Waste processing method

Abstract

The present invention provides a waste processing method that can prevent or suppress the spread of pollution from waste buried in the ground to the surroundings thereof.　Provided is a waste processing method comprising: an excavation step for digging a hole in the ground surface of land in which waste is to be buried; a loading step for loading the waste into the hole; a burying step for filling the soil back into the hole; a spraying step for spraying a treatment chemical agent containing a thermoplastic resin on the surface of the backfilled soil; and a formation step for forming a waterproof layer of the thermoplastic resin on the surface of the soil, wherein in the burying step, an embankment is formed with the soil.

Description

Waste disposal methods

[0001] This invention relates to a method for disposing of waste buried in the ground.

[0002] As people conduct their daily lives in society, vast amounts of various types of waste are continuously generated. Disposing of such waste is a universal challenge in industry and an urgent issue that society as a whole must address. Methods of waste disposal include, for example, landfill, incineration, ocean dumping, and biological treatment. Of these, landfill is relatively simple and low-cost, and does not produce carbon dioxide like incineration, so it remains widely used in many industries.

[0003] When burying waste is chosen as a waste disposal method, measures are required to prevent harmful or toxic substances contained in the buried waste from leaking into the surrounding area due to rainwater or moisture contained in the waste itself. In this regard, there has been a conventional technology to form a synthetic resin film on the surface of the soil layer covering the waste that allows gas to permeate but blocks rainwater (see Patent Document 1).

[0004] According to Patent Document 1, it is possible to prevent most rainwater from seeping into the waste, and since the decomposition gases generated from the waste can be released through the ground, the generation of leachate from rainwater can be reduced as much as possible.

[0005] Japanese Patent Application Publication No. 11-226535

[0006] However, in the method described in Patent Document 1, if the buried waste decreases in volume due to decay, deterioration, oxidation, decomposition, etc., the covering soil layer may sink due to its weight, causing a sinkhole to form in the ground. When the covering soil layer sinks, the synthetic resin film formed on the surface of the covering soil layer is destroyed, and if rainwater or other liquids accumulate in the sinkhole in this state, there is a risk that harmful or toxic substances contained in the waste will dissolve in the water and flow into the surrounding area.

[0007] This invention has been made in view of the above-mentioned problems, and aims to provide a waste treatment method that can prevent or suppress the spread of contamination from waste buried in the soil to the surrounding area.

[0008] The characteristic configuration of the waste treatment method according to the present invention for solving the above problems includes: an excavation step of digging a hole in the ground of the land where the waste will be buried; a deposit step of depositing the waste into the hole; a burial step of backfilling the hole with soil and sand; a spraying step of spraying a treatment agent containing a thermoplastic resin onto the surface of the backfilled soil and sand; and a forming step of forming a waterproof layer of the thermoplastic resin on the surface of the soil and sand, wherein in the burial step, an embankment is formed with the soil and sand.

[0009] This waste disposal method involves a simple process: digging a hole in the ground where the waste will be buried (excavation step), placing the waste into the hole (filling step), backfilling the hole with soil (burial step), spraying a treatment agent containing thermoplastic resin onto the surface of the backfilled soil (spraying step), and then forming a waterproof layer of thermoplastic resin on the surface of the soil (forming step). This method prevents or suppresses water infiltration into the soil, thus reducing the risk of harmful or toxic substances contained in the waste flowing into the surrounding area due to rainfall or flooding, and maintaining a safe environment. Furthermore, by forming an embankment with soil during the burial step, the thickness of the soil covering the waste increases, stabilizing the buried waste under its own weight and allowing for stable storage in the soil over a long period. Even if the buried waste decreases in volume due to decay, deterioration, oxidation, or decomposition, the embankment gradually sinks into the resulting voids in the soil, preventing ground subsidence (collapse). Furthermore, because the embankment sinks gradually, sudden changes in shape do not occur, which maintains the waterproof layer of thermoplastic resin formed on the surface of the soil. As a result, ground subsidence (collapse) is prevented, and rainwater does not accumulate on the ground. Therefore, the spread of contamination from buried waste to the surrounding area can be prevented or suppressed.

[0010] In the waste disposal method according to the present invention, it is preferable not to compact the soil in the burial step.

[0011] According to this waste disposal method, by not compacting the soil during the burial process, the waste in the soil is not crushed by pressure, and the leakage of harmful and toxic substances from the waste can be reduced. Furthermore, since the shape of the soil can be sufficiently maintained by the thermoplastic resin layer (waterproof layer) even without compaction, it can be said that this method is efficient in terms of eliminating the need for compaction work.

