The area’s natural analogues, vitrifi ed forts, combustion technology, and vitrifi ed waste have been reviewed.The purpose was to identify if investigations of vitrifi ed rock in hill forts might be warranted for assessing thelong-term integrity of vitrifi ed waste in natural environments. Wastes that are being vitrifi ed include ash fromincineration of domestic waste, contaminated soil and fi ssion products from reprocessing of spent nuclear fuel.It was found that vitrifi ed materials in at least 200 hill forts constitute good anthropogenic analogues to vitrified waste. The compositions vary considerably from site to site and even within one site and may correspondrelatively well to the spans of parameters in the various vitrifi ed wastes. Glasses in vitrifi ed forts comparefavourably to archaeological artefacts which are soda- and potash-based and consequently have different corrosionbehaviours and may weather too quickly. Natural glasses might be too limited in composition variationand are perhaps also too durable. Combustion technology considerations based on quality of heat analysesindicate that at least some of the vitrifi cations of hill forts were carried out with the specifi c purpose of achievingstrong and durable constructions. This makes it considerably easier to envisage how the vitrifi cations mighthave been carried out, and this, in turn, facilitates comparisons between anthropogenic analogues and modernvitrifi ed wastes.

An information survey was conducted in the areas of natural analogues, vitrified forts, combustion technology and vitrified waste.The main purpose was to identify if vitrified stone material in hillforts might be used as anthropogenic analogues for glass containing waste.Such comparisons are needed in order for predictions to be made regarding the long-term integrity of the waste forms.The scope was to compare the chemistry as well as the processes used for the generation of the glasses. It was found that the vitrified forts contain glass material with wide variations in composition of the major elements.They cover and exceed those in the glasses made of waste with only the exception of phosphorus.Natural glasses as well as archaeological glasses show much narrower ranges of compositions, and they do not coincide with those of the glasses containing waste. Quality of heat analyses indicated that it is likely that the stone material in the forts was melted for the purpose of obtaining long-lasting structures.This narrows the range of possible processes used, and facilitates reconstruction of the ancient methods by means of testing.This, in turn, provides possibilities of comparison between ancient and modern methods, which can then be used as a basis for validation of the use of the analogue.

Carbon in waste can occur as inorganic (IC), organic (OC) and elemental carbon (EC) each having distinct chemical properties and possible environmental effects. In this study, carbon speciation was performed using thermogravimetric analysis (TGA), chemical degradation tests and the standard total organic carbon (TOC) measurement procedures in three types of waste materials (bottom ash, residual waste and contaminated soil). Over 50% of the total carbon (TC) in all studied materials (72% in ash and residual waste, and 59% in soil) was biologically non-reactive or EC as determined by thermogravimetric analyses. The speciation of TOC by chemical degradation also showed a presence of a non-degradable C fraction in all materials (60% of TOC in ash, 30% in residual waste and 13% in soil), though in smaller amounts than those determined by TGA. In principle, chemical degradation method can give an indication of the presence of potentially inert C in various waste materials, while TGA is a more precise technique for C speciation, given that waste-specific method adjustments are made. The standard TOC measurement yields exaggerated estimates of organic carbon and may therefore overestimate the potential environmental impacts (e.g. landfill gas generation) of waste materials in a landfill environment.

Steel slags from high-alloyed tool steel production were used in a full scale cover construction of a municipal solid waste (MSW) landfill. In order to study the long-term stability of the steel slags within the final cover, a laboratory experiment was performed. The effect on the ageing process, due to i.e. carbonation, exerted by five different factors resembling both the material characteristics and the environmental conditions is investigated. Leaching behaviour, acid neutralization capacity and mineralogy (evaluated by means of X-ray diffraction, XRD, and thermogravimetry/differential thermal analysis, TG/DTA) are tested after different periods of ageing under different conditions.Samples aged for 3 and 10 months were evaluated in this paper. Multivariate data analysis was used for data evaluation. The results indicate that among the investigated factors, ageing time and carbon dioxide content of the atmosphere were able to exert the most relevant effect. However, further investigations are required in order to clarify the role of the temperature.

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 27-1 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×ash ratio and ash ratio×compaction energy affected hydraulic conductivity significantly (α = 0.05). Freezing on 5 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 R2adjusted values between 0.75 and 0.86. Independent on the ash ratio and the material, hydraulic conductivity was predicted to be between 1.7 × 10-11 m s-1 and 8.9 × 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.

Fly ash from biofuel incineration and slags from steel production were used in two full scale applications of cover constructions on municipal solid waste (MSW) landfills. The long-term stability of the cover materials is studied in a designed laboratory experiment. The impact of six environmental factors on accelerated carbonation is investigated over a period of three years. Leaching behaviour, acid neutralization capacity, mineral composition (XRD) and thermo gravimetrical behaviour (TG) are tested after different periods of ageing under different conditions. By now samples were taken after three and ten months of ageing. Multivariate data analysis was used for data evaluation. The results indicate the factors material, ageing time and carbon dioxide content of the atmosphere to be most relevant.

