Recent Submissions

  • Pulsating CO2 nucleation radically improves the efficiency of membrane backwash

    Al Ghamdi, Mohanned; Alpatova, Alla; Alhadidi, Abdulsalam; Ghaffour, NorEddine (Desalination, Elsevier BV, 2021-09-11) [Article]
    Although membrane filtration became a dominant water treatment technology globally, it suffers from membrane fouling which aggravates with time and imposes severe adverse effects on process performance, permeate quality and, eventually, its related costs. In this work, we introduce pulsating CO2 solution backwash with intermittent pressure drops to maximize CO2 bubbles yield and radically enhance membrane cleaning. The novel backwash technique was probed during ultrafiltration (UF) of feed waters containing sodium alginate, a model polysaccharide foulants, sea salts enriched in Ca2+, and SiO2. Transmembrane pressures (TMP) observed during the experiments with pulsating CO2 backwash acquired an up/down profile indicating that a considerable portion of TMP was recovered after each backwash cycle, in contrast to insufficient fouling removal and subsequent TMP build-up observed with continuous CO2 and Milli-Q backwashes. Notably, pulsating CO2 backwash alleviated irreversible membrane fouling in highly saline conditions with 30 g/L of sea salts and when it is combined with 1 mg/L of SiO2 (i.e., when conventional membrane backwash was not effective). Furthermore, intense cleaning of the membrane surface and its pores was resembled by a lower fouling resistance in the subsequent UF cycles implying potentially longer operation time with less cleaning frequency and substantial energy savings.
  • Relative Importance of Stochastic Assembly Process of Membrane Biofilm Increased as Biofilm Aged

    Matar, Gerald; Ali, Muhammad; Bagchi, Samik; Nunes, Suzana Pereira; Liu, Wen-Tso; Saikaly, Pascal (Frontiers in Microbiology, Frontiers Media SA, 2021-09-10) [Article]
    The relative importance of different ecological processes controlling biofilm community assembly over time on membranes with different surface characteristics has never been investigated in membrane bioreactors (MBRs). In this study, five ultrafiltration hollow-fiber membranes – having identical nominal pore size (0.1μm) but different hydrophobic or hydrophilic surface characteristics – were operated simultaneously in the same MBR tank with a constant flux of 10 liters per square meter per hour (LMH). In parallel, membrane modules operated without permeate flux (0 LMH) were submerged in the same MBR tank, to investigate the passive microbial adsorption onto different hydrophobic or hydrophilic membranes. Samples from the membrane biofilm were collected after 1, 10, 20, and 30days of continuous filtration. The membrane biofilm microbiome were investigated using 16S rRNA gene amplicon sequencing from DNA and cDNA samples. Similar beta diversity trends were observed for both DNA- and cDNA-based analyses. Beta diversity analyses revealed that the nature of the membrane surface (i.e., hydrophobic vs. hydrophilic) did not seem to have an effect in shaping the bacterial community, and a similar biofilm microbiome evolved for all types of membranes. Similarly, membrane modules operated with and without permeate flux did not significantly influence alpha and beta diversity of the membrane biofilm. Nevertheless, different-aged membrane biofilm samples exhibited significant differences. Proteobacteria was the most dominant phylum in early-stage membrane biofilm after 1 and 10days of filtration. Subsequently, the relative reads abundance of the phyla Bacteroidetes and Firmicutes increased within the membrane biofilm communities after 20 and 30days of filtration, possibly due to successional steps that lead to the formation of a relatively aged biofilm. Our findings indicate distinct membrane biofilm assembly patterns with different-aged biofilm. Ecological null model analyses revealed that the assembly of early-stage biofilm community developed after 1 and 10days of filtration was mainly governed by homogenous selection. As the biofilm aged (days 20 and 30), stochastic processes (e.g., ecological drift) started to become important in shaping the assembly of biofilm community.
  • Real-time membrane fouling analysis for the assessment of reclamation potential of textile wastewater processed by membrane distillation

