A study tested how well wetlands with plants can clean up household wastewater. They set up four different wetlands with different plants and studied how long the water stayed in each one. The wetlands with plants removed almost all of the nitrogen in the water, while the one without plants didn't do as well. The wetlands also did a good job at removing phosphorus. Overall, wetlands with plants, especially ones with Phragmites australis or a mix of plants, were the most effective at cleaning up the water.