JP2002361246A - Method and device for manufacturing drinking water - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method by which drinking water of stable quality can be mass-produced on an industrial scale for a long period by combining selective adsorption/separation of boron by a boron-selective resin with RO treatment. SOLUTION: The method for manufacturing drinking water has primary treatment in which pretreatment for removing suspended matter in raw water is executed and then pretreated water is made to pass through a reverse osmosis membrane, secondary treatment in which boron is removed by making membrane-permeated water of the first treatment pass through the boron- selective resin and neutralization treatment for neutralizing water after secondary treatment. Raw water containing boron ions is subjected to the primary treatment, the secondary treatment, and the neutralization treatment, and drinking water is manufactured. Hydrogen ion concentration (pH) of the water after the secondary treatment is continuously monitored, and when pH of the water after the secondary treatment is below 10, water flow is interrupted and a mineral acid is passed to remove boron. Then, regeneration in which the boron- selective resin is treated by passing a caustic alkali is performed and drinking water is manufactured while maintaining pH of the water after the secondary treatment at >=10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a method and an apparatus for producing drinking water from raw water containing high boron.

[0002]

2. Description of the Related Art Boron contains about 4 to 5 mg / L of seawater contained in seaweed. In addition, various attempts have been made to desalinate seawater, and it is also a monitoring item in Japan's tap water quality standards, and a value of 0.2 mg / L or less is indicated as a guideline. Therefore, it is necessary to remove boron in the process of producing drinking water from water such as seawater containing boron.

By the way, it is difficult to separate boron by adsorption and ion exchange with a general resin.

[0004] Further, boron, which is generally considered to exist as undissociated B (OH) 3 in the vicinity of neutrality in water, is difficult to separate by treatment with a reverse osmosis (RO) membrane. For example, by setting the pH of the water to be treated to be higher than pH 9, B can be separated by RO treatment as much as possible.
After forming into the form of (OH) 4−, a method of treating by passing through RO can be considered, but even in this case, it is only difficult to convert all boron in water to B (OH) 4−. However, when the pH is increased, the tendency of boron to form B (OH) 4− increases, while the hardness component in water (C
a, Mg, etc.) precipitate as hydroxides and clog the RO film, causing a fatal problem as an industrial device.

[0005] Apart from the above, as a method for separating and removing boron in water, it is conceivable to use a boron selective resin described in, for example, Japanese Patent Publication No. 3-10378. The boron selective resin used in this method has a property of introducing a polyhydric alcohol as a functional group capable of selectively adsorbing boron and capable of selectively adsorbing boron. Therefore, by passing boron-containing water through this resin layer, it becomes possible to adsorb and remove boron in water.

As a method using the boron selective resin,
Considering the case of producing drinking water from seawater as an example,
It is considered that salts other than boron are removed by a reverse osmosis membrane, and boron is removed by a boron selective resin.

However, when a boron selective resin is used, there is a problem that the timing of the regeneration can be detected only intermittently conventionally. In other words, the monitoring and final confirmation of the boron ion leakage / removal performance are performed at regular intervals or intermittently by sampling the treated water (boron adsorption tower outlet water) and measuring the boron ion concentration (cumin It is necessary to measure manually by the modified method, Mannit method, JIS K0102, ICP light emission method), it takes a lot of labor and time for the measurement, the operation is complicated, and it is measured due to the difference in the skill of the analyst. The problem is that it is inevitable that the values will differ. In addition, since the sampling method measures off-line, there is a possibility that disturbance due to contamination may be caused depending on the situation. Furthermore, the intermittent sampling measurement method is not suitable for the production of drinking water with stable water quality for a long period of time because it cannot sequentially deal with water quality fluctuations during the sampling period. There are also problems.

[0008]

As described above, it is difficult to produce inexpensively and continuously stable drinking water of any quality by any of the above-described prior arts. unknown.

