JP2006055849A - Apparatus and method for treating organic waste water - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve mutually contradictory problems associated with a system for organic waste water treatment through denitrification and nitrification processes, that when the circulating volume from the nitrification tank to the denitrification tank is increased to achieve high removal of nitrogen, the introduction of a nitrified fluid rich in dissolved oxygen to the denitrification tank causes a reduction in denitrification performance of the denitrification tank by providing an apparatus and method for organic waste water treatment through denitrification and nitrification processes, which apparatus and method achieve high removal of nitrogen without reducing the denitrification performance of denitrification tanks. <P>SOLUTION: According to one embodiment of the present invention, the object stated above is achieved by providing the apparatus for treating the organic waste water which comprises at least two stages of treatment tanks in series, each of which includes the denitrification tank and the nitrification tank connected in this order, comprises a pipe for distributing the water to be treated to the denitrification tank in each stage, a means for filtering and separating at least a part of activated sludge mixture water in at least one of the nitrification tanks, and a pipe for supplying to the denitrification tank at least a part of the concentrated sludge mixture water obtained by the filtration and separation treatment. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to sewage treatment, and more particularly to an apparatus and method for denitrifying and nitrifying organic wastewater such as organic industrial wastewater and domestic wastewater by an activated sludge method.

  Conventionally, in the water treatment with activated sludge, in order to obtain purified treated water, it was necessary to perform solid-liquid separation of the activated sludge mixed liquid. Usually, for this purpose, a method is used in which an activated sludge mixed liquid is introduced into a sedimentation basin, the sludge is sedimented by gravity sedimentation, and the supernatant liquid is discharged from the sedimentation basin as treated water. In this case, a sedimentation basin having a sufficient sedimentation area and residence time is necessary to settle the activated sludge, which has been a factor in increasing the size of the processing apparatus and increasing the installation volume. Further, when the activated sludge has deteriorated in sedimentation due to bulking or the like, the sludge has flowed out of the sedimentation basin, leading to deterioration of the treated water.

In the biological nitrogen removal method by denitrification and nitrification, nitrification liquid is circulated from the nitrification tank to the denitrification tank, and NO _x -N (nitrate nitrogen and nitrite nitrogen) in the nitrification liquid is contained in the activated sludge. It is reduced to nitrogen gas by denitrifying bacteria. At this time, the BOD source of the incoming raw water is used as a hydrogen donor for the denitrification reaction. In such a denitrification / nitrification method, in order to obtain a high nitrogen removal rate, it is necessary to increase the amount of circulation from the nitrification tank to the denitrification tank. However, if the circulation amount of sludge having a high dissolved oxygen concentration from the nitrification tank is increased, there arises a problem that the denitrification performance in the denitrification tank, which is an anaerobic tank, decreases due to the introduction of dissolved oxygen.

  On the other hand, a method of performing solid-liquid separation of activated sludge by membrane separation instead of a settling basin has been used for some time. In this case, a microfiltration membrane or an ultrafiltration membrane is generally used as the solid-liquid separation membrane. However, in this method, suction or pressurization by a pump is necessary as a filtration separation means, and filtration is usually performed at a pressure of several tens of kPa to several hundred kPa, so that the power of the pump is large and the running cost increases. Yes. In addition, clear treated water without any SS can be obtained by membrane separation, while the permeation flux is low, and it is necessary to periodically wash the membrane in order to prevent membrane contamination.

  Recently, as a solid-liquid separation method of activated sludge mixed liquid replacing the sedimentation basin, a filter body made of a water-permeable sheet such as woven fabric, non-woven fabric, and metal net-like material is immersed in an aeration tank, and sludge particles are formed on the surface of the filter body. A method has been proposed in which a deposit layer by itself is secondarily formed, and this sludge layer is used as a filtration layer to obtain clear filtered water at a low head pressure. This method is called dynamic filtration, and the filter body itself made of a water-permeable sheet allows sludge particles to pass through. However, the sludge flocs are attached by generating a cross-flow flow of the activated sludge mixed liquid on the surface of the filter body. A kimono layer is secondarily formed on the water-permeable sheet, and this sludge layer functions as a filtration layer (dynamic filtration layer), so that sludge and SS in the liquid to be treated are solid-liquid separated. The thickness of the dynamic filtration layer increases as the filtration time elapses, and as a result, the filtration resistance increases and the filtration flux decreases, but in that case, the dynamic filtration layer is aerated from the air diffuser installed at the bottom of the filter body. After removing the sludge dynamic filtration layer formed on the filter body surface, a stable filtration flux is obtained by forming the dynamic filtration layer again.

