Colour and AOX Removal from Bleached Kraft Mill Wastewaters Using Catalytic Peroxide Activators, 2001 Environmental Conference Proceedings

Kathryn G. Wingate, Murray J. Robinson, Trevor R. Stuthridge--This paper discusses the application of the PFe activator technology for the remediation of bleached kraft pulp and paper mill wastewaters. The technology, developed at Carnegie Mellon University, uses a novel class of iron (III) macrocyclic tetraamide complexes to catalytically activate hydrogen peroxide in oxidative reactions. The technology had previously been successfully trialed at Forest Research for pulp bleaching applications which demonstrated the potential to remove colour and other recalcitrant constituents from pulp and paper industry wastewaters.

The results of this study showed that the PFe activator/peroxide system removed a significant percentage of colour and AOX from the selected wastewaters. Treatment of a softwood bleach plant wastewater (E-stage) resulted in colour and AOX removals of 56 % and 36 % respectively. The treatment also effectively reduced colour in other kraft wastewaters, including acid-stage bleaching wastewater (73 %), combined bleach plant wastewater (56 %) and whole mill wastewaters (58 % and 30% colour reductions in pre- and post-biological treatment wastewaters respectively).

The removal of recalcitrant organic carbon in the wastewater was only 19 %, as measured by dissolved organic carbon. Since significant reductions in colour and AOX were also achieved under these conditions, the results suggest that the primary effect of the activator was to alter or remove chromophores and organohalogens, rather than destroy the organic material. Mathematical models were developed to describe the removal of colour and AOX from the bleach plant wastewaters. No significant correlation existed between colour and AOX removal suggesting that different modes of action or optimal conditions were required for each of these parameters.

Overall, the results demonstrate the potential application of this technology for the in-mill control and removal of recalcitrant constituents in pulp and paper mill wastewaters.