JP2000167570A - Treatment of waste water - Google Patents

Abstract

PROBLEM TO BE SOLVED: To economically and efficiently treat waste water containing ammonium nitrate. SOLUTION: Ammonia nitrogen in waste water is removed to adjust not only a ratio of ammonia nitrogen and nitrate nitrogen in waste water to 0< ammonia nitrogen/nitrate nitrogen <1 (molar ratio) but also the pH of waste water to 0-5. Next, a reducing agent is added to treated waste water to bring this treated waste water into contact with a solid catalyst at 80-370 deg.C under pressure holding waste water to a liquid phase to perform wet decomposition. Further, the treated water is brought into contact with a solid catalyst at 80-370 deg.C under pressure holding waste water to a liquid phase while an oxygen- containing gas is supplied in an amt. corresponding to 1-5 times a theoretical oxygen amt. necessary for decomposing a nitrogen compd., an org. substance and an inorg. substance in waste water into water and ash to be subjected to wet oxidative decomposition.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for treating wastewater, and more particularly, to a method for treating wastewater for efficiently purifying wastewater containing ammonium nitrate.

[0002]

2. Description of the Related Art It has been a long time since eutrophication caused red tides and musty odors in sea areas, lakes, marshes, and rivers. Nitrogen compounds contained in wastewater containing wastewater and industrial wastewater are one of the causes. Therefore, there is an urgent need to reduce nitrogen compounds in wastewater and the environment.

There are many methods for treating wastewater containing ammonium nitrate as a nitrogen compound. In particular, various improved methods have been proposed for removing nitrate nitrogen at a high decomposition rate. For example, Japanese Patent Application Laid-Open No. 4-61987 discloses that an organic substance is added to wastewater containing ammonium nitrate, and an acid or an acid-generating substance is added in an amount corresponding to the total mole number of ions of alkali metals such as sodium and potassium in the wastewater. And a pH of about 1 to 1 in the presence of a supported catalyst and in the absence of oxygen.
11.5, after wet pyrolysis at a temperature of 100 to 370 ° C,
A method is described in which wet oxidative decomposition is carried out in the presence of a supported catalyst and in the presence of a gas containing 1 to 1.5 times the required theoretical oxygen amount of oxygen. According to the above method, when the ammonium nitrate-containing wastewater further contains an alkali metal ion,
It is said that the decomposition rate of the total nitrogen component is slightly reduced, but the decomposition ratio of the total nitrogen component can be improved by adding an acid. Also,
Examples of the acid include sulfuric acid, hydrochloric acid, and nitric acid. Among these acids, sulfuric acid is considered to be particularly preferable.

[0004]

In the above-mentioned conventional method, an acid or an acid-generating substance is added to waste water, but this does not significantly increase the efficiency of the treatment. Therefore, processing conditions require a high temperature of about 250 ° C. or a high pressure at which water does not boil even at such a high temperature, and the apparatus tends to be expensive. Therefore, development of a method capable of processing under milder conditions has been desired.

[0005] The addition of acids and acid-generating substances to wastewater has the following problems.

When sulfuric acid is used as the acid and the wastewater is made acidic, it is necessary to cope with the corrosion of the device, which further increases the cost of the device. In addition, thiourea, thiosulfuric acid and the like are exemplified as acid generating substances, but when these are added to wastewater, sulfuric acid is generated by the treatment according to the above-described conventional method, and therefore, there is a problem similar to the addition of sulfuric acid. Was.

When hydrochloric acid is used as an acid, it is necessary to cope with the corrosion of the apparatus without making the wastewater acidic.
Equipment costs have been further increased.

When nitric acid is added as an acid, the size of the apparatus is increased due to an increase in nitrate nitrogen to be subjected to a decomposition treatment. Also, drug costs have increased.

An object of the present invention is to solve the above-mentioned problems of the conventional method and to provide a method for economically and efficiently treating wastewater containing ammonium nitrate.

[0010]

Means for Solving the Problems As a result of diligent research, the present inventors have found that ammonium nitrate-containing wastewater is adjusted to pH 0 to 5 and a reducing agent is added thereto to perform wet decomposition, whereby nitrate nitrogen can be efficiently removed. In order to realize the conditions, instead of using a chemical such as sulfuric acid, the ammonium nitrogen in the wastewater containing ammonium nitrate is removed, and the concentrations of the ammonium nitrogen and the nitrate nitrogen in the wastewater are reduced to 0 <ammonia nitrogen / Nitrate nitrogen <1 and pH 0-5
Has been found to be an economically advantageous and efficient method. The present invention has been completed based on such findings.

That is, the present invention relates to a method for treating wastewater containing ammonium nitrate, which comprises the following first and second steps.

