JP2009039700A - Wastewater biological treatment method - Google Patents

Abstract

A microorganism treatment is carried out by adding a microorganism to a biological treatment tank without causing it to be immobilized and flowing it to form a microorganism-supporting carrier having a high sedimentation property.
A gel carrier such as polyacrylic acid is added to a reaction section of a processing tank. The effluent from the reaction unit 11 is separated into solid and liquid by the separation unit 12. The carrier 35 flows vigorously by passing the water through the treatment tank 10 so that the amount of ventilation to the reaction unit 11 is 0.03 m / s or more, or the LV of the separation unit 12 is 2 m / hr or more. Let Thereby, the density of the microorganisms held on the carrier 35 is increased, and a strong granular microorganism holding carrier having excellent sedimentation properties can be obtained. The carrier 35 that has flowed due to the air diffused from the air diffuser 16 is settled by gravity in the separation unit 12, accumulated on the bottom of the treatment tank 10, and returned to the reaction unit 11 that communicates with the separation unit 12 through the opening at the bottom of the partition plate 15. .
[Selection] Figure 1

Description

  The present invention relates to a biological treatment method in which wastewater is introduced into a biological treatment tank to which a carrier is added for biological treatment.

  Conventionally, a carrier addition type biological treatment method in which a carrier is added to a biological treatment tank is known. Microorganisms are retained on the carrier, and the amount of microorganisms retained in the biological treatment tank can be increased by adding the carrier. There are various types of carriers such as porous particles, cylinders, fibers, and the like, and the materials constituting the carriers are also various. For example, many porous granular carriers are made of sponge, foamed urethane, activated carbon, anthracite, etc., and cylindrical carriers are often made of plastic. As the fibrous carrier, cellulose, polyester, polypropylene, or the like is used in the form of a thread or a cloth such as felt.

  A gel carrier made of a swellable resin that absorbs liquid and expands is also known. Examples of the resin for the gel carrier include polyvinyl alcohol (PVA), polyethylene glycol (PEG), acrylamide, polyalkylene oxide, and polyacrylic acid (for example, Patent Document 1). These water-absorbing resins absorb water and expand to have a network-like three-dimensional network structure (network structure).

  The gel carrier can be used by adding it to a biological treatment tank containing microorganisms and absorbing water to expand the network structure so that the microorganisms are retained in the network structure. However, some resin materials of the gel carrier have poor affinity with water and weak microbial retention, and may have low strength.

  For this reason, the gel carrier is often used as a entrapping immobilization carrier in which a microorganism is fixed in a gel by mixing a resin-containing liquid containing a microorganism and then gelling it. However, in order to produce the entrapping immobilization carrier, a process of mixing the material resin and the liquid containing the microorganisms and then gelling the resin into particles of an appropriate size is required, which increases the production cost.

Patent Document 2 discloses a method of obtaining a gel carrier by absorbing a water-absorbing polymer gel and then bringing it into contact with an aqueous solution of an aluminum salt or an iron salt in order to eliminate the need for comprehensive fixing of microorganisms. . According to Patent Document 2, the gel strength can be increased by allowing aluminum hydroxide or iron hydroxide to be present in the surface layer of a polymer gel swollen with water.
Japanese Patent Laid-Open No. 10-180279 Japanese Patent Laid-Open No. 7-8984

  By the way, the carrier generally has a diameter of about 5 to 10 mm and is solid-liquid separated by a screen in which slits are formed. However, the smaller the diameter of the carrier, the larger the surface area per unit volume, and the higher the amount of microorganisms retained. Further, when the carrier diameter is small, the gas easily moves to the inside of the carrier. Therefore, when operating under aerobic conditions, the inside of the carrier is unlikely to become anaerobic, and the aerobic reaction rate can be increased if bacteria are retained inside the carrier. Alternatively, when a biological treatment such as a denitrification reaction is performed under anaerobic conditions, the gas generated inside the carrier tends to escape.

