A preliminary insight into metal cycling within the urban sewer was obtained by determining both ... more A preliminary insight into metal cycling within the urban sewer was obtained by determining both the heavy metal concentrations (Cu, Zn, Pb, Cd, Ni, Cr) in sewage and sediments, and the nature of metal-bearing particles using TEM-EDX, SEM-EDX and XRD. Particles collected from tap water, sump-pit deposits, and washbasin siphons, were also examined to trace back the origin of some mineral species. The results show that the total levels in Cu, Pb, Zn, Ni, and Cr in sewage are similar to that reported in the literature, thus suggesting that a time-averaged heavy metal fingerprint of domestic sewage can be defined for most developed cities at the urban catchment scale. Household activities represent the main source of Zn and Pb, the water supply system is a significant source of Cu, and in our case, groundwater infiltration in the sewer system provides a supplementary source of Ni and Cd. Concentrations in heavy metals were much higher in sewer sediments than in sewage suspended solids, the enrichment being due to the preferential settling of metal-bearing particles of high density and/or the precipitation of neoformed mineral phases. TEM and SEM-EDX analyses indicated that suspended solids, biofilms, and sewer sediments contained similar heavy metal-bearing particles including alloys and metal fragments, oxidized metals and sulfides. Copper fragments, metal carbonates (Cu, Zn, Pb), and oxidized soldering materials are released from the erosion of domestic plumbing, whereas the precipitation of sulfides and the sulfurization of metal phases occur primarily within the household connections to the sewer trunk. Close examination of sulfide phases also revealed in most cases a complex growth history recorded in the texture of particles, which likely reflects changes in physicochemical conditions associated with successive resuspension and settling of particles within the sewer system.
Proceedings of the Water Environment Federation, 2009
ABSTRACT This study suggests a new way of characterizing extracellular polymeric substances (EPS)... more ABSTRACT This study suggests a new way of characterizing extracellular polymeric substances (EPS) using size exclusion chromatography (SEC) coupled with infrared microscopy (μFTIR) before and after enzyme hydrolysis. Previous research has established advantages to the enzymatic treatment of biosolids, through degradation of EPS. The chromatographic fingerprints of EPS were significantly altered using three different enzyme types. Application of either a commercial enzyme mix or an amylase/cellulase combination led to disappearance of molecular weight fractions above 0.5kDa. However protease application changed the chromatographic profile unexpectedly, forming very high molecular weight fractions (>4000 kDa). μFTIR results indicated that these large molecules result from mineral phase association with lower molecular weight organic molecules. EPS characterization confirmed that specific enzymes degraded their target compounds. Although the effect of enzyme treatment was observable using conventional sludge characterization methods, the SEC-μFTIR method provided more specific information on chemical mechanisms responsible for enzyme effects.
A preliminary insight into metal cycling within the urban sewer was obtained by determining both ... more A preliminary insight into metal cycling within the urban sewer was obtained by determining both the heavy metal concentrations (Cu, Zn, Pb, Cd, Ni, Cr) in sewage and sediments, and the nature of metal-bearing particles using TEM-EDX, SEM-EDX and XRD. Particles collected from tap water, sump-pit deposits, and washbasin siphons, were also examined to trace back the origin of some mineral species. The results show that the total levels in Cu, Pb, Zn, Ni, and Cr in sewage are similar to that reported in the literature, thus suggesting that a time-averaged heavy metal fingerprint of domestic sewage can be defined for most developed cities at the urban catchment scale. Household activities represent the main source of Zn and Pb, the water supply system is a significant source of Cu, and in our case, groundwater infiltration in the sewer system provides a supplementary source of Ni and Cd. Concentrations in heavy metals were much higher in sewer sediments than in sewage suspended solids, the enrichment being due to the preferential settling of metal-bearing particles of high density and/or the precipitation of neoformed mineral phases. TEM and SEM-EDX analyses indicated that suspended solids, biofilms, and sewer sediments contained similar heavy metal-bearing particles including alloys and metal fragments, oxidized metals and sulfides. Copper fragments, metal carbonates (Cu, Zn, Pb), and oxidized soldering materials are released from the erosion of domestic plumbing, whereas the precipitation of sulfides and the sulfurization of metal phases occur primarily within the household connections to the sewer trunk. Close examination of sulfide phases also revealed in most cases a complex growth history recorded in the texture of particles, which likely reflects changes in physicochemical conditions associated with successive resuspension and settling of particles within the sewer system.
Proceedings of the Water Environment Federation, 2009
ABSTRACT This study suggests a new way of characterizing extracellular polymeric substances (EPS)... more ABSTRACT This study suggests a new way of characterizing extracellular polymeric substances (EPS) using size exclusion chromatography (SEC) coupled with infrared microscopy (μFTIR) before and after enzyme hydrolysis. Previous research has established advantages to the enzymatic treatment of biosolids, through degradation of EPS. The chromatographic fingerprints of EPS were significantly altered using three different enzyme types. Application of either a commercial enzyme mix or an amylase/cellulase combination led to disappearance of molecular weight fractions above 0.5kDa. However protease application changed the chromatographic profile unexpectedly, forming very high molecular weight fractions (>4000 kDa). μFTIR results indicated that these large molecules result from mineral phase association with lower molecular weight organic molecules. EPS characterization confirmed that specific enzymes degraded their target compounds. Although the effect of enzyme treatment was observable using conventional sludge characterization methods, the SEC-μFTIR method provided more specific information on chemical mechanisms responsible for enzyme effects.
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Papers by Bruno Lartiges