JP5786998B1 - Biological treatment method and apparatus for organic wastewater - Google Patents

Abstract

[PROBLEMS] To stably maintain sludge and micro-animals in biological treatment of organic wastewater to which the activated sludge method is applied, and to greatly reduce the amount of generated sludge and to perform high-load operation. A biological treatment method and apparatus for organic wastewater by an activated sludge method capable of improving the treatment efficiency by the method and stabilizing the treated water quality. A circulation path 27 and an upward flow path 24 are provided in a second biological treatment tank 2 by a partition plate 26 and a partition plate 23. The biologically treated water in the biological treatment chamber 29 is circulated upward in the circulation channel 27 at a higher LV than the upward flow channel 24. The upward flow channel 24 is raised at 0.5 to 5 m / h, and the treated water separated into solid and liquid is taken out from the tank 2. [Selection] Figure 1

Description

  The present invention relates to a biological treatment method and apparatus for organic wastewater that can be widely used for the treatment of organic wastewater such as domestic wastewater, sewage, food factories, pulp factories, semiconductor production wastewater, and liquid crystal production wastewater.

The activated sludge method used when biologically treating organic wastewater is widely used for sewage treatment, industrial wastewater treatment, and the like because of its advantages such as good treated water quality and easy maintenance. However, since the BOD volumetric load in the activated sludge method is generally about 0.5 to 0.8 kg / m ³ / d, a large site area is required. Moreover, since 20 to 40% of the decomposed BOD is converted into microbial cells, that is, sludge, a large amount of excess sludge treatment is also a problem. The activated sludge method includes a membrane activated sludge method that uses a membrane separator for solid-liquid separation of sludge and treated water, and a sedimentation basin type activated sludge method that uses a sedimentation basin. The membrane activated sludge method has the disadvantage that it costs membrane installation, replacement and maintenance. The sedimentation basin type activated sludge method has a disadvantage that the installation area becomes large.

For high load treatment of organic waste water, a fluidized bed method with a carrier added is known. When this method is used, it is possible to operate with a BOD volume load of ³ kg / m ³ / d or more. However, this method has a disadvantage that the amount of generated sludge is about 30 to 50% of the decomposed BOD and is higher than that of the normal activated sludge method.

  In Patent Document 1, organic wastewater is first treated with bacteria in a first treatment tank, and organic matter contained in the wastewater is oxidatively decomposed and converted into non-aggregating bacterial cells, and then in a second treatment tank. It is described that excess sludge can be reduced by predatory removal of the sticking protozoa. Further, this method enables high-load operation and improves the processing efficiency of the activated sludge method.

  In this way, many wastewater treatment methods have been devised that use the predation of protozoa and metazoans located at high levels of bacteria. For example, Patent Document 2 describes a countermeasure against deterioration in processing performance due to fluctuations in the quality of raw water, which is a problem in the processing method of Patent Document 1. As specific methods, “adjust BOD fluctuation of treated water to within 50% from median average concentration”, “measure water quality in first treatment tank and first treated water over time”, The method includes “adding a microbial preparation or seed sludge to the first treatment tank when the quality of the first treated water deteriorates”.

  In Patent Document 3, flocs that are preyed by ultrasonic treatment or mechanical agitation when protozoa or metazoans prey on bacteria, yeast, actinomycetes, algae, molds, wastewater treatment primary sludge or surplus sludge. A method to make the flock size smaller than the animal's mouth is proposed.

  There exists a thing of patent document 4 as a biological treatment method of the organic waste_water | drain by the multistage process of a fluidized bed and an activated sludge process. In this method, the latter activated sludge method is operated at a low load of BOD sludge load 0.1 kg-BOD / kg-MLSS / d, so that the sludge can be self-oxidized and the amount of sludge extraction can be greatly reduced.

  In Patent Document 5, a partition is provided on the drainage outlet side of the biological treatment tank by the activated sludge method to form an upward flow channel, and the biologically treated water is flowed upward at LV1 to 20 m / h in the channel. In addition, an organic wastewater biological treatment tank is described in which the sludge settled in the flow path is returned to the biological treatment tank, and the supernatant water rising in the flow path is discharged to the outside of the tank.

Japanese Patent Laid-Open No. 55-20649 JP 2000-210692 A Japanese Patent Laid-Open No. 55-20649 Japanese Patent No. 3410699 WO2013 / 103124A1

  Methods for maintaining sludge in the biological treatment tank include sludge return by sedimentation basin and treated water separation by membrane. The sludge return by the sedimentation basin type has the disadvantage that the installation area becomes large. In addition, the return of sludge by membranes has the disadvantage of requiring membrane installation costs, replacement and maintenance costs. In addition, the activated sludge method using the predatory action of the above-mentioned micro animals is actually used for organic wastewater treatment, and depending on the target wastewater, the treatment efficiency can be improved and the amount of generated sludge can be reduced. . However, the sludge reduction effect is not stable at present.

