Method for stabilizing controlled-type repository

Abstract

To provide a method for stabilizing a controlled disposal site which stabilizes leachate for the purpose of abolishing the controlled disposal site.SOLUTION: In the method for stabilizing a controlled-type disposal site, for example, the container 4 formed in a bottomed cylindrical shape is immersed in alkaline water stored in the pumping well 56 in the controlled-type sea surface disposal site with the open portion thereof facing downward, and carbon dioxide is enclosed in the space 7 in the container 4 to neutralize the alkaline water, so that leachate can be stabilized for abolishing the controlled-type sea surface disposal site.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a method for stabilizing a controlled landfill site, which stabilizes leachate (water released outside the landfill site) in order to abolish the controlled landfill site. [Background technology]

[0002] Managed landfills, such as managed marine landfills and managed landfills, are facilities where waste materials such as incineration ash and coal ash are reclaimed. When landfilling is complete, the waste fills the managed landfill, eventually covering it with soil to create land. The pH value of water seeping into a managed landfill due to rainfall or watering often becomes alkaline due to the waste, reaching a pH of 9.0 or higher. Furthermore, the reclaimed land of managed marine landfills constructed in port areas is managed to maintain a constant water level (managed water level). By law, in order to decommission a managed landfill, when leachate that flows down or becomes excess due to rainfall into the managed landfill is discharged outside the managed landfill, the pH value of the excess leachate must be 9.0 or lower (5.0 or higher) for managed marine landfills and 8.6 or lower (5.8 or higher) for managed landfills.

[0003] The current situation at a managed offshore landfill site is described below as an example. Because the pH of the pore water (permeation water) within the reclaimed land at a managed offshore landfill site is above 9.0, it is difficult to maintain a pH of 9.0 or below for the water that flows and leaches out of the reclaimed land after rainfall or other sources have infiltrated into the reclaimed land. Maintaining the pH of the permeation water that permeates and flows through the reclaimed land and leachates (water discharged outside the site) to meet discharge standards requires extremely long-term measures, monitoring, and operation of water treatment facilities. This results in inflated maintenance costs and hinders the early utilization of the site. In other words, rainwater that permeates the highly alkaline reclaimed land becomes permeation water that flows down to the drainage area, where it becomes highly alkaline and exceeds discharge standards. In this case, it is necessary to carry out water purification treatment using chemicals, such as neutralizing the collected highly alkaline water (permeated water) at a water treatment facility, and there are many cases where water treatment is continued for several decades even after the landfill is completed, which is currently incurring a lot of expenses.

[0004] To reduce the burden on water treatment facilities, some managed offshore disposal sites install inland water ponds. An inland water pond is a section of the site that is left unfilled and has a water surface. The main functions of this inland water pond are to manage the water level within the site, which increases due to rainfall, and to store excess water before it is pumped to the water treatment facility. It has also been confirmed that maintaining a certain water surface area within the inland water pond allows atmospheric carbon dioxide to dissolve from the water surface, causing a neutralization reaction and lowering the pH value.

[0005] Furthermore, in order to close a disposal site under the Waste Disposal and Public Cleansing Act, closure procedures must be completed beforehand. Closure of a managed offshore disposal site means that a completion notification has been submitted under the Public Water Surface Reclamation Act, which basically means that the entire site of the managed offshore disposal site has been reclaimed. Therefore, current law restricts completion and closure of the site if the inland water pond, which was established to reduce the burden on the water treatment facility, remains in place. If closure is not possible, the decommissioning procedures cannot proceed, and the current situation is that the use of the site as a landfill is limited to the surface use of the completed landfill area, excluding the inland water pond.

[0006] Although there are no established early stabilization measures for decommissioning managed coastal landfills, several methods have been adopted depending on the characteristics of each site. One such method is the installation of collection and drainage pipes. Specifically, by installing collection and drainage pipes at the same height as the managed groundwater level (the managed water level within the reclaimed land) within the site, rainwater and other infiltrating water from the ground surface flows down to the collection and drainage pipes near the managed water level and is collected and drained. This method results in a high pH level in the infiltrated water passing through the reclaimed land below the managed water level for a certain period of time. However, due to the collection and drainage pipes, only a small amount of the infiltrated water from the ground surface seeps into the reclaimed land below the managed water level, where a large amount of alkaline water still remains. As a result, after a large amount of rainwater (infiltration water) washes out most of the alkaline content of the reclaimed land below the collection and drainage pipes, the pH of the infiltrated water is expected to stabilize at a lower level.

