PNNL

Abstract

In situ As removal from groundwater used for water supply has been performed in Daying village of Shanyin County where mild alkaline groundwater contains high dissolved As concentration. The objective of this study was to evaluate in situ As treatment by aquifer Fe coating technology. The groundwater in the studied aquifer contains As dominated by aqueous As(III) and low dissolved Fe(II) concentration, which are unfavorable conditions for forming Fe-oxides/hydroxides for As removal. In addition, high As(III) concentration limits As adsorption onto Fe-oxides/hydroxides. Accordingly, dissolved Fe(II) (5mM) and NaClO (5mM) were injected into the studied aquifer to form Fe-oxides/hydroxides and oxidize As(III) to As(V), creating favorable conditions for As removal via adsorption and/or co-precipitation. During alternatively cycled injection of Fe(II) and NaClO, the As concentration in groundwater from the pumping well significantly decreased to below drinking water standard. The developed approach can be applied similarly in many parts of the world containing high As concentrations.