JPH0217924A - Method for backwashing hollow yarn membrane filter apparatus - Google Patents

Abstract

PURPOSE:To enhance washing capacity by inserting a process for preliminarily discharging a part of the liquid to be treated in a filter chamber between a process for temporarily interrupting the flow of the liquid to be treated and a process for pressurizing a treatment chamber. CONSTITUTION:Hollow yarn membrane modules 9 are suspended from the partition plate 21 for partitioning a hermetically closed container main body 5 into an upper treatment chamber 11 and a lower filter chamber 7, and a liquid to be treated is passed through the hollow yarn membranes 51 of said modules 9 and allowed to flow from the filter chamber 7 to the treatment chamber 11 to be filtered. The flow of the liquid to be treated of this hollow yarn membrane filter apparatus 1 is temporarily stopped and the liquid to be treated is allowed to flow back while the content of the filter chamber 7 is discharged from the overflow pipe 27 provided to the filter chamber 7 by pressing the treatment chamber 11 to backwash the hollow yarn membranes 51 to regenerate the same. In this case, a process for preliminarily discharging a part of the liquid to be treated of the filter chamber 7 is inserted between a process for temporarily interrupting the flow of the liquid to be treated and a process for pressurizing the treatment chamber 11. As a result, the sufficient flow passage of a liquid and a sufficient flow passage area at the time of backwashing are secured to enhance washing capacity.

Description

Detailed Description of the Invention [Objective of the Invention] (Industrial Application Field) This invention relates to a hollow fiber used for radioactive waste liquid treatment in nuclear power plants or reprocessing plants, or double water purification in nuclear or thermal power plants. The present invention relates to a method for backwashing a membrane filtration device, and more particularly to a method for backwashing a hollow fiber membrane filtration device that enables effective backwashing of a hollow fiber membrane filter with a treatment liquid.

(Prior Art) As is well known, a hollow fiber membrane filtration device is a filtration device that uses a hollow fiber membrane made of a polymeric material in the form of fibers as a filter element. Hollow fiber membrane filters have features such as being able to efficiently capture fine particulate insoluble contaminants and being reusable by backwashing, and are used in various liquid processing equipment. In the case of a hollow fiber membrane filtration device used in large-scale equipment such as a nuclear power plant, a hollow fiber membrane module 9 is used as a filter element by bundling and folding a large number of hollow fibers 51 shown in FIG. It is used.

Generally, in nuclear power plants, the generation of corrosion products is suppressed and removed as radiation reduction measures. Corrosion products are removed, for example, by using a hollow fiber membrane filtration device to separate and remove suspended matter present in radioactive waste liquid generated in a nuclear power plant or in the complex water of a nuclear reactor condensate system.

FIG. 6 is a sectional view showing an example of a conventional hollow fiber membrane filtration device (hereinafter referred to as a first conventional example).

In order to filter waste liquid (liquid to be treated) using this hollow fiber membrane filtration device 1, the waste liquid is supplied from the waste liquid supply pipe 3 to the filtration chamber 7 of the container body 5. The supplied waste liquid is filtered by the hollow fiber membrane of each hollow fiber membrane module 9 and guided to the processing chamber 11 through each hollow fiber. The processed liquid (processing liquid) guided into the processing chamber 11 is sent to the outside from the processing liquid discharge pipe 13.

As the filtration function of the hollow fiber membrane progresses, the filtration function gradually decreases, so backwashing must be performed periodically.

As a method for backwashing and regenerating the hollow fiber membrane module, there is a method of backwashing the hollow fiber membrane module using a treatment liquid, as described in, for example, Japanese Patent Laid-Open No. 19002/1983. This backwashing method will be explained using the configuration shown in FIG. That is, during this backwashing process, the supply of the liquid to be processed is stopped, pressurized gas is supplied from the process liquid discharge pipe 13 to the process chamber 11, and the inside of the process chamber 11 is pressurized. This pressurization causes the processing liquid to flow backwards, ejecting the processing liquid from the inside of the hollow fiber to the outside, and removing suspended matter adhering to the outer periphery of the hollow fiber. The removed suspended matter settles at the bottom of the filtration chamber 7.

When pressurized air is applied, air bubbles are simultaneously ejected from the bubbling pipe 15, and the air bubbles vibrate the hollow fibers, thereby smoothly removing suspended matter such as crud.

