about water contaminants

How Do Contaminants Get Into Water?

The sources of drinking water (both tap and bottled water) include rivers, lakes, streams, ponds, reservoirs, springs and wells. As water travels over the surface of the land or through the ground, it dissolves naturally occurring minerals and, in some cases, radioactive material, and can pick up substances resulting from the presence of animals or from human activity.

Contaminants that may be present in source water include:

• Microbial contaminants, such as viruses and bacteria, that may come from sewage treatment plants, septic systems, agricultural livestock operations, and wildlife.

• Inorganic contaminants, such as salts and metals, that can be naturally-occurring or result from urban stormwater runoff, industrial or domestic wastewater discharges, oil and gas production, mining or farming.

• Pesticides and herbicides, which may come from a variety of sources such as agriculture, urban stormwater runoff, and residential uses.

• Organic chemical contaminants, including synthetic and volatile organic chemicals, that are byproducts of industrial processes and petroleum production and can also come from gas stations, urban stormwater runoff, and septic systems.

• Radioactive contaminants, which can be naturally occurring or the result of oil and gas production and mining activities.

In order to ensure that tap water is safe to drink, USEPA and the California Department of Health Services (Department) prescribe regulations that limit the amount of certain contaminants in water provided by public water systems. Department regulations also establish limits for contaminants in bottled water that must provide the same protection for public health.

How is Your Water Protected from Contamination?

The local water used by Sweetwater Authority can be affected by activities within its watershed, a 200-square mile area leading into the streams that feed the Sweetwater River. Sweetwater Authority uses a multiple barrier approach to protect water quality and provides education, stakeholder involvement, and comments to local planners, as well as the "hardware" solutions described here.

• An innovative diversion system captures urban runoff before it enters Sweetwater Reservoir and transports the runoff below Sweetwater Dam, reducing the buildup of mineral salts in the reservoir. The diversion system can also capture and hold runoff from a chemical spill or sewage failure, allowing the contaminants to be removed and trucked away for proper disposal. Water from the reservoir is treated at the Perdue Treatment Plant (see diagram to right.)

• Well sites are closely monitored to assure that contaminants have not entered the well fields. Water from the wells is disinfected with sodium hypochlorite, a concentrated chlorine bleach solution. Brackish groundwater is treated with reverse osmosis, which removes microbial contaminants and 95 percent of minerals before disinfection.
Additional information is available on this web site and, on imported water at www.mwd.dst.ca.us.