JP2007136300A - Membrane filtration apparatus and membrane module contamination detecting method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To surely detect trace of contaminant attached to a membrane module at an early stage. <P>SOLUTION: The membrane filtration apparatus comprising multiple external pressure type membrane modules removing contaminants in supplied raw water and a bubble supply means supplying bubbles to the raw water supply side of the external pressure type membrane modules, is provided with a bubble floating-up means provided connectedly to the raw water outlet side of the membrane module and floating up bubbles flowing in together with the raw water; a contaminant measuring means measuring contaminants floating up to the water surface by the bubble floating-up means; a contamination determining means determining the contamination degree of the membrane module based on the measured values outputted from the contaminant measuring means; and an output means displaying the determination results. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a membrane filtration device that filters and removes contaminants contained in raw water using a plurality of membrane modules, and more particularly to a technique for determining the contamination state of a membrane module.

In medium- and large-scale water purification plants where the treatment flow rate exceeds 5000 M ³ / day, water purification plants employing membrane filtration devices using membrane modules are increasing. At the same time, it is expected that the number of water purification plants that use surface water as raw water as well as underground water will increase.

  Compared to groundwater and underground water, surface water is more likely to cause water quality accidents where foreign substances such as oil and chemicals are mixed upstream. Therefore, the membrane module may be contaminated with water contaminants. When the film is contaminated, film clogging and film deterioration are accelerated. In addition, when the membrane is broken, the risk of contaminants flowing out into the filtered water increases.

  Conventionally, a membrane filtration apparatus often uses groundwater or underground water as raw water, and a technique relating to contamination by impurities in the raw water of the membrane module in the membrane filtration apparatus is not disclosed.

  As a method for detecting contamination due to impurities in the raw water of the membrane module, a method of detecting from filtered water, washing waste water, or raw water can be considered.

  A membrane filtration device is a device that separates and removes impurities (hereinafter referred to as contaminants) such as turbidity and microorganisms contained in raw water, and removes contaminants that are larger than the membrane opening diameter, that is, the membrane nominal diameter. Can be completely removed. However, even when the membrane is contaminated with contaminants, the filtered water is normal, so it is impossible to detect the contamination of the membrane module from the filtered water.

  In order to detect the water quality from the washing waste water, it is necessary to detect the pollutants separated from the membrane. A typical example of a cleaning method for separating contaminants from a membrane is an air scrubbing device using air and water. Patent Document 1 discloses a method of performing chemical scrubbing while raising and lowering the water level by performing air scrubbing by filling the filtration side of the membrane module with air at atmospheric pressure or higher.

  On the other hand, as a method for detecting water pollution from raw water, an oil film detection apparatus for detecting oil pollution, which accounts for the majority of water quality accidents, is known. As the oil film detection device, for the oil film on the water surface, a light reflection type oil film detector and an image monitoring device using a camera are mainly used. For oil in water, the emulsification / turbidity measurement method or ultraviolet absorption measurement method is mainly used.

  In Patent Document 2, oil in the surface or water is detected by the sensor unit, and the signal voltage from the sensor unit is divided into predetermined time segments, and the time period exceeding a predetermined threshold value in each time segment is disclosed. A method of determining an oil detection device that determines a ratio and outputs an alarm when the ratio is larger than a predetermined determination value is disclosed.

JP 2003-265935 A (pages 3 to 5, FIGS. 1 to 5) JP 2002-82054 A (6th page, FIGS. 1 to 3)

  The method disclosed in Patent Document 1 is a method for removing contaminants attached to the surface of a membrane using an air scrubbing device, and is not disclosed at all in terms of detecting the contaminants. Not applicable to substance detection.

  Moreover, since the conventional oil film detection apparatus detects oil content by floating a sensor or camera on the water surface, it is not suitable for detecting oil contamination in a membrane module having a small surface area. For example, when the technique of Patent Document 2 is applied to a membrane filtration device, an oil component is detected by adding signals exceeding a certain threshold. However, when the amount of contaminants adhering to the film is very small, it is difficult for the detection signal to exceed a certain threshold value, and an alarm may not be output. Therefore, it cannot be applied to a contaminant detection apparatus for a membrane module in which a minute amount of contaminants adhering to the membrane is a problem.

  Thus, in the detection of the membrane contaminants in the membrane filtration device, the amount of contaminants attached to each membrane module is very small and is difficult to detect by the sensor.

  In addition, use in special installation environments such as undulations and fluctuations in flow velocity is also described, but there is a risk that a large amount of oil may be erroneously detected as a small amount due to a sudden change in flow velocity.

