JP6829436B2 - Silica-containing water treatment method and its treatment equipment - Google Patents

Description

The present invention relates to a method for treating silica-containing water and a treatment device thereof.

Water treatment technology using reverse osmosis (RO) membranes has become widespread, including desalination of seawater by desalination, as well as application to industrial pure water production processes and wastewater recovery processes. There is. In the filtration process using a reverse osmosis membrane, the problem that silica in water is generated as scale often occurs. Specifically, as the filtration treatment by the reverse osmosis membrane progresses, the silica concentration on the concentrated water side exceeds the saturated solubility of silica, which causes silica precipitation. When the silica scale is generated in this way, not only the filtration capacity of the reverse osmosis membrane is lowered, but also a big problem such as breakage of the reverse osmosis membrane may occur. For this reason, it is common to adjust the concentration ratio by the reverse osmosis membrane so that the silica concentration on the concentrated water side does not exceed the saturated solubility, but in this case, the recovery rate of water by the filtration treatment of the reverse osmosis membrane is low. Become.

Further, in a plant or the like, the circulating water used for a boiler or a cooling tower is generally used repeatedly for a certain period of time and then discharged as blow water. This is to prevent the soluble substances in water such as silica from being concentrated to generate scales due to repeated use, and the scales to be deposited in pipes and the like. In view of such a background, a method and an apparatus for efficiently reducing the silica concentration in silica-containing water are required. The following Patent Documents 1 to 3 disclose various methods and devices for removing silica in water.

Japanese Unexamined Patent Publication No. 2001-149952 Japanese Unexamined Patent Publication No. 7-136648 Japanese Unexamined Patent Publication No. 2004-141799

Patent Document 1 describes that silica in raw water is removed by passing raw water through a column filled with porous silica. In this case, since it is necessary to use expensive porous silica, the processing cost increases, and the energy required for producing the porous silica is large, so that there is a problem that the load on the environment is large. Moreover, since the silica removal rate remains at about 35 to 50%, it cannot be said that it is sufficient for improving the water recovery rate in the reverse osmosis membrane device.

Patent Document 2 describes removing silica in raw water using an ion exchange membrane. Also in this case, since the ion exchange membrane is expensive and the energy required to manufacture the ion exchange membrane is large, there are problems in terms of processing cost and environmental load.

Patent Document 3 describes reducing the silica concentration in raw water by adding a treatment agent such as an iron salt, an aluminum salt or a magnesium salt to raw water and precipitating aggregates under alkaline conditions. ing. In this case, since it is necessary to separate the sludge generated during the silica removal treatment in the subsequent process, there is a problem that the treatment apparatus becomes large.

The present invention has been made in view of the above problems, and an object of the present invention is a method for treating silica-containing water, which has a small burden on the environment, low cost, and enables efficient silica removal treatment in a small space. It is to provide a processing apparatus.

The method for treating silica-containing water according to one aspect of the present invention comprises a raw water supply step of supplying silica-containing raw water to a filling tower, and passing the raw water through the filling tower filled with silica-removed particles. A step of removing silica contained in the raw water by the silica removing particles and a step of taking out the treated water from which the silica has been removed from the filling tower are provided. In the raw water supply step, the pH of the raw water is adjusted so that the pH of the treated water is 6 or more. The silica-removed particles are limonite particles containing 30% by mass or more of FeOOH and 10% by mass or more of SiO ₂ .

The method for treating silica-containing water may further include a replacement step of replacing the silica-removing particles in the filling column. In the exchange step, a filling portion filled with the silica removing particles may be attached to and detached from the tower body having a treatment space for performing the treatment for removing silica from the raw water.

In the method for treating silica-containing water, the difference between the pressure of the raw water and the pressure of the treated water is defined as the operating pressure (kPa), and the flow rate of the treated water (m ³ / h) is defined as the bottom area (m) of the filling tower. ^When the value divided by ² ) and the operating pressure (kPa) is defined as the water flow performance of the filling tower, the water flow performance may be set in the range of 1 or more and 1000 or less.

In the method for treating silica-containing water, the residence time of the raw water in the filling tower may be set to 1 second or longer in the silica removal step.

In the method for treating silica-containing water, in the silica removal step, the space velocity of the raw water in the filling tower may be set to ¹ h ^-1 or more and 3500 h ^-1 or less.

The silica-containing water treatment apparatus according to another aspect of the present invention includes a filling tower, a raw water supply means for supplying silica-containing raw water to the filling tower, silica-removing particles filled in the filling tower, and the raw water. A pH adjusting means for adjusting the pH of silica is provided. The filling tower is configured to allow the raw water to pass through. The pH adjusting means is configured to adjust the pH of the raw water so that the pH of the treated water is 6 or more. The silica-removed particles are limonite particles containing 30% by mass or more of FeOOH and 10% by mass or more of SiO ₂ .

In the silica-containing water treatment apparatus, the filling tower is installed in the processing space while being filled with the silica removing particles and a tower body having a treatment space for performing a treatment for removing silica from the raw water. , A filling portion configured to be removable from the tower body may be provided.

