Phosphorus removal from polluted lake water was studied in a constructed wetland system. The wetland effectively removed phosphorus, with better results in acidic water. The wetland substrate helped regulate water pH. Temperature did not significantly affect phosphorus removal. High hydraulic loads did not always decrease removal rates. Iron and calcium in the substrate played a key role in phosphorus removal. The down-flow chamber captured more phosphorus than the up-flow chamber, indicating the main source of phosphorus release.