JPH10296251A - Method for regulating sludge in sewage treatment tank - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for regulating sludge in a private sewage treatment tank capable of maintaining activated sludge concentration inside the treatment tank to be adequate concentration and velocity of upstream of water to be treated sufficient enough to remove attached objects on membrane surfaces thereby. SOLUTION: In a private sewage treatment tank where water to be treated is circulation-treated by an aerobic tank and an anaerobic tank, sludge concentration in the anaerobic tank 7 or the aerobic tank 8 is kept constant by a method wherein sludge-containing water to be treated is transferred to a sludge storage tank 6 by providing a transferring means (e.g. a sludge pump 19) opening a suction port 20 at an interface 21 of sedimented sludge and supernatant liquid in the anaerobic tank 7. In the private sewage treatment tank where water to be treated is treated while aeration runs and/or stops in the treatment tank, the sludge concentration in the treatment tank is maintained constant by a method wherein the transferring means is provided and opens the suction port at the interface of the sedimented sludge and the supernatant liquid in the treatment tank while the aeration stops and sludge- containing water to be treated is transferred to the sludge storage tank by running the transferring means while the aeration stops.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for storing excess sludge generated in a septic tank in which a membrane separation device is installed and which performs membrane filtration for treatment.

[0002]

2. Description of the Related Art In recent years, as a septic tank for purifying human waste and household wastewater, a septic tank having a high treatment capacity and a septic tank capable of always obtaining stable treated water quality have been required. On the other hand, the installation of septic tanks is often buried underground, and it is necessary to secure a site for it, and miniaturization of the septic tank body from the viewpoint of excavation work is a major issue. .

[0003] In view of such circumstances, for the purpose of reducing the volume of the treatment tank, activated sludge, which is an aggregate of microorganisms responsible for treating pollutants, is maintained at a high concentration, and the treatment speed is increased. Furthermore, a method of immersing a membrane separation device using a filtration membrane such as a microfiltration membrane or an ultrafiltration membrane in a treatment tank, removing solids such as activated sludge through the membrane separation device, and discharging only the liquid component is featured. Many were considered, including Japanese Patent Publication No. 4-70958.

[0004]

However, as the wastewater is continuously treated by biological treatment such as the activated sludge method, the microorganisms repeatedly grow and the activated sludge increases. Furthermore, since only the liquid component is discharged by membrane separation, most of the solid content such as activated sludge remains in the treatment tank, and as a result, the activated sludge concentration in the treatment tank continues to increase and becomes extremely high. come.

[0005] When the activated sludge concentration in the treatment tank becomes too high, the viscosity of the treated water increases, and the fluidity deteriorates, so that aeration by aeration becomes insufficient. On the other hand, in order to perform stable membrane filtration of the treated water for a long period of time by the membrane separation device, in many cases, an air diffuser is disposed immediately below the filtration membrane,
An aeration method is used in which an ascending flow of treated water and air bubbles is passed over the membrane surface, and the gas-liquid mixed flow removes deposits on the filtration membrane surface. However, in this method, when the activated sludge concentration increases and the fluidity deteriorates, the ascending flow velocity of the gas-liquid mixed flow decreases, and the sludge tends to adhere to the surface of the filtration membrane. As a result, stable membrane filtration cannot be maintained. Further, an increase in the viscosity of the treated water may cause the air diffuser holes to be blown out of the diffuser to be closed. This allows
Again, the pressure loss causes a decrease in the amount of air to be aerated, and the dissolved oxygen required for biological treatment becomes insufficient and the quality of treated water deteriorates.

The present invention has been made in view of such circumstances, and it is possible to maintain the concentration of activated sludge in a treatment tank at an appropriate concentration and thereby to sufficiently remove the deposits on the surface of a filtration membrane. It is an object of the present invention to provide a method for adjusting sludge of a sewage treatment tank capable of maintaining a rising flow rate of sludge.

[0007]

Means for Solving the Problems In order to achieve the above-mentioned object, the invention according to claim 1 is characterized in that when storing excess sludge generated in a sewage purification tank for treating sewage by membrane filtration, the effluent is treated. A sewage purification tank characterized by being separated into settled sludge and supernatant water, opening a suction port at the interface between the settled sludge and the supernatant water, sucking the sludge-containing treated water from the suction port, and transferring it to a sludge storage tank. It is a method of adjusting sludge.

[0008] The invention according to claim 2 provides a sewage purification tank of a type in which treated water is circulated and treated in an aerobic tank and an anaerobic tank equipped with a membrane separation device. The method is characterized by providing a transfer means having an opening at the interface between the settled sludge in the anaerobic tank and the supernatant water, and transferring the sludge-containing treated water to the sludge storage tank.

According to the second aspect of the present invention, the opening position of the suction port of the transfer means may be set at the interface between the sludge which is left standing in the anaerobic tank and is deposited by sedimentation and the supernatant water present thereon. However, since the position of the interface fluctuates depending on the concentration of the accumulated sludge, the position of the sludge interface at which a desired sludge concentration is obtained is obtained in advance, and a suction port may be provided at the interface position.

