Transcript WFSC 420 Lesson 11

Environmental Sciences: Towards a
Sustainable Future Chapter 17
Water: Pollution and Prevention
Introduction:
MISSISSIPPI WATERSHED
Mississippi River
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The Mississippi river and its tributaries
encompass 40% of the US land mass.
Eventually delivers water to the Gulf of
Mexico.
As tributaries travel through agricultural
land they carry fertilizer runoff to the
Mississippi then to the Gulf.
Dead zone
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Nitrogen carried to the marine waters causes
eutrophication.
Eutrophication causes an area of depleted
oxygen (dead zone)
This was noticed by biologists in 1974 who
thought it to be similar to the occurrence at
Chesapeake Bay which has seasonal hypoxia
(depleted oxygen/dead zone) but later became
aware of the connection between nitrogen and
the hypoxia.
Gulf Fisheries
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With the dead zone expanding, the
Gulf fishing industry was eventually
affected.
$2.8 billion enterprise
Gained national attention and
eventually congress passed the
Harmful Algal Bloom and Hypoxia
Research and Control Act.
Two key strategies

The two key strategies to mitigating
the problem are:
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Reduce nitrogen loads to streams and
rivers in the Mississippi basin by using
less fertilizer and thereby reducing farm
runoff.
Restoring and promoting nitrogen
retention and denitrification processes
in the basin.
Dead zones around the world:
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Since 1960 the number of dead zones
has doubled every decade.
Worldwide, over 200 dead zones are
now known according to the UN
environment program.
Pollution
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EPA defines Pollution: “the presence
of a substance in the environment that
because of its chemical composition or
quantity prevents the functioning of
natural processes and produces
undesirable environmental and health
effects.”
How does it get there:
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Pollutants are almost always the
byproducts of otherwise worthy
activities…
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Planting crops, creating comfortable
homes, providing energy and
transportation, and manufacturing
products.
Figure 17-2 page 439
Pollution Categories
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Air
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Particulates
Acid-forming compounds
Photochemical smog
CO2
CFC’s
Pollution Categories
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Water and land
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Nutrient oversupply
Solid wastes
Toxic chemicals
Pesticides/herbicides
Nuclear waste
Controlling pollution
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The general strategies to making sure that
pollution will not jeopardize current and
future generations:
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Identify the pollutants
Identify the source
Clean up the environment already impacted
Develop and implement pollution control
Develop and implement alternative means of
meeting the need that do not produce the
pollution.
Point source pollution:
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Involves discharge of substances from
factories, sewage systems, power
plants, underground coal mines and oil
wells.
Relatively easy to identify.
Easier to regulate.
Nonpoint source pollution
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Scattered over broad areas such as
runoff, storm water drainage,
atmospheric deposition.
Harder to identify source
Harder to regulate
Point and Nonpoint Sources of Pollution
Strategies to control water pollution:
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Reduce or remove the source
Treat the water before it is released so
as to remove pollutants or convert them
to harmless forms.
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Water treatment is the best option for
point source
Source reduction can be employed for
both point and non point and is the best
option for non point.
Types of Water Pollutants
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Pathogens
Organic Wastes
Chemical
Sediments
Nutrients
Pathogens
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Disease-causing bacteria, viruses and
other parasitic organisms (Table 17.1)
Safety measures
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purification of public water supply
sanitary collection/treatment of sewage
sanitary practices when processing food
Modern medicine
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Beside modern medicine, the following have
been important factors in controlling waterborne
disease:
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Purification and disinfection of public water
supplies
Sanitary collection and treatment of human and
animal wastes
Maintenance of sanitary standards in all facilities in
which food is processed or prepared
Instruction in personal and domestic hygiene
Good health
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Good health is primarily a result
of prevention of disease through
public-health measures.
Millennium Development Goal Seven
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To cut in half the amount of people
living without sustainable access to
safe drinking water and basic
sanitation by the year 2015.
Cholera Outbreaks
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Peru, 1990.
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Several thousand people died due to a
cholera outbreak caused by unsanitary
conditions.
Sudan, 2006
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Civil unrest lead to disruption of
sanitation practices, several thousand
sick, 500 dead from cholera.
DO
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Dissolved oxygen
The amount of oxygen that water can
hold in solution is very limited.
In cold water dissolved oxygen can
reach 10 ppm and even less in warm
water.
Organic Wastes
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Dissolved oxygen (DO) in the water is
depleted during decomposition of organic
wastes.
Water quality test.
 Biochemical oxygen demand (BOD):
measure of the amount of organic material.
 As BOD increases, dissolved oxygen
decreases.
 If the system goes anaerobic, only bacteria
can live.
Chemical Pollutants
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Inorganic chemicals
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Heavy metals, acids, road
salts
Organic chemicals
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Petroleum, pesticides,
detergents
Biomagnification
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Pollutants are
concentrated as
they pass up the
food chain
Pollution: Sediments on Stream Ecology
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Loss of hiding-resting places for small
fish.
Attached aquatic organisms scoured
from the rocks and sand.
Poor light penetration
Nutrients and aquatic plants
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Nitrogen and phosphorus
Fresh water affected more by
phosphorus
Salt water affected more by nitrogen
Many of these nutrients are found in
water only because of human activity.
NRWQC
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National Recommended Water
Quality Criteria
EPA lists 167 chemicals and
substances as criteria pollutants.
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Identifies pollutants and then
recommends concentrations for fresh,
salt, and human consumption (fish and
shel fish consumption).