The present invention has been made under the above-mentioned circumstances, and one of the objects thereof is to provide an industrial method by combining the selective adsorption and separation of boron with a boron selective resin and the RO treatment. It is intended to enable the large-scale production of drinking water with stable water quality for a long time on a large scale.

Another object of the present invention is to solve the following problems to achieve the above object. : To easily control the production, stop, and regeneration of drinking water in accordance with the operation state of the drinking water production device while providing the drinking water production device with a simple structure. : The accuracy of online monitoring of drinking water quality can be improved, and the operation of a drinking water production device capable of maintaining appropriate water quality can be performed. A: By realizing online water quality monitoring, the conventional process water sampling work can be eliminated and the work can be simplified. A: It is possible to obtain a measurement result that is objectively free from variations in measured values due to differences in the measurers according to the conventional sampling measurement method. : By providing continuous online water quality measurement,
It is possible to manufacture drinking water that can promptly respond to process abnormalities and changes in raw water quality during the production of drinking water.

[0011]

SUMMARY OF THE INVENTION The feature of the method for producing drinking water of the present invention is that the effective points of the RO treatment and the boron-selective resin, which have been conventionally considered individually, are effectively used and used in combination. The present invention has been made to achieve the above-described object by providing a new method that can conveniently utilize the effectiveness of the present invention. The characteristics of the method for producing drinking water are as follows. (1) A primary treatment step in which pretreatment water, which has been subjected to pretreatment for removing suspended substances in raw water as necessary, is passed through a reverse osmosis membrane, and a membrane permeated water in the primary treatment step is passed through a boron selective resin. A secondary treatment step of removing boron by water, and a neutralization step of neutralizing outlet water of the secondary treatment step, wherein the boron-containing raw water is subjected to the primary treatment step → secondary treatment step → neutralization step It is a method of producing drinking water by passing through sequentially, wherein the hydrogen ion concentration (pH) of the outlet water of the secondary treatment step is continuously monitored, and when the pH of the outlet water of the secondary treatment step becomes less than 10 After the removal of boron by passing mineral water and stopping the passing of water by using a regeneration treatment of treating the boron selective resin with passing of caustic alkali, the pH of the secondary treatment process outlet water is 10 or more. A method for producing drinking water, comprising producing drinking water while maintaining the temperature. (2) The method for producing drinking water according to the invention (1), wherein the raw water is seawater or brine. (3) In the above invention (1) or (2), the chemical which passes after desorption of boron by a mineral acid is caustic sodium or potassium, and the passing amount is 1 eq / LR or more. Drinking water production method.

Further, the features of the apparatus for producing drinking water from the boron-containing raw water of the present invention that realizes the above method are as follows. (4) A pretreatment device that removes suspended substances contained in the raw water by passing raw water containing boron, and a pretreatment water flowing out of the pretreatment device is passed through a reverse osmosis membrane. Primary treatment device that obtains primary treatment water that is membrane permeated water, secondary treatment device that obtains secondary treatment water from which boron is removed by passing the primary treatment water through a boron selective resin, and outflow from the secondary treatment device A neutralizing device for neutralizing by passing the secondary treated water through
A monitoring device for monitoring the pH of the secondary treatment water, and a regeneration treatment for interrupting the passage of water when the pH of the secondary treatment water becomes 10 or more, and regenerating the boron selective resin by passing a mineral acid and then a caustic alkali. An apparatus for producing drinking water from raw water containing boron, comprising: an apparatus;

In each of the above-mentioned inventions, the pretreatment refers to a treatment for removing suspended matters and insoluble substances contained in raw water. Is adopted as appropriate.
Typically, in order to remove suspended matters such as nets and fine particles for removing suspended matters, suspended matter sedimentation removing means or sand filtration means can be used. It is not limited. It should be noted that the pretreatment can be omitted if it is not necessary due to the nature of the raw water.

The primary treatment step is a step in which pretreatment water is passed through an apparatus comprising an RO membrane (reverse osmosis membrane) for removing ions, and the apparatus for the primary treatment step using this RO membrane is an RO means. May be a single step or a plurality of steps. As the RO means used here, various types of RO films can be employed without particular limitation.

