JPH0760287A - Method and device for denitrification treatment of polluted water - Google Patents

Abstract

PURPOSE:To provide a treating method and a treating device for denitrifying polluted water by which denitrification treating capacity is enhanced by increasing the concentration of sludge in an aeration tank in a short cycle bacth type activated sludge disposal system in a system for performing batch treatment while using the aeration tank constituted by integrally combining a nitrification tank and a denitrification tank. CONSTITUTION:Attention is not paid to a denitrification treating device of a conventional circulation method but is paid to the so-called short circle batch type denitrification treating method and device. A treating method for denitrifying polluted water is constituted of a nitrification-denitrification process, a sedimentation process, a filtration process through a filtration film 27 for filtrating activated sludge supplied from a settling tank 25 and a return process for returning concentrated sludge in the filtration process to an aeration tank 24. In the nitrification-denitrification process, polluted water is introduced into the aeration tank 24 containing activated sludge and a carrier 40 for immobilization, nitrified and denitrified. In the sedimentation process, activated sludge is settled and compacted in the setting tank 25 for introducing supernatant liquid sent the aeration tank 24.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a denitrification treatment method for wastewater and a denitrification treatment apparatus therefor. Particularly, by increasing the sludge concentration in an aeration tank in a short cycle batch type activated sludge treatment system, denitrification is performed. The present invention relates to a method for denitrifying sewage with improved treatment capacity and a denitrification apparatus for the same.

[0002]

2. Description of the Related Art Generally, nitrogen-containing industrial wastewater, rural village wastewater, wastewater from sewage treatment facilities such as estates, etc. are subjected to a denitrification process using activated sludge, that is, a so-called biological denitrification process. ing.

A conventional denitrification treatment method for sewage and a conventional denitrification treatment apparatus will be outlined with reference to FIG. Figure 3
FIG. 1 is a schematic view of a conventional circulation-type denitrification treatment device 1, which comprises a raw water tank 2 for wastewater, a denitrification tank 3,
It has a nitrification tank 4 and a precipitation tank 5.

The raw water tank 2 supplies waste water to the denitrification tank 3 by a raw water pump 6. This supply amount is 1Q, where “Q” is the amount of raw water treated per day (m ³ / day).

The denitrification tank 3 is provided with a stirring pump 7 and contains denitrifying bacteria as activated sludge. The stirring pump 7 stirs the wastewater, and the denitrifying bacteria decomposes nitrogen oxide (NOx) in the wastewater.・ Assimilate and degas as nitrogen gas.

The nitrification tank 4 contains nitrifying bacteria as activated sludge. Air (oxygen) is supplied from the air introduction pipe 8 and a part of the liquid is denitrified by the circulation pump 9.
Return to. The return amount of this circulating liquid is 10 to 20Q. The nitrifying bacteria decompose nitrogen components (such as ammonia) in wastewater.
Assimilate to form nitric oxide (NOx).

The sludge is settled by supplying the supernatant from the nitrification tank 4 to the settling tank 5 and allowing it to stand, and at the same time, the returning sludge pump 10 returns the sludge to the denitrification tank 3. The returned amount is 1Q. The supernatant of this precipitation tank 5 is discharged as treated water.

A circulation type denitrification treatment apparatus 1 having such a configuration
In the above, a circulation system composed of a denitrification tank 3, a nitrification tank 4 and a precipitation tank 5 is used to provide 10 to 20Q from the nitrification tank 4
A large amount of the circulating fluid of 10 is returned to the denitrification tank 3, and 90 to 9
A denitrification treatment of 5% can be performed.

However, there is a problem that a large pump power is required as the circulation pump 9 for returning a large amount of circulating liquid of 10 to 20Q.

Further, since a large amount of returned water is aerobicized in the denitrification tank 3 due to the amount of dissolved oxygen brought into the denitrification tank 3, a large amount of organic substances such as methanol is used as an energy source necessary for the denitrification action by the denitrifying bacteria. There is a problem of becoming.

Further, when the wastewater to be treated is leachate, when the landfill is stable and the BOD flowing in becomes small, the sludge expands and is dismantled. It became impossible to perform sedimentation consolidation, and the denitrification tank 3
There is a problem that the internal sludge concentration cannot be maintained and denitrification becomes impossible.

[0012]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has a short cycle of a system in which batch processing is performed using an aeration tank in which the above-mentioned nitrification tank and denitrification tank are integrally combined. In the batch type activated sludge treatment system, by increasing the sludge concentration in the aeration tank,
An object of the present invention is to provide a denitrification treatment method for sewage and a denitrification treatment apparatus for the same, which have improved denitrification treatment capacity.

