Struvite pyrolysate cycling technology assisted by thermal hydrolysis pretreatment to recover ammonium nitrogen from composting leachate

Tao Zhang, Xiaosha Wu, Huanhuan Li, Daniel C.W. Tsang, Guoxue Li, Hongqiang Ren

Research output: Journal article publicationJournal articleAcademic researchpeer-review

61 Citations (Scopus)


Composting leachate containing high concentrations of nitrogen imposes a significant burden on aquatic environment. Struvite crystallization to recover ammonium nitrogen from composting leachate is limited by the inefficient capture of organic nitrogen and excessive magnesium and phosphate input. To cope with these challenges, struvite pyrolysate cycling technology coupled with a thermal hydrolysis pretreatment was investigated to recover ammonium nitrogen from composting leachate. Struvite and its pyrolysate were characterized by SEM-EDX, FTIR, and particle size analyzer. The optimal conversion rate of nitrogen in composting leachate with thermal hydrolysis-assisted was obtained at 180 °C for 75 min, achieving an NH4 +-N to total nitrogen proportion of 82.2%. The optimal parameters for struvite pyrolysate generation were found to be: molar ratio of hydroxyl to NH4 +-N of 1:1, heating temperature of 110 °C, and holding time of 3 h. SEM-EDX analysis revealed that the principal struvite pyrolysate was MgNaPO4·7H2O. When the struvite pyrolysate was reprocessed as novel magnesium and phosphate sources, the removal efficiency of NH4 +-N decreased from 98.3 ± 1.3% in the first cycle to 78.1 ± 1.0% in the fifth cycle. FTIR analysis indicated the increase in the impurities content of struvite pyrolysate and the decrease in active phosphorus and magnesium sources. Particle size analysis suggested ammonium precipitation was restricted by the crystal growth size. An economic analysis demonstrated that 59.0% of processing costs could be saved by cycling struvite pyrolysate compared with a non-cycling process.

Original languageEnglish
Article number118442
JournalJournal of Cleaner Production
Publication statusPublished - 1 Jan 2020


  • Biomass waste composting
  • Hydrothermal pretreatment
  • Nutrient resource recovery
  • Phosphate minerals
  • Waste valorization

ASJC Scopus subject areas

  • Renewable Energy, Sustainability and the Environment
  • Environmental Science(all)
  • Strategy and Management
  • Industrial and Manufacturing Engineering


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