JP2006255708A - Method for backwashing of hollow fiber membrane and hollow fiber membrane water treatment apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for backwashing of a hollow fiber membrane that can reduce the number of times of flash backwashing causative of lowered durability of the hollow fiber membrane and can reliably remove fouling components sticking to the hollow fiber membrane. <P>SOLUTION: In this method for backwashing, raw water containing suspended solids is supplied into a shell in a filtration module and is passed through a hollow fiber membrane installed within the shell to conduct filtration treatment. After this water passing step, deposits on the membrane surface and within the fiber layer in the hollow fiber membrane are removed. A blow backwashing step is provided for discharging substantially the whole quantity of concentrated water remaining on the shell side of the filtration module to the outside of the shell. The blow backwashing step is carried out by allowing both the shell side and the lumen side of the filtration module to undergo the supply of air. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a hollow fiber membrane backwash method and a hollow fiber membrane water treatment apparatus used for wastewater treatment, and is particularly suitable for water treatment when raw water contains a high concentration of suspended solids. Technology.

  Conventionally, a water treatment device using a hollow fiber membrane is known as a filtration element of a water treatment device that filters water containing suspended solids of 100 ppm or less, and is generally referred to as a “hollow fiber membrane water treatment device”. being called.

FIG. 5 is a configuration diagram showing a main part of a conventional hollow fiber membrane water treatment apparatus, in which raw water to be treated is guided to a raw water tank (not shown) and stored. The raw water in the raw water tank is guided to the circulation tank 3 through the pipe flow path 2. This circulation tank 3 is connected by a filtration module 10 to be described later and a raw water supply pipe P1 and a raw water return pipe P2, and a water circulation path is formed by the supply pipe P1 and the return pipe P2. .
As shown in FIG. 6, the filtration module 10 is provided with a large number of hollow fiber membranes 14 having both ends supported by partition plates 12 and 13 in a cylindrical shell 11. A raw water supply pipe P1 is connected to the side surface of the shell 11 to connect the circulating water inlet 15 for supplying the raw water before treatment into the shell 11, and a raw water return pipe P2 is connected to discharge the concentrated raw water from the shell 11. A circulating water outlet 16 is provided. Further, outflow outlets 17 and 18 of treated water that has passed through the hollow fiber membrane 14 are provided at both ends of the cylindrical shell 11.
The space inside the hollow fiber membrane formed inside the hollow fiber membrane 14 is generally called “lumen”.

  In the process in which the raw water supplied into the shell 11 of the filtration module 10 flows from the circulating water inlet 15 to the circulating water outlet 16, moisture excluding suspended substances passes through the hollow fiber membrane 14 and flows into the lumen. This treated water (purified water) flows through the lumen to reach the outflow outlets 17 and 18 of the treated water, and is further guided to the next process through the treated water pipe P3 connected to the outflow outlets 17 and 18. In addition, the flow volume of a treated water is suitably adjusted by the opening degree control of the flow control valve 4 provided in the treated water pipe P3.

When water treatment operation (hereinafter referred to as “water flow operation”) in which raw water is flowed in this manner and the suspended matter is removed by the hollow fiber membrane 14 is continued, filtration is performed on the surface of the hollow fiber membrane 14 and in the fiber layer. The suspended matter left after the treatment adheres and becomes dirty. This dirt causes an increase in the transmembrane pressure difference of the hollow fiber membrane 14, that is, the resistance of the treated water permeating through the hollow fiber membrane 14 is increased, resulting in a decrease in the amount of treated water or an increase in water flow power. Therefore, it is necessary to remove dirt by performing an operation generally called “backwash”.
For such backwashing operation, the following method is known. Usually, water passage operation is performed every several tens of minutes or several hours, for example, based on the characteristics of the suspended matter and the hollow fiber membrane 14. It is carried out alternately.

(1) Wash with back pressure using filtered treated water. That is, in the water flow operation, water is flowed from the shell side (outside of the hollow fiber membrane 14) to the lumen side, whereas cleaning is performed by flowing treated water from the opposite lumen side to the shell side.
(2) Back pressure washing with compressed air. That is, cleaning is performed by flowing compressed air from the lumen side to the shell side.
(3) Air bubbling is performed on the shell side to separate the deposits by vibration. That is, the deposits are washed by flowing a two-phase flow of liquid and air on the shell side.

