JP5492243B2 - Water treatment method and water treatment apparatus - Google Patents

Description

  Embodiment described here is related with the water treatment method and water treatment apparatus for isolate | separating the inorganic particle which exists in water.

  Recently, effective use of water resources is required due to industrial development and population growth. For that purpose, the reuse of wastewater such as industrial wastewater is very important. In order to achieve these, it is necessary to purify the water, ie to separate other substances from the water. Various methods are known as a method for separating other substances from a liquid, and examples thereof include a membrane separation method, a centrifugal separation method, an activated carbon adsorption method, an ozone treatment method, and a method for removing suspended substances by aggregation. By these methods, chemical substances having a great influence on the environment such as fluorine, chlorine, phosphorus and nitrogen contained in water can be removed, and oils and clays dispersed in water can be removed. Among these, the membrane separation method is one of the most commonly used methods for removing insoluble substances in water.

In factories such as semiconductor manufacturing factories, LCD manufacturing factories, and crystal processing factories, a large amount of wastewater containing water-soluble fluorine compounds such as HF and H ₂ SiF ₆ is generated as factory wastewater. is there. As a method for removing the fluorine component from the fluorine-containing wastewater, a method of reacting with a calcium agent such as slaked lime or calcium carbonate to separate it as a fluorine compound is known. For example, in Patent Document 1, fluorine ions in water are precipitated in water as calcium fluoride, and a polymer flocculant such as polyaluminum chloride (PAC) is added thereto to aggregate the calcium fluoride to form a floc. A method of separating and recovering after growing large is described.

JP 2010-207755 A

  However, in the conventional method, the purity of calcium fluoride to be separated / recovered falls and it is difficult to recover it as a valuable resource. Moreover, in the conventional method, since the amount of sludge generated by the amount of the added polymer flocculant increases, there is a problem that the disposal cost increases. In addition, such wastewater containing calcium fluoride often contains fine calcium fluoride and is very difficult to remove using a solid-liquid separator using filtration or the like.

  Embodiment described here was made in order to solve the said subject, and it aims at providing the water treatment method and water treatment apparatus which can improve the quality of waste water without using a chemical | medical agent. To do.

In the water treatment method according to the embodiment described herein, (a) calcium carbonate particles having an average particle diameter of 4 to 30 μm are added to raw water containing fluorine ions, and fluorine ions contained in the raw water are reacted with calcium fluoride by reaction. (B) using either sedimentation or centrifugation, so that the particle size distribution of the calcium carbonate particles is larger than the particle size distribution of the calcium fluoride particles. The inorganic particles contained in the water are classified into the calcium carbonate particle group and the calcium fluoride particle group , whereby the raw water contains a first drain containing the calcium carbonate particle group and a second containing the calcium fluoride particle group . (C) The first drainage is sent to a solid-liquid separator having a filter in advance, and the carbonated carbonate is placed on the filter. Depositing the calcium particles, after; (d) step (c), the feed second draining to the solid-liquid separation device, depositing the calcium fluoride particles on the filter, thereby and said calcium carbonate particles A cake layer having the calcium fluoride particles is formed on the filter; and (e) the cake layer is peeled from the filter, and the peeled material is discharged from the solid-liquid separator.

The block diagram which shows the water treatment apparatus which concerns on embodiment. The process drawing which shows the outline | summary of the water treatment process using the apparatus of FIG. (A)-(e) is a schematic diagram which shows a process when the 1st and 2nd particle | grains are isolate | separated one by one by a filtration membrane, and the deposited cake layer is removed from a filtration membrane. (A)-(c) is a schematic diagram which shows the process when a soft particle block | closes the pore of a filtration membrane and produces clogging. The block diagram which shows the water treatment apparatus which concerns on other embodiment. Process drawing which shows the outline | summary of the water treatment process using the apparatus of FIG. The block diagram which shows the water treatment apparatus which concerns on other embodiment. Process drawing which shows the outline | summary of the water treatment process using the apparatus of FIG.

  Hereinafter, various embodiments for solving the above-described problems will be described.

(1) The water treatment method of the embodiment described herein is as follows: (a) Calcium carbonate particles having an average particle size of 4 to 30 μm are added to raw water containing fluorine ions, and fluorine ions contained in the raw water are removed by reaction. Precipitated in the form of calcium fluoride particles , and (b) using either sedimentation or centrifugation, the particle size distribution of the calcium carbonate particles is larger than the particle size distribution of the calcium fluoride particles , The inorganic particles contained in the raw water are classified into the calcium carbonate particle group and the calcium fluoride particle group , whereby the raw water contains the first drainage containing the calcium carbonate particle group and the calcium fluoride particle group . (C) the first waste water is sent to a solid-liquid separator having a filter in advance, and the carbonic acid is placed on the filter. Depositing calcium particles, after; (d) step (c), the feed second draining to the solid-liquid separation device, depositing the calcium fluoride particles on the filter, thereby and said calcium carbonate particles A cake layer having the calcium fluoride particles is formed on the filter; and (e) the cake layer is peeled from the filter, and the peeled material is discharged from the solid-liquid separator.

