The stability of dolomite in landfill leachate-collection systems

This study uses several approaches to examine whether calcium-containing aggregate such as dolostone is a suitable drainage material for landfill leachate-collection systems. The thermodynamic stability of carbonate drainage materials has been assessed using published leachate data from landfills in the United Kingdom and leachate sampled from four large landfill sites of variable age in southern Ontario. Electron-microbeam techniques have been used to check for dissolution in dolomitic stone exhumed from the drainage layer of the Keele Valley Landfill leachate-collection system and from experiments that simulated landfill conditions. The mineralogy of cover soils applied daily to the landfill has been compared to the drainage stone and detrital material occluding pore space in the leachate-collection system to evaluate their relative contributions to clogging. The data suggest that dissolution of dolomitic drainage stone is not significant and contributes little to the clogging of landfill leachate-collection systems. However, crystallization of secondary calcite occurs about the dolomitic stones and sizeable quantities of inorganic fines, including dolomite, were present within some samples of "clog material" exhumed from the Keele Valley collection system. Most of the dolomitic fines probably were generated during construction of the collection system; such creation of fines ought to be minimized in future landfill developments.