JP2021030189A - Water treatment apparatus and water treatment method - Google Patents

Abstract

To provide a water treatment apparatus and a water treatment method capable of treating treated water containing at least one of soluble silica and hardness components at a low cost.SOLUTION: A water treatment apparatus 1 treats treated water containing at least one of soluble silica and hardness components. It includes a pre-treatment apparatus 10 which has at least one of soluble silica removal means and hardness component removal means, a reverse osmosis membrane treatment apparatus 12 which is used as first concentration treatment means to concentrate the pre-treated water obtained in the pre-treatment apparatus 10, a positive osmosis membrane treatment apparatus 14 which is used for treating the concentrated water obtained in the reverse osmosis membrane treatment apparatus 12 by positive osmosis membrane, and a concentration apparatus 16 which is used for concentrating a part of the dilute attraction solution used in the positive osmosis membrane treatment apparatus 14. In the water treatment apparatus 1, a part of the dilute attractant solution used in the positive osmosis membrane treatment apparatus 14 is used in the pre-treatment apparatus 10, and the concentrated attractant solution concentrated in the concentration apparatus 16 is used again as the attractant solution in the positive osmosis membrane treatment apparatus 14.SELECTED DRAWING: Figure 1

Description

The present invention relates to a water treatment apparatus and a water treatment method for treating water to be treated containing at least one of soluble silica and a hardness component.

In order to reduce the impact of wastewater discharge on the environment, there is a growing movement to discharge and dispose of wastewater after purifying and reducing its volume. Solid-liquid separation, membrane separation, vacuum concentration, etc. are used for wastewater treatment, but the hardness components such as soluble silica and calcium contained in the wastewater are insolubilized and adhere to the piping and equipment used for wastewater treatment, so-called. It is known that the performance of the system deteriorates due to scaling. In order to carry out efficient wastewater treatment, it is necessary to remove soluble silica and hardness components in the wastewater.

For example, in Patent Document 1, for soluble silica-containing wastewater, a magnesium salt is added under alkaline conditions to insolubilize the soluble silica, and then solid-liquid separation is performed, and the obtained treated water is subjected to reverse osmosis membrane treatment or forward osmosis. A method of membrane treatment to recover fresh water from wastewater is described.

In the forward osmosis membrane treatment, by allowing the supply water and the attractant solution to exist through the forward osmosis membrane, water can be moved to the attractant solution by osmotic pressure without pressurization. By changing the phase of the diluted attractant solution by means such as heating, the attractant solution can be reused while obtaining fresh water.

As an attracting solution for the forward osmosis membrane treatment, an aqueous solution of ammonium carbonate or a mixture of an inorganic salt and a temperature-sensitive agent is used (see Patent Document 2).

In order to reuse the attractant solution, it is necessary to apply external energy such as heating, and it is necessary to additionally provide a device for reusing the attractant solution (see, for example, FIG. 8: storing the attractant solution). The heating device 206 is required for the attracting solution tank 204), which leads to an increase in the cost of the system as a whole.

As a method for removing the hardness component, Patent Document 3 describes a method in which an alkaline agent is added to the wastewater containing the hardness component to precipitate it (so-called lime softening method), and the filtered water is subjected to reverse osmosis film treatment after aggregation and filtration treatment. Has been done. Further, Patent Document 4 describes a method (resin softening method) of adsorbing and removing a hardness component using an ion exchange resin.

However, the lime softening method requires the addition of an alkaline agent, and the resin softening method requires the passage of high-concentration salt water (sodium chloride aqueous solution) in order to regenerate the ion exchange resin on which the hardness component is adsorbed. Cost reduction is required.

International Patent Application Publication No. 2013/153587 Pamphlet JP-A-2017-056424 JP-A-2017-170275 Japanese Unexamined Patent Publication No. 2014-231039

An object of the present invention is to provide a water treatment apparatus and a water treatment method capable of treating water to be treated containing at least one of soluble silica and a hardness component at low cost.

The present invention is a water treatment apparatus that treats water to be treated containing at least one of soluble silica and a hardness component, and is provided before any one of the soluble silica removing means and the hardness component removing means is provided. A treatment means, a first concentration treatment means for concentrating the pretreated water obtained by the pretreatment means, and a forward osmosis membrane treatment means for treating the concentrated water obtained by the first concentration treatment means with a forward osmosis membrane. A second concentration treatment means for concentrating a part of the dilute attractant solution used in the forward osmosis membrane treatment means, and a part of the dilute attractant solution used in the forward osmosis membrane treatment means is said to be the above. It is a water treatment apparatus used in the treatment means, in which the concentrated attracting solution concentrated by the second concentration treating means is used again as the attracting solution in the forward osmosis membrane treating means.

In the water treatment apparatus, the second concentration treatment means is preferably a concentration means using a semipermeable membrane.

In the water treatment apparatus, the first concentration treatment means is preferably a reverse osmosis membrane treatment means.

In the water treatment apparatus, the attracting solution used in the forward osmosis membrane treatment means is a magnesium salt aqueous solution, and the magnesium salt dilute aqueous solution used in the forward osmosis membrane treatment means is used in the soluble silica removing means. Is preferable.

In the water treatment apparatus, the attracting solution used in the forward osmosis membrane treatment means is an alkaline agent aqueous solution, and the alkaline agent dilute aqueous solution used in the forward osmosis membrane treatment means may be used in the hardness component removing means. preferable.

In the water treatment apparatus, the attractant solution used in the forward osmosis membrane treatment means is an acid aqueous solution or a sodium chloride aqueous solution, and the acid dilute aqueous solution or the sodium chloride dilute aqueous solution used in the forward osmosis membrane treatment means removes the hardness component. It is preferably used by means.

Further, the present invention is a water treatment method for treating water to be treated containing at least one of soluble silica and a hardness component, wherein any one of a soluble silica removing step and a hardness component removing step is performed. A pretreatment step including, a first concentration treatment step for concentrating the pretreated water obtained in the pretreatment step, and a forward osmosis membrane treatment for treating the concentrated water obtained in the first concentration treatment step with a forward osmosis membrane. A part of the dilute attractant solution used in the forward osmosis membrane treatment step is said to include a step and a second concentration treatment step of concentrating a part of the dilute attractant solution used in the forward osmosis membrane treatment step. This is a water treatment method in which the concentrated attracting solution used in the pretreatment step and concentrated in the second concentration treatment step is used again as the attracting solution in the forward osmosis membrane treatment step.

In the water treatment method, the second concentration treatment step is preferably a concentration step using a semipermeable membrane.

In the water treatment method, the first concentration treatment step is preferably a reverse osmosis membrane treatment step.

In the water treatment method, the attractant solution used in the forward osmosis membrane treatment step is a magnesium salt aqueous solution, and the magnesium salt dilute aqueous solution used in the forward osmosis membrane treatment step is preferably used in the soluble silica removal step. ..

In the water treatment method, it is preferable that the attracting solution used in the forward osmosis membrane treatment step is an alkaline agent aqueous solution, and the alkaline agent dilute aqueous solution used in the forward osmosis membrane treatment step is used in the hardness component removing step.

In the water treatment method, the attractant solution used in the forward osmosis membrane treatment step is an acid aqueous solution or a sodium chloride aqueous solution, and the acid dilute aqueous solution or the sodium chloride dilute aqueous solution used in the forward osmosis membrane treatment step is used in the hardness component removing step. It is preferable to use in.

According to the present invention, water to be treated containing at least one of soluble silica and a hardness component can be treated at low cost.

It is a schematic block diagram which shows an example of the water treatment apparatus which concerns on embodiment of this invention. It is a schematic block diagram which shows an example of the concentrating apparatus in the water treatment apparatus which concerns on embodiment of this invention. It is a schematic block diagram which shows another example of the concentrator in the water treatment apparatus which concerns on embodiment of this invention. It is a schematic block diagram which shows another example of the concentrator in the water treatment apparatus which concerns on embodiment of this invention. It is a schematic block diagram which shows another example of the concentrator in the water treatment apparatus which concerns on embodiment of this invention. It is a schematic block diagram which shows another example of the concentrator in the water treatment apparatus which concerns on embodiment of this invention. It is a schematic block diagram which shows another example of the concentrator in the water treatment apparatus which concerns on embodiment of this invention. It is a schematic block diagram which shows the conventional water treatment apparatus.

