Download The Water Cycle

The Water Cycle
13,000
Atmosphere
(111,000)
Ice & Snow
33,000,000
(71,000)
(385,000)
km 3
(40,000)
(425,000)
(km 3/yr)
Groundwaters
15,300,000
Oceans
1,350,000,000
The Water Cycle
0.001%
Atmosphere
Ice & Snow
2.1%
0.2 %
Inland Waters
(Surface Waters)
Groundwaters
0.6%
Oceans
97.1%
The Water Cycle
All Water
Fresh Water
Ground
Water
0.6%
Oceans 97.4%
Ice Caps &
Glaciers 2%
Readily Available
Biota
Rivers
Lakes
0.006%
Soil Moisture
0.004%
Atmos H2O
0.001%
100 liters (26 gal)
3 liters (0.8 gal)
0.003 liters
(1/2 tsp)
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The Water Cycle
Groundwaters
Freshwater found under
the earth’s surface
e.g. Aquifers
&
Surface waters
Freshwater found on
the earth’s surface
Replenished by precipitation
(Renewable but finite)
» Rivers
» Lakes
» Ponds
» Reservoirs
» Wetlands
The Water Cycle - Groundwater
Aquifers
Vadose
Zone
Water
Table
Porous Rock
The Water Cycle - Groundwater
recharge
Aquifers
recharge
Groundwater travels slowly: several millimeters to a few meters per day.
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The Water Cycle - Groundwater
Artesian
well
Aquifers
Water
table
well
The Water Cycle - Groundwater
Groundwater is a NON-renewable resource
It takes 100’s to 1000’s of years for groundwater
to accumulate and only a small % is replaced each
year.
The Water Cycle - Groundwater
» The world’s largest aquifer,
3.3 B acre-feet, would cover
lower 48 states to a bout 2
feet deep
» Every year, 6 million acrefeet withdrawn, about 14 B
gallons per day for farming
and 330 M gallons per day for
human consumption
» But recharge is only 185,000
acre-feet per year
» Will be depleted some time in
the next 200 years
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Water Pollution - Introduction
Groundwater Pollution Sources
HW VOCs
evaporate
pollutants rain-out
landfill
septic
system
nitrates &
phosphates
(farm runoff)
gasoline
storage
sewer
hazardous waste
holding tank
leaking well-casings
Water Pollution - Introduction
Urban Water Pollution Sources
organic wastes, garbage, animal
droppings, grass and leaves
Zinc (Zn) from aging
pipes and gutters
Copper (Cu) from brake
linings, worn pipes and
fittings
N & P from fertilizers
used
motor
oil
storm-drain runoff
Water Pollution - Introduction
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Water Pollution - Clean Drinking H2O
U.S.
U.S.
Popul
Popul
270 M
with
» Sources of municipal water
include:
» Streams, rivers, lakes,
aquifers and reservoirs
Muni
H 2O
232 M
86 %
» Most municipal water supplies
are treated before being used
» Treatment is a 2 - 4 step
process
Water Pollution - Clean Drinking H2O
Treatment is a 2 - 4 step process
1.
Aluminum sulfate [Al 2(SO4)3] is added
to decrease turbidity (i.e. cloudiness).
2.
The water is filtered through sand,
which removes suspended particles and
micro-organisms
3.
Water may be pumped through
charcoal (e.g. a giant Brita® filter)
4.
Water is disinfected
Usual steps
Water Pollution - Disinfection
Three methods of disinfection in use:
Chlorination
Ozonation
Radiation
Chlorine (e.g. as bleach or as
chlorine gas) used to kill microorganisms
Most common - least $$$
bad stuff
in H2O
+ chlorine
worse stuff
in H2O?
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Water Pollution - Disinfection
Three methods of disinfection in use:
Chlorination
Ozonation
Radiation
Ozone [O3] used to kill microorganisms
Less common, used more in Europe
than U.S. - more $$$
Side-effects not well known
Water Pollution - Disinfection
Three methods of disinfection in use:
Chlorination
Ozonation
Radiation
Ultraviolet (UV) radiation used to
kill microorganisms
Common in Europe - more $$$
No ill-health effects
Water Pollution - Treating Wastewater
Three steps:
Primary
Secondary
Tertiary
Physical
process
11% population
served by pri.
