JP2020081973A - Clean water treatment method, and clean water treatment system - Google Patents

Abstract

To provide a clean water treatment method and a clean water treatment system, synergistically utilizing the advantages of both of a membrane separation device of a total amount filtration type and a membrane filtration device of a cross-flow filtration type used in combination.SOLUTION: The operation of a casing-storage type membrane separation device 5 and a tank-immersed type membrane separation device 6 used in combination is controlled according to control indices, which casing-storage type membrane separation device 5 filters raw water fed into a casing which is a closed space storing filtration membranes, and which tank-immersed type membrane separation device 6 filters raw water by immersing a housing which is an open space storing filtration membranes, in a tank storing the raw water.SELECTED DRAWING: Figure 1

Description

TECHNICAL FIELD The present invention relates to a water purification treatment method and a water purification treatment system, and relates to a technique of using two types of membrane separation devices of different systems in combination.

Conventionally, as a general membrane filtration apparatus, there are a casing storage type membrane separation apparatus and a tank immersion type membrane separation apparatus.

The casing storage type membrane separation device is, for example, as disclosed in Patent Document 1.

This membrane component comprises a porous membrane element and a casing that forms a closed cylindrical space that houses the membrane element. The membrane element has a plurality of fluid passage holes formed in a substantially rectangular parallelepiped shape and penetrating between the opposed surfaces, and performs filtration of raw water between the peripheral surface and the inner surface of the fluid passage hole. The casing includes a tubular main body and a pair of lids that close both ends thereof.

In the membrane filtration step, raw water permeates through the membrane element of the casing-enclosed membrane separator from the inner primary side to the outer secondary side while the raw water flows from the bottom to the top of the fluid passage, and the treated water that has permeated the membrane element. Are taken out.

In the back pressure washing step, the back washing water permeates from the outer secondary side of the membrane element to the inner primary side to remove foreign matter adhering to the inner surface of the fluid flow hole to back wash the membrane element. The separated foreign matter is discharged to the outside as backwash drainage together with the backwash water.

The tank immersion type membrane separation device is, for example, as disclosed in Patent Document 2.

This membrane separation device has a plurality of tubular membrane elements housed in a membrane case, and the membrane case forms an open space with its upper end and lower end opened. The membrane element is provided with a filtration membrane on the outer peripheral surface of a tubular porous support made of ceramics. The membrane elements are arranged with the axial direction (length direction) along the horizontal direction, and are arranged in parallel at a predetermined interval. An open flow path is formed between the membrane surfaces of the filtration membranes of the membrane elements facing each other. Below the membrane element, an air diffuser capable of adjusting the amount of air diffused is provided.

In the membrane filtration step, an upward flow of the water to be treated occurs due to the air lift action of the air diffused from the diffuser. The water to be treated circulates inside and outside the membrane case and flows as a gas-liquid mixed phase flow inside the membrane case. The water to be treated receives the natural head in the tank, permeates the filtration membrane, and flows out to the treated water outlet system. The foreign matter remaining on the film surface is washed away by the water to be treated flowing along the film surface.

Further, Patent Document 3 describes a water purification facility that filters the treated raw tap water as water to be treated, inspects the quality of the filtered water, and then distributes the water to the outside. The membrane filtration section is provided with a membrane filtration route through which the water to be treated passes through the filtration membrane and a bypass route not through the filtration membrane, and the membrane filtration treated water flowing down the membrane filtration route and the bypass flowing down the bypass route. Water quality inspection means for inspecting water quality based on water is provided. Based on the inspection result of the water quality inspection means, the membrane filtration control means determines the number of filtration membranes through which the water to be treated passes in the membrane filtration route.

Further, the media and membrane filtration combined filtration equipment of Patent Document 4 comprises a media filtration pond and a membrane separation device arranged in the filtration tank of the media filtration pond. In the membrane separation device, the membrane module is arranged at a position below the water level of the treated water during filtration.

