Effects of sulfate,chloride,and alkalinity on the release of heavy metals in drinking water distribution systems
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(SO42-),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 SO42-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 SO42-and Cl-.When the concentration of SO42-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 CaCO3 to 200mg/L CaCO3,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.
drinking water distribution systemchloridesulfatealkalinityheavy metal
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