An exploratory study on seawater-catalysed urine phosphorus recovery (SUPR)

Ji Dai, Wen Tao Tang, Yi Se Zheng, Hamish Mackey, Ho Kwong Chui, Mark C M van Loosdrecht, Guang Hao Chen

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29 Citations (Scopus)


Phosphorus (P) is a crucial and non-renewable resource, while it is excessively discharged via sewage, significant amounts originating from human urine. Recovery of P from source-separated urine presents an opportunity not only to recover this precious resource but also to improve downstream sewage treatment works. This paper proposes a simple and economic method to recover urine derived P by using seawater as a low-cost precipitant to form struvite, as Hong Kong has practised seawater toilet flushing as an alternative water resource since 1958. Chemical reactions, process conditions and precipitate composition for P precipitation in urine have been investigated to develop this new urine P recovery approach. This study concluded that ureolysis extent in a urine-seawater mixture determines the reaction pH that in turn influences the P recovery efficiency significantly; 98% of urine P can precipitate with seawater within 10min when 40-75% of the urea in urine is ureolysed; the urine to seawater ratio alters the composition of the precipitates. The P content in the precipitates was found to be more than 9% when the urine fraction was 40% or higher. Magnesium ammonium phosphate (MAP) was confirmed to be the predominant component of the precipitates.

Original languageEnglish
Pages (from-to)75-84
Number of pages10
JournalWater Research
Publication statusPublished - 1 Dec 2014
Externally publishedYes



  • Phosphorus recovery
  • Precipitation
  • Seawater
  • Ureolysis
  • Urine

ASJC Scopus subject areas

  • Ecological Modelling
  • Water Science and Technology
  • Waste Management and Disposal
  • Pollution

Cite this

Dai, J., Tang, W. T., Zheng, Y. S., Mackey, H., Chui, H. K., van Loosdrecht, M. C. M., & Chen, G. H. (2014). An exploratory study on seawater-catalysed urine phosphorus recovery (SUPR). Water Research, 66, 75-84.