  By adding a fluidized bed carrier to a biological treatment tank by the activated sludge method, it is possible to stably maintain sludge and micro-animals, but problems such as the need for a separation screen and a decrease in oxygen dissolution efficiency by the carrier There is.

  According to the biological treatment tank of Patent Document 5, an upward flow channel is provided on the drain outlet side, and upward circulation water is supplied at LV1 to 20 m / h, so that sludge and minute animals are stably maintained in the biological treatment tank. It becomes possible to do.

  However, when air bubbles are mixed in the upstream flow channel, the sludge separation efficiency in the upstream flow channel is lowered, and there is a risk that the sludge flows out or the sludge concentration in the biological treatment tank is decreased. .

  The present invention solves the above-mentioned conventional problems, can stably maintain sludge and minute animals in biological treatment of organic wastewater to which the activated sludge method is applied, and greatly reduces the amount of generated sludge. It is another object of the present invention to provide a biological treatment method and apparatus for organic wastewater by an activated sludge method that can improve treatment efficiency by high-load operation and stabilize treated water quality.

The biological treatment method for organic wastewater according to the first invention is a biological treatment method for organic wastewater in which organic wastewater is biologically treated in a biological treatment tank, and sludge in biologically treated water is separated into solid and liquid in the biological treatment tank. In order to do this, a partition plate is provided on the drain outlet side of the biological treatment tank to partition the inside of the biological treatment tank into a biological treatment chamber and an upward flow channel on the drain outlet side, and the biological treatment from the biological treatment chamber In the biological treatment method, water is circulated upward in the upward flow channel at LV 0.5 to 5 m / h, and the supernatant water is discharged out of the tank from the drain outlet at the top of the upward flow channel. By providing a partition plate in the biological treatment chamber along the plate, a circulation channel is formed between the partition plate and the partition plate so that both the upper and lower portions communicate with the biological treatment chamber. than LV at a part of the biologically treated water the upflow passage to the circulation passage between the partition plate and the partition plate And characterized in that the upward flow of water at the hearing LV.

The biological treatment method for organic wastewater of the second invention is a method for biological treatment of organic wastewater in a biological treatment tank provided in multiple stages, in the first stage biological treatment tank, by decomposition of organic matter by dispersal bacteria. A biological treatment method for organic wastewater that produces first biological treated water with increased dispersal bacteria and produces final biological treated water in the last biological treatment tank, wherein sludge in the final biological treated water is In order to perform solid-liquid separation in the biological treatment tank, a partition plate is provided on the drainage outlet side of the biological treatment tank, and the inside of the biological treatment tank is divided into a biological treatment chamber and an upward flow channel on the drainage outlet side, Biologically treated water from the biological treatment chamber is circulated upward into the upward flow channel at LV 0.5 to 5 m / h, and the supernatant water is discharged from the drain outlet at the top of the upward flow channel. In the biological treatment method, a partition plate is provided in the biological treatment chamber along the partition plate. More, between the partition switching plate and partition plate, both the upper and lower forming the circulation flow path communicating with the organism processing chamber, said partition plate and partition plate part of the biologically treated water of the biological treatment chamber Upstream water is circulated in a circulation channel between the LV and the LV larger than the LV in the upward flow channel.

An organic wastewater biological treatment apparatus according to a third aspect of the present invention is an organic wastewater biological treatment apparatus for biologically treating organic wastewater in a biological treatment tank, and sludge in biologically treated water is solid-liquid separated in the biological treatment tank. In order to do this, a partition plate is provided on the drain outlet side of the biological treatment tank to partition the inside of the biological treatment tank into a biological treatment chamber and an upward flow channel on the drain outlet side, and the biological treatment from the biological treatment chamber In a biological treatment apparatus for flowing water upward into the upward flow channel and discharging supernatant water from the drain outlet at the top of the upward flow channel to the outside of the tank, the biological treatment chamber along the partition plate By providing a partition plate, a circulation channel in which the upper part and the lower part both communicate with the biological treatment chamber is formed between the partition plate and the partition plate, and a part of the biological treatment water in the biological treatment chamber is upward flow at greater LV than LV in the upward flow passage to the circulation flow path between said partition plate and partition plate Characterized in that a water passage means.

