JP2008237980A - Membrane separation apparatus for drinking water production, and its operation method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a membrane separation apparatus for drinking water production which has a structure scarcely allowing a chemical to remain in piping although chemical washing and back washing are performed in a relatively short term using a chlorine type chemical with low concentration, and to provide an operation method of the membrane separation apparatus for drinking water production. <P>SOLUTION: In the drinking water production equipment having the membrane separation apparatus comprised of a plurality of membrane modules, a water stop valve is dually installed at the pathway besides the drainage pathway among the pathways connected with the membrane module and a drain valve is installed when the chemical washing by the chemical is performed. According to the structure, the chemical remains in the piping and the chemical is difficult to incorporate into the membrane module permeate after the chemical washing and backwashing are performed. Further, a residual chlorine concentration meter to constantly measure the chlorine concentration in the permeate is installed at the permeate pathway of each membrane module. Thus, the safety of drinking water is assured by stopping the membrane module when the abnormal value of the residual chlorine concentration is measured by the residual chlorine concentration meter. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a drinking water production membrane separation device that periodically performs chemical cleaning and reverse cleaning of a membrane separation device, and has a structure that can effectively prevent contamination of drinking water by a chemical solution. Relates to the device. The present invention also relates to a method of operating such a membrane separator for drinking water production.

  Microfiltration membranes (MF membranes) or ultrafiltration membranes (UF membranes) have high performance for removing fine particles, etc., so solid-liquid separation means that separates fine solids, suspended substances, microorganisms, etc. contained in raw water Used as. In addition, the MF membrane separation device incorporating the MF membrane or the UF membrane separation device incorporating the UF membrane is easy to operate, and is widely used in the fields of medicine, chemistry, semiconductors, and the like in industry. .

  The MF membrane separator or UF membrane separator is usually composed of a plurality of MF membrane modules or UF membrane modules. In each module, the principle is to separate and remove fine solids in raw water using an MF membrane or UF membrane having fine filtration holes. If filtration is continued, the raw water side (primary side) ) Is formed on the membrane surface. When this filtration cake layer is formed, the filtration resistance increases, and the filtration capacity of the MF membrane separation device or UF membrane separation device decreases. Therefore, the cake layer in the membrane module is removed every certain filtration time. Perform membrane cleaning.

  For cleaning the MF membrane or UF membrane, the cleaning water flows from the permeate side (secondary side) of the membrane and the filter cake layer is peeled and removed (physical cleaning), and sodium hypochlorite is added to the cleaning water. In addition, a method (chemical solution cleaning) in which sodium hydroxide is added and chemically removed is also known. By performing such regular membrane cleaning, contamination of the MF membrane or UF membrane is prevented.

  For example, the MF membrane or UF membrane module is made to flow back chlorine water from the secondary side to the primary side of the membrane, hold it for a predetermined time, and then discharge the water staying on the primary side of the membrane. A cleaning method is disclosed in Patent Document 1.

  In addition, after introducing cleaning water containing acid or alkaline chemical components or oxidizing chemical components such as ozone into the filtered water side of the membrane filtration device and infiltrating the membrane for a predetermined time, reverse the washing water containing no chemical components. Patent Document 2 discloses a backwashing method of a membrane filtration device characterized by pressure washing.

Moreover, in a membrane module using a hollow fiber type membrane filter module, raw water filtration and backwashing are made into one cycle, a pause process is provided between the filtration process and the backwash process, and the drug is filtered before transition to the pause process. Patent Document 3 discloses a membrane filtration device characterized by being injected into the raw water flow path side.
Japanese Patent Laid-Open No. 10-15365 JP 2002-52321 A JP 2001-170456 A

  A membrane separation device such as an MF membrane or UF membrane separation device has a reduced filtration capacity due to organic contamination when it is continuously used. Therefore, as in the membrane cleaning methods disclosed in Patent Documents 1 to 3, hypochlorous acid is used. Generally, the MF membrane or the like in the membrane module is washed with a chemical solution using a salt or the like. For example, when a PVDF (polyvinylidene fluoride) membrane is used as the MF membrane or UF membrane, 0.2% to 0.5% (2000 ppm to 5000 ppm) sodium hypochlorite (1% water) is usually used for chemical cleaning. An aqueous solution (containing sodium oxide) was circulated for about 7 to 8 hours to wash the chemical solution, and then the chemical solution was discharged to neutralize the alkali with an acid and further washed with water.

