JP2006167550A - Biological treatment apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provided a biological treatment apparatus which efficiently treats waste water containing organic matter of high concentration and provides high-quality treated water while reducing the required volume of a treatment tank, dispensing with a flocculant for removing waste sludge and preventing the clogging of a immersed membrane by solving the conventional problems of a fluidized bed carrier biological treatment process and a membrane separation activated sludge process. <P>SOLUTION: Organic waste water is treated in an aerobic biological treatment tank 1 in which a microbe-deposited fluidizing carrier is held and then the water treated is separated into precipitated sludge and supernatant water in a first batch precipitation tank 2A and a second batch precipitation tank 2B. The supernatant water in the first and second precipitation tanks 2A, 2B is introduced into a separation membrane-immersed tank 3 where the sludge accompanied by the supernatant water is separated and the water permeated through a separation membrane module 3A is discharged as the treated water. The sludge precipitated in the first and second precipitation tanks 2A, 2B and the sludge separated in the separation membrane-immersed tank 3 are returned to the aerobic biological treatment tank 1. <P>COPYRIGHT: (C)2006,JPO&NCIPI

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 a high concentration of organic matter by biological treatment, there is known a fluidized bed carrier biological treatment method in which a carrier to which microorganisms are attached flows in treated water and the microorganisms consume or absorb the 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 method of such a fluidized bed carrier biological treatment method, for example, Japanese Patent Application 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.

Incidentally, JP 2002-34585 A discloses a method of filtering the treated water of a batch activated sludge treatment apparatus with a submerged membrane separator, but in the method of this JP 2002-34585 A, It is not assumed that the sludge separated and concentrated by the submerged membrane separator is returned to the batch biological treatment equipment. That is, if sludge is returned by this method, it will be returned to one of a plurality of batch-type biological treatment devices, and even if returned alternately, it is difficult to maintain a uniform sludge concentration. Variation occurs and the quality of treated water becomes unstable.
JP-A-9-308892 JP-A-6-47399 JP 2002-34585 A

  However, in the fluidized bed biological treatment method, microorganisms grow and flow out as surplus sludge mixed with the treated water, but this surplus sludge is difficult to flock, so the sedimentation rate is slow, and this is completely removed in the sedimentation tank. It is necessary to provide a large sedimentation tank or forcibly settle using a large amount of aggregating agent.

  On the other hand, the membrane-separated activated sludge method has the advantages of increasing the decomposition rate of organic matter and obtaining clean treated water by maintaining the activated sludge at a high concentration when treating high concentrations of organic matter. Since sludge has adhesiveness, the separation membrane directly immersed in the activated sludge is likely to be clogged, and the cleaning strength and frequency of the separation membrane must be increased.

  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 (Claim 1) accepts organic wastewater, receives an aerobic biological treatment tank holding a fluid carrier carrying microorganisms, and receives the effluent of the aerobic biological treatment tank in a batch manner, Two or more parallelly connected precipitation tanks that perform standing, discharge of the supernatant water and discharge of the precipitated sludge, and receive the supernatant water of the precipitation tank, separate the sludge entrained by the supernatant water, and treated water A separation membrane immersion tank comprising a separation membrane module immersed in the tank and an air diffuser provided below the separation membrane module, and a settling sludge in the precipitation tank. A first sludge returning means for returning to the aerobic biological treatment tank; and a second sludge returning means for returning the sludge from the separation membrane immersion tank to the aerobic biological treatment tank. .

A biological treatment apparatus according to a second aspect is the biological treatment apparatus according to the first aspect, wherein the aerobic biological treatment tank is composed of a first aerobic biological treatment tank and a second aerobic biological treatment tank. And the sludge in the separation membrane immersion tank are returned to the first aerobic biological treatment tank, and the tank load of the first aerobic biological treatment tank is 0.8 to 8.0 kg-BOD / m ³ · d. It is characterized by being.

  The biological treatment apparatus according to claim 3 is characterized in that, in claim 2, 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. To do.

