JPH07214093A - Method for removing cod and nitrogen - Google Patents

Abstract

PURPOSE:To easily and inexpensively remove COD as the biodegradable org. matter and nitrate nitrogen by ozone-oxidizing a raw water and biologically treating the oxidized water successively under aerobic and anaerobic conditions. CONSTITUTION:A raw water is introduced into an ozone contact tank 1 along with ozone, brought into contact with a catalyst 4 and oxidized, and the COD in the raw water is converted to biodegradable org. matter and nitrate nitrogen. The oxidized water is introduced into an aerobic tank 2 from a feed pipe 7, sent up between the porous materials 8 and biologically treated under aerobic conditions when dissolved oxygen is present, hence the biodegradable org. matter is decomposed, and the remaining nitrogen is converted to nitrate nitrogen. The aerobically treated water is introduced into an anaerobic tank 3 from a feed pipe 9, sent downward between the porous materials 11 and biologically treated under anaerobic conditions, and the nitrate nitrogen and biodegradable org. matter are removed. COD and nitrogen are easily and inexpensively removed in this way.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a COD / nitrogen removal method for treating wastewater containing COD such as human waste and landfill leachate.

[0002]

2. Description of the Related Art Generally, C, such as human waste and landfill leachate,
Wastewater containing OD is treated by the activated sludge method.
The conventional processing flow is as follows, for example.

Raw water is supplied to an ozone contact tank, and COD contained in the raw water is oxidatively decomposed into biodegradable organic substances and nitrate nitrogen by ozone contact treatment. Then, after the dissolved oxygen and the dissolved ozone are removed, this oxidized water is sent to an anaerobic tank to biologically decompose and remove biodegradable organic substances and nitrate nitrogen contained in the oxidized water. Next, this anaerobic treated water is sent to an aerobic tank, biologically treated under aerobic conditions to decompose the remaining biodegradable organic matter, and the nitrogen content is nitrified to nitrate nitrogen, A part of the aerobically treated water containing nitrate nitrogen is returned to the anaerobic tank for biological denitrification under anaerobic conditions.

[0004]

However, in the above-described conventional treatment method, in order to remove dissolved oxygen and dissolved ozone contained in the oxidation treated water flowing out from the ozone contact tank, a reducing substance such as sodium sulfite is removed. However, there is a problem that the running cost is high. In addition, there is a problem that handling of powder such as sodium sulfite tends to be avoided by drivers.

The present invention solves the above problems, and an object of the present invention is to provide a COD / nitrogen removing method which can reduce the cost and can be easily implemented.

[0006]

In order to solve the above problems, the method for removing COD and nitrogen according to the present invention is to introduce raw water containing COD into an ozone contact tank and subject it to an ozone oxidation treatment. COD is used as a biodegradable organic substance or nitrate nitrogen, and this oxidation-treated water is introduced into an aerobic tank for biological treatment under aerobic conditions in which the dissolved oxygen supplied in the ozone contact tank exists. By oxidatively decomposing the biodegradable organic matter contained in the oxidatively treated water, the remaining nitrogen content is converted to nitrate nitrogen, and the aerobicly treated water is introduced into an anaerobic tank to perform biological treatment under anaerobic conditions. The characteristic treatment is to remove nitrate nitrogen and biodegradable organic matter contained in the aerobic treated water.

Further, the COD / nitrogen removal method of the present invention is
Characterized by performing biological treatment under aerobic conditions in the presence of dissolved oxygen supplied in an ozone contact tank while supplying an aeration amount of aeration that does not leave dissolved oxygen on the outflow side of the aerobic tank. And

Further, the COD / nitrogen removing method of the present invention is
It is characterized in that biological treatment under anaerobic conditions is carried out while adding methanol as a hydrogen donor based on the redox potential of the anaerobic treated water flowing out from the anaerobic tank.

[0009]

With the above structure, the oxidation-treated water flowing out of the ozone contact tank is biologically treated in the aerobic tank under aerobic conditions in which the dissolved oxygen supplied in the ozone contact tank exists. Since aerobic treated water containing no upper dissolved oxygen is supplied to the anaerobic tank, not only can dissolved oxygen be effectively used, but also anaerobic treatment can be performed without performing dissolved oxygen removal treatment.

Further, the biological treatment under aerobic conditions is carried out by supplying aeration air at an outflow side in the aerobic tank while supplying an aeration amount of dissolved oxygen that does not remain, whereby the aerobic conditions in the aerobic tank are increased. And the anaerobic conditions in the anaerobic tank are secured, and the biological treatment is favorably performed.

