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针对水源切换引发的供水管网铁释放问题,研究了基于游离氯和氯胺调节管网水氧化还原电位(ORP)对铁释放的控制特性。研究表明,ORP≥300 m V时,氧化还原电位与游离氯具有显著正相关性,而与氯胺无相关性。采用游离氯消毒时,在低氧化还原电位(ORP≤300 m V)条件下,管壁的铁锈垢发生还原反应,铁释放随着腐蚀性阴离子浓度的升高而显著增强;在高氧化还原电位(ORP≥400 m V)条件下,管壁的铁锈垢基本稳定,离子强度的升高对铁释放基本无影响。采用氯胺消毒时,管网水的ORP<300 m V,管壁的铁锈垢易发生还原反应而引发铁释放,且离子强度越高,铁释放速率越快。可见,游离氯具有更高的氧化还原电位,对管网铁释放具有更优的控制效果。因此,当水源切换为有机物等耗氯物质含量显著降低的优质水源后,建议水厂将氯胺消毒切换为游离氯消毒。
Aiming at the release of iron in water supply pipe network caused by water source switching, the control characteristics of iron release by ORP in free water and chloramines were studied. Studies have shown that ORP ≥ 300 mV, the redox potential and free chlorine has a significant positive correlation, but no correlation with chloramine. With free chlorine disinfection, the rust scale of the tube wall is reduced under low oxidation-reduction potential (ORP≤300 mV), and the release of iron is significantly enhanced with the increase of the concentration of corrosive anion. At the high redox potential (ORP≥400 mV), the scale of iron rust in the pipe wall is basically stable, and the increase of ionic strength has no effect on iron release. With chloramine disinfection, the ORP of pipe network water is less than 300 mV, and the iron rust is easily released by the reduction of iron rust on the pipe wall, and the higher the iron ion strength, the faster the iron release rate. It can be seen that free chlorine has a higher redox potential and has better control effect on iron release from the pipe network. Therefore, when the water source is switched to a high-quality water source with a significant reduction in the amount of chlorine-containing substances such as organic matter, it is recommended that the water plant switch the chloramine disinfection to free chlorine disinfection.