JP2008032691A - Water quality monitoring system and water quality monitoring method - Google Patents

Description

  The present invention relates to a water quality monitoring system and a water quality monitoring method for monitoring chemical components such as harmful substances in water for water such as rivers and water and sewage systems.

  Monitoring of the quality of environmental water such as effluent from each treatment process of sewage and river water and lake water is very important from the viewpoint of safety as a tap water source and environmental conservation. Currently, water quality measuring instruments that automatically monitor water quality have been developed and are actually being applied. As such a water quality measuring instrument, a pH meter, a conductivity meter, a free chlorine meter, a turbidity meter, a coloring meter, a dissolved oxygen (DO) meter, a redox potential (ORP) meter, an ammonia meter, a nitrate ion meter, Phosphate ion meter, total nitrogen / total phosphorus (TN / TP) meter, sludge concentration (MLSS) meter, UV organic pollution meter, chemical oxygen demand (COD) meter, biological oxygen demand (BOD) meter, total organic carbon (TOC) meter, volatile organic compound (VOC) meter, (MLSS) meter, biosensor and the like.

  In this specification, a “biosensor” is a molecular identification element that recognizes a chemical substance to be measured in sample water, and uses biological functional materials such as enzymes and antibodies, and living organisms such as microorganisms and cells. The biomaterial molecular identification signal is converted into an electrical signal by combining a membrane in which these biological materials are chemically encapsulated or covalently bonded to a porous polymer membrane and a transducer such as an electrochemical detector. It means a sensor that converts and measures various chemical substances contained in sample water. A biosensor is a method in which sample water is brought into contact with an immobilized membrane of biological material, and a concentration change of a substance generated or consumed by a biochemical reaction caused thereby is detected by an electric output (hereinafter referred to as “current” or “voltage”). It is converted to a change in sensor output) and measured. For example, Patent Document 1 describes a biosensor-applied toxic monitor for the purpose of detecting harmful substances in water.

  In such water quality monitoring, especially when using a water quality measuring device for the purpose of measuring soluble components, in order to prevent clogging of piping of the water quality measuring device and failure of a liquid feeding device such as a pump, Pretreatment is necessary to remove turbidity such as mud and dust. Conventionally, a turbidity removal device has been used that removes turbidity by filtering sample water with laminated sand, nonwoven fabric, or screen, but such turbidity removal device cannot remove turbidity of 10 μm or less. There was a problem.

  For this reason, in a water quality measuring instrument that continuously passes sample water and performs continuous monitoring, for example, a membrane filtration using a filtration membrane having a submicrometer order blocking particle size as described in Patent Document 2 It is necessary to use the device. However, when the above membrane filtration device treats water with high turbidity load such as rivers, lake water, or sewage when it rains or melts, the filtration performance becomes extremely bad due to clogging of the filtration membrane surface, The amount of treated water may decrease or the quality of treated water may deteriorate. Therefore, there is a problem that the measured value of the water quality measuring device at the latter stage fluctuates or becomes unable to be measured.

  Therefore, in order to reduce the load of turbidity on the membrane filtration device, a turbidity removal device using a screen or non-woven fabric that can remove turbidity with a particle size on the order of submillimeters can be installed in front of the membrane filtration device. desirable. In addition, automatic maintenance operation methods for membrane filtration devices include backwashing with air or tap water, air scrubbing on the membrane surface, and applying upward or lateral water flow to the sample water by mechanical means such as a pump or propeller, and its shear force. Cleaning of the membrane surface by water, tap water cleaning of filtration water tanks, etc. have been studied (Non-Patent Document 1).

Furthermore, measurement obstruction factors other than pipe blockage due to turbidity in the sample water and device failure include precipitation of hardness components such as calcium ions, pipe blockage due to bacterial growth in the air, and sensor element surface contamination. In this case, since removal with a filtration membrane such as turbidity is difficult, a chemical removal method such as chemical solution cleaning in the apparatus as described in Patent Document 3, or Patent Document 4 and Patent Document 5 As described, physical removal methods such as cleaning of contaminated sites with a wiper or a jet water stream are being studied.
Japanese Patent Publication No. 7-85072 JP 2001-281240 A JP 2000-146893 A JP-A-9-54076 JP-A-7-181130 Inui T, 3 others, “Application of toxicity monitor using nitrifying bacteria biosensor to sewerage systems”, Water Science and Technology (Water science and technology), 2002, 45, 4/5, p. 271-278

  In order to continue stable continuous monitoring of the soluble components of sample water with high turbidity load using the pretreatment device and water quality measuring instrument with the turbidity function as described above, the maintenance work is simplified and the maintenance frequency is reduced. Reduction is required. In addition, the introduction of the device requires a reduction in maintenance costs. However, if the pretreatment device is continuously operated for one month or more in order to reduce the maintenance frequency, the pretreatment device, for example, increases the amount of sludge deposited on the surface of the filtration membrane, which requires a lot of time for manual cleaning work. There is a problem that requires. Further, for example, there is a problem that the filtration membrane may not be reused only by removing the sludge accumulated on the membrane surface due to clogging due to propagation of various bacteria in the filtration membrane. For this reason, the maintenance frequency increases, so that the maintenance cost increases and it is difficult to introduce the apparatus.

  In addition, in the biosensor, precipitates and biological dirt adhere to the surface of the immobilized membrane during continuous operation for a long period of time. When the amount of deposits and biological dirt attached increases, the sensor output decreases, the detection sensitivity necessary for detecting the harmful substances cannot be obtained, and the harmful substances cannot be detected accurately. For this reason, the sensor output of the biosensor is calibrated so that harmful substances can be accurately detected even if the sensor output decreases. Also, if the sensor output falls below a certain value, it is necessary to replace the immobilized membrane. If the sample water contains many germs and precipitates, the frequency will increase and the cost will increase. There is a problem.

