JP6240041B2 - Leachate treatment method and leachate treatment system at landfill site - Google Patents

Description

  The present invention relates to a leachate treatment method and a leachate treatment system in a landfill disposal site.

  Conventionally, as described in Patent Document 1 below, a soil purification method for purifying soil contaminated with oil is known. In this soil purification method, a perforated pipe having a hole on its peripheral surface is buried in the ground, and an oil adsorbent is provided on the outer peripheral surface of this perforated pipe. The oil is adsorbed by the oil adsorbing material by sucking the oil through the hole of the perforated tube. Furthermore, microorganisms that decompose oil are supplied to the oil adsorbent through the holes of the perforated tube.

JP 2009-220089 A

  By the way, in a landfill site for waste, pollutants contained in the waste (for example, naturally-occurring heavy metals and radioactive materials) are eluted into the leachate due to rainfall, etc., and the leachate contains contaminated water containing the pollutants. It becomes. Such leachate is collected by a perforated pipe and then processed in a water treatment facility or the like.

  As described in Patent Document 1, a technique for on-site purification of soil contaminated with oil is known. However, in landfill disposal sites, it is assumed that leachate once collected is treated by a water treatment facility. Therefore, treatment while collecting water is not expected. Because conditions differ between the soil and the landfill site, it is difficult to efficiently remove the pollutants even if the conventional technology is simply applied to the landfill site. For this reason, it has been difficult to reduce the processing load of pollutants in the subsequent water treatment facility.

  The present invention provides a leachate treatment method and a leachate treatment system that can reduce the treatment load of pollutants in a subsequent water treatment facility by collecting pollutants while collecting leachate. Objective.

  The present invention relates to a leachate treatment method in a landfill disposal site, the step of installing a water collection pipe having a hole penetrating a peripheral wall in the landfill disposal site, and at least one of the periphery of the water collection pipe and the water collection pipe A step of forming an adsorbing portion by arranging an adsorbing mat formed by laminating an adsorbent and a water-permeable fiber base material, and a leachate for leaching out leachate from a landfill object buried in a landfill disposal site And in the process of collecting water, contacting the adsorbing part and adsorbing the contaminant contained in the leachate to the adsorbent.

  According to this leachate treatment method, leachate leached from the landfill object buried in the landfill disposal site is collected in the water collection pipe through the hole of the water collection pipe. Since this leachate contains pollutants, it is treated by a water treatment facility installed after the water collection pipe. In the leachate treatment method according to the present invention, the adsorption portion is formed by arranging the adsorption mat around at least one of the water collection pipe and inside the water collection pipe. In the process of collecting the leachate, the leachate comes into contact with the adsorbing portion, and the contaminant contained in the leachate is adsorbed by the adsorbent. Since the adsorption mat includes a fiber base material having water permeability, the leachate reaches the adsorbent without hindrance. Accordingly, in the leachate after being collected by the water collecting pipe, the content concentration of the pollutant is reduced. In this manner, the pollutant treatment load in the subsequent water treatment facility can be reduced by removing the pollutant while collecting leachate.

  In the leachate treatment method described above, the adsorbent has adsorption characteristics of any one of heavy metals, volatile organic compounds, and radioactive substances, and in the step of forming the adsorbing portion, the adsorbing mat is placed on the outer periphery of the water collecting pipe. Wrap around. In this case, it is possible to perform an appropriate and reliable adsorption process by employing an adsorbent according to the type of contamination of the landfill object to be landfilled in the landfill disposal site. Furthermore, since the adsorption mat is disposed so as to cover the hole of the water collecting pipe, the chance of contact between the leachate to be collected and the adsorbent increases, and the adsorption efficiency, that is, the removal rate of the above-mentioned contaminants is increased. It is done.

  In the leachate treatment method described above, in the step of forming the adsorption portion, the adsorption mat is arranged so that the adsorption capability of the adsorption portion changes in the extending direction of the water collecting pipe. Depending on the position of the water collection pipe in the extending direction, the concentration of contaminants in the leachate collected may be different. If the adsorption mat is arranged so that the adsorption capacity of the adsorption unit changes according to the concentration of the contaminant, the contaminant can be more effectively adsorbed and removed. Here, the adsorption capacity of the adsorption unit is a general term for various elements in the adsorption unit, such as the amount of adsorbent for a predetermined portion of the water collecting pipe, the adsorption capacity per unit adsorbent, or the packing density of the adsorbent. .

