JPH06304559A - Method for treating water and device therefor - Google Patents

Abstract

PURPOSE:To restrain the clogging of the reverse osmosis membrane and to make equipment long in service life by providing two processes of a sand filtration one and a superfine filtration or ultrafiltration one, thereby facilitating the removal of impurities in raw water and enabling a reverse osmosis operation. CONSTITUTION:A water treating device for producing ultrapure water used in electronic industry and pharmaceutical industry, etc., has a sand filter 1 into which raw water added with a flocculant 10 as necessary is introduced under pressure by a booster pump 6, and impurities of over 1-100mum particle diameter are removed therein. After the raw water leaving the sand filter 1 is once stored in a storage tank 5, it is sent to a superfine filter 2 by a booster pump 6 and fine particles of over 0.01-10mum particle diameter and microorganisms such as algae are removed mainly therein. Next, after the raw water is once stored in a storage tank 5 similarly, it is fed to a reverse osmosis device 3 through a safety filter 7 and a high pressure pump 8 and dissolved salts and organic materials, etc., are separated therein.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water treatment method and a water treatment apparatus for efficiently producing high-quality pure water, particularly ultrapure water.

[0002]

2. Description of the Related Art A large amount of high-grade pure water is used in various industries such as the electronics industry and the pharmaceutical industry. The quality of pure water required is becoming higher year by year, and the demand volume is also increasing year by year. is doing. In these fields, high quality pure water,
In particular, in the production of ultrapure water, a reverse osmosis device capable of efficiently separating low-molecular compounds and salts is used in most cases. In addition, a large number of reverse osmosis devices have been put to practical use for the circulation use of pure water, water production, and the like. With the spread of reverse osmosis devices, research has been advanced to make them more durable and have a high degree of separation and to be economically used in a wide range of applications. That is,
New reverse osmosis membranes and various composite membranes have been developed, and the usage patterns of separation membranes, that is, modules are spiral type, hollow fiber type
Various types such as tubular type have been put to practical use.

On the other hand, the reverse osmosis membrane is apt to cause troubles due to microorganisms such as algae and suspended particles or colloids having a size of 0.1 to 5 μm. Therefore, when treating raw water containing these impurities with a reverse osmosis device, an electrolyte containing aluminum or iron ions is added to the raw water as a coagulant to agglomerate the fine particles, and then a sand filtration method is used to agglomerate them. A method of removing the particles in advance and then sending the water to be treated to a reverse osmosis device is adopted.

[0004]

As described above, by developing various composite membranes and modules, the reverse osmosis device has technically improved performance, is less likely to cause trouble, and can be used stably for a long period of time. It became so. But,
The reverse osmosis device has been submitted with requests for continuous and stable supply of treated water and improvement of economic efficiency, and the present inventor has studied means for solving the problem. However, development of new reverse osmosis separation membrane and module In addition to, I learned that the problem can be solved by studying the construction of the entire system. The present invention has been completed as a result of research on the most efficient process for the purpose of long-term stable operation of a reverse osmosis device and improvement of economic efficiency.

[0005]

Means for Solving the Problems As a first aspect of the present invention, (a) an impurity contained in raw water and having a diameter exceeding 1 to 100 μm is used by using a sand filter. And (b) using a microfiltration device to remove impurities contained in the treated water from the treated water obtained in the step (a) having a particle size of more than 0.01 to 10 μm. And a step (c) of removing impurities contained in the treated water from the treated water obtained in the step (b) using the reverse osmosis device.

As a second aspect of the invention, (a) the sand filter is used to remove the raw water from the raw water.
A step of removing impurities whose diameter exceeds 1 to 100 μm,
(B) a step of removing impurities contained in the treated water obtained in the step (a) and having a particle size of more than 0.001 to 1 μm using an ultrafiltration device;
(C) A water treatment method is provided, which comprises a step of removing impurities contained in the treated water from the treated water obtained in the step (B) using a reverse osmosis device.

In the first invention or the second invention,
The backwash water and / or the concentrated water obtained from the step (b) can be refluxed into the raw water. Further, the concentrated water obtained in the step (c) can be refluxed in the raw water.
Further, as a third invention, a raw water introducing pipe, a sand filtering device provided with an inlet side connected to the raw water introducing pipe, for removing impurities having a particle size of more than 1 to 100 μm, and an output of the sand filtering device. The particle size is 0.01-10μ
There is provided a water treatment device comprising a microfiltration device for removing impurities exceeding m, and a reverse osmosis device provided by connecting an inlet side to an outlet side of the microfiltration device. In this water treatment device, a pipe connecting the microfiltration device and the raw water introduction pipe can be provided.

