Transmembrane Pressure Values Research Articles

Sludge bound-EPS solubilization enhance CH4 bioconversion and membrane fouling mitigation in electrochemical anaerobic membrane bioreactor: Insights from continuous operation and interpretable machine learning algorithms

Bound extracellular polymeric substances (EPS) are complex, high-molecular-weight polymer mixtures that play a critical role in pore clogging, foulants adhesion, and fouling layer formation during membrane filtration, owing to their adhesive properties and gelation tendencies. In this study, a novel electrochemical anaerobic membrane bioreactor (EC-AnMBR) was constructed to investigate the effect of sludge bound-EPS solubilization on methane bioconversion and membrane fouling mitigation. During the 150-days’ operation, the EC-AnMBR demonstrated remarkable performance, characterized by an exceptionally low fouling rate (transmembrane pressure (TMP) < 4.0 kPa) and high-quality effluent (COD removal > 98.2 %, protein removal > 97.7 %, and polysaccharide removal > 98.5 %). The highest methane productivity was up to 38.0 ± 3.1 mL/Lreactor/d at the applied voltage of 0.8 V with bound-EPS solubilization, 107.6 % higher than that of the control stage (18.3 ± 2.4 mL/Lreactor/d). Morphological and multiplex fluorescence labeling analyses revealed higher fluorescence intensities of proteins, polysaccharides, total cells and lipids on the surface of the fouling layer. In contrast, the interior exhibited increased compression density and reduced activity, likely attributable to compression effect. Under the synergistic influence of the electric field and bound-EPS solubilization, biomass characteristics exhibited a reduced propensity for membrane fouling. Furthermore, the bio-electrochemical regulation enhanced the electroactivity of microbial aggregates and enriched functional microorganisms, thereby promoting biofilm growth and direct interspecies electron transfer. Additionally, the potential hydrogenotrophic and methylotrophic methanogenesis pathways were enhanced at the cathode and anode surfaces, thereby increasing CH₄ productivity. The random forest-based machine learning model analyzed the nonlinear contributions of EPS characteristics on methane productivity and TMP values, achieving R² values of 0.879 and 0.848, respectively. Shapley additive explanations (SHAP) analysis indicated that S-EPSPS and S-EPSPN were the most critical factors affecting CH₄ productivity and membrane fouling, respectively. Partial dependence plot analysis further verified the marginal and interaction effects of different EPS layers on these outcomes. By combining continuous operation with interpretable machine learning algorithms, this study unveils the intricate impacts of EPS characteristics on methane productivity and membrane fouling behaviors, and provides new insights into sludge bound-EPS solubilization in EC-AnMBR.

Mesoporous silica modified alumina improves pressure stability of supported ionic liquid membranes

Supported liquid membranes (including those containing ionic liquids) offer the opportunity for high selectivity for a target gas imparted by the properties of the functional liquid or liquid mixture, along with high flux resulting from gas permeation through a liquid rather than a solid. One disadvantage of supported liquid membranes is limitations on the transmembrane pressure (TMP) they can sustain. Liquids held in the pores of the support by capillary forces are prone to “blow-out” at relatively modest TMP values. Here, we modify anodic aluminum oxide (AAO) membranes with uniformly sized ∼6–8 nm diameter cylindrical silica mesopores to improve the blow-out TMP. This modification increases the feasible TMP for various ionic liquids from ∼4 bar to more than ∼20 bar. Additionally, the liquid in the membrane at depths where the AAO membrane has not been modified (i.e., greater than a few microns) is expelled from the large pores, reducing the effective thickness of the liquid in the membrane and increasing permeance. This approach is analogous to asymmetric polymeric membranes, which are the standard of the commercial membrane industry. These findings open up the opportunity for investigation and use of supported liquid membranes at much higher TMPs than has been previously possible.