  In the leachate treatment method described above, in the step of forming the adsorbing part, the adsorbing mat is arranged so that the adsorbing capacity of the adsorbing part increases as the amount of leachate flowing through the water collection pipe increases. In this case, the adsorbing capacity of the adsorbing portion is increased as the amount of leached water increases, so that contaminants can be adsorbed and removed more effectively.

  In the leachate treatment method described above, the water collection pipe has a water collection direction for collecting the leachate, and in the step of forming the adsorbing portion, the water collection pipe is more concentrated than the upstream side in the water collection direction. The adsorption mat is arranged so that the adsorption capability of the adsorption unit is increased on the downstream side in the water direction. Normally, when leachate is collected in the direction of water collection, the amount of leachate flowing through the water collection pipe increases toward the downstream side. Compared with the upstream side in the water collection direction, the adsorption capacity of the adsorption part is enhanced on the downstream side, so that contaminants can be more effectively adsorbed and removed.

  In the above leachate treatment method, after the landfill object is landfilled, the adsorption mat is buried. Conventionally, leachate containing pollutants has been treated in water treatment facilities. The contaminants removed at the water treatment facility needed to be somehow finally disposed of. According to this leachate treatment method, the adsorption mat is buried as it is, so that it is possible to omit the step of carrying out the pollutant from the water treatment facility and landfilling it. Therefore, the pollutant can be disposed of more easily and safely.

  The present invention relates to a leachate treatment system in a landfill disposal site, which is installed in the landfill disposal site and disposed in at least one of a water collection pipe formed with a hole penetrating a peripheral wall and around the water collection pipe and in the water collection pipe And an adsorption mat formed by laminating an adsorbent and a water-permeable fiber base material.

  According to this leachate treatment system, leachate leached from the landfill object buried in the landfill disposal site is collected in the water collection pipe through the hole of the water collection pipe. Since this leachate contains pollutants, it is treated by a water treatment facility installed after the water collection pipe. In the leachate treatment system according to the present invention, the adsorbing portion is formed by the adsorbing mat disposed at least around the water collecting pipe and inside the water collecting pipe. In the process of collecting the leachate, the leachate comes into contact with the adsorbing portion, and the contaminant contained in the leachate is adsorbed by the adsorbent. Since the adsorption mat is formed by laminating an adsorbent and a water-permeable fiber base material, leachate reaches the adsorbent without any problem. Accordingly, in the leachate after being collected by the water collecting pipe, the content concentration of the pollutant is reduced. In this manner, the pollutant treatment load in the subsequent water treatment facility can be reduced by removing the pollutant while collecting leachate.

  According to the present invention, by removing pollutants while collecting leachate, it is possible to reduce the processing load of pollutants in a subsequent water treatment facility.

It is a figure showing the whole landfill disposal site where the leachate treatment system concerning one embodiment of the present invention was applied. It is sectional drawing along the extension direction of a water collecting pipe. It is sectional drawing perpendicular | vertical to the extension direction of a water collecting pipe. It is a flow which shows the process sequence of the leachate treatment method which concerns on one Embodiment of this invention. FIG. 4 is a front view of the adsorption mat in FIG. 3. It is sectional drawing which shows the layer structure of the adsorption mat of FIG. It is a perspective view which shows how to wind the adsorption mat around a water collection pipe. It is sectional drawing which shows the state which leachate distribute | circulates the inside of a water collection pipe | tube. It is a figure which shows the leachate treatment system which concerns on other embodiment of this invention, and is sectional drawing along the extension direction of a water collection pipe | tube. It is a figure which shows the leachate treatment system which concerns on other embodiment of this invention, and is sectional drawing along the extension direction of a water collecting pipe. It is a figure which shows the leachate treatment system which concerns on other embodiment of this invention, and is sectional drawing along the extension direction of a water collecting pipe. (A) is sectional drawing which shows the state through which the leaching water distribute | circulates the inside of the water collection pipe | tube in FIG. 11, (b) is sectional drawing which shows an example of the flow of the leaching water in the exterior of the water collection pipe | tube of (a). It is.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant descriptions are omitted.

