Ballast water treatment apparatus and methods for preventing foreign aquatic invasive species form entering marine ecological zones by translocation in ship's ballast water. The apparatus includes a housing, a filter member, and UV water treatment chambers. Methods include use of a ship's fire hydrant system or ballast water discharge port for moving ballast water from the ship's ballast tanks into the apparatus for filtration and treatment. In-port service vessels and barges as well as dock-side service vehicles are equipped with the various treatment and filtration apparatus to provided in-port or dock-side ballast water treatment services. Related methods are also provided.