    Elcik, Harun; Fortunato, Luca; Vrouwenvelder, Johannes S.; Ghaffour, NorEddine (Journal of Water Process Engineering, Elsevier BV, 2021-09-09) [Article]
    Understanding the factors that specify the fouling development in membrane distillation (MD) plays a key role to develop effective control strategies with the aim of providing its widespread use in industrial applications, such as textile industry. The present study investigated the fouling mechanisms in textile wastewater treatment by direct contact MD (DCMD), employing an advanced in-situ optical coherence tomography (OCT) technology allowing to monitor MD fouling in real-time. The OCT analysis enabled evaluating the effect of feed temperature, flow rate, dye concentration on the membrane fouling and the long-term performance of MD operation that includes a periodical water flushing. The permeate flux decrease during the initial stages of experiments was attributed to the existence of attractive hydrophobic-hydrophobic interaction between the membrane and dye molecules as no cake fouling was observed at the early stages. Then, a flat and homogeneous cake layer was developed with time in all the fouled membranes regardless of the cake layer thickness. The long-term experiment resulted in both reversible and irreversible fouling and showed that water flushing had limited efficacy against reversible fouling. Additionally, electrostatic repulsive forces occurring between the membrane and textile dye molecules influenced the permeate flux depending on the dye concentration. Finally, among all the operating parameters, feed temperature had the highest impact on the membrane fouling and process performance, changed the heat transfer activity at the membrane-liquid frontier zone, in turn, leading to variations in the flux.
  • UV and bacteriophages as a chemical-free approach for cleaning membranes from anaerobic bioreactors

    Scarascia, Giantommaso; Fortunato, Luca; Myshkevych, Yevhen; Cheng, Hong; Leiknes, TorOve; Hong, Pei-Ying (Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, 2021-09-07) [Article]
    Anaerobic membrane bioreactor (AnMBR) for wastewater treatment has attracted much interest due to its efficacy in providing high-quality effluent with minimal energy costs. However, membrane biofouling represents the main bottleneck for AnMBR because it diminishes flux and necessitates frequent replacement of membranes. In this study, we assessed the feasibility of combining bacteriophages and UV-C irradiation to provide a chemical-free approach to remove biofoulants on the membrane. The combination of bacteriophage and UV-C resulted in better log cells removal and ca. 2× higher extracellular polymeric substance (EPS) concentration reduction in mature biofoulants compared to either UV-C or bacteriophage alone. The cleaning mechanism behind this combined approach is by 1) reducing the relative abundance of Acinetobacter spp. and selected bacteria (e.g., Paludibacter, Pseudomonas, Cloacibacterium, and gram-positive Firmicutes) associated with the membrane biofilm and 2) forming cavities in the biofilm to maintain water flux through the membrane. When the combined treatment was further compared with the common chemical cleaning procedure, a similar reduction on the cell numbers was observed (1.4 log). However, the combined treatment was less effective in removing EPS compared with chemical cleaning. These results suggest that the combination of UV-C and bacteriophage have an additive effect in biofouling reduction, representing a potential chemical-free method to remove reversible biofoulants on membrane fitted to an AnMBR.
  • Effect of Seasonal Variation and Meteorological Parameters on the Environmental Noise Pollution in the Selected Areas of Rawalpindi and Islamabad, Pakistan

    Khan, Bilal; Jamil, Asma; Nawaz, Muhammad Saqib (Polish Journal of Environmental Studies, HARD Publishing Company, 2021-08-30) [Article]
    Environmental noise is one of the most unpredictable pollutants that adversely affect humans‘ physical and mental health. In this study, noise levels were recorded from six different locations of Rawalpindi and Islamabad, Pakistan. The purpose was to evaluate the noise levels and corresponding noise intensities with the variation of seasonal and meteorological factors. The noise levels were recorded with a calibrated digital sound level meter, and corresponding sound intensity levels were calculated. Temperature and humidity values were also recorded. Data was recorded for four different time slots, and 84 readings were recorded from each location over seven months. The average noise level recorded from selected locations of 6th road, Pirwadahi, Raja-bazar, Faizabad Rawalpindi, I-9/3 sector Islamabad and Karachi Company were 71.0, 85.5, 83.7, 79.9, 75.7, and 69.5 dB, respectively. These all exceeded the prescribed limits of the National Environmental Quality Standards (NEQS). A trend of increasing noise levels during summer was observed with increasing humidity levels. Significant variation of noise levels was observed diurnally and seasoned wise between winter and summer months. To control and reduce noise pollution from the selected locations, the authorities should take proper countermeasures.
  • Quinoa Phenotyping Methodologies: An International Consensus

