平原河网区城市水污染特征及控制对策研究

以典型平原河网城市——苏州市为例,进行水污染成因及控制研究。前街后河的棋盘式河网格局体现了苏州市特有的文化风貌,也使得苏州市同样存在平原河网城市共有的环境特征。古城区内,水体流速不大于0.01 m/s,C∶N严重失衡为0.4~1.4(其中C以BOD5计算),水生态系统已遭到严重的破坏。针对苏州市古城区水污染特征,从区域水文循环角度,提出了时空分步实施的综合治理理念。即首先进行内外污染源控制;再通过适当的闸坝调度引入周边太湖或长江清洁水源,改善古城区水体水动力条件、缓解水体碳氮失衡;对于局部污染仍严重的水体进一步实施原位强化净化工程。通过效果评估分析及实施综合治理方案后,可使水体水质达到地表水环境质量Ⅳ类水标准。该方案为其他平原河网城市的水污染控制提供了参考。

Water pollution characteristics and control measures in cities of plain river network area

The causes of water pollution and control measures in Suzhou City,a typical city in the plain river network area,were investigated.The chessboardshaped river network has both the special cultural characteristics of Suzhou and the common water environmental characteristics of the plain river network area.In the ancient urban area,the flow velocity was less than 0.01 m/s and the C/N ratio(the C amount was obtained from BOD5) was unbalanced,in the range of 0.4-1.4.This indicates that the aquatic ecosystem was seriously destroyed. On the basis of the water pollution characteristics of the ancient urban area of Suzhou,an integrated pollution control plan considering the temporal and spatial variation is presented in terms of the regional hydrological cycle.Firstly,external and internal pollution sources will be controlled.Then,clean water from the Yangtze River or Taihu Lake will be diverted to the ancient urban area through dam and sluice control to improve the hydrodynamic conditions of the water and to balance the C/N ratio.Finally,for some channel sections still seriously polluted after the aforementioned two measures,in situ purification projects will be carried out.The efficiency of this plan for water environment improvement is evaluated.Results show that the water quality can reach Class Ⅳ criteria of the Environmental Quality Standards for Surface Water(GB3838-2002) of China after the implementation of the plan.This plan provides references for other cities in the plain river network area.