  However, if membrane cleaning is performed for a long time in this way, the permeated water cannot be obtained in the membrane module being cleaned, and thus the amount of drinking water produced decreases until the cleaning is completed. Also, since high concentrations of hypochlorite, etc. are used, it is necessary to avoid the chemical solution from remaining in the pipe as much as possible. It took time.

  The present invention performs chemical cleaning in a relatively short period of time using a chemical solution at a low concentration, but has a structure in which the chemical solution is unlikely to remain in the pipe, and such membrane separation for drinking water production. The object is to provide a method for operating the apparatus.

  In the drinking water production apparatus having a membrane separation device composed of a plurality of membrane modules, the present inventors, when performing chemical cleaning with a chemical solution, stop water valves in routes other than the drainage route among the routes connected to the membrane module. It is found that the chemical solution remains in the pipe after the chemical solution cleaning and the chemical solution is less likely to be mixed into the membrane module permeated water. The invention has been completed.

Specifically, the present invention
A membrane separation device comprising a plurality of membrane modules;
A chemical path for supplying the chemical from the raw water side of the membrane module;
A backwash path for supplying backwash water from the permeate side of the membrane module;
A drinking water production membrane separator for supplying a chemical solution to a chemical solution path and retaining it for a predetermined time,
A first water stop valve and a second stop valve are respectively provided in a raw water path for supplying raw water to the membrane module, a permeated water path for flowing out the permeated water of the membrane module as drinking water, and a raw water side drainage path and a permeated water side drainage path of the membrane module. Have a water valve,
The present invention relates to a drinking water producing membrane separation device having a drain path provided with a drain valve between a first water stop valve and a second water stop valve (Claim 1).

The present invention also provides:
A membrane separation device comprising a plurality of membrane modules;
A chemical path for supplying the chemical from the raw water side of the membrane module;
A backwash path for supplying backwash water from the permeate side of the membrane module;
In a drinking water production membrane separation apparatus for supplying a chemical solution to a chemical solution path and retaining it for a predetermined time,
A first water stop valve and a second water stop valve are installed in each of the raw water path for supplying raw water to the membrane module, the permeated water path for discharging the permeated water of the membrane module, and the raw water side and the permeated water side drainage path of the membrane module. ,
A drain path provided with a drain valve is installed between the first water stop valve and the second water stop valve. The present invention relates to a method for operating a membrane separator for drinking water production (Claim 5).

  In the membrane separation apparatus that periodically cleans the membrane module with chemical solution, each membrane module has a raw water path for supplying raw water to the membrane module, a permeated water path for discharging the permeated water of the membrane module, a raw water side drainage path for the membrane module, A permeate-side drainage path for discharging drainage on the secondary side of the membrane module after chemical cleaning is connected. Therefore, if two water stop valves, a first water stop valve and a second water stop valve, are installed in these paths, and a drain valve is provided between them, the chemical liquid in the pipe is discharged after the chemical liquid cleaning. It is easy to reduce the amount of the chemical solution remaining in the pipe. Therefore, it is possible to prevent chemical solution from being mixed into the membrane treated water (drinking water).

  When the chemical solution is a chlorine-based chemical solution, and a chlorine concentration meter that constantly measures the chlorine concentration in the permeated water is installed in the permeate passage of each membrane module, and an abnormal value of the chlorine concentration is measured by the chlorine concentration meter Is preferably configured such that the first water stop valve and the second water stop valve of the permeate path of the membrane module in which the abnormal value is measured are closed (Claims 2 and 6).

