WO2022157926A1

WO2022157926A1 - Cleaning device for filtration membrane, water treatment device, and cleaning method for filtration membrane

Info

Publication number: WO2022157926A1
Application number: PCT/JP2021/002232
Authority: WO
Inventors: 祐樹佐藤; 英二今村; 清治野田
Original assignee: 三菱電機株式会社
Priority date: 2021-01-22
Filing date: 2021-01-22
Publication date: 2022-07-28
Also published as: CN116710193A; JP7067678B1; JPWO2022157926A1

Abstract

This cleaning device for a filtration membrane comprises: a circulation passage (25) that connects a flow outlet (40) and a flow inlet (41) of a cleaning liquid storage tank (27); and a supply passage (4) that supplies a circulating cleaning liquid (28) to a filtration membrane (3). The speed of flow of the cleaning liquid (28) is made to be faster in the circulation passage (25) than in the supply passage (4). As a result, it is possible to prevent reduction of the chemical concentration in the cleaning liquid (28) while the cleaning liquid (28) is being supplied from the cleaning liquid storage tank (27) to the filtration membrane (3), and thus it is possible to maintain the chemical concentration of the cleaning liquid (28). Additionally, since the supply flow speed is slower than the circulation flow speed, it is possible to reduce the amount of cleaning liquid (28) used.

Description

Filtration membrane cleaning device, water treatment device, and filtration membrane cleaning method

The present disclosure relates to a filtration membrane cleaning device, a water treatment device, and a filtration membrane cleaning method.

Membrane filtration using a filtration membrane is known as a method for separating and removing contaminants from water to be treated such as sewage and industrial wastewater. Continuing the membrane filtration process causes contaminants to adhere to the surface and pores of the filtration membrane, causing clogging, thereby gradually lowering the filtration performance. Therefore, in order to maintain filtration performance, the filtration membrane is washed with a washing liquid. The cleaning liquid contains chemicals to enhance the cleaning effect.
For example, the water treatment apparatus of Patent Document 1 uses cleaning liquid containing ozone. Ozone has high detergency, but is easily decomposed. Therefore, ozone may be decomposed in the cleaning liquid remaining in the flow path for supplying the cleaning liquid to the filtration membrane. In that case, there is a possibility that the washing liquid in which the ozone is decomposed is supplied to the filtration membrane at the initial stage of washing, and the washing efficiency deteriorates. Therefore, a circulation flow path is provided to return the cleaning liquid in the flow path to the cleaning liquid storage tank, and the ozone-decomposed cleaning liquid remaining in the flow path before cleaning is replaced with the ozone-containing cleaning liquid.

Japanese Patent Application Laid-Open No. 2003-251160

For example, when refurbishing a sewage treatment facility or factory to introduce water treatment equipment, the space available for installation may be limited in advance. In that case, the cleaning liquid storage tank cannot be installed in the vicinity of the membrane separation tank in which the membrane filtration process is performed, and the flow path from the cleaning liquid storage tank to the membrane separation tank may become long. In the conventional water treatment apparatus, when the channel is long, the time required for supplying the cleaning liquid becomes long. As a result, the chemical is decomposed during the supply of the cleaning liquid, and there is a possibility that the concentration of the chemical becomes lower than the predetermined concentration when supplied to the filtration membrane. Therefore, in order to supply the drug to the filtration membrane before it is decomposed, it is devised to increase the supply flow rate. However, increasing the supply flow rate increases the amount of cleaning liquid used.

The present disclosure has been made to solve the above-described problems, and aims to provide a filtration membrane cleaning apparatus that can reduce the amount of cleaning liquid used while maintaining the chemical concentration of the cleaning liquid.

A filtration membrane cleaning apparatus according to the present disclosure stores a cleaning liquid containing a chemical for cleaning a filtration membrane, and includes a cleaning liquid storage tank having an outlet and an inlet, and an outlet and an inlet of the cleaning liquid storage tank. and a supply provided with a supply pump that is connected to the circulation channel and that supplies part of the cleaning liquid circulating in the circulation channel to the filtration membrane. and a controller for controlling at least one of the circulation pump and the supply pump so that the flow rate of the cleaning liquid is faster in the circulation channel than in the supply channel.

In addition, the water treatment apparatus according to the present disclosure includes a membrane separation tank having a filtration membrane for membrane filtration of water to be treated, a membrane filtration tank for storing membrane filtered water subjected to membrane filtration by the membrane separation tank, and a filtration membrane. and a cleaning liquid storage tank having an outlet and an inlet, and a circulation pump connecting the outlet and the inlet of the cleaning liquid storage tank to circulate the cleaning liquid. a circulation channel, a supply channel connected to the circulation channel and provided with a supply pump for supplying part of the cleaning liquid circulating in the circulation channel to the filtration membrane, and a flow rate of the cleaning liquid circulating from the supply channel. and a controller for controlling at least one of the circulation pump and the supply pump to speed up the flow path.

Further, in the method for cleaning a filtration membrane according to the present disclosure, the cleaning liquid is circulated in a circulation channel that connects the outlet and the inlet of a cleaning liquid storage tank that stores the cleaning liquid, and the cleaning liquid circulating in the circulation channel is circulated. A part of the cleaning liquid is supplied from the circulation channel to the filtration membrane via the supply channel for supplying the cleaning liquid to the filtration membrane, so that the flow velocity of the cleaning liquid is faster in the circulation channel than in the supply channel.

According to the present disclosure, a circulation channel connecting the outlet and the inlet of the cleaning liquid storage tank and a supply channel for supplying the circulating cleaning liquid to the filtration membrane are provided, and the flow rate of the cleaning liquid is controlled by the supply channel. By speeding up the circulation flow path, it is possible to provide a filtration membrane cleaning apparatus capable of reducing the amount of cleaning liquid used while maintaining the chemical concentration of the cleaning liquid.

