KR101144316B1 - Advanced wastewater treatment system and method by means of membrane combining forward osmosis using NaCl solution with reverse osmosis - Google Patents

Abstract

The present invention is to install a forward osmosis unit using NaCl solution as an induction solution in the rear end of the bioreactor, the forward osmosis phenomenon by the osmotic pressure gradient between the sewage water supply and the induction solution BOD, SS, nitrogen, phosphorus, E. coli And a combination of forward osmosis and reverse osmosis membrane separation sewage water treatment system, which can first treat dissolved contaminants and concentrate and reuse the induction solution diluted during forward osmosis through a reverse osmosis unit; Membrane separation process control apparatus and control method for.

The present invention is installed in the rear end of the bioreactor, BOD (Biological Oxygen Demand), SS (floating) contained in the wastewater by the forward osmosis phenomenon by the osmotic pressure gradient by flowing the first treated water from the bioreactor Forward osmosis unit for secondary treatment of solids, Suspended Solid), nitrogen (N), phosphorus (P), E. coli and dissolved contaminants; An induction solution input device for supplying a high concentration of an induction solution higher than the feed water to the forward osmosis unit to induce a net flow through the membrane only the water contained in the treated water introduced into the forward osmosis unit; A reverse osmosis unit installed at a rear end of the forward osmosis unit and receiving reprocessed water supplied with the entire amount of the treated water and the induction solution passing through the forward osmosis unit as inflow water; And a forward osmosis and reverse osmosis combined wastewater advanced treatment apparatus including a filtered water storage tank for storing and discharging the filtered water passed through the reverse osmosis unit, and a membrane separation process control apparatus for treating the advanced wastewater applied to the wastewater advanced treatment apparatus. Provide control method.

According to the present invention described above can be said to be a low-energy high-efficiency sewage water treatment technology that can maintain the advantages of the forward osmosis and reverse osmosis process, and complement each other's disadvantages. In addition, it is possible to secure effluents of water quality that can be reused for any purpose without installing a separate reprocessing facility.

Forward Osmosis Unit, Reverse Osmosis Unit, Membrane Separation, Advanced Wastewater Treatment, TDS, Nacl Solution

Description

Advanced wastewater treatment system and method by means of membrane combining forward osmosis using NaCl solution with reverse osmosis}

The present invention relates to a wastewater advanced treatment system and a control method thereof, and more particularly, BOD, SS, nitrogen, phosphorus, E. coli and BOD contained in wastewater using an forward osmosis membrane unit using NaCl as an induction solution. A combination of forward osmosis and reverse osmosis membrane separation and wastewater advanced treatment devices that remove dissolved contaminants and concentrate and reuse the induction solution diluted in the forward osmosis process using a reverse osmosis unit, and the wastewater advanced treatment Membrane separation process control apparatus and control method for the same.

According to the Water Resources Corporation's 2003 United Nations World Water Development Report, by 2025, about 2.7 billion people, or 40% of the world's population, will face fresh water shortages, and about one fifth of the world's countries will experience severe water shortages. Prospect. This is the result of a combination of reduced supply and explosive growth in demand. Recently, as an alternative to solve the water shortage, interest in the effluent of the sewage treatment plant has been amplified. Excessive effluent from existing sewage treatment plant is just discharged into rivers or seas, and many researches have been carried out because it is recognized as a resource in the concept of wastes that effluent cannot use. In the US, in particular, each state has established and operated detailed guidelines for the purpose and purpose of reuse of sewage treatment water. In addition, since the late 1970s, Orange County, California, USA, has used advanced treatment systems to recycle sewage treatment plant effluents for agricultural and groundwater reclaiming water. These advanced treatment systems consist of multilayer filtration, activated carbon, and reverse osmosis membrane processes. .

In general, processes applied for reuse of sewage treatment water include flocculation sedimentation, flocculation filtration, filtration, activated carbon filtration, ozone treatment, membrane separation, and the like. However, the selection of the process for reuse should fully consider the target water quality (the target of the treated water quality), depending on the water quality characteristics of the source water and the purpose of use. Currently, the most commonly used method of recycling sewage water is processes such as flocculation, sedimentation, sand filtration, activated carbon adsorption, and disinfection. Much has been studied and is being applied in practice. As such, the existing sewage treatment plant effluent is not directly reusable, and can be reused as living water, agricultural water, and industrial water only when a separate sewage treatment facility is installed. In addition, as of the end of 2003, the total amount of sewage flowing in amounted to 6.4 billion cubic meters (Ministry of Environment 2004), and the discharged water recycled was 3.5 billion cubic meters, about 5.4%. About 70.3% of reused discharged water is used for toilet water, washing water, cooling water, dilution water, and other water in the sewage treatment plant, and the remaining 29.7% is used for industrial water, agricultural water, environmental water (river maintenance water). ) Is used. The reuse of sewage treatment plant effluents between 2001 and 2003 is increasing at a low rate of 1% per year, and most of the applications are also used inside sewage treatment plants. The low reuse rate of downstream effluent is due to the burden of installation cost of reprocessing facilities and the lack of recovery rate of process water.

