Recovery of Struvite from High-Strength Synthetic Ammoniacal Wastewater

Struvite recovery in the form of magnesium ammonia phosphate (MAP) from high-strength nitrogenous wastewater promotes recycling of nutrients. Moreover, it prevents release of ammonia to the environment. The present study focused on MAP recovery from synthetic wastewater containing ammonia nitrogen ( NH 4 + ─ N ) concentration of 5 g / L by chemical precipitation method. The key operating parameters, i.e., pH and [ Mg 2 + ] ∶ [ NH 4 + ─ N ] ∶ [ PO 4 3 − ─ P ] molar ratio, for the precipitation process were optimized using the central composite design (CCD) to achieve effective MAP recovery. From the batch experimental runs, the following optimum conditions were found: pH = 9.6 and [ Mg 2 + ] ∶ [ NH 4 + ─ N ] ∶ [ PO 4 3 − ─ P ] molar ratio = 1 ∶ 1 ∶ 1.3 . Under these conditions, the overall NH 4 + ─ N removal was ∼ 88 % , and a total of ∼ 140 g / L precipitate was recovered. Visual MINTEQ 4.0 software was used to identi