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International audience; The control of biofouling is required to improve membranes performances for water filtration. In this context, developing bioinspired approaches to modify membranes and give them antifouling properties is an interesting alternative. In this study, we elaborated new anti-biofouling membranes by coating them with vanillin, a natural bioactive molecule acting as a Quorum Sensing Inhibitor (QSI). First, the adsorption of vanillin by filtration was optimized to obtain homogeneous surface modifications. The modified membranes were then characterized in terms of physical-chemical properties: the results showed that they were more hydrophobic and exhibited a 14% decrease in pure water flux. Then, their anti-fouling properties were evaluated using complementary multiscale characterization methodologies; AFM single-cell experiments showed that vanillin adsorption had an effect on both the probability of bacterial cells to adhere to the surface, and on the force of adhesion. Direct EFM and SEM observation and adhesion assays further confirmed the effect of vanillin-modified membranes at the population-scale which showed a decrease in the bacterial coverage rate up to 50%. Altogether, it confirms the multifunctionality of vanillin-coated membranes against biofouling: reduction of bacterial initial adhesion by changing the membranes surface properties and reduction of biofilm formation by quorum sensing inhibition

International audience; While membrane bioreactors (MBR) have been broadly applied to wastewater treatment, membrane ageing studies have focused mainly on: (i) understanding the chemical action of sodium hypochlorite or (ii) monitoring ageing in direct filtration facilities (drinking water, groundwater, etc.). Thus, a comprehensive investigation under full-scale MBR operating conditions is still required. In the present study, polyvinylidene difluoride (PVDF) hollow fibers were sampled from a full-scale MBR in northern Paris during 7 years of operation. In addition, pristine membranes were aged at bench scale by single soaking in hypochlorite solution at a concentration and pH similar to MBR cleaning protocols. Both bench-scale- and full-scale-aged hollow fibers were characterized using similar analytical methods to assess the contributions of chemical action and operating conditions to the ageing process. At bench scale, membranes experienced no changes in mechanical resistance, but intrinsic permeability (i) first increased as a result of the hydrophilic agent oxidation, i.e., polyvinyl pyrrolidone (PVP), increasing porosity with the appearance of small pores (diameter 20 nm), and (ii) then the structure seemed to collapse and permeability decreased as a result. By contrast, membranes aged at full scale experienced a 46% decline in maximum tensile strength probably due to mechanical stress induced by aeration conditions in MBR. Besides, permeability increased for the whole period as a result of a more pronounced oxidation/dislodgement of PVP molecules leading to higher porosity and the appearance of bigger pores (diameter 40 nm). These changes favored irreversible fouling in contrast to bench-scale ageing. Therefore, bench-scale ageing is not completely representative of full-scale ageing and membrane autopsies must be preferred to this end. However, permeability and PVP content measurements may be applied after cleaning as in situ nondestructive tools in full-scale MBR to monitor membrane ageing. Plant operators should be aware that a continuous increase in intrinsic permeability may favor irreversible fouling accumulation demanding more frequent chemical cleanings.

An MBR treating filtrate from sludge ultra-dewatering (FSD) was studied to evaluate the real applicability to concentrated effluents. The MBR operation is comparable to conventional wastewater MBRs in terms of F/M and nitrogen to sludge ratios, SRT and MLSS in biological tanks. On the contrary, the volume treated is lower with a comparable pollution load, the effluent being concentrated in nitrogen and carbon. Very high and stable ammonium (97.7 �� 2.4%), total phosphorus (81.8 �� 11.9%), chemical (89.5 �� 2.3%) and biochemical oxygen demands (98.8 �� 0.7%) removals are observed despite a significant modification of the FSD composition. The MBR removal performances are whether comparable or greater than those reported at full-scale for Sharon or Anammox processes. The evolution of membranes properties, in particular, the decrease of permeability induced by the irreversible fouling, leads to a decrease of the daily permeate volume produced and an increase of the chemical cleaning need. The membrane lifespan was determined to be 5.5 years based on both the permeability loss and TSS in permeate. The permeability is directly correlated to the cumulated filtered flux of colloidal matter and a total of 350 kg O2/m2 of the membrane (COD in the supernatant) is needed to reach a permeability below 100 LMH/bar. The specific energy consumption is comparable to other wastewater MBRs in kWh/kgCOD removed but the intensive chemical cleanings need to be 2.5���4.5 times more frequent. Overall, it can be concluded that MBR is adapted to treat FSD efficiently.

