JPH10202272A - Membrane separation equipment and treatment of fluoride-containing water by the equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably and efficiently obtain a high-quality treated water by efficiently removing the fluoride in the treated water to a high degree, easily controlling the operation and reducing the deposition of scales. SOLUTION: A fluoride-contg. water is treated by this membrane separation equipment consisting of a reaction tank 1, a crystallization tank 2 and a membrane separator 3. The deposit on the surface of the separation membrane 18 of the separator 3 is stripped off by the compressed air sent from the permeated water side 18b of the membrane 18 to the influent water side 18a and/or a pressurized water and again suspended on the influent water side, and the suspended matter resulting from the deposit is used as seed crystal in the reaction process in the crystallization tank 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a membrane separation processing apparatus,
Regarding the method for treating fluoride-containing water by the apparatus, it is a membrane separation processing apparatus that is particularly easy to operate and manage, and has a small scale deposition, and can stably and efficiently obtain high-quality treated water. And a method for treating fluoride-containing water by the same apparatus.

[0002]

2. Description of the Related Art Conventional methods for treating fluoride-containing water are disclosed in, for example, (1) Japanese Patent Application Laid-Open No. Hei 3-118897 and (2) Japanese Patent Application Laid-Open No. Hei 4-371292. Regarding the former method of treating fluoride-containing water, with reference to FIG.
A conventional membrane separation processing device will be described.

In FIG. 1, fluoride-containing water, which is raw water, is introduced from a pipe into a reaction tank 31 provided with a stirrer, and a calcium compound and / or an aluminum compound are supplied to the reaction tank 31. The pH is adjusted to 6 to 8 by adding a pH adjuster. The suspension obtained in the reaction tank 31 is introduced into the circulation tank 32,
Since the (suspended solid matter in water) is concentrated and accumulated, it is discharged out of the system as necessary and sent to the subsequent membrane separation device 33. The concentrated water of the membrane separation process returned from the membrane separation device 33 via the pipe is added to each of the reaction tank 31 and the circulation tank 32 and stirred. The filtered water that has passed through the separation membrane of the membrane separation device 33 is introduced into a pH adjustment tank 34, introduced into an adsorption tower 35 and subjected to adsorption treatment, and the treated water is discharged out of the system. The latter is a method for treating fluoride-containing water that can prevent scale disturbance by using a calcium concentration reducing agent in the reaction step in the same apparatus as in FIG.

[0004] As described above, methods of treating fluoride-containing water by the slaked lime method and the sulfuric acid band method are known, and the pH is adjusted to 6 to 8 by adding a neutralizing agent such as a calcium compound or an aluminum compound to the fluoride-containing water. Then, the obtained suspension is subjected to membrane separation treatment through a circulation tank, and in the precipitation of fluoride ions in the circulation tank, the concentrated water in the concentration step in the subsequent membrane separation step is supplied to the circulation tank. This is a method in which the SS in the concentrated water is used as a seed crystal by introducing it back.

[0005]

In the conventional method for treating fluoride-containing water, the concentration of Ca in the neutralizing agent to be added is reduced,
And in the concentrated water returned to the circulation tank from the membrane separation step to prevent scale formation at the later stage of the treatment process
Acts as a seed crystal and is achieved by its crystallization effect. However, in order to effectively exert the crystallization effect,
It is necessary that the concentration of the seed crystal in the circulation tank is properly maintained. The seed crystal is supplied from the circulation tank 32 to the membrane separator by a pump, and the reaction tank 31 and the circulation tank 32 are supplied from the inflow water side of the membrane separator.
It is difficult to control the amount of suspended water and re-polluted water required as seed crystals, and when the concentration of fluoride to be removed is low, the seed crystals for adsorbing fluorine ions are difficult to control. There is a disadvantage that control becomes difficult.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and it is possible to remove fluoride in treated water with high efficiency and efficiency, to facilitate operation management, to reduce scale deposition, and to provide high-quality treated water. And a method for treating fluoride-containing water using the same.