[0012] In the waste disposal method according to the present invention, it is preferable to use the soil generated in the excavation step as the soil used to backfill the hole in the burial step.

[0013] According to this waste disposal method, the soil generated in the excavation process can be effectively reused in the burial process by using it to backfill the hole. Furthermore, since the same soil is handled in both the excavation and burial processes, the properties of the land where the waste is processed remain unchanged, allowing for safe and appropriate disposal.

[0014] In the waste treatment method according to the present invention, in the spraying step, the content of the thermoplastic resin contained in the treatment agent is preferably 3 to 10.5% by weight.

[0015] According to this waste treatment method, by setting the thermoplastic resin content in the treatment agent to 3 to 10.5% by weight during the spraying process, a good thermoplastic resin layer (waterproof layer) is formed on the surface of the soil, thereby reliably preventing harmful and toxic substances contained in the waste from flowing into the surrounding area due to rainfall or flooding.

[0016] In the waste treatment method according to the present invention, in the spraying step, the amount of the treatment agent sprayed is 0.5 kg / m². ２ It is preferable that the above conditions are met.

[0017] According to the waste treatment method of this configuration, in the spraying process, the amount of treatment agent sprayed is 0.5 kg / m². ２By doing so, the treatment agent penetrates from the soil surface to an appropriate depth, forming a good thermoplastic resin layer (waterproof layer) on the soil surface. As a result, it is possible to reliably prevent harmful or toxic substances contained in the waste from flowing into the surrounding area due to rainfall or flooding.

[0018] In the waste treatment method according to the present invention, it is preferable to put a superabsorbent polymer into the hole together with the waste in the input step.

[0019] According to this waste treatment method, by introducing a superabsorbent polymer into the hole along with the waste during the input process, even if the soil to be buried or the waste itself contains a large amount of moisture, the superabsorbent polymer can absorb the moisture. This reliably prevents harmful or toxic substances contained in the waste from leaking into the surrounding area due to moisture in the soil or moisture seeping from the waste. Furthermore, as the superabsorbent polymer absorbs moisture and swells, the waste buried in the soil is densely surrounded and protected by the swollen superabsorbent polymer, thus contributing to the long-term and stable storage of the waste.

[0020] In the waste treatment method according to the present invention, in the spraying step, it is preferable that the thermoplastic resin contained in the treatment agent is an ethylene vinyl acetate copolymer (EVA).

[0021] According to this waste treatment method, by using ethylene vinyl acetate copolymer (EVA) as the thermoplastic resin contained in the treatment agent, a durable thermoplastic resin layer (waterproof layer) can be formed on the surface of the soil. Furthermore, since the treatment agent containing ethylene vinyl acetate copolymer (EVA) can be sprayed onto the surface of the soil in the form of a solution (emulsion), it can be said to have excellent workability in the spraying process.

[0022] In the waste treatment method according to the present invention, the waste is preferably animal waste.

[0023] This waste disposal method is particularly effective for disposing of animal waste that poses a risk of spreading infection, especially when ordered to be disposed of by local governments. Animal waste buried in the soil is prone to decomposition and its volume is reduced, but even if voids are created in the soil due to this volume reduction, the embankment will gradually sink, preventing ground subsidence (collapse). In addition, because a waterproof layer of thermoplastic resin is present on the surface of the soil, rainwater and other liquids are less likely to penetrate to the animal waste in the soil, thus preventing or suppressing the spread of contamination to the surrounding area.

[0024] Figure 1 is a schematic diagram illustrating the waste treatment method of the present invention.

[0025] The applicant previously invented a method for disposing of chickens culled in response to an outbreak of highly pathogenic avian influenza (avian influenza) and filed a patent application for said invention (although the patent application for said invention was not published at the time of filing the present application, it has been granted a patent). This invention is a groundbreaking technology that can solve the problem of disposing of discarded chickens that becomes apparent when avian influenza outbreaks occur. Subsequently, the applicant has conducted further studies on this technology and made improvements and refinements to make it applicable to many types of waste other than chickens (discarded chickens).

