22 Leachate Management

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Dr.Kurian Joseph, Centre for Environmental Studies, Anna University, Chennai 600 025; E mail : [email protected]

LEACHATE

A complex organic waste that changes with time

Problematic components Degradable & nondegradable organics Hazardous organics and inorganics Ammonia, nitrate, and nitrite

Suspended solids Color and odor Pathogens

Infiltrative water percolates through wastematerials, results in the leaching of organic andinorganic compounds (McBean et al. 1995).


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Leachate

Leachate is the liquid (or wastewater) thatforms when water (rainfall, groundwater)travels through solid waste

Leachate can migrate into underlyinggroundwater, resulting in contamination

Leachate can contain many differentchemicals, depending on what is in thesolid waste

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Kurian Joseph, Centre for Environmental Studies,Anna University, Chennai -600 025 ; E mail:[email protected]


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LeachateContaminated ground water

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REACTOR

Kurian Joseph, Centre for Environmental Studies,Anna University, Chennai -600 025 ; E mail:[email protected]

The engineered landfill is an environmentallysound system for solid waste disposal.

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How is Leachate Produced?

WasteDecomposition

Phase I

Aerobic

Phase II

Anaerobic Facultative

Phase III

Methanogenic

Infiltration% of Rainfall

ContaminantBiodegradation

ContaminatedLeachate

Contaminant

Dissolution


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Leaching Mechanisms

Leaching of inherently soluble materials

leaching of soluble biodegradationproducts

leaching of soluble products of chemicalreactions

washout of fines and colloids

Leachate generation continues for typically 30-40years following site closure

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Importance of Leachate Qualityand Quantity Determination

Design leachate collection systems

Design leachate treatment facilities

Determine acceptability of offsite treatment

Estimate offsite migration potential


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Leachate Management Principles

Chemical composition of leachate varies considerablydepending on:- Waste composition

Site characteristics

Climatic conditions

Age of landfill

Leachate management strategies must be:- Practical

Cost effective

Flexible

Developed for long term environmental management.

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Leachate ManagementTechnologies There is a wide range of leachate management technologies

adopted by Landfill Managers. Technology selection oftendepends on a number of critical factors including:

Composition of leachate

Type of collection method

Volume of leachate generated

Available space on site

Access to sewer Availability of technologies


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Planning Treatment and Disposal

Estimate leachate flow, Q WBM/HELP Variations with site age

Estimate leachate contaminantconc., C Type Variations with age

Identify treatment and disposaloptions with discharge standardsand cost

Select treatment and disposalsystem Introduce uncertainty Maintain flexibility

Q

t

C

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Leachate Production

Characteristics

Soluble chemicalsReadily biodegradablechemicals

Poorly soluble/biodegradablechemicals

Percolate through landfill

surface cover

Leachate contaminants-Dissolves

-Complexes

Stimulates biomass-Organics

-Gases

Leachate

Temporal variations

Time (yr)

Leachatechemical

concentration(mg/L)

Moisture flux pathways


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What Characterizes Leachate?

Phase I Brief CO2 H2

Phase II Years High BOD

>10,000mg/L

High BOD:COD >0.7

Low pH 5-6

Smells High Ammonia

500-1000 mg/L

High Levels Fe, Mg, Zn, Ca,

Mn

Phase III

Decades (never)

High fatty acids

No O2 CH4 CO2 Stabilized (???)

Low BOD

Low BOD:COD

High

Ammonia/Nitrogen High Levels

Fe, Na, K, Cl2,SO4

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Factors Affecting LeachateQuality and Quantity Particle size

Compaction

Waste composition

Site Hydrology

Cover Design

Waste Age

Landfilldesign/operation

Sampling procedures

Interaction of leachatewith environment

Conditions within LandfillChemical & Biological ActivitiesMC %, Temperature, pH, Degree ofStabilization


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What are Trends in Leachate

Contamination?Concentration (mg/L)

