JP2007289899A - Membrane washing method for membrane separation means, and water treatment apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress fouling of a separation membrane to be supplied to a membrane separation technique. <P>SOLUTION: A pump P1 injects a chlorine-based chemical solution stored in a washing chemical solution tank 14 into filtrate discharged from a membrane treating unit 12 for obtaining washing water supplied for washing the separation membrane of the treating unit 12 being a membrane separation means filtering raw water introduced from natural water systems, e.g., rivers. The pump P1 injects the chemical solution to the filtrate at an injection rate of hypochlorite based on the turbidity of the raw water in the membrane washing process of the membrane treating unit 12. In the injection process of the chemical solution, the turbidity of the raw water is recommended to be used as a control factor for feed-forward controlling the injection rate of the chemical solution, and also residual chlorine concentration in washing drain of the treating unit 12 is recommended to be used as a control factor for feed-back controlling the injection rate of the chemical solution. Electrical conductivity of raw water can be used as the control factor for feed-forward controlling in place of the turbidity of the raw water. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  TECHNICAL FIELD The present invention relates to a membrane separation technique applied to a water treatment apparatus for raw water derived from a natural water system exemplified by a river or the like, particularly a water treatment apparatus installed in a water supply facility.

As of March 2005, the cumulative number of membrane separators in waterworks facilities was 442 nationwide, an increase of 68 from the previous year's survey (Survey on Research Center for Water Technology, March 2005). result). In terms of the number of cases by scale, facilities with less than 500 m ³ / day account for 67%, or 3/2. The spread of membrane separation technology is growing steadily and is expected to continue in the future.

  Examples of the membrane separation technique include those disclosed in Patent Documents 1 to 7.

  That is, the water production apparatus described in Patent Document 1 filters the raw water containing ammonia through a microfiltration membrane and / or an ultrafiltration membrane, and further filters this filtered water through a reverse osmosis membrane and / or a nanofiltration membrane. The hollow fiber membrane filtration device described in Patent Document 2 includes a UF membrane module.

  In particular, as a method having a step of cleaning a separation membrane used for membrane separation technology, a cleaning method described in Patent Document 3, a cleaning method for a membrane filtration module described in Patent Document 4, a membrane filtration device and a chemical cleaning device, Patent Literature 5, a method for cleaning a hollow fiber membrane module, a permeation membrane filtration method and apparatus described in Patent Document 6, a membrane filtration apparatus described in Patent Document 7, and the like.

In the membrane separation technology, in order to prevent fouling in the separation membrane of the membrane filtration device, a process for pretreatment of raw water used in the membrane separation process by coagulation sedimentation treatment, sand filtration treatment, activated carbon adsorption, etc. is introduced. (For example, Non-Patent Document 1).
JP2005-185985 JP-A-2005-13992 JP 2004-154707 A JP 2003-265935 A JP2003-251157A JP2002-224540 JP 2001-232160 A “Environmental Technology / Equipment Dictionary” Editorial Committee, “Environmental Technology / Equipment Dictionary I”, first edition, Industrial Research Institute Encyclopedia Publishing Center, February 17, 2003, pp. 720-736

  The reason why the membrane separation technology is introduced is that fully automatic operation is possible and the recovery rate of purified water can be increased. In the membrane separation technique, fouling is suppressed by applying a pretreatment step such as a coagulation sedimentation treatment as shown in Non-Patent Document 1 as a countermeasure against a substance that generates fouling contained in raw water. Therefore, a method of directly supplying raw water introduced from a natural water system such as a river to a membrane separation process has not been adopted. This leads to an increase in the cost of the facility to which the membrane separation technology is applied. Moreover, in the present membrane treatment equipment, even if there is a separation membrane cleaning method for the purpose of removing fouling as shown in Patent Documents 3 to 7, the membrane separation equipment for the purpose of suppressing fouling is used. There is no cleaning control method for the separation membrane.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a membrane cleaning method of a membrane separation means and a water treatment apparatus capable of suppressing fouling of a separation membrane used in membrane separation technology.

  Therefore, the membrane cleaning method of the membrane separation means according to claim 1 is a membrane cleaning method of the membrane separation means for filtering the raw water introduced from the natural water system through the separation membrane, and the cleaning water used for cleaning the separation membrane is used. In order to obtain, there is provided a chemical injection means for injecting a chlorine-based chemical into the filtered water discharged from the membrane separation means, and the chemical injection means is based on the turbidity of the raw water in the membrane cleaning step of the membrane separation means The chemical solution is injected into the filtered water at a chemical solution injection rate.

  The membrane cleaning method for a membrane separation means according to claim 2 is a membrane cleaning method for a membrane separation means for filtering raw water introduced from a natural water system through a separation membrane, in order to obtain washing water used for cleaning the separation membrane. A chemical solution injection means for injecting a chlorine-based chemical solution into the filtered water discharged from the membrane separation means, and in the membrane cleaning step of the membrane separation means, the chemical solution injection means includes the turbidity of the raw water and the The chemical solution is injected into the filtered water at a chemical injection rate based on the residual chlorine concentration of the cleaning waste water from the separation membrane discharged from the membrane separation means, and the turbidity of the raw water is determined as the chemical solution in the chemical solution injection process. The residual chlorine concentration in the washing waste water is used as a control factor for feedback control of the injection rate of the chemical solution.

  The membrane cleaning method for a membrane separation means according to claim 3 is a membrane cleaning method for a membrane separation means for filtering raw water introduced from a natural water system through a separation membrane, in order to obtain washing water for use in cleaning the separation membrane. A chemical injection unit for injecting a chlorine-based chemical into the filtered water discharged from the membrane separation unit, and the chemical injection unit is configured to inject a chemical based on the conductivity of the raw water in the membrane cleaning step of the membrane separation unit. The chemical solution is poured into the filtered water at a rate.

