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19.1 Bottom Construction and Liners
a function: to limit infiltration of leachate to subsoil b materials must be chemically resistant to leachate
c subsoil settlements d stability of construction, subsoil and surrounding slopes
e distance to groundwater
f availability of materials g costs
h experience in building
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Guideline on base liner NL, 1993
1 waste must be 0.7 m above mean high groundwater level 2 settlements subsoil must be less then 0.25 m
3 construction depends on geohydrological situation and sensitivy
of spreading of pollutants
Standard construction NL:
1 overall leakage 5 mmyr with leakproof synthetic and mineral of 20 mmyr
2 combination liner with a slope of 0.25 3 0.50 m drainage sand with drainage system
4 2 mm HDPE or equivalent according to geomembrane guideline 5 0.5 m sandbentonite mixture 0.5 m special clay 0.12 m trisoplast
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Guideline on drainage and monitor systems 1993
1 in drainage layer a leachate drain system is needed 2 HDPE-drains min. diameter 110 mm, max. distance 15 m
3 gravel around the drain 4 slope of 0.25
soil mineral liner
synthetic liner drainage layer
protecting geotextile
gravel with leachate drain
Ground water monitoring
seperating geotextile
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19.2 Landfill gas management
functions: avoiding risk of explosionsfiresodourleakage
• materials must be resistant to leachate • collection of landfill gas by pipes horizontalvertical
• internal transport by pumpingpressure flow • treatment depends on economyenvironment
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degradable materials
gas leachate
Aerobic organic
CO
2
low, but heavily polluted; pH ~8
Hydrolytic large organic molecules small soluble molecules, like low fatty
acids, sugars and amino acids
Acidogenic anaerobic
low fatty acids, sugars and
amino acids CO
2
and H
2
high organic content, dominated by volatile fatty
acids, increased mobility of metals; low pH
Methanogenic anaerobic
fatty acids CO
2
and CH
4
Organic content, low mobility of metals; pH ~7
19.3 Biology of a landfill; phases of degradation
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“a liquid that has passed through or emerged from solid waste and contains soluble, suspended, or miscible
materials removed from such waste”.
This implies that leachate is formed by any water that comes into contact with waste.
19.4 Leachate Production and Collection
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