JP3213667B2 - Control method of catalytic wet oxidizer in treatment of wastewater containing ammonia nitrogen - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a wastewater containing ammonia nitrogen, which is subjected to wet oxidation in the presence of a solid catalyst to convert substances contained in the wastewater into nitrogen, carbon dioxide, water and ash. And a method for detoxifying the waste. More specifically, the present invention relates to a method in which various wastewaters containing ammonia nitrogen represented by industrial wastewater and the like are treated in the presence of a solid catalyst and an oxygen-containing gas at a temperature of 100 to 370 ° C. The present invention relates to a method for detoxifying wastewater by subjecting wastewater to wet oxidation treatment under pressure conditions that maintain a phase, thereby converting substances contained in the wastewater to nitrogen, carbon dioxide, water, and ash.

[0002]

2. Description of the Related Art In marine areas, lakes, rivers, rivers, etc., it has been a long time since eutrophication caused red tides and musty odor substances to be generated, but the cause is contained in wastewater discharged into the waters. It is caused by nutrients such as nitrogen and phosphorus. For this reason, wastewater regulations on nitrogen and phosphorus are being implemented, and these secondary nutrients cannot be sufficiently treated only by secondary treatment by the conventional activated sludge method. Therefore, it is necessary to newly provide a denitrification step.

Conventionally, methods for removing nitrogen include denitrification by living organisms, stripping by aeration, ion exchange, and oxidative denitrification by oxidizing agents such as hypochlorous acid and ozone. Denitrification treatment by living organisms is a method of nitrifying ammonia nitrogen to nitrate nitrogen and then performing anaerobic treatment of nitrate nitrogen to produce nitrogen gas.However, since the treatment time needs to be long, it is inevitable. There is a problem that the apparatus scale becomes large. The stripping method is a method in which gas is injected into the liquid phase and the dissolved ammonia nitrogen is released into the gas phase. Since this is not a fundamental solution, some process for removing ammonia in the gas phase is required. In the ion exchange method, it is necessary to frequently regenerate the ion-exchange base material and waste water, so that the ion-exchange base material contains a large amount of ions other than nitrogen-containing ions. In addition, the denitrification method using hypochlorous acid has a risk of generating organic chlorine, which has recently become a problem. The denitrification method using ozone also requires the presence of bromine ions as a catalyst, and both require a large amount of oxidizing agent. As a result, the cost increases.

On the other hand, as a method of treating wastewater containing a high concentration of ammonium nitrate, a method of treating the wastewater by catalytic wet oxidation has been proposed (JP-A-61-222585, JP-A-61-222586, 61-2
No. 22587, JP-A-61-222588,
JP-A-61-222589, JP-A-61-245
883, JP-A-61-245883, JP-A-61-257290, JP-A-61-25729
No. 1, Japanese Patent Application Laid-Open No. 61-257292,
-59094, JP-A-4-61987, JP-A-4-20069, JP-A-4-200790
No.). These are 100 to 3 in the presence of a specific catalyst.
This is a method of performing wet oxidation treatment at a temperature of 70 ° C. and a pressure condition in which waste water retains a liquid phase.

[0005]

However, when the present inventors treat ammonia-nitrogen-containing wastewater, the treatment efficiency may fluctuate greatly due to fluctuations in the concentration of wastewater and shake of the apparatus itself. Admitted. That is, when treating ammonia-nitrogen-containing wastewater by the catalytic wet oxidation method,
It became clear that stable high treatment efficiency could not be obtained unless the equipment conditions were always kept optimally for the concentration of wastewater.

However, in an actual apparatus, the concentration of waste water is not constant, but always fluctuates. Therefore, in practice, it is impossible to perform a stable and sufficient nitrogen treatment unless the apparatus conditions are always controlled to an optimum state in the treatment of the wastewater containing ammonia nitrogen.

