| Construction and demolition (C&D) waste represents one of the larger components of solid waste from municipal activities in the United States. The waste is often disposed of in unlined C&D waste landfills. It has historically been assumed that leachate produced from C&D waste landfills is innocuous relative to that of municipal solid waste landfills and hazardous waste landfills. Consequently, very little attention has been focused on leachate produced from C&D waste landfills and its characteristics.; In recent years, the potential for adverse environmental impacts posed from C&D waste disposal has been acknowledged, and some impacts have been documented. Consequently, recent federal regulations have increased operating and monitoring for requirements at C&D waste landfills. However, the degree of control needed and the environmental impacts posed still remain a subject of debate. More information is needed to determine the true nature of C&D waste leachate and its potential impacts on the environment.; Research was performed to simulate and characterize C&D waste leachate in the laboratory. Leachate samples were collected and analyzed for a number of chemical parameters including conventional water quality parameters and heavy metals. Experiments were conducted to examine the impact of different components in the C&D waste stream, to examine the depth of landfilled waste, to examine changes in leachate constituents over time, and to identify problematic leachate constituents.; Leachate resulting from laboratory lysimeters (landfill-simulators) containing mixed C&D waste generated a strong hydrogen sulfide odor. Sulfate-reducing bacteria under anaerobic conditions used dissolved sulfate from gypsum drywall to produce hydrogen sulfide. A few potentially problematic contaminants were identified in C&D waste leachate that exceeded the drinking water standards: sulfate, total dissolved solids, arsenic, chromium, iron, and manganese.; Sulfate resulting from dissolution of gypsum drywall was one of the predominant Alkalinity and ions observed in the leachate during solids and ion balance analyses. Alkalinity and high concentrations of sulfate, and calcium were most responsible for total dissolved solids concentrations in the leachate (>90%). The most likely source of arsenic and chromium was chromated copper arsenate (CCA)-treated wood. Arsenic is of particular concern because of the anticipated lowering of the drinking water limit as well as a growing prevalence of CCA-treated wood waste in the C&D waste stream. The contaminant in the leachate that exceeded the drinking water standard by the greatest magnitude was manganese, a result of wood. Copper, iron, and zinc were apparently reduced in concentration in the leachate via precipitation as insoluble metal sulfides.; The concentration ranges of pollutants in leachate from the laboratory investigations were within the range of data reported in the literature for actual C&D waste landfills, suggesting that controlled laboratory scale experiments can provide valuable information regarding leachate quality and formation processes within C&D waste landfills. The information gathered suggests that while leachate form C&D waste landfills should be less harmful to the environment than other types of landfills, unlined C&D waste landfills may impart deleterious characteristics to groundwater in some hydrogeologic settings. |
