How is drinking water treated?

How is drinking water treated?

WATER TESTING AND SAMPLING

Would you like to have your water tested?  Do you have a strange taste in your water?  We can help.  We can test your water and send it off to a lab for final results  and we can design a method to filter your water so that you may enjoy the taste of your water.

Feel free to call me direct at 904-993-3433

How is drinking water treated?

what contaminants may be found in drinking water? where does drinking water come from? how is drinking water treated? what if i have special health needs? what are the health effects of drinking water contaminants? who is responsible for drinking water quality? what is a violation of a drinking water standard? how can i help protect drinking water?

When a water supplier takes untreated water from a river or reservoir, the water often contains dirt and tiny pieces of leaves and other organic matter, as well as trace amounts of certain contaminants.  When it gets to the treatment plant, water suppliers often add chemicals called coagulants to the water.  These act on the water as it flows very slowly through tanks so that the dirt and other contaminants form clumps that settle to the bottom.  Usually, this water then flows through a filter for removal of the smallest contaminants like viruses and Giardia.

Ground water is naturally filtered as it passes through layers of the earth into underground reservoirs known as aquifers.  Water that suppliers pump from wells generally contains less organic material than surface water and may not need to go through any or all of the treatments described in the previous paragraph.  The quality of the water will depend on local conditions.

The most common drinking water treatment, considered by many to be one of the most important scientific advances of the 20th century, is disinfection.  Most water suppliers add chlorine or another disinfectant to kill bacteria and other germs.

Water suppliers use other treatments as needed, according to the quality of their source water.  For example, systems whose water is contaminated with organic chemicals can treat their water with activated carbon, which adsorbs or attracts the chemicals dissolved in the water.

For more information

Who is responsible drinking water quality?

what contaminants may be found in drinking water? where does drinking water come from? how is drinking water treated? what if i have special health needs? what are the health effects of drinking water contaminants? who is responsible for drinking water quality? what is a violation of a drinking water standard? how can i help protect drinking water?

The Safe Drinking Water Act gives the Environmental Protection Agency (EPA) the responsibility for setting national drinking water standards that protect the health of the 250 million people who get their water from public water systems.  Other people get their water from private wells which are not subject to Federal Regulations.  Since 1974, EPA has set national safety standards for over 80 contaminants that may occur in drinking water.

While EPA and state governments set and enforce standards, local governments and private water suppliers have direct responsibility for the quality of the water that flows to your tap.   Water systems test and treat their water, maintain the distribution systems that deliver water to consumers, and report on their water quality to the state.  States and EPA provide technical assistance to water suppliers and can take legal action against systems that fail to provide water that meets state and EPA standards.

For more information

What is a violation of a drinking water standard?

what contaminants may be found in drinking water? where does drinking water come from? how is drinking water treated? what if i have special health needs? what are the health effects of drinking water contaminants? who is responsible for drinking water quality? what is a violation of a drinking water standard? how can i help protect drinking water?

Drinking water suppliers are required to monitor and test their water many times, for many things, before sending it to consumers.  These tests determine whether and how the water needs to be treated, as well as the effectiveness of the treatment process.  If a water system consistently sends to consumers water that contains a contaminant at a level higher than EPA or state health standards or if the system fails to monitor for a contaminant, the system is violating regulations, and is subject to fines and other penalties.

When a water system violates a drinking water regulation, it must notify the people who drink its water about the violation, what it means, and how they should respond.  In cases where the water presents an immediate health threat, such as when people need to boil water before drinking it, the system must use television, radio, and newspapers to get the word out as quickly as possible.   Other notices may be sent by mail, or delivered with the water bill.  Each water suppliers’ annual water quality report must include a summary of all the violations that occurred during the previous year.

Fore more information
  • EPA stores information on all violations of drinking water standards in a database.  You can get access to the information about your water system through EPA’s local drinking water information page.
  • Each state writes an annual report on its systems’ compliance with drinking water rules.  EPA compiles and analyzes these reports in its Compliance Report.  The state report may also be online, and can be located through the local drinking water information page.
Search the Hotline’s Question/Answer Database

Find an answer or ask a question about drinking water and ground water programs authorized under the Safe Drinking Water Act.

Getting Information about your Tap Water

Q: How can I find out if my tap water is safe to drink?
A: Because of water’s different sources and the different ways in which water is treated, the taste and quality of drinking water varies from place to place. Over 90 percent of water systems meet EPA’s standards for tap water quality.

