WO2017164540A1 - Apparatus for predicting membrane fouling in forward osmosis and method for predicting membrane fouling in forward osmosis - Google Patents

Abstract

An apparatus for predicting membrane fouling in forward osmosis, according to one embodiment of the present invention, comprises: a membrane fouling simulation unit having a forward osmosis separation membrane and simulating fouling of the forward osmosis separation membrane during a forward osmosis process; an influent water supplying unit for providing primary influent water to the membrane fouling simulation unit during the forward osmosis process, and providing, to the membrane fouling simulation unit, secondary influent water having a flow velocity greater than the flow velocity of the primary influent water during a cleaning process; and a membrane fouling prediction unit for calculating a forward osmosis membrane fouling index (OFI) by measuring a first water permeation amount (J1) of the primary influent water at an early stage of the forward osmosis process and a third water permeation amount (J3) of the primary influent water after the cleaning process, and for predicting the fouling of the forward osmosis separation membrane from the forward osmosis membrane fouling index (OFI), wherein it is preferred that the forward osmosis membrane fouling index (OFI) is a recovery ratio of the third water permeation amount (J3) to the first water permeation amount (J1).

Description

Forward osmosis membrane fouling prediction device and forward osmosis membrane fouling prediction method

The present invention relates to a forward osmosis membrane fouling prediction device and a forward osmosis membrane fouling prediction method, and more specifically, a forward osmosis membrane fouling prediction device and forward osmosis, wherein the membrane fouling of the forward osmosis membrane can be predicted by the forward osmosis membrane fouling index. It relates to a membrane fouling prediction method.

Seawater desalination or water reuse processes based on membrane filtration technology are considered the ideal alternative to address future water shortages. As a reflection of this, the membrane filtration process that has developed rapidly in recent decades has not only secured new water resources such as seawater desalination (RO / NF), sewage treatment and water reuse (MF / UF, MBR), but also a new concept water treatment process to replace the existing water purification system. (FO) is expanding the scope of application.

Reverse osmosis of the membrane filtration process is rapidly increasing its use due to the provision of water quality superior to conventional water treatment methods.

However, since the reverse osmosis process uses high pressure as a driving force for membrane separation, a large amount of power consumption is required. In addition, the reverse osmosis process is affected by both osmotic pressure and mechanical pressure, densely presses the fouling layer of the reverse osmosis membrane, and reverse osmosis membrane contamination exhibiting irreversible behavior occurs. Therefore, the reverse osmosis process is irreversible membrane fouling phenomenon, only chemical cleaning is possible, physical cleaning is difficult. Reverse osmosis processes require chemical cleaning or pre-treatment of influent, which is less economical and environmentally less than forward osmosis.

Unlike the reverse osmosis process, the membrane fouling layer generated from forward osmosis is reversible, recovering to a certain level through physical cleaning. In this respect, the forward osmosis process is drawing attention as a next generation water treatment technology that can replace the role of the existing process in the field where the reverse osmosis process was mainly used.

The forward osmosis process produces the treated water by the osmotic pressure difference generated without a pressure and between the semipermeable membranes. Since the forward osmosis process is operated in a non-pressurized manner, the membrane fouling mechanism is different from reverse osmosis. In the case of forward osmosis operation using only osmotic pressure difference between influent and induction solution, loose and dispersed membrane fouling layer was observed, unlike reverse osmosis membrane contamination , Generated The membrane fouling layer is reversible, recovering to a certain level through physical cleaning.

Due to the operation characteristics of the forward osmosis process, the forward osmosis process has a relatively low membrane fouling problem due to pressure, compared with the conventional reverse osmosis process, and is environmentally friendly because the membrane contamination can be physically washed. In addition, the forward osmosis process has a long replacement cycle and / or cleaning cycle of the membrane, and physical cleaning is possible compared to the conventional reverse osmosis process, thereby reducing maintenance costs.

Due to the economic and environmental effects of the forward osmosis process as described above, related studies are actively being made for the commercialization of the forward osmosis process. However, the commercialization technology of the forward osmosis process is to improve the quality of the forward osmosis membrane and / or the induction solution, and the development of technology for predicting the membrane fouling cycle of the forward osmosis membrane is insufficient.

In general, the membrane fouling measurement method is performed in the pressurized operation mode of the reverse osmosis process. In the reverse osmosis process, membrane fouling index (SDI, silt density index) is used to measure membrane fouling of the membrane of the reverse osmosis process. Here, the membrane contamination index (SDI, silt density index) is a universal index used as a manufacturer's quality assurance and operation standards in the reverse osmosis membrane.

The membrane fouling index (SDI) in the conventional reverse osmosis process is measured by the SDI index measurement equipment. While SDI index measurement equipment has the advantage of being simple and easy to handle, the material and index measurement of the membrane actually used using MF membranes with pores, not RO, is used to predict membrane contamination in reverse osmosis processes. The material used in the process is different.

The actual reverse osmosis process is cross-flow (CROSS-FLOW), the SDI index measurement was a dead end test (DEAD-END-TEST) in that there was a problem that the actual operating conditions and exponential experimental conditions are different . Even if such a problem exists, the reverse osmosis process can predict membrane fouling of the reverse osmosis membrane by using the SDI index measurement equipment.

On the other hand, the forward osmosis process, unlike the reverse osmosis process, does not have a membrane fouling index of the generalized forward osmosis membrane like SDI, so it is difficult to simulate the forward osmosis process because it does not reflect the actual forward osmosis operating conditions. In addition, there is no equipment for measuring the membrane fouling index of the forward osmosis membrane.

Therefore, a study was conducted to determine whether the application of the membrane fouling index (SDI) of the reverse osmosis process to measure the membrane fouling of the forward osmosis process. In order to examine whether SDI, the membrane fouling index of the reverse osmosis process, can show membrane fouling of the forward osmosis membrane, the sewage secondary treated water is used as feed water and seawater is used as a draw solution. Experiment 1 was carried out to operate the osmosis membrane.

Secondary sewage effluent from the copper sewage treatment plant (A ² O process) was used as the sewage secondary treated water provided as influent, and artificial seawater using NaCl 0.6M (TDS 35,000 mg / L) was used as the influent solution. Was used. As the forward osmosis membrane used in the experiment, a product of HTI company made of triacetyl cellulose (CTA) was used, and a SW30HR-380 product of DOW filmtec company was used as the reverse osmosis membrane.

And, as experimental conditions, the operating temperature was set to 25 ℃ and the recovery rate of the entire process is 50%. When the experiment is conducted under these conditions, the dilution ratio of forward osmosis treated water and seawater is 0.7: 1 (forward osmosis treated water: seawater). SESW and MFSW experiments were performed by diluting with seawater at the same dilution ratio.

The SDI values according to the dilution of raw water and seawater derived by such experiments are shown in FIG. 5A. The SDI value of dilution of raw water and seawater is the result of evaluating how much membrane contamination potential the raw water has.

In FIG. 5A, SE is a sewage secondary treatment water, and SESW is an untreated sewage secondary treatment water diluted in seawater, and MFSW uses MF (Millipore, polypropylene, 0.45 μm) to sewage secondary treatment water. After filtration was diluted in seawater, FOSW is sewage secondary treatment water was diluted in seawater using the osmodilution effect of the forward osmosis membrane.

In FIG. 5A, the SDI value of SE is 6.42 ± 0.5, indicating a membrane contamination potential that is much higher than SDI 3 or less, which is generally recommended for operating reverse osmosis membranes.

Although the SDI values of SESW and MFSW were also diluted to 6.11 ± 0.48 and 5.04 ± 0.33, respectively, the SDI values were still more than 3, showing the membrane fouling potential, which is difficult to use in reverse osmosis membranes. The cost of pretreatment may be incurred when operating the engine.