  In view of the above problems, the present invention provides a water quality monitoring system and a water quality monitoring method capable of continuously operating a water quality monitoring system over a long period of time with simple maintenance work and reduced maintenance frequency and cost. The purpose is to provide.

  In order to achieve the above object, a water quality monitoring system according to the present invention includes a water sampling device that continuously collects sample water from a water source to be monitored, and turbidity in the sample water collected by the water sampling device. A pretreatment device for continuous removal; a water quality measuring device for continuously detecting harmful substances in the sample water pretreated by the pretreatment device; and during the periodic calibration of the water quality measuring device, An operation control device for stopping the operation of the apparatus, stopping the flow of the sample water to the water quality measuring instrument, and controlling the pretreatment device or the water quality measuring instrument to be washed. To do.

  As the pretreatment device, a membrane separation means for filtering the contamination in the sample water with a membrane, and a cleaning is performed by flowing water through a portion where the sample water flows between the membrane separation means and the water quality measuring instrument. What provided the washing | cleaning means is preferable. In this case, it is preferable that the operation control device performs control so that the first cleaning unit is operated during the periodic calibration of the water quality measuring instrument.

  The water quality measuring instrument preferably includes a biosensor and a second cleaning unit that performs cleaning by flowing water or air through a portion of the biosensor in which sample water flows. In this case, it is preferable that the operation control device performs control so that the second cleaning unit is operated when it is determined that there is an abnormality in the periodic calibration of the biosensor.

  Another aspect of the present invention is a water quality monitoring method, in which sample water is continuously collected from a water source to be monitored by a water collection device, and turbidity in the collected sample water is continuously collected by a pretreatment device. The water sampling operation of the water sampling apparatus during the water quality monitoring step of continuously detecting harmful substances in the pre-treated sample water with a water quality measuring instrument and the periodic calibration of the water quality measuring instrument And a calibration step of stopping the water flow of the sample water to the water quality measuring instrument and washing the pretreatment device or the water quality measuring instrument.

  The pretreatment device is preferably provided with a membrane separation means for filtering the contamination in the sample water with a membrane, and the calibration step is performed by supplying water to a portion where the sample water flows between the membrane separation means and the water quality measuring instrument. It is preferable to include performing the 1st washing | cleaning which flows and wash | cleans.

  The water quality measuring instrument is preferably equipped with a biosensor, and when the calibration process determines that there is an abnormality in the calibration of the biosensor, the sample is washed by flowing water or air through the portion where the sample water flows in the biosensor. It is preferable to include performing the 2nd washing | cleaning to perform.

  Further, the water quality monitoring system according to the present invention, as another form, continuously collects a water sampling device that continuously collects sample water from a water source to be monitored, and harmful substances in the sample water collected by this water sampling device. In this biosensor, a biosensor equipped with a membrane to which microorganisms are fixed and a dissolved oxygen electrode for measuring dissolved oxygen is washed, and water or air is passed through a portion where the sample water flows in the biosensor for cleaning. A cleaning unit that performs the cleaning, and an operation control device that controls the cleaning unit to operate when it is determined to be abnormal due to a decrease in sensor output when the biosensor is periodically calibrated. .

  Further, the water quality monitoring method according to the present invention, as another form, continuously collects sample water from a water source to be monitored with a water sampling device, and fixes microorganisms to harmful substances in the collected sample water. A water quality monitoring step for continuously detecting with a biosensor having a membrane and a dissolved oxygen electrode for measuring dissolved oxygen, and when calibrating the biosensor periodically, when it is judged abnormal due to a decrease in sensor output, And a calibration step of washing by flowing water or air in a portion where the sample water flows in the biosensor.

  In this way, even if the water quality monitoring system is operated continuously over a long period of time, the water sampling device should be stopped and the pretreatment device or the water quality measuring device washed while the water quality measuring device is periodically calibrated. Thus, part of the turbidity in the water sampling apparatus is detached due to gravity, and accumulation of turbidity can be prevented, and propagation of germs in the pretreatment apparatus or the water quality measuring instrument can be prevented. Therefore, it is possible to simplify the maintenance work, reduce the frequency and cost of maintenance required for the water quality monitoring system of each sewage treatment process, environmental water such as river water, lake water, etc. Even in the case of high sample water, the stable supply of sample water to the water quality measuring instrument and the maintenance of the measurement accuracy of the water quality measuring instrument can be easily performed.

  In particular, as the cleaning of the pretreatment device, the biosensor is contaminated by performing the first washing in which the sample water flows between the membrane separation means of the pretreatment device and the water quality measuring device to perform the washing. Therefore, it is possible to periodically wash the portion that is a hotbed of various germs, and to easily maintain the measurement accuracy of the water quality measuring instrument with simple maintenance work and with less maintenance frequency and maintenance cost.

  In addition, germs that have propagated in the pretreatment device may flow into and stay in the biosensor, reducing the measurement accuracy. However, the automatic cleaning mechanism of the current water quality measuring instrument adheres to the hardness component of the piping around the biosensor. It is only acid cleaning for the purpose of prevention, and chemical automatic cleaning such as chemical cleaning of the sensor element surface in the biosensor is impossible due to the vulnerability of microorganisms used in the biosensor, and the measurement accuracy can be restored. Have difficulty. Therefore, it is necessary to increase the cleaning frequency of the pretreatment device that is a breeding place for bacteria, but during that time sample water is not passed, so the continuity of measurement is lost, or the cleaning water is washed after the cleaning. When the water is passed through the biosensor, there is a problem in that the biosensor shows a response similar to that at the time of inflow of harmful substances and issues a false alarm. Therefore, when the biosensor is determined to be abnormal by calibration, the second cleaning is performed by flowing water or air through the portion where the sample water in the biosensor flows, so that the germs staying in the biosensor can be removed. In addition, it is possible to physically remove precipitates and biological stains that similarly reduce the sensor output, and maintain measurement accuracy.

