Improved Dewatering of Pulp and Paper Mill Sludges, 1997 Environmental Conference Proceedings

Pulp and paper production generates different types of residues that requires further processing before disposal. Sludge from mills typically requires some form of conditioning, thickening and dewatering to reduce volume prior to disposal. The majority of the North American companies have reduced significantly the fiber losses from the mills and in conjunction, higher efficiencies of the secondary treatment systems are observed. These reduced quantities of primary solids and increased amounts of biological sludge creates a difficult combination of solids for the dewatering equipment. TEMBEC, a specialty pulp production company, as part of its general environmental goal of zero effluent discharge in the next millennium, examined jointly with its partners some options for better sludge handling. These options include the use of refined sawdust and electroosmotic screw press dewatering. Additionally, EKOKAN tested a non chemical conditioning by freezing and subsequent thawing of the biological sludge. It was shown on a laboratory and semi industrial scale that final dryness of more than 40% is achievable. A combination of some of these innovative methods will allow better operation of the existing dewatering equipment in the light of the recent start-up OT Canadian treatment facilities and the probable increased sludge quantities following the implementation of EPA’s cluster rules.