  The membrane cleaning method for membrane separation means according to claim 4 is a membrane cleaning method for membrane separation means for filtering raw water introduced from a natural water system through a separation membrane, in order to obtain washing water for use in washing the separation membrane. A chemical solution injection means for injecting a chlorine-based chemical solution into the filtered water discharged from the membrane separation means, and in the membrane cleaning step of the membrane separation means, the chemical solution injection means includes the conductivity of the raw water and the The chemical solution is injected into the filtered water at a chemical injection rate based on the residual chlorine concentration of the cleaning waste water from the separation membrane discharged from the membrane separation means, and in the process of injecting the chemical solution, the conductivity of the raw water is the chemical solution The residual chlorine concentration in the washing waste water is used as a control factor for feedback control of the injection rate of the chemical solution.

  The water treatment device according to claim 5 is a raw water storage means for storing raw water introduced from a natural water system, a membrane separation means for filtering raw water supplied from the raw water storage means by a separation membrane, and a cleaning of the separation membrane. A chemical solution injection means for injecting a chlorine-based chemical solution into the filtered water discharged from the membrane separation means to obtain wash water to be provided to the membrane, the chemical solution injection means being a turbidity of the raw water stored in the raw water storage means The chemical solution is injected into the filtered water at a chemical injection rate based on the degree.

  The water treatment apparatus according to claim 6 is a raw water storage means for storing raw water introduced from a natural water system, a membrane separation means for filtering raw water supplied from the raw water storage means with a separation membrane, and a cleaning of the separation membrane. A chemical solution injection means for injecting a chlorine-based chemical solution into the filtered water discharged from the membrane separation means in order to obtain washing water to be provided to the raw material water, the chemical solution injection means comprising: raw water stored in the raw water storage means The chemical solution is injected into the filtered water at a chemical injection rate based on turbidity and the residual chlorine concentration of the cleaning wastewater discharged from the membrane separation means, and the turbidity of the raw water is the injection rate of the chemical solution Is used as a control factor for feedforward control, and the residual chlorine concentration in the washing wastewater is used as a control factor for feedback control of the injection rate of the chemical solution.

  The water treatment device according to claim 7 is a raw water storage means for storing raw water introduced from a natural water system, a membrane separation means for filtering raw water supplied from the raw water storage means with a separation membrane, and a cleaning of the separation membrane. A chemical solution injection means for injecting a chlorine-based chemical solution into the filtered water discharged from the membrane separation means to obtain wash water for use in the process, wherein the chemical solution injection means conducts the raw water stored in the raw water storage means The chemical solution is injected into the filtered water at a chemical injection rate based on the rate.

  The water treatment device according to claim 8 is a raw water storage means for storing raw water introduced from a natural water system, a membrane separation means for filtering raw water supplied from the raw water storage means with a separation membrane, and a cleaning of the separation membrane. A chemical solution injection means for injecting a chlorine-based chemical solution into the filtered water discharged from the membrane separation means in order to obtain washing water to be provided to the raw material water, the chemical solution injection means comprising: raw water stored in the raw water storage means The chemical solution is injected into the filtered water at a chemical injection rate based on the electrical conductivity and the residual chlorine concentration of the cleaning waste water discharged from the membrane separation means, and the conductivity of the raw water is the injection rate of the chemical solution Is used as a control factor for feedforward control, and the residual chlorine concentration in the washing wastewater is used as a control factor for feedback control of the injection rate of the chemical solution.

  According to the first, second, fifth, and sixth aspects of the present invention, when a chlorine-based chemical solution is injected into the filtered water of the membrane separation means in order to obtain washing water used for cleaning the separation membrane of the membrane separation means. In addition, since the turbidity of raw water (introduced from a natural water system), which is an index of the fouling substance of the membrane separation means, is used as a control factor for the chemical solution injection, the separation depending on the turbidity of the raw water Membrane fouling is suppressed. In particular, according to the invention of claim 2 and claim 6, in the injection process of the chemical solution, the turbidity of the raw water is used as a control factor for feedforward control of the injection rate of the chemical solution, and the washing drainage Residual chlorine concentration is used as a control factor for feedback control of the injection rate of the chemical solution, so that the residual salt concentration in the cleaning wastewater can be limited and the fouling substance removal state can be controlled when discharging the cleaning wastewater into the natural water system. It becomes possible to grasp.

  According to the third, fourth, seventh, and eighth aspects of the invention, a chlorine-based chemical solution is injected into the filtered water of the membrane separation means in order to obtain washing water used for cleaning the separation membrane of the membrane separation means. In this case, the conductivity of the raw water (introduced from the natural water system), which is an index of the fouling substance of the membrane separation means, is used as a control factor for the chemical injection, and therefore depends on the conductivity of the raw water. Fouling of the separation membrane is suppressed. In particular, according to the invention of claim 4 and claim 8, in the process of injecting the chemical solution, the conductivity of the raw water is used as a control factor for feedforward control of the injection rate of the chemical solution, and the washing drainage Residual chlorine concentration is used as a control factor for feedback control of the injection rate of the chemical solution, so that the residual salt concentration in the cleaning wastewater can be limited and the fouling substance removal state can be controlled when discharging the cleaning wastewater into the natural water system. It becomes possible to grasp.

  According to the above invention, fouling of the separation membrane of the membrane separation means can be suppressed. Thereby, the membrane separation means can directly introduce raw water from a natural water system.

(Embodiment 1)
Many of the separation membranes of the membrane separation treatment apparatus applied to the water treatment technology are MF (microfiltration) membranes. This separation membrane can remove particles having a notary pore diameter of 0.1 μm or more. Since raw water such as rivers changes in turbidity and chromaticity due to seasonal changes and the amount of water, a method for suppressing fouling is necessary. Therefore, the water treatment apparatus of the present embodiment is a membrane separation treatment type treatment apparatus, and controls the injection rate of the membrane cleaning liquid to be used in the membrane cleaning step based on the turbidity of raw water.

