JP3160609B2 - Membrane equipment and membrane treatment equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to sludge in a reaction tank for biological treatment, sludge transferred from the reaction tank or their concentrated sludge, human waste wastewater before biological treatment, an agglutination reaction liquid by adding a flocculant, or a mixture thereof. The present invention relates to a membrane device for membrane-filtering a stock solution such as a concentrated sludge obtained by separating a reaction solution in a sedimentation tank and a supernatant thereof, and a membrane treatment device incorporating the membrane device to realize a membrane treatment process.

[0002]

2. Description of the Related Art Wastewater containing organic matter, nitrogen, phosphorus, etc., which causes pollution of the ocean and rivers, is generally treated as clear water by biological treatment and discharged into rivers and the like.

As means for solid-liquid separation of a biological treatment reaction solution,
Conventionally, a sedimentation tank of a gravity sedimentation type has been used, but recently, a membrane separation technique has been used due to a reduction in installation space, ease of maintenance, and the like.

In membrane separation technology, it is extremely important to obtain a constant amount of filtrate for a long period of time. However, it is generally inevitable that the amount of filtrate decreases with time. As one of the causes, it is considered that a separated and concentrated substance or the like is deposited on the membrane surface to form a gel layer, and this gel layer grows and hinders the permeation of the filtrate. This gel layer is called a concentration polarization layer, and the thickness of the concentration polarization layer tends to increase as the concentration of the pollutant in the sludge increases and the amount of the permeated filtrate increases. Therefore, in the membrane separation technique, it is important how to reduce the thickness of the concentration-polarized layer and how to remove the generated concentration-polarized layer.

[0005] As a membrane separation technique, depending on the type of membrane,
A flat membrane system, a tubular system, and the like are known, and an external installation type in which a membrane is installed outside a reaction tank depending on an installation position of the membrane,
A submerged membrane type in which a membrane is installed in a reaction tank is known.

Conventionally, an apparatus shown in FIG. 4 has been known as a film apparatus or a film processing apparatus using an externally mounted flat film. In the figure, 50 is a membrane device, 51 is a circulation tank for receiving sludge sent from a reaction tank or the like (not shown), and 52 is a circulation pump. Reference numeral 53 denotes a frame that can be disassembled by removing a packing (not shown).
54 is detachably fixed. The membrane-attached plate 54 includes a membrane support member 57 having openings 55 and 56 above and below, and a membrane 58, and the membrane 58 is attached to both surfaces of the membrane support member 57 via a gap 57a. Reference numeral 59 denotes a drain for draining the filtrate. Reference numeral 60 denotes a sludge inlet provided in the frame, and 61 denotes an outlet. 62 is an inter-membrane channel through which sludge or concentrated sludge flows.

The sludge in the circulation tank 51 is introduced into the sludge inlet 60 using the circulation pump 52, enters the inter-membrane channel 62 through the opening 56, and is separated into concentrated sludge and filtrate. The filtrate is taken out through the filtrate discharge groove 59. The concentrated sludge is returned to the circulation tank 51 via the sludge outlet 61, and is mixed with the sludge sent from a reaction tank (not shown). The above circulation operation is repeatedly performed.

In the above-mentioned conventional apparatus, in order to suppress concentration polarization, the circulation flow rate of sludge in the inter-membrane
A method of speeding up to about 2.5 m / s was adopted. But,
Since the circulation flow rate is large and the pressure loss increases, the power of the pump must be increased.

When the membrane is operated by applying pressure to the circulating sludge side (inter-membrane flow path side) of the membrane, the amount of permeate increases temporarily. However, by increasing the amount of permeate, the gel layer on the membrane surface is increased. Grows faster and the filtrate volume decreases. Attempts to maintain high permeate filtrate volumes result in higher power costs.

In the flat membrane method, the gel layer can be completely removed by removing the packing (not shown), disassembling and cleaning the frame. Therefore, there is an advantage that the function of the membrane can be completely restored even if the sludge is clogged. However, since the disassembly and inspection work of the membrane is a dirt work, it is desired to reduce the number of times of the work.

