L/m2/h Research Articles

Integrated System of Reverse Osmosis and Forward Pressure-Assisted Osmosis from ZrO2 Base Polymer Membranes for Desalination Technology

In this work, reverse osmosis and forward osmosis membranes were prepared using base cellulosic polymers with ZrO2. The prepared membranes were rolled on the spiral-wound configuration module. The modules were tested on a pilot unit to investigate the efficiency of the RO membrane and the hydraulic pressure effect on both sides of the FO membranes. The RO membrane provided a rejection of 99% for the seawater desalination, and the brine was used as a draw solution for the FO system. First, seawater was used as a draw solution to indicate the best hydraulic pressure, where the best one was 3 bar for the draw solution side, and 2 bar for the feed side, where the water flux reached 48.89 L/m2·h (LMH) with a dilution percentage of 80% and a low salt reverse flux of 0.128 g/m2·h (gMH) after 5 h of operation time. The integrated system of RO and forward-assisted osmosis (PAO) was investigated using river water as a feed and RO brine as a draw solute, where the results of PAO indicate a high-water flux of 68.6 LMH with a dilution of 93.2% and a salt reverse flux of 0.18 gMH. Therefore, using PAO improves the performance of the system.

A Novel Modeling Optimization Approach for a Seven-Channel Titania Ceramic Membrane in an Oily Wastewater Filtration System Based on Experimentation, Full Factorial Design, and Machine Learning.

This comprehensive study looks at how operational conditions affect the performance of a novel seven-channel titania ceramic ultrafiltration membrane for the treatment of produced water. A full factorial design experiment (23) was conducted to study the effect of the cross-flow operating factors on the membrane permeate flux decline and the overall permeate volume. Eleven experimental runs were performed for three important process operating variables: transmembrane pressure (TMP), crossflow velocity (CFV), and filtration time (FT). Steady final membrane fluxes and permeate volumes were recorded for each experimental run. Under the optimized conditions (1.5 bar, 1 m/s, and 2 h), the membrane performance index demonstrated an oil rejection rate of 99%, a flux of 297 L/m2·h (LMH), a 38% overall initial flux decline, and a total permeate volume of 8.14 L. The regression models used for the steady-state membrane permeate flux decline and overall permeate volume led to the highest goodness of fit to the experimental data with a correlation coefficient of 0.999. A Multiple Linear Regression method and an Artificial Neural Network approach were also employed to model the experimental membrane permeate flux decline and analyze the impact of the operating conditions on membrane performance. The predictions of the Gaussian regression and the Levenberg-Marquardt backpropagation method were validated with a determination coefficient of 99% and a Mean Square Error of 0.07.

Highly permeable and shelf-stable aquaporin biomimetic membrane based on an anodic aluminum oxide substrate

Aquaporin (AQP) biomimetic membranes are a coming-of-age technology for water purification. Although several studies have reported aquaporin biomimetic membrane fabrication to date, these membranes show low water flux mainly due to the low porosity and inherently dense structure of the polymeric substrate materials. Herein, we report a ceramic-based aquaporin biomimetic membrane based on anodic aluminum oxide (AAO) as a substrate, which has a uniform porous structure with a high aspect ratio and pore density compared to conventional polymer substrates and exhibits a high water flux of 27.6 ± 3.6 LMH (L m−2 h−1) and superior membrane selectivity of 0.11 g L−1. Briefly, the AAO substrate was functionalized with amino-silane followed by polydopamine coating, then the AQP vesicles were immobilized on the functionalized AAO substrate surface using an electrokinetic method, and the water rejection performance of the membrane was analyzed in a forward osmosis system. Furthermore, a simple cryodesiccation method is introduced to improve the storage stability and easy transportation of aquaporin membranes, which does not require special environmental conditions to transport or store them.

