130_5-leachate from sanitary landfills

Leachate from sanitary landfills – origin, characteristics, treatment

Assoc. Prof. Irina Kostova, Ph.D.

University of Architecture, Civil Engineering

and Geodesy

“Iskar’s Summer School” – Borovetz, 26-29 July 2006

Landfills

A landfill is defined as a system that is designed and constructed to dispose of discarded waste by burial in

land to minimize the release of contaminants to the environment.

The landfill processWhen biodegradable waste, such as paper, card and

waste food, is disposed of to the oxygen-free (anaerobic)

conditions of a landfill, breakdown by bacteria produces gas and soluble chemicals. The soluble chemicals

combine with liquids in the waste (e.g. rainwater) to form landfill leachate.

Landfill management incorporates:

•Planning;

•Design;

•Operation;

•Environmental monitoring;

•Closure;•Post closure control of landfill.

Types of landfills (according Bulgarian regulations):

I class – landfills for industrial wastes;

II class – landfill for municipal wastes;III class – landfill for hazardous wastes.

Landfills

Landfills

Advantages

• Low-cost

investments;

• Low-cost operational

needs;

• End-off utilization.

Disadvantages

• Need of large areas;

• Negative environment

impact: dust, noise,

smell, litter, insects

and animals, gas

emigration,

groundwater

pollution.

Assessment of existing landfills depending on the risks to the environment and human health

Generation of wastes 2001-2004(According to the National Statistical Institute)

industrial

municipal

hazardous

Municipal solid wastes

average – 480 kg/cap. a

Basic elements of landfills

•Siting considerations;

•Landfilling techniques;

•Cover design;

•Bottom isolation;

•Leachate treatment facilities;

•Landfill gas utilization;

•On-site operation facilities;

•Monitoring facilities.

Landfill construction

Landfill site

Clay isolation

Liner isolation

Landfill daily operation

Landfill compactor

Birds and other animals

Polluted crack

Plastic bags in trees

Landfill cloisure

Suit in flood-site

Suit in mountain terrain-site

What does it mean “leachate”? - Liquid that has seeped through solid waste in a landfill and has extracted soluble dissolved or suspended materials in the process.

It is composed of water, and organic and inorganic chemicals from the decomposition of waste.

The bacteria will degrade the waste to a state which will be relatively harmless if escape to the environment occurs. However, this can take many tens and perhaps hundreds of years.

Leachates are a potential hazardous waste from landfill sites. If not dealt with properly they can cause pollution to groundwater, health problems and effect the environment. It is important that leachates are treated and contained to prevent these occurrences.

Leachate

Precipitation

Evapotranspiration

Surface runoff

Leachate

Percolation into waste

Evapotranspiration

Leachate generation

Landfill body

Gas VentVegetative Soil

Drainage Material

Darin Pipe

Groundwater Monitoring

well

Compacted Clay

Top Liner (FML)

Bottom

Composite Liner

Upper Component

(FML)

Lower Component

(Compacted Soil)

Leachate Collection

System Sump

(Monitoring Compliance

Point)

Drain Pipes

Native Soil Foundation

Leachate Detection,

Collection, and Removal

System (LDCSR)

(i.e. Leak Detection)

Leachate Collection

And Removal System

Waste

Soil

Leachate formation

landfill

Waste material biodegradation

Waste material dissolution

Contaminated leachate

Infiltration from precipitation

LandfillLandfill

Groundwater

table Precipitation

Subsurface

water

Impervious Strata

Impervious Strata

Deep aquifer

Groundwatertable

Hydrological considerations in

landfill site

Mechanisms of leachate flow

Landfill

subgrade

Ground water

inflow

Saturated waste

Waste layer

Leachate mound

Percolation

Perched water

Leachate percloation(vadose zone)

Contaminant

transport

Recompacted barrier layer

Lateral drainage layer (optional)

Vegetation

Surface water runoff(slope)

Vegetative layer (topsoil)

Precipitation EvapotranspirationLandfill

cover

Infiltration

Surfaceleachatebreakout

Leachate

collection line

Clay

liner

Leachate flow line

Compacted solid waste

Drainage layer(2ft. or more)

Leachate

Surface water infiltration

Precipitation

RunoffRunoff

Soil liner for a sanitary landfill

Solid WasteDrainage

layer

Low

Permeable

liner

Collection

pipe

French

drain

Collection tile

Pipeline layout for leachate collection

holding tank holding tank

cleanout access

Factors affecting the composition of

landfill leachate

Type of wastes. Is it biodegradable or non-biodegradable? Is it soluble or insoluble? Organic or inorganic? Liquid or solid? Toxic or nontoxic?

Landfill conditions. The pH, temperature, degree of ongoing decomposition, moisture content, climate, and landfill age.

