Transcript Document

Water Pollution
Point source pollution source is from drain
pipes, ditches, sewer
outfalls, factories and
power plants - easy to
monitor and regulate
Nonpoint source pollution runoff from farm fields and
feedlots, lawns and gardens,
golf courses, construction
sites, atmospheric deposits no specific location so harder
to monitor and regulate
Types and Results of Water Pollution
• Infectious agents - 25 million deaths a year
• Organic materials - biological oxygen demand (BOD)
increase resulting in oxygen sag
• Plant nutrients - eutrophication, toxic tides
• Metals - mercury and lead poisoning
• Nonmetallic salts - poison seeps and springs
• Acids and bases - ecosystem destabilization
• Organic chemicals - birth defects, cancer
• Sediments - clogged estuaries, death of coral reefs
• Thermal pollution - thermal plume
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Infectious Agents
• Main source of waterborne pathogens is untreated and
improperly treated human waste.
– Animal wastes from feedlots and fields is also an important
source of pathogens.
– In developed countries, sewage treatment plants and
pollution-control devices have greatly reduced pathogens.
– Tests for water quality are done for coliform bacteria
(intestinal bacteria). Such tests are easier and cheaper.
• Escherichia coli (E. coli) is the major coliform bacterium
species
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Basics for Understanding Environmental
Implications of Oxygen-Demanding Wastes
• Water with a Dissolved Oxygen Content (DOC) content > 6
parts per million (ppm) will support desirable aquatic life,
whereas water with < 2 ppm oxygen will support mainly
detritivores and decomposers.
• Oxygen is added to water by diffusion from wind and waves,
and by photosynthesis from green plants, algae, and
cyanobacteria. Oxygen is removed from water by respiration
and oxygen-consuming processes.
• Biochemical Oxygen Demand (BOD) is the amount of
dissolved oxygen consumed by aquatic microorganisms in
respiration.
• When organic wastes are added to rivers, microorganisms
demand oxygen for respiration used in consuming the
increase in food resource. As a result, DOC levels decline
downstream (oxygen sag) from a pollution source as
decomposers metabolize organic waste materials.
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Oxygen sag
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Three "waters" I have measured:
Water
mg/liter pH
------------------------------------------------------1)
205 6.9
2)
73,000 2.5
3)
89,000 6.6
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Which one would you rather drink?
Water
mg/liter pH
percent of class
---------------------------------------------------------1)
205 6.9
2)
73,000 2.5
3)
89,000 6.6
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Three "waters" I have measured:
Water
mg/liter pH what is it?
------------------------------------------------------------------1)
205 6.9 Snoqualmie Pass Sewage
2)
73,000 2.5 Coca Cola Classic
3)
89,000 6.6 Whole milk
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Plant Nutrients and Cultural
Eutrophication
• Oligotrophic - Bodies of water
that have clear water and low
biological productivity.
• Eutrophic - Bodies of water that
are rich in organisms and
organic material.
– Eutrophication - Process of
increasing nutrient levels and
biological productivity.
• Cultural Eutrophication Increase in biological
productivity and ecosystem
succession caused by
human activities.
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Toxic Tides
• Excessive nutrients support blooms of deadly
aquatic microorganisms in polluted waters.
– Increasingly common where nutrients and
wastes wash down rivers.
• Pfiesteria piscicida is a poisonous dinoflagellate
recognized as killer of fish and shellfish.
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Inorganic Pollutants
• Metals
– Many metals such as mercury, lead, cadmium, and nickel
are highly toxic.
• Highly persistent and tend to bioaccumulate in food chains.
– Lead pipes are a serious source of drinking water pollution.
– Mine drainage and leaching are serious sources of environmental
contamination.
• Nonmetallic Salts
– Many salts that are non-toxic at low concentrations can be mobilized by
irrigation and concentrated by evaporation, reaching levels toxic to
plants and animals.
• Leaching of road salts has had detrimental effect on many ecosystems.
• Acids and Bases
– Often released as by-products of industrial processes.
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Organic Chemicals
• Thousands of natural and synthetic organic
chemicals are used to make pesticides,
plastics, pharmaceuticals, pigments, etc.
• Two most important sources of toxic organic
chemicals in water are:
– Improper disposal of industrial and household
wastes.
– Runoff of pesticides from high-use areas.
• Fields, roadsides, golf courses
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Sediment
• Human activities have accelerated erosion
rates in many areas.
– Cropland erosion contributes about 25 billion
metric tons of suspended solids to world
surfaces each year.
• Sediment can either be beneficial (nourish
floodplains) or harmful (smother aquatic life).