Constituent 1 Year 5 Years 15 Years

BOD 20,000 2,000 50

TKN 2,000 400 70

Ammonia-N 1,500 350 60

TDS 20,000 5,000 2,000

Chloride 2,000 1,500 500

Sulfate 1,000 400 50

Phosphate 150 50 -

Calcium 2,500 900 300

Sodium, Potassium 2,000 700 100

Iron, Magnesium 700 600 100

Aluminum, Zinc 150 50 -

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Landfill Leachate

Young

Mature

Aging

Old

0.7

0.5

0.3

0.1

Raw, undegraded

Partially degraded

Partially stabilized

Well stabilized

Landfill age BOD5/COD Type of Leachate


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pH

Influence chemical and biological processes ofprecipitation, redox, sorption, methanogenesis

Controlled by volatile acids during acid phase

After methanogenesis begins, controlled bycarbonates and ammonia

Major factor in controlling metal solubility

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Heavy Metals

May act as inhibitors of biologicalstabilization process

Water quality concerns

No discernable chronological pattern

Leachate concentration controlled by sulfide,

carbonate, chloride, and phosphate


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Nitrogen/Phosphorus

Indication of nutrient availability

Phosphorus may be limiting nutrient

Ammonia important buffer

Nitrogen present for long periods of time

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How do you Remove Leachatefrom the Landfill? Drain as much as you can by gravity (liner

system and pipes)

Pump from low points

Penetration through the liner

Pumps inside landfill


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Leachate Collection System

If leachate flow is intercepted or impededby a liner, then it should be removed fromthe landfill by use of a leachate collectionsystem. A leachate collection system is ahigh-permeability layer designed totransmit leachate from the liner.

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Leachate Collection Systemwith Graded Terraces


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How is Leachate Removed

Liner is sloped ~ 2-8%

DrainagePipe

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Leachate is then sent to Treatment

and/or Storage Facility

Landfill

PumpStation

Gravity Drainage

Leachate

Storage

Treatment

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Leachate Storage

Underground storage tanks

Lagoons

Above ground tanks

three days storage at peak annual flow


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How do you Predict LeachateGeneration? You must estimate how much leachate is

generated to design your landfill.

HELP --Hydrologic Evaluation of LandfillPerformance


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HELP

A Water Balance Model

P ETR

Q

L

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Notes about HELP Model

Must assume an area and a depth(therefore not good for an open, operatinglandfill)

Many ways to manipulate

Hydraulic conductivity of waste to high


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Porous cup suction Lysimeter for the collection of liquid samplesfrom the landfill

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Leachate Treatment Systems?

Options

Full On-Site Treatment

Partial On-SiteTreatment

Transport Off-Site

Considerations Recirculation

Proximity of Sewer

Haul Distance

Pump System Costs

WWTP Capacity

Leachate Strength

Local Sewer Use Laws

Sewer Surcharges

Surface Water DischargeStandards (On-Site)


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yp ca eac ate anagementPractices in US

POTW Disposal

(39.9%)

Sewer discharge (14.3%)

Private/industrialtreatment(13.5%)

Not collected(9.0%)

On-sitetreatment

(7.5%)

On-site treatment/sewer or POTW (3.8%)Evaporation (2.3%)

Other (9.7%)

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What are Common LeachateTreatment Types?

Anaerobic or Aerobic Biological Treatment

Physical & Chemical Treatment

Leachate Recirculation & Land Application


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Anaerobic or Aerobic Biological

Treatment

Anaerobic Treatment

Two-Stage Reactor

Fixed Film Filters

Aerobic Treatment

Lagoons

Activated Sludge

RBCs

Trickling Filters

Biological Treatment

Changes the form of Organic Constituents

Removes BOD5, SS,NH3-N, Organic-N &Metals

Generates large quantities of biomass(sludge)

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On-Site TreatmentBiological Treatment

Essential if BOD > 50 mg/L

Expect BOD removal SS removal with sedimentation NH3-N and Org-N removal by biouptake

and nitrification Metal removal by biosorption and

precipitation at oxides and carbonates Priority organics removal


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Leachate Treatment:

Conveyance Stabilisation Pond

Aerated Lagoon Foaming in Leachate Pond

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Leachate Management

TechnologiesTechnology Features Disadvantages Advantages

BiologicalSequential BatchReactor (SBR)

Treat high strengthleachate

Proven technology:leachate Flexible and simple

Low operating costs

High capital cost

Large footprint

Inability to dealwith toxic infeed

6-8 weeks todevelopbiomass

LeachateEvaporation

(thermal oxidation)

Foot print of 300m2

Treat high strengthleachate

Insensitive to leachate

feed variations

High Capital andoperating costs.