Direct Membrane Filtration of Wastewater: A Comparison between Real and Synthetic Wastewater

In this study, a lab scale direct membrane filtration (DMF) system using ultrafiltration membranes was operated to compare synthetic and real wastewater to evaluate their membrane fouling propensity and the partitioning of organics and nutrients during concentration. For fouling prevention, cyclic operation was used which consisted of 90 s of filtration followed by 15 s of relaxation and backwashing conducted every 15 min. The system was tested at a high initial flux of 80 LMH (L/m2·h), and the trials were run until a 90% volume reduction was achieved for each batch. Both the synthetic and real wastewater showed similar fouling propensities and organic and nutrient partitioning. The synthetic and real wastewater had an average flux of 46.3 LMH and 28.5 LMH and an average total chemical oxygen demand rejection of 90.3% and 83.1% after 30 h of operation, respectively. The recovery of organics was similar in both influents, resulting in 65.5% and 64.0% of the total chemical oxygen demand concentrations in the concentrate stream for synthetic and real wastewaters, respectively. The total phosphorous and nitrogen concentrations were also similar in terms of rejection rates resulting in 85% and 78% for the synthetic and 89% and 65% for the fresh WWs, respectively. The comparison revealed that synthetic wastewater, though not identical to real wastewater, can serve as a surrogate in DMF studies. This will help to remove one of the key sources of variability in current DMF studies and will allow for more rapid development of DMF technology.

Enhanced methanogenic degradation and membrane fouling associated with protein-EPS by extending sludge retention time in a high-solid anaerobic membrane bioreactor treating concentrated organic sludge

The improvement of organic sludge destruction efficiency and methanogenic performance is a key concern during anaerobic digestion toward maximum energy recovery. In this study, a high-solid anaerobic membrane bioreactor (AnMBR) was operated continuously for the treatment of organic sludge from Japanese small-scale collective wastewater treatment facility (Johkasou), and digestion efficiency was enhanced by the optimizing solid retention time (SRT). Degradation efficiency of the substrate improved from 36 % to 52 % and the biogas yield was enhanced from 0.37 to 0.51 L/g-VSfed when the SRT was extended from 30 to 60 d. The net energy yield of AnMBR at SRT 60 days was 9.83 kJ/g-VSfed, and the corresponding energy sufficiency ratio was 181 %, indicating that SRT extension could enhance substrate destruction with significant energy recovery potential. However, a long SRT is characterized by high mixed liquor total solids (MLTS), small particle size, high extracellular polymeric substances content, and poor filterability, which exert detrimental effects on membrane operation. Membrane fouling was effectively controlled by regulating the flux at a sustainable rate. The low fouling region and transition region of operating flux were determined as 0.21–4.6 L/m2/h (LMH) and 1.5–5.7 LMH, respectively, when MLTS was 25–50 g/L, and the main contributors to membrane fouling were high protein fractions and small sludge flocs. The current study proposes a promising method to promote digestion efficiency and provided adequate guidance for membrane operation at super-high MLTS by presenting practical engineering applications of AnMBRs in solid waste treatment.

Cross-flow separation characteristics and piloting of graphene oxide nanofiltration membrane sheets and tubes for kraft black liquor concentration

Dewatering of weak black liquor (WBL) in the kraft cycle by evaporation is highly energy intensive. Membranes are an attractive alternative for energy-efficient dewatering, but existing commercial polymeric or ceramic membranes are either degraded in BL or have high capital costs. Our recent works have demonstrated the engineering of graphene oxide (GO) nanofiltration membranes, their stability and promising performance in BL conditions, and preliminary scale-up into sheets and tubes. Here, we describe in detail the separation characteristics of GO membrane sheets and tubes under real BL conditions and crossflow operation. Recycle-mode piloting of a GO tubular membrane showed average “production flux” of 16 L/m2/h (LMH) and high rejections of lignin (98.3%), total solids (66%), and total organic carbon (83%), with no signs of irreversible fouling identified. A corresponding GO sheet membrane produced an average flux of ~25 LMH and maintained high lignin rejection of ~97% during a slipstream pilot at a kraft mill site using WBL with ~16 wt% total solids (TS). Finally, we piloted a Dow/DuPont XUS1808 polyamide composite reverse osmosis (RO) membrane for last-mile processing of the GO nanofiltration membrane permeate. The RO membrane showed a steady state flux of 19 LMH at 65 bar and produced ~0.02 wt% TS water product, which is highly suitable for reuse in pulp washing operations in the kraft process. The results have strong positive implications for the industrial application of GO membranes in BL concentration and other related applications.

