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Open AccessArticle

A Numerical Simulation of Membrane Distillation Treatment of Mine Drainage by Computational Fluid Dynamics

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Water 2020, 12(12), 3403; https://doi.org/10.3390/w12123403 - 03 Dec 2020

Abstract

Membrane distillation (MD) is a promising technology to treat mine water. This work aims to investigate the change in mass and heat transfer in reverse osmosis mine water treatment by vacuum membrane distillation (VMD). A 3D computational fluid dynamics (CFD) model was carried [...] Read more.

Membrane distillation (MD) is a promising technology to treat mine water. This work aims to investigate the change in mass and heat transfer in reverse osmosis mine water treatment by vacuum membrane distillation (VMD). A 3D computational fluid dynamics (CFD) model was carried out using COMSOL Multiphysics and verified by the experimental results. Then, response Surface Methodology (RSM) was used to explore the effects of various parameters on the permeate flux and heat transfer efficiency. In terms of the influence degree on the permeation flux, the vacuum pressure > feed temperature > membrane length > feed temperature membrane length, and the membrane length has a negative correlation with the membrane flux. Increasing the feed temperature can also increase the convective heat transfer at the feed side, which will affect the heat transfer efficiency. Furthermore, the feed temperature also has a critical effect on the temperature polarization phenomenon. The temperature polarization becomes more notable at high temperatures. Full article

(This article belongs to the Special Issue Membrane Technologies and Water Treatment)

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Open AccessArticle

Direct Membrane Filtration for Wastewater Treatment Using an Intermittent Rotating Hollow Fiber Module

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Water 2020, 12(6), 1836; https://doi.org/10.3390/w12061836 - 26 Jun 2020

Abstract

Direct membrane filtration of municipal wastewater has attracted a considerable interest in recent years. Preventing severe membrane fouling is a crucial issue in the process development. This paper aims to assess the effectiveness of a rotating hollow fiber module in enhancing fouling control. [...] Read more.

Direct membrane filtration of municipal wastewater has attracted a considerable interest in recent years. Preventing severe membrane fouling is a crucial issue in the process development. This paper aims to assess the effectiveness of a rotating hollow fiber module in enhancing fouling control. The effect of rotation speed, intermittence and permeate flux was studied in short-term tests at lab-scale. A combined filtration model considering residual fouling, intermediate pore blocking and cake filtration was used to analyze the effect of the shear induced by rotation. Results showed a significant flux improvement by increasing rotation shear stress and showed a nearly linear correlation between the threshold flux (ranged between 12 and 32 L·h⁻¹·m⁻²) and the rotation speed. A proper rotation intermittence (10/15 on/off) was found, which may maintain a fouling control comparable to that achieved for continuous rotation. For a given energy demand, the optimal operating conditions involve high speeds (≥180 rev·min⁻¹) with low to moderate intermittences. Analyzing the relative contribution of the different feedwater fractions on membrane fouling, colloidal particles and macromolecules were found to be the main contributors. Full article

(This article belongs to the Special Issue Membrane Technologies and Water Treatment)

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Open AccessArticle

Nutrients Enrichment and Process Repercussions in Hybrid Microfiltration Osmotic Membrane Bioreactor: A Guideline for Forward Osmosis Development Based on Lab-Scale Experience

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Khum Gurung

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Morten Lykkegaard Christensen

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Mika Sillanpää

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Mohamed Chaker Ncibi

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Mads Koustrup Jørgensen

Water 2020, 12(4), 1098; https://doi.org/10.3390/w12041098 - 12 Apr 2020

Abstract

The effects of reverse salt diffusion through a forward osmosis membrane were studied in a microfiltration osmotic membrane bioreactor. The reactor was used to treat and simultaneously concentrate nutrients from wastewater. The system was operated at different draw solution concentrations, leading to varying [...] Read more.

The effects of reverse salt diffusion through a forward osmosis membrane were studied in a microfiltration osmotic membrane bioreactor. The reactor was used to treat and simultaneously concentrate nutrients from wastewater. The system was operated at different draw solution concentrations, leading to varying salinity conditions. A relatively low, yet stable forward osmosis flux was observed regardless of increasing draw solution conductivities from 10 to 50 mS cm⁻¹. A substantial increase in sludge conductivity from 5.7 to 19.8 mS cm⁻¹ was observed during the operation. Batch transmembrane pressure-step experiments showed a decline in sludge filtration properties with increasing salinity buildup in sludge due to increasing deflocculation and associated release of protein and carbohydrate fractions of extracellular polymeric substances. Mathematical simulations showed that accumulation of total dissolved solids could mainly be attributed to reverse flux of salts from the draw solution rather than by the enrichment of incoming nutrients when forward osmosis membrane’s salt permeability was high and water permeability low. Ideally, salt permeability below 0.010 L m⁻² h⁻¹ and effective water permeability above 0.13 L m⁻² h⁻¹ bar⁻¹ are crucial to ensure enhanced nutrient enrichment and reduce sludge osmotic pressure, microbial inactivation, sludge deflocculation and membrane fouling. Full article

