Comprehensive study on the removal performance of K2FeO4 in domestic wastewater under industrial shock loading: Mechanisms, engineering applications, and machine learning prediction

A domestic wastewater treatment plant(DWWTP) experienced inflow shocks due to the illegal discharge of external industrial wastewater, which adversely affected the effluent quality. This study systematically investigates the removal performance and underlying mechanisms of K₂FeO₄ with respect to various pollutants in both simulated and real wastewater influents. The removal of inorganic pollutants is primarily attributed to the coagulation effect of the in-situ generated Fe(III) (reduction product). Conversely, the degradation of organic pollutants relies on direct oxidation by Fe(VI), wherein high-valent intermediate iron species (Fe(V)/Fe(IV)) serve as critical oxidative intermediates. Engineering trials, integrated with machine learning (ML) model predictions, demonstrate that K₂FeO₄ pretreatment effectively transforms refractory organic phosphorus (O-P) and organic nitrogen (O-N) and significantly enhances wastewater biodegradability, thereby creating favourable conditions for subsequent biological treatment. This work elucidates the synergistic "oxidation-coagulation" mechanism of K₂FeO₄ in wastewater pretreatment, providing a robust theoretical foundation for its full-scale engineering application.