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.
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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
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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
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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.
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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
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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 – Chlorination – Filtration – VOC removal – Nitrate removal – Settling Tanks – pH adjustments (Lime)
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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 Reuse
Inadvertent: – 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