A biological treatment apparatus for organic wastewater according to a fourth aspect of the present invention is an apparatus for biologically treating organic wastewater in a biological treatment tank provided in multiple stages. In the biological treatment tank of the first stage, the organic wastewater is decomposed by dispersal bacteria. A biological treatment apparatus for organic wastewater that generates first biological treated water with increased dispersal bacteria and produces final biological treated water in the last biological treatment tank, wherein sludge in the final biological treated water is removed from the final biological treated water. In order to perform solid-liquid separation in the biological treatment tank, a partition plate is provided on the drainage outlet side of the biological treatment tank, and the inside of the biological treatment tank is divided into a biological treatment chamber and an upward flow channel on the drainage outlet side, In the biological treatment apparatus, the biological treatment water from the biological treatment chamber flows upward into the upward flow channel, and the supernatant water is discharged out of the tank from the drain outlet at the top of the upward flow channel. by providing the partition plate on the organism processing chamber along the plate, partition and the partition switching plate Between, both the upper and lower forming the circulation flow path communicating with the organism processing chamber, a part of the biologically treated water of the biological treatment chamber to the circulation flow path between the partition plate and the partition plate It is characterized in that a water flow means is provided for flowing upward water at an LV larger than the LV in the upward flow channel.

  1st-4th invention WHEREIN: It is preferable that LV of the upward flow in the said circulation flow path shall be 1.5 to 200 times the LV of the said upward flow flow path.

  In the present invention, an upward flow channel is provided in the biological treatment tank, and biological treatment water is flowed upward in the upward flow channel at a high LV (0.5 to 5 m / h). Good sludge is settled and separated in the upward flow channel. As a result, it is possible to selectively hold sludge with good sedimentation in the tank and discharge only sludge with poor sedimentation. For this reason, it becomes possible to keep the sludge density | concentration in a biological treatment apparatus high. Since the sludge concentration in the treated water is low, a solid-liquid separation device for separating sludge can be omitted in some cases. Even if a solid-liquid separation device is provided, it may be smaller and less expensive than the conventional one. It becomes possible.

  If sludge accumulates in the upward flow channel or bubbles due to aeration in the biological treatment tank are mixed into the upward flow channel, there is a risk of causing solid-liquid separation failure of sludge and deterioration of treated water quality. Therefore, in the present invention, a circulation channel is provided by a partition plate before the outlet-side upward flow channel, and the biological treatment liquid in the tank is supplied to the circulation channel from the LV of the outlet-side upward flow channel. Also, the water flows in the upward flow of high LV. Thereby, the outflow of the bubble to the exit side and the outflow of the sludge accompanying it can be prevented.

  In one aspect of the present invention, the raw water is repeatedly passed through and stopped, and a water stoppage period of 1/20 to 1/4 of the water passing time is set, thereby collecting the raw water in the outlet-side upward flow channel. The sludge can be returned to the biological treatment section in the tank, making the treatment more stable.

  Moreover, the sedimentation property is excessively improved, and the sludge that has settled in the lower part of the upward flow channel may be periodically extracted. Moreover, you may return the sludge pulled out in this way to the upstream in the said biological treatment tank.

  In one embodiment of the present invention, biological treatment tanks are provided in multiple stages, the biological treatment tank in the previous stage is a dispersion bacteria tank that converts organic matter into dispersal bacteria, and the last biological treatment tank has an adhesive property that prey on the dispersal bacteria. An oscillating carrier is provided as a scaffold for filtered predatory microanimals. In this treatment, not only the rocking carrier but also sludge with good sedimentation can be used as a scaffold for micro animals, and the microorganism concentration can be kept high.

  By making the rocking floor carrier into a sheet-like foamed plastic, sludge with better sedimentation can be generated and held in the tank.

  Moreover, you may improve the sedimentation property of sludge by adding a flocculant.

It is a block diagram which shows embodiment of the biological treatment method and apparatus of the organic waste water of this invention. It is a block diagram which shows embodiment of the biological treatment method and apparatus of the organic waste water of this invention. It is a block diagram which shows embodiment of the biological treatment method and apparatus of the organic waste water of this invention. It is a block diagram which shows embodiment of the biological treatment method and apparatus of the organic waste water of this invention.

  Embodiments of the organic wastewater biological treatment method and apparatus according to the present invention will be described below in detail with reference to the drawings. 1-3 is a systematic diagram showing an embodiment of a biological treatment method and apparatus for organic wastewater of the present invention.

  1-3, 1 is a 1st biological treatment tank, 2 is a 2nd biological treatment tank, 11 and 21 are aeration pipes, 12 is a fluidized bed carrier, 16 is a screen for carrier separation, 22 is a rocking bed carrier. . 1 to 3, reference numeral 23 denotes a partition plate provided in the second biological treatment tank 2, and 24 denotes an ascending flow path. In the ascending flow path 24, sludge is solid-liquid separated. In the second biological treatment tank 2, a partition plate 26 is installed in the biological treatment chamber along the partition plate 23, and a circulation channel 27 is formed between the partition plate 26 and the partition plate 23. The circulation channel 27 is provided with means for forming an upward flow (in this embodiment, an air diffuser nozzle 28). 1-3, the same code | symbol is attached | subjected to the member which show | plays the same function.

