JPS5857567B2 - Rainwater infiltration prevention device at garbage landfill - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for preventing rainwater infiltration in a garbage landfill, and in particular, to a device for preventing rainwater from infiltrating into the lower layer while removing gas generated in the landfill.

Currently, approximately 150,000 tons of garbage, including incineration residue, is disposed of in landfills nationwide.

The remaining landfill capacity of the 3,000 landfill sites nationwide is only 250 million M, so it will be full within a few years and new landfill sites will have to be secured. is in a state.

Even if we increase the use of incineration and solidification as intermediate treatment, it does not eliminate the need for landfills as final disposal sites, and if business waste is included, a large amount of disposal site will be required, and urban areas It is now almost impossible to find new landfill sites in the region, and land must now be sought in rural areas, inland areas, and coastal areas.

However, with the so-called sand-inch method, which alternately layers garbage and soil as required by law, there are concerns about secondary pollution such as gas generation, sanitary pests, groundwater contamination, and leachate sewage. This makes securing land even more difficult.

Among the above problems, the problem of gas generation can be countered to some extent by degassing methods during soil covering.As a countermeasure against sanitary pests that have sprouted, it is necessary to concentrate the landfill work on one area and cover the soil as early as possible. The problem can be almost solved by using natural enemies or insecticides, and groundwater contamination can be countered by requiring the installation of an impermeable layer at the bottom of a landfill.

Figure 1 is a cross-sectional view of a completed garbage landfill in an onshore valley using conventional technology.

Reference numeral 1 indicates the ground surface of the valley before reclamation, and an impermeable layer portion 2 such as a concrete layer or a synthetic resin layer is laid on the surface.

When the ground surface 1 is a bedrock surface, the impermeable layer portion 2 can be approximately 1.

3 is the first landfill part, and the first part is 2 to 4 meters thick.
This is a garbage reclamation layer, and a first soil covering layer 4 of about 0.5 m thick is placed on top of it, such as mountain top, sand, etc.

5 is the second landfill layer, 6 is the second soil covering layer, and T is the third landfill layer, which are layered with approximately the same thickness as the first layer, and finally a finishing soil covering layer of about 1 to 3 meters. 8 will be constructed.

9 is the gas venting part, and the end is designed to burn with its own blade.

Reference numeral 10 is a side gutter that collects and drains rainwater inside and outside the landfill, and reference numeral 11 is a collection and drainage pipe that collects and drains wastewater that permeates through the landfill layer and flows down the impermeable layer portion 2.

With the conventional structure as described above, rainwater A disappears outside the landfill as surface water B and evapotranspiration water C, and the subtracted amount infiltrates into the finishing soil cover layer 3, which is an average of 500 liters nationwide.
/m2 years.

The infiltrated rainwater a permeates through each layer of the landfill layer and finally collects in the collection and drainage pipe 11, but this leached sewage becomes BOD, and several months after the landfill, it becomes blackish brown with a very high concentration of around 10,000 ppm. It is highly contaminated with a gory odor, but after 1 year it is 1.000ppm and after 3 years it is 1100ppm.
p gradually decreases.

The various types of heavy metals that are separated are initially contained in high concentrations, making countermeasures against the above-mentioned heavy metals the most important from the perspective of pollution prevention.

It is not as if countermeasures have not been taken in the past against the above-mentioned high-concentration pollution.

For example, as a method of preventing rainwater from entering the finishing soil covering layer 8, there are devices in which the finishing soil covering layer 8 is set at a medium height and is instead sloped downward to increase surface water B.

In order to have a complete wall, the entire finishing soil cover layer 8 is made of a paving structure that prevents rainwater from penetrating, but this would block the escape route for the large amount of gas generated from the landfill waste. There is a risk of explosion, and on the other hand, there are drawbacks such as the need to incorporate expensive equipment for gas venting.

As mentioned above, considering that the concentration of leachate sewage will gradually decrease and eventually become leachate that is not harmful, it is impractical to make a huge investment for such a short period of time. It has been desired to develop a new technology that is economical for relatively short-term use.

The present invention was made in response to the above-mentioned needs, and its purpose is to provide a device that exhausts gas while deodorizing the soil at low pressure, and prevents rainwater from penetrating into the underlying garbage landfill layer. There is something to do.

