Estimation of leachate production from a pilot scale lysimeter in Nepal

Abstract

More than eight million tons of solid waste is produced per day in developing countries.
While Europe and industrialized countries go for high-tech solutions (e.g. modern
incineration technologies), there is still a huge demand for proper landfilling in developing
countries. This paper presents the outcome of the research on the water management of
landfill in Nepal using a pilot scale lysimeter. The related leachate production as an effect of
climatological factors is assessed. The Hydrologic Evaluation of Landfill Performance
(HELP) model has been used to compute estimates of water balances. The local weather data
(evapotranspiration data and daily values of rainfall, temperature and solar radiation),
vegetative growth were prepared as required and variable soil and waste data (porosity, field
capacity, wilting point, initial moisture content and saturated hydraulic conductivity of layers
and materials) have been determined.
With the simulation carried out, it indicates that the evapotranspiration (ET) is nearly
constant, but not high. This may be due to the small area of lysimeter and higher portion has
been percolated before evaporation could take place. The trend of leachate generation on
HELP simulation seems to be similar in October to December season, but in June to
September, the trend shows higher percolation rate compared to the model. The annual data
shows that percolation is about 81-84% of rainfall amount whereas evapotranspiration is
about 15-19%. The daily production rate of percolation is about 3.47 L/m2
/day. Within
highest rainfall days during 2000 to 2004 (88 L/m2
/day), average percolation is about 5.78
L/m2
/day (6.5% of the rainfall).
The application of the model in the developing country like Nepal has raised issue like effect
on water balance by the large variation of short-tenn rainfall, which might have greater input
into percolation.