Permeate Flow Rate Research Articles

Influencing factors of polarization coefficient of hollow fiber membrane

PurposeThe purpose of this study is to improve the performance of hollow fiber membrane and improve the separation efficiency.Design/methodology/approachBy establishing a mathematical model of hollow fiber membrane gas separation, the influences of parameters such as pressure difference between the inside and outside of the filament, initial oxygen concentration of intake air, intake air flow rate and back pressure outside the filament on the polarization coefficient were analyzed, so as to explore the degree of influence of operating parameters on the concentration polarization, and put forward a technical scheme to reduce the concentration polarization.FindingsFactors such as pressure difference between the inside and outside of the filament, initial oxygen concentration of intake air, intake air flow rate and back pressure outside the filament have a certain effect on the polarization coefficient. Among them, the polarization coefficient is positively correlated with pressure difference inside and outside the filament, initial oxygen concentration of intake air and back pressure outside the filament, and is negatively correlated with intake air flow.Practical implicationsNegative pressure suction on the permeation side can be used to increase the membrane permeation flow rate and reduce the concentration polarization.Originality/valueThe influence of concentration polarization on membrane performance is reduced by controlling various factors.

RO 해수담수화를 위한 양방향 세척기술개발

The purpose of this research was to compare the RO membrane performance such as permeate flow rate, flux, recovery ratio according to the membrane CIP(Clean-In-Place) methods(One-way CIP and two-way CIP). The seawater used in this research was sampled at a depth of 3∼5 m in the sea located in B City. The average water quality of seawater was found to be turbidity of 1.28 NTU, TDS 30,335 ㎎/L, hardness 3,330 ㎎/L as CaCO₃, and SO₄^2- 1,890 ㎎/L. The flux of the new RO membrane, fouled RO membrane, one-way CIP membrane and two-way CIP membrane were 97.3 L/㎡·hr, 66.5 L/㎡·hr (recovery ratio : 68.0 %), and 81.1 L/㎡·hr (recovery ratio : 83.3 %) and 94.1 L/㎡·hr (recovery ratio : 96.7 %), respectively. It was found that the two-way CIP membrane washing method showed higher washing efficiency than the one-way CIP membrane washing method.

Investigation of the factors affecting reverse osmosis membrane performance using machine-learning techniques

Several factors affecting the RO membrane performance can be investigated mainly in two groups; feed characteristics and operational parameters. In this work, the effect of feed characteristics of a municipal wastewater such as conductivity, oxidation reduction potential (ORP), total suspended solids (TSS), turbidity, chemical oxygen demand (COD) and feed operational parameters such as feed pressure, flow rate, temperature on RO membrane performance monitoring parameters (pressure difference across membranes, salt passage and permeate flow rate) were analyzed in a wastewater recovery plant using different machine learning techniques. Artificial neural networks (ANNs) were found to perform better to predict pressure difference whereas random forest and multiple linear regression models performed better in salt passage and permeate flow rate prediction, respectively. Association rule mining was also employed, and it was found that high feed flow rate, low feed conductivity and low temperature operation are desired for effective RO membrane operation.

PID Control Design Using AGPSO Technique and Its Application in TITO Reverse Osmosis Desalination Plant

Desalination plants have an important concern regarding controlling the permeate flow rate and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">pH</i> during operability. This paper proposes the proportional integral derivative (PID) control design using modified Particle Swarm Optimization (PSO) techniques called autonomous groups PSO (AGPSO) in the two-input two-output (TITO) RO desalination plant to control the permeate flow rate and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">pH</i> . Here, three different versions (AGPSO1, AGPSO2, and AGPSO3) of the AGPSO algorithm are utilized to design PID control for the same TITO plant. In addition, an integral time absolute error ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">J</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ITAE</sub> ) based objective function is utilized to design a PID controller. The simulation results suggest that the proposed controller designs are flexible, self-tuning, and have stable characteristics, while the AGPSO3-PID control design attained a robust design for optimum tuning compared to existing improved grey wolf optimization PID (IGWO-PID) and other versions of AGPSO based PIDs (AGPSO1-PID, AGPSO2-PID). The design of AGPSO-PID achieved a minimum objective function than existing IGWO-PID and other versions of AGPSO based PIDs {AGPSO1-PID, AGPSO2-PID}. Finally, the proposed controller designs outperform the existing IGWO-PID design in literature in terms of control performance, demonstrating a precise control for and the improvement of plant performance.

Cellulose Acetate Membranes Modification by Aminosilane Grafting in Supercritical Carbon Dioxide towards Antibiofilm Properties.

