JP2003094093A - Method for preventing malodor generation from sludge - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for preventing malodor generation from sludge capable of effectively preventing malodor from hydrogen sulfide and so on generated by the sludge in a sewage disposal plant, or the like, and applicable to a large-scale facility operating dehydration continuously day and night as well as a small plant operating dehydration only in the daytime. SOLUTION: This method for preventing the malodor generation from the sludge in a sludge storage tank is achieved by allowing nitrite to exist in the sludge storage tank. The sludge is introduced into the sludge storage tank after mixing nitrite therewith at the outside of the sludge storage tank, sucked out of the sludge storage tank continuously day and night, and is dehydrated. An agitating period per day is not more than a half of an average retention period for the sludge in the sludge storage tank, and meanwhile one agitating period is within one hour, or alternatively, the sludge is sucked out of the sludge storage tank only in the daytime and is dehydrated. The agitation is stopped for more than two hours in operating the dehydration while one agitating period is within one hour.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for preventing odor generation of sludge. More specifically, the present invention can effectively prevent odors derived from hydrogen sulfide, methyl mercaptan, ammonia, amines, etc., generated from sludge in sewage treatment plants, night soil treatment plants, etc. The present invention relates to a sludge odor prevention method that can be applied to both large-scale facilities that operate and small-scale facilities that perform dehydration operation only during the daytime.

[0002]

2. Description of the Related Art Sewage treatment plants, human waste treatment plants, food factories,
Various sludges are generated in the process of treating organic industrial wastewater such as pulp and paper factories. For example, solid-liquid separation of sewage in a first settling basin produces first settling sludge, and treatment of the supernatant of the first settling basin using an aeration tank or the like by a floating organism method increases the amount of activated sludge. The water treated in the aeration tank etc. is guided to the final settling basin, the activated sludge is separated, part of it is returned to the aeration tank etc. as return sludge, and the rest is made into excess sludge. The initial sludge and excess sludge are guided to a sludge thickening tank, and then temporarily stored in a sludge storage tank. The sludge in the sludge storage tank is then dehydrated by a dehydrator, and the obtained sludge dehydrated cake is carried out for landfill or incineration. The sludge stored in the sludge storage tank produces a foul-smelling substance due to decay. Substances often detected as malodorous substances generated in sewage treatment plants are hydrogen sulfide, sulfur compounds such as methyl mercaptan, nitrogen compounds such as ammonia and trimethylamine, and lower fatty acids such as valeric acid and isobutyric acid. Among these, the amounts of hydrogen sulfide and methyl mercaptan produced by the decomposition of the sulfur-containing protein are particularly large. The odor generated in the sludge storage tank moves along with the subsequent movement of the sludge, and causes problems such as deterioration of the working environment and deterioration of the natural environment in the sludge dewatering step, the sludge dewatering cake processing step, and the like. The sludge dewatering machine can be a closed system, but since the sludge dewatering cake is often transported and stored in an open system, odor control is important. In addition, even in the final landfill, the generated odor diffuses, causing unpleasant sensation to nearby residents, which adversely affects the environment. For this reason, it is necessary to take odor prevention measures back to the sludge storage tank, and various odor generation prevention methods have been proposed conventionally. For example, JP-A-5
As a method of preventing the generation of hydrogen sulfide based on microorganisms, Japanese Patent Publication No. 7-187099 proposes a method of allowing nitrite ions to exist in the habitat of the microorganisms. In addition, the inventors of the present invention, as a method for preventing the generation of odor in the entire sludge treatment process, intermittently add nitrite to the sludge in the sludge storage tank, and at the same time, leave the residual nitrite in the sludge one hour after the end of the addition. It has been found that by setting the ion concentration to 20 mg / L or more, the effect of preventing the generation of hydrogen sulfide and methyl mercaptan can be stably maintained even if the amount of nitrite added is the same or reduced. . But,
Since the demand for environmental protection becomes severe with the years, there is a demand for a method that can more effectively prevent the generation of odor of sludge by using a smaller amount of chemicals.

[0003]

The present invention can effectively prevent odors derived from hydrogen sulfide, methyl mercaptan, ammonia, amines, etc. generated from sludge at sewage treatment plants, night soil treatment plants, etc. The object of the present invention is to provide a method for preventing the generation of sludge odor that can be applied to both large-scale facilities that perform dehydration operation continuously during the day and night and small-scale facilities that perform dehydration operation only during the daytime.

