WO2021192002A1

WO2021192002A1 - Water treatment system

Info

Publication number: WO2021192002A1
Application number: PCT/JP2020/012884
Authority: WO
Inventors: 祐樹佐藤; 英二今村; 野田　清治
Original assignee: 三菱電機株式会社
Priority date: 2020-03-24
Filing date: 2020-03-24
Publication date: 2021-09-30
Also published as: JPWO2021192002A1; JP6877656B1; CN115297949A

Abstract

The present invention comprises: a treated-water tank (2) that accommodates water for treatment (1); a membrane module (3) having a filtration membrane that filters the water for treatment (1) and is positioned in the treated-water tank (2); a plurality of chemical-solution-supply units that, in a respective manner, supply a plurality of chemical solutions for cleaning the filtration membrane; a cleaning water tank (18) that accommodates cleaning water (17), which is filtered water that has been filtered by the membrane module (3), the cleaning water (17) being used in order to remove the chemical solutions remaining within piping by which the chemical solution supply units and the treated-water tank (2) are connected; an air supply device that supplies air used in order to remove the chemical solutions remaining within the piping; and an integrating flowmeter (13) that measures the integrated flow rate of the cleaning liquid (17) or the air used in removing the chemical solutions, the integrating flowmeter (13) being positioned in the piping.

Description

Water treatment system

This application relates to a water treatment system.

Membrane treatment using a filtration membrane is used as a method for separating suspended solids in water to be treated. For example, in the treatment of sewage and factory wastewater, after treating the water to be treated by the activated sludge method, suspended solids are separated and removed using a filtration membrane. As the filtration membrane, a cylindrical or sheet-shaped microfiltration membrane and an ultrafiltration membrane are generally used. In addition, as a filtration method, there are an external pressure filtration method in which the water to be treated flows outside the cylindrical or sheet-shaped filtration membrane and the filtered water flows inward, and an external pressure filtration method in which the water to be treated flows inside the cylindrical filtration membrane and filters outside. There is an internal pressure filtration method in which water flows. In the membrane treatment using such a filtration membrane, the filtration performance deteriorates with the continuous use of the filtration membrane.

Specifically, with the continuous use of the filter membrane, the surface of the filter membrane in contact with the water to be treated (outer surface in the external pressure filtration method, the inner surface in the internal pressure filtration method), and the surface of the filter membrane in contact with the filtered water (external pressure filtration method). Then, pollutants adhere to the inner surface, the outer surface in the internal pressure filtration method), or the pores of the filtration membrane, causing clogging, and the filtration performance gradually deteriorates. In particular, when the filtration membrane is clogged, the pressure required for filtration increases, so that the membrane filtration flux (unit time, amount of membrane-filtered water per unit membrane area) also decreases. Therefore, in order to maintain the performance of the filtration membrane, it is necessary to clean the filtration membrane regularly.

Therefore, as a method for maintaining the filtration performance, washing water containing an oxidizing agent such as sodium hypochlorite (also called "sodium hypochlorite") or ozone is used from the secondary side in the direction opposite to the primary side of the filtration film. There is a method of oxidatively decomposing and cleaning pollutants chemically adhered by intermolecular force to the surface of the filter membrane in contact with the membrane-filtered water or the pores of the filter membrane by performing backflow cleaning of the filter membrane using ..

Further, a plurality of chemical solutions, for example, an alkaline substance such as sodium hypochlorite, or an acidic substance such as hydrochloric acid, sulfuric acid, and citric acid are stored in separate chemical solution tanks, and a switching valve is used to sequentially pass a plurality of wash waters through filtration. There is a method for cleaning the membrane (see Patent Document 1).

Further, in order to further enhance the cleaning effect of the oxidizing agent, a method of performing backflow cleaning of the filter membrane with cleaning water containing sodium hypochlorite and then backflow cleaning of the filter membrane with cleaning water containing ozone. There is also (see Patent Document 2).

Japanese Unexamined Patent Publication No. 2005-193132 Patent No. 5933854

In the membrane treatment using the filter membrane, the filter membrane may break with the continuous use of the filter membrane, and suspended solids and dissolved organic substances in the water to be treated may flow out into the filtered water. When the chemical solution remaining in the pipe is removed using the wash water from which the suspended solids and dissolved organic substances in the water to be treated have flowed out, the chemical solution reacts with the suspended solids and dissolved organic substances in the washing water to increase the concentration of the chemical solution. There was a problem that it could not be maintained.

The present application discloses a technique for solving the above-mentioned problems, and an object of the present application is to provide a water treatment system capable of supplying a chemical solution to a filtration membrane while maintaining the concentration of a plurality of chemical solutions. ..

The water treatment system disclosed in the present application comprises a water tank to be treated, a membrane module installed in the water tank to be treated and having a filtration film for filtering the water to be treated, and the filtration membrane. A plurality of chemical solution supply units for supplying a plurality of chemical solutions for cleaning, and filtered water filtered by the membrane module, which remains in a pipe connecting the chemical solution supply unit and the water tank to be treated. A washing water tank containing washing water used for removing the chemical solution, a gas supply device for supplying the gas used for removing the chemical solution remaining in the pipe, and a gas supply device installed in the pipe and described above. It is equipped with an integrated flow meter that measures the integrated flow rate of the washing water or the gas used for removing the chemical solution.
A water treatment system that ends the removal of the chemical solution when the value of the integrated flow meter exceeds the capacity of the pipe in the pipe.

According to the water treatment system disclosed in the present application, the chemical solution can be applied to the filtration membrane while maintaining the concentration of the plurality of chemical solutions.

It is a conceptual diagram which shows the water treatment system which includes the filtration membrane cleaning apparatus which concerns on Embodiment 1. FIG. It is a conceptual diagram which shows the water treatment system which includes the filtration membrane cleaning apparatus which concerns on Embodiment 2. It is a conceptual diagram which shows the water treatment system which includes the filtration membrane cleaning apparatus which concerns on Embodiment 3. FIG. It is a conceptual diagram which shows the water treatment system which includes the filtration membrane cleaning apparatus which concerns on Embodiment 4. FIG.

