Water: Resources and Pollution

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Water Resources and Pollution

• Chapter 10

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Outline

• Hydrologic Cycle
• Water Compartments
• Water Availability
• Freshwater Shortages
• Increasing Water Supplies
• Water Management and Conservation
• Water Pollution
• Water Quality Today
• Water Pollution Control
• Water Legislation

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WATER RESOURCES

• Hydrologic Cycle
• Describes the circulation of water as it
• Evaporates from land, water, and organisms.
  (Transpires from plants)
• Enters the atmosphere.
• Condenses and precipitates back to the earths
  surfaces.
• Moves underground by infiltration or overland
  into rivers, lakes and seas.

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Mean Annual Precipitation
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Water Distribution
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MAJOR WATER COMPARTMENTS

• Groundwater
• Second largest reservoir of fresh water.
• Infiltration - Process of water percolating
  through the soil and into fractures and permeable
  rocks.
• Zone of Aeration - Upper soil layers that hold
  both air and water.
• Zone of Saturation - Lower soil layers where all
  spaces are filled with water.
• Water Table - Top of Zone of Saturation

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Groundwater
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Groundwater

• Aquifers - Porous layers of sand, gravel, or rock
  lying below the water table.
• Artesian - Pressurized aquifer intersects the
  surface. (Water flows without pumping)
• Recharge Zone - Area where water infiltrates into
  an aquifer.
• Recharge rate is often very slow.
• Presently, groundwater is being removed faster
  than it can be replenished in many areas.

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MAJOR WATER COMPARTMENTS CONTD

• Rivers and Streams
• Precipitation that does not evaporate or
  infiltrate into the ground runs off the surface,
  back toward the sea.
• Best measure of water volume carried by a river
  is discharge.
• The amount of water that passes a fixed point in
  a given amount of time.
• Usually expressed as cubic feet per second.

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MAJOR WATER COMPARTMENTS CONTD

• Wetlands
• Play a vital role in hydrologic cycle.
• Lush plant growth stabilizes soil and retards
  surface runoff, allowing more aquifer
  infiltration.
• Disturbance reduces natural water-absorbing
  capacity, resulting in floods and erosion in wet
  periods, and less water flow the rest of the year.

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MAJOR WATER COMPARTMENTS CONTD

• The Atmosphere
• Among the smallest water reservoirs.
• Contains 0.001 of total water supply.
• Has most rapid turnover rate.
• Provides mechanism for distributing fresh water
  over landmasses and replenishing terrestrial
  reservoirs.

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WATER AVAILABILITY AND USE

• Renewable Water Supplies
• Made up of surface runoff and infiltration into
  accessible freshwater aquifers.
• Water-Rich ad Water-Poor Countries
• Water availability usually measured in terms of
  renewable water per capita.
• Highest per capita generally found in countries
  with moist climates and low population densities.

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Water Use

• Withdrawal - Total amount of water taken from a
  source.
• Consumption - Fraction of withdrawn water made
  unavailable for other purposes (Not returned to
  its source).
• Degradation - Change in water quality due to
  contamination making it unsuitable for desired
  use.

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Quantities of Water Used

• Water use has been increasing twice as fast as
  population growth over past century.
• Worldwide, agriculture claims about 70 of total
  water withdrawal.
• In many developing countries, agricultural water
  use is extremely inefficient and highly
  consumptive.
• Worldwide, industry accounts for about 25 of all
  water use.
• Cooling water for power plants is single largest
  industrial use.

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Water Withdrawal
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FRESHWATER SHORTAGES

• Estimated 1.5 billion people lack access to an
  adequate supply of drinking water.
• 3 billion lack acceptable sanitation.
• A country where consumption exceeds more than 20
  of available, renewable supply is considered
  vulnerable to water stress.
• Globally, water supplies are abundant, but, along
  with capital resources, are unevenly distributed.

