JP2013043156A - Desalination system and desalination method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a desalination system and desalination method which can effectively utilize sewage water as much as possible and which can reduce water desalination cost of the overall system.SOLUTION: The desalination system S desalinates sewage water and seawater, and includes a purification device 1 which transmits and purifies the sewage water, a first RO membrane 2 which transmits the water s5a transmitted through the purification device 1 and eliminates salt so as to be included in first concentrated water s6a and generates industrial water s1, a first pretreatment device 3 in which the first concentrated water s6a is subject to at least one of concentrated filtering and filtering with an NF membrane, and a second RO membrane 4 which transmits first treated water s7a subjected to the pretreatment at the first pretreatment device 3, eliminates salt so as to be included in second concentrated water s6b and generates industrial water s2.

Description

  The present invention relates to a desalination system and a desalination method for desalinating sewage and seawater.

In recent years, demand for drinking water and industrial water production in desert areas has become apparent due to global population growth and development of wide-area industries including emerging countries.
Conventionally, there exists desalination system S100 shown in FIG. 7 as a system which desalinates seawater and sewage.
Production of production water s101 (industrial water) using sewage in the desalination system S100 is performed as follows. The salinity of sewage is about 0.1%.

The sewage is sent to MBR (Membrane Bioreactor) 101 to which the membrane separation activated sludge method is applied by pump p101, the activated sludge in the sewage is removed by MBR 101, and the MBR permeated water that has passed through MBR 101 is Water is sent to a low pressure RO membrane (Reverse Osmosis Membrane) 102 by a pump p102.
The MBR permeated water that has passed through the MBR 101 is low at a salt concentration of about 0.1%, so that the low pressure RO membrane 102 is a low pressure RO membrane of about 1 to 2 MPa (megapascal).

  The MBR permeated water sent by the pump p102 is desalinated by permeating the low-pressure RO membrane 102, almost half is produced as production water s101 (industrial water), and the other half is concentrated water s104 containing impurities such as salt. Separated and removed.

  On the other hand, concentrated water s104 having a volume of about ½ of sewage concentrated to a salt concentration of about 0.2% containing impurities such as salt removed by the low-pressure RO membrane 102 is sent from the low-pressure RO membrane 102 to the stirring tank 104. Is done.

Production of production water s102 (industrial water) from seawater in the desalination system S100 is performed as follows. In addition, the salt concentration of seawater is about 3 to 4%.
Seawater is sent to a UF membrane (Ultrafiltration Membrane) 103 by a pump p103, and the particles are removed by the UF membrane 103 and sent to a stirring tank 104. In the agitation tank 104, the UF membrane-permeated seawater that has passed through the UF membrane 103 and the concentrated water s104 having a volume of about ½ of the sewage concentrated from the sewage by the low-pressure RO membrane 102 are generated by stirring. The mixed water s103 is sent to the intermediate pressure RO membrane 105 by the pump p104.

The UF membrane permeated seawater that has passed through the UF membrane 103 has a salinity of 3 to 4%, but is diluted with concentrated water s104 having a salinity of about 0.2%. An RO membrane (reverse osmosis membrane) of about 3-5 MPa is used.
The mixed water s103 fed from the agitation tank 104 to the intermediate pressure RO membrane 105 by the pump p104 is desalinated by passing through the intermediate pressure RO membrane 105, and about half of the production water s102 (industrial water) is desalinated. ) And the remaining half is separated and removed as brine s105 containing impurities such as salt. That is, the production water s102 (industrial water) is produced with a capacity of about 1/2 of seawater plus about 1/4 of sewage.

The brine s105 is separated and drained with a capacity of about 1/2 of seawater plus about 1/4 of sewage.
The pressure energy of the brine s105 is recovered as rotational energy by the power recovery device 106 and used as a power source (energy source) for sending pressure to the intermediate pressure RO membrane 105 of a part of the mixed water s103 that bypasses the pump p104. It is done.

As another conventional desalination system, there is a desalination system S200 shown in FIG.
The desalination system S200 is configured such that the sewage concentrated water s104 in the desalination system S100 of FIG. 7 is not sent to the stirring tank 204, and sewage desalination and seawater desalination are independently configured.

