Effective phosphorus removal using transformed water hyacinth: Performance evaluation in fixed-bed columns and practical applications

This study introduces calcined water hyacinth (CWH), processed at 650°C, as a novel and environmentally friendly adsorbent for phosphorus (P) removal from wastewater. Building on previous findings that identified CWH as a rich source of metal oxides and hydroxides (e.g., Ca(OH)₂, Al₂O₃, MgO, Fe₃O₄), this research explores its application in fixed-bed column systems for continuous adsorption processes. The study demonstrates that CWH effectively removes phosphorus through apatite formation, showcasing its potential for real-world water treatment. The phosphorus adsorption capacity increased from 23.64 to 26.55 mg/g when the flow rate was reduced from 1.5 to 0.5 mL/min. Breakthrough curves fitted to the Thomas, Adams-Bohart, and Yoon-Nelson models provided critical insights into column performance, while the Bed Depth Service Time (BDST) model confirmed the feasibility of employing CWH in continuous-flow systems. The practical tests on synthetic municipal wastewater, which revealed a maximum adsorption capacity of 5.20 mg/g, further demonstrated CWH's effectiveness for treating wastewater with low phosphorus concentrations, providing reassurance about its real-world applicability. Furthermore, the study found that increasing the adsorbent height improved column performance by extending breakthrough and exhaustion times, whereas higher flow rates led to faster saturation and reduced capacity. The exhausted CWH material can be repurposed as a soil amendment or fertilizer feedstock, supporting nutrient recycling.