When extracting phosphor, struvite turns into money instead of clogged pipes!

Stjernholm has been selected as manufacturer and marketing organisation for a new, epochal facility that turns a problem into a resource – and a future source of income for the purification plant.

The plant has been developed in cooperation with the organisations Aarhus Vand and Herning Vand, as well as the companies Norconsult and Grundfos, for the purpose of extracting struvite (also known as struvite stones) from waste water to prevent clogged pipes, heat exchangers, centrifuges etc.

In addition, it has turned out that the struvite, which is extracted during the process, has a chemical composition and structure that makes it well-suited for use as a phosphor fertiliser, and as we import our entire phosphor consumption (currently 11,000 tons per year), we welcome the possibility of selling the recycled phosphor – called PhosphorCare – as an attractive fertiliser product.

The plant works by sending a slip stream of waste water with a high phosphor and nitrogen concentration through a reactor and adding magnesium salt. Through correct regulation, a phosphor- and nitrogen-containing granulate is precipitated which is an excellent fertiliser with both physical and chemical features similar to mineral fertilisers.

The calculated payback time is less than 7 years – achieved only through operational savings. The income from the sale of PhosphorCare is additional.