Here are some ways to remove iron and manganese.
Since iron is highly oxidizable and easily becomes insoluble ferric hydroxide, it is common to remove it by physical filtration alone unless the concentration is high. However, if an oxidizing agent such as sodium hypochlorite cannot be injected, the catalytic oxidation method using the Toyolex F series may be used.
Unlike iron, manganese is extremely difficult to oxidize, so when the pH is near neutral, it hardly oxidizes in air, and it takes several hours to oxidize with a chlorine-based oxidant such as sodium hypochlorite. Therefore, the method using the Ferrorite MC / GC series or the catalytic oxidation method with manganese sand is common.
If the concentration of iron or manganese in the raw water is high, the coagulation precipitation method or catalytic oxidation method may be used as a pretreatment.
The biological treatment method is a treatment method typified by the slow sand filtration method of water purification plants, and it is possible to obtain extremely clear treated water. However, there are also problems such as difficulty in dealing with high concentrations of iron and manganese, and difficulty in removing unless the filtration rate is reduced.
In the case of ion exchange / membrane treatment, iron and manganese adhere to the ion exchange resin and RO membrane, which requires regular chemical washing, so cases where they are used at low concentrations such as those below the tap water quality standard. It can be said that there are many.

Processing method	Overview of processing method
Physical filtration method	A method in which iron ions　or manganese ions in water are oxidized to insoluble ferric hydroxide, manganese dioxide, etc. by an oxidizing agent, precipitated,　and removed by physical filtration.
Contact oxidation method *	In the case of iron, use a filter material coated with iron oxyhydroxide (FeOOH) such as Toyolex F,　and in the case of manganese, use a filter material coated with manganese dioxide such as Ferrorite GC / MC. A method of removing iron ions　and manganese ions by an autocatalytic reaction.
Biological treatment method	A method in which bacteria such as iron bacteria are propagated in a filler such as filtered sand,　and iron　and manganese are removed by the bacteria.
Ion exchange method	A method of removing iron ions　and manganese ions using an ion exchange resin.
Coagulation precipitation method	Similar to the physical filtration method, a method in which iron　and manganese are oxidized　and precipitated by adding an oxidizing agent,　and then iron　and manganese are aggregated　and precipitated by adding a flocculant,　and the clean water (wow water) is recovered.

* The catalytic oxidation method is also called the oxidation catalyst method　or the oxidation filtration method.