[0007] A pumping well (e.g., made of concrete, approximately 1.8 m in diameter and 6 m deep from the ground surface) is installed at the end of this collection and discharge pipe. A drainage pump is installed in the pumping well, and once a certain amount of water has been collected from the collection and discharge pipe into the pumping well, the water is pumped into an inland water pond, where the pH naturally decreases. After that, the water is sent from the inland water pond to a water treatment facility. However, if an inland water pond remains within a managed offshore disposal site, the completion notification under the Public Water Surface Reclamation Act cannot be submitted, and the site is essentially unable to be abolished. To fill the inland water pond and complete the completion procedures, the pumping well must be able to directly send water to the water treatment facility, and the water must be purified by the water treatment facility and meet effluent standards. Furthermore, the burden of water treatment at the water treatment facility must be reduced. Furthermore, if the water can be discharged without purification at a water treatment facility, the water treatment facility can be eliminated. As such, it is necessary to resolve issues in order to quickly stabilize managed disposal sites, including managed offshore disposal sites, in preparation for their decommissioning (closure).

[0008] As a conventional technology capable of purifying a managed offshore disposal site, Patent Document 1 describes a method for stabilizing an existing managed waste disposal site, in which an air supply pipe is buried so that the exhaust outlet is located near the lower limit of the water level of the waste deposit layer where the waste is piled up, and a neutralizing gas containing carbon dioxide is supplied from the air supply pipe. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Japanese Patent Application Publication No. 2019-166504 Summary of the Invention [Problem to be solved by the invention]

[0010] However, in the stabilization method for existing controlled waste disposal sites described in Patent Document 1, the neutralizing gas from the exhaust port of the air intake pipe dissolves in the interstitial water located very close to the exhaust port and can only neutralize the alkaline components in the interstitial water. Furthermore, the water containing dissolved carbon dioxide essentially does not flow and remains in place, limiting the purification area to a very narrow area around the exhaust port, resulting in poor purification efficiency. Therefore, to expand the purification area, multiple air intake pipes must be installed and each air intake pipe must be repeatedly installed and removed. This construction method is inefficient, particularly in terms of construction time and cost. The stabilization method for existing controlled waste disposal sites described in Patent Document 1 makes it difficult to solve the above-mentioned problem of quickly stabilizing controlled disposal sites, including controlled offshore disposal sites, in preparation for decommissioning.

[0011] The present invention has been made in consideration of the above-mentioned problems, and aims to provide a method for stabilizing a controlled landfill site, which stabilizes leachate in preparation for the closure of the controlled landfill site. [Means for solving the problem]

[0012] As a means for solving the above problem, the invention relating to the method for stabilizing a managed landfill site, claim 1, is a method for stabilizing a managed landfill site by neutralizing alkaline water stored in the managed landfill site and which has become alkalized due to waste, and is characterized in that a container shaped like a cylinder with a bottom is submerged in the alkaline water with the open part facing downward, and carbon dioxide is then sealed in the space within the container to neutralize the alkaline water.

[0013] In the invention of claim 1, a cylindrical container with a bottom is submerged in alkaline water stored in a controlled disposal site with its open end facing downward, and carbon dioxide is sealed in the space within the container, thereby neutralizing the alkaline water. That is, the alkaline water in a controlled disposal site contains a large amount of alkaline components eluted from waste in the landfill, and by neutralizing the alkaline components with the carbon dioxide sealed in the space within the container, carbonates such as calcium carbonate and magnesium carbonate are produced, thereby neutralizing the alkaline water.

