JP2003103259A - Method for cleaning filter and reverse osmosis membrane - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a filter and a method for cleaning therefor which are excellent in safety because of not using an acid such as hydrochloric acid and sulfuric acid, or a chlorine base sterilant and the like, and which are simple in structure and capable of cleaning for separating microorganisms from a reverse osmosis membrane and for preventing the generation of scales or the like thereon, using a strongly acidic aqueous solution. SOLUTION: The filter for obtaining permeated water and concentrated water by filtering raw water by using the reverse osmosis membrane comprises providing a strongly acidic aqueous solution generating part for generating the strongly acidic aqueous solution, and a strongly acidic aqueous solution injecting passage, of which the one end is connected to the raw water inlet of a reverse osmosis membrane module accommodating the reverse osmosis membrane and of which the other end is connected to the strongly acidic aqueous solution generating part, for injecting the strongly acidic aqueous solution generated in the strongly acidic aqueous solution generating part to the reverse osmosis membrane module.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a filtering device for filtering raw water through a reverse osmosis membrane to obtain permeated water and concentrated water, and a method for cleaning a reverse osmosis membrane.

[0002]

2. Description of the Related Art Conventionally, as a method for desalinating seawater, a reverse osmosis method using a reverse osmosis membrane, a freeze concentration method in which water is crystallized as ice, an ion in a solution using a membrane having a fixed charge is used. Various methods have been used, such as an electrodialysis method that separates electric potentials by a potential difference. In particular, desalination of seawater by the reverse osmosis method is widely used as the most efficient desalination method of seawater because it requires less energy, and is formed by a reverse osmosis membrane as a desalination device for seawater and a purification device for river water. A filtration device having a reverse osmosis membrane module is generally used. The filtration device having the reverse osmosis membrane module is
By feeding raw water to the reverse osmosis membrane module for reverse osmosis, minute contaminants and bacteria in the raw water can be separated and removed. However, when the pH of the raw water injected into the reverse osmosis membrane module is high, for example, when the pH is 6 or higher, the scale of calcium, sodium, magnesium, etc. contained in the raw water is deposited and the filtration capacity of the reverse osmosis membrane is increased. There was a problem of lowering. For this reason, acid such as hydrochloric acid or sulfuric acid is added to the raw water flowing into the reverse osmosis membrane module, and the raw water in the reverse osmosis membrane module is constantly made to contain a chemical agent such as hydrochloric acid to reduce the pH of the raw water. Raw water was passed through the reverse osmosis membrane module to prevent precipitation of inorganic substances such as calcium, sodium and magnesium in the reverse osmosis membrane module. When adding chemical agents such as hydrochloric acid and sulfuric acid to raw water, the pH of the raw water was restored by adding a strong alkaline reducing agent such as caustic soda to the raw water after passing through the reverse osmosis membrane module. .

When a chemical agent such as a strong acid is added to raw water to prevent scale deposition, the reverse osmosis membrane is generally injected with raw water having a low pH which has been acidified by the chemical agent. As a material of the above, a cellulose triacetate type having resistance to a strong acid was used. However, the reverse osmosis membrane of cellulose triacetate is easily eroded by the bacteria present in the raw water, and the bacteria cannot be sterilized simply by adding a strong acid to the raw water to lower the pH of the raw water. There are problems that bacteria propagate on the surface of the membrane to reduce the function of the reverse osmosis membrane, and that the reverse osmosis membrane is eroded by bacteria and the filtration ability is reduced. Therefore, the reverse osmosis membrane module is sterilized with a chlorine-based sterilizing agent such as hydrochloric acid or dihydrochloric acid constantly or regularly to prevent the growth of bacteria.

As a method of disinfection treatment using a chlorine-based sterilizing agent, Japanese Unexamined Patent Publication No. 2000-42544 (hereinafter referred to as "A") describes "a pretreatment method in a reverse osmosis membrane desalination apparatus. , A reverse osmosis membrane desalination pretreatment method in which a chlorine-based sterilant is intermittently injected into water to be treated to alternately generate the presence and absence of the sterilizer.

[0005]

However, the above-mentioned conventional techniques have the following problems. (1) The reverse osmosis membrane desalination pretreatment method described in (a) uses a sterilizer such as hydrochloric acid or sulfuric acid or a chlorine-based sterilizer, and therefore has a high risk in handling, storage, and transportation. The problem was that it was difficult to handle and lacked safety. (2) In the pretreatment method for desalination using the reverse osmosis membrane method described in Japanese Patent Publication (A) Publication, washing is performed with an addition device and a chemical injection device for adding an acid such as hydrochloric acid or sulfuric acid to raw water, and a chlorine-based sterilizer. Therefore, there is a problem that a device and a system for that purpose are required, the manufacturing cost of the device rises, and the control of the device and the system becomes complicated.

The present invention solves the above-mentioned conventional problems and is excellent in safety because it does not use an acid such as hydrochloric acid or sulfuric acid or a chlorine-based sterilizer, and uses strong acidic water with a simple structure. It is excellent in safety because it does not use a filtering device that can perform sterilization of reverse osmosis membranes or prevent the occurrence of scale, etc., and acids such as hydrochloric acid and sulfuric acid, and chlorine-based sterilizers. It is an object of the present invention to provide a method for cleaning a reverse osmosis membrane, which has a simple structure and is capable of performing sterilization of the reverse osmosis membrane using strongly acidic water and preventing the occurrence of scale and the like.

[0007]

In order to solve the above problems, the filtration device of the present invention has the following constitution.

The filtration device according to claim 1 of the present invention is a filtration device for filtering raw water through a reverse osmosis membrane to obtain permeated water and concentrated water, which is an electrolytic tank to which an electrolytic solution containing an electrolyte is supplied. The anode chamber is divided into a cathode chamber and an anode chamber by an ion-permeable diaphragm, and the cathode chamber and the anode chamber are provided with a negative electrode and a positive electrode, respectively, and a direct current voltage is applied between the negative electrode and the positive electrode to cause the anode. A strongly acidic water producing part for producing strongly acidic water in the chamber, one end is connected to the raw water inlet side of the reverse osmosis membrane module containing the reverse osmosis membrane, and the other end is the strongly acidic water producing part. And a strongly acidic water injection flow path for injecting the strongly acidic water generated by the strongly acidic water generating unit into the reverse osmosis membrane module.