    Stanschewski, Clara; Rey, Elodie; Fiene, Gabriele; Craine, Evan; Wellman, Gordon; Melino, Vanessa J.; Patiranage, Dilan; Johansen, Kasper; Schmöckel, Sandra; Bertero, Daniel; Oakey, Helena; Colque-Little, Carla; Afzal, Irfan; Raubach, Sebastian; Miller, Nathan; Streich, Jared; Amby, Daniel; Emrani, Nazgol; Warmington, Mark; Mousa, Magdi; Wu, David; Jacobson, Daniel; Andreasen, Christian; Jung, Christian; Murphy, Kevin; Bazile, Didier; Tester, Mark A.; on behalf of the Quinoa Phenotyping Consortium (Plants, MDPI AG, 2021-08-24) [Article]
    Quinoa is a crop originating in the Andes but grown more widely and with the genetic potential for significant further expansion. Due to the phenotypic plasticity of quinoa, varieties need to be assessed across years and multiple locations. To improve comparability among field trials across the globe and to facilitate collaborations, components of the trials need to be kept consistent, including the type and methods of data collected. Here, an internationally open-access framework for phenotyping a wide range of quinoa features is proposed to facilitate the systematic agronomic, physiological and genetic characterization of quinoa for crop adaptation and improvement. Mature plant phenotyping is a central aspect of this paper, including detailed descriptions and the provision of phenotyping cards to facilitate consistency in data collection. High-throughput methods for multi-temporal phenotyping based on remote sensing technologies are described. Tools for higher-throughput post-harvest phenotyping of seeds are presented. A guideline for approaching quinoa field trials including the collection of environmental data and designing layouts with statistical robustness is suggested. To move towards developing resources for quinoa in line with major cereal crops, a database was created. The Quinoa Germinate Platform will serve as a central repository of data for quinoa researchers globally.
  • Recovery of Critical Metals from Aqueous Sources

    Can Sener, Serife E.; Thomas, Valerie M.; Hogan, David E.; Maier, Raina M.; Carbajales-Dale, Michael; Barton, Mark D.; Karanfil, Tanju; Crittenden, John C.; Amy, Gary L. (ACS Sustainable Chemistry & Engineering, American Chemical Society (ACS), 2021-08-24) [Article]
    Critical metals, identified from supply, demand, imports, and market factors, include rare earth elements (REEs), platinum group metals, precious metals, and other valuable metals such as lithium, cobalt, nickel, and uranium. Extraction of metals from U.S. saline aqueous, emphasizing saline, sources is explored as an alternative to hardrock ore mining. Potential aqueous sources include seawater, desalination brines, oil- and gas-produced waters, geothermal aquifers, and acid mine drainage, among others. A feasibility assessment reveals opportunities for recovery of lithium, strontium, magnesium, and several REEs from select sources, in quantities significant for U.S. manufacturing and for reduction of U.S. reliance on international supply chains. This is a conservative assessment given that water quality data are lacking for a significant number of critical metals in certain sources. The technology landscape for extraction and recovery of critical metals from aqueous sources is explored, identifying relevant processes along with knowledge gaps. Our analysis indicates that aqueous mining would result in much lower environmental impacts on water, air, and land than ore mining. Preliminary assessments of the economics and energy consumption of recovery show potential for recovery of critical metals.
  • Ultrasound-assisted membrane technologies for fouling control and performance improvement: A review

    Naji, Osamah; Al-juboori, Raed A.; Khan, Abdulaziz; Yadav, Sudesh; Altaee, Ali; Alpatova, Alla; Soukane, Sofiane; Ghaffour, NorEddine (Journal of Water Process Engineering, Elsevier BV, 2021-08-20) [Article]
    Membrane separation is widely used in wastewater treatment and desalination due to its high performance and ability to handle feed solutions of different qualities. Despite vast history of success, membrane fouling remains a major system deficiency that imposes substantial process limitations by reducing permeate production and increasing energy demand. Besides, chemical cleaning-in-place (CIP) adversely affects membrane integrity and generates an extra waste stream. Ultrasound (US) is a relatively new cleaning technique that improves process performance by mitigating fouling accumulation at a membrane surface and improving permeate flux by promoting mass and heat transfer. US-assisted membrane processes is an efficient method for fouling reduction and significant flux improvement. This study comprehensively reviews US applications in pressure-, thermally- and osmotic-driven membrane technologies and their impact on process performance. It also explores the impact of US operating conditions on membrane separation properties and how these parameters can be tuned to achieve the desirable outcome. To date, the application of US in membrane technologies is limited to laboratory tests. In the authors' opinion, there is a niche market for US-assisted membrane technology in heavily contaminated water such as wastewater and brine. After critical analysis of the literature, we found that there are still several aspects of the process need to be scrutinized carefully to make an adequate evaluation of its feasibility on an industrial scale. The most urgent one is the techno-economic evaluation of the technology based on large-scale and long-term tests. The study proposed a set of recommendations for future research directions of US applications in membrane technologies.
  • Overcoming the Challenges of Thermal Infrared Orthomosaics Using a Swath-Based Approach to Correct for Dynamic Temperature and Wind Effects