In the silica-containing water treatment apparatus, the silica-removed particles may be in a fluid state in the filling column.

According to the present invention, it is possible to provide a method and an apparatus for treating silica-containing water, which has a small burden on the environment, a low cost, and enables efficient silica removal treatment in a small space.

It is a figure which shows typically the structure of the silica-containing water treatment apparatus which concerns on Embodiment 1 of this invention. It is a top view which shows the structure of the filling part schematically. It is a figure which shows typically the cross-sectional structure of the filling part along the line segment III-III in FIG. It is a figure which shows typically the structure of the silica-containing water treatment apparatus which concerns on Embodiment 2 of this invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(Embodiment 1)
[Silica-containing water treatment device]
First, the configuration of the silica-containing water treatment device 1 (hereinafter, also simply referred to as “treatment device 1”) according to the first embodiment of the present invention will be described with reference to FIG. The treatment device 1 is a device for removing silica from raw water containing silica to obtain treated water having a reduced silica concentration. As shown in FIG. 1, the treatment apparatus 1 includes a filling tower 10, silica removing particles 60 filled in the filling tower 10, raw water supply means 20 for supplying raw water to the filling tower 10, and treated water from the filling tower 10. The taking-out means 40 for taking out the raw water and the pH adjusting means 30 for adjusting the pH of the raw water are provided.

<Filling tower>
The filling tower 10 is for performing a process of removing silica in the raw water by the silica removing particles 60 filled inside. The filling tower 10 includes a tower main body 11 having a treatment space 10A for performing a treatment for removing silica from raw water, and a plurality of filling towers 10 filled with silica removing particles 60 and installed in the treatment space 10A (4 in this embodiment). It has a filling portion 12 and. The filling portion 12 is a cartridge type and is configured to be removable from the tower main body 11.

The tower body 11 has a substantially cylindrical shape, and is arranged in a vertical direction as shown in FIG. An inflow port 11A for flowing raw water into the treatment space 10A is provided in the lower part of the tower body 11, and an outflow port 11B for flowing out the treated water from the treatment space 10A is provided in the upper part of the tower body 11. There is. In the first embodiment, the filling tower 10 has an upward flow system in which raw water is passed from the lower inflow port 11A toward the upper outflow port 11B. With this configuration, the raw water flowing into the treatment space 10A from the inflow port 11A can be passed upward in the vertical direction.

The tower body 11 preferably has a height of 0.5 m or more and 20 m or less, more preferably 0.5 m or more and 15 m or less, and further preferably 1 m or more and 10 m or less. Further, the tower body 11 preferably has an inner diameter of 5 mm or more and 2000 mm or less, more preferably 5 mm or more and 1000 mm or less, and further preferably 5 mm or more and 500 mm or less.

The height and inner diameter of the tower body 11 are parameters that determine the size of the filling tower 10. If the filling tower 10 is too large, it takes a lot of time and effort to attach and detach the filling portion 12 to and from the tower body 11 when replacing the silica removing particles 60, and the cost for ensuring the pressure resistance of the filling tower 10 is increased. Will increase. On the other hand, if the filling tower 10 is too small, it becomes difficult to secure the required amount of treated water, and there is a problem that it is not suitable for industrial use. From this point of view, the height and inner diameter of the tower body 11 are preferably within the above ranges.

The filling portion 12 has a disk shape that can be brought into close contact with the inner surface of the tower main body 11, and is installed at a distance from each other in the length direction of the tower main body 11. More specifically, the outer peripheral portion of the filling portion 12 is a mounted portion, and the mounted portion can be attached to and detached from the mounting portion provided on the inner surface of the tower main body 11.

The silica removing particles 60 are not filled between the adjacent filling portions 12, and the unfilled portions 13 are spaces through which the raw water passes. As shown in FIG. 1, in the filling tower 10, filled portions 12 and non-filled portions 13 are alternately provided in the flow direction of raw water.

FIG. 2 shows a configuration when the filling portion 12 removed from the tower main body 11 is viewed in a plan view. As shown in FIG. 2, the filling portion 12 includes a frame portion 14 formed of a circular ring and a pair of lattice portions 15, 16 (first lattice portion 15, second lattice portion 16) provided inside the frame portion 14. ) And. The frame portion 14 has substantially the same outer diameter as the inner diameter of the tower main body 11 (FIG. 1), and can be brought into close contact with the inner surface of the tower main body 11 at the outer peripheral portion.

The frame portion 14 and the pair of lattice portions 15 and 16 are each made of a resin such as polyvinyl chloride (PVC). As shown in FIG. 2, the pair of lattice portions 15 and 16 intersect (in a cross shape) at substantially right angles inside the frame portion 14. The intersection of the pair of lattice portions 15 and 16 is located at the center of the circle of the frame portion 14.

