MUNICIPAL SOLID WASTE LANDFILL BARRIER SYSTEM CAPABLE OF PROLONGING BREAKTHROUGH TIME OF LEACHATE AND MANUFACTURING METHOD THEREOF

Abstract

The invention relates to a MSW landfill barrier system capable of prolonging breakthrough time of leachate and a manufacturing method thereof. The system comprises a leachate collection and removal layer, a first HDPE (high-density polyethylene) geomembrane infiltration proof layer (2), a clay liner (5) and a groundwater collection and removal layer (6) which are sequentially stacked from top to bottom. The clay liner (5) is composed of a lower clay liner (51), a middle clay liner (52) and an upper clay liner (53) which are sequentially arranged, wherein the middle clay liner (52) is filled with a medium-fine sand layer (7) laid with sands of particle sizes ranging from 0.1 mm to 0.5 mm and of water content 3%, wherein the saturated hydraulic conductivity of the medium-fine sand layer (7) varies from 110.sup.5 to 110.sup.3. A method of manufacturing the MSW landfill barrier system capable of prolonging breakthrough time of leachate is also provided.

Claims

1-8. (canceled)

9. A municipal solid waste landfill barrier system capable of prolonging breakthrough time of leachate, comprising: a groundwater collection and removal layer in a pit; a clay liner on the groundwater collection and removal layer, wherein the clay liner comprises: a lower clay liner on the groundwater collection and removal layer; a medium-fine sand layer on the lower clay liner, wherein the medium-fine sand layer is with sands of particle sizes ranging from 0.1 mm to 0.5 mm and with water content 3%, so that a saturated hydraulic conductivity of the medium-fine sand layer is from 110.sup.5 to 110.sup.3 cm/s; a middle clay liner surrounding the medium-fine sand layer and on the lower clay liner; and an upper clay liner on the medium-fine layer and the middle clay liner; a first HDPE geomembrane infiltration proof layer on the clay liner; and a leachate collection and removal layer on the first HDPE geomembrane infiltration proof layer.

10. The municipal solid waste landfill barrier system of claim 9, wherein a height of the medium-fine sand layer is 200 cm.

11. The municipal solid waste landfill barrier system of claim 10, wherein the middle clay liner has a thickness of 30 cm, and the lower clay liner has a height of 30 cm, so that the saturated hydraulic conductivity of the clay liner is 110.sup.7 cm/s.

12. The municipal solid waste landfill barrier system of claim 9, further comprising a leachate leakage detection layer laid between the clay liner and the first HDPE geomembrane infiltration proof layer.

13. The municipal solid waste landfill barrier system of claim 12, further comprising a second HDPE geomembrane infiltration proof layer laid between the leachate leakage detection layer and the clay liner.

14. A method for manufacturing the municipal solid waste landfill system capable of prolonging breakthrough time of leachate of claim 9, comprising: drying sands until water content thereof is 3%; screening out medium-fine sands of particle sizes ranging from 0.1 mm to 0.5 mm from the dried sands; digging the pit on a solid waste dumping ground; laying the underground water collection and removal layer in the pit; laying the lower clay liner on the underground water collection and removal layer; laying medium-fine sands on the lower clay liner; compacting the medium-fine sands to form the medium-fine sand layer; laying the middle clay liner around the medium-fine layer; laying the upper clay liner on the medium-fine sand layer and the middle clay liner; laying the first HDPE geomembrane infiltration proof layer on the upper lay layer; and laying the leachate collection and removal layer on the first HDPE geomembrane infiltration proof layer.

15. The method of claim 14, wherein the drying step comprises: keeping the sands exposed to sunlight for 24 hours.

16. The method of claim 14, wherein the drying step comprises: placing the sands into a large-size oven and baking them at a temperature of 105-110 C. to a constant weight.

17. The method of claim 14, further comprising: laying the leachate leakage detection layer between the clay liner and the first HDPE geomembrane infiltration proof layer.

18. The method of claim 17, further comprising: laying the second HDPE geomembrane infiltration proof layer between the leachate leakage detection layer and the clay liner.

19. The method of claim 14, wherein a height of the medium-fine sand layer is 200 cm.

20. The method of claim 19, wherein the middle clay liner has a thickness of 30 cm, and the lower clay liner has a height of 30 cm, so that the saturated hydraulic conductivity of the clay liner is 110.sup.7 cm/s.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0021] FIG. 1 is a structural schematic diagram of the MSW landfill barrier system capable of prolonging breakthrough time of leachate of this invention;

[0022] wherein 1: a leachate collection and removal layer; 2: a first HDPE geomembrane infiltration proof layer; 3: a leachate leakage detection layer; 4: a second HDPE geomembrane infiltration proof layer; 5: a clay liner; 51: a lower clay liner; 52: a middle clay liner; 53: an upper clay liner; 6: a groundwater collection and removal layer; 7: a medium-fine sand layer; 10: solid waste.