Due to this backwashing action, the filter function of the hollow fiber membranes of each hollow fiber membrane module 9 is restored.

During backwashing, the processing liquid in the processing chamber 11 flows back into the filtration chamber 7 through the hollow fibers, so that the excess processing liquid and waste liquid in the filtration chamber 7 are discharged from the overflow pipe 17. At the same time, the air supplied from the bubbling pipe 15 into the filtration chamber 7 is also discharged to the outside via the overflow pipe 17.

In addition, after the backwashing is completed, the waste liquid in the filtration chamber 7 is concentrated due to sedimentation of suspended matter.

The concentrated waste liquid is discharged from the discharge pipe 19.

Thereafter, the waste liquid is introduced again from the waste liquid supply pipe 3, the filtration chamber 7 is filled with the waste liquid, and the process moves to the filtration process. At this time, since it is difficult for air to pass through the hollow fibers of the hollow fiber membrane module 9, the air in the filtration chamber 7 is discharged from the overflow pipe 17 as the liquid level of the waste liquid rises. However, since the overflow pipe 17 is installed at a certain distance from the partition plate 21 that separates the filtration chamber 7 and the processing chamber 11,
After the waste liquid supply into the filtration chamber 7 is completed and before the filtration process is started, air will remain in the upper part of the filtration chamber 7. Therefore, the hollow fiber membrane module 9 has a part that comes into contact with the residual air 23, and this contact part does not contribute to the filtration process, so the effective membrane area of the hollow fiber membrane module 9 decreases and the filtration There is a problem that the rate of movement decreases. Further, since the hollow fiber membrane module 9 comes into contact with the residual air 23, there is a possibility that the hollow fibers that have come into contact with the residual air 23 may deteriorate.

Therefore, as shown in FIG. 7, a conventional system has been proposed in which a flow path 25 is formed in a partition plate 21 and an overflow pipe 26 is connected to this flow path 25 (hereinafter referred to as a second conventional example). In addition, as shown in FIG. 8, the overflow pipe 2
7 upwards in the filtration chamber 7.

Opening 2 of overflow pipe 27 located in filtration chamber 7
4 is located above the lower end of the binding part 28 of the hollow fiber membrane module 9 (hereinafter referred to as the third conventional example). Furthermore, as shown in FIG. 9, the overflow pipe in the first conventional example A weir plate 29 is installed so as to surround the opening in the 17 filtration chambers 7, and the upper end 30 of this weir plate 29 is positioned at the lower end of the binding part 28 of the hollow fiber membrane module 9 (hereinafter referred to as the fourth conventional example). ).

According to the second conventional example shown in FIG. 7, the level of waste liquid in the filtration chamber 7 immediately before the start of backwashing can be raised until it touches the partition plate 21, and the air in the filtration chamber 7 can be purged. Therefore, the hollow fiber membranes of the hollow fiber membrane module 9 can be completely immersed in the waste liquid. Also, Figures 8 and 9
Even in the case of the third and fourth conventional examples shown in the figure, the waste liquid level in the filtration chamber 7 immediately before the start of backwashing is
Since the hollow fibers of the hollow fiber membrane module 9 can be completely immersed in the waste liquid, the hollow fibers of the hollow fiber membrane module 9 can be completely immersed in the waste liquid. Therefore, in the case of these second to fourth conventional examples, it is possible to improve the filtration rate of the hollow fiber membrane module 9 and prevent deterioration of the hollow fibers. Note that the second to fourth conventional examples are disclosed in Japanese Patent Application Laid-open No. 1983
Published in Publication No.-293505.

However, in the second to fourth conventional examples, there is no problem when the number of hollow fiber membrane modules 9 is small, but when the number of hollow fiber membrane modules 9 increases, waste liquid and processing liquid during backwashing In addition, in consideration of the amount of air discharged, it is necessary to increase the diameter of the overflow pipes 26, 27, 17 or increase the number of overflow pipes. However, in the case of the second conventional example shown in FIG. 7, there is a limit to the expansion of the diameters of the overflow pipe 26 and the flow path 25 due to restrictions on the thickness of the partition plate 21. Therefore, there is a problem that a sufficiently large flow path cannot be secured, and the backwash flow rate required to obtain the required backwash performance cannot be obtained, resulting in a decrease in the backwash performance.

