JP4824659B2 - Waste and leachate stabilization methods - Google Patents

Description

  The present invention relates to a method for stabilizing waste and leachate by alternately and repeatedly forming an aerobic environment and an anaerobic environment.

  Conventionally, many semi-aerobic landfill structures have been adopted at waste final disposal sites. In this semi-aerobic landfill structure, the end of the leachate collecting / draining pipe is opened to cause air circulation by natural ventilation through the collecting / draining pipe in the waste layer. In other words, in the semi-aerobic landfill structure, when air is supplied into the waste layer, microorganisms in the waste layer are activated, organic matter decomposition proceeds, and the waste is stabilized.

  In such a semi-aerobic landfill structure, the air supply status varies depending on natural conditions, the waste landfill status, etc., and it generally takes a long time for the organic matter to stabilize. Further, in a waste final disposal site where a semi-aerobic landfill structure is not adopted, it takes a longer period of time for organic matter to stabilize.

  In the waste final disposal site, even after the landfill is completed, rain penetrates into the waste layer and leachate is generated. And until the waste is stabilized, it is necessary to continue water treatment for purifying and discharging leachate. Therefore, the longer the period until the landfilled waste is stabilized, that is, the period until the final disposal site is abolished, the maintenance cost increases. Also, if the waste layer becomes anaerobic before the treatment in the aerobic environment is completed, the concentration of leachate BOD and COD will increase, and it is often used to purify the leachate to a water quality that can be discharged. Load, and the cost becomes great.

Therefore, various techniques have been proposed for shortening the period until the organic matter is stabilized by performing appropriate waste treatment at a waste final disposal site or the like.
For example, technology that improves purification capacity by supplying oxygen, substances such as air, hydrogen peroxide, ozone, etc., into paper waste, garbage, waste that contains a lot of organic matter excavated and collected from disposal sites, or contaminated soil Is disclosed (see Patent Document 1).

Moreover, the technique which improves the purification | cleaning capability is disclosed by supplying the nutrient source of oxygen and a decomposition | disassembly microorganism to contaminated groundwater (refer patent document 2).
JP 2001-129519 A JP 2001-129577 A

  By the way, in order to shorten the period until the organic matter is stabilized in a waste final disposal site, etc., an aerobic environment in which oxygen is supplied to the waste to decompose the organic matter is different from an aerobic environment. It is necessary to switch the anaerobic environment that decomposes the hardly decomposable organic matter by the decomposition action at an appropriate time.

  However, the conventional technology discloses that waste treatment is performed by switching between an aerobic environment and an anaerobic environment, but it is clear what criteria are used to switch from an aerobic environment to an anaerobic environment. There is no disclosure. In addition, it is difficult to grasp how organic substances are actually decomposed in waste, and the current situation is that the timing of switching between aerobic and anaerobic environments depends on the experience and intuition of the processing workers. It is.

  The present invention has been proposed in view of the above-described circumstances, and shortens the period until the organic matter is stabilized by performing appropriate waste treatment with clear criteria for switching from an aerobic environment to an anaerobic environment. An object of the present invention is to provide a method for stabilizing waste and leachate capable of reducing environmental burden.

The method for stabilizing waste and leachate according to the present invention has the following features in order to achieve the above-described object.
That is, the method for stabilizing waste and leachate according to the present invention alternates between an aerobic environment in which the oxygen-containing gas is forcibly supplied into the waste layer and an anaerobic environment in which the supply of the oxygen-containing gas is stopped. In this method, the waste and leachate are stabilized by repeatedly forming, and when at least one value of BOD / COD or BOD / TOC of leachate satisfies the following conditional expression (1) In addition, the waste and leachate are stabilized by shifting from an aerobic environment to an anaerobic environment.
0.05 ≦ x ≦ 0.3 (1)
Furthermore, it is preferable to use the following conditional expression (2) as a reference for switching from an aerobic environment to an anaerobic environment.
0.08 ≦ x ≦ 0.1 (2)
Where x is BOD / COD or BOD / TOC

  In addition, when the oxygen-containing gas is forcibly supplied into the waste layer, it is preferable that the pressurized oxygen-containing gas is intermittently and instantaneously supplied into the waste layer to form an aerobic environment.

  In addition, it is preferable to adjust the amount of water contained in the oxygen-containing gas according to the amount of water in the waste layer.

