Transcript chapter 14 lecture2

Chapter 14
Water Pollution
Chesapeake Bay
• Largest estuary in US
• Drains from watershed full of chemicals, plant
nutrients (phosphates and nitrates) and
sediments
• Cause harmful algal blooms
• Sediments make water turbid and choke out
grass
• Has pesticides and pharmaceuticals
• Negatively affected sexual development of
fish
Key Ideas
• Distinquish between point- and
nonpoint-source pollution
• How does human waste water cause
water pollution
• How is waste water treated
• Identify different types of water
pollutants
• List impacts of oil spills
• Identify nonchemical pollutants
Water Pollution

Water pollution- the contamination of streams, rivers,
lakes, oceans, or groundwater with substances
produced through human activities and that
negatively affect organisms.

Point sources- distinct locations that pump waste into
a waterway.

Nonpoint sources- diffuse areas such as an entire
farming region that pollutes a waterway.
Which is the nonpoint source?
Review Questions
• What is water pollution? Why is it
important to learn about water pollution?
• What are point and nonpoint sources?
How do they differ?
• What are the most common types of
pollutants in the water?
Human Wastewater

Water produced by human activities such as human
sewage from toilets and gray water from bathing and
washing clothes or dishes.
Three Reasons Scientists Are Concerned
about Human Wastewater:

Oxygen-demanding waste- a waste that is
decomposed by bacteria, and puts a large demand
for oxygen in the water

Nutrients that are released from wastewater
decomposition can make the water more fertile
causing eutrophication

Wastewater can carry a wide variety of diseasecausing organisms.
WATER POLLUTION: SOURCES,
TYPES, AND EFFECTS
•
Major sources of water pollution:
– Agriculture
• Sediment, fertilizer, pesticides, bacteria
– Industries
• Organic and inorganic chemicals
– Mining
• Eroded sediments and runoff of toxic
chemicals
Types of Pollutants
- Oxygen-demanding wastes-
-
Organic wastes that can be
decomposed by aerobic bacteria
Degrade water quality by depleting
water of dissolved oxygen; reduction in
aquatic populations.
Source: animal waste feedlots, etc.
Major Water Pollutants
and Their Effects
•
Water quality and dissolved oxygen (DO)
content in parts per million (ppm) at 20°C.
– Only a few fish species can survive in water
less than 4ppm at 20°C.
POLLUTION OF FRESHWATER STREAMS
• Flowing streams can recover from a
moderate level of degradable water
pollutants if they are not overloaded and their
flows are not reduced.
– In a flowing stream, the breakdown of
degradable wastes by bacteria depletes
DO and creates and oxygen sag curve.
• This reduces or eliminates populations of
organisms with high oxygen
requirements.
Water Pollution Problems in
Streams
• Dilution and decay of degradable, oxygendemanding wastes and heat in a stream.
Biochemical Oxygen Demand
(BOD)

BOD- the amount of oxygen a quantity of
water uses over a period of time at a specific
temperature.

Lower BOD values indicate the water is less
polluted and higher BOD values indicate it is
more polluted by wastewater.
What is BOD?
•
Biological Oxygen
Demand (BOD) is the
amount of dissolved
oxygen needed by
aerobic decomposers
to break down the
organic materials in a
certain volume of water
over a 5-day incubation
period at 20°C (68°F)
BOD
Water Quality
1-2
Very Good
3-5
Moderate
6-9
Fairly Polluted
10+
Very Polluted
(PPM)
BOD Effects on Water Quality
All streams have some capability to degrade organic waste.
Problems occur when stream is overloaded with biochemical
oxygen-demanding waste.
Detecting Pollutants
•
•
•
Chemical Analysis- used to determine the
presence and concentrations of most water
pollutants
Living Organisms- used as an indicator species
to monitor water pollution. Ex. Filter-feeding
mussels, Mayflies
Computer Models- used to find complex inputs
and interactions that couldn’t be determined
through chemical or biological methods.
Contaminants in Streams
• Wide variety of
chemicals
•
•
Pharmaceutical
drugs
Hormones
• Come from waste
water, agriculture,
forestry and
industry
Other Water Pollutants

