JP4492268B2 - Biological treatment equipment - Google Patents

Description

  The present invention relates to a biological treatment apparatus for efficiently removing organic matter from wastewater containing high-concentration organic matter.

  Conventionally, as a method for removing organic matter from wastewater containing high-concentration organic matter by biological treatment, there is known a fluidized bed carrier biological treatment method in which a carrier on which microorganisms are attached flows in treated water and the microorganisms consume or absorb organic matter. It has been. This method can take a higher organic substance load per treatment tank volume than a general activated sludge method, and is excellent in treatment efficiency. As a specific technique of such a fluidized bed carrier biological treatment method, for example, Japanese Patent Laid-Open No. 9-308992 discloses that the effluent of a biological treatment tank holding a fluid carrier carrying microorganisms is solid-liquid separated in a sedimentation tank. A method for obtaining treated water is disclosed.

A membrane separation activated sludge method is also widely used in which water containing organic matter is mixed with activated sludge for biological treatment and then filtered using a separation membrane to separate the activated sludge from the treated water. As a method in which the separation activated sludge method is combined with a biofilm treatment tank in which a packed bed of a filter medium on which a biofilm has been formed, JP-A-6-47399 discloses that the effluent water from the biofilm treatment tank is submerged in a membrane membrane type. A method is disclosed in which membrane permeated water is extracted as treated water after being treated in a tempering treatment tank, and sludge in the treatment tank is returned to the preceding biofilm treatment tank.
JP-A-9-308892 JP-A-6-47399

  However, in the fluidized bed biological treatment method, organic substances with good degradability can be absorbed and decomposed at high speed by microorganisms, but the removal ability of organic substances with poor degradability is almost the same as general activated sludge treatment methods. When wastewater containing organic matter is treated to obtain treated water equivalent to a general activated sludge method, there is a disadvantage that the required capacity of the treatment tank becomes excessive. In addition, microorganisms grow and flow out as surplus sludge mixed with the treated water. However, since this surplus sludge is difficult to flock, there is a disadvantage that the use of a flocculant is indispensable to remove this sludge.

  On the other hand, the membrane-separated activated sludge method has a drawback that clogging is likely to occur in the separation membrane directly immersed in the activated sludge because it is necessary to keep the activated sludge at a high concentration when trying to treat a high concentration organic matter.

  The present invention solves the problems of the above-described conventional fluidized bed carrier biological treatment method and membrane separation activated sludge method, reduces wastewater containing high-concentration organic matter, reduces the required capacity of the treatment tank, and removes excess sludge. It is another object of the present invention to provide a biological treatment apparatus that does not require a flocculant and that can be efficiently treated by preventing clogging of the immersion membrane and obtaining high-quality treated water.

The biological treatment apparatus of the present invention includes a first aerobic biological treatment tank that holds a fluid carrier carrying microorganisms and that accepts organic waste water, and a microorganism that accepts effluent water from the first aerobic biological treatment tank. A second aerobic biological treatment tank holding the supported fluid carrier and suspended activated sludge, and the effluent water of the second aerobic biological treatment tank is received, and the effluent water is separated into supernatant water and precipitated sludge. A separation membrane immersion tank that receives the supernatant water of the precipitation tank, separates sludge entrained in the supernatant water, and discharges treated water, the separation membrane module immersed in the tank and the separation A separation membrane immersion tank provided with a diffuser provided below the membrane module, a first sludge return means for returning the sedimented sludge of the settling tank to the second aerobic biological treatment tank, and the separation membrane Return sludge from the immersion tank to the second aerobic biological treatment tank A second sludge return means for, a biological treatment device having a, said organic waste water is a BOD2000mg / L or more drainage, sludge concentration in the separation submerged membrane tank is at 1000~6000mg / L characterized in that there.

The biological treatment apparatus according to claim 2 is characterized in that, in claim 1, the tank load of the first aerobic biological treatment tank is 0.8 to 8.0 kg-BOD / m ³ · d.

  The biological treatment apparatus according to claim 3 is the biological treatment apparatus according to claim 1 or 2, wherein the effective capacity of the second aerobic biological treatment tank is 1 to 10 times the effective capacity of the first aerobic biological treatment tank. Features.

  A biological treatment apparatus according to a fourth aspect is characterized in that, in any one of the first to third aspects, the water area load of the settling tank is 5 to 30 m / d and the residence time is 1 to 18 hours. .