On the other hand, Japanese Patent Application Laid-Open No. 2-86893 discloses a submerged flat membrane device in which a flat membrane is immersed in a reaction tank and suctioned by a suction pump to obtain a filtrate. According to such an apparatus, the power required to obtain the required amount of filtrate can be kept low. In addition, by suppressing the amount of the permeated filtrate, the growth of the gel layer can be suppressed slowly, and the adhesion of sludge can be prevented by aeration bubbles in the reaction tank.

However, in the submerged flat membrane device described in the above publication, since the distance between the air diffuser and the membrane is large, there is a variation in air bubbles entering between the membranes. Therefore, the sludge clogging of the entire membrane tends to vary. Also, in the event that sludge adheres, the entire apparatus is taken out of the water and washed. This is a complicated and dirty operation.

[0013]

Therefore, the first aspect of the present invention
An object of the present invention is to provide a membrane device which can prevent the growth of a gel layer on the membrane surface, can prevent the sludge from being clogged while maintaining a high permeation filtration amount, and can prevent the sludge from being clogged on the entire membrane without variation.

It is a second object of the present invention to provide a flat membrane apparatus which can reduce the number of times of disassembling and cleaning of a frame, is externally installed, and has good maintenance.

A third object of the present invention is to provide a membrane processing apparatus which can eliminate a circulation pump and contributes to cost reduction.

[0016]

According to a first aspect of the present invention, there is provided a membrane device , comprising:
A plurality of filtration membranes are arranged in parallel, and on one side of the filtration membrane,
It has a transmembrane flow path, which is a flow path for the circulating stock solution, and the other
Having a filtrate discharge part on the side of
And a lower portion thereof are closed, and a discharge portion for fine bubbles is provided at a lower end portion of the transmembrane flow path .

[0017]

In order to further solve the above-mentioned problems, the membrane processing apparatus of the present invention comprises a flat membrane-shaped filtration membrane in a frame of a membrane apparatus which can be opened.
The result was several juxtaposed, circulated on one side of the filtration membrane
It has a transmembrane flow path, which is a flow path for the undiluted solution, and has a
It has a filtrate discharge part, and the upper and lower parts of the transmembrane channel are closed.
A membrane device provided with a discharge section for fine bubbles at the lower end of the inter-membrane flow path, an air diffuser for supplying air to the discharge section, and an upper side of a frame of the membrane device. Been formed
Connects to the outlet to guide the concentrated stock solution containing air bubbles from the outlet
And gas-liquid separation.
Concentration with bubbles at the inlet formed below the side of the frame
Power is generated by the density difference between the stock solution and the concentrated stock solution without bubbles.
It is characterized by comprising at least a circulation tank for feeding without intervening, and a filtrate pump for sucking the filtrate.

The upper and lower portions of the membrane device of the present invention are closed.
By having a discharge section for microbubbles at the lower end of the inter-membrane flow path, not only does the flow of the stock solution occur due to the microbubbles discharged from the discharge section, but the microbubbles alone or together with the stock solution contact the membrane surface. Alternatively, because of the rubbing, the growth of the gel layer on the membrane surface can be prevented, and the clogging of sludge can be prevented while maintaining a high permeation filtration amount. Since the air bubbles pass uniformly along the surface of the membrane, it is possible to prevent sludge blockage of the entire membrane without variation.

[0020] In the film device using a flat membrane as a filtration membrane
The above-mentioned contact and / or rubbing phenomenon occurs in the inter-membrane flow path, which can prevent the growth of the gel layer on the membrane surface, and thus can prevent the sludge from being clogged while maintaining a high permeation filtration amount. In addition to the above-mentioned effect that sludge blockage can be prevented without variation, the present invention also has the effect that the number of times of frame disassembly and cleaning peculiar to a flat membrane device can be reduced.

