Paper mills are under constant pressure to increase their profits and to reduce their wastewater treatment costs. Champion International Mill in Hamilton, Ohio, is not an exception. The mill produces 340 to 365 tons/day of coated and uncoated printing and writing papers. Prior to 1996, Champion used less than 60 tons/day of secondary fiber. The usage of secondary fiber has increased to 100 to 114 tons/day. In 1996 improvements were made in the mill to reduce fiber losses. At that time the corporation also changed suppliers of polymers. As a result of these changes, the wastewater treatment plant saw its sludge disposal costs increasing. The solids from their screw presses decreased from 55% to 48%. This paper reports the series of options that were examined to improve the dewatering and to lower disposal costs. Included are changes in polymers and polymer applications, changes in the chemical sludge mixing, improved press orifice cleaning, and screw press motor load control systems. The effects of these changes have resulted in improved dewatering and the potential for even higher solids in the sludge cake. The economics of the sludge dewatering system are reviewed.

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