  FIG. 1 is a schematic view showing an example of a water treatment apparatus of a membrane separation treatment type. The water treatment apparatus 1 includes a raw water tank 11, a membrane treatment unit 12, a treated water tank 13, and a cleaning chemical tank 14.

  The raw water tank 11 is a means for storing raw water and stores river water introduced from an outside natural water system such as a river as raw water. The raw water tank 11 is provided with a turbidimeter 24 and a water level meter LIC2 as means for measuring the quality of the raw water. As the turbidimeter 24 and the water level meter LIC2, known measuring means applied to the water treatment technology is adopted. The raw water stored in the raw water tank 11 is supplied to the membrane processing unit 12 by the pump P2. The pump P2 has an inverter function, and can supply raw water to the membrane treatment unit 12 at an arbitrary flow rate by a control means (not shown). The pump P2 is installed in the pipe 15. One end of the pipe 15 is connected to the bottom of the raw water tank 11, while the other end is connected to a pipe 16 connected to the lower part of the membrane treatment unit 12. In addition to the pump P2, the pipe 15 is provided with at least a flow meter FI2, a valve AV-1, and a pressure gauge PI1. Further, a pipe 22 for discharging the raw water in the raw water tank 11 to the outside of the system is connected to the pipe 15. The pipe 16 is a pipe for discharging the liquid phase in the membrane processing unit 12 out of the system. The pipes 15 and 16 are connected to a drain pipe 23. A manual valve is installed in the pipe 16. Further, a pipe 17 for supplying air generated by the compressor CP <b> 1 to the cleaning process of the film processing unit 12 is connected to the pipe 16. The pipe 17 is provided with at least a valve AV-6 and a flow meter FI5. The valves AV-1 and AV-6 are opened and closed by the control means.

  The membrane treatment unit 12 is a membrane separation means and includes a membrane module that filters raw water through a separation membrane. Examples of the membrane module include membrane modules such as an internal pressure hollow fiber type and an external pressure hollow fiber type having 0.1 μm pores, which are applied to membrane separation technology. A pipe 18 for transferring treated water to the treated water tank 13 is connected to the upper part of the membrane treatment unit 12. The pipe 18 is provided with at least a pressure gauge PI2, a valve AV-4, and a flow meter FIC3. A pipe 19 is connected to the upper part of the membrane processing unit 12. The pipe 19 is a pipe for transferring the cleaning waste water of the membrane module of the membrane processing unit 12 to the raw water tank 11. The pipe 19 is provided with at least a valve AV-2. A pipe 20 is further connected to the pipe 19. The pipe 20 is a pipe for transferring the cleaning waste water of the membrane module of the membrane processing unit 12 to the outside of the system. The pipe 20 is provided with at least a valve AV-3. The valves AV-2, AV-3, and AV-4 are opened and closed by the control means.

  The treated water tank 13 stores the filtered treated water discharged from the membrane treatment unit 12. The treated water tank 13 is provided with a water level gauge LIA3. A pipe 21 for discharging the filtered treated water out of the system is connected to the lower part of the treated water tank 13. The piping 21 is connected to a piping 22 for supplying a part of the filtered water as backwash water to the cleaning process of the membrane processing unit 12. One end of the pipe 22 is connected to the pipe 18. The pipe 22 is provided with at least a pump P3, a flow meter FI4, and a valve AV-5. The pipe 21 is connected to a drain pipe 23. The pump P3 and the valve AV-5 are operated by the control means during the backwash process.

  The cleaning chemical solution tank 14 stores a chemical solution for creating cleaning water supplied to the membrane module of the membrane processing unit 12. Examples of the chemical solution include a chlorine-based chemical solution, specifically, hypochlorous acid water. The cleaning chemical tank 14 includes at least a pump P1 and a liquid level gauge LIA4. The pump P1 is a chemical solution injection means for injecting a chlorine-based chemical solution into the filtered water discharged from the membrane processing unit 12 in order to obtain the washing water. The pump P1 is injected into the backwash water flowing through the pipe 22. The pump P1 is operated by the control means. Further, the pump P1 has variable stroke numbers, rotation speeds, and the like, and can supply the chemical solution quantitatively.

  The raw water drawn from the bottom of the raw water tank 11 is introduced from the bottom of the membrane processing unit 12 and processed by the cross flow method in contact with the membrane of the membrane module. The filtered treated water is transferred to the treated water tank 13 through the pipe 18 in which the valve AV-4 is set to be open. At this time, turbidity, chromaticity and organic components in the raw water are deposited on the membrane surface of the membrane module.

  When the turbidity of the raw water increases, the amount of fouling substances deposited on the film surface also increases, so that it cannot be handled by a constant cleaning process. Therefore, the water treatment apparatus 1 was subjected to a test in which the backwash cycle and the injection rate of the cleaning chemical (hypochlorous acid water) used for backwashing were changed when the raw water turbidity increased.

