JPH0731835A - Operation of packing type biological deodorizing tower - Google Patents

Abstract

PURPOSE:To remove an ammonia offensive smell and to prevent the lowering of deodorizing efficiency by sprinkling water in sprinkling frequency such that the inflow amt. of ammonia flowing in a packed bed does not exceed a specific value until water is sprinkled after water is once sprinkled. CONSTITUTION:Raw gas is supplied to the lower part of the packed bed 2 of a packing type biological deodorizing tower 1 through a raw gas supply pipe 10 by the sucking action of a suction device 13 to be passed through the packing type biological deodorizing tower 1 upwardly and ammonia in the raw gas is removed by bacteria grown on the carrier in the packed bed. The raw gas passed through the packed bed 2 is taken out as treated gas through an exhaust pipe 12. Ammonium nitrate and ammonium nitrite accumulated on the carrier are washed with circulating water sprinkled from the position above the packed bed 2 by a circulating pump 7. Herein, water is sprinkled in water sprinkling frequency such that the inflow amt. of ammonia flowing in the packed bed 2 does not exceed 200g-N/m<3> until water is sprinkled after water is once sprinkled.

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 filling type biological deodorizing 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 action of decomposing odorous components of microorganisms has a lower running cost than physical and chemical deodorizing methods such as a chemical cleaning method and an activated carbon adsorption method, and is easy to maintain and manage. Therefore, it has attracted attention, and nowadays it has become quite popular mainly in the high concentration sulfur odor generated from sludge storage tanks and sludge thickening tanks of sewage treatment plants.

[0003]

However, the odors generated at the sewage treatment plant are not only sulfur-based odorous substances, but also various types of odorous substances such as ammonia and aldehyde are generated from the sludge dehydration / drying process. To do. Among them, especially ammonia, which has a high generation concentration, is one of the major factors that deteriorate the working environment in the treatment plant.

The present invention solves the above problems, and an object of the present invention is to provide a method for operating a packed-type biological deodorization tower which is capable of removing ammonia odor and preventing a decrease in deodorization efficiency.

[0005]

In order to solve the above-mentioned problems, a method for operating a packed-type biological deodorization tower of the present invention is characterized by intermittently sprinkling circulating water into a packed bed packed with a carrier of microorganisms, and In a packed biological deodorization tower for washing ammonium nitrate and ammonium nitrite produced by a chemical reaction between a nitric acid group and a nitrite group produced by the nitrification reaction of ammonia in a gas and the ammonia group in the gas and accumulated on the carrier, water is sprinkled once. The amount of influent ammonia flowing into the packed bed is 200 g-N / m ³ before the next sprinkling of water.
Water is sprinkled at a frequency that does not exceed

[0006]

With the above structure, when circulating water is sprinkled, ammonium nitrate and ammonium nitrite accumulated in the carrier flow down together with the circulating water. However, if a new water film is formed on the microorganism that grows on the carrier by sprinkling water, the amount of ammonia dissolved in the water film is small and the contact between the raw gas and the microorganism is hindered, so the nitrification rate of the microorganism decreases. To do.

Further, when the deodorizing action of ammonia by the microorganisms growing on the carrier progresses, the concentrations of ammonium nitrate and ammonium nitrite accumulated in the packed bed increase,
The concentration of ammoniacal nitrogen dissolved in the holding water of the packed bed becomes high.

On the other hand, the biological activity of the microorganisms growing on the carrier declines as the concentration of ammonia nitrogen increases, and the concentration of ammonia in the holding water increases and the pH value increases. Since the above-mentioned decrease in biological activity becomes stronger as the pH value increases, the activity of microorganisms further declines.

The above phenomenon becomes remarkable when the amount of inflowing ammonia flowing into the packed bed exceeds 200 g-N / m ³ , and ammonia remains in the treated gas discharged from the packed biological deodorization tower.

Therefore, by sprinkling the circulating water so that the amount of ammonia flowing into the packed bed does not exceed 200 g-N / m ³ , it is possible to prevent the decline of the biological activity and the deterioration of the deodorizing efficiency. it can.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of an experimental apparatus for the operating method of the present invention. In FIG. 1, a packing type biological deodorizing tower 1 is provided with a packing layer 2 inside, and the packing layer 2 is packed with a carrier on which microorganisms involved in deodorization are fixed. Packing type biological deodorization tower 1
A water storage section 3 is provided at the bottom of the tank, and the circulating water accumulated in the water storage section 3 is sprinkled from above the packed bed 2 by the water spray pump 4, and the circulating water passing through the packed bed 2 and returned to the water storage section 3 is collected. It is configured to repeat watering.

A pH meter 5 is provided in the water storage unit 3, and a chemical injection pipe 6 for supplying sulfuric acid as a pH adjusting agent is connected via a chemical pump 7. Further, a makeup water pipe 8 and an overflow pipe 9 are provided in the water storage unit 3, and a raw gas supply pipe 10 is connected to a lower portion of the packed bed 2 of the packed biological deodorization tower 1 via a flow meter 11.
The raw gas supply pipe 10 is supplied with a raw gas prepared by diluting a commercially available ammonia gas with air to a predetermined concentration. Further, an exhaust pipe 12 is provided so as to communicate with the upper part of the packed bed 2 of the packed biological deodorization tower 1, and an intake device 13 is provided in the middle of the exhaust pipe 12.

