JP2002233895A - Deodorization method for swage sludge - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of deodorizing sewer sludge by suppressing the generation of hydrogen sulfide, mercaptan, ammonia, etc., in the sewer sludge. SOLUTION: The sewer sludge is forcibly fluidized and air is sucked by an ejector effect into the flowing sewer sludge. The sucked air is made into fine air bubbles by a cavitation effect.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for deodorizing sewage sludge.

[0002]

2. Description of the Related Art Sewage sludge emits odors such as ammonia, hydrogen sulfide and mercaptan secreted by decay of organic matter and anaerobic bacteria, and this is an environmental problem around sewage treatment plants. Conventionally, the method of decomposing by sludge with chemicals or microorganisms has been adopted to control the odor of sludge.
There is an adverse effect that the drug itself remains in the sludge. The method of decomposing by microorganisms is not suitable for mass processing because the processing speed is slow.

[0003]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to provide a method capable of performing a large amount of treatment without using drugs or microorganisms and completely deodorizing.

[0004]

Means for Solving the Problems The present inventor has made intensive studies in view of the above problems and found that the problems can be solved by the following claims 1 to 3. [Claim 1] A method for deodorizing sewage sludge, comprising forcibly flowing sewage sludge and dispersing fine air bubbles in the flowing sludge. [Claim 2] The deodorization method according to claim 1, wherein the fine air bubbles are obtained by sucking air into the flowing sludge by an ejector action and converting the sucked air into fine air bubbles by a cavitation action. [Claim 3] The deodorization method according to claim 1, wherein the fine bubbles are formed into fine bubbles by mechanical shearing force.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION When fine air bubbles are mixed with sludge, the oxygen concentration of the sludge increases, the activity of anaerobic bacteria can be suppressed, and the generation of hydrogen sulfide, mercaptan and the like can be prevented. Further, it is possible to suppress rot and oxidatively decompose ammonia and the like generated by the rot. Since the amount of air dissolved in the sludge is proportional to the surface area of the entire bubble, the smaller the bubble diameter, the better.

As a means for mixing and dispersing fine air bubbles in sludge, a so-called aeration method is effective, but air is blown out from fine holes such as conventionally used diffusers, diffusers and diffusers. In the method, since the sludge is easily clogged in the bubble outlet, for the purpose of the present invention, a structure in which clogging hardly occurs or does not occur at all is preferable.

For the purposes of the present invention, the bubble generator shown in FIGS. The apparatus shown in FIG. 1 is a generator having an air self-priming port 1 at an upper portion, a sludge pressure inlet 2 on a side surface, and a bubble jet port 3. Sludge is injected from the pressure inlet 2 to generate a swirling flow therein. When the sludge is injected from the self-priming port 1, air is sucked in from the self-priming port 1, and the sucked air is mixed with the swirl flow of the sludge. It is a mechanism that is separated into fine bubbles by the shearing action generated at the interface of the mixing and swirling flow and is ejected together with the sludge from the ejection port.

The method shown in FIG. 2 is a mechanism in which air sent from a lower portion by a small blower is divided into fine bubbles in the process of swirling and mixed with sludge, and a large amount of fine bubbles are generated at an outlet at the top. The apparatus shown in FIGS. 1 and 2 has a feature that the clogging hardly occurs because there is no ejection hole for fine bubbles unlike the conventional apparatus.

FIG. 3 shows a method of forming fine bubbles using cavitation. This is the most preferred method for the purposes of the present invention. When cavitation is used, air is self-primed by an ejector action. That is, when sludge is pumped into a pipe using a pump, air is sucked using the principle that air is sucked from a hole drilled in the pipe, and cavitation is generated in the sucked air to convert it into fine bubbles It is. In cavitation, the sludge pumping pipe is connected to the bubble generator, and the diameter of the sludge discharge port of the bubble generator as shown in Fig. 3 is fan-shaped. Negative pressure is generated in the expanded part and cavitation occurs. I do. When the collision plate as shown in FIG. 4 is provided in the enlarged diameter portion, cavitation is effectively generated in the pocket portion. When cavitation occurs, the air disperses into the sludge in fine bubbles of several microns. Further, a shear force of several thousand atmospheres is generated in the sludge flow, and solid particles such as organic wastes in the sludge are disintegrated, suspended and dispersed, and mixed with fine bubbles of the generated air. As a result, decay of organic matter and the activity of anaerobic bacteria are suppressed, and ammonia and the like are oxidatively decomposed. The angle of the enlarged diameter portion of the cavitation generator is preferably 40 to 90 degrees, and the pumping pressure of the pump is preferably about 30 to 200 atmospheres.

