Wang Yang, Zhang Xiao-jian, Chen Chao, Pan An-jun, Xu Yang, Liao Ping-an, Zhang Su-xia, Gu Jun-nong
Department of Environmental Science and Engineering, Tsinghua University, Beijing 100084, China.
Huan Jing Ke Xue. 2009 Dec;30(12):3555-61.
Red water phenomenon occurred in some communities of a city in China after water source switch in recent days. The origin of this red water problem and mechanism of iron release were investigated in the study. Water quality of local and new water sources was tested and tap water quality in suffered area had been monitored for 3 months since red water occurred. Interior corrosion scales on the pipe which was obtained from the suffered area were analyzed by XRD, SEM, and EDS. Corrosion rates of cast iron under the conditions of two source water were obtained by Annular Reactor. The influence of different source water on iron release was studied by pipe section reactor to simulate the distribution systems. The results indicated that large increase of sulfate concentration by water source shift was regarded as the cause of red water problem. The Larson ratio increased from about 0.4 to 1.7-1.9 and the red water problem happened in the taps of some urban communities just several days after the new water source was applied. The mechanism of iron release was concluded that the stable shell of scales in the pipes had been corrupted by this kind of high-sulfate-concentration source water and it was hard to recover soon spontaneously. The effect of sulfate on iron release of the old cast iron was more significant than its effect on enhancing iron corrosion. The rate of iron release increased with increasing Larson ratio, and the correlation of them was nonlinear on the old cast-iron. The problem remained quite a long time even if the water source re-shifted into the blended one with only small ratio of the new source and the Larson ratio reduced to about 0.6.
近日，中国某城市部分社区在水源切换后出现了红水现象。本研究对该红水问题的成因及铁释放机制进行了调查。检测了当地及新水源的水质，并自红水现象出现以来，对受灾地区的自来水水质进行了3个月的监测。对取自受灾地区管道的内部腐蚀垢进行了XRD、SEM和EDS分析。通过环形反应器获得了两种水源条件下铸铁的腐蚀速率。采用管段反应器模拟配水系统，研究了不同水源对铁释放的影响。结果表明，水源切换导致硫酸盐浓度大幅增加被认为是红水问题的原因。拉森比值从约0.4增加到1.7 - 1.9，在使用新水源几天后，一些城市社区的水龙头就出现了红水问题。得出铁释放的机制为：这种高硫酸盐浓度的水源破坏了管道内水垢的稳定外壳，且难以很快自发恢复。硫酸盐对旧铸铁铁释放的影响比对铁腐蚀增强的影响更显著。铁释放速率随拉森比值的增加而增加，在旧铸铁上二者的相关性呈非线性。即使水源重新切换为新水源占比很小的混合水源，拉森比值降至约0.6，该问题仍持续了很长时间。