Novel sodium and potassium carbon quantum dots as forward osmosis draw solutes: Synthesis, characterization and performance testing

Novel draw solutes based on potassium- and modified sodium-functionalized carbon quantum dots (K-CQDs and Na-CQDs) were prepared for seawater desalination. The characteristics of draw solutes were determined using Fourier Transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray (EDX) spectroscopy, and thermal gravimetric analysis (TGA). The results of the FO system with K-CQDs and deionized water (DI) as a feed revealed a high water flux of 10.94–13.924 L/m2.h (LMH), very low reverse solute flux of 0.0161–0.0253 g/m2.h (gMH), and specific reverse solute flux of 0.0015–0.0018 at a concentration of 0.3–0.5 g/mL. The water flux of K-CQDs at a concentration of (0.3–0.5) g/mL for seawater and 0.5 g/mL for Real Persian Gulf (RPG) water (Arabian Gulf) was (3.779–5.371) LMH and 6.1662 LMH, respectively. For Na-CQDs with DI, the obtained water flux, reverse solute flux, and specific reverse solute flux were 10.3433–11.935 LMH, 0.0414–0.0621 gMH of 0.004–0.0052, respectively at a concentration of 0.3–0.5 g/mL at 29 °C. The fluxes of synthetic seawater and RPG with K-CQDs and Na-CQDs were 5.37 and 6.16 LMH and 2.78 and 3.78 LMH, respectively, at CQDs concentration of 0.5 g/mL. The stability test showed that there was only a slight decrease in the flux of 2 % after three-cycle of FO operations with K-CQDs.

Decoration of β-Cyclodextrin and Tuning Active Layer Chemistry Leading to Nanofiltration Membranes for Desalination and Wastewater Decontamination.

Given the huge potential of thin film composite (TFC) nanofiltration (NF) membranes for desalination and micro-pollutant removal, two different sets of six NF membranes were synthesized. The molecular structure of the polyamide active layer was tuned by using two different cross-linkers, terephthaloyl chloride (TPC) and trimesoyl chloride (TMC), reacted with tetra-amine solution containing β-Cyclodextrin (BCD). To further tune the structure of the active layers, the time duration of interfacial polymerization (IP) was varied from 1 to 3 min. The membranes were characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), water contact angle (WCA), attenuated total reflectance Fourier transform infra-red (ATR-FTIR) spectroscopy, elemental mapping and energy dispersive (EDX) analysis. The six fabricated membranes were tested for their ability to reject divalent and monovalent ions followed by rejection of micro-pollutants (pharmaceuticals). Consequently, terephthaloyl chloride turned out to be the most effective crosslinker for the fabrication of membrane active layer with tetra-amine in the presence of β-Cyclodextrin using interfacial polymerization reaction for 1 min. The membrane fabricated using TPC crosslinker (BCD-TA-TPC@PSf) showed higher % rejection for divalent ions (Na2SO4 = 93%; MgSO4 = 92%; MgCl2 = 91%; CaCl2 = 84%) and micro-pollutants (Caffeine = 88%; Sulfamethoxazole = 90%; Amitriptyline HCl = 92%; Loperamide HCl = 94%) compared to the membrane fabricated using TMC crosslinker (BCD-TA-TMC@PSf). For the BCD-TA-TPC@PSf membrane, the flux was increased from 8 LMH (L/m2.h) to 36 LMH as the transmembrane pressure was increased from 5 bar to 25 bar.

Osmotic Microbial Fuel Cell for Groundwater Softening, Defluoridation, Salinity Reduction, and Energy Production

Despite being the major source of freshwater, groundwater is contaminated with hardness, fluorides, salinity, and so on, and hence, its application for domestic/industrial purposes is severely limited. Existing remediation technologies demand both chemical and energy inputs. Therefore, in this study, an osmotic microbial fuel cell (OsMFC) was developed as an energy-positive and chemical-free technology to achieve simultaneous groundwater softening, defluoridation, salinity reduction, and bioelectricity production. High-quality water was extracted from wastewater in the OsMFC and was applied to reduce groundwater contaminants by dilution. The effects of feed/draw solution (FS/DS) ratio, membrane area, reactor volume, and time on water flux, energy production, and reduction efficiencies of Na+, Cl−, total hardness (TH), and F− were studied. The increase in FS/DS ratio and membrane area resulted in considerable improvement in the water flux, energy production, and contaminant reduction. However, an increase in the reactor volume had little effect on the overall performance. A maximum water flux of 9.81 litres per square meter per hour [LMH (L/m2/h)] with reduction efficiencies of 75.81%, 76.27%, 72.22%, and 65.76% for Na+, Cl−, TH, and F−, respectively, were obtained with an extended operating time of 168 h. Maximum chemical oxygen demand (COD) removal of 86.6% and current density of 0.34 mA/m3 were achieved simultaneously. The study demonstrated a sustainable approach of extracting high-quality water from wastewater and its application in groundwater remediation along with energy production.

