Transmembrane Pressure Drop Research Articles

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.

Modeling of cross flow hollow fiber ultrafiltration for treatment of effluent from Railway Workshop

Industrial oily water containing oil, grease and dust has been treated using stage-wise filtration, first by sand bed followed by cross-flow ultrafiltration hollow fiber membrane. The sand bed removes majority of suspended particles and reduces the turbidity from 13.6 NTU to 2.6 NTU. Effects of transmembrane pressure drop and cross flow rate on ultrafiltration performance were investigated. A transport phenomena based model under the framework of boundary layer theory was developed to quantify the flux decline and oil transport through the membrane during cross flow filtration in hollow fiber. The model results matched remarkably well with the experimental data. The mechanism of filtration was analyzed and found to be governed by cake formation. Formation of cake-layer was supported by scanning electron micrography of fresh and fouled membranes and Fourier Transform Infrared spectroscopy. The modeling of separation mechanism and estimates system parameters will aid in scaling up of the filtration set-up to industrial scale for treatment of industrial effluent containing oil.

Fundamental Understanding of Fouling Mechanisms During Microfiltration of Bitter Gourd (Momordica charantia) Extract and Their Dependence on Operating Conditions

Microfiltration of bitter gourd (Momordica charantia) extract using hollow fiber membrane module was carried out in the present study. To identify the dominant fouling mechanism, flux decline behavior was examined using Field model. At lower transmembrane pressure, pore blocking mechanism was found to be more important, while cake filtration was dominant at higher pressure. Higher cross flow rate reduced filtration constant indicating slower rate of membrane fouling. Additionally, surface and particle size analyses were undertaken to validate the findings of modeling. Scanning electron microscope analysis clearly showed prevalence of pore blocking mechanism at lower transmembrane pressure drop, whereas cake filtration was dominant fouling mechanism at higher pressure. Fourier transform infrared spectroscopy analysis supported the role of cake layer as a secondary membrane retaining some amount of polyphenols. Analysis of flux decline ratio also confirmed that for transmembrane pressure of 104 kPa and beyond, cake layer became compact, and hence, increase in cross flow rate was unable to influence the improvement of permeate flux. The current study provides an insight into the fouling mechanism involved in scaling up of clarification of bitter gourd extract for successful processing of this medicinal herb.

Spinning basket membrane ultrafiltration of paper industry waste effluent: Experimental and theoretical aspects

This study explored the treatment of paper industry effluent using spinning basket membrane ultrafiltration. The effects of various MWCO of membranes (5, 10, 30 and 50kDa), transmembrane pressure drops (207–414kPa), rotational speeds (10.47–73.30rads−1) and retentate flow rate (1–4Lmin−1) on permeate flux and permeate quality were analyzed. The rotational speed induces turbulence and shear force on the active membrane surfaces reduces the deposition of rejected particles thereby increasing the permeate flux. 98% removal of chemical oxygen demand (COD) was achieved using 5kDa MWCO membrane with 52.31rads−1 rotational speed. Modified Hermia’s pore blocking mechanism helps to understand the solute particles clogging behavior for all types of membranes. Brownian, rotational and shear-induced diffusion models were applied to evaluate the theoretical flux behavior. Response surface methodology (RSM) has been studied to optimize the filtration process. Optimum permeate quality has been obtained when initial TMP drop, rotational speed, and retentate flow rate were 350.61kPa, 62.83rads−1, and 2Lmin−1, respectively.

074 PATIENT SAFETY EVALUATION FOR COMBINING CONTINUOUS RENAL REPLACEMENT THERAPY WITH EXTRACORPOREAL MEMBRANE OXYGENATION

