JP5874741B2 - Biological treatment method and apparatus for organic wastewater - Google Patents

Description

  The present invention relates to a biological treatment method and apparatus for organic wastewater that can be used for treatment of organic wastewater in a wide concentration range such as domestic wastewater, sewage, food factory, pulp factory, semiconductor production wastewater, and liquid crystal production wastewater. In particular, the present invention relates to a biological treatment method and apparatus for organic wastewater that can improve treatment efficiency and reduce the amount of excess sludge generation without deteriorating the quality of treated water.

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 bacterial cells, that is, sludge, a large amount of excess sludge is generated. 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.

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, in this method, the amount of generated sludge is about 30 to 50% of the decomposed BOD, which is higher than 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. Patent Document 1 describes that according to this method, a high-load operation is possible and the processing efficiency of the activated sludge method is improved.

  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”.

  Patent Document 3 discloses that flocs that are preyed by sonication or mechanical stirring when protozoa or metazoans prey on bacteria, yeast, actinomycetes, algae, fungi, or wastewater treatment primary sediment 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 activated sludge method at the latter stage 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 reduced.

Japanese Patent Laid-Open No. 55-20649 JP 2000-210692 A Japanese Patent Laid-Open No. 55-20649 Japanese Patent No. 3410699

  The above-mentioned multistage activated sludge method using the predatory action of 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, this sludge reduction effect is often not stable.

  For example, as shown in FIG. 5, by adding a fluidized bed carrier to the latter tank of the multistage activated sludge method, it is possible to stably maintain the microanimals, but a separation screen is required, or oxygen is dissolved by the carrier. There are problems such as reduced efficiency.

  The present invention solves the above-mentioned conventional problems, and in the biological treatment of organic wastewater to which the multistage activated sludge method is applied, the amount of generated sludge is greatly reduced and the treatment efficiency is improved by high-load operation and is stable. It is an object of the present invention to provide a biological treatment method and apparatus for organic wastewater for improving the quality of treated water.

The organic wastewater biological treatment method of the present invention is the organic wastewater biological treatment method in which organic wastewater having a COD _Cr volumetric load of 1 kg / m ³ / d or more is biologically treated in a biological treatment tank provided in multiple stages. In the aeration tank , which is the first-stage biological treatment tank , the first biological treatment water with increased dispersal bacteria is generated by the decomposition of organic matter by the dispersal bacteria, and the swing bed carrier is installed in the aeration tank , which is the last-stage biological treatment tank Then, a biofilm is attached to the rocking bed carrier, and the last-stage biological treatment water of the last-stage biological treatment tank is settled in an upward flow of LV1 to 20 m / h in or outside the last-stage biological treatment tank. It is characterized by separating and returning the sedimented sludge to any biological treatment tank.

Biological treatment apparatus of the organic waste water of the present invention, the _{COD Cr} volumetric loading 1kg / m 3 / ^d or more organic wastewater in the biological treatment apparatus of an organic waste water to the biological treatment in multiple stages, in the biological treatment tank in the first stage In one aeration tank , the first biological treatment water in which the dispersal bacteria are increased is generated by the decomposition of the organic matter by the dispersal bacteria, and the swing bed carrier is installed in the aeration tank which is the last biological treatment tank. A biological treatment apparatus for organic wastewater that attaches a biofilm to the bottom and generates last-stage biologically treated water, wherein the last-stage biologically treated water provided inside or outside the last-stage biologically treated tank is LV1 to LV1. It is characterized by comprising sedimentation separation means for sedimentation with an upward flow of 20 m / h, and return means for returning the sedimentation sludge to any biological treatment tank.

  In one aspect of the present invention, the sedimentation separation is performed in a non-aggregating manner. In the present invention, the “non-aggregation method” refers to an operation method in which the flocculant is not added continuously or intermittently from the biological treatment tank to the sedimentation separation means during normal operation. Temporary addition of flocculant at the start-up of equipment with little sludge or sludge disassembly trouble does not fall under "addition of flocculant during normal operation". Even if a flocculant is temporarily added at times, it is included in the “non-aggregation method”. In addition, a case where a small amount of an aggregating agent that does not substantially perform the aggregating treatment is added to the non-aggregating method. The addition amount of a small amount of the flocculant that does not substantially perform the flocculant treatment varies depending on the type of flocculant to be used, but in terms of constant addition, the inorganic flocculant is 100 mg / L or less, high The molecular flocculant is 1 mg / L or less. In addition, the present invention does not exclude any coagulation treatment of the supernatant water obtained by sedimentation separation.

