WO2023053678A1

WO2023053678A1 - Ultrapure water production system and ultrapure water production method

Info

Publication number: WO2023053678A1
Application number: PCT/JP2022/028123
Authority: WO
Inventors: 英昭芝尾; 貴次鬼頭; 規彦鈴木; 修平鳥村
Original assignee: 野村マイクロ・サイエンス株式会社
Priority date: 2021-09-30
Filing date: 2022-07-19
Publication date: 2023-04-06
Also published as: TW202330087A; JP2023051430A

Abstract

This ultrapure water production system comprises: a filtration device provided with a filter through which passes water being treated flowing in a main flow path; a reverse osmosis membrane device provided with a reverse osmosis membrane, the reverse osmosis membrane device being positioned downstream from the filtration device in the flow direction of the water being treated; a first injection part for injecting a slime control agent into the main flow path at a portion upstream from the filtration device in the flow direction of the water being treated; and a second injection part for injecting a scale prevention agent into the main flow path at a portion downstream from the filtration device and upstream from the reverse osmosis membrane device in the flow direction of the water being treated.

Description

Ultrapure water production system, ultrapure water production method

The present disclosure relates to an ultrapure water production system and an ultrapure water production method.

In the ultrapure water production system described in JP-A-2021-126624, the slime control agent and scale inhibitor are injected into the storage tank by a chemical injection pump. The pretreated water in the storage tank flows through piping to the reverse osmosis membrane separation device by a high-pressure pump.

The ultrapure water production system consists of a pretreatment system, a primary pure water system, and a secondary pure water system. In the primary pure water system, for example, there are a water pit to store the water treated in the pretreatment system, a supply pump to discharge the water stored in the pit, and a filter to remove suspended solids from the water to be treated. The filtration device provided, the high-pressure pump, and the reverse osmosis membrane device provided with the reverse osmosis membrane are arranged in order from the upstream side in the flow direction of the water to be treated.

In addition, the primary pure water system is equipped with an ultraviolet irradiation device, an ion exchange device, an electrodeionization device (EDI), a membrane deaeration device, a deaeration device (DG), etc., as required.

In the conventional ultrapure water production system, a slime control agent that suppresses the adhesion of slime to the reverse osmosis membrane and a scale inhibitor that suppresses the adhesion of scale to the reverse osmosis membrane are supplied by discharging the water stored in the pit. The water was injected into the upstream side of the pump or the upstream side of the high-pressure pump that supplies the water to be treated to the reverse osmosis membrane device.

In general, it is believed that slime control agents and scale inhibitors need to be uniformly mixed with the water to be treated in order to fully demonstrate their performance. For this reason, for example, a slime control agent and a scale inhibitor may be injected upstream with respect to the pump. Furthermore, in some cases, a device such as an in-line mixer that promotes mixing of the agents is installed on the downstream side of the injection positions of the slime control agent and the scale inhibitor.

Also, in general, the injection positions of the slime control agent and the scale inhibitor are often almost the same. By installing the supply system of the slime control agent and the scale inhibitor at the same place, the piping of the supply system can be shortened. Furthermore, since the supply system piping is shortened, troubles in the piping system are reduced, and operation management and maintenance are facilitated.

In such a configuration in which the two types of chemicals described above are injected into the reverse osmosis membrane, if a filtration device is provided upstream of the reverse osmosis membrane device, the filter of the filtration device may be clogged with slime (contaminants). often occurred. There was a problem that clogging of this filter had to be suppressed.

In addition, it has become clear that the filter of the filtration device tends to become clogged when two types of chemicals are injected just before the water pit (storage tank) to be treated or the supply pump. This is presumably because the anti-scaling agent serves as a nutrient for the bacteria, and the bacteria grow and adhere to the filter. In addition, it is considered that the bacteria grow and adhere to the filter, causing clogging of the filter during long-term continuous operation, resulting in a decrease in the amount of water permeated through the filter.

The problem of the present disclosure is to suppress the decrease in the amount of water permeated through the filter during long-term continuous operation compared to the case where the slime control agent and scale inhibitor are injected upstream of the filtration device.

As a result of a sincere study, the inventors found that the injection position of the scale inhibitor and slime control agent significantly affects clogging of the filter of the filtration device. By optimizing the injection position, clogging of the filter can be substantially suppressed, and the invention has been completed.

The ultrapure water production system of the first aspect includes a filtration device provided with a filter through which water to be treated flowing in a main flow path passes, and a reverse osmosis membrane disposed downstream of the filtration device in the flow direction of the water to be treated. a reverse osmosis membrane device provided with, a first injection part for injecting a slime control agent upstream of the filtration device in the flow direction of the water to be treated, and a downstream side of the filtration device in the flow direction of the water to be treated and a second injection part for injecting a scale inhibitor upstream of the reverse osmosis membrane device.

