JP3124197B2 - Sewage treatment equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sewage treatment apparatus for performing domestic wastewater treatment and industrial wastewater treatment using an activated sludge method, such as a small-sized combined treatment septic tank.

[0002]

2. Description of the Related Art As this type of sewage treatment apparatus, a sewage treatment apparatus of a suction filtration type as shown in FIG. 7 is generally used. In FIG. 7, reference numeral 1 denotes an aeration tank for biologically treating the water to be treated introduced from the water supply pipe 2. Inside the aeration tank 1, there is provided a membrane separation device 4 in which tubular or flat membrane elements 3 are juxtaposed in the vertical direction. The membrane permeation side of the membrane element 3 is provided with a filtrate header 5 and a filtrate tube 6. It communicates with a negative pressure supply means such as a pump 7 via the pump. A diffuser 10 connected to a blower 8 via an air supply pipe 9 is provided below the membrane element 3, and an excess sludge extraction pipe 12 provided with a pump 11 is provided at the bottom of the aeration tank 1. Have been.

In the above-mentioned sewage treatment apparatus, the water to be treated is introduced into the aeration tank 1 through the water supply pipe 2 and mixed with the activated sludge mainly containing aerobic bacteria in the tank. In a state in which the gas containing oxygen is scattered as bubbles through the device 10, the self-priming force of the pump 7 is used to make the membrane element 3 side of the membrane element 3 a negative pressure. As a result, a gas-liquid mixed flow is generated in the tank by the scattered bubbles, and the water to be treated is filtered by the membrane element 3 while being purified by the action of activated sludge in the presence of oxygen while circulating in the tank. Then, the filtrate is led out of the tank through the filtrate tube 6. At this time, the membrane surface of the membrane element 3 is washed to some extent by the gas-liquid mixed flow passing through the vertical passage between the membrane elements 3 and 3, but the filtration by the membrane separation device 4 is performed intermittently. During the stop of filtration, contaminants deposited on the membrane surface are washed away.

In recent years, besides the above-mentioned suction filtration type sewage treatment apparatus, a gravity filtration type sewage treatment apparatus as shown in FIG. 8 has come to be seen. The gravity filtration type sewage treatment apparatus includes a filtrate tube 6 communicating with the membrane permeation side of the membrane element 3.
Is guided to the outside of the aeration tank 1 at an appropriate position above the top of the membrane separation device 4, and while the membrane separation device 4 is maintained in a immersed state, gravity filtration is performed using the natural head above the membrane separation device 4 as a driving force. It is something to do. According to such a gravity filtration method, the cake layer deposited on the membrane surface of the membrane element 3 is not densified and is removed by a gas-liquid mixed flow in a normal operation state. Can be filtered.

[0005]

However, in the above-mentioned conventional gravity filtration type sewage treatment apparatus, when the aeration is stopped due to a failure of the blower 8 or a blockage of the air diffuser 10, the membrane surface is washed. The gas-liquid mixed flow may stop, and a cake layer may accumulate between the membrane elements 3 and 3 to make filtration impossible. In order to prevent such a situation, a method has been adopted in which the stop of aeration can be detected, and when the stop of aeration is detected, the filtrate tube 6 is forcibly closed with an electromagnetic valve or the like. The reliability is low and filtration may be continued.

In a gravity filtration type sewage treatment apparatus,
As shown in FIG. 8, since the filtrate is discharged to a position lower than the membrane element 3 of the membrane separation device 4, a separate pump is required for transferring or discharging the filtrate to a subsequent processing device. , The sequence becomes complicated, and there are problems in terms of accidents and costs.

