Migration of Phosphorus in Sewage Sludge during Different Thermal Treatment Processes

The utilization of phosphorus (P) in activated sludge discharged from wastewater treatment plants is an important part of the global phosphorus circulation. Thermal treatment of excess sludge would become a promising method for their disposal throughout the world. Herein, we investigated the transformation and migration of P in sewage sludge during different thermal treatment conditions. The results indicate that the temperature can significantly influence the species and content of P in the sewage sludge char or ash (SSC/A), while the atmosphere of thermal treatment has a slight effect on the fate of P. 31P NMR and XRD analysis indicated that P migrated mainly to the medium-term plant available P pool (poolNaOH) on treating the sewage sludge at a low temperature (673–873 K), while it was prone to migration to the long-term plant available P pool (poolHCl) when treated at a high temperature (873–1073 K).