JP7067678B1 - Filtration membrane cleaning equipment, water treatment equipment and filtration membrane cleaning method - Google Patents

Abstract

The filter membrane cleaning device uses a circulation flow path (25) connecting the outlet (40) and the inlet (41) of the cleaning liquid storage tank (27) and a circulating cleaning liquid (28) as a filtration membrane (3). ) Is provided with a supply flow path (4). Then, the flow velocity of the cleaning liquid (28) is made faster in the circulation flow path (25) than in the supply flow path (4). As a result, it is possible to suppress a decrease in the drug 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). The drug concentration can be maintained. Further, since the supply flow rate is slower than the circulation flow rate, the amount of the cleaning liquid (28) used can be reduced.

Description

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

Membrane filtration treatment using a filtration membrane is known as a method for separating and removing pollutants of treated water such as sewage and factory wastewater. If the membrane filtration treatment is continued, pollutants adhere to the surface and pores of the filtration membrane and clogging occurs, so that the filtration performance gradually deteriorates. Therefore, in order to maintain the filtration performance, the filtration membrane is cleaned with a cleaning liquid. The cleaning liquid contains a chemical to enhance the cleaning effect.
For example, in the water treatment apparatus of Patent Document 1, a cleaning liquid containing ozone is used. Ozone has high detergency, but it 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, the cleaning liquid in which ozone is decomposed at the initial stage of cleaning is supplied to the filter membrane, which may deteriorate the cleaning efficiency. Therefore, a circulation flow path is provided in which the cleaning liquid in the flow path is returned to the cleaning liquid storage tank, and the cleaning liquid in which ozone remaining in the flow path is decomposed before cleaning is replaced with the ozone-containing cleaning liquid.

Japanese Patent Application Laid-Open No. 2003-251160

For example, when a sewage treatment facility or a factory is renovated and a water treatment device is introduced, the space that can be introduced may be limited in advance. In that case, the cleaning liquid storage tank cannot be installed in the vicinity of the membrane separation tank for performing the membrane filtration treatment, 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 flow path is long, the time required for supplying the cleaning liquid becomes long. As a result, the chemicals may be decomposed during the supply of the cleaning liquid, and when the chemicals are supplied to the filter membrane, the concentration may be lower than the predetermined chemical concentration. Therefore, in order to supply the drug to the filter membrane before it is decomposed, a device has been 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-mentioned problems, and an object of the present invention is to provide a filter membrane cleaning device capable of reducing the amount of the cleaning liquid used while maintaining the drug concentration of the cleaning liquid.

The filter membrane cleaning device according to the present disclosure stores a cleaning liquid containing a chemical for cleaning the filter membrane, and has a cleaning liquid storage tank having an outlet and an inflow port, and an outlet and an inlet of the cleaning liquid storage tank. A circulation pump that is connected and circulates the cleaning liquid is provided , and a circulation flow path different from the cleaning liquid storage tank and a supply that is connected to the circulation flow path and supplies a part of the cleaning liquid circulating in the circulation flow path to the filter membrane. Control 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 flow path than in the supply flow path when the supply flow path provided with the pump and the circulation pump and the supply pump are driven . It is equipped with a control unit.

Further, the water treatment apparatus according to the present disclosure includes a membrane separation tank having a filter membrane for membrane-filtering the water to be treated, a membrane-filtered water tank for storing membrane-filtered water that has been membrane-filtered by the membrane-separated tank, and a filtration membrane. A circulation pump is provided to store a cleaning liquid containing a chemical for cleaning, connect a cleaning liquid storage tank having an outlet and an inlet, and connect the outlet and the inlet of the cleaning liquid storage tank, and circulate the cleaning liquid . A circulation flow path different from the cleaning liquid storage tank, a supply flow path connected to the circulation flow path and provided with a supply pump for supplying a part of the cleaning liquid circulating in the circulation flow path to the filter membrane, a circulation pump, and a circulation pump . When the supply pump is driven, it is provided with a control unit that controls at least one of the circulation pump and the supply pump so that the flow velocity of the cleaning liquid is faster in the circulation flow path than in the supply flow path.

Further, in the method for cleaning the filtration membrane according to the present disclosure, a circulation pump is provided which connects the outlet and the inlet of the cleaning liquid storage tank for storing the cleaning liquid and circulates the cleaning liquid, and is a circulation flow path different from the cleaning liquid storage tank. In, a part of the cleaning liquid circulating in the circulation flow path is circulated, and a part of the cleaning liquid circulating in the circulation flow path is supplied to the filter membrane through a supply flow path provided with a supply pump for supplying the filter membrane from the circulation flow path. When the circulation pump and the supply pump are driven, the flow velocity of the cleaning liquid is made to be faster in the circulation flow path than in the supply flow path.

