JP5818148B2 - Outside tank type membrane separation activated sludge method and activated sludge treatment equipment - Google Patents

Description

  The present invention relates to an outside tank type membrane separation activated sludge method used for treating various organic wastewater such as sewage, return water, industrial wastewater, waste leachate, human waste, agricultural wastewater, livestock wastewater and aquaculture wastewater. In particular, the present invention relates to the handling of backwash wastewater generated when backwashing a separation membrane installed outside the tank.

  As an organic wastewater treatment method as described above, an activated sludge method in which treatment with microorganisms is performed in a biological reaction tank is common. The water in the biological reaction tank is subjected to solid-liquid separation by gravity sedimentation in the final sedimentation tank, and the supernatant water is taken out as treated water. However, since this method requires a long time for gravity sedimentation, a wide final sedimentation basin must be installed. Therefore, a membrane separation activated sludge method in which the final sedimentation basin is replaced with a separation membrane is becoming widespread.

  In this membrane separation activated sludge method, the separation membrane is immersed in the biological reaction tank and the in-bath type membrane separation activated sludge method in which the water in the tank is directly filtered. The membrane separation activated sludge method, which is filtered outside the tank that filters while circulating, is divided roughly in any case, particles in the vicinity of the membrane pore diameter (membrane blocking substance) trapped on the membrane surface by membrane separation treatment There is a problem in that the film surface differential pressure is increased and the film processing capability is decreased.

  As a means for solving this problem, before the membrane separation treatment step, a step of adding a flocculant as appropriate in the biological reaction tank according to the properties of the water to be treated is provided to form a small block (floc) of the membrane blocking substance. A technique for preventing membrane clogging by promoting it is disclosed (Patent Document 1).

  However, when the flocculant is added to the water to be treated in the biological reaction tank before the membrane separation treatment step, there is a problem that a large amount of the flocculant is required to obtain sufficient aggregation efficiency.

  In addition, when aggregated flocs are formed in the biological reaction tank, it is difficult to ensure the stability of membrane filterability because the membrane surface blocking material cannot be removed from the biological reaction tank to the outside of the tank. was there.

JP 2006-55766 A

  It is an object of the present invention to remove membrane surface clogging materials from a biological reaction tank to the outside in the membrane separation activated sludge method, and to reduce the amount of chemicals added to prevent membrane clogging. Is to provide.

The invention according to claim 1, which has been made in order to solve the above-mentioned problems, is an outside tank type membrane separation activated sludge method in which the in-vessel water of a biological reaction tank is circulated through a separation membrane installed outside the tank and filtrated water is taken out. In addition, the backwash wastewater containing the membrane surface blocking substance produced by backwashing the separation membrane is subjected to agglomeration treatment to form a membrane surface blocking material into a floc floc having a particle size larger than the membrane pore size, It is characterized in that it is first returned to the sedimentation basin without solid-liquid separation . Here, the agglomeration treatment refers to forming an agglomeration floc by adding a flocculant to the water to be treated and then stirring.

Further, the invention according to claim 2, which has been made to solve the above-described problems, is an outside tank type membrane separation activated sludge that circulates in-bath water of a biological reaction tank through a separation membrane installed outside the tank and takes out filtrated water. In this method, the backwash wastewater containing the membrane surface blocking substance produced by backwashing the separation membrane is adsorbed to incorporate the membrane surface blocking material into the adsorbent, and the membrane surface blocking material has a particle size larger than the pore size. The adsorbent fine particle floc is returned to the biological reaction tank or the first sedimentation basin without solid-liquid separation . Here, the adsorption treatment means that the adsorbent is added to the water to be treated and then stirred to form adsorbent fine particle flocs.

  The invention described in claim 3 is characterized in that in the outside-tank membrane separation activated sludge method according to claim 1 or 2, the separation membrane is a ceramic membrane.