  In the desalination system S200, seawater has particles removed by the UF membrane 203, but is not diluted with the water sent from the sewage (sewage concentrate s104 in FIG. 7) in the stirring tank 204, so the salinity is about 3 to 3. As high as 4%. Therefore, a high pressure RO membrane 205 which is a high pressure RO membrane (reverse osmosis membrane) of about 6 to 8 MPa is used.

  In the desalination system S200, sewage passes through the low-pressure RO membrane 202 to be desalinated, and about half of the sewage production water s201 (industrial water) is obtained. On the other hand, particles are removed from the seawater by the UF membrane 203, and are passed through the high-pressure RO membrane 205 to be desalinated, so that the production water s202 (drinking water) in half the amount of seawater is obtained.

Since the other configuration is the same as that of the desalination system S100 of FIG. 7, constituent elements of the desalination system S100 are indicated by reference numerals in the 200s and detailed description thereof is omitted.
In addition, there exists patent document 1 as a prior art document which concerns on this application.

Japanese Patent No. 4,481,345

Incidentally, the conventional desalination systems S100 and S200 have the following problems.
First, it is difficult to cope with a case where needs for industrial water and drinking water are large. For example, in the desalination system S100 of FIG. 7, although industrial water can be increased, the concentrated water s104 is fed to the agitation tank 104 in the seawater desalination process, so that drinking water cannot be taken.
On the other hand, in the desalination system S200 of FIG. 8, although drinking water (product water s202) can be taken, when it is going to increase industrial water, it is necessary to increase the amount of sewage intake. Therefore, it is difficult to increase the amount of industrial water in areas where the amount of sewage is limited.

  2ndly, when the fluctuation | variation of the inflow of sewage is large in desalination system S100, S200, it is not the structure corresponding to the fluctuation | variation of the inflow of sewage. Therefore, it cannot cope with fluctuations in the amount of inflow of sewage.

Thirdly, it is cheaper to desalinate sewage. However, since the sewage is not configured to be used effectively, the cost of the entire system is likely to increase.
For example, in the desalination system S200 of FIG. 8, half of the collected sewage is produced water s201 (industrial water), but half is discharged out of the system as brine. On the other hand, in the desalination system S100 of FIG. 7, half of the sewage is produced water s101 (industrial water) and half of the sewage concentrated water s104 is half produced water s102 (industrial water). Half of this is discharged out of the system as brine.
As a result, 3/4 of the sewage is used as industrial water, but the sewage is not effectively used as much as possible in the desalination system S100.

  On the other hand, since it is expensive to increase the amount of seawater intake instead of sewage, increasing the amount of seawater intake causes an increase in the water production cost of the entire system.

  In view of the above situation, an object of the present invention is to provide a desalination system and a desalination method capable of effectively using sewage as much as possible and reducing the water production cost of the entire system.

  In order to achieve the above object, a desalination system according to the first aspect of the present invention is a desalination system that desalinates sewage and seawater, a purification device that permeates and purifies the sewage, and a permeation through the purification device. The first RO membrane that permeates the permeated water and the salt content thereof is contained and removed in the first concentrated water and generates industrial water, and the first concentrated water is at least concentrated and filtered through an NF membrane. The first pretreatment apparatus in which any one of the pretreatment is performed and the first water to be treated that has been pretreated in the first pretreatment apparatus are permeated, and the salt content thereof is the second concentration. And a second RO membrane that is contained in water and removed and generates industrial water.

  The desalination method according to the third aspect of the present invention is a method for realizing the desalination system according to the first aspect of the present invention.

  A desalination system according to the second aspect of the present invention is a desalination system that desalinates sewage and seawater, and purifies the sewage through and purifies the sewage, and permeates the permeated water that has passed through the purifier. A plurality of RO membranes that produce industrial water while the salt content is contained and removed in the concentrated water, and the concentrated water removed by any of the plurality of RO membranes is at least of concentrated filtration and NF membrane filtration One or a plurality of pre-processing devices in which any pre-processing is performed.

  The desalination method according to the fourth aspect of the present invention is a method for realizing the desalination system according to the second aspect of the present invention.

  According to the desalination system and the desalination method of the present invention, it is possible to realize a desalination system and a desalination method capable of effectively using sewage as much as possible and reducing the water production cost of the entire system.

