JP7168739B2 - Water treatment device and water treatment method - Google Patents

Description

The present invention relates to a water treatment device and a water treatment method.

In recent years, techniques for reducing the volume of wastewater discharged from factories and the like have been proposed. Specifically, a method of concentrating wastewater using a reverse osmosis membrane (RO membrane) or the like to collect permeated water and reducing the volume of wastewater has been proposed. As a method for reducing the volume of wastewater, there is known a Zero Liquid Discharge (ZLD) process that minimizes the generation of waste other than solid content by further distilling or crystallizing concentrated water that has been concentrated by an RO membrane. there is

By the way, if the solubility inside the membrane is exceeded due to concentration in the process of water treatment using a membrane such as an RO membrane, so-called scaling, in which salts are precipitated, will occur, causing clogging of the membrane. Scaling is caused by salts with low solubility, and when scaling occurs, it causes a decrease in the water permeability of the membrane and an increase in pressure loss on the raw water supply side, making it difficult to continue the operation of the water treatment apparatus. Salts that cause scaling are poorly soluble components.

In Non-Patent Document 1, after removing calcium to some extent by coagulation sedimentation, calcium is completely removed by a water softener, and the water to be treated is operated in an environment where the water to be treated is made alkaline by an RO membrane, thereby suppressing silica scaling. A method is disclosed. The technique described in Non-Patent Document 1 is used as a water treatment apparatus that suppresses Ca-based scale and silica scale.

U.S. Patent Application Publication No. 2014/151295 WO2015/002309 Japanese Patent Application Laid-Open No. 2020-018992 JP 2020-058963 A

"California Utility chooses HERO(TM)/Crystallizer for ZLD, Project Profile #35", [online], [searched on June 9, 2020], Internet <URL: https://www.aquatech.com/wp -content/uploads/35.Magnolia-HERO.pdf＞

In the water treatment methods according to the prior art disclosed in Patent Document 1 and Non-Patent Document 1 described above, it is possible to suppress the generation of scale to some extent. It has been desired to improve the recovery rate of water by realizing concentration. This demand is similarly sought in wastewater processes other than ZLD where concentrated wastewater is generated, and there is a technology to further concentrate the concentrated wastewater while suppressing scale generation and improve the recovery rate of water recovered from the water to be treated. was wanted.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to provide a water treatment apparatus capable of improving the recovery rate of water while suppressing the generation of scale when extracting water from water to be treated containing impurities. and to provide a water treatment method.

In order to solve the above-described problems and achieve the object, a water treatment apparatus according to one aspect of the present invention is a water treatment apparatus for extracting water from water to be treated containing impurities containing silica, a plurality of coagulation/sedimentation units for coagulating and removing at least part of the impurities from the treated water; a plurality of water extraction units for extracting permeated water from the water to be treated and discharging concentrated water obtained by extracting the permeated water from the water to be treated, along the flow direction of the water to be treated a first water extracting part, which is a part of the plurality of water extracting parts, and a first water extracting part, which is a part of the plurality of water extracting parts, after the first coagulating sedimentation part, which is a part of the plurality of A second coagulation-sedimentation part, which is the other part of the plurality of coagulation-sedimentation parts, in a subsequent stage, and a second water extraction part, which is the other part of the plurality of water-extraction parts, in a subsequent stage of the second coagulation-sedimentation part. is provided, the second water extraction unit has at least one of the forward osmosis membrane and the reverse osmosis membrane, extracts permeated water from the concentrated water discharged by the first water extraction unit, and extracts permeate water from the concentrated water discharged by the first water extraction unit. Highly concentrated water obtained by further concentrating the concentrated water discharged by the water extraction unit is discharged, and at least a part of the silica is aggregated and removed in the first coagulation-sedimentation unit and the second coagulation-sedimentation unit. .

A water treatment apparatus according to an aspect of the present invention, in the above invention, is provided with a plurality of filtration units for filtering the water to be treated or the concentrated water, and along the flow direction of the water to be treated, the first A first filtration section that is a part of the plurality of filtration sections is provided downstream of the coagulation-sedimentation section and before the first water extraction section, and is downstream of the second coagulation-sedimentation section and the second water extraction section. A second filtering section, which is the other section of the plurality of filtering sections, is provided in the preceding stage.

A water treatment apparatus according to an aspect of the present invention is a water treatment apparatus according to the above invention, wherein the first water extraction unit includes a low pressure reverse osmosis unit having a low pressure reverse osmosis membrane, and the second water extraction unit includes a high pressure reverse osmosis membrane. It is characterized by comprising a high-pressure reverse osmosis section having a membrane or a forward osmosis section having the forward osmosis membrane.

A water treatment apparatus according to an aspect of the present invention, in the above invention, performs distillation and/or crystallization on the highly concentrated water after the second water extraction unit, and discharges purified water. A distillation crystallization unit is provided.

In the water treatment apparatus according to one aspect of the present invention, in the above invention, the impurities include calcium, and along the flow direction of the water to be treated, and at least one of the stage before the second coagulating sedimentation part and the stage before the second water extraction part is provided with a calcium removing part capable of removing the calcium.

In the water treatment apparatus according to one aspect of the present invention, in the above invention, the impurities include calcium, and calcium is dispersed in the water to be treated in a stage prior to the first water extraction unit along the flow direction of the water to be treated. It is characterized by being configured so that an agent can be added.

A water treatment apparatus according to an aspect of the present invention is characterized in that, in the above invention, the flocculant for flocculating the silica in the flocculation-sedimentation section contains flocculation-sedimentation sludge precipitated in the flocculation-sedimentation section.

A water treatment apparatus according to an aspect of the present invention is characterized in that, in the above invention, the impurity contains magnesium.

A water treatment method according to an aspect of the present invention is a water treatment method for extracting water from water to be treated containing impurities containing silica, wherein the silica contained in the impurities is added to the water to be treated. A first coagulation-sedimentation step of flocculating and removing at least a portion, and after the first coagulation-sedimentation step, at least one of the forward osmosis membrane and the reverse osmosis membrane extracts permeated water from the water to be treated, a first water extraction step of discharging the concentrated water obtained by extracting the permeated water from the water to be treated; and after the first water extraction step, the silica contained in the impurities with respect to the concentrated water After the second coagulation-sedimentation step of flocculating and removing at least part of the second coagulation-sedimentation step, at least one of the forward osmosis membrane and the reverse osmosis membrane extracts permeated water from the concentrated water, and a second water extraction step of discharging highly concentrated water obtained by further concentrating the concentrated water.

In the water treatment method according to one aspect of the present invention, in the above invention, the pH of the water to be treated is adjusted to 8 or more and 12 or less in the first coagulation-sedimentation step and the second coagulation-sedimentation step. and

A water treatment method according to an aspect of the present invention is a water treatment method according to the above invention, wherein a first filtration step of filtering the water to be treated after the first coagulation sedimentation step and before the first water extraction step; and a second filtration step of filtering the concentrated water after the second coagulation sedimentation step and before the second water extraction step.

In the water treatment method according to one aspect of the present invention, in the above invention, the first water extraction step includes a low-pressure reverse osmosis step of extracting the permeated water with a low-pressure reverse osmosis membrane, and the second water extraction step is characterized by including a high pressure reverse osmosis step of extracting the permeated water by a high pressure reverse osmosis membrane or a forward osmosis step of extracting the permeated water by the forward osmosis membrane.

A water treatment method according to an aspect of the present invention is a distillation method in which, after the second water extraction step, the highly concentrated water is subjected to a distillation treatment and/or a crystallization treatment, and purified water is discharged. It is characterized by including a crystallization step.

A water treatment method according to an aspect of the present invention is the above invention, wherein the impurity contains calcium, after the first coagulation-sedimentation step and before the first water extraction step, and after the second coagulation-sedimentation step. At least one of after and before the second water extraction step includes a calcium removal step of removing the calcium.

A water treatment method according to an aspect of the present invention, in the above invention, includes a calcium dispersing step of adding a calcium dispersant to the water to be treated before the first water extraction step, wherein the impurities contain calcium. It is characterized by

In the water treatment method according to one aspect of the present invention, in the above invention, the flocculant for flocculating the silica in the coagulation-sedimentation step contains coagulated sedimentation sludge that has been coagulated and sedimented in the coagulation-sedimentation step. .

A water treatment method according to an aspect of the present invention is characterized in that, in the above invention, the impurity contains magnesium.

ADVANTAGE OF THE INVENTION According to the water treatment apparatus and water treatment method of this invention, when extracting water from the to-be-processed water containing an impurity, it becomes possible to improve the recovery rate of water, suppressing scale generation.

FIG. 1 is a block diagram schematically showing a water treatment device according to a first embodiment of the invention. FIG. 2 is a block diagram schematically showing a water treatment device according to a first modification of the first embodiment of the invention. FIG. 3 is a block diagram schematically showing a conventional water treatment apparatus as a comparative example. FIG. 4 is a block diagram schematically showing a water treatment device according to a second embodiment of the invention. FIG. 5 is a block diagram schematically showing a water treatment device according to a second modification of the second embodiment of the invention. FIG. 6 is a block diagram schematically showing a water treatment device according to a third embodiment of the invention. FIG. 7 is a block diagram schematically showing a water treatment device according to a third modified example of the third embodiment of the invention. FIG. 8 is a block diagram schematically showing a water treatment device according to a fourth embodiment of the invention. FIG. 9 is a block diagram schematically showing a water treatment device according to a fourth modified example of the fourth embodiment of the invention. FIG. 10 is a block diagram schematically showing a first configuration example of the coagulation sedimentation section and the filtration section according to the embodiment of the present invention. FIG. 11 is a block diagram schematically showing a second configuration example of the coagulating sedimentation section and the filtering section according to the embodiment of the present invention. FIG. 12 is a block diagram schematically showing a third configuration example of the coagulating sedimentation section and the filtering section according to the embodiment of the present invention. FIG. 13 is a block diagram schematically showing a fourth configuration example of the coagulation-sedimentation section and the filtration section according to the embodiment of the present invention. FIG. 14 is a block diagram schematically showing a first device example of the forward osmosis device according to the embodiment of the present invention. FIG. 15 is a block diagram schematically showing a second device example of the forward osmosis device according to the embodiment of the present invention. FIG. 16 is a block diagram schematically showing a third device example of the forward osmosis device according to the embodiment of the present invention. FIG. 17 is a block diagram schematically showing a fourth device example of the forward osmosis device according to the embodiment of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, in all the drawings of the following embodiments, the same reference numerals are given to the same or corresponding parts. Moreover, the present invention is not limited to the embodiments described below.

The present invention provides water treatment to obtain fresh water by treating blowdown water, sea water, river water, industrial wastewater, and other water-containing solutions as water to be treated, while suppressing scaling caused by calcium salts, silica, etc. It relates to a technique for improving recovery rate.

First, in order to facilitate understanding of the present invention, intensive studies conducted by the inventors will be described below. As described above, when the solubility inside the membrane is exceeded due to concentration in the process of water treatment using a membrane such as a reverse osmosis (RO) membrane, scaling occurs, which causes clogging of the membrane. become. When scaling occurs, it causes a decrease in the water permeability of the membrane and an increase in pressure loss on the raw water supply side, making it difficult to continue the operation of the water treatment apparatus.

Salts that cause scaling are poorly soluble components. Specifically, the causative substances that cause scaling are mainly sparingly soluble salts, such as silica (SiO ₂ , silicon dioxide), calcium carbonate (CaCO ₃ ), calcium sulfate (CaSO ₄ ), magnesium hydroxide ( Mg(OH) ₂ ), barium sulfate (BaSO ₄ ), and calcium fluoride (CaF ₂ ). Suppression of scaling is described below using CaSO ₄ and silica as examples.

First, CaSO ₄ is a sparingly soluble salt and does not dissolve in acids or alkalis, so once precipitated, it is difficult to remove. Therefore, when CaSO ₄ is contained in the water to be treated that is to be concentrated using a membrane, as a method to prevent CaSO ₄ from precipitating, a coagulating sedimentation unit is installed in front of the membrane, or a water softener using a cation exchange resin is installed. For example, a method of removing calcium (Ca) by rinsing the membrane or a method of adding a chemical agent such as a scale dispersant in the front stage of the membrane to suppress the formation of CaSO ₄ are known.

The present inventor conducted various studies and devised a method of removing silica by providing a flocculation/sedimentation section in the front stage of the membrane, since silica is also a sparingly soluble salt. In this specification, silica is a general term for substances composed of silicon dioxide or SiO ₂ . Here, the solubility of silica greatly increases in alkalinity. Therefore, by adding a pH adjuster such as sodium hydroxide (NaOH) to the coagulating sedimentation part to make the water to be treated alkaline, the generation of scale made of silica can be suppressed, but the membrane is resistant to alkali. must have _In addition, although the change in _solubility of silica is very small in an acidic environment, the rate of crystallization is lowered. It may be possible to suppress the generation of scale consisting of. Also, in order to remove silica, a chemical such as a scale dispersant may be added to the front stage of the film, as in the case of CaSO ₄ .

In addition, the present inventors have further studied, and by further performing coagulation sedimentation treatment on concentrated water obtained using a membrane such as an RO membrane, after removing Ca and silica, forward osmosis equipment and high pressure We devised a method of further concentrating the concentrated water using a reverse osmosis membrane. The embodiments described below have been devised based on the above earnest studies of the inventors.

(First embodiment)
(water treatment equipment)
First, a water treatment apparatus according to a first embodiment of the present invention will be described. The water treatment apparatus 1 according to the first embodiment described below uses, for example, blowdown water discharged from a cooling tower or the like as water to be treated, reusable reclaimed water, and highly concentrated salt water or solid waste. Equipment for obtaining salt. FIG. 1 is a block diagram schematically showing a water treatment device 1 according to the first embodiment. As shown in FIG. 1, the water treatment apparatus 1 according to the first embodiment includes a first coagulating sedimentation unit 10, a first filtering unit 20, a water softener 30, a low pressure reverse osmosis unit 40, a second coagulating sedimentation unit 50, a second 2 filter section 60 , forward osmosis device 70 , and distillation crystallization section 80 .

The first coagulation/sedimentation unit 10, which is part of a plurality of coagulation/sedimentation units, adds a coagulant to the water to be treated that contains scale components such as silica and calcium, thereby coagulating and sedimenting the scale components as sludge. Department. In the first coagulating sedimentation section 10, CaCO ₃ and silica are removed as scale components. Alkali such as NaOH or calcium hydroxide (Ca(OH) ₂ ), sodium carbonate (Na ₂ CO ₃ ), and polyaluminum chloride (PAC: AlCl ₃ ) are added to the first coagulating sedimentation unit 10 . . Aluminum chloride (AlCl ₃ ) may be used instead of polyaluminum chloride.

Here, in the first coagulation-sedimentation unit 10, the pH of the reaction tank (not shown in FIG. 1) that causes coagulation-sedimentation is preferably adjusted to 8 or more and 12 or less, for example 10.5. Also, the concentration of Na ₂ CO ₃ is preferably equivalent to Ca, and the concentration of PAC is preferably two equivalents to SiO ₂ , but they are not necessarily limited.

The water to be treated that has been allowed to stand still in the first coagulating sedimentation unit 10 for, for example, 30 minutes or more is supplied to the first filtering unit 20 after the pH is adjusted to about 6.5, for example, between 4 and 8 inclusive. By adjusting the pH of the water to be treated to about 6.5, aluminum (Al) resulting from PAC contained in the water to be treated becomes insoluble.

The first filtering section 20 as part of the plurality of filtering sections is composed of, for example, a sand filter. The first filtration unit 20 may be configured from a membrane filtration device using a predetermined membrane such as a microfiltration membrane (MF membrane) or an ultrafiltration membrane (UF membrane). In the first filtration unit 20, the supplied water to be treated containing PAC is left to stand for, for example, 30 minutes or longer. Thereby, unreacted PAC is removed in the first filtering section 20 . The water to be treated from which the PAC has been removed is supplied to the water softener 30 . Details of the first coagulating sedimentation unit 10 and the filtering unit 20 will be described later.

The water softener 30 as a calcium removing unit replaces cations such as Ca ions and magnesium (Mg) ions contained in the water to be treated with sodium (Na) ions using a cation exchange resin (cation exchange resin). is. When the water to be treated has a high concentration of HCO ₃ or SO ₄ and the scale risk of scale components containing Ca is high, the Ca concentration reduced by coagulation and sedimentation by the first coagulation and sedimentation unit 10 is insufficient. There are cases. In such a case, it is preferable to use the water softener 30 to remove Ca.

In the first embodiment, the water softener 30 is provided upstream of the low-pressure reverse osmosis section 40, but this is not necessarily the case. The water softener 30 is preferably provided between the first coagulating-sedimentation unit 10 or the second coagulating-sedimentation unit 50 and a device that tends to cause scaling. In addition, since Mg can be removed by providing the water softener 30, the scale risk of Mg(OH) ₂ can be efficiently reduced when the low-pressure reverse osmosis unit 40 or the like provided in the latter stage is operated under alkaline conditions. can do.

Here, a sodium chloride (NaCl) aqueous solution is used to regenerate the water softener 30 . Also, in the case of a zero waste water process (ZLD), the regeneration waste liquid can be treated in the distillation and crystallization unit 80 . In addition, when the RO membrane is used under alkaline conditions, the risk of scaling of Mg(OH) ₂ is high, but since Mg can be removed by the water softener 30, the risk of scaling in low-pressure reverse osmosis membranes and high-pressure reverse osmosis membranes is reduced. can. Furthermore, if there is a possibility that a trace amount of Ca may leak from the water softener 30 and cause scale made of CaCO ₃ , a decarbonation tower or a decarbonation membrane (neither of which is shown) may be installed after the water softener 30. It is preferable to suppress the generation of scales made of CaCO ₃ by installing them.

The low-pressure reverse osmosis section 40 as part of the plurality of water extraction sections or as the first water extraction section is configured with a low-pressure reverse osmosis membrane (low-pressure RO membrane). Examples of low-pressure RO membranes include those with trade names of "ESPA2-LD", "ESPA2 MAX", or "ESPA1" (all manufactured by Hydranautics), or with trade names of "TMG20-400", "TMG20-440C", or "TLF-400DG" (both manufactured by Toray Industries, Inc.) or the like is used. The low-pressure reverse osmosis unit 40 obtains permeated water in which the concentration of impurities has been lowered from the water to be treated by reverse osmosis with a low pressure of about 4 MPa, for example, and discharges concentrated water in which impurities are concentrated. The obtained permeated water is collected as reclaimed water. On the other hand, the discharged concentrated water is supplied to the second coagulating sedimentation section 50 .

The second coagulation/sedimentation unit 50, which is the other part of the plurality of coagulation/sedimentation units, is similar to the first coagulation/sedimentation unit 10 in that the scale components contained in the concentrated water, which is the water to be treated, is coagulated and sedimented as sludge. . In the second aggregation/sedimentation section 50, SiO ₂ is removed as a scale component. Therefore, unlike the first coagulation-sedimentation unit 10 , PAC is added as a coagulant to the concentrated water as the water to be treated in the second coagulation-sedimentation unit 50 . As a result, SiO ₂ contained in the concentrated water is aggregated and precipitated as sludge and removed.

The concentrated water left to stand still in the second coagulating sedimentation section 50 for, for example, 30 minutes or more is supplied to the second filtering section 60 after the pH is adjusted to about 6.5, for example, between 4 and 8. By adjusting the pH of the concentrated water to about 6.5, Al caused by PAC contained in the concentrated water becomes insoluble. In addition, it is also possible to adjust the pH of the concentrated water to about 5.

The second filtering section 60 as another part of the plurality of filtering sections is configured in the same manner as the first filtering section 20 . In the second filtering section 60, the unreacted PAC is removed by allowing the supplied concentrated water to stand, for example, for 30 minutes or longer. The concentrated water from which the PAC has been removed is supplied from the second filtering section 60 to the forward osmosis device 70 .

