| 1. |
- Biganzoli, Laura, et al.
(författare)
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Aluminium recovery vs. hydrogen production as resource recovery options for fine MSWI bottom ash fraction
- 2013
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Ingår i: Waste Management: international journal of integrated waste management, science and technology. - : Elsevier BV. - 1879-2456. ; 33:5, s. 1174-1181
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Tidskriftsartikel (refereegranskat)abstract
- Waste incineration bottom ash fine fraction contains a significant amount of aluminium, but previous works have shown that current recovery options based on standard on-step Eddy Current Separation (ECS) have limited efficiency. In this paper, we evaluated the improvement in the efficiency of ECS by using an additional step of crushing and sieving. The efficiency of metallic Al recovery was quantified by measuring hydrogen gas production. The ash samples were also tested for total aluminium content with X-ray fluorescence spectroscopy (XRF). As an alternative to material recovery, we also investigated the possibility to convert residual metallic Al into useful energy, promoting H-2 gas production by reacting metallic Al with water at high pH. The results show that the total aluminium concentration in the <4 mm bottom ash fraction is on average 8% of the weight of the dry ash, with less than 15% of it being present in the metallic form. Of this latter, only 21% can be potentially recovered with ECS combined with crushing and sieving stages and subsequently recycled. For hydrogen production, using 10 M NaOH at 1 L/S ratio results in the release of 6-111 of H-2 gas for each kilogram of fine dry ash, equivalent to an energy potential of 118 kJ. (C) 2013 Elsevier Ltd. All rights reserved.
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| 2. |
- Ilyas, Aamir, et al.
(författare)
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Dielectric properties of MSWI bottom ash for non-invasive monitoring of moisture.
- 2013
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Ingår i: Environmental Monitoring & Assessment. - : Springer Science and Business Media LLC. - 1573-2959 .- 0167-6369. ; 185:8, s. 7053-7063
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Tidskriftsartikel (refereegranskat)abstract
- The dielectric procperties of MSWI bottom ash as a function of volumetric water content (VWC) are reported in this paper. The objective was to aid the development of microwave based non-invasive emission monitoring and control system for various bottom ash applications. The dielectric measurements were made, on a 1.5-year-old bottom ash, with an electrical network analyzer in microwave range (300 MHz-1.5 GHz). The VWC of the samples ranged between 0.05 and 0.40 m(3) m(-3). The relationship between the dielectric permittivity and the VWC was modeled with an empirical model and a physically based Birchak model (BM). The results showed that a linear relationship existed between the permittivity and the VWC at higher water contents (>0.25 m(3) m(-3)). However, at lower water contents (<0.25 m(3) m(-3)), the relationship between the permittivity and the WVC was affected by the composition of the bottom ash. The permittivity measurement, with the current method, was not affected by high salt concentrations (10 and 20 dS/m). The empirical model, as compared to BM, provided the best fit between the actual and the predicted water content. The root mean square error (RMSE) values were 0.008-0.010 and 0.06-0.09 m(3) m(-3) for the empirical and the Birchak model, respectively.
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| 3. |
- Ilyas, Aamir, et al.
(författare)
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Effects of substrate induced respiration on the stability of bottom ash in landfill cover environment.
- 2014
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Ingår i: Waste Management & Research. - 1096-3669. ; 32:12, s. 1241-1246
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Tidskriftsartikel (refereegranskat)abstract
- The municipal solid waste incineration bottom ash is being increasingly used to construct landfill covers in Sweden. In post-closure, owing to increased cover infiltration, the percolating water can add external organic matter to bottom ash. The addition and subsequent degradation of this external organic matter can affect metal mobility through complexation and change in redox conditions. However, the impacts of such external organic matter addition on bottom ash stability have not been fully evaluated yet. Therefore, the objective of this study was to evaluate the impact of external organic matter on bottom ash respiration and metal leaching. The samples of weathered bottom ash were mixed with oven dried and digested wastewater sludge (1%-5% by weight). The aerobic respiration activity (AT4), as well as the leaching of metals, was tested with the help of respiration and batch leaching tests. The respiration and heavy metal leaching increased linearly with the external organic matter addition. Based on the results, it was concluded that the external organic matter addition would negatively affect the quality of landfill cover drainage.
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| 4. |
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| 5. |
- Ilyas, Aamir, et al.
(författare)
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MEASUREMENT OF MOISTURE CONTENT OF WASTE MATERIALS WITH FREQUENCY DOMAIN REFLECTOMETRY(FDR)
- 2009
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Ingår i: [Host publication title missing]. ; , s. 14-14
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Konferensbidrag (refereegranskat)abstract
- Incineration of municipal solid waste (MSW) has resulted in large quantities of residues which can be recycled in roads and landfill covers provided the environmental concerns related to leaching of salts and metals can be mitigated. The pollutant transport from these residues depends on quantity and variability of moisture at re-use sites. For realistic assessment of leaching rates and pollutant transport risks quantifying the moisture variability is important.However due to destructive nature of traditional sampling regimes it is not possible to study moisture content of residues in the field. This study has tested a non invasive frequency domain based method at laboratory scale for its ability to measure moisture content in two different types of waste materials. The results show that despite high salt concentrations in waste samples this technique is robust and does not suffer from errors often encountered in time domain approaches
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| 6. |
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| 7. |
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| 8. |
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| 9. |
- Ilyas, Aamir, et al.