(This article belongs to the Special Issue Membrane Technologies and Water Treatment)

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Open AccessArticle

Identification of Foulants on Polyethersulfone Membranes Used to Remove Colloids and Dissolved Matter from Paper Mill Treated Effluent

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Mayko Rannany S. Sousa

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Jaime Lora-García

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María-Fernanda López-Pérez

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Marc Heran

Water 2020, 12(2), 365; https://doi.org/10.3390/w12020365 - 29 Jan 2020

Cited by 1

Abstract

In this study, membrane fouling caused by paperboard mill treated effluent (PMTE) was investigated based on a dead-end ultrafiltration (UF) pilot-scale study. The membranes employed were commercial hydrophobic UF membranes made of polyethersulfone (PES) with a molecular weight cut-off of 10 kDa, 50 [...] Read more.

In this study, membrane fouling caused by paperboard mill treated effluent (PMTE) was investigated based on a dead-end ultrafiltration (UF) pilot-scale study. The membranes employed were commercial hydrophobic UF membranes made of polyethersulfone (PES) with a molecular weight cut-off of 10 kDa, 50 kDa, and 100 kDa. Membrane fouling mechanism during dead-end filtration, chemical analysis, field emission scanning electron microscopy (FESEM), energy-dispersive spectrophotometry (EDS), attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopy and 3D fluorescence excitation–emission matrix (3DEEM) analysis were applied to understand which fraction of the dissolved and colloidal substances (DCS) caused the membrane fouling. The results indicated that the phenomenon controlling fouling mechanism tended to be cake layer formation (R² ≥ 0.98) for all membranes tested. The 3DEEM results indicate that the majority of the organic foulants with fluorescence characteristics on the membrane were colloidal proteins (protein-like substances I+II) and macromolecular proteins (soluble microbial products, SMP-like substances). In addition, polysaccharide (cellulosic species), fatty and resin acid substances were identified on the fouled membrane by the ATR–FTIR analysis and play an important role in membrane fouling. In addition, the FESEM and EDS analyses indicate that the presence of inorganic foulants on the membrane surfaces, such as metal ions and especially Ca²⁺, can accelerate membrane fouling, whereas Mg and Si are linked to reversible fouling. Full article

(This article belongs to the Special Issue Membrane Technologies and Water Treatment)

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Open AccessEditor’s ChoiceArticle

Membrane Fouling and Performance of Flat Ceramic Membranes in the Application of Drinking Water Purification

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Water 2019, 11(12), 2606; https://doi.org/10.3390/w11122606 - 10 Dec 2019

Cited by 5

Abstract

Membrane technologies have been widely applied in surface water treatment for drinking water purification. The main obstacles to the large scale application of membranes include membrane fouling, energy consumption and high investment. This study systematically investigated the performance of a hybrid system including [...] Read more.

Membrane technologies have been widely applied in surface water treatment for drinking water purification. The main obstacles to the large scale application of membranes include membrane fouling, energy consumption and high investment. This study systematically investigated the performance of a hybrid system including in-situ coagulation and membrane module. The key parameters of a membrane system, including initial flux, operation mode (intermediate or continuous, time intervals, backwashing and aeration) was comprehensively investigated. In addition, the treatment performance in terms of turbidity, organic matter removal, membrane fouling and cleaning, and the effect of coagulants, were also studied. It was found that flat ceramic membranes with in-situ coagulation for surface water treatment performed much better without aeration and frequent backwashing, which gave interesting and important implications for future applications of a flat ceramic membrane, especially in drinking water purification. The hybrid system can achieve a high-water flux of 150 L/m²·h (LMH) for 8 h operation without aeration and backwash. The removal of turbidity, UV₂₅₄ and COD can achieve 99%, 85% and 81%, respectively. The cake layer on the membrane surface formed from the coagulation flocs turned out to prevent the membrane to be exposed to organic pollutant immediately which minimized the fouling problem. In addition, the fouling layer on the membrane surface can be easily cleaned by air scouring and backwash at the end of experiments, with a water flux recovery of higher than 90%. These results in this study provided an alternative strategy for membrane fouling control and energy conservation. Full article

(This article belongs to the Special Issue Membrane Technologies and Water Treatment)

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Open AccessArticle

Treatment of Effluents from the Textile Industry through Polyethersulfone Membranes

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Rodholfo da Silva Barbosa Ferreira

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Aline Florindo Salviano

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Sandriely Sonaly Lima Oliveira

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Edcleide Maria Araújo

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Vanessa da Nóbrega Medeiros

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Hélio de Lucena Lira

Water 2019, 11(12), 2540; https://doi.org/10.3390/w11122540 - 01 Dec 2019

Cited by 1

Abstract

Membranes have been widely used in the treatment of industrial effluents. However, there are still some limitations in the separation and permeability with respect to these effluents. Therefore, this study investigated the addition of 1% and 5% of an inorganic filler (clay) in [...] Read more.