Dissolved organic carbon (DOC) may affect the transport of pollutants from incineration residues when landfilled or used in geotechnical construction. The leaching of dissolved organic carbon (DOC) from municipal solid waste incineration (MSWI) bottom ash and air pollution control residue (APC) from the incineration of waste wood was investigated. Factors affecting the mobility of DOC were studied in a reduced 26-1 experimental design. Controlled factors were treatment with ultrasonic radiation, full carbonation (addition of CO2 until the pH was stable for 2.5 h), liquid-to-solid (L/S) ratio, pH, leaching temperature and time. Full carbonation, pH and the L/S ratio were the main factors controlling the mobility of DOC in the bottom ash. Approximately 60 weight-% of the total organic carbon (TOC) in the bottom ash was available for leaching in aqueous solutions. The L/S ratio and pH mainly controlled the mobilization of DOC from the APC residue. About 93 weight-% of TOC in the APC residue was, however, not mobilized at all, which might be due to a high content of elemental carbon. Using the European standard EN 13 137 for determination of total organic carbon (TOC) in MSWI residues is inappropriate. The results might be biased due to elemental carbon. It is recommended to develop a TOC method distinguishing between organic and elemental carbon.

Co-landfilling of incineration ash and cellulose might facilitate the alkaline degradation of cellulose. A major degradation product is isosaccharinic acid (ISA), a complexing agent for metals. The impact of ISA on the mobility of Pb, Zn, Cr, Cu and Cd from a municipal solid waste incineration dry scrubber residue was studied at laboratory using a reduced 25-1 factorial design. Factors investigated were the amount of calcium isosaccharinate (Ca(ISA)2), L/S ratio, temperature, contact time and type of atmosphere (N2, air, O2). The effects of pH and Ca(ISA)2 as well as other factors on the leaching of metals were quantified and modelled using multiple linear regression (α = 0.05). Cd was excluded from the study since the concentrations were below the detection limit. The presence of Ca(ISA)2 resulted in a higher leaching of Cu indicating complex formation. Ca(ISA)2 alone had no effect on the leaching of Pb, Zn and Cr. A secondary effect on the mobilization was predicted to occur since Ca(ISA)2 had a positive effect on the pH and the leaching of Pb, Zn and Cr increased with increasing pH. The leaching of Pb varied from 24 up to 66 wt.% of the total Pb amount (1.74 ± 0.02 g(kg TS)-1) in the dry scrubber residue. The corresponding interval for Zn (7.29 ± 0.07 g(kg TS)-1) and Cu (0.50 ± 0.02 g(kg TS)-1) were 0.5-14 wt.% of Zn and 0.8-70 wt.% of Cu. Maximum leaching of Cr (0.23 ± 0.03 g(kg TS)-1) was 4.0 wt.%. At conditions similar to a compacted and covered landfill (4 °C, 7 days, 0 vol.% O2) the presence of ISA can increase the leaching of Cu from 2 to 46 wt.% if the amount of cellulose-based waste increases 20 times, from the ratio 1:100 to 1:5. As well, the leaching of Pb, Zn, and Cr can increase from 32 to 54 wt.% (Pb), 0.8-8.0 wt.% (Zn), and 0.5 to 4.0 wt.% (Cr) depending on the amount of cellulose and L/S ratio and pH value. Therefore, a risk (α = 0.05) exists that higher amounts of metals are leached from landfills where cellulose-containing waste and ash are co-disposed. This corresponds to an additional 29 t of Pb and 17 t of Cu leached annually from a compacted and covered landfill in the north of Sweden.

A test road constructed with municipal solid waste incineration (MSWI) bottom ash was monitored over a period of 36 months. Using chemical and toxicological characterisation, the environmental impact of leachates from bottom ash was evaluated and compared with leachates from gravel used as reference. Initial leaching of Cl, Cu, K, Na, NH₄-N and TOC from bottom ash was of major concern. However, the quality of the bottom ash leachate approached that of the gravel leachate with time. Leachates from the two materials were compared regarding the concentration of pollutants using multivariate data analyses (MVDA). A standardized luminescent bacteria assay using Vibrio fischeri did not show any toxicity, most likely because saline contamination can mask the toxic response and stimulate luminescence in these marine bacteria. A mung bean assay using Phaseolus aureus revealed that the toxicity of bottom ash leachate collected at the very beginning of the experimental period (October 2001 and May 2002) might be attributed to the following components and their respective concentrations in mg l^-1: Al (34.2-39.2), Cl (2914-16,446), Cu (0.48-1.92), K (197-847), Na (766-4180), NH₄-N (1.80-8.47), total-N (12.0-18.5), and TOC (34.0-99.0). The P. aureus assay was judged as a promising environmental tool in assessing the toxicity of bottom ash leachate.