LANDFILL SYSTEM

A.V.N.S.GUNASRI

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Topics of discussion

Introduction to landfill Types of landfills Methods of landfill Landfill operation Landfill gas Leachate Landfill liners Final and Post Closure

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LANDFILL

Landfill, is a site for the engineered disposal of waste materials by burial in the earth’s crust.

Most common method. Energy efficient process. Cost effective process.

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Types of landfills

Type of waste1. Hazardous

landfill 2. Sanitary

landfills 3. Open

Dumps

Landfill operation

1. Aerobic landfill

2. Anaerobic landfill

3. Semi aerobic landfill

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Landfill operation 5

The gases found in land fills include air, ammonia Carbon monoxide,hydrogen, sulfide,methane,nitrogen.Carbon monoxide and methane are the principle gases produced from anaerobic decomposition .It involves three steps.• Enzyme mediated transformation• Bacterial conversion for intermediate compounds .•Bacterial conversion of intermediate compounds to low molecular weight compounds.

Methods of landfill

Area method Trench method Open pit method Canyon method.

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Area method7

The area method is used when the terrain is unsuitable for excavation.

The filling operation usually is started by building an earthen levee against which wastes are compacted and placed in thin layers.

At the end of each days operation a 150-300 mm of layer of cover material is placed over the completed landfill.

A completed lift, including the cover material is called a cell

Trench method8

The trench method is ideally suited where there is adequate amount of cover material available and the groundwater level is well below the surface.

Where there is artificial or natural depressions exist those can be effectively used for trench method.

Canyons ,ravines, dry borrow pits and quarries can be used for this purpose.

Landfill Design & Operation

Design Considerations Geometry of cell Support material Leachate collection LFG collection Final closure Liners

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Steps to be followed for landfill design Establish Design Criteria Obtain Data Necessary for Design Prepare Preliminary Layouts and Design Prepare Operations and Maintenance

Plan

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Construction of landfill12

A specific method of filling will depend on the characteristics of the site, Such as the amount of available cover material, topography, and the local hydrology.During construction of landfillthe following must be determinedAccess roads.Equipment shelters.Scales if used.Topsoil stockpiles sites.

Landfill system13

Simple landfill system14

Leachate collection system15

Leachate may be defined as the liquid that has percolated through solidwasteand has extracted dissolved or suspended materials from it.

The rate of seepage of leachate from the bottom of a landfill is estimated by Darcys law.

The use of clay has favored in reducing the leachate percolation .

Landfill gas16

oIn most of the cases as the anaerobic decomposition of the wastes predominates the decomposition process the gases obtain are Carbon dioxide and methane.

oCarbon dioxide as result of its density will move towards the grounwater which can lower the pH of the groundwater and increases the hardness and mineral content in the ground water.

Gas venting system17

The lateral movement of gases produced in a landfill Can be controlled by installing vents made of materials that are more permeable than surrounding soil.

The spacing of vents depends on width of waste cells but usually varies from 18 to 60 m.

Outlet for Gas venting system

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Barrier or well vents also can be used to control the lateral movement of gases.

Well vents also can be used to control the lateral movement of gases. The movement of landfill gases through adjacent soil formations can be controlled by constructions of Barriers that are more impermeable than soilEg; bentonites butyl rubber,illites etc;

Liner systems

Single liner Double liner Composite liner

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Liners used in landfill

Sand Gravel Geonet Geosynthetic membranes

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Final cover and post closure The final cover must be 36” thick layer

of clay. Boundaries must be well protected. Final cover and environmental factors

should be considered. Long term usage of landfill i.e. reusage

of landfill.

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View of a landfill22

CONCLUSION

Effective design of landfill must aim at Public health and safety Long term workability of landfill Control of pests,birds,etc.

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REFERENCES

Environmental engineering- Peavy Urban environmental engineering and

management- Dr. J.Trankler.

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