JPH1157431A - Method for cleaning membrane separation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for cleaning a membrane separation device which dispenses with a troublesome operation to draw a membrane out of the membrane separation device and clean it with a chemical or drain a tank and clean the membrane with a chemical in the tank, cleans the membrane easily and further, has no possibilities that the drain treatment efficiency might be deteriorated. SOLUTION: The method for cleaning the membrane separation device is to wash n-2 pieces of filter membrane unit 3D backward using a membrane- permeating water while filtering a drain with the help of(a) pieces (1<=a<n) of unit 3A, 3B, 3C, out of(n) pieces of filter membrane unit 3A, 3B, 3C, 3D arranged in a membrane separation tank 2. The membrane-permeating water preferably contains hypochlorite soda, the use of which enhances the cleaning efficiency. The concentration of the hypochlorite sode is preferably, 500-5000(mg/ liter), more preferably, 1000-2500(mg/liter). The hypochlorite soda may be of such a grade that is added for sterilizing the membrane-permeating water.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to the treatment of wastewater from various factories such as the chemical, food, pharmaceutical, and fertilizer industries, and wastewater from treatment facilities such as sewage treatment plants and human waste treatment plants by membrane separation. More specifically, the present invention relates to a method for cleaning a membrane separation device.

[0002]

2. Description of the Related Art Conventionally, to clean a membrane of a membrane separation apparatus,
A method has been practiced in which a membrane is drawn from a membrane separation device and washed with a chemical, or water in a tank is drained and the membrane is washed with a chemical.

[0003]

However, these cleaning methods are cumbersome to operate, and improvements are desired. In addition, wastewater treatment cannot be performed during the cleaning of the membrane, and there is a problem in terms of wastewater treatment efficiency.

The present invention does not require a troublesome operation such as drawing out the membrane from the membrane separation device and cleaning the film with chemicals, or removing the water in the bath and then cleaning the film with chemicals in the bath. It is another object of the present invention to provide a method for cleaning a membrane separation apparatus which can perform the wastewater treatment efficiency without reducing the wastewater treatment efficiency.

[0005]

According to the present invention, there is provided a method for cleaning a membrane separation apparatus, comprising the steps of draining water in a (where 1 ≦ a <n) units out of n filtration membrane units disposed in a membrane separation tank. , While back-washing na units with membrane permeated water while performing filtration.

[0006] Preferably, the membrane permeated water contains sodium hypochlorite. The use of sodium hypochlorite enhances the cleaning effect. The concentration of sodium hypochlorite is preferably 5
00 to 5000 (mg / liter), more preferably 1
000 to 2500 (mg / liter). Sodium hypochlorite may be added for disinfection of membrane permeated water.

A disinfection tank for disinfecting the membrane permeated water by adding sodium hypochlorite is provided at a position higher than the water surface of the membrane separation tank,
It is also possible to send backwash water from this disinfection tank to the membrane separation tank by the siphon principle. The capacity of the disinfection tank is preferably 1 to 5 liters, more preferably 1.5 to 3 liters per 1 m ^{2 of the} effective membrane area.

In addition, a cushion tank for receiving sodium hypochlorite is provided at a position higher than the water surface of the tank in the disinfection tank, and normally the sodium hypochlorite is supplied to the disinfection tank by overflow from the cushion tank, At the time of backwash water adjustment, sodium hypochlorite can be supplied to the disinfection tank from a conduit provided at the lower part of the cushion tank. Capacity of the cushion tank, preferably from 0.1 to 0.5 liters relative to film effective area 1 m ^2, more preferably 0.1
5 to 0.3 liters.

After supplying sodium hypochlorite to the disinfection tank from the conduit for adjusting the backwash water of the cushion tank, the valve of the conduit is closed, and the rotation speed of the sodium hypochlorite supply pump is increased to increase the cushion tank. It is preferable to immediately fill the inside with sodium hypochlorite.

Preferably, each of the above operations is performed by sequence control. According to the sequence control, maintenance becomes easy.

[0011]

Embodiments of the present invention will be described with reference to the drawings.

In FIG. 1, a membrane separation tank of a membrane separation device (1)
In (2), four filtration membrane units (3A, 3B, 3C, 3D) are arranged in parallel. Although not shown, each filtration membrane unit (3A, 3B, 3C, 3D) includes a plurality of hollow flat membrane modules, and each flat membrane module includes two flat membrane modules arranged in opposition. And a frame-shaped spacer arranged between the peripheral portions of both flat films. A suction pipe (5) is provided from each filtration membrane unit (3A, 3B, 3C, 3D) of the membrane separation tank (2) to a disinfection tank (8) via a suction pump (4). This suction pipe (5) branches into four at the base end, and these suction branch pipes (6)
Is further branched into a plurality of tubes at each base end, and these suction fine branch tubes (not shown) are connected to each flat membrane module so as to communicate with the inside of the hollow portion. The suction branch pipes (6) are provided with automatic valves (13A, 13B, 13C, 13D), respectively. It should be noted that a flat membrane module using a hollow fiber membrane instead of the flat membrane can be applied to the filtration membrane units (3A, 3B, 3C, 3D). An air diffuser (7) is arranged below each of the filtration membrane units (3A, 3B, 3C, 3D).

