How Wetlands Can Help Clean Water in Small Towns

Wetlands are a cheap and easy way to clean water in small towns. But, most studies on these wetlands don't look at how they work when water flow changes throughout the day. This is important because water use in small towns isn't constant. In a recent study, three types of wetlands were tested. They were filled with different materials: zeolite and woodchips, gravel and woodchips, and just woodchips. The study looked at how well these wetlands cleaned water when different amounts of water were added at different times of the day.The wetlands did a good job at removing organic matter and tiny solid particles from the water. But, the amount of nitrogen removed depended on the type of wetland and the size of the water dose. Zeolite-woodchip wetlands removed the most nitrogen, no matter the dose size. The other two types of wetlands removed less nitrogen as the dose size increased. The study also found that the way the wetlands were set up, with both free-draining and saturated layers, helped to remove nitrogen. The smallest dose size led to the most nitrogen removal in the woodchip-only wetlands. But, in the zeolite-woodchip wetlands, the largest dose size still removed a lot of nitrogen. However, larger doses also led to more bacteria and phosphorus getting into the water. This happened because the water moved through the wetlands too quickly.