The water to be treated supplied to the filtration tank is simultaneously filtered by both the media filtration pond and the membrane separation device, and the purified water after filtration is simultaneously obtained from both the media filtration pond and the membrane separation device.

Patent No. 6175262 JP-A-8-332352 JP 2005-334777 A Patent No. 4672993

The casing-enclosed membrane separator does not need to generate a gas-liquid mixed-phase flow due to air diffusion by the air diffuser during the filtration operation, unlike the tank-immersed membrane separator, and has the advantage of low running cost of power costs. .. However, suspended substances and colloids contained in the supplied raw water that have not permeated the filtration membrane are deposited on the membrane surface of the filtration membrane, so it is necessary to wash the membrane surface by backwashing at appropriate times. Therefore, a value obtained by subtracting the amount of backwash water required for backwashing from the amount of treated water produced is the amount of water that can be supplied to the distribution area.

The frequency of backwashing increases as the turbidity of the raw water increases, and the amount of treated water used as backwashing water increases as the frequency of backwashing increases, resulting in a decrease in water supply.

Since the turbidity of the river water taken in is high due to rainfall, etc., the turbidity of the raw water is often high in the season when typhoons occur. In recent years, the weather environment has often become unstable, and guerrilla heavy rainfall, which is a type of concentrated heavy rainfall, frequently occurs, and the turbidity of raw water may temporarily increase due to sudden changes in weather. Yes, the stability of water supply is hindered.

In the tank immersion type membrane separation device, the higher the flow velocity of the gas-liquid mixed phase flow of the diffused gas and the raw feed water, the more the accumulation of substances such as foreign substances attached to the membrane surface is suppressed. However, in order to increase the flow velocity of the gas-liquid mixed phase flow, the running cost of the power cost required to increase the amount of diffused air increases.

The present invention is to solve the above problems, and to provide a water purification treatment method and a water purification treatment system that use a casing-enclosed membrane separation device and a tank immersion type membrane separation device in combination and synergistically utilize the advantages of both. To aim.

In order to solve the above problems, the water purification method of the present invention is a casing-accommodating membrane separation device that filters raw water supplied into the casing of a closed space that stores a filtration membrane, and a tank that stores the raw water, The tank-immersed membrane separator that immerses the housing of the open space containing the filtration membrane to filter the raw water is used together, and the operation of the casing-enclosed membrane separator and the tank-immersed membrane separator is controlled based on the control index. It is characterized by doing.

In the water purification method of the present invention, the casing-enclosed membrane separation device operates at a high set operating rate when the raw water turbidity of the control index is equal to or lower than a predetermined value, and when the control index exceeds a predetermined value, sets the low level. Operated at an operating rate, the tank submerged membrane separation device is characterized by stopping the operation when the control index is less than or equal to a predetermined value, and operating at a higher set operating rate when the control index exceeds a predetermined value. ..

In the water purification method of the present invention, both membrane separation devices are characterized in that their operation is controlled by changing the number of operating units, changing the operating time, changing the amount of treated water, or a combination of two or more of these.

In the purified water treatment method of the present invention, the treated water supplied from both membrane separation devices is sent downstream through the treated water tank, and the water level of the treated water tank is used as a control index, and the first set water level and the first set water level in the treated water tank. The second set water level lower than the water level is set, the casing-enclosed membrane separation device controls the operation with the first set water level as the control target water level, and the tank immersion type membrane separation device uses the second set water level as the control target water level. It is characterized by controlling the operation.

In the water purification method of the present invention, the treated water supplied from both membrane separation devices is sent downstream through the treated water tank, and the water level of the treated water tank is used as a control index, and the highest first high water level in the treated water tank, and The second higher water level lower than the first high water level, the lowest first lower water level, and the second lower water level higher than the first lower water level are set, and the casing-enclosed membrane separation device restarts operation at the second lower water level. The operation is stopped at the first high water level, and the tank submerged membrane separation device is restarted at the first low water level and stopped at the second high water level.

