2. Specific materials

There are two main types of interaction between the solid phase of the filter and an element dissolved in the liquid phase: adsorption/desorption and precipitation/dissolution. The distinction between these two mechanisms is not always easy to establish from a molecular point of view.

Materials likely to retain phosphorus are those containing iron, aluminum and/or calcium hydroxides, three elements that react strongly with phosphorus. The choice of material, in addition to the economic aspect, results from laboratory evaluation methods followed by tests under real conditions.