Method and facility for stabilizing management type maritime disposal station

Abstract

To provide a method for stabilizing a management type maritime disposal station that stabilizes a management type maritime disposal station early toward abolishment.SOLUTION: A method for stabilizing a management type maritime disposal station includes a step of neutralization treatment of aerating a gas containing carbon dioxide in alkaline water that flows and is stored in a well 56 via a collecting drainpipe 55, thereby stabilizing a management type maritime disposal station 50 early toward abolishment in the management type maritime disposal station 50.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a stabilization method and stabilization equipment for stabilizing a controlled marine disposal site early in preparation for its decommissioning. [Background technology]

[0002] A managed sea surface disposal site is a facility constructed in a port area where waste such as incineration ash and coal ash is reclaimed. In the early stages of reclamation, the managed sea surface disposal site is filled with seawater (referred to as retained water), but when reclamation is completed, it is filled with waste and is eventually covered with soil to become land. As reclamation progresses, the pH value of the retained water in the managed sea surface disposal site becomes more alkaline due to the waste, and when reclamation is completed, the pH value of the pore water (seepage water) in the reclaimed land often becomes alkaline at 9.0 or more. The reclaimed land of the managed sea surface disposal site is managed to maintain a constant water level (managed water level), and by law, in order to abolish the managed sea surface disposal site, when excess leachate due to rainfall or other factors in the managed sea surface disposal site is discharged into the open sea, the pH value of the excess leachate must be (5.0 or more) 9.0 or less.

[0003] However, since the pH value of the pore water (permeation water) in the reclaimed land is 9.0 or more, it is difficult to maintain the pH of the water that flows through the reclaimed land and seeps out after rainfall, etc., has been infiltrated into the reclaimed land at 9.0 or less. In other words, in order to maintain the pH of the permeation water that permeates and flows through the reclaimed land at 9.0 or less and meet the discharge standards as leachate (water discharged into the open sea), very long-term measures, monitoring, and operation of water treatment facilities are required, which results in an increase in maintenance costs and further leads to the problem of not leading to early use of the site. In other words, the water from rainfall that permeates the highly alkaline reclaimed land becomes permeation water that flows down to the drainage section, during which it becomes highly alkaline, and the discharge standard is exceeded at the drainage section. In this case, it is necessary to carry out water purification treatment using chemicals, such as neutralizing the collected highly alkaline water (permeation water) at a water treatment facility, and there are many cases in which water treatment is carried out for several decades even after the completion of landfilling, which requires a lot of expenses.

[0004] In order to reduce the burden on the water treatment facility, some managed offshore landfill sites have installed inland water ponds. An inland water pond is a section of a managed offshore landfill site that is left unfilled and has a water surface. The main functions of this inland water pond are to manage the water level inside the managed landfill site, which increases due to rainfall, etc., and to store the surplus water before it is pumped to the water treatment facility. It has also been confirmed that by keeping the water surface area within the inland water pond constant, carbon dioxide in the atmosphere dissolves from the water surface, causing a neutralization reaction and lowering the pH value.

[0005] In addition, when a disposal site is closed under the Waste Disposal and Public Cleansing Law, closure procedures must be completed beforehand. The closure of a managed marine disposal site means that a completion notification has been submitted under the Public Water Surface Reclamation Law, meaning that the entire site of the managed marine disposal site has been reclaimed. Therefore, under the current law, completion and closure are not possible if the inland water pond, which was installed 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 site is limited to the surface use of the completed landfill area, excluding the inland water pond.

[0006] Although there is no established early stabilization measure for the decommissioning of managed sea surface disposal sites, several methods are adopted according to the characteristics of each managed sea surface disposal site. One of these methods is to install a collection and drainage pipe. In other words, by installing the collection and drainage pipe at the same height as the managed groundwater level (managed water level in the reclaimed land) in the managed sea surface disposal site, the seepage water from rainfall, etc. that seeps from the ground surface flows down to the collection and drainage pipe near the managed water level and is collected and drained. As a result, the seepage water that passes through the reclaimed land shallower than the managed water level for a certain period of time has a high pH value. However, the collection and drainage pipe prevents the seepage water that seeps from the ground surface from seeping into the reclaimed land deeper than the managed water level, where a large amount of alkali still remains. As a result, after most of the alkali in the reclaimed land shallower than the collection and drainage pipe is washed out by a lot of rainfall, etc. (seepage water), the pH value of the seepage water is expected to stabilize at a low value.

