Download Chapter 21: Water Pollution

April 14, 2014
Chapter 21: Water Pollution
April 14, 2014
Point Sources
Nonpoint sources
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Infectious Agents
Types of Water Pollutants
Oxygen-demanding wastes
Plant nutrients
Organic chemicals
Inorganic chemicals
Sediments
Thermal
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Infectious agents
• Bacteria, virus, protozoa, worms
• Diarrhea kills 1.9 million people/year (children)
Fecal coliform bacteria
http://water.me.vccs.edu/courses/ENV195Micro/lab3.htm
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Dissolved Oxygen Content (DOC)
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Freshwater Streams
• natural dilution and biodegradation of waste
• overloaded or disrupted by damming, drought,
water diversion
Oxygen sag curve
Biological oxygen demand = amount of DOC needed
to break down organic waste in a given temperature
and time period
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Stream pollution
• Agriculture, industrial waste, untreated sewage
• Laws to increase waste water treatment plans and
control point-source discharge
• Clean up success stories
• Case Study: Ganges River
> Bathe, drink, religious ceremonies (cremation)
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Freshwater Lakes
• Dilution not effective: layers and little flow
• cultural eutrophication
> Nitrates (NO3 -)and phosphates (PO43-)
> blooms (algae, cyanobacteria, duckweed)
– reduce productivity of phytoplankton
– decomposition depletes O2 content
– Input and output control methods?
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Groundwater
• 50% US population (95% rural) drink water fro
groundwater
• Fertilizer, pesticides, gasoline, organic solvents
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Groundwater
• flows slowly (no dilution), low DOC (no
decomposition), cold (slow decomposition)
• MTBE (Santa Monica, gasoline additive: carciongen)
• Arsenic (Carcinogen)
• Prevention cheaper than clean up
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Ocean
• able to dilute, disperse, degrade large amounts of
degradable pollutants (deep ocean)
• coastal areas most affected
> Untreated sewage often dumped
> threaten coastal ecosystems
• Runoff of sewage and agricultural waste results in
algal blooms
> release toxins
> dead zones (hypoxia)
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Chesapeake Bay: Integrated Coastal Management
• Estuary received waste from huge drainage basin
> industry waste
> sewage treatment
> agricultural and urban runoff
> increased runoff from increased pavement
• Solution
> integrated effort of citizens + government
> land-use regulations
> ban use of phosphate detergents
> upgrade sewage plants
> restore wetlands
– oysters
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Ocean Oil Pollution
• Accidents: Exxon Valdez (1989) spilled oil in to
Alaska's Prince William Sound
• Runoff from urban/industrial runoff: waste oil,
spilled, leaked, motor oil (oil change)
Volatile organic
hydrocarbons: kill
organisms
Floating oil: coats
feathers and fur
Heavy oil: sinks,
smother bottomdwelling organisms
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BP Oil Spill: Gulf of Mexico
• Oil rig in Gulf (Horizone) exploded
• Exposed pipeline
> gushing oil out into ocean
• Accident?
> combination of:
– reduced regulation
– failure to meet safety standards
– not enough monitoring?
• Immediate and long lasting effects
> BP recently had moratorium on off shore
drilling lifted
> Still seeing effects of oil spill--oil and
dispersants found along coast, wildlife
suffering
> Economy suffers
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Clean up?
• Mechanical: floating booms, skimmer boats,
pillows filled with feathers/hair
• Chemical: dispersants to spread oil out or sink
• Fire: burn surface oil
• Bacteria: bioremediation!
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*Side note: Clarification between organic
waste and organic/inorganic chemicals
Organic = things that are alive or once alive
Organic waste = comes from plants/animals that
are biodegradable
Organic chemical = contains carbons (CH4, DDTC14H9Cl5
Inorganic chemicals = no carbons (NO3-, Hg, Pb)
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Pollution Prevention: Nonpoint sources
• Reduce soil erosion--vegetation (cover crops), less
till, etc.
