Transcript Waste Disposal - Waxahachie Independent School District

Chapter 16
Waste Disposal
Photo from Sandia National Laboratory, U.S. Department of Energy
Solid Wastes
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Major source of solid waste in U.S. are:
– Agriculture (crops and animals): more than 50%
– Mineral industry (spoils, tailings, slag, and other
rock and mineral wastes)
– Municipalities (small amount of municipal waste)
– Industry (highly toxic)
Municipal Waste Disposal
Open Dumps – unsightly, unsanitary, and smelly
 Sanitary Landfills – alternate layers of
compacted trash and a covering material
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– In U.S. open dumps no longer tolerated
– Landfill design is important
– Barriers need to lock in toxins and chemicals; must
reduce leakage into the environment
– Important to control the migration of leachate out of
the landfill
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Sites for sanitary landfills often controversial
– NIMBY, NIMFY, NIMEY, and NOPE laws apply
Landfill and Leachate
“bathtub effect”
Remaining landfill capacity
Incineration
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Partial solution to space problems faced by landfills
Burning waste produces abundant carbon dioxide
plus other toxic substances
Recent technology have improved incinerators to
burn hotter that breakdown complex toxic
substances to less dangerous ones
Expensive to operate and still produce a residual
waste; often toxic and require proper storage
+The considerable heat generated by an
incinerator can be recovered and used
Proportions of municipal waste
Waste-to-energy incineration facility
Ocean Dumping
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Ship board incineration, over the open ocean,
and dumping residual waste into the ocean
– Similar to land-based incineration but at sea
– Incineration not 100% effective, residual toxic
materials and chemicals dumped into the ocean will
still pollute the ocean
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Ocean dumping without incineration still popular
in many places around the world
– Very disastrous to local oceans where practiced
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A dumping site for one very high-volume waste
product: dredge spoils
Dumping sediments with pollutants
Reduce Waste Volume
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Less volume means less landfill space and
slower filling of available sites
Easier to Handle (Nontoxic) Organic Matter
– Treated nontoxic organic waste can be fed to swine or
composted
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Recycling – any reuse of waste reduces volume
at landfills
– Recover recyclable waste by source separation;
separate waste into useful categories (wood, paper,
plastics, various metals, …) at the user’s site
– Deposits on reusable material (glass, cans, containers,
…) often attractive incentive
– Many applications to this idea yet unexplored
Recycling Symbols
Recycling
Reduce Waste Volume
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Another options
• Recycle crushed pavement as new roadbed
material
• Recycle steel into other useful objects
• Re-use bricks as footpaths
• Innovations has no limit here
• Definite up and coming new industry
Municipal waste disposal
Main generators of hazardous wastes
Liquid-Waste Disposal
Sewage and by-products of industrial processes
 Main Strategies:
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– Dilute and disperse
– Concentrate and contain
Neither strategy is safe in long term
 Secure Landfills – is it possible?
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– Placing liquid-waste into sealed drums, and covering
with impermeable lining material; idea is to assure
that the leachate will not migrate
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Deep wells – inject deep into the crust
– Leachate not contained
– May act to lubricate faults
– Expensive and unsafe
A secure landfill design for toxic-waste disposal
Deep-well disposal for
liquid wastes
Other Strategies
for liquid Waste diposal
Incineration – produces carbon dioxide
 Treatment by chemicals to breakdown or
neutralized liquid waste is a possibility
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– Generate a less toxic liquid or residue
– Would still require proper storage
Sewage Treatment
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Septic Systems: individual user-level
treatment
– Settling tank: solids separated and bacterial
breakdown begins
– Leach field or absorption field: liquid with
remaining dissolved organic matter seeps out of
porous pipes
– Soil microorganisms and oxygen complete the
breakdown of the organic matter
– Soil permeability and field size are controlling
factors
Septic tank system
Sewage Treatment
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Municipal Sewage Treatment
1. Primary treatment: removal of solids from
organic liquid waste
2. Secondary treatment: bacteria and fungi act
to dissolve and breakdown the organic matter
3. Tertiary or advanced treatment: filtration,
chlorination, and other chemical treatment
may occur
Primary, secondary, and tertiary stages of
municipal treatment
Ghosts of Toxins Past:
Superfund
Disposal of identifiable toxic wastes in U.S.
is currently controlled
 Congress has mandated and provided
billions of dollars to control and clean-up
toxic spills from the past
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– Expensive
– Political dynamite
The first 951 toxic-waste
dump sites
Completed removals of
Superfund, 1980-1990
Radioactive Wastes
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Radioactive Decay – unstable nuclei decay and
produce energy
Radioisotopes each have their own rate of decay
measured in a half-life
Half-lives of different radioisotopes vary from
microseconds to billions of years
**The decay of a radioisotope can not be
accelerated or delayed
Energetic radioisotopes must be contained out
of the environment for ‘ever’
Effects of Radiation
Alpha, beta, and gamma rays are types of ionized
radiation given off by the decay of various
radioisotopes
 Cancer, tumors, tissue burns, and genetic
mutation can result due to exposure of high doses
of radiation
 Large doses result in death
 Accidents have occurred:
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– Chernobyl and Three Mile Island
Nature of Radioactive Wastes
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Radioisotopes with half-lives of a few years to
hundreds of years present the most risk
– Radioactive enough to cause harm
– Persistent in the environment long enough to require
management
– Some are toxic chemical poisons
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Levels of radioactive waste:
– Low-level: do not require extraordinary disposal
precautions
– High-level: require extraordinary precautions; must
be isolated from the biosphere with confidence for a
long time
Historical Suggestions for
Storage
Space
 Antarctic Ice
 Plate Tectonic Subduction Zones
 Seabed Disposal
 Bedrock Caverns for Liquid Waste
 Bedrock Disposal of Solid High-Level Wastes
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– Multiple barrier concept
Waste Isolation Pilot Plant
(WIPP)
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Southeast New Mexico site for storage of
transuranic wastes
– Opened March 26, 1999
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WIPP is located in bedded salt underlain
by evaporites and overlain by mudstone
– Located 2150 feet below the surface in a dry
and stable tectonic region
– Tectonic stable for over 200 million years
Yucca Mountain
Established by Nuclear Waste Policy Act of 1982
– establish a high-level disposal site in the west
 Yucca Mountain Attractive Characteristics:
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1.Rhyolitic tuff host rock
2. Arid climate
3. Low population density (but Las Vegas is 60 miles to
the southeast)
4. Low regional water table
5. Apparent geologic stability
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Geological studies were detailed and revealing