Yuan Yujie, Zhang Tao, Zhao Yaqian, Liu Yuan, He Song, Cai Yamei, Liu Yuanbo, Wang Shu
State Key Laboratory of Water Engineering Ecology and Environment in Arid Area, Xi'an University of Technology, Xi'an, 710048, People's Republic of China.
Powerchina Northwest Engineering Corporation Limited, Xi'an, 710048, People's Republic of China.
Sci Rep. 2025 Jul 1;15(1):20430. doi: 10.1038/s41598-025-09223-4.
Urban rivers, as essential components of ecosystems, have endured severe pollution as a consequence of rapid urbanization and economic development. However, the dynamics of pollution and turbidity in urban rivers within residual red clay alluvial plains remain poorly understood, and there is an urgent need for effective engineering strategies focused on pollution control and turbidity management to improve water quality and restore ecosystem functions. This study endeavored to investigate the spatiotemporal mapping of water quality and corresponding treatment strategy for a slow-flowing urban river with lightly-pollution and seasonal high turbidity within the alluvial plain of southern China. Results from 10 sampling events showed the average concentrations of COD (15.13-22.00 mg/L), NH-N (1.15-11.70 mg/L), and TP (0.14-0.26 mg/L), corresponding to Class III-V of China's environmental quality standards for surface water (EQSSW). Annual water transparency ranged from 25 cm to 30.5 cm, although the average value of SS was only in the range of 6.0 mg/L to 24.5 mg/L. Notably, it presented significant spatiotemporal heterogeneity and frequently exceeded the standard. A total of 28 group field pilot scale in-situ tests of the coagulation-sedimentation-filtration process exhibited a highly satisfactory treatment performance on turbidity and TP. The optimal dosages of polyaluminium chloride (PAC) and polyacrylamide (PAM) were determined to be 50 ppm and 1.5 ppm, respectively. The treatment process achieved exceptional removal efficiencies of 99.53% for turbidity and 94.69% for TP, producing effluent with stabilized turbidity < 1 NTU and TP concentrations as low as 0.017 mg/L, fully compliant with Class II for EQSSW. Furthermore, the system was capable of adapting to flow variations during the rainfall events by adjusting the surface load. These findings are of great significance for the in-depth comprehension of urban river pollution dynamics in the plain area and provide effective scientific and technological support for the remediation of such lightly-polluted river with high turbidity.
城市河流作为生态系统的重要组成部分，由于快速的城市化和经济发展而遭受了严重污染。然而，残积红粘土冲积平原内城市河流的污染和浊度动态仍知之甚少，迫切需要有效的工程策略来控制污染和管理浊度，以改善水质并恢复生态系统功能。本研究旨在调查中国南方冲积平原内一条轻度污染且季节性高浊度的缓流城市河流的水质时空分布图及相应的处理策略。10次采样事件的结果显示，化学需氧量（COD）的平均浓度为15.13 - 22.00毫克/升，氨氮（NH-N）为1.15 - 11.70毫克/升，总磷（TP）为0.14 - 0.26毫克/升，对应于中国地表水环境质量标准（EQSSW）的Ⅲ - Ⅴ类。年水透明度在25厘米至30.5厘米之间，尽管悬浮物（SS）的平均值仅在6.0毫克/升至24.5毫克/升范围内。值得注意的是，其呈现出显著的时空异质性且经常超标。总共28组混凝 - 沉淀 - 过滤过程的现场中试规模试验对浊度和总磷表现出非常令人满意的处理性能。聚合氯化铝（PAC）和聚丙烯酰胺（PAM）的最佳投加量分别确定为50 ppm和1.5 ppm。该处理过程对浊度的去除效率高达99.53%，对总磷的去除效率为94.69%，产生的出水浊度稳定＜1 NTU，总磷浓度低至0.017毫克/升，完全符合EQSSW的Ⅱ类标准。此外，该系统能够通过调整表面负荷来适应降雨事件期间的流量变化。这些发现对于深入理解平原地区城市河流污染动态具有重要意义，并为治理此类轻度污染的高浊度河流提供了有效的科技支持。
