JP3370864B2 - Septic tank - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a septic tank. More specifically, the present invention relates to a septic tank capable of more effectively cleaning a membrane separation device installed in an aeration tank and reducing maintenance work for clogging or the like.

[0002]

2. Description of the Related Art Conventionally, human waste and daily cooking,
There has been provided a septic tank that can purify household wastewater generated by washing, bathing, and the like. One of the septic tanks is, for example, the membrane separation type septic tank shown in FIG. In the membrane separation type septic tank, as shown in FIG. 5, the membrane separation device (5) is added to the aeration tank (4) for aerobically biologically treating the water to be treated with activated sludge, It is installed so that it can be immersed in the water to be treated. The membrane separator (5)
The treated water in the aeration tank (4) is subjected to solid-liquid separation by using the head difference of the treated water as a driving source. In this solid-liquid separation, the activated sludge is retained in the aeration tank (4) while being filtered. The membrane-permeated liquid is sent as treated water to the treated water storage tank (6) for storing treated water which communicates with the aeration tank (4) through the communication pipe (9). The treated water is then pumped from the treated water storage tank (6) by the discharge pump (12), and the discharge pipe (15).
It is sent to the disinfection tank (8) through and then discharged to the outside of the tank.

In such a membrane separation type septic tank, two flow rate adjusting tanks (1) and (2) are provided on the waste water inflow side, and after adjusting the inflow amount of the waste water flowing therein, the transfer pump ( In 3), it is transferred to the aeration tank (4). Reference numeral 14 is a sludge transfer pipe for transferring sludge.
The aeration tank (4) is further provided with an air diffuser (7), and the air sent from the blower connected to this is sent into the aeration tank (4) through this air diffuser (7). The aerobic condition is formed. In the aeration tank (4), activated sludge treatment of the water to be treated is carried out under aerobic conditions.

Then, in the septic tank, the water levels of the two flow rate adjusting tanks (1) and (2) and the aeration tank (4) are detected by the water level detecting units (11) and (13) provided respectively, and the detected water levels are detected. According to the above, the operation of the transfer pump (3) and the discharge pump (12) may be controlled by the control unit (10). The water levels (L1) and (L2) to be detected in both tanks are preset.

[0005]

However, in the conventional membrane separation type septic tank shown in FIG. 5, for example, the membrane separation device (5) is often clogged, and in this case. Since the solid-liquid separation efficiency of the water to be treated decreases, it is necessary to perform maintenance to eliminate clogging.

As one measure for this, the air diffuser (7) is arranged below the membrane separator (5), and the air ejected from the air diffuser (7) aerates the membrane separator (5) from below.
As a result, a rising stirring flow is generated in the water to be treated, and the cake tank attached to the membrane surface of the filtration membrane of the membrane separation device (5) is peeled off,
It may be possible to perform membrane cleaning. However, even with such washing, it is not possible to completely eliminate the adhesion of sludge to the pores of the filtration membrane, and the effect cannot be maintained unless the washing is performed at a relatively short interval. Is pointed out.

The present invention has been made in view of the above circumstances, solves the drawbacks of the conventional membrane separation type septic tank, and more effectively cleans the membrane separation apparatus installed in the aeration tank. The purpose of the present invention is to provide a septic tank that can reduce the time and effort required for maintenance such as clogging.

[0008]

Means for Solving the Problems The present invention is intended to solve the above problems by providing an aeration tank for aerobically biologically treating water to be treated with activated sludge, and a membrane separation device as the water to be treated. It is soaked internally that a treated water storage tank is provided in communication with the aeration tank via this membrane separation device.The membrane separation device separates the water to be treated into solid and liquid, and it is placed between the aeration tank and the treated water storage tank. While the membrane permeate is sent to the treated water storage tank using the head difference of
In the septic tank that holds the activated sludge in the aeration tank, temporarily raise the water level on the treated water storage tank side to a level higher than that of the aeration tank, and apply the reverse head between the aeration tank and the treated water storage tank. Provided is a septic tank characterized by being provided with a backwashing means for backwashing treated water from a treated water storage tank as a drive source and directly supplying it to a membrane separation device for washing.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the septic tank of the present invention will be described in more detail with reference to the accompanying drawings.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a schematic view of the essential parts of an embodiment of the septic tank of the present invention. For example, in the example shown in FIG. 1, the aeration tank (4) is equipped with a membrane separation device (5) having a plurality of flat membranes (16) arranged side by side. One end of a communication pipe (9) that connects the aeration tank (4) and the treated water storage tank (6) is connected to the membrane separation device (5), and solid-liquid separation is performed by each flat membrane (16). The treated water merges at the upper end of the membrane separation device (5) and is guided to the treated water storage tank (6) through the communication pipe (9).

