JP3468732B2 - Carrier stirring separation device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wastewater treatment technology for introducing a carrier for immobilizing microorganisms into a tank for treating wastewater, and relates to a carrier stirring / separating device for preventing the carrier from flowing out of the tank. It is a thing.

[0002]

2. Description of the Related Art In recent years, with the eutrophication of closed water areas becoming more serious, it is required to remove nutrient salts such as nitrogen and phosphorus. Until now, for example, the circulation type nitrification denitrification method has been adopted for removing nitrogen from sewage. In this conventional circulation type nitrification denitrification method, nitrifying bacteria are retained in the system as floating activated sludge, but since the growth rate of nitrifying bacteria is extremely slow, a residence time of 13 to 16 hours in the tank is required. Is.
A reaction tank with a tank capacity that can maintain this residence time has a large installation area, and it was difficult to introduce it in a treatment plant in an urban area where the site area is small.

Under such a technical background, a carrier-introduced activated sludge method was developed for the purpose of removing BOD and nitrogen within a residence time equivalent to that of the standard activated sludge method (6 to 8 hours). Was done. This carrier-introduced activated sludge method is to hold a high concentration of nitrifying bacteria in an aerobic tank by charging a carrier into a nitrification tank and immobilizing (adhering and holding) the nitrifying bacteria on the carrier.

The carrier used in this method has a large specific surface area by being formed into a porous structure to increase the porosity, and is characterized by exhibiting an excellent immobilizing ability against nitrifying bacteria. Has become.

In order to increase the reaction efficiency of the nitrifying bacteria immobilized on these carriers, it is necessary that the carriers flow in the tank by stirring, and a stirring means for well stirring the carrier and the liquid in the tank, The carrier itself is required to have excellent fluidity. Further, in order to maintain the amount of microorganisms in the tank, it is necessary to keep the carrier on which nitrifying bacteria are immobilized in the tank, and a carrier separation device that prevents the carrier from flowing out is required.

In this carrier separating apparatus, a screen for separating the carrier is vertically arranged at a position separating the outflow passage from the tank inner region in which the carrier and the liquid in the tank flow, and the air lift action of the air aerated in the tank. A circulating flow is generated in the tank by the rising stirring flow that is generated, and this circulating flow is made to flow in a fixed direction along the screen to form a sweep flow, and the carrier captured on the screen is constantly washed by this sweep flow to Prevents blockage.

[0007]

By the way, maintaining a high concentration of microorganisms in the tank is effective in increasing the efficiency of the biological reaction even in the denitrification tank. However, if the above-mentioned carrier for immobilizing microorganisms in the nitrification tank is directly applied to the denitrification tank, there are the following problems.

First, since the denitrification tank cannot agitate by aeration, it is impossible to generate a scavenging flow in a certain direction on the screen by utilizing the air lift action, and when a conventional carrier separating device is used. The screen is blocked by the attachment of the carrier and the flow of the carrier is obstructed.

Secondly, for the purpose of enhancing the ability to immobilize microorganisms, nitrogen gas generated due to the denitrification reaction accumulates in the pores formed inside the carrier, the carrier floats, and the liquid in the tank The efficient contact between the substrate and the carrier is impaired.

The present invention is intended to solve the above problems, and an object of the present invention is to provide a carrier stirring / separating device capable of flowing and stirring a carrier in a denitrification tank and satisfactorily separating the carrier by a screen. And

[0011]

In order to solve the above problems, the carrier stirring and separating apparatus of the present invention according to claim 1 is for immersing in a reaction tank containing a carrier for immobilizing microorganisms, It forms a chamber of a hollow cylinder having a circulation channel that penetrates vertically, an outflow pipe that communicates with the chamber channel at one end and reaches the outside of the tank at the other end, and forms the inner wall of the chamber facing the circulation channel. And a screen that separates the chamber internal flow path from the circulation flow path, and an agitator that generates a downward flow by an impeller arranged in the circulation flow path.

With the above-mentioned structure, the carrier to be charged into the tank is preferably formed porous so as to immobilize the microorganisms, and the microorganisms contributing to the biological treatment of the wastewater supplied into the reaction tank are formed on the surface and It is fixed in fine holes. This immobilization is performed by acclimatizing microorganisms according to the environment in the tank.