[0014] Specifically, carbon dioxide sealed in a container dissolves into the water from the water surface inside the container. However, since this stored water is alkaline water, its dissolution rate is faster than that of acidic or neutral water, resulting in an efficient neutralization effect. Furthermore, compared to a neutralization reaction simply performed by aeration in alkaline water without using a container, the carbon dioxide sealed in the container dissolves efficiently in the water without being released from the water into the air via bubbles. This reduces the loss rate, improves dissolution efficiency, and allows for a rapid neutralization reaction, resulting in efficient neutralization of the alkaline water. In this way, by efficiently neutralizing alkaline water stored in a controlled landfill, it is possible to stabilize leachate in preparation for the decommissioning of the controlled landfill.

[0015] The invention of claim 2 relating to the method for stabilizing a managed disposal site is characterized in that, in the invention of claim 1, the water surface in the container is disturbed. Therefore, as a verification experiment, the inventors placed alkalized artificial seawater in a test container, stirred it with a stirrer tip at a rotation speed of 100 to 1000 rpm, and measured the amount of carbon dioxide dissolved when carbon dioxide with a purity of 99.9% or more was blown in under conditions where the stirring speed of the artificial seawater was changed.As a result of the measurement, it was confirmed that more carbon dioxide dissolved in the artificial seawater when the rotation speed was 1000 rpm.

[0016] Based on this verification experiment, the invention of claim 2 can promote the dissolution of carbon dioxide into the alkaline water in the container by disturbing the water surface in the container, thereby improving the efficiency of dissolving carbon dioxide into the alkaline water in the container and allowing the alkaline water to be neutralized quickly. In this way, the faster neutralization speed makes it possible to replace the target alkaline water sequentially and earlier. In other words, it is possible to increase the amount of target alkaline water in the same treatment time. In one embodiment, for example, an underwater propeller device or the like can be placed in the alkaline water below the container, and the underwater propeller device can create a water flow toward the water surface, thereby disturbing the water surface in the container.

[0017] The invention of claim 3 relating to the method for stabilizing a managed landfill site is characterized in that, in the invention of claim 1, alkaline water is circulated so that the alkaline water located above the container is replaced with the alkaline water located below the container. As a premise, when the alkaline water near the water surface in the container is neutralized, the water near the water surface in the container becomes treated water with a low pH value, and the rate at which carbon dioxide dissolves decreases.

[0018] In view of this, in the invention of claim 3, alkaline water is circulated at appropriate times so as to replace the unneutralized alkaline water above the container with the neutralized water below the container, which has a low pH value. This slows down the decrease in the rate of carbon dioxide dissolution in the container, i.e., carbon dioxide can be quickly dissolved in the entire amount of alkaline water stored, resulting in the rapid neutralization of the entire amount of alkaline water stored. In one embodiment, a circulation submersible pump can be placed around the container to circulate the alkaline water around the container.

[0019] The invention of claim 4 relating to the method for stabilizing a managed landfill site is characterized in that, in the invention of claim 1, the container is bell-shaped. As a premise, if the purity of the carbon dioxide sealed in the container is less than 100%, impurity-equivalent, insoluble gas will remain in the container. In order to discharge this residual gas, it is preferable that it be concentrated in a part of the container.

[0020] In view of this, the invention of claim 4 employs a bell-shaped container, which allows residual gas equivalent to impurities to be concentrated in the top of the container. Therefore, by installing an exhaust pipe at the top of the container, it becomes easy to exhaust the residual gas (impurity gas) in the container. This exhaust pipe can also be used as a carbon dioxide supply pipe.

[0021] The invention relating to the stabilization method for a managed landfill site according to claim 5 is characterized in that the container is raised and lowered based on the water level of the alkaline water, thereby maintaining the water depth in the container at an approximately constant level.

[0022] In the invention of claim 5, the container is raised and lowered based on the level of the alkaline water, so a constant water pressure is applied to the water surface in the container, and the gas pressure in the container can be maintained at a predetermined value (as high as possible). As a result, the efficiency of dissolving carbon dioxide in the container into the alkaline water can be improved, and the alkaline water can be quickly neutralized.

[0023] The invention of claim 6 relating to a method for stabilizing a managed disposal site is characterized in that, in the invention of claim 1, the amount of carbon dioxide supplied to the container is controlled based on the spatial volume within the container, the concentration of carbon dioxide within the container, and the pressure of the gas within the container. The premise is that carbon dioxide dissolves faster in alkaline water than other gases such as air and oxygen. Therefore, the amount of carbon dioxide remaining in the container changes significantly. As the amount of carbon dioxide in the container decreases, the neutralization process by dissolution no longer proceeds at a predetermined rate, resulting in a longer processing time for a given amount of alkaline water.