[0026] Specifically, focusing on the fact that many hazardous and toxic substances contained in waste are easily soluble in water or easily transfer to water, we conducted a study based on the understanding that preventing water infiltration into the ground where waste is buried is important in order to prevent the spread of contamination by waste. We then considered that if we built an embankment on top of the buried waste and solidified the surface of the embankment (soil) with a highly water-resistant thermoplastic resin, water infiltration into the ground would be prevented or suppressed, and the risk of hazardous and toxic substances contained in the buried waste dissolving in water or transferring to water and flowing into the surrounding area would be reduced. As will be explained in detail in the examples described later, we sprayed a treatment agent containing ethylene vinyl acetate copolymer (EVA), an example of a thermoplastic resin, onto simulated soil to solidify the surface soil, and conducted an immersion test on this simulated soil, confirming a high water infiltration suppression effect.

[0027] Thus, the present invention was completed based on the discovery that waste can be safely and appropriately treated even after being buried in the ground by treating soil (especially embankments) with a thermoplastic resin. The waste treatment method of the present invention involves spraying a treatment agent containing a thermoplastic resin onto the surface of the soil in which the waste is buried, and is a technology applicable to the treatment of all types of waste buried in the ground. Examples of waste include animal waste such as livestock and fish, plant waste such as vegetable scraps and wood chips, and mineral waste such as concrete rubble and iron scraps.

[0028] The waste treatment method of the present invention is highly safe and therefore particularly effective for treating animal waste where the spread of infection is a concern. Examples of animal waste include pigs culled due to outbreaks of classical swine fever (formerly classical swine cholera), cattle culled due to outbreaks of foot-and-mouth disease, and other animals culled due to outbreaks of statutory infectious diseases of livestock designated under Japan's Act on the Prevention of Infectious Diseases of Domestic Animals. Chickens culled due to outbreaks of avian influenza may also be included, but this is not essential in the present invention.

[0029] The following describes embodiments of the waste treatment method of the present invention. However, the present invention is not limited to these embodiments.

[0030] <Treatment Agent> In the waste treatment method of the present invention, a thermoplastic resin or a composition containing a thermoplastic resin is used as a treatment agent to solidify the soil. Examples of thermoplastic resins include ethylene vinyl acetate copolymer (EVA), polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC), polystyrene (PS), and acrylonitrile-butadiene-styrene copolymer (ABS). Of these thermoplastic resins, ethylene vinyl acetate copolymer (EVA) is preferred. In ethylene vinyl acetate copolymer (EVA), the ratio of ethylene component to vinyl acetate component is not particularly limited, but increasing the proportion of ethylene component allows for the formation of a flexible film, while increasing the proportion of vinyl acetate component allows for the formation of a hard film. Therefore, when selecting an ethylene vinyl acetate copolymer (EVA) to be used as a treatment agent, the ratio of ethylene component to vinyl acetate component should be appropriate depending on the properties of the soil to be treated. For example, by setting the proportion of ethylene component in ethylene vinyl acetate copolymer (EVA) to about 3 to 10% (molar equivalent), a film with a balanced combination of flexibility and hardness can be formed, making it possible to treat a wide range of soils.

[0031] Furthermore, the treatment agent may also contain disinfectants, antibacterial agents, antiviral agents, deodorizers, thickeners, dispersants, etc., in addition to thermoplastic resins.

[0032] The dosage form of the treatment agent is preferably an emulsion in which a thermoplastic resin is dispersed in a solvent, and in particular, an aqueous emulsion in which a thermoplastic resin is dispersed in water. Furthermore, the content of the thermoplastic resin (solids) in this emulsion (treatment agent) is preferably 3 to 10.5% by weight. Within this range, the soil will harden appropriately, so a good thermoplastic resin layer can be formed on the soil surface as a waterproof layer. If the thermoplastic resin content in the treatment agent is less than 3% by weight, the soil may not be able to harden sufficiently. On the other hand, if the thermoplastic resin content in the treatment agent exceeds 10.5% by weight, cracks may occur on the surface of the hardened soil (thermoplastic resin layer).

[0033] When using (spraying) an emulsion-type treatment agent, the amount to use (spray) is 0.5 kg / m² relative to the soil surface (mound surface). ２ Preferably, it is 1 kg / m ２ It is more preferable that the amount of treatment agent used is 0.5 kg / m². ２ If the above conditions are met, the treatment agent will penetrate to an appropriate depth (for example, 1 to 10 cm) from the soil surface, forming a good thermoplastic resin layer (waterproof layer) on the soil surface. The amount of treatment agent used is 0.5 kg / m². ２ If the amount is less than 5 kg / m³, the treatment agent may not penetrate the soil sufficiently, remaining near the soil surface and potentially failing to properly solidify the soil. On the other hand, there is no particular upper limit on the amount of treatment agent to be used, but considering the cost of using the treatment agent, 5 kg / m³ is recommended. ２ The degree is realistic.