[0010] Each of the above-mentioned bubble generators is submerged in a sludge storage tank to generate fine bubbles in the sludge. A pump for pumping sludge to the bubble generator is arranged outside the storage tank. Alternatively, a submersible pump that is used by submerging in a liquid as needed may be used. It is better to arrange the bubble generator in the center of the storage tank. Therefore, in the case of a large storage tank, if the pump is placed outside the storage tank, a long pipe is required to connect to the bubble generator submerged in the sludge. In such a case, a submersible pump may be used. If the submersible pump is submerged in the sludge and connected to the bubble generator, there is an advantage that the pipe can be shortened. Alternatively, if a bubble generator is attached to the tip of the outlet of the pump, the pipe becomes unnecessary.

[0011] The self-priming pipe for sucking in air comes out of the liquid level of the sludge as shown in FIG. 1 and communicates the bubble generator with the outside air.

[0012]

Example 1 (Deodorization of Hydrogen Sulfide) A cavitation generator of FIG. 3 was submerged at the bottom of a storage tank (10 m ³ ) of odorous sewage sludge containing 1000 ppm of hydrogen sulfide, and was placed outside the storage tank. And a hose.
The sludge was circulated at a pressure of 100 atm and cavitation-treated for 5 hours. Results The hydrogen sulfide concentration was reduced to 30 ppm and the odor was gone.

[0013] the bottom of the reservoir of the sludge of Example 2 Sewage sludge 20 m ³ containing ammonia 2000 ppm (deodorizing ammonia), submerged cavitation generator of submersible pump and 4, the pressure sludge by connecting both pipe The solution was circulated at 80 atm and cavitation treated for 3 hours. The ammonia concentration decreased to 30 ppm and the odor disappeared.

Example 3 (Effect of ozone) The cavitation generator shown in FIG. 3 is submerged in the bottom of a storage tank (10 m ³ ) of odorous sewage sludge containing 2500 ppm of hydrogen sulfide, 1000 ppm of mercaptan and 1500 ppm of ammonia, and air Was connected to an ozone generator. The pump was hosed directly to the cavitation generator using a submersible pump. The sludge was circulated at a pressure of 100 atm and cavitation treated for 3 hours. Result The hydrogen sulfide concentration was 10 ppm, and mercaptan was 10 pp.
m, ammonia decreased to almost zero, and the odor was completely deodorized. From the results of Examples 1, 2, and 3, it was confirmed that the method of the present invention was extremely effective in deodorizing hydrogen sulfide, mercaptan, ammonia, and the like.

[0015]

As described in detail above, the present invention has a feature that a large amount of sludge can be economically deodorized without using a drug or a microorganism.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of an embodiment of the present invention.

FIG. 2 is an explanatory view of an embodiment of the present invention.

FIG. 3 is an explanatory view of an embodiment of the present invention, which is an explanatory view when cavitation is used.

FIG. 4 is an explanatory diagram of another cavitation device according to the embodiment of the present invention.

[Explanation of symbols]

 1. Air self-priming port 2. Sludge pressure inlet 3. Air bubble outlet

Claims (3)

[Claims] 1. A method for deodorizing sewage sludge, comprising forcibly flowing sewage sludge and dispersing fine air bubbles in the flowing sludge. 2. The deodorizing method according to claim 1, wherein the fine air bubbles are obtained by sucking air into the flowing sludge by an ejector action and converting the sucked air into fine air bubbles by a cavitation action. 3. The deodorizing method according to claim 1, wherein the fine bubbles are formed into fine bubbles by a mechanical shearing force.