JPH11277062A - Method and apparatus for producing purified water - Google Patents

Abstract

PROBLEM TO BE SOLVED: To facilitate the maintenance of cleaning, sterilizatior by including a primary treatment system in which raw water softening means, a chlorine removing means, and a suspended solid removing means are arranged in this order and a secondary treatment system in which having a hollow fiber membrane module for purifying water treated by the primary treatment system further. SOLUTION: This apparatus for producing purified water includes a primary treatment system 50 in which a water softening device 2, an active carbon filter 3, and a prefilter 4 are arranged in series and a secondary treatment system 70 having a hollow fiber membrane module 30. In the primary treatment system 50, a by-pass line 6 between the water softening device 2 and the active carbon filter 3 and a change-over valve 5 for selecting a channel are installed, and in the secondary treatment system 70, an ultraviolet sterilizer 19 is installed. The membrane module 30 has a polymer containing acrylonitrile. In this way, by using the module 30, backwashing and sterilization can be done frequently, and high membrane separation performance can be maintained over a long period.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a production apparatus and a production method suitable for producing purified water used in the pharmaceutical production field, dialysis medical field and the like.

[0002]

2. Description of the Related Art In recent years, water for hand washing during operation, pharmaceutical water,
Pure water or purified water, such as water for artificial dialysis, is converted into tap water or ground water using a device as shown in FIG. 1, for example, and fine particles and microorganisms (general bacteria and dead bacteria) contained in the raw water are used. Further, a substance having a molecular weight of several thousands or more, such as pyrogen, which is a heat-generating substance, is removed by a UF film or an RO film to manufacture.

The apparatus shown in FIG. 1 is an apparatus for producing purified water using an RO membrane. In this apparatus, tap water or groundwater is supplied by a pump 1 and pretreated by a primary treatment system 50 in which a water softener 2, an activated carbon filter 3, and a prefilter 4 are arranged in series. The pre-treated water is further purified by a secondary treatment system 60 composed of an RO membrane module 8 provided downstream and an ultraviolet germicidal lamp 11 installed in an RO water tank 9.

[0004] This apparatus is gradually polluted during operation, resulting in a decrease in the quality of the produced water. Therefore, the secondary processing system 60 including the RO membrane module 8, the RO water tank 9, the ultraviolet sterilizing lamp 11, and the like is cleaned and sterilized.

[0005] The RO membrane used in this apparatus is gradually contaminated as water is produced. If tap water is used as raw water, the raw water always contains chlorine (Cl ₂ , NaClO, etc.)
Since the RO film is oxidized and deteriorated by chlorine, the activated carbon filter 3 of the first treatment system 50 adsorbs and removes residual chlorine. However, it is difficult to completely remove dissolved chlorine.

[0006] Even if raw water is constantly sterilized with chlorine, RO
The membrane is contaminated. In that case, the operation of the apparatus is temporarily stopped, and the secondary processing system 60 is also sterilized by flowing chlorine. However, the chlorine concentration is preferably higher in terms of sterilizing power, but is preferably lower in consideration of oxidation and deterioration of the RO film, and it is difficult to satisfy both. Further, once the operation is stopped, fine particles are expelled or eluted from the units, pipes and their joints by a shock when the operation is restarted, and the quality of the produced water is reduced. In addition, especially in the field of dialysis medicine, stopping operation for a long time for maintenance is a major obstacle in performing medical activities. When the operation is stopped, the purified water stays in the pipes and the units constituting the system, and bacteria are propagated by organic substances and bacteria that have already adhered to the RO membrane. It elutes from tanks etc. and the quality of purified water deteriorates. For this reason, continuous operation is usually performed, but as a result, operation costs including electric power costs increase. Further, even when the apparatus is suspended for a long period of time, the RO membrane module must be immersed in, for example, a formalin solution having a concentration of about 0.5%.

[0007] A typical example of the RO membrane used in such an apparatus is a cellulose acetate membrane. However, in the case of a cellulose acetate membrane, the hydrolysis of the membrane is caused by raw water, the flexibility of the membrane is lost, and the desalination performance is reduced. Especially,
Hydrolysis is promoted as the pH of the treated water increases. On the other hand, as the pH decreases, corrosion of the device is promoted. Therefore, in practice, the pH must be adjusted to a range of 5 to 5.6. When the RO film is a synthetic polymer film such as a polyamide-based or polyether-based film, oxidative decomposition of the film due to residual chlorine is remarkable, and a decrease in desalination performance is remarkable. Furthermore, a polyether-based synthetic membrane is also degraded by dissolved oxygen in raw water, and requires a deoxidation treatment such as injection of sodium sulfite (Na ₂ SO ₃ ) or the like as a pretreatment.