  As described above, it is preferable that the particle size of the carrier is small. However, if the particle size of the carrier is small, it is difficult to separate with a screen, and it is necessary to perform solid-liquid separation by another means, for example, by precipitation. In order to solid-liquid-separate a support | carrier favorably by precipitation, the sedimentation property of a support | carrier is calculated | required.

  The present invention has an object to improve the sedimentation property and the microorganism holding power of a gel carrier that is easy to manufacture without the need to comprehensively fix microorganisms.

  The present inventors have found that sludge can be densely adhered by vigorously flowing a gel carrier made of a swellable resin having a network structure in a suspension of microorganisms, and completed the present invention. Specifically, the present invention provides the following.

(1) A biological treatment method for wastewater in which wastewater is introduced into a reaction section holding sludge to perform biological treatment, and an effluent from the reaction section is introduced into a separation section to perform solid-liquid separation. A wastewater biological treatment method in which a swellable resin carrier having the above is added to the reaction part, and the swellable resin carrier is flowed with an LV in the separation part of 2 m / hr or more.
(2) The biological treatment method of waste water according to (1), wherein gas is supplied to the reaction part at a ventilation rate of 0.03 m / s or more to flow the swellable resin carrier.
(3) The carrier is a water-insoluble gel carrier mainly composed of polyacrylic acid or polyalkylene oxide, and absorbs water in the range of pH 3 to 10 to increase the apparent volume by 20 times or more. The biological treatment method for wastewater according to (1) or (2), wherein the microorganism is retained after being added and mixed with sludge.
(4) A treatment tank configured such that a partition plate is disposed therein to form a reaction portion and a separation portion, and the reaction portion and the separation portion communicate with each other through an opening formed in a lower portion of the partition plate. A raw water pipe for supplying wastewater to the treatment tank, a swellable resin carrier having a network structure and added to the reaction part, a gas supply means for supplying gas to the reaction part and causing the carrier to flow, And a wastewater biological treatment apparatus configured to supply the wastewater so that at least the raw water pipe has an LV of 2 m / hr or more in the separation unit.

  According to the present invention, a compact biofilm can be supported on a gel carrier obtained by granulating a swellable resin, thereby improving the sedimentation property. Therefore, solid-liquid separation can be facilitated even if the particle size of the adhesive gel carrier is reduced.

  Hereinafter, the present invention will be described in detail with reference to the drawings. Hereinafter, the same members are denoted by the same reference numerals, and description thereof is omitted or simplified.

  FIG. 1 is a schematic cross-sectional view of a biological treatment apparatus 1 used in the biological treatment method for wastewater according to the first embodiment of the present invention. The biological treatment apparatus 1 is configured around a single treatment tank 10 in which the interior is partitioned by a partition plate 15 and two chambers are provided. One of the chambers partitioned by the cut plate 15 is a reaction unit 11 and the other is a separation unit 12. A raw water pipe 31 is connected to the reaction unit 11, and a treated water pipe 33 is connected to the separation unit 12.

  Another partition plate (hereinafter “deposition plate”) 18 is disposed in the reaction unit 11. The upper edge position of the partition plate 15 is higher than the upper edge position of the deposition plate 18, and the liquid level of the processing tank 10 is configured to be located below the upper edge of the partition plate 15. It is preferable that the partition plate 15 has a lower edge above the bottom surface of the processing tank 10. Thereby, the lower part of the partition plate 15 becomes an opening, and the reaction unit 11 and the separation unit 12 communicate with each other below the partition plate 15.

  The depositing plate 18 is arranged to smoothly circulate the carrier 35 added to the reaction unit 11. Hereinafter, among the parts of the reaction part 11 partitioned by the sedimentation plate 18, the part close to the raw water pipe 31 is called the raw water inflow part 11A, and the other part is called the circulation part 11B. The depositing plate 18 is preferably arranged so that its upper edge is below the liquid level and its lower edge is above the bottom surface of the treatment tank 10. Accordingly, the raw water inflow portion 11A and the circulation portion 11B communicate with each other between the upper edge of the sedimentation plate 18 and the lower edge thereof.

