JP2021030178A - Method of stabilizing waste disposal site - Google Patents

Abstract

To provide a method of stabilizing a control-type waste disposal site applicable to existing sea surface waste disposal sites, and capable of facilitating early stabilization of the waste disposal site.SOLUTION: The method of stabilizing a waste disposal site comprises: burying air supply pipes 8 so as to locate each exhaust port near a lower limit of a water level 6 held by a waste deposit layer 3; and supplying a neutralizing gas containing carbon dioxide and an aerobic decomposition promoting gas containing oxygen from the air supply pipes so as to facilitate neutralization of the waste deposit layer deposited with the waste, as well as, aerobic decomposition of organic matters to achieve early stabilization.SELECTED DRAWING: Figure 1

Description

The present invention relates to a method for stabilizing a waste disposal site that promotes stabilization of a managed waste disposal site such as a marine waste disposal site and promotes abolition.

The site of the waste disposal site after the landfill can be effectively used as a land resource by satisfying the drainage standards, etc., but the pH and chemical oxygen demand (chemical oxygen demand) for a long period of time even after the landfill is completed In some cases, the waste disposal site cannot be abolished because the criteria such as COD) and biochemical oxygen demand (hereinafter referred to as BOD) cannot be met.

At the existing sea surface waste disposal site, the water possessed has a wide range from near neutral to pH 13 or higher, and about 40% of the waste disposal site exceeds the standard pH of 9.0, and the same applies to COD. There is also a survey report that the standard of 90 mg / L is exceeded at about 40% of waste disposal sites.

In particular, incineration ash and fly ash contain a large amount of calcium, and the water held at the waste disposal site where this type of waste is input often becomes highly alkaline, which makes it difficult for rainwater to penetrate. Along with this, highly alkaline leachate is generated.

Therefore, conventionally, for the purpose of early stabilization, a collection and drainage pipe is buried in the waste layer, drained to the internal water pond through the collection and drainage pipe, and the wastewater is neutralized by a treatment facility and then discharged. There is also a method of promptly conforming to the abolition standard for the quality of the collected water, etc. by promoting the discharge of the retained water, etc. in the waste layer (see, for example, Non-Patent Document 1). ..

We also propose a method of laying a discharge pipe on the bottom of the storage space for landfill material in advance when constructing a waste disposal site, and supplying a neutralizing gas such as carbon dioxide from the discharge pipe to neutralize the landfill ground. (See, for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 2000-237735

Sea Level Final Waste Disposal Site Closure / Abolition Application Manual (Draft) Examination Survey Consignment Business Report / Japan Environmental Sanitation Center / December 2014 / pp. 2-8-2-9

However, in the conventional technique as described above, since the water held at the waste disposal site where waste such as incineration ash is charged is highly alkaline, the microorganisms that can act in the waste deposit layer are limited to alkalophilic bacteria and the like. Therefore, it becomes difficult for general bacteria to grow, and it is difficult to promote the decomposition of organic substances, so that there is a problem that BOD and COD are high.

In addition, the method of supplying a neutralizing gas such as carbon dioxide to neutralize the landfill ground is effective as a countermeasure against high pH at the disposal site, but promotes the decomposition of organic matter by microorganisms and the reduction of COD and BOD. It wasn't something to do.

Therefore, in view of such conventional problems, the present invention has been made for the purpose of providing a method for stabilizing a waste disposal site that can promote early stabilization of a waste disposal site such as a sea surface waste disposal site. It is a thing.

The feature of the invention according to claim 1 for solving the above-mentioned conventional problems is that the waste deposit layer is retained in the method for stabilizing the waste disposal site having the waste deposit layer on which the waste is deposited. An air supply pipe is embedded so that an exhaust port is located near the lower limit of the water level, and a neutralizing gas containing carbon dioxide and an aerobic decomposition promoting gas containing oxygen are supplied from the air supply pipe.

The feature of the invention according to claim 2 is that, in addition to the configuration of claim 1, the neutralizing gas and the aerobic decomposition promoting gas are mixed and supplied from the air supply pipe.

The feature of the invention according to claim 3 is that, in addition to the configuration of claim 1, the neutralizing gas is supplied from the air supply pipe to lower the pH of the waste deposit layer, and then the aerobic decomposition is promoted. The purpose is to supply gas from the air supply pipe to aerobically decompose organic substances in the waste deposit layer.

