JP6183213B2 - Fresh water generation method and fresh water generation apparatus - Google Patents

Description

  The present invention relates to a fresh water generation method and a fresh water generation apparatus, and more particularly, to improve the production efficiency of production water and to improve biofouling in a post-treatment means even if solid content removal water after water quality measurement is returned to a supply line. The present invention relates to a fresh water generation method and a fresh water generation apparatus that can suppress generation.

  Sea water, sewage, industrial wastewater, etc. are used as raw water, and a fresh water generation method and a fresh water generating apparatus for obtaining product water by treating the raw water in multiple stages have been researched and used in many industries and water treatment fields (for example, Patent Document 1). Specifically, as shown in FIG. 5, the raw water is sent to the supply line p62 using a pump (not shown), and the turbidity is separated from the raw water by the solid content removing unit 604 using an ultrafiltration membrane or a microfiltration membrane. Thus, solid content removal water having a solid content concentration lower than that of the raw water is obtained. Subsequently, the solid content-removed water is further processed by post-processing means 606 using a reverse osmosis membrane or the like to obtain product water.

  Here, in order to confirm the adaptability and productivity to the post-processing means 606, the solid content removal water collecting line p64 is connected to the liquid feed line p63 downstream of the solid content removal section 604, and the solid content removal water is connected. Water quality, such as pH, dissolved oxygen (DO), turbidity, chlorine concentration, etc. is measured with a measuring device 608. Although a measuring device may be installed directly in the liquid feeding line p63, if the device is stopped for maintenance management (calibration, cleaning, replacement of consumables, etc.) of the measuring device, the operating rate is not preferable. Therefore, as described above, the solid content removal water collection line p64 is connected downstream of the solid content removal section 604, and the quality of the solid content removal water is measured. The solid content removal water used for this measurement is discharged out of the system and discarded.

Japanese Unexamined Patent Publication No. 2006-272136

Generally, when the amount of liquid fed to the solid content removal water collecting line p64 is about several liters / minute, various water quality can be measured. Here, for example, if the production volume of production water exceeds 10,000 m ³ / day, there is no particular problem even if the solid content removal water after the water quality measurement is discarded as it is. In the case of small and medium-sized freshwater generators with a water production of 10,000 m ³ / day or less, if the solid content-removed water after the water quality measurement is discarded as it is, the reduction in production efficiency becomes remarkable, and some improvement measures Is required.

  Further, the solid content removal water collection line p64 has a problem that microorganisms are more likely to grow than the liquid feeding line p63. This is because the flow rate of the solid content removal water collection line p64 is smaller than the flow rate of the main supply line, so the line (pipe) contact ratio per unit flow rate is large, and the flow rate is slow at the line (pipe) contact part. This is because the pipes are easy to attach to microorganisms and are prone to multiply on the spot. Further, if the solid content removal water after the water quality measurement is returned to the liquid feeding line p63 in order to increase the production efficiency, the microorganisms grown in the solid content removal water collection line p64 are supplied to the post-processing means 606. It is predicted that biofouling (driving failure caused by microorganisms) in the post-processing means 606 will occur. In particular, when the raw water or the solid content-removed water contains organic waste water or biologically treated water, the above problem becomes remarkable.

  Therefore, the present invention provides a fresh water generation method and a fresh water generation device that can improve the production efficiency of production water and can suppress the occurrence of biofouling in the post-treatment means even if the solid content removal water after the water quality measurement is returned to the supply line. Is intended to provide.