With this configuration, the following operation is achieved. (1) The strong acid water generated in the strong acid water generation unit can be injected into the reverse osmosis membrane module through the strong acid water injection flow path to sterilize the inside of the reverse osmosis membrane module, so that strong acid water is strongly sterilized. Bacteria and the like propagated on the surface of the reverse osmosis membrane can be inactivated and removed by force. (2) Scales such as calcium in raw water can be dissolved and removed by strong acid water before being deposited on the reverse osmosis membrane.

Here, as the strongly acidic water producing part, an electrolytic cell divided into a cathode chamber and an anode chamber by an ion-permeable diaphragm, and a negative electrode and a positive electrode respectively provided in the cathode chamber and the anode chamber, A device having a voltage applying unit for applying a DC voltage between the negative electrode and the positive electrode is used. It is also possible to supply pure water or the like from the outside and add the electrolyte to pure water or the like inside the strongly acidic water producing part to use as an electrolytic solution. In this case, the strongly acidic water producing section has a supply path for supplying pure water and the like, an electrolyte adding section for adding an electrolyte, and the like. Further, it is preferable that the strongly acidic water producing unit is controlled so as to automatically produce strongly acidic water necessary for sterilization of the reverse osmosis membrane and washing of scale and the like before performing the washing operation. As a result, the filtration operation, the cleaning operation, etc. of the filtration device can be automatically performed, and the maintainability is improved. The pH value of the strongly acidic water produced by the strongly acidic water producing unit is 1.8 to 3.5, preferably 2.0.
Set to ~ 2.7. As the pH value of the strongly acidic water produced becomes less than 2.0, high voltage is required for electrolysis to produce strongly acidic water, and it takes a long time for electrolysis to lack energy saving. Further, since it is too acidic to be used for washing the reverse osmosis membrane, it may damage the reverse osmosis membrane, which is not preferable. As the pH value of the strongly acidic water produced becomes larger than 2.7, it is preferable because it lacks disinfection of bacteria and the like generated in the reverse osmosis membrane, and lacks removability of scale and the like generated in the reverse osmosis membrane. Absent. In particular, when the pH value of the strongly acidic water is 1.8 or less or 3.5 or more, these tendencies become more remarkable, which is not preferable. The strongly acidic water injection flow path may be directly connected to the reverse osmosis membrane module, or may be connected to a raw water flow path through which raw water flows and connected to the reverse osmosis membrane module via the raw water flow path. When the strong acidic water injection flow path is connected to the reverse osmosis membrane module via the raw water flow path, the raw water flow path, the feed pump arranged in the raw water flow path, the precision filter, and the inside of the high pressure pump are Since it is possible to disinfect and wash scales, etc., it is possible to remove calcium etc. in the raw water channel,
In addition, bacterial growth can be prevented.

According to a second aspect of the present invention, in the first aspect of the present invention, there is provided a permeated water tank for storing the permeated water obtained by filtering the raw water through the reverse osmosis membrane. Is connected to the permeated water tank and the other end is connected to the strongly acidic water generating unit, and has a configuration including a permeated water supply path for supplying the permeated water to the strongly acidic water generating unit.

With this configuration, in addition to the function of claim 1,
It has the following actions. (1) Since the permeated water obtained by filtering the raw water through the reverse osmosis membrane can be used as the electrolytic solution when generating the strongly acidic water in the strongly acidic water producing part, it can be used from other systems or devices. It is not necessary to obtain an electrolytic solution, and the device can be made compact.

Here, in order to use the permeated water as the electrolytic solution, it is preferable to add an electrolyte such as sodium chloride to the permeated water. It is preferable that an electrolyte addition part for adding an electrolyte to the permeated water is provided in the strongly acidic water generating part and the permeated water is automatically added when the strongly acidic water is generated. Thereby, the strongly acidic water can be automatically generated in the strongly acidic water producing unit according to the amount of the strongly acidic water required for the cleaning operation.

According to a third aspect of the present invention, the filtration device according to the first or second aspect of the present invention has a configuration including a strongly acidic water tank for storing the strongly acidic water injected into the reverse osmosis membrane module. is doing.

With this configuration, in addition to the action of claim 1 or 2, the following action is obtained. (1) Since a strong acidic water tank for storing strong acidic water is provided, the strong acidic water tank generates a required amount of strong acidic water in the strong acidic water generating section before injecting the strong acidic water into the reverse osmosis membrane. Can be stored in the reverse osmosis membrane module at any flow rate. (2) Strongly acidic water generated by another system or device can be stored in a strongly acidic water tank and injected into the reverse osmosis membrane module as needed.

Here, it is preferable that the strongly acidic water tank is provided on the downstream side of the strongly acidic water producing section of the strongly acidic water injection passage. Thereby, the strongly acidic water generated in the strongly acidic water generating unit can be stored in the strongly acidic water tank and injected into the reverse osmosis membrane module via the strongly acidic water injection passage as needed. The capacity of the strongly acidic water tank should be such that at least the amount of strongly acidic water used for washing the reverse osmosis membrane once can be stored, taking into consideration the size of the entire filtration device and the volume of the reverse osmosis membrane module. It is preferable to have a capacity that can be used.

The method for cleaning a reverse osmosis membrane according to claim 4 is
A method for cleaning a reverse osmosis membrane of a filter device for obtaining permeated water and concentrated water by filtering raw water with a reverse osmosis membrane, wherein an electrolytic cell supplied with an electrolyte solution containing an electrolyte is provided with an ion-permeable diaphragm to form a cathode chamber and an anode. A strong acid that generates strong acid water in the anode chamber by applying a DC voltage between the cathode electrode and the anode electrode by applying a DC voltage between the cathode electrode and the anode electrode. And a strong acid water passing step of passing the strongly acidic water through the reverse osmosis membrane module containing the reverse osmosis membrane.

With this configuration, the following effects are obtained. (1) The strongly acidic water generated in the strongly acidic water producing step is injected into the reverse osmosis membrane module through the strongly acidic water injecting channel in the strongly acidic water passing step to let water pass through the inside of the reverse osmosis membrane module. Since bacteria can be sterilized, bacteria that have propagated on the surface of the reverse osmosis membrane can be inactivated and removed by the strong sterilization power of strongly acidic water, and calcium components in raw water can be converted to reverse osmosis membrane by strongly acidic water. It can be dissolved and removed before deposition. (2) Since no chemical agents such as hydrochloric acid and sulfuric acid are used, hydrochloric acid,
Post-treatment such as neutralization after adding sulfuric acid or the like to the raw water to make it acidic is unnecessary, and the number of steps of the cleaning operation can be reduced and energy saving and labor saving can be improved.