During the operation of biologically treating the wastewater in the reaction tank, the impeller of the stirrer is rotationally driven to generate a downward flow in the circulation channel of the chamber. Due to this downward flow, the liquid in the tank and the carrier flow down the circulation flow path of the chamber, flow out from the lower end opening to the lower area inside the tank, become an upward flow around the chamber, and flow to the upper area inside the tank. It flows into the circulation flow path from the upper end opening of, and circulates while being stirred in the tank.

As a result, the substrate in the liquid in the tank and the microorganisms immobilized on the carrier are efficiently brought into contact with each other, and the residence time in the tank necessary for treating the wastewater can be shortened, and the rated tank volume is small. Become.

In the circulation flow path, the downflow flows as a sweep flow along the screen, so that the screen is constantly washed, so that the carrier flows with the downflow without being trapped by the screen, Can be blocked. The liquid in the tank separates the carrier by passing through the screen, and the carrier-separated water that has passed through the screen flows into the channel in the chamber and flows out of the tank through the outflow pipe. Therefore,
It is possible to prevent the carrier from flowing out of the tank and maintain the amount of microorganisms in the tank at a high concentration.

By the way, when the reaction tank is a denitrification tank, the carrier has immobilized denitrifying bacteria, and nitrogen gas is attached by the biological reaction. The carrier to which the nitrogen gas adheres has a small apparent specific gravity and floats in the upper area of the tank, resulting in poor fluidity. The carrier floating in the upper area of the tank is drawn into the downward flow and flows into the circulation channel of the chamber, and the carrier separates the nitrogen gas by contact with the impeller of the stirrer when passing through the circulation channel. Liquidity is restored.

In the carrier agitating and separating apparatus according to the second aspect of the present invention, the downward flow velocity is preferably 0.2 to 3 m / sec, and if there is this flow velocity, the buoyancy of the carrier with the nitrogen gas bubbles adhered thereto is increased. Can be drawn into the liquid in the bath against excessive force, and an excessive flow rate consumes useless energy in the stirrer.

The carrier agitation separation apparatus of the present invention according to claim 3 is for immersing in a reaction tank in which a carrier for immobilizing microorganisms is introduced, and a circulation flow path that penetrates vertically is formed,
A main body cylinder that has an inflow part in the upper part and a chamber of a hollow cylinder in the middle, an outflow pipe that communicates with the channel in the chamber at one end and reaches the outside of the tank at the other end, and the inside of the chamber facing the circulation channel A screen that forms a wall and separates the flow path in the chamber from the circulation flow path, and a submersible stirring type aerator that is connected to the lower end of the main body and arranged to generate a downward flow in the circulation flow path Is.

With the above structure, since the submersible stirring type aerator is located near the bottom of the tank, the water flow generated by the submerged stirring type aerator provides a sufficient stirring effect for the liquid in the tank that stays near the bottom of the tank. It is possible to obtain the cleaning effect for cleaning the screen and the stirring effect with the same power.

In the carrier agitating and separating apparatus of the present invention according to claim 4, a vertical pipe is connected to the other end of the outflow pipe, and a stirring means for generating a downward flow is provided in the vertical pipe. In the above-described configuration, in a state where the outlet of the outflow pipe is submerged below the surface of the water, the carrier-separated water flows by using the head difference between the head of the water acting on the inlet of the outflow pipe and the head of the water acting on the outlet as the driving pressure. on the other hand,
When a downward flow flows in the circulation flow path, the pressure in the circulation flow path lowers the inlet pressure of the outflow pipe. Therefore, when the head of water acting on the inlet of the outflow pipe is equal to the head of water acting on the outlet, the inlet pressure of the outflow pipe becomes smaller than the outlet pressure, and a backflow occurs in the outflow pipe. This backflow is stopped when the head acting on the inlet is higher than the head acting on the outlet by a predetermined head difference.

Therefore, in order for the carrier-separated water to flow from the inlet side to the outlet side of the outflow pipe in the state where the downward flow flows in the circulation flow path, the water head acting on the inlet of the outflow pipe and the water head acting on the outlet of the outflow pipe are required. A redundant head gap between the two is required.