  When this dynamic filtration method is applied to the denitrification / nitrification method, a dynamic filtration module is arranged in the nitrification tank, and a solid-liquid separation tank is provided separately from the denitrification tank / nitrification tank, and the dynamic filtration is performed in the solid-liquid separation tank. It is conceivable to arrange the modules. However, in any embodiment, in order to obtain a high nitrogen removal rate, it is necessary to increase the amount of circulation from the nitrification tank to the denitrification tank. There exists a problem that the denitrification performance of a denitrification tank falls.

  In the organic wastewater treatment system by denitrification and nitrification as described above, the nitrification solution with high dissolved oxygen is obtained by increasing the circulation amount from the nitrification tank to the denitrification tank in order to obtain a high nitrogen removal rate. By flowing into the denitrification tank, the denitrification performance of the denitrification tank is reduced and the conflicting problem is solved, and a high nitrogen removal rate can be achieved without reducing the denitrification performance of the denitrification tank. It aims at providing the processing apparatus and method of organic wastewater by nitriding and nitrification.

The present invention has solved the above problems by the following means.
1. An organic wastewater treatment device in which a treatment tank in which a denitrification tank and a nitrification tank are connected in this order is connected in series in two or more stages, and a pipe for dispensing treated water to each stage of the denitrification tank And means for filtering and separating at least a part of the activated sludge mixed liquid in at least one nitrification tank, and a pipe for supplying at least a part of the concentrated sludge mixed liquid obtained by the filtering and separating process to the denitrification tank An organic wastewater treatment apparatus characterized by comprising:

  2. Filtration separation means is installed in the nitrification tank, and at least a part of the concentrated sludge mixed liquid in the nitrification tank concentrated by the filtration separation process is supplied to the denitrification tank. Processing equipment.

  3. A solid-liquid separation tank is arranged, filtration separation means is installed in the solid-liquid separation tank, and at least a part of the concentrated sludge mixed liquid in the solid-liquid separation tank concentrated by the filtration separation process is in the denitrification tank. The apparatus for treating organic waste water according to claim 1 to be supplied.

  4). The organic material according to any one of Items 1 to 3, wherein a dynamic filter body in which a dynamic filtration layer of activated sludge particles is formed on a water-permeable filtration layer support material is used as the filtration separation means. Wastewater treatment equipment.

5. The apparatus according to claim 4, wherein the water-permeable filter layer support material is composed of one or more of a woven material, a non-woven material, and a metal mesh material.
6). At least a part of the activated sludge mixed liquid in the final stage nitrification tank is introduced and returned to the first stage denitrification tank. The organic wastewater treatment apparatus according to any one of Items 1 to 5, further comprising a pipe.

  7). Any one of the above-mentioned items 1 to 6, wherein an absolute anaerobic tank is connected further upstream of the first stage denitrification tank, and a pipe for dispensing treated water is also connected to the absolute anaerobic tank. Organic wastewater treatment equipment as described in 1.

8). The organic wastewater treatment apparatus according to any one of the above items 1 to 7, wherein a carrier capable of adhering biological cells is filled in at least a part of the denitrification tank and the nitrification tank.
9. A method for treating organic wastewater using an organic wastewater treatment apparatus in which a treatment tank in which a denitrification tank and a nitrification tank are connected in this order is connected in series in two or more stages. In addition to dispensing into the stage denitrification tank, at least a part of the activated sludge mixed liquid in at least one nitrification tank is filtered and separated, and at least a part of the concentrated sludge mixed liquid obtained by the filtration and separation process is removed. A method characterized by supplying to a nitrogen bath.

  10. The method according to item 9, wherein the filtration / separation process is performed by a filtration / separation unit installed in the nitrification tank, and at least a part of the concentrated sludge mixed liquid in the nitrification tank concentrated by the filtration / separation process is supplied to the denitrification tank. .

  11. At least a part of the activated sludge mixed liquid in at least one nitrification tank is supplied to the solid-liquid separation tank disposed in the filtration separation means, and the activated sludge mixed liquid is filtered and separated. The method according to claim 9, wherein at least a part of the concentrated sludge mixed liquid in the solid-liquid separation tank concentrated by the step is supplied to the denitrification tank.

  12 The method according to any one of Items 9 to 11, wherein a dynamic filtration body in which a dynamic filtration layer of activated sludge particles is formed on a water-permeable filtration layer support is used as the filtration separation means.

13. The method according to claim 12, wherein the water-permeable filter layer support is composed of one or more of a woven material, a non-woven material, or a metal network material.
14 At least a part of the activated sludge mixed solution in the final stage nitrification tank is introduced into the sedimentation basin, solid-liquid separation treatment is performed, and at least a part of the sedimentation sludge recovered from the sedimentation basin is returned to the first stage denitrification tank. 14. The method according to any one of items 9 to 13.