  The biological treatment apparatus according to claim 4 is the biological treatment apparatus according to any one of claims 1 to 3, wherein the sludge concentration in the separation membrane immersion tank is 1,000 to 6,000 mg / L, and the residence time is 1 to 18 hours. It is characterized by being.

  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.

  That is, in the biological treatment apparatus of the present invention, first, fluidized bed carrier biological treatment is performed on high-concentration organic wastewater, and the treated water is received in batches, left to stand, discharged from the supernatant water, and discharged from the precipitated sludge. The two or more relatively small sedimentation tanks are efficiently removed, and a slight excess sludge that could not be removed in the sedimentation tank is further solid-liquid 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 a batch type precipitation tank flows in advance, so there are few problems of clogging in membrane filtration. It is possible to efficiently perform the decomposition and removal of the organic matter remaining in the inside and the sludge membrane filtration with the immersion membrane. 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.

  In the present invention, since a batch type sedimentation tank is provided as a sedimentation tank in particular, it is possible to keep the sludge concentration in the separation membrane immersion tank relatively low, reduce the contamination of the separation membrane immersion, and reduce the washing frequency. It is preferable at the point which can do.

  Then, by returning the sedimentation sludge of the batch type sedimentation tank and the separation sludge of the separation membrane immersion tank to the aerobic biological treatment tank, in this aerobic biological treatment tank, removal of poorly degradable organic substances in the fluidized bed carrier biological treatment It is possible to improve the capability and efficiently decompose and remove it.

  For this reason, according to the present invention, a relatively small water tank and a small separation membrane area, and the cleaning strength and frequency of the separation membrane are greatly reduced as compared with the prior art, and accordingly, the operation cost is reduced and a clean process is performed. It becomes possible to obtain water efficiently.

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

  1 and 2 are system diagrams showing an embodiment of the biological treatment apparatus of the present invention.

  In FIG. 1, reference numeral 1 denotes an aerobic biological treatment tank, in which a fluid carrier carrying microorganisms is held, a screen 1a provided at the treated water outflow part, and an air diffuser provided at the lower part in the tank 1b. 2A and 2B are precipitation tanks (first sedimentation tank 2A and second sedimentation tank 2B) that are connected in parallel and extract the excess sludge that has settled from the bottom and discharge the supernatant water from the top. Reference numeral 3 denotes a separation membrane immersion tank, in which a separation membrane module 3A is immersed, and a diffuser 3B is provided below the separation membrane module 3A. 4 is a pump.

  There is no restriction | limiting in particular in the shape of the aerobic biological treatment tank 1, Any of cylindrical shape, a rectangular parallelepiped shape, etc. may be sufficient, and the baffle board etc. for preventing a stagnation inside may be provided.

  The carrier held in the aerobic biological treatment tank 1 is made of a material that immobilizes microorganisms and flows in water, and has a specific gravity equivalent to water and easily adheres to microorganisms. The size of the structure is preferably in the range of 0.5 to 200 mm as the maximum distance when sandwiched between two parallel plates. However, the carrier held in the tank may be uniform in shape, size, material, or the like, or different ones may be mixed. Further, the amount of carrier retained in the aerobic biological treatment tank 1 is 10 to 60 of the effective capacity of the aerobic biological treatment tank 1 when the carrier is randomly stacked on land with the same state as in the water in the tank. % Is preferable.

The screen 1a is for separating the carrier and the effluent water, as long as the opening is smaller than the size of the carrier and the effluent water can be separated from the flowing carrier, and its shape and material are particularly limited. However, for example, a stainless steel screen or a plastic mesh can be used. The surface area of water portion of the screen 1a is effluent ^{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 by the carrier of the screen 1a, a water flow in a direction parallel to the surface of the screen 1a may be sufficiently applied by, for example, providing a diffuser tube or the like below the screen 1a.