The best source of specific information about your drinking water is your water supplier. Water suppliers that serve the same people year-round are required to send their customers an annual water quality report (sometimes called a consumer confidence report).

Contact your water supplier to get a copy or see if your report is posted on-line.

For additional local drinking water information, visit the following EPA Web site:

Top of page

Q. How will I know if my water isn’t safe to drink?
A: Your water supplier must notify you by newspaper, mail, radio, TV, or hand-delivery if your water doesn’t meet EPA or state standards or if there is a waterborne disease emergency. The notice will describe any precautions you need to take, such as boiling your water.

Follow the advice of your water supplier if you ever receive such a notice. The most common drinking water emergency is contamination by disease-causing germs. Boiling your water for one minute will kill these germs. You can also use common household bleach or iodine to disinfect your drinking water at home in an emergency, such as a flood.

Top of page

Q. What’s this new drinking water report that I’ve heard about?
A. Water suppliers must deliver to their customers annual drinking water quality reports (or consumer confidence reports). These reports will tell consumers what contaminants have been detected in their drinking water, how these detection levels compare to drinking water standards, and where their water comes from.

The reports must be provided annually before July 1, and, in most cases, are mailed directly to customers’ homes.

Top of page

Q. How can I get my water tested?
A: If your home is served by a water system, get a copy of your annual water quality report before you test your water. This report will tell you what contaminants have been found in your drinking water and at what level.

After you’ve read this report, you may wish to test for specific contaminants (such as lead) that can vary from house to house, or any other contaminant you’re concerned about.

EPA does not test individual homes, and cannot recommend specific laboratories to test your drinking water. States certify water testing laboratories.

You may call your state certification officer to get a list of certified laboratories in your state. Depending on how many contaminants you test for, a water test can cost from $15 to hundreds of dollars.

Top of page

Drinking Water Standards and Contaminants

Q. What is a drinking water standard?
A. Under the authority of the Safe Drinking Water Act (SDWA), EPA sets standards for approximately 90 contaminants in drinking water.For each of these contaminants, EPA sets a legal limit, called a maximum contaminant level, or requires a certain treatment. Water suppliers may not provide water that doesn’t meet these standards.

Water that meets these standards is safe to drink, although people with severely compromised immune systems and children may have special needs.

For a more detailed description, read about how standards are set.

Top of page

Q. I don’t like the taste/smell/appearance of my tap water. What’s wrong with it?
A. Even when water meets EPA’s standards, you may still object to its taste, smell, or appearance. EPA sets secondary standards based on these aesthetic characteristics (not health effects) which water systems and states can choose to adopt.

Common complaints about water aesthetics include:

  • temporary cloudiness (typically caused by air bubbles), or
  • chlorine taste (which can be improved by letting the water stand exposed to the air).

Top of page

Q. I’m worried about a specific drinking water contaminant [lead, Cryptosporidium, nitrate, radon, etc.]. What should I know?
Drinking water, including bottled water, may reasonably be expected to contain at least small amounts of some contaminants. As long as they occur below EPA’s standards, they don’t pose a significant threat to health, although people with severely compromised immune systems and children may have special needs.

For more information about a specific contaminant, see EPA’s fact sheets on drinking water contaminants, which have more detailed information on every contaminant EPA currently sets standards for and those EPA is considering setting standards for.

Top of page

Special Health Needs of People With Severely Compromised Immune Systems

Q. What if I have a severely compromised immune system?
A. Some people may be more vulnerable to contaminants in drinking water than the general population. People with severely compromised immune systems, such as people with cancer undergoing chemotherapy, people who have undergone organ transplants, people with HIV/AIDS or other immune system disorders, some elderly, and infants can be particularly at risk from infections. These people should seek advice about drinking water from their health care providers.

EPA/Centers for Disease Control guidelines on appropriate means to lessen the risk of infection from Cryptosporidium and other microbial contaminants offer more detailed advice.

Top of page

Private Drinking Water Wells

Q. What should I do if I have my own drinking water well?
A: If you have your own well, you are responsible for making sure that your water is safe to drink. Private wells should be tested annually for nitrate and coliform bacteria to detect contamination problems early. Test more frequently and for other contaminants, such as radon or pesticides, if you suspect a problem. Check with your local health department and local public water systems that use ground water to learn more about well water quality in your area and what contaminants you are more likely to find.

More information is available on EPA’s private drinking water wells Web site.

You can help protect your water supply by carefully managing activities near the water source, to find out how visit EPA’s Source Water Protection Web site.

