Abstract
This study evaluates the effectiveness of vetiver grass (Chrysopogon zizanioides) in floating treatment systems (vetiver FTS) for improving water quality in temperate agricultural regions of Japan. Three types of water—natural surface water (lakes and rivers), synthetic eutrophic water, and livestock wastewater—were treated, and key water quality parameters, including total nitrogen (TN), total phosphorus (TP), chemical oxygen demand (COD), suspended solids (SS), and inorganic ions, were monitored over time. Vetiver consistently reduced TN (up to 60%) and SS in all water types. TP decreased by up to 48% in nutrient-rich waters (synthetic eutrophic water and livestock wastewater), but slightly increased in natural surface water. COD decreased only in livestock wastewater. Nutrient uptake occurred rapidly within 4–7 days, and root development remained stable across all water types. Statistical analysis confirmed significant reductions in TN and TP under high-nutrient conditions. These results indicate that vetiver FTS consistently enhances the removal of nitrogen and suspended solids, partially reduces phosphorus and COD, and holds promise as a cost-effective, low-maintenance phytoremediation strategy for agricultural wastewater in temperate regions of Japan. Further studies are needed to evaluate seasonal variability and rhizosphere processes.
https://ror.org/05jk51a88 
