title: Hydraulic conductivity of fly ash-sewage sludge mixes for use in landfill cover liners.
abstract: Secondary materials could help meeting the increasing demand of landfill cover liner materials. In this study, the effect of compaction energy, water content, ash ratio, freezing, drying and biological activity on the hydraulic conductivity of two fly ash-sewage sludge mixes was investigated using a 2(7-1) fractional factorial design. The aim was to identify the factors that influence hydraulic conductivity, to quantify their effects and to assess how a sufficiently low hydraulic conductivity can be achieved. The factors compaction energy and drying, as well as the factor interactions material x ash ratio and ash ratio x compaction energy affected hydraulic conductivity significantly (alpha=0.05). Freezing on five freeze-thaw cycles did not affect hydraulic conductivity. Water content affected hydraulic conductivity only initially. The hydraulic conductivity data were modelled using multiple linear regression. The derived models were reliable as indicated by R(adjusted)(2) values between 0.75 and 0.86. Independent on the ash ratio and the material, hydraulic conductivity was predicted to be between 1.7 x 10(-11)m s(-1) and 8.9 x 10(-10)m s(-1) if the compaction energy was 2.4 J cm(-3), the ash ratio between 20% and 75% and drying did not occur. Thus, the investigated materials met the limit value for non-hazardous waste landfills of 10(-9)m s(-1).
authors.affiliation: Department of Civil, Mining and Environmental Engineering, Luleå University of Technology, 971 87 Luleå, Sweden. Inga.Herrmann@ltu.se
authors.forename: Inga
authors.initials: I
authors.lastname: Herrmann
authors.forename: Malin
authors.initials: M
authors.lastname: Svensson
authors.forename: Holger
authors.initials: H
authors.lastname: Ecke
authors.forename: Jurate
authors.initials: J
authors.lastname: Kumpiene
authors.forename: Christian
authors.initials: C
authors.lastname: Maurice
authors.forename: Lale
authors.initials: L
authors.lastname: Andreas
authors.forename: Anders
authors.initials: A
authors.lastname: Lagerkvist
mesh_terms: D002244:Carbon / Q000737:chemistry*; D060729:Coal Ash; D016018:Least-Squares Analysis; D008956:Models, Chemical; D052638:Particulate Matter / Q000737:chemistry*; D012722:Sewage / Q000737:chemistry*; D014867:Water / Q000737:chemistry*; D014874:Water Pollutants, Chemical / Q000737:chemistry*
chemical_list: D060729:Coal Ash; D052638:Particulate Matter; D012722:Sewage; D014874:Water Pollutants, Chemical; D014867:Water; D002244:Carbon