JPH05154362A - Membrane filter - Google Patents

Abstract

PURPOSE:To easily and efficiently perform the stages of filtration and washing by a membrane module with one set of water supply pump by sharing a positive displacement screw pump with a pump for filtration and a pump for washing of the external pressure type membrane module. CONSTITUTION:Raw water is introduced into an external pressure type membrane module 3 through a valve 2 for raw water from a supply pipe 1 therefor. In this case, raw water is passed through the membrane module 5 by a uniaxial eccentric screw pump 4, sucked and introduced into a treated water tank 6 through a pipeline 7 for treated water. The rpm of a motor for the pump 4 is controlled by a signal output from a rotary axis controlling device of the pump in accordance with the flow rate of treated water. When blinding of a filtration film proceeds and filtration resistance is raised to the specified value, the valve 2 for raw water is closed and a drainage valve 9 is opened and the motor of the pump 4 is reversely rotated. In such a way, filtration and washing are easily performed by one set of the positive displacement screw pump.

Description

Detailed Description of the Invention

[0001]

The present invention relates to river water, lake water, human waste,
The present invention relates to a membrane filtration device for filtering suspensions contained in raw water such as irrigation water and waste water.

[0002]

2. Description of the Related Art Generally, a microfiltration membrane has a pore size of 0.01 to several μm. Microfiltration membranes having these pore sizes are classified into an external pressure type that filters liquid from the outside to the inside of the membrane and an internal pressure type that filters liquid from the inside to the outside of the membrane.

In the external pressure type membrane module, after the filtration is continued for 0.5 to 2 hours, air or / and treated water is washed from the inside of the membrane to the outside by using air or / and treated water for several minutes. Is washed. Further, in the internal pressure type membrane module, flushing with air and / or treated water is performed in the same or opposite direction to the filtration. At this time, the transmembrane pressure difference applied to the cleaning medium necessary for filtration is generally applied by a pump or by suction.

In a general process, membrane filtration is performed and then treated water is washed. In that case, a pump for feeding raw water and a pump for feeding wash water are required. Also, of course, it is necessary to install a valve for switching the water supply. If the water temperature is different, the viscosity of the water will be different, and the amount of treated water obtained will not be constant even if membrane filtration is performed with the same filtration conditions such as the area of the filtration membrane, the type of filtration membrane or the filtration differential pressure. In order to make it constant, a flow rate adjusting mechanism is required in the device.

When a whirlpool pump, which is generally most commonly used as a water-feeding pump, is used, it is possible to use a membrane pump as described above, whether it is used to feed raw water or to feed wash water during washing. Since the pressure loss of the membrane permeation is different due to the condition of contamination and the difference in water temperature, the amount of treated water obtained and the required amount of washing water vary. In order to keep these constant, it is necessary to control the number of rotations of the pump and install a flow control mechanism such as installing a constant flow valve in the water channel.

Further, generally, the amount of washing water required for washing the external pressure type membrane module is 1 to 3 times the amount of treated water.

FIG. 2 shows a flow chart of a system in which an external pressure type filtration membrane is used, raw water is sent to the filtration membrane by a pressure pump to obtain treated water, and the treatment membrane is used to wash the filtration membrane with a washing pump. .. Specifically, in the figure, the raw water is supplied from the raw water supply pipe 11 to the membrane module 12 by the pressure pump 10 and the raw water valve 1
The treated water obtained by filtering the raw water is treated through the outflow valve 15 and the metering valve 16 (or the flow control valve) provided in the treated water pipe 14 from the water collecting portion of the membrane module 12. It is sent to the aquarium 17.

When the filtration membrane is clogged and the filtration resistance rises to a certain value, the pressurizing pump 10 is stopped, the outflow valve 15 is closed, and the cleaning valve provided from the treated water tank 17 to the cleaning pipe 18 is used. 19 and the drain valve 21 of the membrane module 12 are opened, and the washing pump 22 is operated to wash the membrane module 12. The amount of wash water required is controlled by the metering valve 20. Thus, the system shown in FIG. 2 requires the installation of two pumps and six valves.

FIG. 3 shows a flow chart of a system in which an external pressure type filter membrane is used, raw water is sucked into the filter membrane by a suction pump to obtain treated water, and the treated membrane is washed with a washing pump. .. In the figure, raw water is sent from a raw water supply pipe 31 to a membrane module 32 via a raw water valve 33 by a suction pump 30, and treated water obtained by filtering the raw water is treated water pipe 34 from a water collecting portion of the membrane module 32. Outflow valve 3
5 and the metering valve 36 (or the flow rate control valve) to the treated water tank 37.

When the filtration resistance has risen to a certain value due to the progress of clogging of the filtration membrane, the suction pump 30 is stopped, the outflow valve 35 is closed, and the washing valve 39 provided in the washing pipe 38 from the treated water tank 37. And the drain valve 41 of the membrane module 32 is opened, and the washing pump 42 is operated to wash the membrane module 32. The required amount of cleaning water is controlled by the metering valve 40. Thus, the system shown in FIG. 3 also requires the installation of two pumps and six valves.

[0011]

DISCLOSURE OF THE INVENTION The present invention is a membrane filtration device in which a membrane module is provided in a tank, and the steps of filtration and washing by the membrane module are performed by one water pump, and a raw water valve and drainage are provided. It is an object of the present invention to provide a membrane filtration device that does not require a valve other than a valve and can realize simple and efficient filtration and cleaning.

