progress meeting - rennes - november 2001 1 landfill model specifications fifth framework program...
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Progress Meeting - Rennes - November 2001 1
LANDFILL MODEL SPECIFICATIONS
Fifth Framework Program
Progress meetingRennes, November 27-29, 2001
Progress meetingRennes, November 27-29, 2001
Progress Meeting - Rennes - November 2001 2
Landfill modelling
Aim of work
Methodology
What is a landfill ?
Models specifications
Conclusions
Aim of work
Methodology
What is a landfill ?
Models specifications
Conclusions
Progress Meeting - Rennes - November 2001 3
Aim of work DELIVRABLE:
SPECIFICATIONS OF LANDFILL MODELS Numbers of outputs Parameters Mathematical equation used
AIM: To supply the necessary information according to AWAST objectives
Matter balance Energetic balance Economical balance Environmental aspects
To simulate all the system of waste treatment
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Landfill modelling
Aim of work
Methodology
What is a landfill ?
Models specifications
Conclusions
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MethodologySeveral steps
1. How it works ?
2. Level 0 = a black box inputs outputs performance according to AWAST objectives
3. To increase the level of prediction fundamental parameters (calibration / sizing) cost of used
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Landfill modelling
Aim of work
Methodology
What is a landfill ?
Models specifications
Conclusions
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What is a landfill ?
Leachate generation
Waste
o
Water inflow from rainfall
Deposited Waste
t
Deposited Waste
t+1
Biogas
generation
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Waste degradation phenomenon...
Water (rainfall or waste) waste component mobilisation
Controlled by:• chemical reactions (oxidation, …) • physical aspects (adsorption, …)• biological reactions = principal factor
Authors agree to say reactions of organic matter biodegradation are the most accurate for leachate composition.
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Waste degradation phenomenon...
Principal reactions:
hydrolyze, aerobic oxidation, anaerobic degradation, acidogenesis, acetogenesis and methanogenesis
Final products of biodegradation:• Sulphur which precipitate with metals,• Hydrogen (consumed), • Methane and carbon dioxygen.
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I - Aerobic oxidationII - TransitionIII - Anaerobic degradationIV - Stable phaseV - Stable leachate
10-20 years
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Consequences for modelling tasks:
G° = f(waste composition)
Generation rate = f(time)
Biogas generation
Waste compositionTotal gas potential generation G°Somewhat the degradation rate
But, the degradation rate is much more influenced by landfill operation condition as water content, compaction and so on.
Measurement
Database
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Biogas generation/production
GENERATION
Theory
Total gas potential generation (m3 tons-1)
Reality
Total effective gas generation (m3 tons-1)
Only, a part biomethanized (40 - 50%)
CG *868.1
GG
Common value: C=225 kg C tons-1 G=189 m3 tons-1
COHERENT with literature
PRODUCTION
Total gas production (m3 tons-1)
r: recovery (%)
Gr *
GG *45.0
Total anaerobic degradation of organic carbon
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Leachate composition
LEACHATE COMPOSITION linked to:• Waste (composition, component solubility)
• Parameters controlling biological activity
(water content, temperature, oxygen content, pH, …)
VARIATION with time Stabilisation
[T] annéesen délai :
][ML source la deion concentrat :
10 : DBO
10 : DCO
10 : Chlorures
3-
043,05
0454,0
065,0
t
C
tCtC
tCtC
tCtC
o
tooo
tooo
tooo
Measurement
LITTERATURE
• BDO5, COD decrease = f(time)
• Stabilised waste prediction
• Database = f(landfill age)
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Hydrological balance Water inflow Rainfall
Evapo(transpi)ration
Run-off
Type of cover
Water inflow Leachate generated Waste stocks of water
Leachate generated Leachate collected Leachate remaining
Leachate infiltrated
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0.1
0.2
0.3
0.4
0.5
0.6
+ + + + + + + + + + +
Water inflow
Wat
er c
on
ten
t
Leachate flowrate
min
c
Water retention
max
Water retention
Water release
KINETIC
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Models & AWAST objectivesMatter balance
mean rates (database)Time consideration for more accurate prediction with measurements for
case study and calibration
Economical aspect NO
Energetic balanceBiogas recovered
Environmental balanceBiogas emissionLeachate exfiltration
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Landfill modelling
Aim of work
Methodology
What is a landfill ?
