A study looked at using wetlands to clean up sewage from a train station in a dry, cold area. They checked the water quality going in and coming out, as well as the temperature and flow rate. Different pollutants were removed in different seasons, and they figured out how the wetland cleaned the water. The wetland doesn't need a lot of energy, but it needs to be adjusted for the local weather. They also need to improve the initial treatment, make sure the plants grow well, and keep the wetland warm in winter.