Drinking Water Treatment
Intakes
Surface Water
Reservoirs
Groundwater
Aeration:
The water is mixed to liberate dissolved gases and to
suspended particles in the water column.
Flocculation:
The materials and particles present in drinking water (clay,
organic material, metals, microorganisms) are often quite small and so will not
settle out from the water column without assistance. To help the settling
process along, "coagulating" compounds are added to the water, and
suspended particles "stick" to these compounds and create large and heavy
clumps of material.
Filtration:
The water is run through a series of filters which trap and
remove particles still remaining in the water column. Typically, beds of sand or
charcoal are used to accomplish this task.
Disinfection:
The water, now largely free of particles and microorganisms,
is treated to destroy any remaining disease-causing pathogens. This is
commonly done with chlorination or ultraviolet radiation.
Initial Treatment
90 – 99% viruses
screens
Sedimentation
(flocculation)
Filtration
Final Treatment
Disinfection and Fluoridation
Chlorine Gas
Hypochlorite
Sodium Fluoride (NaF)
Sodium fluorosilicate
Home Water Quality
Florida’s Drinking Water
Confined Aquifer
Pumped well
Plio-pliestocene (sands)
Miocene (clays)
Eocene Limestone
Limestone
Potential Problems:
• Hardness
• Iron + manganese
• Sulfur (sulfides)
• Salt/Salinity
• Pathogens (bacteria/viruses)
• Metals
• Organics
Can be toxic or nuisance contaminants
Nuisance Contamination
Hardness
Iron
Turbidity
Color
Odor
Taste
Calcium Deposits
Hardness
Calcium + Magnesium
Classification
Soft
Slightly hard
mg/l or ppm
0 - 17.1
17.1 - 60
Moderately hard
Hard
Very Hard
60 - 120
120 - 180
180 & over
Soap scum, scale, cooking problems
Hardness Treatment
Water softeners
35 gal/day/person
Hard water
Cation
Exchange
Resin
Soft water
Cation Exchange Resins
Ca2+, Mg2+
Na
Na
Na
Na
Na
Na
Na Neg. Charge
Na
Na
Na Na Na
Mg2+
Na
Na
Na
Na Neg charge
Na
Na
Na
Ca2+
Na Na
4 Na+
Water Hardness and Soap Scum
Soap/Detergent
SO4-
SO4SO4Oil drop
(C,H,O)
SO4-
SO4-
SO4SO4SO4-
Sodium dodecylsulfate
Extremely soluble
Na+
Ca+2
+
-SO
-SO
4
-SO
4
4
Less soluble
Harmful Contaminants
Drinking Water
Potable Water
Free of
• Pathogens
• Harmful Minerals/Metals
• Organic Chemicals
Toxicity
Acute Toxicity
Chronic Toxicity
Within 48 hours
• Long term
• Frequent exposure
• Small amounts
• Pb, As, Hg
Contaminants
Heavy Metals
Metal
Lead
Silver
Mercury
MCL (mg/L)
0.05
0.05
0.0002
MCL = Maximum Contaminant Level
Other Metals
Trace Metals
required metabolic catalysts
Manganese
Iron
Cobalt
Toxicity =
Copper
Zinc
Molybdenum
Chromium
> 40 x requirement
Nitrates
NO3-
MCL = 10 mg/L
Agriculture
Organic Waste Disposal
NO3
-
bacteria
NO2-
Methemoglobin is a form of hemoglobin that does not bind oxygen.
Infants under 6 months are particularly susceptible
Pathogens
Coliform bacteria
MCL < 1 bacterium / 100 ml
(fecal contamination)
Non-coliform bacteria MCL < 200 bacteria / 100 ml
Single required test: Sanitary Quality
Suggested test: mineral/metal content
Treatment
Sanitation/Disinfection
Chlorination
Boiling
UV Radiation
Most common
Ultraviolet Radiation
Scrambled DNA
Bacteria
Viruses
Mold
Yeast
Algae
Home Treatment
Water Filters
Ceramic Filtration
Ion Exchange
Carbon
3-stage water filtration
Ion Exchange Filters
Metals
Pb2+, Hg2+
Na
Na
Na
Na
Na
Na
Na Neg. Charge
Na
Na
Na Na Na
Finite Capacity
Pb2+
Na
Na
Na
Na Neg charge
Na
Na
Na
Hg2+
Na Na
4 Na+
Most Common Filtration
Solid Carbon Block faucet mount filters
The solid carbon block faucet mount filters are reasonably effective in
reducing contaminants.
These filters, by nature, are quite smalland because filter effectiveness is
dependent on contact time of the water with the filter media, a larger, high-quality
solid carbon block filter will be more effective at reducing contaminants at the
same flow rate.
a high-quality solid block activated carbon replacement filter will filter water for
between 7 and 10 cents per gallon. 2 gallons of filtered water per day would cost
between $50 and $100 per year
Activated Carbon
Activation by heating
Extremely porous with high surface area: 500 m2/g
Activated Carbon
Filtration
Particle size removal > 0.5 microns (bacteria, fungi)
Activated Carbon
Absorption: spontaneous movement of primarily
organic contaminants from water to
carbon matrix.
