Recent Submissions

  • Colloidal silica fouling mechanism in direct-contact membrane distillation

    Jang, Yongsun; Lee, Jung-Gil; Fortunato, Luca; Lee, Jieun; Lee, Yejin; An, Alicia Kyoungjin; Ghaffour, NorEddine; Lee, Sangho; Jeong, Sanghyun (Desalination, Elsevier BV, 2022-01-24) [Article]
    Membrane fouling limits the performance of membrane distillation (MD) and its application to seawater brine treatment. Silica fouling is considered one of the most complex type of fouling. In this study, we evaluated the flux decline and fouling ratio due to colloidal silica fouling in direct-contact MD and characterized the fouled membranes. We also tested the efficacy of high flow-rate water flushing for the restoration of flux after fouling. The formation and removal of silica scaling were monitored in real-time with optical coherence tomography (OCT). Our work demonstrated that fouling formation is influenced by silica particle size, feed temperature, salinity, and flow rate. Notably, silica formed cake-layer fouling on the MD membranes. Smaller silica particle size resulted in a higher flux decline and a denser cake layer. A higher feed temperature resulted in a higher flux, but more severe fouling. We also found that fouling was minimized at an optimal flow rate and salinity did not significantly affect fouling formation. OCT monitoring showed that silica fouling deposited on the membrane surface and evaluated the effect of each cleaning strategies on the cake layer. This comprehensive investigation provides valuable insights for the development of silica fouling control strategies in MD.
  • Dye tracing and concentration mapping in coastal waters using unmanned aerial vehicles

    Johansen, Kasper; Dunne, Aislinn F.; Tu, Yu-Hsuan; Almashharawi, Samir; Jones, Burton; McCabe, Matthew (Scientific Reports, Springer Science and Business Media LLC, 2022-01-21) [Article]
    AbstractCoastal water flows facilitate important nutrient exchanges between mangroves, seagrasses and coral reefs. However, due to the complex nature of tidal interactions, their spatiotemporal development can be difficult to trace via traditional field instrumentations. Unmanned aerial vehicles (UAVs) serve as ideal platforms from which to capture such dynamic responses. Here, we provide a UAV-based approach for tracing coastal water flows using object-based detection of dye plume extent coupled with a regression approach for mapping dye concentration. From hovering UAV images and nine subsequent flight surveys covering the duration of an ebbing tide in the Red Sea, our results show that dye plume extent can be mapped with low omission and commission errors when assessed against manual delineations. Our results also demonstrated that the interaction term of two UAV-derived indices may be employed to accurately map dye concentration (coefficient of determination = 0.96, root mean square error = 7.78 ppb), providing insights into vertical and horizontal transportation and dilution of materials in the water column. We showcase the capabilities of high-frequency UAV-derived data and demonstrate how field-based dye concentration measurements can be integrated with UAV data for future studies of coastal water flow dynamics.
  • Digital E. coli Counter: A Microfluidics and Computer Vision-Based DNAzyme Method for the Isolation and Specific Detection of E. coli from Water Samples

    Rauf, Sakandar; Tashkandi, Nouran Abdulatif; De Oliveira Filho, José Ilton; Oviedo-Osornio, Claudia Iluhí; Danish, Muhammad S.; Hong, Pei-Ying; Salama, Khaled N. (Biosensors, MDPI AG, 2022-01-10) [Article]
    Biological water contamination detection-based assays are essential to test water quality; however, these assays are prone to false-positive results and inaccuracies, are time-consuming, and use complicated procedures to test large water samples. Herein, we show a simple detection and counting method for E. coli in the water samples involving a combination of DNAzyme sensor, microfluidics, and computer vision strategies. We first isolated E. coli into individual droplets containing a DNAzyme mixture using droplet microfluidics. Upon bacterial cell lysis by heating, the DNAzyme mixture reacted with a particular substrate present in the crude intracellular material (CIM) of E. coli. This event triggers the dissociation of the fluorophore-quencher pair present in the DNAzyme mixture leading to a fluorescence signal, indicating the presence of E. coli in the droplets. We developed an algorithm using computer vision to analyze the fluorescent droplets containing E. coli in the presence of non-fluorescent droplets. The algorithm can detect and count fluorescent droplets representing the number of E. coli present in the sample. Finally, we show that the developed method is highly specific to detect and count E. coli in the presence of other bacteria present in the water sample.
  • Controlling the hydraulic resistance of membrane biofilms by engineering biofilm physical structure.

