Performance and mechanism of polymorphic phosphorus removal by Fe/Al complexes with extracellular polymers derived...

In response to the production of a large amount of residual sludge in wastewater treatment plants and increasingly stringent phosphorus emission standards, this study utilized sludge from urban wastewater treatment plants as a raw material to prepare Fe/Al complexes with extracellular polymers (Fe/Al-EPS) and applied them for the removal of multi-form phosphorus from wastewater. The compositional surface properties of Fe/Al-EPS were analysed by Fourier transform infrared spectroscopy (FTIR) and inductively coupled plasma-optical emission spectrometer (ICP-OES), and successfully established an evaluation framework for phosphorus removal performance through factor analysis. It was determined that electrical neutralisation and complexation were the key factors influencing the phosphorus removal performance of Fe/Al-EPS. The results demonstrated that the selected Fe/Al-EPS-5 effectively removed inorganic phosphorus (approximately 94 %), particulate phosphorus (87.36 %), and the majority of dissolved organic phosphorus (about 69.67 %) from wastewater, reducing the total phosphorus (TP) concentration from an influent level of 3-4 mg/L to below 0.50 mg/L. The removal process of multi-form phosphorus involved chemical precipitation by metallic aluminum, complexation by Fe-Al polynuclear hydroxyl groups, as well as complexation, adsorption, and bridging by the active sites of polymeric proteins. The findings provide a novel method and insights for the screening of multi-form phosphorus removal materials and the reuse of residual sludge.