[0007] At the end of this collection and drainage pipe, a well (for example, made of concrete, with an inner diameter of about 1.8 m and a depth of about 6 m from the ground surface) is installed. A drainage pump is installed in the well, and when a certain amount of water is collected from the collection and drainage pipe into the well, the water in the well is pumped into an inland water pond, where the pH value is naturally reduced, and then the water is sent from the inland water pond to a water treatment facility. However, it has been the case that if an inland water pond remains in a managed sea surface disposal site, a completion notification based on the Public Water Surface Reclamation Act cannot be submitted, and the managed sea surface disposal site cannot be closed. In order to fill up the inland water pond and complete the completion procedures, it is necessary to be able to send water directly from the well to the water treatment facility, and the sent water must be purified by the water treatment facility and satisfy the effluent standards. Moreover, it is also necessary to reduce the burden on water purification treatment by the water treatment facility. In addition, if the water can be discharged without purification treatment at the water treatment facility and the standard can be maintained and the water can be discharged, the water treatment facility can be eliminated. As such, issues need to be resolved as soon as possible to stabilize managed marine disposal sites that are facing decommissioning (closure).

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

[0009] [Patent Document 1] JP 2019-166504 A Summary of the Invention [Problem to be solved by the invention]

[0010] However, in the stabilization method for an existing controlled waste disposal site described in Patent Document 1, the neutralizing gas from the exhaust port of the air intake pipe dissolves in the interstitial water located in a very close range around the exhaust port of the air intake pipe, and can only neutralize with the alkaline components in the interstitial water. In addition, the water with carbon dioxide dissolved therein does not basically flow and remains in that position, so the purification range is an extremely narrow range around the exhaust port, and the purification efficiency is very poor. Therefore, in order to expand the purification range, it is necessary to provide multiple air intake pipes and repeat the installation and removal work of each air intake pipe many times, but this construction is not efficient, especially in terms of construction period, construction cost, etc. With the stabilization method for an existing controlled waste disposal site described in Patent Document 1, it is difficult to solve the above-mentioned problem of quickly stabilizing a controlled sea surface disposal site toward decommissioning.

[0011] The present invention has been made in consideration of the above-mentioned problems, and aims to provide a stabilization method and stabilization equipment for a managed offshore disposal site, which will quickly stabilize the managed offshore disposal site in preparation for its decommissioning. [Means for solving the problem]

[0012] As a means for solving the above problems, the invention relating to the stabilization method of a managed marine landfill site as claimed in claim 1 is characterized in that within the reclaimed land of the managed marine landfill site, a collection and drainage pipe is arranged to collect and drain the seepage water that seeps through from the surface of the reclaimed land, and a well is provided which communicates with the collection and drainage pipe, and the alkaline water that flows into the well via the collection and drainage pipe and is stored therein is aerated with a gas containing carbon dioxide to neutralize it. In the invention of claim 1, in a controlled sea surface disposal site, alkaline water stored in a well is aerated with gas containing carbon dioxide to produce treated water with a lowered pH value. That is, the alkaline water in the well contains a large amount of alkaline components eluted from waste in the landfill, and by neutralizing the alkaline components with carbon dioxide, carbonates such as calcium carbonate and magnesium carbonate are produced, and the alkaline water in the well can be treated water with a lowered pH value. Then, the treated water with a lowered pH value compared to the alkaline water in the well can be discharged from the inland water pond via a water treatment facility, or directly from the well into the open sea. This shortens the retention time in the inland water pond to obtain a neutralization effect from the atmosphere, eliminates the need for an inland water pond itself, and reduces the burden on water purification by a water treatment facility, thereby enabling the controlled sea surface disposal site to be stabilized early for disposal. Furthermore, if it were possible to maintain the water quality in compliance with wastewater standards without purification treatment at a water treatment facility and if the water could be discharged directly from the well into the open sea, then water treatment facilities would be unnecessary.

