KR100714366B1 - Method for reducing membrane fouling in the membrane bioreactor by using bivalent cation, and membrane bioreactor using the method - Google Patents

Abstract

The present invention relates to a membrane fouling reduction method of a membrane-bound biological reactor using a divalent cation and a membrane-bound biological reactor using the same. More specifically, calcium cations (Ca ^{2 +),} magnesium cations (Mg ^{2 +)} and divalent for reducing fouling contributes to microbial flocs (Floc) formed by adequate concentration implanting positive ions in the membrane-coupled biological reaction tank such as It relates to a method and a membrane-bound biological reactor using the same.

The present invention provides a biological method using a bivalent cation which prevents the formation of deposits on the membrane of the reactor by controlling the supply of the divalent cation such that the monovalent and divalent cations in the membrane-bound biological reactor are maintained within a predetermined ratio range. Provided are a method for reducing membrane fouling in a reactor, and a biological reactor for controlling the supply of divalent cations to the reactor. According to the present invention, it is possible to increase the physical cleaning and chemical cleaning cycles of the membrane by promoting the formation of microbial flocs and reducing the formation of deposits on the membrane.

MBR, reactor, sewage, purification, membrane fouling, cation

Description

Method for Reducing Membrane Fouling in the Membrane Bioreactor by Using Bivalent Cation, and Membrane Bioreactor Using the Method}

1 is a schematic diagram of an immersion membrane-bound biological reactor for the experiment of the membrane fouling reduction method of the membrane-bound biological reactor using a divalent cation according to a preferred embodiment of the present invention,

2 is a view showing a steady state membrane fouling rate in a low calcium ion state,

3 is a view showing the steady state membrane fouling rate in the appropriate calcium ion state,

Figure 4 is a schematic diagram of a membrane-bound biological reactor using the membrane fouling reduction method of the membrane-bound biological reactor using a divalent cation according to a preferred embodiment of the present invention.

<Explanation of symbols for the main parts of the drawings>

10: MBR tank 12: separator

14: diffuser 16: air supply pipe

18 inflow pipe 20 inflow water supply tank

22: transfer pipe 24: pressure gauge

26: thermostat 28: temperature controller

30: divalent cation storage unit 32: divalent cation supply device

34 control unit 36 flow meter

The present invention relates to a membrane fouling reduction method of a membrane-bound biological reactor using a divalent cation and a membrane-bound biological reactor using the same. More specifically, calcium cations (Ca ^{2 +),} magnesium cations (Mg ^{2 +)} and divalent for reducing fouling contributes to microbial flocs (Floc) formed by adequate concentration implanting positive ions in the membrane-coupled biological reaction tank such as It relates to a method and a membrane-bound biological reactor using the same.

In general, sewage is a general term for wastewater generated in daily life, and includes sewage and rainwater such as household sewage and factory wastewater. Treatment of such sewage may be carried out through primary treatment to physically remove suspended substances or sedimentary substances, secondary treatment to biological treatment of organic matter and organic solids dissolved in sewage, and secondary treatment. It can be divided into tertiary treatments to remove nutrients such as nitrogen and phosphorus that have not been removed.

One of the most commonly used biological treatment methods in this treatment is activated sludge process. The activated sludge process returns 20 to 50% of the influent sewage from the final sedimentation basin to the aeration tank (active sludge tank), mixes the influent sewage and activated sludge, and then abandons it for a certain period of time to give sludge at the final sedimentation basin. This is a method of discharging the supernatant by separating it. However, in the conventional activated sludge process, the problem of deterioration of sludge sedimentation caused by inflow load fluctuations is often caused to deteriorate treated water quality. Membrane Bioreactor (MBR), which is resistant to such impact loads and solves the problem of sludge injuries and which can be operated in a compact system, has been introduced at home and abroad. There is a situation.

