Solid Waste Disposal, Constituents and Contamination
|Event Date:||April 19, 2012|
|Speaker:||Terry R. West|
|Speaker Affiliation:||Professor of Earth Science, Purdue University|
|Time:||9:00 - 10:15 a.m.
Solid waste disposal started in the 1960s as open dumps with refuge placed in various depressions at the earth's surface including gravel pits and old surface mines. MSW or municipal solid waste consisted of household trash, garbage and small quantities of organic substances that were later classified as hazardous waste. The pits were unlined and soil cover was not placed over the waste so that fires and vectors (rats, birds) were common occurrences.
Daily cover over the MSW provided the first required improvement to qualify as a solid waste landfill but it lacked a low permeability liner and a leachate collection system. Known as an attenuation type landfill, early landfills were of this type.
The second set of improvements required a compacted clay liner and a basal leachate collection system plus a low permeability clay cap. Older landfills were retrofitted with perimeter leachate collection systems. Only small quantities of hazardous waste were allowed from households and yard waste was relegated to so called "clean fills" that were non regulated.
Subtitle D requirements under the Clean Water act required composite liners of clay and a geomembrane along with a basal leachate collection system and a combined, compacted clay and geomembrane cap. Solid Waste Districts were established to collect the small quantities of house hold hazardous waste for recycling. Hazardous solid waste landfills were also required to take solidified waste (dry) and to have a double leachate collection liner system.
Major improvement have been made from the early open dump. Collection of methane for industrial use and recycling the leachate back into the landfill to enhance decay and consolidation have ensured along with a geocomposite clay liner (GCL) filled with bentonite, employed in new landfill construction. Excess leachate is commonly piped to a sewage treatment plant for disposal.