It is a notional block diagram of the desalination system of Embodiment 1 which concerns on this invention. It is a notional block diagram of the desalination system of the modification of Embodiment 1. FIG. It is a notional block diagram of the desalination system of Embodiment 2. FIG. It is a notional block diagram of the desalination system of the deformation | transformation form of Embodiment 2. FIG. It is a notional block diagram of the desalination system of Embodiment 3. FIG. It is a notional block diagram of the desalination system of the deformation | transformation form of Embodiment 3. FIG. It is a notional block diagram which shows the conventional desalination system. It is a notional block diagram which shows the other conventional desalination system.

Embodiments of the present invention will be described below with reference to the accompanying drawings.
<< Embodiment 1 >>
FIG. 1 is a conceptual configuration diagram of a desalination system according to Embodiment 1 of the present invention.
The desalination system S of Embodiment 1 includes an industrial water freshwater generation system Sa for freshening industrial water s1 and s2 from sewage, and a drinking water freshwater generation system Sb for freshening drinking water s3 from seawater. It has.

  Industrial desalination system Sa of desalination system S generates industrial water s1, MBR (Membrane Bioreactor) 1 that permeates sewage to remove and purify solids and bacteria, and sewage that permeates sewage. And a first low-pressure RO membrane (Reverse Osmosis Membrane) 2 that removes impurities such as salt and ions contained in the water and desalinates it.

  Furthermore, in order to produce the industrial water s2, the industrial water freshwater generation system Sa allows the sewage concentrated water s6a separated by the first low-pressure RO membrane 2 to pass therethrough, and the pretreatment device 3 performs flocculation filtration and / or NF treatment. The second low-pressure RO membrane (Reverse Osmosis Membrane) 4 that permeates the treated water s7a pretreated by the pretreatment device 3 to remove impurities such as salt and ions contained in the treated water s7a and desalinates it. And.

MBR1 performs solid-liquid separation and purifies by removing solids and bacteria from sewage.
The RO membrane (reverse osmosis membrane) is a semipermeable membrane that allows water to pass through but does not allow low-molecular substances such as salt or ions to pass through. Since the first low-pressure RO membrane 2 has a low sewage salinity concentration of about 0.1%, by allowing the sewage to pass through (filtering), the salinity and the like can be reduced at a relatively low permeation pressure of about 1-2 MPa (megapascal). It is a low-pressure RO membrane to be removed.

The pretreatment device 3 has a function of coagulation filtration and / or NF treatment.
In the coagulation filtration of the pretreatment device 3, the sewage concentrated water s6a is coagulated and filtered to reduce the scale, or harmful substances such as cyan (CN) compounds and heavy metals such as chromium are removed.
The NF process of the pretreatment device 3 is a process using an NF film. NF membrane (Nanofiltration Membrane) is selective to elements and ions, and allows sewage to permeate (filter), thereby toxic cyanide (CN) compounds and other low molecular impurities and microorganisms To cut.

  Since the second low-pressure RO membrane 4 has a low salinity concentration of about 0.2% of the water to be treated s7a, it allows a relatively low permeation pressure of about 1 to 2 MPa (megapascal) by allowing sewage to pass through (filtering). This is a low-pressure RO membrane that removes salt and the like.

On the other hand, the drinking water fresh water generation system Sb which produces fresh drinking water in the desalination system S has the following configuration.
The drinking water freshwater generation system Sb uniformly mixes a UF membrane (Ultrafiltration Membrane) 5 that permeates seawater to remove particles contained in seawater, and seawater that has permeated through the UF membrane 5 to remove particles. And a high-pressure RO membrane 7 that removes impurities such as salt and ions contained in the seawater from which particles have been removed and made uniform, and desalinates the water.

The UF membrane (ultrafiltration membrane) 5 permeates (filters) seawater to perform screening at the molecular level according to the pore size of the membrane and the size of the molecules to be removed in the seawater, thereby removing particles in the seawater. To do.
Since the high-pressure RO membrane 7 has a seawater salinity of about 3 to 4%, it allows seawater to permeate (filter) at a relatively high seawater permeation pressure of about 6 to 8 MPa (megapascals). It is a high-pressure RO membrane (reverse osmosis membrane) that removes and the like.