A disinfection tank (8) for disinfecting the membrane permeated water by adding sodium hypochlorite to a position higher than the water surface of the membrane separation tank (2).
Is provided. A cushion tank (9) for receiving sodium hypochlorite is provided on one side of the disinfecting tank (8) at a position higher than the water surface, and the cushion tank (9) is provided.
Sodium hypochlorite tank (10) above the water surface
Is provided. The capacity of the disinfection tank (8) is 1 effective membrane area.
2 liters per m ² . Cushion tank (9)
Is 0.2 liter per 1 m ^{2 of} effective membrane area. The supply of sodium hypochlorite from the sodium hypochlorite tank (10) to the cushion tank (9) is performed by the supply pump (11).
Done by The sodium hypochlorite in the cushion tank (9) usually overflows in the disinfection tank due to overflow.
(8) at 100 ml / h, and a conduit provided at the bottom of the cushion tank (9) during backwash water adjustment.
From (12), it is supplied to the disinfection tank (8) at a stretch. An automatic valve (14) is provided in the middle of the conduit (12).

From the lower part of the disinfection tank (8), the filtration membrane unit (3A,
3B, 3C, 3D) is provided with a supply pipe (15) for backwash water. This supply pipe (15) branches into four tips, and these supply branch pipes
(16) is connected to each suction branch pipe (6) between the automatic valve (13A, 13B, 13C, 13D) and the filtration membrane unit (3A, 3B, 3C, 3D).
Automatic valves (17A, 17B, 17C, 17
D) is provided.

The above wastewater treatment system includes a sequence controller (18) having a timer.
B, 13C, 13D, 14, 17A17B, 17C, 17D) are opened and closed by signals from the sequence controller (18). The rotation speed of the sodium hypochlorite supply pump (11) can be increased or decreased by a signal from the sequence controller (18).

In the above wastewater treatment system, the automatic valves (13A, 13B, 13C, 13D) of each suction branch pipe (6) are normally opened, and the automatic valves (17A, 17B) of each supply branch pipe (16) are opened. , 17B, 17C, 17D) and the automatic valve (14) of the conduit (12) are closed, and the suction pump (4)
By operating, the wastewater supplied into the membrane separation tank (2) is treated by the membrane separation device (1) to remove activated sludge and the like. The permeated water is sent to the disinfection tank (8) via the suction pipe (5). On the other hand, by operating the supply pump (11), sodium hypochlorite is supplied from the sodium hypochlorite tank (10) to the cushion tank (9), and the sodium hypochlorite in the cushion tank (9) is supplied. Is supplied to the disinfection tank (8) by overflow and mixed with the permeated water. The concentration of sodium hypochlorite in the mixed water is 10 (mg / liter). This mixed water is treated as a disinfection tank
(8).

When the membrane of the membrane separation device (1) is clogged and a transmembrane pressure is generated, four filtration membrane units (3A, 3B, 3C) arranged in the membrane separation tank (2) are used. , 3D)
The remaining one filtration membrane unit is backwashed while filtering the wastewater with one filtration membrane unit. In this manner, one of the four filtration membrane units (3A, 3B, 3C, 3D) is sequentially backwashed.

For example, when backwashing the filtration membrane unit (3D), the following operations are performed by sequence control.

A. First, in the operation panel of the sequence controller (18), when the backwash of the filtration membrane unit (3D) is selected, the signal from the sequence controller (18) opens the automatic valve (14) of the conduit (12), The sodium hypochlorite in the cushion tank (9) is supplied to the disinfection tank (8) at a stretch, and the backwash water is adjusted. The concentration of sodium hypochlorite in the backwash water in the disinfection tank (8) is 5000 (mg / liter).

B. Subsequently, the automatic valve (13D) of the suction branch pipe (6) connected to the filtration membrane unit (3D) opens, and the supply branch pipe (16) connected to the suction branch pipe (6) automatically opens. Valve (1
7D) opens. Then, the backwashing water composed of the membrane permeated water and sodium hypochlorite mixed in the disinfection tank (8) passes through the supply pipe (15) including the supply branch pipe (16) according to the siphon principle, and passes through the filtration membrane. It flows into the unit (3D) from the membrane permeation side, whereby the flat membrane constituting each flat membrane module of the filtration membrane unit (3D) is washed.