    Malbeteau, Yoann; Johansen, Kasper; Aragon Solorio, Bruno Jose Luis; Al-Mashhawari, Samir K.; McCabe, Matthew F. (Remote Sensing, MDPI AG, 2021-08-18) [Article]
    The miniaturization of thermal infrared sensors suitable for integration with unmanned aerial vehicles (UAVs) has provided new opportunities to observe surface temperature at ultra-high spatial and temporal resolutions. In parallel, there has been a rapid development of software capable of streamlining the generation of orthomosaics. However, these approaches were developed to process optical and multi-spectral image data and were not designed to account for the often rapidly changing surface characteristics inherent in the collection and processing of thermal data. Although radiometric calibration and shutter correction of uncooled sensors have improved, the processing of thermal image data remains difficult due to (1) vignetting effects on the uncooled microbolometer focal plane array; (2) inconsistencies between images relative to in-flight effects (wind-speed and direction); (3) unsuitable methods for thermal infrared orthomosaic generation. Here, we use thermal infrared UAV data collected with a FLIR-based TeAx camera over an agricultural field at different times of the day to assess inconsistencies in orthophotos and their impact on UAV-based thermal infrared orthomosaics. Depending on the wind direction and speed, we found a significant difference in UAV-based surface temperature (up to 2 °C) within overlapping areas of neighboring flight lines, with orthophotos collected with tail wind being systematically cooler than those with head wind. To address these issues, we introduce a new swath-based mosaicking approach, which was compared to three standard blending modes for orthomosaic generation. The swath-based mosaicking approach improves the ability to identify rapid changes of surface temperature during data acquisition, corrects for the influence of flight direction relative to the wind orientation, and provides uncertainty (pixel-based standard deviation) maps to accompany the orthomosaic of surface temperature. It also produced more accurate temperature retrievals than the other three standard orthomosaicking methods, with a root mean square error of 1.2 °C when assessed against in situ measurements. As importantly, our findings demonstrate that thermal infrared data require appropriate processing to reduce inconsistencies between observations, and thus, improve the accuracy and utility of orthomosaics.
  • Long-Term Continuous Extraction of Medium-Chain Carboxylates by Pertraction With Submerged Hollow-Fiber Membranes

    Xu, Jiajie; Bian, Bin; Angenent, Largus T.; Saikaly, Pascal (Frontiers in Bioengineering and Biotechnology, Frontiers Media SA, 2021-08-13) [Article]
    Medium-chain carboxylic acids (MCCAs), which can be generated from organic waste and agro-industrial side streams through microbial chain elongation, are valuable chemicals with numerous industrial applications. Membrane-based liquid-liquid extraction (pertraction) as a downstream separation process to extract MCCAs has been applied successfully. Here, a novel pertraction system with submerged hollow-fiber membranes in the fermentation bioreactor was applied to increase the MCCA extraction rate and reduce the footprint. The highest average surface-corrected MCCA extraction rate of 655.2 ± 86.4 mmol C m$^{−2}$ d$^{−1}$ was obtained, which was higher than any other previous reports, albeit the relatively small surface area removed only 11.6% of the introduced carbon via pertraction. This submerged extraction system was able to continuously extract MCCAs with a high extraction rate for more than 8 months. The average extraction rate of MCCA by internal membrane was 3.0- to 4.7-fold higher than the external pertraction (traditional pertraction) in the same bioreactor. A broth upflow velocity of 7.6 m h$^{−1}$ was more efficient to extract MCCAs when compared to periodic biogas recirculation operation as a means to prevent membrane fouling. An even higher broth upflow velocity of 40.5 m h$^{−1}$ resulted in a significant increase in methane production, losing more than 30% of carbon conversion to methane due to a loss of H2, and a subsequent drop in the H2 partial pressure. This resulted in the shift from a microbial community with chain elongators as the key functional group to methanogens, because the drop in H2 partial pressure led to thermodynamic conditions that oxidizes ethanol and carboxylic acids to acetate and H2 with methanogens as the syntrophic partner. Thus, operators of chain elongating systems should monitor the H2 partial pressure when changes in operating conditions are made.
  • Physicochemical Properties of Extracellular Polymeric Substances Produced by Three Bacterial Isolates From Biofouled Reverse Osmosis Membranes.

