KR20150001208A - Cleaning system of separation membrane and method using the same - Google Patents

Abstract

A separation membrane cleaning system of the present invention comprises a membrane filtering tank where a separation membrane is installed; a treatment water tank storing a part of treated water produced in the membrane filtering tank and discharging the treated water during back washing; and a control part controlling the back washing flow rate and the back washing time. The treated water is stored in the treatment water tank through a first pipe and a second pipe branched from the first pipe. The treated water stored in the treatment water tank passes through a third pipe connecting the treatment water tank and the first pipe, the first pipe, and the separation membrane and feeds back to the membrane filtering tank. The control part can maintain back washing for the set time by maintaining the driving condition when the flow rate measured by a flow meter installed on the third pipe become the set flow rate. The separation membrane washing system controls the back washing flow rate in a back washing preparing step, and controls the back washing time in a back washing continuing step, thereby improving the back washing efficiency and minimizing the use of treatment water and the energy consumption consumed during back washing.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a separation membrane cleaning system,

The present invention relates to a separation membrane cleaning system and a separation membrane cleaning method using the same.

Membranes are porous, physical boundaries that can separate a mixture by selectively passing certain components from two or more multicomponent mixtures. Water treatment using membrane is advantageous in that less amount of chemicals such as coagulant is used compared to other filtration processes and the required site area can be reduced. Water treatment membranes can separate organic pollutants, inorganic contaminants and aquatic microorganisms contained in water depending on the type. Pressure-driven membranes can be classified into microfiltration (MF) membranes, ultrafiltration (UF) membranes, nanofiltration (NF) membranes, reverse osmosis (RO) membranes, ) Film. The separation membrane is also divided into a polymer organic film and an inorganic film such as ceramic or metal depending on the material. A separation membrane module (or membrane module) configured to be capable of solid-liquid separation by providing a separation membrane in a predetermined housing can be classified into a tubular, a hollow fiber, a spiral wavy, and a plate- Frame, and a rotary disk.

These membranes have innumerable micropores, that is, membrane pores. Therefore, contaminants contained in the raw water are either removed by the separation membrane or accumulated on the surface of the separation membrane when it is passed through or adsorbed in the separation membrane surface or pores to cause membrane contamination. If membrane contamination occurs, the membrane surface is covered by contaminant accumulation during filtration, membrane pores are reduced or clogged, and the permeation flux and performance of raw water are lowered. Therefore, the membrane should be periodically cleaned during filtration to restore the performance of the membrane do.

Methods for cleaning the membrane can be divided into physical washing and chemical washing. A typical method of dual physical cleaning is exemplified by backwash using water and is a method of removing materials accumulated on the membrane surface or membrane pores by passing the produced water through the membrane by pressurizing in the direction opposite to the filtration direction.

The general backwash process takes a relatively short time, such as several tens of seconds, compared to the long filtration process which takes several tens of minutes, and it is necessary to maintain the normal backwash flow rate and backwash duration constant except for the driving time of the backwash pump for the initial several seconds More important than anything else. However, since backwashing may not be effective due to the degree of contamination of the membrane in the backwash process and thus the performance of the backwash pump, development of a membrane washing system and a membrane washing method capable of optimizing backwash flow rate and backwash duration It is urgent.

An object of the present invention is to provide a separation membrane cleaning system capable of controlling backwash flow rate in the backwash preparation stage and controlling backwash time in the backwash continuous stage to improve backwash efficiency and a separation membrane cleaning method using the same.

It is another object of the present invention to provide a separation membrane cleaning system which can more efficiently and economically clean a separation membrane in consideration of membrane fouling characteristics of the separation membrane, and a separation membrane cleaning method using the same.

It is still another object of the present invention to provide a separation membrane cleaning system and a separation membrane cleaning method using the same that minimize the amount of water to be treated and the amount of energy consumed during backwashing.

The above and other objects of the present invention can be achieved by the present invention described below.

One aspect of the present invention relates to a membrane cleaning system, wherein the membrane cleaning system comprises a membrane filtration tank having a membrane; A treatment water tank for storing a part of the treated water produced from the membrane filtration tank and discharging treated water during backwashing; And a control unit for controlling the backwashing flow rate and backwash time, wherein the treated water is stored in the treatment water tank through the first pipe and the second pipe branched from the first pipe, and the treated water stored in the treatment water tank is stored in the treatment water tank The third pipe communicating with the first pipe, the first pipe, and the separation membrane, and the control unit maintains the operation condition when the flow rate measured from the flow meter installed in the third pipe reaches the set flow rate So that the backwash can be continued for the set time.

