WO2013031544A1

WO2013031544A1 - Desalinization system and desalinization method

Info

Publication number: WO2013031544A1
Application number: PCT/JP2012/070794
Authority: WO
Inventors: 暁佐々木; 能登　一彦; 関根　康記; 光太郎北村
Original assignee: 株式会社日立プラントテクノロジー
Priority date: 2011-08-26
Filing date: 2012-08-16
Publication date: 2013-03-07
Also published as: SG2014003578A; JP2013043153A; TW201309597A; IN2014CN01450A

Abstract

The desalinization system (S) in the first present invention, which converts seawater and wastewater to fresh water, is provided with a heat exchanger (6) that exchanges heat between wastewater or treated wastewater and seawater. The desalinization system (S) in the second present invention, which also converts seawater and wastewater to fresh water, is provided with the following: a membrane-separation activated-sludge treatment device (1) that treats wastewater using a membrane-separation activated-sludge method; a first RO membrane (2) that removes salt from the output (s5a) of the membrane-separation activated-sludge treatment device (1) by transferring said salt to first concentrated water (s6), thereby producing industrial-use water (s1); a UF membrane (3) that seawater passes through and that removes particulates from said seawater; a second RO membrane (5), to which treated water (s5b) that has passed through the UF membrane (3) is sent, whereby salt is removed from said treated water (s5b) and transferred to second concentrated water (s7), thereby producing drinking water (s2); and a heat exchanger (6) that exchanges heat between the wastewater or treated wastewater (s5a, s6, s1) and seawater.

Description

Seawater desalination system and seawater desalination method

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

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 seawater desalination system S100 shown in FIG. 6 as a system which desalinates seawater and sewage.
Production of production water s101 (industrial water) using sewage in the seawater desalination system S100 is performed as follows. The salinity of sewage is about 0.1%.

Sewage is sent to MBR (Membrane Bioreactor) 101 to which membrane separation activated sludge method is applied by pump p101, activated sludge is removed by MBR101, and MBR permeated water that has permeated MBR101 is sent to low-pressure RO membrane by pump p102. (Reverse Osmosis Membrane: Reverse osmosis membrane) 102.
The MBR permeated water that has passed through the MBR 101 is low at a salinity 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. As separated and removed.

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 agitation tank 104. .

Production of industrial water as production water s102 from seawater in the seawater desalination system S100 is performed as follows. The salinity of seawater is about 3-4%.
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 stirred, and then pumped. Water is sent to the medium pressure RO membrane 105 by p104.

The UF membrane permeated seawater that has passed through the UF membrane 103 has a salinity of 3-4%, 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.

That is, the brine s105 is removed 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 example, there is a seawater desalination system S200 shown in FIG.
The seawater desalination system S200 is configured such that the sewage concentrated water s104 in the seawater desalination system S100 of FIG. 6 is not sent to the agitation tank 204, and sewage desalination and seawater desalination are configured independently. .

In the seawater desalination system S200, particles of the seawater are removed by the UF membrane 203, but are not diluted with the water from the sewage (the concentrated water s104 of the sewage in FIG. 6) in the stirring tank 204, so the salinity is about 3 It is 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 seawater 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, the seawater has its particles removed by the UF membrane 203, passes through the high-pressure RO membrane 205, and is desalinated, so that production water s203 (drinking water) in half the amount of seawater is obtained.
Since the other configuration is the same as that of the seawater desalination system S100 of FIG. 6, the components of the seawater desalination system S100 are denoted by reference numerals in the 200s and detailed description thereof is omitted.

The conventional seawater desalination system S100 (see FIG. 6) has the following advantages over the seawater desalination system S200 (see FIG. 7).

First, in the seawater desalination system S100 of FIG. 6, the waste water (concentrated water s104) separated and removed in the process of producing the production water s101 from the sewage is used in the process of producing the production water s102 from the seawater. Therefore, there is an advantage that the production amount of production water from seawater can be increased.
Specifically, when wastewater from the sewage (concentrated water s104) is not used, the production water from seawater has a capacity of about 1/2 that of seawater, but the volume of the sewage is increased to about 1/2. Therefore, a large amount of industrial water can be taken from the production water s102.