High energy costs ifcannot utilisemethane

Proven design

Reduce volumeby 97%

Many overseas

applicationsReed Beds(Evapotranspiration)

No chemicals required

No by products orodoursVolume reduction by30%

Land requirement

Set up period

Pre-treatment

Low capital cost

Natural system

Operating costs


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Dr.Kurian Joseph, Centre forEnvironmental Studies, AnnaUniversity, Chennai 600 025;E mail : [email protected]

Sequencing Batch Reactor(SBR)A variation of the activated sludge process

which incorporates equalization, aeration, andclarification.

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How Our SBR WorksInfluent

1

Fill

2

Fill with mix

3

React

4

Settle

Effluent

5

Draw

Process Time

Fill 1 hr.

F il l wi th mix 4 hrs.

React 14 hrs.

Settle 3 hrs.

Decant 2 hrs.


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Biological Treatment Process

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Physical & Chemical Treatment More appropriate treatment as a landfill stabilizes

Polishes biologically treated leachate

Types of Treatment Granular Filtration Carbon Adsorption Chemical Precipitation Ultrafiltration Reverse Osmosis Breakpoint Chlorination Air Stripping Ion Exchange


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Achievable Effluent Levels by ChemicalPrecipitation

Sulfide precipitation0.05Selenium

Hydroxide precipitationSulfide precipitation

0.02~0.070.01~0.02Copper

Sulfide precipitationAlum co-precipitationFerric hydroxide co-precipitationIon exchange

0.01~0.02Mercury

Hydroxide precipitation at pH 100.12Nickel

Hydroxide precipitation at pH 10-11Co-precipitation with ferric hydroxideSulfide precipitation

0.050.05

0.008Cadmium

Hydroxide precipitation at pH 110.1Zinc

Sulfate precipitation0.5Barium

Sulfide precipitation/filtrationCarbon adsorptionFerric hydroxide co-precipitation

0.050.06

0.005Arsenic

TechnologyAchievable eff.conc. (mg/L)Metal

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Reed Bed

Removal of heavy metals, BOD, TSS, Nitrogen, &Phosphorus


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Constructed Wetland

Uses Polishing treatment Complete treatment

Advantages Relatively inexpensive to build/operate Associated with green technologies Wetlands creditsDisadvantages Large land requirement Cold weather Mediocre results especially for complete

treatment systems

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Proposed Leachate Treatment

Chemical

Sludgewasting

Reed bed

Removeammonia(optional)

Remove organics,ammonia, nitrite/nitrate,

and toxic compounds

Polish the effluent

Discharge

Leachate

EqualizationTank

ChemicalPrecipitation

Chemical

Equalize flowRemove heavy

metals and solids(optional)

AirStripping

SBR


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Suitability Of Evaporation

Cost Of Operation Extremely Cost Effective

Relatively High Initial Capital Costs

Minimal Operating Costs

Effect Of Evaporation Leachate Volume Reduction

Extremely Concentrated Solution

Minimal Contamination Level Reduction

Risks Pond Overflow

Leaks - Monitoring Bores

Drowning - Perimeter Fencing


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Local Weather Conditions Evaporation Substantially Higher Than Precipitation