Next, the process of making industrial water s1, s2 from sewage in the industrial water freshwater generation system Sa of the desalination system S will be described.
The sewage is pumped into the industrial water desalination system Sa by the pump p1 and fed to the MBR1. Sewage passes through MBR1 to remove activated sludge flocs and bacteria.

The MBR permeated water s5a that has passed through the MBR1 is sent to the first low-pressure RO membrane 2 by the pump p2, and passes through the first low-pressure RO membrane 2, thereby concentrating sewage containing impurities such as salt and ions. Water s6a is removed and desalinated to produce industrial water s1.
The industrial water s1 is obtained about 1/2 of the sewage, while the remainder of the sewage, that is, about 1/2 of the sewage is removed as the sewage concentrated water s6a containing impurities such as salt and ions.

  The sewage concentrated water s6a separated by the first low-pressure RO membrane 2 is sent to the pretreatment device 3, where it is subjected to coagulation filtration and / or NF treatment to remove scales and cyanide compounds. . The treated water s7a, in which the sewage concentrated water s6a is pretreated by the pretreatment device 3, is sent to the second low-pressure RO membrane 4 by the pump p3 and permeates the second low-pressure RO membrane 4, thereby allowing the salinity and The treated concentrated water s6b containing impurities such as ions is removed and desalinated, and industrial water s2 is produced.

The industrial water s2 is obtained about 1/2 of the sewage concentrated water s6a, while the remainder of the sewage, that is, about 1/2 of the sewage concentrated water s6a is removed as the treated concentrated water s6b containing impurities such as salt and ions. Is done. Since the sewage concentrated water s6a is about 1/2 of the sewage, the industrial water s2 is obtained about 1/4 of the sewage.
As a result, about half of the sewage can be obtained as the industrial water s1, and about ¼ of the sewage can be obtained as the industrial water s2, so that industrial water having a capacity of about 3/4 of the sewage can be taken.

Next, the process of making the drinking water s3 from the seawater in the drinking water freshwater generation system Sb of the desalination system S will be described.
Seawater is pumped into the drinking water freshwater generation system Sb by the pump p4 and fed to the UF membrane 5. Seawater passes through the UF membrane 5 to remove particles in the seawater. The UF membrane-permeated seawater s5b, which is seawater from which particles have been removed by the UF membrane 5, is stirred and made uniform in the stirring tank 6.

Then, the stirred UF membrane permeated seawater s5b is sent to the high pressure RO membrane 7 by the pump p5. By passing through the high-pressure RO membrane 7, the UF membrane-permeable seawater s5b is produced as a brine s8 containing almost half of the salt and impurities such as ions, and the other half is produced as desalinated drinking water s3.
Therefore, drinking water s3 that is about half the amount of seawater can be taken.

According to the desalination system S of the first embodiment, about 3/4 of the amount of industrial water can be taken by the industrial water desalination system Sa, and the drinking water desalination system Sb can increase the intake of inexhaustible seawater. By doing so, the drinking water can be increased.
Therefore, it can be adapted when the needs of industrial water and drinking water are great.

  Further, even when the fluctuation of the inflow amount of sewage is large, since about 3/4 of the industrial water can be taken, it can be dealt with by storing the taken industrial water. Furthermore, even when the amount of sewage is small, since about 3/4 of the amount of industrial water can be taken, a large amount of industrial water can be taken by effectively using the small amount of sewage. Therefore, the reuse rate of sewage can be increased.

  In addition, since the sewage concentrated water s6a is subjected to coagulation filtration and / or NF treatment in the pretreatment device 3 before passing through the second low pressure RO membrane 4, clogging occurs in the second low pressure RO membrane 4 in the subsequent stage. Is prevented in advance.

  In addition, in Embodiment 1, although the case where the desalination system S was equipped with the industrial water desalination system Sa and the drinking water desalination system Sb was illustrated and demonstrated, as shown in FIG. 2, desalination system S It is good also as a structure which comprises only industrial water fresh water generation system Sa in '.

<< Embodiment 2 >>
FIG. 3 is a conceptual configuration diagram illustrating the desalination system of the second embodiment.
In the desalination system 2S of the second embodiment, the second stage of the pretreatment device 3a and the third low-pressure RO membrane 4a are further added to the industrial desalination system Sa of the desalination system S of the first embodiment. The membrane is composed of three stages, and the pretreatment device is composed of two stages.
Since the other configuration is the same as that of the first embodiment, the same components are denoted by the same reference numerals as those of the first embodiment, and detailed description thereof is omitted.

