Abstract: A system for disinfecting a fluid containing contaminants (chemical and biological) includes a plurality of photocatalytic particles secured to a substrate which contacts the fluid to be disinfected. An agitator for imparting translation and/or vibrational movement is in operational communication with the substrate to increase the contact of photocatalytic particles with contaminants in the fluid. The system can include a source of photons having a wavelength corresponding to band gap energy of the photocatalytic particles to illuminate the substrate. Although the invention can be used to disinfect air in air supply registers of a heating, ventilating and air conditioning system, or in air ducts, the disinfection of any fluid (including water) is contemplated.