Effect of mechanical scouring on fouling control in greywater filtration with fluidized bed submerged membrane reactor for decentralized wastewater treatment process

Synthetic greywater was applied into a novel, fluidized submerged membrane reactor (FSMR) to compare membrane fouling with three different types of scouring agents: granular activated carbon (GAC), tubular polyvinylidene fluoride (PVDF) media, and spherical polyethylene terephthalate (PET) beads. Trans-membrane pressure (TMP) was investigated to estimate the extent to the fouling in the FSMR operated at 13 and 40 L/m2.h of permeate flux. The selection of scouring agents affected transient behavior of TMP value significantly to reduce membrane fouling. Fluidization of spherical PET beads driven by recirculating bulk suspension only through the FSMR was a prominent way to mitigate fouling. However, the cake layer was formed on membrane surface extensively as GAC or tubular PVDF media was fluidized over the course of reactor operation. At 13 L/m2.h, the TMP reached 0.74, 0.7, and 0.04 bar after 7 d operation with FSMR added with GAC particles, tubular PVDF media, and spherical PET beads as scouring agent, respectively. For the non-adsorbing PET beads, organic compound such as humic acids and proteins were a main organic fraction in cake layer. The organic removal efficiency was enhanced by complex formation resulting from the concentrated greywater in the reactor operated during extended filtration time. However, small carbon particles produced by the pulverization of GAC particles in the FSMR system disrupted fouling control and led rapid TMP rise.

Low-cost ceramic membranes manufacture using INKJET technology for active layer deposition and validation on membrane bioreactors

The fabrication of eco-friendly ceramic membranes based on low-cost raw materials, using digital INKJET printing techniques for active layer deposition and its validation in a membrane bioreactor (MBR) has been studied. The raw materials used in the manufacture of the support layer were UA50/2 clay, chamotte, calcium carbonate and potato starch. A MBR laboratory plant was operated to treat municipal wastewater with three ceramic membranes with different grammages in the selective layer deposition. The membrane performance at laboratory scale was evaluated in terms of transmembrane pressure (TMP) evolution for a constant permeate flux, permeate quality and mixed liquor characteristics. From these experiments, it was selected the membrane which obtained the lowest TMP profile maintaining appropriate water quality parameters (chemical oxygen demand (COD) removal percentage around 90% and turbidity around 0.06 NTU). This membrane was also operated at pilot plant scale in order to validate it at higher scale. Results indicated that TMP values were in the range of 0.06 and 0.1 bar, COD removal percentage was around 98% and microbiology analysis demonstrated that the quality of the effluent, according to European regulation 2020/741, can be classified as Class A and it can be reused for non-potable purposes.

Skimmed milk microfiltration in diafiltration mode: Impact of solvent nature and concentration factor on spiral-wound membrane performance operated at low temperature

Cold skimmed milk microfiltration using polymeric spiral-wound membranes has a growing interest to separate serum proteins from casein micelles. Diafiltration using reverse osmosis water (ROW-DF) is needed to increase the transmission of serum proteins. The objective of this study was to investigate the performance of skimmed milk microfiltration in ROW-DF mode when operating with single industrially sized standard SW modules at low temperature (∼12 °C). As expected during ROW-DF, the permeation flux increased with the rate of diafiltration, due to both the decrease of permeate viscosity and decrease of ionic strength. It is shown for the first time, that the transmission of protein (mainly β-Lactoglobulin, β-LG, major serum protein of bovine milk) presents different scenarios (increase, decrease and ‘parabolic’ shape) as function of diafiltration rate and operating conditions. These performances are quite different from the ones obtained when operating diafiltration with permeate from milk ultrafiltration, PUF-DF, and can be explained by the modifications induced by ROW on the properties of the fluid (feed) and on the properties of the concentrated layers of casein micelles accumulated at the membrane. The quantity of β-LG which can be released into the permeate was linked to the concentration factor applied before ROW-DF and the ability of deposit to swell was linked to the transmembrane pressure applied as critical conditions could lead to a cohesive deposit unable to swell. If the increase of repulsive electrostatic interactions (induced by the increase of diafiltration rate) between casein micelles and β-LG supported the release of β-LG entrapped in the deposit, it impaired the crossing of β-LG remaining in the retentate. The result was a progressive decrease of β-LG transmission with the increasing diafiltration rate. In summary, transmission of β-LG was maximized for low value of transmembrane pressure (0.7 bar), a high value of concentration factor (3.2) and an intermediate diafiltration rate (2.1).

Performance evaluation of an industrial ceramic nanofiltration unit for wastewater treatment in oil production

An industrial ceramic nanofiltration membrane (pore size 0.9 nm) was tested in a Canadian oil field for more than 12,500 h to treat wastewater directly from daily operations, without any type of pre-treatment. This wastewater contained a high content of total suspended solids (13 to 510 mg/kg), and total organic carbon (31 to 134 mg/kg). The membrane unit was operated at different transmembrane pressure (TMP) set points (4–16 bar) and recovery set points (40–80%). The data show that ion and compound rejection depend strongly on a combination of both TMP and recovery, with the largest rejection occurring at low recovery values and high TMP values. Two mechanisms were responsible for rejection: sieving, which mostly impacted compound rejection, and electrostatic phenomena that impacted ion rejection. It is shown that ion rejection depends linearly on charge density of the ion. Ion rejection was measured as high as 85% and compounds (such as TSS) were rejected as high as 100%. The specific flux varied between 1–10 L/(m2.h.bar). Results from this field testing indicate the possibility of using these types of ceramic membranes for oil field wastewater treatment.

