JP3646537B2 - Method for operating microorganism-supported rotary flat membrane device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for operating a microorganism-supporting rotary membrane device, and in particular, a microorganism layer is formed by adhering microorganisms to the rotary membrane, and the microorganism layer is used to purify water and wastewater. The present invention relates to a method for operating a membrane device.
[0002]
[Prior art]
The microorganism-supported rotary flat membrane device forms a microbial layer by attaching microorganisms to the rotary flat membrane, and biologically purifies ammonia nitrogen in the water to be treated by this microbial layer, and also performs the treatment. Filtration of turbid components in water can be performed.
However, as filtration of the water to be treated continues, microorganisms and solids in the water to be treated further adhere on the microorganism layer, and the layer thickness of the microorganism layer gradually increases. When the layer thickness of the microorganism layer becomes too thick, not only the filtration performance is lowered, but also the biological purification treatment performance is lowered. Therefore, when the layer thickness of the microorganism layer becomes too thick, it is necessary to peel off the microorganism layer.
[0003]
Conventionally, in order to remove the microbial layer, the filtration operation is stopped while the rotating flat membrane is periodically rotated, that is, the suction pump is stopped, so that the microbial layer on the membrane surface is peeled off by the rotation of the rotating flat membrane. It was.
[0004]
[Problems to be solved by the invention]
However, as in the past, when the microbial layer of the rotating flat membrane is to be peeled off by rotating the rotating flat membrane, it is necessary to apply a certain level of shearing force due to turbulent flow to the membrane surface. Must be rotated at high speed. Therefore, it is necessary not only to install a high-power motor that rotates the rotating flat membrane at high speed just for the peeling operation, but also the component parts of the device have good durability, and use parts with higher processing accuracy and assembly accuracy. Therefore, there is a disadvantage that the apparatus cost becomes high.
[0005]
Furthermore, since the microbial layer is peeled off only by rotating the rotating flat membrane, when the microbial layer adheres at a high density, the peeling efficiency is poor and a long time is required for the peeling operation. There is a disadvantage that the operation time of the purification process is greatly reduced.
Since the present invention is made in view of such circumstances, even if a microorganism layer is formed at a high density on the rotating flat membrane, the rotating flat membrane is rotated at a low rotation number to effectively separate the microorganism layer. It is an object of the present invention to provide a method for operating a microorganism-supporting rotary flat membrane device capable of performing the above.
[0006]
[Means for Solving the Problems ]
In order to achieve the above object, the present invention forms a microbial layer by attaching microorganisms to the surface of a rotating flat membrane provided in a membrane separation tank, and biologically purifies the water to be treated by the microbial layer. In the operation method of the microorganism-supporting rotary flat membrane device to be treated, the water to be treated is introduced into the membrane separation tank in a state where the rotary flat membrane is rotated from the vicinity of the periphery of the rotating flat membrane where the flow of the water to be treated is fast. A large number of sponge-like members having different specific gravities are mixed and introduced so as to be evenly distributed over the entire surface of the rotating flat membrane until the vicinity of the center of the rotating flat membrane is slow , and the sponge-like member and the microorganism layer are mixed. The microbial layer is peeled off by contact, and while the microbial layer is being peeled off by the sponge-like member, the rotational speed of the rotating flat membrane is made larger than the rotational speed at the time of purification treatment.
[0007]
According to the present invention, the sponge-like member and the microbial layer of the rotating rotating membrane are brought into contact with each other by introducing the sponge-like member into the membrane separation tank while the rotating flat membrane is rotated. It is scraped off by a sponge-like member. Moreover, since it is a sponge-like member, the film surface of the rotating flat membrane is not damaged.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a preferred embodiment of a method for operating a microorganism-supporting rotary flat membrane device of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a top view of a rotary flat membrane device 10 to which the operation method of the microorganism-supported rotary flat membrane device of the present invention is applied.