[0008] As described above, the apparatus using the RO membrane requires fine management in order to maintain the optimum operating conditions.
Furthermore, it is difficult for small and medium-sized enterprises, research laboratories, hospitals, and the like to secure personnel for that purpose.

[0009]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an apparatus and a method for producing purified water which are easy to maintain such as washing and sterilization.

[0010]

In order to achieve the above object, the present invention provides a primary treatment system comprising a raw water softening means, a chlorine removing means, and a suspended matter removing means arranged in this order. And a secondary treatment system having a hollow fiber membrane module for further purifying the treated water by the primary treatment system.

Here, the hollow fiber membrane module is preferably made of a polymer containing acrylonitrile as a component, and is provided with a bypass line for softening means and chlorine removing means. It is also preferable that the hollow fiber membrane module is provided with a backwashing means, and the secondary treatment system is provided with a sterilizing means.

[0012] The present invention for achieving the above object also provides a method for producing purified water in which raw water is treated with a hollow fiber membrane after removing hardness components, chlorine and suspended substances in the raw water. It is characterized by the following.

At this time, performing back washing of the hollow fiber membrane,
It is preferable to use raw water containing a bactericide. In addition, sterilizing the hollow fiber membrane by supplying raw water to the hollow fiber membrane,
It is also preferable to sterilize the water treated by the hollow fiber membrane.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The apparatus for producing purified water of the present invention is shown in FIG.
As shown in the figure, a primary treatment system 50 in which a water softener 2, an activated carbon filter 3, and a prefilter 4 are arranged in series.
And a secondary processing system 70 including the hollow fiber membrane module 30. And the primary processing system 5
On the upstream side of the raw water flow direction 0, a pump 1 for supplying raw water to the system is provided. The first treatment system 50 has a switching valve 5 for selecting a bypass line 6 and a flow path of the water softener 2 and the activated carbon filter 3, and the second treatment system 70 has an ultraviolet sterilizer 19 and a hollow A water supply line 12 from the yarn membrane module 30 to the ultraviolet sterilizer 19, a pump 10 for sending treated water of the ultraviolet sterilizer 19, and a supply line 15 for supplying the treated water outside the system.
And a circulation line 17 to the hollow fiber membrane module and a circulation line 16 to the ultraviolet sterilizer 19 itself. The water supply line 12 is provided with a three-way valve 22.

Since the apparatus for producing purified water of the present invention uses a hollow fiber membrane module, damage to the membrane due to chlorine is extremely small, and frequent backwashing and disinfection that cannot be performed with an apparatus using an RO membrane are performed. be able to. As a result, the quality of the produced purified water is also high. In addition, the conventional apparatus using the RO membrane had to be operated at a high pressure. However, the apparatus of the present invention uses a hollow fiber membrane module to achieve a compact apparatus. Raw water can be treated efficiently in a short time. As a result, equipment costs and operation costs can be reduced.

The water softener 2 comprises a resin tube filled with ion exchange resin, a regeneration control valve mounted on the top of the resin tube, and a salt water tank for regenerating the ion exchange resin. As the resin, for example, Na
The raw material water is passed through an ion exchange tower filled with this resin using a strong acidic cation exchange resin, and the hardness component (C
a ²⁺ , Mg ²⁺ , Al ²⁺ ) is subjected to Na ⁺ ion exchange to soften raw water. The control valve for regeneration mounted on the top of the resin cylinder of the water softener comprises: (1) a water sampling (water passing) step, (2) a backwashing step, (3) a salt water regeneration step, and (4) a water washing step. The five steps of (extrusion) step and (5) water replenishment (water collection) step are automatically or manually operated. In the case of automatic operation, it is preferable to combine a sequencer and a calendar timer.

If a plurality of water softeners are arranged in parallel, the amount of treated water can be increased, and the switching operation can be performed, so that water can be supplied to the secondary treatment system without stopping the water softening treatment. preferable.

The activated carbon filter 3 has a cylindrical body filled with granular activated carbon and silica sand for reducing resistance and facilitating water collection. These are filled up to about 60% of the volume of the cylinder. A control valve for backwashing is mounted on the top of the cylinder.
(2) backwashing step, (3) resting step, (4) washing step,
(5) The five steps of water replenishment and water sampling can be automatically or manually operated. In the case of automatic operation, it is preferable to combine a sequencer and a calendar timer.

