JP2007209919A - Salt recovery method and salt recovery apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a salt recovery method which enables the efficient recovery of the salt from water to be treated, for example, water containing organic matter and various metal salts or the like, more concretely, wastewater such as bled water or the like flowing out of a final disposal plant of waste by simple and compact equipment and the recovery of the salt suitable in reutilization, and a salt recovery apparatus. <P>SOLUTION: Water to be treated containing the salt is subjected to a reverse osmosis membrane device to obtain concentrated water which is, in turn, brought into contact with activated carbon to recover the salt. The recovery apparatus of the salt from the water to be treated containing the salt has the reverse osmosis membrane device for concentrating the salt in the water to be treated containing the salt by a reverse osmosis membrane and an activated carbon contact device for bringing the concentrated water obtained by the reverse osmosis membrane device into contact with activated carbon. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a salt recovery method and a salt recovery apparatus. More specifically, the present invention relates to a method for recovering salt contained in waste water such as water containing organic matter, various metal salts, etc., for example, leachate flowing out from a final disposal site for waste, and a recovery device for the salt. .

  Currently, the waste is incinerated and processed by landfilling the incinerated product in a final disposal site.

  Furthermore, in such a final disposal site, leachate containing various salts leached from landfilled waste is desalted and treated by electrodialysis, reverse osmosis membrane, etc. (Patent Document 1). . Especially, according to the desalting using the reverse osmosis membrane, leachate can be treated efficiently. That is, by using the reverse osmosis membrane, treated water (membrane permeated water) with extremely good water quality can be obtained.

  On the other hand, the by-product salt generated by the desalting may be reused as a road antifreeze, a storage salt in a leather tanning process, or the like. Further, when the by-product salt is reused, the required properties differ depending on its use.

Japanese Patent Laid-Open No. 11-262738

  However, when leachate is treated with a reverse osmosis membrane, permeated water with extremely good water quality can be obtained, but organic substances and various metals are concentrated in the concentrated water. Due to the fact that the by-produced salt is colored, the use of the by-produced salt may be limited. Therefore, in order to reduce organic substances, various metals, etc. in the concentrated water, pretreatment such as removal of organic substances by organisms and removal of metals by adsorbents, chemicals, etc. is performed before the reverse osmosis membrane treatment. However, as the entire facility becomes complicated and the amount of water to be treated in each pretreatment is not reduced, equipment of a scale corresponding to the amount of water to be treated is necessary, and the amount of pump power used, the amount of adsorbent, chemicals, etc. In addition, there is a drawback that the installation area of the entire equipment becomes larger.

  The present invention has been made in view of the above-mentioned conventional drawbacks, and is to be treated, for example, water containing organic matter, various metal salts, etc., more specifically, leaching outflow from the final disposal site of waste. One object of the present invention is to provide a salt recovery method capable of efficiently recovering salt from waste water such as water with simple and compact equipment and recovering salt suitable for reuse. Let it be an issue. Moreover, this invention makes it one subject to provide the salt collection | recovery apparatus which can collect | recover salt efficiently from the said to-be-processed water, and can collect | recover the salt suitable for reuse. .

The present invention has been made in view of the above-mentioned problems. In one aspect, the water to be treated containing salt is supplied to a reverse osmosis membrane device to obtain concentrated water, and then the concentrated water, activated carbon, It is related with the collection | recovery method of the salt characterized by making contact. In another aspect, the present invention provides a reverse osmosis membrane device for concentrating salt in water to be treated containing salt by a reverse osmosis membrane to obtain concentrated water,
The present invention relates to an apparatus for recovering salt from treated water containing salt, characterized by having an activated carbon contact device for bringing concentrated water obtained by the reverse osmosis membrane device into contact with activated carbon.