  The air diffuser 1b provided in the lower part of the aerobic biological treatment tank 1 causes a necessary and sufficient flow throughout the inside of the aerobic biological treatment tank 1, 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.

The effective capacity (effective volume) of the aerobic biological treatment tank 1 may be designed so that the tank load is 0.8 to 8.0 kg-BOD / m ³ · d when the inflowing organic matter is represented by BOD. preferable. 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.

  The shape of the first and second settling tanks 2A and 2B is not particularly limited, and any shape such as a cylindrical shape or a rectangular parallelepiped may be used, and a baffle plate for preventing stagnation inside, and an inclination for efficiently settling excess sludge. There may be a plate or a stirring device, but it has an introduction part and an outflow part so that the whole becomes an upward flow, and the area velocity of the horizontal plane (water area load) with respect to the amount of treated water (inflow water) Is preferably 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.

  The shapes of the first and second settling tanks 2A and 2B may be different from each other, but it is preferable that sensors 2a and 2b that can detect the water surface height continuously or at three or more points are provided. . The first and second settling tanks 2A and 2B connected in parallel are batch-type raw water receiving, stationary, supernatant water discharge, sediment discharge, and the raw water between the two connected in parallel. The receiving process and the supernatant discharge process are performed by only one settling tank, and the batch pattern is determined so as not to overlap.

  In FIG. 1, two precipitation tanks are arranged in parallel, but three or more tanks may be arranged in parallel.

  In each of the first and second settling tanks 2 </ b> A and 2 </ b> B, the excess sludge separated and precipitated is returned to the aerobic biological treatment tank 1 by the pump 4.

  In the present invention, even if the BOD of the supernatant water in the first and second sedimentation tanks 2A and 2B is about 300 mg / L, no particular problem occurs in the subsequent process. Since it is necessary to increase the volume of the tank 1, the aerobic biological treatment tank 1 has a BOD of the supernatant water discharged from the first and second sedimentation tanks 2 </ b> A and 2 </ b> B in the range of the tank load described above from 150 to 150. The volume of the aerobic biological treatment tank 1 is preferably determined so as to be about 600 mg / L.

  There is no restriction | limiting in particular in the shape of the separation membrane immersion tank 3, 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 3 is 2 hours or more with respect to the amount of treated water (inflow water), for example, 5 to 10 hours, and the separation membrane portion of the separation membrane module 3A can be sufficiently immersed in water. Be larger than size. The sludge concentration (MLSS) in the tank is approximately 6000 mg / L or less, for example, 3,000 to 5,000 mg / L, so that the separation membrane module 3A can maintain a high membrane flux. Furthermore, it is preferable to adjust the amount of sludge withdrawn by the pump 4.

  The separation membrane of the separation membrane module 3A immersed in the separation membrane immersion tank 3 may 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 3A is arranged so that the part related to solid-liquid separation is completely immersed in the water in the tank. The separation membrane module 3A performs aeration from the aeration device 3B provided below as needed to vibrate 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 3A is not particularly defined, but since the sludge concentration in the separation membrane immersion tank 3 can be determined so that it becomes the maximum, 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, what is used at a membrane flux of 0.25 m / d under the condition of a sludge concentration of 10,000 mg / L by a normal membrane-type activated sludge method is shown in the following examples. Thus, in the apparatus to which the present invention is applied, the treatment can be performed with a high membrane flux of about 0.4 m / d on the condition of the sludge concentration of 4500 mg / L.

  The air diffuser 3B provided below the separation membrane module 3A may be any device as long as it causes necessary and sufficient flow throughout the separation membrane immersion tank 3 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 membrane vibration of the separation membrane module 3A described above, or may be performed separately.

  In the present invention, in order to keep the sludge concentration in the separation membrane immersion tank 3 low, a part of the liquid (concentrated sludge) in the separation membrane immersion tank 3 is returned to the aerobic biological treatment tank 1. In order to keep the operating pressure of the separation membrane module 3A constant, it is preferable that the water surface of the water surface is not changed as much as possible, and the return is performed while the discharged water from the first sedimentation tank 2A or the second sedimentation tank 2B flows in. It is preferable to carry out only in the above.