The feature of the invention according to claim 4 is that, in addition to the configuration of any one of claims 1 to 3, the neutralizing gas and the aerobic decomposition promoting gas are supplied to the waste deposit layer from the air supply pipe. The purpose is to carry out monitoring together with the above and review the operating range and operating conditions of the air supply pipe based on the monitoring.

The method for stabilizing a waste disposal site according to the present invention has the configuration according to claim 1, and supplies pH to the waste layer of the waste disposal site by supplying a neutralizing gas containing carbon dioxide. In addition to lowering BOD and COD, by supplying an aerobic decomposition promoting gas in the waste deposit layer with lowered pH, the number of microorganisms can be greatly increased, decomposition of organic substances can be promoted, and BOD and COD can be reduced. It can be stabilized in a short period of time.

Further, in the present invention, by providing the configuration according to claim 2, the neutralizing gas and the aerobic decomposition promoting gas can be efficiently supplied, and in the retained water contained in the waste deposit layer. It is possible to promote the decomposition of sum and organic matter at the same time.

Further, in the present invention, by providing the configuration according to claim 3, the neutralization of the retained water is first efficiently promoted, and the pH of the waste deposit layer is lowered, so that alkalophilic bacteria and the like are formed. A state in which microorganisms other than the above can live is formed, and by supplying an aerobic decomposition promoting gas containing oxygen to this state, the growth of microorganisms such as many bacteria other than alkalophilic bacteria is preferably promoted, and the decomposition of organic substances is promoted. Can proceed.

Further, in the present invention, by providing the configuration according to claim 4, it is possible to focus on promoting stabilization in a high range of pH, BOD, and COD, and to stabilize the disposal site inexpensively and efficiently. be able to.

It is sectional drawing which shows an example of the Embodiment of the stabilization method of the waste disposal site which concerns on this invention. It is a top view which shows the outline of the arrangement of the air supply pipe of the same above. It is a graph which shows an example of the measurement result of the holding water level as above. It is a flowchart which shows the procedure of gas supply in the method of stabilizing the waste disposal site which concerns on this invention. It is a flowchart which shows the other procedure of gas supply in the stabilization method of the waste disposal site which concerns on this invention. It is a graph which shows the result of the experiment which confirms the effect by a neutralizing gas and an aerobic decomposition promoting gas. It is sectional drawing which shows an example of the Embodiment of the stabilization method of the waste disposal site which concerns on this invention. It is a top view which shows the outline of the arrangement of the air supply pipe of the same above.

Next, an embodiment of the method for stabilizing the waste disposal site according to the present invention will be described based on the examples shown in FIGS. 1 to 6. Reference numeral 1 in the figure is a sea surface waste disposal site.

In this sea surface waste disposal site 1, a storage space partitioned by an impermeable revetment is formed, and as shown in FIG. 1, waste is thrown onto the bottom impermeable layer 2 in the storage space to deposit a waste layer. 3 is formed, and the upper surface thereof is covered with soil 4.

Further, in this existing management type sea surface waste disposal site 1, as shown in FIGS. 1 and 2, the vicinity of the lower limit position of the retained water level 6 of the waste deposit layer 3, for example, from the lower limit position of the retained water level 6. The air supply pipe 8 is buried at a predetermined interval d (1 to 10 m) so that the exhaust port 7 is located below, and the air supply pipe 8 contains a neutralizing gas containing carbon dioxide and an aerobic decomposition promoting gas containing oxygen. Is being stabilized by supplying carbon dioxide. Reference numeral 10 is a compressor for supplying gas to the air supply pipe 8.

The air supply pipe 8 is composed of, for example, a pipe made of vinyl chloride, and has a predetermined depth of the waste deposit layer 3 from the surface of the soil cover 4, that is, the exhaust port 7 is from the lower limit of the water level 6 held by the waste deposit layer 3. It is designed to be buried up and down to the lower position.

An exhaust port 7 composed of a large number of water permeation holes 7a, 7a ... Is formed at the lower end of this pipe, and a neutralizing gas and an aerobic decomposition promoting gas are directed toward the waste deposit layer 3 through the exhaust port 7. It is supposed to be supplied.

In some of the plurality of air supply pipes 8, the exhaust port 7 may be located near the retained water level 6 of the waste deposit layer 3 and above the lower limit thereof.

Hereinafter, a specific method for stabilizing the waste disposal site 1 will be described with reference to the figure.

(Survey)
First, the pH, chemical oxygen demand (hereinafter referred to as COD), retained water level 6, water permeability coefficient, heavy metal concentration, etc. of the existing controlled waste disposal site 1 to be targeted are measured in advance, and the situation is investigated. In the landfill-type disposal site, the biochemical oxygen demand (hereinafter referred to as BOD) is measured instead of COD.