[0007]

On the other hand, the inventors of the present invention have conducted intensive studies, and as a result, when treating wastewater containing ammonia nitrogen by the catalytic wet oxidation method, supply the nitrogen into the apparatus with respect to the treatment efficiency of nitrogen. The effect of oxygen content was found to be very large. That is, although the concentration of ammonium ion and nitrate ion remaining in the treated water varies depending on the type of the catalyst used, when the wastewater containing ammonia nitrogen is treated by the catalytic wet oxidation method, it does not matter when any catalyst is used. As shown in the conceptual diagram of FIG. 1, when the supplied oxygen amount is small, the ammonia nitrogen remains in the treated water without being oxidized, and when the supplied oxygen amount becomes excessive, It has been found that nitrogen is converted to nitrate nitrogen and is present in the treated water at a high concentration, so that sufficient treatment cannot be performed as the total nitrogen concentration in the treated water.

Further, it has been found that, when the ammonia-nitrogen-containing wastewater is subjected to the catalytic wet oxidation treatment, the nitrate ion concentration in the treated water discharged from the catalytic wet oxidation device is an index for judging the amount of supplied oxygen. By controlling the amount of oxygen-containing gas flowing into the apparatus so as to control the concentration to within a certain range or to a concentration value, it is possible to easily and stably minimize the influence of fluctuations in the concentration of wastewater and perform stable treatment. I found that it was possible. In addition, when the ammonia-nitrogen-containing wastewater is subjected to catalytic wet oxidation treatment, it has been found that the oxygen concentration in the gas together with the nitrate ion concentration in the treated water discharged from the catalytic wet oxidation device is an index for determining the amount of supplied oxygen, By controlling the amount of oxygen-containing gas that flows into the apparatus based on these measured values, it has been found that it is possible to carry out stable treatment simply and with minimal effects of fluctuations in the concentration of wastewater. . The present invention has been completed based on these findings.

The present invention provides a simple and optimal control method for performing a stable treatment by minimizing the effects of fluctuations in the flow rate and concentration of the wastewater in the catalytic wet oxidation treatment of wastewater containing ammonia nitrogen. To provide.

[0010] The present invention provides a method for treating a wastewater containing ammonia nitrogen in a catalytic wet oxidation treatment , wherein nitric acid in the treated water is treated in advance.
The optimal range of the ion concentration value is set to CL to CH. After the gas-liquid mixed fluid discharged from the catalytic wet oxidizer is separated into gas and liquid, the nitrate ion concentration in the treated water is measured, and the measured nitrate ion concentration value is measured. Is a method for controlling a catalytic wet oxidation apparatus, characterized in that the amount of oxygen-containing gas flowing into the apparatus is controlled so that the gas concentration falls within a range of CL to CH or a set concentration value. In addition, when the ammonia-nitrogen-containing wastewater is subjected to catalytic wet oxidation treatment, the nitrate ion
The optimal range of the gas concentration value is set to CL to CH, the gas-liquid mixed fluid discharged from the catalytic wet oxidizer is separated into gas and liquid, and then the oxygen concentration in the gas phase and the nitrate ion concentration in the treated water are measured. The measured oxygen concentration is within a preset range
Or set concentration value , nitrate ion concentration value is CL ~ CH
And controlling the amount of oxygen-containing gas flowing into the apparatus so that the concentration value falls within the range or a set concentration value .

In the catalytic wet oxidizer, fluctuations in the concentration of waste water affect the temperature of each part of the reactor, the properties of the treated water, the oxygen concentration of the exhaust gas, and the like. The temperature of each part of the reactor changes remarkably when the concentration of the wastewater is extremely different before and after the fluctuation, but the change is usually small, and it is difficult to detect and use the temperature difference for control. is there. On the other hand, the nitrate ion concentration in the treated water and the oxygen concentration in the exhaust gas serve as indicators that clearly indicate the oxidation state in the apparatus.