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

An outline of an example of a water treatment apparatus according to an embodiment of the present invention is shown in FIG. 1, and its configuration will be described.

The water treatment device 1 concentrates the pretreatment device 10 as a pretreatment means including at least one of the soluble silica removing means and the hardness component removing means, and the pretreatment water obtained by the pretreatment device 10. 1 A reverse osmosis membrane treatment device 12 as a concentration treatment means, a forward osmosis membrane treatment device 14 as a forward osmosis membrane treatment means for treating the concentrated water obtained by the reverse osmosis membrane treatment device 12, and a forward osmosis membrane. A concentrating device 16 is provided as a second concentrating treatment means for concentrating a part of the dilute attractant solution used in the processing device 14.

In the water treatment device 1 of FIG. 1, the water treatment pipe 18 is connected to the water inlet of the pretreatment device 10, and the outlet of the pretreatment device 10 and the inlet of the reverse osmosis membrane treatment device 12 are the pretreatment water piping. It is connected by 20. The concentrated water outlet of the reverse osmosis membrane treatment device 12 and the concentrated water inlet of the forward osmosis membrane treatment device 14 are connected by a concentrated water pipe 22, and a permeated water pipe 24 is provided at the permeated water outlet of the reverse osmosis membrane treatment device 12. It is connected. An attractant solution pipe 26 is connected to the attractant solution inlet of the forward osmosis membrane treatment device 14, and the dilute attractant solution outlet of the forward osmosis membrane treatment device 14 and the dilute attractant solution inlet of the pretreatment device 10 are connected to the dilute attractant solution pipe. The FO concentrated water pipe 30 is connected to the FO concentrated water outlet of the forward osmosis membrane treatment device 14 which is connected by 28. The dilute attractant solution pipe 32 branched from the dilute attractant solution pipe 28 is connected to the inlet of the concentrating device 16, and the outlet of the concentrated attracting solution of the concentrating device 16 and the middle of the attracting solution pipe 26 are connected by the concentrated attracting solution pipe 34. ing. A diluent pipe 36 is connected to the diluent outlet of the concentrator 16.

The water treatment method and the operation of the water treatment device 1 according to the present embodiment will be described.

The water to be treated containing at least one of the soluble silica and the hardness component is sent to the pretreatment apparatus 10 through the water to be treated pipe 18. In the pretreatment apparatus 10, at least one of the soluble silica and the hardness component is removed (pretreatment step).

When the water to be treated contains soluble silica, the pretreatment apparatus 10 uses, for example, a magnesium reaction means for adding a magnesium salt to the water to be treated and reacting the water to be treated to insolubilize the soluble silica, and the water to be treated after the reaction. It has a coagulation treatment means for adding a coagulant to coagulate, and a solid-liquid separation means for separating agglomerates from the coagulated water to be treated. In the pretreatment apparatus 10, a magnesium salt is added to the water to be treated under alkaline conditions (for example, pH 10 to 12) to insolubilize the soluble silica (magnesium reaction step). Then, if necessary, a coagulant is added to perform agglutination treatment (aggregation treatment step), and the agglomerates are solid-liquid separated (solid-liquid separation step). The pretreated water obtained by solid-liquid separation is sent to the reverse osmosis membrane treatment device 12 through the pretreated water pipe 20.

When the water to be treated contains a hardness component and the hardness component is removed by a lime softening method, the pretreatment apparatus 10 is, for example, an alkaline agent that insolubilizes the hardness component by adding an alkaline agent to the water to be treated and reacting it. It has a reaction means, a coagulation treatment means for coagulating by adding a coagulant to the water to be treated after the reaction as needed, and a solid-liquid separation means for separating agglomerates from the coagulated water to be treated. .. In the pretreatment apparatus 10, for example, an alkaline agent is added to the water to be treated to insolubilize the hardness component (alkaline agent reaction step). After that, a coagulant is added, agglutination treatment is performed (coagulation treatment step), and agglomerates are solid-liquid separated (solid-liquid separation step). The pretreated water obtained by solid-liquid separation is sent to the reverse osmosis membrane treatment device 12 through the pretreated water pipe 20.

When the water to be treated contains a hardness component and the hardness component is removed by a resin softening method, the pretreatment apparatus 10 has an ion exchange treatment means for performing an ion exchange treatment using, for example, an ion exchange resin. In the pretreatment apparatus 10, for example, water to be treated is passed through an ion exchange tower filled with an ion exchange resin as an ion exchange treatment means, and a hardness component is adsorbed and removed (ion exchange step). The pretreated water obtained by the ion exchange treatment is sent to the reverse osmosis membrane treatment device 12 through the pretreated water pipe 20. When it becomes necessary to regenerate the ion exchange resin, the ion exchange resin is regenerated by passing a regenerating agent through the liquid.

Next, the pretreated water obtained in the pretreatment step is concentrated in the reverse osmosis membrane treatment device 12 (first concentration treatment step). The concentrated water (RO concentrated water) obtained by the first concentration treatment (reverse osmosis membrane treatment) is sent to the forward osmosis membrane treatment device 14 through the concentrated water pipe 22, and the permeated water (RO permeated water) is permeated water. It is discharged through the pipe 24.

The concentrated water obtained by the first concentration treatment (reverse osmosis membrane treatment) is subjected to a forward osmosis membrane treatment in the forward osmosis membrane treatment apparatus 14 (forward osmosis membrane treatment step). In the forward osmosis membrane treatment apparatus 14, the attractant solution is sent to the secondary side of the forward osmosis membrane through the attractant solution pipe 26, and the concentrated water and the attractant solution are present through the forward osmosis membrane to cause water at osmotic pressure. Is transferred to the attractant solution.

A part of the dilute attractant solution used in the forward osmosis membrane treatment step is sent to the pretreatment apparatus 10 through the dilute attractant solution pipe 28, and is used in the pretreatment apparatus 10 in the pretreatment apparatus 10. The FO concentrated water obtained in the forward osmosis membrane treatment step is discharged through the FO concentrated water pipe 30. The FO concentrated water may be further concentrated and solidified by a concentrating device, a crystallization device or the like, if necessary.

A part of the dilute attractant solution used in the forward osmosis membrane treatment step is branched from the dilute attractant solution pipe 28, sent to the concentrator 16 through the dilute attractant solution pipe 32, and concentrated in the concentrator 16 (No. 1). 2 Concentration treatment step). The concentrated attracting solution obtained by the second concentration treatment is supplied to the middle of the attracting solution pipe 26 through the concentrated attracting solution pipe 34, and is used again as the attracting solution in the forward osmosis membrane treatment apparatus 14. The diluent obtained by the second concentration treatment is discharged through the diluent pipe 36. The diluted solution may be recovered and reused after undergoing ultrafiltration membrane (UF membrane) treatment, reverse osmosis membrane (RO membrane) treatment, ion exchange treatment and the like, if necessary.

When the pretreatment apparatus 10 includes an apparatus for removing soluble silica, for example, a magnesium salt aqueous solution is used as the attractant solution in the forward osmosis membrane treatment apparatus 14, and the dilute attractant solution used in the forward osmosis membrane treatment apparatus 14 ( A part of the magnesium salt dilute aqueous solution) may be used as the magnesium salt added in the pretreatment apparatus 10. Further, a part of the dilute attractant solution (magnesium salt dilute aqueous solution) used in the forward osmosis membrane treatment device 14 may be concentrated in the concentration device 16 and used again as the attractant solution in the forward osmosis membrane treatment device 14. ..

When the pretreatment device 10 includes a device that removes a hardness component by a lime softening method, for example, an alkaline agent aqueous solution is used as an attracting solution in the forward osmosis membrane treatment device 14, and is used in the forward osmosis membrane treatment device 14. A part of the dilute attractant solution (dilute aqueous solution of alkaline agent) may be used as an alkaline agent added in the pretreatment apparatus 10. Further, a part of the dilute attractant solution (alkaline agent dilute aqueous solution) used in the forward osmosis membrane treatment apparatus 14 may be concentrated in the concentrator 16 and used again as the attractant solution in the forward osmosis membrane treatment apparatus 14. ..