[0024] In view of this, the invention of claim 6 controls the amount of carbon dioxide supplied to the container based on at least the volume of space in the container, the concentration of carbon dioxide in the container, and the pressure of the gas in the container, thereby enabling flexible operation to maximize the efficiency of dissolving carbon dioxide into alkaline water, such as operation at a constant water level in the container and supplying only the amount of carbon dioxide necessary to treat a constant amount of water. In short, since the environment, such as the carbon dioxide concentration in the container, can be grasped in detail and the amount of carbon dioxide supplied can be controlled, the efficiency of dissolving carbon dioxide into alkaline water in the container can be continuously maximized, and as a result, the stored alkaline water can be quickly neutralized.

[0025] The invention relating to the stabilization method and equipment for a managed landfill site in claim 7 is characterized in that, in the invention of claim 1, the alkaline water stored in the managed landfill site is water retained in a managed offshore landfill site, or alkaline water stored in a pumping well or inland water pond installed in a managed offshore landfill site, or alkaline water stored in a managed landfill site.

[0026] In the invention of claim 7, alkaline water in a pumping well installed as a measure to stabilize leachate in preparation for the decommissioning of a controlled sea surface disposal site, for example, can be efficiently and quickly neutralized, and if the state of the effluent meets the discharge standards, the water can be directly discharged from the pumping well outside the disposal site. This eliminates the need for an inland water pond or water treatment facility within the controlled disposal site, and makes it possible to stabilize leachate in preparation for the decommissioning of the controlled disposal site. [Effects of the Invention]

[0027] The method for stabilizing a controlled landfill site according to the present invention makes it possible to stabilize leachate in preparation for the closure of the controlled landfill site. [Brief explanation of the drawings]

[0028] [Figure 1]Figure 1 is a schematic diagram showing how the neutralization treatment equipment of this embodiment neutralizes alkaline leachate stored in a pumping well from a wastewater collection and drainage facility installed within a managed sea surface disposal site. [Figure 2] FIG. 2 is an enlarged view of the main part of the neutralization treatment equipment shown in FIG. [Figure 3] FIG. 3 is a schematic diagram of the neutralization treatment facility shown in FIGS. 1 and 2 to which an underwater propeller device is added. [Figure 4] FIG. 4 is a schematic diagram of the neutralization treatment equipment shown in FIGS. 1 and 2 to which a submersible circulation pump has been added. [Figure 5] FIG. 5 is a schematic diagram showing how a container is raised and lowered in accordance with the water level of alkaline water in a pumping well in the neutralization treatment facility shown in FIGS. [Figure 6] FIG. 6 is an enlarged view of a main part of a neutralization treatment facility according to another embodiment. [Figure 7] FIG. 7 is a schematic diagram showing how the neutralization treatment equipment shown in FIGS. 1 and 2 neutralizes the water held within the managed offshore disposal site. DETAILED DESCRIPTION OF THE INVENTION

[0029] Hereinafter, an embodiment of the present invention will be described in detail with reference to FIGS. As an example of a managed disposal site, referring to Figure 1, a managed sea surface disposal site 50 is installed adjacent to the open sea, with seawater as the reservoir water and surrounded by a water barrier (a sloped bank 51 in Figure 1). This managed sea surface disposal site 50 is constructed by filling up waste including incineration ash, fly ash, coal ash, etc. into the enclosed reservoir water as a landfill base 53. The landfill of managed sea surface disposal site 50 is completed when waste is piled up until it exceeds the managed water level WL within managed sea surface disposal site 50.