Such backwashing is appropriately selected and combined in consideration of the properties and concentration of suspended substances contained in the raw water, the characteristics and life settings of the hollow fiber membrane 14, the operating conditions of the hollow fiber membrane water treatment device, and the like. It has been implemented.
In the following, an example of a backwash operation combining the above-described (2) and (3), that is, a backwash operation referred to as “flush backwash” will be briefly described with reference to FIGS. In addition, FIG. 7 is a graph which shows the relationship between the operation time of a horizontal axis, and the transmembrane differential pressure of a vertical axis | shaft as an operation example in the conventional hollow fiber membrane water treatment apparatus.

In this operation example, as raw water, a suspended substance concentration of about 10,000 mg / lit. The water drainage operation for 15 minutes and the backwash operation for 3 minutes are alternately repeated as one cycle. 8A shows the state during water flow operation, and FIG. 8B shows the state during flash backwash operation. The solid line in FIG. 8 indicates the flow of drainage and circulating water, and the alternate long and short dash line. The thick line shows the flow of treated water.
Here, the flash backwash operation will be briefly described. For example, compressed air of about 0.59 MPa is supplied into the lumen to pressurize it, and then the atmosphere is released to clean the membrane surface. Further, a series of two-phase flow cleaning is performed in which the circulation pump 5 is operated while supplying air, the drainage (raw water) is flown, the deposits are separated by vibration, and the single-phase flow cleaning is finally performed to rinse with water. This operation is called flush backwashing.

  That is, the dirt component adhering to the hollow fiber membrane 14 is pushed out by the compressed air supplied into the lumen and flows out to the shell side. This dirt component merges with the wastewater supplied into the shell by the operation of the circulation pump 5 together with the compressed air and the treated water, and flows along with the two-phase flow of gas and liquid flowing on the outer surface side of the hollow fiber membrane 14. For this reason, the dirt component adhering to the hollow fiber membrane 14 is also removed by air bubbling, and is collected into the circulation tank 3 through the drain return pipe P2.

  According to the one-cycle enlarged view of FIG. 7, the transmembrane pressure difference rises with an increase in water passage operation time. This indicates that the water flow resistance is increased because the suspended solids contained in the wastewater adhere to the surface of the hollow fiber membrane 14 and block the flow path through which the treated water permeates. Such water flow operation and backwash operation are repeated for a long time, so that the backwash effect is lowered, and the differential pressure gradually increases as a tendency. Therefore, for example, when the operating time reaches 750 hours, chemical washing is performed using chemicals such as acid and alkali, and measures are taken to restore the original differential pressure.

  In FIG. 8, reference numeral 8 in the figure is an SS densitometer that detects the concentration of suspended solids in the circulation tank 3. When this SS densitometer detects a high SS concentration of a predetermined value or more, a concentrated drain pipe The control valve 6 provided in the path P4 is opened to discharge high concentration concentrated waste water out of the circulation path. That is, since the concentration of suspended solids remaining on the shell side increases due to an increase in the treated water that has passed through the hollow fiber membrane 14, the control valve 6 is appropriately opened to drain out of the system.

Depending on the nature and concentration of the suspended matter contained in the raw water, there is a problem that long-term use becomes difficult by the above-described backwashing method.
For example, wastewater in a thermal power plant using coal or heavy oil as a fuel contains suspended solids at a high concentration (approximately 300 ppm or more). In such wastewater treatment, pores formed on the membrane surface of the hollow fiber membrane 14 are particularly likely to be clogged, and a decrease in the amount of treated water or an increase in water flow power is a problem with long-term use. . This is thought to be because the pores on the membrane surface are blocked by repeated backwashing (flush backwashing) due to the coexistence of high-concentration suspended matter.