  The desalination system 2S includes a three-stage low-pressure RO membrane and a two-stage pretreatment apparatus, and includes an industrial water-making water system 2Sa for producing industrial water s1, s2, s2a from sewage. Moreover, the desalination system 2S is equipped with the drinking water fresh water generation system Sb for making the drinking water s3 from seawater similarly to Embodiment 1. FIG.

  The industrial desalination system 2Sa of the desalination system 2S is a second pretreatment that pretreats the concentrated water s6b to be treated, which is removed by the second low-pressure RO membrane 4, in the industrial desalination system Sa of the first embodiment. The apparatus 3a and the 3rd low-pressure RO membrane 4a which permeate | transmits the 2nd to-be-processed concentrated water s7b pre-processed by the 2nd pre-processing apparatus 3a are further provided.

The second pretreatment device 3 a is a device that performs the same coagulation filtration and / or NF treatment as the pretreatment device 3.
As described above, the coagulation filtration of the second pretreatment device 3a is performed by coagulating and filtering the concentrated water s6b to be treated to reduce the scale, or remove harmful substances such as cyan (CN-) compounds and heavy metals such as chromium. To do.

As described above, the NF treatment of the second pretreatment device 3a is a treatment using an NF membrane. By passing the treated concentrated water s6b through the NF membrane, a low molecular weight compound such as a cyan (CN-) compound is obtained. Cut impurities and microorganisms.
Since the third low-pressure RO membrane 4a has a low sewage salt concentration of about 0.4%, the sewage is permeated (filtered) at a relatively low permeation pressure of about 1 to 2 MPa (megapascals), so that the salinity and the like can be reduced. It is a low-pressure RO membrane to be removed.

Next, the process of making industrial water s1, s2, s2a from sewage in the industrial water freshwater generation system 2Sa of the desalination system 2S shown in FIG. 3 will be described.
The sewage is pumped into the industrial water desalination system 2Sa by the pump p1 and fed to the MBR1. Sewage passes through MBR1 (and is filtered) to remove activated sludge flocs and bacteria.

The MBR permeated water s5a that has passed through the MBR1 is sent to the first low-pressure RO membrane 2 by the pump p2, and passes through the first low-pressure RO membrane 2, thereby concentrating sewage containing impurities such as salt and ions. Water s6a is removed and desalinated, and industrial water s1 is produced (generated).
The industrial water s1 is obtained about 1/2 of the sewage, while the remainder of the sewage, that is, about 1/2 of the sewage is removed as the sewage concentrated water s6a containing impurities such as salt and ions.

  The sewage concentrated water s6a separated by the first low-pressure RO membrane 2 is sent to the pretreatment device 3, where it is subjected to coagulation filtration and / or NF treatment to remove scales and cyanide compounds. . The treated water s7a, in which the sewage concentrated water s6a is pretreated by the pretreatment device 3, is sent to the second low-pressure RO membrane 4 by the pump p3 and permeates the second low-pressure RO membrane 4, thereby allowing the salinity and The treated concentrated water s6b containing impurities such as ions is removed and desalinated to produce (produce) industrial water s2.

The industrial water s2 is obtained about 1/2 of the water to be treated s7a, while the remaining amount of the water to be treated s7a, that is, about 1/2 of the water to be treated s7a contains the concentration of impurities such as salt and ions. It is removed as s6b.
Since the to-be-processed water s7a is about 1/2 of the sewage, the industrial water s2 is obtained about 1/4 of the sewage.

  The to-be-processed concentrated water s6b removed by the second low-pressure RO membrane 4 is sent to the second pretreatment device 3a, and is subjected to coagulation filtration and / or NF treatment in the second pretreatment device 3a. Cyanide compounds and the like are removed. The second treated water s7b obtained by pretreating the treated concentrated water s6b by the second pretreatment device 3a is sent to the third low-pressure RO membrane 4a by the pump p3a, and is passed through the third low-pressure RO membrane 4a. By permeating, the second treated concentrated water s6c containing impurities such as salt and ions is removed and desalinated, and industrial water s2a is produced (generated).

