JPH1199388A - Reverse osmotic membrane treatment of raw water and device therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently remove carbon dioxide dissolved in raw water with a simple means by dissolving air into the raw water by pressurizing, spraying the water, in which air is dissolved, using a water spraying means provided in the tank to store the raw water in the storage tank and treating the stored raw water with a reverse osmotic membrane. SOLUTION: Raw water is supplied to a gas-liquid mixer 2 through a raw water supply pipe 1. In the gas-liquid mixer 2, air is sucked and introduced from an air introducing pipe 4 and dissolved in the raw water by pressurizing. The air-containing raw water the gas is sprayed by the water spraying means 5 provided in the upper part space in the raw water storage tank 3 and stored in the raw water storage tank 3. A gas, particularly carbon dioxide dissolved in the raw water is released by the spraying. The released dissolved carbon dioxide is discharged with air from a suction and exhaust pipe 9. The raw water, in which the dissolved carbon dioxide is releases and removed and which is stored in the raw water storage tank 3 as it is, is supplied to a reverse osmotic membrane module 7 through a high pressure pump 6 to be treated with the membrane. As a result, high purity treated water is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for treating a reverse osmosis membrane of raw water, and more particularly, to a process for producing pure water used for washing water of electronic parts, water for producing pharmaceuticals, foods, beverages and the like. The present invention relates to an improvement of a reverse osmosis membrane treatment method of raw water and an apparatus therefor.

[0002]

2. Description of the Related Art In recent years, for cleaning electronic parts, pharmaceuticals, foods,
Although a large amount of pure water is used as drinking water, in the process of producing the pure water, city water, river water, industrial water, etc. are used as raw water, and the raw water is used as a microfiltration device, an ion exchange device,
Pure water is processed by a pure water production apparatus having a configuration in which various reverse osmosis membrane devices and the like are combined. A reverse osmosis membrane device is widely used as an essential device for producing high-purity pure water because it can simultaneously remove organic substances and fine particles in addition to removing salts in raw water. However, the reverse osmosis membrane apparatus has a problem that the purity of the treated water is not improved because the carbon dioxide dissolved in the raw water passes through the reverse osmosis membrane as it is.

[0003] Therefore, conventionally, in order to remove dissolved carbon dioxide gas in raw water, the raw water is previously blown with air in a decarbonation tower,
Alternatively, a method of passing through a degassing membrane module, a method of contacting raw water with nitrogen gas to replace dissolved carbon dioxide, and further adjusting the pH by injecting alkali into raw water to convert dissolved carbon dioxide to bicarbonate ions. After the treatment by a method or the like, a method of preventing the permeation of dissolved carbon dioxide gas by supplying the treated water to a reverse osmosis membrane device is used. However, these treatments increase the equipment cost and running cost of the reverse osmosis membrane device, and are disadvantageous in terms of economy.

[0004]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned drawbacks of the conventional reverse osmosis membrane treatment by dissolving raw water in raw water before being supplied to a reverse osmosis membrane apparatus. It is an object of the present invention to provide a reverse osmosis membrane treatment method capable of efficiently removing carbon dioxide gas by a very simple means and obtaining high-purity treated water, and an apparatus suitable for the method.

[0005]

SUMMARY OF THE INVENTION The present invention provides a method and an apparatus for treating raw water for obtaining high-purity reverse osmosis membrane-treated water suitable for producing high-quality pure water. The first gist is that, in a method of treating raw water stored in a raw water storage tank with a reverse osmosis membrane, air is dissolved under pressure in the raw water, and the raw water in which the air is dissolved is provided in a water sprinkling means provided in an upper space in the raw water storage tank. And storing the raw water in a raw water storage tank, and then subjecting the stored raw water to reverse osmosis membrane treatment. A second gist of the present invention is to provide a gas-liquid mixing device for dissolving air in raw water under pressure, a raw water storage tank provided with a means for spraying raw water in which air is dissolved in the upper part of the tank, and a reverse osmosis membrane of raw water stored in the raw water storage tank. There is a raw water treatment device that is sequentially configured from the treatment device.