The pH value of the strongly acidic water produced in the strongly acidic water producing step is 1.8 to 3.5, preferably 2.0 to.
It is set to 2.7. As the pH value of the strongly acidic water produced becomes less than 2.0, high voltage is required for electrolysis to produce strongly acidic water, and it takes a long time for electrolysis to lack energy saving. Further, since it is too acidic to be used for washing the reverse osmosis membrane, it may damage the reverse osmosis membrane, which is not preferable. As the pH value of the strongly acidic water produced becomes larger than 2.7, it is preferable because it lacks disinfection of bacteria and the like generated in the reverse osmosis membrane, and lacks removability of scale and the like generated in the reverse osmosis membrane. Absent. In particular, when the pH value of the strongly acidic water is 1.8 or less or 3.5 or more, these tendencies become more remarkable, which is not preferable.

A method for cleaning a reverse osmosis membrane according to claim 5 is
In the invention according to claim 4, in the strongly acidic water passing step, the strongly acidic water is injected into the reverse osmosis membrane module containing the reverse osmosis membrane from the inlet side of the raw water of the reverse osmosis membrane module. A strong acidic water injection step, and a strong acidic water discharge step of discharging the strong acidic water injected into the reverse osmosis membrane module in the strong acidic water injection step from the concentrated water outlet side of the reverse osmosis membrane module, It has a configuration including.

With this configuration, in addition to the function of claim 4,
It has the following actions. (1) In the strongly acidic water injecting step, strongly acidic water is injected into the reverse osmosis membrane module through the strongly acidic water injecting channel to sterilize the inside of the reverse osmosis membrane module, and in the strongly acidic water discharging step, the reverse osmosis membrane module Since it can be discharged from the outlet side of the concentrated water of concentrated water, bacteria that have propagated on the surface of the reverse osmosis membrane can be inactivated and removed by the strong disinfecting power of the strongly acidic water. The calcium content and the like can be dissolved and removed before being deposited on the reverse osmosis membrane, and then the strongly acidic water can be discharged from the reverse osmosis membrane module, and the next washing step such as flushing can be promptly performed.

The method for cleaning a reverse osmosis membrane according to claim 6 is
In a fifth aspect of the invention, a cleaning step of cleaning the reverse osmosis membrane with a cleaning solution after the strongly acidic water discharging step is provided.

With this configuration, in addition to the function of claim 5,
It has the following actions. (1) Bacteria and the like in the reverse osmosis membrane module are inactivated by strong acid water in the strong acid water injection step, and after strong acid water is discharged in the strong acid water discharge step, residual bacteria and dissolved calcium components Etc. can be washed away in the washing step. (2) Since strongly acidic water is used for sterilization of bacteria and dissolution of calcium and the like, and chemical agents such as hydrochloric acid and sulfuric acid are not used, there is no need for water treatment after discharging strongly acidic water. It is possible to achieve compactness and labor saving.

Here, in the washing step, flushing or back washing using the permeated water produced when the raw water is filtered as the washing liquid is carried out.

The method for cleaning a reverse osmosis membrane according to claim 7 is:
In the invention according to claim 6, the permeated water obtained by filtering the raw water through the reverse osmosis membrane is used as the cleaning liquid.

With this configuration, in addition to the function of claim 6,
It has the following actions. (1) By using permeated water generated by filtering raw water in the reverse osmosis membrane module as a cleaning liquid used in the cleaning step, it is not necessary to obtain the cleaning liquid from other systems or devices, and filtration is performed. A cleaning liquid can be supplied in the apparatus.

The method for cleaning a reverse osmosis membrane according to claim 8 is
In the invention according to any one of claims 4 to 7, there is provided a configuration including a strongly acidic water retention step of retaining the strongly acidic water in the reverse osmosis membrane module for a predetermined time.

With this configuration, in addition to the operation of any one of claims 4 to 7, the following operation is provided. (1) By the strong acidic water retention step, the strong acidic water can be retained in the reverse osmosis membrane module for a predetermined time, so that the reverse osmosis membrane can be more strongly sterilized, and The calcium content in water can be dissolved before being deposited on the reverse osmosis membrane.

Here, the residence time of the strongly acidic water inside the reverse osmosis membrane module in the strongly acidic water retaining step is 3
0 second to 60 minutes is preferable. It is preferable to use the time necessary for inactivating the bacteria that are considered to exist, considering the resistance of the bacteria to strongly acidic water. For example, since Escherichia coli, Salmonella, etc. are inactivated in about 1 minute and red mold, etc. in about 5 minutes, the retention time is set to about 5 minutes when only E. coli, Salmonella, Red mold are inactivated. As described above, it is preferable to set the residence time in consideration of the time required for inactivating the bacteria that are considered to be present in the raw water.

A method for cleaning a reverse osmosis membrane according to claim 9 is
In the invention according to any one of claims 4 to 8, it has a constitution including a strongly acidic water circulating step of circulating the strongly acidic water through the reverse osmosis membrane module.

With this configuration, in addition to the action of any one of claims 4 to 8, the following action is provided. (1) The strong acid water circulation step allows the strong acid water to be circulated to the reverse osmosis membrane module, so that the reverse osmosis membrane can be sterilized in a short time, and the calcium components in the raw water can be removed by the strong acid water. Can be dissolved before being deposited on the reverse osmosis membrane.

[0032]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to the drawings. (Embodiment 1) FIG. 1 is a block diagram showing a filtering device according to the first embodiment. In FIG. 1, reference numeral 1 is a filtration device according to the first embodiment, and 2 is a reverse osmosis membrane and a reverse osmosis membrane (not shown) which are bundled in a linear shape or a U shape and one end of which is connected and fixed with a resin or the like to form a hollow fiber shape. 2a in which is stored
It is a reverse osmosis membrane module having. As a material of the reverse osmosis membrane, a cellulose triacetate system or the like having resistance to acid is used. The container body 2a has a closed structure, and pipe ports (not shown) are opened on the inflow side of the raw water and the permeated water, and the discharge side of the concentrated water, and a raw water flow passage, a permeated water flow passage, and a concentrated water flow passage, which will be described later, are connected to each other. . In the reverse osmosis membrane module 2, raw water is separated into permeated water that has permeated the reverse osmosis membrane by reverse osmosis and concentrated water that has not permeated the reverse osmosis membrane.

