JP3461676B2 - Sewage treatment equipment - Google Patents

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art As a conventional sewage treatment apparatus for treating organic sewage 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, the membrane separation device 2 needs to be ready for filtration immediately after the inflow of the dirty water 5 into the aeration tank 3 is started. The state in which filtration is possible refers to a state in which aeration is performed through the aeration device 10 installed below the membrane cartridge 2b, and a cross flow occurs on the membrane surface of the membrane cartridge 2b.

For this purpose, apart from the case of continuous aeration through the aeration device 10, it is necessary to interlock the inflow of the dirty water 5 into the aeration tank 3 and the driving of the aeration device 10. It is very difficult in practice to detect the inflow of the dirty water 5. (However, if sewage is introduced by a pump, etc., starting the pump can be interpreted as sewage inflow.) However, continuous aeration not only increases the power cost but also
Biological treatment is adversely affected by over-aeration.

As one method, it is conceivable to install a liquid level gauge in the aeration tank 3. However, since the membrane separation device 2 is configured to start filtration immediately when the liquid level starts to rise as described above, filtration occurs even if a small amount of the dirty water 5 flows into the aeration tank 3. However, depending on the type of level gauge, the level gauge can detect a level fluctuation of 10 cm or more, so until the level gauge detects a level rise, there is no aeration, that is, cross flow. Since the filtration is performed in a state where the water is not supplied, there is a problem that not only the filtration efficiency is poor, but also the membrane surface of the membrane separation device 2 is likely to be clogged.

The present invention is intended to solve the above problems, and it is an object of the present invention to perform aeration in conjunction with the inflow of sewage and to enable efficient filtration in a membrane separation device.

[0012]

In order to solve the above problems, the sewage treatment apparatus of the present invention comprises an activated sludge having a natural head in the tank as a driving pressure inside an aeration tank for treating organic sewage with activated sludge. A sewage treatment apparatus in which a membrane separation device for gravity-filtering a mixed solution is immersed, and an aeration device is arranged below the membrane separation device, and the permeate pipe communicating with the membrane permeation side of the membrane separation device is usually Aeration tank liquid above the operating water level at the start of filtration
The inverted U-shape with the top located at a predetermined position to secure the filtration head between the position and the end, and the terminal end thereof is outside the tank at the same height as the upper end of the membrane separation device or above the atmospheric pressure. It is opened downward and continues to filter by the siphon phenomenon until the liquid level in the aeration tank drops to a position corresponding to the end of the permeate pipe. The filtration is started when the liquid level exceeds the apex of the permeate tube and a filtered water head is secured between the aeration tank liquid level and the apex of the permeate tube.

Preferably, a liquid level measuring means for measuring the liquid level in the aeration tank is provided, and a control device for starting and stopping a blower for supplying air to the aeration device is connected to the liquid level measuring means.
The control device stops the blower when the liquid level measured by the liquid level measuring means falls to a lower limit water level corresponding to a predetermined distance above the terminal end of the permeate pipe, and the upper limit corresponding to the top part of the permeate pipe. Configure the blower to start when the water level rises. The lower limit water level is set as the lowest water level at which filtration is stopped but the membrane surface is not exposed due to the decrease in liquid level caused by stopping aeration.

Further, preferably, as the liquid level measuring means, a liquid level gauge or a pressure gauge for measuring the discharge side pressure of the blower for supplying air to the aeration device is used. According to the above configuration,
The permeate pipe, which communicates with the membrane permeation side of the membrane separation device, is arranged in an inverted U shape with the top located above the normal operating water level, and the end portion thereof is located at the same height as the upper end of the membrane separation device outside the tank. Since it is opened to the atmospheric pressure, the liquid level in the aeration tank corresponds to the end of the permeate pipe due to the siphon phenomenon when the permeate pipe is full and filtration is performed. Filtration continues until it is lowered into position.

On the other hand, once the siphon state is cut off and the filtration is stopped, the filtration does not start immediately even if the sewage flows into the aeration tank, and the liquid level in the aeration tank is set at the top of the permeate pipe. Beyond that, filtration is initiated only when the filtration head is secured between the aeration tank level and the top of the permeate tube.

Since cross flow is not necessarily required between the time when the filtration is stopped and the time when the filtration is restarted, it is possible to stop the aeration, thereby reducing the anaerobic condition for denitrification. It is possible to secure it.
In addition, it is possible to prevent an uneconomical situation in which unnecessary aeration is performed when the inflow of sewage is unknown.

Further, in the membrane separation device in which the permeate pipe is arranged as described above, the difference between the starting water level and the stopping water level of filtration can be made large, so that a liquid level gauge can be used as the liquid level measuring means regardless of the accuracy.

When a pressure gauge for measuring the discharge side pressure of the blower supplying air to the aeration device is used as the liquid level measuring means, the blower discharge side pressure corresponding to the lower limit water level and the upper limit water level in the aeration tank is used. Get in advance.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. 1 to 3 show a sewage treatment apparatus 21 according to an embodiment of the present invention. The sewage treatment apparatus 21 includes the pretreatment tank 1, the aeration tank 3 and the treated water tank 4 which have been described with reference to FIG. It is also possible to form a part of the conventional small combined septic tank provided.

