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Updated: Jul 18, 2026

Measuring Phosphorus Release in Laboratory Microcosms for Water Quality Assessment
Published on: July 22, 2019
Predicting struvite formation for phosphorus recovery from human urine using an equilibrium model
H Harada1, Y Shimizu, Y Miyagoshi
1Graduate School of Global Environmental Studies, Kyoto University, Yoshida-Honmachi, Sakyo-Ku, Kyoto 606-8501, Japan. harada@eden.env.kyoto-u.ac.jp
Recovering phosphorus from urine as struvite is gaining interest. A new model accurately predicts struvite formation, showing optimal pH is 9.4-9.7 for efficient phosphate recovery.
Area of Science:
- Environmental Science
- Chemical Engineering
- Water Treatment
Background:
- Growing interest in phosphorus recovery from urine due to resource scarcity.
- Struvite precipitation (MgNH4PO4 x 6H2O) is a key method for phosphorus recovery from urine.
- Understanding struvite formation is crucial for practical application in wastewater treatment.
Purpose of the Study:
- To develop and validate a new equilibrium model for predicting struvite formation in urine.
- To investigate the effects of ionic strength and temperature on struvite precipitation.
- To determine optimal conditions for maximizing phosphate recovery from urine.
Main Methods:
- Development of a novel equilibrium model considering multiple precipitate formations.
- Inclusion of ionic strength and temperature effects in the model.
- Experimental validation of model predictions using real urine samples.
Main Results:
- The developed model showed good agreement with experimental results for struvite formation.
- Predicted optimal pH range for struvite formation is 9.4-9.7.
- A pH above 8.1 is required to precipitate 99% of phosphate with 1.5x magnesium concentration.
Conclusions:
- The new equilibrium model provides accurate predictions for struvite formation from urine.
- Optimal pH conditions are identified for efficient phosphorus recovery.
- The findings support the practical application of struvite precipitation for urine-derived phosphorus recovery.
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