In the aeration tank (4), an air diffuser pipe (7) is arranged below the membrane separation device (5). An aeration blower (not shown) is connected to the air diffuser (7), and the water to be treated in the aeration tank (4) is supplied by the air sent from the blower and ejected from the air diffuser (7). Oxygen is supplied to the tank to make the inside of the tank aerobic and promote the activated sludge treatment, and the flat membrane (1) installed in the membrane separator (5) is used.
It is also possible to clean the membrane surface of 6).

On the other hand, the treated water storage tank (6) is internally provided with a discharge pump (P1).
The discharge pipe (15) whose one end is connected to the treatment tank faces the disinfection tank (8) connected to the treated water storage tank (6). The treated water transferred from the aeration tank (4) and stored in the treated water storage tank (6) is pumped up by the discharge pump (P1) and guided to the disinfection tank (8). After this, it is discharged outside the tank.

Further, in the example shown in FIG. 1, a valve (V1) and a suction pump (P2) are provided as a backwash means, and these valve (V1) and suction pump (P2) are connected pipes. They are connected in parallel in the middle of (9).
An electromagnetic valve, for example, can be preferably applied to the valve (V1). The suction pump (P2) has a structure in which water does not flow when stopped.

Further, the aeration tank (4) and the treated water storage tank (6) are also provided with water level sensors (13) and (17). The water level sensor (13) is the water level L of the aeration tank (4).
1 is detected. On the other hand, the water level sensor (17) detects two water levels L2 and L3 of the treated water storage tank (6). These water levels have a relationship of L2 <L1 <L3. As the water level sensors (13) and (17), a pressure sensor, various types of float switches, electrode rods and the like can be adopted. Among them, the pressure sensor has an advantage that an arbitrary water level can be detected as a signal only by installing one pressure sensor in one tank.

The above valve (V1) and suction pump (P
2), discharge pump (P1) and water level sensor (13) (1
All of 7) are electrically connected to the control unit (10) illustrated in FIG. The operation of the valve (V1), the suction pump (P2) and the discharge pump (P1) is controlled by the control unit (10) by the water level sensors (13) (17).
It is controlled according to the water level detected in.

The operation of the septic tank having the above structure will be described below. During the aeration process, the valve (V1) is open and the suction pump (P2) does not operate. The water level of the treated water storage tank (6) is below L2, and the discharge pump (P1) does not operate. The discharge pump (P1) is set to operate when the water level becomes higher than L2.

The water level of the aeration tank (4) is above L1, and the treated water that has been solid-liquid separated by the membrane separator (5) is the head of the aeration tank (4) and the treated water storage tank (6). Due to the difference, it is transferred from the aeration tank (4) to the treated water storage tank (6). (Aeration tank water level) ≤ L1 and (Treatment water storage tank water level) ≤
In the case of L2, such a state occurs, for example, when the waste water does not newly flow into the tank at night.

The water levels of the aeration tank (4) and the treated water storage tank (6) are respectively set to L by the water level sensors (13) and (17).
When it is detected as 1, L2, the valve (V1) is closed and the suction pump (P2) is operated. Then, the suction pump (P
2) is forcibly sucked, and the water to be treated is passed through the membrane separation device (5) for solid-liquid separation, and the suction pump (P) of the communication pipe (9).
It is transferred to the treated water storage tank (6) through the channel on the 2) side.
When the treated water storage tank (6) reaches the water level L3, the suction pump (P
2) stops. The water level L3 is defined as L3 = L1 + α with respect to the water level L1 related to the aeration tank (4). [alpha] can be set to an appropriate value depending on, for example, the treatment capacity of the septic tank, and a range of 10 to 60 cm is preferably exemplified. Usually, it can be about 30 cm.

The water level L3 measured by the water level sensor (17)
The detection of can be replaced with the detection of the water level of the aeration tank (4) of the water level sensor (13). That is, the aeration tank (4)
The water level L4 below L1 to the treated water storage tank (6)
Is calculated from the volume between the water levels L2 and L3, and this is set so that the water level sensor (13) detects that the water level in the aeration tank (4) is less than or equal to this water level L4. The detection of the water level L4 of the water level sensor (13) is performed by the water level sensor (17) regarding the water levels of both the aeration tank (4) and the treated water storage tank (6).
This is completely synonymous with the detection of the water level L3 by.