[0004]

Means for Solving the Problems As a result of intensive studies to solve the above-mentioned problems, the present inventors mixed sludge with nitrite outside the sludge storage tank, and then introduced the sludge into the sludge storage tank. It was found that the generation of odor can be effectively prevented by keeping the amount of stirring to a minimum to prevent the separation of
The present invention has been completed based on this finding. That is, the present invention is (1) a method of preventing odor generation of sludge in a sludge storage tank by allowing nitrite to exist in the sludge storage tank, wherein sludge is mixed with nitrite outside the sludge storage tank It is introduced into the storage tank, sludge is continuously extracted from the sludge storage tank day and night, dehydrated, and the stirring time for one day is 1/2 or less of the average sludge retention time in the sludge storage tank, and one time stirring A method for preventing odor generation of sludge, which is characterized by stirring for a duration of less than 1 hour, and (2) preventing odor generation of sludge in the sludge storage tank by allowing nitrite to exist in the sludge storage tank. The method is to mix nitrite with sludge outside the sludge storage tank, then introduce the sludge into the sludge storage tank, extract the sludge from the sludge storage tank only in the daytime to dehydrate, and stop stirring for 2 hours or more during the dehydration operation, and The stirring is continued for 1 hour or less. Odor prevention methods sludge and performing, there is provided a.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The first aspect of the method for preventing odor generation of sludge of the present invention is a method for preventing odor generation of sludge in a sludge storage tank by allowing nitrite to exist in the sludge storage tank,
After mixing nitrite with the sludge outside the sludge storage tank, it is introduced into the sludge storage tank, the sludge is continuously extracted from the sludge storage tank day and night, and dehydrated. Stirring is performed for half the time or less and for one stirring duration of 1 hour or less. The first aspect of the method of the present invention can be applied to a large-scale treatment plant in which dehydration operation is continuously performed day and night. In such a treatment plant, as a general rule, the dehydration operation is performed continuously for 24 hours a day, but the first aspect of the method of the present invention is that the dehydration operation is performed within 8 hours a day for maintenance of facilities. It can also be applied to a treatment plant that involves the suspension of The second aspect of the method for preventing odor generation of sludge of the present invention is a method for preventing the odor generation of sludge in the sludge storage tank by allowing nitrite to exist in the sludge storage tank, in which the sludge is stored outside the sludge storage tank. After mixing nitrite, it is introduced into the sludge storage tank, the sludge is extracted from the sludge storage tank only in the daytime and dehydrated, stirring is stopped for 2 hours or more during the dehydration operation, and one stirring duration is within 1 hour. Stir. The second aspect of the method of the present invention can be applied mainly to a small-scale treatment plant in which dehydration operation is performed only in the daytime. In such a treatment plant, as a general rule, the dehydration operation is carried out for about 8 hours which is a regular working time, but the second aspect of the method of the present invention is 16 hours because of an increase in the sludge treatment amount. It can also be applied to treatment plants with extended operation up to the maximum. It should be noted that both the first aspect and the second aspect include allowing the inside of the sludge storage tank to stand without stirring. The agitation referred to in the present invention means agitation in which sludge is mixed, and does not include agitation at a low speed such that sludge is not mixed.

Nitrite ion decomposes odorous components such as hydrogen sulfide in sludge at a slow rate and suppresses microbial activity related to odor generation in sludge to generate new odorous components from sludge. Has the effect of preventing. Among these effects, the effect of suppressing microbial activity varies depending on the concentration of sludge, the content of oxidizable substances such as odorous components, the microbial activity, and the pH of sludge. It develops by keeping the ion concentration of 20 mg / L or more for 1 hour or more. The sludge storage tank is usually provided with a stirring device for the purpose of uniform mixing of sludge and prevention of precipitation. Especially for sewage sludge treatment facilities, it is stipulated in the design guidelines of the Sewerage Agency that a stirrer is installed. However, even if nitrite is added to such a sludge storage tank or added to the sludge introduced into the sludge storage tank, a satisfactory odor prevention effect cannot be obtained. It was found that when the sludge was stirred in the sludge storage tank, the nitrite ions added to the sludge rapidly disappeared. When nitrite ions are added to the sludge storage tank that is being stirred, for example, the average retention time of the sludge storage tank is 10
Assuming complete mixing in time, when 100 mg / L of nitrite ion is added to the sludge supplied to the sludge storage tank, the concentration of nitrite ion added to the supplied sludge is
Instantly 10 mg / 1/10 of the concentration added to the supplied sludge
Dilute to L. If the nitrite ion added up to that time is present in the sludge storage tank, the residual concentration is added to this, but if the nitrite ion concentration is low, the effect of suppressing microbial activity is small, As a result, the microbial decomposition rate of nitrite ion did not decrease, and the nitrite ion added before that time disappeared. This is because if the amount of nitrite ion added is small, not only the effect of suppressing microbial activity is not observed, but conversely, the number of microorganisms that decompose nitrite ions due to the acclimation phenomenon is considered to increase significantly. As a result, even if a high concentration of nitrite ion is added to the supplied sludge, the nitrite ion is immediately diluted in the sludge storage tank, decomposed in a short time, and the nitrite ion is detected in the sludge storage tank. As a result, the odor prevention effect is not exhibited.