According to the method for stabilizing waste and leachate according to the present invention, the timing for switching from an aerobic environment to an anaerobic environment is defined using the value of BOD / COD or BOD / TOC. Becomes clear and appropriate waste disposal can be performed. For this reason, it is possible to reduce the environmental load by shortening the period until the organic matter is stabilized.
In addition, since the oxygen-containing gas is forcibly supplied into the waste layer to form an aerobic environment, when the depth of the waste layer is large, air can be supplied to that depth even at a depth of about 50 m, for example. By using a simple device, it becomes possible to stabilize waste and leachate.

Hereinafter, an embodiment of a method for stabilizing waste and leachate according to the present invention will be described with reference to the drawings.
<Stabilizer>
First, the stabilization apparatus used in the method for stabilizing waste and leachate according to the present invention will be described. FIG. 1 is a schematic view of a stabilization device used in the method for stabilizing waste and leachate according to the present invention.

  The method for stabilizing waste and leachate according to the present invention performs appropriate waste treatment by switching from an aerobic environment to an anaerobic environment based on a predetermined standard. The treatment process in the aerobic environment includes an oxygen-containing gas compression process, an air supply process for adjusting the amount of moisture contained in the compressed gas, a forced insertion process for forcibly supplying compressed gas into the waste, and a disposal process. It can be roughly divided into a suction exhaust process for discharging organic decomposition gas and the like from the substance, and a purification process for purifying the suction gas and releasing it out of the system.

As shown in FIG. 1, a stabilization device 10 used in the waste and leachate stabilization method according to the present invention includes a compressor 11, a storage tank 12, and a water supply tank 13 disposed in the compression step (A). A pressure vessel 14 disposed in the air supply process (B), an air supply pipe 15 disposed in the forced insertion process (C), and a suction pump 16 disposed in the suction exhaust process (D). The processing filter 17 disposed in the purification step (E), the air supply hose 18 that connects the compressor 11 and the pressure vessel 14 to each other, and the decomposition gas generated in the waste are supplied to the suction pump 16. The main components are an intake pipe 19 and an exhaust pipe 20 for the purpose. Although not shown, an air supply port is provided at the tip of the air supply tube 15, and a plurality of intake ports are provided in the intake tube 19. The air supply port may be provided not only at the distal end portion of the air supply tube 15 but also at the intermediate portion.
In addition, the stabilization device 10 is not limited to the structure shown in FIG. 1, and necessary equipment is added or the detailed structure is changed according to the structure of the waste disposal site where the stabilization process is performed, the weather, or the like. You can do it.

<Treatment in aerobic environment>
Next, a processing procedure in an aerobic environment will be described.
In the method for stabilizing waste and leachate according to the present invention, an aerobic environment is formed using the stabilizing device 10 described above. Prior to the formation of the aerobic environment, the air supply pipe 15 and the intake pipe 19 are inserted into the waste layer 21.
In the stabilization process in an aerobic environment, the compressor 11 is used to produce compressed gas containing 2 to 7 atmospheres of oxygen (compression step (A)). The compressed gas may be an oxygen-containing gas, and air may be used as it is, or oxygen may be added thereto.

  The compressed gas stored in the storage tank 12 of the compressor 11 is sent to the pressure vessel 14 via the air supply hose 18 (air supply process (B)). Here, the amount of water in the compressed gas is adjusted by supplying water from the water supply tank 13 so that the amount of water in the waste layer 21 is maintained at a humidity of 5 to 30%. The moisture content in the waste layer 21 may be detected by a hygrometer or the like installed in the waste layer 21 or a sample may be collected from the waste layer 21. Thus, by adjusting the amount of water in the waste layer 21, the inside of the waste layer 21 can be prevented from being excessively dried, and the environment of microorganisms necessary for the decomposition of the organic matter can be controlled.

  When the compressed gas stored in the storage tank 12 of the compressor 11 reaches a certain pressure, the discharge port of the pressure vessel 14 opens and the compressed gas is discharged. The discharged compressed gas is supplied into the waste from an air supply port provided in the air supply pipe 15 (forced insertion step (C)). The operation of opening the discharge port of the pressure vessel 14 may be performed manually. However, when a pressure gauge is attached to the pressure vessel 14 and the pressure gauge detects that the compressed gas has become a constant pressure, the discharge port is opened. It is preferable to employ a mechanism in which an actuator or the like attached to is operated to automatically open and close the discharge port. In addition, when a plurality of air supply ports are provided at the distal end portion and the intermediate portion of the air supply tube 15, the compressed air discharged from the air supply ports provided at the distal end portion is discharged from the air supply ports provided in the intermediate portion. The pressure is preferably higher than that of compressed air.