  In addition, when a small amount of oil flows, there is also known a method of outputting an alarm when the total time of detected signals exceeds a threshold value. However, since the time when the signal for detecting the oil that has just flowed is output is totaled, it depends on the flow velocity of the oil, and it takes time until the total time of the signal exceeds the threshold.

  Thus, the method described in Patent Document 2 does not consider a method for detecting a small amount of oil at an early stage. For this reason, film contamination cannot be detected, response to chemical cleaning or the like is delayed, and the film life may be shortened. And the method of patent document 2 is a contamination detection method only with respect to an oil film.

  An object of the present invention is to reliably detect a trace amount of contaminants adhering in a membrane module at an early stage.

  The above problems include a plurality of external pressure membrane modules for removing contaminants in the supplied raw water, a bubble supply means for supplying bubbles to the raw water supply side of the plurality of external pressure membrane modules, and a raw water discharge of the membrane module. A bubble floating means that is connected to the side and floats on the liquid surface with the bubbles that flow in along with the raw water, and a pollutant measuring means that measures the contaminant floating on the surface of the water by the bubble floating means; This is solved by a membrane filtration device comprising a contamination determination unit that determines the degree of contamination of the membrane module based on a measurement value output from the contaminant measurement unit, and an output unit that displays the determination result. .

  According to the above configuration, since the bubbles are supplied to the raw water supply side of the external pressure membrane module, the contaminants detached from the external pressure membrane module adhere to the bubbles and flow into the bubble floating means together with the raw water. The bubbles flowing into the bubble floating means float on the liquid surface and disappear, but the contaminants attached to the bubbles remain on the liquid surface as the bubbles disappear. For this reason, as bubbles rise and disappear sequentially, contaminants accumulate on the liquid surface, that is, concentrate.

  This concentrated pollutant is measured by the pollutant measuring means, and the degree of contamination of the membrane module is determined based on the measurement value output from the pollutant measuring means. Therefore, even if there is a trace amount of contaminants attached to individual membrane modules, they are collected on the liquid surface, concentrated, and measured in a concentrated state. Even when the amount of contamination is very small, the degree of contamination can be detected.

  Further, by providing a defoaming means for eliminating the bubbles in the bubble floating means, the bubbles that have risen may be quickly extinguished to promote the collection of contaminants on the liquid surface. In this way, bubbles do not interfere with the measurement when the pollutant measuring means measures.

  In addition, water near the liquid surface of the bubble levitation means is continuously discharged through a pipe line, and the contaminant measurement means is arranged at a location away from the bubble levitation means to measure the contaminant on the flowing liquid surface. May be. In this way, it is not necessary to clean the contaminants concentrated in the bubble floating means.

  Note that the amount of bubbles supplied from the bubble supply means, the length of time for supplying the bubbles, and the timing are preferably controlled based on the output of the determination means. By controlling in this way, it is possible to accelerate the concentration rate of contaminants and shorten the detection time.

  According to the present invention, it is possible to detect a small amount of contaminants by forming the contaminant film by concentrating the contaminants attached to the external pressure membrane module on the liquid surface and performing detection. Therefore, there is an effect that even a small amount of contaminants can be detected early.

  Hereinafter, the backwashing mechanism of the membrane filtration apparatus using the external pressure membrane module according to the embodiment of the present invention will be described with reference to FIG. As shown in FIG. 1, a membrane filtration apparatus using an external pressure membrane module according to an embodiment of the present invention pressurizes and feeds a plurality of external pressure membrane modules 1 arranged in parallel to each other and washing water. Backwash pump 5, discharge pipe 11 connected to the discharge side of backwash pump 5, the downstream end branching into two, and backwash valves 6, 7 connected to each downstream end of discharge pipe 11, Backwashing water supply pipes 12a and 12b for connecting the outlet side of the washing valves 6 and 7 and a washing port 1b which is a backwashing water inlet of the plurality of external pressure membrane modules 1, an air scrubbing device 2 for generating bubbles, Air scrubbing pipes 13a, 13b for connecting the air scrubbing device 2 with the air scrubbing inlets 2a of the plurality of external pressure membrane modules 1 via an air scrubbing valve 8 or 9, and the plurality of external pressure membranes Cleaning waste of module 1 Air scrubbing water discharge pipes 14a and 14b connecting the mouth 1a and the concentration tank 3 which is a bubble floating means, a sensor part 4 which is a pollutant measuring means connected to the concentration tank 3 via a pipe line 15, and a sensor part 4, a water pollution detection device 100 connected to the sensor unit 4 via a signal line, and a signal line connecting the water pollution detection device 100 and the air scrubbing device 2. It consists of

