WO2021199371A1

WO2021199371A1 - Water treatment device and water treatment method

Info

Publication number: WO2021199371A1
Application number: PCT/JP2020/014984
Authority: WO
Inventors: 英二今村; 祐樹佐藤; 佳史林; 野田　清治
Original assignee: 三菱電機株式会社
Priority date: 2020-04-01
Filing date: 2020-04-01
Publication date: 2021-10-07
Also published as: TW202140386A; JP6952930B1; JPWO2021199371A1; TWI764629B; CN115335138B; CN115335138A

Abstract

In a water treatment device that uses ozone water to clean a filter membrane, it is difficult to time the start of ozone water generation and manage a cleaning effect, due to the unstable nature of ozone, and thus sometimes the expected cleaning effect cannot be achieved. In order to solve this problem, the present invention is configured such that a transmembrane pressure difference value is calculated from a measured difference in pressure before and after the filter membrane, and the start of ozone water generation is commanded when the calculated transmembrane pressure difference value, or an estimated value calculated on the basis of said transmembrane pressure difference value, is equal to a reference value or has become greater than said reference value.

Description

Water treatment equipment and water treatment method

This application relates to a water treatment device and a water treatment method.

In water and sewage treatment or wastewater treatment, a membrane filtration method is widely adopted in which the water to be treated is filtered with a filtration membrane to obtain clear filtered water. The filtration membrane used in this method is, for example, an organic material membrane having innumerable fine pores having a pore diameter of about 0.1 micrometer on the surface, or an inorganic material membrane. This membrane makes it possible to remove suspended solids in the water to be treated.

The membrane filtration method has a problem that extremely high quality filtered water can be obtained as treated water by a filtration membrane having a precise structure as described above, while pores of the filtration membrane are blocked by a substance such as a suspended substance. .. On the other hand, in general, a chemical solution containing filtered water, ozone, or hypochlorous acid is passed through the filtration membrane in the direction opposite to the filtration direction of the water to be treated to block the pores of the filtration membrane. A "backwash" is performed to remove. For example, Patent Documents 1 and 2 disclose a method for backwashing a filtration membrane using ozone water, which is water in which ozone is dissolved.

Japanese Unexamined Patent Publication No. 2001-300736 Japanese Unexamined Patent Publication No. 2014-128790

For example, when cleaning the filter membrane with ozone water, it is necessary to generate ozone water containing the ozone concentration required for cleaning each time it is washed. This is due to the instability of ozone. That is, even if ozone water having a target ozone concentration is generated, if the supply of ozone gas is stopped, ozone is decomposed with the passage of time and the ozone concentration is lowered, so that the effectiveness as a cleaning agent is impaired. Therefore, unlike the filtration membrane cleaning with a cleaning agent such as sodium hypochlorite, which has a relatively slow decomposition rate and can be stored, even if the filtration membrane needs to be cleaned, cleaning is started immediately. This cannot be done, and excessive fouling (blockage of pores) occurs in the filtration membrane.

Furthermore, the dissolved ozone concentration is easily affected by the properties of the liquid that is the solvent for ozone gas, and the ozone dissolution rate and the final dissolved ozone concentration change each time it is produced. Therefore, the cleaning effect varies, and the cleaning effect expected in the ozone water cleaning process of injecting ozone water into the filter membrane cannot be obtained, and immediate re-cleaning is required, which may increase the cleaning frequency. be.

This application was made to solve the above-mentioned problems, eliminate the uncertainty caused by the characteristics of ozone in ozone water generation and cleaning, start ozone water generation at an appropriate timing, and stabilize it. It is an object of the present invention to provide a water treatment apparatus and a water treatment method for obtaining a sufficient ozone water cleaning effect.

The water treatment device disclosed in the present application is
A membrane filtration step of filtering the water to be treated with a filtration membrane to obtain the treated water and an ozone water cleaning step of cleaning the filtered membrane with ozone water are performed.
An arithmetic unit that calculates the intermembrane differential pressure value from the measured pressure difference before and after the filtration membrane,
When the calculated intermembrane differential pressure value or the estimated value calculated based on the intermembrane differential pressure value becomes equal to or larger than the reference value, the start of ozone water generation is instructed. It is characterized by having a control unit.