The MBR process combines activated sludge process and membrane separation process, and has advantages such as safety of treated water quality, reduced land ownership, ease of automation, and minimization of excess sludge generation. However, it has been pointed out that the problems of economic performance and maintenance due to membrane contamination in which microorganisms are attached to membranes used in MBRs. Accordingly, studies on membrane fouling by biological characteristics, membranes, and operating conditions in MBR processes are being actively conducted.

Biological properties of MBR are known to be closely related to membrane contamination such as MLSS (Mixed Liquor Suspended Solids), EPS (Extracellular Polymeric Substances), SMP (Soluble Microbial Products), and floc structure and size. In particular, EPS and SMP are closely related to microbial floc formation and have been a major target of bio-fouling studies. EPS is an insoluble sheaths, capsular polymers, condensed gels, loosely bound polymers, and adherent organics to form a biological community. The EPS can be defined as the total substance derived from microorganisms. Metabolite generically. EPS can be converted to SMP by biological mechanisms, the main component of which is composed of carbohydrates and proteins. These EPS and SMP are known to play an important role in the formation of microbial flocs.

Various researches have been conducted to reduce membrane fouling in the related art, but an efficient and convenient method has not been sufficiently presented. Therefore, it is urgent to develop a technology capable of effectively reducing membrane fouling for an effective operation of the MBR process.

The present invention contributes to the formation of microbial flocs by injecting and maintaining a divalent cation at an appropriate concentration in a membrane-bound biological reactor to effectively reduce membrane fouling of MBR in order to enable efficient operation of the conventional MBR process. It is an object of the present invention to provide a membrane fouling reduction method of a membrane-bound biological reactor using a divalent cation to reduce membrane fouling and a membrane-bound biological reactor using the same.

In order to achieve the above object, the present invention, in the method for reducing the adhesion of the membrane-bound biological reactor to the separation membrane, the ratio of 1 to 2: 1 with respect to the monovalent cation contained in the influent flowing into the reactor Provided is a method for reducing membrane fouling in a membrane-coupled biological reactor using a divalent cation, by injecting a divalent cation to prevent deposits on the separator.

In addition, the present invention, the BR tank 10, the separation membrane 12 immersed in the MBR tank 10, the diffuser 14 for aeration, the air supply pipe 16, and the inlet pipe 18 and transfer A membrane-bound biological reactor comprising a tube (22), comprising: a divalent cation storage unit (30) for storing a divalent cation generating material or a divalent cation aqueous solution; A divalent cation supply device (32) for supplying the divalent cation generating material or the divalent cation aqueous solution from the divalent cation storage unit (30) to the MBR tank (10); And a control unit 34 for controlling the divalent cation supply device 32 to maintain a ratio of the monovalent cation and the divalent cation of the MBR tank 10 within a predetermined range. Provide a type biological reactor.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. In describing the present invention, when it is determined that the detailed description of the related well-known configuration or function may obscure the gist of the present invention, the detailed description thereof will be omitted. In addition, the following will describe a preferred embodiment of the present invention, but the technical idea of the present invention is not limited thereto and may be variously modified and modified by those skilled in the art.

The present invention is characterized by providing a membrane-bound biological reactor and a method for reducing membrane fouling to maintain a divalent cation at an appropriate concentration in order to reduce membrane fouling of a membrane-bound biological reactor (MBR).

In general, membrane fouling is known to be more severe membrane fouling as the particles, the higher the concentration of dissolved substances. The main particle in the MBR is the microbial floc, and the larger and better these microbial flocs, the lower the membrane fouling. However, when microbial flocs are dismantled for various reasons, not only the floc size is reduced, but also the dissolved dissolved substances that play an adhesive role in the flocs further exacerbate the membrane fouling.

In the active sludge process, which is a representative biological treatment method, the formation of microbial flocs for sedimentation is a key factor, and thus, there have been many studies on microbial flocs. There are various hypotheses and theories about the mechanism by which microorganisms form flocs, but the so-called "bivalent cation theory" is known as the closest theory. The divalent cation theory is a theory that when a microbe forms a floc, a divalent cation such as calcium plays a role in bridging the floe between the microbes. Proteins and carbohydrate components that exist outside of microbial cells are mostly anions, and it is understood that divalent cations impart the ability to connect cells to cells through electrical neutralization.