[0007]

Means for Solving the Problems The present invention has been made to achieve the above object, and the invention of claim 1 has the following features.
In a method for treating fluoride-containing water by a membrane separation treatment device including a reaction tank, a crystallization tank, and a membrane separation device, the sediment adhering to the membrane surface of the separation membrane of the membrane separation device may be filtered through the permeation water of the separation membrane. Air sent from the side to the inflow side and / or
Alternatively, it is characterized in that it is separated by pressurized water and the inflow water side is suspended again, so that the suspended matter due to the deposit is used as a seed crystal in a reaction step in the crystallization tank. According to the present invention, the seed crystal is always crystallized with the reaction tank by forcibly introducing the pressurized air and / or pressure water sent from the permeate side to the inflow side of the separation membrane into the separation membrane of the membrane separation device. This is a method for treating fluoride-containing water that is introduced into a tank and promotes adsorption of precipitated fluorine ions.

[0008] The invention of claim 2 is a method for treating fluoride-containing water by a membrane separation treatment apparatus comprising a reaction tank, a crystallization tank, and a membrane separation apparatus. A reaction step of adding an aluminum compound to adjust the acidity of the treated water, and a crystallization step having a function of discharging excess sludge while promoting crystallization of the treated water from the reaction step; A membrane separation step of separating the liquid introduced from the step into a permeate and a suspension by the membrane separation device; and deposits attached to the separation membrane surface of the membrane separation device, the permeated water side of the separation membrane. And pressurized air and / or water are sent to the inflow water side to separate them, and a part of the deposits is removed from the reaction step and / or
Or a backwashing step for returning to the crystallization step, wherein the sediment separated from the film surface in the backwashing step is used to resuspend the inflow water side, and the suspended matter due to the sediment is crystallized. It is characterized by being a seed crystal in a tank. In the present invention, by performing the backwashing step of the separation membrane at a predetermined cycle of the membrane separation apparatus, the seed crystal is always introduced into the reaction tank and the crystallization tank, and the fluoride-containing water that promotes the adsorption of fluorine ions is promoted. Processing method.

[0009] In a third aspect of the present invention, there is provided a membrane separation treatment apparatus, wherein the fluoride-containing water contains a calcium compound and / or a calcium compound.
Or adding an aluminum compound, a reaction tank for adjusting the acidity of the treatment water, and a crystallization tank having a function of discharging the excess sludge, promoting crystallization of the treatment water from the reaction step,
A membrane separation device for separating the liquid introduced from the crystallization step into a permeate and a suspension by means of a separation membrane, and a deposit adhering to the membrane surface of the separation membrane flowing from the permeated water side of the separation membrane. Pressure air and / or pressure water generation means for sending pressure air and / or pressure water to the water side for stripping, and control for operating the pressure air and / or pressure water generation means to periodically backwash the separation membrane Means for operating the pressurized air and / or pressurized water generating means to backwash the membrane separation device and re-suspend sediment separated from the membrane surface on the inflow water side. A piping system for introducing the reaction tank and / or the crystallization tank to partially form a seed crystal is provided. According to the present invention, after a predetermined time has passed through the membrane separation of the membrane separation processing apparatus by the pressurized air and / or pressure water generating means, the deposits adhering to the separation membrane are peeled off and the seed crystal is placed in the reaction tank and the crystallization tank. This is a membrane separation treatment device that supplies as a gas and promotes adsorption of fluorine ions.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a membrane separation treatment apparatus of the present invention,
An embodiment of a method for treating fluoride-containing water by the same apparatus will be described with reference to the drawings. The membrane separation treatment apparatus of the present invention is a method for treating fluoride-containing water by a slaked lime method and a sulfate band method. FIG. 1 is a system diagram showing an embodiment of the present invention and a control system thereof, and FIG. 2 is a system diagram showing another embodiment of the present invention and a diagram showing a control system thereof.

Referring to FIG. 1, a membrane separation treatment apparatus includes a reaction tank 1 into which a fluoride-containing water as raw water is introduced through a pipe 11.
The suspension water is introduced from the reaction tank 1 through the pipe 15, and the SS concentrated and accumulated with time is discharged from the pipe 20 through the crystallization tank 2 and the crystallization tank 2 is introduced through the pipe 17 having a pump 16. And a pressure air generator 4 for supplying pressure air and / or pressure supplied from the permeate side to the inflow side of the separation membrane 18 of the separation membrane 18 of the membrane separation device 3 (however, A device for generating pressurized air and / or water), a control device 5 for controlling the operation cycle of the pressurized air generator 4 and the air pressure and / or water pressure, and resuspended water from the inflow water side of the membrane separation device 3. The system includes a pipe 14 for introducing at least a part of the concentrated water into the reaction tank 1 and a piping system including a pipe 20 for discharging the excess suspended water and the concentrated water to the outside.

