Hydraulic Permeability of Sewage Sludge Mixture Added with Bottom Ash, Fly Ash and Lime

Abstract

This research was conducted to study the physico-chemical properties of sewage
sludge and mixing materials (bottom ash, fly ash, and lime) and hydraulic permeability of
sewage sludge mixture added with different mixing material ratios of bottom ash, fly ash and
lime (1, 2, 4, 6, 8, 10, 20, 30, 40 and 50% by weight) and different heights of mixture (5, 10,
and 15 cm). The hydraulic permeability of mixtures was determined by Constant-Head
Permeameter (ASTM D 2434). Data analysis was undertaken using ANOVA and mean comparison
was obtained using Fisher’s Least Significant Difference Test (LSD) at the significant level of
α 0.05.
Results revealed that sewage sludge particles were largely coarse (surface area of
0.869 m2/g.) followed by fine bottom ash particle (surface area of 0.296 m2/g.), whereas fly
ash and lime were fine powder like particles (surface areas of 0.667 m2/g. and 0.434 m2/g.,
respectively). Cadmium, lead and mercury were the heavy metals found in the sewage
sludge and their amounts were not over the limit permitted by the Ministry of Industry.
Hydraulic permeability of mixture of sewage sludge added with bottom ash, fly ash and lime
at a ratio of 50% (1.916x10-4 cm./s) was significantly lower than other ratios (p-value<0.05).
The hydraulic permeability of mixtures at 15 cm was significantly lower than other thicknesses
(6.498x10-5 cm./s) (p-value<0.05).
The hydraulic permeability level was lower than the directives on the use of landfill
base material; however, it could be used as a mixing material for composite liner.