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.