The organization Farm*A*Syst/Home*A*Syst Exit EPA Disclaimer provides information to help farmers and rural residents assess pollution risks and develop management plans to meet their unique needs.

Top of page

Bottled Water

Q. What about bottled water?
A: Bottled water is not necessarily safer than your tap water. 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.

Bottled water and tap water are both safe to drink if they meet these standards, although people with severely compromised immune systems and children 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.

More information on bottled water is available from the International Bottled Water Association, Exit EPA Disclaimer which represents most US bottlers.

Top of page

Home Water Treatment Units

Q. What about home water treatment units?
A: Most people do not need to treat their drinking water at home to make it safe. A home water treatment unit can improve water’s taste, or provide an extra margin of safety for people more vulnerable to the effects of waterborne illness:

Consumers who choose to purchase a home water treatment unit should carefully read its product information to understand what they are buying, whether it is a better taste or a certain method of treatment. Be certain to follow the manufacturer’s instructions for operation and maintenance, especially changing the filter on a regular basis.

EPA neither endorses nor recommends specific home water treatment units. EPA does register units that make germ-killing claims.

No single unit takes out every kind of drinking water contaminant; you must decide which type best meets your needs.

For help in picking a unit, contact one of the following independent non-profit organizations:

Both NSF International and Underwriters Laboratories Inc. test and certify home water treatment units. The Water Quality Association classifies units according to the contaminants they remove as well as listing units that have earned their “Gold Seal” approval. Water treatment units certified by these organizations will indicate certification on their packaging or labels.

Top of page

Drinking Water Sources and Protection

Q. Where does my drinking water come from?
A. Drinking water can come from either ground water sources (via wells) or surface water sources (such as rivers, lakes, and streams). Nationally, most water systems use a ground water source (80%), but most people (66%) are served by a water system that uses surface water. This is because large metropolitan areas tend to rely on surface water, whereas small and rural areas tend to rely on ground water. In addition, 10-20% of people have their own private well for drinking water. To find the source of your drinking water, check your annual water quality report or call your water supplier. You can get more information about specific watersheds by visiting EPA’s Watershed Information Network. You can also learn more about EPA, state, and other efforts to protect sources of drinking water.

Top of page

Q. How can I help protect my drinking water?
A: Drinking water protection is a community-wide effort, beginning with protecting the source of your water, and including education, funding, and conservation. Many communities already have established source water protection programs. Call your local water supplier to find out if your community participates. You can also support efforts to improve operation, maintenance, and construction of water treatment processes. States are now engaged in source water assessments, to work with communities to identify local sources of contamination. You can contact your state source water protection program to find out how to get involved in this process, or join a local group in Adopting a Watershed.

Top of page

For more information

Q. How many public water systems are there in the United States?
A. There are almost 170,000 public water systems in the United States. Visit EPA’s page of water system facts and figures for more information.

Top of page

Q: Where can I get more information?
A: For more information on your drinking water you can:

You can also contact:

EPA has also prepared a citizen’s guide to drinking water called Water on Tap: What You Need To Know.

Current Drinking Water Regulations

Under the Safe Drinking Water Act (SDWA), EPA sets legal limits on the levels of certain contaminants in drinking water. The legal limits reflect both the level that protects human health and the level that water systems can achieve using the best available technology. Besides prescribing these legal limits, EPA rules set water-testing schedules and methods that water systems must follow. The rules also list acceptable techniques for treating contaminated water. SDWA gives individual states the opportunity to set and enforce their own drinking water standards if the standards are at least as strong as EPA’s national standards. Most states and territories directly oversee the water systems within their borders.

Where can I find information about chemical contaminants that EPA regulates?

Top of page

Where can I find information about how EPA regulates the treatment of microbial contaminants in drinking water sources?

Top of page

Where can I find information about unregulated contaminants?

