Tertiary treatment combining nanofiltration and electrochemical oxidation for elimination of pharmaceuticals in wastewater

Le couplage de la nanofiltration et de l'oxydation électrochimique est étudié pour le traitement tertiaire des eaux usées de l'hôpital après leur traitement par bioréacteur à membrane. L'efficacité de la nanofiltration est fortement influencée par le colmatage. Afin d'assurer des flux durables et des performances élevées lors de l'étape de nanofiltration, les mécanismes de colmatage sont étudiés. Les flux critique et limite sont déterminés et liés à l'effet combiné du colmatage colloïdal organique et du dépôt inorganique. L'impact de la couche de colmatage et de la présence de matières organiques dans la matrice sur la rétention des produits pharmaceutiques est également évalué. Le rétentat de la nanofiltration est ensuite traité par oxydation électrochimique sur une anode BDD. L'influence des conditions opératoires et la compétition lors de l'oxydation des constituants au sein du réacteur sont évaluées. Au lieu d'être rédhibitoire au bon fonctionnement du procédé, la présence des ions et des composés organiques dans le concentrat peut accélérer la dégradation des produits pharmaceutiques. En particulier, la formation de composés organohalogénés due à la présence de chlorure peut être contrôlée par le choix de conditions opératoires appropriées. Un modèle décrivant la dégradation des produits pharmaceutiques en fonction du temps d'électrooxydation est établi. Un des objectifs est d'accéder au meilleur compromis entre la minéralisation des produits pharmaceutiques et la consommation d'énergie. Après optimisation des conditions opératoires des 2 procédés, il est démontré que leur couplage est efficace pour l'élimination de produits pharmaceutiques et la diminution de la toxicité de l'effluent, permettant d'envisager son rejet dans l'environnement ou sa réutilisation.The coupling of nanofiltration and electrochemical oxidation is studied for the tertiary treatment of hospital wastewater after membrane bioreactor treatment. The effectiveness of nanofiltration is greatly affected by membrane fouling. In order to ensure sustainable flux and high performances during nanofiltration step, fouling mechanisms are investigated. The critical flux and the limiting flux are determined and associated with the combined effect of the organic colloidal fouling and the scaling. Impact of the fouling layer and of the presence of organic matters in the matrix on pharmaceuticals rejection is also investigated. NF retentate is then treated by electrochemical oxidation on BDD anode. The influence of operating conditions and the competition between components oxidation in the reactor are studied. Rather than a hindering effect, the presence of ions and common organics in the concentrate can accelerate the degradation of pharmaceuticals. In particular, the formation of organohalogens due to the presence of chloride can be controlled thanks to the choice of appropriate operating conditions. A model for the degradation of pharmaceuticals over electrooxidation time is established. One objective is to access to the best compromise between mineralization of pharmaceuticals and energy consumption. After optimization of the operating conditions of both processes, their coupling is confirmed to be efficient for the elimination of pharmaceuticals and the reduction of the toxicity of the effluent, allowing to consider its release into the environment or its reuse

On the role of salts for the treatment of wastewaters containing pharmaceuticals by electrochemical oxidation using a boron doped diamond anode

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

An experimental and modelling study of the electrochemical oxidation of pharmaceuticals using a boron-doped diamond anode

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

Feasibility of a heterogeneous Fenton membrane reactor containing a Fe-ZSM5 catalyst for pharmaceuticals degradation: Membrane fouling control and long-term stability

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

Nanofiltration performances after membrane bioreactor for hospital wastewater treatment: Fouling mechanisms and the quantitative link between stable fluxes and the water matrix

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

Fouling control using critical, threshold and limiting fluxes concepts for cross-flow NF of a complex matrix: Membrane BioReactor effluent

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

Feasibility of Micropollutants Treatment by Coupling Nanofiltration and Electrochemical Oxidation: Case of Hospital Wastewater

In spite of good performances of the membrane bioreactor (MBR) process, permeate from it can still con- tain 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 technolo- gies, which are nanofiltration (NF) and electrochemical oxidation (EO) to treat MBR effluent from hospital waste- water. 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 cipro- floxacin, 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 demon- strated 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

Traitement tertiaire couplant nanofiltration et oxydation électrochimique pour l'élimination des produits pharmaceutiques présents dans les eaux usées

Le couplage de la nanofiltration et de l'oxydation électrochimique est étudié pour le traitement tertiaire des eaux usées de l'hôpital après leur traitement par bioréacteur à membrane. L'efficacité de la nanofiltration est fortement influencée par le colmatage. Afin d'assurer des flux durables et des performances élevées lors de l'étape de nanofiltration, les mécanismes de colmatage sont étudiés. Les flux critique et limite sont déterminés et liés à l'effet combiné du colmatage colloïdal organique et du dépôt inorganique. L'impact de la couche de colmatage et de la présence de matières organiques dans la matrice sur la rétention des produits pharmaceutiques est également évalué. Le rétentat de la nanofiltration est ensuite traité par oxydation électrochimique sur une anode BDD. L'influence des conditions opératoires et la compétition lors de l'oxydation des constituants au sein du réacteur sont évaluées. Au lieu d'être rédhibitoire au bon fonctionnement du procédé, la présence des ions et des composés organiques dans le concentrat peut accélérer la dégradation des produits pharmaceutiques. En particulier, la formation de composés organohalogénés due à la présence de chlorure peut être contrôlée par le choix de conditions opératoires appropriées. Un modèle décrivant la dégradation des produits pharmaceutiques en fonction du temps d'électrooxydation est établi. Un des objectifs est d'accéder au meilleur compromis entre la minéralisation des produits pharmaceutiques et la consommation d'énergie. Après optimisation des conditions opératoires des 2 procédés, il est démontré que leur couplage est efficace pour l'élimination de produits pharmaceutiques et la diminution de la toxicité de l'effluent, permettant d'envisager son rejet dans l'environnement ou sa réutilisation.The coupling of nanofiltration and electrochemical oxidation is studied for the tertiary treatment of hospital wastewater after membrane bioreactor treatment. The effectiveness of nanofiltration is greatly affected by membrane fouling. In order to ensure sustainable flux and high performances during nanofiltration step, fouling mechanisms are investigated. The critical flux and the limiting flux are determined and associated with the combined effect of the organic colloidal fouling and the scaling. Impact of the fouling layer and of the presence of organic matters in the matrix on pharmaceuticals rejection is also investigated. NF retentate is then treated by electrochemical oxidation on BDD anode. The influence of operating conditions and the competition between components oxidation in the reactor are studied. Rather than a hindering effect, the presence of ions and common organics in the concentrate can accelerate the degradation of pharmaceuticals. In particular, the formation of organohalogens due to the presence of chloride can be controlled thanks to the choice of appropriate operating conditions. A model for the degradation of pharmaceuticals over electrooxidation time is established. One objective is to access to the best compromise between mineralization of pharmaceuticals and energy consumption. After optimization of the operating conditions of both processes, their coupling is confirmed to be efficient for the elimination of pharmaceuticals and the reduction of the toxicity of the effluent, allowing to consider its release into the environment or its reuse

Figure S9 from Phospholipase PLCE1 Promotes Transcription and Phosphorylation of MCM7 to Drive Tumor Progression in Esophageal Cancer

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Figure S5 from Phospholipase PLCE1 Promotes Transcription and Phosphorylation of MCM7 to Drive Tumor Progression in Esophageal Cancer

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