Coupled iron-modified biochar and <i>myriophyllum</i> for nutrient and oxytetracycline removal from aquaculture wastewater

To enhance system performance through substrate engineering, iron-modified oyster shell biochar (IOBC) was developed as a functional medium and coupled with <i>Myriophyllum</i> in an ecological purification system. Response surface methodology identified optimal IOBC preparation conditions of 700 °C, a modification ratio of 1:1, and 3.5% iron addition, under which oxytetracycline (OTC) removal reached 89.37%.

The optimized IOBC was subsequently incorporated into a continuous-flow system treating simulated aquaculture wastewater. In the continuous-flow system treating simulated aquaculture wastewater, pollutant removal increased with hydraulic retention time, and the coupled IOBC-<i>Myriophyllum</i> treatment consistently outperformed the filler-only and plant-only systems. At 72 h, the coupled system achieved removal efficiencies of 38.89% for NH₄⁺-N, 38.79% for TN, 72.81% for TP, 67.67% for COD_Mn, and 59.46% for OTC.