Waste Disposal
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Transcript of Waste Disposal
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Waste DisposalChapter 16
Photo from Sandia National Laboratory, U.S. Department of Energy
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Solid Wastes 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)
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Municipal Waste Disposal Open Dumps – unsightly, unsanitary, and
smelly Sanitary Landfills – alternate layers of
compacted trash and a covering material– 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 Sites for sanitary landfills often
controversial– NIMBY, NIMFY, NIMEY, and NOPE laws apply
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Sanitary landfills
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Landfill and Leachate
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“bathtub effect”
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Remaining landfill capacity
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Incineration 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
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Proportions of municipal waste
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Waste-to-energy incineration facility
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Ocean Dumping 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
Ocean dumping without incineration still popular in many places around the world– Very disastrous to local oceans where practiced
A dumping site for one very high-volume waste product: dredge spoils
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Dumping sediments with pollutants
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Reduce Waste Volume Less volume means less landfill space and
slower filling of available sites Handling (Nontoxic) Organic Matter
– Treated nontoxic organic waste can be fed to swine or composted
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
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Solid wastes and paper recycle
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Recycling Symbols
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Recycling
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Reduce Waste Volume Another options
• Recycle crushed pavement as new roadbed material
• Recycle steel into other useful objects• Re-use bricks as footpaths• Innovation has no limit here
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Municipal waste disposal
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Main generators of hazardous wastes
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Liquid-Waste Disposal Sewage and by-products of industrial
processes Strategies:
– Dilute and disperse– Concentrate and contain
Neither strategy is safe in long term Secure Landfills – is it possible?
– Placing liquid-waste into sealed drums, and covering with impermeable lining material; idea is to assure that the leachate will not migrate
Deep wells – inject deep into the crust– Leachate not contained– May act to lubricate faults– Expensive and unsafe
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Careless toxic-waste disposal leads to pollution
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A secure landfill design for toxic-waste disposal
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Deep-well disposal for liquid wastes
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Other Strategies Incineration – produces carbon
dioxide Treatment by chemicals to
breakdown or neutralized liquid waste is a possibility– Generate a less toxic liquid or residue– Would still require proper storage
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Sewage Treatment 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
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Septic tank system
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Sewage Treatment Municipal Sewage Treatment
– Primary treatment: removal of solids from organic liquid waste
– Secondary treatment: bacteria and fungi act to dissolve and breakdown the organic matter
– Tertiary or advanced treatment: filtration, chlorination, and other chemical treatment may occur
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Primary, secondary, and tertiary stages of municipal treatment
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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– Expensive– Political dynamite
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The first 951 toxic-waste dump sites
Completed removals of Superfund, 1980-
1990
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Radioactive Wastes 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’
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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:
– Chernobyl and Three Mile Island
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Nature of Radioactive Wastes
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
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
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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– Multiple barrier concept
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Waste Isolation Pilot Plant (WIPP)
Southeast New Mexico site for storage of transuranic wastes– Opened March 26, 1999
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
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Yucca Mountain Established by Nuclear Waste Policy Act of
1982 – establish a high-level disposal site in the west
Yucca Mountain Attractive Characteristics:– Rhyolitic tuff host rock– Arid climate– Low population density (but Las Vegas is 60
miles to the southeast)– Low regional water table– Apparent geologic stability
Geological studies were detailed and revealing
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