That is, the sewage treatment apparatus 21 is provided with an aeration tank 22 for treating organic sewage with activated sludge and a treated water tank 23. The aeration tank 22 has a sewage supply pipe 24 opened at the upper part thereof and has an internal structure. In addition, the membrane separation device 2 for gravity-filtering the activated sludge mixed liquid 25 in the tank by using the natural head as a driving pressure.
6 is installed by immersion, and the aeration device 2 is provided below the membrane separation device 26.
7 are provided.

The membrane separation device 26 has flat box-shaped membrane cartridges 29 arranged vertically in parallel in the upper part of a box frame-shaped case 28 having an opening at the top and bottom.
The aeration device 27 is arranged below the membrane cartridge 29. Although not shown, the membrane cartridge 29 is a membrane in which filtration membranes are arranged on both surfaces of the filter plate and communicate with the membrane permeate liquid flow path formed between the filter plates or inside the filter plate. A permeated liquid outlet is formed. Case 2
A water collecting pipe 31 that communicates with the membrane permeated liquid outlet of each membrane cartridge 29 via a tube 30 is provided on the upper part of 8, and a permeated liquid pipe 32 that communicates with the water collecting pipe 31 is provided.

The permeate pipe 32 is arranged in an inverted U-shape with a top 32a located at a predetermined position above the normal operating water level NL, and its end 32b is the upper end of the membrane cartridge 29 in the treated water tank 23. It is open to atmospheric pressure at the same height as.

The aeration device 27 is connected to a blower 33 outside the tank, and a pressure gauge 34 is provided on the discharge side of the blower 33, and a controller for connecting to the pressure gauge 34 to start and stop the blower 33. 35 are provided.

A drainage pump 36 and a drainage pipe 37 are provided in the treated water tank 23. The operation of the above configuration will be described. When the organic sewage 38 is introduced into the aeration tank 2 through the sewage supply pipe 24, the organic sewage 38 is mixed with the activated sludge mixed solution 25 in the tank, and the organic matter and the nitrogen content in the organic sewage 38 are converted into the activated sludge. Removed by action.

At this time, as described later, aeration is appropriately performed by the aeration device 27, oxygen is supplied to the activated sludge mixed liquid 25, and bubbles of aerated air and the rising water flow generated thereby are generated between the membrane cartridges 29. Flowing into the gap of the case 28, thereby uniformly cleaning the entire membrane surface, reducing concentration polarization on the membrane surface to reduce filtration resistance, and forming a circulating water flow in the tank circulating inside and outside the case 28. .

In this state, the activated sludge mixed liquid 25
Is a terminal portion 32b where the permeate pipe 32 opens from its liquid surface.
Up to the head of the membrane cartridge 29, that is, the head of the membrane cartridge 29 as a driving pressure, is gravity filtered by the membrane cartridge 29, and the permeate 39 that has permeated the membrane surface of the membrane cartridge 29 is guided to the treated water tank 23 by the permeate pipe 32. .

At this time, as described above, the permeated liquid pipe 32
Is arranged in an inverted U shape in which the top portion 32a is located at a predetermined position above the normal operating water level NL, and the end portion 32b thereof is opened under the atmospheric pressure at the same height position as the upper end of the membrane cartridge 29, As shown in FIG. 1, when the permeated liquid pipe 32 is full and filtration is performed, the filtration is continued due to the siphon phenomenon, and as shown in FIG.
When the liquid level in 2 drops to a position corresponding to the terminal end 32b of the permeate pipe 32, the siphon state is cut off and the filtration is stopped.

Once the filtration is stopped, gravity filtration does not start immediately even if the organic sewage 38 flows into the aeration tank 32, and as shown in FIG. The filtration is started only when the filtration head is secured between the aeration tank liquid level and the top 32b of the permeate pipe 32 beyond the top 32b of the permeate pipe 32.

At this time, the pressure on the discharge side of the blower 33 is measured by the pressure gauge 34, and when the measured pressure falls to a preset lower limit pressure, the control device 35
Thus, the blower 33 is stopped, and when the pressure reaches the upper limit pressure, the control device 35 activates the blower 33. Here, the lower limit pressure is the pressure at the lower limit water level LL of the aeration tank, which is slightly above the terminal end 32b of the permeate pipe 32,
The upper limit pressure is the pressure at the aeration tank upper limit water level HL corresponding to the top 32b of the permeate pipe 32.

In this way, the blower 33 and the aeration device 27 can be stopped while the cross flow is not necessarily required after the filtration is stopped until the filtration is restarted, and the aeration can be performed efficiently. An anaerobic condition for denitrification can be secured.

The permeated liquid 39 in the treated water tank 23 is guided to a disinfecting section (not shown) by a drainage pump 36 and a drainage pipe 37 and then discharged as purified treated water. In addition,
The lower limit water level LL is set as follows.