The water purification system of the present invention includes a casing-storing type membrane separation device and a tank immersion type membrane separation device that are arranged in parallel in the middle of the water purification treatment system, and the casing-storing type membrane separation device is a closed space in which a filtration membrane is stored. When the raw water turbidity of the control index is less than or equal to a specified value, a high operation mode that operates at a higher set operating rate and when the control index exceeds the specified value It has a low operation mode that operates at a low set operation rate, and the tank immersion type membrane separation device filters the raw water by immersing the housing of the open space containing the filtration membrane in the tank that stores the raw water. It has a system, and has an operation stop mode in which the operation is stopped when the control index is less than or equal to a predetermined value, and a normal operation mode in which the operation is performed at a high set operating rate when the control index exceeds the predetermined value.

The water purification system of the present invention is a casing storage type membrane separation device and a tank immersion type membrane separation device arranged in parallel in the middle of the water purification treatment system, and stores the treated water supplied from both membrane separation devices and sends it downstream. The treated water tank is used as a control index, and the treated water tank has a first set water level and a second set water level lower than the first set water level, and the casing storage type membrane separation device stores the filtration membrane. It has a method of filtering raw water supplied into the casing of the closed space, and has a main water supply operation mode in which operation is controlled with the first set water level as a control target water level, and the tank immersion type membrane separation device stores the raw water. A method of filtering raw water by immersing a housing of an open space containing a filtration membrane in a tank to be operated, and having a combined water supply operation mode for controlling operation with the second set water level as a control target water level. To do.

The water purification system of the present invention is a casing storage type membrane separation device and a tank immersion type membrane separation device arranged in parallel in the middle of the water purification treatment system, and stores the treated water supplied from both membrane separation devices and sends it downstream. The treated water tank is used as a control index, and the treated water tank has a first high water level that is the highest, a second high water level that is lower than the first high water level, a lowest first lower water level, and a first lower water level. A higher second lower water level is set, and the casing-enclosed membrane separation device has a method of filtering raw water to be supplied into the casing of the closed space accommodating the filtration membrane, and restarts operation at the second lower water level, It has a main water supply operation mode that stops operation at the first high water level, and the tank immersion type membrane separation device filters the raw water by immersing the housing of the open space containing the filtration membrane in the tank that stores the raw water. It is characterized by having a combined water supply operation mode in which the operation is restarted at the first lower water level and the operation is stopped at the second higher water level.

In the present invention described above, by controlling the operation of the casing storage type membrane separation device and the tank immersion type membrane separation device at the boundary of a predetermined value of turbidity or water level which is a control index, the advantages of both are synergistic. Can be used for.

That is, it is possible to perform stable water purification at a low turbidity, which is an advantage of the casing-containing membrane separation device, and at a low running cost, and to stably purify water at a high turbidity, which is an advantage of the tank immersion type membrane separation device. By combining the treatments that can be performed, stable water purification treatment can be achieved even with changes in turbidity due to seasonal factors such as typhoons and rapid changes in turbidity due to guerrilla heavy rainfall.

The schematic diagram which shows the water purification system in embodiment of this invention. Sectional drawing which shows an example of the casing storage type membrane separation apparatus in the same embodiment. The perspective view which shows the membrane element of the casing storage type membrane separation apparatus in the same embodiment. Sectional drawing which shows an example of the tank immersion type membrane separation apparatus in the same embodiment. The figure which shows the change of the turbidity of the raw water and the operation mode in the same embodiment. A schematic diagram showing a control method in the case of operating a casing-encased membrane separation device and a tank immersion type membrane separation device according to another embodiment of the present invention, using the water level of a water purification reservoir for storing treated water as a control index.

