Amendment of biosolids with waste materials and lime: Effect on geoenvironmental properties and leachate production.
Residuals from wastewater treatment operations (biosolids) were mixed with lime, fly ash, lime kiln dust, or two smelter slags to assess their efficacy as potential stabilisation agents by assessing their effects on the shear strength, compressibility, and solids content of mixtures. In addition, the minerals formed and leachate produced during stabilisation were determined. Tests were performed to explore the change of the geoenvironmental properties of the amended biosolids, while under pressure, at different scales using laboratory, pilot and field scale tests. The settlement characteristics of the amended biosolids under a range of applied pressures were determined using a consolidometer. All amended biosolids mixtures showed higher strength than the unamended biosolids, with mixtures containing a combination of 20% fly ash and 20% lime giving the highest (up to eightfold) increase in strength, and that with lime kiln dust and the smelter slags showing the lowest (up to twofold). The biosolids mixtures with only lime gave the second highest increase in strength (up to fourfold), but produced the largest amount of leachate, with higher level of dissolved calcium. The increase in strength correlated with availability of calcium oxide in the mixtures which lead to calcium carbonate formation, accompanied with higher leachate production and settlement during consolidation. Copper, nickel and zinc concentrations increased with alkaline additives and corresponded to higher pH and DOC levels. Nonetheless, concentrations were within the New Zealand regulatory limits for Class A landfills.
Department of Civil and Environmental Engineering, University of Auckland, Private Bag 92019, Auckland 1142, New Zealand. Electronic address: ckay008@aucklanduni.ac.nz.
Claudia
C
Kayser
Department of Civil and Environmental Engineering, University of Auckland, Private Bag 92019, Auckland 1142, New Zealand. Electronic address: t.larkin@auckland.ac.nz.
Tam
T
Larkin
Department of Civil and Environmental Engineering, University of Auckland, Private Bag 92019, Auckland 1142, New Zealand. Electronic address: n.singhal@auckland.ac.nz.
Naresh
N
Singhal
D002118:Calcium / Q000032:analysis; D017610:Calcium Compounds / Q000032:analysis; D002244:Carbon / Q000032:analysis; D060729:Coal Ash / Q000032:analysis; D004391:Dust / Q000032:analysis; D006863:Hydrogen-Ion Concentration; D007220:Industrial Waste / Q000032:analysis*; D008670:Metals / Q000032:analysis; D009520:New Zealand; D010087:Oxides / Q000032:analysis; D012989:Soil Pollutants / Q000032:analysis*; D062611:Solid Waste / Q000032:analysis*; D014874:Water Pollutants, Chemical / Q000032:analysis*
D017610:Calcium Compounds; D060729:Coal Ash; D004391:Dust; D007220:Industrial Waste; D008670:Metals; D010087:Oxides; D012989:Soil Pollutants; D062611:Solid Waste; D014874:Water Pollutants, Chemical; D002244:Carbon; C016538:lime; D002118:Calcium
Biosolids; Leachate; Metal concentration; Overburden pressure; Settlement; Shear strength