Sustained nutrient removal in constructed wetlands using Equisetum giganteum

Constructed wetlands are a cost-effective, nature-based solution for water pollution control, offering ecological and socioeconomic benefits as a sustainable alternative for secondary and tertiary wastewater treatment. While some Equisetum species act as "nutrient pumps" by removing soil nutrients, research on their use in wastewater treatment remains limited. The aim of this study was to measure the nutrient removal efficiency (N and P) from secondary wastewater comparing two helophytes commonly used in wastewater treatment (Phragmites australis, Typha latifolia) to Equisetum giganteum. A two-year experiment was conducted in outdoor mesocosms, comparing the removal of nutrients from wastewater in these species of plants to control mesocosms with sand. E. giganteum demonstrated consistently high nutrient removal rates throughout the experiment, outperforming all other plant candidates. It removed 76.88 % of total phosphorus and 74.18 % of soluble reactive phosphorus, maintaining over 50 % removal for most of the studied period. Its total phosphorus removal mass rate was significantly higher than that of other species. Similarly, total nitrogen removal was nearly 13 times higher than controls, with an average removal of 57.7 %, remaining positive even during cold seasons. Ammonia nitrogen was almost completely removed, and while nitrates increased, E. giganteum still removed nearly twice as much N-NO₃^- as the other treatments. This study highlights E. giganteum-constructed wetlands as highly efficient for tertiary wastewater treatment, removing significant P and N percentages over extended periods in outdoor conditions. E. giganteum's nutrient absorption provides an eco-friendly solution for nutrient removal and recovery, aligning with green and sustainable wastewater treatment principles.