[0034] <Waste Treatment Method> The waste treatment method of the present invention, which uses the treatment chemicals described above, will now be explained. Figure 1 is a schematic diagram illustrating the waste treatment method of the present invention. The waste treatment method of the present invention comprises five steps: an excavation step, a loading step, a burial step, a spreading step, and a formation step. Each step will be explained in detail below.

[0035] <Excavation Process> In the excavation process, a hole 2 is dug in the ground 1 of the land where the waste to be processed will be buried [Figures 1(a) and (b)]. The land where the waste will be buried is not particularly limited, but if the waste is animal waste such as livestock, it is usually set up on the premises of a facility where livestock are raised. Since the waste is disposed of in flexible container bags, for example, the size of the hole 2 should be large enough to fit several to a dozen or so flexible container bags (diameter 1100 mm, height 1100 mm, capacity 1000 L). Regarding the excavation means 3 for excavating the hole 2, a shovel (spade) is illustrated in Figure 1(b) for the sake of explanation, but it is common to use heavy machinery such as a backhoe. The soil 4 generated by excavating the hole 2 is temporarily placed near the hole 2.

[0036] <Input Process> In the input process, waste (e.g., a flexible container bag containing waste) 5 is put into the hole 2 [FIG. 1(c)]. The waste 5 to be input preferably fits within a depth of about 2 / 3 of the depth of the hole 2. Also, it is desirable that the waste 5 is input so as to be aligned at the bottom of the hole 2. In the input process, it is also possible to input a superabsorbent polymer (not shown) together with the waste 5 into the hole 2. In this case, the superabsorbent polymer may be input together with the waste 5 into the flexible container bag containing the waste 5, or may be input so as to be spread around the flexible container bag containing the waste 5 in preparation for damage to the flexible container bag. By inputting the superabsorbent polymer together with the waste 5 into the hole 2, even when the buried soil or the waste 5 itself contains moisture, the superabsorbent polymer can absorb the moisture, so that harmful substances and toxic substances contained in the waste 5 can be surely prevented from leaking out to the surroundings due to the moisture in the soil or the moisture that has seeped out from the waste 5. Also, since the superabsorbent polymer absorbs moisture and swells, the waste 5 buried in the soil is densely surrounded and protected by the swollen superabsorbent polymer, which can contribute to the long-term and stable storage of the waste 5.

[0037] <Burial Process> In the burial process, the hole 2 is backfilled with soil 4 [Figure 1(d)]. Here, in this invention, it is important to form an embankment with soil 4. Because the thickness of the soil 4 covering the waste 5 increases due to the embankment, the buried waste 5 is stabilized by the weight of the soil 4 and stored stably in the soil. When the waste 5 buried in the soil decreases in volume due to decay, deterioration, oxidation, decomposition, etc., voids may be created in the soil. However, as shown in Figure 1(d), if an embankment is formed with soil 4, as shown in Figure 1(f), the embankment will sink into the voids in the soil created by the volume reduction, thus preventing ground subsidence (collapse). Furthermore, it is preferable not to compact the backfilled soil (embankment) 4. Compaction refers to hardening the ground with tools or heavy machinery such as rollers or rammers. In road construction and the like, the laid soil is usually compacted to increase the strength of the soil surface, but compaction transmits pressure into the soil. In particular, if the waste 5 is relatively soft, such as animal waste, it is preferable not to compact the backfill soil (embankment) 4 in order to avoid crushing the buried waste 5 under pressure. The soil 4 used to backfill the hole 2 is the soil 4 generated in the excavation process. This allows for the effective reuse of the soil 4. Furthermore, since the same soil 4 is handled in both the excavation and burial processes, the properties of the land where the waste 5 is processed do not change, and the waste can be processed safely and appropriately.