Solid waste pollution (garbage)

Sediment pollution (sand, silt and clay)

Thermal pollution

Noise pollution
Types of Pollutants
• Inorganic Plant Nutrients
– Examples include water-soluble nitrates
and phosphates
– Causes overgrowth of algae which leads
to the depletion of dissolved oxygen and
the death of fish
– Sources- runoff from fertilizers, manure
Cultural Eutrophication

Eutrophication- an abundance of fertility
to a body of water.

Cultural Eutrophication- caused by an
increase in nutrients, such as fertilizers,
as a direct result of human activities

Eutrophication can cause a rapid growth
of algae which eventually dies, causing
the microbes to increase the BOD.
Oxygen Depletion in the
Northern Gulf of Mexico
• A large zone of
oxygen-depleted
water forms for
half of the year
in the Gulf of
Mexico as a
result of HAB.
This is called the
“Dead Zone.”
Types of Pollutants
•
Disease-causing agents (infectious
agents)-
– Pathogens that cause disease
– Ex. bacteria, viruses, protozoa, and parasitic
worms
– Source: human and animal wastes
Table 21-2, p. 495
Review Questions
• How does high BOD influence water
quality?
• What is a “dead zone?” How do
nitrogen and phosphorus contribute to
dead zones?
• What pathogens are common in poorly
treated wastewater? Where are they the
biggest threat?
Treatments for Human and
Animal Wastewater

Septic systems- a large container that receives
wastewater from the house.
Reducing Water Pollution Through Sewage
Treatment
•
Raw sewage reaching a municipal sewage
treatment plant typically undergoes:
– Primary sewage treatment- a physical
process that uses screens and a grit tank to
remove large floating objects and allows
settling.
– Secondary sewage treatment- a biological
process in which aerobic bacteria remove as
much as 90% of dissolved and biodegradable
oxygen demanding organic wastes.
Wastewater Treatment
Plants
• Wastewater entering a plant is ~99.94
percent water, only 0.06 percent of the
wastewater is suspended solid material.
• Facility uses a multi-stage process to
process the wastewater.
• Goal is to reduce or remove organic
matter, solids, nutrients, diseasecausing organisms and other pollutants
from wastewater.
Municipal Sewage Treatment
•
Primary- physically separates
large solids from the waste stream
– Metal grating- removes large debris
– Moving screen- filters out smaller
items
– Grit tank- allows sand and sediment
to settle
– Primary sedimentation tank-
about
half the suspended organic solids
settle out as sludge
Bar Screen
Municipal Sewage Treatment
•
Secondary Treatment- biological
degradation of dissolved organic
compounds.
– Aeration tank- waste aerobically
decomposed by bacteria
– Water flows from top of the tank and
sludge is removed from the bottom
– Sludge is disposed in sanitary landfill
– Effluent treated with chlorine, UV light,
or ozone to kill harmful bacteria before
being released to a nearby waterway
Reducing Water Pollution
through Sewage Treatment
• Advanced or tertiary sewage treatment– Uses series of chemical and physical
processes to remove specific pollutants left
(especially nitrates and phosphates).
Reducing Water Pollution
through Sewage Treatment
• Primary and Secondary sewage treatment.
Primary Treatment – Bar Screen
http://blogs.howstuffworks.com/2010/10/27/how-is-waste-water-treated/
Primary Treatment – Settling Tank
Secondary Treatment: Aeration Tanks
Secondary
clarifier
Aerobic
digester
Final Product: Clean Water
Clean water going
out of plant
Noonday Creek:
where water is
discharged
Recycled Water
•
•
Cleaned an sanitized water goes directly from
the waste water treatment plant to the drinking
water plant, where the water is further treated
to make it potable
Advantages:
•
•
•
Keeps water with the same watershed
Prevents water loss during times of drought
Allows community to closely monitor its
drinking water supplies
Treating Water Naturally
•
•
Wetlands naturally
absorb organic and
inorganic pollutants.
Constructed
wetlands can be
used to remove
pollutants before
returning to water
source
Treatments for Human and Animal
Wastewater