1 is a schematic diagram of a water treatment apparatus according to Embodiment 1; FIG. 2 is a schematic diagram of a water treatment apparatus according to Embodiment 2; FIG. 3 is a schematic diagram of a water treatment device according to Embodiment 3. FIG. 3 is a schematic diagram of a water treatment device according to Embodiment 3. FIG.

Embodiment 1.
A water treatment apparatus 100 equipped with a cleaning device for the filtration membrane 3 according to Embodiment 1 will be described with reference to FIG. FIG. 1 is a schematic diagram of a water treatment device 100. As shown in FIG. The water treatment apparatus 100 includes a membrane separation tank 2 having a filtration membrane 3 for membrane filtration of the water 1 to be treated, a membrane filtration tank 18 for storing membrane filtered water 19 that has undergone membrane filtration in the membrane separation tank 2, and a filtration It has a cleaning liquid storage tank 27 for storing a cleaning liquid 28 for cleaning the membrane 3 , and a channel for discharging the membrane filtered water 19 that has been subjected to membrane filtration by the filtration membrane 3 and supplying the cleaning liquid 28 .

In the membrane separation tank 2, pollutants are separated and removed by the filtration membrane 3 from the water 1 to be treated, which has been treated, for example, by the activated sludge method. The water to be treated 1 is, for example, tap water, sewage, secondary treated sewage, industrial waste water, seawater, human waste, etc., and flows into the membrane separation tank 2 through the water flow path 5 to be treated. A sludge withdrawal channel 6 and a sludge circulation channel 7 may be connected to the membrane separation tank 2 . The sludge extraction channel 6 is provided with a sludge extraction pump 9 for extracting sludge, and the sludge circulation channel 7 is provided with a sludge circulation pump 10 for circulating sludge in the membrane separation tank 2 . Also, an air diffuser 8 may be arranged at the bottom of the membrane separation tank 2 . A membrane surface aeration blower 12 is connected to the air diffuser 8 via an air supply pipe 11 .

The material of the filtration membrane 3 is not limited, but a fluorine-based resin compound that has excellent resistance to strong oxidants such as ozone is preferable. Other examples include polyolefins such as polyethylene, polypropylene, and polybutene, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-ethylene copolymer. Fluorinated resin compounds such as coalescence (ETFE), polychlorotrifluoroethylene (PCTFE), chlorotrifluoroethylene-ethylene copolymer (ECTFE), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), cellulose acetate , celluloses such as ethyl cellulose, ceramics, and the like may be used. Also, a combination of two or more of the above materials may be used.

The type of filtration membrane 3 is not limited. For example, various filtration membranes 3 known in the art, such as microfiltration (MF) membranes and ultrafiltration (UF) membranes, may be used.

Although the average pore diameter of the filtration membrane 3 is not limited, it is preferably 0.001 μm or more and 1 μm or less, more preferably 0.01 μm or more and 0.1 μm or less. By using the filtration membrane 3 having an average pore diameter in this range, not only contaminants adhering to the surface of the filtration membrane 3 in contact with the water to be treated 1, but also the surface of the filtration membrane 3 in contact with the membrane filtered water 19 or the filtration membrane 3 Contaminants chemically adhered in the pores of the can be efficiently removed.

The shape of the filtration membrane 3 is not limited. For example, it may have a shape known in the technical field, such as a cylindrical shape or a flat film shape. Alternatively, an immersion type, a casing type, a monolith type, or the like may be employed.

The water flow method of the filtration membrane 3 is not limited. For example, a dead end filtration method or a cross-flow filtration method may be used. An external pressure filtration method may be used in which the water to be treated 1 flows outside the filtration membrane 3 and the filtered water flows inside, or an internal pressure filtration method in which the water to be treated 1 flows inside the filtration membrane 3 and the filtered water flows outside. may be

Membrane filtered water 19 that has been subjected to membrane filtration by the membrane separation tank 2 is stored in the membrane filtered water tank 18 .

The water treatment device 100 includes a washing device for washing the filtration membrane 3 . The cleaning device has a cleaning liquid storage tank 27 in which cleaning liquid 28 containing an agent for cleaning the filtration membrane 3 is stored.
The type of drug is not limited as long as it does not deteriorate the material of the filtration membrane 3 and can decompose organic or inorganic substances. Therefore, it is preferable to use substances known in the technical field. For example, agents capable of decomposing organic matter include sodium hypochlorite, hydrogen peroxide, sodium hydroxide, and ozone. You may use these individually or in combination of 2 or more types. When two or more agents capable of decomposing organic matter are used in combination, the first agent preferably has a standard oxidation-reduction potential (25° C.) of less than 2.0 V measured using a hydrogen electrode, and the second agent preferably has a standard oxidation-reduction potential (25° C.) of 2.0 V or more measured using a hydrogen electrode. For example, sodium hypochlorite may be used as the first chemical, and ozone may be used as the second chemical. Substances capable of decomposing inorganic matter include, for example, inorganic acids such as hydrochloric acid, sulfuric acid and nitric acid, and organic acids such as oxalic acid and citric acid. These may also be used singly or in combination of two or more. Two or more substances capable of decomposing organic substances and substances capable of decomposing inorganic substances may be used in combination. In that case, which one is used as the first drug or the second drug is not limited. For example, when a substance capable of decomposing organic substances is used as the first chemical, a substance capable of decomposing inorganic substances is used as the second chemical. When a substance capable of decomposing inorganic substances is used as the first chemical, a substance capable of decomposing organic substances may be used as the second chemical.

