JPH06170179A - Hollow fiber membrane module filtration equipment - Google Patents

Abstract

PURPOSE:To efficiently add a chemical agent such as a flocculant and to operate hollow fiber membrane filtration equipment over a long period of time without lowering filtering capacity by providing a bypass line between a porous hollow fiber membrane module and the water supply line on the upstream side of a liquid supply pump and providing a chemical soln. injection port on the bypass line. CONSTITUTION:A hollow fiber membrane module 15 having a large number of proous hollow fiber membrane bundles built therein, a liquid supply pump 8 for supplying a liquid to be treated to the module 15 and a chemical soln. injection port 5 for injecting a chemical soln. in the module 15 are provided. A bypass line connection port 2 is provided on the water supply line 1 supplying the liquid to be treated to the module 15 and the chemical soln. injection port 5 is provided on the bypass line connected to the connection port 2. As a result, a chemical agent such as a flocculant can be efficiently added and the hollow fiber membrane filtration equipment can be operated over a long period of time without lowering filtering capacity.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a filtering device using a hollow fiber membrane module for performing a liquid filtering operation and a method of using the same.

[0002]

2. Description of the Related Art General industrial water contains many SS components, fine particles, dust, bacteria, algae, etc. If used as is, clogging of water pipes, bacterial growth, lines It is likely to cause troubles such as scale accumulation inside. Conventionally, various methods such as sand filtration, coagulation filtration, coagulation sedimentation treatment, and cartridge filter filtration have been used in order to remove these water-mixed components, depending on the application. As a new method replacing these general filtration methods, filtration using a porous hollow fiber membrane has recently been put into practical use. The water treatment and filtration using hollow fiber membranes have rapidly spread in recent years, and the fields of application thereof are also expanding year by year.

In filtration of hollow fiber membranes, the hollow fiber membranes are processed into a product form in which thousands to tens of thousands are bundled into a bundle and the ends are fixed with an adhesive. The products processed into these product forms are called hollow fiber membrane modules or modules. Many types of hollow fiber membrane modules capable of filtering liquid have been proposed in the past. Especially as the initial one, there are a filtration module used in combination with an appropriate pretreatment means, one for the purpose of reverse osmosis filtration, one for the purpose of dialysis, etc.
Many module forms have been proposed mainly for these applications, and the main ones thereof are Japanese Patent Publication No. Sho 48.
-28380, JP-A-49-69550,
There are those described in JP-A No. 53-100176. All of these were usually disposed of, or washed with clear water or chemical water or flushed at a stage where a certain amount or more of dirt adhered.

On the other hand, recently, a method has been attempted in which the shape of the hollow fiber membrane module is devised so that the adhered substances on the surface of the hollow fiber membrane are periodically removed by air to recover the performance of the hollow fiber membrane. ing. Japanese Unexamined Patent Publication No. 61-263605 discloses that a hollow fiber membrane is incorporated in a U-shape and used by being housed in a container, and air is regularly introduced from an air introduction port provided at the bottom of the container. The hollow fiber membrane is vibrated by air bubbling to try to remove deposits on the membrane surface. In addition, Japanese Patent Laid-Open No. 60-206415 discloses
It is a fixed-end type module in which hollow fiber membranes are arranged around a central pipe, and is incorporated in a container in the same manner as described above, and deposits on the surface of the hollow fiber membranes are removed by air bubbling. The practical application of these technologies has already started.

[0005]