<First step> The ammonia nitrogen in the waste water is removed, and the ammonia nitrogen and the nitrate nitrogen in the waste water are set to 0 <ammonia nitrogen / nitrate nitrogen <1 (molar ratio), and the waste water is discharged. Adjust the pH to 0-5.

<Second Step> A reducing agent is added to the treated wastewater from the first step, and the treated wastewater is brought into contact with a solid catalyst at a temperature of 80 to 370 ° C. and at a pressure at which the wastewater retains a liquid phase to perform wet decomposition.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The wastewater containing ammonium nitrate to be treated in the present invention means all wastewater containing ammonium nitrate, and may contain an organic substance and an inorganic substance in addition to ammonium nitrate. Specifically, for example, industrial wastewater containing ammonium nitrate from a thermal power plant, a nuclear power plant, a chemical plant, a metal industrial facility, a metal mining facility, a pharmaceutical manufacturing facility, and the like can be mentioned. The present invention provides at least nitrate nitrogen (NO ₃ −) in such waste water containing ammonium nitrate.
N) and ammonia nitrogen (NH ₃ -N) is removed is to purify the waste water. The concentration of ammonium nitrate in the ammonium nitrate-containing wastewater is not particularly limited, and is usually 50 to 300,000 mg / liter (hereinafter, referred to as L). In particular, the method of the present invention is suitably used for treating wastewater having an ammonium nitrate concentration of 500 to 100,000 mg / L.

Hereinafter, the present invention will be described in detail in the order of the first, second and third steps.

<First Step> In the first step, ammonia nitrogen is removed, and the concentration of ammonia nitrogen and nitrate nitrogen in the waste water is 0 <ammonia nitrogen / nitrate nitrogen <1 (molar ratio). And the pH of the waste water is adjusted to 0 to 5, preferably 0.2 to 2.5, more preferably 0.5 to 2.

When the wastewater contains an organic nitrogen compound such as an amine compound or an amide compound in addition to ammonium nitrate, the total amount including ammonia nitrogen and nitrate nitrogen generated by decomposition of the organic nitrogen compound is included. About 0 <ammonia nitrogen / nitrate nitrogen <1
(Molar ratio).

A typical method for carrying out the first step includes the following.

(1) Catalytic wet cracking method The wastewater is treated at 80 to 370 ° C, preferably at 120 to 280 ° C.
More preferably, the wastewater is brought into contact with a solid catalyst at a temperature of 150 to 180 ° C. and a pressure at which the wastewater maintains a liquid phase at the temperature to remove ammonia nitrogen.

The solid catalyst is not particularly limited as long as it can decompose at least ammonium ions (or ammonia) in the ammonium nitrate-containing wastewater.
A solid catalyst generally used for decomposing ammonium ions (or ammonia) can be used. For example, manganese, cobalt, nickel, copper, cerium,
Examples include those containing at least one selected from silver, platinum, palladium, rhodium, gold, iridium and ruthenium. The content of these metal components is
Usually, it is 0.05 to 25% by weight of the solid catalyst. In addition to the above metals, those containing at least one selected from titanium, zirconium, aluminum, silicon, iron and activated carbon are preferably used. The shape is not particularly limited, and may be appropriately selected, such as a pellet, a granule, a ring, and a honeycomb. One type of solid catalyst may be used, but two or more types may be used in combination.

In contacting the waste water with the solid catalyst, an oxygen-containing gas may or may not be supplied. However, by supplying the oxygen-containing gas, the ammonium nitrate-containing wastewater can be efficiently adjusted to 0 <ammonia nitrogen / nitrate nitrogen <1 (molar ratio) and pH 0 to 5. The supply amount of the oxygen-containing gas may be appropriately selected so that the ammonia nitrogen / nitrate nitrogen (molar ratio) and the pH can be adjusted within the above ranges. The oxygen-containing gas according to the present invention is not particularly limited as long as it is a gas containing oxygen gas, but air, an oxygen-enriched gas, an oxygen gas,
Exhaust gas from various plants can be exemplified. Above all, air is generally used. Also,
If necessary, a hydrogen peroxide solution or the like may be added as an oxidation aid.

There is no particular limitation on the supply speed of the waste water, and the space velocity (LHSV) for the solid catalyst is usually set at 0.
It is 5 to 20 hr ^-1 , preferably ¹ to 10 hr ^-1 . (2) Oxidation method (except for oxygen and nitrate) An oxidizing agent such as ozone and hydrogen peroxide is added to oxidize and remove ammonia nitrogen. At this time, irradiation with ultraviolet rays accelerates the processing reaction.

(3) Photo-oxidation method Ammonia nitrogen is oxidized and removed using a photocatalyst.

