• Bioconversion of swine manure into high-value products of medium chain fatty acids.

      Zhang, Wanqin; Yin, Fubin; Dong, Hongmin; Cao, Qitao; Wang, Shunli; Xu, Jiajie; Zhu, Zhiping (Waste management (New York, N.Y.), Elsevier BV, 2020-07-03) [Article]
      This research proposes and demonstrates, for the first time, the utilization of swine manure as a complex feedstock to produce high-value medium chain fatty acids (MCFA). The two-stage anaerobic digestion (AD) carboxylates platform was adopted for the conversion of swine manure to short chain fatty acids (SCFAs) and then SCFAs to MCFA (n-caproate, n-heptanoate, and n-caprylate) with ethanol supplementation. We defined the appropriate initial pH of 10.0 for SCFAs production with a carbon conversion rate of 71.2%, and acetate, propionate were the main products, which accounted for around 72.9% of the total SCFAs in the primary stage (I). Through the addition of ethanol, 61.3% of the converted carbon in the complex SCFAs solution was converted into MCFA (C6-C8) in the chain elongation stage (II), while only 6.7% was attributed to methane formation. The concentrations of n-caproate, n-heptanoate, and n-caprylate reached 8.6 g COD/L (3.9 g/L), 6.4 g COD/L (2.7 g/L), and 2.6 g COD/L (1.07 g/L), respectively. This study achieved a relatively higher concentration of n-heptanoate compared with past studies of MCFA from other feedstock. These findings demonstrated a new route for resource recovery and the operating parameters for producing MCFA from swine manure.
    • Flow field in fouling spiral wound reverse osmosis membrane modules using MRI velocimetry

      Bristow, Nicholas W.; Vogt, Sarah J.; O'Neill, Keelan T.; Vrouwenvelder, Johannes S.; Johns, Michael L.; Fridjonsson, Einar O. (Desalination, Elsevier BV, 2020-06-26) [Article]
      Magnetic Resonance Imaging (MRI) velocimetry was applied to study non-invasively the water flow field inside a spiral-wound desalination membrane module (diameter: 2.5 in.; length: 18.5 in.), located in a pressure vessel, at typical practice operational conditions as a function of alginate fouling, simulating extracellular polymeric substances (EPS). Cross-sectional velocity images were acquired at an in-plane spatial resolution of 0.137 mm at multiple locations along the length of the reverse osmosis module and were acquired as a function of alginate concentration. At a total system alginate concentration of 3.25 mg/l, significant changes in the cross-sectional velocity map were observed near the module inlet due to alginate fouling, with limited changes observed in the middle and outlet regions of the module. When the total system alginate concentration was increased to 75 mg/l, it caused the module brine seal to fail resulting in significant local water flow by-passing the membrane module. This was clearly discernible in this opaque membrane system using MRI and resulting in dramatic changes in fluid velocity distribution through the membrane module. These observations of significant flow field heterogeneity as fouling develops are consistent with ‘irreversible’ fouling effects noted frequently in practice by the water treatment industry.
    • A Robust, Safe and Scalable Magnetic Nanoparticle Workflow for RNA Extraction of Pathogens from Clinical and Environmental Samples

      Ramos Mandujano, Gerardo; Salunke, Rahul; Mfarrej, Sara; Rachmadi, Andri Taruna; Hala, Sharif; Xu, Jinna; Alofi, Fadwa S; Khogeer, Asim; Hashem, Anwar M; Almontashiri, Naif AM; Alsomali, Afrah; Hamdan, Samir; Hong, Pei-Ying; Pain, Arnab; Li, Mo (Cold Spring Harbor Laboratory, 2020-06-29) [Preprint]
      <jats:p>Diagnosis and surveillance of emerging pathogens such as SARS-CoV-2 depend on nucleic acid isolation from clinical and environmental samples. Under normal circumstances, samples would be processed using commercial proprietary reagents in Biosafety 2 (BSL-2) or higher facilities. A pandemic at the scale of COVID-19 has caused a global shortage of proprietary reagents and BSL-2 laboratories to safely perform testing. Therefore, alternative solutions are urgently needed to address these challenges. We developed an open-source method called Magnetic- nanoparticle-Aided Viral RNA Isolation of Contagious Samples (MAVRICS) that is built upon reagents that are either readily available or can be synthesized in any molecular biology laboratory with basic equipment. Unlike conventional methods, MAVRICS works directly in samples inactivated in acid guanidinium thiocyanate-phenol-chloroform (e.g., TRIzol), thus allowing infectious samples to be handled safely without biocontainment facilities. Using 36 COVID-19 patient samples, 2 wastewater samples and 1 human pathogens control sample, we showed that MAVRICS rivals commercial kits in validated diagnostic tests of SARS-CoV-2, influenza viruses, and respiratory syncytial virus. MAVRICS is scalable and thus could become an enabling technology for widespread community testing and wastewater monitoring in the current and future pandemics.</jats:p>
    • A comparison of gap-filling approaches for Landsat-7 satellite data