In the embodiment of FIG. 1, is introduced BOD volume load 1kg ^{/ m} 3 ^/ d or more for example 1~20kg ^{/ m} 3 ^/ d of raw water (organic wastewater) is first biological treatment tank 1, and aerated with aeration tube 11, Dispersible bacteria (non-aggregating bacteria) oxidatively decompose 70% or more, desirably 80% or more, more desirably 85% or more of the organic component (soluble BOD). The pH of the first biological treatment tank 1 is preferably 6 to 8.5. However, when the raw water such as food manufacturing wastewater contains a lot of oil, or when the raw water such as semiconductor manufacturing wastewater or liquid crystal manufacturing wastewater contains a lot of organic solvent or cleaning agent, the pH is 8 It is good also as ~ 9.

The water flow to the 1st biological treatment tank 1 shall be a transient type. The BOD volumetric load of the first biological treatment tank 1 is 1 kg / m ³ / d or more, for example 1 to 20 kg / m ³ / d, HRT (raw water residence time) is 24 h or less, preferably 8 h or less, for example 0.5 to 8 h By doing so, it is possible to obtain treated water predominated by dispersible bacteria, and by shortening the HRT, wastewater having a low BOD concentration can be treated with a high load.

Returning part of the sludge from the subsequent biological treatment tank to the first biological treatment tank 1, making the first biological treatment tank 1 a multistage configuration of two or more tanks, or adding a carrier 12. Thus, high load processing with a BOD volumetric load of 5 kg / m ³ / d or more is also possible.

  The shape of the fluidized bed carrier 12 is arbitrary such as a spherical shape, a pellet shape, a hollow cylindrical shape, a thread shape, and a plate shape, and the size (diameter) is about 0.1 to 10 mm. The material of the carrier 12 is arbitrary, such as a natural material, an inorganic material, or a polymer material, and a gel material may be used. The carrier is not limited to a fluidized bed carrier, and may be a fixed bed carrier or a rocking carrier. When a fixed bed carrier or a rocking carrier is used, the separation screen 16 is not necessary.

  When the filling rate of the carrier added to the first biological treatment tank 1 is high, dispersal bacteria are not generated, and bacteria adhere to the carrier or filamentous bacteria grow. Therefore, the filling rate of the carrier added to the first biological treatment tank 1 is 10% or less, for example 1 to 10% in the case of a fluidized bed carrier, and 5% or less in the case of a fixed bed carrier or a rocking carrier, for example, By setting the content to 0.5 to 5%, it is possible to produce dispersal bacteria that are not affected by concentration fluctuation and are easy to eat.

  The dissolved oxygen (DO) concentration in the first biological treatment tank 1 may be 1 mg / L or less, preferably 0.5 mg / L or less to suppress the growth of filamentous bacteria.

  Treated water from the first biological treatment tank 1 (first biological treated water) is introduced into the second biological treatment tank 2 at the subsequent stage, aerated, and oxidative decomposition of remaining organic components, self-degradation of dispersible bacteria and Reduce excess sludge through predation of micro-animals.

  In the final biological treatment tank (second biological treatment tank 2 in this embodiment), a partition plate 23 is provided so as to surround the outlet portion, and a partition plate 26 is provided along the partition plate 23, The inside of the biological treatment tank 2 is partitioned into a biological treatment chamber 29, a circulation channel 27, and an upward flow channel 24. The upper end of the partition plate 23 protrudes from the water surface of the second biological treatment tank 2. The lower end of the partition plate 23 is located 2 m or more, particularly 3 to 4 m below the water surface of the second biological treatment tank 2. A rising flow path 24 is formed between the partition plate 23 and the tank wall. The sludge settles while the sludge mixed water in the second biological treatment tank 2 rises in this ascending flow path. In the present invention, the LV of the upward flow in the upward flow path 24 is 0.5 to 5 m / h, preferably 1 to 2.5 m / h, and more preferably 1.5 to 2.5 m / h. The second biological treatment tank 2 is provided with an excess sludge extraction pipe 25.

  The connecting position of the excess sludge take-out pipe 25 is not particularly limited, but it is installed so as to be connected below the upward flow passage 24 or the circulation flow passage 27 so as to draw out the excessively settled sludge. May be.

  A part of the treated water in the second biological treatment tank 2 is circulated above the upstream flow passage 24 or upstream from the treated water pipe to prevent LV fluctuation at the time of fluctuation of the raw water flow rate. May be.