In the method of the present invention, the minimum agitation necessary for prevention of sludge separation and the like is performed, and thus the sludge successively introduced into the sludge storage tank is less likely to mix with each other because of its viscosity. Therefore, the nitrite ion added to the sludge acts on the sludge in the added concentration. In this process, nitrite ion is consumed by oxidation of oxidant and microbial decomposition, but nitrite ion contact time required for microbial activity suppression of about 1 hour and 20 mg /
It is possible to sufficiently secure the concentration necessary for reducing the microbial activity judged to be about L. Further, when the sludge storage tank is agitated as in the conventional case, there are the following two problems. Since it takes about 1 hour to develop the effect of decomposing the odorous components of nitrite ion, the odorous components such as hydrogen sulfide already contained in the sludge containing nitrite introduced into the sludge storage tank are Before the decomposition by nitrate ions is completed, sludge disturbance accompanied by stirring causes the emission of odorous gas such as hydrogen sulfide into the atmosphere. In the present invention,
This problem can be solved. When nitrite is added to sludge to prevent odor, most of the decomposition products of nitrite ions are nitrogen gas, but a small part becomes nitric oxide, which is released into the atmosphere by stirring sludge, Furthermore, a part is air-oxidized to nitrogen dioxide. According to the method of the present invention,
When the agitation of the sludge storage tank is stopped, the generated nitric oxide is consumed in the sludge, it is given time to decompose, and the amount of nitrite necessary for odor control is greatly reduced. The release of nitrogen into the atmosphere can also be greatly reduced.

When the stirring of the sludge storage tank is stopped, there is a concern that the sludge cannot be made uniform and that the sludge is floated by the nitrogen gas generated by the decomposition of nitrite ions.
However, the sludge can be homogenized before being introduced into the sludge storage tank, and when the stirring is stopped for 1 to 2 days, the sludge is hardly floated by the nitrogen gas. However, for example, it is not preferable to stop the stirring for one week, so at the treatment plant where the dehydration operation is continuously performed day and night,
In a treatment plant in which the stirring time of day is 1/2 or less of the average residence time of sludge in the sludge storage tank, and the stirring time of one time is 1 hour or less, and the dehydration operation is performed only in the daytime, During the dehydration operation, stop stirring for 2 hours or more, and 1
Stirring is performed with a stirring time of 1 hour or less. For example,
It can be agitated manually or once every one to several days, or after confirming the state of the sludge storage tank. In a treatment plant that performs dehydration operation only in the daytime, for example, the sludge should be extracted from the sludge storage tank and stirred for about 30 minutes automatically using a timer two hours before the start of dehydration operation. You can also According to the method for preventing odor generation of sludge of the present invention, a simple operation method in which nitrite is mixed with sludge outside the sludge storage tank and then introduced into the sludge storage tank, and in the sludge storage tank, minimum stirring is performed. By changing the above, it is possible to efficiently suppress generation of hydrogen sulfide, which is a source of malodor, by using a nitrite that is equivalent to or smaller than the conventional one.