Next, a detailed description will be given according to each component of the membrane separation processing apparatus. In the reaction tank 1, raw water is introduced from a pipe 11 and a calcium compound (for example, Ca (OH) ₂ )
And / or aluminum compounds (eg, Al
A predetermined amount of a neutralizing agent such as ₂ (SO ₄ ) ₃ )
The reaction tank 1 of the membrane separator 3 is provided with a stirrer 12, and at least a part of the concentrated water and the suspension water from the inflow water side of the membrane separator 3 is supplied to the reaction tank 1. The suspension water is sent to the crystallization tank 2. In the reaction tank 1, fluoride ions in the raw water are fixed by using one kind alone or adding two or more kinds of calcium compounds and aluminum compounds to adjust the pH to 6 to 8. That is, the fluoride ions are adsorbed and precipitated by the calcium compound or the aluminum compound. For example, fluoride by a calcium compound is Ca
It is deposited as F _2. Further, in this reaction step, since the concentrated water of the subsequent membrane separation device 3 is returned to the reaction tank 1 and mixed, the SS in the concentrated water is always mixed with the required amount of suspended water which acts as a seed crystal. Water and supplied CaF
₂ etc. are crystallized and scale formation is prevented.

In the crystallization tank 2, the suspension water obtained in the reaction tank 1 is introduced through a pipe 15, and in the crystallization tank 2, a membrane separation device 3 is provided.
(Ca (OH) _2,
Deposits such as Al (OH) ₃ ) are mixed again as suspended water, and crystallization of precipitated CaF ₂ is promoted. The residence time in the crystallization tank 2 is about 1 to 20 hours, and the sludge accumulated in the crystallization tank 2 is discharged from the pipe 20 at the lower part of the tank as needed.

In the membrane separator 3, a microfiltration (MF) membrane is used as the separation membrane, and a hollow fiber made of polypropylene and having a nominal pore size of 0.5 μm or less is used. 0.2 μm is used. The liquid in the crystallization tank 2 is supplied to the inflow water side of the membrane separation device 3 via the pump 16, and the permeate passed through the separation membrane 18 is discharged via a pipe 19. Deposits are attached to the separation film 18.

On the permeated water side of the membrane separator 3, pressure air is supplied from the pressurized air generator 4 at a predetermined cycle from the permeated water side 18b to the inflow water side 18a, and the deposits adhering to the separation membrane 18 are peeled off. Then, the inflow water side 18a is resuspended, a part thereof is discharged from the pipe 20, and the remaining suspension is
And supplied to the reaction tank 1. The pressurized air generator 4 is controlled by the control device 5 and operates at a predetermined cycle to supply the pressurized air to the permeated water side 18b of the membrane separation device 3. The pressurized air generator 4 may supply not only pressurized air but also pressurized water to the permeated water side 18b. Needless to say, as described in the embodiment of FIG. 2, a part of the concentrated water and the suspension may flow from the inflow water side 18a of the membrane separation device 3.

Next, an example based on the above embodiment will be described with reference to FIG. In Example 1, the reaction tank 1
Raw water is introduced into the vessel, and Ca (O)
H) ₂ and Al ₂ (SO ₄ ) ₃ were added at the following ratio, and the mixture was stirred by the stirrer 12 to adjust the pH to 7.
Further, the backwash wastewater from the membrane separation device 3 is returned to the reaction tank 1 and
The reaction was carried out with stirring. The suspension obtained by stirring was introduced into the crystallization tank 2 and further supplied to the membrane separation device 3 under the following conditions to perform a membrane separation treatment.

First, the reaction tank 1 contains Ca (OH)_TwoIs 10
0 mg / l added, Al_Two(SO _Four)_ThreeIs 5mg / l
Was added. In the crystallization tank 2, the liquid residence time is set to 10 hours.
Was. The membrane separation device 3 uses polypropylene as the separation membrane 18.
Precision separation with a hollow fiber diameter of 0.2 μm
A membrane was used.

