Search

International audience; Dehydration is a critical step in many food processes. In this paper, we propose an original strategy, basedon experiments and modelling, to evaluate the performance of the compression dewatering of cassava and tohelp design dewatering equipment. The dewatering of various grated cassava roots was experimentally studiedthrough 42 experiments in a filtration–consolidation cell in the pressure range 4–21 bar. The dewateringperformance was evaluated in terms of moisture content limit and dewatering kinetics. Each filtration–consolidation experiment was first individually fitted with a model combining Hermia cake filtration andShirato consolidation mechanisms using an original systematic approach. Then, a global model, linking the cakefiltration and consolidation properties to the applied pressure, was validated over the whole set of experimentswith an average RMSE of 13% on the cake moisture content. The results demonstrated the relevance of thechosen identification procedure and modelling strategy for the design of a compression dewatering step.

This work aimed at characterizing the viscoelastic behavior and the fouling propensity of orange juice matrices composed of concentrated suspended particles (CSP) with defined size distributions. Small-, medium- and large-CSP (respectively colloids, supra-colloids and large particles) were first isolated and then mixed together according to a mixture design. The shear moduli, the specific resistance to filtration and the compressibility factor of isolated CSP and CSP mixtures were quantified. Small-, medium- and large-CSP were characterized by viscoelastic properties with a predominant solid-like behavior. The deposit layer of large-CSP had the highest shear moduli, while small-CSP presented the highest specific resistance to filtration. Small-, medium- and large-CSP deposit layers were considered as compressible matrices. The rheological behavior and the fouling propensity of mixtures of small-, medium- and large-CSP were analyzed using ternary diagrams. These diagrams revealed that the small-, medium- and large-CSP proportions modulated differently the shear moduli and the fouling propensity of CSP mixtures. Indeed, the solid-like behavior was strongly influenced by large-CSP proportions, the specific resistance to filtration depended mainly on the CSP size polydispersity, while small- or medium-CSP proportions had a major influence on the compressibility factor.

This work studies the role of dispersing and dispersed phases in the rheological properties of fruit juices during concentration operations. A special focus was given to the behavior of the dispersed phase (SS) when it is concentrated singly or simultaneously with the dispersing phase (TSS). The experimental strategy consisted in the characterization of the viscoelastic properties and the flow behavior of various orange juice suspensions containing different concentrations of soluble and suspended insoluble compounds. Results showed that the presence of solutes in the dispersing phase increases the cohesion energies between the particles of the dispersed phase and governs their viscoelastic behavior. As for the flow behavior, the concentration of dispersed particles proved to be the parameter controlling the consistency indexes in the TSS domain between 0% and 30%. Furthermore, results reveal a TSS threshold around 40%, at which great physical alterations may occur to the dispersed phase. This study provides new knowledge concerning the distinctive role of the dispersing and the dispersed phases in the viscoelastic properties and flow behavior of fruit juices. This information could be useful to predict and control the rheological behavior of fruit juices during concentration operations such as vacuum concentration and microfiltration.

This study proposed to investigate the impact of ripening on the physical properties of mango purees. An extensive study of the particle size and rheological properties of mango purees and their dispersed phase was performed using particle size measurements, small deformation rheology, and an innovative technology combining simultaneous rheometry and in situ FTIR spectroscopy. The results revealed a sharp decrease in the solid-like behavior of mango purees, as well as in the energy of cohesion of their dispersed phase during the first 10 days of ripening, leading to a weakening of their gel-structure. The size of suspended insoluble solids in the purees continued to decrease until 15 days of ripening. According to the spectral fingerprints, it was possible to identify some changes in the purees' sugar content occurring upon the physical changes during ripening. The highest sucrose and lowest fructose contents were observed in purees obtained during the first 10 days of ripening, in comparison with the following days. Based on the twin physical and spectral fingerprints, purees obtained from the early days of ripening (

International audience; The aim of this study was to evaluate the potential effect of tributyltin (TBT) on the performance of suspended-growth biological processes. The influence of TBT was evaluated for (i) the endogenous and exogenous respirations of heterotrophic micro-organisms in laboratory-scale batch reactors, taken from a municipal wastewater treatment plant and (ii) chemical oxygen demand (COD) removal, sludge production and oxygen consumption of a pilot-sale membrane bioreactor (MBR) system inoculated with heterotrophic micro-organisms taken from a MBR system. The batch experiments showed that the presence of TBT was likely to modify the activity of bacterial populations in endogenous conditions. The increase in endogenous oxygen needs suggested an increase in the maintenance requirements, essentially to manage the chemical stress induced by the presence of TBT. If the addition of TBT did not perturb COD removal in an MBR system, it limited sludge production and increased oxygen requirements; it is assumed that these modifications were linked with the necessity for the biomass to adapt in this stressful environment, as reflected by an increase in the maintenance requirements. These results emphasised that the respiratory activity of the bacterial cultures was modified by the presence of TBT, in the sense that an excess of oxygen was required to adapt to this chemical stress.; Le but de cette étude était d'évaluer l'effet potentiel du tributylétain (TBT) sur la performance des processus biologiques à croissance suspendue. L'influence du TBT a été évaluée pour (i) les respirations endogène et exogène de micro-organismes hétérotrophes dans des réacteurs batch à l'échelle du laboratoire, provenant d'une station d'épuration municipale et (ii) l'élimination de la demande chimique en oxygène (DCO), la production de boues et la consommation d'oxygène d'un système pilote de bioréacteur à membrane (MBR) inoculé avec des micro-organismes hétérotrophes provenant d'un système MBR. Les expériences en batch ont montré que la présence de TBT était susceptible de modifier l'activité des populations bactériennes en conditions endogènes. L'augmentation des besoins endogènes en oxygène a suggéré une augmentation des besoins de maintenance, essentiellement pour gérer le stress chimique induit par la présence de TBT. Si l'ajout de TBT n'a pas perturbé l'élimination de la DCO dans un système MBR, il a limité la production de boues et augmenté les besoins en oxygène ; on suppose que ces modifications sont liées à la nécessité pour la biomasse de s'adapter dans cet environnement stressant, comme le reflète l'augmentation des besoins de maintenance. Ces résultats ont souligné que l'activité respiratoire des cultures bactériennes était modifiée par la présence de TBT, dans le sens où un excès d'oxygène était nécessaire pour s'adapter à ce stress chimique.