In addition, in the case of the third and fourth conventional examples shown in FIGS. 8 and 9, the distance between the end of the opening 24 of the overflow pipe 27 or the upper end 30 of the weir 29 and the partition plate 21 is set to 61.
If the distance between the lower end of the binding portion 28 of the hollow fiber membrane module 9 and the lower surface of the partition plate 21 is 62, then there is a relationship of δ□<δ2. In addition, when the number of hollow fiber membrane modules 9 is large,
Accordingly, for example, the overflow pipe 2 of the third conventional example
Even if the diameter of the opening 7 is increased to a certain extent, the circumference of the opening 24 will not become so long.
Then, it is expressed as A□=πDδ1. Further, the flow velocity v1 of the fluid flowing through the opening 24 of the overflow pipe 27 is expressed as V=Q/A, where Q is the required flow rate during backwashing. Furthermore, fluid resistance is proportional to the square of the flow velocity.

Therefore, from these reasons, if the distance δ1 is small, the fluid flow path area A1 during backwashing will be insufficient, and therefore the flow velocity v0 will increase and the fluid resistance will increase. As a result of this increase in fluid resistance during backwashing, backwashing of the hollow fiber membrane becomes insufficient, resulting in the inconvenience that the filtration differential pressure is not sufficiently recovered even by backwashing treatment. Such inconveniences also apply to the fourth conventional example.

Figure 11 shows the quantitative determination of an aqueous solution (flow rate 40rd/h, temperature 30°C) containing a mixture of ferric oxide and amorphous iron using a hollow fiber membrane having a surface area of 500 in the third conventional example (Figure 8). These are the test results when filtered. The horizontal axis of the figure is the total amount of undissolved solids captured by the hollow fiber membrane expressed in unit membrane area (g/rrf), and the vertical axis is the filtration differential pressure (inside the waste liquid supply pipe 3 and the treated liquid discharge pressure difference with the inside of the pipe 13). From this graph, we can see that the filtration differential pressure cannot be recovered sufficiently even with backwashing treatment, and especially as the number of backwashing increases, the filtration differential pressure rises rapidly, and as the number of backwashing increases, the backwashing performance cannot be recovered. It turns out that.

In order to prevent such a decline in recovery of backwash performance in the third and fourth conventional examples, these overflow pipes 27.1
It has also been proposed to increase the diameter of 7 or increase the number thereof. However, if the diameter of the overflow pipe 27.17 is increased beyond a certain level, the hole diameter of the penetrating portion of the closed container 5 becomes large, and the strength of the closed container 5 decreases. Furthermore, an increase in the number of overflow pipes 27, 17 is undesirable because it complicates the piping layout connected to the closed container 5.

Furthermore, in the case of the fourth conventional example, undissolved solid content accumulates within the weir plate 29, and especially when this is applied to a nuclear power plant, this undissolved solid content causes an increase in the radiation dose and maintenance The radiation exposure of workers at the time was increasing.

(Problems to be Solved by the Invention) As described above, in the second conventional example, the hollow fiber membrane module 9
Even if the number of overflow pipes 2 increases,
6 and the diameter of the flow path 25 cannot be enlarged, and as a result, a sufficient flow path cannot be ensured, and there is a possibility that the cleaning performance will deteriorate. Further, in the case of the third and fourth conventional examples, since δ1 and δ2 are smaller than δ2, there is a possibility that the fluid flow path area is insufficient, the fluid resistance increases, and the backwash performance deteriorates.

This invention was made in order to solve the above-mentioned problems, and it ensures a sufficient flow path for liquid during backwashing,
Another object of the present invention is to provide a method for backwashing a hollow fiber membrane filtration device, which can secure a sufficient flow path area and improve cleaning performance.

[Structure of the invention]

(Means for Solving the Problems) In the present invention, a hollow fiber membrane of a hollow fiber membrane module vertically installed on a partition plate that partitions a sealed container main body into a processing chamber and a filtration chamber vertically is passed through. The flow of the liquid to be treated in the hollow fiber membrane filtration device, which filters the liquid by flowing it from the filtration chamber to the processing chamber, is temporarily interrupted, the treatment chamber is pressurized, and the process is carried out from the overflow pipe installed in the filtration chamber. In the backwash method for hollow fiber membrane filtration equipment, in which the liquid to be treated flows backward while discharging the contents of the filtration chamber, and the hollow fiber membrane is washed and regenerated, the process of temporarily interrupting the flow of the liquid to be treated and the treatment chamber are performed. A step of previously discharging a portion of the liquid to be treated in the filtration chamber was inserted between the pressurizing step.

