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- Davidsson, Åsa, et al.
(författare)
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Effect of anaerobic digestion at 35, 55 and 60 °C on pharmaceuticals and organic contaminants
- 2014
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Ingår i: Water Science and Technology. - : IWA Publishing. - 0273-1223 .- 1996-9732. ; 69:6, s. 1282-1288
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Tidskriftsartikel (refereegranskat)abstract
- The application of treated sewage sludge on farmland is a suggested method for recycling nutrients and reducing demand for commercial fertilizer. However, sludge needs to be safe from possible contaminants which can cause acute and long-term health and environmental problems. Residual pharmaceuticals and organic contaminants are mentioned as emerging threats since wastewater treatment plants are not designed to degrade these substances. The aim of this study was to screen and evaluate the presence, and reduction, of pharmaceuticals and polycyclic aromatic hydrocarbons (PAHs) during anaerobic digestion of mixed primary and waste-activated sludge at 35, 55 and 60°C and during pasteurization at 70°C. The study showed the difficulty of analysing pharmaceutical compounds in low concentrations in the sludge matrix. No general reduction of these compounds was seen during treatment, but for individual substances some reduction occured. The PAHs were generally not reduced during digestion or pasteurization, but for three substances (indeno[1,2,3-cd]pyrene and dibenzo[a,h]anthracene (analysed together) and benzo[g,h,i]perylene) reduction (up to 60%) during digestion was seen. Digestion at 35 and 55°C resulted in about the same order of reduction of the three individual PAHs, which was higher than for digestion at 60°C.
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| 2. |
- Davidsson, Åsa, et al.
(författare)
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Effect of anaerobic digestion at 35, 55 and 60 °C ON pharmaceuticals and organic pollutants
- 2013
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Ingår i: Presented at the 1st International IWA Conference on Holistic Sludge Management, Västerås, Sweden, May 6-8, 2013. ; , s. 1-8
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Konferensbidrag (refereegranskat)abstract
- The application of treated sewage sludge on farmland is a suggested method for recycling nutrients and reducing demand for commercial fertilizer. However sludge needs to be rendered safe from possible contaminants which can cause acute and long-term health and environmental problems. Residual pharmaceuticals and organic contaminants in sludge are mentioned as emerging threats since wastewater treatment plants are not designed to degrade these substances thus yielding an accumulation in sludge. The aim of this study was to evaluate the presence, and reduction, of pharmaceuticals and polycyclic aromatic hydrocarbons (PAHs) during anaerobic digestion at 35, 55 and 60ºC and during pasteurization at 70°C. The substrate used was mixed primary and secondary sludge from a 300 000 person-equivalents municipal wastewater treatment plant in southern Sweden. In general no reduction of pharmaceuticals could be observed at any temperature or minimum exposure time, except for the beta-blocker Irbesartan and the antibiotic Trimethoprim. The results from pharmaceuticals in mesophilic sludge agreed with results in recent Swedish studies. Also, no reduction of PAHs during digestion or pasteurization (70°C – 1 hour) was seen, but for single PAHs digestion could lead to reduction.
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| 3. |
- Eriksson, Jenny, 1985-, et al.
(författare)
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Evaluation of galling resistance for some selected combinations of tool steels / stainless steel sheet materials/ lubricants using pin-on-disc testing
- 2010
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Ingår i: NordTrib 2010. - Storforsen.
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Konferensbidrag (refereegranskat)abstract
- Stainless steels are well known to be prone to cold welding and material transfer in sliding contacts and therefore difficult to cold form unless certain precautions as discussed in this paper are taken. In the present study different combinations of tool steels/stainless steels/lubricants has been evaluated with respect to their galling resistance using pin-on-disc testing. The results show that a high galling resistance is favored by a high stainless steel sheet hardness and a blasted stainless steel sheet surface topography. The effect of type of lubricant was found to be more complex. For example, the chlorinated lubricants failed to prevent metal-to-metal contact on a brushed sheet surface but succeeded on a blasted sheet surface of the same stainless steel material. This is believed to be due to a protective tribofilm which is able to form on the blasted surface, but not on the brushed surface.
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| 4. |
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| 5. |
- Eriksson, Jenny, 1985-
(författare)
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Galling of high strength steels and stainless steels in sheet metal forming as evaluated using pin-on-disc testing
- 2012
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The thesis focuses on the problem galling in sheet metal forming operations. Galling occurs when sheet metal transfers from the sheet surface onto the tool surface and causes surface damages to following sheets in the forming operation. When this happens the tool must be replaced causing production stops and additional expenses. The increasing use of high strength steel grades combined with the desire to use more environmentally friendly or no lubricants exposes the tools used for sheet metal forming for tougher forming conditions with higher contact pressures and thus an increasing risk for material pick-up and galling. To prevent this new tool steels, lubricants and coatings have been developed. In this thesis a number of tool steels, high strength steels, stainless steels, coatings and lubricants have been investigated with the test method pin-on-disc testing in order to explain how different premises, such as chemical composition, mechanical properties and surface topography influence on the galling tendency in sheet metal forming. The results show that there is a big difference in performance between a conventional cast tool steel and a powder metallurgy tool steel with respect to the galling tendency. The results also show that the surface topography of both the tool steels and the sheet materials influence on the performance of the lubricants and the galling tendency. When coating a tool steel, the substrate hardness is of greatest importance for the performance and wear of the coating. For the different coatings investigated, the performance of the coatings depends on whether the sheet material is zinc coated or not. However, the CrC/C coating investigated show a good performance with respect to the galling tendency in contact with all of the investigated high strength steel grades.