The survey method is to provide multiple observation holes over the entire disposal site and measure continuously for a certain period of time with a self-recording water level gauge. FIG. 3 is an example of the measurement results, and the changes in the retained water level 6 and the internal waters pound water level at each measurement position are shown in chronological order. The retained water level 6 differs depending on each observation hole, and varies depending on conditions such as precipitation and weather.

In addition, the retained water is periodically collected from the internal water pond and the observation hole, and the pH, COD or BOD, heavy metal concentration, etc. are measured. At the time of regular management, the water quality tendency may be confirmed by using total organic carbon (TOC) as an alternative index of BOD or COD.

(Target range / condition setting)
Next, based on the measurement result of the retained water level 6, the lowest water level within the measurement period is set as the lower limit of the retained water level 6, and the installation depth of the air supply pipe 8 is determined. The position of the exhaust port 7 is below the lower limit position of the retained water level 6 of the waste sedimentary layer 3, and is the position up to the controlled water level and the water level of the internal water pond.

For example, in the example shown in FIG. 3, since the lower limit of the retained water level 6 differs depending on each sample position, the line indicated by reference numeral 6a is the lower limit at point 1, and the lower limit is the line indicated by reference numeral 6b at point 2, respectively. Determine the installation depth based on.

In addition, the installation interval d of the air supply pipe 8 is determined based on the measurement results of each observation hole, and the operating conditions (carbon dioxide concentration of the neutralizing gas, oxygen concentration of the aerobic decomposition promoting gas, supply amount, supply time, etc.) are determined. ) Is determined.

Regarding the operating conditions, for example, the installation intervals of the air supply pipe 8 are closely arranged at the position where the measured values of pH, COD or BOD are high, and at the position where the measured values of pH, COD or BOD are low, the air supply pipe 8 is installed. How to widen the installation interval, at the position where the measured value of pH, COD or BOD is high, increase the supply amount of neutralizing gas and aerobic decomposition promoting gas, and the measured value of pH, COD is A method of reducing the supply of neutralizing gas and aerobic decomposition promoting gas at a low position, and increasing the concentration of neutralizing gas at a high pH measurement value, BOD or A method of increasing the concentration of aerobic decomposition promoting gas at a position where the measured value of COD is high, or a neutralizing gas and promoting aerobic decomposition at a position where the measured value of pH, COD or BOD is high. A method of lengthening the supply time of the gas and shortening the supply time of the neutralizing gas and the aerobic decomposition promoting gas can be adopted at a position where the measured values of pH, COD or BOD are low. Further, the optimum conditions may be obtained depending on the combination of each method, that is, the interval between the air supply pipes 8, the supply amount, and the supply time.

(Gas supply)
Then, the air supply pipe 8 is buried based on the determined installation position and depth, and the neutralizing gas containing carbon dioxide and the aerobic decomposition promoting gas containing oxygen are supplied through the air supply pipe 8 based on the set operating conditions. To start. The surplus gas at that time is released into the atmosphere.

As the neutralizing gas, regardless of the oxygen concentration, a gas _{containing carbon dioxide at a higher concentration than the atmosphere (CO 2} concentration of about 400 ppm) is used, and mainly exhaust gas (CO ₂ concentration:) of power plants and incineration facilities. Use a few to a dozen percent of CO ₂ gas).

As the aerobic decomposition promoting gas, a gas having an O2 concentration of about 200,000 ppm is used, and mainly the atmosphere (O2 concentration of about 200,000 ppm) is used.

The surplus gas of the neutralizing gas and the aerobic decomposition promoting gas is originally released into the atmosphere or the atmosphere, and even if the surplus gas is not recovered, it does not have a great influence on the surrounding environment, but it is neutralized. The amount consumed in the reaction of the gas for aerobic decomposition and the gas for promoting aerobic decomposition may be confirmed, and the required amount may be supplied so as not to release excess gas.

As shown in FIG. 4, the supply of the neutralizing gas and the aerobic decomposition promoting gas is _{more carbon dioxide than the atmosphere in the atmosphere (O 2} concentration of about 200,000 _{ppm, CO 2} concentration of about 400 ppm) which is the aerobic decomposition promoting gas. A neutralizing gas containing a high concentration of carbon (about 5%) is supplied and mixed to generate a mixed gas 9, and the mixed gas 9 is sent to the air supply pipe 8 by the compressor 10. The mixing ratio of the aerobic decomposition promoting gas and the neutralizing gas may be changed based on the measurement results in the process of the above investigation.

