JP7106465B2 - Water treatment system and water treatment method - Google Patents

Description

TECHNICAL FIELD Embodiments of the present invention relate to water treatment systems and water treatment methods.

In recent years, laws and regulations for realizing healthy water circulation have been strengthened. ZLD (Zero Liquid Discharge) reduces the risk of water pollution, regenerates wastewater, and reuses water by regenerating and using it within the factory, and furthermore, reduces the wastewater emitted from the factory to zero. The concept is to conserve the water environment by

In order to reduce the wastewater to zero, it is finally necessary to separate the solids and deionized water by an evaporation method. In the evaporation method, wastewater is heated to generate steam, and this steam is cooled to obtain deionized water, thereby separating solids and deionized water. Two-stage flash evaporation method, multi-stage flash evaporation method, etc. have been put into practical use, and this method has the advantage of obtaining deionized water of extremely high purity. It has the drawback of being inefficient. Therefore, from the viewpoint of reducing energy consumption, it is required to reduce the amount of wastewater treated by the evaporation method as much as possible by increasing the degree of concentration of wastewater as much as possible.

For these reasons, a reverse osmosis (RO) membrane (hereinafter referred to as "RO membrane") is used as a separation membrane for separating concentrated wastewater containing solids from fresh water in the preceding stage of the evaporation method. It is A desalination/concentration system using an RO membrane introduces the water to be treated under pressure into the RO membrane, and deionized water that has passed through the RO membrane It consists of the basic processes of obtaining water and water.

RO membranes can become clogged with silica, hardness scale and biofouling. If the RO membrane is clogged, the entire water treatment system needs to be stopped in order to clean the RO membrane, which lowers the operating rate of the water treatment system. In addition, since the concentrated water that has not been concentrated to the expected degree of concentration is subjected to the evaporation treatment, the heat energy required for evaporation increases, leading to an increase in the overall treatment cost.

However, the RO membrane has the effect of removing almost all substances such as ionic substances, fine particles, organic substances, and some dissolved gases. It is widely used because it has the advantage that it can be

As a method of increasing the concentration rate of wastewater using an RO membrane, the hardness components in the wastewater are removed with a water softening device such as an ion exchange resin, and after decarbonation treatment with a degassing tower or the like, the wastewater is raised to a high pH. A method for RO membrane separation is described. In this method, the hardness component, which is one of the causes of clogging of the RO membrane, is removed with a water softener, and the carbonate ion component is removed with a degassing tower, thereby suppressing hardness scale. Further, by operating the RO membrane separation device with the waste water from which the hardness component and the carbonate ion component have been removed is adjusted to a pH (pH≧10) where at least most of the silica exists in an ionic form, the RO membrane by silica is reduced. This suppresses clogging. Moreover, there is also an effect of suppressing biofouling by increasing the pH of the wastewater.

However, when the RO membrane is operated at a high concentration rate under high pH conditions, the higher the pH, the faster the membrane deterioration rate, and the membrane separation performance decreases over time. On the other hand, when the pH is lowered, silica with low solubility tends to precipitate, clogging of the RO membrane with silica scale occurs, and the system operation rate decreases.

As a method for removing silica, a method of adding magnesium salt and iron salt within a specified concentration range to silica-containing water to precipitate and remove silica is described. However, in this method, it is necessary to newly add a magnesium salt, which increases the chemical cost.

In summary, in a water treatment system, cost reduction can be achieved by reducing the thermal energy required for evaporation of wastewater. For this purpose, it is essential to increase the concentration of the wastewater, and generally, the higher the concentration of the wastewater, the easier it is for silica to precipitate. Silica causes clogging of the separation membrane and becomes a factor of lowering the operating rate. Precipitation of silica is suppressed in a highly alkaline environment, but conversely, in a highly alkaline environment, the rate of membrane deterioration increases and the membrane separation performance decreases, which can be a factor in lowering the operating rate.

Considering the above circumstances, in order to obtain highly concentrated wastewater, even when operating in a highly alkaline environment, the deterioration of membrane separation performance is suppressed, and high operation rate and cost reduction are realized. A water treatment system and method are desired.

U.S. Pat. No. 6,537,456 International Publication No. 2014/136651

The problem to be solved by the present invention is to provide a water treatment system and a water treatment method that realize a high operating rate and cost reduction even when operating in a highly alkaline environment in order to obtain highly concentrated wastewater. is to provide

A water treatment system of an embodiment comprises a water softening unit, a first separation unit, a second separation unit, a coagulating sedimentation unit, and a third separation unit. The water softening unit recovers alkaline earth metals from water to be treated to obtain water to be softened, which is water to be treated. The first separation unit performs desalination at a first operating pressure to separate water to be softened into first desalted water and first concentrated water. The second separation unit performs desalination at a second operating pressure higher than the first operating pressure to separate the first concentrated water into a second desalted water and a second concentrated water. The coagulation-sedimentation unit performs coagulation-sedimentation treatment on a mixed liquid of the regenerated liquid used for the regeneration treatment of the cation exchange resin used for recovering the alkaline earth metal and the second concentrated water, and contains a silica component. Form a flocculated precipitate. The third separation unit performs desalting treatment at a third operating pressure higher than the second operating pressure, and separates the mixed liquid from which the aggregated sediment has been removed into a third desalted water and a third concentrated water. do.

BRIEF DESCRIPTION OF THE DRAWINGS It is a block diagram which shows schematic structure of the water treatment system in which the water treatment method of embodiment was applied. BRIEF DESCRIPTION OF THE DRAWINGS It is a block diagram which shows the structural example of the water treatment system of 1st Embodiment. It is a conceptual diagram which shows the structural example of an adjustment unit. FIG. 4 is a conceptual diagram showing a configuration example of a first separation unit; FIG. 4 is a conceptual diagram showing a configuration example of a second separation unit; FIG. 2 is a conceptual diagram showing a configuration example of a coagulation-sedimentation unit; 2 is a flowchart (1/2) showing an operation example of the water treatment system of the first embodiment; 2 is a flowchart (2/2) showing an operation example of the water treatment system of the first embodiment; It is a block diagram which shows the structural example of the water treatment system of 2nd Embodiment. It is a conceptual diagram which shows the structural example of the fine bubble generator applied to the water treatment system of 2nd Embodiment. It is a flowchart (1/2) which shows the operation example of the water treatment system of 2nd Embodiment. It is a flowchart (2/2) which shows the operation example of the water treatment system of 2nd Embodiment. It is a block diagram which shows the structural example of the water treatment system of 3rd Embodiment. It is a conceptual diagram which shows the structural example of the fine bubble generator applied to the water treatment system of 3rd Embodiment. It is a flow chart which shows an example of operation of a water treatment system of a 3rd embodiment. It is a block diagram which shows the structural example of the water treatment system of 4th Embodiment. It is a conceptual diagram which shows the structural example of the fine bubble generator applied to the water treatment system of 4th Embodiment. It is a flow chart which shows an example of operation of a water treatment system of a 4th embodiment.

FIG. 1 is a block diagram showing a schematic configuration of a water treatment system to which the water treatment method of the embodiment is applied.

That is, the water treatment system 10 includes at least a water softening unit 100 , a desalination unit 200 and a heat treatment device 300 .

The water softening unit 100 includes a strongly acidic cation exchange resin tower 110 filled with a strongly acidic cation exchange resin and a weakly acidic cation exchange resin tower 120 filled with a weakly acidic cation exchange resin.

The desalting unit 200 also includes a first separation unit 210 , a second separation unit 220 , a third separation unit 230 , and a coagulating sedimentation unit 240 .

The water softening unit 100 uses a cation exchange resin to recover alkaline earth metals from water a to be treated, such as factory wastewater, to obtain softened water b, which is water to be treated. . Specifically, the water softening unit 100 first passes the water a to be treated through a strongly acidic cation exchange resin tower 110 to recover a first alkaline earth metal such as calcium, then a weak A second alkaline earth metal, such as magnesium, having a lower ion selectivity than the first alkaline earth metal is recovered by passage through an acidic cation exchange resin column 120 .

