### Recent Submissions

• #### Transition from unclassified Ktedonobacterales to Actinobacteria during amorphous silica precipitation in a quartzite cave environment

(Scientific Reports, Springer Science and Business Media LLC, 2021-02-16) [Article]
AbstractThe orthoquartzite Imawarì Yeuta cave hosts exceptional silica speleothems and represents a unique model system to study the geomicrobiology associated to silica amorphization processes under aphotic and stable physical–chemical conditions. In this study, three consecutive evolution steps in the formation of a peculiar blackish coralloid silica speleothem were studied using a combination of morphological, mineralogical/elemental and microbiological analyses. Microbial communities were characterized using Illumina sequencing of 16S rRNA gene and clone library analysis of carbon monoxide dehydrogenase (coxL) and hydrogenase (hypD) genes involved in atmospheric trace gases utilization. The first stage of the silica amorphization process was dominated by members of a still undescribed microbial lineage belonging to the Ktedonobacterales order, probably involved in the pioneering colonization of quartzitic environments. Actinobacteria of the Pseudonocardiaceae and Acidothermaceae families dominated the intermediate amorphous silica speleothem and the final coralloid silica speleothem, respectively. The atmospheric trace gases oxidizers mostly corresponded to the main bacterial taxa present in each speleothem stage. These results provide novel understanding of the microbial community structure accompanying amorphization processes and of coxL and hypD gene expression possibly driving atmospheric trace gases metabolism in dark oligotrophic caves.
• #### A General Framework for Liquid Marbles

(arXiv, 2021-02-12) [Preprint]
Liquid marbles refer to liquid droplets that are covered with a layer of non-wetting particles. They are observed in nature and have practical significance. However, a generalized framework for analyzing liquid marbles as they inflate or deflate is unavailable. The present study fills this gap by developing an analytical framework based on liquid-particle and particle-particle interactions. 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, a single-parameter evaporation model for liquid marbles is developed. Model predictions are in excellent agreement with experimental evaporation data for water liquid marbles of particle sizes ranging from 7 nanometers to 300 micrometers (over four orders of magnitude) and chemical compositions ranging from hydrophilic to superhydrophobic. These findings lay the groundwork for the rational design of liquid marble applications.
• #### Designing a next generation solar crystallizer for real seawater brine treatment with zero liquid discharge

(Nature Communications, Springer Science and Business Media LLC, 2021-02-12) [Article]
AbstractProper disposal of industrial brine has been a critical environmental challenge. Zero liquid discharge (ZLD) brine treatment holds great promise to the brine disposal, but its application is limited by the intensive energy consumption of its crystallization process. Here we propose a new strategy that employs an advanced solar crystallizer coupled with a salt crystallization inhibitor to eliminate highly concentrated waste brine. The rationally designed solar crystallizer exhibited a high water evaporation rate of 2.42 kg m$^{−2}$ h$^{−1}$ under one sun illumination when treating real concentrated seawater reverse osmosis (SWRO) brine (21.6 wt%). The solar crystallizer array showed an even higher water evaporation rate of 48.0 kg m$^{−2}$ per day in the outdoor field test, suggesting a great potential for practical application. The solar crystallizer design and the salt crystallization inhibition strategy proposed and confirmed in this work provide a low-cost and sustainable solution for industrial brine disposal with ZLD.
• #### The role of PQL genes in response to salinity tolerance in Arabidopsis and barley

