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Disposal of Solid Waste

CHAPTER 5D

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At the end of this chapter, the student are expected to;1. Recognize the different landfilling method of MSW2. Explain the function of an engineered landfill and

all the components of a landfill3. Explain the process of landfill design and operation4. Recognize the impact of landfill leachate and gas

their control5. Evaluate the environmental impact of a landfill with

respect to air, water and soil quality

Learning Objectives

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MSW Engineered Landfill

In broad term, operations and processes in an engineered landfill are; Landfill design;- foundation design, liner design, leachate and

gas collection, drainage design, filling design, runoff collection, closure design

Landfill operation;- waste inventory, load, type, cell layout, cell for hazardous waste,

Biochemical raction in landfill;- biological decay rates, slowly biodegradable, rapidly biodegradable, non biodegradable

Leachate management;- collection, treatment, monitoring, reuse.

Landfill gas management;- Monitoring, collection, flaring or using, quantity and quality

Environmental monitoring;- air quality, odour, CH4, H2S, VOCs, groundwater quality monitoring, pets and litter, traffic

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Landfill types

All landfill should be containment type

Attenuate and disperse site or dump site are no longer

acceptable due to the environmental pollution that it will cause

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Dump Site

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Dump Site

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i. Excavated trench / cellii. Area methodiii. Canyon / depression

method

Landfilling Methods(Containment Type)

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Ideal for area with adequate depth of cover Water table is low Trench is excavated in the ground Liner put in place before waste are deposited Excavated earth use back as cover at the end

of each operation

Excavated Trench / Cell

Trench Method

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Terrain not suitable for excavation High groundwater level Liner are place on original ground Cover material hauled from location nearby Compost can be use as alternative

Area method (Ground Level Landfill)

Area Method

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12Area Method or Ground Level Landfill

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Techniques vary with canyon geometryControl of surface water drainage is critical

Canyon / depression method

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Canyon Landfill

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Canyon Landfill

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Landfill

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Cross Section of a Landfill

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Liner

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Landfill Under Construction

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Installation of HDPE Liner

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Construction of a landfill – drainage layer installation

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Construction of Leachate Collection and Gas Escape Pipes

Leachate Collection PipeGas Escape Pipes

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Liner Construction Process

Placing Clay LinerSmooth Drum Rolling Clay

Disking Clay to Dry

Placing GM

Placing Drainage Sand & Collection Trench Gravel

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Depositing of Solid Waste• Solid waste brought to landfill sites in truckloads• Trucks unload the solid waste onto the landfill

operating cell• Dump and spread out by spreader and dozer

and compacted• At the end of the day the compacted solid waste

is covered by cover material up to 20-30 cm thick to prevent rats and other scavenging animals

• Rainfall will seep through the compacted solid waste and form leachate

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Deposition of Solid Waste

Spreading, Compacting and Covering

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Covering with earth

Covering with plastic

Covering with plasticSpreading and compacting

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Leachate• Leachate is contaminated water in landfill which

is drawn out via pumping system from inside the landfill to be treated at an adjacent water treatment plant.

• Typical leachate chemical composition are TSS 500-2500, VSS 3000-8000, COD 5000-30000, BOD 4000-20000. All in mg/l (ppm)

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Leachate Recycling During early stages leachate contain high concentration of TDS, BOD5,

COD, nutrients and heavy metals When leachate re-circulated the constituent are attenuated by biological,

chemical and physical activities reactions occurring within the landfill Leachate Evaporation

The most simple treatment is evaporation in lined leachate storage facility

Leachate Treatment The treatment process selected will depend on the contaminants to be

removed Selection of treatment facilities will depend primarily on characteristics of

contaminants which include TDS, COD, SO42-, heavy metals and other

non-specific toxic constituents Treatment Facilities

Integrated leachate management system Discharge to wastewater treatment plant

Leachate Treatment

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Leachate TreatmentDischarge to waste water treatment plant

In locations where a landfill is located near a waste water collection system or where a pressure sewer can be used to connect the landfill leachate collection to a waste water collection system, leachate is often discharged to the waste water collection system. In many cases, the organic content of leachate required to be reduced before discharged to the sewer.