15. The method according to any one of Items 9 to 14, wherein an absolute anaerobic tank is connected further upstream of the first denitrification tank, and water to be treated is dispensed into the absolute anaerobic tank.
16. The method according to any one of Items 9 to 15, wherein the treatment is performed by filling at least a part of the denitrification tank and the nitrification tank with a carrier to which biological cells can adhere.

According to the present invention, when performing treatment of organic wastewater using an organic wastewater treatment apparatus in which a treatment tank in which a denitrification tank and a nitrification tank are connected in this order is connected in series in two or more stages, Water is dispensed into each stage of the denitrification tank, and the activated sludge mixed liquid in the nitrification tank is filtered and separated, and the concentrated sludge mixed liquid obtained by the filtration and separation process is supplied to the denitrification tank, thereby removing the water. in addition to the sludge concentration can be maintained high in the denitrification tank, NO x _-N in nitrifying liquid is supplied to the denitrification tank, because it is reduced to N ₂ than the denitrifying bacteria in the denitrification tank, the treated water NO _x - N is greatly reduced, and the removal rate of TN (Total Nitrogen) is improved. In addition, the filtered sludge mixed solution is filtered and separated to obtain treated water to obtain a concentrated sludge mixed solution, which is supplied to the denitrification tank, so the concentrated sludge mixed solution supplied to the denitrification tank has a dissolved oxygen concentration However, even if this is returned to the denitrification tank, there is a very low risk of denitrification performance degradation due to the dissolved oxygen being brought in.

  As a filtration / separation means for performing the filtration / separation treatment, a conventionally known immersion type membrane separation apparatus can be used. Further, in a preferred embodiment of the present invention, by using a so-called dynamic filtration module as filtration separation means for performing filtration separation treatment of the sludge mixed solution in the nitrification tank, stable filtered water can be obtained at a low head pressure. . These filtration separation means can be immersed and placed in a nitrification tank, for example.

  Further, in another embodiment of the present invention, a solid-liquid separation tank is separately arranged, and the filtration separation means as described above is immersed therein, and the activated sludge mixed liquid in the nitrification tank is placed in the solid-liquid separation tank. A pipe to be supplied is installed, the activated sludge mixed liquid is filtered and separated in a solid-liquid separation tank, and the resulting concentrated sludge mixed liquid can be supplied to the denitrification tank.

  In particular, when using a dynamic filter as a filtration / separation means, a solid-liquid separation tank is arranged as described above, and the activated sludge mixed liquid is allowed to flow in with as little aeration bubbles as possible, and the dynamic filtration process is performed therein. Is preferred. When the dynamic filter body is immersed in the nitrification tank, it is necessary to form a downflow cross-flow flow on the surface of the filter body by the swirling flow by aeration. In some cases, the distance to the filter body is greatly affected, and the result is considerably non-uniform. If the flow of the sludge mixed liquid with respect to the surface of the filter body is not uniform, the sludge dynamic filtration layer formed on the surface cannot have a uniform thickness, and it is difficult to obtain a stable amount of filtered water. In addition, when the dynamic filter is placed in the nitrification tank (aeration tank), a dynamic filtration layer is formed in the presence of aeration bubbles. Under such conditions, the dynamic filtration layer is formed by aeration bubbles. Since it is easy to peel, it may be difficult to maintain filtered water quality. Since the water level in the nitrification tank varies depending on the inflow water volume and aeration air volume, the filtration pressure is unstable due to fluctuations in the water head difference from the subsequent tank, which not only causes fluctuations in the filtration water volume, but also forms on the filter body surface. It also adversely affects the filtration performance of the sludge filtration layer. However, a solid-liquid separation tank is installed separately from the multi-stage denitrification / nitrification tank, the dynamic filter is immersed in this tank, and the activated sludge mixed liquid in the nitrification tank is supplied to the solid-liquid separation tank. By performing filtration separation of the activated sludge mixture by filtration, even if there are fluctuations in the amount of influent raw water, water quality, or changes in activated sludge particle properties, the amount of filtered water does not fluctuate and the water is treated stably with good quality. Is obtained. In addition, when the solid-liquid separation tank is arranged separately in this way, since only the sludge mixed liquid is supplied from the nitrification tank and the treated water is discharged from the nitrification tank, the solid-liquid separation tank The dissolved oxygen inside decreases as it approaches the outlet. That is, the concentrated sludge mixed solution coming out of the solid-liquid separation tank has a dissolved oxygen concentration of almost 0, and even if it is returned to the denitrification tank, there is no concern about a decrease in the denitrification performance due to bringing dissolved oxygen.

