In-situ electrochemical remediation has emerged as a promising groundwater remediation technology. However, its application has been limited to short-term decontamination. Here, we propose an electrochemical system that combines an e-barrier with pyrite, a sulfide mineral capable of completely removing As(III), Cr(VI), and sulfanilamide continuously for one year. We evaluated the sandbox comprising an e-barrier and pyrite as a flow-through electrochemical reactor on two different scales: (1) a lab-scale small sandbox with sulfanilamide as a model contaminant to assess decontamination performance, and (2) a pilot-scale large sandbox designed for the simultaneous removal of As(III), Cr(VI), and sulfanilamide. The small sandbox achieved 100 % removal of sulfanilamide, demonstrating the effectiveness of the combined system. The large sandbox demonstrated 100 % removal efficiency against contaminants mixture for up to one year, with effluent maintaining a neutral pH even without an external neutralizing process. This remarkable performance was attributed to the activation of pyrite by anodic oxygen (O₂), producing dissolved iron that leads to the formation of iron hydroxide (e.g., green rust), which serves both as an adsorbent and precipitant for contaminants. Our findings indicated that the combination of electrochemical reactions and pyrite is an effective approach for the simultaneous removal of organic and inorganic contaminants.