JP3414609B2 - Operating method of sewage treatment equipment - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method of operating a sewage treatment apparatus for treating organic sewage such as domestic wastewater.

[0002]

2. Description of the Related Art As a conventional wastewater treatment apparatus for treating organic wastewater such as domestic wastewater, for example, an aeration tank 3 and a treated water tank 4 having a pretreatment tank 1 and a membrane separator 2 as shown in FIG. There is a small combined septic tank equipped with.

The membrane separation device 2 is, for example, a flat plate-like membrane cartridge 2b arranged in the up-down direction and arranged in parallel at a constant interval in the upper part of a case 2a which is open at the top and bottom. Although omitted, the membrane permeate is arranged on both surfaces of the filter plate to form a membrane permeate outlet that communicates between the filter plate and the membrane or between the membrane permeate channels formed inside the filter plate. It was done.

In such a small combined septic tank, sewage 5 is introduced into the pretreatment tank 1 to remove impurities such as a screen (not shown) and then guided to the aeration tank 3 through the walls 6 and 7. And mixed with the activated sludge mixed liquid 8 in the aeration tank 3 and aerated by the blower 9 through the aeration device 10 from below the membrane cartridge 2b, organic substances and nitrogen contained in the sewage 5 by the action of the activated sludge. Minutes have been removed.

At this time, the activated sludge mixed liquid 8 in the aeration tank 3
Is subjected to gravity filtration by the membrane cartridge 2b using its natural head as a driving pressure, and the permeate pipe 1 is connected to the membrane permeate outlet of the membrane cartridge 2b via the tube 11 and the water collecting pipe 12.
The permeated liquid 14 is taken out to the treated water tank 4 by 3.

The permeated liquid 14 in the treated water tank 4 is the disinfection section 15
After being guided to and disinfected, the purified treated water 16 is allowed to flow out of the apparatus.

[0007]

In the membrane separation device 2 as described above, the end portion 13a of the permeate pipe 13 is normally opened in the treated water tank 4 at the upper end position of the membrane separation device 2 or at a position higher than it. Therefore, when the liquid level in the aeration tank 3 is lowered to a position corresponding to the terminal end 13a of the permeated liquid pipe 13, the filtration is stopped, and the liquid level in the aeration tank 3 is raised above the terminal end 13a. The filtration is started immediately when the required head difference occurs on both sides of the membrane surface of the membrane separation device 2.

Therefore, when the inflow of the sewage 5 cannot be predicted (however, when the sewage is introduced by a pump or the like, the start of the pump can be interpreted as the inflow of the sewage), the continuous aeration is forced. This is because if the inflow of sewage 5 occurs while the aeration is stopped, the filtration will be performed in a state where there is no cross flow with respect to the membrane surface of the membrane cartridge 2b, so that not only the filtration efficiency is poor, but also the deposit on the membrane surface. This is because it easily occurs. However, continuous aeration increases power costs, and excessive aeration may adversely affect biological treatment.

The present invention solves the above problems, and can efficiently perform aeration in conjunction with the inflow of sewage, reduce the power cost, and prevent the harmful effects on biological treatment due to excessive aeration. It is intended to provide a driving method of.

[0010]

In order to solve the above problems, a method for operating a sewage treatment apparatus according to the present invention comprises a membrane separation device immersed in an aeration tank for treating organic sewage with activated sludge.
Then , the activated sludge mixed solution in the tank is gravity filtered using its head as the driving pressure, and the upper position of the membrane separation device or above
It discharges the permeate to the outside of the tank through the permeate tube opening at location
Upon operating the fouling water treatment device, as well as intermittently driving the aeration device for supplying the bath in liquid cross flow to the film surface of the membrane separation device, the discharge of permeate from the membrane separation device at the time of driving the aerator When the discharge of the permeated liquid is detected, the aeration device is switched to the continuous drive, and when the discharge of the permeated liquid is not detected, the intermittent drive of the aeration device is continued.

Preferably, the stop time when the aerator is intermittently driven is set as a time during which gravity filtration is not normally started due to a rise in the liquid level due to the inflow amount, and the drive time is
It is set as the time required for at least the permeated liquid from the membrane separation device to reach the outlet.

Further, preferably, when the wastewater treatment device is a small combined septic tank, the stop time of the aeration device is set to 10 to 30 minutes and the driving time is set to 1 minute or less.
In the sewage treatment apparatus as described above, when the aeration is stopped, the bubbles of the aerated air do not rise, and the liquid level in the aeration tank is generally lower by about 2 to 3% than that at the time of aeration. A 6 cm drop in liquid level occurs. In addition, a membrane separation device may be installed in a case, for example, a membrane cartridge (100 ×
When a plurality of 49 (width 49 × thickness 0.6 cm) are arranged at intervals of 0.8 cm, the resistance when the ascending flow generated by aeration passes through the gap between the membrane cartridges is equivalent to the water head equivalent (that is, liquid). It becomes about 5 cm in terms of position conversion. Therefore, when the aeration is stopped, the liquid level is lowered by about 10 cm from the aeration.

Therefore, after the filtration is stopped once and the aeration is stopped, the filtration is not started immediately even if the dirty water flows in, and the filtration is started only after the liquid level rises by about 10 cm. On the other hand, the fluctuation of the liquid level varies depending on the shape and scale of the aeration tank and the shape and scale of the membrane separation device, but even in the small combined septic tank with the largest peak coefficient (time maximum wastewater + daily average wastewater) The sudden rise in the liquid level that occurs when water is discharged at one time is at most about 10 cm in 10 minutes.