However, in the case of FOSW diluted in seawater using the osmotic dilution effect of the sewage secondary treated water, the SDI value of FOSW is 1.28 ± 0.12, which shows the membrane contamination potential that is only suitable for the recommended level below SDI 3. It can be seen.

Through the experiments, it can be seen that the membrane fouling index of the conventional reverse osmosis process SDI is used to measure the membrane fouling of the forward osmosis membrane is unbonded.

In addition, the osmotic dilution method of diluting the sewage secondary water (SE) by sea osmosis (FO) was confirmed as the best method in terms of membrane contamination. And, it can be concluded that raw water of SDI value of 6 or more can be treated through the forward osmosis membrane.

Accordingly, there is a need for a technology development capable of simulating the membrane fouling of the forward osmosis membrane and calculating the membrane fouling index in the forward osmosis process that can predict the membrane fouling of the forward osmosis membrane.

An object of the present invention is to provide a forward osmosis membrane fouling prediction device and a forward osmosis membrane fouling prediction method in which the membrane fouling of the forward osmosis membrane can be predicted by the forward osmosis membrane fouling index.

The present invention reflects all the advantages and disadvantages of the membrane fouling index (SDI) measuring device of the conventional reverse osmosis process to calculate the forward osmosis membrane fouling index (OFI) by the membrane fouling of the forward osmosis membrane in the forward osmosis process, the actual forward osmosis It is an object of the present invention to provide a method for predicting forward osmosis membrane fouling, which can predict membrane fouling of forward osmosis membranes in a process.

An apparatus for predicting forward osmosis membrane fouling according to an embodiment of the present invention includes a membrane fouling simulation unit provided with a forward osmosis membrane and simulating membrane fouling of the forward osmosis membrane during the forward osmosis process; An inflow water supply unit that provides the first inflow water to the membrane fouling simulation unit during the forward osmosis process, and provides the second inflow water having a flow rate greater than that of the first inflow water to the membrane contamination simulation unit during the washing process; And the first water permeation rate (J1) of the first inflow water at the beginning of the forward osmosis process and the third water permeation rate (J3) of the first inflow water after the washing process are calculated to calculate the forward osmosis membrane contamination index (OFI). A membrane fouling predictor where the membrane fouling of the forward osmosis membrane is predicted from the osmosis membrane fouling index (OFI), and the forward osmosis membrane fouling index (OFI) is a ratio of the third water permeation (J3) to the first It is preferable that it is a recovery rate.

In one embodiment of the present invention, in the membrane contamination prediction unit, if the forward osmosis membrane contamination index (OFI) is calculated to be greater than 1 (1 <OFI), it is predicted that the forward osmosis membrane is damaged, the forward osmosis membrane contamination index When (OFI) is calculated to be 1 (OFI = 1), it is predicted that the forward osmosis membrane is not contaminated, and the forward osmosis membrane contamination index (OFI) is greater than the critical reversibility (Rc) and less than 1 (Rc <OFI <1). ), If the membrane osmosis of the forward osmosis membrane is predicted, and if the forward osmosis membrane index (OFI) is less than the critical reversibility (Rc) (Rc> OFI), then the forward osmosis membrane is subjected to physical washing only by secondary inflow. It is desirable to predict that the recovery of membrane contamination is impossible.

In one embodiment of the present invention, the critical reversibility (Rc) is 1 after the washing process for the water permeation rate of the first influent water before the washing process in the state that the membrane contamination of the forward osmosis membrane is not recoverable only by physical washing by the second influent water. It is preferable that it is the recovery rate of the permeation | transmission amount of inflow water, and critical reversibility Rc is computed by the following.

( _{Before washing} , water permeation of the primary influent water before the washing process is the water permeation of the first influent _{water after} the washing process, in the state where the membrane contamination of the forward osmosis membrane cannot be recovered.)

In one embodiment of the present invention, the membrane fouling predicting part, when the water permeation rate of the first inflow water is gradually lower than the first water permeation amount J1 by the adhesion layer is measured, the second water permeation amount J2 is measured, the second At the time when the water permeation amount (J2) is measured, it is preferable to provide the secondary inflow water to the membrane fouling simulation unit so that the adhesion layer is removed by the secondary inflow water so that the forward osmosis membrane is washed.

In one embodiment of the present invention, in the membrane fouling prediction portion, it is preferable that the forward osmosis membrane fouling index (OFI) is calculated by the following equation.

(J1 is the water permeation rate of the first inflow water through the forward osmosis membrane before the adhesion layer is formed at the beginning of the forward osmosis process, and J3 is the forward osmosis process after the adhesion layer is removed from the forward osmosis membrane by the washing process. It is the water permeation rate of the primary inflow through the forward osmosis membrane.)

In one embodiment of the present invention, in the forward osmosis process further comprises an induction solution supply for supplying an induction solution having a concentration higher than the primary influent to the membrane fouling simulation unit, the induction solution supply unit by adjusting the molar concentration of the induction solution In the membrane fouling simulation unit, it is preferable to accelerate the formation of the adhesion layer in which the organic matter of the primary influent is accumulated on the surface of the forward osmosis membrane.

In one embodiment of the present invention, connected to the induction solution supply, by adjusting the TDS (total dissolved solids) of the induction solution provided to the membrane fouling simulation unit, by the difference between the TDS of the primary influent and the TDS of the induction solution It is preferable to further include a TDS controller for adjusting the water permeation rate.

On the other hand, the forward osmosis membrane fouling prediction method for predicting the membrane fouling of the forward osmosis membrane in the forward osmosis process by using the forward osmosis membrane fouling prediction apparatus, (A) the primary influent and induction solution is supplied to the membrane fouling simulation unit, Membrane contamination is simulated by the adhesion layer accumulated on the forward osmosis membrane due to the osmotic pressure difference between the primary influent and the induction solution during the forward osmosis process; (B) providing a second inflow water having a flow rate greater than that of the first inflow water to the membrane fouling simulation unit, and washing the forward osmosis membrane by the second inflow water; And (C) measuring the first water permeation rate (J1) of the first influent water at the beginning of the forward osmosis process, and the third water permeation rate (J3) of the first influent water after the washing process, and the forward osmosis membrane contamination index (OFI) is calculated. And a step of predicting membrane fouling of the forward osmosis membrane from the forward osmosis membrane contamination index (OFI), wherein the forward osmosis membrane contamination index (OFI) is a third water permeation rate (J3) relative to the first water permeation (J1). It is preferable that the recovery rate is.

In one embodiment of the present invention, step (C), (C1) if the forward osmosis membrane contamination index (OFI) is calculated to be greater than 1 (1 <OFI), the step of predicting that the case of the forward osmosis membrane is damaged; (C2) if the forward osmosis membrane contamination index (OFI) is calculated to be 1 (OFI = 1), predicting that the forward osmosis membrane is not contaminated; (C3) predicting membrane fouling of the forward osmosis membrane when the forward osmosis membrane contamination index (OFI) is in the range greater than the critical reversibility (Rc) and less than 1 (Rc <OFI <1); And (C4) when the forward osmosis membrane fouling index (OFI) is less than the critical reversibility (Rc) (Rc> OFI), the step of predicting that the forward osmosis membrane is impossible to recover the membrane fouling only by physical cleaning by the secondary influent. The critical reversibility (Rc) is a water permeation rate of the first influent water after the washing process relative to the water permeation rate of the first influent water before the washing process in a state in which membrane fouling of the forward osmosis membrane cannot be recovered only by physical washing by the second influent. It is preferable that the recovery rate is.

