Extracting phosphorous from incinerated sewage sludge ash rich in iron or aluminum

    Research output: Contribution to journalJournal articleResearchpeer-review


    Ashes from mono-incineration of sewage sludge (ISSA) generally contain high concentrations of phosphorous (P) and can be regarded as secondary P resources. ISSA has no direct value as fertilizer as P is not plant available. The present paper experimentally compares P extraction in acid from two different ISSAs; one rich in Al (67g/kg) and the other in Fe (58g/kg). The difference related to P precipitation at the waste water treatment facilities. Another major difference between the ashes was that flue gas purification products were mixed into the first ash and it contained about 5% activated carbon. The Al rich ash had a significantly higher buffering capacity and required more acid for extraction of P. When acid extraction of P from ISSA is the method for recovery, it is thus beneficial to go back to the waste water treatment facility and e.g. choose Fe for P precipitation rather than Al.Formation of a high amount of gypsum crystals in both ashes after extraction in H2SO4 was seen by SEM–EDX. H2SO4 is the cheapest mineral ash, but the gypsum formation must be taken into account when either finding possibility for using the remaining ash in e.g. construction materials or if the choice is deposition, as the gypsum increases the volume significantly.
    Original languageEnglish
    Issue number7
    Pages (from-to)963-969
    Publication statusPublished - 2013


    • Sewage sludge ash
    • Characterization
    • Phosphorous
    • Heavy metals
    • Gypsum


    Dive into the research topics of 'Extracting phosphorous from incinerated sewage sludge ash rich in iron or aluminum'. Together they form a unique fingerprint.

    Cite this