Manure lagoons- large, human-made ponds line with
rubber to prevent the manure from leaking into the
groundwater. After the manure is broken down by
bacteria, it is spread onto fields as fertilizers.
Types of Pollutants cont.
•
Water-soluble inorganic chemicals
– Examples are acids, salts, and
compounds of toxic metals (lead,
mercury and arsenic)
– Affected water is unfit to drink and is
harmful to aquatic life.
– Damages nervous system, liver,
kidneys, skin cancer.
Review Questions
• What problems are associated with
sewage?
• Describe and contrast the two most
common ways to treat wastewater.
• Describe the advantages and
disadvantages of both septic systems
and sewage plants.
• What is the role of bacteria in the
treatment of human and animal waste?
Heavy Metals
• Lead-
• Rarely found naturally in drinking
water
• Primary source is plumbing in older
homes
• Is a neurotoxin
Heavy Metals
• Arsenic
• Naturally occurs in Earth’s crust and
can dissolve in groundwater
• Mining and industrial uses for
arsenic also contaminate water
• It is poisonous
Arsenic in US well water
Heavy Metals
• Mercury
•
•
•
•
Primary source is burning of coal
Also comes from burning or incinerating
garbage, hazardous waste, medical and
dental supplies
Methylmercury is the most poisonous
form, and results from a conversion
from elemental mercury by bacteria
It is a neurotoxin
World mercury production
Acid Deposition
•
•
•
•
Acid deposition- acids deposited on Earth
as rain and snow or as gases and
particles that attach to the surfaces of
plants, soil and water
pH of below 5.6 is considered acidic
Causes a release of poisonous aluminum
ions into soil and water
Primary source is burning fossil fuels
Water Pollution from Mine
Tailings
•
Both sediment and
sulfur contaminate
streams from runoff
• 4FeS2 + 14H2O =
4Fe(OH)3 + 8H2SO4
Low pH water mixes with stream water,
causing iron to precipitate out
•
•
•
Types of Pollutants
Organic chemicals
Examples include gasoline, oil, plastics,
pesticides, cleaning solvents, detergents,
medicines
Threaten human and aquatic life; impacts
nervous system. Can cause cancer in
humans.
Types of Pollutants
• Pharmaceuticals and hormonesthese are not removed by most
wastewater treatments and are
released back into the water supply
•
•
•
Specific Chemical Pollutants
MTBE- additive in gasoline; leaks into ground
water through leaking underground storage
tanks. Tastes and smells bad, makes water
unpotable
PFCs- Pefluorinated compounds, used in
nonstick cookware and stain-resistant
products. Affects hormones and suppresses
immune system
PBDE- Flame retardants in sofa cushions and
electronics. Hormone disruptor, affects
development of fetuses
Review Questions
• Describe the primary dangers
associated with heavy metals in water.
• Explain the role of acid deposition in
water pollution
• Name examples of synthetic
compounds that have been found in our
water supply and explain why they are a
concern.
OCEAN OIL POLLUTION
• Tanker accidents
and blowouts at
offshore drilling
rigs can be
extremely
devastating to
marine life
(especially diving
birds, left).
Sources of Oil in the Ocean
Oil contamination in the ocean comes from a
variety of sources, including transport and
extraction from underneath the ocean.
Oil and the Ocean
• The effects of oil on ocean ecosystems
depend on a number of factors: type of
oil, amount released, distance of
release from shore, time of year,
weather conditions, average water
temperature, and ocean currents.
• Spills can result in the death of
numerous aquatic organisms.
Cleaning Up Oil Spills
•
Mechanical Methods:
– Floating booms to contain the oil spills
or keep it from reaching sensitive areas
– Skimmer boats to vacuum up some of
the oil into collection barges
