Separation and Purification Technology vol:110 pages:150-157
The concern about phosphorus depletion is driving more efficient phosphorus use and recycling. In this
context the precipitation of phosphate as struvite from wastewaters has recently gained considerable
traction. This study investigates the influence of different parameters on the ureolytic phosphate precipitation
(pH increase by means of urease activity). Wastewater with a high phosphate concentration
(>50 mg L1 PO4–P) and low volatile suspended solids (63.0 g L1 VSS) resulted in a high phosphate
removal efficiency (87%) and struvite crystals that could be separated from the sludge. An increase in
ionic strength resulted in a decrease in ureolytic activity. An increase in Mg2+:PO43-
molar ratio increases
the degree of supersaturation with respect to struvite formation, which enhances the phosphate removal.
Above a Mg2+:PO43-
molar ratio of 3, additional Mg2+ dosage did not significantly affect the phosphate
removal efficiency. Wastewater containing low phosphate concentrations (<50 mg L1 PO4–P), needed
disproportionally large chemical additions and are thus not economically rewarding. For those wastewaters
the presence of calcium interfered with the struvite precipitation rendering the precipitation of calcium
phosphate a better option.