The bleach plant of kraft pulp at Mishima mill is composed of three lines. One multistage line has been producing ECF bleached softwood kraft pulp (NBKP) using chlorine dioxide from April 2004. The other two bleaching lines produce bleached hardwood kraft pulp (LBKP) and encompass one displacement tower and one multistage line. Whereas the former was practicing chlorine bleaching up until early March 2007 when it started high-consistency ozone-based ECF bleaching, the latter was already making chlorine dioxide-based ECF-LBKP in April 2004 and has been converting to high-consistency ozone bleaching since April this year. Thus, all the kraft pulps at our Mishima mill are now completely and fully ECF bleached. Compared to the chlorine-bleached pulp, the breaking length and burst factor of the ozone-bleached LBKP are somewhat lower but the tear factor is almost equal. The COD, color and chloroform loads of the bleach plant’s raw effluents are decreased considerably. The AOX and color loads of the treated mill effluent discharged into surrounding receiving water bodies are also reduced, but to a smaller extent.