  The filtration / separation process can be performed in each stage of the nitrification tank, and the concentrated activated sludge mixed solution obtained by the filtration / separation process can be returned to the denitrification tank of that stage. In this way, since the concentrated activated sludge mixture is supplied to the denitrification tanks at each stage, the concentration of MLSS (Mixed Liquor Suspended Solids) in the denitrification and nitrification tanks is increased. This makes it possible to maintain a high nitrogen removal amount. Furthermore, the nitrification liquid from the former stage nitrification tank (for example, 1C in FIG. 1 described later) is efficiently denitrified by the raw water supplied thereto in the latter stage denitrification tank (2B in FIG. 1). Alternatively, in another embodiment of the present invention, the filtration / separation treatment may be performed only in a part of the nitrification tank, particularly in the subsequent nitrification tank. For example, in only the final stage nitrification tank, the activated sludge mixed liquid in the tank can be subjected to filtration and separation treatment, and the resulting concentrated sludge mixed liquid can be returned to any of the preceding denitrification tanks.

  Furthermore, in another aspect of the present invention, a settling basin is further provided after the nitrification tank of the final stage of the multi-stage denitrification / nitrification tank connected in series, and at least a part of the activated sludge mixed liquid of the final stage is provided. It can introduce | transduce into a sedimentation basin and can perform a solid-liquid separation process. By adopting such a configuration, even if the amount of filtered water at each stage decreases due to fluctuations in raw water volume and water quality, solid-liquid separation in the final stage sedimentation basin is possible. If at least a part of the obtained settled sludge is returned to the first-stage denitrification tank, the MLSS in the denitrification tank can be maintained at a higher concentration, and high denitrification performance can be obtained.

  In each stage of denitrification tank and nitrification tank, the nitrification solution can be filtered and separated from the nitrification tank, and the resulting filtrate can be discharged out of the system as treated water, so that the MLSS in the tank can be maintained at a high concentration. In addition, a great effect is obtained in that the amount of nitrogen removed can be increased and the amount of water can be increased.

  In addition, the same effect is acquired even if it uses any of a nonwoven fabric, a woven fabric, a metal net | network, etc. as a water-permeable support material for dynamic filtration tank formation used in a dynamic filter body. In the case of using a woven fabric or a metal net, those having a small diameter of 50 to 200 μm are suitable. As the filter body shape, a flat type is the center, but a cylindrical type or a hollow type can also be used, and a plurality of filter bodies can be bundled and used as a module filter body.

  In addition, when the concentration of phosphorus in the raw water to be treated is high and biological dephosphorization is required, an absolute anaerobic tank is newly provided before the first denitrification tank, If the return sludge flows into the absolute anaerobic tank, selective growth of polyphosphorus accumulating bacteria (PAO) can be performed in the absolute anaerobic tank, and the phosphorus in the raw water can be ingested by the PAO in the nitrification tank. Therefore, it is possible to remove phosphorus in the raw water. In this embodiment, when a sedimentation basin is arranged after the final stage nitrification tank, the sedimentation sludge recovered in the sedimentation basin can be returned to the absolute anaerobic tank, and the sludge from the final stage treatment tank. Is not returned, at least a part of the sludge mixed liquid in the first-stage denitrification tank can be returned to the absolute anaerobic tank.

An absolute anaerobic tank that can be installed for the purpose of removing such phosphorus refers to a reaction tank in which neither DO (dissolved oxygen) nor NO _x -N exists. Bacteria grow preferentially throughout the biological treatment system. Furthermore, as a result, the phosphorus in the raw water is ingested by the polyline-accumulating bacteria as polyline.

  Furthermore, in the present invention, at least a part of each stage of the denitrification tank and nitrification tank can be filled with a carrier to which biological cells can adhere. By filling such a carrier into the denitrification tank and / or the nitrification tank, the effect of shortening the residence time and reducing the capacity of the reaction tank can be obtained. Examples of the carrier that can be used for this purpose include polymer granular materials having a particle diameter of 2 to 4 mm and sponge materials composed of PEG (polyethylene glycol), PVA (polyvinyl alcohol), and the like.

In the following, various embodiments of the present invention will be described in detail with reference to the drawings.
In FIG. 1, an example of the process of raw | natural water by the processing apparatus of the organic waste_water | drain which concerns on 1 aspect of this invention is shown with a flow sheet.