  When a chlorine concentration meter is installed in the permeate path of each membrane module (the path for supplying permeate to drinking water storage facilities such as water purification tanks and water ponds), and the residual chlorine concentration in the permeate is abnormal Reduces the risk of mixing chemicals into drinking water by closing the first and second stop valves in the permeate path to block outflow of permeate from the membrane module where abnormal values are measured Is possible.

  Preferably, the chemical solution is a hypochlorite aqueous solution having a concentration of 5 ppm or more and 1000 ppm or less, and the chemical solution is preferably supplied to the chemical solution supply path once every 5 to 15 days. Hypochlorite (most preferred sodium hypochlorite) is suitable for controlling organic contamination, but if chemical cleaning is performed about once a week, organic contamination will progress. This can be effectively prevented and the time required for cleaning the chemical solution can be shortened. The risk of mixing chemicals into drinking water is also low because of its low concentration compared to conventional chemical cleaning.

  The membrane module is preferably a microfiltration membrane module or an ultrafiltration membrane module.

  According to the membrane separator for drinking water production and the operation method thereof of the present invention, it is possible to prevent clogging of the membrane and stably produce permeated water (drinking water) for a long period of time, and membrane treated water. It is possible to prevent chemical liquid from being mixed into (drinking water). In addition, when a chlorine-based chemical solution is used and an automatic residual chlorine concentration meter is installed in the permeated water path, the risk of chemical solution mixing into the permeated water can be reliably reduced.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings as appropriate. The present invention is not limited to these.

(Normal operation)
The schematic block diagram of the membrane separator for drinking water manufacture of this invention is shown in FIG. The raw water in the raw water tank 1 is supplied to a plurality of raw water passages and supplied to a plurality of membrane modules to produce permeated water. Here, the raw water passage 1 will be described. The raw water supplied to the raw water path 1 is boosted by the raw water pump 2a and supplied to the primary side (raw water side) of the membrane module 6. At this time, the first raw water valve 3a (first water stop valve) and the second raw water valve 3b (second water stop valve) installed in the raw water path are open, and the raw water drain valve 4 of the drain path 5 is closed. ing.

  The permeated water of the membrane module flows out to the permeated water path connected to the secondary side (permeated water side) of the membrane module 6. At this time, the first permeate valve 7a (first stop valve) and the second permeate valve 7b (second stop valve) installed in the permeate path are open, and the drain valve 8 of the drain path 9 is open. Is closed. An automatic residual chlorine concentration meter 10 is installed downstream of the second permeated water valve 7b and constantly monitors the residual chlorine concentration in the permeated water. When the residual chlorine concentration in the permeated water exceeds a set value (appropriately setting the residual chlorine concentration to about 1.0 ppm), the automatic residual chlorine concentration meter 10 causes the first permeated water valve 7a and the second permeated water valve 7b to be turned on. Designed to close. The other processing paths such as the raw water path 2 and the raw water path 3 have the same configuration as the raw water path 1. If the residual chlorine concentration is less than the set value, the permeated water of each membrane module is supplied to a water storage facility such as a water storage tank and used as drinking water.

  During normal operation, the water stop valves and drain valves of the permeate water drainage path and backwash path are all closed. Further, the chemical liquid inlet valve 13 of the chemical liquid path is also closed.

(Chemical cleaning and chemical discharge)
Next, the case where the membrane module 6 is subjected to chemical cleaning and chemical discharging (water cleaning) will be described. First, an aqueous solution (chlorine chemical solution) of a chlorinated drug such as sodium hypochlorite is prepared in the chemical solution tank 11. The concentration of the chlorinated drug is preferably 5 ppm or more and 1000 ppm or less from the viewpoint of securing the film cleaning effect and easy cleaning after the chemical cleaning. It is more preferable to add an alkaline substance such as sodium hydroxide or potassium hydroxide so as to be about 0.1% by weight.