The present invention provides a method for effectively reducing membrane fouling of MBR based on this divalent cation theory.

Example

In order to confirm the membrane fouling reduction effect using divalent cations, the experiment was performed to compare the membrane fouling reduction rate by continuously operating laboratory scale MBR using artificial wastewater.

Figure 1 is a schematic diagram of an immersion membrane-bound biological reactor for the experiment of the membrane fouling reduction method of the membrane-bound biological reactor using a divalent cation according to a preferred embodiment of the present invention.

The separator 12 is provided inside the MBR tank 10, and the air supplied through the air supply pipe 16 is aerated into the MBR tank 10 via the diffuser 14. Meanwhile, the artificial wastewater stored in the inflow water supply tank 20 is supplied to the MBR tank 10 through the inflow pipe 18. Separation membrane 12 is attached to the hollow fiber membrane (membrane pore size 0.4 ㎛) of the polyethylene material to the skid is provided in the MBR tank (10). The treated water treated in the separation membrane 12 is discharged to the outside through the transfer pipe 22. The feed pipe 22 is provided with a pressure gauge 24 to measure the interlayer differential pressure. In order to maintain the temperature of the MBR tank 10, the MBR tank 10 is positioned inside the thermostat 26, and the thermostat 26 is provided with a temperature controller 28 for temperature control.

The artificial waste water is dextrose 234.4 mg / l (250 mg COD / l), ammonium chloride (NH ₄ Cl) 95.5 mg / l, potassium phosphate monobasic (KH ₂ PO ₄ ) 22 mg / l (COD : N: P = 100: 10: 2), sodium hydrogencarbonate (NaHCO ₃ ) 300 mg / l, yeast extract 30 mg / l, trace metal (magnesium sulfate hydrate (MgSO ₄ · 7H ₂ O) 34 mg / l, Manganese sulfate (MnSO ₄ ) 1.7 mg / l, ferrous sulfate (FeSO ₄ · 7H ₂ O) 2.2 mg / l).

Divalent cations to regulate the concentration by using a calcium ion (Ca ^{+ 2)} to supply incoming water supply tank 20 for storing the artificial wastewater. In the case of the low calcium test example, 026 mM was injected into the influent feed tank 20, and in the case of the titration calcium test example, 2.86 mM was injected. In this case, the ratio of monovalent cations to divalent cations is 33: 1 for the low calcium test example, and the ratio of monovalent cations to divalent cations is 1.8: 1 for the titration calcium test. do. For the supply of calcium ions, calcium hydroxide (Ca (OH) ₂ ), calcium chloride (CaCl ₂ ) and the like can be used.

Artificial wastewater stored in the inflow water supply tank 20 was supplied to the MBR tank 10 at a constant flow rate through the inflow pipe 18 to perform a continuous operation (9 minutes supply, 30 seconds rest).

The operating conditions and results in this state are shown in Table 1 below.

Item unit Low calcium Titration calcium Effective volume of MBR tank L 4.50 4.50 Membrane Surface Area m ² 0.03 0.03 Solids Retention Time (SRT) day 10.0 10.0 Hydraulic Dwell Time (HRT) hour 8.52 ± 0.20 (53) 8.31 ± 0.17 (71) Permeate Flux @ 20 ℃ ^{LMH (L / m 2 · h} ) 17.39 ± 0.20 (53) 17.37 ± 0.14 (71) * Normal membrane fouling rate @ 20 ℃ LMH / bard 13.4 2.49 G value / s 390 390 Driving time day 54.0 72.0 Temperature ℃ 22.17 ± 1.30 (53) 22.98 ± 1.13 (71) pH - 7.37 ± 0.23 (14) 7.29 ± 0.12 (14) SVI mL / g 526 128 Nitrate Concentration N-mg / L 21.49 ± 0.93 (14) 20.96 ± 1.08 (17) Ammonia concentration N-mg / L 0.07 ± 0.04 (6) 0.05 ± 0.03 (4) Effluent Turbidity NTU 0.19 ± 0.03 (7) 0.29 ± 0.10 (3) Effluent COD mg / L 5.93 ± 1.99 (9) 4.36 ± 2.00 (10) Reactor SCOD mg / L 24.89 ± 8.96 (18) 17.65 ± 10.8 (10) * MLSS [MLVSS] mg / L [%] 1868 ± 124 (20) [89.8] 2082 ± 148 (19) [90.0]

