env100 note 56.docx

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28 Mar 2012
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ENV100 Lecture Notes Mar 19, 2012
Managing Waste continued
Readings: Chapter 18
Several steps precede the disposal of hazardous waste
For many years, hazardous waste was discarded without special treatment
o Public did not know it was harmful to human health
o It was assumed that substances would disappear or be diluted in the
environment
o Now cities designate sites or special collection days to gather HHW
There are three disposal methods for hazardous waste
Secure landfills
o Design and construction standards are similar but stricter than ordinary sanitary
landfills
o Must have several impervious liners and leachate removal systems
o Must be located far from aquifers
Surface impoundments
Deep-well injection
Surface impoundments store liquid hazardous waste
Shallow depressions are lined with plastic and clay
Residue of solid hazardous waste is transported elsewhere
The underlying clay layer can crack and leak
Rainstorms cause overflow, contaminating nearby areas
In deep-well injection, wastes are stored underground
Well is drilled deep beneath the water table
Waste is injected underground
o Long-term disposal
o Well is intended to be isolated from humans and groundwater
o Wells can become corroded and leak waste into soil
Radioactive waste is especially hazardous
Radioactive waste is particularly dangerous and persistent
Geologic isolation = using the absorptive capacity and impermeability of naturally
occurring rock to block contaminants
Multiple-barrier approach = engineering the facility to place as many barriers as
possible, both physical and chemical, in the pathway of any escaping contaminants
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Contaminated sites are being cleaned up, slowly
11,000 Canadian contaminated sites, including priority sites for cleanup activities:
o Faro Mine, Yukon ($14.6 million)
o Canadian Forces Base Esquimalt, British Columbia ($4.56 million)
o Port Radium Mine, Northwest Territories ($7.1 million)
o Belleville Small Craft Harbour, Ontario ($6.8 million)
Brownfields = sites that have been contaminated but have the potential to be cleaned
up and remediated
Conclusions
Our consumption habits have created more waste than ever before
Finding ways to reduce, reuse and efficiently recycle the materials and goods that we
use stands as a key challenge for this century
Modern methods of waste management are far safer for people and gentler on the
environment
Recycling and composting are making rapid progress
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