Reference numeral 4 is a precision filter for removing particles and the like before flowing raw water into the reverse osmosis membrane module 2, 4a is a discharge passage for a precision filter for discharging particles and the like removed by the precision filter 4, and 4b is a discharge for the precision filter. It is an on-off valve for discharge arranged on the road. The precision filter 4 is made of polyvinylidene fluoride or the like, which has high mechanical strength and resistance to various chemicals. The diameter of the fine holes of the precision filter 4 is 0.
Since it is about 1 to 1 μm, particles having a size of 1 μm or more contained in the raw water by the precision filter 4 are 1
It is discharged from the precision filter discharge passage 4a together with about 0%. The amount of raw water discharged together with the particles from the precision filter discharge passage 4a can be arbitrarily set by adjusting the opening degree of the discharge on-off valve 4b.

A reverse osmosis membrane module 5 is supplied from a raw water supply port (not shown) through a raw water supply valve 5a and a precision filter 4.
A raw water flow path connected to the raw water flow path 6, a feed pump 6 disposed on the upstream side of the precision filter 4 of the raw water flow path 5 for feeding raw water,
Reference numeral 7 denotes a high-pressure pump that is arranged upstream of the reverse osmosis membrane module 2 in the raw water flow path 5 and pressurizes the raw water flowing into the reverse osmosis membrane module 2. By pressurizing the raw water by the high-pressure pump 7, the raw water is separated into permeated water that has been reverse osmosis by the reverse osmosis membrane of the reverse osmosis membrane module 2 and concentrated water that has not been reverse osmosis. The flow rate ratio of the separated permeated water and the concentrated water is set by providing a flow rate adjusting valve on the outlet side of the permeated water and the outlet side of the concentrated water of the reverse osmosis membrane module 2, and setting the flow rate adjusting valve. In the first embodiment, the pressurization of the raw water by the high pressure pump 7 is set to a pressure of about 6 MPa, and the flow rate ratio of the permeated water and the concentrated water to be separated is set to 4: 6.

Reference numeral 8 denotes a backwashing downstream three-way valve disposed upstream of the reverse osmosis membrane module 2 in the raw water flow path 5, and 9 denotes a permeate tank for storing permeated water that has permeated the reverse osmosis membrane module 2. , 9a are permeated water flow passages for feeding the permeated water stored in the permeated water tank 9 to another system (not shown), and 9b.
Is a permeate water supply opening / closing valve arranged in the permeate water supply channel 9a, 10 is a permeate channel connecting the reverse osmosis membrane module 2 and the permeate tank 9, and 11 is a reverse osmosis membrane module 2 to the permeate channel 10 A three-way valve for discharging permeated water, in which the permeated water discharged to the side is discharged via a three-way valve for a permeated water passage described later, 11
Reference symbol a is a three-way valve for permeate flow passage, which is disposed in the permeate flow passage 10 and switches the permeate flow passage between the permeate tank 9 side and the permeate discharge three-way valve 11 side, and 12 is concentrated by the reverse osmosis membrane module 2. A concentrated water tank for storing concentrated water, 12a is a concentrated water flow passage for sending the concentrated water stored in the concentrated water tank 12 to another system (not shown), and 12b is a concentrated water flow passage 12a. Opened / closed valve for concentrated water supply 1
3 is a concentrated water channel connecting the reverse osmosis membrane module 2 and the concentrated water tank 12, 14 is a concentrated water discharge three-way valve disposed in the concentrated water channel 13, 15 is a strongly acidic water tank for storing strongly acidic water, Reference numeral 16 denotes a permeated water supply passage having one end connected to the permeated water tank 9 and the other end connected to a strongly acidic water generating unit described later, for supplying the permeated water stored in the permeated water tank 9 to the strongly acidic water generating unit. , 16a is a three-way valve for a supply path which is disposed in the permeated water supply path 16 and to which a bypass path described later is connected, 17 is a strong acid water generation unit which generates strong acid water and supplies it to the strong acid water tank 15.
18 is a three-way valve for injection 1 whose one end is arranged in the raw water flow path 5.
8a connected to the reverse osmosis membrane module 2 via the raw water flow path 5, and the other end connected to the strongly acidic water tank 15 and connected to the strongly acidic water tank 15 to the strongly acidic water producing part 17 It is a water injection channel. The strongly acidic water stored in the strongly acidic water tank 15 is injected into the reverse osmosis membrane module 2 from the strongly acidic water injection passage 18 through the raw water passage 5 through the injection three-way valve 18a.

Reference numeral 19 is a bypass passage for bypassing and connecting the strongly acidic water supply passage 16 and the strongly acidic water injecting passage 18, and 20 is a bypass provided in the strongly acidic water injecting passage 18 and connected to the bypass passage 19. A three-way valve, 21 is a back-wash bypass passage connecting the downstream three-way valve 8 for back-washing and the permeate supply passage 16
a is provided in the permeated water supply passage 16 and is provided with a backwash bypass passage 21.
Upstream side three-way valve for backwash, 22 is a backwash pump disposed in the backwash bypass passage 21, and 23 is the permeate flow path 1
0, a bypass passage for circulation that connects the permeated water supply passage 16;
24 is provided in the permeated water supply passage 16 and is provided with a bypass passage 2 for circulation.
3 is a connected three-way valve for circulation.

The backwashing method of the filtering device of the first embodiment having the above-described structure will be described below with reference to the drawings.

