Enhanced Simultaneous Phosphate Recovery and Organics Removal by a Nucleation Crystallization Pelleting Process

Naturally co-occurring phosphate (P) and dissolved organic matter (DOM) in raised livestock wastewater have caused increasing public concerns. This study fabricated a novel nucleation crystallization pelleting process (NCP) showing orientated P recovery and HA (as a major fraction of DOM) removal from wastewater. Results showed that after 120 h of continuous operation, the total removal efficiency of P and HA stabilized at 97.5 % and 92 %, respectively, by using a three-stage NCP process. The NCP results further demonstrated that the main recovery mechanism of P involves surface-induced precipitation of P in the form of hydroxyapatite (HAP) on the seed surface by modulating the supersaturation of HAP in the system. The FTIR, SEM-EDS, and XPS analysis combined with DFT calculations revealed the molecular-level mechanisms for removing HA, which were mainly controlled by Calcium ions bridging, H-bonding, and 7C-7C stacking. More importantly, the attached HAP on the seed surface would enhance the mutual interaction with HA, further enhancing the removal efficiency of HA. This contribution not only opens a high potential avenue for further research on the simultaneous capture of P and organic matter but also sheds light on the development of the practical application of the NCP remediation strategies.