[0013] The invention relating to the stabilization method for a managed offshore disposal site of claim 2 is the invention of claim 1, characterized in that the carbon dioxide concentration and the amount of aeration of gas containing carbon dioxide into the well are set based on the pH value of the alkaline water in the well, and the carbon dioxide concentration is lowered and the amount of aeration is reduced as the pH value of the alkaline water in the well decreases. In the invention of claim 2, the carbon dioxide concentration is set to an optimal value based on the pH value of the alkaline water, so that the alkaline water (alkaline component) in the well can be efficiently neutralized. For example, according to the inventors' experimental results, when the alkaline water has a pH of about 11, a carbon dioxide concentration of about 1.5 to 2.0% is efficient. In other words, even if high-concentration carbon dioxide is supplied by aeration, the entire amount does not react, so it is inefficient. When the alkaline water falls below pH 11, it is highly efficient (low loss rate) to supply carbon dioxide at a lower concentration. According to past research results, when the carbon dioxide concentration in the atmosphere is about 400 to 500 ppm (0.04 to 0.05%), the carbon dioxide concentration is too low, so a long time is required for the neutralization reaction, and it is expected that it will be difficult to neutralize the daily amount of water in operation. Therefore, it is essential to aerate with a gas containing carbon dioxide at a concentration higher than the concentration of carbon dioxide in the atmosphere.

[0014] In addition, in the invention of claim 2, the amount of aeration of gas containing carbon dioxide into the alkaline water in the well is set to an optimal value based on the pH value of the alkaline water, so that the alkaline water (alkaline components) in the well can be neutralized efficiently. The higher the pH value of the alkaline water, the greater the aeration amount can be, without impairing the neutralization reaction efficiency. It is preferable to adjust the aeration amount to be smaller as the pH value of the alkaline water decreases. In short, by managing the aeration amount in relation to the pH value of the alkaline water, the loss rate at that time can be reduced to 30% or less.

[0015] The invention relating to the stabilization method for a managed offshore disposal site of claim 3 is characterized in that, in the invention of claim 1, the water depth in the well for aerating the gas containing carbon dioxide into the alkaline water is set based on the depth of the well and the amount of gas containing carbon dioxide aerated into the well. In the invention of claim 3, aeration of the gas containing carbon dioxide at a deep water depth in the well is preferable in terms of high efficiency (low loss rate) of the neutralization reaction, but since energy is required to pump the gas containing carbon dioxide to a deep water depth, it is preferable to aerate at a shallow water depth within a range where efficiency is not impaired, and set it so that the gas reaches a deep water depth. If the well depth is about 2m or more from the controlled water level, and depending on the aeration amount of the gas containing carbon dioxide, the gas containing carbon dioxide can be distributed throughout almost the entire alkaline water in the well by setting the gas release depth (aeration depth) to 1m or more from the controlled water level.

[0016] The invention relating to a method for stabilizing a managed offshore disposal site as claimed in claim 4 is characterized in that, in the invention as claimed in claim 1, the gas containing carbon dioxide is bubbled and the bubble diameter of the bubbles is set to less than 5.0 mm. In the invention of claim 4, fine bubbles, i.e., bubbles with a diameter of less than 5.0 mm, are generated from the gas containing carbon dioxide, so that the contact time between the many bubbles and the alkaline water in the well is long, the dissolution rate of carbon dioxide in the alkaline water is highly efficient, and the neutralization reaction can be promoted. In addition, if the bubbles are fine, the many bubbles flow throughout almost the entire water area in the well due to the advection of the aerated water mass in the well, further promoting the neutralization reaction.