Further, in the membrane separation treatment apparatus of the first embodiment, a part of the backwash wastewater from the membrane separation apparatus 3 is introduced into the reaction tank 1 as the first embodiment, and the backwash wastewater is not introduced into the reaction tank 1. This was designated as Comparative Example 1, and the results of the comparison are shown in Table 1. As is clear from Table 1, in Example 1, the fluorine removal rate was 80.0%.
%, Whereas in Comparative Example 1, only 41.9% was removed. In addition, the membrane permeated water recovery rate was as shown in Example 1.
Is 99.4%, whereas Comparative Example 1 has 90.1%.
% And below. As described above, the fluorine removal rate is improved, and the recovery rate of the permeated water is improved by the backwashing step of periodically removing the deposits adhering to the separation membrane 18.

[0019]

[Table 1]

Next, another embodiment of the membrane separation processing apparatus according to the present invention will be described with reference to FIG. In the embodiment of FIG. 1, in addition to the embodiment of FIG. 1, a pipe 24 having a control valve 25 is provided from the inflow water side 18a of the membrane separation device 3, and a control valve 26 is provided in the pipe 14. A control valve 27 is also provided on the pipe 20 branched from the pipe 14. From the pipe 14 provided with the control valve 26 to the reaction tank 1
The resuspension water and the concentrated water are supplied to the
The re-suspension water and the concentrated water are supplied to the crystallization tank 2 from a pipe 24 provided with the pipe 5. Excess resuspended water and concentrated water are supplied through piping 2
Emitted from 0. These control valves 25 to 27 are controlled by the control device 5, and are connected to the separation membrane 18 of the membrane separation device 3.
The deposits adhering to are separated by the pressurized air or pressurized water or the pressurized air and pressurized water by the pressurized air generator (device for generating pressurized air and / or water) 4
It is supplied to the crystallization tank 2. Also, a control valve 26 is provided in the pipe 14.
, Which are periodically opened and closed. Control valve 25, 2
6 is operated in synchronization with the backwashing step.

The control valve 27 is controlled on the basis of a signal from the control device 5, and by opening the control valve 27, excess resuspended water or concentrated water can be discharged.
Can be adjusted. Of course, even if the control valves 25 to 27 are not provided, the permeated water is discharged by the balance between the pressures of the pump 16 and the pressure air generator 4.

Next, in the embodiment shown in FIG.
And Ca (OH) _TwoAnd Al_Two(S
O_Four)_ThreeAt the following ratio to adjust the pH to 7,
In addition, the concentrated water and backwash wastewater (suspended
Was returned to the reaction tank 1 and reacted by stirring. To the reaction
The obtained mixture was introduced into the crystallization tank 2, and
Was supplied to the membrane separation device 3. Ca (OH) in reaction tank 1_Two
Is 1500 mg / l, and Al_Two(SO_Four)
_ThreeWas added to 30 mg / l. Crystallization tank 2 when liquid stays
The interval was 12 hours. The membrane separation device 3 performs the same
It is a dense separation membrane, and polystyrene is used as the membrane material.
A hollow fiber having a nominal pore size of 0.2 μm was used. Filtration
External pressure type cross flow filtration is used for the method, and the backwashing time is
Filter for 20 minutes and perform backwash for 1 minute.
Was performed periodically.

A part of the backwash wastewater from the membrane separation device 3 is supplied to the reaction tank 1
Example 2 was introduced into the reactor 1, and Comparative Example 2 was not introduced into the reactor 1, and the comparison results are shown in Table 2. As is clear from Table 2, the fluorine removal rate in Example 2 was 81.3%, while Comparative Example 2 was 51.3%.
9.3% was removed. The membrane permeated water recovery was 99.2% in Example 2 and 94.5% in Comparative Example 2.
The fluorine removal rate is improved and the separation membrane 1
The function of the membrane separation device 3 is restored by the backwashing step of stripping off the deposits adhering to 8, and the recovery rate of the permeated water is improved.

[0024]

[Table 2]

In the present embodiment, the deposits deposited on the separation membrane 18 of the membrane separation device 3 are periodically removed and resuspended to form fluoride ion seed crystals. By adsorbing and depositing ions on an aluminum compound or the like, the recovery rate of permeated water is improved, and a large amount of seed crystals can be supplied. In addition, according to the concentration of the fluoride ions, the processing time of the backwashing process and the separation process can be periodically controlled by the control device.
The amount of seed crystals can be controlled according to the amount of fluoride ions in the reaction tank and the crystallization tank.

