JP2014231033A - Cleaning method of membrane surface in flat membrane type membrane separation device and flat membrane type membrane separation device - Google Patents

Cleaning method of membrane surface in flat membrane type membrane separation device and flat membrane type membrane separation device Download PDF

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JP2014231033A
JP2014231033A JP2013112234A JP2013112234A JP2014231033A JP 2014231033 A JP2014231033 A JP 2014231033A JP 2013112234 A JP2013112234 A JP 2013112234A JP 2013112234 A JP2013112234 A JP 2013112234A JP 2014231033 A JP2014231033 A JP 2014231033A
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membrane
air
water
flat membrane
treated
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圭史 和田
Keiji Wada
圭史 和田
穣 森田
Minoru Morita
穣 森田
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株式会社日立製作所
Hitachi Ltd
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Abstract

In a flat membrane type membrane separation apparatus, the cleaning efficiency of a membrane surface is increased rather than continuous aeration.
A flat membrane type membrane separation apparatus (1) is provided with a plurality of flat membrane elements (111) standing in parallel with a separation tank (4) for storing water to be treated (W), and in the separation tank (4) and immediately below the flat membrane element (111), An air diffuser 12 that diffuses into the water to be treated W and causes an upward flow of the water to be treated W between the flat membrane elements 111 by air bubbles, and a controller 151 that controls the air diffused in the air diffuser 12 are provided. . The control unit 151 of the flat membrane type membrane separation apparatus 1 executes a membrane surface cleaning method for controlling the air diffuser of the air diffuser 12 so as to increase or decrease the air diffuser.
[Selection] Figure 1

Description

  The present invention relates to a membrane surface cleaning method of a flat membrane type membrane separation device that filters water to be treated through a flat membrane, and a flat membrane type membrane separation device that executes this membrane surface cleaning method.

  Conventionally, an activated sludge method has been used for sewage treatment. In this method, microorganisms having a sewage purification ability are treated by bringing them into contact with sewage, and sludge resulting from the treatment by the microorganisms is naturally precipitated. This activated sludge method required a large-scale facility consisting of a first sedimentation tank, a reaction tank, a final sedimentation tank, and a disinfection facility. Furthermore, the sludge cannot be separated by natural sedimentation, and has a problem that impedes the treatment function, such as flowing out to the treated water (carry over) and the possibility of containing suspended solids. Moreover, it has the problem that there is much generation amount of sludge.

  In recent years, the membrane separation activated sludge method (Membrane Bioreactor), in which sewage is treated in a reaction tank and then filtered through a separation membrane having fine pores, has begun to spread. According to Non-Patent Document 1, this membrane-separated activated sludge method filters bacteria and suspended solids in order to filter treated water and activated sludge with a separation membrane having pores finer than bacteria instead of conventional sedimentation basins. Clean treated water containing no water is obtained. Thereby, the disinfection process of treated water can be omitted, and further, the aggregation / sand filtration process can be omitted. In addition, the first sedimentation basin, the final sedimentation basin, and the disinfection facility that have been conventionally required are not required, and the treated water is filtered without depending on the natural sedimentation property, so that the space for the treatment facility can be saved. Furthermore, since the concentration of activated sludge can be increased, the capacity of the reaction tank can be reduced, and the amount of sludge generated can be reduced.

Japan Sewerage Corporation, "Membrane separation activated sludge method", [online], created in December 2011, [searched on April 15, 2013], Internet <URL: http://www.jswa.go.jp/ g / g4 / g4g / pdf / mg07.pdf>

In the membrane separation activated sludge method, an apparatus for filtering activated sludge using a flat membrane is called a flat membrane type membrane separation device. In order to prevent clogging of the membrane during filtration operation, this flat membrane type membrane separation device continuously supplies air from the air diffuser installed below the flat membrane and continuously diffuses the air by the air lift effect due to the air diffused. In many cases, a gas-liquid two-phase updraft is generated in the inter-membrane flow path to clean the sludge adhering to the membrane surface.
However, this flat membrane type membrane separation apparatus needs to supply a large amount of air by continuous aeration, and therefore requires a lot of energy for the operation of the blower.

  Accordingly, the present invention provides a membrane surface cleaning method for a flat membrane type membrane separation apparatus in which the membrane surface cleaning efficiency is increased over continuous aeration, and a flat membrane type membrane separation apparatus for executing the membrane surface cleaning method. This is the issue.

  In order to solve the above-described problems, the invention according to claim 1 is provided with a plurality of flat membrane elements standing in parallel with a separation tank filled with water to be treated, and in the separation tank and immediately below the flat membrane element. An air diffuser that diffuses air into the water to be treated and generates an upward flow of the water to be treated between the flat membrane elements by bubbles, and a controller that controls the air diffused by the air diffuser. The membrane surface cleaning method of a flat membrane type membrane separation apparatus comprising the membrane of the flat membrane type membrane separation device, characterized in that the control unit controls the air diffusion of the air diffusion unit to be strong or weak A surface cleaning method was adopted.

  In the invention according to claim 8, a plurality of flat membrane elements standing in parallel in a separation tank filled with the water to be treated, and provided directly under the flat membrane element, diffused into the water to be treated, A flat membrane type membrane separation apparatus comprising: an air diffuser that generates an upward flow of the water to be treated between the flat membrane elements; and a controller that controls the air diffuser of the air diffuser to be strong and weak. .

  In this way, according to the present invention, by increasing and decreasing the aeration, the velocity difference between the bubble liquid phases is repeatedly increased to increase the wake of the bubbles and improve the membrane surface cleaning efficiency. Can do.

  Other means will be described in the embodiment for carrying out the invention.

  According to the present invention, there are provided a membrane surface cleaning method of a flat membrane type membrane separation apparatus in which the membrane surface cleaning efficiency is increased as compared with continuous aeration, and a flat membrane type membrane separation apparatus that executes the membrane surface cleaning method. It becomes possible.