Further, as a fourth invention, a raw water introducing pipe, a sand filtering device which is provided by connecting an inlet side of the raw water introducing pipe and removes impurities having a particle diameter of more than 1 to 100 μm, and the sand. By connecting the inlet side to the outlet side of the filtration device and removing the impurities having a particle size of more than 0.001 to 1 μm, and connecting the inlet side to the outlet side of the ultrafiltration device. Provided is a reverse osmosis device which is provided. In this water treatment device, a pipe connecting the ultrafiltration device and the raw water introduction pipe can be provided. Further, in each of the above-mentioned water treatment devices, a pipe connecting the reverse osmosis device and the raw water introduction pipe can be provided.

[0009]

[Examples and Actions] In the field of water treatment methods and water treatment devices for producing high-purity pure water, especially ultrapure water, conventional research has focused mainly on the development of reverse osmosis membranes and modules. It was going on. On the other hand, the water treatment method and the water treatment apparatus of the present invention were completed by emphasizing the whole process for highly exhibiting the performance of the reverse osmosis apparatus. Hereinafter, the present invention will be described with reference to the drawings, citing examples of embodiments. FIG. 1 is a schematic flow sheet showing an example of an embodiment for embodying the present invention.

Of the water treatment method and water treatment apparatus of the present invention, the first invention comprises at least three steps of a sand filtration step, a microfiltration step and a reverse osmosis step, and the second invention comprises at least a sand filtration step. And a water treatment method including three steps of an ultrafiltration step and a reverse osmosis step. In addition, a third invention includes at least a sand filtration device, a microfiltration device, and a reverse osmosis device, and a fourth invention.
Is a water treatment device including at least a sand filter, an ultrafilter and a reverse osmosis device. The sand filtration is filtration in which raw water is passed through a packed bed of granular filter media such as sand or anthracite to remove mainly contained solids. Both microfiltration and ultrafiltration are filtrations using a porous membrane as a filter medium, and the two are roughly distinguished by the pore diameter of the porous membrane used. Generally, the pore size is 0.01 to
Precision filtration is used when a 1 μm porous membrane is used, and ultrafiltration is used when a porous membrane having a pore size of 0.001 to 0.01 μm is used.

First, the first and third inventions will be described. The sand filtration step removes suspended substances and some organic substances contained in the raw water fed from the raw water introduction pipe 4, and is used in the next microfiltration step and the next reverse osmosis step. 2 and the reverse osmosis device 3 are protected and impurities are separated efficiently. The sand filtration device 1 used in the sand filtration step may be a known pressure type or gravity type,
Usually, a filter medium having an average particle size of 0.3 to 3 mm is used in a single layer or multiple layers. If the desired impurities cannot be sufficiently separated by simple sand filtration, the coagulant can be added to the raw water from the coagulant-adding pipe 10 in advance to coagulate the impurities. Examples of the aggregating agent used include aluminum sulfate, electrolytic aluminum and polyaluminum chloride. In addition, sulfuric acid, sodium hydroxide or the like can be added as a pH adjusting agent, and sodium hypochlorite or the like can be added as a sterilizing agent. In the sand filtration step, flocs formed by the action of the flocculant and particles having a diameter of mainly 1 to 100 μm contained in the raw water are removed. For backwashing, it is advisable to adopt an automatic method represented by a timer method or a differential pressure method.

In the next microfiltration step, microorganisms such as fine particles and algae remaining in the treated water that pass through the sand filtration step are removed to protect the reverse osmosis device 3 used in the next reverse osmosis step. It has the effect of increasing the separation efficiency of impurities. In particular, it is effective for removing troubles in the reverse osmosis membrane and removing microorganisms such as algae that impair permeation efficiency and suspended particles having a particle size of 1 μm or less. Examples of the membrane used in the microfiltration device 2 include a cellulose derivative such as cellulose acetate, an organic polymer such as polysulfone, polyvinyl chloride, acrylic resin, polytetrafluoroethylene and polypropylene, or a porous membrane such as a porous ceramic. To be These porous membranes can be in the form of pleats, such as a cartridge type in which they are spirally wound with a support material, a hollow fiber bundle type, or the like, but any form can be selected according to the embodiment. The microfiltration device 2 may be either a full filtration system or a cross flow system, but it is preferable that the backwash water or the concentrated water is refluxed to the raw water. For this reason, it is preferable to provide a pipe 11 that connects the microfiltration device 2 and the raw water introduction pipe 4.

