A dispersed ultraviolet light source that can excite a photocatalyst has experimentally applied for water decontamination by photocatalytic powder. As a potential source of dispersed ultraviolet light, the present study focuses on electroluminescence (EL), by which cold light is emitted in response to a changing electric field. CaWO(4) powders with substituents of Mo or Cr, which are electroluminescent in the ultraviolet region, were prepared by a simple solid-phase thermal decomposition method. A higher decomposition rate of orangeII in water could be obtained in a system of combined EL and photocatalytic powders, compared with the electrical discharge system. Moreover, doping of CaWO(4) : Mo (3 wt%) powder with several metals on photocatalytic water decontaminating rate was found to be effective, and CaWO(4) : Mo (3 wt%): Ce (2 wt%) and CaWO(4) : Mo (3 wt%) : Dy (1 wt%) were confirmed as the best EL materials for this process. Taking into consideration the materials, energy and time required for preparing these metal-doped EL powders, it was concluded that CaWO(4) : Mo (3 wt%) is the optimum EL powder for practical utilization.