KR100720139B1 - Operation control system using water analysis of membrane filtration device and method thereof - Google Patents

Abstract

The present invention relates to an apparatus for controlling coagulation pretreatment by continuous monitoring of membrane fouling index and a method thereof using a membrane separation advanced water treatment apparatus. In this study, after measuring the values of the indicator factors that can represent the water quality characteristics such as turbidity and membrane fouling index (Korea fouling index), which exist in the incoming water, and then through the coagulation process and membrane separation pretreatment process By calculating the amount of flocculant injection, which is a key driving factor, and controlling it in real time, it is possible to optimize the efficiency of the pretreatment process before the membrane separation process.

According to the present invention, the water treatment can be quickly responded to the real-time change of the water quality and quantity, so that the early warning of membrane contamination is possible, the stability of the treated water quality is secured, as well as the connection to the automatic control device, It can be easily applied to the membrane separation process, and it is possible to reduce the energy consumption by maintaining the stable membrane filtration characteristics by optimizing the injection of bad products by accurately calculating the flocculation conditions and the backwashing conditions and optimizing the operation of the membrane separation process. Can be obtained.

Water treatment, turbidity measurement unit, pressure measurement unit, turbidity, membrane fouling index, pretreatment, flocculation, membrane separation, microfiltration, real time, automatic control

Description

Control system for coagulation pretreatment by continuous monitoring of membrane fouling index using membrane separation and its method {Operation control system using water analysis of membrane filtration device and method

Figure 1 is a schematic diagram showing a coagulation pre-treatment process control apparatus by the membrane fouling index continuous monitoring of the present invention.

Figure 2 is a flow chart illustrating a process of controlling the coagulation pretreatment process of the membrane separation advanced water treatment device in an optimized state using the membrane fouling index continuous monitoring of the present invention.

Figure 3 is a chart showing the results of analyzing the correlation between the membrane fouling index and the interlayer differential pressure in accordance with the present invention.

Figure 4 is a table showing the results of real-time analysis of the membrane fouling index according to the present invention.

Figure 5 is a table showing the results of the sudden fluctuations in the water quality in the process of combining the flocculation and membrane separation when operating the automatic control device according to the invention.

Explanation of symbols on the main parts of the drawings

One ; Online turbidity measurement unit 2; Online pressure measuring unit

3; Calculation unit 4; Control unit

5; Flocculant injection controller 6; Raw water storage tank

7; Mixing tank 8; Agglomeration tank

9; Membrane Separation Unit

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water treatment technology, and in particular, in a membrane separation advanced water treatment device in which water treatment is performed by combining a flocculation and membrane separation process, turbidity and membrane pollution index, which is a cause of membrane contamination in influent water, After measuring the value of the indicator factors that can represent the water quality characteristics such as fouling index (), and through this to calculate the amount of flocculant injection, which is a key operating factor of the flocculation process and membrane separation pretreatment process, and controlling them in real time, before the membrane separation process The present invention relates to a coagulation pretreatment process control apparatus and a method thereof by continuously monitoring the membrane fouling index of an advanced water treatment system using membrane separation to optimize the efficiency of an ongoing pretreatment process.

Conventional water treatment processes consisted of chemical mixing / aggregation / precipitation processes, and processes based on sand filtration and chlorine disinfection. In order to make up for the limitation, advanced water treatment processes using processes such as ozone, activated carbon and membrane separation have been developed and used.

The membrane separation process constituting the advanced water treatment process can be divided into processes such as MF (Microfiltration), UF (Ultrafiltration), NF (Nanofiltration) and RO (Reverse Osmosis) according to the pore size of the membrane surface. As it has the effect of selectively removing particulate matter and dissolved substances, it is recognized as the next generation water treatment technology, and recently it is rapidly spreading in the water treatment process site. It is expected to increase.

In general, the membrane separation process controls the operation by monitoring the change of the interlayer differential pressure after maintaining a constant filtration flow rate and performing backwashing when the predetermined pressure is exceeded or exceeds a predetermined time. In addition, general water quality such as pH, temperature, turbidity, and alkalinity are analyzed for raw water flowing into each process, but it is difficult to find a correlation with membrane filtration performance.

In particular, in the case of the flocculation process, even when used as a pretreatment for membrane separation, the flocculant injection amount is calculated by using a look-up table, empirical formula, or self-test as in the conventional water treatment process. Since the coagulation conditions as the pretreatment of the separation process is different, it causes various problems when applied to the actual site, and also causes the device automation to be difficult.

