JP3008968B2 - Operation method of packed biological deodorization tower - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for operating a packed biological deodorization tower for deodorizing ammonia odor in a sewage treatment plant or the like.

[0002]

2. Description of the Related Art A filling-type biological deodorizing method utilizing the odor component decomposing action of microorganisms has lower running costs and is easier to maintain and manage than physical and chemical deodorizing methods such as a chemical cleaning method and an activated carbon adsorption method. Therefore, it has become quite popular nowadays, mainly due to the high concentration of sulfur-based odors generated from sludge storage tanks and sludge concentration tanks in sewage treatment plants.

[0003]

However, the odors generated in the sewage treatment plant are not only sulfur-based odor substances, but also various other odor substances such as ammonia and aldehyde are generated from the sludge dewatering / drying process. I do. Among them, particularly, ammonia has a high generation concentration, and is one of the major factors that deteriorate the working environment in the treatment plant.

An object of the present invention is to solve the above-mentioned problems, and an object of the present invention is to provide a method of operating a packed biological deodorization tower capable of removing an ammonia odor and preventing a decrease in deodorization efficiency.

[0005]

In order to solve the above-mentioned problems, a method for operating a packed biological deodorization tower according to the present invention comprises intermittently spraying circulating water onto a packed bed filled with a carrier for microorganisms. In a packed biological deodorization tower that cleans ammonium nitrate and ammonium nitrite generated by a chemical reaction between nitrate groups and nitrite groups generated by the nitrification reaction of ammonia in gas and ammonia groups in gas and accumulated on the carrier, circulating water To the circulating water by adding acid to 7.5.
In addition to the following, the ammonia nitrogen concentration in the circulating water is controlled to 1000 mg-N / l or less.

[0006]

According to the above construction, as the deodorizing action of ammonia by the microorganisms grown on the carrier progresses, ammonium nitrate and ammonium nitrite dissolve in the circulating water, and inorganic nitrogen such as ammonia nitrogen, nitrate nitrogen and nitrite nitrogen is dissolved. Accumulates. When the concentration of ammonia in the gas flowing into the deodorization tower is in a stable state, the circulating water is kept neutral. However, when the ammonia concentration in the gas increases rapidly, the nitrification reaction by the microorganism does not accompany the increase in the ammonia concentration, and the pH value of the circulating water increases due to the ammonia dissolved in the circulating water.

On the other hand, when the concentration of ammonia nitrogen in the circulating water of the microorganism growing on the carrier increases, the activity of the microorganism declines. Moreover, the decrease in the activity of the microorganism becomes stronger as the pH value becomes higher.

Therefore, it is possible to prevent a decrease in biological activity and a reduction in deodorizing efficiency by controlling the concentration of ammonia nitrogen in the circulating water to 1000 mg-N / l or less and controlling the pH value to 7.5 or less. it can.

[0009]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram of an experimental apparatus for an operation method according to the present invention. In FIG. 1, a packed biological deodorization tower 1 is provided with a packed layer 2 therein, and the packed layer 2 is filled with a carrier on which microorganisms involved in deodorization are fixed. Packed biological deodorization tower 1
A water storage unit 3 is provided at the bottom of the tank. The circulating water staying in the water storage unit 3 is sprinkled from above the packed bed 2 by a watering pump 4, and the circulating water returned to the water storage unit 3 through the packed bed 2 is It is configured to spray water repeatedly.

[0010] A pH meter 5 is provided in the water storage section 3, and a drug introduction pipe 6 for supplying sulfuric acid as a pH adjuster is connected through a drug pump 7. Further, a replenishing water pipe 8 and an overflow pipe 9 are provided in the water storage section 3, and a raw gas supply pipe 10 is connected to a lower part of the packed bed 2 of the packed biological deodorization tower 1 via a flow meter 11.
The raw gas supply pipe 10 supplies the raw gas adjusted to a predetermined concentration by diluting a commercially available ammonia gas with air. Further, an exhaust pipe 12 is provided in communication with the upper part of the packed bed 2 of the packed biological deodorization tower 1, and an intake device 13 is interposed in the exhaust pipe 12.

The operation of the above configuration will be described below.
The raw gas is sucked into the lower part of the packed bed 2 of the packed biological deodorization tower 1 through the raw gas supply pipe 10 by the intake device 13, and the raw gas is aerated in the packed biological deodorizing tower 1 in an upward flow. The ammonia in the raw gas is removed by microorganisms growing on the carrier. Then, the raw gas that has passed through the packed bed 2 is taken out as a processing gas through the exhaust pipe 12 by the suction device 13.

The mechanism for removing ammonia from the above-described packed bed 2 will be described with reference to FIG. In FIG. 2, the microorganisms that grow on the carrier are nitrifying bacteria, and the nitrifying bacteria decompose ammonia in the raw gas by a nitrification reaction to generate nitrate groups and nitrite groups. These nitrate groups and nitrite groups chemically react with ammonia groups in the raw gas to produce ammonium nitrate and ammonium nitrite.