[0030] Within the reclaimed land 53, a plurality of collection and drainage pipes 55, 55 are buried as collection and drainage facilities to collect and drain seepage water, such as rainfall, that seeps through the surface of the reclaimed land 53. Each collection and drainage pipe 55, 55 is located at approximately the same height as the controlled water level WL within the reclaimed land 53. Each collection and drainage pipe 55, 55 is connected to a pumping well 56. The depth of the pumping well 56 is approximately 2 meters or more below the controlled water level WL within the reclaimed land 53. As a result, seepage water, such as rainfall, that seeps through the surface of the reclaimed land 53 flows down toward each collection and drainage pipe 55, 55 near the controlled water level WL, and flows from each collection and drainage pipe 55, 55 into the pumping well 56, where it is stored, as alkaline water containing a large amount of alkaline components eluted from the waste within the reclaimed land 53. At the bottom of the pumping well 56, a recovery means such as a net 20 is provided for recovering carbonates such as calcium carbonate that are produced when the alkaline water in the pumping well 56 is neutralized. As described above, an inland water pond 58 is usually installed in the managed offshore disposal site 50. The alkaline water stored in the inland water pond 58 is pumped by a water pump 59 to the water treatment facility 17 on the sloping embankment 51 in a state where the pH value has been lowered as carbon dioxide in the atmosphere dissolves from the water surface and undergoes a neutralization reaction.

[0031] 1 and 2, neutralization treatment equipment 1A according to this embodiment neutralizes alkaline water in a pumping well 56 installed in a managed offshore disposal site 50 using carbon dioxide sealed in a space 7 of a container 4 (described later). Specifically, neutralization treatment equipment 1A includes carbon dioxide supply means 3 for supplying carbon dioxide, a container 4 submerged with its open portion facing downward in the alkaline water in the pumping well 56, and a supply / discharge pipe 5 connecting the carbon dioxide supply means 3 to the space 7 in the container 4. Carbon dioxide supply means 3 is composed of, for example, a cylinder or tank filled with carbon dioxide recovered from the atmosphere near the pumping well 56 or from exhaust gases from thermal power plants, oil-related factories, and the like located near the managed offshore disposal site 50, concentrated to the required high purity, and then filled with the carbon dioxide.

[0032] The container 4 is formed in a cylindrical shape with a bottom and is submerged in alkaline water in a pumping well 56 with its open portion facing downward using multiple suspension ropes (not shown). This forms a space 7 within the container 4 submerged in the alkaline water. Initially, the space 7 is filled with air. In this embodiment, the container 4 is bell-shaped. The supply and discharge pipe 5 is connected to the top of the bell-shaped container. With this configuration, when the purity of the carbon dioxide sealed within the container 4 (space 7) is less than 100%, the residual gas that is difficult to dissolve, equivalent to the impurity, can be collected within the top of the container 4 and easily discharged to the outside via the supply and discharge pipe 5. As a result, it is possible to constantly fill the container 4 (space 7) with a high concentration of carbon dioxide. While the present embodiment employs a bell-shaped container 4, the container 4 may also be formed in a cylindrical or rectangular tubular shape with a bottom and submerged in alkaline water with its open portion facing downward. Furthermore, if the container 4 is shallow, there is a possibility that the carbon dioxide inside may unintentionally spill into the water due to shaking in the water, and therefore it is preferable that the container 4 is deep.

[0033] The supply and discharge pipe 5 connects the space 7 within the container 4, which is submerged in alkaline water with its open portion facing downward, with the carbon dioxide supply means 3. An exhaust hole (not shown) is formed in the supply and discharge pipe 5 at its air-exposed portion. A lid member (not shown) for opening and closing the exhaust hole is provided on this exhaust hole. This exhaust hole is used to discharge residual gases other than carbon dioxide remaining in the space 7 within the container 4 to the outside when the supply of carbon dioxide from the carbon dioxide supply means 3 is stopped. When carbon dioxide is being supplied from the carbon dioxide supply means 3 to the space 7 within the container 4, the exhaust hole is airtightly closed by the lid member.

