?VOCs, Underground storage tanks
Acid rain, Industrial waste,Nitrates,
Pathogenic microorganisms, Sewage,
Anthropogenic Contaminants
Gases, Minerals, Organic Matter
Natural Contaminants
Water Contamination
Natural Contaminants
Gases: radon, nitrogen, oxygen, carbon dioxide,
nitrogen oxides (
nonmetal oxides, and others. Acid rain: sulfur and
SO
x and NO
x)
Dissolved minerals: cations and anions. Calcium,
magnesium, and iron salts cause hard water.
potential contaminants of natural waters.
Bacteria, microorganisms, and animal wastes are all
Organic Matter
A pipe with hard-water scale build up
Hard water contains high concentrations of dissolved
Soft water
calcium, magnesium and iron ions.
contains few of these dissolved ions.
Because calcium ions, Ca2+, are generally the largest
parts per million of calcium carbonate (CaCO
contributors to hard water, hardness is usually expressed in
3) by mass.
It specifies the mass of solid CaCO3 that could be formed
from the Ca2+ in solution, provided sufficient CO32- ions were
also present:
Ca2+(aq) + CO32–(aq) ? CaCO3(s)
A hardness of 10 ppm indicates that 10 mg of CaCO3 could be
formed from the Ca2+ ions present in 1 L of water.
Biological Contamination
contamination.
80% of all illness in the world is caused by water
contamination of water supplies. It is estimated that
people in the U.S. are threatened by bacterial
a serious problem. The EPA estimates that 30 million
Contamination of water by pathogenic organisms was
Waterborne Disease
Volatile Organic Chemicals (VOCs)
and illegal dumping of organic wastes.
landfills, leaking underground storage tanks,
industrial activity, oil and brine wells,
many are carcinogenic. Sources include:
undesirable odor to drinking water. Also,
VOCs can contaminate groundwater and add
Industrial Pollution
use water resources.
Manufacturing processes produce waste products and
BOD – Biological Oxygen Demand:
they decompose organic waste found in water
amount of dissolved oxygen microorganisms use up as
TIME
April 1st, 2010
Flushed Away
http://www.time.com/time/specials/
packages/article/0,28804,197690
9_1976907,00.html
Making Water Fit to Drink
More than 170,000 public water systems exist in
the U.S.
The per capita use of water in the U.S. is almost
nations.
This use exceeds the per capita use of other
agricultural, and personal use).
2 million liters per year (industrial,
CWA and SDWA
The Clean Water Act passed in1974.
industries can discharge into surface waters.
Establishes limits on the amount of pollutants that
The Safe Drinking Water Act was first passed in 1974.
enforce national health
The Act authorizes the EPA to set, monitor, and
It was amended in 1986 and 1996.
-based standards for
contaminants in municipal water supplies.
MCLG: Maximum Contaminant Level Goal
The maximum level of a contaminant in
(70kg, 2 L/day/70years)
adverse effecton human health would occur
drinking water at which no known or anticipated
The legal limit for the concentration of a
MCL: Maximum Contaminant Level
contaminant. Practical realities considered.
5.11
and Maximum Contaminant Level
Maximum Contaminant Level Goal
Water Treatment Plants
distributed to homes for consumption.
water treatment plant before it is
In most urban areas, water is treated at a
5.11
Schematic drawing of a typical municipal water treatment facility
Water Treatment Plants
remove odors and the water is aerated to improve taste.
filters. Charcoal is often present in the filtering process to
These are then removed by filtering through sand and gravel
hydroxide which coagulates colloidal particles with bacteria.
The slaked lime and alum form the gelatinous aluminum
to the water :
The first step in water treatment is to add slaked lime and alum
Disinfection
Chlorine is added to kill any remaining bacteria.
Ozone
any point in the distribution system. (THMs)
chlorine so that the water can be free from bacteria at
Municipal drinking water often contains residual
can also be used for bacterial disinfection and
Ultraviolet light (UV)
has the added advantage of killing many viruses.
can also be used to disinfect
protection that chlorine does.
One disadvantage is that it does not offer the residual
water. It is most effective in small scale applications.
Fluorides
acids:
hydroxide ions making the enamel harder and less affected by
called hydroxyapatite. Fluoride ions replace some of the
Tooth enamel is composed of a calcium phosphate complex
prevent tooth decay.
Many municipal water supplies have fluoride added to help
(cavities) in populations using fluoridated drinking water.
Early studies showed a 50 to 70% reduction in dental caries
Lead (Pb)
What should you do?
Where does it come from?
5.15
Distillation
Two water purification techniques:
Reverse osmosis
Tap, Filtered, Bottled
Tap: water treatment plants, safe, chlorine,
fluoride, lead, inexpensive, EPA
Filtered: Tap, improved taste, remove (Pb2+,
Cu2+, Ca2+, Mg2+), 20% cost of bottled
Bottled: Not pure, expensive (aprox. 1000 times
tap water), FDA
Bottled Water
is in decline.
almost everything else
is growing, while
Bottled water’s share
gallons per year.
estimated 182.5
holds steady at an
the average American
liquid consumed by
that the amount of
the industry, reports
which tracks trends in
Beverage Digest,
National Thirst…
Satisfying the
The New York Times July 15, 2007
or 79.5 liters.
makes 21 gallons,
combinations) it
many possible
bottles (one of
you total up these
year XXXXXXXXXXWhen
looked like last
bottled water
consumption of
American’s
average
This is what an
Bottles
… With Lots of
Next time…
Acids
and
Bases