JP2016087564A - Seawater desalination apparatus and method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a seawater desalination apparatus by a membrane separation method and a method therefor removing TEP, preventing the clogging of a reverse osmosis membrane, and efficiently capable of stable working over a long period.SOLUTION: Provided is a seawater desalination apparatus comprising: a seawater taking part 10 of taking seawater; a flocculant adding means 15 of adding a flocculant to the taken seawater; a bubble generation and TEP-containing bubble removing part 20 of removing TEP components from the seawater including a flock formed the addition of the flocculant; a turbidity removing part 30 of removing a turbidity component from the seawater from which the TEP components are removed; and a reverse osmosis membrane treating part 40 of subjecting the seawater from which the turbidity component has been removed to desalting treatment so as to be desalinated.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a seawater desalination apparatus and method, and in particular, includes a seawater desalination apparatus and a TEP component removal equipped with a TEP component removal apparatus that removes TEP (Transparent Exopolymer Particles) components and precursors in brackish water and seawater. The present invention relates to seawater desalination methods.

  A membrane treatment method using a reverse osmosis (RO) membrane is used as an apparatus and method for desalinating seawater or brackish water to desalinate. Reverse osmosis (RO) membranes have a pore size of several nanometers and are therefore easily clogged (fouling). Aggregation method, sand filtration method, pressurized flotation method, MF membrane (microfiltration membrane) / UF membrane (ultrafiltration membrane) ) A pretreatment to remove turbidity contained in seawater or brackish water is necessary alone or in combination. A typical example of a conventional seawater desalination apparatus is shown in FIG.

The seawater desalination apparatus shown in FIG. 15 draws seawater into a water intake pipe 101 for taking seawater, a bactericide adding means 102 for adding a bactericide such as sodium hypochlorite (NaClO) to the water intake pipe 101, and a water intake pipe 101. Intake pump 103, strainer 104 provided in front of intake pump 103 to prevent blockage of intake pump 103 to remove shellfish and large trash, raw water tank 105 for storing the intake seawater, raw water from the original water tank 105 Filtration raw water feed pipe 106 and filtration raw water pump 107 for feeding water to a filtration device 109 for processing (gravity type double-layer sand filtration device in FIG. 15), and raw material water feed pipe 106 are aggregated with iron chloride (FeCl ₃ ) or the like. Treated water feed pipe 1 for feeding the treated water filtered by the flocculant adding means 108 for adding the agent and the filtration device 109 to the reverse osmosis membrane device 115 0 and the supply pump 114 and safety filter 112 and the security filter pump 111 comprises a treated water supply tube 110 to sodium bisulfite (NaHSO ₃₎ residual chlorine removal agent adding means 113 for adding the residual chlorine removal agent such as. In such a conventional seawater desalination apparatus, in order to prevent the pretreatment filtration device 109 and the reverse osmosis membrane device 115 from being blocked, frequent regular maintenance is required, and the life of the reverse osmosis membrane is also short.

Presence of TEP (Transparent Exopolymer Particles), a transparent and sticky jelly-like organic substance in seawater, as a substance (foulant) that causes clogging (fouling) of filtration membranes and reverse osmosis membranes Have been recognized (Patent Document 1, Patent Document 2, Non-Patent Document 1). TEP is a jelly-like substance composed of a polysaccharide derived from Fibril (fibrous substance) or Hydrogel (hydrogel) generated by metabolism of phytoplankton and planktonic bacteria, and has a size of about 0.4 μm to 200 μm. It has been confirmed that it swells in seawater and has a volume concentration of 100 times or more the weight concentration, and is deformed by pressurization and passes through a membrane having a pore size smaller than the particle size. As a TEP analysis method, a method using coloring of acidic mucopolysaccharide using Alcian Blue is used (Non-patent Document 2).
In the present specification and claims, “TEP” means a transparent and highly sticky jelly-like substance that is mainly a polysaccharide, and “TEP precursor” means Fibril (fibrous substance) and Hydrogel (hydrodynamic). Gel) and the like are treated as meaning fine particles of 0.4 μm or less. In addition, since not all organic substances contained in seawater are foulants, the TEP components including TEP and TEP precursors are particularly targeted for removal.

  As a method for removing TEP from seawater, a method is proposed in which magnetic particles are added to seawater, the magnetic particles are attached to TEP, and TEP attached to the magnetic particles by magnetic separation is removed from seawater (Patent Document 1). .

  In addition, a method of removing TEP by using a polytetrafluoroethylene membrane having a pore diameter of 1 μm or more as a pretreatment filter and allowing raw water to pass through at a predetermined flux has been proposed (Patent Document 2).

  Furthermore, as a pretreatment, a method has been proposed in which an alkaline solution of a special novolac-type phenolic resin is added as a flocculant to the membrane feed water supplied to the reverse osmosis membrane device to aggregate and remove the polysaccharide ( Patent Document 3).

  Further, as a method for treating a nonionic surfactant, there has been proposed a method called nonfoam separation in which microbubbles of 50 μm or less are used to adsorb nonionic surfactant to the fine bubbles and overflow from the bubble column. (Patent Document 4).

  Conventional pretreatment techniques for seawater desalination include a coagulating sand filtration method, a biofilm filtration method, a pressurized flotation method, a method using an MF membrane (microfiltration membrane), and a UF membrane (ultrafiltration membrane). In addition, there is a method using a protein skimmer as a seawater purification method for the purpose of breeding and aquaculture of marine organisms. The outline of these will be described below.

Agglomerated sand filtration method is a filtration tower in which a flocculant such as iron chloride (FeCl ₃ ) is added to seawater, suspended substances and some charged soluble substances are adsorbed on flocs, and sand or anthracite is packed. It is a method of removing by. In the biofilm filtration method, seawater is supplied to a filtration tower filled with sand or anthracite filter media with biofilm attached, and filtered by adsorption of organic matter by biofilm, decomposition of biodegradable organic matter, and trapping action by filter media. It is a method to do. The pressure levitation method is used to remove non-soluble suspended solids with relatively low specific gravity, such as algae and oil contained in seawater. Create a floc that incorporates non-soluble substances such as air, pressurize the air to dissolve it in water, release the water into the water to generate fine bubbles, and adsorb many fine bubbles to the floc In this method, the flock is lifted to the liquid surface by the buoyancy of the bubbles and removed from the water (Patent Documents 5 and 6). The membrane filtration method using an MF membrane or a UF membrane is filtration with a fine pore size using a turbidity membrane having a very small pore size of several μm to 0.01 μm or less. In the seawater purification in an aquarium, a protein skimmer, which is a kind of foam separation device, has been put into practical use for the purpose of water quality management in an aquarium. However, the protein skimmer is a method for separating and removing proteins such as mucus, feces, and uneaten food from fish as foams, and discharging them to the outside of the system, and is not applied as a pretreatment for seawater desalination.

JP 2010-58080 A Japanese Patent No. 5019276 JP 2012-166118 A Japanese Patent No. 4379147 JP 2012-223723 A JP 2008-173534 A

Transparent exopolymer particles: Potential agents for organic fouling and biofilm formation in desalination and water treatment plants, Edo Bar-Zeev et al., Desalination and Water Treatment 3 (2009) 136-142 A dye-binding assay for the spectrophotometric measurement of transparent exopolymer particles (TEP), U. Passow, A. L. Alldredge, Limnol. Oceanogr., 40 (7), 1995, 1326-1335

  The TEP removal methods that have been proposed so far use special filtration membranes and special chemicals, and thus cause secondary problems such as filtration membrane maintenance and chemical post-treatment. There is a need to prevent clogging of pretreatment filtration membranes and reverse osmosis membranes due to adhesion of TEP without using special additives or filtration membranes.