When the pretreatment apparatus 10 includes an apparatus for removing a hardness component by a resin softening method, for example, an acid aqueous solution or a sodium chloride aqueous solution is used as an attracting solution in the forward osmosis membrane treatment apparatus 14, and the forward osmosis membrane treatment apparatus 14 is used. A part of the dilute attractant solution (diluted acid aqueous solution or dilute aqueous solution of sodium chloride) used may be used as a regenerating agent for the ion exchange resin in the pretreatment apparatus 10. Further, a part of the dilute attractant solution (acid dilute aqueous solution or sodium chloride dilute aqueous solution) used in the forward osmosis membrane treatment apparatus 14 is concentrated in the concentrator 16 and used again as the attractant solution in the forward osmosis membrane treatment apparatus 14. It should be done.

According to the water treatment method and the water treatment apparatus according to the present embodiment, the water to be treated containing at least one of the soluble silica and the hardness component can be treated at low cost.

By using the dilute attractant solution diluted by the forward osmosis membrane treatment in the pretreatment step, the cost required for reusing the attractant solution, which was originally required, can be reduced, and it is not necessary to provide a regeneration facility. .. The dilute attractant solution is only diluted from what is originally used in the pretreatment step, so there is almost no additional cost.

If the dilute attractant solution diluted in the forward osmosis membrane treatment is greater than the amount required for use in the pretreatment step, a portion of the dilute attractant solution used in the forward osmosis membrane treatment is used in the pretreatment step. By concentrating a part of the dilute attractant solution that was not used in the pretreatment step and reusing it as the attractant solution in the forward osmosis membrane treatment step, the loss of the dilute attractant solution can be reduced. Since the dilute attractant solution to be concentrated at this time is a part, the cost is significantly lower than that of concentrating and reusing the entire amount of the dilute attractant solution.

The water to be treated by the water treatment method and the water treatment apparatus according to the present embodiment may be water containing at least one of soluble silica and a hardness component, and is not particularly limited. Examples thereof include irrigation water, surface water, tap water, groundwater, seawater, seawater desalted treated water obtained by desalting seawater by a back-penetration method or an evaporation method, and various types of wastewater, such as wastewater discharged in a semiconductor manufacturing process.

When soluble silica is contained in the water to be treated, the concentration of soluble silica is, for example, in the range of 5 to 400 mg / L. When the water to be treated contains a hardness component, the concentration of the calcium hardness component is in the range of 5 to 600 mg / L. Total evaporation residue (TDS: Total Dissolved Solids) in the water to be treated is, for example, in the range of 100 to 50,000 mg / L.

In the water treatment method and the water treatment apparatus according to the present embodiment, when the water to be treated contains both soluble silica and a hardness component, the pretreatment means (pretreatment step) is a soluble silica removing means (soluble silica). Both a removal step) and a hardness component removing means (hardness component removing step) may be provided. The order of the soluble silica removing means (soluble silica removing step) and the hardness component removing means (hardness component removing step) is as follows: first, the soluble silica removing means (soluble silica removing step), and second, the hardness component removing means. The (hardness component removing step) may be first, a hardness component removing means (hardness component removing step), and secondly, a soluble silica removing means (soluble silica removing step).

In this case, at least one of a magnesium salt aqueous solution, an alkaline agent aqueous solution, an acid aqueous solution and a sodium chloride aqueous solution is used as the attracting solution in the normal osmotic membrane treatment apparatus 14 (normal osmotic membrane treatment step). The dilute attracting solution used (at least one of a magnesium salt dilute aqueous solution, an alkaline agent dilute aqueous solution, an acid dilute aqueous solution and a sodium chloride dilute aqueous solution) is a soluble silica removing means (dissolving) of the pretreatment apparatus 10 (pretreatment step). It may be used in whichever of the sex silica removing step) and the hardness component removing means (hardness component removing step) is suitable.

The water treatment method and the water treatment apparatus according to the present embodiment may further include turbidity removing means for removing turbidity components and the like in the water to be treated. Examples of the turbidity removing means include a sand filtration device, a membrane filtration device such as an ultrafiltration (UF) membrane, and a pressure levitation device. The installation position of the turbidity removing means is not particularly limited, but when the turbidity removing means is a sand filtration device, for example, it is a pre-stage of the pretreatment device 10 (pretreatment step), and the turbidity removing means is a membrane filtration device. In the case of a pressure levitation device, for example, it is between the pretreatment device 10 (pretreatment step) and the reverse osmosis membrane treatment device 12 (first concentration treatment step).

[Pretreatment step: Removal of soluble silica]
In the pretreatment step when the water to be treated contains soluble silica, for example, a magnesium salt is added to the water to be treated under alkaline conditions to insolubilize the soluble silica (magnesium reaction step).

The magnesium salt used may be a magnesium salt such as magnesium chloride (MgCl ₂ ) or magnesium sulfate (sulfonyl ₄ ) or a hydrate thereof, and is not particularly limited, but the production of a sparingly soluble substance by the addition of the sulfate is performed. Magnesium chloride is preferable from the viewpoint of suppression and the like.

The pH in the magnesium reaction step may be alkaline, and is not particularly limited. For example, the pH is in the range of 10 to 12, preferably in the range of 10.5 to 11.5, and is in the range of 11 to 11.5. More preferably, it is in the range. If the pH in the magnesium reaction step is less than 10 or more than 12, the silica removal rate may be low.

As the pH adjuster, an alkali such as sodium hydroxide or calcium hydroxide may be used, and if necessary, an inorganic acid such as hydrochloric acid or sulfuric acid may be used.

The temperature in the magnesium reaction step may be any temperature as long as the insolubilization reaction of silica proceeds, and is not particularly limited, but is, for example, in the range of 1 ° C. to less than 50 ° C. and in the range of 10 ° C. to less than 50 ° C. Is more preferable. If the temperature in the magnesium reaction step is less than 1 ° C., the insolubilization reaction of silica may be insufficient, and if it is 50 ° C. or higher, the treatment cost may be high.

The reaction time in the magnesium reaction step is not particularly limited as long as the insolubilization reaction of silica can proceed, but is, for example, in the range of 1 minute to 60 minutes, and more preferably in the range of 5 minutes to 30 minutes. preferable. If the reaction time in the magnesium reaction step is less than 1 minute, the insolubilization reaction of silica may be insufficient, and if it exceeds 60 minutes, the reaction vessel may become excessive.

The amount of the magnesium salt added is preferably in the range of 0.1 to 10 times the magnesium concentration, preferably 0.5 to 5 times the weight concentration of silica in the water to be treated. More preferred. If the amount of magnesium salt added is less than 0.1 times the weight concentration of silica in the water to be treated, the insolubilization reaction of silica may be insufficient, and if it exceeds 10 times, the amount of sludge generated. May become excessive.

In addition to the magnesium salt, an aluminum salt such as polyaluminum chloride (PAC) and aluminum sulfate, an iron salt such as ferric chloride and ferric sulfate may be used in order to insolubilize the soluble silica. It is preferable to use a magnesium salt from the viewpoint of silica removal rate and the like.

In the coagulation treatment step, for example, in a coagulation tank, an inorganic coagulant is added to the water to be treated after the magnesium reaction, and the insoluble matter is agglomerated (coagulation step). Then, in the floc forming tank, a polymer flocculant is added to form flocs (flock forming step).

Examples of the inorganic aggregating agent used in the aggregating step include iron-based inorganic aggregating agents such as iron chloride and aluminum-based inorganic aggregating agents such as polyaluminum chloride (PAC). An iron-based inorganic flocculant is preferable.

The amount of the inorganic flocculant added is preferably in the range of 0.1 to 10 times by weight, more preferably 1 to 5 times the amount of the added magnesium salt. If the amount of the inorganic flocculant added is less than 0.1 times the amount of the added magnesium salt by weight, the agglutination may be insufficient, and if it exceeds 10 times, the amount of sludge generated may increase. It may be excessive.

