During this thesis project, a study of the possibility of recovering phosphorus from digested sludge and the return stream from the extractor at Fiskartorpet treatment plant was made. The purpose of the thesis project was to contribute Fiskartorpet with data and knowledge how the digested sludge could be used when it no longer can be lodged. The same knowledge and data will also prepare Fiskartorpet if a request on phosphorus recycling should be relevant in the future. The digested sludge was dried and then incinerated at different temperatures, and phosphorus was then leached from the ashes with hydrochloric acid and sodium hydroxide. The content of phosphorus was then measured with Hach Lange 349 Phosphate and Hach Lange 350 Phosphate. The dried digested sludge, ash and leached ash was analysed with XRF-analysis to measure the content of metals in the leached liquid. To estimate how much phosphorus which could be recovered as struvite a model in Excel was made to theoretically calculate how much struvite could be extracted. Struvite is a chemical compound which is used as fertilizer. The model in Excel was used to calculate how much phosphorus which could be recycled by leaching, struvite process and a combined struvite and leaching process. 43 % of the total amount of phosphorus could be exctraced by leaching and if combined with a struvite process, 48 % could be recovered. If only a struvite process was to be used, 13 % of the phosphorus would be recycled.