Effluent Manganese Limit Poses a Special Problem for a Bleached Kraft Pulp Mill on a Small River, 1999 Pulping Conference Proceedings

Eva Mannisto

EKONO Inc.

Grant Bourree & George Wohlgemuth

Weyerhaeuser Canada

The Weyerhaeuser Grande Prairie mill produces 300,000 ADMt annually of fully bleached softwood kraft pulp. The mill converted to ECF bleaching already in 1992, condensate stripping and enhancement of the LVHC NCG system were implemented in 1993.

Since then the mill has focused on optimizing the process for environmental and cost performance while enhancing product quality through variability reduction. These optimization strategies have allowed the Grande Prairie mill to achieve world class results in these key areas and achieve performance superior to the Cluster Rule requirements without the installation of oxygen delignification.

Because of the strict Alberta surface water quality criteria and the low flow in wintertime in the receiving river, two effluent parameters pose problems to the mill, namely color and manganese. This paper reports the issues the mill experiences because of the uncommon limit for manganese discharge in the final effluent.