ONLY
primary
screen
sand
settling
tank
to secondary
treatment or
disinfection
primary
sludge
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Water Pollution - Treating Wastewater
Three steps:
Primary
Secondary
Tertiary
primary
Biological
process
62% of the population
served by primary and
secondary
secondary
to tertiary
treatment or
disinfection
aeration
tank
settling
tank
sec. sludge
digested sewage sludge
Water Pollution - Treating Wastewater
Three steps:
Primary
Secondary
Tertiary
septic system
waste in
scum
wastewater
sludge
treated
water out
Water Pollution - Treating Wastewater
Three steps:
Primary
Secondary Physical, biological and/or chemical
process
Tertiary
» Physical - filtration through sand
and/or charcoal
» Biological - addition of phosphate
absorbing microorganisms
» Chemical - addition of calcium
hydroxide to remove phosphates
23% population Served by primary,
secondary and tertiary
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Water Pollution - Treating Wastewater
tertiary
secondary
primary
chlorination
phosphorus
nitrogen
viruses
dissolved organics
pathogenic bacteria
sewage solids
Disease-causing Agents
Municipal water sources generally contains many
bacteria, viruses, protozoa, parasitic worms and
other infectious agents that cause human or
animal diseases
Diseases transmitted through water include:
Typhoid - bacterium
Cholera - bacterium
Bacterial dysentery - bacterium
Amoebic dysentery - protozoan
Polio - virus
Infectious hepatitis (type A) - virus
Disease-causing Agents
EXAMPLE - Summer of 1993, Milwaukee, WI
Water supply contaminated by a protozoan
cryptosporidium
not killed by chlorine - killed by ozone
About 400,000 people developed cases of
diarrhea and cramps that lasted up to 22 days!
About 100 people died.
Milwaukee has since spent $36.5 M on an
ozonation system to kill parasites at an annual
cost of $600,000.
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Monitoring for Sewage
Disease-causing agents generally carried
into the waste stream by human and
animal fecal matter
Harmless fecal coliform bacteria are found in
the fecal matter of warm-blooded animals
E. coli is a specific type of fecal coliform
bacteria and is found in our intestines by the
BILLIONS
Therefore we can test for the presence of E.
coli as an indirect indication of fecal
contamination and thus disease-causing agents
Sewage
Sewage - wastewater from toilets,
washing machines, showers, etc - includes
human wastes, soaps and detergents
Carries disease-causing agents
Creates oxygen demand
Causes enrichment
Water Pollution - Oxygen Demand
Sewage is decomposed by aerobic microorganisms
(CH2)n + O2
→
CO2 + H2O
carbon dioxide & water
sewage is made up of
mostly carbon &
hydrogen
oxygen is dissolved in
the water
dissolved oxygen (DO) is
limited and as the temperature increases the DO
decreases
bacteria compete with all
other organisms for oxygen
in the water
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Water Pollution - Oxygen Demand
Problems are exacerbated by
thermal pollution - as temp rises
oxygen levels decrease and
stressed fish use it faster
O2
direction of flow
Water Pollution - BOD & COD
We measure the amount of sewage (i.e.
organic waste) in terms of BOD & COD
Sewage =
BOD =
Organic waste
that bacteria
CAN eat
+
Organic waste
that bacteria
CAN NOT eat
biochemical oxygen demand
COD = chemical oxygen demand
COD ≥ BOD
Water Pollution - BOD Sources
Sewage - also referred to as “oxygen
consuming” wastes because of the oxygen
required to decompose them
Sources:
Humans and animals
Paper mills
Tanneries
Slaughterhouses
Meat packing plants
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Inorganic Plant Nutrients
Fertilizer runoff from agricultural and
residential land is a major contributor of
inorganic plant and algal nutrients which
cause excessive growth of plants.
» Two key nutrients: nitrates & phosphates
NO3
-
PO4 3
» Excessive growth of plants and
algae can cause:
» Bad odors
» High BOD
» Enrichment
Inorganic Plant Nutrients
Inorganic Plant Nutrients
Main sources of nitrates and phosphates
include:
» Nitrogen-containing human waste
» Phosphorus-containing detergents
» Nitrates and phosphates in fertilizers
» Industrial discharge
» Phosphate mining
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Heavy Metal Pollutants
Main sources of inorganic pollutants include:
» Industries
» Mines
» Irrigation runoff
» Oil drilling
» Urban sewer runoff
Many are toxic, but we will limit our
discussion to lead (Pb), mercury (Hg),
cadmium (Cd), chromium (Cr) and arsenic
(As).