Further, since the biological treatment under anaerobic conditions is performed while adding methanol as a hydrogen donor based on the redox potential of the anaerobic treated water flowing out from the anaerobic tank, the biological treatment is good. To be done.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an explanatory view showing the overall configuration of a COD / nitrogen removing device of an embodiment in which the COD / nitrogen removing method of the present invention is performed. In FIG. 1, 1 is an ozone contact tank,
2 is an aerobic tank and 3 is an anaerobic tank, which are arranged in this order.

In the ozone contact tank 1, a raw water supply pipe 5 and an ozone supply pipe 6 led from an ozone generator outside the tank are connected to the bottom of the tank filled with the catalyst 4, and the raw water and the ozone are supplied from the bottom of the tank. Is supplied to raise the inside of the tank, and while the two are mixed, they are brought into contact with the catalyst 4 and the oxidation treated water is caused to flow out from the oxidation treated water supply pipe 7 at the upper part of the tank.

The aerobic tank 2 is filled with a porous material 8 such as ceramic inside the tank, and microorganisms mainly composed of nitrifying bacteria are attached to the porous material 8. An oxidation-treated water supply pipe 7 from the ozone contact tank 1 is connected to the bottom of the tank, and the oxidation-treated water supply pipe 8 supplies the oxidation-treated water from the bottom of the tank to raise the space between the porous materials 8. Further, the oxidized treated water is brought into contact with the nitrifying bacteria, and the aerobic treated water is caused to flow out from the aerobic treated water supply pipe 9 at the upper part of the tank. Aerobic tank 2
At the bottom of the tank, an air supply pipe 1 led from a blower outside the tank
0 is connected.

The anaerobic tank 3 is filled with a porous material 11 such as ceramic inside the tank, and microorganisms mainly composed of denitrifying bacteria are attached to the porous material 11. An aerobic treated water supply pipe 9 from the aerobic tank 2 is connected to the upper part of the tank, and the aerobic treated water is supplied from the upper part of the tank by the aerobic treated water supply pipe 9 to form a porous material 11 The aerobic treated water is brought into contact with the denitrifying bacteria while the space is lowered, and the anaerobic treated water is caused to flow out from the anaerobic treated water outflow pipe 12 at the bottom of the tank. Further, a methanol supply pipe 13 for adding methanol to the aerobic treated water is connected to the pipe line of the aerobic treated water supply pipe 9.

With the above structure, when raw water and ozone are supplied to the ozone contact tank 1, the raw water and ozone come into contact with the catalyst 4 while being mixed with each other while flowing from the bottom and rising in the tank, and COD in the raw water is reduced. Ozone oxidative decomposition to biodegradable organic matter and nitrate nitrogen. Then, the oxidized treated water that has been treated is sent to the aerobic tank 2 through the oxidized treated water supply pipe 7.

Oxidized water sent to the aerobic tank 2 flows in from the bottom of the tank together with aerated air supplied from the air supply pipe 10 as necessary, and in the presence of dissolved oxygen supplied in the ozone contact tank 1, While ascending between the porous materials 8, it is sufficiently contacted with nitrifying bacteria and biologically treated under aerobic conditions. Then, the biodegradable organic matter contained in the oxidized treated water is decomposed, and the aerobic treated water in which the remaining nitrogen content is converted to nitrate nitrogen is sent to the anaerobic tank 3. At this time, the air supply pipe 1
The aeration air supplied from 0 is controlled at the outflow side of the aerobic tank 2 to an aeration amount of, for example, 1 mg / l or less, preferably 0 mg / l, and is an aerobic treatment that does not substantially contain dissolved oxygen. Water flows out from the aerobic treated water supply pipe 9. Then, in the conduit from the aerobic treated water supply pipe 9 to the anaerobic tank 3, methanol as a hydrogen donor is added to the aerobic treated water from the methanol supply pipe 13. The added methanol has an oxidation-reduction potential of about − on the outflow side of the anaerobic tank 3.
The amount is controlled to 100 mV.

The aerobic treated water sent to the anaerobic tank 3 is sufficiently contained in the aerobic treated water while flowing in from the upper part of the tank and descending between the porous materials 11. Biological treatment is carried out under anaerobic conditions using organic matter and methanol as hydrogen donors, and nitrate nitrogen contained in aerobic treated water is removed as nitrogen gas and organic matter is decomposed. Anaerobic treated water flows from the bottom of the tank to the anaerobic treated water outlet pipe 12
Through, and subjected to the next processing.

