JPH11207155A - Desalination device for sea water cr the like - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively subject waste backwashing water of a sand filter to membrane filtering treatment by a spiral membrane module and to subject permeated water to desalinating treatment by a RO device. SOLUTION: In a desalination device wherein after sea water is membrane filtered by a spiral membrane module, it is subjected to desalinating treatment by a RO device, the spiral membrane module has a bag like separation membrane 10 wound around a shaft 20 to form a wound body, and raw water is fed from one end face of the wound body and permeated water and concentrated water are taken out from the other end face of the wound body. The bag like membrane 10 is constituted of an ultrafiltration membrane or precision filtration membrane not having salt content removability at all or hardly having it. The bag like membrane 10 is that having the shape of a square or a rectangle, and it has a first side part 11, a second side part 12, a third side part 13, and a fourth side part 14. In the first side part 11, the second side part 12, and the third side part 13, separation membrane films are adhered to each other by adhesive or the like, and in the fourth side part 14, only a part thereof is adhered.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a method for removing most of the total dissolved solids (TDS) such as seawater to obtain fresh water.
The present invention relates to a desalination apparatus using a reverse osmosis membrane separation device (RO device).

[0002]

2. Description of the Related Art In a seawater desalination apparatus, a pretreatment apparatus is installed in order to prevent the deterioration of performance due to accumulation of suspended matter in seawater in a reverse osmosis membrane separation apparatus (RO apparatus) and maintain the performance. Conventionally, a pre-treatment device has been configured by arranging a sand polishing filter in front of the high-pressure pump and a sand double-layer filter in front of the sand filtration filter.

[0003] In such a conventional pretreatment device, a flocculant such as an iron salt for coagulating suspended matter in the seawater into the seawater supplied to the device, and bacteria grow in the filter layer of the two-layer filter. Therefore, it is necessary to add a germicide to each of the chemical injection devices in order to prevent the occurrence of the above problem, so that the operation cost is increased due to the chemical injection equipment and the cost of the chemicals, and the maintenance and management of the chemical injection must be performed. Further, since the filtration speed of the two-layer filter and the polishing filter is as low as 6 to 15 m / day, the apparatus becomes large, so that a large installation space is required. In addition, since seawater contains SS (suspended solids), the SS captured by the filter layer is removed in order to maintain the performance of the two-layer filter in the first stage of the pretreatment device and the polishing filter in the second stage. Washing requires about 20 to 30 minutes per wash, and when the SS concentration is high, the washing frequency is about once every 3 hours (8 times a day) with a two-layer filter. Since the polishing filter is used about once a day, the desalination operation must be interrupted during the total time, and the operation rate of the desalination apparatus decreases.

In order to eliminate such disadvantages, the present invention uses an improved spiral-type membrane module as a pretreatment device. Next, the configuration of a conventional spiral-type membrane module will be described with reference to FIG. I will explain.

FIG. 6 is a partially exploded perspective view showing the structure of a conventional spiral membrane module. A plurality of bag-shaped separation membranes 2 are wound around a water collecting pipe 1 via a mesh spacer 3.

The water collecting pipe 1 is provided with a slit-like opening communicating between the inside and the outside of the pipe. The separation membrane 2 has a bag shape,
The central part surrounds the water collection pipe 1. A channel material 4 made of a mesh spacer or the like is inserted inside the bag-shaped separation membrane 2, and the inside of the bag-shaped separation membrane (bag-shaped membrane) 2 is a permeated water channel.

A top ring 6 and an end ring 7 are provided at both ends of the wound body 5 of the bag-like membrane 2, and a brine seal 8 is provided around the outer periphery thereof.

The raw water flows into the raw water flow path between the bag-like membranes 2 from the front end face of the wound body 5, flows as it is in the longitudinal direction of the wound body 5, and concentrates from the rear end face of the wound body 5. Leaked as. While flowing through the raw water flow path, water permeates the bag-like membrane 2 and enters the inside thereof, flows into the water collecting pipe 1, and is taken out of the module from the rear end side of the water collecting pipe 1.

