What is it about?

Effectiveness of P precipitation requires a process-based knowledge regarding pH, Mg:PO4 ratio, contact time and their interactions in P recovery and crystal morphology. The study analysis this interaction of factors and highlights those which bring the best combo of recovery + crystal properties. Being that the properties also affect how effective a precipitate is as a fertilizer.

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Why is it important?

Focusing only on mazimizing P recovery not giving relevance to crystal properties may generate a big problem when transitioning to a macroscale operation. Other than that, crystals obtaine dof higher % recovery may present smaller sizes and poor structural properties that lead to bad fertilizers as they will get dissolved easily by rain and will end up accumulate faster in water bodies.


This article highlights several aspects that until now were either dispersed or not available at all in one place. We aimed at understanding the process behind, understanding what was already made before so we can aim at improving the process in the future.

Denis Rodrigues
Instituto Superior de Agronomia da Universidade de Lisboa

Read the Original

This page is a summary of: Recovery of phosphates as struvite from urine-diverting toilets: optimization of pH, Mg:PO4 ratio and contact time to improve precipitation yield and crystal morphology, Water Science & Technology, November 2019, IWA Publishing, DOI: 10.2166/wst.2019.371.
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