The drug concentration of the cleaning liquid 28 is not limited. For example, when using a substance capable of decomposing organic matter, sodium hypochlorite (effective chlorine concentration) is 1.0 g/L or more and 5.0 g/L or less, and sodium hydroxide is 1.0 g/L or more and 4.0 g/L. The following are preferred. Ozone is preferably 10 mg/L or more and 40 mg/L or less, more preferably 20 mg/L or more and 30 mg/L or less. When using a substance capable of decomposing inorganic substances, hydrochloric acid, sulfuric acid, and nitric acid are 1.0 g/L or more and 10.0 g/L or less, oxalic acid is 1.0 g/L or more and 2.0 g/L or less, and citric acid is 1 g/L. L or more and 10 g/L or less is preferable. If the chemical concentration is lower than the above range, it takes time to decompose contaminants adhering to the filtration membrane 3, and as the amount of cleaning liquid 28 used increases, the capacity of the chemical tank also increases. On the other hand, if the concentration of the drug is higher than the above range, the amount of the drug to be used will increase, resulting in an increase in the cost required for the drug.

A flow path is formed by, for example, piping. As shown in FIG. 1 , the flow path includes a circulation flow path 25 , a supply flow path 4 and a membrane filtered water flow path 17 . The circulation flow path 25 is a flow path that connects the outflow port 40 and the inflow port 41 of the cleaning liquid storage tank 27 and circulates the cleaning liquid 28 stored in the cleaning liquid storage tank 27 . The supply flow path 4 is a flow path for supplying the cleaning liquid 28 to the filtration membrane 3 of the membrane separation tank 2, and is also a flow path for supplying the membrane filtration water 19 that has been subjected to membrane filtration by the filtration membrane 3 to the membrane filtration water tank 18. . The membrane filtered water channel 17 is a channel that connects the membrane filtered water tank 18 and the supply channel 4 .

The switching unit 20 is provided in the supply channel 4 and connects the supply channel 4 and the membrane filtered water channel 17 . The switching unit 21 is provided in the circulation channel 25 and connects the circulation channel 25 and the supply channel 4 .
The switching

units

20 and 21 are, for example, three-way valves capable of switching the flow path of the cleaning liquid 28 or the membrane filtered water 19 .

The circulation flow path 25 includes a circulation pump 22 and a circulation flow rate measuring section 23 . Also, a cleaning liquid concentration measuring unit 24 may be provided. The cleaning liquid 28 is returned to the cleaning liquid storage tank 27 through the circulation flow path 25 by the circulation pump 22 . The circulation flow velocity measurement unit 23 is not limited as long as it can measure the flow velocity of the cleaning liquid 28 circulating in the circulation flow path 25 . For example, an electromagnetic current meter, propeller current meter, ultrasonic current meter, or radio wave current meter may be used.

The cleaning liquid concentration measurement unit 24 measures the drug concentration in the cleaning liquid 28 . The cleaning liquid concentration measuring unit 24 may be appropriately selected according to the chemical, such as an absorbance type ozone concentration meter, an electrode type ozone concentration meter, or the like. The cleaning liquid concentration measuring section 24 may be positioned downstream of the circulation pump 22 , the circulation flow rate measuring section 23 and the switching section 21 , and the closer it is to the inlet 41 of the cleaning liquid storage tank 27 , the better. When the cleaning liquid concentration measuring section 24 is arranged near the inlet 41 of the cleaning liquid storage tank 27 , it is possible to measure the chemical concentration when the circulating cleaning liquid 28 is returned to the cleaning liquid storage tank 27 . Therefore, the chemical concentration in the circulating cleaning liquid 28 can be accurately grasped.

The supply flow path 4 includes a supply pump 14 and a supply flow rate measuring section 15 . Also, a pressure gauge 13 may be provided. During the membrane filtration process, it becomes a channel for supplying the membrane filtered water 19 to the membrane filtered water tank 18 by the membrane filtered pump 16 provided in the membrane filtered water channel 17 which will be described later. During the cleaning process of the filtration membrane 3 , the supply pump 14 provided in the supply flow path 4 serves as a flow path for supplying part of the cleaning liquid 28 circulating in the circulation flow path 25 to the filtration membrane 3 .
A supply flow velocity measurement unit 15 measures the flow velocity of the cleaning liquid 28 in the supply channel 4 . The supply flow rate measuring section 15 is not limited as long as it can measure the flow rate of the cleaning liquid 28 circulating in the circulation flow path 25 in the same manner as the circulation flow rate measuring section 23 .

The membrane-filtered water flow path 17 includes a membrane-filtered pump 16 . During the membrane filtration process, the membrane filtered water 19 separated by the membrane filtration pump 16 in the membrane separation tank 2 passes through the supply channel 4 and the membrane filtered water channel 17 and flows into the membrane filtered water tank 18 .

All pumps and switching units are connected to the control unit 26. Moreover, the measurement results of the supply flow velocity measurement unit 15 and the circulation flow velocity measurement unit 23 are transmitted to the control unit 26 . A control unit 26 controls the operation of all pumps and switching units. A control method by the control unit 26 will be described later in the water treatment method.

Next, a water treatment method using the water treatment device 100 will be described. Water treatment methods are roughly divided into membrane filtration and cleaning of the filtration membrane 3 . In the membrane filtration process, after treating the water to be treated 1 by the activated sludge method, the filter membrane 3 is used to separate and remove contaminants. If the membrane filtration treatment is continuously performed, there is a problem that the filtration performance is lowered. Specifically, with continuous use of the filtration membrane 3, contaminants adhere to the surface of the filtration membrane 3 in contact with the water to be treated 1, the surface of the filtration membrane 3 in contact with the filtered water, and the pores of the filtration membrane 3. As a result, clogging occurs, and filtration performance gradually decreases. In particular, when the filtration membrane 3 is clogged, the pressure required for membrane filtration increases. Therefore, the membrane filtration flux, the membrane filtration water amount per unit time and unit membrane area are lowered. Therefore, in order to maintain the performance of the filtration membrane 3, the filtration membrane 3 is periodically washed.

