JPH0663536A - Device for removing organic matter dissolved in water - Google Patents

Abstract

PURPOSE:To stably remove volatile org. matter over a long period by substituting the org. matter for the external air when an aq. soln. contg. org. matter flows in the hollow part of a hollow-fiber membrane, sucking and discharging the org. gas leaving the membrane from an outlet port of an evacuating means. CONSTITUTION:A vessel 1 is provided with a suction port 2 and an exhaust port 3 on its side and the inlet 6 and outlet 7 for an aq. soln. contg. volatile matter on both ends. Many hollow-fiber membranes 4 are arranged in the vessel 1 at regular intervals, and both ends are supported and fixed with a potting agent 5. A partition wall 5 is formed by the potting agent 5 to isolate a space between the membranes from the inlet and outlet 6 and 7. When the device is used, a pressure reducing machine 8 such as a blower is connected to the exhaust port 3 and operated, the org. gas is substituted for the external air when an aq. soln. contg. org. matter flows in the hollow part of the membrane 4, and the org. gas leaving the membrane 4 is sucked and discharged.

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, and carcinogenic or mutagenic trihalomethanes produced by the reaction of organic substances with chlorine ( There is a problem that the concentration of organic substances in which three halogen substances are bound to carbon such as chloroform) increases and the trace amount is dissolved in tap water.

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 trace amounts of these organic halogen substances are present in industrial water for foods and chemicals.In the industry in this field, a technology for removing the trace amount of organic halogen substances dissolved in water is desired. 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) A large amount of gas is sent into the water and the volatile organic substances dissolved in the liquid phase are moved to the gas phase side from the gas partial pressure difference and expelled 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 water to block the transmission of light and uniformly apply 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. In addition, the biological treatment method (d) has the advantage that it is uniformly decomposed 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 devices using the tube (f) or 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.

[0008]

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.

[0009]

The gist of the present invention is (1)
A partition wall that separates a container, a hollow fiber membrane located in the container, an end portion of the hollow fiber membrane, and a space communicating with the hollow portion of the hollow fiber membrane and a space communicating with the outer surface of the hollow fiber membrane. Has and
Exhaust gas in a space formed by an inlet for flowing an aqueous solution containing a volatile dissolved organic substance into the hollow portion of the hollow fiber membrane, a water outlet, and an outer surface of the hollow fiber membrane and an inner wall surface of the container. An apparatus for removing dissolved organic matter in water, which is provided with an exhaust port and an intake port for taking in external air into the space, and (2) a container, a hollow fiber membrane positioned in the container, and an end portion of the hollow fiber membrane. A space having a partition wall that separates a space communicating with the hollow portion of the hollow fiber membrane and a space communicating with the outer surface of the hollow fiber membrane, the space including the outer surface of the hollow fiber membrane and the inner wall surface of the container Dissolved in water, which is provided with an inlet for flowing an aqueous solution containing volatile dissolved organic matter, an outlet for water, an outlet for exhausting gas in the hollow fiber membrane, and an inlet for sucking air into the hollow fiber membrane. It is in an organic matter removal device. Preferably, as the hollow fiber membrane, a composite hollow fiber membrane having a three-layer structure in which a homogeneous layer is sandwiched by porous layers from both sides thereof is used, and the gas on the porous layer side opposite to the porous layer in contact with the aqueous solution is hollow. This is an apparatus for removing dissolved organic matter in an aqueous solution by exchanging with air outside the container at a ventilation rate of 3 Nl / min or more per thread membrane area.

According to the present invention, among dissolved organic matters in water,
It is possible to efficiently remove volatile organic substances having a high gas phase concentration in the gas / liquid equilibrium. Further, among volatile organic substances, particularly highly polar organic halogen substances have high affinity with the polymer material used for the homogeneous layer of the composite hollow fiber membrane and can be efficiently removed.