[0009]
As shown in FIG. 1, two hollow rotating shafts 14 and 14 parallel to the left and right are rotatably arranged in parallel in a membrane separation tank 12 to which water to be treated is supplied. Each of the hollow rotating shafts 14 supports a plurality of rotating flat membranes 16, 16... Having a disk shape so as to face a communication port (not shown) drilled at a predetermined interval in the axial direction. The rotating flat membrane 16 is constituted by coating a microfiltration membrane or an ultrafiltration membrane on a water-permeable spacer such as a nonwoven fabric or a net on a membrane support, and the material of the membrane is polystyrene or polypropylene. A polymer resin film such as polyethylene or polyolefin can be used. The rotating flat membranes 16 supported by the two hollow rotating shafts 14 arranged side by side are configured such that parts of the adjacent rotating flat membranes 16 overlap each other. Both ends of the hollow rotary shaft 14 are extended outside the membrane separation tank 12, and the membrane separation tank 12 and the hollow rotary shaft 14 are secured to the water tightness by the shaft sealing means 18. The one closed end of the hollow rotary shaft 14 is connected to the motors 20 and 20, respectively, and the other open end is connected to the treated water pipes 22 and 22, respectively. The hollow rotary shaft 14 and the rotary flat membrane 16 rotate integrally. Is done. The treated water pipe 22 is composed of branch pipes 24 and 24 respectively connected to the two hollow rotary shafts 14 and a trunk pipe 26 where the branch pipes 24 are joined, and the trunk pipe 26 is provided with a suction pump 28. Further, the connection between the hollow rotary shaft 14 and the branch pipe 24 is connected via connecting devices 30 and 30 for preventing the rotation of the hollow rotary shaft 14. The rotating flat membrane 16 supported by the two hollow rotating shafts 14 is rotated at a low speed in the same direction. In this case, it is preferable to change the number of rotations according to the size of the diameter of the rotating flat membrane 16. Due to the rotation in the same direction, in the overlapping portion of the rotating flat membranes 16, the rotation direction is opposite and turbulence is generated.
[0010]
And in order to make microorganisms adhere to this rotation flat membrane 16 and form the microorganism layer 15, the suction pump 28 is operated and the inside of the rotation flat membrane 16 is made into a negative pressure, The microorganism sludge which floats in to-be-processed water Is attached to the membrane surface. Alternatively, before the operation of the apparatus 10, specific microorganisms such as nitrifying bacteria accumulated separately in advance are put into the membrane separation tank 12 and filtered in a total amount so that the specific microorganisms are concentrated on the surface of the rotating flat membrane 16. You may make it adhere to.
[0011]
The purification operation of the water to be treated by the microorganism-supporting rotary flat membrane device 10 configured as described above is performed by operating the suction pump 28 while rotating the rotary flat membrane 16 by the motor 30. That is, when the suction pump 28 is operated, the inside of the rotary flat membrane 16 becomes negative pressure via the treated water pipe 22 and the hollow rotary shaft 14, and the water to be treated in the membrane separation tank 12 is suction filtered into the rotary flat membrane 16. Then, the turbid component in the for-treatment water is removed. Further, for example, ammonia or organic matter in the water to be treated is biologically treated by the microorganisms in the microbial layer 15 and removed from the water to be treated when the water to be treated passes through the microorganism layer 15 of the rotating flat membrane 16. The treated water that has passed through the rotating flat membrane 16 is drawn out of the apparatus 10 through the hollow rotating shaft 14 and the treated water pipe 22. Thereby, both components, such as ammonia and organic substance, and a turbid component in to-be-processed water can be processed simultaneously.
[0012]
Next, the sponge-like member 32 that is put into the membrane separation tank 12 and peels off the microorganism layer 15 attached to the rotating flat membrane 16 will be described.
2 to 7 show sponge-shaped members 32 having various shapes, FIG. 2 is a sponge ball shape, FIG. 3 is a cube shape, FIG. 4 is a string shape, and FIG. FIG. 6 shows a threadball shape. Moreover, the sponge piece made indefinite shape like FIG. 7 can also be used. As for the size of the sponge-like member 32, it is appropriate to use a member having a minimum dimension of about 1 to 15 mm. The reason for this is that when the amount of sponge-like member 32 introduced into the membrane separation tank 12 is constant, the smaller the sponge-like member 32 is, the larger the total surface area is. However, if the sponge-like member 32 is too small, the grinding force for scraping the microorganism layer 15 is weakened.
[0013]
Since the relationship between the size of the sponge-like member 32 and the peelability is also affected by the number of rotations of the rotating flat membrane 16, it is possible to change the size of the sponge-like member 32 according to the number of revolutions of the rotating flat membrane 16. It is a factor to improve. The specific gravity of the sponge-like member 32 needs to be substantially equal to the specific gravity of the water to be treated so that it can be easily dispersed in the water to be treated when the rotating flat membrane 16 is stirred. However, it is not necessary to make all the specific gravity of the many sponge-like members 32 to be supplied the same, but it is preferable to change the specific gravity. This is because when the rotating flat membrane 16 is rotated, the flow of water to be treated near the periphery of the rotating flat membrane 16 is fast, and the water to be treated near the center of the rotating flat membrane 16 has a slow flow. This is because mixing the sponge-like member 32 makes it easy to uniformly disperse the sponge-like member 32 over the entire surface of the rotating flat film 16. As the material of the sponge-like member 32, any material that does not damage the rotating flat membrane 16, such as porous urethane foam, sponge, etc., can exhibit any grinding force.
