Water and waste interactions in a modern landfill site

Abstract

In a modem society employing recycling and re-use based on the closed-loop philosophy,
a landfill site is more like an industrial facility than a mere final waste disposal site.
Examples of activities carried out at a modem landfill site are: sorting of slag from
incineration residues for subsequent recycling; composting of garden waste and polluted
soil or sludge; wood chipping for fuel production; crushing and sorting of construction
and demolition waste for road construction and anaerobic decomposition of organic waste
for biogas extraction and; landfilling. All these activities have transformed modem
landfill sites into large facilities, which have been called "waste management parks"
(Marques, 2000). Within this perspective, different interactions between waste and water
are expected to generate different potential sources for pollution of surface water as well
as groundwater.
Leachate is considered the most important (often the only) form of pollutant transport by
water at landfill sites. As a consequence, research and environmental monitoring
programmes have traditionally focused mainly on leachate and, occasionally, on the
overland flow from covered landfills. A reduction in the potential pollution of landfills is
forecasted due to changes in the composition of the waste landfilled, particularly in the
EU state members. In the future waste will be pre-treated before landfilling and,
therefore, more inert. Simultaneously, activities carried out in modem waste management
parks, other than landfilling will be intensified. Most of the waste management practices
carried out in such parks are exposed to rainfall. Untreated stormwater is in many cases
discharged directly to the recipient. It is thus important to regard stormwater runoff as a
significant potential form of water pollutant transport.
This paper addresses some constraints faced when modelling the water flows and
interactions with solid waste fractions in a modem landfill site such as:
• Water flow through the waste body (leachate generation) and pollutants transport; • Water flow through the unsaturated zone that separates the landfill bottom and the
aquifer and groundwater contamination; • Stormwater runoff and pollutant transport from surfaces used for storage, sorting and
treatment (e.g.: composting, etc) of waste.