  First, an outline of the landfill site 1 to which the leachate treatment system S of the present embodiment is applied will be described. The landfill object to be landfilled in the landfill site 1 is not particularly limited. The leachate treatment system S and the leachate treatment method of the present embodiment are particularly suitable for landfilling excavated soil or excavation generated in tunnel construction, creation work, etc. involving excavation under conditions where natural heavy metals exist. It is effective for.

  As shown in FIG. 1, the landfill site 1 is constructed, for example, in a valley formed between mountains. In the landfill site 1, a bottom impermeable construction 12 is laid (see FIG. 3). The landfill disposal site 1 is provided with an upper impermeable work 11 after the landfill. In the landfill site 1, a plurality of water collecting pipes are laid. More specifically, the landfill disposal site 1 includes a bottom water collecting pipe 2A as a trunk line installed at the bottom of the landfill space, a bottom water collecting pipe 2B as a branch line connected to the bottom water collecting pipe 2A, and a bottom water collecting pipe 2B. A sloped water collecting pipe 3 connected to the bottom water collecting pipe 4 and a vertical water collecting pipe 4 rising from the bottom water collecting pipe 2A are installed.

  The bottom water collecting pipe 2A, the bottom water collecting pipe 2B, the slope water collecting pipe 3, and the vertical water collecting pipe 4 collect leachate Wc leached from the waste (landfill target) X buried in the landfill disposal site 1. . For convenience, the leachate leached from the waste X is denoted as leachate Wc, the leachate collected by the water collecting pipe is denoted as leachate Wb, and the leachate stored in the catchment pit 6 is leached. Indicated as Wa.

  Next, the leachate treatment system S will be described. In the following description, a case where the leachate treatment system S is constructed for the bottom water collection pipe 2A will be described, but a leachate treatment system may be constructed for a water collection pipe other than the bottom water collection pipe 2A.

  As shown in FIGS. 1 and 2, the bottom water collecting pipe 2 </ b> A, which is a perforated pipe, is installed at a predetermined inclination angle (that is, a gradient) at the bottom of the landfill disposal site 1. The bottom water collecting pipe 2A has an inclination angle, and causes the leachate Wb to flow down in the water collecting direction D1 due to gravity (that is, natural flow). The diameter of the bottom water collecting pipe 2A is, for example, about 600 mm.

  The leachate Wb flowing down in the bottom water collecting pipe 2A is stored in the water collecting pit 6 provided adjacent to the landfill space. The leachate Wa stored in the water collecting pit 6 is transferred to the water treatment facility 10 through the water supply line 8 by the water supply pump 7. The leachate Wa transferred to the water treatment facility 10 is purified by being subjected to predetermined treatment (for example, pretreatment, coagulation sedimentation treatment, biodegradation treatment, etc.).

  The leachate Wc leached from the waste X may contain various contaminants depending on the contamination state of the waste X. Examples of contaminants to be treated by the leachate treatment system S include naturally-derived heavy metals, volatile organic compounds (VOC), radioactive substances, and the like. Examples of the heavy metal include naturally-derived arsenic, fluorine, cadmium, lead and the like. Examples of the volatile organic compound include trichloroethylene and tetrachloroethylene. Examples of the radioactive substance include cesium or iodine.

  As shown in FIGS. 2 and 3, in the leachate treatment system S, a suction part 30 is formed by winding a rectangular suction mat 20 around the outer periphery of the bottom water collecting pipe 2 </ b> A. More specifically, two adsorption mats 20 are wound around the entire circumference of the bottom water collecting pipe 2A. One adsorption mat 20 is wound around the lower half of the outer periphery of the bottom water collecting pipe 2A, and the other adsorption mat 20 is wound around the upper half of the outer periphery of the bottom water collecting pipe 2A. The adsorption mat 20 is fixed to the bottom water collecting pipe 2A.

  As shown in FIG. 8, the bottom water collecting pipe 2 </ b> A has holes 16 that penetrate the peripheral wall at four locations in the circumferential direction. In the extending direction of the bottom water collecting pipe 2A, a plurality of holes 16 are formed at equal intervals. The four holes 16 are covered by the lower adsorption mat 20 and the upper adsorption mat 20. For example, crushed stone 13 is spread around the bottom water collecting pipe 2A in order to ensure water permeability. The adsorption mat 20 is disposed between the crushed stone 13 and the hole 16 of the bottom water collecting pipe 2A. The adsorption mat 20 is not limited to the case where the adsorption mat 20 is disposed between the crushed stone 13 and the hole 16. The adsorption mat 20 may not cover the hole 16. The adsorption mat 20 may be disposed on a series of flow paths from which the leachate Wc is leached and collected.