International audience; In this comprehensive study, the interaction of human serum albumin (HSA) with poly(acrylic acid) (PAA) was explored using small angle X-ray scattering (SAXS) combined with chromatography. The results revealed the formation of a complex between HSA macromolecules and PAA chains but solely under some specific conditions of the ionic strength and pH of the medium. In fact, this binding was found to take place only at pH close to 5 and at low ionic strength (0.15 M). Otherwise, for a higher pH and a salt concentration of 0.75 M the HSA–PAA complex tends to dissociate completely showing the reversibility of the complexation. The assessment of the influence of the HSA/PAA molar ratio on the radius of gyration of the complex suggests that 4 HSA molecules could bind to each 100 kDa PAA chain. In addition, the Porod volume evaluation for the same range of the HSA/PAA ratio confirms this assumption. Finally, an all-atom SAXS modelling study using the BUNCH program was conducted to find a compatible model that fits the HSA–PAA complex scattering data. This model allows us to portray the HSA/PAA complex as a pearl-necklace assembly with 4 HSA molecules on the 100 kDa PAA chain.

International audience; Hemodialysis is an important therapy for treating patients with End Stage Renal Disease (ESRD). These patients visit the hospital 3 times a week and each time their blood is cleansed during 4-hour dialysis sessions using a hollow fiber membrane module; also called artificial kidney. This device mainly achieves removal of small water-soluble toxins and a limited number of middle molecules. To improve the clearance of toxins, especially middle molecules and protein bound toxins, longer treatment via nocturnal dialysis and/or the application of portable/wearable artificial kidney is required. Such therapies require application of membranes with very low fouling and very good blood compatibility. Current membranes often contain hydrophilic additives which could elute during sterilization processes and/or during long-term filtration. In this study, we propose a simple method for developing low fouling blood compatible membranes by blending of polyethersulfone (PES), a material already used for fabrication of dialysis membranes, with small amounts of SlipSkin™ (SS), a blood compatible random copolymer of hydrophilic N-vinylpyrrolidone (NVP) and hydrophobic N-butylmethacrylate (BMA). Our results show that membranes with 2 wt% of SS have high fouling resistance to proteins and middle-size molecules and very good blood compatibility, making these membranes promising for application in dialysis therapy.

International audience; Sub-stoichiometric titanium oxide (TiOx) reactive electrochemical membrane (REM) were integrated for the first time as anode in the electro-Fenton (EF) process. Hydroxyl radicals (•OH) were produced both in the retentate from Fenton's reaction and at the REM from anodic oxidation (AO). Optimal mass transport conditions were implemented because of convection-enhanced mass transport of (i) organic pollutants towards the REM surface during filtration and (ii) dissolved 02 towards cathode active sites owing to the use of a 3D carbon felt cathode in flow-through configuration for H202 generation. The efficiency of the REM/EF process was much higher than EF or REM used as standalone processes. For instance, taking paracetamol as target pollutant, (67 ± 2)% removal of 55 mg L - i of initial TOC was achieved with a high mineralization current efficiency (MCE) of ( 43 ± 1)%. By comparison, standalone REM and EF processes achieved only 47% (MCE = 30%) and 31 % (MCE = 20%) of TOC removal, respectively. By monitoring TOC removal both in retentate and permeate, the effect of homogeneous oxidation in the bulk retentate and heterogeneous oxidation at the REM could be observed separately. It was thus highlighted that the efficiency of AO might be affected by the presence of • OH and Fe2 + in the bulk. It was also emphasized a synergistic effect related to the formation of carboxylic acids in the bulk retentate that are more easily mineralized at the REM where both • OH-mediated oxidation and direct electron transfer occur.

International audience; Membrane fouling by proteins is an important problem in hemodialysis or hemofiltration (artificial kidney). The mechanisms leading to fouling are still not fully understood and then predictable. In this paper we describe a microfluidic chip fitted with a filtration membrane which allows the real time in situ fluorescent analysis of labelled proteins and the measurement of the membrane permeability. The apparent kinetics rates of adsorption derived from the changes in fluorescence signal are combined with permeability measurements. This allows to discriminate two clearly distinct fouling mechanism by Bovine Serum Albumin (BSA) and α-lactalbumin (LALBA). The fouling kinetics of BSA is very rapid, independent of the flow conditions and can then be viewed as a protein monolayer adsorption controlled by protein-membrane interactions. In contrast, the fouling kinetics by LALBA is slower and very sensitive to flow conditions. We also describe a fluorescence quenching induced by protein aggregation and compression at high permeation rate. The fouling mechanism can then be viewed as a flow induced aggregation followed by a deposition of aggregates on the membrane. The complexity of sorption mechanisms on membrane during cross-flow filtration can be unraveled with this experimental set-up.

