Chlorine dioxide is one of the most widely used delignification/bleaching agents in the pulp and paper industry, providing a high-quality, low-cost delignification and bleaching process. Chlorine dioxide treatment is superior to chlorine bleaching processes in that it virtually eliminates all dioxin discharges into the environment, and has accordingly, helped pulp and paper manufactures to employ environmentally friendly processes and to meet environmental requirements. Accordingly, the use of chlorine dioxide treatment is increasing and most pulp and paper mills now have at least one chlorine dioxide delignification or bleaching stage. Chlorine dioxide treatment has also been used to treat wastewater, sludge and other process streams.