  Next, the leachate treatment method will be described with reference to FIG. The leachate treatment method of this embodiment includes a construction process of the landfill disposal site 1 and a landfill process of the waste X to the landfill disposal site 1. First, a water collection pipe is installed in the landfill site 1 (step S1). Here, the bottom water collecting pipe 2A, the bottom water collecting pipe 2B, the slope water collecting pipe 3, and the bowl-shaped water collecting pipe 4 described above are laid. Next, the adsorption mat 20 is disposed on the outer periphery of the bottom water collecting pipe 2A (step S2).

  As shown in FIGS. 5 and 6, the adsorption mat 20 has a rectangular shape of, for example, 0.9 m × 2 m. The adsorption mat 20 includes an adsorbent 21, an upper sheet 22A, a lower sheet 22B, and a sewing thread 23. The adsorbent 21, the upper sheet 22 </ b> A, and the lower sheet 22 </ b> B are sewn across the entire width direction of the adsorption mat 20 with the sewing thread 23. This sewing is performed at equal intervals in the depth direction of the suction mat 20. The interval between the adjacent sewing threads 23 can be set to an appropriate interval of, for example, about 5 to 30 cm so that the thickness of the adsorbent 21 does not change remarkably. Further, a non-adsorption portion 24 that does not have the adsorbent 21 inside is formed at the end in the width direction and the depth direction of the adsorption mat 20. The thickness of the adsorption mat 20 is about 20 to 40 mm throughout.

  The adsorbent 21 has an adsorption characteristic of any of heavy metals, volatile organic compounds, and radioactive substances. Examples of the adsorbent 21 having heavy metal adsorption characteristics include zeolite or iron hydroxide-based granular adsorbent (for example, KAT Beads (Amron Co., Ltd.)). Examples of the adsorbent 21 having VOC adsorption characteristics include activated carbon and zeolite. Examples of the adsorbent 21 having the radioactive substance adsorption property include zeolite and the like (when the radioactive substance is cesium). There are various types of zeolite, such as natural zeolite, artificial zeolite, and synthetic zeolite, but any type is applicable. It is preferable that the pH at which the adsorbent 21 can exhibit the adsorption capacity is in a wide range. For example, it is possible to use an adsorbent 21 that exhibits an adsorption ability at a pH of 3 to 10. The thickness of the adsorbent 21 is about 10 to 20 mm. The adsorbent 21 is, for example, a granule. The particle diameter of the adsorbent 21 is, for example, 5 mm or less, and the specific gravity is less than 1. The adsorbent 21 may be fibrous or powdery.

  As the upper sheet 22A and the lower sheet 22B, a fiber base material such as a nonwoven fabric is used. The upper sheet 22 </ b> A and the lower sheet 22 </ b> B are arranged so as to sandwich the adsorbent 21 so that the adsorbent 21 does not leak out of the adsorption mat 20. The lower sheet 22B is thicker than the upper sheet 22A, for example. The lower sheet 22B may be the same thickness as the upper sheet 22A or thinner than the upper sheet 22A.

As described above, the adsorption mat 20 has a structure in which the upper sheet 22A and the lower sheet 22B made of a fiber base material such as a nonwoven fabric and the adsorbent 21 disposed therebetween are laminated. In other words, the adsorption mat 20 has a sandwich structure in which the adsorbent 21 is sandwiched between the upper sheet 22A and the lower sheet 22B. The upper sheet 22A and the lower sheet 22B have a predetermined water permeability, and allow the leachate Wc to pass through without resistance. On the other hand, the adsorbent 21 also has a predetermined water permeability, and allows the leachate Wc to pass through without resistance. The water permeability of the adsorption mat 20 as a whole is, for example, about 10 ⁻⁴ m / s. The water permeability of the adsorption mat 20 is larger than the water permeability of the soil layer.