    Desmond, Peter; Huisman, Kees Theo; Sanawar, Huma; Farhat, Nadia; Traber, Jacqueline; Fridjonsson, Einar O; Johns, Michael L; Flemming, Hans-Curt; Picioreanu, Cristian; Vrouwenvelder, Johannes S. (Water research, Elsevier BV, 2022-01-08) [Article]
    The application of membrane technology for water treatment and reuse is hampered by the development of a microbial biofilm. Biofilm growth in micro-and ultrafiltration (MF/UF) membrane modules, on both the membrane surface and feed spacer, can form a secondary membrane and exert resistance to permeation and crossflow, increasing energy demand and decreasing permeate quantity and quality. In recent years, exhaustive efforts were made to understand the chemical, structural and hydraulic characteristics of membrane biofilms. In this review, we critically assess which specific structural features of membrane biofilms exert resistance to forced water passage in MF/UF membranes systems applied to water and wastewater treatment, and how biofilm physical structure can be engineered by process operation to impose less hydraulic resistance ("below-the-pain threshold"). Counter-intuitively, biofilms with greater thickness do not always cause a higher hydraulic resistance than thinner biofilms. Dense biofilms, however, had consistently higher hydraulic resistances compared to less dense biofilms. The mechanism by which density exerts hydraulic resistance is reported in the literature to be dependant on the biofilms' internal packing structure and EPS chemical composition (e.g., porosity, polymer concentration). Current reports of internal porosity in membrane biofilms are not supported by adequate experimental evidence or by a reliable methodology, limiting a unified understanding of biofilm internal structure. Identifying the dependency of hydraulic resistance on biofilm density invites efforts to control the hydraulic resistance of membrane biofilms by engineering internal biofilm structure. Regulation of biofilm internal structure is possible by alteration of key determinants such as feed water nutrient composition/concentration, hydraulic shear stress and resistance and can engineer biofilm structural development to decrease density and therein hydraulic resistance. Future efforts should seek to determine the extent to which the concept of "biofilm engineering" can be extended to other biofilm parameters such as mechanical stability and the implication for biofilm control/removal in engineered water systems (e.g., pipelines and/or, cooling towers) susceptible to biofouling.
  • Downstream variations of air-gap membrane distillation and comparative study with direct contact membrane distillation: A modelling approach

    Ansari, Abolfazl; Galogahi, Fariba Malekpour; Thiel, David V.; Helfer, Fernanda; Millar, Graeme; Soukane, Sofiane; Ghaffour, NorEddine (Desalination, Elsevier BV, 2022-01-04) [Article]
    Air-Gap Membrane Distillation (AGMD) promises to reduce heat loss in membrane distillation. Most AGMD models are one-dimensional and do not consider the downstream variations. In addition, a linear function of vapour pressure is used, which either relies on experimentally determined parameters or a simplified mass transfer resistance to model the water permeate flux. This study introduces a new, improved model that simultaneously considers both heat and mass transfer in the AGMD process by coupling the continuity, momentum, and energy equations. A novel precise logarithmic function of vapour pressure was derived to model the water permeate flux, independent of experimentally determined parameters. By varying the inlet temperature, Reynolds number, inlet concentration, and air-gap thickness, the performance of AGMD was evaluated. The results revealed that our model improved the water flux prediction from more than 10% to less than 4% deviation from experimental results. Among the operating conditions, only increasing the Reynolds number improved all the system performance metrics, including higher water flux and lower temperature and concentration polarisation effects. Results were compared with Direct Contact Membrane Distillation (DCMD) outcomes and showed that unlike AGMD, DCMD suffers from a substantial decrease in water flux along the module. For DCMD, the exit water flux value decreased by 50% in comparison with the inlet value, while the water flux decreased by only 2% for AGMD, using a 1 mm air gap thickness.
  • Heterotrophic Bacterioplankton Growth and Physiological Properties in Red Sea Tropical Shallow Ecosystems With Different Dissolved Organic Matter Sources