[0014]
Next, an operation method of the microorganism-supporting rotary flat membrane device 10 including a peeling process for peeling the microorganism layer 15 having the rotary flat membrane 16 attached to the membrane surface using the sponge member 32 will be described.
FIG. 8 shows a combination of a purification operation for biologically treating and filtering water to be treated and a separation operation for removing the microbial layer 15 by the sponge-like member 32. After the purification operation is performed for a certain period of time, the separation operation is performed and the treatment operation is performed again. The operation cycle is configured to perform the following. This operation method is suitable for the case of the quality of the water to be treated having a large solid concentration such that the layer thickness of the microorganism layer 15 is increased quickly.
[0015]
FIG. 9 shows a basic cycle of the purification operation and a self-cleaning operation in which the suction pump 28 is stopped while the rotating flat membrane 16 is rotated, and a peeling operation by the sponge-like member 32 is incorporated as a bypass cycle in the middle of the basic cycle. It is comprised as follows. In the self-cleaning, the microorganism layer 15 is peeled off by the centrifugal force of the rotating flat membrane 16 in a state where the negative pressure in the rotating flat membrane 16 is released. It is difficult to sufficiently remove the microorganism layer 15 only by this self-cleaning. Therefore, this operation method is suitable for the case of the quality of water to be treated having a low solid matter concentration so that the layer thickness of the microorganism layer 15 gradually increases.
[0016]
Also in the case of the operation method of FIG. 8 and FIG. 9, as the timing of performing the peeling operation by the sponge-like member 32, the separation pressure is detected when the filtration pressure during the purification treatment operation is detected and the detected value becomes equal to or higher than a predetermined pressure. Alternatively, the solids concentration of the water to be treated may be detected, and the timing of the peeling operation, in other words, the purification operation time may be set based on the detected value. FIG. 10 is a state diagram in which the sponge-like member 32 is introduced into the membrane separation tank 12 and the microorganism layer 15 formed on the rotating flat membrane is peeled off.
[0017]
A large number of sponge-like members 32 charged into the membrane separation tank 12 are dispersed throughout the membrane separation tank 12 by the stirring action caused by the rotation of the rotary flat membrane 16, and the water to be treated generated by the rotary flat membrane 16 is also dispersed. Move around the treated water in a swirling flow. As a result, the sponge-like member 32 comes into contact with the microbial layer 15 of the rotating flat membrane 16, and the microbial layer 15 is peeled off in a short time by scraping the microbial layer 15. At this time, if the suction pump 28 is stopped, the peelability can be further improved. Then, by controlling the peeling operation time, that is, the time during which the sponge-like member 32 is put into the membrane separation tank, the layer thickness of the microorganism layer 15 can be maintained substantially constant. Further, the peeling efficiency is improved by increasing the number of rotations of the rotating flat membrane 16, so that the layer thickness of the microorganism layer 15 is maintained at a desired layer thickness by controlling the peeling operation time and the rotating number of the rotating flat membrane. It is also possible. In this case, it is not necessary to rotate the rotating flat membrane 16 at a high speed as in the prior art, and for example, about 1.5 to 2 times the rotation speed during the treatment operation of the water to be treated is sufficient. That is, in this peeling operation, the rotation speed of the rotating flat membrane 16 may be a speed that allows the sponge-like member 32 to be dispersed throughout the membrane separation tank 12 in the water to be treated. Can be sufficiently peeled off. Therefore, it is not necessary to use a motor that rotates the rotating flat membrane 16 with a high output, and it is not necessary to use a machine with high accuracy of machining and assembly of other parts related to rotation. Can be reduced.
[0018]
Further, by combining the sponge-like member 32 and the overlap between the rotating flat membranes 16, the sponge-like member 32 enters between the overlapping rotating flat membranes 16, so that the sponge-like member 32 is pressed against the microorganism layer 15. In this state, the microbial layer 15 is scraped off. Therefore, the detachability of the microbial layer 15 can be improved more than simply bringing the sponge-like member 32 and the microbial layer 15 into contact with each other.
[0019]
Further, when air bubbling is performed upward from the lower part in the membrane separation tank 12 in parallel with the peeling operation, the microbial layer 15 is peeled off by the shearing force due to the bubbles, which is coupled with the peeling at the sponge-like member 32. The peeling effect can be further improved.
FIG. 11 shows the relationship between the filtration pressure and the operation time using an iron-based coagulated liquid having a solid concentration of 10,000 mg / L as water to be treated.