[0038] <Spraying Process> In the spraying process, a treatment agent 6 containing a thermoplastic resin is sprayed onto the surface of the backfilled soil (embankment) 4 [Figure 1(e)]. Ethylene vinyl acetate copolymer (EVA) is preferred as the thermoplastic resin. Ethylene vinyl acetate copolymer (EVA) can form a durable thermoplastic resin layer (waterproof layer) 7 on the surface of the soil (embankment) 4. Furthermore, since the treatment agent containing ethylene vinyl acetate copolymer (EVA) can be sprayed onto the surface of the soil (embankment) 4 in the form of a solution (emulsion), it can be said to have excellent workability in the spraying process. The means of spraying the treatment agent 6 are not particularly limited, and for example, a spraying device 11 consisting of a chemical tank 8, a pump 9, and a shower head 10 as shown in the figure can be cited. The thermoplastic resin content in the treatment agent 6 is preferably 3 to 10.5% by weight. The amount of treatment agent 6 sprayed is 0.5 kg / m２ It is preferably the above. These are as described in the previous item of "treatment agent".

[0039] <Forming step> When the treatment agent 6 sprayed on the surface of the earth and sand (fill) 4 dries, a thermoplastic resin layer (waterproof layer) 7 is formed on the surface of the earth and sand 4. The presence of the thermoplastic resin layer (waterproof layer) 7 on the surface of the earth and sand 4 makes it difficult for rainwater and the like to penetrate to the waste 5 in the soil, and it is possible to prevent or suppress the spread of pollution to the surroundings. In particular, when the waste 5 is animal waste, the animal waste becomes easily soluble in water due to decay and decomposition. Furthermore, as shown in Fig. 1(f), the volume may be reduced and the earth and sand 4 may settle. However, by providing the thermoplastic resin layer (waterproof layer) 7 on the surface of the earth and sand 4 to prevent the intrusion of rainwater and the like, it is very useful in that it is possible to prevent or suppress the spread of pollution to the surroundings.

[0040] As described above, the waste disposal method of the present invention involves a simple method in which water infiltration into the soil is prevented or suppressed. This reduces the risk of harmful or toxic substances contained in the waste 5 flowing into the surrounding area due to rainfall or flooding, thus maintaining a safe environment. Furthermore, by forming an embankment with soil 4 during the burial process, the thickness of the soil 4 covering the waste is increased. This stabilizes the buried waste 5 under the weight of the soil 4, allowing it to be stored stably in the soil. Furthermore, even if the waste 5 buried in the soil decreases in volume due to decay, deterioration, oxidation, decomposition, etc., the embankment will sink into the resulting voids in the soil, preventing ground subsidence (collapse). Also, even if the embankment collapses, it will do so gradually, preventing abrupt changes in the shape of the ground, and the thermoplastic resin waterproof layer 7 formed on the surface of the soil will be maintained. As a result, in addition to preventing ground subsidence (collapse), it is possible to prevent rainwater from accumulating on the ground. Therefore, it is possible to prevent or suppress the spread of contamination from the waste 5 buried in the soil to the surrounding area. Moreover, by not compacting the soil 4, the waste 5 in the soil will not be crushed by pressure, and the leakage of harmful and toxic substances from the waste 5 can be reduced. In addition, since the shape of the soil 4 can be sufficiently maintained by the thermoplastic resin layer (waterproof layer) 7 even without compaction of the soil 4, it can be said that this method is efficient in that compaction work can be omitted.

[0041] Furthermore, according to the waste treatment method of the present invention, even if a flexible container (treatment container) buried in the soil is damaged and harmful or toxic substances derived from the waste 5 leak out from the flexible container, the thermoplastic resin layer (waterproof layer) 7 formed on the surface of the soil (embankment) 4 can prevent or suppress the intrusion of water into the soil. Therefore, the risk of harmful or toxic substances contained in the waste 5 leaking out due to rainfall or flooding is reduced, and the waste 5 can be maintained and stored safely in the soil.

[0042] In order to verify the effect of the waste treatment method of the present invention, a soaking test of earth and sand treated with a treatment agent was carried out.

[0043] <Chemicals and Materials Used> The chemicals and materials used in the test are as follows. ・Treatment agent: Ethylene vinyl acetate copolymer (EVA) aqueous emulsion (solid content of the stock solution: 21% by weight) ・Comparative agent: Carboxymethyl cellulose (CMC) ・Clay: Clay produced in Tochigi Prefecture (Tochikure (registered trademark)) ・Sand: Mixed sand obtained by mixing No. 3 silica sand and No. 5 silica sand at a ratio of 1:1 (weight ratio)

[0044] <Reproduction of Rainfall> According to the website of the Ministry of Land, Infrastructure, Transport and Tourism, the annual average precipitation in Japan is 1718 mm. Also, according to the website of the Japan Meteorological Agency, a situation where the hourly rainfall is 50 mm or more and less than 80 mm is defined as "extremely heavy rain", and a situation where the hourly rainfall is 80 mm or more is defined as "violent rain". Based on this information, in this soaking test, the target range was defined as 120 mm × 120 mm (0.0144 m ２ ) and the precipitation (volume) and the intensity of rain (flow rate) were simultaneously reproduced by generating the precipitation for half a year in a short period of time.