      Yin, Gaohong; Mariethoz, Gregoire; Sun, Ying; McCabe, Matthew (Figshare, 2017) [Dataset]
      The purpose of this study is to assess the relative performance of four different gap-filling approaches across a range of land-surface conditions, including both homogeneous and heterogeneous areas as well as in scenes with abrupt changes in landscape elements. The techniques considered in this study include: (1) Kriging and co-Kriging; (2) geostatistical neighbourhood similar pixel interpolator (GNSPI); (3) a weighted linear regression (WLR) algorithm; and (4) the direct sampling (DS) method. To examine the impact of image availability and the influence of temporal distance on the selection of input training data (i.e. time separating the training data from the gap-filled target image), input images acquired within the same season (temporally close) as well as in different seasons (temporally far) to the target image were examined, as was the case of using information only within the target image itself. Root mean square error (RMSE), mean spectral angle (MSA), and coefficient of determination ($\textit{R}$$^{2}$) were used as the evaluation metrics to assess the prediction results. In addition, the overall accuracy (OA) and kappa coefficient ($\textit{kappa}$) were used to assess a land-cover classification based on the gap-filled images. Results show that all of the gap-filling approaches provide satisfactory results for the homogeneous case, with $\textit{R}$$^{2}$ > 0.93 for bands 1 and 2 in all cases and $\textit{R}$$^{2}$ > 0.80 for bands 3 and 4 in most cases. For the heterogeneous example, GNSPI performs the best, with $\textit{R}$$^{2}$ > 0.85 for all tested cases. WLR and GNSPI exhibit equivalent accuracy when a temporally close input image is used (i.e. WLR and GNSPI both have an $\textit{R}$$^{2}$ equal to 0.89 for band 1). For the case of abrupt changes in scene elements or in the absence of ancillary data, the DS approach outperforms the other tested methods.
    • A self-sustainable solar desalination system using direct spray technology

      Chen, Qian; Alrowais, Raid Naif; Burhan, Muhammad; Ybyraiymkul, Doskhan; Shahzad, Muhammad Wakil; Li, Yong; Ng, Kim Choon (Energy, Elsevier BV, 2020-06-07) [Article]
      Solar desalination offers a sustainable solution to growing global water demand due to the geographical coincidence between high solar availability and severe water scarcity. This paper presents a self-sustainable solar desalination system combining a spray-assisted low-temperature desalination system, solar thermal collectors, and heat storage tanks. A mathematical model is firstly developed and validated with laboratory pilot for the proposed large-scale solar-powered desalination system. Afterward, the long-term productivity and energy efficiency of the system is evaluated under the climatic conditions of Makkah, Saudi Arabia. The proposed solar desalination system is able to provide an uninterrupted water supply of 20 kg/day for per square meter solar collector area, and the value can be further increased by optimizing the interactions of the three subsystems, i.e. efficiency of the solar collectors, temperature and heat losses in the storage tank, and energy efficiency of the desalination system. With a collector area of 360 m2, the annual productivity is maximized when the feed flowrate is 1.7 kg/s and the diameter of the heat storage tank is 1.9 m. The desalination cost is estimated to be $1.29/m3, which is much lower than other solar thermal desalination systems.
    • Application of hierarchical oligonucleotide primer extension (HOPE) to assess relative abundances of ammonia- and nitrite-oxidizing bacteria

      Scarascia, Giantommaso; Cheng, Hong; Harb, Moustapha; Hong, Pei-Ying (Figshare, 2017) [Dataset]
      Abstract Background Establishing an optimal proportion of nitrifying microbial populations, including ammonia-oxidizing bacteria (AOB), nitrite-oxidizing bacteria (NOB), complete nitrite oxidizers (comammox) and ammonia-oxidizing archaea (AOA), is important for ensuring the efficiency of nitrification in water treatment systems. Hierarchical oligonucleotide primer extension (HOPE), previously developed to rapidly quantify relative abundances of specific microbial groups of interest, was applied in this study to track the abundances of the important nitrifying bacterial populations. Results The method was tested against biomass obtained from a laboratory-scale biofilm-based trickling reactor, and the findings were validated against those obtained by 16S rRNA gene-based amplicon sequencing. Our findings indicated a good correlation between the relative abundance of nitrifying bacterial populations obtained using both HOPE and amplicon sequencing. HOPE showed a significant increase in the relative abundance of AOB, specifically Nitrosomonas, with increasing ammonium content and shock loading (pÂ
    • Photothermoelectric Response of Ti3C2Tx MXene Confined Ion Channels

