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Disposal and Containmant Techniques

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Presentation on theme: "Disposal and Containmant Techniques"— Presentation transcript:

1 Disposal and Containmant Techniques


3 Selection of sites for Waste Disposal facilities
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

4 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

5 3.Waste and related attributes
Toxicity Radioactivity Ignitability Reactivity Corrosivity Solubility Volatility

6 4.Waste Management related attributes
Physical state Waste quantity Waste compatibility Use of liners Gas Treatment Leachate Treatment Site security Safety measures

7 Siting criteria

8 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

9 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

10 Criteria subcriteria Significance Geology Bedcrop and outcropping Carbonate rocks susceptible to solution Fractured rock-pollution migration Mass permeability Control migration of contaminants Faults Release of pollution

11 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

12 Criteria subcriteria Significance Monitoring aspects Sites that are easy to monitor Slope Slope of ground Slopes greater than 15% or 22% is preffered

13 Criteria subcriteria Significance Topography Slope erodibility runoff Slow runoff ares preffered

14 Hydrogeological aspects of selection of waste disposal sites

15 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

16 Waste Interaction with Hydrologic Cycle


18 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.

19 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.

20 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.

21 Impact on Environment

Deep wells Injection wells Mine Shafts Entrenchment Landfills

23 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.

24 USES Petroleum industries- recovery of oil and for brine waste

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


27 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.


29 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

30 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

31 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


33 Concept of Landfilling

34 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

1. Siting 2. Designing 3. Construction 4. Operation 5. Closure of landfill

36 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%)

37 Climate Low rainfall High surface evaporation rates Groundwater Location and quality Flood plains Outside floodplains Surface water Prevent runoff

38 Air quality Monitored Controlled Availability of transport system Convenient transport facilities Hydrogeology Low permeability ( not exceed 107 cm/s) Texture of soil Fine grained soil – low Leachate penetration

39 2. DESIGNING-Landfill Section
Depending 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

40 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

41 3.Above and below ground landfill--------
4.Slope landfill  5.Valley landfills 

42 Implications of Disposal Above, On and Below Ground Surface
Above Ground Landfills 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.

43 On and Just Below Ground Surafce
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. Advantage 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.

44 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.

45 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.

46 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.


48 Engineered Landfills

49 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

50 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.


52 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

53 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



56 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

57 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.

58 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.

59 3. Construction & Operation Design Process
Site Development Construction Schedule Material and Equipment Requirement Enviornmental Control During Operation Closure and Post Closure Programmes

60 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

61 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

62 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

63 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.

64 4.Closure and post closure plan
A closure and post closure plan shall be made to ensure that a landfill will be maintained for 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.

65 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.


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