JP2014213306A - Pure water production apparatus, pure water and filtered water production apparatus, pure water production method, and pure water and filtered water production method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pure water production apparatus and a pure water production method that can produce pure water without using an acid and alkali as a hazardous substance.SOLUTION: A pure water production apparatus 1 includes a pretreatment device 10 for removing turbidity components and metallic ion components contained in raw water to obtain pretreated water under the condition of not using an acid and alkali as a hazardous substance, and a reverse osmosis membrane treatment device 12 for reverse osmosis membrane treatment of the pretreated water to obtain filtered water as pure water.

Description

  The present invention relates to a pure water production apparatus, a pure water and filtrate production apparatus, a pure water production method, and a pure water and filtrate production method.

  Pure water is used in various applications in industry and the like. As for the production of pure water, an ion exchange method, a reverse osmosis membrane method and the like can be mentioned.

  The ion exchange method is a method using an ion exchanger such as an ion exchange resin. Since the ion exchange method has high water use efficiency, it is widely used as a pure water production method using fresh water such as surface water and well water as raw water. However, a large amount of acid or alkali is used for regeneration of the ion exchange resin. I need.

  The reverse osmosis membrane method is a method using a reverse osmosis membrane, but there is a problem that a scale component is deposited on the membrane surface of the reverse osmosis membrane and clogged unless an appropriate operation is performed. In order to suppress such precipitation of scale components, it is often operated by performing pretreatment before the reverse osmosis membrane treatment, pH adjustment, addition of a scale inhibitor such as a dispersant, and the like. In addition, for the purpose of increasing the removal rate of free carbonic acid, the quality of treated water is often improved by adding chemicals such as alkali.

  For example, Patent Document 1 discloses a method in which an acid is added to raw water to precipitate a scale component, the deposited scale component is subjected to membrane separation treatment, and an alkali is added to permeated water, followed by two-stage reverse osmosis membrane treatment. Is described.

  Patent Document 2 describes a method in which after the scale inhibitor is supplied to the water to be treated, the upstream reverse osmosis membrane treatment is performed, and after the acid is supplied to the concentrated water, the downstream reverse osmosis membrane treatment is performed.

  Patent Document 3 discloses a method of performing a two-stage or three-stage reverse osmosis membrane treatment after adding an acid or the like scale inhibitor to the raw water, or a first-stage reverse osmosis membrane treatment after adding an acid to the raw water. And after adding an alkali to the permeated water, the second and third stages of reverse osmosis membrane treatment are described.

  By the way, depending on the factory, the use of deleterious substances such as acids and alkalis may be prohibited or restricted. Under such conditions where the use of acids and alkalis is prohibited or restricted, the use of acids and alkalis for the purpose of suppressing the precipitation of scale components and improving the quality of treated water is not desirable.

JP-A-9-276865 JP-A-9-206749 JP 2008-161818 A

  An object of the present invention is to provide a pure water production apparatus, a pure water and filtered water production apparatus, a pure water production method, a pure water and a filtration that can produce pure water without using acids and alkalis as deleterious substances. It is to provide a water production method.

  The present invention provides a pretreatment means for obtaining pretreated water by removing turbidity components and metal ion components contained in raw water under the conditions where acid and alkali as deleterious substances are not used, and reverse osmosis of the pretreated water And a reverse osmosis membrane treatment unit that obtains permeate as pure water by membrane treatment.

  Further, in the pure water production apparatus, it is preferable that the recovery rate in the reverse osmosis membrane treatment is set to a condition in which precipitation of scale components hardly occurs in the concentrated water.

  Further, the present invention provides pretreatment means for obtaining pretreated water by removing turbidity components and metal ion components contained in the raw water under the conditions where acids and alkalis as deleterious substances are not used, and the pretreated water A reverse osmosis membrane treatment means that obtains permeate as pure water by reverse osmosis membrane treatment, and reverse osmosis membrane treatment means that obtains concentrated water as filtered water.

