JP6194887B2 - Fresh water production method - Google Patents

Description

  The present invention relates to a method for producing fresh water using a semipermeable membrane unit for producing fresh water from a plurality of types of raw water such as seawater and river water, factory waste water, sewage waste water, and combinations thereof. .

  With the deterioration of the water environment that has become serious in recent years, water treatment technology has become more important than ever, and separation membrane utilization technology has been applied very widely.

  Separation membranes used in water treatment are microfiltration membranes with sub-micrometer order pores, smaller ultrafiltration membranes, nanofiltration membranes capable of nano-order separation, and reverse osmosis membranes capable of sub-nano-order separation It is divided roughly into. Among these, nanofiltration membranes with small pores and reverse osmosis membranes are called semipermeable membranes and are classified as membranes that allow water to permeate but not solutes. Especially reverse osmosis membranes are drinkable from seawater or brackish water. As a technique capable of obtaining fresh water suitable for water, it is particularly widely applied.

  Although freshwater production with semipermeable membranes using seawater as raw water is superior in energy compared to the evaporation method, it is a high pressure process caused by the high osmotic pressure of seawater. Compared to the water production process, the energy required is large. Recently, a system has been proposed in which osmotic pressure is reduced by mixing and diluting seawater and river water, factory wastewater, and sewage wastewater, and lowering the osmotic pressure to reduce energy costs (see Patent Document 1). ). In addition, concentrated wastewater discharged by a process of purifying factory wastewater and sewage wastewater and collecting and reusing it with a semipermeable membrane may be used as dilution water (see Patent Documents 2 to 6).

  Normally, when river water, factory wastewater or sewage wastewater is treated with a semipermeable membrane, it is turbidized by pretreatment and then supplied to the semipermeable membrane. In pretreatment, BOD (Biological Oxygen Demand) In many cases, components, COD (Chemical Oxygen Demand) components, organic polysaccharides such as polymeric polysaccharides and chlorophyll, and microbial components cannot be removed efficiently. Therefore, in a system that processes semi-permeable membranes of river water, factory wastewater, sewage wastewater, and concentrated seawater mixed with these concentrated effluents, which contain many organic and microbial components, microorganisms propagate on the surface of the semipermeable membrane compared to seawater. It is easy to cause a problem that the performance of the semipermeable membrane is deteriorated due to the occurrence of biofouling.

  Furthermore, river water used as dilution water, organic matter components and microbial components of factory wastewater and sewage wastewater vary depending on rainfall and season if river water, and change depending on time zone and season if wastewater, If so, it will vary depending on the production volume, production process, etc., so semi-permeable membrane treatment of seawater mixed with dilution water collected during periods with a large amount of organic or microbial components may cause significant contamination of the semi-permeable membrane. It has become. In particular, when river water, factory wastewater or semi-permeable membrane concentrated water from sewage wastewater is used as dilution water, organic matter components and microbial components are concentrated, and there is contamination of the semipermeable membrane that separates diluted seawater into permeated water and concentrated water. It becomes a problem because it becomes more prominent.

  In addition, in the semipermeable membrane treatment of river water, factory wastewater and sewage wastewater, in order to prevent microbial growth on the surface of the semipermeable membrane, the disinfectant is intermittently or continuously operated as in Non-Patent Documents 1 and 2. Or a flushing cleaning that periodically cleans the surface of the semipermeable membrane with a water flow as in Patent Document 7, or a cleaning liquid that is opposite to the direction of inflow of raw water during fresh water generation as in Patent Document 8 When the counter-flow cleaning is performed to flow in the direction to clean the surface of the semipermeable membrane, dirt containing organic components and microbial components is separated from the semipermeable membrane surface into the semipermeable membrane concentrated water, and diluted seawater is separated into the permeated water and concentrated water. Contamination of the semipermeable membrane that separates into two becomes more prominent, which is a serious problem.

International Publication No. 2011/114967 Japanese Unexamined Patent Publication No. 2010-207805 Japanese Unexamined Patent Publication No. 2012-16695 Japanese Unexamined Patent Publication No. 2012-16696 Japanese Unexamined Patent Publication No. 2010-149100 Japanese Unexamined Patent Publication No. 2010-149123 Japanese Patent No. 4472050 Japanese Unexamined Patent Publication No. 2012-139614

Takuhei Kimura, “Innovative Biofouling Prevention on Seawater Desalination Reverse Osmosis Membrane,” Proceedings of IDA World Congress, BAH01-048 (2001). Katariina Majamaa et al., “Field Trial to Optimize the Use of DBNPA in WRU Application,” Proceedings of IDA World Congress, DB09-076 (2009).

  An object of the present invention is a method for producing fresh water using a semipermeable membrane unit for producing fresh water from a plurality of types of raw water such as seawater and river water, factory waste water, sewage waste water or a combination of these treated waters. It is to efficiently prevent contamination of semipermeable membranes by organic matter and microorganisms contained in river water, factory wastewater, sewage wastewater and concentrated wastewater for diluting seawater.