  In step S2, as shown in FIG. 7, the suction mat 20 is wound so that the extending direction of the sewing thread 23 is along the extending direction of the bottom water collecting pipe 2A (that is, the water collecting direction D1). At this time, the adsorption mat 20 is wound so that the lower sheet 22B of the adsorption mat 20 is on the outer peripheral side and the upper sheet 22A is in contact with the outer peripheral surface of the bottom water collecting pipe 2A. Each of the adsorption mats 20 is wound around the lower half and the upper half of the outer periphery of the bottom water collecting pipe 2A, and these adsorption mats 20 are fixed to the bottom water collecting pipe 2A with a fastener such as a wire. The adsorption mat 20 is wound over the entire length of the bottom water collecting pipe 2A (see FIG. 2). Thus, the adsorbing part 30 for adsorbing and removing contaminants contained in the leachate Wc (and the leachate Wb) is formed.

  In addition, it is not restricted to the case where the adsorption mat 20 is wound over the entire length of the bottom water collecting pipe 2A, and the adsorption mat 20 may be wound only on a part of the extending direction of the bottom water collecting pipe 2A. For example, the adsorbing portion 30 may be formed by winding the adsorbing mat 20 only on the most downstream portion of the bottom water collecting pipe 2A.

  If the adsorption | suction part 30 is formed by installing the adsorption | suction mat 20, the waste X will be reclaimed (step S3). More specifically, after the bottom water collecting pipe 2A is filled with crushed stone 13 (see FIG. 8) and the like, the waste X is reclaimed from above.

  Subsequently, the leachate Wc leached from the waste X due to rain or the like is collected through the respective holes 16 by the bottom water collecting pipe 2B, the slope water collecting pipe 3, the vertical water collecting pipe 4, and the bottom water collecting pipe 2A. Water (step S4). While the leachate Wc flows into the bottom water collection pipe 2A and the leachate Wb flows down through the bottom water collection pipe 2A, it is included in the leachate Wc (and the leachate Wb) by the adsorption part 30 formed in step S2. The contaminant is adsorbed on the adsorbent 21 of the adsorption mat 20. In the example shown in FIG. 8, the leachate Wb occupies more than half of the flow path P of the bottom water collecting pipe 2 </ b> A, but the water level of the leachate Wb may vary depending on the environment of the landfill disposal site 1. Even if the water level of the leachate Wb fluctuates in the bottom water collecting pipe 2A, as long as the contact state between the adsorbent 21 of the adsorption mat 20 and the leachate Wc (and the leachate Wb) is maintained, the adsorption mat 20 (that is, adsorption) Part 30) adsorbs contaminants.

  When the landfilling of the waste X is completed (step S5), the adsorption mat 20 wound around the bottom water collecting pipe 2A is all buried. The adsorption mat 20 maintains the function of adsorbing contaminants as long as the adsorption capacity of the adsorbent 21 remains even after being buried. During the landfill of the waste X and after the landfill, the impossibility of processing contaminants in the water treatment facility 10 is reduced.

  According to the leachate treatment system S and the leachate treatment method described above, the leachate Wc leached from the waste X buried in the landfill site 1 passes through the hole 16 of the bottom catchment pipe 2A and the bottom catchment pipe 2A. Water is collected inside. Since the leachate Wc contains contaminants, it is treated by the water treatment facility 10 installed at the rear stage of the bottom water collecting pipe 2A. In the leachate treatment method described above, the suction portion 30 is formed by arranging the suction mat 20 around the bottom water collecting pipe 2A. In the process of collecting the leachate Wc, Wb, the leachate Wc, Wb comes into contact with the adsorbing portion 30 and the contaminants contained in the leachate Wc, Wb are adsorbed by the adsorbent 21. Since the adsorbent 21 of the adsorbent mat 20 is sandwiched between the upper sheet 22A and the lower sheet 22B made of nonwoven fabric (fiber base material) having water permeability, the leachate Wc, Wb reaches the adsorbent 21 without any trouble. . Therefore, the content concentration of the pollutant is reduced in the leachate Wa after being collected by the bottom water collecting pipe 2A. In this way, the contaminant treatment load in the subsequent water treatment facility 10 is reduced by removing the contaminants while collecting the leachate Wc and Wb. More specifically, labor and cost in the water treatment facility 10 are reduced.