[0034] First, the air that filled the space 7 inside the container 4 at the initial stage of installation is discharged to the outside through the exhaust hole of the supply and exhaust pipe 5. Next, the exhaust hole is closed with a lid member, and carbon dioxide is sealed into the space 7 inside the container 4 from the carbon dioxide supply means 3 via the supply and exhaust pipe 5. When carbon dioxide is sealed into the space 7 inside the container 4, it dissolves in the alkaline water, and carbon dioxide (H2CO3) is converted into bicarbonate ions (HCO3 -) and reacts quickly with carbonate ions (CO3 2- ), and then calcium oxide (CaO) contained in the waste reacts with water (HO) to produce calcium ions Ca 2+ However, the carbonate ion (CO3 2- ) and calcium carbonate (CaCO3) is produced (CaO + H2O → Ca 2+ +2OH - ,CO2+H2O→H2CO3,H2CO3→H + +HCO3 - ,HCO3 - →H + +CO3 2- ,H + +OH - →H2O,Ca 2+ +CO3 2- →CaCO3). When the carbon dioxide sealed in the space 7 in the container 4 is dissolved in the alkaline water in this way, calcium carbonate is produced and the alkaline water in the pumping well 56 is neutralized.

[0035] In this embodiment, the carbon dioxide from the carbon dioxide supply means 3 is not simply supplied (e.g., aerated) into the alkaline water in the pumping well 56, but is sealed in the space 7 inside the container 4 submerged in the alkaline water. This reduces the carbon dioxide loss rate, improves dissolution efficiency, and allows the neutralization reaction to occur quickly, enabling the alkaline water to be efficiently neutralized.

[0036] 1 and 2, as shown in Fig. 3, an underwater propeller device 10 can be placed directly below the vessel 4 in the alkaline water in the pumping well 56, and the underwater propeller device 10 can generate a water current toward the water surface in the vessel 4, thereby disturbing the water surface in the vessel 4. Disturbing the water surface in the vessel 4 in this way can promote the dissolution of carbon dioxide sealed in the space 7 of the vessel 4 into the alkaline water, thereby improving the efficiency with which the carbon dioxide in the vessel 4 (space 7) dissolves into the alkaline water, and enabling the alkaline water to be quickly neutralized.

[0037] Furthermore, in addition to the basic embodiment shown in Figures 1 and 2 above, as shown in Figure 4, a circulation submersible pump 12 can be placed, for example, above the container 4, in the alkaline water in the pumping well 56, and the alkaline water can be circulated at appropriate times by the circulation submersible pump 12 to replace the alkaline water with a high pH value that has not yet been neutralized above the container 4 with the neutralized water with a low pH value below the container 4. In other words, the circulation submersible pump 12 can be placed at an appropriate position around the container 4, and the circulation submersible pump 12 can be used to circulate the alkaline water around the container 4 at appropriate times. This allows carbon dioxide to be quickly dissolved in all the alkaline water stored in the pumping well 56, and as a result, all the alkaline water stored in the pumping well 56 can be quickly neutralized.

[0038] Furthermore, in addition to the basic embodiment shown in FIGS. 1 and 2 , referring to FIG. 5 , a lifting device (not shown) may be attached to the container 4, and the container 4 may be raised and lowered by the lifting device based on the water level of the alkaline water in the pumping well 56, thereby maintaining a substantially constant water depth from the water surface of the container 4. In this embodiment, a water pressure gauge 28 is disposed on the outer surface of the container 4, and the water depth of the container 4 in the pumping well 56 is measured by the water pressure gauge 28. Based on the measurement results, the container 4 is raised and lowered by the lifting device. In this way, the container 4 is raised and lowered based on the water level of the alkaline water, so that a constant water pressure is applied to the water surface in the container 4, and the pressure of the gas in the container 4 (space 7) can be maintained at a predetermined value (as high as possible). As a result, the efficiency of dissolving carbon dioxide in the alkaline water in the container 4 (space 7) can be improved, and the alkaline water can be rapidly neutralized.

[0039] It is also possible to adopt an embodiment in which the embodiments shown in Figures 3, 4, and 5 are all added to the basic embodiment shown in Figures 1 and 2. In this embodiment, the underwater propeller device 10 shown in Figure 3 and the circulation submersible pump 12 shown in Figure 4 need to be raised and lowered together with the container 4 according to the water level of the alkaline water in the pumping well 56.

[0040] 1 and 2, a submersible pump 15 is placed in the alkaline water in the pumping well 56. The submersible pump 15 is connected to a water treatment facility 17 on the inclined embankment 51 via a treated water discharge pipe 16. The treated water that has been neutralized in the pumping well 56 is then transported by the submersible pump 15 to the water treatment facility 17 via the treated water discharge pipe 16. The treated water is then subjected to some purification treatment as necessary in the water treatment facility 17, and is released outside the disposal site after satisfying effluent standards.