    Rehman, Zahid Ur; Vrouwenvelder, Johannes S.; Saikaly, Pascal (Frontiers in microbiology, Frontiers Media SA, 2021-08-05) [Article]
    This work describes the chemical composition of extracellular polymeric substances (EPS) produced by three bacteria (RO1, RO2, and RO3) isolated from a biofouled reverse osmosis (RO) membrane. We isolated pure cultures of three bacterial strains from a 7-year-old biofouled RO module that was used in a full-scale seawater treatment plant. All the bacterial strains showed similar growth rates, biofilm formation, and produced similar quantities of proteins and polysaccharides. The gel permeation chromatography showed that the EPS produced by all the strains has a high molecular weight; however, the EPS produced by strains RO1 and RO3 showed the highest molecular weight. Fourier Transform Infrared Spectroscopy (FTIR), Proton Nuclear Magnetic Resonance (1H NMR), and Carbon NMR (13C NMR) were used for a detailed characterization of the EPS. These physicochemical analyses allowed us to identify features of EPS that are important for biofilm formation. FTIR analysis indicated the presence of α-1,4 glycosidic linkages (920 cm–1) and amide II (1,550 cm–1) in the EPS, the presence of which has been correlated with the fouling potential of bacteria. The presence of α-glycoside linkages was further confirmed by 13C NMR analysis. The 13C NMR analysis also showed that the EPS produced by these bacteria is chemically similar to foulants obtained from biofouled RO membranes in previous studies. Therefore, our results support the hypothesis that the majority of substances that cause fouling on RO membranes originate from bacteria. Investigation using 1H NMR showed that the EPS contained a high abundance of hydrophobic compounds, and these compounds can lead to flux decline in the membrane processes. Genome sequencing of the isolates showed that they represent novel species of bacteria belonging to the genus Bacillus. Examination of genomes showed that these bacteria carry carbohydrates-active enzymes that play a role in the production of polysaccharides. Further genomic studies allowed us to identify proteins involved in the biosynthesis of EPS and flagella involved in biofilm formation. These analyses provide a glimpse into the physicochemical properties of EPS found on the RO membrane. This knowledge can be useful in the rational design of biofilm control treatments for the RO membrane.
  • Periodic chemical cleaning with urea: disintegration of biofilms and reduction of key biofilm-forming bacteria from reverse osmosis membranes

    Sanawar, Huma; Kim, L.H.; Farhat, Nadia; van Loosdrecht, Mark C.M.; Vrouwenvelder, Johannes S. (Water Research X, Elsevier BV, 2021-08) [Article]
    Biofouling is one of the major factors causing decline in membrane performance in reverse osmosis (RO) plants, and perhaps the biggest hurdle of membrane technology. Chemical cleaning is periodically carried out at RO membrane installations aiming to restore membrane performance. Typical cleaning agents used in the water treatment industry include sodium hydroxide (NaOH) and hydrochloric acid (HCl) in sequence. Rapid biofilm regrowth and related membrane performance decline after conventional chemical cleaning is a routinely observed phenomenon due to the inefficient removal of biomass from membrane modules. Since extracellular polymeric substances (EPS) make up the strongest and predominant structural framework of biofilms, disintegration of the EPS matrix should be the main target for enhanced biomass removal. Previously, we demonstrated at lab-scale the use of concentrated urea as a chemical cleaning agent for RO membrane systems. The protein denaturation property of urea was exploited to solubilize the proteinaceous foulants, weakening the EPS layer, resulting in enhanced biomass solubilization and removal from RO membrane systems. In this work, we investigated the impact of repeated chemical cleaning cycles with urea/HCl as well as NaOH/HCl on biomass removal and the potential adaptation of the biofilm microbial community. Chemical cleaning with urea/HCl was consistently more effective than NaOH/HCl cleaning over 6 cleaning and regrowth cycles. At the end of the 6 cleaning cycles, the percent reduction was 35% and 41% in feed channel pressure drop, 50% and 70% in total organic carbon, 30% and 40% in EPS proteins, and 40% and 66% in the peak intensities of protein-like matter, after NaOH/HCl cleaning and Urea/HCl cleaning respectively. 16S ribosomal RNA (rRNA) gene sequencing of the biofilm microbial community revealed that urea cleaning does not select for key biofouling families such as Sphingomonadaceae and Xanthomonadaceae that are known to survive conventional chemical cleaning and produce adhesive EPS. This study reaffirmed that urea possesses all the desirable properties of a chemical cleaning agent, i.e., it dissolves the existing fouling layer, delays fresh fouling accumulation by inhibiting the production of a more viscous EPS, does not cause damage to the membranes, is chemically stable, and environmentally friendly as it can be recycled for cleaning.
  • Nature-inspired wax-coated jute bags for reducing post-harvest storage losses.