It is a schematic block diagram which shows the water treatment system and flat membrane type | mold membrane separator in 1st Embodiment. It is a figure which shows the external appearance of the flat membrane type membrane separation apparatus in 1st Embodiment. It is a figure which shows the flat membrane element in 1st Embodiment. It is a comparison figure of the bubble in still water and the bubble in a liquid phase upflow. It is a figure which shows the intermittent operation | movement operation | movement of the flat membrane type membrane separator in 1st Embodiment. It is a graph which shows the comparison of the transmembrane differential pressure rise by aeration control. It is a graph which shows continuous aeration. It is a graph which shows a stop after 9 seconds aeration. It is a graph which shows a continuous aeration after a 9-second aeration for 3 seconds stop. It is a graph which shows a continuous aeration after 9 seconds aeration for 6 seconds stop. It is a graph which shows 9 seconds aeration 9 stop, and a continuous aeration after that. It is a flowchart which shows the aeration process in 1st Embodiment. It is a schematic block diagram which shows the water treatment system and flat membrane type | mold membrane separator in 2nd Embodiment. It is a graph which shows the deceleration tendency of the liquid phase flow velocity after aeration stop. It is a flowchart which shows the aeration process in 2nd Embodiment.

Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings and mathematical expressions.
(First embodiment)
The flat membrane type membrane separation device generates air and liquid two-phase upward flow in the intermembrane flow path by supplying air from the air diffuser and diffuses it, and the membrane is generated by the shear force of the water flow. The sludge adhering to the surface is washed. At the same time, the present inventors have generated a flow turbulence (wake) resulting from the speed difference between the bubble liquid phases in the intermembrane flow path, and this also cleans the sludge adhering to the membrane surface. I thought.
That is, if the flat membrane type membrane separator continuously diffuses a predetermined amount of air, the speed difference between the bubble liquid phases converges to a predetermined value, and the membrane surface cleaning efficiency decreases. Therefore, the flat membrane type membrane separation apparatus according to the first embodiment generates a speed difference between the bubble liquid phase by a membrane surface cleaning method that increases and decreases aeration, thereby increasing the cleaning efficiency of the membrane surface. It was.

FIG. 1 is a schematic configuration diagram showing a water treatment system 9 and a flat membrane type membrane separation apparatus 1 in the first embodiment.
As shown in FIG. 1, the water treatment system 9 includes a reaction tank 2 for reacting microorganisms with the water to be treated W, a pump 3, a separation tank 4 for separating the water to be treated W into sludge and treated water, and a treatment. A water suction pump 5, a blower 6 that supplies air diffused into the reaction tank 2 and the separation tank 4, and an air switch 7 are provided. The water treatment system 9 purifies sewage (treated water W) into clean treated water. The water purified by the water treatment system 9 can be reused as a water resource.
The reaction tank 2 is an aerobic tank which reacts the to-be-processed water W which flowed in from the anaerobic tank not shown, for example with the microorganisms which have a sewage purification capability. The treated water W purified by the microorganisms is sent to the separation tank 4 described later. The treated water W in the reaction tank 2 holds a predetermined amount of activated sludge having complex microorganisms. Examples of the complex microorganism include nitrifying bacteria, denitrifying bacteria, and anaerobic ammonia oxidizing bacteria.

The reaction tank 2 is provided with an air diffuser 21 at its lower part. The air diffuser 21 is an air diffuser with fine holes, and is configured to supply a fine air diffuser having a relatively small bubble diameter in order to efficiently supply oxygen to activated sludge. Yes. The air diffuser 21 is connected to the air switch 7 with a blower pipe, supplied with air from the blower 6 through the air switch 7, and emits fine bubbles from the holes of the air diffuser. Thereby, as for the to-be-processed water W in the reaction tank 2, dissolved oxygen concentration is maintained by high concentration. In the reaction tank 2, a nitrification reaction is performed in which ammonia in the water to be treated W is decomposed by activated sludge to become nitric acid. Oxygen is supplied to the treated water W in the reaction tank 2 with high efficiency by the air diffused by the air diffuser 21. Thereby, the purification | cleaning of the waste water by microorganisms is performed efficiently. The air switch 7 switches whether the air blown by the blower 6 is supplied to the diffuser 12 or the diffuser 21 of the reaction tank 2. Thereby, the air blower 6 can be continuously blown while the air diffuser 12 is intermittently diffused. Further, the air switch 7 can blow air to either the air diffuser 21 of the reaction tank 2 or the air diffuser 12 of the separation tank 4 without wasting the blown air.
The pump 3 pumps up the water to be treated W in the reaction tank 2 and supplies it to the separation tank 4.

  In the separation tank 4, a flat membrane type membrane separation device 1 is provided, and a membrane unit 11 having a plurality of flat membrane elements 111 and an air diffuser 12 provided below them are installed. Yes. The separation tank 4 is an aerobic tank filled with the water to be treated W supplied by the pump 3 and holds a predetermined amount of activated sludge. The separation tank 4 filters the sewage (treated water W) by the flat membrane type membrane separator 1 to obtain clean treated water.

The flat membrane type membrane separation apparatus 1 includes a membrane unit 11, an air diffuser 12, a viscosity sensor 13, and a control circuit 15.
The membrane unit 11 is a well-known unit and is provided in the separation tank 4 and immersed in the water to be treated W. The membrane unit 11 includes a plurality of flat membrane elements 111 having separation membranes on both sides. The outside of each flat membrane element 111 is in contact with the water to be treated W, and the inside thereof is connected to the treated water suction pump 5 via the discharge pipe 51. By suctioning with the treated water suction pump 5, a pressure difference between the outside and the inside of the flat membrane element 111 is generated, and activated sludge and treated water can be solid-liquid separated from the treated water W. The treated water that has undergone solid-liquid separation permeates into the flat membrane element 111 and is discharged out of the system via the treated water suction pump 5.
At this time, the activated sludge adheres to the separation membrane of the flat membrane element 111. As the thickness of the activated sludge increases, the separation efficiency of the separation membrane per unit area decreases. Therefore, the membrane surface of the flat membrane element 111 is washed by the aeration process by the aeration unit 12 to be described later. Prevents adhesion.

