JP5469947B2 - Wastewater treatment method - Google Patents

Description

The present invention relates to a wastewater treatment how.

  Conventionally, in the wastewater treatment method, activated sludge and wastewater are mixed and biologically treated in a biological treatment tank to obtain sludge-containing biologically treated water, and the sludge-containing biologically treated water is solid-liquid separated to obtain purified water.

  By the way, in such a wastewater treatment method, the viewpoint of improving the solid-liquid separability of sludge-containing biologically treated water (the activated sludge sedimentation rate (SV30), which is an indicator of the solid-liquid separability, is usually the sludge volume index (SVI)). The concentration of activated sludge (MLSS concentration) is multiplied. From such a relational expression, it is considered that SV30 can also be reduced when the MLSS concentration is lowered.) From the MLSS concentration of the sludge-containing biologically treated water The BOD load on the activated sludge (BOD sludge load) is usually set to be larger than 0.2 kgBOD / kgSS / d and not more than 0.4 kgBOD / kgSS / d from the viewpoint of processing space efficiency. (For example, Non-Patent Documents 1 and 2).

Sewerage facility planning and design guidelines and commentary Part 2 2001, Japan Sewerage Association, p82-83 Water Treatment Engineering-Theory and Applications-edited by Tetsuo Ide, p25, Gihodo Publishing Co., Ltd., 1976

  However, the conventional wastewater treatment method has a problem that the sludge-containing biologically treated water cannot be sufficiently solid-liquid separated, and the purified water as the solid-liquid separated treated water cannot be sufficiently obtained.

  On the other hand, when the present inventors diligently researched, while making the density | concentration (MLSS density | concentration) of the activated sludge containing sludge containing biological treatment water 10,000 mg / L or more, the load of BOD with respect to activated sludge (BOD sludge load) Was found to be capable of producing sludge-containing biologically treated water having excellent solid-liquid separation properties by adjusting the amount to 0.2 kg BOD / kg SS / d or less.

  By the way, the MLSS concentration of sludge-containing biological treated water is usually 8,000 mg / L or less, and the sludge-containing biological treated water having an MLSS concentration of 10,000 mg / L or more is obtained from the sludge-containing biological treated water having the normal MLSS concentration. In order to obtain it efficiently, a membrane unit is used to increase the activated sludge concentration in a membrane concentration tank as a biological treatment tank by separating the sludge-containing biologically treated water (for example, having an MLSS concentration of 8,000 mg / L or less) into a membrane. It is conceivable to carry out concentration.

However, in such a method, a soluble microbial metabolite (SMP) that is a causative substance of the filter membrane of the membrane unit is concentrated in the membrane concentration tank, and the lytic microbial metabolite is concentrated. (SMP) causes clogging of the filtration membrane.
Then, due to such clogging, the sludge-containing biologically treated water cannot be sufficiently membrane-separated, and it may be difficult to obtain purified water. On the other hand, in order to remove the soluble microbial metabolite (SMP) that clogs the filtration membrane, it is necessary to wash the membrane with chemicals, etc., which takes time and damages the filtration membrane by chemicals, etc. Problems can also arise.

  In view of the above-mentioned problems, the present invention provides a wastewater treatment method and a wastewater treatment apparatus that are less likely to clog a filtration membrane while obtaining sludge-containing biologically treated water that is excellent in solid-liquid separation by membrane separation. Is an issue.

The present invention is a wastewater treatment method in which activated sludge and wastewater are mixed and biologically treated in a biological treatment tank to obtain sludge-containing biologically treated water, and purified water is obtained by solid-liquid separation of the sludge-containing biologically treated water. A membrane concentration tank that separates and concentrates sludge-containing biologically treated water by a membrane unit disposed inside or outside the tank, and a storage tank formed to be a separate tank from the membrane concentration tank A waste water supply step of supplying waste water to the membrane concentration tank and the storage tank by adjusting a transfer rate of waste water transferred to each of the membrane concentration tank and the storage tank ; Increased activated sludge concentration to increase MLSS concentration to 10,000 mg / L or higher, BOD load on activated sludge (BOD sludge load) to 0.2 kg BOD / kgSS / d or lower, and MLSS concentration increased Part of the sludge-containing biological treatment water is removed from the membrane concentration tank Out, and exhaust out the total amount of sludge containing biologically treated water is supplied to the container tank is accommodated in the accommodating tank, the sludge containing organisms supplying sludge containing biologically treated water of the housing tank to the solid-liquid separation tank A treated water supply step and a purified water generation step for obtaining purified water as solid-liquid separation treated water by solid-liquid separation in the solid-liquid separation tank, and the solid-liquid separation in the sludge-containing biological treated water supply step The sludge-containing biological treated water supplied to the tank returns a part of the sludge concentrated water separated from the purified water by solid-liquid separation in the solid-liquid separation tank to the storage tank, and the returned sludge concentrated water Is a wastewater treatment method characterized by being biologically treated in addition to the sludge-containing biologically treated water discharged from the membrane concentration tank and supplied to the storage tank .