Embodiment 1.
The present embodiment relates to a water treatment system having a filter membrane cleaning device used for separating suspended solids from treated water such as water supply, sewerage, industrial water, and various wastewaters by a filter membrane.
In the method of cleaning the filtration membrane using a plurality of chemical solutions, when different types of chemical solutions are mixed and reacted in the pipe, it is expected that the concentration of the chemical solution used for cleaning will decrease and toxic gas will be generated. Therefore, it is necessary to operate so that these chemicals are not mixed as much as possible. In particular, it is known that when ozone and sodium hypochlorite are mixed, the ozone concentration decreases immediately, and in the method of cleaning the filtration membrane using multiple chemical solutions, a mechanism for removing the chemical solution remaining in the piping should be provided. Is desirable. Therefore, in the method of cleaning the filter membrane using a plurality of chemical solutions, after the chemical solution is supplied to the filter membrane, the washing water (filtered water) is passed through the pipe to eliminate the chemical solution remaining in the pipe. This prevents different types of chemicals from mixing in the pipe and reducing the concentration. The present embodiment provides a water treatment system for preventing different types of chemicals from mixing in a pipe and reducing the concentration.

Hereinafter, a preferred embodiment of the chemical solution removing device according to the present embodiment will be described with reference to the drawings.
FIG. 1 is a conceptual diagram showing a water treatment system including the filtration membrane cleaning device according to the first embodiment. In the figure, the water treatment system is equipped with a filtration device. The filtration device includes a water tank 2 to be treated for accommodating the water to be treated 1, a membrane module 3 having a filtration film for filtering the water to be treated 1, and filtered water filtered by the membrane module 3 (as wash water 17 described later). It has a filtered water pipe 4 for discharging (used). The water tank 2 to be treated is provided with a water supply pipe 5 to be treated to supply the water 1 to be treated, and the filtered water pipe 4 is provided with an integrated flow meter 13 and a second backwash valve 36 from the membrane module 3 side. , The first backwash valve 32, the wash water supply valve 25, the pressure gauge 14, the filter valve 15, and the filter pump 16 are provided in this order. Further, a sludge extraction pipe 6 and a sludge circulation pipe 7 are connected to the water tank 2 to be treated, and an air diffuser 8 is arranged at the bottom of the water tank 2 to be treated. Further, the sludge extraction pipe 6 is provided with a sludge extraction pump 9 for extracting sludge, and the sludge circulation pipe 7 is provided with a sludge circulation pump 10 for circulating sludge in the water tank 2 to be treated. .. Further, a membrane surface aeration blower 12 is connected to the air diffuser 8 via an air supply pipe 11.

When the water to be treated 1 is filtered in this filtration device, the water to be treated 1 is filtered by the membrane module 3 by opening the filtration valve 15 and activating the filtration pump 16. Then, the filtered water filtered by the membrane module 3 is discharged to the washing water tank 18 via the filtered water pipe 4. When the membrane module 3 is continuously filtered with the water to be treated 1, the filtration membrane in the membrane module 3 is clogged with pollutants, so that it is necessary to clean the filtration membrane.
Therefore, this water treatment system is further equipped with a filtration membrane cleaning device. The filter membrane cleaning device uses a method of cleaning the filter membrane using a mixed water in which the first agent is mixed with the cleaning water 17 as a chemical solution, and a mixed water in which the cleaning water 17 is mixed with the second agent as the chemical solution. It is provided with a method of cleaning the filter membrane.

Specifically, as shown in FIG. 1, the filtration membrane cleaning device includes a cleaning water tank 18 for accommodating the cleaning water 17, a first drug storage tank 22 for accommodating the first drug, and a second drug. It is provided with a second drug storage tank 23 for accommodating. The washing water tank 18 is provided with a turbidity meter 41 and a washing water pipe 24. The wash water pipe 24 is provided with a backwash pump 19 and a switching valve 20. Further, the washing water pipe 24 is branched into two, and one washing water pipe 24A is connected to the filtered water pipe 4 by the washing water supply valve 25. The other wash water pipe 24B is connected to the first backwash pipe 26 and the second backwash pipe 27 at the switching valve 21.

The first backwash pipe 26 is connected to the first air supply pipe 39 at the first air supply valve 31, and the second backwash pipe 27 is connected to the second air supply pipe 39 at the second air supply valve 35. It is connected to the air supply pipe 40. A cleaning blower 38 is provided in the first air supply pipe 39 and the second air supply pipe 40. An air supply device for cleaning the filtration membrane is configured by the first air supply pipe 39, the second air supply pipe 40, and the cleaning blower 38. It should be noted that not only air but also other gases may be used, and as will be described later, the chemical solution remaining in the pipe can be eliminated by supplying the gas by the gas supply device.

The first chemical storage tank 22 is provided with a first chemical supply pipe 28, and the first chemical supply pipe 28 is connected to the first backwash pipe 26. The second chemical storage tank 23 is provided with a second chemical supply pipe 29, and the second chemical supply pipe 29 is connected to the second backwash pipe 27. The first drug supply pipe 28 is provided with a first drug supply valve 30 and a first drug supply pump 33 (which also operates as a suction device as described later), and is provided with a second drug supply pipe. The 29 is provided with a second drug supply valve 34 and a second drug supply pump 37 (which also operates as a suction device as will be described later). The drug supply unit is composed of the first drug storage tank 22, the first drug supply pump 33, the first drug supply pipe 28, and the first backwash pipe 26, and the second drug storage tank 23, The chemical supply unit is composed of the second chemical supply pump 37, the second chemical supply pipe 29, and the second backwash pipe 27.
Although not shown, all pumps, valves, and switching valves are connected to a control device, which controls the operation of all pumps, valves, and switching valves.

When the filtration membrane cleaning treatment is performed using the filtration membrane cleaning device having the above configuration, the filtration pump 16 is first stopped, the filtration valve 15 is closed, and then the filtration membrane cleaning treatment is started. The switching from the filtration treatment of the water to be treated 1 to the cleaning treatment of the filtration membrane may be controlled by the time of the filtration treatment.
After the filtration treatment is completed and before the cleaning treatment of the filtration membrane is started, the filtration membrane in the membrane module 3 can be pretreated. For example, by exposing the filtration membrane in the membrane module 3 to air for a certain period of time, it is possible to easily remove pollutants adhering to the surface of the filtration membrane in contact with the water to be treated 1. Further, the switching valve 20, the washing water supply valve 25, the first backwash valve 32, and the second backwash valve 36 are opened to start the backwash pump 19, and the

washing water pipes

24, 24A and filtered water are started from the washing water tank 18. The filter membrane may be pre-cleaned by supplying the cleaning water 17 to the membrane module 3 via the pipe 4.

