A large number of heavy metals are usually contained in mine-derived liquids, which could cause contamination of surrounding water sources. Due to the detrimental effects on the environment and health, conventional treatments have been employed to capture heavy metals in mining-polluted streams. This study shows the results of the operation of a built prototype for the retention of arsenic contained in waters contaminated by mining activities using Technosols (mixtures of local soil with nanoparticles). Our team previously run laboratory tests using fixed-bed columns to find out the best dose of the Technosol (97% soil + 3% nanoparticles). Based on these results, the sizing and building of a scale model were conducted, which in turn was used to evaluate the performance of the treatment in a concrete channel packed with reactive barriers. Variations in water volume, barrier separation and gate opening were tested to analyze the behavior of the proposed system and to obtain the most optimal hydraulic retention time that allowed the prototype to reach an arsenic retention level of a minimum of 70%. Moreover, to analyze the procedure under conditions of high arsenic contamination, samples of mine tailings were enriched with the toxic metalloid. It was found that the content of Fe in the local soil allowed adsorption of the contaminant, which was subsequently compared with the increase in the uptake of As due to the Fe/FeS multicomponent nanoparticles (NPs), dosed in the Technosol in a proportion of 97% soil + 3% NPs. The best treatment achieved 70.5% of As removal in ten cycles with a volume of 44 L. Tests were run at a maximum input flow rate of 43.8 L·min−1, an output flow rate of 13.2 L·min−1, a speed of 6.0 m·min−1 and a hydraulic retention time of 3.4 min per cycle. Results of arsenic retention using this prototype suggest that this simple and inexpensive technological setup could be scaled up to a functional field application to effectively capture the toxic metalloid.