In the forward osmosis device 70 as the other part of the plurality of water extraction parts or the forward osmosis part, for example, forward osmosis processing using a temperature-sensitive water absorbing agent is performed to obtain permeated water from the concentrated water, and the concentrated water is obtained. It is further concentrated to give high-concentration concentrated water (hereinafter referred to as high-concentrated water). In other words, highly concentrated water is concentrated water to concentrated water. The obtained permeated water is combined with the permeated water discharged from the low-pressure reverse osmosis unit 40 as reclaimed water. On the other hand, highly concentrated water is supplied to the distillation and crystallization section 80 .

When the forward osmosis (FO: Forward Osmosis) membrane (not shown in FIG. 1) provided in the forward osmosis device 70 is made of cellulose acetate, cellulose acetate is weak against alkali and can increase the solubility of silica. Under alkaline conditions, forward osmosis apparatus 70 becomes difficult to operate. Therefore, as described above, the water to be treated in the forward osmosis device 70 can be adjusted to be neutral by removing the silica by the second coagulation-sedimentation unit 50 in the front stage of the forward osmosis device 70. Therefore, the FO membrane made of cellulose acetate can maintain driving using Furthermore, in order to suppress silica scale, it is desirable to adjust the pH of the raw water side outlet of the forward osmosis device 70 to about 5.5.

In the distillation and crystallization unit 80, predetermined energy, specifically steam or electric power, is supplied to perform conventionally known purification processes such as distillation and crystallization on the highly concentrated water. . Purified water refined in the distillation and crystallization section 80 is combined with permeated water discharged from the low-pressure reverse osmosis section 40 and recovered as reclaimed water. The salt as a solid component separated from the purified water is discarded outside. This makes it possible to achieve a zero waste water process (ZLD) that minimizes the generation of waste other than solid content.

(First embodiment)
(Water treatment method)
Next, a first example of a water treatment method using the water treatment apparatus 1 according to the first embodiment configured as described above will be described. In the first embodiment, blowdown water discharged from a cooling tower or the like is used as the water to be treated, and 996 L (996 L/h) of reclaimed water is obtained from 1000 L (1000 L/h) of the water to be treated per unit time. In addition, a case of discharging salt equivalent to 4 L (4 L/h) will be described as an example.

First, the flow rate and each component of the water to be treated introduced into the water treatment apparatus 1 are as follows.
Flow rate; 1000 L/h, TDS (Total Dissolved Solids): 4022 mg/L, Ca: 266 mg/L, SiO ₂ : 126 mg/L

(First coagulation sedimentation step)
When the water to be treated is introduced into the water treatment apparatus 1, it is supplied to the first coagulation-sedimentation section 10, and the first coagulation-sedimentation step is performed. The pH adjuster added to the water to be treated in the first coagulating sedimentation unit 10 is, for example, at least one of NaOH and Ca(OH) ₂ , that is, alkali. In addition, as an alkali, it is not limited to these. Thereby, the pH of the water to be treated is adjusted to about 10.5.

The coagulants added to the water to be treated in the first coagulating sedimentation unit 10 are Na ₂ CO ₃ and PAC, for example. Na ₂ CO ₃ to be added here is preferably added in an equivalent amount to Ca, and PAC is preferably added in an amount twice the equivalent amount to SiO ₂ , but they are not limited. In the first coagulation-sedimentation section 10, this state is left at rest for about 30 minutes. In the first coagulation-sedimentation section 10, CaCO ₃ and at least part of silica are coagulated and removed as scale components from the water to be treated. Each component of the water to be treated discharged from the first coagulating sedimentation unit 10 is as follows.
TDS: 4005 mg/L, Ca: 50 mg/L, _SiO2 : 10 mg/L
That is, in the first coagulation-sedimentation section 10, (266-50=) 216 mg/L of Ca and (126-10=) 116 mg/L of SiO ₂ are removed.

(First filtration step)
The supernatant water obtained by coagulating and sedimenting the scale components in the first coagulating and sedimentation section 10 is supplied as the water to be treated to the first filtering section 20, and the first filtering step is performed. In the first filtering section 20, the pH is adjusted to approximately 6.5 by adding an acid such as sulfuric _{acid (} H2SO4) or HCl. In the first filtering section 20, the water to be treated is allowed to stand for 30 minutes or longer to remove unreacted PAC.

(Calcium removal step)
The water to be treated from which the PAC has been removed in the first filtering section 20 is supplied to the water softener 30 and undergoes a calcium removal step. In the water softener 30, Ca is removed from the water to be treated by, for example, a cation exchange resin. Note that the calcium removal step is preferably performed after the first coagulation-sedimentation step and the second coagulation-sedimentation step described later and before a step in which scaling such as calcium salts is likely to occur. Each component of the water to be treated discharged from the water softener 30 is as follows.
TDS: 4030 mg/L, Ca: 0 mg/L, _SiO2 : 10 mg/L
That is, in the water softener 30, approximately (50-0=)50 mg/L (total amount) of Ca is removed.

(Low pressure reverse osmosis process)
The water to be treated from which Ca has been removed in the water softener 30 is supplied to the low-pressure reverse osmosis unit 40 and subjected to a water extraction process or a low-pressure reverse osmosis process as a first water extraction process. In the low-pressure reverse osmosis unit 40, 90% of the reclaimed water is recovered from the water to be treated by the RO membrane to which a predetermined pressure dependent on the TDS, here a pressure of 4.0 MPa is applied, while 10% of the concentrated water is recovered. Ejected. Here, since silica is removed in the first coagulation-sedimentation section 10, the recovery rate of reclaimed water by the low-pressure reverse osmosis section 40 can be improved to 90%.

In the first embodiment, the water to be treated is discharged from the low-pressure reverse osmosis unit 40 at a flow rate of (1000 L/h×90%=) 900 L/h and recovered as reclaimed water. Each component of the reclaimed water is as follows.
TDS: 40 mg/L, Ca: 0 mg/L, _SiO2 : 1 mg/L
That is, in the low pressure reverse osmosis section 40, the TDS is reduced to (40/4030≈)0.01 times and the SiO ₂ is reduced to (1/10≈)0.1 times.

Also, the concentrated water is discharged from the low-pressure reverse osmosis unit 40 at a flow rate of (1000 L/h×10%=) 100 L/h. Each component of the concentrated water is as follows.
TDS: 39940 mg/L, Ca: 0 mg/L, _SiO2 : 91 mg/L
That is, in the low-pressure reverse osmosis unit 40, the water to be treated is concentrated in TDS by (39940/4030≈) 9.9 times and in SiO ₂ by (91/10=) by 9.1 times.

(Second coagulation sedimentation step)
The concentrated water concentrated in the low-pressure reverse osmosis section 40 is supplied to the second coagulation-sedimentation section 50 to undergo the second coagulation-sedimentation step. In the first embodiment, since Ca is removed from the water to be treated by the water softener 30, the flocculant added to the concentrated water of the second coagulation-sedimentation unit 50 is, for example, PAC that aggregates _SiO2 . be. It is preferable to add PAC in an amount twice the equivalent of SiO ₂ . In the first coagulation-sedimentation section 10, this state is left at rest for about 30 minutes. In the first coagulation-sedimentation section 10, at least part of silica is coagulated and removed as a scale component from the water to be treated.

(Second filtration step)
Concentrated water obtained by coagulating and sedimenting silica as a scale component in the second coagulating and sedimentation section 50 is supplied to the second filtering section 60, and the second filtering step is performed. In the second filtering section 60, the pH is adjusted to approximately 5 to 6.5 by adding an acid such as H ₂ SO ₄ or HCl. In the second filtering section 60, the concentrated water is allowed to stand for 30 minutes or longer to remove unreacted PAC.
Each component of the concentrated water discharged from the second filtering section 60 is as follows.
TDS: 40350 mg/L, Ca: 0 mg/L, _SiO2 : 10 mg/L
That is, the second coagulating sedimentation section 50 and the second filtering section 60 remove 81 mg/L of SiO ₂ (91−10=).

(Forward osmosis treatment process)
Next, the concentrated water discharged from the second filtration unit 60 is supplied to the forward osmosis device 70 and subjected to a forward osmosis treatment process. In the forward osmosis device 70, regenerated water is obtained from the concentrated water, and highly concentrated water that is further concentrated is discharged. Specifically, in the forward osmosis device 70, (2/3≈) 67% regenerated water is recovered from the concentrated water by the FO membrane, while (1/3≈) 33% highly concentrated water is discharged.

In the first embodiment, the reclaimed water is discharged from the forward osmosis device 70 at a flow rate of (100 L/h×67%=) 67 L/h and collected. On the other hand, highly concentrated water is discharged from the forward osmosis device 70 at a flow rate of (100 L/h×33%=) 33 L/h. Each component of highly concentrated water is as follows.
TDS: 121050 mg/L, Ca: 0 mg/L, _SiO2 : 30 mg/L
That is, in the forward osmosis device 70, the concentrated water is concentrated three times (1211050/40350=) in TDS and three times (30/10=) in SiO ₂ . That is, in the first embodiment, the water to be treated with a flow rate of 1000 L/h can be discharged as highly concentrated water with a flow rate of 33 L/h. On the other hand, in the prior art, the flow rate of the discharged concentrated water is 250 L/h for the water to be treated having a flow rate of 1000 L/h. That is, according to the water treatment apparatus 1 according to the first embodiment, the water to be treated can be concentrated about 7.6 times more than the conventional one before being discharged, and the recovery rate of the reclaimed water can be greatly improved.

(Distillation crystallization step)
The highly concentrated water concentrated in the forward osmosis device 70 is supplied to the distillation and crystallization section 80 to undergo the distillation and crystallization process. Steam and electric power are supplied to the distillation and crystallization unit 80, and the highly concentrated water is subjected to conventionally known purification treatments such as distillation and crystallization at a temperature of, for example, about 120.degree. Note that the purification treatment is not limited to distillation treatment or crystallization treatment, and various treatments can be employed as long as they are evaporation solidification techniques. Purified water purified by the distillation and crystallization unit 80 is recovered as reclaimed water. The salt as a solid component separated from the purified water is discarded outside. In the first embodiment, 4 L/h of solid components are removed from highly concentrated water with a flow rate of 33 L/h, and purified water with a flow rate of 29 L/h is recovered as reclaimed water.

The permeated water obtained from the low-pressure reverse osmosis unit 40 is supplied with the permeated water obtained from the forward osmosis device 70 and the purified water obtained from the distillation and crystallization unit 80 and recovered. As a result, the water treatment apparatus 1 according to the first embodiment recovers reclaimed water with a flow rate of (900 + 67 + 29 =) 996 L / h from the water to be treated with a flow rate of 1000 L / h, and solid components for 4 L / h is removed. Each component of the reclaimed water is as follows.
TDS: 36 mg/L, Ca: 0 mg/L, _SiO2 : 1 mg/L

(First modification)
Next, the 1st modification of the water treatment apparatus by 1st Embodiment mentioned above is demonstrated. FIG. 2 is a block diagram schematically showing a water treatment device according to a first modified example of the first embodiment. As shown in FIG. 2, the water treatment apparatus 2 according to the first modified example is provided with a high-pressure reverse osmosis section 90 instead of the forward osmosis apparatus 70 of the water treatment apparatus 1 .

The high-pressure reverse osmosis unit 90 as the other portion of the plurality of water extraction units or the second water extraction unit is configured with a high-pressure reverse osmosis membrane (high-pressure RO membrane). Examples of high-pressure RO membranes include "SWC5-LD" or "SWC5 MAX" (both manufactured by Hydranautics), and "TM820M-440", "TM820R-440", or "TM820V-440". (both manufactured by Toray Industries, Inc.) and the like are used. In the high-pressure reverse osmosis unit 90, permeated water with reduced impurity concentration is discharged from the concentrated water by reverse osmosis with a high pressure of about 8 MPa, for example, and highly concentrated water in which the concentrated water is further concentrated is discharged. . The discharged permeated water joins the permeated water discharged from the low-pressure reverse osmosis section 40 as reclaimed water. On the other hand, the discharged highly concentrated water is supplied to the distillation and crystallization section 80 . Other configurations are the same as those of the first embodiment.

Moreover, when a polyamide-based material is used for the high-pressure RO membrane, operation under alkaline conditions becomes possible. Therefore, when the removal rate of silica in the second coagulating sedimentation section 50 is low, scaling to the high pressure RO membrane can be suppressed by operating the high pressure reverse osmosis section 90 under alkaline conditions. In this case, similarly to the forward osmosis apparatus 70 described above, the pH can be adjusted to about 5.5 on the permeate discharge side.

(Second embodiment)
(Water treatment method)
Next, a second embodiment of the water treatment method using the water treatment apparatus 2 according to the first modified example configured as described above will be described. The conditions for the water to be treated in the second embodiment are the same as those for the water to be treated in the first embodiment. First, in the water treatment method according to the second embodiment, the first coagulation-sedimentation step, the first filtration step, the calcium removal step, the reverse osmosis step, the second coagulation-sedimentation step, and the second filtration step are the same as in the first embodiment. is similar to

(High pressure reverse osmosis process)
Next, following the second filtration process, the concentrated water discharged from the second filtration section 60 is supplied to the high pressure reverse osmosis section 90 and subjected to the high pressure reverse osmosis process as the second water extraction process. In the high-pressure reverse osmosis section 90, permeated water is obtained from the concentrated water, and highly concentrated water that is further concentrated is discharged. Specifically, in the high-pressure reverse osmosis unit 90, (1/2=) 50% regenerated water is recovered from the concentrated water by the high-pressure reverse osmosis membrane (high-pressure RO membrane), while (1/2=) 50% Highly concentrated water is discharged.

In the first embodiment, permeated water is discharged from the high-pressure reverse osmosis unit 90 at a flow rate of (100 L/h×50%=) 50 L/h and recovered as reclaimed water. On the other hand, highly concentrated water is discharged from the high-pressure reverse osmosis unit 90 at a flow rate of (100 L/h×50%=) 50 L/h. Each component of highly concentrated water is as follows.
TDS: 80700 mg/L, Ca: 0 mg/L, _SiO2 : 20 mg/L

That is, the high-pressure reverse osmosis unit 90 concentrates the concentrated water twice (80700/40350=) in TDS and twice (20/10=) in SiO ₂ . As a result, in the second embodiment, highly concentrated water with a flow rate of 50 L/h is discharged from the water to be treated with a flow rate of 1000 L/h. On the other hand, in the prior art, the flow rate of the discharged concentrated water is 250 L/h for the water to be treated having a flow rate of 1000 L/h. That is, according to the water treatment apparatus 2 of the second embodiment, the water to be treated can be concentrated about five times more than the conventional one before being discharged, and the recovery rate of reclaimed water can be greatly improved.

(Distillation crystallization step)
The highly concentrated water concentrated in the high-pressure reverse osmosis section 90 is supplied to the distillation and crystallization section 80 to undergo the distillation and crystallization process. In the distillation and crystallization unit 80, the highly concentrated water is subjected to purification treatment at a temperature of about 120° C., for example, and the purified purified water is recovered as reclaimed water. The salt as a solid component separated from the purified water is discarded outside. In the second embodiment, 4 L/h of solid components are removed from highly concentrated water with a flow rate of 50 L/h, and purified water with a flow rate of 46 L/h is recovered as reclaimed water.

The permeated water obtained from the low-pressure reverse osmosis section 40 is supplied with the permeated water obtained from the high-pressure reverse osmosis section 90 and the purified water obtained from the distillation and crystallization section 80 and recovered. As a result, the water treatment device 2 according to the first modification recovers reclaimed water with a flow rate of (900 + 50 + 46 =) 996 L / h from the water to be treated with a flow rate of 1000 L / h, and 4 L / h of solid components. removed. Each component of the reclaimed water is as follows.
TDS: 36 mg/L, Ca: 0 mg/L, _SiO2 : 1 mg/L

(Water treatment equipment according to prior art)
Next, in order to explain the effects of the water treatment apparatuses 1 and 2 described above, a conventional water treatment apparatus will be described. FIG. 3 is a block diagram schematically showing a conventional water treatment apparatus as a comparative example described in Non-Patent Document 1. As shown in FIG.

As shown in FIG. 3 , the prior art water treatment apparatus 100 comprises a coagulating sedimentation section 110 , a filtration section 120 , a water softener 130 , a low pressure reverse osmosis section 140 and a distillation and crystallization section 180 . The coagulation-sedimentation unit 110 is configured with a conventionally known coagulation-sedimentation tank. The filtering unit 120 is configured from a conventionally known sand filtering device. The water softener 130, the low-pressure reverse osmosis section 140, and the distillation crystallization section 180 have the same configurations as the water softener 30, the low-pressure reverse osmosis section 40, and the distillation crystallization section 80 according to the first embodiment, respectively.

(Water treatment method)
(Comparative example)
Next, as a comparative example, a water treatment method using the conventional water treatment apparatus 100 will be described. The conditions of the water to be treated in the comparative example are the same as those of the water to be treated in the first and second embodiments, and the flow rate and components of the water to be treated introduced into the water treatment apparatus 100 are as follows. .
Flow rate; 1000 L/h, TDS: 4022 mg/L, Ca: 266 mg/L, _SiO2 : 126 mg/L

(Coagulation sedimentation process)
When the water to be treated is introduced into the water treatment apparatus 100, it is supplied to the coagulation-sedimentation section 110, where the coagulation-sedimentation step is performed. The pH adjuster added to the water to be treated in the coagulating sedimentation section 110 is at least one of NaOH and Ca(OH) ₂ . Thereby, the pH of the water to be treated is adjusted to about 10 to 10.5. The water to be treated in the coagulating-sedimentation unit 110 contains Na ₂ CO ₃ for coagulating and sedimenting Ca, and Na ₂ CO ₃ is added in an amount equivalent to Ca. In the coagulating sedimentation section 110, CaCO ₃ is coagulated and removed from the water to be treated. Each component of the water to be treated discharged from the coagulating sedimentation unit 110 is as follows.
TDS: 4027 mg/L, Ca: 50 mg/L, _SiO2 : 126 mg/L
That is, in the coagulating sedimentation section 110, Ca is removed by (266-50=) 216 mg/L as in the first embodiment.

(Filtration process)
The supernatant water obtained by coagulating and sedimenting CaCO ₃ in the coagulating-sedimenting section 110 is supplied to the filtering section 120 as water to be treated, and undergoes a filtering process.

(Calcium removal step)
The water to be treated obtained from the filtering unit 120 is supplied to the water softener 130 and undergoes a calcium removing process. Ca is removed from the water to be treated in the water softener 130 . Each component of the water to be treated discharged from the water softener 130 is as follows.
TDS: 4134 mg/L, Ca: 0 mg/L, _SiO2 : 126 mg/L

(Low pressure reverse osmosis process)
The water from which Ca has been removed in the water softener 130 is supplied to the low-pressure reverse osmosis unit 140 to undergo the low-pressure reverse osmosis process. In the low-pressure reverse osmosis section 40, 75% of reclaimed water is recovered from the water to be treated by an RO membrane applied with a pressure of about 4.0 MPa, while 25% of concentrated water is discharged. According to the knowledge of the present inventor, the recovery rate of reclaimed water is at most 75% because the water to be treated supplied to the low-pressure reverse osmosis unit 140 contains silica.

In the comparative example, the water to be treated is discharged from the low-pressure reverse osmosis unit 140 at a flow rate of (1000 L/h×75%=) 750 L/h and recovered as reclaimed water. Each component of the reclaimed water is as follows.
TDS: 40 mg/L, Ca: 0 mg/L, _SiO2 : 3 mg/L
That is, in the low-pressure reverse osmosis section 140, TDS is reduced to (40/4134≈)0.01 times and SiO ₂ is reduced to (3/126≈)0.02 times.