    Silva, Luis; Calleja Cortes, Maria de Lluch; Huete-Stauffer, Tamara M.; Ivetic, Snjezana; Ansari, Mohd Ikram; Viegas, Miguel; Moran, Xose Anxelu G. (Frontiers in Microbiology, Frontiers Media SA, 2022-01-03) [Article]
    Despite the key role of heterotrophic bacterioplankton in the biogeochemistry of tropical coastal waters, their dynamics have been poorly investigated in relation to the different dissolved organic matter (DOM) pools usually available. In this study we conducted four seasonal incubations of unfiltered and predator-free seawater (Community and Filtered treatment, respectively) at three Red Sea coastal sites characterized by different dominant DOM sources: Seagrass, Mangrove, and Phytoplankton. Bacterial abundance, growth and physiological status were assessed by flow cytometry and community composition by 16S rRNA gene amplicons. The Seagrass site showed the highest initial abundances (6.93 ± 0.30 × 10$^{5}$ cells mL$^{–1}$), coincident with maximum DOC concentrations (>100 μmol C L$^{–1}$), while growth rates peaked at the Mangrove site (1.11 ± 0.09 d$^{–1}$) and were consistently higher in the Filtered treatment. The ratio between the Filtered and Community maximum bacterial abundance (a proxy for top-down control by protistan grazers) showed minimum values at the Seagrass site (1.05 ± 0.05) and maximum at the Phytoplankton site (1.24 ± 0.30), suggesting protistan grazing was higher in open waters, especially in the first half of the year. Since the Mangrove and Seagrass sites shared a similar bacterial diversity, the unexpected lack of bacterial response to predators removal at the latter site should be explained by differences in DOM characteristics. Nitrogen-rich DOM and fluorescent protein-like components were significantly associated with enhanced specific growth rates along the inshore-offshore gradient. Our study confirms the hypotheses that top–down factors control bacterial standing stocks while specific growth rates are bottom-up controlled in representative Red Sea shallow, oligotrophic ecosystems.
  • Sliding window neural network based sensing of bacteria in wastewater treatment plants

    Alharbi, Mohammad; Hong, Pei-Ying; Laleg-Kirati, Taous-Meriem (Journal of Process Control, Elsevier BV, 2021-12-24) [Article]
    Ensuring the performance of wastewater treatment processes is important to guarantee that the final treated wastewater quality is safe for reuse. However, bacterial concentration present along the different stages of treatment process is not easily measured routinely for the plant operators. In this paper, a moving horizon sensing approach based on neural networks is proposed to estimate the bacterial concentration in wastewater sampled along different stages of the plant. Due to the difficulties to measure the bacteria and the lack of a sufficiently large dataset, a Wasserstein generative adversarial network (WGAN) is designed to generate synthetic data. The Wasserstein critic loss is computed on a held-out validation set to evaluate the WGAN. Then, the generated data is used to train a long short term memory (LSTM) neural network that is developed to predict the biomass concentration and update the LSTM weights by a sliding window learning approach. Two datasets for WWTP are used to test the proposed method: first, effluent concentrations simulated using a benchmark simulation model no.1 (BSM) based on membrane bioreactor (MBR), where three different weather profiles of influent data were considered then, sampled data from MBR plant at King Abdullah University of Science and Technology (KAUST). Finally, the prediction results indicate that WGAN successfully generates realistic samples that are used to train the LSTM neural network. In addition, estimation performance of the proposed method is compared with a multilayer perceptron neural network (MLP-NN). Results showed that the proposed method improves the bacteria estimation performance compared to MLP-NN.
  • Comprehensive insights into performance of water gap and air gap membrane distillation modules using hollow fiber membranes