  Further, the separation membrane module 3A needs to be periodically washed with a chemical such as 0.1 wt% sodium hypochlorite in order to maintain the permeation flux. Since the sludge concentration is low, the frequency of chemical cleaning can be kept low even if the permeation flux is increased. For example, as shown in the examples described later, the conventional method is 10,000 mg / L, and the permeation flux of the membrane is 0.25 m. In the same manner as when operating at / d, according to the present invention, even when operating at a sludge concentration of 4500 mg / L and a membrane permeation flux of 0.4 m / d, the chemical cleaning frequency with 0.1% sodium hypochlorite is Both can be done every 3 months, and the permeation flux of the membrane can be maintained for a long time.

  The pump 4 returns a part of the excess sludge settled in the first and second settling tanks 2A and 2B and the concentrated sludge in the separation membrane immersion tank 3 to the aerobic biological treatment tank 1, and the sludge in each tank. Provided to pull out to keep the concentration constant. Sludge may be guided alternately from one of the precipitation tank 2A or the precipitation tank 2B and the separation membrane immersion tank 3, or may be guided while mixing from both tanks simultaneously. In addition, in order to keep the sludge concentration in each tank constant, the pump is determined based on the result of manual analysis of the sludge concentration in each tank, the detected value of the sludge concentration meter, or the amount of surplus sludge that is expected to occur from experience or past performance. The discharge side of No. 4 is appropriately switched to the outside, and the extracted sludge is discharged. The type of the pump is not particularly limited as long as it can send activated sludge.

  In such a biological treatment apparatus, raw water (organic waste water) is introduced into the aerobic biological treatment tank 1 and subjected to fluidized bed carrier biological treatment, and then separated into precipitates in the first precipitation tank 2A or the second precipitation tank 2B. Then, the precipitated sludge is returned to the aerobic biological treatment tank 1 together with the concentrated sludge in the separation membrane immersion tank 3 by the pump 4. A part of the sedimentation sludge in the first sedimentation tank 2A or the second sedimentation tank 2B may be discharged out of the system as necessary. The supernatant water of the first and second sedimentation tanks 2A and 2B is then introduced into the separation membrane immersion tank 3, and after aerobic biological treatment with the microorganisms in the tank, the membrane is filtered by the separation membrane module 3A. It is discharged out of the system as treated water. The sludge in the separation membrane immersion tank 3 is returned to the aerobic biological treatment tank 1 by the pump 4 together with the precipitated sludge in the first and second sedimentation tanks 2A and 2B. This return sludge may also be partially discharged outside the system as necessary.

  According to the biological treatment apparatus of FIG. 1, the fluidized bed carrier biological treatment water passed through the aerobic biological treatment tank 1 is separated by precipitation in the first precipitation tank 2A and the second precipitation tank 2B, thereby fluidized bed carrier biological treatment. Most of the excess sludge generated in the above can be separated without using a flocculant. Then, a slight excess sludge contained in the supernatant water of the first and second sedimentation tanks 2A and 2B is separated by membrane filtration in the separation membrane immersion tank 3. Since the relatively low concentration sludge after removing most of the excess sludge in the first and second settling tanks 2A and 2B flows into the separation membrane immersion tank 3 in advance, there is a problem of clogging in membrane filtration. However, the organic matter remaining in the separation membrane immersion tank 3 can be decomposed and removed, and sludge membrane filtration with the immersion membrane can be performed efficiently. The treated water obtained as the permeated water of the separation membrane module 3A of the separation membrane immersion tank 3 is a high-quality treated water that has permeated the MF membrane or the like. Moreover, in the present invention, the sedimentation sludge of the first and second sedimentation tanks 2A and 2B and the separation sludge of the separation membrane immersion tank 3 are returned to the aerobic biological treatment tank 1, thereby the aerobic biological treatment tank 1 The ability to remove organic substances with poor degradability can be improved. For this reason, the effective capacity of the aerobic biological treatment tank 1 is sufficient, and as a result, the overall apparatus capacity can be reduced.