Category: RRT Technique Characteristics Presenter: Mr PETER CHI KEUNG LAI Keywords: Continuous Renal Replacement Therapy, Extracorporeal Membrane Oxygenation, Patient Safety Connecting Continuous Renal Replacement Therapy (CRRT) in parallel with Extracorporeal Membrane Oxygenation (ECMO) is a common practice. However, this technique may potentially lead to complications such as hemolysis, circuit clotting and membrane oxygenator malfunction. To evaluate safety issues related to combining CRRT with ECMO circuit. Retrospective chart review of adult ECMO patients with concomitant CRRT in a university-affiliated hospital in 2015 - 2016. 27 patients received CRRT through ECMO circuitry. 12 received veno-venous ECMO and 15 received veno-arterial ECMO. 4 cases received CRRT with regional citrate anticoagulation, while others received intravenous unfractionated heparin infusion as per ECMO protocol. When patients were stratified for data analysis by ECMO blood flow rate: low flow (LF; <3.0lpm), normal flow (NF; >3 - 4lpm) and high flow (HF; >4lpm), there was no significant between-group difference on patient demographics, survival rate, reasons for ECMO initiation, baseline renal function and fluid balance and CRRT efficacy. ICU length of stay was significantly lower in LF group, indicating less severity of illness (LF vs NF, 3.8 vs 18.3, p 0.02; LF vs HF, 3.8 vs 28.6, p 0.01). CRRT treatment hours (p 0.03) and haemofilter use (p 0.01) was also less in LF group than in HF group. Mean CRRT pressures for inlet, outlet, transmembrane pressure and pressure drop were 123.19mmHg, 215.74mmHg, 86.15mmHg and 37.70mmHg respectively. CRRT return pressure was higher in HF group (p 0.03) than LF group, with peak pressure reaching 343mmHg in one case. Yet, there was no haemolysis nor haemorrhagic event was reported in the study period. CRRT can be effectively incorporated into ECMO circuitry without jeopardizing ECMO treatment and patient safety. Consideration should be taken to monitor CRRT circuit pressures when a higher ECMO blood flow is being used.

Performance of submerged oscillatory membrane photoreactor for water treatment

Enhancement of a slurry hybrid membrane photoreactor (MPR) is investigated using an oscillatory microfiltration membrane and ZnO photocatalyst. The investigation involved the photocatalytic decolourization of methylene blue (MB) dye as a model pollutant compound. The effect of the operating parameters on the dye decolourization and its relation to the membrane-catalyst retention characteristics is studied. The results showed that application of oscillatory motion resulted in minimizing catalyst particles deposition on the membrane which increased its concentration in suspension and led to higher decolourization rates. Such effect was further augmented by the increase in membrane permeate flux due to the lower hydraulic resistance caused by catalyst deposition on the membrane surface. Furthermore, use of ZnO as photocatalyst has the potential of providing several advantages in terms of high UV absorbance as well as alleviating the need for using oxygen scavenging for charge separation. The latter when combined with the relatively low transmembrane pressure drop requirements by microfiltration (MF) membranes, can result in reducing the overall process energy demand. Such effects suggest that the proposed configuration may be considered as an effective approach for augmenting the productivity of membrane photoreactor for water and wastewater treatment applications.

Clarification and storage study of bottle gourd (Lagenaria siceraria) juice by hollow fiber ultrafiltration

Ultrafiltration of bottle gourd juice was undertaken in this study using hollow fibers with the objective to have juice with long shelf life without heat treatment, preservatives and additives maintaining the natural taste, flavor and nutritional quality intact. Five blend hollow fiber membranes (M-1 to M-5) with 15wt% polyacrylonitrile (PAN) and 5wt% cellulose acetate phthalate (CAP) were prepared. No additive was used in M-1 membrane. For M-2 and M-3 membranes polyethylene glycol (PEG) of molecular weight 200Da was used as an additive with concentration 1.5 and 3wt%, respectively. 3wt% PEG of molecular weight 1500Da was used in M-4 and same concentration of PEG of molecular weight 4000Da was used in M-5 membrane. The membranes were characterized in terms of permeability, molecular weight cut off, permeate flux, permeate quality and anti-fouling characteristics. M-3 membrane was selected based on performance. Experiments were conducted both in total recycle and batch concentration mode. In case of total recycle mode, transmembrane pressure drop (TMP) was varied from 35 to 104kPa and that of cross flow rate (CFR) was from 10 to 20l/h. Quality of the filtered juice was analyzed in terms of color, clarity, total soluble solid, polyphenol, concentration of protein, sodium and potassium. TMP 104kPa and CFR 20l/h were found to be suitable operating conditions for filtration. The filtered juice was stored for 8 weeks under normal refrigeration. All the nutritional parameters (total protein, polyphenol, sodium, potassium and total soluble solids) including taste were monitored and it was found that the quality of the juice was maintained with a positive purchase intention.