When the suction pump (P2) stops, the valve (V1) opens. At this time, the water level in the aeration tank (4) is lower than L1 as apparent from the above, and therefore the water level L
There is a head difference between the treated water storage tank (6) and the treated water storage tank (6). On the basis of this water head difference, the treated water in the treated water storage tank (6) passes through the flow passage on the valve (V1) side of the communication pipe (9), contrary to the aeration treatment, and the membrane separation device (5 ) And wash the flat membrane (16) provided there. This backwash voluntarily ends when the water levels in both the aeration tank (4) and the treated water storage tank (6) match.

On the other hand, in the septic tank, the elapsed time from when the water level in the aeration tank (4) became below L1 was measured, and this was set as sufficient from the operation of the suction pump (P2) to the end of backwashing. When the set time is reached, the valve (V
1) is closed, and at the same time, the discharge pump (P1) is activated to return the water level of the treated water storage tank (6) to L2. Valve (V
The timing of closing of 1) and the operation of the discharge pump (P1) not only correspond to such elapsed time but also detect the water level of at least one of the aeration tank (4) and the treated water storage tank (6). It is also possible to correspond. In this case, the water level at which both tanks are in equilibrium at the end of backwashing may be detected by a water level sensor arranged on the detection side.

Thus, when cleaning the membrane separation device (5), the head of water opposite to that at the time of the aeration treatment is applied between the aeration tank (4) and the treated water storage tank (6) to treat the treated water with the membrane separation device. Since it is directly supplied to (5), the cleaning power is improved as compared with the case of performing film cleaning by generating an upward stirring flow in the water to be treated with the air ejected from the aeration pipe (7), and the flat film (16) Adhesion of sludge to the pores can be sufficiently eliminated. As a result, it is possible to lengthen the interval for cleaning the membrane, and it is possible to reduce the time and effort required for maintenance such as clogging.

In the above, when the cleaning timing of the membrane separator (5) is set to start when the aeration tank (4) reaches the minimum water level, no new waste water flows into the septic tank. The membrane separation device (5) can be washed in this state, and the washing effect is further enhanced. FIG. 2 is a main part configuration diagram showing another example of the septic tank of the present invention.

In the example shown in FIG. 2, the structure of the backwash means is different from the example shown in FIG. In the example of FIG. 2, the backwash means includes a wash water storage tank (18) and a valve (V2) connected in series downstream thereof. The wash water storage tank (18) and the valve (V2) are branched from the communication pipe (9) and are connected in the middle of the wash water inflow pipe (19) connected to the discharge pipe (15). The wash water storage tank (18) communicates with the treated water storage tank (6) as well as the disinfection tank (8), and is arranged at a position higher than the aeration tank (4) and the treated water storage tank (6). ing. Further, the wash water storage tank (18) is also provided with a water level sensor (20) for detecting the water level L3. The water level L3 is set higher than the upper part of the wash water inflow pipe (19).

For example, an electromagnetic valve is preferably applied to the valve (V2), and the valve (V2) and the water level sensor (20) provided in the wash water storage tank (18) are the control unit (10) shown in FIG. ) Is electrically connected to. In addition,
As in the example shown in FIG. 1, the communication pipe (9) is provided with a valve (V1) in the middle thereof.

The septic tank provided with the backwash means having such a structure operates as follows. During the aeration process, the valve (V1) provided in the middle of the communication pipe (9) is open, and the suction pump (P2) does not operate. The water level of the treated water storage tank (6) is below L2, and the discharge pump (P1) does not operate. The discharge pump (P1) is set to operate when the water level becomes higher than L2.

The water level of the aeration tank (4) is above L1, and the treated water that has undergone solid-liquid separation by the membrane separation device (5) is the head of the aeration tank (4) and the treated water storage tank (6). The difference is used as a driving source and transferred from the aeration tank (4) to the treated water storage tank (6). When the water level of the treated water storage tank (6) exceeds L2 and this is detected by the water level sensor (17), the discharge pump (P2)
Operates and sucks the treated water into the wash water storage tank (18). The wash water storage tank (18) is provided with an overflow weir that defines the overflow level. Below this overflow weir, the wash water storage tank (18) has a capacity to store a predetermined amount of treated water. have. When the overflow level is exceeded, the treated water flows down to the disinfection tank (8). (Aeration tank water level) ≤ L1 When the water level of the aeration tank (4) becomes L1 or less, the valve (V1) is closed based on the water level detection of the water level detection sensor (13),
The discharge pump (P1) stops. At the same time, the valve (V
2) opens. Since the cleaning water storage tank (18) is arranged at a higher position than the aeration tank (4) and the treated water storage tank (6), it has a head difference from the aeration tank (4). Therefore, the stored predetermined amount of treated water is supplied to the membrane separation device (5) from the washing water inflow pipe (19) through the communication pipe (9) by using the head of the water as a driving source. The flat membrane (16) is washed with this treated water. (Washing water storage tank water level) = L3 When the water level sensor (20) detects that the water level of the washing water storage tank (18) has reached L3, the valve (V2)
Closes. This is because the water level of the wash water storage tank (18) is L3.
This is because, in the following case, air enters the communication pipe (9) and the inside of the membrane separation device (5) through the wash water inflow pipe (19) and the siphon effect is lost.