In one embodiment of the present invention, in the membrane fouling simulation unit, if the forward osmosis membrane contamination index (OFI) is greater than 1 (1 <OFI), the operation of the forward osmosis process is stopped, the forward osmosis membrane contamination index (OFI) Is 1 (OFI = 1), the operation of the forward osmosis process is continued, and if the forward osmosis membrane contamination index (OFI) is greater than the critical reversibility (Rc) and less than 1 (Rc <OFI <1), If the operation is stopped, the forward osmosis membrane washing process is performed, and the forward osmosis membrane contamination index (OFI) is less than the critical reversibility (Rc) (Rc> OFI), the operation of the forward osmosis process is stopped, and chemical cleaning It is preferable that a pretreatment process such as

In one embodiment of the present invention, the forward osmosis membrane contamination index (OFI) is preferably calculated by the following formula.

(J1 is the water permeation rate of the first inflow water through the forward osmosis membrane before the adhesion layer is formed at the beginning of the forward osmosis process, and J3 is the forward osmosis process after the adhesion layer is removed from the forward osmosis membrane by the washing process. It is the water permeation rate of the primary inflow through the forward osmosis membrane.)

In one embodiment of the present invention, the critical reversibility Rc is preferably calculated by the following equation.

( _{Before washing} , water permeation of the primary influent water before the washing process is the water permeation of the first influent _{water after} the washing process, in the state where the membrane contamination of the forward osmosis membrane cannot be recovered.)

In one embodiment of the present invention, in step (B), the water permeation rate of the primary inflow water passing through the forward osmosis membrane is gradually lower than the first water permeation amount J1 by the adhesion layer. At the time point of convergence to J2), washing of the forward osmosis membrane by the second influent is performed, and as the adhesion layer is removed from the forward osmosis membrane, membrane fouling of the normal osmosis membrane is preferably restored.

In one embodiment of the present invention, in step (A), the induction solution is molar concentration is supplied to the membrane fouling simulation unit, it is preferable to accelerate the formation of the adhesion layer.

In one embodiment of the present invention, in step (A), the induction solution is provided to the membrane fouling simulation unit by adjusting the total dissolved solids (TDS) of the induction solution, the first water permeation (J1) is the first influent TDS It is preferable to be controlled by the difference between the TDS and the induction solution.

The present invention can more accurately measure and predict the contamination phenomenon of the forward osmosis membrane generated by the seawater desalination process, the filtration process, the dehydration process, the concentration process, etc. using the forward osmosis method. That is, the present invention simulates the membrane fouling of the forward osmosis membrane used in the forward osmosis process, calculates the forward osmosis membrane contamination index (OFI), and advances the membrane contamination of the forward osmosis membrane from the forward osmosis membrane contamination index (OFI). Can be predicted. Here, the forward osmosis membrane contamination index (OFI) is calculated by reflecting the membrane fouling data (that is, the water permeability and the characteristics of the forward osmosis membrane) measured in the membrane of the forward osmosis membrane simulated.

The present invention can be used to simulate the membrane fouling of the forward osmosis membrane in a short period of time by using the reverse osmosis membrane used in practice, by reducing the membrane fouling time by the forward osmosis process using a reversible, high concentration induction solution of the forward osmosis membrane.

Figure 1 schematically shows the configuration of the apparatus for predicting forward osmosis membrane fouling according to an embodiment of the present invention.

Figure 2 shows the operating time-membrane fouling reversibility graph according to the molar concentration of the induction solution.

3 is a graph of water permeation rate with time change before and after physical washing according to an embodiment of the present invention.

Figure 4 schematically shows a flow chart of a forward osmosis membrane fouling prediction method according to an embodiment of the present invention.

Figure 5a is a SDI result according to the dilution method of raw water and seawater in Experiment 1.

FIG. 5B is a graph showing the results of water permeation and membrane fouling reversibility according to pressurized or reduced pressure conditions in Experiment 2. FIG.

FIG. 5C is a graph of fouling reversibility according to the number of operations under the conditions of pressurization and osmotic pressure in Experiment 3. FIG.

5D is a SDI and TDS graph for four sewage treatment plants.

FIG. 5E is a graph of the flux of four sewage treatment plant secondary treated water over time under the same TDS (250 mg / L) condition.

FIG. 5F shows a graph of fouling reversibility versus the number of operations of four sewage treatment plants.

5G is a graph of concentrations of organics in secondary treated water for four sewage treatment plants.

Figure 5h is a graph of the concentration according to the washing cycle of the four organic materials attached to the forward osmosis membrane.

5i is a graph showing results of fouling reversibility of the forward osmosis membrane according to the operating cycle according to the flow rate, which is a physical washing condition.

Hereinafter, with reference to the accompanying drawings, a description will be given of a forward osmosis membrane fouling prediction apparatus and a forward osmosis membrane fouling prediction method according to a preferred embodiment of the present invention.

As described in the background technology of the invention, according to the conclusion that the membrane contamination index SDI of the conventional reverse osmosis process can not be used for membrane fouling of the forward osmosis membrane, the present invention simulates membrane fouling of the forward osmosis membrane and apply in the field The purpose of this study is to develop the forward osmosis membrane contamination index that reflects the environmental factors, and to measure and predict the membrane contamination of the forward osmosis membrane.

As shown in FIG. 1, the apparatus for predicting forward osmosis membrane contamination according to an embodiment of the present invention 100 includes an inflow water supply unit 110, an induction solution supply unit 120, a membrane contamination simulation unit 130, and a membrane contamination prediction unit. Including the unit 140, to simulate the forward osmosis process and calculate the forward osmosis membrane contamination index.

First, membrane fouling simulation of the forward osmosis membrane 131 by the forward osmosis process is performed by the inflow water supply unit 110, the induction solution supply unit 120 and the membrane contamination simulation unit 130.

The inflow water supply unit 110 is connected to the membrane fouling simulation unit 130. The inflow water supply unit 110 includes an inflow water storage tank 111, a first inflow pipe 112, a first pump 113, and a second inflow pipe 114.

The inflow water storage tank 111 is a tank in which inflow water is stored. The influent refers to the liquid used in the seawater desalination process, the filtration process, the dewatering process, and the concentration process using the forward osmosis method.

The first inlet pipe 112 connects the inlet water storage tank 111 and the first inlet 132a of the membrane fouling simulation unit 130. Here, the inflow water flowing through the first inflow pipe 112 is moved from the inflow water storage tank 111 to the membrane fouling simulation unit 130. The first pump 113 is connected to the first inlet pipe 112 for smooth flow of the inflow water flowing through the first inlet pipe 112. The first pump 113 sucks inflow water stored in the inflow water storage tank 111 and supplies it to the membrane fouling simulation unit 130.

The second inflow pipe 114 connects the inflow water storage tank 111 and the first outlet 132b of the membrane fouling simulation unit 130. Here, the inflow water is concentrated water concentrated by the forward osmosis process with the induction solution in the membrane fouling simulation unit 130. The inflow water passes through the second inflow pipe 114 and flows from the membrane fouling simulation unit 130 to the inflow water storage tank 111.

In the present embodiment, for convenience of description, the influent supplied in the forward osmosis process will be referred to as 'primary influent' and the influent supplied in the washing process will be referred to as 'secondary influent'. Here, the secondary inflow is faster than the primary inflow. In this example, the primary influent is circulated along arrow F1 in the forward osmosis process, and the secondary influent is circulated along arrow F2 in the washing process.

Induction solution supply unit 120 is to provide an induction solution during the forward osmosis process. The induction solution supply unit provides the induced solution membrane fouling simulation unit 130 while controlling the molar concentration of the induction solution. As the molar concentration of the induction solution increases, the adhesion layer formation in the forward osmosis membrane 131 is accelerated. The adhesion layer is formed by the osmotic pressure caused by the difference in concentration between the primary influent and the induction solution during the forward osmosis process.In the process of water in the primary inflow flowing through the forward osmosis membrane to the space containing the induction solution, It is formed while accumulating on the surface of the osmosis membrane.