[0013]

That is, the present invention provides a so-called short cycle batch-type denitrification treatment method in which a denitrification tank and a nitrification tank are integrated, rather than a conventional circulation-type denitrification processing apparatus and a method thereof. Focusing on the device, the first invention is
A method for denitrifying sewage by denitrifying sewage using activated sludge containing nitrifying bacteria and denitrifying bacteria, wherein the sewage is introduced into an aeration tank containing the activated sludge and a carrier for immobilization, and nitrification is performed. A nitrification denitrification step of denitrifying, a precipitation step of settling and consolidating the activated sludge in a precipitation tank introducing the supernatant liquid from the aeration tank, and a filtration step by a filtration membrane for filtering the activated sludge from the precipitation tank And a return step of returning the concentrated sludge in the filtration step to the aeration tank, and a denitrification treatment method for wastewater.

The permeated liquid in the filtration step can be returned to the precipitation tank.

Further, the filtration membrane may be a UF membrane or an MF membrane.

The immobilizing carrier may be added in an amount of 5 to 30% of the capacity of the aeration tank.

A sedimentation separation step incorporating a stationary time for performing sedimentation separation of the activated sludge can be provided between the aeration operation and the outflow operation in the aeration tank.

Further, an outflow box is provided in the aeration tank, and the outflow box is raised above the liquid surface during aeration, and is lowered below the liquid surface when at rest, whereby the activated sludge and the immobilization carrier are immobilized. Can be prevented.

Further, a second invention is a denitrification treatment device for decontaminating wastewater by using activated sludge containing nitrifying bacteria and denitrifying bacteria, which contains the activated sludge and the immobilizing carrier. At the same time, an aeration tank for introducing the sewage to perform nitrification denitrification, a sedimentation tank for introducing the supernatant from the aeration tank and settling and consolidating the activated sludge, and filtering the activated sludge from the sedimentation tank A denitrification treatment device for sewage, which further comprises a filtration membrane capable of returning concentrated sludge obtained by filtration to the aeration tank.

[0020]

In the method for denitrifying sewage and the denitrifying apparatus therefor according to the present invention, a settling tank is provided next to the aeration tank for nitrifying and denitrifying, and the activated sludge can be concentrated by a filtration membrane such as a UF membrane. Since this concentrated sludge is returned to the aeration tank and the carrier for immobilizing activated sludge is stored in this aeration tank, it is possible to maintain a high sludge concentration in the aeration tank and perform denitrification treatment. You can improve your ability.

Further, the sludge is diluted by returning the permeated liquid in the filtration step to the settling tank to promote sedimentation and separation of the sludge in the settling tank to reduce the flow rate load on the filtration membrane in the filtration step. The membrane can be miniaturized.

Further, a sludge concentration in the aeration tank is increased by providing a sedimentation separation step incorporating a stationary time for performing sedimentation separation of the activated sludge between the aeration operation and the outflow operation in the aeration tank to improve the denitrification capacity. Can be improved.

Further, the outflow box provided in the aeration tank is
Activated sludge and activated sludge can be discharged by raising above the liquid level during aeration while supplying air to block the flow of liquid from here, and lowering it below the liquid level when stationary so that the supernatant liquid can flow out. It is possible to prevent the immobilization carrier from flowing out of the aeration tank, hold a high concentration of activated sludge in the aeration tank, and perform highly efficient denitrification treatment.

[0024]

EXAMPLES Next, a so-called short cycle batch type denitrification treatment apparatus 20 (activated sludge treatment apparatus) for carrying out the method for denitrification treatment of wastewater according to the present invention will be described with reference to FIGS. 1 and 2. However, the same parts as those in FIG. 3 are designated by the same reference numerals, and the detailed description thereof will be omitted.

This denitrification treatment device 20 is the same as the raw water tank 2 described above.
, Flow meter 21, wastewater measuring tank 22, organic carbon tank 23, aeration tank 24, settling tank 25, and retention tank 26.
And a UF membrane 27 as a filtration membrane, and a sequence controller 28 for controlling the whole.

A first valve (raw water supply valve) 29 is provided between the waste water measuring tank 22 and the aeration tank 24, and
A second valve (discharge valve) 30 is provided on the outlet side of the membrane 27, and a third valve (permeate return valve) 31 is provided on the return side to the precipitation tank 25.
A fourth valve (first concentrated sludge valve) 32 is provided on the return side from the UF membrane 27 to the retention tank 26, and a fifth valve (excess sludge valve) 33 and a sixth valve (excess sludge valve) 33 are provided on the return side to the wastewater metering tank 22. A valve (second concentrated sludge valve) 34 is provided.

Further, the aeration tank 24 has an air introducing valve 3
5 are provided and each valve 29, 30, 31, 32, 3
The sequence controller 28 controls opening / closing of the units 3, 34, and 35, respectively.

