| Summary: | Kraft pulping dominates chemical pulps production. Conventional bleaching (using elementary chlorine), generates high contamination, and its effluents content dangerous chlorine derived products, including dioxins and furans. The rigorous environmental policies imposed to the industry by the government, conduced to the generation of ECF and TCF bleaching sequences. While ECF (elementary chlorine free) bleaching uses chlorine dioxide in spite of Cl2, TCF (totally chlorine free) bleaching includes the use of non chlorine chemicals. Hydrogen peroxide utilization as oxidant agent generates an increase in chelant application. The objective of this work is to resume references about COD (Chemical Oxygen Demand) levels in different effluents, including effluents from brown stock washing, oxygen delignification (O and Op), peroxide bleaching, and chelant addition in different stages (20 bibliographic references).
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Reduction of the recalcitrant COD of semi-chemical pulp effluents by chemical precipitation