[0017] The invention relating to the stabilization equipment for a managed sea surface disposal site as claimed in claim 5 is characterized in that the managed sea surface disposal site is provided with a collection and drainage pipe arranged within the reclaimed land for collecting and draining seepage water that seeps through the surface of the reclaimed land, and a well connected to the collection and drainage pipe, in which alkaline water that flows in via the collection and drainage pipe is stored, and the well is provided with a carbon dioxide supplying means for supplying carbon dioxide, and a pressure blower for aerating the carbon dioxide supplied from the carbon dioxide supplying means together with air into the alkaline water in the well. In the invention of claim 5, as in the invention of claim 1, the carbon dioxide supply means and the pressure blower can be used to aerate the alkaline water in the well with gas containing carbon dioxide, and the alkaline water in the well can be discharged as treated water with a lowered pH from the inland water pond via a water treatment facility, or directly from the well into the open sea. This allows the controlled sea surface disposal site to be stabilized early in preparation for decommissioning.

[0018] The invention relating to the stabilization equipment for a managed offshore disposal site as claimed in claim 6 is the invention as claimed in claim 5, characterized in that the gas containing carbon dioxide pressure-fed by the pressure blower into the alkaline water in the well is bubbled in the water pumped up from the well. In the invention of claim 6, if the gas containing carbon dioxide is converted into ultrafine bubbles, for example, fine bubbles (microbubbles or ultrafine bubbles) by the bubble generating means, the fine bubbles containing carbon dioxide will float throughout the entire water area in the well for a long period of time, extending their contact time and further increasing their dissolution rate, thereby further promoting the neutralization reaction with the alkaline components in the entire water area in the well. Effect of the Invention

[0019] The stabilization method and stabilization equipment for a controlled marine disposal site according to the present invention makes it possible to stabilize a controlled marine disposal site early in preparation for its decommissioning. [Brief description of the drawings]

[0020] [Figure 1] FIG. 1 is a schematic diagram of the stabilization equipment of the managed offshore disposal site according to this embodiment. [Diagram 2] FIG. 2 is an enlarged view of a main portion of the stabilization equipment shown in FIG. [Diagram 3] FIG. 3 is a diagram showing the advection of bubbles containing carbon dioxide from the air diffuser shown in FIG. [Figure 4] FIG. 4 is an enlarged view of a main part of a stabilization facility for a managed offshore disposal site according to another embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] Hereinafter, an embodiment of the present invention will be described in detail with reference to Figs. With reference to Fig. 1, a managed sea surface disposal site 50 is installed adjacent to the open sea, with seawater as reservoir water surrounded by a water impermeable revetment (inclined embankment 2 in Fig. 1) and the like. This managed sea surface disposal site 50 is constructed by filling up waste materials including incineration ash, fly ash, coal ash, etc. in the enclosed seawater as a reclaimed land 53. The landfilling of the managed sea surface disposal site 50 is completed when waste materials are piled up until the water level exceeds the managed water level WL within the managed sea surface disposal site 50.

[0022] In the reclaimed land 53, a plurality of collection and drainage pipes 55, 55 are buried to collect and drain the seepage water 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 in the reclaimed land 53. Each collection and drainage pipe 55, 55 is connected to a well 56. The depth of the well 56 is about 2m below the controlled water level WL in the reclaimed land 53 or more. As a result, the seepage water such as rainwater that seeps through the surface of the reclaimed land 53 in the controlled sea surface treatment plant 50 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 well 56 as alkaline water containing a large amount of alkaline components dissolved from the waste in the reclaimed land 53 and is stored there. In addition, a recovery means such as a net 22 is provided at the bottom of the well 56 to recover carbonates such as calcium carbonate and magnesium carbonate that are produced by neutralizing the alkaline water (alkaline component) in the well 56 with air bubbles containing carbon dioxide.

[0023] 1 and 2, the stabilization facility 1A of the managed sea surface disposal site according to this embodiment includes a carbon dioxide supplying means 3 that supplies carbon dioxide, and a pressure blower 4 that aerates the carbon dioxide supplied from the carbon dioxide supplying means 3 together with air into the alkaline water in a well 56. The carbon dioxide supplying means 3 is composed of a cylinder or tank in which carbon dioxide is collected, for example, from the atmosphere near the well 56 or from exhaust gases from thermal power plants and oil-related factories near the managed sea surface disposal site 50, concentrated to the required high purity, and filled.

