EVOLUTION OF OZONE FOR THE BLEACHING OF PAPER PULPS

Although ozone has been studied seriously as a substitute for chlorine in the bleaching of pulp for paper making since 1949, it has only bee n since 1992 that ozone has begun to reach its full-scale commercial p otential. In this evolution, ozone has been aided immeasurably by envi ronmental pressures to diminish the discharge of halogenated organics in pulp mill wastewaters. Thanks to the incorporation of ozonation int o bleach processes, not only is the creation of halogenated organics m inimized (and even eliminated in some cases), but this allows some of the processing liquors to be recovered and volumes of bleach plant eff luents to be reduced. As a consequence, this not only decreases the vo lume of wastewater being discharged to the receiving water bodies, but also increases the potential for the Totally Effluent-Free (TEF) blea ched pulp mill to become a future reality. Ozone's evolution in this r apidly growing industry is traced, and some characteristics of the 14 full-scale pulp mills currently using and five additional planning to use ozone for pulp bleaching in various parts of the world will be des cribed.