Further, the switching valve 20, the switching valve 21, the first chemical supply valve 30, the first air supply valve 31, the first backwash valve 32 and the second backwash valve 36 are opened to start the backwash pump 19. The filter membrane may be pre-cleaned by supplying the wash water 17 from the wash water tank 18 to the membrane module 3 via the

wash water pipes

24 and 24B, the first backwash pipe 26, and the filtered water pipe 4.
Further, the switching valve 20, the switching valve 21, the second chemical supply valve 34, the second air supply valve 35, and the second backwash valve 36 are opened to start the backwash pump 19, and the washing water is washed from the washing water tank 18. The filter membrane may be pre-cleaned by supplying the wash water 17 to the membrane module 3 via the

pipes

24 and 24B, the second backwash pipe 27, and the filtered water pipe 4.

Further, the first air supply valve 31, the first backwash valve 32, and the second backwash valve 36 are opened to start the washing blower 38, and the first air supply pipe 39 and the first backwash pipe 26 are started. The filter membrane may be pre-cleaned by supplying air to the membrane module 3 via the filtered water pipe 4.
Further, the second air supply valve 35 and the second backwash valve 36 are opened to start the cleaning blower 38, and the cleaning blower 38 is started via the second air supply pipe 40, the second backwash pipe 27, and the filtered water pipe 4. The filter membrane may be pre-cleaned by supplying air to the membrane module 3.
Similarly, when performing these preliminary cleanings, it is possible to easily remove the pollutant substances adhering to the surface of the filtration membrane in contact with the water to be treated 1.

In the cleaning process of the filter membrane, first, the switching valve 20 is opened to start the backwash pump 19, and the washing water 17 is connected to the first backwashing pipe 26 from the washing water tank 18 via the

washing water pipes

24 and 24B and the switching valve 21. The first drug supply valve 30 is opened to start the first drug supply pump 33, and the first backwash pipe is supplied from the first drug storage tank 22 via the first drug supply pipe 28. The first agent is supplied to 26. As a result, the washing water 17 and the first chemical are mixed in the first backwashing pipe 26, and the mixed water is generated. Although not shown, the first backwash pipe 26 may be provided with a device (for example, a static mixer) that uniformly mixes the wash water 17 and the first chemical.

Then, the mixed water containing the first chemical is supplied to the membrane module 3 via the filtered water pipe 4, and the filtered membrane in the membrane module 3 is backwashed. Alternatively, a tank for accommodating the washing water 17 is provided in the first backwash pipe 26, the first chemical is supplied into the tank, the washing water 17 and the first chemical are uniformly mixed, and the mixed water is mixed. The filtration membrane in the membrane module 3 may be backwashed by supplying the membrane module 3 with a pump. The mixed water containing the first chemical discharged from the membrane module 3 after the backflow cleaning can be discharged into the water tank 2 to be treated and used as the water 1 to be treated used for the filtration treatment. Alternatively, the mixed water containing the first chemical discharged from the membrane module 3 after the backflow cleaning may be separately collected and treated as a treated liquid. The mixed water after each backwashing treatment described below can also be treated in the same manner as described above.

Further, in the method of controlling the chemical solution exclusion, the integrated flow rate meter 13 located between the membrane module 3 and the second backwash valve 36 is used to measure the integrated flow rate in the chemical solution exclusion. The value of the integrated flow meter 13 between the membrane module 3 and the second backwash valve 36 indicates that the mixed water in which the first drug is mixed with the washing water 17 as the chemical solution and the second drug in the washing water 17 as the chemical solution. It is preferable to end the chemical solution elimination step when the mixed water exceeds the capacity of the pipe at the place where the mixed water passes.
Here, the capacity inside the pipe refers to the amount of chemical solution filling the inside of the pipe. For example, if the diameter of the pipe through which the chemical solution passes is 10 cm and the length of the pipe is 10 m in total length, the internal capacity of the pipe is 0.05 m × 0.05 m × 3.14 × 10 m = 0.0785 m ³ . As for the time for removing the chemical solution, it is sufficient to flow the washing water 17 or the gas having a capacity equal to or larger than the capacity of the pipe. For example, if the flow of cleaning water ^{1 m} 3 / min until the pipe inner volume ^{^{^{0.0785m 3, 0.0785m 3 ÷ 1m 3}}} /min=0.0785min next, be allowed to flow washing water 17 or 0.0785Min, the pipe It is possible to replace (eliminate) the chemical solution remaining in.
If the viscosity of the chemical solution to be excluded is 2 cP (CENTI POISE), (mPa · s), it is twice the capacity of the pipe, and if it is 3 cP (mPa · s), the chemical solution is eliminated when it is 3 times or more the capacity of the pipe. It is more preferable to end the process. Further, the method of removing the chemical solution, the exclusion time, and the exclusion flow rate may be different between the mixed water in which the first agent is mixed with the washing water 17 and the mixed water in which the second agent is mixed in the washing water 17. ..

Next, when the turbidity of the wash water 17 measured by the turbidity meter 41 is lower than 1 NTU (NEPHELOMETRIC TURBIDITY UNIT) (1 NTU is set as the turbidity set value), the switching valve 20, the wash water supply valve 25 and the first The backwash valve 32 and the second backwash valve 36 are opened to start the backwash pump 19, and the wash water 17 is supplied from the wash water tank 18 to the membrane module 3 via the

wash water pipes

24 and 24A and the filtered water pipe 4. By doing so, the filter membrane in the membrane module 3 is backwashed.
Alternatively, the switching valve 20, the switching valve 21, the first chemical supply valve 30, the first air supply valve 31, the first backwash valve 32, and the second backwash valve 36 are opened to start the backwash pump 19. By supplying the washing water 17 from the washing water tank 18 to the membrane module 3 via the

washing water pipes

24 and 24B, the first backwashing pipe 26, and the filtered water pipe 4, the filtered membrane in the membrane module 3 is backwashed. do.
Alternatively, the switching valve 20, the switching valve 21, the second chemical supply valve 34, the second air supply valve 35, and the second backwash valve 36 are opened to start the backwash pump 19, and the wash water pipe is connected from the wash water tank 18. By supplying the washing water 17 to the membrane module 3 via the 24, 24B, the second backwash pipe 27, and the filtered water pipe 4, the filtered membrane in the membrane module 3 is backwashed.