  In particular, when the waste X is carried in before the upper water-impervious work 11 is installed in the landfill disposal site 1, rainwater enters the landfill disposal site 1, so that in the water treatment facility 10. The amount of treated water tends to increase. However, by providing the leachate treatment system S, it is possible to prevent the outflow of pollutants by the adsorption mat 20 and reduce the load of water treatment during the construction period, which tends to be longer than the operation period after completion of the construction.

  Further, in the step of forming the adsorbing part 30, the adsorbing mat 20 is arranged so as to cover the hole 16 of the bottom water collecting pipe 2A by winding the adsorbing mat 20 around the outer circumference of the bottom water collecting pipe 2A. Thereby, the contact opportunity of the leachate Wb and Wc collected and the adsorbent 21 is increased, and the adsorption efficiency, that is, the removal rate of the contaminant is increased.

  Further, the adsorbent 21 has an adsorption characteristic of any one of heavy metals, volatile organic compounds, and radioactive substances. In this case, by using the adsorbent 21 according to the type of contamination of the waste X landfilled in the landfill disposal site 1, an appropriate and reliable adsorption process can be performed.

  In addition, after the waste X is landfilled, the adsorption mat 20 is buried. Conventionally, leachate containing pollutants has been treated in the water treatment facility 10. Contaminants removed at the water treatment facility 10 had to be finally disposed of in some way. According to the above leachate treatment method, the adsorption mat 20 is buried as it is, so that the step of carrying out contaminants from the water treatment facility 10 and landfilling is omitted. Therefore, the pollutant can be disposed of more easily and safely. In addition, the adsorbing mat 20 can permanently contain contaminants in the landfill site 1, and the risk of elution or outflow is small.

  Although one embodiment of the present invention has been described, the present invention is not limited to the above embodiment. For example, as shown in FIGS. 9 and 10, in the step of forming the suction portion, the suction mat 20 may be arranged so that the suction capability of the suction portion changes in the extending direction of the bottom water collecting pipe 2A. The adsorption capacity of the adsorption unit may be the amount of the adsorbent 21 with respect to a predetermined location of the bottom water collecting pipe 2A, or may be the adsorption capacity per unit adsorbent 21. Alternatively, the packing density of the adsorbent 21 in the adsorption mat 20 may be used.

  For example, as shown in FIG. 9, the number of adsorption mats 20 may be changed at each location in the extending direction of the bottom water collecting pipe 2A. In the leachate treatment system SA shown in FIG. 9, the adsorption mat 20 is wound in a triple manner at the most downstream position of the bottom water collecting pipe 2 </ b> A, and the first adsorption portion 31 is formed. In addition, on the upstream side of the first suction portion 31, the suction mat 20 is wound twice and a second suction portion 32 is formed. Further, on the upstream side, the suction mat 20 is wound in a single layer, and a third suction portion 33 is formed.

  The adsorption capacity of the adsorption part 30A formed in this way is highest in the first adsorption part 31, and then is high in the second adsorption part 32.

  According to the leachate treatment system SA and the leachate treatment method, even if the concentration of contaminants in the leachate Wc and Wb collected varies depending on the position in the extending direction of the bottom water collecting pipe 2A, Contaminants can be more effectively adsorbed and removed. For example, the number of adsorption mats 20 can be increased so that more adsorbents 21 are arranged in an area where the degree of contamination of the waste X is expected to be high.

  Further, as described above, by arranging the adsorption mat 20 so that the adsorption capacity of the adsorption unit 30A is higher in the portion (the most downstream portion) where the amount of leachate flowing down the bottom water collecting pipe 2A is large, the portion where the amount of leachate is large The adsorption capacity of the adsorption unit 30A is increased as much as possible. That is, the 1st adsorption | suction part 31 which has the highest adsorption | suction capability is formed in the most downstream part with a large amount of leaching water. Thereby, contaminants can be adsorbed and removed more effectively.

  From another viewpoint, in the leachate treatment system SA, the adsorption capacity of the adsorption unit 30A is higher on the downstream side of the water collection direction D1 than on the upstream side of the water collection direction D1 of the bottom water collection pipe 2A. Thus, the adsorption mat 20 is arranged. That is, in the adsorption part 30A, the first adsorption part 31 is provided at the most downstream part in the water collection direction D1, and the adsorption capacity increases in the direction toward the upstream side (in the order of the second adsorption part 32 and the third adsorption part 33). It gets smaller. When collecting the leachate Wc and Wb in the water collection direction D1, the amount of leachate increases toward the downstream side. Compared to the upstream side in the water collecting direction D1, the adsorption capability of the adsorption unit 30A is enhanced on the downstream side, so that contaminants can be more effectively adsorbed and removed.