(Plant Direct, Wiley, 2021-02-10) [Article]
While soil salinity is a global problem, how salt enters plant root cells from the soil solution remains underexplored. Non-selective cation channels (NSCCs) are suggested to be the major pathway for the entry of sodium ions (Na+), yet their genetic constituents remain unknown. Yeast PQ loop (PQL) proteins were previously proposed to encode NSCCs, but the role of PQLs in plants is unknown. The hypothesis tested in this research is that PQL proteins constitute NSCCs mediating some of the Na+ influx into the root, contributing to ion accumulation and the inhibition of growth in saline conditions. We identified plant PQL homologues, and studied the role of one clade of PQL genes in Arabidopsis and barley. Using heterologous expression of AtPQL1a and HvPQL1 in HEK293 cells allowed us to resolve sizable inwardly directed currents permeable to monovalent cations such as Na+, K+, or Li+ upon membrane hyperpolarization. We observed that GFP-tagged PQL proteins localized to intracellular membrane structures, both when transiently over-expressed in tobacco leaf epidermis and in stable Arabidopsis transformants. Expression of AtPQL1a, AtPQL1b, and AtPQL1c was increased by salt stress in the shoot tissue compared to non-stressed plants. Mutant lines with altered expression of AtPQL1a, AtPQL1b, and AtPQL1c developed larger rosettes in saline conditions, while altered levels of AtPQL1a severely reduced development of lateral roots in all conditions. This study provides the first step toward understanding the function of PQL proteins in plants and the role of NSCC in salinity tolerance.
• #### Continuous Flow Microbial Flow Cell with an Anion Exchange Membrane for Treating Low Conductivity and Poorly Buffered Wastewater

(ACS Sustainable Chemistry & Engineering, American Chemical Society (ACS), 2021-02-08) [Article]
Maximum power densities of wastewater-fed microbial fuel cells (MFCs) are limited by low buffer capacities and conductivities. To address these challenges, a continuous flow MFC was constructed using a thin flow channel and an anion exchange membrane (AEM) in a novel configuration. The electrodes were separated only by a thin AEM (∼100 μm), reducing the solution resistance while facilitating transport of hydroxide ions from the cathode into the anolyte (no catholyte). The flow-MFC produced 1.34 ± 0.03 W m–2 using an artificial wastewater specifically designed to have a low buffer capacity (alkalinity of 360 mg L–1), compared to only 0.37 ± 0.01 W m–2 using a more typical cubic-shaped MFC. Internal resistance (Rint = 34 ± 1 mΩ m2) was 83% lower than that of the cubic MFC (202 ± 2 mΩ m2) due to the better mitigation of pH imbalances between the electrodes by using the AEM and zero-gap electrodes. Performance was benchmarked against a higher buffer concentration (50 mM) solution which showed that the maximum power density with additional buffering increased to 2.88 ± 0.02 W m–2. These results show that MFCs designed for selective hydroxide ion transport will enable improved power production even in low conductivity and poorly buffered solutions such as domestic and industrial wastewater.
• #### Multi-sensor remote sensing for drought characterization: current status, opportunities and a roadmap for the future

(Remote Sensing of Environment, Elsevier BV, 2021-02-06) [Article]
Satellite based remote sensing offers one of the few approaches able to monitor the spatial and temporal development of regional to continental scale droughts. A unique element of remote sensing platforms is their multi-sensor capability, which enhances the capacity for characterizing drought from a variety of perspectives. Such aspects include monitoring drought influences on vegetation and hydrological responses, as well as assessing sectoral impacts (e.g., agriculture). With advances in remote sensing systems along with an increasing range of platforms available for analysis, this contribution provides a timely and systematic review of multi-sensor remote sensing drought studies, with a particular focus on drought related datasets, drought related phenomena and mechanisms, and drought modeling. To explore this topic, we first present a comprehensive summary of large-scale remote sensing datasets that can be used for multi-sensor drought studies. We then review the role of multi-sensor remote sensing for exploring key drought related phenomena and mechanisms, including vegetation responses to drought, land-atmospheric feedbacks during drought, drought-induced tree mortality, drought-related ecosystem fires, post-drought recovery and legacy effects, flash drought, as well as drought trends under climate change. A summary of recent modeling advances towards developing integrated multi-sensor remote sensing drought indices is also provided. We conclude that leveraging multi-sensor remote sensing provides unique benefits for regional to global drought studies, particularly in: 1) revealing the complex drought impact mechanisms on ecosystem components; 2) providing continuous long-term drought related information at large scales; 3) presenting real-time drought information with high spatiotemporal resolution; 4) providing multiple lines of evidence of drought monitoring to improve modeling and prediction robustness; and 5) improving the accuracy of drought monitoring and assessment efforts. We specifically highlight that more mechanism-oriented drought studies that leverage a combination of sensors and techniques (e.g., optical, microwave, hyperspectral, LiDAR, and constellations) across a range of spatiotemporal scales are needed in order to progress and advance our understanding, characterization and description of drought in the future.
• #### Unexpected Suppression of Leidenfrost Phenomenon on Superhydrophobic Surfaces