In order to achieve the above object, the present invention consists in combining the following two principles in addition to the prior art shown in FIG. The second method is to lay a hydrophobic synthetic resin membrane directly above the garbage landfill layer, and drill a large number of small holes in it to drain the gas under unsaturated conditions. The aim is to prevent rainwater from penetrating through the roof, but to guide it laterally and allow it to drain naturally.

Hereinafter, one embodiment of the present invention will be described with reference to the drawings from FIG. 2 onwards.

FIG. 2 shows 8 portions of the topmost finishing soil covering layer of the multiple reclaimed layer, and the same parts as shown in FIG. 1 above are given the same reference numerals.

In Fig. 2, 12 is a synthetic resin film, (third)
It is laid on top of the garbage landfill layer 7 with a slope so that the central part is slightly lower.

The synthetic resin membrane 12 is provided with a large number of small holes 12a, as shown in FIG. 5a.

The size of /J"?L 12a is slightly smaller than the grain size of the soil in the upper finishing soil cover layer 8, so as to prevent the soil from falling through the small holes 12a.

Further, the synthetic resin film 12 is a hydrophobic film.

A drainage pipe 13 is provided in the central recess of the synthetic resin membrane 12, and a gravel layer 14 is provided around it.

Reference numeral 15 is a material such as mesh or nonwoven fabric that is covered to prevent the covering soil 8 from falling into the gravel layer 14 and causing budding.

The wastewater from the drain pipe 13 may be drained naturally or may be forcibly discharged using a pump or the like.

Since the apparatus of this embodiment is configured as described above, a part of the rainwater A disappears as surface water B and evapotranspiration water C, and the rest permeates into the finishing soil cover layer 8.

As shown in FIG. 4, the moisture content of the permeated rainwater a decreases as it rises higher from the synthetic resin film 12 on the boundary surface.

Induced capillary water has the characteristic of moving laterally due to the difference in gravity in areas with a high degree of unsaturation, so if the synthetic resin membrane 12 is pressed with a certain slope, the moisture content will remain constant as long as the soil is constant. Arrows a, , a2 in Figure 4 a with curves of
It moves diagonally and horizontally by unsaturated capillary action.

The waste water flowing on the surface of the shredded synthetic resin membrane 120 is a lipid membrane 12.
Because it is a hydrophobic membrane, it exhibits a convex shape at 1J4L 12a as shown in FIG.

On the other hand, if the membrane is hydrophilic, it will become concave at the small holes 12a' and fall, as shown in FIG.

The diameter, position, spacing, etc. of the small holes 12a are preferably determined based on experiments, depending on the nature of the covering soil, the amount of gas, etc.

On the other hand, the gas generated in the garbage landfill layer 7 is absorbed by the small holes 12a.
A part of it may be exhausted to the outside of the soil through a gas vent 9.

The synthetic resin film 12 may be provided not only in the uppermost layer but also in an intermediate layer, for example, between the second landfill layer 6 as shown in FIG. It is almost the same as

It is also effective to combine methods of soil purification by recirculating leached wastewater into soil cover.

As described above, the present invention is designed to prevent rainwater from entering garbage as much as possible, so not only can the quality of the leachate sewage be reduced to a low concentration and the elution of heavy metals can be kept to a small amount. It is possible to maintain aerobic conditions within the garbage layer, speed up garbage decomposition, and sometimes use drainage pipes to force back air to create the aerobic conditions mentioned above. There are advantages.

[Brief explanation of the drawing]

Fig. 1 is a completed sectional view of a conventional land-based landfill, Fig. 2 is a sectional view showing one embodiment of the present invention, Fig. 3 is a sectional view of another embodiment, and Fig. 4a shows water in the covered soil. FIG. 4 is a graph showing the moisture content, FIG. 5a is an enlarged sectional view of the hydrophobic synthetic resin membrane of the present invention, and FIG. 5 is a sectional view of the hydrophilic membrane. 1... Ground surface, 2... Impermeable layer part,
3,5゜7... Garbage landfill layer, 4,6.8...
...Soil covering layer, 12...Synthetic resin film, 12a.
...Small hole.

Claims (1)

[Claims] 1. In a landfill where a garbage landfill layer and a soil covering layer are laminated, a hydrophobic synthetic resin membrane with a large number of small holes is laid between the garbage landfill layer and the soil covering layer. A device for preventing rainwater infiltration in a Go□ landfill, which is characterized by preventing rainwater from infiltrating into the area and allowing gas to be released through small holes.