(Function) When the processing chamber is pressurized for backwashing and the liquid to be treated passes through the hollow fiber membrane and is ejected into the filtration chamber, a part of the liquid to be treated in the filtration chamber is discharged in advance and flows into the filtration chamber. Since an air layer is formed in the overflow pipe, this air is discharged from the overflow pipe. The fluid resistance of air is much smaller than that of liquids, so there is no large pressure drop in the overflow pipe, and the linear flow rate when the liquid to be treated passes through the hollow fiber membrane can be kept high enough. The thread membrane is efficiently backwashed and regenerated.

(Embodiment) An embodiment of the present invention will be described below with reference to FIGS. 1 to 4. In FIGS. 1 to 4, the configuration of the hollow fiber membrane filtration device 1 is the same as that shown in FIG. 6 above, except that the overflow tube is replaced with the overflow tube 27 shown in FIG. Components are shown in Figures 6 and 8.
The same reference numerals as those shown in the drawings are used to omit their explanation.

In FIG. 1, the filtration process is carried out by supplying waste liquid from a waste liquid supply pipe 3 to a filtration chamber 7.

When the supplied waste liquid passes through the hollow fibers 51 of the hollow fiber membrane module 9 disposed in the filtration chamber 7, fine particles in the waste liquid are captured on the membrane surface of the hollow fibers 51 and separated and removed. .

The clear processing liquid from which fine particles have been removed and filtered passes through the hollow fibers 51 of the hollow fiber membrane module 9 and flows into the upper processing chamber 11 . And the processing liquid.

From this processing chamber 11, the processing liquid is sent to the outside, such as a reactor supply water system, through a discharge pipe 13.

As the waste liquid filtration process progresses, fine particles adhere to the membrane surface of the hollow fiber 51 and block the fine permeation pores of the hollow fiber membrane, so that the filtration pressure difference gradually increases. When the filtration differential pressure rises above a certain pressure, the following backwashing process is performed to restore the filtration function of the hollow fiber membrane.

First, a valve (not shown) attached to a pipe connected to the waste liquid supply pipe 3 and the processing liquid discharge pipe 13 is closed to stop the supply of waste liquid. Next, a valve (not shown) connected to the overflow pipe 27 is opened to open the inside of the container body 5 to atmospheric pressure. Thereafter, as shown in FIG. 2, a portion of the waste liquid in the filtration chamber 7 is discharged through the concentrated waste liquid discharge pipe 19. The discharge amount is preferably about the same as the volume inside the processing chamber 11. The discharge amount is controlled by a liquid level needle (not shown). Alternatively, the opening and closing times of the valve of the concentrated waste liquid discharge pipe 19 can be set using a timer. By discharging a portion of the waste liquid, an air layer 33 is formed within the filtration chamber 7.

After this, proceed to the next step immediately.

In the next step, as shown in FIG. 3, pressurized gas is supplied from the processing liquid discharge pipe 13 to the processing chamber 11 to pressurize the inside of the processing chamber 11. Due to this pressurization, the processing liquid flows backward, and the suspended matter is transferred to the hollow fiber 5.
From 1 it will be deleted. Since the amount of water in the filtration chamber 7 naturally increases due to backwashing, the upper air layer 33 is pressurized, but this air is discharged through the overflow pipe 27.

Next, as shown in FIG. 4, after all of the processing liquid in the processing chamber 11 has flowed back, bubbles are ejected from the bubbling tube 15, the hollow fibers are vibrated, and the suspended matter is sieved off.

The fine particles removed from the hollow fiber membrane module 9 are stored at the bottom of the container body 5, but the concentrated waste liquid containing these fine particles is discharged to the outside through the concentrated waste liquid discharge pipe 19 after the backwashing process is completed. .

Thereafter, the waste liquid is introduced again from the waste liquid supply pipe to fill the filtration chamber 7 with the waste liquid, and the process moves to the filtration process.

According to the embodiment described above, the following effects are produced.