In the present invention, as shown in FIG. 2, an optimum range of the nitrate ion concentration in the treated water is set in advance, and the supplied oxygen amount is increased or decreased so as to fall within the set range. The control is performed by increasing the supplied oxygen amount as the nitrate ion concentration in the treated water decreases, and decreasing the supplied oxygen amount as the nitrate ion concentration in the treated water increases. In other words, the stable treatment is performed by setting the optimum range of the nitrate ion concentration in the treated water to CL to CH and controlling the supplied oxygen amount so that the nitrate ion concentration falls within the range of CL to CH. It is. Further, an optimum concentration value of the nitrate ion concentration in the treated water may be set in advance, and the supplied oxygen amount may be increased or decreased so as to approach the set concentration value. The control is performed by increasing the supplied oxygen amount as the nitrate ion concentration in the treated water decreases, and decreasing the supplied oxygen amount as the nitrate ion concentration in the treated water increases. That is, for the nitrate ion concentration in the treated water, the optimum concentration value C is set, and the amount of supplied oxygen is controlled so that the nitrate ion concentration in the treated water approaches C, whereby stable treatment is performed.

As a method of controlling the supplied oxygen amount, the supplied oxygen amount is changed when the amount deviates from a set range, and the supplied oxygen amount is changed according to the deviated amount when the amount deviates from the set range. A general method such as changing the supplied oxygen amount according to a deviation from the set target value is used.
Also, when changing the supplied oxygen amount according to the deviation,
The amount of change can be determined by a commonly used method such as stepwise, proportional, or quadratic curve.

By determining the optimum range or concentration value of the nitrate ion concentration in the treated water, it is possible to detect an increase or decrease in the supplied oxygen amount with respect to the required oxygen amount, and to control the supplied oxygen amount to control an appropriate amount. Processing can be performed. One end of the optimal range of the nitrate ion concentration in the treated water is not determined, and the maximum value of the nitrate ion concentration in the treated water is determined and the supplied oxygen amount is controlled so as not to exceed the value. Proper processing cannot be performed by setting the minimum value and controlling the supplied oxygen amount so as not to fall below the minimum value. In other words, determining the maximum value of the nitrate ion concentration in the treated water and controlling the supplied oxygen amount so as not to exceed the maximum value can detect an excess phenomenon of the supplied oxygen amount, but cannot detect a shortage phenomenon. In some cases, the amount of supplied oxygen is insufficient and ammonium ions may be present in the treated water. In addition, by determining the minimum value of the nitrate ion concentration in the treated water and controlling the amount of supplied oxygen so that it does not fall below that value, it is possible to detect the phenomenon of insufficient oxygen supply, but it is impossible to detect the excess phenomenon. In some cases, the supplied oxygen amount becomes excessively large and nitrate ions may be present in the treated water.

The optimum range or concentration value of the nitrate ion concentration in the treated water greatly depends on the concentration of ammonia nitrogen in the wastewater, the required treatment efficiency, the type of catalyst used, and the sensitivity and accuracy of the nitrate ion concentration meter. However, it is usually set under the condition of not less than the detection limit of the nitrate ion concentration meter and not more than the required treated water quality. If the concentration below the detection limit of the nitrate ion concentration meter is set to the optimum range or concentration value, the phenomenon of insufficient oxygen supply cannot be detected and the treatment efficiency may decrease due to the presence of ammonium ions in the treated water. is there. Further, when the concentration equal to or higher than the required treatment water quality is set to the optimum range or concentration value, the supply oxygen amount is controlled so as to increase the treatment efficiency even when the required treatment efficiency is not obtained. Absent.

The optimum range or concentration value of the nitrate ion concentration in the treated water is lower, the higher the total nitrogen treatment efficiency is.
For the above-mentioned reason, it is set to be higher than the detection limit of the nitrate ion concentration meter. In addition, it is preferable that the width of the control range is smaller, because the control is always performed appropriately. The target value of the nitrate ion concentration may be set without the width of the control range, and the supply amount of oxygen may be constantly controlled. As an example, an iron-zirconium-palladium-based catalyst prepared in a catalyst preparation example described below is used, and the concentration of ammonia nitrogen in wastewater is 1,
When the nitrate ion concentration in the treated water is 500 mg / l and the required nitrate ion concentration in the treated water is 20 mg / l or less, the control range of the nitrate ion concentration in the treated water is set to 1 to 20 mg / l, preferably 3 to 20 mg / l.
The supply oxygen amount is controlled with 15 mg / l or a target value of 10 mg / l.