According to the water treatment apparatus disclosed in the present application, the uncertainty caused by the characteristics of ozone in ozone water generation and cleaning is eliminated, ozone water generation is started at an appropriate timing, and stable and sufficient ozone water cleaning is performed. The effect can be obtained.

It is a figure explaining an example of the structure of the water treatment apparatus in Embodiment 1. FIG. It is a flowchart explaining the operation of the water treatment apparatus in Embodiment 1. It is a figure explaining the start and completion of the ozone water cleaning process in Embodiment 1. It is another figure explaining the start and completion of the ozone water cleaning process in Embodiment 1. It is another figure explaining the start and completion of the ozone water cleaning process in Embodiment 1. It is a figure explaining an example of the structure of the water treatment apparatus in Embodiment 2. It is a flowchart explaining the operation of the water treatment apparatus in Embodiment 2. It is a figure which shows an example of the hardware which comprises the calculation part, control part, setting part, and the intermembrane differential pressure change rate calculation means shown in Embodiments 1 and 2.

Hereinafter, preferred embodiments of the water treatment apparatus according to the present application will be described with reference to the drawings. The same contents and corresponding parts are designated by the same reference numerals, and detailed description thereof will be omitted. Similarly, in the subsequent embodiments, duplicate description of the configurations with the same reference numerals will be omitted.

Embodiment 1.
FIG. 1 shows an example of the configuration of the water treatment apparatus according to the first embodiment. The water treatment device of FIG. 1 includes a storage tank 2 for accommodating the filtration membrane 1. The storage tank 2 is filled with the water to be treated 4, and the filtration membrane 1 is immersed in the water 4 to be treated. Further, the storage tank 2 is provided with a water to be treated pipe 19 for supplying the water to be treated 4. A filtered water pipe 15 is connected to the filtration membrane 1. Further, a pressure gauge 9 is installed on the pipe. The pressure information obtained by the pressure gauge 9 is transmitted to the calculation unit 10 and converted into the intermembrane differential pressure.

The filtration pump 13 is connected to the filtered water pipe 15 so that the filtered water obtained through the filtration membrane 1 can be sent to the filtered water tank 14. Further, the filtered water pipe 15 is connected to the ozone water supply pipe 7. The ozone water supply pipe 7 supplies the ozone water discharged from the ozone water generator 3 via the ozone water supply pump 6 to the filtration membrane 1. The ozone water generator 3 includes an ozone gas generator 12 that generates ozone gas, an ozone water tank 5 that generates ozone water by bringing the generated ozone gas into contact with a liquid stored inside, and a dissolved ozone concentration in the ozone water tank 5. It is composed of an ozone water concentration meter 8 for measuring.

Valves

16 and 17 are installed in the filtered water pipe 15 and the ozone water supply pipe 7, and the supply of filtered water or ozone water is switched by opening and closing these valves. Further, a control unit 11 capable of receiving the operation parameters of each device set by the setting unit 18, the calculation result calculated by the calculation unit 10, information from other devices, or transmitting a command to each device is provided. Be prepared.

Next, a series of operations of water treatment by the water treatment apparatus of FIG. 1 will be described with reference to the flowchart of FIG.
[Membrane filtration process]
In the membrane filtration step (step S1), the water to be treated 4 is received into the storage tank 2 and the water to be treated 4 is filtered by the filtration membrane 1. The water to be treated 4 supplied from the water pipe 19 to be treated is stored in the storage tank 2. By opening the valve 17 (at this time, the valve 16 is closed) and operating the filtration pump 13 to suck the water, the filtration membrane 1 filters the water to be treated 4. The filtered water obtained by filtration is transferred to the filtered water tank 14.

Fowling of the filtration membrane 1, that is, blockage of pores progresses with filtration. As the fouling progresses, the pressure difference (trans-membrane pressure: TMP) before and after the filtration membrane 1 increases. An excessive increase in TMP causes a malfunction of the device such as damage to the filtration membrane 1, so it is desirable to constantly monitor the TMP to grasp the degree of fouling. In the water treatment apparatus of the present embodiment, the pressure information obtained by the pressure gauge 9 is converted into TMP by adding a treatment predetermined by the calculation unit 10 and recorded. The predetermined treatment here is a treatment for obtaining the difference between the pressure acting on the primary side of the filtration film 1 and the pressure acting on the secondary side. Here, the storage tank is used as the pressure acting on the primary side of the filtration film 1. The water pressure generated by the water level of 2 is adopted, and the sum of the water pressure generated by the mounting height of the pressure gauge 9 and the measured value of the pressure gauge 9 is adopted as the pressure acting on the secondary side.