First, the operation of filtering raw water using the reverse osmosis membrane module 2 will be described. As raw water, seawater for desalination, river water for purification, tap water, etc. are used depending on the purpose. In the first embodiment, a case will be described where seawater is used as raw water and the seawater is separated into pure water that is permeate and concentrated water. Raw water is supplied to the raw water flow path 5 from a raw water supply port (not shown) by opening the raw water supply valve 5a. When the raw water is supplied to the raw water flow path 5, first, the feed pump 6 sends it to the precision filter 4 to remove particles such as dust, sand, and soil contained in the raw water and microorganisms larger than the pore size of the precision filter 4. It In addition,
The removed particles and the like are discharged from the precision filter discharge passage 4a together with about 10% of the raw water flowing into the precision filter 4. The raw water that has passed through the precision filter 4 is pumped to the reverse osmosis membrane module 2 by the high pressure pump 7. In the reverse osmosis membrane module 2, salt, calcium, magnesium and the like contained in the raw water are removed, and the permeated water that has permeated the reverse osmosis membrane of the reverse osmosis membrane module 2 flows into the permeated water tank 9 through the permeated water flow passage 10. It is then stored. On the other hand, salt, calcium, magnesium, etc. removed from the fresh water by the reverse osmosis membrane module 2 of the reverse osmosis membrane module 2 are concentrated through the concentrated water flow path 13 as concentrated water together with about 60% of the raw water flowing into the reverse osmosis membrane module 2. The water is stored in the water tank 12. At this time, the permeated water passing through the permeated water flow path 10 and the concentrated water flow path 13 is not stored in the respective tanks, and the permeated water is passed through the permeated water flow path three-way valve 11 a to the permeated water discharge three-way valve 11. Therefore, the concentrated water can be discharged from the three-way valve 14 for discharging concentrated water. In this way, the raw water filtering operation using the reverse osmosis membrane module 2 is performed.

Next, a method of cleaning the reverse osmosis membrane module 2 will be described. As described above, when the raw water is filtered using the reverse osmosis membrane module 2, the function of the reverse osmosis membrane deteriorates due to the growth of bacteria and the accumulation of salts of inorganic substances. Since the pressure difference between the inflow side of the raw water and the outflow side of the permeated water of the membrane module 2 becomes large, and the flow rate of the permeated water that has permeated the reverse osmosis membrane module 2 decreases, strong acid water is removed. The reverse osmosis membrane module 2 is sterilized and the scale is washed.

The strongly acidic water used for sterilization and washing of scale and the like is produced in the strongly acidic water producing section 17 in the strongly acidic water producing step. Hereinafter, the strongly acidic water producing step will be described with reference to the drawings. FIG. 2 is a configuration diagram showing the strongly acidic water producing unit of the filtration device according to the first embodiment. In the figure, 31 is an electrolytic cell, 32 is an ion-permeable diaphragm that divides the inside of the electrolytic cell 31, 33 is an anode chamber formed by partitioning the electrolytic cell 31 with an ion-permeable diaphragm 32, and 34 is an electrolytic cell 31. Is formed by partitioning the ion-permeable diaphragm 32 into a cathode chamber, 35 is a positive electrode arranged in the anode chamber 35, 36 is a negative electrode arranged in the cathode chamber 34, and 37 is a positive electrode 35. A voltage application unit for applying a DC voltage to the negative electrode 36, 38 is connected to the strongly acidic water tank 15, and an anode water flow path for supplying the anode water (strongly acidic water) generated in the anode chamber 33, 39 Cathode chamber 34
The cathode water flow path for discharging the cathode water (strong alkaline electrolyzed water) generated in the above, 40 is an electrolyte adding portion for adding an electrolyte to permeated water to form an electrolytic solution, 41 is the permeated water supply passage 16 to the electrolytic cell 31 A permeate supply pump for supplying permeate to the.
In the strongly acidic water production process, first, the three-way valve for the supply path 1
6a, the upstream three-way valve for backwashing 21a, and the three-way valve for circulation 24 are switched so that the permeated water is supplied from the permeated water tank 9 to the strongly acidic water producing section 17 through the permeated water supply passage 16. Then, the permeated water supply pump 41 is driven to supply the permeated water stored in the permeated water tank 9 to the electrolytic cell 31 of the strongly acidic water producing unit 17. At this time, the electrolyte addition unit 40 adds a predetermined amount of electrolyte to the permeated water to generate an electrolytic solution. In the first embodiment, sodium chloride is used as the electrolyte. The electrolytic cell 31 supplied with the electrolyte solution containing an electrolyte is divided into a cathode chamber 34 and an anode chamber 33 by an ion permeable diaphragm 32, and a cathode 36 and a cathode 35 are respectively provided in the cathode chamber 34 and the anode chamber 33. Since it is provided, when a DC voltage is applied between the negative electrode 36 and the positive electrode 35 by the voltage application unit 37, the electrolytic solution is electrolyzed and strongly acidic water that is anode water is generated in the anode chamber 35. . (Strongly acidic water production process). The strongly acidic water generated in this way is stored in the strongly acidic water tank 15 via the anode water flow path 38. The strong alkaline electrolyzed water, which is the cathode water generated in the cathode chamber 39, is discharged from the cathode water flow channel 39. The strongly acidic water can be produced in the strongly acidic water producing unit 17, and is also necessarily produced in the production process of the strongly alkaline electrolyzed water (produced on the cathode chamber side described above). It is also possible to store strong acid water in the strong acid water tank 15 for use. The strongly acidic water produced in the strongly acidic water producing step is
Since it is set and produced to have a pH value of about 1.8 to 3.5, preferably about 2.0 to 2.7, and a high ORP (oxidation-reduction potential) of 1000 mV or more, preferably 1100 mV or more, Has a strong bactericidal action. This makes it possible to strongly sterilize the inside of the reverse osmosis membrane module 2 by using strongly acidic water. In addition, since the strongly acidic water produced has a low pH, the calcium content in the raw water is prevented from precipitating as calcium sulfate, and the calcium content in the raw water is reduced by the action of hydrogen ions. Can be dissolved and removed before being deposited on the reverse osmosis membrane.