[0009]

As described above, seawater desalination using a conventional pretreatment apparatus has disadvantages in that the space for the pretreatment apparatus is large and the operation efficiency is low.

[0010] A first object of the present invention is to provide a desalination apparatus for seawater or the like having a pretreatment apparatus that overcomes such disadvantages.

By the way, the conventional spiral type membrane module shown in FIG. 6 has the following problems to be solved.

In order to increase the flow rate of the permeated water in the water collecting pipe 1, it is necessary to increase the diameter of the water collecting pipe 1, but in such a case, the diameter of the spiral membrane module also becomes large. The permeated water that has permeated into the bag-shaped membrane 2 flows to the water collecting pipe 1 while spirally flowing through the bag-shaped membrane 2.
The flow resistance in the bag-like membrane 2 is large. Moreover, the flow resistance near the slit portion of the water collecting pipe flowing into the water collecting pipe 1 from the inside of the bag-shaped membrane 2 is large. The flow rate of the raw water flowing through the raw water flow path decreases toward the downstream side. (The flow rate of raw water decreases as much as the raw water is concentrated.)
For this reason, the raw water flow velocity is low in the downstream of the raw water flow path,
Dirt easily adheres.

[0013] The present invention solves the above-mentioned conventional problems and desalination of seawater and the like can efficiently pretreat seawater and the like by using a spiral membrane module which does not require a water collecting pipe and has a low permeated water flow resistance. It is a second object to provide a device.

[0014]

SUMMARY OF THE INVENTION A desalination apparatus for seawater or the like according to the present invention is a desalination apparatus for seawater in which seawater is supplied to a reverse osmosis membrane separator by a high-pressure pump to obtain freshwater. A seawater desalination apparatus in which a seawater type membrane module is arranged and seawater to be supplied to a high-pressure pump is pretreated by the spiral seam type membrane module, and the spiral seam type membrane module winds the membrane around a shaft to form a wound body. The raw water is supplied from one end face of the wound body, and the permeated water is taken out from the other end face of the wound body.

In the apparatus of the present invention, seawater or the like can be efficiently pretreated by the spiral-type membrane module, and the backwashing time of the membrane module can be extremely short. It will be expensive.

Although the apparatus of the present invention is suitable for desalination of seawater, it can also be used for producing freshwater from salt water other than seawater, such as lake water and groundwater.

The spiral membrane module employed in the present invention is a spiral membrane module in which a permeated water flow path material is disposed inside a bag-like membrane, and a raw water flow path material is disposed between the bag-like membranes. The bag-like membrane is substantially rectangular with first, second, third and fourth sides, and the first, second and third sides are sealed and the fourth A part of the side part is an open part and the remaining part is a closed part, and a first side part orthogonal to the fourth side part is applied to a shaft to wind a bag-like membrane to form a wound body, The fourth side faces the rear end face of the wound body, the second side facing the fourth side faces the front end face of the wound body, between the bag-shaped films. The raw water flow path of the third
The entire side of the bag-shaped membrane is sealed, and in the fourth side, a portion overlapping with the open portion of the bag-shaped film is a closed portion, and a portion overlapping with the closed portion of the bag-shaped film is open. It is preferably a part.

In this spiral type membrane module, raw water flows into the raw water flow path from the front end face of the wound body. The raw water flows through the raw water flow path in a direction substantially parallel to the axis of the wound body, and then flows out as concentrated water from the raw water flow path opening at the rear end face of the wound body.

The water that has passed through the bag-like membrane flows in the bag-like membrane in a direction substantially parallel to the axis of the wound body, and flows out of the bag-shaped membrane opening at the rear end face of the wound body.

As described above, since the permeated water flows in the bag-shaped membrane in a direction parallel to the axis of the wound body, the water collecting pipe used in the conventional spiral membrane module becomes unnecessary. Then, there is no flow resistance when flowing into the water collecting pipe from inside the bag-shaped membrane, and the flow resistance of permeated water is reduced.

