JP2001276886A - Sewage water treating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sewage water treating device which can suppress increase of the equipment cost by simplifying the device constitution and can suppress increase of a froth generated accompanying aeration. SOLUTION: This sewage water treating device 10 has at least a pair of tanks 12 and 14 which are switchable to an aerobic state of accelerating the nitrification reaction in a liquid mixture composed of the sewage in the tanks and activated sludge by aerating this liquid mixture ad an anaerobic state of promoting the denitrification reaction in the liquid mixture without aerating the liquid mixture in the liquid mixture composed of the sewage in the tanks and activated sludge, discharge pipes 18 which are respectively disposed in a pair of the tanks 12 and 14 and discharge the treated water exceeding first liquid level positions L1, a communicating pipe 20 which communicates a pair of the tanks 12 and 14 and a sewage water supplying device 22 which is connected to the communicating pipe 20 and supplies the sewage water via the communicating pipe 20 to a pair of the tanks 12 and 14. The communicating pipe 20 communicates a pair of the tanks 12 and 14 between the first liquid level positions L1 in the respective tanks of a par of the tanks 12 and 14 and the second liquid level positions L2 at which the liquid level of the liquid mixture arrives during the aeration.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a sewage treatment apparatus for nitrifying and denitrifying sewage such as night soil.

[0002]

2. Description of the Related Art In a high-load nitrification and denitrification treatment in a sewage treatment facility for night soil and the like, if the treatment scale is large, the nitrification and denitrification tank may be divided into two or more tanks and treated in parallel.

In this case, in the conventional sewage treatment apparatus, a dedicated pump is provided for each tank, and the pump is intermittently operated according to the aeration state of the tank to supply the divided sewage to a plurality of tanks. Was. Alternatively, a valve for selectively switching the supply of sewage to each tank is provided, and the valve is switched in accordance with the aeration state of the tank to divide and supply the sewage to a plurality of tanks.

[0004]

However, a configuration in which a dedicated pump is provided for each of a plurality of tanks,
Alternatively, in a configuration in which a valve for selectively switching the supply of wastewater to each tank is provided, there is a problem in that the apparatus configuration is complicated and equipment costs are increased.

[0005] In a high-load nitrification and denitrification treatment, since the treatment with activated sludge is performed while performing aeration in a small-capacity tank, remarkable foaming occurs. In addition, the generated foam reaches the slab in combination with the rise in the liquid level due to aeration, and the activated sludge may overflow the outside of the tank by pushing up the manhole. there were.

Accordingly, the present invention is a sewage treatment apparatus capable of suppressing an increase in equipment costs by simplifying the apparatus configuration and suppressing an increase in bubbles generated by aeration. The purpose is to provide.

[0007]

The sewage treatment apparatus according to the present invention comprises an aerobic state for aerating a mixed solution of sewage and activated sludge in a tank to promote a nitrification reaction in the mixed solution.
At least one pair of tanks capable of switching between an anaerobic state for promoting a denitrification reaction in the mixed liquid without aerating the mixed liquid of the sewage and activated sludge in the tank, and provided in the pair of tanks, respectively. And a discharge pipe for discharging treated water exceeding the first liquid level, a communication pipe communicating the pair of tanks, and a communication pipe connected to the pair of tanks via the communication pipe. A sewage supply device for supplying sewage, wherein the communication pipe has a first liquid level position in each of the pair of tanks and a second liquid level position at which the liquid level of the mixed liquid reaches during aeration. And a pair of tanks communicating with each other.

In this sewage treatment apparatus, one of the tanks is operated in an aerobic state and the other is operated in an anaerobic state.
In the aerobic state, air is supplied into the mixture by aeration, so that the volume of the mixture expands and the liquid level rises, and many bubbles are generated and accumulated on the liquid surface.

Here, the communication pipe has a pair of a first liquid level position at which discharge of the treated water from the discharge pipe starts and a second liquid level position at which the liquid level of the mixed liquid reaches during aeration. Since the tanks communicate with each other, the mixed liquid flows from the aerobic tank to the anaerobic tank through the communication pipe by an amount corresponding to the rise in the liquid level, and the treated water is discharged from the discharge pipe. At this time, if sewage is supplied into the communication pipe by the sewage supply device, the sewage sent into the communication pipe is anaerobically mixed with the flow of the mixed liquid flowing from the aerobic tank to the anaerobic tank. It is preferentially put into the tank in the state. In addition, a part of the foam accumulated on the liquid surface is sent to the anaerobic tank through the communication pipe, and the rise of the foam is suppressed.

