JP3409863B2 - Removal device for dissolved organic matter in water - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to volatile organic substances dissolved in tap water or well water (particularly trihalomethanes such as chloroform, dichlorobromoform, chlorodibromoform and broloform, 1,1,1-trichloroethane, 1,2,1).
A volatile organic halogen substance such as dichloroethane, trichloroethylene, tetrachloroethylene, etc.) to provide safe drinking water or high-purity water.

[0002]

2. Description of the Related Art In recent years, there has been a tendency to use a large amount of chlorine for sterilization or purification as the concentration of organic substances in river water increases. There is a problem that the concentration of organic matter in which three halogen substances are bonded to carbon increases and that the organic matter is dissolved in tap water in a small amount.

Further, carcinogenic organic halogen substances such as 1,1,1-trichloroethane, 1,2-dichloroethane, trichloroethylene, and tetrachloroethylene permeate underground as industrial waste liquid and are contained in well water as a degreasing agent for dry cleaning and machinery. Things are also a problem at the same time.
In addition, it is extremely dangerous that even a trace amount of these organic halogen substances is present in industrial water for foods and chemicals, and a technology for removing a trace amount of organic halogen substances dissolved in water is highly desired in the industry in this field. ing.

Conventionally, as a method for removing volatile organic substances (in particular, organic halogen substances) dissolved in water, (a) an adsorption treatment method of adsorbing an organic substance on activated carbon or the like, (b) a semiconductor catalyst such as titanium oxide is used. Photodecomposition method of using light to decompose, (c) Metal powder such as iron serves as a reduction catalyst, for example, reduction treatment method of converting trichlorethylene into chlorine ion and chemically stable ethylene gas, (d) organisms such as activated sludge (E) Aeration method in which a large amount of gas is sent into water and volatile organic substances dissolved in the liquid phase are moved to the gas phase side from the gas partial pressure difference to expel it as gas, or by boiling the water A boiling method is known in which volatile organic substances dissolved in the water are expelled to the gas phase side.

On the other hand, as a method for efficiently removing oxygen dissolved in an aqueous solution, (f) a method of degassing by using a tube or a hollow fiber membrane is disclosed in JP-A-57-165007, JP-A-60-25514, and Kaihei 2-303587, Jitsuhei 2-48003, and (g) Degassing method and apparatus using composite membrane are Jaikaihei 3-7908 and JP-A-3-16.
It is proposed in each publication of 9303.

Of the above-mentioned methods, the adsorption treatment method (a) cannot adsorb more than the adsorption capacity of the adsorbent, and it is necessary to use a large amount or to reactivate it, which not only increases the cost. When a substance having a higher adsorption capacity than the target removal substance is present in the vicinity of the adsorbent, there is a risk that the target removal substance is released and may be adsorbed with a substance having a higher adsorption power.

In the photodecomposition method (b), a long reaction time is required for the sludge substance in the water to block the transmission of light and uniformly apply the light to the volatile organic substance to decompose it. In the reduction treatment method of (c), it is difficult to maintain the catalytic activity of the metal powder which is the catalyst, and there is also a risk that the metal powder which is the catalyst is mixed in water.

The biological treatment method (d) has the advantage that it decomposes uniformly and the substance after treatment becomes a chemically stable substance, but the treatment speed is slow and it is not practical. The only practical (a) aeration method that requires a large amount of gas to drive to the gas phase side is not only large in size, but also removes low-volatile organic substances such as tetrachloroethylene. Things are difficult.

On the other hand, in any of the degassing methods and apparatuses using the tube (f) or the hollow fiber membrane or the composite membrane (g), only the method of depressurizing the container or the hollow portion of the hollow fiber is described. However, it is difficult to remove an organic substance such as trihalomethane having a high volatility and a strong interaction with water in an aqueous solution, even if a vacuum pump such as an ordinary water-sealed vacuum pump is used in this method.

In the hollow fiber membrane module, the longer the length of the hollow fiber is, the longer the contact time of the membrane with water is effective, but the longer the fiber length is, the slack of the hollow fiber is liable to occur and defects occur during production. It has the drawbacks that it is likely to occur and that gas exchange through the membrane does not work effectively if the membrane resistance becomes large and the length exceeds a certain length. For these reasons, although the degassing method is smaller than the conventional technology, it does not reach the size that achieves the target removal performance and is popular for household use.