Since the water collecting pipe is eliminated, the length of the bag-like membrane in the winding direction can be increased by that much.
The membrane area can be expanded. And even if the length in the winding direction of the bag-like membrane is increased, the flow resistance of the permeated water does not increase,
The amount of permeated water can be increased.

Further, since the raw water flow path is opened only at a part of the rear end face of the wound body, the flow rate of the raw water (concentrated water) at the downstream side of the raw water flow path can be increased more than before. In addition, the adhesion of dirt in the downstream area of the raw water flow path can be prevented. Therefore, backwashing in a short time is sufficient.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A spiral type membrane module used in an embodiment of the present invention will be described below with reference to the drawings. FIG. 1A is a perspective view of a bag-like membrane of the spiral membrane module and a shaft around which the bag-like membrane is wound. FIGS. 1B and 1C respectively show B in FIG. 1A.
It is sectional drawing which follows the -B line and CC line. FIG. 2 is a sectional view showing a method of winding a bag-like membrane around a shaft, FIG. 3 is a perspective view showing an engagement relationship between a wound body and a socket, and FIG. 4 is a side view of a spiral membrane module.

As shown in FIG. 1, the bag-like membrane 10 is constituted by an ultrafiltration membrane or a microfiltration membrane having no or almost no salt removing ability. The bag-like film 10 has a square or rectangular shape, and includes a first side 11 and a second side 1.
2, a third side 13 and a fourth side 14.
In the first side 11, the second side 12, and the third side 13, the separation membrane films are bonded to each other with an adhesive or the like, and only a part of the fourth side 14 is bonded. In addition, as the bag-like film 10, one long film is folded in two at the second side 12, and the first side 1 is folded.
The first and third sides 13 and a part of the fourth side 14 may be bonded to each other.

From the middle of the fourth side portion 14 to the third side portion 13
The separation membrane films of the bag-like membrane 10 are not adhered to each other, and the opening portion 30 for permeated water outflow is formed. Further, from the middle of the fourth side portion 14 to the first side portion 11, the separation membrane films of the bag-like membrane 10 are adhered to each other, forming a closing portion 31 for preventing outflow of permeated water. I have.

A permeated water channel material (for example, a mesh spacer) 15 is inserted and arranged in the bag-like membrane 10.

On one surface of the bag-like film 10, an adhesive 1
6 is adhered and adhesives 17 and 18 are adhered to the other surface, and the bag-like film 10 is wound around the shaft 20. The adhesive 16 is applied along the first side 11, and the adhesive 17 is applied along the third side 13. The adhesive 18 is applied along the opening 30 for outflow of permeated water from the intermediate portion in the longitudinal direction of the fourth side portion 14 to the third side portion 13.

By winding a plurality of bag-shaped membranes 10 around the shaft 20, the overlapping bag-shaped membranes 10 are joined to each other at the portions of the adhesives 17 and 18 in a water-tight manner. Thus, a raw water flow path through which raw water (and concentrated water) flows is formed between the bag-shaped membranes 10. As the adhesive 18 cures, an open portion for flowing out the raw water (concentrated water) is formed on the rear end surface of the wound body on the inner peripheral side, and a closing portion for preventing raw water outflow is formed on the outer peripheral side. You.

Fins 19 extend from the boundary between the open portion 30 for permeate outflow and the closed portion 31 for permeate outflow prevention in the fourth side portion 14 toward the rear of the wound body. I have. The fins 19 are made of, for example, a synthetic resin film or sheet, and are preferably bonded to the bag-like film 10 by adhesion or the like.

By winding the bag-like membrane 10 around the shaft 20 via a raw water flow path material (mesh spacer) 29 as shown in FIG. 2, a wound body 24 is formed as shown in FIG. The fin 19 extends from the rear end face of the wound body 24. By providing the fins 19 at the same location on the fourth side portion 14 of each bag-like film 10, the fins 19
Are located equiradially from the axis of the winding body 24 and
The fins 19 form a ring-shaped protrusion by overlapping the 9. The rear end of the cylindrical socket 25 is inserted into the ring-shaped protrusion, and the socket 25 and the fin 19 are joined with an adhesive or the like. Note that the socket 25 may be externally fitted to the fin 19. Also, fin 1
A cutting groove may be formed on the rear end face of the wound body 24 along the line 9 by a lathe, and the end of the socket 25 may be embedded in the groove.