FIG. 2 is a characteristic diagram showing the relationship between the hypochlorite injection rate, the raw water turbidity, and the membrane supply pressure in the back washing process of the membrane treatment unit 12. Back-cleaning of membrane treatment unit 12 (equipped with membrane module manufactured by Asahi Kasei Chemicals, effective membrane area 50m ² per membrane module, flux capacity 100m ³ / day when flux 2.0m ³ / m ² · day) The process was carried out approximately every 20-30 minutes (flow rate 1.7 m ³ / hour). At this time, the hypochlorite injection rate of the pump P1 was set to 3 mg / L, but the pressure on the raw water supply side of the membrane treatment unit 12 due to the turbidity increase of about 2 to 3 times of the raw water (1.7 m ³ / hour). (Measurement value of the pressure gauge PI1) reached the limit installation value (220 kPa), and the water treatment apparatus 1 was stopped. Therefore, after the membrane module of the membrane treatment unit 12 is regenerated, the hypochlorite injection rate of the pump P1 is set to 6 mg / L and the continuous operation is performed, and the supply for the increase in turbidity of the raw water (1.7 m ³ / hour) is performed. The change in side pressure was observed. According to this, when the turbidity increase of the raw water continued for about 2 to 3 days, the increase of the supply side pressure was confirmed. Furthermore, when the hypochlorous injection rate of the pump P1 was set to 10 mg / L, a decrease in the pressure on the supply side was confirmed after 1-2 days. From these facts, it was found that fouling can be suppressed by changing the hypochlorite injection rate in response to changes in raw water turbidity.

  Based on the above test results, the pump P1 of the water treatment device 1 injects the chemical solution into the filtered water at a hypochlorous acid injection rate based on the turbidity of the raw water stored in the raw water tank 11.

  An operation example of the water treatment apparatus 1 will be described with reference to FIG.

  In the raw water treatment process, when the water level gauge LIC2 detects that the raw water level in the raw water tank 11 is equal to or higher than the starting water level of the pump P2, the valves AV-2, AV-3, AV-5, AV- The raw water is supplied to the membrane treatment unit 12 by the pump P2 with the valves AV-1 and AV-4 set to open while 6 is set to closed. The supply amount of the raw water is appropriately controlled by the inverter function of the pump P1 while the flow rate and pressure are monitored by the flow meter FI2 and pressure gauges PI1 and PI2. The treated water discharged from the membrane treatment unit 12 is supplied to the treated water tank 13.

  In the washing (back washing) step (for example, 20 to 30 minutes / time) of the membrane processing unit 12, the pump P2 is stopped and at the same time the valves AV-1, AV-2 and AV-4 are set to be closed while the valve AV- 3 is set to open. Next, the valve AV-6 is set to open and the compressor CP1 is activated in order to remove the pollutants that are relatively easily removed from the surface of the hollow membrane. Bubbles generated by the compressor CP1 are provided on the outer peripheral surface side of the separation membrane (hollow fiber membrane) of the membrane processing unit 12. The amount of air from the compressor CP1 is appropriately controlled by the valve AV-6 while being monitored by the flow meter FI5. On the other hand, cleaning water is supplied to the inner peripheral surface side of the separation membrane via a valve AV-5. The washing water is obtained by injecting a chlorine-based chemical into the filtered water of the membrane treatment unit 12. That is, the pump P3 is activated with AV-5 set to open, and filtered water is supplied to the pipes 18 and 22. At this time, the chemical solution in the cleaning chemical solution tank 14 is injected into the filtered water flowing in the pipe 22 by the pump P1. The injection rate of the chemical solution with respect to the filtered water is set based on the turbidity of the raw water in the raw water tank 11 measured by the turbidimeter 24. The washing water thus obtained flows on the inner week surface side of the separation membrane in the direction opposite to the flow direction of the raw water in the water treatment step. The flow rate of the washing water is appropriately controlled while being monitored by the flow meter FI4 and pressure gauges PI2 and PI3. Then, the fouling substance elutes to the outer peripheral surface side of the separation membrane in the process in which the washing water moves to the outer peripheral surface side of the separation membrane. The fouling material is peeled off by the shearing force of the bubbles flowing on the outer peripheral surface side. The washing water containing the fouling substance is discharged out of the system together with the bubbles through the pipe 20 as washing waste water. When the instruction of the cleaning process (for example, 30 minutes / time) of the membrane processing unit 12 is canceled, the water treatment process starts.

  As described above, according to the water treatment apparatus 1, when a chlorine-based chemical solution is injected into the filtered water of the membrane treatment unit 12 in order to obtain washing water used for washing the membrane module provided in the membrane treatment unit 12. In addition, the turbidity of raw water, which is an index of the fouling substance of the membrane processing unit 12, is used as a control factor for the chemical solution injection. Thereby, fouling of the separation membrane depending on the turbidity of the raw water is suppressed.

  Therefore, water sources such as river water and lake water can be directly subjected to membrane separation treatment, and the flocculant and the like can be simplified. Further, since fouling of the membrane surface accompanying the increase in raw water turbidity is suppressed, it is possible to ensure a long membrane regeneration treatment time with acid and alkali.

(Embodiment 2)
FIG. 3 is a schematic view showing the treatment process of the water treatment apparatus according to this embodiment. The water treatment apparatus 2 performs FF control (feed forward control) on the hypochlorous acid injection rate in the backwashing process using the turbidity of the raw water as a control factor in order to suppress fouling.

  An operation example of the water treatment device 2 will be described with reference to FIG. In the cleaning (back washing) process (for example, 20 to 30 minutes / times) of the membrane processing unit 12, the pump P2 is stopped and the valves AV-1, AV-2, and AV-4 are set to be closed at the same time, while the valve AV is set. -3 is set to open. Next, the valve AV-6 is set to open and the compressor CP1 is activated in order to remove the pollutants that are relatively easily removed from the surface of the hollow membrane. Bubbles generated by the compressor CP1 are provided on the outer peripheral surface side of the separation membrane (hollow fiber membrane) of the membrane processing unit 12. The amount of air from the compressor CP1 is appropriately controlled by the valve AV-6 while being monitored by the flow meter FI5. On the other hand, cleaning water is supplied to the inner peripheral surface side of the separation membrane via a valve AV-5. The washing water is obtained by injecting a chlorine-based chemical into the filtered water of the membrane treatment unit 12. That is, the pump P3 is activated with AV-5 set to open, and filtered water is supplied to the pipes 18 and 22. At this time, the chemical solution in the cleaning chemical solution tank 14 is injected into the filtered water flowing in the pipe 22 by the pump P1.

