optimization of the natural attenuation applied to the rehabilitation of the old landfills

NATO CCMS Pilot Study Meeting - Rehabilitation of Old NATO CCMS Pilot Study Meeting - Rehabilitation of Old LandfillsLandfills

Cardiff City Hall / 23Cardiff City Hall / 23rdrd - 26 - 26thth may 2004 may 2004

Thierry CHASSAGNAC 11/14/14

Presentation : Thierry CHASSAGNAC

CSD AZUR




Report

The old landfills produce biogas and leachates

The environment strongly decreases the impacts in particular conditions

Several dozens thousand sites are concerned in France

Interest to study and to develop the

natural attenuation

Objectives of the study (ADEME)

Estimate the number of sites concerned by the natural attenuation

Identify the mechanisms of the natural attenuation

Propose solutions adapted to old landfills




34 evaluation criteria representative of 8 families

- geologic substratum - sensibility of the landscapes and the environments - landfill dimensions - sensibility of groundwater - sensibility of habitat and population - deposit composition - sensibility of surface waters - landfill age

Allocation of a raw note for every criterion (+1 note of doubt by criterion)

34 raw notes (+ 34 doubt notes)

4 environments

Global risk category of the site = Risk category of the most affected environment

Catégory of risk of environment :A, B, C or D




CSD AZUR MethodCSD AZUR Method




Principle of the statistical analysis

6 regional diagnoses of landfills : 1410 referenced sites

34 criteria aggregated in the form of risk notes by environments :

surface waters, groundwater, natural environment, human environment

4 category of risks :

A - emergency situation

B - strong to average potential risk

C - average to weak potential risks

D - weak to no potential risks

Global categories of risks

0,39

40,70 40,31

18,60

0,21

24,75

58,44

16,60

0

10

20

30

40

50

60

70

Categories of risks

Fre

qu

en

cy

connection with groundwater

all

Study interest

Enumeration

18 % of sites are in direct and permanent

connection with groundwater :

7 % spring zone

11 % backfilling of old water

depressions (quarry)

A : emergency B : strong C : middle D : weak




Depth of the groundwater

2,71 1,94

6,20

34,88

54,26

41,35

0,78

19,65

27,09

11,13

0

10

20

30

40

50

60

Distance between the base of wastes and the roof of the groundwater

Fré

qu

ency

connection with groundwaterall

> 20 m 10 à 20 m 2 à 10 m < 2 m

Potential groundwaters resources

1,553,88

38,76

27,52 28,29

8,72

13,83

35,25

23,12

19,08

0

5

10

15

20

25

30

35

40

45

1 2 3 4 5

Risks notes

Fré

qu

ency


all

1 - no resource

2 - improbable resource

3 - likely resource of moderate importance, exploited or not

4 - important to average resource, recognized, not exploited

5 - important resource, exploited and recognized

Potential surface resources

39,92

21,3225,58

13,18

0,00

58,51

14,6819,15

7,66

0,000

10

20

30

40

50

60

70

1 2 3 4 5

Risks notes

Fré

qu

ency


all

1 - no resource

2 - improbable resource

3 - likely resource of moderate importance, exploited or not

4 - important to average resource, recognized, not exploited

5 - important resource, exploited and recognized

Landfill surface

24,03

43,41

14,7317,83

0,00

28,01

53,40

10,508,09

0,000

10

20

30

40

50

60

Landfill surface (m2)

Fré

qu

en

cy


all

< 1000 1000 to 5000 5000 to 10000 > 10000

Typology of sites in connection with groundwater (comparison to the other sites) :

more risks

ground waters :

permeable substratum

potential resources

subsurface groundwater

surface waters :

near streams

high flow

potential resources

nearness and density of population

more vast and less thick




Unitarian processes :

filtration

adsorption

precipitation

dispersal

nitrification

dénitrification

degradation of the organic matter

Parameters :

water

oxygen

geometry of the filter

soil condition

pollution burden to be treated

temperature

pH

redox potential

Mechanisms of natural attenuation for the leachates

1. Underground wet mechanism : the infiltration - percolation


1. Underground wet mechanism : the infiltration - percolation

Parameter Input Outflow EfficiencyMLSS 84 23 73%COD 273 68 75%BOD 148 22 85%NTK 40 9 78%

N-NO3 0,2 32

The infiltration percolation allows :The infiltration percolation allows :to hold the polluting particulate elements

to hold inorganic pollutants (sorption)

the degradation of organic pollutants by microorganism

the treatment of the nitrogenous compounds by particular microorganisms





2. Superficial wet mechanism : lagooning


2. Superficial wet mechanism : lagooning

Unitarian processes :

consumption of nitrogen and phosphor

degradation of organic matter

decantation

volatilization

photolysis

waters disinfection

Parameters :

residence time

oxygen

pollution burden

temperature

pH

redox potential

on leachateson domestic waste

waters

BOD5 80-90 %

COD 40-70 % 78 %

MLSS 55 % 79 %

Nitrogen 85 % 60 à 70 %

Phosphor 60 à 70 %

The lagooning allows :The lagooning allows :the decantation of suspended solids and their trapping in the bottom of ponds

the photolysis notably of halogen compounds

the degradation of the organic compounds by microorganisms

the consumption of nitrogen and phosphor by micro and macrophytes





3. The phytoremediation


3. The phytoremediation Unitarian processes :

phytostabilization in the rhizosphere

adsorption on roots

detention in the roots

rhizodegradation

phytovolatilization

accumulation

degradation

action on the heat flows

Parameters :

water

oxygen

chelates

pollution burden to be treated

plants cycles

The phytoremediation allows :The phytoremediation allows :the consumption of nutriments (nitrogen, phosphor, potassium, micronutrient)

the consumption of trace metals

the degradation of the organic compounds by rhizospheric microorganisms

“ The phytoremediation is the use of plants,

their associated microbiote, amendments and

agricultural technics to eliminate, contain, or

make less toxic environmental pollutants ”

(Cunningham).