  In the method disclosed in Patent Document 1 described above, addition of magnetic particles and magnetic separation equipment are required, and maintenance of not only the membrane separation apparatus but also the magnetic separation equipment is required, resulting in an increase in cost and 0.4 μm or less. TEP precursors such as Fibril (hydrofibrous material) and Hydrogel (hydrogel) cannot be removed.

  In the method disclosed in Patent Document 2, it is necessary to use a specific membrane and control the flux, and to wash and remove TEP trapped on the surface of the pretreatment membrane. The pore diameter is 1 μm or more, and TEP precursors such as Fibril and Hydrogel of less than 1 μm cannot be removed.

  Moreover, in the method disclosed in Patent Document 3, it is necessary to use a special flocculant, which is generally used in combination with a flocculant such as an iron salt used in a pretreatment for seawater desalination. Therefore, there is a problem that the amount of sludge generated increases and must be disposed of.

  In the method referred to as non-foam separation described in Patent Document 4 described above, the nonionic surfactant is removed using microbubbles having a particle size of 50 μm or less. The rising speed of the bubbles is as low as 0.001 m / s or less, and the residence time of water in the apparatus requires a long time of 10 minutes to 60 minutes. Therefore, in order to process a large amount of water, the apparatus becomes large, and providing an apparatus with a small installation area (footprint) has been a problem. Microbubbles do not have sufficient adsorption capacity for TEP having a particle size of 0.4 μm to 200 μm because the bubbles are too fine.

Furthermore, it has been difficult to effectively remove TEP by the aggregate sand filtration method, the biofilm filtration method, the pressure flotation method, and the membrane filtration method using an MF membrane or a UF membrane.
That is, although the TEP described above is partially removed by the agglomerated sand filtration, the TEP taken into the agglomerated flocs is small, and therefore effective TEP removal cannot be performed by the agglomerated sand filtration (see Comparative Example 4 described later). TEP is a substance with low biodegradability, and effective TEP removal cannot be achieved by biofilm filtration.

  The pressurized flotation method is originally intended to remove non-dissolvable suspended solids. By the action of a flocculant, floc-like solids and air are pressurized and dissolved in water to bring the water into the water. The fine bubbles of about 10 to 100 μm generated by discharging are brought into contact with each other, and floated on the water surface as floss (floating matter) using the buoyancy of the fine bubbles contained around or inside the solid matter. The floss laminated on is discharged out of the system. In this case, the rising speed of the fine bubbles is slow, a very large separation area is required, and downsizing of the apparatus has been a problem. In addition, since floating particles including bubbles that have risen are scraped up and discharged by a skimmer, the floating objects are accumulated and stacked to some extent. In some cases, it was dispersed and settled again.

  Since the membrane filtration method using an MF membrane or UF membrane is filtration using a turbidity membrane having a fine pore size, fouling occurs in the MF membrane or UF membrane due to TEP, and frequent chemical cleaning is necessary (comparison described later). Example 5).

As described above, it is difficult to remove TEP efficiently and stably even if any one of agglomerated sand filtration method, biofilm filtration method, pressurized flotation method, and MF membrane or UF membrane membrane filtration method is applied. there were.
That is, without using special chemicals, flocculants, and additives, it is widely used in seawater desalination pretreatment techniques using reverse osmosis membranes, for example, using iron salts, aluminum salts, or acids. Therefore, it has been desired to remove TEP efficiently and stably.

  The object of the present invention is to remove TEP, polysaccharides, Fibril (fibrous substance), Hydrogel (hydrogel), TEP precursor, etc. by adsorbing them to the bubbles, thereby preventing clogging of the reverse osmosis membrane, It is an object of the present invention to provide a seawater desalination apparatus and method capable of stable operation efficiently over a long period of time.

ADVANTAGE OF THE INVENTION According to this invention, the seawater desalination apparatus and its method which have the following structure are provided.
As a first aspect, a seawater desalination apparatus according to the present invention generates bubbles in seawater containing flocculant addition means for adding a flocculant to the taken seawater and flocs formed by the addition of the flocculant, and A TEP component removing device comprising a foam removing unit that adsorbs a TEP component or a condensed floc hydrophobized by adsorbing a TEP component in a bubble, floats the TEP-containing bubble on the water surface, removes moisture, and removes it as a foam from the water surface And a reverse osmosis membrane treatment device that desalinates seawater from which the TEP component has been removed to desalinate it.

As a second aspect, in the seawater desalination method according to the present invention, flocculant is added to the taken seawater to form a floc, bubbles are generated in the seawater containing the floc, and the TEP component in the seawater is generated in the bubbles. A TEP component removing step of removing TEP-containing foam after the TEP-containing bubbles adhering to the TEP component adsorbed and adhering hydrophobic flocs adhering to the surface float to the surface of the water and collecting the bubbles that have risen to form foam It includes a turbidity removing step for removing turbid components from seawater after removing bubbles and a desalting treatment step for desalting seawater after removing the TEP component.
The seawater desalination method according to the present invention includes an acid addition step of adding acid to the taken seawater, and the pH of the seawater after the acid addition is measured, and the acid is adjusted so that the pH is in the range of 5-7. Acid addition control step for controlling the amount of addition, bubbles are generated in the seawater, TEP components in the seawater are attached to the bubbles to cause the TEP-containing bubbles to rise to the surface of the water, and the bubbles that have risen are collected and TEP-containing foam And a TEP component removing step for removing the TEP-containing foam and a desalting treatment step for desalting the seawater from which the TEP component has been removed.

According to the seawater desalination apparatus and method therefor according to the present invention, TEP, polysaccharides, fibrous materials, and hydrogels are used in a pretreatment technology for seawater desalination using a reverse osmosis membrane. The TEP precursor and the like are removed by adsorbing them in the bubbles, thereby preventing the reverse osmosis membrane from being clogged and enabling stable and efficient operation over a long period of time.

It is a general | schematic flow which shows one embodiment of the seawater desalination apparatus of this invention. It is a schematic diagram which shows the embodiment of the seawater desalination apparatus of this invention. It is a schematic diagram which shows another one Embodiment of the bubble generation of the seawater desalination apparatus of this invention, and a floating bubble removal part. It is a schematic diagram which shows another one Embodiment of the bubble generation of the seawater desalination apparatus of this invention, and a floating bubble removal part. It is a schematic diagram which shows another one Embodiment of the bubble generation of the seawater desalination apparatus of this invention, and a floating bubble removal part. It is a schematic diagram which shows another one Embodiment of the bubble generation of the seawater desalination apparatus of this invention, and a floating bubble removal part. It is a schematic diagram which shows another one Embodiment of the bubble generation of the seawater desalination apparatus of this invention, and a floating bubble removal part. It is a schematic diagram which shows another one Embodiment of the bubble generation of the seawater desalination apparatus of this invention, and a floating bubble removal part. It is a schematic diagram which shows another one Embodiment of the bubble generation of the seawater desalination apparatus of this invention, and a floating bubble removal part. It is a schematic diagram which shows another one Embodiment of the bubble generation of the seawater desalination apparatus of this invention, and a floating bubble removal part. It is a schematic diagram which shows another one Embodiment of the bubble generation of the seawater desalination apparatus of this invention, and a floating bubble removal part. It is a schematic diagram which shows another one Embodiment of the bubble generation of the seawater desalination apparatus of this invention, and a floating bubble removal part. It is a schematic diagram which shows another one Embodiment of the bubble generation of the seawater desalination apparatus of this invention, and a floating bubble removal part. 4 is a graph showing fluctuations in pressure of a reverse osmosis membrane in Reference Example 1 and Comparative Example 1. It is a schematic flow which shows the representative example of the seawater desalination apparatus in a prior art. It is a schematic diagram which shows another embodiment of the seawater desalination apparatus which concerns on this invention. It is explanatory drawing which showed the structure of the foam separation part and overflow water level control part (telescope valve) of the embodiment shown in FIG. 4 is a graph showing fluctuations in pressure of a reverse osmosis membrane in Reference Example 2 and Comparative Example 2. It is explanatory drawing which shows the seawater desalination process flow in Example 1. FIG. It is explanatory drawing which shows the seawater desalination process flow in Example 2 and Comparative Example 3. It is explanatory drawing which shows the seawater desalination process flow in Example 3 and Comparative Example 4. It is explanatory drawing which shows the seawater desalination process flow in Example 4. It is explanatory drawing which shows the seawater desalination process flow in Example 5.