  According to the salt recovery method of the present invention, the reverse osmosis membrane is used to discharge water to be treated, for example, water containing organic matter, various metal salts, etc., more specifically, from the final disposal site for waste. Even when applied to effluents such as leachate, it is possible to obtain a salt suitable for reuse, for example, a salt that is not substantially colored (white salt) with simple and compact equipment. There is an excellent effect. In addition, according to the salt recovery apparatus of the present invention, wastewater such as water to be treated, for example, water containing organic substances, various metal salts, etc., more specifically leachate flowing out from the final disposal site for waste. Even from this, an excellent effect is obtained in that a salt suitable for reuse, for example, a salt that is not substantially colored (white salt) can be obtained.

  In one aspect, the present invention is characterized in that treated water containing salt is supplied to a reverse osmosis membrane device to obtain concentrated water, and then the concentrated water and activated carbon are contacted. It relates to a collection method.

  According to the salt recovery method of the present invention, since the concentrated water obtained by subjecting the water to be treated containing salt to the reverse osmosis membrane device and activated carbon are brought into contact with each other, a salt suitable for reuse, for example, A substantially uncolored salt, ie a white salt, can be obtained. Further, according to the salt recovery method of the present invention, since a reverse osmosis membrane device and activated carbon are used in recovering the salt, a salt suitable for reuse, for example, a salt that is not substantially colored [ A substantially white salt (referred to herein as a “white salt”) can be conveniently obtained in high yield.

  Examples of water to be treated containing salt include water containing various organic substances, metal salts, etc., more specifically, drainage such as leachate flowing out from the final landfill disposal site for waste, improper disposal site Examples of such wastewater include wastewater generated when cleaning the waste excavated from the wastewater, wastewater generated when dismantling the incinerator, chemical factory wastewater, seawater, and the like.

As a method for recovering the salt of the present invention, specifically,
(A) The salt-containing water to be treated is supplied to a reverse osmosis membrane device to obtain concentrated water (also referred to as “reverse osmosis membrane treatment step 1”), and (B) obtained in the step (A). The obtained concentrated water is subjected to an activated carbon contact device, and the concentrated water and activated carbon are contacted to obtain a salt as activated carbon treated water (also referred to as “activated carbon contact step 2”),
The method containing is mentioned.

  In the salt recovery method of the present invention, since the step (A) is performed, a part of the components involved in the coloration of the salt, for example, low molecular weight organic carbon is removed from the water to be treated containing the salt. And concentrated water is obtained. Therefore, according to the salt recovery method of the present invention, it is possible to reduce the amount of water to be treated (that is, concentrated water) and the amount of organic carbon to be removed in the activated carbon treatment step described later, Compared with the case where the activated carbon treatment is performed without concentrating, the equipment for performing the activated carbon treatment can be made compact, and further, the excellent effect of reducing the amount of used activated carbon discarded can be exhibited. In addition, according to the salt recovery method of the present invention, since the step (A) is performed, the concentrated water obtained is brought into contact with activated carbon in the step (B) after performing the step (A). Combined with this, it exhibits an excellent effect that the components involved in the coloration of the salt can be efficiently removed.

  The reverse osmosis membrane device preferably includes a device using a reverse osmosis membrane module in which a plurality of spacers are arranged and a flat membrane-like reverse osmosis membrane is interposed between the spacers. Examples include a reverse osmosis membrane module 4 in which a plurality of spacers 7 are arranged and a reverse osmosis membrane (flat membrane 6) is interposed between the spacers 7.

  The reverse osmosis membrane module 4 shown in FIG. 2 has a structure in which disk-type flat membranes and spacers with dimples are alternately laminated. Specifically, in the reverse osmosis membrane module 4, a disk-like flat membrane (reverse osmosis membrane) 6 is provided between the disk-like spacers 7 in a cylindrical reverse osmosis membrane module body 5. A plurality of reverse osmosis membrane portions 8 are laminated. A treated water channel 9 for introducing treated water is provided on the inner peripheral surface of the module body 5 of the reverse osmosis membrane module 4, and treated water is introduced from the treated water channel 9 to the surface of the reverse osmosis membrane. In addition, an end plate 10 is provided on the reverse osmosis membrane portion 8 so as to withstand a pressure higher than the osmotic pressure. In the reverse osmosis membrane module 4 shown in FIG. 2, the permeated water pipe 11 penetrates the central portion of the reverse osmosis membrane portion 8. The treated water separated by the reverse osmosis membrane is discharged by the permeate pipe 11. Further, the concentrated water concentrated by each reverse osmosis membrane is discharged out of the module body 5 by the concentrated water pipe 12. Such concentrated water may contain a salt to be collected.

