JPH07124582A - Aerobic treatment tank and soil water treatment process using tank - Google Patents

Abstract

PURPOSE:To provide an aerobic treatment tank and a soil water treatment process using the aerobic treatment tank which can prevent the lowering of treatment performance following the formation of carrier concentration distribution. CONSTITUTION:In an aerobic treatment tank 1 for soil water in which microbes are kept fixed on carriers 2 in the floating state, the upper and lower ends of the inside of the tank are opened and divided transversely by a flow prevention plate 10 through which water and the carriers 2 can be flowed. One division thus formed is a division A with an oxygen containing gas supply means 3 of relatively large air amount and low melting efficiency, and the other is a division B with an oxygen containing gas supply means 3 of relatively small air amount and high melting efficiency, while a means 6 for preventing the outflow of carriers 2 is provided at an outflow end of the treatment tank. In the aerobic treatment tank, it is preferable to set the air supply amount in a manner of almost uniformizing the oxygen supply speed of the division A and that of the division B.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sewage treatment tank, and particularly to a sewage treatment tank for biologically treating organic wastewater such as sewage, night soil, industrial wastewater, etc. using a microorganism immobilization carrier. The present invention relates to a wastewater treatment method using.

[0002]

2. Description of the Related Art In recent years, activated sludge method, biofilm method, immobilized microbial method, etc. have been remarkably spread, but in Japan where the efficiency of land use is called for, high-performance sewage treatment that can be processed in a smaller area Development of equipment is urgent. Among them, a sewage treatment apparatus using a microorganism-immobilized carrier has been particularly attracting attention in combination with an improvement in the performance of the carrier material.

The present inventors have developed a sewage treatment apparatus using the immobilization carrier shown in FIG. 4, but encountered the following technical problems in the development process. That is, as a result of the immobilized carrier flowing down the biological reaction tank together with the water to be treated,
The carrier concentration at the front end of the reaction tank decreased, and the carrier concentration at the end increased, resulting in a marked decrease in treatment performance.

[0004]

DISCLOSURE OF THE INVENTION The present invention solves the problems of the conventional method and provides a treatment tank and a wastewater treatment method using the same which can prevent the deterioration of the treatment performance due to the formation of the carrier concentration distribution. Is an issue.

[0005]

In order to solve the above problems, according to the present invention, in the aerobic treatment tank for wastewater which holds a carrier on which microorganisms are immobilized in a floating state, the inside and the bottom of the tank are opened. Water and the carrier are divided by a baffle through which they can flow, and one of the sections is defined as a section A in which oxygen-containing gas supply means having a relatively large air flow and a low dissolution efficiency is provided, and the other is relatively defined. The section B is provided with oxygen-containing gas supply means having a small amount of air and high dissolution efficiency, and means for preventing the carrier from flowing out is provided at the outflow end of the processing tank.

In the processing tank, a plurality of baffles may be provided so that the compartments A and the compartments B are alternately arranged. Further, in the processing tank, it is preferable that the oxygen-containing gas supply means arranged in the section A is a diffuser plate and the oxygen-containing gas supply means arranged in the section B is a diffuser. In the present invention, in the sewage treatment method using the aerobic treatment tank, the oxygen-containing gas supply means in the compartment A and the compartment B set the air supply amount so that the oxygen supply speeds of both are substantially uniform. Is good.

Further, in the above treatment method, the anoxic step, the aerobic step and the precipitation step are sequentially connected, the outflow water of the aerobic step is circulated to the anoxic step, and the settled sludge of the precipitation step is returned to the anoxic step. It is preferably used for the aerobic process in the denitrification / dephosphorization activated sludge process, in which the anaerobic process is provided before the circulation nitrification denitrification process or the anoxic process, and the sludge sludge in the precipitation process is returned to the anaerobic process. it can.

As described above, in the present invention, the inside of the aerobic tank is partitioned by the baffle plate so that the amount of supplied air is controlled to form an internal partial circulation flow in the tank based on the air lift action. Further, if there is a bias in the oxygen supply capacity inside the aerobic tank, the treatment performance will be hindered, so different types of air diffusers are combined to make the oxygen supply rate into the tank almost uniform. The vertical opening ratio in the tank of the baffle plate is 10 to 25% in the height direction with respect to the water depth, and normally about 15% is preferable.

The immobilization carrier used in the present invention includes
There are fluid carriers such as sand, activated carbon, plastic pieces, sponges, hydrophilic gels, but the invention is not limited to the application of these carriers. As a means for immobilizing microorganisms on a carrier, an attachment immobilization method is generally used, but an entrapping immobilization method is also applicable. In the present invention, the degree of strength of the air supply amount is preferably set to (section A / section B) ratio = 2 to 4. If it is smaller than this, the effect of correcting the concentration distribution of the immobilized carrier is small, and if it is larger than this, the difference in the oxygen supply amount between the tanks becomes too large, resulting in a shortage of DO in some tanks.