  A diffuser pipe 16 is disposed below the raw water inflow portion 11A near the bottom of the treatment tank 10 as a diffuser. The carrier 35 is flowed by the movement of the liquid in the tank of the reaction unit 11 and the blowing of gas from the diffuser tube 16. The carrier 35 is an adhesive gel carrier obtained by molding a water-absorbing resin into fine particles. The carrier 35 absorbs liquid in the reaction unit 11 and swells, and microorganisms are supported on the internal network structure or on the surface of the carrier. Is.

  The carrier 35 is not particularly limited as long as it does not dissolve in water and can retain its individual shape without losing its outer edge even when it absorbs water and expands, and a known gel carrier material made into fine particles is used. be able to. Examples of the material resin for the gel carrier include PVA, PEG, (poly) acrylamide, N-substituted acrylamide, (poly / meth) acrylic acid or an alkali metal salt thereof, alginic acid, polyalkylene oxide, dimethylaminoethyl (meth) acrylate (DAM). ), Diacetone alcohol (DAA), polyalkylene oxide and the like. More specifically, sodium polyacrylate, copolymer of sodium acrylate and acrylamide, copolymer of sodium acrylate and sodium acrylamide 2-methylpropanesulfonate, sodium acrylate, acrylamide and sodium acrylamide 2-methylpropanesulfonate And terpolymers of dimethylaminoethyl (meth) acrylate and homopolymers of quaternary ammonium or copolymers with acrylamide and the like.

  The above resin is polymerized by a known method, for example, a method disclosed in Patent Document 1, Japanese Patent Publication No. 3-80803, and the like to produce a carrier used in the present invention. Specific examples include a method of drying a gel-like reaction product obtained by carrying out normal aqueous solution polymerization, cutting and pulverizing to form fine particles. The polymerization may be photopolymerization or thermally initiated polymerization. According to reverse phase emulsion polymerization, a fine particle polymer gel is obtained directly from the polymerization solution. Furthermore, after conducting suspension polymerization using a paraffinic oil, an aliphatic organic solvent, or an aromatic organic solvent as a dispersion medium, the polymer is separated from the dispersion medium and dried to obtain fine particles of a polymer gel. it can. You may add a chain transfer agent as needed at the time of superposition | polymerization.

  The carrier 35 obtained by using the above material is insoluble in water and expands by forming a network structure without losing its shape even in water. The carrier 35 used in the present invention does not contain microorganisms in the production process like the entrapping immobilization gel carrier, but after absorbing water, it mixes with activated sludge and flows to retain the microorganisms. Is. Therefore, it is manufactured more easily and at a lower cost than the entrapping immobilization gel carrier.

  As the carrier 35, it is preferable to use a carrier having a network structure that absorbs water in a pH range of 3 to 10 and has an apparent specific gravity of 20 times or more of its own weight. In particular, it is preferable that the size is about 5 mm or less in size (including spheres) when absorbing liquid (particularly water) 30 to 1,000 times its own weight. It is preferable that the carrier 35 is adjusted and used so as to have a size of 5 mm or less, particularly about 1 mm, specifically about 0.5 to 1.5 mm in the reaction unit 11. If the particle size is too large, oxygen is not supplied to the inside of the carrier 35 when the aerobic treatment is performed, and the rate of biodegradation is reduced by oxygen rate control. In addition, since the surface area per volume is reduced, the amount of organisms retained per resin is also reduced, leading to a decrease in the biodegradation rate. When anaerobic treatment is performed, nitrogen gas or the like generated by a biological reaction is difficult to escape from the carrier 35, so that the carrier 35 rises.

