JPH09276846A - Method and apparatus for disposing of highly concentrated waste water - Google Patents

Abstract

PROBLEM TO BE SOLVED: To safely and inexpensively dispose of a highly conc. soln. obtained when a soln. is separated into the highly conc. soln. and a low concn. soln. by preliminarily diluting highly conc. waste water of a reverse osmosis method or a distillation method before discarding the same. SOLUTION: The feed piping 3 of the highly conc. waste water form a highly conc. waste water tank 2 in which highly conc. waste water flows from inflow piping 1 is laid up to a proper offshore place and a disposing tower 4 is formed at the leading end thereof and diluted highly conc. waste water is discharged from the tower 4 by a discarding nozzle 5. At this time, the disposing tower 4 is pref. arranged on the bottom of the sea at a depth of about 5-20m. The disposing nozzle 5 is pref. inclined upwardly at about 35-55 deg.. By this constitution, waste flow 6 can be diffused sufficiently far away. As the drive source feeding highly conc. waste water, there is no special limit but residual energy, the water level difference from the surface of the sea or a pump is used.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for discarding a high-concentration solution when the solution is separated into a high-concentration solution and a low-concentration solution. According to the present invention, unnecessary high-concentration solution can be safely disposed of at low cost while suppressing the influence on the environment, while increasing the concentration ratio of the high-concentration solution to improve the recovery rate of the low-concentration solution to be produced. A method and apparatus that can be improved can be provided. The method and apparatus of the present invention can be used for desalination of seawater and desalination of brackish water by the reverse osmosis method, and are particularly effective when desalination of seawater is performed at a high recovery rate.

[0002]

2. Description of the Related Art Regarding separation of a mixture, there are various techniques for removing substances (for example, salts) dissolved in a solvent (for example, water), but in recent years, membrane separation has been performed as a process for saving energy and resources. The law is being used. For example, the reverse osmosis method is used to desalinate seawater or low-concentration salt water (brine water) to provide industrial, agricultural, or domestic water. According to the reverse osmosis method, desalinated water can be produced by permeating water containing salt through a reverse osmosis membrane at a pressure higher than the osmotic pressure. This technology can obtain drinking water from, for example, seawater, brackish water, and water containing harmful substances, and has also been used for the production of industrial ultrapure water, wastewater treatment, recovery of valuables, etc. .

In particular, seawater desalination using a reverse osmosis membrane is characterized in that there is no phase change such as evaporation, is energy-friendly, and is easy to operate and manage, and has started to be widely used.

Taking the case of seawater desalination using a reverse osmosis membrane as an example, the ratio (recovery rate) of recovering fresh water from seawater in the normal seawater desalination technology is at most 40%, which is 40% of the seawater supply amount. The result is that a significant amount of fresh water permeates the membrane,
Seawater concentration in reverse osmosis membrane module is 3.5% to 6%
It will be concentrated to a certain degree. The concentrated seawater obtained here is discharged into seawater after sufficiently performing an environmental assessment to determine the discharge point.

[0005]

The recovery rate of fresh water relative to the supply of seawater directly contributes to the cost, and the higher the recovery rate, the better. However, actually increasing the recovery rate is various in terms of operation. There was a problem. That is,
One of them is that if the recovery rate is increased, the concentration of concentrated water becomes higher, and the osmotic pressure becomes higher, so that very high pressure is required to obtain fresh water. It is necessary to have enough resistance to this high pressure. In addition, the concentration of seawater components in concentrated water becomes high, and above a certain recovery rate, salts such as calcium carbonate, calcium sulfate, and strontium sulfate, so-called scale component concentrations become more than solubility and precipitate on the membrane surface of the reverse osmosis membrane. There is also the problem of clogging of the membrane. Further, as the recovery rate increases, the concentration of concentrated water also increases. Therefore, if the concentrated water is discarded as it is, environmental and safety problems may occur.