Also, in the activated carbon filter, it is preferable to arrange a plurality of activated carbon filters in parallel because the same effect as in the water softener can be expected.

The pre-filter 4 is preferably provided with one or several cartridge-type thread-wound filter elements made of polypropylene or cotton from the viewpoints of elution from the filter element itself and price. Further, considering that the pressure loss increases due to the size and clogging of the substance to be removed and the amount of filtered water decreases, the filtration accuracy is preferably 1 to 20 μm.

The hollow fiber membrane module 30 of the secondary treatment system comprises a hollow fiber membrane bundle 30a made of a polymer containing acrylonitrile and a potting material 30 at one or both ends thereof.
The bundle is fixed at b, and stored in the container 30e. As shown in FIG. 2, a number of hollow fiber membranes are hung down in a U-shape, and the upper portion is focused and fixed with a potting material 30b so as to communicate with the permeated water extraction chamber 30c, or the permeated water extraction chamber 30 is fixed.
c and hang down in a Ι shape, and the upper part
Focusing and fixing with a potting material 30b so as to communicate with c,
The lower part is sealed with a potting material. This hollow fiber membrane bundle is housed in at least one bundle container to form a hollow fiber membrane module 30. The container 30e is formed by the potting material 30b.
It is divided into a separation treatment chamber 30d for introducing treated water and a permeated water extraction chamber 30c for collecting water permeated through the hollow fiber membrane. It is preferable that such a hollow fiber membrane module 30 is arranged vertically so that the hollow fiber membranes hang down by their own weight and are efficiently backwashed.

It is preferable to use a plurality of hollow fiber membrane modules 30 because a large amount of fresh water can be obtained. In this case, the treated water flows may be arranged in parallel as shown in FIG. 3, or the treated water in some of the hollow fiber membrane modules may be replaced with other hollow fibers as shown in FIG. It may be arranged for further processing in a membrane module. Each permeate is collected and sent to an ultraviolet sterilizer.

In the present invention, it is preferable that the hollow fiber membrane bundle is made of a polymer containing acrylonitrile as the damage by chlorine can be extremely reduced.

The ultraviolet sterilizer 19 includes an ultraviolet sterilizing lamp 1.
1, a disinfecting filter 20 and a water level gauge 21 are provided. The sterilization filter is for removing bacteria when the outside air enters the tank, and is replaced with a new one as needed.

In the above-mentioned primary treatment system, raw water is taken into the system by the pump 1. Primary processing system 5
The raw water supplied to the raw water is supplied to the water softener 2 with Ca ²⁺ , M in the raw water.
^Polyvalent cations such as g ²⁺ and Al ²⁺ are exchanged for Na ⁺ ions to be softened. As a result, the hardness component in the raw water is removed, and scaling on the RO film surface can be prevented. Next, the water softened by the water softener 2 is sent to the activated carbon filter 3, where it absorbs and removes residual chlorine, odor components, organic substances, etc., and at the same time, filters out large suspended substances. The water treated by the activated carbon filter 3 is supplied to the pre-filter 4
Then, the leaked ion exchange resin and activated carbon, and the remaining suspended substances are further removed.

As the water softener 2 continues to operate, its performance deteriorates due to polycations, organic substances and the like in the raw water. Therefore, salt water (NaCl water) having a concentration of about 10% is sucked into the column and brought into contact with the ion exchange resin, whereby the bound polycations are separated and discharged to regenerate the resin. This step is carried out at a frequency commensurate with the quality of the raw water, and is carried out automatically by the control valve in combination with the above-mentioned sequencer and calendar timer. Also,
When it is necessary to perform the operation artificially, such as in an emergency, the operation is performed manually. In addition, the ion-exchange resin gradually reduces its ability to remove hardness during repetition of regeneration, so replace the ion-exchange resin before the specified water quality is no longer obtained.
Or replace the whole water softener.

When the activated carbon filter 3 is also operated,
Backwash as the residual pressure in raw water, suspended solids, organic matter, etc. will increase the pressure difference and decrease the adsorption capacity. The differential pressure is improved by discharging the suspended matter and the like captured by backflowing the raw water to the outside of the filter and loosening the compacted activated carbon layer. This step is also performed by operating the control valve. In addition, since the adsorption capacity of activated carbon is reduced during repeated backwashing, the activated carbon is replaced before the specified water quality is no longer obtained, or the entire activated carbon filter is replaced.