  In addition, the carrier 35 preferably has a mesh having a mesh size of about 1 μm or more in a state after being charged into the reaction unit 11 (for example, in a state where water of about 100 to 1,000 times its own weight is absorbed). By setting the network size of the network structure to about 1 μm or more, bacteria can easily enter the network, so that the adhesion and growth of microorganisms are improved, and in particular, the start-up time at the start of operation can be shortened. However, the carrier used in the present invention may be a gel carrier made of a water-absorbing resin that does not dissolve in water and maintains a granular shape even after water absorption, and a carrier having a small mesh size can be used. When the mesh size is small, microorganisms do not enter the inside of the carrier 35, but the microorganisms are held on the surface of the carrier 35.

  The addition amount of the carrier 35 is preferably such that the addition ratio in the state after being introduced into the reaction part 11 and absorbing water is 5 to 70%, particularly 20 to 50% of the reaction part 11 as a volume ratio. . If the added amount of the carrier 35 is too small, the microorganisms are not sufficiently retained in the reaction section 11, and if it is too large, the carrier 35 cannot be fluidized sufficiently.

  The specific gravity of the carrier is desirably 0.95 to 1.1 g / ml, particularly 1.00 to 1.05 g / ml. If the specific gravity is too low, there is a problem that the carrier floats, and if it is too heavy, it is expected that the carrier will easily sink to the bottom of the reaction vessel. In order to appropriately maintain the specific gravity, it is possible to add a substance that supplies a divalent cation to crosslink the gel carrier. For example, the carrier 35 may be added to the reaction unit 11 and then cross-linked in a state where bacteria enter the mesh. When the gel carrier has polyacrylic acid as the main structure, the carboxyl groups are cross-linked by introducing a divalent or higher cation such as calcium or magnesium. Therefore, it is possible to change the specific gravity of the gel carrier by adding a substance that supplies a divalent or higher cation.

  Since the carrier 35 before being added to the reaction unit 11 does not normally contain water and absorbs water after the addition to the reaction unit 11 and expands, the addition amount of the carrier 35 is determined in consideration of the expansion. For example, when the carrier 35 that absorbs water about 10 times its own weight and expands about 10 times is added so that the addition rate in the reaction unit 11 is 40% by volume, the reaction unit 11 volume 4% of the carrier 35 may be added. Therefore, since the amount of the carrier 35 (that is, before water absorption) to be added to the reaction unit 11 is small, the amount of the carrier 35 used is small, and the addition cost can be reduced.

  The carrier 35 as described above is added to the reaction unit 11, and wastewater containing organic matter, nitrogen and the like is introduced into the reaction unit 11 as raw water, and biological treatment is performed while the carrier 35 is flowing. In the present invention, the carrier 35 is vigorously fluidized so that sparse and weakly adhering microorganisms are washed out without being held by the carrier 35, and the firmly attached and compact sludge is carried on the carrier 35.

  In order to cause the carrier 35 to flow vigorously, the liquid in the reaction unit 11 may be vigorously disturbed, and it is not excluded to stir the reaction unit 11 with a stirrer, but the water flow rate to the treatment tank 10 can be increased. That's fine. Further, the amount of ventilation to the reaction unit 11 may be increased.

  In order to increase the water flow rate, it is preferable to perform water flow at a high speed such that the LV of the separation unit 12 is 2 m / hr or more with the water flow rate of the separation unit 12 as a guide. In the treatment tank 10, if the LV of the separation unit 12 is increased, the water flow rate in the reaction unit 11 will inevitably increase, and the carrier 35 will flow violently. Since the LV of the separation unit 12 is about 0.4 to 0.6 m / hr in a general waste water treatment facility, if the LV is set to 2 m / hr or more, the floating sludge having low adhesion is not held in the carrier 35, Instead, high-pressure sludge is retained. In particular, if the separation unit 12 has an LV of about 3 to 6 m / hr, the carrier 35 flows moderately and retains sludge having high density and good sedimentation.