  Each membrane module 1 is configured by arranging a plurality of tubular filtration membranes in a cylindrical outer cylinder, supplying raw water inside the outer cylinder and outside the filtration membrane, permeating the filtration membrane and entering the filtration membrane It is configured to take out filtered water. Each membrane module 1 is provided with a filtrate section that communicates with the inside of the plurality of filtration membranes. The filtrate is taken out from the filtrate section, and the washing port 1b is connected to the filtrate water. The air scrubbing inlet 2a communicates with the compartment and communicates with the bottom of the raw water compartment to which raw water inside the outer cylinder and outside the filtration membrane is supplied. The washing drain 1a is disposed at the upper part of the raw water compartment, passes through the filtration membrane to the outside of the filtration membrane, and is accompanied by bubbles supplied from the air scrubbing inlet 2a at the bottom of the raw water compartment (also referred to as air scrubbing water). Is discharged from the washing drain 1a.

  As shown in FIG. 3, the concentration tank 3 temporarily stores the cleaning wastewater flowing in from the air scrubbing water inlet 3 a provided near the bottom surface, and reduces the flow velocity. By reducing the flow velocity, it is possible to secure time for the bubbles entrained in the washing wastewater to rise to the surface of the water, and the contaminants attached to the bubbles are collected on the surface of the water and concentrated. In other words, it has a volume sufficient to ensure a sufficient time for air bubbles entrained in the cleaning wastewater to rise to the surface of the water. An antifoaming device 10 is provided at the upper part of the gas phase portion of the concentration tank 3 so as to eliminate the bubbles floating on the water surface. Moreover, the opening which is the concentration drainage port 3b is provided in the side wall surface upper part of the concentration tank 3, and the pipe line 15 is connected to the concentration drainage port 3b. The opening which is the concentration drainage port 3b is arranged at a position where the water surface position comes to the opening.

  The sensor unit 4 measures contaminants concentrated on the liquid surface in the concentration tank 3. Various contaminants can be detected by using various instruments for the sensor unit 4. For example, if a light reflection type oil film detector or a TV camera is used, the oil film can be detected. Moreover, organic pollution can be detected by measuring the amount of organic carbon using a TOC meter.

  As shown in FIG. 1, the water pollution detection apparatus 100 includes a pollution determination apparatus 101 that determines whether or not the membrane module is contaminated based on the measurement value output from the sensor unit 4, and a contamination determination apparatus. 101 is a computer that includes an output device 103 that displays and outputs the determination result of 101, and an air scrubbing control device 102 that controls the air scrubbing device 2 via a signal line using the output of the contamination determination device 101 as an input. The contamination determination apparatus 101 includes rewritable storage means (memory) in which initial values, reference values, threshold values, and the like described later are set and stored.

  In the above description, the configuration related to backwashing of the membrane module of the membrane filtration device is described, and the description of the configuration related to normal filtration is omitted.

  Hereinafter, the backwashing operation of the membrane filtration device having the above configuration will be described. In the present embodiment, the back washing operation of the membrane module is instructed to start every predetermined operation time by the control means not shown in FIG. 1, but the change in the differential pressure of the membrane module is changed. Monitoring may be performed and the backwash operation may be performed when the differential pressure exceeds a predetermined value.

  When the start is instructed, the related valve is operated to a state necessary for the backwash operation, and the backwash is started. The backwash pump 5 is activated, the backwash water 50 is pressurized, passes through the backwash valve 6 and the backwash valve 7, passes through the backwash water supply pipes 12 a and 12 b, and is cleaned by the external pressure membrane module 1. Injected as backwash water from 1b. Simultaneously with the start of backwashing, an activation signal is sent from the control means to the air scrubbing control device 102 in the water pollution detection device 100. Based on this activation signal, the air scrubbing control device 102 activates the air scrubbing device 2, and the air scrubbing device 2 generates bubbles and passes through the air scrubbing tubes 13a and 13b to the air scrubbing inlet 2a of each membrane module 1. Send it in.

  The backwash water injected into the cleaning port 1b of the membrane module 1 enters the inside of the filtration membrane from the filtered water section, permeates the filtration membrane, and moves to the raw water section. Remove hydrophobic contaminants adhering to the filter membrane. The air bubbles sent to the air scrubbing inlet 2a flow into the raw water compartment, and the contaminants 54 that have separated from the filtration membrane while adhering to the air water section adhere to the surface of the air bubbles 53.