Inside the frame portion 14, between the first lattice portion 15 and the second lattice portion 16 is a water passage portion 12A through which raw water passes. In the present embodiment, four water passage portions 12A are provided, which are separated from each other by a pair of lattice portions 15 and 16. The number of the lattice portions 15 and 16 is not limited to this, and only one lattice portion may be provided, or three or more lattice portions may be provided.

FIG. 3 shows a cross section of the filling portion 12 along the line segments III-III in FIG. As shown in FIG. 3, the filling portion 12 includes an upper water passage cloth 17 attached to the upper surfaces of the frame portion 14 and the lattice portion 15 and a lower passage attached to the lower surfaces of the frame portion 14 and the lattice portion 15. It has a water cloth 18. The upper water passage cloth 17 and the lower water passage cloth 18 have a circular shape having substantially the same size as the frame portion 14, and are configured to allow raw water to permeate. In the present embodiment, the upper water passage cloth 17 and the lower water passage cloth 18 are each made of a non-woven fabric.

As shown in FIG. 3, a large number of silica removing particles 60 are filled in the water passage portion 12A by being sandwiched between the upper water passage cloth 17 and the lower water passage cloth 18. Since the silica removing particles 60 have a particle size that cannot pass through the gap between the upper water passing cloth 17 and the lower water passing cloth 18, the silica removing particles 60 are filled in the water passing portion 12A as shown in FIG. Can be done.

Silica scavenging particles 60 are limonite (limonite) particles, its chemical formula is represented by _{FeO (OH) · nH 2 O} . The silica-removed particles 60 contain 30% by mass or more of FeOOH (iron oxide hydroxide) and 10% by mass or more of SiO ₂ (silicon dioxide).

FeOOH (iron oxide hydroxide) consists of at least one of α-FeOOH (needle steel, Geesite) and γ-FeOOH (lepidocrocite). That is, FeOOH may be composed of only α-FeOOH, may be composed of only γ-FeOOH, or may be composed of both α-FeOOH and γ-FeOOH.

Further, the silica-removed particles 60 further contain, for example, Fe ₂ O ₃ (red steel), clay mineral, manganese oxide (II), etc. as components (residual components) other than FeOOH and SiO ₂ . The content of this residual component is 0% by mass or more and 60% by mass or less.

The method for specifying the components contained in the silica-removed particles 60 is not particularly limited, but for example, fluorescent X-rays (ZSX Primus μ manufactured by Rigaku Co., Ltd.) can be used. Thereby, it is possible to identify the main element contained in the silica-removed particles 60 and confirm that the converted value satisfies the above-mentioned concentration range.

As a result of diligent studies, the present inventors have found that the silica removing particles 60 having the above-mentioned component composition have an excellent silica removing effect, and the filling tower 10 filled with the silica removing particles 60 as described above is used. We have built a treatment system that allows raw water to pass through. The principle of removing silica in raw water by the silica removing particles 60 is not clear, but it is presumed as follows.

In the usual coagulation-precipitation method, the iron component added to the raw water forms a coagulation-precipitation of the hydroxide under neutral or alkaline conditions, and silica is entrained at that time to remove the silica in the raw water. .. That is, silica in the raw water is removed by the physical action of entraining silica during the formation of agglomerated precipitates.

On the other hand, in the present embodiment, the iron component (second iron hydroxide) existing on the surface of the silica-removing particles 60 (limonite particles) chemically reacts with the silica in the raw water, and on the surface of the silica-removing particles 60. It is considered that silica in the raw water is removed by precipitating a low-solubility silica-iron reactant as an agglomerate. That is, unlike the usual coagulation-precipitation method, it is considered that silica in the raw water can be removed by a chemical action.

Therefore, the silica removal treatment in the present embodiment is superior to the conventional one in the following points. First, since silica-removing particles 60 (limonite particles), which are naturally occurring resources, can be used, costs can be reduced and the environment can be reduced as compared with the case of using porous silica or an ion exchange membrane. The load can be made smaller.

Further, the silica removal treatment can be performed only by passing raw water through the filling tower 10 filled with the silica removing particles 60. Therefore, unlike the usual coagulation-precipitation method, an apparatus for adding an iron agent such as iron chloride becomes unnecessary. Further, since the iron component of the silica removing particles 60 and the silica in the raw water are chemically reacted, the silica removing efficiency can be further improved as compared with the coagulation precipitation method. Moreover, since the silica-iron reactant is deposited on the surface of the silica-removing particles 60, it is not necessary to perform the operation of solid-liquid separation of sludge and treated water after the silica removal treatment as in the coagulation precipitation method. Therefore, the entire processing device 1 can be saved in space.

When all the iron components contained in the silica removing particles 60 are consumed and the silica removing effect cannot be obtained, that time becomes the breakthrough point of the filling tower 10. In this case, the silica removing particles 60 can be easily replaced by removing the filling portion 12 from the tower main body 11 and attaching the filling portion 12 filled with the new silica removing particles 60 to the tower main body 11.