On the other hand, concentrated water is discharged from the low-pressure reverse osmosis unit 140 at a flow rate of (1000 L/h×25%=) 250 L/h. Each component of the concentrated water is as follows.
TDS: 16420 mg/L, Ca: 0 mg/L, _SiO2 : 495 mg/L
That is, in the low-pressure reverse osmosis unit 140, the water to be treated is concentrated to TDS (16420/4134≈) 3.9 times and SiO ₂ to (495/126≈) 3.9 times.

That is, in the conventional water treatment apparatus 100, the coagulating sedimentation section 110 removes a portion of Ca, and the water softener 130 completely removes Ca. In addition, in the water treatment apparatus 100, the low-pressure reverse osmosis unit 140 is operated under alkaline conditions with a pH of about 10 to 10.5 for the water to be treated from which Ca has been removed, thereby removing silica. Scaling is suppressed (see Non-Patent Document 1, HERO process). However, according to the findings of the present inventor, even if the low-pressure reverse osmosis unit 140 is operated under alkaline conditions with a pH of about 10 to 10.5, the silica concentration precipitation limit is at most about 400 mg/L. , the concentration ratio by the low-pressure RO membrane is at most about 3 to 4 times.

(Distillation crystallization step)
The concentrated water obtained by the low-pressure reverse osmosis unit 140 is supplied to the distillation crystallization unit 180 and subjected to a distillation crystallization process. In the distillation and crystallization unit 180, steam and electric power are supplied, and conventionally known purification processes such as distillation and crystallization are performed on the concentrated water at a temperature of about 120.degree. Purified water purified by the distillation and crystallization unit 80 is recovered as reclaimed water. The salt as a solid component separated from the purified water is discarded outside. In the comparative example, 4 L/h of solid components are removed from concentrated water with a flow rate of 250 L/h, and purified water with a flow rate of 246 L/h is recovered as reclaimed water.

As described above, in the conventional water treatment apparatus 100, reclaimed water with a flow rate of (750 + 246 =) 996 L / h is recovered from the water to be treated with a flow rate of 1000 L / h, and 4 L / h of solid components are removed. be. Each component of the reclaimed water is as follows.
TDS: 30 mg/L, Ca: 0 mg/L, _SiO2 : 2 mg/L

Here, when the power, steam, and cost in the water treatment device 100 adopted in the comparative example are each set to the standard “100”, the water treatment devices 1 and 2 respectively adopted in the first embodiment and the second embodiment The power, steam and cost ratios are shown in Table 1. Table 2 shows the amount of electric power used and the amount of steam used per unit amount of waste water in the water treatment apparatuses 100, 1, and 2 employed in the comparative example, the first embodiment, and the second embodiment.

From Tables 1 and 2, it can be seen that the electric power in the water treatment devices 1 and 2 used in the first and second examples is 2.3 times and 2.0 times that of the comparative example, respectively. . This is because the water treatment devices 1 and 2 have more forward osmosis devices 70 and high-pressure reverse osmosis units 90 than the water treatment device 100 . On the other hand, from Tables 1 and 2, in the water treatment apparatuses 1 and 2, the amount of steam used is 0.23 times and 0.23 times that of the comparative example compared to the water treatment apparatus 100, respectively. It can be seen that it is greatly reduced by 15 times. This is probably because in the water treatment apparatuses 1 and 2 , the water to be treated is concentrated in the low pressure reverse osmosis section 40 to a higher concentration than in the low pressure reverse osmosis section 140 of the water treatment apparatus 100 .

Since the distillation process and the crystallization process consume a large amount of steam and electric power, and the equipment costs tend to increase, it is desirable to reduce the size of the distillation and crystallization unit 80 . In addition, since energy is required to generate steam, by significantly reducing the amount of steam used, the total energy required to operate the water treatment devices 1 and 2 can be compared to the total energy required to operate the water treatment device 100. can be significantly reduced. As a result, as shown in Table 1, according to the water treatment apparatuses 1 and 2 according to the first embodiment, it is possible to reduce the cost required for equipment and operation by 35 to 40%.

That is, in the conventional water treatment method, it is possible to suppress the generation of scale to some extent, but in ZLD in particular, it is necessary to achieve a much higher concentration than in the past. In the above-mentioned conventional technology (see Non-Patent Document 1), ZLD is realized by providing a processing unit that performs distillation and crystallization in the final stage of the water treatment device, but the required energy is said to increase. I had a problem. This problem also exists in waste water processes other than ZLD where concentrated waste water is produced, and there has been a demand for a reduction in the energy required. In contrast, according to the first embodiment, when extracting water from water to be treated containing impurities, the water treatment devices 1 and 2 and the water treatment can reduce the energy required while suppressing the generation of scale. can provide a method.

According to the first embodiment described above, silica is removed in addition to Ca in the first coagulation-sedimentation unit 10 preceding the low-pressure reverse osmosis unit 40, so that the low-pressure RO membrane in the low-pressure reverse osmosis unit 40 Scaling can be suppressed by suppressing the precipitation of silica that occurs in the As a result, the concentration ratio in the low-pressure reverse osmosis section 40 can be improved.

Further, according to the first embodiment, the second coagulation/sedimentation unit 50 is provided between the low-pressure reverse osmosis unit 40 and the forward osmosis device 70 or the high-pressure reverse osmosis unit 90, and the concentrated water obtained by concentrating the water to be treated By removing silica, the occurrence of scaling in the forward osmosis device 70 and the high-pressure reverse osmosis section 90 can be suppressed, and the concentration ratio can be further improved. In addition, a water softener 30 is provided in the front stage of the low-pressure reverse osmosis unit 40, and Ca is further removed from the water to be treated from which Ca has been partially removed in the first coagulation-sedimentation unit 10. Scaling caused by Ca can be suppressed.

In addition, in the conventional water treatment apparatus 100, for example, the concentrated water with a flow rate of 250 L / h was required to be subjected to distillation treatment or crystallization treatment, whereas the water treatment according to the first embodiment and its first modification In the apparatuses 1 and 2, the highly concentrated water with a flow rate of 33 to 50 L/h can be distilled or crystallized, so that the total energy consumption and cost can be reduced.

Furthermore, for example, in the prior art described in Patent Document 2, coagulation sedimentation is performed in two stages, but in the first stage, a dispersant is used and silica is not removed, so compared to the present invention. Therefore, the cost of the dispersant increases, the ability to suppress the generation of scale is low, and high concentration is difficult. That is, in the technique described in Patent Document 2, a dispersant is used to suppress scale caused by silica. is limited.

In the prior art described in Patent Document 3, coagulation sedimentation is performed in one step, and silica is removed by coagulation sedimentation after suppressing scale formation using alkali. That is, Patent Literature 3 discloses a technique using an alkali to suppress scale generated by silica. However, in a highly alkaline environment, deterioration of RO membranes and FO membranes is likely to be accelerated, so it is not preferable for RO membranes and FO membranes to use alkali to suppress the generation of scale. In addition, when an evaporator is provided in the latter stage, there is a high possibility that a large amount of silica will solidify in the evaporator, and the silica will easily adhere to the evaporator, increasing the load on the evaporator. occur.

In the prior art described in Patent Document 4, coagulation-sedimentation is performed in one step, silica is removed by coagulation-sedimentation, and the treated water is passed through the RO membrane and then through the FO membrane. There is a risk of silica scale in the membrane, limiting the improvement in concentration. In contrast, in the present invention, the coagulation sedimentation is performed in two stages, the stage before the RO membrane and the stage before the FO membrane, and silica is removed in both stages of coagulation sedimentation. can be greatly suppressed, and high concentration can be realized.

Furthermore, when the amount of concentrated water becomes extremely small during the process of concentration, it becomes difficult to flow the minimum amount of concentrated water through the high-pressure RO membrane and the FO membrane. Although a circulation system may be provided to secure the concentration flow rate, there arises a problem that the required energy increases. Furthermore, if you try to operate below the minimum concentrated water amount, even if it is below the saturation solubility, there is a high possibility that scale will be generated due to the influence of concentration polarization. From this point of view as well, it is preferable to remove silica by two-stage coagulation sedimentation using the water treatment apparatus 1 according to the first embodiment described above.

(Second embodiment)
Next, a water treatment device according to a second embodiment of the present invention will be described. FIG. 4 is a block diagram schematically showing the water treatment device according to the second embodiment. As shown in FIG. 4, unlike the water treatment apparatus 1 according to the first embodiment, the water treatment apparatus 3 according to the second embodiment is not provided with the water softener 30, and the water discharged from the first filtration unit 20 A mechanism (not shown) is provided for adding a calcium dispersant to the water to be treated. Other configurations are the same as those of the water treatment device 1 according to the first embodiment.

(Water treatment method)
(Third embodiment)
Next, a third example of a water treatment method using the water treatment apparatus 3 according to the second embodiment configured as described above will be described. The water to be treated introduced into the water treatment apparatus 3 in the third embodiment is the same as the water to be treated in the first and second embodiments. In addition, in the water treatment method according to the third embodiment, the first coagulation sedimentation step and the first filtration step are the same as in the first embodiment.
Each component of the water to be treated after the first filtration step is as follows, similarly to the first embodiment.
TDS: 4005 mg/L, Ca: 50 mg/L, _SiO2 : 10 mg/L

(Calcium dispersion step)
By adding a calcium dispersant to the water to be treated from which PAC has been removed in the first filtration unit 20, a calcium dispersing step for suppressing the generation of CaSO ₄ is performed. The amount of calcium dispersant added depends on the type of dispersant, but is preferably 1 mg/L or more and 100 mg/L or less. In addition to the calcium dispersant, H ₂ SO ₄ or HCl is added to adjust the pH of the water to be treated from 6.5 to 5.0 in the first filtration section 20 . In addition, as long as it is an acidic solution, it is not necessarily limited to these. The calcium dispersing step is preferably performed after the first coagulating sedimentation step and before a step in which scaling such as calcium salts is likely to occur.

(Low pressure reverse osmosis process)
The water to be treated whose generation of CaSO ₄ has been suppressed by the addition of the calcium dispersant is supplied to the low pressure reverse osmosis unit 40 and subjected to the low pressure reverse osmosis process. In the low-pressure reverse osmosis unit 40, 90% of the reclaimed water is recovered from the water to be treated by a low-pressure RO membrane applied with a predetermined pressure dependent on the TDS, here, for example, a pressure of 4.0 MPa, while 10% concentration water is discharged.

In the third embodiment, permeated water is discharged from the low-pressure reverse osmosis unit 40 at a flow rate of (1000 L/h×90%=) 900 L/h and recovered as reclaimed water. Each component of the permeated water is as follows.
TDS: 40 mg/L, Ca: less than 1 mg/L, _SiO2 : 1 mg/L
That is, in the low-pressure reverse osmosis section 40, TDS is reduced to (40/4005≈)0.01 times and SiO ₂ is reduced to (1/10≈)0.1 times.

Also, the concentrated water is discharged from the low-pressure reverse osmosis unit 40 at a flow rate of (1000 L/h×10%=) 100 L/h. Each component of the concentrated water is as follows.
TDS: 40050 mg/L, Ca: 500 mg/L, _SiO2 : 100 mg/L
That is, in the low-pressure reverse osmosis unit 40, the water to be treated is concentrated to TDS (40050/4005=) 10 times, Ca to (500/50=) 10 times, and SiO ₂ to (100/10=) 10 times. .

(Second coagulation sedimentation step)
The concentrated water concentrated in the low-pressure reverse osmosis section 40 is supplied to the second coagulation-sedimentation section 50 to undergo the second coagulation-sedimentation step. In the third embodiment, a calcium dispersant is added to the water to be treated and Ca remains. Therefore, a pH adjuster and a flocculant are added to the concentrated water of the second coagulating sedimentation unit 50. be. The pH adjuster to be added is NaOH or Ca(OH) ₂ like the pH adjuster added to the first coagulating sedimentation part 10, but is not necessarily limited. Flocculants added are eg Na ₂ CO ₃ and PAC to flocculate Ca and silica. Also, the concentration of Na ₂ CO ₃ is preferably equivalent to Ca, and the concentration of PAC is preferably two equivalents to SiO ₂ , but they are not necessarily limited. In the second aggregation-sedimentation section 50, this state is left at rest for about 30 minutes. In the second coagulation-sedimentation section 50, CaCO ₃ and part of silica are coagulated and removed as scale components from the water to be treated.

(Second filtration step)
Concentrated water obtained by coagulating and sedimenting CaCO ₃ and silica as scale components in the second coagulating and sedimentation section 50 is supplied to the second filtering section 60 and subjected to the second filtering step. In the second filtering section 60, an acid such as H ₂ SO ₄ or HCl is added to adjust the pH to about 5-6.5. In the second filtering section 60, the concentrated water is allowed to stand for 30 minutes or longer to remove unreacted PAC.
Each component of the concentrated water discharged from the second filtering section 60 is as follows.
TDS: 40000 mg/L, Ca: 50 mg/L, _SiO2 : 10 mg/L
That is, the second coagulating sedimentation section 50 and the second filtering section 60 remove (500-50=) 450 mg/L of Ca and (100-10=) 90 mg/L of SiO ₂ .

(Forward osmosis treatment process)
Next, the concentrated water discharged from the second filtration unit 60 is supplied to the forward osmosis device 70 and subjected to a forward osmosis treatment process, whereby regenerated water is obtained from the concentrated water and highly concentrated water that is further concentrated is discharged. be. Specifically, in the forward osmosis device 70, (2/3≈) 67% regenerated water is recovered from the concentrated water by the FO membrane, while (1/3≈) 33% highly concentrated water is discharged.

In the third embodiment, permeated water is discharged from the forward osmosis device 70 at a flow rate of (100 L/h×67%=) 67 L/h and recovered as reclaimed water. On the other hand, highly concentrated water is discharged from the forward osmosis device 70 at a flow rate of (100 L/h×33%=) 33 L/h. Each component of highly concentrated water is as follows.
TDS: 120000 mg/L, Ca: 150 mg/L, _SiO2 : 30 mg/L
That is, in the forward osmosis device 70, the concentrated water is concentrated three times (120000/40000=) in TDS, three times (150/50=) in Ca, and three times (30/10=) in SiO ₂ . In addition, in the third embodiment, highly concentrated water with a flow rate of 33 L/h can be discharged from the water to be treated with a flow rate of 1000 L/h. , the water to be treated can be concentrated about 7.6 times more than the conventional technology before being discharged, and the recovery rate of reclaimed water can be greatly improved.

(Distillation crystallization step)
The highly concentrated water concentrated in the forward osmosis device 70 is supplied to the distillation and crystallization section 80 in the same manner as in the first embodiment, where the distillation and crystallization process is performed. Purified water purified by the distillation and crystallization unit 80 is recovered as reclaimed water. The salt as a solid component separated from the purified water is discarded outside. In the third embodiment, 4 L/h of solid components are removed from highly concentrated water with a flow rate of 33 L/h, and purified water with a flow rate of 29 L/h is recovered as reclaimed water.

The permeated water obtained from the low-pressure reverse osmosis unit 40 is supplied with the permeated water obtained from the forward osmosis device 70 and the purified water obtained from the distillation and crystallization unit 80 and recovered. Thus, in the third embodiment, the water treatment apparatus 3 according to the second embodiment recovers reclaimed water with a flow rate of (900 + 67 + 29 =) 996 L / h from the water to be treated with a flow rate of 1000 L / h, 4 L/h of solids are removed. Each component of the reclaimed water is as follows.
TDS: 36 mg/L, Ca: less than 1 mg/L, _SiO2 : 1 mg/L

(Second modification)
Next, the 2nd modification of the water treatment apparatus by 2nd Embodiment mentioned above is demonstrated. FIG. 5 is a block diagram schematically showing a water treatment device according to a second modified example. As shown in FIG. 5, the water treatment apparatus 4 according to the second modified example is provided with a high-pressure reverse osmosis section 90 similar to that of the first modified example instead of the forward osmosis device 70 of the water treatment apparatus 3 .

In the high-pressure reverse osmosis unit 90, permeated water with reduced impurity concentration is discharged from the concentrated water by reverse osmosis with a high pressure of about 8 MPa, for example, and highly concentrated water in which the concentrated water is further concentrated is discharged. . The discharged permeated water joins the permeated water discharged from the low-pressure reverse osmosis section 40 as reclaimed water. On the other hand, the discharged highly concentrated water is supplied to the distillation and crystallization section 80 . Other configurations are the same as those of the second embodiment.

(Water treatment method)
(Fourth embodiment)
Next, a fourth embodiment of the water treatment method using the water treatment apparatus 4 according to the second modified example configured as described above will be described. The water to be treated in the fourth embodiment is the same as the water to be treated in the first to third embodiments. First, in the water treatment method according to the fourth embodiment, the first coagulation-sedimentation step, the first filtration step, the calcium dispersion step, the low-pressure reverse osmosis step, the second coagulation-sedimentation step, and the second filtration step are performed in the third embodiment. Same as example.

(High pressure reverse osmosis process)
Next, following the second filtration process, the concentrated water discharged from the second filtration section 60 is supplied to the high pressure reverse osmosis section 90 and subjected to the high pressure reverse osmosis process. In the high-pressure reverse osmosis section 90, permeated water is obtained from the concentrated water, and highly concentrated water that is further concentrated is discharged.

Specifically, in the high-pressure reverse osmosis unit 90, (1/2=) 50% of the permeated water is recovered as reclaimed water from the concentrated water by the high-pressure reverse osmosis membrane (high-pressure RO membrane), while (1/2=) 50% highly concentrated water is discharged. In the fourth embodiment, permeated water is discharged from the high-pressure reverse osmosis unit 90 at a flow rate of (100 L/h×50%=) 50 L/h and recovered as reclaimed water. On the other hand, highly concentrated water is discharged from the high-pressure reverse osmosis unit 90 at a flow rate of (100 L/h×50%=) 50 L/h. Each component of highly concentrated water is as follows.
TDS: 80000 mg/L, Ca: 100 mg/L, _SiO2 : 20 mg/L

That is, the concentrated water is concentrated twice (80000/40000=) in TDS, twice (100/50=) in Ca, and twice (20/10=) in SiO ₂ by the high-pressure reverse osmosis unit 90. . As a result, in the fourth embodiment, highly concentrated water with a flow rate of 50 L/h is discharged from the water to be treated with a flow rate of 1000 L/h. On the other hand, in the prior art, the flow rate of the discharged concentrated water is 250 L/h for the water to be treated having a flow rate of 1000 L/h. That is, according to the water treatment apparatus 2 of the second embodiment, the water to be treated can be concentrated about five times more than the conventional one before being discharged, and the recovery rate of reclaimed water can be greatly improved.

(Distillation crystallization step)
The highly concentrated water concentrated in the high-pressure reverse osmosis section 90 is supplied to the distillation and crystallization section 80 to undergo the distillation and crystallization process. In the distillation and crystallization unit 80, the highly concentrated water is subjected to purification treatment at a temperature of about 120° C., for example, and the purified purified water is recovered as reclaimed water. The salt as a solid component separated from the purified water is discarded outside. In the second embodiment, 4 L/h of solid components are removed from highly concentrated water with a flow rate of 50 L/h, and purified water with a flow rate of 46 L/h is recovered as reclaimed water.

The permeated water obtained from the low-pressure reverse osmosis section 40 is supplied with the permeated water obtained from the high-pressure reverse osmosis section 90 and the purified water obtained from the distillation and crystallization section 80 and recovered. Thus, in the fourth embodiment, the water treatment device 4 according to the second modification recovers reclaimed water with a flow rate of (900 + 50 + 46 =) 996 L / h from the water to be treated with a flow rate of 1000 L / h, and 4 L /h of solids are removed. Each component of the reclaimed water is as follows, similarly to the second embodiment.
TDS: 36 mg/L, Ca: less than 1 mg/L, _SiO2 : 1 mg/L

According to the second embodiment described above, silica is removed in addition to Ca in the first coagulation-sedimentation unit 10 preceding the low-pressure reverse osmosis unit 40, and the low-pressure reverse osmosis unit 40, the forward osmosis device 70, and the high-pressure reverse osmosis unit 40 are removed. By providing the second coagulation/sedimentation section 50 between the permeation section 90 and removing silica from the concentrated water in which the water to be treated is concentrated, the same effect as in the first embodiment can be obtained.