Further, in the gravity filtration type sewage treatment apparatus, since the permeation flux of the membrane separation device 4 is determined by the water head, the permeation flux corresponds to the amount of water to be treated that has flowed into the aeration tank 1. Therefore, in order to perform the constant flow rate operation (constant permeation flux operation), it is necessary to transfer the water to be treated to the aeration tank 1 at a constant flow rate. However, since the water to be treated contains impurities, At present, there are various difficulties in the transfer means.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a sewage treatment apparatus capable of performing a constant flow rate filtration irrespective of a filtration head, easily transferring a filtrate, and preventing blockage of a membrane separation apparatus. It is the purpose.

[0009]

Means for Solving the Problems To solve the above problems, a sewage treatment apparatus according to the present invention is provided with a natural aeration tank inside an aeration tank for treating water to be treated introduced from a treatment water supply pipe. In a sewage treatment apparatus provided with a membrane separation device that gravity-filters water to be treated using a head as a driving pressure, and a diffuser disposed immediately below the membrane separation device, a filtrate communicating with a permeate flow path of the membrane separation device is provided. A filtrate chamber having a closed structure communicating with the filtrate pipe is provided at an appropriate position above the top of the membrane separation device, and a drain pipe having one end connected to a lower part of the filtrate chamber is guided at the other end upward. A U-shaped pipe is provided to connect the filtrate chamber and the drain pipe above the connection position of one end of the drain pipe, and is connected to the upper part of the filtrate chamber to feed air into the filtrate chamber. The filtrate pipe is provided with a backflow prevention mechanism. It is.

Further, the sewage treatment apparatus of the present invention is provided with air supply means for supplying air to the air diffuser and the air supply means.

[0011]

According to the above construction, the water to be treated in the aeration tank is gravity-filtered by the membrane separator using the natural head in the tank as a driving pressure, and the filtrate is guided to the filtrate chamber through the filtrate tube. The filtrate introduced into the filtrate chamber is discharged without backflow to the membrane separation device by the action of the backflow prevention mechanism.

At this time, in a state where air is supplied from above in the filtrate chamber by the air supply means, until the water level of the filtrate exceeds the communicating position of the U-shaped pipe, U remains in the U-shaped pipe. Since the communication of the filtrate between the U-shaped pipe and the drainage pipe is cut off, the supplied air flows out through the U-shaped pipe and the drainage pipe, and the filtrate is stored in the filtrate chamber.

After the water level of the filtrate exceeds the communicating position of the U-shaped pipe, the filtrate is in a communicating state between the filtrate chamber, the U-shaped pipe, and the drainage pipe, so that the supplied air is in the filtrate chamber. The filtrate is stored in the upper part, and the filtrate is discharged from the drainage pipe by the air pressure.
At this time, the introduction of the filtrate is stopped by the action of the backflow prevention mechanism due to the pressure increase in the filtrate chamber. Although the water level of the filtrate decreases as the filtrate is discharged, while the communication of the filtrate between the U-shaped pipe and the drain pipe is maintained, the supplied air is stored in the upper part of the room, The filtrate is discharged by the air pressure.

Then, when the water level of the filtrate drops to the bottom of the U-shaped tube, air flows into the U-shaped tube, cutting off the communication of the filtrate between the U-shaped tube and the drainage tube, and discharging the filtrate. Is stopped. Then, the supplied air flows out through the U-shaped pipe and the drain pipe, and the pressure drop in the filtrate chamber at this time cancels the suspension of the introduction of the filtrate by the action of the backflow prevention mechanism, and the filtrate is introduced into the filtrate chamber. Is done.

In this way, the filtrate is discharged when a certain amount of filtrate is accumulated in the filtrate chamber, so that the filtration by the membrane separation device is intermittent and the deposition of the cake layer on the membrane surface is prevented. . Thereby, blockage of the membrane separation device is prevented.

At this time, since a certain amount of filtrate can be discharged by introducing a certain amount of air into the filtrate chamber, constant-flow filtration (filtration with a constant permeation flux) regardless of the natural head in the aeration tank. Can be performed.

Further, since the filtrate is discharged by air pressure, the head for transfer can be increased as compared with the conventional method using an air lift pump, and constant transfer can be performed.