Further, by being constituted at least by the membrane device, the air diffuser, the circulation tank and the filtrate pump, the relative density of the undiluted solution containing bubbles in the membrane device is reduced, and a new solution is added from the circulation tank to the flow path. Since a density difference is generated between the solution and the stock solution containing no bubbles, a liquid flow is generated in the flow path due to the density difference, and power only for circulation is not required. Therefore, a circulation pump can be eliminated, which contributes to a reduction in cost (both initial and running costs).

[0022]

Embodiments of the present invention will be described below.

[0023]

[0024]

[0025] In a membrane device of the present invention, a flat membrane-like filtration membrane
Formed by alternately forming the discharge portion of the intermembrane channel and the filtrate was several juxtaposed between the filtration membranes, an external stationary membrane apparatus using a flat membrane, the specific structure Kamitaira This is a device capable of attaching and detaching the membrane, that is, a flat membrane device capable of disassembling the frame. In such flat membrane apparatus that have provided the discharge portion of the fine bubbles in the lower portion of the film between the flow path. The mode of use of such a membrane apparatus is arbitrary, and it is preferable to use the membrane apparatus of the present invention.

The membrane processing apparatus of the present invention comprises the flat membrane apparatus described above, an air diffuser for supplying air to a discharge section of the membrane apparatus, an inlet for introducing a concentrated concentrate to the membrane apparatus, and the membrane apparatus. What is necessary is just to have at least a circulation tank connected to the outlet for discharging the concentrated stock solution, and a filtrate pump for sucking the filtrate. Although the flat membrane device and the circulation tank may be separate bodies, they are preferably formed integrally in terms of space.

The filtration membrane used in the present invention is not particularly limited as long as it can be filtered at a relatively low pressure, and may be any of an ultrafiltration membrane and a microfiltration membrane. In the present invention, the transmembrane pressure is 1 kg /
Preference is given to membranes which can be filtered below cm ² .

In the present invention, the undiluted solution includes, for example, sludge in a reaction tank for biological treatment, sludge transferred from the reaction tank (circulation tank sludge, etc.) or their concentrated sludge, human wastewater before biological treatment, coagulant An agglutination reaction liquid by addition or a concentrated sludge obtained by separating the reaction liquid in a sedimentation tank, and a supernatant liquid thereof may be mentioned.

The membrane apparatus of the present invention can be applied to reuse of wastewater, recovery of valuable resources, use of rainwater, various separation and concentration, various separation and concentration purification, and the like. Therefore, the stock solution of the present invention includes various stock solutions to the extent that the object is achieved.

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

FIG. 1 is an explanatory sectional view of a main part showing an example of a film processing apparatus incorporating a film apparatus of the present invention. In FIG.
1 is a membrane device, 2 is a filtrate pump, and 3 is a circulation tank.
Reference numeral 101 denotes a membrane device frame that can be opened.
A plurality of membrane-attached plates 102 are detachably fixed therein.

The membrane-attached plate 102 is composed of a membrane support member 103 having openings vertically and flat membranes 104 fixed on both sides thereof. The flat membrane 104 is fixed by seal ring portions 105 and 106 provided in upper and lower openings.

The membrane support member 103 is formed of a plate material.
The surface of the membrane support member 103 is formed in an uneven shape. 107 is flat membrane
This is a gap formed between 104 and the membrane support member 103. 108
Is an inter-membrane flow path through which a stock solution formed between the plurality of membrane-attached plates 102, for example, sludge or concentrated sludge, flows.

The distance between the transmembrane channels 108 is preferably 3.0 mm or more, more preferably from the viewpoint of preventing blockage of the transmembrane channels.
4.5 mm or more. The upper limit is 8.0 for volumetric efficiency of membrane equipment
mm or less, more preferably 6.0 mm or less.

Reference numeral 109 denotes a filtrate discharge groove.
And is configured to be able to suck the filtrate. 11
Numeral 0 denotes a sludge inlet provided on the frame 101, and 111 denotes an outlet, which are connected to the circulation tank 3 respectively.