According to the present disclosure, a circulation flow path connecting the outlet and the inflow port of the cleaning liquid storage tank and a supply flow path for supplying the circulating cleaning liquid to the filtration membrane are provided, and the flow rate of the cleaning liquid is transmitted from the supply flow path. By increasing the speed in the circulation flow path, it is possible to provide a filter membrane cleaning device capable of reducing the amount of the cleaning liquid used while maintaining the drug concentration of the cleaning liquid.

It is a schematic diagram of the water treatment apparatus of Embodiment 1. FIG. It is a schematic diagram of the water treatment apparatus of Embodiment 2. It is a schematic diagram of the water treatment apparatus of Embodiment 3. It is a schematic diagram of the water treatment apparatus of Embodiment 3.

Embodiment 1.
The water treatment device 100 including the cleaning device for the filtration membrane 3 according to the first embodiment will be described with reference to FIG. FIG. 1 is a schematic view of a water treatment device 100. The water treatment apparatus 100 includes a membrane separation tank 2 having a filtration membrane 3 for membrane filtration treatment of the water to be treated 1, a membrane filtration water tank 18 for storing the membrane filtered water 19 which has been membrane-filtered in the membrane separation tank 2, and filtration. It has a cleaning liquid storage tank 27 for storing the cleaning liquid 28 for cleaning the membrane 3, and a flow path for discharging the membrane-filtered water 19 which has been membrane-filtered by the filtration membrane 3 and supplying the cleaning liquid 28.

In the membrane separation tank 2, for example, the water to be treated 1 treated by the activated sludge method is separated and removed from the pollutant by the filtration membrane 3. The water to be treated 1 is, for example, water supply, sewage, secondary treated sewage, industrial wastewater, seawater, human waste, etc., and flows into the membrane separation tank 2 through the water flow path 5 to be treated. The sludge extraction flow path 6 and the sludge circulation flow path 7 may be connected to the membrane separation tank 2. The sludge extraction flow path 6 is provided with a sludge extraction pump 9 for extracting sludge, and the sludge circulation flow path 7 is provided with a sludge circulation pump 10 for circulating sludge in the membrane separation tank 2. Further, the 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 filter membrane 3 is not limited, but a fluororesin compound having excellent resistance to a strong oxidizing agent such as ozone is preferable. In addition, for example, polyolefins such as polyethylene, polypropylene, and polybutene, tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), and tetrafluoroethylene-ethylene copolymer weight. Fluororesin compounds such as coalescence (ETFE), polychlorotrifluoroethylene (PCTFE), chlorotrifluoroethylene-ethylene copolymer (ECTFE), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), cellulose acetate , Polyethylenes such as ethyl cellulose, ceramics and the like may be used. Further, two or more kinds of the above-mentioned materials may be combined.

The type of the 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.

The average pore size of the filtration membrane 3 is not limited, but is preferably 0.001 μm or more and 1 μm or less, and more preferably 0.01 μm or more and 0.1 μm or less. By using the filter membrane 3 having an average pore size in this range, not only the pollutants adhering to the surface of the filter membrane 3 in contact with the water to be treated 1 but also the surface of the filter membrane 3 in contact with the membrane filtered water 19 or the filter membrane 3 It is possible to efficiently remove pollutants chemically adhering to the pores of.

The shape of the filtration membrane 3 is not limited. For example, a shape known in the art such as a cylindrical shape or a flat film shape may be used. Further, a dipping type, a casing type, a monolith type and the like may be adopted.

The water flow method of the filtration membrane 3 is not limited. For example, a full-volume filtration method or a cross-flow filtration method may be used. An external pressure filtration method in which the water to be treated 1 is flowed to the outside of the filter membrane 3 and the filtered water is flowed to the inside may be used. May be.

The membrane-filtered water 19 that has been membrane-filtered by the membrane separation tank 2 is stored in the membrane-filtered water tank 18.

