1. Hazardous Waste

2. HAZARDOUS WASTE Hazardous waste:
discarded solid or liquid material that is toxic, ignitable, corrosive, or reactive enough to explode or release toxic fumes.
The two largest classes of hazardous wastes:
organic compounds
pesticides, PCBs, dioxins
toxic heavy metals
lead, mercury, arsenic

3. What Harmful Chemicals Are in Your Home?
Cleaning
Gardening
• Disinfectants
• Pesticides
• Drain, toilet, and
window cleaners
• Weed killers
• Ant and rodent killers
• Spot removers
• Septic tank cleaners
• Flea powders
Paint
Automotive
• Latex and oil-based paints
• Gasoline
• Paint thinners, solvents,
and strippers
• Used motor oil
• Antifreeze
• Stains, varnishes,
and lacquers
• Battery acid
• Solvents
Figure 22.15
Science: harmful chemicals found in many U.S. homes. The U.S. Congress has exempted disposal of these materials from government regulation. QUESTION: Which of these chemicals are in your home?
• Wood preservatives
• Brake and
transmission fluid
• Artist paints and inks
General
• Rust inhibitor and
rust remover
• Dry-cell batteries
(mercury and cadmium)
• Glues and cements
Fig , p. 534

4. Two major federal laws regulate hazardous waste in the U.S.:
Resource Conservation and Recovery Act
(RCRA) 1976
Cradle-to-the-grave system to keep track waste.
Requires EPA to set standards for hazardous waste
Permit for more that 100kg per month
Guidelines/financial aid to help state programs
Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA)
Commonly known as Superfund program.

5. Guess what percent of hazardous wastes in the U. S
Guess what percent of hazardous wastes in the U.S. are not regulated by hazardous-waste laws?
95%

6. Brownfields
Land that was polluted by industrial or commercial uses. (Link)
Cleaning up and reinvesting in these properties protects the environment, and takes development pressures off green spaces and working lands.
Does not include superfund sites.

7. Conversion to Less Hazardous Substances
Physical Methods: using charcoal or resins to separate out harmful chemicals.
Chemical Methods: using chemical reactions that can convert hazardous chemicals to less harmful or harmless chemicals.

8. Conversion to Less Hazardous Substances
Biological Methods:
Bioremediation: bacteria or enzymes help destroy toxic and hazardous waste or convert them to more benign substances.
Pros: can be cheaper than landfills if toxin-degrading bacteria can be found.
Cons: works for a few specific ORGANIC wastes
Ex. Oil spills

9. Ex. desalination of agricultural land
Phytoremediation:
involves using natural or genetically engineered plants to absorb, filter and remove contaminants from polluted soil and water.
Ex. desalination of agricultural land

10. Radioactive contaminants Organic contaminants Inorganic
metal contaminants
Poplar tree
Brake fern
Sunflower
Willow tree
Indian mustard
Rhizofiltration
Roots of plants such as
sunflowers with dangling
roots on ponds or in green-
houses can absorb pollutants
such as radioactive strontium-90 and cesium-137 and various
organic chemicals.
Phytostabilization
Plants such as willow trees and poplars can absorb chemicals and keep them from reaching groundwater or nearby surface water.
Phytodegradation
Plants such as poplars
can absorb toxic organic
chemicals and break them down into less harmful compounds which they store or
release slowly into the air.
Phytoextraction
Roots of plants such as Indian
mustard and brake ferns can
absorb toxic metals such as
lead, arsenic, and others and
store them in their leaves.
Plants can then be recycled
or harvested and incinerated.
Landfill
Polluted
groundwater in
Oil
spill
Figure 22.17
Solutions: phytoremediation. Various types of plants can be used as pollution sponges to clean up soil and water and radioactive substances (left), organic compounds (center), and toxic metals (right). (Data from American Society of Plant Physiologists, U.S. Environmental Protection Agency, and Edenspace)
Polluted
leachate
Decontaminated
water out
Soil
Soil
Groundwater
Groundwater