According to such a wastewater treatment method, sludge-containing biologically treated water having excellent solid-liquid separation properties can be obtained by membrane separation by carrying out the high concentration step.
Moreover, according to such a wastewater treatment method, by carrying out the purified water generation step, by discharging a part of the sludge-containing biological treated water having an increased MLSS concentration to the outside of the membrane concentration tank, the membrane Since a part of the soluble microbial metabolite (SMP) in the concentration tank can be discharged out of the membrane concentration tank, it is possible to suppress the accumulation of SMP in the membrane concentration tank, and Clogging can be suppressed.
Therefore, according to such a wastewater treatment method, it is possible to reduce the possibility of clogging of the filtration membrane while obtaining sludge-containing biologically treated water having excellent solid-liquid separation properties by membrane separation.

In addition , according to such a wastewater treatment method, in order to obtain sludge-containing biologically treated water having excellent solid-liquid separability even if the organic matter concentration and the amount of water inflowing wastewater fluctuate by performing the wastewater supply step. Since it is possible to inject an appropriate amount of wastewater into the membrane concentration tank, it is possible to efficiently obtain sludge-containing biologically treated water having excellent solid-liquid separation properties.
Furthermore , according to such a wastewater treatment method, since the sludge-containing biologically treated water in the storage tank has an activated sludge concentration increased by the sludge concentrate, the remaining wastewater that has not been transferred to the membrane concentrate tank Even if it is transferred in a large amount to the storage tank, the organic matter contained in the wastewater can be sufficiently decomposed, so that the activated sludge concentration contained in the sludge-containing biological treatment water can be further increased.
Furthermore, according to such a wastewater treatment method, the concentrated sludge-containing biologically treated water is accommodated in the accommodating tank, and the sludge concentrated water obtained by solid-liquid separation is added to the accommodating tank and biologically treated, thereby By setting the MLSS concentration of the sludge-containing biologically treated water in the tank to 10,000 mg / L or more, the sludge-containing biologically treated water having excellent solid-liquid separation can be efficiently obtained even in the storage tank.
Therefore, according to such a wastewater treatment method, there is an advantage that it is possible to further reduce the possibility of clogging of the filtration membrane while obtaining sludge-containing biologically treated water having excellent solid-liquid separation properties.

  Furthermore, in the wastewater treatment method according to the present invention, preferably, the activated sludge aggregated by a carrier is used.

The present invention also includes a biological treatment unit that mixes activated sludge and wastewater and biologically treats them in the biological treatment tank to obtain sludge-containing biologically treated water, and a solid-liquid separation unit that separates the sludge-containing biologically treated water into solid and liquid. A wastewater treatment apparatus configured to obtain purified water by the biological treatment unit and the solid-liquid separation unit,
The biological treatment unit includes a membrane unit that membrane-separates sludge-containing biological treatment water, and the membrane unit separates sludge-containing biological treatment water to increase the activated sludge concentration in the membrane concentration tank as the biological treatment tank. Configured as
The membrane unit is arranged inside or outside the tank,
The biological treatment section increases the activated sludge concentration of the sludge-containing biological treated water so that the MLSS concentration is 10,000 mg / L or more, and the BOD load on the activated sludge (BOD sludge load) is 0.2 kg BOD / kgSS. / D, and a part of the sludge-containing biologically treated water with an increased MLSS concentration is discharged out of the membrane concentration tank and supplied to the solid-liquid separation tank. The waste water treatment apparatus is configured to obtain purified water as separation treated water.