[0009]

The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. FIG. 1 is a part of a process system diagram of a treatment plant used in Comparative Examples and Examples. In each of the comparative examples and the examples, there is a difference in the size of the facility of the treatment plant, but in all cases, the sludge is treated by the process shown in this figure. The sludge is introduced into the sludge storage tank 2 equipped with a stirring device by the sludge supply pipe 1. The sludge in the sludge storage tank is introduced into the coagulation reaction tank 3, and a macromolecular coagulant is added to coarsen the sludge particles, and then the sludge is fed into the belt press dehydrator 4. In the comparative example and the example, the hydrogen sulfide concentration was measured at two points during the process. The H ₂ S concentration of 1 was obtained by collecting 50 mL of sludge sent from the sludge storage tank to the flocculation reaction tank in FIG. 1A, placing it in a container having a volume of 600 mL, sealing it, shaking it for 2 minutes, and then measuring it in the gas phase part. It is the concentration of hydrogen sulfide. The H ₂ S concentration 2 is the concentration of hydrogen sulfide measured for the gas at the position b 50 cm above the belt surface of the sludge feeding pipe to the belt press dehydrator. The concentration of hydrogen sulfide was measured using a gas detector tube manufactured by Gastec Corporation.
Further, the nitrite ion concentration in the dehydrated filtrate c of the belt press dehydrator was measured according to JIS K 0102 43.1. Comparative Example 1 A mixed sludge is dehydrated at a sewage treatment plant. In this sewage treatment plant, sludge is continuously introduced into the sludge storage tank day and night, and the addition amount of sodium nitrite is 150 mg to 1 L of sludge, that is, 100 mg as nitrite ion, depending on the amount of sludge introduced. In addition, sodium nitrite is continuously added to the sludge storage tank, and the sludge storage tank is continuously stirred. Sludge is continuously extracted from the sludge storage tank day and night and dehydrated by a belt press dehydrator. First
The table is an average daily driving record. Time 1 in this table
In the column of hour, sludge 14.0m ³ was introduced into the sludge storage tank from 12:00 am to 1 am, sludge 12.1 m ³ was extracted and dehydrated, and the storage amount of sludge at 1 am was 122
m ³ and the sludge storage tank is 1 from midnight to 1 am
H ₂ S concentration 1 at 1 am
Is 80 ppm and H ₂ S concentration 2 is 14 ppm, indicating that NO ₂ ⁻ was not detected in the dehydrated filtrate.
This day, 1 hour average 14.0 m ^3, sludge total 335.8M ³ is introduced into the sludge storage tank, 1 hour average 14.0 m ^3,
A total of 336.7 m ³ of sludge was extracted from the sludge storage tank and dehydrated, the average storage amount of the sludge storage tank was 120 m ³ , the average retention time was 8.6 hours, and the sludge storage tank was continuously stirred. ing. The average of H ₂ S concentration 1 is 100 ppm, H ₂ S
The average of concentration 2 is 12 ppm, and the average concentration of NO ₂ ⁻ ions in the dehydrated filtrate is 0.3 mg / L.

[0010]

[Table 1]

Example 1 The method of the present invention was applied to the sewage treatment plant of Comparative Example 1. That is, depending on the amount of sludge introduced, sodium nitrite was continuously added to the sludge supply pipe so that the amount of sodium nitrite added was 112.5 mg per 1 L of sludge, that is, 75 mg as nitrite ions. Then, it was introduced into the sludge storage tank in a state where sodium nitrite was mixed with the sludge. The agitation of the sludge storage tank is from 30:30 from 5:30 am to 6:00 am and 30 minutes from 5:30 pm to 6:00 pm.
The sludge was held once for a total of 1 hour, and was left standing for the rest of the time without stirring the sludge storage tank. Table 2 shows an average daily driving record. This day, 1 hour average 14.1 m ^3, a total 337.8M ³ of sludge is introduced into the sludge storage tank, 1 hour average 14.1 m ^3, sludge total 338.9M ³ is withdrawn from the sludge storage tank The sludge storage tank has an average storage amount of 123 m ³ and an average residence time of 8.7 hours, and the sludge storage tank is agitated only twice, 30 minutes in the morning and 30 minutes in the evening. The average H ₂ S concentration 1 is 1.8 ppm, the average H ₂ S concentration 2 is 0.1 ppm, and the average NO ₂ ⁻ ion concentration in the dehydrated filtrate is 8.3 mg / L.

[0012]

[Table 2]

Summarizing the results of Comparative Example 1 and Example 1,
It is shown in Table 3.