Recently, many researches on reuse of sewage treatment plant have been conducted to solve the water shortage, but currently, it is not possible to reuse direct discharge of sewage treatment plant. The treatment facility must be installed before it can be reused. However, due to the burden of installing and operating the reprocessing facility, only about 5.4% of the effluent is recycled, and due to the reliability of the treated water quality, most of the recycled water is used for cleaning, cooling, and dilution of the sewage treatment plant. The problem is that it is used for water.

Therefore, the present invention has been proposed to solve the above problems, the forward osmosis phenomenon by the osmotic pressure gradient of the wastewater feed water and the induction solution by installing an forward osmosis unit using NaCl solution as an induction solution at the rear end of the bioreactor Combination type of forward osmosis and reverse osmosis that can treat BOD, SS, nitrogen, phosphorus, E. coli and dissolved contaminants contained in the wastewater, and concentrate and reuse the induction solution diluted in the forward osmosis process through the reverse osmosis unit. It is an object of the present invention to provide a membrane separation wastewater advanced treatment apparatus, and a membrane separation process control apparatus and control method for the wastewater advanced treatment.

In addition, the present invention is capable of treating the pollutant contained in the sewage water only by combining the forward osmosis process and the reverse osmosis process without installing a separate retreatment facility in the advanced sewage water treatment apparatus capable of removing nitrogen and phosphorus with organic matter removal. By providing a combination of forward and reverse osmosis membrane separation and wastewater advanced treatment device to secure the discharge water of the water quality that can be reused for the intended use, and a membrane separation process control device and control method for the advanced wastewater treatment. There is another purpose.

In order to achieve the above object, the present invention is installed at the rear end of the bioreactor, and the treated water from the bioreactor is introduced into the waste water as a forward osmosis phenomenon by osmotic pressure gradient BOD (Biological Oxygen Demand) Forward osmosis unit for treating SS (suspended solid), nitrogen (N), phosphorus (P), E. coli and dissolved contaminants; An induction solution input device for supplying a high concentration of an induction solution higher than the feed water to the forward osmosis unit to induce a net flow through the membrane only the water contained in the treated water introduced into the forward osmosis unit; A reverse osmosis unit installed at a rear end of the forward osmosis unit and receiving reprocessed water supplied with the entire amount of the treated water and the induction solution passing through the forward osmosis unit as inflow water; And it provides a forward osmosis and reverse osmosis combined wastewater advanced treatment apparatus comprising a filtered water storage tank for storing and discharged the filtered water passed through the reverse osmosis unit.

In addition, the present invention is a membrane separation process control apparatus for the advanced treatment of sewage water applied to the combination of forward and reverse osmosis type sewage treatment system, installed in the bioreactor, forward osmosis unit, reverse osmosis unit and filtered water storage tank respectively A data collection unit for collecting the measured flow factor and forward osmosis membrane process operator online through a TDS meter and a flow meter for measuring total dissolved solids of the influent; The model predictor receives water quality and process factors from the data collection unit, determines the quality and quantity of wastewater to be treated by combining the concentration polarization model and the dissolution diffusion model, and determines the concentration, recovery rate and membrane area of the induction solution. Control unit; Provided is a membrane separation process control apparatus for advanced wastewater treatment comprising a feedback control unit for calculating and replenishing the error of the induced solution concentration determined by the model prediction control unit 220.

Here, the model prediction controller is a model input unit for receiving the water quality and process factors provided from the data collection unit to convert the TDS of the raw water to osmotic pressure using the following [Equation 1] model equation to determine the osmotic pressure of the waste water wastewater ; Induction solution using the formula of the following formula [2] which is a combined model of concentration polarization model and dissolution diffusion model to determine the production quantity and water quality of the forward osmosis membrane process according to the determined sewage osmotic pressure A first numerical analysis calculating unit to determine the concentration of the; A second numerical calculation unit configured to determine the quality and quantity of the final effluent treated in the reverse osmosis membrane process and the concentration of the induction solution by using the model equation [Equation 3], which is a concentration polarization model for reverse osmosis process prediction control; And a model output unit for verifying the predicted value and actual data of the water quality and quantity of the treated water calculated by the first and second numerical analysis calculation units.