Reference numeral 4 denotes an air diffuser connected to an air diffuser (not shown) (for example, a blower or a compressor). The air diffuser 4 has a plurality of thin tubes near the inlet of the undiluted solution or at the lower end of the transmembrane channel 108. A hole is formed. The pores are the discharge section 401 of the fine bubble in the present invention. Specifically, a plurality of pores are formed in a metal pipe, a resin hose, or the like.
Therefore, when the air diffuser 4 is fed into the opening formed in the seal ring portion 106, fine bubbles can be sent from the discharge portion 401 to the inter-membrane flow path 108. The diameter of the pores is preferably from 100 to 1000 μm.

Further, in the present invention, the portion of the discharge portion formed in the air diffuser itself may be formed of a member such as porous rubber, resin, metal or ceramic. In this case, the discharge portion 401 is formed by the plurality of pores of the porous member. The pore diameter is preferably 100 to 1000 μm.

A plurality of discharge portions 401 of the diffuser 4 are provided at positions where the fine bubbles sent from the inter-membrane flow path directly rise in the inter-membrane flow path portion.

Also, as shown in FIG. 2, it is preferable to increase the diameter of the discharge portion 401 and add a nozzle 402 for generating fine bubbles at that portion. Examples of such nozzles include a pipe containing a mixing member, a ceramic having many pore structures, and a sponge.

It is preferable to set the film interval so that the generated bubbles surely and uniformly rise in the transmembrane flow path 108. Membrane support member 103 further attaching membrane
The uneven waves formed on the surface of the film also play a role such that the diffused air that increases the film interval spreads uniformly over the entire inter-membrane flow path 108 and rises.

At the lower part of the circulation tank 3, an inflow port 301 for sludge is provided.
Is provided, and an outlet 302 is provided at the upper part. The circulation tank 3 may be provided with a vent or the like that can be degassed, but it is also possible to degas after taking it out. In this example of the apparatus, an example in which degassing is performed in the circulation tank 3 will be described.

The sludge is supplied from the circulation tank 3 to the sludge inlet 110.
Through the opening of the seal ring portion 106 at the lower part of the membrane device 1, flows into the inter-membrane channel 108, and rises together with the diffused fine bubbles. The sludge combined with the air bubbles passes through the opening of the seal ring 105 at the top of the membrane device 1 and the sludge outlet 111.
And returns to the circulation tank 3 again.

The sludge flowing from the opening of the upper seal ring 105 is separated by the circulation tank 3 into bubbles.
Accordingly, the sludge sent from the circulation tank 3 to the membrane device 1 via the sludge inlet 110 substantially does not contain bubbles.

The circulation of the sludge is performed without using the power of a circulation pump or the like. That is, the sludge circulates due to the density difference between the sludge supplied from the circulation tank 3 to the membrane device 1 and the sludge containing bubbles in the inter-membrane channel 108.

The circulation tank 3 plays an important role as a gas-liquid separation tank for circulating sludge.
By removing sludge and adding clean water, the membrane can be easily washed, and no special washing device is required. This circulation tank 3
Chemicals can be easily washed by adding chemicals to the system.

The microbubbles diffused in the inter-membrane flow path 108 not only generate a driving force for the sludge circulation due to the density difference from the circulation tank 3 but also create a disturbance in the flow of the inter-membrane flow path 108, and cause Prevents the growth of attached gel layers.

Even when the water washing is being performed, the air diffusion is continued without stopping. As a result, the gel layer and sludge adhered and grown on the membrane surface can be easily washed.

The filtrate is suctioned and taken out by the filtrate pump 2 connected to the filtrate collecting pipe 201 of the membrane device 1. When the filtrate is sucked, the circulating sludge concentration in the membrane device 1 increases. Therefore, sludge is supplied from the inlet 301 to the circulating tank 3 to prevent the sludge concentration from increasing, and a part of the sludge is discharged from the circulating tank 3 to the outlet 302. And returns to the original circulating tank for an ultrafiltration membrane (not shown). This prevents the sludge concentration and the concentration of the concentrated substance in the membrane treatment device from becoming abnormally high.

