Comprehensive Approach to Maximizing Papermachine Productivity in a "Closed Water" System, 1997 Environmental Conference Proceedings

A clay coated board mill in Connecticut experienced serious productivity and environmental compliance problems in 1995 due to elevated TSS and BOD5 levels in mill wastewater, of which 80% was recycled for process usage. These elevated levels were partially caused by poor wastewater treatment system (WTS) efficiency, and exacerbated by increased closure of the mill water systems (elimination of non-contact cooling water from process usage) and poor machine performance which increased pollutant loading to the primary clarifier. The facility undertook a number of measures to improve both wastewater treatment system performance and machine productivity. This included recycling primary clarifier effluent to the mill for process use, improving primary clarifier treatment chemistry, and a comprehensive study of the mill’s water systems by a team consisting of mill environmental, production, and powerhouse personnel as well as chemical and equipment supplier personnel. The immediate goal was to increase machine production and decrease wastewater treatment system loading through improved retention and drainage, while improving finished product quality. Specific action items included: Characterization of water for constituents and particle size. Implementation of standard operating procedures to minimize water, fiber and coating losses that impact the wastewater treatment system. A study was conducted to verify the impact on machine runnability of reusing wastewater from different locations within the wastewater treatment system. Optimization of the clarifier and papermachine polymer programs for improved liquids/solids separation. Evaluation/Optimization of equipment, both existing and add-on.