JPH09174066A - Method for treating hydrazine-containing wastewater - Google Patents

Abstract

PROBLEM TO BE SOLVED: To decompose hydrazine and harmful oxidizing agents reliably within a short time by adding either an oxidizing agent or a catalyst to a hydrazine- containing wastewater and dispersing and adding the oxidizing agent or the catalyst to a plurality of places in a reaction tank. SOLUTION: In order to add a catalyst, an oxidizing agent, and an alkali to a prescribed quantity of hydrazine-containing wastewater supplied to a reaction tank 1 through a flow line 4 for supplying water to be treated, a flow line 7 for supplying a copper sulfate solution, which is a catalyst, a flow line 8 for supplying an aqueous hydrogen peroxide solution, which is an oxidizing agent, and a flow line 9 for supplying a sodium hydroxide solution, which is an alkali for pH adjustment are installed at proper spaces each other while the respective lines being branched into a plurality of lines and addition inlets of the lines being positioned above the surface of the water to be treated in the reaction tank 1 and above an aeration means for partial aeration. The respective lines are connected with storage tanks for chemicals, which are the oxidizing agent, the catalyst, etc., and respective chemicals are supplied by respectively pumps. Consequently, hydrazine and harmful oxidizing agents can be decomposed reliably within a short time.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for oxidizing and treating hydrazine in wastewater containing hydrazine.

[0002]

2. Description of the Related Art Conventionally, in a thermal power plant or the like, when the operation is suspended for the periodic inspection and maintenance of the boiler,
To prevent rust from forming inside the equipment such as the boiler, fill the inside of the equipment such as the boiler with water containing hydrazine, which is a reducing agent, as an anticorrosion agent, and hold it. When restarting, the hydrazine-containing water is discharged.

Since the discharged hydrazine-containing waste water is a reducing substance and has a relatively high concentration of hydrazine serving as a COD source, it is discharged after oxidative decomposition of hydrazine.

As one of conventional treatment methods for hydrazine-containing wastewater, a treatment method is used in which at least one of an oxidant and a catalyst is added to the wastewater to aerate the air to oxidize and decompose hydrazine. Chlorine, hypochlorite, hydrogen peroxide solution, etc. are used, and as the catalyst, a solution of a copper compound, a manganese compound, or a catalyst layer of a noble metal carrier is mainly used.

[0005]

In the conventional method for treating hydrazine-containing wastewater, the oxidizing agent or the catalyst is added by a method of supplying it to one point in the reaction tank.
It is difficult to uniformly diffuse into the entire reaction tank, the oxidative decomposition reaction of hydrazine is delayed, and unreacted oxidizing agent and hydrazine are easily discharged.

Further, even in air aeration, in the past, since the entire surface of the reaction tank was always aerated, when an oxidizing agent or a catalyst was added, they were likely to stay in the feeding place, and in combination with the above-mentioned one-point feeding method, hydrazine was further added. The oxidative decomposition reaction slows down.

In view of the above circumstances, the present invention allows the oxidizing agent and the catalyst to diffuse into the entire reaction vessel as quickly as possible, so that the oxidative decomposition reaction of hydrazine is promptly performed, and at the same time, the hydrazine serving as the COD source and the harmful oxidizing agent are removed. The purpose of the present invention is to provide a method capable of reliably decomposing in a short time and reducing the amount of the chemical used.

[0008]

Means for Solving the Problems The gist of the present invention for achieving the above object is that in claim 1, at least one of an oxidizing agent and a catalyst is added to hydrazine-containing wastewater,
In the treatment method of oxidatively decomposing hydrazine by aerating with air, the treatment method of hydrazine-containing wastewater is characterized in that an oxidizing agent and / or a catalyst is dispersedly added to a plurality of locations in a reaction tank.

According to a second aspect of the present invention, in the treatment method, a swirl flow is generated by partial aeration at the addition site when the oxidizing agent and / or the catalyst is added, and the entire inside of the reaction tank is aerated when not added. Is a method for treating hydrazine-containing wastewater.

[0010]

[Operation] At least one of an oxidant and a catalyst is supplied from a plurality of places in the reaction tank to the hydrazine-containing wastewater supplied into the reaction tank, and at the addition place, partial aeration is performed to generate a swirling flow, thereby adding The oxidant and the catalyst diffused rapidly throughout the reaction layer.