The organic wastewater treatment apparatus shown in FIG. 1 is configured by connecting a treatment tank in which a denitrification tank B and a nitrification tank C are connected in this order in a plurality of stages. In FIG. 1, three stages of denitrification and nitrification tanks are connected in series in a liquid communication state to constitute an apparatus 1B-1C-2B-2C-3B-3C. In such a treatment apparatus, the inflow raw water 1 is divided into 1A, 2A, and 3A, and is dispensed into the first stage denitrification tank 1B, the second stage denitrification tank 2B, and the third stage denitrification tank 3B. Thereby, the organic matter in the raw water is used as a hydrogen donor for the denitrification reaction, and the denitrification reaction proceeds under anaerobic conditions. The effluent from the first-stage denitrification tank 1B flows into the subsequent first-stage nitrification tank 1C where NH ₄ —N (ammonia nitrogen) is nitrified. Each nitrification tank is provided with an air diffuser 9 connected to an air supply pipe 8, whereby aeration is performed to make the atmosphere in the tank aerobic. The nitrification liquid (activated sludge mixed liquid) in the first nitrification tank 1C is supplied to the first solid-liquid separation tank 1D, where it is filtered by the filtration module in the solid-liquid separation tank 1D, and the first-stage filtered water 1F. Is obtained. The filtered water volume shall be less than the inflow raw water volume. The concentrated sludge mixed liquid after filtration is circulated to the first-stage denitrification tank 1B as the first-stage circulation sludge 1E, where NO _x -N is denitrified. In addition, a part of the nitrification liquid in the first stage nitrification tank 1C is sent to the subsequent second stage denitrification tank 2B.

Similarly, in the second-stage denitrification tank 2B and the second-stage nitrification tank 2C, the sludge mixed liquid in the nitrification tank is supplied to the second-stage solid-liquid separation tank 2D to obtain filtered water 2F and concentration after filtration. The sludge mixed liquid is circulated as the circulating sludge 2E to the second-stage denitrification tank 2B, and NO _x -N in the nitrification liquid is denitrified. Similarly, in the third-stage denitrification tank 3B and the third-stage nitrification tank 3C, the nitrification liquid is supplied to the solid-liquid separation tank 3D for filtration, and the obtained concentrated sludge mixed liquid is used as the circulating sludge 3E. Circulate to the stage denitrification tank 3B.

  The amount of filtered water obtained by the first to third solid-liquid separation tanks is smaller than the amount of inflow raw water. In the system shown in FIG. 1, the effluent 4 of the third stage nitrification tank 3 </ b> C, which is the final stage, flows into the subsequent sedimentation basin 5 and is concentrated by sedimentation, and supernatant water is obtained as treated water 6. The sedimentation sludge (concentrated sludge) collected in the sedimentation basin 5 is returned to the first denitrification tank 1B as the return sludge 7.

  As the filtration separation means installed in the solid-liquid separation tank, an immersion type membrane separation apparatus known in the art can be used, or a so-called dynamic filtration module can be used. When a dynamic filtration module is used, stable filtered water can be obtained at a low head pressure. In addition, when installing a dynamic filtration module in a solid-liquid separation tank, a means for forming a cross-flow flow of sludge mixed liquid along the surface of the filtration layer support material in the solid-liquid separation tank is particularly necessary. Rather, the flow rate during the passage of the circulating sludge is sufficient to form a dynamic filtration layer. Moreover, when arrange | positioning a dynamic filtration module in a solid-liquid separation tank, it is preferable to arrange | position the diffuser pipe | tube for air washing | cleaning of a dynamic filter body in a tank.

  FIG. 1 shows an example in which the settling basin 5 is disposed after the final nitrification tank, but the settling basin 5 may not be disposed after the final nitrification tank. The filtered water obtained from the stage solid-liquid separation tank is recovered as treated water. When the sedimentation basin 5 is not provided, the total amount of filtered water in each solid-liquid separation tank is adjusted to the same level as the amount of raw water flowing in.

  The filtration operation in the solid-liquid separation tank can be performed with one or two of them depending on the inflow raw water amount, the water quality and the quality of the treated water, and from the third solid-liquid separation tank 3D. The circulating sludge 3E can also be circulated to the first-stage or second-stage denitrification tanks 1B, 2B. When a high nitrogen removal rate is required, it is desirable to circulate the circulating liquid in the third stage solid-liquid separation tank 3D to the first stage denitrification tank 1B.

  As another embodiment of the present invention, FIG. 2 shows a configuration example of an organic wastewater treatment apparatus in which filtration separation means is immersed in a nitrification tank. In the organic wastewater treatment apparatus shown in FIG. 2, filtration separation means 1G, 2G, and 3G are immersed in the first stage nitrification tank 1C, the second stage nitrification tank 2C, and the third stage nitrification tank 3C, respectively. Yes. Other configurations are the same as those of the apparatus shown in FIG. Filtration water 1F, 2F, and 3F are obtained by the filtration separation means arranged soaked in each nitrification tank. In addition, the concentrated sludge mixed solution after filtration is returned from each nitrification tank to the same denitrification tank (1H, 2H, 3H). As a filtration separation means immersed in each nitrification tank, a conventionally known immersion membrane separation apparatus can be used, or a so-called dynamic filtration module can be used. When the dynamic filtration module is used, the dynamic filtration module is arranged apart from the aeration device 9 arranged in the nitrification tank, and the cross flow is directed downward along the surface of the dynamic filtration module by aeration from the aeration device. It is preferred that a flow be formed. By arranging in this way, the dynamic filtration layer can be stably formed without peeling off the dynamic filtration layer by aeration.