[0024] The pressure blower 4 is a so-called blower that pressure-feeds air. A gas supply pipe 7 having an aeration pipe 8 at its tip is connected to the pressure blower 4. A carbon dioxide supply pipe 10 extending from the carbon dioxide supply means 3 is connected to the middle of the gas supply pipe 7. With reference to Figs. 2 and 3, the aeration pipe 8 is connected to the tip of the gas supply pipe 7. The aeration pipe 8 is expanded along the radial direction inside the well 56. The aeration pipe 8 extends over substantially the entire radial area of ​​the well 56. A large number of small holes 12 are formed at intervals in the aeration pipe 8 over the entire outer peripheral wall. In this embodiment, the hole diameter of the small holes 12 is set to an appropriate value less than 1.0 mm. By setting the hole diameter of the small holes 12 to less than 1.0 mm, the bubble diameter of the bubbles containing carbon dioxide released from the small holes 12 can be appropriately set to less than 5.0 mm. The aeration pipe 8 is disposed at a depth of 1 m or more from the managed water level WL. As a result, bubbles containing carbon dioxide are released from the numerous small holes 12 of the air diffuser 8 into almost the entire alkaline water in the well 56 .

[0025] Then, carbon dioxide is supplied from the carbon dioxide supply means 3 through the carbon dioxide supply pipe 10 to the air in the gas supply pipe 7, which is pumped from the pump blower 4, and mixed with it. The gas containing carbon dioxide is led to the air diffuser 8 through the gas supply pipe 7. Air bubbles containing carbon dioxide with a diameter of less than 5.0 mm are aerated into the alkaline water in the well 56 from each small hole 12 of the air diffuser 8. Then, carbon dioxide dissolves in the alkaline water in the well 56, which contains a large amount of alkaline components eluted from the waste in the landfill 53, and neutralizes the alkaline components, and reacts with ions such as calcium and magnesium contained in the alkaline water to generate carbonates such as calcium carbonate and magnesium carbonate, and the alkaline water in the well 56 becomes treated water with a lowered pH value. In addition, the carbonates such as calcium carbonate and magnesium carbonate generated by neutralizing the alkaline water (alkaline components) in the well 56 with air bubbles containing carbon dioxide are deposited on the net 22, which is a recovery means, arranged on the bottom surface of the well 56.

[0026] A drainage pump 15 is placed in the alkaline water (treated water) in the well 56. The drainage pump 15 is connected to the water treatment facility 20 on the inclined bank 51 via a treated water discharge pipe 16. The neutralized treated water in the well 56 is sent to the water treatment facility 20 via the treated water discharge pipe 16 by the drainage pump 15. The treated water is then subjected to a slight purification treatment in the water treatment facility 20, and discharged to the open sea after satisfying the wastewater standards. Therefore, the purification treatment action in the water treatment facility 20 for the treated water neutralized by the stabilization equipment 1A according to this embodiment is much lighter than the conventional purification treatment action in the water treatment facility 20 for the treated water sent from an internal water pond. In this embodiment, an internal water pond is not required, and the treated water in the well 56 is sent to the water treatment facility 20, but the treated water in the well 56 may be sent to an internal water pond (not shown). Furthermore, if the treated water in the well 56 can be kept in compliance with the wastewater standards without being purified in the water treatment facility 20, it can be discharged directly from the well 56 into the open sea.

[0027] In addition, the carbon dioxide concentration of the bubbles containing carbon dioxide released from each small hole 12 of the air diffuser 8 is set to an optimal value based on the pH value of the alkaline water in the well 56, so that the neutralization process of the alkaline water in the well 56 can be efficiently promoted. In this embodiment, the carbon dioxide concentration is appropriately set within a range of 0.5 to 30% based on the pH value of the alkaline water in the well 56. For example, when the alkaline water in the well 56 has a pH of about 11, a carbon dioxide concentration of about 1.5 to 2.0% is efficient. On the other hand, when the alkaline water falls below pH 11, supplying carbon dioxide with a lower concentration results in high efficiency (low loss rate) for the neutralization reaction. In short, if the loss rate of the neutralization process of the alkaline water in the well 56 by carbon dioxide increases, the amount of carbon dioxide released from the well 56 into the atmosphere increases, which is not preferable as an action toward carbon neutrality.