The filling rate of the silica-removed particles 60 in the packing tower 10 is preferably 5% or more and less than 100%. This filling rate (%) can be calculated as the occupied volume of the silica-removed particles in the filling tower / the volume of the filling tower × 100.

When the filling rate is high, the iron component derived from limonite in the filling tower 10 increases, so that the life of the filling tower 10 can be extended and the replacement frequency of the silica removing particles 60 can be reduced. Can be done. However, as the filling rate increases, the water flow resistance of the filling tower 10 increases and the operating pressure increases, which tends to increase the running cost.

On the other hand, when the filling rate is low, the water flow performance is improved, but the filling tower 10 breaks through early and the silica removing effect is lost, so that the silica removing particles 60 are frequently replaced. Therefore, the cost required for the replacement work of the silica removing particles 60 increases, which leads to an increase in running cost.

Therefore, it is preferable that the filling rate of the silica-removed particles 60 in the filling tower 10 is appropriately adjusted within the above range according to the silica concentration of the raw water and the required amount of treated water in consideration of the above circumstances. For example, when the silica concentration of the raw water is relatively high, the iron component contained in the silica-removing particles 60 is consumed at an early stage, so that it is preferable to suppress the replacement frequency of the silica-removing particles 60. Therefore, in this case, it is preferable to set the filling rate high. When it is necessary to increase the amount of treated water, it is preferable to lower the water flow resistance of the filling tower 10 by lowering the filling rate and keep the operating pressure low.

The silica-removed particles 60 preferably have a minimum particle diameter of 0.1 μm or more and a maximum particle diameter of 2 cm or less. The minimum particle size is more preferably 1 μm or more, and the maximum particle size is more preferably 1 cm or less. The average particle size of the silica-removed particles 60 is preferably about 6 μm.

If the silica-removed particles 60 are too small, it becomes difficult to keep the air velocity of the raw water in the filling tower 10 high. Further, since it becomes difficult to prevent the outflow of particles from the filling tower 10, a separation operation is required in the subsequent stage of the filling tower 10. On the other hand, if the silica-removed particles 60 are too large, the total surface area will be small. In this case, even if the filling rate of the silica removing particles 60 is the same, the life of the filling tower 10 is shortened. From this point of view, it is preferable that the particle size of the silica-removed particles 60 is adjusted as described above.

<Raw water supply means>
The raw water supply means 20 is for supplying raw water containing silica to the filling tower 10. The raw water supply means 20 includes a raw water supply line 21, a raw water pump 22, and a control device 50.

The raw water supply line 21 is composed of a pipe having an internal flow path through which raw water can pass, and the upstream end is connected to a water source (not shown) and the downstream end is connected to the inflow port 11A of the filling tower 10. The raw water pump 22 is provided in the middle of the raw water supply line 21, and its operation is controlled by the control device 50. With this configuration, the raw water pump 22 can be operated by the control device 50 to supply the raw water to the filling tower 10 via the raw water supply line 21.

<Means of removal>
The take-out means 40 is for taking out the treated water whose silica concentration has been reduced in the process of passing through the filling tower 10 from the filling tower 10. The take-out means 40 is composed of a pipe having an internal flow path through which treated water can pass, and its upstream end is connected to the outlet 11B of the filling tower 10.

<pH adjusting means>
The pH adjusting means 30 adjusts the pH of the raw water supplied to the filling tower 10 so that the pH of the treated water taken out from the filling tower 10 is 6 or more. The pH adjusting means 30 is composed of a pH adjusting agent supply line 31, a pH adjusting pump 32, a pH adjusting agent tank 33, a pH detecting unit 34, and a control device 50.

The pH adjuster tank 33 prepares solutions of various pH adjusters and stores the solutions. The pH adjuster is not particularly limited as long as the pH of the raw water can be adjusted. For example, as a pH adjusting agent for adjusting the pH of raw water to the acidic side, acids such as sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid, citric acid or oxalic acid can be used. As the pH adjuster for adjusting the pH of the raw water to the alkaline side, bases such as NaOH, KOH, NH ₃ water, Ca (OH) ₂ , Mg (OH) ₂ , NaOHCO ₃ , and Na ₂ CO ₃ are used. Can be used.

The pH adjuster supply line 31 comprises a pipe having an internal flow path through which the pH adjuster solution flows. As shown in FIG. 1, the upstream end of the pH adjuster supply line 31 is connected to the pH adjuster tank 33, and the downstream end is connected to the raw water supply line 21 (a portion upstream of the raw water pump 22). ing.

The downstream end of the pH adjuster supply line 31 is not limited to this position, and may be connected to a portion downstream of the raw water pump 22. Further, in order to uniformly mix the pH adjuster in the raw water, the mixer may be arranged on the downstream side of the connection portion of the pH adjuster supply line 31 in the raw water supply line 21.

The pH adjusting pump 32 is provided in the middle of the pH adjusting agent supply line 31, and its operation is controlled by the control device 50. The pH detection unit 34 (pH sensor) is provided in the extraction means 40, and detects the pH of the treated water flowing out of the filling tower 10.