In the water treatment by the hollow fiber membrane module, it is effective to remove the deposits on the surface of the hollow fiber membranes by air, and the deposits on the membrane surface are removed (cleaned) by air bubbling. )
Although the membrane can be almost recovered to its original state before filtration, the filtration performance is almost restored, but if water is passed for a long period of time, fine dust clogging the micropores of the membrane and dirt that cannot be removed by air bubbling will adhere to the membrane surface, and the filtration performance will also be improved. In general, it gradually decreases with the passage of water. The causative agent that penetrates into the micropores of the membrane and causes the membrane to be clogged is a very small suspended matter of about 0.005 to 0.5 μm, and the suspended matter in this region is mostly various colloids, especially colloidal silica is also suitable for chemicals. It does not fall off even with strong and simple chemical cleaning, so it accumulates on the micropores and film surface with the passage of water. Therefore, the filtration performance of the hollow fiber membrane module gradually decreases. For this reason, coagulant treatment as a pretreatment has begun to be carried out in some devices.However, coagulant treatment can take sufficient stagnant time for floc formation just by adding the coagulant immediately before the single module. Since it is difficult, it is common to use a flocculant dropping tank, a floc forming tank, and the like, and there is a treatment effect, but the apparatus becomes large, so a simpler means has been required. In addition, when the filtration performance deteriorates, the membrane surface may be cleaned with a chemical solution to remove deposits, but sufficient cleaning cannot be obtained simply by pouring the chemical solution into the module and allowing it to stand and soak. In many cases, a simpler and more effective method for chemical cleaning has been demanded.

[0006]

The object of the present invention is to provide a hollow fiber membrane module containing a large number of porous hollow fiber membrane bundles, a module container for housing the module, and a liquid to be treated in the module. A hollow fiber membrane module filtration device having a liquid feed pump for supplying, a liquid medicine inlet for injecting a liquid medicine into the module, and a liquid medicine pump,
A bypass line is provided between a part of the hollow fiber membrane module and a feed water line for supplying a liquid to be treated to the hollow fiber membrane module, and a chemical solution inlet is provided on the bypass line. It is basically achieved by a hollow fiber membrane module filtration device.

[0007]

The embodiment relating to the present invention is shown in FIGS. 1 and 2, but the present invention is not limited thereto. A conventional technique is shown in FIG.

First, a conventional hollow fiber membrane module filtration device will be described with reference to FIG.

The feed water to be filtered is guided by a pump 8 to a porous hollow fiber filtration membrane module (hereinafter referred to as a hollow fiber membrane module) 15 where the filtration treatment is performed. In the hollow fiber membrane module, the feed water is filtered through innumerable fine pores open on the surface of the hollow fiber membrane, and clear water from which SS components, fine particles, dust, bacteria, etc. have been removed permeates into the hollow fiber membrane. , Filtered water is taken out from the filtered water outlet 19. In the filtration of the hollow fiber membrane module, the larger the raw water pressure is, the larger the amount of filtered water is, but with the passage of filtration time, the SS components, fine particles, etc. adhere to the membrane surface, and colloids smaller than micropores are deposited in the micropores. It is usual that the hollow fiber membrane is clogged more or less and the amount of filtered water per the same pressure gradually decreases. Therefore, in order to continue to use the hollow fiber membrane module for a long period of time, at a suitable time when the clogging of the hollow fiber membrane has progressed and the amount of filtered water has decreased, a cleaning operation such as air bubbling is performed to prevent clogging. Means can be taken to restore the filtered water volume of the hollow fiber membrane to a level close to the previous level.

The method of using the hollow fiber membrane module is not limited, and it can be set according to the wishes of the user. As an example of the operating method, an operating method in which the amount of filtered water is changed by keeping the pressure constant, a method of operating by keeping the amount of filtered water constant while automatically or manually controlling the pressure, a pressure by connecting a module to an appropriate supply water source, It is possible to raise the method such as driving the temperature as it is.

In the apparatus of FIG. 3, if the decrease in the filtration amount and the increase in the supply pressure become noticeable, cleaning is performed by air bubbling. In this case, first supply water inlet valve 9
Is closed and the air vent valve 17 is opened. The cleaning air supply valve 14 is opened to start air bubbling, and after cleaning for a certain period of time, the drain valve 11 is opened to drain the cleaning liquid and then closed. In a long-term view, the amount of filtered water gradually decreases compared to the initial amount of filtered water only by the washing operation by the air bubbling due to the clogging of the fine pores of the membrane due to the colloid.