The above object of the present invention is constituted by the following constitution.
(1) a pretreatment step of removing solids from raw water sent through a supply line and obtaining solids-removed water having a solids concentration lower than that of the raw water;
From the pretreatment step to the posttreatment step, a liquid feeding step for sending the solid content removed water via a liquid feeding line;
A post-treatment step of obtaining product water by removing impurities that could not be removed in the pre-treatment step from the solid content removal water fed through the liquid feed line;
A collection step of collecting a part of the solid content removal water through a branch line branched from the liquid feeding line;
A monitoring step of monitoring the quality of the collected solid-removed water;
A return step for returning the solids removed water after monitoring to the pretreatment step via the branch line;
A method for producing fresh water.
(2) The above-mentioned (1), wherein the flow rate of the solid content removal water sent to the branch line is 0.1 to 10% of the flow rate of the solid content removal water sent through the liquid feed line. The fresh water generation method as described in.
(3) One or more kinds selected from the group consisting of an oxidizing agent, a reducing agent, a pH adjuster, and a bactericidal agent in the liquid feeding line located upstream from the starting point of the branching line or in the branching line The fresh water generation method according to (1) or (2) above, wherein a drug is injected.
(4) Any one of said (1)-(3) which further has the flushing process which wash | cleans the inside of the said branch line by supplying a part of said product water in the said branch line temporarily. The fresh water generation method as described in.
(5) The fresh water generation method according to any one of (1) to (4), wherein at least one of the raw water and the solid content removal water includes organic waste water or biologically treated water thereof.
(6) In any one of the above (1) to (5), in the pretreatment step, the raw water is treated with a porous membrane having an average pore diameter of 1 μm or less to remove the solid content from the raw water. Fresh water generation method.
(7) In the post-treatment step, any one of the above (1) to (6), wherein the solid content removal water is treated to remove a salt content of the solid content removal water or to concentrate the solid content removal water. The fresh water generation method according to item.
(8) a supply line through which raw water is fed;
A pretreatment means provided in the supply line for removing solids from the raw water and obtaining solids-removed water having a solids concentration lower than that of the raw water;
A post-treatment means that is provided in a liquid feed line downstream of the pre-treatment means, and removes impurities that could not be removed by the pre-treatment means from the solid content removal water to obtain product water;
A branch line for collecting a part of the solid content removal water branched from the liquid feeding line between the pretreatment means and the posttreatment means, and connected to the supply line;
A fresh water generator provided with a monitoring means provided on the branch line for monitoring the quality of the collected solid content-removed water.
(9) The fresh water generator according to (8), wherein an inner diameter of the branch line is 3 to 30% of an inner diameter of the liquid feeding line.

  According to the fresh water generation method and fresh water generator of the present invention, raw water is pre-treated in a pre-treatment step to obtain solids-removed water, a part of the raw water is collected through a branch line, and the water quality is monitored. Since the solid content removal water is returned to the pretreatment process, the solid content removal water after monitoring is not discarded, and the production efficiency of the production water is increased. In addition, since the solid content removal water after passing through the branch line is treated again in the pretreatment process to remove microorganisms, biofouling in the post-treatment means will not occur even if this is returned to the supply line. Can be suppressed.

FIG. 1 is a flowchart for explaining a first embodiment of a fresh water generation method and a fresh water generation apparatus according to the present invention. FIG. 2 is a flowchart for explaining a second embodiment of the fresh water generation method and fresh water generator of the present invention. FIG. 3 is a flowchart for explaining a third embodiment of the fresh water generation method and fresh water generator of the present invention. FIG. 4 is a flowchart for explaining a fourth embodiment of the fresh water generation method and fresh water generator of the present invention. FIG. 5 is a flow diagram for explaining a conventional fresh water generation method and fresh water generator.

  Hereinafter, the fresh water generation method and fresh water generator of the present invention will be described in detail with reference to the drawings.

(First embodiment)
FIG. 1 is a flowchart for explaining a first embodiment of a fresh water generation method and a fresh water generation apparatus according to the present invention.
The fresh water generator of the first embodiment is provided in a supply line p12 to which raw water is fed and a supply line p12, and removes solids from the raw water to obtain solids-removed water having a solids concentration lower than that of the raw water. A pre-processing unit 104; a post-processing unit 106 that is provided in a liquid feed line p13 on the downstream side of the pre-processing unit 104; Branch line p14 branched from the liquid feed line p13 between the two and a supply line p12, and a monitoring unit 108 provided on the branch line p14 for monitoring the water quality of the solid content removal water.