(arXiv, 2021-02-04) [Preprint]
The Leidenfrost phenomenon entails the levitation of a liquid droplet over a superheated surface, cushioned by its vapor layer. For water, superhydrophobic surfaces are believed to suppress the Leidenfrost point ($\it{T}$$_{\rm L})-the temperature at which this phenomenon occurs. The vapor film obstructs boiling heat transfer in heat exchangers, thereby compromising energy efficiency and safety. Thus, it is desirable to realize superhydrophobicity without suppressing \it{T}$$_{\rm L}$. Here we demonstrate that the $\it{T}$$_{\rm L} of water on microtextured superhydrophobic surfaces comprising doubly reentrant pillars (DRPs) can exceed those on hydrophilic and even superhydrophilic surfaces. We disentangle the contributions of microtexture, heat transfer, and surface chemistry on \it{T}$$_{\rm L}$ and reveal how superhydrophobicity can be realized without suppressing $\it{T}$$_{\rm L}$. For instance, silica surfaces with DRPs facilitate ~300% greater heat transfer to water droplets at 200$^{\circ}$C in comparison with silica surfaces coated with perfluorinated-nanoparticles. Thus, superhydrophobic surfaces could be harnessed for energy efficient thermal machinery.
• #### Superhydrophobic sand mulches increase agricultural productivity in arid regions

(arXiv, 2021-01-31) [Preprint]
Excessive evaporative loss of water from the topsoil in arid-land agriculture is compensated via irrigation, which exploits massive freshwater resources. The cumulative effects of decades of unsustainable freshwater consumption in many arid regions are now threatening food-water security. While plastic mulches can reduce evaporation from the topsoil, their cost and non-biodegradability limit their utility. In response, we report on superhydrophobic sand (SHS), a bio-inspired enhancement of common sand with a nanoscale wax coating. When SHS was applied as a 5 mm-thick mulch over the soil, evaporation dramatically reduced and crop yields increased. Multi-year field trials of SHS application with tomato (Solanum lycopersicum), barley (Hordeum vulgare), and wheat (Triticum aestivum) under normal irrigation enhanced yields by 17%-73%. Under brackish water irrigation (5500 ppm NaCl), SHS mulching produced 53%-208% higher fruit yield and grain gains for tomato and barley. Thus, SHS could benefit agriculture and city-greening in arid regions.
• #### Organic fouling control in reverse osmosis (RO) by effective membrane cleaning using saturated CO2 solution