The to-be-processed water a becomes the to-be-softened water b by recovering the alkaline earth metal in this manner. The softened water b is supplied to the first separation unit 210 of the desalination unit 200 .

On the other hand, the strongly acidic cation exchange resin tower 110 that recovered the first alkaline earth metal adsorbed the first alkaline earth metal, and the weakly acidic cation exchange resin tower 120 that recovered the second alkaline earth metal. adsorbs the second alkaline earth metal. The strongly acidic cation exchange resin tower 110 and the weakly acidic cation exchange resin tower 120 adsorb not only these alkaline earth metals but also heavy metals such as iron. Therefore, the strongly acidic cation exchange resin tower 110 and the weakly acidic cation exchange resin tower 120 need to be periodically regenerated to remove adsorbed alkaline earth metals and heavy metals. Such regeneration treatment is performed by washing the strongly acidic cation exchange resin tower 110 and the weakly acidic cation exchange resin tower 120 with an acid. The alkaline earth metal adsorbed in the strongly acidic cation exchange resin tower 110 and the weakly acidic cation exchange resin tower 120 is removed from the water softening treatment unit 100 together with the regenerated liquid c, which is the acidic solution used for washing, by this regeneration treatment. Ejected.

This regenerated liquid c is supplied to the coagulation sedimentation unit 240 of the desalination unit 200 by being transported through the cation exchange resin regeneration line L0 by a pump or the like (not shown). In addition, in the water treatment system 10, not only the cation exchange resin regeneration liquid supply line L0 but also many other lines L as described later will be described later, but all of these lines L are, for example, piping.

The regenerated liquid c is not necessarily limited to that generated by the regeneration treatment performed on both the strongly acidic cation exchange resin tower 110 and the weakly acidic cation exchange resin tower 120, and the strongly acidic cation exchange resin tower 110 and the weakly acidic cation exchange resin tower 110 It may also have been obtained from a regeneration process performed on one of the exchange resin towers 120 .

The first separation unit 210 comprises a pressure vessel 211 in which a desalination membrane element 212 having a separation membrane 213, such as an RO membrane, is arranged. Then, the softened water b supplied from the water softening unit 100 is subjected to desalination using the separation membrane 213 at a first operating pressure (preferably about 0 to 3 MPa) to soften the water. The purified water b is separated into demineralized water d1 and concentrated water e1. The concentrated water e1 is more concentrated in TDS (Total Dissolved Solids) than the softened water b. The concentrated water e1 is discharged via line L3 and supplied to the second separation unit 220. As shown in FIG. On the other hand, the desalted water d1 is discharged through the line L4 and reused, for example, in the factory that discharged the water to be treated a.

The second separation unit 220 comprises a pump 227 and a pressure vessel 221 in which a desalination membrane element 222 having a separation membrane 223, such as an RO membrane, is arranged.

The pump 227 is provided in the line L3 and pressurizes the concentrated water e1 discharged from the desalination membrane element 212 to a second operating pressure (preferably 3 to 8 MPa) higher than the first operating pressure, It is supplied to the desalination membrane element 222 . At this time, the concentrated water e1 receives power heat from the pump 227 and is supplied to the desalination membrane element 222 in a heated state. In this way, the pump 227 serves not only as a supply means for supplying the concentrated water e1 to the desalination membrane element 222, but also as a pressurizing/heating means for pressurizing and heating the concentrated water e1 to be supplied to the desalination membrane element 222. It also contributes as a means.

The desalination membrane element 222 desalinates the concentrated water e1 using the separation membrane 223 at a second operating pressure (preferably 3 to 8 MPa) higher than the first operating pressure to concentrate Water e1 is separated into demineralized water d2 and concentrated water e2. Demineralized water d2 is discharged via line L7. The line L7 is connected to the line L4, and the desalted water d2 flows into the line L4, and after being merged with the desalted water d1, is reused, for example, in the factory where the water to be treated a was discharged. The concentrated water e2 is more concentrated in TDS than the concentrated water e1, and is discharged from the desalination membrane element 222 via the line L5.

The line L5 is connected to the coagulation-sedimentation unit 240, and a line L6 for returning part of the concentrated water e2 to the upstream side of the pump 227 of the line L3 is also connected in the middle of the line L5.

Not all of the concentrated water e2 from the desalination membrane element 222 is supplied to the coagulating sedimentation unit 240 through this line L6, but part of it is returned to the line L3 by the pump 227 and mixed with the concentrated water e1. After that, after being pressurized and heated by the pump 227 as described above, it is supplied to the desalination membrane element 222 again. Therefore, to the desalination membrane element 222, not only the concentrated water e1 but also the concentrated water in which the concentrated water e1 and the concentrated water e2 are mixed is supplied to the desalination membrane element 222 while being pressurized and heated by the pump 227 as described above. be. Since this concentrated water has a higher TDS concentration than the concentrated water e1, by returning part of the concentrated water e2 to the line L3 in this way, concentrated water with a higher TDS concentration is supplied to the desalination membrane element 222. It becomes possible to

The coagulating sedimentation unit 240 includes a coagulating sedimentation tank 241 . The concentrated water e2 supplied through the line L5 and the regenerated liquid c supplied through the cation exchange resin regenerated liquid supply line L0 are supplied to the coagulating sedimentation tank 241 and mixed. Since the regenerated liquid c contains an alkaline earth metal such as calcium and magnesium that contributes as a flocculating agent, the mixed liquid of the concentrated water e2 and the regenerated liquid c contains agglomerated sediment f of the silica component. coagulates and precipitates.

The coagulated sediment f is discharged from the coagulated sedimentation tank 241 by a drain or the like. On the other hand, the mixed liquid g from which the flocculated sediment f has been removed is pressurized by a pump or the like from the flocculated sedimentation tank 241 and supplied to the third separation unit 230 .

The third separation unit 230 comprises a pressure vessel 231 in which a desalination membrane element 232 having a separation membrane 233, such as an RO membrane, is arranged. Then, in the desalination membrane element 232, the separation membrane 233 is used to apply the mixed liquid g supplied from the coagulating sedimentation tank 241 to a third operating pressure higher than the second operating pressure (preferably 8 to Desalting treatment is performed at 12 MPa), and the mixture g is separated into desalted water d3 and concentrated water e3. Demineralized water d3 is discharged via line L11. Line L11 is connected to line L4, and desalted water d3 is sent to line L4, combined with desalted water d1 and desalted water d2, and then reused, for example, in the factory that discharged water a to be treated. The concentrated water e3 is more concentrated in TDS than the concentrated water e2, and is supplied to the heat treatment apparatus 300. As shown in FIG.

The heat treatment apparatus 300 concentrates and evaporates the concentrated water e3 supplied from the desalting membrane element 232, thereby extracting salt h, which is a soluble solid content, moisture i, and gaseous volatile components from the concentrated water e3. Collect j.

Salinity h is discarded as concentrated waste. The water i is returned as reclaimed water, for example, to the factory from which the water to be treated a was discharged, and reused. Volatile components j are released into the environment.

Specific embodiments of the water treatment system 10 having such a schematic configuration will be described below. In the following description of each embodiment, the same parts as those shown in FIG. 1 are denoted by the same reference numerals to avoid redundant description.

(First embodiment)
A water treatment system of the first embodiment will be described.

FIG. 2 is a block diagram showing a configuration example of the water treatment system of the first embodiment.

The water treatment system 11 differs from the water treatment system 10 in that it further includes a pretreatment unit 80 and a conditioning unit 180 .

The pretreatment unit 80 is a unit that performs pretreatment including solid content removal treatment, water softening treatment, degassing treatment, and the like on the water to be treated a such as factory wastewater. It is constructed by arranging the device 90, the water softening unit 100 described above, and the degassing device 130 in series.

Pumps (not shown) are provided in front of the solid content removal device 90, the water softening unit 100, and the degassing device 130, respectively, if necessary.