[0015] The secondary treatment step generally refers to a step in which primary treatment water is passed through a boron selective resin tower filled with a boron selective resin as a fixed bed, and the above-mentioned boron selective resin is used. Can be

An important point in the above invention is to maintain the pH of the outlet water in the secondary treatment step at 10 or more, and for this purpose, the alkali treatment of the boron selective resin is important. When boron is desorbed from the boron selective resin that has adsorbed boron to the adsorption limit, a mineral acid such as sulfuric acid or hydrochloric acid is used. In order to maximize the amount of boron adsorbed by the boron selective resin, the boron selective resin is usually desorbed with a mineral acid and then treated with a caustic alkali such as sodium hydroxide. However, when the boron-containing water is passed through using an alkali-treated boron-selective resin, the resulting treated water becomes alkaline and must be neutralized when the treated water is used as drinking water. Therefore, conventionally, in order to prevent the treated water of the boron selective resin from becoming alkaline, the treated water is treated with a caustic alkali followed by a mineral acid, and then a sodium chloride solution is passed (Japanese Patent Publication No. 4-70948) or a mineral acid is used. After desorbing boron by using a mixed solution of sodium chloride and caustic sodium (Japanese Patent Publication No. 4-60700),
Alternatively, a method has been proposed in which an alkali treatment is performed in an incomplete form by desorbing boron with a mineral acid and then subjecting the ion exchange resin to an alkali treatment in a fluidized state (Japanese Patent Publication No. 4-199004). I have.

However, according to the above-mentioned regeneration treatment method, although it is not necessary to adjust the pH of the treatment water of the boron-selective resin after returning to the normal operation state, the sampling method of the above-mentioned modified cumin method or the like is used. No suitable method for continuously and easily detecting the end point of water passage of the boron selective resin has been known so far except for the intermittent method of boron ion concentration measurement by Can not.

On the other hand, the present inventors have found, for the first time as a result of various experiments, the fact that the ability of boron separation / removal by a boron selective resin changes rapidly around pH 10, and after desorbing boron with a mineral acid, According to the present invention, it is possible to measure the pH of the treated water of the regenerated boron-selective resin by simply passing a sufficient amount of caustic alkali, and to detect the end point of the passage of the boron-selective resin based on a sudden change point around pH 10. It was done.

That is, according to the method of the present invention, when the treated water of the boron-selective resin becomes alkaline and becomes drinking water, a neutralization treatment is required. An excellent advantage that the detection can be performed continuously and easily and reliably is obtained, and the problem that the conventional method other than the present invention cannot continuously detect the end of the boron selective resin online is solved. .

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail. Embodiment 1 FIG. 1 is a diagram showing an outline of a flow of a typical apparatus for carrying out the method of the present invention when producing drinking water from seawater.

In this figure, reference numeral 1 denotes raw water, which is passed through a pretreatment device (filtration device: for example, coagulation two-layer filtration + sand filtration, a backwashable UF membrane device) 2 and then subjected to primary treatment. Water is passed through the RO device 3 which is a device. In addition, since the pH of the pre-treated water is not adjusted, it is usually water having a neutral pH.

The RO device 3 has a built-in reverse osmosis membrane (RO) and sends the permeated water as the primary treatment water to the boron adsorption tower 4 side as the secondary treatment device, and the non-permeated water is drained. Since the RO membrane cannot remove carbonate ions, the treated water shows weak acidity.

The secondary treatment device is a boron selective resin (for example, Amberlite (registered trademark: the same applies hereinafter)) IRA
743) as a fixed bed 401
A primary treatment water pH detector 403 for detecting the pH of the water at the inlet of the boron adsorption tower is connected in the middle of the treated water supply pipe 402 upstream of the boron adsorption tower 4. .