International audience; This paper investigates the behavior of conductive Ti4O7 ceramic anode in different electrolytes during the degradation of the anti-inflammatory drug paracetamol (PCM) by advanced electrochemical oxidation processes mainly anodic oxidation with generation of H2O2 (AO-H2O2) and electro-Fenton (EF). Regardless of the medium, better degradation and mineralization efficiency was always observed with EF compared to AO-H2O2. The degradation of PCM was carried out by hydroxyl radical (OH) produced on the anode surface from water oxidation and mediated oxidation in the solution from oxidant species generated at the anode such as sulfate radicals and active chlorine species depending on the supporting electrolytes used, as well as OH generated homogeneously in the solution by electrochemically assisted Fenton’s reaction. Faster degradation was observed in Cl− compared to other media, but the solution was poorly mineralized. Highest total organic (TOC) removal efficiency with excellent degradation rate was attained in SO42− with either process, thus remain the best medium for advanced electrochemical wastewater treatment. Comparative studies with dimensional stable anode (DSA) and boron-doped diamond anode (BDD) showed similar trend of degradation and TOC removal efficiency with DSA anode achieving low mineralization power compared to Ti4O7 anode, whereas BDD showed slightly better efficiency than Ti4O7 in all electrolytes studied. The analysis of concentration of generated active chlorine species, especially ClO−, during AO-H2O2 decreased in the order: DSA > Ti4O7 > BDD. Therefore, the Ti4O7 electrode was found to be a promising anode material for an efficient treatment of PCM in SO42−, NO3− and ClO4− media but less effective in Cl− medium.

International audience; In this work, we present an integrated dynamic cross-flow electro-Fenton (DCF-EF) system for the treatment of the pharmaceutical, acetaminophen (paracetamol), in aqueous medium. A carbonaceous electrocatalytic membrane was used as cathode, allowing the continuous production of H2O2 during EF in dynamic filtration mode. The transmembrane pressure (TMP) and current were the two driving forces of the system, whose influence strongly affected the global efficiency. It was found that H2O2 production from the electrochemical reduction of dissolved O2 was favoured at higher TMP values as a consequence of an increase of the O2 partial pressure, and higher H2O2 amounts entailed an increase in the efficiency of the process. Current also had a positive effect on H2O2 production and acetaminophen degradation and mineralization efficiencies up to an optimal value. Complete degradation of the drug and 44% mineralization were achieved under optimal conditions (2.0 bar and 100 mA). On the other hand, the results pointed out that the use of a Ti4O7 rod as counter electrode (anode) had an important contribution to the mineralization of the acetaminophen’s solutions owing to the formation of hydroxyl radicals (OH) on its surface, which highlighted the oxidative power of this anode material. The oxidation mechanisms involved during the process were assessed by electrochemical measurements with both electrodes (carbon membrane and Ti4O7 rod), and a degradation pathway for paracetamol oxidation was proposed based on the identification of the main aromatic and aliphatic degradation by-products. This DCF-EF process is presented as a potential alternative for water treatment and reuse in which the integration of membrane and electrochemical technologies brings together separation science and advanced oxidation.

The following study aims to analyze and to optimize the technical performances of a desalination plant, based in khenifra city in the central region of Morocco. Reverse osmosis system is used as a desalination process in order to treat the water of the river Oum ErRiaa. The river water quality is variable depending on the season, and its chloride content does not exceed the value of 866 mg/l, which represents the design reference of the reverse osmosis plant. Faced with the decrease of the salinity of this water, the operator was forced to reduce to the third, the operation of this plant, which is composed of three reverse osmosis units functioning every two days alternatively. Moreover, the monitoring of the technical indicators of the plant, revealed the absence of membranes fouling. This is due to frequent membranes rinsing during the units stops. As a result, the plant performances as defined during the design cannot be verified. It was then important to identify other approaches to analyze the performances of this station. The questioning of desalination plant design, led us to make simulations with two different softwares, on a new basis, which is the current quality of the river water, characterized by a conductivity value of only 1230 μs/cm instead of 3013 μS/cm, which was the one taken to design the plant. The results obtained indicated the possibility of reaching a better conversion rate of around 88% for low mineralized waters compared to 78% for the quality of water taken into account for the desalination plant design.

