JPH026591B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a Teita-Bett type fluidized bed biological treatment device using an inorganic carrier with a particle size of several mm.

A foam made of a hydrophobic polymer compound has been proposed as a carrier for use in fluidized bed biological treatment equipment for sewage, but even though it is a foam, the microbial membrane that is useful for sewage purification has low adhesion and is not sufficient. Purification efficiency cannot be obtained.

On the other hand, inorganic substances such as sand, crushed gravel, and activated carbon have excellent adhesion properties for microbial films, but their high specific gravity requires large amounts of power to fluidize them, so they are used as fixed beds rather than as biological treatment equipment. It is used as a device or adsorption device.

Furthermore, even if these inorganic substances are made into fine particles and used as carriers that are easily fluidized, microbial membranes will attach and enlarge during the wastewater treatment process, resulting in changes in particle size and specific gravity.
Furthermore, membrane fusion between carriers is likely to occur.

The purpose of the present invention is to improve the purification efficiency by improving the contact between aerobic or anaerobic microorganisms living on the surface of a carrier in a Teita-Bett type fluidized bed and wastewater, and to improve the purification efficiency by improving the adhering microbial film formed as a result of purification. The microbial flocs are peeled off by the collision and friction between the carriers, and the excess microbial flocs are suspended in purified water and automatically flowed out of the taeta bed.

Therefore, the present invention has a density of 0.4 to 1.0 g/cm ³ and a particle size of 3.
A biological treatment device is provided in which the porous inorganic carrier has a diameter of 15 mm and the ratio of the static layer volume of the carrier to the teta bed is 20 to 80%.

By making the carrier coarse particles of several mm or more, changes in particle size, specific gravity, and particle fusion due to microbial adhesion during the treatment process are smaller than in fine powder carriers, and collisions and friction between microbial film-attached carriers are reduced. It has advantages such as being larger than fine powder, making it easier to prevent the carrier from expanding, and the difference in particle size between the exfoliated microbial floc and the carrier being large, making it easier to remove the floc from the bed.

On the other hand, the disadvantages are that the fluidity is low and the surface area of the carrier is relatively small. This problem can be solved by using materials.

In the present invention, the specific gravity before water absorption is set so that the specific gravity is slightly larger than 1 when the carrier absorbs water.
Use a value in the range of 0.4 to 1.

In addition, to address the drawbacks, by filling the stationary layer volume ratio of the carrier to the teita bed in the range of 20 to 80% (volume), it is possible to achieve the closest packing state in the filter bed of a normal fixed bed treatment equipment. A larger surface area is obtained.

For example, in the case of a carrier particle size of 3 mm, the carrier surface area in a filter bed packed state is approximately 735 m ² /m ³ , so when the static layer volume ratio is in the range of 20 to 80%, it is 147 to 588 m ² /m ³ , which is usually The surface area is approximately twice as large as the 70 to 200 m ² /m ³ surface area of a fixed bed biological treatment device in the closest packed state.

In addition, the lower limit of the above filling range in the present invention is 20%
is the limit at which at least the surface area of a conventional fixed bed filtration bed can be obtained even when the particle size of the carrier is at the lower limit of 3 mm,
If it falls below 20%, the amount of microorganisms that can live in the filter bed will decrease, reducing purification efficiency.

Furthermore, the upper limit of 80% is the limit at which the carriers in the filter bed can undergo theta-type flow; above this limit, collisions between the carriers will decrease, the microbial film will increase in size, and it will be difficult to generate and discharge flocs.

The apparatus according to an embodiment of the present invention will be described with reference to FIG. 1. Reference numeral 1 is a treatment tower or tank, and upper and lower stages are provided with an upper screen 2a and a lower screen 2b having a width smaller than the carrier particle diameter. 3 is a carrier, which is filled in a predetermined amount within the above-mentioned volume range.
Sewage is introduced 5 from below the lower screen 2b, and air is blown through the porous air diffuser 4. The aeration from the air diffuser supplies oxygen necessary for the resident microorganisms, and also causes the carrier to flow up and down.

Furthermore, the slugging caused by rising air bubbles on the lower surface of the upper screen 2a prevents microbial flocs separated from the carrier from adhering to the screen and clogging it.

The purified water is discharged together with flocs from a drain pipe 6 above the upper screen.

In the device shown in FIG. 2, a screen 2c is placed on the water surface and stretched over the overflow port of the tank wall.
The carrier is stirred and fluidized by a gas-liquid mixed flow from the underwater bucket 7.

In this device, the carrier applies centrifugal force to the water in the tank, and also brings in air by coming into contact with the outside air.

When each of the above devices is applied to anaerobic microorganisms, nitrogen gas or the like may be introduced instead of air, or mixed contact may be carried out using a stirrer in a closed tank.

[Brief explanation of drawings]

FIGS. 1 and 2 are sectional views of an embodiment of the present invention.

Claims (1)

[Claims] 1. In a Teita-Bett biological treatment equipment equipped with an aeration means at the bottom of the tank and in which wastewater is supplied as an upward flow to the fluidized bed, the fluidized bed filler maintains sedimentation properties in water and has a dry density of 0.4 to
A porous inorganic carrier with a particle size of 1.0 g/cm ³ and a particle size of 3 to 15 mm has a static layer volume ratio of 20 to the volume of the teita bed.
Teita Vett biological treatment equipment characterized by being filled to ~80%.