Nitrate removal from groundwater by microscale zero‐valent iron and activated carbon: A nonpumping reactive wells experiment

Abstract This study investigated treatment of nitrate‐contaminated groundwater by mixing granular activated carbon (GAC, d 50 = 1 mm) and microscale zero‐valent iron (MZVI, d 50 = 50 nm and specific surface area = 22.5 m 2 g −1 ) in a nonpumping reactive wells (NPRWs) system. A hexagonal pattern of NPRWs was implemented in a laboratory cylindrical aquifer model (80 cm height, Ø 90 cm) filled with natural coarse sand (0.82 mm). Besides NO 3 − (133 mg L −1 ), PO 4 3− in elevated concentration (6.21 mg L −1 ) was also considered as an additional target ion in groundwater (ionic strength = 35 mM). A pumping well in the center of the aquifer model discharges the groundwater at a constant rate of 1 L h −1 . A series of batch experiments was conducted to derive the reduction kinetics of the N species and PO 4 3− in water. Based on the results of the batch experiments, a mixture of GAC/MZVI was also used as reactive materials within NPRWs in the aquifer model to remediate the contaminated groundwater. While the average percentage of NO 3 ‐ N reduction rate from groundwater by GAC‐based NPRWs was 0.6% g −1 , the mixed MZVI/GAC in the same mass indicated an efficiency of 5.5% g −1 . The aquifer tests showed that using mixed MZVI/GAC in NPRWs resulted in insignificant changes in pH (+3%) and EC (+7%) of groundwater outflows. The results of this study revealed that using the GAC‐mixed‐MZVI has great potential application in PRB system for nitrate removal from groundwater.