International audience

International audience; Fenton oxidation is one of the promising advanced oxidation processes for the efficient elimination of pharmaceuticals from wastewater. The strong oxidation ability of this process is attributed to the generation of highly reactive hydroxyl radicals (radical dotOH) in the solution. In the present study, heterogeneous micro-sized zeolite catalysts that contain iron have been used in the Fenton-like process. This process enables operation in a wide pH range and facilitates the reuse of catalysts. Indeed, the coupling of the heterogeneous Fenton reaction with membrane filtration will ensure catalyst retention in the effluent compartment during the continuous water treatment. This study then investigated the fouling control strategies and membrane long-term stability in the heterogeneous Fenton reactor. During the filtration of the zeolite catalyst suspension, the critical flux for irreversible fouling was determined. One of the strategies to control membrane fouling can then be to choose an operating flux below this critical flux. In the case where a flux value above the critical flux is chosen, the results demonstrated total efficiency of hydrodynamic backwashing to eliminate hydraulically reversible fouling. Concerning the question of polymeric membrane long-term stability, it has been demonstrated that due to contact with the Fenton medium, membrane material undergoes oxidation and polymeric chain scissions. This latter is strongly linked to the decline in the mechanical resistance of membranes. In the tested conditions, despite the degradation to membrane material, the critical flux for irreversible fouling remained unchanged on aged membranes.

International audience; The oxidation ability of two prominent eco‐friendly electrochemical advanced oxidation processes (EAOPs), namely anodic oxidation with H2O2 generation (AO‐H2O2) and electro‐Fenton (EF) for complete abatement of acidic solution of 4‐aminophenazone (4‐APZ) has been investigated using conductive boron‐doped diamond (BDD) and sub‐stoichiometric titanium oxide (Ti4O7) anodes and carbon‐felt cathode. The higher performance of EF compared to AO‐H2O2 with either anode was demonstrated. In all trials, 4‐APZ was completely destroyed, following pseudo first‐order kinetics with the rate constant values increasing with applied current and higher values attained with BDD compared to Ti4O7 anode at similar conditions. The absolute rate constant for the reaction between 4‐APZ and hydroxyl radicals was found to be 3.9±0.2×109 L mol−1 s−1. Complete mineralization could be attained with BDD anode, whereas Ti4O7 anode only showed excellent mineralization up to 94 % TOC removal. Therefore, Ti4O7 anode can constitutes a promising anode material thanks to its lower manufacturing cost. Inorganic ions like NO3− and HCO3− at concentration up to 25 mM has no effect on mineralization efficiency during AO‐H2O2, but the presence of Cl− even at lower concentration of 10 mM significantly reduced the TOC removal efficiency. The toxicity of the solution sharply increased at initial stage of treatment, corresponding to the formation of cyclic by‐products but their conversion to carboxylic acids due to longer treatment time involved a sharp toxicity decrease, thus ensuring overall detoxification.

International audience; Treatment combining membrane bioreactors (MBR) and nanofiltration (NF) is becoming an emerging wastewater treatment strategy. The combined process is capable of producing high quality water potentially reusable; however, diverse compositions of MBR effluents induce several types and degrees of NF membrane fouling that impacts process productivity. Moreover, since MBR effluent composition for one type of wastewater source is variable depending on the MBR efficiency at different periods, downstream NF membrane fouling types and degrees may consequently change over time. In that context, the present paper aims at developing effective fouling control strategies of NF membrane in the case of the filtration of MBR effluents taken from a MBR system installed in a French hospital. These effluents were filtrated under various transmembrane pressures, and stable fluxes during these filtrations were determined. Several types and degrees of fouling mechanisms were then identified through surface morphology observation and the analysis of chemical compositions of fouled membranes. The diverse flux behaviour was further associated with the fouling mechanisms and foulant compositions. Based on the study of these mechanisms, the quantitative link between stable fluxes and calcium phosphate concentrations in MBR effluents has been established.