[0006]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is an explanatory diagram of a flow showing an example of an embodiment of the present invention. In the drawing, 1 is a raw water supply pipe, 2 is a gas-liquid mixer, 3 is a raw water storage tank, 5 is a water sprinkling means, and 7 is a reverse water supply means. The osmosis membrane module, 9 represents an intake and exhaust pipe. Raw water to be treated in the present invention is not particularly limited, and includes natural water such as well water and river water, city water and the like, and these raw waters may be subjected to pretreatment such as coagulation sedimentation filtration and activated carbon treatment as necessary. It can also be used after it has been applied. Further, when the purpose is to produce pure water of high purity, the treated water treated with a reverse osmosis membrane can be applied to the method of the present invention as raw water.

[0007] Raw water is supplied to a gas-liquid mixer 2 through a raw water supply pipe 1. In the gas-liquid mixer 2, air is sucked in from the air introduction pipe 4, and the air is dissolved under pressure in the raw water. The dissolution conditions are such that the pressure on the inlet side of the gas-liquid mixer 2 is slightly higher than the pressure on the outlet side (0.1 to 1.0 kg / cm ² G).
Or higher pressure) while maintaining the flow rate of raw water
Air is sucked in while passing at 5 m / h. Normal,
The pressure on the inlet side is about 0.5 to 1.5 kg / cm ² G or more, and the mixing ratio of raw water and air at that time is set so that raw water: air = 1: 1 in volume ratio. Also,
In order to avoid introduction of fine contaminants such as dust accompanying the air, it is effective to provide a dust filter device in the air introduction pipe 4. Examples of the form of the gas-liquid mixer 2 include an ejector, a line mixer, an orifice-type mixer, and the like. There is no particular limitation as long as air is introduced in the raw water supply pipe and gas-liquid mixing is possible. .

The raw water in which the air is dissolved under pressure by the gas-liquid mixer is sprinkled by the water spraying means 5 provided in the upper space inside the raw water storage tank 3 and stored in the raw water storage tank 3. The watering means 5 is not particularly limited as long as the raw water in which air is dissolved is widely and uniformly watered in the space in the raw water storage tank.
For example, there is a pipe having a plurality of small holes having a hole diameter of 2 to 6 mm or a pipe provided with a watering nozzle. Spraying releases gas dissolved in raw water, particularly carbon dioxide gas. In order to release as much carbon dioxide gas as possible, the water flow rate of raw water per one small hole is usually 2 to 5 m / m2.
It is preferable to supply the raw water so as to be sec.
In addition, at the time of watering, at least 30 hours between the surface of the raw water storage tank 3 where the water supply holes are present and the liquid level in the storage tank.
Raw water storage tank 3 so that a space of 0 to 500 mm is secured
It is good to sprinkle water while monitoring the liquid level. If the water hole is too close to the liquid level, the efficiency of gas release from the raw water will decrease.On the other hand, if it is too far away, a space will be created in the raw water storage tank more than necessary, and the released dissolved carbon dioxide gas will be re-absorbed and the efficiency will increase. Not a target. The released dissolved carbon dioxide gas is discharged from the intake / exhaust pipe 9 together with the air.

The raw water from which the dissolved carbon dioxide gas has been released and removed in this way is stored in the raw water storage tank 3 as it is, and then supplied to the reverse osmosis membrane module 7 via the high-pressure pump 6 and subjected to membrane treatment. Purified treated water is obtained. The reverse osmosis membrane module only needs to be used in the pure water production process, and examples of the membrane element structure include a spiral type, a hollow fiber type, and a tubular type. Known materials for the membrane include cellulose acetate, polyamide, crosslinked polyamine, crosslinked polyether, and sulfonated polysulfone. In the present invention, a commercially available reverse osmosis membrane module composed of a membrane made of these materials may be appropriately selected and used. The flow conditions of the raw water from which the carbon dioxide gas is supplied from the raw water storage tank 3 to the reverse osmosis membrane module vary depending on the scale of the treatment apparatus and the quality of the raw water, but usually, the flow rate is 1 to 100 m ³ / h, Water passing pressure 0.5 ~
It is arbitrarily selected in the range of 4 MPa.