(författare)
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Residual organic matter and microbial respiration in bottom ash: Effects on metal leaching and eco-toxicity.
- 2015
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Ingår i: Waste Management & Research. - 1096-3669. ; 33:9, s. 805-811
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Tidskriftsartikel (refereegranskat)abstract
- A common assumption regarding the residual organic matter, in bottom ash, is that it does not represent a significant pool of organic carbon and, beyond metal-ion complexation process, it is of little consequence to evolution of ash/leachate chemistry. This article evaluates the effect of residual organic matter and associated microbial respiratory processes on leaching of toxic metals (i.e. arsenic, copper, chromium, molybdenum, nickel, lead, antimony and zinc), eco-toxicity of ash leachates. Microbial respiration was quantified with help of a respirometric test equipment OXITOP control system. The effect of microbial respiration on metal/residual organic matter leaching and eco-toxicity was quantified with the help of batch leaching tests and an eco-toxicity assay - Daphnia magna. In general, the microbial respiration process decreased the leachate pH and eco-toxicity, indicating modification of bioavailability of metal species. Furthermore, the leaching of critical metals, such as copper and chromium, decreased after the respiration in both ash types (fresh and weathered). It was concluded that microbial respiration, if harnessed properly, could enhance the stability of fresh bottom ash and may promote its reuse.
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| 10. |
- Ilyas, Aamir
(författare)
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Unsaturated Phase Environmental Processes in MSWI Bottom Ash
- 2013
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Every year, Sweden produces 1.5 million tons of incineration residues from waste to energy plants. Among these residues bottom ash(BA) due to its large volume and good geotechnical quality can be reused as an alternative construction material. However there are some negative environmental impacts of this practice such as leaching of salts and metals to soils and groundwater. Environmental processes occuring in the unsaturated phase can determine BA’s environmental impacts as well as provide interesting insights into improving its reuse. However, due to dominant conceptualisation of BA’s environmental impacts as a saturated phase phenomenon, very little work has been done on understanding the usaturated phase environmental processes. There is virtaully nothing known about BA’s dielectric properties which can be an impediment in the development of innovative tools e.g. microwave based monitoring and metal recovery systems. Similarly, release of hydrogen gas in anaerobic phase is considered a problem and its recovery for beneficial use has not been considered yet. Finally, residual organic matter is known to degrade and support microbial respiratory processes in BA. However, little work has been done on exploring its impact on leaching of metals and eco-toxicity of ash leachates.Therefore, the objective of this thesis was to explorethese unsaturated enviromental processes and highlight their role in envrionmental monitoring, reuse and resource recovery.To achieve this objective, the thesis was divided into three subdomains; 1) physical-dielectrics and non invasive monitoring , 2) chemicalanaerobic corrosion and hydrogen production, and 3) biological-microbial respiration and its impacts on the ash quality. During this work, methods such as frequency domain relectometry, respiration tests, hydrogen evolution experiments, batch leaching and ecotoxicity tests were employed. Methods such as gas chromatocgraphy and scanning electron microscopy(SEM) were also used when needed. For data analysis, statistical techniques such as polynomial regression, hierarchical clustering and principal components analysis (PCA) were used. Moreover, during the work on dielectrics, physical models were also used to establish the relationship between dielectric permittivity and volumetric water content. The results of dielectrics showed that in dry state BA acts a non conductor with strong dispersion tendencies especially at high frequencies.From the measured dielectric spectra, it was possible to estimate the moisture content as well as the effective electrical conductivity of BA.The dielectric properties of BA indicate the potential use of microwaves in noninvasive monitoring of moisture,weathering, residual metal contentand wet metal recovery.The results of hydrogen gas formation showed that the gas production from fresh BA was possible at mild conditions of temperature and pressure, and it showeda promise for commercial development. Comparison of hydrogen production with metal recovery showed that as compared to metal recovery,the reaction of metallic Al with alkaline solutions, to generate hydrogen , was more efficient. From the results on respiration tests, it was found that the respiration in fresh ash played a positive role by lowering the pH, reducing the leaching of critical metals and modifying the ash leachate eco-toxicity. However in case of the weathered ash, the microbial respiration negatively affected the ash quality by increasing the leaching heavy metals. The leaching of metals(Cu, Cr, Mo, Ni, Pb, & Zn) and total organic carbon was further enhanced by the addition of external organic matter. Further work on a bench scale hydrogen recovery system, the use of substrate induced respiration in fresh BA for carbonation and the use of microwaves in environmental monitoring and wet metal recovery is suggested.
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