Wastewater Treatment for a Sustainable Future: Overview of Phosphorus Recovery

Abstract

Intensified agriculture in response to the growing population has led to excessive nutrient discharges to natural waters causing environmental problems in the form of eutrophication and its associated risks. Treatment options for this adverse effect include removal and recovery of soluble phosphorus by chemical precipitation, biological uptake, and struvite crystallisation. Chemical precipitation is the most common method due to its simplicity, but the chemical requirements can be prohibitive and the removed phosphorus is less reusable. Biological uptake requires less chemicals but the process is complex and prone to seasonal variations. Phosphorus removal and recovery from wastewater by struvite crystallisation is an attractive option since the crystallisation process converts phosphorus into struvite crystals, i.e. phosphate minerals which have proved to be good fertilizer, hence potentially reduces fertilizer production and the subsequent greenhouse gas emissions. Moreover, struvite crystallisation helps prevent scaling of wastewater treatment facilities. A number of struvite crystallisation projects utilising primarily agricultural wastewater is already operational at industrial scale.