[0006] The present invention provides a method and a device which enable safe disposal of a high-concentration solution when the solution is separated into a high-concentration solution and a low-concentration solution, and suppress the influence on the environment at low cost. Especially, the concentrated seawater obtained when performing reverse osmosis seawater desalination with a high recovery rate of 40% or more is disposed of with low energy efficiently, inexpensively, safely, stably and with little environmental impact. It is an object of the present invention to provide a method and an apparatus capable of performing the above.

[0007]

The present invention has the following arrangement. In other words, it is a "disposal method of high-concentration wastewater characterized by preliminarily diluting and discarding high-concentration wastewater of the reverse osmosis method or distillation method."

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, high-concentration wastewater means concentrated water obtained when a mixed solution is separated, for example, concentrated water of reverse osmosis method or loose RO method, ultrafiltration method, and microfiltration method. Non-permeated water, concentrated water for electrodialysis or concentrated residue for evaporation method. The method of the present invention is effective for discarding these high-concentration liquids, but is particularly effective for the concentrated water of the reverse osmosis method. The concentrated water may be subjected to treatment such as pH adjustment and filtration before being discarded.

When the method of the present invention is used for the concentrated water of the reverse osmosis method or the treated water of the concentrated water, the raw water of the reverse osmosis method is seawater,
In the case of a high-concentration solution such as high-concentration brackish water, the concentration of concentrated water also increases, so the method of the present invention is preferably used.
In particular, in the reverse osmosis method, in which the concentration of permeated water is improved by arranging the modules in multiple stages and separating the concentrated water in the first stage further in the second stage, the concentration of concentrated water in the second stage is higher. Therefore, the method for discarding concentrated water according to the method of the present invention is preferable.

In the reverse osmosis method, the reverse osmosis membrane separation device comprises at least a water intake portion of the feed liquid, a pretreatment portion, and a reverse osmosis membrane portion. The reverse osmosis membrane part is a part for supplying the liquid to be treated to the reverse osmosis membrane module under pressure for the purpose of water production, concentration, separation, etc., and separating it into a permeated liquid and a concentrated liquid. It is composed of a reverse osmosis membrane module consisting of a pressure vessel and a pressure pump.

Here, the reverse osmosis membrane is a semipermeable membrane that allows a part of components in the liquid mixture to be separated, for example, a solvent to pass therethrough and does not allow other components to pass therethrough. As the material, polymer materials such as cellulose acetate polymer, polyamide, polyester, polyimide, and vinyl polymer are often used. The membrane structure has a dense layer on at least one surface of the film, and an asymmetric film having fine pores having a large pore diameter gradually from the dense layer toward the inside of the film or the other surface. There are composite membranes with a very thin active layer formed of a material. The membrane form includes a hollow fiber and a flat membrane. However, the method of the present invention can be used irrespective of the material, membrane structure and membrane form of the reverse osmosis membrane, and is very effective. Typical reverse osmosis membranes include, for example, a cellulose acetate-based or polyamide-based asymmetric membrane and a composite membrane having a polyamide-based or polyurea-based active layer. Among them, the method of the present invention is effective for cellulose acetate-based asymmetric membranes and polyamide-based composite membranes, and is particularly effective for aromatic polyamide-based composite membranes.

The reverse osmosis membrane element is formed by actually using the above-mentioned reverse osmosis membrane. The flat membrane is incorporated in the elements of spiral, tubular, plate and frame, and the hollow fiber is Although they can be used by being bundled and incorporated into the element, the present invention is not dependent on the form of these reverse osmosis membrane elements.

The reverse osmosis membrane module unit is a module in which one or several reverse osmosis membrane elements described above are housed in a pressure vessel and arranged in parallel. The combination, number and arrangement of the modules can be arbitrarily selected according to the purpose. be able to.