In order to solve the above problems, the present invention has the following configurations (1) to (16).
(1) Treated water A is treated with a first semipermeable membrane unit to produce fresh water, and the first concentrated water Ac generated when treated with the first semipermeable membrane unit has a solute concentration. A method of producing fresh water by mixing the water B to be treated higher than the first concentrated water Ac and treating the mixed water with a second semipermeable membrane unit, wherein the first concentrated water Ac is An organic matter / microorganism removal line that passes through the organic matter / microorganism removal unit to reduce the organic concentration or microbial concentration of the first concentrated water Ac and mixes with the treated water B, and the first concentrated water Ac into the organic matter A bypass line that mixes with the treated water B without going through the microorganism removal unit, and an organic substance concentration or a microorganism concentration in the first concentrated water Ac on the upstream side of the organic matter / microorganism removal unit, and The first According to at least one of changes in the differential pressure between the inflow side and the non-permeation side of the first semipermeable membrane unit calculated by subtracting the pressure of the first concentrated water Ac from the pressure of the supply water of the permeable membrane unit A fresh water production method for controlling a flow rate of the first concentrated water Ac to the organic matter / microorganism removal unit.
(2) When the change in the differential pressure between the inflow side and the non-permeate side of the first semipermeable membrane unit exceeds a predetermined value, the first to the organic matter / microorganism removal unit according to the change in the differential pressure. When the flow rate of the first concentrated water Ac is controlled and the change in the differential pressure between the inflow side and the non-permeated side of the first semipermeable membrane unit is not more than a predetermined value, the organic matter in the first concentrated water Ac The fresh water production method according to (1), wherein a flow rate of the first concentrated water Ac to the organic matter / microorganism removal unit is controlled according to a concentration or a microorganism concentration.
(3) The fresh water production method according to (1) or (2), wherein the water to be treated A is treated by a pretreatment unit before being treated by the first semipermeable membrane unit.
(4) The fresh water according to (3), wherein the treatment process constituting the organic matter / microorganism removal unit includes a treatment process different from the treatment process constituting the pretreatment unit in the treated water A. Production method.
(5) A fine bubble generating unit for generating fine bubbles by depressurizing the first concentrated water Ac is provided upstream of the organic matter / microorganism removal unit, and the fine bubbles are generated in the first concentrated water Ac. The fresh water production method according to any one of (1) to (4), wherein:
(6) The fresh water according to any one of (1) to (5), wherein the organic matter / microorganism removal unit is a pressure filtration unit that separates using the water pressure of the first concentrated water Ac. Production method.
(7) The filtration material of the same material as the filtration material of the second semipermeable membrane unit is used as the filtration material of the organic matter / microorganism removal unit, as described in any one of (1) to (6) above. Fresh water production method.
(8) The processing waste water of the organic matter / microorganism removal unit and the concentrated water of the second semipermeable membrane unit are mixed and discharged to the outside of the system, as described in any one of (1) to (7). Fresh water production method.
(9) A method for producing fresh water by mixing treated water A with treated water B having a solute concentration higher than the treated water A, and treating the mixed water with a semipermeable membrane unit. The treated water A is passed through an organic matter / microorganism removal unit, the organic matter / microorganism removal line for reducing the organic matter concentration or microbial concentration of the treated water A and mixing with the treated water B, and the treated water A A bypass line for mixing with the water to be treated B without going through the organic matter / microorganism removal unit, and depending on the organic matter concentration or the microorganism concentration of the water to be treated A on the upstream side of the organic matter / microorganism removal unit, A fresh water production method for controlling a flow rate of the treated water A to an organic matter / microorganism removal unit.
(10) The fresh water production method according to (9), wherein the water to be treated A is treated by a pretreatment unit before being mixed with the water to be treated B.
(11) The fresh water according to (10), wherein the treatment process constituting the organic matter / microorganism removal unit includes a treatment process different from the treatment process constituting the pretreatment unit in the treated water A. Production method.
(12) The fresh water production according to any one of (9) to (11), wherein a filtration material of the same material as the filtration material of the semipermeable membrane unit is used as the filtration material of the organic matter / microorganism removal unit. Method.
(13) The fresh water production according to any one of (9) to (12), wherein the treated wastewater of the organic matter / microorganism removal unit and the concentrated water of the semipermeable membrane unit are mixed and discharged out of the system. Method.
(14) The organic substance concentration or microbial concentration is a total organic carbon concentration (TOC), an assimilable organic carbon (AOC), a soluble organic carbon concentration (DOC), a chemical oxygen demand (COD), or a biological oxygen demand. (1) comprising at least one selected from the group consisting of an amount (BOD), an ultraviolet absorption amount (UV), a transparent extracellular polymer particle (TEP), adenosine triphosphate (ATP), a bacterioac and chlorophyll. )-(13) The fresh water manufacturing method as described in any one of.
(15) The organic matter / microorganism removal unit is at least one selected from the group consisting of flotation separation, precipitation separation, lagoon treatment, sand filtration, microfiltration, ultrafiltration, nanofiltration, agglomeration treatment, oxidation treatment and adsorption treatment. The fresh water manufacturing method as described in any one of said (1)-(14) containing two.
(16) The fresh water production method according to any one of (1) to (15), wherein the organic matter / microorganism removal unit also serves as a pretreatment unit for the treated water B.

  According to the fresh water production apparatus of the present invention, when producing fresh water from a mixed water of plural kinds of raw water such as sea water and river water, factory waste water, sewage waste water or a combination of these treated waters, river water, factory waste water, It is possible to efficiently prevent contamination of the semipermeable membrane that treats the mixed water of organic waste and microorganisms contained in the sewage wastewater and the treated water.

FIG. 1 is a flowchart showing an example of an embodiment of a fresh water production method according to the present invention. FIG. 2 is a flowchart showing an example of another embodiment of the fresh water production method according to the present invention. FIG. 3 is a flowchart showing an example of still another embodiment of the method for producing fresh water according to the present invention. FIG. 4 is a flowchart showing an example of still another embodiment of the method for producing fresh water according to the present invention. FIG. 5 is a flowchart showing an example of still another embodiment of the method for producing fresh water according to the present invention. FIG. 6 is a flowchart showing an example of still another embodiment of the method for producing fresh water according to the present invention. FIG. 7 is a flowchart showing an example of still another embodiment of the method for producing fresh water according to the present invention. FIG. 8 is a flowchart showing an example of still another embodiment of the method for producing fresh water according to the present invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited to the embodiments shown in these drawings.

