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Disposal and Containmant Techniques
Selection of sites for Waste Disposal facilities
1. Receptor related attributes• Population with in 500 m• Distance to nearest drinking well• Use of site by nearby residents• Distance to nearest office building• Land use• Critical Environment
2. Pathway related Attributes• Distance to nearest surface water• Depth to ground water• Type of contamination• Precipitation• Soil permeability• Bed Rock Permeability• Depth to bed rock• Susceptability to erosion and runoff• Climatic factors relating to air pollution• Susceptibility to seismic activity
3.Waste and related attributes• Toxicity• Radioactivity• Ignitability• Reactivity• Corrosivity• Solubility• Volatility
4.Waste Management related attributes• Physical state• Waste quantity• Waste compatibility• Use of liners• Gas Treatment• Leachate Treatment• Site security• Safety measures
Siting criteria Siting criteria
Site investigation criteria
Sub Soil Investigation: type of soil, depth of GWT and bedrock, permeability of various strata, strength parameters, extent of availability of liner materials
Ground Water / Hydro geological Investigation: Depth of GWT, GW flow direction, Baseline GW quality parameters
Topographical Investigation: To compute the earth work quantities precisely
Hydrological Investigation: To estimate the quantities of runoff for appropriate design of drainage facilities
Geological Investigation and Seismic Investigation: to delineate the bedrock profile beneath the landfill base
Criteria subcriteria Significance
Soil
Permeability Release of pollutants- Low permeability required
pH Tendency of soil to aborb heavy metals- high pH
Cation exchange capacity
Ability of soil to attenuate some contaminats- High cation exchange
Surficial soil Affect degree of attenuation-surficial soil with low permeability
Criteria subcriteria Significance
Geology
Bedcrop and outcropping
Carbonate rocks susceptible to solutionFractured rock-pollution migration
Mass permeability
Control migration of contaminants
Faults Release of pollution
Criteria subcriteria Significance
Ground water
Aquifer With low potential use preferred
Ground water quality
Poor groundwater quality- best suitable location
Ground flow system
Sites where direction of GW flow away or flow is upward
Criteria subcriteria SignificanceMonitoring aspects
Sites that are easy to monitor
Slope Slope of ground Slopes greater than 15% or 22% is preffered
Criteria subcriteria Significance
TopographySlope erodibility
runoff Slow runoff ares preffered
Hydrogeological aspects of selection of waste disposal sites
• CONDITIONS AT THE SITE• PROVISION OF DATA FOR DESIGN AND
MANAGEMENT OF WASTE DISPOSAL FACILITIES
• Assessment of regional and local geology• Assessment of local surface hydrology• Identification of main hydrogeological units
(aquifers,aquiclude etc)• Ground water mechanisms• Local structural features• Measuring GWL and hyraulic gradient• Estimating hydraulic conductivity• Ground water chemistry• Surface and ground water receptors of contamination• Present and future development of GW• Characteristics of materials present in saturated and
unsaturated zones
Waste Interaction with Hydrologic Cycle
Changes Occurring in a Waste Dump
Biological Changes
During the aerobic decomposition, carbondioxide is the principal gas produced.
Once the available oxygen has been consumed, the decomposition becomes anaerobic and the organic matter is converted to
Carbondioxide
Methane
Trace amounts of ammonia
Hydrogen sulfide
Many other chemical reactions are also biologically initiated therefore it is difficult to define the condition that will exist in any waste dump at any stated time.
During the aerobic decomposition, carbondioxide is the principal gas produced.
Once the available oxygen has been consumed, the decomposition becomes anaerobic and the organic matter is converted to
Carbondioxide
Methane
Trace amounts of ammonia
Hydrogen sulfide
Many other chemical reactions are also biologically initiated therefore it is difficult to define the condition that will exist in any waste dump at any stated time.
Chemical Changes
The chemical reactions that occurs in a waste dump are
Dissolution
Suspension of waste materials
Biological conversion products in the liquid percolating through the waste
Evaporation and vaporization of chemical compounds
Sorption of volatile and semi volatile organic compounds into the waste material
Decomposition of organic compounds
Oxidation-reduction reactions affecting metals and the solubility of metal salts.