The means for transferring sludge is not particularly limited, and a mechanical pump such as a spiral pump, a diaphragm pump, a plunger pump, or a pump capable of transferring treated water containing sludge such as an air lift pump can be used. What is necessary is just to install a suction port in the sludge interface mentioned above. In addition, the operation method of the transfer means may be always continuous operation, but it is multiplied by the progress of biological treatment of sewage and the sludge is increased, so that the sewage is collectively transferred to the upper part of the suction port when it is accumulated to some extent. For that purpose, it is preferable to operate intermittently at regular intervals because power cost can be reduced. The interval between the operation and the suspension and the operation time may be appropriately determined based on the increase speed and the transfer amount due to the sludge propagation.

According to a third aspect of the present invention, in the method for adjusting sludge of a sewage purification tank according to the second aspect of the present invention, a sludge pump having a suction port opened upward is used as a transfer means, and a sludge storage tank is used as a sludge storage tank. It is characterized by installing a storage tank having a structure in which the supernatant water flows into the anaerobic tank 7 from a water level higher than the water level of the anaerobic tank.

According to the third aspect of the present invention, the sludge deposited on the layer above the opening can be sucked when the sludge pump is operated, and the shape of the opening is not particularly limited. In the sludge storage tank, the treated water containing the transferred sludge is allowed to stand still, only the sludge is settled and separated, and only the supernatant liquid is transferred to the anaerobic tank again. At this time, if the height of the advection port is at least higher than the maximum water level of the anaerobic tank, no sludge will enter from the anaerobic tank, and the water level fluctuation of the anaerobic tank will disturb the treated water settled in the sludge storage tank As a result, sedimentation separation can be conveniently performed.

According to a fourth aspect of the present invention, in the method for adjusting sludge of a sewage purification tank according to the second aspect of the present invention, as a transporting means, an advection which is opened below the surface of the anaerobic tank at the interface between the settled sludge and the supernatant water. It is characterized by the installation of a sludge pump tank communicated with the mouth and a sludge pump for transferring sludge from the sludge pump tank to the sludge storage tank.

In the invention according to claim 4, the lower end portion of the advection port opened to the sludge pump tank is located at the interface between the sludge which is left standing in the anaerobic tank and deposited by sedimentation and the supernatant water present thereon. Since the position of the interface fluctuates depending on the concentration of the accumulated sludge, it may be installed at the position of the interface where the desired sludge concentration is obtained. The sludge pump employs the same method as the sludge transfer means of the second aspect of the present invention. The operation method may also be operated continuously at all times, but may be transferred collectively when the wastewater proliferates due to the progress of biological treatment and the sludge increases to some extent in the upper layer from the lower end of the advection port. For this reason, a method of operating intermittently at regular intervals is preferable because power cost can be reduced. The interval between the operation and the suspension and the operation time may be appropriately determined based on the increase speed and the transfer amount due to the sludge propagation.

According to a fifth aspect of the present invention, the technical idea of the first aspect of the present invention is applied to a sewage purification tank of a type in which treated water is treated while being aerated in a treatment tank equipped with a membrane separation device. In this manner, a transfer means having an opening at the interface between the settling sludge and the supernatant water in the treatment tank during the stop of the aeration is provided, and the transfer means is operated during the stop of the aeration to remove the sludge-containing treated water. It is characterized by being transferred to a sludge storage tank.

In the invention according to the fifth aspect, the treated water and the activated sludge are treated in a state where the treated water and the activated sludge are mixed by aeration and agitation in the treatment tank. Settled and separated at the bottom of the treatment tank due to the difference in specific gravity. The opening position of the suction port of the transfer means may be installed at the interface between the sludge deposited by sedimentation and the supernatant water present thereon, but the position of the interface depends on the concentration of the deposited sludge and the aeration stop time, In order to increase or decrease according to the settling time, the position of the sludge interface at which a desired sludge concentration is obtained is obtained in advance, and a suction port may be provided at the interface position.

The means for transferring the sludge is not particularly limited, but a mechanical pump such as a spiral pump, a diaphragm pump, a plunger pump, or a pump capable of transferring treated water containing sludge such as an air lift pump can be used. What is necessary is just to install a suction port in the sludge interface mentioned above. Further, the transfer amount may be an amount sufficient to transfer the sludge accumulated in the upper layer of the suction port due to the increase of the sludge due to the progress of biological treatment of the wastewater. The operation frequency of the sludge pump may be such that the aeration is temporarily stopped when the sludge concentration increases to some extent, and the sludge pump is transferred in a lump. Further, when the processing tank is performing a process of repeating the operation / stop of the aeration at a constant cycle such as an intermittent aeration system, the process may be carried out at each aeration stop, and the frequency is not particularly limited. However, it is preferable to perform the treatment so that at least the activated sludge concentration in the treatment tank does not significantly increase.

According to a sixth aspect of the present invention, in the method for adjusting a sludge of a sewage purification tank according to the fifth aspect of the present invention, a sludge pump having an upwardly open suction port is used as a transfer means, and the sludge storage tank is used as a sludge storage tank. It is characterized by the installation of a storage tank with a structure in which the supernatant water overflows into the treatment tank from a water level higher than the water level in the treatment tank.

In the invention according to claim 6, the sludge deposited on the layer above the opening during the operation of the sludge pump may be sucked, and the shape of the opening is not particularly limited. Also,
In the sludge storage tank, the treated water containing the transferred sludge is allowed to stand still, only the sludge is settled and separated, and only the supernatant liquid is transferred to the treatment tank again. At this time, if the height of the advection port is installed at least at a position higher than the highest water level of the treatment tank, there is no ingress of sludge from the treatment tank, and fluctuations in the water level of the treatment tank disturb the treated water settled in the sludge storage tank. And sedimentation separation can be conveniently performed.

