Fluidized bed type biological treatment apparatus and its operation method

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 apparatus for treating wastewater, and particularly to a fluidized bed biological treatment apparatus provided with a screen for separating a carrier and treated water in a tank. The present invention also relates to an operation method of this fluidized bed biological treatment apparatus.

Background Art

[0002] For the purpose of increasing the load and improving the water quality of biological treatment apparatuses for wastewater, a fluidized bed biological treatment apparatus using a carrier to which microorganisms are highly attached is known. It is also known to use a screen as a means for solid-liquid separation of this carrier (Patent Documents 1 and 2).

[0003] Patent Document 2 describes that a screen is provided so as to be inclined facing the treated water outlet of the tank, and the screen is washed by diffusing air from below the screen by a diffusing means. Further, FIG. 3 of Patent Document 2 describes that a partition plate is provided parallel to the screen. By providing such a partition plate, bubbles from the diffusing means flow along the screen, and the washing effect of the screen is improved.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the case of a fluidized bed type biological treatment apparatus provided with a partition plate facing a screen as in Patent Document 2, in order to increase the treatment capacity of the apparatus, when the stirring speed is increased and the operation is performed so that the carrier is sufficiently diffused in the tank, the flow velocity and flow rate in the tank increase, and the bubbles diffused from the air diffusing means are carried 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 type biological treatment apparatus and an operation method thereof in which a screen is cleaned by bubbles from an air diffusing means, and to ensure that the screen is sufficiently cleaned.

Means for Solving the Problem

[0007] The fluidized bed type biological treatment apparatus of the present invention includes a tank that houses a fluid carrier, a screen provided in the tank for separating the carrier and guiding treated water to an outlet, a partition plate that divides the inside of the tank into a rectifying region where the screen is disposed and a reaction region where biological treatment is performed, an air diffusing member for flowing bubbles along the surface of the screen on the rectifying region side, and an opening provided in the upper part of the partition plate for transferring the carrier from the rectifying region to the reaction region.

[0008] In one aspect of the present invention, the screen is provided facing the side wall surface of the tank, and the space between the screen and the side wall surface of the tank forms a filtered water chamber, and the outlet for filtered water overflow is provided on the side wall surface of the tank so as to face 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 below the lower end of the screen, and the upper end of the partition plate is located above the water surface level of the reaction region and the water surface level of the rectifying region in the tank.

[0010] In one aspect of the present invention, the partition plate has a main plate facing the screen, the opening is provided at the upper part of the main plate, and the air diffusing member is disposed between the main plate and the 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 side than the middle between the main plate and the downward extension surface.

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

[0013] The operation method of the fluidized bed type biological treatment apparatus of the present invention is a method for operating such a fluidized bed type biological treatment apparatus of the present invention, and includes a steady cleaning step of diffusing air at a steady air volume from the air diffusing member, and a strong cleaning step of increasing the air diffusion amount from the air diffusing member compared to the steady cleaning step.

[0014] In one aspect of the operation method of the present invention, in the steady cleaning step, the opening is closed, in the strong cleaning step, the opening is opened, and the carrier is returned from the rectifying region to the reaction region through the opening.

Advantages of the Invention

[0015] According to the fluidized bed type biological treatment apparatus and its operation method of the present invention, it is possible to prevent the diffusion of bubbles into the tank body, efficiently clean the screen, suppress the clogging of the screen by the carrier and the biofilm attached to the carrier, and perform biological treatment stably.

[0016] In one aspect of the present invention, the partition plate has a main plate facing the screen, the opening is provided at the upper part of the main plate, and the air diffusing member is disposed between the main plate and the downward extension surface of the front surface of the screen. Thereby, the horizontal cross-sectional area of the rectifying region can be reduced, and the cleaning effect of the screen by the diffused air bubbles can be enhanced. Further, the carrier that has entered the rectifying region is likely to gather at the opening and be transferred to the reaction region.

[0017] In one aspect of the present invention, an opening and closing member is provided in the opening above the partition plate. In this aspect, when the water surface level in the reaction region or the rectification region changes according to the operating conditions, the opening and closing of the opening or the adjustment of the opening degree can be appropriately performed according to the situation.

[0018] In the operation method of the fluidized bed type biological treatment apparatus according to the present invention, steady cleaning is performed with a predetermined aeration amount during the biological treatment operation of the drainage, and intensive cleaning is performed by temporarily ejecting an aeration amount larger than that during the steady cleaning. During this intensive cleaning, the transfer of the carrier from the rectification region to the reaction region is promoted through the opening above the partition plate.