  In another aspect of the present invention, in order to settle and separate the last-stage biological treatment water in the tank, a partition is provided on the drain outlet side of the last-stage biological treatment tank to form an ascending flow path. The liquid in the tank is circulated upward at LV1 to 20 m / h to settle and separate the sludge, the settled sludge is returned to the last biological treatment tank, and the supernatant water that has risen through the ascending flow path is discharged out of the tank. To do.

  As the rocking bed carrier, a sheet-like foamed plastic is suitable.

In the present invention, in an organic wastewater biological treatment method and apparatus utilizing the predatory action of microanimals, an oscillating bed carrier is provided as a scaffold for fixed filtration predatory microanimals that prey on dispersal bacteria. Such a rocking bed carrier produces sludge with good sedimentation, so that it has a higher LV (1-20 m / h) than the LV of 0.5 m / h or less generally employed in sedimentation separation after biological treatment. The sedimentation is separated in h).
This sedimentation separation can also be a non-aggregation method. According to the non-aggregation type sedimentation separation, sludge with poor sedimentation can be discharged out of the tank, and sludge with good sedimentation can be selectively retained in the tank. As a result, not only the oscillating bed carrier but also sludge with good sedimentation can be used as a scaffold for minute animals to maintain a high microorganism concentration.

  As a sedimentation separation means, a partition is provided on the outlet side of the last biological treatment tank, and the water in the tank is passed in an upward flow of LV1 to 20 m / h, and only the sludge with good sedimentation property that does not float is left in the tank. It is preferable to do so. As a sedimentation separation means, a sedimentation tank may be provided after the last biological treatment tank.

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

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

  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. 1-4 is a systematic diagram showing an embodiment of a biological treatment method and apparatus for organic wastewater of the present invention.

  1-4, 1 is a first biological treatment tank, 2 is a second biological treatment tank, 11 and 21 are air diffusers, 12 is a fluidized bed carrier, 16 is a carrier separation screen, and 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. Sludge is settled and separated in the ascending flow path 24. In addition, the same code | symbol is attached | subjected to the member which show | plays the same function in FIGS.

In the embodiment of FIG. 1, is introduced in BOD volume load 1kg ^{/ m} 3 ^/ d or more for example 1~20kg ^{/ m} 3 ^/ d raw water (organic wastewater) is first biological treatment tank 1, and aerated with aeration tube 11 In addition, 70% or more, desirably 80% or more, more desirably 85% or more of the organic component (soluble BOD) is oxidatively decomposed by dispersible bacteria (non-aggregating bacteria). 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 retention 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.

A part of the sludge from the subsequent biological treatment tank is returned to the first biological treatment tank 1, the first biological treatment tank 1 is composed of two or more tanks, or a fluidized bed carrier is added. As a result, 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 is any shape 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 is arbitrary such as a natural material, an inorganic material, or a polymer material, and a gel material may be used.

  When the filling rate of the carrier added to the first biological treatment tank 1 is excessively high, dispersal bacteria are not generated, and bacteria adhere to the carrier or filamentous bacteria grow. Therefore, by setting the filling rate of the carrier to be added to the first biological treatment tank 1 to 10% or less, desirably 5% or less, for example 0.5 to 5%, dispersible bacteria that are not affected by concentration fluctuation and are easy to prey. Can be generated. The filling rate of the carrier represents the ratio of the volume of the carrier to the volume of the liquid in the first biological treatment tank 1.

  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 passed through 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 by predation of micro-animals. As the microanimals, filtration predation type microanimals such as stag beetles and stag beetles are suitable.