  Further, in the leachate treatment system SB shown in FIG. 10, a first adsorbing portion 31B in which the adsorbing mat 20 is disposed on the outer periphery and the inside of the bottom collecting tube 2A is formed at the most downstream position of the bottom collecting tube 2A. ing. In this case, before the bottom water collecting pipe 2A is connected, the adsorption mat 20 is laid in the bottom water collecting pipe 2A. At other locations in the water collection direction D1, the adsorption mat 20 is wound around the outer periphery of the bottom water collection pipe 2A so as to form a second adsorption portion 32B.

  Also by the adsorption part 30B having such a first adsorption part 31B and the second adsorption part 32B, the same operations and effects as the adsorption part 30A described above are exhibited. In addition, since the water permeability of the adsorption mat 20 is increased, even if it is disposed in the bottom water collecting pipe 2A, the flow of the leachate Wb is not hindered.

  The adsorption mat 20 is not limited to being wound around the bottom water collecting pipe 2A, and may be sandwiched between the bottom water collecting pipe 2A. The adsorption mat 20 is not limited to the case of covering the entire circumference of the bottom water collecting pipe 2A, and may be disposed only at the lower part of the bottom water collecting pipe 2A. When the leachate Wb accumulates in the lower part of the bottom water collecting pipe 2A and flows through the upper part of the bottom water impermeable construction 12, it is effective to arrange the adsorption mat 20 in the lower part of the bottom water collecting pipe 2A. A spacer may be provided between the bottom water collecting pipe 2 </ b> A and the adsorption mat 20.

  FIG. 11 is a view showing the leachate treatment system SC and is a cross-sectional view along the extending direction of the water collecting pipe. In the leachate treatment system SC shown in FIG. 11, the adsorption mat 20 is wound around the outer periphery of the lower half of the bottom water collecting pipe 2A. In other words, the adsorbing part 30C is formed on the outer peripheral side of the lower half of the bottom water collecting pipe 2A.

  Specifically, as shown in FIG. 12A, the bottom water collecting pipe 2A is provided with a plurality of holes 16 penetrating the peripheral wall in the lower half thereof. That is, the hole 16 is not provided in the upper half of the bottom water collecting pipe 2A. The hole 16 is provided slightly below a virtual plane that divides the bottom water collecting pipe 2A into two equal parts in the vertical direction, and is arranged to face slightly below the horizontal direction. In the extending direction of the bottom water collecting pipe 2A, a plurality of holes 16 are formed at equal intervals. The adsorption mat 20 is provided on the outer periphery of only the lower half of the bottom water collecting pipe 2A, thereby forming an adsorption portion 30C. That is, the adsorption part 30C is not formed in the upper half of the bottom water collecting pipe 2A.

  In the lower half of the bottom water collecting pipe 2A, the adsorption mat 20 is arranged so as not to cover the hole 16. The adsorption mat 20 is disposed only between the holes 16. However, the adsorption mat 20 has a through hole formed at a position corresponding to the hole 16 so that the adsorption mat 20 has a bottom of the bottom water collecting pipe 2 </ b> A. You may arrange | position on the outer periphery of a half part. Further, the adsorption mat 20 may be disposed away from the outer periphery of the bottom water collecting pipe 2A or may be disposed below the bottom water collecting pipe 2A. Thus, the adsorption mat 20 is disposed so as not to cover the hole 16 around the bottom water collecting pipe 2A.

  FIG. 12B is a cross-sectional view showing an example of the flow of leachate outside the bottom water collecting pipe. The leachate Wc leached from the waste X due to rain or the like flows downward. At this time, the leachate Wc flowing down from the upper part of the bottom water collecting pipe 2A flows along the outer periphery of the bottom water collecting pipe 2A (see direction F shown in FIG. 12 (b)) and on the upper part of the bottom water impermeable construction 12. Accumulate. The leachate Wc at the top of the bottom impermeable work 12 flows into the bottom water collecting pipe 2A through the hole 16 (see direction G shown in FIG. 12B). The water level of the leachate Wc accumulated between the crushed stones 13 of the bottom impermeable work 12 becomes substantially the same as the position of the hole 16 (see the gray part shown in FIG. 12B). The level of the leachate Wb in the bottom water collecting pipe 2A is maintained substantially the same as or below the hole 16.