Biological treatment apparatus according to claim 5, in any one of claims 1 to 4, residence distillation time of the separation membrane immersion tank is characterized in that 1 to 18 hours.

  That is, in the present invention, in order to solve the above-mentioned problems, the first and second aerobic biological treatment tanks are provided and the fluidized bed carrier biological treatment is performed in two stages, and then the sludge is settled and extracted. By providing a settling tank that can be used, most of the excess sludge is removed by flocculation without using a flocculant, and the remaining surplus sludge is further separated in a subsequent separation membrane immersion tank. In this separation membrane immersion tank, a relatively low concentration of sludge after removing most of the excess sludge in the precipitation tank flows in advance, so there are few problems of clogging in membrane filtration. The remaining organic matter can be decomposed and removed, and sludge membrane filtration with an immersion membrane can be performed efficiently. The treated water obtained as the permeated water of the submerged membrane in the separation membrane soaking tank is a high quality treated water that has permeated through a microfiltration (MF) membrane or the like. Then, by returning the separated sludge in the settling tank and the separated sludge in the separation membrane soaking tank to the second aerobic biological treatment tank, in this second aerobic biological treatment tank, the degradability in the fluidized bed carrier biological treatment It is possible to improve the ability to remove bad organic substances and efficiently decompose and remove them.

  According to the biological treatment apparatus of the present invention, high-concentration organic wastewater can be efficiently treated by using a relatively small-capacity apparatus without requiring a flocculant and preventing clogging of the immersion film. As a result, high-quality treated water can be obtained.

  Hereinafter, embodiments of a biological treatment apparatus of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a system diagram showing an embodiment of a biological treatment apparatus of the present invention. In FIG. 1, reference numeral 1 denotes a first aerobic biological treatment tank, in which a fluid carrier carrying microorganisms is held, and is provided at a screen 1A provided at a treated water outflow part and at a lower part in the tank. A diffuser 1B is provided. Reference numeral 2 denotes a second aerobic biological treatment tank, in which a fluid carrier carrying microorganisms and suspended activated sludge are held, and is provided at a screen 2A provided at the treated water outflow part and at a lower part in the tank. A diffuser 2B. 3 is a settling tank. Reference numeral 4 denotes a separation membrane immersion tank, in which a separation membrane module 4A is immersed, and an air diffuser 4B is provided below the separation membrane module. 5 is a pump.

  The shape of the first and second aerobic biological treatment tanks 1 and 2 is not particularly limited, and may be any of a cylindrical shape, a rectangular parallelepiped shape, and a baffle plate for preventing stagnation inside. good.

  The carriers held in the first and second aerobic biological treatment tanks 1 and 2 are made of a material that immobilizes microorganisms and flows in water, and has a specific gravity equivalent to that of water and easily adheres to microorganisms. It is preferable that the structure is porous or has a large number of gaps, such as resin, and the size is in the range of 0.5 to 200 mm as the maximum distance when sandwiched between two diameters or two parallel plates. Is preferred. However, the carrier held in the tank may be uniform in shape, size, material, or the like, or different ones may be mixed. In addition, the amount of carrier retained in the first and second aerobic biological treatment tanks 1 and 2 is the volume when the carrier is randomly stacked on land with the same state as in the water in the tank. It is preferable to be 10 to 60% of the effective capacity of 1 and 2.

The screens 1A and 2A are for separating the carrier and the effluent water, as long as the openings are smaller than the size of the carrier and the effluent water can be separated from the flowing carrier. Although not particularly limited, for example, a stainless steel screen, a plastic mesh or the like can be used. Screen 1A, the surface area of the water portion of the 2A outflow water ^{1 m} 3 / d per 0.5 m ² or more, for example, to such a 1～1.5M ² is preferred from the viewpoint of water outflow efficiency. Further, in order to prevent clogging of the screens 1A and 2A by the carrier, a water flow in a direction parallel to the surfaces of the screens 1A and 2A is sufficiently applied by providing an air diffuser or the like below the screens 1A and 2A as necessary. Anyway.

  The air diffusers 1B and 2B provided at the lower part of the first and second aerobic biological treatment tanks 1 and 2 cause necessary and sufficient flow throughout the aerobic biological treatment tanks 1 and 2 and There is no particular limitation on the type and the number of installations as long as the dissolved oxygen can be distributed. For example, a diffuser, an aerator, a perforated diffuser tube, or the like can be used.