DESCRIPTION OF THE EMBODIMENTS

[0023] Hereafter, preferable embodiments of the present invention will be described in combination with the accompany drawings.

[0024] As shown in FIG. 1, the MSW landfill barrier system capable of prolonging breakthrough time of leachate from top to bottom sequentially comprises a leachate collection and removal layer 1, a first HDPE geomembrane infiltration proof layer 2, a clay liner 5 and a groundwater collection and removal layer 6;

[0025] Wherein, the clay liner 5 comprises a lower clay liner 51, a middle clay liner 52 and an upper clay liner 53 which are sequentially arranged. The middle clay liner is filled with a medium-fine sand layer 7 laid with sands of particle sizes ranging from 0.1 mm to 0.5 mm and of water content 3%, so that the saturated hydraulic conductivity of the medium-fine sand layer varies from 110.sup.5 to 110.sup.3 cm/s. The current MSW landfill barrier system has unexpected effects. Though with a simple structure, the system is able to greatly prolong the breakthrough time of leachate and to increase the anti-seepage performance of the landfill infiltration proof layer. Further, the system is low in cost and readily available as sands stockyards widely spread in China. The system does not require use of chemicals, preventing the surrounding environment from secondary pollution so as to benefit the environment. The division of the clay liner 5 into three parts can effectively prevent groundwater from infiltrating into and saturating the medium-fine sand layer 7, so as to keep the medium-fine sand layer in an unsaturated state all the time.

[0026] In the present embodiment, the height of the medium-fine sand layer 7 is preferably 200 cm to further prolong the breakthrough time of leachate. The saturated hydraulic conductivity of the clay liner 5 is 110.sup.7 cm/s, the thickness of the middle clay liner 52 is 30 cm, and the height of the lower clay liner 51 is 30 cm, so as to further prevent groundwater from invading the medium-fine sand layer 7. A leachate leakage detection layer 3 is laid between the clay liner 5 and the first HDPE geomembrane infiltration proof layer 2; and a second HDPE geomembrane infiltration proof layer 4 is laid between the leachate leakage detection layer 3 and the clay liner 5, so as to increase the imperviousness of the landfill barrier system.

[0027] A manufacturing method for the above MSW landfill barrier system capable of prolonging breakthrough time of leachate, comprising the following steps:

[0028] (a) drying sands until the water content thereof is 3%, and then screening out medium-fine sands of particles sizes ranging from 0.1 mm to 0.5 mm, wherein the drying process involves keeping the sands exposed to sunlight for 24 hours or placing the sands into a large-size oven and baking them at a temperature of 105-110 C. for at least 6 hours to a constant weight, wherein the water content of sands is measured by randomly selecting 3 sand samples per 10 m3 for sampling, and measuring the water content in accordance with the requirements of China's Standards for Geotechnical Test Method BG/T50123-1999.

[0029] (b) digging a pit on the solid waste dumping ground and laying the groundwater collection and removal layer 6 therein, then laying the compacted lower clay liner 51 on the groundwater collection and removal layer 6;

[0030] (c) laying medium-fine sands in the lower clay liner 51 and compacting the sands to form the medium-fine sand layer 7; next, laying the compacted middle clay liner 52 around the medium-fine sand layer 7; then laying the compacted upper clay liner 53 on the medium-fine sand layer 7 and the middle clay liner 52;

[0031] (d) sequentially laying the HDPE geomembrane infiltration proof layer 4, the leachate leakage detection layer 3, the first HDPE geomembrane infiltration proof layer 2 and the leachate collection and removal layer 1, from bottom to top, on the upper clay liner 53.

[0032] The above step (a) and step (b) are in no particular orders. Construction should be conducted on clear days. As soon as the laying of the medium-fine sand layer 7 is completed, the clay liner 5 should be laid and compacted thereon to prevent the medium-fine sand layer 7 from absorbing water in the process of construction, causing an increase of water content.

[0033] The above embodiment is only to illustrate the technical idea and features of the present invention, aiming to teach persons skilled in the art about the content of the present invention so as to enable them to practice it, yet not to limit the scope of the claimed invention. It will be understood that any equivalent alteration or modification made without departing from the principles of the present invention shall fall within the scope of the claimed invention.