Next, the aeration of the tank in the aerobic state is stopped, and the aeration of the tank in the anaerobic state is started to switch between the anaerobic state and the aerobic state. Since the volume of the mixed liquid in the tank that has been in the aerobic state has been contracted due to the stop of the aeration, the liquid level is lower than the first liquid level. On the other hand, the volume of the mixed solution expands due to the start of the aeration of the anaerobic tank, the liquid level rises, and many bubbles are generated and accumulated on the liquid level.

At this time, the mixed liquid flows from the aerobic tank to the anaerobic tank through the communication pipe by an amount corresponding to the rise in the liquid level, and the treated water is discharged from the discharge pipe. In addition, the wastewater sent into the communication pipe by the wastewater supply device rides on the flow of the mixed liquid flowing from the aerobic tank to the anaerobic tank, and is preferentially injected into the anaerobic tank. You. In addition, a part of the foam accumulated on the liquid surface is sent to the anaerobic tank through the communication pipe, and the rise of the foam is suppressed.

As described above, by the flow of the mixed liquid from the aerobic tank to the anaerobic tank, the sewage is supplied to the anaerobic tank by the sewage supply device provided commonly to the pair of tanks. Can be given priority. Therefore, it is not necessary to provide a dedicated sewage supply device for each tank, or to provide a valve for selectively switching the supply of sewage to each tank, thereby simplifying the device configuration. An increase in equipment costs is suppressed.
In addition, since the rise of the liquid level is suppressed and the bubbles generated by the aeration can be sent to another tank through the communication pipe, the rise of the bubbles is suppressed and the generated bubbles overflow the outside of the tank. This makes it possible to avoid such problems.

Further, in the sewage treatment apparatus of the present invention, it is preferable that the flow passage area of the communication pipe is larger than the flow passage area of the discharge pipe. By doing so, the amount of the mixed solution passing through the communication pipe becomes larger than the amount of treated water discharged from the discharge pipe, and it is possible to send more foam from the aerobic tank to the anaerobic tank. As a result, it is possible to further suppress the rise of bubbles.

[0014]

Embodiments of the present invention will be described below with reference to the accompanying drawings. Note that the same components are denoted by the same reference numerals, and redundant description will be omitted.

FIG. 1 is a configuration diagram schematically showing one embodiment of a sewage treatment apparatus of the present invention.

As shown, the sewage treatment apparatus 10 has a pair of tanks 12 and 14. One of these is the first
The other tank is referred to as a second tank 14. Each of the first and second tanks 12 and 14 has a stirring and aerating device 16 and has a configuration capable of switching between an aerobic state and an anaerobic state. Here, an aerobic state refers to a state in which aeration is performed in a mixed solution of sewage and activated sludge in a tank to promote a nitrification reaction in the mixed solution.
It refers to a state in which aeration is not performed on the mixed solution in the tank and the denitrification reaction in the mixed solution is promoted. Each of the first and second tanks 12, 14 is provided with a discharge pipe 18 for discharging treated water by an amount exceeding the overflow line (first liquid level position) L1. These discharge pipes 18 are connected to a tank (not shown) for performing the next treatment such as biological activated carbon treatment, and the treated water subjected to the nitrification and denitrification treatment is sent to the next tank through the discharge pipe 18. Can be

Further, the sewage treatment apparatus 10 includes a communication pipe 20 for communicating the first tank 12 and the second tank 14. The communication pipe 20 includes an overflow line (first liquid level position) L1 at which discharge of the treated water from the discharge pipe 18 starts, and an aeration line (second liquid level position) L2 at which the liquid level of the mixed liquid reaches during aeration.
The first tank 12 and the second tank 14 communicate with each other.
It is known that the liquid level rises by about 5% due to the aeration, and the aeration line L2 is defined taking this into consideration.

Here, the flow passage area of the communication pipe 20 is the discharge pipe 1
Preferably, it is larger than the flow path area of No. 8. By doing so, the amount of the mixed liquid passing through the communication pipe 20 becomes larger than the amount of the treated water discharged from the discharge pipe 18. The channel area refers to the area of the opening on the inner surface of the pipe when the communication pipe 20 is cut in a direction perpendicular to the axis. If the channel area changes depending on the cutting position, the average is taken.

Further, a sewage supply device 22 for supplying sewage such as human waste is connected to the communication pipe 20. The sewage supply device 22 has a pump (not shown), and sewage can be continuously supplied into the communication pipe 20 by continuous operation of the pump.