If the turbidity of the washing water 17 is 1 NTU or more as measured by the turbidity meter 41, the first air supply valve 31, the first backwash valve 32, and the second backwash valve 36 are opened for washing. Filtering in the membrane module 3 by activating the blower 38 and supplying air (gas) to the membrane module 3 via the first air supply pipe 39, the first backwash pipe 26, and the filtered water pipe 4. Backwash the membrane.
Alternatively, the second air supply valve 35 and the second backwash valve 36 are opened to start the cleaning blower 38, and the cleaning blower 38 is started via the second air supply pipe 40, the second backwash pipe 27, and the filtered water pipe 4. By supplying air (gas) to the membrane module 3, the filtration membrane in the membrane module 3 is backwashed.

If the cleaning blower 38 cannot be used, after closing the cleaning water supply valve 25, the first backwash valve 32, the second backwash valve 36, the first air supply valve 31, and the first chemical supply valve 30 is opened to start the first chemical supply pump 33 (suction device), and the filtered water pipe 4 and the backwash are passed through the filtered water pipe 4, the first backwash pipe 26 and the first chemical supply pipe 28. The mixed water in which the first chemical is mixed with the washing water 17 in the pipe 26 is suction-transferred to the first chemical storage tank 22.

By eliminating such a chemical solution, it is possible to efficiently eliminate the chemical solution remaining in the pipe and further prevent the chemical solution and the washing water used for removing the chemical solution from reacting with each other. Therefore, the mixed water can be applied to the filtration membrane while maintaining the concentration of the mixed water containing the second chemical solution.
That is, consider the case where only the washing water 17 is used as the method for removing the chemical solution. When the washing water 17 is used as a method for removing the chemical solution, if the water quality of the washing water 17 is poor (suspended solids or dissolved organic substances are contained in the washing water 17), the suspended solids or dissolved substances in the washing water 17 are contained. Suspended solids may react with the second drug solution (supplied after the elimination of the mixed water mixed with the first drug). Unlike the stage where the washing water 17 and the chemicals are mixed in the backwash pipe to generate the mixed water, it is necessary to keep the state as clean as possible at the stage where the chemical solution remaining in the pipe is removed. If the cleaning water 17 reacts with the second chemical solution in the pipe, the concentration of the second chemical solution decreases before it reaches the filtration membrane, which may lead to a decrease in the cleaning ability of the filtration membrane. In order to prevent such a phenomenon, cleaning with air and further suction transfer are performed.

Further, the mixed water containing the first chemical discharged from the membrane module 3 after the chemical solution is removed can be discharged into the water tank 2 to be treated and used as the water 1 to be treated used for the filtration treatment. Alternatively, the mixed water containing the first chemical discharged from the membrane module 3 after the backflow cleaning may be separately collected and treated as a treated liquid.

Next, after closing the washing water supply valve 25 and the first backwash valve 32, the second backwash valve 36 is opened to start the second chemical supply pump 37, and the washing water pipe 24 from the washing water tank 18 The wash water 17 is supplied to the second backwash pipe 27 via the 24B and the switching valve 21. Then, the second drug supply valve 34 is opened to start the second drug supply pump 37, and the second drug storage tank 23 is connected to the second backwash pipe 27 via the second drug supply pipe 29. Supply the drug. As a result, the washing water 17 and the second chemical are mixed in the second backwash pipe 27 to become mixed water. Although not shown, the second backwash pipe 27 may be provided with a device (for example, a static mixer) that uniformly mixes the wash water 17 and the second chemical. Then, the mixed water containing the second chemical is supplied to the membrane module 3 via the filtered water pipe 4, and the filtered membrane in the membrane module 3 is backwashed. Alternatively, a tank for accommodating the washing water 17 is provided in the second backwash pipe 27, the second chemical is supplied into the tank, the washing water 17 and the second chemical are uniformly mixed, and the mixed water is mixed. The filtration membrane in the membrane module 3 may be backwashed by supplying the membrane module 3 with a pump.

In the above-mentioned filtration membrane cleaning device, the case where two kinds of mixed water containing a drug is used has been described, but when three or more kinds of mixed water containing a drug are used, the drug storage tank is increased and the same applies. The cleaning process can be performed by the above method.
When the cleaning process using the filtration membrane cleaning device is completed, the second backwash valve 36, the first backwash valve 32, the washing water supply valve 25 and the filtration valve 15 are opened, the filtration pump 16 is started, and the subject is covered. By performing the filtration treatment of the treated water 1 again, the filtration treatment of the water to be treated 1 can be continuously and efficiently performed.

According to the filtration membrane cleaning device having the above configuration, in the method for removing the chemical solution when cleaning the filtration membrane using a plurality of chemical solutions, a plurality of chemical solutions remaining in the pipe are efficiently removed. It can be applied to the filtration membrane while maintaining the concentration of the chemical solution. In addition, since a method other than washing with washing water can be selected for removing the chemical solution, the washing water can be saved.
It is also possible to eliminate the chemical solution in the pipe by alternately circulating the washing water and the gas filtered by the filtration membrane. Such a method is a cleaning method called "pulse cleaning", and when liquid and gas are alternately circulated, the cleaning ability for the filter membrane or the pipe is higher than when only liquid or gas is circulated. improves.

In the method for removing chemicals according to the present embodiment, in order to avoid mixing of different types of chemicals in the pipe, the filter membrane is washed with the mixed water in which the first chemical is mixed with the washing water 17, and then remains in the pipe. The mixed water in which the first chemical was mixed with the washed water 17 was removed, and the filter membrane was washed with the mixed water in which the second chemical was mixed with the washing water 17, and then the washing water 17 remaining in the pipe was used for the second. It is a method of removing the mixed water in which the two chemicals are mixed. In this case, if the turbidity of the washing water is low, wash water is used to remove the chemical solution remaining in the pipe, and if the washing water cannot be supplied, gas is used to remove the chemical solution remaining in the pipe, and the gas supply device. If it cannot be used, suction is used to remove the chemical solution remaining in the pipe.