The closing timing of this valve (V2) is
It is also possible before the water level reaches L3. In this case, the required time may be set and the opening time of the valve (V2) may be measured by a timer. Water level sensor (2
0) can be omitted. In the case of the septic tank shown in FIG. 2 described above, just as in the example of FIG. 1, when cleaning the membrane separation device (5), aeration treatment is performed between the aeration tank (4) and the treated water storage tank (6). The treated water can be directly supplied to the membrane separation device (5) by applying a head opposite to the time. Therefore, effective cleaning of the membrane separation device (5) becomes possible, and the flat membrane (16)
It is possible to sufficiently eliminate the adhesion of sludge to the pores. The membrane cleaning interval can be set longer, reducing the time and effort required for maintenance such as clogging.

FIG. 3 is a schematic view of the essential part showing another example of the septic tank of the present invention. In the example shown in FIG. 3,
The backwashing means comprises a stretchable airbag (21) and a means for sending and exhausting the airbag (21). The airbag (21) is installed in the aeration tank (4). As shown in FIG. 4, the air supply / exhaust means of the airbag (21) is connected to, for example, a branch pipe (23) from an aeration blower (22) provided in the septic tank and the branch pipe (23). The valve (V4) (V5) can be configured. In the example shown in FIG. 4, the valve (V4) is provided in the middle of the branch pipe (23). The valve (V5) is provided for exhaust, is arranged on the blower (22) side with respect to the valve (V4), and is the branch pipe (23).
Is connected to. In this way, the airbag (2
By using the blower (22) installed in the septic tank instead of separately providing the air source of 1) and using it together, it is possible to suppress the cost increase of the septic tank due to the attachment of the backwashing means. The septic tank may be made compact.

The septic tank shown in FIG.
Similarly to the example shown in FIG. 2, the communication pipe (9) is provided with a valve (V1) in the middle thereof. The septic tank provided with the backwashing means having the above-described configuration operates as follows. The valve (V1) provided in the middle of the communication pipe (9) during the aeration process is open, and the membrane separation is performed from the aeration tank (4) whose water level is higher than L1 toward the treated water storage tank (6). The treated water that has been solid-liquid separated by the device (5) is transferred based on the head difference between the aeration tank (4) and the treated water storage tank (6). The water level of the treated water storage tank (6) rises with the transfer of the treated water, and the discharge pump (P1) operates when the water level becomes higher than L2. (Aeration tank water level) ≤ L1 and (Treatment water storage tank water level) ≤
When the water levels L1 and L2 are detected by the water level sensors (13) and (17) at L2, respectively, the discharge pump (P1) is stopped. At the same time, air is sent from the blower (22) shown in FIG. 4 to the airbag (21) installed inside the aeration tank (4). At this time, the valve (V4) is open and the valve (V5) is closed.

As the air is sent from the blower (22), the airbag (21) gradually expands, and the apparent volume of the water to be treated in the aeration tank (4) increases. As a result, the water to be treated in the aeration tank (4) is forcibly passed through the membrane separation device (5) and transferred to the treated water storage tank (6). As a result, the water level in the treated water storage tank (6) rises. When (water level of treated water storage tank) ≧ L3, when the water level sensor (17) detects that the water level of the treated water storage tank (6) has reached L3, the blower (22) stops and the airbag (21) ) To the air) stops. at the same time,
The valve (V5) shown in FIG. 4 opens and the airbag (2
The air in 1) is discharged from this valve (V5) through the branch pipe (23), and the air in the airbag (21) is deflated. Therefore, the airbag (21) contracts, the water level of the aeration tank (4) becomes lower than the water level L3 of the treated water storage tank (6), and a water head difference occurs. The treated water flows from the treated water storage tank (6) through the communication pipe (9) into the membrane cleaning device (5) by using the water head opposite to that at the time of aeration as a drive source, and cleans the membrane cleaning device (5). .