The induction solution supply unit 120 includes an induction solution storage tank 121, a first induction solution tube 122, a second pump 123, a second induction solution tube 124, and a TDS controller 125.

Induction solution storage tank 121 is a tank in which the induction solution is stored. Induction solutions have a higher concentration than primary influent.

The first induction solution pipe 122 connects the induction solution storage tank 121 and the second outlet 133b of the membrane fouling simulation unit 130. Here, the induction solution flowing through the first induction solution tube 122 is moved from the membrane fouling simulation unit 130 to the induction solution storage tank 121. Here, the induction solution flowing through the first induction solution tube 122 is in a diluted state by the forward osmosis process with the primary influent from the membrane fouling simulation unit 130.

A second pump 123 is connected to the first induction solution tube 122 for smooth flow of the induction solution flowing through the first induction solution tube 122. The second pump 123 sucks the induction solution discharged from the membrane fouling simulation unit 130 and supplies it to the induction solution storage tank 121.

The second induction solution pipe 124 connects the induction solution storage tank 121 and the second inlet 133a of the membrane fouling simulation unit 130. Here, the induction solution flowing through the second induction solution tube 124 is a substance having a higher concentration than the primary influent.

The TDS controller 125 is connected to the induction solution storage tank 121. The TDS controller 125 controls the total dissolved solids (TDS) of the induction solution provided to the membrane fouling simulation unit 130. The TDS controller 125 may control the first water permeation amount by adjusting the TDS of the induction solution. Here, the first water permeation rate is based on the difference between the TDS of the primary influent and the TDS of the induction solution. The first water permeation amount J1 is the water permeation rate of the primary inflow water passing through the forward osmosis membrane 131 at the beginning of the forward osmosis process before the adhesion layer is formed on the forward osmosis membrane 131.

On the other hand, the membrane fouling simulation unit 130 is to perform a forward osmosis process, to simulate the membrane fouling of the forward osmosis membrane 131 by a repeated forward osmosis process. The membrane fouling simulation unit 130 is provided with a first space 132 and a second space 133 separated by the forward osmosis membrane 131.

The membrane fouling simulation unit 130 is provided with a first inlet 132a and a first outlet 132b in a portion where the first space 132 is provided. Here, the first inlet pipe 112 is connected to the first inlet 132a, and the second inlet pipe 114 is connected to the first outlet 132b.

The first space 132 is a space in which the inflow water circulating in the inflow water supply unit 110 is stored. In the forward osmosis process, the primary influent flows along the arrow F1 in the inlet storage tank 111-> the first inlet pipe 112-> the first space 132-> the second inlet pipe of the membrane fouling simulation unit 130. (114)-> Circulate the influent storage tank (111).

In addition, the membrane fouling simulation unit 130 is provided with a second inlet 133a and a second outlet 133b at a portion where the second space 133 is provided. The second induction solution tube 124 is connected to the second inlet 133a, and the first induction solution tube 122 is connected to the second outlet 133b. The second space 133 is a space in which the induction solution circulating in the induction solution supply unit 120 is stored.

Induction solution circulates through the induction solution supply unit 120 and the membrane fouling simulation unit 130 along the F3. Specifically, the induction solution along the F3 induction solution storage tank 121-> the second induction solution tube 124-> the second space 133 of the membrane fouling simulation unit 130-> the first induction solution tube ( 122)-> Circulate the induction solution storage tank 121. At this time, the circulation direction F3 of the induction solution is opposite to the circulation direction F1 of the primary influent.

The primary influent was cross-flowed while being separated from the induction solution by the forward osmosis membrane 131, and the osmotic pressure applied to the forward osmosis membrane 131 by the concentration difference between the primary influent and the induction solution. As a result, the primary influent water at a low concentration is transferred to a high concentration induction solution.

In this process, in the process of the first influent water is moved from the first space 132 to the second space 133, an organic layer in the primary influent water is accumulated on the surface of the forward osmosis membrane 131 to form an adhesion layer. . The forward osmosis membrane 131 is membrane fouled by an adhesion layer.

As shown in FIG. 2, the adhesion layer varies in speed at the forward osmosis membrane 131 according to the molar concentration of the induction solution. Figure 2 shows the operating time-membrane fouling reversibility graph according to the molar concentration of the induction solution. Here, membrane fouling reversibility (fouling reversibility) refers to the recovery ability of the forward osmosis membrane 131 according to the physical wash.

Operating time-membrane fouling reversibility graph according to the molar concentration of the induction solution shows that the recovery rate of the forward osmosis membrane 131 recovers before and after the washing process as the forward osmosis process and the washing process are repeatedly performed. The result shows whether or not

Referring to FIG. 2, when the washing is performed after driving for about 20 to 30 minutes with a molar concentration of 3M induction solution, an experimental result of reaching a critical critical reversibility (Rc) can be obtained. In the graph of FIG. 5F, the results correspond to the membrane fouling reversibility of repeating the operation 5 times using the induction solution of seawater conditions.

Critical reversibility (Rc) is the membrane fouling reversibility (R) in the state that the membrane fouling of the forward osmosis membrane 131 is not recoverable only by physical washing by the second influent according to the repeated osmosis and washing process.

Referring to FIG. 2, the membrane fouling reversibility of the forward osmosis membrane 131 converges to 75% over time when the forward osmosis process is performed using a 2M induction solution, while using an induction solution of 3M or more. It can be seen that the convergence to about 60% when performing the forward osmosis process. In other words, the concentration of 2M did not show sufficient experimental results, and 4M can reduce the time, but considering the chemical cost and equipment corrosion, 3M is the most economical.

2, it can be seen that the higher the molar concentration of the induction solution, the faster the membrane fouling reversibility of the forward osmosis membrane 131. Accordingly, it can be seen that the higher the molar concentration of the induction solution, the faster the adhesion layer attached to the forward osmosis membrane 131.

When the forward osmosis membrane 131 is membrane fouled by the above-mentioned forward osmosis process, the membrane fouled forward osmosis membrane 131 is washed by the secondary inflow to recover the membrane contamination of the forward osmosis membrane 131.

In the washing process, the secondary inflow water follows the arrow F2 in the inlet water storage tank 111-> the first inlet pipe 112-> the first space 132 of the membrane fouling simulation unit 130-> the second inlet pipe ( 114)-> Circulate the influent storage tank (111). Here, the circulation direction F2 of the secondary inflow is the same as the circulation direction F1 of the primary inflow.

The secondary inflow has a higher flow rate than the primary inflow. The secondary inflow water circulates the inflow water supply unit 110 and the membrane fouling simulation unit 130 at a high flow rate, and washes the forward osmosis separation membrane 131.

The secondary inflow water is provided to the membrane fouling simulation unit 130 at the time when the second water permeation amount J2 is measured. When the secondary inflow water circulates through the membrane fouling simulation unit 130, the induction solution is stopped from the induction solution supply unit 120 to the membrane fouling simulation unit 130.

As shown in FIG. 3, the second water permeation amount J2 is a water permeation rate of the primary inflow water passing through the forward osmosis membrane 131 by an adhesion layer formed on the surface of the forward osmosis membrane 131. Therefore, it is gradually lowered and is a constant convergence of water penetration.

Hereinafter, the membrane fouling prediction unit 140 predicting membrane fouling of the forward osmosis membrane 131 by measuring the forward osmosis membrane contamination index (OFI) will be described.

The membrane contamination prediction unit 140 includes a first water permeation amount J1, a second water permeation amount J2, and a first water permeation amount J1 which is a water permeation rate of the first inflow water passing through the forward osmosis membrane 131 according to the operation time of the forward osmosis process. 3 The water permeation rate (J3) is measured, and the forward osmosis membrane contamination index (OFI) is calculated therefrom, and the membrane contamination of the forward osmosis membrane 131 is predicted from the forward osmosis membrane contamination index (OFI).

