JPH0144395B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a fluidized bed biofilm process comprised of microbially attached particles.

The fluidized bed biofilm method, in which a fluidized bed is formed by particles to which microorganisms are attached, wastewater is treated in the fluidized bed, and the microorganism-adhered particles are separated from the treated water above the fluidized bed, is well known. In the fluidized bed biofilm method, if the microorganisms attached to the particles grow and become too large, the particles will flow out of the treatment tank, so the excessively attached microorganisms must be peeled off from the particles. In this case, the conventional method has the following drawbacks.

(i) If the particles are drawn through the pump,
Particles are damaged and the pump is also worn.

(ii) If a stirrer is attached to the top of the treatment tank and attached microorganisms are mechanically removed, particle breakage and abrasion of the stirrer will occur.

The present invention was made with the aim of eliminating such conventional problems. Specifically, the present invention forms a fluidized bed in a treatment tank using particles to which microorganisms are attached, and treats wastewater within the fluidized bed. In a fluidized bed biological treatment method for wastewater that separates enlarged microorganism-adhered particles from treated water above the fluidized bed, a portion of the wastewater containing enlarged microorganism-adhered particles is passed from the top of the treatment tank through a circulation line installed outside the layer. While taking it out through
The adhering microorganisms are separated from the particles by passing through a liquid cyclone installed on the line, and the separated microorganism mixture from the upper outlet of the liquid cyclone is returned to the lower part of the treatment tank through the circulation line, while the liquid from the lower outlet is The particle mixture is subjected to solid-liquid separation in a closed sedimentation type solid-liquid separation tank, and the separated liquid is merged with the liquid from the upper outlet of the hydrocyclone.Meanwhile, the settled particles are deposited in a closed type particle storage tank, and a predetermined amount is stored in the tank. After the particles have accumulated, a part of the circulating liquid that has passed through the circulation pump is passed through a storage tank, and is returned to the lower part of the treatment tank while being accompanied by the accumulated particles. Concerning layer processing method.

The method of the present invention will be explained in detail below with reference to the flow diagram shown in the drawings.

In FIG. 1, a fluidized bed zone 2 and a solid-liquid separation zone 3 are formed in a wastewater treatment tank 1. A fluidized bed is formed by adhering microorganisms to particles of sand, activated carbon, coke, anthracite, plastic, glass, silica gel, silica-alumina, etc. in advance and suspending them. The particle size of the particles for microbial adhesion varies depending on the material, but in the case of sand, which is optimal in terms of cost, ease of acquisition, ease of microbial adhesion, etc.
It is about 0.1 to 3 mm. The amount of particles that should be retained in the wastewater treatment tank 1 varies depending on the amount of microorganisms attached to the particles, but usually the sludge concentration in the tank (MLVSS)
It is best to set the amount to be about 5000 to 4000 mg/. The wastewater is supplied into the treatment tank 1 from the supply line 4 through the circulation line 5, and in the treatment tank 1, while rising through the fluidized bed zone 2, the BOD components and/or the wastewater are added to the microorganism-adhered particles forming the fluidized bed. Alternatively, a portion of the nitrogen component rises within the solid-liquid separation zone 3 and is taken out of the system as treated water through the line 6. The microorganism-adhered particles enlarged due to the production of microorganisms float above the interface 7 between the fluidized bed 2 and the solid-liquid separation zone 3, so they are transported out of the tank through the circulation line 5 together with a part of the recycled wastewater. It is taken out and forced to pass through a liquid cyclone 8 installed in the middle of the tank ring line 5 by the suction action of a circulation pump 9 installed behind the cyclone 8, and mainly adheres from the manure particles in the liquid cyclone 8. Removes microorganisms. Since the liquid containing the detached microorganisms rises to the upper part of the liquid cyclone 8,
The particles are returned to the lower part of the processing tank 1 from the upper outlet through the circulation line 5, and on the other hand, particles descend to the lower part of the hydrocyclone 8, so they are sent together with some liquid from the lower outlet through the downcomer pipe 10. It is lowered by its own weight into a sedimentation type sealed separation tank 11. In the separation tank 11, the liquid rises in the tank, so it is transferred to the line 1.
2 to join the circulation line 5 behind the cyclone 8, while the particles descend in the tank,
This is passed through a downcomer pipe 13 to a closed particle storage tank 1.
4 and deposit it automatically. After a predetermined amount of particles have accumulated in the reservoir tank 14, the valve 13a provided in the downcomer pipe 13 is closed to stop the automatic descent of the particles, while a part of the circulating fluid that has passed through the circulation pump 9 is diverted. The circulating liquid is passed through the tank 14 from the upper part to the lower part through the line 15, and the accumulated particles are returned to the lower part of the processing tank 1 via the downcomer pipe 16 and the circulation line 5. After returning the deposited particles, the valve 15a of the branch line 15 and the valve 16a of the downcomer pipe 16 are closed to stop particle return, while the valve 13a of the downcomer pipe 13 is opened to resume particle deposition. By repeatedly performing such a particle return operation, the particles can be regenerated and recycled. Valve 1 in particle return operation
Opening/closing switching operations of 3a, 15a, and 16a can be performed periodically by a combination of a solenoid valve and a timer. Further, for the purpose of increasing the amount of circulating liquid flowing through the reservoir tank 14, a constriction part (not shown) can be formed in the middle of the circulation line 5 between the branch line 15 and the downcomer pipe 16.

According to the treatment method of the present invention, particles regenerated in the liquid cyclone 8 are effectively utilized in part of the circulating liquid, without passing through the circulation pump 9 at all.
It can be returned to the lower part of the treatment tank 1, eliminating problems such as particle damage and pump wear.

[Brief explanation of drawings]

FIG. 1 is a flow diagram showing one embodiment of the present invention, and FIG. 2 is an enlarged view of the main part of FIG. In the figure, 1 is a treatment tank, 2 is a fluidized bed zone,
3 is a solid-liquid separation zone, 4 is a wastewater supply line, and 5 is a solid-liquid separation zone.
is a circulation line, 6 is a line, 7 is an interface, 8 is a hydrocyclone, 9 is a circulation pump, 10 is a downcomer, 1
1 is a solid-liquid separation tank, 12 is a line, 13 is a downcomer pipe,
14 is a reservoir, 15 is a branch line, and 16 is a downcomer pipe.

Claims (1)

[Claims] 1. Fluidized bed biological treatment of wastewater in which a fluidized bed is formed in a treatment tank using particles to which microorganisms are attached, the wastewater is treated in the fluidized bed, and the enlarged microorganism-adhered particles are separated from the treated water above the fluidized bed. In this method, a part of the wastewater containing enlarged microorganism-adhering particles is removed from the upper part of the treatment tank through a circulation line installed outside the layer, and the wastewater is passed through a liquid cyclone installed on the line, thereby removing the adhering microorganisms from the particles. The separated microbial mixture from the upper outlet of the hydrocyclone is returned to the lower part of the treatment tank through the circulation line, while the particle mixture from the lower outlet is separated into solid and liquid in a closed sedimentation type solid-liquid separation tank. The liquid from the upper outlet of the hydrocyclone is mixed with the liquid, while the settled particles are deposited in a closed particle storage tank. After a predetermined amount of particles have accumulated in the tank, a part of the circulating liquid after passing through the circulation pump is A fluidized bed treatment method for wastewater, characterized in that the wastewater is passed through a storage tank and returned to the lower part of the treatment tank while being accompanied by deposited particles.