JP3098965B2 - Water treatment method and water treatment device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to raw water containing salts,
For example, the present invention relates to a water treatment method and a water treatment apparatus for desalinating leached sewage and the like in a general waste final disposal site.

[0002]

2. Description of the Related Art At present, wastes are generally disposed of in landfills after incineration. The leachate generated at this final disposal site contains calcium and nitrogen leached from incinerated waste,
When discharged as it is, for example, calcium ions react with carbonate ions and sulfate ions to form insoluble calcium salts, which adhere to pipes and facilities as scales, causing a problem that the facilities are lowered.

Therefore, conventionally, a water treatment apparatus as shown in FIG. 4 has been used to remove calcium, phosphorus, nitrogen and the like from leachate.

[0004] That is, the sewage is stored in the flow rate adjusting tank 21, and after the calcium is removed in the calcium removing tank 22, the wastewater is denitrified in the biological treatment tank 23. The treated water is supplied to a sand filtration tank 25.
And after passing through the activated carbon treatment tank 26 and the chelate adsorption treatment 27, it is treated as treated water.

[0005]

However, when leachate is treated with such a water treatment apparatus, components such as calcium, nitrogen, and phosphorus can be removed, but salts other than calcium, such as magnesium, sodium, and chlorine. Ions, sulfate ions, and other soluble salts cannot be removed, and if they are discharged to rivers or the like as treated water, there is a problem that these salts may contaminate rivers and soil. Was.

In order to solve this problem, an electrodialyzer 28 is provided as a device for desalination in a water treatment device, and salts in the leachate are separated from the treated water as concentrated water.

[0007] However, when a large amount of this concentrated water is generated, it takes time and labor for treatment. Therefore, it is desired to concentrate the concentrated water to a high concentration so that the amount of the concentrated water is reduced as much as possible. In the apparatus 28, the concentration is usually about 5 to 10 times the concentration of the raw water, and it is difficult to reduce the concentrated water by concentrating it to a higher concentration.

The present invention has been made in order to solve such a problem, and it is possible to easily perform a desalination treatment of sewage such as leachate containing salt, and to increase a salt concentration rate to increase salt concentration. An object of the present invention is to provide a water treatment method and a treatment device that can easily perform treatment.

[0009]

SUMMARY OF THE INVENTION The present invention has been made as a water treatment method and a water treatment apparatus in order to solve such a problem, and the feature of the water treatment method is that the raw water containing salts is reverse osmosis. In a water treatment method of separating treated water and concentrated water containing salts by passing through a membrane, the concentrated water separated by the reverse osmosis membrane is filtered by a permeable membrane, and the permeated water filtered by the permeable membrane is further concentrated. While the highly concentrated water separated by permeation through the reverse osmosis membrane for water treatment is discharged, the concentrated water filtered by the permeable membrane is crystallized, and the supernatant generated during the crystallization treatment is introduced into the permeable membrane. It is in.

[0010] The water treatment apparatus is characterized by a reverse osmosis membrane apparatus 1 for permeating raw water containing salts and separating it into treated water and concentrated water containing salts, and a concentrator separated by the reverse osmosis membrane apparatus 1. A permeable membrane device 2 for filtering water, and the permeable membrane device
A reverse osmosis membrane device for concentrated water treatment 3 through which the permeated water filtered by 2 is permeated; a discharge path A for discharging highly concentrated water separated by the reverse osmosis membrane device 3 for concentrated water treatment; A crystallization tank 4 into which the concentrated water filtered by the apparatus 2 is introduced, and an introduction path B for introducing the supernatant generated in the crystallization tank 4 into the permeable membrane apparatus 2 are provided.

That is, as described above, in the present invention, raw water such as leachate containing salts is treated by the reverse osmosis membrane.
Salts and phosphorus composed of calcium, magnesium, sodium, chloride ions, sulfate ions, etc. contained in the raw water,
Nitrogen and the like can be easily and reliably separated by a reverse osmosis membrane to obtain desalted water.

Further, the concentrated water in which the salts separated by the reverse osmosis membrane are concentrated is treated with the permeable membrane, and then permeates through the reverse osmosis membrane for treating the concentrated water. The concentrated water that is generated is a highly concentrated highly concentrated water and has a small amount of generation, and it is sufficient to treat this small amount of concentrated water, so that the treatment can be easily performed.

Further, before the concentrated water is further concentrated by the concentrated water treatment reverse osmosis membrane, some of the salts in the concentrated water can be removed by the permeable membrane, so that the scale adheres to the concentrated water treatment reverse osmosis membrane. Thus, it is possible to prevent the processing performance of the film from being lowered.