    Im, Baek-Gyu; Francis, Lijo; Santosh, Ravichandran; Kim, Woo-Seung; Ghaffour, NorEddine; Kim, Young-Deuk (Desalination, Elsevier BV, 2021-12-22) [Article]
    A commercially available microporous polypropylene hollow fiber membranes were employed for air gap and water gap membrane distillation (i.e., AGMD and WGMD, respectively) processes. In both configurations, the outer surface of commercially available dense polypropylene hollow fibers was used as the condensing surface of the permeate. The performance levels of the AGMD and WGMD processes utilizing microporous polyvinylidene fluoride membranes fabricated in-house were compared with those using polypropylene membranes. Under the given specific operating conditions, the maximum mean permeation flux values in AGMD and WGMD using polypropylene hollow fiber membranes were approximately 24 and 27 kg/m2h, respectively. In addition, theoretical studies on AGMD and WGMD using the designed hollow fiber module configuration were performed. The predicted results were found to well agree with the experimental results, thus verifying their validity. Moreover, parametric studies were conducted to identify the optimum evaporation-to-condensation surface area ratio (i.e., optimum numbers of hollow fiber membranes and hollow fiber condensers) in terms of specific energy consumption.
  • Recent Update on UV Disinfection to Fulfill the Disinfection Credit Value for Enteric Viruses in Water

    Augsburger, Nicolas; Rachmadi, Andri Taruna; Zaouri, Noor A.; Lee, Yunho; Hong, Pei-Ying (Environmental Science & Technology, American Chemical Society (ACS), 2021-12-09) [Article]
    Ultraviolet (UV) radiation alone or in combination with other oxidation processes is increasingly being considered for water disinfection because of stringent regulatory requirements for pathogen inactivation. To fulfill this requirement, an appropriate UV dose or fluence (mJ/cm2) is applied to combat enteric viruses in surface or treated water. There is a need for a cumulative review on the effectiveness of current and emerging UV technologies against various types of human enteric viruses. We extracted the kinetics data from 52 selected experimental studies on enteric virus inactivation using low pressure (LP-UV), medium pressure (MP-UV), UV-LED, and advanced oxidation processes (AOPs) and applied a simple linear regression analysis to calculate the range of UV fluence (mJ/cm2) needed for 4-log10 inactivation. The inactivation of adenoviruses with LP-UV, MP-UV, and UV/H2O2 (10 mg/L) required the highest fluence, which ranged from 159 to 337, 45, and 115 mJ/cm2, respectively. By contrast, when using LP-UV, the inactivation of other enteric viruses, such as the Caliciviridae and Picornaviridae family and rotavirus, required fluence that ranged from 19 to 69, 18 to 43, and 38 mJ/cm2, respectively. ssRNA viruses exhibit higher sensitivity to UV radiation than dsRNA and DNA viruses. In general, as an upgrade to LP-UV, MP-UV is a more promising strategy for eliminating enteric viruses compared to AOP involving LP-UV with added H2O2 or TiO2. The UV-LED technology showed potential because a lower UV fluence (at 260 and/or 280 nm wavelength) was required for 4-log10 inactivation compared to that of LP-UV for most strains examined in this critical review. However, more studies evaluating the inactivation of enteric viruses by means of UV-LEDs and UV-AOP are needed to ascertain these observations.
  • Suppression of Leidenfrost effect on superhydrophobic surfaces

    Shi, Meng; Das, Ratul; Arunachalam, Sankara; Mishra, Himanshu (Physics of Fluids, AIP Publishing, 2021-12) [Article]
    The Leidenfrost phenomenon entails the levitation of a liquid droplet over a superheated surface, cushioned by its vapor layer. This vapor layer can obstruct boiling heat transfer in heat exchangers, thereby compromising energy efficiency and safety. For water, superhydrophobic surfaces are believed to reduce the Leidenfrost point (TL)—the temperature at which this phenomenon occurs. Therefore, superhydrophobic surfaces are not commonly utilized in thermal machinery despite their benefits such as reducing frictional drag. Here, we demonstrate that it is possible to achieve superhydrophobicity without lowering TL by surface engineering and fine-tuning liquid–solid adhesion. We demonstrate that TL of water on superhydrophobic surfaces comprising doubly reentrant pillars (DRPs) can exceed that on hydrophilic and even superhydrophilic surfaces. Via theory and computation, we disentangle the contributions of microtexture, heat transfer, and surface chemistry on the onset of the Leidenfrost phenomenon. Remarkably, coating-free and superhydrophobic DRP architecture can facilitate ∼300% greater heat transfer to water droplets at 200 °C in comparison with conventional superhydrophobic surfaces. These findings advance our understanding of the Leidenfrost phenomenon and herald technological applications of superhydrophobic surfaces in thermal machinery.
  • Micro/Nanopatterned Superhydrophobic Surfaces Fabrication for Biomolecules and Biomaterials Manipulation and Analysis