  In addition, in a biosensor equipped with a microbial membrane and a dissolved oxygen electrode, precipitates and biological dirt adhere to the surface of the microbial membrane during continuous operation for a long period of time, reducing the amount of oxygen passing through. For this reason, the amount of oxygen measured by the dissolved oxygen electrode is reduced, and the sensor output is reduced. This decrease in sensor output can be detected from the calibration value when the biosensor is periodically calibrated. When it is determined that the sensor output is abnormal, the precipitate or biological dirt is removed by flowing water or air through the portion of the biosensor where sample water flows, and the sensor output is restored to the original state. Can be returned. Therefore, it is possible to prevent the sensor output from being lowered to a value at which the microbial membrane should be replaced, to reduce the maintenance frequency and to reduce the cost. In addition, since the amount of oxygen supplied to the microbial membrane can be maintained, it is possible to prevent a decrease in the life of the microbial organism and to reduce costs in this respect.

  Hereinafter, an embodiment of a water quality monitoring system and a water quality monitoring method according to the present invention will be described with reference to the accompanying drawings. FIG. 1 is a schematic diagram showing a schematic configuration of an embodiment of a water quality monitoring system according to the present invention. FIG. 2 is a schematic diagram showing the internal structure of the biosensor shown in FIG. FIG. 3 is a schematic diagram showing the configuration of the microbial membrane and the dissolved oxygen electrode shown in FIG. FIG. 4 is a schematic diagram showing a peripheral configuration of the biosensor shown in FIG.

  As shown in FIG. 1, the water quality monitoring system of the present embodiment includes a water sampling device 1 that collects sample water from a water source to be monitored, a pretreatment device 2 that removes turbidity from the sample water, and sample water. It is mainly composed of a water quality measuring device 3 that detects the harmful substances and an operation control device 4 that automatically controls the operation of the water quality monitoring system.

(1. Water sampling device)
As the water sampling apparatus 1, a submersible pump is used. The water sampling device 1 continuously collects sample water from the water source and passes the sample water through the pretreatment device 2. In addition, when the water sampling apparatus 1 is always operated, turbidity gradually accumulates in the flow path in the submersible pump, which closes the flow path, stops water sampling, and maintenance of the submersible pump requires much labor. You may have to do work. Therefore, since it is not necessary to pass the sample water through the water quality measuring instrument 3 while the water quality measuring instrument 3 performs the periodic calibration, the operation of the water sampling apparatus 1 is stopped during the above calibration, and intermittently. By setting the operation, a part of the turbidity in the pump can be desorbed by gravity, and the maintenance frequency can be reduced.

(2. Pretreatment device)
The pretreatment device 2 is mainly composed of a membrane filtration device 11 and a screen 12 at the preceding stage. Thus, by setting it as a 2 step | paragraph structure, the turbid load of the membrane filtration apparatus 11 can be reduced, and a maintenance frequency can be reduced. In addition, when the turbidity load of the water source to be monitored is low, the screen 12 may not be provided and the configuration of the membrane filtration device 11 alone may be used.

  The screen 12 is made of a material such as stainless steel having a high anticorrosion property, and a horizontal slit is formed on the filtration surface. In the screen 12, the sample water from the water sampling device 1 is guided to the upper part of the screen 12, and solid-liquid separation is performed by allowing the sample water to fall naturally on the filtration surface of the screen. The suspended matter trapped on the filtration surface falls to the screen drainage tank 71 due to water flow and gravity and is discharged. On the other hand, the filtered water is stored in a screen filtered water tank 72 inside the screen 12. The filtrate in the screen filtration water tank 72 is supplied to the membrane filtration device 11 by the water supply pump 58. Excess filtered water in the screen filtered water tank 72 is discharged to the screen drain tank 71 via an overflow pipe (not shown). The slit is preferably 0.1 to 1 mm wide. Thereby, the suspended matter with a particle size of 0.1-1 mm or more can be filtered and removed.

  As a maintenance method for the screen 12, a brush (not shown) attached to the back side of the filtration surface of the screen 12 is always operated with a motor or intermittently operated with a timer to remove adhering turbidity (hereinafter, “ Screen backside brush cleaning ”is used. Further, a method of periodically guiding the tap water instead of the sample water from the tap water pipe 63 and cleaning the front side of the filtration surface of the screen 12 (hereinafter referred to as “screen surface tap water cleaning”) is used. As a secondary effect of the screen surface tap water cleaning, since the introduced tap water is passed through the raw water tank 52 of the subsequent membrane filtration device 11, the membrane surface of the membrane filtration device 11 is washed with tap water. Is possible.

  As the membrane filtration device 11, a membrane module 51 in which several hundreds of hollow fiber membranes are bundled as a filtration membrane is used. The membrane module 51 is disposed in a raw water tank 52 filled with sample water from the screen 12, and one end of the membrane module 51 is attached to a flange of the raw water tank 52 (hereinafter referred to as a water tank flange 54). By using 59, the pipe internal pressure is increased, so that the filtered water that has passed through the membrane module 51 is sent to the water quality measuring instrument 3 side. In this way, by using the internal pressure type membrane module 51 in a cross-flow manner, sample water with a high turbidity load such as sewage and drainage can be appropriately pretreated. An external pressure type may be adopted instead of the internal pressure type.