Mango has an abundant production leading to important post-harvest losses. Mango processing is an alternative to reduce these losses. Nowadays, the lack of instrumental tools suitable to sort mangos according to their ability to be processed into products with specific quality is a main setback for their processing. The aim of this study was to develop new tools, mainly non-destructive, to sort easily fresh mangos according to their maturity stage and to the specific properties of their purees. To this end, an innovative experimental strategy combining textural, rheological and physico-chemical analyses was proposed to characterize mangos and their purees. Results showed that mango firmness is a great indicator of mango heterogeneity and has an important impact on the properties of mango purees. A non-destructive compression test was reliable to measure accurately mango firmness and to anticipate rheological and particles size properties of mango purees.

The objective of this work was to describe the dispersion state of flavonoids (i.e. naringin and narirutin) in the press liquor obtained after filtration-compression of fresh citrus (grapefruit) peels. An original methodology for the quantification of the dispersion, based on a size fractionation, and its evolution over time was proposed. Three fractions were identified: (i) a particulate fraction, (ii) a large-colloidal fraction and (iii) a small-colloidal and soluble fraction. Narirutin and naringin were initially found on small-colloidal/soluble form. During time, an aggregation of the compounds present in the press liquor, revealed by turbidity measurements, was observed. This aggregation resulted in an increase of the particulate fraction, at the expense of the colloidal one. This aggregation seemed to trap naringin, that progressively appeared in the particulate fraction, although that no evolution of narirutin location was observed. The tendency to sediment of the formed aggregates was evaluated, by a Turbiscan® optical analyser, in the objective of their future isolation. The stability study of the press liquor over time showed that this suspension was physically stable; the aggregates/flocs were not able to settle at room temperature, certainly because of interparticle repulsion or other reasons as low floc density, porous floc structure, etc.

Initiative of waste treatment has to be based on user-friendly technologies, using robust, cost-effective and low-energy consuming processes. The global objective of this study was to reduce technical steps for the extraction of flavonoids (naringin and narirutin) from citrus peel (grapefruit peel). After a first fresh peel grinding, the relevance of a simple filtration-compression, as a first downstream process, of the obtained slurry was studied. An optimization of this solid-liquid separation was proposed and the impact of a pectinolytic enzymatic treatment, resulting potentially in a larger release of flavonoids, was investigated. The results demonstrated that a preliminary step of filtration-compression, directly realized on fresh grinded peels as downstream processing for flavonoids extraction could be pertinent and that the enzymatic treatment improved the slurry filterability. An optimal separation was obtained with a transmembrane pressure of 5 bar, leading to highest extractable liquid phase volume and to an extraction around 80% of naringin and narirutin. A modelling of the filtration step, essential for the scaling of a filtration-compression process on site, was proposed. An originality of this work was to identify the dispersion state of the flavonoids within the liquid phase, capital identification for a relevant choice of the subsequent extraction step of these compounds.

The objective of this work was to characterize the foulant propensity of three Grape Processing Residues (GPR) in relation with their physicochemical properties. Therefore, a physicochemical characterization of GPR was firstly carried-out, with a focus on the separation/characterization of relevant size-classes of particles. Then, lab-scale experiments were performed using a dead-end filtration module with different membranes (three average pore diameters) in order to identify for each GPR the main foulant size-classes of particles and the related fouling mechanisms. Results showed that this study allowed getting more insight into how different fractions of GPR are involved in membrane fouling according to their size. Moreover, size-cartographies of GPR foulant compounds were built to provide a better understanding and control of membrane fouling. The obtained results showed that it was possible to use this simple and cost-effective tool to choose the appropriate filtration conditions. Industrial relevance The valorization of Grape Processing Residues (GPR) is a major economic and ecological challenge. GPR contain a high amount of phenolic compounds, well known for their several biological properties. In the light of this, membrane technologies have been widely used for the extraction and the purification of these bioactive compounds from GPR. However, the performance of these processes is highly challenged by membrane fouling, which is partially dependent on the feed suspension characteristics. To date, different operating strategies have been used industrially to prevent membrane fouling. However, the use of costly and time-consuming strategies has not often been validated by characterization of the feed suspension prior to filtration. Thus, it is mandatory to analyze GPR intrinsic characteristics in relation with their fouling in order to identify the appropriate operation conditions for large-scale filtration. For this purpose, an innovative strategy was developed in this work. This study was useful to develop a simple and cost-effective tool providing reliable guidelines for the development of efficient pilot-scale processes for the extraction of phenolic compounds from GPR.