  The first raw water valve 3a and the second raw water valve 3b, the first permeate water valve 7a and the second permeate water valve 7b are closed. At this time, the first permeate-side drain valve 16a (first stop valve) and the second permeate-side drain valve 16b (second stop valve) installed in the permeate-side drain path and the backwash path are installed. The first backwash valve 20a (first stop valve), the second backwash valve 20b (second stop valve), and the drain valve 17 are also closed. Then, the raw water pump 2a is stopped.

  The drain valve 14 installed in the membrane module drainage path 15 is opened, and the raw water in the membrane module 6 is drained. After draining is completed, the drain valve 14 is closed. The chemical liquid pump 12 is activated, the chemical liquid inlet valve 13 is opened, and the chlorinated chemical liquid in the chemical liquid tank 11 is supplied from the chemical liquid path to the primary side of the membrane module 6. At this time, the permeate-side drainage path drain valve 17 of the permeate-side drainage path is closed, and the first permeate-side drainage valve 16a and the second permeate-side drainage valve 16b are opened. The chemical solution passes through the membrane 6a in the membrane module, moves from the primary side to the secondary side, is stored (filled) in the membrane module 6, and when the chemical solution is filled in the membrane module 6, the chemical solution pump 12 is stopped. The second permeated water side drain valve 16b is closed, and the membrane 6a is chemically cleaned.

  In the membrane separator for drinking water production of the present invention, in order to suppress organic contamination of the membrane 6a to the minimum and shorten the chemical cleaning time, it is 5-15 by using a low concentration chlorine based chemical solution of 5 ppm to 1000 ppm. It is preferable to perform chemical cleaning once a day, specifically about once a week. In addition, it is preferable to store a chlorine-type chemical | medical solution in the membrane module 6 for about 1 hour-24 hours. In particular, chemical cleaning is performed by storing a low concentration chlorinated chemical solution with a concentration of 50 to 500 ppm in the membrane module 6 once every 6 to 8 hours for 1 to 5 hours. It is more preferable because the chemical cost can be reduced and the chemical cleaning time can be shortened while ensuring.

  After completion of the chemical cleaning with the low-concentration chemical solution, the drain valve 14 and the drain valve 17 are opened, and the chemical solution in the membrane module 6 is drained to the drain paths 15 and 18. Thereafter, the chemical solution is processed by a drainage facility.

  Next, the chemical solution is discharged (washed with water). First, the chemical solution inlet valve 13, the first raw water valve 3a and the second raw water valve 3b of the raw water path are closed, and the raw water drain valve 4 is opened. Wash water supplied to the backwash path from a wash water source (may be a facility that stores permeate from the membrane separator, but can supply wash water of the same quality as the permeate) The pressure is increased by the backwash pump 19. The first backwash valve 20 a and the second backwash valve 20 b are opened, and wash water is supplied to the secondary side of the membrane module 6. At this time, the membrane 6 a in the membrane module is washed with water, and the wash water that has flowed to the primary side of the membrane module 6 is drained to the drainage path through the drainage drain valve 14.

  About the washing waste water drained to the drainage channel 15, it is desirable to finish the water washing if the residual chlorine concentration is below a predetermined value (approx. 0.5 ppm is appropriate) or less. First, the second backwash drain valve 20b is closed and the backwash pump 19 is stopped. The backwash path drain valve 21 is opened, and the wash water in the backwash path is drained. The drain valve 14 is also closed. Next, the raw water drain valve 4 is closed, the second raw water valve 3b, the first permeated water side drain valve 16a and the second permeated water side drain valve 16b are opened, and the permeated water side drain path drain valve 17 is closed. The raw water pump 2a is restarted, the first raw water valve 3a is opened, and the raw water path 1 is washed. If it is confirmed that the residual chlorine concentration of the drainage in the permeate side drainage channel is below the specified value (approx. 0.5ppm is appropriate), close all valves and stop the raw water pump.