Coupling anaerobic fluidized membrane bioreactors with microbial electrolysis cells towards improved wastewater reuse and energy recovery

Anaerobic Membrane Bioreactors (AnMBRs) combine the advantages of anaerobic processes and MBR technology to improve effluent quality and energy recovery. However, these systems are associated with operational challenges such as membrane fouling and loss of dissolved methane that increases operation and energy expenses. In this study, a new configuration was developed combining AnMBRs with Microbial Electrolysis Cells (MECs). The effectiveness of the coupled AnFMBR-MEC system was tested by monitoring several indicators during the treatment of synthetic wastewater. The new configuration exhibited a 25-day shorter startup period, a 56% enhanced average methane yield, and a reduced membrane fouling with a maximum transmembrane pressure value nearly 6.5 folds lower than that exhibited by the AnFMBR alone. AnFMBR-MEC had an average CE of 40% and both reactors achieved around 90% COD removal. Similar bacterial communities existed in both reactors but with different relative abundance and localization. In the AnFMBR-MEC, the Direct Interspecies Electron Transfer was the likely dominant route for acetate consumption due to the abundance of Geobacter and Methanosarcina on the granular activated carbon and in suspension. The new system offers a promising technology with less fouling and improved resource recovery from wastewater due to the presence of different environmental niches (GAC, anode, cathode) for microbial colonization and growth, which resulted in the reduction of biomass in suspension and the proliferation of electroactive bacteria and methanogens as biofilms.

Treatment of Wastewater from a Food and Beverage Industry Using Conventional Wastewater Treatment Integrated with Membrane Bioreactor System: A Pilot-Scale Case Study.

This study compares the performance of the Hollow Fiber (HF) and Flat Sheet (FS) types of membrane bioreactors (MBRs) for the treatment of food and beverage (F&B) industry wastewater in a pilot-scale study of a wastewater treatment plant (WWTP). HF and FS membrane configurations were evaluated at two different Mixed Liquor Suspended Solid (MLSS) levels: 6000 mg/L and 12,000 mg/L. The performance of each configuration was evaluated in terms of Chemical Oxygen Demand (COD) and Total Suspended Solid (TSS) removals for effluent quality measurement. The transmembrane pressure (TMP), flux rate, and silt density index (SDI) were monitored and calculated for membrane fouling assessment. The results show that the rejection rates of COD and TSS for HF and FS membrane types were more than 84% for the two different MLSS levels. During the study, the HF membrane recorded 0.3 bar transmembrane pressure, which complies with the recommended range (i.e., two to three times of chemical cleaning). On the other hand, the FS membrane operates without chemical cleaning, and the TMP value was below the recommended range at 0.2 bar. It was found that the flux values recorded for both the HF and FS systems were within the recommended range of 40 L/m2/h. Analysis of SDI revealed that the calculated index ranged between 1 and 2.38 and was within the allowable limit of 3. Both types of MBR consistently achieved an 80% to 95% rejection rate of COD and TSS. Effluent quality measurement of treated F&B wastewater in this pilot-scale study using a WWTP integrated with an MBR indicated a good achievement with compliance with the Malaysia industrial effluent discharge standards.

Nitrogen Removal Using a Membrane Bioreactor with Rubber Particles as the Fouling Reducer

The use of granule activated carbon (GAC) and rubber particles as the bio-fouling reducer in a membrane bioreactor (MBR) was evaluated in this study. The addition of GAC tends to temporarily reduce Transmembrane Pressure (TMP). Then, after the initial reduction, TMP gradually increased back up to 0.7 bar, indicating significant fouling on the membrane. Low TMP values were observed after adding 0.5% (V/V) rubber particles to the same MBR. The organic compound and nitrogen removal efficiencies of the MBR under intermittent aeration were over 94% and 93.3%, respectively. The results showed that Dysgonomonas, Acidobacteria, and Pantoea sp. contributed to the nitrification process while Lactobacillus, Erythrobacter, Phytobacter, and Mycobacterium contributed to the denitrification process.