The dissolution of biological conversion into the leachate is of special importance because these materials can be transported out of the waste dump with the leachate.
The chemical reactions that occurs in a waste dump are
Dissolution
Suspension of waste materials
Biological conversion products in the liquid percolating through the waste
Evaporation and vaporization of chemical compounds
Sorption of volatile and semi volatile organic compounds into the waste material
Decomposition of organic compounds
Oxidation-reduction reactions affecting metals and the solubility of metal salts.
The dissolution of biological conversion into the leachate is of special importance because these materials can be transported out of the waste dump with the leachate.
Physical Changes
The important physical changes in waste dumps are
Lateral movement of gases in the waste
Emission of gases to the surrounding environment
Movement of leachate within the waste and into underlying soils
Settlement caused by consolidation and decomposition of the waste.
The important physical changes in waste dumps are
Lateral movement of gases in the waste
Emission of gases to the surrounding environment
Movement of leachate within the waste and into underlying soils
Settlement caused by consolidation and decomposition of the waste.
Impact on Environment
SUBSURFACE DISPOSAL TECHNIQUES
1. Deep wells2. Injection wells3. Mine Shafts4. Entrenchment5. Landfills
1.Deep-well Disposal In rock (not soil), isolated from freshwater aquifers; waste is injected into a permeable rock layer hundreds to thousands of meters below the surface.
Deep-well injection of oil-field brine has been important to control water pollution in oil fields for many years.
USES
• Petroleum industries- recovery of oil and for brine waste
2.INJECTION WELL DISPOSAL
• Deep-well injection system -- disposal in sandstone or fractured limestone capped by impermeable rock and isolated from fresh water. Monitoring wells are a safety precaution.
• Disposal of hazardous waste
• Hazardous liquid waste placed in well confined geological formations that are deep below earths surface
• Deep well injection directly introduces liquids into a deep aquifer in the subsurface environment via pressurized wells.· CLASS I WELLS - used for disposal of hazardous and
non-hazardous industrial or municipal wastes. · CLASS II WELLS - used for injection of oil field
brines and other hydrocarbon wastes. · CLASS III WELLS - used for solution mining
processes. · CLASS IV WELLS - those which historically disposed
of radioactive wastes (this is no longer done). · CLASS V WELLS - used for any activity not
mentioned above, such as geothermal steam mining operations.
Parameters- Construction of deep wells• Low pressure• Large area extent• High porosity and permeability• Nature of aquifer• Seperation from freshwater horizon• Geological strata• Type of waste
3. MINE SHAFTS
• Solidified waste packed in non breakable containers ( concrete cylinders, drums)
• These are transported down the shafts placed in chambers
• Chambers sealed• Indefinite life- unless corroded from inside• Sites chosen – Salt, potash and gypsum
deposits
4.Entrenchment• Modified landfill method• Refuse placed in trenches & buried• Trenches- 3m deep, 1mwide, 10m long• Monitored for 24 months• If made in clayey soil- no problems of GW
contamination & odour problem• Sites can be used for vegetable production
Concept of Landfilling
The components of the engineered landfill are– Liner system – Leachate collection and treatment facility– Gas collection and treatment facility– Final cover system– Surface water drainage system– An environmental monitoring system– A closure and post closure plan
PHASES OF LANDFILL PROJECT
1. Siting2. Designing3. Construction4. Operation5. Closure of landfill
1. SITING A LANDFILL
Topography• Alluvial/ sedimentary formations suitable• Base above saturation zone• Prevent standing water• Prevent erosion and runoff• Excessive sloping (1% but less than 10%)
Climate• Low rainfall• High surface evaporation ratesGroundwater• Location and qualityFlood plains• Outside floodplainsSurface water• Prevent runoff
Air quality• Monitored• ControlledAvailability of transport system• Convenient transport facilitiesHydrogeology• Low permeability ( not exceed 107 cm/s)• Texture of soil• Fine grained soil – low Leachate penetration
2. DESIGNING-Landfill SectionDepending on:• Topography of the area• Depth of ground water table• Availability of suitable daily cover material.
1.Above ground landfills
Above ground landfills are used in those areas where GWT is high.