(Third embodiment)
Next, a water treatment device according to a third embodiment of the present invention will be described. FIG. 6 is a block diagram schematically showing the water treatment device according to the third embodiment. As shown in FIG. 3, unlike the water treatment apparatus 3 according to the second embodiment, the water treatment apparatus 3 according to the third embodiment is not provided with the distillation and crystallization unit 80, and the water discharged from the forward osmosis apparatus is discharged from the forward osmosis apparatus. The highly concentrated water is discarded as concentrated waste water. Other configurations are the same as those of the water treatment device 3 according to the second embodiment.

(Fifth embodiment)
(Water treatment method)
Next, a fifth example of a water treatment method using the water treatment apparatus 5 according to the third embodiment configured as described above will be described. The water to be treated introduced into the water treatment apparatus 5 in the fifth embodiment is the same as the water to be treated in the first to fourth embodiments. Further, in the water treatment method according to the fifth embodiment, the first coagulation-sedimentation step, the first filtration step, the calcium dispersion step, the low-pressure reverse osmosis step, the second coagulation-sedimentation step, the second filtration step, and the forward osmosis treatment step is similar to Example 3, while the distillation crystallization step is not performed.

In the fifth embodiment, the flow rate of the water to be treated discharged from the forward osmosis device 70 in the forward osmosis treatment process is 33 L/h, and each component is as follows.
TDS: 120000 mg/L, Ca: 150 mg/L, _SiO2 : 30 mg/L

In the fifth embodiment, permeated water is discharged from the forward osmosis device 70 at a flow rate of (100 L/h×67%=) 67 L/h and recovered as reclaimed water. On the other hand, highly concentrated water is discharged from the forward osmosis device 70 at a flow rate of (100 L/h×33%=) 33 L/h. Each component of highly concentrated water is as follows.
TDS: 120000 mg/L, Ca: 150 mg/L, _SiO2 : 30 mg/L
That is, in the forward osmosis device 70, the concentrated water is concentrated three times (120000/40000=) in TDS, three times (150/50=) in Ca, and three times (30/10=) in SiO ₂ . In addition, in the fifth embodiment, highly concentrated water with a flow rate of 33 L/h can be discharged from the water to be treated with a flow rate of 1000 L/h. , the water to be treated can be concentrated about 7.6 times more than the conventional technology before being discharged, and the recovery rate of reclaimed water can be greatly improved.

Further, in the fifth embodiment, the highly concentrated water discharged from the forward osmosis device 70 is discarded, and the permeated water obtained from the forward osmosis device 70 is supplied to the permeated water obtained from the low-pressure reverse osmosis unit 40 and recovered. be done. Thus, in the fifth embodiment, the water treatment apparatus 5 according to the third embodiment recovers reclaimed water with a flow rate of (900 + 67 =) 967 L / h from the water to be treated with a flow rate of 1000 L / h, 33 L/h of highly concentrated water is discarded. Each component of the reclaimed water is as follows.
TDS: 37 mg/L, Ca: less than 1 mg/L, _SiO2 : 1 mg/L

(Third modification)
Next, the 3rd modification of the water treatment apparatus by 3rd Embodiment mentioned above is demonstrated. FIG. 7 is a block diagram schematically showing a water treatment device according to a third modified example. As shown in FIG. 7, the water treatment device 6 according to the third modified example is provided with a high-pressure reverse osmosis section 90 similar to the first and second modified examples instead of the forward osmosis device 70 of the water treatment device 3 . In the high-pressure reverse osmosis unit 90, the permeated water in which the concentration of impurities has been lowered is discharged from the concentrated water by reverse osmosis with a high pressure of about 8 MPa, for example, and recovered as reclaimed water, and the concentrated water is further concentrated. Highly concentrated water is discarded as concentrated waste water. Other configurations are the same as those of the third embodiment.

(Water treatment method)
(Sixth embodiment)
Next, a sixth embodiment of the water treatment method using the water treatment apparatus 6 according to the third modification constructed as described above will be described. The water to be treated in the sixth embodiment is the same as the water to be treated in the first to fifth embodiments. First, in the water treatment method according to the sixth embodiment, the first coagulation-sedimentation step, the first filtration step, the calcium dispersion step, the low-pressure reverse osmosis step, the second coagulation-sedimentation step, and the second filtration step are performed in the third It is similar to the embodiment. Also, in the water treatment method according to the sixth embodiment, the high-pressure reverse osmosis step is the same as in the first and second modifications.

In the sixth embodiment, highly concentrated water with a flow rate of 50 L/h is discharged from the water to be treated with a flow rate of 1000 L/h. On the other hand, in the prior art, the flow rate of the discharged concentrated water is 250 L/h for the water to be treated having a flow rate of 1000 L/h. That is, according to the water treatment apparatus 6 according to the sixth embodiment, the water to be treated can be concentrated about five times as much as the conventional one before being discharged, and the recovery rate of the reclaimed water can be greatly improved.

The permeated water obtained from the high-pressure reverse osmosis section 90 is supplied to the permeated water obtained from the low-pressure reverse osmosis section 40 and recovered. Thus, in the sixth embodiment, the water treatment apparatus 6 according to the third modification recovers reclaimed water with a flow rate of (900 + 50 =) 950 L / h from the water to be treated with a flow rate of 1000 L / h, and 50 L /h of concentrated waste water is discarded. Since the flow rate of the permeate collected from the high-pressure reverse osmosis unit 90 is lower than the flow rate of the permeated water collected from the forward osmosis device 70, the TDS is greater than in the third embodiment. Therefore, each component of the reclaimed water is as follows.
TDS: 38 mg/L, Ca: less than 1 mg/L, _SiO2 : 1 mg/L

According to the third embodiment described above, the first coagulation-sedimentation unit 10 is provided upstream of the low-pressure reverse osmosis unit 40 , and the first By providing the second coagulation-sedimentation part 50, the same effects as those of the first and second embodiments can be obtained.

(Fourth embodiment)
Next, a water treatment device according to a fourth embodiment of the present invention will be described. FIG. 8 is a block diagram schematically showing the water treatment device according to the fourth embodiment. As shown in FIG. 8, unlike the water treatment apparatus 1 according to the first embodiment, the water treatment apparatus 3 according to the fourth embodiment does not include the water softener 30 before the low-pressure reverse osmosis section 40. , is provided in front of the forward osmosis device 70 . In addition, in the fourth embodiment, the water softener 30 is further provided after the second filtering section 60 . Other configurations are the same as those of the water treatment device 1 according to the first embodiment.

(Water treatment method)
(Seventh embodiment)
Next, a seventh example of a water treatment method using the water treatment apparatus 7 according to the fourth embodiment configured as described above will be described. The water to be treated introduced into the water treatment apparatus 7 in the seventh embodiment is the same as the water to be treated in the first to sixth embodiments. In addition, in the water treatment method according to the seventh embodiment, the first coagulating sedimentation step and the first filtration step are the same as in the first embodiment.
Each component of the water to be treated after the first filtration step is as follows, similarly to the first embodiment.
TDS: 4005 mg/L, Ca: 50 mg/L, _SiO2 : 10 mg/L

(Low pressure reverse osmosis process)
The water to be treated from which the PAC has been removed in the first filtering section 20 is supplied to the low-pressure reverse osmosis section 40 to undergo the low-pressure reverse osmosis process. In the low-pressure reverse osmosis unit 40, 90% of the reclaimed water is recovered from the water to be treated by the low-pressure RO membrane applied with a predetermined pressure dependent on the TDS, for example, a pressure of 4.0 MPa, while 10% of the concentrated water is recovered. Ejected. Here, since silica is removed in the first coagulation-sedimentation section 10, the recovery rate of reclaimed water by the low-pressure reverse osmosis section 40 can be improved to 90%.

In the seventh embodiment, permeated water is discharged from the low-pressure reverse osmosis unit 40 at a flow rate of (1000 L/h×90%=) 900 L/h and recovered as reclaimed water. Each component of the permeated water is as follows.
TDS: 40 mg/L, Ca: less than 1 mg/L, _SiO2 : 1 mg/L
That is, the low-pressure reverse osmosis unit 40 reduces TDS to (40/4005≈) 0.01 times, Ca to (1/50=) 0.02 times, and SiO ₂ to (1/10≈) 0.1 times be done.

Also, the concentrated water is discharged from the low-pressure reverse osmosis unit 40 at a flow rate of (1000 L/h×10%=) 100 L/h. Each component of the concentrated water is as follows.
TDS: 40050 mg/L, Ca: 500 mg/L, _SiO2 : 100 mg/L
That is, in the low-pressure reverse osmosis unit 40, the water to be treated is concentrated to TDS (40050/4005=) 10 times, Ca to (500/50=) 10 times, and SiO ₂ to (100/10=) 10 times. .

(Second coagulation sedimentation step)
The concentrated water concentrated in the low-pressure reverse osmosis section 40 is supplied to the second coagulation-sedimentation section 50 to undergo the second coagulation-sedimentation step. In the seventh embodiment, since Ca remains in the water to be treated, a pH adjuster and a flocculant are added to the concentrated water of the second coagulation-sedimentation unit 50 . The pH adjuster to be added is, for example, NaOH or Ca(OH) ₂ like the pH adjuster added to the first aggregation-sedimentation part 10, but is not necessarily limited. Flocculants added are eg Na ₂ CO ₃ and PAC to flocculate Ca and silica. The concentration of Na ₂ CO ₃ is preferably equivalent to Ca, and the concentration of PAC is preferably twice equivalent to SiO ₂ , but they are not necessarily limited. In the second aggregation-sedimentation section 50, this state is left at rest for about 30 minutes. In the second coagulation-sedimentation section 50, CaCO ₃ and part of silica are coagulated and removed as scale components from the water to be treated.

(Second filtration step)
Concentrated water obtained by coagulating and sedimenting CaCO ₃ and silica as scale components in the second coagulating and sedimentation section 50 is supplied to the second filtering section 60 and subjected to the second filtering step. In the second filtering section 60, an acid such as H ₂ SO ₄ or HCl is added to adjust the pH to about 5-6.5. In the second filtering section 60, the concentrated water is allowed to stand for 30 minutes or longer to remove unreacted PAC.
Each component of the concentrated water discharged from the second filtering section 60 is as follows.
TDS: 40000 mg/L, Ca: 50 mg/L, _SiO2 : 10 mg/L
That is, the second coagulating sedimentation section 50 and the second filtering section 60 remove (500-50=) 450 mg/L of Ca and (100-10=) 90 mg/L of SiO ₂ .

(Calcium removal step)
The water to be treated from which the PAC has been removed in the second filtering section 60 is supplied to the water softener 30 and undergoes a calcium removing step. In the water softener 30, Ca is removed from the water to be treated by, for example, a cation exchange resin. Each component of the water to be treated discharged from the water softener 30 is as follows.
TDS: 40350 mg/L, Ca: 0 mg/L, _SiO2 : 10 mg/L
That is, in the water softener 30, (50-0=) 50 mg/L (total amount) of Ca is removed.

(Forward osmosis treatment process)
Next, the concentrated water discharged from the water softener 30 is supplied to the forward osmosis device 70 and subjected to a forward osmosis treatment process. In the forward osmosis treatment step, reclaimed water is obtained from the concentrated water, and highly concentrated water that is further concentrated is discharged.

Specifically, in the forward osmosis device 70, (2/3≈) 67% regenerated water is recovered from the concentrated water by the FO membrane, while (1/3≈) 33% highly concentrated water is discharged. In the seventh embodiment, permeated water is discharged from the forward osmosis device 70 at a flow rate of (100 L/h×67%=) 67 L/h and recovered as reclaimed water. On the other hand, highly concentrated water is discharged from the forward osmosis device 70 at a flow rate of (100 L/h×33%=) 33 L/h. Each component of highly concentrated water is as follows.
TDS: 121050 mg/L, Ca: 0 mg/L, _SiO2 : 30 mg/L

That is, the concentrated water is concentrated about three times (12105/40000≈) in TDS and three times (30/10=) in SiO ₂ in the forward osmosis device 70 . Further, in the seventh embodiment, highly concentrated water with a flow rate of 33 L/h can be discharged from the water to be treated with a flow rate of 1000 L/h. As a result, according to the water treatment device 7 adopted in the seventh embodiment, as in the first embodiment, the water to be treated can be concentrated about 7.6 times more than the conventional technology before being discharged. The recovery rate can be greatly improved.

(Distillation crystallization step)
The distillation crystallization process after the forward osmosis treatment process is the same as in the first embodiment. That is, in the seventh embodiment, 4 L/h of solid components are removed from highly concentrated water with a flow rate of 33 L/h, and purified water with a flow rate of 29 L/h is recovered as reclaimed water.

The permeated water obtained from the low-pressure reverse osmosis unit 40 is supplied with the permeated water obtained from the forward osmosis device 70 and the purified water obtained from the distillation and crystallization unit 80 and recovered. Thus, in the seventh embodiment, the water treatment apparatus 7 according to the fourth embodiment recovers reclaimed water with a flow rate of (900 + 67 + 29 =) 996 L / h from the water to be treated with a flow rate of 1000 L / h, 4 L/h of solids are removed. Each component of the reclaimed water is as follows.
TDS: 36 mg/L, Ca: less than 1 mg/L, _SiO2 : 1 mg/L

(Fourth modification)
Next, a fourth modification of the water treatment device according to the fourth embodiment described above will be described. FIG. 9 is a block diagram schematically showing a water treatment device according to a fourth modification. As shown in FIG. 9, the water treatment apparatus 8 according to the fourth modification is provided with a high-pressure reverse osmosis unit 90 similar to that of the first modification instead of the forward osmosis apparatus 70 of the water treatment apparatus 7 according to the fourth embodiment. be done.

In the high-pressure reverse osmosis unit 90, permeated water in which the concentration of impurities has been reduced is discharged from the concentrated water, and highly concentrated water in which the concentrated water is further concentrated is discharged. The discharged permeated water joins the permeated water discharged from the low-pressure reverse osmosis section 40 as reclaimed water. On the other hand, the discharged highly concentrated water is supplied to the distillation and crystallization section 80 . Other configurations are the same as those of the fourth embodiment. In the fourth modification, the water softener 30 is provided in the preceding stage of the high-pressure reverse osmosis unit 90, so that the scale risk of Mg(OH) ₂ is reduced when the high-pressure reverse osmosis unit 90 is operated under alkaline conditions. can be reduced.

(Water treatment method)
(Eighth embodiment)
Next, an eighth embodiment of the water treatment method using the water treatment apparatus 8 according to the fourth modification constructed as described above will be described. The water to be treated in the eighth embodiment is the same as the water to be treated in the first to seventh embodiments. First, in the water treatment method according to the eighth embodiment, the first coagulation-sedimentation step, the first filtration step, the low-pressure reverse osmosis step, the second coagulation-sedimentation step, the second filtration step, and the calcium removal step are performed in the seventh embodiment. Same as example.

(High pressure reverse osmosis process)
Next, following the calcium removal process, the concentrated water discharged from the water softener 30 is supplied to the high pressure reverse osmosis unit 90 and subjected to the high pressure reverse osmosis process. In the high-pressure reverse osmosis section 90, permeated water is obtained from the concentrated water, and highly concentrated water that is further concentrated is discharged.

Specifically, in the high-pressure reverse osmosis unit 90, (1/2=) 50% permeated water is recovered as reclaimed water from the concentrated water by the high-pressure RO membrane, while (1/2=) 50% highly concentrated water is discharged. In the eighth embodiment, the permeated water is discharged from the high-pressure reverse osmosis unit 90 at a flow rate of (100 L/h × 50% =) 50 L / h and recovered as reclaimed water, and (100 L / h × 50% =) 50 L / Highly concentrated water is discharged at a flow rate of h. Each component of highly concentrated water is as follows.
TDS: 80700 mg/L, Ca: 100 mg/L, _SiO2 : 20 mg/L

That is, the high-pressure reverse osmosis unit 90 concentrates the concentrated water twice (80700/40350=) in TDS and twice (20/10=) in SiO ₂ . As a result, in the eighth embodiment, highly concentrated water with a flow rate of 50 L/h is discharged from the water to be treated with a flow rate of 1000 L/h. According to this method, the water to be treated can be concentrated about five times more than the conventional method before being discharged, and the efficiency of generating reclaimed water can be greatly improved.

(Distillation crystallization step)
The highly concentrated water concentrated in the high-pressure reverse osmosis section 90 is supplied to the distillation and crystallization section 80 to undergo the distillation and crystallization process. In the distillation and crystallization unit 80, the highly concentrated water is subjected to purification treatment at a temperature of about 120° C., for example, and the purified purified water is recovered as reclaimed water. The salt as a solid component separated from the purified water is discarded outside. In the second embodiment, 4 L/h of solid components are removed from highly concentrated water with a flow rate of 50 L/h, and purified water with a flow rate of 46 L/h is recovered as reclaimed water.

The permeated water obtained from the low-pressure reverse osmosis section 40 is supplied with the permeated water obtained from the high-pressure reverse osmosis section 90 and the purified water obtained from the distillation and crystallization section 80 and recovered. Thus, in the eighth embodiment, the water treatment apparatus 4 according to the second modification recovers reclaimed water with a flow rate of (900 + 50 + 46 =) 996 L / h from the water to be treated with a flow rate of 1000 L / h, and 4 L /h of solids are removed. Each component of the reclaimed water is as follows, as in the fourth embodiment.
TDS: 36 mg/L, Ca: less than 1 mg/L, _SiO2 : 1 mg/L

According to the fourth embodiment described above, in the first coagulation-sedimentation unit 10 preceding the low-pressure reverse osmosis unit 40, silica is removed in addition to Ca, and the low-pressure reverse osmosis unit 40, the forward osmosis device 70, and the high-pressure reverse osmosis unit 40 are removed. By providing the second coagulation sedimentation unit 50 between the permeation unit 90 and removing silica from the concentrated water in which the water to be treated is concentrated, the same effects as those of the first to third embodiments can be obtained. can be done. Furthermore, by providing the water softener 30 in the front stage of the forward osmosis device 70 and the high-pressure reverse osmosis unit 90, it is possible to suppress the scaling of Ca that tends to occur in the FO membrane and the RO membrane. The water concentration rate can be improved compared to conventional water treatment equipment.

(Coagulation sedimentation section and filtration section)
Next, configurations of the coagulating sedimentation section and the filtration section employed in the water treatment apparatuses 1 to 8 according to the first to fourth embodiments will be described. The coagulation-sedimentation section and the filtration section refer to at least one of the first coagulation-sedimentation section 10 and the first filtration section 20 and the second coagulation-sedimentation section 50 and the second filtration section 60 .

Silicate ions (SiO ₄ ⁴⁻ ), which are the causative substances of silica in particular, have been known to take various forms in water. is one. In order to remove silicate ions (SiO ₄ ⁴⁻ ), two methods have been investigated: a removal method using resins or adsorbents, and a removal method by coprecipitation or coagulation sedimentation by administration of a drug.

Among these methods, a silica removal method using an ion exchange resin is known in the pure water production process as a method for removing silica using a resin or an adsorbent. However, in wastewater containing high concentrations of silica and in wastewater with high anion-rich salt concentration in which many anions other than silica are present, the frequency of regeneration of the ion-exchange resin increases, making water treatment costly. It is not preferable because it becomes In addition, in the vicinity of the exchange capacity of the ion exchange resin, the adsorbed silica is eluted, resulting in a rapid increase in silica concentration. In this case, scale due to irreversible silica suddenly occurs, which poses a serious problem in water treatment processes using semipermeable membranes. Therefore, if a method of removing silica by administering a flocculant is used, the cost of the flocculant will increase, so there is a need to reduce the amount of flocculant used when treating the water to be treated. rice field.

