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Leachate production |
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University of Padua IMAGE Department |
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Principal factors: v Water availability v Characteristics of final cover v Characteristics of tipped waste v Method of impermeabilization |
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Hydrological Balance |
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L = P + S + G + R* - R + DUs + DUw - ET + b |
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L = Leachate generated P = Precipitation (actually plus recirculated leachate and surface input) S, G = infiltration from surface water or groundwater DUs = Change in moisture storage in top cover ET = Actual evapotranspiration R, R* = Surface run-off DUw = Change in moisture content of refuse b = biochemical water production or consumption |
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Infiltration |
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I = P + R* - R + DUs - ET |
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Surface run-off |
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R = C · P |
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R = surface run-off (mm/d) C = run-off coefficient P = uniform rate of rainfall intensity (mm/d) |
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C = a · bi |
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a : depends on the presence of the final cover, on the kind of materials used and on the slope. |
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b : depends on soil moisture content in the different months |
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Run-off Coefficients |
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Evapotranspiration (ET) |
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• Potential ET (ETp): Maximal ET from surface covered with a homogeneous, green crop with optimal water supply • Governing factors: • Meteorological factors: Wind, Temperature, Relative humidity • Soil and plant factors: Type/state of crop, Soil type |
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Actual evapotranspiration: |
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ET = ETp.U/FC U = actual moisture content FC = field capacity |
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Potential evapotranspiration
Thorntwaite Formula: |
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▪ PEi = potential evapotranspiration of the i-month (mm/month) ▪ Ti = monthly average temperature (°C) |
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Estimation of Leachate Volume for Europe |
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A rough estimation of leachate production may be given as a percentage of rainfall, as a function of waste density in landfill: • low compacted landfill: 25 - 50 % of rainfall • high compacted landfill: 15 - 25 % of rainfall |
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As a consequence, for an average precipitation of 700 mm/y the leachate production expected is: • low compacted landfill : 5 - 10 m³ / (ha.d) • high compacted landfill : 4 - 5 m³ / (ha.d) |