  A circulation channel 27 is formed between the partition plate 23 and the partition plate 26. The upper end of the partition plate 26 is lower than the water surface of the second biological treatment tank 2, and the lower end is higher than the bottom surface of the second biological treatment tank 2. Thereby, the upper part and the lower part of the circulation channel 27 communicate with the biological treatment chamber 29. A diffuser nozzle 28 is provided in the circulation flow path 27.

  By diffusing from the diffusing nozzle 28, an upward flow of LV 1.5 to 200 times, preferably 2 to 150 times LV of the upward flow passage 24 is formed in the circulation flow passage 27, and the outlet Outflow of bubbles to the side, that is, the upward flow passage 24 and sludge outflow associated therewith are prevented. As a method for generating an upward flow in the circulation flow path 27, mechanical agitation by a propeller may be employed in addition to aeration.

  A diffuser tube 21 is provided in the biological treatment chamber 29 as a means for aerating the biological treatment chamber 29. When aeration is used as a means for generating the upward flow of the circulation channel 27, the air diffuser 21 can be omitted, but both the DO in the biological treatment chamber 29 and the LV of the circulation channel 27 are appropriately used. In order to maintain, it is preferable that the means for aeration of the biological treatment chamber 29 and the upward flow generating means of the circulation flow path 27 are provided individually.

  In the second biological treatment tank 2, it is necessary to use an operation condition and a treatment apparatus that allow the microanimal and the bacteria to remain in the system in order to use the action of the microanimal having a slower growth rate than the bacteria and the autolysis of the bacteria. . Therefore, in this embodiment, in the second biological treatment tank 2, the swing bed carrier 22 is installed in the biological treatment chamber 29 to increase the amount of micro-animal retained in the tank.

As the swing bed carrier 22, a soft sheet-like material satisfying the following conditions is preferable.
(1) The length of the sheet is 100 to 400 cm in the depth direction of the tank, the depth in the horizontal direction of the tank is 5 to 200 cm, and the thickness is 0.5 to 5 cm. (It has an apparent surface area that is large enough for micro-animals to lay eggs and grow easily.)
(2) It has at least two surfaces having an apparent surface area of 500 cm ² or more. (It has an apparent surface area that is large enough for micro-animals to lay eggs and grow easily.)
(3) The material is preferably a foamed synthetic resin, particularly a flexible polyurethane foam. (Because it has flexibility, it does not interfere with water flow and the biofilm is easy to peel off)
(4) The hole diameter is 0.05 to 10 mm. (The size is easy for sludge to adhere and peel off.)
(5) The number of foamed cells is 5 to 125/25 mm. (It is a cell distribution in which sludge easily adheres and peels off.)
When a porous sheet-like oscillating bed carrier such as a thin plate-like or strip-like lightweight polyurethane foam is installed in the second biological treatment tank 2, the oscillating bed carrier has sufficient elasticity, Even if it is thin, it has sufficient mechanical strength and does not break by being bent in the flow of water in the tank. Moreover, by bending, it mixes uniformly, without inhibiting the water flow in a tank, and a sludge containing liquid comes to flow uniformly also into the porous structure of a support | carrier.

  As the conditions for the foamed cells of the porous carrier, those having a uniform distribution of the foamed cells are preferable. If there are too many foamed cells or the cell diameter is too large, the mechanical strength of the porous carrier will be reduced, so as described above, as the number of cells / 25 mm (number of cells existing in a 25 mm length range), The upper limit is preferably about 125 pieces / 25 mm. Conversely, if the number of foamed cells is too small or the cell diameter is too small, the function as a porous carrier cannot be obtained sufficiently. The lower limit of / 25 mm is preferably about 5/25 mm. For the number of cells / 25 mm, a photo of the porous carrier taken with a scanning electron microscope was used to measure the number of foamed cells intersecting the straight line 25 mm in the length direction at a plurality of locations. The average value of the results can be calculated and obtained.

  The second biological treatment tank 2 may be filled with a fluidized bed carrier that can be separated by the upward flow channel 24 in addition to the rocking bed carrier.

  In the second biological treatment tank 2, a large amount of scaffolding for maintaining micro-animals is required. However, if the filling rate of the carrier is excessively high, mixing in the tank, sludge decay, etc. may occur. The filling rate is preferably 0.5 to 30%, particularly preferably about 1 to 20%.

