A study in rural China looked at how well a system combining a wetland and an oxidation pond cleaned up household wastewater. The system did a good job removing organic matter and phosphorus in the first year. After 3 years, some parts of the wetland got clogged, but changing the substrate and increasing the pond depth improved the system's ability to remove pollutants like COD and TP. The wetland reduced ammonia and total nitrogen levels by a lot, mainly by creating an oxygen-free environment in the substrate.