JPH07214092A - COD / nitrogen removal method - Google Patents

Abstract

(57) [Abstract] [Purpose] In a COD / nitrogen removal method in which raw water containing COD is sequentially introduced into an ozone contact tank and an anaerobic filter bed, the object to be treated is supplied from the ozone contact tank to the anaerobic filter bed. Dissolved oxygen contained in water is removed at low cost to ensure anaerobic conditions in anaerobic filter beds. [Structure] Oxidized water 6 flowing out from the ozone contact tank 2 is introduced into the dissolved oxygen removing tank 3 and aeration of the nitrogen gas 7 is carried out, whereby dissolved oxygen contained in the oxidized water 6 is completely removed.

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. Then, this anaerobic treated water is sent to an aerobic tank and biologically treated under aerobic conditions to decompose the remaining biodegradable organic matter and nitrify the nitrogen content into nitrate nitrogen, and A portion of the aerobically treated water containing nitrate nitrogen is returned to the anaerobic tank for biological denitrification under anaerobic conditions.

[0004]

However, in the conventional processing method described above, PSA (Pressure Swing Ad
When ozone is supplied by using a sorption type ozone generator, the dissolved oxygen concentration of the oxidation treated water flowing out from the ozone contact tank becomes as high as 20 to 30 mg / l. Therefore, when anaerobic treatment is performed in the latter stage, a reducing substance such as sodium sulfite is added in an amount of 400 to 500 mg / l in order to remove dissolved oxygen.
Therefore, there is a problem that the chemical cost becomes high.

The present invention solves the above problems, and an object thereof is to provide a COD / nitrogen removing method capable of removing dissolved oxygen at low cost.

[0006]

In order to solve the above problems, the COD / nitrogen removing method of the first structure of the present invention is
In a COD / nitrogen removal method in which raw water containing OD is introduced into an ozone contact tank for ozone oxidation treatment, and the oxidized water is introduced into an anaerobic filter bed and biologically treated under anaerobic conditions. The oxidation-treated water flowing out of the tank is introduced into a dissolved oxygen removal tank and aerated with nitrogen gas, and the dissolved oxygen contained in the oxidation-treated water is completely removed before being introduced into the anaerobic filter bed.

In the COD / nitrogen removing method of the second aspect of the present invention, raw water containing COD is introduced into an ozone contact tank for ozone oxidation treatment, and the oxidized water is introduced into an anaerobic filter bed. In the COD / nitrogen removal method of biologically treating under anaerobic conditions, the oxidation treated water flowing out from the ozone contact tank is introduced into the dissolved oxygen removal tank and aerated, and then a reducing agent is added to perform oxidation. The feature is that the dissolved oxygen contained in the treated water is completely removed and then introduced into the anaerobic filter bed.

[0008]

According to the first construction, the oxidized water flowing out of the ozone contact tank is supplied to the anaerobic filter bed after the dissolved oxygen is completely removed by the nitrogen gas aeration in the dissolved oxygen removing tank. Therefore, the anaerobic condition in the anaerobic filter bed is secured, and the biological treatment is favorably performed.

According to the second construction, the oxidized water flowing out of the ozone contact tank is reduced in dissolved oxygen by aeration of air in the dissolved oxygen removing tank, and then dissolved oxygen is completely removed by adding a reducing agent. After that, the anaerobic filter is supplied to the anaerobic filter bed, so that the anaerobic condition in the anaerobic filter bed is secured and the biological treatment is favorably performed.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a flow chart for explaining a COD / nitrogen removal method according to an embodiment of the present invention. As shown in the figure, raw water 1 is sequentially supplied with an ozone contact tank 2, a dissolved oxygen removal tank 3, an anaerobic filter bed 4, and an anaerobic filter bed. It is supplied to the temper filter bed 5.

The ozone contact tank 2 supplies the raw water 1 from the bottom of the tank filled with the catalyst to raise the inside of the tank.
During this period, the raw water 1 is mixed with ozone supplied from a PSA-type ozone generator or the like, and the ozone-oxidized water 6 is allowed to flow out from the upper part of the tank.

The dissolved oxygen removing tank 3 is provided with an aeration device for aerating the aeration gas 7 which is air or nitrogen gas and a reducing agent injection device for injecting the reducing agent 8 at the bottom of the tank. While the sent ozone oxidation treated water 6 is introduced from the upper part of the tank and lowered, the aeration gas 7 is aerated to the oxidation treated water 6 and the reducing agent 8 is injected as necessary to remove dissolved oxygen. The water 9 is configured to flow out from the bottom of the tank.

The anaerobic filter bed 3 is obtained by filling the inside of a tank with a porous material to which microorganisms mainly composed of denitrifying bacteria are adhered, and the dissolved oxygen removing treated water 9 supplied from the dissolved oxygen removing tank 3 is supplied. Is brought into contact with denitrifying bacteria while passing between the porous materials, and the denitrification treated water 10 is caused to flow out.

The aerobic filter bed 5 is filled with a porous material having microorganisms mainly composed of nitrifying bacteria attached to the inside of the tank and is provided with an air diffuser for supplying an oxygen-containing gas such as air. , Denitrification treated water 1 supplied from anaerobic filter bed 4
While passing 0 between the porous materials, the nitrifying bacteria are brought into contact with the nitrifying bacteria in a state where the oxygen-containing gas is supplied, and the nitrification-treated water 11 is caused to flow out.

In the above structure, when the raw water 1 is supplied to the ozone contact tank 2, the raw water 1 flows in from the bottom and is mixed with ozone while being in contact with the catalyst, and COD in the raw water 1 is biodegradable organic matter or nitric acid. Ozone is oxidatively decomposed into nitrogen.
Then, the ozone-oxidized water 6 containing the biodegradable organic matter and nitrate nitrogen is sent to the dissolved oxygen removing tank 3.

