JPH02157007A - Method for washing filament filtration column - Google Patents

Abstract

PURPOSE:To obtain a washing method by which differential pressure can be restored by bringing hot water of 50 deg.C or higher and/or aqueous solutions of oxidizing agents into contact with filament bundles in a column. CONSTITUTION:After the completion of back-washing process in which compressed air and/or back-washing water is used, a filtration column 1 is kept in such a state that it is filled with water, while a valve 10 and a valve 14 are opened, whereby an aqueous solution of about 2% sodium hypochlorite is caused to flow into the column 1 from a raw water inlet line 5 so that water in the column 1, particularly that above a perforated plate 2, is replaced by the aqueous solution of sodium hypochlorite so as to fill the inside of the column 1 therewith, and thereafter the valves 10 and 14 are closed and a valve 12 and a valve 11 are opened, whereby the column is left as it is for about three hours, while compressed air is caused to flow intermittently thereinto from a back-washing air inlet line 7. The valve 11 is kept opened and a valve 13 is opened to let back-washing water flow into the column through a back- washing water inlet line 9 so that sodium hypochlorite and attached matters having been separated from filament bundles in the column are discharged through a back-washing water discharge line 6.

Description

[Detailed description of the invention] <Industrial application field> The present invention is applicable to various types of recovered water such as earthwork tap water, sewage, river water, lake water, flocculation sedimentation supernatant water, intermediate water in various processes, and recovered water in paper manufacturing processes. , relates to a filter tower cleaning method using long fiber bundles for removing suspended matter in various wastewaters, treated water from biological treatment equipment, liquids containing valuables, alcohol, oil, etc., at high flow rates. This relates to a cleaning method when the differential pressure does not recover in a normal backwashing process.

<Conventional technology> The applicant of the present invention previously disclosed a filtration tower using long fiber bundles.

As shown in FIG. 1, this filtration tower has a perforated plate 2 installed horizontally in the lower part of the filtration tower 1, and a support 3 for long fiber bundles, which will be described later, is attached to the perforated plate 2. fiber bundle 4
The long fiber bundle 4 is set upright in the filtration tower 1 by fixing the lower end of the fiber bundle and making the upper end of the long fiber bundle 4 a free end, and filling the tower relatively densely with the long fiber bundle 4. It is.

Further, as shown in FIG. 2, the long fiber bundle support 3 has an upper lid-like body 16 having a large number of holes 15 in the upper and side body parts, and an upper and lower end having slits 17 in the side body parts. It consists of a lower cylindrical body 18 and is attached to the perforated plate 2 as described below.

That is, a T-shaped bolt 19 is attached above the lower cylindrical body 18, and the lower cylindrical body 18 is fixed by the T-shaped bolt 19.
Then, after inserting the tip of the 1-shaped port 19 from the bottom of the hole 20 of the perforated plate 2 and inserting the upper part of the lower cylindrical body 18 into the hole 20, the nut 22 having the leg 21 is inserted into the 1-shaped port 19. The 1-shaped port 19 is fixed to the hole 20 by a screw leg 21.

Next, the lower end of the long fiber bundle 4 is tightened and fixed in advance around the entire circumference of the side trunk of the upper lid-like body 16 using the hand 23, and the upper lid-like body 16 to which the long fiber bundle 4 is fixed is fixed in advance.
To install the perforated plate 2, insert the T-bolt 19 into the hole 24.
20 is covered with the upper lid-like body 16, and then the nut 25 is closed.
The upper lid-like body 16 is fixed to the upper part of the hole 20 by screwing into the T-shaped bolt 19.

The long fiber bundle 4 is an aggregate of untwisted single fibers such as acrylic fibers, polyester fibers, and polyamide fibers with a thickness of 10 μm to 80 μm, and usually has a length of 0.4 m to 3.0 m. .

In the so-called filtration process in which the stock solution containing suspended matter is filtered in the filter tower, the valve 10 and the valve 14 are opened and the stock solution is introduced from the stock solution inlet pipe 5 from one end to the lower end of the long fiber bundle 4. The stock solution is passed through in a downward flow, and through such a filtration process, suspended matter is captured in the voids formed by the long fiber bundles 4, and the filtrate is passed through the hole 15 in the upper lid-like body 16 into the support body 3. and then through the lower tubular body 18 to the filtrate outflow pipe 8
It is something that flows out from.

