JP2003080287A - Immersion membrane type water treatment equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide immersion membrane type water treatment equipment which can produce stably large amount of a filtrate for a long period of time without causing the clogging of a membrane even when there are clogging of a diffuser or failure of air supply. SOLUTION: The equipment is provided with a means which measures an air flow rate to aerate through the diffuser by using a flow rate sensor and controls a membrane permeate flow rate on the basis of the signal of the flow rate sensor when the air flow rate changes from a prescribed level.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water treatment device for filtering raw water containing suspended matter and the like. More specifically, river water, lake water, groundwater, seawater, or
The present invention relates to a water treatment device that performs large-scale sterilization and sterilization by membrane filtration using activated sludge and the like for biological treatment of domestic wastewater and factory wastewater as raw water.

[0002]

2. Description of the Related Art As a device for treating organic wastewater such as domestic wastewater such as a combined treatment septic tank, a device utilizing a membrane separation device has been put into practical use. In the immersion type membrane separation water treatment device, a method of blowing air to the membrane during filtration is known. By blowing air to the immersion type membrane module to some extent, the filtration of the membrane surface while removing the contamination is prevented from decreasing the membrane permeate amount.

In Japanese Patent Laid-Open No. 10-156154, at least one of the inflow rate of the raw water to be treated and the membrane permeate rate is controlled by detecting the discharge pressure of the air supply device. However, if only the discharge pressure is controlled, when the air diffuser is clogged, the amount of air diffused will decrease despite the increase in discharge pressure, while the amount of raw water to be treated and the amount of membrane permeate will increase. Therefore, the problem is that the inflow rate of the raw water to be treated and the membrane permeate rate cannot be controlled as intended.

In Japanese Patent Laid-Open No. 11-156360, an operation method is adopted in which the air flow rate is controlled according to the increase / decrease in the amount of membrane permeate. However, there is no mention of stabilization of the filtration operation when the air source fails, and the control of the amount of membrane permeated liquid due to the trouble of the air source is not sufficient.

[0005]

SUMMARY OF THE INVENTION According to the present invention, even if there is a clogging of an air diffuser or a failure of an air source, the membrane is not clogged and a high amount of membrane filtrate is stably maintained for a long period of time. It is an object of the present invention to provide an immersion membrane type water treatment device that can be used.

[0006]

Means for Solving the Problems In order to solve the above problems, the present inventor measured the flow rate of air aerated through an air diffusing device when filtering raw water to be treated using an immersion type membrane separator, When the measured flow rate fluctuates with respect to the set air flow rate, the flow rate sensor detects the fluctuation and controls the amount of membrane permeated liquid to be sucked in, so that a high amount of membrane filtrate can be stably maintained for a long period of time. Focusing on what can be done, the present invention has been completed.

That is, the present invention is as follows. (1) The raw water to be treated is allowed to flow into the tank, the membrane module is immersed and installed in the tank, and the raw water to be treated is filtered by the membrane module while being diffused by an air diffuser, and the membrane permeated liquid is stored in the tank. In the water treatment device to be taken out to the outside of the device, a flow rate sensor is provided in a line for supplying air to the air diffuser, and a means for controlling the amount of permeated liquid suction which operates based on the signal of the sensor is provided. Immersion membrane type water treatment device.

(2) The raw water to be treated is allowed to flow into the tank, the membrane module is dipped and installed in the tank, and the raw water to be treated is filtered by the membrane module while being diffused by an air diffuser to pass through the membrane. In a water treatment device that takes out the liquid to the outside of the tank, it has a flow rate sensor in the line that supplies air to the air diffuser, and when the air flow rate drops below a preset value, it will be automatically operated based on the signal from the sensor. An immersion membrane type water treatment device, characterized in that it is provided with means for stopping the suction of the membrane permeate.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below with reference to FIG. FIG. 1 shows a membrane module 1 in a submerged membrane tank 14.
1 of the present invention in which 3 is added and suction filtration is performed by the pump 17.
Here is an example. By inserting the flow rate sensor 12 between the air supply device 11 such as an air compressor and the air diffuser 15, and reducing the amount of the membrane permeated liquid to be sucked when the flow rate of the air falls below the set value, the rapid membrane permeation It is possible to prevent a decrease in liquid volume. As a method of controlling the amount of the membrane permeated liquid to be sucked, there is a method of controlling the rotation speed of the suction pump by an inverter or the like, and adjusting the opening degree by inserting an electric valve or an air driven valve into the valve 16. . Further, in order to completely stop the filtration, it is possible to introduce an electromagnetic valve or the like into the valve 16 in addition to the electrically operated valve and the air driven valve. When the air flow rate is increased, the pump 17 can be used to increase the suction amount of the membrane-permeated liquid.

That is, according to the present invention, the flow rate sensor detects the air flow rate when the air volume to the membrane module fluctuates,
It is a membrane separation system that automatically controls the amount of membrane permeate. In particular, when the air flow rate is significantly reduced, it is possible to stop the suction of the membrane permeate by the pump, which prevents clogging of the membrane and prevents the amount of membrane permeate from decreasing. Further, in the present invention, it is possible to use the above-mentioned mechanism and use it as a water treatment device for obtaining a desired amount of filtered water by positively controlling the flow rate of air from the air supply device. Examples of the present invention will be described below.
This does not limit the invention.