EPA uses the Unregulated Contaminant Monitoring (UCM) program to collect data for contaminants suspected to be present in drinking water, but that do not have health-based standards set under the Safe Drinking Water Act (SDWA). Every five years EPA reviews the list of contaminants, largely based on the Contaminant Candidate List

Top of page

More information about contaminants of interest:

List of Contaminants & their MCLs

Microorganisms
Contaminant MCLG1
(mg/L)2		 MCL or TT1
(mg/L)2		 Potential Health Effects from Long-Term Exposure Above the MCL (unless specified as short-term) Sources of Contaminant in Drinking Water
Cryptosporidium (pdf file)
zero
TT 3
 Gastrointestinal illness (e.g., diarrhea, vomiting, cramps) Human and animal fecal waste
Giardia lamblia
zero
TT3
 Gastrointestinal illness (e.g., diarrhea, vomiting, cramps) Human and animal fecal waste
Heterotrophic plate count
n/a
TT3
 HPC has no health effects; it is an analytic method used to measure the variety of bacteria that are common in water. The lower the concentration of bacteria in drinking water, the better maintained the water system is. HPC measures a range of bacteria that are naturally present in the environment
Legionella
zero
TT3
 Legionnaire’s Disease, a type of pneumonia Found naturally in water; multiplies in heating systems
Total Coliforms (including fecal coliform and E. Coli)
zero
5.0%4
 Not a health threat in itself; it is used to indicate whether other potentially harmful bacteria may be present 5 Coliforms are naturally present in the environment; as well as feces; fecal coliforms and E. coli only come from human and animal fecal waste.
Turbidity
n/a
TT3
 Turbidity is a measure of the cloudiness of water. It is used to indicate water quality and filtration effectiveness (e.g., whether disease-causing organisms are present). Higher turbidity levels are often associated with higher levels of disease-causing microorganisms such as viruses, parasites and some bacteria. These organisms can cause symptoms such as nausea, cramps, diarrhea, and associated headaches. Soil runoff
Viruses (enteric)
zero
TT3
 Gastrointestinal illness (e.g., diarrhea, vomiting, cramps) Human and animal fecal waste

Top of page

Disinfection Byproducts
Contaminant MCLG1
(mg/L)2		 MCL or TT1
(mg/L)2		 Potential Health Effects from Ingestion of Water Sources of Contaminant in Drinking Water
Bromate
zero
0.010
 Increased risk of cancer Byproduct of drinking water disinfection
Chlorite
0.8
1.0
 Anemia; infants & young children: nervous system effects Byproduct of drinking water disinfection
Haloacetic acids (HAA5)
n/a6
0.060
 Increased risk of cancer Byproduct of drinking water disinfection
Total Trihalomethanes (TTHMs)
–> –> 0.080
 Liver, kidney or central nervous system problems; increased risk of cancer Byproduct of drinking water disinfection

Top of page

Disinfectants
Contaminant MRDLG1
(mg/L)2		 MRDL1
(mg/L)2		 Potential Health Effects from Ingestion of Water Sources of Contaminant in Drinking Water
Chloramines (as Cl2) MRDLG=41 MRDL=4.01 Eye/nose irritation; stomach discomfort, anemia Water additive used to control microbes
Chlorine (as Cl2) MRDLG=41 MRDL=4.01 Eye/nose irritation; stomach discomfort Water additive used to control microbes
Chlorine dioxide (as ClO2) MRDLG=0.81 MRDL=0.81 Anemia; infants & young children: nervous system effects Water additive used to control microbes

Top of page

Inorganic Chemicals
Contaminant MCLG1
(mg/L)2		 MCL or TT1
(mg/L)2		 Potential Health Effects from Ingestion of Water Sources of Contaminant in Drinking Water
Antimony
0.006
0.006
 Increase in blood cholesterol; decrease in blood sugar Discharge from petroleum refineries; fire retardants; ceramics; electronics; solder
Arsenic
07
0.010
as of 01/23/06
 Skin damage or problems with circulatory systems, and may have increased risk of getting cancer Erosion of natural deposits; runoff from orchards, runoff from glass & electronicsproduction wastes
Asbestos
(fiber >10 micrometers)
7 million fibers per liter
7 MFL
 Increased risk of developing benign intestinal polyps Decay of asbestos cement in water mains; erosion of natural deposits
Barium
2
2
 Increase in blood pressure Discharge of drilling wastes; discharge from metal refineries; erosion of natural deposits
Beryllium
0.004
0.004
 Intestinal lesions Discharge from metal refineries and coal-burning factories; discharge from electrical, aerospace, and defense industries
Cadmium
0.005
0.005
 Kidney damage Corrosion of galvanized pipes; erosion of natural deposits; discharge from metal refineries; runoff from waste batteries and paints
Chromium (total)
0.1
0.1
 Allergic dermatitis Discharge from steel and pulp mills; erosion of natural deposits
Copper
1.3
TT8;
Action Level=1.3
 Short term exposure: Gastrointestinal distressLong term exposure: Liver or kidney damage

People with Wilson’s Disease should consult their personal doctor if the amount of copper in their water exceeds the action level