According to a seventh aspect of the present invention, there is provided the method for adjusting sludge of a sewage purification tank according to the fifth aspect of the present invention, wherein an interface between the settled sludge and the supernatant water, which is stopped aeration below the surface of the treatment tank, is used as a transfer means. And a sludge pump for transferring sludge from the sludge pump tank to the sludge storage tank.

In the invention according to claim 7, the position of the lower end of the advection port opened to the sludge pump tank is the sludge which is left standing still during the aeration stop of the treatment tank and is deposited there by sedimentation and separation. Since the position of the interface may fluctuate depending on the concentration of the accumulated sludge, it may be installed at the position of the sludge interface where a desired sludge concentration is obtained, similarly to the invention according to claim 5. I just need. Further, the sludge pump employs the same method as the sludge transfer means of the present invention.

Further, the operation frequency of the sludge pump may be such that the aeration is temporarily stopped when the concentration of the sludge has increased to some extent, and the sludge pump is transferred in a lump. In addition, when the processing tank is performing a process of repeating the operation / stop of the aeration at a fixed cycle such as an intermittent aeration system, the process may be carried out at each aeration stop, and the frequency is not particularly limited. However, it is preferable to perform the treatment so that at least the activated sludge concentration in the treatment tank does not significantly increase. According to the first aspect of the present invention, the treated water is separated into settled sludge and supernatant water, and a suction port is opened at an interface between the settled sludge and the supernatant water to discharge the sludge-containing treated water into a sludge storage tank. The activated sludge concentration in the treatment tank for performing biological treatment can be kept substantially constant.

That is, if a suction port is provided at the interface between the settled sludge and the supernatant water, the activated sludge increases due to the propagation of the biological treatment in the treatment tank as the biological treatment proceeds, and the sludge interface rises accordingly. The rising amount, that is, the increasing amount of the activated sludge is transferred from the suction port to the sludge storage tank, and the concentration of the activated sludge is kept constant.

According to the second aspect of the present invention, since the sewage purification tank of the type in which the treated water is circulated and treated in the aerobic tank and the anaerobic tank is targeted, the biological treatment of the pollutant in the aerobic tank proceeds with the progress of the biological treatment. When the activated sludge is circulated to the anaerobic tank, it settles down and deposits in the anaerobic tank, but the accumulated activated sludge is pulled out by the transfer means and transferred to the sludge storage tank. Can be adjusted depending on the position of the suction port. Since the treated water in the anaerobic tank and the aerobic tank is constantly circulated, the concentrations of the activated sludge in the anaerobic tank and the aerobic tank are apparently substantially equal.

According to the third aspect of the present invention, as shown in FIG. 1, the suction port 20 of the sludge pump 19 is opened upward. Only the sludge and the treated water deposited on the upper layer are sucked and transferred to the sludge storage tank 6. Therefore, the volume of the activated sludge settled and deposited in the anaerobic tank 7 can be easily adjusted at the position of the opening of the suction port 20.

According to the fourth aspect of the present invention, as shown in FIG. 2, of the activated sludge deposited in the anaerobic tank 7, only the sludge that has a volume higher than the lower end of the advection port 24 flows into the sludge pump tank 23. Since the sludge is pumped by the sludge pump 19 to the sludge storage tank 6, the volume of activated sludge deposited in the anaerobic tank 7 can be easily adjusted at the lower end of the advection port 24.

[0027] The invention according to claim 5 is directed to a sewage purification tank of a type in which treated water is treated in an aerated operation in a treatment tank equipped with a membrane separation device, so that biological treatment of pollutants is performed in the treatment tank. The activated sludge that has multiplied with the progress of sedimentation settles during the stoppage of the aeration of the treatment tank and accumulates in the treatment tank.The accumulated activated sludge is pulled out by the sludge transfer means and transferred to the sludge storage tank. The volume of the activated sludge to be produced can be adjusted by the position of the suction port.

According to the sixth aspect of the present invention, as shown in FIGS. 3 and 4, since the suction port 115 of the sludge transfer means 114 is opened upward, the activated sludge deposited in the treatment tank 106 is formed. Among them, only the sludge and the treated water accumulated in the upper layer from the suction port 115 are sucked and transferred to the sludge storage tank 105. Therefore, the volume of the activated sludge deposited in the processing tank 106 can be easily adjusted at the position of the opening of the suction port 115.

According to the invention of claim 7, as shown in FIG. 5, of the activated sludge deposited in the processing tank 106, only the sludge deposited in the upper layer from the lower end of the advancing port 119 flows into the pump tank 118, Since the activated sludge is transferred to the sludge storage tank 105 by the sludge pump 114, the volume of the activated sludge deposited in the processing tank 106 can be easily adjusted at the lower end of the advection port 119.

[0030]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing an example in which the sludge adjusting method of the present invention is applied to a sewage purification tank of a type in which treated water is circulated in an aerobic tank and an anaerobic tank.

In FIG. 1, a septic tank main body 1 includes partition plates 2 and 2.
A flow control tank 5, a sludge storage tank 6, an anaerobic tank 7, and an aerobic tank 8 are partitioned by 3, 4. The sewage flowing into the flow control tank 5 is temporarily stored, and then transferred to the anaerobic tank 7 by a transfer pump 9 in a fixed amount. The transferred sewage is anaerobically treated with activated sludge existing in an anaerobic state at a concentration of about several thousand mg / L to 20,000 mg / L in the anaerobic tank 7 and then provided on the upper part of the partition plate 4. The sludge flows into the aerobic tank 8 through the communication port 10.

