WORLD PULP&PAPER 51 At least one mill has taken advantage of this mechanism to reduce the loading of their recovery boilers in order to increase production while maintaining a neutral impact upon the effluent discharge quality. We typically see a 15-20% reduction in chlorine dioxide usage, therefore, effluent from the bleach plant has a lower toxicity. The net result in the effluent quality from the wastewater treatment plant to the receiving body may have an increase in BOD/COD levels but will also have a lower AOX content. The impact of a bleaching enzyme upon the wastewater treatment plant must be closely monitored during mill trials. There have been cases where a mill has no prebleached washing and an overloaded activated sludge treatment system operating close to their permit discharge limits. In cases such as this, the additional inlet COD load could not be tolerated. In conclusion, the use of xylanases in bleaching can result in significant savings to a mill in the reduction of chlorine dioxide. The perceived detrimental impacts caused by xylanases can be avoided by the judicious control of dosages. Adverse impacts, if any, are brought about by significantly overfeeding xylanases and/or significant adjustments of brownstock pH and should be avoided. REFERENCES Industrial use of enzymes - Matti Leisola, Jouni Jokela, Ossi Pastinen, and Ossi Turunen Helsinki University of Technology, Finland, Hans E. Schoemaker DSM Research, The Netherlands Next Generation Technology for Enhancing Pulp Bleaching - Phillip Hoekstra TAPPI PEERS 2016