      Hong, Seunghyun; Zou, Guodong; Kim, Hyunho; Huang, Dazhen; Wang, Peng; Alshareef, Husam N. (ACS Nano, American Chemical Society (ACS), 2020-06-15) [Article]
      With recent growing interest in biomimetic smart nanochannels, a biological sensory transduction in response to external stimuli has been of particular interest in the development of biomimetic nanofluidic systems. Here we demonstrate the MXene-based subnanometer ion channels that convert external temperature changes to electric signals via preferential diffusion of cations under a thermal gradient. In particular, coupled with a photothermal conversion feature of MXenes, an array of the nanoconfined Ti3C2Tx ion channels can capture trans-nanochannel diffusion potentials under a light-driven axial temperature gradient. The nonisothermal open-circuit potential across channels is enhanced with increasing cationic permselectivity of confined channels, associated with the ionic concentration or pH of permeant fluids. The photothermoelectric ionic response (evaluated from the ionic Seebeck coefficient) reached up to 1 mV·K–1, which is comparable to biological thermosensory channels, and demonstrated stability and reproducibility in the absence and presence of an ionic concentration gradient. With advantages of physicochemical tunability and easy fabrication process, the lamellar ion conductors may be an important nanofluidic thermosensation platform possibly for biomimetic sensory systems.
    • Average monthly and annual climate maps for Bolivia

      Vicente-Serrano, S.M.; El Kenawy, Ahmed M.; Azorin-Molina, C.; Chura, O.; Trujillo, F.; Aguilar, E.; Martín-Hernández, N.; López-Moreno, J.I.; Sanchez-Lorenzo, A.; Moran-Tejeda, E.; Revuelto, J.; Ycaza, P.; Friend, F. (Figshare, 2015) [Dataset]
      This study presents monthly and annual climate maps for relevant hydroclimatic variables in Bolivia. We used the most complete network of precipitation and temperature stations available in Bolivia, which passed a careful quality control and temporal homogenization procedure. Monthly average maps at the spatial resolution of 1 km were modeled by means of a regression-based approach using topographic and geographic variables as predictors. The monthly average maximum and minimum temperatures, precipitation and potential exoatmospheric solar radiation under clear sky conditions are used to estimate the monthly average atmospheric evaporative demand by means of the Hargreaves model. Finally, the average water balance is estimated on a monthly and annual scale for each 1 km cell by means of the difference between precipitation and atmospheric evaporative demand. The digital layers used to create the maps are available in the digital repository of the Spanish National Research Council.
    • A Calibration Procedure for Field and UAV-Based Uncooled Thermal Infrared Instruments.

      Aragon Solorio, Bruno Jose Luis; Johansen, Kasper; Parkes, Stephen; Malbeteau, Yoann; Almashharawi, Samir; Al-Amoudi, Talal; Andrade, Cristhian F; Turner, Darren; Lucieer, Arko; McCabe, Matthew (Sensors (Basel, Switzerland), 2020-06-14) [Article]
      Thermal infrared cameras provide unique information on surface temperature that can benefit a range of environmental, industrial and agricultural applications. However, the use of uncooled thermal cameras for field and unmanned aerial vehicle (UAV) based data collection is often hampered by vignette effects, sensor drift, ambient temperature influences and measurement bias. Here, we develop and apply an ambient temperature-dependent radiometric calibration function that is evaluated against three thermal infrared sensors (Apogee SI-11(Apogee Electronics, Santa Monica, CA, USA), FLIR A655sc (FLIR Systems, Wilsonville, OR, USA), TeAx 640 (TeAx Technology, Wilnsdorf, Germany)). Upon calibration, all systems demonstrated significant improvement in measured surface temperatures when compared against a temperature modulated black body target. The laboratory calibration process used a series of calibrated resistance temperature detectors to measure the temperature of a black body at different ambient temperatures to derive calibration equations for the thermal data acquired by the three sensors. As a point-collecting device, the Apogee sensor was corrected for sensor bias and ambient temperature influences. For the 2D thermal cameras, each pixel was calibrated independently, with results showing that measurement bias and vignette effects were greatly reduced for the FLIR A655sc (from a root mean squared error (RMSE) of 6.219 to 0.815 degrees Celsius (℃)) and TeAx 640 (from an RMSE of 3.438 to 1.013 ℃) cameras. This relatively straightforward approach for the radiometric calibration of infrared thermal sensors can enable more accurate surface temperature retrievals to support field and UAV-based data collection efforts.
    • Fouling investigation of a full-scale seawater reverse osmosis desalination (SWRO) plant on the Red Sea: Membrane autopsy and pretreatment efficiency