Next, the operation of the sewage treatment apparatus 10 described above,
That is, a sewage treatment method using the sewage treatment apparatus 10 will be described.

First, the mixed liquid in the first tank 12 is aerated by the stirring and aerator 16 to maintain the first tank 12 in an aerobic state. On the other hand, the mixed solution in the second tank 14 is not aerated, and the second layer 14 is maintained in an anaerobic state. At this time, in the first tank 12, the oxidation of ammonia and other nitrogen components in the wastewater is promoted by the action of nitrifying bacteria, nitrifying bacteria, etc., to become nitrous acid, nitric acid and the like. On the other hand, in the second tank 14, reduction of nitrogen gas such as nitrite and nitric acid in sewage is promoted by the action of denitrifying bacteria requiring an organic carbon source.

In the aerobic state, air is supplied into the mixed solution by aeration, so that the volume of the mixed solution expands and is indicated by an arrow A in FIG.
As described above, the liquid level of the mixed liquid in the first tank 12 rises from the overflow line L1 to the aeration line L2. here,
The liquid level of the mixed solution in the second tank 14 has decreased to the base line L0 due to the contraction of the volume of the mixed solution due to the stop of the previous aeration process. In addition, due to the aeration, countless bubbles 24 are generated and accumulated on the liquid surface of the mixed liquid in the first tank 12.

As the liquid level rises, the mixed liquid flows from the aerobic first tank 12 to the anaerobic second tank 14 through the communication pipe 20 as shown by the arrow B in FIG.
The treated water is discharged from the discharge pipe 18 as indicated by an arrow D in FIG. At this time, since the sewage is continuously supplied into the communication pipe 20 by the sewage supply device 22, the sewage sent into the communication pipe 20 is in the first aerobic state as shown by arrow C in FIG. The second tank 1 in the anaerobic state rides on the flow of the mixed liquid flowing from the tank 12 to the second tank 14 in the anaerobic state.
4 In addition, a part of the bubbles 24 accumulated on the liquid surface in the first layer 12 passes through the communication pipe 20 and the second anaerobic state
It is sent to the tank 14.

In this way, the wastewater is preferentially charged into the anaerobic second tank 14. It is widely known that efficient treatment can be performed by introducing sewage in an anaerobic state.
Wastewater is preferentially fed into the sewage system to improve the efficiency of treatment. In addition, a part of the foam 24 is
Since the bubbles are sent from the tank 12 to the second tank 14, the rise of the bubbles is suppressed, and the bubbles are more easily disappeared by contacting the air with a wider area.

The aerobic treatment in the first tank 12 by aeration is continued for about 15 minutes. At this time, the mixed liquid flows into the second tank 14 by an amount corresponding to the rise in the liquid level, and the treated water is discharged from the discharge pipe 18. Therefore, the first and second
The liquid levels in the tanks 12 and 14 are stable at the position of the overflow line L1.

Next, the aeration of the first tank 12 is stopped to switch to the anaerobic state, and the mixed liquid in the second tank 14 is aerated to switch to the aerobic state. At this time, the second tank 1
In No. 4, the oxidation of ammonia and other nitrogen components in the wastewater is promoted by the action of nitrifying bacteria, nitrifying bacteria, etc., to become nitrite, nitric acid and the like. On the other hand, in the first tank 12, nitrite in sewage is removed by the action of denitrifying bacteria that require an organic carbon source.
Reduction to nitrogen gas such as nitric acid is promoted.

When the aeration of the first tank 12 is stopped to switch to the anaerobic state, the volume of the mixed liquid in the first tank 12 contracts as shown by an arrow E in FIG. 3 and the liquid surface of the mixed liquid reaches the base line L0. Go down. On the other hand, when the mixed liquid in the second tank 14 is aerated and switched to the aerobic state, the volume of the mixed liquid expands, and the liquid level of the mixed liquid in the second tank 14 becomes as shown by the arrow F in FIG. It rises from the overflow line L1 to the aeration line L2. In addition, due to the aeration, countless bubbles 24 are generated and accumulated on the liquid surface of the mixed liquid in the second tank 14.