In the first aspect, the first injection section injects the slime control agent upstream of the filtration device in the flow direction of the water to be treated. As a result, it is possible to suppress the adhesion of slime to the filter by suppressing the growth of bacteria and the attachment of the bacteria to the filter provided in the filtering device.

In addition, the second injection unit injects the anti-scaling agent downstream of the filtration device and upstream of the reverse osmosis membrane device in the flow direction of the water to be treated. As a result, the anti-scaling agent serves as a nutrient for the bacteria, and there is no risk of the bacteria growing and adhering to the filter.

From the above, compared to the case where the slime control agent and scale inhibitor are injected upstream of the filtration device, it is possible to suppress the decrease in the amount of water permeated through the filter during long-term continuous operation.

A second aspect of the ultrapure water production system is the ultrapure water production system according to the first aspect, comprising an activated carbon device arranged upstream of the filtering device in the flow direction of the water to be treated, The injection part is characterized by injecting the slime control agent upstream of the filtering device and downstream of the activated carbon device in the flow direction of the water to be treated.

In the second aspect, the first injection section injects the slime control agent upstream of the filtration device and downstream of the activated carbon device in the flow direction of the water to be treated. As a result, the slime control agent is not adsorbed to the activated carbon by the adsorption treatment of the activated carbon device. Therefore, a small amount of the chemical suppresses bacteria from multiplying and adhering to the filter.

As described above, compared with the case where the slime control agent is injected upstream of the activated carbon device in the flow direction of the water to be treated, a small amount of the agent can suppress bacteria from multiplying and adhering to the filter. .

A third aspect of the ultrapure water production system is the ultrapure water production system according to the first or second aspect, wherein the first injection part and the second injection part suck out the chemical in the tank by their respective ejectors. In the main flow path, driving water is injected into each ejector of the first injection section and the second injection section from a branch flow path branching from the downstream side of the reverse osmosis membrane device in the flow direction of the water to be treated. The ejector of the first injection part is arranged in a first unique channel having one end connected to the branch channel and the other end connected to the upstream side of the filtering device, The ejector of the second injection part has a second unique flow path, one end of which is connected to the branch flow path, and the other end of which is connected to the downstream side of the filtering device and the upstream side of the reverse osmosis membrane device. It is characterized in that it is arranged in

In the third aspect, a common pump causes the water to be treated to flow through the branch flow paths and further through the first inherent flow path and the second inherent flow path. The slum control agent flows out of the tank of the first injection section, flows into the ejector, and joins the first inherent flow path. The combined slime control agent flows through the first unique channel and is injected into the upstream side of the filtration device.

On the other hand, the anti-scaling agent flows out from the tank of the second injection part, flows into the ejector, and joins the second unique flow path. The combined anti-scaling agent flows through the second unique flow path and is injected downstream of the filtration device and upstream of the reverse osmosis membrane device.

As described above, the number of pumps can be reduced compared to the case of having both a pump for sucking the medicine from the tank of the first injection part and a pump for sucking the medicine from the tank of the second injection part.

A fourth aspect of the ultrapure water production system is the ultrapure water production system according to any one aspect of the first to third aspects, wherein the first injection section controls slime for the water to be treated flowing through the main flow path. The slime control agent is injected so that the concentration of the agent is 1 ppm or more and 100 ppm or less.

In the fourth aspect, the slime control agent with a concentration of 1 ppm or more and 100 ppm or less is injected into the water to be treated flowing through the main flow path. This effectively suppresses bacteria from multiplying and adhering to the filter, thereby suppressing a decrease in the amount of water permeated through the filter during long-term continuous operation.

An ultrapure water production system according to a fifth aspect is the ultrapure water production system according to any one aspect of the first to fourth aspects, wherein the second injection section prevents the water to be treated flowing through the main flow path from scaling. The anti-scaling agent is injected so that the concentration of the agent is 1 ppm or more and 100 ppm or less.

In the fifth aspect, the anti-scaling agent with a concentration of 1 ppm or more and 100 ppm or less is injected into the water to be treated flowing through the main flow path. As a result, adhesion of scale to the reverse osmosis membrane is effectively suppressed, and a decrease in the amount of water permeated through the reverse osmosis membrane can be suppressed in long-term continuous operation.

In the ultrapure water production method of the sixth aspect, the water to be treated flowing through the main flow channel is filtered to remove suspended solids, the water to be treated generated by the filtration is treated with a reverse osmosis membrane to remove salts, and the A slime control agent is injected upstream of the filtration process in the flow direction of the treated water, and scale prevention is performed downstream of the filtration process and upstream of the reverse osmosis membrane process in the flow direction of the water to be treated. It is characterized by injecting a drug.

In the sixth aspect, the slime control agent is injected upstream of the filtration process in the flow direction of the water to be treated. This suppresses the growth and adhesion of bacteria to the filter provided in the filtering device, thereby suppressing the adhesion of slime to the filter.