The regeneration and backwashing of the water softener and the activated carbon filter may be performed during a time when purified water is not required or when the amount of purified water used is small.
For example, it is preferably performed at night, but since the primary treatment system is provided with the bypass line 6, it can cope with a case where purified water needs to be produced at the time of regeneration and backwashing.

The treated water of the primary treatment system 50 passes through the treated water supply valve 31 and passes through the secondary treatment system 70.
To the hollow fiber membrane module. The treated water sent is
Into the separation processing chamber 30d, pyrogen as a heating substance and suspended substances that could not be removed by the pretreatment are removed. The permeated water that has passed through the hollow fiber membrane is collected in the permeated water removal chamber 30c.

The water collected in the permeate discharge chamber 30c is
It is extruded by water pressure and sent to the ultraviolet sterilizer 19 through the water supply line 12. A part of the treated water of the ultraviolet sterilizer 19 is supplied to the supply line 15 by the pump 10.
, And is sent to the use point 26 of the purified water. At this time, the amount of purified water can be adjusted by the purified water delivery control valve 36. Then, the remaining purified water is returned to the ultraviolet sterilizer 19 through the circulation line 16. When performing backwashing of the hollow fiber membrane module, a part of purified water is further sent to the hollow fiber membrane module through the circulation line 17.

In the hollow fiber membrane module 30, since suspended matter, bacteria, pyrogen and the like accumulate on the membrane surface, the filtration operation is periodically temporarily stopped and backwashing is performed to recover the performance. At the time of backwashing, permeated water is injected as backwashing water into the hollow fiber membrane module from the side from which the permeated water is taken out, and the deposits adhering to the hollow fiber membrane surface are lifted off the membrane surface. For this reason, it is necessary to apply a pressure higher than the pressure acting on the hollow fiber membrane surface from the outside from the inside, which is 1.2 to 1.5 times the pressure of the treated water sent to the hollow fiber membrane module during filtration. Is preferred. Then, compressed air of about 0.03 to 0.1 MPa is introduced from a compressed air supply valve 32 provided at a lower portion of the hollow fiber membrane module, and the sediment floating on the membrane surface is shaken off by air bubbling. The water used for the backwash is drained out of the system by opening the backwash water discharge valve 33. These steps are repeated. By doing so, it is possible to remove deposits on the filter medium and suppress a decrease in the amount of filtered water.

In the present invention, after backwashing, water containing an oxidizing agent as a disinfectant or disinfectant is sent from the bypass line 6 to the hollow fiber membrane module 30 without passing through the water softener 2 and the activated carbon filter 3. Then, the hollow fiber membrane module 30 is disinfected. By feeding and filling the water until it overflows from the overflow valve 35, dead space is prevented from being generated in the hollow fiber membrane module. When the water containing the oxidizing agent is sent until it flows out of the overflow valve 35, the valve 35 and the raw water supply valve 31 are closed, and this state is maintained. In this way, sterilization can be performed.

The water to be filled here has a chlorine concentration of 0.2.
About ppm is preferable. When the chlorine concentration is less than 0.1 ppm, an oxidizing agent is separately injected when water is supplied to the secondary treatment system. As the oxidizing agent, sodium hypochlorite and calcium hypochlorite are preferable from the viewpoint of easy handling.

The time for filling the hollow fiber membrane module 30 with water containing an oxidizing agent is preferably 2 hours or more, more preferably 4 hours or more when the chlorine concentration is about 0.2 ppm. When the operation is stopped for several days or more, the oxidizing agent is consumed. Therefore, it is preferable to replace the raw water containing the oxidizing agent with fresh water.

Usually, the backwashing is performed after the completion of the filtration operation. Therefore, it is preferable to fill with the water containing the oxidizing agent and sterilize until the filtration operation is restarted as described above. By doing so, it is possible to prevent bacteria from growing and contaminating in the apparatus, and to prevent performance degradation due to membrane surface contamination of the membrane module and water quality of purified water to be produced.

It is preferable to provide sampling valves S1, S2, S3 and S4 at important points in order to check the operating state of the apparatus, particularly the presence of bacteria and pyrogen.

