Clean is Your Water?
because water comes from the tap or in a bottle,
does that necessarily mean it's clean?
No. Water purity varies greatly depending on the
source and whether it's a purified, distilled,
spring, mineral, artesian, or some other type of
water. But how is water purity measured?
Water purity and quality are directly related to the
amount of Total Dissolved Solids (TDS) found in the
water. This includes anything present in water other
than the pure water (H20) molecule such as suspended
solids like minerals, salts, or metals. TDS is
expressed in units of milligrams per unit volume of
water (mg/L), also referred to as parts per million
Dissolved Solids can come from 3 different sources
1) organic, 2) inorganic and 3) metals.
1. Some dissolved solids come from organic sources
such as leaves, silt, plankton, and industrial waste
and sewage. Other sources come from runoff from
urban areas, road salts used on street during the
winter, and fertilizers and pesticides used on lawns
2. Dissolved solids also come from inorganic
materials such as rocks and air that may contain
calcium bicarbonate, nitrogen, iron phosphorous,
sulfur, and other minerals. Many of these materials
form salts, which are compounds that contain both a
metal and a nonmetal. Salts usually dissolve in
water forming ions. Ions are particles that have a
positive or negative charge.
3. Water may also pick up metals such as lead or
copper as they travel through pipes used to
distribute water to consumers.
The EPA Secondary Regulations advise a maximum
contamination level (MCL) of 500mg/liter (500 parts
per million (ppm)) of total dissolved solids for
safe drinking water. Numerous water supplies exceed
this level. When TDS levels exceed 1000mg/L it is
generally considered unfit for human consumption. A
high level of TDS is an indicator of potential
concerns, and warrants further investigation. Most
often, high levels of TDS are caused by the presence
of potassium, chlorides and sodium. These ions have
little or no short-term effects, but toxic ions
(lead arsenic, cadmium, nitrate and others) may also
be dissolved in the water.