title: Comparison of phosphorus recovery from incineration and gasification sewage sludge ash.
abstract: Incineration of sewage sludge is a common practice in many western countries. Gasification is an attractive option because of its high energy efficiency and flexibility in the usage of the produced gas. However, they both unavoidably produce sewage sludge ashes, a material that is rich in phosphorus, but which is commonly landfilled or used in construction materials. With current uncertainty in phosphate rock supply, phosphorus recovery from sewage sludge ashes has become interesting. In the present work, ashes from incineration and gasification of the same sewage sludge were compared in terms of phosphorus extractability using electrodialytic (ED) methods. The results show that comparable recovery rates of phosphorus were achieved with a single ED step for incineration ashes and a sequential combination of two ED steps for gasification ashes, which was due to a higher influence of iron and/or aluminium in phosphorus solubility for the latter. A product with lower level of metallic impurities and comparable to wet process phosphoric acid was eventually obtained from gasification ashes. Thus, gasification becomes an interesting alternative to incineration also in terms of phosphorus separation.
authors.affiliation: Department of Civil Engineering, Technical University of Denmark, Building 118, 2800 Kongens Lyngby, Denmark E-mail: rapv@byg.dtu.dk.
authors.forename: Raimon
authors.initials: R
authors.lastname: Parés Viader
authors.affiliation: Department of Civil Engineering, Technical University of Denmark, Building 118, 2800 Kongens Lyngby, Denmark E-mail: rapv@byg.dtu.dk.
authors.forename: Pernille Erland
authors.initials: PE
authors.lastname: Jensen
authors.affiliation: Department of Civil Engineering, Technical University of Denmark, Building 118, 2800 Kongens Lyngby, Denmark E-mail: rapv@byg.dtu.dk.
authors.forename: Lisbeth M
authors.initials: LM
authors.lastname: Ottosen
authors.affiliation: Department of Chemical and Biochemical Engineering, Technical University of Denmark, Building 313, 4000 Roskilde, Denmark.
authors.forename: Tobias P
authors.initials: TP
authors.lastname: Thomsen
authors.affiliation: Department of Chemical and Biochemical Engineering, Technical University of Denmark, Building 313, 4000 Roskilde, Denmark.
authors.forename: Jesper
authors.initials: J
authors.lastname: Ahrenfeldt
authors.affiliation: Department of Environmental, Social and Spatial Change, Roskilde University, 4000 Roskilde, Denmark.
authors.forename: Henrik
authors.initials: H
authors.lastname: Hauggaard-Nielsen
mesh_terms: D003956:Dialysis; D004553:Electric Conductivity; D004563:Electrochemistry; D005740:Gases / Q000032:analysis*; D006863:Hydrogen-Ion Concentration; D017745:Incineration; D010758:Phosphorus / Q000302:isolation & purification*; D012722:Sewage / Q000737:chemistry*
chemical_list: D005740:Gases; D012722:Sewage; D010758:Phosphorus