JPH11156360A - Method for operation of water treatment plant - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for operation of a water treatment plant wherein fouling hardly occurs even when the filtration quantity of a membrane separation apparatus is increased. SOLUTION: Filtration is caused through a membrane surface by making the suction pressure of a suction pump 29 act on a permeated water channel of a membrane separation apparatus. When membrane permeated water flowing into the permeated water channel after permeating a membrane surface is discharged through a permeated water discharging pipe 28, a specific flow quantity of aerated air which is set according to the quantity of a discharged water flow rate of the membrane permeated water is ejected through an aeration device 21, and a membrane surface of the upward membrane separation apparatus 22 is washed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for operating a water treatment apparatus having an aeration tank in which a diffuser and a membrane separator are installed.

[0002]

2. Description of the Related Art As a conventional water treatment apparatus, for example, FIG.
As shown in FIG. 2, there is a purification tank provided with a flow control tank 1, an aeration tank 4 in which an aeration device 2 and a membrane separation device 3 are immersed and installed. The membrane separation device 3 includes a tubular or flat membrane element 3a.
Are arranged such that each membrane element 3a is located above the air diffuser 2, and the permeated water outlet pipe 5 communicating with the permeated water flow path of each membrane element 3a is connected to the suction pump 6. It is interposed and opened outside the septic tank.

In such a purification tank, the raw water 7 flowing into the flow control tank 1 is transferred to the aeration tank 4, and inside the aeration tank 4.
In the state of aeration from the diffuser 2, the BO in the raw water 7
D and nitrogen are decomposed by activated sludge, and the activated sludge mixed liquid 8 is filtered on the membrane surface of each membrane element 3a by applying the suction pressure of the suction pump 6 to the permeated water flow path of each membrane element 3a. Membrane permeated water that has passed through the surface and flowed into the permeated water flow path is led out of the tank through the permeated water outlet pipe 5. At this time, the membrane surface of the membrane element 3a is cleaned using aerated air rising from the air diffuser 2.

[0004]

By the way, in the above-mentioned septic tank, conventionally, the capacity of the flow rate adjusting tank has been sufficiently increased in case a large amount of raw water flows. However, since the septic tank capacity inevitably increases, the amount of raw water transferred from the flow control tank to the aeration tank is increased when the water level in the flow control tank exceeds a predetermined high water level. There is also proposed a membrane separation device in which the filtration amount is increased to reduce the size of the device.
However, in the latter, there is a problem that it is not enough to prevent fouling of the membrane surface of the membrane separation device because the amount of aerated air by the air diffuser is fixed.

An object of the present invention is to solve the above-mentioned problem, and an object of the present invention is to provide a method of operating a water treatment apparatus in which fouling is less likely to occur even when the filtration amount of the membrane separation apparatus is increased.

[0006]

In order to solve the above-mentioned problems, a method for operating a water treatment apparatus according to claim 1 of the present invention comprises:
An aeration device in which a membrane separation device is immersed and installed in an aeration tank, a suction pump is interposed in a permeated water outlet pipe provided in communication with the permeated water flow path of the membrane separation device, and the air supply source such as a blower is connected. Is a method of operating a water treatment apparatus provided below the membrane separation device, wherein filtration is performed on the membrane surface by applying the suction pressure of the suction pump to the permeated water flow path of the membrane separation device, and permeation through the membrane surface is performed. When the membrane permeated water that has flowed into the permeated water flow path is led out by the permeated water outlet pipe, a predetermined amount of aerated air set according to the magnitude of the flow rate of the permeated water discharged through the diffuser is blown out, and The membrane surface of the membrane separation device is washed.

According to a second aspect of the present invention, there is provided a method for operating a septic tank, comprising the steps of: measuring a raw water level in a flow regulating tank in a water treatment apparatus provided with a flow regulating tank; The raw water is transferred to an aeration tank, and a predetermined flow rate of the membrane permeated water set according to the transfer flow rate of the raw water is derived.

According to the above-described structure, when the flow rate of the membrane permeated water is increased, a large amount of aerated air corresponding to the flow rate is jetted through the air diffuser, and the upward flow generated by the aerated air causes an upward flow. Since the membrane surface of the membrane separation device is effectively cleaned, fouling hardly occurs.

When the flow rate of the raw water is large and the water level in the flow control tank rises, a large amount of raw water corresponding to the water level is transferred from the flow control tank to the aeration tank, and the aeration tank controls the flow rate. Since filtration is performed, the raw water residence time in the flow control tank is short, and the flow control capacity is small.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. The purification tank shown in FIG. 1 includes a flow control tank 20 and an aeration tank 23 in which a diffuser 21 and a membrane separator 22 are immersed, and a raw water transfer pipe guided from the flow control tank 21 to the aeration tank 23. A transfer pump 25 and a flow control valve 26 are interposed in 24.

The air diffuser 21 communicates with a blower 27 capable of adjusting the amount of air supply. The membrane separation device 22 is configured by arranging tubular or flat membrane elements 22 a, and is installed such that each membrane element 22 a is located above the air diffuser 21. The permeated water outlet pipe 28 communicating with the permeated water flow path (not shown) of each membrane element 22a has a suction pump 29 and a flow control valve 30 interposed in the middle of the pipe, and an external discharge flow path (not shown). Is led to.

A water level measuring means such as a water level gauge 31 is provided inside the flow rate adjusting tank 20, and is electrically connected to the water level gauge 31, the flow rate adjusting valve 26 and the flow rate adjusting valve 30, and
A control device 32 is provided for controlling the opening and closing of the flow control valve 26 and the flow control valve 30 at predetermined high water level HWL, middle water level MWL, and low water level LWL measured by the water level gauge 32. The transfer pump 25 and the suction pump 28 are driven at a constant rotation speed.