Evaluation of concentration process of bovine, goat and buffalo whey proteins by ultrafiltration.

In this research, the protein concentration, the permeate flux, and the predominant fouling mechanisms were investigated during ultrafiltration of different whey samples. The research was carried out at different values of transmembrane pressure and temperature using an experimental design, and a protein concentration of approximately 37gL-1 was obtained for the bovine whey powder solution, at 60kPa and 40°C. The maximum flux observed was 8.9 and 7.9kgm-2h-1, respectively, for the bovine whey powder solution and bovine whey, at 50kPa and 30°C. Although goat and buffalo whey presented lower permeate flux, probably due to high solutes and calcium contents, protein concentrates of around 40gL-1 were obtained using the ultrafiltration process. This demonstrates the potential of ultrafiltration to obtain non-bovine protein concentrates. The best fit,verified by Ho and Zydney model, suggests that the fouling for all analyzed whey occurs due to pore blocking and subsequent deposit on the membrane surface.

Fluid–Structure Interaction and Flow Redistribution in Membrane-Bounded Channels

The hydrodynamics of electrodialysis and reverse electrodialysis is commonly studied by neglecting membrane deformation caused by transmembrane pressure (TMP). However, large frictional pressure drops and differences in fluid velocity or physical properties in adjacent channels may lead to significant TMP values. In previous works, we conducted one-way coupled structural-CFD simulations at the scale of one periodic unit of a profiled membrane/channel assembly and computed its deformation and frictional characteristics as functions of TMP. In this work, a novel fluid–structure interaction model is presented, which predicts, at the channel pair scale, the changes in flow distribution associated with membrane deformations. The continuity and Darcy equations are solved in two adjacent channels by treating them as porous media and using the previous CFD results to express their hydraulic permeability as a function of the local TMP. Results are presented for square stacks of 0.6-m sides in cross and counter flow at superficial velocities of 1 to 10 cm/s. At low velocities, the corresponding low TMP does not significantly affect the flow distribution. As the velocity increases, the larger membrane deformation causes significant fluid redistribution. In the cross flow, the departure of the local superficial velocity from a mean value of 10 cm/s ranges between −27% and +39%.

Artificial neural network modeling and optimization of wheat starch suspension microfiltration using twisted tape as a turbulence promoter

The aim of this study was the modeling and optimization of the turbulence promoter-assisted starch suspension microfiltration process using artificial neural networks. The main aim was to analyze the influence of process parameters (transmembrane pressure, suspension flow rate, and concentration) on permeate flux (with and without twisted tape) and energy consumption in order to find the optimal combination of process parameters needed for the efficient use of the turbulence promoter. The obtained results showed a very good agreement between artificial neural network predictions and experimental data. Permeate flux was mostly influenced by suspension concentration, while the suspension flow rate had the highest impact on the reduction of the specific energy consumption. Performed optimization, using a genetic algorithm, indicated that microfiltration process should be carried out at the maximum value of transmembrane pressure (0.9 bar), at a suspension flow rate in the range from 80 to 93 L/hr, and at a suspension concentration of 5 g/L. Practical applications Practical application of this research presents the possibility for the wastewater treatment in the wheat starch processing industry that produces a significant amount of wastewater annually, mainly consisting of starch. Adequate treatment of wastewater can recover water-soluble and partly suspended substances from the raw material and at the same time, recycle and purify wastewater prior to releasing to the ecosystem. In the last decades, cross-flow microfiltration has shown many advantages in wastewater treatment operations comparing to conventional methods. In this research, cross-flow microfiltration with twisted tape, as a turbulence promoter, is chosen in order to achieve higher values of permeate flux, simultaneously, by paying attention on energy efficiency. The multi-response optimization, performed by applying the genetic algorithm, enables the determination of process parameters necessary for the accomplishment of economic and cost-effective microfiltration process.