The study explores the grafting of cellulose acetate microfiltration membranes with an aminosilane to attain antibiofilm properties. The grafting reaction was performed in the supercritical carbon dioxide used as a transport and reaction medium. The FTIR analyses and dissolution tests confirmed the covalent bonding between the aminosilane and polymer. The membranes’ microstructure was investigated using a dual-beam SEM and ion microscopy, and no adverse effects of the processing were found. The modified membranes showed a more hydrophilic nature and larger water permeate flow rate than the neat cellulose acetate membranes. The tests in a cross-filtration unit showed that modified membranes were considerably less blocked after a week of exposure to Staphylococcus aureus and Escherichia coli than the original ones. Microbiological investigations revealed strong antibiofilm properties of the grafted membranes in experiments with Staphylococcus aureus, Listeria monocytogenes, Escherichia coli, and Salmonella Enteritidis.

Temperature Impact on Reverse Osmosis Permeate Flux in the Remediation of Hexavalent Chromium

Reverse osmosis technique was applied in removing hexavalent chromium ions from artificial wastewater. Different operating conditions were studied to monitor the separation process using commercial Reverse Osmosis BW30XFR membrane. Different concentrations of hexavalent chromium; 5, 30, and 100 ppm were tested. Samples were subjected to incrementally increasing operating pressure; 10, 30, and 45 bar and flow rates; 2.2, 3.4, and 4.5 L/min under various temperatures; 25, 35, 45, and 55 °C. Collected permeate and concentrations were measured after each experiment using a UV spectrophotometer. Results obtained presented a higher rejection percentage at lower feed concentrations with a value up to 99.8% for 5 ppm in comparison to 94.3% for 30 ppm and 77.2% for 100 ppm concentration due to concentration polarization; however, it showed no effect of increasing operating flow rates. Moreover, the increase in feed temperature from 25 to 55 °C had positively increased permeate flux to more than 300 times. The permeate flux at 25 °C is recorded for all tested samples in the range of 30 to 158 kg/h·m2, this range has risen at 55 °C under the same conditions to the range of 70 to 226 kg/h·m2, indicating alteration within the membrane pore size due to temperature increase and high applied pressure concluding high sensitivity of polymeric membranes towards changing permeate flow rate with increasing temperatures.

Characterization of fouling for a full-scale seawater reverse osmosis plant on the Mediterranean sea: membrane autopsy and chemical cleaning efficiency

Membrane fouling is a serious problem facing most reverse osmosis plants used for the remediation and desalination of surface and ground waters. Herein, the fouling and cleaning behaviors of RO membranes, of full-scale seawater reverse osmosis (SWRO) plant after eight months of operation, were thoroughly investigated via membrane autopsies and foulants' characterization. Various techniques were applied to characterize the fouling layers; i.e., X-ray diffraction (XRD), Field emission scanning electron microscopy (FESEM), energy dispersion X-ray analysis (EDX), Fourier transform infrared spectroscopy (FTIR), X-ray fluorescence spectrometry (XRF) and thermogravimetric analysis (TG). The FESEM analysis of the membrane coupons revealed the presence of heterogeneous fouling layer with particles embedded in an amorphous matrix. The main elements detected with EDX were Si, Al, and Fe. However, FTIR spectra revealed the contribution of polysaccharides, proteins, and aromatic compounds to the fouling layer. Moreover, the normalized permeate flow rate, and differential pressure, as representatives of the plant performance, were monitored during the eight months’ study period. Based on the membrane autopsy results, membranes were regenerated by chemical cleaning with a commercial Hydrex® 4730 alkaline product; after that, Zeta potential and contact angle measurements were applied to investigate the surface charge and hydrophilicity of the surface of virgin, fouled, and cleaned RO membranes.

Study of the Permeation Flowrate of an Innovative Way to Store Hydrogen in Vehicles

With the global warming of the planet, new forms of energy are being sought as an alternative to fossil fuels. Currently, hydrogen (H2) is seen as a strong alternative for fueling vehicles. However, the major challenge in the use of H2 arises from its physical properties. An earlier study was conducted on the storage of H2, used as fuel in road vehicles powered by spark ignition engines or stacks of fuel cells stored under high pressure inside small spheres randomly packed in an envelope tank. Additionally, the study evaluated the performance of this new storage system and compared it with other storage systems already applied by automakers in their vehicles. The current study aims to evaluate the H2 leaks from the same storage system, when inserted in any road vehicle parked in conventional garages, and to show the compliance of these leaks with European Standards, provided that an appropriate choice of materials is made. The system’s compliance with safety standards was proved. Regarding the materials of each component of the storage system, the best option from the pool of materials chosen consists of aluminum for the liner of the spheres and the envelope tank, CFEP for the structural layer of the spheres, and Si for the microchip.