■ The fluid passing through the overflow pipe 27 during backwashing becomes gas instead of liquid, so there is no pressure loss due to the overflow pipe 27, and a sufficient fluid flow rate during backwashing can be secured, so backwashing performance can be improved. .

In order to clarify this using specific numerical values, a hollow fiber membrane filtration device 1 using 50 hollow fiber membrane modules 9 will be considered as an example.

In this case, the flow rate Q of backwashing required to obtain proper backwashing performance is 0.03 m/s according to an experiment.

For example, overflow pipe 2 with an inner diameter of 102.3m+n
7, and in order to prevent deterioration of the hollow fibers 51 of the hollow fiber membrane module 9, for example, if the distance δ1 from the upper end of the overflow pipe z7 to the lower end of the partition plate 21 is set to 15, the distance between the overflow pipe 27 during backwashing is Flow path area A of the opening
is expressed as A = πDδ, where D is the inner diameter of the tip of the opening. Further, at this time, the flow velocity V of the fluid flowing over the tip of the opening is represented by (1), =n. From these facts, A=πDδ, = πx 102.3 x 15= 482
0 m+" = 6.2 Il/s. In other words, in order to perform proper backwashing,
It is necessary to flow the fluid through a narrow gap of 15 m above the opening of the overflow pipe 27 at a speed of 6 m+/s or more. Flowing liquid under these conditions causes extremely large pressure loss and fluid vibration.

This is difficult to realize as it may cause erosion.

However, in this embodiment, the fluid flowing through the overflow pipe 27 during backwashing is gas, and in the case of gas, the flow velocity of 6 m/s is about the same as a breeze, and the pressure loss is small, so it is possible to obtain an appropriate backwash flow rate. I can do it.

Looking further at the flow velocity ratio between gas and liquid fluids, it is generally known that the pressure loss ΔP of the fluid is proportional to the density ρ of the fluid and proportional to the square of the flow velocity V. Therefore, when backwashing is performed by adding pressurized air at the same pressure using the conventional backwashing method (subscript 1) and the backwashing method of the present invention (subscript 2), the density of water ρ□=1000 (kg
/Bo), the density of air, ρ, = 1.293 (kg/Bo), so if ΔP = ΔP2, then ρ, V' = ρ寞V2'' In other words, according to the present invention, the same pressure This allows for a flow rate of 28 times that of conventional methods.In reality, the pressure loss in the hollow fiber membrane filter is also added, so even if the same pressure is applied, a flow rate difference of 28 times cannot be obtained, but it is extremely effective for backwashing. It is clear that the flow velocity can be increased.

In other words, in this embodiment, since the fluid density is significantly lower than that of the conventional example, the fluid resistance can be reduced to about 1/800 of that of the conventional example. As a result, the hollow fibers 51 can be sufficiently backwashed.

As described above, in this embodiment, a sufficient flow rate during backwashing can be ensured, so that backwashing performance can be improved. As a result, it is also possible to extend the life of the hollow fiber membrane module 9.

FIG. 10 is a graph showing the test results of the quantitative filtration test of this example. In this test, the hollow fiber membrane surface area of the hollow fiber membrane module 9 was set to 500 mm, and an aqueous solution (flow rate 40 m/h, temperature 30° C.) was subjected to quantitative filtration. In the figure, the horizontal axis represents the total amount of undissolved solids captured by the hollow fiber membrane per unit membrane area (g/rrr), and the vertical axis represents the filtration differential pressure. According to this graph, the filtration differential pressure reliably decreases and recovers to the value at the start of use with each backwash, and the filtration differential pressure does not increase even if the number of backwashes increases. Therefore, the first
Comparing with Figure 1, it can be seen that the backwashing performance has improved dramatically.

■ It is possible to improve the filtration rate and prevent deterioration of hollow fibers.

That is, the liquid level of the waste liquid in the filtration chamber 7 is located further above the lower end of the binding part 28 of the hollow fiber membrane module 9 or on the same horizontal plane. Therefore, the entire hollow fiber 51 is immersed in the liquid.

Since the entire hollow fiber membrane module 9 can contribute to filtration, the effective membrane area can be expanded and the filtration rate can be improved. At the same time, since the upper end portions of the hollow fibers 51 do not come into contact with air, washing of the hollow fibers 51 can be prevented.