Example 1
Hereinafter, a water purification system according to an embodiment of the present invention will be described with reference to the drawings. 1 to 5, the present water treatment system includes a casing-accommodating membrane between a water intake facility 3 including a landing well 1 and a mixing basin 2 and a water basin 4 that stores the purified water and distributes it to a downstream region. This is a water purification system in which a separation device 5 and a tank immersion type membrane separation device 6 are arranged in parallel.
(Casing type membrane separator)
The casing-storing membrane separation device 5 is a casing-storing membrane separation device that filters the entire amount of the raw feed water supplied into the casing of the closed space that stores the filtration membrane. For example, the basic unit is shown in FIGS. It has the structure shown and is composed of a plurality of basic units. In the present embodiment, ceramics will be described as an example of the film material, but the present invention is not limited to the film material. Further, there is no limitation by a so-called internal pressure type, external pressure type or the like.

Here, the membrane element 101 is composed of a plurality of ceramics molded bodies 101a having a substantially rectangular parallelepiped shape, and the porous ceramics molded bodies 101a are bonded to each other via a bonding material layer 101b. In the membrane element 101, a plurality of through channels 104 are formed so as to penetrate between a pair of opposed end surfaces 102 and 103. The inner surface side of the through channel 104 forms the primary side, and the outer surface side of the membrane element 101 forms the secondary side.

A plurality of slits 105 are formed in the membrane element 101. The slit 105 extends in the axial direction of the through channel 104 and has a groove shape that opens to the side surface 106 of the membrane element 101, and both ends of the slit 105 are closed in the vicinity of the end surfaces 102 and 103 of the membrane element 101. ..

The membrane element 101 is housed inside the casing 112. The casing 112 has an upper primary chamber 114 formed in the upper part and a lower primary chamber 115 formed in the lower part. The upper end of the membrane element 101 is exposed in the upper primary chamber, the lower end of the membrane element 101 is exposed in the lower primary chamber 115, and the through channel 104 communicates with the upper primary side chamber 114 and the lower primary chamber 115.

A raw water supply system 130 communicates with a raw water inlet 109 of a lower primary chamber 115 of the casing 112 through a first valve 116, and a backwash water discharge system 131 communicates through a second valve 118. ..

The casing 112 has a treated water outlet 110 on its side, and the treated water outlet 110 communicates with the space surrounding the secondary side of the membrane element 101. A treated water system 132 communicates with the treated water outlet 110 via a third valve 117, and a backwash water supply system 133 communicates with the treated water outlet 110 via a fourth valve 119.

A pressurized gas supply system 134 is connected to the pressurized gas inlet 111 of the upper primary chamber 114 of the casing 112 via a fifth valve 120.
(Membrane filtration process)
The first valve 116 of the raw water supply system 130 and the third valve 117 of the treated water system 131 are opened, and the other valves 118, 119 and 120 are closed, so that the raw water W2 is supplied from the raw water inlet 109 to the lower primary side chamber 107. Supply.

The raw water W2 supplied to the lower primary-side chamber 107 permeates the membrane element 101 from the primary side to the secondary side in the casing-enclosed membrane separation device while flowing from the bottom to the top in the through-flow passage 104, and then passes through the membrane element 101. The water W3 is taken out from the treated water outlet 110 to the treated water system 132.
(Back pressure cleaning process)
The second valve 118 of the backwash water discharge system 131 and the fourth valve 119 of the backwash water supply system 133 are opened, and the other valves 116, 117, 120 are closed, and the backwash water W1 is fed to the treated water outlet 110. To the membrane element 101.