The backwash includes a backwash preparation stage and a backwash continuous stage, and the control unit controls the backwash flow rate in the backwash preparation and controls the backwash time in the backwash continuous stage.

If the flow rate measured in the backwashing preparation step is less than the set flow rate, the controller can control the flow rate so as to reach the set flow rate within the set time.

The separation membrane may be an immersion type separation membrane.

The first pipe may be provided with a production water pump, and the third pipe may be provided with a backwash pump.

The third piping further includes a pressure gauge, and the information of the pressure gauge may be transmitted to the control unit.

One or more of the first to third pipelines may be provided with an on-off valve so that the on / off operation thereof can be controlled by the control unit.

Another aspect of the present invention is a method for treating a membrane filtration tank, comprising the steps of: storing a part of treated water in a membrane filtration tank in a treatment tank and discharging the remainder to the outside; Stopping the membrane filtration; Transporting the treated water stored in the treated water tank for backwashing to the membrane filtration tank via the separation membrane; A backwashing preparation step of controlling the flow rate of the treated water conveyed to the membrane filtration tank; And a backwash lasting step of controlling the backwash time while maintaining the operating conditions upon reaching the set flow rate.

If the flow rate measured in the backwashing preparation step is less than the set flow rate, the flow rate can be controlled so as to reach the set flow rate within the set time.

The treated water can be stored in the treated water tank by the produced water pump or taken out to the outside.

The treated water stored in the treatment water tank can be returned to the membrane filtration tank via the separation membrane by the backwash pump.

The separation membrane cleaning system of the present invention and the separation membrane cleaning method using the same can control the backwash flow rate in the backwash preparation stage and improve the backwash efficiency by controlling the backwash time in the backwash continuous stage, Can be minimized.

1 is a conceptual view schematically showing a separation membrane cleaning system according to one embodiment of the present invention.
FIG. 2 is a conceptual diagram schematically showing a filtration process of a membrane cleaning system according to an embodiment of the present invention.
3 is a conceptual diagram schematically showing a backwashing process of the membrane cleaning system according to one embodiment of the present invention.
4 is a graph showing the flow rate according to the backwashing time in the normal backwash according to one embodiment of the present invention.
FIG. 5 is a graph showing the backwash water flow rate according to the backwash time during the abnormal backwashing.
FIG. 6 is a graph showing the flow rate according to the backwashing time in the normal backwash according to another embodiment of the present invention. FIG.

Embodiments of the present application will now be described in more detail with reference to the accompanying drawings. However, the techniques disclosed in the present application are not limited to the embodiments described herein but may be embodied in other forms. It should be understood, however, that the embodiments disclosed herein are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. In the drawings, the width, thickness, and the like of the components are enlarged in order to clearly illustrate the components of each device. In addition, although only a part of the components is shown for convenience of explanation, those skilled in the art can easily grasp the rest of the components. It is to be understood that when an element is described above as being located above or below another element, it is to be understood that the element may be directly on or under another element, It means that it can be done. It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit and scope of the invention. In the drawings, the same reference numerals denote substantially the same elements.

Membrane cleaning system

1 schematically shows a conceptual diagram of a separation membrane cleaning system according to one embodiment of the present invention. 1, the membrane cleaning system includes a membrane filtration tank 100; A treatment water tank 200 for storing a part of the treated water produced from the membrane filtration tank and discharging treated water during backwashing; And a controller 300 for controlling the backwash flow rate and backwash time.

The membrane filtration tank is provided with a separation membrane 110, and the separation membrane 110 may be an immersion type separation membrane. The treated water filtered in the separation membrane in the membrane filtration tank can be discharged to the outside through the first pipeline L1 connected to the collection section of the separation membrane 110 by the suction pressure of the production water pump P1, L1 via the second pipe L2 branched from the second pipe L2. The valves V1 and V2 may be provided before and after the production water pump P1 on the first pipe L1 and the valve V3 may be provided on the second pipe L2. The treatment water tank 200 and the first pipe L1 may communicate with each other through the third pipe L2 in order to use the treated water transported and stored in the treatment water tank 200 as backwash water. A backwash pump P2, a flow meter FS, and a valve V4 may be further provided on the third pipe L2, and a pressure gauge PS may further be provided. The information of the flowmeter FS and the pressure gauge PS can be transmitted to the control unit.

The membrane cleaning system may include a controller 300 to control backwash flow rate and backwash time. In the present invention, the backwash includes the backwash preparation stage and the backwash continuous stage, and the controller 300 controls the backwash flow rate in the backwash preparation stage and controls the backwash time in the backwash continuous stage.