When a large amount of suspended matter is trapped in the voids of the long fiber bundle 4 due to the continuation of such filtration, the differential pressure gradually increases, and as the differential pressure increases, the suspended matter rises upright from the lower part of the long fiber bundle 4. A phenomenon occurs in which the long fiber bundles 4 begin to bend, and the vertical height of the long fiber bundles 4 gradually decreases.

When the differential pressure reaches a certain value,
Valve 10 and valve 14 are closed to complete the filtration process and the following backwash process is performed to restore the differential pressure. That is, the valves 11 and 12 are opened to allow compressed air to flow in from the backwash air inflow pipe 7.

Since the lower part of the perforated plate 2 is filled with filtrate, the filtrate first flows out from each member 15 of the upper lid-like body 16 through the lower cylindrical body 18 due to the inflow of compressed air, but soon As shown in FIG. 2, a liquid level is formed below the perforated plate 2, a compressed air waste trap is formed above the liquid level, and a slit 1 is located above the liquid level.
From 7 the compressed air enters the lower cylindrical body 18 and then blows out from each person 15 of the upper lid-like body 16.

Due to the inflow of the compressed air, the water in the filter tower 1 is stirred, the long fiber bundles 4 are vibrated, the voids formed between the fibers are destroyed, and the aggregates of suspended substances are destroyed. The suspended matter adhering to the long fiber bundle 4 is peeled off.

Particularly in the initial stage of inflow of compressed air, the liquid existing below the porous plate 2 is pushed up by the compressed air at once, becomes a powerful piston flow, flows out from each member 15 of the upper lid-like body 16, and then is compressed. Since the air flows out, the entire long fiber bundle 4 is effectively cleaned.

Continue the inflow of compressed air as described above, or close valve 1.
2 is closed to stop the inflow of compressed air, the valve 13 is opened, and backwash water flows in from the backwash water flow pipe 9. The inflowing backwash water enters the lower cylindrical body 18 from the lower end opening thereof, and then flows out from each member 15 of the upper lid-shaped body 16.

Since the lower end of the long fiber bundle 4 is fixed and its upper end is free, the upward flow of backwash water causes the long fiber bundle 4 to elongate like a windsock, and each fiber vibrates. do. Therefore, the suspended matter separated from the long fiber bundle 4 due to the shock caused by the inflow of the compressed air is washed away, and the backwash water containing the suspended matter is sent to the backwash discharge pipe 6.
flows out from.

In addition to the above-mentioned steps, the backwashing process also includes a procedure in which a certain amount of backwash water flows in from the backwash water flow pipe 9 and compressed air intermittently flows in from the backwash air inflow pipe 7. It is being said.

After the backwashing process as described above is completed, the filtration process described above is performed again, and both processes are repeated in sequence.If the differential pressure recovers to the initial differential pressure by the backwashing process, the operation can be performed without any problem. I can continue.

However, depending on the type of stock solution to be filtered, if the operation is continued for a long period of time, the differential pressure may not recover even if the backwashing step is performed.

In order to investigate the cause of this, we dismantled the filter tower in this condition, and found that relatively sticky microorganisms were present in the lower part of the long fiber bundles, especially around the upper lid. It was found that a large amount of what appeared to be slime was attached.

Since the adhesion is relatively sticky, it seems that it cannot be removed well by cleaning with compressed air and/or backwash water as described above, but as mentioned above, the differential pressure does not recover by the backwashing process. This shortens the filtration time, which is extremely undesirable.

<Problems to be Solved by the Invention> The present invention solves the problem of reducing the differential pressure in a long fiber bundle filtration tower when the differential pressure does not recover even after performing a backwash step using compressed air and/or backwash water. The purpose is to provide a cleaning method that allows recovery.

