JP3368682B2 - Septic tank and its operation method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a septic tank for biologically treating domestic wastewater, industrial wastewater and the like, and a method of operating the same.

[0002]

2. Description of the Related Art A method disclosed in Japanese Unexamined Patent Publication No. 4-108600 is known as a method for operating a septic tank for biologically treating wastewater from households such as toilets, washrooms, baths and kitchens, and industrial wastewater. ing. As shown in FIG. 7, the operation method disclosed in this prior art allows wastewater to continuously flow into the bioreaction chamber and performs aeration and filtration from the highest water level (HWL) to the lowest water level (LWL). The aerobic treatment is performed at the same time, and conversely, the anaerobic treatment without aeration or filtration is performed from the lowest water level (LWL) to the highest water level (HWL).

[0003]

In the above-mentioned prior art, since the wastewater constantly flows into the biological reaction chamber, oxygen is brought in with the inflow of the wastewater, and the dissolved oxygen concentration in the biological reaction chamber is increased. Does not decrease sufficiently and anaerobic treatment cannot be performed efficiently. Further, since the anaerobic treatment cannot be performed in a stable state where a constant water level is maintained, the denitrification reaction does not proceed sufficiently. Furthermore, when the wastewater flows into the biological reaction chamber at the beginning of the aerobic treatment by aeration or in the middle of the aerobic treatment, organic carbon contained in the inflowing wastewater required for the denitrification reaction during the anaerobic treatment is generated. It is consumed during aerobic reaction, and the denitrification reaction is not smooth. Also, in septic tanks that use membranes, contaminants such as coarse particles and fibrous substances such as hair that are brought into the tank together with wastewater clog the raw water path of the membrane, or adhere to the membrane surface, causing deterioration of filtration characteristics. There was a point.

[0004]

In order to solve the above-mentioned problems, a septic tank according to the present invention comprises a biological reaction chamber in which an aeration device is arranged, and a flow rate adjusting unit for adjusting the amount of waste water flowing into the biological reaction chamber. And a transfer means for transferring the wastewater in the flow rate adjusting unit to the biological reaction chamber, and a membrane separation device for separating the wastewater in the biological reaction chamber into a permeate and a retentate, the septic tank being the biological reaction chamber. Minimum water level (LW
L.) and a high water level (HWL) are detected by the water level detecting means, and the water level detecting means and the shifting means make the water level in the biological reaction chamber the lowest water level (LWL) and the highest water level (LWL).
HWL) within the range, and the water level detecting means controls the minimum water level (LW) in the biological reaction chamber.
After receiving the signal of L.), the transfer operation of the wastewater is controlled for a certain time or until a certain amount or the maximum water level (HWL) is reached, and after a certain time has elapsed from the stop of the transfer operation,
The control part which controls to start aeration operation and filtration operation was provided.

It should be noted that it is possible to dispose a contaminant removing means for removing contaminants such as coarse particles, hair and fibrous substances in the inflowing wastewater before the biological reaction chamber. As the filter, a filter bed or a screen provided in the flow rate adjusting unit may be considered, and when a hollow fiber membrane is selected as the separation membrane constituting the membrane separation device, the contaminants are fibrous substances having a length of 0.2 mm or more. It is preferable to remove the substance.

In the method for operating the septic tank according to the present invention, the biological reaction chamber in which the aeration device is arranged, the flow rate adjusting unit for adjusting the amount of waste water flowing into the biological reaction chamber, and the waste water in the flow rate adjusting unit are provided. To a biological reaction chamber,
A method for operating a septic tank equipped with a membrane separation device for separating waste water in the biological reaction chamber into a permeate and a retentate, and a water level detecting means for detecting a minimum water level (LWL) and a maximum water level (HWL) in the biological reaction chamber. In the above, the aeration of the biological reaction chamber is intermittently performed by a timer, the operation of the membrane separation device is started at approximately the same time as or slightly later than the start of the operation of the aeration device, and the water level in the biological reaction chamber is the lowest water level (LWL). )
When it reaches the maximum water level (HWL), or when the water level in the bioreaction chamber reaches the maximum water level (HWL), The transfer is stopped when a fixed amount of transfer is completed or when the transfer is performed for a predetermined time. here,
The transition time of the wastewater is preferably 1/2 or less, more preferably 1/3 or less of the operating time of the aeration device.

Further, by disposing a filter bed and a screen in the flow rate adjusting unit, impurities such as coarse particles and fibrous substances in the inflowing wastewater that deteriorate the filtration characteristics are removed in advance on the upstream side of the biological reaction chamber. By treating the wastewater with water, the filtration characteristics can be stabilized for a long period of time.