[0041] Therefore, the purification treatment at the water treatment facility 17 for treated water neutralized by the neutralization treatment equipment 1A according to this embodiment requires a much lighter burden than the conventional purification treatment at the water treatment facility 17 for treated water transported from the inland water pond 58 (see FIG. 1). Furthermore, if the treated water in the pumping well 56 can be maintained in a state that satisfies the effluent standards without being purified by the water treatment facility 17, it can also be released directly from the pumping well 56 to the outside of the disposal site. In this way, by efficiently and quickly neutralizing the alkaline water stored in the pumping well 56 using the neutralization treatment equipment 1A according to this embodiment, it is possible to stabilize the leachate in preparation for the closure of the managed offshore disposal site 50.

[0042] Next, a neutralization treatment equipment 1B according to another embodiment will be described with reference to Fig. 6. When describing the neutralization treatment equipment 1B according to another embodiment, only differences from the neutralization treatment equipment 1A shown in Figs. 1 to 5 will be described. A neutralization treatment facility 1B according to another embodiment includes a water level gauge 22 for measuring the volume of space within the container 4, a carbon dioxide concentration meter 23 for measuring the concentration of carbon dioxide within the container 4 (space 7), a gas pressure meter 24 for measuring the pressure of the gas within the container 4 (space 7), and a control device 25 for controlling the amount of carbon dioxide supplied from the carbon dioxide supply means 3 to the container 4 (space 7) based on the measurement results from the water level gauge 22, the carbon dioxide concentration meter 23, and the gas pressure meter 24. The container 4 is cylindrical with a bottom and is submerged in alkaline water with its open end facing downward. The water level gauge 22 measures the distance (height) from the top surface of the container 4 to the water surface, thereby enabling the volume of space within the container 4 to be measured and the amount of alkaline water flowing into the container 4 (space 7) to be determined.

[0043] An optimal amount of carbon dioxide to be supplied based on the measurement results from the water level gauge 22, the carbon dioxide concentration meter 23, and the gas pressure meter 24 is input into the control device 25 in advance. Then, based on the measurement results from the water level gauge 22, the carbon dioxide concentration meter 23, and the gas pressure meter 24, the control device 25 opens and closes an open / close valve 26 provided in the supply / discharge pipe 5, thereby sealing an optimal amount of carbon dioxide into the space 7 of the container 4. In addition, in the neutralization treatment equipment 1B according to another embodiment, a pH meter 27 may be disposed on the outer surface of the container 4, and the pH value of the alkaline water in the pumping well 56 may be constantly managed by the control device 25 using the pH meter 27. When the pH value of the alkaline water in the pumping well 56 is high, the dissolution rate of carbon dioxide increases, and therefore the supply rate (supply amount) of carbon dioxide may also be adjusted by the control device 25.

[0044] Furthermore, a water pressure gauge 28 may be placed on the outer surface of the container 4, and the water depth of the container 4 in the pumping well 56 may be managed by the control device 25 using the water pressure gauge 28. As described above, the control device 25 may drive the lifting device based on the measurement results from the water pressure gauge 28, so that the container 4 can be submerged at an appropriate water depth at all times, and the gas pressure inside the container 4 (space 7) may be maintained at a predetermined value (as high as possible).

[0045] Furthermore, in the neutralization treatment equipment 1B according to another embodiment, by grasping the spatial volume within the container 4, i.e., the amount of alkaline water flowing into the container 4, the carbon dioxide concentration within the container 4 (space 7), and the gas pressure within the container 4 (space 7), it is possible to freely operate the system to maximize the efficiency of dissolving carbon dioxide into alkaline water, for example by sealing in only the amount of carbon dioxide necessary to treat the amount of alkaline water flowing into the container 4. In short, by grasping the environment within the container 4 (space 7) in detail and controlling the amount of carbon dioxide supplied, it is possible to continuously maximize the efficiency of dissolving carbon dioxide into alkaline water within the container 4 (space 7), and as a result, the stored alkaline water can be quickly neutralized.