    Odokonyero, Kennedy; Gallo Junior, Adair; Mishra, Himanshu (Scientific reports, Springer Science and Business Media LLC, 2021-07-29) [Article]
    Post-harvest storage of grains is crucial for food and feed reserves and facilitating seeds for planting. Ironically, post-harvest losses continue to be a major food security threat in the developing world, especially where jute bags are utilized. While jute fabrics flaunt mechanical strength and eco-friendliness, their water-loving nature has proven to be their Achilles heel. Increased relative humidity and/or precipitation wets jute, thereby elevating the moisture content of stored seeds and causing fungal growth. This reduces seed longevity, viability, and nutritional value. To address this crucial weakness of jute bags, we followed a nature-inspired approach to modify their surface microtexture and chemical make-up via alkali and wax treatments, respectively. The resulting wax-coated jute bags (WCJBs) exhibited significant water-repellency to simulated rainfall and airborne moisture compared to control jute bags (CJBs). A 2 months-long seed storage experiment with wheat (Triticum aestivum) grains exposed to 55%, 75%, and 98% relative humidity environments revealed that the grains stored in the WCJBs exhibited 7.5-4% lesser (absolute) moisture content than those in the CJBs. Furthermore, WCJBs-stored grains exhibited a 35-12% enhancement in their germination efficacy over the controls. This nature-inspired engineering solution could contribute towards reducing post-harvest losses in the developing world, where jute bags are extensively utilized for grain storage.
  • A spray-assisted multi-effect distillation system driven by ocean thermocline energy

    Chen, Qian; Burhan, Muhammad; Kum Ja, M.; Li, Yong; Ng, Kim Choon (Energy Conversion and Management, Elsevier BV, 2021-07-29) [Article]
    Ocean thermocline energy is a sustainable and reliable heat source for seawater desalination in remote islands that has no access to primary energy. To adapt to the unique features of thermocline energy, i.e., a sensible heat source with a small temperature gradient, we propose a novel desalination system combining the direct-spray technology and multi-effect distillation (MED). The steam generator of a conventional MED is replaced by a tubeless spray evaporator, which eliminates the thermal resistance across the heat transfer surface. The merits of this system, which is named spray-assisted multi-effect distillation (SMED), include reduced internal losses, higher productivity, and smaller heat transfer areas. To quantify the potential of the thermocline-driven SMED system, we firstly conducted a thermodynamic analysis. Comparing with MED, SMED boosts freshwater productivity by 35%, while the pumping power consumption and required heat transfer area are reduced by 58% and 17%, respectively. Based on the thermodynamic performances, the economic potential of SMED is assessed. The SMED system demonstrates significant economic benefits due to the reduced heat transfer area and higher productivity. The optimal cost of freshwater is $1.53/m3, 55% lower than MED under the same operating conditions. The originality and novelty of this study can be summarized as follows: (a) a novel desalination system that maximizes thermocline energy utilization is proposed; (b) a detailed process model is developed and validated for system design and optimization; and (c) a thermo-economic analysis is conducted to maximize the desalination performance. The derived results highlight the thermodynamic and economic potentials of the proposed SMED system, making it a competitive and appealing solution for thermocline desalination.
  • How particle-particle and liquid-particle interactions govern the fate of evaporating liquid marbles.

