JPS5861887A - Treatment of waste water - Google Patents

Abstract

PURPOSE:To facilitate the removal of the clogging materials in washing cycles by making combination use of particles having smaller particle sizes and higher specific gravities with particles having larger particle sizes and lower specific gravities as carrier particles and forming an upper stationary bed of a tank with the latter particles. CONSTITUTION:The carrier of smaller particles 3 are charged on a perforated plate 2 placed near the bottom of a treating tank 1 of semifluidized beds, whereby a lower fluidized bed (a) is formed. The carrier of larger particles 4 are charged thereon, whereby an upper stationary bed (b) is formed. A supply pipe 6 for raw water is connected to the lower part of the tank 1 and an outflow pipe 7 for treated water is connected thereto. Raw waste water is first introduced through an inflow pipe 9 into an oxygen dissolving device 8 where the water dissolves sufficiently oxygen supplied through a blowing pipe 13. This water is supplied through the pipe 6 into the tank 1 where the water suffers biological treatments while it passes through the bed (a) and the bed (b). The treated water is discharged thrugh the pipe 7 at the upper part of the tank 1.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improved method for microbial treatment of wastewater using a semi-fluidized bed treatment tank consisting of an upper fixed bed and a lower fluidized bed.

In the microbial aerobic treatment of wastewater, it is known to use semi-fluidized bed treatment vessels forming a bed of finely divided solids, fluidized in the lower part and stationary in the upper part. That is,
Fill the tank with carrier particles such as sand to which microorganisms have adhered17.
A method has been proposed for treating wastewater by flowing wastewater upward to fluidize the carrier particles, and then pressing the fluidized bed from above with a porous plate to form a fixed bed at the top. By combining a fluidized bed section and a fixed bed section, this semi-fluidized bed treatment has the advantages of both high-speed processing due to complete mixing in the fluidized bed section and finishing treatment using a dense microbial layer in the fixed bed section. can get. In addition, the use of carrier particles to which such microorganisms are attached can increase the microorganism concentration per unit volume, and it is possible to reduce the size of the processing tank in addition to the above-mentioned high-speed processing (% opening 55-10
See Publication No. 6594, etc. ) As a result of repeated research on the microbial treatment method for wastewater using semi-liquid raw material as described in @tI, the inventor discovered that as the treatment cycle progresses, the microbial flocs and twigs detached from the suspended solids or carrier particles in the wastewater. It has been found that there is a problem in that the fixed bed section is clogged due to such problems, and wastewater treatment must be temporarily interrupted and cleaning treatment must be carried out frequently. Also in the above-mentioned Japanese Unexamined Patent Publication No. 55-106594, the degree of occlusion of the fixed bed part is detected by pressure observation,
Wastewater treatment is interrupted for cleaning cycles.

It has been newly discovered that the above-mentioned difficulties can be smoothly and advantageously overcome by using carrier particles with different diameters and specific gravity of tin particles. That is.

Carrier particles with relatively high specific gravity and small particle diameter (hereinafter referred to as small carrier particles) and carrier particles with relatively low specific gravity and large particle diameter (hereinafter referred to as large carrier particles) Fill the treatment tank with both, and press the top with a perforated plate to allow the wastewater to flow upward from the bottom.

A fluidized bed portion of small carrier particles is formed in the lower part of the tank, and (2) a fixed bed part of large carrier particles is formed in the upper part of the tank. As a result, since the fixed bed section is formed of large carrier particles, clogging in the fixed bed section is greatly alleviated, and the operation cycle time of wastewater treatment can be increased. Further, by employing a fixed bed section made of large carrier particles, it becomes easy to remove blockages during the cleaning cycle, and the cleaning cycle time can also be shortened.

The present invention has thus been completed based on the above findings, and consists of passing wastewater upward through a semi-fluidized bed treatment tank in which carrier particles with microorganisms attached form a fluidized bed at the bottom and a fixed bed at the top. In this method, small carrier particles having a small particle size and relatively high specific gravity and large carrier particles having a large particle size and relatively low specific gravity are used together as the carrier particles, and the carrier particles are fixed at the upper part of the tank. A novel method for treating wastewater is provided, characterized in that the bed is formed of large carrier particles.