In the above, the membrane treatment method of the raw water by the apparatus unit composed of the raw water storage tank provided with the gas-liquid mixer, the water sprinkling means and the reverse osmosis membrane apparatus has been described. In a preferred embodiment, there is a two-stage reverse osmosis membrane treatment. In such a case, the above-described apparatus units can be combined in two stages, and the treatment can be performed using the treated water obtained in the first stage reverse osmosis membrane treatment as the second stage raw water. In some cases, a normal reverse osmosis membrane treatment can be performed in the first stage, and a reverse osmosis membrane treatment of the present invention can be performed in the second stage using the permeated water as raw water. As described above, by performing the treatment in multiple stages, the carbon dioxide gas that has passed through the first-stage reverse osmosis membrane can be efficiently removed in the second stage, so that higher-purity treated water can be obtained.

[0011]

Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples unless it exceeds the gist.

Example 1 According to the reverse osmosis membrane treatment flow of the present invention shown in FIG.
Reverse osmosis membrane treatment was performed using city water having the water quality as shown in FIG. 1 as raw water. Raw water is first supplied to an air-blowing ejector as a gas-liquid mixer, and the raw water / intake air amount is 1/1.
(Volume ratio), and air was pressurized and dissolved in raw water. The raw water in which the air was dissolved was stored in a raw water storage tank having a capacity of 2 m ³ while being sprinkled by a water spray facility having a plurality of small holes having a diameter of 4 mm in a horizontal pipe provided at an upper part of the storage tank. At that time, the watering speed was 2 m / sec. The stored raw water is reverse osmosis membrane module SU-7
10 (trade name; manufactured by Toray Industries, Inc.) with a supply pressure of 12 kg / c
m ² G (1.2 MPa), flow rate 6.0 m ³ / h, recovery rate 6
The treated water was supplied at 0%, and the electric conductivity and pH of the obtained treated water were measured. The results are shown in Table 1.

Comparative Example For comparison, in the reverse osmosis membrane treatment flow of FIG.
The raw water shown in Table 1 was subjected to reverse osmosis membrane treatment under the same conditions as in Example 1 except that the gas-liquid mixer and the watering means in the raw water storage tank were removed. Table 1 shows the results.

[0014]

[Table 1] Item Raw water Example 1 Comparative example Electric conductivity 90 to 130 3.4 to 5 9.0 to 10.0 (μS / cm, 25 ° C) pH 6.0 to 6.5 5.5 to 6.5 4.0 to 5.0

[0015]

As described above, according to the method of the present invention, the carbon dioxide gas dissolved in the raw water is removed by an extremely simple device, so that the equipment cost and running cost of the reverse osmosis membrane device are greatly reduced. And high-purity treated water can be obtained. Therefore, incorporating the method of the present invention into the pure water production process greatly contributes to the improvement of economic efficiency.

[Brief description of the drawings]

FIG. 1 is a schematic explanatory diagram of a flow showing an embodiment of a reverse osmosis membrane treatment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Raw water supply pipe 2 Gas-liquid mixer 3 Raw water storage tank 4 Air introduction pipe 5 Water sprinkling means 6 High pressure pump 7 Reverse osmosis membrane module 8 Treated water outlet pipe 9 Suction and exhaust pipe

Claims (3)

[Claims] In a method of treating raw water stored in a raw water storage tank with a reverse osmosis membrane, air is pressurized and dissolved in the raw water, and the raw water in which the air is dissolved is dispersed by a watering means provided in an upper space in the raw water storage tank. A reverse osmosis membrane treatment method for raw water, comprising sprinkling water and storing the raw water in a raw water storage tank, and then treating the stored raw water with a reverse osmosis membrane. 2. A gas-liquid mixing device for pressurizing and dissolving air in raw water, a raw water storage tank provided with an air-dissolved raw water sprinkling means in an upper part of the tank, and a reverse osmosis membrane treatment device for raw water stored in the raw water storage tank. A raw water treatment device configured. 3. The method according to claim 1, wherein the raw water is water treated by a reverse osmosis membrane.