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| 2. |
- Mamo, Gashaw, et al.
(författare)
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Preface
- 2020
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Ingår i: Alkaliphiles in Biotechnology. - 0724-6145. ; 172
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Bokkapitel (övrigt vetenskapligt/konstnärligt)
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| 3. |
- 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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| 5. |
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| 6. |
- Punzi, Marisa, et al.
(författare)
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Combined anaerobic-ozonation process for treatment of textile wastewater : Removal of acute toxicity and mutagenicity
- 2015
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Ingår i: Journal of Hazardous Materials. - : Elsevier BV. - 0304-3894 .- 1873-3336. ; 292, s. 52-60
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Tidskriftsartikel (refereegranskat)abstract
- A novel set up composed of an anaerobic biofilm reactor followed by ozonation was used for treatment of artificial and real textile effluents containing azo dyes. The biological treatment efficiently removed chemical oxygen demand and color. Ozonation further reduced the organic content of the effluents and was very important for the degradation of aromatic compounds, as shown by the reduction of UV absorbance. The acute toxicity toward Vibrio fischeri and the shrimp Artemia salina increased after the biological treatment. No toxicity was detected after ozonation with the exception of the synthetic effluent containing the highest concentration, 1. g/l, of the azo dye Remazol Red. Both untreated and biologically treated textile effluents were found to have mutagenic effects. The mutagenicity increased even further after 1. min of ozonation. No mutagenicity was however detected in the effluents subjected to longer exposure to ozone. The results of this study suggest that the use of ozonation as short post-treatment after a biological process can be beneficial for the degradation of recalcitrant compounds and the removal of toxicity of textile wastewater. However, monitoring of toxicity and especially mutagenicity is crucial and should always be used to assess the success of a treatment strategy. © 2015 Elsevier B.V.
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| 7. |
- Punzi, Marisa, et al.
(författare)
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Degradation of a textile azo dye using biological treatment followed by photo-Fenton oxidation : Evaluation of toxicity and microbial community structure
- 2015
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Ingår i: Chemical Engineering Journal. - : Elsevier BV. - 1385-8947 .- 1873-3212. ; 270, s. 290-299
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Tidskriftsartikel (refereegranskat)abstract
- Many commercial dye preparations are cocktails of active dyes and various by-products that are recalcitrant to biological degradation and end up in significant amounts in the effluent after the dyeing process. Conventional wastewater treatment processes are not able to degrade such compounds and detoxify the effluent, thus alternative treatments should be developed.In our work we suggest to use photo-Fenton oxidation as post-treatment after an anaerobic biofilm process, in a way to minimize the reagents needed. This process was used for treatment of synthetic textile wastewater containing the commercial azo dyestuff Remazol Red, starch and sodium chloride. The treated textile effluent had COD lower than 18. mg/l even when using initial Fenton reagents concentration as low as 1. mM ferrous ions and 10. mM hydrogen peroxide. The acute toxicity was higher in the biologically treated than in the untreated effluent. Photo-Fenton oxidation successfully reduced the toxicity and the final effluent was non-toxic to Artemia salina and Microtox, with the exception of the effluent containing high concentration of sodium chloride, which was moderately toxic to Microtox. For the first time the presence of algae was detected in a reactor treating textile wastewater using denaturing gradient gel electrophoresis (DGGE); bacteria and fungi were also abundant.The results of this study suggest that using advanced oxidation after biological treatment is an effective way to degrade the organic compounds and remove toxicity from textile effluents.
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| 8. |
- Adlercreutz, Patrick, et al.
(författare)
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Aspects of biocatalyst stability in organic solvents
- 1987
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Ingår i: Biocatalysis and Biotransformation. - : Informa UK Limited. - 1024-2422. ; 1:2, s. 99-108
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Forskningsöversikt (refereegranskat)abstract
- The stability of biocatalysis in systems containing organic solvents is reviewed. Among the examples presented are homogeneous mixtures of water and water-miscible organic solvents, aqueous/organic two-phase systems, solid biocatalysts suspended in organic solvents, enzymes in reverse micelles and modified enzymes soluble in water immiscible solvents. The stability of biocatalysts in organic solvents depends very much on the conditions. The hydrophobicity or the polarity of the solvent is clearly of great importance. More hydrophobic solvents (higher log P values) are less harmful to enzymes than less hydrophobic solvents. The water content of the system is a very important parameter. Some water is essential for enzymatic activity; however, the stability of enzymes decreases with increasing water content. Mechanisms of enzyme inactivation are discussed.
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| 9. |
- Adlercreutz, Patrick, et al.
(författare)
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Characterization of Gluconobacter oxydans immobilized in calcium alginate
- 1985
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Ingår i: Applied Microbiology and Biotechnology. - 0175-7598. ; 22:1, s. 1-7
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Tidskriftsartikel (refereegranskat)abstract
- Gluconobacter oxydans cells were immobilized in calcium alginate and the preparation was used for the oxidation of glycerol to dihydroxyacetone. The characterization was done according to the guidelines given by the Working Party on Immobilized Biocatalysts of the European Federation of Biotechnology. The pH optimum of the preparation was found to be 5.0 and the temperature optimum was 40°C. However, the operational stability was better at 30°C. The glycerol concentration required to obtain half the maximal reaction rate was about 5 mM for both immobilized and free cells. At low concentrations of glycerol and high concentrations of dihydroxyacetone a slight inhibition was noted. No loss of activity of the immobilized preparation was observed after storage for 68 days at +4°C. Investigation of the operational stability revealed a half-life of 5 days. Studies of the influence of particle size and cell densities as well as that of oxygen concentration revealed that the oxygen supply was the rate limiting step.
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| 10. |
- ADLERCREUTZ, PATRICK, et al.
(författare)
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Enzymatic Peptide Synthesis in Organic Media
- 1990
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Ingår i: Annals of the New York Academy of Sciences. - : Wiley. - 0077-8923 .- 1749-6632. ; 613:1, s. 517-520
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Tidskriftsartikel (refereegranskat)
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