The mixed water used in the method for cleaning the filtration membrane according to the present embodiment is not particularly limited as long as it is plural, but if the number of mixed waters is too large, the types of chemicals used for each mixed water must be increased. .. Therefore, the mixed water used in the method for cleaning the filtration membrane according to the present embodiment is preferably 2 or 3 types, more preferably 2 types, from the viewpoint of reducing the cleaning cost. In the above, the method for cleaning the filtration membrane using two kinds of mixed water has been described as an example, but the method for cleaning the filtration membrane using three or more kinds of mixed water can also be adopted.

In the method for cleaning the filter membrane according to the present embodiment, after the cleaning water is passed through the filtration membrane, the cleaning water may be held in the membrane as it is, or the filtration membrane is immersed in the cleaning liquid and held. May be good.
The washing water used for removing the chemical solution according to the present embodiment needs to be changed in real time to a method for removing the chemical solution other than the washing water according to the amount of suspended solids in the washing water. Therefore, it is necessary to measure the turbidity of the washing water in real time using an online turbidity meter for the washing water used for removing the chemical solution according to the present embodiment. The lower the turbidity in the washing water, the more preferable, but it is preferably lower than 1 NTU, more preferably 0 NTU.

As the gas used for removing the chemical solution according to the present embodiment, it is preferable to use a gas having low toxicity, but if a gas requiring a cylinder is used, the cost required for removing the chemical solution cannot be suppressed. Therefore, it is preferable to use air generated by a blower as the gas used in the chemical solution removing method according to the present embodiment.
Further, the filter membrane to be the target of the filter membrane cleaning method according to the present embodiment is a pollutant by filtering water to be treated such as water supply, sewerage, secondary treated sewage water, industrial wastewater, seawater, and urine. Is a filtration film in a state where is adhered to the surface or in the pores.

The material of the filtration membrane that can be used in the method for cleaning the filtration membrane of the present embodiment is not particularly limited as long as it is not deteriorated by a chemical agent. Examples of materials for filtration membranes include polyolefins such as polyethylene, polypropylene and polybutene. Examples of the material of the filter membrane include tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP (FLUORINATED ETHYLENE PROPYLENE)), and tetrafluoroethylene-ethylene. Polymers (ETFE (ETHYLENE TETRAFLUOROETHYLENE)), polychlorotrifluoroethylene (PCTFE (POLYCHLOROTRIFLUOROETHYLENE)), chlorotrifluoroethylene-ethylene copolymer (ECTFE (ETHYLENE CHLOROTRIFLUOROETHYLENE) There are fluororesin compounds such as polytetrafluoroethylene (PTFE (POLYTETRAFLUOROETHYLENE)). Examples of the material of the filtration membrane include celluloses such as cellulose acetate and ethyl cellulose, and ceramics. Among them, the material of the filtration membrane is preferably a fluororesin compound having excellent resistance to a strong oxidizing agent such as ozone. Further, the material of the filtration membrane may be a single substance or a combination of two or more of the above substances.

The type of the filtration membrane is not particularly limited, and various filtration membranes such as a microfiltration (MF (MICROFILTRATION MEMBRANE)) membrane and an ultrafiltration (UF (ULTRAFILTRATION MEMBRANE)) membrane can be used. The average pore size of the filtration membrane is not particularly limited, but is preferably 0.001 μm to 1 μm, and more preferably 0.01 μm to 0.1 μm. If the filtration membrane has an average pore size in this range, the filtration membrane cleaning method of the present embodiment can be used not only for pollutants adhering to the surface of the filtration membrane in contact with the water to be treated, but also for the filtration membrane in contact with the cleaning water. The pollutant that is chemically attached to the surface or the pores of the filtration membrane can be efficiently removed. The shape of the filtration membrane is not particularly limited, and can be a cylindrical shape or a flat membrane shape. Among them, the shape of the filtration membrane is preferably cylindrical. The filtration membrane may be incorporated in the membrane module 3, and the membrane module 3 may be an immersion type, a casing type, or a monolith type. Further, the filtration method of the filtration membrane can be either a total filtration method or a cross-flow filtration method.

The water flow method of the filter membrane is not particularly limited, and is an external pressure filtration method in which the water to be treated flows outside the filter membrane and the wash water flows inside, and the water to be treated flows inside the filter membrane and the wash water flows outside. It may be any of the internal pressure filtration methods in which water is flowed.
The mixed water in which the first chemical is mixed with the washing water 17 and the mixed water in which the second chemical is mixed with the washing water 17 are not particularly limited as long as they are substances capable of decomposing organic substances or inorganic substances. Examples of chemical solutions capable of decomposing organic substances include sodium hypochlorite, hydrogen peroxide, sodium hydroxide, ozone water and the like. These can be used alone or in combination of two or more.
As the chemical solution mixed with the first drug, mixed water in which sodium hypochlorite or hydrogen peroxide is dissolved in washing water 17 can be used. As the chemical solution in which the second drug is mixed, mixed water in which ozone is dissolved in the washing water 17 can be used.

Further, as a substance capable of decomposing an inorganic substance, an inorganic acid such as hydrochloric acid, sulfuric acid or nitric acid, or an organic acid such as oxalic acid or citric acid can be used. These can also be used alone or in combination of two or more. Further, two or more kinds of substances capable of decomposing organic substances and substances capable of decomposing inorganic substances can be used in combination. When two or more kinds of substances capable of decomposing organic substances and substances capable of decomposing inorganic substances are used in combination, which one is used as the mixed water in which the first drug is mixed or the mixed water in which the second drug is mixed is particularly limited. Instead, when a substance capable of decomposing an organic substance is used as a mixed water mixed with a first agent, a substance capable of decomposing an inorganic substance is used as a mixed water mixed with a second agent, and a substance capable of decomposing an inorganic substance is used as a mixed water. When the mixed water in which the first drug is mixed is used, a substance capable of decomposing an organic substance may be used as the mixed water in which the second drug is mixed.