  Thus, in the leachate treatment system SC, the hole 16 and the adsorption mat 20 are provided only in the lower half of the bottom water collecting pipe 2A. Therefore, the leachate Wc that has flowed down accumulates in the upper portion of the bottom impermeable construction 12 so that the leachate Wc and the adsorption mat 20 can sufficiently contact each other. Therefore, the adsorption performance by the adsorption part 30C is sufficiently exhibited. Further, the suction mat 20 is disposed so as not to cover the hole 16. Therefore, even if the soil or the like flows down together with the leachate Wc, the adsorption mat 20 is not easily clogged. Therefore, the sufficient water collecting function of the bottom water collecting pipe 2A can be maintained.

  Moreover, in order to prevent the re-elution of the adsorbed contaminant more reliably, a mechanism for adjusting the pH in the vicinity of the adsorption mat 20 may be provided. A pH adjusting function may be imparted to the adsorption mat 20 itself. Further, as a countermeasure against clogging of the adsorption mat 20, the leachate Wa from the water collecting pit 6 may be pumped in the direction opposite to the water collecting direction D1 to perform back washing.

  A water collection pipe is not restricted to having a slope. That is, the water collecting pipe may not have an inclination angle. The present invention is not limited to collecting leachate under natural flow, and may take a form of collecting leachate in the direction of collecting water by a pump. A plurality of water collecting pipes may be provided in the depth direction. The landfill object is not limited to the waste X, and may be soil or rock.

  DESCRIPTION OF SYMBOLS 1 ... Landfill disposal site, 2A ... Bottom water collecting pipe, 10 ... Water treatment facility, 16 ... Hole part, 20 ... Adsorption mat, 21 ... Adsorbent, 22A ... Upper sheet (fiber base material), 22B ... Lower sheet (fiber base) Material), 30, 30A, 30B, 30C ... adsorbing part, D1 ... water collection direction, S, SA, SB, SC ... leachate treatment system, Wa, Wb, Wc ... leachate, X ... waste (landfill object) ).

Claims (7)

A leachate treatment method at a landfill site,
In the landfill site, a step of installing a water collecting pipe in which a hole penetrating a peripheral wall is formed;
A step of forming an adsorbing portion by arranging an adsorbing mat formed by laminating an adsorbent and a fiber base material having water permeability around at least one of the water collecting pipe and the water collecting pipe;
Contacting the adsorbing part in the process of collecting leachate leached from the landfill object buried in the landfill site with the water collecting pipe, and adsorbing the contaminant contained in the leachate to the adsorbent; And a leachate treatment method comprising: The adsorbent has adsorption characteristics of any of heavy metals, volatile organic compounds, and radioactive substances,
The leachate treatment method according to claim 1, wherein in the step of forming the adsorption portion, the adsorption mat is wound around an outer periphery of the water collecting pipe.   3. The leachate treatment method according to claim 1, wherein in the step of forming the adsorbing portion, the adsorbing mat is arranged so that the adsorbing capacity of the adsorbing portion changes in the extending direction of the water collecting pipe.   In the step of forming the adsorbing part, the adsorbing mat is arranged so that the adsorbing capacity of the adsorbing part becomes higher as the amount of leachate flowing through the water collecting pipe is larger. The leachate treatment method described. In the water collecting pipe, a water collecting direction for collecting the leachate is set,
2. The step of forming the suction part includes arranging the suction mat so that the suction capacity of the suction part is higher on the downstream side in the water collection direction than on the upstream side in the water collection direction. The leachate treatment method according to any one of -4.   The leachate treatment method according to any one of claims 1 to 5, wherein the adsorption mat is buried after the landfill object is landfilled. A leachate treatment system at a landfill site,
A water collecting pipe installed in the landfill site and having a hole formed through the peripheral wall;
A leachate treatment system comprising: an adsorption mat that is disposed around at least one of the water collection pipe and within the water collection pipe and is formed by laminating an adsorbent and a fiber base material having water permeability.