  In the last 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 is divided into an ascending flow path 24 and a biological treatment chamber. . 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. The partition plate 23 faces a part of the side wall of the second biological treatment tank 2, and a rising channel 24 is formed between the side wall and the partition plate 23. The lower part of the ascending channel 24 communicates with the biological treatment chamber in the second biological treatment tank 2. From the upper part of the ascending flow path 24, the supernatant water flows out of the tank 2 through the outlet part of the tank 2. The air diffuser 21 is installed away from the ascending channel 24, and the air diffuser 21 does not exist below the ascending channel 24. This is to prevent bubbles from the diffuser tube 21 from directly flowing into the ascending flow path 24.

  Sludge settles while the sludge mixed water in the second biological treatment tank 2 rises in the ascending flow path 24. In the present invention, the LV of the upward flow in the upward flow path 24 is 1 to 20 m / h, preferably 3 to 15 m / h. A surplus sludge take-out pipe 25 is provided in the biological treatment chamber of the second biological treatment tank 2. The sludge settled in the ascending flow path 24 returns to the second biological treatment tank 2. The supernatant water from which the sludge is separated by ascending the ascending channel 24 flows out of the tank 2 from the outlet. The supernatant water that flows out may contain sludge with poor sedimentation.

The dissolved oxygen (DO) concentration in the second biological treatment tank 2 is preferably about 1 to 4 mg / L.
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, the second biological treatment tank 2 is provided with a rocking bed carrier 22, and sludge is adhered to the surface to form a biological film. By installing this rocking bed carrier, the amount of micro-animal retained in the tank increases. The swing bed carrier 22 is preferably disposed above the air diffuser 21.

The swing bed carrier preferably has an apparent surface area that is large enough for a micro animal to lay eggs and grow easily. Moreover, the rocking bed carrier is preferably one that has flexibility, does not inhibit water flow, and easily peels off the biofilm. As the swing bed carrier, a soft sheet that satisfies the following conditions is preferable.
1) It is preferable that the length of the tank in the depth direction is 100 to 400 cm, the depth of the tank in the horizontal direction is 5 to 200 cm, and the thickness is 0.5 to 5 cm.
2) It is preferable to have at least two surfaces having an apparent surface area of 500 cm ² or more.
3) The material is preferably a foamed synthetic resin (foamed plastic), particularly a flexible polyurethane foam.
4) It is preferable that the pore diameter is 0.05 to 10 mm in order to allow sludge to adhere easily and to be easily removed. Moreover, it is preferable that the cell number of a foam cell is 5-125 pieces / 25mm. Furthermore, as a porous support | carrier, a thing with uniform distribution of a foam cell is preferable.
If there are too many foamed cells in the porous carrier or if the cell diameter is too large, the mechanical strength of the porous carrier will be reduced. Therefore, as described above, the number of cells / 25 mm (cells existing in a 25 mm length range) Number) is preferably about 125/25 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.

  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 is not damaged by bending in the water flow 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.

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 internal surface area of the porous body. 2)
(Ii) The filling rate of the rocking bed carrier is 0.1 to 20% of the total volume of the biological treatment tank (including the biological treatment tank in the return line) after the biological treatment tank with micro animals. . (Increased carrier amount with increasing load)
(Iii) A strip-shaped sheet is installed in the tank as the rocking bed carrier so that the longitudinal direction of the rocking 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 use them in the depth direction of the second biological treatment tank and / Or a predetermined number in parallel in the width direction, fixing a fastener with a carrier attached to a frame material made of SUS or the like to form a unit, and further, this carrier unit in the second biological treatment tank as needed Provide multiple sheets in the direction of water flow.

  The second biological treatment tank 2 may be further filled with a fluidized bed carrier in addition to the rocking bed carrier. As the fluidized bed carrier, the aforementioned one used for the first biological treatment tank is suitable.

  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 10%.

  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 prioritized, 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 aggregate predation type micro-animals, it is desirable to control SRT (sludge retention time) to be constant within a range of 60 days or less, preferably 45 days or less. However, if the SRT is less than 15 days, it is unnecessarily frequent and the number of not only the aggregate predation type micro-animals but also the filter predation type micro-animals is reduced too much.

  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.