The first water permeation amount J1 is the water permeation rate of the primary inflow water passing through the forward osmosis membrane 131 at the beginning of the forward osmosis process before the adhesion layer is formed on the forward osmosis membrane 131.

As described above, the second water permeation amount J2 is a number that is constantly converged even if time passes by the first inflow water passing through the forward osmosis membrane 131 by the adhesion layer formed on the surface of the forward osmosis membrane 131. It is a transmission amount.

The third water permeation amount J3 is the water permeation rate of the first inflow water passing through the forward osmosis membrane 131 in the forward osmosis process after the adhesion layer of the forward osmosis membrane 131 is removed by the washing process.

The forward osmosis membrane contamination index OFI is calculated from the first water permeation amount J1 and the third water permeation amount J3. The forward osmosis membrane contamination index OFI is a recovery rate of the third water permeation amount J3 relative to the first water permeation amount J1.

The forward osmosis membrane contamination index (OFI) is a primary osmosis membrane 131, which is contaminated by an adhesion layer, is washed by secondary inflow water, and then passes through the forward osmosis membrane 131 in the forward osmosis process after washing. It is an index of how much the third water permeation amount J3 of the influent is recovered compared with the first water permeation amount J1 at the beginning of the forward osmosis process.

The membrane contamination prediction unit 140 predicts that the forward osmosis membrane contamination index (OFI) is greater than the critical reversibility (Rc) and less than 1 (Rc < OFI <

As described above, the critical reversibility (Rc) is the membrane fouling reversibility in the state that the membrane fouling of the forward osmosis membrane 131 is not recoverable only by physical washing by secondary inflow according to the repeated osmosis process and the washing process. Critical reversibility (Rc) is a value in which membrane fouling reversibility is constantly converged over time.

Membrane fouling reversibility is the ability of the forward osmosis membrane 131 to recover according to physical cleaning. Membrane fouling reversibility is the rate of recovery of the water permeation rate of the first influent water after the washing process to the water permeation rate of the first influent water before the washing process.

Hereinafter, a method for predicting forward osmosis membrane fouling according to an embodiment of the present invention will be described with reference to FIG. 4. The forward osmosis membrane fouling prediction method is a method of predicting membrane fouling in the forward osmosis process using the forward osmosis membrane fouling prediction apparatus 100.

First, actual operating conditions in consideration of variables are applied, and membrane fouling of the forward osmosis membrane 131 by the forward osmosis process is simulated in the membrane fouling simulation unit 130 (S1). That is, due to the osmotic pressure due to the difference in the concentration of the primary inflow of the influent water supply unit 110 supplied to the membrane fouling simulation unit 130 of the forward osmosis membrane fouling prediction device 100 and the induction solution of the induction solution supply unit 120 As the osmosis process is performed, membrane fouling of the forward osmosis membrane 131 by the adhesion layer formed by stacking the organic material of the primary inflow water is simulated on the surface of the forward osmosis membrane 131.

At this time, the induction solution is supplied to the membrane fouling simulation unit 130 by adjusting the molar concentration, it is possible to accelerate the formation of the adhesion layer. In addition, the inductive solution is controlled by the TDS controller 125 to control TDS (total dissolved solids) of the inductive solution provided to the membrane fouling simulation unit 130. The first water permeation rate is controlled by the difference between the TDS of the primary influent and the TDS of the draw solution. Here, the first water permeation amount is the water permeation rate of the primary inflow water passing through the forward osmosis membrane 131 at the beginning of the forward osmosis process before the adhesion layer is formed on the forward osmosis membrane 131.

Thereafter, the membrane contamination prediction unit 140 measures the water permeation rate of the primary inflow water passing through the forward osmosis membrane 131 according to the operation time and the number of operation of the forward osmosis process in the membrane contamination simulation unit 130 and From this, the forward osmosis membrane contamination index (OFI) is calculated (S2). The forward osmosis membrane contamination index (OFI) is preferably greater than the critical reversibility (Rc).

The forward osmosis membrane fouling index (OFI) is calculated by equation (1).

Equation (1)

In Equation (1), J1 is the first water permeation rate, J3 is the primary influent water passing through the forward osmosis membrane 131 in the forward osmosis process after the adhesion layer of the forward osmosis membrane 131 is removed by the washing process. It is the third water transmission amount which is the water transmission amount of.

The membrane contamination prediction unit 140 predicts membrane fouling of the forward osmosis membrane 131 from the forward osmosis membrane contamination index (OFI). The prediction process is as follows.

If the forward osmosis membrane contamination index (OFI) is calculated to be greater than 1 (1 <OFI), the membrane contamination prediction unit 140 predicts that the forward osmosis membrane 131 is damaged (S3). When the forward osmosis membrane 131 is damaged, the forward osmosis process in the membrane fouling simulation unit 130 is stopped.

Next, when the forward osmosis membrane contamination index (OFI) is calculated to be 1 (OFI = 1), the membrane contamination prediction unit 140 predicts that the forward osmosis membrane 131 is not contaminated (S4). In this case, the forward osmosis process in the membrane fouling simulation unit 130 continues.

When the forward osmosis membrane index (OFI) is in the range greater than the critical reversibility (Rc) and less than 1 (Rc <OFI <1), the membrane fouling predictor 140 is in a state in which the forward osmosis membrane 131 is membrane contaminated. In this case, the forward osmosis membrane 131 is washed (S5). This is to recover the membrane fouling of the normal osmosis membrane as the adhesion layer is removed from the forward osmosis membrane 131 by washing the forward osmosis membrane 131 by the secondary inflow water.

Operation of the forward osmosis process is stopped when the forward osmosis membrane 131 is washed. Then, secondary inflow water is provided from the inflow water supply unit 110 to the membrane fouling simulation unit 130, and the forward osmosis separation membrane 131 is washed by the secondary inflow water. The time point at which the washing proceeds is a time point at which the water permeation is converged according to the operation time of the forward osmosis process.

In the present embodiment, for convenience of description, the water permeation amount converged as the operation time of the forward osmosis process is referred to as "second water permeation amount". The second water transmission amount J2, J1> J2 is less than the first water transmission amount J1.

The critical reversibility (Rc) is the number of primary influent waters before the washing process in a state in which the membrane contamination of the forward osmosis membrane 131 cannot be recovered only by physical washing by the second influent water by repeating the forward osmosis process and the washing process. a recovery ratio of the transmission amount (J _{before washing) (after cleaning} J) cleaning the first influent can permeation amount of the subsequent steps for, is calculated by the equation (2).

Equation (2)

Critical reversibility (Rc) is a value in which membrane fouling reversibility is constantly converged over time. Critical reversibility (Rc) is the membrane fouling reversibility (R) in the state that the membrane fouling of the forward osmosis membrane 131 is not recoverable only by physical washing by the second influent according to the repeated osmosis and washing process. Membrane fouling reversibility is a recovery capability of the forward osmosis membrane 131 according to physical washing, and is a recovery rate of the water permeation rate of the first influent water after the washing process with respect to the water permeation rate of the first influent water before the washing process.

Before the washing process applied to the critical reversibility, the water permeation rate of the first inflow water ( _before J _cleaning ) is the water permeation rate even if the operation number of the forward osmosis process is increased because the adhesion layer accumulated in the forward osmosis membrane 131 is not removed by physical washing. This is a constantly converged value. On the other hand, the first water permeation amount is the water permeation amount before the washing step in the initial operation of the forward osmosis process, and the measured water permeation values differ from each other.

