JP2012045510A - Membrane separation activated sludge processing apparatus and membrane surface washing method of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a membrane separation activated sludge processing apparatus and a membrane surface washing method of the membrane separation activated sludge processing apparatus which does not require complicated operation management, makes such highly efficient membrane surface washing as to hardly cause membrane surface blocking possible and does not accompany air diffusion of excessive air amount.SOLUTION: The membrane separation activated sludge processing apparatus is characterized in that an immersion type membrane separation device is arranged in a reaction tank, an air diffuser is arranged on the lower side of the immersion type membrane separation device and a water jet device having a submerged pump disposed outside the range on the vertically lower side of the immersion type membrane separation device and on the lower part of the reactor tank as a power source, is disposed on the upper side or the lower side of the diffuser.

Description

  The present invention relates to a submerged membrane separation apparatus for solid-liquid separation of a microorganism-containing liquid containing activated sludge using a membrane. Specifically, the present invention relates to wastewater treatment using a so-called membrane separation activated sludge method, in which sewage such as sewage is subjected to membrane treatment after activated sludge treatment.

  Conventionally, there is an activated sludge treatment as a method of treating organic sludge, and there is a membrane separation activated sludge treatment that maintains a high activated sludge concentration in a tank by using a membrane separator together. In a general membrane separation activated sludge method, an immersion membrane separation device is installed in the reaction tank, an aeration device is placed below the immersion membrane separation device, and oxygen is supplied by air diffused from the diffusion device. The activated sludge treatment is performed, and an upward flow generated by the air lift action of air is caused to act as a scavenging flow on the membrane surface of the submerged membrane separation device to continuously wash the cake adhering to the membrane surface. As the immersion type membrane separation apparatus to be used, an apparatus comprising a number of flat membrane elements and a number of hollow fiber membrane elements is used. Also, when performing membrane separation treatment, coarse bubbles having a high membrane surface cleaning effect are generated, and the membrane surface is cleaned by causing a gas-liquid mixed upward flow generated by the coarse bubbles to act on the membrane surface. Yes.

  Here, the greater the bubbles acting on the membrane surface, the higher the shearing force against the deposited sludge on the membrane surface, so that the cleaning efficiency of the separation membrane surface can be increased. Therefore, it is considered necessary to use coarse bubbles for cleaning the separation membrane. However, the coarse bubble diffusing device giving priority to the effect of cleaning the membrane surface has the disadvantage that (i) irregular vibration accompanying aeration is large and the membrane itself is easily damaged. In addition, (ii) oxygen dissolution efficiency is low, and oxygen supply capacity necessary for biological treatment with activated sludge may be insufficient. For this reason, in order to supply oxygen sufficiently, it is necessary to diffuse an excessive amount of air more than the amount of air necessary for cleaning the membrane surface, leading to an increase in aeration power.

  Therefore, (i) as a method for cleaning the outer surface of the membrane while preventing the membrane surface from being damaged by irregular vibrations caused by a large amount of aeration, an aeration device is provided below the submerged membrane separation device. There has been proposed a water treatment apparatus that is arranged and provided with a rotary blade that causes the water to be treated to flow toward the membrane element (Patent Document 1). In addition, (ii) in order to increase the efficiency of air diffusion, it has been studied to minimize the amount of air diffusion for supplying oxygen necessary for biological treatment while maintaining the cleaning efficiency of the separation membrane surface with coarse bubbles. An air diffusion method for generating both bubbles and coarse bubbles has been proposed. For example, a processing apparatus has been proposed in which both a coarse bubble diffuser and a fine bubble diffuser are installed below the submerged membrane separation device to generate both coarse bubbles and fine bubbles (Patent Document 2). reference).