The inventors of the present invention have conducted extensive studies on a method for more reliably recovering the filtration performance before clogging, based on the method for cleaning the hollow fiber membrane module.
The present invention has been found.

The hollow fiber membrane module filtration device of the present invention will be described with reference to FIG.

In the present invention, the feed line bypass line connection port 2 provided at an arbitrary position on the feed water line 1 and upstream of the feed water pump 8, that is, at the suction side of the pump, and at an arbitrary position of the hollow fiber membrane module. The chemical liquid supply port 5 is provided on the provided hollow fiber membrane module side bypass line. When a coagulant is added to prevent a decrease in the amount of filtered water in the module, the coagulant is added from the chemical liquid injection port 5 provided on the bypass line. The supply water is pumped from the supply water line 1 by the operation of the supply pump 8 and supplied into the container of the hollow fiber membrane module 15, and a part of the supply water is taken out from the filtered water outlet 19 as filtered water, while a part of the supplied water is The hollow fiber membrane module side bypass line connection port 18 passes through the bypass line and is returned to the upstream side of the supply pump 8. For this reason, the flocculant added from the chemical liquid inlet 5 is circulated between the hollow fiber membrane module 15 and the bypass line and the supply pump 8 so that sufficient retention time is obtained and thus flocs are sufficiently formed to cause flocculation. The effect is enhanced.

The effect of the coagulation by the coagulant has a great influence on the hollow fiber membrane module. Colloids that are the same as or smaller than the micropores that are expected to be clogged in the micropores of the raw water supply can be flocculated by flocculation to be larger than the micropores of the membrane. By making the residence time necessary for agglomeration sufficient, colloids that have entered and accumulated in the micropores of the film and were the cause of clogging can be made much larger than the micropores of the film. It is possible to remove it sufficiently without clogging. In addition, since it is in a floc state and is deposited on the film surface in a bulky manner, the pressure loss due to the deposit is reduced and the pressure increase rate due to clogging is also reduced, so that the number of cleanings can be reduced. In addition, depending on the type of coagulant and the type of raw water, there may be a case where the residence time is not particularly required. At this time, the switching valve 6 on the bypass line
By appropriately switching 61, the coagulant added from the chemical liquid injection port 5 may be directly added to the supply line side bypass line connection port 2 or the hollow fiber membrane module side bypass line connection port. From the chemical solution inlet 5, not only a coagulant, but also a surfactant for improving cleaning efficiency during air bubbling, an acid for cleaning inorganic salts such as iron rust, microorganisms, and an alkali for cleaning proteins and the like. Can be added. Also at this time, it is possible to decide whether to circulate by the bypass line or to directly inject, depending on the chemical solution to be added. Further, in the present invention, when the cleaning liquid is discharged, the amount of the waste liquid is the amount of the liquid medicine for the hollow fiber membrane module, so that there is an advantage that the amount of the waste liquid medicine is not required. In addition, as shown in FIG.
As shown in (3), it is entirely acceptable to provide a plurality of chemical liquid injection ports and injection pumps for injection on the bypass line.

As the aggregating agent, a general-purpose aggregating agent can be used, and polyaluminum chloride, aluminum sulfate, polyferric sulfate, ferrous sulfate, ferric sulfate, ferric chloride, sodium aluminate, activated silica. Although acids and various polymer flocculants can be used, polyaluminum chloride and ferric sulfate, which have a high flocculating effect, are preferably used because they have the effects of decreasing the rate of increase in supply pressure and excellent cleaning recovery. Although the concentration of the coagulant varies depending on the raw water, it is usually about 0.1 to 100 ppm, but preferably 1 to 10 ppm is recommended from the viewpoint of effect and economy.

The hollow fiber membrane module of the present invention may be of any type as long as it uses a bundle of porous hollow fiber membranes as a filtering material. As an example of the preferable shape of the hollow fiber membrane module, after sealing both ends or one end of a bundle of a large number of hollow fiber membranes with an adhesive, the hollow fiber membrane is opened by cutting one end or both ends of the adhesive seal part. There is a structure in which the hollow fiber membrane element perforated is housed inside the container as an integrated type or a built-in type. Further, one or more modules having the above-mentioned structure may be housed in a container.