The water to be treated 4 is not particularly limited, and may be, for example, natural water collected from rivers, lakes, oceans, etc., or sewage, industrial wastewater, or the like. When operating as a membrane separation bioreactor, activated sludge may be stored in the storage tank 2, water 4 to be treated may be introduced therein, and the mixed liquid may be filtered by the filtration membrane 1.

Also, the filtration may be continuous or intermittent. For example, the filtration may be stopped at predetermined time intervals to allow the filtered water to flow back to perform backwashing, and then the filtration may be restarted. The shape of the filtration membrane 1 may be either a hollow yarn type or a flat membrane type, and the material of the filtration membrane 1 is an inorganic material such as ceramics, for example, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), or the like. Fluororesin-based organic materials can be used. In any case, the filtration membrane 1 to be used is not limited as long as the water to be treated 4 has a pore diameter that can be filtered to the target water quality and has a structure or material having sufficient ozone resistance.

[Ozone water generation process]
As described above, the fouling of the filtration membrane 1 progresses with the filtration, and the TMP increases. There is a limit to the TMP that can be given to the filtration membrane 1, and if filtration is continued with a TMP exceeding the limit, the filtration membrane 1 may be damaged. Further, even if the TMP is within the limit, if the high TMP is maintained and the filtration is continued, it may be difficult to reduce the TMP by washing. Therefore, it is desirable to perform ozone water cleaning when _{the limit value P max of} TMP input to the setting unit 18 in advance is reached. For example, it is preferable to set _{P max to 10 to 50 kPa.}

By the way, when the filtration membrane 1 is washed with ozone water, it is necessary to generate ozone water necessary for filtration each time. This is due to the characteristics of ozone. That is, since the half-life is extremely short, it is not possible to retain the ozone water required at one time for a long period of time. Or, if it is to be retained, it is necessary to continuously supply ozone gas even when ozone water is unnecessary, which is inefficient. Therefore, to start the washing Upon reaching P _max, from the viewpoint of efficiency, it is necessary to start generating ozone water before the predetermined time to reach P _max which defines.

The water treatment apparatus shown in this embodiment is equipped with a device for solving such a problem. That is, the TMP is sequentially calculated by the calculation unit 10 from the measured value of the pressure gauge 9 during the membrane filtration step execution, and transmitted to the control unit 11. As a result, the TMP acting on the filtration membrane 1 is constantly monitored. Further setting unit 18 in advance input _{P max,} and the _{P sub} and TMP is _{P max} constant value lower TMP than the control unit 11 compares sequentially (step _{S2), and} it has reached the _{P sub,} i.e., When the control unit 11 detects that the TMP is _{equal to or greater than the P sub} , ozone water generation is started (step S3). It _{is preferable to set the P sub} _{in the setting unit 18 so that the time from P sub} to P _max is longer than the time that ozone water generation can be completed, and the time required for ozone water generation is about 10 to 120 minutes. Therefore, for example, it is preferable to set _Psub to a value 5 to 20 kPa lower than _{P max.}

As described above, in the membrane filtration step, when the TMP _{reaches Psub} , the ozone water generation step is started, the ozone gas generator 12 operates, and the ozone gas supply to the ozone water tank 5 is started. A liquid that can be a solvent for ozone is stored in the ozone water tank 5 in advance, and ozone water is generated by bringing this liquid into contact with ozone gas. For example, tap water, industrial water, pure water, ultrapure water, or a part of the filtered water stored in the filtered water tank 14 may be transferred and used as this liquid. When ozone water is generated in the ozone water tank 5, acidic chemicals such as hydrochloric acid and sulfuric acid, or radical scavengers (for example, carbon dioxide gas) are injected into the liquid in the ozone water tank 5 at the same time as ozone gas or prior to ozone gas supply. You can keep it. By adding such an operation, it is possible to suppress the decomposition of ozone, and it is possible to obtain high-concentration ozone water in a shorter time.