The water treatment device 100 includes a cleaning device for cleaning the filtration membrane 3. The cleaning device has a cleaning liquid storage tank 27 in which a cleaning liquid 28 containing a chemical for cleaning the filter membrane 3 is stored.
The type of the chemical is not limited as long as it does not deteriorate the material of the filter membrane 3 and can decompose organic substances or inorganic substances. Therefore, it is advisable to use a substance known in the art. For example, chemicals capable of decomposing organic substances include sodium hypochlorite, hydrogen peroxide, sodium hydroxide, ozone and the like. These may be used alone or in combination of two or more. When two or more agents capable of decomposing organic substances are used in combination, the standard redox potential (25 ° C.) measured using a hydrogen electrode of the first agent is preferably less than 2.0 V, and the second agent. The standard redox potential (25 ° C.) measured using a hydrogen electrode is preferably 2.0 V or higher. For example, sodium hypochlorite may be used as the first agent and ozone may be used as the second agent. The substances capable of decomposing inorganic substances are, 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 alone or in combination of two or more. Two or more kinds of substances capable of decomposing organic substances and substances capable of decomposing inorganic substances may be used in combination. In that case, which is used as the first agent or the second agent is not limited. For example, when a substance capable of decomposing an organic substance is used as the first drug, a substance capable of decomposing an inorganic substance is used as the second drug. When a substance capable of decomposing an inorganic substance is used as the first agent, a substance capable of decomposing an organic substance may be used as the second agent.

The drug concentration of the cleaning solution 28 is not limited. For example, when a substance capable of decomposing organic substances is used, 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 is preferable. Ozone is preferably 10 mg / L or more and 40 mg / L or less, and more preferably 20 mg / L or more and 30 mg / L or less. When a substance capable of decomposing an inorganic substance is used, 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. It is preferably L or more and 10 g / L or less. If the drug concentration is lower than the above range, it takes time to decompose the pollutant adhering to the filter membrane 3, and the capacity of the drug tank increases as the amount of the cleaning liquid 28 used increases. On the other hand, when the drug concentration is higher than the above range, the amount of the drug used increases, so that the cost required for the drug increases.

The 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 outlet 40 and the inlet 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 which has been membrane-filtered by the filtration membrane 3 to the membrane filtration water tank 18. .. The membrane filtered water flow path 17 is a flow path connecting the membrane filtered water tank 18 and the supply flow path 4.

The switching unit 20 is provided in the supply flow path 4, and connects the supply flow path 4 and the membrane filtered water flow path 17. The switching portion 21 is provided in the circulation flow path 25 and connects the circulation flow path 25 and the supply flow path 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 velocity measuring unit 23. Further, the cleaning liquid concentration measuring unit 24 may be provided. The cleaning liquid 28 is returned to the cleaning liquid storage tank 27 via the circulation flow path 25 by the circulation pump 22. The circulation flow velocity measuring 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, a propeller type current meter, an ultrasonic type current meter, or a radio wave type current meter may be used.

The cleaning liquid concentration measuring 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 drug, for example, an absorbance-type ozone densitometer, an electrode-type ozone densitometer, or the like. The position of the cleaning liquid concentration measuring unit 24 may be located on the downstream side of the circulation pump 22, the circulating flow rate measuring unit 23, and the switching unit 21, and the closer the distance to the inflow port 41 of the cleaning liquid storage tank 27, the better. When the cleaning liquid concentration measuring unit 24 is arranged near the inflow port 41 of the cleaning liquid storage tank 27, the drug concentration when the circulating cleaning liquid 28 returns to the cleaning liquid storage tank 27 can be measured. Therefore, the drug 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 velocity measuring unit 15. Further, the pressure gauge 13 may be provided. At the time of the membrane filtration treatment, the membrane filtration water 19 is supplied to the membrane filtration water tank 18 by the membrane filtration pump 16 provided in the membrane filtration water flow path 17 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 a part of the cleaning liquid 28 circulating in the circulation flow path 25 to the filtration membrane 3.
The supply flow velocity measuring unit 15 measures the flow velocity of the cleaning liquid 28 of the supply flow path 4. The supply flow velocity measuring unit 15 is not limited as long as it can measure the flow velocity of the cleaning liquid 28 circulating in the circulation flow path 25, similarly to the circulation flow rate measuring unit 23.

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

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

Next, a water treatment method using the water treatment device 100 will be described. The water treatment method is roughly classified into a membrane filtration treatment and a cleaning treatment of the filtration membrane 3. In the membrane filtration treatment, the water to be treated 1 is treated by the activated sludge method, and then the pollutant is separated and removed using the filtration membrane 3. If the membrane filtration treatment is continuously performed, there is a problem that the filtration performance is deteriorated. Specifically, with the continuous use of the filtration membrane 3, pollutants 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, respectively. As a result, clogging occurs and the filtration performance gradually deteriorates. In particular, when the filtration membrane 3 is clogged, the pressure required for the membrane filtration treatment increases. Therefore, the membrane filtration flux, the unit time, and the amount of membrane filtered water per unit membrane area decrease. Therefore, in order to maintain the performance of the filtration membrane 3, the filtration membrane 3 is periodically cleaned.