It is desirable to attach a check valve to the bypass line used in the present invention, because the pressure of the supply water may be increased in the bypass line leading to the supply water pipe and the liquid may flow back to the chemical liquid pipe. The material of the check valve is not particularly limited as long as it is a material that can withstand a chemical liquid such as a flocculant, an acid or an alkali, but preferably stainless steel, polypropylene, polyethylene or the like can be used.

The hollow fiber membrane material constituting the hollow fiber membrane module used in the present invention is not particularly limited as long as it is a porous hollow fiber membrane, but polyethylene, polypropylene,
Polysulfone, polyether sulfone, polyvinyl alcohol, cellulose acetate, polyacrylonitrile, and other materials can be selected. Among these, a particularly preferable hollow fiber membrane material is a hollow fiber membrane made of a polymer containing at least one component of acrylonitrile. The most preferable acrylonitrile-based polymer is at least 50 mol or more of acrylonitrile, preferably 60 mol% or more and 50% or less of one or more vinyl compounds having copolymerizability with the acrylonitrile. Is an acrylonitrile-based copolymer composed of 0 to 40 mol%. Further, it may be a mixture of two or more kinds of these acrylonitrile-based polymers and further other polymers. The vinyl compound may be a known compound having copolymerizability with acrylonitrile, and is not particularly limited, but preferable copolymer components include acrylic acid, itaconic acid, methyl acrylate, methyl methacrylate, Examples thereof include vinyl acetate, sodium allyl sulfonate, sodium p-styrene sulfonate, and the like.

The next preferred hollow fiber membrane material is composed of one or more olefin polymers such as ethylene propylene or 4-methylpentene, and has a hollow fiber membrane shape with a major axis of 0.1 to 1 μm on the surface. Minor axis 0.
Those having slit-shaped pores of 05 to 0.5 μm are suitable.

[0021]

【Example】

Example 1 Feed water pump, chemical injection pump, hollow fiber membrane module,
A hollow fiber membrane filtration device shown in FIG. 1 equipped with a module container, a bypass line and a chemical solution inlet was manufactured. As a hollow fiber membrane module, outer diameter 450μm, inner diameter 320μ
m, a hollow fiber membrane composed of 10,000 polyacrylonitrile porous hollow fiber membranes having an average pore size of 0.01 μm, is fixed at both ends with an epoxy adhesive, and then one end of the adhesive fixing portion is cut off to form a hollow fiber membrane. A hollow fiber membrane module having a diameter of 12 cm and a length of 100 cm stored in the container is used. Using this device, the lake water of Lake Biwa was pumped up by a feed water pump and supplied to the hollow fiber membrane module for long-term continuous filtration. In the filtration process, the flow rate is adjusted to 10 liters / minute by automatic adjustment of the pressure, and even if the module is clogged, the pressure increases according to the degree and the predetermined flow rate is maintained. ing. As a pretreatment for filtration, 10 pp of coagulant (polyaluminum chloride), which is almost equivalent to the colloid concentration pre-analyzed from the chemical injection port in the middle of the lake water supply pipe
It was injected from a tank with a chemical injection pump so as to be m.
The circulation rate of the bypass line was adjusted to be 2 liters / minute. At the start of the operation, the pressure at the entrance of the module was 0.30 kg / cm ² G, but after the start of the operation, the pressure gradually started to rise and increased to 1.15 kg / cm ² G in 24 hours. Therefore, stop the feed water pump, close the feed water inlet cock, open the air valve, and set the bubbling to 10
It was carried out for a minute and a washing operation was performed. After the washing was completed, the drain cock was opened, and when the washing water was exhausted, the feed water inlet cock was opened to start normal operation. At this time, the inlet pressure is 0.30kg
/ Cm ² G.

