METHODS TO DECREASE AND ELIMINATE AOX IN THE BLEACH PLANT .1. LOWERING AOX LEVELS IN THE BLEACH PLANT

The options available to decrease the AOX in bleach plant effluent inc lude removing as much of the lignin from the pulp before the bleaching process, using chlorine dioxide instead of molecular chlorine in the chlorination stage, adjusting the Cl2 and ClO2 addition strategy so th at the chlorine is added first in the chlorination stage, and combinin g the above alternatives. Other technologies are enzyme treatment of t he brownstock which decreases the chlorine requirement and more extens ive use of peroxide in the bleaching sequence.