(Resumption of normal operation)
Next, the first permeated water valve 7 a and the drain valve 8 are opened while the second permeated water valve 7 b of the permeated water path is closed, and the permeated water of the membrane module 6 is drained to the drain path 9. At this time, the permeate-side drainage path to the first permeate valve 7a drainage valve is washed with the permeate of the membrane module 6. When the chlorine concentration of the drainage water in the drain passage 9 becomes a predetermined value (approx. 0.5 ppm is appropriate) or less, the drain valve 8 is closed and the second permeated water valve 7b is opened.

  An automatic residual chlorine concentration meter 10 is installed downstream of the second permeated water valve 7b, and continuously measures the chlorine concentration in the permeated water of the membrane module 6 supplied to the water storage facility. Chlorine chemicals used for chemical cleaning may contain harmful substances such as sodium hydroxide, so all chemicals remaining in the piping are discharged by water cleaning after chemical cleaning, raw water and permeated water cleaning. There is a need. In the membrane separator for drinking water production of the present invention, the pipe connected to the membrane module 6 can be thoroughly cleaned by the double water stop valve and the drain valve installed between them. By measuring the chlorine concentration with the automatic residual chlorine concentration meter 10, a final safety check is made before being supplied to the water storage facility.

  When the automatic residual chlorine concentration meter measures that the chlorine concentration in the permeated water is an abnormal value equal to or higher than a predetermined value (approx. 1.0 ppm is appropriate), at least one of the first permeated water valve 7a and the second permeated water valve 7b Is preferably configured to automatically close. At this time, the raw water pump 2a is also preferably configured to automatically stop.

  The raw water path 2 and the like have the same configuration as that of the raw water path 1, and the permeated water from the membrane module in which the permeated water residual chlorine concentration is abnormal is prevented from being supplied to the water storage facility. In addition, since only the water stop valve of the permeate path of the membrane module in which an abnormality is observed in the residual chlorine concentration in the permeated water among the plurality of membrane modules is closed, the production of permeated water may be continued in other membrane modules. Is possible.

[Example]
With the membrane separator for drinking water production of the present invention consisting of four MF membrane (made of polyvinylidene fluoride (PVDF)) modules, the well water in four shallow wells was used as raw water and the MF membrane permeated water was produced as drinking water. The processing conditions of this membrane separator for drinking water production were as shown in Table 1.

  In this example, as the physical cleaning during normal operation, as shown in Table 1, reverse cleaning was performed once every 30 minutes. For physical cleaning, MF membrane module permeate with a hypochlorous acid concentration of 3 ppm was used, and air scrubbing was also performed at the time of reverse cleaning. Moreover, 500 ppm sodium hypochlorite was used for the chemical | medical solution washing | cleaning by a low concentration chemical | medical solution, and it was immersed for 1 hour once a week. The chemical cleaning of each MF membrane module with a low concentration chemical was sequentially performed with a 24-hour time lag.

  Production of MF membrane permeated water was carried out for 11 months from February 2006. Initially, only physical cleaning (reverse cleaning) was performed, and chemical cleaning with a low concentration chemical solution was not performed. Fig. 2 shows the changes in the transmembrane pressure difference of the MF membrane module over the past 11 months (No. 1 value among the 4 systems, and the corrected transmembrane pressure value is the value corrected to the pressure at 25 ° C (kPa)). Show. The normal raw water turbidity was about 0.1 degree, and permeated water could be produced stably for two months until April.

  However, on April 12 and 13, 2006, the raw water turbidity increased to about 1 degree due to heavy rain. This increase in turbidity increased the transmembrane pressure from 70 kPa to about 150 kPa in two days. By repeatedly performing physical cleaning (back cleaning) once every 30 minutes, a temporary decrease in the transmembrane pressure difference was observed, but after the physical cleaning, the transmembrane pressure difference started to increase in a short time. It was.

  Therefore, in addition to physical cleaning on April 14, chemical cleaning with a low concentration chemical was performed, and thereafter, chemical cleaning with a low concentration chemical was performed once a week. As a result, the transmembrane pressure difference decreased to a level before April 11, and stable operation could be continued for 8 months thereafter.