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A Precious Resource

• Currently, 45 countries, most in Africa or Middle
  East, cannot meet the minimum essential water
  requirements of their citizens.
• More than two-thirds of worlds households
  retrieve water from outside the home.
• Availability does not automatically equate to
  affordability.
• Sanitation levels decline when water is expensive.

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Depleting Groundwater

• Groundwater is the source of nearly 40 of fresh
  water in the U.S.
• On a local level, withdrawing water faster than
  it can be replenished leads to a cone of
  depression in the water table,
• On a broader scale, heavy pumping can deplete an
  aquifer.
• Ogallala Aquifer
• Mining non-renewable resource.

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Depleting Groundwater
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Depleting Groundwater Contd

• Withdrawing large amounts of groundwater in a
  small area causes porous formations to collapse,
  resulting in subsidence.
• Sinkholes form when an underground channel or
  cavern collapses.
• Saltwater intrusion can occur along coastlines
  where overuse of freshwater reservoirs draws the
  water table low enough to allow saltwater to
  intrude.

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INCREASING WATER SUPPLIES

• Seeding Clouds
• Condensation Nuclei
• Towing Icebergs
• Cost
• Desalination
• Most common methods are distillation and reverse
  osmosis.
• Three to four times more expensive than most
  other sources.

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INCREASING WATER SUPPLIES CONTD

• Dams, Reservoirs, and Canals - Trap excess water
  in areas of excess and transfer it to areas of
  deficit.
• Environmental Costs
• Upsets natural balance of water systems.
• Ecosystem Losses
• Loss of wildlife habitat.
• Reservoir Size
• Water Quality

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Dams, Reservoirs, and Canals

• Displacement of People
• Three Gorges Dams in China will force relocation
  of over a million people.
• Evaporation, Leakage, Siltation
• Evaporative losses from Lake Mead and Lake Powell
  on the Colorado River is about 1km3 per year (264
  billion gallons).
• Dams slow water flow, allowing silt (nutrients)
  to drop out.
• Loss of Free-Flowing Rivers

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Price Mechanisms and Water Policy

• Throughout most of U.S. history, water policies
  have generally worked against conservation.
• Eastern - Riparian Use Rights
• Western - Prior Appropriation Rights
• In most federal reclamation projects, customers
  have been charged only for the immediate costs of
  water delivery.

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WATER MANAGEMENT AND CONSERVATION

• Watershed Management
• Watershed - All the land drained by a stream or
  river.
• Retaining vegetation and ground cover helps
  retard rainwater and lessens downstream flooding.
• Additionally, retaining crop residue on fields
  reduces flooding and minimizing plowing and
  forest cutting on steep slopes protects
  watersheds.

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Domestic Conservation

• Estimates suggest many societies could save as
  much as half of current domestic water usage
  without great sacrifice or serious change in
  lifestyle.
• Largest domestic use is toilet flushing.
• Small volume of waste in large volume of water.
• Significant amounts of water can be reclaimed and
  recycled.
• Purified sewage effluent

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Pollution of Water Bodies

• Eutrophication- the excessive growth of algae in
  rivers and streams and oceans due to the presence
  of large amounts of ammonia phosphorous in
  streams/rivers
• (example brown tides on long island)

• Slow turnover of water

• Thermal Pollution
• (e.g. Con Edison)

Fig. 19.5, p. 482
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WATER POLLUTION

• Any physical, biological, or chemical change in
  water quality that adversely affects living
  organisms can be considered pollution.
• Point Sources - Discharge pollution from specific
  locations.
• Factories, power plants, oil wells
• Non-Point Sources - Scattered or diffuse, having
  no specific location of discharge.
• Agricultural fields, feedlots, golf courses
• Atmospheric Deposition

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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.
• Coliform bacteria - Intestinal bacteria.
• Escherichia coli (E. coli)

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Oxygen-Demanding Wastes

• Water with an oxygen content gt 6 ppm will support
  desirable aquatic life.
• Water with lt 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.

