Safe Drinking Water
The United States has one of the safest water supplies in the world, but that statistic doesn’t tell you about the quality and safety of the water coming out of your tap. Drinking water quality varies from place to place, depending on the condition of the source water from which it is drawn, and the treatment it receives.
Starting in 1999, every community water supplier was required to provide an annual report to its customers. This often comes with the community information we receive at the end of the calendar year. The report provides information on your local drinking water quality, including the water’s source, the contaminants found in the water, and how consumers can get involved in protecting drinking water.
You may want more information, or you may have more questions. One place you can go is to your water supplier, who is best equipped to answer questions about your specific water supply.
What Contaminants Are Found In Drinking Water?
In nature, all water contains some impurities... there is no such thing as naturally pure water.
As water flows in streams, sits in lakes, and filters through layers of soil and rock in the ground, it dissolves or absorbs the substances that it touches. Some of these substances are harmless. In fact, some people prefer mineral water precisely because minerals give it an appealing taste.
However, at certain levels, minerals, just like man-made chemicals, are considered contaminants that can make water unpalatable or even unsafe. Some contaminants come from the erosion of natural rock formations. Other contaminants are substances discharged from factories, applied to farmlands, or used by consumers in their homes and yards.
Sources of contaminants might be in your neighborhood or might be many miles away.
Your local water quality report tells which contaminants are in your drinking water, the levels at which they were found, and the actual or likely source of each contaminant. Some ground water systems have established wellhead protection programs to prevent substances from contaminating their wells. Similarly, some surface-water systems protect the watershed around their reservoir to prevent contamination. Right now, states and water suppliers are working systematically to assess every source of drinking water, and to identify potential sources of contaminants. This process will help communities to protect their drinking water supplies from contamination.
Where does drinking water come from?
A clean, constant supply of drinking water is essential to every community. People in large cities frequently drink water that comes from surface-water sources, such as lakes, rivers and reservoirs. Sometimes, these sources are close to the community. Other times, drinking water suppliers get their water from sources many miles away. In either case, when you think about where your drinking water comes from, it’s important to consider not just the part of the river or lake that you can see, but the entire watershed.
The watershed is the land area over which water flows into the river, lake or reservoir.
In rural areas, people are more likely to drink ground water that was pumped from a well.
Side note: The EPA doesn't regulate private wells, but recommends that well owners have their water tested each year.
These wells tap into aquifers, the natural reservoirs under the earth’s surface, that may be only a few miles wide, or may span the borders of many states. As with surface water, it is important to remember that activities many miles away from you may affect the quality of ground water.
How Is Drinking Water Treated?
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. Most ground water is naturally filtered as it passes through layers of the earth into underground reservoirs known as aquifers.
The quality of the water will depend on local conditions. The most common drinking water treatment is disinfection. Typically, 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.
Side Note: If your water comes from the Detroit system, it is among the cleanest public water in America.
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