In-situ Denitrification of Nitrate-nitrogen Contaminated Groundwater by a Permeable Reactive Barrier Using Sulfur–Limestone

Abstract

 The remediation effects of a permeable reactive barrier (PRB) using sulfur-limestone are investigated. The results show that highly concentrated NO₃⁻ (133-180 mg/L) in shallow groundwater decreased below the detection limit within the PRB. This phenomenon was maintained for approximately 300 days; therefore, the remediation effects within the PRB and its durability are demonstrated. It is suggested that the remediation effects due to the PRB are not solely restricted to the area within the barrier, because the decrease in NO₃⁻ extended 4.0 m downstream. Furthermore, the results of ORP_SHE, δ¹⁵N, and isotopic fractionation factor (ɛ) indicate that a reductive condition forms within the PRB, where sulfur-oxidizing denitrifying bacterium preferentially exists. Before installing the PRB, three-dimensional (3-D) groundwater flow systems around the study site and detailed hydrogeological setting should be investigated first.