Second, seawater (salt concentration of about 3 to 4%) is added to the concentrated water s104 (salt concentration of about 0.2%) separated by the low-pressure RO membrane 102 of the sewage, so the seawater is diluted and the salinity is increased. descend. Therefore, when wastewater from the sewage (concentrated water s104) is not used, seawater has a high salinity, so the high-pressure RO membrane 205 was necessary, but the medium-pressure RO was diluted with the concentrated water s104. The membrane 105 is sufficient, and the power of the pump p104 can be reduced as compared with the case of the high-pressure RO membrane 205.

This is because the permeation pressure of the medium pressure RO membrane is about 3 to 5 MPa, whereas the permeation pressure of the high pressure RO membrane is about 6 to 8 MPa. Requires more power (energy).
In addition, there exists patent document 1 as a prior art document which concerns on this application.

Japanese Patent No. 4481345

Incidentally, the conventional seawater desalination systems S100 and S200 have the following problems.
First, the permeability of the UF membrane or RO membrane is highly dependent on the temperature of the permeated liquid.
Seawater desalination systems S100 and S200 desalinate seawater, but the seawater may be cold in some countries and regions. In this case, in the seawater desalination system S100, the seawater permeability of the UF membrane 103 and the medium pressure RO membrane 105 is reduced due to an increase in viscosity due to low temperature seawater. Therefore, extra power is required for the pumps p103 and p104 to allow low temperature seawater to permeate the UF membrane 103 and the medium pressure RO membrane 105, resulting in a problem that the power is increased.

Similarly, in the seawater desalination system S200, the seawater permeability of the UF membrane 203 and the high-pressure RO membrane 205 decreases due to low-temperature seawater. Therefore, in order to permeate low-temperature seawater through the UF membrane 203 and the high-pressure RO membrane 205, the power of the pumps p203 and p204 is necessary and there is a problem that the power increases.

Secondly, the concentrated water s104 separated by the low-pressure RO membrane 102 of the seawater desalination system S100 is pumped by the pump p102, but the pressure energy of the concentrated water s104 is not utilized. Similarly, the brine s202 separated by the low pressure RO membrane 202 of the seawater desalination system S200 is pressurized by the pump p202, but the pressure energy of the brine s202 is not utilized.
Therefore, it cannot be said that energy is used effectively.

Third, the seawater desalination systems S100 and S200 have four pumps, which require pump manufacturing costs, installation costs, maintenance costs, etc., and may increase costs.

In view of the above circumstances, an object of the present invention is to provide a seawater desalination system and a seawater desalination method that can effectively use energy and have low energy costs.

In order to achieve the above object, a seawater desalination system according to claim 1 is a seawater desalination system for desalinating seawater and sewage, wherein the heat exchanger exchanges heat between the sewage or its treated water and the seawater. It has.
The seawater desalination method of claim 6 is a method for realizing the seawater desalination system of claim 1.

The seawater desalination system according to claim 2 is a seawater desalination system for desalinating seawater and sewage, wherein the membrane separation activated sludge treatment apparatus treats the sewage by a membrane separation activated sludge method, and the membrane separation activated sludge. The permeated water that has passed through the treatment device is permeated, and the salt content thereof is contained in the first concentrated water to be removed, and at the same time, the first RO membrane that generates industrial water and the seawater are permeated to remove particles in the seawater. The UF membrane to be removed, the second RO membrane that allows the treated water that has passed through the UF membrane to pass through, the salt content of the treated water is contained and removed in the second concentrated water, and generates drinking water, and the sewage Or the heat exchanger which heat-exchanges with the treated water and the said seawater is comprised.
The seawater desalination method of claim 7 is a method for realizing the seawater desalination system of claim 2.