In the embodiment described here, first, as a pretreatment step, an additive is added to raw water containing fluorine ions, and the fluorine ions and the components of the additive are reacted to precipitate fluorine compound particles. In the pretreatment step, a fine powder of calcium carbonate can be added to the raw water as an additive to precipitate the fluorine ions contained in the raw water in the form of calcium fluoride particles (Tables 1 and 2). By using the precipitated particles, the specific gravity of the inorganic particles becomes relatively high, and gravity sedimentation separation in a sedimentation separation tank as a solid-liquid separation device and centrifugal separation in a cyclone are facilitated. Next, the inorganic particles in the water are roughly classified into two particle groups according to the size of the particle diameter, and the calcium carbonate particle group having the larger particle diameter is sent to the solid-liquid separation device in advance, and the calcium carbonate particle group is filtered. (FIGS. 3A and 3B). Next, the calcium fluoride particle group having a smaller particle diameter is sent to the solid-liquid separator, and the calcium fluoride particle group is filtered with a filter (FIGS. 3C and 3D). As a result, the calcium carbonate particles are deposited on the filter of the solid-liquid separator , and the calcium fluoride particles are further deposited thereon to form a two-layer cake layer. Then, release water is sprayed onto the cake layer from the side of the solid-liquid separator, and the cake layer is peeled off from the filter to break up into pieces, and together with the release water, inorganic particles (decomposed product of the cake layer) are separated into solid and liquid The product is discharged from the apparatus (FIG. 3 (e)).
In the embodiment described here, calcium carbonate particles are added to raw water containing fluorine ions as a pretreatment step to precipitate calcium fluoride particles. The average particle diameter of the calcium carbonate particles is 4 to 30 μm. This is because the generated calcium fluoride particles have a particle diameter of approximately 0.5 to 2 μm, and thus are preferable particle diameters for separating and laminating solids in water.
The added calcium carbonate dissolves in water to generate carbonate ions as shown in the following formula (1).
CaCO ₃ → Ca ²⁺ + CO ₃ ^2- (1)
The generated carbonate ions react with the fluorine ions in the waste water, and calcium fluoride is deposited according to the following formula (2). Incidentally, the average particle diameter of calcium fluoride particles precipitated in water is about 0.5 to 2 μm.
^{_{Ca 2+ + 2F - → CaF 2}} ↓ ... (2)
Water to be treated containing precipitated calcium fluoride particles (specific gravity 3.18) is sent to a sedimentation separation tank or cyclone, and in the sedimentation separation tank or cyclone, a calcium carbonate particle group having a large particle diameter and a calcium fluoride particle group having a small particle diameter are used. Classify .

  Thus, when the inorganic particles to be removed are divided into two groups and individually filtered with a solid-liquid separator, there are various merits described below.

  First, by laminating large particles on the filter first, it is possible to avoid contacting fine particles directly on the filter, thereby extending the filter life (filter life extension). Second, large eye filters can be used because large particles are first laminated onto the filter. The ability to use such a filter means a reduction in pressure loss and an increase in the amount of treated water is expected (improvement in treatment efficiency). Thirdly, since large particles are first laminated on the filter, small particles are captured in the pores between the large particles, so even particles that are much smaller than the filter diameter can be captured (improvement of removal rate). .

(2) In the above (1), in the classification step (b), the raw water can be divided into the first waste water and the second waste water using the sedimentation separation method (FIGS. 1, 2, 7, and FIG. 8).

The “sediment separation method” is defined as a method for separating a solid substance into one having a large mass and one having a small mass by utilizing a difference in sedimentation speed in water. As means for utilizing the sedimentation separation method, a sedimentation separation tank having a partition plate inside, or a cascade-type sedimentation tank or sedimentation tank can be exemplified. By using such a mechanical separation process, it is possible to classification with less energy consumption in water of the inorganic particles and calcium carbonate particles and calcium fluoride particles.

(3) In the above (1), in the classification step (b), the raw water can be divided into a first drainage and a second drainage using a centrifugal separation method (FIGS. 5 and 6).

The “centrifugation method” is defined as a method for separating a solid into one having a large mass and one having a small mass by utilizing the action of centrifugal force. As a means for utilizing the centrifugal separation method, a hydrocyclone having a conical body and a lowermost pot can be exemplified. By using such a mechanical separation method, it is possible to quickly and highly efficiently classify inorganic particles in water into calcium carbonate particles and calcium fluoride particles .

(4) In any one of the above (1) to (3), in the classification step (a), the difference Δd between the average particle diameter of the calcium carbonate particle group and the average particle diameter of the calcium fluoride particle group is the first value. It is preferable that the average particle diameter d _L of the particle group is in the range of 6% to 50% (0.06 d _L <Δd ≦ 0.50 d _L ).

When classifying inorganic particles in water, the difference Δd between the average particle diameter of the calcium carbonate particle group and the average particle diameter of the calcium fluoride particle group contained in each of the two wastewaters is determined as the difference of the calcium carbonate particle group. When 6% greater than the range of 50% or less of the average particle diameter d _L, it is possible to perform efficiently the water treatment. This is because when the difference Δd in the average particle diameter is 6% or less of the average particle diameter d _L of the calcium carbonate particle group, there is no merit of separately filtering the calcium carbonate particle group and the calcium fluoride particle group . On the other hand, when the difference Δd in the average particle diameter exceeds 50% of the average particle diameter d _L of the calcium carbonate particle group, the gap between the particles of the calcium carbonate particle group in which large particles are laminated on the filter is defined as the calcium fluoride particle group. This is because there is a possibility that small particles may pass through the filter. As a result of various studies, the inventors of the present application have confirmed that the particle diameter that can be taken in a layer in which arbitrary particles are laminated is approximately 6% of the particles.

  (5) In said (1), it is preferable that the filter of a solid-liquid separator has a filtration surface orthogonal to the direction where gravity acts.