This backwash voluntarily ends when the water levels in both the aeration tank (4) and the treated water storage tank (6) match. On the other hand, in the septic tank, the elapsed time from when the water level in the aeration tank (4) becomes equal to or lower than L1 is measured, and when the preset time until the end of the backwash is reached, the valve (V
1) is closed, and at the same time, the discharge pump (P1) is activated to return the water level of the treated water storage tank (6) to L2. The timing of closing the valve (V1) and operating the discharge pump (P1) does not only correspond to the elapsed time as in the example of FIG. 1, but also the aeration tank (4) and the treated water storage tank (6). It is also possible to support at least one of the water level detections.

As is clear from the above, in the case of the septic tank shown in FIG. 3, the same effect as in the example of FIGS. 1 and 2 can be obtained. Of course, the present invention is not limited to the above examples. It goes without saying that various aspects are possible in details such as the structure and structure of the membrane separation device, valves, suction and discharge pumps, water level sensors, and the like.

[0034]

As described in detail above, according to the present invention, when cleaning the membrane separation device, a head opposite to the normal state is applied between the aeration tank and the treated water storage tank to treat the treated water from the treated water storage tank. Water can be fed directly to the membrane separator. By the backflow of the washing water, the washing power of each surface of the filtration membrane is increased, and the adhesion of sludge to the pores can be sufficiently eliminated. It is possible to lengthen the interval for cleaning the membrane and reduce the time and effort required for maintenance against clogging.

[Brief description of drawings]

FIG. 1 is a main part configuration diagram showing an embodiment of a septic tank of the present invention.

FIG. 2 is a main part configuration diagram showing another example of the septic tank of the present invention.

FIG. 3 is a main part configuration diagram showing another example of the septic tank of the present invention.

4 is a main part configuration diagram showing an air supply / exhaust means of the airbag in the example shown in FIG.

FIG. 5 is a configuration diagram showing a conventional membrane separation type septic tank.

[Explanation of symbols]

1, 2 flow rate adjustment tank 3 Transfer pump 4 aeration tank 5 Membrane separation device 6 treated water storage tank 7 Air diffuser 8 disinfection tank 9 communication tubes 10 Control unit 11, 13, 17, 20 Water level sensor 14 Transfer tube 15 Discharge pipe 18 Wash water storage tank 19 Wash water inflow pipe 21 Airbag 22 Blower 23 Branch piping P1 discharge pump P2 suction pump V1, V2, V3, V4, V5 valves L1, L2, L3 Water level

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takayoshi Nakaoka 1048 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Works, Ltd. (56) References JP-A-8-89960 (JP, A) JP-A-6- 218237 (JP, A) JP 6-71279 (JP, A) JP 3-151030 (JP, A) JP 3-42018 (JP, A) JP 61-136404 (JP, A) JP-A-8-24855 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) C02F 1/44 B01D 61/00-65/10 C02F 3/12

Claims (6)

(57) [Claims] 1. A membrane separation device is installed inside a aeration tank for aerobically biologically treating treated water by activated sludge so that the treated water can be immersed in the treated water, and a treated water storage tank is provided through the membrane separation device. Is provided in communication with the aeration tank, and the membrane separation device performs solid-liquid separation of the water to be treated, and sends the membrane permeate to the treated water storage tank by using the head difference between the aeration tank and the treatment water storage tank as a drive source. On the other hand, activated sludge is a septic tank that holds it in the aeration tank.The water level on the treated water storage tank side is temporarily higher than that of the aeration tank, and a head opposite to the normal time is applied between the aeration tank and the treated water storage tank. A septic tank characterized by being provided with a backwash means for backwashing treated water from the treated water storage tank by using this as a drive source and directly supplying it to the membrane separation device for washing. 2. The backwash means is provided with a valve and a suction pump in parallel, and each of these valve and suction pump is connected in the middle of a communication pipe that connects the aeration tank and the treated water storage tank. The described septic tank. 3. A communication pipe that connects the aeration tank and the treated water storage tank is provided, the treated water storage tank is provided with a discharge pump and a discharge pipe for pumping the treated water, and the backwash means is an aeration tank and treated water storage. A washing water storage tank arranged at a position higher than the tank and a valve connected in series to the downstream side of the washing water storage tank and the valve branching from the communication pipe, and the washing water inflow pipe connected to the discharge pipe. The septic tank according to claim 1, which is connected midway. 4. The septic tank according to claim 1, wherein the backwashing means comprises an expandable and contractible airbag and an air supply / exhaust means for the airbag, and the airbag is installed inside the aeration tank. 5. The septic tank according to claim 4, wherein the air supply / exhaust means of the airbag comprises a branch pipe from an aeration blower and a valve connected to the branch pipe. 6. The septic tank according to claim 1, wherein the cleaning timing of the membrane separation device is set when the water level of the aeration tank reaches a set minimum water level.