  In addition, the present invention provides a pretreatment step for obtaining pretreatment water by removing turbidity components and metal ion components contained in the raw water under the condition that no acid and alkali as deleterious substances are used, and the pretreatment water. And a reverse osmosis membrane treatment step of obtaining permeate as pure water by reverse osmosis membrane treatment.

  In the pure water production method, it is preferable that the recovery rate in the reverse osmosis membrane treatment is set to a condition in which precipitation of scale components hardly occurs in the concentrated water.

  In addition, the present invention provides a pretreatment step for obtaining pretreatment water by removing turbidity components and metal ion components contained in the raw water under the condition that no acid and alkali as deleterious substances are used, and the pretreatment water. And a reverse osmosis membrane treatment step of obtaining permeated water as pure water by performing reverse osmosis membrane treatment and obtaining concentrated water as filtered water.

  In the pure water production apparatus and the pure water production method of the present invention, pure water can be produced without using acids and alkalis as deleterious substances. Moreover, in the pure water and filtered water manufacturing apparatus and the pure water and filtered water manufacturing method of the present invention, pure water and filtered water can be manufactured without using acids and alkalis as deleterious substances.

It is a schematic block diagram which shows an example of the pure water manufacturing apparatus which concerns on embodiment of this invention.

  Embodiments of the present invention will be described below. This embodiment is an example for carrying out the present invention, and the present invention is not limited to this embodiment.

  The outline of an example of the pure water manufacturing apparatus which concerns on embodiment of this invention is shown in FIG. 1, and the structure is demonstrated. The pure water production apparatus 1 includes a pretreatment device 10 and a reverse osmosis membrane treatment device 12.

  1, the raw water pipe 14 is connected to the inlet of the pretreatment apparatus 10, and the outlet of the pretreatment apparatus 10 and the inlet of the reverse osmosis membrane treatment apparatus 12 are connected by a pretreatment water pipe 16. The permeate outlet 18 of the reverse osmosis membrane treatment apparatus 12 is connected to the permeate outlet 18, and the concentrate outlet 20 is connected to the concentrate outlet 20. A raw water tank may be provided on the upstream side of the pretreatment device 10 as necessary.

  The operation of the pure water manufacturing method and the pure water manufacturing apparatus 1 according to the present embodiment will be described.

  The raw water to be treated is fed to the pretreatment apparatus 10 through the raw water pipe 14 and the pretreatment apparatus 10 does not use acid and alkali (hereinafter sometimes simply referred to as “acid and alkali”) as deleterious substances. Thus, turbidity components and metal ion components contained in the raw water are removed to obtain pretreated water (pretreatment step). As used herein, the term “deleterious substance” refers to a deleterious substance defined by Article 2 of the Poisonous and Deleterious Substances Control Law and the Poisonous and Deleterious Substance Designation Ordinance. When the pretreated water contains an oxidizing agent, it is possible to deteriorate the reverse osmosis membrane, so it is desirable to perform a reduction treatment. Examples of the reduction treatment include a method of adding a reducing agent and a method of contacting with activated carbon. The pretreated water is fed to the reverse osmosis membrane treatment device 12 through the pretreatment water pipe 16 and is subjected to the reverse osmosis membrane treatment in the condition where no acid and alkali are used in the reverse osmosis membrane treatment device 12 so that the permeated water becomes pure water. Obtained (reverse osmosis membrane treatment step). The permeated water in the reverse osmosis membrane treatment device 12 may be returned to the upstream side of the pretreatment device 10 and mixed with the raw water, or may be used as filtered water.

  The raw water to be treated is not particularly limited, and examples thereof include surface water and fresh water such as well water. In particular, raw water containing hardness components such as calcium and magnesium, metal ion components such as iron ions, manganese ions, and aluminum ions, silica components, and the like are treated.