According to the seawater desalination system and seawater desalination method of the present invention, a seawater desalination system and seawater desalination method that can effectively use energy and have low energy costs can be realized.

It is a notional block diagram of the seawater desalination system of Embodiment 1 which concerns on this invention. It is a conceptual diagram which shows the variation of the heat exchanger in the seawater desalination system of Embodiment 1, (a) is a conceptual diagram which shows the heat exchanger which sends seawater to the flow path of sewage, and heat-exchanges, (b) FIG. 2 is a conceptual diagram showing a heat exchanger that exchanges heat by sending sewage to a seawater channel, and (c) is a heat exchanger that exchanges heat by sending a heat medium to the sewage channel and seawater channel. FIG. It is a figure which shows the position which heat-exchanges sewage in the seawater desalination system of Embodiment 1. FIG. It is a notional block diagram which shows the seawater desalination system of Embodiment 2. FIG. It is a notional block diagram which shows the seawater desalination system of Embodiment 3. FIG. It is a notional block diagram which shows the conventional seawater desalination system. It is a notional block diagram which shows the other conventional seawater 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 seawater desalination system according to Embodiment 1 of the present invention.
The seawater desalination system S according to Embodiment 1 includes an MBR (Membrane Bioreactor) 1 that treats sewage by a membrane separation activated sludge method to produce industrial water s1 from sewage, and salt and ions contained in the sewage. And a low pressure RO membrane (Reverse Osmosis Membrane) 2 that removes impurities and desalinates the water.

MBR1 performs solid-liquid separation to separate and remove activated sludge 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. The low-pressure RO membrane 2 is a low-pressure RO membrane that removes the salinity and the like with a relatively low permeation pressure of about 1 to 2 MPa (megapascal) since the salinity of the sewage is as low as about 0.1%.

In addition, the seawater desalination system S has a UF membrane (Ultrafiltration Membrane) 3 that removes particles contained in seawater and a UF membrane 3 to remove particles in order to produce drinking water s2 from seawater. And a high-pressure RO membrane 5 that removes impurities such as salt and ions contained in the seawater agitated in the agitation tank 4 from which particles have been removed and desalinates the water. is doing. The agitation tank 4 also has a role of storing the seawater supplied to the pump p4 to enable stable operation of the pump p4.

The UF membrane (ultrafiltration membrane) 3 allows the seawater to permeate and performs molecular level sieving according to the pore size of the membrane and the molecular size of the substance to be removed in the seawater, thereby removing particles in the seawater.
The high-pressure RO membrane 5 is a high-pressure RO membrane that removes salt and the like with a relatively high permeation pressure and about 6 to 8 MPa (megapascal) because the salt concentration of seawater is about 3 to 4%.

By the way, since the sewage used for the seawater desalination system S flows in the ground, for example, in a temperate region, it is relatively warm and has a temperature of about 15 to 20 ° C. On the other hand, since the seawater used in the seawater desalination system S is exposed to the atmosphere, it is easily affected by climate change, that is, it is easily affected by temperature fluctuation, and it may be as low as about 10 ° C in the beginning of autumn. is there.
As described above, the UF membrane 3 and the high-pressure RO membrane 5 used for desalinating seawater have high temperature dependency of the permeated liquid, and the permeability is low when the temperature is low, while the permeability is high when the temperature is high. It tends to be high.

Therefore, the seawater desalination system S includes a heat exchanger 6 that performs heat exchange to give the heat of sewage to the seawater. Specifically, the heat exchanger 6 separates sewage flowing through the flow path r11 upstream of the MBR1 in the path for desalinating sewage and seawater flowing through the flow path r2 upstream of the UF membrane 3 in the path for desalinating seawater. Heat exchange is performed, and the heat of sewage is given to seawater by heat exchange.

