Sappi’s Cloquet Mill Effluent TSS Reduction Project Achieves Sets Standard on Water Preservation

Sappi’s Cloquet Mill utilizes two primary treatment clarifiers to eliminate solids from its pulp mill and paper mill effluent. After most solids are removed in these clarifiers, the effluent wastewater is conveyed via a pipeline to the Western Lake Superior Sanitary District (WLSSD), the local and publicly owned treatment plant in Duluth, MN, for final treatment. WLSSD assesses treatment fees to the mill based on the amount of biological oxygen demand (BOD), total suspended solids (TSS), and flow that is delivered to their treatment plant.

The challenge that Sappi’s Cloquet Mill encountered was to reduce the amount of chemicals necessary for pH control that would eventually enter the local community’s wastewater system. By aligning its business and product strategy with the United Nations Sustainable Development Goals (SDGs), Sappi aligned with UN SDG 6 through this project: sustainably managing water use and discharge.

The program underwent several iterations to overcome its challenge between 2015 and 2022 to ensure the project’s long-term viability. The third and final iteration of this project, completed in 2022, yielded an immediate and consistent reduction in TSS and an overall resolution. The substantial reduction in TSS and subsequent decrease in BOD not only minimized wastewater substances but also reduced costs for the mill and achieved a significant reduction in the load sent to WLSSD. Furthermore, the substantial decrease in Mercury sent to WLSSD allowed their organization to maintain compliance and target its mercury effluent limit for a record 10 consecutive months.

Sappi’s process of fine-tuning and perfecting iterations in the projects reflects the company’s unwavering commitment to sustainability. Each phase of the project produced noteworthy and positive results that Sappi continued to enhance. As an industry leader in the pulp and paper sector, this project serves as an inspiration for others to invest in sustainable changes. Other entities producing wastewater within the industry can attain similar results through capital investments and the consistent application of innovation and R&D to bolster sustainability.