Next, the cleaning operation of the reverse osmosis membrane module 2 will be described. First, the concentrated water discharge three-way valve 14 serving as an outlet for the strongly acidic water that has passed through the reverse osmosis membrane module 2 is switched from the reverse osmosis membrane module 2 to the discharge direction. Next, the injection three-way valve 18a is moved from the strongly acidic water injection flow path 18 to the raw water flow path 5
To the feed pump 6 side. Feed pump 6
Is driven, the strongly acidic water stored in the strongly acidic water tank 15 is injected from the strongly acidic water injection passage 18 into the raw water passage 5 through the injection three-way valve 18a, and the feed pump 6, the precision filter 4, It is injected into the reverse osmosis membrane module 2 through the high pressure pump 7 and the backwashing downstream side three-way valve 8 (strong acidic water injection step). At this time, the high-pressure pump 7 can also pressurize the passing strongly acidic water with a pressure of about 0.5 MPa. Thereby, strong acid water can be reversely osmosis | permeated the reverse osmosis membrane of the reverse osmosis membrane module 2, and the inside of the hollow fiber-shaped reverse osmosis membrane can be sterilized and a scale etc. can be washed. In addition, when the strongly acidic water is permeated into the reverse osmosis membrane, the permeated water flow passage three-way valve 11a is replaced by the permeated water discharge three-way valve
It is switched to the 1 side so that the strongly acidic water can be discharged from the reverse osmosis membrane module 2 by the permeated water discharge three-way valve 11.

In the concentrated water discharge three-way valve 14 and the permeated water discharge three-way valve 11, the raw water remaining in the raw water flow path 5 and the reverse osmosis membrane module 2 is discharged immediately after the feed pump 6 is driven. When the reverse osmosis membrane module 2 is filled with strongly acidic water after a predetermined time is opened, the concentrated water discharge three-way valve 14 and the permeated water discharge three-way valve 11 are closed, and the feed pump 7 and high pressure By stopping the driving of the pump 7, strongly acidic water is retained in the reverse osmosis membrane module 2 (strongly acidic water retention step). In the strongly acidic water retention step, strongly acidic water is retained in the reverse osmosis membrane module 2 for a predetermined time. In the first embodiment, it was retained for 60 minutes.

After the strongly acidic water is retained in the reverse osmosis membrane module 2 in the strongly acidic water retention step, the concentrated water discharge three-way valve 14 is used.
The strongly acidic water in the reverse osmosis membrane module 2 is discharged from. At the time of discharging, the three-way valve 16a for the supply path is set to the strongly acidic water supply path 1
6 to the bypass passage 19, and further to connect the bypass three-way valve 20 to the strong acid water injection passage 18 on the side of connection from the bypass passage 19 to the raw water passage 5 to drive the feed pump 6 for permeation. The permeated water in the water tank 9 is supplied to the permeated water supply passage 1
6, supply path three-way valve 16a, bypass path 19, bypass three-way valve 20, strong acid water injection flow path 18, injection three-way valve 1
8a into the raw water flow path 5, and then into the reverse osmosis membrane module 2 via the feed pump 6, the precision filter 4 and the high-pressure pump 7, and the strong acid water in the line of the filtration device 1 and in the reverse osmosis membrane module 2 is injected. Then, the concentrated water is discharged from the concentrated water discharge three-way valve 14 through the concentrated water flow path 13 (strong acidic water discharge step).

After the step of discharging the strongly acidic water, the permeated water stored in the permeated water tank 9 can be used to flush the reverse osmosis membrane of the reverse osmosis membrane module 2 (washing step). Note that the washing step can be continuously performed following the strongly acidic water discharging step by using the same channel as the permeated water channel used in the strongly acidic water discharging step. Further, in the washing step, the precision filter 4 can be washed by backwashing. On the other hand, the reverse osmosis membrane module 2 cannot perform back washing due to the nature of the reverse osmosis membrane. Precision filter 4
When the backwashing is performed, the backwashing upstream three-way valve 21a is communicated from the permeated water supply passage 16 on the permeate tank 9 side to the backwashing bypass passage 21, and the backwashing three-way valve 8 is backwashed. From the bypass passage 21 for water to the raw water flow passage 5 on the side of the precision filter 4 and driving the backwash pump 22 so that the permeated water in the permeate tank 9 passes through the permeated water supply passage 16 and the upstream three-way valve for backwash 21a. ,
Through the backwash bypass passage 21, the backwash pump 22, the backwash downstream side three-way valve 8, and the high-pressure pump 7, the precision filter 4 is injected, the precision filter 4 is backwashed, and the precision filter discharge passage 4a. Discharge from. At this time, since the high pressure pump 7 is not driven, the permeated water can pass through the high pressure pump 7 without resistance. In addition, the flow path from the strong acid water tank 15 to the precision filter 4 is connected via the backwash bypass path 21, and the backwash pump 22 is driven to store water in the strong acid water tank 15 in this flow path. It is also possible to inject the strong acid water into the precision filter 4, discharge it from the precision filter discharge passage 4a, and backwash the precision filter 4 with the strong acid water.

It is also possible to carry out a strongly acidic water circulating step of circulating strongly acidic water in the reverse osmosis membrane module 2 subsequent to the strongly acidic water pouring step of injecting strongly acidic water into the reverse osmosis membrane module 2. When performing the strongly acidic water circulation step, the backwashing downstream side three-way valve 8, the permeate flow path side three-way valve 11a, the permeated water discharge three-way valve 11, the circulation three-way valve 24, and the backwashing upstream three-way valve 21a are switched. A flow path that circulates from the reverse osmosis membrane module 2 to the reverse osmosis membrane module 2 through the circulation bypass passage 23, the permeated water supply passage 16, and the backwash bypass passage 21 is formed, and the backwash pump 22 is driven. Strongly acidic water is circulated in this flow path (strongly acidic water circulation step). As a result, the strongly acidic water can be circulated in the reverse osmosis membrane module 2, and the reverse osmosis membrane can be sterilized and the calcium content can be washed in a short time. At this time, the backwash pump 22 applies a predetermined pressure to the circulating strongly acidic water to pump the strongly acidic water to the reverse osmosis membrane module 2. As a result, the strong acid water is made to flow into the reverse osmosis membrane of the reverse osmosis membrane module 2 in the reverse osmosis membrane, and the strong acid water is made to flow toward the permeate flow path 10. At this time, the concentrated water discharge three-way valve 14 is closed so that the strongly acidic water in the reverse osmosis membrane module 2 does not flow to the concentrated water channel 13 side. In the first embodiment, the circulation path is formed on the side of the permeated water flow path 10, but a circulation path is formed on the side of the concentrated water flow path 13 and the strong acid water is circulated in the reverse osmosis membrane module 2 by this circulation path. You may do it.

In the first embodiment, the feed pump 6 is used to inject the strongly acidic water into the reverse osmosis membrane module 2, but the feed pump 6 is not limited to this, and for example, the strongly acidic water injection flow may be used. An injection pump or the like may be provided in the passage 18, and the strongly acidic water may be injected into the reverse osmosis membrane module 2 using the injection pump.