Moreover, in the flow direction of the water to be treated, the scale inhibitor is injected downstream of the filtration process and upstream of the reverse osmosis membrane process. As a result, the anti-scaling agent does not permeate the filter of the filtration device. In other words, the anti-scaling agent serves as a nutrient for bacteria, and there is no fear that the bacteria will multiply and adhere to the filter.

From the above, compared to the case where the slime control agent and scale inhibitor are injected on the upstream side of the filtration process, it is possible to suppress the decrease in the permeation amount of the filter during long-term continuous operation.

A seventh aspect of the ultrapure water production method is the ultrapure water production method according to the sixth aspect, wherein natural organic matter is removed by adsorption treatment on the water to be treated on the upstream side of the filtration treatment in the flow direction of the water to be treated. and the slime control agent is injected downstream of the adsorption treatment in the flow direction of the water to be treated.

In the seventh aspect, the slime control agent is injected downstream of the adsorption treatment in the flow direction of the water to be treated. As a result, the slime control agent is not adsorbed to the activated carbon by the adsorption treatment of the activated carbon device. Therefore, a small amount of the chemical suppresses bacteria from multiplying and adhering to the filter.

As described above, compared with the case where the slime control agent is injected upstream of the adsorption treatment in the flow direction of the water to be treated, a small amount of the agent can suppress bacteria from growing and adhering to the filter. .

The ultrapure water production method of the eighth aspect is the ultrapure water production method according to the sixth or seventh aspect, wherein the concentration of the slime control agent in the water to be treated flowing through the main flow channel is 1 ppm or more and 100 ppm or less. , characterized by injecting a slime control agent.

In the eighth aspect, the concentration of the slime control agent in the water to be treated flowing through the main flow path is 1 ppm or more and 100 ppm or less. This effectively suppresses bacteria from multiplying and adhering to the filter, and can suppress a decrease in the amount of water permeated through the filter during long-term continuous operation.

A ninth aspect of the ultrapure water production method is the ultrapure water production method according to any one of the sixth to eighth aspects, wherein the concentration of the scale inhibitor in the water to be treated flowing through the main flow channel is 1 ppm or more and 100 ppm. It is characterized by injecting a scale inhibitor as follows.

In the ninth aspect, the concentration of the scale inhibitor in the water to be treated flowing through the main flow path is 1 ppm or more and 100 ppm or less. As a result, adhesion of scale to the reverse osmosis membrane is effectively suppressed, and a decrease in the amount of water permeated through the reverse osmosis membrane can be suppressed in long-term continuous operation.

In the present disclosure, compared to the case of injecting the slime control agent and scale inhibitor into the upstream side of the filtration device, it is possible to suppress the decrease in the amount of water permeated through the filter during long-term continuous operation.

1 is a schematic configuration diagram showing an ultrapure water production system according to this embodiment; FIG. It is drawing which showed the evaluation graph about the Example which concerns on this embodiment, and the comparative example with respect to an Example.

An ultrapure water production system 10 and an ultrapure water production method according to this embodiment will be described below with reference to FIGS. This ultrapure water production system 10 includes a primary pure water device 12 and a secondary pure water device 112 .

(Primary pure water device 12)
As shown in FIG. 1, the primary pure water device 12 includes a water pit 14 in which water to be treated is stored, a first pump 18, a flow meter (FIQ) 20, a heat exchanger (HEX) 22, an activated carbon device (AC) 24 , ultraviolet oxidizer (UV) 26 and filtration device 30 . Further, the primary pure water device 12 includes a second pump 34, a first reverse osmosis membrane device (RO) 38, a deionized water pit 40, an electrodeionization device (EDI) 42, an ion exchange resin device (MB) 44, and a pure water tank 46 .

Then, along the main flow path 100 in which the water to be treated flows, the water to be treated pit 14, the first pump 18, the flow meter 20, the heat exchanger 22, the activated carbon device 24, An ultraviolet oxidation device 26, a filtration device 30, a second pump 34, a first reverse osmosis membrane device 38, a deionized water pit 40, an electrodeionization device 42, an ion exchange resin device 44, and a pure water tank 46 are lined up. . The first reverse osmosis membrane device 38 is an example of a reverse osmosis membrane device.

In addition, the primary pure water device 12 includes a second reverse osmosis membrane device (RO) 48 arranged in a branch channel 102 branching from the first reverse osmosis membrane device 38, and a drug injection system for injecting a drug into the main channel 100. 60.

Each device will be described below.
The to-be-treated water pit 14 stores to-be-treated water (liquid up to ultrapure water). The water to be treated is raw water, and examples of the water to be treated include industrial water, tap water, groundwater, and river water. The first pump 18 causes the water to be treated stored in the water to be treated pit 14 to flow downstream in the direction of flow of the water to be treated (hereinafter sometimes referred to as "water flow direction") along the main flow path 100. .