Support legs 112 and a casing 113 are formed in the lower part of the membrane unit 11. The support legs 112 are connected to the four corners of the bottom surface of the membrane unit 11 and support the bottom surface of the membrane unit 11 so as to maintain a predetermined height from the bottom surface of the separation tank 4. Thereby, the air diffuser 12 can be provided below the membrane unit 11 and when the liquid phase ascending flow is formed in the gaps between the flat membrane elements 111 by the aeration, the amount of liquid in the ascending flow is reduced. It can flow in from the outside of the membrane unit 11.
The casing 113 is formed in a cylindrical shape surrounding the connection portion between the support leg 112 and the membrane unit 11. By providing the casing 113, the bubbles rising from the air diffuser 12 are prevented from flowing out from the bottom surface of the membrane unit 11 to the side portion, so that the bubbles flow into the bottom surface of the membrane unit 11. Note that the membrane unit 11 and the like are well-known and will not be described in detail.

  The separation tank 4 is provided with an air diffuser 12 that can discharge fine bubbles. The air diffuser 12 is an air diffuser tube having a plurality of fine holes, and is attached to a location where the membrane unit 11 is disposed above when the separation tank 4 is viewed in plan. The air diffuser 12 is supplied with air from the blower 6 through the air switch 7, and discharges fine bubbles from the hole, and the gas-liquid two-phase is introduced into the flow path between the flat membrane elements 111 by the air lift effect. As a result, the sludge adhering to the membrane surface can be washed. The air diffuser 12 further releases fine bubbles to maintain the dissolved oxygen concentration of the water to be treated W in the separation tank 4 at a high concentration. Thereby, the complex microorganisms in the activated sludge of the separation tank 4 can breathe dissolved oxygen and perform an aerobic treatment using ammonia contained in the water to be treated W as nitrate nitrogen.

The viscosity sensor 13 is a sensor that measures the viscosity of the water to be treated W in the separation tank 4 and is connected to a control circuit 15 described later.
The control circuit 15 includes a control unit 151 and a storage unit 152 that stores a stop time / viscosity table 1521. The control circuit 15 switches the air switching unit 7 according to the viscosity of the water to be treated W, thereby intermittently repeating the aeration and stop of the aeration unit 12 to add strength to the aeration. is there. The control unit 151 is realized by a CPU (Central Processing Unit) (not shown) of the control circuit 15 reading and executing a control program from a ROM (Read Only Memory) (not shown) to a RAM (Random Access Memory). .
The stop time / viscosity table 1521 is a table showing the relationship between the viscosity of the water to be treated W and the stop time of aeration, and is set so that the stop time of aeration increases as the viscosity increases. After measuring the viscosity of the water to be treated W based on the viscosity sensor 13, the control unit 151 can control the stop time of the aeration operation by referring to the stop time / viscosity table 1521.

FIG. 2 is a view showing an appearance of the flat membrane type membrane separation apparatus 1 in the first embodiment.
The flat membrane type membrane separation apparatus 1 includes a membrane unit 11 including a plurality of flat membrane elements 111 and an air diffuser 12. In addition, the support leg 112 (refer FIG. 1) and the casing 113 (refer FIG. 1) formed in the lower part of the membrane unit 11 are not illustrated.
The plurality of flat membrane elements 111 of the membrane unit 11 are arranged so as to stand upright in parallel at a predetermined interval. Side surfaces on both sides of each flat membrane element 111 are aligned, and side plates (not shown) are joined. Thereby, the plurality of flat membrane elements 111 are integrated, the side surface direction is sealed, and the upper end and the lower end are opened. A plurality of gaps are provided between the flat membrane elements 111.

The air diffuser 12 is provided in the separation tank 4 and directly below the plurality of flat membrane elements 111. Bubbles are generated by aeration of the diffuser portion 12, the plurality of gaps between the flat sheet membrane elements 111, upward flow of the water to be treated W which is a speed U F is generated.
The membrane-sensitive channel cross-sectional area A indicates the horizontal cross-sectional area of the portion where the upward flow is generated in the membrane unit 11.
The membrane unit 11 other than the portion in the separation tank 4, downward flow of the water to be treated W which is a speed S F is produced.

FIG. 3 is a diagram showing the flat membrane element 111 in the first embodiment.
The inside of the flat membrane element 111 is a water channel that conveys treated water that has passed through a filtration membrane (not shown). The flat membrane element 111 includes a header channel 1115 that is erected in the vertical direction and into which treated water conveyed through the channel flows, and a branch channel 1114 that is arranged in the vertical direction and connects the channel and the header channel 1115. Is provided.

  In the flat membrane element 111, a plurality of partition plates 1113 are provided in the horizontal direction, and the water channel is divided into a plurality of regions 1112 by the partition plates 1113. In the example shown in FIG. 3, the water channel is divided into five regions 1112 arranged in the vertical direction. Each of these regions 1112 is connected to the header channel 1115 via one or a plurality of branch channels 1114. The header channel 1115 has the same cross-sectional shape and extends linearly in the vertical direction. A water collection port 1116 is provided at the upper end of the header channel 1115, and the discharge pipe 51 is connected to the water collection port 1116. The water collection port 1116 is an opening for taking out and collecting the treated water conveyed in the header channel 1115 to the outside.

  In each region 1112 in the flat membrane element 111, spacers 1111 are arranged in a grid pattern. By installing the spacer 1111 in the flat membrane element 111, the filtration membrane (not shown) is attracted to the membrane support plate (not shown) side that supports the filtration membrane by the negative pressure generated by the suction of the treated water suction pump 5. Thus, the width between the filtration membrane and the membrane support plate is prevented from becoming narrow, and the filtration efficiency is prevented from decreasing. Each flat membrane element 1111 allows water to flow through the flat membrane element 1111. However, each partition plate 1113 does not allow water to flow through the partition plate 1113.

4 (a) and 4 (b) are diagrams showing a comparison between bubbles 8a in still water and bubbles 8b in a liquid phase upward flow. FIG. 4A shows a bubble 8a in still water. FIG. 4B shows bubbles 8b in the liquid phase upward flow.
The wake 81a in the lower part of the bubble 8a is a turbulent flow accompanying the rising of the bubble 8a. The bubble 8a is rising at the velocity V B of the bubble 8a in still water.
The wake 81b in the lower part of the bubble 8b is a turbulent flow accompanying the rising of the bubble 8b. The liquid phase is water to be treated W is increased at a rising rate U F. The bubble 8b is rising at a rising speed (U F + V R ). With respect to the liquid phase, the bubble 8b rises at a relative speed V R and is slower than the rise speed V B of the bubble 8a in still water. Thereby, the wake 81b in the liquid phase upward flow is shorter than the wake 81a of the still water. Therefore, the cleaning effect of the film surface by the wake 81b is lower than the cleaning effect of the film surface by the wake 81a. The inventors focused on this point.

