Keywords: 
• zero-valent iron /
• nitrate /
• permeable reactive barrier /
• sawdust /
• denitrification

Abstract: Nitrate contamination in groundwater attracts extensive attention since it is very widespread in the world, hard removal and potential harm to people. Nitrate pollution remediation in the groundwater using simulated permeable reactive barrier (PRB) based zero-valent iron(Fe0) packed columns was evaluated under different conditions (influent water pH, the volume ratio of sand and Fe0 and adding sawdust). The results indicated that the influent pH exhibited slight impact on nitrate reduction, in part because of the alkalinity and buffer effect of the tested soil. The volume ratio of sand and Fe0 of 5~6∶1 was wonderful, which not only enhanced the efficiency of Fe0 but also promoted nitrate removal and extended the longevity of PRB. The permeability and reaction of PRB decreased because of cementation induced by the accumulation of iron corrosion products, especially near the inlet of reactive zone. Although acid-pretreated Fe0 improved nitrate reduction, it also resulted in clog easily. But the addition of active carbon extended the longevity and efficiency of PRB. So it is a very good assistant material for nitrate reduction by Fe0. Nitrate was removed completely after adding sawdust and Fe0 as well as improved the quality of effluent water, which exhibited a good potential for field applications. In all treatments, the concentrations of ammonia and nitrite in the effluent, the product of nitrate reduction by Fe0, were very different, but the total dissoluble iron was almost below the drinking water standard (0.3 mg/L). Chemical reduction by Fe0 and biological denitrification by sawdust are the main mechanisms. This study demonstrated that it is potential for in-situ remediation nitrate contamination in the neutral or alkaline groundwater using iron-based PRB.