JPH04190882A - How to treat water containing ammonia or nitrite nitrogen - Google Patents

Abstract

PURPOSE:To enhance the removal rate of NH4-N and/or NO2-N and obtain the treated liq. of a high water quality by a method wherein the liq. containinng ammoniacal nitrogen or nitrite nitrogen and carbonic acid component is denitrified and, thereafter, heated to cause the reaction. CONSTITUTION:The liquid contg. ammoniacal nitrogen or nitrite nitrogen and carbonic acid component is heated to cause the reaction in the presence of ammoniacal nitrogen and nitrite nitrogen and, upon decomposition into nitrogen gas, raw water is decarboxylated to conduct the aforesaid reaction. As a NH4-N contg. water, there are the sewage treated liq. and the waste liq. of ammonium sulfate and, as a NO2-N contg. liquid, there is the waste liq. from the desulfurization of flue gas. By the aforesaid reaction, the NH4-N and NO2-N in the raw water react to decompose NH4NO2 into N2 gas. At this time, if the carbonic acid component is present, a highly purified liq. low in concn. of NH4-N and NO2-N is obtained by the decarboxylation, although the content of NH4-N and NO2-N is high in the liq. thus obtained. It is obvious that this reason is not due to a mere lowering in the pH.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for treating water containing ammonia or nitrite nitrogen.

[Conventional technology]

As a treatment method for water containing ammonia nitrogen (hereinafter sometimes referred to as NH4-N) or (and) nitrite nitrogen (hereinafter sometimes referred to as NO□-N), raw water is
Heating and reacting in the coexistence of 4-N and No2-N,
A method of decomposing N84No□ (ammonium nitrite) into nitrogen gas has been proposed (for example, in JP-A-49-110
No. 148).

In this method, NH4-N and NO□-
N reacts to generate N2 gas by decomposition of NH and NO□, and NH4-N or (and) NO□-N is removed from the raw water.

NH4++ NO2- → N2+ 2 H2O- (1) Although this method has the advantage of using relatively small equipment and can be treated in a relatively short time with simple operations, the treatment effect is poor and a certain amount of NH4-N or (
and) NO□-N remains and there is a problem that high purity treated water may not be obtained.

[Problem to be solved by the invention]

The purpose of the present invention is to solve such problems,
In a method of decomposing NH4No2 by heating and reacting in the coexistence of H4-N and N02-N, N)1. -N
Another object of the present invention is to propose a method for treating ammonia- or nitrite-nitrogen-containing water that has a high removal rate of No and -N and can obtain treated water of high quality.

Means for Solving UAM] The present invention heats and reacts water containing ammonia nitrogen or nitrite nitrogen and a carbonate component in the coexistence of ammonia nitrogen and nitrite nitrogen, thereby producing nitrogen gas. A method for treating water containing ammonia or nitrite nitrogen, characterized in that the reaction is carried out by decarboxylating raw water.

As a result of investigating the cause of the poor treatment effect in the NH4NO2 decomposition method, the present inventor found that the cause was the carbonic acid component contained in the raw water.

The raw water to be treated in the present invention is NH4-N
or (and) water containing NO, -N and carbonic acid components. For NH4-N and NO□-N, NH4
-Water containing only N, water containing only NO□-N,
and water containing NH4-N and ~0□-N. Examples of water containing NH4-N include treated human waste water and ammonium sulfate wastewater. Examples of water containing N02-N include flue gas desulfurization wastewater. -QH
Examples of water containing 4-N and NO□-N include nitrification-denitrification treated human waste water, ammonium nitrate wastewater, and the like. Since the present invention is a method for decomposing NH4NO2 by reacting NH, -N and No2-N, the raw water to be treated is NH4
-N and No2- Although water containing N is suitable for the treatment, water containing only either one may be used. Also N
It may also contain other forms of nitrogen such as O and -N.

The carbonic acid components contained in raw water include 1(2Co, H
Mainly inorganic carbonic acid components such as CO, -1co3''-,
Organic carbonic acid components that produce these inorganic carbonic acid components through decomposition etc. are also targeted.

Decarboxylation is an operation that removes the carbonic acid components contained in raw water, but when adding NH4 salts, NO□ salts, etc. to raw water and causing a reaction, decarboxylation , decarboxylation may be performed after addition. Further, if 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, ion exchange, etc. can be adopted. The degree of decarboxylation varies depending on the target quality of the treated water, but is preferably 1000n+g/Q or less, more preferably 500m
g/Q or less, most preferably 200B/Q or less.

In the present invention, the decarboxylated raw water is heated and reacted in the coexistence of NH4-N and NO□-N, and NH4N
Perform o2 decomposition. If the raw water contains approximately equivalent amounts of NH4-N and NO□-N, the reaction can be carried out as is, but if either one is insufficient, NH4 salt, N
The reaction is carried out by adding NH4-Ng or No,-Ng such as o2 salt. NH4No, decomposition is NH4-N and No2-
Although the reaction is an equivalent reaction of N, it is preferable that a slight excess of No2-N is present.