While the ozone water generation step is executed, the membrane filtration step is continued. That is, in the membrane filtration step, the filtration pump 13 operates and filters the water to be treated 4 through the filtration membrane 1, but the operation of the equipment related to ozone water generation and the operation of the equipment related to membrane filtration are independent. Unless the TMP _{reaches P max} , i.e., when the TMP is _{equal to or greater than P max} , it is not always necessary to shut down these devices and stop the membrane filtration process during ozone water production. This is one aspect of the effect of the present embodiment, and _{by starting ozone water generation before the limit value P max} of the intermembrane differential pressure requiring cleaning, the filtration stop time can be shortened to the ultimate. can. _{When the P max} is reached before the ozone water generation is completed, the filtration process can be stopped or the filtered water amount (filtration flux) can be reduced until the ozone water generation is completed.

The ozone water concentration during ozone water generation is constantly monitored by the ozone water concentration meter 8 and transmitted to the calculation unit 10. The concentration information received by the calculation unit 10 is transmitted to the control unit 11, and when the control unit 11 determines that _{the ozone water concentration at the time of monitoring has reached the predetermined concentration Cartget set in advance by the setting unit 18, the ozone water} Start the cleaning process.

[Ozone water cleaning process]
Dissolved ozone concentration of the ozone water in the control unit 11 has reached a concentration _{C target} a predetermined, _i.e., after a determination is made that equal to or greater and _{C target,} stopping the membrane filtration step (Step S4). Meanwhile, while the ozone gas supply to the ozone water tank 5 by the ozone gas generator 12 is continued, the ozone water supply to the filtration membrane 1 is started. That is, a command is transmitted from the control unit 11, the filtration pump 13 is stopped, the valve 17 is closed, and the valve 16 is opened. Further, the ozone water supply pump 6 operates, and the ozone water stored in the ozone water tank 5 is supplied to the filtration film 1 through the ozone water supply pipe 7. The supplied ozone water chemically decomposes fouling-causing substances (organic components such as biofilms, etc.) that block the pores of the filtration membrane in the process of permeating from the secondary side to the primary side of the filtration membrane. Or physically peel off.

In the operation of the water treatment equipment, it is necessary to always obtain the cleaning effect intended by the operation manager in a stable manner. However, the cleaning mechanism of the filtration membrane for water treatment with ozone water has not been clarified in many cases, and it has been difficult to control the cleaning effect. In addition, the concentration of ozone water obtained as a result of ozone water generation changes depending on the properties of the liquid that is the solvent for ozone gas, making it even more difficult to control the cleaning effect.

On the other hand, as a result of diligent studies by the inventors, the CT value obtained by the product of the cleaning effect, that is, the effect of reducing TMP, and the concentration of ozone water used for cleaning and the cleaning time in the ozone water cleaning of the water treatment filter membrane. It became clear that there could be a correlation with. That is, when the filtered membrane in which water in which an organic substance such as sugar or protein is dissolved is filtered and fouled until it shows a predetermined TMP is washed with ozone water, even if the ozone water concentration C changes each time. By adjusting the ozone water cleaning time so that the CT value, which is the product of the ozone water concentration C and the cleaning time T in ozone water, is constant, the TMP can be used after any cleaning in which the ozone water concentration C has changed. The amount of reduction was about the same. As a result, it is considered possible to manage the ozone water cleaning effect by managing the cleaning time while grasping the change in the ozone water concentration obtained as a result of ozone water generation.

In the water treatment apparatus shown in the present embodiment, the concentration of ozone water stored in the ozone water tank 5 in the ozone water generation step is measured by the ozone water concentration meter 8. The measured values are sequentially transmitted to the calculation unit 10, and the calculated current ozone water concentration information is transmitted to the control unit 11. Control unit 11 compares the current concentration of ozone water that has been transmitted from the control unit, and a concentration of ozone water C _target set in the preset unit 18. As shown in FIG. 3, _{when it is determined that the Cartaget} has been reached, the ozone water cleaning step is started (step S5).

