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Frequently Asked Questions
highlights many potential effects of animal feeding operations (AFOs) that were discussed at a meeting co-sponsored by the USGS Office of Water Quality and the
2.Q: How does bioremediation clean up gasoline and oil spills?
A: Bioremediation
is the process by which microbes (generally bacteria) or plants transform a
harmful water contaminant into a non-harmful substance, much as we turn
sugar into carbon dioxide and water. Bioremediation can help clean up
ground water
contaminated with gasoline, solvents, and other contaminants. Often, the
bacteria are already present in the soil or aquifer, and bioremediation
takes place naturally. In some cases, the rate of bioremediation is too
slow to effectively clean up a plume of contaminated water before it
gets to a spring, well, lake, or stream. In those cases, the rate of
bioremediation can sometimes be enhanced by adding a substance that acts
like a fertilizer to make the bacteria grow and feed more rapidly. This
substance, which depends on the local chemistry and hydrology, might be
nitrate, or oxygen, or iron, or something else. Additional information is on a
fact sheet.
3.Q: Where can I find information about bottled water?
and States regulate bottled water. For general information about bottled water, some sources are the
The The U.S. Environmental Protection Agency (EPA) provides the following information on bottled water and tap water:
Bottled water is not necessarily safer than your tap water. EPA sets standards for tap water provided by
the Food and Drug Administration sets bottled water standards based on EPA's tap water standards. Bottled water and tap water are both safe to drink if they meet these standards, although people with
may have special needs. Some bottled water is treated more than tap water, while some is treated less or not treated at all. Bottled water costs much more than tap water on a per gallon basis. Bottled water is valuable in emergency situations (such as floods and earthquakes), and high quality bottled water may be a desirable option for people with weakened immune systems. Consumers who choose to purchase bottled water should carefully read its label to understand what they are buying, whether it is a better taste, or a certain method of treatment. For more information, download the U.S. Environmental Protection Agency booklet: . (Source: )
4.Q: What can be causing our water to have a reddish color?
A: Your water might be affected by iron, a
commonly occurring constituent of drinking water. Iron tends to add a rusty,
reddish brown (or sometimes yellow) color to water, and leaves particles of
same color. If the color is more like black, it could be a combination
and manganese. Both of these metals can cause staining of plumbing
or laundry, but they are not known to cause health problems.
5.Q: Can you give me some advice on commercial products such as water filters?
A: As a government agency, the USGS does not comment on commercial
products, but many organizations evaluate consumer products and post product
reports on the Internet.
(which EPA and others established for the purpose of certifying water treatment products, among other things), the
(the trade association of treatment companies),
, or your local health department may also provide information.
Where can I get information about drinking water contaminants and standards?
The U.S. Environmental Protection Agency has
for many drinking water contaminants on their Web page
Click on "What are the health effects of contaminants in drinking water?" This
page also addresses the standards for levels of contaminants in drinking
water under the heading Drinking Water Standards Program.
These drinking water standards were developed by EPA after considering
information on the occurrence and distribution of the contaminant, the health
effects of the contaminant at various concentrations, and the economic costs
for treatment to remove the contaminant. More information can be obtained from
What if my drinking water contains E. coli?
A: "E. coli is a type of fecal coliform bacteria commonly found in the intestines of animals and humans.
E. coli is short for Escherichia coli.
The presence of E. coli in water is a strong indication of recent sewage or animal waste contamination. Sewage may contain many types of disease-causing organisms."
is on the web at: http://www.epa.gov/safewater/ecoli.html
The fact sheet begins with a discussion of one rare strain of E. coli, strain 0157:H7, that has caused serious disease.
Fortunately this strain is rarely encountered.
The great majority of E. coli strains do not themselves cause disease.
However, since E. coli typically grows in the gut of humans, warm-blooded mammals, and birds, and is normally excreted by the billions in their waste, and it normally dies or is eaten by other microbes within a few days or weeks of being released into the environment, then finding E. coli in your drinking water is a good indication that sewage or animal waste was recently in contact with your water.
And since sewage and animal waste can carry a wide variety of other microbes, some of which do cause disease, the presence of E. coli suggests that other, more dangerous, microbes might be present.
Public water supplies are usually disinfected with chlorine, ozone, or some other process.