5 (a) and 5 (b) are diagrams illustrating an intermittent operation of the flat membrane separator 1 according to the first embodiment.
Fig.5 (a) has shown the time change of the amount of aeration. The vertical axis | shaft of Fig.5 (a) has shown the amount of diffused air [L / min]. The horizontal axis of Fig.5 (a) has shown time (second).
The control circuit 15 of the flat membrane type membrane separation apparatus 1 performs the aeration to the separation tank 4 over the aeration time Tb, then stops the aeration to the separation tank 4 over the stop time Ts, Instead, air is diffused into the reaction tank 2. By repeating this, the control circuit 15 performs control so that the air diffused by the air diffuser 12 is intermittently repeated and the air diffused by the air diffuser 12 is increased or decreased. Thereby, a film surface can be washed suitably. Furthermore, since the air blowing when the air diffusion to the separation tank 4 is stopped can be used for the air diffusion to the reaction tank 2, the 6 energy efficiency of the blower can be increased.

FIG. 5B shows a temporal change in the rising speed of the bubbles and the liquid phase. The vertical axis | shaft of FIG.5 (b) has shown the raise speed [mm / sec]. The horizontal axis of FIG.5 (b) has shown the time (second) common to Fig.5 (a).
When the flat membrane type membrane separation apparatus 1 first starts to diffuse into the separation tank 4 by the control circuit 15, the rising speed of the liquid phase in the separation tank 4 (upflow speed of the water to be treated W) is 0. At this time, the bubbles rise at the rising speed V B.

As the flat membrane type membrane separation device 1 continues the aeration operation, the rising speed of the liquid phase in the separation tank 4 increases, and the rising speed of the bubbles also increases. However, the relative rising speed of the bubbles with respect to the liquid phase gradually decreases. The efficiency of membrane cleaning due to the speed difference between the bubble liquid phase also gradually decreases.
The control circuit 15 switches the air switch 7 to the reaction tank 2 side to stop the air diffusion to the separation tank 4, and the liquid phase rising speed gradually decreases.
When the flat membrane type membrane separation apparatus 1 switches the air switch 7 to the separation tank 4 side and restarts the air diffusion to the separation tank 4, the rising speed of the liquid phase in the separation tank 4 is reduced. The relative rising speed of the bubbles with respect to the liquid phase increases again and becomes sufficiently large. Therefore, the membrane cleaning efficiency due to the speed difference between the bubble liquid phases also increases again.

  By repeating these controls, the flat membrane type membrane separation apparatus 1 repeatedly increases the speed difference between the rising speed of the bubbles and the rising speed of the water W to be treated. The cleaning efficiency of the film surface can be increased as compared with the case. That is, the film surface cleaning method according to the first embodiment intermittently diffuses the diffuser 12 to decelerate the upward flow of the liquid phase when stopped and accelerate the upward flow of the liquid phase when diffused. Thus, a speed difference is generated between the bubble liquid phases, and the flow disturbance contributing to the film surface cleaning is promoted.

  At this time, an important operating factor is the setting of the aeration time Tb and the stop time Ts. If the air diffusion time Tb is too short, the liquid phase does not sufficiently rise and there is a possibility that a sufficient cleaning effect cannot be obtained. Moreover, even if the stop time Ts is too long, there is a possibility that the upward flow of the liquid phase is too slow and a sufficient cleaning effect cannot be obtained. By optimally setting the aeration time Tb and the stop time Ts, the membrane cleaning effect can be optimized to stabilize the membrane filtration operation, and the amount of aeration can be reduced to obtain an energy saving effect.

6 (a) and 6 (b) are graphs showing a comparison of the increase in transmembrane pressure difference due to aeration control.
Here, four patterns in which the aeration time Tb and the stop time Ts are changed are measured. The first operation pattern is continuous operation, in which the aeration time Tb is infinite and the stop time Ts is set to zero. The second operation pattern is intermittent operation with an aeration time Tb of 10 seconds and a stop time Ts of 5 seconds. The third operation pattern is intermittent operation with an aeration time Tb of 5 seconds and a stop time Ts of 5 seconds. The fourth operation pattern is an intermittent operation in which the aeration time Tb is 2 seconds and the stop time Ts is 5 seconds.
In measuring the increase in transmembrane pressure difference in these operation patterns, a plurality of flat membrane elements 111 having an effective filtration area of 1.4 square meters per one sheet are immersed in the separation tank 4 and separated during the evaluation period. The sludge concentration in the tank 4 is adjusted to be around a predetermined value.
Note that, in the fourth operation pattern (intermittent operation where the aeration time Tb is 2 seconds and the stop time Ts is 5 seconds), the increase in the transmembrane pressure difference is extremely large, so the third operation pattern shown in FIG. The other graph compared with is shown.

FIG. 6A is a graph showing the change over time of the transmembrane pressure difference increase value in each operation. The vertical axis in FIG. 6 (a) indicates the transmembrane pressure difference increase value (kPa), and the horizontal axis in FIG. 6 (a) indicates the elapsed time of operation in days.
The black rhombus marker indicates the time change of the transmembrane pressure difference in the continuous operation.
The white diamond-shaped marker indicates the change over time in the increase in transmembrane pressure difference in the intermittent operation in which the aeration for 10 seconds and the stop for 5 seconds are repeated. The black triangular marker indicates the change over time in the increase in transmembrane pressure difference in the intermittent operation in which the aeration for 5 seconds / stop for 5 seconds is repeated.

