Published: 27. Jun 2018

Phosphorcare - from wastewater to valuable fertilizer


At Aaby and Marselisborg Wastewater Treatment Plants Aarhus Vand extract phosphorus from the wastewater and sell it as valuable fertiliser under the name PhosphorCare.

In 2013, Aarhus Vand opened the first full scale demonstration plant in Denmark at Aaby Wastewater Treatment Plant to test the viability of renewable phosphate production in Denmark. Today the plant is able to extract 60 percent of the amount of phosphorus in the wastewater.

This is the result of a collaboration between a number of private and public partners, and with it comes the added bonus that the challenges of clogged-up pipes in the sewage works have been considerably minimised. This, in turn, reduces the expenses of maintaining the sewage works.

Recovering phosphorus has great potential. If similar systems were established at the 50 largest plants in Denmark, the country would be more or less self-sufficient in phosphorus. Phosphate is a finite resource with few global suppliers. With the world facing twin crises of excessive energy use and diminishing resources, the project is consistent with Aarhus Vand’s corporate focus on sustainability. It is in the planning to introduce this process to two additional plants. The partnership behind the project also includes two other Danish water utilities (Herning Vand and Horsens Vand), Grundfos, Norconsult and the Danish Agricultural Advisory Service.

Marselisborg WWTP – the biggest phosphorus-recovery plant in the Nordic countries

In 2019 we opened the largest phosphorus-recovery plant in the nordic countries which recovers phosphorus from a concentrated side stream in the wastewater treatment plant. This plant is a further development of the experimental plant in Aaby and is situated at Marselisborg Wastewater Treatment Plant. The plant has the potential to utilize up to 30 percent of the phosphorus that enters the treatment plant.

At both plants, the struvite is precipitated as a ‘ready-to-use fertiliser’ and sold to the market. An official approval of the product as commercial fertiliser has been obtained for the struvite produced at both plants under the name PhosphorCare. Both plants are the result of a collaboration between a number of private and public partners. The partnership behind the plant at Aaby includes Aarhus Vand, Herning Vand, Grundfos, Norconsult and the Danish Agricultural Advisory Service. The partnership behind the project at Marselisborg includes Aarhus Vand, SUEZ and Stjernholm.