The industrial water s2a is obtained about ½ of the second treated water s7b, while the remainder of the second treated water s7b, that is, about ½ of the second treated water s7b is salt or ions. It removes as 2nd to-be-processed concentrated water s6c containing impurities, such as.
Since the second treated water s7b is about ¼ of sewage, industrial water s2a is obtained about ８ of sewage.

  As a result, about half of the industrial water s1 is obtained, about ¼ of the industrial water s2 is obtained, and about 下 of the industrial water s2a is obtained. About 7/8 capacity of industrial water can be taken.

According to the second embodiment, since the pretreatment device has two stages and the low-pressure RO membrane has three stages, a capacity of about 7/8 of sewage taken by industrial water is obtained, and more industrial water is obtained from the sewage. Can be produced.
Other functions and effects of the first embodiment are similarly achieved.

In the second embodiment, the case where the desalination system 2S includes the industrial water desalination system 2Sa and the drinking water desalination system Sb is illustrated. However, as shown in FIG. 4, the desalination system 2S ′ includes the industrial desalination system 2S ′. It is good also as a structure which comprises only the fresh water system 2Sa.
In the second embodiment, the pretreatment apparatus has two stages and the low pressure RO membrane has three stages. However, the pretreatment apparatus has three stages or more and the low pressure RO membrane has four stages or more. It is good also as a structure similar to the form 2. Thereby, more industrial water can be produced (generated) from sewage.

<< Embodiment 3 >>
FIG. 5 is a conceptual configuration diagram illustrating a desalination system according to the third embodiment.
The desalination system 3S of the third embodiment has a configuration in which the multi-stage pretreatment device described in the first and second embodiments and the industrial water amount switching means (switching means) for switching the multi-stage low-pressure RO membrane to an arbitrary number of stages are provided. It is a thing.
Since the other configuration is the same as the desalination systems S and 2S of the first and second embodiments, the same components are denoted by the same reference numerals as those of the first embodiment, and detailed description thereof is omitted.

  The desalination system 3S includes industrial water for producing industrial water s1, s2, s2a, s2b,... From the sewage by providing a plurality of low pressure RO membranes, a plurality of pretreatment devices, industrial water amount switching means, and the like. A fresh water generation system 3Sa and a drinking water fresh water generation system Sb for freshly forming drinking water s3 from seawater are provided.

  The first, second, third, and fourth low pressure RO membranes 2, 4, 4a, 4b,... Have sewage salinity concentrations of 0.1%, 0.2%, 0.4%,. Since it is low at about 8%,..., It is a low-pressure RO membrane that removes salt and the like by permeating (filtering) sewage at a relatively low permeation pressure of about 1 to 2 MPa (megapascal).

  The pretreatment device 3, the second pretreatment device 3a, the third pretreatment device 3b,... Are devices that perform coagulation filtration and / or NF treatment, respectively. In the coagulation filtration, as described above, brine (concentrated water) is coagulated and filtered to reduce the scale, or harmful substances such as cyan (CN-) compounds and heavy metals such as chromium are removed. In the NF treatment, as described above, brine (concentrated water) is permeated (filtered) through the NF membrane to cut low-molecular impurities such as cyan (CN-) compounds and microorganisms.

The industrial water amount switching means includes valves v1, v2,... And a switching control device 9 that switches the flow paths of the valves v1, v2, v3,.
The valves v1, v2, v3,... Are three-way valves, and are respectively from the first low-pressure RO membrane 2, the second low-pressure RO membrane 4, the third low-pressure RO membrane 4a, the fourth low-pressure RO membrane 4b,. The brine (concentrated water) is drained or switched to the pre-treatment device 3, the second pre-treatment device 3a, the third pre-treatment device 3b,. The valves v1, v2,... May be drained or flowed to a downstream pretreatment device, or the longer duration may be set to the normal state.

  The switching control device 9 is a control device that controls switching of the valves v1, v2, v3,..., And the valves v1, v2, v3,... Are respectively the first low-pressure RO membrane 2 and the second low-pressure RO membrane 4. , Whether the brine from the third low-pressure RO membrane 4a,... Is drained or passed to the pre-processing device 3, the second pre-processing device 3a, the third pre-processing device 3b,. Perform switching control.

