JP2740613B2 - Membrane treatment method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention uses a membrane processing apparatus having a closed loop circulation line formed on the raw water side of a membrane module .
The present invention relates to a film processing method .

[0002]

2. Description of the Related Art In a film processing apparatus of the above type, if air is mixed into a circulation line, the following problems occur. Because air remains in the circulation line,
Even if the raw water is supplied, the pressure to be filtered cannot be directly applied to the membrane because the air shrinks, and stable filtration cannot be performed. If air remains in the membrane module, filtration cannot be performed in the air part, so the effective area of the membrane becomes smaller,
Occlusion of the membrane is promoted. The circulation pump installed in the circulation line causes cavitation, which increases the possibility of causing a decrease in the discharge amount, a decrease in the discharge pressure, a failure of the pump, and the like. When backwashing with high-pressure air from the permeate side or backwashing using pressurized water, if there is an air pocket inside the membrane module, the air shrinks at the time of pressurization and air or backwashing pressurized water flows to the raw water side. Leakage reduces the backwashing effect.

[0003] Conventionally, as shown in FIG. 4, an open type tank 3 has been installed in a circulation line composed of a membrane module 1 and a circulation pump 2 to remove air from the circulation line. However, the film processing method of FIG. 4 has the following problems. A large-capacity tank 3 is required to prevent inhalation of air bubbles. Since the circulation line includes the open tank 3, the valve 4 is closed and a constant pressure is applied to the membrane module 1 by the circulation pump 2 (constant pressure filtration method).
However, this method cannot secure a stable amount of filtered water because the amount of filtered water decreases as the membrane becomes clogged. Since the energy loss in the valve 4 is large, when the liquid is circulated and cross-flow filtration is performed,
Large economic loss.

[0004]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned conventional problems and provides a membrane treatment method which does not require a large-sized facility for removing air and can secure a stable amount of filtered water. It was completed for.

[0005]

Means for Solving the Problems A membrane processing method according to the present invention, which has been made to solve the above-mentioned problems, is directed to a method for forming a membrane module.
Supply raw water to the closed loop circulation line formed on the water side
And the raw water sent through the membrane module
Pumped into the membrane module again by the circulation pump,
Circulates raw water without biological and biological treatment
To make the circulation line pressurized by the supply pressure of raw water.
Membrane treatment method to continue filtration operation while holding
Suction of said membrane module and said circulation pump
The cross-sectional area of the pipe between the
A vertical air separator with a larger size is provided.
Raw water flows downward at a flow rate of 0.5 m / sec or less inside the parator.
Floating air bubbles in raw water by distributing
From the air release valve at the top of the air separator.
It is characterized by discharging .

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in more detail with reference to the illustrated embodiments. 1 and 2, reference numeral 1 denotes a membrane module, and 2 denotes raw water circulated through the membrane module and sent out again to the membrane module by a circulating pump so that the raw water is not subjected to chemical and biological treatment. A circulation pump provided in a circulation line for circulation,
Reference numeral 5 denotes a raw water tank, and reference numeral 6 denotes a supply pump for supplying raw water from the raw water tank 5 to the circulation line, and for continuing the filtration operation while maintaining the inside of the closed loop circulation line in a pressurized state by the supply pressure. An air separator 8 is provided in the middle of the pipeline 7 between the membrane module 1 and the suction side of the circulation pump 2.

The air separator 8 is a sealed vertical cylindrical member as shown in an enlarged view in FIG. 2, and has a much larger cross-sectional area than the cross-sectional area of the pipeline 7. is there. For this reason, the flow velocity of the circulating fluid flowing from the pipe 7 and flowing downward inside the air separator 8 rapidly decreases inside the air separator 8, and the air bubbles in the circulating fluid separate and float. For this purpose, the flow velocity in the air separator 8 is 0.5 m
/ sec or less, more preferably 0.1 to 0.2 m / sec, and the cross-sectional area of the air separator 8 is determined to be 0.16 m / sec in the embodiment. Further, the shape of the air separator 8 is preferably vertically long whose height is twice or more the diameter in order to surely perform the air separation. In the embodiment in which the circulating liquid amount is 50 liters per minute, the diameter is 80 mm. Height 300mm
It has been.

At the upper end of the air separator 8, an air release valve 9 is provided. In the embodiment, a float vent is employed, and when the air amount reaches a certain amount, the float 10 is pushed down to open the valve, and the air is discharged to the outside. It is preferable that the ceiling surface of the air separator 8 is provided with a gradient so that air can be easily collected at the air release valve 9.

[0009]

According to the present invention, there is provided a film processing apparatus constructed as described above.
In the membrane treatment method, the raw water is circulated to the raw water side of the membrane module 1 by the circulating pump 2, while the raw water is supplied from the raw water tank 5 to the circulating line by the supply pump 6 while maintaining the pressurized state in the circulating line. The filtration is performed by the membrane module 1. At this time, the air contained in the circulating fluid flows downward at a flow rate of 0.5 m / sec or less through the inside of the vertical air separator 8 having a cross-sectional area larger than that of the pipe 7.
The air is separated and floats while flowing through the air, and is discharged into the atmosphere from the air release valve 9 at the upper end. Therefore, the filtration can be continuously performed while the circulation line is maintained in a pressurized state by the supply pump 6, and stable filtration can be performed without the above-described trouble caused by air. When the membrane module 1 is closed, it is necessary to perform backwashing using high-pressure air or pressurized water. At this time, air mixed into the raw water side can be quickly removed by the air separator 8.

As described above, according to the present invention, stable filtration is possible. However, when the air separator 8 is not installed, the discharge amount of the circulation pump 2 is insufficient, the mechanical seal of the circulation pump 2 is broken, and the permeation flux is reduced. And the membrane was clogged prematurely. Although the circulation pump 2 is provided at the position shown in FIG. 1 in the above-described embodiment, the same operation and effect can be obtained by providing the circulation pump 2 at the position shown in FIG.

[0011]

As described above, the film processing of the present invention
The method is to provide a vertical air separator having a cross-sectional area larger than that of the pipeline between the membrane module and the suction side or the discharge side of the circulation pump, and the inside of the air separator.
Flow raw water downward at a flow rate of 0.5 m / sec or less
Air bubbles contained in the raw water
The air vent valve at the top of the
Since those were not require large facilities for conventional such air removal, yet upon which can stable filtration, there is the advantage that it is possible to obtain an excellent backwash effect.
In addition, since the removal of air and the supply of raw water can be performed at the same time, the permeation flux can always be kept constant. Therefore, the present invention greatly contributes to industrial development as a film processing method that solves the conventional problems.

[Brief description of the drawings]

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

FIG. 2 is an enlarged sectional view of a main part of the embodiment.

FIG. 3 is a piping system diagram showing another embodiment.

FIG. 4 is a piping system diagram showing a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Membrane module 2 Circulation pump 7 Pipe line 8 Air separator 9 Air release valve

Claims (1)

(57) [Claims] 1. A closed loop formed on a raw water side of a membrane module.
Feed water to the circulation line of the
Raw water sent through the circulation is re-membraneized by a circulation pump.
Into modules for chemical and biological processing
Circulates raw water without
The filtration operation is continued while keeping the circulation line pressurized.
The method for treating a membrane, comprising:
Between the suction side and the discharge side of the circulation pump
A vertical air cell with a cross section larger than that of the pipe
A parator is provided, and raw water is added to the inside of this air separator.
Raw water by flowing downward at a flow rate of 5 m / sec or less
Air bubbles contained in the air
That the air was released from the air vent valve at the end.
Characterized film processing method.