  On the other hand, in order to increase the amount of ventilation to the reaction unit 11 to flow the carrier 35 and granulate high density sludge, the ventilation rate of the gas supplied to the reaction unit 11 is set to 0.03 m / s or more. . A preferable range of the aeration rate is 0.04 to 0.1 m / s. If the aeration rate is too high, the biofilm formed on the carrier 35 is excessively peeled, and the granulation is performed using the carrier 35 as a nucleus. The sludge may be damaged.

  If the water to be treated is introduced from the raw water pipe 31 to the reaction unit 11 so that the LV of the separation unit 12 falls within the above range, microorganisms with poor adhesion are not retained on the carrier 35, and microorganisms with high adhesion are retained on the carrier 35. Be dominant. Therefore, if the LV of the separation unit 12 is increased, the microorganisms can be tightly held on the carrier 35, and the amount of ventilation through the diffuser 16 is not limited.

  However, if the aeration amount in the reaction unit 11 is increased and the LV of the separation unit 12 is increased, the carrier 35 with better sedimentation can be obtained. For this reason, even if LV is 6 m / hr or more, it is possible to prevent the biofilm 35 from being detached from the carrier. Therefore, the biological treatment apparatus 1 can be operated with a high load of LV 10 m / hr or more.

  Hereinafter, a flow of biological treatment performed under the condition that the carrier 35 is disturbed by the above-described method will be described. Water to be treated is introduced into the reaction unit 11 from the raw water pipe 31 and descends through the raw water inflow portion 11A. On the other hand, the carrier 35 is wound up by receiving diffused air from the diffuser 16 at the raw water inflow portion 11A. In this way, the carrier 35 and the water to be treated are mixed and stirred in the reaction section 11, the organic matter contained in the water to be treated is decomposed by the microbial sludge held in the reaction section 11, and the microorganisms grow. In the present invention, microorganisms adhere tightly to the carrier 35 by causing the carrier 35 to flow vigorously. The reason why the microorganisms adhere firmly to the carrier 35 by vigorously flowing the carrier 35 may be influenced by the high contact speed between the microorganisms and the carrier 35, but is not certain.

  The carrier 35 ascends the raw water inflow portion 11A and enters the circulation portion 11B beyond the upper edge of the sedimentation plate 18. Since no gas is supplied to the circulation part 11B, the carrier 35 naturally settles and accumulates on the bottom of the treatment tank 10. The processing tank 10 is configured so that the side wall is inclined inward as it goes to the bottom surface, and the carrier 35 and sludge descending near the side wall are collected at the center of the processing tank 10 and accumulated on the bottom surface.

  Since raw water is introduced into the raw water inflow portion 11A, the liquid component that has passed through the circulation portion 11B does not enter the raw water inflow portion 11A but enters the separation portion 12 through the lower edge of the partition plate 15. The carrier 35 and sludge (solid content) contained in the liquid flowing out from the circulation part 11B settled in the process of the mixed liquid ascending the separation part 12, and the clarified treated water was connected to the upper part of the treatment tank 10. It is taken out from the treated water pipe 33.

  In the present invention, by vigorously flowing the carrier 35, the density of the biofilm held on the carrier 35 is increased and the sedimentation property of the carrier 35 is improved. For this reason, the particle size of the carrier 35 can be made small so as to take advantage of the characteristics of the gel carrier having a network structure, and the outflow of the carrier 35 can be prevented. In addition, the strength of the carrier 35 can be increased by causing sludge to adhere to the carrier 35 densely.

  In particular, when the biological treatment apparatus 1 in which the reaction unit 11 and the separation unit 12 communicate with each other at the lower part is used, it is not necessary to return the carrier 35 separated from the liquid component to the reaction unit 11 with a pump. Furthermore, it is not necessary to provide a screen to prevent the carrier 35 from flowing out of the reaction section 11.

