SUBSCRIBE to our eNews and SCOPE Newsletter


Read earlier SCOPE and eNews editions.

Process & contact

Member of DPP
Contact; ;


Updated 1/2022

Input materials5tetra1

Input: sewage sludge incineration ash, from sewage works using biological and/or chemical P-removal.

Output products

- phosphoric acid
- gypsum
- iron and aluminium salts
- mineral ash residues

Process description

1) ash is leached using phosphoric acid, so solubilising phosphorus and calcium but not most of the iron or heavy metals

2) addition of sulphide to precipitate heavy metals and maximise the proportion of these which stay in the leached ash (solid fraction)

3) solid-liquid separation

4) from the liquid fraction (enriched phosphoric acid), calcium is precipitated as gypsum, by addition of sulphuric acid, and the gypsum is separated out by vacuum belt filter and water washing.

5) the resulting phosphoric acid is partially returned back to leaching process. The additional acid production is purified by ion-exchanger and optionally nano-filtration membrane

6) the resulting purified phosphoric acid is then concentrated (preferably using secondary heat, e.g. from a sludge incinerator)

7) regeneration of the ion-exchange resin produces (using hydrochloric acid) produces a metal salt solution, which can be potentially recycled to sewage works for phosphorus removal

Operating status

Pilot plant: Hamburg, Germany and Elverlingsen, Germany, 50 kg/h ash (photo)

Full scale plant: Hamburg, Germany (commissioning underway 2022) Throughput: 20,000 t/y ash.

Further full scale plants are in project phase in Kiel, (Germany), L√ľnen (Germany) and Moerdijk (The Netherlands).


SUBSCRIBE to our eNews and SCOPE Newsletter


Read earlier SCOPE and eNews editions.