  According to FIG. 6A, the transmembrane pressure difference increase value is smaller in both the intermittent operation in which the 10-second air diffusion / 5-second stop is repeated and the intermittent operation in which the 5-second air diffusion / 5-second stop is repeated than in the case of continuous operation. Thus, it can be seen that the cleaning effect of the film surface is increased. The amount of diffused air per hour for intermittent operation that repeats a 10-second diffuser / stop for 5 seconds is two-thirds of the continuous diffuser, and the intermittent operation per hour for intermittent operation that repeats a 5-second diffuser / stop for 5 seconds. The amount of aeration is one half. Thereby, since the amount of aeration can be reduced, the energy amount used for the air blower 6 can be reduced.

FIG. 6B is a graph showing the change over time of the increase in transmembrane pressure difference in each operation. The vertical axis in FIG. 6 (b) indicates the transmembrane pressure difference increase value (kPa), and the horizontal axis in FIG. 6 (b) indicates the elapsed time of operation in time (h).
The black triangular marker indicates the change over time in the increase in transmembrane pressure difference in the intermittent operation in which the aeration for 5 seconds / stop for 5 seconds is repeated. The white triangular marker indicates the change over time in the increase in transmembrane pressure difference in the intermittent operation in which the aeration for 2 seconds and the stop for 5 seconds are repeated.

FIG. 6B shows that in the intermittent operation in which the aeration for 5 seconds / the suspension for 5 seconds is repeated, the increase in transmembrane pressure difference is maintained at a predetermined value, and the cleaning effect on the membrane surface is high. On the other hand, in the intermittent operation in which the aeration for 2 seconds / 5 the stop for 5 seconds is repeated, the increase in the transmembrane pressure difference is abruptly increased, indicating that the effect of cleaning the membrane surface is low.
Thereby, it is understood that the aeration time Tb is preferably 5 seconds or more. If the aeration time Tb is too short, it is considered that the cleaning performance deteriorates due to a decrease in the upward flow velocity of the liquid phase. This liquid phase upward flow velocity can be calculated by numerical analysis.

FIGS. 7A to 7C are graphs showing continuous aeration. FIG. 7A shows the case where the viscosity of the water to be treated W is 1 mPa · s. FIG. 7B shows a case where the viscosity of the water to be treated W is 5 mPa · s. FIG.7 (c) is a case where the viscosity of the to-be-processed water W is 20 mPa * s. The vertical axis in FIG. 7 indicates all upward flow velocities, and the horizontal axis indicates time (seconds).
From the graphs of FIG. 7, it can be seen that the viscosity of the water to be treated W increases and the rising speed of the liquid phase in the steady state decreases.

FIGS. 8A to 8C are graphs showing a stop after 9 seconds of aeration. Here, “stop after 9 seconds of aeration” refers to stopping the aeration after performing aeration for 9 seconds. FIG. 8A shows the case where the viscosity of the water to be treated W is 1 mPa · s. FIG. 8B shows the case where the viscosity of the water to be treated W is 5 mPa · s. FIG. 8C shows the case where the viscosity of the water to be treated W is 20 mPa · s. The vertical axis in FIG. 8 indicates the upward flow velocity, and the horizontal axis indicates time (seconds).
From each graph in FIG. 8, it is possible to know the time until the upward flow of the liquid phase stops after the aeration is stopped for each viscosity. As shown in FIG. 8A, when the viscosity of the water to be treated W is 1 mPa · s, the upward flow of the liquid phase stops in 7 seconds after the aeration is stopped. As shown in FIG. 8B, when the viscosity of the water W to be treated is 5 mPa · s, the upward flow of the liquid phase stops in 8 seconds after the aeration is stopped. From FIG.8 (c), when the viscosity of the to-be-processed water W is 20 mPa * s, an upflow of a liquid phase stops in 15 seconds after stopping aeration. That is, it can be seen that the higher the viscosity is, the more difficult it is to increase the flow rate and it is difficult for the flow rate to decrease.

  FIG. 9A to FIG. 9C are graphs showing a 9-second aeration for 3 seconds and a continuous aeration thereafter. FIG. 9A shows the case where the viscosity of the water to be treated W is 1 mPa · s. FIG.9 (b) is a case where the viscosity of the to-be-processed water W is 5 mPa * s. FIG. 9C shows a case where the viscosity of the water to be treated W is 20 mPa · s. The vertical axis in FIG. 9 indicates all upward flow velocities, and the horizontal axis indicates time (seconds).

From each graph of FIG. 9, it is possible to know the upward flow velocity of the liquid phase when the aeration is resumed after the aeration is stopped for 3 seconds in the case of each viscosity. At any viscosity, the rising speed of the liquid phase is not sufficiently lowered, and there is no speed difference between the bubble liquid phases when resuming the aeration, so that the membrane surface cannot be sufficiently washed.
In the graphs of FIGS. 9 (a) and 9 (b), the upward flow velocity when the first 9 seconds of air diffused is the largest, and the upward flow when the continuous air diffusion is resumed after the air diffusion is stopped for 3 seconds. The speed is slower than that. This is because when the viscosity of the water to be treated W is low, the upward flow velocity is insufficiently braked due to aeration and overshoots. Since this overshoot converges with time, the upward flow velocity when continuous aeration is resumed is slower than the initial upward flow velocity.

  FIGS. 10A to 10C are graphs showing 9 seconds of aeration for 6 seconds and subsequent continuous aeration. FIG. 10A shows the case where the viscosity of the water to be treated W is 1 mPa · s. FIG. 10B shows the case where the viscosity of the water to be treated W is 5 mPa · s. FIG. 10C shows the case where the viscosity of the water to be treated W is 20 mPa · s. The vertical axis in FIG. 10 indicates the upward flow velocity, and the horizontal axis indicates time (seconds).

  From the respective graphs of FIG. 10, it is possible to know the upward flow velocity of the liquid phase when the aeration is resumed after the aeration is stopped for 6 seconds in the case of each viscosity. At any viscosity, the upward flow velocity of the liquid phase is sufficiently reduced, and a velocity difference between the bubble liquid phase occurs when recirculation is resumed. Therefore, the film surface can be sufficiently cleaned.

  FIGS. 11A to 11C are graphs showing a 9-second aeration for 9 seconds and a continuous aeration thereafter. FIG. 11A shows a case where the viscosity of the water to be treated W is 1 mPa · s. FIG. 11B shows a case where the viscosity of the water to be treated W is 5 mPa · s. FIG. 11C shows the case where the viscosity of the water to be treated W is 20 mPa · s. The vertical axis in FIG. 11 indicates the upward flow velocity, and the horizontal axis indicates time (seconds).

