Technical Bulletin No. 0163: Research on Thickening and Dewatering of Clarifier Underflows

The attached technical bulletin was first distributed in 1963. It was noted then that while considerable progress had been made in recent years in dewatering and disposal of sludges resulting from the clarification of pulp and paper mill effluents, research was continuing on methods and procedures to make the process more efficient and economical. At that time National Council research in this field was concentrated in the Central-Lake States Regional Center at Kalamazoo College and the attached bulletin summarized the more significant results of this work. Processes reported on included pressure filtration, flotation, and vacuum precoat filtration with fly ash. Currently the Central-Lake States Center, now located in the Department of Paper Technology at Western Michigan University, is also active in the study of new approaches to sludge dewatering. Active projects include freezing and thawing thermal treatment, chemical hydrolysis, and use of bark as a filter aid.