The method of the present invention utilizes the excellent advantages of semi-fluidized bed treatment, namely, the ability to maintain a high concentration of microorganisms as described above, the possibility of high-speed treatment, the possibility of finishing treatment in a fixed bed section, and the flow rate of wastewater. In addition to being able to respond to changes, it is also possible to achieve the above-mentioned effects of significantly alleviating blockage in the fixed bed section.

In the present invention, it is important to use large carrier particles and small carrier particles in combination, and the specific gravity of both carrier particles must be greater than the specific gravity of water. Furthermore, it is important that the specific gravity of the large carrier particles and the small carrier particles is greater than that of the former.

As the carrier particles, a wide range of known and well-known materials can be used, including sand, coal, carbon, alumina, glass, plastics, and ceramics. and.

These carrier particles are appropriately selected and used as large carrier particles and small carrier particles. In the present invention, the particle diameter of the large carrier particles is selected from the range of 1 to +OU, preferably about 2 to 5 mj, and the particle diameter of the small carrier particles is selected from the range of α1 to 10 mj.
．． Preferably, it is selected from the range of about 0.02 to 0.6 u. Further, the specific gravity is usually selected from a range of about 11 to 5, and is selected so that the specific gravity of large carrier particles is smaller than that of small carrier particles. Selection of large carrier particles and small carrier particles is possible by changing the type of carrier particles, or by using particles of the same type but with different particle sizes and specific gravity. .

In the present invention, the semi-fluidized bed treatment tank is filled with a combination of large carrier particles and small carrier particles as described above, and the upper fixed bed is formed by the large carrier particles.

Although the lower fluidized bed is formed from small carrier particles, this does not preclude large carrier particles from being mixed into the lower fluidized bed.

In some cases, small carrier particles may be mixed into the lower part of the upper fixed bed, or a fixed bed of small carrier particles may be formed at the lower end of the upper fixed bed. However, it is desirable to operate in such a way that a lower end fixed bed of small carrier particles is not formed.

As a means for maintaining the upper fixed bed, there is usually employed means for pressing the bed from above using a perforated plate. Such means are described in the above-mentioned Japanese Unexamined Patent Publication No. 55-106594. The pores in the perforated plate allow the treated water to pass through, but allow the carrier particles to remain in the bath.
It is preferable that the particle diameter is smaller than that of the carrier particles. others,
Conditions for the structure of the semi-fluidized bed treatment tank may be selected from known or well-known conditions. For example, the wastewater is flowed upwardly at a rate sufficient to fluidize at least the lower fluidized bed, and specifically at a rate of 1, eg, 12 to 6 times, significantly higher than the minimum fluidization rate. Maintaining the height and thickness of the upper fixed bed by raising and lowering the perforated plate, wastewater flow rate, etc.

Further changes are possible, and it is also possible to provide an alternative location for the treated water outlet or a waste gas exhaust hole.

In the present invention, the ratio of the upper fixed bed section and the lower fluidized bed section constituting the semi-fluidized bed can be varied. Usually, the fixed bed section is smaller in height and thickness than the fluidized bed section. In the present invention, the proportion of the upper fixed bed portion can also be changed by appropriately selecting the proportion of large carrier particles and small carrier particles. Typically, large carrier particles are comprised of 10 to 50 microns of total carrier particles.

In the method of the present invention, by employing an upper fixed bed made of large carrier particles, clogging is greatly alleviated, but if clogging occurs in the fixed bed, the same washing cycle as in the conventional method is carried out. obtain. for example.

Wastewater treatment can be temporarily interrupted and the porous grate holding the upper fixed bed pushed up, allowing the entire bed to fluidize and wash away the blockage deposits.

In order to promote washing by such fluidization, stirring action may be used in combination.

The method of the present invention can be applied to the microbial treatment of wastewater in each machine, and any number of microorganisms attached to carrier particles can be adopted in each machine accordingly. For example, it can be applied not only to treatments under aerobic conditions such as BOP removal and ammonia nitrogen removal from wastewater, but also to treatments under anaerobic conditions such as denitrification and digestion treatments.

Next, nine embodiments of the method of the present invention will be further described. The accompanying drawings, FIGS. 1 and 2, each schematically show a type of apparatus suitable for applying the invention.

In Fig. 1, 1 is a semi-fluidized bed treatment tank, and a porous plate 2 attached near the bottom of the tank is filled with J\ carrier particles 5 to form upper and lower fluidized beds a1, and large carrier particles are placed on top of it. 4 is filled to form a fixed bed 11b on the upper floor, and a porous plate 5 for preventing the +1 carrier particles 4 from flowing out is disposed on the upper surface of the fixed bed.