The backwash water W1 permeates from the secondary side on the outer side of the membrane element 101 to the primary side on the inner side, and foreign matters adhering to the inner peripheral surface of the through channel 104 are peeled off to backwash the membrane element 101 with pressure. The separated foreign matter flows together with the backwash water W1 from the top to the bottom in the through-flow passage 104 into the lower primary side chamber 107, and is discharged to the outside from the raw water inlet 109 as backwash drainage.
(Flushing process)
In the flushing process which is a part of the back pressure cleaning process, the fifth valve 120 is further opened. As a result, the pressurized gas G1 in the pressurized gas supply system 134 is supplied from the pressurized gas inlet 111 into the upper primary side chamber 114 while supplying the backwash water W1. The backwash water W1 remaining in the casing 102 is surely discharged from the raw water inlet 109 through the backwash water discharge system 131 together with the separated foreign matter by the pressurized gas G1.
(Tank immersion type membrane separator)
The tank immersion type membrane separation device 6 immerses the housing of the open space containing the filtration membrane in the tank for storing the raw water, circulates the raw water in the tank inside and outside the housing, and surrounds the membrane surface of the filtration membrane. Is a tank-immersed membrane separator for filtering a solid-liquid mixed-phase flow that flows in a so-called cross flow, and has a structure shown in FIG. In FIG. 4, one tank immersion type membrane separation device 6 is disclosed as an example, but in this embodiment, a plurality of tank immersion type membrane separation devices 6 are arranged inside the processing tank 7. As described above, the present invention is not limited by the film material, and is not limited by the so-called internal pressure type, external pressure type or the like.

Here, the tank-immersion type membrane separation device 6 has a plurality of tubular membrane elements 51 and a membrane case 52 as a housing for housing these membrane elements 51. The membrane case 52 has a rectangular cross section and has an open upper end and a lower end to form an open space.

Each membrane element 51 has a porous membrane support 53 made of ceramics and a filtration membrane 54 attached to the surface thereof, and the inside thereof communicates with a treated water outlet system (not shown) for leading out treated water.

The membrane elements 51 are arranged with the axial direction (length direction) along the horizontal direction, and are arranged in parallel at a predetermined interval. Between the membrane surfaces of the filtration membranes 54 of the membrane elements 51 facing each other, a flow path 56 that is open vertically is formed. Below the membrane element 51, an air diffuser 57 capable of adjusting the amount of air diffused is provided.
(Membrane filtration process)
The air lift action of the air diffused from the air diffuser 57 causes an upward flow of the gas-liquid mixed phase flow of the water to be treated and the air, the water to be treated in the tank circulates inside and outside the membrane case 52, and the membrane case 52 The inside of the filter flows around the membrane surface of the filtration membrane 54.

The raw water W4 to be supplied receives a suction pressure acting on the inside of the membrane element 51, permeates the filtration membrane 54, and flows out to the treated water outlet system 55. The foreign matter remaining on the film surface is washed away by the water to be treated flowing along the film surface.
(Operation control)
The operations of the casing storage type membrane separation device 5 and the tank immersion type membrane separation device 6 are controlled at a predetermined value set as a control index.

For example, the casing storage type membrane separation device 5 has a high operation mode and a low operation mode. Assuming that the rated amount of purified water produced by the casing-enclosed membrane separation device 5 that operates at an operating rate of 100% is 3,750 m3/d here, it operates at a high setting operating rate of 93% in the high operating mode. 3,600 m3/d of purified water is produced, and in the low operation mode, it operates at a low set operating rate of 45% to produce 1,688 m3/d of purified water.

The tank immersion type membrane separation device 6 has an operation stop mode and a normal operation mode. In the normal operation mode, the operation is performed at a high setting operation rate of 100%, and purified water of 1250 m3/d, which is the rated amount of treated water of the tank immersion type membrane separation device 6, is manufactured.
(When the turbidity of raw water is used as a control index)
The turbidity of raw water may fluctuate due to rainfall or discharge of upstream dams when river water is taken in, and may suddenly fluctuate due to heavy rainfall in the summer, when there is a lot of rainfall, or in the autumn when there are many typhoons.