  In the step (B), for example, the concentrated water obtained in the step (A) is brought into contact with the activated carbon. By performing such a step, surprisingly, a salt suitable for reuse, for example, a salt that is not substantially colored (white salt) can be obtained.

  The activated carbon used in the salt recovery method of the present invention is not particularly limited as long as it exhibits a high organic carbon adsorption capacity, and examples thereof include activated carbon using coal as a raw material.

  The amount of activated carbon brought into contact with the concentrated water obtained in the step (A) can be appropriately set according to the composition of the water to be treated, the type of activated carbon, the amount of concentrated water, the organic carbon removal rate necessary for whitening, and the like. .

  In the salt recovery method of the present invention, the contact between the water to be treated and the activated carbon can be efficiently performed by using, for example, the activated carbon contact device 13 shown in FIG.

  The activated carbon contact device 13 shown in FIG. 3 is configured such that the concentrated water to be treated is passed through two activated carbon packed columns 15 and 15 and the activated carbon treated water obtained after the treatment is discharged. The activated carbon packed column 15 may be used alone or in combination of two or more. The activated carbon packed column 15 is provided with a concentrated water flow channel for introducing concentrated water to be treated. When two or more activated carbon packed columns 15 are connected, a treated water flow path for introducing treated water after treatment by another activated carbon packed column 15 located upstream into the activated carbon packed column 15, and the activated carbon packed column 15 And an activated carbon treated water passage for discharging the activated carbon treated water from the activated carbon.

  The activated carbon packed column 15 is packed with the activated carbon.

After the step (B), a salt can be obtained as activated carbon-treated water, that is, a salt aqueous solution. Therefore, in the salt recovery method of the present invention, for example, as shown in FIG. 1, after performing the steps (A) and (B),
(C) a step of removing moisture from the activated carbon treated water obtained in the step (B), that is, a salt solution (also referred to as “drying step 3”);
By performing the above, a salt can be obtained as a dry salt.

  In the step (C), water is removed from the activated carbon-treated water to obtain a salt. In addition, when the amount of the activated carbon treated water is small, in this step (C), evaporation to dryness is performed by a conventional evaporator or the like.

  In addition, the salt obtained by the salt recovery method of the present invention can be evaluated for the presence or absence of coloring by observation with three monitors, for example. The salt recovered by the salt recovery method of the present invention is a substantially white salt, that is, a white salt.

  In the salt recovery method of the present invention, if necessary, agglomeration / removal treatment for agglomerating and removing fine particles and the like; chelation treatment for removing and chelating harmful heavy metals such as lead and arsenic, etc. Also good.

  In the agglomeration / removal treatment, an aggregating agent such as polyaluminum chloride or ferric chloride is added to the water to be treated before step (A) to agglomerate suspended substances and the like. The pH is adjusted and, for example, the solid (aggregate) is removed by using a membrane filter having a pore size of 0.1 to 10 μm, sand filtration or the like. By performing such treatment, suspended substances that cause clogging of the flow path of the reverse osmosis membrane and the activated carbon packed tower are removed, which is excellent in that the facility can be stably operated.

  The chelation treatment is performed by removing toxic metals such as lead and arsenic by bringing the water to be treated into contact with a chelate resin or the like, for example. By performing such treatment, harmful metals and the like are removed, and therefore, for example, when the recovered salt is used as a snow melting agent, the environment and the human body are not adversely affected. In addition, it is preferable to perform a chelation process with respect to the to-be-processed water after implementing step (A) from a viewpoint of compactization of a chelate processing apparatus, and the compactization of a chelate processing apparatus and the performance maintenance of a chelate resin are maintained. From a viewpoint, it is more preferable to perform with respect to the to-be-processed water after implementing step (B).