Membrane reciprocation as energy-efficient fouling control with high biogas recovery in a pilot-scale anaerobic membrane bioreactor

Anaerobic membrane bioreactor (AnMBR) as a primary treatment has the benefit of energy recovery through biogas generation. However, high energy consumption for fouling control remains the bottleneck for its applications. To this end, this study investigated the energy outlook of using membrane reciprocation as fouling control method in a pilot-scale AnMBR treating domestic wastewater, as compared to using conventional biogas sparging. The carbon balance calculation was conducted during the AnMBR operation to identify the methane conversion from organic carbon, setting the basis for energy evaluation. Both fouling control strategies were investigated under different biogas sparging speeds and membrane reciprocation frequencies. Critical flux tests and energy calculations have shown membrane reciprocation to consume 0.59 kWh/m3 at 7 L/m2/h (LMH), 62% less energy contrasting biogas sparging (1.56 kWh/m3 at 6 LMH). With the high biogas recovery and energy-efficient fouling control, positive net energy balance (0.55–0.74 kWh/m3) was achieved in this AnMBR, highlighting the potential of AnMBR with membrane reciprocation as an energy-positive A-stage in domestic sewage treatment.

Fabrication of highly permeable thin-film composite forward osmosis membrane using poly-l-lysine as an additive in polysulfone substrate

Forward osmosis (FO) has received considerable interest for water and energy-related applications in recent years. However, FO has not been commercialized yet because of a few reasons. The lack of a high-performance FO membrane is one of the important barriers. To overcome this issue, a novel high-performance thin-film composite (TFC) membrane was successfully fabricated via interfacial polymerization with poly-L-lysine incorporated polysulfone substrate (PSf). Compared to the pristine PSf substrate, the incorporation of lysine (ranging 1 – 15 wt.%) meaningfully alternates the substrates chemical structure, porosity, contact angle, and morphology leading to an enhancement of the lysine -TFC membranes performance. The results showed that the new substrates with higher porosity, more hydrophilic, and smaller in pore size after the introduction of L-lysine. The membrane achieved the highest FO water flux at 15% concentration of lysine and the maximum FO water flux was 35 L/m2.h (LMH) with a comparable specific salt flux (Js/Jw) of 0.002 g/L in the active layer facing the feed side (AL-FS) when 1M NaCl was applied as draw solution. The water flux was increased with increasing concentration of lysine. The addition of poly-L-Lysine in casting solution resulted in a more porous and hydrophilic support layer.

Recovering and reuse of textile dyes from dyebath effluent using surfactant driven forward osmosis to achieve zero hazardous chemical discharge

This experimental study explores the feasibility of the reuse of dyes recovered from denim and polyester dyebath effluents using forward osmosis (FO) system to achieve zero hazardous material discharge. In batch experiments, the sodium dodecyl sulfate (SDS) at 0.5 M concentration generated an average flux of 3.5 L/m2/h (LMH) and reverse salt flux (RSF) of only 0.012 g/m2/h (GMH), while maintaining 100% dye rejection. This flux stability comes from the property of surfactants to form micelles and exert a stable osmotic pressure (π) above their critical micelle concentration (CMC). The low RSF is due to the greater micelle size. A colored fouling layer was formed on the membrane active layer (AL), which was easily removed using sodium hydroxide (NaOH) and citric acid. According to Fourier transform infrared spectra and atomic forces microscopy images of the AL, the interaction between foulants and membrane active groups did not significantly affect the physiochemical properties of the membrane. In the semi-continuous experiment, a very stable average flux of 7.3 LMH and RSF of 0.03 GMH was obtained using 0.75 M SDS as draw solution. The stacked 1D proton nuclear magnetic resonance analysis (1HNMR) spectra of both original and recovered disperse dyes showed 100% similarity, which validates the concept that the recovered dyes maintained their integrity during reconcentration and can be reused in the next batch dyeing process. Importantly, the diluted SDS concentration can be directly reused within the same textile industry in scouring and finishing processes. The processes of dye recovery and reuse developed in this study do not produce any waste or hazardous by-products and are suitable for scale-up and onsite industrial applications.