  In addition, this invention can also be implemented with the biological treatment apparatus which comprised the reaction part and the separation part by a separate tank, and connected both with piping. Specifically, an aeration tube is arranged in the first tank to form a reaction part (biological treatment tank), and a second tank (precipitation tank) is provided as a separation part in the subsequent stage. Connect with piping. The treated water pipe is connected to the sedimentation tank, and the raw water pipe is connected to the biological reaction tank. In addition, one end of a drawn tube for taking out the separated carrier and sludge is connected to the settling tank, and the other end is connected to the biological reaction tank. Then, the carrier and sludge separated from the liquid in the sedimentation tank are returned from the drawing tube to the biological reaction tank.

  Since the carrier has a high sedimentation property and is well separated in the sedimentation tank, it is not necessary to provide a screen for preventing the carrier from flowing out in the biological reaction tank. In addition, since the particle size of the carrier is small, there is less risk of the biofilm being peeled off by the return pump when the carrier is returned by the drawing tube than when a carrier having a large particle size is used. However, since the biological treatment apparatus 1 in FIG. 1 does not return the carrier 35 with a pump, there is a possibility that the biological film is peeled when the carrier 35 is returned, and the reaction unit and the separation unit are configured as separate tanks. This is surely avoided as compared with the case of using a biological treatment apparatus.

[Example 1]
In Example 1, the biological treatment apparatus 1 shown in FIG. 1 was used. The treatment tank 10 has an effective volume of 30 / L and a water surface area of 360 cm ² . The partition plate 15 was arranged so that the lower edge was positioned at a height of 25 cm from the bottom surface of the treatment tank 10 and the water surface area of the separation unit 12 was 28.3 cm ² . The bottom of the treatment tank 10 was inclined to prevent the volume and blockage of the carrier 35.

  From the raw water pipe 31, simulated waste water in which sodium acetate, polypeptone, yeast extract, and sodium monohydrogen phosphate were mixed with pure water desalted as treated water was introduced into the raw water inflow section 11A. The simulated waste water was adjusted to have a BOD concentration of 600 mg / L, a nitrogen concentration of 40 mg-N / L, and a phosphorus concentration of 8 mg / L.

As an adhesive gel carrier to be added to the reaction part 11, a water-absorbing gel carrier comprising polyacrylic acid as a main component (acrylic acid polymer partial sodium salt cross-linked product: manufactured by Sanyo Chemical Industries, Ltd., trade name "Aqua Pearl DSC30" ) Was used. The gel carrier was immersed in pure water and used for 12 hours. The average particle diameter of the gel carrier after water absorption was about 2.5 mm, and absorbed about 400 times as much water as its own weight before water absorption. In order to adjust the particle size of the water-absorbed gel carrier, CaCl ₂ · 2H ₂ O was added at a concentration of 1,000 mg / L. As a result, the gel carrier was reduced to an average particle size of 1.2 mm.

  In this way, 9 L of the gel carrier whose particle size has been adjusted by adding calcium after water absorption is added to the reaction unit 11 and floating activated sludge as an inoculum is added to the reaction unit 11 at a concentration of 1,000 mg-VSS / L. Simulated wastewater was passed as raw water. Air was blown into the reaction unit 11 from the air diffuser 16 at a blowing rate of 40 L / min, and the ventilation rate was maintained at 0.037 m / s.

  A pH meter (not shown) was installed in the treatment tank 10 and hydrochloric acid was added to maintain the pH at 7.0 to 7.2, and the water temperature was adjusted to 25 ° C.

  Under the above conditions, first, a batch operation for 3 days was performed as a start-up stage, and then simulated wastewater was supplied to the treatment tank 10 at a flow rate of 1 L / hr and operated for one week. Subsequently, it was operated for 2 weeks at a flow rate of 2.5 L / hr (LV of the separation unit 12 was 2.1 m / hr). By setting the flow rate to 2.5 L / hr, most of the floating sludge added as an inoculum was contained in the treated water and flowed out. On the other hand, in the treatment tank 10, the gel carrier 35 with the biofilm attached thereto was held.