International audience; Reactive Electrochemical Membrane (REM) prepared from carbothermal reduction of TiO2 is used for the mineralization of biorefractory pollutants during filtration operation. The mixture of Ti4O7 and Ti5O9 Magnéli phases ensures the high reactivity of the membrane for organic compound oxidation through •OH mediated oxidation and direct electron transfer. In cross-flow filtration mode, convection-enhanced mass transport of pollutants can be achieved from the high membrane permeability (3300 LMH bar-1). Mineralization efficiency of oxalic acid, paracetamol and phenol was assessed as regards to current density, transmembrane pressure and feed concentration. Unprecedented high removal rates of total organic carbon and mineralization current efficiency were achieved after a single passage through the REM, e.g. 47 g m-2 h-1 - 72% and 6.7 g m-2 h-1 - 47% for oxalic acid and paracetamol, respectively, at 15 mA cm-2. However, two mechanisms have to be considered for optimization of the process. When the TOC flux is too high with respect to the current density, aromatic compounds polymerize in the REM layer where only direct electron transfer occurs. This phenomenon decreases the oxidation efficiency and/or increases REM fouling. Besides, O2 bubbles sweeping at high permeate flux promotes O2 gas generation, with adverse effect on oxidation efficiency.

International audience; This paper deals with an experimental and modelling study on the electrochemical oxidation of refractory pharmaceuticals using a boron-doped diamond (BDD) anode. Different parameters have been investigated, such as the role of salts (sulfates), the presence of other organics, and the influence of applied current intensity. Ciprofloxacin (CIP), Sulfamethoxazole (SMX) and Salbutamol (SALBU) were used for models of pharmaceuticals, and urea as a model for a common organic. The complete removal of pharmaceuticals was observed in all electrolyses under galvanostatic conditions. The presence of common organic waste or other pharmaceutical has no significant impact on the degradation of the CIP target molecule. A mathematical model predicting the temporal concentration variation of organics with electroxidation time has been developed. In this model, different oxidation pathways have been considered: the transfer of electrons (direct oxidation) or of oxygen atoms via the reaction with either hydroxyl radicals or/and with strong electrogenerated oxidants. Excellent correlation with experiments is obtained under all experimental conditions.

International audience; Electro-oxidation processes are promising options for the removal of organic pollutants from water. The major appeal of these technologies is the possibility to avoid the addition of chemical reagents. However, a major limitation is associated with slow mass transfer that reduces the efficiency and hinders the potential for large-scale application of these technologies. Therefore, improving the reactor configuration is currently one of the most important areas for research and development. The recent development of a reactive electrochemical membrane (REM) as a flow-through electrode has proven to be a breakthrough innovation, leading to both high electrochemically active surface area and convection-enhanced mass transport of pollutants. This review summarizes the current state of the art on REMs for the electro-oxidation of organic compounds by anodic oxidation. Specific focuses on the electroactive surface area, mass transport, reactivity, fouling and stability of REMs are included. Recent advances in the development of sub-stoichiometric titanium oxide REMs as anodes have been made. These electrodes possess high electrical conductivity, reactivity (generation of •OH), chemical/electrochemical stability, and suitable pore structure that allows for efficient mass transport. Further development of REMs strongly relies on the development of materials with suitable physico-chemical characteristics that produce electrodes with efficient mass transport properties, high electroactive surface area, high reactivity and long-term stability.

The present study aims at shedding light on the transport mechanisms involved in a functionalized membrane designed for improving hemodialysis. This membrane is prepared by embedding absorptive micro particles within its porous structure. To understand the transport mechanism through the membrane and make suggestions for its optimization, a mathematical model coupling convection, diffusion and adsorption is developed and validated by comparison of experimental and theoretical results. In fact, the model provides a description of the concentration profile from the donor (feed) compartment across the several layers with different properties to the acceptor (dialysate) compartment. In addition, the model allows to predict the influence of various parameters such as molecule diffusivity, membrane thickness, presence of convection, content of adsorptive particles on the flux intensification across the membrane. Comparison with experimental measurements demonstrates that the model is able to describe the transmembrane mass flux variation over time as a function of hydrodynamic conditions and membrane/module geometric parameters. The model also illustrates how the proposed double-layer membrane concept offers significant benefits in terms of toxin removal in comparison to conventional dialysis. As so, the main achievement of the developed model is that it may serve as tool for the further improvement of functionalized membrane in terms of toxin removal and optimization of process conditions.

Reactive Electrochemical Membrane (REM) prepared from carbothermal reduction of TiO

Les membranes de filtration, connues depuis le debut du XXeme siecle, connaissent un essor en traitement de l’eau depuis les annees 1980.Par le large eventail de seuils de coupure qu’elles offrent, les operations de microfiltration, d'ultrafiltration, de nanofiltration et d'osmose Inverse, se placent comme des technologies de choix dans la palette du traitement des eaux. Cet article propose un apercu des potentialites de ces technologies, illustrees de quelques exemples dans les domaines du dessalement de l’eau de mer, de la production d’eau destinee a la consommation humaine a partir des eaux douces et du traitement des eaux usees en vue de leur reutilisation.

