Solid Waste Management

Solid Waste Management

Department of

Geology and Environment science

at Islamic University of Gaza (IUG) -represent-

-March 2007-

Presented by

Prof. Dr. Samir Afifi

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4- Landfills 4- Landfills

4-Landfills

4.1 Introduction4.2 Planning4.3 Classification4.4 Sound technical options4.5 Additional considerations4.6 Conclusion

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4.1 Introduction

• The ultimate storehouse of a city's MSW

• In some cases, landfill is the only MSWM option available

• Effective operation depends on planning, administration, and management of MSWM system. (Institutional, policy, regulations)

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4.2 Planning

Key considerations in landfill planning

Required capacity Not In My Back Yard (NIMBY) Hydro-geology Cost Post-closure land use

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Required capacity:

• Capacity refers area and volume required over the useful life

• It depends on the generation rate, rate of population growth, density and waste compacted at landfill and maximum in-place elevation.

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Not In My Back Yard (NIMBY):

NIMBY refers to community opposition to the sitting and operation of MSW facilities close to their neighborhood. Residents concerns include:Health and environmental risks; Negative impact on aesthetics in the area; Lowering of property values; Increased traffic, noise and dust; and…

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Hydro-geology:

Include water table, hydrological conductivity of the soil, surface water, precipitation and others; ideally, landfill should be sited in an area:

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Continue Hydro-geology:

Low hydrological conductivity with low water table

Landfills should not be sited in wetlands, to avoid contamination ecologically sensitive areas.

Landfills should not be sited in floodplains, to minimize the risk of waste washout during flooding.

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Costs:

The costs may be broken into:

Capital costs which often determine the type of facility that can be constructed. Operating costs of the facility

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Planned post-closure use:

Post-closure use will have an impact on how the land is developed during use as a landfill.

• Planned heavy building construction require the use of high density compaction equipment • Recreational uses planned, as golf courses or parks, site must be graded with vegetation replanted on closed areas of the operating facility.

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4.3 Classification

Three general categories:

1. Open dumps 2. Controlled dumps 3. Sanitary landfills

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Open dumps and the need to upgrade them

Due to the low initial costs of open dumps, and lack of expertise and equipment, these sites are common in developing countries.

Significant risks to human health and the environment,

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Continue Open dumps and the need to upgrade them

Remediating cost can easily exceed their total lifetime capital and operating costs.

Contaminated groundwater may never be returned to usable condition

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Continue Open dumps and the need to upgrade them

Open dumps attract birds that feed on the wastes, which can make serious disease vectors than flies or rodents.

High need to upgrade open dumps and construct new controlled landfills in developing countries.

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4.4 Sound technical options

Planning landfill phases are:

1. Sitting 2. Design 3. Construction, operation, and

environmental monitoring 4. Closure and post-closure.

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Sound practices for MSW landfills

• Leachate management and environmental impact minimization

• Gas management and risk reduction

• Secure access and maintenance of gate records

• Compaction and daily cover

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Continue Sound practices for MSW landfills

• Documented operating procedures, and worker training and safety programs

• Establishment and maintenance of good community relations

• Closure and post-closure planning

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Sitting

Sitting can be one of the most difficult processes in the landfill process. The main considerations are:

• Capacity • Public involvement in the sitting process • Hydro-geology/cover material • Access • Proximity to airports

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Capacity:

Available land area to minimize costs associated with design, permitting, sitting, and closure and post-closure requirements, Ideally capacity for 10 - 20 years of operation in case of sanitary landfills.

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Public Involvement:

The planner must be prepared to involve potentially affected communities in the sitting process.

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Hydro Geology:

It is desirable to take advantage of the geology of a site (types of soil and rock)

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Sitting guidelines related to hydro-geology

Do not site landfills:

• in wetlands or in an area with a high water table; • in floodplains; • in areas that are close to drinking water supplies; or • Along geological faults or areas which experience frequent seismic activity.