The feedback control unit may include an error calculator that calculates an error of the concentration of the induction solution calculated through the first numerical calculator; And a feedback calculating unit calculating a proper supplementary solution concentration replenishment amount based on the value calculated by the error calculating unit so that the inductive solution calculated by the first numerical analysis calculating unit acts as an effective osmotic pressure required for driving the forward osmosis membrane process. do.

In addition, the present invention after determining the flow rate and the water quality of the final treated water treated in the bioreactor, the first step of measuring the TDS of the treated wastewater; A second step of determining the osmotic pressure of the wastewater by using the measured TDS using the model formula of Equation 1 below; The permeation experiments for the pure permeability and the concentration of the induced solution were determined in advance, and the filtration coefficients (A, B), the internal concentration polarization coefficient (K), and the external concentration polarization coefficient (k) of the predetermined forward osmosis membrane and reverse osmosis membrane were determined by Equation 2 below. A third step of calculating the concentration and flow rate of the induction solution for the target amount by a combined equation of the concentration polarization model and the dissolution diffusion model for the forward osmosis membrane of A fourth method for calculating the concentration ratio of the induced solution diluted by osmotic process in the forward osmosis unit and the quantity and quality of the final treated water using the concentration polarization model and the dissolution diffusion model for the reverse osmosis membrane of Equation 3 below. step; A fifth step of comparing the calculated value of the quantity and quality of the final treated water previously set in the first step with the result calculated by the numerical analysis calculating unit to determine whether it is within 10% of the tolerance; A sixth step of determining the concentration and flow rate of the NaCl-derived solution as an operating condition when the comparison result between the predicted value and the target value by the model is within 10% of the tolerance in the fifth step; If the comparison result between the predicted value and the target value by the model does not satisfy the tolerance within 10% from the fifth step, the osmotic pressure induced by the induction solution is determined to be an effective osmotic pressure for driving forward osmosis. A seventh step of calculating; An eighth step of repeating the third step if the effective osmotic pressure for operation in forward osmosis is performed in the seventh step; otherwise, determining whether the target flow rate can be changed; And a ninth step of generating an alarm when two conditions of the seventh and eighth steps are not satisfied at the same time.

[Equation 1] to [Equation 3] presented in the membrane separation process control apparatus and control method for the advanced wastewater treatment are as follows.

[Equation 1]

Model for determining osmotic pressure of sewage water through TDS

π: osmotic pressure of sewage

TDS: Concentration of Total Dissolved Solids

[Equation 2]

Combined model equation of concentration polarization model and dissolution diffusion model to determine the production quantity and quality of forward osmosis membrane process

J _v : Permeate flux of produced water

J _s : Permeate flux of solute

A: water filtration coefficient

B: filtration coefficient of the solute

p _{D , b} : Osmotic pressure of induction solution

p _{F , b} : inflow and wastewater osmotic pressure

K: Internal concentration polarization coefficient

k: external concentration polarization coefficient

&Quot; (3) "

Concentration Polarization Model for Predictive Control of Reverse Osmosis Process to Determine Water Quality and Yield of Final Effluent and Concentration of Induction Solution

J _v : Permeate flux of produced water

J _s : Permeate flux of solute

A: water filtration coefficient

B: filtration coefficient of the solute

ΔP: interlude differential pressure

Δπ: osmotic pressure

C _m : concentration of solute at the membrane surface

C _p : concentration of solute in the filtrate

C _b : concentration of solute in membrane influent

k: mass transfer coefficient

It is characterized by that.

As described above, according to the present invention.

Since the forward osmosis process uses an osmotic pressure gradient instead of water pressure, it consumes less energy and does not compress the contaminants due to water pressure on the membrane surface, which is advantageous in terms of preventing membrane contamination and has a better cleaning effect. It is a technology that can drastically improve the quality of treated water because it uses membranes. Therefore, the present invention maintains the advantages of the forward osmosis process and the reverse osmosis process using NaCl solution as the induction solution, and can complement the disadvantages of the two processes as it is possible to perform low energy high efficiency wastewater treatment have.

In addition, the present invention has another effect of ensuring the discharge of water quality that can be reused for any purpose without installing a separate reprocessing facility in the advanced sewage treatment system that can remove nitrogen and phosphorus with organic matter removal. have.

Hereinafter, with reference to the accompanying Figures 1 to 4 will be described an embodiment of the present invention;

Combined forward and reverse osmosis combined membrane separation wastewater treatment apparatus according to the present invention, the membrane separation process control apparatus and its control method for the advanced treatment of wastewater, and the reverse osmosis and reverse osmosis combination membrane separation using NaCl solution as an induction solution By installing the advanced sewage treatment system in the existing sewage treatment plant, the sewage treatment is performed with low energy and high efficiency, and it is implemented to secure the discharged water quality that can be reused for any purpose without installing a separate reprocessing facility.