    Allione, Marco; Limongi, Tania; Marini, Monica; Torre, Bruno; Zhang, Peng; Moretti, Manola; Perozziello, Gerardo; Candeloro, Patrizio; Napione, Lucia; Pirri, Candido Fabrizio; Di Fabrizio, Enzo (Micromachines, MDPI AG, 2021-11-30) [Article]
    Superhydrophobic surfaces display an extraordinary repulsion to water and water-based solutions. This effect emerges from the interplay of intrinsic hydrophobicity of the surface and its morphology. These surfaces have been established for a long time and have been studied for decades. The increasing interest in recent years has been focused towards applications in many different fields and, in particular, biomedical applications. In this paper, we review the progress achieved in the last years in the fabrication of regularly patterned superhydrophobic surfaces in many different materials and their exploitation for the manipulation and characterization of biomaterial, with particular emphasis on the issues affecting the yields of the fabrication processes and the quality of the manufactured devices.
  • Demystifying integrated power and desalination processes evaluation based on standard primary energy approach

    Shahzad, Muhammad Wakil; Ng, Kim Choon; Burhan, Muhammad; Chen, Qian; Jamil, Muhammad Ahmad; Imtiaz, Nida; Xu, Ben Bin (Thermal Science and Engineering Progress, Elsevier BV, 2021-11-29) [Article]
    The energy efficiency of seawater desalination processes is usually expressed in terms of kWh electricity or low-grade heat per cubic meter of water produced. This energy efficiency evaluation criteria unfortunately omitted the embedded quality of derived energy input. To have fair comparison of assorted desalination processes, it is important to consider quantity as well as quality of derived energy input based on their generation mechanisms. The numerator (m3 of distillate produced) and denominator (kWh_derived energy consumption) terms in energy efficiency evaluation are to be benchmark onto a common platform for fair evaluation and comparison. An inadequate comparison may result in an inferior adaptation of desalination methods that can lead to high economical destruction. In this article, a detailed thermodynamic framework has been developed to convert cogeneration-based electricity and heat into standard primary energy input. The proposed standard primary energy platform will help to demystify the quality and quantity aspects of derived energy supply. The thermodynamic based rigorous calculations show that 1.813 units of primary energy are required to produce one unit of electricity due to conversion efficiencies and loses involved in the power plant. On the other hand, one unit low-pressure steam to operate thermally driven desalination cycles need only 0.0944 units of primary energy. This stark difference clearly shows that omitting the grade of energy in performance evaluation can lead to an in-efficient installation decision. This proposed framework will provide a basic ground for future efficient processes selection and assorted processes evaluation at common platform.
  • Early season prediction of within-field crop yield variability by assimilating CubeSat data into a crop model