The concentration of the chemical solution in the washing water is not particularly limited, but 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 used. It is preferably 1.0 g / L or more and 4.0 g / L or less. For ozone water, it is preferably 5 mg / L or more and 100 mg / L or less, and more preferably 20 mg / L or more and 30 mg / L or less. When a substance capable of decomposing inorganic substances 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 concentration of the chemical solution is lower than the above range, it takes time to decompose the pollutants adhering to the filtration membrane. In addition, as the required amount of wash water increases, the capacity of the drug storage tank also increases. On the other hand, if the concentration of the mixed water mixed with the first drug or the mixed water mixed with the second drug is higher than the above range, the consumption of the chemical solution increases, so that the cost required for the chemical solution increases.

The cleaning time of the filtration membrane using the mixed water containing the chemical solution is not particularly limited, and may be appropriately set according to the amount of pollutants adhering to the filtration membrane. Generally, 90 minutes or less is preferable when sodium hypochlorite is used, and 5 to 7 minutes is preferable when oxalic acid or citric acid is used.
It is preferable that the washing time is short, and when the washing time is long, the total washing time is long and the time for interrupting the filtration treatment by the filtration membrane of the water to be treated is also long, so that the amount of water to be filtered through the filtration membrane is reduced.
That is, normally, in the filtration treatment using a filtration membrane for sewage and wastewater treatment, the water to be treated is filtered all day long. Since the chemical solution cleaning of the filtration membrane is performed by stopping the filtration treatment of the water to be treated, the longer the cleaning time, the shorter the time for filtering the water to be treated. That is, since the time for filtering the water to be treated is shortened, the amount of water that can be filtered (the amount of washing water) is also reduced.

The membrane surface permeation flux (water permeation amount per membrane area) of the mixed water containing the chemical solution is not particularly limited. In general, it is sufficient to secure a flux that can be filled up to the end of the filtration membrane, and particularly when ozone water is used, it is sufficient to secure a flux that can maintain the concentration during transportation. Specifically, when sodium hypochlorite is used, it is 6 LMH (L / m ² / h) or less, when ozone water is used, it is 50 LMH (L / m ² / h) or less, and more preferably 30 LMH (L / h). m ² / h) or less. If the permeation flux is too high, the cost of the drug increases as the required amount of mixed water increases. It also increases the capacity of the drug storage tank. If the permeation flux on the membrane surface is too low, the mixed water will not be filled to the end of the filtration membrane, and the pollutants adhering to the filtration membrane cannot be decomposed. When ozone water is used, the concentration decreases during transportation.

As the method used for removing the chemical solution, washing water and gas are generally used, and further, a suction method is used. Among them, gas is preferably used, and washing water is more preferable. In the state where the filtration membrane is not broken, that is, the suspended solids or dissolved organic substances in the water to be treated do not flow out into the washing water, the turbidity of the washing water generally shows 0 NTU. On the other hand, when the filtration membrane is broken, that is, when suspended solids or dissolved organic substances in the water to be treated are flowing out into the washing water, the turbidity of the washing water generally shows 1 NTU or more.

When the washing water from which the suspended solids or dissolved organic substances in the water to be treated have flowed out is used as a method for removing the chemical solution remaining in the pipe, the chemical solution reacts with the suspended solids or dissolved organic substances in the washing water, and the concentration of the chemical solution is concentrated. Cannot be maintained. That is, unlike the stage where the washing water 17 and the chemicals are mixed in the backwash pipe to generate the mixed water, it is necessary to keep the state as clean as possible at the stage where the chemical solution remaining in the pipe is removed. Therefore, in the selection of the chemical solution exclusion method, the washing water is preferentially selected, but when the turbidity of the washing water is 1 NTU or more, a gas is selected. If it is difficult to supply gas, select a suction method.

The timing of removing the chemical solution is before the supply of the mixed water mixed with the first drug, between the supply of the mixed water mixed with the first drug and the mixed water mixed with the second drug, and further. It is preferable after the supply of the mixed water mixed with the second agent, but more preferably between the supply of the mixed water mixed with the first agent and the supply of the mixed water mixed with the second agent. ..
The direction of chemical solution exclusion is the same flow direction as the mixed water mixed with the first drug and the mixed water mixed with the second drug, the mixed water mixed with the first drug and the mixed water mixed with the second drug. The flow direction may be opposite to that of the above, but it is preferable that the flow direction is the same as that of the mixed water in which the first agent is mixed and the mixed water in which the second agent is mixed.
That is, there are two directions for removing the chemical solution, one is from the secondary side to the primary side of the filtration membrane (the same direction as the flow of the chemical solution), and the other is from the primary side to the secondary side of the filtration membrane. The direction (the same direction as the direction in which the water to be treated 1 is filtered). In removing the chemical solution, either direction may be used, but the same direction as the chemical solution (direction from the secondary side to the primary side of the filtration membrane) is preferable because the chemical solution in the pipe and the inside of the filtration membrane can be completely eliminated.

Further, the method for treating the chemical solution excluded by the chemical solution exclusion is not particularly limited. When the flow direction is the same as that of the mixed water mixed with the first drug and the mixed water mixed with the second drug, it is preferable to eliminate the water in the filtration membrane or the reaction tank (water tank 2 to be treated), but it is excluded in the filtration membrane. It is more preferable to do so.
Further, in the case of the flow direction opposite to that of the mixed water in which the first drug is mixed and the mixed water in which the second drug is mixed, it is preferable to remove the drug into the drug storage tank or the treated water tank (washing water tank 18). It is more preferable to remove it into the storage tank.
Generally, the time for removing the chemical solution may be any time as long as it can secure a flow rate equal to or larger than the capacity of the pipe at the place where the mixed water mixed with the first drug and the mixed water mixed with the second drug pass. .. If the removal time is short, the chemical solution remaining in the pipe cannot be completely removed, so that the concentration of the chemical is lowered when the mixed water containing the chemical is supplied. If the exclusion time is long, the total washing time is long, so that the time for interrupting the filtration treatment of the water to be treated by the filtration membrane is also long, and the amount of water treated by the filtration membrane is reduced.