  As described above, according to the present invention, it is possible to reduce the possibility of clogging of the filtration membrane while obtaining sludge-containing biologically treated water having excellent solid-liquid separation properties by membrane separation.

1 is a schematic diagram of a wastewater treatment apparatus according to an embodiment. AA arrow sectional drawing of FIG. 1 is a schematic diagram of a wastewater treatment apparatus according to an embodiment. 1 is a schematic diagram of a wastewater treatment apparatus according to an embodiment. 1 is a schematic diagram of a wastewater treatment apparatus according to an embodiment. 1 is a schematic diagram of a wastewater treatment apparatus according to an embodiment. 1 is a schematic diagram of a bioaggregation tank according to an embodiment. 1 is a schematic diagram of a bioaggregation tank according to an embodiment. 1 is a schematic diagram of a bioaggregation tank according to an embodiment. 1 is a schematic diagram of a wastewater treatment apparatus according to an embodiment. Combination of MLSS concentration and BOD sludge load in biological treatment of mixed water carried out in Test Example 1. Combination of MLSS concentration and BOD sludge load in biological treatment of mixed water carried out in Test Example 2.

  Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.

  First, the wastewater treatment apparatus according to this embodiment will be described.

  In the wastewater treatment apparatus of this embodiment, activated sludge and wastewater are mixed to produce mixed water, the mixed water is biologically treated to obtain sludge-containing biologically treated water, and the sludge-containing biologically treated water is solid-liquid separated. To obtain purified water.

  The wastewater is not particularly limited as long as it contains organic matter that can be biodegraded. For example, domestic wastewater, food factory, chemical factory, electronics industry factory, pulp factory, etc. Examples include factory wastewater.

Specific examples of the biological treatment include wastewater treatment.
The wastewater treatment is a treatment in which activated sludge having biological species such as bacteria, protozoa, and metazoans is mixed with wastewater containing organic matter while aeration, and the organic matter is decomposed by the biological species.

  Specifically, as shown in FIG. 1, the wastewater treatment apparatus 1 of the present embodiment mixes activated sludge and wastewater A to generate mixed water, and biologically treats the mixed water in a biological treatment tank 21. The biological treatment section 2 for obtaining the sludge-containing biological treated water, and the solid-liquid separation treated water and the activated sludge having a content of activated sludge less than the sludge-containing biological treated water by solid-liquid separation from the sludge-containing biological treated water. The solid-liquid separation part 3 which has the solid-liquid separation tank 31 which produces | generates the sludge concentrated water C concentrated rather than the said sludge containing biologically treated water is provided.

  Moreover, the wastewater treatment apparatus 1 of this embodiment is configured to obtain purified water B by the biological treatment unit 2 and the solid-liquid separation unit 3.

Furthermore, the wastewater treatment apparatus 1 of the present embodiment is configured such that the raw water A is supplied to the biological treatment unit 2. Moreover, in the wastewater treatment apparatus 1 of the present embodiment, the sludge-containing biological treatment water generated by the biological treatment unit 2 is the solid-liquid separation unit 3, and the solid-liquid separation treatment water generated by the solid-liquid separation unit 3 is purified water. As B, the sludge concentrated water C generated in the solid-liquid separation unit 3 is transferred to the purified water storage unit (not shown) to the sludge concentrated water storage unit (not shown) and / or the biological treatment unit 2. Consists of.
Specifically, the wastewater treatment apparatus 1 of the present embodiment includes a raw water supply path 4a for supplying raw water A, a sludge-containing biologically treated water transfer path 4b for transferring sludge-containing biologically treated water to the solid-liquid separator 3, Purified water transfer path 4c for transferring purified water B to a purified water storage part (not shown), sludge concentrated water transfer path 4d for transferring sludge concentrated water C to a sludge concentrated water storage part (not shown), and sludge A sludge concentrated water return path 4e for transferring (returning) the concentrated water C to the biological treatment unit 2 is provided.

  The biological treatment unit 2 includes a membrane unit 24 for membrane filtration of sludge-containing biological treated water, and a membrane concentration tank aeration means 23 for aerating the inside of the membrane concentration tank 21, and the sludge-containing biological treated water is produced by the membrane unit 24. The membrane is separated so that the activated sludge concentration in the membrane concentration tank 21 as the biological treatment tank 21 is increased. The membrane concentration tank 21 is configured such that the raw water A is supplied via the raw water supply path 4a.