Finding E. coli in a public water supply indicates that the disinfection process was not working, or that contact with the waste occurred after the water was treated.
If your sample was from a public water supply, you should notify the water supplier.
If your sample was from a private well or other source, you should take some actions to protect that source.
Suggestions can be found in:
USDA Farm*A*Syst/Home*A*Syst:
http://www.uwex.edu/farmasyst/
If you suspect the water source, whether public or private, may still be contaminated, you should consider drinking bottled water, or boiling your drinking water, or treating it with iodine, bleach, or disinfection tablets as described in EPA's fact sheet on .
What are the federal health limits for water used for drinking water, as well as for swimming and boating?
A: The U.S.
Environmental Protection Agency sets standards for water that could affect
human health and works with local government officials to reduce health risks
in water where you swim or play. You may want to contact your local health
deparment or state drinking water office for information specific to your area. Some EPA
Web sites you may wish to check are:
Another source is the USGS .
9.Q: Where can I find fish consumption advisories for my state?
A: Most states have set fish (and wildlife) consumption advisories
and recommended
consumption levels. The state agency responsible for these limits varies. Check the state government section of your local telephone directory for listings
such as the
Department of Health, Department of Natural Resources, or Division of
Environmental Protection. Examples of consumption advisory information
can be found at .
What are the usual causes of fish kills?
A: Many, but
not all, fish kills in the summer result from low concentrations of dissolved
oxygen in the water. Fish, like all other complex life forms, need oxygen to
survive. They get theirs in the form of oxygen gas dissolved in the water.
That's why it's important to have an aeration device, a bubbler, in your home
aquarium. Warm water holds less dissolved oxygen than cold water, so summer is
the time when fish can have a hard time getting enough oxygen. Other organisms
use oxygen, too, including the algae that grow in the summer and bacteria that
degrade organic matter. During the day, the algae produce oxygen through
photosynthesis, but at night, when photosynthesis stops, they and other
organisms keep respiring, using up oxygen. So on warm summer nights during
algal blooms, the dissolved-oxygen concentration sometimes drops too low for the
fish, and a die-off can occur. This can occur as a result of purely natural
conditions or because of human activity that results in adding
nutrients, nitrogen and phosphorus, to water systems. Nutrients come from many
sources, fertilizers, automobiles, sewage, manure, and others. An excess of
nutrients tends to speed up the growth of algae and diminish the availability
of dissolved oxygen, especially in hot weather, sometimes resulting in fish
kills. Low dissolved oxygen can result from other factors, too, such as poor
flushing or circulation, dredging, or a sudden rain after a dry spell.
Fish kills also can occur as a result to toxic compounds released into a body
of water. In order for this to occur, the toxic compound must be fairly highly
concentrated. In a large water body (such as the Chesapeake Bay) this would
require a very large amount of the toxic compound, and a release site fairly
close to the affected fish.
Another cause of fish kills, which has had a lot of publicity in the last few
years, is infections caused by fish pathogens such as the dinoflagellate,
pfiesteria. If you would like more information about this topic, one source of
information is the Web page USGS Chesapeake Bay Activities.
11.Q: Where can I find a glossary of water terms?
A:The USGS
Web site has a link to . This page offers links to additional glossaries. The U.S. Environmental Protection Agency also has a .
Do you have information about water hardness in the United States?
A: You can view a . Hardness data (reflecting mostly calcium, plus a little magnesium) for individual drinking-water suppliers is on the following pages:
It is important to note that the U.S.
Environmental Protection Agency has not set a legal limit or standard for
hardness in water. This is primarily because the constituents that contribute
to hardness (generally calcium and magnesium ions) that is,
do not cause harmful health effects. Instead, there is a generally accepted
division of water into categories of soft, moderately hard, hard, and very
hard, as explained in the . Most
water utilities try to provide water that is not in the very hard category
because of the unpleasant effects such as scaling in equipment and the
need for more soap and synthetic detergents. In addition, many homeowners in
hard-water areas use water softeners to further reduce hardness by
substituting sodium for calcium and magnesium.
13.Q: Where can I find information
about the health effects of contaminants in drinking water?
A: The EPA Office of Ground Water and Drinking
Water Web page
has a link to "What are the health effects of contaminants in drinking water?"
This link connects you to fact sheets for many contaminants.
