benoit lefevre

Recently microporous and mesoporous materials were found to be particularly suitable for a new type of applications in the mechanical field. This paper reports experimental features about the dissipative forced intrusion of water in highly hydrophobic mesoporous materials: this phenomenon can be used to develop a new type of dampers and/or actuators. Silica-based materials behavior was investigated. Among them, MCM-41 exhibit original and interesting properties towards the potential developments of dampers and appear to be of great interest for the comprehension of energy dissipation mechanisms.

ABSTRACT The present study was conducted to track dissolved organic carbon (DOC) through the different stages of a drinking water treatment plant that includes a conventional treatment CT (coagulation/flocculation, sedimentation and sand filtration) and two parallel advanced treatments consisting of ozonation plus activated carbon filtration (AT1) and ultrafiltration (UF) and reverse osmosis (RO) (AT2), respectively. Fractionation of DOC was performed by high-performance size exclusion chromatography (HPSEC), whereby DOC fractions are separated according to their molecular weight. Results demonstrated that the dominant fraction in the raw feed water was constituted by humic substances (HS) (28–54%), followed by the fractions building blocks (BB) and low molecular weight neutrals (LMWN) (20–25%). The fraction with highest molecular weight constituted by biopolymers (BP) was found in the range 4–8%. These fractions exhibited different treatability along the treatment units. High molecular weight compounds (fractions BP and HS) were more effectively removed by CT than low molecular weight compounds (fractions BB and LMWN), which were better removed by AT1 and AT2 than CT. Differences in DOC fractions removal were also observed between AT1 and AT2. The passage through AT1 led to a decrease of BP and HS during ozonation, in opposition to BB and LMWN, which were removed to a greater extent during GAC filtration. In AT2, BP was removed by UF and RO, while HS, BB and LMWN were marginally removed by UF but largely by RO. Backwash stream water from UF membranes was also analysed to provide insight into the fouling reversibility of DOC fractions.

The removal of natural organic matter (NOM) and, more particularly, its individual fractions by two different GACs was investigated in full-scale filters in a drinking water treatment plant (DWTP). Fractionation of NOM was performed by high performance size exclusion chromatography (HPSEC) into biopolymers, humic substances, building blocks and low molecular weight organics. The sorption capacity of GAC in terms of iodine number (IN) and apparent surface area (SBET), as well as the filling of narrow- and super-microporosity were monitored over the 1-year operation of the filters. Both GACs demonstrated to be effective at removing NOM over a wide range of fractions, especially the low and intermediate molecular weight fractions. TOC removal initially occurred via adsorption, and smaller (lighter) fractions were more removed as they could enter and diffuse more easily through the pores of the adsorbent. As time progressed, biodegradation also played a role in the TOC removal, and lighter fractions continued to be preferentially removed due to their higher biodegradability. The gained knowledge would assist drinking water utilities in selecting a proper GAC for the removal of NOM from water and, therefore, complying more successfully the latest water regulations.

Under normal operation conditions, granular activated carbon (GAC) employed in drinking water treatment plants (DWTPs) for natural organic matter (NOM) removal can be colonised by microorganisms which can eventually establish active biofilms. The formation of such biofilms can contribute to NOM removal by biodegradation, but also in clogging phenomena that can make necessary more frequent backwashes. Biofilm occurrence and evolution under full-scale-like conditions (i.e. including periodic backwashing) are still uncertain, and GAC filtration is usually operated with a strong empirical component. The aim of the present study was to assess the formation and growth, if any, of biofilm in a periodically backwashed GAC filter. For this purpose, an on-site pilot plant was assembled and operated to closely mimic the GAC filters installed in the DWTP in Sant Joan Despí (Barcelona, Spain). The study comprised a monitoring of both water and GAC cores withdrawn at various depths and times throughout 1 year operation. The biomass parameters assessed were total cell count by confocal laser scanning microscopy (CLSM), DNA and adenosine triphosphate (ATP). Visual examination of GAC particles was also conducted by high-resolution field emission scanning electron microscopy (FESEM). Additionally, water quality and GAC surface properties were monitored. Results provided insight into the extent and spatial distribution of biofilm within the GAC bed. To sum up, it was found that backwashing could physically detach bacteria from the biofilm, which could however build back up to its pre-backwashing concentration before next backwashing cycle.

... a, Julien Iapichellaa, Benoît Lefèvrea, Christine Biolleya, Jean-Pierre Bellatb, François Fajulaa and Anne Galarneau*a. a Institut Charles Gerhardt Montpellier-UMR 5253 CNRS/ENSCM/ Matériaux Avancés pour la Catalyse et la Santé, Ecole Nationale Supérieure de Chimie de ...

The wetting state of a solid/fluids system depends on the relative value of the surface tensions acting at the different interfaces. Whereas the free energy of a given solid/fluid interface is not directly measurable, the internal energy part can be relatively easily determined in the case of powders by microcalorimetry. In this paper, the various energy data that can thus