– Absorbent pads or large feather-filled
pillows to soak up oil on beaches or in
shallow water.
Cleaning Up Oil Spills
• Chemical Methods:
– Coagulating agents to cause floating
oil to clump together for easier
pickup or sink to the bottom where it
will do less harm
– Dispersing agents to break up oil
slicks
Cleaning Up Oil Spills
• Fire can burn off floating oil, but this
method causes more harm than good
(air pollution).
• Natural Action:
– Wind and waves will mix oil with water
– Bacteria will biodegrade some of the
oil
Gulf Oil Spill
Burning off surface oil
Deepwater Horizon rig in
flames, last April.
Seabird caught in the oil slick
on a beach on Louisiana's
East Grand Terre Island
Review Questions
• Name several ways in which oil gets
into the ocean.
• Describe the effects of an oil spill.
• What are three ways to remediate an oil
spill?
Solid Waste Pollution
•
Garbage is dumped
in the ocean and
washes up on shore
•
•
It is hazardous and
deadly to wildlife
Leachate from coal
ash and slag can
contaminate
groundwater
Citarum River in Indonesia
Ocean Pollution
http://plastic-waste-pollution.weebly.com/
http://www.midwayfilm.com/
http://pubs.acs.org/doi/abs/10.1021/es400663f
Microplastic Pollution
• Plastic will break
down into tiny
pieces, which can
be ingested by
organisms
http://www.commondreams.org/news/2014/04/17/how-one-state-takingmicro-plastics-polluting-its-waterways
• If they remain in the
organism, it is
possible that they
could
bioaccumulate
http://www.lfpress.com/2015/03/30/ottawa-mpp-is-leading-the-charge-to-ban-theuse-of-microbeads-in-ontario
Ocean Garbage Patches
•
•
•
•
Form in ocean gyres
Have high concentration of
plastic pelagic garbage in
upper water columns
The plastics break down to
molecular sizes and get into
the food chain
en:Image:Oceanic gyres.png.
For more information:
Marine Debris Program Marine Debris Info
Photo courtesy of AP /
Scripps Institution of
Oceanography / Mario
Aguilera
Types of Pollutants
• Sediment/Suspended Matter
– Biggest class
– Examples include insoluble particles of
soil and other solids released by
erosion.
– Sediments cloud water and disrupt
aquatic food webs.
Types of Pollutants
•
Thermal pollution
– Caused by the heat absorbed by the water used
to cool nuclear power plants. This water is
returned to natural environment warm.
– Lowers dissolved oxygen levels
– Causes an abrupt change in temperature- thermal
shock.
Types of Pollution
• Noise pollution- noise so loud that it
disrupts organisms’ ability to
communicate with each other
• Sources include military sonar,
underwater air guns, ships and
submarines
Review Questions
• Name three types of nonchemical water
pollution.
• How can nonchemical water pollution
be addressed?
• What are some examples of noise
polltuion as it relates to water?
Water Legislation

Clean Water Act- (1972) supports the
“protection and propagation of fish, shellfish,
and wildlife and recreation in and on the
water”.

Issued water quality standards that defined
acceptable limits of various pollutants in U.S.
waterways.
Water Lesgislation

Safe Drinking Water Act- (1974, 1986, 1996)
sets the national standards for safe drinking
water.

It is responsible for establishing maximum
contaminant levels (MCL) for 77 different
elements or substances in both surface water
and groundwater.
Green Solutions to
Wastewater Treatment
Microbes, algae,
plants and snails
can be used to
consume excess
nutrients present
in wastewater.
Tertiary treatment
occurs in a manmade wetland
inside a
greenhouse.
Review Questions
• What is an MCL?
• What is the relationship between
economic development and clean
water?
• Describe some of the legislative actions
taken to protect clean water and why
they are significant.