Landfills, designing,Principle, methods, advantages, disadvantages

1. Landfill: Design and
Operation
Arushe Tickoo
M. Tech

2. • A landfill is an engineered method for land disposal of
solid and hazardous waste.
• Landfilling is the term used to describe the process by
which solid waste is placed in the landfill.
• Landfills for individual waste constituents such as
combustion ash, asbestos and other similar wastes are
known as monofills.
• Landfills for the disposal of hazardous wastes are called
secure landfills.
Landfill

3.  Principle
 The purpose of landfilling is to bury/ alter the chemical composition of the waste so that they do
not pose any threat to environment/public health.
 Landfills are usually made up of cells in which a discrete volume of waste is kept isolated from
adjacent waste cells by a suitable barrier.
 The term cell is used to describe the volume of material placed in a landfill during one operating
period.
Requirements For a Landfill
There are four minimum requirements
1) Full/ partial hydrological isolation
2) Formal engineering preparation
3) Permanent control
4) Planned waste placement and covering

4. Types of Solid Waste
 Municipal Solid Waste (MSW)
 Industrial Hazardous Waste
 Bio Medical Waste(from Hospital)
 E- Waste (Electronic Waste)
Landfill operation:
 Aerobic landfill
 Anaerobic landfill
 Semi – aerobic
landfill
Consists of :
• Household waste (From Kitchen &
household Rubbish)
• Construction and demolition
debris
• Commercial waste (from shops-
offices)
Petrochemical industries
• Metallurgical industries
• Pharmaceutical industries
• Fertilizer industries

5. Landfill operation
 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.

6. LANDFILL DESIGN

9. Methods of landfill
• 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
Area method

10. • 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 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.
Trench method

11. • Technique involves placement and compaction of SW in canyon/ depression.
• It differs with geometry of site, characteristics of available cover material, hydrology, geology of
the site.
• Control of surface drainage is often a critical factor in this method.
• Filling starts at the headed of canyon and ends at mouth, to prevent accumulation of water
behind the landfill.
Canyon/depression method

12. Landfill Design & Operation
• Geometry of cell
• Support material
• Leachate collection
• LFG collection
• Final closure
• Liners
Design Considerations
o Leachate availability
o Leachate recirculation methods

13. Site selection process
The suitability of a landfill site is determined by
• Its size/area/volume
• Technical and environmental factors
• Climate and hydrological conditions.
• It requires a development of a working plan,
description of site location, operation,
engineering work and site restoration.
• People are reluctant to allow construction of
new landfill, thus siting approval authority is
important.

14. Construction
• 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 landfill the
following must be determined
 Access roads.
 Equipment shelters.
 Scales if used.
 Topsoil stockpiles sites.

15. Leachate collection system
• Leachate may be defined as the
liquid that has percolated through
solidwaste and 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 .

16. Landfill gas
• In most of the cases as the anaerobic
decomposition of the wastes
predominates the decomposition process
the gases obtain are Carbon dioxide and
methane.
• Carbon dioxide as result of its density
will move towards the groundwater
which can lower the pH of the
groundwater and increases the hardness
and mineral content in the ground water.

17. • 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.
Gas venting system

18. • 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 soil
Eg; bentonites, butyl rubber, illites etc;
Outlet for Gas venting system

19. Liner systems
Single liner
Double liner
Composite liner
Sand Gravel Geonet
Example

20. Final cover and post closure
• The final cover must be 36” thick layer of clay. Boundaries must be well protected.
• Long term usage of landfill i.e. reusage of landfill.
• Once the landfill reaches design height, a final cap is placed to minimize infiltration of rainwater.
• Facilitate long term maintenance of the landfill.
• The final cover shall have a barrier soil layer.
• On the top of barrier soil layer, there shall be drainage layer of 15 cm.
• On the top of the drainage there shall be a vegetative layer of 45 cm to support natural plant growth
and to minimize erosion.