  From each graph of FIG. 11, it is possible to know the upward flow velocity of the liquid phase when the aeration is resumed after the aeration is stopped for 9 seconds in the case of each viscosity. At any viscosity, the upward flow velocity of the liquid phase is sufficiently reduced, and a velocity difference between the bubble liquid phase occurs when recirculation is resumed. However, since the aeration is stopped for 9 seconds, a period in which the upward flow of the liquid phase is stopped occurs. During this period, the membrane surface is not cleaned, and thus activated sludge and the like may adhere to the membrane surface.

  By measuring data as shown in each graph of FIGS. 6 to 11 and examining the aeration time Tb and the stop time Ts, the optimum setting can be known.

FIG. 12 is a flowchart showing the aeration process in the first embodiment.
The control unit 151 of the control circuit 15 starts the operation of the flat membrane separation apparatus 1 and starts the following aeration process.
In step S <b> 10, the control unit 151 switches the air switch 7 to aeration to the separation tank 4.
In step S11, the control unit 151 waits for the aeration time Tb. The aeration time Tb is set in advance and stored in the storage unit 152 or the like.
In step S <b> 12, the control unit 151 switches the air switch 7 to aeration to the reaction tank 2.

In step S <b> 13, the control unit 151 measures the viscosity of the sewage by the viscosity sensor 13.
In step S14, the control unit 151 acquires the stop time Ts from the measured viscosity of the sewage based on the stop time / viscosity table 1521.
In step S15, the control unit 151 waits for the stop time Ts, returns to the process of step S10, and further repeats each process. The stop time Ts is set in advance and stored in the storage unit 152 or the like.
Thereby, the control part 151 can make the air diffuser 12 intermittently repeat the air diffusion and the stop.

(Second Embodiment)
FIG. 13 is a schematic configuration diagram showing a water treatment system 9A and flat membrane separators 1a and 1b in the second embodiment. The same code | symbol is provided to the element same as the water treatment system 9 of 1st Embodiment. The water treatment system 9A includes a reaction tank (not shown) similar to that of the first embodiment.
The water treatment system 9A according to the second embodiment includes a second separation tank 4b configured similarly in addition to the first separation tank 4a similar to the separation tank 4 according to the first embodiment.
The pump 3a supplies water to be treated W from a reaction tank (not shown) to the first separation tank 4a. The pump 3b supplies the to-be-processed water W of a reaction tank (not shown) to the 2nd separation tank 4b.

  The flat membrane separation apparatus 1a includes a membrane unit 11a, an air diffuser 12a, and a flow rate sensor 14a. The flat membrane separation apparatus 1b includes a membrane unit 11b, an air diffuser 12b, and a flow rate sensor 14b. The flat membrane type membrane separation apparatuses 1a and 1b are provided with a common control circuit 15A. The flat membrane type membrane separation apparatus 1a is installed in the first separation tank 4a. The flat membrane type membrane separation apparatus 1b is installed in the second separation tank 4b. The first separation tank 4a of the second embodiment is provided with a membrane unit 11a and an air diffuser 12a similar to the membrane unit 11 and the air diffuser 12 of the first embodiment. It is comprised so that the downward flow speed of may be measured. The second separation tank 4b of the second embodiment is also provided with a similar membrane unit 11b and a diffuser 12b, and is configured to measure the downflow velocity of the liquid phase with the flow velocity sensor 14b.

Unlike the first embodiment, the control circuit 15A of the second embodiment does not include the stop time / viscosity table 1521. This eliminates the need to reset the stop time / viscosity table 1521 in accordance with the membrane units 11a and 11b and the air diffusers 12a and 12b, thereby reducing the man-hours associated with the new separation tank 4. it can.
Unlike the first embodiment, the air switch 7 is piped so as to switch between the air diffuser 12a and the air diffuser 12b to blow air. Thereby, when the air diffuser 12 is intermittently diffused, the blower 6 can be continuously blown. Further, the air switch 7 can send air to the air diffuser 12a of the first separation tank 4a or the air diffuser 12b of the second separation tank 4b without wasting the blown air. .

FIG. 14 is a diagram showing a deceleration tendency of the liquid phase flow velocity after the aeration is stopped. The vertical axis in FIG. 14 indicates the flow velocity, and the horizontal axis indicates the passage of time. The dashed line shows the rising velocity U F between the flat sheet membrane element 111, the solid line indicates the downward flow velocity S F of the outer membrane unit 11. Here, it is assumed that air is continuously aerated when time t <0, the aeration is stopped when time t is 0, and the aeration is continuously stopped thereafter. Time t1 is increased flow velocity U F is the rise velocity V B becomes equal to time of the bubble still water. Time t2 is downflow velocity S F is the rise velocity V B becomes equal to time of the bubble still water.

(Relationship between upflow and downflow in separation tank)
For example, when the aeration unit 12a stops the aeration, the upward flow velocity U F between the flat membrane elements 111 of the first separation tank 4a is slowly reduced. Here, in order not to reduce the cleaning efficiency of the membrane surface, control unit 151, upward flow velocity U F is preferably controlled to always be faster than the rising speed V B of the bubble still water. In other words, upward flow velocity U F is, if it is detected that slower than the rising speed V B of the bubble still water, may be controlled so as to air diffusion from the re-spraying component 12a. However, it is difficult to measure the upflow velocity U F directly. This is because the liquid phase and the gas phase are mixed between the flat membrane elements 111.

As shown in FIG. 14, to become sufficiently close to the upward flow velocity U F flows downward speed S F over time, the time t2 and the time t1, it may be almost considered that there is no difference.
Downflow velocity S F of the liquid phase, membrane unit 11 outside of the flow velocity sensor 14a in the separation tank 4, by measuring provided 14b, is easily and accurately measurable. Therefore, downward flow speed S F is, if it is detected that slower than the rising speed V B of the bubble still water, may be controlled so as to air diffusion from the re-spraying component 12a.