Synthesis of Zeolitic Imidazolate Framework Membrane Using Temperature-Switching Synthesis Strategy for Gas Separation

In this work, ZIF-9 membranes were successfully synthesized using temperature-switching synthesis method. Compared with the conventional hydrothermal synthesis at a constant temperature, this method could promote the growth of crystals on the support. Scanning electron microscopy (SEM) demonstrated that the obtained membranes had continuous and well-intergrown layer with a denser surface and better crystal size uniformity. As a result, gas separation performance was enhanced. It is also found that the properties of membrane can remain almost stable at a relatively broad range of operating temperature and transmembrane pressure drop, which is beneficial for the practical operation of membrane in the separation process. More importantly, this synthesis strategy can be conveniently extended to the preparation of other MOF membranes with improved performance.

Impact of graphene oxide on removal of heavy metals using mixed matrix membrane

The graphene oxide (GO) impregnated mixed matrix membrane (MMM) was prepared by non-solvent induced phase inversion method. MMM was characterized in terms of molecular weight cut-off, porosity, permeability, average pore size, pore size distribution, contact angle, zeta potential and mechanical strength. The membrane became highly permeable, hydrophilic and charged on addition of GO. The surface morphology and roughness were studied through scanning electron and atomic force microscopy. Efficacy of MMM for removal of heavy metals was explored using the developed MMM. It showed high adsorption capacity for Pb2+ (79mg/g), Cu2+ (75mg/g), Cd2+ (68mg/g) and Cr6+ (154mg/g) at natural pH, 6.7, 6.5, 6.4 and 3.5, respectively. The steady state permeate flux was around 30l/m2h for 50mg/l feed concentration at 414kPa transmembrane pressure drop and 40l/h cross flow rate. Rejection of Pb, Cu, Cd and Cr were in between 90% and 96% for various operating conditions and the breakthrough time was around 10h for different metal ions. The membrane was regenerated in-situ, by acidic solution at pH 5.5.

Preparation, characterization and application of powdered activated carbon‐cellulose acetate phthalate mixed matrix membrane for treatment of steel plant effluent

Preparation, characterization and industrial application of a mixed matrix membrane (MMM) using powdered activated carbon (PAC) in cellulose acetate phthalate (CAP) have been reported in this study. The objective of this work is to fabricate a less energy intensive, highly selective (to phenolic compounds) adsorptive membrane with high throughput in a scalable platform for simultaneous removal of organic as well chemical oxygen demand (COD) from a steel plant effluent. The membrane with 25 wt% PAC has maximum adsorption capacity of phenol 35 mg/g at pH 5.5. Effluent with total phenolic compounds (23 mg/g) and COD of 5200 mg/l is treated in continuous cross‐flow configuration. Breakthrough time is 44 hr for a filtration area of 0.008 m2 with total phenol concentration in permeate as per World Health Organization (WHO), 1 mg/l. Throughput of the system is high, 40 l/m2 hr at transmembrane pressure drop 276 kPa and cross‐flow rate 20 l/hr. Maximum rejection of phenol is obtained at low pressure and cross‐flow rate. Removal of phenolic compounds is achieved by adsorption by PAC in CAP matrix and satisfactory reduction of COD and complete removal of non‐volatile solids are due of sieving mechanism. A simple chemical regeneration method is proposed to recover the permeate flux beyond 90%. Copyright © 2015 John Wiley &amp; Sons, Ltd.

Comparison between Centrifugation and Microfiltration As Primary Clarification of Bottle Gourd (Lagenaria siceraria)Juice

Centrifugation and microfiltration (MF) were used for primary clarification of raw bottle gourd juice. The optimized conditions (time and speed) of centrifugation and those of MF (transmembrane pressure drop [TMP] and cross flow rate) were determined using response surface methodology. Clarified juice was analyzed in terms of clarity, total solids, protein, polyphenol, total soluble solids, sodium and potassium. The performance of both of these methods was compared based on the quality of the clarified juice and power consumption. Microfiltered juice had enhanced clarity (97%), but polyphenol concentration was less (8 mg GAE/100 mL) compared with centrifugation (13 mg GAE/100 mL). Practical Applications Bottle gourd is a traditional medicinal plant. Its juice has tremendous therapeutic qualities including antidiabetic, anticarcinogenic and cardioprotective properties. It is a rich source of various vitamins, minerals like potassium and antioxidants like flavonoids. Therefore, extraction of bottle gourd juice and subsequent clarification followed by fractionation would lead to selective separation of medicinally and nutritionally important bioactive components. This can be attained by a primary clarification to remove undesirable higher sized molecules and suspended materials followed by a more specialized membrane-based separation process. The present work highlights a comparison of the performance of centrifugation and MF as a primary clarification of bottle gourd extract. Thus, this work has direct relevance as an initial step of final scaled up production unit.

