The study looked at how long wastewater stays in a wetland affects the removal of pollutants. They tested two wetlands, one with occasional air bubbles and one without. The wetland with air bubbles removed more pollutants like COD, TN, and phosphorus compared to the one without. This is because the air bubbles help different processes work together to clean the water better. So, adding air bubbles to wetlands can make them more effective at cleaning wastewater.