The pump P1 is FF controlled based on the turbidity X of the raw water measured by the turbidimeter 24 in the raw water tank 11 _FF (Y _FF = a · X + b, Y _FF : Chemical solution injection rate (mg / L), a: slope (−), b: minimum injection rate (mg / L), X: raw water turbidity (degree)), and the chemical solution is injected into the filtered water. The wash water thus obtained flows on the inner week surface side of the separation membrane in the direction opposite to the flow direction of the raw water in the water treatment step. The flow rate of the washing water is appropriately controlled while being monitored by the flow meter FI4. Then, the fouling substance elutes to the outer peripheral surface side of the separation membrane in the process in which the washing water moves to the outer peripheral surface side of the separation membrane. The fouling material is peeled off by the shearing force of the bubbles flowing on the outer peripheral surface side. The washing water containing the fouling substance is discharged out of the system together with the bubbles through the pipe 20 as washing waste water. When the instruction of the cleaning process (for example, 30 minutes / times) of the membrane processing unit 12 is canceled, the water treatment process starts. In this water treatment process, pumps and valves operate in the same manner as the water treatment apparatus 1.

  As described above, according to the water treatment apparatus 2, water sources such as river water and lake water can be directly subjected to membrane separation treatment, so that the flocculant and the like can be simplified. Further, since fouling of the membrane surface accompanying the increase in raw water turbidity is suppressed, it is possible to ensure a long membrane regeneration treatment time with acid and alkali. Furthermore, using the raw water turbidity, which is an index of raw water quality, as a control factor, it is possible to automatically control the hypochlorite injection rate during the backwashing process.

  In particular, in the water treatment device 2, the turbidity of the raw water is used as a control factor for feedforward control of the injection rate of the chemical liquid in the process of injecting the chemical liquid, thereby injecting the chemical liquid according to the turbidity of the raw water. You can control.

(Embodiment 3)
FIG. 4A is a schematic explanatory diagram illustrating a process in which raw water is filtered by a separation membrane. FIG. 4B is a schematic explanatory diagram illustrating a process in which a fouling substance is removed in the backwashing cleaning process. Moreover, FIG. 5 is the schematic which showed the process of the water treatment apparatus which concerns on this embodiment.

  When the water treatment device 3 discharges the backwash wastewater to the river, the residual chlorine concentration of the wash wastewater is measured by the residual chlorine meter 31 to limit the residual chlorine concentration of the wash wastewater in order to restrict the residual chlorine concentration. It is controlled not to discharge chlorine. The residual chlorine meter 31 is installed in the pipe 20. As the residual chlorine meter 31, a known measuring means applied to water treatment technology is adopted.

  The relationship between the fouling substance and residual chlorine was also clarified from the result of continuous operation of the water treatment apparatus 1 of the first embodiment. That is, in the filtration process shown in FIG. 4A, it was confirmed that the fouling substance adhering to the separation membrane is composed of an organic substance and an inorganic substance. In particular, it was confirmed that the inorganic substances were clayey, iron and manganese. In the backwashing step shown in FIG. 4B, wash water containing hypochlorous acid water is passed from the inner surface of the separation membrane. As a result, the filing substance is discharged to the outer surface of the separation membrane. The fouling material deposited on the outer surface of the separation membrane is peeled off by the effect of bubble cleaning. It was confirmed that the residual chlorine concentration of the washing waste water at this time was hardly detected. And it was confirmed that when this back washing process is repeated, the fouling substances are also removed, and the residual chlorine concentration in the washing waste water is increased.

Based on this result, the water treatment device 3 is equipped with a residual chlorine meter in the cleaning drainage system as shown in FIG. 5 to measure residual chlorine (ReClI) in the cleaning drainage. Then, when the measured value is larger than the set value from the difference between the measured value and the residual chlorine set value (ReCl _set ), the chemical solution injection rate on the FF control side is controlled to be lowered. As a result, the waste water can be discharged under controlled water quality conditions when returning to the natural water system such as a river.

  The control formula of the water treatment device 3 is shown below.

Y _ReCl = Y _FF -βY _FB
Y _FF = a · X + b
Y _FB = k _BMCl (ReCl _set -ReClI)
Y _ReCl : Hypochlorite injection rate (mg / L) by FF control and FB control
Y _FF : Hypochlorite injection rate by FF control (mg / L)
Y _FB : Hypochlorine injection rate by FB control (mg / L)
a: Inclination (-)
b: Minimum injection rate (mg / L)
X: Raw water turbidity (degree)
ReCl _set : Residual chlorine set value (mg / L)
k _BMCl : FB control gain (-)
β: Weight coefficient (-)
An example of the operation of the water treatment device 2 will be described with reference to FIG. In the cleaning (back washing) process (for example, 20 to 30 minutes / times) of the membrane processing unit 12, the pump P2 is stopped and the valves AV-1, AV-2, and AV-4 are set to be closed at the same time, while the valve AV is set. -3 is set to open. Next, the valve AV-6 is set to open and the compressor CP1 is started in order to remove the pollutants that are relatively easily removed from the surface of the hollow membrane. Bubbles generated by the compressor CP1 are provided on the outer peripheral surface side of the separation membrane (hollow fiber membrane) of the membrane processing unit 12. The amount of air from the compressor CP1 is appropriately controlled by the valve AV-6 while being monitored by the flow meter FI5. On the other hand, cleaning water is supplied to the inner peripheral surface side of the separation membrane via a valve AV-5. The washing water is obtained by injecting a chlorine-based chemical into the filtered water of the membrane treatment unit 12. That is, the pump P3 is activated with AV-5 set to open, and filtered water is supplied to the pipes 18 and 22. At this time, the chemical solution in the cleaning chemical solution tank 14 is injected into the filtered treated water flowing into the pipe 22 by the pump P1.