  The switching control device 9 is stored in a controller (not shown) that controls the entire desalination system 3S. Specifically, the switching control device 9 includes a microcomputer, an interface circuit such as an A / C / D / C converter, a current control circuit that switches operations of the valves v1, v2, v3,. The The switching operation of the valves v1, v2, v3,... Is described in a control program stored in a ROM (Read Only Memory) of the microcomputer.

Control of the switching control device 9 is performed as follows.
As a first mode, the valve v1 is switched to the drain side. The other valves v2, v3,... May be switched to any side because the sewage concentrated water s6a is drained by the upstream valve v1.
Thereby, the industrial water s1 which MBR permeated water s5a permeate | transmitted the 1st low voltage | pressure RO membrane 2 is obtained from sewage.

In the second mode, only the valve v1 is opened to the second low-pressure RO membrane 4, while the valve v2 is switched to the drain side. The other valves v3,... May be switched to any side because the treated concentrated water s6b is drained by the upstream valve v2.
Thereby, the industrial water s1 in which the MBR permeated water s5a has permeated the first low-pressure RO membrane 2 and the water to be treated s7a pretreated by the pretreatment device 3 have permeated the second low-pressure RO membrane 4 from the sewage. Industrial water s2 is obtained.

As a third mode, the valves v1 and v2 are opened to the second low pressure RO membrane 4 and the third low pressure RO membrane 4a, respectively, while the valve v3 is switched to the drain side. The other valves may be switched to any side because the treated concentrated water s6c is drained by the upstream valve v3.
Thereby, the industrial water s1 in which the MBR permeated water s5a has permeated the first low-pressure RO membrane 2 and the water to be treated s7a pretreated by the pretreatment device 3 have permeated the second low-pressure RO membrane 4 from the sewage. Industrial water s2 and industrial water s2a in which the second treated water s7b pretreated by the second pretreatment device 3a has permeated the second low-pressure RO membrane 4a are obtained.

As a fourth mode, the valves v1, v2, and v3 are opened to the second low pressure RO membrane 4 and the third low pressure RO membrane 4a, respectively, while the other valves are switched to the drain side.
Thereby, the industrial water s1 in which the MBR permeated water s5a has permeated the first low-pressure RO membrane 2 and the water to be treated s7a pretreated by the pretreatment device 3 have permeated the second low-pressure RO membrane 4 from the sewage. Industrial water s2, industrial water s2a in which the second treated water s7b pretreated by the second pretreatment device 3a has permeated the second low-pressure RO membrane 4a, and pretreatment by the third pretreatment device 3b The third treated water s7c thus made passes through the fourth low-pressure RO membrane 4b to obtain industrial water s2a. Note that the third treated concentrated water s6d is removed from the fourth low-pressure RO membrane 4b.
Similarly, industrial water can be increased by opening an arbitrary number of valves on the low-pressure RO membrane side.

According to the third embodiment, the valves v1, v2, v3,... For switching whether to drain or drain the brain (concentrated water) to the plurality of stages of low-pressure RO membranes, the plurality of stages of pretreatment devices, and the next-stage low-pressure RO membranes. Since the switching control device 9 for controlling the switching of the valve is provided, the amount of industrial water to be taken can be freely changed depending on the amount of demand for industrial water and the amount of sewage.
Other functions and effects of the first and second embodiments are similarly achieved.

  In the third embodiment, the case where the desalination system 3S includes the industrial water desalination system 3Sa and the drinking water desalination system Sb is illustrated. However, as shown in FIG. It is good also as a structure which comprises only the fresh water system 3Sa.

  Further, in the industrial water amount switching means described in the third embodiment, the pretreatment apparatus has two stages and the low pressure RO membrane has three stages. However, the pretreatment apparatus has three stages or more, and the low pressure RO has three stages. It is good also as a structure similar to Embodiment 2 which makes a film | membrane 4 steps or more. Thereby, more industrial water can be produced from sewage.

  Of course, the configuration of the industrial water amount switching means (switching means) (valves v1, v2, v3,..., Switching control device 9) described in the third embodiment can be applied to the first and second embodiments.

Moreover, in the said embodiment, although MBR1 was illustrated as a purification apparatus which purifies sewage, purification apparatuses other than MBR, such as a natural precipitation method, sand filtration, and disinfection, may be applied.
In addition, the numerical value used by description of the said embodiment shows an example, and is not limited to these numerical values.