The pH in the aggregation step is, for example, in the range of 3-11. If the pH in the agglutination step is less than 3 or more than 11, agglutination failure may occur. Further, if the pH in the aggregation step is less than 9, silica may dissolve out from the flocs, so it is desirable to perform the aggregation step in the range of pH 9 to 11.

The temperature in the agglomeration step is, for example, in the range of 1 ° C. to 80 ° C. If the temperature in the agglutination step is less than 1 ° C. or exceeds 80 ° C., poor agglutination may occur.

Examples of the polymer flocculant used in the floc forming step include cationic polymer flocculants such as polyacrylamide and polyacrylic acid ester, anionic polymer flocculants, and nonionic polymer flocculants. An anionic polymer flocculant is preferable from the viewpoint of properties and the like.

Examples of commercially available polymer flocculants include anionic polymer flocculants such as Orfflock OA-3H (manufactured by Organo Corporation).

The amount of the polymer flocculant added is preferably in the range of 0.1 to 10 mg / L, more preferably in the range of 1 to 5 mg / L with respect to the amount of raw water. If the amount of the polymer flocculant added is less than 0.1 mg / L with respect to the amount of raw water, floc formation may not be improved, and if it exceeds 10 mg / L, the polymer flocculant dissolved in the treated water may be present. It may remain.

The pH in the floc forming step is, for example, in the range of 3-11. If the pH in the floc forming step is less than 3 or more than 11, agglutination failure may occur. Further, if the pH in the flock step is less than 9, silica may be dissolved from the flock. Therefore, it is desirable to carry out the flock forming step in the range of pH 9 to 11.

The temperature in the floc forming step is, for example, in the range of 1 ° C. to 80 ° C. If the temperature in the floc forming step is less than 1 ° C. or exceeds 80 ° C., poor aggregation may occur.

In the above coagulation treatment, an inorganic coagulant and a polymer coagulant are used as the coagulation step and the floc forming step, but at least one of the inorganic coagulant, the polymer coagulant and the like may be used, and iron-based inorganic. It is preferable to use at least one of a flocculant and an anionic polymer flocculant. When at least one of an iron-based inorganic flocculant and an anionic polymer flocculant is used when agglomerating insolubilized silica by reacting with a magnesium salt, cohesiveness and solid-liquid separability are improved.

In the solid-liquid separation step, for example, in a settling tank, floc-formed agglomerates are solid-liquid separated (solid-liquid separation step). The pretreated water obtained by solid-liquid separation is sent to the reverse osmosis membrane treatment device 12. On the other hand, sludge is discharged through sludge piping. Sludge may be collected and reused.

Examples of the solid-liquid separation in the solid-liquid separation step include settling separation by natural sedimentation, pressure flotation treatment, membrane filtration treatment, and the like, and sedimentation separation is preferable from the viewpoint of separability and the like.

[Pretreatment process: Removal of hardness components by lime softening method]
When the water to be treated contains a hardness component, the hardness component may be removed by a lime softening method. The hardness components are classified into primary hardness and permanent hardness. The primary hardness is removed by an alkaline agent such as sodium hydroxide (NaOH), and the permanent hardness is removed by the addition of a carbonate such as _{sodium carbonate (NaCO 3).} For convenience, carbonates are also described herein as alkaline agents. That is, in the pretreatment step, an alkaline agent is added to the water to be treated to insolubilize the hardness component (alkaline agent reaction step).

Examples of the alkaline agent used include calcium hydroxide (Ca (OH) ₂ ), sodium hydroxide (NaOH), potassium hydroxide (KOH), calcium hydrogen carbonate (Ca (HCO ₃ ) ₂ ), magnesium hydrogen carbonate (). Mg (HCO ₃ ) ₂ ), sodium carbonate (Na ₂ CO ₃ ), potassium carbonate (K ₂ CO ₃ ) and the like can be mentioned, and one or more of these can be used. That is, it is also possible to add sodium hydroxide and sodium carbonate, respectively, as needed. Sodium carbonate is preferable from the viewpoint of insolubilization efficiency and the like.

The pH in the alkaline agent reaction step may be an alkaline condition and is not particularly limited, but is preferably in the range of pH 9 to 13, preferably in the range of 11 to 12. If the pH in the alkaline agent reaction step is less than 9, the hardness component removal rate is low, and if it exceeds 13, the amount of the alkaline agent added may be large.

The temperature in the alkaline agent reaction step may be any temperature as long as the insolubilization reaction of the hardness component proceeds, and is not particularly limited, but is, for example, in the range of 1 ° C. to 80 ° C. If the temperature in the alkaline agent reaction step is less than 1 ° C., the insolubilization reaction of the hardness component may be insufficient, and if it exceeds 80 ° C., the heat resistant temperature of the equipment may become a problem.

The reaction time in the alkaline agent reaction step is not particularly limited as long as the insolubilization reaction of the hardness component can proceed, but is, for example, in the range of 10 minutes to 30 minutes. If the reaction time in the alkaline agent reaction step is less than 10 minutes, the insolubilization reaction of the hardness component may be insufficient, and if it exceeds 30 minutes, the reaction vessel may become large and the equipment cost may increase.

The amount of the alkaline agent added is preferably in the range of 1.0 to 2.0 times, preferably 1.0 to 1.2 times the molar concentration of the hardness component in the water to be treated. Is more preferable. If the amount of the alkaline agent added is less than 1.0 times the molar concentration of the hardness component in the water to be treated, the insolubilization reaction of the hardness component may be insufficient, and if it exceeds 2.0 times the amount. , Chemical costs may be high.

Subsequent agglomeration treatment step and solid-liquid separation step are the same as the above pretreatment step (silica removal with magnesium salt). The pretreated water obtained by solid-liquid separation is sent to the reverse osmosis membrane treatment device 12.

[Pretreatment process: Removal of hardness components by resin softening method]
In the pretreatment step by the resin softening method when the water to be treated contains a hardness component, for example, the water to be treated is passed through an ion exchange tower filled with an ion exchange resin, and the hardness component is adsorbed and removed (ion exchange). Process). The pretreated water obtained by the ion exchange treatment is sent to the reverse osmosis membrane treatment device 12.

The ion exchange resin used in the ion exchange step is a cation exchange resin, and examples thereof include Amberlex 100Na and IRC-76 (manufactured by Organo Corporation).

When it becomes necessary to regenerate the ion exchange resin, the ion exchange resin is regenerated by passing a regenerating agent through the liquid.

Examples of the regenerating agent used include acid aqueous solutions such as hydrochloric acid, sulfuric acid and nitric acid, sodium chloride aqueous solutions, potassium chloride aqueous solutions and the like, and one or more of these can be used. That is, it is also possible to regenerate with an aqueous acid solution and then additionally regenerate with an aqueous sodium chloride solution, if necessary. From the viewpoint of reusing the attractant solution, an acid aqueous solution and a sodium chloride aqueous solution are preferable. When regenerated with an aqueous acid solution, the ion exchange resin becomes H-type, and when regenerated with an aqueous sodium chloride solution, the ion exchange resin becomes Na-type.

[First concentration treatment step]
The first concentration treatment means may be any one capable of concentrating the pretreated water, and is not particularly limited, but in addition to the reverse osmosis membrane treatment device, a membrane filtration device using a nanofiltration membrane or the like, and a distillation device. , One or more of electrodialysis devices and the like can be used. That is, if necessary, the concentrated water obtained by the reverse osmosis membrane treatment apparatus may be further concentrated by the electrodialysis treatment, or the concentrated water obtained by the first reverse osmosis treatment may be further concentrated by the second reverse osmosis treatment. It may be further concentrated. A reverse osmosis membrane treatment apparatus is preferable because it can be efficiently treated when the TDS in the pretreatment water is low.