Drinking water standards
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Drinking water standards are stricter.
Drinking water standards and health
advisory: set of tables updated
periodically.
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Covering 94 contaminates
Under authority of SWDA (safe water
drinking act)
NPDES
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National pollution discharge
elimination system
Addresses point sources and issues
permits that regulate discharges from
waste water treatment plants and
industrial sources.
TMDL
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Total maximum daily load
Evaluates all sources of pollutants
entering a body of water, espaecially
non-point sources, according to the
water’s ability to assimilate the
pollutant.
Lesson 17.2
WASTEWATER
MANAGEMENT AND
TREATMENT
History of waste removal
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Before late 1800’s: wastes were disposed of in the
outdoor privy (or behind the nearest bush)
 Frequently contaminated drinking water.
Late 1800’s excrements disposed of in the already
existent storm water drains.
 Floods and over flow sent wastes floating in the
streets.
1900 the first waste water treatment facilities were built.
Gradually storm and waste water pipes were separated.
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Storm drains are not sewers
Sewers
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Most sewer bound materials are 99.9% water,
0.1% waste.
The pollutants of waste water are divided into
four categories:
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Debris and grit
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Particulate organic matter
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Fecal matter, food wastes, toilet paper
Colloidal and dissolved organic matter
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Rags, plastic bags, course sand and gravel
Bacteria, urine, soaps
Dissolved inorganic matter.
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Nitrogen, phosphorus
Waste water treatment facility
1.
2.
3.
Preliminary treatment
• screening of debris and
settling of grit
Primary treatment
• Water moves slowly
through tanks, organic
matter settles and is
removed (raw sludge).
Secondary treatment
• Live organisms break
down organic matter to
CO2, mineral nutrients,
and water.
Activated sludge system:
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Oxygen is added to the secondarytreatment system through an airbubbling system. A mixture of debris
eating organisms (activated sludge) is
added to the water and is vigorously
aerated. Organisms reduce the
biomass of the organic materials.
BNR
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Biological Nutrient Removal
A secondary activated-sludge system
added to remove nutrients and oxidize
detritus. (added because of culturaleutrophication).
Because this water is actually purer
than the body of water that it enters, it
will dilute the pollutants in the body of
water, improving the quality.
Raw Sludge
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Gray, foul smelling, syrupy liquid with a water
content of 97%-98%.
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Pathogens are certain to be present.
Biologically hazardous
However, as a nutrient-rich organic material, it
has the potential to be a good fertilizer if it is
treated to kill pathogens.
Anaerobic digestion
 Composting
 Pasteurization
 Unclear which will prove to be best and most cost
effective
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Anaerobic digestion
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Bacteria feed on detritus in the
absence of oxygen.
Sludge digesters turn the organic
matter into CO2, methane, and water.
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Biogas (2/3 methane gas product)
The leftover 1/3 makes a good organic
fertilizer.
Composting
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Used to treat sewage sludge.
Raw sludge mixed with wood chips or
some other water absorbing material.
It is then placed in long rows
(windrows)that allow air to circulate.
A machine turns the material, bacteria
and other decomposers break it down
turning it into an excellent humus-like
material.
Pasteurization
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Heated sufficiently to kill pathogens.
The product, a dry odorless organic
pellet.
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Used as organic fertilizer.
Alternative Treatment Systems
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Individual septic systems
Wastewater effluent irrigation
Reconstructed wetland systems
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Beaumont, TX
The waterless toilet
Septic Tank Treatment
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Aerobic digestion
of solids in septic
tank.
Flow of liquids
into drain field for
evaporation,
infiltration, or
irrigation.
Suggestions for maintenance
1.
Use caution when disposing of
materials down the drain.
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2.
3.
4.
Can fill up or clog system.
Have system inspected regularly
Considering disabling garbage
disposals
Keep heavy equipment off your field
Lesson 17.3
EUTROPHICATION
What is eutrophication?
Aquatic Plant Life
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Benthic plants
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Emergent vegetation
Submerged aquatic vegetation (SAV’s)
Phytoplankton
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Green filamentous and single cell
Bluegreen single cell
Diatoms single cell
Nutrient Enrichment
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Oligotrophic: nutrient-poor water
Eutrophic: nutrient-rich water
What kind of plants would dominate in
oligotrophic and eutrophic conditions?
Eutrophication
Oligotrophic
Eutrophic
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As nutrients are
added from
pollution, an
oligotrophic
condition rapidly
becomes
eutrophic.
Eutrophic or Oligotrophic?
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High dissolved O2
Deep light penetration
High phytoplankton
Eutrophic or Oligotrophic?
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Turbid waters
High species diversity
Good recreational qualities
High detritus decomposition
Eutrophic or Oligotrophic?
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Low bacteria decomposition
Benthic plants
Warm water
High nutrient concentration
BOD
High sediments
Natural Vs. Cultural Eutrophication
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Natural eutrophication
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aquatic succession
occurs over several hundreds of years
Cultural eutrophication
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driven by human activities
occurs rapidly
Combating Eutrophication
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Attack the symptoms
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Chemical treatment
Aeration
Harvesting aquatic weeds
Drawing water down
Combating Eutrophication
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Getting at root cause
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Controlling point sources
Controlling nonpoint sources
Collecting Ponds
Biological Nutrient Removal
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Activated sludge: 3 zones
Conversion of NH4 to NO3
NO3 converted to N gas and released
PO4 taken up by bacteria and released
with excess sludge
Biological Nutrient Removal