In another aspect, the present invention provides a reverse osmosis membrane device that concentrates a salt in water to be treated containing a salt via a reverse osmosis membrane to obtain concentrated water;
The present invention relates to an apparatus for recovering salt from treated water containing salt, characterized by having an activated carbon contact device for bringing concentrated water obtained by the reverse osmosis membrane device into contact with activated carbon.

  According to the salt recovery apparatus of the present invention, the salt recovery method of the present invention can be easily performed.

In one embodiment, the salt recovery apparatus of the present invention is a reverse osmosis membrane device for concentrating salt in water to be treated containing salt by a reverse osmosis membrane to obtain concentrated water;
An activated carbon contact device for contacting the concentrated water obtained by the reverse osmosis membrane device with activated carbon,
A reverse osmosis membrane device and an activated carbon contact device, the treated water is supplied to the reverse osmosis membrane device, and the salt in the treated water is concentrated through the reverse osmosis membrane to obtain concentrated water,
The present invention relates to an apparatus having a configuration in which the concentrated water is introduced into an activated carbon contact apparatus and arranged to come into contact with activated carbon. Therefore, according to such a salt recovery device, water to be treated, for example, water containing organic matter, various metal salts, etc., more specifically, from wastewater such as leachate flowing out from the final disposal site of waste. It exhibits an excellent effect that it is possible to obtain a salt that is efficient and suitable for reuse, for example, a salt that is not substantially colored (white salt).

  Further, according to the salt recovery apparatus of the present invention, the reverse osmosis membrane device and the activated carbon contact device supply the treated water to the reverse osmosis membrane device, and the salt in the treated water is concentrated by the reverse osmosis membrane. Thus, concentrated water is obtained, and the concentrated water is introduced into the activated carbon contact device and has a configuration in which the concentrated water is brought into contact with the activated carbon. Some of the components involved in salt coloring, such as low molecular weight organic carbon, are removed from the water, and concentrated water is obtained. Further, such concentrated water is introduced into the activated carbon contact device, and in the activated carbon contact device, the activated carbon contact device is contacted with activated carbon to further remove components involved in the coloration of the salt from the concentrated water. Therefore, according to the salt recovery apparatus of the present invention, in the activated carbon contact device, after the treated water comes into contact with the activated carbon, the obtained treated water is arranged to be concentrated in the reverse osmosis membrane device. Even when the amount of activated carbon disposed in the activated carbon contact device is equal to or less than that of the device having the same, a salt suitable for reuse can be obtained. Furthermore, according to the salt recovery apparatus, the amount of water to be treated (concentrated water amount in the activated carbon contact apparatus) to be brought into contact with activated carbon in the activated carbon contact apparatus is such that the treated water is brought into contact with the activated carbon in the activated carbon contact apparatus. In order to reduce the amount of water to be treated compared to a device having a configuration arranged to condense the treated water using a reverse osmosis membrane device, it is possible to reduce the size of equipment such as a pump and to recover salt. Energy can be reduced.

In another embodiment, the salt recovery apparatus of the present invention is a reverse osmosis membrane device for concentrating salt in water to be treated containing salt by a reverse osmosis membrane to obtain concentrated water;
In addition to the activated carbon contact device for contacting the concentrated water obtained by the reverse osmosis membrane device with activated carbon,
The present invention relates to an apparatus further comprising a moisture removing device for removing moisture from activated carbon treated water obtained after contact between concentrated water and activated carbon by the activated carbon contact device to obtain a dry salt. Since the salt recovery apparatus according to this embodiment includes the water removal apparatus, a salt in a dry state can be easily obtained.

  As the reverse osmosis membrane device in the salt recovery device of the present invention, preferably, a plurality of spacers are arranged, and a flat membrane-like reverse osmosis membrane is interposed between each spacer, and the reverse osmosis membrane contains a salt. Examples thereof include a reverse osmosis membrane device that concentrates the salt in the treated water to obtain concentrated water.

  The salt obtained by the salt recovery apparatus of the present invention is a substantially white salt, that is, a white salt.