  The backwash water that has moved to the raw water compartment rises as air scrubbing water with air bubbles 53 with contaminants 54 adhering to the surface and contaminants 54 that have detached from the permeation membrane, and the washing drain port 1a on the upper side of the membrane module 1 Discharged from. The discharged air scrubbing water flows into the concentration tank 3 through the air scrubbing water discharge pipes 14a and 14b and the air scrubbing water inlet 3a, and is temporarily stored. The air scrubbing water bubbles 53 temporarily stored rise to the water surface with the contaminants 54 attached. The bubbles 53 rising to the water surface are extinguished by the water released from the defoaming device 10. Since the bubbles 53 disappear on the surface of the water, the contaminants 54 attached to the bubbles 53 are accumulated near the surface of the water and a film of the concentrated contaminants 54 is formed.

  Air scrubbing water in the concentration tank 3 in which a film of the pollutant 54 is formed in the vicinity of the water surface is guided to the sensor unit 4 via the concentration drainage port 3b and the pipe line 15. At this time, since the water surface of the concentration tank 3 is in the opening of the concentration drainage port 3b and the pipe line 15 is arranged so as to be kept horizontal, the film of the pollutant 54 formed on the water surface of the air scrubbing water is destroyed. Without being guided to the sensor unit 4.

  The film of the pollutant 54 on the surface of the air scrubbing water led to the sensor unit 4 is discharged together with the air scrubbing water through the drain line 16 after the amount (hereinafter referred to as “contamination concentration”) is detected by the sensor unit 4. Is done. The sensor unit 4 transmits the detected contamination concentration information to the water contamination detection apparatus 100 via the signal line.

  The contamination concentration information received by the water contamination detection device 100 is input to the contamination determination device 101, and the degree of contamination is determined. The result determined by the contamination determination device 101 is output to the output device 103 and displayed on the screen and printed out. When the contamination concentration exceeds a preset value, an alarm is output by sound or blinking of an indicator lamp. The determination result of the contamination determination apparatus 101 is output to the air scrubbing control apparatus 102, and the air scrubbing control apparatus 102 controls the air scrubbing apparatus 2 based on the input determination result.

  The determination procedure of the contamination determination apparatus 101 will be described with reference to FIG. Step 200 is a process in the sensor unit 4. Step 201 to step 206 are processes of the contamination determination apparatus 101, and step 207 is a process of the air scrubbing control apparatus 102. The processing result of the contamination determination device 101 is output to the output device 103 and the air scrubbing control device 102. In the memory of the contamination determination apparatus 101, a reference value A and a threshold value B (A <B) are set and stored in advance. The reference value A is a concentration information value for determining whether or not the membrane module is contaminated, and the threshold value B is a concentration information value for determining that the contamination is large.

  First, in step 200, the contamination concentration is detected by the sensor unit 4, and the detected contamination concentration information (hereinafter referred to as concentration X) is transmitted to the contamination determination apparatus 101.

  Next, in step 201, it is confirmed whether or not the initial value density i is set in the memory. If not, the density X transmitted from the sensor unit 4 is set as the initial value density i. move on. If the initial value has been set, the process proceeds to step 202 as it is.

  In step 202, the density X and the reference value A are compared. When the reference value A ≦ concentration X, it is determined that the membrane module 1 or the membrane is contaminated, and the process proceeds to step 203. When the reference value A> concentration X, it is determined that the membrane module 1 or the membrane is not contaminated, and the process proceeds to step 205.

  In step 203, the density X and the threshold value B are compared to determine which is larger. If the density X is less than or equal to the threshold value B, it is determined that the contamination is small, and the process proceeds to step 204. When the concentration X is larger than the threshold value B, it is determined that contamination is large and chemical cleaning or replacement is necessary, and the determination result is output to the output device 103. In this case, the backwash operation is stopped, but it is desirable to give an alarm by sound or flashing of an alarm lamp.

  In step 204, the density X and the initial value density i are compared to determine which is larger. If the density X is smaller than the density i, it is determined that the contamination is decreasing, and the process proceeds to step 205. When the concentration X is equal to or higher than the concentration i, it is determined that the contamination is still large and it is necessary to increase the air strength of the air scrubbing device 2, the determination result is output to the output device 103, and the process proceeds to step 206. To increase the air strength is to increase the amount of air scrubbing sent into the membrane module 1 or to increase the time for outputting bubbles.

  In step 205, it is determined that the air intensity of the air scrubbing device 2 is maintained as it is, the determined result is output to the output device 103, the initial value is rewritten to the current density X, and the process proceeds to step 206.