In order to solve the above-described problems, the first configuration example, the second configuration example, the third configuration example, and the fourth configuration of the coagulation-sedimentation unit and the filtration unit (hereinafter collectively referred to as the coagulation-sedimentation unit) described below An example is a coagulating/sedimenting part that can reduce the amount of coagulant to be added when treating water to be treated.

(agglomeration sedimentation part)
(First configuration example)
First, a first structural example of the coagulating sedimentation section of the water treatment apparatuses 1 to 8 according to the embodiment of the present invention will be described. FIG. 10 is a block diagram schematically showing the coagulation-sedimentation unit according to the first configuration example. As shown in FIG. 10, the coagulating sedimentation units 10A and 50A according to the first configuration example include a receiving tank 11, a reaction tank 12, a pH adjusting tank 13, a pump 14, a dehydrator 15, silica concentration meters 16 and 17, and a filtering unit. 20 and 60.

The receiving tank 11 is a tank into which water to be treated such as waste water discharged from a cooling tower (not shown) or the like flows. A silica concentration (SiO ₂ concentration) in the receiving tank 11 is measured by a silica concentration meter 51 . Water to be treated containing silica is supplied to the reaction tank 12 after being stored in the receiving tank 11 . In the reaction tank 12, a flocculating agent such as PAC for flocculating and precipitating silica and Na ₂ CO ₃ for flocculating and precipitating Ca is added. Along with this, in the reaction tank 12, the pH is adjusted to about 8 or more and 12 or less, for example about 10.5, and scale components such as Ca and silica are removed from the water to be treated. The reaction tank 12 can be composed of a plurality of tanks such as two tanks or three tanks in which the water to be treated can flow in parallel, so that the flow of the treated water can be configured as a plurality of lines.

The supernatant water obtained in the reaction tank 12 is supplied to the pH adjustment tank 13 and adjusted to pH 4 or more and 8 or less, for example about 6.5. This makes Al in the supernatant water insoluble. The silica concentration in the pH adjustment tank 13 is measured by a silica concentration meter 52 . Al-containing water, which is regulated water whose pH has been adjusted in the pH adjustment tank 13 , is supplied to the filtration units 20 and 60 . Filtration units 20 and 60 are configured with sand filters or predetermined membranes. In the filtration units 20 and 60, a filtration process for removing Al from the conditioned water is performed to obtain treated water.

As described above, scale components containing Ca and silica are removed in the reaction tank 12 in the coagulating sedimentation sections 10A and 50A. That is, for example, water to be treated discharged from a cooling tower or the like is temporarily stored in the receiving tank 11 as water to be treated containing Ca and silica, and then supplied to the reaction tank 12 . The initial state of the reaction tank 12 is a state in which a part of the sludge S as coagulated sludge remains after the coagulating sedimentation treatment has already been performed a plurality of times. The pH of the reaction tank 12 is adjusted to a basic pH.

Next, in the reaction tank 12, stirring is performed by a stirring unit (not shown) while injecting PAC or a chemical such as Na ₂ CO ₃ in order to remove, for example, scale components. In the first configuration example, the stirred sludge S functions as a flocculant and mixes with the silica contained in the water to be treated, and part of the silica precipitates. Note that scale components mainly include silica containing SiO ₂ and compounds of Ca such as CaCO ₃ , CaSO ₄ and CaF ₂ .

A part of the sludge S is discharged by the pump 14 from the reaction tank 12 in which the sludge has settled and is supplied to the dehydrator 15 . It is preferable that the discharge amount of the sludge S is the increased amount of the sludge S that is increased with respect to the amount of the sludge S in the initial state. The discharged sludge S is dehydrated by the dehydrator 15 to become a dehydrated cake, which is discarded or reused for a predetermined purpose.

Next, in the reaction tank 12, a pH adjusting agent is added by a chemical injection device (not shown) as pH adjusting means, while stirring is performed by a stirring section (not shown) as stirring means. As a result, the sludge S is stirred again and becomes suspended. In the first configuration example, the suspended sludge S functions as a flocculant, and part of the silica is adsorbed to the sludge S from the water to be treated and is removed by precipitation. Further, PAC may be added according to the silica concentration measured in the reaction tank 12 described above. After the sludge S is precipitated, the supernatant water is supplied to the downstream pH adjustment tank 13 . Also, the water treatment reverts to inflow/chemical injection.

(coagulated sedimentation sludge)
Next, the sludge S, which is coagulated sedimentation sludge that functions as a coagulant, will be described. First, the present inventor's intensive study on silica contained in the water to be treated, such as the waste water from the cooling tower, which flows into the reaction tank 12 will be described.

That is, according to the findings of the present inventors, silica is classified into soluble silica and insoluble colloidal silica in waste water. According to the inventor's experiments and extensive investigations associated with the experiments, it is believed that the flocculated sludge generated by the administration of aluminum salt has the following effects on soluble silica and colloidal silica.

First, soluble silica mainly containing silicate ions is negatively charged under basic conditions of pH 8 or more and 12 or less. Generally, soluble silica under basic conditions is known to polymerize into insoluble silica at a high reaction rate. On the other hand, flocculated sludge flocs containing aluminum salts have localized positively charged sites derived from aluminum ions. Therefore, when the present inventor conducted an experiment to reuse the coagulated sediment sludge, the coagulated sludge floc captured more soluble silica than the ionic strength derived from the valence and molar number of aluminum ions. It turned out that

Therefore, the mechanism of reaction of soluble silica to flocculated sludge is considered as follows. That is, the negatively charged soluble silica is electrostatically attracted to and adsorbed by positively charged portions (adsorption active sites) such as aluminum ions in flocculated sludge flocs. Under basic conditions, the rate of polymerization of silicate ions is high, so soluble silica polymerizes with other soluble silica that approaches the site where silicate ions are adsorbed, and is adsorbed to flocculated sludge flocs. be. Therefore, the amount of silica that can be adsorbed is greater than the amount derived from the valence of aluminum. Stirring increases the probability of contact between the soluble silica and the adsorptive active sites in the flocculated sludge flocs, thereby improving the removal rate of silica. Furthermore, by increasing the number of times the sludge S is used, that is, the number of cycles, it is possible to reduce unused adsorption active sites.

Colloidal silica is obtained by polymerizing soluble silica with each other to have a size of several tens of nanometers to several hundreds of nanometers. In the colloidal form, the sedimentation property is extremely low due to the small particle size. In addition, colloidal silica under basic conditions is partly dissolved into a form similar to that of soluble silica, and a reaction similar to the reaction mechanism described above occurs. Even undissolved colloidal silica has a negatively charged surface, and is electrostatically attracted to the positive charge of aluminum ions, and aggregates and polymerizes to improve sedimentation. Thereby, silica is removed from the water to be treated.

As described above, the sludge S obtained by adding a flocculating agent such as PAC to the water to be treated can be reused multiple times, although the silica removal rate is lowered. The present inventor conducted an experiment on the silica removal rate according to the pH in the reaction tank 12. When the pH of the water to be treated in the reaction tank 12 was set to 8, silica It was found that the removal rate was reduced from about 47% to about 27%. Furthermore, when the present inventor sets the pH of the water to be treated in the reaction tank 12 to 10.5, the silica removal rate increases from about 97% to about 70% with the number of cycles of the sludge S. was found to be reduced to That is, compared to the case where the pH of the water to be treated in the reaction tank 12 is 8, when the pH is 10.5 and the basicity is strengthened, the silica removal rate is improved by about 2 to 2.6 times. did. Therefore, when the silica removal treatment is performed on the water to be treated in the reaction tank 12, by setting the pH of the water to be treated and the amount of PAC added when adding PAC, the desired silica concentration can be obtained.

As described above, according to the first configuration example of the coagulation-sedimentation unit, the sludge S, which is the coagulation-sedimentation sludge generated when silica is removed, is used again as silica adsorption nuclei, that is, as a coagulant. It is possible to reduce the amount of chemicals such as PAC required for silica removal. Furthermore, since the amount of discharged sludge can be reduced by using the sludge S as a flocculant, the cost required for post-treatment of the discharged sludge S can be reduced.

(Second configuration example)
Next, a second configuration example of the aggregation-sedimentation section will be described. FIG. 11 is a block diagram showing a coagulation-sedimentation unit according to the second configuration example. As shown in FIG. 11, the coagulating sedimentation units 10B and 50B according to the second configuration example include a receiving tank 11, a reaction tank 12, a pH adjusting tank 13, a pump 14, a dehydrator 15, silica concentration meters 16 and 17, and a sludge storage tank. 18, and filtration units 20 and 60. The receiving tank 11, the reaction tank 12, the pH adjusting tank 13, the pump 14, the dehydrator 15, the silica concentration meters 16 and 17, and the filtering units 20 and 60 are the same as in the first configuration example. The sludge storage tank 18 is a tank for temporarily storing the sludge S discharged from the reaction tank 12 using the pump 14 and then returning it to the reaction tank 12 .

Scale components containing silica are removed in the reaction tank 12 in the coagulating sedimentation sections 10B and 50B. That is, the water to be treated is temporarily stored in the receiving tank 11 and then supplied to the reaction tank 12 . The initial state of the reaction tank 12 is a state in which a part of the sludge S as coagulated sludge remains after the coagulating sedimentation treatment has already been performed a plurality of times. The pH of the reaction tank 12 is adjusted to a basic pH, for example, 8 or more and 12 or less, 10.5.

Next, in the reaction tank 12, stirring is performed by a stirring unit (not shown) while a chemical such as Na ₂ CO ₃ for removing scale components such as Ca compounds is injected. Here, in the second configuration example, part of the sludge S stored in the sludge storage tank 18 is supplied to the dehydrator 15 for dehydration, while at least part of the remaining sludge S is supplied to the reaction tank 12. do. As a result, the sludge S stirred in the reaction tank 12 functions as a flocculating agent, mixes with the silica in the water to be treated, and part of the silica precipitates.

At least part, preferably all of the sludge S is supplied to the sludge storage tank 18 by the pump 14 from the reaction tank 12 in which the sludge S has settled. Here, it is preferable that the amount of sludge S supplied to the dehydrator 15 out of the sludge S stored in the sludge storage tank 18 is an increased amount with respect to the amount of sludge S in the initial state.

Next, in the reaction tank 12, while adding a pH adjuster, stirring is performed by a stirring unit (not shown). As a result, the sludge S is stirred again and becomes suspended. In the second configuration example, the suspended sludge S functions as a flocculant, and part of silica is adsorbed by the sludge S and removed from the water to be treated by precipitation. PAC may be further added according to the silica concentration measured by the silica concentration meter described above. When PAC is added, the amount added is preferably 1 equivalent or more and 2 equivalents or less of the silica concentration. After the sludge S is precipitated, the supernatant water is supplied to the downstream pH adjustment tank 13 . Other configurations are the same as those of the first configuration example.

As described above, according to the second configuration example of the coagulation-sedimentation unit, the sludge S, which is the coagulation-sedimentation sludge obtained by the coagulation-sedimentation treatment in the reaction tank 12, is used as a silica flocculant, whereby the first Effects similar to those of the configuration example can be obtained. Furthermore, by discharging at least part, preferably all, of the sludge S from the reaction tank 12 and temporarily storing it in the sludge storage tank 18, the reaction between the aluminum flocculant and contaminants other than silica is suppressed. Therefore, the amount of medicine used can be reduced, and the cost of the medicine can be reduced.

(Third configuration example)
Next, a third configuration example of the aggregation-sedimentation section will be described. FIG. 12 is a block diagram showing a coagulation-sedimentation unit according to the third configuration example. As shown in FIG. 12, the coagulation sedimentation units 10C and 50C according to the third configuration example include a receiving tank 11, a first reaction tank 121 provided with a chemical injection device 19, a second reaction tank 122, a sedimentation tank 123, a pH adjustment A tank 13 , a pump 14 , a dehydrator 15 , silica concentration meters 16 and 17 , and filtration units 20 and 60 are provided. The receiving tank 11, the pH adjusting tank 13, the pump 14, the dehydrator 15, the silica concentration meters 16 and 17, and the filtering units 20 and 60 are the same as those in the first configuration example.

(Reaction step)
In the first reaction tank 121 as a reaction tank constituting the reaction part, the pH is adjusted by a pH adjustment part (not shown) so as to make the water to be treated containing silica basic. , preferably about 10.5. In the first reaction tank 121, a flocculating agent such as Na ₂ CO ₃ is injected in order to remove mainly scale components other than silica, such as sparingly soluble salts of Ca. In the first reaction tank 121, stirring is performed by the stirring unit 121a, and the water to be treated is suspended. The water to be treated is overflowed from the upper part of the first reaction tank 121 and supplied to the lower part of the second reaction tank 122 .

When the water to be treated is supplied to the second reaction tank 122, the second reaction tank 122 is added with sludge S, which is coagulated sedimentation sludge collected in the subsequent sedimentation tank 123, as a coagulant. On the other hand, in the second reaction tank 122 as a reaction tank constituting the reaction section, a flocculant such as PAC An aluminum salt such as is added. The amount of PAC to be added to the second reaction tank 122 is determined based on the silica concentration measured by the silica concentration meters 16 and 17 . In the second reaction tank 122, stirring is performed by the stirring part 122a, and the water to be treated is suspended. The water to be treated is supplied from the second reaction tank 122 to the sedimentation tank 123 . If the silica concentration measured by the downstream silica concentration meter 17 is equal to or less than a predetermined silica concentration, it is not necessary to add an aluminum salt such as PAC.

(Precipitation process)
In the sedimentation tank 123, since the water to be treated is left still, the agitated sludge S functions as a flocculant and mixes with the silica contained in the water to be treated to precipitate the sludge S containing silica. That is, in the second reaction tank 122, the suspended sludge S functions as a flocculant, and part of the silica from the water to be treated is adsorbed by the sludge S and precipitated in the sedimentation tank 123 to be removed. be. In addition, in the sedimentation tank 123, the pH of the water to be treated may be adjusted to 8 or more and 12 or less, preferably about 10.5, by a pH adjuster (not shown).

(Sludge transportation process)
At least part of the sludge S that has settled in the sedimentation tank 123 is withdrawn by the pump 14 as a sludge transporter. The amount of sludge S withdrawn by the pump 14 may be substantially the entire amount of sludge S in the sedimentation tank 123 . In this case, the pump 14 supplies a part of the drawn sludge S, for example, 20% of the sedimented amount of the sludge S, or the amount of the sedimented amount during the time of the drawing cycle, to the dehydrator 15 such as a filter press. can be done. In this case, 80% of the total sedimentation amount of the sludge S sedimented in the sedimentation tank 123 and the remainder excluding the old sludge S of approximately the same amount as the amount sedimented during the withdrawal cycle time is the second reaction tank 122 is put into

Also, the pump 14 may be configured to draw out only part of the sludge S in the sedimentation tank 123 . In this case, it is also possible to supply the dehydrator 15 with the sludge S that has been in contact with the water to be treated a predetermined number of times or more, for example, 5 times or more. In addition, the pump 14 can also adjust the withdrawal amount so that a substantially constant amount of sludge S remains in the sedimentation tank 123 . Here, the fixed amount can be about five times the amount of sludge S that increases in the time of one cycle of pulling out the sludge S. As a result, the function of the sludge S as a flocculant can be ensured.

A part of the withdrawn sludge S is supplied to the second reaction vessel 122 by the pump 14 . The remainder of the drawn sludge S is supplied to the dehydrator 15 to be dehydrated, turned into a dehydrated cake, and discarded or reused for a predetermined purpose.

A silica concentration meter 17 is provided on the outflow side of the water to be treated, which is the rear stage of the sedimentation tank 123 , and on the inflow side, which is the front stage of the pH adjustment tank 13 . The silica concentration meter 17 continuously measures the silica concentration of the supernatant water of the sedimentation tank 123 at intervals of, for example, 6 to 10 minutes. After that, the addition amount of aluminum salt in the second reaction tank 122 is determined by feedback control based on the silica concentration measured by the silica concentration meters 16 and 17 . Specifically, sludge S is added to the second reaction tank 122, and the suspended sludge S functions as a flocculant, thereby removing silica in the water to be treated. Subsequently, the amount of aluminum salt required for the silica concentration measured by the silica concentration meter 17 to be less than or equal to the desired silica concentration from the silica concentration measured by the silica concentration meter 16 is added to the amount of aluminum salt added. decide. When PAC is added as an aluminum salt, the amount added is preferably 1 equivalent or more and 2 equivalents or less of the measured silica concentration. As a result, the amount of aluminum salt added can be reduced as compared with the conventional method.

In addition, in the above-described coagulating sedimentation units 10C and 50C, a plurality of first reaction tanks 121, second reaction tanks 122, and settling tanks 123 are provided, and from the first reaction tank 121, second reaction tank 122, and settling tank 123, A plurality of water treatment lines may be arranged in parallel to form a plurality of lines such as two lines or three lines capable of treating the water to be treated.

In addition, in the coagulating sedimentation units 10C and 50C described above, at least one other reaction tank may be provided on the upstream side of the first reaction tank 121 along the flow direction of the water to be treated. Further, at least one other reaction tank may be provided between the first reaction tank 121 and the second reaction tank 122 along the flow direction of the water to be treated. In these cases, the second reaction tank 122 may be the most downstream reaction tank along the flow direction of the water to be treated among the plurality of reaction tanks forming the reaction section. Further, at least one reaction tank may be provided downstream of the second reaction tank 122 along the flow direction of the water to be treated. In this case, the first reaction tank 121 may be the most upstream reaction tank along the flow direction of the water to be treated among the plurality of reaction tanks forming the reaction section. Furthermore, it is also possible to combine these configurations. That is, the reaction section is composed of a plurality of reaction tanks of three or more tanks, one reaction tank of these three or more reaction tanks is the first reaction tank 121, and at least the downstream side of the first reaction tank 121 One of the one reaction tanks may be used as the second reaction tank 122 .

Also, the first reaction vessel 121 may be composed of a plurality of reaction vessels, and the second reaction vessel 122 may be composed of a plurality of reaction vessels. Similarly, the sedimentation tank 123 constituting the sedimentation section may be composed of a plurality of sedimentation tanks in which the water to be treated is transported in series.

(Aluminum removal step)
The supernatant water obtained in the sedimentation tank 123 is supplied to the pH adjustment tank 13 and adjusted to pH 4 or more and 8 or less, for example about 6.5. As a result, the Al in the supernatant water becomes insoluble and is removed. Al-containing water, which is regulated water whose pH has been adjusted in the pH adjustment tank 13 , is supplied to the filtration units 20 and 60 . A portion of the Al-containing water whose pH has been adjusted in the pH adjustment tank 13 may be returned to the second reaction tank 122 .

In the filtration units 20 and 60 , a filtration process is performed to remove Al from the adjusted water supplied from the pH adjustment tank 13 . Thereby, treated water is obtained.

As described above, by providing the first reaction tank 121 for removing contaminants other than silica in the preceding stage of the second reaction tank 122 which is a silica treatment tank, in the second reaction tank 122, the aluminum salt is It is possible to suppress consumption by substances other than silica.

As described above, according to the third configuration example of the coagulation-sedimentation unit, the sludge S, which is the coagulation-sedimentation sludge precipitated in the sedimentation tank 123, is transferred to the preceding reaction tank of the sedimentation tank 123, specifically the second reaction tank 122. to remove silica from the water to be treated. That is, in the third configuration example, the sludge S coagulated and sedimented in the sedimentation tank 123 is put into the second reaction tank 122 and used again as adsorption nuclei of silica, that is, as a flocculant. It is possible to reduce the required amount of chemicals such as PAC. Furthermore, since the amount of sludge S to be discharged can be reduced by using the sludge S as a flocculant, the cost required for post-treatment of the discharged sludge S can be reduced.

