Carbohydrate-derived chlorinated compounds in ECF bleaching of hardwood pulps: formation, degradation, and contribution to AOX in a bleached kraft pulp mill.

Five monochlorinated compounds derived from glucuronoxylan were identified in the liquid process streams of a kraft pulp mill producing hardwood pulp with ECF bleaching, representing ca. 15-20% of the AOX of the bleaching filtrates. The environmental risk of such compounds is negligible because a major fraction (70-80%) is degraded during effluent mixing and neutralization, and about 20-30% is degraded during the biological treatment of the mixed effluent. Only less than 3.5% (0.009-0.017 kg/ tAD) of the compounds formed in the bleaching leave the mill in the final effluent.