Phosphorus Recovery through Waste Transformation: Implication for an Alternative Fertilizer

Abstract

Presently, the recovery and reuse of phosphorus are still far from being a mainstream practice. Yet, the techniques already accepted and applied differ by the origin of the used matter (wastewater, sludge, ash) and are mainly focused on the process of precipitation. One of these techniques is struvite (magnesium ammonium phosphate; MAP; MgNH4PO4·6H2O) precipitation, which can be implemented in wastewater treatment plants that use enhanced biological or semi-biological/chemical phosphorus (P) removal. Struvite/MAP is formed by a basic precipitation reaction in different stages of the wastewater treatment process, where magnesium (Mg2+), ammonium (NH4+), and orthophosphate (PO4−3). This chapter aims to discuss: (i) the progress in extraction of P from sewage sludge and animal manure; (ii) the methods to create optimal conditions for struvite precipitation in such media; (iii) the avenues for overcoming the problems associated with choosing the right Mg source, pH adjustment and the non-acceptable level of organic matter in the initial suspension; and (iv) the implication of struvite as an alternative fertilizer for the global agriculture sector.