水中氯离子和腐植酸对管网铁释放的影响

Effects of chloride and humic acid on iron release in water distribution system

为研究腐蚀钢管管垢层物理化学特征和管网水质条件对供水管网中铁释放现象的影响,对管龄为10～15a钢管的管垢样品进行扫描电镜(SEM)、能谱扫描(EDS)和X射线衍射(XRD)分析,利用室内管段反应器模拟水力停滞时管网水环境,研究停滞10h内,含不同浓度的氯离子、腐植酸、溶解氧的管网水对铁释放量的影响.结果表明,管垢层表面为受创硬壳层,腐蚀瘤内部具有多孔松散特点,管垢主要元素组成为Fe、O、C,主要物质组成为Fe3O4、FeOOH和FeCO3等铁氧化物.水中氯离子和腐植酸浓度与管段总铁释放量均存在正相关关系.氯离子引起的铁释放形式主要为沉淀态铁,占总体比例85.02%以上,出水浊度与总铁释放量变化一致,最高为45.5.在腐植酸存在的情况下,铁释放中的沉淀态铁比例大幅下降,最高为39.39%,平均为20.41%,在低溶解氧浓度情况下,水中总铁浓度与溶解态铁浓度比正常溶解氧浓度时高54.9%和67.7%.

In order to acquire better understanding of steel pipe scale constructions and how water quality factors influence iron release process,pipe scale samples of 10 to 15 year-old pipes were collected and analyzed with SEM,EDS and XRD.Using indoor pipe reactor simulating stagnation environment,experiments were conducted to study effects of chloride,humic acid and dissolved oxygen on iron release process under different concentrations.Results indicate that pipe scale surface is covered with shell-like layer and filled with loose and porous course inside.Major elements are Fe,O and C,and main substances are Fe3O4,FeOOH and FeCO3.Concentrations of chloride and humic acid both have significant positive correlation with iron release quantity.Iron release caused by chloride is mainly precipitant state with a proportion more than 85.02%,and water turbidity acts the same with iron concentration with maximum value of 45.5.Under conditions with humic acid,the proportion of precipitant iron decreases dramatically with an average value of 20.41% and maximum value of 39.39%.Thus water turbidity change is not significant.Under low initial dissolved oxygen condition,total iron and dissolved iron concentration increases 54.9% and 67.7% compared to normal condition.