The solid content removal device 90 is realized using, for example, a microfiltration (MF: Microfiltration) membrane, an ultrafiltration (UF: Ultrafiltration) membrane, and a membrane separation technology such as an MBR (Membrane Bioreactor) method. Such a solid matter removal device 90 filters the water a to be treated and removes the solid matter from the water a to be treated. The water a1 from which solids have been removed is supplied from the solids removal device 90 to the water softening unit 100 by a pump (not shown) provided upstream of the water softening unit 100, for example.

The water softening unit 100 softens the water a1 to be treated using a strongly acidic cation exchange resin and a weakly acidic cation exchange resin. For this reason, the water softening unit 100 has a strongly acidic cation exchange resin tower 110 filled with a strongly acidic cation exchange resin in the front stage and a weakly acidic cation exchange resin tower 120 filled with a weakly acidic cation exchange resin in the rear stage. configured as For example, an ion exchange resin having sulfonic acid groups as exchange groups can be used as the strongly acidic cation exchange resin, and an ion exchange resin having carboxylic acid groups as exchange groups can be used as the weakly acidic cation exchange resin.

With such a configuration, the water softening unit 100 uses the strongly acidic cation exchange resin tower 110 and the weakly acidic cation exchange resin tower 120 to remove hardness components composed of alkaline earth metals such as calcium and magnesium from the water to be treated a1. By the removal, the water to be treated a1 is softened to obtain the water to be softened b in which the concentration of the hardness component is reduced.

The water to be softened b is supplied from the water softening unit 100 to the degassing device 130 by a pump (not shown) provided upstream of the degassing device 130, for example.

If a large amount of hardness components such as calcium and magnesium or heavy metals such as iron are adsorbed on the cation exchange resin, the cation exchange resin becomes saturated and the hardness components leak out. Need to implement.

When the strongly acidic cation exchange resin tower 110 is regenerated, a concentrated NaCl solution is supplied to the strongly acidic cation exchange resin tower 110 to exchange hardness components and heavy metals adsorbed on the strongly acidic cation exchange resin with Na. This regenerates the strongly acidic cation exchange resin.

When the weakly acidic cation exchange resin tower 120 is regenerated, a hydrochloric acid solution is supplied to the weakly acidic cation exchange resin tower 120 to exchange hardness components and heavy metals adsorbed on the weakly acidic cation exchange resin with H ^{2 +} . This regenerates the weakly acidic cation exchange resin. Incidentally, after the regeneration treatment with a hydrochloric acid solution, a sodium hydroxide solution may be supplied to regenerate the Na ⁺ -type weakly acidic ion exchange resin.

Furthermore, hydrochloric acid is supplied to the weakly acidic cation exchange resin tower 120 . As a result, the regenerated liquid c (weakly acidic exchange resin regenerated liquid) discharged from the weakly acidic cation exchange resin tower 120 and containing the hardness component is obtained. This regeneration liquid c is supplied to the coagulation-sedimentation tank 241 of the coagulation-sedimentation unit 240 via the cation-exchange resin regeneration-liquid supply line L0.

The degassing device 130 can be an existing one used in pure water production, etc., and can be realized using, for example, a packed decarboxylation tower, an aeration device, a membrane degassing device, a vacuum degassing device, or the like. . In either case, acid such as hydrochloric acid or sulfuric acid is added to the water to be softened b to lower the pH of the water to be softened b to 7 or less, more preferably 5.5 or less, in order to improve the degassing efficiency. is preferred. In the case of the gas-liquid contact type, the G/L ratio (Nm ³ /m ³ ) is preferably in the range of 5-20. Note that the deaerator 130 can be realized using a known technique, and there is no limit to its application.

Such a deaerator 130 deaerates the water to be softened b to deaerate gas such as carbon dioxide from the water to be softened b. The softened water b1 thus deaerated is supplied to the adjustment unit 180 via the line L1.

The adjustment unit 180 is equipment for adjusting the pH of the water to be softened b1 introduced into the first separation unit 210, and the like.

FIG. 3 is a conceptual diagram showing a configuration example of an adjustment unit.

As illustrated in FIG. 3, the adjustment unit 180 includes a liquid mixing tank 181 and a pump 182 provided in a line L1 for supplying softened water b1 from the deaerator 130 to the liquid mixing tank 181. , a chemical solution line La for supplying the chemical solution k to the liquid mixing tank 181, a water quality meter 184 for measuring the water quality of the water to be softened b1 stored in the liquid mixing tank 181, and a line L2, A pump 183 is provided for supplying water to be softened b2, which has undergone pH adjustment or the like in the liquid mixing tank 181, to the desalination membrane element 222.

The chemical liquid k supplied to the liquid mixing tank 181 through the chemical liquid line La includes, for example, a pH adjuster, a disinfectant, a scale inhibitor, a biofouling inhibitor, and a membrane cleaning agent. The chemical solution k is selected according to, for example, the water quality measured by the water quality meter 184 and the material and performance of the separation membranes 213 , 223 and 233 used in the desalination membrane elements 212 , 222 and 232 of the desalination unit 200 . Further, the chemical solution k can be used properly according to the time of steady operation, the time of maintenance, and the like.

Alkaline agents such as caustic soda (NaOH) and potassium hydroxide (KOH) can be used as pH adjusters. With such a pH adjuster, the adjustment unit 180 adjusts the pH of the softened water b1 in the liquid mixing tank 181 to 10 or more, preferably 10.5 or more.

The water quality meter 184 is a pH meter that measures the pH of the softened water b1 that has been pH-adjusted in the liquid mixing tank 181 . Furthermore, a water level meter for measuring the water level of the water to be softened b1 stored in the liquid mixing tank 181, a conductivity meter for measuring the conductivity, and the like may be appropriately included.

The pump 183 is operated when the water quality meter 184 detects that the water quality such as pH of the water to be softened b1 stored in the liquid mixing tank 181 has become suitable for being supplied to the desalination membrane element 222. is activated. As a result, the water to be softened b2 adjusted to a predetermined water quality in the liquid mixing tank 181 is pressurized to a preset pressure by the pump 183, and the desalination membrane element of the first separation unit 210 is sent through the line L2. 212.

The preset pressure is a pressure higher than the osmotic pressure of the separation membrane 213 in the desalination membrane element 212, and is preferably about 0 to 3 MPa, for example.

FIG. 4 is a conceptual diagram showing a configuration example of the first separation unit.

As mentioned above, the first separation unit 210 comprises a pressure vessel 211 in which a desalination membrane element 212 having a separation membrane 213, such as an RO membrane, is arranged. As an example, FIG. 4 shows an example in which the first separation unit 210 includes one pressure vessel 211 and one desalination membrane element 212 is arranged in the pressure vessel 211 . However, the number of pressure vessels 211 provided in the first separation unit 210 is not limited to singular, and may be plural. Also, the number of desalination membrane elements 212 installed inside the pressure vessel 211 is not limited to one, and may be plural.

The desalination membrane element 212 has a separation membrane 213 inside, and also has one inlet 214 and two outlets 215 and 216 .

The introduction part 214 is connected to the line L2 and is an inlet for introducing the softened water b2 supplied from the adjustment unit 180 via the line L2 into the desalination membrane element 212 .

The separation membrane 213 is, for example, a spiral or hollow fiber membrane, filters the water to be softened b2 introduced from the introduction part 214, and desalted water d1 that has passed through the separation membrane 213 and the separation membrane 213 is separated into concentrated water e1 in which TDS is concentrated.

The discharge part 215 is an outlet for discharging the concentrated water e1 from the desalination membrane element 212, and the discharge part 216 is an outlet for discharging the desalted water d1 from the desalination membrane element 212.

The concentrated water e1 discharged from the discharge portion 215 is sent toward the second separation unit 220 on the downstream side through the line L3 connected to the discharge portion 215. As shown in FIG. The desalted water d1 is discharged from the discharge portion 216 and flows into the line L4.

FIG. 5 is a conceptual diagram showing a configuration example of the second separation unit.

