Iron and magnesium are often found in their divalent form in anaerobic groundwater. Upon exposure to air these highly soluble ions are oxidized and react typically with hydroxides to form insoluble hydroxide precipitates that can be removed by the bead filter as particles. The oxidation process is slow, taking a few minutes, and the rate is highly dependent on pH. The rate improving with increasing pH. It is generally recommended that the iron/magnesium be fully oxidized to prevent precipitation directly on the surface of the beads. A condition that can lead to the sinking of beads under conditions of low pH and low oxygen tension. Bulk removal of iron is generally straight forward, but development of persistently low concentration (<1 ppm) may require some testing of pH, bead coatings, and flowrates through the bed.

Other heavy metals that are in the particulate form can be removed typically as hydroxide precipitates (TSS removal) in a bead filter. The process can be enhanced by pH adjustment or coagulant addition. The strategy for heavy metals removal is specific to the metal(s) targeted and is highly dependent on the chemistry of the water being treated.

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