  FIG. 1 is a flowchart showing an example of an embodiment of a fresh water production method according to the present invention. After the to-be-treated water A is stored in the to-be-treated water A tank 1, it is supplied to the first pretreatment unit 3 by the to-be-treated water A supply pump 2 and subjected to pretreatment such as turbidity removal, After being temporarily stored in the first pretreatment water tank 4, it is processed by the first semipermeable membrane unit 6 by the first booster pump 5. In the first semipermeable membrane unit 6, the semipermeable membrane treated water that has been pretreated with the treated water A is separated into a permeable component (permeated water) and a non-permeable component (concentrated water) of the semipermeable membrane. Hereinafter, the first permeated water Ap may be stored in the first permeated water tank 7 as fresh water. On the other hand, the concentrated water discharged from the first semipermeable membrane unit 6 (hereinafter referred to as “first concentrated water Ac”) is temporarily stored in a first concentrated water tank 9 provided with a water quality sensor 8a.

  The fresh water production method of the present invention controls the flow rate of the first concentrated water Ac to the organic matter / microorganism removal unit 12 according to the detection value of the water quality sensor 8a. Examples of means for controlling the flow rate of the first concentrated water Ac include the first concentrated water supply valve 10a and the second concentrated water supply valve 10b. By adjusting the opening / closing degree of the first concentrated water supply valve 10a and the second concentrated water supply valve 10b, the first concentrated water Ac is transferred to the organic matter / microorganism removal unit 12 by the first concentrated water pump 11. The amount of water flowing and the amount of water flowing to the bypass line 13 that bypasses the organic matter / microorganism removal unit 12 are controlled. The entire amount of the first concentrated water Ac may flow through the bypass line 13, or the entire amount thereof may be passed through the organic matter / microorganism removal unit 12 and processed. In the present invention, the flow rate of the first concentrated water Ac to the organic matter / microorganism removal unit 12 and the bypass line 13 is a first half obtained from a detection value of the water quality sensor 8a and / or a pressure sensor 21 described later. Control is performed according to a change in the differential pressure between the inflow side and the non-permeation side of the permeable membrane unit 6.

  The first concentrated water Ac that has passed through the organic matter / microorganism removal unit 12 or the bypass line 13 is merged at the downstream side of the organic matter / microorganism removal unit 12 and temporarily stored in the mixed water tank 14 that mixes the water to be treated B. Is done.

  The treated water B is stored in the treated water B tank 15 and then supplied to the second pretreatment unit 17 by the treated water B supply pump 16 and subjected to pretreatment such as turbidity removal. Thereafter, the mixed water tank 14 is supplied. After the mixed water composed of the first concentrated water Ac and the water to be treated B in the mixed water tank 14 is pressurized by the second booster pump 18, it is processed by the second semipermeable membrane unit 19, and the second semipermeable membrane unit 19 is processed. The permeated water of the permeable membrane unit 19 (hereinafter sometimes referred to as “second permeated water Bp”) is stored in the second permeated water tank 20. The permeated water in the first permeated water tank 7 and the second permeated water tank 20 is used after adjusting the pH, Langeria index, bactericidal agent concentration, and mineral concentration as needed.

  The treated water A and the treated water B to be treated by the fresh water production method of the present invention are not particularly limited as long as the concentration of the solute that affects the osmotic pressure is different. For example, high-concentration seawater or concentrated seawater, River water, ground water, sewage waste water, factory waste water, and treated water thereof having a lower concentration than seawater can be used. Examples of treated water include filtered water and concentrated water. As illustrated in FIG. 1, when the first concentrated water Ac obtained by treating the water to be treated A with a semipermeable membrane unit is used as dilution water, it is possible to effectively utilize the concentrated wastewater that is normally discharged out of the system. Is effective. On the other hand, as illustrated in FIG. 2 and FIG. 3, to-be-treated water A (for example, seawater) having a high concentration without being treated with a semipermeable membrane unit. ) Is preferable because it can be easily prepared while reducing capital investment. 2 and FIG. 3, in the example of FIG. 2, a specific method for controlling the amount of water flow is that the treated water A is treated by the first pretreatment unit 3 and the water quality sensor 8 b of the pretreated water obtained is used. Based on the detected value, it can be supplied to the mixed water tank 14 via the organic matter / microorganism removing unit 12 and / or the bypass line 13 and mixed with the water B to be treated. In the example of FIG. 3, the water quality of the water to be treated A is detected by the water quality sensor 8c, and the mixed water tank 14 is passed through the organic matter / microorganism removal unit 12 and / or the bypass line 13 based on the obtained detection value. Can be mixed with the water B to be treated. In any case, depending on the detection value of the water quality sensor 8c provided in the treated water A tank 1 or the water quality sensor 8b provided in the first pretreated water tank 4, the treated water A or the organic matter / microorganism removal unit or It is possible to control the amount of pretreatment water to be treated A to be treated. 2 and 3, the description of the reference numerals common to FIG. 1 is omitted.

  The pretreatment unit 3 may be any process that can treat suspended substances and organic substances, for example, flotation separation, precipitation separation, lagoon treatment, sand filtration, microfiltration, ultrafiltration, nanofiltration, aggregation treatment, oxidation treatment, adsorption A process etc. can be mentioned and you may combine a some processing process in series.