The membrane filtration process will be described. The operations of the pump and the switching unit, which will be described later, are controlled by the control unit 26.
First, the circulation flow path 25 side of the switching unit 20 is closed, the membrane separation tank 2 side and the membrane filtration water flow path 17 side are opened, and the membrane filtration pump 16 is started. 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 flow path 4 side and the membrane-filtered water flow path 17. ..

Next, the cleaning process of the filtration membrane 3 will be described.
If the membrane filtration treatment has been performed, the membrane filtration pump 16 is stopped to end the membrane filtration treatment. Then, the switching unit 20 closes the membrane filtration water flow path 17 side and opens the membrane separation tank 2 side and the circulation flow path 25 side. After the membrane filtration treatment is completed and before the cleaning treatment of the filtration membrane 3 is started, the filtration membrane 3 may be pretreated. For example, by exposing the filtration membrane 3 to air for a certain period of time, it is possible to easily remove pollutants adhering to the surface of the filtration membrane 3 in contact with the water to be treated 1. Further, the filter membrane 3 may be pre-cleaned by preparing a pre-cleaning solution containing no chemicals. Preliminary cleaning can facilitate the removal of pollutants adhering to the surface of the filtration membrane 3 in contact with the water to be treated 1.

Next, the cleaning liquid 28 is circulated. First, the supply flow path 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 started to circulate the cleaning liquid 28 containing the drug from the cleaning liquid storage tank 27 via the circulation flow path 25. As a result, the old cleaning liquid 28 remaining in the circulation flow path 25 can be replaced with the new cleaning liquid 28. Therefore, even when the chemicals in the old cleaning liquid 28 remaining in the circulation flow path 25 are decomposed, the cleaning efficiency at the initial stage of cleaning can be improved. Further, the drug concentration of the cleaning liquid 28 is measured by the cleaning liquid concentration measuring unit 24 provided in the circulation flow path 25. This confirms whether the cleaning liquid 28 can secure a predetermined drug concentration. At this time, the measurement result of the cleaning liquid concentration measuring unit 24 is transmitted to the control unit 26, and when the cleaning liquid 28 can secure a predetermined drug concentration, it is controlled to start supplying the cleaning liquid 28 to the filtration membrane 3 described later. You may. Although not shown, the circulation flow path 25 may include, for example, a static mixer that uniformly mixes the cleaning liquid 28.

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

The circulation pump 22 and the supply pump 14 are controlled by the control unit 26. At that time, the flow velocity of the circulation flow path 25 is set to be faster than the flow velocity of the supply flow path 4. Further, the flow velocity is adjusted so that the residence time of the cleaning liquid 28 from the cleaning liquid storage tank 27 to the filtration membrane 3 and the residence 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 velocity may be adjusted by both the circulation pump 22 and the supply pump 14, or one of them may be controlled.

A method of controlling, for example, the circulation pump 22 to adjust the flow velocity will be described with reference to FIG. First, the flow velocity of the cleaning liquid 28 in the circulation flow path 25 is set to be faster than the flow velocity of the cleaning liquid 28 in the supply flow path 4. At that time, the supply flow velocity and the circulation flow velocity are measured by using the supply flow velocity measuring unit 15 and the circulation flow velocity measuring unit 23. For example, when the value of the supply flow rate measuring unit 15 is high, the input to the motor of the circulation pump 22 is increased 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. When controlling the supply pump 14, it is preferable to reduce the input of the supply pump 14 to the motor so that the value of the supply flow rate measuring unit 15 is lower than the value of the circulation flow rate measuring unit 23. When controlling both the circulation pump 22 and the supply pump 14, adjust the inputs of the circulation pump 22 and the supply pump 14 to the motor 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.

Further, the circulation pump 22 is controlled so that the residence time of the cleaning liquid 28 from the cleaning liquid storage tank 27 to the filtration membrane 3 and the residence 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 flow path 4 is formed in a flow path shorter than the circulation flow path 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 unit 24 by the flow velocity obtained by the circulation flow rate measuring unit 23, the cleaning liquid 28 from the cleaning liquid storage tank 27 to the cleaning liquid concentration measuring unit 24 The residence time of can be obtained. Further, the value obtained by dividing the pipe length from the cleaning liquid storage tank 27 to the switching unit 21 by the flow velocity obtained by the circulation flow rate measuring unit 23 and the pipe length from the switching unit 21 to the filtration membrane 3 are obtained by the supply flow rate measuring unit 15. By adding the value divided by the obtained flow rate, the residence time of the cleaning liquid 28 from the cleaning liquid storage tank 27 to the filtration membrane 3 can be obtained.

