Dutch Water Technology

Nitrogen recovery from wwtp sludge (biodrying)


Nitrogen recovery from wwtp sludge (biodrying)

Watercycle reference

The air that aerates the compost of GMB BioEnergie sludge in the biological drying tunnels contains a lot of ammonia. Emission of this ammonia-rich air has led to odor problems and caused problems in the biological air purification in the past.

GMB BioEnergie has developed a full scale method that treats the process air in an sulfuric acid scrubber. The ammonia is fixed as ammonium sulphate. After the fixation, the product is neutralized. The ammonium sulfate is concentrated to about 38% and remains liquid. 
Now we see this air as a source of nutrients. The product is a nitrogen-containing sulfur fertilizer that is officially recognized and traded as such. It has a fertilizer value of 80 kg nitrogen and 90 kg sulfur per tonne. Due to this process, odor complaints also belong to the past.

GMB produces approximately 18.000 tonnes of ammonium sulphate from sewage sludge per year at its locations in Tiel and Zutphen. 

In Zutphen, a storage facility of 4.000 m3 has been realized to enable ammonium sulphate to be used during the growing season.

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