Microfiltration is widely used to ensure the a thermal stabilization, clarification and concentration of various fruit-based suspensions (e.g. fruit juices, food by-products, wine). However, the performances of membrane filtration remain highly challenged by membrane fouling. To prevent membrane fouling, cross-flow filtration is generally performed. Nevertheless, this intensive working mode is considered as highly energy consuming due to the intensive pumping required to circulate the suspension at high velocities. In the light of this, immersed membranes configurations have been developed in many fields, as they allow working in energy-friendly operating conditions. Thus, this work investigated for the first time the performances of an immersed membranes configuration for fruit-based suspensions microfiltration, in terms of productivity (membrane fouling, permeate flux) and selectivity (clarification, concentration of bioactive compounds). This study focused on three fruit-based suspensions: a grapefruit juice and two winery by-products. Concerning the process selectivity, pilot-scale experiments showed that immersed membranes filtration allowed producing retentate and permeate of quality as least as good as the one related to conventional cross-flow filtration. Concerning the process productivity, cross-flow filtration allowed reaching higher fluxes compared to immersed membranes filtration, in accordance with the conventional order of magnitude specific to each configuration. Immersed membranes configuration could find interesting applications within small production units of fruit juices and/or industries dealing with the valorization of low added-value byproducts thanks to its various advantages (high compactness, easy handling and mobility, low investment and operational costs).

Side-stream tubular membranes are largely used to perform cross-flow microfiltration of fruit juices. However, this configuration presents well-known drawbacks (e.g. energy consumption). Immersed membranes configurations have been developed in many fields to overcome these disadvantages. This paper investigates for the first time the possibility of using immersed configuration for fruit juices microfiltration. Firstly, a lab-scale methodology was adopted to characterize the fouling propensity of the juice, while studying the impact of transmembrane pressure, membrane material and the role of large particles on the juice fouling behavior. Secondly, pilot-scale experiments were performed to identify the optimal operating conditions for both configurations. Both lab-scale and pilot-scale experiments suggested that the operating conditions of immersed configuration (no removal of large particles, low pressure and organic membranes) could be suitable to perform juice microfiltration. The optimal permeate flux of immersed configuration was in accordance with the ones reported in other fields. A productivity similar to the one related to side-stream configuration might be obtained through an increase of the filtration surface, made possible by the great packing density and low membrane cost related to immersed configuration. These findings offer new application for immersed membrane configuration in the microfiltration of delicate fruit juices.

A high molecular weight chitosan was chemically modified to quantitatively incorporate quaternary ammonium groups. Its efficiency was evaluated in the liquid-solid separation for various liquors, and compared with the one of a polyelectrolyte usually used for this utilization. The performance of the liquid-solid separation was estimated through the determination of two parameters measured after the screening- settling of the mixture liquor/flocculating agent: the separation efficiency (EV) and the TS removal efficiency (ETS). Apart for liquor 6, TS removal was always better after an addition of functionalized chitosan. Furthermore, whatever the type of liquor, the distribution was modified by an increased presence of high-size particles when functionalized chitosan was added. Moreover, chitosan addition tended to homogenize the size of the particles, which could facilitate the choice of the liquid-solid separation process. This homogenization was particularly observed for the liquor initially highly dispersed in size, i.e. liquors 1, 4, 6 and 8.

Biomass concentrations 2 to 5 times higher than in a conventional activated sludge (CAS) process can be achieved in a membrane bioreactor system (MBR). These non–conventional operating conditions, i.e. high sludge concentration, can induce different sludge characteristics and dewatering aptitude, essential parameters for the optimization of the sludge post–treatment, like mechanical dewatering. The objective of this work is to study the dewatering behavior of MBR sludge, and particularly the influence of high total suspended solids concentration, on viscosity and on the key dewaterability indicators. Operating conditions are chosen to obtain MBR sludge with constant characteristics, except TSS concentration. The results confirm that the sludge viscosity is dependent on the TSS concentration. The high viscosity obtained for high TSS concentration can be unfavorable to an efficient mixing in the MBR unit, as well as to acceptable membrane permeability. However, good settleability is obtained with high TSS concentration although the sludge presents high compressibility property and a large part of bound water. This large part of bound water seems to not disturb the sludge filterability, which stays relatively good in comparison with CAS. Consequently, high–TSS concentration in MBR system can be coherent with an efficient sludge post–treatment.

Although the role of the solids concentration on the rheological characteristics of sludge is greatly documented in the literature, few studies focused on the impact of the nature of these solids. How the nature of solutes can modify the solid-liquid interactions and thus the rheological properties of the sludge are also slightly explored. Thus, the objective of this study is to investigate the rheological characteristics of activated sludge in relation with the nature of the compounds present in the solid and liquid phases. Rheological measurements were carried out on raw sludge and on sludge modified by mechanical actions and/or addition of solids or solutes. The rheological properties of raw and modified sludges were measured according to flow and dynamic measurements. Results demonstrated that if suspended solid concentration affected sludge rheological parameters, the nature of the solids was quite of importance. The key role of nature and molecular weight of solutes was also highlighted. The results contribute to a better knowledge of the relationship between sludge composition and its rheological properties, which is useful for the optimization of sludge mixing, pumping or aeration and also for the improvement of sludge dewatering, notably by a relevant choice of adjuvant.

Despite the several advantages of microfiltration, applications of this separation technique in fruit juice industries have been challenged by its low economical productivity due to membrane fouling. Although several studies aimed to identify operating conditions (e.g. juice pretreatment, crossflow filtration mode, etc.) to achieve acceptable performances, only few studies focused on the fouling propensity of fruit juices and on the identification of their foulant compounds. The aim of this work was to evaluate the fouling behavior of two orange juices and focused on the identification of relevant size-classes of foulant particles. Lab-scale filtration tests were carried out in conjunction with juice size-fractionation with the aim of quantifying the resistance to filtration of the juices. Based on a resistance-in-series approach, size-cartographies of foulant particles that are juice and membrane-specific were built. These cartographies were provided for two mineral membranes M 1.2 and M 0.2 with different average pore diameters (1.2 and 0.2 μm). M 1.2 results showed that the fouling is mainly external for both juices and due to particles larger than 2 µm. In contrast, results concerning M 0.2 filtration tests showed that four different size-classes of fruit juices compounds are involved in different fouling mechanisms. Moreover, the hydraulic reversibility of the fouling mechanisms was evaluated through the impact of shear rate on the measured resistances. It was seen that the fouling was mainly reversible when M 1.2 was used for both juices filtration while it was not the case when juices were filtered with M 0.2 . This information would be interesting to choose the appropriate strategy in order to enhance the microfiltration of these juices at large scale. Moreover, the proposed size-cartography strategy would greatly satisfy the industrial demand for practical tool to identify the different size-classes of compounds governing the overall membrane fouling.

