A study tested eight different plants in floating wetlands to see how well they could remove nitrogen and phosphorus from wastewater. They found that different plants removed different amounts of nitrogen and phosphorus, with purple loosestrife being the best at removing nitrogen and Thalia dealbata being the best at removing phosphorus. All plants effectively removed nitrogen and phosphorus, and the water quality met standards for municipal wastewater treatment. The longer the plants were in the water, the more nitrogen and phosphorus they removed.