JP2009000585A - Membrane filtration device - Google Patents

Abstract

The object of the present invention is to prevent water from staying in a pipe for backwashing, and to prevent erroneous determination and judgment delay of a fine particle counter.
A membrane filtration apparatus 100 includes a first pipe 105 that communicates a permeate side of a membrane module 101 that filters water to be treated and a storage tank 106, and a second pipe 108 that forms a backwash line. The backwashing pump 109 provided in the middle of the second pipe 108 is arranged at a position higher than the storage tank 106, and one end of the second pipe 108 is connected to the inside of the storage tank 106. The filtrate was inserted below the water level. When switching from backwashing to filtration, the backwashing pump 109 is stopped, the second valve 110 is closed and the first valve 107 is opened, and the backwashed filtered water in the second pipe 108 is self-weighted. And it decided to discharge to the storage tank 106 by the water supply of the pump for filtration.
[Selection] Figure 1

Description

  The present invention is capable of cleaning a membrane module for filtering surface water such as lake water or groundwater by supplying cleaning water from the permeate side to the raw water side (hereinafter referred to as backwashing), and detecting a membrane abnormality. The present invention relates to a membrane filtration device equipped with the device.

  Membrane filtration devices are used to remove Cryptosporidium, which is a chlorine-resistant protozoa, mixed in surface water such as lake water, which is raw water, or ground water (environmental water). The membrane module that removes Cryptosporidium and the like in the membrane filtration device is periodically cleaned. 2. Description of the Related Art Conventionally, there is a membrane filtration apparatus that employs a backwashing method in which filtered water is supplied from the permeate side of a membrane module toward the raw water side to peel and remove deposits on the membrane module (see, for example, Patent Document 1).

With reference to FIG. 3, the membrane filtration apparatus which employ | adopted the conventional backwashing system is demonstrated.
When the raw water is filtered, the raw water is sent to the membrane module 302 via the supply pipe 301. The filtered water filtered by the membrane module 302 is sent to the storage tank 307 via the first pipe 305, and is sent to the particulate counter 304 via the connecting pipe 303 branched from the first pipe 305. The particle counter 304 counts the number of particles and checks the water quality.

  When the membrane module 302 is washed, filtered water is supplied from the permeate side of the membrane module 302 toward the raw water side. Therefore, the first valve 306 is closed and the second valve 310 is opened, the backwash pump 309 is driven, and the filtered water stored in the storage tank 307 is supplied to the second pipe (backwash pipe) 308. Via the fine particle counter 304, it is supplied to the permeate side of the membrane module 302. In this manner, the membrane module 302 is washed by sending the treated water in the storage tank 307 to the membrane module 302 from the backwash line (308).

When switching from cleaning of the membrane module 302 to filtration of raw tap water, the second valve 310 provided in the second pipe 308 is closed.
JP 2006-272136 A

  By the way, in the said conventional membrane filtration apparatus, when the 2nd valve | bulb 310 of the 2nd piping 308 was closed in order to switch from a backwash process to a filtration process, the state which filtrated water retained in the 2nd piping 308 It was. For this reason, fine particles may grow in the second pipe 308 due to oxidation or aggregation. These fine particles adhere to the permeate side of the membrane module 302 at the time of backwashing, peel off from the membrane module 302 at the time of resumption of filtration, and cause the phenomenon that abnormal values are measured by the fine particle counter 304 as noise. For this reason, even though there is no abnormality in the membrane module 302, the particle counter 304 may indicate a numerical value indicating that there is an abnormality in the membrane module 302, which may cause an erroneous determination.

  Further, the value that should be indicated by the particle counter 304 needs to be 100 pieces / mL or less. However, once the value of the particle counter 304 is increased, it takes time to return to a normal value. The filtered water cannot be sent to the next stage. For this reason, the filtered water cannot be supplied until the value of the particulate counter 304 returns to a normal value, but at this time, the filtration process itself does not stop, so the filtered water is, for example, upstream (upper) from the membrane module. It is necessary to return to the raw water line (raw water tank) or to drain the water.