Further, since air is supplied to the air diffuser and the air supply means by a single air supply means, the air supply means is stopped and the gas-liquid mixed flow by the air diffuser is not generated. At this time, the filtrate is not discharged from the filtrate chamber, and the filtration is stopped. This also prevents blockage of the membrane separation device.

[0019]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows the overall configuration of a sewage treatment apparatus according to one embodiment of the present invention. Provided.

The aeration tank 21 is for biologically purifying the water by mixing the water to be treated supplied from the water supply pipe 24 with the activated sludge mixture 25 in the tank. A sludge extraction pipe 27 provided with a pump 26 is provided.

The membrane separation device 22 includes a rectangular box frame 28 having both upper and lower surfaces open, and vertically immersed membrane elements 29 in parallel at regular intervals, and submerges the tops thereof in an activated sludge mixture 25. The activated sludge mixture 25 is gravity-filtered using the natural head in the tank as a driving pressure. The membrane element 29 has an organic filtration membrane disposed on both surfaces of a flat membrane support formed of stainless steel, plastic, or the like, and forms a filtration water passage between the organic filtration membrane and the membrane support. The filtration water passage is connected to the filtrate tube 30.

The filtrate tube 30 communicates with the filtrate chamber 23 at an appropriate position above the top of the membrane element 29 via the filtrate header 31, and the filtrate header 31 and the filtrate chamber 2 are connected.
3 is interposed with a check valve 32.

The filtrate chamber 23 is provided with a drainage pipe 33 at the bottom, and the end of the drainage pipe 33 is guided upward and the processing chamber 21
Is led outside. Above the position where the drain pipe 33 is connected to the filtrate chamber 23, a U-shaped pipe 34 that connects the filtrate chamber 23 and the drain pipe 33 is provided.

The aeration tank 21 has a blower 35 outside the room, and one branch pipe 36a of an air supply pipe 36 from the blower 35.
Is connected to an air diffuser 37 disposed immediately below the membrane element 29, and the other branch pipe 36 b of the air supply pipe 36 is provided above the filtrate chamber 23 through a flow control valve 38 and a flow meter 39. Connected.

The operation of the above configuration will be described below.
The water to be treated introduced into the aeration tank 21 from the treated water supply pipe 24 is mixed with the activated sludge mixed liquid 25 in the tank, and aerated air is supplied from the blower 35 through an air supply pipe 36 a and a diffuser 37. Under aerobic conditions, it is biologically treated by the action of activated sludge in the tank while being stirred by the gas-liquid mixed flow generated by the aerated air, and organic matter and nitrogen contained in the water to be treated are decomposed and removed. Is done.

At this time, the activated sludge mixture 25 in the aeration tank 21 is gravity-filtered by the membrane separation device 22 using the natural head in the tank as a driving pressure, and the filtrate is filtrated by the filtrate tube 30 and the filtrate header 3.
The liquid is led to the filtrate chamber 23 through 1. Air is fed into the filtrate chamber 23 from above from a blower 35 through an air supply pipe 36b.

The operation in the filtrate chamber 23 will be described with reference to FIGS. As shown in FIG. 2, until the water level of the filtrate in the filtrate chamber 23 reaches the communication position H of the U-shaped tube 34,
The communication of the filtrate between the U-shaped pipe 34 and the drainage pipe 33 is cut off by the air remaining in the U-shaped pipe 34, and the supplied air passes through the U-shaped pipe 34 and the drainage pipe 33. The filtrate flows out and flows into the room while the check valve 32 of the filtrate tube 30 is open, and is stored.