The flow meter 20 measures the flow rate of the water to be treated flowing through the main flow path 100 . The heat exchanger 22 adjusts the temperature of the water to be treated by heat exchange. The activated carbon device 24 removes natural organic matter, residual chlorine, trihalomethane, etc. from the water to be treated by adsorption treatment. The ultraviolet oxidation device 26 sterilizes the water by irradiating it with ultraviolet rays to decompose viable germs, bacteria, and the like contained in the water to be treated.

The filtering device 30 is provided with a filter (pre-filter) through which the water to be treated passes. Then, the filtering device 30 removes suspended matter such as residual chlorine, free chlorine, or fine particles by filtering. Here, as the water to be treated passes through the filter, microorganisms such as bacteria and algae that do not pass through the filter are removed by the filter. Generally, the UV oxidation device 26 located upstream of the filter device 30 will not cause any problems because the growth of bacteria and algae will be suppressed. However, under certain conditions, slime (contaminants) may be formed by some bacteria and algae (microorganisms) whose growth is not controlled.

A microfilter for turbidity removal can be used as the prefilter. Either depth type or surface filtration type filters can be used. Filtration accuracy is preferably 0.5 to 50 μm, preferably 1 to 10 μm. As for the shape, a cartridge type, a non-woven fabric type, a spool type, a pleated type, a bag type, etc. can be used. As materials, organic polymer materials such as polyethylene and polypropylene, and metal materials such as stainless steel can be used. Specifically, Micro-Wind thread-wound filter cartridge, NW series (manufactured by Sumitomo 3M), Micro-Klean (TM) thread-wound filter cartridge, D series (manufactured by Sumitomo 3M), thread-wound filter cartridge, WF series (manufactured by BJY Corporation), bag-type filters, and BF series (manufactured by BJY Corporation) are exemplified. Filters with added adsorption performance such as activated carbon filters and ion exchange filters are not preferable because they may adsorb slime control agents and scale inhibitors.

The second pump 34 is a high-pressure pump, and flows the water to be treated from which impurities have been removed by the filtration device 30 to the first reverse osmosis membrane device 38 .

The first reverse osmosis membrane device 38 is provided with a reverse osmosis membrane through which the water to be treated permeates. and separate the water to be treated. As the water to be treated passes through the reverse osmosis membrane in this way, there is a risk that scale such as silica and calcium that has not passed through the reverse osmosis membrane will adhere to the reverse osmosis membrane. In addition, slime (contaminants) formed by microorganisms such as bacteria and algae that have not permeated the reverse osmosis membrane may adhere to the reverse osmosis membrane. In addition, the scale is a precipitated and hardened substance such as calcium or silica dissolved in a liquid.

The deionized water pit 40 temporarily stores permeated water that has passed through the reverse osmosis membrane of the first reverse osmosis membrane device 38 . The electrodeionization device 42 performs deionization while electrically regenerating the water to be treated (permeated water). The ion exchange resin device 44 is a mixed bed type ion exchange device of anion resin and cation resin, and removes inorganic ions from the water to be treated. The pure water tank 46 stores primary pure water produced by the primary pure water device 12 .

[Second reverse osmosis membrane device 48]
The second reverse osmosis membrane device 48, as shown in FIG. 1, is arranged in the middle of a branch channel 102 branching from the first reverse osmosis membrane device 38. As shown in FIG. The branch channel 102 is a channel through which the concentrated water separated by the first reverse osmosis membrane device 38 flows, one end of which is connected to the first reverse osmosis membrane device 38 and the other end of which is connected to the water pit 14 to be treated. ing.

The second reverse osmosis membrane device 48 is provided with a reverse osmosis membrane through which the concentrated water permeates. It is separated into treated water from which ions and salts have been removed and waste water (oxidized water). Drainage is stored in the drainage pit 52 and treated water is returned to the treated water pit 14 .

As the concentrated water permeates the reverse osmosis membrane of the second reverse osmosis membrane device 48 in this way, the reverse osmosis membrane of the second reverse osmosis membrane device 48 contains silica, calcium, etc. that did not permeate the reverse osmosis membrane. scale may adhere. Furthermore, the reverse osmosis membrane of the second reverse osmosis membrane device 48 may be contaminated with slime (contaminants) formed by microorganisms such as bacteria and algae that have not permeated the reverse osmosis membrane.

[Drug injection system 60]
The drug injection system 60 includes a third pump 50, a first injection section 62, and a second injection section 82, as shown in FIG. A third pump 50 is arranged in a branched channel 104 a having one end connected to the deionized water pit 40 . The third pump 50 is an example of a pump.

