JPH0739881A - Pretreatment of raw water - Google Patents

Abstract

PURPOSE:To unnecessitate a chemical for raw water pretreatment or to sharply reduce its quantity and to prolong the water gathering time and the resin life of an ion exchange resin by giving raw water activation pretreatment with a water passing utensil packed with granulated electric stones and passing it through a reverse osmosis membrane and an ion exchange resin in order, allowing main treatment to be performed. CONSTITUTION:When raw water 5 is passed through a water passing utensil 10 packed with granulated electric stones E, calcium hydroxide, magnesium hydroxide, etc., are ionized to generate no scale by surface activity action due to hydroxyl ions, and an oxidizing agent, such as chlorine and hydrogen peroxide is reduced by reduction action. In this way, the raw water 5 is pretreated just in front of the 1st RO membrane 1 to prevent the deterioration of the 1st RO membrane 1 due to an oxidizing agent and the clogging of it due to scale without hydrochloric acid and a chemical for pretreatment, such as a reducing agent being used. Or even if the raw water pretreatment effect is detected and hydrochloric acid and the chemical for pretreatment are used, their used quantity is sharply decreased than here to fore. After that, main treatment, such as demineralization is finally performed through an ion exchange resin 4 as in the conventional manner.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for pretreatment of raw water which is main treated with a reverse osmosis membrane and an ion exchange resin.

[0002]

2. Description of the Related Art For example, in a pure water production plant for purifying city water as raw water, a reverse osmosis membrane and an ion exchange resin are used. An example of the apparatus will be described below with reference to FIG. In the figure, (1) is the first reverse osmosis membrane (hereinafter referred to as the first R
It is called an O film. ), (2) is a degassing tower, (3) is a second reverse osmosis membrane (hereinafter referred to as a second RO membrane), and (4) is an ion exchange resin tower. The first RO membrane (1) is composed of a semipermeable membrane, and when high-pressure city water of about 20 to 25 Kg / m ² is introduced as raw water (5) with the drain valve of brine water (6) being throttled, the membrane is formed. A fairly high pressure is applied to the surface,
In the raw water (5) that has passed through the semipermeable membrane, particles larger than water molecules such as salts, ions and organic substances therein are blocked by the semipermeable membrane and filtered. On the other hand, it does not penetrate the semipermeable membrane,
Raw water (5) containing salts, ions, organic matter, etc. concentrated to a high concentration is discharged as brine water (6) from a drain port different from the treated water. The deaeration tower (2) is filled with pressurized nitrogen, and the dissolved oxygen and carbon dioxide gas in the treated water that has permeated the first RO membrane (1) are deaerated and supplied to the next stage by a pump (7). The second RO membrane (3) again filters the degassed treated water. The ion-exchange resin tower (4) contains an ion-exchange resin and finally removes the ions and the like that could not be removed up to that point.

Here, the city water (5) contains a large amount of metal components such as Ca, Mg and Al, while the used water is recovered and reused in the city water (5). Becomes basic, crystals of calcium hydroxide, magnesium hydroxide, etc. are deposited, which becomes scale and causes clogging of the first semipermeable membrane (1). Therefore, as a pretreatment, the pH value of city water (5) is automatically measured and compared with the set value,
Correspondingly, a predetermined amount of hydrochloric acid (8) or the like is injected before the first RO membrane (1) to acidify the city water (5) to prevent precipitation of calcium hydroxide or the like. Further, when the used water that is partially recovered is used, it contains a small amount of an oxidizing agent such as chlorine or hydrogen peroxide, and therefore, when the water containing the oxidizing agent passes through the first RO membrane (1), the RO membrane deteriorates. Therefore, similarly to the above, the redox value of the city water (5) is automatically measured and compared with the set value, and a predetermined amount of the reducing agent (9) is provided before the first RO membrane (1).
Is injected to reduce the oxidant contained in the city water (5) and R
It prevents the deterioration of the O film.

[0004]

The problem to be solved is to inject hydrochloric acid, a reducing agent, etc. into the raw water (1) at the front stage of the first RO membrane (1) as a pretreatment of the raw water (5) and replace it at the rear stage. This is the point that the ion becomes excessive and the ion exchange resin tower (4) becomes overloaded, and the water collection time and life of the ion exchange resin are significantly reduced.

