JPH07328694A - Method for operating septic tank - Google Patents

Abstract

PURPOSE:To maintain the permeation flow flux of a membrane separator built into a septic tank at a specified flow flux or above for a long period of time by intermittently operating an aerator and executing operation of this membrane separator just before the operation start of the next aerator during the downtime of the aerator. CONSTITUTION:The septic tank has the aerator 2, the membrane separator 3 and a water level sensor 4 in a biological reaction chamber 1. Air is supplied from a blower B to the aerator 2 and the blower B and a pump P of the membrane separator 3 are turned on and off by receiving the signal from the water level sensor 4. Further, this pump P is turned on and off as well by the water level sensor 9 of a fixed volume discharging vessel 8 in which the permeated liquid is stored. The aerator 2 is intermittently operated and the operation of the membrane separator 3 is executed just before the start of the next aerator 2 in the downtime of the aerator 2. As a result, the activated sludge settles and the membrane sepn. treatment of the waste water which is nearly a supernatant liquid is executed.

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 septic tank for biologically treating domestic wastewater, industrial wastewater and the like.

[0002]

2. Description of the Related Art As an operating method of a septic tank for biologically treating domestic wastewater such as toilets, washrooms, baths and kitchens, industrial wastewater, etc., Japanese Patent Laid-Open No. 4-108600 discloses an aeration device and a membrane separation device. A method using both is proposed.

In the above prior art, the highest water level (HWL) to the lowest water level (L.
Aerobic treatment that performs aeration and filtration at the same time up to WL), conversely from the lowest water level (LWL) to the highest water level (HW
Up to L.), anaerobic treatment without aeration and filtration was performed.

[0004]

According to the above-mentioned prior art, since one biological reaction tank can be used for both aerobic treatment and anaerobic treatment, a compact septic tank can be obtained. During operation, the biological reaction tank is agitated by aeration, and a large amount of particles such as activated sludge are suspended. Then, in this state, since the filtration operation is performed using the membrane separation device, the separation membrane is clogged within a short period of time, and the permeation flux is reduced.

Further, in the conventional method for operating the septic tank, in order to secure the permeation flux, the operation of the septic tank is stopped and cleaning is performed to ensure a constant permeation flux.
Stopping the operation of the septic tank in this manner causes a reduction in the purification efficiency.

[0006]

In order to solve the above-mentioned problems, the first invention of the present application is to dispose an aeration device and a membrane separation device in a biological reaction tank and blow air to waste water in the biological reaction tank by the aeration device. In the method for operating the septic tank, the waste water in the biological reaction tank containing the activated sludge is separated into the permeate and the retentate by the membrane separator, and the operation of the aeration device is performed intermittently. The operation of the membrane separation device was performed between the suspension of the operation of the aeration device and immediately before the start of the operation of the next aeration device.

In the second invention of the present application, an aeration device and a membrane separation device are arranged in the biological reaction tank, and air is blown into the waste water in the biological reaction tank by the aeration device and agitated, and activated sludge is generated by the membrane separation device. In a method of operating a septic tank in which wastewater in a biological reaction tank containing is separated into a permeate and a retentate, the aeration device is intermittently operated, and the membrane separation is performed during the suspension of the operation of the aeration device. The device was cleaned.

The membrane separator may be operated so that the water level in the biological reaction tank is maintained between the highest water level (HWL) and the lowest water level (LWL). In the second aspect of the invention, cleaning such as back pressure cleaning, back flow cleaning, or flush cleaning may be performed immediately before the start of the operation of the aeration device.

[0009]

[Function] The wastewater supplied to the biological reaction tank is subjected to aerobic / anaerobic biological treatment by switching on / off the operation of the aeration device, and by operating the membrane separation device, the wastewater containing activated sludge is removed. The permeate is separated.