In the above embodiment, the case where a plate having unevenness on the surface is used as the membrane support member has been described. However, the present invention is not limited to this, and the membrane support member may be a porous plate. The membrane support member may be a plate made of synthetic fiber.

[0050]

Hereinafter, the present invention will be described in more detail with reference to Examples of the present invention. However, the present invention is not limited by these Examples.

(1) Test sample The activated sludge in the biological treatment reaction tank of the human waste treatment facility was used as the stock solution, and the sludge concentration was 10,000 to 15,000 mg / liter. The temperature of the stock solution was 32-35 ° C.

(2) Test Apparatus The membrane apparatus shown in FIG. 1 was used as a test apparatus.

The type of the membrane device and the configuration of the membrane are as follows. Model of membrane device: UFP-71 (manufactured by Mitsui Petrochemical Industries, Ltd.) Structure of membrane: 1S-31P (30 sheets with membrane, membrane area)
10.5m ² ) The brand of the membrane used for the membrane device and the molecular weight of the membrane fraction of the membrane are as follows. Brand of membrane: IRIS 3038 (Material: polyacrylonitrile) Molecular weight cut off of membrane: 20,000

A total of 30 plates with membranes were set so that the intervals between the membranes would be 3.0 mm, 4.5 mm, and 6.0 mm, each with 10 plates.

As the air diffuser provided with the discharge section, a porous synthetic resin tube having an inner diameter of 16.5 mm and an outer diameter of 21.0 mm was used. The approximate pore diameter of the discharge section of the air diffuser was 300 μm. The supply amount of the undiluted sludge was 2 m ³ / hr. The filtrate was produced by a suction filtration method. The suction filtrate flux is 1)
20 l / m ² / hr, 2) 30 l / m ² / hr were set for two cases.

(3) Test Results Test 1 As basic data of continuous stable operation, the suction pressure at that time was measured while the suction filtrate volume was constant, and the change in suction pressure at that time was measured. saw. The result is shown in FIG.

In FIG. 3, curve I shows the relationship between suction pressure and filtration time when trying to obtain a suction filtrate flux of 20 l / m ² / hr, and curve II shows a suction filtrate flux of 30 l / m ² / hr. Shows the relationship between the suction pressure and the filtration time when trying to obtain.

As is apparent from FIG. 3, 30 liters / m ² /
In hr, continuous operation was possible for about 4 days (curve II), and in 20 liters / m ² / hr for about 1 week (curve I), a lower set flux was more favorable for long-term continuous operation.

Suction filtration flux 30 liter / m ² / hr 4
When the operation was stopped after elapse of one day, water was washed for one hour and restarted (see the fifth day of curve II), the suction pressure was -0.37 kg.
/ cm ² to −0.12 kg / cm ² . It was confirmed that there was a considerable washing effect.

The distance between the membranes was tested by incorporating three types of 3.0 mm, 4.5 mm, and 6.0 mm into one unit. From the results of the continuous test, there was a difference due to the setting of the suction filtration flux. There was slight sludge adhesion at 3.0mm and 4.5mm. At 6.0 mm, there was almost no adhesion of sludge, and it was in a very clean state.

When the continuous operation was stopped, the sludge in the circulation tank was drained, the tap water was injected, and the air was washed by aeration for 1 hour. The sludge was cleanly cleaned. Further, the gel layer thinly deposited on the membrane was almost completely removed. I was able to get rid of it.

Test 2 From the favorable results of Test 1, the film interval was 4.5 mm and the number of films was 60
Under the operating condition of suction filtration flux of 30 l / m ² / hr, the operation was stopped once a day before the suction pressure began to drop and the water washing was incorporated. As a result, long-term stable operation for about 60 days was achieved. It has become possible.