  In addition, in the embodiment of FIG. 7, the flush back washing described above is performed every 15 minutes of water-flowing operation, and therefore is performed about 20000 to 30000 times per year, so that the membrane surface is damaged. The performance deteriorates, and the problem of deterioration in durability that the desired life cannot be satisfied arises.

  The present invention has been made in view of the above circumstances, and reduces the number of flush backwashing that causes a decrease in the durability of the hollow fiber membrane, and reliably removes dirt components adhering to the hollow fiber membrane. An object of the present invention is to provide a hollow fiber membrane backwashing method and a hollow fiber membrane water treatment device that can be used.

The present invention employs the following means in order to solve the above problems.
In the method for backwashing the hollow fiber membrane according to claim 1, the raw water containing the suspended substance is supplied into the shell of the filtration module, and the hollow fiber membrane installed in the shell is passed through to perform the filtration treatment. A hollow fiber membrane backwashing method for removing deposits in the membrane surface and fiber layer of the hollow fiber membrane after the water flow step, wherein substantially all of the concentrated water remaining on the shell side of the filtration module is removed from the shell. A blow backwashing step for discharging is provided, and the blow backwashing step is performed by receiving supply of air to both the shell side and the lumen side of the filtration module.

According to such a hollow fiber membrane backwashing method, a blow backwashing process for discharging the concentrated water remaining on the shell side of the filtration module to the outside of the shell is provided, which is preferable for maintaining the performance and durability of the hollow fiber membrane. It is possible to efficiently remove the soil components adhering to the hollow fiber membrane by minimizing the number of flush backwashing.
In the blow back washing process, since air is supplied to both the shell side and the lumen side of the filtration module, the remaining water can be drained out of the filtration module.
At this time, the air supplied into the lumen can flush the dirt component from the inside to the outside together with the water remaining in the lumen, thereby floating the dirt on the membrane surface.
In addition, the air supplied to the shell side discharges the waste water to the outside of the filtration module, and causes the dirt component that has floated to the membrane surface to flow out.

  In the backwashing method of the hollow fiber membrane according to claim 1, it is preferable to perform the flush backwashing step once after repeating the water flow step and the blow backwashing step a predetermined number of times, thereby minimizing Dirty components can be efficiently removed by the number of flush backwashes.

The hollow fiber membrane water treatment apparatus according to claim 3, wherein the hollow fiber membrane comprises a filtration module in which raw water containing suspended substances is filtered by passing through a hollow fiber membrane installed in the shell. In membrane water treatment equipment,
A blow backwash drainage path for draining substantially all of the concentrated water remaining on the shell side of the filtration module to the outside of the shell is provided, and the blow backwash drainage passage is configured to supply air to both the shell side and the lumen side of the filtration module. The condensed water is drained by receiving the supply.

According to such a hollow fiber membrane water treatment device, the blow backwash drainage path for draining the concentrated water remaining on the shell side of the filtration module to the outside of the shell is provided. Cleaning can be performed, and as a result, the number of times of flush backwashing can be minimized.
In addition, the blow backwash drainage path drains the concentrated water by supplying air to both the shell side and the lumen side of the filtration module, so the water remaining in the filtration module is drained outside the filtration module. can do.
At this time, the air supplied into the lumen can flush the dirt component from the inside to the outside together with the water remaining in the lumen, thereby floating the dirt on the membrane surface.
In addition, the air supplied to the shell side discharges the waste water to the outside of the filtration module, and causes the dirt component that has floated to the membrane surface to flow out.

  In the hollow fiber membrane water treatment device according to claim 3, it is preferable that the blow backwash drainage path is connected to the concentrated drainage pipe, thereby including a dirt component removed by blow backwashing. Blow effluent with higher suspended solids concentration than the raw water can be led to the concentrated drainage pipe and drained.

According to the hollow fiber membrane backwashing method and the hollow fiber membrane water treatment apparatus of the present invention, the following effects are obtained.
According to the first aspect of the present invention, there is provided a blow back washing process for discharging the concentrated water remaining on the shell side of the filtration module to the outside of the shell, and the blow back washing process is performed on both the shell side and the lumen side of the filtration module. Since the hollow fiber membrane backwashing method is performed by receiving air supply, the number of times of flush backwashing, which is undesirable for maintaining the performance and durability of the hollow fiber membrane, is minimized and adhered to the hollow fiber membrane. The dirt component can be efficiently removed, and the remarkable effect of ensuring the performance of the hollow fiber membrane and improving the durability can be obtained. The flash backwashing may be performed once after the blow backwashing process is performed a predetermined number of times (for example, about 5 to 20 times).