Renewable Thermal Energy Driven Desalination Process for a Sustainable Management of Reverse Osmosis Reject Water

A sustainable circular economy involves designing and promoting products with the least environmental impact. This research presents an experimental performance investigation of direct contact membrane distillation with feed approaching supersaturation salinity, which can be useful for the sustainable management of reverse osmosis reject water. Traditionally, reject water from the reverse osmosis systems is discharged in the sea or in the source water body. The reinjection of high salinity reject water into the sea has the potential to put the local sea environment at risk. This paper presents a design of a solar membrane distillation system that can achieve close to zero liquid discharge. The theoretical and experimental analysis on the performance of the lab scale close to zero liquid discharge system that produces supersaturated brine is studied. The lab-based experiments were conducted at boundary conditions, which were close to the real-world conditions where feed water temperatures ranged between 40 °C and 85 °C and the permeate water temperatures ranged between 5 °C and 20 °C. The feed water was supplied at salinity between 70,000 ppm to 110,000 ppm, similar to reject from reverse osmosis. The experimental results show that the maximum flux of 17.03 kg/m2·h was achieved at a feed temperature of 80 °C, a feed salinity of 10,000 ppm, a permeate temperature of 5 °C and at constant feed and a permeate flow rate of 4 L/min. Whereas for the same conditions, the theoretical mass flux was 18.23 kg/m2·h. Crystal formation was observed in the feed tank as the feed water volume reduced and the salinity increased, reaching close to 308,000 ppm TDS. At this condition, the mass flux approached close to zero due to crystallisation on the membrane surface. This study provides advice on the practical limitations for the use of membrane distillation to achieve close to zero liquid discharge.

Machine Learning Models Applied to Manage the Operation of a Simple SWRO Desalination Plant and Its Application in Marine Vessels

In this work, two machine learning techniques, specifically decision trees (DTs) and support vector machines (SVMs), were applied to optimize the performance of a seawater reverse osmosis (SWRO) desalination plant with a capacity of 100 m3 per day. The input variables to the system were seawater pH, seawater conductivity, and three requirements: permeate flow rate, permeate conductivity, and total energy consumed by the desalination plant. These requirements were decided based on a cost function that prioritizes the water needs in a vessel and the maximum possible energy savings. The intelligent system modifies the actuators of the plant: feed flow rate control and high-pressure pump (HPP) operating pressure. This tool is proposed for the optimal use of desalination plants in marine vessels. Although both machine learning techniques output satisfactory results, it was concluded that the DTs technique (HPP pressure: root mean square error (RMSE) = 0.0104; feed flow rate: RMSE = 0.0196) is more accurate than SVMs (HPP pressure: RMSE = 0.0918; feed flow rate: RMSE = 0.0198) based on the metrics used. The final objective of the paper is to extrapolate the implementation of this smart system to other shipboard desalination plants and optimize their performance.

Effects of gas permeation on the sealing performance of PEMFC stacks

The sealing performance of gaskets is critical to the safety of PEMFC stacks. Leak through the interface between gasket and BPP or MEA frame has been widely investigated, while gas permeation through gaskets is ignored in most studies. In this work, helium mass spectrometry leak measurement and finite element calculation were used to investigate the leaking and sealing mechanisms. It shows that interfacial leak and gas permeation of gaskets could be distinguished by their difference in terms of steady-state flow rate and stabilization process. Gas permeation is the main leak path of gaskets. The permeation flow rate is non-negligible for the safety of fuel cell stacks and needs to be considered when designing gaskets.

Exergy Analysis of a Direct Contact Membrane Distillation (DCMD) System Based on Computational Fluid Dynamics (CFD).

Understanding the energy efficiency of direct contact membrane distillation (DCMD) is important for the widespread application and practical implementation of the process. This study analyzed the available energy, known as exergy, in a DCMD system using computational fluid dynamics (CFD). A CFD model was developed to investigate the hydrodynamic and thermal conditions in a DCMD module. After the CFD model was verified, it was used to calculate the temperature polarization coefficient (TPC) and exergy destruction magnitudes under various operating conditions. The results revealed that slight decreases and increases in the TPC occurred with distance from the inlet in the module. The TPC was found to increase as the feed temperature was reduced and the feed and permeate flow rates were increased. The exergy destruction phenomenon was more significant under higher feed temperatures and higher flux conditions. Although the most significant exergy destruction in the permeate occurred near the feed inlet, the effect became less influential closer to the feed outlet. An analysis of exergy flows revealed that the efficiency loss in the permeate side corresponded to 32.9–45.3% of total exergy destruction.

