Accumulation of Nitrogen Species from Industrial Wastewater by Vetiver Grass (Chrysopogon zizanioides)

Industrial munition facilities are increasingly manufacturing insensitive high explosives (IHEs) to improve safety. The explosive residues in wastewater from these facilities are treated to meet regulatory standards. However, the resulting effluent contains elevated levels of mineralized nitrogen species. This study evaluated the potential of vetiver grass (Chrysopogon zizanioides), a non-invasive perennial species, to remove high concentrations of nitrate, nitrite, and ammonium from munition plant wastewater. Vetiver was grown hydroponically in synthetic wastewater containing high levels of nitrogen compounds simulating munitions plant effluents. Vetiver plants were treated with one nitrogen species at a time, with concentrations ranging from 165 to 24,700 mg N/L of nitrate, 100 to 4000 mg N/L of nitrite, and 260 to 39,000 mg N/L of ammonium. Nitrogen concentrations in the media and plant responses were monitored over time. The results showed significant nitrogen removal at lower concentration ranges. When concentrations exceeded 3800 mg N/L of nitrate, 800 mg N/L of nitrite, and 2600 mg N/L of ammonium, the removal rates declined after 7 days. At higher nitrogen levels, vetiver exhibited stress symptoms such as chlorosis and elevated antioxidant enzyme activity. Our study demonstrates the potential of vetiver grass in treating nitrogen-rich wastewater from the munition industry and provides a baseline for future large-scale studies to optimize the technology.