 Corrosion of household plumbing systems; erosion of natural deposits
Cyanide (as free cyanide)
0.2
0.2
 Nerve damage or thyroid problems Discharge from steel/metal factories; discharge from plastic and fertilizer factories
Fluoride
4.0
4.0
 Bone disease (pain and tenderness of the bones); Children may get mottled teeth Water additive which promotes strong teeth; erosion of natural deposits; discharge from fertilizer and aluminum factories
Lead
zero
TT8;
Action Level=0.015
 Infants and children: Delays in physical or mental development; children could show slight deficits in attention span and learning abilitiesAdults: Kidney problems; high blood pressure Corrosion of household plumbing systems; erosion of natural deposits
Mercury (inorganic)
0.002
0.002
 Kidney damage Erosion of natural deposits; discharge from refineries and factories; runoff from landfills and croplands
Nitrate (measured as Nitrogen)
10
10
 Infants below the age of six months who drink water containing nitrate in excess of the MCL could become seriously ill and, if untreated, may die. Symptoms include shortness of breath and blue-baby syndrome. Runoff from fertilizer use; leaching from septic tanks, sewage; erosion of natural deposits
Nitrite (measured as Nitrogen)
1
1
 Infants below the age of six months who drink water containing nitrite in excess of the MCL could become seriously ill and, if untreated, may die. Symptoms include shortness of breath and blue-baby syndrome. Runoff from fertilizer use; leaching from septic tanks, sewage; erosion of natural deposits
Selenium
0.05
0.05
 Hair or fingernail loss; numbness in fingers or toes; circulatory problems Discharge from petroleum refineries; erosion of natural deposits; discharge from mines
Thallium
0.0005
0.002
 Hair loss; changes in blood; kidney, intestine, or liver problems Leaching from ore-processing sites; discharge from electronics, glass, and drug factories

Top of page

Organic Chemicals
Contaminant MCLG1
(mg/L)2		 MCL or TT1
(mg/L)2
Potential Health Effects from Ingestion of Water
 Sources of Contaminant in Drinking Water
Acrylamide
zero
TT9

Nervous system or blood problems; increased risk of cancer

 Added to water during sewage/wastewater treatment
Alachlor
zero
0.002

Eye, liver, kidney or spleen problems; anemia; increased risk of cancer

 Runoff from herbicide used on row crops
Atrazine
0.003
0.003

Cardiovascular system or reproductive problems

 Runoff from herbicide used on row crops
Benzene
zero
0.005

Anemia; decrease in blood platelets; increased risk of cancer

 Discharge from factories; leaching from gas storage tanks and landfills
Benzo(a)pyrene (PAHs)
zero
0.0002

Reproductive difficulties; increased risk of cancer

 Leaching from linings of water storage tanks and distribution lines
Carbofuran
0.04
0.04

Problems with blood, nervous system, or reproductive system

 Leaching of soil fumigant used on rice and alfalfa
Carbon
tetrachloride
zero
0.005

Liver problems; increased risk of cancer

 Discharge from chemical plants and other industrial activities
Chlordane
zero
0.002

Liver or nervous system problems; increased risk of cancer

 Residue of banned termiticide
Chlorobenzene
0.1
0.1

Liver or kidney problems

 Discharge from chemical and agricultural chemical factories
2,4-D
0.07
0.07

Kidney, liver, or adrenal gland problems

 Runoff from herbicide used on row crops
Dalapon
0.2
0.2

Minor kidney changes

 Runoff from herbicide used on rights of way
1,2-Dibromo-3-chloropropane (DBCP)
zero
0.0002

Reproductive difficulties; increased risk of cancer

 Runoff/leaching from soil fumigant used on soybeans, cotton, pineapples, and orchards
o-Dichlorobenzene
0.6
0.6

Liver, kidney, or circulatory system problems

 Discharge from industrial chemical factories
p-Dichlorobenzene
0.075
0.075

Anemia; liver, kidney or spleen damage; changes in blood

 Discharge from industrial chemical factories
1,2-Dichloroethane
zero
0.005

Increased risk of cancer

 Discharge from industrial chemical factories
1,1-Dichloroethylene
0.007
0.007

Liver problems

 Discharge from industrial chemical factories
cis-1,2-Dichloroethylene
0.07
0.07

Liver problems

 Discharge from industrial chemical factories
trans-1,2-Dichloroethylene
0.1
0.1

Liver problems

 Discharge from industrial chemical factories
Dichloromethane
zero
0.005

Liver problems; increased risk of cancer

 Discharge from drug and chemical factories
1,2-Dichloropropane
zero
0.005

Increased risk of cancer

 Discharge from industrial chemical factories
Di(2-ethylhexyl) adipate
0.4
0.4

Weight loss, liver problems, or possible reproductive difficulties.