    Ziliani, Matteo G.; Altaf, Muhammad; Aragon, Bruno; Houburg, Rasmus; Franz, Trenton E.; Lu, Yang; Sheffield, Justin; Hoteit, Ibrahim; McCabe, Matthew (Agricultural and Forest Meteorology, Elsevier BV, 2021-11-29) [Article]
    Accurate early season predictions of crop yield at the within-field scale can be used to address a range of crop production, management, and precision agricultural challenges. While the remote sensing of within-field insights has been a research goal for many years, it is only recently that observations with the required spatio-temporal resolutions, together with efficient assimilation methods to integrate these into modeling frameworks, have become available to advance yield prediction efforts. Here we explore a yield prediction approach that combines daily high-resolution CubeSat imagery with the APSIM crop model. The approach employs APSIM to train a linear regression that relates simulated yield to simulated leaf area index (LAI). That relationship is then used to identify the optimal regression date at which the LAI provides the best prediction of yield: in this case, approximately 14 weeks prior to harvest. Instead of applying the regression on satellite imagery that is coincident, or closest to, the regression date, our method implements a particle filter that integrates CubeSat-based LAI into APSIM to provide end-of-season high-resolution (3 m) yield maps weeks before the optimal regression date. The approach is demonstrated on a rainfed maize field located in Nebraska, USA, where suitable collections of both imagery and in-situ data were available for assessment. The procedure does not require in-field data to calibrate the regression model, with results showing that even with a single assimilation step, it is possible to provide yield estimates with good accuracy up to 21 days before the optimal regression date. Yield spatial variability was reproduced reasonably well, with a strong correlation to independently collected measurements (R2 = 0.73 and rRMSE = 12%). When the field averaged yield was compared, our approach reduced yield prediction error from 1 Mg/ha (control case based on a calibrated APSIM model), to 0.5 Mg/ha (using satellite imagery alone), and then to 0.2 Mg/ha (results with assimilation up to three weeks prior to the optimal regression date). Such a capacity to provide spatially explicit yield predictions early in the season has considerable potential to enhance digital agricultural goals and improve end-of-season yield predictions.
  • Phosphorus Concentration in Water Affects the Biofilm Community and the Produced Amount of Extracellular Polymeric Substances in Reverse Osmosis Membrane Systems

    Javier, Luisa; Pulido Beltran, Laura; Kruithof, Joop; Vrouwenvelder, Johannes S.; Farhat, Nadia (Membranes, MDPI AG, 2021-11-26) [Article]
    Biofouling is a problem that hinders sustainable membrane-based desalination and the stratification of bacterial populations over the biofilm’s height is suggested to compromise the efficiency of cleaning strategies. Some studies reported a base biofilm layer attached to the membrane that is harder to remove. Previous research suggested limiting the concentration of phosphorus in the feed water as a biofouling control strategy. However, the existence of bacterial communities growing under phosphorus-limiting conditions and communities remaining after cleaning is unknown. This study analyzes the bacterial communities developed in biofilms grown in membrane fouling simulators (MFSs) supplied with water with three dosed phosphorus conditions at a constant biodegradable carbon concentration. After biofilm development, biofilm was removed using forward flushing (an easy-to-implement and environmentally friendly method) by increasing the crossflow velocity for one hour. We demonstrate that small changes in phosphorus concentration in the feed water led to (i) different microbial compositions and (ii) different bacterial-cells-to-EPS ratios, while (iii) similar bacterial biofilm populations remained after forward flushing, suggesting a homogenous bacterial community composition along the biofilm height. This study represents an exciting advance towards greener desalination by applying non-expensive physical cleaning methods while manipulating feed water nutrient conditions to prolong membrane system performance and enhance membrane cleanability.
  • Green Synthesis of Silver-Peptide Nanoparticles Generated by the Photoionization Process for Anti-Biofilm Application

    Seferji, Kholoud; Susapto, Hepi Hari; Khan, Babar Khalid; Rehman, Zahid Ur; Abbas, Manzar; Emwas, Abdul-Hamid M.; Hauser, Charlotte (ACS Applied Bio Materials, American Chemical Society (ACS), 2021-11-23) [Article]
    An alarming increase in antibiotic-resistant bacterial strains is driving clinical demand for new antibacterial agents. One of the oldest antimicrobial agents is elementary silver (Ag), which has been used for thousands of years. Even today, elementary Ag is used for medical purposes such as treating burns, wounds, and microbial infections. In consideration of the effectiveness of elementary Ag, the present researchers generated effective antibacterial/antibiofilm agents by combining elementary Ag with biocompatible ultrashort peptide compounds. The innovative antibacterial agents comprised a hybrid peptide bound to Ag nanoparticles (IVFK/Ag NPs). These were generated by photoionizing a biocompatible ultrashort peptide, thus reducing Ag ions to form Ag NPs with a diameter of 6 nm. The IVFK/Ag NPs demonstrated promising antibacterial/antibiofilm activity against reference Gram-positive and Gram-negative bacteria compared with commercial Ag NPs. Through morphological changes in Escherichia coli and Staphylococcus aureus, we proposed that the mechanism of action for IVFK/Ag NPs derives from their ability to disrupt bacterial membranes. In terms of safety, the IVFK/Ag NPs demonstrated biocompatibility in the presence of human dermal fibroblast cells, and concentrations within the minimal inhibitory concentration had no significant effect on cell viability. These results demonstrated that hybrid peptide/Ag NPs hold promise as a biocompatible material with strong antibacterial/antibiofilm properties, allowing them to be applied across a wide range of applications in tissue engineering and regenerative medicine.
  • The Air–Water Interface of Water Microdroplets Formed by Ultrasonication or Condensation Does Not Produce H2O2