JP-A-4-247288 Japanese Patent Laid-Open No. 2002-224665

  However, in the conventional configuration described above, (i) when a rotating blade is used as the circulating flow generating means, the power of the driving device is large and the running cost is increased. Further, since the air diffuser is disposed above the rotor blade, the distance between the air diffuser and the bottom of the submerged membrane separation device is shortened. For this reason, the dispersion of the bubble flow aerated from the air diffuser becomes worse, and it becomes difficult to provide a uniform circulating flow over the entire surface of the membrane cartridge. On the other hand, (ii) In order to use the coarse bubble diffuser and the fine bubble diffuser together, appropriate operation management according to the inflowing sewage is required, and the operation management is difficult and costly. Moreover, it is difficult to set an appropriate air volume of air, and depending on the set air volume, the effect of cleaning the membrane surface is reduced and the overall power consumption of air is increased.

  The present invention solves the above-mentioned problems. With regard to (i), the running cost can be reduced, and a uniform circulating flow can be applied to the entire surface of the membrane element. To provide a membrane-separated activated sludge treatment apparatus that can perform highly efficient membrane surface cleaning at low cost and does not involve excessive air volume diffusion without requiring operation management, and a membrane surface cleaning method thereof. With the goal.

  In order to achieve the above object, a membrane separation activated sludge treatment apparatus and a membrane surface cleaning method thereof according to the present invention have any of the following configurations.

(1) A submerged membrane separation device is arranged in the reaction tank, above or below the diffuser disposed below the submerged membrane separation device, outside the range below the submerged membrane separation device and below the reaction tank. A membrane separation activated sludge treatment apparatus characterized by having a water flow device that uses an installed submersible pump as a power source.
(2) The membrane separation activated sludge treatment apparatus according to (1), wherein the air diffuser has a fine bubble tube that generates fine bubbles having a diameter of 1 mm or less.
(3) The membrane separation activated sludge treatment apparatus according to (1) or (2), wherein the submersible pump is arranged at a position separated from the bottom of the reaction tank by 50 mm or more and 150 mm or less.

(4) A submerged membrane separation device is arranged in the reaction tank, above or below the diffuser arranged below the submerged membrane separation device, outside the range vertically below the submerged membrane separation device, and below the reaction tank. A membrane surface cleaning method in a membrane separation activated sludge treatment device having a water flow device using a submersible pump as a power source, which is caused by an air lift action caused by bubbles diffused from the air diffusion device and a water flow generated from the water flow device. A membrane surface cleaning method in a membrane separation activated sludge treatment apparatus, characterized in that an ascending flow of a gas-liquid mixed phase is applied as a sweep to the membrane surface of the submerged membrane separation apparatus.
(5) The membrane surface cleaning method for a membrane separation activated sludge treatment apparatus according to (4), wherein the air diffuser has a microbubble tube that generates microbubbles having a diameter of 1 mm or less.

  According to the membrane surface cleaning method in the membrane separation activated sludge treatment method of the present invention, since the air lift action of air is promoted by the water flow generated from the water flow device, a small amount of diffused air that can ensure the minimum necessary dissolved oxygen concentration In this case, a sufficient film surface cleaning effect can be obtained.

  In addition, the water flow generated from the water flow device can use low power because the head pressure from the liquid level in the reaction tank can be used by using a submersible pump installed in the lower part of the reaction tank as a power source.

  Furthermore, by installing the submersible pump outside the vertically lower range of the submerged membrane separation device, the space occupied by the air diffuser and the water flow device in the air diffuser case can be made compact compared to when the rotor blades are installed. . Thereby, it becomes possible to ensure the distance from the diffuser to the bottom of the submerged membrane separator, and the dispersibility of the bubble flow aerated from the diffuser is improved.