 Discharge from chemical factories
Di(2-ethylhexyl) phthalate
zero
0.006

Reproductive difficulties; liver problems; increased risk of cancer

 Discharge from rubber and chemical factories
Dinoseb
0.007
0.007

Reproductive difficulties

 Runoff from herbicide used on soybeans and vegetables
Dioxin (2,3,7,8-TCDD)
zero
0.00000003

Reproductive difficulties; increased risk of cancer

 Emissions from waste incineration and other combustion; discharge from chemical factories
Diquat
0.02
0.02

Cataracts

 Runoff from herbicide use
Endothall
0.1
0.1

Stomach and intestinal problems

 Runoff from herbicide use
Endrin
0.002
0.002

Liver problems

 Residue of banned insecticide
Epichlorohydrin
zero
TT9

Increased cancer risk, and over a long period of time, stomach problems

 Discharge from industrial chemical factories; an impurity of some water treatment chemicals
Ethylbenzene
0.7
0.7

Liver or kidneys problems

 Discharge from petroleum refineries
Ethylene dibromide
zero
0.00005

Problems with liver, stomach, reproductive system, or kidneys; increased risk of cancer

 Discharge from petroleum refineries
Glyphosate
0.7
0.7

Kidney problems; reproductive difficulties

 Runoff from herbicide use
Heptachlor
zero
0.0004

Liver damage; increased risk of cancer

 Residue of banned termiticide
Heptachlor epoxide
zero
0.0002

Liver damage; increased risk of cancer

 Breakdown of heptachlor
Hexachlorobenzene
zero
0.001

Liver or kidney problems; reproductive difficulties; increased risk of cancer

 Discharge from metal refineries and agricultural chemical factories
Hexachlorocyclopentadiene
0.05
0.05

Kidney or stomach problems

 Discharge from chemical factories
Lindane
0.0002
0.0002

Liver or kidney problems

 Runoff/leaching from insecticide used on cattle, lumber, gardens
Methoxychlor
0.04
0.04

Reproductive difficulties

 Runoff/leaching from insecticide used on fruits, vegetables, alfalfa, livestock
Oxamyl (Vydate)
0.2
0.2

Slight nervous system effects

 Runoff/leaching from insecticide used on apples, potatoes, and tomatoes
Polychlorinated
biphenyls (PCBs)
zero
0.0005

Skin changes; thymus gland problems; immune deficiencies; reproductive or nervous system difficulties; increased risk of cancer

 Runoff from landfills; discharge of waste chemicals
Pentachlorophenol
zero
0.001

Liver or kidney problems; increased cancer risk

 Discharge from wood preserving factories
Picloram
0.5
0.5

Liver problems

 Herbicide runoff
Simazine
0.004
0.004

Problems with blood

 Herbicide runoff
Styrene
0.1
0.1

Liver, kidney, or circulatory system problems

 Discharge from rubber and plastic factories; leaching from landfills
Tetrachloroethylene
zero
0.005

Liver problems; increased risk of cancer

 Discharge from factories and dry cleaners
Toluene
1
1

Nervous system, kidney, or liver problems

 Discharge from petroleum factories
Toxaphene
zero
0.003

Kidney, liver, or thyroid problems; increased risk of cancer

 Runoff/leaching from insecticide used on cotton and cattle
2,4,5-TP (Silvex)
0.05
0.05

Liver problems

 Residue of banned herbicide
1,2,4-Trichlorobenzene
0.07
0.07

Changes in adrenal glands

 Discharge from textile finishing factories
1,1,1-Trichloroethane
0.20
0.2

Liver, nervous system, or circulatory problems

 Discharge from metal degreasing sites and other factories
1,1,2-Trichloroethane
0.003
0.005

Liver, kidney, or immune system problems

 Discharge from industrial chemical factories
Trichloroethylene
zero
0.005

Liver problems; increased risk of cancer

 Discharge from metal degreasing sites and other factories
Vinyl chloride
zero
0.002