(Fourth configuration example)
Next, the aggregation-sedimentation part according to the fourth configuration example will be described. FIG. 13 is a block diagram showing a coagulation-sedimentation unit according to the fourth configuration example. As shown in FIG. 13, the coagulation-sedimentation units 10D and 50D according to the fourth structural example include a receiving tank 11, a first reaction tank 121, a second reaction tank 122, a sedimentation tank 123, and a pH adjusting tank, as in the third structural example. A tank 13 , a pump 14 , a dehydrator 15 , silica concentration meters 16 and 17 , a chemical injection device 19 and filtration units 20 and 60 are provided.

In the fourth configuration example, the water to be treated is allowed to stand still in the sedimentation tank 123, so that the stirred sludge S functions as a flocculant and is mixed with the silica contained in the water to be treated to contain silica. Sludge S settles. At least part of the settled sludge S is withdrawn by the pump 14 . The amount of sludge S to be drawn out is preferably the increased amount of sludge S in the sedimentation tank 123, but is not limited. In other words, in the sedimentation tank 123, it is preferable to adjust the withdrawal amount so that a substantially constant amount of sludge S remains. In the fourth configuration example, unlike the third configuration example, part of the drawn sludge S is supplied to the first reaction vessel 121 by the pump 14 . As a result, the sludge S is transported from the subsequent sedimentation tank 123 and added to the first reaction tank 121 . A part of the silica in the first reaction tank 121 is removed by the added sludge S.

On the other hand, in the first reaction tank 121, the pH is adjusted so as to make the water to be treated basic, for example, 8 or more and 12 or less, preferably about 10.5. In addition, in the first reaction tank 121, a Ca flocculant such as Na ₂ CO ₃ is injected in order to remove mainly scale components other than silica, such as Ca salts, which are poorly soluble. In the first reaction tank 121, stirring is performed by the stirring unit 121a, and the water to be treated is suspended. As a result, in the first reaction tank 121, the Ca flocculant removes the poorly soluble Ca salt and the like, and the sludge S removes part of the silica.

The water to be treated in a suspended state overflows from the top of the first reaction tank 121 and is supplied to the bottom of the second reaction tank 122 . The silica concentration of the water to be treated is measured by a silica concentration meter 16 provided downstream of the first reaction tank 121 and upstream of the second reaction tank 122 . In addition, the silica concentration of the water to be treated may be measured in the first reaction tank 121 .

In the fourth configuration example, based on the silica concentration of the water to be treated flowing out from the first reaction tank 121 and the silica concentration of the water to be treated flowing out from the sedimentation tank 123, the The amount of aluminum salt, eg, PAC, to be added to the treated water is determined. That is, the silica concentration meter 17 continuously measures the silica concentration of the supernatant water of the sedimentation tank 123 at intervals of, for example, 6 to 10 minutes. Similarly, the silica concentration meter 16 measures the silica concentration of the water to be treated discharged from the first reaction tank 121 at intervals of 6 to 10 minutes, for example. Feedback control based on the silica concentrations measured by the silica concentration meters 16 and 17 determines the amount of aluminum salt to be added to the second reaction tank 122 . Other configurations are the same as those of the third configuration example.

As described above, according to the fourth configuration example of the coagulation-sedimentation unit, the sludge S, which is the coagulation-sedimentation sludge obtained by the coagulation-sedimentation treatment in the first reaction tank 121, the second reaction tank 122, and the sedimentation tank 123, By using it as a flocculant for silica, it is possible to obtain the same effect as in the first to third configuration examples. Furthermore, according to the fourth configuration example, the sludge S that functions as a flocculant is put into the first reaction tank 121, and the silica concentration is measured on the downstream side of the first reaction tank 121, so that the sludge S Since the concentration of adsorbed silica can be measured more accurately, the amount of aluminum salt to be added in the second reaction tank 122 can be optimized. In addition, the water to be treated is injected from the receiving tank 11 into the lower part of the first reaction tank 121, and the water to be treated is overflowed from the upper part of the first reaction tank 121 and injected into the lower part of the second reaction tank 122. As a result, the amount of sludge S entering can be suppressed, so that the reaction between newly injected aluminum salt such as PAC and sludge S can be suppressed, and the silica removal rate can be further improved compared to the third configuration example.

With respect to the coagulation/sedimentation unit and the filtration unit according to the first to fourth configuration examples described above, the first coagulation/sedimentation unit 10 and the second coagulation/sedimentation unit 50 may have the same configuration, or may have different configurations.

The agent used as the flocculant in the above-described first to fourth configuration examples includes a flocculant that causes flocculation and sedimentation when added to the water to be treated, and silica flocculated and precipitated by this flocculant. It is a chemical agent consisting of coagulated sediment sludge obtained by adding a coagulant to water and coagulating and sedimenting it. Here, the flocculant that causes flocculation and sedimentation when added to the water to be treated is composed of at least one compound selected from aluminum salts, magnesium salts, iron salts, and polymer-based flocculants.

Further, the agent used as a flocculant in the first to fourth configuration examples described above includes a step of adding the flocculant to the water to be treated, and a step of coagulating and sedimenting silica contained in the water to be treated to generate coagulated sedimentation sludge. and can be manufactured by a manufacturing method including: At this time, it is preferable to adjust the pH of the water to be treated to 8 or more and 12 or less.

(forward osmosis device)
Next, the configuration of the forward osmosis apparatus employed in the water treatment apparatuses 1 to 8 according to the first to fourth embodiments will be described.

First, in the conventional forward osmosis apparatus, when the water-separated draw solution is circulated and used as the draw solution in the forward osmosis apparatus, there is a problem that the high temperature regenerated draw solution is insufficiently cooled. Therefore, a method of providing a cooling mechanism for cooling the high-temperature draw solution is conceivable, but if a cooling mechanism is newly provided, the energy required for the water treatment apparatus increases, resulting in a problem of increased running costs. Therefore, in the forward osmosis apparatus, there has been a demand for a technique that can stabilize the energy balance by suppressing the energy consumption required for cooling and heating while simplifying the piping structure as much as possible. The first device example, the second device example, the third device example, and the fourth device example of the forward osmosis device described below simplify the piping structure, suppress the energy consumption required for cooling and heating, and reduce the energy consumption. It is a forward osmosis device that can stabilize the balance of

(Forward osmosis device according to the first device example)
First, a first device example of the forward osmosis device 70 of the water treatment devices 1 to 8 according to the embodiment of the present invention will be described. FIG. 14 is a block diagram schematically showing a forward osmosis device according to the first device example. As shown in FIG. 14 , the forward osmosis apparatus 71 according to the first apparatus example is configured with a membrane module 711 , heat exchangers 712 and 713 , a heater 714 , a separation tank 715 and a final treatment unit 716 .

The membrane module 711 is, for example, a cylindrical or box-shaped container in which a semipermeable membrane 711a as a forward osmosis membrane is installed, thereby dividing the interior into two chambers by the semipermeable membrane 711a. The configuration of the membrane module 711 can include various configurations such as a spiral module type, a laminated module type, and a hollow fiber module type. As the membrane module 711, a known semipermeable membrane device can be used, and a commercially available product can also be used.

The semipermeable membrane 711a provided in the membrane module 711 is preferably capable of selectively permeating water, and an FO membrane is used, but an RO membrane may be used. The material of the separation layer of the semipermeable membrane 711a is not particularly limited, and examples thereof include cellulose acetate-based, polyamide-based, polyethyleneimine-based, polysulfone-based, and polybenzimidazole-based materials. The semipermeable membrane 711a may be composed of only one material (one layer) used for the separation layer, and has a support layer that physically supports the separation layer and does not substantially contribute to separation. It may be composed of more than one layer. Materials such as polysulfone-based, polyketone-based, polyethylene-based, polyethylene terephthalate-based, and general non-woven fabrics can be used for the support layer. The form of the semipermeable membrane 711a is not limited either, and membranes of various forms such as a flat membrane, a tubular membrane, or a hollow fiber can be used.

Inside the membrane module 711, a water-containing solution can be flowed into one chamber partitioned by the semipermeable membrane 711a, and a draw solution, which is an absorbent water, can be flowed into the other chamber. The introduction pressure of the draw solution to the membrane module 711 is 0.1 MPa or more and 0.5 MPa or less, for example 0.2 MPa in the first device example. The water-containing solution is, for example, concentrated water, seawater, brackish water, brackish water, industrial wastewater, produced water, or sewage, or a water-containing solution containing water as a solvent obtained by filtering these waters as necessary.

As the draw solution, a solution mainly composed of a temperature-sensitive water absorbing agent (polymer) having at least one cloud point is used. A temperature-sensitive water-absorbing agent is hydrophilic at low temperatures, dissolves well in water, and absorbs a large amount of water. It is matter.

In the first device example, the polymer is preferably a block or random copolymer containing at least a hydrophobic part and a hydrophilic part, and containing an ethylene oxide group and at least one group consisting of propylene oxide and butylene oxide in the basic skeleton. Examples of basic skeletons include glycerin skeletons and hydrocarbon skeletons. In one embodiment of this, the polymer is used, for example, an agent having polymers of ethylene oxide and propylene oxide (such as GE1000-BBPP (A3)). The temperature at which such polymers change between water solubility and water insolubility is called the cloud point. When the temperature of the draw solution reaches the cloud point, the hydrophobized temperature-sensitive water absorbing agent aggregates and becomes cloudy. Temperature-sensitive water absorbing agents are used as various surfactants, dispersants, emulsifiers, and the like. In a first device example, the draw solution is used as an attractant to attract water from a water-containing solution. In the membrane module 711, water is attracted from the water-containing solution to the draw solution, and a diluted draw solution (diluted draw solution) is discharged.

The heat exchanger 712 is provided on the upstream side of the membrane module 711 along the flow direction of the water-containing solution. The heat exchanger 712 is provided downstream along the flow direction of the draw solution to be reused (hereinafter referred to as regenerated draw solution) flowing out from the separation tank 715 described later, and the regenerated draw solution flowing out from the separation tank 715 and a water-containing solution supplied from the outside. The flow rate of the water-containing solution flowing into the heat exchanger 712 is temperature-controlled so that the temperature of the regenerated draw solution supplied to the membrane module 711 reaches a predetermined temperature. The regenerated draw solution supplied to the membrane module 711 is temperature-controlled to a predetermined temperature of 25°C or higher and 50°C or lower, for example, about 40°C. In addition, when it is necessary to keep the flow rate of the water-containing solution supplied to the membrane module 711 constant while maintaining the temperature of the regenerated draw solution at a desired temperature, an adjustment It is desirable to provide a blow valve (not shown) as a valve.

The heat exchanger 713 is provided downstream of the membrane module 711 along the flow direction of the diluted draw solution. In addition, the heat exchanger 713 is provided on the downstream side along the flow direction of the water-rich solution flowing out from the separation tank 715 described later, and the dilute draw solution flowing out from the membrane module 711 and the heat exchange with the water-rich solution.

A heater 714 as a means for heating the draw solution is provided upstream of the separation tank 715 along the flow direction of the draw solution. The heater 714 heats the dilute draw solution that has flowed out of the membrane module 711 and has been heat-exchanged by the heat exchanger 713 above the cloud point temperature. The dilute draw solution heated above the cloud point temperature by heater 714 is phase separated into polymer and water.

In a separation tank 715 as water separation means, the diluted draw solution phase-separated by the heater 714 is separated into a water-rich solution mainly composed of water and a draw solution mainly composed of polymer and having a lower water content than the water-rich solution. be done. The draw solution, which has a lower water content than the water-rich solution, is supplied to membrane module 711 via heat exchanger 712 as regenerated draw solution.

The final treatment unit 716 as separation treatment means is composed of, for example, a coalescer, an activated carbon adsorption unit, a UF membrane unit, a nanofiltration membrane (NF membrane) unit, or an RO membrane unit. A final treatment unit 716 separates the remaining polymer from the water-rich solution discharged from the separation tank 715 to produce fresh water as permeate. The polymer solution containing polymer separated by the final processing unit 716 may be discarded or introduced into the diluted draw solution at least upstream of the heater 714 . Further, it is also possible to discard a portion of the separated polymer solution and introduce the remaining polymer solution as draw solution to at least the diluted draw solution upstream of heater 714 or upstream of heat exchanger 713. . Here, the method of introducing the polymer solution into the diluted draw solution includes not only a method of introducing the diluted draw solution into a pipe through which the diluted draw solution flows, but also a method of introducing into a tank (not shown) that temporarily stores the diluted draw solution. , various methods can be adopted.

(Forward osmosis treatment process)
Next, the forward osmosis treatment process using the forward osmosis device 71 according to the first device example will be described.

(Inflow side heat exchange process)
An inflow-side heat exchange process is performed in the heat exchanger 712 as the inflow-side heat exchange means. That is, the water-containing water supplied to the water treatment apparatus 1 from the outside is first supplied to the heat exchanger 712 . On the other hand, the heat exchanger 712 is supplied with the regeneration draw solution discharged from the separation tank 715 . In the first apparatus example, the heat exchanger 712 adjusts the regenerated draw solution to a predetermined temperature, specifically, a temperature of about 40°C. As will be described later, the heated dilute draw solution flows into the separation tank 715, so the temperature of the regenerated draw solution flowing out of the separation tank 715 is higher than that of the water-containing solution. Therefore, the heat exchanger 712 lowers the temperature of the regenerated draw solution. The flow rate of the wet water entering heat exchanger 712 is adjusted to cool the regenerated draw solution to a predetermined temperature. That is, in heat exchanger 712, the regenerated draw solution is cooled by the regenerated draw solution while the regenerated draw solution is heated by the regenerated draw solution. A blow valve (not shown) as a regulating valve is provided between the membrane module 711 and the heat exchanger 712 to maintain the temperature of the regenerated draw solution at a desired temperature while supplying the hydrated solution to the membrane module 711. It is also possible to adjust the flow rate of the constant. The regenerated draw solution whose temperature has been lowered by heat exchange is supplied to the other chamber of the membrane module 711, and the water-containing solution whose temperature has been raised by heat exchange is supplied to one chamber of the membrane module 711. be.

(forward osmosis process)
In the membrane module 711 as forward osmosis means, a forward osmosis process is performed as a second water extraction process. That is, in the membrane module 711, the water-containing solution and the regenerated draw solution are brought into contact with each other through the semipermeable membrane 711a, whereby the water in the water-containing solution passes through the semipermeable membrane 711a due to the osmotic pressure difference and moves to the regenerated draw solution. . From one chamber to which the water-containing solution is supplied, a concentrated water-containing solution flows out of which the water is moved and concentrated. The other chamber, to which the regenerated draw solution is supplied, is displaced by water and outflows a diluted dilute draw solution. Here, in the heat exchanger 712, heat is exchanged between the water-containing solution and the regenerated draw solution. , the water is moved. Therefore, the temperature of the diluted draw solution flowing out of the membrane module 711 is approximately the same as the temperature of the regenerated draw solution.

(Heating process)
A heating process is performed in a heater 714 as a heating means. That is, the dilute draw solution diluted by the movement of water from the water-containing solution by the forward osmosis process is heated in the outflow side heat exchange process described later, and then heated to a temperature equal to or higher than the cloud point by the heater 714. , causing at least a portion of the polymer to aggregate and phase separate. The heating temperature in the heating process can be adjusted by controlling heater 714 . The heating temperature is preferably 100° C. or lower, and in the first device example, the heating temperature is higher than the cloud point and lower than 100° C., for example, 88° C.

(Water separation step)
A water separation process is performed in the separation tank 715 . That is, in the separation tank 715, the diluted draw solution is separated into a water-rich solution containing a large amount of water and a concentrated regenerated draw solution containing a high concentration of polymer. Note that the pressure in the separation tank 715 is the atmospheric pressure. Phase separation between the water-rich solution and the regenerated draw solution can be performed by standing at a liquid temperature equal to or higher than the cloud point. In the first device example, the liquid temperature is above the cloud point and below 100°C, for example 88°C. The concentrated draw solution separated from the diluted draw solution is supplied to the membrane module 711 as a regenerated draw solution. The draw concentration of the regenerated draw solution is, for example, 60-95%. Meanwhile, the water-rich solution separated from the diluted draw solution is fed to the final processing unit 716 via heat exchanger 713 . A water-rich solution is, for example, 99% water with a draw concentration of 1%.

(Outflow side heat exchange process)
An outflow-side heat exchange process is performed in the heat exchanger 713 as an outflow-side heat exchange means. That is, the diluted draw solution that has flowed out of the membrane module 711 is first supplied to the heat exchanger 713 . On the other hand, the heat exchanger 713 is supplied with the water-rich solution obtained in the separation tank 715 . In the first device example, the heat exchanger 713 adjusts the water-rich solution to a predetermined temperature, specifically, a temperature of about 45.degree. As described above, in the separation tank 715, the water separation process is performed at a liquid temperature above the cloud point and below 100.degree. Therefore, the water-rich solution flowing out of the separation tank 715 has a higher temperature than the dilute draw solution flowing out of the membrane module 711 after being cooled in the heat exchanger 712 . On the other hand, the processing temperature in the latter final processing unit 716 is, for example, 20° C. or higher and 50° C. or lower, preferably 35° C. or higher and 45° C. or lower, for example 45° C. in the first apparatus example. Therefore, in the heat exchanger 713, temperature adjustment is performed to lower the temperature of the water-rich solution to a predetermined temperature. That is, in heat exchanger 713, the water-rich solution is cooled by the diluted draw solution, while the diluted draw solution is heated by the water-rich solution.

(Final treatment process)
In the final processing unit 716, a final processing step as a separation processing step is performed. That is, the polymer may remain in the water-rich solution separated in the separation tank 715 . Thus, in the final treatment unit 716, permeate water, such as fresh water, is obtained by separating the polymer solution, which becomes the separation treatment draw solution, from the water-rich solution.

The permeate separated from the water-rich solution is supplied to external required applications as a final product obtained from the water-containing solution. In the final treatment unit 716, the draw solution separated from the permeated water is a polymer solution with a draw concentration of about 0.5 to 25%, and is either discarded externally or at least in the heater 714 or the heat exchanger 713. is introduced into the diluted draw solution upstream of the It is also possible to discard a portion of the permeate and separated polymer solution and introduce the remaining polymer solution into the diluted draw solution at least upstream of the heater 714 or upstream of the heat exchanger 713 .

(First device embodiment)
Next, a first embodiment of the forward osmosis apparatus 71 configured as above will be described. In the first embodiment of the apparatus, the forward osmosis apparatus 71 is used to generate fresh water (permeated water) with a flow rate of 67 L/h from a water-containing solution (concentrated water) with a flow rate of 100 L/h. do.

In the first device embodiment, the heat exchanger 712 exchanges heat with the concentrated water introduced into the forward osmosis device 71 from the outside, and the concentrated water at a temperature of 40° C. is supplied to the membrane module 711 . The concentrated water concentrated by the membrane module 711 is discharged from the membrane module 711 at a flow rate of 33 L/h. That is, water is transferred in the membrane module 711 at a flow rate of 67 L/h.

On the other hand, the regenerated draw solution at a temperature of 40° C. that has been heat-exchanged by the concentrated water in the heat exchanger 712 is supplied to the membrane module 711 and diluted, and flows out as a diluted draw solution. Here, the flow rate of the regeneration draw solution is 100 L/h. The temperature of the diluted draw solution discharged from the membrane module 711 is 40° C. and the flow rate is 167 L/h. After that, the diluted draw solution is heat-exchanged with the water-rich solution of 88° C. in the heat exchanger 713 to be heated, raised to a temperature of 40° C. to 52° C., and then supplied to the heater 714 to be further heated. , from 52°C to a temperature of 88°C. The diluted draw solution is fed to separation tank 715 to phase separate into a regenerated draw solution and a water-rich solution.

