Abstract: A system for treating an effluent includes a cap assembly and a reactor module. The cap assembly captures the effluent discharge from a source. The reaction module includes a reaction chamber housing a substrate and an illumination device. In operation, the effluent is drawn into the cap assembly and directed downstream, into the reactor module. The effluent flows over the substrate, causing adsorption of bacteria to substrate. Additionally, the illumination device is selectively activated to direct photons toward the effluent for selected periods of time. With this configuration, a biomass formed of algae develops in the reaction chamber (e.g., on the substrate). The biomass is effective to reduce the amount of contaminates within the effluent.