[0026]

As described above, according to the present invention, a fluoride ion is precipitated as CaF ₂ by adding a calcium compound to fluoride-containing water, or a fluoride ion is precipitated by adding an aluminum compound. Separation treatment device that adsorbs and precipitates on aluminum compounds and discharges it as sludge, and a method of treating fluoride-containing water, in which the separation membrane of the membrane separation device is periodically backwashed and adhered to the separation membrane Is removed and sent to a reaction tank or the like, where Ca is a seed crystal effective for precipitation of fluoride ions.
It is possible to keep deposits such as (OH) ₂ and Al (OH) ₃ at a high concentration, and S
Even when S is at a low concentration, the seed crystal has an effect of efficiently removing the fluoride in accordance with the concentration of the fluoride ion, and there is an advantage that the scale precipitation is small. In addition, there is an advantage that the controller can adjust the backwashing time of the membrane separation device to adjust according to the concentration of fluoride ions in the raw water.

[Brief description of the drawings]

FIG. 1 is a system diagram showing an embodiment of a membrane separation processing apparatus according to the present invention, and a diagram showing a control system thereof.

FIG. 2 is a system diagram showing an embodiment of a membrane separation processing apparatus according to the present invention, and a diagram showing a control system thereof.

FIG. 3 is a system diagram illustrating an example of a conventional membrane separation processing apparatus, and a diagram illustrating a control system thereof.

[Description of Signs] 1 Reaction tank 2 Crystallization tank 3 Membrane separator 4 Pressure air generator 5 Controller 16 Pump 18 Separation membrane 18a Inflow water side 18b Permeate water side

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI B01D 61/16 B01D 61/16 65/02 65/02 520 520 C02F 1/44 C02F 1/44 E 9/00 502 9/00 502G 502Z 503 503G 504 504B 504E (72) Inventor Haruto Yokota 1-2-1 Marunouchi, Chiyoda-ku, Tokyo Nihon Kokan Co., Ltd.

Claims (3)

[Claims] 1. A method for treating fluoride-containing water using a membrane separation treatment device comprising a reaction tank, a crystallization tank, and a membrane separation device, wherein the deposit attached to the membrane surface of the separation membrane of the membrane separation device is
The separation membrane is separated by pressurized air and / or pressure water sent from the permeated water side to the inflow water side, and the inflow water side is suspended again to suspend suspended matter due to the sediment in the crystallization tank. A method for treating fluoride-containing water, comprising using a seed crystal in the reaction step. 2. A method for treating fluoride-containing water by a membrane separation treatment device comprising a reaction tank, a crystallization tank, and a membrane separation device, comprising: adding a calcium compound and / or an aluminum compound to the fluoride-containing water; A reaction step of adjusting the acidity of the treated water, and promoting crystallization of the treated water from the reaction step,
A crystallization step having a function of discharging excess sludge; a membrane separation step of separating a liquid introduced from the crystallization step into a permeate and a suspension by the membrane separation device; The deposit adhering to the separation membrane surface is peeled off by sending pressurized air and / or pressure water from the permeate side to the inflow water side of the separation membrane, and a part of the deposit is subjected to the reaction step and / or the crystallization step. A backwashing step, wherein the sediment separated from the film surface in the backwashing step is used to re-suspend the inflow water side, and a suspended substance due to the deposit is seeded in the crystallization tank. A method for treating fluoride-containing water. 3. A membrane separation treatment apparatus, comprising: a reaction tank for adjusting a degree of acidity by adding a calcium compound and / or an aluminum compound to fluoride-containing water; A crystallization tank having a function of discharging sludge, a membrane separation device that separates a liquid introduced from the crystallization step into a permeate and a suspension using a separation membrane, and a deposition attached to the membrane surface of the separation membrane. Pressure air and / or pressure water generating means for sending pressure air and / or pressure water from the permeated water side to the inflow water side of the separation membrane to peel off the substance; and activating the pressure air and / or pressure water generating means. Control means for periodically backwashing the separation membrane, and actuating the pressurized air and / or pressure water generating means to backwash the membrane separation apparatus and flow the sediment separated from the membrane surface. water A membrane system for introducing into the reaction tank and / or the crystallization tank in order to make at least a part of the suspended water resuspended on the side as seed crystals.