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International audience; Membrane processes are used for drinking water production and medical applications to remove and/or produce viruses using organic membranes. It appears that backwashing is not sufficient to remove all the viruses stopped by the membrane. The use of "one-shot" membranes or chlorinated solution filtration can be considered with an additional cost and accelerated aging of the membranes respectively. The inactivation of bacteria, spores and/or viruses has been demonstrated by the use of supercritical fluid. The use of a supercritical CO 2 treatment of organic membranes is studied with the aim to investigate the impact of this treatment on the membrane performances and on virus destruction. It is demonstrated that whatever the operating conditions, the membrane materials and the application modes, the permeability and the retention of the membrane are not impacted. TEM observation of the viruses after treatment shows no virus integrity.

International audience; Removal of pathogenic microorganisms as viruses during drinking water production was evaluated by ultrafiltration. Two enteric viruses (ADV 41 and CV-B5) were compared to the MS2 bacteriophage, largely used in literature and by membrane producers as enteric virus surrogate. The effect of feed concentration of viruses on the ultrafiltration efficiency has been assessed. For the three viruses, low retentions about 1 log were observed at the lowest concentrations. At higher concentrations, an increase of removal up to 3.0 log for CV-B5 and MS2 phage and 3.5 log for ADV 41 was observed. These results highlight the potential overestimation of UF efficiency during laboratory experiments realized at high concentrations, compared to low concentrations found in environmental resources used for drinking water production. Virus removals with Evian water and real groundwater were compared and groundwater achieved similar or slightly higher removals for the three viruses. Finally, impact of membrane ageing after chlorine exposure was checked. It was observed that membrane degradations, visible by a water permeability increase with exposure dose did not affect the removal of viruses at low feed concentrations.

Disinfection by-products are of great concern in swimming pool water where water treatment generally involves a disinfection step with chlorine. In fact, swimmers can contribute a large quantity of organic matter that can lead to the formation of chloramines, chloroform and chloroacetic acids. These compounds can lead to health problems among the staff and pool users, especially babies or little children. The water quality improvement and productivity performance of the hybrid process, ultrafiltration–adsorption, is investigated. An original work, this paper presents results obtained in a real pool system for the first time. An industrial unit was installed in a municipal swimming pool in Marseille (France) and the process was studied for more than 18 months. After a study on water quality according to pool usage (activity and number of swimmers), the influence of transmembrane pressure and filtration time on ultrafiltration performance was evaluated. Optimal ultrafiltration operating conditions were found to be at a transmembrane pressure (TMP) of 0.45 bar and a filtration time ( T f ) of 60 min for the entire range of each water quality parameter studied. The filtration unit enabled water clarification, and the adsorption step limited the concentration of combined chlorine in water to 0.35 ppm, well below the limit given by the French legislation (0.6 ppm). Due to a succession of filtration and backwashes, permeability never decreased below 160 L h −1 m −2 bar −1 . In spite of difficult conditions in terms of frequent pool usage and total chlorine concentration, the membranes have shown promising flexibility in this hybrid process.

Industrial textile processing comprises the operations of pretreatment, dyeing, printing and finishing. These production processes are not only heavy consumers of energy and water; they also produce a substantial amount of chemical pollution. Of all dyed textile fibres, cotton occupies the number-one position, and more than 50% of its production is dyed with reactive dyes, owing to their technical characteristics. Unfortunately, this class of dyes is also the most unfavorable one from the ecological point of view, as the effluents produced are relatively heavily colored, contain high concentrations of salt and exhibit high BOD/COD values. Dyeing 1 kg of cotton with reactive dyes requires an average of 70–150 L water, 0.6 kg NaCl and 40 g reactive dye. The composition of the dye bath which we propose to treat contains solid particles (cotton fibres), dyeing auxiliaries (organic compounds), hydrolyzed reactive dyes, substantial quantities of alkalis (sodium carbonate and soda ash) and very high concentration of sodium chloride or sodium sulfate. This paper presented the state of the art of the different processes currently used for the treatment of dye house wastewaters and evaluated a four-step process [1] to recover the water and the mineral salts, while leaving the spent dyes in the reject stream. Processes evaluated included (1) cartridge filtration to remove textile fibres, (2) acidification to make the brine recovered, suitable for reuse and further dyeing operations, (3) nanofiltration (NF) to concentrate the hydrolyzed dyes and (4) reverse osmosis (RO) to further concentrate the salts for reuse in the dyeing process. A cut-off of 100 μm is sufficient to trap textile fibres, regardless of the type of effluent and the texture of the textile dyed. The hydrolyzed reactive dyes present in the treated effluents comprise the entire range of possible types of reactive dyes. For this acidification, we studied the influence of the concentration of sodium chloride, the influence of the temperature and we verified that the volume neither depends on the concentrations of reactive hydrolyzed dyes nor sodium chloride. After defining the nanofiltration membrane, we studied the effect of the pH, temperature, pressure and velocity as well as the experimental procedure on the permeate flux, recovery of the salt and removal of the color. An increase of either of the parameters temperature and pressure leads to an increase of the permeate flux. On the other hand, a rise in the pH leads to a decrease of the permeate flux. The retention factor of the sodium chloride is low when the concentration of sodium chloride is high in the retentate. Our aim was to recover 80–90% of the sodium chloride, but our experiments showed that the recovery went as high as 99%. Depending on the dyes used, the experimental procedure can be carried out in one, two or three steps. The dye retention level was always higher than 98%. After studying the operating variables, experiments with the recycled brines in new dyeing operations were carried out with specimen dyeings prepared with usual water using different classes of reactive dyes. There was no difference in the results in terms of depth, shade or fastness properties, whichever type of water was used. These last results therefore validate our process and its special innovative feature: recycling not only the water but also the mineral salts.

In order to rationalize the effect of Dean vortices on mass transfer improvement during membrane filtration, we present preliminary calculations of the wall shear stress in curved tube with non-porous walls. Previous experimental work has already shown strong positive effect of Dean vortices on mass transfer. In this paper, a numerical simulation of shear stress is proposed in order to determine the influence of the geometric parameters in four different tubes: straight, torus, helical and woven tube. The simulation results are tested against the analytical solutions which are available for velocity and pressure distributions in straight tubes. The simulation gives local values from which the location of Dean vortices in cross-section can be deduced and which depends on geometry and Reynolds number. Moreover, published results dealing with oxygenation of water by a membrane process and pervaporation of organic volatile compounds are considered using the present simulation results.

A new ultrafiltration module containing woven hollow fibers was tested. The purpose of this paper is (i) to present ultrafiltration performance of the new module with dextran solutions and (ii) to compare the performance with those obtained in helical and straight modules containing identical hollow fibers. The effect of velocity on limiting permeation flux was studied and the same increase was obtained in the woven hollow fiber module as in the helical module. The energy consumption was also investigated and the woven hollow fiber module performed better. At a given energy consumption, the limiting flux observed in the woven hollow fiber module was higher than that in the helical and straight modules. Also pointed out was the lower stress of the fibers in the woven hollow fiber module than that in the helical module.

International audience; A helically wound hollow-fibre (or tubular) membrane module was studied in an oxygenation operation with water flowing in the laminar regime inside the tube. Data are compared with a conventional module where straight hollow-fibre membranes are in parallel alignment. In the former design, the results are analyzed taking into account the formation of secondary flow (Dean vortices) and a new mass transfer correlation is presented. In the latter design, results are consistent with the Lévêque equation. It is shown that the presence of vortices gives better performance in terms of oxygen transfer. Improvement factors were in the range of 2 to 4.