In the aeration tank (water depth 2 m), the case (height 13
When a membrane separator (100 cm in length × 49 in width × 0.6 cm in thickness) arranged at 0.8 cm intervals is installed in 0 cm), and the membrane surface is aerated with a strength sufficient for cleaning by an aeration device. Since the bubbles of the aerated air do not rise when the aeration is stopped, the liquid level in the aeration tank is usually lowered by about 2 to 3% as compared with the aeration, and in this case, the liquid level is lowered by 4 to 6 cm. On the other hand, the resistance when the ascending flow generated by the aeration passes through the gap between the membrane cartridges is about 5 cm in terms of water head (that is, in terms of liquid level).

Therefore, in the aeration tank, the liquid level is lowered by about 10 cm due to the stop of the aeration. Therefore, the lower limit water level LL at the time of the aeration in which the filtration is stopped by the stop of the aeration but the membrane surface is not exposed, Set about 10 cm above the upper edge of the membrane of the membrane cartridge.

In the above-described embodiment, the blower 33 is started and stopped based on the discharge side pressure of the blower 33. However, according to the membrane separation device 26 in which the permeate pipe 32 is arranged as described above, Since the difference between the starting water level and the stopping water level of filtration can be as large as about 30 cm, the blower 33 can be started and stopped by using the liquid level gauge. Various membrane cartridges can be used as long as they can be gravity-filtered, such as tube-shaped cartridges and ceramic cartridges.

[0035]

As described above, according to the sewage treatment apparatus of the present invention, the permeate pipe communicating with the membrane permeation side of the membrane separator is
It was arranged in an inverted U-shape with the top located above the normal operating water level, and its end was opened outside the tank at the same height as the upper end of the membrane separator under atmospheric pressure, so filtration was stopped once. After that, even if there is inflow of sewage, the filtration is not started immediately, and the filtration is restarted only when the liquid level in the aeration tank exceeds the top of the permeate pipe. Therefore, it is possible to stop the aeration device between the time when the filtration is stopped and the time when the filtration is restarted, whereby it is possible to secure the anaerobic state for denitrification.

In order to efficiently start and stop the aeration device, a liquid level measuring means and a control device for starting and stopping a blower for supplying air to the aeration device are provided so that the aeration tank liquid level is set at a lower limit water level set in advance. The blower should be stopped when the water level has dropped to the upper limit, and the blower should be started when the water level has reached the upper limit.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a state during normal operation of a water treatment device according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a state of the water treatment apparatus shown in FIG. 1 when filtration is stopped.

FIG. 3 is an explanatory diagram showing a state of the water treatment device shown in FIG. 1 at the start of filtration.

FIG. 4 is a vertical cross-sectional view showing the overall configuration of a conventional water treatment device.

[Explanation of symbols]

21 Sewage treatment equipment 22 Aeration tank 23 Treated water tank 25 Activated sludge mixture 26 Membrane separation device 27 Aeration device 32 Permeate tube 32a top 32b termination 33 blower 34 Pressure gauge (liquid level measuring means) 35 Control device 38 Organic wastewater NL Normal operating water level LL lower water level HL upper limit water level

─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-5-185078 (JP, A) JP-A-8-39088 (JP, A) JP-A-7-328694 (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 for gravity-filtering an activated sludge mixed solution using a natural head of the tank as a driving pressure is immersed in an aeration tank for treating organic sludge with activated sludge, and is placed below the membrane separator. In the sewage treatment device provided with an aeration device, the permeate pipe communicating with the membrane permeation side of the membrane separation device has a filtered water between the aeration tank liquid level at the start of filtration above the normal operating water level.
It is arranged in an inverted U-shape with the top located at a predetermined position for securing the head, and its end is opened outside the tank at the same height as or above the upper end of the membrane separation device under atmospheric pressure. , The filtration is continued by the siphon phenomenon until the liquid level in the aeration tank drops to a position corresponding to the end of the permeate pipe,
Filtration starts when the liquid level in the aeration tank exceeds the top of the permeate pipe and the filtration head is secured between the liquid level in the aeration tank and the top of the permeate pipe after the siphon condition is cut off and filtration is stopped. A sewage treatment device characterized by being processed. 2. A liquid level measuring means for measuring the liquid level in the aeration tank is provided, and a control device for starting and stopping a blower for supplying air to the aeration device is provided by being connected to the liquid level measuring means. , When the liquid level measured by the liquid level measuring means is lowered to a lower limit water level corresponding to a predetermined distance above the terminal end of the permeate pipe, the blower is stopped and raised to an upper limit water level corresponding to the top of the permeate pipe. The sewage treatment apparatus according to claim 1, wherein the blower is activated at times. 3. The sewage treatment apparatus according to claim 2, wherein the liquid level measuring means is a liquid level gauge or a pressure gauge for measuring the discharge side pressure of the blower that supplies air to the aeration device.