Feasibility study of struvite production from Saravan landfill leachate

High concentrations of ammonium and phosphate in leachate allow producing the struvite mineral (MgNH4PO4·6H2O), which is a valuable slow-release fertilizer in agriculture. In this study, the possibility of struvite precipitation from the Saravan landfill leachate was considered. The research was conducted in the Soil Sciences Department of the University of Guilan in 1400. Leachate was sampled and the concentration of ammonium, phosphate and magnesium ions in the leachate was measured. Struvite precipitation was evaluated in three molar ratios 1:1:1, 1:1.2:1.2, and 2.5:2:1 of [NH4+]:[Mg2+]:[PO43−] and at two different pHs; 9 And 9.5. Since, the amount of ammonium in the leachate was much higher than magnesium and phosphate, the tested molar ratios were established based on the ammonium concentration and the magnesium and phosphate concentrations were adjusted by magnesium chloride (MgCl2.6H2O) and phosphoric acid (H3PO4), respectively. XRD and FTIR analysis were used to assess the precipitated struvite mineralogy. The position and intensity of the peaks in the precipitate formed in all treatments were in good agreement with the standard struvite peak, which confirmed the precipitation of this mineral. FT-IR analysis showed the spectrum of struvite mineral in all tested molar ratios. Comparison of the formed precipitate showed that at pH= 9.5 the amount of struvite formed in molar ratios of 1:1:1, and 1:1.2:1.2 of [NH4+]:[Mg2+]:[PO43−] was more than that at pH=9. Removal of ammonium from the leachate at pH=9.5 and in molar ratios of 2.5:2:1, 1:1.2:1.2, and 1: 1: 1 was 45.5, 39.7 and 32.7%, respectively. Therefore, the use of resources such as landfill leachate in the struvite production, while removing ammonium, can reduce the production cost of this fertilizer.