Landfill Disposal of Solid Waste 01
Simply ‘Duping of solid waste’ is illegal. Further it will cause hazardous effect upon living beings and environment. Hence, ‘Controlled landfilling’ is the best practice of disposal of MSW.
They have to disposed off, selecting suitable land and best suitable methods.
Land Disposal of solid waste
The solid wastes such as, plastics, glass bottles, etc., are not bio-degradable. .ie, they do not break down by organic or inorganic processes. When they accumulate, they pose health threat to the public and also affect terrestrial organisms and reduce the land cover required for other beneficial uses.
The common practices followed in land disposal of solid wastes are:
- Waste Buried under soil
Major problems encountered in solid waste land disposal:
It produces the following pollutant gases in significant amounts:
- Biogenic Carbon-di-oxide
- Non-Methane Volatile Organic Compound
- Nitrous Oxide in smaller amounts
- Nitrogen Oxide
- Carbon monoxide
Landfills are the physical facilities used for the disposal of residual solid wastes in the surface soils of the earth.
Sanitary landfill refers to an engineered facility for the disposal of MSW designed and operated to minimize public health and environment impacts.
A site for the disposal of solid waste in which refuse is buried between layers of dirt or clay so as to fill in or reclaim low-lying ground.
Gases are produced in landfills due to the anaerobic digestion by microbes. In a properly managed landfill, Energy recovery is possible in producing biogas and generation of electricity.
Landfill Cycle/Landfill Practices
- Planning Phase
- Construction Phase
- Operation Phase
- Completed Phase
- Final Storage Phase
Selection criteria for disposal method
The Following factors govern the selection of disposal methods:
Type of wastes, their composition, Characteristics and quantity.
Impact, anticipated by-product, requirement for their treatment.
It involves the ability and willingness of responsible agencies to operate and manage the system by evaluating structures, roles and responsibilities, operational capacity and Incentives.
This refers the ability to finance the implementation, operation and maintenance of the system by evaluating the Finance and cost recovery, Current revenue and expenditure on waste management.
This helps to avoid adverse social Impact by evaluating waste picking, Health and income implications and public opinions on the existing and proposed system.
It aims in setting up an environment friendly disposal system by evaluating Initial environment risks and long-term Risks.
Site Selection for Sanitary Landfill
The topographic information is a basic requirement in the development of an adequate design and determination of the landfill site. The importance of topography arises in part from the fact that precipitation will pond easily on a relatively flat site. Slopes greater than 1% and less than 20% generally would be satisfactory.
The availability of soil of proper characteristics for the construction of bottom liners, of cover systems, or both is usually one of the more important considerations when analysing and selecting a landfill site.
Geological information of a site is required for properly engineering a facility.
Identification of Geological hazards.
Provision of information for facility design and assessment of vulnerability of the site to ground water contamination due to the hydrology of the site.
Groundwater pollution at the landfill site depends, to a considerable extent, on depths to ground water, Nature and approximate thickness of water-bearing formations or aquifers near the landfill, Site topography, Soil Infiltration rate and effects of nearby pumping wells.
The type of vegetation includes small trees, shrubs, herbaceous annuals, perennials and groundcovers.
Trees and shrubs are planted to serve as a buffer, to reduce dust, noise, door and visibility problems for site beautification.
· Land use
Compatibility of use of the site for the landfill with the present and future uses of adjoining land areas and availability of soil for necessary cover material.
- Landfill layout is a combination of Cells.
- The term cell is used to describe the volume of material placed in a landfill during one operating period, usually one day. A cell includes the solid waste deposited and the daily cover material surrounding it.
- The purpose of the daily cover is to control the blowing of waste materials to prevent, rats, flies, and other disease vectors and to control the entry of water into the landfill during operation.
- A lift is a complete layer of cells over the active area of the landfill. Typically, landfills are comprised of a series of lifts.
- A bench is commonly used where the height of the landfill exceeds 50-70 ft.
- Benches are used to maintain the slope stability, for the placement of surface water drainage channels and for the location of landfill gas recovery piping.
- The final lift includes the cover layer. The final cover layer is applied to the entire landfill surface after all landfilling operations are complete.
There are some works which is done by the landfill layout-
- Protects Against (wind-blown debris, odour, animals)
- Minimize the amount of cover needed
- Plastic sheet
- Foams which are sprayed on and last overnight
- C&D fines (without wallboard)
- Revenue generating material
- Lime stabilized sludge
- Use soil as a fire break weekly
- Stockpile cover for wet and freezing periods
Sanitary landfill is an engineered method of waste disposal where the waste is buried either underground or in large piles. This method of waste disposal is designed, operated controlled and monitored very closely in order to minimize public health and environmental impacts.
Leachate is the term used to describe liquids that leach or leak form the landfill, and this system collects the leachates. These components of the sanitary landfill help prevent materials and liquids from spreading to the surrounding ground and waterways.
Bottom liner system – separates trash and subsequent leachate from groundwater
Cells (old and new) – where the trash is stored within the landfill
Storm water drainage system – collects rain water that falls on the landfill
Leachate collection system – collects water that has percolated through the landfill itself and contains contaminating substances (leachate)
Methane collection system – collects methane gas that is formed during the breakdown of trash.
Covering or cap – seals off the top of the landfill. Each of these parts is designed to address specific problems that are encountered in a landfill. So, as we discuss each part of the landfill, we’ll explain what problem is solved.
Components of Landfill
- 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
Landfill gas is a mixture of gases generated in landfills, due to anaerobic decomposition by microbes.
A solid waste landfill can be conceptualized as a biochemical reactor, with solid waste and water as the major inputs and the landfill gas and leachate as the outputs.
Recovered landfill gas can be used to produce energy.
|COMPONENTS||% (DRY VOLUME BASIS)|
|Sulphides, disulphides, mercaptans||0-1|
Generation of Principal Landfill Gases
The generation of the principal landfill gases is thought to occur in five, more or less, sequential phases,
- Initial Adjustment- Biological decomposition occurs under aerobic conditions, because a certain amount of air is trapped within the landfill.
- Transition Phase- O2 is depleted and anaerobic conditions begin to develop.
- Acid Phase- Microbial activity initiated in phase 2 accelerates with the production of significant amounts of organic acid phase into CH4 and CO2.
- Methane Fermentation Phase- The second Group of microbes which convert the acetic acid and H2 formed in acid phase into CH4 and CO2.
- Maturation Phase- It occurs after the readily available biodegradable organic material has been converted to CH4 and CO2 in phase 4.
|High Heating Value (Btu/sft Cube)||400-500|
Factors affecting gas production
Waste composition– The more organic waste present in a landfill, the more landfill gas (eg carbon dioxide, methane, nitrogen, and hydrogen sulfide) is produced by the bacteria during decomposition. The more chemicals disposed of in the landfill, the gases will be produced either through volatilization or chemical reactions.
Age of refuse– Generally, more recently buried waste (i.e., waste buried less than 10 years) produces more landfill gas through bacterial decomposition, volatilization, and chemical reactions than does older waste (buried more than 10 years). Peak gas production usually occurs from 5 to 7 years after the waste is buried.
Presence of oxygen in the landfill– Methane will be produced only when oxygen is no longer present in the landfill.
Moisture content– The presence of moisture (unsaturated conditions) in a landfill increases gas production because it encourages bacterial decomposition. Moisture may also promote chemical reactions that produce gases.
Temperature– As the landfill’s temperature rises, bacterial activity increases, resulting in increased gas production. Increased temperature may also increase rates of volatilization and chemical reactions. The box on the following page provides more detailed information about how these variables affect the rate and volume of landfill gas production.