In the aerobic tank 8, an air diffuser 11 is installed near the bottom, and air supplied from a blower 12 separately installed outside the septic tank main body 1 via an air pipe 13 is diffused by the air diffuser 11. Fine bubbles are ejected into the aerobic tank 8 to supply oxygen into the aerobic tank 8 and generate an aerated swirling flow. Due to this, in the aerobic tank 8, several thousand meters
Aerobic treatment is performed with activated sludge that exists in an aerobic state at a concentration of about g / L to 20,000 mg / L.

A part of the treated water in the aerobic tank 8 is returned to the anaerobic tank 7 by the circulation pump 14 together with the activated sludge, and is repeatedly treated. A part of the treatment water treated in the aerobic tank 8 is separated into solid and liquid by a filtration membrane 15 immersed in the aerobic tank 8 and only the liquid is discharged out of the tank by a suction pump 17 via a suction pipe 16. It has become.

In the anaerobic tank 7, the flow control tank 5 and the aerobic tank 8
Activated sludge having a specific gravity greater than that of the treated water is placed at the bottom of the anaerobic tank 7 until the treated water transferred from the anaerobic tank 7 passes through the anaerobic tank 7 and flows from the communication port 10 to the aerobic tank 8. Settles and deposits.

A part of the deposited activated sludge 18 is transferred from the communication port 10 to the aerobic tank 8 together with the treated water, and is repeatedly treated.

A sludge pump 19 is installed in the anaerobic tank 7,
The suction port 20 is opened at the sludge interface 21 of the accumulated activated sludge and the supernatant water in the upper layer.
Thus, a part of the treated water containing the activated sludge is sent to the sludge storage tank 6. The treated water sent to the sludge storage tank 6 is allowed to stand still,
Activated sludge is settled and separated by the specific gravity difference and accumulates at the bottom of the sludge storage tank 6, and only the supernatant liquid is transferred from the anaerobic tank 7 through the advection port 22.
Overflow and processed again.

As described above, when the suction port 20 is provided at the sludge interface 21 of the anaerobic tank 7, the activated sludge concentration in the anaerobic tank 7 and the aerobic tank 8 can be maintained substantially constant. The reason is described below.

First, the activated sludge in the treated water depends on its concentration,
It is known that there is a certain correlation between the volume of the settled sludge and the volume of the settled sludge when it is allowed to stand and separated by settling. Therefore, if the suction port 20 of the sludge pump 19 is installed at the sludge interface 21 of the anaerobic tank 7 at a constant activated sludge concentration in the aerobic tank 8, the concentration of the activated sludge is increased by the biological treatment in the aerobic tank 8 as the biological treatment proceeds. Is increased, the activated sludge concentration in the treated water transferred to the anaerobic tank 7 by the circulation pump 14 also increases, and the sludge interface 21 of the anaerobic tank 7 rises accordingly. At this time, when the sludge pump 19 is operated, only the increased activated sludge above the suction port 20 is transferred to the sludge storage tank 6, and as a result, the activated sludge concentration in the anaerobic tank 7 and the aerobic tank 8 decreases, and the concentration before the increase is increased. It will return to the concentration.

FIG. 2 is a view showing another example in which the sludge adjusting method of the present invention is applied to a sewage purification tank of a type in which treated water is circulated in an aerobic tank and an anaerobic tank. The basic structure of the sewage treatment tank of FIG. 2 is the same as that of FIG. 1 described above, and the clarification tank main body 1 is divided into flow rate adjustment tanks 5, sludge storage tanks 6, anaerobic tanks 7, and aerobic tanks by partition plates 2, 3, and 4. It is divided into eight.

In the sewage purification tank of FIG. 2, a sludge pump tank 23 is installed inside the anaerobic tank 7, and the sludge pump tank 23
The anaerobic tank 7 is configured to communicate with the anaerobic tank 7 at an advection port 24 opened below the surface of the water, and the activated sludge and the treated water flowing from the advection port 24 are transferred from the bottom of the sludge pump tank 23 to the sludge storage tank 6. A sludge pump 19 for transferring is installed, and among the activated sludge deposited in the anaerobic tank 7, only the sludge deposited in the upper layer from the lower end of the advection port 24 flows into the pump tank 23, and is introduced into the sludge storage tank 6 by the sludge pump 19. Be transported.

In FIG. 2, the advection port 24 is installed
It may be installed so that its lower end is located at the sludge interface 21 of the accumulated activated sludge and the supernatant water in the upper layer.
Further, the shape of the advection port 24 may be a rectangle so that the activated sludge accumulated in the upper layer from the lower end of the advection port 24 flows down to the sludge pump tank 23 without being accumulated, and may be opened so that one side thereof is horizontal.

FIG. 3 and FIG. 4 show a sewage purification tank of a type that treats treated water while performing aeration operation / stop in the treatment tank.
It is a figure which shows the example which applied the sludge adjustment method of this invention. 3 and 4 show a state during the aeration operation and a state during the aeration stop, respectively.

