The final “polishing” of the water from the clarifiers occurs as the water is directed to the tertiary sand filters for removal of fine suspended and colloidal solids. The filters contain a dual-media to trap these fine solids which are returned to the Bardenpho process for further treatment.
Following filtration, the effluent is disinfected through the use of ultraviolet treatment. The water passes through enclosed vessels containing lights that emit ultraviolet light. The ultraviolet light kills any remaining bacteria, to conform with discharge and reuse compliance standards issued by the U.S. EPA and the Arizona Department of Environmental Quality.