Further, since the concentrated water filtered through the permeable membrane is precipitated as a solid content, salts can be more reliably removed, and the salts discharged as concentrated water can be further reduced.

Further, in the case where a reverse osmosis membrane for further treating the treated water treated by the reverse osmosis membrane is provided downstream of the reverse osmosis membrane, the quality of the treated water can be further improved. .

[0016]

Embodiments of the present invention will be described below with reference to the drawings. First, the configuration of the water treatment apparatus according to the present embodiment will be described. Reference numeral 1 shown in FIG. 1 denotes a reverse osmosis membrane apparatus into which leachate is introduced as raw water. As shown in FIG. Inside, a disc-shaped reverse osmosis membrane 12
A plurality of reverse osmosis membrane portions 14 provided between the disc-shaped spacers 13 are also laminated.

A raw water flow path 15 for introducing raw water is provided on the inner peripheral surface of the apparatus main body 11 of the reverse osmosis membrane apparatus 1.
Raw water is introduced to the surface of the reverse osmosis membrane 12 from the above. Further, an end plate 16 is provided on the reverse osmosis membrane section 14 so as to withstand an osmotic pressure or more.

Reference numeral 18 denotes a treated water pipe penetrating the central portion of the reverse osmosis membrane section 14. The treated water pipe 18 discharges the treated water separated by the reverse osmosis membrane 12. Reference numeral 19 denotes a concentrated water pipe for discharging the concentrated water concentrated by each reverse osmosis membrane 12 to the outside of the apparatus main body 11.

Reference numeral 2 denotes an NF membrane device provided with a nanofilter (NF) as a permeable membrane through which the concentrated water separated by the reverse osmosis membrane device 1 is introduced and filtered. Thus, salts in the concentrated water, particularly salts of divalent or higher negative ions, for example, CaCO ₃ and CaSO ₄ can be removed by filtration.

In the NF membrane device 2, a large number of NF membranes are accommodated in a cylindrical main body in a stacked state, and the upper and lower portions of the main body are sealed by end plates provided with water holes. I have.

Reference numeral 3 denotes a high-pressure reverse osmosis membrane device for concentrated water treatment provided for further desalting the permeated water filtered by the NF membrane device 2. The high-pressure reverse osmosis membrane device 3 comprises As in the osmosis membrane device 1, a plurality of modules each having a disc-shaped reverse osmosis membrane provided between spacers are stacked in a cylindrical device main body. The high-pressure reverse osmosis membrane device 3 is formed so as to be capable of performing a separation process of applying a higher pressure than the reverse osmosis membrane device 1 to highly concentrate the concentrated water.

4 is a crystallization tank into which the concentrated water separated in the NF membrane device 2 and the high pressure reverse osmosis membrane device 3 is introduced.
In the crystallization tank 4, salts remaining in the treated water are precipitated as solids 6.

The supernatant generated in the crystallization tank 4 is N
It is sent to the F membrane device 2 via the introduction path B together with the concentrated water introduced from the osmosis membrane device 1, filtered by the NF membrane device 2, and then circulated to the high pressure reverse osmosis membrane device 3.

Further, a part of the concentrated water separated by the high-pressure reverse osmosis membrane device 3 is directly treated as a highly concentrated water from the discharge path A, and the remaining concentrated water is sent to the crystallization tank 4.

Reference numeral 5 denotes a second reverse osmosis membrane device into which the treated water separated by the reverse osmosis membrane device 1 is introduced. The second reverse osmosis membrane device 2 also has the same configuration as the reverse osmosis membrane device 1. .

The treated water separated in the second reverse osmosis membrane device 5 is directly discharged as purified water from the main body of the device, while the concentrated water is introduced into the reverse osmosis membrane device 1 together with raw water.
The treated water separated by the high-pressure reverse osmosis membrane device 3 is introduced into the second reverse osmosis membrane device 5.

Next, a method of treating leachate by the leachate treatment apparatus 20 having the above-described configuration will be described.

First, leachate leached from a waste treatment plant is introduced as raw water into the reverse osmosis membrane device 1 to desalinate raw water. The reverse osmosis membrane is a semipermeable membrane that can be filtered at the molecular level when a pressure higher than the osmotic pressure is applied, and can remove phosphorus, organic substances, nitrogen, and various salts such as calcium and sodium.

As described above, the reverse osmosis membrane device 1 has a structure in which the disc-shaped reverse osmosis membrane 12 is laminated, and the pressure is applied when the raw water flows between the surface of the reverse osmosis membrane 12 and the spacer 13. When applied, the reverse osmosis membrane 12 permeates only water and the demineralized treated water accumulates inside the membrane, and the treated water passes through a treated water pipe 18 vertically provided in the central part of the apparatus main body 11, and the reverse osmosis membrane apparatus From 1 is discharged as treated water.