It can be raised and lowered as needed, as shown by the arrows.

A wastewater supply pipe 6 is connected to the bottom of the treatment tank 1, and a wastewater supply pipe 6 is connected to the top of the treatment tank 1, and an outflow pipe is connected to the top of the treatment tank 1 to take out the treated water that has undergone biological treatment in the tank. 7 is connected. Additionally, an oxygen dissolving device 8 is provided attached to the semi-fluidized bed treatment tank 1. An oxygen-containing gas (including pure oxygen) admission pipe 1S is connected to this device 8, an inlet pipe 9 for raw wastewater is connected to the upper part of the device 8, and the above-mentioned supply pipe is connected to the lower part of the device 8. 60 proximal crab connected [
There is.

Therefore, the raw wastewater first flows from the inlet pipe 9 to the oxygen dissolving device fi.
8, where the oxygen supplied from the blowing pipe 13 is sufficiently dissolved, and then supplied from the supply pipe 6 to the semi-fluidized bed treatment tank 1, where it is subjected to biological treatment as it passes through the fluidized bed a and the fixed bed. Then, it is taken out from the outflow pipe 7 at the top of the tank 1. In a system like this Figure 1, the BOD is 1
It is suitable for raw wastewater of 000 W/It or less.

FIG. 2 shows another embodiment, in which the same parts as in the embodiment of FIG. 1 are given the same reference numerals. The configurations of the semi-fluidized bed treatment tank 1 and the oxygen dissolving device 8 are similar to those shown in FIG. The upper part of the oxygen dissolving device 8 and the upper part of the processing tank 1 are connected by a take-out pipe 11 via a circulation pump 10, and the lower part of the oxygen dissolving device 8 and the lower part of the processing tank 1 are connected by a supply pipe 12. A circulation route is formed.

Therefore, the raw wastewater that flows into the treatment tank 1 from the inflow pipe 9 undergoes biological treatment in the tank and is taken out from the upper small flow pipe 7, but some of the treated water that has undergone this treatment is ,
An extraction pipe 11 is connected to the upper part of the treatment tank 1 by a circulation pump 10.
After entering the oxygen dissolving device 8 through the supply pipe 12 and sufficiently dissolving the oxygen blown in from the blowing pipe 13,
The raw water is supplied to the lower part of the pipe 9, where it joins with the raw water from the first pipe 9, and the circulation is repeated. That is, the processing tank 1 has a take-out pipe -11t #! Oxygen is constantly supplied by the liquid circulating in the circulation path having the elementary dissolution device 8 and the supply pipe 12. The system shown in FIG. 2 or the system shown in FIG. 1 can also be used.

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[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of one embodiment of an apparatus to which the present invention is applied, and FIG. 2 is a schematic diagram of another embodiment. 1... Semi-fluidized bed treatment tank, λ5... Porous plate, 5
...Small carrier particles, 4-...Large carrier particles, 6... Supply pipe, 7... Outflow pipe, 8... Oxygen dissolving device, ? −・・
Inflow pipe, 10...Circulation pump, 11--Output pipe, 12
...Supply pipe, 15...Blowing pipe, a...Fluidized bed, b
=・Fixed floor

Claims (1)

[Claims] (11) A method for treating wastewater by flowing it upward through a semi-fluidized bed treatment tank in which carrier particles with microorganisms attached form a fluidized bed at the bottom and a fixed bed at the top. As the carrier particles, small carrier particles having a small particle size and relatively high specific gravity and large carrier particles having a large particle size and relatively low specific gravity are used in combination.The upper fixed bed of the tank is a large carrier particle. A method for treating wastewater, characterized in that it is formed by particles. +21 A patent claim characterized in that the wastewater is introduced into an oxygen dissolving device, where oxygen is blown thereinto to dissolve it, and then the wastewater is caused to flow into a semi-fluidized bed treatment tank. A method for treating wastewater according to item 1. (3; A circulation path connecting one part of the semi-fluidized bed treatment tank and the lower part is provided, and an oxygen dissolving device is provided in the circulation path for the liquid in the treatment tank. The wastewater treatment method according to claim 1, characterized in that the wastewater is introduced into the treatment tank, dissolved therein, and introduced into the treatment tank from the lower part thereof.