It is a model front view which shows the processing apparatus of the sewage in embodiment of this invention. It is a schematic plan view which shows the wastewater treatment apparatus in embodiment in this invention. It is a model front view which shows the processing apparatus in the past. (Comparative Example 1) It is a model front view which shows another conventional wastewater treatment apparatus. (Comparative Example 2) It is a model front view which shows the further another wastewater processing apparatus in the past. (Comparative Example 3)

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In FIG. 1, a sewage supply system 2 for supplying organic sewage is connected to a reaction tank 1, and a submerged membrane separation device 3 is disposed in the reaction tank 1 at a depth of water (500 to 1500 mm) L1. The submerged membrane separation device 3 has a plurality of flat membrane elements 4 arranged in the case 5 along the vertical direction, and the flat membrane elements 4 are arranged in parallel at predetermined intervals. Between the adjacent flat membrane elements 4, a flow path is formed through which the activated sludge mixed liquid in the tank flows by cross flow. The case 5 is divided into an upper membrane case 6 that houses the flat membrane element 4 and a lower air diffuser case 7, and the air diffuser case 7 includes an air diffuser 8 and a water flow device 9 in two upper and lower stages. It arrange | positions and it forms so that the whole quantity of the air and water flow which eject from the diffuser 8 and the water flow apparatus 9 may enter into the membrane case 6. FIG. In the flat membrane element 4, filtration membranes are arranged and bonded to both surfaces of a filter plate made of ABS resin, and a permeate flow path formed on the filter plate is communicated with the permeate outlet tube 10.

  The water flow device 9 is arranged at a distance (0 to 200 mm) L4 from the bottom of the reaction tank 1, and the air diffuser 8 is located above the water flow device 9 by a distance (50 to 100 mm) L3, so that the immersion membrane It arrange | positions in the position which separated the distance (50-200 mm) L2 below the separation apparatus 3, the diffuser 8 diffuses a coarse bubble or a fine bubble, and the water flow apparatus 9 produces | generates a water flow. A blower 11 is connected to the air diffuser 8 to adjust a predetermined amount of air, and the water flow device 9 is provided with a submersible pump 12 installed outside the range below the submerged membrane separator 3 and below the reaction tank 1. Connect to adjust the predetermined water flow rate. These predetermined air amount and water flow rate supply the minimum oxygen amount necessary for the activated sludge treatment in the reaction tank 1 and clean the membrane surface of the flat membrane element 4 of the submerged membrane separation device 3. This is for causing an effective air lift action, and differs depending on the properties and the amount of inflow of the target sewage.

  Here, in the figure, the water flow device 9 is disposed below the air diffuser 8, but the intended effect can be obtained, and the positional relationship may be reversed if there is no problem in the connection. The diffuser 8 only needs to supply a minimum amount of oxygen necessary for the activated sludge treatment in the reaction tank 1 and may be a coarse bubbler, but a fine bubble diffuser is more preferable from the viewpoint of power cost. Can be used for In addition, about arrangement | positioning distance L1-L4 between each apparatus, it does not specifically limit but shows the range which can be used conveniently.

  Regarding the air diffuser 8, a coarse bubble diffuser having a large number of large air holes (2-15 mm in diameter) with a predetermined diameter can be used, and the fine bubble diffuser can generate fine bubbles. It is not particularly limited as long as it is an air diffuser having a diffuser surface that can be formed, and is formed by a large number of small air diffuser holes (diameter 0.5 to 1 mm) having a predetermined diameter, and by expansion and contraction covering the central tube and the central tube A material made of an elastic sheet having a large number of diffused holes to be opened and closed can be used (for example, FLEXAIR T-SERIES diffused holes 2 mm extra fine slit / EDI). Here, coarse bubbles in the present invention are bubbles having a diameter larger than 1 mm, and fine bubbles are bubbles having a diameter of 1 mm or less. In addition, about microbubble, since dissolved oxygen efficiency in activated sludge can be made high, so that a bubble diameter is small, if it is a microbubble of micro and nano level (for example, 100 nm-100 micrometers), it can use more preferably. .

  The water flow device 9 only needs to have a structure that is uniform in the discharge direction and has no clogging of sludge. Those having a slit length of 50 to 300 mm can be used.