(Separation and Purification Technology, Elsevier BV, 2021-01-30) [Article]
Although reverse osmosis (RO) currently dominates the global desalination market, membrane fouling remains a major operational obstacle, which penalizes sustainable plant operation. This study explores a new membrane cleaning technique that uses a saturated CO2 solution to alleviate membrane fouling caused by organic matter, without any additional chemicals. When the CO2 saturated solution is injected into the membrane module at a given pressure, CO2 bubbles start nucleating throughout the membrane surface. This phenomenon is intensified underneath the deposited foulants. The porous structure of the foulants presents cavities, which are considered as imperfection sites that act as a substrate for CO2 bubbles nucleation, leading to an effective membrane cleaning. In this study, sodium alginate, a model polysaccharide, was mixed with different concentrations of Ca2+ to evaluate the cleaning efficiency of the CO2 technique under severe operating conditions when formed Ca2+/alginate fouling layers significantly impend the RO process performance. Furthermore, the effect of hydrodymamic conditions and CO2 saturation pressure on efficiency of permeate flux recovery and membrane morphology is also evaluated and the results are compared to those achieved with Milli-Q water and acidic solution at pH 4 cleanings. Better permeate flux recoveries were observed at higher Ca2+ concentrations comparing to fouling expriments at lower concentrations. The observed effect was attributed to a transition from the gel layer to a looser cake layer which makes CO2 bubble nucleation and subsequent permeate flux recovery more effective due to the presence of a larger number of CO2 nucleation sites as a result of a formation of more porous fouling structures. Permeate flux recovery increased with the increase in cleaning time, cross-flow velocity and CO2 saturation pressure.
• #### Role of surfactants in cleaning of PVDF ultrafiltration membranes fouled by emulsified cutting oil

(Journal of Water Process Engineering, Elsevier BV, 2021-01-28) [Article]
Chemical cleaning with anionic, cationic and non-ionic surfactants was studied for polyvinylidene (PVDF) hollow fiber ultrafiltration (UF) membranes irreversibly fouled by cutting fluid with anionic emulsifiers. The membrane cleaning efficiency of the surfactants was determined by pure water permeability and the results are in agreement with morphological observations of the membrane surfaces and molecular vibrational analyses. The anionic surfactants sodium dodecyl sulfate (SDS) and sodium dodecylbenzene sulphonate (SDBS), showed better cleaning through the combined effect of electrostatic repulsion with emulsified oil particles and re-emulsification of the oil layer. Inclusion of the phenyl group in the dodecyl sulfate anion had a significant role in cleaning. Molecular vibrational analyses indicated a higher presence of residual surfactant on the membranes after cleaning with cationic (cetyltrimethylammonium bromide (CTAB)) and non-ionic (Tween 85 (T-85)) surfactants, which also resulted in higher apparent hydrophilicity of the membrane surface. Alkalizing the anionic surfactant solution improved cleaning efficiency, but had no significant effect for cationic and non-ionic surfactants. The effect of surfactant concentration and ionic strength on cleaning efficacy was analyzed for SDBS. As mass transport increased, higher cleaning efficacy was observed at higher SDBS concentration. The cleaning efficacy of SDBS was also influenced to varying degrees by solution pH and ionic strength.
• #### A Universal Mathematical Methodology in Characterization of Materials for Tailored Design of Porous Surfaces

(Frontiers in Chemistry, Frontiers Media SA, 2021-01-26) [Article]
• #### A type dependent effect of treated wastewater matrix on seed germination and food production.

(The Science of the total environment, Elsevier BV, 2021-01-21) [Article]
Municipal wastewater treated by membrane bioreactor, either aerobically (AeMBR) or anaerobically (AnMBR), can be reused to irrigate crops. However, post-AeMBR and post-AnMBR effluent have different water quality that may impact crop growth and yield. This study aims to assess for differences in water quality from both AeMBR and AnMBR, and determine if the type of treated wastewater matrix would impact seed germination and crop yield. Compared to post-AeMBR and control, post-AnMBR effluent had a negative impact on seed germination for both tomatoes and lettuces. The use of post-AnMBR but not post-AeMBR effluent also resulted in a higher number of unripe tomato fruits at the time of harvesting. However, when post-AnMBR effluent was diluted to 25% and 75% v/v with tap water, higher lettuce biomass was harvested compared to the same concentrations of post-AeMBR effluent and control. The observed differences in germination and yield were likely due to differences in the concentrations of heavy metals (e.g. Zn) and steroids or phytohormones (e.g. testosterone, gibberellic acid) present in both post-MBR effluents. This study demonstrated that the type of treated wastewater generated from different upstream treatment technologies can potentially impact crop yield based on the crop type. By understanding how the type of treated wastewater affect downstream agricultural activities, changes in management practices can be made accordingly.
• #### Estimating the minimum number of SARS-CoV-2 infected cases needed to detect viral RNA in wastewater: To what extent of the outbreak can surveillance of wastewater tell us?