  The membrane module 51 is not limited to the above-described configuration, and various materials can be used for the material and shape of the filtration membrane, the filtration method, and the like as long as a microfiltration membrane or the like is used as a filter medium. For example, the material of the filtration membrane may be inorganic such as ceramic, or organic such as polyacrylonitrile or cellulose acetate, and the shape may be any of tube, hollow fiber, flat membrane, or spiral. The method may be a cross flow method or a total filtration method. The membrane module 51 is preferably one that can remove turbidity having a particle size of 0.2 μm or more by filtration.

  The filtered water that has passed through the membrane module 51 is configured to be stored in the filtered water tank 56 via the filtered water pipe 55. The filtrate pipe 55 is provided with a pressure gauge 57 that measures the pressure of the filtrate pipe 55 and a filtration pump 59 that sends the filtrate to the filtrate tank 56. The filtered water tank 56 is provided with an overflow pipe for discharging the filtered water in the filtered water tank 56.

  As a maintenance method of the membrane filtration device 11, a method in which an air diffusion pipe 53 is installed in the vicinity of the membrane module 51 in the raw water tank 52, and the membrane surface is constantly washed with bubbles by the air pump 61 (hereinafter referred to as “air scrubbing”), A method of applying air pressure to the inside of the membrane using the air pump 60 from the water tank flange 54 side and removing the turbidity trapped on the membrane surface by backwashing (hereinafter referred to as “backwashing”) is used. The backwashing may use water pressure instead of air pressure.

  Furthermore, in order to prevent the propagation of germs in the membrane filtration device 11, a method of periodically washing a site that is a breeding place of germs using tap water (hereinafter referred to as "filter device tap water washing") is used. . Therefore, the filtered water pipe 55 is provided with a tap water pipe 62 for introducing the water guide water into the filtered water pipe 55, and an open / close valve provided in the filtered water pipe 55 and a water tank flange 54. The drainage pipe and the overflow pipe of the filtered water tank 56 are configured so that the water tank flange 54, the filtered water pipe 55 and the filtered water tank 56 can be separately washed with tap water. The cleaning waste water discharged from the drain pipe of the water tank flange 54 and the overflow pipe of the filtered water tank 56 is discharged to the screen drain tank 71. In addition, when supply water pressure is too high with respect to the tap water piping 62 and 63 which introduces the tap water used for washing | cleaning, you may provide flow regulating valves, such as a pressure regulating valve and a needle valve which are not shown in figure.

(3. Water quality measuring instrument)
The water quality measuring device 3 is configured by combining a biosensor 13, a pH meter 14, and a coloring degree meter 15. By performing continuous monitoring by combining the biosensor 13 and the pH meter 14, it is possible to determine whether the cause of the abnormality is due to acid / alkali waste liquid or a harmful substance such as cyan when the abnormality alarm is output from the biosensor 13. . Further, by performing continuous monitoring by combining the colorimeter 15, it is possible to detect the mixing of coloring components such as a staining agent and hexavalent chromium that are difficult to detect with both of them. Note that the water quality measuring device 3 may be a single biosensor 13 depending on the water source to be monitored.

  When the pH meter 14 and the color meter 15 are combined with the biosensor 13, it may be an on-line type with automatic cleaning and automatic calibration functions, or a simple type for a laboratory. Is preferred. In that case, the glass electrode of the pH meter 14 is installed in the filtered water tank 56 of the membrane filtration device 11, and the color meter 15 is configured to pass sample water from the filtered water tank 56 using a tube pump. According to this structure, the glass electrode of the pH meter 14 and the measurement cell of the color degree meter 15 can be simultaneously washed with tap water when the membrane filtration device tap water is washed. The biosensor 13 is also configured to pass sample water from the filtered water tank 56 using a tube pump.

  As shown in FIG. 2, the biosensor 13 includes a microbial membrane 21 in which a nitrifying bacterium, which is a microorganism that is extremely weak against harmful substances as a biological material, is alive and is sealed in a polymer porous membrane, and dissolved oxygen as a detector. It is a respiratory activity detection type biosensor in combination with an electrode 22. The microbial membrane 21 is configured to come into contact with the sample water flowing through the sample channel 25 inside the flow cell 24.

  As shown in FIG. 3, the dissolved oxygen electrode 22 includes an oxygen permeable membrane 81 arranged in contact with the microorganism membrane 21, a bowl-shaped cathode electrode 82 arranged in contact with the oxygen permeable membrane 81, and a cathode electrode The galvanic cell is composed of an insulator 84 that surrounds the side of the shaft portion of 82, an anode electrode disposed on the outer peripheral portion of the insulator 84, and an internal liquid 85 filled in the outer peripheral portion of the insulator 84. .

  In addition, as shown in FIG. 4, the biosensor 13 is installed in the thermostatic chamber 26, and the heat exchanger 27 is installed in the previous stage of the biosensor 13, so that the temperature measured by the biosensor 13 is set. It is kept constant. Further, an air blowing / feeding mechanism 29 having an open / close valve is installed to send various liquids and gases separately or mixed to the biosensor 13.

  In the sample flow path 25 of the biosensor 13, a mixed solution of the sample water from the filtered water tank 56 of the membrane filtration device 11 and a buffer solution (hereinafter referred to as “feed solution”) containing a substrate and essential nutrients is usually provided. Supplied by the air blowing mechanism 29 in an oxygen saturated state. In the biosensor, as shown in FIG. 5, the substrate 88 in the mixed solution flowing through the sample flow path 25 is nitrified by the nitrifying bacteria 87 in the microorganism film 21, and oxygen 89 in the mixed solution is consumed at this time. The amount of oxygen 89 that has passed through the microbial membrane 21 is measured by the dissolved oxygen electrode 22 (the sensor output at this time is referred to as “measured value”).