The control unit 26 circulates the supply pump 14 so that the residence time of the cleaning liquid 28 from the cleaning liquid storage tank 27 to the filtration membrane 3 and the residence time of the cleaning liquid 28 from the cleaning liquid storage tank 27 to the cleaning liquid concentration measuring unit 24 are the same. Controls the input of the pump 22 to the motor. For example, a case where the residence time from the cleaning liquid storage tank 27 to the filter membrane 3 is longer than the residence time from the cleaning liquid storage tank 27 to the cleaning liquid concentration measuring unit 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 supply pump 14, the input of the supply pump 14 to the 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.
This makes it 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.

Up to this point, as a method of adjusting the flow velocity, an example of adjusting using the value of the flow velocity measured by the supply flow velocity measuring unit 15 and the circulation flow velocity measuring unit 23 has been described. As another method, the flow rate may be measured by the supply flow rate measuring unit 15 and the circulation flow rate measuring unit 23, and the flow rate may be calculated from the measured flow rate. 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 cross section of the pipe.

Further, when the flow rate is measured by the supply flow rate measuring unit 15 and the circulation flow rate measuring unit 23, the pipe diameters of the flow paths may be different. For example, the pipe diameters of the supply flow path 4 and the circulation flow path 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 section and the length. Therefore, by dividing the value of the flow rate obtained by the circulation flow velocity measuring unit 23 by the piping 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 You can ask for time. Further, the value obtained by dividing the value of the flow rate 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 value of the flow rate obtained by the supply flow rate measuring unit 15 are divided by the filtering membrane from the switching unit 21. By adding the value divided by the pipe capacity up to 3, the residence time from the cleaning liquid storage tank 27 to the filtration membrane 3 can be obtained.

The cleaning time of the filter membrane 3 using the cleaning liquid 28 containing the drug may be appropriately set according to the amount of the pollutant substance adhering to the filter membrane 3 and the like. Generally, 90 minutes or less is preferable when sodium hypochlorite is used, 60 minutes or less when ozone water is used, and 5 minutes or more and 7 minutes or less when oxalic acid or citric acid is used. When the washing time becomes long, the time for interrupting the membrane treatment of the water to be treated 1 also becomes long, and the amount of membrane filtered water decreases. Therefore, the washing time should be short.

The membrane permeation flux, which is the amount of water supplied per membrane area of the cleaning liquid 28 containing the drug, is not limited. In general, it suffices to secure a flux that can be filled up to the end of the filtration membrane 3. 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 permeation flux is too high, the drug cost increases with the increase in the required amount of the cleaning liquid 28, the capacity of the drug tank increases, and the filtration film 3 breaks. If the membrane permeation flux is too low, the cleaning liquid 28 will not be filled to the end of the filter membrane 3, and the pollutants adhering to the filter membrane 3 cannot be decomposed, or if ozone is used as a chemical, the concentration will decrease during supply. Or.

The cleaning method of the filtration membrane 3 according to the present embodiment is a cleaning method in which the cleaning liquid 28 is passed through the filtration membrane 3 and then the cleaning liquid 28 is held in the membrane as it is, and the filtration membrane 3 is immersed in the cleaning liquid 28 and held. It is advisable to use a cleaning method or the like.

After the cleaning process of the filtration membrane 3 is completed, the circulation pump 22 and the supply pump 14 are stopped, the circulation flow path 25 side of the switching unit 20 is closed, and the membrane filtration pump 16 is opened. Then, the membrane filtration pump 16 can be started and the membrane filtration treatment of the water to be treated 1 can be performed again. Thereby, the membrane filtration treatment of the water to be treated 1 can be continuously and efficiently performed.

The conventional cleaning device for the filtration membrane 3 supplies 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, since the drug is supplied before it is decomposed, the amount of the cleaning liquid used increases when the flow rate is increased.

The cleaning device for the filtration membrane 3 in the present embodiment has 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. It is provided with a road 4. Then, at least one of the circulation pump 22 and the supply pump 14 is controlled so that the flow velocity of the cleaning liquid 28 is faster in the circulation flow path 25 than in the supply flow path 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 a decrease in the drug 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. As a result, the drug concentration of the cleaning liquid 28 can be maintained. Further, since the supply flow rate is slower than the circulation flow rate, the amount of the cleaning liquid 28 used can be reduced.

