Removal and recovery of phosphate anion as struvite from wastewater

Phosphorus is one of the controlling factors for water eutrophication, but it is also an essential nutrient for all living organisms and non-renewable resource. A feasibility study on PO43- recovery and conversion to struvite (NH4MgPO4 center dot 6H(2)O), a slow-release fertilizer, has been reported. However, the fertilizer efficiency of struvite is determined by its purity, which depends on the forms and molar ratio of reactants under different initial pH of the solution. Laboratory-scale experiments were carried out to determine the optimum initial pH of the solution and molar ratio of reactants on struvite crystallization. Meanwhile, the purity of the synthesis product struvite was analyzed. The experiment results revealed the optimum initial pH being 10 with molar ratio of PO43-:Mg2+:NH4+=1:1.3:1 and 1:2:5 for struvite formation, which the removal of the PO43-, Mg2+ and NH4+ being 98, 92, 95% and 99.5, 85, 90%, respectively. A chemical equilibrium model (Visual Minteq) corroborated the experimental results. Thus, the possibility of synthesizing struvite from simulated wastewater utilizing the phosphate ions (PO43-) was confirmed. [GRAPHICS] .