Making the phosphous in wastewater and sewage available to industry is just one of the goals of a research team in Germany.

The consumption of natural resources by modern industrial societies is leading to a shortage of essential raw materials. This includes phosphorus, an important raw material for fertilisers, and therefore food production.

There are hardly any geological sources of phosphorus in the European Union and stocks elsewhere are finite and depleting. In order to conserve resources and become independent of imports, a research team at the University of Kaiserslautern-Landau (UKL) is developing processes to recover phosphorus and other raw materials from wastewater and sewage sludge, and making them usable for industry.

“We are working on possible solutions to reduce the phosphorus concentration in municipal wastewater from the inlet to the outlet by a factor of around 100,” explains Professor Sergiy Antonyuk, head of the Institute of Particle Process Engineering at UKL. “At the same time, our aim is to process the removed phosphorus in in such a way that it can be made available again as a resource for industry in line with the recycling principle.”

Phosphorus is included in a list of 30 critical raw materials with a high supply risk and high economic importance, by the European Commission, yet large quantities from homes and industry are discharged into municipal sewers, offering potential for recovery during treatment. Further, wastewater effluent - the treated water discharged into the environment - usually contains phosphorus, which can contribute to algae formation and eutrophication, leading to dead zones in rivers and lakes affecting wildlife and plant-life.

An additional advantage of developing processes to extract more phosphorus from wastewater is the positive impact on the environment by preventing it reaching the environment from treatment plants.

“The phosphorus concentration in the outlet of wastewater treatment plants also needs to be further reduced in order to protect our waters from algae formation," explains Professor Heidrun Steinmetz, head of the Department of Resource Efficient Wastewater Technologies at UKL.

"There are already pilot projects implementing this idea for individual sewage treatment plants, but not in combination with P recovery. However, there are considerable gaps in our knowledge - which processes are promising under which conditions. This is what we hope to find a solution for.”

As part of the research programme, the University of Kaiserslautern-Landau combines expertise from the natural sciences and engineering. It also involves an investigation into tailor-made adsorber materials on which phosphorus compounds can accumulate.

Another research project is investigating basic mechanisms of crystallisation and precipitation. These are separation processes that can be used to recover phosphorus from sewage sludge in the form of plant-available fertilisers.

“In addition, we will use and further develop innovative methods of characterisation, measurement techniques and simulation methods to describe the influences of boundary conditions in the real wastewater system on the efficiency of phosphorus recovery with crystallisation and adsorption processes and the product quality,” Steinmetz adds. “We perform the investigation using an experimental wastewater treatment and recycling plant installed as a pilot project on the University of Kaiserslautern-Landau in Kaiserslautern.

"Our ultimate goal is to transfer the developed materials and processes to other raw materials and adapt them to recover nitrogen, potassium or organic carbons, for example.”

The research is funded by the German Research Foundation.