Heavy Metal Pollutants
U.S. Environmental Protection Agency has
established maximum permissible levels in
drinking water for 11 metals:
» Antimony,
arsenic,
barium,
beryllium,
cadmium, chromium, lead, mercury, nickel,
selenium and thallium
Additionally, they also regulate radium (Ra),
uranium (U) and all other alpha and beta emitters
Heavy Metal Pollutants - Lead (Pb)
» Lead-based paint was banned in the U.S. in
1978, but the EPA estimates that more than
3/4 of all U.S. homes still have lead present.
» Most people think of lead poisoning as being an
inner-city problem when in fact lead is
everywhere. There are many sources of lead
contamination.
» Natural sources:
» Volcanoes
» Wind-blown dust
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Heavy Metal Pollutants - Lead (Pb)
Anthropogenic sources:
» Antiknock agents in gasoline ( e.g. tetraethyl lead )
» Paint
» Solder
» Lead-acid batteries
» Leachate from incinerator ash
» Old factories that lack air-pollution control
devices
» Pesticide residues ( e.g. PbAsO3)
» Dinnerware ( e.g. ceramics, leaded-crystal)
Heavy Metal Pollutants - Lead (Pb)
» According to the EPA during the mid-1990s
more than 10% of all large and medium-sized
municipal H2O supplies contain lead levels
higher than those allowed by the Safe Drinking
Water Act - 5 ppb at source
» Additionally, tap water often contains HIGHER
levels than those present in the municipal
supply ( e.g. Boston)
» The current U.S. Pb drinking water standard is
15 ppb at a 10% action level.
Heavy Metal Pollutants - Lead (Pb)
» Millions of Americans (many of them children)
have damaging levels of lead in their bodies.
According to the Agency for Toxic Substances
and Disease Registry ( located in Atlanta, GA) 17% of
American children have blood lead levels that
exceed 150 ppb; the dangerous level is set at
100 ppb.
» Three groups at greatest risk:
» Middle-aged men (hypertension)
» Pregnant women (miscarriage, still-birth, premature
delivery)
» Children (partial hearing loss, hyperactivity, ADD,
lowered IQ, learning disabilities)
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Heavy Metal Pollutants - Mercury (Hg)
» Small amounts of mercury occur naturally in
the environment. However, because it is used
in a variety of industrial processes, its
presence is widespread.
» Sources include:
» Combustion of coal - 40 Million tons
annually
» Industrial wastewater release
» Incineration of household
batteries, paints, plastics
trash
-
» Mining for precious metals in lesser
developed countries (e.g. S. America)
Heavy Metal Pollutants - Mercury (Hg)
» In its natural state mercury is relatively
harmless - probably pass right through your
system.
» However anaerobic bacteria, easily convert it
to an organic form - methylmercury which is
readily absorbed by humans and aquatic
organisms ( e.g. salmon, tuna, swordfish, shark).
» Methylmercury persists in the environment
and prolonged exposure causes - retardation,
kidney failure, irreversible CNS damage and
death.
Heavy Metal Pollutants -Cadmium (Cd)
» Cadmium has many uses. We find it in » Paints, plastics, Ni-Cad batteries and
Cadmium sulfide photodetectors
» Even with all these sources, a major concern is
its presence as a contaminant in zinc ore
» So wherever zinc is used, cadmium is present
» Intake of cadmium is known to increase the
risk of heart disease... it is also known to
displace zinc from the liver
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Heavy Metal Pollutants -
Chromium (Cr)
Cr(III) is not harmful to humans
Cr(VI) is harmful and
is generally present
as chromate CrO4-2,
which mimics sulfate
in the body
Heavy Metal Pollutants -
Arsenic (As)
Arsenic occurs naturally in the environment
highest levels
lowest levels
insufficient data
Heavy Metal Pollutants -
Arsenic (As)
Current std
is 50 ppb
supposed to
be lowered
to 10 ppb
conc [ppb]
> 50
10 - 50
5 - 10
< 5
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Heavy Metal Pollutants -
Arsenic (As)
» Arsenic occurs naturally in rocks and soil, air,
water, plants and humans.
» Natural sources include
» Anthropogenic sources include
» Volcanoes
» Wood preservatives
» Erosion of rocks
» Paints, dyes
» Forest fires
» Drugs, soaps
» Long term exposure can cause skin lesions and keratosis
and has been linked to cancer of the bladder, lungs,
skin, kidney, nasal passages, liver and prostate.
» Low exposures have been shown to cause cardiovascular,
pulmonary, immunological, neurological and endocrine
effects.
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