Investigation of the Efficiency of Small-Scale NF/RO Seawater Desalination by Using Artificial Neural Network Modeling

An attempt is conducted in this paper to develop an artificial neural network (ANN) model for predicting the efficiency of small-scale NF/RO seawater desalination, then applied to the simulation of permeate flow rate and water recovery. A feed-forward back-propagation neural network with the Levenberg-Marquardt learning algorithm is considered. The performance of ANN compared to the multiple linear regression (MLR) is based on the calculated value of the coefficient of determination (R2). For ANN, R2 permeate flow rate was 0.997, and R2 permeate water recovery was 0.999, and for MLR, R2 permeate flow rate was 0.508, and R2 permeate water recovery was 0.713. It was observed that ANN performed better than the MLR.

Influence of activated sludge dissolved oxygen concentration on a membrane bioreactor performance with intermittent aeration

This study measured the effect of low activated sludge dissolved oxygen (DO) concentration on a membrane bioreactor (MBR) treating real urban wastewater with respect to organic matter and nitrogen removal efficiency and transmembrane pressure evolution. For this purpose, a full-scale experimental pre-denitrification MBR system was operated at a constant permeate flow rate of Q = 0.45 m3h−1 with intermittent aeration. The experimental installation worked at high hydraulic retention time, variable sludge retention time and with activated sludge temperatures of between 22.0 to 31.3 °C. Mean DO concentrations in the activated sludge were gradually decreased from 1.25 mgO2L−1 to less than 0.20 mgO2L−1. Variations in DO set points did not affect the main operational parameters of the MBR system and no clear relation was shown between DO concentration decrease and membrane fouling. At DO concentrations lower than 0.2 mgO2L−1, a deterioration in MBR effluent quality was observed, mainly with respect to chemical oxygen demand, biochemical oxygen demand at five days and NH4 +, however, the opposite effect was observed for NO3 -. These results indicate that employing low DO set points is a promising strategy for application in MBR systems.

Desalination of brackish water using cascade Rankine cycle based reverse osmosis system

The desalination of brackish ground water using cascade Rankine cycle is proposed. A pair of a Rankine cycle like steam Rankine cycle (SRC) and organic Rankine cycle (ORC) as a waste heat recovery. The single stage steam turbine for the SRC unit while the scroll expander for ORC unit is selected. Simulation of cascade RO system performance is considered using R245fa as a working fluid for ORC unit. The saturated steam from solar Scheffler disc will expand into steam turbine, where the reject heat from steam turbine will utilize for evaporation of ORC working fluid. The high-pressure RO pumps integrated with SRC and ORC turbines to provide net driving pressure to the RO module. This type of system is well suitable for desalination of brackish water due to moderate working temperature & pressure. Result shows that the pair of Rankine cycle will increase the overall (cascade) efficiency of the system. The basic input parameters are optimised with Taguchi approach. The performance of the system shows a good agreement with variation of mass flow rate of the steam in which the permeate flow rate from RO will increase along with the cycle efficiencies.

A Case Study of Industrial MBR Process for Poultry Slaughterhouse Wastewater Treatment

The wastewater discharged from the poultry slaughterhouse always contains high levels of chemical oxygen demand (COD) and biochemical oxygen demand (BOD) and thus, it requires proper treatment to minimize its negative impacts on the receiving water bodies. In this work, we presented a local case study of the full-scale implementation of membrane bioreactor (MBR) process with capacity of 144 m3/day to treat the poultry slaughterhouse wastewater. Over the 6-month monitoring period, our results showed that the permeate flow rate of the MBR process was relatively stable and only suffered from approximately 16% flux decline for the entire period with 8-h operation daily. Such flux deterioration is acceptable given the membrane was not subjected to any cleaning process. With respect to the separation efficiencies, the MBR process showed a very promising performance by meeting almost all of the parameters’ limit of the National Water Quality Standards (Class IIB Limit), except for the dissolved oxygen (DO) that displayed slightly higher value than the maximum limit. A chemical cleaning process using sodium hydrochloride as agent was found to be effective to retrieve the permeate flow rate of the fouled membrane by 99%, indicating the deposited organic foulants were mainly reversible ones. The findings from this case study clearly demonstrated the potential of MBR process for treatment of poultry slaughterhouse wastewater and played an important role to minimize the negative impacts of discharged effluents on the environment.

