JP2013052326A - Water treatment method and water treatment apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a water treatment apparatus capable of detecting the clogging of a membrane while suppressing the initial cost and the maintenance cost of the water treatment apparatus.SOLUTION: The water treatment apparatus includes: a membrane module 2; a liquid feed pump P1 for passing processed water through the membrane module 2; a wattmeter 22 for measuring a power consumption of the liquid feed pump P1; a flowmeter 23 for measuring the flow of the filtrated water that has passed through the membrane module 2; and a washing time detection means 30 for obtaining the power consumption per a unit flow of the liquid feed pump P1 based on the measured values of the wattmeter 22 and the flowmeter 23, and determining the cleaning timing when a value corresponding to the power consumption exceeds a predetermined value.

Description

  The present invention relates to a water treatment method and a water treatment apparatus for treating water to be treated by membrane filtration with a membrane module.

  In a water treatment apparatus using a membrane module, suspended substances, organic substances, and the like in the water to be treated are gradually deposited on the surface of the membrane over a long period of operation, and the membrane is clogged. When the membrane is clogged, the membrane pressure increases, the filtration flux decreases, etc., the water purification efficiency decreases, and the overall operation efficiency of the water treatment device decreases. Therefore, in the operation cycle of the water treatment device, the membrane module is washed after the membrane filtration treatment step for a predetermined time.

  As described in Patent Document 1, the determination of the cleaning time of the membrane module is carried out by providing a differential pressure gauge downstream of the membrane module and steadily measuring the transmembrane pressure difference, and determining the cleaning time based on the transmembrane pressure difference. The method of determining is generally done.

Japanese Patent No. 4018990

  However, since the differential pressure gauge is an expensive instrument, there is a problem that the initial cost of the water treatment apparatus increases by providing the differential pressure gauge. In addition, since the differential pressure gauge requires regular maintenance such as removal of clogging of the pressure guiding tube, there is a problem that the maintenance requires labor and cost.

  Therefore, the objective of this invention is providing the water treatment method and water treatment apparatus which can detect the clogged state of a membrane module, suppressing the initial cost and maintenance cost of a water treatment apparatus.

  In order to achieve the above-described object, the water treatment method of the present invention performs a membrane filtration process by passing the water to be treated through a membrane module by a liquid feed pump, and according to the power consumption per unit flow rate of the liquid feed pump. When the value exceeds a predetermined value, the membrane module is cleaned.

  When the membrane module is clogged, the load applied to the liquid feed pump increases, and the amount of power consumed per unit flow rate of the liquid feed pump increases. Thus, the power consumption per unit flow rate of the liquid feed pump has a high correlation with the clogged state of the membrane module. Therefore, according to the water treatment method of the present invention, when the value corresponding to the power consumption per unit flow rate of the liquid feed pump exceeds a predetermined value, it is detected that the membrane module is clogged, and the membrane module Therefore, the membrane module can be clogged and the water to be treated can be stably filtered over a long period of time. Further, when detecting the clogged state of the membrane module, there is no need to provide a differential pressure gauge as in the prior art, and only the power consumption of the liquid feed pump and the flow rate of filtered water need only be measured. Since these are inexpensive instruments that are unlikely to fail, the initial cost and maintenance cost of the water treatment apparatus can be reduced.

  In the water treatment method of the present invention, the temperature of the water to be treated is measured, and the value obtained by correcting the power consumption with the temperature coefficient of the water to be treated is a value corresponding to the power consumption, or It is preferable that the power consumption is a value corresponding to the power consumption, the temperature of the water to be treated is measured, and a value obtained by correcting a reference threshold value with a temperature coefficient of the water to be treated is the predetermined value. . This is because the viscosity of the liquid changes depending on the temperature as shown in FIG. 4. Generally, the higher the temperature, the lower the viscosity of the liquid. The decrease in viscosity leads to a decrease in power consumption of the pump. Therefore, a characteristic diagram of the pump as shown in FIG. 5 is created in advance, and the temperature coefficient is calculated. According to this aspect, even in the water to be treated whose fluidity greatly varies depending on the temperature, the clogging state of the intermembrane Joule can be detected with high accuracy. For this reason, it is possible to accurately detect the clogged state of the inter-membrane module and clean the membrane module at the optimum timing regardless of the property of the water to be treated.