Figure 1 is a process diagram showing an embodiment of the forward osmosis and reverse osmosis combined membrane separation wastewater advanced treatment apparatus according to the present invention.

As shown in the figure, the present invention includes a bioreactor 2 provided with an acid engine 4 at a bottom thereof to perform a biological reaction against raw water introduced from the outside; An air injection pump 6 installed outside the bioreactor manifold 4 for injecting air into the diffuser 4; A first TDS (Total Dissolved Solid) measuring device (8) for measuring the total dissolved solids contained in the raw water introduced into the bioreactor; It is installed at the rear end of the bioreactor (2), BOD (biological oxygen demand, Biological Oxygen Demand), SS (included in the wastewater by forward osmosis due to the osmotic pressure gradient by introducing the treated water from the bioreactor 2) A forward osmosis unit 10 for treating suspended solids, suspended solids, nitrogen (N), phosphorus (P), E. coli and dissolved pollutants; In order to induce a net flow of only water from the treated water flowing into the forward osmosis unit 10 from the bioreactor 2, the NaCl solution having a higher concentration than the treated water is used as an induction solution, and the forward osmosis unit Induction solution replenishment input device 12 for supplying to (10); A wastewater circulation pump 14 for reintroducing some of the treated water flowing into the forward osmosis unit 10 into the bioreactor 2; A first transfer line 15 for discharging the treated water passing through the screen of the forward osmosis unit 10 to another process facility; A second TDS (Total Dissolved Solid) measuring device (16) installed on the first transfer line (15) for measuring the total dissolved solids contained in the treated water; A first flow meter (18) installed at one side of the second TDS measuring device (16) to measure the flow rate of the treated water; A high pressure pump (20) installed in the first transfer line (15) located at one side of the first flow meter (18) to send the treated water to the reverse osmosis unit side to be described later; A pressure gauge 22 installed at one side of the high pressure pump 20; A reverse osmosis unit (24) installed at the rear end of the forward osmosis unit (10) and receiving the treated water and the NaCl induction solution as a source of inflow water passing through the forward osmosis unit (10) for reprocessing; Concentrated water recovery line 25 for supplying the induction solution diluted in the forward osmosis process in the reverse osmosis unit 24 into the concentrated water through the reverse osmosis process and resupply to the forward osmosis unit 10 side; ; A third TDS measuring device (26) installed on the brine recovery line (25) for measuring total dissolved solids contained in the brine; A second flow meter (28) installed at one side of the third TDS measuring device (26) to measure the flow rate of the concentrated water; A filtered water storage tank (30) for storing the filtered water passing through the screen of the reverse osmosis unit (24); A second transfer line (35) for discharging the filtered water from the reverse osmosis unit (24) to the filtered water storage tank (30); A fourth TDS measuring device (32) installed on the second transfer line (35) for measuring the total dissolved solids contained in the filtered water; A third flow meter 34 installed at one side of the fourth TDS measuring device 32 to measure a flow rate of the treated water; A third transfer line 37 for re-introducing a part of the filtered water stored in the filtered water storage tank 30 into the forward osmosis unit 10 to perform membrane cleaning; A backwash pump (36) installed on the third transfer line (37) for supplying filtered water to the forward osmosis unit (10); A sodium hypochlorite input device (38) installed on the third transfer line (37) to disinfect filtrate; The sodium hypochlorite injection device 38 includes a scale inhibitor injection device 40 installed on one side.

In the present invention configured as described above, the forward osmosis process carried out through the forward osmosis unit 10 is an osmotic process using a semi-permeable membrane to separate water from dissolved solutes, using water pressure as a driving force for separation. Unlike reverse osmosis, the process uses an osmotic pressure gradient between the feed water and the induction solution. In forward osmosis, an induction solution is used, which is a very high concentration of solution compared to the feed water to induce a net flow through the membrane only in the feed water. To be used as an induction solution, the osmotic pressure must be higher than that of the feed solution, and the induction solution diluted in the forward osmosis process should be easy to reconcentrate.

Since the forward osmosis uses an osmotic pressure gradient instead of water pressure, energy consumption is low, and contaminants are not squeezed by water pressure at the membrane surface, which is advantageous in terms of preventing membrane contamination, and has a good cleaning effect, and MBR (Membrane Bio-) It is a technology that can dramatically improve the water quality of treated water because it uses a membrane of fine pores rather than a reactor process.

In the embodiment of the present invention, the forward osmosis unit 10 having the above-described advantages is installed at the rear end of the bioreactor 2. In addition, the high osmotic pressure is generated, and an example of using a reusable NaCl solution as an induction solution can be easily concentrated by a reverse osmosis process.

Referring to the working state through the above configuration is as follows.

