Geo Science Study Guide 3rd Exam
Solid Waste Disposal
U.S.A. leader in world in per capita household wastes: the problem is mainly
•Agriculture (crops and animals): more than 50% (animals 39%, crops 14%)
•Mineral industry (spoils, tailings, slag, and other rock and mineral wastes) 38%
•Municipalities (small amount of municipal waste) 5%
•Industry (highly toxic) 3%
What are the major sources of solid waste in U.S.?
•On-site disposal – kitchen food waste
•Incineration – reduction of combustible waste to inert residue by burning at high
temperatures (900 to 1000C)
•Open dumps – unsightly, unsanitary, and smelly
oIn U.S. open dumps no longer tolerated
•Sanitary & Landﬁlls – a method of waste disposal that functions without creating a
hazard to public health or safety (American Society of Civil Engineering)
Open landfills vs. sanitary landfills. What is the difference?
Open landfills are unsightly, unsanitary, and smelly.
Sanitary Landfills are a method of waste disposal that functions without creating a hazard to
public health or safety.
Features of a modern sanitary landfill: What is leachate? What problems does
it cause? Why it is important to line a landfill?
Alternate layers of compacted trash and a covering material
•Landfill design is important
•Barriers need to lock in toxins and chemicals – cover (plastic liner) or soil (clay) must
reduce leakage into the environment
•Important to control the migration of leachate out of the landfill: potential hazards
Leachate is the liquid material generated in a landfill from infiltration of rainwater and snow,
leakage of groundwater or internal generation from decay processes in the waste itself. Attempts
to create dry landfills seek to minimize leachate production by eliminating all liquids from
entering the accumulated waste. Lack of such liquids also retards the chemical decay processes,
which create or mobilize some of the hazardous elements. Leachate is usually contaminated with
toxic elements such as heavy metals, acids, or hazardous microorganisms and is especially
dangerous due to its mobility in the event of leakage. A properly run landfill cannot prevent
leachate formation but will seek to contain and collect all leachate for detoxification and
processing on site.