By joining the socket 25 and the fin 19 in this manner, a permeated water outflow area on the outer peripheral side of the rear end face of the wound body 24 and a concentrated water outflow area on the inner peripheral side of the socket 25 are defined. .

When the bag-like film 10 is wound around the shaft 20, as shown in FIG.
A raw water flow path material (mesh spacer) 29 is interposed between them. The raw water flow path is formed by interposing these mesh spacers 29.

As shown in FIG. 4, a top ring 26 and an end ring 27 are provided on the leading edge and the trailing edge of the wound body 24, respectively.
Is formed by a synthetic resin mold or the like, and the top ring 26 is formed.
A brine seal 28 is provided around the outer periphery of.

The desalination apparatus for seawater or the like according to the present invention is such that seawater or the like is pre-treated by the spiral membrane module configured as described above and then supplied to an RO apparatus to obtain desalination. FIG. 5 is a system diagram showing an example of this desalination apparatus. Seawater is supplied to a spiral membrane module 51 by a pump 50. As shown in FIG. 4, this seawater is supplied from the front end face of the wound body 24 to the bag-like membrane 10 as raw water.
It flows into the raw water channel between them. This raw water is wound 2
4 flows in the raw water flow path in a direction substantially parallel to the axis of
From the inner end face of the socket 25 at the rear end.
Then, while the raw water flows through the raw water flow path, the water permeates into the bag-like membrane 10, and the permeated water flows out from the outer peripheral side of the socket 25 on the rear end surface of the wound body 24.

The permeated water is supplied to the RO device 53 by the high-pressure pump 52 at a high pressure of, for example, 50 to 70 kg / cm ² , and is subjected to a desalination treatment. RO device 53 may be of any type, such as a single-stage desalination type or a two-stage desalination type. As the type of the RO device 53, a spiral type module is preferable as a type that does not easily cause clogging, but another type may be used. The permeated water of the RO device is taken out as fresh water.

In the spiral membrane module 51, the permeated water flows in the bag-like membrane 10 in a direction parallel to the axis of the wound body 24 and is taken out from the rear end face. There is no need for the water collection pipe used in the project. For this reason, the flow resistance when flowing from the bag-like membrane into the water collecting pipe is eliminated, and the permeated water flow resistance is significantly reduced.

The water collecting pipe is omitted, and the length of the bag-shaped membrane 10 in the winding direction can be increased by that much.
It is possible to increase the film area. Even if the length of the bag-like membrane in the winding direction is increased, the permeated water flow resistance does not increase,
The amount of permeated water can be increased.

In this spiral type membrane module, the outlet portion of the raw water flow path is provided only inside the socket 25, and the outlet (the most downstream part) of the raw water flow path is narrowed. The flow rate of the raw water (concentrated water) becomes sufficiently large also on the downstream side of the road, and the adhesion of dirt in the downstream area of the raw water flow path can be prevented. The area inside and outside the socket 25 (the length of the adhesive 18 in the side portion 14 direction) is preferably determined according to the water recovery rate of the spiral membrane module.

The spiral-wound membrane module can very efficiently perform the membrane separation treatment of seawater, and can sufficiently separate and remove fine suspended matter in seawater. As a result, the propagation of bacteria in the RO device is significantly reduced, and the addition of a bactericide is not required.

In the above embodiment, the permeated water outlet is arranged on the outer peripheral side of the socket 25,
Although the concentrated water outflow portion is disposed inside the inside, the inside of the socket 25 may be configured as the permeated water outflow portion, and the outer peripheral side of the socket 25 may be configured as the concentrated water outflow portion.