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| 6. |
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| 7. |
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| 8. |
- Eriksson, Jenny, 1985-, et al.
(författare)
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Ranking the performance of lubricants, tool steels and PVD coatings for the forming of high strength steel using pin-on-disc testing
- 2009
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Ingår i: Tool09.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The increasing use of high strength steels in a variety of mechanical engineering applications has illuminated problems associated with galling in sheet metal forming operations. Galling is a tribological phenomenon associated with transfer of material from the steel sheet to the tool surface during forming resulting in seizure of the tool/steel sheet contact and extensive scratching of the steel sheet surface. As a result, a number of concepts have been developed in order to reduce the tendency to galling in sheet metal forming, including the development of new dry lubricants, new forming tool steel grades and improved surface engineering treatments such as the deposition of low friction CVD- and PVD-coatings. In the present study the potential performance of these concepts in the forming of hot and cold rolled high strength steel as well as electro and hot-dip galvanized high strength steel has been evaluated using pin-on disc testing. In the tests, two different lubricants, a dry lubricant and a pre-lube oil, two different cold work tool steels, a conventional steel grade and a nitrogen alloyed PM steel grade, and two different PVD coatings, (Ti,Al)n and CrC/C, were evaluated. Post-test examination of the tribosurfaces using FEG-SEM, EDX and 3D surface profilometry was performed in order to evaluate the mechanisms controlling the material transfer and wear. In summary, the results show that the laboratory testing combined with post-test microscopy and surface analysis give valuable information in order to rank the galling resistance of lubricants, tool steels and PVD-coatings.
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| 9. |
- Eriksson, Jenny, 1985-, et al.
(författare)
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Tribological testing of commercial CrN, (Ti,Al)N and CrC/C PVD coatings : Evaluation of galling and wear characteristics against different high strength steels.
- 2011
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Ingår i: Surface & Coatings Technology. - Lausanne : Elsevier BV. - 0257-8972 .- 1879-3347. ; 205:16, s. 4045-4051
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Tidskriftsartikel (refereegranskat)abstract
- The increasing use of high strength steels in a variety of mechanical engineering applications has illuminatedproblems associated with galling in sheet metal forming operations. Galling is a tribological phenomenonassociated with transfer of material from the steel sheet to the tool surface during forming resulting in seizureof the tool/steel sheet contact and extensive scratching of the steel sheet surface. As a result, a number ofconcepts have been developed in order to reduce the tendency of galling in sheet metal forming, including thedevelopment of new dry lubricants, new forming tool steel grades and improved surface engineeringtreatments such as the deposition of low friction CVD- and PVD-coatings. In the present study the potentialperformance of three commercial PVD coatings, including CrN, (Ti,Al)N and a CrC/C DLC-based coating, in theforming of hot and cold rolled high strength steel as well as electro and hot-dip galvanized high strength steelhas been evaluated using pin-on-disc testing under lubricated contact conditions. Post-test examination ofthe tribosurfaces using FEG-SEM and EDS analyses was performed in order to evaluate the mechanismscontrolling the tendency to material transfer and wear. The results show that in contact with the hot and coldrolled steel the material pick-up tendency of the PVD coatings tend to increase in the order CrC/C–CrN–(Ti,Al)N while in contact with the two galvanized steel sheets, the CrC/C and the (Ti,Al)N coating show a significantlylower material pick-up tendency as compared with the CrN coating. Further, the substrate hardness has astrong influence on the wear of the PVD coatings and consequently on the friction characteristics and gallingtendency of the coating/substrate composite. Low substrate hardness, resulting in a low load bearing capacity,increases the tendency to cracking and subsequently chipping of the brittle coating.
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| 10. |
- Karlsson, Patrik, 1973-, et al.
(författare)
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Galling resistance evaluation of tool steels by two different laboratory test methods for sheet metal forming
- 2012
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Ingår i: Lubrication Science. - : John Wiley & Sons. - 0954-0075 .- 1557-6833. ; 24:6, s. 263-272
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Tidskriftsartikel (refereegranskat)abstract
- Adhesive accumulation of work material on the tool surface is today a major problem in many sheet metal-forming applications. Different laboratory test methods are used to investigate galling with respect to different tool materials, lubricants and process conditions. In the present study, the galling resistance of a modern nitrogen-alloyed powder metallurgy tool steel and an conventional ingot cast D2 type tool steel was evaluated under lubricated sliding against ferritic stainless steel sheets using a commercial pin-on-disc (POD) and an in-house made slider-on-flat-surface (SOFS) tribotester. The investigated tool steels ranked similarly in terms of galling resistanc in both test methods. However, sliding distances to galling were longer for the SOFS equipment due to continuous sliding on new lubricated sheet surface. Best performance was demonstrated by the powder metallurgy tool steel treated to 65 HRC. Differences in friction behaviour and galling initiation were analysed on the basis of the two different working conditions, i.e. open (SOFS) and closed (POD) tribosystems. Copyright © 2012 John Wiley & Sons, Ltd.
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