In the aerobic tank of the present invention, the immobilization carrier is substantially evenly distributed, but the immobilization carrier sometimes gathers at the terminal outflow portion of the aerobic tank depending on the amount of air supplied. In such a case, a pump may be installed to transfer the immobilized carrier from the terminal part to the tip part of the aerobic tank, and the carrier may be transferred. In this case, as a transfer pump installed at the end of the aerobic tank, since a carrier and a biofilm may be destroyed in a general centrifugal pump, a non-blocking vortex type pump, a special pump such as an air lift pump may be used. It is desirable to use. In addition, in transferring, other than the pump, means capable of transferring without destroying the carrier and the biofilm may be appropriately used. Further, as in the device disclosed in JP-A-5-26139, a carrier separating means such as a liquid cyclone or a trommel sieve is provided in the middle of the carrier transfer pipe,
The carrier may be distributed to the aerobic tank in each processing device provided with the transfer water in the preceding stage.

Further, at the outflow end of the aerobic tank, a carrier outflow preventing means composed of a porous member such as a net, a grating and a punching plate for preventing outflow of the carrier is provided, and the above carrier transfer machine is installed. In this case, it is advantageous to provide a simple concentration mechanism for the carrier on the suction side of the carrier transfer machine because the amount of transferred water can be reduced. Further, it is desirable that the amount of water transferred by the carrier transfer device can be arbitrarily changed by changing the motor rotation speed by frequency control.

[0012]

According to the present invention, the immobilization carrier can be prevented from being biased to the downstream side due to the formation of the circulation flow in the tank due to the difference in the air supply amount. Furthermore, by providing a carrier transfer device from the end of the aeration tank to the tip, fine adjustment of the carrier concentration becomes possible. Oxygen supply is achieved by arranging a diffuser plate with low oxygen dissolution efficiency (10%) in the first half where the air supply amount is large, and arranging a fine bubble diffuser with high oxygen dissolution efficiency (20%) in the latter half. The amount can be the same in the first half and the second half. As a result, high processing performance can be obtained in the entire aerobic tank.

[0013]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. Example 1 FIG. 1 is a plan view showing an example of an aerobic treatment tank for wastewater of the present invention, and FIG. 2 is a vertical sectional view of FIG. In FIG. 1 and FIG. 2, the aeration tank 1 is divided into two parts A and B by one baffle plate 10.
The case of division into sections is shown. The aeration amount is set strong in the first half section A and the second half section B is weakly set, and the air volume ratio is 3: 1. In the air diffuser, the ordinary air diffuser plate 3 is arranged on the entire surface in the section A, and the fine bubble diffuser 9 is set in the section B.
Are placed on the entire surface.

In this aeration tank, the circulating flow as shown in FIG. 2 is formed by the pressure difference based on the air flow difference. The immobilization carrier 2 moves to the compartment B as the water to be treated 7 flows down, but returns from the compartment B to the compartment A by the circulation flow in the reverse direction formed at the bottom of the tank. A circulation flow from the compartment A to the compartment B is formed in the upper part of the tank, but here, the moving amount of the immobilization carrier 2 is not so large as in the bottom part. As a result, as a whole, the circulation flow causes the division from the division B to the division A.
The immobilized carrier will be returned to.

By forming the circulating flow in the tank, the immobilization of the immobilization carrier 2 on the downstream side can be prevented. Further, by providing the carrier transfer pump 12 from the terminal of the aeration tank to the tip and transferring the carrier 2, the carrier concentration can be finely adjusted. 1 and 2, 6 is a carrier separator, 8 is a treated water outflow pipe, 4 is a blower, 5 is an air pipe,
Reference numeral 11 is an air flow meter.

As described above, in this embodiment, the diffuser plate 3 having a low oxygen dissolution efficiency (10%) is arranged in the section A having a large aeration amount, and the oxygen dissolution efficiency is high (20%) in the section B.
By arranging the fine bubble diffuser 9, the oxygen supply amount can be made equal in the first half section A and the second half section B. As a result, high treatment performance could be obtained in the entire aeration tank. In this embodiment, an example in which the aeration tank is divided into two by one baffle plate is shown, but it is also divided into a plurality of baffle plates and the sections A and B are alternately provided. The same operational effects as the present embodiment are achieved, and such an aspect is also included in the present invention.

Example 2 Next, a circulation type nitrification denitrification method using the aerobic treatment tank of the present invention will be described. FIG. 3 shows a schematic vertical sectional view of an apparatus used for the circulating nitrification and denitrification method. In FIG. 3, an aeration tank 1
Uses the aerobic treatment tank of the present invention. In this example, three baffle plates 9 are installed, and compartments are provided alternately with A, B, A, and B, and each symbol is the first embodiment. Has the same meaning as. Further, 14 is an anoxic tank, 17 is an underwater mixer, and 16 is a circulating nitrification liquid pipe.

