JP2767367B2 - Treatment method for wastewater containing ammonia nitrogen - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a method for increasing the amount of ammoniacal nitrogen .
The present invention relates to a method for treating wastewater contained at a concentration .

[0002]

2. Description of the Related Art A high concentration of ammonia nitrogen (for example, 11
(00 mg / l or more) is discharged from flue gas desulfurization equipment and condensate desalination treatment equipment at power plants, but at present, there is no legal regulation on the discharge. However, it has already been shown that nitrogen and phosphorus are the major contributors to eutrophication in marine areas. The Environment Agency has set environmental standards for sea areas where eutrophication is progressing, and in order to achieve these standards, has set drainage standards for factories and business establishments discharging into those sea areas. There is a tendency to regulate emissions.

[0003] As a method for treating wastewater containing ammoniacal nitrogen, there are a biological treatment method using microorganisms, an ammonia stripping method by distillation, and a chlorine oxidation method using a chemical reaction with chlorine. In the ammonia stripping method,
There is a drawback that the method of disposal of the recovered ammonia has not been established. The chlorine oxidation method is not generally employed because it is difficult to adjust the concentration of chlorine to be injected in accordance with the NH ₃ —N concentration.

[0004] The biological treatment method is technically established,
Has been put to practical use. However, since the biological treatment method performs denitrification by microorganisms, a storage tank and a biological treatment tank for keeping the nitrogen load constant are required, and a considerable space is required.

Therefore, development of a new method for treating ammoniacal nitrogen-containing wastewater is desired for business establishments that cannot secure the required space.

[0006]

SUMMARY OF THE INVENTION The present invention provides a method for treating wastewater containing a high concentration of ammonia nitrogen with simple means and without requiring a large space. Its main purpose is to:

[0007]

Means for Solving the Problems The present inventor has conducted intensive studies in view of the state of the art as described above, and as a result, oxidized ammonia-containing nitrogen-containing wastewater using pelletized bleaching powder. In this case, it has been found that the ammonia nitrogen content can be significantly reduced.

That is, the present invention provides a method for treating ammoniacal nitrogen-containing wastewater, comprising treating wastewater containing 1100 mg / l or more of ammoniacal nitrogen with a bleaching powder in the form of pellets .

The bleaching powder used in the present invention includes a general commercially available product containing calcium hypochlorite as a main component and a product containing 100% calcium hypochlorite.

In the present invention, the exfoliated pellets are brought into contact with the wastewater containing ammonia nitrogen to oxidatively decompose the ammonia nitrogen in the wastewater.

The method for treating ammoniacal nitrogen-containing wastewater with bleaching powder does not require any special equipment, and can be carried out by any means as long as both are in good contact. For example, the treatment can be performed by passing the wastewater through a porous container filled with bleaching powder. Alternatively, bleaching powder may be added to the waste water and stirred.

The amount of bleached powder used may be about the same molar amount as the amount of calcium hypochlorite contained in the bleached powder and the ammonia nitrogen contained in the waste water.

As described above, the ammoniacal nitrogen and the pellet
When it comes into contact with the flour- like flour (Ca (ClO) ₂ ),
Both react instantaneously, and the following reaction formulas (1) and (2)
As shown in, calcium chloride, calcium hydroxide, water,
Generates nitrogen gas and chlorine gas. As a result, the amount of ammonia nitrogen in the wastewater can be significantly reduced.

2NH ₄ OH + 2Ca (ClO) ₂ → N ₂ + 2CaCl ₂ +4 H ₂ O + 2OH ⁻ (1) (dissolution in water) Ca (ClO) ₂ +2 H ₂ O → Ca (OH) ₂ + Cl ₂ + H ₂ O (2) In the above reaction, calcium chloride and calcium hydroxide generated by the decomposition of ammoniacal nitrogen are naturally present in large quantities, and do not adversely affect the environment even if they are discharged as they are. Although free chlorine gas generated during the oxidation reaction is harmful, it can be easily treated by existing technology, and does not adversely affect the environment.

In the present invention, it is essential to oxidize and decompose ammoniacal nitrogen using a bleaching powder in the form of pellets .
Only then can the intended purpose be achieved. For example,
Other oxidizing agents, such as chlorine gas and sodium hypochlorite, used in the chlorine oxidation method are dangerous to handle and require storage tanks and injection equipment, whereas pellets are used. Exposed flour has less danger due to scattering and does not require special storage tanks, injection equipment, etc.,
Since it is in the form of pellets , there are also advantages such as easy handling and operation. Moreover, the bleaching powder can very advantageously treat the ammoniacal nitrogen-containing wastewater in that it is inexpensive and has excellent preservability.

Further, the biological treatment method is characterized in that wastewater from a flue gas desulfurization unit of a power plant, washing wastewater from an air preheater, an electric precipitator, and the like are used in addition to ammonia nitrogen to remove iron which inhibits the activity of microorganisms. Pretreatment (coagulation precipitation, hydrazine decomposition, pH adjustment, etc.) is required. On the other hand, the present invention does not require such pretreatment, and thus is advantageous as compared with the biological treatment method.

When the wastewater containing a large amount of heavy metals such as iron is treated by the method of the present invention, iron (oxidized) in the wastewater is oxidized to ions (molecules). Therefore, the amount of the coagulant (including the coagulant) used in the coagulation and precipitation treatment in the next step can be reduced.

Further, in the course of carrying out the method of the present invention, hydroxyl ions are generated when the exposed powder is dissolved in water, so that the pH of the water to be treated (strongly acidic water of about pH = 1 to 2) is increased.
Is increased, so that p required for pH adjustment in the next step is increased.
The use amount of the H adjusting agent can be reduced.