  According to the invention of claim 3, the blow backwash drainage path for draining the concentrated water remaining on the shell side of the filtration module to the outside of the shell is provided, and the blow backwash drainage channel is provided on the shell side and the lumen side of the filtration module. Since the hollow fiber membrane water treatment device that discharges the concentrated water by receiving air supply to both of them, blow back washing can be performed to wash the hollow fiber membrane, and as a result, flush reverse It is possible to minimize the number of washing operations. Therefore, it is possible to efficiently remove the dirt components adhering to the hollow fiber membrane by minimizing the number of flush backwashing, which is undesirable for the maintenance and durability of the hollow fiber membrane, and the performance of the hollow fiber membrane. The remarkable effect of ensuring the durability and improving the durability is obtained.

Hereinafter, an embodiment of a backwashing method of a hollow fiber membrane and a hollow fiber membrane water treatment device according to the present invention will be described with reference to the drawings.
As shown in FIG. 2, the hollow fiber membrane water treatment apparatus includes a circulation tank 3, a circulation pump 5, and a filtration module 10.

Raw water to be subjected to water treatment is led from a raw water generation source (not shown) to a raw water tank (not shown) and stored.
The raw water to be treated here is not particularly limited as long as it is water containing suspended solids, but is particularly suitable when the concentration of suspended solids contained in the raw water is a high concentration of 300 ppm or more. . Specific examples of raw water are diverse, such as water for use, electric power drainage, sewage, and industrial drainage (for example, chemical industry, steel industry, food manufacturing industry, paper and textile industry, etc.).

  Among these, as for electric power drainage, unsteady drainage of thermal power plants that use oil-fired boilers that use coal-fired boilers or heavy oil as fuel, specifically, electric dust collectors, air heaters, boilers, etc. were washed It is particularly effective for wastewater treatment. Such electric power drainage has a peculiar situation that solids containing fine ash water with fine particles are contained at a high concentration.

In addition, the raw water to be treated is not limited to the case where the suspended water is contained in the raw water described above, but the suspended matter is generated or concentrated in the treatment process to have a suspended solid concentration of 300 ppm or more. Include.
An example in which suspended substances are generated in the treatment process is, for example, a case where hydroxide is precipitated by raising the pH.

The raw water is guided to the circulation tank 3 through the pipe flow path 2. The circulation tank 3 is connected to the filtration module 10 via a drainage supply pipe P1 and a drainage return pipe P2, and a drainage circulation path is formed by the drainage supply pipe P1 and the drainage return pipe P2. .
The drainage supply line P1 is provided with a circulation pump 5 that feeds the wastewater in the circulation tank 3 to the filtration module 10.

As illustrated in FIG. 6, the filtration module 10 has a large number of hollow fiber membranes 14 installed in a cylindrical shell 11. Each hollow fiber membrane 14 is a hollow cylindrical elongated member, and both end portions thereof are supported by partition plates 12 and 13.
On the side surface of the shell 11, a circulating water inlet 15 and a circulating water outlet 16 are provided in the vicinity of the inside of the partition plates 12 and 13, respectively. One circulating water inlet 15 is connected to a drainage supply pipe P <b> 1 that supplies wastewater before treatment into the shell 11. The other circulating water outlet 16 is connected to a drain return pipe P <b> 2 through which untreated drainage flows out from the shell 11. Moreover, the outflow outlets 17 and 18 of the treated water which passed the hollow fiber membrane 14 are provided in the both ends of the cylindrical shell 11, and the treated water pipe line P3 is connected together.
In addition, a flow rate control valve 4 is provided in the treated water pipe P3 in order to control the flow rate of treated water supplied to the next process.

