Investigative and management techniques for cement kiln dust and pulp and paper process wastes

Abstract

AbstractKnowledge of the characteristics of industrial process wastes allows for some innovative and cost savings techniques for investigating and managing these wastes over conventional methods. This paper explores examples of some of these techniques employed on cement kiln dust (CKD) and pulp and paper mill process waste. Similar to Portland Cement, unleached CKD contains free lime and sources of reactive silica and/or alumina. Thus, it can “set up” in the presence of water. Properly moisture‐conditioned CKD has been successfully used in Michigan as a landfill liner and cover material on closures of old CKD piles and newly permitted fills. However, CKD also contains high concentrations of soluble salts and when improperly managed can generate a leachate with high total dissolved solid concentrations. Surface and downhole geophysical methods employing electromagnetic conductivity have proven effective in delineating the horizontal and vertical extent of groundwater plumes caused by releases of CKD leachate.At one paper mill in alabama where dewatered filter cake had been placed in a lined solid waste facility, liquids that had migrated to the surface due to excessive gas pressures caused unstable working conditions at the surface. Large, vertical french drains and a horizontal drainage blanket consisting of geogrid and sand constructed over the existing waste resulted in dewatering and a substantial increase in waste stability, allowing a vertical expansion to proceed. At a kraft mill in the southeastern United States, a geotechnical investigation of a lime mud pond revealed that the stability of the unit would increase by construction of an overlying dike, thereby allowing a vertical expansion to proceed. Finally, laboratory testing and modeling of the behavior of paper mill sludges indicates that they can be used as a landfill cover with permeabilities equivalent to or better than compacted clay. In‐place closures of sludge impoundments and landfills have been approved and implemented in at least three states.