Examples of the raw water include, but are not limited to, seawater, sewage, industrial wastewater, biologically treated water, brine, river water, lake water, and the like.
The raw water is first sent to the supply line p12 using a pump (not shown), then the solid content is removed by the pretreatment means 104 installed in the supply line p12, and the solid content removal water having a lower solid content concentration than the raw water. Is done.

  The pretreatment means 104 only needs to be able to remove suspended substances (solid content) contained in the raw water. For example, sand filtration, activated carbon filtration, membrane filtration, aggregation, and precipitation can be adopted. From the viewpoint of achieving both good removal, membrane filtration is preferably employed. Examples of the filtration membrane include an ultrafiltration membrane (UF), a microfiltration membrane (MF), and a membrane bioreactor (MBR) that combines biological treatment with activated sludge and UF or MF. The shape of UF or MF is not particularly limited, and examples thereof include a hollow fiber type, a sheet type (flat membrane), a tubular type, and a monolith type. Moreover, the form of membrane filtration is a pressurized type in which the UF membrane or MF membrane is housed in a cylindrical case and pressurized from the raw water side (primary side) to obtain filtered water (solid content removal water), or contains raw water. Examples include an immersion type in which a UF membrane or an MF membrane is immersed in a tank to be filtered, and filtrate water is obtained by making the filtrate water side (secondary side) negative pressure or using the head of raw water. Examples of materials for the MF film and UF film include polyethylene, polypropylene, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polysulfone, polyethersulfone (PES), polyether-etherketone (PEEK), and polyphenylene sulfide. Examples thereof include organic substances such as sulfone (PPSS), polyphenylene sulfone (PPSO), polyvinyl alcohol, cellulose acetate, polyacrylonitrile, polyamide, and polyimide, and inorganic substances such as ceramic and metal. In particular, a polyvinylidene fluoride (PVDF) film having excellent chemical resistance is preferable.

  The average pore diameter of the porous filtration membrane is preferably 1 μm or less, more preferably 0.45 μm or less, and further preferably 0.1 μm or less from the viewpoint of certainty of removing microorganisms. The microorganisms that propagate are bacteria, fungi, archaea, and the like, but most of the microorganisms can be removed by using a filtration membrane having an average pore size of 1 μm or less. Moreover, it is preferable that the average pore diameter of a filtration membrane is 1 nm or more, and it is more preferable that it is 5 nm or more. When the average pore diameter is 1 nm or more, the filtration rate can be increased, and good productivity is maintained.

The solid-content-removed water that has passed through the pretreatment means 104 is subsequently post-treated by the post-treatment means 106 provided in the liquid feed line p13 to obtain product water.
The post-treatment means 106 can be variously changed depending on the required characteristics and quality of the production water. Examples include means capable of concentrating the solid content-removed water. As such means, for example, semi-permeable membranes such as reverse osmosis membrane (RO) and nanofiltration membrane (NF), forward osmosis membrane (FO), electrodialysis, membrane distillation, ion exchange and the like can be employed. Among these, it is preferable to use a semipermeable membrane from the viewpoint of productivity, durability, and salt rejection.

  Examples of the material of the semipermeable membrane include polymer materials such as cellulose acetate polymer, polyamide, polyester, polyimide, and vinyl polymer. In addition, the membrane structure has a dense layer on at least one side of the membrane, and an asymmetric membrane having fine pores gradually increasing in size from the dense layer to the inside of the membrane or the other side, and a dense membrane on the asymmetric membrane. And a composite membrane having a very thin separation functional layer formed of the above material. Examples of membrane forms include hollow fibers and flat membranes. In the semipermeable membrane treatment step, a membrane separation element that normally contains a semipermeable membrane, structurally separates raw water (solid content removal water) and permeated water (product water), and collects the permeated water. Is used. The form of the membrane separation element is not particularly limited. However, in the case of a hollow fiber membrane, a structure in which a plurality of hollow fibers are bundled and an end is bonded to a permeate collecting part. Examples include a spiral structure in which an envelope is formed, an end is bonded to a central pipe serving as a water collecting pipe, and a flat membrane is wound around and fixed. Furthermore, permeated water and concentrated water can be obtained by accommodating one or more membrane separation elements in a pressure-resistant container and pressurizing from the raw water (solid content removal water) side. At that time, a connection configuration of a plurality of pressure-resistant containers (such as a configuration in which permeate or concentrated water is connected to a different pressure-resistant container), recovery rate of permeate, concentration rate of concentrated water, solid content to the post-processing means 106 The processing conditions such as the flow rate of the removed water, the processing time, the processing temperature, and the like are appropriately changed depending on the type of the post-processing means 106, the scale of the apparatus, the production capacity, the required water quality, and the like.