[0046] 3, a control device 25 may be electrically connected to a control board that controls the drive of the underwater propeller device 10, i.e., the ON / OFF of the underwater propeller device 10 and the number of rotations per unit time of the underwater propeller device 10. This allows the control device 25 to control the drive of the underwater propeller device 10 based on the measurement results from the water level meter 22, carbon dioxide concentration meter 23, and gas pressure meter 24 inside the vessel 4.

[0047] 4, a control device 25 may be electrically connected to a control board that controls the operation of the circulation submersible pump 12, i.e., the ON / OFF of the circulation submersible pump 12 and the circulation volume (suction volume and discharge volume) per unit time by the circulation submersible pump 12. This allows the control device 25 to control the operation of the circulation submersible pump 12 based on the measurement results from the water level meter 22, carbon dioxide concentration meter 23, and gas pressure meter 24 in the container 4. By adopting such an embodiment, the efficiency of dissolving carbon dioxide in the container 4 (space 7) into the alkaline water can be improved.

[0048] Furthermore, although the neutralization treatment equipment 1A, 1B described above is equipped with one container 4, multiple containers may be provided, and multiple water level gauges 22, carbon dioxide concentration meters 23, gas pressure gauges 24, underwater propeller devices 10, etc. corresponding to the container 4 may be provided as needed.

[0049] In the above explanation, the neutralization treatment facilities 1A and 1B neutralize alkaline water stored in a pumping well 56 installed in a managed sea surface disposal site 50, but it is also possible to neutralize water stored in a managed sea surface disposal site 50 surrounded by a watertight revetment (sloping bank revetment 51) or the like, as shown in Figure 7, i.e., alkaline water that has become alkalized due to waste. Note that Figure 7 only shows the neutralization treatment facility 1A shown in Figures 1 and 2.

[0050] Although not shown in the figures, the neutralization treatment equipment 1A and 1B can also neutralize alkaline water stored in an inland water pond 58 (see Figure 1) installed within the managed sea surface disposal site 50. Furthermore, although not shown in the figures, the neutralization treatment equipment 1A and 1B can also neutralize alkaline water stored in wells that collect leachate within the managed land disposal site. [Explanation of symbols]

[0051] 1A, 1B Neutralization treatment equipment, 3 Carbon dioxide supply means, 4 Container, 7 Space, 10 Underwater propeller device, 12 Circulation submersible pump, 22 Water level meter, 23 Carbon dioxide concentration meter, 24 Gas pressure meter, 25 Control device, 50 Managed offshore disposal site (managed disposal site), 56 Pumping well, 58 Inland water pond

Claims

1. A method for stabilizing a controlled landfill site by neutralizing alkaline water stored in the controlled landfill site and which has become alkaline due to waste, comprising: A method for stabilizing a managed disposal site, characterized in that a container formed in the shape of a cylinder with a bottom is submerged in the alkaline water with the open part facing downward, and then carbon dioxide is sealed in the space within the container to neutralize the alkaline water.

2. 2. The method for stabilizing a controlled disposal site according to claim 1, characterized in that the water surface in the container is disturbed.

3. The method for stabilizing a managed disposal site as described in claim 1, characterized in that alkaline water is circulated so that the alkaline water located above the container is replaced with the alkaline water located below the container.

4. 2. The method for stabilizing a controlled disposal site according to claim 1, wherein the container is bell-shaped.

5. 2. The method for stabilizing a controlled disposal site according to claim 1, wherein the container is raised and lowered based on the level of the alkaline water to maintain the water depth of the container at a substantially constant level.

6. The method for stabilizing a managed disposal site according to claim 1, characterized in that the amount of carbon dioxide supplied to the container is controlled based on the spatial volume within the container, the concentration of carbon dioxide within the container, and the pressure of the gas within the container.

7. The alkaline water stored in the controlled disposal site is Retained water within a managed offshore disposal site, or alkaline water stored in a pumping well or inland pond installed within a managed offshore disposal site, Alternatively, the method for stabilizing a controlled landfill site according to claim 1, characterized in that the alkaline water is stored in the controlled landfill site.

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