The control device 50 includes a personal computer or the like, and controls the operation of the pH adjusting pump 32 based on the detection result by the pH detection unit 34. When raw water is passed through the filling tower 10, the pH shifts to the acidic side due to the iron component contained in the silica-removed particles 60. Then, when the pH of the treated water becomes 6 or less, the silica removal treatment in the filling column 10 becomes difficult. Therefore, the control device 50 supplies the pH adjusting agent to the raw water supply line 21 by operating the pH adjusting pump 32, and adjusts the pH of the raw water so that the pH of the treated water becomes 6 or more. That is, the pH detection unit 34 monitors the pH of the treated water and feeds back the result to the supply amount of the pH adjuster.

[Method for treating silica-containing water]
Next, a method for treating silica-containing water according to the present embodiment, which is carried out using the silica-containing water treatment device 1, will be described.

First, the raw water containing silica is supplied to the filling tower 10 by the raw water supply means 20 (raw water supply step). Specifically, by operating the raw water pump 22 by the control device 50, the raw water is passed through the raw water supply line 21, and the raw water is supplied from the inflow port 11A into the filling tower 10. The silica concentration of the raw water is, for example, 100 mg / l.

In this raw water supply step, the pH of the raw water is adjusted so that the pH of the treated water flowing out from the filling tower 10 is 6 or more. More specifically, the pH detection unit 34 monitors the pH of the treated water, and the pH adjusting pump 32 is operated so that the pH of the treated water is 6 or more to determine the amount of the pH adjusting agent supplied to the raw water. adjust. In the present embodiment, the amount of the pH adjuster supplied to the raw water is adjusted so that the pH of the raw water is 9 or more.

Next, by passing raw water through the filling tower 10, silica contained in the raw water is removed by the silica removing particles 60 (silica removing step). More specifically, raw water flows into the filling tower 10 from the inflow port 11A, the raw water is passed from the lower part to the upper part in the filling tower 10, and flows out from the outflow port 11B to the outside of the filling tower 10. .. As shown in FIG. 1, the raw water alternately passes through the non-filled portion 13 in which the silica removing particles 60 are not filled and the filling portion 12 filled with the silica removing particles 60 in the filling tower 10.

As described above, the silica-removed particles 60 are limonite particles containing 30% by mass or more of FeOOH and 10% by mass or more of SiO ₂ . Therefore, when the raw water passes through the silica-removing particles 60 (filling portion 12), the iron component (ferrous hydroxide) contained in the silica-removing particles 60 chemically reacts with the silica in the raw water, and the reaction product (reactant). A silica-iron reactant) precipitates on the surface of the silica-removed particles 60. As a result, silica contained in the raw water is gradually removed in the process of the raw water passing through each filling portion 12, and the silica concentration in the raw water is reduced. After that, the treated water from which the silica has been removed is taken out from the filling tower 10 via the outlet 11B (take-out step).

In the silica removing step, the water flow performance of the filling tower 10 is preferably set to 1 or more and 1000 or less, more preferably 1 or more and 800 or less, and further set to 1 or more and 500 or less. preferable.

"Water flow performance of filling tower" (m / d / kPa) is as shown in the following formula (1) when the difference between the pressure of raw water and the pressure of treated water is the operating pressure (kPa). The flow rate (m ³ / h) can be defined as a value obtained by dividing the flow rate (m ³ / h) by the bottom area (m ² ) and the operating pressure (kPa) of the filling tower 10 and multiplying by 24 (hours). In addition, "d" in "m / d / kPa" which is a unit of water flow performance of a filling tower means one day (24 hours).
Water flow performance (m / d / kPa) = Flow rate of treated water (m ³ / hr) ÷ Bottom area of filling tower (m ² ) ÷ Operating pressure (kPa) x 24 (hours) ... (1)
The water flow performance defined by the above formula (1) is a parameter indicating the water flow capacity of the filling tower 10. It is preferable that the water flow performance is high because the liquid feeding pump can be made smaller and a large amount of treated water can be secured. When the water flow performance is low, the pressure required to obtain the desired amount of treated water increases, and the capacity of the liquid feed pump required also increases. In particular, when the water flow performance is less than 1 m / d / kPa, only a small amount of treated water can be secured, which is not preferable as a specification for industrial use in which a large amount of treated water needs to be obtained.

In the silica removal step, the residence time of the raw water in the filling tower 10 is preferably set to 1 second or more, more preferably 1 second or more and 3600 seconds or less, and further set to 1 second or more and 1500 seconds or less. preferable. By securing the residence time of the raw water in the filling tower 10 for 1 second or more, silica in the raw water can be efficiently removed.