[0005]

According to the present invention, raw water is passed through a water-passing device filled with a large number of tourmaline particles to perform pretreatment for activation, and then the raw water is converted into a reverse osmosis membrane and an ion exchange resin. The feature is that the main treatment is carried out by sequentially passing water.

[0006]

According to the above technical means, the raw water is passed through the water-passing device filled with a large number of granular tourmaline, and the raw water pre-treatment is performed in place of the raw water pre-treatment chemical solution such as hydrochloric acid or a reducing agent. After that, if the raw water is passed through the reverse osmosis membrane and the ion-exchange resin one after another for main treatment, the use of raw water pretreatment liquid chemical is unnecessary or the chemical liquid consumption is greatly reduced, and at the same time the latter-stage ion-exchange resin water sampling The time and life are greatly increased.

[0007]

EXAMPLE An example of a method for pretreating raw water according to the present invention will be described below with reference to FIG. The same parts as those shown in FIG. 2 are designated by the same reference numerals and the description thereof will be omitted. The difference is that instead of a raw water pretreatment chemical such as hydrochloric acid or a reducing agent, a water passing device (10) filled with a large number of bead-shaped tourmaline (E) having a diameter of 3 to 5 mm is attached to the first RO membrane (1). ) Was installed in front of the first RO membrane (1) and pretreated by passing the city water as raw water (5) through the first RO membrane (1). Water passing equipment (1) filled with tourmaline (E)
0) in the the passage of water, hydroxyl ions as activated surfactant (H ₃ O ₂₎ ^- is born, the following occurs water with surfactant wrapped with a monomolecular film of hydroxyl ions Exerts an action. First, "penetration", "wetness",
Crystals that exhibit surface-active effects such as "colloidization", "dispersion", "emulsification", etc., especially when calcium, silica, etc. are deposited at the interface, are formed by the directionality of hydroxyl ions oriented at the interface. It does not have scales and does not form scales. In addition, the water at the interface shows a reducing property to the solid surface to help passivate and maintain the metal, and chlorine in water is hydrolyzed and loses its volatility and irritation and becomes inactive. To be done. Therefore, the tourmaline (E) is currently used as a water-activating device for washing water, drinking / cooking water, water supply / drainage pipe system, and the like.

In the above structure, when the city water (5) is passed through the water passing device (10) filled with the tourmaline particles (E) before the first RO membrane (1), the surface active action by the hydroxyl ions is exerted. As a result, calcium hydroxide, magnesium hydroxide, etc. are ionized and scales are not generated, and the reducing action reduces oxidizing agents such as chlorine and hydrogen peroxide. Therefore, the raw water (1) is pretreated immediately before the first RO membrane (1) without using a pretreatment chemical such as hydrochloric acid or a reducing agent, and the first RO membrane (1) is deteriorated by an oxidant or caused by scale. Prevent clogging. Alternatively, a pretreatment chemical such as hydrochloric acid or a reducing agent may be appropriately used by detecting the raw water pretreatment effect, but even in that case, the amount of the chemical used is significantly reduced as compared with the conventional case. Then, as in the conventional case, the raw water (5) is finally subjected to a main treatment such as a purification treatment through the ion exchange resin tower (4).

[0009]

EFFECTS OF THE INVENTION According to the present invention, raw water is passed through a water passing device filled with a large number of granular tourmaline to be pretreated, and then the raw water is passed through a reverse osmosis membrane and an ion exchange resin in sequence. Since the main treatment such as deionized water is not required, the use of raw water pretreatment chemicals is not necessary or the amount of chemicals used is drastically reduced, and the load on the ion-exchange resin in the latter stage is greatly reduced, and the ion-exchange resin water sampling It is possible to extend the time and the resin life.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a raw water pretreatment method according to the present invention.

FIG. 2 is a block diagram showing an example of a conventional raw water pretreatment method.

[Explanation of symbols]

 1 Reverse osmosis membrane 3 Reverse osmosis membrane 4 Ion exchange resin 5 Raw water 10 Water passing equipment E Tourmaline

Claims (2)

[Claims] 1. A raw water is passed through a water-flowing device filled with a large number of tourmaline particles for pre-activation treatment, and then the raw water is sequentially passed through a reverse osmosis membrane and an ion exchange resin for main treatment. A method for pretreatment of raw water, which comprises: 2. The pretreatment method for raw water according to claim 1, wherein this treatment is a purification treatment using city water as raw water.