JP2001129565A - Treatment of wastewater containing nitrate nitrogen - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To efficiently treat wastewater containing nitrate nitrogen with a small device, and to perform stable treatment against load fluctuations such as changes in the amount of nitrate nitrogen. Provided is a method capable of effectively treating even concentrations of nitrate nitrogen. SOLUTION: Hydrazine and divalent copper ions are added to wastewater containing nitrate nitrogen to be brought into contact with a Raney nickel catalyst or a ruthenium catalyst to reduce nitrate nitrogen. The amount of hydrazine added is 3 to 4 equivalents of nitrate nitrogen in the waste water to be treated, and the amount of copper ion added is 0.2 to 3 mg / l in the concentration in the waste water to be treated. The wastewater to be treated is p
It is preferable to adjust H11.7 or more.

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 discharged from a business or a factory using a large amount of nitric acid, particularly wastewater containing a high concentration of nitrate nitrogen.

[0002]

2. Description of the Related Art As a method for treating nitrate nitrogen contained in wastewater, there are physicochemical treatments such as a biological treatment method utilizing the denitrification ability of microorganisms, an ion exchange method, a reverse osmosis method, and an electrodialysis method. And a chemical treatment method of reducing the nitrate nitrogen in the presence of a catalyst by dissolving hydrogen gas in the wastewater to be treated under pressure.

[0003] The biological treatment method is the most widespread method because of its low running cost. However, since the reaction speed is low, a large-sized wastewater treatment apparatus requires a large-sized treatment apparatus. Further, it is difficult to apply the method to wastewater containing a high concentration of nitrate nitrogen of about 1 g / l or more. Easy to be.

[0004] The physicochemical processing method is a method in which a processing apparatus may be small and reliable processing can be expected. However, since this method separates and concentrates nitrate nitrogen in water, it is necessary to separately treat a liquid in which nitrate nitrogen is finally concentrated, and basically treats nitrate nitrogen. It doesn't matter.

On the other hand, the chemical treatment method uses clean hydrogen gas for the reduction of nitrate nitrogen in wastewater, and can reduce the size of the apparatus because the reaction rate is higher than that of the biological treatment method. There are features. However, due to the low solubility of hydrogen gas in water, it is very difficult to treat wastewater containing high concentrations of nitrate nitrogen, as in biological treatment.

[0006]

SUMMARY OF THE INVENTION In view of the above-mentioned circumstances, the present invention can easily treat wastewater containing nitrate nitrogen with a small apparatus, and can treat the wastewater such as a change in the concentration of nitrate nitrogen. It is an object of the present invention to provide a method capable of performing a stable treatment with respect to fluctuations in the load on the apparatus and effectively treating a high concentration of nitrate nitrogen.

[0007]

In order to achieve the above object, the present invention provides a method for treating a nitrate-nitrogen-containing wastewater, which comprises adding hydrazine and divalent copper ions to the wastewater to be treated to form a Raney nickel catalyst. Alternatively, the catalyst is brought into contact with a ruthenium catalyst.

[0008]

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for chemically treating nitrate nitrogen contained in waste water, wherein hydrazine is added as a hydrogen donor and nitrate is added using a Raney nickel catalyst or ruthenium catalyst. Nitrogen is chemically reduced to nitrogen (N ₂ ). The contact method between the catalyst and the waste water to be treated may be a batch type or a continuous type.

Hydrazine, which is added to the wastewater to be treated as a hydrogen donor, has an extremely high solubility in water, and is therefore effective for treating wastewater containing a high concentration of nitrate nitrogen. However, if the addition amount is too large, it is not only economically disadvantageous but also the amount of produced ammonia increases. If ammonia remains in the wastewater to be treated, the removal of all nitrogen components becomes insufficient, so it is desirable to suppress the generation of ammonia.
On the other hand, when the amount of hydrazine added is small, hydrazine is depleted while the reduction of nitrate nitrogen is insufficient, and further reduction of nitrate nitrogen does not proceed. For this reason, the amount of hydrazine added is desirably 3 to 4 times the equivalent of nitrate nitrogen in the wastewater to be treated.