In Table 1, "±" represents standard deviation and "()" represents the number of measurements. On the other hand, "*" indicates a result measured in the steady state.

As shown in the above results, the membrane fouling rate is 13.4 LMH / bar · d for low calcium, but 2.49 LMH / bar · d for titrated calcium, when low calcium ions are present in the presence of appropriate calcium ions. It can be seen that membrane fouling is reduced by about five times. In addition, in the case of titration calcium, the COD concentration in the reactor and the effluent was lower.

In particular, analysis of the sludge volume index (SVI), which is an indirect indicator of the status of microbial flocs, showed that sludge sedimentability was high because titrated calcium showed smaller values than low calcium. The smaller the SVI value, the higher the sludge density and the better sedimentation, thereby reducing the contamination of the separator.

The results are graphed as follows.

2 is a view showing a steady state membrane fouling rate in a low calcium ion state, Figure 3 is a view showing a steady state membrane fouling rate in a suitable calcium ion state.

In the case of FIG. 2, the chemical cleaning was performed twice when the contamination of the separator was increased, and when the contamination of the separator was increased and when the diffuser was malfunctioning, chemical cleaning was performed.

As shown in FIG. 2, it can be seen that in a low calcium ion state, a specific flux in the separator and a unit area flux per hour at a predetermined pressure decrease. The slope of the specific flux represents the membrane fouling rate. As can be seen in Figure 2 in the low calcium ion state after a certain period of time the membrane fouling occurs to be subjected to chemical cleaning.

According to the result of FIG. 3, in the proper calcium ion state, membrane fouling occurs in the early stage of operation as in the case of low calcium, but from about 10 days of operation, the membrane fouling rate starts to show a tendency to gradually decrease, and after 40 days of operation, the membrane It shows a sharp decrease in contamination (i.e. certain flux maintains a constant value).

The membrane fouling rate equal to the low calcium ion state at the beginning of operation in the appropriate calcium ion state is considered to be due to the acclimation period of the microorganisms. In general, it is known that the state of steady state after the period of 3 SRT in consideration of the change and acclimation period of the microbial species in the biological reactor. Thus, the effects of calcium ion implantation may require some adaptation periods in view of changes in microbial species.

As can be seen from the above results, it is confirmed that the membrane contamination of membrane-bound biological reactors can be reduced by controlling the concentration of divalent cations such as calcium ions.

On the other hand, in the above embodiment was to control the divalent cation concentration by injecting calcium ions into the influent water supply tank 20, in practical implementation it is also possible to directly inject the calcium ions into the MBR tank (10).

Figure 4 is a schematic diagram of a membrane-bound biological reactor using the membrane fouling reduction method of the membrane-bound biological reactor using a divalent cation according to a preferred embodiment of the present invention.

As described above, the membrane-bound biological reactor includes an MBR tank 10, a separator 12 immersed in the MBR tank 10, an aeration pipe 14, an air supply pipe 16, and an inlet pipe for aeration. 18 and the feed pipe 22 are provided. In addition, the membrane-bound biological reactor further includes a divalent cation reservoir 30 and a divalent cation feeder 32.

Divalent cations storage section 30, the calcium ions (Ca ^{2 +)} or magnesium ions, calcium hydroxide (Ca (OH) ₂₎ or magnesium hydroxide with 2 such as (Mg ^{2 +)} to generate a cation (Mg (OH ₂ ) can be stored in an aqueous solution.