(4) Separation method Ammonium ions are removed by ion exchange resin or electrodialysis.

Of the above, the method (1) is preferably used. In the case of the method (1), it can be carried out efficiently under relatively mild conditions, in particular, at a temperature of 120 to 280 ° C., more preferably 150 to 180 ° C., and under a pressure sufficient to maintain a liquid phase at this temperature. . For this reason, even if a unique device is provided for performing the first step, a compact device made of generally used inexpensive materials can be obtained. In addition, the first step and the second step, or the first step and the second and third steps can be performed in the same reaction column (this will be described in detail later). In these cases, the construction cost of the device required to carry out the present invention can be reduced. <Second step> In the second step, the treated wastewater from the first step is solidified in the presence of a reducing agent at pH 0 to 5, at a temperature of 80 to 370 ° C, and at a pressure at which the treated wastewater retains a liquid phase. Contact with catalyst. By the treatment in the second step, nitrate groups in the treated wastewater from the first step can be decomposed with a high decomposition rate.

The above reducing agent means one having the ability to reduce nitrate nitrogen by depriving oxygen atoms from nitrate. Representative examples include hydrogen, sulfite, and water-soluble organic compounds. Among them, a water-soluble organic compound is preferably used. Representative examples of the water-soluble organic compound include alcohols such as methanol, ethanol, and propanol; aldehydes such as formaldehyde, acetaldehyde and propylaldehyde; and ketones such as acetone. Among them, alcohols and formaldehydes, particularly methanol, are preferably used. These reducing agents may be used alone or in combination of two or more.
Further, wastewater containing these reducing agents may be used.

The reducing agent has the following reducing agent / oxidizing agent ratio of 0.8 to 5, preferably 1 to 3, more preferably 1.0.
Add so as to be 5 to 2. If the reducing agent / oxidizing agent ratio is less than 0.8, nitrate nitrogen cannot be sufficiently removed. Further, even if the reducing agent is added until the ratio of the reducing agent / oxidizing agent exceeds 5, the removal rate of nitrate nitrogen and the processing speed are not improved correspondingly, and an extra reducing agent is added. Therefore, it is not economical and the load related to the treatment of the reducing agent in the next step increases, which is not preferable.

Reducing agent / oxidizing agent ratio = (total of gram equivalents of reducing agent present in treated wastewater per unit volume + total of gram equivalents of reducing agent added to treated wastewater per unit volume) /
(Total of gram equivalents of oxidizing agent present in treated wastewater per unit volume) Here, the total of gram equivalents of reducing agent present in treated wastewater per unit volume refers to the reducing agent added in the second step. Other than the above, substances capable of reducing nitrate nitrogen contained in the treated wastewater from the first step, specifically, ammonium ions (or ammonia) remaining without being decomposed in the first step, organic or inorganic COD It means the sum of gram equivalent numbers of components and the like. On the other hand, the total of the gram equivalent number of the oxidizing agent is the gram equivalent number of the nitrate group when the substance acting as the oxidizing agent in the wastewater is substantially only the nitrate group.

The gram equivalent number is obtained by the following equation.

Gram equivalent number = (weight (g) of the substance)
/ (1 gram equivalent of the substance (g)) Here, 1 gram equivalent means the weight (g) per 1 mol of the substance, and when the substance is a reducing agent, the reducing agent is released during the reaction. In the case of an oxidizing agent, it is divided by the number of moles of electrons received by the oxidizing agent during the reaction. Specifically, ammonium ions (NH
₄ ⁺ ), methanol (CH ₃ OH) and nitrate (N
O ₃ ⁻ ) is described as an example as follows.

(1) Ammonium ion Since the pH of the treated wastewater is from 0 to 5, almost all of the ammonia nitrogen is present as ammonium ions. The reaction formula for ammonium ions when ammonium ions reduce nitrate nitrogen is as follows.

NH ₄ ⁺ → (1/2) N ₂ + 4H ⁺ + 3e ^- That is, 1 mol of ammonium ion emits 3 mol of electrons when reducing nitrate nitrogen. Therefore, one gram equivalent of ammonium ion is 14 g / 3 = 4.67 g.
It is.

(2) Methanol The reaction formula for methanol when methanol reduces nitrate nitrogen is as follows.

CH ₃ OH + OH ⁻ → CO ₂ + 5H ⁺ + 6e ⁻ That is, 1 mol of methanol emits 6 mol of electrons when reducing nitrate nitrogen. Therefore, one gram equivalent of methanol is 32 g / 6 = 5.33 g.

(3) Nitrate The reaction formula for nitrate when nitrate is reduced to nitrogen gas is as follows.