The silica removal step, it is preferable to set the space velocity of the raw water in the packed column 10 to ^{1h -1} or 3500H ^-1 or less, it is more preferable to set the following ^{1h -1} or 3000h ^{-1, 1h -1} or more 2000h It is more preferable to set it to ^-1 or less. When the space velocity is larger than 3500 h- ^1, it becomes difficult to secure a sufficient residence time of the raw water in the filling tower 10, and the silica removal efficiency is lowered. On the other hand, when the space velocity is smaller than 1h- ¹ , the device becomes large and it becomes difficult to secure a sufficient amount of treated water, so that it is not suitable for industrial use. Therefore, the spatial velocity of raw water is preferably set within the above range.

Further, the method for treating silica-containing water further includes an exchange step of exchanging the silica-removing particles 60 in the filling column 10. That is, after passing raw water through the filling tower 10 for a certain period of time, the silica removing particles 60 in which the iron component has been consumed are taken out from the filling tower 10, and new silica removing particles 60 are filled in the filling tower 10. Specifically, the filling portion 12 in use is removed from the tower main body 11, and the filling portion 12 filled with the new silica removing particles 60 is attached to the tower main body 11. As described above, the method for treating silica-containing water according to the present embodiment is carried out.

(Embodiment 2)
Next, Embodiment 2 of the present invention will be described with reference to FIG. The second embodiment is basically the same as the first embodiment, but the filling tower 10 is in a downward flow system and the silica removing particles 60 are in a fluidized state (fluidized bed) in the filling tower 10. Is different from the first embodiment. Hereinafter, only the differences from the first embodiment will be described.

[Silica-containing water treatment device]
As shown in FIG. 4, in the second embodiment, the raw water inflow port 11A is provided in the upper part of the filling tower 10, and the treated water outlet 11B is provided in the lower part of the filling tower 10. Then, the downstream end of the raw water supply line 21 is connected to the inflow port 11A at the upper part of the filling tower 10, and the upstream end of the take-out means 40 is connected to the outflow port 11B at the lower part of the filling tower 10. Therefore, the filling tower 10 in the second embodiment has a downward flow system in which raw water is passed from the upper part to the lower part. In this case, in order to prevent the silica-removed particles 60 from flowing out from the inflow port 11A and the outflow port 11B, it is preferable to install an outflow prevention member such as a strainer in the vicinity of the inflow port 11A and the outflow port 11B.

Further, as shown in FIG. 4, the silica-removing particles 60 are not filled in the filling portion 12 (cartridge) as in the first embodiment, but are directly filled in the tower main body 11 and inside the filling tower 10. It is in a fluid state. That is, in the second embodiment, the silica removing particles 60 are not confined in a specific region (inside the cartridge) in the filling tower 10. Therefore, the apparatus configuration can be simpler than the case where the filling portion 12 is provided as in the first embodiment.

[Method for treating silica-containing water]
In the second embodiment, as in the first embodiment, after the raw water containing silica is supplied to the filling tower 10 by the raw water supply means 20, the silica is removed by passing the raw water from the upper part to the lower part of the filling tower 10. The steps are taken. At this time, the iron component contained in the silica-removed particles 60 reacts with the silica in the raw water, and the reaction product is precipitated on the surface of the silica-removed particles 60 to obtain the silica in the raw water as in the first embodiment. Can be removed. Then, the treated water having a reduced silica concentration is taken out from the outlet 11B at the lower part of the filling tower 10.

(Other embodiments)
In the first and second embodiments, the reverse osmosis membrane device may be arranged after the filling tower 10. As a result, the treated water whose silica concentration is sufficiently reduced by the treatment devices 1 and 2 can be sent to the reverse osmosis membrane device, so that even if the recovery rate of the treated water in the reverse osmosis membrane device is increased, the reverse is reversed. The generation of silica scale in the osmosis membrane can be suppressed.

(Example 1)
<Raw water>
As raw water containing silica, RO concentrated water was diluted with pure water to adjust the silica (SiO ₂ ) concentration to 100 mg / l.

<Processing device>
The silica-containing water treatment apparatus 1 shown in FIG. 1 was prepared. The tower main body 11 has a raw water inlet 11A and a treated water outlet 11B, and is prepared in a cylindrical shape having an inner diameter of 200 mm and a height of 1000 mm. Further, the filling portion 12 (cartridge) having the plastic frame portions 14 and the lattice portions 15 and 16 shown in FIG. 2 and the upper water passage cloth 17 and the lower water passage cloth 18 made of the non-woven fabric shown in FIG. 3 is 4 The filling portion 12 was filled with limonite particles as silica-removing particles 60. Then, each filling portion 12 was installed in the tower main body 11 as shown in FIG.

As for the limonite particles used at this time, the main elements were identified by fluorescent X-rays (ZSX Primus μ manufactured by Rigaku Co., Ltd.), and as a result of conversion, the FeOOH content was 35% by mass, and the SiO ₂ content was It was 15% by mass, and Al, Ca, Mg, Na, K, Mn, S and the like were detected as impurities in addition to organic substances (C, H, N, O).

Since the volume of the filling tower 10 was 0.0314 m ³ and the occupied volume of the silica-removed particles 60 was 0.0025 m ³ , the filling rate was 8%.