FIG. 8 is a graph showing the relationship between the size of the opening of the contaminant removal screen and the change of the permeation flux with the passage of operating time. As can be seen from this graph, the size (particle size) () Exceeds 0.1 mm causes adhesion to the surface of the membrane, clogging, and clogging of the flow channel, resulting in deterioration of the membrane filtration characteristics. Therefore, it is necessary to remove particles having a size exceeding 8 mm at least as impurities.

In particular, when the separation membrane is a hollow fiber membrane, the distance between the membrane elements is around 0.2 mm, so fibers having a length of 0.2 mm or more are entangled in the bundle of membrane elements, and particles are further deposited there. As a result, the flow of waste water on the membrane surface is obstructed, and the membrane filtration characteristics are deteriorated. The fibers include pulp and hair, and the average length of pulp is 0.2 mm. Therefore, a fibrous substance having a length exceeding 0.2 mm and a particulate substance having a particle diameter exceeding 0.1 mm, preferably a fibrous substance having a length exceeding 8 mm and a particle diameter of 8 mm. It is preferable to remove particulate matter having a size of more than 3 as contaminants.

[0010]

[Function] In aerobic treatment, ammonia nitrogen (N
H ₄ ⁺⁾ is nitrate nitrogen (NO ₃ ^-) and nitrite nitrogen (N
O ₂ ^-) in the oxidative decomposition, also in anaerobic processes, anaerobic denitrifying bacteria using organic carbon, they nitrate nitrogen (N
O ₃ ^-) and nitrite nitrogen (NO ₂ ^-) and reduced nitrogen (N
₂ ) Convert to.

[0011]

Embodiments of the present invention will be described below with reference to the accompanying drawings. Here, FIG. 1 is a cross-sectional view of the septic tank and the septic tank used for implementing the operating method according to the present invention. The septic tank 1 has a flow rate adjusting section S1 and a biological reaction chamber S2 defined by a partition wall 2, The adjustment section S1 is provided with a wastewater introduction pipe 3 and a water level sensor 4 for detecting the highest water level (HWL) and the lowest water level (LWL).
L.) or the minimum water level (LWL) is detected, the septic tank 1 is stopped or an alarm is issued.

Further, a filter bed 20 is arranged in the flow rate adjusting section S1 to remove impurities in the inflowing wastewater.

A pump 5 and a pipe 6 for transferring wastewater from the flow rate adjusting unit S1 to the biological reaction chamber S2 are provided between the flow rate adjusting unit S1 and the biological reaction chamber S2. In addition, pump 5
It is also possible to use an air lifter or the like instead of using.

On the other hand, in the biological reaction chamber S2, a membrane separation device 7
And the aeration device 12 is arranged below the membrane separation device 7. Here, the membrane separation device 7 includes a separation membrane 8 such as a hollow fiber membrane, a water collection pipe 9, a pipe 10 and a pump 11.
Composed of.

Further, the biological reaction chamber S2 is provided with a water level sensor 13 for detecting the maximum water level (HWL) and the minimum water level (LWL) of the wastewater, and a signal from the water level sensor 13 is sent to the controller 1
4 and the signal from the control unit 14 turns on / off the pump 5 for transferring wastewater from the flow rate adjusting unit S1 to the biological reaction chamber S2, the pump 11 for the membrane separation device 7 and the blower 15 for the aeration device 12. I am trying.

FIG. 2 is a sectional view of another type of septic tank used for carrying out the method of operating the septic tank according to the present invention. In this embodiment, the separation membrane 18 is not immersed in the biological reaction chamber S2. Further, the membrane module 17 is provided outside, and the liquid concentrated by the separation membrane 18 is returned to the biological reaction chamber S2 via the ejector 16. By using the ejector 16 in this way, the aeration effect is improved. The separation membrane 18 may be a tubular membrane or a flat membrane. In this embodiment, a contaminant removing chamber S3 having a screen 21 is installed in front of the flow rate adjusting unit S1.

Next, an example of the method for operating the septic tank according to the present invention will be described with reference to FIGS. 3 to 6 showing processing patterns. First, in the processing pattern shown in FIG. 3, transfer of waste water from the flow rate adjusting unit S1 to the biological reaction chamber S2 (batch transfer)
One pattern is set from the end to the end of the next transition, and this is repeated. That is, the transfer of the waste water is performed by a signal from the control unit 14 when the sensor 13 detects the maximum water level (HWL), when the transfer of the waste water of a certain amount is completed, or when the waste water is transferred for a predetermined time. This is performed by stopping the pump 5, and the anaerobic treatment is performed while maintaining a constant water level without operating the aeration device 12 or the membrane separation device 7 for a predetermined time from the end of the transition of the wastewater. In this way, by not performing a driving operation during the anaerobic treatment and maintaining a stable state, consumption of the dissolved oxygen in the biological treatment chamber S2 progresses rapidly, a sufficient anaerobic time can be secured, and the treatment effectively proceeds.