  In the water treatment method of the present invention, the treated water is preferably activated sludge mixed water after activated sludge treatment. According to this aspect, even if the water to be treated contains an organic substance, the organic substance is decomposed and removed by the activated sludge treatment, so that an extremely clean filtered water free from the organic substance and fresh substances can be obtained. .

  In the water treatment method of the present invention, it is preferable that the washing means is at least one selected from bubbling, backwashing, chemical addition backwashing, brush washing, and water discharge washing.

  Further, the water treatment apparatus of the present invention includes a membrane module that performs membrane filtration treatment of water to be treated, a liquid feed pump that passes the water to be treated through the membrane module, and a wattmeter that measures power consumption of the liquid feed pump. And, based on the flow meter for measuring the flow rate of the filtered treated water that has passed through the membrane module, and the measured values of the power meter and the flow meter, obtaining the power consumption per unit flow rate of the liquid feeding pump, A cleaning time detecting means for determining that it is a cleaning time when a value corresponding to the amount of power consumption exceeds a predetermined value is provided.

  According to the water treatment apparatus of the present invention, the power consumption per unit flow rate of the liquid feeding pump is obtained based on the measured value of the flow meter and the measured value of the wattmeter, and a value corresponding to the consumed power amount is predetermined. If it exceeds the value, it is equipped with a cleaning time detection means that determines that it is the cleaning time, so that it is possible to determine the cleaning time of the membrane module by detecting the clogged state of the membrane without providing a differential pressure gauge as in the past. The water to be treated can be membrane-filtered stably over a long period of time while suppressing the initial cost and maintenance cost of the treatment apparatus.

  The water treatment apparatus of the present invention further includes a cleaning device for cleaning the membrane module, and a control device for operating the cleaning device for a predetermined time when the cleaning time detection means determines that it is a cleaning time. It is preferable.

  The water treatment apparatus of the present invention further includes a thermometer for measuring the temperature of the water to be treated, and the cleaning time detection unit is configured to use the power consumption based on the temperature of the water to be treated measured by the thermometer. The value corrected by the temperature coefficient of the water to be treated is a value corresponding to the power consumption amount, or the power consumption amount is a value corresponding to the power consumption amount and measured by the thermometer. It is preferable that a value obtained by correcting a reference threshold value with a temperature coefficient of the water to be treated is set as the predetermined value based on the temperature of the water to be treated.

  It is preferable that the water treatment apparatus of the present invention further includes an activated sludge treatment tank, and the membrane module is disposed downstream of the activated sludge treatment tank or in the generated sludge treatment tank.

  In the water treatment apparatus of the present invention, the cleaning apparatus is preferably an apparatus that performs at least one selected from bubbling, backwashing, chemical addition backwashing, brush cleaning, and water discharge cleaning.

  According to the present invention, when the value corresponding to the power consumption per unit flow rate of the liquid feed pump exceeds a predetermined value, it is detected that the membrane module is clogged, and the timing for applying the membrane module cleaning means is determined. Since it is determined, clogging of the membrane of the membrane module is eliminated, and the water to be treated can be subjected to membrane filtration treatment stably over a long period of time. In addition, when detecting the clogged state of the membrane, it is not necessary to provide a differential pressure gauge as in the prior art, and the initial cost and maintenance cost of the water treatment apparatus can be suppressed.

It is a schematic block diagram of the water treatment apparatus of this invention. It is a sequence diagram of 1st Embodiment of the washing | cleaning time detector of the water treatment apparatus. It is a sequence diagram of 2nd Embodiment of the washing | cleaning time detector of the water treatment apparatus. It is a graph showing the temperature dependence of the viscosity of water at 1 atm. It is the graph which showed the example of the temperature dependence of the power consumption of a commercial pump.

  An embodiment of the water treatment apparatus of the present invention will be described with reference to FIG.

  A pipe L <b> 1 extending from the water to be treated is connected to the activated sludge treatment tank 1.

  The activated sludge treatment tank 1 is not particularly limited as long as the activated sludge containing microorganisms stays in the tank and the activated sludge can be treated by decomposing organic substances by the action of microorganisms. For example, an aeration tank containing aerobic microorganisms such as ammonia oxidizing bacteria and nitrite oxidizing bacteria, an intermittent aeration tank containing anaerobic microorganisms such as nitrite oxidizing bacteria and anaerobic microorganisms such as denitrifying bacteria can be used.

