Membrane stripping - production of nitrogen-rich fertilizers

Production of nitrogen-rich fertilizers starting from WWTP anaerobic sludge by membrane stripping
Digestion sludge contains an important amount of nitrogen. The so-called centrate (the liquid part of these sludges, after centrifugation), is normally conveyed back to the inlet of the WWTP. A new process developed by Alpha Wassertechnik ( and Membratec allows the extraction of a large part of this nitrogen to be exploited as a mineral fertilizer. This technology is based on a membrane process that allows the dissolved gaseous components to be separated from their liquid. 85% of the nitrogen contained in the centrate is thus concentrated as a fertilizer in the form of ammonium sulphate, at a concentration of 80 gN / l. 

This process has the following benefits for WWTPs: 

  • Valorisation of nitrogen waste as fertilizer. 
  • Reduction of the ammonium load in the wastewater treatment: 
    • Reduction in the use of oxygen in the biological treatment step;
    • Reduction of the ammonium load in the treated waste water; 
    • Reduction of the N2O production (the main greenhouse gas produced by WWTPs), with the possibility of accessing Klik subsidies.
  • Limited space requirement and modularity of the process (unlike stripping towers). 

For further information:

Membratec SA
Ecoparc de Daval C 1
CH - 3960 Sierre

Tél.+41 (0)27 456 86 30

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