Paper Mill Sludge Dewatering Using Dredge-Filled Geotextile Tubes, 2001 Environmental Conference Proceedings

Mark Taylor, C. Joel Sprague, David Elliott and Sandra McGee--Wastewater treatment systems at pulp and paper mills typically include aerated stabilization basins and, less commonly, activated sludge plants. A maintenance issue with these systems is the accumulation of primary and secondary sludge. This material, typically composed of less than 10% solids, reduces treatment efficiency and capacity as it accumulates, and can cause violations of permit limits for BOD and TSS. In order to reuse or dispose of this sludge it must first be dewatered to at least 30% solids - normally a very costly undertaking involving presses and polymers.

This paper describes the development and initial results of a sludge removal project that entails dredging into large-diameter, 600-foot-long geotextile tubes and consolidation/thickening by gravity. The tubes were made of woven textiles fitted with piping to facilitate solids concentration and liquid removal. After thickening in the tubes, solids were air-dried prior to combustion as fuel.

The tubes were filled repeatedly and then monitored to document the progress of the thickening process. Samples of influent, the contents of the tubes, and filtrate were collected to quantify the amount of thickening achieved. Additionally, tube height measurements were periodically made and related to the degree of thickening. After a season of operation, preliminary comparisons to conventional dewatering have been made.