The flow velocity for removing the chemical solution may be appropriately set according to the amount of the chemical solution remaining in the pipe. It is preferable that the exclusion flow velocity is high, and if the exclusion flow velocity is slow, the chemical solution adhering to the pipe cannot be completely removed due to the decrease in shear stress caused by the exclusion flow rate. Decreases.
The chemical solution exclusion control method is controlled by measuring the integrated flow rate of the fluid used for chemical solution exclusion using an integrated flow meter 13 located between the filtration membrane and the second backwash valve 36. The value of the integrated flow meter 13 between the filtration membrane and the second backwash valve 36 is the capacity of the pipe where the mixed water mixed with the first chemical and the mixed water mixed with the second chemical pass. When the above is reached, it is preferable to end the chemical solution exclusion step. If the viscosity of the chemical solution to be excluded is 2 cP (mPa · s), it is twice the capacity of the pipe, and if it is 3 cP (mPa · s), it is 3 times or more the capacity of the pipe, the chemical solution removal step is terminated. Is more preferable. Further, the chemical solution exclusion method, the exclusion time, and the exclusion flow rate may be different between the mixed water in which the first drug is mixed and the mixed water in which the second drug is mixed.

In the present embodiment, when the filtration membrane is washed with a plurality of chemicals, the filtration membrane is washed with mixed water containing the first chemical in order to avoid mixing of different kinds of chemicals in the pipe. A chemical solution removing step is introduced between the cleaning of the filtration membrane with the mixed water containing the second chemical, and the chemical solution remaining in the pipe is removed. When the turbidity of the washing water 17 that has passed through the filtration membrane is low, the washing water 17 is used to remove the chemical solution remaining in the pipe, and when the turbidity of the washing water 17 is high, gas is used to remain in the pipe. When the gas cannot be supplied, the chemical solution remaining in the pipe is eliminated by using suction.
As a result, when the filtration membrane is washed with a plurality of chemical solutions, the chemicals remaining in the piping are efficiently removed, the chemical solutions are prevented from reacting with each other, and the filtration is performed while maintaining the concentration of the multiple chemical solutions. Can be applied to the membrane. In addition, the washing water can be saved by selecting a method other than washing with washing water that has passed through the filtration membrane for removing the chemical solution.

Embodiment 2.
FIG. 2 is a conceptual diagram showing a water treatment system including the filtration membrane cleaning device according to the second embodiment. Since the basic configuration of the water treatment system including the filter membrane cleaning device according to the present embodiment is the same as that of the water treatment system including the filter membrane cleaning device according to the first embodiment, only the differences are obtained. explain. Further, the same reference numerals are given to the same configurations as those of the water treatment system including the filtration membrane cleaning device according to the first embodiment.

In FIG. 2, the water treatment system including the filtration membrane cleaning device according to the present embodiment has a structure suitable for using ozone as the mixed water mixed with the second chemical. That is, in the water treatment system including the filtration membrane cleaning device according to the present embodiment, the ozone water generation tower 45 is connected to the second backwash pipe 27 branched by the second backwash valve 36. Therefore, it is different from the water treatment system provided with the filtration membrane cleaning device according to the first embodiment. An air diffuser 44 is arranged at the bottom of the ozone water generation tower 45, and an ozone generator 42 is connected to the air diffuser 44 via an ozone supply pipe 43. The ozone raw material supplied to the ozone generator 42 is not particularly limited, and for example, liquid oxygen or oxygen generated by PSA (PRESSURE SWING ADSORPTION) or PVSA (PRESSURE VACUUM SWING ADSORPTION) can be used.

In a water treatment system having such a structure, when backflow cleaning is performed using mixed water in which ozone (second chemical) is mixed with the cleaning water 17, the switching valve 20, the switching valve 21, and the second chemical are supplied. The valve 34 is opened, the backwash pump 19 is started, and the wash water 17 is supplied from the wash water tank 18 to the ozone water generation tower 45 via the

wash water pipes

24 and 24B and the second chemical supply valve 34. Further, by supplying the ozone gas generated by the ozone generator 42 from the air diffuser 44 via the ozone supply pipe 43, ozone water as a mixed water in which ozone is mixed with the washing water 17 in the ozone water generation tower 45. To generate. Then, the ozone water generated in the ozone water generation tower 45 is supplied to the membrane module 3 via the second backwash pipe 27 and the filtered water pipe 4, and the filtered membrane in the membrane module 3 is backwashed. Further, in the water treatment system according to the present embodiment, the ozone exhaust pipe 46, the ozone exhaust treatment equipment 47, and the treated ozone pipe 48 are provided.

By providing the ozone water generation tower 45 in this way, ozone water can be efficiently generated. Further, although FIG. 2 illustrates the case where the air diffuser 44 is used as the ozone gas supply device, the device is not particularly limited as long as it can generate ozone water in which the ozone gas and the cleaning water 17 are in contact with each other. For example, an ozone gas supply device such as an ejector type, a mechanical stirring type, or a downward injection type can be used. Although not shown, all pumps, valves, and switching valves are connected to a control device, and the operation of all pumps, valves, and switching valves is controlled by this control device.

Further, in the filter membrane cleaning device of the present embodiment, the case where ozone is used as the mixed water mixed as the second chemical has been described, but either ozone or a chemical other than ozone is mixed as the first chemical. Whether it is used as mixed water or mixed water mixed as a second drug is not particularly limited, and when ozone is used as a mixed water mixed as a first drug, a drug other than ozone is mixed as a second drug. It may be used as water.

Embodiment 3.
FIG. 3 is a conceptual diagram showing a water treatment system including the filtration membrane cleaning device according to the third embodiment. Since the basic configuration of the water treatment system including the filter membrane cleaning device according to the present embodiment is the same as that of the water treatment system including the filter membrane cleaning device according to the first embodiment, only the differences are obtained. explain. Further, the same reference numerals are given to the same configurations as those of the water treatment system including the filtration membrane cleaning device according to the first embodiment.

In FIG. 3, the water treatment system including the filtration membrane cleaning device according to the present embodiment cleans the filtration membrane according to the first embodiment in that a water supply pipe 49 is provided instead of the backwash pump 19. It is different from the water treatment system equipped with the device. The water supply pipe 49 is connected to the first backwash pipe 26 and the second backwash pipe 27 via the wash water pipe 24B branched by the switching valve 20. Further, the water supplied from the water supply pipe 49 according to the present embodiment is not particularly limited as long as the turbidity is lower than 1 NTU. Examples include tap water, groundwater, reservoir water, surface water, underground water, lake water, and seawater.

