JP3540804B2 - Removal system for dissolved organic matter in water - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to volatile organic substances dissolved in tap water or well water (particularly, trihalomethane such as chloroform, dichlorobromoform, chlorodibromoform, and broloform, 1,1,1-trichloroethane, 1,2-dichloroethane, trichloroethylene, tetrachloroethylene, and the like). A volatile organic halogen substance) and provides a safe drinking water or a highly pure water.
[0002]
[Prior art]
In recent years, as the concentration of organic substances in river water has increased, there has been a tendency to use a large amount of chlorine for sterilization or purification, and carcinogenic or mutagenic trihalomethanes (carbons such as chloroform and halogen substances formed by the reaction of organic substances with chlorine). However, there is a problem that the concentration of the organic substance (three of which are bonded to each other) is increased and dissolved in tap water in a trace amount.
[0003]
In addition, carcinogenic organic halogen substances such as 1,1,1-trichloroethane, 1,2-dichloroethane, trichloroethylene, tetrachloroethylene, etc. penetrate underground as factory wastewater and are contained in well water as dry cleaning and degreasing agents for machinery. At the same time it is a problem. In addition, it is extremely dangerous that even small amounts of these organic halogen substances are present in industrial water for food and medicine, and there is a long-awaited need in the industry in this field to remove trace organic halogen substances dissolved in water. Have been.
[0004]
Conventionally, methods for removing volatile organic substances (especially organic halogen substances) dissolved in water include (a) an adsorption treatment method for adsorbing organic substances on activated carbon or the like, and (b) a semiconductor catalyst such as titanium oxide. Photodecomposition method that decomposes by light, (c) Reduction treatment method in which metal powder such as iron serves as a reduction catalyst to convert, for example, trichlorethylene to chlorine ion and chemically stable ethylene gas, (d) Decomposition by living organisms such as activated sludge (E) An 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 by a gas partial pressure difference and expelled as gas, or dissolved in water by boiling. There is known a boiling method in which volatile organic substances are expelled to the gas phase.
[0005]
On the other hand, as a method for efficiently removing oxygen dissolved in an aqueous solution, (f) a method of deaeration using a tube or a hollow fiber membrane is disclosed in JP-A-57-165007, JP-A-60-25514, and JP-A-2-303587 and JP-A-2-48003, and (g) a deaeration method and apparatus using a composite membrane are proposed in JP-A-3-7908 and JP-A-3-169303. .
[0006]
[Problems to be solved by the invention]
The method of treating organic substances (especially organic halogen substances) dissolved in water by adsorption cannot be adsorbed with a capacity higher than the adsorption equilibrium of the adsorbent, and requires the use of a large amount or the need for frequent reactivation. Not only will the cost increase, but if a substance with higher adsorption capacity than the target removal substance is present in the vicinity of the adsorbent, the target removal substance will be released and may be adsorbed with a substance with higher adsorption power. Sex is also considered.
[0007]
An object of the present invention is to provide a device after the adsorbent for removing when the adsorbent reaches the adsorption equilibrium and cannot remove the target substance to be removed or when it is replaced by a substance having a higher adsorption capacity and released. An object of the present invention is to provide a compact system for removing dissolved organic matter in water, which efficiently removes organic halogen substances dissolved in water, exhibits stable removal performance over a long period of time, and is compact.