Similarly to the first separation unit 210, the second separation unit 220 also includes a pressure vessel 221, and a desalination membrane element 222 is arranged inside the pressure vessel 221. The configuration of the desalination membrane element 222 is the same as the configuration of the desalination membrane element 212, and the separation membrane 223, the introduction section 224, and the two discharge sections 225, 226 are connected to the separation membrane 213, the introduction sections 214, and 2, respectively. Since it corresponds to the two ejection units 215 and 216, redundant description is avoided. In addition, the number of pressure vessels 221 provided in the second separation unit 220 and the number of desalination membrane elements 222 installed inside the pressure vessels 221 are not limited to one, and may be plural. 1 separation unit 210 is the same.

The second separation unit 220 also includes a pump 227 provided in line L3.

The pump 227 raises the pressure of the concentrated water e1 flowing in the line L3 to a pressure higher than the osmotic pressure of the separation membrane 223 of the desalination membrane element 222, and supplies it from the introduction part 224 into the desalination membrane element 222. This pressure is higher than the osmotic pressure of the separation membrane 213 of the desalination membrane element 212, preferably about 3 to 8 MPa. Also, at this time, the concentrated water e1 receives power heat from the pump 227, and is supplied to the desalination membrane element 222 in a heated state. In this way, the pump 227 serves not only as a supply means for supplying the concentrated water e1 to the desalination membrane element 222, but also as a pressurizing/heating means for pressurizing and heating the concentrated water e1 to be supplied to the desalination membrane element 222. It also contributes as a means.

In the desalination membrane element 222, the concentrated water e1 introduced from the introduction part 224 is filtered by the separation membrane 223, and the desalted water d2 that has passed through the separation membrane 223 and the TDS that has not passed through the separation membrane 223 are further concentrated. and the concentrated water e2.

The demineralized water d2 is discharged from the discharge portion 226 and flows into the line L7. The line L7 is connected to the line L4, and the desalted water d2 flows into the line L4, and after being merged with the desalted water d1, is reused, for example, in the factory where the water to be treated a was discharged.

The concentrated water e2 is discharged out of the desalination membrane element 222 from the discharge part 225 . A line L5 leading to the coagulating sedimentation tank 241 of the coagulating sedimentation unit 240 is connected to the discharge part 225 .

The line L5 is also connected to a line L6 for returning part of the concentrated water e2 to the upstream side of the pump 227 of the line L3. Therefore, as described above with reference to FIG. 1, not all of the concentrated water e2 from the desalination membrane element 222 is supplied to the coagulating sedimentation tank 241, but part of it is returned to the line L3 by the pump 227. , and the concentrated water e1, and after being pressurized and heated by the pump 227 as described above, it is supplied to the desalination membrane element 222 again.

Therefore, not only concentrated water e1 but also concentrated water in which concentrated water e1 and concentrated water e2 are mixed is supplied to desalination membrane element 222 while being pressurized and heated by pump 227 . With such a configuration, it becomes possible to supply concentrated water with a higher TDS concentration to the desalination membrane element 222 .

FIG. 6 is a conceptual diagram showing a configuration example of a coagulating sedimentation unit.

The coagulation-sedimentation unit 240 includes a coagulation-sedimentation tank 241, a water quality meter 242, a pump 243, and a chemical solution line Lb.

The coagulating sedimentation tank 241 is supplied with the concentrated water e2 from the desalination membrane element 222 via the line L5. Further, the regenerated liquid c is supplied from the water softening unit 100 via the cation exchange resin regenerated liquid supply line L0. As a result, in the coagulating sedimentation tank 241, the concentrated water e2 and the regenerated liquid c are mixed and stored as a mixed liquid.

The chemical liquid m is further supplied to the coagulating sedimentation tank 241 through the chemical liquid line Lb. Examples of the chemical solution m include alkaline agents such as caustic soda and potassium hydroxide, and pH adjusters such as acid agents such as hydrochloric acid. As a result, in the coagulating sedimentation tank 241, the pH of the mixed solution is adjusted to a pH at which silica efficiently precipitates, preferably pH 8 to 10.5.

As described above, in addition to containing alkaline earth metals such as calcium and magnesium that contribute as flocculating agents in the regenerating liquid c, such pH adjustment makes , aggregated sediment f of the silica component is aggregated and sedimented. In addition, aggregation precipitation of a silica component is accelerated|stimulated, so that temperature is high. As described above, the pump 227 also contributes as a heating means, so that the heating effect of the pump 227 causes the silica component to precipitate more efficiently in the mixed liquid stored in the coagulation-sedimentation tank 241. Become. The coagulated sediment f is discharged from the coagulated sedimentation tank 241 through the drain pipe L8.

The water quality meter 242 is a pH meter that measures the pH of the mixed liquid. The water quality meter 242 may further include a water level meter for measuring the water level of the liquid mixture stored in the coagulating sedimentation tank 241, a conductivity meter for measuring conductivity, and the like.

The pump 243 is provided on a line L9 leading to the desalination membrane element 232 of the third separation unit 230 and is activated according to the measurement result of the water quality meter 242. For example, the pump 243 is activated when the pH value measured by the water quality meter 242 reaches a suitable value for supplying to the desalination membrane element 232 . As a result, the pump 243 supplies the mixed liquid g from which the aggregated sediment f has been removed to the desalination membrane element 232 while raising the pressure to a preset pressure.

The preset pressure is a pressure higher than the osmotic pressure of the separation membrane 233 in the desalination membrane element 232 . This pressure is higher than the osmotic pressure of the separation membrane 223 of the desalination membrane element 222, and is preferably about 8 to 12 MPa, for example.

Similarly to the first separation unit 210, the third separation unit 230 also includes a pressure vessel 231, and a desalination membrane element 232 is arranged inside the pressure vessel 231. The structure of the desalination membrane element 232 is the same as the structure of the desalination membrane element 212. In addition to the separation membrane 233 corresponding to the separation membrane 213, the introduction part 214 and the two discharge parts 215 and 216 corresponding to the introduction part and the Since the two discharge units are also provided in the same manner, redundant description is avoided. Further, the number of pressure vessels 231 provided in the third separation unit 230 and the number of desalination membrane elements 232 installed inside the pressure vessels 231 are not limited to one, and may be plural. 1 separation unit 210 is the same.

The desalting membrane element 232 uses the separation membrane 233 to separate the liquid mixture g supplied from the coagulation-sedimentation unit 240 through the line L9 into desalted water d3 and concentrated water e3. The concentrated water e3 has a higher TDS concentration than the concentrated water e2.

The desalted water d3 is discharged from the desalted membrane element 232 and flows into the line L11. The line L11 is connected to the line L4, and the desalted water d3 flows into the line L4, and after being combined with the desalted water d1 and the desalted water d2, is reused, for example, in the factory that discharged the water to be treated a.

On the other hand, the concentrated water e3 is supplied to the heat treatment apparatus 300 through the line 10 by a pump (not shown) provided in the line L10.

The heat treatment apparatus 300 includes, for example, an evaporative concentration apparatus, an evaporative drying apparatus, an organic substance heat treatment apparatus, and the like, and performs at least one or more heat treatment processes such as distillation recovery using heat, evaporative drying treatment, incineration, and catalytic oxidation. heat treatment process. For example, when the main component of the ions in the concentrated water e3 is organic amines such as alkanolamine, the organic matter can be separated, concentrated, and discarded by the heat treatment process of the organic matter heat treatment apparatus. In addition, the heat treatment process of the organic matter heat treatment apparatus produces heat treated carbon and recovers moisture.

In this manner, the heat treatment apparatus 300 recovers the salt content h, the water content i, and the volatile component j, which are soluble solids, from the concentrated water e3 by concentrating and evaporating the concentrated water e3. Salinity h is discarded as concentrated waste. The water i is returned as reclaimed water, for example, to the factory from which the water to be treated a was discharged, and reused. Volatile components j are released into the environment.