  The pretreatment device 10 may be any device as long as it can remove turbidity components and metal ion components such as iron ions, manganese ions, and aluminum ions without using acid and alkali. . Examples of the pretreatment device 10 include a coagulation sedimentation device, a pressure levitation device, and a membrane filtration device. However, since it is desirable to adjust the pH as the optimum flocculation condition for flocculation / precipitation equipment, pressure levitation equipment, etc. that use the flocculating agent, the amount of flocculating agent used increases under conditions that do not use acid and alkali. It may become a large facility. From such a viewpoint, a membrane filtration device is preferable. Examples of the membrane filtration device include a membrane filtration device using a microfiltration (MF) membrane or an ultrafiltration (UF) membrane.

  When the raw water contains metal ion components such as iron and manganese, an oxidizing agent such as sodium hypochlorite is added to the raw water so that iron and manganese can be oxidized and removed with a membrane filtration device. Then, the treatment may be performed with a membrane filtration apparatus.

  In this case, if the added oxidizing agent such as sodium hypochlorite remains in the pretreated water, although biological growth is suppressed, there is a possibility that the reverse osmosis membrane in the next step may be oxidized and deteriorated. The oxidant may be removed by an oxidant removal treatment means such as contact with activated carbon or addition of a reducing agent on the rear side of the treatment apparatus 10 and the front stage side of the reverse osmosis membrane treatment apparatus 12. When activated carbon is used as the oxidant removal treatment means, there is a possibility that fine particles of activated carbon may be mixed in the oxidant removal treatment water, so that it is safe before the oxidant removal treatment water is introduced into the reverse osmosis membrane treatment apparatus 12. Fine particle removing means such as a filter may be provided.

  In the reverse osmosis membrane treatment apparatus 12, the reverse osmosis membrane treatment is performed under conditions where no acid and alkali are used. In the reverse osmosis membrane treatment step, it is preferable to operate by setting the recovery rate (permeated water amount / (permeated water amount + concentrated water amount)) in the reverse osmosis membrane treatment to a condition where precipitation of scale components does not easily occur in the concentrated water.

  Typical examples of the scale component include components derived from hardness components such as calcium and magnesium, silica components, metal ion components, and the like.

  Usually, in order to cope with the hardness component, removal by a softening device or the like is effective, but the device becomes large. Although there is a technique for suppressing the precipitation of scale components by lowering the pH when water is passed through the reverse osmosis membrane, it is difficult to use conditions that do not use acid and alkali. Therefore, for example, it is preferable to set the recovery rate within a range in which the Langeria index (LSI) of the concentrated water is negative.

  The Langeria index (LSI) is a numerical value that serves as an index of occurrence of scale component precipitation. As a method for calculating the Langeria index (LSI), a simple calculation method is generally used. The simple calculation method is a method for calculating the Langeria index using the Langeria index (Kenji Fujita (2003) “Water Treatment Chemical Handbook”, pages 51-52).

  The more the value of the Langeria index (LSI) is positive and the larger the value, the more easily the hardness component is precipitated. If it is zero, the hardness component is in an equilibrium state where neither precipitation nor dissolution occurs. , Indicating that the hardness component is difficult to precipitate.

  When the raw water contains a silica component, it is effective that the concentration of silica in the concentrated water is not more than the solubility of silica in order to correspond to the silica component. Since the solubility of silica changes depending on the pH, precipitation of silica scale can be suppressed, for example, by setting the concentrated water to an alkaline condition of about pH 10, but it is difficult to use a condition that does not use an acid and an alkali. Therefore, it is preferable to set the recovery rate within a range where the concentration of silica in the concentrated water is not more than the solubility of silica.