A preferred installation form of the swing bed carrier is as follows.
(I) In the biological treatment tank in which the rocking bed carrier is installed, [apparent surface area of the rocking bed carrier] / [biological treatment tank volume] is 1 to 50 [m−1]. (Increase the amount of carrier as the load increases.)
The apparent surface area is the surface area of the outer surface that does not take into account the surface area inside the porous body. For example, in the case of a rectangular parallelepiped, the total surface area of six surfaces (length × width × 2 + length × thickness × 2 + thickness × width × 2)
(Ii) The filling rate of the rocking bed carrier is 1 to 20% of the total volume of the biological treatment tank after the biological treatment tank with micro animals (including the biological treatment tank in the return line). (Increased carrier amount with increasing load)
(Iii) A strip-shaped sheet (longitudinal direction × short direction × thickness direction) is installed in the tank as the swinging bed carrier so that the longitudinal direction of the swinging bed carrier is the depth direction of the tank (vertically downward). . At this time, the direction in the short direction of the swing bed carrier is not particularly limited, and for example, it can be installed in the tank so as to be substantially perpendicular to the direction of water flow from the inflow side to the outflow side.
(Iv) When the capacity of the second biological treatment tank is larger than the size of the carrier, prepare a plurality of pieces with fasteners attached to the upper and lower surfaces of the carrier, And / or a predetermined number in the width direction, and a unit having a carrier attached to a frame material made of SUS or the like is fixed to form a unit, and this carrier unit is further installed in the second biological treatment tank as necessary. Provide multiple sheets in the direction of water flow.

  In order to promote predation by the minute animals, the pH of the second biological treatment tank 2 may be 7.0 or less.

  In the second biological treatment tank 2, not only the filtration predation type micro-animal that prey on the dispersed cells, but also the aggregate predation type micro-animal that can prey on the flocked sludge grows. Since the latter prey on flocs while swimming, if priority is given, sludge is eaten and becomes sludge in which fine floc pieces are scattered (sludge with poor sedimentation). In addition, this floc piece causes clogging of the membrane particularly in the membrane activated sludge method in which membrane separation is performed in the latter stage. Therefore, in order to thin out the aggregate predatory microanimals, it is desirable to control the SRT to be constant within a range of 60 days or less, preferably 45 days or less. However, if it is less than 15 days, it is unnecessarily frequent, and the number of not only aggregate predation type micro-animals but also filtration predation type micro-animals is excessively reduced.

  In the first biological treatment tank 1, it is necessary to decompose most of the organic matter, that is, 70% or more of the wastewater BOD, desirably 80% or more, and convert it into microbial cells. When the organic substances are completely decomposed, flocs are not formed in the second biological treatment tank 2, and there is not enough nutrients for the growth of micro-animals. Only sludge with poor compaction (sludge with poor sedimentation) is excellent. It becomes an occupied biological treatment tank. Therefore, as shown in FIG. 2, a part of raw water is bypassed and supplied to the second biological treatment tank 2, and the sludge load due to the soluble BOD in the second biological treatment tank 2 is 0.025 kg-BOD / kg-MLSS / You may drive | work so that it may become d or more. The MLSS at this time includes MLSS for the carrier adhering.

  Further, when the sedimentation property is deteriorated, a coagulant may be temporarily added to improve the sedimentation property. As the flocculant, it is desirable to add one or both of an inorganic flocculant and an organic flocculant in the last stage of the biological treatment tank. As the inorganic flocculant, not only iron-based and aluminum-based ones, but also slag, silica, calcium and the like used for usual waste water treatment can be used. Similarly, as the organic flocculant, in addition to the anionic polymer and the cationic polymer, those used for ordinary waste water treatment can be used, and among them, the cationic polymer flocculant is preferable.

  When the rocking carrier cannot be installed or when the installation amount is limited, the sedimentation property may be maintained by increasing the frequency of addition of the flocculant, and the LV is set low within 0.5 to 5 m / h. You may maintain sludge.

  In order to obtain a higher quality of treated water for the separated water settled and separated at LV 0.5-5 m / h as in the present invention, membrane separation, coagulation sedimentation, and pressurized flotation are performed as solid-liquid separation. Also good. In addition, when performing coagulation sedimentation or pressure levitation, the amount of coagulant added can be reduced. The sedimentation separated water from the second biological treatment tank 2 is agglomerated in a coagulation tank, and then precipitated in a solid-liquid separation tank (sedimentation tank) to be separated into treated water and sedimented sludge. Further, the flocculant may be directly added to the second biological treatment tank without providing the flocculated solid-liquid separation, and the treated water quality may be improved. At this time, if the sedimentation is good, it is only necessary to add a cationic polymer. The amount of the cationic polymer flocculant added to the second biological treatment tank is preferably about 0.5 to 20 mg / L, more preferably 1 to 10 mg / L.