■ As mentioned above, since the pressure loss in the overflow pipe is reduced, the backwashing performance can be improved even if the diameter of the overflow pipe 27 is made small. The hole can be made small in diameter without causing a decrease in the strength of the container body 5, and accordingly, there is no need to reinforce the container body 5.

Furthermore, for the same reason, the number of overflow pipes 27 can be reduced, so the layout of the piping connected to the container body 5 can be simplified.

(a) In this embodiment, since the weir plate 29 as in the fourth conventional example (FIG. 9) is not used, a situation in which undissolved solid content is deposited in the weir plate 29 does not occur. Therefore, when this embodiment is applied to a nuclear power plant, the radiation dose of the hollow fiber membrane filtration device 1 is low, and the radiation exposure of workers during maintenance can be significantly reduced.

Furthermore, in the present invention, as shown in FIG. 5, a partial discharge pipe 35 is provided on the side wall of the filtration chamber 7 portion of the container body 5 at a position higher than the waste liquid supply pipe 3, so that a partial discharge pipe 35 is provided at a position higher than the waste liquid supply pipe 3, so that a partial discharge pipe 35 is provided in the side wall of the filtration chamber 7 portion of the container body 5. The partial discharge pipe 35 may be used to partially discharge the waste liquid.

According to this method, the amount of the air layer is automatically determined by the position of the partial discharge pipe 35, and the valve opening/closing device using a liquid level gauge or a timer, which was necessary in the above-described embodiment, becomes unnecessary. Note that the other functions and effects are exactly the same as those of the embodiment described above.

〔Effect of the invention〕

As explained above, according to the method for backwashing a hollow fiber membrane filtration device according to the present invention, backwashing is performed after forming an air layer in the filtration before starting backflow for backwashing. At times, the fluid flowing in the overflow pipe becomes a gas, and the pressure loss becomes sufficiently small, and the backwash flow rate can be increased, resulting in an effect that the backwash performance can be improved.

[Brief explanation of the drawing]

Figures 1 to 4 are longitudinal sectional views showing one embodiment of the present invention in the order of steps, Figure 5 is a sectional view showing another embodiment of the present invention, and Figure 6 is a diagram of a conventional hollow fiber membrane filtration device. A sectional view of a hollow fiber membrane filtration device for explaining the backwashing method, FIGS. 7 to 9 are enlarged sectional views of main parts of a conventional hollow fiber membrane filtration device, and FIG.
The figure is a line diagram for explaining the effect of one embodiment of the present invention, Figure 11 is a line diagram for explaining the effect of the conventional backwashing method for hollow fiber membrane filtration equipment, and Figure 12 is a line diagram for explaining the effect of the conventional hollow fiber membrane filtration device. It is a perspective view showing a module. 1... Hollow fiber membrane filtration device 5... Container body 7... Filtration chamber 9... Hollow fiber membrane module 11... Processing chamber 21... Partition plate 17, 26° 27... Overflow Pipe 51...Hollow fiber 35...Partial discharge pipe

Claims (1)

[Claims] 1. The liquid to be treated is filtered by passing through the hollow fiber membrane of a hollow fiber membrane module installed vertically on a partition plate that vertically divides the inside of the sealed container body into a processing chamber and a filtration chamber. Temporarily interrupting the flow of the liquid to be treated in a hollow fiber membrane filtration device that flows from the chamber to the treatment chamber to filter the liquid to be treated, pressurizing the treatment chamber and passing from an overflow pipe provided in the filtration chamber. causing the liquid to be treated to flow back while discharging the contents of the filtration chamber;
In the method for backwashing a hollow fiber membrane filtration device in which the hollow fiber membrane is backwashed and regenerated, between the step of temporarily interrupting the flow of the liquid to be treated and the step of pressurizing the processing chamber, A method for backwashing a hollow fiber membrane filtration device, characterized in that a step of previously discharging a portion of the liquid to be treated is inserted. 2. The liquid to be treated in the filtration chamber, which is partially discharged in advance, is discharged through a partial discharge pipe provided on a side wall of the filtration chamber portion of the container body. A method for backwashing a hollow fiber membrane filtration device according to item 1. 3. The hollow space according to claim 1, characterized in that the amount of the liquid to be treated in the filtration chamber from which a portion is discharged in advance is the same as the amount of the liquid to be treated that fills the processing chamber. Backwashing method for thread membrane filtration equipment.