If the flow rate measured in the backwashing preparation step is less than the set flow rate, the control unit 300 can control the flow rate to reach the set flow rate within the set time.

For example, the control unit 300 may monitor the flow rate measured by the flow meter FS provided on the third pipe, increase the output of the backwash pump P2 to increase the backwash flow rate when the flow rate is less than the set flow rate, The backwash can be maintained for the set time by maintaining the operating condition.

2 is a conceptual view schematically showing the filtration process of the membrane cleaning system. Hereinafter, unless otherwise stated, valves other than open valves shall be considered closed.

Referring to FIG. 2, when the valves V1 and V2 are opened and the production water pump P1 is operated, the raw water can be filtered by the separation membrane 100 by the suction pressure of the production water pump and can be produced as treated water. The filtered treated water can be discharged to the outside via the first pipe. In addition, when the valves V1 and V3 are opened and the production water pump P1 is operated, the produced treated water can be transferred to and stored in the treated water tank 200, and the stored treated water can be used as a backwash water .

3 is a conceptual diagram schematically showing a backwashing process of the membrane cleaning system. The treated water stored in the treated water tank 200 can be transported in the order of the third pipe L3, the first pipe L1 and the separation membrane 110 when the valve V4 is opened and the backwash pump P2 is operated, It can be used as stationary water.

Separation membrane cleaning method

The separation membrane cleaning method of the present invention comprises the steps of: storing a part of treated water in a membrane filtration tank in a treatment tank and discharging the remainder to the outside; Stopping the membrane filtration; Transporting the treated water stored in the treated water tank for backwashing to the membrane filtration tank via the separation membrane; A backwashing preparation step of controlling the flow rate of the treated water conveyed to the membrane filtration tank; And a backwash lasting step of controlling the backwash time while maintaining the operating condition upon reaching the set flow rate.

In the present invention, the backwashing preparation step may be defined as a process until the set flow rate after the backwash pump operation is reached. In the backwash maintenance step, the backwashing is continued for the set time while maintaining the operating condition after reaching the set flow rate Can be defined.

4 is a graph showing the reverse water flow rate according to the backwash time of the normal backwash according to one embodiment of the present invention. Referring to Fig. 4, the normal backwash may include backwashing preparation step (A-1) and backwash continuous step (A-2). As a specific example, the normal backwashing step of FIG. 4 stops production and operates the backwash pump. Then, the flow rate measured from the flow meter FS is monitored to increase the output of the backwash pump when the flow rate is less than the set flow rate K It is possible to increase the backwash flow rate and to control the flow rate so as to reach the set flow rate K within the set time. Referring back to FIG. 4, after the backwash pump is turned on, the output is increased to reach the set flow rate K in 10 seconds after starting the backwash, and the backwash continues for the set time (20 seconds) have.

On the other hand, FIG. 5 is a graph showing the reverse water flow rate according to the backwash time of the abnormal backwash. Referring to FIG. 5, it can be seen that the abnormal backwashing has a high contamination degree of the separation membrane, and the time required for reaching the set flow rate K in the backwashing preparation step (B-1) is excessively long. As shown in FIG. 4, in case of normal backwash, the set flow rate (K) is reached in 10 seconds through the flow control after the backwash start. In the case of the abnormal backwash, the pump output and backwash pressure are controlled for the flow control (K) which is less than the set flow rate (K) after 10 seconds has elapsed and the time to reach the set flow rate K is extended by 10 seconds from the backwashing preparation step of the normal backwash, Resulting in shorter time. If the time required for the backwashing preparation step is prolonged and the duration of the backwash continuation step is shortened as described above, the energy cost and the overall backwash efficiency may be lowered when the backwash pump is operated.

6 is a graph showing a flow rate with time to explain a separation membrane cleaning method according to another embodiment of the present invention.

6, the set flow rate is set to K in the backwashing preparation step, but the flow rate is not controlled in the backwashing preparation step (C-1) in the same manner as the backwashing preparation step in the abnormal backwashing, And reached the set flow rate K only after 20 seconds had elapsed. However, after reaching the set flow rate K, the backwash duration of the backwash continuous stage (C-2) was controlled to obtain the desired backwash duration of 20 seconds, which resulted in the desired backwash.

Example

In the following Examples 1-2 and Comparative Example 1, the degree of contamination of the membrane before backwashing is the same, and the set flow rate in the backwashing preparation step is 30 L / m 2 / hr.

