A wetland was built to clean water from a river flowing into a lake. Different zeolites were used to help remove nitrogen. After five months, the wetland removed a lot of ammonia and nitrite, but only some of the total nitrogen and phosphorus. The main way nitrogen was removed was through nitrification and denitrification. However, because there wasn't enough carbon, denitrification was stronger than nitrification, leading to high nitrate levels in the cleaned water.