Characteristics of entering water. The pH, temperature, and amount.

The direction of groundwater flow. Groundwater moves slowly and continuously through the open spaces in soil and rock. If a landfill contaminates groundwater, a plume of contamination will occur. Wells in that plume will be contaminated, but other wells, even those close to the landfill, may be unaffected if they are not in the plume.

The amount of leachate produced is directly linked to the amount of precipitation around the landfill.

Leachate characteristics

Concentration (mg/L)

100 -11 000 1 000-57 000 100 – 3 500 4 - 120

Transition

phase

Years 0-5

Acid-formation

phase

Years 5-10

Methane

fermentation

phase

Years 10-20

Final

maturation

phase

>20 years

Leachate

constituent

BOD5

COD

TOC

NH4-N

NO3-N

Total diss.

solids

500 -22 000 1 500-71 000 150 – 10 000 30 - 900

100 -3 000 500 - 28 000 50 – 2 200 70 - 260

0 -190 30-3 000 6 – 430 6 - 430

0,1 - 500 0,1 - 20 0,1 – 1, 5 0,5 – 0,6

2 500 -14 000 4 000-55 000 1 100 – 6 400 1 460 – 4 640

• The anticipated flow rate that will require treatment. This mainly depends on the water inflow into the landfill.

• Composition of leachate at source which is carried out in an equipped laboratory.

• Discharge composition required by the authorities.

Factors affecting the choice of

leachate treatment

Leachate treatment options

Treatment choice

On-site treatmentDischarge or transport to off-site treatment plant

Recirculation through the landfill body

Complete treatment

Partial treatment

Discharge in surface waters

Discharge or transport to off-site treatment plant

Leachate treatment processes

Biological processes

Application Comments

Aerobic system Removal of

organics

Refractory or slowly degrading

compounds are not removed. Process

cannot tolerate influent toxics. Biological

sludge is produced. Needs separate

clarifier.

Aerated stabilization

ponds (lagoons)Removal of

organics

Requires large land area.

Fixed-film processes

(trickling filters,

biological contractors)

Removal of

organics

Temperature-sensitive in cold weather.

Cover may be needed.

Biological processes


Anaerobic systems

(anaerobic contractors

and lagoons)

Removal of

organics

Low operating costs and sludge

production. Requires heating. Long

detection times for high removal levels.

Typically cannot tolerate influent toxics or

high concentrations of some inorganics.

Nitrification and

denitrification

Removal of

nitrogen

Nitrification/denitrification can be

accomplished along with removal of

organics.



Physical – Chemical processes


Sedimentation Removal of

suspended

solids

Can remove only heavier material by

gravity. Usually used in conjunction with

other treatment processes.

Dissolved air

flotation

Dissolved contaminates are not removed.

Additional treatment is required.

Filtration Removal of

suspended

matter

Is combined with other technologies.

Useful as a polishing process.

Removal of

suspended

solids, oil and

grease



Ultra filtration Removal of

bacteria and

high-molecular-

weight organics

Possibility of fouling. Limited applicability

to leachate.

Steam stripping Effective removals of volatile organics.

Expensive process.

Absorption Removal of

organics

Costs depend on the leachate quality.

Removal of

volatile organics

or ammonia





Ion-exchange Removal of

dissolved organic

and inorganic

Ions of alkaline earth metals are difficult

to remove.

Neutralization Frequently used in conjunction with other

treatment.

Chemical

precipitation

Removal of

some metals,

specially Cd,

Cr, Cu, Pb, Ni

A wet sludge is produced that may

require disposal as a hazardous waste.

pH

adjustment



Oxidation Removal of

organics.

Detoxification of

some

inorganics.

Incomplete oxidation can produce

compounds that may be more

undesirable than the parent compounds.

Complete oxidation is usually impossible.

Works well on dilute waste streams. High

oxidant demand by leachate.

Evaporation Where leachate

discharge is not

permitted

Process sludge may be hazardous.


Stream A

Equalization

Lime/

caustic Polymer Clarifier

Mixed

Media

filtration

Rapid

mix

Flocculation

Sludge

holding

tank

Sludge

Pressure

filter

Stream B

Equalization

Dewatered

sludge

Dirty filter

backwash

storage

Carbon

transfer

vessel

Carbon

adsorbtion

contact

vessels

Clean

backwash

and effluent

storage

Trucked

Technological scheme for chemical

treatment of the leachate

Monitoring system

direction of groundwater flow

landfill

Monitoring well

(upstream)

depth 6 m

Monitoring well

Monitoring well

(downstream)

depth 24 mMonitoring well

(downstream)

depth 12 m

Monitoring well

(downstream)

depth 30 m

130_5-leachate from sanitary landfills

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