The septic tank main body 101 includes partition plates 102, 10
3, the wastewater flowing into the flow control tank 104 is temporarily stored and then temporarily transferred to the processing tank 106 by the transfer pump 107, as shown in FIG. A certain amount is transferred. In the processing tank 106, an air diffuser 108 is installed near the bottom, and air supplied from an air pipe 110 from a blower 109 separately installed outside the septic tank main body 101 is supplied with fine air bubbles into the processing tank 106 by the air diffuser 108. To supply oxygen into the processing tank 106 and generate an aerated swirling flow. As a result, in the treatment tank 106, several thousand mg
/ L to about 20,000 mg / L.

A part of the treatment water treated in the treatment tank 106 is separated into a solid and a liquid by the filtration membrane 111 immersed in the treatment tank 106, and only the liquid component is passed through the suction pipe 112 through the suction pump 1.
At 13 the water is released outside the tank.

When the aeration is stopped, the oxygen dissolved in the treated water in the aeration is consumed by the activated sludge and becomes anoxic, and the sewage is anaerobically treated by the activated sludge.

On the other hand, as shown in FIG. 4, when the sewage purification tank is under aeration stop, in the treatment tank 106, the treatment liquid in the tank is left stationary due to the aeration stop, and the solid content having a specific gravity larger than the treatment water is increased. Sludge settles and accumulates on the bottom of the processing tank 106. A sludge pump 114 is installed in the processing tank 106,
The suction port 115 is open at the sludge interface 116 of the accumulated activated sludge and the supernatant water in the upper layer. A part of the treated water containing the activated sludge is sent to the sludge storage tank 105 by the sludge pump 114. The treated water sent to the sludge storage tank 105 is allowed to stand still, and the activated sludge is settled and separated by the difference in specific gravity and accumulates at the bottom of the sludge storage tank 105, and only the supernatant liquid flows from the advancing port 117 to the treatment tank 106. Processed again.

As described above, the sludge interface 1 of the treatment tank 106
When the suction port 115 is provided in the treatment tank 16, the activated sludge concentration in the treatment tank 106 can be kept substantially constant. The reason is described below.

It is found that there is a certain correlation between the concentration of the activated sludge in the treated water and the volume of the settled sludge that has been settled and sedimented, and the volume of the settled sludge increases as the sludge concentration increases. ing. Therefore, when the processing tank 106 is operated at a constant activated sludge concentration, the aeration is stopped, and the suction port 115 of the sludge pump 114 is installed at the sludge interface 116 of the processing tank 106 at a certain settling time. In the case where the concentration of the activated sludge increases due to the proliferation with the progress of the biological treatment in 106, the sludge interface 116 of the treatment tank 106
Rises by that amount. At this time, when the sludge pump 114 is operated, only the activated sludge increased above the suction port 115 is transferred to the sludge storage tank 105.
The activated sludge concentration of 06 decreases and returns to the concentration before the increase.

FIG. 5 is a diagram showing another example in which the sludge adjusting method of the present invention is applied to a sewage purification tank of a type that performs treatment while performing aeration operation / stop in the treatment tank. The basic structure of the sewage purification tank of FIG. 5 is the same as that of FIGS. 3 and 4 described above.
04, a sludge storage tank 105 and a treatment tank 106.

In the sewage purification tank of FIG. 5, a sludge pump tank 118 is installed inside the treatment tank 106, and the sludge pump tank 1
18 is an advection port 119 opened below the surface of the processing tank 106.
And a sludge pump 114 for transferring the activated sludge and the treated water flowing from the transfer port 119 to the sludge storage tank 105 from the bottom of the sludge pump tank 118. Of the activated sludge deposited in the tank 106, only the sludge deposited in the upper layer from the lower end of the advancing port 119 flows into the sludge pump tank 118, and is transferred to the sludge storage tank 105 by the sludge pump 114.

In FIG. 5, the advection port 119 may be installed such that its lower end is located at the sludge interface 116 of the accumulated activated sludge and the supernatant water in the upper layer. Further, the shape of the advection port 119 may be a rectangle so that the activated sludge accumulated in the upper layer from the lower end of the advection port 119 flows down into the sludge pump tank 118 without being accumulated, and may be opened so that one side thereof is horizontal.

[0052]

Embodiments of the present invention will be described below. <Embodiment 1-1> In the sewage treatment tank having the structure shown in FIG. 1, a diffuser 11 is installed in aerobic tank 8 whose water level varies from 2 m to 1.7 m at a point 0.2 m from the tank bottom. Then, air was supplied to the air diffuser 11 through the air pipe 13 by the blower 12 installed outside the tank, and aeration was performed at an air flow rate of 60 L / min. In the aerobic tank 8, the treated water was stirred by the swirling flow of bubbles generated by aeration, and oxygen was dissolved in the treated water to make the activated sludge concentration about 10,000 mg / L. A part of the treated water was transferred to the anaerobic tank 7 by a circulation pump 14 in an amount three times the amount of wastewater.

On the other hand, in the anaerobic tank 7,
The water level fluctuated from 2 m to 1.7 m. A submersible swirl-type sludge pump as a sludge pump 19 was installed at the bottom of the tank, and the suction port 20 was opened at a water level of 1.5 m. This sludge pump 19 is operated once a day at 10 L / min for 5 minutes,
The activated sludge and the treated water were transferred to the sludge storage tank 6.