<Silica removal treatment>
Raw water is supplied to the filling tower 10 from the inflow port 11A via the raw water supply line 21, and the raw water is passed from the lower part to the upper part of the filling tower 10 (upward flow method) and then treated from the outflow port 11B. The water was taken out. This operation was performed for about 10 minutes. The pH of the raw water was stable at 9, and the pH of the treated water was stable at 7. Then, the silica concentration of the treated water was measured, and the silica removal rate (%) was calculated based on the silica concentration of the raw water and the silica concentration of the treated water.

During the passage of raw water, the pH of the treated water was monitored by the pH detection unit 34, and the pH adjusting pump 32 was operated so that the pH of the treated water was 6 to 12, and NaOH was added to the raw water.

The flow rates of the raw water and the treated water were 60 m ³ / h, the operating pressure was 100 kPa, and the bottom area of the filling tower 10 was 0.0314 m ² . The water flow performance of the filling tower 10 calculated by these parameters was 459 m / d / kPa. The space velocity of the raw water in the filling tower 10 was 1911h- ¹ , and the residence time was 2 seconds.

(Example 2)
The treatment was carried out under the same conditions as in Example 1 above, except that the raw water was passed from the upper part to the lower part of the filling tower 10 (downward flow method).

(Example 3)
<Processing device>
The silica-containing water treatment apparatus 2 shown in FIG. 4 was prepared. The filling tower 10 has a raw water inlet 11A and a treated water outlet 11B, and is prepared in a cylindrical shape having an inner diameter of 200 mm and a height of 1000 mm. The filling tower 10 was filled with limonite particles as a fluidized bed. The inflow port 11A and the outflow port 11B were filled with a cotton plug and sea sand to prevent the outflow of limonite particles. Since the volume of the filling tower 10 was 0.0314 m ³ and the occupied volume of the limonite particles was 0.0310 m ³ , the filling rate was 99%.

<Silica removal treatment>
Raw water is supplied to the filling tower 10 from the inflow port 11A via the raw water supply line 21, and the raw water is passed from the upper part to the lower part of the filling tower 10 (downward flow method), and then treated from the outflow port 11B. The water was taken out.

The flow rates of the raw water and the treated water were 1 m ³ / h, the operating pressure was 100 kPa, and the bottom area of the filling tower 10 was 0.0314 m ² . The water flow performance of the filling tower 10 calculated by these parameters was 8 m / d / kPa. The space velocity of the filling tower 10 was 32 h- ¹ , and the residence time was 113 seconds. Other conditions were the same as in Example 1 above.

(Example 4)
<Processing device>
The silica-containing water treatment apparatus 2 shown in FIG. 4 was prepared. The filling tower 10 has a raw water inlet 11A and a treated water outlet 11B, and is prepared in a cylindrical shape having an inner diameter of 360 mm and a height of 3000 mm. The filling tower 10 was filled with limonite particles as a fluidized bed. The inflow port 11A and the outflow port 11B were filled with a cotton plug and sea sand to prevent the outflow of limonite particles. Since the volume of the filling tower 10 was 0.3052 m ³ and the occupied volume of the limonite particles was 0.301 m ³ , the filling rate was 99%.

<Silica removal treatment>
Raw water is supplied to the filling tower 10 from the inflow port 11A via the raw water supply line 21, and the raw water is passed from the upper part to the lower part of the filling tower 10 (downward flow method), and then treated from the outflow port 11B. The water was taken out.

The flow rates of the raw water and the treated water were 0.8 m ³ / h, the operating pressure was 100 kPa, and the bottom area of the filling tower 10 was 0.1017 m ² . The water flow performance of the filling tower 10 calculated by these parameters was 2 m / d / kPa. The space velocity of the filling tower 10 was 3h- ¹ , and the residence time was 1373 seconds. Other conditions were the same as in Example 1 above.

(Example 5)
The pH adjusting pump 32 was operated so that the pH of the treated water was 11 to 13, and NaOH was added to the raw water. The pH of the raw water was stable at 13, and the pH of the treated water was stable at 12. Other conditions were the same as in Example 1 above.

(Comparative Example 1)
The treatment was carried out under the same conditions as in Example 1 above, except that the pH of the treated water was not adjusted and NaOH was not added to the raw water. The pH of the raw water was stable at 7, and the pH of the treated water was stable at 4.

(Comparative Example 2)
<Processing device>
The silica-containing water treatment apparatus 2 shown in FIG. 4 was prepared in the same manner as in Example 3 except that the limonite particles were changed to filtered sand. The filtered sand is a soil containing 80% by weight or more of SiO ₂ and less than 1% by weight of iron.

<Silica removal treatment>
Raw water is supplied to the filling tower 10 from the inflow port 11A via the raw water supply line 21, and the raw water is passed from the upper part to the lower part of the filling tower 10 (downward flow method), and then treated from the outflow port 11B. The water was taken out.