Example 2 When washing a hollow fiber membrane module filtered under the same apparatus and operating conditions as in Example 1, an aqueous citric acid solution was dripped from a chemical solution injection port installed on the upper part of the hollow fiber membrane module. Meanwhile, air bubbling was carried out for 10 minutes to carry out chemical cleaning. After the washing was completed, the drain cock was opened and the washing water was collected in a separate container for treatment. Supply pressure at the start of operation is 0.30 kg /
What was cm ² G was 1.15 after water treatment for 24 hours.
It rose to kg / cm ² G, but recovered to the same 0.30 kg / cm ² G and at the start of operation by chemical cleaning.

Comparative Example 1 A hollow fiber membrane module, which was operated under the same apparatus and operating conditions as in Examples 1 and 2 except that a bypass line was not installed, was washed by air bubbling for 10 minutes. The chemical injection port was designed to be added directly before the supply pump, and the residence time of the coagulant was 60 seconds or less. The supply pressure at the start of operation was 0.30 kg / cm ² G, but was 2
The water flow rate increased to 1.15 kg / cm ² G after 4 hours of water treatment, but only 0.32 kg / cm ² G was recovered by air bubbling cleaning.

[0024]

Industrial Applicability According to the present invention, chemicals such as a flocculant can be efficiently added, and the hollow fiber membrane filtering apparatus can be operated for a long period of time without lowering the filtering performance.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a filtration device in which a chemical solution inlet of the present invention is installed.

FIG. 2 is a schematic configuration diagram of a filtration device having a plurality of chemical liquid injection ports according to the present invention.

FIG. 3 is a schematic configuration diagram of a conventional filtration device.

[Explanation of symbols]

 1: Supply water line piping 2: Supply line side bypass line connection port 3: Chemical solution tank 31: Chemical solution tank 4: Chemical solution injection pump 41: Chemical solution injection pump 5: Chemical solution injection port 51: Chemical solution injection port 6: Switching valve 61: Switching Valve 7: Check valve 8: Supply water pump 9: Supply water inlet valve 10: Raw water supply port 11: Drain valve 12: Drain port 13: Air supply port 14: Air supply valve 15: Hollow fiber membrane module 16: Air vent Port 17: Air bleeding valve 18: Hollow fiber membrane module side bypass line connection port 19: Filtered water outlet 20: Filtered water pipe

Claims (6)

[Claims] 1. A hollow fiber membrane module containing a large number of porous hollow fiber membrane bundles, a liquid feed pump for supplying a liquid to be treated to the module, and a liquid medicine inlet for injecting a liquid medicine into the module. A hollow fiber membrane module filtering device having: a bypass line provided between a part of the hollow fiber membrane module and a feed water line for supplying a liquid to be treated to the hollow fiber membrane module. A hollow fiber membrane module filtration device, characterized in that a chemical solution inlet is provided on the top. 2. The method according to claim 1, wherein a valve is provided on the bypass line between the chemical solution inlet and the hollow fiber membrane module or on the bypass line between the chemical solution inlet and the feed water line to enable selection of the flow direction of the chemical solution. The hollow fiber membrane module filtration device described. 3. The hollow fiber membrane module filtration device according to claim 1, wherein a bypass line connection port on the feed water line is provided on the upstream side of the liquid feed pump. 4. The hollow fiber membrane module filtration device according to claim 1, wherein a check valve is provided on the bypass line between the bypass line connection port on the feed water line and the chemical liquid injection port. 5. The hollow fiber membrane module according to claim 1, wherein the hollow fiber membrane forming the porous hollow fiber membrane is made of a polymer containing at least one component of acrylonitrile or an olefin polymer. Filtration device. 6. A hollow fiber membrane module containing a large number of porous hollow fiber membrane bundles, a liquid feed pump for supplying a liquid to be treated to the module, and a liquid medicine inlet for injecting a liquid medicine into the module. A hollow fiber membrane module filtering device having: a bypass line provided between a part of the hollow fiber membrane module and a feed water line for supplying a liquid to be treated to the hollow fiber membrane module. A filtration method using a hollow fiber membrane module filtration device, characterized in that a chemical injection port is provided on the top.