  In step 206, a signal corresponding to the determination results in steps 202 and 204 is output to the air scrubbing control device 102. The air scrubbing control device 102 controls the air scrubbing device 2 based on the input signal, and increases the amount of air scrubbing air or outputs a bubble (step 207).

  The above process is repeated at predetermined sampling time intervals while backwashing is being performed. When the backwash operation is completed, the initial value of the memory is erased.

  According to the above embodiment, the contaminants removed from the membrane module during the backwash operation of the membrane module are concentrated on the surface of the backwash water (air scrubbing water) coming out of the membrane module. Even if the amount is small, the amount can be detected, and the membrane module can be reliably decontaminated by backwashing.

  It is possible to always detect the contamination of the membrane module 1 by operating the air scrubbing device 2 not only during backwashing but also during normal operation.

  Further, by providing a valve immediately before the cleaning port 1b of the backwash water supply pipes 12a and 12b for each membrane module 1, the contamination concentration for each membrane module 1 can be measured and contamination detection can be performed.

It is a system configuration | structure figure which shows the membrane module water pollution detection method of the membrane filtration apparatus which concerns on embodiment of this invention. It is a schematic diagram which expands and shows the membrane module shown in FIG. It is a schematic diagram which expands and shows the concentration tank shown in FIG. It is a flowchart which shows the example of the procedure of the contamination detection which concerns on embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 External pressure type membrane module 1a Cleaning drainage port 1b Cleaning port 2 Air scrubbing device 2a Air scrubbing injection port 3 Concentration tank 3a Air scrubbing water inlet 3b Concentration drainage port 4 Sensor part 5 Backwash pump 6, 7 Backwash valve 8, 9 Air Scrub valve 10 Defoaming device 53 Bubble 54 Contaminant 100 Water contamination detection device 101 Contamination determination device 102 Air scrubbing control device 103 Output device

Claims (7)

  A plurality of external pressure membrane modules for removing contaminants in the supplied raw water; a bubble supply means for supplying bubbles to the raw water supply side of the plurality of external pressure membrane modules; and a raw water discharge side of the membrane module. A bubble floating means configured to float on the liquid surface bubbles that flow in accompanying the raw water, and a pollutant measuring means for measuring a contaminant floating on the liquid surface by the bubble floating means, A membrane filtration apparatus comprising a contamination determination unit that determines the degree of contamination of a membrane module based on a measurement value output from the contaminant measurement unit, and an output unit that displays a determination result.   2. The membrane filtration apparatus according to claim 1, wherein the bubble floating means includes a defoaming means for eliminating the bubbles.   3. The membrane filtration apparatus according to claim 1, wherein the bubble levitation means includes an opening formed at a position that forms a boundary between the liquid phase portion and the gas phase portion, and the pollutant measurement means is provided in the opening. A membrane filter device connected to a passage and configured to measure contaminants on a water surface discharged from the bubble floating means through the conduit.   4. The membrane filtration device according to claim 1, further comprising a bubble supply amount control means for controlling the bubble supply means with an output of the contamination determination means as an input. .   5. The membrane filtration device according to claim 1, wherein the determination unit includes a storage unit that stores a preset value, and compares the input measurement value with the set value to determine the membrane. A membrane filtration device configured to determine the degree of module contamination.   6. The membrane filtration device according to claim 1, wherein the determination unit includes a storage unit that stores a measurement value output from the contaminant measurement unit each time backwashing is performed. Comparing the measured value output from the pollutant measuring means at the time of backwashing with the measured value at the previous backwashing stored in the storage means, the increase or decrease in the degree of contamination of the membrane module is determined. A membrane filtration device. A plurality of external pressure membrane modules for removing contaminants in the supplied raw water; a bubble supply means for supplying bubbles to the raw water supply side of the plurality of external pressure membrane modules; and a raw water discharge side of the membrane module. A bubble floating means configured to float on the liquid surface the bubbles flowing in accompanying the raw water, and a pollutant measuring means for measuring the contaminant floating on the water surface by the bubble floating means Membrane module contamination of a membrane filtration device comprising: a contamination determination unit that determines the degree of contamination of the membrane module based on a measurement value output from the contaminant measurement unit; and an output unit that displays the determination result In the detection method, bubbles are supplied to the raw water supply side of the plurality of external pressure membrane modules, and the raw water and the bubbles that have passed through the membrane modules are guided to the bubble floating means to defoam and float on the water surface. Contaminants was measured, the membrane module contamination detection method of determining membrane filtration device of the degree of contamination of the membrane module on the basis of the measurement results.

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