Furthermore, in the present invention, it is preferable that the oxygen concentration in the exhaust gas is detected together with the nitrate ion concentration in the treated water, and the supplied oxygen amount is controlled based on the detected nitrate ion concentration and oxygen concentration. By measuring the oxygen concentration of the exhaust gas and reflecting it in the control of the supplied oxygen amount, the concentration fluctuation of the water to be treated can have a shorter time lag than in the case of the control using only the nitrate ion concentration in the treated water, and a rapid It is possible to perform processing corresponding to the density fluctuation. In addition, by detecting the oxygen concentration in the exhaust gas together with the nitrate ion concentration in the treated water, and controlling the amount of supplied oxygen based on the detected nitrate ion concentration and oxygen concentration, the treated water is more controlled than the oxygen concentration alone in the exhaust gas. The properties can be accurately grasped, and more stable processing can be performed. In addition to these, detecting the nitrate ion concentration in the treated water as well as the oxygen concentration in the exhaust gas, and controlling the supplied oxygen amount based on the detected nitrate ion concentration and the oxygen concentration means measuring the nitrate ion concentration in the treated water. In order to accurately detect when the supplied oxygen amount is excessive, and to measure quickly and accurately when the supplied oxygen amount is insufficient by measuring the oxygen concentration in the exhaust gas, Highly efficient and stable processing becomes possible.

When the supply oxygen amount is controlled by using both the nitrate ion concentration in the treated water and the oxygen concentration of the exhaust gas, the nitrate ion concentration in the treated water is required to be a maximum value of the nitrate ion concentration in advance. Set below water quality,
The supply oxygen amount may be controlled so that the nitrate ion concentration in the treated water does not exceed the set value. That is, when the supplied oxygen amount is too small, the detection can be performed by the oxygen concentration in the exhaust gas, so that it is not necessary to set the minimum value of the optimum range of the nitrate ion concentration. As a control method, it is preferable to decrease the amount of supplied oxygen as the nitrate ion concentration increases.

When the amount of oxygen supplied is controlled by using both the nitrate ion concentration in the treated water and the oxygen concentration of the exhaust gas, the minimum value of the oxygen concentration in the exhaust gas is determined in advance by using the oxygen concentration meter. May be set at or above the detection limit, and the supplied oxygen gas amount may be increased or decreased so as to exceed the set value. By determining the minimum value of the oxygen concentration in the exhaust gas, the phenomenon of an insufficient amount of supplied oxygen is detected, and the shortage of supplied oxygen prevents the concentration of ammonium ions in the treated water from increasing. The control is performed by increasing the supplied oxygen amount as the oxygen concentration in the exhaust gas decreases. The minimum value of the oxygen concentration to be set is the required treated water quality,
The catalyst to be used and the oxygen concentration in the oxygen-containing gas to be used greatly vary, but, for example, an iron-zirconium-palladium-based catalyst prepared in a catalyst preparation example described below is used, and air is used as the oxygen-containing gas. ,
Ammonia nitrogen concentration in wastewater is 1,500mg / l,
When the required total nitrogen concentration in the treated water is 20 mg / l or less, it is 1 vol%.

The oxygen-containing gas in the present invention is a gas containing oxygen, and specific examples thereof include air, oxygen-enriched air, and exhaust gas containing oxygen. The oxygen concentration in the oxygen-containing gas is 3 vo
l% or more, preferably 5 vol% or more. When the oxygen concentration in the oxygen-containing gas is 3 vol% or less, the oxygen concentration in the exhaust gas after treatment becomes too low, and the reliability of the measurement value obtained by the oximeter becomes low. In some cases, the amount of oxygen supplied decreases, and the control of the supplied oxygen amount cannot be performed accurately, so that stable processing cannot be performed. In addition, since the above oxygen concentrations are all on a dry basis and are concentration values in a state where water vapor is separated, when performing measurement without separating water vapor, it is necessary to correct an error due to water vapor to determine a control value. I just need.

