Non-point source pollution poses a significant threat to the environment and can be difficult to prevent and remediate. One contributor to this is mine drainage, which can contain numerous contaminants of concern. Passive treatment systems have been developed as a method of remediating mine drainage. The behavior of manganese within these systems has raised questions regarding its ability to be retained by the organic substrate used for remediation, with a prior study showing manganese sometimes being released in higher concentrations than when it entered the system. The goal of this current study is to further research on the behavior of manganese and determine if there is a pattern of its release within treatment systems. For this study, cubitainers are set up containing an organic substrate and a manganese solution. Biweekly testing is currently being conducted to measure pH, dissolved oxygen, conductivity, and oxidation-reduction potential. Along with this, samples of water from each container are being analyzed for manganese concentrations. This is an ongoing project, and samples will continue to be taken into the next academic year. At the end of the semester, three of the containers will be sacrificed to analyze the manganese content within the organic substrate itself. This information will be used to determine in which part of the substrate the manganese is retained. This will provide further insight into improving passive treatment systems for a variety of contaminants.