Therefore, even if aeration is started about 10 minutes after the inflow of sewage, a cross flow will occur almost at the same time when the filtration is started. Until then, a cross flow is not always necessary, but intermittently. Since the aeration can be performed, the power cost can be reduced and the adverse effect on the biological treatment due to the excessive aeration can be prevented.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. The method for operating the sewage treatment apparatus according to the embodiment of the present invention can be implemented in the conventional small combined septic tank previously described with reference to FIG. 2, and therefore will be described with reference to FIG. However, in the small combined septic tank, the permeated liquid pipe 13 communicating with the membrane permeated liquid outlet of the membrane cartridge 2b is provided with a contact alarm flowmeter (not shown).

In such a small combined septic tank, the sewage 5 flowing into the pretreatment tank 1 is transferred to the aeration tank 3 and mixed with the activated sludge mixed liquid 8 in the tank, and continuous aeration is performed through the aeration device 10. In this state, the organic matter and nitrogen content in the wastewater 5 are removed by the action of activated sludge.

At this time, the activated sludge mixed liquid 8 is gravity-filtered by the membrane cartridge 2b by using the water head from the liquid surface to the upper end of the membrane cartridge 2b as a driving pressure, and the permeated liquid 14 that has permeated the membrane surface of the membrane cartridge 2b is It is guided to the treated water tank 4 by the permeated liquid pipe 13.

At this time, the presence or absence of the permeated liquid 14 is checked in the permeated liquid pipe 12 by a flow meter.
When 4 is detected as “present”, blower 9 and aerator 1
0 is continuously driven and continuous aeration is performed.

According to the aeration, oxygen is supplied to the activated sludge mixed liquid 8 and the bubbles of the aerated air and the rising water flow generated thereby flow into the gaps between the membrane cartridges 2b, whereby the entire membrane surface. Is uniformly washed, and the concentration polarization on the membrane surface is reduced to lower the filtration resistance,
In addition, a circulating water flow in the tank that circulates inside and outside the case 2a is formed.

While the continuous aeration is performed, the sewage 5
Is stopped or reduced, the liquid level in the aeration tank 3 is lowered to a position corresponding to the end portion 13b of the permeated liquid tube 13, and filtration is stopped, whereby the permeated liquid 14 is "absent" by the flowmeter. When it is detected, the blower 9 and the aeration device 10 are switched to intermittent driving, and a cycle of aeration stop for a predetermined time (10 to 30 minutes) and aeration for about 1 minute is repeated.

During the intermittent aeration, the sewage 5 is transferred and the liquid level in the aeration tank 3 rises. At the time of aeration, filtration is started by the membrane cartridge 2b and the permeated liquid 14 is detected by the flow meter. Is detected, the blower 9 and the aeration device 10 are switched to continuous drive, and continuous aeration is performed.

As described above, the blower 9 and the aeration device 10 can be driven intermittently while the cross flow from the time when the filtration is stopped to the time when the filtration is restarted is not necessary. It is possible to prevent adverse effects on biological treatment due to excessive aeration, and to reduce power costs.

Note that other permeated liquid detecting means such as a flow switch may be used instead of the above-mentioned flow meter with contact alarm. Further, the method described above can be carried out without being limited to the small combined septic tank.

[0024]

As described above, according to the present invention, it is possible to detect the inflow of sewage without delay by utilizing the increase in the liquid level in the aeration tank due to aeration, so that the liquid level meter with a highly accurate analog output can be detected. It is possible to efficiently turn on / off the aeration device without using the, and reduce the power cost and prevent the harmful effects of excessive aeration.

When the aeration device is intermittently driven, if the aeration is stopped for a predetermined time when gravity filtration is not started due to the inflowing amount of organic sewage, the activated sludge is maintained in a substantially floating state and thus denitrified. If the aeration is carried out for a predetermined time period during which the presence or absence of discharge of the permeate from the membrane separation device can be confirmed without causing a decrease in efficiency, there is no excessive dissolution of oxygen and the decrease in the nitrogen removal rate is small.

[Brief description of drawings]

FIG. 1 is a flowchart illustrating a method of operating a water treatment device according to the present invention.

FIG. 2 is a vertical cross-sectional view of a conventional small combined septic tank in which a method for operating a water treatment device of the present invention is implemented.

[Explanation of symbols]

2 membrane separator 3 aeration tank 5 dirty water 8 Activated sludge mixture 10 Aeration device 14 Permeate

─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-10-156380 (JP, A) JP-A-8-141566 (JP, A) JP-A-5-185078 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) C02F 1/44 ZAB B01D 65/02 520

Claims (3)

(57) [Claims] 1. A membrane separator is immersed in an aeration tank for treating organic sludge with activated sludge, and the activated sludge mixed solution in the tank is gravity-filtered by using the head of the membrane as a driving pressure.
Through the permeate pipe that opens at the end position or above.
Upon operating the permeate to fouling water treatment device you discharged to the outside of the tank and the tank in the liquid to the film surface as well as intermittently driving the supply aeration device in cross flow of the membrane separation device, the aerator Whether or not the permeate is discharged from the membrane separator during driving is detected, the aerator is switched to continuous drive when the permeate is detected, and the aerator is intermittently driven when the permeate is not detected. A method for operating a sewage treatment device, characterized by continuing. 2. The stop time when intermittently driving the aeration device is set as a time during which gravity filtration is not normally started due to a liquid level increase due to the inflow amount, and the driving time is at least when the permeated liquid from the membrane separation device is The method for operating a sewage treatment apparatus according to claim 1, wherein the time required to reach the discharge port is set. 3. The wastewater treatment device is a small combined septic tank,
The method for operating a sewage treatment apparatus according to claim 2, wherein the stop time of the aeration device is set to 10 to 30 minutes and the drive time is set to 1 minute or less.