Pesticides, volatile organics
Carbon Filter Removal
2,4-D
2.4.5-TP (Silvex)
Alachlor
Atrazine
Carbofuran
Chlordane
Endrin
Heptachlor Epoxide
Lindane
Methoxychlor
Simazine
Toxaphene
Benzene
Carbon Tetrachloride
Chlorobenzene
Ethylbenzene
Monochlorobenzene
MTBE
O-Dichlorobenzene
P-Dichlorobenzene
Styrene
Tetrachloroethene
Toluene
Trichloroethene
VOCs
Antidepressants
Steroids/Hormones
Prednisone,
Prednisolone,
Progesterone,
Testosterone,
Cortisol/Hydrocortisone
Antibiotics
Reverse Osmosis
Extremely Effective
Osmosis
Net movement of water
Salt molecule
Spontaneous
movement
of water
No salts
Membrane permeable to
Water only
Reverse Osmosis
Purified water
pressure
Membrane permeable to
Water only
Contaminants to drain
Drawbacks:
Energy intensive
Saline/contaminant by-product
inefficient: high volume reject water
Activated Carbon Filters
Chlorine
Tastes
Odors
Organics
Ion Exchange Resins
Removal of charged
Contaminants (metals)
Reverse Osmosis
Sediments, viruses, bacteria, dissolved solutes
What about Bottled Water?
The global consumption of bottled water reached
41 billion gallons in 2004, up 57 percent in just five years.
In 2007, US consumers purchased more
than 33 billion liters of bottled water
More than 5 trillion gallons of bottled water is shipped internationally each year.
Supplying Americans with plastic water bottles for one
year consumes more than 47 million gallons of oil
According to a NRDC study, U.S. consumers paid between 240
and 10,000 times more per gallon for bottled water than for tap water
For the price of one bottle of Evian, Americans
can receive 1,000 gallons of tap water
The energy required to produce 33 billion liters is equivalent to 32-54 million barrels of oil
What’s the Source?
More than 25 percent of bottled water
comes from a public source.
National Resource Defense Council
If water is packaged as "purified" or "drinking water,"
It likely originated from a municipal water supply, and
unless the water has been “substantially” altered,
it must state on the label that the water comes
from a municipal source.
Both Aquafina (Pepsi) and Dasani (Coca-Cola)
originate from municipal water systems
Artesian water, groundwater, spring water, well water - water from an
underground aquifer which may or may not be treated. Well water and artesian
water are tapped through a well. Spring water is collected as it flows
spontaneously to the surface or via a borehole. Ground water can be either.
Distilled water - steam from boiling water is recondensed and bottled.
Distilling water kills microbes and removes water’s natural minerals
Drinking water – water intended for human consumption and sealed in bottles
or other containers with no ingredients except that it may optionally contain safe
and suitable disinfectants. Fluoride may be added within limitations
Purified water - water that originates from any source but has been treated to meet
the U.S. Pharmacopeia definition of purified water. Purified water is essentially free
of all chemicals. Reverse osmosis is often used.
Other terms used on the label about the source, such as “glacier water” or “mountain
water," are not regulated standards of identity and may not indicate that the water is
necessarily from a pristine area
Is it safe?
Most bottled water appears to be safe.
(NRDC independent testing of 1000 bottles)
EPA sets standards for tap water provided by public water
systems; the Food and Drug Administration sets bottled
water standards based on EPA's tap water standards
Most bottled water is treated more than tap water;
however, some is treated less or not treated at all .
About 22 percent of the brands tested by NRDC contained,
in at least one sample, some chemical contaminant
PET
polyethylene terephthalate (PET) bottles
phthalates
known to disrupt testosterone and other hormones,
can leach into bottled water overtime.
One study found that water that had been stored for 10 weeks in
plastic bottles contained phthalates, suggesting that the chemicals
could be coming from the bottle, the plastic cap or the liner
It also appears possible that some as-yet unidentified
chemicals in plastics have the potential to interfere
with estrogen and other reproductive hormones
Antimony
Royal Society of Chemistry Publication
The study stressed that amounts of antimony were well below
official recommended levels. But it also discovered that the
levels almost doubled when the bottles were stored for three months
The study collected 48 brands of water in PET bottles from its source
in the ground at a German bottling plant. The water had 4 ppt of
antimony before being bottled, the contents of a new bottle had
360 ppt and one opened three months later had 700 ppt.
The U.S. EPA has established 6.0 parts per billion (ppb) as a safe level
The health effects of antimony ingestion are not well known
Where are all the old bottles?
88% of water bottles are not recycled
In 2005, 2 million tons of plastic water bottles were not recycled
In 2006, 2 billion half-liter bottles of water were shipped to U.S. ports