  At this time, if no harmful substances are mixed in the mixed solution, almost all the oxygen in the mixed solution is consumed by the microbial membrane 21, so that the oxygen consumption rate is almost 100% as shown in FIG. The sensor output of the oxygen electrode 22 has a very low value. On the other hand, if harmful substances are mixed in the mixed solution, the activity of nitrifying bacteria 87 is inhibited and the oxygen respiration rate is reduced, so that the oxygen consumption rate is reduced and the dissolved oxygen electrode 22 detects oxygen. Sensor output increases. This makes it possible to detect whether or not harmful substances are mixed in the sample water.

In addition, the sample channel 25 of the biosensor 13 is periodically calibrated once a day for calibration, for example, pure water and a buffer solution that does not contain a substrate but contains essential nutrients (hereinafter referred to as “calibration”). The liquid mixture is supplied by the blowing liquid feeding mechanism 29 in an oxygen saturated state. In the biosensor, since the substrate is not contained in the mixed solution, the nitrifying bacteria consume almost no oxygen. Therefore, as shown in FIG. 6, the oxygen consumption rate is almost 0%, and the sensor output of the dissolved oxygen electrode is low. Increases greatly (this value is called “span calibration value”). Here, the oxygen consumption rate is obtained by the following formula 1.
Oxygen consumption rate (%) = {1- (arbitrary sensor output during measurement) / (span calibration value)} × 100 (1)

The respiratory inhibition rate is obtained by the following formula 2. When the respiratory inhibition rate exceeds a predetermined monitoring threshold (for example, 10%), an alarm is given that a harmful substance has been detected in the sample water.
Respiration inhibition rate (%) = {1− (oxygen consumption rate when contaminated with harmful substances) / (oxygen consumption rate immediately before mixing of harmful substances)} × 100 (2)

  Furthermore, tap water is supplied to the sample flow path in the air blowing mechanism 29 and the sample flow path 25 of the biosensor 13 by the water supply pressure in the event of an abnormality, thereby washing the sample water path with tap water (hereinafter referred to as the tap water). , “Biosensor tap water cleaning”), the accumulated germs, the deposits attached to the surface of the microbial membrane 21 and biological dirt are physically removed, and the sensor output is reduced due to these. Can be prevented.

  In addition, in order to wash | clean the sample water piping between the filtration water tank 56 and the biosensor 13, acid washing water is regularly supplied into this sample water piping by the ventilation liquid feeding mechanism 29, and acid washing is carried out. Done. Thereby, it can prevent that a hardness component adheres in piping. In order to prevent the acid cleaning water from flowing into the sample flow path 25 of the biosensor 13, when the acid cleaning water is supplied, the open / close valve (not shown) is switched so that the acid cleaning water flows to the bypass flow path 28. To do. Thereby, it is possible to avoid the microorganisms of the biosensor 13 from coming into contact with the acid cleaning water.

(4. Operation control device)
As shown in FIG. 7, the operation control device 4 is set in advance based on analog-to-digital signal converters 46 that read various signals from the above-described components such as sensor outputs of biosensors, and these signals. A central processing unit 47 that performs arithmetic processing, and a digital-analog signal converter 48 that transmits various signals to the above-described components based on the processing results are mainly configured. The operation control device 4 is provided with timers 31 to 42 for setting a time for transmitting a signal. Further, the central processing unit 47 is configured to set an upper limit value or lower limit values AL1 to AL3 as to whether or not to send a command signal to each component based on the received signal.

  In the timer 31 of the operation control device 4, an operation interval time T <b> 1 for cleaning the screen back surface brush on the screen 12 is set. If this time T1 is set, the screen back surface brush cleaning is intermittent operation, and if it is not set, it is always operated.

  The timer 32 of the operation control device 4 has the backwash time T2 of the membrane filtration device 11, the timer 33 has the backwash interval time T3 of the membrane filtration device 11, and the timer 34 has the membrane filtration device tap water washing time T4. The timer 35 is set with a membrane filtration device tap water washing interval time T5. In addition, at the time of this periodic membrane filtration apparatus tap water washing, it controls so that supply of sample water from filtration water tank 56 to biosensor 13 may be stopped.

  The pressure gauge 57 that measures the suction pressure in the filtrate water pipe 55 is configured to transmit the value of the measured suction pressure to the operation control device 4. A maintenance threshold AL1 is set in the operation control device 4, and when the received value becomes AL1 or more, a backwash signal is transmitted to the membrane filtration device 11. The membrane filtration device 11 that has received the backwash signal performs backwashing. When the backwash signal is transmitted, the timer 33 of the backwash interval time T3 is reset.

  The timer 36 of the operation control device 4 has a calibration time T6 of the biosensor 13, the timer 37 has a calibration interval time T7 of the biosensor 13, and the timer 38 has an acid cleaning time T8 of the biosensor 13. Is the acid cleaning interval time T9 of the biosensor 13, the timer 40 is the biosensor tap water cleaning time T10, the timer 41 is the biosensor tap water cleaning interval time T11, and the timer 42 is the biosensor 13 after calibration is completed. The measurement waiting time T12 is set.

  In order to periodically calibrate the biosensor 13, the operation control device 4 periodically calibrates the water sampling device 1, the pretreatment device 2, and the water quality measuring device 3 during the calibration time T6 at every calibration interval time T7. A signal is emitted. The water sampling apparatus 1 stops operation while receiving this periodic calibration signal. While receiving the periodic calibration signal, the pretreatment device 2 performs screen surface tap water cleaning on the screen 12, and resets the timer 34 of the membrane filtration device tap water cleaning time T4, so that the membrane filtration device tap water cleaning is performed. Repeat. Membrane filtration device tap water cleaning is performed in the order of the water tank flange 54, the filtrate water pipe 55, and the filtration water tank 56. The membrane filter device tap water cleaning time (calibration time T6) at the time of periodic calibration of the biosensor 13 is used. It is preferable to set it to 10 times or more of the tap water cleaning time T4 at the time of the above periodic membrane filtration device tap water cleaning.