After this, the control unit 14 incorporating a timer
The operation of the aeration device 12 and the membrane separation device 7 is started at the same time according to the signal from, and the operation of the membrane separation device 7 (filtration operation) is stopped at the time when the water level reaches the minimum water level (LWL), and at the same time when the filtration time ends 5 is started to start the transfer (batch transfer) of the waste water from the flow rate adjusting unit S1 to the biological reaction chamber S2. Then, when the maximum water level (HWL) is reached, or when the transfer of a certain amount of waste water is completed, or when the waste water is transferred for a predetermined time, the transfer of the waste water and the operation of the aeration device 12 are stopped at the same time.

Within the filtration time, the pattern of FIG. 3 is used to obtain a fixed amount of permeate, or the filtration rate is set fast,
It is also possible to adopt the pattern of FIG. 4 in which the filtering is completed early within the filtering time.

In the processing pattern shown in FIG. 5, the start time of the filtration operation by the membrane separation device 7 is slightly delayed from the start time of the operation of the aeration device 12, and other configurations are as shown in FIG.
It is the same as the pattern shown in. In this way, by slightly performing aeration before filtration, the ammonia in the wastewater is oxidized and the concentration of ammonia in the membrane permeate decreases. Further, when an immersion type hollow fiber membrane is used as the separation membrane, the effect of cleaning the membrane surface is enhanced.

In the treatment pattern shown in FIG. 6, the operations of the aeration device 12 and the membrane separation device 7 are started at the same time, stopped at the same time, and the transfer of waste water (batch transfer) is started at the end of the filtration time. I am trying to do it. By adopting such a pattern, the transfer of wastewater and aeration do not overlap, and the organic carbon supplied with the transfer of wastewater is not aerobically treated, that is, biooxidized. The denitrification reaction by organic carbon is effectively performed.

In the processing pattern shown in FIG. 6, aeration may be carried out before filtration.

[0023]

The following (Table 1) compares the method of the present invention shown in FIG. 3 with the conventional method shown in FIG. 7 in terms of treated water quality. According to this, it can be seen that, compared with the conventional method, the amount of nitrate nitrogen detected in the treated water among the nitrogen components is small, and the denitrification reaction is sufficiently advanced.

[0024]

[Table 1]

As is clear from the above description and (Table 1), according to the present invention, the biological reaction chamber in which the aeration device is disposed, and the flow rate adjustment for adjusting the amount of waste water flowing into this biological reaction chamber. When operating the septic tank equipped with the membrane section and the membrane separation device that separates the wastewater in the biological reaction chamber into the permeate and the retentate, the transition of the wastewater from the flow rate adjusting unit to the biological reaction chamber depends on the water level in the biological reaction chamber. Start from the time of reaching the lowest water level (LWL) until reaching the highest water level (HWL), or the time when the transfer of a certain amount of wastewater is completed, or the time when the wastewater is transferred for a predetermined time, and the aeration The operation of the apparatus is started after a lapse of a predetermined time after the transfer of the waste water from the flow rate adjusting unit to the biological reaction chamber is stopped, and is stopped at substantially the same time as the start or stop of the transfer of the next waste water, and further the operation of the membrane separation device is stopped. Before driving It starts at about the same time as the start of operation of the aeration device, or slightly later, and the lowest water level (LW
Since it was stopped at the time when it reached L.), there is no inflow of wastewater during anaerobic treatment, so the concentration of dissolved oxygen in the bioreaction chamber is sufficiently reduced, and anaerobic treatment can be performed efficiently. After the completion of the transition, the anaerobic treatment will be performed while maintaining a constant water level, and the denitrification reaction can be sufficiently advanced.

In particular, the transition time of wastewater is set to 1/2 or less, preferably 1/3 or less of the operating time of the aeration device, and the transition of wastewater is collected immediately before or after the end of aeration (aerobic treatment) and the biological reaction is summarized. By supplying it indoors, the organic carbon required for anaerobic treatment is sufficiently supplied, and the denitrification reaction during anaerobic treatment proceeds smoothly.

