Aspects of exemplary fluid disinfection apparatus and methods are described. One aspect is a disinfection apparatus comprising a body comprising a reflecting chamber, a fluid channel to direct a fluid into reflecting chamber, and radiation source positioned to output a disinfecting radiation into the chamber. The body may include an inlet and outlet. For example, the inlet may extend through the body to receive a fluid at a first velocity； the reflecting chamber may extend along an axis of the body； and the outlet may extend through an end of the reflecting chamber to discharge the fluid from the body. In this example, the fluid channel may direct the fluid from the inlet into the reflecting chamber at a second velocity smaller than the first velocity； and the radiation source may be positioned to output the disinfecting radiation into the reflecting chamber toward the outlet.