  Therefore, water was passed through the treatment tank 10 at a flow rate of 5 L / hr, and the LV of the separation unit 12 was set to 4.2 m / hr. As a result, 50 days after the start of operation, the biofilm adhered to the carrier 35 was dense, and the carrier 35 became granular sludge having an average diameter of 1.3 mm and granulated microorganisms. This granule was satisfactorily solid-liquid separated in the separation part 12, and the carrier 35 (granule sludge) was not contained in the treated water. However, the treated water contained microorganisms that were not retained on the carrier 35 as an insoluble suspension (SS), and the concentration thereof was 174 mg / L.

The BOD volumetric load on the treatment tank 10 during the period of operation at a flow rate of 5 L / hr was 2.4 kg-BOD / m ³ -d, and the soluble BOD removal rate was 97%.

[Comparative Example 1]
As Comparative Example 1, the water flow rate and simulated drainage for the treatment tank 10 that was operating in Example 1 were changed. Specifically, in Comparative Example 1, the water flow rate to the treatment tank 10 was halved, and the LV of the separation unit 12 was 1.1 m / L. Moreover, in the comparative example 1, the simulated waste_water | drain adjusted so that it might become BOD density | concentration 1200 mg / L, nitrogen density | concentration 80 mg-N / L, and phosphorus density | concentration 16 mg / L was used.

  As a result, two weeks after the start of the experiment of Comparative Example 1, suspended sludge in which microorganisms were flocked was included in the treated water. Moreover, the sedimentation property of the granules was also deteriorated, and the carrier 35 was included in the treated water.

[Example 2]
Next, as Example 2, the processing tank 10 was operated at a higher load. In Example 2, the same apparatus as the biological treatment apparatus 1 of FIG. 1 was used.

  As the raw water supplied from the raw water pipe 31, simulated drainage similar to the raw water used in Example 1 was used. A water-absorbing gel carrier mainly composed of polyalkylene oxide (manufactured by Sumitomo Seika Co., Ltd., trade name “Aqua Coke TWB-PC”) was added to the reaction part 11. . The gel carrier was immersed in pure water and used for 12 hours. The particle diameter of the gel carrier after water absorption was about 1.2 mm, and absorbed about 30 times as much water as its own weight before water absorption.

  In Example 2, 9 L of gel carrier after water absorption was added to the reaction part 11, and activated sludge was added at a concentration of 1,000 mg-VSS / L as an inoculum. In Example 2, air was blown into the reaction unit 11 from the air diffuser 16 at a blowing rate of 40 L / min, and the ventilation rate was maintained at 0.037 m / s. The liquid in the treatment tank 10 was adjusted to pH 7.0 to 7.2 with hydrochloric acid, and the water temperature was adjusted to 25 ° C.

  Under the above conditions, first, a batch operation for 3 days was performed as a start-up stage, and then simulated drainage was supplied to the treatment tank 10 at a water flow rate of 2.5 L / hr (LV 2.1 m / hr of the separation unit 12). Operation continued for a week. At the start-up stage, most of the floating sludge added as an inoculum was contained in the treated water and flowed out. On the other hand, in the treatment tank 10, the gel carrier 35 with the biofilm attached thereto was held.

  Therefore, when the water flow rate to the treatment tank 10 is increased to 5 L / hr and the LV in the separation unit 12 is set to 4.2 L / hr for about 3 weeks, granulated sludge having an average diameter of about 1.3 mm is formed. It was done. This sludge was formed by supporting a biofilm having a high pressure density on the carrier 35, and the SVI (Sludge Volume Index) was 26 ml / g. In addition, SVI shows the volume which 1 g of sludge (MLSS) occupies by ml number, when sludge is left still for 30 minutes.

The BOD volumetric load during the operation period in Example 2 with LV 4.2 m / hr was 2.4 kg-BOD / m ³ / d, and the soluble BOD removal rate was 96%.