절삭유 수용액내 침지식 평막 모듈에 대한 사인파형 투과유속 연속운전 방식의 특성

본 연구에서는 emulsion 및 semi-synthetic 절삭유 수용액에 침지된 평막형 분리막의 막간 압력차(TMP)를 투과유속에 따라서 측정하였다. 사용한 정밀여과막은 유효 막면적이 <TEX>$0.02m^2$</TEX>이고 공칭 세공크기가 <TEX>$0.15{\mu}m$</TEX>이었다. 저장조 내에 2개의 분리막 모듈을 침지시키고 운전/휴직(R/S) 및 사인파형 투과유속 연속운전(SFCO) 실험을 동시에 실시하였다. Emulsion 수용액의 경우 SFCO에 의한 TMP는 R/S에 비하여 60% 이하로 유지되었으며 투과유속이 증가함에 따라서 TMP 감소효과는 줄어들었다. Semi-synthetic 수용액은 emulsion 수용액보다 탁도가 낮아 막오염이 적게 유발되었으며 장시간 운전할 경우 SFCO에 의한 TMP 효과도 감소하였다. In this study transmembrane pressure (TMP) was measured with respect to permeate flux through the submerged flat sheet membrane for the emulsion and semi-synthetic cutting oil solutions. The effective area and nominal pore size of the used microfiltration membrane were <TEX>$0.02m^2$</TEX> and <TEX>$0.15{\mu}m$</TEX>, respectively. The experiments were carried out simultaneously for run/stop (R/S) and sinusoidal flux continuous operation (SFCO) modes using two submerged membrane module in the reservoir. TMP for the case of SFCO was maintained under 60% of R/S, and the effect on TMP drop decreased as the permeate flux increased for emulsion cutting oil solution. Membrane fouling for the semisynthetic solution showing low turbidity was induced lower comparing to the emulsion solution. Also, the effect on TMP drop for SFCO decreased during long-term operation.

Ozonation and ultrafiltration for the treatment of olive mill wastewaters: effect of key operating conditions and integration schemes.

With the objective of reaching suitable techniques for olive mill wastewater treatment, ozonation and ultrafiltration were studied individually and combined. A continuous reactor was run for the treatment of a phenolic mixture mimicking an actual olive mill wastewater (OMW) by ozonation. The effect of the main operating parameters was analysed (pH, liquid flow rate and ozone inlet concentration). The increase of pH and ozone dose improved ozonation efficiency. As expected, the highest residence time led to higher steady-state degradation (35 % of chemical oxygen demand (COD) abatement). Even if the rise on ozone inlet gas concentration was able to remove COD in a higher extent, it should be taken into consideration that with the lowest oxidant load (15 g O3/m(3)), the maximum steady-state biochemical oxygen demand (BOD5)/COD ratio was reached which would reduce the process costs. These operating conditions (pH 9, 1 mL/min of liquid flow rate and 15 g O3/m(3)) were applied to an actual OMW leading to 80 % of phenolic content abatement and 12 % of COD removal at the steady state. Regarding ultrafiltration, it was concluded that the best total phenolic content (TPh) and COD abatement results (55 and 15 %) are attained for pH 9 and using a transmembrane pressure drop of 1 bar. Among the integration schemes that were tested, ultrafiltration followed by ozonation was able to reach 93 and 20 % of TPh and COD depletion, respectively. Moreover, this sequence led to an effluent with a BOD5/COD ratio of about 0.55 which means that it likely can be posteriorly refined in a municipal wastewater treatment plant.