  In the present invention, a part of the solid content-removed water obtained by the pretreatment means 104 is collected and the water quality is monitored. A branch line p14 branched from the liquid feed line p13 between the pretreatment means 104 and the posttreatment means 106 and connected to the supply line p12 on the upstream side of the pretreatment means 104 is provided, and the branch line p14 is used as the monitoring means 108. A measuring instrument is detachably provided from the branch line p14. A part of the solid content removal water is collected through the branch line p14, the quality of the solid content removal water is measured by the monitoring means 108, and the solid content removal water after the measurement can be returned to the supply line p12. Further, the branch line p14 is provided with two or more open / close valves so as to sandwich the monitoring means 108, and when maintenance such as cleaning and calibration of the monitoring means 108 is performed, water supply is stopped by closing the open / close valve, and the fresh water generator Maintenance can be performed safely without stopping the entire system.

  The water quality to be monitored varies depending on the type of raw water and management method. For example, pH, dissolved oxygen (DO), temperature, turbidity, redox potential (ORP), pre-organic carbon, chlorine concentration Biofouling measurement devices and the like may be mentioned, and the monitoring means 108 may be equipped with a water quality measurement related device for measuring these.

  In the present invention, the inner diameter of the branch line p14 is preferably 3 to 30%, more preferably 5 to 20%, and further preferably 7 to 10% of the inner diameter of the liquid feeding line p13. If the inner diameter of the branch line P14 is less than 3% with respect to the inner diameter of the liquid supply line p13, the branch line p14 is likely to be blocked, and the amount of pipe contact per unit flow rate of the branch line p14 increases, so that microorganisms propagate. This is not preferable because there is an increased concern that the flow rate of the branch line p14 becomes insufficient and the reliability as a representative value of the measurement value by the monitoring unit 108 decreases. Further, if it exceeds 30%, a large amount of the solid content removal water treated by the pretreatment means 104 is returned to the supply line p12 as described above, and this solid content removal water is again treated in a large amount again. From the viewpoint of

  Moreover, as a flow volume of the solid content removal water sent to the branch line p14, it is preferable that it is 0.1 to 10% of the flow volume of the solid content removal water sent to the liquid feed line p13, 0.3 -8% is more preferable, and 0.5-5% is more preferable. If the flow rate of the solid content removal water sent to the branch line p14 is less than 0.1% of the flow rate of the solid content removal water sent to the liquid feed line p13, the amount of pipe contact per unit flow rate of the branch line p14 is This is not preferable because it increases the concern that microorganisms are likely to grow, the flow rate of the branch line p14 is insufficient, and the reliability as a representative value of the measurement value by the monitoring means 108 is reduced. On the other hand, if it exceeds 10%, a large amount of the solid content removal water treated by the pretreatment means 104 is treated again, which is not preferable from the viewpoint of productivity.

  The flow rate can be adjusted by controlling a pump (not shown) installed in the branch line p14, setting the inner diameter of the branch line p14, and adjusting the opening of a valve installed in the branch line p14. . Further, the flow rate is variously changed depending on the type of the monitoring means 108, device characteristics, and the like.