Superior methylparaben removal by anaerobic fluidized bed ceramic membrane bioreactor with PVDF tubular fluidized biocarrier: Reactor performance and microbial community

An anaerobic fluidized bed ceramic membrane bioreactor (AFCMBR) was operated with fluidized tubular biocarrier consisting of polyvinylidene difluoride (PVDF) for treating synthetic low-strength wastewater containing high dosage of methylparaben. The AFCMBR was run over 150 d to investigate the effect of hydraulic retention time (HRT) on the removal efficiency of methylparaben and any potential adverse impact of the addition of methylparaben on methane content in the biogas produced by AFCMBR. The fluidization of the PVDF biocarrier along the membrane surface played a key role in cleaning the membrane by maintaining the transmembrane pressure below 0.05 bar at 10.4 L/m2·h (LMH) of permeate flux (corresponding to 8 h of HRT). The fouling rate was also effectively reduced by conducting intermittent backwashing with the permeate produced by AFCMBR. Continuous feeding of methylparaben into the AFCMBR did not deteriorate microbial activity during the entire operational period applied in this study. Biodegradation through the biofilm formed on PVDF media was thought to be the dominant pathway to remove methylparaben. Microbial analysis of the biofilm community revealed the presence of aromatic-compound-degrading syntrophs (Syntrophorhabdus and Longilinea), propionate-oxidizing syntrophs (Syntrophobacter and Smithella), acetoclastic Methanothrix, and hydrogenotrophic methanogens (Methanobacterium, Methanolinea, and Methanoregula), indicating a syntrophic partnership for metabolizing methylparaben and propionate in the feed wastewater.

Recovery of water and valuable metals using low pressure nanofiltration and sequential adsorption from acid mine drainage

Acid mine drainage (AMD) contains an array of valuable resources such as Rare Earth Elements (REE) and Copper (Cu) which can be recovered along with fresh water. Low pressure nanofiltration with NF90 membrane was first studied to recover fresh water from synthetic AMD and concentration of dissolved metals for subsequent efficient selective recovery. Organic matter (OM) present in AMD was found to cause membrane fouling which resulted in significant flux decline. Powdered eggshell was investigated as a low-cost adsorbent for OM removal. The study showed that a 0.2 mg/l dose of powdered eggshell adsorbed 100% of OM and Fe with no significant loss of other dissolved metals. A steady permeate flux of 15.5 ± 0.2 L/m 2 h (LMH) was achieved for pre-treated AMD with a solute rejection rate of more than 98%. A chromium-based metal organic framework (MOF) modified with N - (phosphonomethyl) iminodiacetic acid (PMIDA) and an amine-grafted mesoporous silica (SBA15) material was synthesized for selective recovery of REE and Cu, respectively. The two adsorbents were used sequentially to selectively adsorb REE (91%) and Cu (90%) from pH adjusted concentrated feed. The formation of coordinating complexes with carboxylate and phosphonic groups on MOF was found to be the primary driving force for selective REE adsorption. Selective uptake of Cu onto amine-grafted SBA15 was due to the formation of strong chelating bonds between Cu and amine ligands. Both adsorbents remained structurally stable over 5 regeneration cycles. The findings here highlight the practical potential of membrane/adsorption hybrid systems for water and valuable metal (REE) recovery from AMD. • Low pressure NF achieved 80% permeate recovery while concentrating dissolved ions. • Modified MOF and SBA15-NH 2 selectively adsorbed 91% of REE and 90% of Cu. • REE show high affinity to deprotonated phosphonic and carboxyl groups in MOF. • Chelating bonds between Cu and amine groups in SBA15 promotes high selectivity. • High reuse capacity over multiple cycles recorded for both adsorbents.

Modification of Polyethersulfone Ultrafiltration Membrane Using Poly(terephthalic acid-co-glycerol-g-maleic anhydride) as Novel Pore Former.

In this research, poly terephthalic acid-co-glycerol-g-maleic anhydride (PTGM) graft co-polymer was used as novel water-soluble pore formers for polyethersulfone (PES) membrane modification. The modified PES membranes were characterized to monitor the effect of PTGM content on their pure water flux, hydrophilicity, porosity, morphological structure, composition, and performance. PTGM and PES/PTGM membranes were characterized by field emission scanning electron microscopy (FESEM), Fourier-transform infrared spectroscopy (FTIR), and contact angle (CA). The results revealed that the porosity and hydrophilicity of the fabricated membrane formed using a 5 wt.% PTGM ratio exhibited an enhancement of 20% and 18%, respectively. Similarly, upon raising the PTGM ratio in the casting solution, a more porous with longer finger-like structure was observed. However, at optimum PTGM content (i.e., 5%), apparent enhancements in the water flux, bovine serum albumin (BSA), and sodium alginate (SA) retention were noticed by values of 203 L/m2.h (LMH), 94, and 96%, respectively. These results illustrated that the observed separation and permeation trend of the PES/PTGM membrane may be a suitable option for applications of wastewater treatment. The experimental results suggest the promising potential of PTGM as a pore former on the membrane properties and performance.