  If the filtration surface of the filter is orthogonal to the direction in which gravity acts, that is, if the filtration surface of the filter is horizontal, the particles stacked on the filter will be stabilized, and the quality of treated water that has passed through the filter will improve. It is.

(6) The water treatment apparatus of the embodiment described herein includes (A) an additive addition apparatus 4 for adding calcium carbonate particles having an average particle diameter of 4 to 30 μm to raw water containing fluorine ions, and (B) raw water. the inorganic particles contained, as more of the particle size distribution of the calcium carbonate particles is larger than the particle size distribution of the group calcium fluoride particles, said to a secondary classifying the calcium fluoride particles and calcium carbonate particles, thereby and classification means 5,9 to divide the raw water into two and second effluent containing first effluent and the calcium fluoride particles containing the calcium carbonate particles, relative to the direction of action (C) gravity And an upper space 81 which is partitioned vertically by the filter, and in which the first and second drainage are respectively guided from the classification means onto the filter. , A solid-liquid separator 8 and a lower space 82 through which the water having passed through the filter, (D) in between the said classifying means to said solid-liquid separator, said first and said second water discharge (E) a first temporary storage tank 6 provided in the drainage supply line for temporarily storing the first drainage from the classification means; (F) a second temporary storage tank 7 provided in the waste water supply line and temporarily storing the second waste water from the classification means; and (G) provided in the waste water supply line, And a switching valve V3 for switching the waste water supply line communicating with the solid-liquid separator between the first temporary storage tank and the second temporary storage tank.

In the embodiment described here, after the inorganic particles in the water are classified by a classification means such as a sedimentation separation tank or a cyclone, the first drainage and the second drainage are separated from the classification means at different timings provided with a time difference. By introducing each into a solid-liquid separator, a cake layer having a two-layer structure comprising a calcium carbonate particle group and a calcium fluoride particle group can be formed on the filter.

(7) In the above (6), the classification means is preferably a sedimentation separation tank that separates inorganic particles into calcium carbonate particles and calcium fluoride particles using the action of gravity (FIGS. 1 and 2). 7).

As means for utilizing the sedimentation separation method, a sedimentation tank having a partition plate inside can be used. By using such a mechanical separation device, it is possible to classification with less energy consumption in water of the inorganic particles and calcium carbonate particles and calcium fluoride particles.

(8) In the above (6), the classifying means is preferably a cyclone that separates the inorganic particles into calcium carbonate particles and calcium fluoride particles using the action of centrifugal force (FIG. 5).

A liquid cyclone having a conical body and a lowermost pot can be used as a means for utilizing the centrifugal separation method. By using such a mechanical separation device, it is possible to quickly and efficiently classify the inorganic particles in water into calcium carbonate particles and calcium fluoride particles .

(9) In any one of the above (6) to (8), it may further include a pump and a raw water tank for supplying waste water containing fluorine ions as raw water to the classification means (FIG. 7).

In the embodiment described here, the raw water is directly sent from the raw water tank to the classifying means without pretreatment, and the inorganic particles contained in the raw water are directly fluorinated with the first drainage containing the calcium carbonate particles. Separated into second drainage containing calcium particles . In the process of separating suspended solids (SS) other than the precipitated particles, the inorganic water particles can be separated and removed from the water with less energy consumption by directly connecting the raw water tank to the classification means and pumping the raw water. it can.

  Further details of the embodiment will be described.

[Classification process to divide into two particle groups with different particle size distribution]
An arbitrary method can be used to divide the calcium carbonate particles and calcium fluoride particles contained in the waste water into two particle groups having different particle size distributions . For example, the difference in sedimentation speed can be used in gravity sedimentation, the difference in movement speed can be utilized in centrifugation, or magnetism or a sieve can be used. In the embodiment described here, it is particularly preferable to use a sedimentation separation method or a centrifugal separation method because the process does not become complicated. For example, in the sedimentation separation method, a sedimentation tank such as a thickener can be used. In this case, for example, a certain settling time is determined, and large particles concentrated from the lower part of the settling tank can be separated by removing fine particles from the supernatant.

In the centrifugal separation method, for example, a cyclone can be used to separate the inorganic particles into a calcium carbonate particle group and a calcium fluoride particle group . A cyclone flows water in the circumferential direction of an inclined cylindrical main body, and separates large particles at the bottom and small particles at the top. Using this principle, the inorganic particles can be divided into a large particle size calcium carbonate particle group and a small particle size calcium fluoride particle group .

  When the inorganic particles are classified by these classification means, the difference in the average particle size of the inorganic particles contained in the two wastewaters is the average particle size of the small particle size, the large particle size When the average particle diameter of the particles is 6 to 50%, water treatment can be performed efficiently. If the particle size is smaller than 6%, fine particles may pass between the particles with large particles laminated on the filter. If the particle size is larger than 50%, the two particle sizes are close to each other, and the advantage of filtering separately is lost. There is a case. As a result of investigations, the inventors of the present application have confirmed that the particle diameter that can be taken in a layer in which arbitrary particles are laminated is approximately 6% of the particles.

[Solid-liquid separator]
The solid-liquid separation device may have any filter (membrane) capable of laminating large particles, but it is preferable to use a filter having a horizontal filter surface. If the filter surface is horizontal, it will be perpendicular to gravity and the particles stacked in the filter surface will be stable, so that the quality of filtered water can be improved.