[0019] In one aspect 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 of the influent raw water and the dissolved oxygen weight due to the water surface and aeration does not exceed 10% of the total weight obtained by further adding the oxygen weight of the treatment target component contained in the influent raw water. Thereby, even when aeration is performed with an oxygen-containing gas, the DO contained in the water transferred from the rectification region to the reaction region is rapidly consumed, so that the anaerobicity of the reaction region can be maintained.

Brief Description of the Drawings

[0020]

Figure 1

Figure 2

Figure 3

Embodiments for Carrying Out the Invention

[0021] Hereinafter, a fluidized bed type biological treatment apparatus according to an embodiment and its operation method will be described with reference to FIGS. 1 to 3.

[0022] This fluidized bed biological treatment apparatus 1 includes a tank body 2, a drive shaft 3 disposed at the axial center position of the tank body 2, a rotating blade (agitating blade) 4 fixed to the drive shaft 3, and the like. 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. However, the drive shaft 3 may be suspended from above. The drive shaft 3 is rotationally driven by a drive device M.

[0023] In this embodiment, the tank body 2 is a square corner tank with 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 upper part of one wall surface 2a of the tank body 2, and an outlet 10 for treated water (overflow port) is provided at the upper part of the other wall surface 2b on the opposite side. The inlet 5 is arranged above the outlet 10. Instead of the inlet 5, a raw water inflow pipe may be provided. In this embodiment, the fluidized bed biological treatment apparatus 1 is an anaerobic biological treatment tank, and the upper 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 planar, the screen 7 is also in a flat plate shape. The screen 7 is preferably made of a bar screen, mesh, wedge wire, punching metal, or the like.

[0026] The spaces between both side edges of the flat plate-shaped screen 7 extending in the vertical direction and the wall surface 2b are closed by side plates 7a (FIG. 3), respectively. The space between the lower edge 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, preferably above the upper edge of the outlet 10 or higher.

[0028] Between the screen 7 and the wall surface 2b of the tank body 2, there is a filtered water chamber 6 surrounded by the screen 7, the side plate 7a, and the bottom plate 7b. The outlet 10 is arranged so as to face the inside of the filtered water chamber 6. The lower edge level of the outlet 10 is the water surface level WL2 of the rectifying region of the tank body 2.

[0029] In this embodiment, although the screen 7 extends in a substantially vertical direction, the screen 7 can also be extended in an inclined direction such 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. When the lower end of the screen 7 is arranged in contact with the wall surface 2b of the tank body 2, the bottom plate 7b can be omitted.

[0030] A partition plate 8 extends vertically 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 with respect to the partition plate 8) is the rectifying region, and the outer region of the partition plate 8 (the region on the rotating blade 4 side) is the reaction region.

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

[0032] It is desirable that the main plate 8a and the side plates 8b of the partition plate 8 extend in a substantially vertical direction, but there is no problem as long as it is within ±5° in 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. The space between the lower side of the partition plate 8 and the wall surface 2b is an open portion, and water containing the carrier C can flow from the reaction region to the rectifying region through this open portion.

[0035] In order to flow bubbles along the surface on the main plate 8a side of the screen 7 (hereinafter sometimes referred to as the front surface of the screen), a diffusing member 9 such as a diffuser pipe is installed. As the diffuser pipe, it is preferable that the diffuser pipe extends in a direction parallel to the width direction of the screen 7 and has a length not exceeding the width of the screen 7.

[0036] In this embodiment, the diffusing member 9 is disposed above the lower end of the partition plate 8 and below the lower end of the screen 7. The diffusing member 9 is preferably disposed closer to the lower extension surface side than the middle between the lower extension surface of the front surface of the screen 7 and the main plate 8a. Thereby, the bubbles diffused from the diffusing member 9 rise along the front surface of the screen 7, and the 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 instead of the vertical direction as described above, the diffusing member 9 is preferably disposed 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 the carrier from the rectifying region to the reaction region when the water level WL2 in the rectifying region inside the partition plate 8 is higher than the lower end of the opening 11.

[0038] The lateral width of the opening 11 is desirably 50% or more of the lateral width of the screen 7. Also, the lateral width of the opening 11 is desirably 150 cm or less. Thereby, the carrier staying near the water surface in the rectifying region can be efficiently returned to the reaction region through the opening 11.

[0039] The lower edge of the opening 11 is located below the lower end of the inflow port 5. The height difference between the lower edge of the opening 11 and the lower end of the inflow port 5 is desirably 40 cm or less, particularly preferably 10 to 30 cm. The upper edge of the opening 11 is located above the lower end of the inflow port 5. The height difference between the upper edge of the opening 11 and the lower end of the inflow port 5 is desirably 40 cm or less, particularly preferably 10 to 30 cm. The vertical width of the opening 11 is desirably about 20 to 60 cm.