  The water quality measuring instrument 3 is calibrated while receiving the periodic calibration signal. The biosensor 13 is supplied with a mixture of pure water and calibration liquid, and the measured value, that is, the span calibration value is transmitted to the operation control device 4 as shown in the flowchart of FIG. When the span calibration abnormality threshold AL2 is set in the operation control device 4 and the span calibration value at the end of calibration is less than AL2, the operation control device 4 starts the biosensor tap water washing in the water quality measuring instrument 3. A signal is transmitted, the tube pump in the blast liquid feeding mechanism 29 is stopped, the sample flow paths of the blast liquid feeding mechanism 29 and the biosensor 13 are cleaned, and the water sampling device 1 and the pretreatment device 2 are A signal is transmitted so as to maintain the operation stop of the water sampling device 1 and the membrane filtration device tap water cleaning. After the biosensor tap water cleaning time T10 has elapsed, a signal for ending the biosensor tap water cleaning is transmitted to the water quality measuring instrument 3, and then periodically calibrated to the water sampling apparatus 1, the pretreatment apparatus 2, and the water quality measuring instrument 3 again. Send a signal and calibrate again. If the span calibration value is greater than AL2, start measurement and return to water quality monitoring.

  In the operation control device 4, an upper limit value AL3 of the number of repetitions of the biosensor tap water cleaning at the time of the abnormality is set. Even if the span calibration value is less than AL2, if the number of repetitions of the cleaning reaches AL3, the measurement is started and the process returns to water quality monitoring.

  Further, when the span calibration value is AL2 or more and measurement is started, a measurement interruption signal is transmitted from the operation control device 4 to the water quality measuring device 3, and a timer 42 with a measurement waiting time T12 is started. And a measurement start signal is transmitted to the water quality measuring device 3 from the operation control apparatus 4 after progress of T12. During calibration, the membrane filtration device tap water is washed, and the inside of the filtered water tank 56 is filled with tap water, so that the measurement with the biosensor 13 is interrupted until it is replaced with sample water, that is, during T12. .

  While water quality monitoring is being performed, if a harmful substance is mixed into the sample water and the respiratory activity of nitrifying bacteria falls below the monitoring threshold by the biosensor 13, an alarm signal is transmitted from the biosensor 13 to the operation control device 4. To do. In this way, the water quality monitoring system is operated while performing automatic maintenance and automatic cleaning of the water quality monitoring system.

  In the above embodiment, tap water is used to remove germs that have propagated on the biosensor 13, but deposits and biological stains that are difficult to remove with tap water adhere to the surface of the biosensor 13. In this case, compressed air or pressurized water can be used instead of tap water.

  When using compressed air, as shown in FIG. 9, a switching valve 93 is provided in a pipe for supplying air to the sample flow path in the air blowing / feeding mechanism 29, and a system for normal operation and a system for cleaning are provided. The air tank 91 and the tank valve 94 are arranged at the outlet of the system at the time of cleaning. According to such a configuration, during normal operation, the tank valve 94 is closed, and during cleaning, the internal pressure of the air tank 91 is increased by the air pump, and then the tank valve 94 is opened, whereby compressed air is supplied to the biosensor 13. It is possible to remove the deposits and deposits such as biological dirt.

  When using pressurized water, a water tank 92 is installed in place of the air tank 91 as shown in FIG. Tap water is supplied to the water tank. According to such a configuration, during normal operation, the tank valve 94 is closed, and during cleaning, the internal pressure of the water tank 92 is increased by an air pump, and then the tank valve 94 is opened, so that pressurized water is supplied to the biosensor 13. The sample can be passed through the sample channel 25 to remove deposits and deposits such as biological dirt.

  In the above embodiment, the pretreatment device is used. However, when the water whose water quality is to be monitored does not require pretreatment such as water supply, the pretreatment device need not be installed. Even with a water quality monitoring system with such a configuration, during continuous operation for a long period of time, deposits and biological dirt adhered to the surface of the biosensor's microbial membrane can be removed during tap calibration. Since it can be removed with pressurized water or compressed air, the sensor output can be prevented from being lowered and the life of the microorganism can be prevented from being lowered. Therefore, the replacement frequency of the microorganism membrane can be reduced, and the cost can be reduced.

(Example 1)
Unless otherwise stated, a water quality monitoring system similar to the configuration shown in Fig. 1 is installed in a sand basin at a sewage treatment plant, and is continuously operated with automatic maintenance and automatic cleaning under the following conditions to conduct a water quality monitoring test. It was.

  A submersible pump was used as the water sampling device 1 and the flow rate was adjusted to about 50 L / min, and sample water was introduced to the screen 12. The filtration surface slit width of the screen 12 was 0.5 mm, and the flow rate at the time of cleaning the screen surface tap water was about 20 L / min. In the membrane filtration device 11, an internal pressure type membrane module 51 in which several hundreds of hollow fiber membranes were bundled was used in a cross flow method, and the flow rate of water into the raw water tank 52 was set to about 5 L / min. Air scrubbing by the air diffuser 53 was always performed. Air pressure was applied during backwashing. The flow rate at the time of membrane water washing with tap water was about 4 L / min. As the water quality measuring instrument 3, only the biosensor 13 was used. The flow rate when the biosensor 13 was washed with tap water was about 3 L / min.