<First injection part 62>
The first injection part 62 has one end connected to the other end of the branch channel 104a and the other end connected to the channel 100a in the main channel 100 between the ultraviolet oxidation device 26 and the filter device 30. A first ejector 64 is arranged in the unique channel 104b. Furthermore, the first injection part 62 includes a first tank 70 in which a liquid slime control agent is stored, a first flow meter (FIQ) 66 and a first flow control valve (FCV) 68 .

Also, the first flow meter 66 and the first flow control valve 68 are arranged in the first injection flow path 106 connecting the first tank 70 to the suction port 64 a of the first ejector 64 . Specifically, the first flow meter 66 and the first flow control valve 68 are arranged in this order from the first tank 70 toward the suction port 64 a of the first ejector 64 .

The slime control agents stored in the first tank 70 are mainly classified into hydrazine-based, organic nitrogen-based, aromatic-based, and silver ion-based agents. Specifically, slime control agents include 2,2-dibromo-3-nitropropionate, 5-chloro-2-methyl-4-isothiazolin-3-one (Cl-MIT), 2-methyl-4- isothiazolin-3-one (MIT), 4,5-dichloro-1,2-dithiolan-3-one, 2-bromo-2-nitropropane-1,3-diol, benzisothiazolin-3-one, glutaraldehyde , silver compounds such as silver nitrate and silver sulfate, copper compounds such as copper sulfate and copper nitrate, and nickel compounds such as nickel chloride and nickel sulfate.

In this configuration, the first flow control valve 68 is controlled based on the measurement data of the first flow meter 66 and the measurement data of the flow meter 20. As a result, the slime control agent flows through the first injection channel 106 and passes through the first ejector 64 to the first It merges with the unique channel 104b. Furthermore, the slime control agent that joins the first unique channel 104b and flows is injected into the channel 100a in the portion between the ultraviolet oxidation device 26 and the filtering device 30. As shown in FIG. In other words, the first injection part 62 injects the slime control agent into the channel 100 a between the ultraviolet oxidation device 26 and the filtering device 30 . If the ultraviolet oxidation device 26 is not installed, the first injection section 62 injects the slime control agent into the flow path 100a between the activated carbon device 24 and the filter device 30 .

The slime control agent is contained in the water to be treated flowing through the channel 100a. The slime control agent contained in the water to be treated flows through the main flow path 100 and permeates the filter of the filtration device 30 to reach the first reverse osmosis membrane device 38 . The slime control agent that reaches the first reverse osmosis membrane device 38 is contained in the concentrated water without passing through the reverse osmosis membrane of the first reverse osmosis membrane device 38 and flows through the branch channel 102 . Here, the concentration of the slime control agent contained in the concentrated water without passing through the reverse osmosis membrane of the first reverse osmosis membrane device 38 is the concentration of the slime control agent in the state before reaching the first reverse osmosis membrane device 38. higher compared to

Furthermore, the concentrated water containing the highly concentrated slime control agent flows through the branch channel 102 and reaches the second reverse osmosis membrane device 48 . The slime control agent that reaches the second reverse osmosis membrane device 48 is included in the wastewater without permeating the reverse osmosis membrane of the second reverse osmosis membrane device 48 and is discharged to the wastewater pit 52 .

<Second injection part 82>
The second injection part 82 has one end connected to the other end of the branch channel 104a and the other end connected to the channel 100b in the main channel 100 between the filtering device 30 and the second pump 34. A second ejector 84 is arranged in the second unique channel 104c. Furthermore, the second injection part 82 includes a second tank 90 in which a liquid scale inhibitor is stored, a second flow meter (FIQ) 86 and a second flow control valve (FCV) 88 .

Also, the second flow meter 86 and the second flow control valve 88 are arranged in the second injection flow path 108 connecting the second tank 90 to the suction port 84 a of the second ejector 84 . Specifically, the second flow meter 86 and the second flow control valve 88 are arranged in this order from the second tank 90 toward the suction port 84 a of the second ejector 84 .

In addition, scale inhibitors are mainly classified into phosphonic acid-based, polycarboxylic acid-based, and acrylic acid-based. Specifically, the scale inhibitors include the "Orpersion" series manufactured by Organo Corporation, the "Flocon (registered trademark)" series manufactured by BWA Water Additives, the "PermaTreat (registered trademark)" series manufactured by Nalco, "Hypersperse (registered trademark)" series manufactured by General Electric Company, "Kuriverter (registered trademark)" series manufactured by Kurita Water Industries Ltd., and the like.

In this configuration, the second flow control valve 88 is controlled based on the measurement data of the second flow meter 86 and the measurement data of the flow meter 20. As a result, the anti-scaling agent flows through the second injection passage 108 and passes through the second ejector 84 so that the concentration of the anti-scaling agent in the water to be treated flowing through the main passage 100 is 1 ppm or more and 100 ppm or less. It merges with the unique channel 104c. Furthermore, the anti-scaling agent that joins the second unique flow path 104 c is injected into the flow path 100 b in the portion between the filtering device 30 and the second pump 34 . In other words, the second injection section 82 injects the anti-scaling agent into the flow path 100b in the portion between the filtering device 30 and the second pump 34 .