• Reduce use of fertilizer and pesticides
> integrated pest management
• Reduce runoff
> Bufferzones of vegetation
> locate feedlots, waste sites away from sloped
land, water, flood zones
• Reduce/reuse animal waste
> natural gas (methane digester)
> building material?
http://commons.wikimedia.org/wiki/File:2004_0609_Italian_ryegrass_cover_crop.jpg
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Pollution Prevention: Point sources
• Legislation
> Water Quality Act
– States develop and set water quality
standards for interstate waters
– Not enough to just set standards
> Clean Water Act (amended in 1972)
– discharge permits
> possible discharge trading policy?
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Sewage Treatment
• Septic tank (small scale, for a house)
• Oil/grease floats to top
• Solids fall to bottom: decomposed by bacteria
• Partially treated wastewater discharged in drainage field:
filtered by soil
• Sludge/scum need to be taken out every few years
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Sewage Treatment: Sewage treatment plants
• primary sewage treatment = physical process
> screen-remove floating objects
> grit chamber-allow sand/rocks to settle
> settling tank-suspended organic solids settle
out as sludge
– removes 60% suspended solids, 30-40% of
oxygen-demanding organic waste
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Sewage Treatment: Sewage treatment plants
• secondary sewage treatment = biological process
> aeration tank-aerobic bacteria remove 90%
dissolved and biodegradable oxygen demanding
organic waste
> settling tank-settles out microbes (activated
sludge
• tertiary treatment
• chlorination (safe?)
> kills microbes
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Sewage Sludge--contains bacteria, toxic chemicals,
metals
• 9% --> compost for soil conditioner
• 36% --> biosolids for fertilizer
• 55% --> land fills or incinerated
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Ways to reduce sludge
• require industry to remove toxic and hazardous
wastes from water before sending to sewage
• encourage elimination or reduced use of toxic
chemicals
• composting toilet systems
• Using wetlands to treat sewage (wetland instead of
septic tank)
• genetic engineering
http://www.extension.umn.edu/environment/water/onsite-sewage-treatment/innovative-sewage-treatment-systems-series/constructed-wetlands/index.html
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Drinking Water: Water Purification Plants
• Reservoirs-improves clarity, increase DOC, allow
particles to settle
> filtration if necessary
• Purification plant
> disinfection
– ozonation
– chlorination
• *Cheaper to protect watershed than build water
purification
Other additives:
• fluoride
• softener
http://www.columbus.gov/Templates/Detail.aspx?id=16049
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Drinking Water in Developing Countries
• lack centralized water treatment systems
• Use:
> Sun!-Heat + UV (plastic bottles)
> Small, portale filters
– cloth
– LifeStraw
– nanofilters?
> Water purification packets (Chemicals)
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Safe Drinking Water Act (1974)
• maximum contaminant levels
• not always met
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Safe Drinking Water Act and the Clean Water Act
Who likes them? Who doesn't? What's the right
solution?
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Bottled Water
• Necessity in some parts of the world
• in US
> some is just tap water (Dasani anyone?)
> regulated by FDA and EPA standards
(same as tap)
– FDA sets certain criteria for using
words like "purified" or adding fluoride
>
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Indirect Potable Reuse or "Toilet to Tap"
• Sewage --> Drinking Water
• Take effluent from sewage treatment center +
further processing
> filtration
> reverse osmosis
> disinfection (hydrogen peroxide, UV, chlorine)
• Natural processing
> recharge basin
> lakes/ponds
> pumped into aquifer
http://content.time.com/time/health/article/0,8599,1866469,00.html
Percolation Pond in Anaheim, CA
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Activity 1: (7 minutes) In groups of 4 discuss the
following assigned topic about the Clean Water Act
and Safe Drinking Water Act. Each group will then
share with the class.
1. Summarize the essential components of the Clean Water
Act.
2. Summarize the essential components of the Safe Drinking
Water Act.
3. What are similarities between the two acts?
4. What are differences between the two acts?
5. What groups or individuals are interested in strengthening
the two acts? What arguments would they make?
6. Who opposes the strengthening of the two acts or is
fighting to weaken them? What arguments would they make?
7. What new components would you recommend adding to
the acts and why?
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Activity 2: (10 minutes) Diagram the water cycle,
but incorporate human water use and treatment.
*What aspects of sewage treatment, potable water
purification, and "toilet to tap" mimic natural
processes?
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