NuReDrain tests on phosphorus adsorbing materialsP removal can be achieved by the adsorption of P on specific materials. In practice, these materials contain iron (Fe) or calcium (Ca) to which phosphates are bound. For Fe containing sorbents, Fe oxides act as a strong sorbent of phosphate, e.g.
XOH + H2PO4- > X-O-P(OH)O- + H2O
Several sorbent materials are commercially available on the market. In addition, ‘new’ materials are popping up such as glauconite minerals, biochars and especially iron oxide sludge, iron coated sand produced during drinking water production and iron oxide coated porous materials.
NUREDRAIN established a database summarizing the technical and economic characteristics of 15 P adsorbing materials. Important parameters such as removal efficiency, price and availability were compared. Finally, lab experiments were conducted on 11 P adsorbing materials to determine the adsorption kinetics at high (25 mg P/l), medium (5 mg P/l) and low (0,5 mg P/l) nutrient load. The 5 most promising materials are currently being tested for their P saturation kinetics.
Lab tests performed by KU Leuven, Ghent University and VITO also revealed that filter materials used to remove low concentrations of P can later on be reused to remove high concentrations of P.
A glance of the filter materials being tested for P adsorption
Phosphorus removal can also be visualized: check the blue colored solution becoming transparent once the solution passed the filter material