A variety of effluents from the several stages of chlorine based bleaching are produced which is a major pollution load of kraft bleach plant. The amount of bleaching agents used for high brightness without degrading cellulose or hemicellulose, thus preserving strength, will depend on the chlorine demand of the pulp, the type of pulp being bleached, the desired brightness and strength reguired. The biodegradation of chlorinated aromatic compounds by white - rot fungi Phanerochaete chrysosporium has been demonstrated for scale - up and optimization studies.