  The biological treatment apparatus shown in FIG. 1 performs one-stage fluidized bed carrier biological treatment in a single aerobic biological treatment tank, but the biological treatment apparatus of the present invention has an aerobic biological treatment tank as shown in FIG. Two tanks may be provided, and the two-stage fluidized-bed carrier biological treatment may be performed by introducing the effluent from the first aerobic biological treatment tank 1A into the second aerobic biological treatment tank 1B.

  In FIG. 2, 1A is a first aerobic biological treatment tank, in which a fluid carrier carrying microorganisms is held, and is provided at a screen 1Aa provided at the treated water outflow part and at a lower part in the tank. A diffuser 1Ab is provided. 1B is a second aerobic biological treatment tank, in which a fluid carrier carrying microorganisms and suspended activated sludge are held, and is provided in a screen 1Ba provided in the treated water outflow part and in the lower part in the tank. A diffuser 1Bb. Other configurations are the same as those of the biological treatment apparatus shown in FIG. 1, and members having the same functions are denoted by the same reference numerals.

  The shape of the first and second aerobic biological treatment tanks 1A and 1B, the type and holding amount of the carrier held in the tank, the configuration of the screens 1Aa and 1Ba, and the configuration of the air diffusers 1Ab and 1Bb are shown in FIG. The same as the aerobic biological treatment tank 1.

  The first and second aerobic biological treatment tanks 1A and 1B basically have the same specifications, but different configurations may be adopted for both. Sludge from the first and second precipitation tanks 2A and 2B and the separation membrane immersion tank 3 in the subsequent stage is returned to the first aerobic biological treatment tank 1A.

Regarding the effective capacity (effective volume) of the first and second aerobic biological treatment tanks 1A and 1B, when the inflowing organic matter is represented by BOD, the tank load is 0.8 to 8.0 kg-BOD / m ^3. It is preferable to design so as to be 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. The effective capacity of the second aerobic biological treatment tank 1B is preferably larger than the effective capacity of the first aerobic biological treatment tank 1A, for example, 5 of the effective capacity of the first aerobic biological treatment tank 1A. It is preferably ˜8 times. If the effective capacity of the second aerobic biological treatment tank 1B is smaller than this range, it is not possible to sufficiently remove the hardly decomposable organic matter.

  In addition, the configurations and conditions of the first and second sedimentation tanks 2A and 2B, the separation membrane immersion tank 3, the pumps 5 and 6, and the like are the same as those of the biological treatment apparatus of FIG.

  In the biological treatment apparatus of FIG. 2 as well, raw water (organic wastewater) is sequentially introduced into the first aerobic biological treatment tank 1A and the second aerobic biological treatment tank 1B and subjected to biological treatment on the two-stage fluidized bed carrier. After that, precipitation is separated in the first precipitation tank 2A or the second precipitation tank 2B, and the precipitated sludge is returned to the second aerobic biological treatment tank 1B together with the concentrated sludge in the separation membrane immersion tank 3 by the pump 4. In addition, the sedimentation sludge of 1st, 2nd sedimentation tank 2A, 2B may be discharged | emitted out of the system as needed. The supernatant water of the first and second sedimentation tanks 2A and 2B is then introduced into the separation membrane immersion tank 3, and after aerobic biological treatment with the microorganisms in the tank, the membrane is filtered by the separation membrane module 3A. It is discharged out of the system as treated water. The sludge in the separation membrane immersion tank 3 is returned by the pump 4 to the first aerobic biological treatment tank 1A together with the precipitated sludge in the first and second precipitation tanks 2A and 2B. This return sludge may also be partially discharged outside the system as necessary.