Reverse osmosis membranes used in reverse osmosis membrane treatment equipment include ultra-low pressure reverse osmosis membranes and low pressure reverse osmosis membranes used for pure water production and wastewater recovery, as well as for seawater desalination. Examples thereof include medium-pressure reverse osmosis membranes and high-pressure reverse osmosis membranes used. Examples of the ultra-low pressure reverse osmosis membrane and the low pressure reverse osmosis membrane include ES15 (manufactured by Nitto Denko), TM720D (manufactured by Toray), BW30HRLE (manufactured by Dow Chemical), and LFC3-LD (manufactured by Hydranatics). Examples of the high-pressure reverse osmosis membrane include SWC5-LD (manufactured by Hydranatics), TM820V (manufactured by Toray), and XUS180808 (manufactured by Dow Chemical).

In the first concentration treatment step, chemicals such as a pH adjuster, a scale dispersant that suppresses scaling of inorganic salts in the system, and a fungicide that suppresses the generation of microorganisms in the system may be added.

[Forward osmosis membrane treatment process]
The shape of the forward osmosis membrane used in the forward osmosis membrane treatment step is not particularly limited, and for example, a hollow fiber membrane, a spiral membrane, a tubular membrane, a membrane having a plate-and-frame structure, or the like can be used. Examples of the membrane material of the forward osmosis membrane include aromatic polyamide type and cellulose acetate type. It is also possible to use a membrane in which a functional protein, an inorganic material, or the like is incorporated into the base material of the separation membrane to impart separation performance, water permeability, and the like. Examples of the forward osmotic membrane include HP5230 (manufactured by Toyobo), HFFO2 (manufactured by Aquaporin), and OsmoF2O (manufactured by Fruid Technology Solutions). These forward osmosis membranes may be used in a single stage or may be used by connecting a plurality of stages in series. That is, the FO concentrated water obtained by the first forward osmosis membrane treatment may be further concentrated by the second forward osmosis membrane treatment.

As described above, examples of the attracting solution used in the forward osmosis membrane treatment step include a magnesium salt aqueous solution, an alkaline agent aqueous solution, an acid aqueous solution, and a sodium chloride aqueous solution. In addition to the above, any chemical used in this water treatment device can be used without limitation. That is, it is also possible to use various coagulants used in the coagulation treatment step, a scale dispersant, a bactericidal agent, etc. used in the concentration treatment step as the attracting solution.

When performing a plurality of stages of forward osmosis membrane treatment in the forward osmosis membrane treatment step, the above-mentioned attractant solutions may be used in combination. For example, an aqueous sodium chloride solution is used as the attractant solution for the first forward osmosis membrane treatment step, and an aqueous magnesium salt solution is used as the attractant solution for the second forward osmosis membrane treatment step. Further, for example, the dilute sodium chloride solution obtained in the first forward osmosis membrane treatment step is used as a regenerating solution for the softened resin, and the dilute magnesium salt solution obtained in the second forward osmosis membrane treatment step is soluble silica. It can be used as a magnesium source in the removal process.

[Second concentration treatment step]
The second concentration treatment means may be any as long as it can concentrate the dilute attractant solution used in the forward osmosis membrane treatment step, and is not particularly limited, but a nanofiltration membrane treatment apparatus, a reverse osmosis membrane treatment apparatus, and the like. One or more of a concentrator using a semipermeable membrane such as a forward osmosis membrane treatment device and a pressure assisted reverse osmosis membrane treatment device, a membrane filtration device using a nanofiltration membrane, a distillation device, an electrodialysis device, and the like can be used. .. From the viewpoint of reducing the concentration cost and the like, a concentrator using a semipermeable membrane is preferable, and a pressure-assisted reverse osmosis membrane treatment device capable of reducing the influence of osmotic pressure when the TDS concentration of the water to be treated exceeds 5% is more preferable.

FIG. 2 shows an example of a concentrating device in the water treatment device according to the present embodiment.

The concentrator 160 shown in FIG. 2 is an example of a pressure-assisted reverse osmosis membrane treatment device. The concentrator 160 includes two or more concentrating means for concentrating the water to be treated using a semipermeable membrane, supplies the diluted attractant solution to the primary side of the semipermeable membrane in the first stage, and dilutes the liquid to the secondary side. Is supplied, a concentrated solution is obtained from the other flow path on the primary side, a diluted solution is obtained from the other flow path on the secondary side, and the diluted solution is supplied to the primary side of the semipermeable membrane of the next stage. This is a device that pressurizes the primary side of the semipermeable membrane of each stage to allow the water contained in the primary side to permeate through the secondary side to sequentially obtain a concentrated solution and a diluted solution.

The concentrator 160 includes, for example, a first-stage semipermeable membrane processing device 40, a second-stage semipermeable membrane processing device 42, and a third-stage semipermeable membrane processing device 44. Each semipermeable membrane processing apparatus has a primary side (first space) 46 and a secondary side (second space) 48 partitioned by the semipermeable membrane 50.

In the concentrating device 160 shown in FIG. 2, a pipe 52 is connected to the inlet of the primary side 46 of the first stage semipermeable membrane processing device 40 via a pump 67, and a pipe 54 is connected to the outlet of the primary side 46. There is. The outlet of the primary side 46 of the second-stage semipermeable membrane processing device 42 and the inlet of the secondary side 48 of the first-stage semipermeable membrane processing device 40 are connected by a pipe 56, and the first-stage semipermeable membrane processing device 40 The outlet of the secondary side 48 and the inlet of the primary side 46 of the second stage semipermeable membrane processing device 42 are connected by a pipe 58 via a pump 68. The outlet of the primary side 46 of the third-stage semipermeable membrane processing device 44 and the inlet of the secondary side 48 of the second-stage semipermeable membrane processing device 42 are connected by a pipe 60, and the second-stage semipermeable membrane processing device 42 The outlet of the secondary side 48 and the inlet of the primary side 46 of the third stage semipermeable membrane processing device 44 are connected by a pipe 62 via a pump 70. A pipe 64 is connected to the inlet of the secondary side 48 of the third-stage semipermeable membrane processing device 44, and a pipe 66 is connected to the outlet of the secondary side 48.

The concentrating device 160 is a device using a multi-stage semipermeable membrane processing device having a primary side 46 and a secondary side 48 partitioned by a semipermeable membrane 50. _{A dilute attracting solution (for example, MgCl 2} : 8% by mass) used in the forward osmosis membrane treatment device 14 which is the water to be treated is passed through a pipe 52 through a pump 67 through the primary side 46 of the first stage semipermeable membrane treatment device 40. some were passed through, the second concentrate obtained in the second stage semipermeable membrane treatment apparatus 42 to be described later through the pipe 56 to the secondary side 48 (e.g., MgCl _2: 10 wt%) was passed through the primary the water side 46 is included in the primary side 46 is pressurized is transmitted to the secondary side 48, the first concentrate (e.g., MgCl _2: 30 wt%) and a first diluent (e.g., MgCl _2: 5 Mass%) is obtained (concentration step (first stage)). The first concentrated solution (concentrated attracting solution) is discharged through the pipe 54 and is used again as the attracting solution in the forward osmosis membrane treatment device 14.

The first diluent is passed through the pipe 58 to the primary side 46 of the second stage semipermeable membrane treatment device 42 by the pump 68, and is passed through the pipe 60 to the secondary side 48 in the third stage semipermeable membrane treatment device 44 described later. The obtained third concentrate (for example, MgCl ₂ : 3% by mass) is passed through the water, the primary side 46 is pressurized, and the water contained in the primary side 46 is permeated through the secondary side 48 to concentrate the second. A liquid (for example, MgCl ₂ : 10% by mass) and a second diluted liquid (for example, MgCl ₂ : 1% by mass) are obtained (concentration step (second stage)). The second concentrated liquid is passed through the pipe 56 to the secondary side 48 of the first-stage semipermeable membrane processing device 40.