(Environmental research, Elsevier BV, 2021-01-19) [Article]
There is increasing interest in wastewater-based epidemiology (WBE) of SARS-CoV-2 RNA to serve as an early warning system for a community. Despite successful detection of SARS-CoV-2 RNA in wastewaters sampled from multiple locations, there is still no clear idea on the minimal number of cases in a community that are associated with a positive detection of the virus in wastewater. To address this knowledge gap, we sampled wastewaters from a septic tank (n = 57) and biological activated sludge tank (n = 52) located on-site of a hospital. The hospital is providing treatment for SARS-CoV-2 infected patients, with the number of hospitalized patients per day known. It was observed that depending on which nucleocapsid gene is targeted by means of RT-qPCR, a range of 253-409 positive cases out of 10,000 persons are required prior to detecting RNA SARS-CoV-2 in wastewater. There was a weak correlation between N1 and N2 gene abundances in wastewater with the number of hospitalized cases. This correlation was however not observed for N3 gene. The frequency of detecting N1 and N2 gene in wastewater was also higher than that for N3 gene. Furthermore, nucleocapsid genes of SARS-CoV-2 were detected at lower frequency in the partially treated wastewater than in the septic tank. In particular, N1 gene abundance was associated with water quality parameters such as total organic carbon and pH. In instances of positive detection, the average abundance of N1 and N3 genes in the activated sludge tank were reduced by 50 and 70% of the levels detected in septic tank, suggesting degradation of the SARS-CoV-2 gene fragments already occurring in the early stages of the wastewater treatment process.
• #### Power effect of ultrasonically vibrated spacers in air gap membrane distillation: Theoretical and experimental investigations

(Separation and Purification Technology, Elsevier BV, 2021-01-18) [Article]
This study investigates the efficiency of low-power ultrasound in the range of 3.5–30.0 W to improve permeate flux and alleviate membrane fouling in an air–gap membrane distillation (AGMD) system. Natural groundwater and reverse osmosis (RO) reject water were fed into the AGMD system on which fouling experiments were conducted with hydrophobic polyvinylidene fluoride (PVDF) membrane. After 35 h of AGMD system operation with groundwater and RO reject water, fouling caused the permeate flux to decrease by 30% and 40% respectively. Concentration polarization, intermediate pore blocking, and cake filtration appear to be the main reasons for flux decline with both feedwater types. Ultrasound application for a short period of 15 min resulted in flux improvement by as high as 400% and 250% for RO reject and groundwater, respectively. Modelling of the heat and mass transfers showed that the flux increase was mainly due to membrane permeability improvements under ultrasonic vibration. Fouling visualisation using Scanning Electron Microscopy revealed that ultrasound effectively removed membrane fouling without compromising the membrane's structure. Importantly, permeate flux improvements with targeted low-power ultrasound appears to be proportionally higher than those of high-power ultrasound applied to the whole system, on a flux improvement per ultrasound W/m2 basis.
• #### Preface: Natural deep eutectic solvents: A third liquid phase in living organisms? Discovery, theory, biology, and applications