In this regard, the present inventors have applied a continuous membrane fouling index that quantifies the performance of membrane filtration in order to overcome various limitations of existing manual control and operation methods in the high water purification process that combines the conventional coagulation pretreatment and membrane separation process. We have developed and proposed a control technology for the flocculation and membrane separation process that operates based on monitoring.

That is, the present invention is to overcome the problems of the prior art described above, in the high-purity water treatment apparatus consisting of a coagulation pretreatment process and a membrane separation process, by measuring the value of turbidity, membrane fouling index, etc. present in the influent source water Membrane Pollution Index Continuous Monitoring of Advanced Water Treatment Equipment using Membrane Separation to Optimize Pretreatment Process by Calculating Membrane Permeation Flow Rate, Backwash Cycle and Backwashing Method It is an object of the present invention to provide a control device for coagulation pretreatment.

Another object of the present invention is to provide a method for controlling the coagulation pretreatment process of an advanced water treatment apparatus using membrane separation in an optimized state by monitoring the filtration characteristics of the flocculation flocs using the calculated membrane fouling index.

Agglomeration pretreatment process control device by continuous monitoring of the membrane fouling index of the advanced water treatment apparatus using the membrane separation of the present invention for achieving the above object, comprising a raw water storage tank, a mixing tank, a flocculation tank and a membrane separation unit In the purified water treatment device, the purified water treatment device is connected to the control device to control the coagulation pre-treatment process, the control device is connected to be installed so as to continuously analyze the turbidity of the influent of the raw water reservoir and the membrane separation unit Online turbidity measurement unit; An online pressure measurement unit connected to and installed to measure the intermembrane differential pressure in the membrane separation unit; A calculation unit for receiving the online turbidity data and the pressure data analyzed through the online turbidity measurement unit and the pressure measurement unit and calculating the membrane fouling index based on the received data; A control unit which collects / databases and displays the membrane fouling index data determined by the calculation unit; It characterized in that it comprises a coagulant injection controller for controlling the coagulant input to the chemical mixing tank through the control of the control unit.

According to another aspect, the on-line turbidity measurement unit is characterized by repeatedly measuring the turbidity in the inflow water and the membrane separation unit at a set time interval to cope with instantaneous water quality fluctuations.

According to another aspect, the on-line pressure measuring unit is characterized by repeatedly measuring the pressure change in the influent water and the membrane separation unit at a set time interval to correspond to the instantaneous change in the membrane filtration characteristics.

According to another aspect, the control unit has a function of displaying the determined membrane fouling index so that the plant operator can manually switch the operation mode according to the membrane fouling index determined by the calculation unit.

In addition, the method of controlling the coagulation pretreatment process by continuous monitoring of the membrane fouling index of the advanced water treatment apparatus using the membrane separation of the present invention, the step of measuring the turbidity of the influent through the online turbidity measurement unit; Measuring the intermembrane differential pressure of the influent via an online pressure measurement unit; Calculating a membrane fouling index using the measured turbidity and interlayer differential pressure; Comparing the calculated membrane fouling index with a set value; It is characterized in that it comprises a step of maintaining the current operating conditions or controlling the adjustment of the flocculant input amount using the flocculant injection controller according to the comparison result.

The membrane fouling index, which is a key factor of the present invention, is calculated from the following equation.

KFI: Fouling index ^{(10 -12 · m -2 · NTU} -1)

C: Influent Turbidity (NTU)

TMP: Intermembrane Pressure (kPa)

N: Number of membrane modules operated (EA)

A: Membrane area per membrane module (㎡)

η: viscosity of influent (centipoise)

J: flux of filtered water (L / m ² -hr)

R ₁ : Membrane filtration resistance (m ^-1 ) at the start of one cycle of membrane filtration (t ₁ )

R ₂ : Membrane filtration resistance (m ^-1 ) at specific time (t ₂ )

V: total volume of filtered water obtained between times t ₁ and t ₂ (m ² )

The membrane fouling index has the same meaning as the specific cake resistance of the contaminant layer formed on the surface of the membrane, so that the membrane fouling index may represent not only the speed of membrane fouling but also the characteristics of the material causing the membrane fouling.

In the present invention, the data can be collected / database and displayed by real-time analysis of on-line measurable items such as turbidity of influent water flowing into the membrane separation device and membrane fouling index calculated from the rate of increase of the interlayer differential pressure of the membrane module. The operational factors of each unit process can be calculated from the quantified operational data to control the process, further improving the stability and reliability of the water treatment. In addition, by linking the collected data with the automatic control device it is possible to automate the operation of the membrane separation process.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

Figure 1 is a schematic diagram showing a control device for flocculation pretreatment process by the continuous monitoring of the membrane fouling index of the present invention, as shown, the present invention is a membrane separation water treatment unit for water treatment of influent raw water, and from the water treatment unit It is provided with a control device for controlling the operation mode of the purified water treatment unit by receiving and receiving the incoming water quality of the water.