14.Q: What is a good home treatment for purifying drinking water in case of an emergency?
A: The Federal Emergency Management Agency (FEMA) lists several ways to purify water for human consumption on their
Web page. Also, the EPA fact sheet
is available in English and Spanish.
15.Q: Where can I find information about the quality of the water in a lake or river near me?
A: The USGS Web site
can direct you to
information about your local water body. Under the heading "Local Information"
click on "Local Websites & USGS Contacts in Your State!" There you can
select your state on a map to find local information.
Below "Local Information" on this site is a link to "Connections." If you click
on the link "Search USGS Websites" and type a name (such as "Mississippi") in
the Search field and then click "seek", a list of search results is shown.
16.Q: Where can I find information about my local drinking water supply?
A: The best way to learn about your local drinking water quality is to read the annual drinking water quality report/consumer confidence report that water suppliers now send out by July 1 of each year. The reports often are sent out with water bills, but they may be sent separately. The reports tell where drinking water comes from, what contaminants are in it, and at what levels.
Environmental Protection Agency offers information about local drinking water
systems through their
Many water suppliers are now posting their water-quality monitoring results on
the Web, and these results can be accessed from this site.
Another source of information is the EPA site
site answers questions such as, "Where does my drinking water come from?"
17.Q: Where can I find information about mercury contamination in water?
A: Information is available through the USGS .
18.Q: How does the gasoline additive MTBE contaminate our
water and cause health problems?
A: Suggestions for reading about methyl tert-butly ether (MTBE), one of a group of
volatile organic chemicals used as solvents, fuel additives, fuels, and
disinfection byproducts, is available at the USGS Web page . EPA also has a page on .
19.Q: Why are high nitrate or nitrogen concentrations in water a problem, and what can be done to maintain safe levels?
A: Nitrate (NO3) is a common inorganic form of nitrogen.
Chemically, it is an anion with a single negative charge, consisting of one
atom of nitrogen and three atoms of oxygen. Because it is an anion, it is
soluble in water. Plants normally use nitrate as their source of the nitrogen
needed by all living things, and so nitrate is considered a nutrient for plants. Excessive concentrations of nitrate in lakes and streams greater than about 5 milligrams per liter (measured as nitrogen), depending on the water body, can cause excessive growth of algae and other plants, leading to accelerated eutrophication or "aging" of lakes, and occasional loss of dissolved oxygen. Animals and humans cannot use inorganic forms of nitrogen, so nitrate is not a nutrient for us. If nitrate-nitrogen exceeds 10 milligrams per liter in drinking water, it can cause a condition called methemoglobinemia or "blue baby syndrome" in infants. Some recent studies have indicated a possible connection between elevated nitrate concentrations and cancer.
Nitrate can get into water directly as the result of runoff of fertilizers
containing nitrate. Some nitrate enters water from the atmosphere, which carries nitrogen-containing compounds derived from automobiles and other sources. Nitrate can also be formed in water bodies through the oxidation of other, more reduced forms of nitrogen, including nitrite, ammonia, and organic nitrogen compounds such as amino acids. Ammonia and organic nitrogen can enter water through sewage effluent and runoff from land where manure has been applied or stored.
Water-quality regulatory agencies seek to avoid high concentrations of nitrate in water to minimize both of the problems noted above. Nitrate standards take two forms: drinking-water standards, designed to prevent adverse human-health effects, and ambient-water standards, designed to prevent excessive eutrophication in lakes and streams. Drinking-water standards for nitrate have been around since at least 1974, when the Safe Drinking Water Act was passed, and probably well before. States may set their own drinking-water standard for nitrate, but most or all use the EPA standard of 10 milligrams per liter (measured as nitrogen). Ambient-water standards have also been around for years, but each State has decided on what standards to use, if any. The EPA is just now setting guidelines for determination of ambient nitrate standards for different water bodies in different regions. General information of EPA's programs for water-quality standards and criteria is available at:
A good contact at EPA to answer questions about standards is the .