As shown in FIG. 3, the ozone water concentration after the start of the ozone water cleaning process is averaged by adjusting the ozone gas concentration or flow rate supplied to the ozone water tank 5 by changing the output of the ozone gas generator 12. It may be operated so as to become a C _target. In this case, the measured value of the ozone water concentration meter 8, the control unit 11 received via the operation unit 10 is, the ozone gas generator in accordance with a deviation between the C _target is the current concentration of ozone water and the target value Increase or decrease the ozone gas concentration or flow rate emitted from 12. In this way, the ozone gas generator 12 is controlled by the control unit 11 so that the ozone water concentration during the execution of the ozone water cleaning step _{becomes a Cartaget on average.} _{Further, the control unit 11 calculates the required cleaning time α1 from the CT target} and the ozone water concentration C _target , which are predetermined target CT values, in the setting unit 18, and executes the ozone water cleaning step for the required cleaning time α1.

Further, the ozone water concentration may be adjusted without changing the ozone gas concentration, the flow rate, or other conditions. In this case, the control unit 11 sequentially acquires the measured value of the ozone water concentration meter 8 and records it as the ozone water concentration via the calculation unit 10. The product of the recorded ozone water concentration and the elapsed time of the ozone water cleaning step is accumulated, and when the accumulated value _{reaches the CT target} (step S6), that is, when it is equal to or larger than the _{CT target, ozone is used.} The water washing step may be completed (step S7). For example, at this time, the following formula may be introduced into the calculation unit 10, and the calculation result may be sequentially compared and determined _{with the CT target.}

CT _present = Σ (C _present × Δt)
here,
CT _present indicates the current cumulative CT value.
C _present indicates the current ozone water concentration.
Δt indicates the elapsed time from the previous CT _{present calculation.}

In addition, when the ozone water concentration during the ozone water cleaning process is taken as a matter of course, as shown in FIG. 4, the average ozone water concentration _Ave at each time point from the start of the ozone water cleaning process is sequentially calculated, and this calculated value is used. The ozone water cleaning process completion point may be determined by comparing the _{∫Cave ·} dt value obtained by multiplying the ozone water cleaning process execution time at the same time point with the _{CT target (step S6).}

Further, in the present embodiment, the ozone water cleaning process start condition is set to the ozone water concentration. That is, when the preset ozone water concentration _Cartage is reached, the ozone water cleaning step is started. However, for example, even if the ozone water generation step is operated so as to forcibly start the ozone water cleaning step when the predetermined time β has elapsed, as shown in FIG. 5, without defining the _Cartaget. good. At this time, the ozone water concentration at the start of the ozone water cleaning process is not always constant, but since the cleaning effect itself by the ozone water can be controlled by the CT value, the ozone water cleaning is performed according _{to the ozone water concentration and the CT target to be measured sequentially.} The process execution time may be adjusted.

After the ozone water cleaning process is completed, the ozone gas supply from the ozone gas generator 12 and the ozone water supply by the ozone water supply pump 6 are stopped, the valve 16 is closed, and the filtration process is restarted (step S8).

As described above, according to the present embodiment, high-concentration ozone water can be obtained in a shorter time with the start of the ozone water generation process. Further, by managing the cleaning time while grasping the change in the ozone water concentration, it is possible to manage the ozone water cleaning effect. Due to these remarkable effects, the uncertainty caused by the characteristics of ozone in ozone water generation and cleaning can be eliminated, ozone water generation can be started at an appropriate timing, and a stable and sufficient ozone water cleaning effect can be obtained. ..

Embodiment 2.
In a water treatment device that obtains treated water by filtering the water 4 to be treated with a filtration membrane, fouling of the filtration membrane proceeds as described above, but the fouling rate, that is, the rate of change in differential pressure between membranes is not always constant. It does not change depending on the filtration conditions, such as the water-based condition to be treated from time to time. Therefore, by determining the ozone water generation start timing according to the rate of change in the differential pressure between the membranes, more efficient operation becomes possible.

The water treatment apparatus shown in the first embodiment, the TMP and P _sub at each time point, was determined ozone water generation process start timing by comparing the control unit 11, in this embodiment, shown in FIG. 6 As described above, by adding the intermembrane differential pressure change rate calculation means 110 to the control unit 11, the ozone water generation process start timing can be determined more accurately.