[0012]

Means for Solving the Problems The above problem is to provide a membrane filtration device in which at least an external pressure type membrane module is provided, and a system in which a volumetric screw pump is used as both a filtration pump and a cleaning pump of the external pressure type membrane module. It is achieved by a membrane filtration device characterized by:

Since the positive displacement screw pump used in the present invention is a positive displacement pump, the amount of water supplied is constant, and the amount of water supplied can be changed by controlling the rotational speed of the pump. Further, the motor can be rotated in the reverse direction, and by rotating the motor in the reverse direction, the water supply direction can be reversed while maintaining the constant flow rate of the water supply amount, so that it can be used as both a filtering pump and a cleaning pump. A uniaxial eccentric screw pump is particularly preferably used as the positive displacement screw pump used in the present invention.

The membrane filtration device provided with a membrane module is generally an internal pressure type membrane module or an external pressure type membrane module, and these membrane filtration devices as a whole are subjected to the filtration and washing steps. May be operated with one positive displacement screw pump.

When filtering a suspension contained in raw water such as river water, lake water, human waste, irrigation water, waste water, etc., the raw water is subjected to membrane filtration by a suction method by immersing the membrane filtration device in these raw water tanks. It is an advantageous membrane filtration method, and therefore, it is a preferred embodiment to immerse the membrane module in a raw water tank to perform membrane filtration of raw water by a suction method.

The type of membrane used for the external pressure type membrane module may be a hollow fiber membrane or a ceramic membrane. The membrane filtration device may be of a type that is used by being immersed in an open tank or a type in which a membrane is sealed in a closed case, but a type of being used by being immersed in an open tank is preferable. In the case of the type that is used by immersing it in an open tank, it is convenient in most cases to use a suction method for water supply.

The suction pressure of the uniaxial eccentric screw pump is about -8.
Since it is mAq, in the present invention, when the uniaxial eccentric screw pump is used, the membrane to be applied is such that permeated water can be obtained at a membrane pressure difference of about 0.8 kg / cm ² or less.

The membrane filtration device of the present invention can also be used for the treatment of sewage by the activated sludge method, and can be used in place of the settling basin for activated sludge treatment, or for biological treatment by allowing activated sludge to exist in the treatment tank. The efficiency of the activated sludge treatment process can be improved.

[0019]

EXAMPLES Specific examples of the present invention will be shown below, but the present invention is not limited thereto. The present invention will be described with reference to the membrane filtration device shown in FIG. 1 in which an external pressure type membrane module is immersed in an open tank. Raw water is transferred from a raw water supply pipe 1 to an external pressure type membrane module 3 via a raw water valve 2. be introduced.
Raw water passes through the external pressure type membrane module 3 and is sucked by the uniaxial eccentric screw pump 4 and flows into the treatment tank 6 through the treated water pipe 7. The flow rate of the treated water is controlled by controlling the rotation speed of the motor of the uniaxial eccentric screw pump 4 by a signal from the rotation speed control device of the pump.

When the filtration resistance has risen to a certain value due to the progress of the clogging of the filtration membrane, the raw water valve 2 is closed and the drain valve 9 is opened to clean the filtration membrane with the treated water. Reverse rotation is performed. At this time, the wash water is sent from the treated water tank 6 to the external pressure type membrane module 3 through the treated water pipe 7, passes from the inside of the membrane to the outside, and is drained through the drain valve 8. The amount of washing water is controlled by controlling the rotation speed of the motor of the uniaxial eccentric screw pump 4 by a signal from the rotation speed control device.

Since the required amount of washing water is 1 to 3 times the amount of treated water, the number of rotations of the motor of the uniaxial eccentric screw pump 4 during washing is controlled to be higher than that during filtration.

[0022]

According to the present invention, a volumetric screw pump and a controller for controlling the number of revolutions thereof are incorporated in a membrane filtration device, so that filtration and washing are performed by using one volumetric screw pump, and the conventional filtration device is realized. The two pumps, the raw water feed pump and the wash water supply pump, which were built in, can be used in one unit, and the four valves such as the treated water flow valve, the constant flow valve and the wash valve can be eliminated, and the membrane filtration device can be used. Since the treated water tank can be connected with a single pipe via a positive displacement screw pump, the device is much simpler than the conventional system and the maintenance is greatly reduced.

[Brief description of drawings]

FIG. 1 is a process flow chart of performing filtration by operating a membrane filtration device in which an external pressure type membrane module is immersed in an open tank of the present invention by a uniaxial eccentric screw pump and its rotation control device.

FIG. 2 is a process flow diagram of a conventional membrane filtration device in which a pressurizing pump and a cleaning pump are used, and filtration and cleaning are controlled by a valve.

FIG. 3 is a process flow diagram of a conventional membrane filtration device in which a suction pump and a cleaning pump are used and a valve controls filtration and cleaning.

[Explanation of symbols]

 1 Raw water supply pipe 2 Raw water valve 3 Membrane module 4 Uniaxial eccentric screw pump 6 Treated water tank 7 Treated water pipe 8 Drain valve 10 Pressurizing pump 11 Raw water supply pipe 12 Membrane module 13 Raw water valve 14 Treated water pipe 15 Outflow valve 16 Quantitative valve 17 Treatment Water tank 18 Cleaning pipe 19 Cleaning valve 20 Metering valve 21 Drain valve 22 Cleaning pump 30 Suction pump 31 Raw water supply pipe 32 Membrane module 33 Raw water valve 34 Treated water pipe 35 Outflow valve 36 Quantitative valve 37 Treated water tank 38 Cleaning pipe 39 Wash valve 40 Metering valve 41 Drain valve 42 Cleaning pump

Claims (1)

[Claims] 1. A membrane filtration apparatus in which a membrane module is provided in a tank, wherein the volumetric screw pump serves as a filtration pump and a washing pump for the membrane module.