Constructed wetlands were used to clean up polluted water in an urban river in North China. By combining different types of wetlands, the system effectively removed pollutants like COD, ammonia, nitrogen, phosphates, and solids. The floating-bed wetland was best at removing solids, while the sub-surface flow wetland was great at removing ammonia, nitrogen, and phosphates. The surface flow wetland further purified the water by removing nitrogen. The total cost of this eco-friendly system was $12,000, much cheaper than traditional sewage treatment. This study shows that constructed wetlands can be a cost-effective way to clean up polluted urban rivers.