A ballast water treatment apparatus and a ballast water treatment system having a ballast water treatment apparatus are provided. The ballast water treatment apparatus includes a ballast water transport line configured to transport ballast water between a first location and a second location, the transported ballast water being passed through at least one injector, and a plasma generation device configured to be fed with a feed gas optionally comprising oxygen, and configured to generate a feed gas plasma by a streamer type discharge in a discharge area to provide a treated gas at a treated-gas outlet. The injector includes a liquid passage having an area constructed such as to increase a velocity of the passed-through water in a region of increased velocity, and an injector gas inlet provided in the region of increased velocity. The treated-gas outlet is in gaseous connection with the injector gas inlet.