Increased risk of cancer

 Leaching from PVC pipes; discharge from plastic factories
Xylenes (total)
10
10

Nervous system damage

 Discharge from petroleum factories; discharge from chemical factories

Top of page

Radionuclides
Contaminant MCLG1
(mg/L)2		 MCL or TT1
(mg/L)2		 Potential Health Effects from Ingestion of Water Sources of Contaminant in Drinking Water
Alpha particles
none7
———-
zero
15 picocuries per Liter (pCi/L)
 Increased risk of cancer Erosion of natural deposits of certain minerals that are radioactive and may emit a form of radiation known as alpha radiation
Beta particles and photon emitters
none7
———-
zero
4 millirems per year
 Increased risk of cancer Decay of natural and man-made deposits ofcertain minerals that are radioactive and may emit forms of radiation known as photons and beta radiation
Radium 226 and Radium 228 (combined)
none7
———-
zero
5 pCi/L
 Increased risk of cancer Erosion of natural deposits
Uranium
zero

30 ug/L
as of 12/08/03

 Increased risk of cancer, kidney toxicity Erosion of natural deposits

Top of page

Notes

1 Definitions:
Maximum Contaminant Level Goal (MCLG) – The level of a contaminant in drinking water below which there is no known or expected risk to health. MCLGs allow for a margin of safety and are non-enforceable public health goals.
Maximum Contaminant Level (MCL) – The highest level of a contaminant that is allowed in drinking water. MCLs are set as close to MCLGs as feasible using the best available treatment technology and taking cost into consideration. MCLs are enforceable standards.
Maximum Residual Disinfectant Level Goal (MRDLG) – The level of a drinking water disinfectant below which there is no known or expected risk to health. MRDLGs do not reflect the benefits of the use of disinfectants to control microbial contaminants.
Treatment Technique – A required process intended to reduce the level of a contaminant in drinking water.
Maximum Residual Disinfectant Level (MRDL) – The highest level of a disinfectant allowed in drinking water. There is convincing evidence that addition of a disinfectant is necessary for control of microbial contaminants.

2 Units are in milligrams per liter (mg/L) unless otherwise noted. Milligrams per liter are equivalent to parts per million.

3 EPA’s surface water treatment rules require systems using surface water or ground water under the direct influence of surface water to (1) disinfect their water, and (2) filter their water or meet criteria for avoiding filtration so that the following contaminants are controlled at the following levels:

  • Cryptosporidium: Unfiltered systems are required to include Cryptosporidium in their existing watershed control provisions.
  • Giardia lamblia: 99.9% removal/inactivation
  • Viruses: 99.99% removal/inactivation
  • Legionella: No limit, but EPA believes that if Giardia and viruses are removed/inactivated, according to the treatment techniques in the Surface Water Treatment Rule, Legionella will also be controlled.
  • Turbidity: For systems that use conventional or direct filtration, at not time can turbidity (cloudiness of water) go higher than 1 nephelolometric turbidity unit NTU), and samples for turbidity must be less than or equal to 0.3 NTU in at least 95 pervent of the samples in any month. Systems that use filtration other than the conventional or direct filtration must follow state limits, which must include turbidity at no time exceeding 5 NTU.
  • HPC: No more than 500 bacterial colonies per milliliter.
  • Long Term 1 Enhanced Surface Water Treatment: Surface water systems or (GWUDI) systems serving fewer than 10,000 people must comply with the applicable Long Term 1 Enhanced Surface Water Treatment Rule provisions (e.g. turbidity standards, individual filter monitoring, Cryptosporidium removal requirements, updated watershed control requirements for unfiltered systems).
  • Long Term 2 Enhanced Surface Water Treatment Rule This rule applies to all surface water systems or ground water systems under the direct influence of surface water. The rule targets additional Cryptosporidium treatment requirements for higher risk systems and includes provisions to reduce risks from uncovered finished water storage facilities and to ensure that the systems maintain microbial protection as they take steps to reduce the formation of disinfection byproducts.
  • Filter Backwash Recycling; The Filter Backwash Recycling Rule requires systems that recycle to return specific recycle flows through all processes of the system’s existing conventional or direct filtration system or at an alternate location approved by the state.

4 No more than 5.0% samples total coliform-positive in a month. (For water systems that collect fewer than 40 routine samples per month, no more than one sample can be total coliform-positive per month.) Every sample that has total coliform must be analyzed for either fecal coliforms or E. coli if two consecutive TC-positive samples, and one is also positive for E.coli fecal coliforms, system has an acute MCL violation.