That is, in the present embodiment, during the execution of the membrane filtration step, the TMP is calculated by the calculation unit 10 from the measured values of the pressure gauge 9, and is sequentially recorded in the control unit 11. That control unit 11 includes a current transmembrane pressure P _n, was predetermined at the setting unit 18 sequentially records the transmembrane pressure P _n-1 before a predetermined time T ₁ than the current, P _n _{From the difference between P n-1} and P n-1, and from T ₁ , the average intermembrane differential pressure change rate v from P _n _{-1 to P n is calculated.}

Further, the control unit 11 sequentially calculates in the _{setting unit 18, ΔP, which is the product of the predetermined time T 2} and the average intermembrane differential pressure change rate v, and the _{value P n + x,} which is the sum of _{this ΔP and P n.} The control unit 11 sequentially compares _{this value P n + x} _{with the P max} preset by the setting unit 18, _{and when it is determined that P n + x} has _{reached P max} (step S9), the ozone water generation step is started. (Step S3).

P _{n + x} is an estimated intermembrane pressure after _{time T 2} starting from the current time. T ₁ needs to be a time suitable for predicting the intermembrane differential pressure in the near future from the current time from the intermembrane differential pressure increase rate near the current time, and is set between 10 minutes and 240 minutes. Is good. If T ₁ is shorter than 10 minutes, it is greatly affected by the change in the differential pressure between the membranes due to a slight fluctuation in the filtration flow rate in the filtration step, and v is calculated to be excessively large or small.

On the other hand, if T ₁ is longer than 240 minutes, it is affected when the intermembrane pressure suddenly rises or falls for some reason in the process _{from P n-1} to P _n _{, and v and P n + x} are calculated. It becomes inappropriate.

For T _{2, it} is preferable to input the time required from the start of ozone water generation _{to the arrival of the required ozone water concentration Cartaget} , which is 10 to 120 minutes. _{That is, when it is determined that the intermembrane differential pressure can reach P max} or more defined as the limit intermembrane differential pressure when the time required for ozone water generation elapses from the current time, the ozone water generation process is immediately started. do.

Even when the intermembrane differential pressure change rate changes from moment to moment as described above, it is possible to estimate the future intermembrane differential pressure by sequentially calculating and recording the local intermembrane differential pressure change rate. By using this, the ozone water generation start timing can be accurately determined.

FIG. 8 shows an example of the hardware constituting the calculation unit 10, the control unit 11, the setting unit 18, and the intermembrane differential pressure change speed calculation means 110. It is composed of a processor 100 and a storage device 200, and although not shown, the storage device includes a volatile storage device such as a random access memory and a non-volatile auxiliary storage device such as a flash memory. Further, an auxiliary storage device of a hard disk may be provided instead of the flash memory. By executing the program input from the storage device 200, the processor 100 performs each calculation and each control described with reference to, for example, FIG. 2 or FIG. In this case, a program for calculation or control is input from the auxiliary storage device to the processor 100 via the volatile storage device. Further, the processor 100 may output data such as a calculation result to the volatile storage device of the storage device 200, or may store the data in the auxiliary storage device via the volatile storage device. A plurality of processors 100 may be mounted, and the arithmetic unit 10, the control unit 11, and the setting unit 18 may be configured by one processor 100.

Although the present application describes various exemplary embodiments and examples, the various features, embodiments, and functions described in one or more embodiments are applications of a particular embodiment. It is not limited to, but can be applied to embodiments alone or in various combinations.
Therefore, innumerable variations not illustrated are envisioned within the scope of the techniques disclosed herein. For example, it is assumed that at least one component is modified, added or omitted, and further, at least one component is extracted and combined with the components of other embodiments.