<Means for Solving the Problems> In order to achieve the above object, the method for cleaning a long fiber bundle filtration tower according to the present invention fixes the lower end of the long fiber bundle inside the tower, and fixes the upper end of the long fiber bundle inside the tower. The raw solution is introduced from above the filtration tower in which long fiber bundles are installed upright throughout the inside of the tower as the free end, and the raw solution is passed from the upper end of the long fiber bundles to the lower end. A filtration step for capturing suspended matter and a backwashing step for flowing compressed air and/or backwash water from below the long fiber bundle and discharging the captured suspended matter outside the column are repeated. In the fiber filtration tower, when the differential pressure of the filtration tower does not recover even after performing the above backwashing step, 5
This method of cleaning a long fiber filtration tower is characterized by bringing hot water at 0° C. or higher and/or an aqueous solution of an oxidizing agent into contact with long fiber bundles in the tower.

The present invention will be explained in detail below.

<Function> The present inventors have found that when a long fiber bundle filtration tower is operated for a long period of time, the highly adhesive deposits that adhere to the lower part of the long fiber bundle, especially around the upper lid-shaped body, can be effectively removed. When we investigated a cleaning method that could remove the deposits, we found that when the long fiber bundles were brought into contact with hot water at 50°C or higher and/or an aqueous solution of an oxidizing agent, the stickiness of the deposits decreased, and when the long fiber bundles were brought into contact with hot water at 50°C or higher and/or an aqueous solution of an oxidizing agent, It has been found that the deterioration occurs in a form that can be easily peeled off during a backwashing process using backwash water.

When using hot water, hot water of 50°C or lower is ineffective, and hot water of 50°C or higher is required; however, if the temperature is too high, the long fiber bundles or the internal structure of the filter tower may deteriorate due to heat. Therefore, hot water with a temperature of 50°C or more and 80°C or less is preferable, and hot water of 60°C to 70°C is usually used. Further, the contact time of the hot water is at least 30 minutes or more, and preferably about 3 hours.

In addition, as a specific method of contacting, the water in the filtration tower may be replaced with hot water and then left to stand, or the hot water may be flowed into the filtration tower in an upward or downward flow.

In addition, when using an aqueous solution of an oxidizing agent, sodium hypochlorite, hydrogen peroxide, ozone, etc. can be used as the oxidizing agent, and the concentration of these oxidizing agents is 2% (wt%,
The same applies hereafter) It is preferable to make it before and after.

Note that the contact time with the oxidizing agent is at least 30 minutes or more, as in the case of hot water, and preferably about 3 hours.

Note that the desired purpose can be achieved by bringing only hot water or an aqueous solution of an oxidizing agent into contact with the long fiber bundle under the conditions described above;
Alternatively, it is more effective to contact with an aqueous solution of an oxidizing agent heated to 50° C. or higher.

Further, it is more effective to bubble the hot water and/or the aqueous solution of the oxidizing agent with air while contacting the long fiber bundle.

The specific procedure will be described below with reference to FIGS. 1 and 2, taking as an example the case where an aqueous solution of an oxidizing agent is used.

That is, after the above-mentioned backwashing process using compressed air and/or backwash water is completed, the filter tower 1 is filled with water, valves 10 and 14 are opened, and approximately 2% of A sodium hypochlorite aqueous solution flows into the filter tower 1, and the water in the filter tower 1, particularly above the perforated plate 2, is replaced with the sodium hypochlorite aqueous solution.

In addition, instead of injecting the approximately 2% sodium hypochlorite aqueous solution from the stock solution inflow pipe 5, the manhole ( If a small amount of sodium hypochlorite stock solution (not shown) is added and diluted with water in the filtration tower 1, the concentration of sodium hypochlorite in the filtration tower 1 will be approximately 2%. No problem.

After filling the filter tower 1 with the sodium hypochlorite solution in this way, the valves 10 and 14 are closed, and the valves 12 and 11 are closed.
is opened and left for about 3 hours while compressed air is intermittently introduced from the backwash air inflow pipe 7.

Next, the valve 13 is opened while the valve 11 remains open, and backwash water flows in from the backwash water flow pipe 9 to remove 2111% of the deposits from the sodium hypochlorite and long fiber bundles 4 in the tower. It is made to flow out from the wash water discharge pipe 6.

The above is one of the steps of the cleaning method of the present invention. By the cleaning of the present invention, relatively strong adhesion can be completely washed out, and the differential pressure is restored thereafter, so the above-mentioned filtration step, Operation can be continued with a backwash step using compressed air and/or backwash water.

Further, if the differential pressure does not recover again by continuing the operation, the cleaning method of the present invention may be carried out each time.