When the combined wastewater was treated in the above-mentioned sewage purification tank, the activated sludge concentration in the aerobic tank 8 was maintained at the initial 10,000 mg / L for 6 months. As a result, the membrane surface of the filtration membrane 15 immersed in the aerobic tank 8 was sufficiently washed, and the treated water could be stably filtered by suction. <Embodiment 1-2> In the sewage treatment tank having the structure shown in FIG. 2, a diffuser 11 is installed at a point 0.2 m from the tank bottom in the aerobic tank 8 in which the water level varies from 2 m to 1.7 m. Then, air was supplied to the air diffuser 11 through the air pipe 13 by the blower 12 installed outside the tank, and aeration was performed at an air flow rate of 60 L / min. In the aerobic tank 8, the treated water was stirred by the swirling flow of bubbles generated by aeration, and oxygen was dissolved in the treated water to make the activated sludge concentration about 10,000 mg / L. A part of the treated water was transferred to the anaerobic tank 7 by a circulation pump 14 in an amount three times the amount of wastewater.

On the other hand, in the anaerobic tank 7, a sludge pump tank 23 is installed inside, and the advection port 24 is set at a position where the water level is 1.5 m.
A sludge pump 19 is installed to communicate with the anaerobic tank 7 and to transfer the activated sludge and the treated water flowing from the transfer port 24 from the bottom of the sludge pump tank 23 to the sludge storage tank 6. Configuration. Sludge pump 19
A submersible pump for sewage sludge was installed. This sludge pump 19 is operated once a day at 10 L / min for 5 minutes,
The activated sludge and the treated water were transferred to the sludge storage tank 6.

When the combined wastewater was treated in the above-mentioned sewage treatment tank, the activated sludge concentration in the aerobic tank 8 was maintained at the initial 10,000 mg / L for 6 months. As a result, the membrane surface of the filtration membrane 15 immersed in the aerobic tank 8 was sufficiently washed, and the treated water could be stably filtered by suction. <Comparative Example 1> The sewage purification tank used in Comparative Example 1 is shown in FIG.
As shown in FIG. 1, a conventional purification tank including a flow control tank 205, an anaerobic tank 207, and an aerobic tank 208 is used.
The sewage flowing into the tank 5 is transferred to the anaerobic tank 207 by the transfer pump 209, and the treated water and the activated sludge subjected to the anaerobic treatment in the tank 207 are transferred again from the outlet 210 to the aerobic tank 208.

In Comparative Example 1, in the septic tank shown in FIG. 6, an air diffuser 211 is installed in the aerobic tank 208, and air is supplied from the blower 212 installed outside the tank to the air diffuser 211 via the air pipe 213. And aerated with an air volume of 60 L / min. A part of the treated water was transferred to the anaerobic tank 207 by a circulation pump 214 in an amount three times the amount of wastewater.

When the combined wastewater was treated in the above sewage purification tank, the activated sludge concentration in the anaerobic tank 207 and the aerobic tank 208 was as follows:
It increased gradually, from 10,000 mg / L at the beginning to 25000 mg / L after 6 months.
As a result, the viscosity of the treated water increased, the flow in the aerobic tank 208 became poor, and a large amount of sludge adhered to the membrane surface of the filtration membrane 215. As a result, the filtration resistance increased and the treated water could not be filtered by suction. <Embodiment 2-1> In the sewage treatment tank having the configuration shown in FIGS. 3 and 4, the treatment tank 1 whose water level varies from 2 m to 1.7 m.
06, a diffuser 108 is installed at a point 0.2 m from the bottom of the tank, and an air pipe 11 is provided by a blower 109 installed outside the tank.
Air was supplied to the air diffuser 108 through the air outlet 0 and aerated at an air flow rate of 60 L / min. In the aerated operation, the blower 109 is controlled by a timer (not shown), and the operation / stop time is set to 6 hours.
Intermittent operation was performed at 0 minutes / 60 minutes. During aeration, the treated water was stirred by the swirling flow of bubbles generated by the aeration, and oxygen was dissolved in the treated water to make the concentration of the activated sludge about 10,000 mg / L.

A sludge pump 114 is provided at the bottom of the processing tank 106.
A submersible pump for swirl-type sludge is installed as
5 was opened to a water level of 1.5 m. This sludge pump 114
Once a day at a fixed time, 10L after 55 minutes of aeration stop
Per minute for 5 minutes to store activated sludge and treated water in sludge storage tank 1
05.

When the combined wastewater was treated in the above-mentioned wastewater purification tank, the activated sludge concentration in the treatment tank 106 was maintained at the almost initial 10,000 mg / L for 6 months. As a result, the membrane surface of the filtration membrane 111 immersed in the treatment tank 106 was sufficiently cleaned, and the treated water could be stably filtered by suction. <Example 2-2> In the sewage purification tank having the configuration shown in FIG. 5, an intermittent aeration operation was performed in the same manner as in Example 2-1 and a sludge pump tank 118 was installed inside the treatment tank 106.
An opening is formed at a position where the water level is 1.5 m so as to be at the lower end of the advancing port 119, and communicates with the treatment tank 106, and the activated sludge and the treated water flowing from the advection port 119 are stored in the sludge pump tank 118 from the bottom thereof. The configuration was such that a sludge pump 114 for transferring to the tank 105 was provided. Sludge pump 114
A submersible pump for sewage sludge was installed. This sludge pump 114 is operated once a day at a fixed time once a day at a fixed time, at a rate of 10 L / min for 5 minutes after 55 minutes of aeration stop, and the activated sludge and the treated water are transferred to the sludge storage tank 105. Transferred.