  The first and second aerobic biological treatment tanks 1 and 2 basically have the same specifications, but may have different configurations. However, since the sludge from the subsequent settling tank 3 and the separation membrane immersion tank 4 is returned only to the second aerobic biological treatment tank 2, the first aerobic biological treatment tank 1 and the second aerobic biological treatment are performed. Even if there is no supply of water from the first aerobic biological treatment tank 1 to the second aerobic biological treatment tank 2, the tank 2 refers to the first aerobic biological treatment tank 2 from the first aerobic biological treatment tank 2. It is preferable to be connected so that no backflow to the aerobic biological treatment tank 1 occurs.

Regarding the effective capacity (effective volume) of the first and second aerobic biological treatment tanks 1 and 2, the effective capacity of the first aerobic biological treatment tank 1 is the tank load when the inflowing organic matter is represented by BOD. It is preferable to design so that it may become 0.8-8.0kg-BOD / m < ³ > * d. If the tank load is larger than this range, sufficient organic matter removal cannot be performed, and if it is smaller than this range, the capacity of the apparatus is undesirably increased. In addition, the effective capacity of the second aerobic biological treatment tank 2 is preferably larger than the effective capacity of the first aerobic biological treatment tank 1, for example, the effective capacity of the first aerobic biological treatment tank 1 is 5 It is preferably ˜8 times. When the effective capacity of the second aerobic biological treatment tank 2 is smaller than this range, it is not possible to sufficiently remove the hardly decomposable organic matter.

  There is no restriction | limiting in particular in the shape of the sedimentation tank 3, Any, such as cylindrical shape and a rectangular parallelepiped shape, may be sufficient, and the baffle plate etc. for preventing a starch from being produced inside may be provided. In addition, a stirrer or the like for efficiently sinking excess sludge may be provided, but it has an introduction part and an outflow part so that the whole becomes an upward flow, and the amount of treated water (inflow water) is reduced. On the other hand, it is preferable that the area velocity (water area load) of the horizontal plane is 30 m / d or less, for example, 6 to 10 m / d, and the residence time is 2 hours or more, for example, 10 to 12 hours.

  There is no restriction | limiting in particular in the shape of the separation membrane immersion tank 4, Any, such as a cylindrical shape and a rectangular parallelepiped shape, may be provided, and the baffle plate etc. for preventing a stagnation inside may be provided. The effective volume of the separation membrane immersion tank 4 is such that the residence time is 2 hours or more, for example, 10 to 12 hours with respect to the amount of treated water (inflow water), and the separation membrane portion of the separation membrane module can be sufficiently immersed in water. More than that. In addition, the sludge concentration in the tank is about 20000 mg / L or less, for example, 3,000 to 5,000 mg / L, and is described later so that the separation membrane module can maintain a high membrane flux. It is preferable to adjust the amount of sludge drawn by the pump 5.

  The separation membrane of the separation membrane module 4A immersed in the separation membrane immersion tank 4 only needs to have a pore diameter equal to or smaller than that of the MF membrane, and the shape thereof may be hollow or planar, and the material is not particularly defined. The separation membrane module 4A is arranged so that the part related to solid-liquid separation is completely immersed in the water in the tank. This separation membrane module 4A performs aeration from the aeration device 4B provided below as needed, thereby vibrating the membrane surface to prevent microorganisms from sticking, and the cross-flow flow causes the membrane flux to flow. Improvements may be made. The membrane flux of the separation membrane module 4A is not particularly defined, but the sludge concentration in the separation membrane immersion tank 4 can be determined so that this is maximized, so it should be higher than the flux in the original membrane activated sludge method. Can do. For example, in the case of a hollow fiber MF membrane made of polyethylene, an apparatus to which the present invention is applied is used with a membrane flux of 0.25 m / d under the condition of a sludge concentration of 10000 mg / L by a normal membrane activated sludge method. Then, the treatment can be performed with a high membrane flux having a membrane flux of about 0.4 m / d under a sludge concentration of 5000 mg / L.

  The diffuser 4B provided below the separation membrane module 4A may be any device as long as it causes necessary and sufficient flow throughout the separation membrane immersion tank 4 and can distribute dissolved oxygen to microorganisms. There are no particular restrictions on the type or number of installations, but for example, a diffuser, an aerator, a perforated diffuser tube, or the like can be used. This aeration may be performed as an aeration for the membrane vibration of the separation membrane module 4A described above, or may be performed separately.