NH, -N and NO□ to perform N H4N 02 decomposition
The general ratio of -N is 0.5 to 2 times equivalent, preferably 0.9 to 1.5 times equivalent, of NO□-N to NH4-H.

NH, No□ decomposition may be carried out in the presence or absence of a catalyst. Examples of catalysts that can be used include platinum-supported alumina catalysts.

The reaction temperature for NH4No2 decomposition varies depending on the presence or absence of a catalyst, but is generally 70-300°C, preferably 70-200°C.
00°C, and when the reaction is carried out in the presence of a catalyst, the reaction proceeds in a relatively low temperature range. The reaction mode may be continuous or batchwise. When using a catalyst, it is preferable to introduce decarboxylated raw water and necessary additives into a heated catalyst-packed bed for reaction. The reaction time varies depending on the temperature, the presence or absence of a catalyst, and the reaction form, but is generally 10 to 6
0 minutes, preferably about 15 to 30 minutes.

Through the above reaction, NH4-N and NO□-N in the raw water react according to the above formula [1], and N2 gas is generated by NH4NO2 decomposition. If carbonic acid components are present at this time,
Although the resulting treated water has a high content of NH4-N and NO□-N, decarboxylation reduces Nl(, -N and
High purity treated water with low concentration can be obtained. Although the reason for this is not clear, it is clear that it is not due to a simple decrease in pH.

〔Example〕

Next, examples of the present invention will be described.

Example 1 1.500 mg of NH4-N #1 in pure water. Ammonium chloride and sodium nitrite were added so that No2-N was 1500 mg/Q, and further added to the specified concentration (0,200,
Sodium hydrogen carbonate (Na) ICO,) was added to the solution to give a concentration of 500, 1000 or 3000 mg/Q) to prepare a solution in which the concentration of the carbonic acid component was changed stepwise, and this was used as raw water.

Each raw water was heated in the absence of a catalyst at a temperature of 200° C. and a residence time of 20 minutes to perform NH4NO2 decomposition, and the concentrations of NH4-N and No, -N in the treated water were measured. Figure 1 shows the relationship between the concentration of sodium bicarbonate in raw water and the nitrogen concentration in treated water. Furthermore, the relationship between the pH of raw water and the nitrogen concentration of treated water is shown in FIG. In addition, 012 in Figure 2
The numerical value 00.500.1000.3000 indicates the concentration (+g#) of sodium bicarbonate in the raw water.

From the above results, the smaller the amount of carbonic acid component, the more NH4-N
It can be seen that the NO□-N removal rate is high and highly purified treated water can be obtained.

Comparative Example 1 Ammonium chloride and sodium nitrite were added to pure water so that NH4-N was 1500 + g/12 and No, -N was 1500 mg/Q, and sodium hydrogen carbonate was added at 30 g/Q.
After adding the solution to a concentration of 00+++g#t, the pH was adjusted to 6.6 with hydrochloric acid.

This liquid was used as raw water, heated under the same conditions as in Example 1, and N
After decomposing H4No, the NH, -N and NO□-N concentrations of the treated water were measured. The results are shown in Figure 2.

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

Example 2 1450 mg/L NH4-N 160 mg/L HCoff-
Refrigerate leachate containing mg/12 to pH4.5 with hydrochloric acid.
and decarboxylated by blowing air for 1 hour, HCO,-
The concentration was set at 5 g/Ω.

This raw water contains NaN0. 1590mg as No, -N
Add #l.

It was heated at 200° C. for 20 minutes to perform NH and No□ decomposition. The results are shown in Table 1.

Comparative Example 2 In Example 2, the same conditions were used for the case where decarboxylation was not performed. The results are shown in Table 1.

Table 1 From the results above the concentration after skewer decarboxylation, NH4-N and NO□
- It can be seen that the N removal rate becomes higher and the quality of the treated water becomes higher.

〔Effect of the invention〕

As explained above, according to the present invention, NH4-N
Or, since the water containing NO□-N is decarboxylated to decompose NH4NO2, the efficiency is lower than NH4-N and N.
02-N can be decomposed and high quality treated water can be obtained.

[Brief explanation of drawings]

FIG. 1 is a graph showing the relationship between the sodium bicarbonate concentration of raw water and the nitrogen concentration of the treated water in Example 1, and FIG. 2 is a graph showing the relationship between the PH of the raw water and the nitrogen concentration of the treated water. Agent Patent Attorney Sei Yanagihara Figure 1 Raw water NaHCO3 concentration (mg/j) Figure 2 o: NH4-N (-true', J'fqige-
11)・: N02-N (Class 51・11) Δ: N
H4-N (specific gravity 1#+1) pH of raw water (-)

Claims (1)

[Claims] (1) A method in which water containing ammonia nitrogen or nitrite nitrogen and carbonic acid components is heated and reacted in the coexistence of ammonia nitrogen and nitrite nitrogen to decompose it into nitrogen gas. A method for treating water containing ammonia or nitrite nitrogen, characterized in that the reaction is carried out by carbonation.