Abstract
Over the past decades, constructed wetlands (CWs) have been widely used to treat domestic, industrial or agricultural waste waters. There are few cases in which this technology is being applied to the treatment of eutrophic waters, but their use is growing up in the last years. This study presents results of dry biomass, nutrients content, and potential use of three different plants (Iris pseudacorus, Phragmites spp., Typha spp.) in the Tancat de la Pipa free water surface constructed wetlands (TPCWs) aimed at treating eutrophic water within a natural park (Albufera de Valencia, Spain). Sampling and analyses were performed according to official methods. Measured tissue concentrations are on average 10.1, 10.8 and 11.7 mg N/g dw and 1.7, 2.1 and 1.2 mg P/g dw for iris, cattail and reed respectively. The maximum above-ground biomass reached is 1.85, 3.35 and 14.00 kg dw/m2 for cattail, iris and reed respectively. Among the plants studied, Iris pseudacorus is presented as a viable option in this type of system. Reed and cattail have certain advantages in terms of nutrient removal: reed has the highest dry biomass per unit area; whereas cattail has the highest phosphorus content. However, they have proved impractical in the long term in the TPCWs: reed does not spread properly and cattail is subject to a high bird predation. In contrast, iris spreads suitably and is aesthetic throughout the year. Additionally, harvest experiments have shown that after two or more harvests per year, iris grows properly, whereas reed does not.