In the present invention, when arranging the membrane modules in multiple stages, it is characterized by using a plurality of the reverse osmosis membrane module units and the arrangement thereof. In the arrangement of the reverse osmosis membrane module units, it is important that the flow of the feed liquid or the concentrate is in series, that is, the concentrate of one reverse osmosis membrane module unit becomes the feed liquid of the next reverse osmosis membrane module unit. . For example, the equipment for obtaining fresh water from ordinary seawater with a concentration of 3.5% at a very high recovery rate of 60% is basically two reverse osmosis membrane module units, one pressure pump, and one unit. Reverse osmosis separation device consisting of a booster pump. Seawater is 60-65 atm by a pressure pump after the suspended components are removed by pretreatment.
And is supplied to the first-stage reverse osmosis membrane module unit. In the first-stage reverse osmosis membrane unit, the feed liquid is separated into a low-concentration permeate liquid that has permeated the membrane and a high-concentration concentrated liquid that does not permeate the membrane. Next, the permeate is used as it is, but the concentrate has a pressure of 60 to 65 (pressure loss is ignored for the sake of simplicity) to 90 atm, which is essential for separating highly concentrated water with a recovery rate of 60%. The pressure is further increased by the booster pump and is supplied to the second-stage reverse osmosis membrane module unit, and the reverse osmosis separation is performed again to separate the second-stage permeated liquid and the concentrated liquid. The ratio of the total amount of water supplied to this reverse osmosis membrane plant and the total of the first-stage permeate and the second-stage permeate is the fresh water recovery rate, which in this case is 60%. The number of stages and the number of pumps are not limited to this, and can be set arbitrarily.

Regarding the desalination recovery rate of the reverse osmosis membrane facility, the effect of the present invention is remarkably exhibited in a particularly high recovery rate area, but the present invention is not particularly limited to this, and 40% recovery in the present desalination of seawater. It can also be applied under the conditions of.

The concentration of solute in the high-concentration wastewater is not particularly limited, but the solute concentration is preferably 5.0% by weight or more. Further, particularly preferably, the effect of the present invention is exerted particularly when seawater having a high osmotic pressure or high concentration brackish water having a salt concentration of about 1% or more is subjected to reverse osmosis separation.

The high-concentration wastewater is diluted by mixing a solution having a lower concentration than the wastewater. As the low-concentration solution, for example, water in the dilution range or part of the raw water used for separation can be used as it is as the dilution water. When diluting water and raw water are used, it is preferable in terms of cost to use the water without taking any special treatment. However, raw water may be filtered or a chemical solution may be added for use as necessary.

The dilution ratio depends on the concentration and volume of the high-concentration wastewater, the concentration of the solution used for dilution, and the method of discharging the diluted solution, but is usually 1.5 to 20 times. If the dilution ratio is small, the concentration at the time of disposal will be high, and if the dilution ratio is too high, the amount of the low-concentration solution used for dilution will be too large and the processing cost will be high. For example, fresh water recovery rate 6
0% seawater desalination concentrate has a concentration of about 8.8% and 1m ³ of this concentrate requires 0.5-10m of seawater.
It is ³ , and preferably 0.5 to ⁵ m ³ .

The diluting method is the high-concentration drainage tank (2) of FIG.
A method of mixing a high-concentration wastewater and diluting water into a mixing tank with an appropriate stirring mechanism, a method of injecting or aspirating the diluting water into the high-concentration wastewater transport pipe (3),
On the contrary, there is a method of injecting high-concentration wastewater into the dilution water pipe, and these mixing methods can be arbitrarily selected depending on the flow rate of high-concentration wastewater and the size of the plant.

Further, in the case of concentrated water of the reverse osmosis method, the raw water is pressurized for reverse osmosis separation, and the concentrated waste water also has pressure energy. Therefore, this pressure energy is recovered, then diluted and discarded. Preferably. Examples of energy recovery methods include a method of recovering with an energy recovery device attached to a high-pressure pump and a method of recovering with a booster pump, but the method of the present invention is not limited to these energy recovery methods.