  Here, the submersible pump 12 connected to the water flow device 9 is preferably installed in the lower part where the head pressure from the liquid level of the reaction tank 1 can be used as a power source. However, since the highly viscous sludge (sludge-like sludge) accumulated at the bottom may block the suction port of the submersible pump 12, it is more preferable to install it at a predetermined distance (50 to 150 mm) L5 from the bottom.

  Further, the submersible pump 12 is installed outside the submerged membrane separation device 3 in order to make the device space inside the diffuser case 7 compact. And the arrangement should be arranged at a position where the swirl flow (circulation flow) composed of the upward flow generated inside the submerged membrane separator 3 and the downward flow generated around the submerged membrane separator 3 is not hindered. It is preferable to arrange the submersible pump 12 in the H shaded portion shown in FIG. The submersible pump 12 is preferably adjusted according to the nature and amount of the target sewage flowing into the reaction tank 1, and can be arbitrarily used, such as a CV adjustment type and an inverter control type, but from the viewpoint of power cost. An inverter control type can be suitably used.

  Next, the operation of the above configuration will be described. The blower 11 and the submersible pump 12 are driven to supply a predetermined amount of air (15 to 25 times the amount of treated water) and a water flow (10 to 20 times the amount of treated water), and below the submerged membrane separation device 3 In the region, the water flow zone L3 is formed by the water flow A generated from the water flow device 9, and the aeration water mixing zone L2 is formed by the fine bubbles B diffused from the air diffusion device 8 and the water flow A of the water flow device 9.

  In the aeration water flow mixing zone L2, the fine bubbles A and the water flow B are mixed, and the upward flow of the gas-liquid mixed phase generated by the air lift action of the fine bubbles A and the water flow B flows between the adjacent flat membrane elements 4 and becomes active. The sludge mixed liquid is supplied to the submerged membrane separation device 3 by cross flow and solid-liquid separated, and the upward flow acts as a sweep on the membrane surface of the submerged membrane separation device 3. At this time, the flow velocity of the gas-liquid mixed phase flowing into the submerged membrane separation device 3 is remarkably increased by giving the water flow A a certain initial velocity in the fine bubbles B as compared with the conventional air diffusion method. As a result, the fine bubbles B having high velocity energy and the water flow A flow into the flow path between the adjacent flat membrane elements 4 to cause an effective air lift action and to adhere to the cake surface. The membrane surface of the flat membrane element 4 can be washed with high efficiency by the shearing action and collision action of the fine bubbles B.

  In addition, the entire amount of the fine bubbles B and the water flow A enter the membrane case 6 and the rising flow rate is remarkably increased as compared with the conventional air diffusion method. Therefore, the upward flow generated in the submerged membrane separation device 3 and the submerged type The downward flow generated around the membrane separation device 3 is clearly separated, and a swirl flow is generated in the reaction tank 1 without any trouble, so that the stirring in the tank can be performed smoothly. Further, by installing the submersible pump 12 outside the vertically lower range of the submerged membrane separation device 3, the device space inside the diffuser case 7 can be made compact. Thereby, it becomes possible to ensure the distance to the bottom part of the diffuser 8 and the submerged membrane separator 3, and the dispersibility of the bubble flow aerated from the diffuser improves. In addition, even if local diffused clogging occurs in the diffuser 8 used in combination, bubbles can be dispersed by the water flow A, so that the film surface blockage of the cake due to diffused clogging is reduced, and long-term stable operation is possible.

  By the way, the water flow generated from the water flow device 9 can utilize the head pressure from the liquid surface of the reaction tank 1 by using the submersible pump 12 installed in the lower part of the reaction tank 1 as a power source, so As compared with conventional coarse bubble diffusers and fine bubble diffusers, lower power is required. Further, since a sufficient film surface cleaning effect can be obtained even with a small amount of aeration that can ensure the necessary minimum dissolved oxygen concentration, the power of the aeration device 8 used in combination can be extremely reduced. Thus, the driving cost can be reduced comprehensively by driving the minimum aeration blower power and the low power water flow pump 12 together.