However, when a downward flow is generated in the vertical pipe provided at the other end of the outflow pipe by the stirring means, the outlet pressure of the outflow pipe is lowered due to the pressure drop in the vertical pipe, and the pressure in the circulation passage is decreased. The drop value of the inlet pressure and the drop value of the outlet pressure, which have decreased due to the drop, are balanced. This eliminates the need for a redundant head difference between the head of water that acts at the inlet of the outflow pipe and the head of water that acts at the outlet, and the carrier-separated water is the head of water that acts at the inlet and outlet of the outflow pipe. Flow smoothly according to the difference.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. 1 and 2, a denitrification tank 1 which is a reaction tank is incorporated in a nitrification denitrification treatment system for biologically treating sewage wastewater, and is connected to an upstream side or a downstream side of a nitrification tank (not shown). However, in this embodiment, the raw water to be treated flows from the inflow pipe 2.

The denitrification tank 1 is charged with a carrier 3 for immobilizing microorganisms that contribute to denitrification, and the carrier 3 is preferably formed in a porous form to immobilize the microorganisms. It is immobilized on its surface and fine pores.
This immobilization is performed by acclimatizing microorganisms according to the environment in the tank.

Carrier agitation separation device 4 arranged in denitrification tank 1
Has a chamber 5 having an annular hollow body to be immersed in the tank, and the chamber 5 has a circulation channel 6 vertically penetrating in the center thereof. The chamber 5 has an inner wall facing the circulation channel 6 formed by a screen 7. The screen 7 is a wedge wire screen and separates the circulation channel 6 and the chamber channel 8 for separating the carrier 3.

An impeller 10 of a stirrer 9 is provided in the circulation channel 6.
Are arranged, and the impeller 10 generates a downward flow by its rotation. One end of the outflow pipe 11 communicates with the flow path 8 in the chamber, and the other end reaches the outside of the tank to reach a nitrification tank (not shown).
From the nitrification tank to the denitrification tank 1.
2 are in communication.

The operation of the above configuration will be described below. During operation, the wastewater to be treated is supplied from the inflow pipe 2 to the denitrification tank 1, and the impeller 10 of the stirrer 9 is rotationally driven to generate a downward flow D in the circulation flow path 6 of the chamber 5. This downward flow has a flow rate of 0.2 to 1 m / sec, and this flow rate draws the carrier 3 into the liquid in the tank against the buoyancy of the nitrogen gas bubbles.

The liquid in the tank and the carrier 3 flow down through the circulation flow path 6 of the chamber 5 by the downward flow D, flow out from the lower end opening to the lower region of the tank, and thereafter, as an upward flow U around the chamber 5. Then, it flows into the upper region of the tank, flows into the circulation channel 6 from the upper end opening of the chamber 5, and circulates while being stirred in the tank.

By circulating and circulating the carrier 3, the substrate in the liquid in the tank and the microorganisms immobilized on the carrier 3 are efficiently brought into contact with each other, and the carrier 3 retains the microorganisms at a high density. The retention time in the tank required for denitrification can be shortened, and the rated tank volume can be reduced.

In the circulation flow path 6, the downward flow D flows as a sweep flow along the screen 7, so that the screen 7
Can be always washed, the carrier 3 does not flow together with the downward flow D and is not captured by the screen 7, and the clogging of the screen 7 can be prevented. At this time, the liquid in the tank separates the carrier 3 by passing through the screen 7, and the carrier-separated water T that has passed through the screen 7 flows into the channel 8 in the chamber and flows out of the tank through the outflow pipe 11. , Into a nitrification tank (not shown). As a result, the carrier 3 does not flow out of the tank and the amount of microorganisms in the tank can be maintained at a high concentration.

Nitrogen gas is attached to the carrier 3 by the biological reaction of the denitrifying bacteria. The carrier 3 to which the nitrogen gas adheres has a small apparent specific gravity, and floats in the upper area of the tank to deteriorate the fluidity. However, the downward flow D having a predetermined flow velocity draws the carrier 3 floating in the upper area in the tank into the circulation flow path 6 of the chamber 5, and when the carrier 3 passes through the circulation flow path 6, the impeller 10 of the stirrer 9 Separates the nitrogen gas by contact with and restores good fluidity.

FIG. 3 shows another embodiment of the present invention. The same numbers are assigned to the elements that perform the same operations as those in the previous embodiment, and the description thereof will be omitted. In FIG. 3, the carrier separating / stirring device 21 forms a circulation flow path 6 that vertically penetrates by a main body cylinder 22. The main body cylinder 22 has an inflow portion 23 in the upper portion, and a chamber 5 of a hollow cylinder is provided on the way. The chamber 5 has an outflow pipe 11 in which one end communicates with a channel in the chamber and the other end reaches the outside of the tank.
And a screen 7 that separates the in-chamber channel 8 and the circulation channel 6 from each other is provided on the inner wall facing the circulation channel 6.