Local Weather Data

Theoretical Evaporation Greater Than Actual Evaporation

Leachate Composition Leachate Composition Affects Evaporation Rate

Salinity and Concentration Reduce Evaporation Rate

Dark Colour Increases Evaporation RateEvaporation vs Precipitation

0

100

200

300

400

500

J an Feb Mar Apr May Jun Jul Au g S ep Oc t Nov Dec

Months

mm Evaporation

Precipitation

Source Data: Bureau of Meteorology Perth Airport

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Site Constraints Large Surface Area Required

Possible Odour Issues Hence Buffer Zones Required

Wind Direction And Intensity

Regulatory Approval Possible Regulatory Approval Required

Location and Design Constraints

Operational and ManagementConstraints


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Leachate treatment-issues High strength and magnitude of pollution potential

Variation from landfill to landfill

Seasonal and temporal variations in quantity andquality

Processes designed to treat the leachates from anyoung landfill should be modified in the future to treatold leachate/ to achieve changes in eff luent standards

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Leachate Properties Affecting TreatmentFlow Fluctuation

10

0

m3/haday

0 5 10 15 20 25Time, months

Options

Overdesign and treat peak flow

Equalize flow in landfill (recycle) or storage

tanks


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Leachate Properties Affecting TreatmentContaminant Concentration Fluctuation

Some peak quickly and decline: e.g. BOD

Some persist for long periods: e.g. NH3-N

Daily and seasonal variations occur

Options

Same as for flow Modify treatment system

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Leachate Properties Affecting Treatment

Organic Contaminants

Young Leachate - Biological Treatment

BOD in 10,000s

Mostly VFA Older Leachate - Carbon Adsorption

BODs in 100s; COD in 1,000s

Humic and fulvic acids

Priority organics


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Nitrogen and Heavy Metals

Nitrogen

Ammonia (NH3-N) - Air Stripping

Organic (Org-N) - Chlorination

Combined - 100s mg/L - Biouptake,Biological Nitrification/Denitrification

Heavy Metals - Chemical PrecipitationIron (Fe) mainly; Zn, Pb, Cu

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Conservative Ions and Acidic pH

Conservative Ions - Reverse Osmosis

High TDSChloride Sulfate Sodium

Acidic pH - Neutralization


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Dr.Kurian Joseph, Centre for Environmental Studies, Anna University, Chennai 600 025; E mail :

[email protected]

Leachate Recirculation & Land

Application Leachate is collected & returned to the top of landfillAccelerates the stabilization of organic materials

present in the MSW Spray Irrigation or Well Injection Evapotranspiration

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Landfill as a BioreactorMeasure of Success Faster landfill stabilization

Increased air space

Reduced leachate management costs

Reduced gases and odors

Reduced long-term care costs

Possibly, mining to regenerate covermaterial - a perpetual landfill?


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Leachate Recirculation(continued)

Disadvantages

Ponding/localized accumulation of leachate Severe localized subsidence/side slope stability

problems Other management requirement due to excess

leachate production Selective attenuation of contaminants

recirculation, thus further treatment required Mass/fluid transfer limitation

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Leachate Recirculation(continued)

Methods of Recirculation

Spray irrigation

Working face application

Gravity well/trench

Injection well/trench

Infiltration ponds


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[email protected]

Full-Scale Leachate Recirculation HydraulicApplication Rates

Recirculationmethod

Application rates

Prewetting 48 gal/ton or 1000 lb/yd3

Vertical injectionwells

a. 1 to 2.5 gpm/2,5-inch diameter well1.7 to 4.1 gpd/ft2 landfill area

b. 20 to 200 gpm/4 ft diameter well0.12 to 2.3 gpd/ft2 landfill area

Horizontal trenches25~50 gpd/ft of trench length at 60 to 100gpm

Surface ponds 0.13~0.19 gal/ft2/day

Spray irrigation18 gpd/ft2 of landfill area

0.025 to 0.078 gpd/ft2 of landfill area

Source: Reinhart, D.R. and Carson, D. (1993)..

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It is important to consider Leachate characteristics

Its hazardous nature

Discharge alternatives

Regulatory limits

Operational needs

Costs Conduct of treatability studies


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[email protected]

Questions

Documents

22 Leachate Management