In the above, it is preferable to supply both the oxidizing agent and the catalyst at the same time so that the hydrazine can be decomposed in a short time and reliably, but depending on the properties of the water to be treated,
Only one of the oxidant and the catalyst may be added, and an alkali such as sodium hydroxide is usually added to control the pH to 9 to 11, but not limited thereto.

As the oxidizer, hydrogen peroxide solution, chlorine, hypochlorite, etc. are used. However, hydrogen peroxide solution is used because of the ease of handling and the control of the addition amount required for the reaction. It is preferably used, and the addition amount thereof is preferably 0.5 to 1.0 molar ratio with respect to the amount of hydrazine contained.

As the catalyst, a solution of a copper compound, a manganese compound or the like or a catalyst layer using a noble metal carrier is used, but it is preferable to use the copper compound in view of reaction rate, price or easiness of aftertreatment. Among the compounds, it is more preferable to use copper sulfate. The addition amount is 0.
2 to 2.0 mg Cu / l is suitable, but 0.5 to 1.0 mg Cu / l is preferable.

The supply of the oxidant and the catalyst is stopped, and the inside of the reaction tank is entirely aerated, so that the oxidative decomposition reaction of hydrazine is performed in the entire reaction layer, and after a predetermined time elapses, the aeration is stopped and the reaction is completed. Treated water is discharged from the tank.

In the above, PH and C in the reaction tank are
The OD is automatically measured at any time, and the amounts of the oxidizing agent, the catalyst, the alkali, etc. are appropriately controlled and supplied based on the measured values.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a system diagram of a treatment apparatus used in a treatment method for hydrazine-containing wastewater according to an embodiment of the present invention, FIG.
FIG. 4 is a schematic plan view of a reaction tank section.

1, an upper end surface is opened, an upper part is connected with a supply flow path 4 for water to be treated which is hydrazine-containing waste water, a lower part is connected with a discharge flow path 10 for treated water after treatment, and air is supplied to an inner bottom part. This is a reaction tank provided with an air diffuser 2 for aerating substantially the entire bottom surface and an air diffuser 3 for partial aeration.

Further, in order to add a catalyst, an oxidizing agent and an alkali to the water to be treated in the reaction tank 1, a supplying passage 7 for a copper sulfate solution as a catalyst and a supplying passage for a hydrogen peroxide solution as an oxidizing agent. 8 and a supply channel 16 of a sodium hydroxide solution which is an alkali for pH adjustment are branched into a plurality of reactors, respectively.
The addition ports are located on the surface of the water to be treated and substantially above the aeration means 3 for partial aeration, and are arranged at appropriate intervals.

The copper sulfate solution supply passage 7, the hydrogen peroxide solution supply passage 8 and the sodium hydroxide solution supply passage 9 are respectively provided from the chemical storage tanks 14, 15, 16 respectively. It is connected to be supplied by pumps 11, 12, and 13.

The operation of the hydrazine-containing wastewater treatment apparatus having the above-mentioned structure will be described below. A copper sulfate solution as a catalyst is added from the storage tank 14 to the hydrazine-containing wastewater, which is supplied in a predetermined amount from the supply passage 4 of the water to be treated, into the reaction tank 1 via the supply passage 7 by the pump 11. Further, hydrogen peroxide solution which is an oxidant is added from the storage tank 15 via the supply channel 8 by the pump 12, and the sodium hydroxide solution for pH adjustment is further supplied from the storage tank 16 via the supply channel 9 by the pump 13. Is supplied at multiple points and is partially aerated by the air diffusing means 3 via the air supply flow path 6, whereby a swirling flow is generated, and the added oxidizing agent, catalyst and alkali are rapidly diffused throughout the reaction tank. It

In the above description, both the oxidizing agent and the catalyst are supplied at the same time. However, depending on the property of the water to be treated, only one of the oxidizing agent and the catalyst may be added,
In addition, alkali such as sodium hydroxide may not be added depending on the properties.

Although hydrogen peroxide solution is used as the oxidizing agent, chlorine or hypochlorite may be used. Further, copper sulfate is used as a catalyst, but other copper compounds or manganese compounds may be used. .