[0028] As described above, the aeration pipe 8 is preferably disposed 1 m or more below the controlled water level WL in the well 56. Referring to Fig. 3, by aeration of the air bubbles containing carbon dioxide into the alkaline water in the well 56, the alkaline water in the well 56 is transported upward from the water depth (aeration position) where the air bubbles containing carbon dioxide are released due to the air bubble coupling effect, and is transported downward from the water surface as a return flow. Depending on the aeration amount, i.e., the pumped amount of the gas (air bubbles) containing carbon dioxide from the pumping blower 4, the water may be transported up to about 3 m below the water depth (aeration depth) where the air bubbles containing carbon dioxide are released. Therefore, when the depth of the well 56 is about 4 m below the controlled water level WL, the air bubbles containing carbon dioxide can be distributed throughout almost the entire alkaline water in the well 56 if the water depth where the air bubbles are released is 1 m or more below the controlled water level WL. In short, the water depth of the aeration pipe 8 within the well 56 is set based on the depth of the well 56 and the amount of air bubbles containing carbon dioxide being aerated into the well 56, so that the air bubbles containing carbon dioxide can be distributed throughout almost the entire alkaline water within the well 56.

[0029] The aeration amount by the pressure blower 4, that is, the pressure-feed amount of gas containing carbon dioxide, is set based on the pH value of the alkaline water in the well 56. The higher the pH value of the alkaline water, the greater the aeration amount can be without impairing the neutralization reaction efficiency. On the other hand, it is preferable to adjust the aeration amount to be smaller as the pH value of the alkaline water decreases. That is, by controlling the aeration amount based on the pH value of the alkaline water, the loss rate at that time can be kept low, for example, to 30% or less, and preferably to 10% or less. In short, as described above, if the loss rate of the neutralization treatment of the alkaline water in the well 56 by carbon dioxide increases, the amount of carbon dioxide released from the well 56 into the atmosphere increases, which is not preferable as an action toward carbon neutrality. In this embodiment, the aeration amount is set based on the pH value of the alkaline water in the well 56, and is set to 10% per 1 m of alkaline water in the well 56. 3 The flow rate is appropriately set within the range of 10 to 1000 L / min.

[0030] As described above, the amount of aeration from the air diffuser 8 is set based on the pH value of the alkaline water in the well 56, and the concentration of carbon dioxide is also set based on the pH value of the alkaline water in the well 56. Therefore, the carbon dioxide supply pipe 10 may be provided with a concentration conversion valve (not shown). When the pH value of the alkaline water in the well 56 is high, the concentration conversion valve may be opened to a predetermined aperture to increase the concentration of carbon dioxide and increase the amount of air pumped from the pressure blower 4. On the other hand, when the pH value of the alkaline water in the well 56 is low, the concentration conversion valve may be narrowed to a predetermined aperture to decrease the concentration of carbon dioxide and decrease the amount of air pumped from the pressure blower 4. These controls may be performed manually at regular intervals, or may be automatically controlled by monitoring the pH value of the alkaline water in the well 56.

[0031] In the present embodiment described above, the alkaline water that flows into the well 56 via the collection and discharge pipes 55, 55 and is stored therein can be neutralized by aerating gas containing carbon dioxide. As a result, the treated water, the pH value of which is lowered with respect to the alkaline water in the well 56, can be discharged into the open sea via the water treatment facility 20. This eliminates the need for an inland water pond that has been conventionally provided in the managed sea surface disposal site 50, and the managed sea surface disposal site 50 can be stabilized early for disposal. Moreover, since the treated water with a lowered pH value is sent to the water treatment facility 20 by the discharge pump 15, the burden of purifying the treated water in the water treatment facility 20 can be reduced. Even when the treated water in the well 56 is sent to the inland water pond, the residence time for obtaining the neutralization effect from the atmosphere in the inland water pond can be shortened. As mentioned above, if the treated water in well 56 can be kept in compliance with the wastewater standards without being purified by water treatment facility 20, it can be discharged directly from well 56 into the open sea, in which case water treatment facility 20 will be unnecessary.