  In order to obtain a higher quality of treated water, the separated water separated and settled by the upward flow of LV1 to 20 m / h may be subjected to any of membrane separation, coagulation sedimentation, and pressurized flotation as solid-liquid separation. In addition, when performing coagulation sedimentation (FIG. 3) or pressure levitation, the amount of coagulant added can be reduced. In FIG. 3, the supernatant water after sedimentation from the second biological treatment tank 2 is coagulated in the coagulation tank 4, and then precipitated in the solid-liquid separation tank (sedimentation tank) 5 to be separated into treated water and sedimented sludge. To do.

  As the flocculant, it is preferable to use an inorganic flocculant or an inorganic flocculant and an organic polymer flocculant.

  There is no restriction | limiting in particular as an inorganic flocculant, Any inorganic flocculant conventionally used for the coagulation sedimentation processing of waste_water | drain can be used.

  Specifically, ferrous sulfate, ferric sulfate, ferrous chloride, ferric chloride, ferric sulfate and other iron-based flocculants, aluminum sulfate, aluminum chloride, polyaluminum chloride and other aluminum-based A flocculant etc. are mentioned.

  These inorganic flocculants may be used individually by 1 type, and 2 or more types may be mixed and used for them.

  The amount of the inorganic flocculant added varies depending on the type of the inorganic flocculant and the properties of the raw water, and cannot be generally specified, but is usually about 50 to 500 mg / L.

  In the agglomeration treatment in which the inorganic flocculant is added, it is preferable to adjust the pH conditions suitable for the inorganic flocculant. In that case, an alkali such as sodium hydroxide or an acid such as sulfuric acid or hydrochloric acid can be used for pH adjustment.

  In such a coagulation treatment with an inorganic coagulant, it is preferable to stir the coagulation reaction tank at about 70 to 200 rpm.

  There is no particular limitation on the organic polymer flocculant used to coarsen the flocs formed by the flocculant treatment with the inorganic flocculant, and any organic polymer flocculant usually used in wastewater flocculation can be used. is there. For example, poly (meth) acrylic acid, a copolymer of (meth) acrylic acid and (meth) acrylamide, and alkali metal salts thereof may be used as long as they are anionic. If it is nonionic, poly (meth) acrylamide etc. are mentioned. In the case of a cationic system, a homopolymer composed of a cationic monomer such as dimethylaminoethyl (meth) acrylate or a quaternary ammonium salt thereof, dimethylaminopropyl (meth) acrylamide or a quaternary ammonium salt thereof, or a copolymer with these cationic monomers. Examples thereof include a copolymer with a polymerizable nonionic monomer. These organic polymer flocculants may be used alone or in combination of two or more.

  The addition amount of the organic polymer flocculant is appropriately determined according to the type of organic polymer flocculant and the properties of the raw water, but is usually about 0.5 to 5 mg / L.

  In such a coagulation treatment with an organic polymer flocculant, it is preferable to stir the coagulation reaction tank at about 30 to 100 rpm.

  1-3, although sludge is settled and separated by the ascending flow path 24 in the second biological treatment tank 2, the sludge mixed water in the second biological treatment tank 2 is taken out as shown in FIG. Introduced into the separation tank 3 and separated into solid and liquid, separated into treated water and settled sludge, a part of the settled sludge (tank sludge) is returned to the second biological treatment tank 2 and the remainder as extra sludge You may make it take out. Sludge mixed water is introduced into the lower part of the solid-liquid separation tank 3 and is raised at LV1 to 20 m / h for solid-liquid separation. The supernatant water is taken out from the upper part of the tank 3. The settled sludge is taken out from the bottom of the tank 3. In FIG. 4, neither the partition plate 23 nor the trough is provided in the outflow part of the second biological treatment tank 2.

  1 to 4 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.

  1-4, the final stage biological treatment tank is provided with the rocking bed carrier 22, and the final stage biological treatment water is supplied at LV1 to 20 m / h in or outside the final stage biological treatment tank. By sedimentation and returning the sludge to one of the biological treatment tanks, it is possible to suppress the prioritization of aggregate predation type micro-animals, achieve both reduction of sludge and improvement of treated water quality, and stability. High load processing is possible.