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Oxygen-Demanding Wastes Contd

• Biochemical Oxygen Demand - Amount of dissolved
  oxygen consumed by aquatic microorganisms.
• Dissolved Oxygen Content - Measure of dissolved
  oxygen in the water.
• Effects of oxygen-demanding wastes on rivers
  depend on volume, flow, and temperature of river
  water.
• Oxygen Sag - Oxygen levels decline downstream
  from a pollution source as decomposers metabolize
  waste materials.

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Oxygen Sag
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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 in polluted rivers and estuaries.

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Hidden along the Caribbean coast is one of the
most spectacular Bioluminescent Bays in the
world. The mysterious blue-green light is created
by micro-organisms which thrive in an environment
uniquely suited to their needs. A trip into the
bay on a balmy night is a magical experience.
Fish flash by in dark water
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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.
• Mercury released from incinerators and
  coal-burning power plants is the most widespread
  toxic metal contamination in North America.
• Mine drainage and leaching are serious sources of
  environmental contamination.

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Inorganic Pollutants Contd

• 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, private lawns

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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 use 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

• Areas of Progress
• Clean Water Act (1972) established a National
  Pollution Discharge Elimination System, which
  requires a permit for any entity dumping wastes
  in surface waters.
• In 2003, EPA reported 91 of all monitored river
  miles and 88 of all accessed lake acres are
  suitable for their designated uses.
• Most progress due to municipal sewage treatment
  facilities.

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Water Quality Today
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Watershed Approaches

• In 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.

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Remaining Problems

• 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
  U.S. 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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Problems and Progress in Other Countries

• Sewage treatment in wealthier countries of Europe
  generally equal or surpass the U.S.
• 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 Indias surface waters are
  contaminated sufficiently to be considered
  dangerous to human health.

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Groundwater Pollution

• About half the U.S. population, and 95 of rural
  residents, depend on underground aquifers for
  drinking water.
• For decades, groundwater was assumed impervious
  to pollution and was considered the gold standard
  for water quality.
• Estimated 1.5 million Americans fall ill from
  fecal contamination annually.
• Cryptosporidium outbreaks

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Groundwater and Drinking Water

• EPA estimates 4.5 trillion liters of contaminated
  water seep into the ground in the U.S. every day.
• MTBE - Gasoline additive, and suspected
  carcinogen, is present in many urban aquifers.
• In agricultural areas, fertilizers and pesticides
  commonly contaminate aquifers and wells.

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Groundwater Pollution
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Ocean Pollution

• Estimated 6 million metric tons of plastic
  bottles, packaging material, and other litter
  tossed from ships into the ocean annually.
• Few coastlines in the world remain uncontaminated
  by oil or oil products.

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Ocean Pollution
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POLLUTION CONTROL

• Source Reduction
• Cheapest and most effective way to reduce
  pollution is avoid producing it or releasing it
  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

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Sewage Treatment

• 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.

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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.

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Municipal Sewage Treatment Contd

• 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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Municipal Sewage Treatment
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Oxygen Depleting Reaction

• Biological Oxygen Demand (BOD) - a measure of the
  amount of organic material in a water sample.

• Organics O2 Bacteria ? CO2 H2O More
  Bacteria
• Wastewater has a considerable amount of organic
  material
• Discharge of wastewater with a high BOD to a
  stream will
• lead to the depletion of oxygen in the stream

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Variation of Water Quality with Dissolved Oxygen
(DO)
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GRIT CHAMBER
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PRIMARY SETTLING TANKS
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AERATION TANKS
Organics O2 Bacteria ? CO2 H2O More
Bacteria
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SECONDARY SETTLING TANKS
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Chlorine Contact Tank
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Wastewater Effluent Outfall
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Low-Cost Waste Treatment

• Artificial Wetlands
• Natural water purification
• Effluent can be used to irrigate crops or raise
  fish for human consumption.

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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.