Mechanisms of natural attenuation for the gas releasesMechanisms of natural attenuation for the gas releases

Parameters :

thickness of the cover

food continuance

organic matter ( use of compost)

vegetal density of the cover

inhibitors

The properties of the cover :

interception of meteoric waters

limitation of the flight of wastes

support of the vegetalization

the oxidation of the methan : methanotrophic microorganisms

510

1520

2530

5°C

10°C

20°C

25°C30°C

0

1

2

3

4

5

6

7

8

9

10

Ox

ida

tio

n r

ate

of

me

tha

n (

ng

/g/h

)

GroundsTime of

unsteady stateOxidation rate

(mol of CH4.m-2.day-1)

Oxidizedpercentage

Coarse sand 13 days 10.4 61

Fine sand 135 days 6.9 41

Clay 60 days 6.8 40




Element of treatment Function

3. Microphytelagoon

Decrease of the organic load Consumption of nutriments Nitrification

4. Superficialfiltration bedwithmacrophytes

Transfer and filtration of theaerobic lagoon effluents

Consumption of the nitrogenand the phosphor

Reduction of the stream byevapotranspiration

5. Undergroundfiltration bed withmacrophytes

Denitrification Metals trapping

Typical solution for sites in spring zone

Element of treatment Function

1. Unaerobiclagoon

Decantation MLSS Metals precipitation Pretreatment of the oxygen need

2. Waterfall

Transfer of waters from a lagoonto the other one

Oxygenation Volatilization




Typical solution for sites in backfilling of old water depressions

Element oftreatment

Function

Peripherallagoon withmicrophytes

Decrease of the organic load,Consumption of the nitrogen and thephosphor,Nitrification,Deletion of the hydraulic pressure gradient

Bank betweenlagoons

Filtration,Denitrification,Metals trapping by reduction,Degradation of the organic matter

Lagoon withmacrophytes

Degradation of the organic matter,Consumption of the nitrogen and thephosphor,Nitrification,Possible metals trapping

Poplar zone

Decrease of streams by consumption ofwater,Consumption of possible nitrates « fugitives »,Denitrification,Possibility of cometabolism,Seclusion of pollution,Increase of the acceptability of the site




Comparison of the costs of rehabilitation to those of the classic treatmentsComparison of the costs of rehabilitation to those of the classic treatments

1. Case of sites in spring zone1. Case of sites in spring zone

2. Case of a backfilling of an old water depression2. Case of a backfilling of an old water depression

Water-treatmentplant

Physico-chemicaltreatment

Natural attenuationtreatment

Investment 150 k€ 300 k€ 21 k€

Functioning 26 280 €/year 26 280 €/year 3 000 to 5000 €/year

Classic treatmentNatural attenuation

treatment

Investment 600 à 2 200 k€ 400 k€

Functioning 30 000 €/year 5 000 €/year

7 - 14 times less high investment costs7 - 14 times less high investment costs

1,5 - 5 times less high costs1,5 - 5 times less high costs

Typical landfill of 2 hectars on 10 meters in thickness (200 000 m3) and having received 10 000 tons of waste during 20 years




Identical costs to those of a classic cover (600 k€ / 2 ha),Identical costs to those of a classic cover (600 k€ / 2 ha),

supplement from 1 to 3 € / msupplement from 1 to 3 € / m2 2 for organic amendmentfor organic amendment

Treatment of the gas releases (case of the weak production of biogas) :

methan oxidation in the cover

Treatment of the gas releases (case of the weak production of biogas) :

methan oxidation in the cover

Composition of the cover (from bottom to top)

screen limiting water input

drainage layer of infiltrated waters

treatment layer of biogas :

mineral layer

organic layer

vegetation




Plans of the superficial filtration bed with macrophytes

SECTION

Surface filtration bed : channel type

Surface filtration bed : baffle type

DETAIL SECTION

Soil baffle

PLANE




Plans of the underground filtration bed with macrophytes

SECTION

PROFILE

Low permeability

soil

Gravel 0-30

Sand 0-10

Control piezometric tubes

Distorsion of the clogged zone

Clogged zone

Piezometric level




Plans of the peripheral lagoon with microphytes




Plan of the lagoon with macrophytes

Water level fluctuation zone

Macrophytes zone

Microphytes zone

Macrophytes zone

Optional overpit




IN :Raw

leachates

OUT

PhragmitesTyphaWillows

COD N-NH4 N-total MLSS

Efficiency mean value (%) 60,4 85,1 62,7 77,7

1

Biological treatment

1

4 3 2

3 42

optimization of the natural attenuation applied to the rehabilitation of the old landfills

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