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

[Example 1 (flow: FIG. 1)]
In FIG. 1, COD _Cr 1250 mg / L (BOD 800 mg / L) organic wastewater (food manufacturing 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 ) Was carried out. As illustrated, the second biological treatment tank 2 is provided with an ascending flow path 24 partitioned by a partition plate 23. The liquid in the tank was circulated through the ascending flow path 24 at an LV of 5 m / h, and the sludge was settled and separated. The settled sludge returns to the second biological treatment tank 2 and the supernatant water flows out of the second biological treatment tank 2. Excess sludge in the second biological treatment tank 2 was taken out from the take-out pipe 25. The DO of the first biological treatment tank 1 was set to 0.5 mg / L, and the second biological treatment tank 2 was operated so that the DO was 2 to 3 mg / L.

A fluidized bed carrier 12 having a filling rate of 5% and 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. One swing bed carrier 22 was installed. _{COD Cr} volumetric load on the first biological treatment tank ^{_{8.6kg-COD Cr / m 3 /d,HRT3.5h}} , under conditions of _{COD Cr} volumetric loading ^_2kg-COD Cr / m 3 _/d,HRT9.5h throughout Drove.

As a result, SS in the treated water is 30 mg / L, the sludge conversion rate combined with excess sludge fraction was withdrawn from the second biological treatment tank in SRT = 30d became _{0.15kg-SS / kg-COD Cr} .

[Example 2 (flow: FIG. 3)]
As shown in FIG. 3, 50 mg / L of PAC as an aggregating agent and 1 mg / L of an anionic polymer aggregating agent (Cliff Rock PA331 manufactured by Kurita Kogyo Co., Ltd.) are added to the second biologically treated water from the second biological treatment tank 2. After the addition, the coagulation tank 4 and the precipitation tank 5 were subjected to coagulation sedimentation treatment. As shown in FIG. 3, the second biological treatment tank 2 is not provided with the partition plate 23 and the ascending flow path 24. Otherwise, the operation was performed under the same conditions as in Example 1.

As a result, the SS of the treated water is 5 mg / L or less, and the sludge conversion rate combined with the sludge derived from coagulation sediment and the excess sludge extracted from the second biological treatment tank at SRT = 30d is 0.15 kg-SS / kg- COD _Cr (excluding PAC).

[Example 3 (flow: FIG. 1)]
The process is performed under the same conditions as in Example 1 except that the position of the partition plate 23 is adjusted so that the LV of the ascending channel 24 becomes 1 m / h and the horizontal sectional area of the ascending channel 24 is increased five times. went.

As a result, SS in the treated water is 35 mg / L, the sludge conversion rate combined with excess sludge fraction was withdrawn from the second biological treatment tank in SRT = 30d became _{0.16kg-SS / kg-COD Cr} .

[Example 4 (flow: FIG. 1)]
The process is performed under the same conditions as in Example 1 except that the position of the partition plate 23 is adjusted so that the LV of the ascending channel 24 becomes 15 m / h and the horizontal sectional area of the ascending channel 24 is reduced to 1/3. Went.

As a result, SS in the treated water is 40 mg / L, the sludge conversion rate combined with excess sludge fraction was withdrawn from the second biological treatment tank in SRT = 30d became _{0.16kg-SS / kg-COD Cr} .

[Example 5 (flow: FIG. 1)]
The process is performed under the same conditions as in Example 1 except that the position of the partition plate 23 is adjusted so that the LV of the ascending channel 24 is 20 m / h and the horizontal sectional area of the ascending channel 24 is reduced to ¼. Went.

As a result, SS in the treated water is 50 mg / L, the sludge conversion rate combined with excess sludge fraction was withdrawn from the second biological treatment tank in SRT = 30d became _{0.16kg-SS / kg-COD Cr} .

[Example 6 (flow: FIG. 4)]
In FIG. 4, a first biological treatment tank 1 having a capacity of 36 L, a second biological treatment tank 2 having a capacity of 150 L, and a solid-liquid separation tank 3 having an LV = 5 m / h were used. The second biological treatment tank 2 is not provided with the partition plate 23 and the ascending flow path 24. Instead, a part of the settled sludge in the solid-liquid separation tank 3 was returned to the second biological treatment tank 2. The sedimentation sludge was not returned to the first biological treatment tank 1. The other processes were performed under the same conditions as in Example 1.