Keeping drinking water free of excessive concentrations of nitrate involves a multiple-barrier approach. The most effective strategy is prevention--keeping chemicals that contain or can generate nitrate out of the water. This means managing agricultural operations to minimize application of fertilizer and to minimize runoff of fertilizer that is applied. Some farmers are now using computerized maps of their fields, calibrated to the specific soil and water conditions in various parts of their fields, to restrict the application of fertilizer to only what is needed for each part of the field. In some countries, for example Switzerland, drinking-water providers enter into contracts with farmers in their source areas in which farmers receive subsidies to eliminate fertilizers and use organic farming methods. Prevention also means proper handling of manure and animal waste lagoons, to minimize the discharge of animal waste or waste runoff to streams. Nitrate contributions from other sources can also be curtailed, for example by adding tertiary treatment, or by nutrient removal, to sewage treatment plants, and by controlling emissions from automobiles.
In addition to prevention, drinking-water providers may use advanced treatment techniques to remove nitrate from water.
For example, Des Moines Water Works uses advanced ion-exchange technology to remove excess
nitrate and remain below the 10 mg/L standard. In a typical year, this is needed mostly during the spring, following spring runoff after the application of fertilizer.
A good article about the occurrence of methemoglobinemia can be found at:
20.Q: What can cause our water to have an earthy odor or to smell like rotten eggs?
A: A frequent cause of musty, earthy odors,
especially toward the end of the summer, is naturally occurring organic
compounds derived from the decay of plant material in lakes and reservoirs.
odors can be objectionable, but generally are not harmful to health. However, odors
can be caused by other constituents as well, so you may want to call your local
Health Department and mention the odor to them.
In some parts of the country, drinking water
can contain the chemical hydrogen sulfide gas, which smells like rotten eggs.
This can occur when water comes into contact with organic matter or with some
minerals, such as pyrite. The situation mostly occurs as ground water filters
through organic material or rocks.
The best way to find out what is in your water is to have the water tested by a state certified laboratory.
A list of these labs is available from your .
21.Q: How does the use of pesticides affect our Nation's water quality?
A: Information on pesticides and herbicides and on nutrients is available from the USGS
22.Q: Where does pure, natural water come from?
A. This seems like a pretty straightforward question,
but there are some interesting issues that come up in making a response.
First, the words "pure" and "natural" don't really mean the same thing. Pure
water is a kind of theoretical concept, it means water that has nothing in it
except H2O (hydrogen and oxygen). Absolutely pure water doesn't really exist in
nature. Water, known as the "universal solvent," always contains traces of the
substances with which it has been in contact. These may include gases such as
carbon dioxide, nitrogen, and oxygen from the air, minerals such as calcium and
silica from rocks, and organic matter such as weak organic acid from soil and
vegetation. This is not bad. Most of these naturally occurring substances are
harmless and, in some cases, beneficial. Most people think the taste of water
is improved by moderately low concentrations of naturally occurring minerals,
such as calcium carbonate. In the laboratory, with processes such as
distillation, reverse osmosis, and de-ionization, we can remove almost all of
these natural impurities from water and make it almost pure. Most people think
such water has little taste. And when it comes to oxygen dissolved in water,
fish and other organisms that live in water would not be able to live without
this "impurity."
So, by "pure, natural" water, you probably mean natural, potable water that
contains no contaminants introduced by humans, such as pesticides, pathogenic
microbes, nitrates, metals, and other toxic chemicals. Notice the term
"potable." Some natural waters contain too much of naturally
occurring drinking-water contaminants--salt, arsenic, sulfur, or radon, for
example--to be drinkable or good-tasting. Another common natural ground-water
contaminant is iron. Iron is not harmful, but at high concentrations it stains laundry
and plumbing fixtures. The best way to find uncontaminated natural potable
water is to look for parts of the hydrologic cycle where water has been
isolated from both these natural contaminants and from human influence. The
oceans are out, because of the salt. So is the atmosphere, because moisture in
clouds picks up traces of pollutants from the air. This also eliminates rain.
Most rivers and most lakes are affected by impurities in rain and in the runoff
that comes from the land surface. (It's interesting to note, however, that the
water from a huge tropical river such as the Amazon has a fairly high level of
purity, since most of the material that can be leached from the soils of its
watershed have already been leached out. Likewise, the water in rivers and
lakes in fairly pristine areas such as northern Canada is relatively pure.)
Getting back to the question, we're left with ground water and ice. Glacial ice
that has been frozen and isolated for thousands of years is a good source of
uncontaminated natural water, and some bottling companies take advantage of
this fact. With ground water, the level of purity depends on the isolation.