    Musskopf, Nayara H.; Gallo Junior, Adair; Zhang, Peng; Petry, Jeferson; Mishra, Himanshu (The Journal of Physical Chemistry Letters, American Chemical Society (ACS), 2021-11-18) [Article]
    Recent reports on the production of hydrogen peroxide (H2O2) on the surface of condensed water microdroplets without the addition of catalysts or additives have sparked significant interest. The underlying mechanism is thought to be ultrahigh electric fields at the air–water interface; smaller droplets present larger interfacial areas and produce higher (detectable) H2O2 yields. To gain insights into this phenomenon, we performed condensation experiments and quantified H2O2 formation as a function of the vapor source. Specifically, we compared the H2O2 concentration in water microdroplets condensed from the vapor realized via (i) heating water in the range of 50–70 °C and (ii) ultrasonic humidification (as exploited in the original report). Experimental results revealed that the H2O2 level inside water microdroplets condensed via heating water was below our detection limit (≥0.25 μM), regardless of the droplet size or the substrate wettability. In contrast, water droplets condensed via ultrasonic humidification contained significantly higher (∼1 μM) H2O2 concentrations. We conclude that the ultrasonic humidifiers contribute to H2O2 production, not droplet interfacial effects.
  • Rapid photodegradation of organic micro-pollutants in water using high-intensity pulsed light

    Fortunato, Luca; Yarali, Emre; Sanchez Huerta, Claudia; Anthopoulos, Thomas D. (Journal of Water Process Engineering, Elsevier BV, 2021-11-17) [Article]
    The rising concentration of organic micro-pollutants (OMPs) in water resources has become a major concern for aquatic ecosystems and human health. Advanced oxidation processes (AOPs), based on ultraviolet (UV) photolysis and photochemical reactions, have been suggested for the degradation of various micropollutants present in water and wastewater. However, the application of these methods on large scale is limited due to the long treatment times. Here we evaluate the efficiency of high-intensity pulsed light treatment (HIPL) for the degradation of organic compounds in aqueous conditions. A solution containing 11 OMPs was treated with short (<2 ms) and high-intensity light pulses produced by a Xenon flash lamp. It was observed that the HIPL parameters, such as the number of pulses and optical energy dose, have a significant impact on the efficiency of the treatment. The main advantage of HIPL is the fast kinetics that allows efficient photodegradation of OMPs from the aqueous solution rapidly and within milliseconds. The present work showcases the potential of HIPL technique for the post-treatment of contaminated water containing pharmaceuticals and endocrine disruptor compounds.
  • Zwitterions Layer at but Do Not Screen Electrified Interfaces