11. Aesthetically pleasing
Trade-Offs
Phytoremediation
Advantages
Disadvantages
Easy to establish
Slow (can take several
growing seasons)
Inexpensive
Less erosion
Aesthetically pleasing
Less habitat
Destruction vs. removing soil and taking it to a land fill
Vegetation is now hazardous
May introduce exotic species
Effective only
at depth plant
roots can
reach
Can reduce material dumped into landfills
Some toxic organic chemicals may evaporate from plant leaves
Produces little air pollution compared to incineration
Figure 22.18
Trade-offs: advantages and disadvantages of using phytoremediation to remove or detoxify hazardous waste. QUESTION: Which single advantage and which single disadvantage do you think are the most important?
Some plants can become toxic to
animals
Low energy use
Fig , p. 538

12. Conversion to Less Hazardous Substances
Incineration:
heating many types of hazardous waste to high temperatures – up to 2000 °C (3,600 ° F)– in an incinerator can break them down and convert them to less harmful or harmless chemicals.
Cons- same as before, toxic ash

13. Conversion to Less Hazardous Substances
Plasma Torch:
passing electrical current through gas to generate very high temperatures (10,000oC or 18,000oF) can create plasma.
The plasma process can be carried out in a torch which can decompose liquid or solid hazardous organic material.

14. Mobile. Easy to move to different sites Produces CO2 and CO
Trade-Offs
Plasma Arc
Advantages
Disadvantages
Small
High cost
Mobile. Easy to move to different sites
Produces CO2 and CO
Can release particulates and chlorine gas
Produces no
toxic ash
Figure 22.19
Trade-offs: advantages and disadvantages of using a plasma arc torch to detoxify hazardous wastes. QUESTION: Which single advantage and which single disadvantage do you think are the most important?
Can vaporize and release toxic metals and radioactive elements
Fig , p. 538

15. Long-Term Storage of Hazardous Waste
Deep-well disposal: liquid hazardous wastes are pumped under pressure into dry porous rock far beneath aquifers.
Surface impoundments: excavated depressions such as ponds, pits, or lagoons into which liners are placed and liquid hazardous wastes are stored.

16. Long-Term Storage of Hazardous Waste: Chemicals you can’t detoxify
Long-Term Retrievable Storage: Metal drums stored them in areas that can be inspected
Secure Landfills: waste are put into drums and buried in carefully designed and monitored sites.

17. Case Study: Lead Lead is especially harmful to children
Leaded gas, paint
Partial paralysis
Mental retardation
Palsy
Neurological damage
Stored in bones
Lead Pollution
More info
Figure 22-24

18. high levels in some types of fish neurotoxin Minamata disease
Case Study: Mercury
burning coal
incinerating wastes
high levels in some types of fish
neurotoxin
Minamata disease
More info
Figure 22-26

19. Fig. 22-25, p. 542 AIR WINDS PRECIPITATION WINDS PRECIPITATION
Hg and SO2
Hg2+ and acids
Hg2+ and acids
Photo-
chemical
Human sources
Elemental
mercury
vapor
(Hg)
Inorganic mercury
and acids
(Hg2+)
Inorganic mercury
and acids
(Hg2+)
Coal-
burning
plant
Incinerator
Deposition
Runoff of Hg2+ and acids
Deposition
WATER
Large fish
Vaporization
Deposition
Small fish
BIOMAGNIFICATION
IN FOOD CHAIN
Deposition
Figure 22.25
Science: cycling of mercury in aquatic environments, in which mercury is converted from one form to another. The most toxic form to humans is methylmercury (CH3Hg+), which can be biologically magnified in aquatic food chains. Some mercury is also released back into the atmosphere as mercury vapor. QUESTION: What is your most likely exposure to mercury?
Phytoplankton
Zooplankton
Bacteria
and acids
Oxidation
Elemental
mercury liquid
(Hg)
Inorganic
mercury
(Hg2+)
Organic
mercury
(CH3Hg+)
Bacteria
Settles
out
Settles
out
Settles
out
SEDIMENT
Fig , p. 542

20. Global Outlook: International Action to Reduce Hazardous Waste
Stockholm Convention: An international treaty calls for phasing out POPs (persistent organic pollutants)
POPs are soluble in fat.
The U.S has not ratified this treaty.
DDT, PCBs, dioxins, other chlorine containing pesticides
Basel Convention: stops shipping of hazardous waste to countries without permission. (usually developed to developing)