An example of the embodiment of the salt recovery apparatus of the present invention is, for example, the salt recovery apparatus shown in FIG. The salt recovery device 19 shown in FIG. 4 includes a reverse osmosis membrane device 17 comprising a reverse osmosis membrane module 4 and a high-pressure pump 16 for supplying treated water to the reverse osmosis membrane module 4, and an activated carbon contact device 13. And
The reverse osmosis membrane device 17 and the activated carbon contact device 13 introduce water to be treated containing salt into the reverse osmosis membrane device 17 to concentrate the salt in the water to be treated, and then the obtained concentrated water is activated carbon. It is characterized by having a configuration that is introduced into the contact device 13 and arranged to come into contact with the activated carbon.

  The reverse osmosis membrane device 17 includes, for example, a reverse osmosis membrane module 4 and a high-pressure pump 16 for supplying water to be treated to the reverse osmosis membrane module 4. The water to be treated is reverse osmosis via the high-pressure pump 16. It has a configuration that is introduced into the membrane module 4 and arranged to be separated into permeated water and concentrated water.

  Examples of the activated carbon contact device 13 include the same ones as described above.

  The reverse osmosis membrane device 17 and the activated carbon contact device 13 are, for example, the concentrated water pipe 12 and the activated carbon contact device 13 for storing the concentrated water discharged from the concentrated water pipe 12 and the concentrated water pipe 12 of the reverse osmosis membrane module 4. The treated water containing salt is introduced into the reverse osmosis membrane module 4 of the reverse osmosis membrane device 17 and concentrated, and the obtained concentrated water is temporarily stored in the concentrated water storage tank 18. The concentrated water stored and then stored in the concentrated water storage tank 18 is introduced into the activated carbon contact device 13 and arranged so as to come into contact with the activated carbon.

  The salt recovery device 19 shown in FIG. 4 may further include a water removal device for removing moisture from the activated carbon treated water obtained by the activated carbon contact device 13 to obtain a dry salt. Examples of the moisture removing device include an evaporation drying device.

  EXAMPLES Hereinafter, although an Example etc. demonstrate this invention in detail, this invention is not limited to this Example.

(Test Example 1)
Table 1 shows the results of water quality analysis of treated water (raw water). In the table, “pH” is JIS K 0102 (1998) 12.1, “electrical conductivity” is JIS K 0102 (1998) 13, and “total evaporation residue” is JIS K 0102 (1998) 14. 2. “Chromaticity” is JIS K 0101 (1998) 10.1, “BOD” is JIS K 0102 (1998) 21 and 32.3, “COD” is JIS K 0102 (1998) 17, “ “Total organic carbon content” is JIS K 0102 (1998) 22.2, “Total nitrogen content” is JIS K 0102 (1998) 45.5, “Calcium” is JIS K 0102 (1998) 50.2, “Magnesium” means JIS K 0102 (1998) 51.2, “Sodium” means JIS K 0102 (1998) 48.2, “Potassium” means JIS K 0 02 (1998) 49.2, “chloride ion” is JIS K 0102 (1998) 35.3, “sulfate ion” is JIS K 0102 (1998) 41.3, “lead and its compounds” are JIS K 0102 (1998) 35.3 It is a value measured according to K 0102 (1998) 54.3.

  The leached water raw water A and 10 L of leached water raw water B were each supplied to the reverse osmosis membrane module 4 shown in FIG. 2 and concentrated by reverse osmosis membrane treatment. The concentration method is circulation concentration, and the concentration ratio is 3 times for the raw leachate water A and 5 times for the raw leachate water B. As a result, 3.3 L of concentrated water was obtained from the raw leachate water A, and 2 L of concentrated water was obtained from the raw leachate water B. Table 2 shows the results of water quality analysis of each of the obtained concentrated waters.

