Recovering phosphorus from wastewater streams – the process
The process is based on a two-stage system: conditioning (or stripping) followed by crystallisation, and can be adapted to different types of feedstock:
- Feedstock preparation
Liquid streams such as wastewater centrate, digestate or sludge-derived liquids are directed into the system. - Conditioning and stripping
The liquid is adjusted (e.g. pH and magnesium levels) to create optimal conditions for struvite formation. - Crystallisation
In the reactor, controlled conditions allow struvite crystals to form and grow. - Flexible configurations
The system can operate in different modes depending on the feedstock, including direct treatment of centrate, digestate, or more complex sludge streams.
The waste sludge from the wastewater treatment plant is directed to Bio-P sludge leaching, and after to a sludge thickening unit. The liquid fraction produced flows into the crystallization reactor, the solid fraction proceeds to anaerobic digestion. After AD, the digestate enters the stripping unit for pH control. The liquid fraction is then moved to crystallizer where MgCl2 is added.
The final product
The main product is struvite (magnesium ammonium phosphate), a slow-release fertiliser suitable for agricultural use.