[0014]

[Table 3]

As can be seen from Table 3, in Example 1 to which the method of the present invention was applied, the amount of sodium nitrite added was reduced to 75% as compared with Comparative Example 1 of the conventional method. , The concentration of hydrogen sulfide is 1/50 to 50
It is reduced to one-third. This is because in Comparative Example 1,
Almost no nitrite ions are found in the dehydrated filtrate, whereas in Example 1, since nitrite ions remain in the dehydrated filtrate, nitrite is mixed with the sludge outside the sludge storage tank. However, by the method of the present invention of performing minimal stirring in the sludge storage tank, it is understood that the decomposition of nitrite ions is suppressed, effectively contributing to the decomposition of hydrogen sulfide and the prevention of hydrogen sulfide generation. . Comparative Example 2 The mixed sludge is dehydrated at a sewage treatment plant, which is smaller than the sewage treatment plant of Comparative Example 1 and performs dehydration operation only in the daytime. At this sewage treatment plant, only sludge is received in the sludge storage tank at night, and at the start of work every morning, the amount of sodium nitrite added to 1 L of sludge is 200 mg, that is, 13 as nitrate ion
Sodium nitrite was added all at once to the sludge storage tank so that it became 3 mg, and the amount of sodium nitrite added to 1 L of sludge was 20 during the day depending on the amount of sludge introduced into the sludge storage tank.
Sodium nitrite was continuously added to the sludge storage tank so that 0 mg, that is, 130 mg as nitrite ion,
The sludge storage tank is continuously stirred only during the working hours. Table 4 shows an average daily driving record. On this day, stirring of the sludge storage tank was started at 6 am and continued until 4 pm. The sludge extraction from the sludge storage tank was started at 9:00 am, and a total of 71.0 m ³ of sludge was dehydrated. The average H ₂ S concentration 1 during sludge dewatering operation is 61 ppm,
The average H ₂ S concentration 2 is 12 ppm, and NO in the dehydrated filtrate is
The average ₂ ^- ion concentration was 1.6 mg / L, and it was detected only for 1 hour out of 7 hours of the dehydration operation.

[0016]

[Table 4]

Example 2 The method of the present invention was applied to the sewage treatment plant of Comparative Example 2. That is, depending on the amount of sludge introduced, sodium nitrite was continuously added to the sludge feed pipe so that the amount of sodium nitrite added to 1 L of sludge was 150 mg, that is, 100 mg as nitrite ions, The sludge was mixed with sodium nitrite and introduced into the sludge storage tank. Table 5 shows an average daily driving record. On this day, stirring of the sludge storage tank was performed for 30 minutes from 5:30 am to 6:00 am using a timer, and the rest of the sludge storage tank was allowed to stand without stirring. The sludge extraction from the sludge storage tank was started before 9 am, and a total of 71.9 m ³ of sludge was dehydrated. Average concentration of H ₂ S 1 in the sludge dewatering operation is 0.14 ppm, the average of the concentration of H ₂ S 2 is 0.14 ppm, NO in the dehydration filtrate ₂ ^- average ion concentration 9.0 mg /
L was detected in 5 hours out of 7 hours in the dehydration operation.

[0018]

[Table 5]

The results of Comparative Example 2 and Example 2 are summarized below.
It is shown in Table 6.

[0020]

[Table 6]

As can be seen from Table 6, in Example 2 to which the method of the present invention was applied, the amount of sodium nitrite added was reduced to 75% as compared with Comparative Example 2 of the conventional method. , The concentration of hydrogen sulfide is reduced to about 1/100. This is because, in Comparative Example 2, the amount of nitrite ions in the dehydrated filtrate was small, whereas in Example 2, the nitrite ions remained in the dehydrated filtrate at a high concentration. By the method of the present invention of mixing nitrite with sludge outside the sludge storage tank, and performing minimum stirring in the sludge storage tank,
It can be seen that the decomposition of nitrite ions is suppressed, which effectively contributes to the decomposition of hydrogen sulfide and the prevention of hydrogen sulfide generation. Comparative Example 3 A coagulation sedimentation sludge is dehydrated at a wastewater treatment plant of a paper mill. In this wastewater treatment plant, sludge is continuously introduced into the sludge storage tank day and night, and the amount of sodium nitrite added is 130 mg per 1 L of sludge, that is, 86.7 mg as nitrite ion, depending on the amount of sludge introduced. Sodium nitrite is continuously added to the sludge storage tank, and the sludge storage tank is continuously stirred. Sludge is continuously extracted from the sludge storage tank day and night and dehydrated by a belt press dehydrator. Table 7 is an average daily driving record. On this day, an average of 22.2 m ³ per hour, a total of 533 m ³ of sludge was introduced into the sludge storage tank, and an average of 21.8 m ³ per hour, a total of 523 m ³ of sludge was extracted from the sludge storage tank and dehydrated, The sludge storage tank has an average storage amount of 49 m ³ and an average retention time of 2.2 hours, and the sludge storage tank is continuously stirred. The average of H ₂ S concentration 1 was 124 ppm, the average of H ₂ S concentration 2 was 17.5 ppm, and NO ₂ ⁻ ions were not detected at all in the dehydrated filtrate.