Next, the fresh water generation method of 1st Embodiment of this invention is demonstrated.
The raw water sent through the supply line p12 is first subjected to the removal of suspended solids (solid content) in the pretreatment means 104 to obtain solid content removal water having a solid content concentration lower than that of the raw water (pretreatment step). The solid-content-removed water sent from the pretreatment means 104 is sent to the post-processing means 106 through the liquid-feeding line p13 (liquid-feeding process). Is removed to obtain product water (post-treatment step). On the other hand, a part of the solid content-removed water obtained in the pretreatment step is collected through the branch line p14 (collection step), and a desired water quality measurement is performed by the monitoring means 108 (monitoring step). The solid content removed water after monitoring is returned to the supply line p12 upstream of the pretreatment means 104 via the branch line p14 (returning step).

  According to the fresh water generation method of the present invention, the solid removal water after monitoring is returned to the supply line p12 on the upstream side of the pretreatment means 104 via the branch line p14, and is treated again by the pretreatment means 104. The solid removal water after monitoring is not discarded, and the production efficiency of production water is increased. The performance of the post-processing means 106 may be remarkably deteriorated due to the adhesion / growth of microorganisms. In the present invention, however, the post-treatment means 106 has passed through the branch line p14 where microorganisms are likely to propagate as compared with the supply line p12 as described above. Since the microorganisms are removed again by the pretreatment means 104, even if the microorganisms grow in the branch line p14, the supply of microorganisms to the posttreatment means 106 can be suppressed as much as possible. Performance can be improved. In particular, when at least one of the raw water and the solid content removal water contains organic waste water or its biological treatment water, the solid content removal water passing through the branch line p14 contains a large amount of organic matter, and microorganisms propagate in the branch line p14. Although possibility increases, in the fresh water generation method of this invention, since it processes in the pre-processing means 104 again, the effect of improving the performance of the post-processing means 106 is high.

  In the present invention, an oxidizing agent, a reducing agent, a pH adjuster, and a sterilizing agent are provided on the liquid feeding line p13 or the branch line p14 located upstream from the start point s1 of the branch line p14 branched downstream of the pretreatment means 104. One or more drugs m selected from the group consisting of drugs can be injected.

  Various chemicals are sometimes used in the fresh water production process for biofouling suppression and pH adjustment. For example, the post-processing means 106 is injected by injecting the medicine m used for biofouling suppression of the liquid feeding line p13 and the post-processing means 106 into the liquid feeding line p13 located upstream from the starting point s1 of the branch line p14. In addition to the solid content removing water flowing into the branch line p14, the chemical can be introduced into the solid content removing water flowing into the branch line p14. In addition, for example, when a medicine m such as a bactericide is introduced at a point s2 upstream of the monitoring means 108 in the branch line p14, the branch line p14 can be washed and the generation of microorganisms is further suppressed, Production costs can also be reduced. Furthermore, since the medicine m such as the bactericidal agent supplied to the branch line p14 as described above is also supplied to the pretreatment unit 104, it is effective for suppressing biofouling in the pretreatment unit 104 and the like. This also contributes to improving the performance of the means 104. Furthermore, since it is supplied to the liquid feeding line p13 and the post-processing means 106 and exhibits the effect, the effect of the medicine can be sufficiently exerted, and the production can be stabilized and the production cost can be reduced. .

(Second Embodiment)
FIG. 2 is a flowchart for explaining a second embodiment of the fresh water generation method and fresh water generator of the present invention.
The fresh water generation method and fresh water generator in the second embodiment have substantially the same configuration as that of the first embodiment, but a part of the production water is temporarily supplied into the branch line p14 via the line p16 and branched. The difference is that it further includes a flushing step for cleaning the inside of the line p14. Since the production water post-treated by the post-treatment means 106 has a good water quality from which impurities have been removed, the inside of the branch line p14 is washed with the production water, so that the microorganisms generated in the branch line p14 are removed. Peeling and removal can be further promoted. The frequency of the flushing process and the flow rate of the production water to the branch line p14 may be appropriately determined according to the scale of the apparatus. Moreover, since the said production water is supplied to the supply line p12 without being discarded as it is, it contributes to the improvement of production efficiency.