[0011]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a compact apparatus for removing organic halogenated substances dissolved in water efficiently, exhibiting stable removal performance for a long time, and removing dissolved organic substances in water. It is in.

[0012]

Means for Solving the Problems The gist of the present invention is as follows: 1) Support a container, a hollow fiber membrane located in the container, an end of the hollow fiber membrane, and communicate with the hollow portion of the hollow fiber membrane. An inlet for introducing an aqueous solution containing a volatile dissolved organic substance into the hollow portion of the hollow fiber membrane and a water outlet and a hollow having a partition wall separating the space and the space communicating with the outer surface of the hollow fiber membrane. An outer surface of the hollow fiber membrane and an inner wall surface of the container, which face the exhaust opening with a plurality of exhaust ports for exhausting gas in a space formed by the outer surface of the fiber membrane and the inner wall surface of the container, and the hollow fiber membrane. And a plurality of inlets for taking in external air are provided in a space constituted by and an outlet for flowing an aqueous solution of a water-dissolved organic substance removal module a and an aqueous solution of a module b having the same structure as the module a. And an exhaust port for exhausting the gas of the module a. It is an apparatus for removing dissolved organic matter in water, which is formed by connecting the intake ports of the module b for taking in air .

[0013]

The organic matter which can be removed among the dissolved organic matter in water is not particularly limited, but the volatile organic matter having a high gas phase concentration in the gas / liquid equilibrium can be efficiently removed. Further, among volatile organic substances, particularly highly polar organic halogen substances have high affinity with the polymer material used for the homogeneous layer and can be efficiently removed.

The hollow fiber membrane used in the module for removing dissolved organic matters in water may be a hydrophobic porous membrane having a pore size of 0.05 μm or less, but if it is used for a long time, water vapor will leak, resulting in the formation of water. A multilayer composite hollow fiber membrane comprising a homogeneous membrane (A) having a membrane thickness of 8 μm or less and a porous membrane (B) having a reinforcing function, since it has a risk of leaking from the porous membrane. A) and the porous membrane (B) are alternately laminated, and the layer of the multilayer composite hollow fiber membrane which is in contact with the aqueous solution is the homogeneous membrane (A) or the porous membrane (B), and the layer which is not in contact with the aqueous solution is The layer has a structure of a porous membrane (B), and the chloroform permeation rate of the composite hollow fiber membrane is 1 × 10 ⁻³ (cm ³ (STP) / cm ² / sec /
A hollow fiber membrane having a permeation performance of not less than cmHg) is preferable.

Chloroform transmission rate is 1 × 10 ^-3 (cm
^If it is less than ³ (STP) / cm ² / sec / cmHg), the permeation rate of permeation through the composite film of the organic substance dissolved in water is slow and the organic substance cannot be removed efficiently.

As a material for forming the porous layer of such a composite film, polyethylene, polypropylene, poly 3-
Polyolefins such as methylbutene-1, poly-4-methylpentene-1 and vinylidene fluoride, F-based polymers such as polytetrafluoroethylene, and polymers such as polysulfone, polyetheretherketone and polyetherketone can be used. Polyolefin, which is a crystalline polymer capable of easily forming a porosity, is preferable.

The materials used for the homogeneous layer of the composite membrane include segmented polyurethane, silicone polymer, low density polyethylene, and poly-4-methylpentene-
Polyolefins such as 1 and polyacrylamides are considered, but polymers having high affinity with organic halogen substances are preferable.

Such a composite membrane is disclosed, for example, in Japanese Patent Publication No. 3-44.
According to the method described in Japanese Patent No. 811 and the like, a polymer forming a homogeneous film A and a polymer forming a porous film B are alternately arranged by using a multi-cylindrical spinning nozzle, and melt-spun, and then the homogeneous film A. Porous Membrane B Without Making Porous
It is produced by a method of stretching under the condition that only the material is made porous.

Further, in the air intake device incorporated in the device, the gas in the porous layer on the side opposite to the side in contact with water of the composite hollow fiber membrane is 3 Nl / min / m ² or more per hollow fiber membrane area (preferably 4 Nl / min / It is a necessary condition that the device can exchange with the air outside the container at a ventilation rate of m ² or more). At an exhaust rate of less than 3 Nl / min per hollow fiber membrane area, the difference in the molar amount between the organic gas that permeates the hollow fiber membrane and the exhausted organic gas is small, and the organic gas removal performance is greatly reduced.