Example  One

After stopping the production, the backwash pump was operated to control the flow rate to reach the set flow rate for the set time (10 seconds) in the backwash preliminary stage and to maintain the operating condition for the set time (20 seconds) Respectively. The time required in each step, the amount of backwashed water, the required power, and the backwash degree are shown in Table 1 below.

Example  2

After the production was stopped, the backwash pump was operated and the backwash preparation stage was performed until the set flow rate was reached. After the set flow rate was reached, the backwash continuous stage was performed by maintaining the operating condition for the set time (20 seconds). The time required in each step, the amount of backwashed water, the required power, and the backwash degree are shown in Table 1 below.

Comparative Example  One

After the production was stopped, the backwash pump was operated to perform the backwash preparation step until the set flow rate was reached without controlling the flow rate, and the backwash continuous step was performed by maintaining the operating conditions when the set flow rate was reached. The time required for each step is shown in Table 1, and the amount of backwashed water, the required power, and the backwash degree are shown in Table 1 below.

Condition duration
(sec) Station water usage
(L) Backward electricity consumption
(Wh) Backwash effect Example 1 Stage Preparation Stage 10 2.5 0.33 ○ Stage of backwash lasting 20 5.0 0.67 Sum 30 7.5 1.00 Example 2 Stage Preparation Stage 20 5.0 0.67 ○ Stage of backwash lasting 20 5.0 0.67 Sum 40 10.0 1.33 Comparative Example 1 Stage Preparation Stage 20 5.0 0.67 × Stage of backwash lasting 10 2.5 0.33 Sum 30 7.5 1.00

* Back-pressure required Power measurement condition: Power consumption of backwash pump (pilot) based on 120W

* Backwash effect: Good (○), poor (X)

As can be seen from the results of Table 1, in Example 1, in which the duration was controlled in the flow rate and backwash continuous stage in the backwashing preparation stage, and in Example 2, in which the duration was controlled in the backwash continuous stage, It can be seen that the backwash effect is superior to that of Example 1.

It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims. As will be understood by those skilled in the art. It is to be understood, therefore, that the embodiments described above are intended to be illustrative in all respects and not restrictive.

Claims (11)

Membrane filtration with membrane;
A treatment water tank for storing a part of the treated water produced from the membrane filtration tank and discharging treated water during backwashing; And
And a controller for controlling the backwash flow rate and backwash time,
The treated water is stored in the treatment water tank through the first pipe and the second pipe branched from the first pipe,
The treated water stored in the treated water tank is returned to the membrane filtration tank via the third pipe, the first pipe, and the separation membrane that communicate the treatment water tank and the first pipe,
Wherein the control unit maintains the operating condition and continues backwashing for a set time when the flow rate measured from the flow meter installed in the third pipe reaches the set flow rate.
The method according to claim 1,
The backwash comprises a backwash preparation step and a backwash continuous phase,
The control unit controls the backwashing flow rate in the backwashing preparation step,
And the backwash time is controlled in the backwash continuous stage.
3. The method of claim 2,
If the flow rate measured in the backwashing preparation step is less than the set flow rate
Wherein the control unit controls the flow rate so as to reach the set flow rate within the set time.
The method according to claim 1,
Wherein the separation membrane is an immersion type separation membrane.
The method according to claim 1,
The first pipe is provided with a production water pump,
Wherein the third pipe is provided with a backwash pump.
The method according to claim 1,
Wherein the third pipe further comprises a pressure gauge, and the information of the pressure gauge is transmitted to the control unit.
7. The method according to any one of claims 1 to 6,
Wherein at least one of the first pipe to the third pipe is provided with an opening / closing valve, and the opening / closing is controlled by the control unit.
Storing a part of the treated water of the membrane filtration tank in the treated water tank and discharging the remainder to the outside;
Stopping the membrane filtration;
Transporting the treated water stored in the treated water tank for backwashing to the membrane filtration tank via the separation membrane;
A backwashing preparation step of controlling the flow rate of the treated water conveyed to the membrane filtration tank; And
And a backwash duration step of controlling the backwash time while maintaining the operating conditions when the set flow rate is reached.
9. The method of claim 8,
If the flow rate measured in the backwashing preparation step is less than the set flow rate,
And the flow rate is controlled so as to reach the set flow rate within the set time.
9. The method of claim 8,
Wherein the treated water is stored in a treated water tank by the production water pump or is carried out to the outside.
11. The method of claim 10,
And the treated water stored in the treated water tank is conveyed to the membrane filtration tank via the separation membrane by the backwash pump.

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