The University of Liège has developed the PULSE (Phosphorus ULiège Sludge Extraction) demonstrator, a pilot plant that recovers phosphorus from dried wastewater sewage sludge. The process was developped within the Phos4You project, funded by INTERREG NWE, with additional support by the Wallonie region.
April 26th 2021, a press conference took place with la Professeure Angélique LÉONARD, présidente de l’Unité de recherche Chemical Engineering de l’ULiège, M. Jean-Luc MARTIN, Président du Comité de direction de la Société Publique de Gestion de l’Eau (SPGE), and le Pr Andreas PFENNIG et l’équipe scientifique en charge du développement du démonstrateur PULSE.
The process starts with the dewatering of the sludge, which is crushed afterwards. The next step is leaching, which involves mixing the sludge with hydrochloric acid to obtain a black liquid with a high phosphorus content. The solvent then goes through the extraction stage to remove all contaminants. The last step is precipitation. After this process, a phosphate salt is obtained that meets the legal requirements of the fertiliser industry.
This recovery process makes it possible to compensate for the lack of European phosphorus resources, as Angélique Léonard, a professor at University of Liège, explains: "For the most part, we depend on imports. In Belgium, this phosphorus comes in particular from Morocco and Russia. It is essential to close the loop because this phosphorus is a limited scarce raw material and must therefore be recovered.”
This process is more sustainable and environmentally friendly because it replaces the incineration of sludge which is highly energy consuming. While 70% of the sludge is used in agriculture, 30% cannot be re-used because of the included heavy metals and is therefore incinerated. With the PULSE process, it can be used for phosphorus extraction.
It is estimated that this process could recover 113,000 tonnes of material per year. The phosphorus recovery demonstrator is currently operational at the AIDE wastewater treatment plant in Oupeye, near Liège. It will soon be transferred to a wastewater treatment plant in Scotland to be operated by further Phos4You project partners.
Find more about the PULSE process and its outcome material P-salts in the Phos4You information sheets here.
The pictures below show the pilot plant.
Copyright all pictures: Uni Liège Michel Houet.
