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 (https://www.alphawt.ch
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
- Valorisation of nitrogen waste as fertilizer.
- Reduction of the ammonium load in the wastewater
- Reduction in the use of oxygen in the biological
- Reduction of the ammonium load in the treated
- 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).