The membrane filtration process will be explained. The operation of the pump and the switching unit, which will be described later, is controlled by the control unit 26 .
First, the switching unit 20 is closed on the circulation channel 25 side, opened on the membrane separation tank 2 side and the membrane filtered water channel 17 side, and the membrane filtration pump 16 is activated. As a result, the water to be treated 1 is membrane-filtered by the filtration membrane 3, and the membrane-filtered water 19 filtered by the filtration membrane 3 is discharged to the membrane-filtered water tank 18 via the supply channel 4 side and the membrane-filtered water channel 17. .

Next, the cleaning treatment of the filtration membrane 3 will be described.
When the membrane filtration process is being performed, the membrane filtration pump 16 is stopped to terminate the membrane filtration process. Then, the switching unit 20 closes the membrane filtered water channel 17 side and opens the membrane separation tank 2 side and the circulation channel 25 side. After completion of the membrane filtration treatment, the filtration membrane 3 may be pretreated before starting the washing treatment of the filtration membrane 3 . For example, by exposing the filtration membrane 3 to air for a certain period of time, contaminants adhering to the surface of the filtration membrane 3 in contact with the water 1 to be treated can be easily removed. Alternatively, the filtration membrane 3 may be pre-washed by preparing a pre-wash liquid containing no chemicals. By performing preliminary washing, contaminants attached to the surface of the filtration membrane 3 in contact with the water 1 to be treated can be easily removed.

Next, the cleaning liquid 28 is circulated. First, the supply channel 4 side of the switching unit 21 is closed, and the outflow port 40 side and the inflow port 41 side of the cleaning liquid storage tank 27 are opened. Then, the circulation pump 22 is activated to circulate the washing liquid 28 containing the chemicals from the washing liquid storage tank 27 through the circulation flow path 25 . As a result, the old cleaning liquid 28 remaining in the circulation channel 25 can be replaced with the new cleaning liquid 28 . Therefore, even if the chemicals in the old cleaning liquid 28 remaining in the circulation flow path 25 are decomposed, the cleaning efficiency in the initial stage of cleaning can be improved. Also, the chemical concentration of the cleaning liquid 28 is measured by the cleaning liquid concentration measuring section 24 provided in the circulation flow path 25 . Thereby, it is confirmed whether or not the washing liquid 28 has a predetermined chemical concentration. At this time, the measurement result of the cleaning liquid concentration measuring unit 24 is sent to the control unit 26, and when the cleaning liquid 28 can secure a predetermined drug concentration, the cleaning liquid 28 is controlled to start supplying the cleaning liquid 28 to the filtration membrane 3, which will be described later. You may Although not shown, the circulation flow path 25 may be provided with, for example, a static mixer or the like for uniformly mixing the cleaning liquid 28 .

Next, the cleaning liquid 28 is supplied to the filtration membrane 3 . The switching unit 21 opens all directions on the supply channel 4 side, the outflow port 40 side and the inflow port 41 side of the cleaning liquid storage tank 27 . Then, the supply pump 14 is started to supply part of the cleaning liquid 28 circulating in the circulation flow path 25 to the filtration membrane 3 via the supply flow path 4 to back wash the filtration membrane 3 . The cleaning liquid 28 discharged from the filtration membrane 3 after backwashing can be discharged into the membrane separation tank 2 and used as the water 1 to be treated for membrane filtration. Alternatively, the washing liquid 28 discharged from the filtration membrane 3 after back washing may be separately collected and treated as a treated liquid. The cleaning liquid 28 after each backwashing process, which will be described later, is also processed in the same manner as described above.

The circulation pump 22 and the supply pump 14 are controlled by the controller 26 . At that time, the flow velocity of the circulation channel 25 is made faster than the flow velocity of the supply channel 4 . Also, the flow rate is adjusted so that the retention time of the cleaning liquid 28 from the cleaning liquid storage tank 27 to the filtration membrane 3 and the retention time of the cleaning liquid 28 from the cleaning liquid storage tank 27 to the cleaning liquid concentration measuring unit 24 are the same. The flow rate may be adjusted by controlling both the circulation pump 22 and the supply pump 14, or by controlling either one.

A method of controlling the circulation pump 22 to adjust the flow rate, for example, will be described with reference to FIG. First, the flow velocity of the cleaning liquid 28 in the circulation channel 25 is made faster than the flow velocity of the cleaning liquid 28 in the supply channel 4 . At that time, the supply flow velocity and the circulation flow velocity are measured using the supply flow velocity measurement unit 15 and the circulation flow velocity measurement unit 23 . For example, when the value of the supply flow velocity measurement unit 15 is high, the input to the motor of the circulation pump 22 is increased so that the value of the circulation flow velocity measurement unit 23 becomes higher than the value of the supply flow velocity measurement unit 15 . When controlling the supply pump 14 , the input to the motor of the supply pump 14 should be lowered so that the value of the supply flow velocity measurement unit 15 becomes lower than the value of the circulation flow velocity measurement unit 23 . When controlling both the circulation pump 22 and the supply pump 14, the inputs to the motors of the circulation pump 22 and the supply pump 14 should be adjusted so that the value of the circulation flow rate measuring unit 23 is higher than the value of the supply flow rate measuring unit 15. Just do it.