In this embodiment, the interval at which the discharge port opens is set to 20 to 60 seconds, and the compressed gas is forcibly and intermittently supplied into the waste layer 21 intermittently. The amount of compressed gas forcedly fed into the waste layer 21 is preferably 0.5 to 10 liter / min per 1 m ^{3 of} the waste layer. By forcibly and instantaneously supplying compressed gas into the waste layer 21, the oxygen-containing gas does not pass through the same path (gap) in the waste layer 21, and different routes ( Through the gap). For this reason, the whole waste layer 21 can be made into an aerobic environment uniformly.
The compressed gas forcedly fed into the waste layer 21 makes the inside of the waste layer 21 an aerobic environment, and aerobic microorganisms are activated. In this aerobic environment, decomposition of readily decomposable organic substances contained in the waste layer 21 is promoted.

The compressed gas forcedly fed into the waste and the gas generated in the decomposition process of the organic matter are forcibly discharged out of the waste layer 21 through the intake pipe 19 and the exhaust pipe 20 by the suction force of the suction pump 16. (Suction / exhaust step (D)).
The exhaust gas that has been forcibly discharged is purified by passing through the processing filter 17 and discharged outside the system (purification step (E)). The processing filter 17 is appropriately selected according to the harmful substance contained in the exhaust gas, and for example, an activated carbon filter can be used.

  As microorganisms for decomposing organic substances in an aerobic environment, methane-utilizing bacteria, toluene-utilizing bacteria, phenol-utilizing bacteria, ammonia-oxidizing bacteria, nitrite-oxidizing bacteria, propane-oxidizing bacteria, isopropylene-oxidizing bacteria Etc.

<Switching from an aerobic environment to an anaerobic environment>
Processing in an aerobic environment is performed by performing the above-described steps, but in the present invention, an aerobic environment and an anaerobic environment are switched based on a predetermined reference value related to BOD / COD or BOD / TOC. .
As a result of intensive studies on the timing of switching from an aerobic environment to an anaerobic environment, the inventors of the present invention use a predetermined reference value for BOD / COD or BOD / TOC until the organic matter is stabilized. It has been found that the environmental load can be reduced while shortening the period.

The criteria for switching from an aerobic environment to an anaerobic environment will be described with reference to FIGS. 2 is a correlation diagram of BOD / COD, and FIG. 3 is a correlation diagram of BOD / TOC.
As is clear from FIG. 2, when the anaerobic environment and the aerobic environment are compared, when the value of BOD / COD is larger than 0.3, the aerobic environment is dominant with respect to the treatment of organic matter. In particular, when the value of BOD / COD is larger than 0.1, the superiority of the aerobic environment with respect to the treatment of organic substances is outstanding. On the other hand, when the anaerobic environment and the aerobic environment are compared, when the value of BOD / COD is smaller than 0.05, the anaerobic environment is superior with respect to the treatment of organic matter. In particular, when the value of BOD / COD is smaller than 0.08, the superiority of the anaerobic environment with respect to the treatment of organic substances is remarkable.

  In addition, as is clear from FIG. 3, when the anaerobic environment and the aerobic environment are compared, when the value of BOD / TOC is larger than 0.3, the aerobic environment is dominant for the treatment of organic matter. Yes. In particular, when the value of BOD / TOC is larger than 0.1, the superiority of the aerobic environment with respect to the treatment of organic substances is outstanding. On the other hand, when the anaerobic environment and the aerobic environment are compared, when the value of BOD / TOC is smaller than 0.05, the anaerobic environment is superior with respect to the treatment of organic matter. In particular, when the value of BOD / TOC is smaller than 0.08, the superiority of the anaerobic environment is remarkable with respect to the treatment of organic substances.