The aeration tank 24 is provided with a stirring motor 36 and a vertical movement motor 37, and the retention tank 26 is provided with a circulation pump 38.

From the raw water tank 2 of the dirty water by the raw water pump 6,
A batch process is performed in which sewage is supplied to the sewage metering tank 22, and when a certain amount is accumulated, the sewage is supplied to the aeration tank 24.

An organic carbon source such as methanol is supplied from the organic carbon tank 23 to the sewage metering tank 22 for nutrition of denitrifying bacteria.

The aeration tank 24 corresponds to the one in which the denitrification tank 3 and the nitrification tank 4 are integrated and supplies air from the air introduction pipe 39 to enable the nitrification action by nitrifying bacteria and the stirring motor 36. Drive to stir.

In the aeration tank 24, nitrifying bacteria and denitrifying bacteria are stored as activated sludge, and the immobilizing carrier 4 is used.
0 is suspended. Therefore, the slow-growing nitrifying bacteria are immobilized on the immobilizing carrier 40, the concentration of the nitrifying bacteria is increased, and the nitrification load can be increased.

As the immobilization carrier 40, any carrier such as a fluid carrier such as a sponge-shaped carrier or a marimo-shaped carrier, or a fixed carrier such as a plastic can be adopted. It is intended to improve the nitrification capacity, and is 5 to 30% of the capacity of the aeration tank 24.

As the agitation system of the aeration tank 24, the mechanical agitation system is mainly used when the immobilization carrier 40 is a fluid carrier, and the pump agitation system is mainly used when the immobilization carrier 40 is a fixed carrier. .

The outflow box 41 is floated on the liquid surface of the aeration tank 24, and the supernatant liquid in the aeration tank 24 is settled in the precipitation tank 2
5 can be supplied.

However, by allowing the outflow box 41 to move up and down by the vertically moving motor 37, the outflow box 41 is raised above the liquid level during aeration (solid line in the figure), and the outflow box 41 is moved below the liquid level when stationary. (The phantom line in the figure) is used to prevent the supernatant liquid from flowing out while preventing the sludge and the immobilization carrier 40 from flowing out.

The settling tank 25 includes the supernatant of the aeration tank 24 and the UF membrane 2 from the part of the settling tank feed well 42.
The permeated liquid from No. 7 is received, the supernatant liquid can be discharged as treated water, and the sludge, which is settled and compacted at the bottom, can be supplied to the retention tank 26.

The retention tank 26 temporarily stores the sludge from the settling tank 26 and supplies it to the UF membrane 27 by the circulation pump 38.

UF (Ultra Filtration)
n) The membrane 27 is a high-density filtration membrane, and the second
It is discharged as treated water through the valve 30 of
It is returned to the settling tank 25 as permeated water through the third valve 31. In addition, as a filtration membrane, MF (Medium F
It is also possible to employ an illumination film.

Excess sludge discharged from the fifth valve 33 is appropriately dehydrated.

FIG. 2 is a timing chart showing the control timing in the aeration tank 24 by the sequence controller 28. First, the first valve 29 is opened to aerate a predetermined amount of raw water from the waste water measuring tank 22. 24, and the fourth valve 32 and the sixth valve 34 are “closed” and the sixth valve 34 is “open”.
Then, the concentrated sludge is returned to the aeration tank 24.

When the raw water is introduced, the stirring motor 36 is driven to start the stirring (denitrification action), and the air introduction valve 35 is opened from the middle to introduce air to start aeration (nitrification action). ).

After completion of the aeration and stirring, a settling separation step is carried out in which the activated sludge is settled and separated after a stationary time,
The outflow box 41 is lowered by driving the vertical movement motor 37, and the supernatant liquid is allowed to flow out of the outflow box 41 into the settling tank 25.

By repeating such a cycle,
A predetermined amount of dirty water can be supplied as a batch process into the aeration tank 24 for denitrification.

The stationary settling time in the settling / separation step in one cycle is several minutes, but 1/24 to 1/96 of sludge settling with respect to 24 volumes of the aeration tank is sufficiently possible. The concentration can be maintained at 1-2%.

Next, the liquid from the aeration tank 24 is concentrated to the maximum extent in the settling tank 25, and a predetermined amount of sludge is retained in the next-stage retention tank 26. Supply and filter.

The treated water discharged from the UF membrane 27 is the second
When the valve 30 is opened, it is discharged, and when the third valve 31 is opened, the settling tank 2 is used as a permeate.
Returned to 5.

That is, when the second valve 30 is "open", the third valve 31 is "closed",
Sludge is supplied from the settling tank 25 to the retention tank 26, and further filtered by the UF membrane 27.

When the third valve 31 is "open", the second valve 30 is "closed", and the liquid that has passed through the UF membrane 27 is used as a permeated liquid in the settling tank feedwell of the settling tank 25. Since it is returned to the settling tank 25 through 42, the supernatant of the settling tank 25 is discharged as treated water.