[0040] As a result, the carrier can be efficiently transferred from the rectification region to the reaction region. In particular, due to the air-lift effect of aeration, the water level in the rectification region may rise and become higher than the water level in the reaction region. Even in such a case, the carrier can be efficiently transferred to the reaction region.

[0041] In addition, in FIG. 1, the water level WL1 in the reaction region and the water level WL2 in the rectification region are drawn to be at the same height. However, as described above, the water level WL1 in the reaction region and the water level WL2 in the rectification region may vary depending on the operating conditions. For example, when the raw water flow rate is high, the water level WL1 in the reaction region rises, and when the aeration amount of the aeration member 9 is large, the water level WL2 in the rectification region rises. In addition, the water level WL2 in the rectification region also fluctuates depending on the water level in the subsequent reaction tank.

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

[0043] The rotary blade 4 is arranged near the middle in the vertical direction of the drive shaft 3. The height of the upper edge of the rotary blade 4 (the height from the bottom surface of the tank body. The same applies hereinafter) H2 is preferably 20 to 80%, particularly about 50 to 70% of the water depth H1 of the tank body 2. The vertical width H3 of the rotary blade 4 is preferably 5 to 60%, particularly about 10 to 40% of the water depth H1 of the tank body 2. The height H4 of the lower edge of the rotary blade 4 is preferably 20 to 80%, particularly about 30 to 50% of the tank body water depth H1.

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

[0045] The tank body 2 is filled with a carrier C. The carrier can be made of any material, but preferably a granular gel of a polymer cross-linked body that is resistant to wear.

[0046] Examples of the resin of the gel carrier include polyolefin, PVA, PEG, (poly)acrylamide, N-substituted acrylamide, (meth)acrylic acid or its alkali metal salt, alginic acid, polyalkylene oxide, dimethylaminoethyl (meth)acrylate (DAM), diacetone alcohol (DAA), polyalkylene oxide, etc. More specifically, sodium polyacrylate, a copolymer of sodium acrylate and acrylamide, a copolymer of sodium acrylate, acrylamide and sodium 2-methylpropanesulfonate, a terpolymer of sodium acrylate, acrylamide and sodium 2-methylpropanesulfonate, and a tertiary salt or quaternary ammonium homopolymer of dimethylaminoethyl (meth)acrylate or a copolymer with acrylamide, etc. are exemplified.

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

[0048] The filling amount of the carrier is preferably such that the bulk volume of the carrier is 5 to 50% with respect to the volume of the reaction region below the water surface level WL1 of the reaction region. If the amount of the carrier is less than this, the treatment efficiency becomes low, and if it is more than 50%, the stirring power becomes excessive.

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

[0050] The rotational speed of the drive shaft 3 of the rotary blade 4 is preferably adjusted so that the G value is 100 to 200, and is preferably approximately 5 to 20 rpm.

[0051] A part of the water agitated in the reaction region in the tank body 2 circulates under the partition plate 8 and enters the space (rectifying region) between the partition plate 8 and the screen 7. Then, the filtered water that has passed through the screen 7 and flowed into the filtered water 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, by diffusing air from the air diffusing member 9 and raising the bubbles along the front surface of the screen 7, the deposits are removed from the front surface of the screen 7. Hereinafter, this operation may be referred to as the cleaning of the screen 7.

[0053] In this embodiment, since the rectifying region is surrounded by the partition plate 8, it is possible to prevent the diffusion of bubbles into the reaction region in the tank body 2, efficiently clean the screen 7, and suppress the clogging of the screen 7 by the carrier C and the biofilm adhering to the carrier C.

[0054] As the cleaning method of the screen 7, during the operation of the fluidized bed type biological treatment apparatus 1, there are a steady cleaning in which a gas of a predetermined flow rate is continuously ejected from the air diffusing member 9 to continuously clean the surface of the screen 7, and a strong cleaning performed when the screen 7 is suspected of being clogged, when removing the accumulated deposits, or when carriers are accumulated between the screen 7 and the partition plate 8.

[0055] In steady cleaning, it is preferable to constantly eject a predetermined flow rate of gas from the air diffusing member 9 during the operation of the fluidized bed type biological treatment apparatus 1, but the ejection may be intermittently stopped.

[0056] For intensive cleaning, it is desirable to temporarily increase the air diffusing amount to 2 times or more, particularly about 3 to 5 times that during steady cleaning, and perform it for a length of several seconds to several tens of seconds (for example, 5 to 70 seconds). During this intensive cleaning, since the amount of air bubbles in the water increases on the front side of the screen 7, the fluid density as a mixed fluid of liquid and gas decreases, and based on the same principle as an air lift pump, the flow rate of the filtered water passing through the screen 7 increases. Therefore, during intensive cleaning, it is preferable to open the opening 11 and transfer the water inside the partition plate 8 to the reaction region through the opening 11 so that the flow rate of the filtered water does not become excessive.