The mixed liquid flows from the second tank 14 in the aerobic state to the first tank 12 in the anaerobic state through the communication pipe 20 as shown by the arrow G in FIG.
The treated water is discharged from the discharge pipe 18 as indicated by the arrow I in FIG. At this time, since the sewage is continuously supplied into the communication pipe 20 by the sewage supply device 22, the sewage sent into the communication pipe 20 is in the aerobic second state as shown by arrow H in FIG. The first tank 1 in the anaerobic state rides on the flow of the mixed liquid flowing from the tank 14 toward the first tank 12 in the anaerobic state.
2 In addition, a part of the bubbles 24 accumulated on the liquid surface in the second layer 14 is sent to the anaerobic first tank 12 through the communication pipe 20.

Thus, the first tank 1 in the anaerobic state
Sewage is preferentially input to 2. It is widely known that efficient treatment can be performed by introducing sewage in an anaerobic state.
Wastewater is preferentially fed into the sewage system to improve the efficiency of treatment. In addition, a part of the foam 24 is
Since the bubbles 24 are sent from the tank 14 to the first tank 12, the rise of the bubbles 24 is suppressed, and the bubbles 24 are more easily disappeared by contacting the air with a wider area.

The aerobic treatment in the second tank 14 by aeration is continued for about 15 minutes. At this time, the mixed liquid flows into the first tank 12 by an amount corresponding to the rise in the liquid level, and the treated water is discharged from the discharge pipe 18. Therefore, the first and second
The liquid levels in the tanks 12 and 14 are stable at the position of the overflow line L1.

Next, when the aeration of the second tank 14 is stopped and switched to an anaerobic state, the volume of the mixed liquid in the second tank 14 is contracted as shown in FIG. Down to. On the other hand, when the mixed liquid in the first tank 12 is aerated and switched to the aerobic state, the volume of the mixed liquid expands, and the liquid level of the mixed liquid in the first tank 12 becomes as shown by arrow A in FIG. It rises from the overflow line L1 to the aeration line L2. In addition, due to the aeration, countless bubbles 24 are generated and accumulated on the liquid surface of the mixed liquid in the first tank 12.

As described above, the first and second tanks 12 and 14
By repeating the processing while switching between the aerobic state and the anaerobic state in the above, the nitrification and denitrification treatment of the wastewater to be supplied can be continuously performed.

The treated water which has been subjected to the nitrification and denitrification treatment and discharged from the discharge pipe 18 to the next tank (not shown) is subjected to other treatments such as biological activated carbon treatment and discharged to rivers and the like.

As described above, in the present embodiment, the flow of the mixed liquid through the connecting pipe 20 from the aerobic tank to the anaerobic tank causes the wastewater commonly provided for the pair of tanks 12 and 14 to flow. The supply of the sewage from the supply device 22 to the anaerobic tank can be preferentially performed. Therefore, there is no need to provide a dedicated sewage supply device 22 for each tank or to provide a valve for selectively switching the supply of sewage to each tank, thereby simplifying the device configuration. Thus, it is possible to suppress an increase in equipment cost.

If the sewage supply device 22 is operated continuously, it is possible to automatically switch the tank into which the sewage is charged by a change in the flow of the mixture flowing through the connecting pipe 20. Therefore, it is not necessary to intermittently operate the separately provided sewage supply device or to switch the valve in order to supply sewage in the anaerobic state as in the related art, and the load on the device is reduced, resulting in failure and the like. It is possible to continuously perform stable sewage treatment by reducing the frequency of occurrence of sewage.

Further, in the sewage treatment apparatus 10 of the present embodiment, the rise in the liquid level is suppressed, and the bubbles generated due to the aeration can be sent to another tank through the communication pipe 20, so that the bubbles rise. Thus, it is possible to avoid such a problem that the manhole is pushed up and overflows out of the tank by suppressing reaching the slab.

In particular, the flow passage area of the communication pipe 20 is reduced by the discharge pipe 18.
Is larger than the flow path area, the amount of the mixed liquid passing through the communication pipe 20 is larger than the amount of the treated water discharged from the discharge pipe 18, and more bubbles are transferred from the aerobic tank to the anaerobic tank. And the rise of bubbles can be further suppressed.

Conventionally, it has been necessary to spray water on the foam on the liquid surface, add an antifoaming agent, or beat the foam with a rotating blade to break the foam. In the sewage treatment apparatus 10 of the present embodiment, there is no need to defoam using such a mechanical structure or chemicals, and it is possible to simplify the apparatus configuration and suppress an increase in equipment cost.

