A brief history of phosphorus: from the philosopher's stone to nutrient recovery and reuse

The element phosphorus has no substitute in sustaining all life and food production on our planet. Yet today's phosphorus use patterns have resulted in both a global environmental epidemic of eutrophication and led to a situation where the future availability of the world's main sources of phosphorus is uncertain. This paper examines the important history of human interference with the phosphorus cycle from initial discovery to present, highlighting key interrelated events and consequences of the Industrial Revolution, Sanitation Revolution and Green Revolution. Whilst these events led to profound advances in technology, public health and food production, they have fundamentally broken the global phosphorus cycle. It is clear a 'Fourth Revolution' is required to resolve this dilemma and ensure humanity can continue to feed itself into the future while protecting environmental and human health.

Recovery of struvite from stored human urine

In previous work, synthetic urine was used as a readily available proxy for real urine for determining the factors which affect the recovery of struvite from urine. Based on these findings with synthetic urine, we recovered struvite from real urine and, thus, showed that a) the synthetic urine served as an adequate model for determining the processes which affect struvite precipitation, and b) high quality struvite can be recovered from real human urine. For urine solutions diluted up to four times, an average of 23% of phosphorus and 80% of magnesium was precipitated naturally; the remaining supernatant was then dosed with magnesium to recover the phosphorus still in solution. The struvite recovered was approximately 99% pure regardless of storage conditions although full strength urine was best for struvite recovery since it contains the greatest mass of harvestable phosphorus. We conclude that synthetic urine can be used as a proxy for real urine when investigating struvite recovery provided the synthetic mixture is consistent with the expected composition in the specific context.

Effects of storage on phosphorus recovery from urine

In laboratory experiments using synthetic urine the effect of temperature, faecal contamination, dilution and headspace on urine to be used as a feedstock for struvite recovery were examined. The effects of adding different quantities of magnesium on the amount of phosphorus that could be removed from solution was also examined. An average of 62% of phosphorus could be removed in the form of struvite when magnesium was added to the urine solution after ureolysis had forced the precipitation of calcium and magnesium minerals. Dilution and the presence of faecal urease were found to affect the rate of ureolysis but not the purity of the struvite recovered. These results indicate that, by simply storing urine until it achieves a pH of 8 or greater, struvite can be recovered from source-separated urine with only a magnesium addition.