Further, as shown in FIG. 5, the neutralizing gas is supplied to the air supply pipe 8 by the compressor 10 until the pH value drops to a predetermined value, and then the gas supply is switched to the aerobic decomposition promoting gas to COD. The aerobic decomposition promoting gas may be supplied to the air supply pipe 8 by the compressor 10 until the value (BOD instead of COD in the landfill-type disposal site) drops to a predetermined value.

In the waste deposit layer 3, the following neutralization reaction occurs by supplying a neutralizing gas containing carbon dioxide.
CO ₂ + H ₂ O → H ₂ CO ₃
Ca (OH) ₂ + H ₂ O → CaCO ₃ + 2H ₂ O

At that time, _{the solubility of calcium carbonate CaCO 3} in water is small (0.00015 mol / L (25 ° C.), and if there is no change in the environment such as a large pH tilt to acidity, it will be redissolved and carbon dioxide will be released. It's few.

Further, carbonic acid generated by carbon dioxide is a weak acid, and even if the supply amount is excessive, the pH of the waste is large and does not tend to be acidic.

On the other hand, in the waste deposit layer 3, the pH is lowered by the supply of the neutralizing gas, so that not only alkalophilic bacteria but also many other bacteria easily inhabit, so oxygen is contained here. By supplying the aerobic decomposition promoting gas, many microorganisms such as bacteria grow.

At that time, the number of microorganisms increases to about ^{108 to 9 / g.} Incidentally, the general bacterial counts in the soil, 10 ⁹ / g of about medium to the downstream common bacterial number in river water ¹⁰⁶ / ml, the bacteria in near source of river upstream ^{10 3-4} / Ml.

Then, the organic matter is aerobically decomposed by the growth of bacteria, and BOD or COD is efficiently reduced.

The following shows the experimental results of examining the pH, the number of heterotrophic bacteria, and COD when the neutralizing gas and the aerobic decomposition promoting gas are supplied.

In the experiment, incineration ash is filled in a cylindrical column (diameter 50 mm x height 200 mm) and neutralized with a predetermined aerobic decomposition promoting gas (atmosphere, oxygen concentration about 200,000 ppm, CO2 concentration: about 400 ppm) from below the column. The gas is mixed and the mixed gas whose CO2 concentration is adjusted to about 5% is supplied at a constant supply amount (1000 ml / min), the supply of the mixed gas is stopped after one month, and water is sprinkled from the upper part of the column to the lower part of the column. The work of collecting leachate from the gas was repeated for 5 months, and the pH, the number of dependent vegetative bacteria and COD at that time were measured. In addition, after 5 months, incineration ash was collected and the number of heterotrophic bacteria was measured.

As a result, as shown in FIG. 6A, the pH dropped below the standard value after one month in the case where the mixed gas was supplied, whereas the pH dropped substantially in the case of air alone. I didn't.

As for the number of heterotrophic bacteria in the leachate, as shown in FIG. 6B, in the case where a mixed gas of a neutralizing gas and an aerobic decomposition promoting gas is supplied, one to two months later. greatly increased to after, while reaching up to 10 ⁸ / ml, in case of supplying only air, since the remains high pH, 5 months after ^{10 3-4} at / around ml (gas supply before Level). As for the number of heterotrophic bacteria in the incineration ash collected 5 months later, as shown in Table 1 below, the number of heterotrophic bacteria increased significantly in the case where the mixed gas was aerated.

Further, regarding COD, as shown in FIG. 6C, in the case where the mixed gas was supplied, the COD of the leachate decreased to 90 mg / L or less, which was the standard, whereas when only air was supplied. Although the COD was lowered by washing out the COD by watering, no further remarkable decomposition was observed.

(Review of settings)
On the other hand, along with the supply of neutralizing gas and aerobic decomposition promoting gas from the air supply pipe 8, the pH of the retained water, the chemical oxygen demand (COD), and the biochemical oxygen demand (BOD) in the observation hole and the inner water pond. ), Heavy metal concentration, etc. are monitored regularly, and the operating range and operating conditions of the air supply pipe 8 are reviewed based on the monitoring. At the landfill site, BOD will be monitored instead of COD.