This filter can be selected according to the required water quality of the treated water. For example, a filter having an air permeability of 30 to 1500 cc / cm ² · min is used. Here, the air permeability is measured by the Frazier method. Specifically, when the filter is made of a woven fabric (filter cloth), it can be measured with a Frasile-type air permeability tester (trade name) manufactured by Yasuda Seiki Seisakusho. As this filter, for example, a filter cloth for a dehydrator can be generally used, and examples include pyrene (polypropylene), tetron (polyester), and nylon (polyamide). Of these, a material having good peelability of the cake layer is more effective. For example, polypropylene is preferable because it is not only inexpensive, but also has a stable differential pressure after recovery of the cake layer and little deterioration, so that it can be easily used for water treatment. Further, the filter cloth can take various weaving methods such as plain weave, twill weave and satin weave, but is not particularly limited. The air permeability and weaving method of the filter cloth that are desirable for use may be appropriately selected in view of the manufacturing cost, and polypropylene or plain weave is particularly preferable. These filter cloths may be calendered if necessary.

[Water treatment method using calcium carbonate]
The water treatment method of the embodiment described here is suitable for removing fluoride ions in water using calcium carbonate. Calcium carbonate reacts with fluoride ions in water to form a calcium fluoride film on the surface of calcium carbonate, which peels off and separates calcium fluoride into water, and the newly born calcium carbonate surface reacts again. It is a mechanism for removing fluoride ions. For this reason, fine calcium fluoride and calcium carbonate having a large particle diameter coexist. If this wastewater is applied to the whole volume filter as it is, the particle size distribution is wide, so a fine filter must be used to stop fine particles. In addition, since the fine particles clog the filter, the filter life is shortened.

  In order to prevent this, among the inorganic particles in water, the particles are divided into particles having a large particle size and particles having a small particle size, and the large particles (first particle group) precede the small particles (second particle group). By laminating on the filter, a coarse filter can be used, and the life of the filter can be extended. Furthermore, rather than preparing and laminating other particles, separating and laminating the particles contained in the wastewater also reduces the amount of cake layer that is ultimately formed, reducing the amount of waste as a whole. be able to.

  Hereinafter, various embodiments will be described with reference to the accompanying drawings.

  There are two types of water treatment methods according to the present embodiment, a sedimentation separation method and a centrifugal separation method. Since the apparatus used for each method is different, each will be described below.

(Water treatment apparatus of the first embodiment)
First, the water treatment apparatus used in the first embodiment will be described with reference to FIG.

  The water treatment apparatus 1 of this embodiment is an apparatus used for a sedimentation method using a sedimentation tank (settler) as a classification means. The water treatment apparatus 1 includes a reaction tank 2, a raw water tank 3, an additive addition apparatus 4, a sedimentation separation tank 5, a first temporary storage tank 6, a second temporary storage tank 7, a solid-liquid separation apparatus 8, and a treated water tank. 10 and the concentrate tank 11, and these devices and apparatuses are connected to each other by a plurality of piping lines L1 to L8. Various pumps P1 to P3, valves V1 to V2, a measuring instrument and a sensor (not shown) are attached to the piping lines L1 to L8, respectively. Detection signals are input from these measuring instruments and sensors to an input section of a controller (not shown), and control signals are output from the output section of the controller to the pumps P1 to P3 and valves V1 to V2, respectively, and their operations are controlled. It has become so. As described above, the entire water treatment apparatus 1 is comprehensively controlled by a controller (not shown).

  The reaction tank 2 is a pretreatment apparatus for pretreating raw water, and is added from the additive addition apparatus 4 while raw water containing fluorine ions is introduced from the raw water tank 3 and temporarily stored. Calcium carbonate is added to the raw water as an agent. In the reaction tank 2, fluorine ions and carbonate ions contained in the raw water react to precipitate calcium fluoride particles. Note that the reaction vessel 2 may optionally have a stirring screw.

  The sedimentation tank 5 is divided into two upper spaces having different areas by a partition plate 51. Of the upper space of the settling / separation tank 5, the area with a small volume is connected to the reaction tank 2 via a raw water supply line L1 having a pump P1. A second drainage discharge line L3 is connected to an area where the volume of the upper space is large.

  On the other hand, the lower space of the sedimentation tank 5 is connected to a first drainage discharge line L2 having a valve V1. This first drainage discharge line L2 is connected to the upper part of the first temporary storage tank 6 and flows down the first drainage containing the first particle group to the first temporary storage tank 6 by the action of gravity. .

  The solid-liquid separator 8 incorporates a filter 83 that partitions the interior horizontally into an upper space 81 and a lower space 82. The upper space 81 of the solid-liquid separator is connected to the first and second temporary storage tanks 6 and 7 via drainage supply lines L4 and L5 having a pressure feed pump P2. Further, a stripping water supply line L7 and a concentrate discharge line L8 having a pump (not shown) are connected to the sides of the upper space 81, respectively. The line L8 has a pump P3 and discharges the concentrated liquid (peeled material) from the solid-liquid separator 8 to the concentrated liquid tank 11. On the other hand, the lower space 82 of the solid-liquid separator is connected to the treated water supply line L6, and the treated water is sent to the treated water tank 10 via the line L6.

(Water treatment method of the first embodiment)
Next, the water treatment method according to the first embodiment using the above apparatus will be described with reference to FIG.

  The sedimentation separation method is particularly effective when the flow rate of waste water containing a solid content of water-insoluble matter is large. In the sedimentation separation method, first, calcium carbonate is added to water to be treated containing fluorine ions as a pretreatment step to precipitate calcium fluoride particles (step S1). The amount of calcium carbonate added is, for example, about 0.6 to 1.0 mole per mole of fluoride ions. The particle size of calcium carbonate is approximately 4 to 30 μm. After the raw water and calcium carbonate are put into the reaction tank 2, the time required to sufficiently react them is stirred. The stirring time is, for example, 5 to 60 minutes.