<Effects> As explained above, in a long fiber bundle filtration tower, when the differential pressure does not recover even if the backwash step using compressed air and/or backwash water is performed, by implementing the cleaning method of the present invention. Since the relatively sticky deposits adhering to the long fiber bundle can be completely removed, the pressure difference is the same as in the first cycle, and the long fiber filtration tower can be operated without any problem.

Furthermore, the cleaning method of the present invention does not require dismantling the filter tower.
Since the operation is relatively simple, it has the advantage that automatic operation can be performed easily.

Examples will be described below to clarify the effects of the present invention.

Example 1 A perforated plate was installed horizontally at the bottom of a stainless steel filtration tower with a diameter of 100 R and a straight part height of 2,000 mm. The length is 35μ and the length is 1,5001m.

The lower end of a long fiber bundle made of an aggregate of non-twisted acrylic single fibers with a packing density of 75 kg/m was fixed, and the upper end was used as a free end.

The supernatant water (suspended solids concentration 3
When the raw water was filtered at LV50m/H, the initial pressure difference was 0.1 kg/crA G and the suspended solids concentration was 1/7! of filtered water was obtained.

The filtration process is stopped when the differential pressure reaches 1, Q kg/ct G, and the LVI rises from the bottom of the filtration tower, 0OON.
compressed air of rn'/rrl for 1 minute, then compressed air (l
, 00ONnr/r4) and backwash water with a rising LV of 100 m/H for 3 minutes, and a backwashing process of backwashing only with backwash water with a rising LV of 100 m/H for 1 minute, and then the filtration process and the backwashing process. repeated.

When the filtration process and backwashing process were repeated for a long period of time, the initial differential pressure was 0.2 kg even after the backwashing process.
/cdG, so the water in the filtration tower was replaced with a 2% sodium hypochlorite aqueous solution, air bubbled for about 30 minutes, then left to stand for 3 hours, and then backwashed water was used to remove hypochlorous acid. The sodium aqueous solution was washed out and a normal backwashing process was performed. Thereafter, when the same raw water was filtered under the same conditions, the initial differential pressure was restored to 0.1 kg/cA G.

Example 2 Following Example 1, when the filtration process and backwashing process were repeated for a long period of time, the initial differential pressure rose again to 0.2 kg/csA G even after the backwashing process, so the filtration process The long fiber bundles were brought into contact with the hot water by flowing hot water at 70°C from the bottom of the tower at an ascending LV of 20 m/h for about 1 hour, followed by a normal backwashing process, followed by the same raw water under the same conditions. After the filtration treatment, the initial pressure difference was restored to 0.1 kg/c♂G.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing the flow of a long fiber bundle filtration tower used in the present invention, and FIG. 2 is an enlarged sectional view showing a support for the long fiber bundle used in the filtration tower. 1... Filter tower 2... Perforated plate 3...
Support for long fiber bundle 4... Long fiber bundle 5... Stock solution inflow pipe 6... Backwash discharge pipe 7... Backwash air inflow pipe 8... Filtrate outflow pipe 9... Reverse Washing water inflow pipe 10-14... Valve 15... Hole
16..." two-part lid-like body 17... slit
18...Lower cylindrical body I9...T-shaped bolt
20...hole 21...leg 22...
Nut 23... Tighten with band 24... Mount with hole 25... Nand

Claims (1)

[Claims] The lower end of the long fiber bundle is fixed inside the tower, and the upper end is set as a free end, and the raw solution is introduced from above the filtration tower in which the long fiber bundle is set upright throughout the inside of the tower, from the upper end of the long fiber bundle to the lower end. A filtration step in which suspended matter is captured in the voids within the long fiber bundle by passing the stock solution toward the target, and compressed air and/or backwash water is introduced from the lower part of the long fiber bundle to trap the suspended matter in the voids within the long fiber bundle. In long-fiber filtration towers that repeatedly undergo a backwashing process to discharge turbid substances to the outside of the tower, when the differential pressure in the filtration tower does not recover even after performing the above backwashing process, hot water of 50°C or higher and/or oxidation A method for cleaning a long fiber filtration tower, the method comprising bringing an aqueous solution of an agent into contact with long fiber bundles in the tower.