(Third embodiment)
FIG. 3 is a flowchart for explaining a third embodiment of the fresh water generation method and fresh water generator of the present invention.
The fresh water generation method and fresh water generation apparatus in the third embodiment have substantially the same configuration as that of the first embodiment, but a mixed liquid n different from the raw water is added to the solid content removal water to obtain the mixed solid content removal water, and mixed. The difference is that a part of the solid content removal water is collected by the branch line p14 and the water quality is monitored by the measuring device 108, and the mixed solid content removal water is post-treated by the post-treatment means 106. For example, when seawater is used as the raw water and organic wastewater or biologically treated water thereof is used as the mixed solution, the seawater has a high salt pressure, so that the osmotic pressure is high and the post-processing means 106 consumes more energy. According to the third embodiment, the organic waste water having a salt concentration lower than that of seawater or the mixed liquid n which is biologically treated water is added to the solid content removal water, so that the osmotic pressure of the solid content removal water is lowered. And the energy consumption of the post-processing means 106 can be suppressed. At the same time, the mixed solid content removal water contains a large amount of organic matter, which increases the risk of microbial reproduction in the branch line p14. However, since the microorganisms can be removed by the pretreatment means 104, the performance of the posttreatment means 106 is reduced as much as possible. Can be suppressed. Examples of organic wastewater or biologically treated water include sewage, industrial wastewater, and activated sludge treated water.

  In FIG. 3, the mixed liquid n is injected into the liquid supply line p13 upstream of the start point s1 of the branch line p14, but may be injected into the supply line p12 upstream of the pretreatment means 104. In addition, in order to suppress the adverse effect on the post-treatment means 106, the organic waste water or the mixed liquid n with the biologically treated water is separated in a separate apparatus by a solid content removal unit such as UF, MF, MBR as described above. In addition, it is preferable to perform the processing in advance by post-processing means such as RO.

(Fourth embodiment)
FIG. 4 is a flowchart for explaining a fourth embodiment of the fresh water generation method and fresh water generator of the present invention.
In the first to third embodiments, the pre-processing unit 104 and the post-processing unit 106 are installed one by one. However, the present invention is not limited to this. For example, as shown in FIG. 4, the preprocessing means may be composed of two means 1042 and 1044, and the post-processing means may be composed of two means 1062 and 1064. For example, by providing a plurality of porous membranes having different pore diameters, it is possible to efficiently and more reliably process.

  In the fourth embodiment, an example in which the preprocessing means and the postprocessing means are each provided with two means has been described, but each may be configured by three or more means independently. In FIG. 4, the solid-removed water after monitoring is returned by the branch line p14 at a point upstream of the pretreatment unit 1042, but may be between the pretreatment unit 1042 and the pretreatment unit 1044. . That is, the solid content removal water after monitoring may pass through at least one pretreatment means. In addition, the distinction between the pretreatment means and the posttreatment means is arbitrary. For example, the pretreatment means is intended to remove microorganisms, and the purpose is to increase the purity of water from which microorganisms are substantially removed. It can also be a post-processing means.

  In the first to fourth embodiments, the form of the fresh water generator provided with one monitoring unit 108 has been described, but the present invention is not limited to this. For example, a plurality of branch lines p14 are provided in the liquid supply line p13 on the downstream side of the pretreatment unit 104, and each branch line p14 is provided with a desired water quality measurement related device, or one branch line p14 is branched in the middle. Each may be equipped with water quality measurement related equipment.

  Hereinafter, the present invention will be further described with reference to Examples and Comparative Examples.

Example 1
An experiment was conducted using a small-medium scale fresh water generator having a production water volume of 500 m ³ / day as shown in FIG.
Seawater was used as the raw water, and the raw water was fed to the supply line p12 at a flow rate of 1250 liters / minute. The inner diameters of the supply line p12 and the liquid feeding line p13 were 65 mm. The pretreatment means 104 installed in the supply line p12 is an ultrafiltration membrane (UF) (average pore diameter 0.01 μm), and the posttreatment means 106 is a reverse osmosis membrane (RO) for seawater (manufactured by Toray Industries, Inc., model number). TM820C) was used. In addition, three branch lines p14 are provided in the liquid feed line p13, each has an inner diameter of 6 mm, and a pH meter, an ORP meter, and a water temperature meter are provided as the monitoring means 108, respectively.
The flow rate of the solid content removal water in the branch line p14 was adjusted to 5 liters / minute using a valve (not shown). 2,2-Dibromo-3-nitrilopropionamide (DBNPA) was injected into the liquid feeding line p13 at a frequency of 1 hour / day at an injection rate of 10 ppm as the drug m upstream from the starting point s1 of the branch line p14.
As a result of producing water using the above apparatus, 500 m ³ / day of production water was obtained as prescribed, and almost no increase in transmembrane pressure difference was confirmed in UF, and stable operation could be realized.