As a result, SS in the treated water is 30 mg / L, the sludge conversion rate combined with excess sludge fraction was withdrawn from the second biological treatment tank in SRT = 30d became _{0.15kg-SS / kg-COD Cr} .

[Comparative Example 1 (flow: FIG. 1)]
The process is performed under the same conditions as in Example 1 except that the position of the partition plate 23 is adjusted so that the LV of the ascending channel 24 becomes 0.5 m / h and the horizontal sectional area of the ascending channel 24 is increased 10 times. Went.

In the comparative example 1, the horizontal cross-sectional area of the ascending flow path 24 surrounded by the partition plate 23 occupies about 40% of the entire horizontal cross-sectional area of the second biological treatment tank 2. As a result, the biological treatment did not proceed sufficiently. SS in the treated water is 90 mg / L, the sludge conversion rate combined with excess sludge fraction was withdrawn from the second biological treatment tank in SRT = 30d became _{0.22kg-SS / kg-COD Cr} .

[Comparative Example 2 (flow: FIG. 1)]
The processing is performed under the same conditions as in Example 1 except that the position of the partition plate 23 is adjusted so that the LV of the ascending channel 24 is 25 m / h and the horizontal sectional area of the ascending channel 24 is reduced to 1/5. Went.

In Comparative Example 2, the upward flow velocity of the ascending flow path 24 is large, the sludge sedimentation is insufficient, and the amount of sludge flowing out from the second biological treatment tank 2 together with the treated water is increased. As a result, SS in the treated water is 100 mg / L, and the sludge conversion rate combined with excess sludge fraction was withdrawn from the second biological treatment tank in SRT = 30d became _{0.22kg-SS / kg-COD Cr} .

[Comparative Example 3 (flow: FIG. 5)]
As shown in FIG. 5, the swing bed carrier 22 was not provided in the second biological treatment tank 2. A carrier for separating the fluidized bed carrier by adding a 5 mm square fluidized bed carrier (the same fluidized bed carrier as filled in the first biological treatment tank 1) to the second biological treatment tank 2 at a filling rate of 5%. A separation screen 26 was provided. Otherwise, the operation was performed under the same conditions as in Example 6.

As a result, SS in the treated water is 200 mg / L, the sludge conversion rate combined with excess sludge fraction was withdrawn from the second biological treatment tank in SRT = 30d became _{0.23kg-SS / kg-COD Cr} .

[Comparative Example 4 (flow: FIG. 6)]
Raw water was treated according to the flow of FIG. 6 which is the same as FIG. 4 except that the solid-liquid separation tank is not provided. As shown in FIG. 6, the solid-liquid separation of the effluent from the second biological treatment tank and the return of excess sludge were not performed. Otherwise, the process was performed under the same conditions as in Example 6.

As a result, SS in the treated water is 300 mg / L, the sludge withdrawal from the bath is not carried out, the sludge conversion rate was _{0.24kg-SS / kg-COD Cr} .

Although the present invention has been described in detail using specific embodiments, it will be apparent to those skilled in the art that various modifications can be made without departing from the spirit and scope of the invention.
In addition, this application is based on the Japanese patent application (Japanese Patent Application No. 2012-001288) for which it applied on January 6, 2012, The whole is used by reference.

DESCRIPTION OF SYMBOLS 1 1st biological treatment tank 2 2nd biological treatment tank 3 Solid-liquid separation tank 12 Fluidized bed carrier 16,26 Carrier separation screen 22 Oscillating bed carrier 23 Partition plate 24 Ascending flow path

Claims (15)

