Waste DisposalChapter 16

Photo from Sandia National Laboratory, U.S. Department of Energy

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)

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

Sanitary landfills

Landfill and Leachate

“bathtub effect”

Remaining landfill capacity

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

Proportions of municipal waste

Waste-to-energy incineration facility

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

Dumping sediments with pollutants

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

Solid wastes and paper recycle

Recycling Symbols

Recycling

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

Municipal waste disposal

Main generators of hazardous wastes

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

Careless toxic-waste disposal leads to pollution

A secure landfill design for toxic-waste disposal

Deep-well disposal for liquid wastes

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

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

Septic tank system

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

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– Expensive– Political dynamite

The first 951 toxic-waste dump sites

Completed removals of Superfund, 1980-

1990

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’

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

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

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

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

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