| The inactive landfill is characterized and modelled as a layered, packed bed biological reactor, subject to unsaturated, trickling moisture flow and distribution, temperature and heat content variation, multiple substrate kinetics, and anaerobic and aerobic conditions. Analyses of reactor kinetics versus substrates behavior include examination of (a) effect of final cover moisture exclusion capacity upon specific and global waste decomposition over time, (b) the effect of temperature variation, (c) the effect of leachate recycle upon decomposition and emissions concentration, (d) the effect of anaerobic versus aerobic regimes upon wastes and leachate quality, and (e) site settlement response whether these options can be applied at an unlined site, where moisture flow has to be restricted to avoid or minimize additional leachate release. Wastes and soil composition and moisture and temperature behavior are characterized, and properties and parameters are incorporated into a waste decomposition model. Monthly moisture inputs past typical final cover types including fine soil and geomembrane, are used as seasonally varying inputs to the waste column, for four locations broadly representative of temperature and precipitation ranges. simulation periods of months to several years are used to track the global and specific decomposition of municipal solid wastes (MSW) components, and generation of effluents. For recycle a fraction of leachate generated is reintroduced, and the bioreactor effect evaluated. Alternative anaerobic/aerobic regimes is also investigated, and other options discussed. |