Computational fluid dynamics simulation study of hypersaline water desalination via membrane distillation: Effect of membrane characteristics and operational parameters

In this study, a comprehensive model was developed using Computational Fluid Dynamics (CFD), and the behaviour of a direct contact membrane distillation (DCMD) system was investigated at hypersaline feedwater conditions. The effects of various operating parameters including feed and permeate velocities, temperatures and salinities, as well as different membrane characteristics like thickness, porosity, and thermal conductivity were studied. The developed simulation model was also validated using experimental data. The results showed that the membrane conductivity and thickness had a significant impact on the DCMD performance, and the optimum operational condition was necessary to be determined. The results showed that increasing the feedwater salinity from 50 to 200 g/l decreased the membrane flux by up to 33%, while a four times decrease in thermal conductivity of the membrane could lead to an increase in the membrane flux from 11.2 to 32.4 l/m2·h (LMH). In addition, the optimal membrane thickness was found to increase with salinity, reaching >120 μm for treatment of 22 wt% NaCl feedwater solution. However, the flux declined from >32 LMH to <13 LMH upon the increase in feedwater salinity (up to 22 wt% NaCl solution). It is also shown that a thinner membrane performed better for desalination of low salinity feedwater, while the thicker one produces higher separation performance and thermal efficiency for hypersaline brine desalination.

Cake layer reformation rates on self forming dynamic membranes and performance comparison with microfiltration membranes

Dynamic membranes (DMs) keep on attracting attention progressively as an alternative to conventional membranes because they can be operated with relatively higher fluxes and lower fouling rates. However, there are many factors affecting the performance of DMs, such as DM pore size, structure, and operating conditions. In this study, mainly focused on the investigation of cake formation rates both in initial formation and reformation rates after physical/chemical cleaning. In this context, it has been evaluated the performances of DMs with different pore sizes (171 μm, 90 μm, and 30 μm) and different structures under the same conditions and compared their performances with microfiltration (MF) membranes (0.45 μm and 0.22 μm) in a single reactor. In the study, the effects of different fluxes (15-, 20-, 25 L/m2·h (LMH), SADm (1-, 0.8-, 0.5 m3-air /m2·h) and F/M (0.095, 0.125, 0.19 g-COD/g-MLSS·day) conditions on the treatment and filtration performance of DMs were investigated. High COD (>95%) and turbidity (<10 NTU) removals were obtained in this study. In particular, the 30 μm DM (0.65 ± 0.47 NTU) produced quite close effluent turbidity compared to MFs (0.12 ± 0.05 NTU). Low SADm and high F/M values resulted in increased effluent COD concentrations and turbidity values. By decreasing the SADm, the cake formation rate and the fouling rate increased, which showed that there is a definite relationship between the cake formation rates and the fouling rates. Additionally, considering all the results, the most stable operation was obtained in the 30 μm DM, although it has been occurred the least fouling in the 90 μm membrane in the study. This study, focused on cake reformation rates, attempts to show that DMs can be used as an alternative to MBRs. Especially, when taking into account the results of the reformation rate of 30 μm DM (6.09 NTU/h) and other high filterability features.

A Simple Approach to Fabricate Composite Ceramic Membranes Decorated with Functionalized Carbide-Derived Carbon for Oily Wastewater Treatment.