The pump P1 circulates through the FF control (Y _FF = a · X + b) based on the turbidity X of the raw water measured by the turbidimeter 24 in the raw water tank 11 and the pipe 20 measured by the residual chlorine meter 31. The chemical solution is injected into the filtered water at the injection rate Y _ReCl (= Y _FF -βY _FB ) by the FB control (Y _FB = k _BMCl · (ReCl _set -ReCl I)) based on the residual chlorine concentration ReCl I of the washing waste water. To do. The wash water thus obtained flows on the inner week surface side of the separation membrane in the direction opposite to the flow direction of the raw water in the water treatment step. The flow rate of the washing water is appropriately controlled while being monitored by the flow meter FI4 and pressure gauges PI2 and PI3. Then, the fouling substance elutes to the outer peripheral surface side of the separation membrane in the process in which the washing water moves to the outer peripheral surface side of the separation membrane. The fouling material is peeled off by the shearing force of the bubbles flowing on the outer peripheral surface side. The washing water containing the fouling substance is discharged out of the system together with the bubbles through the pipe 20 as washing waste water. When the instruction of the cleaning process (for example, 30 minutes / times) of the membrane processing unit 12 is canceled, the water treatment process starts. In this water treatment process, pumps and valves operate in the same manner as the water treatment apparatus 1.

  Since the water source such as river water and lake water can be directly subjected to membrane separation treatment as in the water treatment apparatus 3 described above, the flocculant and the like can be simplified. Further, since fouling of the membrane surface accompanying the increase in raw water turbidity is suppressed, it is possible to ensure a long membrane regeneration treatment time with acid and alkali. Furthermore, using the raw water turbidity, which is an index of raw water quality, as a control factor, it is possible to automatically control the hypochlorite injection rate during the backwashing process.

  In particular, in the water treatment device 3, the wastewater discharged from the wastewater is combined with the hypochlorite injection rate control (FF control) during the reverse cleaning process using the turbidity of the raw water and the residual chlorine concentration control (FB control) of the washing wastewater. When returning to river water, lake water, etc., residual salt concentration in the drainage can be limited, water quality monitoring can be automated, and hypochlorite water can be used for backwashing to determine the removal status of fouling substances. .

(Embodiment 4)
FIG. 6 is a schematic view showing the treatment process of the water treatment apparatus according to this embodiment.

  When there is a proportional relationship between the turbidity in the raw water and the conductivity, the water treatment device 4 measures with the conductivity meter 32 having better maintainability than the turbidimeter 24, and the measured value is used as a control factor for the membrane. The optimal injection rate of the chemical solution for obtaining the cleaning water of the processing unit 12 is calculated, and the pump P1 is FF controlled. As the conductivity meter 33, a known measuring means applied to water treatment technology is adopted.

  An example of the operation of the water treatment device 4 will be described with reference to FIG. In the washing (back washing) step (for example, 20 to 30 minutes / time) of the membrane processing unit 12, the pump P2 is stopped and at the same time the valves AV-1, AV-2 and AV-4 are set to be closed while the valve AV- 3 is set to open. Next, the valve AV-6 is set to open and the compressor CP1 is activated in order to remove the pollutants that are relatively easily removed from the surface of the hollow membrane. Bubbles generated by the compressor CP1 are provided on the outer peripheral surface side of the separation membrane (hollow fiber membrane) of the membrane processing unit 12. The amount of air from the compressor CP1 is appropriately controlled by the valve AV-6 while being monitored by the flow meter FI5. On the other hand, cleaning water is supplied to the inner peripheral surface side of the separation membrane via a valve AV-5. The washing water is obtained by injecting a chlorine-based chemical into the filtered water of the membrane treatment unit 12. That is, the pump P3 is activated with AV-5 set to open, and filtered water is supplied to the pipes 18 and 22. At this time, the chemical solution in the cleaning chemical solution tank 14 is injected into the filtered water flowing in the pipe 22 by the pump P1.

The pump P1 is FF controlled based on the conductivity of the raw water measured by the conductivity meter 32 of the raw water tank 11 _FF (Y _FF = a · X + b, Y _FF : Chemical solution injection rate (mg / L ), A: slope (−), b: minimum injection rate (mg / L), X: raw water conductivity (μS / cm))). The wash water thus obtained flows on the inner week surface side of the separation membrane in the direction opposite to the flow direction of the raw water in the water treatment step. The flow rate of the washing water is appropriately controlled while being monitored by the flow meter FI4 and pressure gauges PI2 and PI3. Then, the fouling substance elutes to the outer peripheral surface side of the separation membrane in the process in which the washing water moves to the outer peripheral surface side of the separation membrane. The fouling material is peeled off by the shearing force of the bubbles flowing on the outer peripheral surface side. The washing water containing the fouling substance is discharged out of the system together with the bubbles through the pipe 20 as washing waste water. When the instruction of the cleaning process (for example, 30 minutes / times) of the membrane processing unit 12 is canceled, the water treatment process starts. In this water treatment process, pumps and valves operate in the same manner as the water treatment apparatus 1.

  According to the water treatment apparatus 4 described above, fouling of the membrane surface accompanying an increase in the conductivity of the raw water is suppressed, so that a long membrane regeneration treatment time with acid and alkali can be secured. In addition, since the raw water conductivity is used as an index of the quality of the raw water, it is possible to automatically control the hypochlorite injection rate during the backwash process. In particular, when the raw water contains a large amount of soluble iron and manganese, fouling is likely to occur, and thus measuring conductivity is an effective means.

  Further, in the water treatment device 4, in the process of injecting the chemical solution, the conductivity of the raw water is used as a control factor for feedforward control of the injection rate of the chemical solution, thereby controlling the injection of the chemical solution according to the conductivity of the raw water. Can be done.