As shown in FIG. 3, when the water level of the filtrate reaches the communicating position H of the U-shaped pipe 34, the filtrate chamber 23 and the U-shaped pipe 34
Since the filtrate is in a state of communication between the liquid and the drain pipe 33, the supplied air is stored in the upper part of the room, and the filtrate is pressed by the air pressure. Thereby, the check valve 32 is opened to stop the introduction of the filtrate, and the filtrate is discharged from the drain pipe 33 as shown in FIG. 4 as the air pressure in the room increases. When the filtrate is discharged, the water level of the filtrate in the filtrate chamber 23 decreases. However, while the communication of the filtrate between the U-shaped pipe 34 and the drain pipe 33 is maintained, the air that has been introduced is not supplied to the room. And the filtrate is discharged by the air pressure.

As shown in FIG. 5, when the water level of the filtrate falls below the bottom position L of the U-tube 34, the U-tube 34
When the air flows into the inside, the communication of the filtrate between the U-shaped pipe 34 and the drain pipe 33 is cut off, and the discharge of the filtrate is stopped. And
The supplied air flows out through the U-shaped pipe 34 and the drain pipe 33, and the pressure drop in the filtrate chamber 23 at this time opens the check valve 32 of the filtrate pipe 30, as shown in FIG. The filtrate is introduced into the filtrate chamber 23 in the same manner as described above.

At this time, if a fixed amount of air corresponding to a desired permeation flux is fed into the filtrate chamber 23 by the flow control valve 38 and the flow meter 39, the filtrate at a constant flow rate from the filtrate chamber 23 Is discharged, so that constant flow filtration (filtration with a constant permeation flux) can be performed regardless of the natural head in the aeration tank 21.

As described above, the filtrate is discharged when a certain amount of filtrate has accumulated in the filtrate chamber 23, and the filtrate filtered by the membrane separation device 22 is guided to the filtrate chamber 23 after the discharge is completed. The intermittent filtration is performed by the membrane separation device 22 without using an electrical mechanism such as the above. Therefore, this prevents the cake layer from depositing on the film surface,
In addition to stabilizing the permeation flux, it is possible to prevent a situation where filtration is impossible. The smaller the filtrate chamber 23, the more the fixed amount of filtrate is accumulated in a short period of time and the filtration is stopped. Therefore, if the filtrate chamber 23 is made small, the aeration stop due to the blockage of the diffuser 37 or the like occurs. Also, only a small cake layer is deposited on the film surface, and the cake layer formed in a short time can be easily separated by the gas-liquid mixed flow when aeration is restarted.

Further, since air is supplied to both the diffuser 37 and the filtrate chamber 23 by the blower 35, when the blower 35 stops and the gas-liquid mixed flow is not generated by the diffuser 37. Does not discharge the filtrate from the filtrate chamber 23 and stops the filtration. Therefore, this can also prevent a situation where filtration is impossible.

Further, since the filtrate in the filtrate chamber 23 is discharged by air pressure, the head for transfer can be increased as compared with the conventional method using an air lift pump, and a pump, a complicated sequence, etc. The filtrate can be quantitatively transferred to a subsequent processing device or the like without using the same.

As described above, by adjusting the amount of air introduced into the filtrate chamber 23, the amount of filtrate guided to the filtrate chamber 23 can be adjusted, and contamination of the membrane surface of the membrane separation device 4 can be prevented. Therefore, it is possible to prevent a change in the amount of water to be treated in the aeration tank 1 and to maintain a constant operating condition for biological treatment.

FIG. 6 shows the overall configuration of a sewage treatment apparatus according to another embodiment of the present invention. Since the sewage treatment apparatus of this embodiment has substantially the same configuration as the sewage treatment apparatus of the above-described embodiment, members having the same functions are denoted by the same reference numerals and description thereof will be omitted.

The sewage treatment apparatus differs from the sewage treatment apparatus of the above-described embodiment in that the filtrate chamber 23 is provided outside the aeration tank 21. With this configuration, the same operation and effect as those of the above-described sewage treatment apparatus can be obtained.