In the reverse osmosis step, impurities that have passed through the above steps and remain in the treated water, such as dissolved salts and organic substances, are separated. The reverse osmosis device 3 used is not particularly limited. As the reverse osmosis membrane, a cellulose acetate-based, polyamide-based, polyethyleneimine-based, polyethylene oxide-based or polyether-based asymmetric membrane or composite membrane can be used. The module may be a spiral type, a pleated type, a hollow fiber type or the like. Normally, the high pressure pump 8 is provided on the suction side of the high pressure pump 8 that supplies water to the reverse osmosis device 3.
The filter 7 for security is inserted in advance. The pure water from which the impurities have been separated and removed is taken out from the pipe 9. The concentrated water may be extracted from the drainage pipe 13 to the outside of the system, but it is preferable to return the concentrated water to the raw water through the pipe 12 that connects the reverse osmosis device 3 and the raw water introducing pipe 4 because the pure water acquisition rate is improved. The result is obtained.

Depending on the type of impurities in the raw water and the particle size distribution, the second or fourth invention may be used instead of the first or third invention. In 2nd or 4th invention, it replaces with the said microfiltration apparatus 2 and uses the ultrafiltration apparatus 2 '. The ultrafiltration step is effective for removing particles having a size of 0.001 to 1 μm and remaining in the treated water after passing through the sand filtration step, and the colloidal particles or proteins close to the colloidal particles are treated in the treated water. In the case where a large amount of dissolved polymer such as the above exists, the load on the reverse osmosis device 3 can be reduced and protected. As the ultrafiltration membrane, an organic membrane such as polyacrylonitrile or polysulfone, an inorganic membrane using graphite or porous ceramics, or the like can be used. The shape and distribution method of the module conforms to the above-mentioned microfiltration step. The backwash water or concentrated water of the ultrafiltration device 2'is preferably returned to the raw water,
It is advisable to provide a pipe 11 ′ that connects the ultrafiltration device and the raw water introduction pipe. In addition, in order to carry out each of the above-described inventions, although not shown in the drawings, each device is usually provided with a pump and piping for backwashing. Moreover, temperature adjustment, pH adjustment, etc. are also carried out as necessary. A storage tank 5 of treated water may be provided between the respective steps so that the present invention can be easily carried out. Then, depending on the type of impurities in the raw water and the purpose of using pure water, for example, ion exchange treatment, activated carbon treatment, ultraviolet ray or chlorine sterilization treatment may be performed between the steps of the present invention. .

[0015]

EXAMPLES The present invention will be described below with reference to examples. Conventionally, the water treatment method consisting of a sand filtration step and a reverse osmosis step was used to supply pure water for a thermal power generation boiler. This is an example in which a microfiltration process was inserted between the two to provide excellent results. The FI value in the following description is
It is a value measured according to the method described in ASTM D4189.

In this case, sulfuric acid was added to industrial water having an FI of 5.5 to 6.3 to adjust the pH to 6, and polyaluminum chloride was added as a coagulant to 5 ppm. This raw water was passed through a two-layer sand filter with an inner diameter of 60 cm filled with 60 cm of anthracite having an average diameter of 1.6 mm and 40 cm of sand having an average diameter of 0.6 mm at a filtration speed of 10 m / h. There was water. The FI of the treated water that had been subjected to sand filtration was 3.0 to 4.0. In the conventional water treatment method, this treated water is directly sent to the reverse osmosis step to produce pure water. The reverse osmosis membrane module used was Membrane SU-720 (manufactured by Toray Industries, Inc.). The amount of pure water obtained was 100 m ³ / h, and 33 m ³ / h of concentrated water had been discharged out of the system. That is, the recovery rate of conventional raw water was 75.2%. Further, the reverse osmosis membrane needs to be washed with citric acid once in February, and its average life is 24 months.

