Go to top

A new technique to concentrate a fertilizer produced from wastewater

For their semester project, two Master’s students in Environmental Engineering at EPFL, chose to focus on the Yverdon-les-Bains wastewater treatment plant. This plant is known as a pioneer in Switzerland for nitrogen recovery. Taking inspiration from the osmotic distillation technique commonly used to concentrate fruit juice, the students developed a method to increase the nitrogen concentration in a liquid fertilizer that could be incorporated into existing wastewater treatment processes. They conducted lab experiments to bring the nitrogen concentration close to its saturation point and quantified the steam flow rate through the membrane so that engineers can later design the equipment needed to implement the technology at full scale. The students tested their new osmotic distillation method with a pilot unit provided by Membratec, a Sierre-based firm. Their project was supervised by Christophe Bonvin from Membratec and Christof Holliger, full professor at EPFL and head of the School’s Laboratory for Environmental Biotechnology (LBE).