As a method of evacuating with an evacuating rate of 3 Nl / min or more, it is possible to use a vacuum pump with a large evacuating rate such as using a roots type vacuum pump having a large evacuating rate under high vacuum, but the apparatus becomes large in size. Not preferable. By installing an intake port that takes in outside air when exhausting the gas in the container void, it is possible to exhaust under a low vacuum, and it is easy to use a small pressure reducer with a small torque to generate 3 Nl.
The gas can be exhausted at a rate of / min / m ² or more.

As a method of exchanging air with the outside air, there is a method of pressurizing the outside air with a device such as a compressor instead of sucking the outside air and sending it. The method of sucking the outside air is preferable because of the large size and the danger that the hollow fibers are bundled to cause channeling of air.

Further, as a method of connecting an outlet for flowing an aqueous solution of a module to an inlet for flowing an aqueous solution of a module having the same structure as that of the module, another module end surface for connecting a single module with a tube, a hose or the like is used. There is a method of dividing the same with a cap or the like. At this time, the gas in the porous layer on the side of the hollow fiber membrane opposite to the side in contact with water must be connected so as to be ventilated at ³ Nl / min / m ² or more.

FIG. 1 shows one mode of a portion where a volatile organic substance or water vapor is evaporated in a device for removing dissolved organic matter in water according to the present invention. For example, a container 1 has a plurality of intake ports 2 for sucking outside air. And a plurality of hollow fibers that face the intake port 2 across the hollow fiber membrane 4.
It has a number of devolatilizing organic substances and water vapor ports 3, and a large number of hollow fiber membranes 4 are supported and fixed inside the container at predetermined intervals by partition walls 5 made of potting agent. It is installed in. Further, at both ends of the container 1, there are provided an inlet port 6 and an outlet port 7 for an aqueous solution containing a volatile organic substance, which communicate with the hollow fiber membrane 4 supported and fixed by the potting agent and the space formed between the inner walls of the container 1, respectively. It is provided.

The potting agent blocks the space formed between the large number of hollow fiber membranes 4, 4, ... 4 from the inlet 6 and outlet 7 of the aqueous solution containing the volatile organic substance. A partition wall is formed. Further, in a part of the periphery of the container 1, a devolatilizing organic substance and a water vapor port 3 which communicate with a space formed between the hollow fiber membranes 4, 4, ... ) 8 is connected.

FIG. 2 is a diagram showing a case where two modules having the same structure are connected by a tube, a hose and the like. For example, the container 1 has an intake port 2 for sucking the outside air and a devolatilizing organic substance and water vapor port 3, and the devolatilizing organic substance and vapor port 3 of the module a are connected to a module b by a connecting portion 9 such as a tube and a hose. Is connected to the intake port 2 that sucks in the outside air.

At this time, the outside air is the intake port 2 for sucking the outside air.
Through the outer wall of a large number of composite hollow fiber membranes 4 and the inner wall of the container 1, which are arranged at a predetermined interval in the container 1, and through the connecting portion 9 to the composite hollow fiber of the module b. It is introduced into the space formed by the membrane 4 and the inner wall of the container 1, and is further introduced into the devolatilizing organic substance and water vapor port 3 of the module b.

The devolatilizing organic substance and water vapor port 3 of the module B are connected to a pressure reducer (intake blower) 8.
Further, partition walls 5 made of a potting agent for supporting and fixing the composite hollow fiber membrane 4 are arranged at both ends of the container 1, and a space composed of an inner wall of the container 1 and an outer wall of the composite hollow fiber membrane 4 and an aqueous solution containing a volatile organic substance. It becomes the partition wall 5 of the space consisting of the inlet 6 or outlet 7 and the inner wall of the composite hollow fiber membrane 4.

The aqueous solution containing a volatile organic substance is introduced from the aqueous solution inlet 6, introduced into the space A composed of the inlet 6 and the partition wall 5, and led out into the space B passing through the inside of the composite hollow fiber membrane 4. The aqueous solution led to the space B is led to the space C of the module b via the connecting portion 10 such as a tube and a hose. The aqueous solution introduced into the space C is stored in the container 1 of the module b.
It passes through the inside of the composite hollow fiber membrane 4 arranged inside, passes through the space D, and is led out from the outlet 7.