Further, a concentrated drainage pipe P4 that branches from the middle of the drainage return pipe P2 described above is provided, and a control valve 6 is provided in the concentrated drainage pipe P4.
The drain return pipe P2 is provided with an on-off valve 7 at a position downstream of the branch point of the concentrated drain pipe P4, that is, on the circulation tank 3 side from the branch point.

Hereinafter, the state at the time of water flow operation in the hollow fiber membrane water treatment apparatus having the above-described configuration will be described. In FIG. 2, the flow path through which the waste water actually flows is shown by a solid line, and the flow path through which the treated water actually flows is shown by a one-dot chain line.
The waste water in the circulation tank 3 is supplied to the filtration module 10 through the waste water supply pipe P <b> 1 by the operation of the circulation pump 5. In the process in which the wastewater supplied into the shell 11 of the filtration module 10 flows from the circulating water inlet 15 to the circulating water outlet 16, moisture excluding suspended substances permeates through the hollow fiber membrane 14 and enters the inside of the hollow fiber membrane. It flows into the middle part (lumen). This treated water (purified water) flows through the lumen to reach the treated water outflow outlets 17 and 18, and is further guided to the next process through the treated water pipe P3 connected to the outflow outlets 17 and 18. In addition, the flow volume of a treated water is suitably adjusted by the opening degree control of the flow control valve 4 provided in the treated water pipe P3.

  On the other hand, the main flow of waste water that has flowed out of the circulating water outlet 16 without passing through the hollow fiber membrane 14 is returned to the circulation tank 3 through the drain return pipe P2. As a result, the main stream (circulated drainage) of the wastewater sent from the circulation tank 3 circulates through the circulation path including the filtration module 10 and the drainage return pipe P2.

Next, the state at the time of blow back washing operation is demonstrated based on FIG. In FIG. 3, the flow path through which the waste water actually flows is indicated by a solid line.
This blow back washing operation is for removing suspended substances (hereinafter referred to as “dirt components”) in the wastewater that remain attached to the surface of the hollow fiber membrane 14 and the fiber layer by continuing the water flow operation. Driving. In this case, it is preferable that the circulation pump 5 is stopped and compressed air having a relatively low pressure (for example, about 0.98 MPa) is supplied into the filtration module 10 from the drainage supply pipe P1 and the treated water pipe P3.
In the drainage supply pipe P1 and the treated water pipe P3, the compressed air is prevented from flowing out to the circulation tank 3 side and the treated water supply side by an on-off valve (not shown).

When the compressed air is supplied in this way, the waste water remaining in the shell 11 is drained through the drain return line P2 via the lower part of the module by receiving the pressure of the compressed air. At this time, the on-off valve 7 of the drain return pipe P2 is closed, and the control valve 6 of the concentrated drain pipe P4 is opened. As a result, a blow backwash drainage path is formed, and residual wastewater in the shell 11 is discharged as blow water from the concentrated drainage pipe P4 to the outside of the circulation path. Since this blow water contains the dirt component removed from the hollow fiber membrane 14, it is generally a waste water whose suspended substance concentration is about 1.2 to 1.5 times higher than the circulating water. . For this reason, the suspended solids concentration in the circulating water can be lowered compared to the conventional method, and further, by discharging the blow water to the sludge treatment system outside the circulation system, the fluctuation of the raw water SS concentration of the drainage can be reduced. For example, stable operation can be performed without providing an SS densitometer.
The compressed air supplied into the shell 11 also has a function of removing and discharging the dirt component from the surface by shaking the hollow fiber membrane 14 in the process of pushing out and flowing out the residual waste water. .

When the compressed air described above is supplied to the lumen of the hollow fiber membrane 14, the treated water remaining in the lumen (water that has passed through the hollow fiber membrane) receives the pressure of the compressed air, so that the hollow fiber membrane 14 Is transmitted in the reverse direction from the inside to the outside. At this time, the dirt component remaining on the surface of the hollow fiber membrane 14 and the fiber layer is pushed out to the shell side by the flow of the treated water, so that the dirt component is removed more efficiently.
In this way, the dirt component in the fiber layer is pushed out from the lumen side to the shell side, and the dirt component adhering to the surface is lifted and peeled off, so that it can be easily removed by the flow of residual drainage flowing in the shell. Can do.