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Leachate Treatment Plant

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Selection of Gas Control Facilities

To determine the size of the gas collection & processing facilities needed, the quantity of landfill gas must first be estimated

The decision to use horizontal or vertical gas recovery wells depends on the design & capacity of the landfill

The decision to flare or to recover energy from the landfill gas is determined by the capacity of the landfill site & the opportunity to sell power produced from the conversion of landfill gas to energy

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Normal condition-gas release to atmosphere through diffusion In active landfill-internal pressure is greater and gas release thru

covection and diffusion Movement of Principal Landfill Gases Upward Migration of Landfill Gases Downward Migration of Landfill Gases Movement of Traces Landfill Gases

Movement of Principal Landfill Gases Most escape to atmosphere Some will migrate laterally (case were recorded where gas

concentration of 40% at distance of 400 ft of unlined landfill) Methane can accumulate in lateral distance if unvented Can accumulate under building or enclosed space Carbon dioxide (heavier than air) tend to move downward

Movement of Landfill Gases

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Passive Control Active Control With

Perimeter Facilities Active Control With

Vertical and Horizontal Extraction Wells

Control Of Landfill Gases

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• Pressure relief vents / Flare in landfill cover• Perimeter interceptor trench• Perimeter barrier trench / slurry wall• Impermeable barriers within landfill• Sorption barriers within landfill for trace gas

Passive Control

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Perimeter gas extraction and odor control well Perimeter gas extraction trenches Perimeter air injection well (air curtain system )

Active Control With Perimeter Facilities

Gas Extraction Systems

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processed to remove detrimental impurities

Gas Energy Recovery Systems

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Flaring Common method of

gas management Also called thermal destruction Methane will be burned together with other gas

Management of Landfill Gases

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Selection of Landfill Cover Configuration

The use of a geo-membrane liner as a barrier layer is favored by most landfill designers to limit the entry of surface water & to control the release of landfill gases

The specific cover configuration selected will depend on the location of the landfill & the climatalogical conditions

To ensure the rapid removal of rainfall from the completed landfill & to avoid the formation of puddles, the final cover should have a slope of about 3% to 5%

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Surface Water Drainage Facilities

An important step in the design of a landfill is to develop an overall drainage plan for the area that shows the location of;

Storm drains Culverts Ditches Subsurface drain

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Storm Drains

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Properly equipped tractors can be used to perform all necessary operation at sanitary landfill including :

1. Spreading2. Compacting3. Covering4. Trenching5. Hauling cover material

Equipment Requirements

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Equipment Requirements The type, size & amount of equipment required will

depend on the size of the landfill & the method of operation

Type of equipment used at sanitary landfills include :1. Crawler tractors2. Scrapers (self loading earth moving scraper)3. Compactors (high track compactor with trash blade

& steel-wheeled compactor with trash blade)4. Draglines (for excavation of landfill cells & trenches)5. Motorgraders

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LANDFILL MACHINERIESCrawlwer ractor with dozer blade

Self loading scraper Motor grader

Steel wheel compactor with trash blade

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Public Health and Safety

Health and safety of workers The federal government through OSHA regulations &

states through OSHA-type programs have established requirements for a comprehensive health & safety program for the workers at landfill site

Attention must be given to the types of protective clothing & boots, air-filtering head gear & punctureproof gloves supplied to the workers

Safety of the public The use of a convenience transfer station at the landfill

site, to minimize the public contact with the working operations of the landfill is gaining in popularity

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Completed Landfill

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Factors Affecting Longterm Integrity of Landfill Cap

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Post Closure Care

• Routine Inspections• Infrastructure Maintenance• Environmental Monitoring System

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Capped Landfill(and it will be active for 50-100yrs)

End

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