  In addition, even if the amount of oxygen necessary to treat the target sewage with activated sludge varies depending on the season or water temperature, it is sufficient to satisfy the minimum amount of air that can ensure the required dissolved oxygen concentration. Even if it is set based on the high water temperature when consumption increases, a small amount of aeration is sufficient. Therefore, complicated operation management and air volume setting are not required if the air volume at a high water temperature at which oxygen consumption is increased is set constant. Moreover, by incorporating inverter control into the submersible pump 12, the water flow rate can be adjusted according to the nature and amount of inflow of the target sewage flowing into the reaction tank 1, and the flow rate required for membrane cleaning can be varied appropriately. Thus, the driving power can be further reduced.

  Hereinafter, the present invention will be specifically described with reference to specific examples and comparative examples.

[Example]
The organic waste water was treated using the sewage treatment apparatus of FIG. This waste water treatment apparatus is composed of a reaction tank 1 (volume 3 m ³ ) and an anaerobic tank (not shown / volume 3 m ³ ) communicating with the reaction tank 1. General sewage (BOD 100-300 mg / L) was introduced as organic wastewater at 30 m ³ / day, and membrane separation activated sludge treatment was performed continuously. The submerged membrane separator 3 is provided with 50 flat membrane elements 4 (PVDF flat membrane, pore size 0.1 μm) adjacent to each other, and a predetermined suction pump (not shown) connected to the permeate outlet tube 10. The treated water is obtained continuously. In addition, the sludge was suitably extracted so that the biological concentration (MLSS) in the reaction tank 1 would be constant at about 10,000 mg / L.

  The membrane surface cleaning device includes an air diffuser 8 (a fine bubble tube having a large number of holes of 0.5 mm diameter, a bubble diameter of about 0.5 mm), and a blower 11 (rated output 0.75 kw, air amount 450 NL / min, 30 kPa), a water flow device 9 (a discharge pipe having a large number of holes of 10 mm in diameter), and a submersible pump 12 (rated output 0.75 kW, discharge rate) installed outside the submerged membrane separation device 3 and below the reaction tank 1 300 L / min, INV control). As for the arrangement distance between each device, the distance L4 from the bottom of the reaction tank 1 to the water flow device 9 is about 200 mm, the distance L3 from the water flow device 9 to the air diffuser 8 is about 100 mm, and the diffuser membrane 8 is submerged by membrane separation. The distance L2 to the lower part of the apparatus 3 was set to about 200 mm. The test was carried out for two months from October 2009 to November 2009, and the continuous operation was performed with the amount of air diffused at 250 NL / min and the water discharge rate constant at 200 L / min (INV output 70%).

As a result, no significant increase was observed in the transmembrane pressure difference (unit: kPa) of all flat membrane elements 4, and the differential pressure increase rate was 0.05 kPa / day (flux 0.7 m / day) over 2 months. Long-term stable operation was possible. Moreover, almost no cake was seen on the membrane surface of each flat membrane element 4, and the effect of dispersing fine bubbles B by the water flow A was seen. The power consumption was calculated from the integrated power consumption of the entire sewage treatment apparatus, and was 2286.5 kwh per total treated water volume of 1800 m ³ (30 m ³ / day × 60 day) for 2 months. The amount was 1.27 kwh / m ³ .

[Comparative Example 1]
The organic wastewater was treated using the sewage treatment apparatus of FIG. The configuration of the sewage treatment apparatus and the treatment conditions were the same as in the example. In addition, although an Example and an operation period (year) differ, the water temperature and property of sewage and sludge were substantially the same. The flat membrane element 4 having the same performance was used.

  The membrane surface cleaning device is composed of a diffuser 8 (a coarse bubble tube having a large number of apertures of 6 mm, a bubble diameter of about 5 mm), and a blower 11 (rated output 1.5 kW, air amount 750 NL / min, 30 kPa). Is done. Regarding the arrangement distance between the devices, the distance L7 from the bottom of the reaction tank 1 to the diffuser 8 was set to about 300 mm, and the distance L6 from the diffuser 8 to the lower part of the submerged membrane separator 3 was set to about 200 mm. The test was conducted for two months from October 2008 to November 2008, and the continuous operation was performed with the amount of air diffused at 600 NL / min.

