Turning wastewater sludge into energy and mineral salts

A system developed by EPFL spin-off TreaTech can turn sludge from wastewater treatment plants into mineral salts - which could be used in fertilizer, for example - and biogas. The firm's research is being funded by several privateand public-sector entities, and a large-scale pilot plant is now being built. The system is scheduled to be installed at a wastewater treatment plant in 2022. Wastewater treatment plants produce an effluent commonly known as sludge. Plant operators previously disposed of this sludge directly as fertilizer, but that was made illegal in Switzerland a little over ten years ago due to the growing concentration of pollutants found in effluents. As a result, the sludge is usually dried into cakes and burned, taking thousands of tons of phosphorus with it every year. That matters because phosphorus is an essential compound in several biological processes, including photosynthesis, but there was no feasible method for recycling the phosphorus in effluent streams until now.