The scale inhibitor is contained in the water to be treated flowing through the flow path 100b. The scale inhibitor contained in the water to be treated flows through the main flow path 100 and reaches the first reverse osmosis membrane device 38 . The anti-scaling agent that reaches the first reverse osmosis membrane device 38 is contained in the concentrated water without permeating the reverse osmosis membrane of the first reverse osmosis membrane device 38 and flows through the branch channel 102 . Here, the concentration of the scale inhibitor contained in the concentrated water without passing through the reverse osmosis membrane of the first reverse osmosis membrane device 38 is the concentration of the scale inhibitor in the state before reaching the first reverse osmosis membrane device 38. higher compared to

Further, the concentrated water containing the highly concentrated scale inhibitor flows through the branch channel 102 and reaches the second reverse osmosis membrane device 48 . The anti-scaling agent that has reached the second reverse osmosis membrane device 48 is contained in the wastewater without permeating the reverse osmosis membrane of the second reverse osmosis membrane device 48 and is discharged to the wastewater pit 52 .

(Secondary pure water device 112)
The secondary pure water device 112 is arranged downstream of the pure water tank 46 in the direction of water flow, as shown in FIG.

In this configuration, the secondary pure water device 112 further removes impurities from the primary pure water. The ultrapure water obtained by the secondary pure water device 112 is sent to the point of use 120 where it is used. Of the ultrapure water sent to the point of use 120, the ultrapure water that has not been used is directly returned to the pure water tank 46 and stored in the pure water tank 46 together with the primary pure water.

(Example 1, Comparative Example 1, Comparative Example 2)
Next, the present application will be described in more detail by way of Example 1 and Comparative Examples 1 and 2 for Example 1. FIG. However, the present application is not limited to the contents of the following examples.

[Comparative Example 1]
In Comparative Example 1, a scale inhibitor and a slime control agent are injected downstream of the filtering device 30 in the direction of water flow. Specifically, a scale inhibitor and a slime control agent are injected into the channel 100b shown in FIG.

[Comparative Example 2]
In Comparative Example 2, a scale inhibitor and a slime control agent are injected upstream of the filtering device 30 in the direction of water flow. Specifically, a scale inhibitor and a slime control agent are injected into the channel 100a shown in FIG.

[Comparative Example 3]
In Comparative Example 3, the scale inhibitor is injected upstream of the filtering device 30 in the water flow direction, and the slime control agent is injected downstream of the filtering device 30 . Specifically, a scale inhibitor is injected into the flow path 100a shown in FIG. 1, and a slime control agent is injected into the flow path 100b.

[Example 1]
In Example 1, the slime control agent is injected upstream of the filtering device 30 in the direction of water flow, and the anti-scaling agent is injected downstream of the filtering device 30 . Specifically, the slime control agent is injected into the channel 100a shown in FIG. 1, and the scale inhibitor is injected into the channel 100b.

[Evaluation conditions]
Flux 20m/h, filtration accuracy (nominal) 1μm, filter type bag type.
In Comparative Example 1, Comparative Example 2, and Example 1, the evaluation conditions other than the drug injection position are all the same.

〔Evaluation results〕
FIG. 2 graphically shows the evaluation results of Comparative Example 1 and Example 1. As shown in FIG. The vertical axis of the graph is the difference between the water pressure on the upstream side and the water pressure on the downstream side of the filtration device 30 (water flow differential pressure), and the horizontal axis is the time for the water to be treated to permeate the filtration device 30 (general water time).

As for Comparative Example 1, as shown in the graph of FIG. 2, the change in the water flow differential pressure increases after about seven days of continuous operation. This is the level at which functional problems arise, resulting in shutdown or replacement of the filter.

As for Comparative Example 2, similar to Comparative Example 1, the change in the water flow differential pressure increases after approximately seven days of continuous operation. This is the level at which functional problems arise, resulting in shutdown or replacement of the filter.

As for Comparative Example 3, similar to Comparative Example 1, the change in the water flow differential pressure increases after approximately seven days of continuous operation. This is the level at which functional problems arise, resulting in shutdown or replacement of the filter.

As for Example 1, as shown in the graph of FIG. 2, the change in the water flow differential pressure is small after 50 days of continuous operation. That is, as compared with Comparative Examples 1, 2 and 3, the decrease in the amount of water permeated through the filter is suppressed in long-term continuous operation. This is not a level at which functional problems occur, and operation can be continued.

(summary)
As described above, the first injection unit 62 injects the slime control agent into the channel 100a between the ultraviolet oxidation device 26 and the filtering device 30. As shown in FIG. The slime control agent contained in the water to be treated flows through the main flow path 100 and permeates the filter of the filtering device 30 . This suppresses the growth of bacteria adhering to the filter.