    Gallo Junior, Adair; Tavares, Fernanda; Das, Ratul; Mishra, Himanshu (Soft matter, Royal Society of Chemistry (RSC), 2021-07-28) [Article]
    Liquid marbles refer to droplets that are covered with a layer of non-wetting particles. They are observed in nature and have practical significance. These squishy objects bounce, coalesce, break, inflate, and deflate while the liquid does not touch the substrate underneath. Despite the considerable cross-disciplinary interest and value of the research on liquid marbles, a unified framework for describing the mechanics of deflating liquid marbles-as the liquid evaporates-is unavailable. For instance, analytical approaches for modeling the evaporation of liquid marbles exploit empirical parameters that are not based on liquid-particle and particle-particle interactions. Here, we have combined complementary experiments and theory to fill this gap. To unentangle the contributions of particle size, roughness, friction, and chemical make-up, we investigated the evaporation of liquid marbles formed with particles of sizes varying over 7 nm-300 μm and chemical compositions ranging from hydrophilic to superhydrophobic. We demonstrate that the potential final states of evaporating liquid marbles are characterized by one of the following: (I) constant surface area, (II) particle ejection, or (III) multilayering. Based on these insights, we developed an evaporation model for liquid marbles that takes into account their time-dependent shape evolution. The model fits are in excellent agreement with our experimental results. Furthermore, this model and the general framework can provide mechanistic insights into extant literature on the evaporation of liquid marbles. Altogether, these findings advance our fundamental understanding of liquid marbles and should contribute to the rational development of technologies.
  • Cost analysis of multiple effect evaporation and membrane distillation hybrid desalination system

    Ali, Emad; Orfi, Jamel; AlAnsary, Hany; Soukane, Sofiane; Elcik, Harun; Alpatova, Alla; Ghaffour, NorEddine (Desalination, Elsevier BV, 2021-07-26) [Article]
    This work addresses the feasibility of a previously proposed hybrid desalination system comprising multiple effect evaporation (MEE) and membrane distillation (MD) processes. The feasibility study introduced here focuses on the impact of the hybridization of two separate processes on desalination plant economics. The water cost of the hybrid system is found to be 2.05 $/m3, which compares well with previously reported values and is 17% lower than that of standalone MEE system. The sensitivity of the water production cost to the MD feed flow rate indicated the existence of an optimal cost at a single-pass feed flow rate of 900 L/h. In addition, the sensitivity of the water cost with respect to the MD unit cost indicated a 0.0084 $/m3 change in water production cost for every unit change in the MD module cost. A modified structure of the hybrid system that leverages the thermal energy of all MEE effluents has also been suggested. With this system, the overall water recovery ratio can reach as high as 52% and the water cost can further be reduced to 1.84 $/m3.
  • An in-situ assessment of post-synthesis thermal annealing of platinum nanoparticles supported on graphene

    Palanisamy, Tamilarasan; Alazmi, Amira; Batra, Nitin M; Da Costa, Pedro M. F. J. (Materials Science and Engineering B: Solid-State Materials for Advanced Technology, Elsevier BV, 2021-07-21) [Article]
    The catalytic activity of as-synthesised nanoparticles is hindered by several factors such as impurities and lattice imperfections. Often, a post-synthesis treatment is mandatory to optimize the performance of these particles but little is known in regards to what this does to them. Here, graphene-supported platinum (Pt) nanoparticles were subjected to thermal annealing in a reductive atmosphere. Surface migration and re-structuring of the particles were observed through in-situ structural and chemical analysis. In addition, residual organic impurities were removed, though the oxide layer coating the Pt surface is not eliminated. Notwithstanding, the interaction of the nanoparticles and the substrate improved with the annealing step, and so did their electrochemically active surface area (ECSA). In these circumstances, better catalytic performance in nano-scaled Pt systems may be a result of the enhancement in ECSA and catalyst-substrate interaction, as opposed to the commonly used argument of surface oxide removal.
  • A Model for Shelled Micro-Bubble in Geometric Confinement under Acoustics Field

    Qamar, Adnan (Journal of Applied Fluid Mechanics, Academic World Research, 2021-07-21) [Article]
    A theoretical model to predict the dynamics of a shelled micro-bubble driven by acoustic field in a tubular geometric confinement is proposed in the present study. The model is derived from first principle and may not be considered as a variant of Rayleigh-Plesset solution. A semi-analytical model is derived in the form of an ordinary differential equation connecting all parameters involved. Results obtained are in agreement with the available experimental data. The model is further linearized to obtain expression for the forced resonant frequency, which is shown to depend on geometric parameter of confinement as D/ L where D and L are the tube diameter and length, respectively. Further, linear viscous damping coefficient is also studied and is found that an overdamped or an underdamped state exist base on shelled micro-bubble size and parameters of geometric confinement (L and D). The state of damping clearly indicate when the shelled micro-bubble in confinement would respond linearly or non-linearly under the influence of acoustic field.
  • The impact of COVID-19 lockdowns on surface urban heat island changes and air-quality improvements across 21 major cities in the Middle East.