As described above, since the filtering device and the backwashing method therefor according to the first embodiment are configured, they have the following actions. (1) The strong acid water generated in the strong acid water generation unit 17 is injected into the reverse osmosis membrane module 2 through the strong acid water injection flow path 18 and the raw water flow path 5, and the inside of the reverse osmosis membrane module 2 is sterilized. Since it is possible to remove bacteria such as bacteria that have propagated on the surface of the reverse osmosis membrane by the strong sterilizing power of the strongly acidic water, the calcium components in the raw water are deposited on the reverse osmosis membrane by the strongly acidic water. It can be dissolved and removed before. (2) Strong acid water injection flow path 18 in the strong acid water injection step
Also, strong acidic water is injected into the reverse osmosis membrane module 2 through the raw water flow path 5, and the strong acidic water is retained in the reverse osmosis membrane module 2 for a predetermined time by the strong acidic water retention step to cause The bacteria can be strongly sterilized, and the strong acid water can be discharged from the concentrated water outlet side of the reverse osmosis membrane module 2 in the strong acid water discharge step. Propagated bacteria and the like can be inactivated and removed, and calcium components and the like in the raw water can be dissolved and removed by strong acid water before being deposited on the reverse osmosis membrane. (3) After the strongly acidic water retention step, the strongly osmotic water can be discharged from the reverse osmosis membrane module 2 using the permeated water, and the next washing step such as flushing can be promptly performed, and the strongly acidic water is inactive. It is possible to wash away the transformed bacteria and the like and dissolved calcium and the like in the washing step. (4) Since the permeated water stored in the permeated water tank 9 can be used as the electrolytic solution when generating the strongly acidic water in the strongly acidic water generating unit 17, the electrolytic solution can be used from other systems or devices. You don't have to get it. (5) Since the strong acidic water tank 15 for storing the strong acidic water is provided, the necessary amount of strong acidic water is generated in the strong acidic water generating unit 17 before the strong acidic water is injected into the reverse osmosis membrane. The water can be stored in the water tank 15 and can be injected at an arbitrary flow rate during injection. (6) By using permeated water generated by filtering raw water in the reverse osmosis membrane module 2 as the cleaning liquid used in the cleaning step, it is not necessary to obtain the cleaning liquid from other systems or devices, A cleaning liquid can be supplied in the filtration device 1.

[0048]

As described above, according to the filtering device and the backwashing method thereof of the present invention, the following advantageous effects can be obtained.

According to the invention described in claim 1, (1) the strongly acidic water produced in the strongly acidic water producing section is injected into the reverse osmosis membrane module through the strongly acidic water injection passage, To provide a filter device excellent in sterilization and cleaning properties that can inactivate and remove bacteria and the like that have propagated on the surface of the reverse osmosis membrane by the strong sterilization power of strongly acidic water. You can (2) It is possible to provide a filtration device having excellent sterilization properties and cleaning properties that can dissolve and remove scales such as calcium in raw water before depositing on a reverse osmosis membrane with strongly acidic water.

According to the invention of claim 2, claim 1
In addition to the effect of (1), since permeated water obtained by filtering raw water with a reverse osmosis membrane can be used as an electrolytic solution when producing strongly acidic water in the strongly acidic water producing section, It is possible to provide a filtration device that can be used alone without the need to obtain an electrolytic solution from a system or device.

According to the invention of claim 3, claim 1
Or, in addition to the effect of (2), (1) a strongly acidic water tank for storing strongly acidic water is provided, so strongly acidic water is required in the strongly acidic water generating part before injecting the strongly acidic water into the reverse osmosis membrane. It is possible to provide a filtration device that can be produced in an amount and stored in a strongly acidic water tank and that can be injected into the reverse osmosis membrane module at an arbitrary flow rate during injection and which can be easily controlled. (2) It is possible to provide a filtration device that can store strongly acidic water generated by another system or device in a strongly acidic water tank and inject it into the reverse osmosis membrane module as needed.

According to the invention described in claim 4, (1) the strong osmotic water produced in the strongly acidic water producing step is passed through the strongly acidic water injecting channel in the strongly acidic water passing step to form the reverse osmosis membrane. Reverse osmosis membrane can be sterilized by injecting water into the module and reverse osmosis membrane module can be sterilized. Therefore, bacteria that have propagated on the surface of the reverse osmosis membrane can be inactivated and removed by the strong sterilizing power of strongly acidic water. A method of cleaning a membrane can be provided. (2) Since no chemical agents such as hydrochloric acid and sulfuric acid are used, hydrochloric acid,
A reverse osmosis membrane that does not require post-treatment such as neutralization after adding sulfuric acid or the like to raw water to make it acidic and can reduce the number of steps of cleaning operation and improve energy saving and labor saving A cleaning method can be provided.

According to the invention of claim 5, claim 4
In addition to the effect of (1), in the strongly acidic water injecting step, strong acidic water is injected into the reverse osmosis membrane module through the strongly acidic water injecting flow path to sterilize the inside of the reverse osmosis membrane module, and the strongly acidic water discharging step Since it can be discharged from the outlet side of the concentrated water of the reverse osmosis membrane module, the bacteria etc. propagated on the surface of the reverse osmosis membrane can be inactivated and removed by the strong disinfecting power of the strongly acidic water. It is possible to provide a method for cleaning a reverse osmosis membrane, in which strongly acidic water is discharged from the reverse osmosis membrane module and the next step such as flushing can be promptly performed.

According to the invention of claim 6, claim 5
In addition to the above effects, (1) bacteria etc. in the reverse osmosis membrane module are inactivated by strong acid water in the strong acid water injection step, and bacteria etc. that remain after the strong acid water is discharged in the strong acid water discharge step It is possible to provide a method for cleaning a reverse osmosis membrane that can wash away calcium components and the like in raw water dissolved in strong acidic water in a cleaning step. (2) Since strongly acidic water is used for sterilization of bacteria and dissolution of calcium and the like, and chemical agents such as hydrochloric acid and sulfuric acid are not used, there is no need for water treatment after discharging strongly acidic water. It is possible to provide a method for cleaning a reverse osmosis membrane, which can achieve downsizing and labor saving.

