7
BASIC PRINCIPLES
CONTAMINANTS FOUND IN WATER
IRON (Fe)
Iron concentrations as low as 0.3 ppm will cause staining. The iron concentration, together with the flow
rate demand and the consumption rate of the water, determines the basic size filter system. The higher
these factors are, the larger the required system. The AIO filter system is capable of filtering out the
three main types of iron found in water supplies:
Soluble iron
(also known as “clear water” or ferrous
iron),
precipitated iron
(also known as “red water” or ferric iron) and
bacterial iron
(also known as iron
bacteria). There is no apparent upper limit of iron concentration for the filter, but special care must be
taken when selecting a filter model if your water has a combination of high iron, very low pH, and/or
manganese.
MANGANESE (Mn)
The presence of manganese can be bothersome, even for a chemical free iron filter. As little as 0.05 ppm
of manganese can produce a brownish or black stain. The ability of the filter to remove manganese
depends on its concentration and the pH of the water.
Manganese tends to “coat” the filter media, rendering it incapable of increasing the pH, and therefore
ineffective in removing either the iron or the manganese. Manganese, however, will precipitate in the
filter bed when the pH is increased.
pH
The pH of water measures its acidity or its alkalinity. Water with a pH of less than 7.0 is acidic, above 7.0
it is alkaline, and a pH of 7.0 is neutral. The lower the pH value is below 7.0 the greater the acidity, and
the higher the pH value is above 7.0 the more alkaline. Acidic water (pH less than 7.0) is corrosive to
pipes, appliances, etc. A pH of 7.0 or higher facilitates iron removal — which is why the filter is designed
to increase the pH when it is less than 7.0.
TANNINS (Humic Acid)
Tannins (also known as humic acid) which are present in some water supplies, are the result of decaying
vegetable matter. If the tannin concentration is above approximately 0.5 ppm, it will form a sticky coating
on the media, thus rendering it incapable of filtering the iron. A chemical-free iron filter is not
recommended under this condition. If the tannin concentration is less than 0.5 ppm, a chemical-free iron
filter may be installed.
HYDROGEN SULFIDE (H2S)
Hydrogen sulfide (often referred to as “sulfur”), is easily detectable by its objectionable “rotten egg”
odor. Sulfur corrodes iron, brass, copper and silver. A chemical-free iron filter is capable of removing
sulfur
in concentrations of up to 3 to 5 ppm. Whenever hydrogen sulfide is present, backwashing must be
performed at more frequent intervals.