  Even in the biological treatment apparatus of FIG. 2, the two-stage fluidized bed carrier biological treatment water that has passed through the first and second aerobic biological treatment tanks 1A and 1B is precipitated in the first precipitation tank 2A or the second precipitation tank 2B. By separating, most of the excess sludge generated by the fluidized bed carrier biological treatment can be separated without using a flocculant. Then, a slight excess sludge contained in the supernatant water of the first and second sedimentation tanks 2A and 2B is separated by membrane filtration in the separation membrane immersion tank 3. Since the relatively low concentration sludge after removing most of the excess sludge in the first and second settling tanks 2A and 2B flows into the separation membrane immersion tank 3 in advance, there is a problem of clogging in membrane filtration. However, the organic matter remaining in the separation membrane immersion tank 3 can be decomposed and removed, and sludge membrane filtration with the immersion membrane can be performed efficiently. The treated water obtained as the permeated water of the separation membrane module 3A of the separation membrane immersion tank 3 is a high-quality treated water that has permeated the MF membrane or the like. Moreover, the second aerobic biological treatment tank is obtained by returning the precipitated sludge of the first and second sedimentation tanks 2A and 2B and the separated sludge of the separation membrane immersion tank 3 to the first aerobic biological treatment tank 1A. The ability to remove organic substances with poor degradability in 1B can be improved. For this reason, the effective capacity of the second aerobic biological treatment tank 1B is sufficient, and as a result, the overall apparatus capacity can be reduced. And if it is this biological treatment apparatus, the treated water of much better water quality can be obtained by performing a two-stage fluidized bed carrier biological treatment.

  Therefore, according to the present invention, a biological treatment apparatus for removing organic matter from water containing a high concentration of organic matter does not require a large sedimentation tank or flocculant for separation of sludge and treated water. And the washing | cleaning intensity | strength and frequency of a separation membrane are reduced significantly, and reduction of an operating cost can be aimed at.

  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
With the biological treatment apparatus of the present invention shown in FIG. 1, the confectionery manufacturing waste water with a BOD concentration of 2,000 mg / L was treated at a flow rate of 100 L / d. The specifications of each tank are as follows.
Aerobic biological treatment tank 1: Effective capacity = 100L
BOD load = 2kg-BOD / m ³ · d
Carrier type = square shape with particle size of 3-10 mm
Material: Polyurethane foam
Carrier holding amount = 50% of tank effective capacity
First sedimentation tank 2A: Effective capacity = 15.7L
Treatment water retention time = 5 hours Second sedimentation tank 2B: Effective capacity = 15.7L
Treatment water retention time = 5 hours Separation membrane immersion tank 3: Effective capacity = 30 L
Residence time = 7.2 hours
Membrane type of separation membrane module = hollow fiber type polyethylene membrane

  The precipitated sludge in the first and second settling tanks 2A and 2B was returned to the aerobic biological treatment tank 1 at a total flow rate of 150 L / d, and 150 L / d of separated water was introduced into the separation membrane immersion tank 3. In the separation membrane immersion tank 3, sludge in the tank was returned to the aerobic biological treatment tank 1 at a flow rate of 50 L / d, and 100 L / d of membrane filtrate was taken out as treated water. The sludge concentration in the separation membrane immersion tank 3 was maintained at about 4500 mg / L.

  As a result, BOD concentration of 10 mg / L or less and high-quality treated water not containing SS could be stably obtained with a high membrane flux of 0.4 m / d without causing clogging of the separation membrane module.

  In the conventional membrane activated sludge method, the sludge concentration (MLSS) of the separation membrane immersion tank when the chemical cleaning frequency of the hollow fiber type separation membrane with a pore diameter of 0.4 μm is equal every three months, and the separation membrane module The relationship with the permeation flux is as shown in FIG. As is apparent from this figure, according to the biological treatment apparatus of the present invention, it is possible to set the sludge concentration in the separation membrane immersion tank to about 4500 mg / L, even though the organic wastewater with high concentration is treated. Therefore, the permeation flux of the separation membrane can be 0.4 m / d or more at the chemical cleaning frequency every three months. Therefore, it can be seen that the area of the separation membrane can be reduced by that amount compared to the conventional method, and the chemical cleaning frequency at that time can be equal to or less than that of the conventional method.