  The semipermeable membrane unit 6 can be selected from a nanofiltration membrane having a small pore, a reverse osmosis membrane, and the like.

  The organic matter / microorganism removal unit 12 may be any treatment process that can reduce organic matter components and microorganism components composed of microorganisms, metabolites, and by-products, etc., which are to be removed, such as flotation separation, precipitation separation, lagoon treatment, Examples thereof include sand filtration, microfiltration, ultrafiltration, nanofiltration, agglomeration treatment, oxidation treatment, and adsorption treatment. The organic matter / microorganism removal unit 12 may combine a plurality of treatment processes in series, or may switch the treatment processes according to detection values of the water quality sensors 8a, 8b, and 8c in parallel. I do not care.

The removal target substance of the organic matter / microorganism removal unit 12 is composed of microorganisms, their metabolites, by-products, etc., and it is preferable to measure a water quality index usually used in the water treatment field as the organic matter concentration or the microorganism concentration. There are no particular restrictions on the measurement of organic matter concentration and microbial concentration, but for organic matter concentration, TOC (total organic carbon content), AOC (assimilable organic carbon), DOC (dissolvable organic carbon), COD (chemical oxygen) Demand amount), BOD (biological oxygen demand amount) and the like are common. Regarding the microorganism concentration, TEP (transparent extracellular polymer particles), bacterioac, ATP (adenosine triphosphate), chlorophyll and the like can be applied.
The water quality sensors 8a, 8b, and 8c may be any sensor that can measure the organic substance concentration and the microorganism concentration described above. The water quality sensors 8a, 8b, and 8c may be manual measuring instruments or measuring instruments capable of online measurement, but the water quality sensors 8a, 8b, and 8c are water quality of the treated water A and the first concentrated water Ac. From the viewpoint of being able to respond to changes instantly, it is preferable to be an on-line measuring instrument.

  Examples of means for controlling the amount of water flow to the organic matter / microorganism removal unit 12 include various valves and three-way valves capable of adjusting the flow rate. For example, when the water quality sensors 8a, 8b, and 8c are TOC meters, if the TOC of the first concentrated water Ac is less than 5 mg / l, the water flow rate to the bypass line 13 is increased, and the TOC is 5 mg / l or more. Can adjust the degree of opening and closing of the first concentrated water supply valve 10a and the second concentrated water supply valve 10b so as to increase the amount of water flow to the organic matter / microorganism removal unit 12. In FIG. 1, the flow rate of the first concentrated water Ac is controlled by adjusting the opening / closing degree of the first concentrated water supply valve 10a and the second concentrated water supply valve 10b. It is also possible to switch all amounts using a three-way valve.

  In addition, biofouling generated inside the first semipermeable membrane unit 6 grows excessively on the semipermeable membrane surface or receives stress due to changes in the water temperature or water quality, so that organic matter is generated from the semipermeable membrane surface. There is a risk of peeling off as dirt containing components and microbial components, dispersing in the first concentrated water Ac, and contaminating the downstream second semipermeable membrane unit 19. Further, it may be peeled off by adding a bactericidal agent or cleaning the membrane surface, causing a reduction in the quality of the first concentrated water Ac and contaminating the downstream second semipermeable membrane unit 19. In this case, the biofouling substance is removed (peeled), so that the first semipermeable membrane unit 6 does not permeate from the pressure of the supply water (supply side pressure) of the first semipermeable membrane unit 6. The differential pressure (flow path pressure loss) on the non-permeation side in the first semipermeable membrane unit 6 calculated by subtracting the pressure of the obtained concentrated water (non-permeation side pressure) is reduced. That is, it is possible to predict the water quality change of the first concentrated water Ac from the change in the differential pressure between the inflow side and the non-permeation side of the first semipermeable membrane unit 6. For this reason, according to the change in the differential pressure between the inflow side and the non-permeation side of the first semipermeable membrane unit 6, the opening / closing degrees of the first concentrated water supply valve 10a and the second concentrated water supply valve 10b are adjusted, The flow rate of the first concentrated water Ac to the organic matter / microorganism removal unit 12 can be controlled.

  As shown in FIG. 4, the pressure difference between the inflow side and the non-permeate side of the first semipermeable membrane unit 6 detects the pressure of the first supply water Af and the first concentrated water Ac, and Measurement can be performed by arranging a pressure sensor 21 that indicates a differential pressure (flow path pressure loss). In the fresh water production method using a semipermeable membrane, the differential pressure between the inflow side and the non-permeate side of the first semipermeable membrane unit is an important parameter for monitoring the degree of biofouling formation, In many cases, a fresh water production apparatus using a semipermeable membrane is provided with a pressure sensor that detects a differential pressure between the inflow side and the non-permeate side of the semipermeable membrane unit. Water quality for monitoring the water quality change of the first concentrated water Ac by controlling the opening / closing degree of the first concentrated water supply valve 10a and the second concentrated water supply valve 10b according to the change in the differential pressure on the permeate side This is preferable because the sensor 8a can be omitted and the equipment cost can be reduced.

  Regarding the change in the differential pressure between the inflow side and the non-permeate side of the first semipermeable membrane unit 6, for example, when the differential pressure is reduced by 10 kPa or more, that is, when the biofilm on the semipermeable membrane surface is peeled off, It is preferable to increase the water flow rate to the microorganism removal unit 12, and further increase the water flow rate to the organic matter / microorganism removal unit 12 when the pressure decreases by 20 kPa or more. More preferably, the entire amount of concentrated water Ac is passed through. Further, for example, when a disinfectant is added to the water to be treated of the first semipermeable membrane unit 6, the differential pressure between the inflow side and the non-permeate side of the semipermeable membrane unit 6 is compared with the non-added system. Even when the decrease is small, the opening / closing degrees of the first concentrated water supply valve 10a and the second concentrated water supply valve 10b can be adjusted so as to increase the amount of water flow to the organic matter / microorganism removal unit 12.