The operation of the above structure will be described below.
The raw gas supply pipe 10 by the suction action of the intake device 13
The raw gas is supplied to the lower part of the packed bed 2 of the packed biological deodorizing tower 1 through the above, the raw gas is aerated in the packed biological deodorizer tower 1 in an upward flow, and the raw gas is produced by the microorganisms grown on the carrier in the packed bed 2. Remove the ammonia inside. Then, the raw gas that has passed through the packed bed 2 is taken out as a processing gas through the exhaust pipe 12.

A mechanism for removing ammonia in the above packed bed 2 will be described with reference to FIG. In FIG. 2, the microorganism that adheres to the carrier and grows is a nitrifying bacterium, and the nitrifying bacterium decomposes ammonia in the raw gas by a nitrification reaction to generate a nitrate group and a nitrite group. The nitrate group and the nitrite group chemically react with the ammonia group in the raw gas to produce ammonium nitrate and ammonium nitrite.

When the deodorizing action of ammonia by the microorganisms growing on the carrier progresses, the concentrations of ammonium nitrate and ammonium nitrite accumulated in the packed bed increase, and the concentration of ammoniacal nitrogen dissolved in the holding water of the packed bed increases.

On the other hand, the biological activity of the microorganisms growing on the carrier declines as the concentration of ammonia nitrogen increases, and the concentration of ammonia in the holding water increases and the pH value increases. The higher the pH value is, the stronger the biological activity is, so that the activity of the microorganism is further deteriorated.

3 (a) to 3 (c) show the relationship between the ammonia concentration in the raw gas and the ammonia concentration in the treated gas when the raw gas having an ammonia concentration of 75 ppm is passed through the packed biological deodorization tower 1. (A) shows a case where watering is not performed, (b) shows a case where watering is performed 24 times a day, and (c) shows a case where watering is performed 4 times a day. ing.

As is clear from FIG. 3A, the ammonia concentration was detected in the treated gas after 7 hours when no water was sprinkled, and the cause is considered to be the decline in the biological activity of the microorganisms. To be At this time, the amount of ammonia per unit volume M [g-N / N of the packed bed supplied to the packed biological deodorization tower 1 during 7 hours from the start of the supply of the raw gas until the ammonia concentration is detected in the treated gas. m ³ ] can be calculated by the following equation.

[0019]

[Equation 1]

In the above-mentioned structure, when the amount of ammonia flowing into the packed bed exceeds 200 g-N / m ³ , it becomes remarkable, and ammonia remains in the treated gas discharged from the packed biological deodorization tower.

Therefore, the ammonium nitrate and ammonium nitrite accumulated in the carrier are washed by the circulating pump 7 with the circulating water sprayed from above the packed bed 2. By the way, as is clear from FIG. 3B, when water is sprinkled 24 times a day, the ammonia concentration is detected in the treated gas immediately after water sprinkling. As a cause of this, if a new water film is formed on the microorganisms that grow on the carrier by sprinkling water, the amount of ammonia dissolved in the water film is small, and the contact between the raw gas and the microorganisms is hindered. It seems to decrease.

Therefore, as shown in FIG. 3 (c), when the watering frequency is changed and watering is performed four times a day,
Almost no ammonia concentration was detected in the process gas. Further, if the frequency of sprinkling is further reduced, the removal performance will again decrease. This optimum watering frequency naturally changes depending on the ammonia load of the raw gas, and it is necessary to increase the watering frequency as the load increases and the temperature decreases. Incidentally, when the ammonia concentration in the raw gas was 200 ppm, the optimum watering frequency was about 12 times a day. Table 1 shows the difference in the optimum watering frequency depending on the ammonia concentration.

[0023]

[Table 1] As is clear from Table 1, even when the raw gas ammonia load is different, the amount of ammonia supplied per packed bed is 200 g-N / m before the ammonia concentration is detected in the treated gas after water is once sprinkled. It is about ³ . Therefore,
The amount of inflowing ammonia flowing into the packed bed is 200 g-N / m
By sprinkling the circulating water so as not to exceed ³ , it is possible to prevent the decline of the biological activity and the deterioration of the deodorizing efficiency.

[0024]

As described above, according to the present invention, when the inflowing ammonia amount flowing into the packed bed exceeds 200 g-N / m ³ , the biological activity of microorganisms is significantly deteriorated, and the packed-type biological deodorizing tower is used. since ammonia so remaining in the treatment gas to be discharged from, as the amount of ammonia flowing into the packed bed does not exceed 200g-N / m ^3, by sprinkling the circulating water, preventing the decline of the biological activity However, it is possible to prevent the deodorization efficiency from decreasing.

[Brief description of drawings]

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

FIG. 2 is a schematic view showing an ammonia removal mechanism in the example.

3 (a) to 3 (c) are relationship diagrams showing a relationship between a watering frequency and an ammonia gas concentration in the same example, respectively.

[Explanation of symbols]

 1 Packing type biological deodorization tower 2 Packed layer 3 Water storage part 4 Sprinkling pump 5 pH meter 6 Chemical input pipe 8 Make-up water pipe 10 Raw gas supply pipe

Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location B01D 53/58 B01D 53/34 131

Claims (1)

[Claims] 1. A chemical reaction between a nitrate group and a nitrite group produced by a nitrification reaction of ammonia in a gas by a microorganism by intermittently sprinkling circulating water in a packed bed filled with a carrier of the microorganism and an ammonia group in the gas. In a packed type biological deodorization tower for washing ammonium nitrate and ammonium nitrite generated by the above and accumulated in the carrier, the amount of inflowing ammonia flowing into the packed bed is 200 g-N / m between the time of once watering and the time of next watering. ^A method for operating a packed biological deodorization tower, which is characterized by sprinkling water at a sprinkling frequency not exceeding ³ .