  The activated sludge treatment tank 1 is provided with a thermometer 21 that measures the temperature of the treatment liquid in the tank. The measured value of the thermometer 21 is input to the cleaning time detector 30. From the lower part of the activated sludge treatment tank 1, a sludge extraction pipe L2 extends.

  In this embodiment, the membrane module 2 is disposed in the activated sludge treatment tank 1 and is immersed in the treatment liquid in the tank. The membrane module 2 may be arranged outside the activated sludge treatment tank 1.

  From the secondary side of the membrane module 2 (the side where the filtered treated water circulates), a pipe L3 in which the pump P1 and the flow meter 23 are arranged extends, and the treatment in the tank is performed by operating the pump P1. Water is subjected to membrane filtration treatment in the membrane module 2. A power meter 22 for measuring the power consumption of the pump P1 is disposed in the pump P1. The measured values of the wattmeter 22 and the flow meter 23 are input to the cleaning time detector 30. The operation of the pump P <b> 1 is controlled by the control device 40.

  As a filtration membrane used for the membrane module 2, any general filtration membrane can be used. For example, a reverse osmosis (RO) membrane, an ultrafiltration (UF) membrane, a microfiltration (MF) membrane, a hollow fiber (HF) membrane, etc. are mentioned. Examples of the material for the filtration membrane include polyacrylonitrile, polyimide, polyethersulfone, polyphenylene sulfide sulfone, polytetrafluoroethylene, polyvinylidene fluoride, polypropylene, and polyethylene. The form of the membrane module 5 is not particularly limited, and examples thereof include a hollow fiber membrane module, a flat membrane type module, a spiral type module, and a tubular module.

  An aeration (bubbling) device 3 is disposed below the membrane module 2 so as to prevent clogging of the membrane module 1 by aeration. The operation of the aeration apparatus 3 is controlled by the control device 40. In this embodiment, the aeration apparatus 3 corresponds to a “cleaning apparatus” in the present invention.

  In this embodiment, an aeration apparatus is used as the cleaning apparatus. However, the present invention is not limited to the aeration apparatus, and a conventionally known cleaning apparatus can be used. For example, a washing device that backwashes a part of the filtered water from the secondary side of the membrane module 2 back to the primary side, or sodium hypochlorite, hydrogen peroxide, citric acid, A cleaning device that adds back chemicals such as acid, hydrochloric acid, or a commercially available membrane cleaning agent from the secondary side to the primary side of the membrane module 2 and backwashes the chemical, or the primary side of the membrane module 2 A brush cleaning device, a device that discharges and cleans the primary side of the membrane module 2, and the like are listed as preferable examples, and these may be used. A plurality of types of cleaning devices may be used in combination.

  When the cleaning start signal is input from the cleaning time detector 30, the control device 40 inputs a stop signal to the pump P <b> 1 and an operation signal to the aeration device 3 to clean the membrane module 2 for a predetermined time. Is set. In addition, you may wash | clean with the aeration apparatus 3, continuing a driving | operation, without stopping the pump P1.

  Next, an embodiment of the water treatment method of the present invention will be described using the water treatment apparatus shown in FIG. In addition, there is no limitation in particular as to-be-processed water used as the process target of the water treatment method of this invention. For example, sewage, factory wastewater discharged from chemical factories and food factories, and the like can be mentioned.

  First, the water to be treated is supplied to the activated sludge treatment tank 1 and treated with activated sludge. Then, the treated water after the activated sludge treatment is subjected to membrane filtration treatment by the membrane module 2, and the filtered water is sent to a drainage system, and chlorine and the like are added to drain out of the system. In addition, the sludge that has accumulated at the bottom of the activated sludge treatment tank 1 is periodically extracted from the pipe L2 and sent to a sludge treatment system (not shown) to be processed by drying or dehydrating.

  In this way, the water to be treated is subjected to the membrane filtration treatment by the membrane module 2 to perform the water treatment. If the membrane filtration treatment is continued, the organic matter and the fresh matter in the treatment water are Adhering to the inside of the membrane, the membrane filtration efficiency decreases.

  Therefore, in the present invention, the cleaning time of the membrane module 2 is determined as follows, and when the cleaning time has been reached, the membrane module 2 is cleaned.

  Hereinafter, the first embodiment of the method for determining the cleaning time by the cleaning time detector 30 will be described with reference to FIG.