  The added calcium carbonate fine powder is dissolved in water to generate carbonate ions as shown in the following formula (1).

CaCO ₃ → Ca ²⁺ + CO ₃ ^2- (1)
The generated carbonate ions react with the fluorine ions in the waste water, and calcium fluoride is deposited according to the following formula (2). The average particle diameter of the calcium fluoride particles precipitated in water is about 1 to 2 μm.

_{^{Ca 2+ + 2F - → CaF 2}} ↓ ... (2)
Water to be treated containing precipitated calcium fluoride particles (specific gravity 3.18) is sent to the sedimentation separation tank 5 and classified into a particle group having a large particle size and a small particle group in the sedimentation separation tank 5 (step S2). That is, in the sedimentation tank 5, large particles can be taken out from the lower part of the sedimentation tank 5 and small particles can be taken out from the upper part of the sedimentation tank 5. The settling time depends on the size of the particles and the settling speed, but is, for example, 15 minutes to 120 minutes. The slurry liquid sent from the reaction tank 2 by the pump P1 is partially settled by the action of gravity, and liquids containing large particles from the lower part and small particles from the upper part are discharged. A first wastewater containing a particle group having a large particle diameter, that is, a first particle group having a larger particle size distribution is stored in the first temporary storage tank 6. On the other hand, a second waste water containing a particle group having a small particle diameter, that is, a second particle group having a smaller particle size distribution is stored in the second temporary storage tank 7.

  Next, the first drainage is supplied from the first temporary storage tank 6 to the solid-liquid separator 8 by operating the switching valve V2 and the pressure feed pump P2 ((a) of FIG. 3). The particles of the first particle group are separated from the first waste water by the filter 83. As a result, as shown in FIG. 3B, the particles 22 of the first particle group having a large particle size distribution are formed on the filter 83. Deposit (step S3). In the separation step S3 of the first particle group, the supply pressure of the pressure pump P2 is adjusted to a range of 0.2 to 0.5 MPa. The pump P2 is stopped and the first particle group separation step S3 is terminated.

Next, the switching valve V2 is switched, the pumping pump P2 is restarted, and the second drainage is supplied from the second temporary storage tank 7 to the solid-liquid separator 8 ((c) in FIG. 3). The filter 83 separates the particles of the second particle group from the second waste water. As a result, the particles 23 of the second particle group having a small particle size distribution on the particles 22 of the first particle group on the filter 83. Is further deposited (step S4). In this case the particle size d ₂ of the second particle group 23 has the diameter df is smaller than the filter pores 84, the first particle group 22 serving as a base layer as shown in FIG. 3 (d) A second particle group of particles 23 is deposited on the deposited layer. In this way, a cake layer 24 composed of the particles 22 and 23 of the first and second particle groups is formed on the filter 83. Similarly, in the second particle group separation step S4, the supply pressure of the pressure feed pump P2 is adjusted to a range of 0.2 to 0.5 MPa. The pump P2 is stopped and the second particle group separation step S4 is completed. Next, peeling water is sprayed onto the filter 83 from the side of the solid-liquid separator 8, and the cake layer 24 is peeled and removed from the filter 83 (step S5). That is, the cake layer 24 is peeled off from the filter 83 by spraying peeling water from the side of the solid-liquid separator 8, and discharged to the tank 11 as a concentrated liquid through the discharge line L8 communicating with the discharge port. As a result, the filter 83 is washed and regenerated, and solid-liquid separation can be performed again.

  In the above embodiment, the calcium fluoride particles precipitated by the pretreatment are classified, separated and removed, but the target particles are not limited to calcium fluoride particles, and hard particles 22 that are difficult to deform, If it is 23, it can be processed.

  However, the soft particles 26 cannot be processed because they tend to deform and become clogged as shown in FIG. That is, since the soft particles 26 that have been pumped are deformed and fitted into the pores 84 of the filter, not only the water flow rate decreases rapidly, but also from the side as shown in FIG. This is because the soft particles 26 cannot be peeled off from the filter 83 even if the peeling water is sprayed. Examples of such soft particles include agglomerated polymers and water-insoluble oils.

(Second Embodiment)
(Device of Second Embodiment)
Next, a water treatment apparatus 1A used in the water treatment method of the second embodiment will be described with reference to FIG. In addition, description of the part which this embodiment overlaps with said embodiment is abbreviate | omitted.

  The water treatment apparatus 1A of the present embodiment is used for a centrifugal separation method and is particularly effective when the flow rate is small or the installation area of the apparatus is small. The difference between the apparatus 1A of the present embodiment and the apparatus 1 of the first embodiment is that the apparatus 1A is provided with a cyclone 9 instead of the settling separation tank 5 as classification means, and the reaction tank 2A is packed in a packed tower. It is that. The cyclone 9 has a conical cylinder shape in which the upper part of the main body is wide and the lower part is gradually narrowed, and a pot 91 for collecting separated matters is attached to the lowermost part. The pot 91 is connected to the upper part of the first temporary storage tank 6 by a line L2 having a valve V1. When the valve V1 is opened, the slurry containing the separated heavy particles (first particle group) flows down by the action of gravity and is discharged to the first temporary storage tank 6. On the other hand, water and light particles (second particle group) are discharged to the second temporary storage tank 7 through a line L3 connected to the upper part of the cyclone.