In addition, in general, when injecting a chemical into a water purifier, it is required to uniformly mix the chemical. Thus, for example, medication is injected upstream with respect to the pump. However, in the case of the method of the present invention, the injected slime control agent reaches the filter without being uniformly mixed, so that a higher effect of suppressing slime generation can be obtained. It is presumed that the filter media in contact with the slime control agent of high concentration is highly effective in suppressing the generation of slime. In addition, since the high-concentration slime control agent comes into contact with the filter media in sequence, the generation of slime can finally be suppressed in the entire filter.

In order to achieve the above effect, it is more preferable not to install a device such as an in-line mixer or a pump that promotes mixing of the drug between the downstream side of the injection position of the drug and the filtering device 30 .

On the other hand, the second injection part 82 injects the scale inhibitor into the channel 100b between the filtering device 30 and the second pump 34 . As a result, the anti-scaling agent does not permeate the filter of the filtration device. In other words, the anti-scaling agent serves as a nutrient for bacteria, and there is no fear that the bacteria will multiply and adhere to the filter.

As described above, in the ultrapure water production system 10 and the ultrapure water production method, compared to the case where the slime control agent and the scale inhibitor are injected upstream of the filtration device 30, the amount of water permeated through the filter during long-term continuous operation can be suppressed.

Also, the first injection part 62 injects the slime control agent into the channel 100a on the downstream side of the activated carbon device 24 in the water flow direction. Therefore, the slime control agent does not pass through the activated carbon device 24 . That is, the adsorption treatment of the activated carbon device 24 does not cause the slime control agent to be adsorbed to the activated carbon. Therefore, a small amount of the chemical suppresses the growth of bacteria on the filter.

Similarly, when the ultraviolet oxidation device 26 is installed, it is preferable to inject the slime control agent downstream of the ultraviolet oxidation device 26 in order to avoid ultraviolet decomposition of the slime control agent in the ultraviolet oxidation device 26 . . It should be noted that when the method of the present disclosure is used, the growth of bacteria on the filter is suppressed by the slime control agent, so the ultraviolet oxidation device 26 does not have to be installed.

As described above, in the ultrapure water production system 10 and the ultrapure water production method, compared with the case where the slime control agent is injected upstream of the activated carbon device 24 in the flow direction of the water to be treated, a small amount of the agent It can remarkably suppress bacteria from growing and adhering to the filter.

Also, the third pump 50 is arranged in a branched flow path 104 a having one end connected to the deionized water pit 40 . Furthermore, the third pump 50 causes part of the water to be treated stored in the deionized water pit 40 to flow through the first unique channel 104b and the second unique channel 104c. Then, the slime control agent flows through the first injection channel 106, passes through the first ejector 64, and joins the first unique channel 104b. Also, the anti-scaling agent flows through the second injection channel 108, passes through the second ejector 84, and joins the second unique channel 104c.

Thus, the common third pump 50 causes the water to be treated to flow through the first unique channel 104b and the second unique channel 104c.
From the above, compared to the case of having both a pump for sucking the slime control agent from the first tank 70 of the first injection part 62 and a pump for sucking the scale inhibitor from the second tank 90 of the second injection part 82 , the number of pumps can be reduced.

Also, the slime control agent contained in the water to be treated flows through the main flow path 100 and permeates the filter of the filtration device 30 to reach the first reverse osmosis membrane device 38 . Furthermore, the scale inhibitor contained in the water to be treated flows through the main flow path 100 and reaches the first reverse osmosis membrane device 38 .

As described above, in the ultrapure water production system 10 and the ultrapure water production method, adhesion of slime to the reverse osmosis membrane provided in the first reverse osmosis membrane device 38 is suppressed. Furthermore, adhesion of scale to the reverse osmosis membrane provided in the first reverse osmosis membrane device 38 is suppressed. As a result, in long-term continuous operation, it is possible to suppress a decrease in the amount of water permeated through the reverse osmosis membrane provided in the first reverse osmosis membrane device 38 .

Also, the concentrated water containing the highly concentrated slime control agent reaches the second reverse osmosis membrane device 48 . Further, the concentrated water containing the highly concentrated scale inhibitor reaches the second reverse osmosis membrane device 48 .

As described above, in the ultrapure water production system 10 and the ultrapure water production method, adhesion of slime to the reverse osmosis membrane provided in the second reverse osmosis membrane device 48 is suppressed. Furthermore, adhesion of scale to the reverse osmosis membrane provided in the second reverse osmosis membrane device 38 is suppressed. Thereby, in long-term continuous operation, it is possible to suppress a decrease in the amount of water permeated through the reverse osmosis membrane provided in the second reverse osmosis membrane device 48 .

