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- Björn, Annika, 1972-
(författare)
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Microbial Transformation of Organotin Compounds under Simulated Landfill Conditions
- 2007
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Mono- and di-alkyltins are used extensively as heat stabilizers for processing of poly vinyl chloride (PVC). Tin mercaptide stabilizers are some of the most effective PVC stabilizers available. The main applications for tin stabilizers are building/construction products, such as pipes, fittings, siding and profiles (windows etc.), packaging and flexible PVC plastics. Most PVC products have been and are subjected to landfilling, when their use is terminated. The structure of the polymer itself and the substances used as additives have been a concern for environmental authorities in many countries since long, which also includes their presence in landfills. In the case of the organotin stabilizers their leaching out from (PVC) plastics into the leachate phase of landfills with the risk for further transport to ground and surface waters is in focus.The main objectives of this thesis take their start in this background and, thus, included the elucidation of whether organotin compounds (OTs) in stabilized PVC products contribute to the pool of OTs observed in landfill leachates and if these compounds are degradable by the microorganisms developing under anaerobic landfill conditions.To reach these aims and the research questions raised the forwarded PVC materials were added to muniscipal solid waste (MSW) processed in containers used to simulate the ageing of landfills under forced conditions. These include traditional landfill simulation reactors (LSRs) at a scale of ca 100 L and also at a smaller scale ca 5 L constructed for the purpose of this study, i.e. the modular environmental test system (METS). The latter were used to investigate temperature effects on the possible release of OTs from different types of PVC materials. The capacity by microorganisms in landfill environments were used to investigate their capacity to degrade or transform organotin stabilizer compounds focused on in this thesis. Differences in this capacity in relation to the ageing of landfills and exposure to the alkyltin stabilizers were studied with microorganisms sampled from LSRs spiked with PVC over time and from landfill site.Access to sensitive and reliable equipment and analytical protocols for the analysis of OTs and their transformation intermediates and end products are prerequisites for this kind of studies. This necessitated an adoption and adaptation of analytical methods for the low concentrations occurring in the environment. Two methods were established and well served the requirements.Indeed OTs migrated out from especially flexible PVC materials, while rigid PVC was less prone for OT release as judged from the METS simulations. The METS studies showed that the OT release increase substantially at higher temperatures and especially so when the temperature was higher than the glass transition of the PVC.materials.The organotin stabilizers were transformed, partly or completely degraded, by anaerobic microorganisms derived from landfill environments. Upon prolonged exposure to OTs leaching from PVC in LSR simulations the microorganisms displayed a higher efficiency in degradation of the leached OTs. The microorganisms would methylate inorganic tin and metyltin present in the MSW material as well as perform dealkylation depending on the tin concentrations prevailing. During these studies it was discovered that the organotin stabilzers were inhibiting the methanogens and fermentative bacteria, which lead to a retardation of the anaerobic mineralisation of the MSW in the assays. An in depth study revealed that the OTs themselves but also their ligands and degradation products from these together effected the inhibition.However, given the extent of leaching in relation to the water flows in landfills, the concentrations will mainly be too low to pose any risks to the surrounding environment.
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| 2. |
- Björn (Fredriksson), Annika, et al.
(författare)
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Impacts of Temperature on the Leaching of Organotin Compounds From Poly(vinyl chloride) Plastics : A Study Conducted Under Simulated Landfill Conditions
- 2007
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Ingår i: Journal of Vinyl and Additive Technology. - : Wiley. - 1083-5601 .- 1548-0585 .- 0193-7197 .- 1548-0577. ; 13:4, s. 176-188
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Tidskriftsartikel (refereegranskat)abstract
- The aim of the study was to investigate whether organotin-stabilized poly(vinyl chloride) (PVC) products could contribute to the pool of organotins observed in landfill leachates, and if the possible release could be related to different temperatures and landfill degradation phases. Small-scale anaerobic reactors filled with generic household waste, a mixture of inocula, and different PVC plastics were used in the study and incubated at 20, 37, 55, and 70°C. The reactor units incubated at temperatures of 20-55°C underwent the anaerobic degradation phases that are characteristic for the aging of landfilled waste material. There were, however, differences in the duration of the phases as well as in the total biogas production among the units. Under methanogenic conditions greater losses of organotin compounds were observed as compared to acidogenic conditions. It was shown that the release of organotin stabilizers increases considerably at temperatures above the glass transition of the PVC products. A dealkylation from di- into monoalkyltin species was observed, as well as a possible methylation of inorganic tin. However, the main part of the organotins was adsorbed into the solid waste matrix.
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| 3. |
- Karlsson, Anna, 1969-, et al.
(författare)
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Effects of temperature, hydraulic retention time and hydrogen extraction rate on hydrogen production from the fermentation of food industry residues and manure
- 2008
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Ingår i: International journal of hydrogen energy. - : Elsevier BV. - 0360-3199 .- 1879-3487. ; 33:3, s. 953-962
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Tidskriftsartikel (refereegranskat)abstract
- The production of H2 from food residues and manure has been optimised using a central composite face-centred (CCF) design. In all 17 assays were run, varying the temperature (20, 37 and 55 {ring operator} C), hydraulic retention time (2, 5 and 8 days) and N2-flow rates (5, 25 or 125 mL/min). Completely stirred tank reactors (2 L) were operated for three hydraulic retention times and hydrogen production was determined during the course of a 24-h period before termination. The concentrations of H2, CH4 and volatile fatty acids were measured, together with pH, throughout the experiment. A temperature of 55 {ring operator} C, combined with a sparging rate of 125 mL/min, and a hydraulic retention time of 2 days resulted in the highest hydrogen formation. The maximal production experimentally obtained was 16.5 mL H2/g VS. A model was calculated from the data with a squared correlation coefficient (R2) of 0.97 and a predictive power of 0.64 (Q2). © 2007 International Association for Hydrogen Energy.
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