After the washing process applied to the critical reversibility, the water permeation rate of the first influent ( _{after washing} J) is the permeation rate even if the number of operations of the forward osmosis process is increased because the adhesion layer accumulated in the forward osmosis membrane 131 is not removed by physical washing. This is a constantly converged value. On the other hand, the third water permeation rate is the water permeation rate when the adhesion layer is removed from the forward osmosis membrane 131 by washing.

On the other hand, if the forward osmosis membrane contamination index (OFI) is less than the critical reversibility (Rc) (Rc> OFI), the forward osmosis membrane 131 predicts that the membrane contamination cannot be recovered only by physical cleaning by secondary inflow. The operation of the forward osmosis process is stopped, and a pretreatment process such as chemical cleaning is performed (S6).

The present invention simulates the forward osmosis membrane membrane fouling and develops the forward osmosis membrane fouling index reflecting the variables due to environmental factors applied in the field, it is possible to measure and predict the membrane fouling of the forward osmosis membrane.

The present invention calculates the forward osmosis membrane contamination index (OFI) for each forward osmosis membrane, and predicts the membrane fouling time of the forward osmosis membrane according to the forward osmosis membrane contamination index (OFI), the forward osmosis membrane to the critical reversible point The pretreatment or washing process may be performed before reaching to increase the operation efficiency and operation period of the forward osmosis process apparatus.

Due to environmental policy, it is forbidden to spill wastewater into the ocean, and the concentration of the forward osmosis process is applied to the technology to discharge the wastewater. Water treatment technology by forward osmosis process is increasingly used in environmental and economic aspects.

The present invention calculates the membrane fouling time of the forward osmosis membrane with the passage of operation time through OFI, the contamination phenomenon of the forward osmosis membrane generated by the seawater desalination process, filtration process, dehydration process, concentration process using the forward osmosis method Can be measured and predicted more accurately in advance.

Hereinafter, the experimental results derived from why the membrane fouling simulation of the forward osmosis membrane in the membrane fouling simulation unit is performed by osmotic pressure, and the experiment applied to derive the formula for calculating the forward osmosis membrane contamination index (OFI) will be described. Let's do it.

As described in the background technology of the present invention, membrane fouling can be simulated according to the conclusion that the existing membrane fouling index cannot be used for membrane fouling of the forward osmosis membrane and a new method for simulating the membrane fouling of the forward osmosis membrane is needed. Experiment 2 was performed on the method.

As a method for simulating membrane fouling of the membrane, there is a membrane fouling simulation method by pressurization, decompression, and osmotic pressure, in which Experiment 2 simulates membrane fouling on the forward osmosis membrane under pressure or reduced pressure.

In Experiment 2, the membrane fouling simulation method using the reduced pressure condition simulated membrane fouling by reducing the pressure to about 1 bar using a vacuum pump in the absence of osmotic pressure without using a draw solution.

The membrane fouling simulation method using the pressurized condition simulates membrane fouling by applying a pressure of 1 bar to 9 bar to the forward osmosis membrane using a pump in the same manner as the reverse osmosis membrane is operated.

5b is a graph showing the results of water permeation and reversibility of the forward osmosis membrane according to the pressurized or reduced pressure conditions in Experiment 2.

Membrane fouling reversibility (R) was calculated by equation (2). In Eq. (2), _before J _cleaning is the flux when running at 704 h for a flow rate of 8.54 cm / s. _{After washing} J is the flux measured by washing for 10 minutes at 25.62 cm / s with a three-fold increase in flow rate and then driving at 8.54 cm / s.

Referring to FIG. 5B, when the experimental results of the decompression condition are examined, it can be seen that flux is almost never generated in the forward osmosis membrane, and the flux is very low, and the fouling layer is attached to the surface of the separator. Since no formation was made the fouling reversibility was measured close to 100%. Based on these results, it can be concluded that the operation of forward osmosis membrane is difficult and membrane fouling cannot occur when the membrane fouling is simulated by the reduced pressure method.

Referring to FIG. 5B, the experimental results of the pressurization condition showed that very little about 1 LMH flux occurred at a pressure of 1 bar, and 7 LMH flux was obtained at a pressure of 7 bar. It can be seen.

In addition, the membrane's ability to recover from physical washing can be expressed as fouling reversibility. According to the results in Fig. 1b, the membrane is obtained at 7 bar, which is equivalent to the normal osmotic operating condition, to obtain the initial flux. Pollution reversibility was observed at around 50%.

Subsequently, experiment 3 was conducted to verify whether the pressurization condition fully reflected the membrane fouling phenomenon of the forward osmosis condition, and the results for the experiment 3 are shown in FIG. 5C.

In Experiment 3, the pressurization condition is a case where a pressure of 7 bar is applied to the forward osmosis membrane, and the osmotic pressure condition is an induction solution having an osmotic pressure higher than the influent flowing into the apparatus. Under pressurized conditions and osmotic conditions, the first permeation rate is 7 LMH, the process run time is 70 minutes, and the physical washing at triple flow rate is performed without replacing the membrane for 10 minutes.

Figure 5c is a graph of fouling reversibility (fouling reversibility) according to the operating cycle in the conditions using the pressurized conditions and osmotic pressure.

Referring to FIG. 5C, it can be seen that the reversiblity of the forward osmosis membrane operated under the pressurized condition is observed at 50%. On the other hand, the forward osmosis membrane operated using osmotic pressure showed reversibility close to 100% at the first operation, and has 80% reversiblity (fouling reversiblity) even after repeating the operation four times. That is, it can be seen that the forward osmosis membrane operated by using osmotic pressure has a higher reversibility than the forward osmosis membrane under pressurized conditions even if the number of operations increases.

According to the above experimental results, the forward osmosis membrane is difficult to operate the forward osmosis process due to lack of driving force when operating under reduced pressure and pressure, when operating the forward osmosis membrane in a reduced pressure. In addition, when the forward osmosis membrane is operated under pressure, the membrane fouling layer is consolidated, and thus the membrane fouling recovery ability, which is one of the characteristics of the forward osmosis membrane, does not appear, thereby simulating the high fouling reversibility of the forward osmosis membrane. We can judge that it is hard to do. Thus, in order to simulate the membrane fouling of the forward osmosis membrane, the result that the osmotic pressure should be used is derived.

Accordingly, Experiment 4 was performed to derive which factors affect the membrane fouling index in the forward osmosis process when using the osmotic pressure to simulate membrane fouling of the forward osmosis membrane.

For Experiment 4, secondary sewage treatment water from four sewage treatment plants (Jungnang, Tancheon, Nanji, and Copper) near Seoul was collected. This is to ensure the representativeness of the raw water used by selecting the sewage treatment plant of very large capacity to the sewage treatment plant of small and medium scale.

Table 1 shows the results of secondary water quality analysis for four sewage treatment plants.

Table 1

Sewage Treatment Plant	Treatment method	Capacity (million m 3 / d)	BOD	COD	SS	TN	TP
Jungnang	A 2 O + aggregation	159	5.7 ± 0.1	12.4 ± 0.3	7.6 ± 0.4	9.3 ± 0.6	0.18 ± 0.02
Tancheon	MLE + aggregation	90	5.4 ± 0.3	10.9 ± 0.5	9.4 ± 0.6	7.3 ± 0.7	0.15 ± 0.08
Nanji	MLE + aggregation	86	6.8 ± 0.2	13.4 ± 0.5	4.7 ± 0.5	8.3 ± 0.2	0.17 ± 0.05
Copper	A 2 O + aggregation	11	4.6 ± 0.2	10.4 ± 0.4	6.3 ± 0.5	7.4 ± 0.5	0.12 ± 0.05

In Table 1, MLE is a Modified Ludzack Ettinger process and A ² O is an Anaerobic-Anoxic-Aerobic process.