  The present invention has been made in view of such points, and can completely drain filtered water from the backwashing pipe when switching from backwashing to filtration, preventing erroneous determination immediately after the start of filtration. An object of the present invention is to provide a membrane filtration device that can maintain the numerical value of the fine particle counter at a normal value and has no determination delay.

  The membrane filtration device of the present invention communicates a membrane module that filters the water to be treated, a storage tank that stores the treated water filtered by the membrane module, and a permeate side of the membrane module and the storage tank. A first pipe, a first valve provided in the middle of the first pipe, one end is inserted below the permeate water level in the storage tank, and the other end is the first pipe of the first pipe. A second pipe connected between the first valve and the membrane module, a second valve provided in the middle of the second pipe, and a position higher than the water level of the storage tank. A backwashing pump installed in the middle of the second pipe on the storage tank side with respect to the second valve, and one end connected to the storage tank side with respect to the first valve of the first pipe, and the other end A third pipe connected to the storage tank side of the backwash pump of the second pipe; Characterized by comprising.

  According to this configuration, the backwash pump is disposed at a position higher than the water level of the storage tank, and the predetermined point on the storage tank side and the second pipe for backwashing the first valve of the first pipe. Since a predetermined point on the storage tank side of the pump is connected by the third pipe, when the first valve is opened when the filtration process is resumed, the treated water in the second pipe is discharged to the storage tank, and the filtration process is performed. Sometimes, the treated water can be prevented from staying in the second pipe. This prevents fine particles from growing due to oxidation or aggregation due to water staying in the second pipe, and the fine particles adhere to the permeate side of the membrane module during backwashing, and the fine particles peel from the membrane module when filtration is resumed. As a result, it is not measured by the fine particle counter. In addition, the backwash treated water staying in the second pipe is discharged by its own weight and the flow of treated water when switching to the filtration process, but one end of the second pipe is connected to the permeated water in the storage tank. Since it is inserted below the water level, air can be prevented from entering the second pipe, and the backwash process water can be sucked up when the pump is started in the next backwash process.

  In the membrane filtration apparatus, when the membrane module performs filtration, the first valve is opened and the second valve is closed to supply the water to be treated to the raw water side of the membrane module. The treated water discharged from the permeate side of the membrane module is sent to the storage tank through the first pipe, and a part of the treated water flowing through the first pipe is sent to the first via the third pipe. When the membrane module is backwashed, the first valve is closed and the second valve is opened to turn the backwash pump on. When the treated water sucked from the storage tank is driven and sent to the first pipe via the second pipe and supplied to the permeate side of the membrane module, and the backwash process is switched to the filtration process. The backwash The pump is stopped, opening said first valve closes the second valve, characterized by discharging the treated water in the second pipe to the reservoir.

  In this way, by operating the first valve and the second valve, the treated water can be completely discharged from the second pipe when switching from the backwashing process to the filtration process. Since part of the treated water flowing through the first pipe is sent to the second pipe via the third pipe and sent from the second pipe to the storage tank, there is no concern that the treated water will remain in the third pipe.

  According to the present invention, at the time of switching from backwashing to filtration, treated water can be completely discharged from the backwashing pipe, preventing erroneous determination immediately after resumption of filtration, and maintaining the value of the particulate counter at a normal value. This can prevent a determination delay.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a schematic configuration diagram of a membrane filtration device according to the present embodiment.
The membrane filtration apparatus 100 of this Embodiment shall filter raw water supply with a horizontal hollow fiber membrane in a water purification plant or the like. The membrane filtration device 100 is provided with a membrane module 101 composed of a horizontal type hollow fiber membrane. One end of the supply pipe 102 is connected to the raw water side of the membrane module 101, and raw tap water is supplied from the supply pipe 102. The filtered water as the treated water obtained by filtering the raw water as the treated water in the membrane module 101 is discharged from the permeate side. One end of a first pipe 105 is connected to the permeate side of the membrane module 101, and the other end of the first pipe 105 is inserted into a storage tank 106 that stores treated water. A first valve 107 is provided in the middle of the first pipe 105. At the time of the filtration process, the filtered water filtered by the membrane module 101 passes through the first pipe 105 and flows into the storage tank 106. The first pipe 105 is provided with a fine particle counter 104 via a connecting pipe 103. The fine particle counter 104 continuously monitors the concentration of raw water (initial) particles supplied to the membrane module 101, and changes the membrane treated water particles due to the influence of raw water leakage to the permeate side of the membrane module 101 when the membrane module 101 breaks. Monitor the concentration continuously. This fine particle counter 104 uses a device capable of measuring fine particles of 0.5 μm or more in order to continuously monitor the raw water (initial) particle concentration and raw water leakage.