1 MBR (Purification device)
2 First low-pressure RO membrane (first RO membrane, RO membrane)
3 Pre-processing device (first pre-processing device, pre-processing device)
3a Second pretreatment device (second pretreatment device, pretreatment device)
3b Third pretreatment device (first pretreatment device, pretreatment device)
4 Second low-pressure RO membrane (second RO membrane, RO membrane)
4a Third low-pressure RO membrane (third RO membrane, RO membrane)
4b Fourth low pressure RO membrane (fourth RO membrane, RO membrane)
5 UF membrane 7 High-pressure RO membrane (RO membrane)
9 Switching control device (switching means)
S, 2S, 3S, S ', 2S', 3S 'desalination system s1, s2, s2a, s2b Industrial water s3 Drinking water s5a MBR permeated water (permeated water)
s5b UF membrane permeated seawater (treated water)
s6a Sewage concentrated water (first concentrated water, concentrated water)
s6b Processed concentrated water (second concentrated water, concentrated water)
s6c Second treated concentrated water (third concentrated water, concentrated water)
s6d Third treated concentrated water (concentrated water)
s7a treated water (first treated water)
s7b Second treated water (second treated water)
v1, v2, v3 valves (switching means)

Claims (10)

A desalination system that desalinates sewage and seawater,
A purification device for permeating and purifying the sewage,
A first RO membrane that permeates the permeated water that has passed through the purification device, the salt content of which is contained and removed in the first concentrated water, and generates industrial water;
A first pretreatment device in which the first concentrated water is subjected to at least a pretreatment of concentration filtration and NF membrane filtration;
A second RO membrane that permeates the first water to be treated that has been pretreated by the first pretreatment device, the salt content of which is contained and removed in the second concentrated water, and generates industrial water; A desalination system characterized by comprising: A second pretreatment device in which the second concentrated water is subjected to at least one of pretreatment of concentration filtration and NF membrane filtration;
A third RO membrane that permeates the second treated water that has been pretreated by the second pretreatment device and removes the salt contained in the third concentrated water and generates industrial water; The desalination system according to claim 1, comprising: A desalination system that desalinates sewage and seawater,
A purification device for permeating and purifying the sewage,
A plurality of RO membranes that permeate the permeated water that has passed through the purification device, and whose salt content is contained and removed in the concentrated water and that generates industrial water;
The concentrated water removed by any of the plurality of RO membranes comprises at least one or a plurality of pretreatment devices for performing any pretreatment of concentration filtration and NF membrane filtration. Desalination system. The switching device according to claim 1, further comprising: a switching unit that switches between draining the concentrated water and flowing it to the downstream pretreatment device downstream of the concentrated water removed by the RO membrane. The desalination system as described in any one of them. A UF membrane that permeates the seawater to remove particles in the seawater;
The RO membrane which permeate | transmits the treated water which permeate | transmitted the said UF membrane, removes the salt of the said treated water, and produces | generates drinking water is provided, The one of Claims 1-4 characterized by the above-mentioned. The desalination system according to one item. A desalination method for desalinating sewage and seawater,
The sewage is passed through the purification device and the first RO membrane to produce industrial water,
The first concentrated water removed by the first RO membrane is subjected to at least a pretreatment of either concentration filtration or NF membrane filtration, and then passed through the second RO membrane to supply industrial water. The desalination method characterized by producing | generating. The second concentrated water removed by the second RO membrane is subjected to at least a pretreatment of either concentration filtration or NF membrane filtration, and then passes through the third RO membrane to supply industrial water. It produces | generates. The desalination method of Claim 6 characterized by the above-mentioned. A desalination method for desalinating sewage and seawater,
Purifying the sewage through a purification device,
The process of generating the industrial water by permeating the permeated water that has passed through the purification device to the RO membrane, and the pre-treatment of at least one of the concentration filtration and the filtration of the NF membrane as the concentrated water removed by the RO membrane A desalination method characterized by repeatedly performing the process in which water is discharged. The downstream of the concentrated water side removed by the RO membrane, the concentrated water is switched between draining or flowing to the pretreatment performed downstream. The desalination method as described in any one of Claims. The desalination method according to any one of claims 6 to 9, wherein the seawater is passed through a UF membrane and an RO membrane to generate drinking water.

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