21. A cap consists of from top to bottom
• Vegetation and supporting soil (6 inches)
• Filter and drainage layer – protective material (18-36 inches)
drainage material (12 inches)
• A hydraulic barrier– clay layer (24 inches), LDPE barrier
• Foundation for hydraulic barrier– gravel layer ( 6 inch) sand
bedding for LDPE (4 inch)
Final cap Specification
• Mulch is a layer of material applied to the surface of soil,
for conservation of soil moisture, improving fertility and
health of the soil

22. Landfill Settling Process
1. Primary consolidation
• Substantial amount of settling occurs at
• this stage.
• It is caused by weight of the waste
layers, truck movements, bulldozers ,
mechanical compactors.
• After this stage aerobic degradation of
waste occurs.
2. Secondary compression
• Rate of settling is much lower than first stage.
• Settling occurs through compression
3. Decomposition
• It is the degradation process. Organic
material is
• converted to gas and leachate.
• Settling rate increases as compare to
secondary stage, but with the passage of time
it gradually decreases.
• It continues till the organic matter is
degraded.

23. • Biological process is most important aspect in landfilling which determines the quantity
and quality of leachate and gas.
• After the disposal, large part of waste becomes anaerobic(due to absence of oxygen).
• Microbial activity degrade the solid organic carbon and produces methane and carbon
dioxide.
• In an anaerobic process solid and dissolved organic compounds are hydrolyzed and
fermented to volatile fatty acids, alcohols, hydrogen and carbon dioxide.
• The methanogenic bacteria convert acetic acid to methane and carbon dioxide.
• Hydrogenophilic bacteria convert hydrogen and carbon dioxide to methane.
Microbial Degradation Process

24. Composition Of Landfill Gas

25. Factors Affecting The Landfill Gas And Leachate Generation
1. Nature of waste – amount of gas depends on the content of biodegradable matter
in the waste.
2. Moisture content – microorganisms require minimum 12% moisture for growth,
thus it is important factor in determining gas production.
3. pH – methanogens grow only at low pH around neutrality. % of gas depends on
pH.
4. Particle size and density – particle size affects density achieved by compaction
that affects surface area and hence volume. This affects the moisture absorption and
thus the biological degradation.
5. Temperature – Increase in temperature tends to increase in gas production. It
affects microbial activity.

26. • In addition to provide an option for waste management, it also serves to improve/
reclaim poor quality land.
• It raises the ground elevation/surface grade of the site. Completed landfills have
been converted to municipal parks, playgrounds, golf courses, community land use
projects.
• It is the most economical alternative for SW disposal which accounts for its
frequent application.
• Other disposal methods are not entirely safe and efficient throughout the year.
• Incineration is a costly process, residue requires ultimate disposal on land.
• Composting is a seasonal option.
• It is not possible to reclaim and recycle all SW material.
Advantages of Landfilling

27. • Difficult to find suitable site within economically feasible distance.
• It is not possible to build a completely safe and secure SW landfill.
• Some of the pollutants may escape in the environment in the form of leachate.
• Potential harm to public health due to air, soil, water and noise pollution
• Damage to local ecosystem.
• Hydrology (GW flow) and geology (Rock type, soil permeability) of the site has a
direct influence on the possibility of water pollution (GW pollution).
Disadvantages

28. 1. Laying of Geo-Textile
2. Laying of sand layer over gravels bed
3. Laying of gravels at the
bottom
Geotextiles are permeable fabrics which, when used in association with
soil, have the ability to separate, filter, reinforce, protect, or drain.
Made from polypropylene or polyester, geotextile fabrics come in
three basic forms: woven (resembling mail bag sacking), needle
punched or heat bonded (resembling ironed felt)

29. 7. Lateral Leachate pipes6. Laying of clay layer over HDPE sheets
5. Marking of detected leakages4. Laying of HDPE sheets

30. THANK YOU…..