  In addition, the wastewater treatment apparatus 1 of the present embodiment is configured such that the sludge concentrated water C is added to the sludge-containing biological treated water whose activated sludge concentration is increased by the membrane unit 24 via the sludge concentrated water return path 4e. It becomes.

  Furthermore, in the wastewater treatment apparatus 1 of the present embodiment, a part of the sludge-containing biological treatment water having an increased MLSS concentration is discharged out of the membrane concentration tank 21 and supplied to the solid-liquid separation tank 31, and by solid-liquid separation, It is comprised so that the purified water B which is a solid-liquid separation process water may be obtained.

Further, the wastewater treatment apparatus 1 of the present embodiment is configured to transfer the permeated water obtained by the membrane unit 24 as purified water B to a purified water storage unit (not shown).
Specifically, the wastewater treatment apparatus 1 of this embodiment includes a permeate transfer path 4f that transfers permeate obtained by the membrane unit 24 as purified water B to a purified water storage unit (not shown). Become.

  The membrane unit 24 is arranged in a tank, and specifically, is installed as a submerged membrane below the liquid surface in the membrane concentration tank 21. The membrane unit 24 includes membrane aeration means (not shown) that removes dirt such as agglomerated sludge adhering to the filtration membrane by aeration of the filtration membrane constantly or intermittently.

  The type of filtration membrane of the membrane unit 24 is not particularly limited, and examples thereof include an ultrafiltration membrane (UF membrane) and a microfiltration membrane (MF membrane).

  As the structure of the filtration membrane, a so-called hollow fiber membrane formed into a hollow fiber shape having a diameter of several mm formed of a material such as cellulose acetate, aromatic polyamide, polyvinyl alcohol, polyvinylidene fluoride, polytetrafluoroethylene, and the like Conventionally known types such as a so-called type and a type called a flat membrane which is a thin plate-like film can be employed.

In addition, the biological treatment unit 2 includes a carrier 22 for aggregating activated sludge as necessary.
Specifically, the biological treatment unit 2 is configured to agglomerate activated sludge by the carrier 22 and separate the activated sludge (aggregated sludge body) agglomerated from the carrier 22. Furthermore, the biological treatment unit 2 is configured to generate a mixed water by mixing the agglomerated activated sludge (aggregated sludge body) and the waste water A.

  The carrier 22 is provided under the water surface in the membrane concentration tank 21 as shown in FIG. The carrier 22 includes an attachment 22a to which the activated sludge is attached and a support portion 22b that supports the attachment 22a. Further, the carrier 22 is configured such that the adhering body 22a is swung by a water flow generated by aeration.

The adhering body 22a is formed in a thread shape.
Although the material which comprises the said adhesion body 22a will not be specifically limited if the said activated sludge adheres easily, As this material, an acrylic resin, polyester, polyethylene, carbon fiber etc. are mentioned, for example. .

  The material constituting the support portion 22b is not particularly limited as long as it supports the adherend 22a. Examples of the material include resins such as polyester, acrylic resin, polyethylene, and stainless steel. A metal is mentioned.

  Further, as shown in FIG. 1, the biological treatment unit 2 is formed so as to be a separate tank from the membrane concentration tank 21, and contains sludge-containing biological treatment water discharged from the membrane concentration tank 21. The storage tank 25, the storage tank aeration means 26 for aerating the inside of the storage tank 25, and the sludge-containing biologically treated water transfer path 4g for transferring the sludge-containing biologically treated water discharged to the outside of the membrane concentration tank 21 to the storage tank 25 And comprising.

  Furthermore, in the wastewater treatment apparatus 1 of the present embodiment, the sludge-containing biological treated water is added to the sludge-containing biological treated water in the storage tank 25 through the sludge concentrated water return path 4e and biologically treated. The solid-liquid separation tank 31 is configured to be supplied.

  In addition, the wastewater treatment apparatus 1 of the present embodiment is configured such that the raw water A is supplied to the storage tank 25 by the raw water supply path 4a, and the sludge content of the storage tank 25 is supplied by the sludge-containing biologically treated water transfer path 4b. The biologically treated water is configured to be transferred to the solid-liquid separation unit 3.

