is in the water before it's treated?
drinking water, including both tap water and bottled water, originates in
rivers, lakes, streams, ponds, reservoirs, springs, and wells. Drinking water
may reasonably be expected to contain at least small amounts of some contaminants.
The presence of contaminants does not necessarily indicate that the drinking
water poses a health risk. However, any watershed may contain sources of contamination.
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 waters before they are
contaminants, such as viruses and bacteria, which may come
from sewage treatment plants, septic systems, agricultural livestock operations,
- Inorganic contaminants,
such as, salts and metals which can be naturally occurring or result from
urban storm water 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, which are by-products
of industrial process and petroleum productions and can also come from gas
stations, urban stormwater runoff and septic systems.
- Radioactive contaminants,
which can be naturally occurring or be the result of oil and gas production
and mining activities.
information about contaminants and potential health effects can be obtained
the Environmental Protection Agency Safe Drinking Water Hotline
is the water treated?
City operates three water treatment plants which have a combined capacity
of 50 million gallons per day (MGD). Water treatment includes:
- Aluminum salts and chemicals called polymers are mixed with the water to
make the particles in the water stick together.
- Flocculation - The coagulated particles are slowly mixed so that they can collide and form
larger particles, known as floc.
- Sedimentation - Water flows through a large tank which allows the floc to settle
to the bottom of the tank and be removed.
- Water is passed through filters made of sand and anthracite coal to filter
out remaining particles.
- Chlorine is added to kill any remaining bacteria or other disease-causing
- Fluoride is added to help prevent tooth decay.
- Stabilization - Small amounts of soda ash (sodium carbonate) or sodium hydroxide are added
to make the water less corrosive to pipes and plumbing.
This page updated
August 27, 2009
City of Longmont Public Works & Natural Resources