  The measured value of the thermometer 21, the measured value of the wattmeter 22, and the measured value of the flow meter 23 are input to the first calculation unit 31, and the unit of the temperature-corrected pump P 1 is calculated based on the following equation (1). The power consumption per flow rate is calculated.

Power consumption per unit flow rate of the pump P1 corrected for temperature = {(measured value of the wattmeter 22) / (measured value of the flowmeter 23)} × t / T (1)
(In Equation (1), t is a temperature coefficient, and T is a measured value of the thermometer 21)

  Next, the value of power consumption per unit flow rate of the pump P <b> 1 whose temperature is corrected and the reference threshold value calculated by the first calculation unit 31 are input to the determination unit 32.

  The reference threshold value is set in advance as a reference threshold value by measuring in advance the value of power consumption per unit flow rate of the pump P1 when the membrane module 2 needs to be cleaned.

  When the power consumption per unit flow rate of the temperature-corrected pump P1 is equal to or greater than the reference threshold value, the determination unit 32 determines that the membrane module 2 is clogged and has reached the cleaning time, and the cleaning start signal Is input to the control device 40. When the cleaning start signal is input to the control device 40, the operation of the pump P1 is stopped, the aeration device 3 is operated, and the membrane module 2 is cleaned for a predetermined time.

  On the other hand, when the power consumption per unit flow rate of the temperature-corrected pump P1 is less than the reference threshold value, it is determined that the membrane module 2 is not clogged and the cleaning time has not been reached, and the membrane filtration process is performed. A signal is input to the control device 40 to continue, and the membrane filtration process is continued.

  The determination of the cleaning time by the cleaning time detector 30 may be performed as shown in the sequence diagram of FIG. That is, in FIG. 2, the power consumption per unit flow rate of the pump P1 as an actual measurement value obtained from the measurement value of the power meter 22 and the measurement value of the flow meter 23 is compared with the reference threshold value. Although the cleaning time is determined, the cleaning time may be determined by comparing the value obtained by correcting the temperature of the reference threshold with the power consumption per unit flow rate of the pump P1 as an actual measurement value.

  Hereinafter, a second aspect of the method for determining the cleaning time by the cleaning time detector 30 will be described with reference to FIG.

  The measurement value of the thermometer 21 and the measurement value of the wattmeter 22 are input to the second calculation unit 33, and the power consumption per unit flow rate of the pump P1 as the actual measurement value is calculated based on the following equation (2). The

Power consumption per unit flow rate of pump P1 as an actual measurement value = {(measured value of power meter 22) / (measured value of flow meter 23)} (2)

  Further, the reference value and the measured value of the thermometer 21 are input to the third calculation unit 34, and the temperature-corrected reference threshold value is calculated based on the following equation (3).

Temperature corrected reference threshold = reference threshold × t / T (3)
(In Expression (3), t is a temperature coefficient, and T is a measured value of the thermometer 21)

  Next, the value of power consumption per unit flow rate of the pump P1 as an actual measurement value calculated by the second calculation unit 33 and the temperature-corrected reference threshold value calculated by the third calculation unit 34 are as follows. Input to the determination unit 35.

  When the power consumption per unit flow rate of the pump P1 as the actual measurement value is equal to or higher than the temperature-corrected reference threshold value, it is determined that the membrane module 2 is clogged and the cleaning time has been reached, and the cleaning start signal is controlled. 40.

  On the other hand, when the power consumption per unit flow rate of the pump P1 as an actual measurement value is less than the temperature-corrected reference threshold value, it is determined that the membrane module 2 is not clogged and the cleaning time has not been reached. A signal is input to the control device 40 to continue the filtration process, and the membrane filtration process is continued.

  When the viscosity of the water to be treated is low and its fluidity hardly fluctuates depending on the temperature, the power consumption per unit flow rate of the pump P1 as an actual measurement value and the reference threshold need not be temperature corrected. That is, the cleaning time detector 30 directly compares the power consumption per unit flow rate of the pump P1 as the actual measurement value with the reference threshold value, and the power consumption per unit flow rate of the pump P1 as the actual measurement value is larger. In this case, it is determined that the cleaning time has been reached, and a cleaning start signal is input to the control device 40. When the power consumption per unit flow rate of the pump P1 as an actual measurement value is smaller, the membrane filtration process is continued. The signal may be input to the control device 40 as much as possible.