The flow rates of the raw water and the treated water were 20 m ³ / h, the operating pressure was 100 kPa, and the bottom area of the filling tower 10 was 0.0314 m ² . The water flow performance of the filling tower 10 calculated by these parameters was 153 m / d / kPa. The space velocity of the filling tower 10 was 637 h- ¹ , and the residence time was 6 seconds. Other conditions were the same as in Example 3 above.

(Comparative Example 3)
As raw water containing silica, RO concentrated water was diluted with pure water to adjust the silica (SiO ₂ ) concentration to 100 mg / l. Iron (III) chloride was added to the raw water so that the iron concentration was 300 mg / l. Then, the pH was adjusted to 8 and the mixture was stirred for 10 minutes. Then, the supernatant was taken out as treated water, and its silica concentration was measured.

(Discussion)

The conditions of Examples 1 to 5 and Comparative Examples 1 to 3 and the results of the silica removal rate (%) are as shown in Table 1 above.

In Comparative Example 2 using filtered sand, the silica removal rate was 0%, whereas in Examples 1 to 5 using limonite particles, a silica removal rate of 65 to 70% could be obtained. This value was also higher than 52% in the coagulation precipitation method of Comparative Example 3. From this result, it was found that a high silica removal rate can be achieved by using limonite particles as silica removal particles.

In Comparative Example 1 in which the pH of the treated water was 4, the silica removal rate was 0%, whereas in Examples 1 to 5 in which the pH of the treated water was 6 or more, the silica removal rate as described above was obtained. Was done. From this result, it was found that when the treated water is acidic, the silica removal treatment cannot be performed in the filling tower, and it is necessary to adjust the pH of the raw water so that the pH of the treated water is 6 or more. ..

Further, in the case of the fluidized beds of Examples 3 and 4, a better silica removal rate was obtained than in the case of the fixed beds of Examples 1, 2 and 5. Further, when the pH of the treated water was 12, as in Example 5, the silica removal rate was improved as compared with the case where the pH of the treated water in Examples 1 and 2 was 7.

It should be understood that the embodiments and examples disclosed this time are exemplary in all respects and are not restrictive. The scope of the present invention is shown by the scope of claims rather than the above description, and it is intended to include all modifications within the meaning and scope equivalent to the scope of claims.

1, 2, Silica-containing water treatment device 10 Filling tower 10A Treatment space 11 Tower body 12 Filling part 20 Raw water supply means 30 pH adjusting means 40 Extraction means 60 Silica removal particles 91 Raw water

Claims (8)

A raw water supply step that supplies silica-containing raw water to the filling tower,
A silica removing step of removing silica contained in the raw water by the silica removing particles by passing the raw water through the filling tower filled with silica removing particles.
A take-out step of taking out treated water from which silica has been removed from the filling tower is provided.
In the raw water supply step, the pH of the raw water is adjusted so that the pH of the treated water is 6 or more.
A method for treating silica-containing water, wherein the silica-removing particles are limonite particles containing 30% by mass or more of FeOOH and 10% by mass or more of SiO ₂ . Further comprising a replacement step of replacing the silica-removing particles in the filling column
The first aspect of the exchange step is to attach / detach a filling portion filled with the silica removing particles to / from a tower body having a treatment space for removing silica from the raw water. The method for treating silica-containing water according to the above method. The difference between the pressure of the raw water and the pressure of the treated water is defined as the operating pressure (kPa), and the flow rate of the treated water (m ³ / h) is defined as the bottom area (m ² ) of the filling tower and the operating pressure (kPa). According to claim 1 or 2, when the value obtained by dividing by and multiplying by 24 hours is defined as the water flow performance of the filling tower, the water flow performance is set in the range of 1 or more and 1000 or less. The method for treating silica-containing water according to the above method. The method for treating silica-containing water according to any one of claims 1 to 3, wherein in the silica removing step, the residence time of the raw water in the filling tower is set to 1 second or more. The silica-containing water according to any one of claims 1 to 4, wherein in the silica removing step, the space velocity of the raw water in the filling tower is set to ¹ h ^-1 or more and 3500 h ^-1 or less. Processing method. Filling tower and
A raw water supply means for supplying raw water containing silica to the filling tower, and
The silica-removing particles filled in the filling tower and
A pH adjusting means for adjusting the pH of the raw water is provided.
The filling tower is configured to allow the raw water to pass through.
The pH adjusting means is configured to adjust the pH of the raw water so that the pH of the treated water is 6 or more.
A silica-containing water treatment apparatus, wherein the silica-removing particles are limonite particles containing 30% by mass or more of FeOOH and 10% by mass or more of SiO ₂ . The filling tower
A tower body having a treatment space for performing a treatment for removing silica from the raw water,
The silica-containing water according to claim 6, wherein the silica-containing water is filled with the silica-removing particles and is installed in the treatment space and has a filling portion configured to be detachable from the tower body. Processing equipment. The silica-containing water treatment apparatus according to claim 6, wherein the silica-removing particles are not confined in a specific region in the filling tower.

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