  As shown in FIG. 3, an anaerobic tank 30 may be provided, and the second biological treatment tank sludge may be circulated therein to suppress the growth of the aggregate predatory microanimal. In this case, the HRT of the anoxic tank 30 is set to 30 min or more, and in order to consume DO, a part of the raw water or a part or the whole amount of the first biological tank treated water may be passed.

In the present invention, the supply of raw water and the supply stop may be repeated. In this case, the relationship between the raw water supply time T _F and the raw water supply stop time T _S is preferably such that T _S / T _F is 1/20 to 1/4. T _F about 1~12h is preferable.

  1-3 show an example of an embodiment of the present invention, and the present invention is not limited to the illustrated one. For example, the biological treatment tank may be provided in three or more stages by providing a third biological treatment tank after the first biological treatment tank 1 and the second biological treatment tank 2. In addition, each tank may be provided independently, or each tank may be formed by partitioning one tank with a partition plate.

  In the present invention, the biological treatment tank 2 having the partition plate 26 and the partition plate 23 may be installed alone to perform wastewater treatment. FIG. 4 shows an example, and raw water is directly supplied to the biological treatment tank 2 and processed.

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

[Example 1 (flow: FIG. 1)]
In FIG. 1, the following treatment was performed on raw water (food production wastewater) using a first biological treatment tank 1 (no sludge return) having a capacity of 88 L and a second biological treatment tank 2 having a capacity of 150 L. Only DO in the first biological treatment tank 1 was set to 0.5 mg / L, and the second biological treatment tank 2 was operated at DO = 2 to 3 mg / L.

Further, a fluidized bed carrier 12 having a filling rate of 5% and a 5 mm square is added to the first biological treatment tank 1, and a plate-like polyurethane foam (length 100 cm × width 30 cm × thickness 1 cm) is added to the second biological treatment tank 2. / 1 sheet) was provided. The raw water CODcr is 1250 mg / L (BOD = 800 mg / L), the CODcr volumetric load on the first biological treatment tank is 8.6 kg-CODcr / m ³ / d, HRT 3.5 h, the total CODcr volumetric load 2 kg-CODcr / m ^It was operated under the conditions of ^{3 /} d, HRT 9.5h.

  By diffusing from the diffusing nozzle 28, the LV of the upward flow in the circulation flow path 27 was set to 10 m / h. The upward flow LV in the upward flow channel 24 is 5 m / h.

  As a result, the SS of the treated water was 30 mg / L, and the sludge conversion rate combined with the excess sludge extracted from the second biological treatment tank at SRT = 30d was 0.15 kg-SS / kg-CODcr.

[Comparative Example 1]
The treatment was performed under the same conditions as in Example 1 except that the partition plate 26, the circulation channel 27, and the diffuser nozzle 28 were not provided.

As a result, the SS of the treated water was usually 30 mg / L, but sludge accumulation and floating occurred periodically in the outlet channel, and the SS of the treated water at that time rose to 100 mg / L. The sludge conversion rate combined with the excess sludge extracted from the second biological treatment tank at SRT = 30d was 0.18 kg-SS / kg-CODcr.
[Example 2]
In Example 1, it processed on the same conditions except having added 5 mg / L of cationic polymer flocculants (Kurita Industrial Co., Ltd. Kuri farm PC728) to the 2nd biological treatment tank 2. FIG.

As a result, the SS of the treated water was 15 mg / L, and the sludge conversion rate combined with the excess sludge extracted from the second biological treatment tank at SRT = 30d was 0.12 kg-SS / kg-CODcr.
[Example 3]
In Example 1, the treatment was performed under the same conditions except that the raw water was supplied at T _F = 2h and the supply / stop at which the raw water supply was stopped at T _S = 100 min was repeated.

  As a result, the SS of the treated water was 20 mg / L, and the sludge conversion rate combined with the excess sludge extracted from the second biological treatment tank at SRT = 30d was 0.13 kg-SS / kg-CODcr.

DESCRIPTION OF SYMBOLS 1 1st biological treatment tank 2 2nd biological treatment tank 12 Fluidized bed support | carrier 23 Partition plate 24 Upflow flow path 26 Partition plate 27 Circulation flow path 28 Aeration nozzle 29 Biological treatment chamber 30 Anoxic tank

Claims (10)