NO ₃ ⁻ + 6H ⁺ + 5e ⁻ → (1/2) N ₂ + 3H ₂ O That is, 1 mol of nitrate is reduced to nitrogen gas by 5 mol of electrons. Therefore, one gram equivalent of nitrate nitrogen is 14 g / 5 = 2.80 g.

In the second step, the treated waste water from the first step is brought into contact with the solid catalyst under the conditions of pH 0 to 5, preferably 0.2 to 3, more preferably 0.5 to 2. If the pH of the treated wastewater exceeds 5, the removal rate of nitrate nitrogen decreases.

The solid catalyst used in the second step is not particularly limited as long as it can decompose nitrate to nitrogen gas, and a solid catalyst generally used for decomposing nitrate can be used. For example, the same solid catalyst as described in the first step can be used. The solid catalysts used in the first step and the second step may be the same or different.

In the second step, the oxygen-containing gas is not usually supplied when the waste water is brought into contact with the solid catalyst. However, there is no particular problem even if oxygen is dissolved in the treated waste water from the first step. The processing temperature is 80 to 370 ° C, preferably 1 to
The temperature is 20 to 240 ° C, more preferably 150 to 180 ° C. At a temperature lower than 80 ° C, the decomposition rate of nitrate is low,
On the other hand, if it exceeds 370 ° C., it exceeds the critical temperature of water,
The treated wastewater cannot be kept in the liquid phase.

There is no particular limitation on the supply rate of the treated wastewater from the first step, and the space velocity (LHSV) for the solid catalyst
Is usually 0.5 to 20 hr ^-1 , preferably ¹ to 10 hr ^-1 .

The main advantages of the second step of the present invention are as follows.

Nitrate nitrogen can be removed more efficiently under mild conditions of low temperature and low pressure as compared with the conventional method.

The method can be carried out under mild conditions without adding an acid or the like to be added by the above-mentioned conventional method, so that it can be carried out using a compact apparatus made of inexpensive materials. Further, it can be carried out in the same reaction tower together with the first step and / or the third step.

The construction cost and the running cost can be reduced.

<Third Step> The treated wastewater obtained through the first and second steps usually contains ammonia nitrogen and a reducing agent which is not consumed and remains. For this reason, in the present invention, it is preferable to provide a step for removing the remaining ammonia nitrogen and the reducing agent as the third step.

A typical method for carrying out the third step includes the following.

(1) Wet oxidation method This wet oxidation method can be carried out according to a conventionally known method. Specifically, the treated wastewater from the second step is converted into a nitrogen oxide, an organic substance and an inorganic substance in the wastewater, nitrogen, carbon dioxide gas, water and ash content of 1 to 1 of the theoretical amount of oxygen required for decomposition. The solid catalyst is brought into contact with the solid catalyst at a temperature of 80 to 370 ° C. and a pressure at which the wastewater retains a liquid phase at a temperature of 80 to 370 ° C. under the supply of an oxygen-containing gas corresponding to 5 times the amount. Thereby, the ammonia nitrogen in the waste water and the reducing agent remaining without being consumed can be efficiently removed.

As the above-mentioned solid catalyst, a solid catalyst generally used for wet oxidation can be used. For example, the same solid catalyst as described in the first step can be used. The solid catalyst used in the first, second and third steps may be the same or different.

The processing temperature is from 80 to 370 ° C., preferably from 120 to 280 ° C., more preferably from 150 to 180 °.
° C. If the temperature is lower than 80 ° C., the removal rate of ammonia nitrogen and the reducing agent is low. On the other hand, if the temperature exceeds 370 ° C., the critical temperature of water is exceeded, so that the treated wastewater cannot be kept in the liquid phase.

As the oxygen-containing gas, pure oxygen may be used, but usually, air, an oxygen-enriched gas or the like is used.
Above all, air is generally used. The supply amount of the oxygen-containing gas is 1 to 5 times the theoretical amount required to decompose nitrogen compounds, organic substances and inorganic substances in the wastewater to nitrogen, carbon dioxide, water and ash, and is preferably The amount is 1.05 to 4 times, more preferably 1.1 to 2.5 times. If the amount is less than 1 time, the removal of ammonia nitrogen and the like is insufficient, and even if the amount exceeding 5 times is supplied, the processing efficiency is not improved.

There is no particular limitation on the supply speed of the waste water, and the space velocity (LHSV) for the solid catalyst is usually set at 0.
It is 5 to 20 hr ^-1 , preferably ¹ to 10 hr ^-1 . (2) Biological treatment method Ammonium nitrogen is nitrified into nitrate nitrogen by aerobic treatment, followed by anaerobic treatment to reduce nitrate nitrogen to nitrogen gas.

(3) Ammonia stripping method Gas is injected into the treated wastewater to release dissolved ammonia.