When performing the spiral membrane module backwash, for example, the bag-like membrane 1 of the spiral membrane module is used.
Gas pressure is applied to the permeated water flow path within 0. Then, the remaining permeated water in the bag-like membrane 10 flows into the raw water flow path between the bag-like membranes 10, and first, water backwashing is performed. When the gas supply is continued (gas is supplied continuously or intermittently), the amount of the remaining permeated water is reduced, and the permeated water and the gas flow back in a gas-liquid mixed state, whereby the gas-liquid mixed backwash is performed. . When the residual permeated water substantially disappears, only the gas flows back and gas backwashing is performed. This backwash is very short. For this reason, the operation efficiency of the desalination apparatus becomes extremely high.

[0042]

As described above, the desalination apparatus for seawater and the like according to the present invention pretreats seawater with the improved spiral membrane module and then desalinates the seawater with the RO apparatus. The module enables very efficient separation of fine turbidity in seawater, and does not require the addition of a flocculant because the fine turbidity required to be used in the conventional two-layer filter is flocculated. In addition, since a granular filter layer such as a conventional two-layer filter is not used, mud balls due to turbidity accumulated in the filter layer are not generated. Therefore, the proliferation of bacteria is reduced, so that it is not necessary to add a bactericide. For this reason, the maintenance of the medicine cost, the chemical injection equipment, and the chemical injection are all unnecessary, and the equipment cost and the operating cost are significantly reduced.

This spiral type membrane module has a large amount of permeated water and is compact. Further, since the backwashing time can be shortened, the operation efficiency of the desalination apparatus becomes extremely high.

[Brief description of the drawings]

FIG. 1A is a perspective view of a bag-like membrane of a spiral-type membrane module used in a desalination apparatus for seawater or the like according to an embodiment, and FIG. 1B is a view taken along a line BB in FIG. Sectional view along the
FIG. 3C is a cross-sectional view taken along line CC in FIG.

FIG. 2 is a cross-sectional view showing a method of winding a bag-like membrane of the spiral membrane module of FIG.

FIG. 3 is a perspective view showing an engagement relationship between a wound body and a socket of the membrane module of FIG. 1;

FIG. 4 is a side view of the spiral membrane module of FIG. 1;

FIG. 5 is a system diagram of a desalination apparatus of the present invention.

FIG. 6 is a partially exploded perspective view showing the structure of a conventional spiral type membrane module.

[Explanation of symbols]

 Reference Signs List 10 bag-like membrane 11 first side 12 second side 13 third side 14 fourth side 15 flow path material 16, 17, 18 adhesive 19 fin 20 shaft 24 wound body 25 socket 29 Mesh spacer 30 Open part for permeated water outflow 31 Closed part for permeated water outflow prevention 50 Pump 51 Spiral type membrane module 52 High pressure pump 53 RO device

Claims (2)

[Claims] A seawater desalination apparatus for supplying seawater to a reverse osmosis membrane separation apparatus with a high-pressure pump to obtain freshwater, wherein a spiral-type membrane module is disposed in front of the high-pressure pump to supply seawater to the high-pressure pump. A seawater desalination apparatus for pretreatment with a spiral-type membrane module, wherein the spiral-type membrane module is formed by winding a membrane around a shaft to form a roll, and raw water is supplied from one end surface of the roll to supply water. A desalination apparatus for seawater or the like, wherein water is taken out from the other end surface of the wound body. 2. The bag according to claim 1, wherein the membrane is a bag-like membrane in which a permeated water channel material is disposed, and the bag-like membrane is a first membrane.
It is a substantially rectangular shape having second, third and fourth sides, the first, second and third sides are sealed, the fourth side is partially open, and the remainder is The spiral-type membrane module is a closed part, and the first side part orthogonal to the fourth side part is applied to a shaft to wind a bag-like membrane into a roll, and the fourth side is formed. Part facing the rear end face of the wound body, a second side part facing the fourth side part facing the front end face of the wound body, and a raw water flow path between the bag-shaped membranes. The third side portion is entirely sealed, and in the fourth side portion, a portion overlapping with the open portion of the bag-shaped film is a closed portion, and the closed portion of the bag-shaped film is closed. A desalination device for seawater or the like, characterized in that the device is a spiral-wound membrane module having a portion overlapping with the opening.