[0010]

Embodiments of the present invention will be described below with reference to the accompanying drawings. Here, FIG. 1 is a cross-sectional view showing an example of a septic tank for carrying out the method of the present invention. In the septic tank, an aeration device 2, a membrane separation device 3 and a water level sensor 4 are arranged inside the biological reaction tank 1, and the aeration device 2 Is supplied with air from the blower B, and the blower B and the pump P of the membrane separation device 3 can be turned on / off by receiving a signal from the water level sensor 4. Further, the pump P is also configured to be turned on / off by a signal from the water level sensor 9 of the fixed amount discharge container 8 in which the permeated liquid is stored. In the embodiment, a case where the aeration device 2 and the membrane separation device 3 are turned on / off by a timer will be described.

The membrane separation device 3 is provided with a separation membrane 5 such as a hollow fiber membrane, a water collecting portion 6 and a suction pipe 7 connected to the water collecting portion 6, and a permeated liquid sucked by a pump P is discharged in a fixed amount. I am trying to put it in 8.

A water level sensor 9 is provided in the fixed quantity discharge container 8, and a signal from the water level sensor 9 is output to the pump P to discharge a substantially constant amount of treated water from the fixed quantity discharge container 8. . A disinfection function may be added to the fixed amount discharge container 8.

An operating method according to the first aspect of the invention using the above septic tank will be described with reference to FIG. In this operating method, the operation of the aeration device 2 is performed intermittently, and the operation of the membrane separation device 3 is performed between the suspension of the operation of the aeration device 2 and immediately before the start of the next operation of the aeration device 2. When the operation of the membrane separation device 3 is performed just before the start of the operation of the aeration device 2 as described above, the wastewater in the biological reaction tank 1 is in a calm state, that is, activated sludge is settled, and the wastewater close to the supernatant liquid is removed. Membrane separation treatment is possible and high permeation flux can be maintained for a long time.

Here, the operation interval of the aeration device 2 is set in consideration of the balance between the aerobic treatment and the anaerobic treatment, and the operation (filtration) time of the membrane separation device 3 is considered in consideration of the balance with the inflowing wastewater. The water level of the wastewater in the biological reaction tank 1 is always the highest (H.
WL) Keep it between the minimum water level (LWL). still,
In the embodiment, the continuous filtration operation is performed within the set time of the operation (filtration) of the membrane separation device 3, but the intermittent filtration operation may be performed.

FIG. 3 shows an operating method according to the second aspect of the present invention. In this operating method, the aeration device 2 is operated intermittently, and while the aeration device 2 is operating, the membrane separation device 3 is operated at the same time. When the operation of the aeration apparatus 2 is stopped, the membrane separation apparatus 3 is continuously washed to stop the filtration operation of the membrane separation apparatus 3 immediately before the operation of the aeration apparatus 2 is started and the separation membrane is operated. The filtered material layer (cake layer) attached to the surface is removed to prevent clogging.

Here, as the cleaning method, for example, back pressure cleaning in which pressure is reversely applied from the pump P, backflow cleaning in which the permeated liquid in the fixed amount discharge container 8 is used to supply from the permeated liquid side, or bubbling with excess air is performed. Use flash cleaning or the like.
In the embodiment, the membrane separation device 3 is operated at the same time as the aeration device 2 is operated, but the membrane separation device 3 may be operated while the aeration device 2 is out of operation. .

The case where the aeration device 2 and the membrane separation device 3 are turned on / off by the timer has been described above. However, the signals from the water level sensor 4 in the biological reaction tank are used in FIGS.
Even if the operation (filtration) of the membrane separation device 3 shown in (1) is determined, and the intermittent level filtration operation is performed by receiving the signal from the water level sensor 9 of the constant volume discharge container 8 even during the filtration operation time. Good. In the embodiment shown in FIGS. 2 and 3, the operating time of the membrane separation device is adapted to the operation of the aeration device, but the operation of the aeration device is adapted to the operation of the membrane separation device. Good. That is, regarding the operation of the membrane separation device, it is performed from the maximum water level (HWL) to the minimum water level (LWL) of the biological reaction tank, and is stopped until the minimum water level (LWL) to the maximum water level (HWL), The operation or cleaning of the aeration device may be started immediately after the operation of the membrane separation device is stopped. By doing this,
Aerobic / anaerobic biological treatment can be performed without waste.