5 Fecal coliform and E. coli are bacteria whose presence indicates that the water may be contaminated with human or animal wastes. Disease-causing microbes (pathogens) in these wastes can cause diarrhea, cramps, nausea, headaches, or other symptoms. These pathogens may pose a special health risk for infants, young children, and people with severely compromised immune systems.

6 Although there is no collective MCLG for this contaminant group, there are individual MCLGs for some of the individual contaminants:

  • Trihalomethanes: bromodichloromethane (zero); bromoform (zero); dibromochloromethane (0.06 mg/L): chloroform (0.07mg/L).
  • Haloacetic acids: dichloroacetic acid (zero); trichloroacetic acid (0.02 mg/L); monochloroacetic acid (0.07 mg/L). Bromoacetic acid and dibromoacetic acid are regulated with this group but have no MCLGs.

7 Lead and copper are regulated by a Treatment Technique that requires systems to control the corrosiveness of their water. If more than 10% percent of tap water samples exceed the action level, water systems must take additional steps. For copper, the action level is 1.3 mg/L, and for lead it is 0.015 mg/L.

8 Each water system must certify, in writing, to the state (using third-party or manufacturer’s certification) that when it uses acrylamide and epichlorohydrin are used to treat water, the combination (or product) of dose and monomer level does not exceed the levels specified, as follows:

  • Acrylamide = 0.05% dosed at 1 mg/L (or equivalent)
  • Epichlorohydrin = 0.01% dosed at 20 mg/L (or equivalent)

Top of page

National Secondary Drinking Water Regulations

National Secondary Drinking Water Regulations (NSDWRs or secondary standards) are non-enforceable guidelines regulating contaminants that may cause cosmetic effects (such as skin or tooth discoloration) or aesthetic effects (such as taste, odor, or color) in drinking water. EPA recommends secondary standards to water systems but does not require systems to comply. However, states may choose to adopt them as enforceable standards.

List of National Secondary Drinking Water Regulations
Contaminant
Secondary Standard
Aluminum
0.05 to 0.2 mg/L
Chloride
250 mg/L
Color
15 (color units)
Copper
1.0 mg/L
Corrosivity
noncorrosive
Fluoride
2.0 mg/L
Foaming Agents
0.5 mg/L
Iron
0.3 mg/L
Manganese
0.05 mg/L
Odor
3 threshold odor number
pH
6.5-8.5
Silver
0.10 mg/L
Sulfate
250 mg/L
Total Dissolved Solids
500 mg/L
Zinc
5 mg/L

Top of page

Unregulated Contaminants

This list of contaminants which, at the time of publication, are not subject to any proposed or promulgated national primary drinking water regulation (NPDWR), are known or anticipated to occur in public water systems, and may require regulations under SDWA. For more information check out the list, or vist the Drinking Water Contaminant Candidate List (CCL) web site.

Public Water Systems

Drinking Water Links

Have questions about Drinking Water?

A to Z Topics

About Our Office

Contact Us

Overview

A public water system (PWS) is a system for the provision to the public of water for human consumption through pipes or other constructed conveyances, if such system has at least fifteen service connections or regularly serves at least twenty-five individuals.

The public drinking water systems regulated by EPA, and delegated states and tribes, provide drinking water to 90 percent of Americans. These public drinking water systems, which may be publicly- or privately-owned, serve at least 25 people or 15 service connections for at least 60 days per year. Private, individual household wells, are not regulated by EPA.  For more information on these wells visit our Private Drinking Water Wells site.  Below we have listed some of the activities that EPA, states, and tribes undertake to regulate public water supplies.

Providing safe drinking water is a partnership that involves EPA, the states, tribes, water systems and their operators.  To learn more about this important network of public health providers, you can select from this variety of information sources.

EPA/State/Tribal Implementation

Water Systems/Operators

Resources

National Drinking Water Advisory Council

EPA is committed to working with its stakeholders, the people for whom safe drinking water is an important aspect of daily and/or professional life. One of the formal means by which EPA works with its stakeholders is the National Drinking Water Advisory Council (NDWAC).

The Council, comprising members of the general public, state and local agencies, and private groups concerned with safe drinking water, advises the EPA Administrator on everything that the Agency does relating to drinking water.

NDWAC has working groups that make recommendations to the full Council, which in turn advise EPA on individual regulations, guidances, and policy matters.

These NDWAC working groups consist of approximately 20 members with a variety of viewpoints. All NDWAC working group meetings and full NDWAC meetings are open to the public.

Leave a Reply

You must be logged in to post a comment.