Also, the circulation pump 22 is controlled so that the retention time of the cleaning liquid 28 from the cleaning liquid storage tank 27 to the filtration membrane 3 and the retention time of the cleaning liquid 28 from the cleaning liquid storage tank 27 to the cleaning liquid concentration measuring unit 24 are the same. In that case, the supply channel 4 is formed to be a channel shorter than the circulation channel 25 . When the pipe diameters of the flow paths are the same, the residence time of the cleaning liquid 28 can be obtained by dividing the pipe length by the flow velocity. Specifically, by dividing the pipe length from the cleaning liquid storage tank 27 to the cleaning liquid concentration measuring section 24 by the flow velocity obtained by the circulation flow rate measuring section 23, the cleaning liquid 28 from the cleaning liquid storage tank 27 to the cleaning liquid concentration measuring section 24 is calculated. can be obtained. Also, the value obtained by dividing the pipe length from the cleaning liquid storage tank 27 to the switching unit 21 by the flow speed obtained by the circulation flow speed measuring unit 23 and the pipe length from the switching unit 21 to the filtration membrane 3 by the supply flow speed measuring unit 15 The retention time of the cleaning liquid 28 from the cleaning liquid storage tank 27 to the filtration membrane 3 can be determined by adding the values obtained by dividing the obtained flow rate.

The control unit 26 controls the supply pump 14 and circulation so that the retention time of the cleaning liquid 28 from the cleaning liquid storage tank 27 to the filtration membrane 3 and the retention time of the cleaning liquid 28 from the cleaning liquid storage tank 27 to the cleaning liquid concentration measurement unit 24 are the same. Controls the input to the pump 22 motor. For example, a case where the retention time from the cleaning liquid storage tank 27 to the filtration membrane 3 is longer than the retention time from the cleaning liquid storage tank 27 to the cleaning liquid concentration measuring section 24 will be described. When controlling the circulation pump 22, the input to the motor of the circulation pump 22 is increased. When controlling the feed pump 14, the input to the feed pump 14 motor is lowered. When controlling the circulation pump 22 and the supply pump 14, the input to the motor of the circulation pump 22 is increased and the input to the motor of the supply pump 14 is decreased.
As a result, it becomes possible to estimate the drug concentration in the cleaning liquid 28 supplied to the filtration membrane 3 from the value of the cleaning liquid concentration measuring unit 24 .

So far, an example of adjusting the flow velocity using the flow velocity values measured by the supply flow velocity measurement unit 15 and the circulation flow velocity measurement unit 23 has been described as a method for adjusting the flow velocity. As another method, the flow rate may be measured by the supply flow rate measuring section 15 and the circulation flow rate measuring section 23, and the flow rate may be calculated from the measured flow rates. Specifically, when the pipe diameters of the flow paths are the same, the flow velocity can be obtained by dividing the flow rate by the pipe cross-sectional area.

Also, when the flow rate is measured by the supply flow velocity measurement unit 15 and the circulation flow velocity measurement unit 23, the pipe diameters of the flow paths may be different. For example, the pipe diameters of the supply channel 4 and the circulation channel 25 may be different. In that case, the residence time of the cleaning liquid 28 can be obtained by dividing the flow rate per hour by the pipe capacity. The pipe capacity can be obtained by multiplying the pipe cross-sectional area and length. Therefore, by dividing the value of the flow rate obtained by the circulation flow rate measuring unit 23 by the pipe capacity from the cleaning liquid storage tank 27 to the cleaning liquid concentration measuring unit 24, the retention of the cleaning liquid 28 from the cleaning liquid storage tank 27 to the cleaning liquid concentration measuring unit 24 can be calculated. You can ask for time. In addition, the value obtained by dividing the flow rate value obtained by the circulation flow rate measuring unit 23 by the piping capacity from the cleaning liquid storage tank 27 to the switching unit 21 and the flow rate value obtained by the supply flow rate measuring unit 15 are obtained from the switching unit 21 to the filtration membrane. By adding the values divided by the pipe capacity up to 3, the retention time from the cleaning liquid storage tank 27 to the filtration membrane 3 can be obtained.

The cleaning time of the filtration membrane 3 using the cleaning liquid 28 containing the drug may be appropriately set according to the amount of contaminants adhering to the filtration membrane 3 and the like. In general, it is preferable to use sodium hypochlorite for 90 minutes or less, ozone water for 60 minutes or less, and oxalic acid or citric acid for 5 minutes or more and 7 minutes or less. When the washing time is long, the time during which the membrane treatment of the water 1 to be treated is interrupted is also long, and the amount of membrane-filtered water is reduced. Therefore, the shorter the washing time, the better.

The membrane surface permeation flux, which is the amount of water supplied per membrane area of the washing liquid 28 containing the chemical, is not limited. In general, it suffices if a flux that can be filled up to the end of the filtration membrane 3 can be secured. Specifically, when sodium hypochlorite is used, it is preferably 6 LMH (L/(m ² ·h)) or less, and when ozone water is used, it is preferably 30 LMH (L/(m ² ·h)) or less. If the membrane surface permeation flux is too high, the required amount of the cleaning liquid 28 increases, resulting in an increase in chemical costs, an increase in the capacity of the chemical tank, and breakage of the filtration membrane 3 . If the membrane surface permeation flux is too low, the washing liquid 28 will not be filled up to the end of the filtration membrane 3, making it impossible to decompose contaminants adhering to the filtration membrane 3, or, if ozone is used as the chemical, the concentration will decrease during supply. or

The cleaning method of the filtration membrane 3 according to the present embodiment includes a cleaning method in which the cleaning liquid 28 is passed through the filtration membrane 3 and then the cleaning liquid 28 is retained in the membrane as it is, and a cleaning method in which the filtration membrane 3 is immersed in the cleaning liquid 28 and retained. It is recommended to use a cleaning method that

After the filtration membrane 3 has been washed, the circulation pump 22 and the supply pump 14 are stopped, the circulation channel 25 side of the switching unit 20 is closed, and the membrane filtration pump 16 is opened. Then, the membrane filtration pump 16 is activated, and the membrane filtration treatment of the water 1 to be treated can be performed again. Thereby, the membrane filtration process of the to-be-processed water 1 can be performed continuously and efficiently.