Membrane-based oil–water separation has shown huge potential as a remedy to challenge oily wastewater with ease and low energy consumption compared to conventional purification techniques. A set of new composite ceramic membranes was fabricated to separate surfactant-stabilized oil/water (O/W) emulsion. Carbide-derived carbon (CDC) was functionalized by 3-aminopropyltriethoxy silane (APTES) and subsequently deposited on a ceramic alumina support and impregnated with piperazine as an additional amine. The APTES functionalized CDC-loaded membrane was then crosslinked using terephthalyol chloride (TPC). Different loadings of functionalized CDC (50 mg, 100 mg and 200 mg) were employed on the ceramic support resulting in three versions of ceramic membranes (M-50, M-100 and M-200). The fabricated membranes were thoroughly characterized by Scanning electron microscopy (SEM), X-ray diffraction (XRD), Attenuated total teflectance Fourier transform infrared (ATR-FTIR) spectroscopy, Energy dispersive x-ray spectroscopy (EDX) and elemental mapping. The highest permeate flux of 76.05 LMH (L m−2 h−1) at 1 bar using 67.5 ppm oil-in-water emulsion (as feed) was achieved by the M-50 membrane, while an oil separation efficiency of >99% was achieved by using the M-200 membrane. The tested emulsions and their respective permeates were also characterized by optical microscopy to validate the O/W separation performance of the best membrane (M-100). The effect of feed concentration and pressure on permeate flux and oil–water separation efficiency was also studied. A long-term stability test revealed that the M-100 membrane retained its performance for 720 min of continuous operation with a minor decrease in permeate flux, but the O/W separation efficiency remained intact.

Assessment of anaerobic membrane distillation bioreactor hybrid system at mesophilic and thermophilic temperatures treating textile wastewater

The performance of a lab-scale anaerobic membrane distillation bioreactor (An-MDBR) system was evaluated treating high-strength synthetic textile wastewater with a Chemical Oxygen Demand (COD) concentration of 3000 ± 130 mg/L. A novel hybrid process incorporating membrane distillation in a submerged anaerobic membrane bioreactor was developed at mesophilic and thermophilic temperatures and instigated. The An-MDBR process attained 99.99% inorganic salt rejection irrespective of the operating temperatures and high initial flux between 5.9 and 11.5 L/m2·h (LMH) at 35–50 °C. Removal efficiencies (%) of COD and color were in the range of 40–69% and 43–74%, respectively in an anaerobic bioreactor, whereas overall MD performance was in the range of 99 ± 0.9% for COD as well as color. Among the four temperatures, 40 °C exhibited the optimum performance for 47 days with the average COD and color removal efficiencies of 99 ± 0.9%, respectively with steady biogas production. Furthermore, the conductivity of An-MDBR was maintained at 4.0 ± 0.5 mS/cm using low-cost Woven Fiber Microfiltration (WF-MF) coupled with An-MDBR and the flux was optimized at 2 LMH. The removal efficiency of NH4+1-N was greater in the range of 89 to 93% at mesophilic temperatures while smaller in the range of 79 to 86% at thermophilic temperatures by maintaining pH between 6.8 and 7.2. The concentration of PO4−3-P in the permeate water was near zero, showing that PO4−3 can be rejected completely by the MD membrane. Due to membrane biofouling and scaling, wetting was observed for different durations at different temperatures.

In-Situ H2O2 Cleaning for Fouling Control of Manganese-Doped Ceramic Membrane through Confined Catalytic Oxidation Inside Membrane.

This work presents an effective approach for manganese-doped Al2O3 ceramic membrane (Mn-doped membrane) fouling control by in-situ confined H2O2 cleaning in wastewater treatment. An Mn-doped membrane with 0.7 atomic percent Mn doping in the membrane layer was used in a membrane bioreactor with the aim to improve the catalytic activity toward oxidation of foulants by H2O2. Backwashing with 1 mM H2O2 solution at a flux of 120 L/m2/h (LMH) for 1 min was determined to be the optimal mode for in-situ H2O2 cleaning, with confined H2O2 decomposition inside the membrane. The Mn-doped membrane with in-situ H2O2 cleaning demonstrated much better fouling mitigation efficiency than a pristine Al2O3 ceramic membrane (pristine membrane). With in-situ H2O2 cleaning, the transmembrane pressure increase (ΔTMP) of the Mn-doped membrane was 22.2 kPa after 24-h filtration, which was 40.5% lower than that of the pristine membrane (37.3 kPa). The enhanced fouling mitigation was attributed to Mn doping, in the Mn-doped membrane layer, that improved the membrane surface properties and confined the catalytic oxidation of foulants by H2O2 inside the membrane. Mn3+/Mn4+ redox couples in the Mn-doped membrane catalyzed H2O2 decomposition continuously to generate reactive oxygen species (ROS) (i.e., HO• and O21), which were likely to be confined in membrane pores and efficiently degraded organic foulants.