For example, when the main component of the ions in the concentrated water e3 is inorganic ions, the concentration/evaporation drying process by the heat treatment device 300 makes it possible to recover the ions as solid salts.

Note that the heat treatment apparatus 300 may be provided with a crystallizer, a centrifugal separator, and the like. Thereby, it becomes possible to collect solid salt more smoothly.

Next, an operation example of the water treatment system 11 of the first embodiment configured as described above will be described.

7 and 8 are flowcharts showing an operation example of the water treatment system of the first embodiment.

As an example of the operation of the water treatment system 11, a case where water to be treated a such as factory wastewater is treated will be described.

Water to be treated a to be treated by the water treatment system 11 is sent by, for example, a pump to the solid content removal device 90 of the pretreatment unit 80, filtered in the solid content removal device 90, and solid content is removed (S1). . The water to be treated a1 from which solids have been removed is supplied to the strongly acidic cation exchange resin tower 110 of the water softening unit 100 by, for example, a pump.

In the strongly acidic cation exchange resin tower 110, hardness components, which are alkaline earth metals with high ion selectivity such as calcium, are removed from the water a1 to be treated, and the water a1 to be treated is softened (S2).

The softened water to be treated a1 is then supplied to the weakly acidic cation exchange resin tower 120, where alkaline earths such as magnesium having ion selectivities lower than calcium By removing metal hardness components, the water is further softened (S3), and supplied as softened water b to the degassing device 130 by, for example, a pump (S4).

On the other hand, due to the processing in step S2, the strongly acidic cation exchange resin tower 110 adsorbs an alkaline earth metal such as calcium, and due to the processing in step S3, the weakly acidic cation exchange resin tower 120 adsorbs Alkaline earth metals and heavy metals such as iron are adsorbed. Therefore, the strongly acidic cation exchange resin tower 110 and the weakly acidic cation exchange resin tower 120 need to be periodically regenerated to remove adsorbed alkaline earth metals and heavy metals.

When performing regeneration treatment of the strongly acidic cation exchange resin tower 110, a concentrated NaCl solution is supplied to the strongly acidic cation exchange resin tower 110 to remove hardness components and heavy metals adsorbed on the strongly acidic cation exchange resin, Na is exchanged with This results in regeneration of the strongly acidic cation exchange resin.

When the weakly acidic cation exchange resin tower 120 is to be regenerated, a hydrochloric acid solution is supplied to the weakly acidic cation exchange resin tower 120 to remove hardness components and heavy metals adsorbed on the weakly acidic cation exchange resin, and H ⁺ is exchanged with This results in regeneration of the weakly acidic cation exchange resin.

Furthermore, hydrochloric acid is supplied to the weakly acidic cation exchange resin tower 120 . As a result, the regenerated liquid c (weakly acidic exchange resin regenerated liquid) discharged from the weakly acidic cation exchange resin tower 120 and containing the hardness component is obtained. This regenerated liquid c is supplied to the coagulating sedimentation unit 240 through the cation exchange resin regenerated liquid supply line L0, as described in step S10 later.

In step S4, the softened water b is deaerated in the deaerator 130, and a gas such as carbon dioxide is deaerated from the softened water b (S4). The softened water b1 thus degassed has a TDS concentration of, for example, about 1000 mg/L to several 1000 mg/L. It is supplied to the bath 181 (S5).

The liquid mixing tank 181 is also supplied with a chemical liquid k such as a pH adjuster, a disinfectant, a scale inhibitor, a biofouling inhibitor, and a membrane cleaning agent from a chemical liquid line La. As the pH adjuster, for example, caustic soda (NaOH) or an alkaline agent such as potassium hydroxide (KOH) is used. The pH of the water to be softened b1 is adjusted to 10 or more, preferably 10.5 or more in the liquid mixing tank 181 by such a pH adjuster.

The pH of the water to be softened b1 that has been pH-adjusted in the liquid mixing tank 181 in this way is measured by the water quality meter 184 . When the water quality meter 184 detects that the pH is 10 or more, more preferably 10.5 or more, the pump 183 is activated, and the water to be softened b2 is discharged from the liquid mixing tank 181 by the pump 183. , is supplied to the first separation unit 210 through the line L2 while being raised to a preset pressure (S6). The preset pressure is a pressure higher than the osmotic pressure of the separation membrane 213 in the desalination membrane element 212 of the first separation unit 210, and is preferably about 0 to 3 MPa, for example.

The softened water b2 supplied to the first separation unit 210 is introduced into the desalination membrane element 212 from the introduction section 214, and the permeated water that permeates the separation membrane 213 is desalinated water d1 from the discharge section 216. It is discharged into line L4. On the other hand, the concentrated water e1 in which the TDS is concentrated without passing through the separation membrane 213 is discharged from the discharge portion 215 into the line L3 (S7).

A pump 227 is provided in the line L3, and the pump 227 causes the concentrated water e1 flowing in the line L3 to be pumped at a pressure higher than that of the permeable membrane of the separation membrane 223 of the desalination membrane element 222 of the second separation unit 220. It is supplied to the desalination membrane element 222 of the separation unit 220 while being pressurized to a certain value, for example, about 3 to 8 MPa (S8).

In the desalination membrane element 222, permeated water that has passed through the separation membrane 223 is discharged from the discharge part 226 into the line L7 as desalted water d2. On the other hand, concentrated water e2 in which TDS is more concentrated than concentrated water e1 without passing through separation membrane 223 is discharged from discharge portion 225 into line L5 (S9).

The line L5 extends to the coagulating sedimentation tank 241 of the coagulating sedimentation unit 240, and is also connected to the line L6 for returning part of the concentrated water e2 to the upstream side of the pump 227 of the line L3. Therefore, not all of the concentrated water e2 discharged from the discharge part 225 is supplied to the coagulating sedimentation tank 241, but a part of it is returned to the line L3 by the pump 227 and mixed with the concentrated water e1. , and after being pressurized and heated by the pump 227, it is again supplied to the desalination membrane element 222 of the second separation unit 220, and the process of step S8 is repeated. As a result, concentrated water with a higher TDS concentration is supplied to the desalination membrane element 222 .

Of the concentrated water e2 discharged from the discharge part 225 to the line L5, the concentrated water e2 that is not returned to the line L3 is supplied to the coagulating sedimentation tank 241 of the coagulating sedimentation unit 240. In addition, in the coagulation sedimentation tank 241, the regeneration liquid c containing the hardness component, which is an alkaline earth metal such as calcium and magnesium, obtained in step S3 is coagulated and sedimented through the cation exchange resin regeneration liquid supply line L0. It is supplied to the coagulating sedimentation tank 241 of the unit 240 (S10).

As a result, in the coagulating sedimentation tank 241, a mixed liquid of the concentrated water e2 and the regenerated liquid c is stored.

The chemical liquid m is further supplied to the coagulating sedimentation tank 241 through the chemical liquid line Lb. The chemical liquid m is, for example, a pH adjuster, and by supplying the pH adjuster to the coagulation sedimentation tank 241, the pH of the mixture is adjusted to a pH at which silica efficiently precipitates, preferably pH 8 to 10.5. .

As described above, the regenerated liquid c contains alkaline earth metals such as calcium and magnesium that contribute as flocculating agents, and in addition, the pH is adjusted in this way, so that the flocculation sedimentation tank At 241, the aggregated sediment f of the silica component is efficiently aggregated and sedimented in the mixed liquid. The coagulated sediment f is discharged from the coagulated sedimentation tank 241 through the drain pipe L8.

A line L9 from the coagulation sedimentation tank 241 to the desalination membrane element 232 of the third separation unit 230 is provided with a pump 243 that is activated according to the measurement result of the water quality meter 242 . For example, when the water quality meter 242 is a pH meter, the pump 243 adjusts the pH value of the liquid mixture measured by the pH meter to an appropriate value for supplying to the desalination membrane element 232 of the third separation unit 230. is activated when

As a result, the mixed liquid g from which the coagulated sediment f has been removed is supplied from the coagulating sedimentation tank 241 to the third separation unit 230 via the line L9 while being pressurized to a preset pressure by the pump 243. (S11).