A conventional cleaning device for the filtration membrane 3 supplied the cleaning liquid 28 from the cleaning liquid storage tank 27 to the filtration membrane 3 at a constant flow rate. Therefore, when the flow path from the cleaning liquid storage tank 27 to the filtration membrane 3 is long, the chemicals in the cleaning liquid are decomposed during supply and the concentration is lowered. In addition, increasing the flow rate increases the amount of cleaning liquid used in order to supply the chemicals before they are decomposed.

The cleaning apparatus for the filtration membrane 3 in this embodiment includes a circulation flow path 25 connecting the outlet 40 and the inlet 41 of the cleaning liquid storage tank 27 and a supply flow for supplying the circulating cleaning liquid 28 to the filtration membrane 3. a path 4; At least one of the circulation pump 22 and the supply pump 14 is controlled so that the flow rate of the cleaning liquid 28 is faster in the circulation channel 25 than in the supply channel 4 . By making the circulation flow rate of the cleaning liquid 28 faster than the supply flow rate to the filtration membrane 3 , it is possible to suppress the decrease in the chemical concentration in the cleaning liquid 28 while the cleaning liquid 28 is being supplied from the cleaning liquid storage tank 27 to the filtration membrane 3 . can. Thereby, the drug concentration of the cleaning liquid 28 can be maintained. Furthermore, since the supply flow rate is slower than the circulation flow rate, the amount of cleaning liquid 28 used can be reduced.

In addition, the water treatment apparatus 100 in the present embodiment includes a cleaning device for the filtration membrane 3 that can reduce the usage of the cleaning liquid 28 while maintaining the chemical concentration of the cleaning liquid 28 as described above. As a result, since the cleaning liquid storage tank 27 can be installed at a distance, the degree of freedom in designing the water treatment apparatus 100 is improved. Furthermore, since the cleaning liquid storage tank 27 can be installed at a distance, the degree of freedom of the installation location of the water treatment device 100 is improved.

In addition, since the water treatment apparatus 100 repeats the membrane filtration process and the cleaning process of the filtration membrane 3, the supply and stop of the cleaning liquid 28 are repeated. Therefore, while the supply of the cleaning liquid 28 is stopped, the chemicals in the cleaning liquid 28 remaining in the flow path may be decomposed. Water treatment apparatus 100 in the present embodiment circulates cleaning liquid 28 before supplying cleaning liquid 28 to filtration membrane 3 . As a result, the old cleaning liquid 28 remaining in the circulation channel 25 can be replaced with the new cleaning liquid 28 . Therefore, even if the chemicals in the old cleaning liquid 28 remaining in the circulation flow path 25 are decomposed, the cleaning efficiency in the initial stage of cleaning can be improved. Also, the chemical concentration of the cleaning liquid 28 is measured by the cleaning liquid concentration measuring section 24 provided in the circulation flow path 25 . This confirms whether or not the cleaning liquid 28 in the cleaning liquid storage tank 27 has a predetermined chemical concentration.

Also, the retention time of the cleaning liquid 28 from the cleaning liquid storage tank 27 to the filtration membrane 3 and the retention time of the cleaning liquid 28 from the cleaning liquid storage tank 27 to the cleaning liquid concentration measuring section 24 are set to be the same. As a result, the concentration of the cleaning liquid 28 supplied to the filtration membrane 3 can be estimated from the value of the cleaning liquid concentration measuring section 24 . Therefore, the concentration of the cleaning liquid 28 in the cleaning liquid storage tank 27 and the concentration of the cleaning liquid 28 supplied to the filtration membrane 3 can be confirmed by one cleaning liquid concentration measuring unit 24 .

In addition, in the cleaning apparatus for the filtration membrane 3 of the present embodiment, the case of using the cleaning liquid 28 containing one type of chemical has been described, but when using the cleaning liquid 28 containing two or more types of chemicals, the cleaning liquid storage tank A plurality of 27 may be provided and the cleaning process may be performed by the same method.

Embodiment 2.
A water treatment apparatus 100 equipped with a cleaning device for the filtration membrane 3 according to Embodiment 2 will be described with reference to FIG. 2 . FIG. 2 is a schematic diagram of the water treatment device 100. As shown in FIG. Embodiment 2 shows an example of using ozone as the cleaning liquid 28 as the cleaning liquid 28 because the decomposition of the cleaning liquid occurs immediately after the cleaning liquid is generated and it is particularly difficult to maintain the concentration of the cleaning liquid. That is, the cleaning liquid storage tank 27 stores ozone water as the cleaning liquid 28 . Other configurations are the same as those of the first embodiment. The same reference numerals are assigned to the same configurations as in the first embodiment.

As shown in FIG. 2, the cleaning liquid storage tank 27 has an air diffuser 31 at its bottom, and an ozone generator 29 is connected to the air diffuser 31 via an ozone supply pipe 30 . The ozone raw material supplied to the ozone generator 29 is not limited. For example, oxygen generated by liquid oxygen, PSA (Pressure Swing Adsorption), or PVSA (Pressure Vacuum Swing Adsorption) may be used. Further, the ozonized water that is no longer needed is treated by the exhaust ozone treatment equipment 33 via the exhaust ozone pipe 32 and discharged to the treatment ozone pipe 34 .

Next, a method for generating ozone water in the cleaning liquid storage tank 27 will be described. Other water treatment methods are the same as in the first embodiment.
First, ozone gas generated by the ozone generator 29 is supplied from the air diffuser 31 to the cleaning liquid storage tank 27 via the ozone supply pipe 30 . Ozone water is thereby generated in the cleaning liquid storage tank 27 . Then, the ozone water generated in the cleaning liquid storage tank 27 is supplied to the filtration membrane 3 through the circulation flow path 25 and the supply flow path 4 to backwash the filtration membrane 3 .