Then, ammonium nitrate and ammonium nitrite accumulated on the carrier are supplied to the packed bed 2 by a circulation pump 7.
Wash with circulating water sprinkled from above. With the above-described configuration, when the deodorizing action of ammonia by the microorganisms grown on the carrier progresses, ammonium nitrate and ammonium nitrite dissolve in the circulating water to accumulate inorganic nitrogen such as ammonia nitrogen, nitrate nitrogen, and nitrite nitrogen. I do. When the concentration of ammonia gas in the raw gas flowing from the raw gas supply pipe 10 into the packed biological deodorization tower 1 is in a stable state, the amounts of ammonia nitrogen and nitrate nitrogen deposited in the circulating water are equal, and The pH value of the water is kept neutral.

However, the activity of the microorganisms growing on the carrier decreases as the concentration of ammonia nitrogen in the circulating water increases, and the decrease in the activity increases as the pH value increases. When this biological activity declines, the production of nitrate and nitrite groups by the nitrification reaction decreases, and on the other hand, the concentration of ammonia dissolved in the circulating water increases, so that the pH value of the circulating water increases, resulting in the activity of microorganisms. Decline further.

The above situation is shown in FIGS. FIG. 3 shows a change in the ammonia removal performance with a change in the ammonia nitrogen concentration in the circulating water. As is clear from FIG. 3, when the concentration of ammonia nitrogen in the circulating water increases,
Even if the concentration of ammonia gas in the raw gas is constant, the concentration of ammonia gas remaining in the processing gas increases. That is, as the concentration of ammonia nitrogen in the circulating water increases, the ammonia removing performance, that is, the deodorizing efficiency decreases.

FIG. 4 shows a change in the nitrification rate of ammonia in microorganisms with a change in the concentration of ammonia nitrogen in the circulating water. As is evident from FIG. 4, when the ammonia nitrogen concentration in the circulating water exceeds 1000 mg-N / l, the nitrification rate of ammonia by microorganisms decreases as the ammonia nitrogen concentration increases. That is, as the concentration of ammonia nitrogen in the circulating water increases, the biological activity of the microorganism declines, and the nitrification reaction decreases.

FIG. 5 shows the change in the removal rate of ammonia in the raw gas passing through the packed bed as the pH value of the circulating water changes. As is clear from FIG. 5, as the pH value of the circulating water increases, the removal rate of ammonia gas by microorganisms decreases. That is, as the pH value of the circulating water increases, the biological activity of the microorganisms decreases, and stripping of ammonia also occurs. In particular, when the pH value exceeds 7.5, the decrease in the removal rate becomes remarkable.

Therefore, by controlling the concentration of ammonia nitrogen in the circulating water to 1000 mg-N / l or less and controlling the pH to 7.5 or less, it is possible to prevent a decrease in biological activity and a decrease in deodorization efficiency. it can.

For this purpose, sulfuric acid as a neutralizing agent is appropriately fed into the circulating water through the drug feed pipe 6 by the drug pump 7, an appropriate amount of dilution water is supplied to the reservoir 3 through the makeup water pipe 8, and excess water is discharged. It is taken out of the system through the overflow tube 9.

[0020]

As described above, according to the present invention, the concentration of ammonia nitrogen in the circulating water is adjusted to 1000 mg-N / l or less and the pH value is adjusted so that the biological activity of the microorganisms growing on the carrier is not impaired. By controlling to 7.5 or less, it is possible to prevent a decrease in the performance of removing ammonia and obtain a stable deodorizing efficiency.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a configuration of a packed biological deodorization tower in one embodiment of the present invention.

FIG. 2 is a schematic diagram showing a mechanism for removing ammonia in the embodiment.

FIG. 3 shows the relationship between the ammonia nitrogen concentration in the circulating water and the ammonia removal performance in the same embodiment,
_{It is a 4-} N concentration-ammonia gas concentration diagram.

FIG. 4 is a circulating water NH ₄ —N concentration-nitrification rate diagram showing the relationship between the ammonia nitrogen concentration in the circulating water and the nitrification rate in the same example.

FIG. 5 is a pH-removal rate diagram showing the relationship between the pH value of circulating water and the ammonia removal rate in the example.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 packed biological deodorization tower 2 packed bed 3 water storage unit 4 sprinkling pump 5 pH meter 6 drug input pipe 8 makeup water pipe 10 raw gas supply pipe

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-5-92121 (JP, A) JP-A-54-109070 (JP, A) JP-A-2-99116 (JP, A) JP-A-5-92116 200243 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B01D 53/38 B01D 53/58 B01D 53/77

Claims (1)

(57) [Claims] 1. A chemical reaction between a nitrate group and a nitrite group generated by a nitrification reaction of ammonia in a gas by a microorganism and an ammonia group in the gas by intermittently spraying circulating water on a packed bed filled with a microorganism carrier. In a packed biological deodorization tower for washing ammonium nitrate and ammonium nitrite generated by the above and accumulated on the carrier, an acid is added to the circulating water to suppress the pH value of the circulating water to 7.5 or less, and the ammonia in the circulating water is added. A method for operating a packed biological deodorization tower, comprising controlling the concentration of reactive nitrogen to 1000 mg-N / l or less.