The preset pressure is a pressure higher than the osmotic pressure of the separation membrane 233 in the desalination membrane element 232 . This pressure is higher than the osmotic pressure of the separation membrane 223 of the desalination membrane element 222, and is preferably about 8 to 12 MPa, for example.

The mixed liquid g supplied to the third separation unit 230 is supplied to the desalination membrane element 232, and permeated water that has passed through the separation membrane 233 is discharged into the line L11 as desalted water d3. On the other hand, the concentrated water e3, which does not pass through the separation membrane 233 and is more concentrated in TDS than the liquid mixture g, is discharged into the line 10 (S12) and supplied to the heat treatment apparatus 300 (S13).

In step S13, in the heat treatment device 300, the concentrated water e3 is subjected to, for example, a concentration/evaporation drying process, whereby salt content h, water content i, and volatile components j, which are soluble solids, are removed from the concentrated water e3. It is collected (S14).

The salinity h recovered in step S14 is discarded (S15), the volatile component j is released to the environment (S16), and the moisture i is returned as reclaimed water, for example, to the factory that discharged the water to be treated a, It is reused (S17). In addition, the desalted water d1 recovered in step S7, the desalted water d2 recovered in step S9, and the desalted water d3 recovered in step S12 are also returned to the factory from which the water to be treated a was discharged and reused. (S17).

As described above, the water treatment system 11 reduces the possibility of clogging of the separation membrane and suppresses membrane deterioration even when the separation membrane is used in a highly alkaline environment. , it is possible to improve the operating rate.

That is, the water treatment system 11 can supply the concentrated water e3 having a higher TDS concentration to the heat treatment apparatus 300 because of the structure in which the three desalination membrane elements 212, 222, and 232 are connected in series.

In particular, not all of the concentrated water e2 from the desalination membrane element 222 is supplied to the coagulation sedimentation tank 241, but part of it is supplied to the desalination membrane element 222 again. As a result, the TDS concentration of the concentrated water e3 supplied to the heat treatment apparatus 300 is also, for example, 80,000 mg/L or more, preferably 100,000 mg/L. It is possible to obtain extremely high values as described above.

The higher the TDS concentration of the concentrated water e3, the smaller the amount of water contained in the concentrated water e3. Therefore, it is possible to reduce the thermal energy consumed during the concentration/evaporation drying process in the heat treatment apparatus 300. . This makes it possible to reduce costs. It also becomes possible to reduce the amount of waste.

When treating concentrated water having a high TDS concentration in this way, the separation membranes 213, 223, and 233 in the desalination membrane elements 212, 222, and 232 are more likely to be clogged with silica or the like.

However, in the water treatment system 11, solid components, hardness components, carbonic acid components, etc. are removed in the solid content removal device 90, and silica components are precipitated and removed in the coagulation sedimentation tank 241, so that the separation membrane 213 , 223, 233 of silica or the like can be reduced.

In particular, when the concentrated water e1 and a part of the concentrated water e2 are supplied again to the desalination membrane element 222, they are heated by the operation heat of the pump 227, so the solubility of silica contained in these concentrated waters is Raised. As a result, in the coagulation sedimentation tank 241, more coagulation sediment f of the silica component can be condensed and precipitated and removed, so the risk of clogging of the separation membranes 213, 223, 233 can be reduced.

Thus, according to the water treatment system 11, clogging of the separation membranes 213, 223, 233, hardness scale deposition, and silica scale deposition are reduced, so that each desalination membrane element 212, 222, 232 can be operated for a long period of time, thereby improving the operating rate.

In addition, magnesium, calcium, etc., which contribute as a flocculating agent for the generation of the flocculated sediment f in the flocculated sedimentation unit 240, are recovered by the cation exchange resin of the water softening treatment unit 100. There is no need to newly add calcium or the like, and chemical costs can be reduced.

As described above, according to the water treatment system of the first embodiment, in order to concentrate the waste liquid to a high concentration using the separation membrane, even when operating in a highly alkaline environment, separation By keeping the possibility of clogging of the membrane low, it is possible to improve the operating rate and reduce costs.

Next, second to fourth embodiments will be described. In addition, in the following description of each embodiment, the same reference numerals are used to denote the same parts as those already described, and redundant description is avoided.

(Second embodiment)
FIG. 9 is a block diagram showing a configuration example of the water treatment system of the second embodiment.

The water treatment system 12 has a configuration in which a fourth separation unit 400 and a fine bubble generation unit 500 are added to the water treatment system 11 .

The fourth separation unit 400, like the first separation unit 210, the second separation unit 220 and the third separation unit 230, comprises a pressure vessel 401 in which a separation membrane, for example an RO membrane, is placed. A desalination membrane element 402 having 403 is arranged. As an example, FIG. 9 shows an example in which the fourth separation unit 400 includes one pressure vessel 401 and one desalination membrane element 402 is arranged in the pressure vessel 401 . However, the number of pressure vessels 401 provided in the fourth separation unit 400 is not limited to singular, and may be plural. Also, the number of desalination membrane elements 402 installed inside the pressure vessel 401 is not limited to one, and may be plural.

The desalination membrane element 402 has an inlet 404 connected to the line L4.

The introduction part 404 introduces into the desalination membrane element 402 the desalted water d (mixture of desalted waters d1, d2, and d3) supplied via the line L4.

Similar to the separation membranes 213, 223, and 233, the separation membrane 403 is, for example, a spiral or hollow fiber membrane, and filters the desalted water d introduced from the introduction part 404 to pass through the separation membrane 403. and the concentrated water e4 that does not permeate the separation membrane 403 and is concentrated in TDS.

The discharge part 405 is an outlet for discharging the concentrated water e4 from the desalination membrane element 402, and the discharge part 406 is an outlet for discharging the permeated water n from the desalination membrane element 402.

The concentrated water e4 discharged from the discharge part 405 is supplied to the fine bubble generation unit 500 via the line L12 connected to the discharge part 405. The permeated water n discharged from the discharge part 406 is discharged from the desalination membrane element 402 via the line L13 connected to the discharge part 406, and is reused, for example, in the factory where the water to be treated a was discharged.

The fine bubble generation unit 500 is a fine bubble generation device 501 that generates fine bubbles from gas dissolved in the concentrated water e4 by reducing the pressure of the concentrated water e4 supplied from the desalination membrane element 402 via the line L12. It has

FIG. 10 is a conceptual diagram showing a configuration example of a fine bubble generator applied to the water treatment system of the second embodiment.

FIG. 10 shows a venturi-type fine-bubble generator 501, which includes a venturi tube 502 having a nozzle portion 503 to reduce and expand the cross-sectional area.

The upstream side (upper side in the drawing) of the venturi tube 502 is connected to the line L12, and the concentrated water e4 is introduced from the line L12 to the venturi tube 502 by a pump (not shown).

When the concentrated water e4 introduced into the venturi tube 502 passes through the nozzle part 503, the rapid decompression causes the gas dissolved in the concentrated water e4 to expand, resulting in bubbles. It is finely pulverized to generate fine bubbles q.

The fine bubble generator 501 is not limited to the venturi type shown in FIG. 10, and may be an executor type (not shown) that introduces gas from the outside. In the executor type, gas is sucked in using the negative pressure generated by the amount of liquid passing through a narrow channel at high speed, and the cavitation caused by the expansion of the downstream channel breaks the sucked gas into fine particles. generate bubbles.

The downstream side (lower side in the figure) of the venturi tube 502 is connected to the line L13, and the concentrated water e4 containing the fine bubbles q generated by the fine bubble generator 501 is sent to the liquid mixing tank 181 via the line L13. supplied to

The fine bubbles q have an average diameter of 1000 nm or less, have high permeability in the separation membranes 213, 223, 233, and 403 as well as stability in liquid, and prevent scale and biofouling in the separation membranes 213, 223, 233, and 403. increase the effect of preventing In addition, since the surface of the fine bubbles q is hydrophobic and charged, it becomes easy to attach scale inhibitors, biofouling anti-fouling agents, pH adjusters, bactericides, membrane cleaning agents, and the like. Therefore, not only the bubble stability but also the permeability of the separation membranes 213, 223, 233, 403 are enhanced, and the scale and biofouling prevention effect are enhanced.