[0057] The gas diffused from the air diffusing member 9 is preferably a gas with a low oxygen content rate for maintaining the anaerobic state in 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 so that the total of the dissolved oxygen weight of the influent raw water and the dissolved oxygen weight due to the water surface and air diffusion does not exceed 10% of the total weight obtained by further adding the oxygen weight of the component to be treated contained in the influent raw water. Under this condition, even when diffusing with an oxygen-containing gas, 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 state of the reaction region can be maintained.

[0058] In addition, it is desirable to add an excess amount of organic substances such as methanol and IPA (isopropanol) consumed by the microorganisms in the tank body 2 during respiration in addition to the amount corresponding to the treatment load.

[0059] The tank volume load is 0.3 kgN / m 3 / d or more, for example, 0.3 to 10 kgN / m 3 / d is desirable. If the load is equal to or greater than a predetermined value, even if a certain amount of oxygen gas enters the reaction region, the microorganisms in the reaction region immediately consume the DO, so that anaerobic conditions can be maintained. On the other hand, if the load is too high, the amount of floating sludge increases too much in addition to the carrier-attached sludge, increasing the risk of screen clogging due to the sludge.

[0060] According to the fluidized bed type biological treatment apparatus and its operation method of the present embodiment described above, the diffusion of bubbles from the rectification region to the reaction region in the tank body 2 is prevented, the screen is efficiently washed, the clogging of the screen by the carrier and the biofilm attached to the carrier is suppressed, and biological treatment can be stably performed.

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

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

Explanation of reference numerals

[0063] 1 Fluidized bed type biological treatment apparatus 2 Tank body 3 Drive shaft 4 Rotating blade 5 Inlet 6 Filtered water chamber 7 Screen 8 Partition plate 8a Main plate 9 Diffuser member 10 Outlet (overflow port) 11 Opening

Claims

1. A tank containing a fluid carrier, a screen provided in the tank for separating the carrier and guiding the treated water to an outlet, a partition plate for partitioning the inside of the tank into a rectifying region where the screen is disposed and a reaction region for performing anaerobic biological treatment, a diffusing member for flowing bubbles along the surface of the screen on the rectifying region side, an opening provided at the upper part of the partition plate for transferring the carrier from the rectifying region to the reaction region, and having a fluidized bed type anaerobic biological treatment apparatus in which the diffusing member is located above the lower end of the partition plate.

2. The screen is provided facing the side wall surface of the tank, a filtered water chamber is formed between the screen and the side wall surface of the tank, The fluidized bed type anaerobic biological treatment apparatus according to claim 1, wherein the outlet for filtered water overflow is provided on the side wall surface of the tank so as to face the filtered water chamber.

3. The partition plate extends in the vertical direction along the screen, the lower end of the partition plate is located below the lower end of the screen, The fluidized bed type anaerobic biological treatment apparatus according to claim 2, wherein the upper end of the partition plate is located above the water surface level of the reaction region and the water surface level of the rectifying region in the tank.

4. The partition plate has a main plate facing the screen, the opening is provided at the upper part of the main plate, The fluidized bed type anaerobic biological treatment apparatus according to claim 3, wherein the diffusing member is disposed between the main plate and the downward extension surface in front of the screen.

5. The fluidized bed type anaerobic biological treatment apparatus according to claim 4, wherein the diffusing member is disposed closer to the downward extension surface side than the middle between the main plate and the downward extension surface.

6. The fluidized bed type anaerobic biological treatment apparatus according to claim 1, wherein an opening / closing member is provided at the opening.

7. An operation method of a fluidized bed type anaerobic biological treatment apparatus for treating raw water by the fluidized bed type anaerobic biological treatment apparatus according to any one of claims 1 to 6, a steady cleaning step of diffusing air at a steady air volume from the diffusing member, An operation method of a fluidized bed type anaerobic biological treatment apparatus having an intensive cleaning step of increasing the air diffusion amount from the diffusing member more than that in the steady cleaning step.

8. The fluidized bed type anaerobic biological treatment apparatus is the fluidized bed type anaerobic biological treatment apparatus according to claim 6, in the steady cleaning step, the opening is closed, In the intensive washing step, the opening is kept open, and the carrier is returned from the rectification region to the reaction region through the opening. The operation method of the fluidized bed anaerobic biological treatment apparatus according to claim 7.

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