As in Embodiment 1, the filtration membrane 3 cleaning apparatus in this embodiment includes a circulation channel 25 and a supply channel 4, and the flow velocity of the cleaning liquid 28 is made faster in the circulation channel 25 than in the supply channel 4. . As a result, the amount of the cleaning liquid 28 used can be reduced while maintaining the chemical concentration of the cleaning liquid 28 .

Further, ozone water can be generated in the cleaning liquid storage tank 27 by supplying the ozone gas generated by the ozone generator 29 from the air diffuser 31 to the cleaning liquid storage tank 27 via the ozone supply pipe 30 . As a result, even when ozonized water, which is easily decomposed, is used as the cleaning liquid 28, the concentration of the ozonated water stored in the cleaning liquid storage tank 27 can be easily maintained.

Although the case where the air diffuser 31 is used as the means for supplying ozone gas has been described, other supply means may be used as long as it can generate ozone water. For example, an ejector type, mechanical stirring type, downward injection type, or other ozone gas supplying means may be used.

Also, although an example using ozone as a chemical has been described, cleaning liquid 28 containing ozone and a chemical other than ozone may be used in combination.

Embodiment 3.
A water treatment apparatus 100 equipped with a cleaning device for the filtration membrane 3 according to Embodiment 3 will be described with reference to FIG. FIG. 3 is a schematic diagram of the water treatment device 100. As shown in FIG. In the water treatment apparatus 100 according to Embodiment 3, the flow path from the outflow port 40 to the inflow port 41 of the cleaning liquid storage tank 27 forms a channel shorter than the circulation flow channel 25, and the flow path of the cleaning liquid storage tank 27 is controlled by the circulation pump 22. On the 41 side, there is a connection channel 37 that connects two points of the circulation channel 25 on the side of the cleaning solution storage tank 27 from the cleaning solution concentration measuring unit 24 to the outflow port 40 side. Other configurations are the same as those of the first embodiment. The same reference numerals are assigned to the same configurations as in the first embodiment.

For example, the circulation flow path 25 includes a switching section 38 between the circulation pump 22 and the circulation flow rate measuring section 23 and the switching section 21 , and a switching section 39 between the switching section 21 and the cleaning liquid concentration measuring section 24 . By providing the connection flow path 37 connected to the switching section 38 and the switching section 39, a flow path from the outflow port 40 to the inflow port 41 of the cleaning liquid storage tank 27 can be formed shorter than the circulation flow path 25. .

Next, a water treatment method using the water treatment device 100 will be described.
When cleaning the filtration membrane 3 , first, the cleaning liquid 28 is circulated through the connection channel 37 .
The switching section 21 side of the switching section 38 is closed, and the circulation flow velocity measuring section 23 side and the switching section 39 side are opened. The switching section 39 closes the switching section 21 side and opens the cleaning liquid concentration measuring section 24 side and the switching section 38 side. Next, the circulation pump 22 is activated to circulate the cleaning liquid 28 through the outlet 40 of the cleaning liquid storage tank 27 , the switching portion 38 , the connecting channel 37 , the switching portion 39 and the inlet 41 of the cleaning liquid storage tank 27 in this order. In this manner, the cleaning liquid 28 is supplied to the cleaning liquid concentration measuring section 24 through a channel shorter than the circulation channel 25 via the connection channel 37 . This makes it possible to more accurately confirm whether the chemical concentration in the cleaning liquid 28 supplied from the cleaning liquid storage tank 27 is at a predetermined concentration.

Next, the circulation of the cleaning liquid 28 when supplied to the filtration membrane 3 will be described.
The switching unit 38 closes the switching unit 39 side and opens the circulation flow velocity measuring unit 23 side and the switching unit 21 side. The switching section 39 closes the switching section 38 side and opens the cleaning liquid concentration measuring section 24 and the switching section 21 side. The switching unit 21 closes the supply channel 4 side and opens the switching unit 38 side and the switching unit 39 side. Next, the circulation pump 22 is activated to circulate the cleaning liquid 28 through the outlet 40 of the cleaning liquid storage tank 27, the switching section 21, and the inlet 41 of the cleaning liquid storage tank 27 in this order. As a result, the old cleaning liquid 28 remaining in the circulation channel 25 can be replaced with the new cleaning liquid 28 . Therefore, even if the chemicals in the old cleaning liquid 28 remaining in the circulation flow path 25 are decomposed, the cleaning efficiency in the initial stage of cleaning can be improved. Other water treatment methods are the same as in the first embodiment.

Also, the cleaning liquid storage tank 27 cannot be installed near the membrane separation tank 2 in some cases. In this case, since the flow path from the cleaning liquid storage tank 27 to the filtration membrane 3 is lengthened, the circulation flow path 25 from the cleaning liquid storage tank 27 to the cleaning liquid concentration measuring section 24 is also lengthened. In such a water treatment apparatus 100, when the chemical concentration measured by the cleaning liquid concentration measuring unit 24 is low, the chemical concentration of the cleaning liquid 28 supplied from the cleaning liquid storage tank 27 is low, or during the supply to the filtration membrane 3 It is not possible to determine whether the drug concentration has decreased. To solve this problem, in the present embodiment, the circulation flow path 25 is arranged to store the cleaning liquid more than the circulation pump 22 so that the flow path from the outflow port 40 to the inflow port 41 of the cleaning liquid storage tank 27 forms a flow path that is shorter than the circulation flow path 25 . This problem can be solved by providing a connection channel 37 that connects two points on the side of the inlet 41 of the tank 27 from the cleaning liquid concentration measuring unit 24 to the outlet 40 of the cleaning liquid storage tank 27 . With this configuration, the chemical concentration of the cleaning liquid 28 supplied from the cleaning liquid storage tank 27 and the chemical concentration of the cleaning liquid 28 supplied to the filtration membrane 3 can be confirmed separately.