Furthermore, the action of free chlorine gas generated when the exposed powder is dissolved in water sterilizes and bleaches the organic substances generated in the filters (sand, pebbles, anthracite) and the adsorber in the integrated wastewater treatment equipment. Therefore, the effects of extending the life of the filler in the filter and the adsorber and preventing the occurrence of a differential pressure at the entrance and exit of the apparatus are also achieved.

The method of the present invention is applicable not only to wastewater containing ammonia nitrogen from a power plant, but also to wastewater containing other high-concentration ammonia nitrogen, for example, wastewater from a high-rise apartment house.

[0021]

EXAMPLES Examples and comparative examples are shown below to further clarify the features of the present invention.

Example 1 Wastewater from a flue gas desulfurization unit containing ammonia nitrogen discharged from a power plant (ammonia nitrogen concentration = 1,100 m
g / l) of 500 cc of pelletized bleaching powder (calcium hypochlorite, trade name "Hycron-100", manufactured by Nippon Soda Co., Ltd., containing at least 70% of available chlorine). Drained from below.

Table 1 shows the ammonia nitrogen concentration in the wastewater before and after the above treatment.

[0024]

[Table 1]

As is clear from the results shown in Table 1, according to the method of the present invention, the wastewater containing ammonia nitrogen can be highly treated by a simple operation. Also, when the ammoniacal nitrogen-containing wastewater further contains iron,
It is clear that the iron content has been significantly reduced.

Example 2 Wastewater from a condensate desalination treatment apparatus containing ammonia nitrogen discharged from a power plant (ammonia nitrogen = 16,000 m
g / l) were treated as in Example 1.

Table 2 shows the ammonia nitrogen concentration in the waste water before and after the above treatment.

[0028]

[Table 2]

As is clear from the results shown in Table 2, according to the method of the present invention, wastewater having a high concentration of ammonia nitrogen can be highly treated by a simple operation, and the pH of the liquid after the treatment can be increased. By increasing, it becomes unnecessary to adjust pH by adding an alkaline substance which is usually required.

REFERENCE EXAMPLE General Treatment of Ammonia Nitrogen-Containing Wastewater and Example 1
Table 3 shows a comparison with the treatment with bleached powder of No. 2.

The comparison items and the evaluation method are as follows.

(A) Processing capacity; ＝= instantaneous ＝= several tens × = several hours (B) Running cost; ＝= low price 安 価 = normal ×
= High cost (C) Equipment cost; ◎ = Low ○ = Normal × = High (D) Chemical handling; ◎ = No problem ○ = Normal × = Dangerous (E) Controllability; ◎ = Easy ○ = Normal × = Difficult (F ) Required space; ◎ = small space ○ = normal
× = Huge (G) By-product; ◎ = No problem ○ = Can be processed with existing technology × = Cannot be processed (H) Work period; ◎ = Short ○ = Normal × = Long

[0033]

[Table 3]

From the results shown in Table 3, it can be seen that the method for treating ammoniacal nitrogen-containing wastewater according to the present invention has no essential drawbacks, and can exhibit an overall excellent effect as compared with any known method. It is clear that.

[0035]

According to the method of the present invention, the nitrogen content of the wastewater containing ammoniacal nitrogen can be greatly reduced, so that the treated wastewater can be discharged in a safe state.

Further, the method of the present invention can perform the processing operation safely and easily, and does not require a large equipment space.

Further, in order to carry out the method of the present invention,
No special treatment equipment is required and it is economical.

Furthermore, the treatment can be carried out even when the ammoniacal nitrogen-containing wastewater contains metals such as iron.

In addition, when the ammoniacal nitrogen-containing wastewater contains metals such as iron, the amount of the coagulant used in the next step can be reduced, and the amount of the pH adjusting agent can be reduced. it can.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Hidekazu Nakajima 3-2-2, Nakanoshima, Kita-ku, Osaka-shi, Osaka Prefecture Inside Kansai Electric Power Company (72) Inventor Fukunaga Politics 3-3-1 Nakanoshima, Kita-ku, Osaka, Osaka 22 Kansai Electric Power Co., Inc. (72) Kiyoshi Gotanda 3-22 Nakanoshima, Kita-ku, Osaka City, Osaka Prefecture 22 Kansai Electric Power Co., Ltd. (72) Katsuhiro Katsumi, 3-3-Nakanoshima Kita-ku, Osaka City, Osaka Prefecture 22 Kansai Electric Power Co., Inc. (72) Kozo Shimono Inventor 3-2-2 Nakanoshima, Kita-ku, Osaka-shi, Osaka Prefecture Kansai Electric Power Co., Ltd. (72) Kenji Tominaga 3-chome, Nakanoshima, Kita-ku, Osaka, Osaka No. 22 Kansai Electric Power Co., Inc. (56) References JP-A-4-141295 (JP, A) Japanese Utility Model Application Showa 55-155596 (JP, U) Irrigation Wastewater Handbook Handbook Editing Committee “Revision 2nd Edition” Water Wastewater Handbook "(Akira 48-10-30) Maruzen Co., Ltd. P. 393-394 (58) Field surveyed (Int. Cl. ⁶ , DB name) C02F 1/72 C02F 1/76

Claims (1)

(57) [Claims] 1. A method for treating wastewater containing nitrogen, comprising treating wastewater containing 1100 mg / l or more of ammoniacal nitrogen with a bleaching powder in the form of pellets .