(Control 1)
In the apparatus shown in FIG. 1, an apparatus having the same structure as that of Example 1 was used except that the solid removal water after monitoring was not returned to the supply line p12 and was discarded. Although the production water quality was almost the same as in Example 1, the production water volume was 490 m ³ / day. Further, a gradual increase in transmembrane pressure difference was observed in UF, and chemical cleaning was required once every two months to recover the transmembrane pressure difference.

  Although the present invention has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention. This application is based on a Japanese patent application filed on July 10, 2012 (Japanese Patent Application No. 2012-154735), the contents of which are incorporated herein by reference.

  The present invention relates to a method for producing industrial water, drinking water, and the like from seawater, sewage, industrial wastewater, and the like, and an apparatus therefor, which can increase production efficiency and stabilize the apparatus.

104, 1042, 1044, 604 Pre-processing means 106, 1062, 1064, 606 Post-processing means 108, 608 Monitoring means (measuring instrument)
p12, p62 supply line p13, p63 liquid feed line p14, p64 branch line p16 line m drug n mixture s1 start point s2 point

Claims (8)

A pretreatment step of removing solids from the raw water sent through the supply line and obtaining solids-removed water having a lower solids concentration than the raw water;
From the pretreatment process to the semipermeable membrane treatment process, a liquid feeding process for sending the solid content removal water via a liquid feeding line;
A semipermeable membrane treatment step of obtaining permeated water and concentrated water from the solid content removed water sent through the liquid feeding line using a semipermeable membrane ;
A collection step of collecting a part of the solid content removal water through a branch line branched from the liquid feeding line;
A monitoring step of monitoring the quality of the collected solid-removed water;
A return step for returning the solids removed water after monitoring to the pretreatment step via the branch line;
A method for producing fresh water.   2. The structure according to claim 1, wherein a flow rate of the solid content removal water fed to the branch line is 0.1 to 10% of a flow rate of the solid content removal water fed through the liquid feed line. Water way.   One or more kinds of drugs selected from the group consisting of an oxidizing agent, a reducing agent, a pH adjuster and a bactericidal agent are injected into the liquid feeding line located upstream from the start point of the branch line or into the branch line. The fresh water generation method according to claim 1 or claim 2. The structure according to any one of claims 1 to 3, further comprising a flushing step of cleaning the inside of the branch line by temporarily supplying a part of the permeated water into the branch line. Water way.   The fresh water generation method of any one of Claims 1-4 in which at least one of the said raw | natural water and the said solid content removal water contains organic waste water or its biological treatment water.   The fresh water generation method according to any one of claims 1 to 5, wherein in the pretreatment step, the raw water is treated with a porous membrane having an average pore diameter of 1 µm or less to remove the solid content from the raw water. . A supply line through which raw water is fed,
A pretreatment means provided in the supply line for removing solids from the raw water and obtaining solids-removed water having a solids concentration lower than that of the raw water;
A semipermeable membrane treatment means which is provided in a liquid feed line downstream of the pretreatment means, and obtains permeate and concentrated water from the solid content-removed water using a semipermeable membrane ;
A branch line for collecting a part of the solids-removed water, branched from the liquid supply line between the pretreatment means and the semipermeable membrane treatment means, and connected to the supply line;
A fresh water generator provided with a monitoring means provided on the branch line for monitoring the quality of the collected solid content-removed water. The fresh water generator according to claim 7 , wherein an inner diameter of the branch line is 3 to 30% of an inner diameter of the liquid feeding line.

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