JPH026824A - Method and apparatus for filtration - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention is a filtration device using a hollow fiber filtration module including a hollow fiber filtration membrane, in which the filtration function is restored when the hollow fiber filtration membrane is clogged. However, the present invention relates to a filtration method for continuously performing filtration treatment of water to be treated, and an apparatus therefor.

[Conventional technology]

Hollow fiber filtration membranes have excellent filtration performance and a large membrane area that can be accommodated in a unit volume, so they are used to treat fluids containing various suspended substances. . Generally, in filtration using porous hollow fibers, suspended particles filtered through the pores of the hollow fibers adhere to and accumulate on the outer surface of the hollow fibers, so the filtration flow rate gradually decreases or The differential pressure required for filtration increases. For this reason,
Normally, the membrane is reused after performing fA filter function recovery treatment several times, and when the degree of recovery by such function recovery treatment is insufficient, it is replaced with a new hollow fiber filtration membrane. It was common.

Conventionally known functional recovery methods for hollow fiber filtration membranes, particularly functional recovery treatment methods performed with a filtration module including a hollow fiber filtration membrane installed in filtration equipment, include:
There are two typical methods: vibrating the hollow fibers with air bubbles to shake off the deposits, and washing away the deposits on the outer surface of the hollow fibers by flowing the fluid in the opposite direction to that used in normal filtration. It was something like that.

However, these methods for restoring the filtration function require stopping the normal filtration operation in the filter, and are therefore not suitable for continuous treatment of water to be treated. Therefore, when it is necessary to continuously treat water to be treated, it is necessary to prepare a plurality of filtration facilities.

[Problem that the invention seeks to solve]

The purpose of the present invention is to provide a filtration device using a hollow fiber membrane.
It is an object of the present invention to provide a filtration method and an apparatus therefor, which can continuously perform filtration treatment of water to be treated while performing recovery treatment of filtration function against clogging of hollow fibers.

[Means for solving problems]

That is, in the filtration method of the present invention, inlets and outlets for the water to be treated are arranged at both ends of a straight pipe, a hollow fiber filtration membrane is built in the straight pipe, and filtration is carried out through the hollow fiber filtration membrane from a side pipe connected to the straight pipe. A process of supplying and circulating the water to be treated to a circulation channel in which a plurality of cross-flow type filters having a structure for taking out the purified water and a circulation pump are connected in series, and a process of circulating the water to be treated, and A step of taking out purified water from the pipe, a step of sequentially washing the filters by intermittently supplying a part of the purified water back to each filter, and interlocking with the washing, the circulation flow path described above. The method is characterized by having a step of opening a drainage port attached therein and discharging cleaning wastewater.

Further, in the filtration device of the present invention, inlets and outlets for the water to be treated are arranged at both ends of the straight pipe, and a hollow fiber filtration membrane is built in the straight pipe,
A circulation line in which a plurality of cross-flow type filters having a structure for taking out purified water filtered by a hollow fiber filtration membrane from a side pipe connected to the straight pipe and a circulation pump are connected in series to form a circulation flow path. , a water supply line that guides the water to be treated to the circulation line, and a purified water collection line that collects purified water taken out from a side pipe of the filter; A backwash water supply line for washing the precision filter by flowing water back from the side pipe of each precision filter into the straight pipe, and a backwash control valve for controlling implementation of this backflow are attached, and The apparatus is characterized in that a drainage control valve is provided for discharging a part of the cleaning drainage produced by the cleaning by opening a drainage basin 1 attached to the circulation line.

(Preferred mode for carrying out the invention) The filtration method of the present invention is described in the flow sheet shown in FIG.
, (I will explain.

In the filtration method of the present invention, first, water to be treated is introduced through a water supply line 1 into a circulation line 4 in which a plurality of cross-flow type filters 2a to 2e are connected to form a circulation flow path. Any type of water to be treated may be introduced into the circulation line, but the filtration performance of the filter with a built-in hollow fiber membrane installed in the circulation line should be considered. In the case of water to be treated containing a large amount of coarse suspended matter, it is preferable that the coarse suspended matter be removed. Filtration machines for pre-treating water to be treated include sand filtration equipment, diatomaceous filtration equipment,
A typical example is a cartridge filtration device, or, of course, unprocessed water may be introduced using such a 11-pass machine.

The circulation line 4 includes a plurality of cross-flow type filters 2a.
A circulation channel is formed by connecting each of the straight pipe sections 2e to 2e in series, and the water to be treated introduced thereto is circulated by the circulation pump 3 in this circulation channel.

The cross-flow type filtration machine used in the present invention has an inlet and an inlet for water to be treated at both ends of a straight pipe, and a hollow fiber filtration membrane is arranged within the straight pipe almost parallel to the straight pipe. It has a structure in which purified water filtered by a filtration membrane is taken out from a side pipe connected to the side of this straight pipe,
Typically, JP-A-Sho [i
Examples include those disclosed in No. 1-291008 and JP-A-62-132503.