(Regarding the steady solution of bubble rising speed)
If the cell diameter D B is known, by the following equation (1) can be obtained steady-state solution of the bubble rising speed of.

The term of liquid drag is obtained by the following equation (2).

The term of gravity is obtained by the following equation (3).

The drag coefficient is obtained by the following equation (4).

The Reynolds number is obtained by the following equation (5).

FIG. 15 is a flowchart showing the aeration process in the second embodiment.
The control unit 151 of the control circuit 15A starts the operation of the flat membrane separators 1a and 1b and starts the following aeration process.
In step S20, the control unit 151 switches the air switch 7 to aeration to the first separation tank 4a.
In step S21, the control unit 151 waits for the aeration time Tb. Here aeration time Tb may be set as upward flow velocity U F of the first separation tank 4a is sufficiently large.
In step S22, the control unit 151, the flow velocity sensor 14b, for detecting the downward flow velocity S F of the second separation tank 4b.

In step S23, the control unit 151, downflow velocity S F of the second separation tank 4b determines whether it is less than the speed V B. If the determination condition is not satisfied (No), the control unit 151 returns to the process of step S22. If the determination condition is satisfied (Yes), the control unit 151 performs the process of step S24.
In step S24, the control unit 151 switches the air switch 7 to aeration to the second separation tank 4b. Thus, the control unit 151 can descending flow speed S F treated water W in the second separation tank 4b is if equal to or less than the predetermined value, control is again enhance aeration.
In step S25, the control unit 151 waits for the aeration time Tb. Here aeration time Tb may be set as upward flow velocity U F of the second separation tank 4b becomes sufficiently large.
In step S26, the control unit 151, the flow rate sensor 14a, which detects the downward flow velocity S F of the first separation tank 4a.

In step S27, the control unit 151, downflow velocity S F of the first separation tank 4a determines whether it is less than the predetermined speed V B. If the determination condition is not satisfied (No), the control unit 151 returns to the process of step S26. If the determination condition is satisfied (Yes), the control unit 151 returns to the process of step S20 and performs the next intermittent operation. repeat. Thus, the control unit 151 can descending flow speed S F treated water W of the first separation tank 4b is if equal to or less than the predetermined value, control is again enhance aeration.

As shown in Figure 14, the upward flow velocity U F flows downward speed S F, so come gone difference over time, the control unit 151, upward flow velocity U F of the water to be treated W is predetermined When the value falls below the value, it can be controlled to increase the aeration again.
By controlling in this way, the control unit 151 can obtain a suitable film surface cleaning efficiency when the aeration unit 12 is intermittently operated. Therefore, the evaluation of the cleaning efficiency of the film surface in the combination of the air diffusion time Tb and the stop time Ts can be omitted.
Furthermore, since the air blowing to the first separation tank 4a is stopped can be used for the air diffusion to the second separation tank 4b, and vice versa, the energy efficiency of the blower 6 is increased. Can do.

(Modification)
The present invention is not limited to the embodiments described above, and includes various modifications. For example, the above-described embodiment has been described in detail for easy understanding of the present invention, and is not necessarily limited to the one having all the configurations described. A part of the configuration of one embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of one embodiment. Moreover, it is also possible to add, delete, and replace other configurations for a part of the configuration of each embodiment.

  A part or all of the above-described configurations, functions, processing units, processing means, and the like may be realized by hardware such as an integrated circuit. Each of the above-described configurations, functions, and the like may be realized by software by a processor interpreting and executing a program that realizes each function. Information such as programs, tables, and files for realizing each function may be stored in a recording device such as a memory, a hard disk, or an SSD (Solid State Drive), or a recording medium such as a flash memory card or a DVD (Digital Versatile Disk). it can.

In each embodiment, the control lines and information lines indicate what is considered necessary for the explanation, and not all control lines and information lines on the product are necessarily shown. In practice, it may be considered that almost all the components are connected to each other.
Examples of modifications of the present invention include the following (a) to (d).

(A) In the first and second embodiments, the air diffuser 12 is intermittently operated by the air switch 7. However, the present invention is not limited to this, and the flat membrane separators 1, 1 a, 1 b may perform the intermittent operation of the air diffuser 12 by causing the blower 6 to perform the intermittent operation. Thereby, the air switch 7 becomes unnecessary.

(B) The flat membrane separators 1, 1 a, 1 b are provided with an air tank at the rear stage of the blower 6, compressed air is stored in the air tank, and the stored air is intermittently supplied by the air switch 7. Alternatively, the air diffuser 12 may be guided and intermittently operated. Thereby, while omitting the piping which blows air to another tank, the air blower 6 can be continuously operated to increase the air blowing efficiency and the energy efficiency.

(C) In the first and second embodiments, the air diffuser 12 is intermittently operated to add strength to the air diffuser. However, the present invention is not limited to this, and the flat membrane separators 1, 1 a, 1 b may increase or decrease the aeration by gradually decreasing the aeration amount and then increasing the aeration amount. It is not limited to intermittent operation.

(D) a flat membrane type membrane separation apparatus 1a of the second embodiment, in 1b, the speed S F of the descending flow, when it becomes smaller than the rising speed V B of the bubble still water, by performing again the air diffuser Yes. However, not limited to this, conditions for the re-aeration, the speed S F of the descending flow, may be when it becomes smaller than any increase speed. This arbitrary rising speed can be set depending on whether or not it is suitable for cleaning the film surface.