C. A predetermined time from the start of backwashing (for example, about 5
Minutes), the automatic valve (14) of the conduit (12) and the supply branch pipe (1)
6) The automatic valve (17D) closes, and the rotation speed of the sodium hypochlorite supply pump (11) increases.
The supply amount of sodium hypochlorite to (9) is 13 liters per second. As a result, the cushion tank (9) is quickly filled with sodium hypochlorite, so that the supply of sodium hypochlorite from the cushion tank (9) to the disinfection tank (8) can be quickly performed without time delay. It can be restarted by overflow.

D. When the cushion tank (9) is filled with sodium hypochlorite, this is detected by, for example, a level detector (not shown) installed in the cushion tank (9), and a signal from the detector is sent to the sequence controller ( By being sent to 18), the rotation speed of the sodium hypochlorite supply pump (11) decreases until normal time.

E. Then, the washing state in which the backwash water is held in each flat membrane module of the filtration membrane unit (3D) is maintained for a predetermined time (for example, about 2 to 3 hours). During this time, wastewater treatment is continuously performed by the other filtration membrane units (3A, 3B, 3C). After that, the automatic valve (13D) of the suction branch pipe (6) is opened, and the operation panel of the sequence controller (18) has a display (lighting of lamp, etc.) indicating the end of washing of the filtration membrane unit (3D). The membrane unit (3D) returns to normal operation.

The remaining filtration membrane units (3A, 3B, 3C) are sequentially backwashed by the same operation as described above.

[0025]

According to the method for cleaning a membrane separation device of the present invention, it is troublesome to draw out the membrane from the membrane separation device and perform chemical cleaning, or to drain the water in the tank and then perform chemical cleaning of the membrane in the same tank. The membrane can be easily cleaned without requiring any special operation. In addition, since the wastewater treatment can be continuously performed by the remaining films while cleaning a part of the films, the efficiency of the wastewater treatment does not decrease.

Further, the maintenance of the membrane separation device becomes easy, and the running cost can be reduced.

Furthermore, since the chemical used for disinfection is used for cleaning, the initial cost does not increase.

[Brief description of the drawings]

FIG. 1 is a flowchart showing an embodiment of the present invention.

[Explanation of symbols]

 (1)… Membrane separation equipment (2)… Membrane separation tank (3A, 3B, 3C, 3D)… Filtration membrane unit (8)… Disinfection tank (9)… Cushion tank (12)… Conduit (11)… Sodium chlorate supply pump

Claims (13)

[Claims] 1. While filtering waste water with a (where 1 ≦ a <n) units of n filtration membrane units disposed in a membrane separation tank, na units are permeated through a membrane. A method for cleaning a membrane separation device, comprising backwashing with water. 2. The method according to claim 1, wherein the permeated water comprises sodium hypochlorite. 3. A sodium hypochlorite concentration of 500 to 50.
3. The method according to claim 2, wherein the amount is 00 (mg / liter). 4. The concentration of sodium hypochlorite is 1000-2.
3. The method according to claim 2, wherein the amount is 500 (mg / liter). 5. The method according to claim 1, wherein the sodium hypochlorite is added for disinfection of membrane permeated water. 6. A disinfection tank for disinfecting membrane permeated water by adding sodium hypochlorite is provided at a position higher than the water surface of the membrane separation tank, and backwash water is removed from the disinfection tank by the principle of siphon. 6. The method according to claim 5, wherein the method comprises: 7. The method according to claim 6, wherein the capacity of the disinfection tank is 1 to 5 liters per 1 m ^{2 of the} effective area of the membrane. 8. The disinfection tank has a capacity of 1.5 to 3 liters per 1 m ^{2 of} effective membrane area.
The described method. 9. A cushion tank for receiving sodium hypochlorite is provided at a position higher than the surface of the water in the disinfecting tank. Normally, sodium hypochlorite is supplied from the cushion tank to the disinfecting tank by overflow to adjust the backwash water. The method according to any one of claims 6 to 8, wherein sodium hypochlorite is supplied to the disinfection tank from time to time through a conduit provided at a lower portion of the cushion tank. 10. The method according to claim 9, wherein the capacity of the cushion tank is 0.1 to 0.5 liter per 1 m ^{2 of the} effective area of the membrane. 11. The method according to claim 9, wherein the capacity of the cushion tank is 0.15 to 0.3 liter per 1 m ^{2 of} effective membrane area. 12. After supplying a predetermined amount of sodium hypochlorite to a disinfection tank from a conduit for adjusting backwash water of a cushion tank,
The valve of the conduit is closed, and the rotation speed of the sodium hypochlorite supply pump is increased to quickly fill the cushion tank with sodium hypochlorite.
The method according to claim 1. 13. The method according to claim 1, wherein each operation is performed by sequence control.