  As shown in FIG. 1, the fresh water production method of the present invention controls the flow rate of the first concentrated water Ac to the organic matter / microorganism removal unit 12 according to the detection value of the water quality sensor 8a, or FIG. As shown, a change in the differential pressure between the inflow side and the non-permeation side of the semipermeable membrane unit 6 calculated by subtracting the pressure of the first concentrated water Ac from the pressure of the first supply water Af of the semipermeable membrane unit 6. The flow rate of the first concentrated water Ac to the organic matter / microorganism removal unit 12 is controlled in accordance with the detection value of the water quality sensor 8a and the inflow side of the semipermeable membrane unit 6 as shown in FIG. The flow rate of the first concentrated water Ac to the organic matter / microorganism removal unit 12 can be controlled in accordance with the change in the differential pressure on the non-permeating side.

  In the method for producing fresh water shown in FIG. 5, the flow rate of the first concentrated water Ac to the organic matter / microorganism removal unit 12 can be controlled based on the detection values of both the water quality sensor and the pressure sensor as described above. The water quality sensor 8a and the pressure sensor 21 can be used simultaneously. At this time, the flow rate of water to the organic matter / microorganism removal unit can be controlled with priority given to the change in the differential pressure between the inflow side and the non-permeation side of the first semipermeable membrane unit detected by the pressure sensor 21. For example, the first concentration to the organic matter / microorganism removal unit according to the detection value of the water quality sensor 8a when the change in the differential pressure is less than 10 kPa, and the detection value of the pressure sensor when the change in the differential pressure is 10 kPa or more. The amount of water Ac passed can be controlled.

  The organic matter and microorganisms in the first concentrated water Ac include organic matter and microorganisms that could not be removed by the first pretreatment unit 3, so the organic matter / microorganism removal unit 12 is the first pretreatment unit. 3 and at least one preferably include different processing processes. For example, when the first pretreatment unit 3 performs solid-liquid separation such as membrane filtration such as sand filtration, microfiltration, and ultrafiltration, the organic matter / microorganism removal unit 12 performs oxidation treatment such as ozone and biological treatment to obtain solid-liquid separation. Organic substances and microorganisms that could not be removed by separation may be decomposed and removed, or flocculants and adsorbents may be added to remove organic substances and microorganisms. For example, as shown in FIG. 1, by arranging a flocculant tank or adsorbent tank 22a and a flocculant addition pump or adsorbent addition pump 23a upstream of the organic matter / microorganism removal unit 12, the first concentrated water Ac is obtained. It is possible to decompose and remove organic substances and microorganisms by adding a flocculant and an adsorbent to.

  Furthermore, from the viewpoint of reducing the facility cost of the organic matter / microorganism removal unit 12, it is preferable to use the second pretreatment unit 17 for treating the water to be treated B as an organic matter / microorganism removal unit as illustrated in FIG. . In FIG. 6, after the to-be-treated water A is stored in the to-be-treated water A tank 1, the treated water A is supplied to the first pretreatment unit 3 by the to-be-treated water A supply pump 2, and after pretreatment, Once stored in one pretreatment water tank 4, it is processed by the first semipermeable membrane unit 6 by the first booster pump 5. In the first semipermeable membrane unit 6, the semipermeable membrane permeate Ap is stored in the first permeate tank 7 as fresh water. On the other hand, the first concentrated water Ac discharged from the first semipermeable membrane unit 6 flows out to a pipe provided with the water quality sensor 8. In the example of FIG. 7, the first concentrated water tank and the first concentrated water pump are not arranged, and the first concentrated water according to the detection value of the water quality sensor 8 due to the pressure of the first concentrated water Ac. The opening / closing degrees of the supply valve 10a and the second concentrated water supply valve 10b are adjusted and supplied to the mixed water tank 14 that mixes the second pretreatment unit 17 or the water to be treated B. Here, the flocculant tank or adsorbent tank 22b and the flocculant addition pump or adsorbent addition pump 23b are arranged upstream of the second pretreatment unit 17, so that the flocculant and adsorbent are adsorbed to the first concentrated water Ac. An organic agent and microorganisms can be decomposed and removed by adding an agent. Further, the treated water B is stored in the treated water B tank 15 and then supplied to the second pretreatment unit 17 by the treated water B supply pump 16, and at least a part of the first concentrated water Ac described above. At the same time, after being pretreated, the mixed water tank 14 is supplied. After the mixed water composed of the first concentrated water Ac and the water to be treated B in the mixed water tank 14 is pressurized by the second booster pump 18, it is processed by the second semipermeable membrane unit 19, and the second semipermeable membrane unit 19 is processed. The permeated water (second permeated water Bp) of the permeable membrane unit 19 is stored in the second permeated water tank 20.

  In the fresh water production method of the present invention, the organic matter / microorganism removal unit is preferably a group consisting of flotation separation, precipitation separation, lagoon treatment, sand filtration, microfiltration, ultrafiltration, nanofiltration, aggregation treatment, oxidation treatment and adsorption treatment. A processing unit including at least one selected from Among these, flotation separation is suitable when there are many light oils and surfactants, and pressure flotation separation in which fine bubbles such as microbubbles and nanobubbles are introduced under pressure is effective. The fine bubbles may be generated by blowing compressed air, or may be generated by rapidly depressurizing pressurized water. Furthermore, if a large site can be secured, a lagoon treatment in which an aerobic treatment is performed simultaneously in the upper layer and an anaerobic treatment is performed simultaneously in the lower layer reduces organic matter and microorganisms in the first concentrated water Ac without power. It is preferable because it is possible. In the lagoon treatment, it is preferable to stay for about 5 to 30 days in a reservoir having a water depth of usually 1.2 to 2.5 m.