International audience; The optimization of permeate flux is a particularly interesting strategy to control fouling and, as a consequence, enhance productivity for nanofiltration (NF) processes. Critical flux, threshold flux and limiting flux theories represent significant advance in this strategy. The aim of this study was to apply these concepts to achieve fouling control during NF of a real complex matrix: hospital wastewater after Membrane BioReactor treatment (MBR permeate). At low pressure (3 bar) no flux decline was observed, revealing no fouling conditions. By applying a range of transmembrane pressure and using the square-wave method, the critical flux for irreversibility (70 L h−1m−2) and the corresponding critical pressure (3.4 bar) were then determined for the NF process in this complex matrix. Above these critical conditions, irreversible fouling started to occur. The threshold pressure and related flux (transition points between low and high fouling regions) were then searched by critical flux data conversion. Our results suggest, even if an exact value for the threshold pressure could not be determined, that it could be located in the range 3.4–10 bar. Operating in this pressure range should lead to acceptable fouling rate and flux decline. During filtrations conducted above the critical flux in the MBR effluent, two stable fluxes behaviours were observed indicating that different fouling stages occur: pseudo stable flux was 67 L h−1m−2 at 5 bar, whereas 33 L h−1m−2 at 10–35 bar. It can be then confirmed that a limiting flux occurred in this system, the value of which 33 L h−1m−2 is rather lower than that of the critical flux. This flux behaviour was proved to be related to a severe fouling in the pressure range 10–35 bar due to a combined effect of colloidal silica and organics fouling and calcium phosphate scaling. The early fouling stage at 5 bar was expected to be solely related to colloidal silica and organics accumulation. To characterise this change in fouling behaviour, a method allowing the estimation of the permeability before scaling was proposed. The combination of the permeability before scaling and critical flux has enabled a NF working diagram to be drawn from which the fouling stage for a given transmembrane pressure and corresponding permeate flux was able to be determined.

International audience; Living particles such as bacteria are able to transfer through membrane pores that are smaller than cell size due to the specific stiffness of this type of microorganism. This phenomenon can lead to a significant loss of selectivity in the filtration process, which is a major cause of concern in the sterilizing filtration step. This study investigates the retention of three bacteria strains: Escherichia coli CIP 54124, Pseudomonas aeruginosa CIP 103467 and Staphylococcus aureus CIP 53154 by model porous membranes for various operating conditions (transmembrane pressure, feed concentration and the physicochemical composition of filtered media with antibacterial agent added at sublethal concentration). The first part of this study is dedicated to defining the size and the nanomechanical properties of the envelope of the studied bacteria by microscopic techniques (Transmission electron microscopy & Atomic-force microscopy), in order to then explore the role of these quantifiable characteristics on the cell transfer through the pores by deformation mechanisms. Our results lead to the development of a numerical model to connect the observed retention efficiency of the filtration experiment and the microscopic information about individual particles.

International audience; Refractory pharmaceuticals remain in biologically treated wastewater and are continuously discharged into aquatic systems due to their limited biodegradability. Electrochemical oxidation is promising for the treatment of such refractory compounds, in particular using a boron doped diamond (BDD) anode. This study investigates the role of salts, such as sulfates and chlorides in the electrochemical treatment of wastewater. The presence of sulfates accelerated the removal of ciprofloxacin and sulfamethoxazole, but had no effect on the oxidation of salbutamol. This comparison highlights the selectivity of the reaction between organics and sulfate radicals. The addition of chlorides into the solution led to a remarkably-faster degradation of ciprofloxacin. However, incomplete mineralization was observed at high current densities due to the significant formation of halogenated organic compounds (AOX). The formation of refractory and toxic compounds such as ClO4− and AOX can be limited under the control of (i) applied current intensity and (ii) duration of electrolysis. Electrochemical oxidation of concentrated biologically-treated hospital wastewater investigated the excellent removal of biorefractory pharmaceuticals and confirmed the acceleration effect of salts on pharmaceutical degradation.