[0045] [Precipitation (Volume)] Although the calculation formula is omitted, the precipitation (volume) for half a year that fell in the range of 0.0144 m from the annual average precipitation of 1718 mm in Japan is determined to be approximately 13 (L). ２

[0046] [Intensity of Rain (Flow Rate)] By continuously spraying tap water at a flow rate of 1.3 (L / min) for 10 minutes using a gardening shower, the precipitation (volume) for half a year, which is 13 (L), was reproduced. Although the calculation formula is omitted, when this precipitation (volume) is converted to the precipitation per hour, it is 78 mm, which corresponds to "extremely heavy rain" defined by the Japan Meteorological Agency.

[0047] ​<Preparation of Reproduced Soil> Assuming soil generated when excavating the ground of land where waste is buried, clay and sand were mixed by weight in the following proportions: (1) 100%:0%, (2) 70%:30%, and (3) 50%:50%. Each mixed soil was then watered and stirred until it reached a state equivalent to typical excavated soil to obtain reproduced soils A to C. Note that when water is added to the mixed soil, some of the soil aggregates, increasing the variation in particle size. Furthermore, because the gaps between aggregated soils become larger, it may become difficult to accurately evaluate the soil immersion test. Therefore, a sieve with a mesh size of 2.0 mm was used for sieving, and the material that passed through the sieve was used as the reproduced soil for the test. The proportions of reproduced soils A to C are shown in Table 1.

[0048]

[0049] <Immersion Test> Immersion tests of soil were conducted using the treatment agents described in Examples 1 to 8 below. For comparison, similar soil immersion tests were also conducted using the treatment agent described in Comparative Example 1, or under the conditions of Comparative Examples 2 and 3.

[0050] [Example 1] A stock solution of ethylene vinyl acetate copolymer (EVA) aqueous emulsion with a solid content of 21% by weight was diluted twice with water to serve as the treatment agent for Example 1 (solid content 10.5% by weight).

[0051] [Example 2] A stock solution of ethylene vinyl acetate copolymer (EVA) aqueous emulsion with a solid content of 21% by weight was diluted five times with water to be used as the treatment agent for Example 2 (solid content 4.2% by weight).

[0052] [Example 3] A stock solution of ethylene vinyl acetate copolymer (EVA) aqueous emulsion with a solid content of 21% by weight was diluted six times with water to be used as the treatment agent for Example 3 (solid content of 3.5% by weight).

[0053] [Example 4] A stock solution of ethylene vinyl acetate copolymer (EVA) aqueous emulsion with a solid content of 21% by weight was diluted 7 times with water to be used as the treatment agent for Example 4 (solid content 3.0% by weight).

[0054] [Example 5] A stock solution of ethylene vinyl acetate copolymer (EVA) aqueous emulsion with a solid content of 21% by weight was diluted eight times with water to be used as the treatment agent for Example 5 (solid content 2.6% by weight).

[0055] [Example 6] A stock solution of ethylene vinyl acetate copolymer (EVA) aqueous emulsion with a solid content of 21% by weight was diluted 9 times with water to be used as the treatment agent for Example 6 (solid content 2.3% by weight).

[0056] [Example 7] A stock solution of ethylene vinyl acetate copolymer (EVA) aqueous emulsion with a solid content of 21% by weight was diluted 10 times with water to be used as the treatment agent for Example 7 (solid content 2.1% by weight).

[0057] [Example 8] A stock solution of ethylene vinyl acetate copolymer (EVA) aqueous emulsion with a solid content of 21% by weight was diluted 15 times with water to be used as the treatment agent for Example 8 (solid content 1.4% by weight).

[0058] [Comparative Example 1] A CMC aqueous solution, obtained by dissolving carboxymethylcellulose (CMC) in water, was used as the treatment agent for Comparative Example 1 (solid content 0.5% by weight).

[0059] [Comparative Example 2] No treatment agent was used.

[0060] [Comparative Example 3] No treatment chemicals were used, but the soil was compacted.

