Transcript Waste Disposal

Chapter 15
Waste Disposal
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)
Figure 15.1
Figure 15.2
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
Figure 15.3
Fig. 15.4 Sanitary landfills
Fig. 15.5 landfill and Leachate
Fig. 15.6 “bathtub effect”
Figure 15.7 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
Figure 15.8 Proportions of municipal waste
Figure 15.9 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
Figure 15.10 Dumping sediments with pollutants
Reduce Waste Volume
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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
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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
Figures 15.12 Solid wastes and paper recycle
Figure 15.13 Recycling Symbols
Figures 15.14 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
• Innovation has no limit here
Figure 15.15 Municipal waste disposal
Figure 15.16 Main generators of hazardous wastes
Liquid-Waste Disposal
Sewage and by-products of industrial processes
 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
Fig. 15.17 Careless toxic-waste disposal leads to pollution
Figure 15.18 A secure landfill design for toxic-waste disposal
Fig. 15.19 Deep-well
disposal for liquid wastes
Other Strategies
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
Figure 15.20 Septic tank system
Sewage Treatment
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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
Figure 15.21 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
Figure 15.22 The first 951
toxic-waste dump sites
Figure 15.23 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’
Figure 15.27
Figure 15.25
Table 15.2
Figure 15.26
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
Figure 15.28
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
Figure 15.29 a
Figure 15.29 b
Figure 15.30
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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– Tuff host rock
– Arid climate
– Low population density
– Low regional water table
– Apparent geologic stability
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Geological studies were detailed and
revealing
Figure 15.31 a
Figure 15.31 b
Figure 15.32