As described above, by arranging the aerobic tank and the anaerobic tank in sequence downstream of the ozone contact tank, in the aerobic tank, the dissolved oxygen supplied in the ozone contact tank is effectively used to produce organisms. The biological treatment can be carried out, and a treatment for removing dissolved oxygen from the oxidation treated water flowing out from the ozone contact tank, such as adding sodium sulfite, becomes unnecessary. Further, at this time, since the aeration air is supplied in an amount insufficient for the dissolved oxygen supplied in the ozone contact tank and the aerobic treated water containing no dissolved oxygen is supplied to the anaerobic tank, Aerobic conditions and anaerobic conditions in the anaerobic tank are secured respectively. Also, based on the redox potential of the anaerobic treated water flowing out of the anaerobic tank, the amount of methanol that is insufficient for the organic matter contained in the water to be treated in the tank is added as a hydrogen donor. Is prevented.

[0020]

As described above, according to the present invention, an aerobic tank and an anaerobic tank are sequentially arranged downstream of the ozone contact tank, and the oxidized water flowing out from the ozone contact tank is treated with ozone in the aerobic tank. Biological treatment was performed under aerobic conditions in which dissolved oxygen was supplied in the contact tank, and aerobic treated water containing substantially no dissolved oxygen was supplied to the anaerobic tank. This allows
Not only can dissolved oxygen be utilized effectively, but anaerobic treatment can be performed without performing dissolved oxygen removal treatment. Therefore, the devices and reagents that were conventionally required to remove dissolved oxygen are not required, and for example, the use of nitrogen gas generators for aeration of nitrogen gas and reducing substances such as sodium sulfite is unnecessary. Cost can be reduced.

Further, biological treatment under aerobic conditions is performed by supplying aeration air in an amount insufficient for the dissolved oxygen supplied in the ozone contact tank to obtain aerobic treated water containing no dissolved oxygen. Since it is configured to supply anaerobic tank,
The aerobic condition in the aerobic tank and the anaerobic condition in the anaerobic tank are secured, and the biological treatment is favorably performed.

Further, the biological treatment under anaerobic conditions is insufficient with organic substances contained in the aerobic treated water sent from the aerobic tank based on the redox potential of the anaerobic treated water flowing out from the anaerobic tank. Since the configuration is performed by adding as much hydrogen as a hydrogen donor as a hydrogen donor, the processing flow can be completed by adding relatively inexpensive methanol, and the running cost can be reduced.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing the overall configuration of a COD / nitrogen removing device of one embodiment in which a COD / nitrogen removing method of the present invention is performed.

[Explanation of symbols] 1 ozone contact tank 2 aerobic tank 3 anaerobic tank 5 raw water supply pipe 6 ozone supply pipe 10 air supply pipe 13 methanol supply pipe

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI Technical indication location B01D 19/00 ZAB Z C02F 1/20 ZAB A 1/78 ZAB 3/30 ZAB Z (72) Invention Taichi Uesaka 1-47 Shikitsuhigashi 1-47, Naniwa-ku, Osaka-shi, Osaka

Claims (3)

[Claims] 1. COD in raw water is obtained by introducing raw water containing COD into an ozone contact tank and subjecting it to ozone oxidation treatment.
As a biodegradable organic substance or nitrate nitrogen, and introducing this oxidation-treated water into an aerobic tank for biological treatment under aerobic conditions in which the dissolved oxygen supplied in the ozone contact tank exists. The oxidative decomposition of the biodegradable organic matter contained in the oxidatively treated water causes the residual nitrogen content to become nitrate nitrogen, and this aerobicly treated water is introduced into an anaerobic tank to allow biological treatment under anaerobic conditions. The method for removing COD / nitrogen, which comprises removing nitrate nitrogen and biodegradable organic matter contained in the aerobic treated water by treating the COD and nitrogen. 2. Biological treatment under aerobic conditions,
2. The COD / nitrogen removing method according to claim 1, wherein the COD / nitrogen removal is carried out in the presence of dissolved oxygen supplied in the ozone contact tank while supplying aeration air at an outflow side in the aerobic tank in which the dissolved oxygen does not remain. . 3. Biological treatment under anaerobic conditions,
The COD / nitrogen removal method according to claim 1, wherein the method is performed while adding methanol as a hydrogen donor based on the redox potential of the anaerobic treated water flowing out from the anaerobic tank.