Although both the Raney nickel catalyst and the ruthenium catalyst have the effect of promoting the reduction of nitrate nitrogen, the Raney nickel catalyst is more effective.
Raney nickel catalysts are obtained by eluting aluminum from an alloy of nickel and aluminum and are widely used for hydrogenating organic compounds. The ruthenium catalyst is obtained by supporting ruthenium on a carrier such as alumina.

In the method of the present invention, divalent copper ions are added to the wastewater to be treated in order to further promote the reduction of nitrate nitrogen. Divalent copper ions can be added in the form of copper chloride, copper nitrate or the like. The more copper ion is added, the more the reaction is promoted. However, considering that the copper content described in Appendix 2 of the Prime Minister's Ordinance that sets wastewater standards is 3 mg / l, the concentration in the treated wastewater is A range of 0.2 to 3 mg / l is desirable.

It is preferable that the pH of the waste water to be treated is adjusted to 11.7 or more. PH of treated wastewater is 11.7
If the amount is less than the above, the reduction of the nitrate nitrogen becomes insufficient. The pH of the waste water to be treated is adjusted by sodium hydroxide,
This is performed by adding sulfuric acid or the like.

[0013]

【Example】Example 1  Tests the effect of different catalysts to promote nitrate nitrogen reduction
In order to make Ru the alumina carrier 0.5% by weight
, And a Raney nickel catalyst.

Next, 1 mol / mol adjusted to pH 12.7
To 100 ml of sodium nitrate solution, 1 ml of copper (II) chloride solution (200 mg Cu / l), 15 ml of hydrazine hydrate reagent (20 mol / l), and 0.5 g of each of the above catalysts were added in a dry weight of 0.5 g. Was stirred for 4 hours while maintaining the temperature at 35 ° C.

After the test was completed, the concentration of nitrate ions remaining in the solution was analyzed, and the results are shown in Table 1 below together with the case without a catalyst. From the results in Table 1, it can be seen that all of the catalysts have an action of promoting the reduction reaction of nitrate nitrogen, and among them, the Raney nickel catalyst has the highest reaction promoting ability.

[0016]

[Table 1]Ru catalyst Raney Ni catalyst Without catalyst  Residual nitrate nitrogen concentration (mol / l) 0.2 <2 × 10^-5 0.95

[0017]Example 2  Use Raney nickel catalyst and reduce the amount of hydrazine added.
Same as in Example 1 except that it was changed as shown in Table 2.
Thus, reduction treatment of nitrate nitrogen was performed. That is, pH
1mol / l sodium nitrate solution adjusted to 12.7
100 ml of copper (II) chloride solution (200 mg Cu / l)
1 ml, hydrated hydrazine reagent (20 mol / l)
0.5 g of Raney nickel catalyst was added in the amount shown in Table 2.
The solution was stirred for 4 hours while maintaining the solution at 35 ° C.

After the test was completed, the concentrations of nitrate ion, ammonia and hydrazine remaining in the solution were analyzed, and the results obtained are shown in Table 2 below. As can be seen from the results, the amount of hydrazine added to nitrate nitrogen was 2
With double equivalents, the reaction is completed with insufficient treatment of nitrate nitrogen, but with three equivalents or more, treatment of nitrate nitrogen is sufficiently achieved. However, as the amount of hydrazine added increases, the amount of ammonia produced tends to increase. In order to suppress the amount of residual ammonia, the amount of hydrazine added is desirably 3 to 4 times the equivalent of nitrate nitrogen.

[0019]

[Table 2]Hydrazine addition amount  10 ml (2 equivalents) 15 ml (3 equivalents) 20 ml (4 equivalents)  Residual nitrate nitrogen concentration (mol / l) 0.04 <2 × 10^-5 <2 × 10^-5  Residual ammonia concentration (mol / l) 0.4 0.4 0.8 Residual hydrazine concentration (mol / l) <3 × 10^-5 2 × 10^-4 2 × 10^-4

[0020]Example 3  1 mol / l sodium nitrate adjusted to pH 12.7
Solution and 0.1 mol / l sodium nitrate solution
In 200 ml of copper (II) chloride solution (200 mg Cu
/ L) and 1 ml of a hydrated hydrazine reagent (200 mol / l).
l) with 3 equivalents of nitrate nitrogen and Raney nickel catalyst
Add 0.5 g and stir for 4 hours while keeping the solution at 35 ° C
did.