According to the invention of claim 7, claim 6
In addition to the effect of (1), as the cleaning liquid used in the cleaning step, the permeated water generated by filtering the raw water in the reverse osmosis membrane module is used to obtain the cleaning liquid from other systems or devices. It is possible to provide a method for cleaning a reverse osmosis membrane that can supply a cleaning liquid in the filtration device without the need.

According to the invention described in claim 8, claim 4
In addition to the effect of any one of the items 1 to 7, (1) strong acid water can be retained in the reverse osmosis membrane module for a predetermined time by the strong acid water retention step, so that the reverse osmosis membrane can be made stronger. A method for cleaning a reverse osmosis membrane with excellent sterilization and cleaning properties that can be sterilized with water and dissolves and removes calcium components in raw water with strongly acidic water before depositing on the reverse osmosis membrane. Can be provided.

According to the invention of claim 9, claim 4
In addition to the effect of any one of 8 to 8, (1) strong acid water can be circulated to the reverse osmosis membrane module by the strong acid water circulation step, so that the reverse osmosis membrane can be sterilized in a short time. It is possible to provide a method for cleaning a reverse osmosis membrane which is excellent in sterilization and cleaning ability and which can dissolve calcium components in raw water before being deposited on the reverse osmosis membrane with strongly acidic water.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a filtration device according to a first embodiment.

FIG. 2 is a configuration diagram showing a strongly acidic water generation unit of the filtration device according to the first embodiment.

[Explanation of symbols]

1 Filtration device 2 Reverse osmosis membrane module 2a container 4 Precision filter 4a Discharge path for precision filter 4b Discharge on-off valve 5 Raw water flow path 5a Raw water supply valve 6 feed pump 7 High pressure pump 8 Downstream three-way valve for backwash 9 Permeate water tank 9a Permeate water flow path 9b Open / close valve for permeate water supply 10 Permeate flow path 11 Permeated water discharge three-way valve 11a Three-way valve for permeate flow path 12 Concentrated water tank 12a Concentrated water flow passage 12b Open / close valve for concentrated water supply 13 Concentrated water flow path 14 Three-way valve for discharging concentrated water 15 Strongly acidic water tank 16 Permeate supply channel 16a Three-way valve for supply path 17 Strongly acidic water generator 18 Strong acidic water injection channel 18a Three-way valve for injection 19 Bypass 20 3-way valve for bypass 21 Bypass for backwash 21a Upstream three-way valve for backwash 22 Backwash pump 23 Circulation bypass 24 three-way valve for circulation 31 Electrolyzer 32 Ion-permeable diaphragm 33 Anode chamber 34 Cathode chamber 35 Positive electrode 36 negative electrode 37 Voltage application section 38 Anode water flow path 39 Cathode water flow path 40 Electrolyte addition part 41 Permeate supply pump

Continued front page    F-term (reference) 4D006 GA03 GA07 HA03 KC02 KC03                       KC16 KD11 MA01 MA22 MC18                       MC29 PA01 PB03 PB04 PB06                       PB22 PB27                 4D061 DA02 DB07 EA02 EB02 EB04                       EB13 EB19 ED12

Claims (9)

[Claims] 1. A filter device for filtering raw water through a reverse osmosis membrane to obtain permeated water and concentrated water, wherein an electrolytic cell supplied with an electrolyte solution containing an electrolyte is used as an ion permeable diaphragm for a cathode chamber and an anode chamber. Strongly acidic water that is divided into regions, a negative electrode and a positive electrode are provided in the cathode chamber and the anode chamber, respectively, and a DC voltage is applied between the negative electrode and the positive electrode to generate strongly acidic water in the anode chamber. A generation part, one end of which is connected to the inlet side of the raw water of the reverse osmosis membrane module accommodating the reverse osmosis membrane, and the other end of which is connected to the strong acid water generation part and generated by the strong acid water generation part. A strong acid water injection flow path for injecting the strong acid water thus prepared into the reverse osmosis membrane module. 2. A permeated water tank for storing the permeated water obtained by filtering the raw water through the reverse osmosis membrane, one end of which is connected to the permeated water tank and the other end of which produces the strongly acidic water. The filtration device according to claim 1, further comprising a permeated water supply path that is connected to the portion and that supplies the permeated water to the strongly acidic water generating unit. 3. The filtration device according to claim 1, further comprising a strongly acidic water tank for storing the strongly acidic water injected into the reverse osmosis membrane module. 4. A method for cleaning a reverse osmosis membrane of a filtration device, wherein raw water is filtered by a reverse osmosis membrane to obtain permeated water and concentrated water, wherein an electrolytic cell supplied with an electrolyte solution containing an electrolyte is used as an ion permeable membrane. The cathode chamber and the anode chamber are divided into two regions, and the cathode chamber and the anode chamber are respectively provided with a negative electrode and a positive electrode, and a DC voltage is applied between the negative electrode and the positive electrode to strongly acidic the anode chamber. Reverse osmosis characterized by comprising a strongly acidic water producing step of producing water and a strongly acidic water passing step of letting the strongly acidic water pass through the reverse osmosis membrane module containing the reverse osmosis membrane. Membrane cleaning method. 5. The strongly acidic water injection step of injecting the strongly acidic water into the reverse osmosis membrane module housing the reverse osmosis membrane from the raw water inlet side of the reverse osmosis membrane module in the strongly acidic water passing step. And a step of discharging the strongly acidic water that has been injected into the reverse osmosis membrane module in the strongly acidic water injection step from the outlet side of the concentrated water of the reverse osmosis membrane module. The method for cleaning a reverse osmosis membrane according to claim 4, wherein. 6. The method of cleaning a reverse osmosis membrane according to claim 5, further comprising a cleaning step of cleaning the reverse osmosis membrane with a cleaning liquid after the step of discharging the strongly acidic water. 7. The method for cleaning a reverse osmosis membrane according to claim 6, wherein the permeated water obtained by filtering the raw water through the reverse osmosis membrane is used as the cleaning liquid. 8. The reverse process according to claim 4, further comprising a strong acidic water retention step of retaining the strong acidic water in the reverse osmosis membrane module for a predetermined time. Method for cleaning osmotic membrane. 9. The cleaning of a reverse osmosis membrane according to claim 4, further comprising a strong acid water circulation step of circulating the strong acid water through the reverse osmosis membrane module. Method.