[0061] The soil immersion tests and evaluations were carried out according to the following procedures (1) to (8). (1) A hole with a radius of 3 cm was made in the center of a non-permeable plastic plate (120 mm x 120 mm), and nonwoven fabric (repurposed ventilation fan filter) was attached to cover the hole. (2) A polyvinyl chloride pipe (inner diameter: approximately 3 cm, height: approximately 10 cm) was placed on the plate with the nonwoven fabric side facing up, with the nonwoven fabric in place, aligned with the hole. A funnel was placed on top of the polyvinyl chloride pipe, and 100 g of reproduced soil was poured in, allowing the soil to accumulate in the polyvinyl chloride pipe by gravity. (3) For Examples 1 to 8 and Comparative Examples 1 to 2, the polyvinyl chloride pipe was removed upwards as is. This reproduced the state in which an embankment was formed on the plate. For Comparative Example 3, the hole in the plate was covered from the opposite side of the polyvinyl chloride pipe, and the area was compacted 25 times with a 2.5 kg rammer before the polyvinyl chloride pipe was removed. (4) Apply the treatment agent from Examples 1 to 8 to the surface of the soil obtained in (3) using a spray bottle at a rate of 1 kg / m². ２A considerable amount is sprayed and allowed to air dry for about a day in a room with controlled temperature and humidity (temperature: 20±5℃, humidity: 50±10%). For Comparative Example 1, because the viscosity of CMC is high and spraying with a spray bottle is difficult, water is first sprayed onto the surface of the soil, then the treatment agent is sprayed using a syringe, and then allowed to air dry for about a day. For Comparative Example 2, only air drying for about a day is performed. For Comparative Example 3, after compaction (tamping), air drying for about a day is performed. (5) Place each dried sample (soil + board) on a beaker with the soil side facing up, and then install a shower 100 mm above it. (6) Spray tap water from the shower in mist mode (flow rate: 1.3 L / min, time: 10 minutes). At this time, the water that permeates through the soil accumulates in the beaker, and the water that does not permeate through the soil flows out of the beaker. (7) After the watering is finished, measure the amount of water W (L) accumulated in the beaker and calculate the permeability R (%) from the following formula: Permeability R (%) = L / 13 × 100 (8) Evaluate the flood control effect comprehensively from the permeability R and the condition of the soil. Note that for samples where the soil collapsed before it could withstand 10 minutes of watering, it is not possible to measure the permeability R, so the flood control effect will be evaluated based on the time until collapse. The evaluation criteria are shown below. ・A ＋ : The soil does not collapse for more than 10 minutes, and the permeability is 10% or less. ・A 　 : The soil does not collapse for more than 10 minutes. ・B 　 The time it takes for the soil to collapse is 2 to 10 minutes. 　 : The time it took for the soil to collapse was less than 2 minutes. ・D 　 The soil collapses instantly (in about 1 second).

[0062] <Test Results> The results of the soil inundation test are shown in Table 2.

[0063]

[0064] <Discussion> As shown in Examples 1 to 4, when the undiluted ethylene vinyl acetate copolymer (EVA) aqueous emulsion (21% solids by weight) was diluted 2 to 7 times with water (3.0 to 10.5% solids by weight) and used as the treatment agent, no collapse occurred in any of the reproduced soils A to C after 10 minutes of continuous watering. Thus, it was found that the treatment agents in Examples 1 to 4 exhibited an excellent flood suppression effect (rating A or higher). In particular, when the treatment agents in Examples 1 to 3, diluted 2 to 6 times, were used on reproduced soil A, when the treatment agents in Examples 1 to 4, diluted 2 to 7 times, were used on reproduced soil B, and when the treatment agents in Examples 1 to 4, diluted 2 to 7 times, were used on reproduced soil C, the permeability was 10% or less, demonstrating an extremely excellent flood suppression effect (rating A). ＋ ).

[0065] As shown in Examples 5 to 8, when a solution of ethylene vinyl acetate copolymer (EVA) aqueous emulsion (21% solids by weight) diluted 8 to 15 times with water (1.4 to 2.6% solids by weight) was used as the treatment agent, none of the reproduced soil samples A to C could withstand 10 minutes of continuous watering. However, since it took more than 2 minutes for them to collapse, a certain degree of flood suppression effect was observed (Evaluation B).