Invention of Claim 4 is the activated sludge processing apparatus used for the outside tank installation type | mold membrane separation activated sludge method of Claim 1 or 2, Comprising: The activated sludge process in a biological reaction tank is carried out in the back | latter stage of a biological reaction tank. A cross-flow type separation membrane that supplies treated water that has undergone the separation to separate the treated water and the concentrated water, and a concentrated water return channel that returns the concentrated water to the biological reaction tank. A backwash drainage tank that stores backwash water discharged during backwashing, a flocculant or adsorbent addition device that adds a flocculant or adsorbent into the backwash drainage tank, and a flocculant or adsorbent are added. Backwash wastewater return flow that returns the backwash water containing flocs generated by the addition of flocculant or adsorbent to the biological reaction tank or first sedimentation tank without solid-liquid separation. A road is provided.

The invention described in claim 5 is an activated sludge treatment apparatus used in the outside tank type activated membrane separation activated sludge method according to claim 1 or 2, wherein the activated sludge treatment in the biological reaction tank is performed after the biological reaction tank. A cross-flow type separation membrane that supplies treated water that has undergone the separation to separate the treated water and the concentrated water, and a concentrated water return channel that returns the concentrated water to the biological reaction tank. A backwash drainage tank for storing backwash water discharged during backwashing, a flocculant or adsorbent addition device for adding a flocculant or adsorbent to the backwash drainage discharged from the backwash drainage tank, and a flocculant Alternatively, the line mixer that stirs the backwash water to which the adsorbent is added and the backwash water containing flocs generated by the addition of the flocculant or adsorbent are returned to the biological reaction tank or the first sedimentation tank without solid-liquid separation. Characterized by having a backwash drainage return channel Than is.

According to the first aspect of the present invention, after the membrane surface blocking substance contained in the waste water generated by backwashing the separation membrane provided outside the biological reaction tank is agglomerated to form agglomerated floc, the agglomerated floc can be separated without solid-liquid separation. It is returned to the biological reaction tank as appropriate. Further, the invention according to claim 2, after adsorbing the membrane surface blocking substance contained in the waste water generated by backwashing the separation membrane provided outside the biological reaction tank to form the adsorbent fine particle floc, It is returned to the biological reaction tank as appropriate without solid-liquid separation . Therefore, according to the present invention, compared with the case where the water in the biological reaction tank itself is agglomerated or adsorbed by aggregating or adsorbing the backwash wastewater containing the membrane surface blocking substance in a high concentration, Aggregation efficiency or adsorption efficiency is increased, and the amount of flocculant or adsorbent added can be suppressed. Further, according to the present invention, the membrane surface blocking substance can be removed as a flocculant floc or adsorbent fine particle floc having a particle size larger than the membrane pore size and removed from the biological reaction tank. Can be ensured. By returning the backwash waste water to the biological reaction tank after the aggregation treatment or adsorption treatment, the biological activity can be maintained without excessively reducing the MLSS concentration in the biological reaction tank.

  According to the invention described in claim 3, by adopting a high-strength ceramic membrane as the separation membrane, it is possible to perform backwashing at a high pressure, and it is possible to surely remove the membrane surface blocking substance blocked on the membrane surface. It becomes.

It is explanatory drawing which shows embodiment of this invention. It is explanatory drawing which shows embodiment of this invention.

Preferred embodiments of the present invention are shown below.
In FIG. 1, reference numeral 1 denotes a biological reaction tank, in which raw water which is organic wastewater, for example, sewage, is treated with activated sludge by an aerobic microorganism as in the prior art. Reference numeral 2 denotes a separation membrane installed outside the biological reaction tank 1, and water in the tank of the biological reaction tank 1 is supplied to the primary side by a circulation pump 3 and membrane filtered. In this embodiment, cross-flow filtration is performed, and the membrane filtrate that has permeated the membrane surface to the secondary side is taken out as treated water to the treated water tank 4, and the concentrated water is returned from the end on the primary side. It returns to the biological reaction tank 1 through the pipe line 5.

  The type of the separation membrane 2 is a UF membrane or an MF membrane, and the material is preferably a ceramic membrane from the viewpoint of membrane strength. The membrane shape may be any of a monolith membrane, a tubular membrane, a flat membrane, and a hollow fiber membrane, and the pressurization method may be either an internal pressure type or an external pressure type. In the case of a monolithic membrane or a tubular membrane, it is preferable that the flow path on the primary side has a circular cross section or a polygon that is a quadrangle or more. In general, the UF membrane has a pore size of about 0.001 μm to 0.01 μm, and the MF membrane has a pore size of about 0.01 μm to several μm.

