20 research outputs found
The degradation of poly(vinyl acetate) as a material for design objects: A multi-analytical study of the effect of dibutyl phthalate plasticizer. Part 1
No full textThe influence of dibutyl phthalate (DBP) plasticizer on poly(vinyl acetate) (PVAc) degradation was investigated. A multi-analytical approach (combining FTIR and Fluorescence spectroscopy, NMR and DSC analyses) was used to study how thermal- and photo-oxidative ageing treatments act on the polymer and assess the role of the additive in the degradation pattern. Standard and plasticized PVAc films were artificially aged at 60 °C in a thermal regime and irradiated at wavelengths above 290 nm in a photo-oxidative ageing regime, with exposure between 100 and 2000 h. The two types of ageing differ mainly in the formation of C{double bond, long}C double bonds along the polymer backbone, enhanced by thermal ageing, and the formation of aldehydic structures, following photo-oxidative treatment and in the degree to which plasticizer is lost. The integration of results from different analytical methods highlights the utility in combining complementary analyses for the study of PVAc degradation
The degradation of poly(vinyl acetate) as a material for design objects: A multi-analytical study of the Cocoon lamps. Part 2
No full textFluorescence and Fourier-transform infrared spectroscopyfor the analysis of iconic Italian design lamps madeof polymeric materials
No full textMateriali per il design: caratterizzazione di blend polimerici e studio di fenomeni dei degrado
No full textAdvanced non-invasive fluorescence spectroscopy and imaging for mapping photo-oxidative degradation in acrylonitrile–butadiene–styrene: A study of model samples and of an object from the 1960s
No full textConversion of Polymeric Substrates by Aerobic Granular Sludge
No full textDomestic wastewater is treated prior to its return to natural water bodies, to minimize its polluting effect. Biological wastewater treatment removes organic matter and nutrients from the wastewater, by employing the activity of microorganisms, which consume polluting compounds present in wastewater to grow. One of such technologies is aerobic granular sludge (AGS), which consists of self-immobilized microorganisms growing in spherical biofilms. The granular structure facilitates the separation between treated water and the biomass due to its excellent settling properties. This way, energy and space are saved in comparison to flocculent sludge-based treatment. Despite its many advantages, the granular structure can pose some challenges too, particularly regarding the degradation of polymeric substrates. The higher mass-transfer resistance in granules compared to flocs challenges the degradation of these substrates, which have a size spanning from a few kDa to several micrometres. Polymeric substrates, furthermore, need to undergo hydrolysis before microorganisms can take them up, which is generally a slow process. Most AGS applications rely on microbial selection driven by the application of a sequencing batch reactor (SBR) cycle. The cycle consists of an anaerobic substrate feeding and a subsequent aerobic starvation period, which selects for intracellular polymer-storing organisms, such as polyphosphate accumulating organisms (PAO) and glycogen accumulating organisms (GAO). Substrates that experience high mass-transfer limitation and low degradation rates may interfere with the microbial selection strategy applied to AGS, especially when they are not (fully) taken up in the anaerobic feeding period and continue degrading aerobically in the next cycle phase. Some lab-scale studies have reported detrimental effects of polymeric substrates in AGS structure and activity, while others have managed to maintain a stable granule bed and suggest that the microbial utilization of polymeric substrates can contribute to good nutrient removal. The degradation of polymeric substrates by full-scale aerobic granules is still poorly understood. Sanitary Engineerin
Gas-phase enantiodifferentiation of chiral molecules. Chiral recognition of 1-phenyl-1-propanol/2-butanol cluster by resonance enhanced multiphoton ionization spectroscopy
No full textThe first application of REMPI combined with TOF mass spectroscopy to discriminate supersonically expanded van der Waals diastereomeric mol. complexes, was illustrated
Anaerobic hydrolysis of complex substrates in full-scale aerobic granular sludge: enzymatic activity determined in different sludge fractions
No full textComplex substrates, like proteins, carbohydrates, and lipids, are major components of domestic wastewater, and yet their degradation in biofilm-based wastewater treatment technologies, such as aerobic granular sludge (AGS), is not well understood. Hydrolysis is considered the rate-limiting step in the bioconversion of complex substrates, and as such, it will impact the utilization of a large wastewater COD (chemical oxygen demand) fraction by the biofilms or granules. To study the hydrolysis of complex substrates within these types of biomass, this paper investigates the anaerobic activity of major hydrolytic enzymes in the different sludge fractions of a full-scale AGS reactor. Chromogenic substrates were used under fully mixed anaerobic conditions to determine lipase, protease, α-glucosidase, and β-glucosidase activities in large granules (>1 mm in diameter), small