  Next, activated carbon of the amount shown in Table 3 or Table 4 is added to 0.2 L of the obtained concentrated water, and the resulting mixture is shaken at 200 rpm in a shaker adjusted to 20 ° C. for 24 hours. Then, the activated carbon treatment was performed. As the activated carbon, activated carbon A [trade name: Diahop 008B (manufactured by Mitsubishi Chemical Calgon)], activated carbon B [trade name: Calgon WP-A0 (manufactured by Mitsubishi Chemical Calgon)], activated carbon C [trade name: Kuraray KW] (Manufactured by Kuraray Co., Ltd.) or activated carbon D [trade name: Calgon CAL (manufactured by Mitsubishi Chemical Calgon Co., Ltd.)]. Thereafter, the mixture was subjected to No5C filter paper (manufactured by Advantech) and filtered to obtain a filtrate.

  The obtained filtrate was put in a magnetic dish, heated in a hot water bath for 5 hours to evaporate water, and further dried in a thermostatic bath at 105 ° C. for 24 hours to obtain a dried salt.

  Moreover, the said activated carbon of the quantity shown in Table 3 or Table 4 was added to 0.2 L of raw | natural leachate raw water A and leachate raw | natural water B as a comparison control. The resulting mixture was shaken for 24 hours at 200 rpm in a shaker adjusted to 20 ° C. Thereafter, in the same manner as described above, filtration was performed, and moisture was removed from the obtained filtrate, followed by drying to obtain a dried salt.

  About the obtained dried salt, the presence or absence of coloring was evaluated by observation by three monitors. The results of the leachate raw water A are shown in Table 3, and the results of the leachate raw water B are shown in Table 4.

  As a result, as shown in Table 3, when the raw leachate A was subjected to reverse osmosis membrane treatment and then activated carbon treatment, it was converted as the amount of activated carbon added to the amount of raw water before reverse osmosis membrane treatment. It can be seen that a colorless dry salt can be obtained by using 1 g of activated carbon.

  In addition, as shown in Table 4, when the raw leachate B was subjected to reverse osmosis membrane treatment and then activated carbon treatment, it was converted as the amount of activated carbon added to the amount of raw water before reverse osmosis membrane treatment. It can be seen that a colorless dry salt can be obtained by using 0.04 g of activated carbon, which is a smaller amount than when the leachate raw water B is treated with activated carbon as it is.

(Test Example 2)
Table 5 shows the water quality analysis results of the raw leachate C used in this test example. In Table 5, “All Iron” means JIS K 0102 (1998) 57.4, “Manganese” means JIS K 0102 (1998) 56.4, “Aluminum” JIS K 0102 (1998) 58.4, “Iodine” is a value measured according to JIS K 0102 (1998) 36.

(1) Example 1
1) Aggregation / removal treatment Polyaluminum chloride (manufactured by Shinko Environmental Maintenance Co., Ltd., trade name: SP Flock) was added to the treated water (raw leachate raw water) to a final concentration of 150 mg / L. Subsequently, 0.01N hydrochloric acid or 0.01N NaOH was added to the obtained mixture to adjust to pH 7. The resulting mixture was stirred at 125 rpm for 5 minutes or 30 rpm for 10 minutes. Thereafter, the resulting product was filtered through a membrane filter (manufactured by Advantech) having a pore size of 0.45 μm to obtain a filtrate.

2) Reverse Osmosis Membrane Treatment The filtrate obtained in 1) above was subjected to the reverse osmosis membrane module 4 shown in FIG. 2 and concentrated 5 times by circulation concentration to obtain concentrated water.

3) Activated carbon treatment Activated carbon [trade name: Diahop 008B (manufactured by Mitsubishi Chemical Calgon Co., Ltd.)] was pulverized with a ball mill or an automatic mortar, and the obtained pulverized product was subjected to a 200 mesh sieve (passed through the 200 mesh sieve). Activated carbon was dried for 2 hours at 100 ° C., and the resulting product was cooled in a desiccator 70 g (corresponding to 157 ml) of the activated carbon after cooling was placed on a 20 mm (inner diameter) × height 1000 mm column. Two columns of the activated carbon packed columns were connected in series to construct a water-activated activated carbon contact device 13 (FIG. 3) having a two-column downward flow.

Prior to supplying the concentrated water obtained in 2) to the activated carbon contact device 13, the pH of the water to be treated was adjusted to 6-9. The water to be treated after pH adjustment was supplied to the activated carbon contact device 13 and treated under water flow conditions of water flow rate (LV): 3 m / hour, space velocity (SV): 2 m ³ / m ³ · hour.