Here, when the load of the sewage treatment is low, the amount of aeration air is also small, so that the rise of the liquid level is also small. In this case, since the flow of the mixed liquid does not sufficiently occur between the first tank 12 and the second tank 14, the wastewater is not preferentially charged into the tank in the anaerobic state, and the first and second tanks 12 are not charged. , 14 may be charged. However, when the load is low, there is no problem even if sewage is introduced into the tank in the aerobic state, and the treatment can be performed sufficiently efficiently. That is,
In the sewage treatment apparatus 10, it is only necessary that the sewage can be preferentially charged into the anaerobic tank only when the load of the sewage treatment is high, and the above-mentioned remarkable effect can be obtained when the load of the sewage treatment is high.

The present invention can be variously modified without being limited to the above embodiment.

For example, in the above embodiment, the sewage treatment apparatus 10 is constituted by a pair of tanks 12 and 14,
Without being limited to this, the sewage treatment apparatus may be configured by a plurality of pairs of tanks such as two pairs or three pairs. In this case, each pair of tanks is provided with the configuration of the above-described embodiment. In this way, it is possible to treat a large amount of sewage in parallel at a time, and it is possible to increase the scale of treatment.

Further, a structure for defoaming each of the first and second tanks 12 and 14, such as a device for injecting water into the foam on the liquid surface, a device for breaking the foam by rotating blades, and the like. A mechanical structure may be provided, or a structure for adding a chemical such as an antifoaming agent to sewage may be provided. By doing so, the rise of bubbles can be further suppressed.

The number of communication pipes 20 is not limited to one, and a plurality of communication pipes may be provided. In this case, each communication pipe connects the first tank 12 and the second tank 1 between the overflow line L1 and the aeration line L2.
4 is provided so as to communicate therewith. Also, a plurality of discharge pipes 18 may be provided. Even in this case, it is preferable that the total flow area of all the communication pipes 20 is larger than the total flow area of all the discharge pipes 18.

[0044]

According to the sewage treatment apparatus of the present invention, the sewage treatment apparatus is provided in common for a pair of tanks by the flow of the mixed solution through the connecting pipe from the aerobic tank to the anaerobic tank. The sewage can be preferentially input from the sewage supply device to the anaerobic tank. Therefore, it is not necessary to provide a dedicated sewage supply device for each tank, or to provide a valve for selectively switching the supply of sewage to each tank, thereby simplifying the device configuration. It is possible to suppress an increase in equipment costs.

If the sewage supply apparatus is operated continuously, it is possible to automatically switch the tank into which the sewage is charged according to a change in the flow of the mixture flowing through the connecting pipe. Therefore, in order to supply sewage in an anaerobic state as in the past, an intermittent operation of a separately provided sewage supply device,
In addition, there is no need to switch the valve, and the load on the device is reduced, so that the frequency of failures and the like is reduced, and stable sewage treatment can be continuously performed.

Further, in the sewage treatment apparatus of the present invention, the rise of the liquid level is suppressed, and bubbles generated by aeration can be sent to another tank through the communication pipe. It is possible to avoid problems such as bubbles overflowing out of the tank.

[Brief description of the drawings]

FIG. 1 is a configuration diagram schematically showing one embodiment of a sewage treatment apparatus of the present invention.

FIG. 2 is a diagram showing a flow of a mixed solution when a process is started by the sewage treatment apparatus of FIG. 1;

FIG. 3 is a diagram illustrating a flow of a mixed liquid when an anaerobic state and an aerobic state are switched from the state illustrated in FIG. 2;

[Explanation of symbols]

10: sewage treatment apparatus, 12: first tank, 14: second tank, 1
8 ... discharge pipe, 20 ... communication pipe, 22 ... sewage supply device, L1
... Overflow line, L2 ... Aeration line.

Claims (2)

[Claims] 1. An aerobic state for aerating a mixed solution of sewage and activated sludge in a tank to promote a nitrification reaction in the mixed solution, and an aerobic state in a mixed solution of sewage and activated sludge in the tank. At least a pair of tanks capable of switching between an anaerobic state for promoting a denitrification reaction in the mixed liquid without aeration, and a pair of tanks provided respectively in the pair of tanks, the first tank being located above the first liquid level position. A discharge pipe for discharging the treated water, a communication pipe communicating the pair of tanks, and a sewage supply connected to the communication pipe and supplying sewage to the pair of tanks via the communication pipe. A communication device, wherein the communication pipe is provided between the first liquid level position in each of the pair of tanks and a second liquid level position at which the liquid level of the mixed liquid reaches during aeration. A sewage treatment apparatus characterized by connecting a pair of tanks. 2. The sewage treatment apparatus according to claim 1, wherein a flow passage area of the communication pipe is larger than a flow passage area of the discharge pipe.