granules (0.2–1 mm), flocculent sludge (0.045–0.2 mm), and bulk liquid. Furthermore, composition and hydrolytic activity of influent wastewater samples were determined. Our results showed an overcapacity of the sludge to hydrolyze wastewater soluble and colloidal polymeric substrates. The highest specific hydrolytic activity was associated with the flocculent sludge fraction (1.5–7.5 times that of large and smaller granules), in agreement with its large available surface area. However, the biomass in the full-scale reactor consisted of 84% large granules, making the large granules account for 55–68% of the total hydrolytic activity potential in the reactor. These observations shine a new light on the contribution of large granules to the conversion of polymeric COD and suggest that large granules can hydrolyze a significant amount of this influent fraction. The anaerobic removal of polymeric soluble and colloidal substrates could clarify the stable granule formation that is observed in full-scale installations, even when those are fed with complex wastewaters. Key points: • Large and small granules contain >70% of the hydrolysis potential in an AGS reactor. • Flocculent sludge has high hydrolytic activity but constitutes <10% VS in AGS. • AGS has an overcapacity to hydrolyze complex substrates in domestic wastewater. <!-- Query ID="Q2" Text=" Graphical abstract contains text below the minimum required font size of 6pts inside the artwork, and there is no sufficient space available for the text to be enlarged. Please provide replacement figure file." -->Graphical abstract: [Figure not available: see fulltext.
Effect of an increased particulate cod load on the aerobic granular sludge process: A full scale study
No full textHigh concentrations of particulate COD (pCOD) in the influent of aerobic granular sludge (AGS) systems are often associated to small granule diameter and a large fraction of flocculent sludge. At high particulate concentrations even granule stability and process performance might be compromised. However, pilot-or full-scale studies focusing on the effect of real wastewater partic-ulates on AGS are scarce. This study describes a 3-month period of increased particulate loading at a municipal AGS wastewater treatment plant. The pCOD concentration of the influent increased from 0.5 g COD/L to 1.3 g COD/L, by adding an untreated slaughterhouse wastewater source to the influent. Sludge concentration, waste sludge production and COD and nutrient removal performance were monitored. Furthermore, to investigate how the sludge acclimatises to a higher influent particulate content, lipase and protease hydrolytic activities were studied, as well as the microbial community composition of the sludge. The composition of the granule bed and nutrient removal efficiency did not change considerably by the increased pCOD. Interestingly, the biomass-specific hydrolytic activities of the sludge did not increase during the test period either. However, already during normal operation the aerobic granules and flocs exhibited a hydrolytic potential that ex-ceeded the influent concentrations of proteins and lipids. Microbial community analysis also revealed a high proportion of putative hydrolysing and fermenting organisms in the sludge, both during normal operation and during the test period. The results of this study highlight the robust-ness of the full-scale AGS process, which can bear a substantial increase in the influent pCOD concentration during an extended period.Sanitary EngineeringWater ManagementBT/Environmental Biotechnolog
Understanding the impact of a pressure sewer on municipal wastewater: a pre-treatment for AGS plants
No full textThe performance of AGS reactors treating municipal wastewater can be optimised by converting influent particulate matter into readily available substrate. This can be done via anaerobic hydrolysis and fermentation of the influent. Anaerobic processes taking place in pressure sewers are not fully understood but show the potential to act as a pre-treatment for the wastewater reaching AGS reactors. Moreover, the contribution of the influent to the hydrolytic activity of the reactor is unknown. This research evaluated the impact of a pressure sewer on wastewater characteristics, as a possible pre-treatment of sewage before reaching the treatment plant. The variations of sewage in terms of physicochemical composition and microbial activity were monitored in a full-scale pressure sewer, focusing on the hydrolysis and fermentation of organic matter for further treatment in AGS reactors. Moreover, the contribution of the influent to the enzymatic activity of a full-scale AGS reactor was assessed.Inaccuracies deriving from sampling on a full-scale pressure sewer might have affected the results. However, statistical analyses helped to derive trends from the collected data. The pressure sewer primarily affected the degree of fermentation of the wastewater and the concentration of suspended solids. It is hypothesised that such variations could benefit the performance of AGS reactors. Although the biodegradability and enzymatic activity of the wastewater did not improve significantly, anaerobic conveyance seemed more appropriate than aerobic transport for AGS reactors. However, the influent did not seem to have a large contribution to the total reactor activity, due to the high concentration of granular biomass