Membranes have been widely used in the treatment of industrial effluents. However, there are still some limitations in the separation and permeability with respect to these effluents. Therefore, this study investigated the addition of 1% and 5% of an inorganic filler (clay) in polyethersulfone polymer membranes. By contact angle analysis, it was observed that the clay influenced the hydrophilicity of the membrane. The presence of the clay had an important role in the morphology of the membrane, modifying and favoring a greater quantity of pores and macropores for the porous support. For the tensile test, it was seen that the high clay content decreased the membranes properties. The flow tests, having a flow stabilized around 300 L/h·m² for membranes containing clay, evidenced the efficiency of the membrane for the treatment of indigo blue, representing a 200% increase in relation to polyethersulfone membrane. The membrane containing 1% of clay presented the highest level of rejection to the effluent, around 94.0%. Thus, it was evident that the addition of montmorillonite clay modified the membrane structure contributing to a higher selectivity and permeability. Full article

(This article belongs to the Special Issue Membrane Technologies and Water Treatment)

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Open AccessFeature PaperArticle

Techno-Economic Assessment of Air and Water Gap Membrane Distillation for Seawater Desalination under Different Heat Source Scenarios

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David Amaya-Vías

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Juan Antonio López-Ramírez

Water 2019, 11(10), 2117; https://doi.org/10.3390/w11102117 - 12 Oct 2019

Cited by 5

Abstract

Membrane distillation (MD) has a great deal of potential and this is currently being explored by the scientific community. However, this technology has not yet been implemented by industry, and an estimation of final product costs is key to its commercial success. In [...] Read more.

Membrane distillation (MD) has a great deal of potential and this is currently being explored by the scientific community. However, this technology has not yet been implemented by industry, and an estimation of final product costs is key to its commercial success. In this study a techno-economic assessment of air gap MD (AGMD) and water gap MD (WGMD) for seawater desalination under different capacities and heat source scenarios was developed. The simplified cost of water (SCOW) method, which estimates investment costs, fixed and variable costs, as well as amortization factors and price influence over time was applied. In addition, experimental data from a laboratory-scale MD desalination plant were also used. The results showed water costs in the range of 1.56 to 7.53 €/m³ for WGMD and 2.38 to 9.60 €/m³ for AGMD. Specifically, the most feasible scenario was obtained for WGMD with a capacity of 1000 m³ daily using waste and solar heat. Finally, the costs obtained for MD were similar to those of conventional desalination technologies at the same scale factor. Therefore, although large-scale pilot studies and optimization of manufacturing processes are needed, MD shows very promising results that should be considered further. Full article

(This article belongs to the Special Issue Membrane Technologies and Water Treatment)

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Open AccessArticle

Heterotrophic Kinetic Study and Nitrogen Removal of a Membrane Bioreactor System Treating Real Urban Wastewater under a Pharmaceutical Compounds Shock: Effect of the Operative Variables

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Antonio Monteoliva-García

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Juan Carlos Leyva-Díaz

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Water 2019, 11(9), 1785; https://doi.org/10.3390/w11091785 - 28 Aug 2019

Cited by 1

Abstract

Numerous studies have analyzed the viability of the biodegradation and removal of different compounds of emerging concern in biological systems for wastewater treatment. However, the effect on the heterotrophic biomass of organic matter removal is sometimes missed. The aim of the present research [...] Read more.

Numerous studies have analyzed the viability of the biodegradation and removal of different compounds of emerging concern in biological systems for wastewater treatment. However, the effect on the heterotrophic biomass of organic matter removal is sometimes missed. The aim of the present research was to study the effect of the addition of a mix of three pharmaceuticals (carbamazepine, ciprofloxacin, and ibuprofen) on the behavior of the biomass in two different membrane-based biological systems treating urban wastewater. The present research studied a membrane bioreactor (MBR) pilot plant operating at a similar mixed liquor suspended solids (MLSS) concentration (about 5.5 g/L). This system works as an MBR and is combined with a moving bed biofilm reactor (MBBR-MBR) to treat real urban wastewater at 6 and 10 h of hydraulic retention time (HRT) under three different shocks of pharmaceuticals with increasing concentrations. In all cases, the organic matter removal was, in average terms, higher than about 92% of biochemical oxygen demand on the fifth day (BOD₅), 79% of chemical oxygen demand (COD), and 85% of total organic carbon (TOC). Nevertheless, the removal is higher in the MBBR-MBR technology under the same HRT and the MLSS is similar. Moreover, the removal increased during the shock of pharmaceutical compounds, especially in the MBR technology. From a kinetic perspective, MBBR-MBR is more suitable for low HRT (6 h) and MBR is more effective for high HRT (10 h). This could be due to the fact that biofilm systems are less sensitive to hostile environments than the MBR systems. The removal of N-NH₄⁺ decreased considerably when the pharmaceutical compounds mix was introduced into the system until no removal was detected in cycle 1, even when biofilm was present. Full article

(This article belongs to the Special Issue Membrane Technologies and Water Treatment)

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