As for the hollow fiber f1, a microporous hollow fiber made of polyolefin is suitable because it can filter out fine particles with a particle size of up to about 0.05p and can provide a relatively large processing flow rate per unit membrane area. A typical example thereof is a polyethylene porous hollow fiber membrane (for example, EHF, trade name, manufactured by Mitsubishi Rayon@), which is appropriately made hydrophilic.

The appropriate number of filters to be connected and arranged in series in the circulation line 4 is about 2 to 10, preferably 3 to 8. If the number of precision filters disposed in the circulation line is too large, the flow path resistance of the precision filtration circulation line will increase, which is not preferable. The appropriate flow rate of the water to be treated in the circulation channel is about 0.5 to 2 m/sec, and 0.5 to 2 m/sec.
．． 7~! , 2m/sec is preferable.

From the side pipe of each filter in the circulation flow path, the hollow fiber membrane wall is
The purified water filtered through the LA into the hollow part of the hollow fibers is taken out, and this purified water is collected via the purified water recovery pump 7 into the purified water collection line 8 .

If the filtration process is continued for a long time in the circulation line,
As suspended matter in the water to be treated adheres and accumulates on the surface of the hollow fiber filtration membrane in the cross-flow type IM filtration machine, the treatment efficiency gradually decreases and the flow rate of purified water obtained from each filtration machine decreases. , the differential pressure required for filtration increases.

Therefore, in the method of the present invention, a part of the purified water in the purified water collection line 8 is supplied in a reverse flow to one or more of the cross-flow type filters via the backwash water supply line 9. An operation of cleaning and removing deposits adhering to the outer surface of the hollow fiber filtration membrane in the filter (hereinafter, this operation will be abbreviated as "backwashing") is performed intermittently. In other words, during normal filtration, the outside side of the hollow fiber is pressurized and the water to be treated passes through the hollow part of the hollow fiber to obtain purified water from the side pipe, but during backwashing, purified water is obtained from the side pipe. The backwash control valves 5a to 6c are operated so that the flow flows into the hollow fibers (one or two of 5a to 5e are closed, and the corresponding 6
8 to 6e), and by applying water pressure, the deposits on the outer surface of the hollow fibers are washed away into the water to be treated in the straight pipe. The pressure applied to the hollow fiber module during backwashing is preferably 1 to 5 g/rn2, preferably 2 to 3 g/rn', and the flow rate of the wash water flowing back during backwashing is usually 11! 1 of ``The flow of time''
- It is preferable to increase the amount by about 4 times.

This backwashing operation can be done by using some of the filters arranged in series for backwashing while using other filters for filtration. I'm never invited.

In other words, if the number of filters connected in series is 10 or less, one or two filters are backwashed at a time, and the next filtration is performed after the backwashing is completed or after a predetermined period of time. After all the filters have been backwashed, the backwashing can be repeated in order from the filter that was backwashed first. As a result, even during backwashing, each i! The filtration function of the lt filter is gradually restored, and the circulation line 4 can always perform a partial filtration function. Although backwashing may be carried out on the 211 (-a road machines) at one time, it is preferable to carry out the backwashing on only one machine at a time because stable operation can be achieved.

When this backwashing is performed, the deposits on the outer surface of the hollow fibers are released into the water to be treated flowing through the straight pipe.
Backwash wastewater with concentrated dirt is generated in the circulation line. Therefore, in conjunction with the implementation of backwashing, the drain port 1O provided in the circulation line 4 is opened to discharge a portion of this backwash wastewater. The number of drainage ports is not limited to one, and for example, the same number as the number of cross-flow filters may be provided. To open and close the drain port 10,
For example, a drain control valve may be activated.

Cross-flow type filters 2a to 2c with 4 or 5 circulation lines
For example, 10
Backwashing of 20 seconds each can be performed on each filter sequentially every minute, so that one cycle of backwashing the entire circulation line can be completed in 50 minutes. At this time, by operating the backwash control valves 58 to 6e as appropriate, normally only one filter is backwashed, and the remaining filters continue to carry out normal filtration. The opening and closing of the drain port 10 during backwashing should be done in consideration of the distance from the precision filters 28 to 2e that perform backwashing to the drainage branch pipe, so that the backwash wastewater passes near the drainage branch pipe. All you have to do is open the drainage control valve and discharge the backwash drainage at the same time.

In the method of the present invention, backwash wastewater is discharged from the purified water obtained! The ratio (1) is influenced by the ratio between the normal filtration time and backwashing time in the -based filter, and the ratio between the flow rate of purified water generated during normal filtration and the flow rate of washing water supplied during backwashing.

Although it varies depending on the quality of the water to be treated, the discharge rate of backwash wastewater is usually 0.0% of the purified water obtained. It is preferable to set it to about 0.3 times the previous value. In addition, compared to the cross flow module with backwashing which combines the same vague modules as used in the device of the present invention, it costs 8 times or a fraction of the cost of a circulation pump.
Just the capacity of the backwash pump! It has the advantage that the number of stages can be reduced to 1/1, and there is no need to turn the circulation pump on and off frequently, which reduces the burden on the pump.

