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Lean
More |
The
following articles from the National Drinking Water
Clearinghouse are available to view with Adobe Acrobat
Reader. If you do not have Adobe Acrobat Reader
you can download it by clicking on the Acrobat Reader
icon below: |
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Slow
Sand Filtration |
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First
used in the US in 1872, slow sand filters are the oldest
type of municipal water filtration. Today, they remain
a promising filtration method for small systems with low
turbidity or algae-containing source waters. Slow sand
filtration does not require pretreatment or extensive
operator control-which can be important for small system
operators with several responsibilities. |
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Download
Slow Sand Filtration PDF |
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Consumer
Confidence Report |
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Detailed
instructions from the National Drinking Water Clearinghouse
on how to complete a Consumer Confidence Report. |
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Download
Consumer Confidence Report PDF |
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Lime
Softening |
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Hard
water can cause scaling problems in water heaters and
soap does not lather well in hard water. Therefore, some
water utilities soften water to improve its quality for
domestic use. Lime softening is best suited to groundwater
sources, which have relatively stable water quality. The
combination of variable source water quality and the complexity
of the chemistry of lime softening may make lime softening
too complex for small systems that use surface water sources.
To learn more about lime softening including the American
Water Works Association Standard for quicklime and hydrated
lime (ANSI/AWWA B202-93) simply click on the Adobe PDF
picture to download the complete fact sheet. |
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Download
Lime Softening PDF |
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Residuals
Management |
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Water
treatment plants produce a wide variety of waste products
as well as safe drinking water. These residuals may be
organic and inorganic compounds in liquid, solid, and
gaseous forms depending on the source of raw water and
the type of treatment processes, commonly, coagulation/filtration,
precipitative softening plant, membrane separation, ion
exchange, granular activated carbon. To learn more download
the PDF file.
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Residuals Management PDF |
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Organic
Removal |
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Some
small drinking water systems face contamination of raw
water by natural or synthetic organic chemicals (SOCs).
Natural organic materials might be present in water supplies,
especially from surface water sources. Dissolved organics
may cause taste, odor, or color problems in a community's
drinking water, resulting in consumer complaints. Sources
of SOCs include leaking underground gasoline/storage tanks,
agricultural runoff containing herbicides or pesticides,
solid waste or hazardous waste landfills, and improperly
disposed chemical waste. The technologies most suitable
for organic contaminant removal in drinking water systems
are granular activated carbon (GAC) and aeration. To learn
more download the PDF file. |
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Organic Removal PDF |
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Ion
Exchange and Demineralization |
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Ion
exchange and membrane processes are becoming used extensively
in water and wastewater treatment. Ion exchange is primarily
used for the removal of hardness ions, such as magnesium
and calcium, and for water demineralization. Reverse osmosis
(RO) and electrodialysis, both membrane processes, remove
dissolved solids from water using membranes. To learn
more download the PDF file. |
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Download
Ion Exchange and Demineralization
PDF |
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Corrosion
Control |
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Corrosion
occurs because metals tend to oxidize when they come in
contact with water, resulting in the formation of stable
solids. Corrosion in water distribution systems can impact
consumers' health, water treatment costs, and the aesthetics
of finished water. Various methods can be used to diagnose,
evaluate, and control corrosion problems. Techniques for
controlling it include distribution and plumbing system
design considerations, water quality modifications, corrosion
inhibitors, cathodic protection, and coatings and linings.
To learn more download the PDF file. |
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Download
Corrosion Control PDF |
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Filtration |
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Filtration
is the process of removing suspended solids from water
by passing the water through a permeable fabric or porous
bed of materials. Groundwater is naturally filtered as
it flows through porous layers of soil. However, surface
water and groundwater under the influence of surface water
is subject to contamination from many sources. Some contaminants
pose a threat to human health, and filtration is one of
the oldest and simplest methods of removing them. Federal
and state laws require many water systems to filter their
water. Filtration methods include slow and rapid sand
filtration, diatomaceous earth filtration, direct filtration,
packaged filtration, membrane filtration, and cartridge
filtration. To learn more download the PDF file. |
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Download
Filtration PDF |
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Radionuclides |
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Radionuclide
contamination of drinking water is a significant, emerging
issue. Until now, manmade radioactivity in drinking water
has not been a major problem. Natural sources have been
the primary cause of contamination. However, the potential
for contamination exists throughout the country as releases
from medical facilities or nuclear power plants may wind
up in drinking water. Because of their potential health
effects and widespread occurrence, natural radionuclides-including
radon, radium, and uranium-cause much concern. To learn
more download the PDF file. |
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Radionuclides PDF |
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Ozone |
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New
water treatment goals for disinfection byproducts (DBP)
and for microbial inactivation will increase the need
to consider new disinfection technologies. Ozone is an
attractive alternative. This technology has evolved and
improved in recent years, thereby increasing its potential
for successful application. It is important to note that
ozone, like other technologies, has its own set of advantages
and disadvantages that show up in differing degrees from
one location to the next. To learn more download the PDF
file. |
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Download
Ozone PDF |
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Membrane
Filtration: Alternative to Conventional Filtration |
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A
membrane or, more properly, a semipermeable membrane,
is a thin layer of material capable of separating substances
when a driving force is applied across the membrane. Once
considered a viable technology only for desalination,
membrane processes are increasingly employed for removal
of bacteria and other microorganisms, particulate material,
and natural organic material, which can impart color,
tastes, and odors to the water and react with disinfectants
to form disinfection byproducts (DBP). As advancements
are made in membrane production and module design, capital
and operating costs continue to decline. The pressure-driven
membrane processes discussed in this fact sheet are microfiltration
(MF), ultrafiltration (UF), nanofiltration (NF), and reverse
osmosis (RO). To learn more download the PDF file. |
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Download
Membrane Filtration: Alternative to
Conventional Filtration PDF |
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Disinfection |
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Disinfection
is an important step in ensuring that water is safe to
drink. Water systems add disinfectants to destroy microorganisms
that can cause disease in humans. The Surface Water Treatment
Rule requires public water systems to disinfect water
obtained from surface water supplies or groundwater sources
under the influence of surface water. Primary methods
of disinfection are chlorination, chloramines, ozone,
and ultraviolet light. Other disinfection methods include
chlorine dioxide, potassium permanganate, and nanofiltration.
Since certain forms of chlorine react with organic material
naturally present in many water sources to form harmful
chemical by-products, the U.S. Environmental Protection
Agency has proposed maximum levels for these contaminants.
To learn more download the PDF file. |
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Disinfection PDF |
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Iron
and Manganese Removal |
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Iron
and manganese are common in groundwater supplies used
by many small water systems. Exceeding the suggested maximum
contaminant levels (MCL) usually results in discolored
water, laundry, and plumbing fixtures. This, in turn,
results in consumer complaints and a general dissatisfaction
with the water utility. There are secondary standards
set for iron and manganese, but these are not health related
and are not enforceable. The secondary (aesthetic) MCLs
for iron and manganese are 0.3 milligrams per liter (mg/l)
and 0.05 mg/l, respectively. Small water plants may choose
to either sequestrate or remove iron and manganese. Sequestration
only works for combined iron and manganese concentrations
up to 1.0 mg/L and only in cases where the treatment is
not permanent. Removal is usually achieved through ion
exchange or oxidation/filtration. There are a number of
chemical oxidants and filtration media available that
can be used in various combinations. To learn more download
the PDF file. |
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Download
Iron and Manganese Removal
PDF |
