Ion-exchange softening of human urine to control precipitation

Treavor H. Boyer, Kyle Taylor, Alesandra Reed, Daniel Smith

Research output: Contribution to journalArticlepeer-review

11 Scopus citations


A major barrier to widespread implementation of urine source-separation is the uncontrolled precipitation of magnesium (Mg) and calcium (Ca) minerals in waterless urinal plumbing, which results in clogging that increases maintenance requirements. The goal of this research was to investigate the use of ion-exchange softening of undiluted, fresh human urine to control precipitation reactions in hydrolyzed urine. The working hypothesis was that selective removal of Ca and Mg from undiluted, fresh urine by cation exchange resin would decrease the precipitation of Ca and Mg minerals in hydrolyzed urine. Ion-exchange experiments and precipitation experiments were used to investigate ion-exchange reactions in synthetic urine. Cation exchange resin (Amberlite A200C) removed both Ca and Mg from undiluted, fresh urine with a greater affinity for Ca over Mg. Precipitation experiments showed that struvite, MgNH4PO4·6H2O, and hydroxyapatite, Ca5(PO4)3(OH), were the dominant minerals in untreated and ion-exchange treated hydrolyzed urine. Overall, ion-exchange softening decreased the mass of solids that would be deposited in the urinal plumbing and increased the phosphate available for nutrient recovery.

Original languageEnglish (US)
Pages (from-to)564-571
Number of pages8
JournalEnvironmental Progress and Sustainable Energy
Issue number2
StatePublished - Jul 2014
Externally publishedYes


  • calcium
  • ion exchange
  • magnesium
  • phosphate
  • polymeric resin

ASJC Scopus subject areas

  • Water Science and Technology
  • General Environmental Science
  • Waste Management and Disposal
  • General Chemical Engineering
  • Environmental Engineering
  • Renewable Energy, Sustainability and the Environment
  • Environmental Chemistry


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