  As described above, according to the present invention, the cleaning time of the membrane module 2 is determined based on the value corresponding to the power consumption of the pump P1 per unit flow rate. Therefore, the membrane module 2 is cleaned at an optimal timing. Clogging can be eliminated, and the water to be treated can be subjected to membrane filtration treatment stably over a long period of time. Further, since it is not necessary to provide a differential pressure gauge as in the prior art when detecting the clogged state of the membrane module, the initial cost and maintenance cost of the water treatment apparatus can be suppressed.

  In addition, when performing a water treatment only for the purpose of removal of a foreign matter, it is not necessary to use the activated sludge treatment tank 1. In this case, the same treatment may be performed by immersing the cleaning of the membrane module in the storage tank of the water to be treated, or the membrane filtration treatment may be performed by supplying the water to be treated directly to the membrane module.

  On the other hand, in the case of water to be treated containing organic matter, when it is desired to remove not only fresh matter but also organic matter, the activated sludge treatment tank 1 is located upstream of the membrane module 2 as shown in FIG. The treated water is introduced into the activated sludge treatment tank 1 and treated with activated sludge to remove organic matter, etc., and then passed through the membrane module 2 to allow floating microorganisms and other suspended substances (abbreviated as SS). In other words, clean treated water from which organic substances, fresh substances, and the like are removed can be obtained by subjecting the fresh substances to membrane filtration treatment and solid-liquid separation.

1: Activated sludge treatment tank 2: Membrane module 3: Aeration device 21: Thermometer 22: Power meter 23: Flow meter 30: Cleaning time detector 40: Control devices L1 to L3: Piping P1: Pump

Claims (11)

Water to be treated is subjected to membrane filtration treatment by passing it through a membrane module by a liquid feed pump,
When the value according to the power consumption per unit flow rate of the liquid feed pump exceeds a predetermined value, the membrane module cleaning means is applied.   The water treatment method according to claim 1, wherein the temperature of the water to be treated is measured and a value obtained by correcting the power consumption with a temperature coefficient of the water to be treated is a value corresponding to the power consumption.   The power consumption is a value corresponding to the power consumption, the temperature of the treated water is measured, and a value obtained by correcting a reference threshold value with a temperature coefficient of the treated water is the predetermined value. The water treatment method according to 1.   The water treatment method according to any one of claims 1 to 3, wherein the water to be treated is activated sludge mixed water after activated sludge treatment.   The water treatment method according to any one of claims 1 to 4, wherein the cleaning means is at least one selected from bubbling, backwashing, chemical addition backwashing, brush cleaning, and water discharge cleaning. A membrane module for subjecting water to be treated to membrane filtration;
A liquid feed pump for passing the treated water through the membrane module;
A power meter for measuring the power consumption of the liquid pump;
A flow meter for measuring the flow rate of filtered water that has passed through the membrane module;
Based on the measured values of the power meter and the flow meter, the power consumption per unit flow rate of the liquid feeding pump is obtained, and if the value corresponding to the power consumption exceeds a predetermined value, it is determined that it is a cleaning time. A water treatment apparatus comprising: a cleaning time detection means. And a cleaning device for cleaning the membrane module;
The water treatment apparatus according to claim 6, further comprising: a control device that operates the cleaning device for a predetermined time when the cleaning time detection unit determines that it is a cleaning time. A thermometer for measuring the temperature of the water to be treated;
The cleaning time detection means, based on the temperature of the water to be treated measured by the thermometer, a value obtained by correcting the power consumption amount with a temperature coefficient of the water to be treated, and a value according to the power consumption amount The water treatment apparatus according to claim 6 or 7. A thermometer for measuring the temperature of the water to be treated;
The cleaning time detection means sets the power consumption to a value corresponding to the power consumption, and sets a reference threshold value based on the temperature of the water to be treated measured by the thermometer as a temperature coefficient of the water to be treated. The water treatment apparatus according to claim 6 or 7, wherein the value corrected in step (a) is set as the predetermined value.   The water treatment according to any one of claims 6 to 9, further comprising an activated sludge treatment tank, wherein the membrane module is disposed downstream of the activated sludge treatment tank or in the generated sludge treatment tank. apparatus.   The water treatment apparatus according to any one of claims 6 to 10, wherein the cleaning apparatus is an apparatus that performs at least one selected from bubbling, backwashing, chemical addition backwashing, brush cleaning, and water discharge cleaning.