In the present invention, the oxygen-containing gas is continuously introduced into the apparatus and used for treating wastewater. When introduced intermittently, anoxic portions appear in the wastewater, and the treatment is not performed. As a result, there is a possibility that the treatment efficiency is lowered, which is not preferable.

In the present invention, the term "ammonia nitrogen" is a general term for ammonia and ammonium ions dissolved in a liquid phase. For example, dissolved salts such as ammonium sulfate and ammonium chloride, aqueous ammonia, etc. But are not limited to these.

In the present invention, the concentration of ammonia nitrogen in the wastewater to be treated is not limited as long as it is dissolved in an aqueous solution.

As the catalyst used in the present invention, any catalyst may be used as long as it is a solid catalyst having durability and activity under wet oxidation reaction conditions. For example, titanium, silicon, At least one element selected from the group consisting of zirconium, manganese, iron, cobalt, nickel, tungsten, cerium, copper, silver, gold, platinum, palladium, rhodium, ruthenium, and iridium, is insoluble or hardly soluble in water. It is a solid catalyst containing a compound. Further, the catalyst A component is selected from the group consisting of manganese, iron, and at least one element insoluble or hardly soluble in water, and the catalyst B component is selected from the group consisting of titanium, silicon, and zirconium. Water-insoluble or hardly soluble compound of at least one element, and cerium, tungsten, copper, silver, gold, platinum, palladium,
It is preferable to use a solid catalyst containing a water-insoluble or hardly soluble compound of at least one element selected from the group consisting of rhodium, ruthenium, and iridium. The ratio of each catalyst component in the catalyst is such that component A is 20 to 98.9% by weight in the form of an oxide, component B is 1 to 80% by weight in the form of an oxide, and component C is 0 to 8% by weight in the form of a metal or a compound. A suitable range is from 0.1 to 20% by weight. Preferably, component A ranges from 40 to 95% by weight in oxide form, component B ranges from 5 to 60% by weight in oxide form, and component C ranges from 0.1 to 15% by weight in metal or compound form. is there. When the component A is out of the above range, the catalytic activity is insufficient. When the component C is also below the above range, the catalytic activity becomes insufficient. In the case of a noble metal such as platinum, palladium and rhodium, the catalytic activity becomes insufficient. If the ratio exceeds, the raw material cost increases, and a correspondingly sufficient effect cannot be expected.

The catalyst used in the present invention preferably has the composition specified as described above.
Various things such as a granular form, a pellet form, and an integrated structure such as a honeycomb can be adopted.

If the wastewater containing ammonia nitrogen is treated using the above catalyst, the total nitrogen treatment efficiency will be greatly increased.

In the present invention, the temperature during wastewater treatment is 100.
370 ° C, preferably 150 ° C to 300 ° C. If the temperature at the time of wastewater treatment is 100 ° C. or less, it is not possible to sufficiently remove ammonia nitrogen.
In the above case, the temperature exceeds the critical temperature of water, and the reactor becomes expensive, which is not preferable. Pressure at processing temperature,
Set the pressure at which the wastewater holds the liquid phase. In the wet oxidation reaction, the higher the oxygen partial pressure, the faster the reaction proceeds.The higher the pressure during the process, the faster the reaction. However, the higher the pressure of the device, the more expensive the device itself. , May be set appropriately according to the processing efficiency.

In the present invention, the inflow velocity of the waste water is preferably in the range of 0.5 to 20 / hr in space velocity (LHSV) with respect to the catalyst. If the LHSV is 0.5 / hr or less, the treatment efficiency does not increase with respect to the amount of the catalyst, and the cost becomes high. If the LHSV is 20 / hr or more, the processing efficiency of ammonia nitrogen is insufficient, which is not preferable.

In the present invention, the supply amount of the oxygen-containing gas is
There is no particular limitation because it is automatically controlled during the processing.