Therefore, as shown in FIG. 5, when the turbidity of the raw water is within a normal range, for example, when the turbidity of the raw water is 500 degrees or less, the casing-containing membrane separation device 5 operates in the high operation mode and The immersion type membrane separation device 6 basically stops its operation or operates intermittently to save energy in water purification treatment. Such low turbidity operation is performed, for example, for 11.5 months or more per year.

When the turbidity of the raw water is in the range of high turbidity, for example, when the turbidity of the raw water is more than 500 degrees and less than 1000 degrees, the casing-enclosed membrane separation device 5 operates in the low operation mode and operates at low load. To do. On the other hand, the tank immersion type membrane separation device 6 is continuously operated in the normal operation mode. Such high turbidity operation is performed, for example, in a period of 0.5 months or less per year.

In the casing storage type membrane separation device 5 and the tank submerged type membrane separation device 6, when the amount of treated water is changed, the operation rate is changed, and when the operation time is changed, the operation rate is changed. In that case, the change in the operating number is the change in the operating rate.

More specifically, the operation rate of the casing-containing type membrane separation device is changed from the high operation mode to the low operation mode as follows. For example, the amount of treated water per membrane separation device in the membrane filtration step is reduced. Alternatively, the back pressure washing step is performed at shorter intervals. Alternatively, the number of operating membrane separation devices is reduced. Further, the back pressure washing step is performed while the membrane separation device is stopped.

In Example 1, the measurement of the turbidity of the raw water may be performed by arranging a turbidity meter in the landing well 1 or the like into which the raw water flows and automatically measuring the turbidity, or may be measured manually.
Example 2
In the second embodiment, the casing storage type membrane separation device 5 and the tank immersion type membrane separation device 6 are the same as those described above with reference to FIGS. 1 to 4, and the description thereof will be omitted by using the same reference numerals. Here, the casing storage type membrane separation device 5 and the tank immersion type membrane separation device 6 are controlled in operation by using the water level of the water purification basin 4 as a control index. Treated water supplied from both membrane separators is sent downstream through the water purification basin 4.

As shown in FIG. 6, the water purification pond 4 constitutes a treated water tank for storing treated water. In the water purification pond 4, a plurality of water levels are set as predetermined values (threshold values) of the control index, and the highest first high water level H1, the second high water level H2 lower than the first high water level, and the lowest first water level H2. The lower water level L1 and the second lower water level L2, which is higher than the first lower water level.

The casing-enclosed membrane separation device 5 has a main water supply operation mode in which the operation is restarted at the second lower water level L2 and the operation is stopped at the first high water level H1 as a predetermined value.

The tank submerged membrane separation device 6 has a combined feed water operation mode in which the operation is restarted at the first lower water level L1 and stopped at the second higher water level H2.

The casing-enclosed membrane separation device 5 that operates in the main water supply operation mode operates at the high set operating rate of 93% described in Example 1 above to produce purified water of 3,600 m3/d. Then, when the water level of the water purification reservoir 4 increases and reaches the first upper water level H1, the operation is stopped, and when the water level of the water purification reservoir 4 decreases and reaches the second lower water level L2, the operation is restarted.

The tank submerged membrane separation device 6 operating in the combined feed water operation mode operates at the high set operating rate of 100% described in the first embodiment to produce purified water of 1250 m3/d. Then, when the water level of the water purification tank 4 increases and reaches the second high water level H2, the operation is stopped, and when the water level of the water purification tank 4 decreases and reaches the first lower water level L1, the operation is restarted.

Therefore, when the demand level is high and the water level of the water purification basin 4 continues to decrease even when water is supplied by the casing-encased membrane separation device 5, the tank submerged membrane separation device 6 starts operation at the second lower water level L2, By supplying water by the immersion type membrane separation device 6 and the casing-enclosed type membrane separation device 5, sufficient water can be supplied to the water purification basin 4. Further, when the demand amount decreases and the water supply amount exceeds the demand amount, when the water level reaches the second upper water level H2, the operation of the tank submersion type membrane separation device 6 is stopped and the casing storage type membrane separation is performed. The operation of the device 5 can be continued to balance the demand amount and the water supply amount.