In addition, since the effect of preventing scale and biofouling increases as the average diameter decreases, the average diameter of the fine bubbles q is preferably 150 nm or less.

Next, an operation example of the water treatment system 12 of the second embodiment configured as above will be described.

11 and 12 are flowcharts showing an operation example of the water treatment system of the second embodiment.

Differences from FIGS. 7 and 8 will be described below.

The desalted water d1 discharged in step S7, the desalted water d2 discharged in step S9, and the desalted water d3 discharged in step S12 join in line L4, are mixed, and then supplied to the fourth separation unit 400. (S20), and the mixed desalted water is separated into concentrated water e4 and permeated water n by separation membrane 403 (S21).

In step S17, the permeated water n is returned as reclaimed water, for example, to the factory that discharged the water to be treated a and reused (S17).

On the other hand, the concentrated water e4 is supplied to the fine bubble generation unit 500, and the fine bubbles q are generated from the concentrated water e4 in the fine bubble generation device 501 (S22). The generated fine bubbles q are supplied to the adjustment unit 180 together with the concentrated water e4, and are mixed with the softened water b1 in the liquid mixing tank 181 before the process of step S5 is performed.

As a result, fine bubbles q are contained in the solution treated in each of the desalination membrane elements 212, 222, 232, 402. It is possible to increase permeability and enhance the effect of preventing scale and biofouling.

(Third embodiment)
FIG. 13 is a block diagram showing a configuration example of the water treatment system of the third embodiment.

FIG. 14 is a conceptual diagram showing a configuration example of a fine bubble generator applied to the water treatment system of the third embodiment.

The water treatment system 13 of the third embodiment is a modification of the water treatment system 12 of the second embodiment, and the configuration of the fine bubble generation unit 600 provided in the water treatment system 13 is It differs from the configuration of the provided fine bubble generation unit 500 .

As shown in FIG. 14, the fine-bubble generating unit 600 includes a fine-bubble generating device 601 having a configuration in which the fine-bubble generating device 501 further includes an air introduction line 602 for taking in air r.

A fine bubble generator 601 exemplified in FIG. 14 is of the venturi type as in FIG. , and an air introduction line 602 for taking in air r from the surroundings.

The air introduction line 602 is connected to the venturi tube 502 upstream of the nozzle portion 503 where the cross-sectional area of the venturi tube 502 is the smallest. As a result, the concentrated water e4 enters the nozzle section 503 while being mixed with the air r and containing bubbles of the air r.

When the concentrated water e4 containing air bubbles passes through the nozzle part 503, the rapid decompression causes the air bubbles to expand. q occurs.

With such a configuration, the fine bubble generator 601 mixes not only the gas dissolved in the concentrated water e4 but also the air r taken in from the air introduction line 602 with the concentrated water e4 to reduce the pressure. A fine bubble q can be generated.

Like the fine bubbles q generated by the fine bubble generator 501, the fine bubbles q generated by the fine bubble generator 601 are also preferably bubbles with an average diameter of 1000 nm or less, preferably 150 nm or less.

As described above, even in the configuration in which the fine bubbles q are generated using not only the bubbles of the expanded gas dissolved in the concentrated water e4 but also the air bubbles of the air r taken in from the surroundings, the separation membranes 213 and 223 , 233, and 403 can be suppressed from occurring scale deposition and biofouling.

In particular, when the fine bubbles q contain carbon dioxide, it is known that the bactericidal effect and the biofouling suppressing effect are enhanced. Since air contains carbon dioxide, the fine bubbles q generated by the fine bubble generator 601 can further enhance the sterilization effect and the biofouling suppression effect.

Therefore, as a modification, the fine bubble generator 601 uses air taken in from an air cylinder or a carbon dioxide cylinder instead of using the air r taken in from the surroundings to generate the fine bubbles q. Carbon dioxide can also be used. In particular, fine bubbles q generated using carbon dioxide taken from a carbon dioxide cylinder have a higher carbon dioxide content than fine bubbles q generated using air. For this reason, it is also possible to realize a higher sterilization effect and a higher biofouling suppression effect by the fine bubbles q generated using the carbon dioxide taken in from the carbon dioxide cylinder.

Next, an operation example of the water treatment system 13 of the third embodiment configured as above will be described.

FIG.15 and FIG.12 is a flowchart which shows the operation example of the water treatment system of 3rd Embodiment.

Below, FIG. 15 will be described with respect to points different from FIG. 11 . Processing other than that shown in FIG. 15 is the same as that shown in FIG. 12, which has already been described, so redundant description is avoided.

The concentrated water e4 generated in step S21 is supplied to the fine bubble generation unit 600, and fine bubbles q are generated from the concentrated water e4 mixed with air r in the fine bubble generation device 601 (S31). The generated fine bubbles q are supplied to the adjustment unit 180 and mixed with the water to be softened b1 in the liquid mixing tank 181 before the process of step S5 is performed.

As a result, fine bubbles q are contained in the solution treated in each of the desalination membrane elements 212, 222, 232, 402. It is also possible to increase the permeability and enhance the anti-scaling and biofouling effect. Moreover, due to the effect of carbon dioxide, it is possible to achieve a higher sterilization effect and a higher biofouling suppression effect than in the case of the water treatment system 12 .

(Fourth embodiment)
FIG. 16 is a block diagram showing a configuration example of the water treatment system of the fourth embodiment.

FIG. 17 is a conceptual diagram showing a configuration example of a fine bubble generator applied to the water treatment system of the fourth embodiment.

The water treatment system 14 of the fourth embodiment is a modification of the water treatment system 13 of the third embodiment, and the configuration of the fine bubble generation unit 700 included in the water treatment system 14 is It differs from the configuration of the provided fine bubble generation unit 600 . Further, a line L14 is provided for supplying the degassed gas s, such as carbon dioxide, degassed in the deaerator 130 to the fine bubble generation unit 700. As shown in FIG.

The fine bubble generation unit 700 includes a fine bubble generation device 701 having a deaeration gas introduction line 702 instead of the air introduction line 602 in the fine bubble generation device 601, as shown in FIG. The degassed gas introduction line 702 is connected to the line L14. As a result, the deaerated gas s supplied from the deaerator 130 is supplied to the fine bubble generator 701 from the deaerated gas introduction line 702 via the line 14 .

In the fine bubble generator 701, the degassing gas introduction line 702 is connected to the venturi tube 502 upstream of the nozzle portion 503 where the cross-sectional area of the venturi tube 502 is the smallest. As a result, the concentrated water e4 is mixed with the degassed gas s and enters the nozzle part 503 while containing bubbles of the degassed gas s.

When the concentrated water e4 containing bubbles of the degassed gas s passes through the nozzle part 503, the rapid decompression causes the bubbles of the degassed gas s to expand. fine bubble q is generated.

With such a configuration, the fine bubble generator 701 mixes not only the gas dissolved in the concentrated water e4 but also the degassed gas s taken in from the degassed gas introduction line 702 with the concentrated water e4 to reduce the pressure. A fine bubble q can also be generated by

The fine bubbles q generated by the fine bubble generator 701 are also preferably bubbles with an average diameter of 1000 nm or less, preferably 150 nm or less.

In this way, even in the configuration in which the fine bubbles q are generated using not only the bubbles expanded by the gas dissolved in the concentrated water e4 but also the bubbles of the degassed gas s from the deaerator 130, each The occurrence of scale deposition and biofouling in the separation membranes 213, 223, 233, and 403 can be suppressed.

As described above, when the fine bubbles q contain carbon dioxide, it is known that the sterilization effect and the biofouling suppression effect are enhanced. It also contains carbon. Therefore, the fine bubbles q generated by the fine bubble generator 701 can also enhance the sterilization effect and the biofouling suppression effect.