  Hereinafter, the present invention will be described in detail with reference to the accompanying drawings, but the present invention is not limited thereto.

  The present inventors separate polysaccharides, in particular TEP components containing soluble polysaccharides, by adsorbing them on the surface of bubbles, floating them on the surface of the water, condensing them into bubbles, or concentrating them into foams to separate them from moisture. The TEP component can be easily removed, and by adding a flocculant before foam separation, the TEP component is also adsorbed on the formed flock surface and the flock surface is hydrophobized. And flocs are more easily adsorbed by bubbles, and it has been found that not only the TEP component but also the suspension in seawater can be efficiently removed, and the present invention has been completed. The TEP component has a hydrophilic group and a hydrophobic group as a molecular structure, and can be adsorbed on the bubble surface by directing the hydrophobic group toward the bubble surface. The TEP component adsorbed by the bubbles in the water floats on the surface of the water and separates the water to become foam and is removed. Further, by adsorbing the hydrophilic group toward the aggregated floc surface, the hydrophobic group is conversely directed to the outside of the aggregated floc and the floc surface becomes hydrophobic.

  In the present specification and claims, “TEP component” means TEP, a TEP precursor, and a polysaccharide. Among polysaccharides, those having a size of 1 μm or less are referred to as “soluble polysaccharides”, and those having a size exceeding 1 μm are referred to as “insoluble polysaccharides”. According to the method of the present invention, since a TEP component of 1 μm or less can be removed, among the polysaccharides, soluble polysaccharides that have been difficult to remove can be removed well.

  The seawater desalination method of the present invention includes (1) a flocculant addition step in which flocculant is added to the collected seawater to form flocs, and (2) bubbles are generated in the seawater containing the flocs. A TEP component removal step in which the TEP-containing bubbles formed by adhering the TEP component in the surface rise to the surface of the water, and the collected bubbles are collected to form bubbles, and then the TEP-containing bubbles are removed; and (3) the TEP-containing bubbles are removed. A turbidity removing step for removing turbid components from the seawater after the removal, and (4) a desalting treatment step for desalting the seawater after removing the turbidity components.

As the flocculant, inorganic flocculants such as iron salts and aluminum salts can be preferably used. Ferric chloride (FeCl ₃ ), ferric sulfate (Fe ₂ (SO ₄ ) ₃ ), PAC (polyaluminum chloride) ) Can be cited as a suitable example.

The seawater desalination method according to the present invention includes an acid addition step of adding acid to the taken seawater, and the pH of the seawater after the acid addition is measured, and the acid is adjusted so that the pH is in the range of 5-7. Acid addition control step for controlling the amount of addition, bubbles are generated in the seawater, TEP components in the seawater are attached to the bubbles to cause the TEP-containing bubbles to rise to the surface of the water, and the bubbles that have risen are collected and TEP-containing foam And then, a TEP component removing step for removing the TEP-containing foam and a desalting treatment step for desalting the seawater from which the TEP component has been removed.

  That is, before the TEP component removal step, acid is added to seawater or seawater containing flocs, and the pH is in the range of 5.0 to 7.0, preferably in the range of 6.0 to 7.0, most preferably. It is desirable to adjust to 6.8. By adjusting the pH, it is possible to improve the ease and stability of foam formation and improve the TEP removal rate, and it is possible to prevent inorganic scale adhesion in the subsequent RO membrane separation. Examples of the acid to be added include sulfuric acid and hydrochloric acid, but sulfuric acid which is widely used at low cost is preferable.

  The TEP component removal step further includes a concentration step for densifying and concentrating the TEP-containing foam and / or a concentration step for collecting the TEP-containing foam in a predetermined region on the water surface. The concentration step and concentration step of the TEP-containing foam can be performed in the same step.

  The bubble diameter of the bubbles for adsorbing the TEP component is desirably 50 μm to 2 mm, and the microbubbles of 50 μm or less are too fine for the TEP component to have a low adsorption capacity and the rising speed is slow. Absent. In addition, a coarse bubble exceeding 2 mm has a high ascent rate and a small bubble surface area. Therefore, there is a tendency that the adsorption ability with respect to the TEP component is lowered and the bubble tends to break on the water surface.

  In the TEP component removal step, by dropping the taken seawater into the TEP component removal tank, or by colliding the taken seawater with the collision member, or using an air diffuser, an aeration device, a stirring aerator, and an ejector, Bubbles can be generated in seawater. Also, by disposing a diffuser, aeration device, stirring aerator, and ejector at the bottom of the TEP component removal tank, bubbles are generated and TEP-containing bubbles in which the TEP component is adsorbed are collected in a predetermined region. You can also.

  The removal of the TEP-containing foam in the TEP component removal step is the separation and removal in the foam separation section that raises the TEP-containing foam along the wall surface where the cross-sectional area decreases upward and drops (dehydrates) moisture to concentrate the foam component. This is achieved by at least one of separation and removal of seawater and foam by a movable weir that can position the weir port below the water surface, scraping of the foam by a skimmer, and suction of the foam by a pump. After collecting and concentrating the TEP-containing bubbles in a predetermined region, the TEP-containing bubbles can be separated and removed more easily by removing the TEP-containing bubbles.

  FIG. 1 shows the flow of the seawater desalination apparatus and method of the present invention, and FIG. 2 is a schematic view showing an embodiment of the seawater desalination apparatus of the present invention.

  The seawater desalination apparatus of the present invention includes a seawater intake facility 10 serving as a seawater intake unit for taking seawater, a flocculant addition means 15 for adding a flocculant to the taken seawater, and seawater containing flocs formed by adding the flocculant. Generation of bubbles for removing TEP components, foaming / foam removing equipment 20 as a TEP-containing bubble removing unit, pretreatment as a turbidity removing unit for removing turbid components from seawater from which TEP components have been removed (also referred to as “filtered raw water”) The facility 30 and the RO facility 40 as a reverse osmosis membrane treatment unit for desalinating seawater from which turbid components have been removed (also referred to as “RO raw water”) are provided.

In addition, as shown in FIG. 22, an acid addition means for adding acid to the seawater or seawater containing the floc, and the seawater or floc are included in the front stage of the foaming / foam removing equipment 20 as a TEP component removal tank. Acid addition amount control means for controlling the addition amount of the acid by measuring the pH of the seawater is further provided.

Further, as shown in FIG. 23, a flocculant addition means may be provided after the acid addition means and the acid addition control means. In this case, the TEP removal rate can be further improved by the synergistic effect of the acid addition and the FeCl ₃ addition.