Further, by disposing a filter bed, a screen, etc. in the flow rate adjusting section or in the front stage thereof, the impurities in the inflowing wastewater are removed on the upstream side of the biological reaction chamber, so that the membrane filtration characteristics can be improved. Long-term stabilization can be achieved.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a septic tank according to the present invention and a septic tank used for operating the method of operating the same.

FIG. 2 is a cross-sectional view of another type of septic tank used for implementing the operation method.

FIG. 3 is a graph showing a processing pattern of the driving method according to the first invention.

FIG. 4 is a graph showing a processing pattern of a driving method according to another invention.

FIG. 5 is a graph showing a processing pattern of a driving method according to another invention.

FIG. 6 is a graph showing a processing pattern of a driving method according to another invention.

FIG. 7 is a graph showing a processing pattern of a conventional driving method.

FIG. 8 is a graph showing the relationship between the size of the openings of the contaminant removal screen and the change in permeation flux with the passage of operating time.

[Explanation of symbols]

1 ... Septic tank, 4, 13 ... Water level sensor, 5, 11 ... Pump, 7 ... Membrane separation device, 8 ... Separation membrane, 12 ... Aeration device, 1
4 ... Control part, 20 ... Filter bed, 21 ... Screen, S1 ... Flow control part, S2 ... Biological reaction chamber, S3 ... Contaminant removal chamber.

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Yuichi Okuno Yuichi Okuno 2-1-1 Nakajima, Kokurakita-ku, Kitakyushu-shi, Fukuoka Totoki Kikai Co., Ltd. (56) Reference JP-A-4-108600 (JP, A) JP-A-6-47387 (JP, A) Actual development 4-99294 (JP, U) (58) Fields investigated (Int.Cl. ⁷ , DB name) C02F 3/00 C02F 3/12

Claims (8)

(57) [Claims] 1. A biological reaction chamber in which an aeration device is arranged, a flow rate adjusting unit for adjusting the amount of waste water flowing into the biological reaction chamber, and a transfer means for transferring the waste water in the flow rate adjusting unit to the biological reaction chamber. And a membrane separation device for separating the wastewater in the biological reaction chamber into a permeate and a retentate, the septic tank detecting the minimum water level (LWL) and the maximum water level (HWL) in the biological reaction chamber. Means for controlling the water level in the biological reaction chamber by the water level detection means and the transfer means so as to fall within the range of the minimum water level (LWL) and the maximum water level (HWL), and the biological reaction by the water level detection means. After receiving the signal of the minimum water level (LWL) in the room, a certain time or a certain amount or the maximum water level (
The septic tank is provided with a control unit that controls the transfer operation of the wastewater until HWL) and starts the aeration operation and the filtration operation after a lapse of a certain time from the stop of the transfer operation. 2. The septic tank according to claim 1, wherein a contaminant removing means for removing contaminants such as coarse particles, hair and fibrous substances in the inflowing wastewater is arranged in front of the biological reaction chamber. A septic tank characterized by. 3. The septic tank according to claim 2, wherein the foreign matter removing means is a filter bed or a screen provided in a flow rate adjusting section. 4. The septic tank according to claim 2, wherein the screen is a screen having an opening of 0.1 mm to 10 mm. 5. The septic tank according to claim 2 or 3, wherein the impurities to be removed are particulate substances having a diameter of 0.1 mm or more. 6. The septic tank according to claim 4, wherein the separation membrane constituting the membrane separation device is a hollow fiber membrane, and the contaminants are fibrous substances having a length of 0.2 mm or more. A septic tank. 7. A biological reaction chamber in which an aeration device is arranged, a flow rate adjusting unit for adjusting the amount of waste water flowing into the biological reaction chamber, and a transfer means for transferring the waste water in the flow rate adjusting unit to the biological reaction chamber. And a membrane separation device for separating the waste water in the biological reaction chamber into a permeate and a retentate, and a water level detection means for detecting the minimum water level (LWL) and the maximum water level (HWL) in the biological reaction chamber. In the operating method, aeration of the biological reaction chamber is intermittently performed by a timer, the operation of the membrane separation device is started at substantially the same time as or slightly later than the start of operation of the aeration device, and the water level in the biological reaction chamber is the minimum water level. (LWL) is reached, the transfer of wastewater to the bioreaction chamber starts at the end of the time secured for membrane separation, and the water level in the bioreaction chamber reaches the maximum water level (HW
L.) is reached, a certain amount of transfer is completed, or the transfer is performed for a predetermined time, the process is stopped, and the septic tank is operated. 8. The method for operating the septic tank according to claim 7, wherein the transition time of the wastewater is 1 / the operating time of the aeration device.
A method for operating a septic tank, which is characterized in that the number is 2 or less.