Although the raw materials for fertilizer production are becoming increasingly scarce, at the same time large quantities of nutrients are being lost via the sewage system and further energy consumption. The state of the art in most municipal wastewater treatment plants is the removal of nitrogen compounds such as ammonium (NH4+) and nitrate (NO3-) using nitrification and denitrification processes. With high energy consumption, these compounds are converted into gaseous nitrogen that escapes into the air.
Phosphate is removed by chemical precipitation by adding aluminium or iron salts. These phosphate salts are landfilled because they are not available to plants or can release iron and aluminium in concentrations that are toxic to plants. It is estimated that approximately 4.3 million tonnes of phosphorus are lost in this way worldwide each year.
For this reason, the Fraunhofer IGB is developing new technologies for recovering nutrients from wastewater.