When the combined wastewater was treated in the above-mentioned wastewater purification tank, the activated sludge concentration in the treatment tank 106 was maintained at the initial 10,000 mg / L for 6 months. As a result, the membrane surface of the filtration membrane 111 immersed in the treatment tank 106 was sufficiently cleaned, and the treated water could be stably filtered by suction. <Comparative Example 2> The sewage purification tank used in Comparative Example 2 is shown in FIG.
As shown in the figure, the wastewater flowing into the flow rate adjusting tank 304 is transferred to the processing tank 306 by the transfer pump 307 in the conventional purification tank including the flow rate adjusting tank 304 and the processing tank 306, and the processing performed in the processing tank 306 is performed. Part of the water is solid-liquid separated by a filtration membrane 311 immersed in a treatment tank 306, and only the liquid component is discharged out of the tank by a suction pump 313 via a suction pipe 312.

In Comparative Example 2, an air diffuser 308 was installed in the treatment tank 306 in the sewage purification tank shown in FIG.
Air was supplied from a blower 309 installed outside the tank to an air diffuser 308 via an air pipe 310, and aerated at an air flow rate of 60 L / min. In the aerated operation, the blower 309 is controlled by a timer (not shown), and the operation / stop time is set to 60 minutes / 6.
Intermittent operation was performed for 0 minutes. At the time of aeration, the treated water is stirred by the swirling flow of bubbles generated by the aeration, and oxygen is dissolved in the treated water to reduce the concentration of the activated sludge to about 1%.
It was about 0000 mg / L.

When the operation was carried out using the above-mentioned combined wastewater, the activated sludge concentration in the treatment tank 306 gradually increased and was initially 1%.
What was 00000 mg / L, about 6 months later,
Increased to 5000 mg / L. As a result, the viscosity of the treated water increased, the flow in the treatment tank 306 became poor, and a large amount of sludge adhered to the membrane surface of the filtration membrane 311. As a result, the filtration resistance increased, and the treated water could not be filtered by suction.

[0064]

As described above, according to the first aspect of the present invention, the treated water is separated into settled sludge and supernatant water.
A suction port is opened at the interface between the settled sludge and the supernatant water to transfer the sludge-containing treated water to the sludge storage tank, so that the activated sludge concentration in the biological treatment tank can always be maintained at an appropriate concentration. Accordingly, it is possible to maintain an ascending flow rate of the treated water capable of sufficiently removing the deposits on the surface of the filtration membrane. As a result, the surface of the filtration membrane is sufficiently washed, and stable membrane filtration can always be continued.

In the method for adjusting sludge of a sewage treatment tank according to the second aspect of the present invention, in a sewage treatment tank of a type in which treated water is circulated and treated in an aerobic tank and an anaerobic tank, the amount increases in the anaerobic / aerobic tank. The activated sludge is automatically transferred to and stored in the sludge storage tank, so that the activated sludge concentration in the anaerobic tank or the aerobic tank can be kept constant. By keeping the activated sludge concentration in each tank in this way, the increase in the viscosity of the treated water can be suppressed, and the aeration tank can be sufficiently stirred by aeration, so that stable biological treatment can be maintained. Further, the rising flow rate of the gas-liquid mixed flow of the filtration membrane installed in the aerobic tank can be maintained at a high speed, and the surface of the filtration membrane can be sufficiently washed, and stable membrane filtration can be continued. Furthermore, as for the extraction of surplus sludge during maintenance, only the sludge accumulated in the sludge storage tank needs to be drawn out, and no measurement work is required for adjusting the activated sludge concentration in the treatment tank. Maintenance is very easy.

In the method for adjusting sludge of a sewage purification tank according to the third aspect of the present invention, of the activated sludge deposited in the anaerobic tank, only the sludge deposited in the upper layer from the suction port and the treated water are sucked to collect the sludge. The volume of the activated sludge that accumulates in the anaerobic tank, that is, the sludge concentration in the anaerobic tank, can be easily adjusted by appropriately setting the position of the opening of the suction port.

In the method for adjusting sludge of a sewage treatment tank according to the present invention, the activated sludge deposited in the anaerobic tank is
Only the sludge accumulated in the upper layer from the lower end of the advection port flows into the pump tank, and is transferred to the sludge storage tank by the sludge pump.By appropriately setting the position of the lower end of the advection port,
The volume of activated sludge deposited in the anaerobic tank, that is, the sludge concentration in the anaerobic tank can be easily adjusted.

According to a fifth aspect of the present invention, there is provided a method for adjusting sludge in a sewage treatment tank, wherein a treatment tank equipped with a membrane separation device is treated with aeration while treating treated water. Since the increased activated sludge is automatically transferred to and stored in the sludge storage tank, the activated sludge concentration in the treatment tank can be kept constant. By keeping the concentration of the activated sludge in the treatment tank constant, an increase in the viscosity of the treatment water can be suppressed, and the treatment tank can be sufficiently stirred by aeration, so that stable biological treatment can be maintained. Furthermore, the rising flow rate of the gas-liquid mixed flow of the filtration membrane installed in the treatment tank can be maintained at a high speed, and the surface of the filtration membrane can be sufficiently washed, and stable membrane filtration can be continued. Furthermore, as for the extraction of surplus sludge during maintenance, only the sludge accumulated in the sludge storage tank needs to be drawn out, and no measurement work is required for adjusting the activated sludge concentration in the treatment tank. Maintenance becomes very easy.

