Impact of Ozone Bleaching on Effluent Discharge

摘要

The pulp and paper industry has been sharply improving its effluent quality since the 1990s with the spread of secondary effluent treatment, the ban on chlorine bleaching, development of modified cooking and generalization of oxygen delignification. These developments supported the increase in fiberline capacity from 1,500 adt/d in 1993 at Alberta-Pacific to 6,120 adt/d in 2017 at Fibria Tres Lagoas. But a result is that COD discharge at one single point is potentially higher than 30 years ago and new pulp mills, because of today's straitening environmental regulations, often face the need to implement costly third effluent treatment stages. An alternative has been available and successful in reducing effluent discharge flow while improving effluent quality: ozone bleaching allows for partial recirculation of the bleaching filtrates to oxygen delignification and evaporation. Authors will review ozone bleaching fundamentals allowing for lower effluent discharge and present results showing that increasing capital and operating expenditures of the effluent treatment plant can be avoided by decisions on the bleaching process.