Effect of Different Organic Compounds on Phosphorus Removal by Ferric Iron-dependent in Wastewater Treatment

The iron ion (Fe(III)-dependent phosphorus removal process) is frequently observed to be inefficient in current wastewater treatment technologies, particularly in the presence of organic compounds in the wastewater. However, the precise mechanism by which this occurs remains unclear. In this study, the effects of different organic compounds, including citric acid, xanthate, polysorbate 80, bovine serum albumin, glucose, and starch, on the efficiency of Fe(III)-dependent phosphorus removal were investigated in depth through the use of well-designed batch experiments combined with the analytical techniques of Fourier Transform Infrared Spectroscopy (FTIR) and X-ray Diffraction (XRD). The experimental results yielded a significant finding: carboxylic organics, particularly polycarboxylic organics such as citric acid, exerted a markedly greater influence on phosphorus removal efficiency than hydroxy organics, exhibiting an intensity index as high as 5 to 20 times that of other organics. Specifically, citric acid was observed to reduce the number of binding sites available for phosphate, competing with phosphate for the surface binding sites of iron hydroxyl oxides (Fe-HFOs). This resulted in a significant reduction in phosphorus removal efficiency. Furthermore, this study presents an innovative mechanistic model to elucidate the mechanism by which organic matter “seizes” the surface of Fe-HFO, leading to the reduction of phosphorus removal efficiency. This study not only enriches the theoretical basis of chemical phosphorus removal but also provides new perspectives and technical support for the pretreatment of organic matter in practical wastewater treatment. This is of great theoretical and practical significance for improving the efficiency of wastewater treatment in the future.