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Thermal Pollution
• Raising or lowering water temperatures from normal
levels can adversely affect water quality and aquatic life.
– Oxygen solubility in water decreases as temperatures
increase.
• Species requiring high oxygen levels are adversely affected by
warming water.
• Industrial cooling often uses heat-exchangers to extract
excess heat, and discharge heated water back into
original source.
– Thermal Plume
• Produce artificial environments which attract many forms of wildlife.
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Water Quality Today
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Percentage of
impaired river
miles in the
U.S. by source
of damage
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• Areas of Progress
– Clean Water Act (1972) established a National Pollution Discharge System
which requires a permit for any entity dumping wastes in surface waters.
• In 1999, EPA reported 91.4% of all monitored river miles and 87.5% of all
accessed lake acres are suitable for their designated uses.
– Most progress due to municipal sewage treatment facilities.
• Watershed Approach Is Also an Improvement
– 1998, EPA switched regulatory approaches. Rather than issue standards on a
site by site approach, the focus is now on watershed-level monitoring and
protection.
– States are required to identify waters not meeting water quality goals and
develop total maximum daily loads (TMDL) for each pollutant and each listed
water body.
• Persistent Environmental Problems That Remain
– Greatest impediments to achieving national goals in water quality are sediment,
nutrients, and pathogens, especially from non-point discharges.
– About three-quarters of water pollution in the US comes from soil erosion, air
pollution fallout, and agricultural and urban runoff.
• Single cow produces 30 kg manure/day.
– Some feedlots have 100,000 animals.
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Groundwater and Drinking water
Pollution
• About half the US population, and 95% of
rural residents, depend on underground
aquifers for drinking water.
– For decades, groundwater was assumed
impervious to pollution. It was considered the
gold standard for water quality.
• An estimated 1.5 million Americans fall ill from
fecal contamination annually.
– Cryptosporidium outbreaks
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Groundwater Pollution
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Progress and Problems in Other
Countries
• Sewage treatment in
wealthier countries of
Europe generally equal or
surpass the US.
• In Russia, only about half of
the tap water supply is safe
to drink.
• In urban areas of South
America, Africa, and Asia,
95% of all sewage is
discharged untreated into
rivers.
• Two-thirds of India's surface
waters are contaminated
sufficiently to be considered
dangerous to human health.
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Location of Oil Pollution in the Oceans
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Pollution Control
• Nonpoint Pollution Sources and Land Management
– Reduce nutrient loading thru land use regulations
– Source reduction is cheapest and most effective way to
reduce pollution. To work society must get public and
business leaders to avoid producing or releasing
substances into the environment.
• Studies show as much as 90% less road salt can be used without
significantly affecting winter road safety.
• Soil Conservation
• Banning phosphate detergents
• Sewage Treatment
• Remediation
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Sewage Treatment
• Rationale
– More than 500 pathogenic bacteria, viruses, and parasites
can travel from human or animal excrement through
water.
• Natural Processes
– In many areas, outdoor urination and defecation is the
norm.
• When population densities are low, natural processes can
quickly eliminate waste.
• Artificial Wetlands Are a Low Cost Method
– Natural water purification
• Effluent can be used to irrigate crops or raise fish for human
consumption.
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Municipal Sewage Treatment
• Primary Treatment - Physical separation of large solids from the
waste stream.
• Secondary Treatment - Biological degradation of dissolved
organic compounds.
– Effluent from primary treatment transferred into trickling bed, or
aeration tank
• Effluent from secondary treatment is usually disinfected (chlorinated) before
release into nearby waterway.
• Tertiary Treatment - Removal of plant nutrients (nitrates and
phosphates) from secondary effluent.
– Chemicals, or natural wetlands.
• In many US cities, sanitary sewers are connected to storm
sewers.
– Heavy storms can overload the system, causing by-pass dumping
of raw sewage and toxic runoff directly into watercourses.
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Sewage Treatment
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Water Remediation
• Containment methods confine liquid wastes
in place, or cap surface with impermeable
layer to divert water away from the site.
• Extraction techniques are used to pump out
polluted water for treatment.
– Oxidation, reduction, neutralization, or
precipitation.
• Living organisms can also be used effectively
to break down polluted waters.
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WATER LEGISLATION
• Clean Water Act (1972)
– Goal was to return all U.S. surface waters to "fishable
and swimmable" conditions.
• For Point Sources, Discharge Permits and Best Practicable
Control Technology are required.
– Set zero discharge for 126 priority toxic pollutants.
• Areas of Contention
– Draining or Filling of Wetlands
• Many consider this taking of private land.
– Un-funded Mandates
• State or local governments must spend monies not repaid by
Congress.
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