Paper Sludge Layer as Low Permeability Barrier on Waste Landfills

Abstract

The use of paper sludge as a hydraulic barrier material in landfills is a technology that has gained some attention since the early 1990s and is an innovative way to recycle paper mill residuals. The geotechnical properties of paper sludge are similar to those of compacted clays.

A laboratory test has been performed to evaluate the suitability of Slovenian waste paper sludge as landfill covering or sealing material. The sludges obtained from Slovene paper mills were examined for their geomechanical, chemical and sealing properties, as well as for their microbiological stability. The results of preliminary geotechnical studies of paper sludges indicate the expected relatively low strength properties (14 kPa < σ _c < 81 kPa), high compressibility and a low coefficient of permeability 5.0* 10⁻¹⁰ < k < 7.8* 10⁻¹¹. The pH values of the eluates are within the permissible limits 6.6–7.0. The strength properties of paper sludges and various composites of paper sludge can be improved by additives (fly ash, bentonite, cement) and various composites of different types of paper sludges. We improved the strength properties (273 kPa < σ _c < 1064 kPa) of these paper sludges, but the coefficient of permeability k also increased slightly.

This paper also aims to evaluate the suitability of paper mill sludge collected from various Slovene paper mills for use as hydraulic barrier in landfill covers.

Keywords:

• barrier protection layer
• field testing
• paper sludge
• Slovenia
• waste
• waste landfill

Acknowledgements

The authors gratefully acknowledge funding from the Slovene Ministry of Higher Education, Science and Technology, Slovene Research Agency, Karbon and EKO. We would also like to thank Sinteza-Lining for providing geosynthetic materials and their staff for performing the construction works, as well as Vipap Videm Krsko for providing de-inking paper sludge and covering the transportation costs to our field test cells.