  In FIG. 1, the foaming / foam removing equipment 20 is divided into a bubble generating unit that generates bubbles in the intake seawater and a TEP-containing bubble removing unit that removes TEP-containing bubbles including TEP components adsorbed or adhered to the bubbles. It may be divided into

In FIG. 2, the seawater intake section includes intake pipe 11 and intake pipe 11 that take in seawater or brackish water (hereinafter, for the sake of brevity, seawater and brackish water are collectively referred to as “seawater”). In order to prevent clogging of the intake pump 13, a disinfectant addition means 12 for adding a disinfectant such as sodium hypochlorite (NaClO) to the intake pipe 11, a intake pump 13 for pumping seawater into the intake pipe 11, Sulfuric acid addition means for adding sulfuric acid (H ₂ SO ₄ ) for the purpose of lowering the pH of seawater in order to prevent inorganic scale from adhering to the strainer 14 and reverse osmosis membrane device 41 that are provided to remove shellfish and large dust In addition, a flocculant addition means for adding a flocculant such as ferric chloride (FeCl ₃ ) in front of the bubble introduction and floating bubble removal unit 20 is included.

  The bubble introduction and floating bubble removal unit 20 stores the taken seawater and removes the TEP component from the seawater, generates bubbles in the seawater in the TEP component removal tank 21, and generates bubbles in the TEP in the seawater. It includes bubble generating means 22 that floats on the surface of the water as TEP-containing bubbles formed by adhering components and aggregated flocs, and foam removing means 23 that removes the floated TEP-containing bubbles from the water surface. Further, the bubble density of the TEP-containing bubbles floating on the water surface is increased and concentrated, and the bubble directing means 25 for collecting the TEP-containing bubbles floating on the water surface in a predetermined region, and the bubbles floating on the water surface are in the subsequent turbidity part 30. It is preferable to include foam outflow prevention means 26 for preventing inflow into the raw filter water.

  The turbidity removal device 30 is used for pretreatment of raw water (filtered raw water) from which TEP and TEP precursor have been removed by the bubble generation and floating bubble removal unit 20, and for feeding the filtered raw water to the filtration device 31. The filtered raw water feed pipe 32 and the filtered raw water pump 33 are included. As the filtration device 31, a general pretreatment filtration device can be used without limitation, and the filtration device 31 is filled with a porous substance such as sand, anthracite, glass, garnet, activated carbon, fiber member, cartridge filter, and the like. It can be a device. As the turbidity removing device 30, membrane separation including an organic membrane such as a UF membrane or an MF membrane may be applied. Moreover, as the turbidity removing device 30, not only filtration but also a pressure levitation method and a precipitation method known to those skilled in the art can be applied.

The reverse osmosis membrane treatment device 40 is a RO raw water feed pipe 42, a feed pump 43, and a safety filter that feed seawater (RO raw water) filtered by the turbidity removal device 30 to remove turbid components to the reverse osmosis membrane device 41. 44, a safety filter pump 45, and a residual chlorine remover adding means 46 for adding a residual chlorine remover such as sodium bisulfite (NaHSO ₃ ) to the RO raw water feed pipe 42.

  Next, a preferred embodiment of the bubble generation and TEP-containing bubble removal unit 20 will be described with reference to FIGS. In addition, the same code | symbol is attached | subjected to the same component shown by previous drawing, and description is abbreviate | omitted.

  FIG. 3 shows a standing partition 26a standing from the bottom surface of the TEP component removal tank 21 to below the water surface level as a foam outflow prevention means for preventing the TEP-containing foam floating on the water surface from flowing into the turbidity removing part 30. This is an example in which a bubble introduction area 21a and a filtered raw water outflow area 21b are divided, and an aeration device 22a is arranged as a bubble generation means in the bubble introduction area 21a. The aeration device 22a is positioned at the bottom of the bubble introduction area 21a of the TEP component removal tank 21, generates bubbles in seawater, adsorbs the TEP components to the bubbles, floats and collects them as TEP-containing bubbles, and creates bubbles on the water surface. To do. A filtered raw water feed pipe 32 shown in FIG. 2 is connected to the lower part of the filtered raw water outflow area 21b divided by the standing partition 26a.

  FIG. 4 is an example in which an ejector 22 b is attached to the tip of the intake pipe 11 as seam generation means to the bubble introduction area 21 a of the TEP component removal tank 21, and seawater is supplied to the TEP component removal tank 21 from above. In the ejector 22b, outside air is taken into the seawater flowing down on the principle of the Venturi tube, and raw water containing bubbles flows into the TEP component removal tank 21. Since the raw water falls into the TEP component removal tank 21 from above, the sea water in the TEP component removal tank 21 is affected by the impact of the bottom surface of the TEP component removal tank 21 and the water surface of the seawater stored in the TEP component removal tank 21. Furthermore, bubbles are generated. Moreover, the TEP component in seawater is adsorbed by the bubbles due to the turbulent flow generated by the impact, and the TEP-containing bubbles rise.

  FIG. 5 shows a bubble generating means for the bubble introduction area 21 a of the TEP component removal tank 21, in which an ejector 22 b is attached to the tip of the intake pipe 11, and seawater containing bubbles is introduced from below the side wall of the TEP component removal tank 21. This is an example.

  FIG. 6 shows an example in which a collision material 22c is positioned directly below the outlet of the intake pipe 11 and seawater is supplied to the TEP component removal tank 21 from above as a bubble generating means to the bubble introduction area 21a of the TEP component removal tank 21. It is. Seawater splashes by colliding with the collision material 22c and takes in bubbles. As the impact material, natural solids such as stones or artificial bio balls can be used.

  FIG. 7 shows an example in which a stirring aerator 22 d is provided at the bottom of the TEP component removal tank 21 as means for generating bubbles to the bubble introduction area 21 a of the TEP component removal tank 21. The agitating aerator 22d releases the outside air taken in by driving the motor into seawater.

  8, in addition to the mode shown in FIG. 3, an inclined partition 25a is provided in the bubble introduction area 21a of the TEP component removal tank 21 as the bubble directing means 25 that collects the TEP-containing bubbles floating on the water surface in a predetermined area. It is an example. The inclined partition 25a is provided so as to be inclined so that the water cross-sectional area in the region defined by the seawater inflow side wall and the outflow side wall of the TEP component removal tank 21 is reduced upward. The bubbles introduced into the seawater by the aeration device 22a are directed to a predetermined region along the inclined surface of the inclined partition 25a when the TEP component is adsorbed and rises as a TEP-containing bubble. Further, since the TEP-containing bubbles are concentrated in a narrow area partitioned by the inclined partition 25a, the contact frequency with the TEP component is increased, and the bubble density of the TEP-containing bubbles is increased and concentrated. The inclined partition 25a only needs to be inclined to such an extent that the TEP-containing bubbles can be prevented from flowing out to the filtered raw water outflow region 21b.

  FIG. 9 shows a plurality of standing structures installed between opposing walls of the TEP component removal tank 1 as a foam concentration means for increasing and concentrating the density of the TEP-containing foam floating on the water surface in addition to the embodiment shown in FIG. This is an example in which a wall 24a is provided. The TEP-containing foam that floats and collects on the water surface is scooped up and concentrated along the wall surfaces of the plurality of standing walls 24a. Further, the TEP-containing foam can be easily removed by scraping off the TEP-containing foam attached to the wall surface of the standing wall 24a.

  3 to 9 show various modes of the bubble generating means 22, but each bubble generating means 22 and each TEP-containing foam removing means 23 can be arbitrarily combined.

  FIG. 10 shows an example in which a scraper 23a and a pipe skimmer 23b are provided as foam removing means for removing, from the water surface, TEP-containing bubbles formed by adsorbing a TEP component precursor to bubbles in addition to the embodiment shown in FIG. It is. The TEP-containing foam that has floated on the water surface is scraped to the periphery of the pipe skimmer 23b by the scraper 23 and discharged through the pipe skimmer 23b.