The heat exchanger 6 is configured in various embodiments as follows.
FIG. 2 is a conceptual diagram showing variations of the heat exchanger in the seawater desalination system. FIG. 2A is a conceptual diagram showing a heat exchanger that exchanges heat by flowing seawater through a sewage flow path, and FIG. 2B is a conceptual diagram that shows a heat exchanger that exchanges heat by flowing sewage through a flow path of seawater. FIG. 2 (c) is a conceptual diagram showing a heat exchanger that exchanges heat by flowing a heat medium through a flow path of sewage and a flow path of seawater.
The heat exchanger 6A shown in FIG. 2 (a) causes the seawater in the flow path r2 upstream of the UF membrane 3 to flow in the sewage flow path r11 upstream of the MBR1, thereby exchanging the heat of the sewage by the heat exchange. It is the composition given to.

The heat exchanger 6B shown in FIG. 2 (b) causes the sewage heat to flow into the seawater by heat exchange by flowing the sewage of the flow path r11 upstream of the MBR1 into the flow path r2 of seawater upstream of the UF membrane 3. It is the structure which gives.
The heat exchanger 6C shown in FIG. 2 (c) pumps a liquid heat medium n that easily transfers heat into the sewage flow path r11 upstream of the MBR1 and the seawater flow path r2 upstream of the UF membrane 3. And the heat of the sewage in the flow path r11 upstream of the MBR1 is carried by the heat medium n and given to the seawater in the flow path r2 upstream of the UF membrane 3.
These are the heat exchangers 6 of a kind called shell & coil type or shell & tube type.

FIG. 1 illustrates the case where the heat exchanger 6 is disposed downstream of the pump p1 of the sewage flow path r11 and downstream of the pump p3 of the seawater flow path r2, but the heat exchanger 6 is Can be arranged regardless of the upstream and downstream of the pump p1 of the flow path r11, and can be arranged regardless of the upstream and downstream of the pump p3 of the seawater flow path r2.
Further, in the case of the heat exchanger 6A of FIG. 2A, the downstream side of the pump p3 of the seawater flow path r2 (see FIG. 1) is the pressure feeding force to the seawater sewage flow path r11 (in the flow path r11). (Pumping force to a coil or the like placed) is more preferable. In this case, the heat exchanger 6A may be disposed either upstream or downstream of the pump p1 of the sewage flow path r11.

Similarly, in the case of the heat exchanger 6B of FIG. 2B, the downstream of the pump p1 of the sewage flow path r11 (see FIG. 1) provides a pumping force to the sewage seawater flow path r2. More preferred. In this case, the heat exchanger 6B may be disposed either upstream or downstream of the pump p3 in the seawater flow path r2.
Of course, any type of heat exchanger, such as a counter flow heat exchanger, a parallel flow heat exchanger, or a cross flow heat exchanger, may be selected and used as the heat exchanger 6.

FIG. 3 is a diagram illustrating a position where the sewage exchanges heat with seawater in the seawater desalination system.
In the seawater desalination system S, the position where sewage is heat-exchanged with seawater is the position A of the sewage flow path r11 upstream of the MBR1, the position B of the flow path r12 after permeating the MBR1, and the low pressure RO membrane 2. Either the position C of the flow path r13 of the brine s6 or the position D of the flow path r14 after passing through the low-pressure RO membrane 2 may be used.
However, the upstream side of the sewage flow path is thermally preferable in the order of the position A, the position B, the position C, and the position D on the upstream side because the sewage has more heat.

Next, in the seawater desalination system S shown in FIG. 1, the process of making industrial water s1 from sewage will be described.
The sewage is pumped into the seawater desalination system S by the pump p1, exchanges heat with the seawater flowing through the flow path r2 via the heat exchanger 6, gives heat to the seawater, and is sent 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 low-pressure RO membrane 2 by the pump p2, and passes through the low-pressure RO membrane 2, thereby removing the brine s6 containing impurities such as salt and ions, and desalinating it. Industrial water s1 is produced.
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 brine s6 containing impurities such as salt and ions.