      Fortunato, Luca; Alshahri, Abdullah; Farinha, Andreia S.F.; Zakzouk, Islam; Jeong, Sanghyun; Leiknes, TorOve (Desalination, Elsevier BV, 2020-06-10) [Article]
      In this study, the membrane autopsy was performed on a full-scale seawater reverse osmosis (SWRO) desalination plant located on the Red Sea. Several techniques were employed to characterize the nature and the fate of the foulants in the process, including LCOCD, ICP-MS, SEM-EDS, TSS, and ATP. The efficiency of the pretreatment in removing the fouling potential was assessed by analyzing the seawater after the intake feed pump, after the spruce media filter (SMF) and after the cartridge filter (CF). The autopsy of the membrane modules and CF operated for long-term revealed the presence of a heterogeneous fouling layer. The organic fraction composition of the fouling layer depended on the module position in the vessel. The inorganic deposits embedded in the layer were mainly composed of aluminum, iron, and magnesium silicate. The inorganic sediments entered the plants from the shoreline seawater intake and accumulated on the CF filter and the membrane. The analysis of the pretreatment performance showed an increase of TSS and ATP after CF, highlighting the inappropriate CF filter replacement time.
    • Mini Review: Metagenomics as a tool to monitor reclaimed water quality.

      Hong, Pei-Ying; Mantilla Calderon, David; Wang, Changzhi (Applied and environmental microbiology, American Society for Microbiology, 2020-06-07) [Article]
      Many biological contaminants are disseminated through water, and their occurrence has potential detrimental impacts on public and environmental health. Conventional monitoring tools rely on cultivation and are not robust in addressing modern water quality concerns. This review proposes metagenomics as a means to provide a rapid, nontargeted assessment of biological contaminants in water. When further coupled with the appropriate methods (e.g., quantitative PCR and flow cytometry) and bioinformatic tools, metagenomics can provide information concerning both the abundance and diversity of biological contaminants in reclaimed waters. Further correlation between the metagenomic-derived data of selected contaminants and the measurable parameters of water quality can also aid in devising strategies to alleviate undesirable water quality. Here, we reviewed metagenomic approaches (i.e., both sequencing platforms and bioinformatic tools) and studies that demonstrated their use for reclaimed water quality monitoring. We also provide recommendations on areas of improvement that will allow metagenomics to significantly impact how the water industry performs reclaimed water quality monitoring in the future.
    • Extreme Engineering: How Antarctic Algae Adapt to Hypersalinity.

      Julkowska, Magdalena M. (Plant physiology, American Society of Plant Biologists (ASPB), 2020-06-05) [Article]
      Photosynthetic organisms can be found across most environments on Earth, including the most extreme ones. The McMurdo Valleys in Antarctica are among the driest and coldest places on the planet, and lakes in that region are permanently covered by 5 m of ice (Priscu et al., 1998). Lake Bonney, one of the McMurdo lakes, is home to a single-cell algal species, Chlamydomonas sp. UWO 241, which can withstand low temperatures, salinity levels exceeding those of seawater, and low light availability caused by the permanent ice coverage. The photosynthetic machinery of this organism is unique: it does not undergo state transitions (Morgan-Kiss et al., 2002), which usually adjust the distribution of light absorption between PSI and PSII.
    • Small But Powerful: MicroRNA-Derived Peptides Promote Grape Adventitious Root Formation.