The purified water treatment unit, a raw water storage tank (6) for temporarily storing the incoming source water, and a mixing tank (7) for receiving the raw water temporarily stored in the raw water storage tank (6) to administer and mix the NB flocculant; An agglomeration tank (8) which receives the mixed water through the mixing tank (7) to form a flocculation floc; It comprises a membrane separation unit (9) for receiving the aggregated water through the coagulation tank (8) to immerse the hollow fiber membrane module in the filter tank and to reduce the pressure to filter the water.

In addition, the operation mode control unit is an on-line turbidity measurement unit (1) for continuously analyzing the turbidity of the inflow of raw water and the membrane unit influent received from the raw water storage tank (6), and the on-line differential pressure in the membrane unit A calculation unit (3) for receiving the on-line turbidity data and pressure data analyzed through the pressure measurement unit (2), the turbidity measurement unit (1), and the pressure measurement unit (2), and calculating the membrane fouling index based thereon; The control unit 4 collects / databases and displays the membrane fouling index data calculated through the calculation unit 3 and the coagulant input into the chemical mixing tank 7 through the control unit 4 manually or It is configured to include a coagulant injection controller (5) to automatically control.

At this time, the on-line turbidity measurement unit (1) is preferably measured by repeating the turbidity in the inflow water and the membrane separation unit (9) at a predetermined time interval so as to respond to the instantaneous water quality change, more preferably the The time is set to a time interval within 10 minutes.

In addition, the on-line pressure measurement unit (2), it is preferable to repeatedly measure the pressure change in the inflow source water and the membrane separation unit (9) at a predetermined time interval to correspond to the instantaneous change in the membrane filtration characteristics, more Preferably, the time is set to a time interval within 10 minutes.

The high-purity water treatment device having such a configuration is characterized in that the inflow of the raw water storage tank 6 is mixed with the flocculant such as PAC supplied from the flocculant injection controller 5 in the mixing tank 7 and then at low speed in the flocculation tank 8. After the floc is formed to form a floc, the formed floc is removed from the membrane separation unit 9. In the process, floc precipitates on the surface of the membrane to increase the differential pressure of the membrane module with time.

The concentration of the floc flowing into the membrane module is continuously measured using the on-line turbidity measurement unit 1, and the intermembrane differential pressure changed by precipitation of the floc is continuously measured using the on-line pressure measurement unit 2. The turbidity data and the interlayer differential pressure data measured in this way are transmitted to the calculation unit 3 to calculate the membrane fouling index by using Equations 1 and 2 above.

The membrane fouling index calculated from the calculation unit 3 is used to control the membrane fouling combination process according to the flowchart shown in FIG. This control device is an automatic control technology of the coagulation pretreatment and membrane separation process for efficiently suppressing membrane contamination in the membrane separation advanced water treatment device for the constant water intake source with large change in surface water quality throughout the year.

Therefore, as shown in FIG. 2, when the membrane fouling index is maintained at or below the set value, current operating conditions are maintained, but when the membrane fouling index is exceeded, the flocculant injection amount is adjusted to adjust the amount of flocculant. When the amount of coagulant injection is determined in the calculation unit 3 according to the increase or decrease rate of the contamination index, the control unit 4 is used to control the coagulant administration of the coagulant injection controller 5.

In addition, the calculation unit 3 is used to correct the set value by storing the measured turbidity, interlude differential pressure, membrane fouling index and operating conditions in a database. At this time, each set value can be input by the field operator, and may vary slightly depending on the type, material and raw water quality conditions of the purified water treatment facility and the membrane separation module.

Figure 3 shows an example of the results showing the relationship between the membrane fouling index and the interlayer differential pressure. According to this, the membrane fouling index means the membrane fouling potential per unit concentration of particulate membrane pollutant, and thus the proportional relationship between the membrane fouling index multiplied by the turbidity value and the interlayer differential pressure is established. Therefore, by monitoring the membrane fouling index and turbidity, it is possible to predict the increase of intermembrane pressure.

4 shows the results of experiments for 48 hours on the change in the turbidity and membrane fouling index of the membrane influent with time. Symbols indicate membrane influent turbidity and curves indicate membrane fouling index. According to this, the membrane fouling index changes irrespective of influent turbidity because the membrane fouling index is a value that characterizes the flocs produced during the flocculation process. Therefore, high membrane fouling index means that the flocs produced tend to cause membrane fouling, so in this case, it is necessary to change the flocculation conditions.