[0011]

Example 1 As shown in FIG. 1, filtration was performed with the membrane module while sending air to the membrane module with an air supply device. Air is supplied at 25 ° C. per 1 m ^{2 of} filtration membrane area and 1 m ³ / hr at atmospheric pressure, and the lower limit of the air flow rate is 25 ° C. per 1 m ² .
The atmospheric pressure was set to 0.7 m ³ / hr. Water temperature 25 ℃, water pressure on the filtration membrane 10kPa, 0.5m ³ / m ² ·
Although the membrane permeated liquid amount of day was obtained, it was not possible to send air to the membrane module due to a failure of the air supply device, and the air flow rate fell below the set lower limit value, so the sensor worked and the valve 16 automatically Was closed, pump 17 was stopped, and filtration was stopped.

The air supply device is repaired and the membrane module is again placed at 25 ° C. per 1 m ² of filtration membrane area and 1 m ³ / at atmospheric pressure.
The air of hr was supplied and the filtration was started. When the water temperature was 25 ° C. and the water pressure applied to the filtration membrane was 10 kPa, the membrane permeated liquid amount was 0.5 m ³ / m ² · day, and the same amount as before the filtration was stopped could be obtained.

[0013]

Example 2 As shown in FIG. 1, filtration was performed with the membrane module while sending air to the membrane module with the air supply device. Air was supplied at 25 ° C. per 1 m ^{2 of} filtration membrane area and 1 m ³ / hr at atmospheric pressure, and the lower limit value of the air flow rate was set to 25 ° C. per 1 m ² and 0.7 m ³ / hr at atmospheric pressure. Water temperature is 25 ° C, water pressure on the filtration membrane is 10 kPa, and 0.5 m ³ / m ² · d
Although the membrane permeated liquid amount of ay was obtained, it became impossible to send air to the membrane module due to clogging of the air diffuser,
Since the air flow rate is below the set value, the sensor works,
The pump 17 automatically adjusts the amount of membrane permeate to 0.01 m ³ / m ² ·
The filtration was continued while controlling the day.

After fixing the clogging of the air diffuser, the membrane module was again placed at 25 ° C. per 1 m ² of filtration membrane area and 1 m ³ / h at atmospheric pressure.
Air of r was supplied and filtration was started. When the water temperature was 25 ° C. and the water pressure applied to the filtration membrane was 10 kPa, the membrane permeated liquid amount was 0.5 m ³ / m ² · day, and the same amount as that before the control could be obtained.

[0015]

COMPARATIVE EXAMPLE 1 As shown in FIG. 2, filtration was carried out by the membrane module while sending air to the membrane module by the air supply device. Air of 1 m ³ / hr was supplied at 25 ° C. per 1 m ^{2 of the} filtration membrane area at atmospheric pressure, the water temperature was 25 ° C. at the conversion value at 25 ° C. and the filtration pressure was 10 kPa, and the water pressure applied to the filtration membrane was 10 kPa.
Although the membrane permeated liquid amount of 5 m ³ / m ² · day was obtained, it became impossible to send air to the membrane module due to a failure of the air supply device, and the air flow rate was 0.6 m ³ / m ² per filtration membrane area. It was less than hr, but suction filtration was 1
I continued for 2 hours. As a result, the membrane permeated liquid amount was 0.1 m ³ / m ² · day in terms of a converted value at 25 ° C. and a filtration pressure of 10 kPa.

The air supply device is repaired, and the membrane module is again placed at 25 ° C. per 1 m ² of filtration membrane area and 1 m ³ / at atmospheric pressure.
The air of hr was supplied and the filtration was started. When the water temperature was 25 ° C. and the water pressure applied to the filtration membrane was 10 kPa, the amount of liquid permeated into the membrane was 0.1 m ³ / m ² · day, and after 24 hours, it became 0.
It recovered to 15m ³ / m ² · day, but after 48 hours remained 0.15m ³ / m ² · day. Even after 1 week, it did not recover to 0.5 m ³ / m ² · day.

[0017]

The failure of the air supply device is detected by monitoring the air flow rate with the flow rate sensor between the air supply device and the air diffuser, and the membrane permeated liquid amount is controlled based on this to detect the failure. Can maintain a high amount of membrane permeate for a long period of time, and can improve the reliability of the entire water treatment device.

[Brief description of drawings]

FIG. 1 is a schematic view showing an example of a submerged membrane type water treatment device used in Examples 1 and 2 of the present invention.

FIG. 2 is a schematic view showing an example of a submerged membrane type water treatment device used in Comparative Example 1 of the present invention.

[Explanation of symbols]

11 Air supply device 12 Flow sensor 13 membrane module 14 Immersion membrane tank 15 Air diffuser 16 Automatic valve 17 Suction pump 18 Filtrate tank 19 Treated raw water introduction line 21 Air supply device 22 membrane module 23 Immersion membrane tank 24 Air diffuser 25 Manual valve 26 Suction pump 27 Filtrate tank 28 Raw water introduction line for treatment

Claims (2)

[Claims] 1. The raw water to be treated is allowed to flow into the tank, the membrane module is immersed in the tank, and the raw water to be treated is filtered by the membrane module while being diffused by an air diffuser,
In a water treatment device that takes out the membrane permeated liquid to the outside of the tank, has a flow rate sensor in a line that supplies air to the air diffuser,
An immersion membrane type water treatment device comprising a means for controlling a suction amount of a permeated liquid that operates based on a signal from the sensor. 2. The raw water to be treated is allowed to flow into the tank, the membrane module is immersed in the tank, and the raw water to be treated is filtered by the membrane module while being diffused by an air diffuser,
In a water treatment device that takes out the membrane permeated liquid to the outside of the tank, has a flow rate sensor in a line that supplies air to the air diffuser,
When the air flow rate drops below a preset value,
An immersion membrane type water treatment device comprising means for automatically stopping suction of a membrane permeate based on a signal from the sensor.