In the method for adjusting sludge of a sewage treatment tank according to the present invention, of the activated sludge accumulated in the treatment tank, only the sludge accumulated in the upper layer from the suction port and the treated water are sucked to store the sludge. Since the liquid is transferred to the tank, the volume of the activated sludge deposited in the processing tank, that is, the sludge concentration in the processing tank, can be easily adjusted by appropriately setting the position of the opening of the suction port.

In the method for adjusting sludge of a sewage treatment tank according to the present invention, of the activated sludge deposited in the treatment tank,
Only the sludge accumulated in the upper layer from the lower end of the advection port flows into the pump tank, and is transferred to the sludge storage tank by the sludge pump.By appropriately setting the position of the lower end of the advection port,
The volume of activated sludge deposited in the treatment tank, that is, the sludge concentration in the treatment tank can be easily adjusted.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example in which the sludge adjusting method of the present invention is applied to a sewage purification tank of a type in which treatment is performed while circulating treated water in an aerobic tank and an anaerobic tank.

FIG. 2 is a diagram showing another example in which the sludge adjustment method of the present invention is applied to a sewage purification tank of a type in which treatment is performed while circulating treated water in an aerobic tank and an anaerobic tank.

FIG. 3 is a diagram showing an example in which the sludge adjusting method of the present invention is applied to a sewage purification tank of a type in which treated water is treated while performing aeration operation / stop in the treatment tank, showing a state during the aeration operation.

FIG. 4 is a diagram showing an example in which the present invention is applied to a sewage septic tank, showing a state in which aeration is stopped.

FIG. 5 is a diagram showing another example in which the sludge adjusting method of the present invention is applied to a sewage purification tank of a type that treats treated water while performing aeration operation / stop in the treatment tank.

FIG. 6 is a diagram showing a configuration of a sewage purification tank used in Comparative Example 1 of the present invention.

FIG. 7 is a diagram showing a configuration of a sewage purification tank used in Comparative Example 2 of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Septic tank main body 2, 3, 4 Partition plate 5 Flow control tank 6 Sludge storage tank 7 Anaerobic tank 8 Aerobic tank 9 Transfer pump 10 Communication port 11 Air diffuser 12 Blower 13 Air piping 14 Circulation pump 15 Filtration membrane 16 Suction pipe 17 Suction pump 18 Sludge 19 Sludge pump 20 Suction port 21 Sludge interface 22 Outflow port 23 Sludge pump tank 24 Outflow port 101 Purification tank main body 102, 103 Partition plate 104 Flow control tank 105 Sludge storage tank 106 Processing tank 107 Transfer pump 108 Aeration device 109 Blower 110 Air pipe 111 Filtration membrane 112 Suction pipe 113 Suction pump 114 Sludge pump 115 Suction port 116 Sludge interface 117 Outflow port 118 Sludge pump tank 119 Outflow port

Continued on the front page (51) Int.Cl. ⁶ Identification code FI C02F 3/12 C02F 3/12 K

Claims (7)

[Claims] When storing excess sludge generated in a sewage purification tank for treating sewage by membrane filtration, the treated water is separated into settled sludge and supernatant water, and a suction port is provided at an interface between the settled sludge and the supernatant water. Wherein the sludge-containing treated water is suctioned from the suction port and transferred to a sludge storage tank. 2. A sewage purification tank of a type in which treated water is circulated and processed in an aerobic tank and an anaerobic tank equipped with a membrane separation device, wherein a suction port is opened at an interface between the settled sludge and the supernatant water in the anaerobic tank. The method for adjusting sludge in a sewage purification tank according to claim 1, wherein a transfer means is provided to transfer the sludge-containing treated water to a sludge storage tank. 3. A storage device having a structure in which a sludge pump having a suction port opened upward is used as the transfer means, and the sludge storage tank has a structure in which supernatant water flows from a water level higher than the anaerobic tank to the anaerobic tank. The method for adjusting sludge of a sewage purification tank according to claim 2, wherein a tank is installed. 4. As the transfer means, a sludge pump tank communicated with a settling port opened at the interface between the settled sludge and the supernatant water below the surface of the anaerobic tank, and the sludge is transferred from the sludge pump tank to the sludge storage tank. The method for adjusting sludge of a sewage purification tank according to claim 2, wherein a sludge pump is installed. 5. A sewage purification tank of a type in which treated water is treated in an aerated operation in a treatment tank equipped with a membrane separation device, wherein a suction port is provided at the interface between the settled sludge of the treatment tank and the supernatant water while the aeration is stopped. The sludge adjustment of the sewage purification tank according to claim 1, wherein a transfer means having an opening is provided, and the transfer means is operated while the aeration is stopped to transfer the sludge-containing treated water to the sludge storage tank. Method. 6. A sludge pump having a suction port opened upward as the transfer means, and the sludge storage tank has a structure in which supernatant water flows from a water level higher than the water level of the processing tank into the processing tank. The method for adjusting sludge of a sewage purification tank according to claim 5, wherein a tank is provided. 7. The sludge pump tank communicated by a transfer port opened at an interface between the settling sludge which is under aeration and suspended in the aeration tank below the surface of the treatment tank, and the sludge pump tank from the sludge pump tank to the sludge storage tank. The method for adjusting sludge of a sewage treatment tank according to claim 5, wherein a sludge pump for transferring sludge is installed.