  FIG. 11 is an example in which a scum pump 23c is provided as a foam removing unit that removes TEP-containing bubbles formed by adsorbing a TEP component precursor to bubbles from the water surface in addition to the embodiment shown in FIG. The scum pump 23c floats on the water surface by the float 23d, and sucks and discharges the TEP-containing foam that has floated on the water surface.

  In addition to the embodiment shown in FIG. 3, FIG. 12 shows a movable weir that can position a weir port below the water surface as foam removing means for removing the TEP-containing bubbles formed by adsorbing the TEP component precursor to the air bubbles from the water surface. This is an example in which 23e is attached to one wall surface of the TEP component removal tank 21. By positioning the weir port of the movable weir 23e below the water surface, the TEP-containing foam is discharged together with the surface water.

  10 to 12 show various modes of the foam removing means 23, but each bubble generating means 22 and each foam removing means 23 can be arbitrarily combined.

  FIG. 13 shows an example in which the bubble generation and foam removal unit 20 and the turbidity removal unit 30 are incorporated into a TEP component removal tank 21 and integrated. The bubble generation and foam removing unit 20 is provided in the upper part of the raw water tank 21, and the turbidity removing part 30 is provided in the lower part of the TEP component removing tank 21. An aeration device 22a is provided at the bottom of the bubble generation and foam removal unit 20, the bubbles introduced into the seawater are raised, and the TEP-containing bubbles float on the water surface and are collected and removed as bubbles. The turbidity removal part 30 provided in the lower part of the TEP component removal tank 21 includes a filtration device 31 filled with a filter medium. The seawater from which the TEP component has been removed flows from the bottom of the bubble introduction and foam removal unit 20 into the filtration device 31 of the turbidity removal unit 30 and descends while being filtered in contact with the filter medium.

  FIG. 16 is a schematic view showing another embodiment of the seawater desalination apparatus of the present invention. In addition, the same code | symbol is attached | subjected to the structure which is common in FIG. 2 mentioned above, and description is abbreviate | omitted. In FIG. 16, what is characteristic is that the bubble generation and foam removal unit 20 is combined with the foam separation unit 200 and the overflow water level control unit (telescope valve) 210.

  FIG. 17 shows an example of details of the bubble generation and foam removal unit 20. The bubble generation and foam removal unit 20 includes a seawater supply unit 201 that supplies seawater from the top of the TEP component removal tank, an air diffuser 202 that generates bubbles at the bottom of the TEP component removal tank, and an air diffuser 202. A rectifying plate 203 that controls the rising direction of the generated bubbles, a foam separation unit 204 that concentrates the separated bubbles without breaking them and separates them from seawater, and a water level that allows the seawater separated by the foam separation unit 204 to overflow. A telescope valve 210 for controlling. As the air diffuser 202, a membrane air diffuser, a ceramic air diffuser or an ejector having a hole diameter for ejecting bubbles of about 1 mm or less is suitable.

  The foam separating unit 204 includes a bottom surface 204a that is parallel to the water surface, and a plurality of reverse funnel-shaped rising portions 204b that form an opening 204c at the rising top obliquely from the bottom surface 204a. The TEP-containing foam that collects the TEP component-containing bubbles that have floated by the current plate 203 is brought into contact with the bottom surface 204a of the foam separating section 204 and concentrated, and moves toward the rising section 204b along the wall surface of the rising section 204b. Reaches the opening 204c, is discharged from the opening 204c, and is separated to the upper surface side of the bottom surface 204a. Since the rising portion 204b has a reverse funnel shape, the rising portion 204b can be quickly moved without destroying the foam. Seawater from which the TEP-containing bubbles are separated and removed is drained as overflow water.

  The overflow water level control unit 210 includes a drain outlet 210a provided at the bottom of the TEP component removal tank, a rising pipe 210b that flows upward from the drain outlet 210a, and a telescope valve that controls the overflow water level from the rising pipe 210b. 210c. The telescope valve is not particularly limited, and a telescope valve generally used for water level adjustment can be used. The overflow water level control unit 210 can adjust the amount of foam separation by changing the overflow water level according to the seawater quality. That is, when the overflow water level is lowered, the amount of overflow water is increased, the distance between the bottom surface 200a of the foam separation unit 200 and the water surface is increased, the amount of foam staying on the water surface is increased, the concentration proceeds, and the rising portion 200b. And the foam amount discharged | emitted from the opening 200c reduces. Conversely, when the overflow level of the treated water is increased, the amount of overflow water is reduced, the distance between the bottom surface 200a of the foam separation unit 200 and the water surface is reduced, the amount of foam remaining on the water surface is reduced, and the concentration proceeds. The amount of foam discharged from the rising portion 200b and the opening 200c increases. In this embodiment, a telescope valve is used to control the overflow water level. However, any telescope valve having the same function can be applied. For example, a control valve or the like is used. You can also.

  According to the seawater desalination apparatus and method of this embodiment, it is possible to remove fine TEP, precursors thereof, and soluble polysaccharides that could not be removed by the conventional TEP removal method. Since long-term use is possible, the frequency of cleaning and maintenance is reduced, and stable and efficient operation is possible over a long period. In addition, by removing the suspended matter in seawater as agglomerated floc in the process of removing the foam first, the amount of solid matter in the subsequent turbidity process is reduced, so that the frequency of backwashing is increased, for example, in sand filtration. In the case of MF membranes and UF membranes, the amount of cleaning chemicals used is reduced by reducing the frequency of backwashing.

In addition, in the case of facilities where the turbidity process is first performed as a pretreatment for seawater desalination, for example in the case of a sand filtration device due to a sudden deterioration in the quality of the intake water due to natural phenomena such as red tide and sand, the filtration layer is clogged and rapidly In the case of MF membranes and UF membranes, for example, the differential pressure of the membrane rises rapidly and the frequency of backwashing increases, making it virtually impossible to treat, and when the water quality deteriorates, the seawater desalination facility is stopped. However, according to the seawater desalination apparatus and method of the present invention, by providing a foam separation step before the turbidity step, it plays a role in relieving rapid water quality deterioration. The operation of the facility can be continued while suppressing the impact of water quality changes on the equipment.

  Moreover, it is not necessary to use a special filtration membrane, a special flocculant, magnetic particles, and the like, and the running cost can be reduced.

  By adding an aggregating agent before removing the TEP component, the surface of the floc formed by the suspension of the suspension in seawater is hydrophobized using the surface active function of the TEP component or protein to be removed. It can be easily adsorbed by air bubbles, can increase the removal rate of not only the TEP component but also the suspended matter, can suppress the blockage of the RO membrane in the latter stage, and sand filtration or filtration membrane in the previous turbidity process, etc. By reducing the solids load, the frequency of backwashing and the amount of cleaning chemicals added can be greatly reduced. The rate can be improved.

  Furthermore, by adding an acid before removing the TEP component and adjusting the pH to 5.0 to 7.5, the TEP component is easily adsorbed by bubbles, and the removal rate of the TEP component is improved. Moreover, since the stability of the TEP-containing foam is also improved, the removal rate of the TEP component is further improved. Furthermore, by adjusting the pH to 5.0 to 7.5, the inorganic matter in seawater is prevented from being deposited as scale.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto.

[Reference Example 1]
In the seawater desalination apparatus of the present invention shown in FIG. 2, when the flocculant addition position is provided not in the front stage of the bubble generation and foam removal unit 20 but in the subsequent filtered raw water water pipe 32 (Reference Example 1), FIG. The seawater desalination apparatus (Comparative Example 1) of the prior art shown in FIG. 15 is installed in parallel in the same site facing the sea, under the same conditions for 9 months from June to March of the following year, I drove continuously.