Models specifications
Conclusions
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Landfill models
2 inputs: Waste + Rainfall
4 outputs:
Collected leachate
Infiltration of leachate
Biogas emission to the atmosphere
Biogas recovered
(Run-off – evapo-transpiration)
2 aspects: Biogas + Leachate
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Biogas model(0)A fixed production rate 5.5 m3 ton-1 year -1 for 75% recovery
55% CH4 - 45% CO2 - pollutants ?
Calculation of mean production rate
History of landfilling
Lag time
Total gas production /ton
GT
nQwQb *
* 1 dntT
5.5
Gt
Where:Qb: average flowrate of biogas production (m3/year)
Qw: flowrate of waste deposited per year (ton/year)n: duration of deposition (years)G: total production of biogas per ton of deposited waste (m3/ton)T: Total time of release (years)t: time of release for each ton (years)d: lag time (years)
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Leachate - Model (0)Calculation of water inflow
= f (type of cover, total rainfall per year)
Calculation of exfiltration
1- Passive: clay - K=10-9m/s
2- Passive and active =f(holes in geomembrane)
NO calculation of generated leachate collectedDarcy law
No top cover(operating landfill) P*6.0
Simple top cover(naked soil)
P*4.0
Mid-permeable top cover(permeability typically between 10-8 and 10-6 m/s)
2100*)224*48.0(*12 P for aslope of 2 to 5%
Non-permeable top cover P*2.0 at least in mid term
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Leachate - Model (0)
Landfill age(years)
DCO(mg/l)
DBO5
(mg/l)NTK(mg/l)
1 year 15000-30000 5000-10000 1500-20001-3 years 8000 2000 15003-10 years 5000 1000 1000 10 years 2000 400 500
Composition Database
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Parameters - Model(0)Filled section
1: Area (m²)
2: Useful Height (m)
3: Density (m3/ton)
4: Top cover type (Simple, Mid-permeable, Impermeable)
5: Bottom cover type (Passive, Passive and active)
6: Recovery of biogas (%)
Active section
7: Area (m²)
8: Age of the landfill section (years)
9: Bottom cover type (Passive, Passive and active)
10: Total rainfall per year (mm)
11: % of biodegradation (hidden parameter)
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Biogas model(1)
t: time (from the landfilling)
G: effective gas production (m3 ton-1)
gmax: maximum gas production rate (m3 ton-1 year-1)
tmax: time of maximum gas production rate (year)
k*: biodegradation coefficient (year-1)
max1max *exp* ttkgg
ttkgg max*
max *exp*
Gkg **max
max
max
1
01.0ln
t
g
k
According to waste composition
Parameters - Adjustement parameters
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Biogas model(1)Specific gas production rate (m3/year/ton)
0
1
2
3
4
5
6
7
8
9
0 10 20 30 40 50 60
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Leachate model(1)Hydrological balance
P Rainfall
Collected leachate
Infiltration
ETP Evapo-transpiration
Run-off
Water inflow
Top cover
Bottom coverRemaining leachate
S: Stock of water contained in waste
RU: Stock of water contained in soil layer
ETR = k*ETPk (type of plant)
RUmax (type of soil)
k ’
Permeability DataAim of calculation
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Collected leachate
• Calculation of input water for waste water retention (Cp)
• Calculation of waste water content from water input and waste input• Calculation of water release
Leachate model(1)
If WC > WC c, then cd
WCWCt
WC
d
dT
2ln
Where:
Td: Time of midterm release (month)
WC: waste water content
WCc: critical water content
Adjustement parameters
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CONCLUSION
REMAINING TO DO:• Leachate composition - Model (1): Database?• Biogas valorisation• Economic aspect• Finalisation
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