Therefore, the sludge in the settling tank 25 is diluted by the permeated liquid returned from the UF membrane 27, and the solid-liquid separation action in the settling tank 25, that is, the settling separation action is promoted.

By repeating the settling action in the settling tank 25 and the filtering action in the UF membrane 27, the concentrated sludge is returned to the aeration tank 24, and the treated water denitrified to a predetermined concentration is discharged.

As described above, by adopting the short cycle batch type activated sludge system for one cycle in the aeration tank 24 of, for example, 15 to 60 minutes, the circulation return water amount of the conventional circulation denitrification system as shown in FIG. At the magnification corresponding to, the returned amount is 24 to 96Q, and the nitrogen removal rate can be made extremely high.

[0053]

As described above, according to the present invention, the carrier for immobilization is put in the aeration tank, and the sedimentation tank and the filtration membrane are combined to further return the concentrated sludge in the filtration step to the aeration tank. Therefore, the concentration of sludge can be kept high and nitrogen can be removed with good efficiency.

[0054]

[Brief description of drawings]

FIG. 1 is a so-called short cycle batch type denitrification treatment apparatus 20 for carrying out the method for denitrification treatment of wastewater according to the present invention.
It is a schematic diagram of (activated sludge treatment device).

FIG. 2 is a timing chart showing the control timing of the aeration tank 24 by the sequence controller 28.

FIG. 3 is a schematic diagram of a conventional circulation-type denitrification treatment apparatus 1.

[Explanation of symbols]

 1 Circulation type denitrification equipment 2 Wastewater raw water tank 3 Denitrification tank 4 Nitrification tank 5 Precipitation tank 6 Raw water pump 7 Stirring pump 8 Air introduction pipe 9 Circulation pump 10 Return sludge pump 20 Denitrification treatment equipment (active sludge treatment equipment) 21 Flowmeter 22 Wastewater Measuring Tank 23 Organic Carbon Tank 24 Aeration Tank 25 Precipitation Tank 26 Retention Tank 27 UF Membrane 28 Sequence Controller 29 First Valve (Raw Water Supply Valve) 30 Second Valve (Discharge Valve) 31 Third Valve (Permeate return valve) 32 Fourth valve (first concentrated sludge valve) 33 Fifth valve (excess sludge valve) 34 Sixth valve (second concentrated sludge valve) 35 Air introduction valve 36 Stirrer Motor 37 Vertical movement motor 38 Circulation pump 39 Air introduction pipe 40 Immobilization carrier 41 Outflow box 42 Lees tank feed well

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location C02F 3/12 QS

Claims (7)

[Claims] 1. A method for denitrifying sewage, comprising denitrifying sewage by a short cycle batch type activated sludge treatment system using activated sludge containing nitrifying bacteria and denitrifying bacteria, wherein the activated sludge and the immobilizing carrier are used. Introducing the sewage into the aeration tank containing the, nitrification denitrification step of nitrifying and denitrifying, and in the precipitation tank introducing the supernatant liquid from the aeration tank,
A settling step of settling and consolidating the activated sludge, a step of filtering with a filtration membrane for filtering the activated sludge from the settling tank, and a step of returning the concentrated sludge in this filtering step to the aeration tank. A characteristic method for denitrifying sewage. 2. The method for denitrifying sewage according to claim 1, wherein the permeated liquid in the filtration step is returned to the settling tank. 3. The method for denitrifying sewage according to claim 1, wherein the filtration membrane is a UF membrane or an MF membrane. 4. The method for denitrifying sewage according to claim 1, wherein the immobilization carrier is added in an amount of 5 to 30% of the capacity of the aeration tank. 5. A sewage system according to claim 1, further comprising a settling separation step incorporating a stationary time for performing settling separation of the activated sludge between an aeration operation and an outflow operation in the aeration tank. Denitrification treatment method. 6. The sewage according to claim 1, wherein the aeration tank is provided with an outflow box, and the outflow box is raised above the liquid level during aeration and lowered below the liquid level during rest. Denitrification treatment method. 7. A denitrification treatment apparatus for sewage, which denitrifies sewage by a short cycle batch activated sludge treatment system using activated sludge containing nitrifying bacteria and denitrifying bacteria, wherein the activated sludge and the immobilization carrier Accommodating
An aeration tank for introducing the wastewater to carry out nitrification denitrification, a sedimentation tank for introducing the supernatant liquid from the aeration tank and settling and consolidating the activated sludge, and filtering the activated sludge from the sedimentation tank, A denitrification treatment device for sewage, comprising: a filtration membrane capable of returning concentrated sludge obtained by filtration to the aeration tank.