The nitrate ion concentration meter used in the present invention continuously measures the nitrate ion concentration in the liquid phase,
Any device having a function of outputting a detection value may be used. Detectors include conductivity detection by ion chromatography and FT by gas chromatography.
Various known elements such as D and ion electrodes can be applied.

As the oxygen concentration meter used in the present invention, any device can be used as long as it has a function of continuously measuring oxygen in the gas phase and outputting a detected value.
For example, commercially available ones such as a zirconia oxygen analyzer, a galvanic cell oxygen analyzer, and a magnetic oxygen analyzer are used.

[0032]

EXAMPLES Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited thereto.

(Catalyst Preparation Example) Ferric nitrate is dissolved in water, zirconyl nitrate and palladium nitrate are added, an aqueous solution of sodium hydroxide is added to adjust the pH to 9, and the cake obtained by filtering and washing the resultant is filtered. It is dried, calcined at 700 ° C., and pulverized to obtain an iron-zirconium-palladium oxide powder (weight ratio Fe 2 O 3: ZrO 2: Pd = 60: 39.5: 0.
5) was obtained.

The thus obtained oxide powder is added with starch,
After adding water and mixing well, the mixture was shaped into a pellet (cylindrical, average diameter 5 mm, length 6 mm), dried, and calcined at 400 ° C. for 4 hours to obtain a completed catalyst.

(Example 1) Wastewater having the composition shown in Table 1 was treated according to the flow shown in FIG. First, the drain water sent from the tank 5 is
The pressure was increased to 70 kg / cm ² G at a flow rate of liter / hr and supplied into the apparatus. A 10% by weight aqueous sodium carbonate solution was pressurized and supplied by the pump 4 at a flow rate of 100 ml / hr through the line 12, and was mixed with the wastewater. On the other hand, the air supplied from the line 13 is supplied to the compressor 7
And then mixed into the mixture. This gas-liquid mixture was heated to 250 ° C. in the heat exchanger 2 and the heater 16 via the line 14 and then introduced into the wet oxidation tower 1. In the wet oxidation tower 1, the catalyst 0.5 obtained in the catalyst preparation example was added.
The wastewater was treated in the wet oxidation tower 1, and the treated water was cooled in the heat exchanger 2 via the line 15 and flowed to the gas-liquid separator 6. In the gas-liquid separator 6, the liquid level is detected by a liquid level controller (LC).
The liquid level control valve 8 is operated to maintain a constant liquid level, and the pressure is detected by a pressure controller (PC) to operate the pressure control valve 9 to maintain a constant pressure. The oxygen concentration in the gas discharged from the pressure control valve 9 is constantly monitored by an oxygen concentration meter 10, and the nitrate ion concentration in the treated water is constantly monitored by a nitrate ion detector 11.

When the value of the nitrate ion concentration meter 11 is 5 mg / l
The supply gas amount was automatically controlled so that the concentration of wastewater was changed within the range shown in Table 1 every 24 hours, and a continuous treatment test was performed for 100 hours.

FIG. 4 shows the time-dependent changes in the concentration of ammonia in the wastewater and the concentrations of ammonia and nitric acid in the treated water. Incidentally, nitrite ions were not detected in the treated water.

(Comparative Example 1) A processing test was performed under the same conditions as in Example 1 except that the supplied air amount was fixed without following the nitrate ion concentration in the treated water and the oxygen concentration in the exhaust gas. The results are shown in FIG. Incidentally, nitrite ions were not detected in the treated water.

(Example 2) The supply air amount was such that the oxygen concentration of the exhaust gas was 0.5 vol% or more and the nitrate ion concentration of the treated water was 5 mg /
A processing test was performed under the same conditions as in Example 1 except that the control was performed so as to be 1 or less. FIG. 6 shows the results.
Incidentally, nitrite ions were not detected in the treated water.

Comparative Example 2 The supply air amount was not made to follow the oxygen concentration of the exhaust gas, and the nitrate ion concentration in the treated water was 5 mg /
A processing test was performed under the same conditions as in Example 1 except that the control was performed so as to be 1 or less. FIG. 7 shows the results.
Incidentally, nitrite ions were not detected in the treated water.