    Ridwan, Muhammad Ghifari; Shrestha, Buddha Ratna; Maharjan, Nischal; Mishra, Himanshu (arXiv, 2021-11-02) [Preprint]
    The role of ionic electrostatics in colloidal processes is well-understood in natural and applied contexts; however, the electrostatic contribution of zwitterions, known to be present in copious amounts in extremophiles, has not been extensively explored. In response, we studied the effects of glycine as a surrogate zwitterion, ion, and osmolyte on the electrostatic forces between negatively charged mica-mica and silica-silica interfaces. Our results reveal that while zwitterions layer at electrified interfaces and contribute to solutions' osmolality, they do not affect at all the surface potentials, the electrostatic surface forces (magnitude and range), and solutions' conductivity across 0.3-30 mM glycine concentration. We infer that the zwitterionic structure imposes an inseparability among the positive and negative charges and that this inseparability prevents the buildup of a counter charge at interfaces. These elemental experimental results pinpoint how zwitterions enable extremophiles to cope with the osmotic stress without affecting finely tuned electrostatic force balance.
  • Effects of Superhydrophobic Sand Mulching on Evapotranspiration and Phenotypic Responses in Tomatoes (Solanum lycopersicum) under Normal and Reduced Irrigation

    Odokonyero, Kennedy; Gallo Junior, Adair; Dos Santos, Vinicius; Mishra, Himanshu (Cold Spring Harbor Laboratory, 2021-10-28) [Preprint]
    Irrigated agriculture in arid and semi-arid regions is a vital contributor to the global food supply; however, these regions endure massive evaporative losses that are compensated by unsustainable freshwater withdrawals. Plastic mulches have been used to curtail evaporation, improve water-use efficiency, and ensure food and water security, but they are non-biodegradable and their disposal is unsustainable. We recently developed superhydrophobic sand (SHS), which comprises sand grains with a nanoscale wax coating that could offer a more sustainable mulching solution. Here, the effects of adding a 1.0 cm-thick layer of SHS mulch on the evapotranspiration and phenotypic responses of tomato (Solanum lycopersicum) plants are studied under normal and reduced irrigation. Under both irrigation regimes, SHS mulching suppressed evaporation and enhanced transpiration by 78% and 17%, respectively relative to the bare soil. Overall, SHS mulching enhanced root xylem vessel diameter, stomatal aperture, stomatal conductance, and chlorophyll content index by 21%, 25%, 28%, and 23%, respectively. Total fruit yields, total dry mass, and harvest index increased in SHS-mulched plants by 33%, 20%, and 16%, respectively than in bare soil. These findings demonstrate the potential of SHS to boost irrigation efficiency in water-limited environments and provide mechanistic insights behind yield enhancement by SHS mulching.
  • Detecting Plant Stress Using Thermal and Optical Imagery From an Unoccupied Aerial Vehicle

    Stutsel, Bonny Margaret; Johansen, Kasper; Malbeteau, Yoann; McCabe, Matthew (Frontiers in Plant Science, Frontiers Media SA, 2021-10-27) [Article]
    Soil and water salinization has global impact on the sustainability of agricultural production, affecting the health and condition of staple crops and reducing potential yields. Identifying or developing salt-tolerant varieties of commercial crops is a potential pathway to enhance food and water security and deliver on the global demand for an increase in food supplies. Our study focuses on a phenotyping experiment that was designed to establish the influence of salinity stress on a diversity panel of the wild tomato species, Solanum pimpinellifolium. Here, we explore how unoccupied aerial vehicles (UAVs) equipped with both an optical and thermal infrared camera can be used to map and monitor plant temperature (Tp) changes in response to applied salinity stress. An object-based image analysis approach was developed to delineate individual tomato plants, while a green–red vegetation index derived from calibrated red, green, and blue (RGB) optical data allowed the discrimination of vegetation from the soil background. Tp was retrieved simultaneously from the co-mounted thermal camera, with Tp deviation from the ambient temperature and its change across time used as a potential indication of stress. Results showed that Tp differences between salt-treated and control plants were detectable across the five separate UAV campaigns undertaken during the field experiment. Using a simple statistical approach, we show that crop water stress index values greater than 0.36 indicated conditions of plant stress. The optimum period to collect UAV-based Tp for identifying plant stress was found between fruit formation and ripening. Preliminary results also indicate that UAV-based Tp may be used to detect plant stress before it is visually apparent, although further research with more frequent image collections and field observations is required. Our findings provide a tool to accelerate field phenotyping to identify salt-resistant germplasm and may allow farmers to alleviate yield losses through early detection of plant stress via management interventions.

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