(Embodiment 5)
FIG. 7 is a schematic view showing the treatment process of the water treatment apparatus according to this embodiment.

  In the water treatment device 5, in order to limit the residual chlorine concentration when flowing the cleaning wastewater into the river, the residual chlorine meter 34 monitors the residual chlorine concentration in the cleaning wastewater and prevents the discharge of residual chlorine outside the system. The relationship between the fouling substance and residual chlorine was also clarified from the result of continuous operation of the water treatment apparatus 1 of the first embodiment. That is, as described in the third embodiment, in the cleaning process of the membrane treatment unit 12, filing substances are discharged to the outer surface of the separation membrane by passing cleaning water containing hypochlorous acid water from the inner surface of the separation membrane. Is done. The fouling material deposited on the outer surface of the separation membrane is peeled off by the effect of bubble cleaning. It was confirmed that the residual chlorine concentration of the washing waste water at this time was hardly detected. And it was confirmed that when this back washing process is repeated, the fouling substances are also removed, and the residual chlorine concentration in the washing waste water is increased.

Based on this result, the water treatment apparatus 5 is equipped with a residual chlorine meter in the cleaning drainage system as shown in FIG. 7 and measures residual chlorine (ReClI) in the cleaning drainage. When the measured value is larger than the set value from the difference between the measured value and the residual chlorine set value (ReCl _set ), control is performed to lower the injection rate on the FF control side. As a result, the waste water can be discharged under controlled water quality conditions when the washing waste water is returned to a water source such as a river.

  The control formula of the water treatment device 3 is shown below.

Y _ReCl = Y _FF -βY _FB
Y _FF = a · X + b
Y _FB = k _BMCl (ReCl _set -ReClI)
Y _ReCl : Hypochlorite injection rate (mg / L) by FF control and FB control
Y _FF : Hypochlorite injection rate by FF control (mg / L)
Y _FB : Hypochlorine injection rate by FB control (mg / L)
a: Inclination (-)
b: Minimum injection rate (mg / L)
X: Raw water conductivity (μS / cm)
ReCl _set : Residual chlorine set value (mg / L)
k _BMCl : FB control gain (-)
β: Weight coefficient (-)
An example of the operation of the water treatment device 5 will be described with reference to FIG. In the washing (back washing) step (for example, 20 to 30 minutes / time) of the membrane processing unit 12, the pump P2 is stopped and at the same time the valves AV-1, AV-2 and AV-4 are set to be closed while the valve AV- 3 is set to open. Next, the valve AV-6 is set to open and the compressor CP1 is activated in order to remove the pollutants that are relatively easily removed from the surface of the hollow membrane. Bubbles generated by the compressor CP1 are provided on the outer peripheral surface side of the separation membrane (hollow fiber membrane) of the membrane processing unit 12. The amount of air from the compressor CP1 is appropriately controlled by the valve AV-6 while being monitored by the flow meter FI5. On the other hand, cleaning water is supplied to the inner peripheral surface side of the separation membrane via a valve AV-5. The washing water is obtained by injecting a chlorine-based chemical into the filtered water of the membrane treatment unit 12. That is, the pump P3 is activated with AV-5 set to open, and filtered water is supplied to the pipes 18 and 22. At this time, the chemical solution in the cleaning chemical solution tank 14 is injected into the filtered water flowing in the pipe 22 by the pump P1.

The pump P 1 circulates in the FF control (Y _FF = a · X + b) based on the conductivity X of the raw water measured by the conductivity meter 32 in the raw water tank 11 and the pipe 20 measured by the residual chlorine meter 31. The chemical solution is injected into the filtered water at the injection rate Y _ReCl (= Y _FF -βY _FB ) by the FB control (Y _FB = k _BMCl · (ReCl _set -ReCl I)) based on the residual chlorine concentration ReCl I of the washing waste water. To do. The wash water thus obtained flows on the inner week surface side of the separation membrane in the direction opposite to the flow direction of the raw water in the water treatment step. The flow rate of the washing water is appropriately controlled while being monitored by the flow meter FI4 and pressure gauges PI2 and PI3. Then, the fouling substance elutes to the outer peripheral surface side of the separation membrane in the process in which the washing water moves to the outer peripheral surface side of the separation membrane. The fouling material is peeled off by the shearing force of the bubbles flowing on the outer peripheral surface side. The washing water containing the fouling substance is discharged out of the system together with the bubbles through the pipe 20 as washing waste water. When the instruction of the cleaning process (for example, 30 minutes / times) of the membrane processing unit 12 is canceled, the water treatment process starts. In this water treatment process, pumps and valves operate in the same manner as the water treatment apparatus 1.

  Like the water treatment device 5 described above, hypochlorous acid injection rate control (FF control) and residual chlorine concentration control (FB control) of cleaning wastewater during the reverse cleaning process using the conductivity of raw water for fouling suppression With the combination control, the residual salt concentration in the drainage can be limited and the water quality monitoring can be automated when returning the washing drainage to river water, lake water, etc. Moreover, when hypochlorous water is used for backwashing, the removal state of a fouling substance can be grasped by residual salt measurement.

Schematic which showed the process of the water treatment apparatus which concerns on Embodiment 1. FIG. The characteristic view which showed the relationship between the hypochlorous acid injection rate in the backwashing process of the said water treatment apparatus, raw | natural water turbidity, and a membrane supply pressure. Schematic which showed the process of the water treatment apparatus which concerns on Embodiment 2. FIG. (A) The schematic explanatory drawing explaining the process in which raw | natural water is filtered by a separation membrane, (b) The schematic explanatory drawing explaining the process by which a fouling substance is removed by a backwashing washing process. Schematic which showed the process of the water treatment apparatus which concerns on Embodiment 3. FIG. Schematic which showed the process of the water treatment apparatus which concerns on Embodiment 4. FIG. Schematic which showed the process of the water treatment apparatus which concerns on Embodiment 5. FIG.

