RELATIONSHIP OF WASTE CHARACTERISTICS TO THE FORMATION OF MINERAL DEPOSITS IN LEACHATE DRAINAGE SYSTEMS

摘要

A common operational problem in leachate collection systems is clogging due to the formation of deposits within the pore spaces and collection pipes. This study was conducted to evaluate the importance of biological reactions for producing carbon dioxide and yielding carbonate, and the role of combustion residues from Waste-to-Energy (WTE) facilities for providing calcium and other minerals influencing the formation of precipitates that cause clogging of landfill leachate drainage systems. Five parallel lysimeters were filled (monofills or mixtures) with combinations of municipal solid waste (MSW), MSW combustion residues, and water and wastewater treatment byproducts. Each lysimeter received a regular application of leachate to simulate wet and dry conditions. Chemical tests of the leachates were conducted over a seven month period. The waste composition and the presence/absence of biological activity influenced leachate properties; biological activity influenced redox potential, pH, and alkalinity, which impacted the rate and extent of biological degradation and chemical solubility. Calcium carbonate was identified as one of the most abundant chemical precipitates along with calcium sulfate and calcium phosphate. The ash monofill condition generated leachates with high pH and high levels of calcium and other minerals such as potassium and sodium, but it was a carbonate limited environment due to lack of biological activity. The MSW monofill generated high levels of biological activity, a rich carbonate system, and leachates with lower concentrations of calcium. The mixture of the different kinds of wastes generated leachate that was not limited in either calcium or carbonate, creating the necessary conditions for the formation of precipitates.