On the other hand, as an apparatus for diluting concentrated wastewater and discarding it, it is necessary to have an apparatus for diluting highly concentrated wastewater and an apparatus for discarding and discharging the diluted wastewater.
As a device for diluting high-concentration wastewater, the dilution water is pumped into the concentrated wastewater and dilution water inlets, the diluted wastewater outlet, and the mixing tank equipped with a stirring and mixing device, and the concentrated wastewater piping. It is possible to use a mixing device for mixing in a pipe, a suction device for diluting water by an ejector or aspirator mechanism using the flow (7) of concentrated waste water shown in FIG. 2, and a mixing device in a pipe. Further, it is effective to provide a backflow prevention valve (9) in order to prevent the high-concentration wastewater from flowing back from the diluent inlet. The mixing tank may be used as a discharge water tank. In some cases, the device for diluting the highly concentrated wastewater and the device for discarding and discharging the wastewater may be a single device having both functions. For example, the waste and discharge nozzles are doubled to simultaneously discharge high-concentration wastewater and dilution water, and a device for mixing and diluting immediately after discharge or an ejector-type suction port is installed in the discharge nozzle to take in surrounding water as dilution water and mix it. It is a device that dilutes and releases.

A device as shown in FIG. 1 is suitable as a mechanism for finally discharging the diluted high-concentration wastewater. That is, the high-concentration wastewater transfer pipe (3) is piped to an appropriate location offshore, and a waste tower (4) is provided. From the waste nozzle (5), the diluted high-concentration wastewater is discharged.
The waste tower (4) is preferably installed on the seabed at a water depth of about 5 to 20 m. If it is shallower than this, it will hinder ship navigation,
If it is deeper than this, installation work becomes difficult. It is also preferable to lay concrete or the like in the ground on the bottom of the sea floor to prevent the waste tower from being washed away by the ocean current. Also, the waste nozzle (5) is preferably directed upwards of approximately 35-55 degrees. If it is smaller than this angle, the waste stream (6) does not flow sufficiently high, and if it is large, it does not spread far enough, and in any case, there is a possibility that it will not be diluted enough to not affect the ecosystem.

The drive source for transporting high-concentration wastewater is not particularly limited, but residual pressure energy, water level difference from the sea surface, or a pump may be used.

[0024]

【Example】

Example 1 A module device in which two modules containing two reverse osmosis membrane elements SU-820 manufactured by Toray Industries Inc. were installed in parallel was used as a first-stage module device, and a module device in which one module was installed was second. It was a module device at the stage. First
A high-pressure pump is connected to the feed liquid inlet line of the first-stage module device, the concentrated water line of the first-stage module device is connected to a booster pump, and further connected to the feed-liquid inlet line of the second-stage module device. did. Filter to this device, pH
Adjusted and injected chemical water to supply freshwater recovery rate of 60
Separation was performed in%. 4. The resulting concentrated wastewater with a salt concentration of 8.8% by weight is placed in a discharge water tank equipped with a stirring facility, and raw water with a salt concentration of 3.5% is mixed with 1.3 times the concentrated wastewater in the discharge water tank. When diluted to 8% and released into the sea diagonally upward at a water depth of 10 m, the seawater concentration was 5% or less at the seabed 20 m away from the outlet.

Comparative Example 1 Concentrated water having a salt concentration of 8.8% by weight obtained in the same manner as in Example 1 was discharged into the sea in the same manner as in Example 1 without diluting, and it was 20 m away from the discharge port. Concentration is 5 at the point
% Or more.

Example 2 Discharging into the sea in the same manner as in Example 1 except that the mixed amount of seawater was made equal to the concentrated wastewater, and the seawater concentration was 5% or less at the seabed 20 m away from the discharge port. .

Example 3 When discharged into the sea in the same manner as in Example 1 except that the mixed amount of seawater was 0.5 times the concentrated wastewater, 2 from the outlet.
The seawater concentration was 5% or less at the seabed 0 m away.

Example 4 In the drainage pipe of concentrated water obtained in the same manner as in Example 1 and having a salt concentration of 8.8% by weight, two dilution water inlets were provided, and the salt concentration was 3.5% from the inlet. When the total amount of seawater of the raw water was mixed with 1.3 times the concentrated wastewater and diluted to 5.8% and discharged into the sea in the same manner as in Example 1, the seawater concentration at the seabed 20 m away from the outlet was It was below 5%.

Example 5 When discharged into the sea in the same manner as in Example 4 except that the mixed amount of seawater was made equal to the concentrated wastewater, the seawater concentration was 5% or less on the seabed 20 m away from the discharge port. .