4) Chelation treatment A chelate resin [manufactured by Purolite International Co., Ltd., trade name: PUROLITE (registered trademark) S-950] was packed into a 20 mm (inner diameter) × 1000 mm height column to obtain a chelate treatment apparatus.

The product obtained in the above 3) was subjected to the chelate treatment apparatus and treated under a water flow condition with a space velocity (SV) of 12 m ³ / m ³ · hour.

5) Drying treatment The product obtained in 4) above is put in a magnetic dish, heated in a hot water bath for 5 hours to evaporate the moisture, and further dried in a thermostatic bath at 105 ° C. for 24 hours to obtain a dried salt. It was.

(2) Comparative Example 1
The same operation as in Example 1 was performed except that the activated carbon treatment was not performed, and a dry salt was obtained.

(3) Composition analysis of dry salt 30 g of the dry salt obtained in Example 1 was dissolved in 300 mL of water. Similarly, 30 g of the dry salt obtained in Comparative Example 1 was dissolved in 300 mL of water. The water quality of each solution obtained was examined as described above. The results are shown in Table 6.

(4) Evaluation of salt Each of the dried salt obtained in Example 1 and the dried salt obtained in Comparative Example 1 was evaluated for the presence or absence of coloring by observation with three monitors. The results are shown in Table 7.

  As a result, it can be seen that when the activated carbon treatment is performed, the salt is not substantially colored.

  According to the present invention, it is possible to efficiently recover a salt suitable for reuse, for example, a salt that is not substantially colored (white salt), with simple and compact equipment, from the water to be treated containing the salt. become.

FIG. 1 is a schematic explanatory diagram of an example of a flow of a salt recovery method. FIG. 2 is a schematic explanatory diagram of an example of a reverse osmosis membrane module used in the reverse osmosis membrane device. FIG. 3 is a schematic explanatory diagram of an example of the activated carbon contact device. FIG. 4 is a schematic explanatory diagram of an example of a salt recovery apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Reverse osmosis membrane treatment step 2 Activated carbon contact step 3 Drying step 4 Reverse osmosis membrane module 5 Reverse osmosis membrane module main body 6 Flat membrane 7 Spacer 8 Reverse osmosis membrane part 9 Processed water flow path 10 End plate 11 Permeated water pipe 12 Concentrated water pipe 13 activated carbon contact device 14 pump 15 activated carbon packed column 16 high pressure pump 17 reverse osmosis membrane device 18 concentrated water storage tank 19 recovery device

Claims (8)

  A method for recovering salt, comprising subjecting treated water containing salt to a reverse osmosis membrane device to obtain concentrated water, and then bringing the concentrated water into contact with activated carbon.   The salt recovery method according to claim 1, wherein the reverse osmosis membrane device is a reverse osmosis membrane device in which a plurality of spacers are arranged, and a flat membrane-like reverse osmosis membrane is interposed between the spacers.   The salt recovery method according to claim 1 or 2, wherein moisture is removed from the activated carbon treatment product obtained by bringing concentrated water into contact with activated carbon to obtain a dry salt.   The salt recovery method according to any one of claims 1 to 3, wherein the salt to be recovered is a substantially white salt. A reverse osmosis membrane device for concentrating salt in treated water containing salt by a reverse osmosis membrane to obtain concentrated water;
An apparatus for recovering salt from water to be treated containing salt, comprising: an activated carbon contact device for contacting the concentrated water obtained by the reverse osmosis membrane device with activated carbon.   The salt recovery device according to claim 5, wherein the reverse osmosis membrane device is a reverse osmosis membrane device in which a plurality of spacers are arranged, and a flat membrane-like reverse osmosis membrane is interposed between the spacers.   The salt recovery device according to claim 5 or 6, further comprising a moisture removing device for removing moisture from the activated carbon treatment product obtained by the activated carbon contact device to obtain a dried salt.   The salt recovery apparatus according to claim 5, wherein the obtained salt is a substantially white salt.

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