-Used when terrain is unsuitable for excavations
1.Above ground landfills
Above ground landfills are used in those areas where GWT is high.
-Used when terrain is unsuitable for excavations
2.Below ground landfill
•suitable for areas where adequate cover material is available and GWT is not near the surface.
•Solid waste dumped in trenches excavated in soil
•Trenches-
Length :100 to 300m
Depth: 3 m
Width :5 to 15 m
Side slope : 2:1
2.Below ground landfill
•suitable for areas where adequate cover material is available and GWT is not near the surface.
•Solid waste dumped in trenches excavated in soil
•Trenches-
Length :100 to 300m
Depth: 3 m
Width :5 to 15 m
Side slope : 2:1
3.Above and below ground landfill--------3.Above and below ground landfill--------
4.Slope landfill ------------------------------4.Slope landfill ------------------------------
5.Valley landfills----------------------------5.Valley landfills----------------------------
Implications of Disposal Above, On and Below Ground Surface
Above Ground LandfillsAdvantage
Drainage of leachate is by gravity.
Thickness of unsaturated zone below
the landfill is large.
Landfill is conspicuous and thus cannot
be ignored.
Poor surface drainage due to
settlement of final landfill surface can
be avoided.
Inspection of the entire facility i.e. final
cover, leachate collection system and
gas collection system is easier.
Advantage
Drainage of leachate is by gravity.
Thickness of unsaturated zone below
the landfill is large.
Landfill is conspicuous and thus cannot
be ignored.
Poor surface drainage due to
settlement of final landfill surface can
be avoided.
Inspection of the entire facility i.e. final
cover, leachate collection system and
gas collection system is easier.
Disadvantage
They alter the land use
pattern of the area.
They have more surface area
exposed to elements of nature
such as wind, rain and require
significant erosion control
measures.
Disadvantage
They alter the land use
pattern of the area.
They have more surface area
exposed to elements of nature
such as wind, rain and require
significant erosion control
measures.
On and Just Below Ground SurafceAdvantage• More waste can be stored
per unit land area in comparison to above ground landfills.
• Efficient use can be made of the excavated material but using it as landfill cover.
• Productive use of the flat landfill surface can be made on completion of landfill.
• Long term slope stability and erosion control requirements are not very critical in such landfills.
Disadvantage
Leachate collection through
regular pumping.
Require good surface water
drainage measures if
located in low lying areas
and are closer to ground
water table than above
ground landfills.
Disadvantage
Leachate collection through
regular pumping.
Require good surface water
drainage measures if
located in low lying areas
and are closer to ground
water table than above
ground landfills.
Landfills Deep Beneath the Earth’s Surafce
• Wastes can also be dumped in underground openings, tunnels or caverns, however the cost of construction in such cases is extremely high.
• If the disposal is in soil where water table is high, the waste would always be surrounded by ground water and, irrespective of the multiple barriers used for waste isolation, the potential of ground water contamination would always be high.
•If waste is disposed in strong competent rock: the very low permeability of the rock mass coupled with multiple barriers layers ensures long term containment of the waste.
•Such disposal techniques are adopted for extremely hazardous waste
•Waste disposal deep beneath the ground surface has the least impact on the land use pattern.
•If waste is disposed in strong competent rock: the very low permeability of the rock mass coupled with multiple barriers layers ensures long term containment of the waste.
•Such disposal techniques are adopted for extremely hazardous waste
•Waste disposal deep beneath the ground surface has the least impact on the land use pattern.
Landfill Layout
A landfill site will comprise of the area in which the waste will be filled as well as additional area for support facilities. With in the area to be filled, work may proceed in phases with only a part of the area under active operation.
Engineered Landfills
Main Design Phase
The main design phase includes
• Design of liner, leachate collection and Treatment
• Gas Collection and Treatment• Cover System• Landfill Stability• Surface Water Drainage • Environmental Monitoring
a. Phase:- • sub area of the landfill. • consists of cells, lifts, daily cover,
intermediate cover, liner and leachate collection facility, gas control facility and final cover over the sub-area.