From the experimental results described above, when the value of BOD / COD or BOD / TOC is x, at least one of the values of BOD / COD or BOD / TOC of leachate satisfies the following conditional expression (1) The waste can be efficiently stabilized by stopping the supply of the oxygen-containing gas from the aerobic environment forcibly supplying the oxygen-containing gas to the anaerobic environment.
0.05 ≦ x ≦ 0.3 (1)
Further, it is more preferable to use the following conditional expression (2) as a reference for switching from an aerobic environment to an anaerobic environment.
0.08 ≦ x ≦ 0.1 (2)

<Treatment in anaerobic environment>
When the processing in the aerobic environment described above is performed and the value of BOD / COD or BOD / TOC becomes the reference value for shifting to the anaerobic environment, the operation of the stabilization device 10 is stopped, and the air supply hose 18 and the exhaust pipe 20 are By closing the valve, the waste layer 21 is transferred to an anaerobic environment. In the anaerobic environment, the decomposition of the hard-to-decompose organic matter different from the aerobic environment is promoted, the heavy metals existing in the waste layer 21 are insolubilized, and fixed in the waste landfill.
In an anaerobic environment, it is preferable to adjust so that the moisture content in the waste layer 21 is maintained at a humidity of 20 to 50%.

<Switching from anaerobic environment to aerobic environment>
And if the stabilization process in an anaerobic environment is continued and the methane gas density | concentration in the atmosphere of the waste layer 21 will be in the state stabilized by 20 to 50%, the driving | operation of the stabilization apparatus 10 will be restarted and it will be in an aerobic environment. Transition.

As described above, in the method for stabilizing waste and leachate according to the present invention, the timing of switching from an aerobic environment to an anaerobic environment is defined by using the value of BOD / COD or BOD / TOC. Standards will be clear and appropriate waste disposal will be possible. In other words, the conventional technology can further effectively promote the decomposition process of organic matter that has been affected by the natural environment, and can reduce the environmental burden in the early stabilization of waste and leachate treatment. it can.
In addition, the period which makes the waste layer 21 forcibly aerobic environment is about 3 to 24 months, for example, and the period which makes anaerobic environment is about 1 to 6 months, for example. And stabilization processing is performed for about 3 to 5 years, for example, switching an aerobic environment and an anaerobic environment.

<Other processing for stabilization>
In addition to the above-described processes, other processes may be performed in order to shorten the period until the organic matter is stabilized and reduce the environmental load.
For example, the decomposition of organic substances can be promoted by adding nutrients and chemical substances preferable for aerobic microorganisms in the compressed gas. Preferred nutrients and chemical substances for aerobic microorganisms include nitrogen, phosphoric acid, potassium, silicon, manganese, carbon, hydrogen, oxygen, and the like.

The schematic diagram of the stabilization apparatus used with the stabilization method of the waste material and leachate which concerns on this invention. The correlation figure of BOD / COD which shows the standard switched from an aerobic environment to an anaerobic environment. The correlation figure of BOD / TOC which shows the standard switched from an aerobic environment to an anaerobic environment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Stabilizer 11 Compressor 12 Storage tank 13 Water supply tank 14 Pressure vessel 15 Air supply pipe 16 Suction pump 17 Processing filter 18 Air supply hose 19 Intake pipe 20 Exhaust pipe 21 Waste layer A Compression process B Air supply process C Forced insertion Process D Suction / exhaust process E Purification process

Claims (4)

Stabilization of waste and leachate by alternately forming an aerobic environment that forcibly supplies oxygen-containing gas into the waste layer and an anaerobic environment that stops supplying oxygen-containing gas It is a method to plan,
Waste and leachate stability characterized by shifting from an aerobic environment to an anaerobic environment when at least one of the values of BOD / COD or BOD / TOC of leachate satisfies the following conditional expression (1) Method.
0.05 ≦ x ≦ 0.3 (1)
Where x is BOD / COD or BOD / TOC Stabilization of waste and leachate by alternately forming an aerobic environment that forcibly supplies oxygen-containing gas into the waste layer and an anaerobic environment that stops supplying oxygen-containing gas It is a method to plan,
Waste and leachate stability characterized by shifting from an aerobic environment to an anaerobic environment when at least one value of BOD / COD or BOD / TOC of leachate satisfies the following conditional expression (2) Method.
0.08 ≦ x ≦ 0.1 (2)
Where x is BOD / COD or BOD / TOC   The method for stabilizing waste and leachate according to claim 1 or 2, wherein the pressurized oxygen-containing gas is intermittently and instantaneously supplied into the waste layer to form an aerobic environment.   The method for stabilizing waste and leachate according to any one of claims 1 to 3, wherein the amount of water contained in the oxygen-containing gas is adjusted according to the amount of water in the waste layer.

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