As the hollow fiber membrane, a hydrophobic porous membrane having a pore size of 0.05 μm or less can be used, but if it is used for a long time, water vapor leaks, and as a result, water may leak from the porous membrane. There is a nature. Therefore, a multilayer composite hollow fiber membrane comprising a homogeneous membrane (A) having a thickness of 8 μm or less and a porous membrane (B) having a reinforcing function, wherein the homogeneous membrane (A) and the porous membrane (B) are alternately laminated. The multilayer composite hollow fiber membrane has a structure in which the layer in contact with the aqueous solution is a homogeneous membrane (A) or a porous membrane (B), and the layer in the side not in contact with the aqueous solution is a porous membrane (B). In addition, the chloroform permeation rate of the composite hollow fiber membrane was 1 × 10 ⁻³ (cm ³ (STP) / cm
It is preferably a hollow fiber membrane having a permeation performance of ² / sec / cmHg) or more. Chloroform transmission rate is 1 ×
10 ^-3 (cm ³ (STP) / cm ² / sec / cmH
If it is less than g), the permeation speed of permeation through the composite film of the organic substance dissolved in water is slow and the organic substance cannot be efficiently removed. As a material for forming the porous layer of such a composite film, a polyolefin such as polyethylene, polypropylene, poly-3-methylbutene-1, poly-4-methylpentene-1 or a vinyl fluoride such as vinylidene fluoride or polytetrafluoroethylene is used. Polymers such as polysulfone, polyetherketone, and polyetheretherketone can be used, but polyolefins, which are crystalline polymers capable of easily forming a porous structure, are preferable. The material used for the homogeneous layer of the composite film may be segmented polyurethane, silicone polymer, low density polyethylene, polyolefin such as poly-4-methylpentene-1, polyacrylamide, etc. Higher polymers are preferred.

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 (preferably 4 Nl / min) per hollow fiber membrane area. It is a necessary condition that the device be capable of exchanging 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 / m ² per hollow fiber membrane area, the difference in 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 a displacement of ³ Nl / min / m ² or more, a Roots-type vacuum pump having a large displacement under high vacuum can be used, but a decompressor with a large displacement can be used, but the device becomes larger. Not preferable.
By installing an intake port for taking in outside air when exhausting the gas in the container void, it is possible to exhaust under a low vacuum, and a small pressure reducer with a small torque can easily generate 3N.
It is possible to exhaust 1 / min / m ² or more. Also, 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 in, but the membrane resistance of the gas side surface of the composite hollow fiber membrane increases. In addition, since the hollow fibers are bundled and there is a risk that channeling of air may occur, the method of sucking the outside air is preferable.

FIG. 1 shows a preferred embodiment of the apparatus for removing dissolved organic matter in water according to the present invention. Reference numeral 1 is an intake port 2 for sucking outside air and a gas exhaust port 3 containing volatile organic substances and water vapor
A plurality of hollow fiber membranes 4 are arranged at predetermined intervals inside the container so that both ends thereof are supported and fixed by the potting agent 5. 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. By the potting agent,
A partition wall 5 for blocking 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 is formed. Further container 1
The hollow fiber membranes 4, 4, ...
An exhaust port 3 for exhausting a gas containing volatile organic substances and water vapor existing in a space formed therebetween is connected to a decompressor (intake blower) 8.

As a result of intensive studies using a device for removing dissolved organic matter in water, the present invention was surprisingly surrounded by a porous layer and a container on the side opposite to the side in contact with water of the composite hollow fiber membrane. The gas in the space is 3 Nl / m per area of the composite hollow fiber membrane.
It was further found that the removal efficiency is remarkably improved by controlling to exchange with the air outside the apparatus at a speed of in / m ² or more.

[0016]

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 organic gas is almost outside air on the outer surface (or hollow portion) of the hollow fiber membrane. Since the volatile organic substances dissolved in water become gas, they permeate the hollow fiber membrane and are exhausted to the outside. Therefore, the water flowing through the organic substance removing apparatus of the present invention does not enter the outside air and is not charged with 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.

Further, even if it is used for a long period of time, the removal performance of volatile organic substances such as organic halogen substances does not deteriorate as in the case of activated carbon adsorption, and water having a low concentration of volatile organic substances can be stably supplied.

[0018]

EXAMPLES The present invention will be described in more detail below with reference to examples.