5 shows the result of changing the aggregation conditions in the membrane separation process using the membrane fouling index. At first, the operation was started without the administration of the flocculant, but the membrane fouling index was high initially. Thereafter, the membrane fouling index tended to decrease on the 7th day of operation, thereby gradually decreasing the flocculant dose. In addition, although the coagulant dose was continuously decreased, the intermembrane pressure was able to be stably maintained below 35 kPa. From this, it can be seen that the control method using the membrane fouling index is effective for the stable operation and the reduction of the coagulant dose.

Therefore, according to the present invention, the control of the flocculation pretreatment is automatically optimized and set according to the water quality conditions, thereby maximizing the treatment cost of the membrane separation process.

As described above, the present invention has been described with reference to specific embodiments, but is not necessarily limited thereto, and modifications and variations may be made without departing from the scope of the technical idea of the present invention.

According to the apparatus and method for controlling the flocculation pretreatment process by continuous monitoring of the membrane fouling index of the advanced water treatment system using the membrane separation according to the present invention, the water quality factor and membrane fouling index of the incoming raw water are measured and analyzed in real time, and the data is analyzed. By collecting and providing the database to the driver or linking it with the automatic control device, it can be quantified and judged by the water quality analysis data and the membrane contamination factor of the operation status of the membrane separation process, and the previous data and the current data stored in the database can be determined. Synthesis / analysis can easily predict future membrane fouling progress.

Therefore, the water treatment is possible by quickly responding to the real-time change of the water quality and quantity, so that the early warning of membrane contamination is possible, the stability of the treated water quality is secured, it is possible to link to the automatic control device, and the existing membrane separation It can be easily applied to the process, and it is possible to reduce the energy consumption by optimizing the chemical injection amount, maintaining stable membrane filtration characteristics, and optimizing the operation of the membrane separation process by accurately estimating flocculation conditions and backwash conditions. .

In addition, it is possible to analyze and determine the progress of membrane contamination in accordance with the change in the water quality of raw water in a short time, so that the driver can cope immediately and optimize the operation of the water treatment device in connection with the automatic control device of the membrane separation process. In this way, the automation and stabilized operation of the entire device can be achieved.

Claims (5)

In the purified water treatment device comprising a raw water storage tank (6), a mixing tank (7), a coagulation tank (8) and a membrane separation unit (9), The purified water treatment device is connected to the control device to control the coagulation pretreatment process, The control device, An online turbidity measurement unit (1) connected and installed to continuously analyze the turbidity of the influent of the raw water storage tank (6) and the membrane separation unit (9); An online pressure measurement unit (2) connected and installed to measure the intermembrane differential pressure in the membrane separation unit (9); A calculation unit (3) for receiving the online turbidity data and the pressure data analyzed through the online turbidity measurement unit (1) and the pressure measurement unit (2) and calculating a membrane fouling index based on the received data; A control unit (4) which collects / databases and displays the membrane fouling index data determined by said calculation unit (3); Membrane fouling index of the high water purification apparatus using membrane separation, characterized in that it comprises a flocculant injection controller (5) for controlling the coagulation agent input to the chemical mixing tank (7) through the control of the control unit (4) Control device for coagulation pretreatment by continuous monitoring. The method of claim 1, wherein the online turbidity measurement unit (1), Controlling the coagulation pretreatment process by continuous monitoring of the membrane fouling index of the advanced water treatment system using membrane separation, characterized by repeatedly measuring turbidity in the influent water and the membrane separation unit at a set time interval to cope with instantaneous water quality fluctuations Device. 2. The on-line pressure measuring unit 2 according to claim 1, Agglomeration by continuous monitoring of membrane fouling index of advanced water treatment equipment using membrane separation, characterized in that the pressure change in the influent water and membrane separation unit is repeatedly measured at set time intervals to cope with the instantaneous membrane filtration characteristics change. Pretreatment Process Control. The method of claim 1, wherein the control unit 4, According to the membrane fouling index determined by the calculation unit (3) has a function of displaying the determined membrane fouling index so that the plant operator can manually switch the operation mode of the high-purity water treatment apparatus using membrane separation Control device for coagulation pretreatment by continuous monitoring of membrane contamination index Measuring the turbidity of the influent through the online turbidity measuring unit (1); Measuring the intermembrane differential pressure of the influent via the on-line pressure measuring unit (2); Calculating a membrane fouling index using the measured turbidity and interlayer differential pressure; Comparing the calculated membrane fouling index with a set value; Membrane contamination index continuous in the advanced water treatment apparatus using membrane separation comprising the step of maintaining the current operating conditions or controlling the control of the flocculant input amount using the flocculant injection controller (5) according to the comparison result Control of flocculation pretreatment process by monitoring.

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