Transcript Chapter 21

Chapter 22
Water Pollution and
Treatment
Water Pollution
• Degradation of water quality
• Any biological, physical or chemical
substance that, in an identifiable excess is
known to be harmful to other desirable
living organisms
• Heavy metals, sediment, radioactive
isotopes, heat, coliform bacteria,
phosphorus, nitrogen, pathogenic bacteria
Water pollution
• US EPA has set limits on certain pollutants
(contaminants)
• Difficulties in determining effects of
exposure to low levels of pollutants.
• Standards have been set for a small fraction
of more than 700 identified drinking water
contaminants.
Biochemical Oxygen Demand
• The amount of oxygen required for
biochemical decomposition process
• When BOD is high the oxygen content is
low, to support life.
• 3 zones
A pollution zone – BOD high
An active decomposition zone
DO reaches a minimum to
actively decompose
A recovery zone – DO increases
And BOD is reduced
Waterborne Disease
• Outbreaks of waterborne diseases
– Milwaukee, WI – Cryptosporidium – 100 deaths
– Fecal Coliform Bacteria – 1998 Ga Water Park
– Walkerton, ON – E.Coli – Cow manure washed into
water supply wells from heavy rains.
• 5 people died, 20 ICU, 500 ill – CUT BACKS IN
TESTING
Nutrients
• Eutrophication
– The process by which a body of water develops
a high concentration of nutrients – Phophorus
or nitrogen
• Cultural Eutrophication
– When eutrophication is accelerated by human
processes that add nutrients to a body of water
• Fertilizers, detergents, sewage treatment plants
Eutrophication
• A body of water develops a high concentration of
nutrients.
• The nutrients cause an increase in the growth of
aquatic plants as well as photosynthetic blue-green
bacteria and algae
• Algae may form surface mats, shading and
reducing light to the algae below; reducing
photosynthesis.
• Algae die and decompose, bacteria feed on the
dead algae,BOD increases, oxygen is reduced.
Other organisms die.
Acid Mine Drainage
• Water with a high concentration of sulfuric
acid that drains from mines
• Serious water pollution problem
• Damages aquatic ecosystems, pollutes
bodies of water and degrades water quality
Surface Water Pollution
• Water Pollutants are emitted from
– Point Sources
• Distinct and confined sources such as pipes from
industrial or municipal sources.
• Old sewage treatment systems
– Nonpoint Sources
• Diffused and intermittent
• Ex) runoffs from streets, agriculture, mining,
forestry.
• Difficult to monitor and control
Approaches to surface water pollution
• Reduce the sources of pollution
– Most environmentally preferable way
• Treat the water to remove pollutant
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Chlorination
Filtration
VOC removal
Nitrate removal
Settling Tanks
pH adjustments (Lime)
Groundwater Pollution
• 50% of people in US
depend on groundwater
as a water source.
-Groundwater has always
been thought to be PURE
-Pollution sources can be
dumping chemicals, leaking
underground tanks, natural
occurring elements
Wastewater Treatment
• Septic Tank Disposal Systems
• Waste Treatment Plants
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Primary Treatment
Secondary Treatment
Advanced Treatment
Chlorine Treatment
Wastewater Renovation and
Conservation Cycle
• Steps:
– 1. Return of treated wastewater to crops
– 2. Renovation or natural purification by slow
percolation of the wastewater into soil to
eventually recharge the groundwater resource
with clean water
– 3. Reuse of the treated water
Water Reuse
Inadvertent:
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water is withdrawn, treated and returned to the
environment
Indirect:
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Ex) the wastewater renovation and conservation cycle
Direct:
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The use of treated wastewater that is piped directly
from a treatment plant to the next user
Water Pollution and
Environmental Law
• Environmental Law
– The branch of law dealing with conservation
and use of natural resources and control of
pollution