Explanation of symbols

1, 2, 3, 4, 5 ... water treatment device 11 ... raw water tank 12 ... membrane treatment unit 13 ... treatment water tank 14 ... cleaning chemical tanks P1, P2, P3 ... pump CP1 ... air compressors AV-1, AV-2 , AV-3, AV-4, AV-5 ... valve 24 ... turbidity meter 31 ... residual chlorine meter 32 ... conductivity meter

Claims (8)

A membrane cleaning method for membrane separation means for filtering raw water introduced from a natural water system through a separation membrane,
A chemical solution injection means for injecting a chlorine-based chemical solution into the filtered water discharged from the membrane separation means in order to obtain wash water for use in cleaning the separation membrane;
The membrane cleaning method for membrane separation means, wherein the chemical solution injection means injects the chemical solution into the filtered water at a chemical injection rate based on the turbidity of the raw water in the membrane cleaning step of the membrane separation means. A membrane cleaning method for membrane separation means for filtering raw water introduced from a natural water system through a separation membrane,
A chemical solution injection means for injecting a chlorine-based chemical solution into the filtered water discharged from the membrane separation means in order to obtain wash water for use in cleaning the separation membrane;
In the membrane cleaning step of the membrane separation means, the chemical solution injection means supplies the chemical solution at a chemical injection rate based on the turbidity of the raw water and the residual chlorine concentration in the separation wastewater discharged from the membrane separation means. Pour into the filtered water,
In the process of injecting the chemical solution, the turbidity of the raw water is used as a control factor for feedforward control of the injection rate of the chemical solution, and the residual chlorine concentration in the washing wastewater is a control factor for feedback control of the injection rate of the chemical solution A membrane cleaning method for a membrane separator characterized by being used as: A membrane cleaning method for membrane separation means for filtering raw water introduced from a natural water system through a separation membrane,
A chemical solution injection means for injecting a chlorine-based chemical solution into the filtered water discharged from the membrane separation means in order to obtain wash water for use in cleaning the separation membrane;
The membrane cleaning method for membrane separation means, wherein the chemical solution injection means injects the chemical solution into the filtered water at a chemical injection rate based on the conductivity of the raw water in the membrane cleaning step of the membrane separation means. A membrane cleaning method for membrane separation means for filtering raw water introduced from a natural water system through a separation membrane,
A chemical solution injection means for injecting a chlorine-based chemical solution into the filtered water discharged from the membrane separation means in order to obtain wash water for use in cleaning the separation membrane;
In the membrane cleaning step of the membrane separation unit, the chemical solution injection unit supplies the chemical solution at a chemical solution injection rate based on the conductivity of the raw water and the residual chlorine concentration of the separation membrane cleaning wastewater discharged from the membrane separation unit. Pour into the filtered water,
In the process of injecting the chemical solution, the conductivity of the raw water is used as a control factor for feedforward control of the injection rate of the chemical solution, and the residual chlorine concentration in the washing wastewater is a control factor for feedback control of the injection rate of the chemical solution. A membrane cleaning method for a membrane separator characterized by being used as: Raw water storage means for storing raw water introduced from natural water systems;
Membrane separation means for filtering the raw water supplied from the raw water storage means with a separation membrane;
A chemical solution injection means for injecting a chlorine-based chemical solution into the filtered water discharged from the membrane separation means in order to obtain wash water for use in cleaning the separation membrane,
The said chemical | medical solution injection | pouring means inject | pours the said chemical | medical solution into the said filtered water at the chemical | medical solution injection | pouring rate based on the turbidity of the raw | natural water stored by the said raw | natural water storage means. Raw water storage means for storing raw water introduced from natural water systems;
Membrane separation means for filtering the raw water supplied from the raw water storage means with a separation membrane;
A chemical solution injection means for injecting a chlorine-based chemical solution into the filtered water discharged from the membrane separation means in order to obtain wash water for use in cleaning the separation membrane,
The chemical solution injection means performs the filtration treatment of the chemical solution at a chemical injection rate based on the turbidity of the raw water stored in the raw water storage means and the residual chlorine concentration in the washing waste water of the separation membrane discharged from the membrane separation means. Poured into water,
The turbidity of the raw water is used as a control factor for feedforward control of the injection rate of the chemical solution, and the residual chlorine concentration of the washing wastewater is used as a control factor for feedback control of the injection rate of the chemical solution. Water treatment equipment. Raw water storage means for storing raw water introduced from natural water systems;
Membrane separation means for filtering the raw water supplied from the raw water storage means with a separation membrane;
A chemical solution injection means for injecting a chlorine-based chemical solution into the filtered water discharged from the membrane separation means in order to obtain wash water for use in cleaning the separation membrane,
The said chemical | medical solution injection | pouring means inject | pours the said chemical | medical solution into the said filtered water with the chemical | medical solution injection | pouring rate based on the electrical conductivity of the raw | natural water stored by the said raw | natural water storage means. Raw water storage means for storing raw water introduced from natural water systems;
Membrane separation means for filtering the raw water supplied from the raw water storage means with a separation membrane;
A chemical solution injection means for injecting a chlorine-based chemical solution into the filtered water discharged from the membrane separation means in order to obtain wash water for use in cleaning the separation membrane,
The chemical injection unit is configured to filter the chemical solution at a chemical injection rate based on the conductivity of the raw water stored in the raw water storage unit and the residual chlorine concentration of the cleaning membrane drainage discharged from the membrane separation unit. Poured into water,
The conductivity of the raw water is used as a control factor for feedforward control of the injection rate of the chemical solution, and the residual chlorine concentration of the cleaning wastewater is used as a control factor for feedback control of the injection rate of the chemical solution. Water treatment equipment.

Images