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Continue Sitting guidelines related to hydro-geology

Do site landfills:

• above clay soils; • above igneous rock; and • where cover material is available nearby.

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Cover material.

The compacted MSW must be covered by 15-30 centimeters of soil at the end of each day's operations. The availability of cover material is also an important consideration in the sitting decision.

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Access:

The ideal location would therefore be sufficiently far from the city to allow for future population growth, but close enough to be reasonably accessible.

The roads that provide access to a landfill must be adequate to handle the types and quantity of vehicles that will be used.

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Proximity to Airports:

A landfill should not be sited closer than two kilometers from the nearest airport. Birds converging at the landfill may pose a problem for aircraft

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Other Considerations:

Sloping area will facilitate leachate collection.

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Landfills should not be sited:

• in very windy areas,• near existing gas, sewer, water, or electrical lines,• near residential areas, churches, schools, etc.

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An environmental risk assessment (EnRA)

should be made once the final site is selected. EnRA should detail the risks to ground and surface water from the facility, the risks from gaseous emissions, the impact of vermin, traffic, litter, and noise on the area and the potential for recovery of the land after post-closure period.

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In the case upgrading open dump in to a controlled dump or sanitary landfill, planner applies the above procedure to the areas for proposed expansion of the existing site.

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Items for consideration at the design stage

• Capacity • Public/private ownership/operation • Monitoring and control of leachate • Monitoring and control of landfill gas • Access and tipping area • Pre-processing and waste picker policy • Operations and safety manuals • Closure and post-closure plans • Community relations program

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Capacity

Controlled Dump: In case of planned capacity may not be protected by zoning and land use restriction, the landfill planner must use the designated site strategically to minimize the risk of future incursion by municipal development and maximize the total area available over the lifetime (acquisition of property surrounding site)

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Continue capacity

Sanitary landfill: Capacity is granted by regulatory permits on an incremental basis. So, planner develops it in two- to five-year increments once the overall site meets the required zoning and land use requirements.

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Public/private ownership and operation

In most developing countries landfills are owned and operated by local governments. Where expertise is available in the private sector, municipal planners should explore the option of privatizing landfill operations on a contractual basis. This option should be weighed carefully in bases of cost recovery and the payment of fees.

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Monitoring and control of leachate:

Leachate management is a key factor in safe landfill design and operation. The natural decomposition of MSW and rain infiltration into the site causes potentially toxic contaminants. The wetter the climate is the greater potential risks of ground- and surface water contamination. The geology of a site can exacerbate or reduce amount of leachate.

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Continue Monitoring and control of leachate:

Household hazardous waste (e.g., paint products, garden pesticides, automotive products, batteries) and hazardous wastes from commercial and industrial generators can release organic chemical and heavy metals contaminants in leachate.

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Natural or synthetic materials are used to line the bottom and sides of landfills to protect ground and surface water. Two feet or more of compacted clay, thin sheets of plastic made from a variety of synthetic materials and others used in lining landfills. Natural and synthetic liners can crack, if improperly installed, or can lose strength over time.

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More than one liner or a mix of natural and synthetic liners, called a composite liner, is a recommended alternative. To minimize production of leachate, covering material should be applied after each day of MSW is spread.

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Leachate collection and treatment:

Leachate collection systems are installed above the liner and consist of a perforated piping system which collects and carries the leachate to a storage tank. Periodically, leachate removed from the storage tank and treated or disposed of.

Most common leachate management methods are: discharge to wastewater treatment plant, on-site treatment and recirculation back into the landfill.

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Leachate recirculation

over waste in landfills showed an increase the quantity (by factor of 10) and quality of methane gas for recovery as well as possibly reduces the concentration of contaminants in leachate and enhances the settling of the waste.

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Leachate reinjection may be appropriate for areas with low rainfall. This technology could be more cost-effective than other treatment systems.

