PHYSICAL-PROPERTIES OF DEWATERED WASTE-WATER SLUDGE FOR LANDFILLING

In the context of landfilling dewatered wastewater sludge in Hong Kong , with landfills up to 140 m high, one of the most significant propert ies of sludge is its physical nature with regard to moisture character istics and associated geotechnical stability. Commonly, lower limits a re set on total solids content, but no geotechnical stability criteria are applied with the exception of Germany where a minimum requirement for vane shear strength is set at 25 kN/m(2). The purpose of this stu dy was to determine and evaluate dewatered wastewater sludge from thre e Hong Kong municipal wastewater treatment plants with regard to the f ollowing physical and geotechnical properties: (i) vane shear strength ; (ii) consolidation characteristics such as compression index, compre ssibility factor, coefficient of consolidation and compressibility coe fficient; and (iii) hydraulic characteristics such as permeability and intrinsic resistance. Although dewatered sludge exhibits quite differ ent characteristics as compared to soils, predictive logarithmic relat ionships may be established between various properties which are consi stent with the critical state model for soils, conventional filtration and consolidation theory. Such representation provides a valuable bas is for understanding the sludge characteristics and behaviour to landf ill design. Copyright (C) 1996 IAWQ. Published by Elsevier Science Ltd .