International audience; The purpose of this work is to apply FTIR mapping to the analysis of the coating and fouling behaviour of PVDF membranes coated with two different types of PS-PEGMA copolymers – diblock and random. The coating conditions involve the variation of coating solution concentration and of coating time. We have carried out adsorption experiments with BSA as the foulant, and also filtration experiments. The analysis of the results is mainly performed by image analysis of the mapped surfaces with two approaches: taking the average grey value/peak height of the whole surface for the coating and foulant signals, and by defining coating/fouling levels as an initial approach to analyse heterogeneity. Our results show that there is an heterogeneous distribution of the coating and fouling layers on the membrane surface at a millimetre scale. Moreover, the diblock copolymer has a slightly better anti-adsorption performance than the random one. Coating conditions should be carefully chosen and conclusions regarding the anti-fouling properties of the membranes should be drawn by taking into account both adsorption and filtration tests. All in all, FTIR mapping is a technique that should be taken into account for the study of fouling phenomena.

International audience; Drinking water production plants using membrane filtration processes report membrane failure issues. According to the literature, membrane degradation is often induced by exposure to sodium hypochlorite, an oxidant widely used during in-place cleanings. The present study focused on quantifying the effect of membrane exposure mode to hypochlorite on properties modifications of a PES/PVP ultrafiltration membrane widely used for drinking water production. For this purpose effects of sodium hypochlorite concentration, contact duration and exposure mode (static or dynamic) were investigated. The pH of the hypochlorite solution was set to 8 as it was demonstrated in numerous previous works that the pH range 7–8 leads to the most severe modification in the membrane characteristics. Membrane degradation was monitored at molecular scale by attenuated total reflectance infrared spectroscopy and at macroscopic scale by pure water permeability and elongation at break measurements. The results obtained in static (soaking) and dynamic (filtration and filtration/backwashing cycles) hypochlorite exposure modes indicated that PES/PVP membrane degradation progress was predominantly governed by hypochlorite oxidation rate. In the tested conditions, mechanical stress (pressure differentials) did not significantly contribute to membrane ageing. The correlation between molecular and macroscopic characterizations demonstrated that PVP degradation is responsible for the membrane integrity loss. A linear relationship between the loss of ductility of the membrane and the progress of the PVP degradation was obtained whatever the exposure mode. Thanks to experiments conducted at various hypochlorite concentrations and exposure durations, the hypochlorite dose parameter (hypochlorite concentration times contact time), widely used in the literature, was demonstrated to be inappropriate to describe the degradation rate: the hypochlorite concentration impact was shown to be dominating the exposure time's one on the degradation rate.

In spite of good performances of the membrane bioreactor (MBR) process, permeate from it can still contain refractory pollutants that have to be removed before water reuse or discharge. The present study is an attempt to combine the advantages of two well-known technologies, which are nanofiltration (NF) and electrochemical oxidation (EO) to treat MBR effluent from hospital wastewater. The concept is based on a preconcentration of micropollutants with a reduction of the wastewater volume by NF and treatment of the NF retentate by oxidation. During filtration process the rejection of ciprofloxacin, as a target molecule, reached beyond 97%. Then the NF retentate was treated by EO using a boron-doped diamond anode (BDD). Galvanostatic electrolyses showed that this anode is efficient to mineralize not only ciprofloxacin but also all the micropollutants and organics contained in MBR effluent. The results demonstrated that rapid mineralization occurred: the removal of total organic carbon and chemical oxygen demand (COD) reached 97% and 100%, respectively, in our conditions in 300 min maximum. The specific energy consumption for the total removal of COD was calculated to be 50 kW h kg˗1 COD.

International audience; The objective of the present work is to correlate the evolution of membrane characteristics due to contact with hypochlorite used as cleaning agent to its selectivity towards model solutes. Accelerated ageing experiments were performed by soaking the membrane at ambient temperature in hypochlorite solutions. The total free chlorine concentration of these solutions was fixed at 350 ppm and the pH at 8. The model solute selected was T500 Dextran. The experimental results demonstrated that hypochlorite induced membrane degradation, on one hand modified the solutes–membrane interactions increasing irreversible fouling and, on the other hand, lowered the selectivity. These results have been correlated with the modification of the pore size distribution following a protocol in which fouling did not affect membrane characterization. The most probable scenario of distribution evolution over degradation process was an increase of the pore radius of the initial population, accompanied by a decrease in their number, coupled with the appearance of defects, whose radius increased with the progress of the degradation.