As the membrane separation device 22 provided inside the aeration tank 21, a device provided with various membrane elements such as a flat membrane element and a tubular membrane element can be used. The blowers 35 may be provided separately without being shared by one unit as described above.

[0038]

As described above, in the sewage treatment apparatus of the present invention, the water to be treated in the aeration tank is gravity-filtered by the membrane separator using the natural head in the tank as a driving pressure, and the filtrate is sealed in a filtrate chamber having a closed structure. , And a certain amount of filtrate is discharged by air pressure, and after the discharge is completed, a new filtrate is guided into the room by utilizing a decrease in air pressure in the filtrate chamber. As described above, since the filtrate is discharged from the filtrate chamber and the filtrate is introduced into the filtrate chamber sequentially,
Filtration by the membrane separation device is also intermittent, and intermittent filtration is performed without using an electric mechanism such as a timer to stabilize permeation flux and prevent clogging of the membrane separation device. In addition, a fixed amount of air corresponding to a desired permeation flux is fed into the filtrate chamber, whereby a constant flow rate of the filtrate can be discharged, and constant flow rate filtration can be achieved regardless of the natural head in the aeration tank. Furthermore, since the filtrate is discharged by air pressure, the head for transfer can be increased as compared with the conventional method using an air lift pump, and quantitative transfer becomes possible.

Further, since the air is supplied to the air diffuser and the air supply means by a single air supply means,
When the gas supply means is stopped and the gas-liquid mixed flow by the diffuser is not generated, the filtrate discharge from the filtrate chamber can be stopped to stop the filtration by the membrane separation device. Blockage can be prevented.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing an overall configuration of a sewage treatment apparatus according to one embodiment of the present invention.

FIG. 2 is a cross-sectional view illustrating a filtrate discharging operation in the sewage treatment apparatus of FIG.

FIG. 3 is another sectional view for explaining a filtrate discharging operation.

FIG. 4 is still another cross-sectional view for explaining a filtrate discharging operation.

FIG. 5 is still another cross-sectional view illustrating a filtrate discharging operation.

FIG. 6 is an explanatory diagram showing the overall configuration of a sewage treatment apparatus according to another embodiment of the present invention.

FIG. 7 is an explanatory view showing an entire configuration of a conventional sewage treatment apparatus.

FIG. 8 is an explanatory diagram showing the overall configuration of another conventional sewage treatment apparatus.

[Explanation of symbols]

 21 Aeration tank 22 Membrane separator 23 Filtrate chamber 24 Water supply pipe for treated water 30 Filtrate pipe 32 Check valve 33 Drain pipe 34 U-shaped pipe 35 Blower 37 Air diffuser

Continuation of the front page (56) References JP-A-7-299949 (JP, A) JP-A-7-299490 (JP, A) JP-A 8-89960 (JP, A) (58) Fields studied (Int .Cl. ⁷ , DB name) C02F 1 / 44,3 / 12

Claims (2)

(57) [Claims] An aeration tank for treating water to be treated introduced from a supply pipe for the water to be treated is provided with a membrane separation device for gravity-filtering the water to be treated by using a natural head in the vessel as a driving pressure. In a sewage treatment apparatus provided with an aeration device directly below a separation device, a filtrate tube communicating with a permeate flow path of the membrane separation device is provided, and the filtrate tube is provided at an appropriate position above the top of the membrane separation device. A filtrate chamber having a hermetically sealed structure is provided, and a drain pipe having one end connected to a lower part of the filtrate chamber is provided by guiding the other end upward, and the filtrate chamber and the drain pipe are connected to one end of the drain pipe. A U-shaped tube communicating above the position is provided, air feeding means is connected to the upper part of the filtrate chamber to feed air into the filtrate chamber, and a backflow prevention mechanism is interposed in the filtrate pipe. A sewage treatment apparatus characterized by the above-mentioned. 2. An air supply means for supplying air to the air diffuser and the air supply means.
A sewage treatment apparatus as described in the above.