Therefore, when the operation was continued by increasing the water flow rate so that the LV of the separation unit 12 was changed from 4.2 m / hr to 12.7 m / hr, the solid-liquid separation property of the granular sludge was maintained well, and the treated water There was no carrier 35 that flowed out. As a result, the operation was performed with a high load of BOD volume load of 7.2 kg-BOD / m ³ / d, and the soluble BOD removal rate was 96%, which was a good treatment.

[Reference Example 1]
As Reference Example 1, a batch operation was performed for 3 days under the same conditions as in Example 2 except that the amount of air blown into the reaction unit 11 was 20 L / min and the aeration rate was reduced to 0.019 m / s. Thereafter, the simulated waste water was supplied to the treatment tank 10 at a water flow rate of 2.5 L / hr for one week to start up. At the start-up stage, most of the floating sludge added as an inoculum flowed out, but the gel carrier 35 to which the biofilm adhered was retained in the treatment tank 10.

  Therefore, when the amount of water flowing into the treatment tank 10 was increased and the LV in the separation unit 12 was operated at 4.2 m / hr for about 3 weeks, the microorganisms on the surface of the carrier 35 became sparse compared to Example 2, and the carrier 35 The diameter of the granular sludge having the core is about 2 to 4 mm. The SVI of this sludge was 63 ml / g. Next, when the operation was continued by increasing the water flow rate so that the LV of the separation unit 12 was changed from 4.2 m / hr to 12.7 m / hr, solid-liquid separation in the separation unit 12 was not performed well, and the carrier About half of 35 was contained in the treated water and flowed out.

Table 1 shows the processing conditions and results for Example 2 and Reference Example 1. In the table, “*” represents that measurement was impossible due to carrier outflow.

  As shown in Reference Example 1, when the air flow rate was low, the density of the biofilm held by the carrier 35 was lowered and the carrier 35 flowed out when the LV was set to an extremely high LV exceeding 10 m / L. On the other hand, as shown in Example 2, when the ventilation rate is set to 0.03 m / s or more, the carrier 35 can be densified even when the LV is set to 10 m / L or more, and a favorable treatment can be performed.

  The present invention can be used for biological treatment of wastewater.

The schematic diagram of the biological treatment apparatus which concerns on one Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Biological treatment apparatus 10 Processing tank 11 Reaction part 12 Separation part 15 Partition plate 16 Aeration pipe 18 Sedimentation plate 35 Carrier

Claims (4)

A biological treatment method for wastewater that introduces wastewater into a reaction section that holds sludge and performs biological treatment, and introduces an effluent from the reaction section into a separation section to perform solid-liquid separation,
A biological treatment method for wastewater, wherein a swellable resin carrier having a network structure is added to the reaction part, and the swellable resin carrier is flowed with an LV in the separation part of 2 m / hr or more.   The biological treatment method of waste water according to claim 1, wherein gas is supplied to the reaction part at a ventilation rate of 0.03 m / s or more to flow the swellable resin carrier.   The carrier is a water-insoluble gel carrier mainly composed of polyacrylic acid or polyalkylene oxide, absorbs water in the range of pH 3 to 10 and increases its apparent volume by 20 times or more, and is added to the reaction part to add sludge and The biological treatment method of waste water according to claim 1 or 2, wherein microorganisms are retained after mixing. A treatment tank configured to have a partition plate disposed therein, a reaction portion and a separation portion are formed, and the reaction portion and the separation portion communicate with each other through an opening formed in a lower portion of the partition plate;
A raw water pipe for supplying wastewater to the treatment tank;
A swellable resin carrier having a network structure and added to the reaction part;
Gas supply means for supplying gas to the reaction section and causing the carrier to flow,
A biological wastewater treatment apparatus configured to supply the wastewater so that at least the raw water pipe has an LV of 2 m / hr or more in the separation unit.

Images