  In addition, when using a dynamic filtration module as a filtration separation means, the filtrate obtained by a dynamic filtration module may be once supplied to another sedimentation basin, and the supernatant liquid obtained from it may be collect | recovered as treated water.

  If the concentration of phosphorus in the raw water is high and the biological dephosphorization process is required to be performed together, an absolute anaerobic tank will be newly installed in front of the first stage denitrification tank. It is possible to remove phosphorus in raw water by incorporating a method that allows a part and return sludge to flow into an absolute anaerobic tank. 3 and 4 show a configuration example of an apparatus in which an absolute anaerobic tank is newly provided before the first stage denitrification tank.

  The apparatus shown in FIG. 3 has the same configuration as the apparatus shown in FIG. 1 except that an absolute anaerobic tank 10 is newly provided upstream of the first stage denitrification tank 1B. In this case, the returned sludge from the final sedimentation tank 5 is supplied to the absolute anaerobic tank 10. The raw water 1 is also dispensed into the absolute anaerobic tank 10 by the branch pipe 10A. In the apparatus shown in FIG. 3, the raw water 1 is not dispensed into the first-stage denitrification tank 1B. Moreover, the apparatus shown in FIG. 4 is the same structure as the apparatus shown in FIG. 2 except that an absolute anaerobic tank 10 is newly provided in the previous stage of the first stage denitrification tank 1B.

The present invention will be specifically described below with reference to examples. However, the present invention is not limited to this example.
Example 1
The collective groundwater was treated by the organic wastewater treatment apparatus shown in FIG.

Table 1 shows the processing conditions of this example.
5 m ³ / d of raw water was dispensed and supplied to each of the first to third denitrification tanks 1B, 2B and 3B. The amount of circulating sludge from each stage of the solid-liquid separation tank to each stage of the denitrification tank was 15 m ³ / d. First stage to third-stage solid-liquid separation tank 1D, respectively 2D, filtered water obtained from 3D was a 4m ³ /d,4.5m ³ / d and 5 m ³ / d. 2 m ³ / d return sludge was returned from the settling basin 5 to the first stage denitrification tank 1B. MLSS in the first stage denitrification / nitrification tank was 4000 mg / L. The denitrification tank and the nitrification tank MLSS in the second and subsequent stages were 3500 mg / L.

In this example, in each of the first to third solid-liquid separation tanks, three planar water-permeable filter bodies having an effective filtration area of 0.6 m ² / sheet are immersed in the solid-liquid separation tank as a filter body module. installed. A polyester woven cloth having a thickness of about 0.1 mm and a pore diameter of 114 μm was used as the water-permeable filter. The sludge dynamic filtration layer was formed on the filter body surface by setting the water head pressure at the time of filtration to about 10 cm and the cross flow velocity of the sludge mixed liquid on the filter body surface to 0.015 m / s on average. .

  The filtration operation was stopped at a rate of once per 2 hours of filtration operation, and the dynamic filter was washed. First, the outside of the filter body is cleaned by air bubbles by aeration from an air diffuser arranged below the filter body, and then water is injected into the filter body to inject the inside of the filter body. Was washed (backwashing with water). After the water backwash, normal filtration operation was performed, but the filtered water was returned to the denitrification tank as sludge (waste mud) without collecting the filtered water during the predetermined drainage time. .

  Table 2 shows the processing conditions of the solid-liquid separation tank.

FIG. 5 shows the average filtration flux progress of the first to third solid-liquid separation tanks in this example.
In operation for about 2 months from the start of the treatment, the filtration flux was about 2.7 m / d, and a stable treatment was obtained.

Table 3 shows the average water quality of raw water and all treated water. Here, the “average water quality of all the treated water” is the average value of the water quality values of the filtered water and the settling basin effluent of each stage of the solid-liquid separation tank.
The SS of inflow raw water was 120 mg / L, whereas the total treated water SS was 5.6 mg / L.

On the other hand, NH ₄ -N of the influent raw water was 45 mg / L by nitrification denitrification treatment, whereas NH ₄ -N of the total treated water was 0.5 mg / L, indicating that almost complete nitrification was performed. It was done. Further, _NO x -N total treated water was 5.0 mg / L. TN was 62 mg / L for raw water, but 7.5 mg / L for all treated water, and a removal rate of about 88% was obtained.

Example 2
The collective groundwater was treated with an organic wastewater treatment apparatus shown in FIG.
Table 4 shows the processing conditions of this example.