Reference Example 1 A high-density polyethylene (Mitsui Petrochemical Co., Ltd. Hize) as a polymer material to be supplied to an inner layer and an outer layer of a hollow fiber manufacturing nozzle having three discharge ports arranged concentrically.
x2200J) is used as a polymer material for supplying the intermediate layer to the segmented polyurethane (Thermedics).
Inc. Tecoflex EG80A manufactured by Kogyo Co., Ltd. was used for spinning at a discharge temperature of 165 ° C. and a winding speed of 180 m / min. The obtained hollow undrawn yarn was annealed at 100 ° C. for 1 hour. Next, the annealed yarn is 80% at room temperature.
The composite hollow fiber membrane was obtained by stretching and then hot stretching in a heating furnace heated to 105 ° C. until the thermal stretch ratio reached 130%.

The obtained composite hollow fiber membrane has a three-layer structure of a porous layer, a homogeneous layer, and a porous layer in this order from the innermost layer as shown in FIG. 3. The inner diameter is 200 μm and each 25 μm from the innermost layer.
m, 1 μm, and 30 μm in a concentric pattern. As a result of observing the surface of the porous layer of the composite hollow fiber membrane 2 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 hollow fiber membrane 2 is
2 × 10 ^-3 (cm ³ (STP) / cm ² · sec · cm
Hg).

Reference Example 2 For a hollow fiber manufacturing nozzle having three discharge ports arranged concentrically, highly crystalline poly-4-methylpentene-1 (Mitsui Petrochemical ( Co., Ltd. TPX RT18) is a low crystalline poly-4-methylpentene-polymer material for supplying the intermediate layer.
1 (TPX MX001 manufactured by Mitsui Petrochemical Co., Ltd.), discharge temperature 265 ° C., winding speed 100 m / min
Spun in. The obtained hollow fiber membrane was annealed at 150 ° C. for 1 hour. Then, the annealed yarn is kept at room temperature for 30
% Stretched, and then hot stretched in a heating furnace heated to 150 ° C. until the heat stretch ratio reached 150% to obtain a composite hollow fiber membrane.

The obtained 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. 3, the inner diameter is 220 μm and each 25 μm from the innermost layer.
They were arranged in concentric circles having a thickness of m, 0.2 μm, and 25 μm. As a result of observing the porous layer surface of the composite hollow fiber membrane 2 with a scanning electron microscope, the width was 0.03 to 0.05 μm.
m, and a slit-shaped hole having a length of 0.05 to 0.1 μm was formed. The chloroform permeation rate of this hollow fiber membrane 2 is 1 × 10 ⁻³ (cm ³ (STP) / cm ² · sec · cm
Hg).

Reference Example 3 High density polyethylene (Mitsui Petrochemical Co., Ltd. Hize) 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.
x2200J) is used as a polymer material for supplying the intermediate layer to the segmented polyurethane (Thermedics).
Inc. Tecoflex EG80A manufactured by Kogyo Co., Ltd. was used for spinning at a discharge temperature of 165 ° C. and a winding speed of 180 m / min. The obtained hollow undrawn yarn was annealed at 100 ° C. for 1 hour. Next, the annealed yarn is 80% at room temperature.
The composite hollow fiber membrane was obtained by stretching and then hot stretching in a heating furnace heated to 105 ° C. until the thermal stretch ratio reached 130%.

The obtained 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. 3, 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, 20 μm, and 30 μm. As a result of observing the surface of the porous layer of the composite hollow fiber membrane 2 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 hollow fiber membrane 2 is
1 × 10 ^-5 (cm ³ (STP) / cm ² · sec · cm
Hg).

Reference Example 4 Poly 4 methyl pentene-1 (TPXRT1 manufactured by Mitsui Petrochemical Co., Ltd.) as a polymer material to be supplied to a hollow fiber membrane manufacturing nozzle having concentrically arranged discharge ports.
8), discharge temperature 265 ° C, winding speed 100m
Spinning was performed at a speed of / min. The obtained hollow fiber membrane was subjected to 1 at 150 ° C.
A time annealing process was performed. Next, the annealed yarn was stretched by 30% at room temperature, and subsequently, was thermally stretched in a heating furnace heated to 150 ° C. until the thermal stretch ratio reached 150%, to obtain a hollow fiber membrane.