  In order to suppress the precipitation of the hardness component and the silica component, there is a method of adding a scale inhibitor such as a dispersant. However, when the silica concentration is increased in the presence of metal ions, particularly in the presence of aluminum ions, the effect of a scale inhibitor such as a dispersant may be significantly reduced, and scale components may be precipitated. Although it is desirable to remove the metal ion component by the pretreatment apparatus 10 described above, since it is difficult to remove the aluminum ion unless the pH condition is optimum under the condition where no acid and alkali are used, the pretreatment is performed. Even if it treats with the equipment 10, it may remain in the pretreated water. Therefore, when aluminum ions are present in the raw water, the concentration of the osmosis water treatment apparatus 12 that suppresses the precipitation of scale components due to such aluminum ions is, for example, about 0.25 mg-Al / L or less in the concentrated water. It is preferable to set a recovery rate such that

  Therefore, the recovery rate in the reverse osmosis membrane treatment that satisfies the above conditions is, for example, in the range of about 30 to 50%. In the pure water production apparatus and the pure water production method according to the present embodiment, the reverse osmosis membrane treatment apparatus 12 is set to a recovery rate lower than the recovery rate that is normally set, so that the concentrated water that is normally drained is required. Therefore, it is configured with attention paid to the fact that it can also be used as filtered water.

  Although the permeated water obtained by the pure water production apparatus and the pure water production method according to the present embodiment has a salt concentration of about 30 to 50% higher than the normal salt concentration, the turbidity treatment is performed. Since it is operated under conditions in which the scale components are not easily precipitated by the reverse osmosis membrane treatment, water quality without concern that scale is generated can be obtained.

  On the other hand, concentrated water can be used as filtered water because it is not necessary to use a scale inhibitor such as the above-mentioned dispersant that may become a residual component in filtered water.

  Further, the deaeration process may be performed by installing a deaeration apparatus on the rear stage side of the reverse osmosis membrane treatment apparatus 12. Thereby, the quality of the pure water obtained can be further improved.

  When the required conductivity of pure water is not satisfied by the single-stage reverse osmosis membrane treatment by the reverse osmosis membrane treatment device 12, at least one reverse osmosis membrane treatment device is installed on the rear side of the reverse osmosis membrane treatment device 12. Thus, a multi-stage reverse osmosis membrane treatment may be performed. Thereby, the quality of the pure water obtained can be improved more.

  When performing a multi-stage reverse osmosis membrane treatment, at least the first-stage reverse osmosis membrane treatment is performed with a recovery rate such that the concentration of scale components hardly occurs in the concentrated water as described above, for example, the recovery rate is about 30 to 50%. It is sufficient to set the range to operate. In the reverse osmosis membrane treatment after the first stage, for example, the recovery rate may be set in the range of about 80 to 90%.

  When performing deaeration treatment, a deaeration treatment device such as a deaeration membrane between a plurality of reverse osmosis membrane treatment devices, for example, between a first-stage reverse osmosis membrane treatment device and a second-stage reverse osmosis membrane treatment device. May be installed. The quality of the pure water obtained can be further improved by performing the decarboxylation treatment with the deaeration treatment apparatus.

  An exchangeable ion exchange resin tower may be installed at the permeate outlet of the reverse osmosis membrane treatment apparatus at the last stage, or an electric regeneration type ion exchange resin treatment apparatus may be installed. Thereby, the quality of the pure water obtained can be improved more.

  The pure water production apparatus and the pure water production method according to the present embodiment as described above have high water use efficiency, and can supply filtered water as needed in addition to pure water.

  Hereinafter, although an example and a comparative example are given and the present invention is explained more concretely in detail, the present invention is not limited to the following examples.

Example 1
Using the pure water production apparatus shown in FIG. 1, the treatment was performed under the following conditions. Two-stage reverse osmosis membrane treatment was performed using two reverse osmosis membrane treatment devices as reverse osmosis membrane treatment means. The results are shown in Table 1.
Raw water: Industrial water Pretreatment device: UF membrane (DOW, SFP-2880)
Reverse osmosis membrane treatment equipment: RO membrane (Organic, OFR-240HJ8)
Calcium concentration of raw water: 82.5mg-CaCO ₃ / L
Alkalinity of raw water: 79.1 mg-CaCO ₃ / L
Evaporation residue of raw water: 320mg / L
Water temperature: 15 ° C
pH: 7.5
First stage reverse osmosis membrane treatment recovery rate: 35%
Second stage reverse osmosis membrane treatment recovery rate: 80-90%