A better comprehension of the interactions between suspended solids is necessary to optimize the performance and reduce energy requirement during different operations in fruit juice processing (thermal treatment, sedimentation, centrifugation, filtration, spray drying, etc.). In this context, the aim of this study was to propose a rheological approach to get more insight into the energy of cohesion of orange juice suspended solids (SS). The specific energy of cohesion of suspended solids was obtained from rheological measurements in dynamic mode carried out on orange juices fractions with different suspended solids concentrations and size-classes. Results showed that the specific energy of cohesion increased as the SS content increased, independently of the particles size. However, the solid-like behavior of the juice was enhanced by the presence of large particles. The results obtained show that particles network strength and the viscoelastic behavior of juice result of complex interactions between all juice particles. Even if it was demonstrated that these complex interactions depend on the size of the particles, they might depend also on the physicochemical nature of these latter. The knowledge, for the studied fruit juices, of the evolution of their viscoelastic behavior as function of the SS content might be useful to control and optimize the different operations of their transformation chain.

International audience; This work was designed to study the hydraulic properties of sludge deposit, focusing on the impact of operating conditions (i.e. loads and feeding frequencies) on air entrance (aerobic mineralization optimization) into the sludge deposit. The studied sludge deposits came from six 2 m2 pilot-scale SDRBs that had been in operation for 50 months with three different loads of 30, 50, and 70 kg of SS m2 y1. Two influents were assessed (i.e. activated sludge and septage) presenting different characteristics (i.e. pollutant contents, physical properties. . .). Two experimental approaches were employed based on establishing the water retention curve (capillary pressure versus volumetric water content) and the hydrotextural diagram to determine the hydraulic properties of sludge deposit. The study obtained valuable information for optimizing operating conditions, specifically for efficient management of loading frequency to optimize aerobic conditions within the sludge deposit.

The aim of this work consists in evaluating the influence of carmabazepine (CBZ) (i) on the endogenous and exogenous respirations, in batch reactors, of bacterial populations taken from a conventional activated sludge process (CAS) and a pilot-scale membrane bioreactor (MBR) and (ii) on COD removal, sludge production and oxygen requirement of a lab-sale MBR system. In batch experiments, the increase in endogenous oxygen needs suggests an increase in maintenance requirements, essentially to manage the chemical stress induced by the CBZ presence. The decrease of exogenous oxygen needs seems to suggest a change in the metabolic pathways of the substrate or a change in the active bacterial species. However, in spite of these momentary changes, no inhibition is observed in the presence of CBZ in the test tank. This result is confirmed by the MBR experiment where no significant difference COD removal, sludge production and oxygen requirement is observed, with and without CBZ.

Volatile fatty acids (VFA), the preferred carbon source for biological nutrients removal, can be produced by waste activated sludge (WAS) anaerobic fermentation. However, because the rate of VFA accumulation is limited by that of WAS hydrolysis and VFA is always consumed by methanogens at acidic or neutral pHs, the ultrasonic pretreatment which can accelerate the rate of WAS hydrolysis, and alkaline adjustment which can inhibit the activities of methanogens, were, therefore, used to improve WAS hydrolysis and VFA accumulation in this study. Experiment results showed that the combination of ultrasonic pretreatment and alkaline adjustment caused significant enhancements of WAS hydrolysis and VFA accumulation. The study of ultrasonic energy density effect revealed that energy density influenced not only the total VFA accumulation but also the percentage of individual VFA. The maximal VFA accumulation (3109.8mg COD/L) occurred at ultrasonic energy density of 1.0kW/L and fermentation time of 72h, which was more than two times that without ultrasonic treatment (1275.0mg COD/L). The analysis of VFA composition showed that the percentage of acetic acid ranked the first (more than 40%) and those of iso-valeric and propionic acids located at the second and third places, respectively. Thus, the suitable ultrasonic conditions combined with alkaline adjustment for VFA accumulation from WAS were ultrasonic energy density of 1.0kW/L and fermentation time of 72h. Also, the key enzymes related to VFA formation exhibited the highest activities at ultrasonic energy density of 1.0kW/L, which resulted in the greatest VFA production during WAS fermentation at pH 10.0.

The objective of this paper is (i) to investigate correlations between MBR membrane fouling and MBR sludge physical properties, and (ii) to develop the parameters for control membrane fouling especially physical properties in term of dewatering parameters. The experiments are performed in a submerged membrane bioreactor, in sub-critical flux conditions. The physical sludge characteristic is studied for two running periods, characterized by different organic loads (VLR) and/or solid retention times (SRT). The physical sludge characteristics (SMP, SCOD, CST, SRF, viscosity and SVI) are quantified and correlated with the fouling rate. The soluble fraction is the major parameter affecting physical sludge characteristics, with the polymeric linkage. The CST can be a reliable parameter to predict the extent of second stage membrane fouling rate in MBR filtration and can be useful for monitoring the MBR system.

The hydro-textural properties of different urban residual sludges, characterized by their organic matter content, were estimated and correlated with their limit water content, corresponding to their minimum water content obtained after constant high-pressure filtration. A conventional compression-permeability (C-P) cell was used to determine the limit water content ( w lim ) whereas standardized soil mechanics tests were run to determine the liquid limit ( w L ) and plastic limit ( w P ) content, characterizing the hydro-textural properties. The results demonstrated that w lim , w L and w P parameters depend on sludge composition: high organic matter content ratio is unfavorable to a low w lim but favorable to a high plastic range and so a high deformation of the sludge. It appeared that the w lim value was close to the w P value, but lower than that obtained after mechanical dewatering in the wastewater treatment plants (WWTPs). It appears thus that the totality of the mechanically extractable water is not extracted by the WWTPs mechanical dewatering devices.

The sorption of hydrophobic micropollutants in sludge is one of the major mechanisms which drive their fate within wastewater treatment systems. The objective of this study was to investigate the influence of both sludge and micropollutant characteristics on the equilibria of sorption to particles and to dissolved and colloidal matter (DCM). For this purpose, the equilibrium constants were measured for 13 polycyclic aromatic hydrocarbons, 5 polychlorobiphenyls and the nonylphenol, and five different sludge types encountered in treatment systems: a primary sludge, a secondary sludge, the same secondary sludge after thermal treatment, after anaerobic digestion, and after both treatments. After thermal treatment, no more sorption to DCM was observed. Anaerobic biological treatment was shown to enhance micropollutants sorption to particles and to DCM of one logarithmic unit, due to matter transformation. Partial least-squares linear regressions of sorption data as a function of micropollutant and sludge properties revealed that sludge physical and chemical characteristics were more influential than micropollutant characteristics. Two models were provided to predict the sorption of such micropollutants in any sludge. To our knowledge, this is the first time that a three-compartment approach is used to accurately model micropollutant sorption in sludge and to understand the driving mechanisms.

The aim of this work is to investigate the rheological behaviour of MBR sludge for prolonged sludge retention time and during unsteady state conditions. The role of the total suspended solids and of the soluble organic matter is specifically studied through two running periods characterized by different organic loads and/or solid retention times. Diverse rheological parameters are examined. They are obtained from flow measurements carried out for an extent range of shear stress values. The obtained results show clearly that operating conditions capable of changing the total suspended solid (TSS) and soluble organic compound (COD) concentrations modify the rheological behaviour of the sludge. In comparison with the TSS concentration, the soluble organic compounds greatly affect the cohesion and the rigidity of the sludge three dimensional network. On the other hand, the COD concentration and the TSS content have equivalent quantitative influence on the rheological parameters characterizing the flow of the sludge. The results obtained are of great importance because operating conditions leading to the modification of the soluble microbial product concentration, and of the sludge rheological characteristics in the reactor, can strongly modify not only the mixing and aeration performances but also the membrane fouling of the MBR unit.

The aim of this work consists in analysing the dewatering and the shrinkage of a residual urban sludge during convective drying with the objective to find correlations between dewatering and hydro-textural characteristics of the sludge. Laboratory drying experiments are performed in immobile atmosphere, at a temperature of 30 °C, with various relative humidities. Kinetics curves of dewatering and deformation are obtained. A coupled analysis of dewatering and induced volume shrinkage is proposed. This analysis allows: (i) to distinguish the respective parts played by the intrinsic characteristics of the sludge and the process parameter and (ii) to find correlations between the hydro-textural characteristics of the sludge, and its drying and shrinkage aptitudes. Attention is given to the fact that the process parameter, i.e. relative humidity, controls the first constant rate period of the dewatering and that the hydro-textural state of the sludge determine the transitions between the different dewatering periods. The relationships between the hydro-textural characteristics and the dewatering and shrinkage aptitude allow predicting the sludge behaviour during drying according to its characteristics, which is essential information in the choice of the drying strategy.

The objective of this research is to study the effect of the substrate/biomass ratio (F/M) on the performance of two immersed membrane bioreactors operating, respectively with a sequential (SMBR) or a continuous (CMBR) mode. A synthetic organic substrate was selected to analyse the mixed culture behaviour and an average 1 g COD L −1 day −1 volumetric organic load was imposed in both MBRs. Each system worked during a 150 days operational period without any sludge extraction. In both cases, the global performance was relevant due to the porous membrane selectivity and to the high reactors biomass concentration. In fact, the COD removal efficiency was more than 94%, and the permeate free from suspended solids with a turbidity lower than 0.5 NTU. Due to non-continuous conditions, the SMBR system appeared hardly less successful than the CMBR system, with a COD effluent concentration and a sludge production, respectively equal to 125 mg COD L −1 and 0.092 g COD P g COD T −1 which are approximately twice higher than in CMBR system. These differences are presumably linked with the very high instantaneous F/M ratios imposed on the SMBR system during the feed periods (from 12 g COD g MLVSS −1 day −1 at the beginning of the experiment to 2.5 g COD g MLVSS −1 day −1 at the end of the operation). These brief high F/M ratios could favour a cell replication behaviour which is generally linked to important microbial soluble compounds production (soluble COD) and unfortunately associated with an accumulation of products coming from cell lysis (sludge production). Despite these observations, the SMBR system appears as an appropriate solution in case of non-continuous wastewater productions as often observed on industrial sites.

The main objective of this study is to evaluate the performance and the structure of the microbial community of a submerged membrane bioreactor (MBR) for seafood processing wastewater treatment and reuse. This system was operated continuously under favourable biological conditions, with complete biomass retention. In terms of organic removal and membrane performance, the MBR had a good efficiency to treat high strength with organic loading variation characteristic of real seafood processing wastewater. The overall results showed the importance of ecological microbial compositions in each stage of development that were different in MBR in comparison with conventional activated sludge. The MBR sludge could tolerate real stresses such as salinity and variation of COD and SS inlet in a wide range, with always good removal efficiencies in terms of BOD and COD. At the beginning period, bulking sludge was present. After 700 h of operation, the sludge characteristics not only showed healthy floc formations and good settling, but also confirmed the stable state of the system without overgrowth filamentous bacteria. In evaluating the fouling potential of membrane by cake filtration theory, it was found that soluble substances, soluble microbial products and/or residual organics play a key role in inducing membrane fouling. The αW values of the soluble fraction were three times higher than those of the particulates of bacterial floc.

The aim of this work is to analyse the biological performances of two immersed membranes bioreactors focusing on the biomass adaptation to complex substrate degradation and the performance in term of permeate quality. Two influents were selected: a synthetic complex influent (acetate/Viandox®, MBR1) and a real seafood processing wastewater (surimi product, MBR2). The MBR systems were operated for long periods without any sludge extraction except for sampling. Organic matter removal, sludge production and quality of the treated wastewater were analysed and studied. COD removal efficiencies after a period of biomass adaptation were higher than 97% and 95% for the synthetic and real wastewater respectively. In both cases, the COD of the treated wastewater was lower than 50 mg.L−1. In spite of salt concentration in the real wastewater a biomass adaptation process occurs. In the overall operational period, a 0.058 gCODP.gCODT−1 and a 0.12 gCODP.gCODT−1 observed sludge yields were obtained for the MBR1 and MBR2 respectively. These values are approximately 5 to 10 times lower than those measured in conventional activated sludge process. These results showed that the presence of particular and some of non-easily degradable compounds in the influent of MBR2 didn't limit the performance of MBR in term of COD removal achieved. The results have also confirmed the excellent permeate quality for water reuse from MBRs systems.

The objective of this work was to study the biological performance of a submerged membrane bioreactor working with complete sludge retention that is susceptible to induce high biomass concentration and consequently low F/M ratio. A synthetic organic influent was used and the biological behavior of the system was studied for three different volumetric organic loads. In spite of continuous increase in the VSS concentration, a steady state in terms of removal efficiency and respiratory activity was achieved. High organic matter removal efficiency and no decline of the membrane performance were observed. Cycles of biomass synthesis and biomass loss by predation, lysis and decay could be considered so that a reduction of the biomass production seemed to be possible while keeping high treatment efficiency. Most of the cells were assumed to stay in a physiological state in which cell division was not favored, and the degraded substrate was essentially used to ensure maintenance requirements and storage products synthesis.

This work focuses on the performances of two immersed membrane bioreactors used for the treatment of easily biodegradable organic matter present in food industry effluents, for the purpose of water reuse. Two reactor functioning modes (continuous and sequencing) were compared in terms of organic carbon removal and of membrane permeability. For each working mode, pollutant removal was very high, treated water quality presented a low COD concentration (

The objective of this study is to establish some relations between the physical properties of the sludge (i.e., specific resistance to filtration, capillary suction time …) and membrane fouling in a submerged membrane bioreactor, for high solid retention time (SRT) conditions. The analysis of the membrane performances, carried out with an analysis of the depollution performances and of the activated sludge physical properties, is proposed in an experimental membrane bioreactor (MBR) unit working with complete biomass retention. It is first confirmed that high-SRT conditions involve a high degree of organic degradation, with low sludge yield. A continuous increase of the viscosity can be observed during time but the sludge dewatering behaviour can be considered as constant, despite the total suspended solids (TSS) increase. No direct correlation is established between the transmembrane pressure (TMP) evolution and the conventional parameters used to describe sludge dewaterability but it can be assumed that the sludge filtration is not possible when TSS and viscosity reach “critical” values. Soluble microbial substances and mean floc size diameter evolutions cannot explain the decrease of membrane permeability, although these compounds may enhance fouling. The characterisation of the bulk suspension seems to not provide enough informations to anticipate the evolution of the membrane fouling and some complementary methodologies, allowing the characterisation of the environment close to the membrane, have to be developed.

The aim of this work is to study and compare the performances of two immersed membrane bioreactors especially respect to effluent quality for water reuse; one is operating in a sequencing way (MSBR), the other one in a continuous way (MCBR). Organic matter removal and membrane permeability were studied and analysed. The COD removal efficiency was higher for the continuous operation and reached a value — after a period of biomass adaptation — higher than 97% with a COD in the effluent lower than 50 mg/L. The COD removal efficiency was close to 94% with a COD in the effluent lower than 125 mg/L for the sequential operation. The filtration performance was better for the continuous operation, with a nearly constant evolution of transmembrane pressure. In this case the filtration conditions allowed a long time operation period (3600 h) without the requirement of membrane regeneration. The results show better performance for the continuous membrane reactor respect to the organic matter removal and filtration performances. In both systems the quality of water treated was conform to the legislative France constrains (COD < 125 mg/L), but in the context of water reutilization the potential of the continuous system is higher than the sequential one.

The membrane bioreactor (MBR) is based on the combination of a suspended biomass reactor and a separation step on porous membrane filtration. It presents several advantages in terms of water resource protection because of the great quality of the treated water that can be reused as well for irrigation, cleaning or cooling water on industrial site, domestic purposes (e.g. toilet flushing). The quality of the water, notably the absence of solids in suspension and turbidity, allows considering the MBR as a perfect tool for pre-treatment before desalination or preparation of water of very high quality. Moreover, because of its modular property, the MBR may also be favourable for developing a new wastewater network configuration in an urban area.

The aim of this work is to characterize the convective drying aptitude of residual urban sludge in isothermal conditions at atmospheric pressure. Three examples of biological sludge are studied, taken from various wastewater treatments, after mechanical dewatering. Total and volatile solids content, dryness and water content are quantified using standard methodologies. The consistency limits (liquidity and plasticity) are determined using standardized soil mechanics trials based on Atterberg's limits. A desorption unit is used to dehydrate the sludge under controlled humidity (RH ranging from 7% to 96%) at a temperature of 30°C in an immobile drying atmosphere. The influence of relative humidity on dewatering and shrinkage is quantified. The coupled analysis of the dewatering and induced shrinkage curves shows correlations between the hydric and the textural characteristics. Emphasis is placed on the influence on these correlations of the nature of the sludge, characterized by their organic matter content. These results offer a description of the drying and shrinkage aptitudes of biological sludge for a controlled atmospheric drying process.

