Environmental Science
mcd72170
lecture_9.pptWASTE DISPOSAL METHODS
SOURCES OF WASTE
1) Agriculture – largest producer of non-point air and water pollution and includes:
manure
branches and slash
by-products of food processing
animal wastes
pesticides and pesticide residues
2) Mining and metal processing – includes mine tailings, overburden
from strip mines, and smelter slag
- Road and Construction wastes
4) Industrial wastes – most is recycled, converted, destroyed, or
disposed of in private landfills or in deep
injection wells
- Municipal wastes – household and commercial refuge
6) Hazardous wastes – wastes that are dangerous to living things or
the environment
All of these are components of the WASTE STREAM = steady flow of the varied wastes we produce.
METHODS OF WASTE DISPOSAL #1
OPEN DUMPS
Waste collected, compacted and dumped on the ground in a suitable site. Organic matter rots or is consumed by a variety of organisms. Burning in evening hours is often employed.
It is the predominate method of waste disposal in developing nations.
It is illegal in most developed countries, especially in urban areas.
OPEN DUMPS: ADVANTAGES AND DISADVANTAGES
ADVANTAGES
- is cheap
DISADVANTAGES:
- waste is often burned intentionally, accidentally, or by spontaneous
- combustion thus causing air pollution
- pollutes water by runoff into nearby streams or seepage into ground water
- toxins accumulate
- attracts pests which can spread disease
- is a breeding ground for disease
- litter leaving dump site
- is ugly
- smells
DEVELOPING NATION OPEN DUMP
- What are the bulldozers doing?
- What are the people doing?
- What does the top picture
show?
Examples of illegal roadside dumps in the U.S.
4. Why would this be an illegal dump?
METHODS OF WASTE DISPOSAL #2
OCEAN DUMPING
Barges carry wastes out to sea and dump in into natural trenches, canyons, or onto the deep ocean floor (abyssal plain).
Is prohibited by federal regulations, but still occurs in developing nations or
illegally in developed nations.
OCEAN DUMPING: ADVANTAGES AND DISADVANTAGES
ADVANTAGES
- is cheap
DISADVANTAGES
- destroys ocean ecosystems
- washes ashore
- kills various aquatic animals
- accumulates in floating “masses”, especially the non-degradable plastics
What problem with ocean dumping is shown here?
An example of the consequences of ocean dumping
OCEAN AREAS WHERE THE CURRENTS CAUSE FLOATING MATS OF GARBAGE (ESPECIALLY PLASTICS) TO ACCUMULATE
A FLOATING MAT OF GARBAGE IN THE OCEAN
A FLOATING MAT OF PLASTICS IN THE OCEAN
HARM TO SEA LIFE DUE TO PLASTICS DUMPED IN THE OCEAN
EXAMPLE #1
HARM TO SEA LIFE DUE TO PLASTICS DUMPED IN THE OCEAN
EXAMPLE #2
HARM TO SEA LIFE DUE TO PLASTICS DUMPED IN THE OCEAN
EXAMPLE #3
ANOTHER FLOATING MAT OF PLASTICS IN THE OCEAN
METHODS OF WASTE DISPOSAL #3
Deep pit dug, lined with plastic lining or impervious clay to prevent hazardous substances/contaminated rainwater from seeping into surrounding environment. Trash is compacted daily and covered with 6 inches of soil.
Placement of the landfill must be carefully considered. They are usually placed away from lakes, rivers, floodplains, fault lines, and aquifer (=groundwater) recharge zones.
SANITARY LANDFILLS
ADVANTAGES
- not a source of disease
- not ugly
- doesn’t pollute if properly engineered
- may reclaim “useless” land
- doesn’t smell
- doesn’t attract insects or rodent populations
- litter is not a problem
- may be designed for methane recovery
DISADVANTAGES
- becoming expensive due to rising transportation and land costs,
- stricter EPA regulations, construction and maintenance costs, lad
- scarcity, LULU’s and NIMBY’s.
- land conversion to a landfill not always desirable
- depletion of resources (many recyclable or useable materials lost forever)
SANITARY LANDFILL: ADVANTAGES AND DISADVANTAGES
CONSTRUCTION OF A LINED SANITARY LANDFILL
COMPACTING A LAYER OF TRASH IN A SANITARY LANDFILL
CROSS-SECTION OF AN ACTIVE LANDFILL – NOTE DAILY SOIL COVER
SCHEMATIC OF AN ENERGY RECOVERY SANITARY LANDFILL COUPLED TO AN ELECTRICITY GENERATING PLANT
METHODS OF WASTE DISPOSAL #4
Shipping wastes, especially hazardous wastes, to less developed nations. (This is a form of toxic colonialism or “garbage imperialism”. May also be a form of environmental racism.)
EXPORTING WASTES (aka TOXIC COLONIALISM)
TOXIC WASTES EXPORTEDTO A DEVELOPING NATION
METHODS OF WASTE DISPOSAL #5
Waste is burned.
Two types:
1) Simple incinerators burn the wastes.
2) Those that use heat from the burning wastes to produce steam and/or
electricity.
Some incinerators are run on REFUSE-DERIVED FUELS (unburnable and recyclable materials removed before burning) while others are MASS BURN Incinerators (everything except extremely large appliances is dumped and burned).
INCINERATION (aka: ENERGY RECOVERY):
INCINERATION: ADVANTAGES AND DISADVANTAGES
ADVANTAGES
- reduces the waste stream
- saves landfill space
- can recover natural resources if use refuse-derived fuels
- can be linked to generation of electricity
- waste stream increasing in paper and cardboard content
DISADVANTAGES
- initially expensive to build
- not everything can be burned
- ash (especially bottom ash) and unburnable wastes must be disposed of, usually in a landfill
- can be toxins (furans, lead, cadmium, mercury, dioxins, PCB’s) in
- smoke which can cause air pollution; these can also be in fly ash (fine particles that leave with the smoke) which can also cause air/water pollution
- tipping fees generally higher than landfill disposal fees
- burning of certain wastes produces acidic gases (PVC materials)
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EXAMPLES OF INCINERATORS
TRASH BEING BURNED INSIDE AN INCINERATOR
QUESTIONS
What do you think the advantages and disadvantages of exporting wastes to other countries are:
- for the exporting country, and
- for the receiving country?