Further, the water treatment device 100 in the present embodiment includes a cleaning device for the filtration membrane 3 capable of reducing the amount of the cleaning liquid 28 used while maintaining the drug concentration of the cleaning liquid 28 as described above. As a result, the cleaning liquid storage tank 27 can be installed at a distance, so that the degree of freedom in designing the water treatment device 100 is improved. Further, since the cleaning liquid storage tank 27 can be installed separately, the degree of freedom in the installation location of the water treatment device 100 is improved.

Further, since the water treatment device 100 repeats the membrane filtration treatment and the cleaning treatment 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. The water treatment device 100 in the present embodiment circulates the cleaning liquid 28 before supplying the cleaning liquid 28 to the filtration membrane 3. As a result, the old cleaning liquid 28 remaining in the circulation flow path 25 can be replaced with the new cleaning liquid 28. Therefore, even when the chemicals in the old cleaning liquid 28 remaining in the circulation flow path 25 are decomposed, the cleaning efficiency at the initial stage of cleaning can be improved. Further, the drug concentration of the cleaning liquid 28 is measured by the cleaning liquid concentration measuring unit 24 provided in the circulation flow path 25. This confirms whether the cleaning liquid 28 in the cleaning liquid storage tank 27 can secure a predetermined drug concentration.

Further, the residence time of the cleaning liquid 28 from the cleaning liquid storage tank 27 to the filter membrane 3 and the residence time of the cleaning liquid 28 from the cleaning liquid storage tank 27 to the cleaning liquid concentration measuring unit 24 are made the same. This makes it possible to estimate the concentration of the cleaning liquid 28 supplied to the filtration membrane 3 from the value of the cleaning liquid concentration measuring unit 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 the cleaning device for the filtration membrane 3 of the present embodiment, the case where the cleaning liquid 28 containing one kind of chemical is used has been described, but when the cleaning liquid 28 containing two or more kinds of chemicals is used, the cleaning liquid storage tank A plurality of 27 may be provided and the cleaning treatment may be performed by the same method.

Embodiment 2.
The water treatment device 100 including the cleaning device for the filtration membrane 3 in the second embodiment will be described with reference to FIG. FIG. 2 is a schematic view of the water treatment apparatus 100. In the second embodiment, an example is shown in which ozone, which is particularly difficult to maintain the concentration of the drug because the decomposition of the drug occurs immediately after the cleaning solution is generated, is used as the drug of the cleaning solution 28. That is, the cleaning liquid storage tank 27 stores ozone water as the cleaning liquid 28. Other configurations are the same as those in the first embodiment. The same reference numerals are given to the same configurations as those in the first embodiment.

As shown in FIG. 2, an air diffuser 31 is arranged at the bottom of the cleaning liquid storage tank 27, 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, liquid oxygen, oxygen generated by PSA (Pressure Swing Adsorption), PVSA (Pressure Vacuum Swing Adsorption) may be used. Further, the ozone water that is no longer needed is treated by the waste ozone treatment equipment 33 via the waste ozone pipe 32 and discharged to the treated ozone pipe 34.

Next, a method of generating ozone water in the cleaning liquid storage tank 27 will be described. Other water treatment methods are the same as those in the first embodiment.
First, the 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. As a result, ozone water is 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 via the circulation flow path 25 and the supply flow path 4, and the filtration membrane 3 is backwashed.

Similar to the first embodiment, the cleaning device for the filtration membrane 3 in the present embodiment includes the circulation flow path 25 and the supply flow path 4, and makes the flow velocity of the cleaning liquid 28 faster in the circulation flow path 25 than in the supply flow path 4. .. As a result, the amount of the cleaning liquid 28 used can be reduced while maintaining the drug concentration of the cleaning liquid 28.

Further, 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, ozone water can be generated in the cleaning liquid storage tank 27. As a result, even when the ozone water that is easily decomposed is used as the cleaning liquid 28, it is easy to maintain the concentration of the ozone water stored in the cleaning liquid storage tank 27.

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

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

Embodiment 3.
The water treatment device 100 including the cleaning device for the filtration membrane 3 in the third embodiment will be described with reference to FIG. FIG. 3 is a schematic view of the water treatment device 100. In the water treatment device 100 according to the third embodiment, the inflow port of the washing liquid storage tank 27 from the circulation pump 22 is formed so that the outflow port 40 to the inflow port 41 of the washing liquid storage tank 27 forms a flow path shorter than the circulation flow path 25. On the 41 side, the cleaning liquid concentration measuring unit 24 has a connecting flow path 37 connecting two places of the circulation flow path 25 on the outlet 40 side of the cleaning liquid storage tank 27. Other configurations are the same as those in the first embodiment. The same reference numerals are given to the same configurations as those in the first embodiment.