That is, as a result of monitoring, the neutralizing gas and the aerobic decomposition promoting gas are in the range of the observation holes that meet the abolition standards (pH: 5.0 to 9.0, COD: 90 mg / L or less) of the sea surface disposal site. In the range of the observation hole where the supply of the gas is stopped or decreased and the value is still high, the supply amount of the neutralizing gas and the aerobic decomposition promoting gas is increased or the air supply pipe 8 is added as necessary.

Then, the neutralizing gas and the aerobic decomposition promoting gas are repeated while repeating the above setting review until the retained water at each measurement position reaches the abolition standard (pH: 5.0 to 9.0, COD: 90 mg / L or less). Supply.

When the waste deposit layer is landfilled and covered with soil in multiple layers at the waste disposal site 1 being landfilled, the above steps are repeated for each layer.

The method for stabilizing the waste disposal site 1 configured in this way supplies a neutralizing gas containing carbon dioxide and an aerobic decomposition promoting gas containing oxygen to the waste deposit layer 3 of the waste disposal site 1. As a result, the pH is lowered by the neutralizing gas, and as the pH is lowered, it is possible for microorganisms other than highly alkaline bacteria to inhabit, and the aerobic decomposition promoting gas is supplied to the state, which makes it alkaline. Microorganisms such as bacteria other than microorganisms proliferate, decomposition of organic substances is promoted, reduction of COD and BOD is promoted, and stabilization can be achieved in a short period of time.

Further, as described above, the neutralizing gas and the neutralizing gas while repeating the above setting review until the retained water at each measurement position reaches the abolition standard (pH: 5.0 to 9.0, COD: 90 mg / L or less). Since the aerobic decomposition promoting gas is supplied, it is possible to focus on promoting stabilization in a high pH range and a high COD and BOD range.

Furthermore, since no deleterious substances such as hydrochloric acid and sulfuric acid are used, handling and management can be performed easily, and adverse effects on the surrounding environment can be suppressed.

In the above-described embodiment, the example in which the air supply pipe 8 is buried in the vertical direction has been described, but as shown in FIGS. 7 and 8, the air supply pipe 20 may be buried in the horizontal direction. The same components as those in the above-described embodiment are designated by the same reference numerals, and the description thereof will be omitted.

The air supply pipe 20 has an exhaust hole (exhaust port) as a whole, and the neutralizing gas and the aerobic decomposition promoting gas can be discharged toward the waste deposit layer 3 through the exhaust hole.

The burial depth and interval d of the air supply pipe 20 are determined based on a preliminary survey as in the above-described embodiment, and are located near the lower limit of the retained water level 6, for example, below the lower limit of the retained water level 6. Install so that In the figure, reference numerals 21 and 22 are observation wells, and reference numeral 23 is an internal water pound.

The horizontal piping of the air supply pipe 20 is not limited to the embodiment shown in FIG. 7, and may be arranged in a plurality of stages above and below the lower limit of the retained water level 6.

In the above-described embodiment, the sea surface disposal site has been described as an example, but the method of the present invention can also be applied to a land-based controlled waste disposal site.

1 Existing management type sea surface waste disposal site 2 Bottom impermeable layer 3 Waste deposit layer 4 Soil cover 6 Retained water level 7 Exhaust port 8 Air supply pipe 9 Mixed gas 10 Compressor 20 Air supply pipe 21 Observation well 22 Observation well 23 Inland water Pond 24 open / close valve

Claims (4)

In the method of stabilizing a waste disposal site having a waste deposit layer on which waste is accumulated,
An air supply pipe is buried so that the exhaust port is located near the lower limit of the retained water level of the waste deposit layer, and a neutralizing gas containing carbon dioxide and an aerobic decomposition promoting gas containing oxygen are separated from the air supply pipe. A method of stabilizing a waste disposal site, which is characterized by supplying. The method for stabilizing a waste disposal site according to claim 1, wherein the neutralizing gas and the aerobic decomposition promoting gas are mixed and supplied from the air supply pipe. After the neutralizing gas is supplied from the air supply pipe to lower the pH of the waste deposit layer, the aerobic decomposition promoting gas is supplied from the air supply pipe to favor the organic matter in the waste deposit layer. The method for stabilizing a waste disposal site according to claim 1, wherein the waste disposal site is thermally decomposed. Claims 1 to 3 in which the neutralizing gas and the aerobic decomposition promoting gas are supplied to the waste deposit layer from the air supply pipe and monitored, and the operating range and operating conditions of the air supply pipe are reviewed based on the monitoring. The method for stabilizing a waste disposal site according to any one of the above.

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