Furthermore, the wastewater treatment apparatus 1 of this embodiment adjusts the transfer ratio of the wastewater A that is transferred to the membrane concentration tank 21 and the storage tank 25, respectively, so that the wastewater A is transferred to the membrane concentration tank 21 and the storage tank 25. It is comprised so that it may supply.

  In the wastewater treatment apparatus 1 of the present embodiment, the biological treatment unit 2 increases the activated sludge concentration of sludge-containing biological treated water so that the MLSS (floating activated sludge) concentration becomes 10,000 mg / L or more. However, the load of BOD (BOD sludge load) on the activated sludge is set to 0.2 kgBOD / kgSS / d or less.

  The solid-liquid separation tank 31 is configured such that solid-liquid separation treated water and sludge concentrated water C are generated from sludge-containing biologically treated water by gravity sedimentation.

  The wastewater treatment apparatus of this embodiment is configured as described above. Next, the wastewater treatment method of this embodiment will be described.

  In the wastewater treatment method of the present embodiment, activated sludge and wastewater A are mixed and biologically treated to obtain sludge-containing biologically treated water, and the sludge-containing biologically treated water is subjected to solid-liquid separation to obtain purified water B.

  Further, in the wastewater treatment method of the present embodiment, the membrane unit 24 separates the sludge-containing biological treatment water in the membrane concentration tank 21 to increase the activated sludge concentration of the sludge-containing biological treatment water to a MLSS concentration of 10. 2,000 mg / L or more, BOD load on activated sludge (BOD sludge load) is 0.2 kg BOD / kgSS / d or less, and a part of the sludge-containing biological treated water with increased MLSS concentration A purified water generating step for discharging the membrane concentration tank 21 to the solid-liquid separation tank 31 and supplying the purified liquid B as solid-liquid separation treated water by solid-liquid separation is performed.

  The MLSS concentration of the sludge-containing biological treatment water is preferably 10,000 to 30,000 mg / L, and more preferably 15,000 to 20,000 mg / L.

  The BOD sludge load is preferably 0.10 to 0.19 kg BOD / kg SS / d, and more preferably 0.05 to 0.15 kg BOD / kg SS / d.

The BOD volumetric load is preferably 0.1 to 6 kg BOD / m ³ / d, more preferably 1 to ³ kg BOD / m ³ / d.

In the wastewater treatment method of this embodiment, preferably, the BOD sludge load is 0.2 kgBOD while continuously increasing the MLSS concentration of the sludge-containing biological treatment water to 10,000 mg / L or more for a duration of 1 day or more. / KgSS / d or less.
“To keep the BOD sludge load within a predetermined range while keeping the MLSS concentration in the sludge-containing biologically treated water within a predetermined range continuously for a duration of one day or longer” In particular, the case where the MLSS concentration is out of the predetermined range and / or the BOD sludge load is out of the predetermined range is also included. For example, a case where “a total period of 1/20 of the continuous period is in a state where the MLSS concentration is out of a predetermined range and / or the BOD sludge load is out of a predetermined range” is included. Furthermore, a case where “a total period of 1/10 of the continuous period is in a state where the MLSS concentration is out of the predetermined range and / or the BOD sludge load is out of the predetermined range” is included.

  The duration is preferably 2 days or more, more preferably 7 days or more, and further preferably 30 days to 20 years.

Further, the wastewater treatment method of the present embodiment, using a storage tank 25, a membrane concentration tank 21 wastewater A by adjusting the transfer rate of the waste water A, which is transported to each membrane concentration tank 21 and the container tank 25 accommodating A wastewater supply step to be supplied to the tank 25, and a biological treatment by adding the sludge-containing biologically treated water discharged from the membrane concentration tank 21 to the storage tank 25 and adding the sludge concentrated water C obtained by solid-liquid separation; A sludge-containing biologically treated water supply step for supplying the generated sludge-containing biologically treated water to the solid-liquid separation tank 31 is performed.

  Further, in the wastewater treatment method of the present embodiment, the activated sludge is agglomerated by the carrier 22.

  Although the wastewater treatment apparatus and the wastewater treatment method of the present embodiment have the above-described configuration, the wastewater treatment apparatus and the wastewater treatment method of the present invention are not limited to the above-described configuration, and can be appropriately changed in design. .