[0032] In this embodiment, the concentration of carbon dioxide and the amount of aeration of gas containing carbon dioxide into the well 56 are set based on the pH value of the alkaline water in the well 56, and as the pH value of the alkaline water in the well 56 decreases, the concentration of carbon dioxide is lowered and the amount of aeration is reduced. This makes it possible to reduce the loss rate of the neutralization treatment of the alkaline water in the well 56 with carbon dioxide, and thus to suppress the amount of carbon dioxide released from the well 56 into the atmosphere, thereby contributing to carbon neutrality. In addition, in this embodiment, the carbon dioxide supply means 3 is provided, and as described above, the carbon dioxide supply means 3 is composed of a cylinder or tank filled with carbon dioxide recovered and concentrated from exhaust gas from a thermal power plant, an oil-related factory, or the like in the vicinity of the managed sea surface disposal site 50, and can therefore greatly contribute to reducing the amount of carbon dioxide emissions toward carbon neutrality.

[0033] Furthermore, in this embodiment, when the depth of the well 56 is about 2 m or more below the controlled water level WL, and based on the aeration volume by the pressure blower 4, the depth at which the gas containing carbon dioxide is aerated into the alkaline water in the well 56 is set to 1 m or more below the controlled water level WL. This allows the air bubbles containing carbon dioxide to spread throughout almost the entire alkaline water in the well 56.

[0034] Furthermore, in this embodiment, the air diffuser 8 has small holes 12 with a diameter of less than 1.0 mm, so that the gas containing carbon dioxide can be made into bubbles with a fine diameter, i.e., a diameter of less than 5.0 mm. This makes it possible to increase the contact time between the many bubbles and the alkaline water in the well 56, increasing the dissolution rate of carbon dioxide into the alkaline water and promoting the neutralization reaction. Furthermore, if the bubbles are made fine, the many bubbles will flow throughout almost the entire water area in the well 56 due to the advection of the aerated water mass in the well 56, further promoting the neutralization reaction.

[0035] Next, a stabilization facility 1B for a managed marine disposal site according to another embodiment will be described in detail with reference to Fig. 4. In describing the stabilization facility 1B according to the other embodiment, only the differences from the stabilization facility 1A according to the present embodiment shown in Figs. 1 to 3 will be described in detail. 4, stabilization equipment 1B according to another embodiment includes carbon dioxide supplying means 3 for supplying carbon dioxide, a pressure blower 4 for aerating the carbon dioxide supplied from the carbon dioxide supplying means 3 together with air into alkaline water in a well 56, and bubble generating means 23 for generating bubbles in the water pumped up from the well 56 from the gas containing carbon dioxide pressure-fed into the alkaline water in the well 56 by the pressure blower 4. The specific configurations of the carbon dioxide supplying means 3 and the pressure blower 4 have been described above, and therefore detailed description thereof will be omitted here. The bubble generating means 23 is connected to the gas supply pipe 7 downstream of the connection position with the carbon dioxide supply pipe 10.

[0036] The bubble generating means 23 converts the gas containing carbon dioxide, which is pumped from the pressure blower 4 and flows through the gas supply pipe 7, into bubbles in the water pumped up by the water pump 25 in the well 52. The bubble generating means 23 generates the gas containing carbon dioxide into bubbles with an ultrafine diameter. Specifically, the bubble generating means 23 generates the gas containing carbon dioxide into fine bubbles (bubble diameter less than 0.1 mm), and more specifically, generates microbubbles (bubble diameter less than 100 μm (= 0.1 mm) and 1 μm (= 0.001 mm) or more) or ultrafine bubbles (bubble diameter less than 1 μm).

[0037] In the stabilization equipment 1B according to another embodiment, the bubble generating means 23 is provided, so that gas containing carbon dioxide can be turned into fine bubbles (microbubbles or ultrafine bubbles) from the tip of the bubble supply pipe 29 described below, and these bubbles can be aerated into the alkaline water in the well 56. For example, ultrafine bubbles containing carbon dioxide move irregularly due to Brownian motion faster in water than they rise to the surface. Therefore, ultrafine bubbles containing carbon dioxide in alkaline water do not rise to the surface immediately, but drift radially in the well 56 for a long period of time.

