JPH0571320B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an improvement in a fluidized bed biofilm method composed of enlarged microorganism-attached particles.

Prior art and its problems A fluidized bed biofilm method in which a fluidized bed is formed using particles to which microorganisms are attached, wastewater is treated within the fluidized bed, and the enlarged microorganism-adhered particles are separated from the treated water above the fluidized bed. is publicly known. In such a 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,
The particles are damaged and the pump is also worn out.

(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.

As a result of various studies aimed at solving the above-mentioned drawbacks of the prior art, the present inventors have found that the objective can be substantially achieved by using a hydrocyclone as a means for removing attached microorganisms from particles. Heading: Patent application has already been filed (Japanese Patent Laid-Open No. 1983-
No. 139394). This prior invention by the present inventors is
This is an excellent invention with practicality, but if it were possible to remove particles and attached microorganisms more efficiently and reduce the amount of alkaline agent used to adjust the pH of the circulating water in the treatment system, it would be possible to improve its effectiveness. Usability will be further improved.

Means for Solving the Problems In view of the current situation as described above, the present inventor has conducted repeated research to further improve and develop the invention of the prior application, and as a result, the present inventor has installed a static mixer between the processing tank and the liquid cyclone. When wastewater is mixed with air in advance and passed through this static mixer, particles and attached microorganisms are better separated, and the amount of alkaline agent required is also greatly reduced. I found out what to do. That is, the present invention relates to the following wastewater treatment method.

A fluidized bed treatment method for wastewater in which a fluidized bed is formed in a treatment tank using particles to which microorganisms are attached, the wastewater is treated within the fluidized bed, and the enlarged microorganism-adhered particles are separated from the treated water above the fluidized bed. While taking out a part of the wastewater containing enlarged microorganism-adhered particles from the upper part of the treatment tank through a circulation line installed outside the layer,
By mixing air with the extracted wastewater and passing it sequentially through a static mixer and a liquid cyclone installed on the line, attached microorganisms are separated from the particles, and the mixed gas is released from the upper opening of the liquid cyclone. At the same time, the separated microbial 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 particle mixture from the lower outlet is returned to the lower part of the treatment tank along with a part of the circulating fluid after passing through the circulation pump. A fluidized bed treatment method for wastewater, which is characterized by: ” 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, silcar-alumina, etc. in advance and suspending them. The particle size of the particles for microbial adhesion varies depending on the material, the size of the treatment tank 1, the type of raw waste water, etc., but sand is the most suitable in terms of cost, ease of acquisition, ease of adhesion of microorganisms, etc. If usually
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 factors such as microbial adhesion to the particles, but usually the sludge concentration in the tank (MLVSS) is
It is best to keep it at around 10,000 to 15,000mg/. The wastewater is supplied into the treatment tank 1 from the supply line 13 together with the circulating liquid passing through the circulation line 5, and in the treatment tank 1, while rising through the fluidized bed zone 2, the wastewater is attached to microorganism-adhered particles forming a fluidized bed.
A portion of the BOD component and/or nitrogen component rises within the solid-liquid separation zone 3 to line 6.
The treated water is taken out of the system as treated water. The microorganism-attached particles enlarged due to the growth of microorganisms float to the interface 7 between the fluidized bed 2 and the solid-liquid separation zone 3, and are taken out of the tank through the circulation line 5 together with a part of the recycled wastewater. The mixed air from the line 14 is passed through the static mixer 4. The wastewater whose speed has been increased by the mixing of air is vigorously agitated by the spiral motion within the static mixer 4, and the particles and attached microorganisms are separated. The wastewater discharged from the static mixer 4 is forced to pass through a liquid cyclone 8 installed in the middle of the circulation line 5 by the suction action of a circulation pump 9 installed after the cyclone 8, and is separated from enlarged particles. The detachment of attached microorganisms is further promoted. The air mixed with the wastewater is released into the atmosphere from the upper opening of the liquid cyclone 8, accompanied by the carbon dioxide gas dissolved in the wastewater.
By extension, the amount of neutralizing agent used for properly adjusting the pH of the liquid in the wastewater treatment tank 1 is reduced. The liquid containing the detached microorganisms rises to the upper part of the liquid cyclone 8, and is returned to the lower part of the processing tank 1 from the upper outlet through the circulation line 5. On the other hand, since particles descend to the lower part of the liquid cyclone 8, a part of the circulating liquid passing through the circulation line 5 is sent to the water ejector 12 via the branch line 11,
The particles in the liquid cyclone 8 are suctioned and removed from 0.
It is returned to the lower part of the wastewater treatment tank 1 together with the branch circulating liquid. By repeating such a particle return operation, the particles are regenerated and recycled.

The addition of a calcareous agent for pH adjustment can be carried out at any point, such as in the circulating water in the circulation line 5 or in the treated water in the wastewater treatment tank 1. Supply of oxygen or oxygen-containing gas to maintain the inside of the wastewater treatment tank 1 in aerobic conditions can also be performed at any point in the circulation line 5 or the like.

Effect of the invention According to the present invention, the following effects are achieved.

(i) Microorganisms can be efficiently separated from microorganism-adhered particles. Incidentally, as an example, in the flow diagram shown in FIG.
The microbial detachment rate [particle weight before detachment - particle weight after detachment / particle weight before detachment × 100] when oxygen was not supplied from the sample and static mixer 4 was not used was approximately 10% at most. In contrast, in the case of the present invention, it was 30% or more.

(ii) Since the carbon dioxide gas contained in the liquid leaving the treatment tank is effectively removed, the amount of alkaline agent used for neutralization is greatly reduced. Incidentally, as an example, the first
In the flow diagram shown in the figure, when treated water is aerated using an independent aeration device without mixing air from line 14, approximately 5 times as much NaOH for neutralization is required as compared to the method of the present invention. It was hot.

(iii) As a result of () and () above, construction costs, operating costs, etc. are significantly reduced, and the space required for equipment is also reduced.

[Brief explanation of the drawing]

FIG. 1 is a flow diagram illustrating one embodiment of the present invention. 1... Processing tank, 2... Fluidized bed zone, 3... Solid-liquid separation zone, 4... Static mixer, 5
... Circulation line, 6 ... Treated water take-out line, 8 ... Fluid cyclone, 9 ... Circulation pump,
11...branch line, 12...water ejector,
13...Wastewater supply line.

Claims (1)

[Claims] 1 A fluidized bed treatment method for wastewater in which a fluidized bed is formed in a treatment tank using particles to which microorganisms are attached, the wastewater is treated within the fluidized bed, and the enlarged microorganism-adhered particles are separated from the treated water above the fluidized bed. While taking out a part of the wastewater containing enlarged microorganism-adhered particles from the upper part of the treatment tank through a circulation line installed outside the layer,
By mixing air with the extracted wastewater and passing it sequentially through a static mixer and a liquid cyclone installed on the line, attached microorganisms are separated from the particles, and the mixed gas is released from the upper opening of the liquid cyclone. At the same time, 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 particle mixture from the lower outlet is returned to the lower part of the treatment tank together with a part of the circulating liquid after passing through the circulation pump. A fluidized bed treatment method for wastewater characterized by returning it.