5m ³ / d of raw water was dispensed and supplied to the absolute anaerobic tank 10, the second and third denitrification tanks 2B and 3B, respectively. The amount of circulating sludge from each stage of the solid-liquid separation tank to each stage of the denitrification tank was 15 m ³ / d. First stage to third-stage solid-liquid separation tank 1D, respectively 2D, filtered water obtained from 3D was a 4m ³ /d,4.5m ³ / d and 5 m ³ / d. 2 m ³ / d return sludge was returned from the sedimentation basin 5 to the absolute anaerobic tank 10. The MLSS of the mixed solution in the absolute anaerobic tank 10 was 4000 mg / L. The denitrification tank and nitrification tank MLSS after the second stage were 3500 mg / L.

In this example, in each of the first to third solid-liquid separation tanks, three planar water-permeable filter bodies having an effective filtration area of 0.6 m ² / sheet are immersed in the solid-liquid separation tank as a filter body module. installed. A polyester woven cloth having a thickness of about 0.1 mm and a pore diameter of 114 μm was used as the water-permeable filter. The sludge dynamic filtration layer was formed on the filter body surface by setting the water head pressure at the time of filtration to about 10 cm and the cross flow velocity of the sludge mixed liquid on the filter body surface to 0.015 m / s on average. .

  The filtration operation was stopped at a rate of once per 2 hours of filtration operation, and the dynamic filter was washed. First, the outside of the filter body is cleaned by air bubbles by aeration from an air diffuser arranged below the filter body, and then water is injected into the filter body to inject the inside of the filter body. Was washed (backwashing with water). After the water backwash, normal filtration operation was performed, but the filtered water was returned to the denitrification tank as sludge (waste mud) without collecting the filtered water during the predetermined drainage time. .

  Table 5 shows the processing conditions of the solid-liquid separation tank.

In operation for about 2 months from the start of the treatment, the filtration flux was about 2.7 m / d, and a stable treatment was obtained.
Table 6 shows the average water quality of raw water and all treated water. Here, the “average water quality of all the treated water” is the average value of the water quality values of the filtered water and the settling basin effluent of each stage of the solid-liquid separation tank.

The SS of the influent raw water was 120 mg / L, whereas the total treated water SS was 6.5 mg / L. By providing the absolute anaerobic tank 10, it is possible to grow polyline-accumulating bacteria, and as a result, TP (total phosphorus) of raw water was 4 mg / L, whereas TP of total treated water was Was 0.8 mg / L. Moreover, in the absolute anaerobic tank 10, the phosphorus concentration (PO ₄ -P) was 25 mg / L due to the presence of polyline accumulating bacteria.

On the other hand, NH ₄ -N of the influent raw water was 45 mg / L by nitrification denitrification treatment, whereas NH ₄ -N of the total treated water was 0.5 mg / L, indicating that almost complete nitrification was performed. It was. Further, _NO x -N total treated water was 5.0 mg / L. TN was 62 mg / L for raw water, but 7.5 mg / L for all treated water, and a removal rate of about 88% was obtained.

Industrial applicability

According to the present invention, two or more stages of treatment tanks in which a denitrification tank and a nitrification tank are connected in this order are connected in series, and water to be treated is dispensed into each stage of the denitrification tank, and the activity in the nitrification tank is By filtering and separating the sludge mixed liquid and returning the obtained concentrated sludge mixed liquid to the denitrification tank, the sludge concentration in the denitrification tank can be kept high, and NO _x -N in the nitrification liquid is supplied to the denitrification tank. Since this is reduced to N ₂ by denitrifying bacteria in the denitrification tank, the NO _x -N of the treated water is greatly reduced, and the removal rate of TN is improved.

  In addition, the filtered sludge mixed solution is filtered and separated to obtain treated water to obtain a concentrated sludge mixed solution, which is supplied to the denitrification tank, so the concentrated sludge mixed solution supplied to the denitrification tank has a dissolved oxygen concentration However, even if this is returned to the denitrification tank, there is a very low risk of denitrification performance degradation due to the dissolved oxygen being brought in.

  Furthermore, in one form of the present invention, the activated sludge mixed liquid in the nitrification tank is supplied to the solid-liquid separation tank in which the filtration means is immersed, so that the amount of raw inflow water, fluctuations in water quality and activated sludge particle properties Even if there is a change in water, the amount of filtered water does not fluctuate, and treated water with good quality can be obtained stably.

  Furthermore, in a preferred embodiment of the present invention, by disposing a sedimentation basin after the final nitrification tank, solid-liquid separation in the sedimentation basin is possible even if the amount of filtered water decreases due to fluctuations in raw water volume and water quality. is there. Moreover, since most of the treated water is discharged as filtered water by the filtering means at each stage, the amount of water flowing into the settling basin is small and the return sludge concentration is high. Therefore, if this sludge is returned to the denitrification tank, the MLSS in the denitrification tank can be maintained at a high concentration, and high denitrification performance can be obtained.