First, the air supplied from the air injection pump 6 is ejected through the diffuser 4 to perform the primary treatment of the raw water introduced into the bioreactor 2. When the treated water is introduced into the forward osmosis unit 10 after the treatment step of the bioreactor 2, NaCl solution is supplied from the induction solution input device 12 to the forward osmosis unit 10, the forward osmosis by the osmotic pressure gradient As a phenomenon occurs, the secondary treatment of BOD, SS, nitrogen, phosphorus, E. coli and dissolved contaminants contained in the treated water. When the forward osmosis membrane process of the forward osmosis unit 10 is performed, some inflow water is subjected to a circulation process introduced into the bioreactor 2 through the circulation pump 14. In addition, the treated water and the induction solution treated in the forward osmosis membrane unit 10 are transferred to the inflow source water in the total reverse osmosis unit 24 and reprocessed through the reverse osmosis membrane process.

In the reverse osmosis process, the induction solution diluted in the forward osmosis process is concentrated by a reverse osmosis process, and the concentrated water is re-supplied to the forward osmosis unit 10 through the concentrated water recovery line 25.

By repeatedly performing the forward osmosis process and the reverse osmosis process as described above, the final filtrate flows into the filtrate storage tank 30, and the partial filtrate stored in the filtrate storage tank 30 is backwashed on the third transfer line 37. It is supplied to the forward osmosis unit 10 through the pump 36. At this time, the sodium hypochlorite is introduced into the third transfer line 37 from the sodium hypochlorite injector 38 to disinfect the filtered water, and the scale inhibitor is introduced from the scale inhibitor injector 40 to backwash the forward osmosis membrane. Will be performed.

Next, a membrane separation process control apparatus and control method for predicting and evaluating the performance of the forward osmosis and reverse osmosis combination process in the forward osmosis and reverse osmosis combined membrane separation wastewater advanced treatment apparatus will be described.

Figure 2 shows a block diagram of a membrane separation process control apparatus for determining the induction solution concentration determination, the treated water quality and the yield prediction value by using the mathematical model prediction controller according to the present invention.

As shown in the figure, the membrane separation process control apparatus for the advanced sewage treatment of the present invention, in the configuration of the advanced sewage treatment system shown in Figure 1, the total dissolved solids of the incoming source water introduced into the bioreactor 2 The first TDS measuring device 8 for measuring, the second TDS measuring device 16 for measuring the total dissolved solids of the treated water treated in the forward osmosis unit 10, and the forward osmosis unit ( 10) a third TDS measuring device 26 for measuring the total dissolved solids of the concentrated water returned to 10) and a fourth TDS for measuring the total dissolved solids of the filtered water flowing into the filtrate storage tank 30 from the reverse osmosis unit 24; A data collection unit 210 for collecting the flow rate factor and the forward osmosis membrane process factor measured through the meter 32 and the first to third flow meters 18, 28, and 34 online; The water quality factor and the process factor are received from the data collection unit 210 to determine the water quality and quantity of the wastewater to be treated by combining the concentration polarization model and the dissolution diffusion model, and determine the concentration, recovery rate and membrane area of the induction solution. A model prediction control unit 220; And a feedback control unit 230 for calculating and replenishing an error with respect to the induction solution concentration determined by the model prediction control unit 220.

Here, the model prediction controller 220 receives the water quality factor and the process factor provided from the data collection unit 210 to convert the TDS of the raw water into osmotic pressure using the [Equation 1] model equation to determine the osmotic pressure of the wastewater. A model input unit 221; Induction solution using the formula of formula [2] which is a combined model of concentration polarization model and dissolution diffusion model to determine the production quantity and water quality of the forward osmosis membrane process according to the osmotic pressure of the sewage A first numerical analysis calculation unit 222 for determining the concentration of; A second numerical analysis unit 223 for determining the quality and quantity of the final effluent treated in the reverse osmosis membrane process and the concentration of the induction solution by using the model equation [Equation 3], which is the concentration polarization model for the reverse osmosis process prediction control. ; And a model output unit 224 for verifying the predicted values and actual data of the water quality and quantity of the treated water calculated by the first and second numerical analysis calculation units 222 and 223.

The feedback controller 230 may include an error calculator 232 for calculating an error of the concentration of the induction solution calculated by the first numerical calculator 222; Feedback calculation unit for calculating the appropriate supplementary solution concentration replenishment amount based on the value calculated by the error calculation unit so that the induction solution calculated by the first numerical analysis calculation unit 222 acts as an effective osmotic pressure required for driving forward osmosis membrane process It includes.