  INDUSTRIAL APPLICABILITY The membrane separation apparatus for producing drinking water and the method for operating the same of the present invention are useful in the environment and hygiene fields as a technique for using membrane permeated water as drinking water.

It is a schematic block diagram of the membrane separator for drinking water manufacture of this invention. It is the graph showing the change of the average value of the transmembrane differential pressure | voltage of the MF membrane module in an Example.

Explanation of symbols

1: Raw water tank 2a-2c: Raw water pump 3a: First raw water valve 3b: Second raw water valve 4: Raw water drain valve 5, 9, 18, 22: Drain path 6: Membrane module 6a: Membrane 7a: First permeate Valve 7b: Second permeated water valve 8, 17, 21: Drain valve 10: Automatic chlorine concentration meter 11: Chemical liquid tank 12: Chemical liquid pump 13: Chemical liquid inlet valve 14: Drain valve 15: Drainage path 16a: First permeate side Drain valve 16b: second permeated water side drain valve 19: backwash pump 20a: first backwash valve 20b: second backwash valve

Claims (8)

A membrane separation device comprising a plurality of membrane modules;
A chemical path for supplying the chemical from the raw water side of the membrane module;
A backwash path for supplying backwash water from the permeate side of the membrane module;
A drinking water production membrane separator for supplying a chemical solution to a chemical solution path and retaining it for a predetermined time,
A first water stop valve and a second stop valve are respectively provided in a raw water path for supplying raw water to the membrane module, a permeated water path for flowing out the permeated water of the membrane module as drinking water, and a raw water side drainage path and a permeated water side drainage path of the membrane module. Have a water valve,
A drinking water producing membrane separation apparatus comprising a drain path having a drain valve between a first water stop valve and a second water stop valve. The chemical solution is a chlorine-based chemical solution, and a chlorine concentration meter that constantly measures the chlorine concentration in the permeated water is installed in the permeate path of each membrane module,
2. The first stop valve and the second stop valve of the permeate passage of the membrane module where the abnormal value is measured are closed when an abnormal value of the chlorine concentration is measured by the chlorine concentration meter. Membrane separator for drinking water production.   The membrane separator for drinking water production according to claim 1 or 2, wherein the chemical solution is a hypochlorite aqueous solution having a concentration of 5 ppm or more and 1000 ppm or less, and the chemical solution is supplied to the chemical solution supply path once every 5 to 15 days.   The membrane separator for drinking water production according to any one of claims 1 to 3, wherein the membrane module is a microfiltration membrane module or an ultrafiltration membrane module. A membrane separation device comprising a plurality of membrane modules;
A chemical path for supplying the chemical from the raw water side of the membrane module;
A backwash path for supplying backwash water from the permeate side of the membrane module;
In a drinking water production membrane separation apparatus for supplying a chemical solution to a chemical solution path and retaining it for a predetermined time,
A first water stop valve and a second water stop valve are installed in each of the raw water path for supplying raw water to the membrane module, the permeated water path for discharging the permeated water of the membrane module, and the raw water side and the permeated water side drainage path of the membrane module. ,
A method for operating a membrane separator for drinking water production, wherein a drain path including a drain valve is installed between a first water stop valve and a second water stop valve. The chemical solution is a chlorine-based chemical solution, and a chlorine concentration meter that constantly measures the chlorine concentration in the permeated water is installed in the permeate path of each membrane module,
The first stop valve and the second stop valve of the permeate path of the membrane module in which the abnormal value is measured are closed when an abnormal value of the chlorine concentration is measured by the chlorine concentration meter. Method of the membrane separator for drinking water production of the present invention.   The operation of the membrane separator for drinking water production according to claim 5 or 6, wherein the chemical solution is a hypochlorite aqueous solution having a concentration of 5 ppm or more and 1000 ppm or less, and the chemical solution is supplied to the chemical solution supply path once every 5 to 15 days. Method.   The method for operating a membrane separator for drinking water production according to any one of claims 5 to 7, wherein the membrane module is a microfiltration membrane module or an ultrafiltration membrane module.

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