INVESTIGATIONS ON THE HYDRAULIC CONDUCTIVITY AND PHYSICAL PROPERTIES OF SILT AND SLUDGE AS POTENTIAL LANDFILL CAPPING MATERIAL

Abstract

Landfills have been the most common methods of municipal solid waste disposal in developing
countries. Landfill capping is a containment technology that forms a barrier between the contaminated media and
the surface. Presently, the commonest capping materials for landfills are sandy material and laterite soil. The
permeability and the strength of the material against slope failure are among the important parameters to be
considered. The objective of this research was to study the suitability of silt from Ulu Kinta dam in Malaysia and
sludge (domestic wastewater sludge and water treatment sludge) as alternative materials for landfill capping.
Both materials have little commercial values in Malaysia to date. The two materials were mixed with varying
proportions of pure silt, 20, 40, 60, 80 and 100% of the sludge. Investigations were made on the hydraulic
conductivity and physical properties of the mix. The results showed that silt material has a moderate hydraulic
conductivity with k of value 4.81x10-4 cm/s, poor cohesion strength, 7.64 kN/m2 and good friction angle, 36.2°.
Sewage sludge has the best properties among the three materials, good hydraulic conductivity with k of 2.07x10-
6 cm/s, moderate cohesion strength, 8.95 kN/m2 and very high friction angle of 45.7°. Water treatment sludge’s
hydraulic conductivity, k was 2.9x10-6 cm/s which is good, but having poor cohesion strength and friction angle
of 6.16 kN/m2 and 6.1°, respectively. Silt and sludge were also mixed to test whether the method improves the
properties of the final product; the result was negative. The use of 100% sewage sludge exhibited better results
than others.