  The pump 5 returns the excess sludge settled in the settling tank 3 and a part of the sludge in the separation membrane immersion tank 4 to the second aerobic biological treatment tank 2 and keeps the sludge concentration in each tank constant. It is provided to extract sludge as much as possible. The sludge extraction from the sedimentation tank 3 and the separation membrane immersion tank 4 by the pump 5 may be performed continuously or intermittently. Alternatively, the sludge extraction from the settling tank 3 and the sludge extraction from the separation membrane immersion tank 4 may be performed alternately, and the sludge extraction from both tanks 3 and 4 may be performed simultaneously while mixing them. You may return to the aerobic biological treatment tank 2 of 2. In addition, in order to keep the sludge concentration in each tank at a suitable level, surplus that is expected to be generated from the results of manual analysis of sludge concentration in each tank, the detected value of the sludge concentration meter, or from experience or past performance. Depending on the amount of sludge, the discharge side of the pump 5 may be appropriately switched to the outside so that the extracted sludge is discharged out of the system. The pump 5 is not particularly limited as long as it can transfer activated sludge. The sludge extraction pump of the sedimentation tank 3 and the sludge extraction pump of the separation membrane immersion tank 4 may be provided separately, and a switching valve and a flow rate control valve may be provided in the sludge flow paths of both tanks.

  In such a biological treatment apparatus of the present invention, raw water (organic waste water) is sequentially introduced into the first aerobic biological treatment tank 1 and the second aerobic biological treatment tank 2, and is then supplied to the two-stage fluidized bed carrier organism. After the treatment, solid-liquid separation is performed in the sedimentation tank 3, and the separated sludge is returned to the second aerobic biological treatment tank 2 by the pump 5. A part of the separated sludge in the settling tank 3 may be discharged out of the system as necessary. The supernatant water of the sedimentation tank 3 is then introduced into the separation membrane immersion tank 4, subjected to aerobic biological treatment with microorganisms in the tank, and then filtered through the separation membrane module 4 </ b> A, and the membrane permeate is discharged out of the system as treated water. The The sludge in the separation membrane immersion tank 4 is returned to the second aerobic biological treatment tank 2 by the pump 5. This return sludge may also be partially discharged outside the system as necessary.

  According to the present invention, surplus sludge generated by fluidized bed carrier biological treatment by solid-liquid separation of the two-stage fluidized bed carrier biologically treated water that has passed through the first and second aerobic biological treatment tanks 1 and 2 in the sedimentation tank 3. Most of this can be flocculated and separated by sedimentation without using a flocculant. Then, a slight excess sludge contained in the supernatant water of the sedimentation tank 3 is separated by membrane filtration in the separation membrane immersion tank 4. Since relatively low concentration sludge after removing most of the excess sludge in the sedimentation tank 3 flows into the separation membrane immersion tank 4 in advance, there is little problem of clogging in membrane filtration. The organic matter remaining in 4 can be decomposed and removed, and sludge membrane filtration with an immersion membrane can be performed efficiently. The treated water obtained as the permeated water of the separation membrane module 4A of the separation membrane immersion tank 4 is a high quality treated water that has permeated through a microfiltration (MF) membrane or the like. Moreover, in the present invention, the separation sludge in the sedimentation tank 3 and the separation sludge in the separation membrane immersion tank 4 are returned to the second aerobic biological treatment tank 2, so that the degradability in the second aerobic biological treatment tank 2 is achieved. The ability to remove bad organic substances can be improved. For this reason, the effective capacity of the second aerobic biological treatment tank 2 may be relatively small, and as a result, the overall apparatus capacity can be reduced.

  Such a biological treatment apparatus of the present invention is effective for biological treatment of organic wastewater such as food wastewater and liquor production wastewater such as cooking waste, and particularly among such organic wastewater. It is effective for biological treatment of high-concentration organic wastewater whose organic matter concentration is 2,000 mg-BOD / L or more.

  Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples.