[0018]

As described above, according to the first invention of the present application, in operating the septic tank provided with the aeration device and the membrane separation device, the aeration device is intermittently operated, and Since the operation is performed between the operation of the aeration device and immediately before the start of the operation of the next aeration device, the inside of the bioreaction tank is calm, and a liquid close to the supernatant liquid in which a large amount of activated sludge does not float is solidified. Since the liquid can be separated, the efficiency of the membrane treatment is improved and the permeation flux can be kept high for a long period of time.

Further, according to the second invention of the present application, in operating the septic tank provided with the aeration device and the membrane separation device, the aeration device is intermittently operated, and the membrane is operated while the operation of the aeration device is stopped. Since the separation device is cleaned, it is possible to incorporate cleaning as one step of continuous operation,
The permeation flux can be recovered without stopping the operation of the septic tank.

In the first and second inventions of the present application,
When operating the membrane separator, set the water level in the bioreactor to the maximum water level (HW
L) and the minimum water level (LWL) are maintained so that the capacity of water level fluctuation can be used for the flow adjustment capacity that absorbs the peak fluctuation of inflowing wastewater, and the processing speed of the wastewater in the biological treatment tank. Therefore, high processing performance can be obtained.

Further, in the second aspect of the present invention, if cleaning such as back pressure cleaning or flush cleaning is performed immediately before the start of the operation of the aeration device, the filtered material layer (cake layer) deposited on the separation membrane surface is effective. Can be removed.

[Brief description of drawings]

FIG. 1 is a sectional view showing an example of a septic tank for carrying out the method of the present invention.

FIG. 2 is a graph illustrating a method of operating the septic tank according to the first invention.

FIG. 3 is a graph illustrating a method of operating the septic tank according to the second invention.

[Explanation of symbols]

1 ... Biological reaction tank, 2 ... Aeration device, 3 ... Membrane separation device, 4 ...
Water level sensor, 5 ... Separation membrane, B ... Blower, P ... Pump.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁶ Identification number Internal reference number FI Technical indication location C02F 1/44 K 9538-4D 3/00 ZAB B (72) Inventor Katsuritsu Uryu Kitakyushu City, Fukuoka Prefecture 2-1-1 Nakajima, Kokurakita-ku, Totokikai Co., Ltd. (72) Inventor Yuichi Okuno 2-1-1, Nakajima, Kokurakita-ku, Kitakyushu, Fukuoka

Claims (5)

[Claims] 1. A biological reaction tank in which an aeration device and a membrane separation device are arranged in a biological reaction tank, air is blown into and agitated into wastewater in the biological reaction tank by the aeration device, and activated sludge is contained by the membrane separation device. In the method for operating a septic tank configured to separate the wastewater in the liquid into a permeated liquid and a retentate, the aeration device is operated intermittently, and the membrane separation device is operated while the aeration device is not operating and A method for operating a septic tank, which is characterized in that it is carried out immediately before the start of operation of the aeration device. 2. A biological reaction tank in which an aeration device and a membrane separation device are arranged in the biological reaction tank, air is blown into the waste water in the biological reaction tank by the aeration device and the mixture is stirred, and the activated sludge is contained by the membrane separation device. In a method for operating a septic tank in which the waste water in the inside is separated into a permeate and a retentate, the aeration device is operated intermittently, and the membrane separation device is washed while the operation of the aeration device is stopped. A method of operating a septic tank, which is characterized in that 3. The method for operating the septic tank according to claim 1 or 2, wherein the operation of the membrane separation device maintains the water level of the biological reaction tank between the highest water level (HWL) and the lowest water level (LWL). A method for operating a septic tank, which is characterized in that it is performed as follows. 4. The method for operating a septic tank according to claim 2, wherein the cleaning is performed immediately before the operation of the aeration device is started. 5. The method of operating the septic tank according to claim 2, wherein the cleaning is back pressure cleaning, backflow cleaning, or flush cleaning.