  In the case of sand filtration, it is possible to apply gravity-type filtration that naturally flows down, and it is also possible to apply pressure-type filtration in which a pressure tank is filled with sand. As the sand to be filled, single-component sand can be applied. For example, anthracite, silica sand, garnet, pumice and the like can be combined to increase the filtration efficiency. In addition, the first concentrated water Ac is passed through the water-permeable layer, and has a function of purifying and decomposing anaerobic and aerobic useful microorganisms such as photosynthetic bacteria, yeast, lactic acid bacteria, filamentous fungi, actinomycetes, etc. existing in the ground. Utilizing it, the organic substance concentration or microbial concentration of the first concentrated water Ac may be reduced, and then the water stored in the underground aquifer may be used as dilution water.

  The microfiltration membrane and the ultrafiltration membrane are not particularly limited, and flat membranes, hollow fiber membranes, tubular membranes, pleats, and any other shapes can be used as appropriate. The material of the membrane is not particularly limited, and polyacrylonitrile, polyphenylene sulfone, polyphenylene sulfide sulfone, polyvinylidene fluoride, polypropylene, polyethylene, polysulfone, polytetrafluoroethylene, polyvinyl alcohol, cellulose acetate, polyamide, polyester, polyimide Inorganic materials such as vinyl polymer and ceramic can be used. Moreover, even if it is a filtration system, any of the pressure filtration system which pressurizes and filters supply water, and the suction filtration system which sucks and filters the permeation | transmission side are applicable. Furthermore, it is also possible to apply a pressure flotation filtration that combines pressure flotation and sand filtration or a submerged membrane filtration unit. In particular, in the case of the suction filtration method, so-called agglomerated membrane filtration or membrane-based activated sludge method (MBR), in which a microfiltration membrane or an ultrafiltration membrane is immersed in a coagulation sedimentation tank or a biological treatment tank for filtration, may be applied. preferable.

  For semi-permeable membranes such as nanofiltration membranes and reverse osmosis membranes, polymer materials such as cellulose acetate polymers, polyamides, polyesters, polyimides, and vinyl polymers can be used as membrane materials. In addition, the membrane structure has a dense layer on at least one side of the membrane, and an asymmetric membrane having fine pores with gradually larger pore diameters from the dense layer to the inside of the membrane or the other side, or on the dense layer of the asymmetric membrane. The composite film may be a composite film having a very thin functional layer formed of another material. However, from the viewpoint of protecting the second semipermeable membrane unit 19 from components that are easily adsorbed to the semipermeable membrane, the filtration material of the organic matter / microorganism removal unit is the same material as the filtration material of the second semipermeable membrane unit. It is preferable.

  The agglomeration treatment that constitutes the organic matter / microorganism removal unit is a treatment for adding a flocculant to flock organic matter and microorganisms in water to improve solid-liquid separation efficiently. In this case, the first concentrated water Ac that has been subjected to the agglomeration treatment is sedimented using a slanted plate or the like, and then subjected to sand filtration, microfiltration, or ultrafiltration, whereby the second semipermeable material is obtained. Supply water suitable for passing through the membrane unit can be obtained. The flocculants are roughly classified into inorganic flocculants and organic polymer flocculants. The inorganic flocculants include aluminum flocculants such as aluminum sulfate (sulfuric acid band) and polyaluminum chloride (PACl), and chlorides. There are iron-based flocculants such as ferric iron and polyferric sulfate. In addition, the polymer organic flocculants include cationic polymer flocculants such as aminoalkyl (meth) acrylate quaternary salt (co) polymers, anionic polymer flocculants such as acrylamide / sodium acrylate copolymers, There are nonionic polymer flocculants such as polyacrylamide. These aggregating agents may be used alone or may be used in combination with an inorganic aggregating agent as an aggregating aid. Moreover, since the generation of sludge can be suppressed by using an organic polymer flocculant rather than an inorganic flocculant, an inorganic flocculant and an organic polymer flocculant are used rather than using an inorganic flocculant alone. It is preferable to use together. In addition, since the effect of aggregation is greatly affected by the pH of the water to be treated, it is preferable to adjust the pH to an appropriate range using an alkali such as caustic soda, lime, or bicarbonate, or an acid such as hydrochloric acid or sulfuric acid.

  Examples of the oxidation treatment include biological treatment, irradiation with ozone, ultraviolet rays or gamma rays, addition of fluorine or hydrogen peroxide, catalyst treatment, and the like. It is also possible to apply accelerated oxidation treatment performed by combining at least two. Considering the influence on the environment, ozone, ultraviolet irradiation, hydrogen peroxide addition, and catalyst treatment are preferable. Examples of the catalyst include catalysts such as iron, copper, and manganese that can increase the oxidizing power in combination with ozone and hydrogen peroxide, and metal oxides having a so-called photocatalytic function, such as titanium oxide. Accelerated oxidation treatment is called AOP (= Advance Oxidance Process) and uses ozone, ultraviolet rays, hydrogen peroxide, catalyst (photocatalyst, etc.) together to generate hydroxy radicals with high oxidizing power in water, and to produce organic matter. It is a method of decomposing. Furthermore, the feature of this accelerated oxidation treatment is that secondary waste is not generated, and the treatment effect can be deodorized, decolorized, sterilized, etc. in addition to the decomposition of organic matter. As the combination of the accelerated oxidation treatment, a combination that generates more hydroxy radicals that contribute to oxidative decomposition is preferable, and a combination of hydrogen peroxide and ultraviolet light, ozone and hydrogen peroxide, or ozone and ultraviolet light is more preferable. In the case of combining ozone, ultraviolet rays, and hydrogen peroxide, it is preferable because oxidative decomposition can be performed more efficiently.