  The reaction tank 2A is filled with a granular filler 21 mainly composed of calcium carbonate. When raw water containing fluorine ions is supplied from the raw water tank 3 to the reaction tank 2A, the fluorine ions react with calcium carbonate contained in the filler 21 to precipitate calcium fluoride particles.

(Method of Second Embodiment)
Next, a centrifugal separation method as a second water treatment method using the above apparatus will be described with reference to FIGS.

  As a pretreatment step, fluorine ions contained in the raw water and calcium carbonate are reacted in the reaction tank 2A to precipitate calcium fluoride particles (step K1). Separation process K2 of this embodiment is performed by cyclone 6 instead of a sedimentation tank. The cyclone 9 classifies the particles into large particles and small particles (step K2). Water to be treated containing precipitated calcium fluoride particles (specific gravity 3.18) is sent to the cyclone 9, and the water introduced into the cyclone 9 rotates at high speed along the circumference of the cyclone. Separated from water, particles having a large particle diameter are accumulated in a slurry state in the lower pot 91 of the cyclone 9. The particle-containing slurry stored in the pot 91 at the lower part of the cyclone is sent to the first temporary storage tank 6 through the line L2 by opening the valve V1. The opening and closing of the valve V1 may be performed periodically, or may be performed at any time according to the amount of slurry in the pot 91.

  A first wastewater containing a particle group having a large particle diameter, that is, a first particle group having a larger particle size distribution is stored in the first temporary storage tank 6. On the other hand, a particle group having a small particle diameter flows out from the upper part of the cyclone 9. A second waste water containing a particle group having a small particle diameter, that is, a second particle group having a smaller particle size distribution is stored in the second temporary storage tank 7.

  Next, the first drainage is supplied from the first temporary storage tank 6 to the solid-liquid separator 8 by operating the switching valve V2 and the pressure feed pump P2 ((a) of FIG. 3). The particles of the first particle group are separated from the first waste water by the filter 83. As a result, as shown in FIG. 3B, the particles 22 of the first particle group having a large particle size distribution are formed on the filter 83. Deposit (step K3). In the separation step S3 of the first particle group, the supply pressure of the pressure pump P2 is adjusted to a range of 0.2 to 0.5 MPa. The pump P2 is stopped and the first particle group separation step S3 is terminated.

Next, the switching valve V2 is switched, the pumping pump P2 is restarted, and the second drainage is supplied from the second temporary storage tank 7 to the solid-liquid separator 8 ((c) in FIG. 3). The filter 83 separates the particles of the second particle group from the second waste water. As a result, the particles 23 of the second particle group having a small particle size distribution on the particles 22 of the first particle group on the filter 83. Is further deposited (step K4). In this case the particle size d ₂ of the second particle group 23 has the diameter df is smaller than the filter pores 84, the first particle group 22 serving as a base layer as shown in FIG. 3 (d) A second particle group of particles 23 is deposited on the deposited layer. In this way, a cake layer 24 composed of the particles 22 and 23 of the first and second particle groups is formed on the filter 83. Similarly, in the second particle group separation step S4, the supply pressure of the pressure feed pump P2 is adjusted to a range of 0.2 to 0.5 MPa. The pump P2 is stopped and the second particle group separation step S4 is completed. Next, peeling water is sprayed onto the filter 83 from the side of the solid-liquid separator 8, and the cake layer 24 is peeled off from the filter 83 (step K5). That is, the cake layer 24 is peeled off from the filter 83 by spraying peeling water from the side of the solid-liquid separator 8, and discharged to the tank 11 as a concentrated liquid through the discharge line L8 communicating with the discharge port. As a result, the filter 83 is washed and regenerated, and solid-liquid separation can be performed again.

(Third embodiment)
(Apparatus of the third embodiment)
Next, with reference to FIG. 7, the water treatment apparatus 1B used for the water treatment method of 3rd Embodiment is demonstrated. In addition, description of the part which this embodiment overlaps with said embodiment is abbreviate | omitted.

  In the apparatus 1B of the present embodiment, the raw water is directly sent from the raw water tank 3 to the settling separation tank 5 without pretreatment of the raw water, and the inorganic particles contained in the raw water are directly transferred to the first particle group (first The waste water is divided into a second particle group (second waste water).

  In the process of separating suspended solids (SS) other than the precipitated particles, the inorganic water particles can be separated and removed from the water with less energy consumption by directly connecting the raw water tank to the classification means and pumping the raw water. it can.

  According to the above embodiment, the quality of the treated water can be improved by dividing the particle size distribution of the inorganic particles in the wastewater without using a special agent.

  This will be described in more detail with reference to examples.

(Preparation of calcium carbonate)
(Calcium carbonate particles A)
Calcium carbonate particles A (average particle size 15 μm) were prepared.

(Calcium carbonate B)
Calcium carbonate particles B (average particle size 4 μm) were prepared.

(Calcium carbonate C)
Calcium carbonate particles C (average particle size 30 μm) were prepared.

  All particles A, B, and C were obtained by pulverizing commercially available calcium carbonate reagent (manufactured by Wako Pure Chemical Industries, Ltd.) with a ball mill, removing particles larger than 40 microns, and adjusting the average particle size by wind sorting. is there. Here, the average particle diameter is obtained by calculation using a plurality of actual measurement values measured by a laser diffraction method. Specifically, the particle size of the filter aid was measured using a SALD-DS21 measuring device (product name) manufactured by Shimadzu Corporation. In addition, the average particle diameter of a filter aid is defined as a volume average particle diameter (Mean Volume Diameter).