  By the way, although it is preferable to supply the compressed air mentioned above to both the shell side and the lumen side, it may be supplied to only one of them. Further, even if no compressed air is supplied, a water flow is formed by draining the residual wastewater in the shell 11 to the outside of the shell, so that the flow of this residual wastewater causes the flow from the surface of the hollow fiber membrane 14. Dirt components can be removed.

Finally, the state during the flash backwash operation will be described with reference to FIG. In FIG. 4, the flow path through which the waste water actually flows is indicated by a solid line.
In the flush back washing operation, drainage is supplied to the shell 11 to perform water filling following blow back washing. In this state, compressed air having a pressure higher than that in the blow back washing operation described above, for example, compressed air of about 0.59 MPa, is supplied into the lumen and pressurized, and then released to the atmosphere, and the inside of the hollow fiber membrane 14 and Clean the membrane surface.
After performing the reverse pressure cleaning (pressurized flush) using such compressed air, the circulating pump 5 is operated while supplying compressed air (for example, about 0.59 MPa) to the drainage supply pipe P1, and drainage ( The raw water) is circulated, and the dirt component deposits are separated by vibration by the circulating drainage and the compressed air (bubbles) in the circulating drainage. After carrying out the two-phase flow cleaning in which the hollow fiber membrane 14 is cleaned with the two-phase flow consisting of the water flow of the circulating drainage and the compressed air bubbles, the supply of the compressed air is finally stopped and the washing is performed only with the circulating drainage. Perform a single phase wash.

That is, the flash backwash operation in the present embodiment is a combination of a pressurized flash and two-phase flow cleaning using air bubbles.
When such a flush back washing operation is performed, the treated water in the lumen is pushed out to the shell side by the pressurized flash and flows out to the shell side, and at that time, adheres to the surface of the hollow fiber membrane 14 and the fiber layer. The dirt component is removed as it is pushed out. This dirt component merges with the wastewater supplied into the shell by the operation of the circulation pump 5 together with the compressed air and the treated water, and flows along with the two-phase flow of gas and liquid flowing on the outer surface side of the hollow fiber membrane 14. For this reason, the dirt component adhering to the hollow fiber membrane 14 is also removed by air bubbling, and is collected into the circulation tank 3 through the drain return pipe P2.

Further, in the above-described flush cleaning operation, the pressurized flash using compressed air and the two-phase flow cleaning using air bubbles are combined, but only one of them may be used.
In addition, after such a flush washing | cleaning operation is complete | finished, it returns to a water flow operation.

Now, the water flow operation, blow backwash operation, and flush backwash operation described above are performed according to the procedure shown in the flowchart of FIG.
When the operation of the hollow fiber membrane water treatment device is started, the first water flow operation _ST1 is first started and continued for a predetermined time (for example, 15 minutes). Thereafter, the first round of the blow backwash operation S _B1 stop and start the water flow operation S _T1, ends after a predetermined operation.
As a result, the first water flow / backwash operation cycle C1 is completed.

Then, the above-mentioned water flow operation and blow backwash predetermined number of times water flow-backwash operation cycle consisting of operation, after repeated n times until Cn in the illustrated example, the series of operations of the flash backwash operation S _F1 in turn Do. After flash backwash operation S _F1 is completed, the water passing-backwash operation cycle C _{n + 1} is started to perform the flash backwash operation every Similarly water passing-backwash operation cycle n times less.

Thus, according to the hollow fiber membrane water treatment apparatus of the present invention, it is possible to employ a backwashing method in which the flush backwash operation is performed once every time the blow backwash operation is performed n times. By adopting this backwashing method, it is possible to minimize the number of flush backwashing operations that impair the durability of the hollow fiber membrane 14 and to suppress a decrease in filtration performance.
That is, a hollow fiber membrane that has treated wastewater containing high-concentration suspended solids by adopting a backwash operation method in which backwashing is performed mainly in blow backwashing operation and the frequency of flush backwashing operation is reduced. The 14 contamination components are reliably removed, and the durability is not lowered.