[Equation 1]

Model for determining osmotic pressure of sewage water through TDS

π: osmotic pressure of sewage

TDS: Concentration of Total Dissolved Solids

[Equation 2]

Combined model equation of concentration polarization model and dissolution diffusion model to determine the production quantity and quality of forward osmosis membrane process

J _v : Permeate flux of produced water

J _s : Permeate flux of solute

A: water filtration coefficient

B: filtration coefficient of the solute

p _{D , b} : Osmotic pressure of induction solution

p _{F , b} : inflow and wastewater osmotic pressure

K: Internal concentration polarization coefficient

k: external concentration polarization coefficient

&Quot; (3) "

Concentration Polarization Model for Predictive Control of Reverse Osmosis Process to Determine Water Quality and Yield of Final Effluent and Concentration of Induction Solution

J _v : Permeate flux of produced water

J _s : Permeate flux of solute

A: water filtration coefficient

B: filtration coefficient of the solute

ΔP: interlude differential pressure

Δπ: osmotic pressure

C _m : concentration of solute at the membrane surface

C _p : concentration of solute in the filtrate

C _b : concentration of solute in membrane influent

k: mass transfer coefficient

Next, a control method of the membrane separation process control apparatus will be described with reference to FIGS. 3 and 4.

Figure 3 is a flow chart showing the process of the membrane separation process control apparatus for the advanced treatment of the forward and reverse osmosis combined membrane separation using the NaCl solution as an induction solution according to the present invention, Figure 4 is according to the present invention As an example of the forward osmosis combination reverse osmosis process operation program, the figure shows the result of predicting the induced solution concentration, the treated water quality and the yield by the program.

As shown in FIG. 3, first, the flow rate and water quality of the final treated water treated in the bioreactor 2 are determined (S301), and then the TDS of the wastewater to be treated is measured (S302).

Next, the measured TDS is used to determine the osmotic pressure of the sewage water using the model formula [Equation 1] (S303).

Permeation experiments for pure permeability and induction solution concentrations were performed to determine the filtration coefficients (A, B), the internal concentration polarization coefficient (K) and the external concentration polarization coefficient (k) of the predetermined forward and reverse osmosis membranes. Calculate the concentration and flow rate of the induction solution for the target water by the equation combining the concentration polarization model and the dissolution diffusion model for the forward osmosis membrane (S304).

After performing the step S304, using the concentration polarization model and the dissolution diffusion model for the reverse osmosis membrane [Equation 3], the concentration of the induction solution diluted by the osmosis process in the forward osmosis unit 10 and the amount of the final treated water and Calculate the water quality (S305).

In step S301, the amount of water and the quality of the final treatment water set in advance are compared with the result calculated by the numerical analysis calculating unit to determine whether the error is within 10% of tolerance (S306).

When the comparison result between the predicted value by the model and the target value in step S306 satisfies within 10% of tolerance, the concentration and flow rate of the NaCl derived solution are determined as the operating conditions and ends (S307).

In step S306, when the comparison result between the predicted value and the target value by the model does not satisfy the tolerance within 10%, recalculate whether the osmotic pressure induced by the induction solution is an effective osmotic pressure for driving forward osmosis. (S308).

If the effective osmotic pressure to operate the forward osmosis in step S308 to perform the step S303 again, otherwise it is determined whether the change in the target flow rate is possible to change the operation if possible (S309), the two steps S308, S309 If the condition is not satisfied at the same time, an alarm is generated (S310).

The present invention described above is not limited to the above-described embodiments and the accompanying drawings, and various substitutions, modifications, and changes are possible in the art without departing from the technical spirit of the present invention. It will be clear to those of ordinary knowledge.

Figure 1 is a schematic process diagram showing the configuration of one embodiment of the forward and reverse osmosis combined membrane separation sewage treatment system using NaCl solution as an induction solution according to the present invention,

Figure 2 is a block diagram of a membrane separation process control apparatus for advanced sewage water treatment to determine the concentration of the induced solution, the treated water quality and the yield prediction value using the mathematical model prediction controller according to the present invention;

Figure 3 is a floor chart showing the process of the membrane separation process control device for the advanced treatment of the forward and reverse osmosis combined membrane separation sewage water using NaCl solution according to the present invention,

Figure 4 is an example of the forward osmosis combination reverse osmosis process operating program according to the present invention, it is a figure showing the result of predicting the induced solution concentration, treated water quality and quantity by the program.