At the start of operation, the overflow valve 35 and the backwash water discharge valve 33 are opened, and the water filled in the hollow fiber membrane module 30 is discharged out of the system. After discharge, the backwash water discharge valve 33
Is closed, the raw water supply valve 31 is opened, and the permeated water switching valve 22 is opened to the b side, and the switching valve 5 is opened to the a side. Then, the treated water pretreated by the water softener 2 and the activated carbon filter 3 is supplied to the hollow fiber membrane module 30, and the water is caused to flow out of the overflow valve 35 to eliminate the air pool in the separation treatment chamber 30d. The overflow valve 35 is closed to start the filtration. After the start of filtration, 2
Since the permeated water of the hollow fiber membrane module 30 for about 0 to 30 minutes contains chlorine, the permeated water switching valve 22 is opened to the b side and discharged from the permeated water blow line 27 to the outside of the system. If the drainage time from the permeated water blow line 27 is short, the oxidizing agent in the raw water remains in the hollow fiber membrane module, permeates into the hollow fiber membrane module as the filtration is performed, and mixes with the purified water. If it is too long, the permeated water will be wasted.

After the backwashing / disinfection has been performed as described above, the switching valve 22 is opened to the side a, and the fresh water generating operation is restarted.

[0039]

EXAMPLE Using the apparatus for producing purified water shown in FIG. 2, a turbidity of 0.2 to 1.3 NTU and a chlorine concentration of 0.1 to 0.3 pp were used.
m, and tap water having a water supply pressure of 0.3 to 0.35 MPa was used as raw water for 2 months. Purified water was produced.

The operating conditions were as follows: filtration started at 6:00 every morning,
Occasionally stopped driving. The production of the purified water was suspended only on Sunday, but the system after the hollow fiber membrane module 30 always continued the continuous operation as a measure for preventing bacterial generation. The treatment capacity increases as the temperature and pressure of the raw water increase, but is basically 1200 l / Hr.

As a pump for supplying raw water, 300 k
A spiral pump made of gunmetal of Pa was used.

As the water softener 2, a cartridge / bomb type ion exchange apparatus filled with 40 l of ion exchange resin and having a maximum water flow of 2500 l / Hr and having a fully automatic regeneration function was used. Regeneration was carried out once a day for 7 minutes / 120 minutes.

The activated carbon filter 3 is filled with 35 liters of activated carbon and 5 liters of silica, and has a maximum water flow of 2 liters.
A 500 l / Hr cartridge / bomb type filter equipped with a fully automatic regeneration function was used. The backwashing cycle was 1 day / 1 time, the backwashing time was 60 minutes, and the backwashing and the filling of the hollow fiber membrane module were performed.

As the pre-filter, a thread-wound type filter element made of polypropylene having a size of 5 μm × 20 inches was used.

As the hollow fiber membrane module, 8,000 porous hollow fiber membranes made of acrylonitrile and having an outer diameter of 450 μm, an inner diameter of 350 μm, an average pore size of 0.01 μm, and an effective membrane area of 12 m ² are formed in a U-shape. And three pieces housed in a transparent hard vinyl chloride container having an outer diameter of 114 mm and an inner diameter of 104 mm were used in parallel. The backwashing was performed once a day for 10 minutes after the operation was stopped after the operation was stopped. After the backwashing, the water that had bypassed the water softener and the activated carbon filter was filled until the operation was restarted, and the inside of the system was sterilized. The regeneration cycle of the water softener 2 was set to be performed once every seven days at midnight on Saturday.

As a pump for supplying permeated water of the hollow fiber membrane module, a spiral pump made of stainless steel was used.

As an ultraviolet sterilizer, a water level gauge is provided in a hard vinyl chloride sealed tank having a capacity of 150 liters.
The one provided with an external line germicidal lamp and a sterilization filter made of polypropylene was used.

For 30 minutes after resuming the filtration, the permeated water of the hollow fiber membrane module 30 was blown out from the permeated water blow line 27 to the outside of the system. At this time, no residual chlorine was detected in the sampling water from the sampling valve S3.

During continuous operation for two months, samples were obtained from the sampling valves S1, S2, S3, S4,
Endotoxin measurements were performed. Endotoxin measurement
The gelation method specified in the Japanese Pharmacopoeia was used. In addition, since the water which stagnated in the piping was contaminated with time, the sample was collected under flowing water. After the sample was washed with running water for 10 minutes or more, a full amount of water was collected in a collection container sterilized with pressurized steam, and immediately measured.

Table 1 shows the endotoxin measurement results. From the sampling valve S3, permeated water of about 100 EU / liter was stably obtained from the sample. This water quality is equivalent to that of a conventional RO membrane device, and is a water quality level that does not cause any problem as a dialysate.