[0008]
[Means for Solving the Problems]
The gist of the present invention is as follows: 1) a container, a composite hollow fiber membrane located in the container, a composite hollow fiber membrane, and a water purifier comprising an adsorbent for chlorine and high molecular organic substances or the adsorbent and a porous hollow fiber membrane. A partition wall supporting an end of the fiber membrane and isolating a space communicating with the hollow portion of the composite hollow fiber membrane from a space communicating with the outer surface of the composite hollow fiber membrane; An inlet and an outlet for flowing an aqueous solution containing a volatile organic substance into the hollow portion; and (2) an exhaust port for exhausting gas in a space formed by the outer surface of the composite hollow fiber membrane and the inner wall surface of the container. An apparatus for removing dissolved organic matter in water, which is provided with an intake port for taking in external air, is provided at a stage subsequent to the water purifier , and the composite hollow fiber membrane has a homogeneous membrane (A) and a porous membrane having a reinforcing function ( A multilayer composite hollow fiber membrane comprising B) and a homogeneous membrane (A) and a porous membrane (B) The layers of the multilayer composite hollow fiber membrane that are alternately laminated have a structure in which a layer in contact with the aqueous solution and a layer that is not in contact with the aqueous solution are both porous membranes (B). Removal of dissolved organic matter in water provided with an intake device for exchanging gas in the porous layer (B) on the side opposite to the side in contact with air outside the container at a ventilation rate of ³ Nl / min / m ² or more per hollow fiber membrane area System [0009]
And 2) an adsorbent for chlorine and high molecular organic substances or a water purifier comprising the adsorbent and a porous hollow fiber membrane, a container, a composite hollow fiber membrane located in the container, and an end of the composite hollow fiber membrane. And a partition separating the space communicating with the hollow portion of the composite hollow fiber membrane and the space communicating with the outer surface of the composite hollow fiber membrane, and (1) the outer surface of the composite hollow fiber membrane and the container. Inlet and outlet for flowing an aqueous solution containing volatile dissolved organic matter into the space defined by the inner wall surface, and (2) an exhaust port for exhausting gas into the hollow part of the composite hollow fiber membrane and taking in external air An underwater dissolved organic matter removing device provided with an air inlet is provided at a stage subsequent to the water purifier , and the composite hollow fiber membrane is a multilayer comprising a homogeneous membrane (A) and a porous membrane (B) having a reinforcing function. A composite hollow fiber membrane, wherein a homogeneous membrane (A) and a porous membrane (B) are alternately stacked. The layer of the multilayer composite hollow fiber membrane that is in contact with the aqueous solution and the layer that is not in contact with the aqueous solution are both porous membranes (B). The system for removing dissolved organic matter in water is provided with an intake device for exchanging the gas of the porous layer (B) on the opposite side with air outside the container at a ventilation rate of ³ Nl / min / m ² or more per hollow fiber membrane area. .
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 is a conceptual diagram showing a preferred example of the system for removing dissolved organic matter in water according to the present invention. The aqueous solution containing volatile organic matter is introduced into the removal system through the water inlet 2 and supplied to the water purifier A using the adsorbent or the adsorbent and the porous membrane from the water inlet 4 of the water purifier A. From the water outlet 5 and is sent to the underwater dissolved organic matter removing device B. The water that has passed through the water purifier A is supplied to the removal module C from the water inlet 6 of the removal module C.
[0011]
The water that has passed through the removal module C is led from the water outlet 7 of the removal module C to the water outlet 3 of the removal system, and is supplied to a drinking port outside the removal system. In order to ventilate the gas present in the gap of the removal module C, the pressure inside the removal module C is reduced by a pressure reducer (intake blower) 10 and the outside air is sucked into the removal system through the outside air intake port 11 which sucks the outside air into the removal system. Thus, the outside air is supplied into the module C through the outside air intake port 8 of the removal module C.
[0012]
The gas containing the volatile organic gas existing in the gap formed between the outer wall of the composite hollow fiber membrane of the removal module C and the container 20 is exhausted from the exhaust port 9 of the removal module C by the decompressor 10, and the gas of the removal system is removed. Air is exhausted from the exhaust port 12 to the outside air.
[0013]
FIG. 2 shows an example of the water purifier A. The water purifier A is configured by arranging activated carbon 15 as an adsorbent and a porous hollow fiber membrane 16 in a container 13. The water is supplied from the water inlet 4 of the water purifier A, passes through the porous sintered mesh 14, passes through the activated carbon 15 and the porous hollow fiber membrane 16, and is discharged from the water outlet 5 of the water purifier A.
[0014]
An example of the removal module C is shown in FIG. The removal module C includes a container 20, a composite hollow fiber membrane 18, and a partition wall 19 made of an adhesive. The water is supplied to the removal module C from the water inlet 6 of the removal module C, passes through the hollow portion of the composite hollow fiber membrane 18, and is discharged from the water outlet 7 of the removal module C. The outside air is sucked from the outside air intake port 8 of the removal module C into a space surrounded by the composite hollow fiber membrane 18, the partition wall 19 made of the adhesive, and the container 20 of the removal module C, and the decompressor is discharged from the exhaust port 9 of the removal module C. Exhausted at 10.