〔Effect of the invention〕

Conventionally, in filtration devices using hollow fiber membranes, when the filtration function has deteriorated due to clogging of the hollow fibers, when performing a function recovery process, the normal filtration operation in the filtration machine is stopped. Ta. However, according to the filtration method of the present invention,
As for the filtration device as a whole, the function recovery treatment can be performed while performing normal filtration treatment, so there is no need to prepare multiple filtration equipment even when it is necessary to continuously treat the water to be treated. be.

Furthermore, since the frequency of the function recovery process for each hollow fiber filtration module can be freely set, the effective usage period of the module can be extended to the maximum extent by taking into account the function recovery process and the degree of recovery resulting from it.

In addition, compared to a cross-flow module with backwashing that combines modules with the same membrane area as used in the device of the present invention, the capacity of the circulation pump is a fraction of that, and the capacity of the backwash bomb is equivalent to the number of stages. It has the advantage of requiring only 1, and since there is no need to turn the circulation pump on and off frequently, there is an advantage that the burden on the pump can be reduced accordingly.

〔Example〕

Hereinafter, the filtration method and apparatus of the present invention will be more fully explained based on examples.

Example 1 U-shaped membrane filtration machine (membrane area: 0.3 rn
”) Purification treatment of simulated wastewater containing 4 units of colloidal silica containing 0.1% was performed using the trough equipment whose flow sheet is shown in Figure 1, in which 5 units were connected in series.
Water supply line 1 to circulation line 4 in the original size of 20Il/hr
The flow rate at the membrane surface in the first stage filtration module was set to 1 m/sec, and the flux in each module was set to 80.C/m''·hr.
This water was taken out through a purified water collection line and joined with the water to be treated except for use in backwashing, and the colloidal silica concentration of the simulated wastewater was adjusted as appropriate to maintain it at 0.1%. One hour after the start of the simulated wastewater purification process, backwashing was carried out by back-flowing filtered water for 20 seconds at a flow rate of 200 u/hr from the side pipe 11^ at a time to each filter in the circulation line. carried out. In addition, when the backwash water passes near the branch pipe for drainage, the drain port 8 is opened by operating the control valve, and about half of the amount of backwash water supplied is discharged. Backwashing is performed on each filter in sequence every 10 minutes, and one backwash of the entire circulation line is carried out in 50 minutes.
After the cycle was completed, the simulated wastewater was purified while continuing the backwashing operation in this 50-minute cycle. As a result, the filtrate water did not contain any colloidal silica, and even after 2 months of this treatment, the filtrate stream 1i) maintained about 80% of the initial stream ijl in constant pressure filtration.

[Brief explanation of the drawing]

FIG. 1 is a flow sheet showing an example of the filtration method of the present invention, and FIGS. 2 and 3 are schematic cross-sectional views showing a typical example of a cross-flow precision filtration machine used in the method and apparatus of the present invention. It is. 1: Water supply line 2a to 2C: Filter 3: Circulation pump 4: Circulation line 5a to 5e: Backwash control valve 7: Purified water recovery pump 9: Backwash water supply line 1: Straight pipe 1 Coni fixing member 8: Purification Water collection line 10: Drain port 12: Hollow fiber 14: Side pipe

Claims (1)

[Claims] 1) Inlets and outlets for the water to be treated are arranged at both ends of the straight pipe, a hollow fiber filtration membrane is built in the straight pipe, and the water to be treated is filtered by the hollow fiber filtration membrane from a side pipe connected to the straight pipe. A process of supplying and circulating the water to be treated to a circulation channel in which a plurality of cross-flow type filters having a structure for taking out purified water and a circulation pump are connected in series, and a side pipe of each filter. a step of taking out purified water from the filter, a step of sequentially cleaning the filters by intermittently supplying a portion of the purified water to each filter by flowing backwards, and a step of cleaning the filters in sequence in conjunction with the cleaning. A filtration method comprising the step of: opening an attached drain port and discharging cleaning waste water. 2) A structure in which inlets and outlets for treated water are arranged at both ends of a straight pipe, a hollow fiber filtration membrane is built into the straight pipe, and purified water filtered by the hollow fiber filtration membrane is taken out from a side pipe connected to the straight pipe. a circulation line in which a plurality of cross-flow filters and a circulation pump are connected in series to form a circulation flow path;
In a filtration device comprising a water supply line that guides the water to be treated to the circulation line and a purified water collection line that collects purified water taken out from a side pipe of the filter, the purified water in the purified water collection line is A backwash water supply line for washing the filter by backflowing from the side pipe of each filter into the straight pipe, and a backwash control valve for controlling the implementation of this backflow are attached, and A purification device comprising a drainage control valve for discharging cleaning drainage by opening a drainage port attached to a circulation line.