Organotin compounds (OTs) have been widely used for their biocidal properties and as stabilizers in various industrial applications. Due to their high toxicity, organotins are subject to many studies regarding their behavior in wastewater treatment plant and aquatic environment. However, few studies are available regarding their behavior in lagoon sewage system, although such treatment is commonly used for sewage treatment in low-population areas. The present study aimed at studying the fate of organotins (monobutyltin (MBT), dibutyltin (DBT), and tributyltin (TBT)) in lagoon sewage system. Short-term experiments, carried out at lab scale, consisted in sampling sludge from aerobic stabilization ponds, and then quantifying sorption and desorption of the different organotin species, as well as their respective transformation, under defined operating conditions (e.g., tributyltin spike and dilution) simulating possible change in the surrounding environment of sludge in the lagoon. Results established that a very important percentage of the OTs was localized in the solid phase of the sludge (more than 98 %), whatever the operating conditions may be; however, transformation and locations of the three OT species differed according to the different conditions of sludge dilution, TBT spiking, and test duration. After dilution of lagoon sludge, TBT desorption from sludge was observed; it was supposed that dealkylation of TBT after desorption occurred rapidly and increased dissolved MBT and DBT in liquid phase; MBT sorbed subsequently on solid phase. The nature of the diluent (i.e., tap water or saline solution) appeared to slightly influence the sludge behavior. After TBT spiking, TBT was supposed to be rapidly sorbed but also transformed in DBT and MBT that would as well sorbed on the sludge, which explained the decrease of these species in the liquid phase. Tests aimed at studying long-term effect of TBT spiking demonstrated that the sorbed species could be remobilized and transformed after a dilution.

Cross-flow microfiltration has replaced conventional fining methods for clarifying fruit juices, resulting in the combination of clarification and preservation in one single continuous operation. However the performance of this process is limited by the fouling mechanism during the filtration operation, related to the fruit juice fouling propensity. The aim of this work was to study the possibility of predicting the fruit juices filterability, according to some of their intrinsic characteristics. Therefore, 9 different commercial orange juices were chemically and physicochemically characterized (17 characterization parameters) and laboratory scale filtration tests, in an agitated and pressurized filtration module, were carried out at constant transmembrane pressure (1.5 bar). Fruit juices filterability was evaluated from the permeate flux evolution during the filtration operation. Partial Least Squares (PLS) method was particularly used for the analysis of relationship between the fruit juices filterability and the juice studied characteristics. PLS was initially performed using the whole set of predictor variables. The aim of this first analysis was to highlight the most important juice characteristics among the 17 studied ones; a simplified PLS model was performed using model-wise method and PLS–VIP method as important variable selection procedure. It was possible to predict satisfactorily ( R 2 > 0.9) fruit juices filterability according to only 5 physicochemical characteristics, reflecting the different phases of the studied juices (dry matter, total soluble solids, pH, conductivity, and surface area average diameter).

International audience; The nitrifying/denitrifying activated sludge process removes several micropollutants from wastewater by sorption onto sludge and/or biodegradation. The objective of this paper is to propose and evaluate a lab-scale experimental strategy for the determination of partition coefficient and biodegradation constant for micropollutant with an objective of modelling their removal. Four pharmaceutical compounds (ibuprofen, atenolol, diclofenac and fluoxetine) covering a wide hydrophobicity range (log Kow from 0.16 to 4.51) were chosen. Dissolved and particulate concentrations were monitored for 4 days, inside two reactors working under aerobic and anoxic conditions, and under different substrate feed conditions (biodegradable carbon and nitrogen). We determined the mechanisms responsible for the removal of the target compounds: (i) ibuprofen was biodegraded, mainly under aerobic conditions by cometabolism with biodegradable carbon, whereas anoxic conditions suppressed biodegradation; (ii) atenolol was biodegraded under both aerobic and anoxic conditions (with a higher biodegradation rate under aerobic conditions), and cometabolism with biodegradable carbon was the main mechanism; (iii) diclofenac and fluoxetine were removed by sorption only. Finally, the abilities of our strategy were evaluated by testing the suitability of the parameters for simulating effluent concentrations and removal efficiency at a full-scale plant.

The present study focused on the influence of both hydrodynamic conditions and suspension characteristics on changes in a filtering medium. The results obtained demonstrate (i) airflow increased local turbulence leading to a decrease in the rate of change of TMP, (ii) less biomass was jammed in the lowest fiber density module, that presented systematically the highest fouling rate, (iii) high concentrations of soluble bacterial products in the suspension favored a irreversible marked change in TMP, (iv) the presence of accumulated biomass on the membrane wall appeared to have a beneficial effect, acting like a dynamic membrane in pre-retaining soluble matter.

The aim of this study was to evaluate and quantify the filterability of various defined solutions/suspensions according to their nature and their composition. A laboratory-scale filtration unit with plane organic membranes was used. The fouling potential of different compounds, like bentonite, ferric hydroxide, powdered activated carbon (PAC), latex, humic acid, protein, bacterial compounds, was studied and the filterability of the solutions/suspensions was examined with and without conditioning by ferric chloride and powdered activated carbon addition. Experimental results showed very clearly that the resistance coefficients of mineral suspensions were lower than the ones of organic suspensions in the same conditions of concentration. Suspension conditioning or adsorption, adding ferric chloride or CAP, allowed reducing the membrane fouling due to the soluble and colloidal fractions retention in the particular elements. For bacterial suspensions, adsorption phenomena and particular deposit could explain the fouling observed.