The hollow fiber membrane obtained had an inner diameter of 220 μm.
Then, it was configured as a concentric circle having a thickness of 50 μm. As a result of observing the porous layer surface of the hollow fiber membrane with a scanning electron microscope, a width of 0.03 to 0.05 μm and a length of 0.05
Slit-shaped holes of ˜0.1 μm were formed. The chloroform permeation rate of this hollow fiber membrane was 2 × 10 ⁻³ (cm ³
(STP) / cm ² · sec · cmHg).

Example 1 Using the organic halon remover shown in FIG. 1, 0.5 liter / min of water containing 100 ppb of chloroform and 50 ppb of each of tetrachloroethylene, trichloroethylene, and 1,1,1-trichloroethylene as organic halogen substances.
Flow rate of / m ^{2 and} the apparatus using the hollow fiber membranes obtained in Reference Examples 1 to 4 was prepared using each hollow fiber, and the removal rate of each organic halon dissolved in water was calculated from the formula 1. evaluated.

Removal rate of organic halon (%) = [1- (Ci-
Co) / Ci] × 100 Ci; concentration of each organic halon contained in water entering the device Co; concentration of each organic halon contained in water exiting the device Table 1 shows the evaluation results using various hollow fiber membranes. Further, FIG. 4 shows the removal rate of the organic halogen substances at each ventilation rate in the system using the hollow fiber membranes of Reference Example 1 and Reference Example 2. However,
The water temperature at the time of this evaluation was 25 ° C.

[0029]

[Table 1]

[Brief description of drawings]

FIG. 1 is a schematic view showing an example of an apparatus for removing dissolved organic matter in water according to the present invention.

FIG. 2 is a schematic view showing an example of a device for removing dissolved organic matter in water according to the present invention.

FIG. 3 is a schematic diagram of a composite hollow fiber membrane having a three-layer structure of a porous layer, a homogeneous layer, and a porous layer.

FIG. 4 is a graph showing the organic halogen substance removal rate at each exhaust rate in the system using the hollow fiber membranes of Reference Examples 1 and 2.

[Explanation of symbols]

 1,11 Container 2,12 Intake port for sucking in outside air 3,13 Gas exhaust port 4,14 Hollow fiber membrane 5,15 Partition wall consisting of potting agent 6,16 Aqueous solution inlet 7,17 Aqueous solution outlet 8,18 Decompression Machine (intake blower)

Claims (5)

[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 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, and volatilizes in the hollow portion of the hollow fiber membrane. With an inlet for flowing an aqueous solution containing a soluble organic substance, an outlet for water, and an exhaust port 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 outside of the space An in-water dissolved organic matter removing device provided with an intake port for taking in air. 2. A container and a hollow fiber membrane located in the container,
A container that supports the end of the hollow fiber membrane and has a partition wall that separates a space communicating with the hollow portion of the hollow fiber membrane and a space communicating with the outer surface of the hollow fiber membrane, and the outer surface of the hollow fiber membrane and the container. Inlet for introducing an aqueous solution containing volatile dissolved organic matter into the space formed by the inner wall surface of the inner wall, outlet of water, outlet for exhausting gas in the hollow fiber membrane, and intake for sucking air into the hollow fiber membrane A device for removing dissolved organic matter in water, which is provided with a mouth. 3. The removing apparatus according to claim 1, wherein the volatile organic substance is an organic halogen substance. 4. A hollow fiber membrane is a composite hollow fiber membrane having a three-layer structure in which a homogeneous layer is sandwiched by porous layers from both sides thereof, and the gas on the porous layer side opposite to the porous layer in contact with the aqueous solution is hollow. The removal device according to claim 1 or 2, wherein air is exchanged with air outside the container at a ventilation rate of ³ Nl / min / m ² or more per yarn membrane area. 5. The chloroform permeation rate of the composite hollow fiber membrane is 1 × 10 ⁻³ (cm ³ (STP) / cm ² / sec / cm.
The removal device according to claim 4, which has a permeation performance of Hg) or higher.