On the design of sustainable antifouling system for the crossflow filtration of oily water systems: A multicontinuum and CFD investigation of the periodic feed pressure technique

The problem of fouling is considered a major reason for deteriorating the performance of porous membranes. Even though the accumulations of materials at the membrane surface are inevitable, efforts are continuously spent to minimize their drawbacks. Several techniques have been tested to minimize the problem of fouling. Some of these methods, however, confront some technical difficulties that make their use unfeasible. For example, in polymeric-type membranes, back flushing may result in the loss of bonding between the active and the support layers resulting thereby to the disintegration of the membrane. Recently, an interestingly new approach has been proposed that minimizes the problem of fouling and maintains the integrity of the membrane. The so-called periodic feed pressure technique, PFPT, cleans the surface of the membrane by reducing the adherence of the droplets to the membrane giving the chance to the crossflow field to sweep off pinned droplets. In this work, some of the features of the PFPT technique are highlighted using results from CFD simulation. Then we further investigate the PFPT technique in the realm of the multicontinuum modeling approach in which both the emulsion and the membrane are treated as overlapping continua. The behavior of the membrane is studied considering different transmembrane pressure values to highlight the fates of the different oil continua upon interacting with membrane continua. From the CFD highlights, it is found that during the half cycle when the TMP is set to zero, oil droplets at the surface of the membrane becomes unstable and it becomes easier for the crossflow field to dislodge them. The multicontinuum study, on the other hand, provides macroscopic analysis on the effects of different TMP cycles on important macroscopic parameters that influence the design, including the rejection capacity of membranes.

Differential ATR FTIR spectroscopy of membrane fouling: Contributions of the substrate/fouling films and correlations with transmembrane pressure

This study examined the formation of fouling films deposited on the surface of a polyethersulfone (PES) membrane during the filtration of alginate solutions with various ionic strengths. Membrane fouling was characterized by changes of the transmembrane pressure (TMP) and ex situ measured attenuated total reflectance (ATR) Fourier-transform IR (FTIR) spectra at varying stages of filtration runs. The ATR spectra that comprise the vibration bands characteristic of the PES substrate and the deposited film were processed taking into the gradual weakening of the PES substrate-specific bands, whose intensity was shown to depend on the wavenumber of IR radiation and the thickness of the deposited layer. Strongly linear correlations between ratios of first derivatives intensity and wavenumbers of the PES reference lines were established. Calculations of the PES bands’ attenuation coefficients allowed determining the apparent thickness and ATR FTIR vibrations of the fouling films per se. Strong correlations between TMP development and ATR-determined apparent thickness of the fouling layers were observed. The intensity of ATR absorbance at 3200 cm−1 was linearly correlated with TMP development for small TMP values before the point of rapidly developing failure of the hydraulic permeability of the system was reached.

Measuring intradialyser transmembrane and hydrostatic pressures: pitfalls and relevance in haemodialysis and haemodiafiltration.

BackgroundPost-dilutional haemodiafiltration (HDF) with high convection volumes (HCVs) could improve survival. HCV-HDF requires a significant pressure to be applied to the dialyser membrane. The aim of this study was to assess the pressure applied to the dialysers in HCV-HDF, evaluate the influence of transmembrane pressure (TMP) calculation methods on TMP values and check how they relate to the safety limits proposed by guidelines.Methods Nine stable dialysis patients were treated with post-dilutional HCV-HDF with three different convection volumes [including haemodialysis (HD)]. The pressures at blood inlet (Bi), blood outlet (Bo) and dialysate outlet (Do) were continuously recorded. TMP was calculated using two pressures (TMP2: Bo, Do) or three pressures (TMP3: Bo, Do, Bi). Dialysis parameters were analysed at the start of the session and at the end of treatment or at the first occurrence of a manual intervention to decrease convection due to TMP alarms.ResultsDuring HD sessions, TMP2 and TMP3 remained stable. During HCV-HDF, TMP2 remained stable while TMP3 clearly increased. For the same condition, TMP3 could be 3-fold greater than TMP2. This shows that the TMP limit of 300 mmHg as recommended by guidelines could have different effects according to the TMP calculation method. In HCV-HDF, the pressure at the Bi increased over time and exceeded the safety limits of 600 mmHg provided by the manufacturer, even when respecting TMP safety limits.ConclusionsThis study draws our attention to the dangers of using a two-pressure points TMP calculation, particularly when performing HCV-HDF.

Membrane Deformation and Its Effects on Flow and Mass Transfer in the Electromembrane Processes.