Therefore, the present invention was carried out by newly providing a microfiltration step after the sand filtration step. The microfiltration membrane used was a polysulfone hollow fiber membrane with a pore size of 0.01 μm. The FI of the treated water that has undergone the microfiltration process has a FI of 0.3 to 1.
It became 0. This treated water was treated in the reverse osmosis process. As a result, the amount of pure water obtained increased to 120 m ³ / h, and even if the recovery rate of raw water was improved to 90%, the number of citric acid washes could be reduced to once a year. Average life expectancy could be extended to 48 months.

[0018]

EFFECTS OF THE INVENTION By using the water treatment method and the water treatment apparatus of the present invention, the conventional reverse osmosis apparatus causes troubles and burdens in the two steps of the sand filtration step and the microfiltration or ultrafiltration step. Impurities in the raw water, which had been increasing, are removed, and stable reverse osmosis operation becomes possible. As a result, the clogging of the reverse osmosis membrane is drastically reduced, the membrane is hardly required to be cleaned, and its life is extended. Furthermore, the amount of treatment can be increased, and the economic effect is large. Further, by refluxing the backwash water discharged from the microfiltration or ultrafiltration step and / or the concentrated water discharged from the reverse osmosis step to the raw water, the acquisition rate of pure water is significantly improved.

[Brief description of drawings]

FIG. 1 is a schematic flow sheet showing an exemplary embodiment for embodying the present invention.

[Explanation of symbols]

1: Sand filtration device 2: Microfiltration device 2 ': Ultrafiltration device 3: Reverse osmosis device 4: Raw water introduction pipe 5: Storage tank 6: Booster pump 7: Security filter 8: High pressure pump 9: Pure water delivery pipe 10: Flocculant addition pipe 11: Pipe connecting microfiltration device and raw water introduction pipe 11 ': Pipe connecting ultrafiltration device and raw water introduction pipe 12: Pipe connecting reverse osmosis device and raw water introduction pipe 1
3: Drainage pipe

Claims (9)

[Claims] (A) Using a sand filter, from raw water,
A step of removing impurities contained in the raw water, the diameter of which exceeds 1 to 100 μm, and (b) using a microfiltration device, from the treated water obtained in the step (a), to the treated water. A step of removing impurities having a particle size of from 0.01 to more than 10 μm, and (c) using a reverse osmosis device, from the treated water obtained from the step (b), to the treated water. Water treatment method including the step of removing existing impurities. 2. (a) Using a sand filter, from raw water,
A step of removing impurities contained in the raw water, the diameter of which exceeds 1 to 100 μm, and (b) an ultrafiltration device, from the treated water obtained in the step (a) to the treated water. A step of removing impurities contained therein, the particle size of which exceeds 0.001 to 1 μm; Water treatment method, which comprises removing impurities present in the water. 3. The water treatment method according to claim 1, wherein the backwash water and / or the concentrated water obtained in the step (b) is refluxed into the raw water. 4. The water treatment method according to claim 1, 2 or 3, wherein the concentrated water obtained in step (c) is refluxed into raw water. 5. A raw water introducing pipe, a sand filtering device provided with an inlet side connected to the raw water introducing pipe, for removing impurities having a particle size exceeding 1 to 100 μm, and an inlet side of the sand filtering device. And a reverse osmosis device provided by connecting the inlet side to the outlet side of the microfiltration device, which is provided by connecting the sides thereof to remove impurities having a particle size of from 0.01 to 10 μm or more. Water treatment device characterized by being 6. A raw water introducing pipe, a sand filtering device provided with an inlet side connected to the raw water introducing pipe, for removing impurities having a particle size exceeding 1 to 100 μm, and an inlet side of the sand filtering device. An ultrafiltration device, which is provided by connecting the sides thereof to remove impurities having a particle size of more than 0.001 to 1 μm, and a reverse osmosis device which is provided by connecting the inlet side to the outlet side of the ultrafiltration device. A water treatment device characterized by being provided. 7. The water treatment device according to claim 5, further comprising a pipe connecting the microfiltration device and the raw water introduction pipe. 8. The water treatment device according to claim 6, further comprising a pipe connecting the ultrafiltration device and the raw water introduction pipe. 9. The water treatment device of claim 5, 6, 7 or 8 comprising a pipe connecting the reverse osmosis device and the raw water introduction pipe.