  If the separation membrane 2 installed outside the tank as shown in FIG. 1 is used, the solid-liquid separation of the water in the biological reaction tank 1 can be easily performed, which is compared with the conventional wastewater treatment facility using the final sedimentation basin. Thus, the entire waste water treatment facility can be reduced in size. However, among the activated sludge and the solid content in the water in the tank, an insoluble substance having a particle size in the vicinity of the pore size of the separation membrane 2 becomes a membrane surface blocking material and accumulates on the membrane surface of the separation membrane 2. Alternatively, it is necessary to stop the circulation pump 3 when the membrane differential pressure rises and to inject the treated water from the treated water tank 4 to the secondary side of the separation membrane 2 by the backwash pump 6 to perform backwashing of the membrane surface. It becomes. The frequency of backwashing varies greatly depending on the properties of the raw water, but is preferably about once every 10 minutes when the raw water is highly contaminated, and about once every 3 hours when the raw water is dirty.

  The backwash drainage generated by this backwash is discharged to the backwash drain tank 7. This backwash drainage contains activated sludge and membrane surface blocking substances that have been separated from the membrane surface. Conventionally, the backwash waste water is returned to the biological reaction tank 1 as it is. However, in the present invention, the flocculant or adsorbent is added from the flocculant or adsorbent addition device 8 to perform the flocculant treatment or adsorption treatment.

  The backwash drainage tank 7 includes stirring means 9 and mixes the flocculant or adsorbent with the backwash drainage. The agitation means 9 used in the agglomeration process is preferably a normal rotary agitation blade as shown in FIG. 1 from the viewpoint of preventing destruction of the agglomeration flocs, but in the case of the adsorption process, as shown in FIG. In addition, a line mixer can also be used. The degree of stirring can be represented by the G value, and the preferred range is 100-500. If the G value is lower than this range and stirring is insufficient, the agglomeration effect is reduced and floc formation is not performed well. Conversely, if the stirring is excessive, the formed floc is destroyed, which is not preferable.

  As the flocculant, any commonly used flocculant such as polyaluminum chloride, sulfate band, ferric chloride, polyiron sulfate, etc. may be used. As the adsorbent, any commonly used adsorbent such as activated carbon, bennite and viscosity may be used. After the addition of the flocculant, the water to be treated is stirred to agglomerate the membrane plugging substance having a particle size in the vicinity of the pore size of the separation membrane 2, and the aggregate floc having a particle size larger than the pore size of the separation membrane 2 Become. Further, by stirring the water to be treated after addition of the adsorbent, the membrane plugging substance having a particle size in the vicinity of the pore size of the separation membrane 2 is taken into the absorbent, and has a particle size larger than the pore size of the separation membrane 2. It becomes adsorbent fine particle floc having. The particle diameter of the aggregate floc or adsorbent fine particle floc is preferably 10 μm or more. The amount of the flocculant or adsorbent added is preferably about 100 to 800 mg / L per backwash wastewater amount.

  A part of the drainage of the backwash drainage tank 7 is discharged from the backwash drainage tank 7 by the backwash drainage discharge pump 13, and a part of the drainage is returned to the biological reaction tank 1 or the first sedimentation tank 11 by the drainage return pump 10. Will be returned. Since the membrane surface blocking substance contained in the backwash drainage is a floc having a particle size larger than the membrane pore size by the agglomeration treatment or the adsorption treatment, this return makes it near the membrane pore size in the biological reaction tank 1. There is no increase in the amount of the membrane-occluding substance composed of particles. Therefore, according to the present invention, the membrane filtration performance of the separation membrane 2 is not rapidly reduced, and stable filtration is possible over a long period of time.

Moreover, according to the present invention, part of the floc is returned to the biological reaction tank 1 or the first sedimentation basin 11 as described above, so that the MLSS concentration in the biological reaction tank 1 does not decrease, and the biological activity of the biological reaction tank 1 is reduced. It can be kept stable.
Examples of the present invention are shown below.