  The adsorption treatment is a treatment for adsorbing a relatively small organic substance having a molecular weight of several hundred or less in water on the solid surface by adding an adsorbent. Examples of the adsorbent include activated carbon, ion exchange resin, zeolite, and the like. From the viewpoint that handling is relatively easy, it is preferable to use powdered activated carbon. When the adsorbent is granular, it is configured so that the water is filled in the column, and when the adsorbent is powder, it is added directly to the first concentrated water Ac, and solid-liquid separation such as precipitation separation or membrane filtration is performed. It is good to use in combination. Moreover, you may use the adsorbent filter represented by adsorbents, such as activated carbon and an ion exchange resin.

  By the way, in the case of low salt concentration water such as river water, factory wastewater, and sewage wastewater, a semipermeable membrane such as a low pressure reverse osmosis membrane or a nanofiltration membrane is applied as the semipermeable membrane unit 6. Since it is low, a high recovery rate operation can be performed, and as a result, the amount of the first concentrated water Ac decreases. Therefore, even if an energy recovery unit is installed on the downstream side from which the concentrated water of the semipermeable membrane unit is discharged, the energy that can be recovered is small, the cost performance of the energy recovery unit is small, and it is often not economically appropriate. For this reason, the semipermeable membrane unit 6 for treating low salt concentration water is not usually recovered and is often discharged out of the system. Therefore, as illustrated in FIG. 7, as an organic matter / microorganism removal unit that reduces the organic substance concentration or microbial concentration of the first concentrated water Ac, a pressure filtration unit 12 a that can be filtered with concentrated water pressure is a first semipermeable membrane unit. Direct connection to 6 is preferable because the organic substance concentration or microbial concentration can be reduced without power. For pressure filtration unit 12a, cartridge filters, disk filters, microfiltration, ultrafiltration, sand filtration, biological carrier filtration, nanofilters, sand filtration, precoat filters, adsorbent filters represented by activated carbon and ion exchange resins Etc. can be used.

  Moreover, when the low salt concentration water like river water, factory waste water, or sewage waste water is subjected to a semipermeable membrane treatment, the first concentrated water Ac maintains a concentrated water pressure of about 0.8 to 1.5 MPa. For this reason, it is preferable to provide a fine bubble generating unit 24 that rapidly reduces the pressure of the first concentrated water Ac and generates fine bubbles in the first concentrated water Ac. By generating fine bubbles in the concentrated water of the first semipermeable membrane unit 6 by the fine bubble generating unit 24, the organic matter / microorganism removal unit generates fine bubbles in the case of pressure levitation separation or biological treatment. It is preferable because it can reduce the energy of the blower and compressor, and when the organic matter / microorganism removal unit is a membrane separation unit adopting the cross flow method, it separates into permeate and concentrated water while washing the membrane surface with fine bubbles. This is preferable. Examples of the fine bubble generating unit 24 that rapidly reduces the pressure of the first concentrated water Ac include an aspirator. The position where the fine bubble generating unit 24 is arranged may be any position as long as the pressure of the concentrated water is applied, but as illustrated in FIG. 7, the first concentrated water Ac is concentrated. When the organic matter / microorganism removal unit (pressure filtration unit 12a) is separated using water pressure, it is necessary to generate fine bubbles while maintaining a balance with the energy necessary for the separation.

  In the present invention, physical washing wastewater containing a large amount of organic matter and microorganisms from the organic matter / microorganism removal unit and concentrated wastewater from the membrane separation unit adopting the crossflow method are discharged. As illustrated in FIG. By mixing the treated wastewater such as the washing wastewater and concentrated wastewater 25 of the pressure filtration unit 12a with the concentrated water Bc of the second semipermeable membrane unit 19, and discharging them to the outside through the discharge line 26, there are many organic substances and microorganisms. Since the washing waste water and concentrated waste water of the contained organic matter / microorganism removal unit can be diluted, and the high concentration concentrated water Bc of the second semipermeable membrane unit 19 can also be diluted, it is preferable to the environment.

  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 Mar. 22, 2013 (Japanese Patent Application No. 2013-059548), the contents of which are incorporated herein by reference.

  The present invention produces fresh water from a plurality of types of raw water, such as a combination of seawater and river water, ground water or wastewater treated water, and a fresh water production method and a fresh water production method using a semipermeable membrane unit. Provided is a fresh water production method for efficiently preventing contamination of a semipermeable membrane with organic matter and microorganisms contained in concentrated waste water.