In addition, in the above-described Example 1, the tank-immersed membrane separation device 6 that operates for a short period of time can be regularly operated, so that it is possible to prevent spoilage of raw water stored in the tank and blockage of the filtration membrane. it can.

In Example 2, as the predetermined value (threshold value) of the control index, the highest first high water level H1, the second high water level H2 lower than the first high water level, the lowest first lower water level L1, and the first lower water level. A higher second lower water level L2 was set.

However, the first high water level H1 is set as the first set water level in the treated water tank, the second high water level H2 is set as the second set water level, and the casing-enclosed membrane separation device 5 sets the first set water level as the control target water level. It is also possible to have a main water supply operation mode for controlling the operation as, and a configuration in which the tank submerged membrane separation device 6 has a combined water supply operation mode for controlling the operation with the second set water level as the control target water level.

That is, the casing storage type membrane separation device 5 operates so as to maintain the first set water level in the main water supply operation mode, and stops operation when the water level reaches the first set water level, and the water level is the first set water level. After a certain time has elapsed from the time when it was detected that the temperature has dropped further, the operation is restarted by a timer or the like.

Further, in the combined water supply operation mode, the tank submerged membrane separation device 6 operates so as to maintain the second set water level, and stops operation when the water level reaches the second set water level, and the water level is the second set water level. After a certain time has elapsed from the time when it was detected that the temperature has dropped further, the operation is restarted by a timer or the like.

In Examples 1 and 2 described above, the casing-enclosed membrane separation device 5 is exemplified by a substantially rectangular parallelepiped ceramic membrane element. However, the shape of the membrane element may be cylindrical or polygonal. Further, not only the monolith type, but also a membrane element using a tubular membrane or a hollow fiber membrane may be used, and the material of the membrane is not limited, and may be made of resin.

A tubular membrane element made of ceramics is exemplified as the tank immersion type membrane separation device 6. However, the membrane element may be a flat membrane or a hollow fiber membrane, the material of the membrane is not limited, and may be made of resin.

In the above-mentioned Examples 1 and 2, examples in which the turbidity of raw water was used as a control index and those in which the water level of the treated water tank was used as a control index were illustrated as separate examples. However, the water purification treatment may be performed by controlling the operation of each membrane separation device by using both the concentration of raw water and the water level of the treated water tank as the control index. In this case, the control of each membrane separation device may be set not to stop but to give priority to the operation.

1 Water well 2 Mixing basin 3 Water intake facility 4 Purification basin 5 Casing storage type membrane separation device 6 Tank immersion type membrane separation device 7 Treatment tank 51 Membrane element 52 Membrane case 53 Membrane support 54 Filtration membrane 56 Flow channel 57 Air diffuser 101 Membrane elements 102, 103 End surface 104 Through flow path 105 Slit 106 Side surface 109 Raw water inlet 110 Treated water outlet 111 Pressurized gas inlet 112 Casing 114 Upper primary chamber 115 Lower primary chamber 116 First valve 117 Third valve 118 Third 2nd valve 119 4th valve 120 5th valve 130 Raw water supply system 131 Backwash water discharge system 132 Treated water system 133 Backwash water supply system 134 Pressurized gas supply system 135 Deposit discharge system G1 Pressurized gas W1 Backwash Water W2 Supply raw water W3 Treated water W4 Supply raw water H1 1st high water level H2 2nd high water level L1 1st low water level L2 2nd low water level

Claims (8)

