IMPACT ASSESSMENT OF URBAN WASTE PROCESSING SYSTEMS USING A MULTIBOX MODEL

A set of 14 household waste management system scenarios have been ranked according to the environmental impact of their respective refuse outputs. Each system has been characterized by the annual release of 8 chemical elements, namely: S, Cl, Fe, Cu, Zn, Cd, Hg and Pb. The method relies on the determination of a load factor. which is defined as the ratio between the actual pollutant concentration and the accepted norm for this concentration. These figures are calculated via a three box model, where the three boxes are air. water and soil. The model considers the pollutant output from each scenario, the dilution or accumulation in each box as well as dry deposition from air to water and soil. The pollutant load factors are then aggregated in order to obtain a score. These scores allow a final scenario grade to be determined, which can then be used to rank the various scenarios. The final grades are strongly dependant on the presence of deposition terms as well as on the values chosen for the individual pollutant concentration norms, whereas they are reasonably independent of all other parameters.