<Example>
Using the hollow fiber membrane water treatment device and the hollow fiber membrane backwash method configured as described above, an operation test was performed under the following conditions.
1. Drainage (raw water) SS concentration: 2000 mg / lit.
2. Circulating tank SS concentration: 7000 to 10000 mg / lit.
3. Wastewater SS concentration: 10000-15000 mg / lit.
As a result, the frequency of flush backwash operation is 1/6 of blow backwash operation (ie, n = 6 in FIG. 1), there is no increase in transmembrane pressure due to continuous operation, and repeated flush backwashing It was possible to suppress the decrease in the amount of treated water or the increase in water flow power due to the clogging of the pores on the membrane surface. In addition, compared with the prior art which implements only flash backwashing, it was confirmed that long-term use of about 5 times was possible.
In addition, the frequency of the flush backwash operation varies depending on various conditions such as the concentration of the drainage SS and the type and nature of the suspended solids, but in general, it is preferable that the frequency is once in 5 to 20 blow backwash operations. It could be confirmed.

  In particular, the hollow fiber membrane water treatment apparatus and the hollow fiber membrane backwash method described above are suitable for the treatment of high-concentration waste water having a suspended substance concentration of 300 ppm or more.

  In addition, the structure of this invention is not limited to embodiment mentioned above, In the range which does not deviate from the summary of this invention, it can change suitably.

It is a flowchart which shows one Embodiment of the backwashing method of the hollow fiber membrane which concerns on this invention. It is a figure which shows one Embodiment of the hollow fiber membrane water treatment apparatus which concerns on this invention, and is a block diagram of the principal part which shows the state at the time of water flow operation. It is a block diagram which shows the state in which the hollow fiber membrane water treatment apparatus of FIG. 2 is performing the blow backwash operation. It is a block diagram which shows the state in which the hollow fiber membrane water treatment apparatus of FIG. 2 is performing the flash backwash operation. It is a figure which shows the outline | summary of the conventional hollow fiber membrane water treatment apparatus. It is sectional drawing which shows the structural example of a filtration module. It is a figure which shows the transmembrane differential pressure which fluctuates with driving time in the conventional driving | operation method. It is a block diagram of the principal part which shows the conventional hollow fiber membrane water treatment apparatus, (a) is the state at the time of water flow operation, (b) is the state at the time of flush backwash operation.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 pH adjustment tank 3 Circulation tank 4 Flow control valve 5 Circulation pump 6 Control valve 10 Filtration module 11 Shell 14 Hollow fiber membrane P1 Raw water (drainage) supply pipeline P2 Raw water (drainage) return pipeline P3 Treated water pipeline P4 Concentration drainage pipe Road

Claims (4)

The membrane surface of the hollow fiber membrane and the fiber layer are supplied after the water passing step of supplying the raw water containing the suspended substance into the shell of the filtration module and allowing the hollow fiber membrane installed in the shell to pass through the filtration process. A method for backwashing the hollow fiber membrane to remove the deposits inside,
A blow back washing process is provided for discharging substantially all of the concentrated water remaining on the shell side of the filtration module to the outside of the shell, and the blow back washing process receives supply of air to both the shell side and the lumen side of the filtration module. A method for backwashing a hollow fiber membrane, characterized in that   The method for backwashing a hollow fiber membrane according to claim 1, wherein the flush backwashing step is performed once after the water flow step and the blow backwashing step are repeated a predetermined number of times. In a hollow fiber membrane water treatment apparatus comprising a filtration module in which raw water containing suspended solids is filtered by passing through a hollow fiber membrane installed inside the shell,
A blow backwash drainage path for draining substantially all of the concentrated water remaining on the shell side of the filtration module to the outside of the shell is provided, and the blow backwash drainage path supplies air to both the shell side and the lumen side of the filtration module. The hollow fiber membrane water treatment apparatus is characterized by draining the concentrated water by receiving the water.   The hollow fiber membrane water treatment device according to claim 3, wherein the blow backwash drainage path is connected to a concentrated drainage pipe.

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