In the seawater desalination apparatus of the present invention, the bubble generation and foam removal unit 20 stands in the TEP component removal tank 21 with a standing partition 26a as a TEP-containing foam outflow prevention means from the bottom surface of the TEP component removal tank 21 to below the water level. As a bubble generating means, an ejector 22b and an aeration device 22a are provided at the bottom of the intake pipe 11 at the tip of the intake pipe 11, and a TEP-containing foam concentrating means (and a TEP-containing bubble directing means) is inclined between the opposing wall surfaces. The partition 25a was constructed, and the scraper 23a and the pipe skimmer 23b were provided as TEP-containing bubble removing means. Seawater from the intake pipe 11 was supplied from above the TEP component removal tank 21. Table 1 shows the specifications of the bubble generation and foam removal unit 20.

  In the raw water tank 105 in the conventional seawater desalination apparatus shown in FIG. 15, seawater from the intake pipe 101 was supplied to the vicinity of the bottom of the raw water tank 105.

Table 2 shows the specifications of the turbidity removing unit 30 (gravity-type double-layer sand filtration device in the prior art) in the seawater desalination apparatus of Reference Example 1.

The RO membrane of the desalination treatment apparatus 40 (reverse osmosis membrane desalination apparatus in the conventional apparatus) in the seawater desalination apparatus of Reference Example 1 was a 4-inch spiral RO membrane. The strainer 14 (104) provided in the water intake section 10 (101) has a width of 5 mm, and after removing dust in the seawater, the water was sent to the TEP component removal tank 21 (105). 1 mg / L sodium hypochlorite (NaClO) is added to the seawater in the intake pipe 11 (101) as a disinfectant, and 3 mg / L iron chloride (as a flocculant is added to the seawater in the raw water pipe 32 for filtration. FeCl ₃ ) was added, and sodium bisulfite (NaHSO ₃ ) was added to the seawater in the RO raw water feed pipe 42 as a residual chlorine remover. The amount of water intake was 10 m ³ / day.

  In the seawater desalination apparatus of Reference Example 1, seawater mixed with bubbles is ejected to the TEP component removal tank 21 by the ejector 22b. Seawater stays in the TEP component removal tank 21, is aerated by the aeration device 22a, is further mixed with bubbles, and the TEP component in the seawater is adsorbed by the bubbles and floats as TEP-containing bubbles. Due to the inclined partition 25a provided in the TEP component removal tank 21, the rising TEP-containing bubbles are collected in a part of the bubble introduction region 21a, and the TEP-containing bubbles floating on the water surface are concentrated. The floated TEP-containing foam stays on the water surface of the TEP component removal tank 21, is collected by the scraper 23a at the suction port of the pipe skimmer 23b, and is taken out and discharged. On the other hand, the seawater passes below the inclined partition 25a, crosses above the upright partition 26a, and is sent from the filtered raw water discharge area 21b to the turbidity removing part (gravity type two-layer sand filter) 30 by the filtered raw water water pipe. It is done.

In the conventional apparatus shown in FIG. 15, seawater is supplied from the intake pipe 101 to the raw water tank 105, stays for a certain period of time, and then sent to the gravitational double-layer sand filter 109. Seawater filtered by the turbidity removal unit (gravity type double-layer sand filtration device) 109 passes through the RO membrane through the safety filter for protecting the reverse osmosis membrane (RO membrane) of the reverse osmosis membrane desalination device 115. Is done. The water recovery rate of the RO membrane was set to 30%, and the flow rate of the RO supply pump 114 was automatically controlled so that 3 m ³ / day of RO permeated water (fresh water) would flow. Since the RO membrane pressure increased with the RO membrane fouling (clogging) situation, the RO membrane was cleaned with chemicals when the discharge pressure of the RO supply pump 114 increased to 6.5 MPa.

The amount and type of TEP are strongly influenced by seasonality, especially phytoplankton, so the fixed point of each process is twice a month, especially in September when the TEP concentration rises and in January when the TEP concentration is relatively low. TEP concentration was measured. TEP is measured by filtering a seawater sample with a filter paper made of polycarbonate having a pore diameter of 0.4 μm, staining the sample captured on the surface of the filter paper with Alcian blue, and measuring xanthan gum (XG) with a spectrophotometer as a standard. The unit is indicated by μg-XG / L. TEP that can be quantified by this analytical method is an acidic mucopolysaccharide. Table 3 shows the TEP measurement results.

  In September, red tides were subsided, but the TEP concentration was about 2.5 times higher than in January of the following year.

  In Reference Example 1, seawater treated by the bubble generation and foam removing unit 20 was taken at the inlet of the turbidity removal device 30 (gravity-type double-layer sand filtration device 31), and the TEP concentration was measured. Since the TEP concentration in the taken seawater was 1,620 μg-XG / L and the TEP concentration in the seawater after the treatment was reduced to 502 μg-XG / L, the TEP removal rate was 69%. On the other hand, in Comparative Example 1, the TEP concentrations were 1,540 μg-XG / L and 1,550 μg-XG / L even through the raw water tank, and were almost unchanged.

In the turbidizer (sand filter device) 30, the TEP removal rate in September was 31% in Example 1, 34% in Comparative Example 1, January was 33% in Reference Example 1, and 31% in Comparative Example 1. In both Reference Example 1 and Comparative Example 1, a decrease in TEP concentration was observed. This is considered to be due to the aggregation effect and filtration effect of FeCl ₃ .

  The TEP concentration in seawater at the inlet of the desalination treatment device (RO membrane device) 40 is 340 μg-XG / L in Reference Example 1 in September, 1018 μg-XG / L in Comparative Example 1, and Reference Example in January. In Example 1, 150 μg-XG / L, and in Comparative Example 1 469 μg-XG / L, Example 1 had a significantly lower TEP concentration than Comparative Example 1.

  Since the jelly-like TEP adheres to the RO membrane surface and leads to fouling of the RO membrane, it leads to an increase in the RO membrane pressure and an increase in cleaning frequency. FIG. 14 shows the pressure change of the RO membrane during the experiment period in Reference Example 1. In FIG. 14, the pressure of the RO membrane was about 5 MPa at the start of operation, and increased with the continuation of operation. In Comparative Example 1, since the set pressure reached 6.5 MPa from June in about 4 months (120th day), the RO membrane was cleaned with a chemical solution. On the other hand, in Reference Example 1, the pressure reached 6.5 MPa in about 7.5 months (230th day) from June, and the chemical cleaning of the RO membrane was performed.

  In the reference example 1, the RO membrane can be continuously operated about 1.9 times longer than the comparative example 1, and in the continuous operation for 10 months from June to March of the following year, the comparative example 1 is the cleaning of the RO membrane. However, in Reference Example 1, only one cleaning was required.

  According to the seawater desalination apparatus and method of Reference Example 1, separating TEP components (polysaccharides and TEP, precursors) from seawater without adding special filtration membranes, special flocculants, magnetic particles, or the like. Therefore, the reverse osmosis membrane is prevented from being blocked, and stable operation can be performed efficiently over a long period of time.

[Reference Example 2]
A conventional apparatus (Comparative Example 2) shown in FIG. 15 is used by using a seawater desalination apparatus (Reference Example 2) having a foam separation part 200 and an overflow water level control part (telescope valve) 210 shown in FIG. Under the same conditions, the vehicle was continuously operated in parallel for 9 months from June to March of the following year. Table 4 shows the specifications of the foam separation unit 200.

