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.