Shallow ground water, such as you might draw from a 100-foot deep domestic
well, probably has been in the ground less than 50 years, and so might contain
human-derived contaminants (not all shallow wells are contaminated, but most
have at least trace amounts of some contaminants). The huge volume of ground
water stored in deep aquifers, especially in deep aquifers protected by
overlying impermeable layers, is a major source of uncontaminated natural
water. This water may have been underground for more than 10,000 years. If this
water has not been in contact with the naturally occurring contaminants
mentioned above, it can be an excellent source of drinking water. Many water
bottling companies make use of wells or springs that tap these aquifers. They
can be found in many parts of the United States and in many foreign countries.
We have been describing a special case of safe
that is, natural, potable water that has no trace of human-induced
contaminants. Many other types of water can be considered safe for most users.
If the concentrations of contaminants are so low that they are well below the levels
shown to cause health problems, the water is considered safe, even though it is
not pure or totally contaminant-free.
A: A basic introduction to natural filtering of water can be found on-line at the USGS "Water Science for Schools" website. The address for the
site's ground-water-quality page is:
Natural filtering is a big topic. Some filtering takes place when water flows
over the ground, such as when muddy water from a plowed field or a construction site flows through grass or weeds on its way to a stream. Some of the mud is
filtered out. In addition, some filtering takes place when the water is in
lakes or streams, through the actions of plants and bottom-dwelling animals
(like freshwater clams and mussels) that take in water, remove nutrients, and
put it out again. Here's a page that talks about filtering in wetlands:
Here's another, longer, but very good piece about wetlands. The part about natural filtering is in the section called "maintenance of water quality":
A lot of filtering takes place in the uppermost layer of sediment at the bottom of a lake or stream. This is called the hyporheic zone, and it's full of bacteria and other microorganisms that bring about chemical changes in the water. Here are a couple of web pages with more information about the hyporheic zone:
Finally, a lot of filtering takes place as water moves through the ground, through soil, the unsaturated zone (where both water and air fill the pore spaces, or spaces between soil particles), and in aquifers (where water alone fills the pore spaces). Large particles, such as silt, leaves, and twigs are filtered out because they can't fit through the small pore spaces. Smaller particles such as suspended clay and microorganisms become adsorbed (get stuck) onto soil particles. Some microorganisms are eaten by other organisms. And some dissolved chemicals such as nitrates and pesticides are taken up by bacteria that live underground. This doesn't mean that all chemical or microbiological pollutants are filtered out of ground water--untreated ground water can in some cases contain
harmful pollutants. But ground water is usually cleaner than surface water. The natural filtering process that removes pollutants from ground water is sometimes called "natural attenuation". Here is a web page about a report on the topic:
Some cities use the natural filtering ability of aquifers as a way to help treat their public water supplies. They put large wells along the banks of a river, or even under the bottom of the river. The river water flows through the ground on the way to the well, and undergoes some filtration in the hyporheic zone and the aquifer, on the way to the well. This is called riverbank filtration. Many European cities have been using riverbank filtration for 50 years or more, and it is becoming popular in this country, as well, in places like Cincinnati, O Lincoln, N Louisville, K and Parkersburg, West Virginia.
There are even some cities where clean natural water is so scarce that treated sewage is reused by filtering it through the ground.
24.Q: Where can I get information on water purification techniques?
A: A good source of information on home drinking-water treatment technology and performance of specific products is , which offers a listings database for products on their
25.Q: Can you define safe water?
water means water that will not harm you if you come in contact with it. The
most common use of this term applies to drinking water, but it could also apply
to water for swimming or other uses. To be safe, the water must have
sufficiently low concentrations of harmful contaminants to avoid sickening
people who use it. The list of harmful contaminants includes disease-causing
microbes such as bacteria, viruses, cancer-causing chemicals
such as many pesticides, organic solvents, petroleum products, chlorinated
byproducts of the disinfection process, and some m
nitrates and nutrients, endocrine-disrupting compounds, strong acids, strong
bases, radionuclides, and any other acutely toxic substance. Defining safe
water becomes a matter of risk assessment, in which you consider the chance of
illness or injury from drinking the water, in comparison to the risk of illness
or injury from the many other hazards in our lives,for example, riding in a
car, or breathing the air, or shaking hands, or exposure to radiation from the
sun, or to contaminants in the food we eat. In comparison to such other
activities, drinking U.S. public tap water, or any of the bottled waters, or
water from most domestic wells, is very safe indeed. These waters might come
from wells or springs that tap shallow or deep aquifers, from rivers or lakes,
or glaciers, or even from rain-water collectors, fog collectors, or from
desalinated sea water. Most of these waters are filtered and treated to kill
microbes and keep contaminants at safe levels.
