JP3104253B2 - Method of treating water containing ammonia or nitrite nitrogen - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for treating water containing ammonia or nitrite nitrogen.

[Conventional technology]

As a method for treating water containing ammonia nitrogen (hereinafter sometimes referred to as NH ₄ —N) or (and) nitrite nitrogen (hereinafter sometimes referred to as NO ₂ —N), raw water is treated with NH ₄
There has been proposed an NH ₄ NO ₂ (ammonium nitrite) decomposition method in which a reaction is caused by heating under the coexistence of —N and NO ₂ —N to decompose into nitrogen gas (for example, JP-A-49-110148).

In this method, NH ₄ —N and NO ₂ —N
Reacts to generate N ₂ gas by decomposition of NH ₄ NO ₂ , and NH ₄ −
N or (and) NO ₂ -N are removed from the raw water.

_{^{NH 4 + + NO 2 - →}} N 2 2H 2 O ... (1) This method uses a relatively small device, although there is an advantage that a relatively short time can be processed by a simple operation, poor treatment effect In addition, there is a problem that a certain amount of NH ₄ —N and / or NO ₂ —N remains in the treated water, and high-purity treated water cannot be obtained.

[Problems to be solved by the invention]

An object of the present invention is to solve such a problem.
The reaction is carried out by heating in the presence of NH ₄ —N and NO _{2
In the} method of decomposing ₄ NO ₂ , NH ₄ —N or (and) N
An object of the present invention is to propose a method for treating ammonia or nitrite-nitrogen-containing water, which has a high removal rate of O ₂ -N and can obtain treated water of high quality.

[Means for solving the problem]

The present invention provides a method of heating and reacting water containing ammonia nitrogen or nitrite nitrogen and a carbonate component in the presence of ammonia nitrogen and nitrite nitrogen to decompose the raw water into nitrogen gas. A method for treating ammonia- or nitrite-nitrogen-containing water, wherein the reaction is carried out by decarboxylation.

The present inventor investigated the cause of the case where the treatment effect in the NH ₄ NO ₂ decomposition method was poor, and found that the cause was due to the carbonic acid component contained in the raw water.

Raw water to be treated in the present invention is water containing NH ₄ —N or (and) NO ₂ —N and a carbonate component. For NH ₄ —N and NO ₂ —N, water containing only NH ₄ —N, water containing only NO ₂ —N, and NH ₄ —N
Any water containing N and NO ₂ —N may be used. NH ₄ −
Examples of the water containing N include human wastewater, ammonium sulfate wastewater, and the like. Examples of water containing NO ₂ -N include flue gas desulfurization wastewater. Examples of water containing NH ₄ —N and NO ₂ —N include nitrification and denitrification water of night soil, nitrate wastewater, and the like. The present invention reacts NH ₄ —N with NO ₂ —N to form NH ₄ N
Because it is a method of decomposing O ₂ , as raw water to be treated,
Although water containing NH ₄ —N and NO ₂ —N is suitable for treatment, water containing only one of them may be used. Also NO ₃
Other forms of nitrogen such as -N may be contained.

The carbonic components contained in the raw _{water, H 2 CO 3, HCO 3} -,
An inorganic carbonate components of CO ₃ ^2- and the like are mainly organic carbonate component for generating these inorganic carbonate components by decomposition also of interest.

Decarboxylation is an operation to remove the carbonic acid component contained in the raw water, but when adding NH ₄ salt, NO ₂ salt, etc. to the raw water and reacting, it is necessary to remove the carbonic acid component contained in these additives. After the addition, decarboxylation may be performed. In the case where a carbonic acid component is generated due to decomposition or the like during the reaction, decarboxylation can be performed during the reaction. As a method for decarboxylation, any method such as stripping by aeration under acidic conditions, precipitation separation, and ion exchange can be employed. The degree of decarboxylation varies depending on the quality of the treated water, but is preferably 1000
mg / or less, more preferably 500 mg / or less, and most preferably 200 mg / or less.

In a state in which the raw water to decarboxylation in the present invention, and reacted by heating in the presence of NH ₄ -N and NO ₂ -N, performs NH ₄ NO ₂ decomposition. When the raw water contains almost equivalent amounts of NH ₄ —N and NO ₂ —N, the reaction can be carried out as it is. However, when either one is insufficient, NH ₄ salts such as NH ₄ salts and NO ₂ salts are used. the reaction is carried out by adding -N source or NO ₂ -N source. NH ₄ NO ₂ decomposition is N
Although the reaction is an equivalent reaction of H ₄ —N and NO ₂ —N, it is preferred that NO ₂ —N is present in a small excess. NH for performing NH ₄ NO ₂ decomposition ₄ -
General proportions of N and NO ₂ -N is, NO ₂ -N to NH ₄ -N
Is 0.5 to 2 equivalents, preferably 0.9 to 1.5 equivalents.