  The set values of the timers of the operation control device 4 are: T1: 3 hours, T2: 2 minutes, T3: 28 minutes, T4: 3 minutes, T5: 6 hours, T6: 45 minutes, T7: 1 day, T8: 15 Minutes, T9: 1 day, T10: 1 minute, T11: 7 days, T12: 10 minutes. Moreover, each control value of the operation control apparatus 4 was AL1: -50 kPa, AL2: 1.5 mV, AL3: 5 times.

  When the clogging of the inside or the surface of the hollow fiber membrane proceeds, the negative pressure during the filtration operation increases, so the measured value of the pressure gauge 57 during the filtration operation (hereinafter referred to as “suction pressure”) It can be used as an index of filtration performance. Even when backwashing was performed, when the suction pressure became AL1 or higher, the membrane filtration device 11 was determined to be unable to continue operation.

  Further, if bacteria or hardness components adhere to the biosensor 13, oxygen diffusion to the microorganism film 21 is inhibited and the span calibration value becomes small. Therefore, the span calibration value is used as an index of the degree of contamination in the biosensor 13. It can be. The biosensor 13 is determined to be unable to continue operation when the number of repetitions of biosensor tap water cleaning when the span calibration value is an abnormal value reaches AL3.

  11 and 12 show the results of the water quality monitoring test of Example 1. FIG. FIG. 11 is a graph showing the transition of the suction pressure, which is an index of the filtration performance of the membrane filtration device 11. FIG. 12 is a graph showing the transition of the span calibration value that is an index of the degree of contamination in the biosensor 13.

  As shown in FIG. 11, the suction pressure gradually increased from about 4 kPa at the start of operation, but it was −10 kPa or less after 30 days, and maintained a level with no problem as filtration performance. Further, when the appearance of the hollow fiber membrane is observed, the amount of sludge accumulated on the surface of the hollow fiber membrane, the amount of bacteria adhering to the inside of the water tank flange 54 and the end surface of the mounting portion of the hollow fiber membrane, and the hollow fiber membrane can be reused I found out.

  In addition, for air scrubbing, backwashing, and tap water cleaning, which are cleaning methods for the surface of the hollow fiber membrane, a cleaning test was performed under the above conditions, and the most effective was tap water cleaning. I understood. From this, the backwashing interval time T3 can be made longer than the set value, and the risk of backflow of germs into the hollow fiber membrane due to backwashing can be reduced. That is, at the time of backwashing, there is a risk that the germs adhering in the water tank flange 54 will be pushed into the membrane by backwashing pressure, so the frequency of backwashing for the purpose of washing the membrane surface is reduced and the tap water into the raw water tank 52 is reduced. It is preferable to supplement the membrane surface cleaning with water.

  As shown in FIG. 12, the span calibration value was always 2 mV or more, and stable measurement could be continued without performing biosensor tap water cleaning. Moreover, when the external appearance of the filtered water piping 55 and the filtered water tank 56 was observed, both bacteria adhesion was slight. Moreover, since the measurement of the biosensor 13 was interrupted when the membrane filtration device tap water was washed, no false alarm was generated due to a difference in water quality between tap water and sewage as sample water.

  As described above, in Example 1, the water quality monitoring system could be stably and continuously operated for a long period of 30 days or more with simple maintenance work and with low maintenance frequency and maintenance cost.

(Example 2)
Among the operating conditions of Example 1, a water quality monitoring test was performed under the same operating conditions as in Example 1 except that the setting was changed so that the membrane filtration device tap water was not washed during biosensor calibration. The results are shown in FIG. 13 and FIG. FIG. 13 is a graph showing the transition of the suction pressure, and FIG. 14 is a graph showing the transition of the span calibration value.

  As shown in FIG. 13, the suction pressure gradually increased from about 5 kPa at the start of operation and reached about −40 kPa after 30 days, and the suction pressure was significantly increased as compared with Example 1. When the operation was continued without maintenance of the membrane filtration device 11, the suction pressure did not recover even after 40 days of backwashing, and the operation could not be continued. At this point, when the appearance of the hollow fiber membrane was observed, the amount of sludge deposited on the surface of the hollow fiber membrane was as small as in Example 1, but the amount of germs in the water tank flange 54 and the end surface of the hollow fiber membrane attachment portion was small. It was prominent, and it was found that the inside of the hollow fiber membrane was clogged with various bacteria, and it could not be reused by simple maintenance alone.

  When the hollow fiber membrane is reused, it is considered necessary to clean the inside of the hollow fiber membrane. However, if the removal of the inside of the membrane after the chemical cleaning is insufficient, the hollow fiber membrane is hollowed into the biosensor 13 after restarting. There is a possibility that the chemical solution remaining inside the yarn film flows in, damages the microbial film 21 and generates a false alarm. Therefore, it is considered that the maintenance labor for reusing the hollow fiber membrane is drastically increased.

  As shown in FIG. 14, the span calibration value gradually decreased from about 3 mV at the start of operation, and after about 2 weeks, the biosensor tap water cleaning was surely started 1 to 3 times during regular calibration. FIG. 15 shows an example of a calibration waveform of the biosensor 13 at the start of biosensor tap water cleaning. By washing the biosensor tap water, the bacteria and deposits attached to the biosensor 13 were peeled and discharged, and the span calibration value was AL2 or more, so the measurement could be continued after 40 days. . From this result, it was found that the effect of cleaning the biosensor when the span calibration is abnormal is high.

  Moreover, when the external appearance of the filtered water piping 55 and the filtered water tank 56 at this time was observed, both bacteria adhesion was remarkable. From this, in Example 1, the washing effect of the filtration water pipe 55 and the filtration water tank 56 of the membrane filtration device tap water washing is particularly high, and almost no germs flowed from the membrane filtration device 11 to the biosensor 23. It was found that the above results were obtained.

