or biofilms attached to the carriers is suppressed, thereby enabling stable biological treatment.

[0061] The above-described embodiment is merely an example of the present invention, and the present invention may be embodied in other forms than those described above.

[0062] For example, in the above embodiment, the outlet 10, the screen 7 and the partition plate 8 are disposed near the center in the width direction of the side wall surface 2b of the tank body 2, but they may be disposed at a corner portion of the tank body 2. [Explanation of symbols]

[0063] 1. Fluidized bed biological treatment equipment 2 tank body 3 Drive shaft 4 Rotor 5 Inlet 6 Filtered water chamber 7 Screen 8 compartment plate 8a Main plate 9. Air diffusion material 10 Outlet (overflow port) 11 Aperture

Claims

1. A tank body containing a fluid carrier; a screen provided in the tank body for separating the carrier and directing the treated water to an outlet; a partition plate that divides the inside of the tank into a flow straightening area in which the screen is disposed and a reaction area in which biological treatment is performed; an air diffusing member for causing air bubbles to flow along a surface of the screen on the side of the flow straightening area; an opening provided in the upper portion of the partition plate for transporting the carrier from the flow straightening region to the reaction region; A fluidized bed biological treatment device comprising:

2. The screen is provided facing a side wall surface of the tank body, A space between the screen and the side wall surface of the tank body forms a filtrate chamber, 2. A fluidized bed biological treatment apparatus according to claim 1, wherein said side wall of said tank body is provided with said outlet for overflowing filtrate so as to face said filtrate chamber.

3. The partition plate extends in a vertical direction along the screen, The lower end of the partition plate is located lower than the lower end of the screen, 3. A fluidized bed biological treatment apparatus according to claim 2, wherein the upper ends of said partition plates are positioned above the water level in said reaction region and the water level in said flow straightening region within said tank body.

4. The partition plate has a main plate facing the screen, The opening is provided in an upper portion of the main plate, 4. A fluidized bed biological treatment apparatus according to claim 3, wherein said air diffuser is disposed between said main plate and a downward extension of the front surface of said screen.

5. 5. A fluidized bed biological treatment apparatus according to claim 4, wherein said air diffusing member is disposed closer to said downward extension surface than the middle point between said main plate and said downward extension surface.

6. 2. A fluidized bed biological treatment device according to claim 1, wherein an opening and closing member is provided at said opening.

7. A method for operating a fluidized bed biological treatment device for treating raw water using any one of claims 1 to 6, a steady cleaning process in which a steady amount of air is diffused from the air diffuser; and a strong cleaning step in which the amount of air diffused from the air diffuser is made greater than that in the steady cleaning step.

8. The fluidized bed biological treatment device is the fluidized bed biological treatment device according to claim 6, In the steady cleaning step, the opening is closed, In the strong washing step, the opening is opened, and the carrier is returned from the flow straightening area to the reaction area through the opening. The method for operating a fluidized bed biological treatment apparatus according to claim 8.

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