    El Kenawy, Ahmed M; Lopez-Moreno, Juan I; McCabe, Matthew; Domínguez-Castro, Fernando; Peña-Angulo, Dhais; Gaber, Islam M; Alqasemi, Abduldaem S; Al Kindi, Khalifa M; Al-Awadhi, Talal; Hereher, Mohammed E; Robaa, Sayed M; Al Nasiri, Noura; Vicente-Serrano, Sergio M (Environmental pollution (Barking, Essex : 1987), Elsevier BV, 2021-07-20) [Article]
    This study investigates changes in air quality conditions during the restricted COVID-19 lockdown period in 2020 across 21 metropolitan areas in the Middle East and how these relate to surface urban heat island (SUHI) characteristics. Based on satellite observations of atmospheric gases from Sentinel-5, results indicate significant reductions in the levels of atmospheric pollutants, particularly nitrogen dioxide (NO2), sulfur dioxide (SO2), and carbon monoxide (CO). Air quality improved significantly during the middle phases of the lockdown (April and May), especially in small metropolitan cities like Amman, Beirut, and Jeddah, while it was less significant in “mega” cities like Cairo, Tehran, and Istanbul. For example, the concentrations of NO2 in Amman, Beirut, and Jeddah decreased by −56.6%, −43.4%, and −32.3%, respectively, during April 2020, compared to April 2019. Rather, there was a small decrease in NO2 levels in megacities like Tehran (−0.9%) and Cairo (−3.1%). Notably, during the lockdown period, there was a decrease in the mean intensity of nighttime SUHI, while the mean intensity of daytime SUHI experienced either an increase or a slight decrease across these locations. Together with the Gulf metropolitans (e.g. Kuwait, Dubai, and Muscat), the megacities (e.g. Tehran, Ankara, and Istanbul) exhibited anomalous increases in the intensity of daytime SUHI, which may exceed 2 °C. Statistical relationships were established to explore the association between changes in the mean intensity and the hotspot area in each metropolitan location during the lockdown. The findings indicate that the mean intensity of SUHI and the spatial extension of hotspot areas within each metropolitan had a statistically significant negative relationship, with Pearson's r values generally exceeding - 0.55, especially for daytime SUHI. This negative dependency was evident for both daytime and nighttime SUHI during all months of the lockdown. Our findings demonstrate that the decrease in primary pollutant levels during the lockdown contributed to the decrease in the intensity of nighttime SUHIs in the Middle East, especially in April and May. Changes in the characteristics of SUHIs during the lockdown period should be interpreted in the context of long-term climate change, rather than just the consequence of restrictive measures. This is simply because short-term air quality improvements were insufficient to generate meaningful changes in the region's urban climate.
  • An exergoeconomic and normalized sensitivity based comprehensive investigation of a hybrid power-and-water desalination system

    Ahmad Jamil, Muhammad; Yaqoob, Haseeb; Abid, Asad; Umer Farooq, Muhammad; us Sabah, Noor; Bin Xu, Ben; Dala, Laurent; Ng, Kim Choon; Wakil Shahzad, Muhammad (Sustainable Energy Technologies and Assessments, Elsevier BV, 2021-07-20) [Article]
    Cogeneration of power-and-water is one of the potential solutions for ever-rising energy and freshwater demand. These systems have shown superior thermodynamic and economic performance compared to their standalone counterparts because of processes synergy and shared utilities resources. The current study investigates a multi-effect distillation system operated on bleed-out steam from the last stages of low-pressure steam turbine of a combined cycle gas turbine power plant (CCGT + MED). For this purpose, a component-based exergoeconomic investigation integrated with normalized sensitivity analysis for energy, exergy, and economic evaluation. The performance indicators include specific fuel consumption, thermal efficiency, exergy destruction, exergy efficiency, stream cost, and product cost (electricity and freshwater). The analysis showed that the cogeneration scheme reduced the electricity cost by 16.8% and freshwater production cost by 24.5% compared to the standalone power plant and MED systems. Moreover, the payback period for the MED system is calculated as 2.59 years with freshwater selling at $1.6 /m3. The sensitivity analysis showed that the electricity and the freshwater production cost are the most sensitive to gas turbine efficiency, fuel cost, and fuel heating value with normalized sensitivity coefficients of 1.71, 0.86, and 0.80 for electricity and 0.76, 0.42 and 0.40, for freshwater cost, respectively. While the other parameters such as interest rate, cost index factor, steam turbine efficiencies etc. showed a remarkably low impact on the cost of the products.

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