  The foam separation unit 200 incorporates a control method according to the water quality fluctuation because the phenomenon that the foam separation becomes unstable due to the water quality fluctuation of the intake seawater is confirmed when the operation condition is fixed and continuously operated.

In Reference Example 2, the overflow water containing foam in the overflow water level control unit (telescope valve) 210 so that the amount of foam separation is 0.347 L / min, which is 5% of the seawater flowing into the foam separation unit 200. The position was automatically adjusted. Comparative Example 2 was operated with the same specifications as Comparative Example 1. Table 5 shows the results of measuring the TEP concentration at a fixed point of each process twice in September when the TEP concentration increases and twice in December when the TEP concentration is relatively low.

  In Reference Example 2, since the TEP concentration in seawater taken in September is 2,020 μg-XG / L, and the TEP concentration in seawater after treatment has decreased to 632 μg-XG / L, TEP removal The rate was 69%. On the other hand, in Comparative Example 2, the TEP concentration was 1,980 μg-XG / L and remained unchanged even through the raw water tank.

  In the turbidizer 30 (gravity type double-layer sand filter 31), the TEP removal rate in September was 38% in Reference Example 2, 32% in Comparative Example 2, and 36% in Reference Example 2 in December, Comparative Example 2. It was 33%. In both Reference Example 2 and Comparative Example 2, a decrease in TEP concentration was observed.

  The TEP concentration in seawater at the 40 inlet of the desalination treatment device (RO membrane device) is 330 μg-XG / L in Reference Example 2 in September, 1,333 μg-XG / L in Comparative Example 2, and reference in December. Example 2 had 130 μg-XG / L, Comparative Example 2 had 330 μg-XG / L, and Reference Example 2 had a significantly lower TEP concentration than Comparative Example 2.

  Moreover, when Reference Example 1 and Reference Example 2 were compared, stable foam separation became possible by controlling the overflow water level by the overflow water level control unit (telescope valve) 210. FIG. 18 shows the pressure change of the RO membrane 41 during the experiment. In FIG. 18, the RO membrane pressure was 4.8 MPa at the start of operation, and increased with the continuation of operation. In Comparative Example 2, since the temperature rapidly increased from June and reached the set pressure of 6.5 MPa in July (110th day), the RO membrane was cleaned with a chemical solution. On the other hand, in Reference Example 2, the pressure reached 6.5 MPa in November (230th day), and the RO membrane was subjected to chemical cleaning. In Reference Example 2, the RO membrane can be continuously operated about 2.1 times longer than in Comparative Example 2, and in the continuous operation for 9 months from April to December, Comparative Example 2 cleans the RO membrane. While it took two times, in Reference Example 2, only one washing was necessary.

  In addition, as long as it has the same structure as the foam separation part 200 used in Reference Example 2, a commercially available protein skimmer for seawater fish breeding / aquaculture may be used.

[Example 1]
When operating for 1 week using the seawater desalination treatment flow shown in FIG. 19, measuring the TEP component concentration in the outlet drainage of the foam separation unit, and adding ferric chloride (FeCl ₃ ) as a flocculant to the collected seawater The removal performance of the TEP component was confirmed when (Example 1) and when not added (Comparative Example 3). The amount of ferric chloride added was 5 mg / L (as FeCl ₃ ) with respect to the intake seawater. The foam separator used was a protein skimmer manufactured and sold for aquariums.

TEP is measured by filtering a seawater sample with a filter paper made of polycarbonate having a pore diameter of 0.4 μm, staining the sample captured on the surface of the filter paper with Alcian blue, and measuring xanthan gum (XG) with a spectrophotometer as a standard. The unit is indicated by μg-XG / L. TEP that can be quantified by this analytical method is an acidic mucopolysaccharide.
Table 6 shows the specifications of the foam separation apparatus used in this example and the comparative example.

Table 7 shows the TEP component measurement results of Example 1 and Comparative Example 3.

In Example 1, the TEP removal rate was 78.2%, and in Comparative Example 3, the TEP removal rate was 53.0%, indicating that 25.2 points were improved.
Even in comparison with Reference Examples 1 and 2 (56 to 69%) in which the flocculant was not added before removing the TEP component, the TEP component removal rate by the method of the present invention was improved by 9 to 22 points. I understand.

[Example 2]
20 days of operation using the seawater desalination treatment flow shown in FIG. 20, ferric chloride (FeCl ₃ ) is added to the collected seawater as a coagulant, and then TEP component removal and separation is performed, and the sand filter is discharged from the outlet. When the TEP component concentration was measured (Example 2), and after adding ferric chloride (FeCl ₃ ) as a flocculant to the collected seawater, sand filtration was performed without performing TEP component removal and separation. The removal performance of the TEP component was confirmed when the concentration of the TEP component in the outlet drainage was measured (Comparative Example 4). The amount of ferric chloride added was 5 mg / L (as FeCl ₃ ) with respect to the intake seawater. The foam separation apparatus is the same as that used in Example 1. The sand filtration device has a structure in which filtration resistance due to clogging of the filtration layer is detected, and backwashing is automatically performed when the filtration resistance becomes constant (10 kPa). Table 8 shows the specifications of the sand filter.

Table 9 shows the TEP component measurement results of Example 2 and Comparative Example 4.

In Example 2, the TEP removal rate was 89.2%, and in Comparative Example 4, the TEP removal rate was 43.4%, indicating that it was improved by 45.8 points.
In comparison with Reference Examples 1 and 2 (56 to 69%) in which the flocculant was not added before removing the TEP component, the TEP component removal rate according to Example 2 was improved by 20 to 33 points. I understand.
Moreover, the backwash frequency of the sand filtration tank could be significantly reduced from 16 times / week in Comparative Example 3 to 2 times / week and 1/8. When the frequency of backwashing is significantly reduced, the amount of treated water used as backwashing water is also greatly reduced, so that the amount of treated water obtained by seawater desalination, that is, the water recovery rate is greatly improved.

[Example 3]
It was operated for one week using the seawater desalination treatment flow shown in FIG. 21, and after adding ferric chloride (FeCl ₃ ) as a coagulant to the collected seawater, TEP component removal separation was performed, and the outlet drainage of the UF membrane separator When measuring the concentration of medium TEP component (Example 3), after adding ferric chloride (FeCl ₃ ) as a coagulant to the collected seawater, UF membrane separation was performed without performing TEP component removal separation, and UF membrane The removal performance of the TEP component in the case where the concentration of the TEP component in the outlet drainage of the separator was measured (Comparative Example 5) was confirmed. The foam separation apparatus is the same as that used in Examples 1 and 2. The amount of ferric chloride added was 5 mg / L (as FeCl ₃ ) with respect to the intake seawater. The UF membrane separation device has a structure in which a differential pressure between the inlet side and the outlet side is detected, and the backwashing is automatically performed when a certain differential pressure (55 kPa) is reached. Table 10 shows the specifications of the UF membrane separator.

Table 11 shows the TEP component measurement results of Example 3 and Comparative Example 5.

In Example 3, the TEP removal rate was 94.2%, and in Comparative Example 5, the TEP removal rate was 84.2%.
Even in comparison with Reference Examples 1 and 2 (56 to 69%) in which the flocculant was not added before removing the TEP component, the TEP component removal rate according to Example 3 was improved by 25 to 38 points. I understand.
Moreover, the backwash frequency of the UF membrane separator was significantly reduced from 252 times / week in Comparative Example 5 to 35 times / week to 14% or less. When the frequency of backwashing is significantly reduced, the amount of treated water used as backwashing water is also greatly reduced, so that the amount of treated water obtained by seawater desalination, that is, the water recovery rate is greatly improved. In addition, since sodium hypochlorite is used for backwashing the UF membrane separator, the amount of chemicals used is greatly reduced, which contributes to a reduction in maintenance costs.