On the other hand, the raw water passes between the reverse osmosis membrane 12 and the spacer 13, passes through the concentrated water pipe 19, and is discharged from the reverse osmosis membrane device 1 as concentrated water.

Next, the concentrated water is introduced into the NF membrane device 2, and then the permeated water treated by the NF membrane device 2 is introduced into the high-pressure reverse osmosis membrane device 3.

On the high-pressure reverse osmosis membrane of the high-pressure reverse osmosis membrane device 3, when monovalent ions and divalent or higher ions are present, monovalent ions precipitate and become scales to form a membrane. It may cause a decrease in processing capacity. Therefore, in order to prevent this, it is necessary to selectively remove divalent or higher valent ions in advance from the liquid to be treated on the high-pressure reverse osmosis membrane,
The NF membrane is composed of salts in concentrated water, especially CaCO ₃ and CaS
Bivalent or more negative ions such as O ₄ can be effectively removed by filtration.

As described above, selective removal of divalent or higher-valent ions cannot be normally performed with a UF membrane (ultrafiltration membrane) or an MF membrane (microfiltration membrane). Can be selectively removed. In particular, when the concentration of ions contained in water is low, for example, the reverse osmosis membrane device 1
In the second reverse osmosis membrane device 5 or the second reverse osmosis membrane device 5, scale is hardly generated even without providing such an NF membrane, but in the high pressure reverse osmosis membrane device 3, the concentrated water separated by the reverse osmosis membrane device 1 is treated. Since the ion concentration is high and scale is easily generated, the scale can be effectively prevented by providing the NF film device 2.

Then, since this concentrated water is further processed by the high-pressure reverse osmosis membrane device 3, highly concentrated highly concentrated water is obtained. At this time, the highly concentrated water is concentrated to about 2.5% with respect to the raw water introduced into the reverse osmosis treatment apparatus 1, and thus a high recovery rate of 97.5% is obtained.

On the other hand, the treated water discharged from the reverse osmosis membrane device 1 is further desalted in the second reverse osmosis membrane device 5 and discharged as high-purity treated water. The concentrated water separated in the second reverse osmosis membrane device 5 is returned to the reverse osmosis membrane device 1 together with the raw water, so that even a small amount of salts can be reliably removed and prevented from being discharged outside the device.

Further, the concentrated water generated in the NF membrane device 2 and a part of the highly concentrated concentrated water generated in the high pressure reverse osmosis membrane device 3 are introduced into the crystallization tank 4. The crystallization tank 4
Then, salts contained in these can be precipitated and removed as solids. The supernatant liquid generated in the crystallization tank 4 is again introduced into the NF membrane device 2 via the introduction path B together with the concentrated water from the reverse osmosis membrane device 1. As described above, since a part of the salts is precipitated as a solid in the crystallization tank 4,
The amount of salts discharged as concentrated water can be further reduced.

Further, the treated water separated in the high pressure reverse osmosis membrane device 3 is introduced into the second reverse osmosis membrane device 5 together with the treated water discharged from the reverse osmosis membrane device 1, and is subjected to a desalination treatment without fail.

Further, a plurality of reverse osmosis membrane units 14 each having a disc-shaped reverse osmosis membrane 12 provided between spacers 13 are laminated on the reverse osmosis membrane device 1, the high pressure reverse osmosis membrane device 3, and the second reverse osmosis membrane device 5. Since the reverse osmosis membrane device is used, a wide flow path for permeating the treated water through the membrane can be secured, so that complicated pretreatment and chemical treatment for preventing clogging are unnecessary. In addition, since the flow in the reverse osmosis membrane device 1 becomes turbulent, it is possible to prevent adhesion of scale and dirt and blockage of the membrane, and it is also easy to clean the surface of the reverse osmosis membrane after long-term use. I can do it.

In the above embodiment, a part of the concentrated water highly concentrated by the high pressure reverse osmosis membrane device 3 is returned to the crystallization device 4 to further improve the concentration efficiency. It is not a condition to return a part of the highly concentrated concentrated water to the crystallization tank 4 as described above.

Further, in the above embodiment, the treated water separated by the reverse osmosis membrane device 1 is treated by the second reverse osmosis membrane device 5 provided further downstream, but such a second reverse osmosis membrane device is used. The provision is not a condition. However, if a plurality of stages of reverse osmosis membrane treatment are performed as in the above embodiment, the quality of the treated water will be further improved.