  That is, although the wastewater treatment apparatus 1 of this embodiment is provided with the storage tank 25, as shown in FIG. 3, the wastewater treatment apparatus 1 of this invention may be an aspect without the storage tank 25.

  Such a wastewater treatment apparatus 1 may be configured such that the sludge-containing biological treatment water discharged from the membrane concentration tank 21 is transferred to the solid-liquid separation unit 3 through the sludge-containing biological treatment water transfer path 4b.

  Moreover, the waste water treatment apparatus 1 may be configured such that the sludge concentrated water C is added to the sludge-containing biologically treated water in the membrane concentration tank 21.

  Furthermore, although the wastewater treatment apparatus 1 of this embodiment is comprised so that solid-liquid separation treated water may be transferred to the purified water storage part (not shown) as the purified water B, the wastewater treatment apparatus of this invention is 4, the solid-liquid separation unit 3 is provided with a membrane unit 32 that performs membrane filtration of the solid-liquid separation treated water, and purified water B that is permeated by membrane filtration by the membrane unit 32 from the solid-liquid separation treated water. It may be configured to obtain In this case, the wastewater treatment apparatus 1 of the present embodiment may be configured to discharge a part of the non-permeated water of the membrane unit 32. Such a wastewater treatment apparatus 1 can suppress clogging of the filtration membrane by suppressing the accumulation of SMP in the solid-liquid separation tank 31.

  The membrane unit 32 is installed as an immersion membrane below the liquid surface in the solid-liquid separation tank 31. The membrane unit 32 includes membrane aeration means (not shown) that aerates the filtration membrane constantly or intermittently to remove dirt such as agglomerated sludge adhering to the filtration membrane.

  As shown in FIG. 4, the membrane unit 32 is installed as an immersion membrane. As shown in FIG. 5, the membrane unit 32 is a type in which a filtration membrane is housed in a container. The solid-liquid separation treated water may be configured to be supplied to the membrane unit 32 after being pressurized via the pump 33. Also in this case, the wastewater treatment apparatus 1 of the present embodiment may be configured to discharge a part of the non-permeate water of the membrane unit 32 for the reason described above.

  In the wastewater treatment apparatus in which the membrane unit 32 is installed outside the solid-liquid separation tank 31, the non-permeated water generated by the membrane unit 32 is transferred to the biological treatment unit 2 as part of the mixed water. It is made up of. Specifically, a non-permeate water transfer path 4h for transferring the non-permeate water is provided.

Moreover, although the wastewater treatment apparatus 1 of this embodiment is comprised so that a coagulation sludge body may be produced | generated in the membrane concentration tank 21, the wastewater treatment apparatus of this invention is the storage tank 25 instead of the membrane concentration tank 21. FIG. It may be configured to generate a coagulated sludge body, and may be configured to generate a collected sludge body in the membrane concentration tank 21 and the storage tank 25.
As shown in FIG. 6, in the wastewater treatment apparatus 1 of the present embodiment, the biological treatment unit 2 includes a biological flocculation tank 27 that generates a flocculated sludge body by the biological flocculation means, and the solid-liquid separation unit The sludge concentrated water C generated by 3 may be transferred to the biological flocculation tank 27, and the flocculated sludge body generated by the biological flocculation tank 27 may be transferred to the storage tank 25. The agglomerated sludge produced by the biological aggregating tank 27 may be transferred to the membrane concentrating tank 21.
Such a wastewater treatment apparatus 1 is configured such that the activated sludge contained in the sludge concentrated water C in which the activated sludge has been concentrated is aggregated, and thereby has an advantage that the aggregated sludge body can be generated more efficiently. is there. Moreover, there is an advantage that the energy for returning the sludge concentrated water C can be used effectively.

  Such a wastewater treatment apparatus 1 includes a sludge concentrated water transfer path 4 i for transferring the sludge concentrated water C generated by the solid-liquid separation unit 3 to the biological coagulation tank 27, and the aggregated sludge generated in the biological coagulation tank 27. And an agglomerated sludge body transfer path 4j for transferring the body to the membrane concentration tank 21.

  In addition, the wastewater treatment apparatus 1 includes a biocoagulation tank aeration means (not shown) for aeration of the inside of the biocoagulation tank 27 as necessary, but the biocoagulation tank aeration means (not shown). ) May not be provided.