Example 6 Discharging into the sea in the same manner as in Example 4 except that the amount of seawater mixed was 0.5 times the concentrated wastewater, 2 from the discharge port.
The seawater concentration was 5% or less at the seabed 0 m away.

Example 7 Concentrated water having a salt concentration of 8.8% by weight obtained in the same manner as in Example 1 was discarded from a discharging device provided with an ejector-type suction port at the base of the discharging nozzle. At that time, when the surrounding seawater was taken into the nozzle in an amount of about 1.3 times the concentrated water amount and diluted, and was discharged into the sea in the same manner as in Example 1, the seawater concentration was 20 m away from the discharge port. It was below 5%.

Example 8 Discharging into the sea in the same manner as in Example 7 except that the mixed amount of seawater was made equal to concentrated wastewater, and the seawater concentration was 5% or less at the seabed 20 m away from the discharge port. .

Example 9 When discharged into the sea in the same manner as in Example 7 except that the mixed amount of seawater was 0.5 times the concentrated wastewater, 2 from the outlet.
The seawater concentration was 5% or less at the seabed 0 m away.

[0034]

Industrial Applicability According to the present invention, it is possible to provide a safe, inexpensive and environmentally friendly method for discarding highly concentrated wastewater, especially for discarding concentrated water that has been subjected to reverse osmosis separation with a high recovery rate. it can.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a disposal facility of the present invention.

FIG. 2 is a cross-sectional view of an exeter used in the present invention.

[Explanation of symbols]

 1: High-concentration drainage inflow pipe 2: High-concentration drainage tank 3: High-concentration drainage transfer pipe 4: Disposal tower 5: Waste nozzle 6: Waste flow 7: High-concentration drainage flow 8: Intake diluent flow 9: Check valve

Claims (13)

[Claims] 1. A method of disposing high-concentration wastewater, which comprises diluting high-concentration wastewater of the reverse osmosis method or distillation method in advance and discarding it. 2. The method of disposing high-concentration wastewater according to claim 1, wherein the high-concentration wastewater is concentrated water of a reverse osmosis method. 3. The method of disposing high-concentration wastewater according to claim 2, wherein the raw water of the reverse osmosis method is seawater or high-concentration brackish water. 4. The method of disposing high-concentration wastewater according to claim 2, wherein the reverse osmosis method is a method of arranging membrane modules in multiple stages and further separating the concentrated water in the first stage in the second stage. . 5. The method of disposing high-concentration wastewater according to claim 1, wherein the solute concentration of the high-concentration wastewater is 5.0% by weight or more. 6. The method of disposing high-concentration wastewater according to claim 1, wherein seawater or high-concentration brackish water is used for diluting the high-concentration wastewater. 7. The method for discarding highly concentrated waste water according to claim 2, wherein the concentrated water of the reverse osmosis method is diluted with raw water and discarded. 8. The method for discarding high-concentration wastewater according to claim 2, wherein the concentrated water of the reverse osmosis method is diluted with the water in the discharge area and discarded. 9. After recovering the pressure energy of the concentrated water,
The method for discarding highly concentrated wastewater according to claim 2, wherein the method is diluted and discarded. 10. An apparatus for discarding concentrated wastewater, comprising a device for mixing concentrated wastewater with dilution water, and a means for discarding the diluted concentrated wastewater. 11. The concentrate according to claim 10, wherein the device for mixing the concentrated wastewater with the diluting water comprises an inlet for the concentrated wastewater and the diluting water, an outlet for the diluted wastewater, and a stirring and mixing device. Wastewater disposal device. 12. The device for discarding concentrated wastewater according to claim 10, wherein the device for mixing the concentrated wastewater with the dilution water is a device for injecting the diluted water into the pipe for the concentrated wastewater. 13. The concentrating device according to claim 10, wherein the device for mixing the concentrated effluent with the diluting water includes a device for sucking the diluting water by an ejector or aspirator mechanism utilizing the flow of the concentrated effluent and a mixing device. Wastewater disposal device.