Despite a long history of development, the hemodialysis procedure (artificial kidney) still possesses some limitations, such as loss of the initial properties of the membrane due to fouling and poor removal of the middle sized uremic toxins. The present study is part of an European project named BioArt the aim of which was to overcome these limitations. In that objective, one of the partners of BioArt project reported on the development of the novel promising concept of double layer membrane with embedded adsorptive particles. A thorough characterization of the new membrane was then necessary, more precisely the extent to which mixed matrix layer can improve the removal of the uremic toxins from various groups needed to be evaluated, as well as the propensity of the membrane material to become fouled. The studies of the fouling phenomena are conventionally performed at the macro scale (bundle of hollow fibers) without insights of what is happening at the scale of an isolated fiber. Therefore, the primary aim of the present Thesis was to transfer the research of the protein-induced membrane fouling from the macro to the micro scale. A novel transparent microfluidics device with the polymeric membrane inside has been developed and applied for the filtration of model proteins: bovine serum albumin (BSA) and a-lactalbumin. Thanks to the coupling of the microchip with the fluorescent microscopy, different patterns of protein deposition on the membrane surface were observed and related to the variations in the hydrodynamic conditions inside the microchip. It was found that at certain conditions one may observe the difference in protein accumulation in the inlet, the middle, and the outlet of the channel while at other conditions this effect vanishes. Additionally, the unexpected phenomena of a-lactalbumin aggregation was observed over the course of filtration. The location and shape of the aggregates were also dependent on the hydrodynamic conditions and the applied transmembrane pressure. Aiming to address the problem of membrane design optimization for the enhancement of the middle molecules elimination from the bloodstream, a mathematical model, which accounts for the presence of adsorptive particles inside the complex double-layer membrane, has been proposed. The objective of the model was to understand the interplay of three solute removal mechanisms: convection, diffusion, and adsorption. The model allows predicting the influence of various parameters such as molecule diffusivity, membrane thickness, the presence of convection, content of adsorptive particles on the flux intensification across the membrane. The developed model seems to be a useful tool, which may be applied to design optimized membranes for the removal of toxins.; Malgré une longue histoire de développement, l'hémodialyse (rein artificiel) possède encore quelques limitations, telles que la perte des propriétés initiales de la membrane en cours de traitement à cause du colmatage et la mauvaise élimination des toxines urémiques de taille moyenne. La présente étude fait partie d'un projet européen nommé BioArt dont le but est d'apporter des solutions à ces limites. Dans cet objectif, l'un des partenaires du projet a proposé le développement d'un nouveau concept de membrane double couche au sein de laquelle sont incorporées des particules adsorbantes. Une caractérisation complète de cette nouvelle membrane était alors nécessaire, plus précisément l'impact de la matrice mixte sur l'élimination des toxines urémiques de divers groupes devait être évalué, ainsi que la propension du matériau membranaire à se colmater. Les études des phénomènes de colmatage sont classiquement menées à l'échelle macroscopique (faisceau de fibres creuses) sans analyse à l'échelle d'une fibre isolée. Le but premier de la présente thèse a alors été de proposer un dispositif permettant une étude du colmatage membranaire induit par la protéine à l'échelle microscopique. Un dispositif microfluidique transparent dans lequel la membrane polymère est insérée a été élaboré et mis en œuvre pour la filtration des protéines modèles : l'albumine de sérum bovin (BSA) et l'a-lactalbumine. Grâce au couplage avec la microscopie de fluorescence, différents modes d'adsorption des protéines sur la surface de la membrane ont été observés et liés aux variations des conditions hydrodynamiques à l'intérieur de la puce. Il a été constaté, sous certaines conditions, une différence dans l'accumulation de protéines entre l'entrée, le centre et la sortie du canal tandis que dans d'autres conditions cet effet s'annule. En outre, un phénomène inattendu, l'agrégation de l'a-lactalbumine, a été observé au cours de la filtration. La localisation dans le canal et la forme des agrégats dépendent également des conditions hydrodynamiques et de la pression transmembranaire appliquée. Dans le but d'optimiser la conception de la membrane vis à vis de son aptitude à éliminer des molécules de taille moyenne de la circulation sanguine, un modèle mathématique a été proposé. L'objectif du modèle était, en prenant en compte la présence de particules adsorbantes à l'intérieur de la membrane double couche, de rendre compte de la combinaison des trois mécanismes d'élimination du soluté : la convection, la diffusion et l'adsorption. Le modèle permet de prédire l'influence de divers paramètres tels que la diffusivité de la molécule, l'épaisseur de la membrane, la présence de la convection, la charge en particules adsorbantes, sur l'intensification des flux à travers la membrane. Le modèle semble être un outil utile pouvant être appliqué à l'optimisation de membranes pour l'élimination des toxines.