[0022]

[Table 7]

Example 3 The method of the present invention was applied to the wastewater treatment plant of Comparative Example 3. That is, depending on the amount of sludge introduced, sodium nitrite was continuously added to the sludge feed pipe so that the amount of sodium nitrite added to 1 L of sludge was 130 mg, that is, 86.7 mg as nitrite ions. Then, it was introduced into the sludge storage tank in a state where sodium nitrite was mixed with the sludge. The agitation of the sludge storage tank is from 30:30 from 5:30 am to 6:00 am and 30 minutes from 5:30 pm to 6:00 pm.
The sludge was held once for a total of 1 hour, and was left standing for the rest of the time without stirring the sludge storage tank. Table 8 is an average daily driving record. On this day, an average of 22.3 m ³ per hour, a total of 535 m ³ of sludge was introduced into the sludge storage tank, and an average of 22.3 m ³ per hour, a total of 535 m ³ of sludge was extracted from the sludge storage tank and dehydrated, The average storage amount of sludge storage tank is 13
The average retention time is ³ m ³ , the average time is 6.0 hours, and the sludge storage tank is agitated only twice, 30 minutes in the morning and 30 minutes in the evening.
The average H ₂ S concentration 1 is 3.6 ppm, the average H ₂ S concentration 2 is 1.2 ppm, and the average NO ₂ ⁻ ion concentration in the dehydrated filtrate is 9.5 mg / L.

[0024]

[Table 8]

The results of Comparative Example 3 and Example 3 are summarized below.
It is shown in Table 9.

[0026]

[Table 9]

As can be seen from Table 3, in comparison with Comparative Example 3 of the conventional method, in Example 3 to which the method of the present invention was applied, the sulfurization was carried out even though the addition amount of sodium nitrite was the same. The hydrogen concentration is reduced to about 1/30 to 1/15. This is because, in Comparative Example 3, no nitrite ion was found in the dehydrated filtrate,
In Example 3, since nitrite ions remained in the dehydrated filtrate, nitrite was mixed with the sludge outside the sludge storage tank,
It can be seen that the method of the present invention in which a minimum amount of stirring is performed in the sludge storage tank suppresses the decomposition of nitrite ions and effectively contributes to the decomposition of hydrogen sulfide and the prevention of hydrogen sulfide generation.

[0028]

According to the sludge odor generation preventing method of the present invention, the nitrite is mixed with the sludge outside the sludge storage tank and then introduced into the sludge storage tank, and the sludge storage tank performs minimum stirring. By simply changing the operating method, it is possible to effectively suppress the generation of malodorous hydrogen sulfide and the like by using a nitrite which is equivalent to or smaller than the conventional one. The method of the present invention can be economically carried out because it is possible to reduce the agitation power by simply adding a device for mixing nitrite outside the sludge storage tank without requiring a major modification of the equipment. can do.

[Brief description of drawings]

FIG. 1 is a part of a process system diagram of a treatment plant to which the method of the present invention is applied in Examples.

[Explanation of symbols] 1 Sludge supply pipe 2 Sludge storage tank 3 Aggregation reaction tank 4 Belt press dehydrator

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Claims (2)

[Claims] 1. A method for preventing odor generation of sludge in a sludge storage tank by allowing nitrite to exist in the sludge storage tank, which is introduced into the sludge storage tank after mixing nitrite with the sludge outside the sludge storage tank. Then, the sludge is continuously extracted from the sludge storage tank day and night and dehydrated, and the agitation time of one day is 1/2 or less of the average retention time of the sludge in the sludge storage tank, and the duration of one agitation is 1 time. A method for preventing the generation of odor in sludge, which comprises performing stirring within a period of time. 2. A method for preventing odor generation of sludge in a sludge storage tank by allowing nitrite to exist in the sludge storage tank, which is introduced into the sludge storage tank after mixing nitrite with the sludge outside the sludge storage tank. The sludge odor is characterized in that sludge is extracted from the sludge storage tank only during the daytime and dehydrated, stirring is stopped for 2 hours or more during the dehydration operation, and stirring is performed once within 1 hour. Prevention method.