The nitrification denitrification method will be described with reference to FIG. 3. Waste water flows from the inflow pipe 7 into the anoxic tank 14 together with the circulating nitrification solution from 16 and is subjected to denitrification treatment and then anoxic. The gas flows into the aeration tank through an inlet provided at the bottom of the partition wall 18 that separates the tank and the aeration tank. In the aeration tank 1, a circulation flow is generated by the diffuser plate 3 provided in the compartment A and the diffuser 9 provided in the compartment B, and the treated water is sufficiently nitrified by the action and effect described in the first embodiment, and the treated water is treated. Exits through the carrier separator 6. A part of the effluent water is discharged, and the rest is circulated to the anoxic tank 14 by the nitrification solution circulation pump 15 through the circulation nitrification solution pipe 16.

Next, an example of the treatment of nitrifying and denitrifying will be shown below with reference to FIG. (A) Treated water Urban sewage (b) Device configuration Anoxic tank ・ ・ ・ 400m ³ (residence time 4.0 hours) Aerobic tank ・ ・ ・ 400m ³ (retention time 4.0 hours) ³ baffles The wall divided into 100 m ³ × 4 tanks. ─────────────────────────────── Total 800m ³ (HRT = 8.0 hours) ・ Treatment amount: 100m ³ / hour・ Returned sludge amount: 50 m ³ / hour ・ Nitrification solution circulation amount: 200 m ³ / hour ・ MLSS: 2000 mg / liter

Aeration amount: aerobic tank (A) 1/4 part 240 Nm ³ / hour aerobic tank (B) 2/4 part 60 Nm ³ / hour aerobic tank (A) 3/4 part 240 Nm ³ / hour good Air tank (B) 4/4 parts 60 Nm ³ / hour ・ Oxygen dissolution efficiency is 20 in 2/4 and 4/4 parts of aerobic tank (B)
%% fine bubble diffuser is placed on the entire surface.・ Oxygen dissolution efficiency is 10 for 1/4 and 3/4 parts of aerobic tank (A)
% Diffuser is placed on the entire surface.

(C) Result of operation In the aerobic tank, the circulation flow from 2/4 part of (B) to 1/4 part of (A) and 3/4 of (A) from 4/4 part of (B). A circulating flow to / 4 part was formed at the bottom and the immobilized support was returned in the upstream direction. As a result, the deviation of the carrier in the aerobic tank is +
It was within -5%. In addition, nitrification performance can be maintained at a high level in the entire aeration tank, and ammonia in the treated water is always 1
It was below mg / liter.

[0022]

As described above, according to the present invention, in a water treatment apparatus using a microorganism-immobilized carrier, the formation of carrier concentration distribution can be prevented and eliminated, and the oxygen supply rate in the tank can be made uniform. Therefore, high processing performance can be obtained in the entire tank.

[Brief description of drawings]

FIG. 1 is a plan view showing an example of an aerobic treatment tank of the present invention.

FIG. 2 is a vertical cross-sectional view of FIG.

FIG. 3 is a schematic vertical sectional view of an apparatus used for the nitrification denitrification method of the present invention.

FIG. 4 is a cross-sectional explanatory view showing an example of an aerobic treatment tank using a conventional carrier.

[Explanation of symbols]

1: aerobic tank, 2: immobilized carrier, 3: diffuser plate, 4: blower, 5: air pipe, 6: carrier separator, 7: inflow pipe, 8: outflow pipe, 9: fine bubble diffuser, 10 : Baffle, 1
1: air flow meter, 12: carrier transfer pump, 13: carrier transfer pipe, 14: oxygen-free tank, 15: nitrification solution circulation pump, 1
6: Circulating nitrification liquid pipe, 17: Underwater mixer, 18: Partition wall

Front page continuation (72) Inventor Kazuo Fujita 1-6-27 Konan, Minato-ku, Tokyo Ebara-in Filco Co., Ltd. (72) Masato Nishiwaki 1-27 Konan, Minato-ku, Tokyo Ebara-in Filco Stock In the company

Claims (3)

[Claims] 1. An aerobic treatment tank for sewage in which a carrier on which microorganisms are immobilized is held in a floating state, and the inside of the tank is opened at the upper and lower ends to be divided transversely by baffles through which water and the carrier can flow. Then, one of the compartments is defined as a compartment A in which an oxygen-containing gas supply means having a relatively large air volume and a low dissolution efficiency is provided, and the other is a compartment in which an oxygen-containing gas supply means having a relatively small air volume and a high dissolution efficiency is arranged. In addition, the aerobic treatment tank is characterized in that B is provided with means for preventing the outflow of the carrier at the outflow end of the treatment tank. 2. The method for treating sewage using an aerobic treatment tank according to claim 1, wherein the oxygen-containing gas supply means in the compartments A and B supplies air so that the oxygen supply rates of both are substantially uniform. A sewage treatment method characterized by setting an amount. 3. A circulation type nitrification denitrification in which an anoxic process, an aerobic process and a precipitation process are sequentially connected, the aerobic process outflow water is circulated to the anoxic process and the sludge sludge of the precipitation process is returned to the anoxic process. Or a denitrification / dephosphorization activated sludge method in which an anaerobic step is provided before the oxygen-free step and the sedimented sludge of the precipitation step is returned to the anaerobic step, and the aerobic step has a sewage treatment method according to claim 2. A method for treating sewage, which comprises: