Membrane-assisted reactive crystallisation for the recovery of dissolved phosphorus in vivianite form from liquid effluents

Novel membrane crystallisation processes resolve the mixing challenge on conventional crystallisers, by providing fixed interfacial area over which supersaturation is controlled for nucleation. Moreover, the membrane surface is thought to reduce interfacial energy and encourage micromixing. In this regard, a novel membraneassisted reactive crystallisation (MARC) process was used in this work for the dissolved phosphorous recovery in form of vivianite crystals from a phosphate-rich solution by means of the dosing of iron (II). To characterise the role of the boundary layer in controlling nucleation, a batch lab-scale system was used for the crystallization tests, and different hydraulic conditions (Reynolds ranging from 105 to 395) and polymeric membranes were tested. The crystallisation process was influenced by the hydraulic conditions, in which a low liquid velocity led to a lower induction time and vivianite supersaturation, and therefore, higher nucleation rates. Membrane properties were characterised to establish their role in the modification of the critical free energy requirement for nucleation, and for the promotion of micromixing, as possible factors that can be used to modify nucleation kinetics. As result, the bulk induction time tended to decrease with the increase in membrane hydrophobicity, roughness, pore size and porosity. Spherical vivianite nanoparticles were always synthesised with a mean size around 35 nm and a narrow distribution independently of the hydraulic conditions and membrane used. Finally, the crystallisation kinetic conformed to a diffusion-dependent nucleation mechanism, in which higher residence times for mixing increased the ion collision probability for nucleation. Importantly, this study demonstrated that MARC is an attractive prospect for nutrient recovery from wastewaters where crystal nucleation can be easily controlled by setting the operational conditions and membrane properties, eliciting considerable process intensification over existing conventional crystalliser.European Union funding: 71408

Impact of membrane configuration on fouling in anaerobic membrane bioreactors

The filtration performance of flocculated and granulated configured anaerobic membrane bioreactors (MBR) treating domestic wastewater has been evaluated and compared to conventional aerobic MBR. Immersed hollow fibre (HF) and external tubular membrane geometries were additionally compared with the latter operated in both pumped and gas-lift mode. After 200d of operation, both granular and flocculated anaerobic MBR (AnMBR) suspensions were characterised by an increased population of colloidal particles while the aerobic MBR retained a unimodal particle size distribution with a d of 20μm. Consequently, the flocculated AnMBR supernatant was characterised by a soluble microbial product (SMP) concentration ca. 500% higher than the aerobic MBR, such that the lowest critical fluxes for both HF and tubular membranes were recorded for the AnMBR. In comparison, the granulated AnMBR sludge was characterised by a low mixed liquor suspended solids concentration and an SMP concentration below 50% that of the flocculated anaerobic MBR. Consequently, similar fluxes to those of the aerobic MBR were achieved with the granulated anaerobic sludge using immersed HF membranes. Operating external tubular membranes in gas-lift appeared less effective for the granular AnMBR than the Aerobic MBR. However, critical fluxes >40Lmh were achieved using pumped mode. Results suggest granular AnMBR systems to be most suited to domestic wastewater treatment using either immersed HF membranes or external tubular membranes in pumped crossflow mode

Réponses postprandiales à l’ingestion de produits laitiers chez l’homme : effet du type de produit et de l’âge

Introduction et but de l’étude : De nombreuses études montrent que la consommation de produits laitiers (PL) est associée à des bénéfices pour la santé, mais ceux-ci peuvent différer en fonction du type de PL, notamment en raison de la fermentation. Cependant, associer la consommation de chaque PL avec des bénéfices santé spécifiques reste complexe en raison de la précision insuffisante de l'évaluation des profils de consommation par les relevés alimentaires. La métabolomique incluant des biomarqueurs de consommation de PL pourrait permettre une évaluation plus objective. Ces signatures sont aussi dépendantes des différences des réponses métaboliques, notamment au cours du vieillissement. Notre objectif est d’identifier les caractéristiques métaboliques postprandiales (PP) associées à la consommation de deux PL : lait (L) et lait fermenté avec lesbactéries du yaourt (Y) chez l’homme adulte et âgé.Matériel et méthodes : Etude clinique randomisée, contrôlée et en cross-over sur des 28 hommes jeunes (14 J, 20-35 ans) et âgés (14 A, 65-80 ans) en bonne santé. Après 3 semaines d’exclusion de PL et de produits fermentés (PF), les sujets ont ingéré à jeun 600 mL de L ou de Y. Les niveaux de glucose, d’insuline, de triglycérides, de peptide insulinotrope dépendant du glucose (GIP), et Interleukine IL-6 ont été suivis durant les 6h après l’ingestion.Résultats et Analyse statistique : L’augmentation des niveaux circulants de glucose a été plus importante 30 min après la consommation de L vs Y dans les 2 groupes d’âge (J : 6,0±0,2 vs 5,3±0,2, A : 5,9±0,2 vs 5,2±0,1 mmol/L, P<0,05), ce qui est confirmé par l’aire sous la courbe PP (AUC, J : -20±18 vs -67±12 P<0,05, A : 4±19 vs -20±17 P=0.06, mmol/L/min). L’insulinémie PP a également été plus importante après la consommation de L vs Y dans les 2 groupes (J : 204±30 vs 159±21, A : 147±17 vs 119±11 pmol/L à 30 min, P<0,05). Inversement, les taux circulants de GIP ont augmenté plus fortement 60 min après la consommation de Y vs L chez les J et les A (J : 347±33 vs 229±34, A : 406±50 vs 264±28 pg/ml, P<0,05). Concernant les effets liés à l’âge, la réponsePP des niveaux de triglycérides a été plus importante chez les A vs J, indépendamment du produit consommé, et particulièrement 180 min après l’ingestion (AUC L : 72±11 vs 26±16, Y : 77±9 vs 40±15 mmol/L/min, P<0,05). Alors que nous n’avons pas observé de changement significatif chez les J, les niveaux d’IL-6 ont diminué chez les A 1h après la consommation de Y (-14% vs t0, P<0.05), avec une tendance similaire chez les J (-19% vs t0, p=0,12) après la consommation de L.Conclusion : Ces résultats confirment que le changement de la matrice laitière suite à l’application de certains procédés (la fermentation) induit des différences de réponses métaboliques. Les réponses métaboliques peuvent être également influencées par l’âge des sujets. Les analyses métabolomiques en cours devraient permettre de préciser ces différences et d’identifier des biomarqueurs signant la consommation des différents PL.Remerciements : Ce projet bénéfice d'un soutien financier de la part du CNIEL et Syndifrais

Microbiota and Metabolite Modifications after Dietary Exclusion of Dairy Products and Reduced Consumption of Fermented Food in Young and Older Men.

The gut microbiota adapts to age-related changes in host physiology but is also affected by environmental stimuli, like diet. As a source of both pre- and probiotics, dairy and fermented foods modulate the gut microbiota composition, which makes them interesting food groups to use for the investigation of interactions between diet and ageing. Here we present the effects of excluding dairy products and limiting fermented food consumption for 19 days on gut microbiota composition and circulating metabolites of 28 healthy, young (YA) and older (OA) adult men. The intervention affected gut microbial composition in both groups, with significant increases in Akkermansia muciniphila and decreases in bacteria of the Clostridiales order. Lower fasting levels of glucose and insulin, as well as dairy-associated metabolites like lactose and pentadecanoic acid, were observed after the intervention, with no effect of age. The intervention also decreased HDL and LDL cholesterol levels. Dairy fat intake was positively associated with the HDL cholesterol changes but not with the LDL/HDL ratio. In conclusion, restricting the intake of dairy and fermented foods in men modified their gut microbiota and blood metabolites, while the impact of the dietary restrictions on these outcomes was more marked than the effect of age