In the forward osmosis process, the initial permeability is determined by the TDS difference between the feed water and the draw soultion. Experiment 4 was carried out by diluting with DI water (250 mg / L) using DI water (DeIonize water).

Toray osmosis membrane used in this experiment was used PA membrane membrane of Toray Co., Ltd. and draw solution was used after filtering seawater from offshore water of Hanga 7 Hangdong, Jung-gu, Incheon, after filtering with 0.45 ㎛ PP material membrane (TDS 31,900 ± 200 mg / L ).

The raw water to be used was diluted with DI water using SDI 5.5 and then subjected to forward osmosis membrane experiment. This experiment was carried out to observe the difference between forward osmosis flux and reversiblity when the membrane fouling index is the same but the pollutants in the raw water are different.

In Experiment 4, TDS and SDI were measured to evaluate the membrane fouling potential of the raw water to be used. Referring to FIG. 5D, all of the sewage treatment waters of the four sewage treatment plants were observed to have SDI 6 or more and TDS 280 mg / L or more. 5D is a SDI and TDS graph for four sewage treatment plants.

On the other hand, referring to Figure 5e, it was found that it is difficult to observe the tendency of membrane fouling only by the flux of the initial water permeation of about 25 LMH under the same osmotic conditions. In the case of forward osmosis membranes, there is no need to analyze the membrane fouling tendency with long term operation because the membrane fouling tendency is not shown with short term operation. Here, Figure 5e is a graph of the flux of the four sewage treatment plant secondary treatment water according to the operating time in the same TDS (250 mg / L) conditions.

However, the long-term observation of membrane fouling prediction is difficult to apply in the field where immediate response to membrane fouling is required, and the prediction after membrane fouling is not necessary. The osmotic pressure should be applied to accelerate the membrane contamination and shorten the measurement time. Thus, in the present invention, a high concentration induction solution is used to shorten the measurement time of membrane fouling.

Referring to FIG. 5F, after 10 times of continuous washing without physical membrane replacement after physical washing (3 times flow rate, 10 minutes), membrane fouling reversibility dropped up to 55%, despite the same SDI value. It can be seen that each raw water exhibits different fouling reversibility. FIG. 5F shows a graph of fouling reversibility versus the number of operations of four sewage treatment plants.

Through the graph shown in Figure 5f, it can be seen that it is impossible to utilize the membrane fouling index used in the conventional reverse osmosis process. Accordingly, accurate membrane fouling can be derived by reflecting the characteristics of a foulant in raw water, that is, a factor causing the difference in reversibility of the forward osmosis membrane, in the forward osmosis membrane fouling index.

On the other hand, referring to Figure 5f, compared to other sewage treatment plants in the Tancheon sewage treatment plant has a lower recovery rate of fouling (fouling reversibility), it can be seen that close to the minimum recovery rate.

Therefore, the organic material forming the fouling layer after inspecting the surface of the forward osmosis membrane tested with the secondary treatment water of the Tancheon sewage treatment plant showing the lowest fouling reversibility at each washing cycle. Analysis was performed by LC-OCD, and the experimental results were shown in FIG. 5G. 5G is a graph of concentrations of organics in secondary treated water for four sewage treatment plants.

Referring to FIG. 5G, the organic matter distribution of the secondary treated water of the four sewage treatment plants is present in a similar ratio, and all of them are based on biological treatment, so that the humics occupy the largest portion, and a trace amount of biopolymer ( biopolymers) are also present.

Referring to FIG. 5H, four types of biopolymers, humics, building blocks, and low MW neutrals may be easily removed from the surface of the forward osmosis membrane by physical cleaning only. However, it can be observed that the accumulation of substances on the surface of the forward osmosis membrane in trace amounts in each cleaning cycle, especially from the third wash, a large amount of biopolymers and humics are observed.

Looking at the tendency of organic matter to accumulate on the surface of the forward osmosis membrane, it can be seen that the most of the biopolymers (biopolymers) remaining on the surface of the forward osmosis membrane. In general, biopolymers based on proteins or polysaccharides are known to be difficult to remove by physical washing due to their sticky substance.

The phenomenon that the irreversible membrane fouling material such as biopolymers deteriorates the performance of the forward osmosis membrane should be reflected in the forward osmosis membrane contamination index.

The best method is to measure the concentration of substances in raw water, but it is difficult to cope with immediate membrane contamination because these methods have limitations in in situ application in the field and the measurement time is very long. .

Therefore, by measuring the fouling reversibility of the forward osmosis membrane by physical washing in the same manner as the above experiment, the amount of irreversible membrane pollutants such as biopolymers in the raw water indirectly It is judged that the membrane fouling index that can provide the signal for pretreatment strength to the pretreatment process is the most reasonable method.

In addition, in order to reflect membrane fouling reversibility (fouling reversibility) in the development of the membrane fouling index of the forward osmosis membrane, it is essential to analyze the effects of physical washing conditions. FIG. 5i shows a graph showing the results of the fouling reversibility of the forward osmosis membrane according to the operating cycle according to the flow rate, which is a physical washing condition.

After the forward osmosis process is performed for 70 hours at a flow rate of 8.54 cm / s, physical washing of the forward osmosis membrane proceeds for 10 minutes. At this time, the flow rate of the physical cleaning is carried out for each operating cycle at 17.08 cm / s, 25.62 cm / s, 34.16 cm / s, and 42.70 cm / s.

Referring to FIG. 5I, when the forward osmosis membrane is washed to 25.62 cm / s or less, the fouling layer of the forward osmosis membrane is not sufficiently removed from the forward osmosis membrane, so that low fouling reversibility is observed. Able to know.

The same observed results in FIGS. 5F and 5I show that the fouling reversibility of the forward osmosis membrane converges in the fifth to sixth cycles as the operation is repeated. From this, it is possible to set the state in which the forward osmosis membrane is no longer recoverable by physical washing only as 'critical reversibility', and it can be derived from the membrane fouling reversibility to predict the membrane contamination of the forward osmosis membrane.

The Forward Osmosis Membrane Contamination Index (OFI) is an index of membrane fouling of the forward osmosis membrane, and it is determined how much the water permeation rate of the influent flowing through the forward osmosis membrane is recovered over time in a range larger than the critical reversibility (Rc). Can be derived.

The present invention described above is not limited to the above-described embodiment and the accompanying drawings, and various substitutions, modifications, and changes are possible within the scope without departing from the technical spirit of the present invention. It will be evident to those who have knowledge of.

Claims (15)

1. Membrane contamination simulation unit provided with a forward osmosis membrane, the membrane fouling of the forward osmosis membrane during the forward osmosis process;

   An inflow water supply unit providing a first inflow water to the membrane fouling simulation unit during a forward osmosis process, and a second inflow water having a flow rate greater than that of the first inflow water to the membrane fouling simulation unit during a washing process; And

   At the beginning of the forward osmosis step, the first water permeation rate (J1) of the primary inflow water and the third water permeation rate (J3) of the primary inflow water after the washing process are measured to calculate the forward osmosis membrane contamination index (OFI). And a membrane fouling prediction unit for predicting membrane fouling of the forward osmosis membrane from the forward osmosis membrane fouling index (OFI),

   The forward osmosis membrane contamination index (OFI) is a forward osmosis membrane contamination prediction apparatus, characterized in that the recovery rate of the third water penetration amount (J3) to the first water penetration amount (J1).
2. The membrane fouling prediction unit according to claim 1,

   When the forward osmosis membrane contamination index (OFI) is calculated to be greater than 1 (1 <OFI), it is predicted that the forward osmosis membrane is damaged,

   When the forward osmosis membrane contamination index (OFI) is calculated to be 1 (OFI = 1), it is predicted that the forward osmosis membrane is not contaminated,

   When the forward osmosis membrane contamination index (OFI) is in the range larger than the critical reversibility (Rc) and less than 1 (Rc <OFI <1), membrane fouling of the forward osmosis membrane is predicted,

   If the forward osmosis membrane contamination index (OFI) is less than the critical reversibility (Rc) (Rc> OFI), the membrane is predicted to be unable to recover the membrane contamination only by physical cleaning by the secondary influent. Forward osmosis membrane fouling prediction device, characterized in that.
3. The method of claim 2,

   The critical reversibility (Rc) is the first influent water after the washing step for the water permeation rate of the first influent water before the washing step in a state in which the membrane contamination of the forward osmosis membrane cannot be recovered only by physical washing by the second influent water. Is the recovery rate of

   The critical reversible membrane contamination prediction device, characterized in that the critical reversibility (Rc) is calculated by equation (2).