An underwater stirring type aerator 24 for generating a downward flow in the circulation flow path 6 is provided at the lower end of the main body cylinder 22. The submerged stirring type aerator 24 has a discharge port 26 that discharges a water flow along the bottom of the tank on the lower end side of the casing 25,
The impeller 27 and the impeller 2 are provided inside the casing 25.
An underwater motor 28 for rotating 7 is provided. An air outlet 30 is provided in the guide portion 29 arranged on the downstream side of the impeller 27.

With the above-described structure, the downward flow D is circulated by driving the underwater stirring type aerator 24 during operation.
The carrier 3 is drawn into the liquid in the tank by this downward flow (0.2 to 3 m / sec).

The liquid in the tank and the carrier 3 flow into the main body 22 from the inflow portion 23, flow down the circulation channel 6 of the chamber 5 by the downward flow D, flow out from the discharge port 26 to the vicinity of the bottom of the tank, and are stirred. While being circulated, it circulates and flows in the tank. At this time, since the underwater stirring type aerator 24 is located near the bottom of the tank, the water flow ejected from the discharge port 26 can obtain a sufficient stirring effect for the liquid in the tank staying near the bottom of the tank.

In the circulation flow path 6, the downward flow D flows as a sweep flow along the screen 7, so that the screen 7
Can be always washed, the carrier 3 does not flow together with the downward flow D and is not captured by the screen 7, and the clogging of the screen 7 can be prevented. At this time, the liquid in the tank separates the carrier 3 by passing through the screen 7, and the carrier-separated water T that has passed through the screen 7 flows into the channel 8 in the chamber and flows out of the tank through the outflow pipe 11. . By this,
The carrier 3 does not flow out of the tank and the amount of microorganisms in the tank can be maintained at a high concentration.

FIG. 4 shows another embodiment of the present invention. The same numbers are assigned to the elements that perform the same operations as those in the previous embodiment, and the description thereof will be omitted. In FIG. 4, the outflow pipe 11 communicates with the nitrification tank 31 adjacent to the denitrification tank 1 below the water surface, and a vertical pipe 32 is provided at the outlet of the outflow pipe 11. Inside the vertical pipe 32, the impeller 34 of the stirrer 33 is installed.
The impeller 34 generates a downward flow by its rotation.

With the above structure, in a state where the outlet of the outflow pipe 11 is submerged below the water surface of the nitrification tank 31, the carrier separation water acts on the inlet of the outflow pipe 11 and the head of the denitrification tank 1 and the nitrification tank that acts on the outlet. The difference between the head and the head of 31 flows as the driving pressure.

On the other hand, when a downward flow flows through the circulation passage 6, the pressure inside the circulation passage 6 drops, and the inlet pressure of the outflow pipe 11 drops. Therefore, when the water head acting on the inlet of the outflow pipe 11 is equal to the water head acting on the outlet, the inlet pressure of the outflow pipe 11 becomes smaller than the outlet pressure, and a backflow occurs in the outflow pipe 11. This backflow is stopped when the head of water acting on the inlet becomes higher than the head of water acting on the outlet by a predetermined head difference Δh.

Therefore, in order for the carrier separation water to flow from the inlet side of the outflow pipe 11 to the outlet side in the state where the downward flow flows in the circulation flow path 6, the head of the denitrification tank 1 acting at the inlet of the outflow pipe 11 is required. And a redundant head difference Δh between the head of the nitrification tank 31 acting on the outlet and the head of the nitrification tank 31 is essential.

However, the impeller 34 of the stirrer 33 is rotated to generate a downward flow in the vertical pipe 32 provided at the other end of the outflow pipe 11, and the outflow pipe is generated due to the pressure drop inside the vertical pipe 32. By reducing the outlet pressure of 11,
The decrease amount of the inlet pressure and the decrease amount of the outlet pressure, which decrease due to the pressure drop in the circulation flow path 6, are balanced.