[0041]

[Table 1]

[Brief description of the drawings]

FIG. 1 is a conceptual diagram showing the relationship between the amount of supplied oxygen and the concentrations of ammonium ions and nitrate ions in treated water when treating wastewater containing ammonia nitrogen by a catalytic wet oxidation method.

FIG. 2 is a conceptual diagram when the amount of supplied oxygen is controlled by a nitrate ion concentration in treated water. CH: the maximum value of the optimal range of the nitrate ion concentration in the treated water CL: the minimum value of the optimal range of the nitrate ion concentration in the treated water C: the target value of the nitrate ion concentration in the treated water QH: the nitrate ion in the treated water is CH QL: Supply oxygen amount when nitrate ion in treated water is CL Q: Supply oxygen amount when nitrate ion in treated water is C

FIG. 3 shows a flow of a preferred processing apparatus according to the present invention. 1. 1. Catalytic wet oxidation reactor Heat exchanger 3. Drainage field pump ４． 4. Aqueous sodium carbonate solution field pump Drain tank 6. 6. Gas-liquid separator 7. Air compressor Liquid level control valve 9. Pressure control valve 10. Oxygen meter 11. Nitrate ion concentration meter 12. 12. Sodium carbonate aqueous solution field line Air line 16. Electric heater

FIG. 4 shows the results of Example 1, showing the states of the ammonium ion concentration and the nitrate ion concentration of the treated water when the ammonium ion concentration in the wastewater is changed stepwise every 24 hours.

FIG. 5 shows the results of Comparative Example 1, showing the ammonium ion concentration and nitrate ion concentration of treated water when the ammonium ion concentration in the wastewater is changed stepwise every 24 hours.

FIG. 6 shows the results of Example 2, showing the ammonium ion concentration and nitrate ion concentration of treated water when the ammonium ion concentration in the wastewater is changed stepwise every 24 hours.

FIG. 7 shows the results of Comparative Example 2, showing the states of the ammonium ion concentration and the nitrate ion concentration of the treated water when the ammonium ion concentration in the wastewater is changed stepwise every 24 hours.

──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Kiichiro Mitsui 992, Nishioki, Okihama-shi, Abashiri-ku, Himeji-shi, Hyogo Prefecture Examiner, Nippon Shokubai Catalysis Research Institute Co., Ltd. Wataru Sugie (56) References JP-A 55-86584 (JP, A) JP-A-2-265696 (JP, A) JP-A-3-181390 (JP, A) JP-A-59-55390 (JP, A) JP-A-4-250888 (JP, A) (58) Survey Field (Int.Cl. ⁷ , DB name) C02F 1 / 72,1 / 58

Claims (2)

(57) [Claims] 1. A method for treating a wastewater containing ammonia nitrogen, which comprises subjecting the wastewater containing ammonia nitrogen to catalytic oxidation treatment to a nitrate ion concentration in the treated water in advance.
The optimal range of the degree value is set to CL to CH, the gas-liquid mixed fluid discharged from the catalytic wet oxidizer is separated into gas and liquid, and then the nitrate ion concentration in the treated water is measured. A method for controlling a catalytic wet oxidation apparatus, comprising controlling an amount of an oxygen-containing gas flowing into the apparatus so as to be within a range of CL to CH or a set concentration value. 2. The process of subjecting the wastewater containing ammonia nitrogen to catalytic wet oxidation treatment in advance to enrich nitrate ions in the treated water.
The optimal range of the degree value is set to CL to CH, and after the gas-liquid mixed fluid discharged from the catalytic wet oxidation device is separated into gas and liquid, the oxygen concentration in the gas phase and the nitrate ion concentration in the treated water are measured.
If the measured oxygen concentration is within the preset range or
Is the set concentration value and the nitrate ion concentration value is in the range of CL to CH.
A method for controlling a catalytic wet oxidation apparatus, comprising: controlling an amount of an oxygen-containing gas flowing into an apparatus so as to have a concentration value within or set in an enclosure .