The ozone-oxidized water 6 is aerated by the nitrogen gas supplied from the aeration device 7 while flowing in from the upper part of the dissolved oxygen removing tank 3 and descending in the tank, and dissolved in the ozone-oxidized water 6 is dissolved. Oxygen is almost completely removed. Then, the dissolved oxygen-removed water 9 from which dissolved oxygen has been removed is sent to the anaerobic filter bed 4 from the bottom of the tank. As the nitrogen gas at this time, the exhaust gas of the PSA ozone generator used in the ozone contact tank or the nitrogen gas generated by the nitrogen generating PSA device is used. In this way, the dissolved oxygen is almost completely removed without using a reducing agent, so that the running cost for removing the dissolved oxygen is reduced to almost zero.

The dissolved oxygen-removed treated water 9 sent to the anaerobic filter bed comes into sufficient contact with the denitrifying bacteria while passing between the porous materials in the tank, so that the dissolved oxygen-removed treated water 9 is The biodegradable organic matter and nitrate nitrogen contained are biologically decomposed and removed in a state where dissolved oxygen is removed and anaerobic conditions are secured, and biologically treated denitrification water 1
0 is sent to the aerobic filter bed 5.

Then, the denitrification treated water 10 sent to the aerobic filter bed 5 is sufficiently brought into contact with the nitrifying bacteria while flowing in together with the oxygen-containing gas and passing between the porous materials, so that the denitrification treated water 10 The biodegradable organic matter remaining therein is biologically degraded under aerobic conditions. Nitrification treated water after biological treatment 11
Is sent to the processing of the next system.

In the dissolved oxygen removing tank 3 as described above, the ozone oxidation treated water 6 may be aerated with air 7 instead of the nitrogen gas 7 being aerated. In this case, the dissolved oxygen contained in the ozone oxidation treated water 6 at a time of flowing into the dissolved oxygen removing tank 3 is reduced to 6 to 7 mg / l by air aeration,
After that, from the reducing agent injection device, sodium sulfite (Na ₂ S
A reducing agent 8 such as O ₃ ) is injected to completely remove dissolved oxygen and peroxides such as MnO ₄ ^{2− in} the ozone oxidation treated water 6. By adding the reducing agent 8 after reducing the dissolved oxygen by the aerated air 7, the amount of the reducing agent 8 used for removing the dissolved oxygen can be reduced to about 1/3 and the running cost can be reduced.

As shown in FIG. 2, the dissolved oxygen removing tank 3 may be of a two-tank type in which the air 7 is aerated in the upstream tank 3a and the reducing agent 8 is injected in the downstream tank 3b. As in the embodiment shown in FIG. 1, the dissolved oxygen contained in the ozone-oxidized water 6 can be completely removed, and the anaerobic conditions in the anaerobic filter bed 4 can be secured while reducing the running cost. Can be biologically processed.

[0021]

As described above, according to the present invention, the oxidized water flowing out of the ozone contact tank is introduced into the dissolved oxygen removing tank and aerated with nitrogen gas to completely remove the dissolved oxygen contained in the oxidized water. Since it is configured to be supplied to the anaerobic filter bed after being removed to the anaerobic filter bed, dissolved oxygen can be removed without using a reducing agent, and anaerobic conditions in the anaerobic filter bed can be secured. Processing can be performed.

In addition, the oxidation-treated water flowing out from the ozone contact tank is introduced into the dissolved oxygen removal tank, the dissolved oxygen contained in this oxidation-treated water is reduced by aeration with air, and then the remaining dissolved oxygen and peroxide are reduced. Since it is configured to be completely removed by the agent and supplied to the anaerobic filter bed, the anaerobic conditions in the anaerobic filter bed can be secured while reducing the amount of the reducing agent used,
In this case as well, the biological treatment can be favorably performed while reducing the cost.

[Brief description of drawings]

FIG. 1 is a flowchart illustrating an embodiment of a COD / nitrogen removal method of the present invention.

FIG. 2 is a flowchart showing a modified embodiment of the COD / nitrogen removal method of FIG.

[Explanation of symbols]

 1 Raw water 2 Ozone contact tank 3 Dissolved oxygen removal tank 4 Anaerobic filter bed 5 Aerobic filter bed 6 Oxidized water 7 Nitrogen gas / air 8 Reducing agent

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI Technical display location B01D 19/00 ZAB Z C02F 1/20 ZAB A 1/58 ZAB T 1/70 ZAB Z 1/78 ZAB 3/28 ZAB Z (72) Inventor Taichi Uesaka 1-247 Shikitsu Higashizu, Naniwa-ku, Osaka City, Osaka Prefecture Kubota Corporation

Claims (2)

[Claims] 1. COD / nitrogen removal in which raw water containing COD is introduced into an ozone contact tank for ozone oxidation treatment, and this oxidized water is introduced into an anaerobic filter to biologically treat under anaerobic conditions. In the method, the oxidation-treated water flowing out from the ozone contact tank is introduced into the dissolved oxygen removal tank to be aerated with nitrogen gas, and the dissolved oxygen contained in the oxidation-treated water is completely removed before being introduced into the anaerobic filter bed. Characteristic COD / nitrogen removal method. 2. COD / nitrogen removal in which raw water containing COD is introduced into an ozone contact tank for ozone oxidation treatment, and this oxidized water is introduced into an anaerobic filter to biologically treat under anaerobic conditions. In the method, the oxidized water flowing out from the ozone contact tank is introduced into the dissolved oxygen removal tank and aerated with air, and then a reducing agent is added to completely remove the dissolved oxygen contained in the oxidized water and then anaerobic. A method for removing COD and nitrogen, which is characterized in that the COD is introduced into a filter bed.