On 7 September 2016 struvite fertilising pellets were applied to the areas next to Schiphol airport’s runways Schiphol-Rijk and Noord-West. The pellets were developed in a sustainability pilot in which a phosphorus compound (struvite) is recovered from wastewater taken from aircraft. With this pilot, conducted within the TKI Water Technology programme by Schiphol, Evides Industriewater, Vewin and KWR, the airport contributes to decreasing its environmental impact.
Sustainability is one of Schiphol’s strategic pillars. Leon Bakuwel, Utility Services advisor at Schiphol says: ‘People can’t live without phosphorus. It is important for plant growth and therefore for food supply. But phosphorus resources are finite.’ Rosanne Blijleven, Schiphol’s Habitat Management specialist adds that ‘the pellets help keep the grass healthy, which means that weeds have no chance. This also contributes to keeping birds away. Returning the material to the soil is one of the last steps in the process of grassland improvement.’
Creating struvite pellets
During the process of wastewater treatment, bacteria stuff themselves with substances that are in the water. When the water then flows into a sedimentation tank, the bacteria sink to the bottom, forming a sludge layer. Above this sludge is clarified water which is discharged into the Ringvaart canal. The sludge left behind is then put into a digestion tank. The water that is released from the digestion process is the water that has the highest phosphorus content. This water is pumped to a reactor, where the struvite pellets are formed.
‘The practical objective of the pilot project was the recovery of phosphorus from Schiphol’s wastewater, so that it could be used as an artificial fertiliser in the airport’s surroundings. It’s great that it has worked out,’ says KWR researcher Kees Roest. The pilot required setting up the reactor in the water treatment installation. ‘Evides will soon be refurbishing the installation,’ says Bakuwel. ‘We’re currently in the preparatory stage and are studying whether the extraction of struvite should be a permanent part of the process.’