  Further, the wastewater treatment apparatus 1 is formed such that the biological aggregation tank 27 is a separate tank from the membrane concentration tank 21 and the storage tank 25.

Further, in the wastewater treatment apparatus 1, it is preferable that the biological aggregating means is generated by aggregating the activated sludge by the carrier 22 and separating the agglomerated sludge body from the carrier 22. The adhering body 22a to which the activated sludge is adhered and the support portion 22b that supports the adhering body 22a are provided, and the sludge concentrated water is transferred from the sludge concentrated water transfer path 4i to the biological coagulation tank 27 by the water flow The adhering body 22a is configured to swing.
Such a wastewater treatment apparatus 1 has an advantage that the aggregated sludge body can be separated from the carrier 22 with high energy efficiency by being configured such that the adhering body 22a is swung by a water flow. Further, since the aggregated sludge body can be efficiently generated, there is an advantage that the size of the carrier 22 can be reduced without reducing the generation efficiency of the aggregated sludge body.

  In addition, the wastewater treatment apparatus 1 is configured such that the sludge concentrated water C can be transferred in a turbulent flow as the biocoagulation tank 27 instead of the biocoagulation tank 27 configured to aggregate the activated sludge with the carrier 22. 7 in which the length of the transfer path is extended, the path is subdivided, specifically, the flow path as shown in FIG. 7 is zigzag, or a multi-tubular shape as shown in FIG. (Honeycomb-shaped) and those provided with a static mixer as shown in FIG. 9 may be provided. According to such a waste water treatment apparatus 1, since activated sludge can collide with a wall-like thing at high speed, there exists an advantage that a coagulated sludge body can be produced | generated efficiently.

  Furthermore, although such a waste water treatment apparatus 1 is arranged in the tank, it may be arranged outside the tank. Specifically, as shown in FIG. 10, such a wastewater treatment apparatus 1 is a type in which a membrane unit 24 has a filtration membrane housed in a container, is installed outside the membrane concentration tank 21, and contains sludge. The biologically treated water may be configured to be supplied to the membrane unit 24 after being pressurized via the pump 28.

  In the wastewater treatment apparatus 1 in which the membrane unit 24 is installed outside the membrane concentration tank 21, the non-permeated water generated by the membrane unit 24 is transferred to the membrane concentration tank 21 as a part of the mixed water. It is made up of. Specifically, the wastewater treatment apparatus 1 includes a non-permeate water transfer path 4k that transfers the non-permeate water to the membrane concentration tank 21 as a part of the mixed water.

  Next, the present invention will be described more specifically with reference to test examples.

(Test Example 1)
Tank (water storage capacity: 10L, internal dimensions: 0.15m (width) x 0.15m (depth) x 0.45m (height)), Biofringe (registered trademark) as a carrier (NTT And a pump as an aeration means to agglomerate activated sludge, mix the agglomerated activated sludge (aggregated sludge body) and waste water to produce mixed water, and biologically treat the mixed water Sludge containing biologically treated water was obtained. Specifically, the MLSS concentration in the sludge-containing biologically treated water storage tank is set to a predetermined value, and the BOD load (BOD sludge load) on the activated sludge in the tank is set to a predetermined value for 30 to 90 days. Maintaining the above, the mixed water was biologically treated to obtain sludge-containing biologically treated water.
While maintaining the MLSS concentration in the sludge-containing biologically treated water storage tank at a predetermined value, the BOD load (BOD sludge load) on the activated sludge in the sludge-containing biologically treated water storage tank is maintained at a predetermined value. If the period to be used is 10 days or more, the SV30, SVI, and 5C permeation amount is not affected by the difference in the period.
FIG. 11 shows combinations of MLSS concentration and BOD sludge load in the biological treatment of mixed water carried out in Test Example 1.
The MLSS concentration and BOD sludge load were measured and calculated according to JIS B 9944-1978.

(Test Example 2)
A sludge-containing biologically treated water was obtained in the same manner as in Test Example 1 except that no carrier was used.
FIG. 12 shows a combination of the MLSS concentration and the BOD sludge load in the biological treatment of the mixed water carried out in Test Example 2.

  The sludge-containing biologically treated water of the test example was subjected to the following test.

