Evaporation

	Urine contains most of the nutrients excreted from human metabolism. Treatment processes are needed to concentrate and stabilise the nutrients. A complete recovery of all nutrients is possible in an evaporation reactor.
	Stabilise nutrients
	Salt production by evaporation is a well-known and rather simple process, but in the case of urine, the initial solution has to be pretreated. If stored urine is evaporated directly, ammonia is lost by volatilisation. This problem can be prevented, if urine is stabilised with nitrification: bacteria oxidise half of the ammonium to nitrate (NO3-) and adjust the pH between 5.5 and 6.5.
	Crystallise nutrients
	With laboratory experiments, we were able to show that evaporation allows to concentrate almost all nutrients from nitrified urine in clear crystals; less than 3% of the initial dissolved nitrogen was lost by volatilisation. Due to the high temperature during evaporation, the product is free of pathogens.

Nutrient product

At the Eawag main building, a process combining nitrification and evaporation transforms the collected urine into a complete nutrient product.

Further readings:

• Brochure: Nutrient recovery from Urine [English] - [Français] - [Deutsch]
  
• Udert, K.M., Wächter, M. (2012) [pdf] Complete nutrient recovery from source-separated urine by nitrification and distillation. Water Research 46(2), 453-464.
  
• Presentation: Udert, K.M., Waechter, M. (2010) Complete Nutrient Recovery from Source-Separated Urine. 7th IWA Leading-Edge Conference on Water and Wastewater Technologies, 2-4 June 2010, Phoenix, Arizona.

Research Collaborators

Johannes Kluge: Institute of Process Engineering, MAVT, ETHZ

Marco Mazzotti: Institute of Process Engineering, MAVT, ETHZ