[0038] Also, an air bubble supply pipe 29 extends from the bubble generating means 23. The tip of the air bubble supply pipe 29 is located in the alkaline water in the well 56. In the stabilization equipment 1B according to another embodiment, the air diffuser 8 is not connected to the tip of the air bubble supply pipe 29, and the tip of the air bubble supply pipe 29 is located in the well 56 at a depth of 1 m or more from the controlled water level WL. Then, the air bubbles (fine bubbles) containing carbon dioxide from the tip of the air bubble supply pipe 29 are aerated into the alkaline water in the well 56 to generate neutralized treated water. Then, if the gas containing carbon dioxide is made into ultrafine bubbles, for example, fine bubbles (microbubbles or ultrafine bubbles) by the bubble generating means 23, the fine bubbles containing carbon dioxide float in the entire water area to every corner of the well 56 for a long time, and the contact time is long and the dissolution rate is further increased, and as a result, the neutralization reaction with the alkaline components in the entire water area in the well 56 is further promoted.

[0039] In this embodiment, after neutralization by aerating carbon dioxide-containing air bubbles into the alkaline water in the well 56, the resulting carbonates such as calcium carbonate and magnesium carbonate can be collected by a net 22 or the like (collection means) laid on the bottom of the well 56 and effectively utilized in a general manner, such as by mixing them as fine aggregate in concrete. That is, the net 22 or the like laid on the bottom of the well 56 can be pulled up at regular intervals to collect and dry the accumulated carbonates, which can then be effectively utilized for various purposes, including as fine aggregate in concrete. [Explanation of symbols]

[0040] 1A, 1B Stabilization equipment, 3 Carbon dioxide supply means, 4 Pressure blower, 20 Water treatment facility, 23 Bubble generating means, 50 Managed sea surface disposal site, 53 Reclaimed land, 55 Collection and drainage pipe, 56 Well, WL Managed water level

Claims

1. Within the reclaimed land of the managed sea surface disposal site, a collection and drainage pipe is arranged to collect and drain the seepage water that seeps through the surface of the reclaimed land, and a well is provided in communication with the collection and drainage pipe; A method for stabilizing a managed marine disposal site, comprising aerating and neutralizing gas containing carbon dioxide into the alkaline water that has flowed into the well through the collection and drainage pipe.

2. The concentration of carbon dioxide and the amount of aeration of the gas containing carbon dioxide into the well are set based on the pH value of the alkaline water in the well; 2. The method for stabilizing a managed offshore disposal site according to claim 1, characterized in that the concentration of carbon dioxide is lowered and the amount of aeration is reduced as the pH value of the alkaline water in the well decreases.

3. The stabilization method for a managed marine disposal site as described in claim 1, characterized in that the depth of the well at which the gas containing carbon dioxide is aerated into the alkaline water is set based on the depth of the well and the amount of gas containing carbon dioxide aerated into the well.

4. 2. The method for stabilizing a managed offshore disposal site according to claim 1, wherein the gas containing carbon dioxide is turned into bubbles, and the diameter of the bubbles is set to less than 5.0 mm.

5. The managed sea surface disposal site is provided with a collection and drainage pipe disposed within the reclaimed land for collecting and draining seepage water that seeps through the surface of the reclaimed land, and a well communicating with the collection and drainage pipe, and alkaline water that flows in through the collection and drainage pipe is stored in the well, A carbon dioxide supply means for supplying carbon dioxide; a pressure blower for aerating the carbon dioxide supplied from the carbon dioxide supply means together with air into the alkaline water in the well; The stabilization facility for a managed marine disposal site is characterized by having:

6. The stabilization equipment for a managed marine disposal site as described in claim 5, further comprising a bubble generating means for generating bubbles in the water pumped up from the well by the gas containing carbon dioxide pressurized into the alkaline water in the well by the pressure blower.

Images