The advantage of a two-stage nitrification method for fertilizer recovery from human urine

Zhiqiang Zuo, Yan Chen, Yaxin Xing, Siqi Li, Shaolin Yang, Guangming Jiang, Tao Liu, Min Zheng, Xia Huang, Yanchen Liu

Research output: Journal article publicationJournal articleAcademic researchpeer-review

8 Citations (Scopus)


Recycling nutrients (nitrogen, phosphorus, and potassium) from human urine can potentially offset more than 13% of global agricultural fertilizer demand. Biological nitrification is a promising method for converting volatile ammonia in high-strength human urine into stable ammonium nitrate (a typical fertilizer), but it is usually terminated in the intermediate production of nitrite due to the inhibition of nitrite-oxidizing bacteria by free nitrous acid (FNA). This study aimed to develop a stable nitrification process in a unique two-stage bioreactor by removing critical barriers associated with FNA inhibition. Experimental results show that half of the ammonium in high-strength urine was successfully converted into nitrate, forming valuable ammonium nitrate (with a nitrogen concentration greater than 1500 mg N/L). The ammonium nitrate solution could retain most phosphorus (75% ± 3%) and potassium (96% ± 1%) in human urine, resulting in nearly full nutrient recovery. Once concentrated, the liquid compound fertilizer of ammonium nitrate was generated. Based on an assessment of economic and environmental impacts at the urban scale, urine diversion for nutrient recovery using a technical combination of nitrification and reverse osmosis could reduce total energy input by 43%, greenhouse gas emission by 40%, and cost by 33% compared to conventional wastewater management. Further research is needed to optimize the two-stage nitrification method on a larger scale.

Original languageEnglish
Article number119932
JournalWater Research
Publication statusPublished - 15 May 2023
Externally publishedYes


  • Fertilizer
  • Free nitrous acid
  • Nitrification
  • Two-stage method
  • Urine

ASJC Scopus subject areas

  • Environmental Engineering
  • Civil and Structural Engineering
  • Ecological Modelling
  • Water Science and Technology
  • Waste Management and Disposal
  • Pollution


Dive into the research topics of 'The advantage of a two-stage nitrification method for fertilizer recovery from human urine'. Together they form a unique fingerprint.

Cite this