Among the above methods (1) to (3), the method (1) is preferable because it can efficiently remove ammonia nitrogen and nitrate nitrogen.

The treatment method of the present invention comprises the first and second steps or the first, second and third steps, and can be specifically carried out as follows.

(1) First and second steps, or first,
The reaction is performed by providing a reaction tower corresponding to each of the second and third steps (Examples 1 to 4).

(2) The first and second steps are performed in the same reactor (Example 5), or the first and second steps are performed in the same reactor, and the third step is performed in another reactor. This is performed (Example 6).

(3) The first step is carried out in one reaction tower, and the second and third steps are carried out simultaneously by providing another reaction tower (Example 7). (4) First, second and third steps The process is performed in the same reaction tower (Example 8).

Among the above methods, according to the methods (2) to (4), the number of reaction towers required for the treatment can be reduced, thereby reducing the construction cost. In addition, the running cost is reduced during implementation.

[0059]

The main effects of the present invention are listed below.

By removing nitrate nitrogen, and thus nitrate nitrogen and ammonia nitrogen at a high removal rate, the wastewater containing ammonium nitrate can be efficiently purified.

There is a step that becomes acidic during the treatment,
Since the acid is nitric acid, an inexpensive material device generally used can be used.

The first, second and third steps can all be carried out under mild conditions.

The construction cost and the running cost of the apparatus can be reduced, which is economical.

[0064]

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples.

Example 1 The wastewater containing ammonium nitrate (10,000 mg / L of ammonia nitrogen, 7,000 mg / L of nitrate nitrogen) was treated using the treatment apparatus shown in FIG.

(First Step) The waste water in the waste water tank 1 was pressurized by the waste water supply pump 2 and supplied into the system at a flow rate of 1 L / hr. The pressure in the system is detected by a pressure controller (PIC) and 0.9 MPa by a pressure control valve 21.
Was adjusted to The air supplied from the line 4 is pressurized by the compressor 3 and the flow rate is adjusted to 20 NL by the flow control valve 5.
/ Hr and mixed with the wastewater supplied from the pump 2 via the valve 7. The obtained gas-liquid mixture was heated to 160 ° C. by the heater 6 and introduced into the reaction tower 8. Reaction tower 8
Was filled with 1 L of a solid catalyst composed of platinum (Pt) -titania. The gas-liquid mixture in the reaction tower 8 was treated while being maintained at 160 ° C. by a heater 9 attached to the reaction tower 8. The pH of the treated wastewater collected from the sampling line 10 is 1.
2, the ammonia nitrogen concentration and the nitrate nitrogen concentration were 5,000 mg / L and 6,100 m, respectively.
g / L (ammonia nitrogen / nitrate nitrogen (molar ratio) = 0.82).

(Second Step) Methanol is supplied to the treated wastewater from the reaction tower 8 from the reducing agent supply pump 12 at a rate of 12
g (reducing agent / oxidizing agent ratio = 1.5),
After mixing the treated wastewater from the reaction tower 8 with methanol,
It was introduced into the reaction tower 13. The reaction tower 13 was filled with 1 L of a solid catalyst made of platinum-titania, and the inside of the reaction tower 13 was maintained at 160 ° C. by a heater 14. The pH of the treated wastewater collected from the sampling line 15 was 7, and the concentrations of ammonia nitrogen and nitrate nitrogen were 100 mg / L and 20 mg / L, respectively. The decomposition rate of nitrate nitrogen is as follows.

Nitrate nitrogen decomposition rate: 99.7% Example 2 In Example 1, following the first step and the second step, the following third step was performed. (Third step) Compressed air supplied from the air compressor 3 is mixed with the treated wastewater from the reaction tower 13 by adjusting the flow rate to 51 NL / hr by the flow control valve 16,
Was introduced. The supply amount of oxygen was 1.7 times the theoretical amount. The reaction column 17 was filled with 1 L of a solid catalyst composed of platinum-titania, and the inside of the reaction column 17 was maintained at 160 ° C. by a heater 18. The treated wastewater from the reaction tower 17 was cooled by the cooler 20 and discharged from the pressure control valve 21. The pH of the treated waste water from the pressure control valve 21 is 6, and the ammonia nitrogen concentration and the nitrate nitrogen concentration are 2
mg / L and 10 mg / L. C in treated wastewater
The OD value (manganese method) was 9 mg / L. The decomposition rate of ammonia nitrogen, the decomposition rate of nitrate nitrogen, and the total nitrogen decomposition rate are as follows.

Ammonia nitrogen decomposition rate: 99.9% or more Nitrate nitrogen decomposition rate: 99.9% Total nitrogen decomposition rate: 99.9% Example 3 Using a treatment apparatus shown in FIG. (8,000 mg / L, nitric acid nitrogen: 8,000 mg / L).

