Phosphorous recycling in sewage plants by controlled post-precipitation and sludge separation (P-REC: DBU)


To save on natural phosphorous reserves, the 2017 and more recent versions of the sewage sludge ordinance introduced the obligation to recycle P from waste water. Operators of sewage plants are obliged to submit their concepts for P recycling until 2023. This project thus aims at further developing economic and safe solutions for P recycling.

Most of the actual processes for communal sewage plants are focussing on P recycling from sludge ashes. Even though the processes became more efficient, the need for drying and combustion of sewage sludge followed by an extraction of P from ashes constitute technically demanding and economically expensive solutions. Actual tested processes involving acid digestion are similarly demanding. Thus, this project aims at showing ways to recycle P directly from sludges. The concept includes recycling P from P-enriched precipitated sludges by deliberately diverting P from the biological stage towards a post-process precipitation.

The resulting sludge (tertiary sludge) shall directly be used in agriculture and reduce the need for mineral P fertilizers from fossil resources. HGoTECH takes the responsibility to comprehensively test the resulting products and search for the most suited ways for application.

Project partners:

  • Emscher Water Technologies GmbH (PI)
  • Emscher Cooperative