The second diluent is passed through the pipe 62 to the primary side 46 of the third stage semipermeable membrane processing device 44 by the pump 70, and passed through the pipe 64 to the secondary side 48 to be a dilute liquid (for example, MgCl ₂ : 1% by mass). Water is passed through, the primary side 46 is pressurized, and the water contained in the primary side 46 is permeated through the secondary side 48, so that the third concentrated solution (for example, MgCl ₂ : 3% by mass) and the third diluted solution (for example, MgCl 2: 3% by mass) are passed. For example, MgCl ₂ : <1% by mass) is obtained (concentration step (third stage)). The third concentrated liquid is passed through the pipe 60 to the secondary side 48 of the second stage semipermeable membrane processing device 42. The third diluent is discharged through the pipe 66. A part of the second concentrated solution and the third concentrated solution may be used again as an attracting solution in the forward osmosis membrane treatment apparatus 14. The third diluent may be recovered and reused after undergoing ultrafiltration membrane (UF membrane) treatment, reverse osmosis membrane (RO membrane) treatment, ion exchange treatment, etc., if necessary.

This pressure-assisted reverse osmosis membrane treatment device can reduce the osmotic pressure difference between the primary side 46 and the secondary side 48, and can be operated with less energy than a normal reverse osmosis membrane treatment device, and at a lower cost. Can drive.

As described above, the concentrated attractant solution obtained from the dilute attractant solution is used again as the attractant solution in the forward osmosis membrane treatment apparatus 14.

In the concentrating device 160 shown in FIG. 2, the liquid passing through the secondary side 48 of the first-stage semipermeable membrane processing device 40 and the second-stage and subsequent semipermeable membrane processing devices is subjected to the first-stage semipermeable membrane treatment. It may be a liquid having a component different from the dilute attracting solution that allows water to pass through the primary side 46 of the device 40. FIG. 3 shows an example of such a concentrator.

The concentrator 161 shown in FIG. 3 is an apparatus having the same configuration as the concentrator 160 shown in FIG. _{A dilute attracting solution (for example, MgCl 2} : 8% by mass) used in the forward osmosis membrane treatment apparatus 14 which is water to be treated is passed through a pipe 52 through a pump 67 through the primary side 46 of the first stage semipermeable membrane treatment apparatus 40. A part of water is passed through the secondary side 48, and the second concentrated solution (for example, glucose: 20% by mass) obtained by the second-stage semipermeable membrane processing device 42 described later is passed through the secondary side 48, and the primary side is passed. The 46 is pressurized and the water contained in the primary side 46 is permeated through the secondary side 48, so that the first concentrated solution (for example, MgCl ₂ :30% by mass) and the first diluted solution (for example, glucose: 10% by mass) are permeated. ) (Concentration step (first stage)). The first concentrated solution (concentrated attracting solution) is discharged through the pipe 54 and is used again as the attracting solution in the forward osmosis membrane treatment device 14.

The first diluent is passed through the pipe 58 to the primary side 46 of the second stage semipermeable membrane treatment device 42 by the pump 68, and is passed through the pipe 60 to the secondary side 48 in the third stage semipermeable membrane treatment device 44 described later. The obtained third concentrated solution (for example, NaCl: 3% by mass) is passed through the water, the primary side 46 is pressurized, and the water contained in the primary side 46 is permeated through the secondary side 48, and the second concentrated solution is used. (For example, glucose: 20% by mass) and a second diluent (for example, NaCl: 1% by mass) are obtained (concentration step (second stage)). The second concentrated liquid is passed through the pipe 56 to the secondary side 48 of the first-stage semipermeable membrane processing device 40.

The second diluent is passed through the pipe 62 to the primary side 46 of the third stage semipermeable membrane processing device 44 by the pump 70, and the dilute liquid (for example, NaCl: 1% by mass) is passed through the pipe 64 to the secondary side 48. Water is passed, the primary side 46 is pressurized, and the water contained in the primary side 46 is permeated through the secondary side 48, and a third concentrated solution (for example, NaCl: 3% by mass) and a third diluted solution (for example, for example) are passed. NaCl: <1% by mass) is obtained (concentration step (third stage)). The third concentrated liquid is passed through the pipe 60 to the secondary side 48 of the second stage semipermeable membrane processing device 42. The third diluent is discharged through the pipe 66. The third diluent may be recovered and reused after undergoing ultrafiltration membrane (UF membrane) treatment, reverse osmosis membrane (RO membrane) treatment, ion exchange treatment, etc., if necessary.

The liquid that passes through the secondary side 48 of the first-stage semipermeable membrane treatment device 40 and the second-stage and subsequent semipermeable membrane treatment devices may be a liquid having an osmotic pressure, and is not particularly limited. .. Examples thereof include an aqueous solution containing an inorganic salt such as sodium chloride, an aqueous solution containing an organic substance such as glucose, an aqueous solution containing a polymer, and an ionic liquid. From the viewpoint of reducing the influence of component diffusion from the primary side to the secondary side, use a solution having the same component as the dilute attracting solution that allows water to pass through the primary side 46 of the first-stage semipermeable membrane processing device 40. Is preferable.

FIG. 4 shows another example of the concentrating device 16 in the water treatment device 1 according to the present embodiment.

The concentrator 162 shown in FIG. 4 is an example of a pressure-assisted reverse osmosis membrane treatment device. The concentrator 162 is provided with one or more concentrating means for concentrating the water to be treated using a semipermeable membrane and further concentrating the concentrated solution using the semipermeable membrane, and is provided on the primary side of the semipermeable membrane in the first stage. The dilute attractant solution is supplied, and the concentrated solution is sequentially supplied to the primary side of the semipermeable membrane of each stage, and a part or any of the dilute attractant solutions is supplied to the secondary side of the semipermeable membrane of each stage. It is a device that supplies a part of the concentrated solution, pressurizes the primary side of the semipermeable membrane of each stage, and allows the water contained in the primary side to permeate to the secondary side.

The concentrator 162 includes, for example, a first-stage semipermeable membrane processing device 78, a second-stage semipermeable membrane processing device 80, and a third-stage semipermeable membrane processing device 82. Each semipermeable membrane processing apparatus has a primary side (first space) 84 and a secondary side (second space) 86 partitioned by the semipermeable membrane 88.

In the concentrating device 162 shown in FIG. 4, a pipe 90 is connected to the inlet of the primary side 84 of the first-stage semipermeable membrane processing device 78 via a pump 106. The outlet of the primary side 84 of the first-stage semipermeable membrane processing device 78 and the inlet of the primary side 84 of the second-stage semipermeable membrane processing device 80 are connected by a pipe 92. The outlet of the primary side 84 of the second-stage semipermeable membrane processing device 80 and the inlet of the primary side 84 of the third-stage semipermeable membrane processing device 82 are connected by a pipe 94. A pipe 96 is connected to the outlet of the primary side 84 of the third-stage semipermeable membrane processing device 82. The pipe 98 branched from the pipe 96 is connected to the inlet of the secondary side 86 of the third stage semipermeable membrane processing device 82. The outlet of the secondary side 86 of the third-stage semipermeable membrane processing device 82 and the inlet of the secondary side 86 of the second-stage semipermeable membrane processing device 80 are connected by a pipe 100. The outlet of the secondary side 86 of the second-stage semipermeable membrane processing device 80 and the inlet of the secondary side 86 of the first-stage semipermeable membrane processing device 78 are connected by a pipe 102. A pipe 104 is connected to the outlet of the secondary side 86 of the first-stage semipermeable membrane processing device 78. If necessary, pipes 92, 94, 96, 98, 100, 102 are provided with a pressure adjusting mechanism such as a valve and treated water for adjusting the pressure applied to the pressurizing and liquid feeding pumps and the semipermeable membrane. A tank or the like for temporary storage may be provided.

In concentrator 162, dilute attraction solution used in the forward osmosis membrane treatment apparatus 14 is a treated water (e.g., MgCl _2: 10 wt%) part of, through the pipe 90 by the pump 106, the first stage semipermeable The liquid is sent to the primary side 84 of the membrane processing device 78. On the other hand, the diluent (secondary treated water) (for example, the secondary treated water) returned from the third-stage semipermeable membrane treatment device 82 in the final stage to be described later via the secondary side 86 of the second-stage semipermeable membrane treatment device 80. MgCl ₂ : 6% by mass) is sent to the secondary side 86 of the first-stage semipermeable membrane processing device 78 through the pipe 102. In the first-stage semipermeable membrane processing apparatus 78, the primary side 84 of the semipermeable membrane is pressurized and the water contained in the primary side 84 is permeated through the secondary side 86 (concentration step (first stage)).