FIG. 2 shows the structure of the secondary treatment apparatus in more detail. A discharge pipe 411 on the treated water outlet side of the boron adsorption tower 4 is provided with outlet water (secondary treated water) of the same. In order to detect pH, the secondary treatment water p which is normally open but is closed during resin regeneration is provided with an on-off valve 406 in the middle.
The H detection tube 405 is branched and connected. Downstream of the on-off valve 406, a secondary treatment water pH detector 407 is provided, and the information detected here is transmitted to the recording unit 408 of the control device, and the calculation unit / control unit 409 performs the operation of regenerating the boron-selective resin. It is used as information for detecting a necessary time (interruption of water supply, passage of regenerated medicine), and is used so that it can be visually confirmed on an external display device 410 such as a monitor. In addition,
A discharge pipe 411 on the treated water outlet side for discharging the outlet water (outflow water) of the boron adsorption tower 4 has an on-off valve 412 for opening and closing water flow.
Is provided and one system of boron separation. Water flow for removal,
The system is provided so that the interruption can be controlled, and a plurality of secondary treatment devices mainly composed of the boron adsorption tower 4 are provided, and water is supplied to or blocked from the inlet side and the outlet side for each system. As a result, it is possible to realize an operation that enables continuous production of drinking water. After the regeneration with the mineral acid, by passing caustic sodium or the like as an alkali treatment, the boron selective resin is regenerated, and the water to be treated after the regeneration is adjusted to pH 10 or more. This pH 1
In order to make it 0 or more, the amount of passing caustic alkali is 1 eq / L
-R or more is preferable. By doing so, the pH of the secondary treatment water will surely be 10 or more. FIG.
Pipes 4021, 4022, 4023 and pipe 41 in
Reference numerals 11, 4112, and 4113 indicate connection pipes to the secondary processing devices of the plurality of systems.

Although not shown, for example, a regenerating device for regenerating the boron selective resin is provided, and typically, a mineral acid (for example, 5% concentration) which is a regenerating agent for separating boron adsorbed on the resin. Of sulfuric acid), an extruder using pure water, etc., an alkali ionizer for adjusting pH as a regenerant, an extruder using pure water, etc., by a regeneration and washing process using mineral acid and then caustic. Playback processing is performed.

The secondary treatment water treated in the boron adsorption tower 4 as a secondary treatment device is then supplied to a neutralization device 5 and adjusted to a pH (neutral) suitable for drinking water. The secondary processing device 5 can be configured using, for example, a carbon dioxide gas injection device. As the neutralizing device 5, a device for injecting an acid solution can also be used, but by using a carbon dioxide gas injecting device, even if the amount of carbon dioxide gas injected becomes large, it is possible to maintain the pH within a suitable beverage. Therefore, it is preferable to use a carbon dioxide gas injection device.

Reference numeral 6 denotes a pH detector for detecting the pH of the water passed through the neutralizing device 5, which is used to confirm and monitor the suitability of the final product (manufactured drinking water 7). Can be

[0028]

EXAMPLE 1 Drinking water was produced from seawater under the following conditions on an experimental scale using the apparatus shown in FIGS. The conditions of raw water (seawater) are as shown in Table 1 below.

[0029]

[Table 1]

The pretreatment device 2 used a backwashable UF membrane (microfiltration membrane: molecular weight cut off 150,000), and the flow rate of water was 5 m ³ / day.

The RO device 3 as a primary processing device is an RO device.
The membrane was formed using Toyobo's hollow HR5355, and the water quality of feed water (pre-treatment water) and first-stage RO permeate water (primary treatment water) of this RO apparatus was as shown in Table 2 below. The second stage R obtained by treating the RO permeated water for reference with the same RO membrane
The water quality of O permeated water is also shown.

[0032]

[Table 2]

As can be seen from the results in Table 2, the water quality of the first-stage permeated water is such that ions other than boron are suitable for drinking.