(SV30, SVI measurement)
The activated sludge sedimentation rate (SV30) and sludge volume index (SVI) of the sludge-containing biologically treated water of the test examples were measured and calculated according to JIS B 9944-1978.

(Measurement of 5C transmission)
5 kinds of C (JIS P 3801) filter paper (Advantech Toyo Co., Ltd., diameter: 15 cm) is placed on the filter, and 50 mL of the biological sludge-containing biological treatment water of the test example is dropped on the filter paper. The amount of filtrate (permeated water) that permeated through the filter paper when 5 minutes passed (5C permeation amount) was measured.

  The test results are shown in Table 1 for Test Example 1 and in Table 2 for Test Example 2. In Tables 1 and 2, calculated average values are shown as SVI, MLSS concentration, SV30, and 5C permeation amount.

In the sludge-containing biologically treated water of Test Examples 1-4 and 2-4, Test Example 1-1 under the condition that the BOD sludge load exceeds 0.2 kgBOD / kgSS / d and the MLSS concentration is less than 10,000 mg / L, Test example 1-2 under the condition where the MLSS concentration is less than 10,000 mg / L, Test example 1-3 under the condition where the BOD sludge load exceeds 0.2 kgBOD / kgSS / d, and a test example using no carrier SV30 and SVI showed lower values than 2-1 to 2-3.
Moreover, in the sludge containing biologically treated water of Test Examples 1-4 and 2-4, the 5C permeation amount showed a higher value than Test Examples 1-1 to 1-3 and 2-1 to 2-3. .

  1: waste water treatment apparatus, 2: biological treatment unit, 3: solid-liquid separation unit, 4a: raw water supply route, 4b: sludge-containing biological treatment water transfer route, 4c: purified water transfer route, 4d: sludge concentrated water transfer route, 4e: sludge concentrated water return path, 4f: permeated water transport path, 4g: sludge containing biologically treated water transport path, 4h: non-permeated water transport path, 4i: sludge concentrated water transport path, 4j: agglomerated sludge body transport path, 4k : Non-permeate water transfer path, 21: biological treatment tank (membrane concentration tank), 22: carrier, 22a: adherent, 22b: support, 23: membrane concentration tank aeration means, 24: membrane unit, 25: storage tank, 26: storage tank aeration means, 27: biological coagulation tank, 28: pump, 31: solid-liquid separation tank, 32: membrane unit, 33: pump, A: waste water, B: purified water, C: sludge concentrated water

Claims (2)

A wastewater treatment method in which activated sludge and wastewater are mixed and biologically treated in a biological treatment tank to obtain sludge-containing biologically treated water, and purified water is obtained by solid-liquid separation of the sludge-containing biologically treated water, Using a membrane concentration tank that separates and concentrates sludge-containing biologically treated water by a membrane unit disposed outside the tank, and a storage tank formed to be a tank separate from the membrane concentration tank, the membrane Adjusting the transfer ratio of the wastewater transferred to each of the concentration tank and the storage tank to supply wastewater to the membrane concentration tank and the storage tank, and the activated sludge concentration in the membrane concentration tank Increase the MLSS concentration to 10,000 mg / L or higher, increase the BOD load on activated sludge (BOD sludge load) to 0.2 kgBOD / kgSS / d or less, and sludge-containing biological treatment with increased MLSS concentration part of the water is discharged out of the membrane concentration tank, the The sludge-containing biologically treated water supply step of supplying the entire amount of the sludge-containing biologically treated water to the storage tank and storing it in the storage tank, and supplying the sludge-containing biologically treated water in the storage tank to the solid-liquid separation tank And a purified water generation step for obtaining purified water as solid-liquid separation treated water by solid-liquid separation in the solid-liquid separation tank, and is supplied to the solid-liquid separation tank in the sludge-containing biologically treated water supply step. The sludge-containing biologically treated water returns a part of the sludge concentrated water separated from the purified water by solid-liquid separation in the solid-liquid separation tank to the storage tank, and the returned sludge concentrated water is used as the membrane. A wastewater treatment method characterized by being biologically treated in addition to sludge-containing biologically treated water discharged from a concentration tank and supplied to a storage tank . Wherein as active sludge, wastewater treatment method according to claim 1 Symbol placement using those aggregated by a carrier.

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