Next, in the seawater desalination system S, the process of making drinking water s2 which is production water from seawater will be described.
The seawater is pumped into the seawater desalination system S by the pump p 3, warmed by the heat of the sewage through the heat exchanger 6, and fed to the UF membrane 3. Seawater warmed by the heat exchanger 6 passes through the UF membrane 3 and particles in the seawater are removed. The UF membrane permeated seawater s5b, which is seawater from which particles have been removed by the UF membrane 3, is stirred and made uniform in the stirring tank 4.

Then, the stirred UF membrane permeated seawater s5b is sent to the high pressure RO membrane 5 by the pump p4. By passing through the high-pressure RO membrane 5, the UF membrane-permeated seawater s5b is produced as a brine s7 containing almost half of the salt or impurities such as ions, and the other half is produced as desalinated drinking water s2.

According to the seawater desalination system S of the first embodiment, in the heat exchanger 6, low-temperature seawater recovers and heats the heat of sewage at a temperature higher than seawater. Each RO membrane 5 can be easily and satisfactorily permeated.
In connection with this, each motive power of the pumps p3 and p4 for pumping seawater can be reduced. Therefore, energy saving of the seawater desalination system S can be realized.

<< Embodiment 2 >>
FIG. 4 is a conceptual configuration diagram illustrating the seawater desalination system according to the second embodiment.
The seawater desalination system 2S according to the second embodiment is provided with an energy recovery device 21 that recovers pressure energy of the brine s6 of the seawater desalination system S according to the first embodiment.
Since other configurations are the same as the seawater desalination system S 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 seawater desalination system 2S includes an energy recovery device 21 that recovers the pressure energy of the brine s6 removed by the low-pressure RO membrane 2 as electrical energy or rotational energy (mechanical energy).
The energy recovery device 21 recovers mechanical energy as electrical energy (electric power) by, for example, generating small hydraulic power from the pressure energy of the brine s6 using a water wheel or a gear. The electric power recovered by the energy recovery device 21 is used as electric power of a pump p3 that pumps seawater to the UF membrane 3 (indicated by a broken line in FIG. 4). In addition, you may divert not to use as electric power of pump p3 but to other electric power.

Alternatively, the energy recovery device 21 recovers the pressure energy of the brine s6 as rotational energy (mechanical energy), applies it to the seawater flowing through the UF membrane 3, and does not include the pump p3.
Alternatively, when the rotational energy (mechanical energy) recovered by the energy recovery device 21 is not large, a pump p3 may be provided to reduce the power of the pump p3.
Or it is good also as a structure which gives the pressure of the brine s6 directly to the seawater which flows into the UF membrane 3 as the energy recovery apparatus 21 of a known pressure direct conversion system.
The rotational energy (mechanical energy) and pressure energy recovered by the energy recovery device 21 may be applied to other locations without being applied to the seawater flowing through the UF membrane 3.

According to the second embodiment, the pressure energy of the brine s6 is recovered by the energy recovery device 21, so that energy saving can be realized. Therefore, energy cost can be reduced.
In addition, in the seawater desalination system 2S of Embodiment 2, although the case where the heat exchanger 6 is provided is illustrated, you may comprise without providing the heat exchanger 6 in the area where the temperature of seawater is high.

<< Embodiment 3 >>
FIG. 5 is a conceptual configuration diagram illustrating the seawater desalination system according to the third embodiment.
The seawater desalination system 3S according to the third embodiment is configured such that the brine s6 separated by the low-pressure RO membrane 2 of the seawater desalination system S according to the first embodiment is merged with the seawater flow path r2.
Since other configurations are the same as the seawater desalination system S 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 seawater desalination system 3S merges the brine s6 separated by the low-pressure RO membrane 2 into the seawater flow path r2, and uses the pressure energy of the brine s6 to obtain a pumping force of seawater to the UF membrane 3. . For this reason, the pump p3 is not provided.
In this case, the production water s9 obtained from seawater is industrial water. The production water s9 may be used as drinking water.

