Our drinking water sources can come from rivers, lakes, reservoirs, springs, groundwater wells and, in some cases, seawater. As surface and groundwater travel over and through the soil, various substances become dissolved into the water. In addition, water can also contain insoluble substances that remain suspended in the water. These dissolved and suspended substances can include naturally-occurring minerals, microscopic organisms and a number of contaminants associated with human activity. The following are descriptions of different types of contaminants that can be found in water:
- Microbial Contaminants, such as viruses and bacteria, can come from sewage treatment plants, septic systems, agricultural livestock operations and wildlife.
- Inorganic Contaminants, such as salts and metals, can be naturally occurring or may result from urban stormwater runoff, industrial or domestic wastewater discharges, oil and gas production, mining, or farming.
- Pesticides and Herbicides may come from a variety of sources, including agriculture, urban stormwater runoff, and residential uses (i.e., lawn care products).
- Organic Chemical Contaminants, including synthetic and volatile organic chemicals, are by-products of industrial processes and petroleum production. For example, gasoline and diesel fuel contain an array of organic compounds that can be released into the environment from leaking fuel tanks. Other organic chemicals can make their way into the water via urban stormwater runoff or poorly maintained septic systems.
- Radioactive Contaminants can be naturally occurring or may be the result of oil and gas production and mining activities.
To ensure that tap water is safe to drink, the U.S. Environmental Protection Agency (EPA) has issued regulations that limit the amount of these substances that can be present in public drinking water supplies. Public water systems are required to monitor its water for these substances, and if found in concentrations above their acceptable limits, modify its treatment operations to reduce their levels. Water utilities are also responsible for making the results of these tests available to the public on an annual basis through the issuance of a water quality report called a Consumer Confidence Report.