Migration and transformation mechanism of phosphorus in waste activated sludge during anaerobic fermentation and hydrothermal conversion

This study investigated migration and transformation mechanism of P in waste activated sludge (WAS) during anaerobic fermentation (AF) process the subsequent hydrothermal conversion (HTC) process. Control pH AF processes was found to be significant, whereby use acidic (pH = 5.5) or alkaline conditions 9.5) facilitated release either apatite phosphorus (AP) non-apatite inorganic (NAIP) organic phosphorus, respectively. At same 9.5, NaOH promoted transfer into liquid phase, solid phase mainly form NAIP. In contrast, Ca(OH)2 enhanced incorporation products, with AP. The HTC NAIP transferred AP, bioavailability products decreased. K-edge X-ray absorption near edge structure analysis provided detailed information about phosphates. It demonstrated that Ca8H2PO4·6.5H2O Ca5(PO4)3·OH by under condition. sheds lights on speciations processes, which would provide fundamental for effective utilization bio-wastes.