DESCRIPTION OF THE REFERENCE NUMERALS

2: bioreactor 4: acid engine

6: air injection pump 8: first TDS measuring instrument

10: forward osmosis unit 12: induction solution input device

14: circulation pump 15: the first transfer line

16 second TDS measuring instrument 18 first flow meter

20: high pressure pump 22: pressure gauge

24: reverse osmosis unit 25: concentrated water recovery line

26: third TDS measuring instrument 28: second flow meter

30: filtered water storage 32: fourth TDS measuring instrument

34: second flow meter 35: second transfer line

37: third transfer line

38: sodium hypochlorite input device

40: scale inhibitor input device

Claims (13)

It is installed at the rear of the bioreactor, and the treated water from the bioreactor enters the reverse osmosis by osmotic pressure gradient, so that BOD (Biological Oxygen Demand), SS (suspended solid), Forward osmosis unit for secondary treatment of nitrogen (N), phosphorus (P), E. coli and dissolved pollutants; An induction solution input device for supplying a high concentration of an induction solution higher than the feed water to the forward osmosis unit to induce a net flow through the membrane only the water contained in the treated water introduced into the forward osmosis unit; A reverse osmosis unit installed at a rear end of the forward osmosis unit and receiving reprocessed water supplied with the entire amount of the treated water and the induction solution passing through the forward osmosis unit as inflow water; And A filtered water storage tank for storing and discharging the filtered water passing through the reverse osmosis unit Forward osmosis and reverse osmosis combination type sewage treatment system comprising a. The method of claim 1, Combined forward osmosis and reverse osmosis type sewage treatment system further comprising a wastewater circulation pump for re-introducing some of the treated water flowing into the forward osmosis unit into a bioreactor. The method of claim 1, Combined forward osmosis and reverse osmosis type sewage treatment apparatus further comprising a backwashing means for re-introducing a portion of the filtered water discharged from the filtrate storage tank into the forward osmosis unit. The method of claim 1, Forward osmosis and reverse osmosis further comprising concentrated water recovery means for supplying the induction solution diluted in the forward osmosis process into a concentrated water through a reverse osmosis process and re-supplied to the forward osmosis unit side of the treated water introduced into the reverse osmosis unit. Combined sewage treatment system. The method of claim 1, Combined forward and reverse osmosis type sewage treatment system, characterized in that the induction solution supplied from the induction solution input device is NaCl. The method of claim 1, A first TDS meter for measuring total dissolved solids for the treated water in the bioreactor; A second TDS measuring device installed on the discharge line of the forward osmosis unit, for measuring total dissolved solids in the treated water; A first flow meter installed on one side of the second TDS meter; A fourth TDS meter installed on the discharge line of the reverse osmosis unit; And Combined forward osmosis and reverse osmosis type sewage treatment system further comprising a third flow meter installed on one side of the fourth TDS measuring device. The method of claim 4, wherein The concentrated water recovery means A concentrated water transfer line for supplying concentrated water from the reverse osmosis unit to the forward osmosis unit; A third TDS meter installed on the brine transfer line and configured to measure total dissolved solids for the brine; And Combination forward and reverse osmosis sewage water treatment device comprising a second flow meter installed on one side of the third TDS measuring device. The method of claim 3, wherein The backwashing means A filtered water return line for transferring the filtered water from the filtered water storage tank to the forward osmosis unit; A backwash pump installed on the filtered water return line; An anti-scale agent input device installed on one side of the filtered water return line of the backwash pump; And Combination forward and reverse osmosis sewage water treatment device comprising a sodium hypochlorite injector is installed on one side of the scale inhibitor input device to disinfect the filtered water. The method of claim 6, A high pressure pump installed at one side of the first flow meter; And Combined forward osmosis and reverse osmosis type sewage treatment system further comprising a pressure gauge installed on one side of the high pressure pump. In the membrane separation process control apparatus for advanced wastewater treatment, which is applied to the forward and reverse osmosis combined wastewater advanced treatment apparatus according to any one of claims 1 to 9, Collected flow factors and forward osmosis membrane process factors through TDS meter and flow meter installed in the bioreactor, forward osmosis unit, reverse osmosis unit, and filtered water storage tank respectively to measure the total dissolved solids of the incoming influent. Data collection unit for; The model predictor receives water quality and process factors from the data collection unit, determines the quality and quantity of wastewater to be treated by combining the concentration polarization model and the dissolution diffusion model, and determines the concentration, recovery rate and membrane area of the induction solution. Control unit; And Feedback control unit for calculating and replenishing the error for the concentration of the induced solution determined by the model prediction control unit Membrane separation process control device for advanced wastewater treatment comprising a. 11. The method of claim 10, The model prediction control unit A model input unit which receives the water quality and process factors provided from the data collection unit and converts the TDS of the raw water into osmotic pressure using the following [Equation 1] model equation to determine the osmotic pressure of the wastewater; Using the formula of the formula [2] below, which is a combination model of concentration polarization model and dissolution diffusion model for determining the production quantity, water quality, and concentration of the induction solution of the forward osmosis membrane process according to the determined osmotic pressure of the waste water. A first numerical analysis calculation unit to determine the concentration of the induction solution; A second numerical analysis to determine the quality and quantity of the final effluent treated in the reverse osmosis membrane process and the concentration of the induction solution using the model equation [3] below, which is the concentration polarization model for the reverse osmosis process prediction control. A calculator; And And a model output unit for verifying the predicted values and actual data of the water quality and quantity of the treated water calculated by the first and second numerical analysis calculating units. [Equation 1] Model for determining osmotic pressure of sewage water through TDS