For example, the circulation flow path 25 includes a circulation pump 22, a switching unit 38 between the circulation flow rate measuring unit 23 and the switching unit 21, and a switching unit 39 between the switching unit 21 and the cleaning liquid concentration measuring unit 24. Then, by providing the connection flow path 37 connected to the switching unit 38 and the switching unit 39, it is possible to form a flow path shorter than the circulation flow path 25 from the outflow port 40 to the inflow port 41 of the cleaning liquid storage tank 27. ..

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

Next, the circulation of the cleaning liquid 28 when supplying 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 unit 39 closes the switching unit 38 side and opens the cleaning liquid concentration measuring unit 24 and the switching unit 21 side. The switching unit 21 closes the supply flow path 4 side and opens the switching unit 38 side and the switching unit 39 side. Next, the circulation pump 22 is started to circulate the cleaning liquid 28 in the order of the outlet 40 of the cleaning liquid storage tank 27, the switching unit 21, and the inflow port 41 of the cleaning liquid storage tank 27. As a result, the old cleaning liquid 28 remaining in the circulation flow path 25 can be replaced with the new cleaning liquid 28. Therefore, even when the chemicals in the old cleaning liquid 28 remaining in the circulation flow path 25 are decomposed, the cleaning efficiency at the initial stage of cleaning can be improved. Other water treatment methods are the same as those in the first embodiment.

Similar to the first embodiment, the cleaning device for the filtration membrane 3 in the present embodiment includes the circulation flow path 25 and the supply flow path 4, and makes the flow velocity of the cleaning liquid 28 faster in the circulation flow path 25 than in the supply flow path 4. .. As a result, the amount of the cleaning liquid 28 used can be reduced while maintaining the drug concentration of the cleaning liquid 28.

In addition, the cleaning liquid storage tank 27 may not be installed in the vicinity of the membrane separation tank 2. In that case, since the flow path from the cleaning liquid storage tank 27 to the filtration membrane 3 becomes long, the circulation flow path 25 from the cleaning liquid storage tank 27 to the cleaning liquid concentration measuring unit 24 also becomes long. In such a water treatment apparatus 100, when the drug concentration measured by the cleaning liquid concentration measuring unit 24 is low, it may be that the drug concentration of the cleaning liquid 28 supplied from the cleaning liquid storage tank 27 is low, or while the chemical concentration is being supplied to the filtration membrane 3. It is not possible to determine if the drug concentration has decreased. In response to this problem, in the present embodiment, the circulation flow path 25 stores the cleaning liquid from the circulation pump 22 so that the flow path from the outlet 40 to the inflow port 41 of the cleaning liquid storage tank 27 forms a flow path shorter than the circulation flow path 25. This can be solved by having a connection flow path 37 connecting two places on the inflow port 41 side of the tank 27 from the cleaning liquid concentration measuring unit 24 on the outflow port 40 side of the cleaning liquid storage tank 27. With this configuration, the drug concentration of the cleaning liquid 28 supplied from the cleaning liquid storage tank 27 and the drug concentration of the cleaning liquid 28 supplied to the filtration membrane 3 can be confirmed separately.

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 within a range that does not deviate from the gist.

For example, the second embodiment and the third embodiment may be combined. FIG. 4 is a schematic view of the water treatment apparatus 100. In the water treatment device 100 shown in FIG. 4, an ozone generator 29 is connected to the cleaning liquid storage tank 27 via an ozone supply pipe 30. Further, from the cleaning liquid concentration measuring unit 24 on the inflow port 41 side of the cleaning liquid storage tank 27 from the circulation pump 22 so that the flow path from the outlet 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 flow path 37 connecting two places on the outlet 40 side of the cleaning liquid storage tank 27.

Also in such an embodiment, the circulation flow path 25 and the supply flow path 4 are provided, and the flow rate of the cleaning liquid 28 is made faster in the circulation flow path 25 than in the supply flow path 4. As a result, the amount of the cleaning liquid 28 used can be reduced while maintaining the drug concentration of the cleaning liquid 28 containing ozone, which is easily decomposed.

Further, even in the case of the cleaning liquid 28 containing 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 confirmed separately. ..