(First Step) The same operation as in the first step of Example 1 was performed except that the valve 6 was closed and air was not supplied to the reaction tower 8.

The pH of the treated wastewater collected from the sampling line 10 was 1.3, and the concentrations of ammonia nitrogen and nitrate nitrogen were 6,000 mg / L and 6,800 mg / L, respectively (ammonia state). nitrogen/
Nitrate nitrogen (molar ratio) = 0.88).

(Second step) The methanol supply amount was reduced to 1 L of waste water.
The same operation as in the second step of Example 1 was performed, except that the amount was 13 g per unit (ratio of reducing agent / oxidizing agent = 1.5). The pH of the treated wastewater collected from the sampling line 15 was 7, and the ammonia nitrogen concentration and the nitrate nitrogen concentration were 60 mg / L and 40 mg / L, respectively. The decomposition rate of nitrate nitrogen is as follows.

Nitrate nitrogen decomposition rate: 99.5% Example 4 In Example 3, the following third step was performed following the first step and the second step. (Third Step) The same operation as in the third step of Example 2 was performed.
The supply amount of the oxygen-containing gas (air) was 1.5 times the theoretical amount. The pH of the treated wastewater from the pressure control valve 21 was 6, and the ammonia nitrogen concentration and the nitrate nitrogen concentration were 2 mg / L and 10 mg / L, respectively. The COD value (manganese method) in the treated wastewater was 10 mg / L. The decomposition rates of ammonia nitrogen, nitrate nitrogen, and total nitrogen are as follows.

Ammonia nitrogen decomposition rate: 99.9% or more Nitrate nitrogen decomposition rate: 99.9% Total nitrogen decomposition rate: 99.9% Example 5 Using a treatment apparatus shown in FIG. (1,000 mg / L of nitrogen nitrogen, 1,000 mg / L of nitrate nitrogen).

(First Step and Second Step) Drain Tank 1
The drainage in the inside is pressurized by the drainage supply pump 3 and is 1 L / hr
At a flow rate of. The pressure in the system was detected by a pressure controller (PIC) and adjusted to 0.9 MPa by a pressure control valve 21. This waste water was heated to 160 ° C. by the heater 7 and introduced into the reaction tower 8. Reaction tower 8
Was filled with 2 L of a solid catalyst composed of platinum-titania. The waste water in the reaction tower 8 is supplied to a heater 9 attached to the reaction tower 8.
At 160 ° C. for processing. The pH of the treated wastewater collected from the sampling line 10 was 2.0, and the concentrations of ammonia nitrogen and nitrate nitrogen were 680 mg / L and 810 mg / L, respectively (ammonia nitrogen / nitrate nitrogen (mol Ratio) = 0.84).

The reducing agent supply pump 1 is provided in the middle of the reaction tower 8.
A line for supplying methanol from 2 is provided,
Methanol was supplied at a flow rate of 1 g per liter of wastewater (ratio of reducing agent / oxidizing agent = 1.2). Sampling line 1
The pH of the treated wastewater collected from 5 was 6, and the ammonia nitrogen concentration and the nitrate nitrogen concentration were all 7 mg.
/ L. The decomposition rate of nitrate nitrogen is as follows.

Nitrate nitrogen decomposition rate: 99.7% Example 6 In Example 5, the following third step was performed following the first step and the second step. (Third step) Compressed air supplied from the air compressor 3 is mixed with the treated wastewater from the reaction tower 8 at a flow rate of 2.5 NL / hr by the flow rate control valve 16 and mixed with the reaction tower 17.
Was introduced. The supply amount of oxygen was 2.1 times the theoretical amount. The reaction column 17 was filled with 1 L of a solid catalyst composed of platinum-titania, and the inside of the reaction column 17 was maintained at 160 ° C. by a heater 18. The treated wastewater from the reaction tower 17 was cooled by the cooler 20 and discharged from the pressure control valve 21. The pH of the treated waste water from the pressure control valve 21 is 6, and the ammonia nitrogen concentration and the nitrate nitrogen concentration are both 1
mg / L. The COD value (manganese method) in the treated wastewater was 2 mg / L. The decomposition rate of ammonia nitrogen, the decomposition rate of nitrate nitrogen, and the total nitrogen decomposition rate are as follows.

Ammonia nitrogen decomposition rate: 99.9% Nitrate nitrogen decomposition rate: 99.9% Total nitrogen decomposition rate: 99.9% Example 7 Using a treatment apparatus shown in FIG. (12,000 mg / L of nitrogen and 12,000 mg / L of nitrate nitrogen).