The concentrated liquid (primary side treated water) (for example, MgCl ₂ : 18% by mass) of the first-stage semipermeable membrane treatment device 78 is sent to the primary side 84 of the second-stage semipermeable membrane treatment device 80 through the pipe 92. Will be done. _{On the other hand, the diluent (secondary side treated water) (for example, MgCl 2} : 15% by mass) returned from the third-stage semipermeable membrane treatment device 82 in the final stage, which will be described later, passes through the pipe 100 and the second-stage semipermeable membrane. The liquid is sent to the secondary side 86 of the processing device 80. In the same manner as in the first stage, in the second stage semipermeable membrane processing apparatus 80, the primary side 84 of the semipermeable membrane is pressurized and the water contained in the primary side 84 is permeated through the secondary side 86 (concentration). Process (second stage)).

The concentrated liquid (primary side treated water) (for example, MgCl ₂ : 23% by mass) of the second stage semipermeable membrane treatment device 80 is sent to the primary side 84 of the third stage semipermeable membrane treatment device 82 through the pipe 94. Will be done. _{On the other hand, the concentrated liquid (for example, MgCl 2} : 30% by mass) returned from the third-stage semipermeable membrane processing device 82 in the final stage, which will be described later, passes through the pipe 98 to the secondary of the third-stage semipermeable membrane processing device 82. The liquid is sent to the side 86. In the same manner as in the first and second stages, in the third stage semipermeable membrane processing device 82, the primary side 84 of the semipermeable membrane is pressurized and the water contained in the primary side 84 is permeated through the secondary side 86. (Concentration step (third stage)).

A part of the concentrated solution (primary treated water) (for example, MgCl ₂ : 30% by mass) of the third-stage semipermeable membrane treatment device 82 in the final stage is discharged through the pipe 96 and attracted by the forward osmosis membrane treatment device 14. Used again as a solution. The remaining part of the concentrated liquid of the third-stage semipermeable membrane processing device 82 is sent to the secondary side 86 of the third-stage semipermeable membrane processing device 82 through the pipes 96 and 98. As described above, in the third-stage semipermeable membrane processing apparatus 82, the primary side 84 of the semipermeable membrane is pressurized and the water contained in the primary side 84 is permeated through the secondary side 86 (concentration step (three stages (three stages)). Eye)).

The diluted solution (secondary side treated water) (for example, MgCl ₂ : 15% by mass) of the third stage semipermeable membrane treatment device 82 is passed through the pipe 100 to the secondary side 86 of the second stage semipermeable membrane treatment device 80. The liquid is sent. As described above, in the second-stage semipermeable membrane processing apparatus 80, the primary side 84 of the semipermeable membrane is pressurized and the water contained in the primary side 84 is permeated through the secondary side 86 (concentration step (second stage). Eye)).

The diluted solution (secondary side treated water) (for example, MgCl ₂ : 6% by mass) of the second stage semipermeable membrane treatment device 80 is passed through the pipe 102 to the secondary side 86 of the first stage semipermeable membrane treatment device 78. The liquid is sent. As described above, in the first-stage semipermeable membrane processing apparatus 78, the primary side 84 of the semipermeable membrane is pressurized and the water contained in the primary side 84 is permeated through the secondary side 86 (concentration step (1st stage). Eye)). The diluent (secondary treated water) of the first-stage semipermeable membrane treatment device 78 (for example, MgCl ₂ : <1% by mass) is discharged through the pipe 104. The diluted solution may be recovered and reused after undergoing ultrafiltration membrane (UF membrane) treatment, reverse osmosis membrane (RO membrane) treatment, ion exchange treatment and the like, if necessary.

Since a pressure-assisted reverse osmosis membrane treatment device such as this concentrator 162 uses a part of the water to be treated as a diluent for osmotic pressure assistance, it is not necessary to prepare a separate diluent, and the device configuration is also as follows. It can be simplified from a pressure-assisted reverse osmosis membrane treatment device such as the concentrator 160.

As described above, the concentrated attractant solution obtained from the dilute attractant solution is used again as the attractant solution in the forward osmosis membrane treatment apparatus 14.

In a pressure-assisted reverse osmosis membrane treatment device such as the concentrator 162, a concentrated solution of a part or any of the dilute attractant solutions used in the forward osmosis membrane treatment device 14 is placed on the secondary side of the semipermeable membrane of each stage. It suffices to supply a part of the above, and there is no particular limitation on the method.

For example, as shown as the concentrator 164 in FIG. 5, the dilute attractant solution used in the forward osmosis membrane treatment device 14 which is the water to be treated is distributed, and the primary side 84 of the first stage semipermeable membrane treatment device 78, The concentrated solution and the permeated solution are supplied to the secondary side 86, respectively, and the concentrated solution and the permeated solution are sequentially supplied to the primary side 84 and the secondary side 86 of the semipermeable membrane of each stage, and the primary side of the semipermeable membrane of each stage is pressurized. The water contained in the primary side may be permeated to the secondary side.

As shown as the concentrator 166 in FIG. 6, the dilute attractant solution used in the forward osmosis membrane treatment device 14 which is the water to be treated is supplied to the primary side 84 of the first stage semipermeable membrane treatment device 78, and the concentrate solution thereof. Is sequentially supplied to the primary side of the semipermeable membrane of each stage, and a part of the concentrated solution of the third-stage semipermeable membrane processing device 82 of the final stage is supplied to the secondary side 86 of the first-stage semipermeable membrane processing device 78. Then, even if the permeate is sequentially supplied to the secondary side of the semipermeable membrane of each stage and the primary side of the semipermeable membrane of each stage is pressurized to allow the water contained in the primary side to permeate to the secondary side. Good.

As shown as the concentrator 168 in FIG. 7, the dilute attractant solution used in the forward osmosis membrane treatment device 14 which is the water to be treated is supplied to the primary side 84 of the first-stage semipermeable membrane treatment device 78, and the concentrate solution thereof. Is sequentially supplied to the primary side of the semipermeable membrane of each stage, and a part of the concentrated solution of the semipermeable membrane processing device of each stage is supplied to the secondary side 86 of the semipermeable membrane processing device itself. The primary side of the permeable membrane may be pressurized to allow the water contained in the primary side to permeate to the secondary side.

In the above-mentioned concentrators 160, 161, 162, 164, 166, 168, the number of stages of the semipermeable membrane treatment device may be determined according to the concentration of the target treated water and the like. For example, in the concentrators 162, 164, 166, 168, when it is desired to obtain a concentrated treated water (concentrated attracting solution) from a dilute attracting solution having a lower concentration, the number of stages of the semipermeable membrane treating device may be increased. ..

In the concentrating device 160, 161, 162, 164, 166, 168, a membrane module unit including two or more membrane modules connected in parallel may be used as the semipermeable membrane processing device of each stage. The number of membrane modules in each membrane module unit may be determined by the flow rate of the dilute attractant solution to be treated or the like.

Examples of the semipermeable membrane included in the semipermeable membrane processing apparatus include a semipermeable membrane such as a reverse osmosis membrane (RO membrane), a forward osmosis membrane (FO membrane), and a nanofiltration membrane (NF membrane). The semipermeable membrane is preferably a reverse osmosis membrane, a forward osmosis membrane, or a nanofiltration membrane. When a reverse osmosis membrane, a forward osmosis membrane, or a nanofiltration membrane is used as the semipermeable membrane, the pressure of the target solution on the primary side is preferably 0.5 to 10.0 MPa.

The material constituting the semipermeable membrane is not particularly limited, and examples thereof include cellulose-based resins such as cellulose acetate-based resins, polysulfone-based resins such as polyethersulfone-based resins, and polyamide-based resins. The material constituting the semipermeable membrane is preferably a cellulose acetate resin.

The shape of the semipermeable membrane is not particularly limited as long as it has a structure in which a solution can be supplied to the primary side and the secondary side of the membrane, and examples thereof include a spiral type, a hollow fiber membrane, and a plate and frame type.