Example 1
An apparatus schematically shown in FIG. 1 was produced. As the water to be treated, an aqueous hydrogen fluoride solution containing 1000 mg / L of fluoride ions was prepared. This treated water is put into the reaction tank 2 and calcium carbonate A is added to 1 mol in terms of calcium per 1 mol of fluoride ions and mixed for 10 minutes. The concentration of fluoride ions in the water is 8 mg / It confirmed that it was below L.

  Thereafter, the mixture was transferred from the reaction tank 2 to the sedimentation separation tank 5 via a pump, and the sedimentation was performed by adjusting the flow rate so that the average residence time was 20 minutes. From the lower part of the sedimentation separation tank 5, the average particle size was about 20 μm. And a slurry having particles with an average particle diameter of about 4 μm were obtained from the upper part of the sedimentation separation tank 5 and transferred to the large particle-containing drainage tank 6 and the small particle-containing drainage tank 7, respectively. Thereafter, the slurry of the large particle-containing drainage tank 6 was passed through a pump through a solid-liquid separator 8 having a filter 83 horizontal to the ground. The filter 83 was a polypropylene filter cloth. After passing the slurry and laminating about 1 mm particles on the filter 83, the slurry was supplied from the small particle-containing drainage tank 7 to the solid-liquid separation device 8 to separate and collect the small particles. The solid concentration of the treatment liquid at this time was 10 mg / L or less, and the concentration of fluoride ions was 8 mg / L or less.

  Thereafter, the treatment liquid is passed through the washing water supply port installed at the upper part of the solid-liquid separator 8 by an amount of 5% of the total water flow rate, and the carbonic acid concentrated 20 times from the washing water collection port. A calcium / calcium fluoride mixed solution was obtained.

  When this test was repeated, the initial pressure loss of the filter 83 increased by 0.05 MPa by the third time, but it did not increase any more and could be used stably.

(Comparative Example 1)
A test was conducted in the same manner except that the water to be treated was directly supplied from the reaction tank 2 to the solid-liquid separation apparatus 8 and directly filtered without using the sedimentation tank 5 of FIG. The treated water obtained from the solid-liquid separator 8 passed fine particles during the first 3 minutes and contained an average of 46 mg / L of particles. Thereafter, the passage of fine particles disappeared and the filtration was completed. In the same manner as in Example 1, this treatment liquid is passed through the washing water supply port installed in the upper part of the solid-liquid separation device 8 by an amount of 5% of the total water flow amount, and is concentrated 20 times from the washing water collection port. A calcium carbonate / calcium fluoride mixed solution was obtained. When this test was repeated, by the third time, the initial pressure loss of the filter 83 increased by 0.2 MPa, and it became impossible to use.

(Example 2)
The same apparatus as in Example 1 was used, and a test was performed in the same manner except that calcium carbonate B was used instead of calcium carbonate A. In the sedimentation separation tank 5, the particles were divided into particles having an average of 11 μm and an average of 2.3 μm, and the treatment could be performed in the same manner. The solid concentration of the treatment liquid at this time was 10 mg / L or less, and the concentration of fluoride ions was 8 mg / L or less. When this test was repeated, the initial pressure loss of the filter 83 increased by 0.08 MPa by the third time, but it did not increase any more and could be used stably.

(Example 3)
The same apparatus as in Example 1 was used, and the test was performed in the same manner except that calcium carbonate C was used instead of calcium carbonate A. In the sedimentation / separation tank 5, the particles were divided into particles having an average of 35 μm and an average of 5 μm, and the treatment could be performed in the same manner. The solid concentration of the treatment liquid at this time was 15 mg / L, and the concentration of fluoride ions was 8 mg / L or less. When this test was repeated, the initial pressure loss of the filter 83 increased by 0.04 MPa by the third time. However, the initial pressure loss did not increase any more and could be used stably.

(Example 4)
The test was performed in the same manner as in Example 1 except that the apparatus 1A shown in FIG. The cyclone 9 was a Toshiba cyclone S-30. After passing through the cyclone, a slurry containing particles having an average particle diameter of 18 μm was obtained from the lower part of the cyclone, and a slurry containing particles having an average particle diameter of 4 μm were obtained from the upper part. When this was passed through the solid-liquid separator 8 and treated in the same manner as in Example 1, the solid concentration of the treatment liquid at this time was 10 mg / L or less, and the concentration of fluoride ions was 8 mg / L or less. It was. When this test was repeated, the initial pressure loss of the filter 83 increased by 0.05 MPa by the third time. However, the pressure loss did not increase any more and the filter 83 could be used stably.

(Example 5)
Waste water was treated using the apparatus 1B shown in FIG. As the water to be treated, a slurry liquid containing 300 mg / L in total of magnetite having an average of 3 μm and manganese magnesium ferrite having an average of 35 μm was prepared. This treated water is transferred to the sedimentation / separation tank 5 via a pump, and the flow rate is adjusted so that the average residence time is 20 minutes. A slurry having a diameter and a slurry having particles having an average particle diameter of about 3 μm were obtained from the upper part of the sedimentation separation tank 5 and transferred to a large particle-containing drainage tank 6 and a small particle-containing drainage tank 7, respectively. Thereafter, the slurry of the large particle-containing drainage tank 6 was passed through a pump through a solid-liquid separator 8 having a filter 83 horizontal to the ground. A polypropylene filter cloth was used for this filter. The slurry was passed through and about 1 mm particles were laminated on the filter 83, and then the slurry was supplied from the small particle-containing drainage tank 7 to the solid-liquid separator 8 to collect the small particles. The solid concentration of the treatment liquid at this time was 2 mg / L.

