Floating wetlands are natural systems that may be simple and rather odd but they could become a very effective treatment for wastewater due to their double purpose of taking up pollutants from water and serve as habitat for small fish and amphibians.
Scientists believe that a combination of different factors and processes are responsible for the good functioning including bacterial and plant metabolism and physical factors such as temperature and nutrient concentration. There are however some issues related to the wetlands malfunctioning. For instance algae blooms can significantly impact their efficiency.
Further studies need to be done in order to increase the efficiency of such natural systems and, their low to zero-maintenance and high sustainability.
Please read the whole article for more information