Flow management strategies for a connected purification process.

This paper describes different flow management strategies for a connected purification process which includes two polishing steps, virus filtration and tangential flow filtration. Connecting these unit operations avoids introducing large intermediate product pool vessels in small manufacturing facilities. However, a connected-downstream process requires an elaborate control strategy enabling multiple unit operations to function as a single unit. The key strategy to enable the connected-downstream process is a robust management of flow disparities among unit operations. During a typical ultrafiltration step, product concentration increases as mass is added to the retentate tank, leading to a permeate flux decline. In a connected-downstream process, the inlet stream is directly connected to the prior unit operation and any decrease in permeate flow rate could cause a flow disparity. Four different flow management approaches are proposed to manage potential flow disparities and their advantages and challenges are discussed. Bench-scale results of these strategies are presented and evaluated.

Modeling and optimization of small-scale NF/RO seawater desalination using the artificial neural network (ANN)

The performance of seawater hybrid NF/RO desalination plant including permeate conductivity; permeate flow rate and permeate recovery. Under different feed parameters time, inlet temperature, inlet pressure, inlet conductivity and inlet flow rate were modelled by Artificial Neural Network (ANN) back-propagation based on Levenberg– Marquardt training algorithm. The optimal ANN model had a 5-8-3 architecture with a hyperbolic tangent transfer function in hidden layer and linear transfer function at the output layer. The ability of ANN performed model was compared with multiple linear regression (MLR). The results show that MLR is not satisfactory for predicting the performance of NF/RO hybrid desalination process with a correlation coefficient about 0.6. The trained ANN model has presented a good agreement between the prediction and the experimental data during the training with reasonable statistical metrics values (RMSE, MAE and AARD). The coefficient of determination values for the prediction of permeate conductivity, permeate flow rate and recovery by ANN were 0.969, 0.942, and 0.963, respectively. Therefore, the ANN model can successfully predict the performance of NF/RO hybrid seawater desalination plant.

Pervaporation of Aqueous Ethanol Solutions through Rigid Composite Polyvinyl-Alcohol/Bacterial Cellulose Membranes

The paper focuses on synthesis, characterization and testing in ethanol-water separation by pervaporation of new membrane types based on polyvinyl alcohol (PVA) and bacterial cellulose (BC). A technology for obtaining these membranes deposited on a ceramic support is presented in the experimental section. Three PVA-BC composite membranes with different BC content were obtained and characterized by FTIR, SEM and optic microscopy. The effects of operating temperature (40–60 °C), permeate pressure (18.7–37.3 kPa) and feed ethanol concentration (24–72%wt) on total permeate flow rate (0.09–0.23 kg/m2/h) and water/ethanol selectivity (5–23) were studied based on an appropriate experimental plan for each PVA-BC membrane. Statistical models linking the process factors to pervaporation performances were obtained by processing the experimental data. Ethanol concentration of the processed mixture had the highest influence on permeate flow rate, an increase in ethanol concentration leading to a decrease in the permeate flow rate. All 3 process factors and their interactions had positive effects on membrane selectivity. Polynomial regression models were used to assess the effect of BC content in the dried membrane on pervaporation performances. Values of process performances obtained in this study indicate that these membranes could be effective for ethanol-water separation by pervaporation.

Design of reverse osmosis filtration system for the supply of clean water from saltwater wells in tanjung lame village

Groundwater sources from community wells in Tanjung Lame village, Pandeglang regency, are not suitable for consumption, due to high salinity. In addition, reverse osmosis (RO) filtration system is a typical and efficient alternative technology adopted during the processing of clean water from saltwater sources. However, large amount of pressure is usually involved for a conventional single-stage RO. The purpose of this study, therefore, was to design a multi-stage RO filtration system capable of operating at low pressures. Therefore, the adopted model with a configuration of hybrid RO/NF permeate staging has proven to produce potable water from saltwater wells in Tanjung Lame village at low pressures. Moreover, the system was operated at the first and second stage RO/NF pressure of 6 and 3 bar, respectively. Under these circumstances, salt rejection and permeate TDS were estimated at 97.02% and 86 ppm, respectively in order to obtain optimum outcome. Furthermore, the product water recovery rate was evaluated at 37%, and a permeate flow rate of 1.85 liters/minute. The systems’ specific energy consumption (SEC) was estimated to be 1.802 kWh/m3, while a reduced value of 58.39% was observed for conventional single-stage RO.