Further, in order to investigate the chlorine resistance of the hollow fiber membrane, the hollow fiber membrane module was disassembled after the operation for two months, and the water permeability, tensile strength and elongation of the single hollow fiber were examined. At the same time, the residual chlorine concentration was 1 ppm and 10 ppm
200 hours, 600 hours, 120
After operating for 0 hours, the hollow fiber membrane module was disassembled and the water permeability, tensile strength and elongation of the hollow fiber single yarn were examined.

Table 2 shows the results as ratios to the initial values. As is clear from this table, no significant change in water permeability, strength, and elongation was observed even after the treatment of tap water for two months. Further, the residual chlorine concentration was 1 ppm and 10 pp.
m when used as raw water, water permeability,
No significant change was observed in strength and elongation. From these results, it can be seen that when the hollow fiber membrane is used in the purified water production apparatus, backwashing and disinfection can be performed, and the same water quality as when the RO membrane is used can be obtained.

[0053]

[Table 1]

[Table 2]

[0054]

According to the apparatus for producing purified water of the present invention, since the hollow fiber membrane module is used, backwashing and disinfection can be performed frequently, and as a result, high membrane separation performance can be maintained for a long period of time. . Further, since purified bacteria and pyrogen can be removed, the purified water to be produced has sufficient water quality for use in the fields of electronics industry, drug production, dialysis medical field and the like. The hollow fiber membrane module can easily and easily make the whole apparatus compact, so that a large amount of purified water can be produced stably at low cost.

[Brief description of the drawings]

FIG. 1 is a schematic flow chart of a conventional apparatus for producing purified water.

FIG. 2 is a schematic flow chart of an apparatus for producing purified water, showing one embodiment of the present invention.

FIG. 3 is a schematic flow chart of a hollow fiber membrane module showing one embodiment of the present invention.

FIG. 4 is a schematic flow chart of a hollow fiber membrane module showing one embodiment of the present invention.

[Explanation of symbols]

 1: pump 2: water softener 3: activated carbon filter 4: pre-filter 5: switching valve (three-way valve) 6: bypass line 7: RO pump 8: RO membrane module 9: RO water tank 10: pump 11: ultraviolet sterilizing lamp 12: Water supply line 13: Concentrated water line 14: Concentrated water return line 15: Supply line 16: Circulation line 17: Circulation line 19: Ultraviolet sterilizer 20: Sterilization filter 21: Water level gauge 22: Switching valve (three-way valve) 26 : Use point 27: Permeated water blow pipe 30: Hollow fiber membrane module 30a: Hollow fiber membrane bundle 30b: Potting material 30c: Permeated water extraction chamber 30d: Separation processing chamber 30e: Container 31: Treated water supply valve 32: Compressed air supply Valve 33: Backwash water extraction valve 34: Backwash water supply valve 35: Overflow valve 36: Purification Delivery control valve 50: first-order processing system 60: Second processing system 70: Second processing system S1: Sampling valve S2: Sampling valve S3: Sampling valve S4: Sampling valve

Continued on the front page (51) Int.Cl. ⁶ Identification code FI C02F 9/00 502 C02F 9/00 502J 502Z 502D 502H 502F 502N 503 503B 504 504B

Claims (10)

[Claims] 1. A primary treatment system in which raw water softening means, chlorine removing means and suspended matter removing means are arranged in this order, and a hollow fiber membrane for further purifying treated water by the primary treatment system. An apparatus for producing purified water, comprising: a secondary treatment system having a module. 2. The apparatus for producing purified water according to claim 1, wherein the hollow fiber membrane module is made of a polymer containing acrylonitrile as a component. 3. The purified water producing apparatus according to claim 1, wherein a bypass line is provided in the softening means and the chlorine removing means. 4. The apparatus for producing purified water according to claim 1, further comprising at least one of a backwash means and a sterilization means for the hollow fiber membrane module. 5. The apparatus for producing purified water according to claim 1, wherein the secondary treatment system includes a means for sterilizing treated water using a hollow fiber membrane module. 6. A method for producing purified water, wherein raw water is treated with a hollow fiber membrane after removing hardness components, chlorine and suspended substances in the raw water. 7. The method for producing purified water according to claim 6, wherein the hollow fiber membrane is backwashed. 8. The method for producing purified water according to claim 6, wherein raw water containing a bactericide is used. 9. The method according to claim 8, wherein raw water is supplied to the hollow fiber membrane to sterilize the hollow fiber membrane. 10. The method for producing purified water according to claim 6, wherein the water treated by the hollow fiber membrane is sterilized.