π: osmotic pressure of sewage TDS: Concentration of Total Dissolved Solids [Equation 2] Combined model equation of concentration polarization model and dissolution diffusion model to determine the production quantity and quality of forward osmosis membrane process

J _v : Permeate flux of produced water J _s : Permeate flux of solute A: water filtration coefficient B: filtration coefficient of the solute p _{D , b} : Osmotic pressure of induction solution p _{F , b} : inflow and wastewater osmotic pressure K: Internal concentration polarization coefficient k: external concentration polarization coefficient &Quot; (3) " Concentration Polarization Model for Predictive Control of Reverse Osmosis Process to Determine Water Quality and Yield of Final Effluent and Concentration of Induction Solution

J _v : Permeate flux of produced water J _s : Permeate flux of solute A: water filtration coefficient B: filtration coefficient of the solute ΔP: interlude differential pressure Δπ: osmotic pressure C _m : concentration of solute at the membrane surface C _p : concentration of solute in the filtrate C _b : concentration of solute in membrane influent k: mass transfer coefficient 11. The method of claim 10, The feedback control unit An error calculator for calculating an error of the concentration of the induction solution calculated by the first numerical analysis calculator; And It includes a feedback calculation unit for calculating the appropriate induction solution concentration replenishment amount based on the value calculated in the error calculation unit so that the induction solution calculated by the first numerical analysis calculation unit can act as an effective osmotic pressure required for driving the forward osmosis membrane process. Membrane separation process control device for advanced wastewater treatment. Determining the flow rate and water quality of the final treated water treated in the bioreactor, and then measuring the TDS of the treated wastewater; A second step of determining the osmotic pressure of the wastewater by using the measured TDS using the model formula of Equation 1 below; The permeation experiments for the pure permeability and the concentration of the induced solution were determined in advance, and the filtration coefficients (A, B), the internal concentration polarization coefficient (K), and the external concentration polarization coefficient (k) of the predetermined forward osmosis membrane and reverse osmosis membrane were determined by Equation 2 below. A third step of calculating the concentration and flow rate of the induction solution for the target amount by a combined equation of the concentration polarization model and the dissolution diffusion model for the forward osmosis membrane of A fourth step of calculating the concentration rate of the induction solution diluted by osmotic process in the forward osmosis unit, the quantity and the quality of the final treated water using the concentration polarization model and the dissolution diffusion model for the reverse osmosis membrane of Equation 3 below. ; A fifth step of comparing the calculated value of the quantity and quality of the final treated water previously set in the first step with the result calculated by the numerical analysis calculating unit to determine whether it is within 10% of the tolerance; A sixth step of determining the concentration and flow rate of the NaCl-derived solution as an operation condition when the comparison result between the predicted value and the target value by the model is within 10% of the tolerance in the fifth step; If the comparison result between the predicted value and the target value by the model does not satisfy the tolerance within 10% from the fifth step, the osmotic pressure induced by the induction solution is determined to be an effective osmotic pressure for driving the forward osmosis. A seventh step of calculating; An eighth step of repeating the third step if the effective osmotic pressure for operating the forward osmosis in the seventh step; otherwise, determining whether the target flow rate can be changed; And A ninth step of generating an alarm when the two conditions are not satisfied at the same time; Control method of the membrane separation process control apparatus for advanced wastewater treatment comprising a. [Equation 1] Model for determining osmotic pressure of sewage water through TDS

π: osmotic pressure of sewage TDS: Concentration of Total Dissolved Solids [Equation 2] Combined model equation of concentration polarization model and dissolution diffusion model to determine the production quantity and quality of forward osmosis membrane process

J _v : Permeate flux of produced water J _s : Permeate flux of solute A: water filtration coefficient B: filtration coefficient of the solute p _{D , b} : Osmotic pressure of induction solution p _{F , b} : inflow and wastewater osmotic pressure K: Internal concentration polarization coefficient k: external concentration polarization coefficient &Quot; (3) " Concentration Polarization Model for Predictive Control of Reverse Osmosis Process to Determine Water Quality and Yield of Final Effluent and Concentration of Induction Solution

J _v : Permeate flux of produced water J _s : Permeate flux of solute A: water filtration coefficient B: filtration coefficient of the solute ΔP: interlude differential pressure Δπ: osmotic pressure C _m : concentration of solute at the membrane surface C _p : concentration of solute in the filtrate C _b : concentration of solute in membrane influent k: mass transfer coefficient

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