• designed for a period of 12 to 18 months.
b. Cell:- • volume of material placed in a landfill
during one operating period usually one day.
c. Daily cover:- -It consists of 15 to 30 cm of native soil
that is applied to the working faces. Purpose of cover :• To control the blowing of waste materials• To prevent rats, flies and other disease
vectors from entering or exiting the landfill
• To control the entry of water into the landfill during operation
d. Lift:- -It is a complete layer of cells over the active area of the landfill. -Typically each landfill phase is comprised of a series of lifts. -Intermediate covers are placed at the end of each phase; these are thicker than daily covers and remain exposed till the next phase is placed over it.
e. Bench:- -A bench is a terrace which is used when the height of the landfill exceeds 15 to 20 m.
F. FINAL COVER LAYER The final lift includes the cover layer.applied to area after all landfill operations
g. Leachate Collection Systems• To prevent migration of leachate generated inside a landfill
from reaching the soil and ground water beneath the landfill.
• Function of leachate collection facility:• Remove leachate contained with in the landfill by the
liner system for treatment and disposal.• Control and minimize leachate heads with in the
landfill.• Avoid damage to the liner system.
– Landfill liner comprise of• Compacted clays• Geomembranes• Geosynthetic clay liner• Combinations
h. Gas Collection Systems• The uncontrolled release of landfill gas, methane contributes to
the green house effect. • Landfill gas can migrate laterally and potentially cause explosions. • Landfills are therefore provided with gas collection and processing
facilities. • The rate of gas production varies depending on the operating
procedure. • The decision to use horizontal or vertical gas recovery wells
depends on the design and capacity of the landfill.
Reasons why landfill operated in phases• Progressive use of the landfill area such that at any given
instant of time a part of the site may have -a final cover, -a part being actively filled, -a part being prepared to receive waste and -a part in an undisturbed state.• Minimizes the area required for landfill operations-
concentrates waste disposal activities within prepared areas.
• Reduces leachate generation by keeping areas receiving waste to a minimum.
• Enables progressive installation of leachate and gas control.• Allows clean surface water runoff to be collected
separately.
3. Construction & Operation Design Process
• Site Development• Construction Schedule• Material and Equipment Requirement• Enviornmental Control During Operation• Closure and Post Closure Programmes
1. Material requirement • Material requirement plan for the construction of various
phases of the proposed landfill -prepared • Materials may be required for
– Granular material for ground water drainage, leachate drainage blanket, gas venting and collection
– Clay, sand, synthetic membrane for the liner system and final cover system
– Suitable fill for internal and external bunds– Base course and sub base course materials for haul
roads– Suitable material during site operations for daily
cover– Suitable soils or granular or screened material for
pipe work zone, drainage and protection layers above the barrier layer
– Sub soil and top soil for restoration layers
2.Equipment Requirement• The type, size and number of equipment
required will depend on the size of the landfill and maneuverability in restricted spaces.
• Equipments are required at the landfill site– For excavating, spreading and leveling operations
crawler tractors/dozers are required– Compactors/rollers for compacting– Wheeled loader-back hoes for excavating,
trenching, loading and short hauling
3. Environmental control during operation
• Carried out to minimize the impact of the landfilling operation on the nearby residents. This can be done by:– Providing screens in the active areas
• Presence of birds at the landfill site (nuisance if the landfill is being constructed near the airport)
over come by:–Use of noise makers–Use of over head wires–Use of recording of the sounds made by birds
• Problems of wind-blown paper, plastics etc overcome by
–Portable screens near the operating faces–Daily removing the accumulated materials
on the screen–Dust control can be achieved by spraying
water• Problems of flies, pests, mosquitoes and rodents
can be controlled by : -placing daily cover -by eliminating stagnant water.
4.Closure and post closure planA closure and post closure plan shall be made to ensure that a
landfill will be maintained for 30-50 years in the future
A closure plan includes•Landfill cover and landscaping of the completed site.
•Long term plans for the control of runoff, erosion, gas and leachate collection & treatment.
Post closure plan includes• Routine inspection of completed landfill.
• Maintenance of surface water diversion
facilities, landfill surface grades, the condition
of liners.
• Maintenance of landfill gas and leachate
collection equipment.
• Long term environmental monitoring plan so
that no contaminants is released from the
landfill site.