  Further, a second pipe 108 that is a backwash pipe that branches from the upstream side of the first valve 107 in the first pipe 105 and reaches the storage tank 106 is provided. The pipe end of the second pipe 108 is inserted below the water level of filtrate from the upper part of the storage tank 106. The second pipe 108 is provided with a second valve 110 in the vicinity of the connecting portion with the first pipe 105. The second pipe 108 is provided with a backwash pump 109 at a position higher than the water level of the storage tank 106 and at a position closer to the storage tank 106 than the second valve 110.

  In addition, a third pipe 113 is provided that connects the first pipe 105 and the second pipe 108 in the middle of the pipe. One end of the third pipe 113 is connected to the downstream side of the first valve 107 in the first pipe 105 (between the first valve 107 and the storage tank 106, and the connection point is indicated by reference numeral 111). Yes. Further, the other end of the third pipe 113 is connected to the storage tank 106 side (the connection point is indicated by reference numeral 112) rather than the backwash pump 109 in the second pipe 108. That is, in the present embodiment, when the first valve 107 is opened and the second valve 110 is closed, the treated water remaining in the second pipe 108 can be discharged to the storage tank 106. The piping structure is devised.

Next, operation | movement of the membrane filtration apparatus 100 comprised as mentioned above is demonstrated.
When starting the filtration process, the first valve 107 is opened and the second valve 110 is closed. Then, a supply pump (not shown) is driven to supply raw water from the supply pipe 102 to the raw water side of the membrane module 101. Filtrated water obtained by filtering raw tap water in the membrane module 101 is discharged from the permeate side of the membrane module 101, and a part thereof is sent to the fine particle counter 104 via the connecting pipe 103 to check the particle concentration. . Further, the filtrate discharged from the permeate side of the membrane module 101 flows into the storage tank 106 through the first pipe 105 and is stored. Further, part of the filtered water sent to the first pipe 105 flows into the second pipe 108 via the third pipe 113. The filtered water that has flowed into the second pipe 108 from the third pipe 113 is pushed out by water pressure and flows into the storage tank 106. The fine particle counter 104 continuously counts the raw water (initial) particle concentration and raw water leakage by counting the number of fine particles of the filtered water taken in.

  When switching from the filtration process to the backwash process, the first valve 107 is closed and the second valve 110 is opened. By driving the backwash pump 109, the filtered water stored in the storage tank 106 is pulled up through the second pipe 108 and sent to the first pipe 105 from the connecting portion with the first pipe 105. Since the first valve 107 is closed, the backwash filtered water sent to the first pipe 105 is supplied from the permeate side of the membrane module 101 toward the raw water side. As a result, filtered water for backwashing is supplied from the permeate side of the membrane module 101 toward the raw water side, so that deposits adhering to the raw water side of the membrane are peeled off and removed, and the inside of the membrane module is removed. Particles are swept out of the membrane module and removed.

  After backwashing, switch from backwashing to filtration. Therefore, the backwash pump 109 is stopped, the second valve 110 is closed, and the first valve 107 is opened. The second pipe 108 with the second valve 110 closed communicates with the first pipe 105 with the first valve 107 opened through a third pipe 113. For this reason, the filtered water for backwashing filled in the second pipe 108 when the second valve 110 is closed is caused by the self-weight and the pumping water supplied when the first valve 107 is opened. It is discharged from the second pipe 108 to the storage tank 106. Accordingly, the backwash filtrate in the second pipe 108 located below the second valve 110 is completely discharged out of the second pipe 108. In addition, since one end of the second pipe 108 is inserted below the level of filtrate water in the storage tank 106, air can be prevented from entering the second pipe 108, and backwashing is performed in the next backwashing process. When the water pump 109 is started, filtered water for backwashing can be sucked up.