[0015]
The composite hollow fiber membrane used for the removal module C in the present invention is, for example, a composite hollow fiber membrane having a three-layer structure in which a homogeneous layer is sandwiched between porous layers from both sides thereof, and is opposite to the porous layer in contact with the aqueous solution. The dissolved organic matter in the aqueous solution is removed by exchanging the gas on the porous layer side with air outside the container at a ventilation rate of 3 Nl / min or more per hollow fiber membrane area.
[0016]
ADVANTAGE OF THE INVENTION According to this invention, the volatile organic substance whose gaseous phase density | concentration in vapor / liquid equilibrium is high among dissolved organic substances in water can be removed efficiently. Further, among the volatile organic substances, particularly strong 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.
[0017]
When a hydrophobic porous membrane having a pore diameter of 0.05 μm or less is used as a hollow fiber membrane, water vapor leaks when used for a long time, and as a result, there is a risk that water leaks from the porous membrane. The hollow fiber membrane is a multi-layer 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 used. ) Are laminated alternately, and the multilayer composite hollow fiber membrane has a structure in which the layer in contact with the aqueous solution is the porous membrane (B), and the layer in contact with the aqueous solution is the porous membrane (B). Is used. Further, it is preferable that the composite hollow fiber membrane is a hollow fiber membrane having a permeability of 1 × 10 ⁻³ (cm ³ (STP) / cm ² / sec / cmHg) or more.
[0018]
If the chloroform permeation rate is less than 1 × 10 ⁻³ (cm ³ (STP) / cm ² / sec / cmHg), the permeation rate of the organic matter dissolved in water through the composite hollow fiber membrane is low and the organic matter is efficiently removed. Can not. Examples of a material for forming the porous layer of such a composite hollow fiber membrane include polyolefins such as polyethylene, polypropylene, poly-3-methylbutene-1, and poly-4-methylpentene-1, and vinylidene fluoride and polytetrafluoroethylene. A polymer such as a fluorine-based polymer, polysulfone, polyetherketone, or polyetheretherketone can be used, but polyolefin, which is a crystalline polymer that can easily form a porous material, is preferable.
[0019]
Examples of the material used for the homogeneous layer of the composite hollow fiber membrane include segmented polyurethane, silicon-based polymer, polyolefin such as low-density polyethylene and poly-4-methylpentene-1, and polyacrylamide. Polymers having a high affinity for halogen are preferred.
[0020]
Such a composite hollow fiber membrane is obtained by, for example, a method described in Japanese Patent Publication No. 3-44811 or the like, using a multi-cylindrical spinning nozzle to form a homogenous membrane (A) and a porous membrane (B) with a polymer. The polymer to be formed is alternately arranged and melt-spun, and then stretched under the condition that only the porous film (B) is made porous without making the homogeneous film (A) porous.
[0021]
In addition, an air suction device incorporated in the device is capable of discharging gas of the porous layer on the opposite side of the composite hollow fiber membrane from the side in contact with water to 3 Nl / min / m ² or more per hollow fiber membrane area (preferably 4 Nl / min / m ^2). It is a necessary condition that the device can be exchanged with the air outside the container at the ventilation speed described above.
[0022]
At a pumping speed of less than 3 Nl / min / m ² per hollow fiber membrane area, the difference in the molar amount between the organic gas passing through 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 at a displacement of ³ Nl / min / m ² or more, a decompressor having a large displacement such as a roots vacuum pump having a large displacement under a high vacuum can be used. Not preferred.
[0023]
By installing an intake port for taking in outside air when exhausting the gas in the container gap, it is possible to exhaust under a low vacuum and easily exhaust 3Nl / min / m ² or more with a small torque reducer having a small torque. can do.
[0024]
As a method of exchanging air with the outside air, there is also a method of, for example, compressing and sending the outside air with a device such as a compressor instead of sucking the outside air, but the film resistance of the gas side surface of the composite hollow fiber membrane is reduced. A method of sucking outside air is preferred because the size of the hollow fibers becomes large and there is a risk of air channeling occurring.
[0026]
【The invention's effect】
According to the system for removing dissolved organic matter in water according to the present invention, problems such as re-elution caused by a decrease in the removal capacity of an adsorbent or a water purifier using an adsorbent and a porous membrane due to long-term use, etc., are permanently present at the rear. By installing a removal device capable of removing dissolved volatile organic matter in water, water from which volatile organic matter has been removed can be supplied stably.