The pH in the above operation is preferably controlled to 9 to 11 from the viewpoint of reaction efficiency, and the addition amount of copper sulfate is suitably 0.2 to 2.0 mg Cu / l, but preferably 0. 5 to 1.0 mg Cu / l, and the addition amount of hydrogen peroxide water is 0.5 to 0.5 with respect to the amount of hydrazine contained.
It is 1.0 molar ratio.

The supply of the oxidant and the catalyst is stopped, and the air is supplied from the air diffusing means 2 to the substantially entire bottom surface of the reaction tank 1 through the air supply flow path 5, and the entire surface is aerated to oxidize and decompose hydrazine. The reaction is carried out in the entire reaction tank 1, and after a lapse of a predetermined time, air aeration is stopped and the treated water is discharged from the reaction tank 1 through the treated water discharge passage 10.

In the above, PH and C in the reaction tank are
The OD is automatically measured at any time by a measuring device and a control device (not shown), and the added amounts of the oxidizing agent, the catalyst and the alkali are appropriately controlled and supplied based on the measured values.

[0026]

[Examples] Examples in which hydrazine-containing wastewater discharged from a thermal power plant was treated using the treatment method according to one embodiment of the present invention and a single supply flow path for each of an oxidant, a catalyst and an alkali A comparative example in which the gas is added from above and aeration is carried out over the entire surface in the reaction tank will be described. The properties of the drainage used are
COD: 50 mg / l, hydrazine: 120 mg / l,
It was PH: 9.5.

In the examples, hydrogen peroxide solution: 500 mg /
1, copper sulfate: 0.5 mg / l, sodium hydroxide: 24
As a result of treatment by adding 0 mg / l, PH:
10.2, COD: 22 mg / l, hydrazine: 53 m
g / l, PH: 10.2 after 60 minutes, COD: 8 mg
/ L, hydrazine: 13 mg / l.

In the comparative example, hydrogen peroxide solution: 700 mg /
1, copper sulfate: 1.0 mg / l, sodium hydroxide: 24
As a result of treatment by adding 0 mg / l, PH:
10.2, COD: 33 mg / l, hydrazine: 74 m
g / l, PH: 10.2 after 60 minutes, COD: 18 m
g / l, hydrazine: 37 mg / l.

As described above, in the present invention and the conventional method, the method of the present invention can oxidize and decompose hydrazine in a shorter time,
It can also be seen that the amount of chemicals such as oxidizer and catalyst can be reduced.

[0030]

INDUSTRIAL APPLICABILITY In the method for treating hydrazine-containing wastewater of the present invention, the oxidizing agent and the catalyst diffuse into the entire reaction tank as quickly as possible, and the oxidative decomposition reaction of hydrazine is carried out quickly, and at the same time, hydrazine serving as a COD source is obtained. The harmful oxidant can be decomposed surely in a short time, and the amount of the chemicals used can be reduced.

[Brief description of the drawings]

FIG. 1 is a system diagram of a processing device used in a processing method according to an embodiment of the present invention.

FIG. 2 is a schematic plan view of a reaction tank portion used in the processing method according to the embodiment of the present invention.

[Explanation of symbols]

 1: Reaction tank 2: Aeration means for full aeration 3: Diffusion means for partial aeration 4: Supply passage 4 for treated water 5: Air supply passage for full aeration 6: Air supply passage for partial aeration 7: Copper sulfate solution supply flow path 8: Hydrogen peroxide water supply flow path 9: Sodium hydroxide solution supply flow path 10: Treated water discharge flow path 11, 12, 13: Pump 14, 15, 16: Storage tank

Claims (2)

[Claims] 1. A treatment method in which at least one of an oxidant and a catalyst is added to hydrazine-containing wastewater and aerating with air to oxidatively decompose hydrazine, the oxidant and / or the catalyst are dispersed and added to a plurality of locations in a reaction tank. A method for treating hydrazine-containing wastewater, comprising: 2. A treatment method in which at least one of an oxidant and a catalyst is added to hydrazine-containing wastewater, and aeration is performed by air to oxidize and decompose hydrazine, and when the oxidant or / and the catalyst is added, partial aeration at the addition place is performed. 2. The method for treating hydrazine-containing wastewater according to claim 1, wherein the inside of the reaction tank is fully aerated when a flow is generated and is not added.