A biological treatment method for organic wastewater, wherein biological wastewater is biologically treated in a biological treatment tank,
In order to solid-liquid separate sludge in biological treatment water in the biological treatment tank, a partition plate is provided on the drainage outlet side of the biological treatment tank, and the biological treatment chamber and the drainage outlet side flow upward in the biological treatment tank. The biologically treated water from the biological treatment chamber is circulated upward into the upward flow channel at LV 0.5 to 5 m / h and discharged from the drain outlet at the top of the upward flow channel. In the biological treatment method of discharging the supernatant water outside the tank,
By providing a partition plate in the biological treatment chamber along the partition plate, a circulation channel is formed between the partition plate and the partition plate so that both the upper and lower portions communicate with the biological treatment chamber. organic a part of the biologically treated water in the treatment chamber, characterized in that upwardly flowing water in greater LV than LV in the upward flow passage to the circulation passage between the partition plate and the partition plate Biological treatment method of waste water. A method of biologically treating organic wastewater in a biological treatment tank provided in multiple stages,
In the first-stage biological treatment tank, the first biological treatment water in which the dispersal bacteria are increased by the decomposition of the organic matter by the dispersal bacteria is generated,
In the last stage biological treatment tank, a biological treatment method for organic waste water that produces final biological treated water,
In order to solid-liquid separate sludge in the final biological treatment water in the biological treatment tank at the last stage, a partition plate is provided on the drainage outlet side of the biological treatment tank, and the biological treatment tank and the drainage outlet side are disposed in the biological treatment tank. The biological treatment water from the biological treatment chamber is circulated through the upward flow passage at an LV of 0.5 to 5 m / h, and the upper portion of the upward flow passage is In the biological treatment method of discharging the supernatant water from the drain outlet to the outside of the tank,
By providing a partition plate in the biological treatment chamber along the partition plate, a circulation channel is formed between the partition plate and the partition plate so that both the upper and lower portions communicate with the biological treatment chamber. organic a part of the biologically treated water in the treatment chamber, characterized in that upwardly flowing water in greater LV than LV in the upward flow passage to the circulation passage between the partition plate and the partition plate Biological treatment method of waste water.   3. The organic wastewater biological treatment method according to claim 2, wherein in the last biological treatment tank, biofilm treatment is performed on the rocking bed to produce final biological treatment water.   4. The biological treatment method for organic waste water according to claim 3, wherein the rocking floor carrier is a sheet-like foamed plastic.   The method according to any one of claims 1 to 4, wherein the flow of raw water and the stop of water flow are repeated, wherein the water flow stop time is set to 1/20 to 1/4 of the water flow time. Biological treatment method for organic wastewater.   The biological treatment method for organic wastewater according to any one of claims 1 to 5, wherein an upward flow is formed in the circulation channel by aeration in the circulation channel.   The organic drainage organism according to any one of claims 1 to 6, wherein the LV of the upward flow in the circulation channel is 1.5 to 200 times the LV of the upward flow channel. Processing method.   The biological treatment method for organic wastewater according to any one of claims 1 to 7, wherein a cationic polymer flocculant is added to the biological treatment tank. An organic wastewater biological treatment device for biologically treating organic wastewater in a biological treatment tank,
In order to solid-liquid separate sludge in biological treatment water in the biological treatment tank, a partition plate is provided on the drainage outlet side of the biological treatment tank, and the biological treatment chamber and the drainage outlet side flow upward in the biological treatment tank. The biological treatment water from the biological treatment chamber is circulated upward into the upward flow passage, and the supernatant water is discharged out of the tank from the drain outlet at the top of the upward flow passage. In biological treatment equipment,
By providing a partition plate in the biological treatment chamber along the partition plate, a circulation channel is formed between the partition plate and the partition plate so that both the upper and lower portions communicate with the biological treatment chamber. that a part of the biologically treated water in the treatment chamber provided with a water passage means for the upward flow of water in greater LV than LV in the upward flow passage to the circulation passage between the partition plate and the partition plate Organic wastewater biological treatment equipment. An apparatus for biological treatment of organic wastewater in a biological treatment tank provided in multiple stages,
In the first-stage biological treatment tank, the first biological treatment water in which the dispersal bacteria are increased by the decomposition of the organic matter by the dispersal bacteria is generated,
In the biological treatment tank at the last stage, an organic wastewater biological treatment device for producing final biological treated water,
In order to solid-liquid separate sludge in the final biological treatment water in the biological treatment tank at the last stage, a partition plate is provided on the drainage outlet side of the biological treatment tank, and the biological treatment tank and the drainage outlet side are disposed in the biological treatment tank. Divided into an upward flow channel, the biologically treated water from the biological treatment chamber is circulated upward into the upward flow channel, and the supernatant water is discharged from the drain outlet at the top of the upward flow channel. In biological treatment equipment discharged into
By providing a partition plate in the biological treatment chamber along the partition plate, a circulation channel is formed between the partition plate and the partition plate so that both the upper and lower portions communicate with the biological treatment chamber. that a part of the biologically treated water in the treatment chamber provided with a water passage means for the upward flow of water in greater LV than LV in the upward flow passage to the circulation passage between the partition plate and the partition plate Organic wastewater biological treatment equipment.

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