As a result, the differential pressure increase rate of all flat membrane elements 4 was 0.30 kPa / day (flux 0.7 m / day) in two months, which was a higher value than in the example. Moreover, some local cakes were seen on the membrane surface of each flat membrane element 4, and membrane surface blockage due to non-uniform air diffusion was seen. Consumption power is 2662.3 kwh per 1800 m ^{3 of} total treated water for 2 months, and power consumption per basic unit is 1.48 kwh / m ^3, which is a higher value than in the example. It was.

[Comparative Example 2]
Organic wastewater was treated using the sewage treatment apparatus of FIG. The configuration of the sewage treatment apparatus and the treatment conditions were the same as in the example. However, the operation period (year, month) was different from the examples, and the sludge properties were good and the conditions were suitable. The flat membrane element 4 having the same performance was used.

  The membrane surface cleaning device includes an air diffuser 8 (a fine bubble tube having a large number of holes of 0.5 mm diameter, a bubble diameter of about 0.5 mm), and a blower 11 (rated output 0.75 kw, air amount 450 NL / min, 30 kPa) and a rotating blade 13 (small underwater mixer, rated output 1.5 kW, flow rate 500 L / min) installed at the bottom of the reaction tank 1. About the arrangement distance between each apparatus, the distance L10 from the bottom part of the reaction tank 1 to the diffuser 8 is about 450 mm (the distance L9 from the upper part of the rotary blade 13 to the diffuser 8 is about 100 mm), and from the diffuser 8 The distance L8 to the lower part of the submerged membrane separator 3 was set to about 50 mm. The test was carried out for two months from August to September 2008, and the continuous operation was performed with the amount of air diffused at 250 NL / min and the stirring flow rate at 500 L / min.

As a result, the differential pressure increase rate of all flat membrane elements 4 was 0.10 kPa / day (flux 0.7 m / day) in 2 months, and stable operation was possible. It was a high value compared to the time of Moreover, some local cakes were seen on the membrane surface of each flat membrane element 4, and membrane surface blockage due to non-uniform air diffusion was seen. Consumption power is 3158.6 kwh per 1800 m ^{3 of} total treated water for 2 months, and power consumption per unit is 1.75 kwh / m ^3, which is a higher value than in the example. It was.

[Comparative Example 3]
Organic wastewater was treated using the sewage treatment apparatus of FIG. The configuration of the sewage treatment apparatus and the treatment conditions were the same as in the example. However, the working period (monthly) was different from the examples, and the sludge properties were good and the conditions were suitable for treatment. The flat membrane element 4 having the same performance was used.

  The membrane surface cleaning device includes an air diffuser 8 (a fine bubble tube having a large number of holes of 0.5 mm diameter, a bubble diameter of about 0.5 mm), and a blower 11 (rated output 0.75 kw, air amount 450 NL / min, 30 kPa), a water flow device 9 (a discharge pipe having a large number of holes of 10 mm in diameter), and a submersible pump 12 (rated output of 0) installed in the range vertically below the submerged membrane separation device 3 and below the reaction tank 1 .75 kw, discharge amount 300 L / min, INV control). Regarding the arrangement distance between the devices, the distance L4 from the bottom of the reaction tank 1 to the water flow device 9 is 350 mm, the distance L3 from the water flow device 9 to the air diffuser 8 is 100 mm, and the submerged membrane separation device 3 from the air diffuser 8 to the air diffuser 8. The distance L2 to the lower side of was set to 50 mm. The test was carried out for two months from August to September 2009, and the continuous operation was performed with the air diffusion rate being fixed at 250 NL / min and the water flow discharge amount being constant at 200 L / min (INV output 70%).