The regeneration draw solution has a temperature of 88° C. and a flow rate of 100 L/h. The water-rich solution has a temperature of 88° C. and a flow rate of 67 L/h. The regenerated draw solution is supplied to a heat exchanger 712 to exchange heat with a cold water-containing solution to lower the temperature from 88°C to 40°C.

The water-rich solution is supplied to the heat exchanger 713 to exchange heat with the 40° C. dilute draw solution to lower the temperature from 88° C. to 45° C. before being supplied to the final processing unit 716 . In the final treatment unit 716, permeate is obtained at a flow rate of 67 L/h. It should be noted that the draw solution separated from the permeate in the final treatment unit 716 is not considered due to its small amount. As described above, permeated water with a flow rate of 67 L/h is obtained from concentrated water with a flow rate of 100 L/h.

As described above, according to the first apparatus example, the regenerated draw solution supplied to the membrane module 711 is adjusted to a desired temperature using the water-containing solution such as concentrated water that flows in from the outside. As a result, the temperatures of the water-containing solution and the draw solution can be made close to each other in the membrane module 711, so that the treatment in the membrane module 711 can be stabilized. In addition, after the temperature of the diluted draw solution that has flowed out of the membrane module 711 is raised using the high-temperature water-rich solution that has flowed out of the separation tank 715, the diluted draw solution that is supplied to the separation tank 715 is heated to above the cloud point by the heater 714. It is heated to a temperature below 100°C. As a result, the temperature range to be raised when heating the diluted draw solution by the heater 714 can be reduced, so the energy required for heating by the heater 714 can be reduced. can be reduced. Further, the temperature of the diluted draw solution and the regenerated draw solution is adjusted by heat exchange without branching the diluted draw solution into two flow paths. As a result, it is possible to easily adjust the balance of the flow rate in the flow path, thereby simplifying the piping structure and suppressing the energy consumption required for cooling and heating, thereby stabilizing the energy balance.

(Second device example)
(Forward osmosis device and forward osmosis treatment process)
First, a second device example of the forward osmosis device 70 of the water treatment devices 1 to 8 according to the embodiment of the present invention will be described. FIG. 15 is a block diagram schematically showing a forward osmosis device according to the second device example. As shown in FIG. 15, the forward osmosis device 72 according to the second device example includes a membrane module 721 provided with a semipermeable membrane 721a inside, heat exchangers 722, 723, 724, a heater 725, a separation tank 726, and It comprises a final processing unit 727 . The membrane module 721, the semipermeable membrane 721a, the heat exchangers 722 and 723, the heater 725, the separation tank 726, and the final treatment unit 727 in the forward osmosis device 72 are respectively the membranes in the forward osmosis device 71 according to the first device example. Similar to module 711 , semipermeable membrane 711 a , heat exchangers 712 and 713 , heater 714 , separation vessel 715 and final treatment unit 716 .

In the forward osmosis device 72 according to the second device example, unlike the first device example, it is located downstream of the heat exchanger 723 along the flow direction of the diluted draw solution and upstream of the heater 725 along the flow direction of the regenerated draw solution. A heat exchanger 724 is provided downstream of the separation tank 726 and upstream of the heat exchanger 722 along the line. An intermediate heat exchange process is performed by the heat exchanger 724 as an intermediate heat exchange means. That is, in the forward osmosis treatment process according to the second apparatus example, the dilute draw solution that has flowed out of the membrane module 721 is heat-exchanged with the high-temperature water-rich solution in the heat exchanger 723, and then heated. Furthermore, heat is exchanged between the water-rich solution and the regenerated draw solution having a temperature similar to that of the water-rich solution in the heat exchanger 724 to raise the temperature. Heater 725 then heats the diluted draw solution to a temperature above the cloud point and below 100°C. Other configurations are the same as those of the first device example.

(Second device embodiment)
In the second device embodiment, the heat exchanger 722 exchanges heat with the concentrated water introduced into the forward osmosis device 72 from the outside, and the concentrated water at a temperature of 40° C. is supplied to the membrane module 721 . The concentrated water concentrated by the membrane module 721 is discharged from the membrane module 721 at a flow rate of 33 L/h. That is, in membrane module 721, water is transferred at a flow rate of 67 L/h.

On the other hand, the regenerated draw solution at a temperature of 40° C. that has been heat-exchanged by the concentrated water in the heat exchanger 722 is supplied to the membrane module 721 and diluted, and flows out as a diluted draw solution. Here, the flow rate of the regeneration draw solution is 100 L/h. The dilute draw solution discharged from the membrane module 721 has a temperature of 40° C. and a flow rate of 167 L/h. The diluted draw solution is then heated by heat exchanger 723 to a temperature of 52° C. before being supplied to heat exchanger 724 .

The diluted draw solution is heated by exchanging heat with the regenerated draw solution at 88° C. by the heat exchanger 724 and heated from 52° C. to 71° C., and then supplied to the heater 725 to be further heated, 71 °C to 88°C. The diluted draw solution is fed to a separation tank 726 to phase separate into a regenerated draw solution and a water-rich solution.

The regeneration draw solution has a temperature of 88° C. and a flow rate of 100 L/h. The water-rich solution has a temperature of 88° C. and a flow rate of 67 L/h. The regenerated draw solution is cooled from 88° C. to 63.5° C. by heat exchanger 724 and then from 63.5° C. to 40° C. by heat exchanger 722 .

The water-rich solution is supplied to final processing unit 727 after being cooled from 88° C. to 45° C. by heat exchanger 723 . In the final treatment unit 727, permeate is obtained at a flow rate of 67 L/h. Note that the draw solution separated from the permeate in the final treatment unit 727 is not taken into account due to its small amount. As described above, permeated water with a flow rate of 67 L/h is obtained from concentrated water with a flow rate of 100 L/h.

According to the second device example described above, heat is exchanged by the heat exchangers 722 and 723, so that the same effects as those of the first device example can be obtained. In addition, while the temperature of the regenerated draw solution to be supplied to the membrane module 721 is decreased by the heat exchanger 724, the temperature of the dilute draw solution to be supplied to the separation tank 726 is increased, so that the heater 725 can further reduce the temperature range to be raised when heating the diluted draw solution. Therefore, the energy required for heating by the heater 725 can be further reduced, and the energy consumed for heating in the forward osmosis device 72 can be further reduced.

(Third device example)
(Forward osmosis device and forward osmosis treatment process)
Next, a third device example of the present invention will be described. FIG. 15 shows a forward osmosis device 73 according to a third device example. As shown in FIG. 15, the forward osmosis device 73 according to the third device example includes a membrane module 731 provided with a semipermeable membrane 731a inside, heat exchangers 732, 733, 734, a heater 735, a separation tank 736, and It comprises a final processing unit 737 . The membrane module 731, the semipermeable membrane 731a, the heat exchangers 732 and 733, the heater 735, the separation tank 736, and the final treatment unit 737 in the forward osmosis device 73 are respectively the membranes in the forward osmosis device 71 according to the first device example. Similar to module 711 , semipermeable membrane 711 a , heat exchangers 712 and 713 , heater 714 , separation vessel 715 and final treatment unit 716 .

In the forward osmosis device 73 according to the third device example, unlike the first device example, the flow direction of the regenerated draw solution and the downstream side of the membrane module 731 along the flow direction of the diluted draw solution and the upstream side of the heat exchanger 733 A heat exchanger 734 is provided downstream of the separation vessel 736 and upstream of the heat exchanger 732 along the line. The heat exchanger 734 serving as the pre-heat exchange means performs the pre-heat exchange step. That is, in the forward osmosis treatment step according to the third apparatus example, the diluted draw solution that has flowed out of the membrane module 731 first undergoes heat exchange in the heat exchanger 734 with the high-temperature regenerated draw solution that is supplied from the separation tank 736. is performed to raise the temperature. Subsequently, heat is exchanged with the high-temperature water-rich solution supplied from the separation tank 736 in the heat exchanger 733 to raise the temperature. Heater 735 then heats the diluted draw solution to a temperature above the cloud point and below 100°C. Other configurations are the same as those of the first device example.

(Third device embodiment)
In the third device embodiment, the heat exchanger 732 exchanges heat with the concentrated water introduced into the forward osmosis device 73 from the outside, and the concentrated water at a temperature of 40° C. is supplied to the membrane module 731 . The concentrated water concentrated by the membrane module 731 is discharged from the membrane module 731 at a flow rate of 33 L/h. That is, water is transferred in the membrane module 731 at a flow rate of 67 L/h.

On the other hand, the regenerated draw solution at a temperature of 40° C. that has been heat-exchanged by the concentrated water in the heat exchanger 732 is supplied to the membrane module 731 and diluted, and flows out as a diluted draw solution. Here, the flow rate of the regeneration draw solution is 100 L/h. The diluted draw solution discharged from the membrane module 731 has a temperature of 40° C. and a flow rate of 167 L/h.

Thereafter, the diluted draw solution is heated to a temperature of 52° C. by exchanging heat with the 88° C. regenerated draw solution supplied from the separation tank 736 in the heat exchanger 734 , and then to the heat exchanger 733 . supplied. The diluted draw solution is heat-exchanged with the 88° C. water-rich solution supplied from the separation tank 736 in the heat exchanger 733 and heated to a temperature of 61° C., and then supplied to the heater 735 to be further heated, The temperature is raised from 61°C to 88°C. The diluted draw solution is fed to a separation tank 736 to phase separate into a regenerated draw solution and a water-rich solution.

The regeneration draw solution has a temperature of 88° C. and a flow rate of 100 L/h. The water-rich solution has a temperature of 88° C. and a flow rate of 67 L/h. The regenerated draw solution is cooled from 88° C. to 72.4° C. by heat exchanger 734 and then from 72.4° C. to 40° C. by heat exchanger 732 .

The water-rich solution is supplied to final processing unit 737 after being cooled from 88° C. to 57° C. by heat exchanger 733 . If the heat resistance of the final processing unit 737 is low, such as when a membrane processing apparatus is used as the final processing unit 737, a cooling means (Fig. (not shown) may cool the water-rich solution to a predetermined temperature.

In the final treatment unit 737, permeate is obtained at a flow rate of 67 L/h. Note that the draw solution separated from the permeate in the final treatment unit 737 is not taken into account due to its small amount. As described above, permeated water with a flow rate of 67 L/h is obtained from concentrated water with a flow rate of 100 L/h.

As described above, according to the third device example, heat is exchanged by the heat exchangers 732 and 733, so that the same effects as those of the first device example can be obtained. Further, the heat exchanger 734 lowers the temperature of the regenerated draw solution to be supplied to the membrane module 731 and raises the temperature of the diluted draw solution, thereby obtaining the same effect as in the second device example. be able to.

(Fourth device example)
(Forward osmosis device and forward osmosis treatment process)
Next, a forward osmosis apparatus according to a fourth apparatus example of the present invention will be described. FIG. 17 is a block diagram schematically showing a forward osmosis device 74 according to the fourth device example. As shown in FIG. 17, the forward osmosis device 74 according to the fourth device example includes a membrane module 741 having a semipermeable membrane 741a, heat exchangers 742a, 742b, and 742c, a pretreatment unit 743, a heater 744, a separation tank 745, It comprises a final processing unit 746 , thermometers 747 a and 747 b , a flow meter 748 , control valves 749 a and 749 b and a controller 750 . Membrane module 741, semipermeable membrane 741a, heat exchangers 742a, 742b, 742c, heater 744, separation tank 745, and final treatment unit 746 in forward osmosis device 74 are each the same as in forward osmosis device 72 according to the second device example. , membrane module 721 , semipermeable membrane 721 a , heat exchangers 722 , 723 , 724 , heater 725 , separation vessel 726 , and final treatment unit 727 .

A pretreatment unit 743 as a pretreatment means is provided upstream of the membrane module 741 along the flow direction of the water-containing solution. The pretreatment unit 743 removes impurities such as turbidity contained in the water-containing solution before introducing the water-containing solution supplied from the outside into the membrane module 741 . As the pretreatment unit 743, conventionally known pretreatment devices such as sand filtration and pretreatment membranes such as MF membranes and UF membranes can be employed.

The heat exchanger 742a is located upstream of the membrane module 741 in the direction of flow of the water-containing solution and downstream of the separation tank 745 in the direction of flow of the regenerated draw solution discharged from the separation tank 745 and reused. provided in The heat exchanger 742a exchanges heat between the regenerated draw solution flowing out of the separation tank 745 and the water-containing solution supplied from the outside.

A thermometer 747a as a means for measuring the temperature of the water-containing solution is located at least on the upstream side of the membrane module 741 along the flow direction of the water-containing solution. It is provided downstream. The thermometer 747 a measures the temperature of the water-containing solution heat-exchanged by the heat exchanger 742 a and supplies the temperature measurement value to the controller 750 .

A thermometer 747b as a draw solution temperature measuring means is provided at least upstream of the membrane module 741 along the flow direction of the regenerated draw solution and downstream of the heat exchanger 742a along the flow direction of the regenerated draw solution. be provided. The thermometer 747 b measures the temperature of the regenerated draw solution heat-exchanged by the heat exchanger 742 a and supplies the measured temperature value to the controller 750 .

A flow meter 748 as flow measurement means is provided at least upstream of the membrane module 741 along the flow direction of the water-containing solution. The flow meter 748 measures the flow rate of the water-containing solution flowing into the membrane module 741 and supplies the measured value of the flow rate to the controller 750 .

The control valve 749a is provided at least on the upstream side of the membrane module 741 along the flow direction of the water-containing solution, and in the fourth device example, on the upstream side of the pretreatment unit 743 and downstream of the heat exchanger 742a. The control valve 749 a is forward osmosis flow control means for adjusting the flow rate of the water-containing solution flowing into the pretreatment unit 743 and the flow rate of the water-containing solution flowing into the membrane module 741 . The opening of the control valve 749a is controlled by the controller 750 based on the flow rate of the water-containing solution measured by the flowmeter 748 and the temperature measured by the thermometers 747a and 747b. Specifically, the control unit 750 adjusts the opening degree of the control valve 749a so that the flow rate of the water-containing solution flowing into the pretreatment unit 743 is constant and the flow rate of the water-containing solution flowing into the membrane module 741 is constant. be done.

A control valve 749b as heat exchange flow rate control means is provided in a bypass pipe as bypass means. The bypass pipe is configured to communicate from the upstream side to the downstream side of the heat exchanger 742c along the flow direction of the diluted draw solution so that the diluted draw solution can pass through. Thus, by adjusting the opening degree of the control valve 749b, the flow rate of the diluted draw solution passing through the heat exchanger 742c as intermediate heat exchange means can be adjusted.

That is, when the opening degree of the control valve 749b is 0 and it is fully closed, the entire diluted draw solution flowing out of the membrane module 741 passes through the heat exchanger 742c. On the other hand, when the opening degree of the control valve 749b is maximum and fully open, the diluted draw solution that has flowed out of the membrane module 741 passes through the control valve 749b in an amount that can flow into the bypass pipe. In this case, the flow rate of diluted draw solution through heat exchanger 742c is minimized. In this manner, the flow rate of the diluted draw solution heat-exchanged in the heat exchanger 742c can be adjusted according to the degree of opening of the control valve 749b. As a result, the temperature of the regenerated draw solution flowing out of the separation tank 745 can be adjusted according to the degree of opening of the control valve 749b.

It is desirable to adjust the temperature of the regenerated draw solution so that the temperature measured by the thermometer 747b is substantially constant, specifically about 40.degree. In this way, by controlling the opening degree of the control valve 749b so as to maintain the temperature of the regenerated draw solution supplied to the membrane module 741 substantially constant at a predetermined temperature, the forward osmosis device 74 as a whole is heat exchanged. Since the efficiency can be improved and the amount of water-containing water discharged through the control valve 749a can be reduced, the energy required for feeding the blowdown water can be reduced.

A device called a sequencer can be used for the control unit 750 as a control means. Physically, it is an electronic circuit mainly composed of a well-known microcomputer including a CPU (Central Processing Unit), RAM (Random Access Memory), ROM (Read Only Memory) and interfaces. The control unit 750 performs calculations using data input to the RAM and data pre-stored in the ROM or the like, and outputs the calculation result as a command signal. The control unit 750 loads a program stored in the ROM into the RAM and executes it by the CPU, thereby operating various devices of the forward osmosis device 74 based on the control of the CPU, Data is read and written to RAM. The controller 750 receives measurement data from the thermometers 747a and 747b and the flow meter 748, and controls the opening degrees of the control valves 749a and 749b.

Next, the forward osmosis treatment process using the forward osmosis device 74 according to the fourth device example will be described. In the forward osmosis treatment process according to the fourth apparatus example, the forward osmosis process, the heating process, the water separation process, the outflow side heat exchange process, and the final treatment process are the same as those in the first apparatus example.

(Pretreatment step)
A pretreatment process is performed in a pretreatment unit 743 as a pretreatment means. That is, in the pretreatment unit 743, a process for removing impurities such as turbidity contained in the water-containing solution is performed on the water-containing solution supplied from the outside. The water-containing solution that has undergone the pretreatment step is supplied to the membrane module 741 .

(Inflow side heat exchange process)
In the fourth device example, the inflow side heat exchange process is performed by the heat exchanger 742a, the control valve 749b, and the control section 750 as the inflow side heat exchange means. That is, the water-containing solution supplied to the forward osmosis device 74 from the outside is first supplied to the heat exchanger 742a. On the other hand, the heat exchanger 742a is supplied with the regenerated draw solution that has flowed out of the separation tank 745 and passed through the heat exchanger 742c. In the fourth device example, the heat exchanger 742a adjusts the temperature of the regenerated draw solution and the water-containing solution to a predetermined temperature, for example, about 40.degree. Here, the inflow-side heat exchange step for adjusting the temperatures of the water-containing solution and the regenerated draw solution to predetermined temperatures in the fourth apparatus example will be described.

First, thermometer 747b measures the temperature downstream of heat exchanger 742a along the flow direction of the regenerated draw solution. The measured temperature value is supplied to the control unit 750 . On the other hand, the thermometer 747a measures the temperature downstream of the heat exchanger 742a along the flow direction of the water-containing solution. The measured temperature value is supplied to the control unit 750 . The control unit 750 compares the measured values supplied from the thermometers 747a and 747b with the predetermined temperature when supplied to the membrane module 741, which is set in advance. A heat exchange flow rate adjustment step is performed to adjust the flow rate of the

(Heat exchange flow rate adjustment step and intermediate heat exchange step)
In heat exchanger 742c, an intermediate heat exchange step occurs in which heat is exchanged between the dilute draw solution and the regenerated draw solution. The control unit 750 performs a heat exchange flow rate adjustment step of adjusting the control valve 749b based on the measured temperature values supplied to the control unit 750 from the thermometers 747a and 747b. The control unit 750 adjusts the regulating valve 749a based on the measured temperature values supplied to the control unit 750 from the thermometers 747a and 747b as necessary.

That is, the controller 750 controls the opening degrees of the control valves 749a and 749b so that the temperatures measured by the thermometers 747a and 747b are maintained substantially constant. Also, the opening degrees of the control valves 749a and 749b are independently controlled by the control unit 750. FIG. An example of a control method for controlling the opening degrees of the control valves 749a and 749b so as to keep the temperatures measured by the thermometers 747a and 747b substantially constant will be described below. Note that the control method of the control valves 749a and 749b is not limited to the following method.

First, when the measured value by the thermometer 747a is higher than a predetermined temperature, the controller 750 performs control to lower the temperature of the regenerated draw solution passing through the heat exchanger 742a. In this case, the controller 750 reduces the flow rate of the diluted draw solution flowing through the bypass pipe by reducing the degree of opening of the control valve 749b. Accordingly, the flow rate of the diluted draw solution flowing through the heat exchanger 742c increases, and the amount of heat transferred from the regenerated draw solution to the diluted draw solution in the heat exchanger 742c increases. As a result, the temperature of the regenerated draw solution passing through the heat exchanger 742a is lower than before the degree of opening of the control valve 749b is reduced, and the temperature rise of the water-containing solution is also suppressed.