This eliminates the need for a redundant head difference Δh between the head of the denitrification tank 1 acting on the inlet of the outflow pipe 11 and the head of the nitrification tank 31 acting on the outlet, and the carrier-separated water is discharged from the outflow pipe 11. The water flows smoothly in accordance with the head difference between the head of the denitrification tank 1 that acts on the inlet and the head of the nitrification tank 31 that acts on the outlet.

When the stirrer 9 is installed above the outflow pipe 11, the outflow pipe 1 may be reversed depending on the discharge pressure.
The inlet pressure of 1 may increase, but in that case, if the stirrer 33 is arranged above the vertical pipe 32, the pressure can be similarly balanced. It goes without saying that the carrier stirring and separating apparatus described above can be applied to both a denitrification tank and a nitrification tank.

[0044]

As described above, according to the present invention, a downward flow is generated in the circulation channel of the chamber by the impeller, and the downward flow circulates the liquid in the tank and the carrier while stirring in the tank. Since the liquid is allowed to flow, the substrate in the liquid in the tank and the microorganisms immobilized on the carrier are efficiently brought into contact with each other, and the residence time in the tank necessary for treating the wastewater can be shortened to reduce the size of the tank body. In the circulation flow path, the downflow flows as a sweep flow along the screen to wash the screen at all times, so that the carrier flows with the downflow without being trapped by the screen, and the clogging of the screen can be prevented. The carrier separates nitrogen gas by contact with the impeller of the stirrer when passing through the circulation flow path, and recovers good fluidity. The downward flow preferably has a flow velocity of 0.2 to 3 m / sec, and this flow velocity allows the carrier having nitrogen gas bubbles attached thereto to be drawn into the liquid in the tank against its buoyancy. Different flow rates consume wasted energy in the stirrer. In addition, since the submerged aeration type aerator is located near the bottom of the tank, it is possible to obtain a sufficient agitation effect for the liquid in the tank that accumulates near the bottom of the tank, and the cleaning effect for cleaning the screen and the agitation effect are the same. It can be obtained by the power of. Further, by balancing the drop value of the inlet pressure of the outflow pipe and the drop value of the outlet pressure, the carrier-separated water flows smoothly according to the head difference between the head acting on the inlet of the outflow pipe and the head acting on the outlet. .

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a carrier stirring and separating apparatus according to an embodiment of the present invention.

FIG. 2 is a plan view of the carrier stirring and separating apparatus.

FIG. 3 is a cross-sectional view of a carrier stirring and separating apparatus according to another embodiment of the present invention.

FIG. 4 is a cross-sectional view of a carrier stirring / separating device according to another embodiment of the present invention.

[Explanation of symbols]

1 denitrification tank 2 inflow pipe 3 carriers 4 Carrier agitation separator 5 chambers 6 circulation channels 7 screen 8 Chamber flow path 9 stirrer 10 impeller 11 Outflow pipe

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-9-117785 (JP, A) JP-A-10-305290 (JP, A) JP-A-11-47786 (JP, A) JP-A-2001-991 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) C02F 3/02-3/10 C02F 3/28-3/34

Claims (4)

(57) [Claims] 1. A chamber of a hollow cylinder having a circulation flow path that penetrates vertically, which is immersed in a reaction tank containing a carrier for immobilizing microorganisms, and one end of which communicates with a flow path in the chamber. And the screen that forms the inner wall of the chamber facing the circulation flow path to separate the chamber internal flow path from the circulation flow path, and the impeller placed inside the circulation flow path. A carrier stirring and separating apparatus, comprising: a stirrer for generating a countercurrent. 2. The carrier stirring / separating device according to claim 1, wherein the downward flow velocity is 0.2 to 3 m / sec. 3. A method of immersing in a reaction vessel containing a carrier for immobilizing microorganisms, which forms a circulation flow path that penetrates vertically, has an inflow part at the top, and has a hollow barrel chamber in the middle. A main body cylinder provided, an outflow pipe having one end communicating with a channel in the chamber and the other end reaching the outside of the tank, and an inner wall of the chamber facing the circulation channel to form a chamber inner channel and a circulation channel. A carrier stirring / separating device, comprising: a screen separating the above and a submersible stirring type aeration device which is disposed so as to be connected to the lower end of the main body cylinder and generates a downward flow in the circulation flow path. 4. The carrier according to claim 1, wherein a vertical pipe is connected to the other end of the outflow pipe, and stirring means for generating a downward flow is provided in the vertical pipe. Stirrer separation device.