[0020]
The operation method of the present invention is performed by an operation method configured such that the purification operation and the self-cleaning operation described in FIG. 9 are set as basic cycles, and the peeling operation by the sponge member 32 is included as a bypass cycle in the middle of the basic cycle, The sponge-like member 32 was charged once every 3 hours of purification operation.
On the other hand, as a conventional operation method, the operation cycle of FIG. 9 is excluded from the peeling operation by the sponge-like member 32, and the operation method is a combination of the purification operation and the self-cleaning operation. In FIG. 11, the thick line is the operation method of the present invention, and the thin line is the conventional operation method. In both the present invention and the prior art, when the filtration pressure reached 40 kPa, chemical cleaning was performed to restore the filtration pressure to about 6 kPa.
[0021]
As can be seen from FIG. 11, in the case of the conventional operation method, it was necessary to perform chemical cleaning once every 300 hours, but in the operation method of the present invention, once every 1000 hours. It was only necessary to perform chemical cleaning, and the chemical cleaning interval could be increased by three times or more than the conventional operation method. Moreover, although the solid substance of the iron-based agglomerated liquid adhered to the rotating flat membrane at a high density, the microbial layer 15 could be efficiently peeled according to the present invention.
[0022]
In the present embodiment, the sponge-like member 32 is intermittently charged. However, if the microorganism layer is to be completely removed, the sponge-like member 32 may be constantly charged in the membrane separation tank 12. Is possible. Moreover, although the two hollow rotating shafts have been described, the number may be one or two or more.
[0023]
【The invention's effect】
As described above, according to the method of operating the microorganism-supporting rotating flat membrane device of the present invention, even if a microorganism layer is formed at a high density on the rotating flat membrane, the rotating flat membrane is rotated at a low rotational speed to The layer can be effectively peeled off.
Therefore, since the time for the peeling operation for peeling the microorganism layer can be greatly shortened, the treatment operation for treating the water to be treated can be efficiently performed. Further, unlike the prior art, it is not necessary to rotate the rotating flat membrane at a high speed for the separation of the microorganism layer, so that the apparatus cost can be reduced.
[Brief description of the drawings]
FIG. 1 is a top view of a rotating flat membrane device. FIG. 2 is a perspective view of a sponge-like member having a sponge ball shape. FIG. 3 is a perspective view of a sponge-like member having a cubic shape. FIG. 5 is a perspective view of a cloud-like sponge-like member. FIG. 6 is a perspective view of a thread-like sponge-like member. FIG. 7 is a perspective view of an irregular-shaped sponge-like member. FIG. 9 is a diagram showing an example of the operation method of the rotating flat membrane apparatus of the mold type. FIG. 9 is a diagram showing another example of the operating method of the microorganism-supporting rotating flat membrane apparatus of the present invention. Fig. 11 is a state diagram in which the microbial layer adhering to the surface is peeled. Fig. 11 is a graph comparing the microbial layer peeling effect between the operation method of the present invention and the conventional operation method.
DESCRIPTION OF SYMBOLS 10 ... Rotating flat membrane apparatus 12 ... Membrane separation tank 14 ... Hollow rotating shaft 15 ... Microorganism layer 16 ... Rotating flat membrane 20 ... Motor 22 ... Treated water piping 28 ... Suction pump 32 ... Sponge-like member

Claims (3)

A method for operating a microorganism-supported rotary flat membrane apparatus, wherein a microorganism layer is formed by attaching microorganisms to the surface of a rotary flat membrane provided in a membrane separation tank, and the treated water is biologically purified by the microorganism layer. In
In the state where the rotating flat membrane is rotated, the rotation from the vicinity of the periphery of the rotating flat membrane where the flow of the water to be processed is fast to the vicinity of the center of the rotating flat membrane where the flow of the water to be processed is slow A plurality of sponge-like members having different specific gravities are mixed and introduced so as to be evenly distributed over the entire surface of the flat membrane , and the sponge layer and the microorganism layer are brought into contact with each other to peel off the microorganism layer, and the sponge A method for operating a microorganism-supporting rotary flat membrane device, wherein the rotational speed of the rotating flat membrane is set to be larger than the rotational speed at the time of purification treatment while the microbial layer is being peeled off by the shaped member. 2. The microorganism-supported rotary flat membrane device according to claim 1, wherein the solid content concentration of the water to be treated is detected, and an interval of time for intermittently inserting the sponge-like member is adjusted according to the detected value. how to drive. The method for operating a microorganism-supporting rotary flat membrane device according to claim 1, wherein the filtration pressure of the rotary flat membrane is detected, and the time interval for intermittently inserting the sponge-like member is adjusted according to the detected value. .

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