1: Filtration membrane, 2: Storage tank, 3: Ozone water generator, 4: Treated water, 5: Ozone water tank, 6: Ozone water supply pump, 7: Ozone water supply pipe, 8: Ozone water concentration meter, 9 : Pressure gauge, 10: Calculation unit, 11: Control unit, 12: Ozone gas generator, 13: Filtration pump, 14: Filtered water tank, 15: Filtered water pipe, 16, 17: Valve, 18: Setting unit, 19: Covered Treated water piping

Claims

In a water treatment apparatus that performs a membrane filtration step of filtering water to be treated with a filter membrane to obtain treated water and an ozone water cleaning step of cleaning the filter membrane with ozone water.
An arithmetic unit that calculates the intermembrane differential pressure value from the measured pressure difference before and after the filtration membrane,
The generation of ozone water starts when the calculated intermembrane differential pressure value or the estimated value calculated based on the intermembrane differential pressure value becomes equal to or larger than the reference value. And the control unit that instructs
A water treatment device characterized by being equipped with.
When comparing the intermembrane differential pressure value with the reference value, the reference value is a second value that is constant lower than the first value that makes it difficult to reduce the intermembrane differential pressure value by the ozone water cleaning step. The water treatment apparatus according to claim 1, wherein the value is set.
The constant value is characterized in that the time from the second value to the first value is set to be longer than the time from the start of generation of ozone water to the completion of generation of ozone water. The water treatment apparatus according to claim 2.
When the calculated intermembrane differential pressure value is equal to or larger than the first value that makes it difficult to reduce the intermembrane differential pressure value by the ozone water cleaning step, the above-mentioned The water treatment apparatus according to claim 2, wherein the membrane filtration step is stopped.
The first aspect of the present invention is that when the estimated value is compared with the reference value, the reference value is a limit value at which it is difficult to reduce the intermembrane differential pressure value by the ozone water cleaning step. Water treatment equipment.
The estimated value is the intermembrane differential pressure change rate from the difference between the intermembrane differential pressure value calculated by the calculation unit and the intermembrane differential pressure value predetermined time before the intermembrane differential pressure value. The water treatment apparatus according to claim 5, wherein the value is calculated and the intermembrane differential pressure value after a predetermined time is calculated based on the intermembrane differential pressure change rate.
When the calculated intermembrane differential pressure value is equal to or larger than the limit value at which it is difficult to reduce the intermembrane differential pressure value by the ozone water cleaning step, the filtration membrane step is performed. The water treatment apparatus according to claim 5, wherein the water treatment apparatus is stopped.
The water treatment apparatus according to any one of claims 1 to 7, wherein the ozone water cleaning step is started after the concentration of the generated ozone water reaches a predetermined target concentration.
The water treatment apparatus according to claim 8, wherein the ozone water cleaning step is terminated when the integrated value of the ozone water concentration and the elapsed time of the ozone water cleaning step reaches a set value.
The water treatment apparatus according to claim 8, wherein the control unit adjusts the ozone gas concentration and the flow rate of the ozone gas generator so that the ozone water concentration in the ozone water cleaning step becomes the target concentration on average. ..
In a water treatment method having a membrane filtration step of filtering water to be treated with a filtration membrane to obtain treated water and an ozone water cleaning step of cleaning the filtered membrane with ozone water.
The intermembrane differential pressure value is calculated from the measured pressure difference before and after the filtration membrane.
When the intermembrane differential pressure value is equal to or larger than the reference value set to be a constant value lower than the limit value at which it is difficult to reduce the intermembrane differential pressure value by the ozone water cleaning step. To start the generation of ozone water,
After the concentration of the generated ozone water reaches a predetermined target concentration, the filtration membrane step is stopped and the ozone water cleaning step is started.
A water treatment method characterized in that the ozone water cleaning step is terminated when the integrated value of the ozone water concentration and the elapsed time of the ozone water cleaning step reaches a set value.
In a water treatment method having a membrane filtration step of filtering water to be treated with a filtration membrane to obtain treated water and an ozone water cleaning step of cleaning the filtered membrane with ozone water.
The intermembrane differential pressure value is calculated from the measured pressure difference before and after the filtration membrane.
The estimated value of the intermembrane differential pressure value after a certain period of time calculated based on the intermembrane differential pressure value is equal to or equal to the limit value at which it is difficult to reduce the intermembrane differential pressure value by the ozone water washing step. When it becomes larger than the limit value, the generation of the ozone water is started, and the ozone water is generated.
After the concentration of the generated ozone water reaches a predetermined target concentration, the filtration membrane step is stopped and the ozone water cleaning step is started.
A water treatment method characterized in that the ozone water cleaning step is terminated when the integrated value of the ozone water concentration and the elapsed time of the ozone water cleaning step reaches a set value.