After the test was completed, the concentration of nitrate ions remaining in the solution was analyzed, and the obtained results are shown in Table 3 below. As can be seen from these results, it was confirmed that stable treatment performance was obtained with respect to fluctuations in the concentration of nitrate nitrogen in the water to be treated.

[0022]

[Table 3]Initial nitrate nitrogen concentration  0.1mol / l 1.0mol / l  Residual nitrate nitrogen concentration (mol / l) <2 × 10^-5 <2 × 10^-5

[0023]Example 4  1 mol / l sodium nitrate adjusted to pH 12.7
Copper (II) chloride was added to 100 ml of the solution in the amount shown in Table 4 below.
Solution (200 mg Cu / l) and
The drazine reagent (20mol / l) is 3 times equivalent to nitrate nitrogen
0.5 g of Raney nickel catalyst was added and the solution was brought to 35 ° C.
While stirring for 4 hours.

After the test was completed, the concentration of nitrate ions remaining in the solution was analyzed, and the results obtained are shown in Table 4 below. From these results, it can be seen that the addition of divalent copper ions has the effect of accelerating the treatment of nitrate nitrogen. The effect is greater as the amount of copper ions added is greater, and the concentration in the solution is about 0.2 m.
It can be seen that nitrate nitrogen reduction treatment is efficiently performed at g / l (0.1 ml of copper chloride solution) or more.

[0025]

[Table 4]Copper chloride solution addition amount  0 0.1ml 1.0ml  Residual nitrate nitrogen concentration (mol / l) 1 <2 × 10^-5 <2 × 10^-5

[0026]Example 5  1 mol / l sodium nitrate adjusted to the pH shown in Table 5 below
Copper chloride (II) solution (2
1 mg of hydrazine reagent (2 mg
0 mol / l) 3 times equivalent of nitrate nitrogen, Raneynicke
0.5 g catalyst was added and the solution was kept at 35 ° C. for 4 hours.
Stirred for hours.

After the test was completed, the concentration of nitrate ions remaining in the solution was analyzed, and the obtained results are shown in Table 5 below. As can be seen from the results, the pH of the solution was 11.7.
If it is less than the above, the reduction treatment of nitrate nitrogen is insufficient.
Above 11.7, the concentration of residual nitrate nitrogen was at the lower limit of quantification.

[0028]

[Table 5]Solution pH  10.7 11.7 12.7 13.7  Residual nitrate nitrogen concentration (mol / l) 0.05 <2 × 10^-5 <2 × 10^-5 <2 × 10^-5

In each of the above embodiments, a hydrated hydrazine reagent is used as hydrazine, and divalent copper ions are added in the form of copper chloride. However, the present invention is not limited to these. is not.

[0030]

According to the present invention, nitrate nitrogen contained in wastewater can be easily reduced to nitrogen by a chemical treatment method using a small apparatus, and the amount of nitrate nitrogen in wastewater can be changed. In addition, it is possible to perform a stable process with respect to a change in the load on the processing apparatus, and also to effectively process a high-concentration nitrate nitrogen of 1 g / l or more.

Claims (4)

[Claims] In the treatment of wastewater containing nitrate nitrogen, hydrazine and divalent copper ions are added to the wastewater to be treated, and the wastewater is brought into contact with a Raney nickel catalyst or a ruthenium catalyst. Processing method. 2. The method for treating nitrate nitrogen-containing wastewater according to claim 1, wherein the amount of hydrazine to be added is 3 to 4 times the equivalent of nitrate nitrogen contained in the wastewater to be treated. 3. The wastewater containing nitrate nitrogen according to claim 1, wherein the amount of the divalent copper ion added is 0.2 to 3 mg / l in the wastewater to be treated. Processing method. 4. The method for treating nitrate nitrogen-containing wastewater according to claim 1, wherein the pH of the wastewater to be treated is adjusted to 11.7 or more.