Performance of Perlite and Sawdust in Continuous Barrier, Funnel‐and‐Gate, and Non‐Pumping Reactive Well Permeable Reactive Barriers ( <scp>PRBs</scp> ): An Experimental Study

Abstract This study experimentally evaluates the effectiveness of three permeable reactive barrier (PRB) configurations—continuous barrier (CB), funnel‐and‐gate (FG), and non‐pumping reactive wells (NPRWs)—for remediating iron‐contaminated groundwater, using perlite and sawdust‐sand mixtures as reactive media. Preliminary column tests identified an optimal media ratio of 1:1 perlite‐to‐sand based on achieving the best balance between iron removal efficiency and hydraulic performance. While 2:1 sawdust‐to‐sand was the most widely validated ratio in literature, it provides the highest adsorption capacity. Pilot‐scale experiments were conducted in a custom sandbox (1.4 m × 0.4 m × 0.3 m) under water head difference between upstream and downstream reservoirs of 5, 10, and 15 cm. Results revealed that both perlite and sawdust achieved high iron removal efficiencies (>98%) across all configurations and hydraulic gradient conditions. However, sawdust consistently outperformed perlite. Regarding PRB design, the continuous barrier configuration demonstrated the highest performance (up to 99.98% removal), particularly under low hydraulic gradient. At the same time, NPRWs showed comparable remediation capability to the CB at low‐to‐moderate hydraulic gradients. Conversely, the funnel‐and‐gate system exhibited the lowest efficiency due to structural limitations, including media bypass and poor sealing at the gate interface. These results highlight that both reactive media selection and hydraulic design are critical factors for the efficient in situ remediation of heavy metals using PRBs.