In Example 1, the recovery rate was set so that the Langerian index of the concentrated water of the first-stage reverse osmosis membrane treatment apparatus was a negative value (−0.4) as follows.
Concentrated water CaCO ₃ calculation value: 126.9 mg-CaCO ₃ / L → 2.53 meq / L
Calculated alkalinity of concentrated water: 121.7 mg-CaCO ₃ / L → 2.43 meq / L
Concentrated water Sd (soluble substance TDS concentration) value: 492.3 mg / L
When the Langeria index (Kenji Fujita (2003) “Water Treatment Chemicals Handbook”, pages 51-52) is calculated using the Langeria Index,
Coefficient A based on total solid content (Sd value of concentrated water) = 0.2
Coefficient based on temperature B = 2.2
Coefficient based on calcium hardness C = 1.7
Coefficient D based on alkalinity D = 2.1
pHs = 9.3 + A + B- (C + D)
= 9.3 + 0.2 + 2.2− (1.7 + 2.1)
= 7.9
Langeria Index (LSI) = pH-pHs
= 7.5-7.9
= -0.4

(Comparative Example 1)
Except that the recovery rate of the first stage reverse osmosis membrane treatment was 80 to 90%, and 10 mg / L of a dispersant (Olperion, Organo) was added as a scale inhibitor before the first stage reverse osmosis membrane treatment. The treatment was performed in the same manner as in Example 1. The results are shown in Table 1.

  By performing the treatment as in Example 1, pure water could be produced without using acid and alkali. Further, in Example 1, pure water could be produced with almost no scale component precipitated without using a dispersant.

  DESCRIPTION OF SYMBOLS 1 Pure water manufacturing apparatus, 10 Pretreatment apparatus, 12 Reverse osmosis membrane treatment apparatus, 14 Raw water piping, 16 Pretreatment water piping, 18 Permeated water piping, 20 Concentrated water piping.

Claims (6)

In the condition where acid and alkali are not used as a deleterious substance,
Pretreatment means for removing turbidity components and metal ion components contained in raw water to obtain pretreated water;
A reverse osmosis membrane treatment means for obtaining a permeated water as pure water by subjecting the pretreated water to a reverse osmosis membrane;
A pure water production apparatus comprising: It is a pure water manufacturing apparatus of Claim 1, Comprising: The recovery rate in the said reverse osmosis membrane process is set to the conditions where precipitation of a scale component does not occur easily in concentrated water. In the condition where acid and alkali are not used as a deleterious substance,
Pretreatment means for removing turbidity components and metal ion components contained in raw water to obtain pretreated water;
A reverse osmosis membrane treatment means for obtaining a permeated water as pure water by treating the pretreated water with a reverse osmosis membrane;
An apparatus for producing pure water and filtered water, comprising: In the condition where acid and alkali are not used as a deleterious substance,
A pretreatment step of obtaining pretreated water by removing turbidity components and metal ion components contained in the raw water;
A reverse osmosis membrane treatment step of obtaining a permeate as pure water by subjecting the pretreated water to a reverse osmosis membrane;
The pure water manufacturing method characterized by including. It is a pure water manufacturing method of Claim 4, Comprising: The recovery rate in the said reverse osmosis membrane process is set to the conditions which precipitation of a scale component does not occur easily in concentrated water. In the condition where acid and alkali are not used as a deleterious substance,
A pretreatment step of obtaining pretreated water by removing turbidity components and metal ion components contained in the raw water;
A reverse osmosis membrane treatment step of obtaining a permeated water as pure water by treating the pretreated water with a reverse osmosis membrane, and obtaining concentrated water as filtered water;
A method for producing pure water and filtered water, comprising:

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