In the above embodiment, the reverse osmosis membrane device 1 is used.
The concentrated water generated by the above is directly introduced into the NF membrane device 2 as a permeable membrane. For example, as shown in FIG. 3, the concentrated water generated in the reverse osmosis membrane device 1 is further introduced into the reverse osmosis membrane device 1a,
The concentrated water generated here can be introduced into the NF membrane device 2 to concentrate the concentrated water to a higher concentration.

In the above-described embodiment, the high-concentration water is discharged outside the apparatus and is separately treated. For example, as a method for treating the concentrated water, the concentrated water is returned to the waste treatment plant again. Is also good. As described above, when the salt is returned to the waste treatment plant, the salt is treated again as leachate, so that the salt is not discharged from the treatment facility.

Further, when returning the concentrated water to the waste treatment plant in this way, a tank such as a crystallization tank is provided at the return place,
The salts may be precipitated as solids by evaporating the water. Alternatively, fine mist may be applied and water may be sprinkled and returned so that salts may be naturally precipitated. In any case, since salts can be obtained as solids, the treatment and handling are easy.

Further, in the above embodiment, a reverse osmosis membrane device using a disc-shaped flat reverse osmosis membrane was used as the reverse osmosis membrane device. A reverse osmosis membrane of any shape such as a hollow fiber type, a spiral type and a tubular type may be used.

Further, in the above embodiment, the leachate was directly introduced into the reverse osmosis membrane device 1 as raw water, but, for example, the leachate was once stored in a storage tank, pH was adjusted, etc., and then the reverse osmosis membrane was used. May be transmitted. In this case, since the flow rate can be adjusted, the management and control of the apparatus can be performed more easily.

In the above embodiment, leachate is treated as raw water, but the present invention can be applied to desalination treatment of water containing salts discharged from general equipment in addition to leachate.

[0047]

As described above, according to the present invention, desalination of sewage containing salt such as leachate discharged from a disposal site can be surely performed, and at the same time, concentrated water containing salt to be recovered can be used. By reducing the amount, it becomes possible to simplify the treatment of the collected salts.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a water treatment apparatus as an example of an embodiment of the present invention.

FIG. 2 is a schematic sectional view of a reverse osmosis membrane device.

FIG. 3 is a schematic configuration diagram of a water treatment apparatus as another embodiment.

FIG. 4 is a schematic configuration diagram of a conventional water treatment apparatus.

[Explanation of symbols]

 1 reverse osmosis membrane device (reverse osmosis membrane) 2 NF membrane device (permeable membrane) 3 high pressure reverse osmosis membrane device (reverse osmosis membrane for concentrated water treatment) 4 crystallization tank

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI B01D 61/02 500 B01D 61/02 500 61/10 61/10 61/58 61/58 (72) Inventor Kenichi Ushikoshi Kako, Hyogo 540-41 Nakamura, Inami-cho, Gunma (72) Inventor Tetsushi Nishimoto 7-17-1 Tsujii, Himeji-shi, Hyogo (56) References JP-A-8-290164 (JP, A) JP-A-54-77281 (JP, A) A) (58) Field surveyed (Int. Cl. ⁷ , DB name) B01D 61/00-61/58 C02F 1/44

Claims (4)

(57) [Claims] 1. A water treatment method in which raw water containing salts is permeated through a reverse osmosis membrane to separate treated water and concentrated water containing salts, wherein the concentrated water separated by the reverse osmosis membrane is filtered through a permeable membrane. The permeated water filtered by the permeable membrane is further passed through a reverse osmosis membrane for concentrated water treatment to discharge the separated highly concentrated water, and the concentrated water filtered by the permeable membrane is subjected to crystallization treatment. A water treatment method, wherein a supernatant generated during the precipitation treatment is introduced into the permeable membrane. 2. The water treatment method according to claim 1, wherein the treated water separated by the reverse osmosis membrane is further treated with a reverse osmosis membrane. 3. A reverse osmosis membrane device (1) for permeating salt-containing raw water to separate treated water and concentrated water containing salts, and filtering the concentrated water separated by the reverse osmosis membrane device (1). A permeable membrane device (2), a reverse osmosis membrane device for concentrated water treatment through which permeated water filtered by the permeable membrane device (2) is transmitted, and a reverse osmosis membrane device for concentrated water treatment (3) And a crystallization tank (4) into which the concentrated water filtered by the permeable membrane device (2) is introduced, and the crystallization tank (4). A) an introduction path (B) for introducing the supernatant liquid produced in the above) into the permeable membrane apparatus (2). 4. A reverse osmosis membrane device (5) through which the treated water separated by the reverse osmosis membrane device (1) is transmitted is provided downstream of the reverse osmosis membrane device (1). A water treatment apparatus according to item 1.