NH ₄ NO ₂ decomposition may be performed in the presence or absence of a catalyst. Examples of the catalyst that can be used include a platinum-supported alumina catalyst.

The reaction temperature of NH ₄ NO ₂ decomposition varies depending on the presence or absence of a catalyst, but is generally 70 to 300 ° C., preferably 70 to 200 ° C. When the reaction is performed in the presence of a catalyst, the reaction takes place in a relatively low temperature region. Progresses. The reaction mode may be any of a continuous batch type. When using a catalyst, the heated catalyst packed bed
It is preferable to react by introducing decarbonated raw water and necessary additives. The reaction time varies depending on the temperature, the presence or absence of a catalyst, and the reaction mode, but is generally about 10 to 60 minutes, preferably about 15 to 30 minutes.

By the above reaction, NH ₄ —N and NO ₂ —N in the raw water react according to the above formula [1], and N ₂ gas is generated by decomposition of NH ₄ NO ₂ . At this time, if a carbonic acid component is present, the resulting treated water has a high NH ₄ —N and NO ₂ —N content, but the decarbonation results in high-purity treated water with low NH ₄ —N and NO ₂ —N concentrations. can get. The reason is not clear, but it is clear that it is not due to a simple drop in pH.

〔Example〕

 Next, examples of the present invention will be described.

Example 1 Ammonium chloride and sodium nitrite were added to pure water so that NH ₄ —N was 1500 mg / NO ₂ —N was 1500 mg /
Furthermore, at a predetermined concentration (0, 200, 500, 1000 or 3000 mg /
), Sodium bicarbonate (NaHCO ₃ ) was added to prepare a liquid in which the concentration of the carbonic acid component in the solution was changed stepwise, and this was used as raw water.

Each raw water temperature 200 ° C., and under the conditions of retention time of 20 minutes, then heated in the absence of a catalyst performs NH ₄ NO ₂ decomposition, NH ₄ treated water
The concentration of -N and NO ₂ -N was measured. The relationship between the concentration of sodium bicarbonate in raw water and the nitrogen concentration of treated water is
Shown in the figure. FIG. 2 shows the relationship between the pH of the raw water and the nitrogen concentration of the treated water. In FIG. 2, 0, 200, 500, 1000,
The value of 3000 is the concentration of sodium bicarbonate in raw water (mg /
).

From the above results, the smaller the amount of the carbonic acid component, the more NH ₄ -N
It can be seen that high NO ₂ -N removal rate and high-purity treated water can be obtained.

Comparative Example 1 Ammonium chloride and sodium nitrite were added to pure water so that NH ₄ —N was 1500 mg / NO ₂ —N was 1500 mg /
Further, after adding sodium hydrogen carbonate to a concentration of 3000 mg /, the pH was adjusted to 6.6 with hydrochloric acid.

This liquid was used as raw water and heated under the same conditions as in Example 1.
After decomposition of NH ₄ NO ₂ , NH ₄ -N and NO ₂ -N
The concentration was measured. The results are shown in FIG.

From the above results, it can be seen that simply adjusting the pH with a pH adjuster cannot provide the same effect as decarboxylation.

EXAMPLE 2 NH ₄ -N to 1450 mg /, HCO ₃ ^- and adjusted to pH4.5 by the hydrochloric acid waste leachate to 160 mg / containing, by blowing a one hour air decarboxylated, HCO ₃ ^- and concentration 5mg / a. NaN in this raw water
O ₂ was added as NO ₂ —N at 1590 mg / day and heated at 200 ° C. for 20 minutes to perform NH ₄ NO ₂ decomposition. Table 1 shows the results.

Comparative Example 2 In Example 2, a case where decarboxylation was not performed was processed under the same conditions. Table 1 shows the results.

From the above results, NH ₄ —N and NO ₂ —N
It can be seen that the removal rate increases and the quality of the treated water increases.

〔The invention's effect〕

As described above, according to the present invention, NH ₄ —N
Alternatively, since the water containing NO ₂ -N is decarbonated to decompose NH ₄ NO ₂ , NH ₄ -N and NO ₂ -N can be efficiently decomposed, and high-quality treated water can be obtained. it can.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between the concentration of sodium hydrogen carbonate in raw water and the nitrogen concentration of treated water in Example 1, and FIG. 2 is a graph showing the relationship between the pH of raw water and the concentration of nitrogen in treated water.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-198696 (JP, A) JP-A-63-278591 (JP, A) JP-A-60-1222099 (JP, A) JP-A-57-1982 131098 (JP, A) JP-A-55-51701 (JP, A) JP-A-49-110148 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C02F 1/02 C02F 1 / 20 C02F 1/58 CDH

Claims (1)

(57) [Claims] 1. A method of decomposing water containing ammonia nitrogen or nitrite nitrogen and carbon dioxide by heating and reacting in the presence of ammonia nitrogen and nitrite nitrogen into nitrogen gas. Of ammonia or nitrite-nitrogen-containing water, wherein the reaction is carried out by decarboxylation.