This study shows the changes in transmembrane pressure in a membrane bioreactor (MBR) operating at a constant flux and in well-defined biological conditions. Despite the initial choice of filtration conditions at sub-critical flux, gradual fouling is seen to develop in membrane material which, after long periods of experimentation without intermediary membrane regeneration, proves to be hydraulically irreversible. Thus a single parameter model was set up, whose value could be derived from monitoring the changes in transmembrane pressure. It works on the hypothesis that the open surface is reduced due to a successive blocking of membrane pores. The development of this model has shown that, despite operating conditions held at constant flux, an increase occurs in the rate of circulation in the pores which remain open, which may reach critical local filtration conditions, resulting in the formation of deposits which are reversible but induce an abrupt change in transmembrane pressure.

The aim of this study was to quantify the specific effect of adsorption on membrane fouling during filtration of a membrane bioreactor (MBR) mixed liquor suspension. Adsorption experiments were performed on well-defined protein solutions (β-lactoglobulin solutions) to provide reference results and compare them to those obtained during the filtration of MBR suspensions (raw suspension and settled suspension). Two different methods were used to quantify the role of adsorption in membrane fouling: a “static” method in which membranes were immersed in the biological suspension and a “dynamic” method supposing that the resistance due to adsorption is an irreversible phenomenon that remains after filtration and back-washing. It was shown for the two types of suspensions that (i) due to limited diffusion, the dynamic method appears to be more adapted than the static method; (ii) adsorption is a rapid fouling phenomenon that induces irreversible resistance and that, in frontal mode takes place at the beginning of the operation; (iii) the adsorption phenomenon shows specific hydraulic resistance of the same order of magnitude as the clean membrane resistance; (iv) other phenomena, i.e. progressive pore clogging, can also take place though subcritical hydrodynamic conditions.

A membrane bioreactor used for denitrification of a synthetic substrate was studied in term of membrane fouling. For standard pH and temperature conditions, subcritical conditions were defined to ensure the process stability. The stepwise method was used to determine the critical flux for the deposition of colloidal particles. Under standard physicochemical conditions, only a low and constant fouling resistance was observed if the permeate flux was maintained below the critical flux. The influence of physicochemical variations was then investigated by varying pH and temperature in the biological reactor. It was observed that, when the pH value was higher than a critical one, the membrane was rapidly fouled. This maximum admissible pH value decreased when the temperature increased. On analysing the reversible nature of fouling and the variations of ionic concentrations with the pH, the role of carbonate calcium precipitation was pointed out. By using classical filtration models, it was shown that the fouling mechanism could be the deposition of CaCO3 particles formed in the bulk suspension by bulk crystallisation.

Electrodialysis (ED) is an efficient process for the treatment of drinking water with high nitrate concentration. However it achieves only a transfer of pollution by producing concentrated brines. This study demonstrated the feasibility of ED brine denitrification in a membrane bioreactor (MBR). The results showed the high efficiency of the MBR despite the drastic conditions of nitrate concentration, pH and salinity of the ED concentrates. The denitrification kinetics close to 0.01 mgNO 3 – -N mgVSS –1 h –1 were in agreement with the literature values obtained with usual conditions. Next, the efficiency and performance of the hybrid process to treat ground water contaminated by nitrate was demonstrated in situ at Rodilhan (France). After ED treatment, the nitrate concentration of the treated water remained below the acceptable value (50 mg l –1 ) and a softening of the treated water was obtained. The membrane bioreactor allowed the almost total destruction of ED concentrate nitrate (99 %) with kinetics close to 0.3 kgNO 3 – -N kgVSS –1 d –1 and a sludge production of 0.5 gVSS gNO 3 – .

International audience; Bio-remediation technologies often offer efficiency, cost and environmental impact benefits against physico-chemical technologies. Concerning the remediation of radionuclide-containing water, a few bio-based technologies have been proposed but none is currently operational in highly radioactive environments. A new radio-tolerant micro-alga, isolated from a nuclear facility, possesses properties that offer new decontamination prospects for the nuclear industry or for the clean-up of environmental water. A pilot-scale treatment unit based on this alga is currently under development for the decontamination of radioactive water. It includes separation and/or concentration steps relying on membrane filtration. This work aims at verifying the feasibility of microfiltration as separation step for the targeted algae separation. Recommendations about the choice of operating conditions limiting and/or controlling the membrane fouling are provided with the objective to enhance the separation efficiency. Lab-scale dead-end filtration tests were implemented and the key factors involved in the separation performances were investigated. Membrane characteristics, biomass composition, and hydrodynamic conditions were considered. Organic membranes provided adequate filtration performance. Membrane fouling was essentially induced by a rapid reversible algae deposit and to a lesser extent by irreversible pore blockage caused by smaller particles and dissolved organic matter. To cancel the reversible fouling, hydrodynamic actions such as stirring and back-flush efficiently prevented algae deposit, allowing higher filtration productivity. This study demonstrates the feasibility of membrane separation for micro-algae harvesting at laboratory-scale and specifies the suitable working conditions. (C) 2014 Elsevier B.V. All rights reserved.

Porntip Choksuchart Sridang*, Jansongkod Kaiman, Anthony Pottier, Christelle Wisniewski* Department of Civil Engineering, Faculty of Engineering, Prince of Songkla University, Thailand, 90112 Tel./Fax +(66) 74212891; email: porntip.c@psu.ac.th Faculty of Environmental Management, Prince of Songkla University, Thailand, 90112 Laboratoire de Genie des Procedes et d’Elaboration de Bioproduits, UMR CIRAD 016, Universite Montpellier II, Place Eugene Bataillon, 34095, Montpellier Cedex 05, France email: wisniews@univ-montp2.fr