硫酸根、氯离子和碱度对管网金属释放的影响

Effects of sulfate,chloride,and alkalinity on the release of heavy metals in drinking water distribution systems

针对给水管网水质变化引发的重金属释放、管网水变色以及潜在的健康风险等问题,利用静态模拟实验系统,研究了硫酸根(SO_(4)^(2-))、氯离子(Cl^(-))和碱度含量变化对给水管网铁(Fe)、锰(Mn)、砷(As)和铜(Cu)释放的影响.结果表明.随着SO_(4)^(2-)和Cl^(-)浓度的增加,钢管和铸铁管中的溶解氧(DO)含量不断降低,浊度不断升高;而随着碱度的增大,两种管道中的DO含量和浊度均逐渐降低.SO_(4)^(2-)和Cl^(-)浓度的增加能够促进Fe、Mn、As和Cu的释放.当SO_(4)^(2-)浓度为100mg/L时,钢管四种金属最大浓度分别为2.20mg/L,45.15,0.74和5.41μg/L;铸铁管内最大浓度分别为1.06mg/L,9.31,0.76和5.43μg/L.同样的.当Cl^(-)浓度达到100mg/L时.Fe、Mn、As和Cu的浓度达到最大值.而碱度的增加则对金属释放起抑制作用.静置48h后.碱度从70mg/LCaCO_(3)提高到200mg/LCaCO_(3)时.钢管内四种金属释放量分别减少了0.38mg/L,7.60,0.09和2.30μg/L;同样条件下,铸铁管分别减少了0.44mg/L,3.73,0.12和1.29μg/L.Fe和Mn释放受管材差异影响较大.而As和Cu的释放在钢管和铸铁管中差异较小.本研究可为给水管网水质二次污染控制提供理论基础和技术支持.

Changes of drinking water quality can cause the release of heavy metals in drinking water distribution systems(DWDSs),resulting in water discoloration and potential risk to human health.In this study,the influences of sulfate(SO_(4)^(2-)),chloride(Cl^(-))and alkalinity on metal release in DWDSs were investigated using static experimental systems,including iron(Fe),manganese(Mn),arsenic(As),and copper(Cu).The results show that the concentrations of dissolved oxygen(DO)were decreased with the increase of SO_(4)^(2-)and Cl^(-),while the values of turbidity were increased dramatically.Under higher alkalinity,both DO and turbidity were reduced gradually.The release of Fe,Mn,As,and Cu were promoted by SO_(4)^(2-)and Cl^(-).When the concentration of SO_(4)^(2-)was 100mg/L,the maximum concentrations of Fe,Mn,As,and Cu in steel pipes were 2.20mg/L,45.15,0.74,and 5.41μg/L,respectively.The values in cast iron pipes were 1.06mg/L,9.31,0.76,and 5.43μg/L,respectively.Similarly,with the Cl^(-)level of 100mg/L,the concentration of the four metals were highest.However,the increase of alkalinity inhibited metal release.When the alkalinity was increased from 70mg/L CaCO_(3) to 200mg/L CaCO_(3),the release of Fe,Mn,As,and Cu at 48h in steel pipes were reduced by 0.38mg/L,7.60,0.09,and 2.30μg/L,respectively.Under the same condition,the release of the four metals in cast iron pipes were decreased by 0.44mg/L,3.73,0.12,and 1.29μg/L,respectively.Significant differences of Fe and Mn release were observed between steel and cast iron pipes.Nevertheless,pipe materials had fewer influences on As and Cu release.This research can provide theoretical basis and technological support for the control of drinking water secondary pollution.