[Brief description of the drawings]
FIG. 1 is a conceptual diagram showing a preferred example of a system for removing dissolved organic matter in water according to the present invention.
FIG. 2 is a conceptual diagram showing an example of a water purifier used in the system for removing dissolved organic matter in water according to the present invention.
FIG. 3 is a conceptual diagram showing an example of a removal module used in the system for removing dissolved organic matter in water according to the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Housing 2 Water inlet 3 Water outlet 4 Water inlet of water purifier A 5 Water outlet of water purifier A 6 Water inlet of removal module C 7 Water outlet of removal module C 8 Outside air intake of removal module C 9 Exhaust port of removal module C 10 Pressure reducer (intake blower)
DESCRIPTION OF SYMBOLS 11 Outside air intake port 12 Exhaust port A Water purifier B Underwater dissolved organic matter removal apparatus C Removal module 13 Container 14 Porous sintered mesh 15 Activated carbon 16 Porous hollow fiber membrane 17 Partition wall made of adhesive 18 Composite hollow fiber membrane 19 From adhesive Septum 20 removal module container

Claims (4)

A container, a composite hollow fiber membrane located in the container, and an end of the composite hollow fiber membrane are supported by a water purifier comprising an adsorbent for chlorine and high molecular organic substances or the adsorbent and a porous hollow fiber membrane. A partition that separates a space that communicates with the hollow portion of the composite hollow fiber membrane from a space that communicates with the outer surface of the composite hollow fiber membrane; (1) volatile organic substances are contained in the hollow portion of the composite hollow fiber membrane; (2) an exhaust port for exhausting gas in a space formed by the outer surface of the composite hollow fiber membrane and the inner wall surface of the container, and an intake port for taking in external air. An apparatus for removing dissolved organic matter in water that is provided is attached at a later stage than the water purifier ,
The composite hollow fiber membrane is a multilayer composite hollow fiber membrane comprising a homogeneous membrane (A) and a porous membrane (B) having a reinforcing function, wherein the homogeneous membrane (A) and the porous membrane (B) are alternately laminated. Wherein the layer of the multilayer composite hollow fiber membrane that is in contact with the aqueous solution and the layer that is not in contact with the aqueous solution are both porous membranes (B),
An intake device is provided for exchanging gas in the porous layer (B) on the opposite side of the composite hollow fiber membrane from the side in contact with water with air outside the container at a ventilation rate of ³ Nl / min / m ² or more per hollow fiber membrane area. A system for removing dissolved organic matter in water. A container, a composite hollow fiber membrane located in the container, and an end of the composite hollow fiber membrane are supported by a water purifier comprising an adsorbent for chlorine and high molecular organic substances or the adsorbent and a porous hollow fiber membrane. And a partition separating the space communicating with the hollow portion of the composite hollow fiber membrane and the space communicating with the outer surface of the composite hollow fiber membrane, and (1) the outer surface of the composite hollow fiber membrane and the inner wall surface of the container. An inlet and an outlet for flowing an aqueous solution containing volatile dissolved organic matter into the space composed of: (2) an exhaust port for exhausting gas into the hollow portion of the composite hollow fiber membrane and an intake port for taking in external air. An apparatus for removing dissolved organic matter in water that is provided is attached at a later stage than the water purifier ,
The composite hollow fiber membrane is a multilayer composite hollow fiber membrane comprising a homogeneous membrane (A) and a porous membrane (B) having a reinforcing function, wherein the homogeneous membrane (A) and the porous membrane (B) are alternately laminated. Wherein the layer of the multilayer composite hollow fiber membrane that is in contact with the aqueous solution and the layer that is not in contact with the aqueous solution are both porous membranes (B),
An intake device is provided for exchanging gas in the porous layer (B) on the opposite side of the composite hollow fiber membrane from the side in contact with water with air outside the container at a ventilation rate of ³ Nl / min / m ² or more per hollow fiber membrane area. A system for removing dissolved organic matter in water. 3. The removal system according to claim 1, wherein the volatile organic substance is an organic halogen substance. 3. The removal system according to claim 1, wherein the adsorbent for chlorine and high molecular organic matter is activated carbon.

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