Comparative Example 1
In Example 1, the treatment was performed in the same manner except that the settling tank was omitted and the effluent from the aerobic biological treatment tank 1 was directly introduced into the separation membrane immersion tank 3. As a result, the BOD concentration of the obtained treated water 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 3 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, the treatment was performed in the same manner except that the separation membrane immersion tank was omitted and the amount of treated water in the precipitation tank was reduced by the amount returned from the separation membrane immersion tank to the aerobic biological treatment tank. As a result, the BOD concentration of the obtained treated water was 200 to 500 mg / L, and the SS was 1,000 to 5,000 mg / L, and it was not possible to obtain high quality treated water.

Example 2
In Example 1, as shown in FIG. 2, the following first and second aerobic biological treatment tanks 1A and 1B are provided as the aerobic biological treatment tanks, and the two-stage fluidized bed carrier biological treatment is performed. Processing was carried out in the same manner.
First aerobic biological treatment tank 1A: Effective capacity = 10L
BOD load = 3kg-BOD / m ³ · d (second
Together with aerobic biological treatment tanks)
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 1B: Effective capacity = 57L
Carrier type = square shape with particle size of 3-10 mm
Material: Polyurethane foam
Carrier holding amount = 50% of tank effective capacity

  As a result, as in Example 1, the sludge concentration in the separation membrane immersion tank 3 is maintained at about 4500 mg / L, and stable operation with a high membrane flux of 0.4 m / d without causing clogging of the separation membrane module. It was possible to obtain a very high quality treated water containing no SS and having a BOD concentration of 10 mg / L or less.

It is a systematic diagram which shows embodiment of the biological treatment apparatus of this invention. It is a systematic diagram which shows other embodiment of the biological treatment apparatus of this invention. In the membrane activated sludge method, the sludge concentration (MLSS) of the separation membrane immersion tank and the permeation flux of the separation membrane module when the chemical cleaning frequency of the hollow fiber type separation membrane with a pore diameter of 0.4 μm is equal every three months, It is a graph which shows the relationship.

Explanation of symbols

1 aerobic biological treatment tank 1A first aerobic biological treatment tank 1B second aerobic biological treatment tank 2 flotation separation tank 2A first precipitation tank 2B second precipitation tank 3 separation membrane immersion tank 3A separation membrane module 3B Air diffuser

Claims (4)

An aerobic biological treatment tank holding a fluid carrier carrying microorganisms and receiving organic waste water;
Two or more parallel-connected precipitation tanks that receive the effluent of the aerobic biological treatment tank in a batch manner, and are allowed to stand, discharge the supernatant water, and discharge the 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, wherein the separation membrane module is immersed in the tank and below the separation membrane module A separation membrane immersion tank comprising a diffuser provided in
First sludge return means for returning the settling sludge of the settling tank to the aerobic biological treatment tank;
A second sludge return means for returning the sludge of the separation membrane immersion tank to the aerobic biological treatment tank;
A biological treatment apparatus comprising: In Claim 1, the said aerobic biological treatment tank is comprised by the tank of a 1st aerobic biological treatment tank and the tank of a 2nd aerobic biological treatment tank, The sludge of the said sedimentation tank and the sludge of the said separation membrane immersion tank are The biological treatment is returned to the first aerobic biological treatment tank, and the tank load of the first aerobic biological treatment tank is 0.8 to 8.0 kg-BOD / m ³ · d. apparatus.   3. The biological treatment apparatus according to claim 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.   The biological treatment apparatus according to any one of claims 1 to 3, wherein the sludge concentration in the separation membrane immersion tank is 1,000 to 6,000 mg / L and the residence time is 1 to 18 hours. .

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