Transcript ENVIRONMENTAL SCIENCE

Chapter 11
Water Resources
&
Water Pollution
Water
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Hydrogen bonding – strong attractive forces
Water expands when it freezes
Liquid phase is 0ºC (32ºF) to 100ºC (212ºF)
High heat capacity (4.184 J/g-ºC)
Excellent solvent – dissolves many cmpds
Self ionization of water
Filters UV in aquatic systems
High surface tension
High wetting ability
Water Supports All Life
• Poorly managed resource
– We waste it
– We pollute it
• Availability
– 97.4% is salt water
– 2.6% is usable for fresh water
• Usable water
Usable Fresh Water
• The 2.6% is the following:
– Polar caps
– Deep ground water (gw)
– Usable fresh water is:
• Ground water
• Water vapor
• Streams & lakes
• World supply of water
– Equated to 26 gal total:2.5 teaspoons for us
• Hydrologic Cycle
Global Warming
• Global warming can increase the rate of
evaporation
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Shift precipitation patterns
Disrupt water supplies
Disrupt food supplies
River & stream flow rates may change
Types of Water Resources
• Surface water – does not penetrate the
ground
– Runs off to bodies of water
– Evaporates into the atmosphere
• Ground water – percolates through the soil
and rocks
– Zones of saturation
Ground Water
• Zones of Saturation
– Water table is the top
– Aquifers lie along the bedrock
• Naturally recharge
• Fluctuates by elevation & pressure
• Flow depends on the level of the water
table, stream elevation, etc
Human Influence
• Data from 2002
– During the last century, the population increased 3X
while the water consumption increased 7X
– Use 55% of the available water
– For over 500 million people, water is scarce
• Projected for 2025
– Use will increase to 70% of available water
– 2.4-3.4 billion people, water will be scarce
Annual Precipitation
• 41cm or less/year
– Western US
• 41-81cm/year
– Middle US states
• 81-122cm/year
– Northeastern US
• 122cm or more/year
– Southeastern states
– West costal land
• Much of the US experience water shortages
Fresh Water Supply
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Dams and reservoirs stop runoffs
Reroute surface water to more needed areas
Withdraw gw from depths
Desalinate water to remove salt
Reduce waste
Reclaim fresh water
Desalination
• Processes
– Distillation – boiling off water & purifying it
– Reverse osmosis – forcing it through a
membrane to remove the salt
• Disadvantages
– Expensive
– Produces large amounts of waste salts
• Example - web
Flooding
• Heavy rain & snow melts
• Floodplains – productive wetlands
– Fertile soil
– Ample water
– Suitable water recreation
• Recharge the ground water
Reduce Flooding
• Channelization
– Straighten streams
– Deepen stream beds
– Increase stream flow, you increase erosion
• Build levees
– Contain and speed up flow
• Build dams
– Contain water in reserves
• Identify and manage flood prone areas
Sources of Water Pollution
• Change in water quality
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Infectious agents
Oxygen demanding waste
Inorganic chemicals
Organic chemicals
Excess plant nutrients
Sediments
Radioactive materials
Heat (thermal pollution)
Water Quality
• Coli form bacteria
– WHO 0/100ml drinking water
– EPA 200 colonies/100 ml swimming water
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Dissolved oxygen
Biological oxygen demand - BOD
Chemical analysis – chemical pollutants
Indicator species – reveal certain pollutants
Sources of Water Pollution
• Point Source – can identify the source of the
pollution
– For example – a water or sewer pipe
• Non-point Source – can not be traced to any
one particular site
– For example – agricultural runoff (which
farm?)
Safe Drinking Water
• 1970 – 30% of developed countries had safe
drinking water
• 2000 – 72% had safe drinking water
• Still 1.4 billion people world wide that do
not have safe drinking water
• Cost would be $23 billion/year for 8-10
years to provide safe drinking water for all
Pollution of Fresh Water
• Flowing streams can recover fast
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US Stream Data
Large amount of aquatic species die
Hudson River clean-up
Burning of Cuyahoga River (1959 & ‘69)
• Lakes flow less and contain stratified layers
– Pollution remains longer
– Settles in the benthic layer in a concentration of
pollutants
– Eaten by organisms that are part of the food web
Cultural Eutrophication (CE)
• Nutrient rich inputs into a lake
• Nutrients added by humans (nitrates &
phosphates)
• Hot weather promotes dense growth of
weeds
• Decomposition of weed produce excess
nutrients
• Anaerobic bacteria take over
Preventing CE
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Waste water treatment
Ban or limit the use of phosphate soaps
Soil conservation
Clean-up
– Mechanically remove weeds
– Control weeds by herbicides & algaecides
– Introduce oxygen into the water
Groundwater Pollution
• Principle water supply
• Can not recover
• One or more organic chemical pollutants are
found in 45% of municipal water supplies
• Out of 26,000 industrial waste pond &
lagoons, 1/3 are not lined to prevent toxic
liquid waste from entering the groundwater
Ocean Pollution
• Off shore dumping
– Dredge spoils
– Sewage sludge – toxic mixture of chemicals and
infectious agents
• Coastal areas input waste directly and many are
untreated
• Beach pollution
• Shellfish contamination
• Human viruses from raw sewage
• Crude oil & refined petroleum spills
Oil Spill Clean-up
• Mechanical methods
– Vacuum
– Floating booms
– Absorbent agents
• Chemical methods
– Coagulating agents
– Dispersing agents
– Fire
• Physical methods
– Natural wave action
• Biological methods
– Bacteria
Clean Water Acts
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1972 – Federal Water Pollution Act
1977 – Clean Water Act
1987 – Water Quality Act
All set standards
– Allowable levels of key pollutants
– Requires polluters to have permits
– Discharge trade policy (buy credits from permit
holders)
Point Source
• Water Treatment Technologies
– Primary – screens debris and allows solids to
settle
– Secondary – biological process (aerobic
bacteria degrade 90%
– Port Labelle www.southerndatastream.com
Slides for NSF Research Trip
• Miller Brewing Company in Fulton, NY had
an underground chemical tank rupture.
– The next slide is a picture of the abatement
tower that allowed the water to pass over a
column of resin beads to remove the
contaminated VOC’s.
– The aquifer under the Miller plant contaminated
the water supply for villages surrounding the
area
Miller Brewing Company
Oswego City Harbor
• Core samples were taken from the Oswego
Harbor looking for lead, zinc and other
metals in the sediment.
– The next 2 slides show the sampling of the
sediment in the harbor
Core Sample – Lake Ontario
Core Sample – Lake Ontario