[0066] The results from Examples 1 to 8 showed that when a treatment agent containing ethylene vinyl acetate copolymer (EVA) was used, the higher the solid content concentration of ethylene vinyl acetate copolymer (EVA) in the treatment agent, the greater the water infiltration suppression effect tended to be. In addition, in the reproduced soil samples A to C, Example 1 (solid content 10.5% by weight), in which the undiluted solution was diluted twice, had a slightly lower water permeability than Example 2 (solid content 4.2% by weight), in which the undiluted solution was diluted five times. This is thought to be because when the solid content concentration of the treatment agent exceeds a certain level, cracks occur in the waterproof layer (EVA layer) formed on the soil surface after drying, and some water penetrates through these cracks.

[0067] In contrast, as shown in Comparative Example 1, when an aqueous solution of carboxymethylcellulose (CMC) (solid content 0.5% by weight) was used as the treatment agent, the soil collapsed in about 1 minute for all of the reproduced soils A to C, and no flood suppression effect was observed (Evaluation C).

[0068] As shown in Comparative Example 2, in the cases where no treatment agent was used, the soil collapsed immediately (in about 1 second) in all of the reproduced soil samples A to C, and no flood suppression effect was observed at all (Evaluation D).

[0069] As shown in Comparative Example 3, in the case where no treatment chemicals were used but the soil was compacted, the soil collapsed in approximately 30 seconds for all of the reproduced soils A to C, and no flood suppression effect was observed (Evaluation C).

[0070] As described above, according to the waste treatment method (example) of the present invention, in addition to the stable storage of waste in the soil due to the weight of the soil (embankment), the thermoplastic resin layer (waterproof layer) formed on the surface of the soil (embankment) prevents or suppresses the infiltration of water into the soil. Therefore, the risk of harmful or toxic substances contained in the waste flowing into the surrounding area due to rainfall or flooding is reduced, and a safe condition can be maintained.

[0071] Incidentally, in Examples 1 to 4, the soil did not collapse, and in Examples 5 to 8, a certain amount of time was required before the soil collapsed. Therefore, the waste treatment method of the present invention (examples) is evaluated as being able to suppress soil collapse to a certain extent or more. Furthermore, even if the soil (embankment) collapses (settles) due to exposure to severe weather conditions such as prolonged heavy rain, the thermoplastic resin layer (waterproof layer) formed on the surface of the soil (embankment) has a certain strength, so the settlement rate of the soil (embankment) is very slow. As a result, no sudden change in shape occurs on the surface of the embankment, and the waterproof layer of thermoplastic resin formed on the surface of the soil (embankment) is maintained. Therefore, the waste treatment method of the present invention can prevent ground settlement (collapse) and suppress the accumulation of rainwater on the ground.

[0072] Furthermore, because the soil is not compacted, the waste in the soil is not crushed by pressure, and in this respect, the waste treatment method of the present invention can be said to be highly safe. Moreover, the waste treatment method of the present invention can maintain the shape of the soil sufficiently by the thermoplastic resin layer (waterproof layer) without compacting the soil, and can be said to be highly efficient in that compaction work can be omitted.

[0073] The waste treatment method of the present invention can be used for the purpose of treating various types of waste by burying them in the ground.

[0074] 1. Ground 2. Hole 3. Excavation method 4. Soil and sand 5. Waste 6. Treatment chemical 7. Thermoplastic resin layer (waterproof layer) 8. Chemical tank 9. Pump 10. Shower head 11. Spraying device

Claims

1. A waste treatment method comprising: an excavation step of digging a hole in the ground of land to be buried; a deposit step of depositing waste into the hole; a burial step of backfilling the hole with soil and sand; a spraying step of spraying a treatment agent containing a thermoplastic resin on the surface of the backfilled soil and sand; and a forming step of forming a waterproof layer of the thermoplastic resin on the surface of the soil and sand, wherein in the burial step, soil and sand are used to form an embankment.

2. The waste disposal method according to claim 1, wherein the soil is not compacted in the burial process.

3. The waste disposal method according to claim 1, wherein in the burial step, the soil generated in the excavation step is used as the soil to backfill the hole.

4. The waste treatment method according to claim 1, wherein in the spraying step, the content of the thermoplastic resin contained in the treatment agent is 3 to 10.5% by weight.

5. In the spraying process, the amount of the treatment agent sprayed is 0.5 kg / m². ２ The waste disposal method according to claim 4.

6. The waste treatment method according to claim 1, wherein in the input step, a superabsorbent polymer is introduced into the hole together with the waste.

7. The waste treatment method according to claim 1, wherein in the spraying step, the thermoplastic resin contained in the treatment agent is ethylene vinyl acetate copolymer (EVA).

8. The waste disposal method according to any one of claims 1 to 7, wherein the waste is animal waste.

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