(First Step) The waste water in the waste water tank 1 was pressurized by the waste water supply pump 3 and supplied into the system at a flow rate of 1 L / hr. The pressure in the system is detected by a pressure controller (PIC) and 0.9 MPa by a pressure control valve 21.
Was adjusted to This waste water was heated to 160 ° C. by the heater 7 and introduced into the reaction tower 8. The reaction column 8 was packed with 2 L of a solid catalyst composed of platinum-titania. The waste water in the reaction tower 8 is heated to 160 ° C. by a heater 9 attached to the reaction tower 8.
And processed. The pH of the treated wastewater collected from the sampling line 10 is 0.8, and the ammonia nitrogen concentration and the nitrate nitrogen concentration are 5,500 m, respectively.
g / L and 8,100 mg / L (ammonia nitrogen / nitrate nitrogen (molar ratio) = 0.68).

(Second Step and Third Step) Methanol is supplied from the reducing agent supply pump 12 to the treated wastewater from the reaction tower 8 at a flow rate of 22 g per 1 L of the wastewater, and the treated wastewater from the reaction tower 8 After mixing with methanol, the mixture was introduced into the reaction tower 13 (ratio of reducing agent / oxidizing agent = 1.8). The reaction tower 13 is filled with 1.5 L of a solid catalyst made of platinum-titania.
C. was maintained. The pH of the treated wastewater collected from the sampling line 15 was 7, and the ammonia nitrogen and the nitrate nitrogen contained 100 mg / L and 1 mg / L, respectively.
(Nitrate nitrogen decomposition rate: 99.9% or more).

A line for supplying compressed air from the air compressor 3 is provided at a position about 1/3 from the bottom of the reaction tower 13, and the compressed air is supplied by the flow control valve 16 to 80 NL / hr (oxygen is theoretically The flow rate was adjusted to 1.2 times) and mixed with the treated wastewater. The treated wastewater from the reaction tower 13 was cooled by the cooler 20 and discharged from the pressure control valve 21. The pH of the treated wastewater from the pressure control valve 21 is 6,
The ammonia nitrogen concentration and the nitrate nitrogen concentration were 3 mg / L and 1 mg / L or less, respectively. COD
The value (manganese method) was 12 mg / L. The decomposition rates of ammonia nitrogen, nitrate nitrogen, and total nitrogen are as follows.

Ammonia nitrogen decomposition rate: 99.9% or more Nitrate nitrogen decomposition rate: 99.9% or more Total nitrogen decomposition rate: 99.9% or more Example 8 Ammonium nitrate-containing wastewater using the treatment apparatus shown in FIG. (Ammonia nitrogen 10,000 mg / L, nitrate nitrogen 10,000 mg / L).

(First to Third Steps) The waste water in the waste water tank 1 was pressurized by the waste water supply pump 3 and supplied into the system at a flow rate of 1 L / hr. The pressure in the system was detected by a pressure controller (PIC) and adjusted to 0.9 MPa by a pressure control valve 21. The waste water is removed by heater 7 for 1
The temperature was raised to 60 ° C. and introduced into the reaction tower 8. The reaction column 8 was filled with 1 L of a solid catalyst composed of platinum-titania. The wastewater in the reaction tower 8 was treated while being maintained at 160 ° C. by a heater 9 attached to the reaction tower 8. Sampling line 1
The pH of the treated wastewater collected from 0 was 1.2, and the ammonia nitrogen concentration and the nitrate nitrogen concentration were respectively
7,600 mg / L and 8,600 mg / L (ammonia nitrogen / nitrate nitrogen (molar ratio) = 0.8
8).

At a position about 1/3 from the bottom of the reaction tower 8,
A line for supplying methanol from the reducing agent supply pump 12 is provided.
(Reducing agent / oxidizing agent ratio = 1.
3). The pH of the treated wastewater collected from the sampling line 15 was 7, and the ammonia nitrogen concentration and the nitrate nitrogen concentration were 50 mg / L and 45 mgL, respectively (nitrate nitrogen decomposition rate: 99.6%).

At a position about 2/3 from the bottom of the reaction tower 8,
A line for supplying compressed air from the air compressor 3 is provided.
The flow rate was adjusted to 2 NL / hr (oxygen was 2.0 times the theoretical amount) and mixed with the treated wastewater. The treated wastewater from the reaction tower 13 was cooled by the cooler 20 and discharged from the pressure control valve 21. The pH of the treated wastewater from the pressure control valve 21 is 6,
The ammonia nitrogen concentration and the nitrate nitrogen concentration were 2 mg / L and 12 mg / L, respectively. The COD value (manganese method) was 8 mg / L. The decomposition rates of ammonia nitrogen, nitrate nitrogen, and total nitrogen are as follows.