   

   (J _{before washing} is a film _after at not possible contamination recovery state, wherein the first number of transmission amount of incoming water prior to the washing process, _washing J is the number of the first inlet water after the cleaning process the permeation amount of the forward osmosis membrane.)
4. The membrane fouling prediction unit according to claim 2,

   When the water permeation rate of the primary inflow water is gradually lowered than the first water permeation amount J1 by the adhesion layer, when the second water permeation amount J2 converged is measured,

   At the time point when the second water permeation J2 is measured, the secondary inflow water is provided to the membrane fouling simulation unit, so that the adhesion layer is removed by the secondary inflow water so that the forward osmosis membrane is washed. Forward osmosis membrane fouling prediction device.
5. The membrane fouling prediction unit according to claim 1,

   The forward osmosis membrane fouling index (OFI) is calculated by the following equation.

   

   (J1 is the water permeation rate of the primary inflow water passing through the forward osmosis membrane before the adhesion layer is formed at the beginning of the forward osmosis process, and J3 is the adhesion layer removed from the forward osmosis membrane by the washing process). After the water is passed through the forward osmosis membrane in the forward osmosis process, the water permeation rate of the primary influent.)
6. The method of claim 1,

   Further comprising an induction solution supply for supplying an induction solution having a concentration higher than the primary inlet to the membrane fouling simulation unit in the forward osmosis process,

   The induction solution supply unit adjusts the molar concentration of the induction solution and forward osmosis, characterized in that to accelerate the formation of the adhesion layer formed by the organic matter of the primary influent in the membrane fouling simulation unit stacked on the surface of the forward osmosis membrane Membrane fouling prediction device.
7. The method of claim 6,

   The first water permeation rate due to the difference between the TDS of the first influent and the TDS of the induction solution by controlling the TDS (total dissolved solids) of the induction solution, which is connected to the induction solution supply unit and provided to the membrane fouling simulation unit. Forward osmosis membrane fouling prediction device further comprising a TDS controller for controlling the.
8. In the forward osmosis membrane fouling prediction method for predicting the membrane fouling of the forward osmosis membrane in the forward osmosis step using the forward osmosis membrane fouling prediction apparatus of claim 1,

   (A) The first inflow and induction solution is supplied to the membrane fouling simulation unit, the membrane contamination is simulated by the adhesion layer accumulated on the forward osmosis membrane by the osmotic pressure difference between the first inflow and the induction solution during the forward osmosis process Becoming;

   (B) providing a second influent water having a flow rate greater than that of the first influent water to the membrane fouling simulation unit, and washing the forward osmosis membrane by the second influent water; And

   (C) measuring the first water permeation rate (J1) of the primary inflow water at the beginning of the forward osmosis process, and the third water permeation rate (J3) of the primary inflow water after the washing process, and the forward osmosis membrane contamination index (OFI). ) Is calculated to predict the membrane fouling of the forward osmosis membrane from the forward osmosis membrane contamination index (OFI),

   The forward osmosis membrane contamination index (OFI) is a forward osmosis membrane contamination prediction method, characterized in that the recovery rate of the third water penetration amount (J3) to the first water penetration amount (J1).
9. According to claim 8, wherein (C) step,

   (C1) if the forward osmosis membrane contamination index (OFI) is calculated to be greater than 1 (1 <OFI), predicting that the forward osmosis membrane is damaged;

   (C2) if the forward osmosis membrane contamination index (OFI) is calculated to be 1 (OFI = 1), predicting that the forward osmosis membrane is not contaminated;

   (C3) predicting membrane fouling of the forward osmosis membrane when the forward osmosis membrane contamination index (OFI) belongs to a range larger than the critical reversibility (Rc) and less than 1 (Rc <OFI <1); And

   (C4) When the forward osmosis membrane contamination index (OFI) is less than the critical reversibility (Rc) (Rc> OFI), the membrane may not recover the membrane contamination only by physical washing with the secondary influent. D) a step of being predicted,

   The critical reversibility (Rc) is the first influent water after the washing step for the water permeation rate of the first influent water before the washing step in a state in which the membrane contamination of the forward osmosis membrane cannot be recovered only by physical washing by the second influent water. The forward osmosis membrane fouling prediction method, characterized in that the recovery rate of permeation.
10. The method according to claim 9, wherein in the membrane fouling simulation unit,

    If the forward osmosis membrane contamination index (OFI) is greater than 1 (1 <OFI), the operation of the forward osmosis process is stopped,

    If the forward osmosis membrane contamination index (OFI) is 1 (OFI = 1), the operation of the forward osmosis process is continued,

    If the forward osmosis membrane contamination index (OFI) is greater than the critical reversibility (Rc) and less than 1 (Rc <OFI <1), the operation of the forward osmosis process is stopped, and the washing process for the forward osmosis membrane proceeds. Become,

    When the forward osmosis membrane contamination index (OFI) is less than the critical reversibility (Rc) (Rc> OFI), the operation of the forward osmosis process is stopped, the forward osmosis, characterized in that the pretreatment process such as chemical cleaning is performed How to predict membrane fouling.
11. The method of claim 9,

    The forward osmosis membrane contamination index (OFI) is a forward osmosis membrane fouling prediction method, characterized in that calculated by the following equation.

    

    (J1 is the water permeation rate of the primary inflow water passing through the forward osmosis membrane before the adhesion layer is formed at the beginning of the forward osmosis process, and J3 is the adhesion layer removed from the forward osmosis membrane by the washing process). After the water is passed through the forward osmosis membrane in the forward osmosis process, the water permeation rate of the primary influent.)
12. The method of claim 9,

    The critical reversibility (Rc) is a forward osmosis membrane fouling prediction method, characterized in that calculated by the following equation.

    

    (J _{before washing} is a film _after at not possible contamination recovery state, wherein the first number of transmission amount of incoming water prior to the washing process, _washing J is the number of the first inlet water after the cleaning process the permeation amount of the forward osmosis membrane.)
13. The method of claim 8, wherein step (B)

    When the water permeation rate of the primary inflow water passing through the forward osmosis membrane is gradually lower than the first water permeation amount J1 by the adhesion layer, at the point of convergence to the second water permeation rate J2, J1> J2, the second Washing of the forward osmosis membrane by the inflow of the primary water is in progress, the membrane fouling prediction method of the normal osmosis membrane, characterized in that the membrane fouling of the normal osmosis membrane is recovered as the adhesion layer is removed from the forward osmosis membrane.
14. The method of claim 8, wherein in the step (A),

    The induction solution is molar concentration is controlled is supplied to the membrane fouling simulation unit, forward osmosis membrane fouling prediction method, characterized in that to accelerate the formation of the adhesion layer.
15. The method of claim 8, wherein in the step (A),

    The induction solution is provided to the membrane fouling simulation unit by adjusting the total dissolved solids (TDS) of the induction solution,

    The first water permeation (J1) is a forward osmosis membrane fouling prediction method, characterized in that controlled by the difference between the TDS of the first influent and the TDS of the induction solution.

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