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possible drawbacks of leachate recirculation include clogging of leachate collection systems, increasing release of leachate to the environment and increasing odor problems. After weighing these advantages and disadvantages, federal regulators in the US decided to allow leachate recirculation only at landfills that have a composite liner and a leachate collection system that meets specified performance requirements.

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At controlled dumps monitoring operations may involve the scheduled withdrawal of samples to test for indicator contaminants such as bacteria, heavy metal ions, and toxic organic acids.

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Monitoring operations at sanitary landfills may involve computerized statistical sampling and automatic reporting of results at the regulatory agency. Such systems are costly and require skilled personnel.

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Monitoring and control of landfill gas

Gas management is required at sanitary landfills. At controlled dumps, it should be monitoring to determine if dangerous amounts of gas are being released. A low-cost design (passive collection system) to handle landfill gas consists of covered vertical perforated pipes, using natural pressure of gas to collect and vent or flare it at surface. More costly active collection systems utilize covered network of pipes and pumping to trap it. Gas is processed and used for process heat or electricity. This collection system is risky and expensive.

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Continue Monitoring and control of landfill gas

Gas management is required at sanitary landfills. At controlled dumps, it should be monitoring to determine if dangerous amounts of gas are being released. A low-cost design (passive collection system) to handle landfill gas consists of covered vertical perforated pipes, using natural pressure of gas to collect and vent or flare it at surface. More costly active collection systems utilize covered network of pipes and pumping to trap it. Gas is processed and used for process heat or electricity. This collection system is risky and expensive.

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Necessary conditions for economic capturing of landfill gas

• Sufficient methane is generated;

• Capital is available for processing the gas;

• There is local demand for natural gas or a means to transport it elsewhere;and

• The market price for natural gas is relatively high.

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In many situations, not all of the conditions stated above are fulfilled, and landfill gas recovery is not economical.

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These are two enclosed methane flares at a Landfill.

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A county technician checking on a gas collection well

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An example of the electrical generation equipment in one of the Michigan CogenerationSystem Plants. These engines burn only landfill gas as a fuel andoperate 24 hours a day. Each engine produces 750 kw of electricity

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A methane "flare" is used for burning landfill gas.

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Access and tipping area

Fencing should be designed to restrict unauthorized access to the landfill and to keep out animals. A staffed gate should be the point of entry to the facility for vehicles and any waste pickers. Gate should be equipped with scales for the weighing of vehicles as they enter and exit the facility. They provide critical information for planning purposes and for operational management of collection vehicles.

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Tipping area should be at the working cell. This requires the design of access roads to these locations within the site.

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Pre-processing and waste picker policy

Landfill is the least efficient alternative for materials recovery operations. Where composting is attractive at the landfill and/or waste picking activity is permitted, sorting of the waste should occur close to the gate or tipping area rather than at the working cell. Such activities reduce the volume of material to be landfilled and extend the life of the facility.

Waste picking policy should be established during the design phase of the facility

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Operations and safety manuals

Manuals should be prepared during the design phase of the landfill. This permits their content to be specifically adapted to the processes for which the facility is designed. Clear operating procedures and well-trained workers are vital to safe and effective landfill operations.

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Closure/post-closure plans

Essential closure and post-closure elements are:

• Plans for the sealing and application of final cover (including vegetation) • Plans for long-term leachate and gas management system monitoring;

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Continue Closure/post-closure plans

• Plans for long-term ground and surface water monitoring;

• Financial assurance guarantees to the local or state government; and

• Land use restrictions for the site

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In the case of controlled dumps in most developing countries, closure and post-closure plans are not prepared. However, ongoing monitoring and control of the facility after its useful life is an unavoidable for periods that may exceed 30 years after their closure.

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Community relations

The designer should establish a program for ongoing dialog with community. This should be based on transparency in landfill operations and procedures to addressing community concerns. Some facilities offer give-backs to their host community.

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Solid Waste Management