1, 1a, 1b Flat membrane type membrane separation device 11, 11a, 11b Membrane unit 111 Flat membrane element 1111 Spacer 1112 Region 1113 Partition plate 1114 Branch flow channel 1115 Header flow channel 1116 Water collecting port 112 Support leg 113 Casing 12, 12a, 12b Air diffuser 13 Viscosity sensor 14a, 14b Flow rate sensor 15, 15A Control circuit 151 Controller 152 Storage unit 1521 Stop time / viscosity table 2 Reaction tank 21 Air diffuser 3, 3a, 3b Pump 4 Separation tank 4a First separation tank 4b Second separation tank 5 Treated water suction pump 51 Discharge pipe 6 Blower 7 Air switch 8a, 8b Air bubbles 81a, 81b Back flow 9, 9A Water treatment system

Claims (12)

  1. A plurality of flat membrane elements that stand upright in parallel with a separation tank that fills the water to be treated;
    An air diffuser that is provided in the separation tank and directly below the flat membrane element, diffuses air to the water to be treated, and causes an upward flow of the water to be treated between the flat membrane elements by bubbles.
    A control unit for controlling aeration of the aeration unit;
    A membrane cleaning method for a flat membrane type membrane separation apparatus comprising:
    The controller is
    Controlling the air diffuser of the air diffuser to be strong or weak,
    A membrane cleaning method for a flat membrane separator.
  2. The controller is
    After the air diffuse is weakened, if the upward flow speed of the water to be treated falls below a predetermined value, control is performed to increase the air diffuse again.
    The method of cleaning a membrane surface of a flat membrane type membrane separation apparatus according to claim 1.
  3. The flat membrane separation apparatus further includes a flow rate sensor that measures a downward flow velocity of a portion where the water to be treated is descending,
    The controller is
    After the aeration is weakened, if the downflow speed of the water to be treated falls below a predetermined value, control is performed to increase the aeration again.
    The method for cleaning a membrane surface of a flat membrane membrane separator according to claim 2.
  4. The controller is
    After the air diffuse is weakened, if the downflow speed of the water to be treated becomes lower than the rising speed of the bubbles in the still water, control is performed to increase the air diffuse again.
    The method for cleaning a membrane surface of a flat membrane membrane separator according to claim 2.
  5. The controller is
    Control so that the speed difference between the rising speed of the bubbles and the rising speed of the water to be treated increases repeatedly.
    The method of cleaning a membrane surface of a flat membrane type membrane separation apparatus according to claim 1.
  6. The controller is
    By intermittently repeating the aeration and stop of the aeration part, the intensity of the aeration is added,
    The method of cleaning a membrane surface of a flat membrane type membrane separation apparatus according to claim 1.
  7. The flat membrane type membrane separation apparatus further includes a viscosity sensor for measuring the viscosity of the water to be treated.
    The controller is
    The higher the viscosity of the water to be treated, the longer the stop time of aeration.
    A membrane surface cleaning method for a flat membrane separator according to claim 6.
  8. A plurality of flat membrane elements that stand upright in parallel with a separation tank that fills the water to be treated;
    An air diffuser that is provided directly below the flat membrane element, diffuses into the treated water, and causes an upward flow of the treated water between the flat membrane elements by bubbles,
    A control unit for controlling the air diffuser of the air diffuser to be strong or weak;
    A flat membrane type membrane separation apparatus.
  9. The controller is
    Controlling the air diffuser to intermittently repeat aeration and stop,
    The flat membrane type membrane separator according to claim 8.
  10. A blower,
    An air switch for switching whether to supply the air blown by the blower to the air diffuser,
    Is further provided,
    The controller is
    By switching the air switch, the air diffuser and the air diffuser are intermittently repeated.
    The flat membrane type membrane separation apparatus according to claim 9.
  11. The air switch is capable of supplying air to the air diffuser of the reaction tank,
    The controller is
    When not supplying air to the air diffuser, switching to supply air to the air diffuser of the reaction tank,
    The flat membrane type membrane separation apparatus according to claim 10.
  12. The air switch can supply air to the air diffuser of another separation tank,
    The controller is
    When not supplying air to the diffuser, switch to supply air to the diffuser of the other separation tank,
    The flat membrane type membrane separation apparatus according to claim 10.

JP2013112234A 2013-05-28 2013-05-28 Cleaning method of membrane surface in flat membrane type membrane separation device and flat membrane type membrane separation device Withdrawn JP2014231033A (en)

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CN105481086A (en) * 2015-12-31 2016-04-13 天津厚普德科技有限公司 Novel sewage treatment membrane frame
CN105502644A (en) * 2015-12-31 2016-04-20 天津厚普德科技有限公司 Sewage treatment membrane frame
CN105502645A (en) * 2015-12-31 2016-04-20 天津厚普德科技有限公司 Intelligent wastewater treatment membrane frame
CN105540828A (en) * 2015-12-31 2016-05-04 天津厚普德科技有限公司 Efficient wastewater treatment membrane frame
US9333464B1 (en) 2014-10-22 2016-05-10 Koch Membrane Systems, Inc. Membrane module system with bundle enclosures and pulsed aeration and method of operation
USD779632S1 (en) 2015-08-10 2017-02-21 Koch Membrane Systems, Inc. Bundle body

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JP2012176396A (en) * 2010-11-30 2012-09-13 Jfe Engineering Corp Membrane separation activated sludge apparatus

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JPH04265128A (en) * 1991-02-20 1992-09-21 Ebara Infilco Co Ltd Membrane separation equipment
JPH11314025A (en) * 1998-03-03 1999-11-16 Inax Corp Method for cleaning membrane
JP2006015274A (en) * 2004-07-02 2006-01-19 Nishihara Engineering Co Ltd Water treatment apparatus
JP2012176396A (en) * 2010-11-30 2012-09-13 Jfe Engineering Corp Membrane separation activated sludge apparatus

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US9956530B2 (en) 2014-10-22 2018-05-01 Koch Membrane Systems, Inc. Membrane module system with bundle enclosures and pulsed aeration and method of operation
US9333464B1 (en) 2014-10-22 2016-05-10 Koch Membrane Systems, Inc. Membrane module system with bundle enclosures and pulsed aeration and method of operation
USD779631S1 (en) 2015-08-10 2017-02-21 Koch Membrane Systems, Inc. Gasification device
USD779632S1 (en) 2015-08-10 2017-02-21 Koch Membrane Systems, Inc. Bundle body
CN105502645A (en) * 2015-12-31 2016-04-20 天津厚普德科技有限公司 Intelligent wastewater treatment membrane frame
CN105540828A (en) * 2015-12-31 2016-05-04 天津厚普德科技有限公司 Efficient wastewater treatment membrane frame
CN105481086A (en) * 2015-12-31 2016-04-13 天津厚普德科技有限公司 Novel sewage treatment membrane frame
CN105502644A (en) * 2015-12-31 2016-04-20 天津厚普德科技有限公司 Sewage treatment membrane frame

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