In a biological treatment method for organic wastewater, wherein organic wastewater having a COD _Cr volumetric load of 1 kg / m ³ / d or more is biologically treated in a biological treatment tank provided in multiple stages,
In the aeration tank , which is the first-stage biological treatment tank , the first biological treatment water in which the dispersal bacteria increased is generated by the decomposition of the organic matter by the dispersal bacteria,
Install the swing bed carrier in the aeration tank which is the last biological treatment tank , and attach the biofilm to the swing bed carrier,
The last-stage biological treatment water in the last-stage biological treatment tank is settled and separated in an upward flow of LV1 to 20 m / h in or outside the last-stage biological treatment tank, and the sedimented sludge is returned to any biological treatment tank. A method for biological treatment of organic wastewater.   2. The biological treatment method for organic wastewater according to claim 1, wherein the last-stage biological treatment water is settled and separated in a non-flocculating manner inside or outside the last-stage biological treatment tank.   In claim 1 or 2, in order to settle and separate the last-stage biological treatment water in the last-stage biological treatment tank, a partition is provided on the drainage outlet side of the last-stage biological treatment tank to form an upward flow channel, The last-stage biologically treated water is circulated upward into the flow path at LV1 to 20 m / h, the sedimented sludge is returned to the last-stage biologically treated tank, and the supernatant water that has risen through the flow path is discharged outside the tank. Biological treatment method for organic wastewater.   The biological treatment method for organic wastewater according to any one of claims 1 to 3, wherein the rocking floor carrier is a sheet-like foamed plastic.   5. The organic wastewater treatment method according to claim 4, wherein the cell diameter of the foamed plastic cell is 0.05 to 10 mm, and the number of cells is 5 to 125/25 mm.   In any 1 item | term of Claim 1 thru | or 5, The dissolved oxygen concentration of a 1st biological treatment tank is 1 mg / L or less, The dissolved oxygen concentration of a 2nd biological treatment tank is 1-4 mg / L, It is characterized by the above-mentioned. Biological treatment method for organic wastewater. The biological treatment method for organic wastewater according to any one of claims 1 to 6, wherein the BOD volumetric load of the first biological treatment tank is 1 to 20 kg / m ³ / d.   The biological treatment method for organic wastewater according to any one of claims 1 to 7, wherein the raw water retention time (HRT) of the first biological treatment tank is 0.5 to 24 h.   The biological treatment method for organic waste water according to any one of claims 1 to 8, wherein the SRT of the second biological treatment tank is 15 to 60 days. In an organic wastewater biological treatment apparatus for biologically treating organic wastewater with a COD _Cr volumetric load of 1 kg / m ³ / d or more in multiple stages,
In the aeration tank , which is the first-stage biological treatment tank , the first biological treatment water in which the dispersal bacteria increased is generated by the decomposition of the organic matter by the dispersal bacteria,
A biological treatment apparatus for organic wastewater that installs a swing bed carrier in an aeration tank that is the last biological treatment tank , attaches a biofilm to the swing bed carrier, and generates last biological treatment water,
A sedimentation / separation means provided within or outside the last-stage biological treatment tank, for separating and separating the last-stage biological treatment water with an upward flow of LV1 to 20 m / h;
A biological treatment apparatus for organic wastewater, comprising: return means for returning the settled sludge to any biological treatment tank.   11. The organic wastewater biological treatment apparatus according to claim 10, wherein the sedimentation separation means is means for sedimentation and separation of the last-stage biological treatment water by a non-flocculation method.   In Claim 10 or 11, in order to settle and separate the last-stage biological treatment water in the last-stage biological treatment tank, a partition is provided on the drain outlet side of the last-stage biological treatment tank as the sedimentation separation means, and the upward flow A path is formed, water flows upward into the flow path at LV1 to 20 m / h, the sedimented sludge is returned to the last biological treatment tank, and the supernatant water that has risen through the flow path is discharged outside the tank. Organic wastewater biological treatment equipment.   The biological treatment apparatus for organic wastewater according to any one of claims 10 to 12, wherein the rocking floor carrier is a sheet-like foamed plastic.   14. The organic wastewater biological treatment apparatus according to claim 13, wherein the pore diameter of the cell of the foamed plastic is 0.05 to 10 mm, and the number of cells is 5 to 125/25 mm.   The biological treatment apparatus for organic wastewater according to any one of claims 10 to 14, wherein a diffuser pipe is provided in each of the first biological treatment tank and the second biological treatment tank.

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