Test 3 (Comparison) In order to confirm the effect of the sludge circulation and the prevention of sludge adhesion by the air diffusion, a change in suction pressure when the air diffusion was stopped and the operation was performed was tested.

Immediately after the start of the test, the suction pressure began to drop, and the operation became inoperable only 16 minutes after the start of the test. After further washing with water for 1 hour, the filtration test was restarted, and the suction pressure was recovered to almost the initial level.
As in the case of the first time, it became inoperable in 13 minutes. When the frame was disassembled in this state, the sludge was completely blocked between all the membranes between the membranes. The attached sludge was very viscous and attached so as to cling to the membrane surface.

[0065]

According to the present invention, the growth of the gel layer on the membrane surface can be prevented, the sludge can be prevented from being clogged while maintaining a high permeation filtration amount, and the sludge can be completely prevented from being blocked on the entire membrane.

Further, the number of times of disassembling and cleaning of the frame can be reduced, and a flat membrane device which is externally installed and has good maintenance can be provided.

Further, a circulating pump can be eliminated, and a membrane processing apparatus that contributes to cost reduction can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of an essential part showing an example of a film processing apparatus incorporating a film apparatus of the present invention.

FIG. 2 is a schematic diagram showing an improved example of a diffuser tube;

FIG. 3 is a graph showing test results.

FIG. 4 is a sectional view of a main part showing a conventional membrane device.

[Explanation of symbols]

 1: Membrane device 101: Frame 102: Plate with membrane 103: Membrane support plate 104: Flat membrane 105: Upper sealing part 106: Lower sealing part 107: Gap 108: Intermembrane flow path 109: Filtrate discharge groove 110: Sludge inlet 111: Sludge outlet 2: Filtrate pump 201: Collecting pipe 3: Circulation tank 301: Sludge inlet 302: Sludge outlet 4: Air diffuser 401: Discharge unit 402: Nozzle

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI C02F 3/12 C02F 3/12 S (72) Inventor Hiroshi Irie 3-216 Onocho, Ichikawa-shi, Chiba Prefecture (72) Inventor Tadaaki Hashimoto 1-35-11 Yukarigaoka, Sakura City, Chiba Prefecture (56) References JP-A-52-143975 (JP, A) JP-A-6-15151 (JP, A) JP-A-7-16591 (JP, A) (58) ) Surveyed field (Int.Cl. ⁷ , DB name) B01D 25/12 B01D 63/08 B01D 65/02 520 B01D 65/08 C02F 1/44 C02F 3/12

Claims (2)

(57) [Claims] 1. A flat film-like structure in a frame of a film device capable of being opened.
A plurality of filtration membranes are juxtaposed and circulated on one side of the filtration membrane.
It has a transmembrane flow path, which is a flow path for the undiluted solution,
The surface side has a filtrate discharge part, and the upper and lower parts of the intermembrane flow path
A membrane device which is closed and has a discharge section for fine bubbles at a lower end portion of the intermembrane flow path . 2. A becomes to several juxtaposed the flat membrane of the filtration membrane to the frame of the Hirakiwaku possible membrane device, 循on one surface of the filtration membrane
It has a transmembrane flow path, which is a flow path for the undiluted solution,
On the surface side, there is a filtrate discharge part, and the upper and lower parts of the transmembrane flow path
A membrane device which is closed and has a discharge portion for fine bubbles provided at a lower end portion of the inter-membrane flow path, an air diffusion device for supplying air to the discharge portion, and a side portion above a frame of the membrane device Formed into
Concentrate containing air bubbles connected to the outlet
Liquid and gas-liquid separation.
Air bubbles into the inlet formed below the side of the frame.
Due to the density difference between the concentrated stock solution and the concentrated stock solution without bubbles
A membrane processing apparatus comprising at least a circulation tank that feeds in without intervening power, and a filtrate pump that sucks the filtrate.