Nutrient Platform

Nutrient Platform

Nitrogen Recovery from Sewage Sludge - Case Study

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Courtesy of Nutrient Platform

Ammonium Sulphate from process air
The air with which the compost from sludge processor GMB BioEnergie is aerated in the biological drying tunnels contains a lot of ammonia. The emission of this ammonia-rich air led to odor complaints in the past. Now we see this air as a source of nutrients. We pass the air through an air scrubber with sulfuric acid. This sulfuric acid binds the ammoniacal nitrogen, resulting in ammonium sulphate. A nitrogenous sulfur fertilizer that is officially recognized and traded as such. Good for a fertilising value of 80 kg of nitrogen and 90 kg of sulfur per tonne. Thanks to this process, odor complaints are also a thing of the past.

In Zutphen, a storage facility of 4000 m3 has been realized to be able to use ammonium sulphate during the growing season. 12,000 tonnes of ammonium sulphate is produced each year with a 38% solution. In the biological drying of sewage sludge (composting) a lot of ammonia (nitrogen) is released. This ammonia is discharged via the process air. GMB has developed a method whereby the process air is treated in an acid scrubber. The ammonia is recorded as ammonium sulphate. After the recording, the product is neutralized. The ammonium sulphate is concentrated to about 38% and remains liquid. GMB produces approximately 12,000 tonnes of ammonium sulphate from sewage sludge at its Tiel and Zutphen sites each year. This product has a positive value, is recognized as fertilizer (Appendix AA of the Implementation Regulation for the Fertilizers Act,

The special thing about the large-scale extraction of nitrogen from sewage sludge is that in sewage treatment plants the nitrogen compounds are often the most critical substances to remove from the waste water and so a relatively large amount of effort is being made to finally let the nitrogen volatilize again in the atmosphere. On the other hand, in industrial extraction, the (atmospheric) nitrogen with the use of fossil fuels (natural gas) has to be recovered (the Haber-Bosch process). Globally, about 3.3% of world natural gas production is spent on nitrogen extraction (0.75% of world energy consumption). The combination of nitrogen removal from process air that is released during biological sludge drying and recovery as ammonium sulphate is therefore distinctive.

Status
For several years fullscale in operation

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