It is a mimetic diagram showing a schematic structure of one embodiment of a water quality monitoring system concerning the present invention. It is a schematic diagram which shows the internal structure of the biosensor shown in FIG. It is a schematic diagram which shows the structure of the microbial membrane and dissolved oxygen electrode which are shown in FIG. It is a schematic diagram which shows an example of the periphery structure of the biosensor shown in FIG. It is a schematic diagram explaining the mechanism in which a biosensor detects a harmful substance. It is a graph which shows the oxygen consumption rate in a biosensor. It is a schematic diagram which shows the structure of the operation control apparatus in FIG. It is a flowchart which shows the washing | cleaning algorithm of a biosensor. It is a schematic diagram which shows another example of the periphery structure of the biosensor shown in FIG. It is a schematic diagram which shows another example of the periphery structure of the biosensor shown in FIG. 3 is a graph showing a change in suction pressure in Example 1. 4 is a graph showing a transition of span calibration values in Example 1. 6 is a graph showing changes in suction pressure in Example 2. 10 is a graph showing a transition of span calibration values in Example 2. It is a graph which shows the calibration waveform at the time of wash | cleaning a biosensor with tap water.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Water sampling apparatus 2 Pretreatment apparatus 3 Water quality measuring instrument 4 Operation control apparatus 11 Membrane filtration apparatus 12 Screen 13 Biosensor 14 pH meter 15 Colorimeter 21 Microbial membrane 22 Dissolved oxygen electrode 24 Flow cell 25 Sample flow path 26 Constant temperature bath 27 Heat Exchanger 28 Bypass channel 29 Blowing and feeding mechanism 31-42 Timer 46 Analog-digital signal converter 47 Central processing unit 48 Digital-analog signal converter 51 Membrane module 52 Raw water tank 53 Aeration pipe 54 Water tank flange 55 Filtration water pipe 56 Filtration Water tank 57 Pressure gauge 58 Water supply pump 59 Filtration pump 60 Backwash air pump 61 Air scrubbing air pump 62, 63 Tap water piping 71 Screen drainage tank 72 Screen filtration water tank 81 Oxygen permeable membrane 82 Cathode electrode 83 Anode electrode 84 Cathode insulation 85 internal solution 87 nitrifying bacteria 88 substrate 89 oxygen 91 air reservoir 92 water tank 93 changeover valve 94 Tank Valve

Claims (8)

  A water collection device that continuously collects sample water from the water source to be monitored, a pretreatment device that continuously removes turbidity in the sample water collected by this water collection device, and a pretreatment device that is pretreated by this pretreatment device During the periodical calibration of the water quality measuring instrument that continuously detects harmful substances in the sample water and the water quality measuring instrument, the operation of the water sampling device is stopped and the sample water is passed to the water quality measuring instrument. A water quality monitoring system comprising: an operation control device that controls to stop water and wash the pretreatment device or the water quality measuring instrument.   A first cleaning in which the pretreatment device performs cleaning by flowing water through a portion of the sample water flowing between the membrane separation unit and the water quality measuring device between the membrane separation unit that filters the contamination in the sample water with a membrane. The water quality monitoring system according to claim 1, wherein the operation control device controls the first cleaning means to operate during the periodic calibration of the water quality measuring instrument.   The water quality measuring instrument includes a biosensor and a second cleaning unit that performs cleaning by flowing water or air through a portion in which the sample water flows in the biosensor, and the operation control device includes: 3. The water quality monitoring system according to claim 1, wherein when the biosensor is determined to be abnormal by periodic calibration, the second cleaning unit is controlled to operate.   A water sampling device that continuously collects sample water from the water source to be monitored, and a biosensor that continuously detects harmful substances in the sample water collected by this water sampling device, dissolved in a membrane with immobilized microorganisms When a biosensor provided with a dissolved oxygen electrode for measuring oxygen, a cleaning means for cleaning by flowing water or air in a portion where the sample water flows in the biosensor, and periodically calibrating the biosensor, A water quality monitoring system comprising: an operation control device that controls to operate the cleaning means when it is determined to be abnormal due to a decrease in sensor output.   Sample water is continuously collected from the water source to be monitored by the water sampling device, turbidity in the collected sample water is continuously removed by the pretreatment device, and harmful substances in the pretreated sample water are removed. During the water quality monitoring process, which is continuously detected by the water quality measuring instrument, and during the periodic calibration of the water quality measuring instrument, the sampling operation of the water sampling device is stopped, and the sample water is passed through the water quality measuring instrument. A water quality monitoring method including a calibration step of stopping and cleaning the pretreatment device.   The pretreatment apparatus is provided with a membrane separation means for filtering the contamination in the sample water with a membrane, and the calibration step is performed at a portion where the sample water flows between the membrane separation means and the water quality measuring instrument. The water quality monitoring method according to claim 5, comprising performing a first cleaning in which water is passed to perform cleaning.   When the water quality measuring instrument is equipped with a biosensor, and the calibration step determines that there is an abnormality in the calibration of the biosensor, the sample is washed with water or air flowing through the portion where the sample water flows in the biosensor. The water quality monitoring method according to claim 5, further comprising performing a second cleaning.   A biosensor comprising a sample water sampled continuously from a water source to be monitored and a harmful substance in the sample water sample, a membrane fixed with microorganisms and a dissolved oxygen electrode for measuring dissolved oxygen When water quality is monitored continuously in the process and the biosensor is calibrated periodically, if it is determined that there is an abnormality due to a decrease in sensor output, water or air is allowed to flow through the portion of the biosensor where sample water flows. Water quality monitoring method including calibration process for cleaning.

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