Implementations of the present disclosure relate to an apparatus and a method for reducing a selenium-content of a fluid-input stream. The present disclosure includes components and steps for performing chemical modifications of a fluid-input stream and further components and steps for performing physical modifications of a chemically-manipulated fluid stream. When the fluid-input stream has a selenium content the chemical modification of the fluid-input stream drives at least a portion of the selenium content into a selenium-containing solids phase. The chemical modifications include at least oxidation, coagulation, chelation and flocculation. The present disclosure also includes components and steps for performing physical modifications that separate and remove some or all of the selenium-containing solids phase from the liquid phase, which reduces the selenium content of the liquid phase.