Chlorine dioxide generating system

A system for generating chlorine dioxide for use as a disinfectant in water or wastewater treatment, the system output including a percentage of chlorine at an acceptably low level, thereby avoiding the deleterious effect of chlorine in the disinfection process. The system is provided with a source of chlorine gas and a source of aqueous sodium chlorite, both of which are fed into a reactor to generate chloride dioxide therein. The output of the reactor is coupled to an ejector operated by a water stream to create a vacuum which draws chlorine dioxide from the reactor into the ejector to dilute the chlorine dioxide before it is supplied to a process being treated. The resultant negative pressure in the reactor acts to draw the chlorine gas therein from the source through a vacuum regulator which maintains the flow of chlorine gas into the reactor at a constant rate and acts to cut off the supply of chlorine in the absence of negative pressure.