[Other examples of water treatment equipment]
In the water treatment apparatus according to the embodiment of the present invention, an attractant solution preparation tank is further provided as a preparation means for preparing a magnesium salt aqueous solution to be used as an attractant solution by mixing magnesium hydroxide and an acid and reacting them at pH 7 or less. You may. In the attractant solution preparation tank, magnesium hydroxide and acid are mixed and reacted at pH 7 or less to prepare a magnesium salt aqueous solution (preparation step), and the prepared magnesium salt aqueous solution is used as a forward osmosis membrane of the forward osmosis membrane treatment apparatus 14. The solution may be sent to the secondary side of the above and used as an attracting solution.

Examples of the acid used in the preparation step include hydrochloric acid, sulfuric acid, nitric acid and the like, and hydrochloric acid or nitric acid is preferable from the viewpoint of suppressing the production of poorly soluble substances.

The pH in the preparation step may be 7 or less and is not particularly limited, but is, for example, in the range of pH 1 to 7, preferably in the range of 2 to 5. If the pH in the preparation step exceeds 7, the magnesium salt may be insufficiently dissolved, and if it is less than 1, the amount of acid added may be excessive.

The temperature in the preparation step may be any temperature as long as the dissolution reaction of the magnesium salt proceeds, and is not particularly limited, but is, for example, in the range of 1 ° C. to 80 ° C. If the temperature in the preparation step is less than 1 ° C., the dissolution reaction of the magnesium salt may be insufficient, and if it exceeds 80 ° C., the heat resistance of the equipment may become a problem.

The reaction time in the preparation step is not particularly limited as long as the dissolution reaction of the magnesium salt can proceed, and is, for example, in the range of 5 minutes to 120 minutes. If the reaction time in the preparation step is less than 5 minutes, the dissolution reaction of the magnesium salt may be insufficient, and if it exceeds 120 minutes, the equipment may become a problem.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples.

<Example 1>
Industrial water containing 100 ppm of TDS and 15 ppm of soluble silica was concentrated using the water treatment apparatus shown in FIG. It was concentrated to 8% TDS by a reverse osmosis membrane treatment device. This concentrated water was supplied to a forward osmosis membrane treatment apparatus (forward osmosis membrane: HP5230 (manufactured by Toyobo)), and a 30 wt% magnesium chloride solution was further supplied as an attractant solution to obtain FO concentrated water having a TDS of 20%. A part of the dilute magnesium chloride solution diluted by the forward osmosis membrane treatment is added as it is to the soluble silica removing device, and the rest is concentrated to 30% magnesium chloride using the concentrator having the configuration shown in FIG. It was reused as an attractant solution for the membrane treatment device. The energy cost used for the forward osmosis membrane treatment was calculated. The results are shown in Table 1.

<Comparative example 1>
In the water treatment apparatus used in Example 1, a concentration operation using an evaporator instead of the forward osmosis membrane treatment apparatus was carried out to obtain concentrated water having a TDS of 20%. The energy cost used for the evaporator was calculated and compared with Example 1. The results are shown in Table 1.

<Comparative example 2>
In the water treatment apparatus used in Example 1, a 30 wt% ammonium carbonate solution was used as an attractant solution for the forward osmosis membrane treatment apparatus, and concentrated water having a TDS of 20% was also obtained. The dilute ammonium carbonate solution diluted by the forward osmosis membrane treatment was sent to a regeneration device and regenerated by heat (regeneration step). The energy cost used for the forward osmosis membrane treatment was calculated (including the energy used in the regeneration process). The results are shown in Table 1.

As described above, the treatment method of Example 1 can be concentrated at a lower energy cost than the treatment methods of Comparative Examples 1 and 2, and the water to be treated containing at least one of the soluble silica and the hardness component. Was found to be able to be processed at low cost.

1,3 Water treatment equipment, 10,200 Pretreatment equipment, 12 Reverse osmosis membrane treatment equipment, 14,202 Normal osmosis membrane treatment equipment, 16,160,161,162,164,166,168 Concentrator, 18 Water to be treated Piping, 20 pre-treated water piping, 22 concentrated water piping, 24 permeable water piping, 26 attracting solution piping, 28, 32 dilute attracting solution piping, 30 FO concentrated water piping, 34 concentrated attracting solution piping, 36 diluted solution piping, 40, 78 1st stage semipermeable membrane treatment device, 42,80 2nd stage semipermeable membrane treatment device, 44,82 3rd stage semipermeable membrane treatment device, 46,84 primary side, 48,86 secondary side, 50,88 Semipermeable membrane, 52,54,56,58,60,62,64,66,90,92,94,96,98,100,102,104 piping, 67,68,70,106 pump, 204 attractant solution tank , 206 Heating device.

Claims (10)

A water treatment apparatus that treats water to be treated containing at least one of soluble silica and a hardness component.
A pretreatment means including any one of a soluble silica removing means and a hardness component removing means, and a pretreatment means.
The first concentration treatment means for concentrating the pretreatment water obtained by the pretreatment means, and
A forward osmosis membrane treatment means for treating the concentrated water obtained by the first concentration treatment means with a forward osmosis membrane, and a forward osmosis membrane treatment means.
A second concentration treatment means for concentrating a part of the dilute attractant solution used in the forward osmosis membrane treatment means, and a second concentration treatment means.
With
A part of the dilute attractant solution used in the forward osmosis membrane treatment means is used in the pretreatment means, and the concentrated attractant solution concentrated by the second concentration means is reused as an attractant solution in the forward osmosis membrane treatment means. A water treatment device characterized by being osmotic. The water treatment apparatus according to claim 1.
The water treatment apparatus, wherein the second concentration treatment means is a concentration treatment means using a semipermeable membrane. The water treatment apparatus according to claim 1 or 2.
The water treatment apparatus, wherein the first concentration treatment means is a reverse osmosis membrane treatment means. The water treatment apparatus according to any one of claims 1 to 3.
A water treatment characterized in that the attractant solution used in the forward osmosis membrane treatment means is a magnesium salt aqueous solution, and the magnesium salt dilute aqueous solution used in the forward osmosis membrane treatment means is used in the soluble silica removing means. apparatus. The water treatment apparatus according to any one of claims 1 to 3.
A water treatment apparatus characterized in that the attractant solution used in the forward osmosis membrane treatment means is an alkaline agent aqueous solution, and the alkaline agent dilute aqueous solution used in the forward osmosis membrane treatment means is used in the hardness component removing means. .. The water treatment apparatus according to any one of claims 1 to 3.
The attractant solution used in the forward osmosis membrane treatment means is an acid aqueous solution or a sodium chloride aqueous solution, and the acid dilute aqueous solution or the sodium chloride dilute aqueous solution used in the forward osmosis membrane treatment means is used in the hardness component removing means. A water treatment device characterized by. A water treatment method for treating water to be treated containing at least one of soluble silica and a hardness component.
A pretreatment step including any one of a soluble silica removing step and a hardness component removing step, and a pretreatment step.
The first concentration treatment step of concentrating the pretreatment water obtained in the pretreatment step, and
A forward osmosis membrane treatment step of treating the concentrated water obtained in the first concentration treatment step with a forward osmosis membrane, and a forward osmosis membrane treatment step.
A second concentration treatment step of concentrating a part of the dilute attractant solution used in the forward osmosis membrane treatment step, and a second concentration treatment step.
Including
A part of the dilute attractant solution used in the forward osmosis membrane treatment step is used in the pretreatment step, and the concentrated attractant solution concentrated in the second concentration treatment step is reused as an attractant solution in the forward osmosis membrane treatment step. A water treatment method characterized by that. The water treatment method according to claim 7.
The water treatment method, wherein the second concentration treatment step is a concentration treatment step using a semipermeable membrane. The water treatment method according to claim 7 or 8.
The water treatment method, wherein the first concentration treatment step is a reverse osmosis membrane treatment step. The water treatment method according to any one of claims 7 to 9.
A water treatment method characterized in that the attractant solution used in the forward osmosis membrane treatment step is a magnesium salt aqueous solution, and the magnesium salt dilute aqueous solution used in the forward osmosis membrane treatment step is used in the soluble silica removal step.

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