According to the seawater desalination system 3S of the third embodiment, since the pump p3 is not provided, the manufacturing cost, the installation cost, the maintenance management cost, etc. of the pump p3 are eliminated, and the cost can be reduced.
In addition, when the pressure energy of the brine s6 is not large and the pumping force of seawater to the UF membrane 3 is insufficient, the pump p3 may be provided. In this case, since the power of the pump p3 can be reduced, energy saving can be achieved. Therefore, energy cost can be reduced.
In addition, in the seawater desalination system 3S of Embodiment 3, although the case where the heat exchanger 6 was provided was illustrated, you may comprise without providing the heat exchanger 6 in the area where the temperature of seawater is high.

<< Other Embodiments >>
In the first to third embodiments, the case where sewage and seawater are desalinated to produce industrial water and drinking water has been exemplified, but the present invention desalinates sewage and seawater to produce drinking water. The present invention is also applicable when industrial water is produced without water. For example, the present invention is also applicable to the case where a part of the sewage in FIG. 7 is introduced into a path for desalinating seawater to produce industrial water.
As described above, the present invention can be widely applied to any system that desalinates sewage and seawater.

1 MBR (Membrane separation activated sludge treatment equipment)
2 Low pressure RO membrane (first RO membrane)
3 UF membrane 5 High-pressure RO membrane (second O membrane)
6, 6A, 6B, 6C Heat exchanger 21 Energy recovery device S, 2S, 3S Seawater desalination system s1 Industrial water (treated water for sewage)
s2 Drinking water s5a MBR permeated water (permeated water, treated sewage water)
s5b UF membrane permeated seawater (treated water)
s6 brine (first concentrated water, treated sewage)
s7 brine (second concentrated water)

Claims

A seawater desalination system that desalinates seawater and sewage,
A seawater desalination system comprising a heat exchanger for exchanging heat between the sewage or its treated water and the seawater.
A seawater desalination system that desalinates seawater and sewage,
A membrane separation activated sludge treatment apparatus for treating the sewage by a membrane separation activated sludge method;
A first RO membrane that permeates the permeated water that has passed through the membrane-separated activated sludge treatment device, the salt content of which is contained and removed in the first concentrated water, and generates industrial water;
A UF membrane that permeates the seawater to remove particles in the seawater;
A second RO membrane that allows the treated water that has permeated through the UF membrane to pass through, the salt content of the treated water is contained and removed in the second concentrated water, and generates drinking water;
A seawater desalination system comprising a heat exchanger for exchanging heat between the sewage or treated water thereof and the seawater.
The heat exchanger is
Of the seawater upstream of the UF membrane, sewage upstream of the membrane separation activated sludge treatment device, permeated water that has passed through the membrane separation activated sludge treatment device, the first concentrated water, or the generated industrial water The seawater desalination system according to claim 2, wherein heat exchange is performed with any of the above.
The seawater desalination system according to claim 2, further comprising an energy recovery device that recovers pressure energy of the first concentrated water.
The seawater desalination system according to claim 2 or 3, wherein the first concentrated water is merged with the seawater upstream of the UF membrane.
A seawater desalination method for desalinating seawater and sewage,
Heat exchange is performed between the sewage or treated water in the process of desalinating the seawater and the seawater.
A seawater desalination method for desalinating seawater and sewage,
Heat exchange between the sewage or treated water in the process of desalinating it and the seawater;
The sewage is passed through the membrane separation activated sludge treatment device and the first RO membrane to produce industrial water,
A seawater desalination method, wherein the seawater is passed through a UF membrane and a second RO membrane to produce drinking water.
The seawater desalination method according to claim 7, wherein pressure energy of the first concentrated water removed by the first RO membrane is recovered.
The seawater desalination method according to claim 7, wherein the first concentrated water removed by the first RO membrane is joined to the seawater upstream of the UF membrane.