Also, the first injection unit 62 injects the slime control agent so that the concentration of the slime control agent in the water to be treated flowing through the main flow path 100 is 1 ppm or more and 100 ppm or less. For this reason, slime adheres to the filter provided in the filtration device 30, slime adheres to the reverse osmosis membrane provided in the first reverse osmosis membrane device 38, and the reverse osmosis membrane provided in the second reverse osmosis membrane device 48 Adhesion of slime to can be effectively suppressed. In order to fully exhibit the effect of the present disclosure, the concentration of the slime control agent is more preferably 2-20 ppm. 4 to 10 ppm is more preferred.

In addition, the second injection unit 82 injects the anti-scaling agent so that the concentration of the anti-scaling agent in the water to be treated flowing through the main flow path 100 is 1 ppm or more and 100 ppm or less. Therefore, the adhesion of scale to the reverse osmosis membrane provided in the first reverse osmosis membrane device 38 and the adhesion of scale to the reverse osmosis membrane provided in the second reverse osmosis membrane device 48 can be effectively suppressed. can. In order to fully exhibit the effects of the present disclosure, the concentration of the scale inhibitor is more preferably 2 to 20 ppm. 4 to 10 ppm is more preferred.

In the above description, the slime control agent is injected into the channel 100a on the downstream side of the activated carbon device 24, but the slime control agent may be injected on the upstream side of the activated carbon device 24. In this case, the effect achieved by injecting the slime control agent into the channel 100a on the downstream side of the activated carbon device 24 is not exhibited.

Also, in the above description, the third pump 50 is arranged in the branch channel 104a with one end connected to the deionized water pit 40 . Also, the first unique channel 104b and the second unique channel 104c are connected to the branch channel 104a. However, if the first intrinsic flow path is connected to the deionized water pit 40 and the second intrinsic flow path is connected to the deionized water pit 40, the first intrinsic flow path and the second intrinsic flow path You may arrange|position a pump to each. In this case, the effect of the arrangement of the third pump 50 in the branch flow path 104a is not achieved.

Claims

a filtration device provided with a filter through which the water to be treated flowing through the main flow path passes;
a reverse osmosis membrane device disposed downstream of the filtering device in the flow direction of the water to be treated and provided with a reverse osmosis membrane;
a first injection part for injecting a slime control agent upstream of the filtration device in the flow direction of the water to be treated;
a second injection section for injecting a scale inhibitor downstream of the filtration device and upstream of the reverse osmosis membrane device in the flow direction of the water to be treated;
An ultrapure water production system.
an activated carbon device arranged upstream of the filtration device in the flow direction of the water to be treated,
The first injection part injects the slime control agent upstream of the filtration device and downstream of the activated carbon device in the flow direction of the water to be treated.
The ultrapure water production system according to claim 1.
The first injection part and the second injection part are configured to suck out the medicine in the tank by each ejector and inject it into the main flow path,
a common pump that supplies drive water to the respective ejectors of the first injection section and the second injection section from a branch flow path branching from the downstream side of the reverse osmosis membrane device in the flow direction of the water to be treated;
The ejector of the first injection section is arranged in a first unique flow path having one end connected to the branch flow path and the other end connected to the upstream side of the filtering device, and the ejector of the second injection section is , one end is connected to the branch channel and the other end is arranged in a second unique channel connected to the downstream side of the filtration device and the upstream side of the reverse osmosis membrane device;
The ultrapure water production system according to claim 1.
The first injection part injects the slime control agent so that the concentration of the slime control agent in the water to be treated flowing through the main flow channel is 1 ppm or more and 100 ppm or less.
The ultrapure water production system according to claim 1.
The second injection unit injects the anti-scaling agent so that the concentration of the anti-scaling agent in the water to be treated flowing through the main flow path is 1 ppm or more and 100 ppm or less.
The ultrapure water production system according to any one of claims 1 to 4.
removing suspended solids by filtering the water to be treated flowing through the main flow channel;
Salts are removed by reverse osmosis membrane treatment of the water to be treated generated in the filtration treatment,
Injecting a slime control agent upstream of the filtration treatment in the flow direction of the water to be treated,
A method for producing ultrapure water, in which a scale inhibitor is injected downstream of the filtration process and upstream of the reverse osmosis membrane process in the flow direction of the water to be treated.
removing natural organic matter by adsorption treatment on the water to be treated on the upstream side of the filtration treatment in the flow direction of the water to be treated;
injecting a slime control agent downstream of the adsorption treatment in the direction of flow of the water to be treated;
The method for producing ultrapure water according to claim 6.
Injecting the slime control agent so that the concentration of the slime control agent with respect to the water to be treated flowing through the main flow channel is 1 ppm or more and 100 ppm or less.
The method for producing ultrapure water according to claim 6.
Injecting the anti-scaling agent so that the concentration of the anti-scaling agent with respect to the water to be treated flowing through the main flow channel is 1 ppm or more and 100 ppm or less.
The method for producing ultrapure water according to any one of claims 6 to 8.