Water and waste interactions in a modern landfill site

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 fromincineration residues for subsequent recycling; composting of garden waste and pollutedsoil or sludge; wood chipping for fuel production; crushing and sorting of constructionand demolition waste for road construction and anaerobic decomposition of organic wastefor biogas extraction and; landfilling. All these activities have transformed modemlandfill sites into large facilities, which have been called "waste management parks"(Marques, 2000). Within this perspective, different interactions between waste and waterare expected to generate different potential sources for pollution of surface water as wellas groundwater.Leachate is considered the most important (often the only) form of pollutant transport bywater at landfill sites. As a consequence, research and environmental monitoringprogrammes have traditionally focused mainly on leachate and, occasionally, on theoverland flow from covered landfills. A reduction in the potential pollution of landfills isforecasted due to changes in the composition of the waste landfilled, particularly in theEU state members. In the future waste will be pre-treated before landfilling and,therefore, more inert. Simultaneously, activities carried out in modem waste managementparks, other than landfilling will be intensified. Most of the waste management practicescarried out in such parks are exposed to rainfall. Untreated stormwater is in many casesdischarged directly to the recipient. It is thus important to regard stormwater runoff as asignificant potential form of water pollutant transport.This paper addresses some constraints faced when modelling the water flows andinteractions 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 theaquifer and groundwater contamination; • Stormwater runoff and pollutant transport from surfaces used for storage, sorting andtreatment (e.g.: composting, etc) of waste.