1 treated water, 2 membrane separation tank, 3 filter membrane, 4 supply flow path, 5 treated water flow path, 6 sludge extraction flow path, 7 sludge circulation flow path, 8 air diffuser, 9 sludge extraction pump, 10 sludge circulation Pump, 11 air supply pipe, 12 membrane surface exposure blower, 13 pressure gauge, 14 supply pump, 15 supply flow velocity measuring unit, 16 membrane filtration pump, 17 membrane filtration water flow path, 18 membrane filtration water tank, 19 membrane filtration water, 20 switching Unit, 21 Switching unit, 22 Circulation pump, 23 Circulation flow rate measurement unit, 24 Cleaning liquid concentration measurement unit, 25 Circulation flow path, 26 Control unit, 27 Cleaning liquid storage tank, 28 Cleaning liquid, 29 Ozone generator, 30 Ozone supply pipe, 31 Air diffuser, 32 waste ozone pipe, 33 waste ozone treatment equipment, 34 treatment ozone pipe, 36 switching part, 37 connection flow path, 38 switching part, 39 switching part, 40 outlet, 41 inlet, 100 water treatment device

Claims (8)

A cleaning liquid storage tank that stores a cleaning liquid containing a chemical for cleaning the filter membrane and has an outlet and an inlet,
A circulation pump that connects the outlet and the inlet of the cleaning liquid storage tank and circulates the cleaning liquid is provided, and a circulation flow path different from that of the cleaning liquid storage tank is provided.
A supply flow path connected to the circulation flow path and provided with a supply pump for supplying a part of the cleaning liquid circulating in the circulation flow path 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 becomes faster in the circulation flow path than in the supply flow path when the circulation pump and the supply pump are driven. ,
A filter membrane cleaning device. The filter membrane cleaning device according to claim 1, wherein the agent contains at least ozone. The filter membrane cleaning device according to claim 2, wherein the cleaning liquid storage tank has an air diffuser connected to an ozone generator. The circulation flow path has a cleaning liquid concentration measuring unit for measuring the drug concentration in the cleaning liquid.
The control unit has the circulation pump and the circulation pump so that the residence time of the cleaning liquid from the cleaning liquid storage tank to the filter membrane and the residence time of the cleaning liquid from the cleaning liquid storage tank to the cleaning liquid concentration measuring unit are the same. The filter membrane cleaning device according to any one of claims 1 to 3, wherein the supply pump is controlled at least one of them. The cleaning liquid storage tank is said to be shorter than the circulation flow path from the outlet to the inflow port of the cleaning liquid storage tank on the inlet side of the cleaning liquid storage tank from the circulation pump and from the cleaning liquid concentration measuring unit. The filter membrane cleaning device according to claim 4, further comprising a connecting flow path connecting two points of the circulation flow path on the outlet side. A membrane separation tank having a membrane that filters the water to be treated by membrane filtration,
A membrane-filtered water tank for storing membrane-filtered water that has been membrane-filtered by the membrane separation tank, and a membrane-filtered water tank.
A cleaning liquid storage tank that stores a cleaning liquid containing a chemical for cleaning the filter membrane and has an outlet and an inlet,
A circulation pump that connects the outlet and the inlet of the cleaning liquid storage tank and circulates the cleaning liquid is provided, and a circulation flow path different from that of the cleaning liquid storage tank is provided.
A supply flow path connected to the circulation flow path and provided with a supply pump for supplying a part of the cleaning liquid circulating in the circulation flow path 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 becomes faster in the circulation flow path than in the supply flow path when the circulation pump and the supply pump are driven. ,
A water treatment device equipped with. A circulation pump is provided which connects the outlet and the inlet of the cleaning liquid storage tank for storing the cleaning liquid and circulates the cleaning liquid, and circulates the cleaning liquid in a circulation flow path different from the cleaning liquid storage tank .
A part of the cleaning liquid circulating in the circulation flow path is supplied to the filtration membrane through a supply flow path provided with a supply pump for supplying the filter membrane from the circulation flow path.
A method for cleaning a filter membrane , wherein when the circulation pump and the supply pump are driven, the flow rate of the cleaning liquid is made faster in the circulation flow path than in the supply flow path. The drug concentration in the cleaning liquid was measured by a cleaning liquid concentration measuring unit provided in the circulation flow path.
The cleaning of the filter membrane according to claim 7, wherein the residence time from the cleaning liquid storage tank to the filtration membrane and the residence time from the cleaning liquid storage tank to the cleaning liquid concentration measuring unit are the same. Method.

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