Potential of extraction of Steviol glycosides using cellulose acetate phthalate (CAP) – polyacrylonitrile (PAN) blend hollow fiber membranes

Cellulose acetate phthalate (CAP) – Polyacrylonitrile (PAN) blend hollow fibers were spun in the present work and their efficacy in extraction of Steviol glycosides was investigated. Various compositions of blend hollow fibers were characterized in terms of scanning electron microscopy (SEM), permeability, contact angle, pore size distribution and breaking stress. Concentration of CAP was varied up to 5 wt.% in a total polymer concentration of 20 wt.%. It was observed from SEM images that finger like pores in the cross-section became tear drop like with decrease in concentration of CAP, making them denser. Pure PAN membrane showed the highest permeability around 238 l/m2.h.bar and the lowest molecular weight cut off (MWCO) 12 kDa and the highest pore density 2.8 × 1018 m−2. CAP-PAN (4:16) blend membrane of MWCO 30 kDa was found to be the most suitable for extraction of Steviol glycosides. At 34 kPa transmembrane pressure drop (TMP) and cross flow rate (CFR) 10 l/h, glycoside recovery was 55 % and purity was 30 % under total recycle mode of operation. Steady state permeate flux was 8 l/m2.h at 102 kPa TMP. A three stage diafiltration was carried out at 34 kPa TMP and 5 l/h flow. Enhanced 94 % recovery and 54 % purity of the Steviol glycosides was obtained under these conditions.

Removal of reactive dyes using a high throughput-hybrid separation process

Toxic and carcinogenic reactive dyes are abundantly used in textile industries due to their wide variety of colour and texture. In this study, a hybrid separation process was used to remove four common reactive dyes (reactive yellow, red, black and brown) from aqueous solution. Synthetic solution of these dyes was subjected to adsorption by activated carbon followed by microfiltration (MF), using a ceramic membrane module. Dyes were completely removed by adsorption at pH 4.5 and the dye-loaded adsorbents were removed by cross-flow MF. Maximum Langmuir adsorption capacity of activated carbon for these four dyes was in the range of 88–106 mg/g. Effects of trans-membrane pressure drop and cross-flow rate on the throughput of the combined process was investigated. Membrane fouling was due to the cake type of layer formed by the activated carbon particles. Five different washing protocols were tested for their efficiency and the acid–alkali wash was found to be the most effective.

Separation of Rebaudioside-A from stevia extract: Membrane selection, assessment of permeate quality and fouling behavior in laminar flow regime

This study is aimed to purify Rebaudioside-A (Reb-A) from aqueous stevia extract by ultrafiltration both in batch and cross flow operations. Performance of four different polyether-sulfone membranes of molecular weight cut off 10, 20, 30 and 50kDa was investigated for permeate flux and quality in terms of its color, clarity, total solid, purity and selectivity. Hermia’s fouling models, namely, complete, standard, intermediate pore blocking and cake filtration have been tested for their fitness in flux decline regime. 30kDa membrane was found to be the most effective for Reb-A separation. The effect of transmembrane pressure (TMP) drops and Re numbers on the permeate flux and quality in cross flow process were investigated. Steady state permeate flux increased with TMP drops and flow rate. Purity and selectivity of Reb-A in permeates also increased with TMP drops and flow rates. TMP drop of 414kPa and Re number of 1667 were found to be most suitable operative conditions with selectivity of 0.45 and flux value of 5.86×10−6m3m−2s−1. Individual fouling model could not fit entire flux decline data; however, combination of two models well described the flux profile. Cake filtration showed best fitting under the operating conditions.

Analysis of Fouling Characteristics and Flux Decline during Humic Acids Batch Ultrafiltration

This work focuses on the membrane ultrafiltration technique to separate humic acids from aqueous solution. An unstirred dead end ultrafiltration of synthetic aqueous humic acids solutions of 50, 150 and 250 mg L-1 was performed with Polyethersulfone membrane. To observe the effects of applied transmembrane pressure (TMP) drops during separation, the experiments were carried out at 207, 276, 345 and 414 kPa with 50 kDa molecular weight cutoff (MWCO) membrane. The performance of this process is expressed in terms of volume reduction factor (VRF). To analyze flux decline and pore blocking behavior, Hermia’s fouling mechanism models, namely, complete, standard, intermediate and cake filtration models have been studied in search of best fittings in flux decline system. After completion of the experiment with 50 mg L-1 feed solution, the concentration of Humic acids in permeate was 2.9 mg L-1, revealing 94% rejection during the membrane ultrafiltration.

