The invention relates to a device (10) for the photochemical treatment or purification of polluted water. Said device (10) comprises at least one flow channel (16) for guiding the polluted water, which is defined at least in sections by a UV light output face (14) of least one of the UV-light generating bodies (12). The at least one flow channel (16) can comprise swirling elements (22; 24; 26; 28; 30) for the polluted water.