Example 1
The tofu production waste water having a BOD concentration of 2,000 mg / L was processed at a flow rate of 100 L / d by the biological treatment apparatus of the present invention shown in FIG. The specifications of each tank are as follows.
First aerobic biological treatment tank 1: Effective capacity = 15L
BOD load = 1.56 kg−BOD / m ³ · d (second
Combined with aerobic biological treatment tank)
Carrier type = square shape with particle size of 3-10 mm
Material: Polyurethane foam
Carrier holding amount = 50% of tank effective capacity
Second aerobic biological treatment tank 2: Effective capacity = 100 L
Carrier type = square shape with particle size of 3-10 mm
Material: Polyurethane foam
Carrier holding amount = 50% of tank effective capacity
Sedimentation tank 3: Effective capacity = 30L
Water area load = 6.7 m / d
Residence time = 7.2 hours Separation membrane immersion tank 4: Effective capacity = 30L
Residence time = 7.2 hours
Membrane type of separation membrane module = hollow fiber type polyethylene membrane

  The separated sludge in the settling tank 3 was returned to the second aerobic biological treatment tank 2 at a flow rate of 100 L / d, and the supernatant water 125 L / d was introduced into the separation membrane immersion tank 4. Moreover, in the separation membrane immersion tank 4, sludge in the tank was returned to the second aerobic biological treatment tank 2 at a flow rate of 25 L / d, and 100 L / d of membrane filtrate was taken out as treated water. The sludge concentration in the separation membrane immersion tank 4 was maintained at 4,000 to 6,000 mg / L.

  As a result, BOD concentration of 2 to 10 mg / L, high-quality treated water not containing SS can be stably obtained for 2 months with a high membrane flux of 0.4 m / d without causing clogging of the separation membrane module. It was.

Comparative Example 1
In Example 1, the treatment was performed in the same manner except that the settling tank was omitted and the outflow water of the second aerobic biological treatment tank 2 was directly introduced into the separation membrane immersion tank 4. As a result, the BOD concentration of the treated water obtained was 10 to 20 mg / L and SS was not included, and the water quality was relatively high, but the sludge concentration in the separation membrane immersion tank 4 was 25,000 mg / L for 3 days. Due to the clogging of the separation membrane module, the membrane flux decreased to 0.1 m / d or less, making it difficult to continue the operation.

Comparative Example 2
In Example 1, when it processed similarly except having omitted the separation membrane immersion tank, the BOD density | concentration of the obtained treated water was 100-500 mg / L, SS was 1,000-5,000 mg / L. It was not possible to obtain high quality treated water.

Comparative Example 3
In Example 1, the first aerobic biological treatment tank was omitted, the organic waste water was directly introduced into the second aerobic biological treatment tank, and the effective capacity of the second aerobic biological treatment tank was 115 L. When the treatment was performed in the same manner except that the BOD concentration of the obtained treated water was 5 to 30 mg / L, it was not possible to obtain treated water with high quality.

It is a systematic diagram which shows embodiment of the biological treatment apparatus of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 1st aerobic biological treatment tank 2 2nd aerobic biological treatment tank 3 Precipitation tank 4 Separation membrane immersion tank 4A Separation membrane module 4B Air diffuser

Claims (5)

A first aerobic biological treatment tank that holds a fluid carrier carrying microorganisms and that accepts organic waste water;
A second aerobic biological treatment tank that retains a fluid carrier carrying microorganisms and suspended activated sludge that receives the effluent of the first aerobic biological treatment tank;
A settling tank that receives the effluent of the second aerobic biological treatment tank and separates the effluent into supernatant water and precipitated sludge;
A separation membrane immersion tank that receives the supernatant water of the sedimentation tank, separates sludge entrained in the supernatant water, and discharges treated water, the separation membrane module immersed in the tank, and the lower part of the separation membrane module A separation membrane immersion tank comprising a diffuser provided in
First sludge return means for returning the settling sludge in the settling tank to the second aerobic biological treatment tank;
A second sludge return means for returning the sludge of the separation membrane immersion tank to the second aerobic biological treatment tank;
A biological treatment apparatus comprising :
The biological treatment apparatus , wherein the organic waste water is waste water having a BOD of 2000 mg / L or more, and a sludge concentration in the separation / immersion membrane tank is 1000 to 6000 mg / L. 2. The biological treatment apparatus according to claim 1, wherein a tank load of the first aerobic biological treatment tank is 0.8 to 8.0 kg-BOD / m ³ · d.   3. The biological treatment apparatus according to claim 1, wherein an effective capacity of the second aerobic biological treatment tank is 1 to 10 times an effective capacity of the first aerobic biological treatment tank.   4. The biological treatment apparatus according to claim 1, wherein the sedimentation tank has a water area load of 5 to 30 m / d and a residence time of 1 to 18 hours. In any one of claims 1 to 4, biological treatment and wherein the residence distillation time of the separation membrane dipping bath is 1 to 18 hours.

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