A surface‐renewal model for constant flux cross‐flow microfiltration

ABSTRACTA mathematical model using classical cake‐filtration theory and the surface‐renewal concept is formulated for describing constant flux, cross‐flow microfiltration (CFMF). The model provides explicit analytical expressions for the transmembrane pressure drop (TMP) and cake‐mass buildup on the membrane surface as a function of filtration time. The basic parameters of the model are the membrane resistance, specific cake resistance, and rate of surface renewal. The surface‐renewal model has two forms: the complete model, which accounts for cake compressibility; and a subsidiary model for incompressible cakes, which can be derived from the complete model. The subsidiary model is correlated against some of the experimental TMP data reported by Miller et al. (J Membrane Sci 2014, 452, 171) for constant flux CFMF of a soybean‐oil emulsion in a cross‐flow filtration cell having unmodified and surface‐modified, fouling‐resistant membranes, and has an average root‐mean‐square (RMS) error of 6.2%. The complete model is fitted to the experimental TMP data reported by Ho and Zydney (J Membrane Sci, 2002, 209, 363) for constant flux microfiltration of a bovine serum albumin solution in a stirred cell using polycarbonate track‐etched membranes and has an average RMS error of 11.5%. This model is also correlated against the TMP data of Kovalsky et al. (J Membrane Sci 2009, 344, 204) for constant flux yeast filtration in a stirred cell (average RMS error = 9.2%). © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41778.

In-situ biofilm characterization in membrane systems using Optical Coherence Tomography: Formation, structure, detachment and impact of flux change

Biofouling causes performance loss in spiral wound nanofiltration (NF) and reverse osmosis (RO) membrane operation for process and drinking water production. The development of biofilm formation, structure and detachment was studied in-situ, non-destructively with Optical Coherence Tomography (OCT) in direct relation with the hydraulic biofilm resistance and membrane performance parameters: transmembrane pressure drop (TMP) and feed-channel pressure drop (FCP). The objective was to evaluate the suitability of OCT for biofouling studies, applying a membrane biofouling test cell operated at constant crossflow velocity (0.1 m s−1) and permeate flux (20 L m−2h−1).In time, the biofilm thickness on the membrane increased continuously causing a decline in membrane performance. Local biofilm detachment was observed at the biofilm–membrane interface.A mature biofilm was subjected to permeate flux variation (20 to 60 to 20 L m−2h−1). An increase in permeate flux caused a decrease in biofilm thickness and an increase in biofilm resistance, indicating biofilm compaction. Restoring the original permeate flux did not completely restore the original biofilm parameters: After elevated flux operation the biofilm thickness was reduced to 75% and the hydraulic resistance increased to 116% of the original values. Therefore, after a temporarily permeate flux increase the impact of the biofilm on membrane performance was stronger. OCT imaging of the biofilm with increased permeate flux revealed that the biofilm became compacted, lost internal voids, and became more dense. Therefore, membrane performance losses were not only related to biofilm thickness but also to the internal biofilm structure, e.g. caused by changes in pressure.Optical Coherence Tomography proved to be a suitable tool for quantitative in-situ biofilm thickness and morphology studies which can be carried out non-destructively and in real-time in transparent membrane biofouling monitors.

Effects of co-existed anions on retention characteristics of chromate by MEUF

Micellar enhanced ultrafiltration (MEUF) process was proposed to evaluate effects of anions (nitrate and sulfate) in single- and multi-component aqueous solutions for chromate removal with cationic surfactant (cetyltrimethylammonium bromide, CTAB) under constant transmembrane pressure drop (40 psi), temperature (25°C), and surfactant/chromium (S/M) molar ratio of 3 (S/M = 3 mM/1 mM). First of all, in the single-component anion (only one anion was used) solutions, the order of removal efficiency was: chromate 99.9% > sulfate 96.1% > nitrate 94.0%. These results indicate that chromate preferentially binds on the CTAB micelles but sulfate and nitrate bind less. On the other hand, in the multi-component anions (chromium together with co-existed anions) solution, the removal efficiency of chromate decreased (99.4–98.4%) with the increase of sulfate and nitrate. The retention of surfactant was enhanced by the addition of electrolytes into solution due to the counterion dissolved from electrolyte reduced the repulsive electrostatic force between the head groups of cationic surfactant molecule. In addition, the effect of temperature in multi-component on MEUF was evaluated simultaneously.