The operation of the above configuration will be described. The raw water 33 is introduced into the flow control tank 20, and the water level of the raw water 33 in the flow control tank 20 is continuously or intermittently measured by the water level meter 31.

When the measured water level is at the intermediate water level MWL between the predetermined high water level HWL and the low water level LWL, the control device 32 controls the flow through the flow control valve 26 and the flow control valve 30 so that the constant flow C1 flows. Maintain the opening. Further, the blower 2 is blown through the air diffuser 21 so as to be aerated at a predetermined constant flow rate A1 with respect to the constant flow rate C2 at which the membrane permeated water is discharged.
Maintain 7

In this state, the transfer pump 2
5, the raw water 33 in the flow regulating tank 20 is transferred to the aeration tank 23 at a constant flow rate C1 through the raw water transfer pipe 24,
Inside, the raw water 33 flowing in is treated with activated sludge while aeration is performed at a constant flow rate A1 by the air diffuser 21. The suction pump 28 cleans the upper surface of the membrane element 22a by the upward flow generated by the aerated air.
The activated sludge mixture 34 in the tank is filtered by each membrane element 22a by the suction pressure acting on the permeated water flow path of each membrane element 22a, and the permeated water permeating through the membrane surface and flowing into the permeated water flow path is permeated. The water is led out of the aeration tank 23 through the water outlet pipe 27 at a constant flow rate C1.

In the flow control tank 20, a predetermined high water level HW
When a water level higher than L is measured, the control device 32 adjusts the flow control valve 26 and the flow control valve 29 to transfer the raw water 33 having a constant flow rate C2 (> C1) to the aeration tank 23, A state where the membrane permeated water of C2 is led out of the aeration tank 23 and the blower 27 is adjusted to aerate at a constant flow rate A2 (> A1) set in advance with respect to the constant flow rate C2 at which the membrane permeated water is led out. In the same manner as above.

In the flow control tank 20, a predetermined low water level LW
When a water level lower than L is measured, the control device 32 adjusts the flow control valve 26 and the flow control valve 29 to transfer the raw water 33 having a constant flow rate C3 (<C1) to the aeration tank 23, A state in which the membrane permeated water of C3 is led out of the aeration tank 23 and the blower 27 is adjusted to aerate at a predetermined aeration flow rate A3 (<A1) with respect to a constant flow rate C3 at which the membrane permeated water is led out. In the same manner as above.

That is, as the flow rate of the raw water 33 increases and the water level in the flow control tank 20 rises, the transfer amount of the raw water 33 from the flow control tank 20 to the aeration tank 23 increases, and the aeration tank 2
Since the amount of filtration in step 3 is increased, the raw water residence time in the flow control tank 20 is shortened, and the flow control capacity is small.

Since the aeration amount is increased as the filtration amount is increased, a fast upward flow is supplied when the membrane element 22a is likely to be clogged. Is effectively cleaned.

In the above description, the transfer amount of the raw water and the discharge amount of the membrane permeated water are respectively adjusted by the flow control valve in a state where the transfer pump and the suction pump are driven at a constant rotation speed. In the device configuration, the transfer pump and the suction pump may be controlled by an inverter.

In the above description, the flow control tank is described, but a denitrification tank having a flow control function may be operated in the same manner.

[0022]

As described above, according to the present invention, the aeration amount is increased in accordance with the increase in the filtration amount, so that the membrane surface of the membrane separation device installed above the diffuser is cleaned. An appropriate shear flow can be secured, fouling can be prevented, and the life of the membrane can be extended.

When the flow rate of the raw water is large and the water level in the flow control tank rises, the transfer rate of the raw water from the flow control tank to the aeration tank is increased, and the filtration amount of the membrane separation device in the aeration tank is increased. Is increased, the flow rate adjustment capacity can be designed to be small, and the apparatus can be made compact.

[Brief description of the drawings]

FIG. 1 is a schematic overall configuration diagram of a septic tank illustrating an operation method of the septic tank in one embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a schematic overall configuration of a conventional septic tank.

[Explanation of symbols]

 20 Flow control tank 21 Aerator 22 Membrane separator 22a Membrane element 23 Aeration tank 24 Raw water transfer pipe 27 Blower 28 Permeate discharge pipe 29 Suction pump 31 Water level gauge 33 Raw water 34 Activated sludge mixture

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Koichi Okada 1-1-1 Hama, Amagasaki-shi, Hyogo Inside Kubota Research Institute of Technology (72) Inventor Kazuyuki Honda 2 Takamatsu, Kosai-cho, Koga-gun, Shiga Prefecture 1 Kubota Shiga Plant

Claims (2)

[Claims] 1. A membrane separation device is immersed and installed in an aeration tank, and a suction pump is interposed in a permeated water outlet pipe provided in communication with a permeated water flow passage of the membrane separation device, and is connected to an air supply source such as a blower. An operating method of a water treatment apparatus provided with a communicating aeration device below the membrane separation device, wherein filtration is performed on the membrane surface by applying suction pressure of the suction pump to a permeated water flow path of the membrane separation device, When the membrane permeated water that has passed through the membrane surface and flowed into the permeated water flow path is led out by the permeated water outlet pipe, aeration air having a predetermined flow rate set according to the magnitude of the flow rate of the derived permeated water is passed through the air diffuser. A method for operating a water treatment apparatus, comprising jetting and washing a membrane surface of an upper membrane separation apparatus. 2. In a water treatment apparatus provided with a flow control tank, a raw water level in the flow control tank is measured, and raw water having a predetermined flow rate set according to the measured water level is transferred to an aeration tank. The method for operating a water treatment apparatus according to claim 1, wherein a predetermined flow rate of the membrane permeated water set according to the magnitude of the transfer flow rate of the raw water is derived.