  In each denitrification tank and nitrification tank, the sludge mixed liquid in the nitrification tank is filtered by a filtration means and the filtrate water is discharged outside the tank, so that the MLSS in the tank can be maintained at a high concentration, and the amount of nitrogen removal is increased. A great effect is obtained such that it can cope with an increase in the amount of water.

It is a conceptual diagram of the processing apparatus of the organic waste_water | drain which concerns on 1 aspect of this invention. It is a conceptual diagram of the processing apparatus of the organic waste_water | drain which concerns on the other aspect of this invention. It is a conceptual diagram of the processing apparatus of the organic waste_water | drain which concerns on the other aspect of this invention. It is a conceptual diagram of the processing apparatus of the organic waste_water | drain which concerns on the other aspect of this invention. It is a graph which shows the average filtration flux progress of the solid-liquid separation tank in the Example of this invention.

Claims (16)

An organic wastewater treatment device in which a treatment tank in which a denitrification tank and a nitrification tank are connected in this order is connected in series in two or more stages, and a pipe for dispensing treated water to each stage of the denitrification tank And means for filtering and separating at least a part of the activated sludge mixed liquid in at least one nitrification tank, and a pipe for supplying at least a part of the concentrated sludge mixed liquid obtained by the filtering and separating process to the denitrification tank An organic wastewater treatment apparatus characterized by comprising: The organic wastewater treatment according to claim 1, wherein filtration separation means is installed in the nitrification tank, and at least a part of the concentrated sludge mixed liquid in the nitrification tank concentrated by the filtration separation process is supplied to the denitrification tank. apparatus. A solid-liquid separation tank is arranged, filtration separation means is installed in the solid-liquid separation tank, and at least a part of the concentrated sludge mixed liquid in the solid-liquid separation tank concentrated by the filtration separation process is in the denitrification tank. The organic wastewater treatment apparatus according to claim 1 to be supplied. The organic wastewater treatment apparatus according to any one of claims 1 to 3, wherein a dynamic filter body in which a dynamic filtration layer is formed on a water-permeable filtration layer support material is used as the filtration separation means. The apparatus according to claim 4, wherein the water-permeable filter layer support material is composed of one or more of a woven material, a non-woven material, and a metal mesh material. A sedimentation basin for introducing at least part of the activated sludge mixed solution in the final stage nitrification tank and solid-liquid separation, and a pipe for returning the sedimentation sludge recovered from the sedimentation tank to the first stage denitrification tank are further provided. The organic wastewater treatment apparatus according to any one of claims 1 to 5. The absolute anaerobic tank is further connected to the first stage of the denitrification tank of the first stage, and a pipe for dispensing treated water is also connected to the absolute anaerobic tank. Organic wastewater treatment equipment. The organic wastewater treatment apparatus according to any one of claims 1 to 7, wherein a carrier capable of adhering to biological cells is filled in at least a part of the denitrification tank and the nitrification tank. A method for treating organic wastewater using an organic wastewater treatment apparatus in which a treatment tank in which a denitrification tank and a nitrification tank are connected in this order is connected in series in two or more stages. In addition to dispensing into the stage denitrification tank, at least a part of the activated sludge mixed liquid in at least one nitrification tank is filtered and separated, and at least a part of the concentrated sludge mixed liquid obtained by the filtration and separation process is removed. A method characterized by supplying to a nitrogen bath. The method according to claim 9, wherein the filtration / separation process is performed by a filtration / separation unit installed in the nitrification tank, and at least a part of the concentrated sludge mixed liquid in the nitrification tank concentrated by the filtration / separation process is supplied to the denitrification tank. At least a part of the activated sludge mixed liquid in at least one nitrification tank is supplied to the solid-liquid separation tank disposed in the filtration separation means, and the activated sludge mixed liquid is filtered and separated. The method according to claim 9, wherein at least a part of the concentrated sludge mixed liquid in the solid-liquid separation tank concentrated by is supplied to the denitrification tank. The method according to any one of claims 9 to 11, wherein a dynamic filtration body in which a dynamic filtration layer is formed on a water-permeable filtration layer support material is used as the filtration separation means. The method according to claim 12, wherein the water-permeable filter layer support is composed of one or more of a woven material, a non-woven material, or a metal network material. 9. At least a part of the activated sludge mixed liquid in the final stage nitrification tank is introduced into the settling basin, solid-liquid separation treatment is performed, and the settling sludge collected from the settling basin is returned to the first stage denitrification tank. 14. The method according to any one of 13. The method according to any one of claims 9 to 14, wherein an absolute anaerobic tank is connected further upstream of the first stage denitrification tank, and water to be treated is dispensed into the absolute anaerobic tank. The method according to any one of claims 9 to 15, wherein the treatment is performed by filling at least a part of the denitrification tank and the nitrification tank with a carrier to which biological cells can adhere.

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