Struvite precipitation from anaerobic sludge supernatant and mixed fresh/stale human urine

Phosphorus recovery attracts increasing attentions because phosphorus is a non-renewable and exhausted resource. This study for the first time remarkably improves the efficiency of phosphorus recovery in the form of struvite using the mixture of two kinds of phosphorus-rich wastewater (i.e., anaerobic sludge supernatant and human urine). An optimal volumetric ratio (VRs/f) of 1:9 of fresh and 10-d stale human urine could yield phosphorus recovery of 90.8% at [Mg2+]:[NH4 +-N]:[PO4 3?-P] = 1.2:1.05:1, pH 10, and reacting time 15 min. The SEM and XRD analyses confirmed the precipitates were struvite. Struvite precipitation was determined by relative supersaturation in both nucleation and crystal growth phases, with homogenous nucleation predominated in the latter phase. One liter of mixed urine could recover the PO4 3?-P content in 41.9 L of anaerobic sludge supernatant to form 182.3 g of struvite. ? 2018 Elsevier B.V.