chapter 22 water pollution and treatment. water pollution degradation of water quality any...
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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
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.
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
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 zonesA pollution zone – BOD high
An active decomposition zoneDO 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
Approaches to surface water pollution
• Reduce the sources of pollution– Most environmentally preferable way
• Treat the water to remove pollutant– Chlorination– Filtration– Settling Tanks– pH adjustments (Lime)– VOC removal – Nitrate removal
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– 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 ReuseInadvertent: – water is withdrawn, treated and returned to the
environment
Indirect:– Ex) the wastewater renovation and conservation cycle
Direct:– 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