Pres münnich

Los retos en la gestión de residuos urbanos en una economía globalizada
Els reptes en la gestió de residus urbans en una economia globalitzada
Challenges in waste management in a globalized economy

MBT: CONSEQUENCES ON CONSTRUCTION AND
OPERATION OF LANDFILLS

Kai Münnich
Leichtweiß-Institute for Hydraulic Engineering and
Water Resources
Department of Waste and Resource Management

ORGANIZADO POR: CON LA COLABORACIÓN DE:


Common practice of waste disposal….

© Now Public


MBT disposal on landfills…
Practice of waste disposal in future…. !?


Fresh waste MBT material
Why MBT?

Reduction of
- risks by emissions during
landfill operation
- time necessary for aftercare
- effort for aftercare

Changes in construction and
operation?

< 60 mm < 25 mm


Quality of MBT waste in Germany:

- Criteria in annex 3 of Landfill Ordinance (2009).
 low concentrations in leachate

- Stability parameter:
- respiration rate: ≤ 5 mg/g (DS) or
- digestion rate: ≤ 20 l/kg (DS)
- TOCEluate : ≤ 300 mg/l

 low concentrations of organics in leachate
 low gas emissions

- Utilisation parameter:
- Upper calorific value: ≤ 6000 kJ/kg (DS) or
- TOCsolid: ≤ 18 M. % (DS)

 material size < 40 – 60 mm


Waste disposal: no requirements in view of physical parameters
but: maximal emplacement density should be achieved
 less settlement
 less leachate
 higher mechanical stability
 longer lifespan until end of backfilling

How to determine waste density?
- measurement of landfill surface (e.g. GPS)
but, settlement of old waste layers and subsoil is enclosed
- sampling on landfill area
problems in sampling
- proctortests
maximal size < 60 mm
static test  dynamic compaction on landfill  differences?


Results from proctortests:

90

Bidlingmaier et al (1999)
Kühle-Weidemeier (2004)
80 Rettenberger (2005)
Entenmann/Wendt (2007)
Heyer et al (2008)
Entenmann (2009)
LWI (anaerob-aerob)
70 LWI (aerob)
Water content [w-% DS]

60

50

40

30

Fresh Waste 0.5 – 1.0
MBT material 0.8 – 1.5
20
0,5 0,6 0,7 0,8 0,9 1 1,1 1,2 1,3
Proctordensity [t/m3 DS]


Proctorcurve and material size

1,20
MH <60
1,10 WHV <60
NH <60
Bu < 60
1,00
Dry density [t/m3]

0,90

0,80

0,70

0,60

0,50
5 10 15 20 25 30 35 40 45
Water content [w-% WS]


Slope stability:

Reason: plastics are able to take up
40 tensile forces
 „grouted anchor“ for
the slope
56
3.0
1.0
18

sgs engineers

MBT: - screening to <60 mm
 reduction of reinforcing material (fibres)
from >25 M.-% to < 5 M.-%  Tensile strength??


Surface settlement:
Calculation based on the physical properties of the waste is not
possible at the moment

 Total settlement:
MBT Fresh waste
primary settlement (load): 15 - 20 35 – 50 %
secondary settlement (creep, biol. processes) : < 5 15 - 30 %

 after total filling settlement is completed in large part
 as a result of the homogeneity of MBT material large differences
in settlement are not to be expected

 Consequences for construction and operation:
 final surface sealing system can be installed earlier
 time and effort for monitoring in the closing and aftercare phase
are reduced distinctly


Hydraulic properties:

Parameters important for the movement of water and the generation of
leachate at the base of the landfill body:

 Infiltration-rate F and
 saturated hydraulic conductivity k
F>k!

German recommendation: MBT-material: k = 1*10-6 – 1*10-9 m/s
Fresh waste: k = 1*10-3 – 1*10-6 m/s

 Low permeabilities?
- Surface runoff possible  less leachate at the landfill base
- Pore water pressure?  slope stability?
- higher evaporation rate  less leachate


k-values from laboratory tests

1E-04
< 60 mm
Fresh waste
< 40 mm
< 30 mm
Saturated hydr. conductivity [m/s]

1E-05

1E-06

1E-07
MBT

1E-08

1E-09
0,6 0,7 0,8 0,9 1 1,1 1,2

Dry density [t/m³]


Landfill operation - emplacement technology
Engines:
For distribution: bulldozer/tracked loaders
For compaction: compactor?
pad foot roller
and vibrating smooth roller


Design of the emplacement surface:

Why ?
To avoid impoundment of surface water
 soaking of the surface
 impassability of the area


Design of the emplacement surface:
 Covering with foils?
Problems:
Generation of condense
respectively impounded water
underneath the foil
 trafficability ? © Rettenberger

 slipping of the foil ?

 Slope of the surface ( 5 %)
 daily rolling with smooth roller
 catchment and treatment of surface runoff!


Emissions from MBT landfills: Leachate
 volume

Leachate at the basis + surface runoff = ~ 65 % of precipitation

Leachate at the basis : surface runoff = 55 : 45 %


Emissions from MBT landfills: Leachate
 quality
3000
F1 Basis
F1 Surface
new waste layer
- Leachate and surface runoff must be collected
- Dilution effects esp. on concentrations in surface runoff
2000
- A purification of both streams might be necessary
COD [mg/l]

- Increase in concentrations after emplacement of new waste layers
- Concentrations much lower than in fresh wastes, typical for landfills in
the stable methane phase
- Biostability is already high (BOD5/COD = 0,02 – 0,15)
1000

0
Apr/ 10 Mai/ 10 Jul/ 10 Aug/ 10 Okt/ 10 Dez/ 10 Jan/ 11 Mrz/ 11 Mai/ 11 Jun/ 11


Emissions from MBT landfills: Gas

 By MBT the gas potential is reduced of about 80 – 90 % to 10 – 45 Nm3/Mg DS
 The gas flux is expected to be low: low permeability of the MBT material
low temperatures in the MBT landfill
 Active degassing does not make sense in technical and economical view
 Passive system, e.g. methane oxidation layer
Methane oxidation potential:
Soil layer: 2,5 – 12 l CH4/m2*h > Methane flux from MBT
Compost substrate: 12 – 30 l CH4/m2*h

H2O CO2 O2

Recultivation- and methane
oxidation layer

CH4
CH4
CH4


Changes in construction and operation of MBT landfills in comparison
to „traditional“ landfills
Modification

Water household • lower volume of leachate at the base
• lower concentrations in leachate
• collection treatment of runoff
Stability • higher density
• low settlement
• flat slopes
Gas • no active degassing and gas treatment
Operation • changes in engines for disposal and compaction
• less infrastructure
• longer lifespan
• less staff
Aftercare • less monitoring
• shorter duration


Summary:

 Physical behaviour of MBT output material has to be tested before disposal
 The construction (slope, engines etc.) and the operation (covering,
drainage etc.) have to be adapted to the specific local conditions
 Leachate from the base has still to be treated, but the volumes
and concentrations are definitely lower
 Surface runoff has to be collected and possibly be treated
 The low volumes of gas can be collected and treated by passive
systems
 Time and effort during operation phase is increased, during the
aftercare phase clearly reduced

 The better the intensity of treatment (or the degree of stabilization) the
smaller the effort necessary after closure of the landfill


Thank you for your attention !

Dr.-Ing. K. Münnich
k.muennich@tu-bs.de

Pres münnich

Recomendados

Recomendados

Mais conteúdo relacionado

Semelhante a Pres münnich

Semelhante a Pres münnich (20)

Mais de FIRASBD

Mais de FIRASBD (14)

Último

Último (20)

Pres münnich