A homeowner on well water recently contacted us. They had purchased a Filox iron filter online, and was told by the supplier that it would remove the iron, manganese and hydrogen sulfide odors without the use of chemicals. It worked for one week and then their water turned bad again, full of iron and manganese and odors. Based on the water chemistry we recommended a chlorinator be installed ahead of the iron filter so it would work properly.
This particular Filox iron filter used an air charger control valve which keeps a head of air at the top of the filter tank. As the water enters the tank, it falls through air trapped inside the top of the filter tank. This adds oxygen to the water and helps the Filox iron filter media work correctly. The iron filter back-washed every night with a strong backwash from the well pump.
However, this water had 3 PPM of iron, 0.5 PPM of manganese and was high in hydrogen sulfide odors. The maximum recommended levels for drinking water is 0.3 PPM iron, 0.05 PPM manganese and no detectable hydrogen sulfide.
Filox is an excellent iron filter media that is manufactured from solid manganese oxide media. Filox is a trademark of Matt-Son, Inc. It is similar to Pyrolox, MangOX and other brands of high purity manganese oxide media.
For many well waters, this media requires an oxidation step ahead of the iron filter such as chlorination, or air injection. However, for some water chemistry the air charger type iron filters are best for removing iron alone.
If manganese and/or hydrogen sulfide are present in the water, a small head of air at the top of the tank is not sufficient to cause the high level of oxidation necessary for the manganese oxide media to work properly.
Depending on the water chemistry and especially the ORP level of the water, an additional oxidation step is required. Chlorine injection and or a large amount of aeration with sufficient contact is needed for Filox, Pyrolox and other manganese oxide media to remove manganese and hydrogen sulfide (‘rotten-egg”) odors.
In some applications a Maxi-Vent tank with an air compressor can be used. Chlorination works best however, as it not increases the ORP (the Oxidation Reduction Potential) can be the most important factor to take into consideration in certain waters.
Highly reducing waters may cause premature exhaustion or even destruction of the Filox media, according to the manufacturer and best practices. Generally we want to see a minimum level of 200 mv ORP for manganese oxide media to work correctly. Many deep well waters high in iron have a very low ORP level and the manganese oxide media will not work properly without an additional oxidation step.
Another advantage of chlorination prior to the manganese oxide media filters is the disinfection that occurs. Iron and sulfur bacteria are destroyed and this prevents the iron filter media from becoming coated and slimed with these organisms. A small contact tank after chlorine injection is recommended for best results.
It is best to get a complete water analysis and before choosing your iron filter.