On the contrary, when the measured value by the thermometer 747a is lower than the predetermined temperature, the controller 750 performs control to raise the temperature of the regenerated draw solution passing through the heat exchanger 742a. That is, the controller 750 increases the flow rate of the diluted draw solution flowing through the bypass pipe by increasing the opening of the control valve 749b. Concomitantly, the flow rate of the diluted draw solution through heat exchanger 742c is reduced, thereby reducing the amount of heat transferred from the regenerated draw solution to the diluted draw solution in heat exchanger 742c. As a result, the temperature of the regenerated draw solution passing through the heat exchanger 742a rises compared to before the degree of opening of the control valve 749b is reduced, and the temperature of the water-containing solution also rises.

Specifically, when the control valve 749b is fully closed or relatively throttled, the heat exchanger 742a is supplied with the regeneration draw solution at a lower temperature than when the control valve 749b is fully open. be. At this time, since a relatively small amount of the water-containing solution supplied to the heat exchanger 742a is sufficient to lower the temperature of the regenerated draw solution, the water-containing solution supplied to the pretreatment unit 743 and the membrane module 741 is kept constant. is reduced from the control valve 749a.

On the other hand, when the control valve 749b is fully open or relatively open, the temperature of the regenerated draw solution supplied to the heat exchanger 742a is higher than when the control valve 749b is fully closed. At this time, in order to cool the regenerated draw solution and maintain the temperature of the water-containing solution measured by the thermometer 747a at a predetermined temperature, it is necessary to increase the water-containing solution supplied to the heat exchanger 742a. The waste volume from valve 749a increases.

Based on the above control principle, the opening degree of the control valve 749b is adjusted so that the temperature measured by the thermometer 747b is maintained at a predetermined temperature, for example, 40° C., and the temperature of the thermometer 747a is increased to a predetermined temperature, for example, The degree of opening of the control valve 749b is adjusted so as to maintain the temperature at 40°C. Here, if it is difficult to keep the measured values of the thermometers 747a and 747b constant only by adjusting the opening of the control valve 749b, the temperature The measured values of totals 747a and 747b are both adjusted to be constant.

As described above, the control unit 750 controls the opening degrees of the control valves 749a and 749b based on the measured values of the thermometers 747a and 747b, so that the temperature of the water-containing solution and the temperature of the regenerated draw solution are approximately equal to each other. The temperature is controlled to be the same and the predetermined temperature. The regenerated draw solution whose temperature has been lowered by heat exchange in the heat exchanger 742 a is supplied to the other chamber of the membrane module 741 , and the water-containing solution whose temperature has been raised by heat exchange is sent to the pretreatment unit 743 . supplied to remove turbidity. The water-containing solution flowing out from the pretreatment unit 743 passes through a flow meter 748 and is supplied to one chamber in the membrane module 741 . By raising the temperature of the water-containing solution before being supplied to the membrane module 741, the permeation water amount (m/day) of the membrane module 741 can be improved. Further, by keeping the temperature of the water-containing solution supplied to the membrane module 741 constant, the amount of permeated water in the membrane module 741 can be stabilized.

(Forward osmosis flow control step)
Further, in the fourth device example, a forward osmosis flow rate control step is performed by the flow meter 748, the control valve 749a, and the controller 750 to control the flow rate of the water-containing solution flowing into the membrane module 741. FIG.

That is, the water-containing water supplied to the forward osmosis device 74 from the outside is supplied to the membrane module 741 after the turbidity is removed by the pretreatment unit 743 via the heat exchanger 742a. The flow meter 748 measures the flow rate on the upstream side of the membrane module 741 along the flow direction of the water-containing solution and supplies the measured value to the controller 750 .

The control unit 750 compares the measured value supplied from the flow meter 748 with a preset flow rate for supplying to the membrane module 741 . If the measured value is greater than the predetermined flow rate, the controller 750 performs control to reduce the flow rate of the water-containing solution flowing into the membrane module 741 .

That is, the control unit 750 increases the flow rate of the water-containing solution to be discharged to the outside on the upstream side of the pretreatment unit 743 by increasing the opening of the control valve 749a. As a result, the flow rate of the water-containing solution supplied to the pretreatment unit 743 is reduced, and the flow rate of the water-containing solution supplied to the membrane module 741 is reduced. Conversely, when the measured value is smaller than the predetermined flow rate, the controller 750 performs control to increase the flow rate of the water-containing solution flowing into the membrane module 741 . That is, the controller 750 reduces the flow rate of the water-containing solution to be discharged to the outside on the upstream side of the pretreatment unit 743 by reducing the opening degree of the control valve 749a. As a result, the flow rate of the water-containing solution supplied to the pretreatment unit 743 is increased, and the flow rate of the water-containing solution supplied to the membrane module 741 is increased. Therefore, the flow rate of the water-containing solution flowing into the membrane module 741 can be maintained at a substantially constant predetermined flow rate.

(Fourth device embodiment)
Next, a fourth embodiment of the forward osmosis device 74 constructed as above will be described. In the fourth embodiment, an example will be described in which the forward osmosis device 74 is used to generate 67 L/h of permeated water from blowdown water having a flow rate of 100 L/h.

In the fourth embodiment, the heat exchanger 742a exchanges heat with the blowdown water introduced into the forward osmosis device 74 from the outside. The blowdown water is heated to 40° C. by heat exchanger 742 a and supplied to pretreatment unit 743 and membrane module 741 .

Here, the opening degree of the control valve 749b is controlled according to the temperature of the upstream side of the pretreatment unit 743 along the flow direction of the water-containing solution and the downstream side of the heat exchanger 742a, and the water passes through the heat exchanger 742c. The flow rate of diluted draw solution is controlled. This controls the amount of heat transferred from the regenerated draw solution to the dilute draw solution in heat exchanger 742c, thereby controlling the temperature of the regenerated draw solution passing through heat exchanger 742a and transferring from the regenerated draw solution to the blowdown water. Heat is controlled. The blowdown water concentrated by the membrane module 741 is discharged from the membrane module 741 at a flow rate of 33 L/h. That is, in membrane module 741, water is transferred at a flow rate of 67 L/h.

On the other hand, the temperature of the regenerated draw solution is adjusted by heat exchange with the blowdown water in the heat exchanger 742a, and the temperature is lowered to 40°C. The regenerated draw solution is fed to the membrane module 741, diluted, and exits as diluted draw solution. Here, the flow rate of the regeneration draw solution is 100 L/h. The dilute draw solution exiting the membrane module 741 has a temperature of 40° C. and a flow rate of 167 L/h. The diluted draw solution is then heat exchanged with the water-rich solution having a temperature of 88°C in the heat exchanger 742b and heated to a temperature of 40°C to 52°C.

The diluted draw solution is then supplied to heat exchanger 742c for heat exchange. In the heat exchanger 742c, the temperature of the diluted draw solution is controlled according to the opening of the control valve 749b, which is controlled according to the temperature on the upstream side of the membrane module 741 along the flow direction of the water-containing solution. The temperature is raised to a temperature of 52°C or higher and 71°C or lower. After that, it is supplied to the heater 744 and further heated to a temperature of 88°C.

The diluted draw solution is fed to a separation tank 745 and phase separated into a regenerated draw solution and a water-rich solution. The regenerated draw solution discharged from the separation tank 745 has a temperature of 88° C. and a flow rate of 1000 L/h. The regenerated draw solution is fed to heat exchanger 742c to exchange heat with the cold diluted draw solution. The temperature of the heat exchange in the heat exchanger 742c is controlled according to the degree of opening of the control valve 749b, and the temperature is lowered from 88°C to 65°C or more and less than 88°C.

The water-rich solution discharged from the separation tank 745 has a temperature of 88° C. and a flow rate of 67 L/h. The water-rich solution is supplied to heat exchanger 742b to exchange heat with the 40° C. dilute draw solution to reduce the temperature from 88° C. to 45° C. before being supplied to final processing unit 746. In the final treatment unit 746, permeate is obtained at a flow rate of 67 L/h. It should be noted that the draw solution separated from the permeate in the final treatment unit 746 is not considered due to its small volume. As described above, permeated water with a flow rate of 67 L/h is obtained from blowdown water with a flow rate of 100 L/h.

As described above, according to the fourth device example, the adjustment valve 749b for adjusting the flow rate of the bypass pipe that bypasses the upstream side and the downstream side along the flow direction of the diluted draw solution in the heat exchanger 742c is provided. By controlling the opening degree of the control valve 749b according to the temperature of the water-containing solution flowing into the module 741, the heat exchange between the water-containing solution and the regenerated draw solution is controlled. The aqueous solution and regenerated draw solution are adjusted to the desired temperature. As a result, the temperature of the water-containing solution and the draw solution in the membrane module 741 can be made very close to each other, so that the treatment efficiency in the membrane module 741 can be stabilized.

According to the fourth device example, a control valve 749a is provided at least on the upstream side of the membrane module 741 along the flow direction of the water-containing solution, and the opening degree of the control valve 749a is adjusted according to the flow rate on the upstream side of the membrane module 741. As a result, the water-containing solution supplied to the membrane module 741 can be maintained at a predetermined flow rate. Thereby, the treatment efficiency in the membrane module 741 can be further stabilized.

It should be noted that the forward osmosis device 74 may be configured without the heat exchanger 742b. That is, in the forward osmosis device 74, a configuration in which heat exchange is not performed between the diluted draw solution and the water-rich solution is also possible. Further, the forward osmosis device 74 may be configured without the pretreatment unit 743 or without the pretreatment unit 743 and the heat exchanger 742b. In this case, in the stage prior to introduction into the forward osmosis device 74, the water-containing solution is pretreated to remove turbidity and the like.

Although the embodiments of the present invention have been specifically described above, the present invention is not limited to the above-described embodiments, and various modifications based on the technical idea of the present invention are possible. For example, the numerical values given in the above-described embodiments are merely examples, and different numerical values may be used if necessary. is not limited.

For example, in the above-described embodiment, PAC is used as a flocculant for silica, but flocculants other than PAC can also be used, and the sludge S precipitated in the reaction tank can be used as a flocculant. It is possible. Specifically, in addition to PAC, aluminum salts such as aluminum hydroxide (Al(OH) ₃ ) and aluminum sulfate (Al ₂ (SO ₄ ) ₃ ), such as Mg(OH) ₂ and magnesium chloride (MgCl ₂ ). iron salts such as ferric chloride (FeCl ₃ ), ferric sulfate (Fe ₂ (SO ₄ ) ₃ ), polysilica iron (PSI), and polymeric flocculants such as polyacrylamide based At least one selected flocculant, or a flocculant obtained by combining two or more of the flocculants described above, can also obtain the same effects as in the case of PAC by going through the same reaction mechanism as described above. be.

The water treatment apparatuses 1 to 8 according to the first to fourth embodiments and the first to fourth modifications described above can be appropriately combined. For example, it is possible to provide both the water softener 30 downstream of the first coagulation-sedimentation unit 10 according to the first embodiment and the water softener 30 downstream of the second coagulation-sedimentation unit 50 according to the fourth embodiment.

1, 2, 3, 4, 5, 6, 7, 8 Water treatment equipment 10 First coagulation-sedimentation section 10A, 10B, 10C, 10D, 50A, 50B, 50C, 50D Coagulation-sedimentation section 11 Receiving tank 12 Reaction tank 13 pH Adjustment tank 14 Pump 15 Dehydrator 16, 17, 51, 52 Silica concentration meter 18 Sludge storage tank 19 Chemical dosing device 20 First filtration unit 30 Water softener 40 Low pressure reverse osmosis unit 50 Second coagulation sedimentation unit 60 Second filtration unit 70 , 71, 72, 73, 74 forward osmosis device 80 distillation crystallization unit 90 high-pressure reverse osmosis unit 121 first reaction tanks 121a, 122a stirring unit 122 second reaction tank 123 sedimentation tanks 711, 721, 731, 741 membrane module 711a, 721a, 731a, 741a Semipermeable membranes 712, 713, 722, 723, 724, 732, 733, 734, 742a, 742b, 742c Heat exchangers 714, 725, 735, 744 Heaters 715, 726, 736, 745 Separation tank 716, 727, 737, 746 final treatment unit 743 pretreatment unit 747a, 747b thermometer 748 flow meter 749a, 749b control valve 750 controller S sludge

Claims (19)

A water treatment apparatus for extracting water from water to be treated containing impurities containing silica,
a plurality of coagulation-sedimentation units that coagulate and remove at least part of the impurities from the water to be treated;
At least one of a forward osmosis membrane and a reverse osmosis membrane capable of extracting water from a water-containing solution containing water as a solvent is provided to extract permeated water from the water to be treated, and the permeated water is extracted from the water to be treated. a plurality of water extraction units for discharging concentrated water obtained by
A first water extracting section, which is a part of the plurality of water extracting sections, is located downstream of the first coagulating and sedimenting section, which is a part of the plurality of coagulating and sedimenting sections, along the flow direction of the water to be treated. and a second coagulation/sedimentation unit which is the other part of the plurality of coagulation/sedimentation units after the first water extraction unit, and the other of the plurality of water extraction units after the second coagulation/sedimentation unit. A second water extraction unit is provided,
The first coagulation/sedimentation unit adds a coagulant that aggregates silica to the water to be treated whose pH is adjusted to 8 or more and 12 or less, removes a part of the silica, and removes the water to be treated from the 1 supplied to the water extraction part,
The first water extraction unit extracts the permeated water from the water to be treated from which part of the silica has been removed, discharges the concentrated water, and supplies the concentrated water to the second coagulation sedimentation unit. ,
The second coagulation and sedimentation unit adds a coagulant that aggregates silica to the concentrated water adjusted to a pH of 8 or more and 12 or less, removes the remaining silica, and then extracts the concentrated water with the second water extraction. supply the department,
The second water extraction unit has at least one of the forward osmosis membrane and the reverse osmosis membrane, extracts permeated water from the concentrated water supplied from the second coagulation sedimentation unit, and further extracts the concentrated water. A water treatment device characterized by discharging concentrated highly concentrated water. A plurality of filtering units are provided for filtering the water to be treated or the concentrated water,
Along the flow direction of the water to be treated,
A first filtration unit, which is a part of the plurality of filtration units, is provided downstream of the first coagulation-sedimentation unit and upstream of the first water extraction unit,
2. The water according to claim 1, wherein a second filtration section, which is the other section of the plurality of filtration sections, is provided downstream of the second coagulation-sedimentation section and upstream of the second water extraction section. processing equipment. The pH of the water to be treated supplied to the first filtration unit and the concentrated water supplied to the second filtration unit are configured to be adjustable to a pH of 4 or more and 8 or less. 2. The water treatment device according to 2. The first water extraction unit comprises a low-pressure reverse osmosis unit having a low-pressure reverse osmosis membrane, and the second water extraction unit comprises a high-pressure reverse osmosis unit having a high-pressure reverse osmosis membrane or a forward osmosis unit having the forward osmosis membrane. The water treatment device according to any one of claims 1 to 3, characterized by comprising: A distillation and crystallization unit for performing at least one of a distillation process and a crystallization process on the highly concentrated water and discharging purified water is provided after the second water extraction unit. The water treatment device according to any one of claims 1 to 4. the impurities include calcium;
Along the flow direction of the water to be treated,
A calcium remover capable of removing the calcium is provided in at least one of a stage subsequent to the first coagulation/sedimentation section and a stage prior to the first water extraction section and a stage subsequent to the second coagulation/sedimentation section and prior to the second water extraction section. The water treatment device according to any one of claims 1 to 5, further comprising a part. the impurities include calcium;
A calcium dispersant can be added to the water to be treated in a stage prior to the first water extractor along the flow direction of the water to be treated, according to any one of claims 1 to 6. The water treatment device according to . The coagulant that aggregates the silica in the coagulation-sedimentation section is polyaluminum chloride or aluminum chloride, and coagulation-sedimentation sludge that is added to the water to be treated and is precipitated in the coagulation-sedimentation section; including
The water treatment apparatus according to any one of claims 1 to 7, wherein the coagulated sedimentation sludge is withdrawn from the coagulated sedimentation unit and added to the coagulated sedimentation unit without being subjected to regeneration treatment. The water treatment equipment according to any one of claims 1 to 8, characterized in that said impurities contain magnesium. A water treatment method for extracting water from water to be treated containing impurities containing silica,
A first coagulation sedimentation step of adjusting the pH of the water to be treated to 8 or more and 12 or less, adding a coagulant that coagulates silica, and coagulating and removing a part of the silica contained in the impurities. ,
After the first coagulation-sedimentation step, at least one of a forward osmosis membrane and a reverse osmosis membrane is used to extract permeate water from the water to be treated, and concentrated water obtained by extracting the permeate water from the water to be treated is a first water extraction step to discharge;
After the first water extraction step , the pH of the concentrated water is adjusted to 8 or more and 12 or less, a flocculant that flocculates silica is added, and the rest of the silica contained in the impurities is flocculated and removed. a second coagulating sedimentation step;
After the second coagulation sedimentation step, a second water extraction step of extracting permeated water from the concentrated water by at least one of a forward osmosis membrane and a reverse osmosis membrane and discharging highly concentrated water obtained by further concentrating the concentrated water. A water treatment method comprising: The water treatment method according to claim 10, wherein the pH of the concentrated water is adjusted to 8 or more and 12 or less in the second coagulating sedimentation step. a first filtration step of filtering the water to be treated after the first coagulation sedimentation step and before the first water extraction step;
The water treatment method according to claim 10 or 11, further comprising a second filtration step of filtering the concentrated water after the second coagulation sedimentation step and before the second water extraction step. Adjusting the pH of the water to be treated in the first filtration step to 4 or more and 8 or less,
The water treatment method according to claim 12, wherein the pH of the concentrated water in the second filtering step is adjusted to 4 or more and 8 or less. The first water extraction step includes a low pressure reverse osmosis step of extracting the permeated water with a low pressure reverse osmosis membrane, and the second water extraction step is a high pressure reverse osmosis step of extracting the permeated water with a high pressure reverse osmosis membrane. , or a forward osmosis step of extracting the permeated water by the forward osmosis membrane. The water treatment method according to any one of claims 10 to 13. 15. The method according to any one of claims 10 to 14, further comprising a distillation crystallization step of subjecting the highly concentrated water to at least one of distillation treatment and crystallization treatment and discharging purified water after the second water extraction step. The water treatment method according to any one of items 1 and 2. the impurities include calcium;
A calcium removal step of removing the calcium in at least one of after the first coagulation sedimentation step and before the first water extraction step and after the second coagulation sedimentation step and before the second water extraction step. The water treatment method according to any one of claims 10 to 15, comprising the impurities include calcium;
The water treatment method according to any one of claims 10 to 16, further comprising a calcium dispersing step of adding a calcium dispersant to the water to be treated before the first water extraction step. In the first coagulation-sedimentation step and the second coagulation-sedimentation step, the flocculant for flocculating the silica is polyaluminum chloride or aluminum chloride, and the water to be treated is added with polyaluminum chloride or aluminum chloride to form the first flocculation. Coagulating and sedimentation sludge that has been coagulated and sedimented in at least one of the sedimentation step and the second coagulation and sedimentation step,
10. The coagulating/sedimentary sludge is withdrawn from the coagulating/sedimentary section in which at least one of the first coagulating/sedimentary process and the second coagulating/sedimentary process is performed, and is added to the coagulating/sedimentary section without performing regeneration treatment. 18. The water treatment method according to any one of 17. The water treatment method according to any one of claims 10 to 18, characterized in that said impurities contain magnesium.

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