A study looked at how well a wetland in Zhoushan city cleaned up wastewater. They found that from May to October in 2010, the wetland removed around 65% of COD, 45% of BOD5, 73% of TN, 61% of NH4-N, and 35% of NO3-N pollutants. However, they also discovered some issues like not enough water going into the wetland and poor plant management.