Constructed wetlands can play an active role in improving the water quality of urban rivers. In this study, a sequential series system of the floating-bed constructed wetland (FBCW), horizontal subsurface flow constructed wetland (HSFCW), and surface flow constructed wetland (SFCW) were constructed for the urban river treatment in the cold regions of North China, which gave full play to the combined advantages. In the Yitong River, the designed capacity and the hydraulic loading of the system was 100 m3/d and 0.10 m3/m2d, respectively. The hydraulic retention time was approximately 72 h. The monitoring results, from April to October in 2016, showed the multiple wetland ecosystem could effectively remove chemical oxygen demand (COD), ammonia nitrogen (NH4+-N), total nitrogen (TN), total phosphate (TP), and suspended solids (SS) at average removal rates of 74.79%, 80.90%, 71.12%, 78.44%, and 91.90%, respectively. The removal rate of SS in floating-bed wetland was the largest among all the indicators (80.24%), which could prevent the block of sub-surface flow wetland effectively. The sub-surface flow wetland could remove the NH4-N, TN, and TP effectively, and the contribution rates were 79.20%, 64.64%, and 81.71%, respectively. The surface flow wetland could further purify the TN and the removal rate of TN could reach 23%. The total investment of this ecological engineering was $12,000. The construction cost and the operation cost were $120 and $0.02 per ton of polluted water, which was about 1/3 to 1/5 and 1/6 to 1/3 of the conventional sewage treatment, respectively. The results of this study provide a technical demonstration of the restoration of polluted water in urban rivers in northern China.

中文翻译：

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序贯人工湿地对城市河流污水的净化效果

人工湿地可以在改善城市河流水质方面发挥积极作用。本研究构建了浮床人工湿地（FBCW）、水平潜流人工湿地（HSFCW）和地表流人工湿地（SFCW）的序贯串联系统，用于华北寒冷地区的城市河流治理。 ，充分发挥了综合优势。在伊通河，系统的设计容量和水力负荷分别为100 m3/d和0.10 m3/m2d。水力停留时间约为 72 小时。2016年4-10月监测结果表明，多湿地生态系统能有效去除化学需氧量（COD）、氨氮（NH4+-N）、总氮（TN）、总磷酸盐（TP）、和悬浮固体 (SS) 的平均去除率分别为 74.79%、80.90%、71.12%、78.44% 和 91.90%。浮床湿地对SS的去除率在各项指标中最大（80.24%），可以有效防止次表层流湿地的堵塞。次表层流湿地能有效去除NH4-N、TN和TP，贡献率分别为79.20%、64.64%和81.71%。地表流湿地可以进一步净化TN，TN去除率可达23%。这项生态工程的总投资为12,000美元。每吨污水的建设成本和运营成本分别为120美元和0.02美元，分别约为常规污水处理的1/3至1/5和1/6至1/3。