FIG. 3 shows an example in which a cap provided with a partition for dividing the end face of one module is used. A container 1 having a suction port 2 for sucking outside air and a devolatilizing organic substance and a steam port 3, a decompressor (intake blower) connected to the devolatilizing organic substance and a steam port 3, and a predetermined space inside the container 1. The large number of composite hollow fiber membranes 4 arranged in this way and the partition wall 5 made of a potting agent that supports and fixes the composite hollow fiber membranes 4 have the same functions as in FIG.

An aqueous solution containing a volatile organic substance is introduced from an introduction port 6 into a space E isolated by a cap 11 having a partition wall 12 for dividing the module end face. The aqueous solution introduced into the space E passes through the inside of the composite hollow fiber membrane 4 existing on the module end surface divided by the partition wall 12, is guided to the space F isolated by the cap 11 having the partition wall and the module end surface, and further, It passes through the inside of the composite hollow fiber membrane 4 and reaches the isolated space G.

At this time, the composite hollow fiber membrane 4 existing on the module end surface of the space F becomes an aqueous solution outlet if one exists in the space E and becomes an aqueous solution inlet if one exists in the space G. The aqueous solution thus introduced into the space G is
Next, it is introduced into the space H, further reaches the space I, and is led out from the aqueous solution outlet 7.

The inventors of the present invention have made earnest studies using a device for removing dissolved organic matter in water, and as a result, even if the membrane area is the same, if the hollow fiber becomes long, the flow velocity becomes high, and therefore the membrane resistance is increased. It was discovered that the removal efficiency is improved due to the decrease. Moreover, since the module shape is shorter than the elongated shape, the device design becomes easier and the size can be reduced.

[0034]

According to the present invention, the aqueous solution containing a volatile organic substance flows through the hollow portion (or outer surface) of the hollow fiber membrane, and at the same time, the outer surface (or hollow portion) of the hollow fiber membrane converts the organic gas into almost ambient air. Since it is exchanged, the volatile organic matter dissolved in water becomes a gas, permeates the hollow fiber membrane, and is exhausted to the outside.

Therefore, the water flowing through the organic substance removing apparatus of the present invention is free from the invasion of outside air and the introduction of chemicals, so that bacteria and drugs in the air are not mixed. Further, unlike the aeration method, it is not necessary to send in a large amount of gas, which saves energy, and since a hollow fiber membrane is used, the contact area with the gas side of water is large and the apparatus can be downsized.

Furthermore, since the elongated module is shortened by dividing one module into several modules, it is possible to realize a module size of the water-dissolved volatile organic substance removal device which is widely used in households. became. Further, even if it is used for a long time, the removal performance of volatile organic substances such as organic halogen substances does not deteriorate unlike the adsorption of activated carbon, and water with a low concentration of volatile organic substances can be stably supplied.

[0037]

EXAMPLES The present invention will be specifically described below based on examples. Reference Example 1 A high-density polyethylene (Mitsui Petrochemical Co., Ltd., Hi, manufactured by Mitsui Petrochemical Co., Ltd.) was used as a polymer material for supplying the inner layer and the outer layer to a hollow fiber manufacturing nozzle having three discharge ports arranged concentrically.
segmented polyurethane (Thermedic)
s Ink. Manufactured by Tecoflex EG80A), discharge temperature 165 ° C., winding speed 180 m / min
Spun in. The obtained undrawn hollow fiber was annealed at 100 ° C. for 1 hour. Next, the annealed yarn was stretched by 80% at room temperature, and subsequently, was thermally stretched in a heating furnace heated to 105 ° C. until the thermal stretch ratio reached 130% to obtain a composite hollow fiber membrane.

The resulting composite hollow fiber membrane has a three-layer structure of a porous layer, a homogeneous layer and a porous layer in order from the innermost layer as shown in FIG. 4, the inner diameter is 200 μm and each 25 μm from the innermost layer.
They were arranged in concentric circles having a thickness of m, 1 μm, and 30 μm. As a result of observing the surface of the porous layer of the composite hollow fiber membrane 4 with a scanning electron microscope, the width was 0.06 to 0.09 μm.
m, and a slit-shaped hole having a length of 0.1 to 0.5 μm was formed. The chloroform permeation rate of this composite hollow fiber membrane 4 was 2 × 10 ⁻³ (cm ³ (STP) / cm ² · sec /
cmHg).