It should be noted that the configuration shown in the above-described embodiment is an example, and can be combined with another known technique. Further, it is possible to combine the embodiments, and it is also possible to omit or change a part of the configuration without departing from the gist of the invention.

For example, Embodiment 2 and Embodiment 3 may be combined. FIG. 4 is a schematic diagram of the water treatment device 100. As shown in FIG. A water treatment apparatus 100 shown in FIG. 4 has an ozone generator 29 connected to a cleaning liquid storage tank 27 via an ozone supply pipe 30 . In addition, the cleaning liquid concentration measuring unit 24 measures the concentration of the cleaning liquid from the cleaning liquid storage tank 27 at the inlet 41 side of the cleaning liquid storage tank 27 from the circulation pump 22 so that the flow path from the outflow port 40 to the inflow port 41 of the cleaning liquid storage tank 27 forms a flow path shorter than the circulation flow path 25 . It has a connection channel 37 that connects two locations on the outflow port 40 side of the cleaning liquid storage tank 27 .

Also in this embodiment, the circulation channel 25 and the supply channel 4 are provided, and the flow velocity of the cleaning liquid 28 is made faster in the circulation channel 25 than in the supply channel 4 . As a result, it is possible to reduce the usage amount of the cleaning liquid 28 while maintaining the chemical concentration of the cleaning liquid 28 containing ozone, which is easily decomposed.

Further, even if the cleaning liquid 28 contains ozone, which is easily decomposed, the ozone concentration of the cleaning liquid 28 supplied from the cleaning liquid storage tank 27 and the ozone concentration of the cleaning liquid 28 supplied to the filtration membrane 3 can be checked separately. .

1 Water to be treated, 2 Membrane separation tank, 3 Filtration membrane, 4 Supply channel, 5 Water channel to be treated, 6 Sludge extraction channel, 7 Sludge circulation channel, 8 Air diffuser, 9 Sludge extraction pump, 10 Sludge circulation Pump, 11 Air supply pipe, 12 Membrane surface aeration blower, 13 Pressure gauge, 14 Supply pump, 15 Supply flow rate measuring part, 16 Membrane filtration pump, 17 Membrane filtration water flow path, 18 Membrane filtration water tank, 19 Membrane filtration water, 20 Switching section, 21 switching section, 22 circulation pump, 23 circulation flow rate measurement section, 24 cleaning liquid concentration measurement section, 25 circulation flow path, 26 control section, 27 cleaning liquid storage tank, 28 cleaning liquid, 29 ozone generator, 30 ozone supply pipe, 31 Aeration device, 32 exhaust ozone pipe, 33 exhaust ozone treatment equipment, 34 treated ozone pipe, 36 switching part, 37 connection flow path, 38 switching part, 39 switching part, 40 outlet, 41 inlet, 100 water treatment device

Claims

a cleaning liquid reservoir storing a cleaning liquid containing an agent for cleaning the filtration membrane and having an outlet and an inlet;
a circulation channel connecting the outflow port and the inflow port of the cleaning liquid storage tank and provided with a circulation pump for circulating the cleaning liquid;
a supply channel connected to the circulation channel and provided with a supply pump that supplies part of the cleaning liquid circulating in the circulation channel to the filtration membrane;
a control unit that controls at least one of the circulation pump and the supply pump so that the flow rate of the cleaning liquid is faster in the circulation channel than in the supply channel;
Filtration membrane cleaning device.
2. The filtration membrane cleaning apparatus according to claim 1, wherein the chemical contains at least ozone.
3. The filtration membrane cleaning apparatus according to claim 2, wherein said cleaning liquid storage tank has an air diffuser connected to an ozone generator.
the circulation channel has a cleaning solution concentration measuring unit that measures the concentration of chemicals in the cleaning solution;
The controller controls the circulation pump and 4. The filtration membrane cleaning apparatus according to claim 1, wherein at least one of the supply pumps is controlled.
The cleaning liquid storage tank is moved from the cleaning liquid concentration measuring unit to the cleaning liquid storage tank on the inflow side of the cleaning liquid storage tank from the circulation pump so that the distance from the outflow port to the inflow port of the cleaning liquid storage tank is shorter than the circulation flow path. 5. The filtration membrane cleaning apparatus according to claim 4, further comprising a connection channel for connecting two of said circulation channels on the outlet side.
a membrane separation tank having a filtration membrane for membrane filtration of water to be treated;
a membrane filtration water tank for storing membrane filtered water that has been subjected to membrane filtration by the membrane separation tank;
a cleaning liquid storage tank for storing a cleaning liquid containing an agent for cleaning the filtration membrane and having an outlet and an inlet;
a circulation channel connecting the outflow port and the inflow port of the cleaning liquid storage tank and provided with a circulation pump for circulating the cleaning liquid;
a supply channel connected to the circulation channel and provided with a supply pump that supplies part of the cleaning liquid circulating in the circulation channel to the filtration membrane;
a control unit that controls at least one of the circulation pump and the supply pump so that the flow rate of the cleaning liquid is faster in the circulation channel than in the supply channel;
water treatment equipment.
circulating the cleaning liquid in a circulation channel that connects an outlet and an inlet of a cleaning liquid storage tank that stores the cleaning liquid;
supplying part of the cleaning liquid circulating in the circulation channel to the filtration membrane through a supply channel for supplying the filtration membrane from the circulation channel;
A method for cleaning a filtration membrane, wherein the flow rate of the cleaning liquid is made faster in the circulation channel than in the supply channel.
measuring the chemical concentration in the cleaning liquid by a cleaning liquid concentration measuring unit provided in the circulation flow path;
8. The cleaning of the filtration membrane according to claim 7, wherein the retention time from the cleaning liquid storage tank to the filtration membrane is the same as the retention time from the cleaning liquid storage tank to the cleaning liquid concentration measuring unit. Method.