The primary treated water (first-stage RO permeated water) that has been treated by the RO device 3 has a pH of 4.5 to 5.3 because the free carbonic acid of the raw water leaks as it is,
This was supplied to the boron selective resin tower 4 constituting the secondary treatment apparatus to separate and remove boron. In addition, this secondary treatment apparatus was used under the following configuration and water-passing conditions, and also subjected to a regeneration treatment under the conditions shown in Table 5 below.

Configuration of Boron Adsorption Tower • Configuration of Resin Tower Tower column: φ22 mm × L1500 mm Resin used: Amberlite (registered trademark) IRA743 Resin layer height: 900 mm Resin amount: 342 ml • Water quality of feed water pH: 4. 5 to 5.3 Boron concentration: 1.8 (mgB / L) Water flow conditions Water flow rate: 3.42 L / hr, SV10 Water flow temperature: 22 ° C. Regeneration conditions Elution: 5% H ₂ SO ₄ 850 ml SV4 extrusion : Pure water 342 ml SV4 Alkaline treatment: 4% NaOH 880 ml SV4 (2.6 eq / LR) Extrusion: pure water 342 ml SV4 Washing: pure water 2052 ml SV12 Water supplied to the secondary treatment apparatus and water to be treated during a normal operation period The water quality of (secondarily treated water) is as shown in Table 3 below.

[0036]

[Table 3]

The treated water subjected to the secondary treatment as described above is
The neutralized state was controlled by injecting carbon dioxide gas in the neutralizing device 6 to obtain the production water (drinking water) 7. Table 4 below shows the relationship between the pH of the supply water and the outlet water of the neutralization device 6.

[0038]

[Table 4]

Table 5 shows the test results under the above conditions.

[0040]

[Table 5]

FIG. 3 shows the time-dependent changes in the pH and the concentration of boron leaked from the outlet water of the secondary treatment apparatus.

As can be seen from the results shown in FIG. 3, the leakage of boron rapidly increases near the pH of the water at the outlet of the secondary treatment device falling below 10, and therefore, the structure of the present invention is used. Thus, it was confirmed that the end of boron removal of the boron selective resin can be detected by a simple method of continuously monitoring the pH of the secondary treatment device outlet water.

Comparative Example 1 The treatment was carried out in the same manner as in Example 1 except that the configuration of the boron adsorption tower 4 after the regeneration treatment was as follows, and the results are shown in Table 5 and FIG.

Regeneration conditions Elution: 850 ml of 5% H ₂ SO ₄ SV4 Extrusion: 342 ml of pure water SV4 Alkaline treatment: 880 ml of 1% NaOH SV4 (0.64 eq / L-R) Extrusion: 342 ml of pure water SV4 Washing: 2052 ml of pure water SV12 As can be seen from the results in FIG. 4, when the amount of the caustic soda used in the alkali treatment is not sufficient, the pH of the outlet water of the secondary treatment device 4 after the regeneration treatment of the boron selective resin becomes neutral or acidic, and It can be seen that it is difficult to detect the end of use of the boron selective resin due to a subtle change in pH even when monitoring the change in pH.

Example 2 The treatment was carried out in the same manner as in Example 1 except that the configuration of the boron adsorption tower 4 after the regeneration treatment was as follows, and the results are shown in Table 5 and FIG.

Regeneration conditions Elution: 5% H ₂ SO ₄ 850 ml SV4 Extrusion: pure water 342 ml SV4 Alkaline treatment: 1.5% NaOH 880 ml SV4 (1.0 eq / LR) Extrusion: pure water 342 ml SV4 Washing: pure water 2052 ml SV12 As can be seen from the results shown in FIG. 5, even if the amount of caustic soda used for the alkali-treated water is 1.0 eq / LR, the pH of the treated water of the boron-selective resin becomes 10 or more, and the decrease in the outlet pH decreases the boron ion. Could be detected.