1: treated water A tank 2: treated water A supply pump 3: first pretreatment unit 4: first pretreated water tank 5: first booster pump 6: first semipermeable membrane unit 7: 1st permeated water tank 8, 8a, 8b, 8c: Water quality sensor 9: 1st concentrated water tank 10a: 1st concentrated water supply valve 10b: 2nd concentrated water supply valve 11: 1st concentrated water pump 12: Organic matter / microorganism removal unit 12a: pressurized filtration unit 13: bypass line 14: mixed water tank 15: treated water B tank 16: treated water B supply pump 17: second pretreatment unit 18: second Booster pump 19: second semipermeable membrane unit 20: second permeated water tank 21: pressure sensor 22a, 22b: flocculant tank or adsorbent tank 23a, 23b: flocculant addition pump or adsorbent addition pump 24: fine Bubbles Raw Unit 25: organic / microbial removal unit detergent drain line or concentrated water discharge line 26: discharge line

Claims (16)

The treated water A is treated with the first semipermeable membrane unit to produce fresh water, and the first concentrated water Ac generated when treated with the first semipermeable membrane unit has a solute concentration of the first semipermeable membrane Ac. A method for producing fresh water by mixing the water to be treated B higher than the concentrated water Ac of the water, treating the mixed water with a second semipermeable membrane unit,
An organic matter / microorganism removal line that passes the first concentrated water Ac through an organic matter / microorganism removal unit, reduces the organic matter concentration or microbial concentration of the first concentrated water Ac, and mixes with the treated water B;
Having a bypass line for mixing the first concentrated water Ac with the treated water B without going through the organic matter / microorganism removal unit;
The pressure of the first concentrated water Ac from the organic substance concentration or microbial concentration in the first concentrated water Ac on the upstream side of the organic matter / microorganism removal unit, and the pressure of the supply water of the first semipermeable membrane unit Of the first concentrated water Ac to the organic matter / microorganism removal unit according to at least one of the changes in differential pressure between the inflow side and the non-permeation side of the first semipermeable membrane unit calculated by subtracting A fresh water production method for controlling the amount of water flow.   When the change in the differential pressure between the inflow side and the non-permeate side of the first semipermeable membrane unit exceeds a predetermined value, the first concentration to the organic matter / microorganism removal unit according to the change in the differential pressure When the flow rate of water Ac is controlled and the change in the differential pressure between the inflow side and the non-permeation side of the first semipermeable membrane unit is less than or equal to a predetermined value, the concentration of organic matter or microorganisms in the first concentrated water Ac The fresh water production method according to claim 1, wherein a flow rate of the first concentrated water Ac to the organic matter / microorganism removal unit is controlled according to a concentration.   The fresh water manufacturing method of Claim 1 or Claim 2 which processes the to-be-processed water A by a pre-processing unit, before processing by the said 1st semipermeable membrane unit.   The fresh water manufacturing method according to claim 3, wherein the treatment process constituting the organic matter / microorganism removal unit includes a treatment process different from the treatment process constituting the pretreatment unit in the treated water A.   A fine bubble generating unit that generates fine bubbles by depressurizing the first concentrated water Ac on an upstream side of the organic matter / microorganism removal unit, and generating fine bubbles in the first concentrated water Ac. The fresh water manufacturing method of any one of Claims 1-4.   The fresh water production method according to any one of claims 1 to 5, wherein the organic matter / microorganism removal unit is a pressure filtration unit that separates using the water pressure of the first concentrated water Ac.   The fresh water production method according to any one of claims 1 to 6, wherein a filtration material of the same material as the filtration material of the second semipermeable membrane unit is used as the filtration material of the organic matter / microorganism removal unit. .   The fresh water production method according to any one of claims 1 to 7, wherein the treated wastewater of the organic matter / microorganism removal unit and the concentrated water of the second semipermeable membrane unit are mixed and discharged out of the system. . Processed water A is a method for producing fresh water by mixing treated water B having a solute concentration higher than the treated water A, and treating the mixed water with a semipermeable membrane unit.
An organic matter / microorganism removal line that passes the treated water A through an organic matter / microorganism removal unit, reduces the organic matter concentration or microbial concentration of the treated water A, and mixes with the treated water B;
A bypass line for mixing the water to be treated A with the water to be treated B without going through the organic matter / microorganism removal unit;
A fresh water production method for controlling a flow rate of the water to be treated A to the organic matter / microorganism removal unit according to an organic matter concentration or a microorganism concentration of the water to be treated A on the upstream side of the organic matter / microorganism removal unit.   The fresh water manufacturing method according to claim 9, wherein the water to be treated A is treated by a pretreatment unit before being mixed with the water to be treated B.   The fresh water manufacturing method according to claim 10, wherein the treatment process constituting the organic matter / microorganism removal unit includes a treatment process different from the treatment process constituting the pretreatment unit in the treated water A.   The fresh water production method according to any one of claims 9 to 11, wherein a filtration material of the same material as the filtration material of the semipermeable membrane unit is used for the filtration material of the organic matter / microorganism removal unit.   The fresh water manufacturing method of any one of Claims 9-12 which mixes the treated waste_water | drain of the said organic substance / microbe removal unit, and the concentrated water of the said semipermeable membrane unit, and discharges it out of the system.   The organic substance concentration or microbial concentration is the total organic carbon concentration (TOC), assimilable organic carbon (AOC), soluble organic carbon concentration (DOC), chemical oxygen demand (COD), biological oxygen demand (BOD). ), Ultraviolet absorption (UV), transparent extracellular polymer particles (TEP), adenosine triphosphate (ATP), bacterioacites, and chlorophyll. 14. The fresh water manufacturing method of any one of 13.   The organic matter / microorganism removal unit includes at least one selected from the group consisting of flotation separation, sedimentation separation, lagoon treatment, sand filtration, microfiltration, ultrafiltration, nanofiltration, flocculation treatment, oxidation treatment, and adsorption treatment. The fresh water manufacturing method of any one of Claims 1-14. The fresh water manufacturing method of any one of Claims 1-15 provided with the pre-processing unit which processes the said to-be-processed water B, and combining the said pre-processing unit with the said organic matter / microorganism removal unit.

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