[Example 4]
An embodiment in the case where foam is separated by adding acid to seawater and adjusting pH in the processing flow shown in FIG. 22 will be described. In addition, sulfuric acid was used as the acid.
Sulfuric acid was added to the taken-in seawater to adjust the pH to 4.0 to 7.0, and the mixture was treated with a foam separator, and the TEP component concentration in the outlet drainage of the foam separator was measured. The results are shown in Table 12.

  It can be seen that the TEP removal rate of Example 4 in which the pH was adjusted was improved as compared with Comparative Example 6 in which the pH was not adjusted. In particular, an improvement of about 10 points or more was confirmed in the range of pH 5.0 to 7.0. In general, in order to prevent inorganic scale from adhering to the RO membrane in seawater, a method is generally used in which sulfuric acid is added immediately before the RO membrane to lower the pH to about 6.8. Therefore, in accordance with the method of the present invention, sulfuric acid is added before foam separation to lower the pH to 6.8, thereby improving the TEP removal rate in foam separation without increasing the amount of sulfuric acid added and inorganic to the RO membrane. Scale adhesion can also be prevented.

[Example 5]
When sulfuric acid is added to seawater and the pH is adjusted to 6.0 in the treatment flow shown in FIG. 23, ferric chloride is added as 5 mg / L (as FeCl ₃ ) to the seawater and foam separation is performed. Examples will be described. The TEP component concentration in the outlet drainage of the foam separation part was measured. The results are shown in Table 13.

  Compared with Comparative Example 7 in which pH adjustment was not performed and no flocculant was added, Comparative Example 8 in which only pH adjustment was performed improved the TEP removal rate by 10.3 points. It can be seen that when the pH is further adjusted and the flocculant is added, it is improved by 21.4 points compared to Comparative Example 6 and 11.1 points compared with Comparative Example 7. Depending on the quality of the intake seawater to be treated, only acid addition is required before foam separation, or when higher TEP removal rate is targeted, acid may be added and a flocculant added. it can.

10: Seawater intake section 15: Coagulant addition means 20: Bubble generation and foam removal section 21: TEP component removal tank 22: Bubble generation means 23: Foam removal means 24: Foam concentration means 25: Bubble directing means 26: Prevention of foam outflow Means 30: Turbidity removal device (part)
31: Filtration device 40: Reverse osmosis membrane treatment device 200: Foam separation unit 210: Overflow water level control unit (telescope valve)

Claims (19)

A flocculant addition means for adding a flocculant to the taken seawater;
Bubbles are generated in seawater containing flocs formed by aggregation of suspension in seawater with a flocculant, and TEP-containing bubbles formed by adsorbing TEP components to the bubbles are collected on the water surface and removed as TEP-containing foams. A TEP component removal tank having a foam removal unit;
A reverse osmosis membrane treatment apparatus for desalinating seawater from which TEP components have been removed;
A seawater desalination apparatus comprising: The seawater desalination apparatus according to claim 1, wherein the foam removal unit includes a foam concentration unit that densifies and concentrates the TEP-containing foam that has floated on the water surface. The seawater desalination apparatus according to claim 2, wherein the foam concentrating part is one or a plurality of partition walls provided between opposing walls of the TEP component removal tank. The seawater desalination apparatus according to claim 1, wherein the foam removing unit includes a bubble directing unit that collects TEP-containing bubbles floating on the water surface in a predetermined region. The bubble directing means is an inclined partition provided in the TEP component removal tank, and is inclined so that a water cross-sectional area in one region partitioned by the inclined partition is reduced upward. The seawater desalination apparatus according to claim 4. The said foam removal part contains at least 1 sort (s) of a pipe skimmer or a scum pump, The seawater desalination apparatus of any one of Claims 1-5 characterized by the above-mentioned. The TEP component removal tank is provided with a standing partition standing from the bottom surface to below the water surface level, or a movable weir capable of positioning a weir port below the water surface, and the outflow of the TEP-containing foam floating on the water surface The seawater desalination apparatus according to any one of claims 1 to 6, wherein The foam removing unit includes a bottom surface that is parallel to the water surface, and a plurality of inverted funnel-shaped rising portions that obliquely rise from the bottom surface and form openings at the top portion. Seawater desalination equipment. The said TEP component removal tank is further equipped with the overflow water level control part which controls the waste_water | drain amount of the seawater after TEP component removal, and makes the foam removal amount in the said foam removal part constant. The seawater desalination apparatus according to any one of the above. The said TEP component removal tank contains at least 1 sort (s) of an aeration apparatus, an aeration apparatus, a stirring-type aerator, an ejector, an ultrafine bubble generator, or the colliding member which collides the picked-up seawater, It is characterized by the above-mentioned. 9. The seawater desalination apparatus according to any one of 9 above. The seawater desalination apparatus according to any one of claims 1 to 10, further comprising a turbidity removing apparatus that removes turbid components from the seawater from which the TEP component has been removed or the taken-in seawater. The said turbidity removal apparatus is a filtration apparatus formed by filling at least one selected from MF membrane, UF membrane, sand, anthracite, glass, garnet, activated carbon, and fiber member as a filter medium. Item 12. A seawater desalination apparatus according to item 11. An acid addition means for adding acid to the seawater or seawater containing the flock, and an acid addition for controlling the amount of acid added by measuring the pH of the seawater or seawater containing the flock before the TEP component removal tank The seawater desalination apparatus according to any one of claims 1 to 12, further comprising a quantity control means. A flocculant addition step of adding flocculant to the taken seawater to agglomerate the suspension in seawater to form a floc;
Bubbles are generated in seawater containing the floc, TEP components in the seawater are attached to the bubbles, the TEP-containing bubbles are floated on the surface of the water, and the bubbles that have risen are collected to form a TEP-containing foam. A TEP component removing step to be removed;
A turbidity removing step for removing turbidity from the taken seawater or seawater after removing TEP-containing bubbles;
A desalting treatment step of desalinating seawater after removing the TEP component;
The seawater desalination method characterized by comprising. An acid addition step of adding acid to the taken seawater;
An acid addition control step of measuring the pH of the seawater after acid addition and controlling the acid addition amount so that the pH is in the range of 5-7;
A TEP that generates bubbles in the seawater, attaches a TEP component in the seawater to the bubbles, causes the TEP-containing bubbles to float on the surface of the water, collects the bubbles that have risen into TEP-containing bubbles, and then removes the TEP-containing bubbles Component removal step;
A desalinating process for desalinating the seawater from which the TEP component has been removed;
The seawater desalination method characterized by comprising. The seawater desalination method according to claim 14 or 15, wherein the TEP component removal step includes a concentration step of concentrating the TEP-containing foam by increasing the density. The seawater desalination method according to claim 14 or 15, wherein the TEP component removal step includes a TEP-containing bubble directing step for collecting the TEP-containing bubbles in a predetermined region on the water surface. The bubbles are
It is formed by dropping the taken seawater into the aquarium, colliding the taken seawater with the collision member, or using an air diffuser, an aeration device, an agitating aerator, an ejector, or an ultrafine bubble generating device. The seawater desalination method according to claim 14 or 15. The removal of the TEP-containing foam that has floated on the water surface in the TEP component removal step is performed by separation / removal using a reverse funnel-shaped foam separation unit provided above the water surface, separation / removal from seawater by a movable weir floating on the water surface, and a skimmer on the water surface. The seawater desalination method according to any one of claims 14 to 18, wherein the seawater desalination method is performed by at least one kind of scraping by the above and suction by a pump.