As a result, the differential pressure increase rate of all flat membrane elements 4 was 0.10 kPa / day (flux 0.7 m / day) in 2 months, and stable operation was possible. It was a high value compared to the time of. Moreover, some local cakes were seen on the membrane surface of each flat membrane element 4, and membrane surface blockage due to non-uniform air diffusion was seen. Consumption power was 2306.4 kwh per 1800 m ^{3 of} total treated water for 2 months, and the power consumption per basic unit was 1.28 kwh / m ³ , which was almost the same as in the example.

  Table 1 shows the results of Examples and Comparative Examples. When a conventional coarse bubble tube is used alone (Comparative Example 1), and when the fine bubble diffuser 8 and the rotary blade 13 are used together (Comparative Example 2). ), When the fine bubble diffusing device 8 and the water flow device 9 were used in combination (Example), long-term stable operation was possible at low cost. Further, in the case where the fine bubble diffusing device 8 and the water flow device 9 are used in combination, the submersible pump is out of the vertically lower range than when the submersible pump is installed in the vertically lower range of the submerged membrane separation device 3 (Comparative Example 3). When installed in (Example), the dispersibility of the aeration was improved (there was no cake adhesion), and stable operation was possible for a longer period.

  The membrane-separated activated sludge treatment apparatus and the membrane surface cleaning method of the present invention can be used in fields such as sewage treatment containing organic sewage.

1: Reaction tank 2: Sewage supply system 3: Submerged membrane separator 4: Flat membrane element 5: Case 6: Membrane case 7: Air diffuser case 8: Air diffuser 9: Water flow device 10: Permeate outlet tube 11: Blower 12: Submersible pump 13: Rotary blade A: Water flow B: Fine bubbles L1: Distance from reaction vessel liquid level to membrane case L2: Distance from diffuser to membrane case (FIGS. 1 and 5)
L3: Distance from the water flow device to the air diffuser (FIGS. 1 and 5)
L4: distance from the bottom of the reaction tank to the underwater device (FIGS. 1 and 5)
L5: distance from bottom of reaction tank to submersible pump L6: distance from diffuser to membrane case (Fig. 3)
L7: Distance from the bottom of the reaction tank to the diffuser (Fig. 3)
L8: Distance from the diffuser to the membrane case (Fig. 4)
L9: Distance from the top of the rotor blade to the diffuser (Fig. 4)
L10: Distance from the bottom of the reaction tank to the diffuser (FIG. 4)

Claims (5)

A submerged membrane separation device is placed in the reaction tank, and the water placed above or below the diffuser placed below the submerged membrane separation device and outside the vertical bottom of the submerged membrane separation device and below the reaction tank. A membrane separation activated sludge treatment apparatus comprising a water flow device using a pump as a power source. The membrane separation activated sludge treatment apparatus according to claim 1, wherein the air diffuser has a fine bubble tube that generates fine bubbles having a diameter of 1 mm or less. 3. The membrane separation activated sludge treatment apparatus according to claim 1, wherein the submersible pump is disposed at a position separated from the bottom of the reaction tank by 50 mm or more and 150 mm or less. A submerged membrane separation device is placed in the reaction tank, and the water placed above or below the diffuser placed below the submerged membrane separation device and outside the vertical bottom of the submerged membrane separation device and below the reaction tank. A membrane surface cleaning method in a membrane separation activated sludge treatment apparatus having a water flow device using a pump as a power source, wherein the gas and liquid are generated by air lift action due to bubbles diffused from the air diffuser and water flow generated from the water flow device A membrane surface cleaning method in a membrane separation activated sludge treatment apparatus, wherein a rising phase of a mixed phase is used as a sweep flow to act on the membrane surface of the submerged membrane separation apparatus. 5. The membrane surface cleaning method in a membrane separation activated sludge treatment apparatus according to claim 4, wherein the air diffuser has a fine bubble tube that generates fine bubbles having a diameter of 1 mm or less.

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