Ammonia nitrogen decomposition rate: 99.9% or more Nitrate nitrogen decomposition rate: 99.9% Total nitrogen decomposition rate: 99.9% Comparative Example Here, without performing the first step of the present invention, FIG.
The wastewater containing ammonium nitrate (8,000 mg / L of ammonia nitrogen, 8,000 mg / L of nitrate nitrogen) was obtained by the following second step and third step using the treatment apparatus shown in (1).
Was performed. (Second step) To the wastewater in the wastewater tank 1, 13 g of methanol was added to 1 L of the wastewater and mixed sufficiently. This wastewater was pressurized by a wastewater supply pump 3 and supplied into the system at a flow rate of 1 L / hr. The pressure in the system is controlled by a pressure controller (PI
C), the pressure is detected, and 0.9
It was adjusted to MPa. The waste water is heated at 160 ° C. by the heater 7.
And then introduced into the reaction tower 13. The reaction tower 13 is filled with 1 L of a solid catalyst composed of platinum-titania,
The inside of the reaction tower 13 was maintained at 160 ° C. by the heater 14.
The pH of the treated wastewater collected from the sampling line 15 is 7, and the ammonium nitrogen concentration and the nitrate nitrogen concentration are 8,100 mgL and 7,500 mg, respectively.
/ L. The decomposition rate of nitrate nitrogen was 6%.

(Third Step) Next, the compressed air supplied from the air compressor 3 is mixed with the treated wastewater from the reaction tower 13 at a flow rate of 51 NL / hr by the flow rate control valve 16 and mixed with the reaction tower 17. Introduced. Platinum-
One liter of a solid catalyst composed of titania was charged, and the inside of the reaction tower 17 was maintained at 160 ° C. by a heater 18. The treated wastewater from the reaction tower 17 was cooled by the cooler 20 and discharged from the pressure control valve 21. The ammonia nitrogen concentration and the nitrate nitrogen concentration of the treated wastewater from the pressure control valve 21 were 7,000 mg / L and 7,400 mg / L, respectively.
Met. The decomposition rates of ammonia nitrogen, nitrate nitrogen, and total nitrogen are as follows.

Ammonia nitrogen decomposition rate: 13% Nitrate nitrogen decomposition rate: 8% Total nitrogen decomposition rate: 10%

[Brief description of the drawings]

FIG. 1 is a flow sheet showing one embodiment of the present invention.

FIG. 2 is a flow sheet showing another embodiment of the present invention.

FIG. 3 is a flow sheet showing another embodiment of the present invention.

FIG. 4 is a flow sheet showing another embodiment of the present invention.

FIG. 5 is a flow sheet showing another embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Drain tank 2 Drain supply pump 3 Air compressor 4 Air supply line 5 Flow control valve 6 Valve 7 Heater 8 Reaction tower 9 Heater 10 Sampling line 11 Reducing agent tank 12 Reducing agent supply pump 13 Reaction tower 14 Heater 15 Sampling line 16 Flow rate control Valve 17 Reaction tower 18 Heater 19 Cooling water line 20 Cooler 21 Pressure control valve PIC Pressure controller

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4D050 AA13 AB35 AB37 BA06 BA12 BA14 BB01 BB09 BC01 BC02 BC04 BC06 BD02 BD03 BD06 BD08 CA01 CA08 CA10 CA13 CA17

Claims (3)

[Claims] 1. A method for treating wastewater containing ammonium nitrate, comprising the following first and second steps: <First step> The ammonia nitrogen in the wastewater is removed, and the ammonia nitrogen and the nitrate nitrogen in the wastewater are reduced to 0 <
Ammonia nitrogen / nitrate nitrogen <1 (molar ratio) and the pH of the waste water is adjusted to 0-5. <Second step> A reducing agent is added to the treated wastewater from the first step,
It is wet-decomposed by contacting with a solid catalyst at a temperature of 80 to 370 ° C. and a pressure at which the wastewater maintains a liquid phase. 2. The method according to claim 1, comprising the following third step. <Third step> The treated wastewater from the second step is converted into a nitrogen compound, an organic substance, and an inorganic substance in the wastewater by nitrogen, carbon dioxide gas, water and an amount of 1 to 1 of a theoretical oxygen amount necessary for decomposing it into ash.
Under supply of an oxygen-containing gas corresponding to 5 times the amount, the
The wet oxidative decomposition is carried out by contacting the solid catalyst at 370 ° C. and under a pressure at which the wastewater maintains a liquid phase. 3. The method according to claim 1, wherein in the second step, the reducing agent is added so that the ratio of the reducing agent / oxidizing agent is 0.8 to 5.