Some demonstrative embodiments of the invention include an illumination-based liquid disinfection device (100). The disinfection device (100) includes a light transparent conduit (101) to carry a flowing liquid to be disinfected, the conduit (101) having an inlet (106) to receive the liquid and an outlet (108) to discharge the liquid, a substantially light transparent sleeve (102) having external dimensions smaller than the internal dimensions of the conduit (101), the sleeve (102) positioned within the conduit (101) substantially perpendicular to the axis of symmetry of the conduit (101) and a light source (104) positioned within the sleeve (102).