(Advances in Botanical Research, Elsevier, 2021-01-14) [Article]
About 20 years ago the concept of metabolomics was introduced with the aim of qualitative and quantitative chemical analysis of all compounds present in an organism or any biological material. This approach should ideally give a total picture of all small molecules in an organism, and complement the data obtained by proteomics, transcriptomics, and genomics. The methods applied are mass spectroscopy (MS) and nuclear magnetic resonance-spectroscopy (NMR), either stand alone or coupled with a chromatographic system (LC-MS, GC-MS, and LC-NMR) (Schripsema & Verpoorte, 1991; Verpoorte, Choi, & Kim, 2007; Wolfender, Rudaz, Choi, & Kim, 2013). These methods are capable of analyzing complex mixtures, and in combination with various chemometric methods new insights can be obtained from the large data sets generated in various experiments. The omics were the beginning of a paradigm shift of doing research, moving from a hypothesis-based strategy to a systems biology approach. The latter is based on as many observations as possible and analyzing the huge data sets by chemometric methods, e.g., to identify which genes, proteins, and compounds correlate with the resistance of a plant against pests and diseases (Kim, Choi, & Verpoorte, 2010; Leiss, Choi, Verpoorte, & Klinkhamer, 2011; Mouden, Klinkhamer, Choi, & Leiss, 2017).
• #### A zero liquid discharge system integrating multi-effect distillation and evaporative crystallization for desalination brine treatment

(Desalination, Elsevier BV, 2021-01-13) [Article]
• #### Elucidating the Role of Virulence Traits in the Survival of Pathogenic E. coli PI-7 Following Disinfection

(Frontiers in bioengineering and biotechnology, Frontiers Media SA, 2021-01-08) [Article]
Reuse and discharge of treated wastewater can result in dissemination of microorganisms into the environment. Deployment of disinfection strategies is typically proposed as a last stage remediation effort to further inactivate viable microorganisms. In this study, we hypothesize that virulence traits, including biofilm formation, motility, siderophore, and curli production along with the capability to internalize into mammalian cells play a role in survival against disinfectants. Pathogenic E. coli PI-7 strain was used as a model bacterium that was exposed to diverse disinfection strategies such as chlorination, UV and solar irradiation. To this end, we used a random transposon mutagenesis library screening approach to generate 14 mutants that exhibited varying levels of virulence traits. In these 14 isolated mutants, we observed that an increase in virulence traits such as biofilm formation, motility, curli production, and internalization capability, increased the inactivation half-lives of mutants compared to wild-type E. coli PI-7. In addition, oxidative stress response and EPS production contributed to lengthening the lag phase duration (defined as the time required for exposure to disinfectant prior to decay). However, traits related to siderophore production did not help with survival against the tested disinfection strategies. Taken together, the findings suggested that selected virulence traits facilitate survival of pathogenic E. coli PI-7, which in turn could account for the selective enrichment of pathogens over the nonpathogenic ones after wastewater treatment. Further, the study also reflected on the effectiveness of UV as a more viable disinfection strategy for inactivation of pathogens.
• #### Hole-Type Spacers for More Stable Shale Gas-Produced Water Treatment by Forward Osmosis

(Membranes, MDPI AG, 2021-01-03) [Article]
An appropriate spacer design helps in minimizing membrane fouling which remains the major obstacle in forward osmosis (FO) systems. In the present study, the performance of a hole-type spacer (having holes at the filament intersections) was evaluated in a FO system and compared to a standard spacer design (without holes). The hole-type spacer exhibited slightly higher water flux and reverse solute flux (RSF) when Milli-Q water was used as feed solution and varied sodium chloride concentrations as draw solution. During shale gas produced water treatment, a severe flux decline was observed for both spacer designs due to the formation of barium sulfate scaling. SEM imaging revealed that the high shear force induced by the creation of holes led to the formation of scales on the entire membrane surface, causing a slightly higher flux decline than the standard spacer. Simultaneously, the presence of holes aided to mitigate the accumulation of foulants on spacer surface, resulting in no increase in pressure drop. Furthermore, a full cleaning efficiency was achieved by hole-type spacer attributed to the micro-jets effect induced by the holes, which aided to destroy the foulants and then sweep them away from the membrane surface.
• #### Combining Nadir, Oblique, and Façade Imagery Enhances Reconstruction of Rock Formations Using Unmanned Aerial Vehicles

(IEEE Transactions on Geoscience and Remote Sensing, IEEE, 2021) [Article]