How do you define "safe levels"? The
U.S. Environmental Protection Agency (EPA) sets Maximum Contaminant Levels
(MCLs) for many harmful contaminants, based on health-effects research,
contaminant occurrence data, economic analysis, and risk analysis. The
MCLs for currently regulated drinking-water contaminants are listed on
Web page under "Drinking water standards program."
Keep this in mind: water that is safe for one person may be unsafe for
another. If your immune system is weakened by HIV/AIDS, or by a recent
bone-marrow transplant, or if you are a young child or an elderly
person, or pregnant or a nursing mother, you are more susceptible to
contaminants in drinking water than the rest of the population. Your
doctor may urge you to take extra precautions with the safety of your
drinking water. An online reference is EPA/CDC's .
26.Q: Where can I find detailed sampling methods for surface water and ground water?
A: USGS protocols for the collection of ground-water and surface-water samples have been published in the report . The National Field Manual was published in chapters, and copies of this Techniques of Water-Resources Investigations, Book 9, handbook can be ordered by calling 1-888-ASK-USGS or at .
27.Q: If the sulfur content in my well water is a little high, is it still safe to drink?
A: Sulfur is
not regulated as a primary drinking-water contaminant, so there is no official level of sulfur that represents a threshold between healthy and unhealthy concentrations.
Sulfur is required by all living things as part of their normal metabolism, so the body needs a certain amount of sulfur just to live.
Any adverse effects of sulfur in drinking water appear to be related to the following issues:
Hydrogen sulfide (H2S) is sometimes present in well water. A few tenths of a milligram of hydrogen sulfide per liter can cause drinking water to have a rotten-egg odor.
While unpleasant, it is not harmful to health. (See
on this web page, which discusses odor and smell.)
High concentrations of sulfate (SO4--) may be associated with diarrhea.
For this reason, and for aesthetic reasons related to taste and odor, the Environmental Protection Agency currently has a secondary drinking-water standard of 250 milligrams per liter (mg/L) sulfate.
Further information on sulfate and drinking water can be found at this web site:
Some waters with elevated sulfate also tend to have low pH (as in acid mine drainage).
The pH of water is usually checked when well water is tested.
A pH between 6.5 and 8.5 is in the range recommended by EPA.
Bottom line:
If you are not bothered by a rotten-egg odor, and you don't have a sulfate concentration over 250 mg/L, you should have nothing to worry about from the sulfur.
28.Q: Whom do I contact to have my well water tested?
A: You can contact your county or state health department or check with your
for a list of state certified laboratories in your area that do water testing. The cost will vary, depending on the laboratory and the test(s), but people usually consider the cost to be reasonable.
29.Q. What are the permissible levels of trace elements (such as arsenic, copper, iron, lead, and zinc) in water for the water to still be considered safe for exposure/bioaccumulation by people and aquatic life?
A: Several of these trace elements are regulated by the EPA and are on their list of primary drinking
water standards. These include arsenic, copper, and lead, as well as cadmium,
chromium, mercury, and selenium. Iron is not a regulated contaminant because it
is not known to cause health problems, but there is a secondary drinking water
standard based on its tendency to stain laundry and plumbing fixtures.
Manganese, copper (again), silver, and zinc are also included in the secondary
standards. The primary and secondary standards are available on the EPA Web
The above standards are national drinking water standards. Other water-quality
standards are set by states to protect aquatic life. You can check with your
state environmental or natural resources agency to see what aquatic life
water-quality standards are in effect in your state. EPA is currently reviewing
its recommendations for aquatic life criteria. Information on the current review of standards is available on
Aquatic Life Water Quality Criteria.
also has current
information on trace elements across the United States, including links to specific studies and current items in the news.}