In a water treatment system having such a structure, when the chemical solution is removed from the water supply pipe 49, the switching valve 20, the washing water supply valve 25, the first backwash valve 32 and the second backwash valve 36 are opened to release water. Supply. Alternatively, the switching valve 20, the switching valve 21, the first chemical supply valve 30, the first air supply valve 31, the first backwash valve 32, and the second backwash valve 36 are opened to supply water. Alternatively, the switching valve 20, the switching valve 21, the second chemical supply valve 34, the second air supply valve 35, and the second backwash valve 36 are opened to supply water. By providing the water supply pipe 49 in this way, it is possible to efficiently remove the chemical solution while saving the washing water.

Embodiment 4.
FIG. 4 is a conceptual diagram showing a water treatment system including the filtration membrane cleaning device according to the fourth embodiment. Since the basic configuration of the water treatment system including the filter membrane cleaning device according to the present embodiment is the same as that of the water treatment system including the filter membrane cleaning device according to the first embodiment, only the differences are obtained. explain. Further, the same reference numerals are given to the same configurations as those of the water treatment system including the filtration membrane cleaning device according to the first embodiment.

In FIG. 4, the water treatment system including the filtration membrane cleaning device according to the present embodiment is provided with a gas cylinder 50 as a gas supply device instead of the cleaning blower 38, and the filtration according to the first embodiment is provided. It differs from a water treatment system equipped with a membrane cleaning device. The gas cylinder 50 is connected to the first backwash pipe 26 branched by the first air supply pipe 39 and the first air supply valve 31. Further, the gas cylinder 50 is connected to the second backwash pipe 27 branched by the second air supply pipe 40 and the second air supply valve 35.
Further, the gas supplied from the gas cylinder 50 according to the present embodiment is not particularly limited as long as it is not toxic to the human body, and a substance known in the art can be used. Examples include oxygen, nitrogen, carbon dioxide and carbon dioxide.

In a water treatment system having such a structure, when the chemical solution is removed by the gas cylinder 50, the first air supply valve 31, the first backwash valve 32 and the second backwash valve 36 are opened to supply gas. .. Alternatively, the second air supply valve 35 and the second backwash valve 36 are opened to supply gas. By providing the gas cylinder 50 in this way, the chemical solution can be removed using a gas other than air. Therefore, even in the membrane treatment in an anaerobic and anoxic environment where air or oxygen cannot be used, the chemical solution using gas can be removed. Further, when the filter membrane cleaning device according to the present embodiment is implemented in an anaerobic and oxygen-free environment, the air diffuser 8, the air supply pipe 11, and the membrane aeration blower 12 related to the supply of oxygen are omitted.

When the gas cylinder 50 used for supplying the gas is used, the chemical elimination method can be selected according to the pressure of the gas cylinder 50. Furthermore, when an air pump is used, a chemical solution elimination method can be selected according to the pressure of the air pump. For example, when the residual pressure of the gas cylinder 50 decreases, the pressure of the pressure gauge 14 decreases. In addition, if the air pump also fails or a pipe leaks, the pressure of the pressure gauge 14 also drops. Even if such a problem occurs, another chemical solution exclusion method can be selected, so that the chemical solution elimination is not hindered.
That is, when the pressure of the gas supplied from the gas supply device is lower than the reference value, the chemical solution remaining in the pipe is removed by using the washing water 17, or the chemical solution remaining in the pipe is removed by the suction device in the chemical storage tank. One of the methods of suction transfer to 22 and 23 is selected.

Although the present application describes various exemplary embodiments and examples, the various features, embodiments, and functions described in one or more embodiments are applications of a particular embodiment. It is not limited to, but can be applied to embodiments alone or in various combinations.
Therefore, innumerable variations not illustrated are envisioned within the scope of the techniques disclosed in the present application. For example, it is assumed that at least one component is modified, added or omitted, and further, at least one component is extracted and combined with the components of other embodiments.

1 Water to be treated, 2 Water tank to be treated, 3 Membrane module, 13 Integrated flow meter, 17 Wash water, 18 Wash water tank, 22 1st drug storage tank, 23 2nd drug storage tank, 33 1st drug supply pump , 37 Second drug supply pump, 38 Cleaning blower.

Claims

A water tank to be treated and a water tank to be treated
A membrane module having a filtration membrane installed in the water tank to be treated and filtering the water to be treated,
A plurality of chemical solution supply units for supplying a plurality of chemical solutions for cleaning the filtration membrane, and
A washing water tank containing the washing water filtered by the membrane module and used for removing the washing water remaining in the pipe connecting the chemical solution supply unit and the water tank to be treated.
A gas supply device that supplies a gas used for removing the chemical solution remaining in the pipe, and a gas supply device.
It is provided with an integrated flow meter installed in the pipe and measuring the integrated flow rate of the washing water or the gas used for removing the chemical solution.
A water treatment system that ends the removal of the chemical solution when the value of the integrated flow meter exceeds the capacity of the pipe in the pipe.
The water treatment system according to claim 1, further comprising a suction device for suction-transferring the chemical solution remaining in the pipe to the chemical solution supply unit.
When the turbidity of the washing water is lower than the turbidity set value, the washing water is used to remove the chemical solution remaining in the pipe.
When the turbidity of the washing water is equal to or less than the turbidity set value, the gas is supplied by the gas supply device, or when the gas supply device cannot be used, the suction device remains in the pipe. The water treatment system according to claim 2, wherein the chemical solution is suction-transferred to the chemical solution supply unit.
Claim 1 in which the removal of the chemical solution remaining in the pipe by using the washing water and the removal of the chemical solution remaining in the pipe by supplying the gas by the gas supply device are alternately executed. The water treatment system described.
When the pressure of the gas supplied from the gas supply device is lower than the reference value, the washing water is used to eliminate the chemical solution remaining in the pipe, or the suction device is used to remove the chemical solution remaining in the pipe. The water treatment system according to claim 2, wherein one of the two methods of suction-transferring the chemical solution to the chemical solution supply unit is selected.
The water treatment system according to any one of claims 1 to 5, wherein mixed water in which sodium hypochlorite is dissolved in the washing water is used as the chemical solution.
The water treatment system according to any one of claims 1 to 5, wherein a mixed water in which hydrogen peroxide is dissolved in the washing water is used as the chemical solution.
The water treatment system according to any one of claims 1 to 5, wherein mixed water in which ozone is dissolved in the washing water is used as the chemical solution.