[0047]

As described above, the present invention relates to a conventional method known as a method for removing boron from boron-containing water when producing drinking water from boron-containing raw water.
By skillfully combining the O treatment method and the method using a boron-selective resin, a method that enables a large-scale production of drinking water with stable water quality over a long period of time on an industrial scale, which has not been known at all, has been proposed. The present invention can provide a method and an apparatus which are extremely useful for desalination of seawater (production of drinking water).

The invention described in each claim of the present invention has the following effects in addition to the above effects.

While providing a drinking water production device with a simple structure, the production of drinking water in accordance with the operation status of the device,
Stop and playback control can be easily performed.

The accuracy of monitoring the quality of drinking water online can be improved, and appropriate water quality can be maintained.

By realizing online water quality monitoring,
It is possible to eliminate the conventional treatment water sampling work, and to realize the simplification of the work, and to implement the method industrially,
It is extremely effective as a device.

There is no variation in measured values due to differences in the skill of the measurer in the conventional sampling measurement method, and a measurement result having no objective difference can be reliably obtained.

Since continuous water quality measurement can be realized, it is possible to produce drinking water that can quickly respond to process abnormalities and changes in raw water quality during the production of drinking water.

[Brief description of the drawings]

FIG. 1 is a flowchart showing an outline of a device configuration of a first embodiment which is an example of the present invention.

FIG. 2 is a schematic diagram showing details of a configuration of a secondary processing device of FIG. 1;

FIG. 3 is a diagram showing a change in water quality when the processing according to the first embodiment of the present invention is performed.

FIG. 4 is a diagram showing a change in water quality when a process of Comparative Example 1 for the present invention is performed.

FIG. 5 is a diagram illustrating a change in water quality when the processing according to the second embodiment of the present invention is performed.

[Explanation of symbols]

 1: Raw water 2: Pretreatment device 3: RO device 4: Boron adsorption tower 401: Fixed bed 402: Supply water supply pipe 403: pH detector 404: Discharge pipe 405: Secondary treatment water pH detection pipe 406: Open / close valve 407: pH meter for secondary treated water 418: Recording unit 419: Operation unit / control unit 410: External display device 411: Discharge pipe 412: Open / close valve 5: Neutralizer 6: pH detector 7: Drinking water

Claims (4)

[Claims] A first treatment step of passing pretreatment water, which has been subjected to a pretreatment for removing suspended substances in raw water as necessary, through a reverse osmosis membrane; A secondary treatment step of removing boron by passing water through, and a neutralization step of neutralizing outlet water of the secondary treatment step, wherein the boron ion-containing raw water is subjected to the primary treatment step-> secondary treatment step-> A method for producing drinking water through the order of the summation process, wherein the hydrogen ion concentration (pH) of the outlet water of the secondary treatment process is continuously monitored, and the pH of the secondary treatment process outlet water is less than 10. When the water flow is interrupted, boron is desorbed by passing a mineral acid, and then regeneration of the boron selective resin is processed by passing a caustic alkali. A method for producing drinking water, characterized in that drinking water is produced while maintaining it as follows. 2. The method according to claim 1, wherein the raw water is seawater or brackish water. 3. The method according to claim 1 or 2, wherein after the boron is eliminated by passing a mineral acid, the passing drug is caustic sodium or caustic potassium, and the passing amount is 1 eq / LR or more. A method for producing drinking water, comprising: 4. A pretreatment device for removing suspended substances contained in raw water by passing raw water containing boron, and passing pretreatment water flowing out of the pretreatment device through a reverse osmosis membrane. A primary treatment device that obtains primary treated water that is a membrane permeated water, a secondary treatment device that obtains secondary treated water from which boron has been removed by passing the primary treated water through a boron selective resin, and a secondary treatment device Neutralization device that neutralizes by passing secondary treatment water flowing out of the reactor, monitoring device that monitors the pH of secondary treatment water, and interrupts water supply when the pH of secondary treatment water becomes 10 or more An apparatus for producing drinking water from boron-containing raw water, the apparatus comprising: a regenerating treatment apparatus for regenerating a boron-selective resin by passing a mineral acid and then a caustic alkali.