(Comparative Example 1)
When the test was conducted in the same manner as in Example 5 except that a slurry containing a total of 300 mg / L of magnetite with an average of 2 μm and an average of 35 μm of manganese magnesium ferrite was used as the water to be treated in Example 5, the sedimentation separation tank A slurry having an average particle diameter of about 35 μm was obtained from the lower part of 5, and a slurry having an average particle diameter of about 2 μm was obtained from the upper part of the sedimentation separation tank 5, respectively. Thereafter, the slurry of the large particle-containing drainage tank 6 was passed through a pump through a solid-liquid separator 8 having a filter 83 horizontal to the ground. A polypropylene filter cloth was used for this filter. The slurry was passed through and about 1 mm particles were laminated on the filter 83, and then the slurry was supplied from the small particle-containing drainage tank 7 to the solid-liquid separator 8 to collect the small particles. The solid concentration of the treatment liquid at this time was 12 mg / L, which was worse than Example 5.

1, 1A ... water treatment device, 2, 2A ... reaction tank (packed tower),
3 ... Raw water tank, 4 ... Additive addition device,
5 ... Settling separation tank (classification means), 51 ... Partition plate,
6 ... Large particle-containing drainage tank (first temporary storage tank),
7 ... small particle-containing drainage tank (second temporary storage tank),
8 ... solid-liquid separator, 83 ... filter, 84 ... fine pores,
9 ... Cyclone (classification means), 91 ... Pot,
10 ... treated water tank, 11 ... concentrate tank,
22, 23 ... hard particles (CaF ₂ particles, etc.), 24 ... cake layer, 26 ... soft particles,
P1-P3 ... pump, V1-V2 ... valve,
L1 ... Raw water supply line, L2 ... First drainage discharge line, L3 ... Second drainage discharge line, L4 ... Second drainage supply line, L5 ... First drainage supply line, L6 ... Treatment water supply line, L7 ... Peeling water supply Line, L8 ... Concentrate supply line.

Claims (9)

(A) Calcium carbonate particles having an average particle size of 4 to 30 μm are added to raw water containing fluorine ions, and fluorine ions contained in the raw water are precipitated in the form of calcium fluoride particles by reaction,
Using either (b) sedimentation separation method or a centrifugal separation method, as more of the particle size distribution of the calcium carbonate particles is larger than the particle size distribution of the group calcium fluoride particles, the inorganic particles contained in the raw water Classification into a calcium carbonate particle group and the calcium fluoride particle group , whereby the raw water is divided into a first drainage containing the calcium carbonate particle group and a second drainage containing the calcium fluoride particle group. Divided,
(C) leading the first waste water to a solid-liquid separator having a filter, and depositing the calcium carbonate particles on the filter;
After; (d) step (c), the feed second draining to the solid-liquid separation device, the depositing the calcium fluoride particles on the filter, thereby the calcium carbonate particles and the calcium fluoride particles Forming a cake layer on the filter,
(E) The cake layer is peeled off from the filter, and the peeled material is discharged from the solid-liquid separator.
A water treatment method characterized by the above. 2. The method according to claim 1, wherein in the step (b), the raw water is divided into the first drainage and the second drainage using a sedimentation separation method. The method according to claim 1, wherein in the step (b), the raw water is divided into the first waste water and the second waste water using a centrifugal separation method. Wherein in the step (b), the difference Δd between the average particle diameter of the average particle diameter and the calcium fluoride particles of the calcium carbonate particles is 6% greater than 50% of the average particle diameter d _L of the calcium carbonate particles The method according to any one of claims 1 to 3, characterized in that it is in the following range (0.06 d _L <Δd ≤ 0.50 d _L ).   2. The method according to claim 1, wherein the filter of the solid-liquid separator has a filtration surface orthogonal to the direction in which gravity acts. (A) an additive addition device for adding calcium carbonate particles having an average particle size of 4 to 30 μm to raw water containing fluorine ions;
The inorganic particles contained in (B) the raw water, as more of the particle size distribution of the calcium carbonate particles is larger than the particle size distribution of the group calcium fluoride particles, the said calcium carbonate particles with the calcium fluoride particles sizing and classification means for thereby dividing the raw water into two and second effluent containing first effluent and the calcium fluoride particles containing the calcium carbonate particles,
(C) having a filter having a filtration surface perpendicular to the direction in which gravity acts, partitioned vertically by the filter, and guiding the first and second drainage from the classification means onto the filter, respectively. A solid-liquid separator having an upper space to be formed and a lower space through which water that has passed through the filter passes,
(D) a drainage supply line provided between the classification means and the solid-liquid separator, and through which the first and second drainage respectively pass;
(E) a first temporary storage tank that is provided in the waste water supply line and temporarily stores the first waste water from the classification means;
(F) a second temporary storage tank provided in the waste water supply line and temporarily storing the second waste water from the classification means;
(G) a switching valve that is provided in the drainage supply line and switches the drainage supply line communicating with the solid-liquid separator between the first temporary storage tank and the second temporary storage tank;
A water treatment apparatus comprising: 7. The apparatus according to claim 6, wherein the classifying means is a sedimentation separation tank that separates the inorganic particles into the calcium carbonate particles and the calcium fluoride particles using the action of gravity. The apparatus according to claim 6, wherein the classifying means is a cyclone that separates the inorganic particles into the calcium carbonate particles and the calcium fluoride particles using an action of centrifugal force. The apparatus according to any one of claims 6 to 8, further comprising a pump and a raw water tank for supplying waste water containing fluorine ions to the classification means as the raw water.

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