Example 1 Using the composite hollow fiber membrane obtained in Reference Example 1, modules having the module form shown in FIG. 1 and having the same membrane area but different composite hollow fiber membrane lengths were prepared and dissolved in water. An aqueous solution containing 100 ppb of chloroform as a volatile organic substance was caused to flow at a flow rate of 0.2 to 1.0 l / min / m ² , and the removal rate of chloroform dissolved in the aqueous solution was calculated by the following formula and evaluated.

Chloroform removal rate (%) = {1- (Ci
−Co) / Ci} × 100 Ci; Chloroform concentration contained in the aqueous solution entering the module Co; Chloroform concentration contained in the aqueous solution leaving the module

The evaluation results using various modules are shown in FIG.
The composite hollow fiber membrane obtained in Reference Example 1 was used to fabricate the module shown in FIG. 1 by changing the length of the composite hollow fiber membrane, and the removal rate at each flow rate was shown. As shown in Figure 5
In addition, even if the membrane area is the same, if the hollow fiber becomes long, it can be removed.
It can be seen that the efficiency is improved. The present invention is such
By dividing the module with improved removal efficiency into several
To shorten the long and slender module and spread it for household use
Achieved in all sizes.

[Brief description of drawings]

FIG. 1 is a conceptual diagram showing an example of a module used in the present invention.

FIG. 2 is a conceptual diagram showing an example of the present invention in which two modules are combined.

FIG. 3 is a conceptual diagram showing an example of the present invention in which a partition wall for dividing an end face of one module is provided.

FIG. 4 is a conceptual diagram of a composite porous membrane.

FIG. 5 is a graph showing the removal rate of chloroform with the flow rate of water containing chloroform.

[Explanation of symbols]

1 container 2 Intake port that sucks in outside air 3 Volatile organic matter and water vapor port 4 hollow fiber membranes 5 Septa made of potting agent 6 Aqueous solution inlet 7 Water solution outlet 8 Pressure reducer (intake blower) 9 Connection part of the above 2 and 3 10 Connection part of 6 and 7 above 11 Module end face split cap 12 module end face partition wall

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-3-80983 (JP, A) JP-A-50-20989 (JP, A) JP-A-52-56795 (JP, A) JP-A-3- 169303 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) C02F 1/20 B01D 19/00

Claims (4)

(57) [Claims] 1. A container and a hollow fiber membrane located in the container,
The hollow fiber membrane has a partition wall that supports the end portion of the hollow fiber membrane and separates a space communicating with the hollow portion of the hollow fiber membrane from a space communicating with the outer surface of the hollow fiber membrane. Inlet for flowing an aqueous solution containing a soluble organic substance, outlet for water, and a plurality of outlets for exhausting gas in a space formed by the outer surface of the hollow fiber membrane and the inner wall surface of the container, and the hollow fiber membrane Aqueous solution of water-dissolved organic matter removal module a, which is provided with a plurality of air intake ports for taking in external air into a space formed by the outer surface of the hollow fiber membrane and the inner wall surface of the container, facing the exhaust port across Is connected to an inlet for flowing an aqueous solution of the module b having the same structure as the module a, and an outlet for exhausting gas of the module a and an inlet for taking air of the module b are respectively connected. Dissolved organic matter removal device in water that is connected. 2. Organic matter dissolved in an aqueous solution is volatile.
The organic halogen substance according to claim 1, characterized in that
Dissolved organic matter removal device in water. 3. A homogeneous layer is sandwiched by porous layers from both sides thereof.
Contact with an aqueous solution using a complex hollow fiber membrane with a three-layer structure
The gas on the porous layer side opposite to the porous layer side is fed to the hollow fiber membrane area.
Or outside the container at a ventilation rate of ³ Nl / min / m ² or more.
Dissolved organic matter in the aqueous solution is removed by exchanging with air.
The device for removing dissolved organic matter in water according to claim 1, which is removed. 4. The organic halogen permeation rate of the composite hollow fiber membrane is
1 × 10 ^-3 (cm ³ (STP) / cm ² / sec / cm
It is a hollow fiber membrane with a permeation performance of Hg) or higher.
The dissolved organic matter removing device in water according to claim 3, which is used as a characteristic.