Synthetic filters, such as zeolite, requires less backwash water and softens the water as it removes the iron and manganese. Small chemical pumps are used to add chlorine bleach, potassium permanganate, or hydrogen peroxide into the water. After a retention time of at least 20 minutes to allow for oxidation of ferrous iron into the insoluble ferric form, the solid particles are filtered out. When chlorine is used, the treated water can have an unpleasant taste if a particle filter of calcite, sand, anthrocite, or aluminum silicate is used. Use an activated carbon filter to remove both excess chlorine and solid iron and manganese particles.
Some units have an automatic backwash cycle.
However, adding phosphates to water supplies is not allowed by law in North Carolina. A multistage treatment operation may be necessary if your water has high levels of iron and manganese and they are in both the dissolved and solid forms. For example, the water could first be aerated, than chlorinated to oxidize residual iron and kill iron bacteria, and then filtered through a mechanical device to remove particles. This can be followed by activated carbon filtration to remove excess chlorine and a water-softener for hardness control as well as removal of any residual dissolved iron and manganese. Reddish-brown or black slime Iron bacteria.