Abstract
The research goal was to investigate the hydraulic conductivity of compacted lime-softening sludge as a material to be applied to landfill liners. In doing so, the effect of compaction and moulding moisture content on the sludge hydraulic conductivity was assessed. An approximate polynomial k10mean at hydraulic gradients ≥30 for degree of compaction (0.95–1.05) and moulding moisture content (28%–36%) was determined. The results of short-term tap water permeation tests revealed that all hydraulic conductivity values were less than 2.5•10–8 m/s. A lowest hydraulic conductivity of 6.5•10–9 m/s, as well as a corresponding moisture content of 31% were then established. The long-term hydraulic conductivity was measured with tap water, distilled water, NaOH and HCl solutions and municipal waste leachate. The factors of permeating liquids and permeation time significantly affected the initial hydraulic conductivity. The long-term hydraulic conductivity increased for NaOH and HCl solutions and decreased for tap and distilled water. A significant reduction of hydraulic conductivity was observed for leachate permeation. The investigated material met the requirements for the liner systems of inert landfill sites regardless of pH and the limit value for hazardous and non-hazardous waste landfills.
Highlights
1.1 BackgroundSafe utilization of billions of tons of municipal and industrial wastes is one of today’s major problems
The hydraulic conductivity tests performed on limesoftening sludge revealed that the compaction and the moulding moisture content significantly affected limesoftening sludge hydraulic conductivity
The results of short-term tap water permeation tests showed that all hydraulic conductivity values at hydraulic gradients ≥30 were less than 2.5·10−8 m/s, when water content was between 27.7% to 36.7% and the degree of compaction was between 0.95 to 1.05
Summary
1.1 BackgroundSafe utilization of billions of tons of municipal and industrial wastes is one of today’s major problems. Wastes are partially recycled and thermally neutralized, but waste storage in landfill sites is still the common way of its disposal. The landfill sites should guarantee safe waste disposal storage at minimum hazard for the environment. A landfill site should be equipped with a low permeability liner if the natural soil is not impermeable enough to protect the surrounding environment (the soils, ground water and surface water) from being contaminated by waste leachate generated within the landfill. Tighten requirements concerning natural environmental protection have brought about the need for more attention to be drawn to proper selection of liner system, depending on waste landfills and soils with optimal characteristics and the appropriate criteria of their use in applied liner systems. There are 2 kind of liner systems recommended and predominantly used for hazardous waste landfill: a single composite liner
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