  As described above, according to the present embodiment, since the backwash filtered water does not stay in the second pipe 108 after the backwashing is completed, the backwash filtered water stays in the second pipe 108. There is no possibility that the inside will be contaminated, and fine particles grown in the pipe will not adhere to the permeate side of the membrane module 101 during backwashing. Therefore, it is possible to prevent the fine particle counter 104 that measures the fine particles peeled off from the permeate side of the membrane module 101 when the filtration is resumed from showing an abnormal value and erroneously determining as raw water leakage or the like. In addition, since the fine particles grown in the pipe are not separated and the value of the fine particle counter 104 does not increase, the conventional time loss that must be waited until the value returns to a normal value can be reduced.

Hereinafter, the results of verifying the prevention of water retention in the backwash process using the membrane filtration device 100 will be described.
FIG. 2 shows the result of measuring the number of fine particles of 0.5 μm or more in the treated water with the fine particle counter 104 when filtration is resumed. Abnormality detection by the fine particle counter 104 determines that the number of fine particles is 100 / mL or more as abnormal.

  In the conventional apparatus, filtered water for backwashing stays in the second pipe 308 and the inside of the pipe is contaminated. Therefore, the number of fine particles in the treated water at the time of resuming filtration is stabilized to 100 or less even after 1 hour or more. There wasn't. For this reason, the fine particle counter 104 has erroneously determined that an abnormality has been detected or has made a determination delay.

  In this membrane filtration device 100, the retention of filtered water for backwashing in the second pipe 108 has been eliminated, so that the number of fine particles in the filtered water at the time of resumption of filtration is stable to 100 or less within 30 minutes. I understand. As a result, the problem of erroneous determination and discrimination delay of the particle counter 104 can be solved.

  The present invention is applicable to a membrane filtration device that performs backwashing by supplying backwashed filtrate water supplied from a backwash line from the permeate side of the membrane module to the raw water side.

The block diagram of the membrane filtration apparatus concerning one embodiment of this invention The figure which shows the verification result which compared the number of microparticles | fine-particles after backwashing with the membrane filtration apparatus of the said one embodiment, and the conventional membrane filtration apparatus Configuration of conventional membrane filtration device

Explanation of symbols

  DESCRIPTION OF SYMBOLS 100 ... Membrane filtration apparatus, 101 ... Membrane module, 104 ... Fine particle counter, 105 ... 1st piping, 106 ... Storage tank, 107 ... 1st valve, 108 ... 2nd piping, 109 ... Backwash pump, 110 ... Second valve, 113 ... Third piping

Claims (2)

  A membrane module that filters the water to be treated, a storage tank that stores the treated water filtered by the membrane module, a first pipe that communicates the permeate side of the membrane module and the storage tank, and A first valve provided in the middle of the first pipe, one end inserted below the permeate water level in the storage tank, and the other end of the first valve of the first pipe and the membrane module; A second pipe connected between the second pipe, a second valve provided in the middle of the second pipe, and a storage tank higher than the water level of the storage tank. A backwashing pump installed in the middle of the second pipe on the side, one end connected to the storage tank side of the first valve of the first pipe, and the other end of the backwashing of the second pipe And a third pipe connected to the storage tank side of the pump for use. That membrane filtration device. When performing filtration with the membrane module, the first valve is opened and the second valve is closed to supply water to be treated to the raw water side of the membrane module, and discharged from the permeate side of the membrane module. The treated water is sent to the storage tank through the first pipe, and a part of the treated water flowing through the first pipe is sent to the second pipe via the third pipe. Sent to the reservoir,
When the membrane module is backwashed, the first valve is closed and the second valve is opened to drive the backwash pump, and the treated water sucked up from the storage tank is drawn into the second pipe. Through the first pipe to supply to the permeate side of the membrane module,
When switching from the backwash process to the filtration process, the backwash pump is stopped, the second valve is closed and the first valve is opened, and the treated water in the second pipe is supplied to the storage tank. The membrane filtration device according to claim 1, wherein the membrane filtration device is discharged.

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