Next, an operation example of the water treatment system 14 of the fourth embodiment configured as above will be described.

FIG.18 and FIG.12 is a flowchart which shows the operation example of the water treatment system of 4th Embodiment.

Below, FIG. 18 will be described with respect to points different from FIG. 15 . Processing other than that shown in FIG. 18 is the same as that shown in FIG. 12, which has already been explained, so redundant explanation is avoided.

Step S40 is executed instead of step S4. In step S40, similarly to step S4, the degassing device 130 deaerates the water to be softened b, degassing a gas such as carbon dioxide from the water to be softened b, In addition to the degassed water to be softened b<b>1 being supplied to the liquid mixing tank 181 of the adjustment unit 180 , the degassed gas s is supplied to the fine bubble generation unit 700 .

Also, the concentrated water e4 generated in step S21 is also supplied to the fine bubble generation unit 700. FIG.

In the fine bubble generation unit 700, the fine bubble generation device 701 generates fine bubbles q from the concentrated water e4 mixed with the degassed gas s (S41). The generated fine bubbles q are supplied to the adjustment unit 180 and mixed with the water to be softened b1 in the liquid mixing tank 181 before the process of step S5 is performed.

As a result, fine bubbles q are contained in the solution treated in each of the desalination membrane elements 212, 222, 232, 402. It is also possible to increase the permeability and enhance the anti-scaling and biofouling effect. In addition, since the degassed gas s also contains carbon dioxide, as described in the third embodiment, a higher sterilization effect and higher biofouling than in the case of the water treatment system 12 It becomes possible to realize the suppression effect.

As described above, according to the water treatment systems of the first to fourth embodiments, the separation membrane is used to concentrate the waste liquid to a high degree of concentration, even when operating in a highly alkaline environment. Also, by suppressing the possibility of clogging of the separation membrane, it is possible to improve the operating rate and reduce the cost.

While several embodiments of the invention have been described, these embodiments have been presented by way of example and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, replacements, and modifications can be made without departing from the scope of the invention. These embodiments and their modifications are included in the scope and spirit of the invention, as well as the scope of the invention described in the claims and equivalents thereof.

10 to 14 Water treatment system 80 Pretreatment unit 90 Solid content removal device 100 Water softening unit 110 Strongly acidic cation exchange resin tower 120 Weakly acidic cation exchange resin Column 130 Deaerator 180 Adjustment unit 181 Liquid mixing tank 182, 183 Pump 184 Water quality meter 200 Desalting unit 210 First separation unit 211 pressure vessel 212 desalination membrane element 213 separation membrane 214 introduction part 215, 216 discharge part 220 second separation unit 221 pressure vessel 222 Desalination membrane element 223 Separation membrane 224 Introduction section 225, 226 Discharge section 227 Pump 230 Third separation unit 231 Pressure vessel 232 Desalination Membrane element 233 Separation membrane 240 Coagulation sedimentation unit 241 Coagulation sedimentation tank 242 Water quality meter 243 Pump 300 Heat treatment device 400 Fourth separation unit 401 Pressure vessel 402 Desalination membrane element 403 Separation membrane 404 Introduction section 405, 406 Discharge section 500 Fine bubble generation unit 501 Fine bubble generation device 502 • Venturi tube 503 Nozzle part 600 Fine bubble generation unit 601 Fine bubble generation device 602 Air introduction line 700 Fine bubble generation unit 701 Fine bubble generation device 702・・Deaeration gas introduction line.

Claims (13)

a water softening unit for recovering alkaline earth metals from water to be treated to obtain water to be softened, which is the water to be treated which has been softened;
a first separation unit that desalinates at a first operating pressure and separates the water to be softened into a first desalted water and a first concentrated water;
a second separation unit that performs desalination at a second operating pressure higher than the first operating pressure to separate the first concentrated water into a second desalted water and a second concentrated water;
Aggregation sedimentation treatment is performed on a mixed solution of the regenerated liquid used in the regeneration treatment of the cation exchange resin used for recovering the alkaline earth metal and the second concentrated water, and a flocculation sediment containing a silica component is obtained. a coagulating sedimentation unit for producing
Desalting is performed at a third operating pressure higher than the second operating pressure, and the mixed liquid from which the aggregated sediment has been removed is separated into a third desalted water and a third concentrated water. A water treatment system, comprising: a separation unit. 2. The water treatment system according to claim 1, wherein said regenerating liquid contains alkaline earth metals recovered by said cation exchange resin. A pH adjusting agent is added to water to be softened, which is interposed between the water softening unit and the first separation unit and obtained by the water softening unit, and desalted by the first separation unit. 2. The water treatment system according to claim 1, further comprising an adjusting unit for rendering said softened water to be treated alkaline with a pH equal to or higher than a predetermined value. The water treatment system according to claim 1, further comprising a heating unit that heats the first concentrated water desalinated by the second separation unit. A pump that recovers part of the second concentrated water separated by the second separation unit, mixes it with the first concentrated water, and supplies it to the second separation unit;
5. The water treatment system according to claim 4, wherein the pump functions as the heating unit by the power heat of the pump heating the first concentrated water and the recovered second concentrated water. The water softening unit uses a strongly acidic cation exchange resin and a weakly acidic cation exchange resin as the cation exchange resin, and removes a first alkaline earth metal from the water to be treated by the strongly acidic cation exchange resin. 2. The water treatment system of claim 1, wherein recovering and then recovering a second alkaline earth metal having a lower ion selectivity than said first alkaline earth metal by said weakly acidic cation exchange resin. . 7. The water treatment system of claim 6, wherein said regeneration liquid comprises a second alkaline earth metal recovered by said weakly acidic cation exchange resin. 7. The water treatment system of claim 6, wherein said first alkaline earth metal is calcium and said second alkaline earth metal is magnesium. is interposed between the water softening unit and the adjusting unit, performs deaeration processing on the water to be softened obtained by the water softening unit, and deaerates the deaerated water to be softened 4. The water treatment system of claim 3, further comprising a deaerator feeding said conditioning unit. a fourth separation unit that separates the desalted water obtained by mixing the first desalted water, the second desalted water, and the third desalted water into a fourth desalted water and a fourth concentrated water;
The gas deaerated from the water to be softened by the deaerator is mixed with the fourth concentrated water and decompressed to generate bubbles in the fourth concentrated water, and the fourth gas containing the bubbles is decompressed. 10. The water treatment system according to claim 9, further comprising a bubble generating unit for supplying concentrated water of to said conditioning unit. a fourth separation unit that separates the desalted water obtained by mixing the first desalted water, the second desalted water, and the third desalted water into a fourth desalted water and a fourth concentrated water;
A bubble generating unit that decompresses the fourth concentrated water to generate bubbles from gas dissolved in the fourth concentrated water, and supplies the fourth concentrated water containing the bubbles to the adjustment unit. 4. The water treatment system of claim 3, further comprising: The bubble generation unit has a function of taking in air, and in addition to generating bubbles from gas dissolved in the fourth concentrated water, the air taken in by the function is transferred to the fourth concentrated water. 12. The water treatment system of claim 11, wherein the bubbles are also produced by mixing with and decompressing. recovering an alkaline earth metal from water to be treated to obtain water to be softened, which is the water to be treated which has been softened;
performing desalination treatment at a first operating pressure to separate the softened water into a first desalted water and a first concentrated water;
performing desalination treatment at a second operating pressure higher than the first operating pressure to separate the first concentrated water into a second desalted water and a second concentrated water;
Aggregation sedimentation treatment is performed on a mixed solution of the regenerated liquid used in the regeneration treatment of the cation exchange resin used for recovering the alkaline earth metal and the second concentrated water, and a flocculation sediment containing a silica component is obtained. and
performing desalting treatment at a third operating pressure higher than the second operating pressure, and separating the mixed liquid from which the aggregated sediment has been removed into a third desalted water and a third concentrated water; A water treatment method, comprising:

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