In the membrane processes, a trans-membrane pressure (TMP) may arise due to design features or operating conditions. In most applications, stacks for electrodialysis (ED) or reverse electrodialysis (RED) operate at low TMP (<0.1 bar); however, large stacks with non-parallel flow patterns and/or asymmetric configurations can exhibit higher TMP values, causing membrane deformations and changes in fluid dynamics and transport phenomena. In this work, integrated mechanical and fluid dynamics simulations were performed to investigate the TMP effects on deformation, flow and mass transfer for a profiled membrane-fluid channel system with geometrical and mechanical features and fluid velocities representative of ED/RED conditions. First, a conservatively high value of TMP was assumed, and mechanical simulations were conducted to identify the geometry with the largest pitch to height ratio still able to bear this load without exhibiting a contact between opposite membranes. The selected geometry was then investigated under expansion and compression conditions in a TMP range encompassing most practical applications. Finally, friction and mass transfer coefficients in the deformed channel were predicted by computational fluid dynamics. Significant effects of membrane deformation were observed: friction and mass transfer coefficients increased in the compressed channel, while they decreased (though to a lesser extent) in the expanded channel.

Application of asymmetric Si3N4 hollow fiber membrane for cross-flow microfiltration of oily waste water

The asymmetric morphology of silicon nitride (Si3N4) ceramic hollow fiber membrane with a selective spongiform outer layer was optimized by the air gap distance and the internal rate of coagulate for oil/water emulsion microfiltration. The effect of trans-membrane pressure (TMP), feed flow rate (FFR), and pH of the feeding emulsion on the separation performance were determined experimentally. Membrane fouling has increased by dissociation of oil droplets during filtration at high TMP and FFR values. Fouling phenomena were studied based on standard pore blocking model. The pH by affecting the surface charge of the Si3N4 hollow fibers and zeta potential of the feed emulsion has also been introduced as a prominent influential factor on separation efficiency. The highest values of permeate flux (390 Lm−2h-1) and oil rejection (95%) were recorded in alkaline pH. The fabricated Si3N4 ceramic membranes were completely recovered (≤99%) by simple thermal treatment at 400 °C.

A crucial factor towards a sustainable process for municipal wastewater treatment: Fouling effects of different statuses of biomass in the membrane bioreactors with no sludge discharge

Abstract This work aimed at illustrating a crucial factor towards a sustainable municipal wastewater treatment process, namely, the membrane fouling caused by different statuses of biomass in the membrane bioreactors (MBRs) with no sludge discharge, and tried to explore the essential reasons leading to membrane fouling. By parallelly operating the MBRs with or without bio-carriers for 90 days under the same conditions, their operating characteristics and the accumulated membrane foulants were comparatively studied by using multi-methods. The results indicated that the added bio-carriers mitigated the membrane fouling, especially inhibited the formation of the reversible and the permanent resistance of membrane modules, and reduced the accumulation of foulants on membrane surface. When the trans-membrane pressure value of the bioreactor with bio-carriers reached 32.5 kPa for the first time, the trans-membrane pressure value of the bioreactor without bio-carriers had reached 32.5 kPa for the third time. The growing status of biomass was changed by the bio-carriers, which influenced the micro-habitat of microorganisms and varied the structure of microbial communities within the MBRs. The variation of the growing status of biomass is an essential reason leading to exhibiting differences in the membrane fouling of these MBRs.

Dynamic cross-flow electro-Fenton process coupled to anodic oxidation for wastewater treatment: Application to the degradation of acetaminophen

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

Influence of the Backwash Cleaning Water Temperature on the Membrane Performance in a Pilot SMBR Unit

In this work, different backwash (BW) schemes were applied on identical hollow fiber (HF) membranes in a membrane bioreactor (MBR) treating municipal wastewater. The effect of BW duration (1 min, 3 min and 8 min) and water temperature (8 °C, 18 °C, 28 °C and 38 °C) on membrane fouling were investigated. Specifically, the transmembrane pressure (TMP) drop and the membrane permeability increase caused by the BW was investigated. Furthermore, the time required for the membrane to return to the state just before each BW experiment, was also examined. It was found that membranes presented better operating performance, as the BW temperature and the backwash duration were increased. Specifically, for 1 min backwash duration at the BW temperatures of 8 °C, 18 °C, 28 °C and 38 °C, TMP decreased by 7.1%, 8.7%, 11.2% and 14.2% respectively. For 8 min BW duration at 8 °C, 18 °C, 28 °C and 38 °C, TMP values decreased by 12%, 17.5%, 23.7% and 30.2% respectively. Increased BW water temperature and duration also improved the membrane permeability. Using higher BW water temperatures, more hours were required to return the membranes to the condition just before cleaning. The selected BW water temperatures did not adversely affect the permeate quality.