A casing storage type membrane separation device that filters the raw water supplied to the casing of the closed space that stores the filtration membrane and a tank that stores the raw water are immersed in the housing of the open space that stores the filtration membrane to remove the raw water. A water purification method characterized in that a tank-immersed membrane separation device for filtering is also used, and the operations of the casing-enclosed membrane separator and the tank-immersed membrane separator are controlled based on a control index. The casing storage type membrane separation device operates at a high set operating rate when the raw water turbidity of the control index is below a predetermined value, and operates at a low set operating rate when the control index exceeds a predetermined value,
The tank immersion type membrane separation device is stopped when the control index is equal to or lower than a predetermined value, and is operated at a higher set operating rate when the control index exceeds the predetermined value. Water treatment method. 3. The purified water according to claim 1 or 2, wherein both membrane separation devices control the operation by changing the number of operating units, changing the operating time, changing the amount of treated water, or a combination of two or more of these. Processing method. Treated water supplied from both membrane separators is sent downstream through the treated water tank, and the water level of the treated water tank is used as a control index, and the first set water level and the second set water level lower than the first set water level are set in the treated water tank. Set,
The casing storage type membrane separation device controls the operation with the first set water level as a control target water level,
The water purification method according to claim 1, wherein the tank immersion type membrane separation device controls the operation with the second set water level as a control target water level. Treated water supplied from both membrane separators is sent downstream through the treated water tank, and the water level in the treated water tank is used as a control index, and the highest water level in the treated water tank is the highest water level and the second water level is lower than the first water level. Set the water level, the lowest first lower water level, and the second lower water level higher than the first lower water level,
The casing-enclosed membrane separation device restarts operation at the second lower water level and stops operation at the first higher water level,
The water purification method according to claim 1, wherein the tank submerged membrane separation device restarts operation at a first lower water level and stops operation at a second higher water level. Equipped with a casing storage type membrane separation device and a tank immersion type membrane separation device arranged in parallel in the middle of the water purification system,
The casing storage type membrane separation device has a method of filtering the raw water supplied into the casing of the closed space containing the filtration membrane, and operates at a high set operating rate when the turbidity of the raw water as a control index is below a predetermined value. And a low operation mode that operates at a low set operation rate when the control index exceeds a predetermined value.
The tank submerged membrane separation device has a method of filtering raw water by immersing the housing of the open space containing the filtration membrane in the tank that stores the raw water, and stops the operation when the control index is below a predetermined value. A water purification system characterized by having an operation stop mode for operating and a normal operation mode for operating at a high set operating rate when the control index exceeds a predetermined value. A casing storage type membrane separation device and a tank immersion type membrane separation device arranged in parallel in the middle of the water purification system, and a treated water tank that stores the treated water supplied from both membrane separation devices and sends it downstream.
Using the water level of the treated water tank as a control index, set the first set water level and the second set water level lower than the first set water level in the treated water tank,
The casing storage type membrane separation device has a method of filtering raw water supplied into the casing of the closed space in which the filtration membrane is stored, and has a main water supply operation mode in which operation is controlled with the first set water level as a control target water level. ,
The tank immersion type membrane separation device has a method of filtering raw water by immersing the housing of the open space containing the filtration membrane in the tank that stores the raw water, and controls the operation with the second set water level as the control target water level. A water purification system characterized by having a combined water supply operation mode. A casing storage type membrane separation device and a tank immersion type membrane separation device arranged in parallel in the middle of the water purification system, and a treated water tank that stores the treated water supplied from both membrane separation devices and sends it downstream.
Using the water level of the treated water tank as a control index, the highest high water level of the treated water tank, the second high water level lower than the first high water level, the lowest first lower water level, and the second lower water level higher than the first lower water level. Set
The casing storage type membrane separation device has a method of filtering the raw water supplied into the casing of the closed space in which the filtration membrane is stored, and restarts the operation at the second lower water level and stops the operation at the first higher water level. It has a water supply operation mode,
The tank submerged membrane separation device has a method of filtering the raw water by immersing the housing of the open space containing the filtration membrane in the tank storing the raw water, restarting the operation at the first lower water level, and A water purification system having a combined water supply operation mode in which operation is stopped at a high water level.

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