  Using the treatment apparatus shown in FIG. 1, the activated sludge treatment of sewage was performed. The MLSS concentration in the biological reaction tank was 10,000 mg / L. The separation membrane is a monolithic ceramic membrane, and the membrane pore diameter is 0.1 μm. Cross flow filtration was performed by circulating water in the biological reaction tank, and membrane filtrate was taken out as treated water.

  The separation membrane was back-washed by stopping the filtration operation every hour. The backwash wastewater containing the membrane surface blocking substance was collected in a backwash wastewater tank and subjected to a coagulation treatment in which a flocculant was added. The amount of flocculant added is 200 mg / L per backwash drainage. The entire amount of coagulated backwash wastewater was returned to the biological reaction tank.

  When the flocculation treatment is not performed (conventional example) and the flocculation treatment is performed (example), the properties of the treated water are both the same, but in the conventional example, the membrane filtration flux of the separation membrane is 1. While it was 8 m / day, in the example, it was 2.2 m / day, and it was confirmed that the membrane filtration performance was greatly improved by the aggregation treatment. In addition, the MLSS concentration in the bioreactor remained at 10000 mg / L and did not decrease.

DESCRIPTION OF SYMBOLS 1 Biological reaction tank 2 Separation membrane 3 Circulation pump 4 Treated water tank 5 Return flow line 6 Backwash pump 7 Backwash drainage tank 8 Coagulant or adsorbent supply device 9 Stirring means 10 Return pump 11 First sedimentation tank 12 Line mixer 13 Flock discharge pump

Claims (5)

In the outside installed type membrane separation activated sludge method, which circulates the in-vessel water of the biological reaction tank to the separation membrane installed outside the tank and takes out the filtered water,
The backwash wastewater containing the membrane surface blocking substance produced by backwashing the separation membrane is agglomerated to form the membrane surface blocking material into a floc floc having a particle size larger than the membrane pore size, An outside tank type membrane separation activated sludge method characterized by returning to the sedimentation basin without solid-liquid separation . In the outside installed type membrane separation activated sludge method, which circulates the in-vessel water of the biological reaction tank to the separation membrane installed outside the tank and takes out the filtered water,
Backwash wastewater containing membrane surface clogging material generated by backwashing the separation membrane is adsorbed to incorporate the membrane surface clogging material into the adsorbent, and adsorb the membrane surface clogging material with a particle size larger than the membrane pore size. A membrane-separated activated sludge method installed outside the tank, which is returned to the biological reaction tank or the first sedimentation tank without solid-liquid separation after the fine particle floc is formed.   The membrane separation activated sludge method according to claim 1 or 2, wherein the separation membrane is a ceramic membrane. An activated sludge treatment apparatus for use in an outside tank type membrane separation activated sludge method according to claim 1 or 2,
A cross-flow type separation membrane that supplies treated water that has undergone activated sludge treatment in the biological reaction tank and separates it into treated water and concentrated water, and the concentrated water in the biological reaction tank. Concentrated water return flow path to return
Further, a backwash drainage tank for storing backwash water discharged during backwashing of the separation membrane, a flocculant or adsorbent addition device for adding a flocculant or an adsorbent into the backwash drainage tank, and a flocculant Alternatively, the agitation means for agitating the backwash water to which the adsorbent is added and the backwash water containing flocs generated by the addition of the flocculant or adsorbent are returned to the biological reaction tank or the first sedimentation tank without solid-liquid separation. An activated sludge treatment apparatus comprising a backwash drainage return flow path. An activated sludge treatment apparatus for use in an outside tank type membrane separation activated sludge method according to claim 1 or 2,
A cross-flow type separation membrane that supplies treated water that has undergone activated sludge treatment in the biological reaction tank and separates it into treated water and concentrated water, and the concentrated water in the biological reaction tank. Concentrated water return flow path to return
Further, a backwash drainage tank for storing backwash water discharged during backwashing of the separation membrane, and a flocculant or adsorbent for adding a flocculant or adsorbent to the backwash drainage discharged from the backwash drainage tank An addition device, a line mixer that stirs the backwash water added with the flocculant or adsorbent, and the backwash water containing flocs generated by the addition of the flocculant or adsorbent are solidified in the bioreactor or first sedimentation basin. An organic wastewater treatment apparatus comprising a backwash drainage return channel that returns without liquid separation .

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