The divalent cation supply device 32 transfers the divalent cations from the divalent cation storage unit 30 to the MBR tank 10 according to the characteristics and flux of the influent water supplied to the MBR tank 10 through the inlet pipe 18. Perform the function of supplying. The divalent cation supply device 32 is preferably a metering pump driven by a solenoid or a motor. In addition, although not shown in Figure 4, the divalent cation supply device 32 is preferably controlled by a separate control unit 34.

The controller 34 preferably controls the supply amount of the divalent cation supply device 32 by receiving average information such as nitrate concentration, ammonia concentration, COD, etc. of the influent water treated in the MBR tank 10 in advance. In addition, the inflow pipe 18 is provided with a flow meter 36 so that the inflow water flux information from the inflow pipe 18 is transmitted to the control unit 34 so that the control unit 34 can supply the divalent cation supply device 32 in accordance with the inflow water flux. It is preferable to control the amount of supply.

The above description is merely illustrative of the technical idea of the present invention, and various modifications, changes, and substitutions may be made by those skilled in the art without departing from the essential characteristics of the present invention. will be. Accordingly, the embodiments disclosed in the present invention and the accompanying drawings are not intended to limit the technical spirit of the present invention but to describe the present invention, and the scope of the technical idea of the present invention is not limited by the embodiments and the accompanying drawings. . The protection scope of the present invention should be interpreted by the following claims, and all technical ideas within the equivalent scope should be interpreted as being included in the scope of the present invention.

As described above, according to the present invention, there is an effect that can effectively reduce the membrane fouling of the membrane-bound biological reactor. Accordingly, the physical and chemical cleaning cycles of the membrane can be increased to reduce the power, chemicals, and membrane replacement costs required for cleaning, and the stabilization of the process can improve the ease of operation, microbial activity, and effluent water quality. There is an advantage that can be obtained.

Claims (7)

In the method for reducing the adhesion of the membrane-bound biological reactor to the separation membrane, Membrane-bound biological reactor using divalent cations to prevent deposits on the membrane by injecting divalent cations in a ratio of 1 to 2: 1 with respect to the monovalent cations contained in the inflow water flowing into the reaction tank To reduce membrane fouling. The method of claim 1, The divalent cation is any one or more of calcium ions (Ca2 +) and magnesium ions (Mg2 +) membrane fouling reduction method of the membrane-bound biological reactor. The method according to claim 1 or 2, The divalent cation is injected directly into the reactor, membrane fouling reduction method of the membrane-bound biological reactor. The MBR tank 10, the separator 12 immersed in the MBR tank 10, the diffuser 14 and the air supply pipe 16 for aeration, and the inlet pipe 18 and the transfer pipe 22 are included. In the membrane-bound biological reactor, A divalent cation storage unit 30 storing a divalent cation generating material or a divalent cation aqueous solution; A divalent cation supply device (32) for supplying the divalent cation generating material or the divalent cation aqueous solution from the divalent cation storage unit (30) to the MBR tank (10); And Control unit 34 to control the divalent cation supply device 32 to maintain the ratio of the monovalent cation and the divalent cation of the MBR tank 10 within a predetermined range. Membrane-bound biological reactor comprising a. The method of claim 4, wherein The divalent cation supply device 32 is a membrane-bound biological reactor, characterized in that the metering pump. The method according to claim 4 or 5, The control unit 34 controls the divalent cation supply device 32, so that the ratio of the monovalent cation and the divalent cation is maintained at a ratio of 1 to 2: 1. The method of claim 6, The inflow pipe 18 is provided with a flow meter 36 for measuring the flow rate of the inflow water and the flow rate information of the flow meter 36 is transmitted to the control unit 34, the control unit 34 according to the flow rate information Membrane-bound biological reactor, characterized in that for controlling the divalent cation supply device (32).

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