      Julkowska, Magdalena M. (Plant physiology, American Society of Plant Biologists (ASPB), 2020-06-05) [Article]
      Although plant genomes typically contain hundreds of microRNA (miRNA)-encoding genes, we know little about how miRNA expression is regulated (Wang et al.,2019). The expression of Arabidopsis miRNA171, which targets SCARECROW-like transcription factors involved in lateral root formation, was previously described to be controlled by small peptides derived from small open reading frames (ORFs) on the same primary transcript as miRNA171 itself (Fig. 1; Lauressergues et al., 2015). This discovery of miRNA-derived peptides (miPEPs) opened the door for new technologies controlling gene expression without the need for genetic modification.
    • Suitability of airborne and terrestrial laser scanning for mapping tree crop structural metrics for improved orchard management

      Wu, Dan; Johansen, Kasper; Phinn, Stuart; Robson, Andrew (Remote Sensing, MDPI AG, 2020-05-21) [Article]
      Airborne Laser Scanning (ALS) and Terrestrial Laser Scanning (TLS) systems are useful tools for deriving horticultural tree structure estimates. However, there are limited studies to guide growers and agronomists on different applications of the two technologies for horticultural tree crops, despite the importance of measuring tree structure for pruning practices, yield forecasting, tree condition assessment, irrigation and fertilization optimization. Here, we evaluated ALS data against near coincident TLS data in avocado, macadamia and mango orchards to demonstrate and assess their accuracies and potential application for mapping crown area, fractional cover, maximum crown height, and crown volume. ALS and TLS measurements were similar for crown area, fractional cover and maximum crown height (coefficient of determination (R2) ≥ 0.94, relative root mean square error (rRMSE) ≤ 4.47%). Due to the limited ability of ALS data to measure lower branches and within crown structure, crown volume estimates from ALS and TLS data were less correlated (R2 = 0.81, rRMSE = 42.66%) with the ALS data found to consistently underestimate crown volume. To illustrate the effects of different spatial resolution, capacity and coverage of ALS and TLS data, we also calculated leaf area, leaf area density and vertical leaf area profile from the TLS data, while canopy height, tree row dimensions and tree counts) at the orchard level were calculated from ALS data. Our results showed that ALS data have the ability to accurately measure horticultural crown structural parameters, which mainly rely on top of crown information, and measurements of hedgerow width, length and tree counts at the orchard scale is also achievable. While the use of TLS data to map crown structure can only cover a limited number of trees, the assessment of all crown strata is achievable, allowing measurements of crown volume, leaf area density and vertical leaf area profile to be derived for individual trees. This study provides information for growers and horticultural industries on the capacities and achievable mapping accuracies of standard ALS data for calculating crown structural attributes of horticultural tree crops.
    • Fouling control in a gravity-driven membrane (GDM) bioreactor treating primary wastewater by using relaxation and/or air scouring

      Fortunato, Luca; Ranieri, Luigi; Naddeo, Vincenzo; Leiknes, TorOve (Journal of Membrane Science, Elsevier BV, 2020-05-21) [Article]
      Gravity-driven membrane bioreactors (GD-MBR) have been proposed as a sustainable water treatment due to the low energy requirements in terms of operation. The objective of this study is to investigate the effect of different physical cleaning strategies on the membrane performance in a gravity-driven membrane bioreactor treating primary wastewater. The Optical Coherence Tomography (OCT) allowed evaluating the impact of the physical cleaning on the biomass developed on the membrane surface. Applying relaxation did not enhance the membrane performance, however, it led to an increase in thickness and a decrease in the biomass specific hydraulic resistance. Using air scouring under continuous filtration increased the biomass specific hydraulic resistance by compressing the biomass (~50% decrease in thickness). When air scouring was applied at the end of a relaxation cycle, a higher biomass removal and a significant increase in flux (250%) were observed. Biopolymers were found to constitute 55% of the fouling layer. This study highlighted the suitability of an in-situ monitoring approach as a key tool to evaluate the impact of different physical cleaning strategies on the biomass removal in membrane filtration process.
    • ZIF-induced d-band Modification in Bimetallic Nanocatalyst: Achieving >44% Efficiency in Ambient Nitrogen Reduction Reaction.

      Sim, Howard Yi Fan; Chen, Jaslyn Ru Ting; Koh, Charlynn Sher Lin; Lee, Hiang Kwee; Han, Xuemei; Phan-Quang, Gia Chuong; Pang, Jing Yi; Lay, Chee Leng; Pedireddy, Srikanth; Phang, In Yee; Yeow, Edwin Kok Lee; Ling, Xing Yi (Angewandte Chemie (International ed. in English), Wiley, 2020-05-29) [Article]
      Electrochemical nitrogen reduction reaction (NRR) offers a sustainable solution towards ammonia production but suffers poor reaction performance due to preferential catalyst-H formation and the consequential hydrogen evolution reaction (HER). Herein, we electronically modify PtAu electrocatalyst d-band structure using zeolitic-imidazole framework (ZIF) to achieve a faradaic efficiency (FE) of >44% with high ammonia yield rate of >161 µg.mg cat -1 .h -1 at ambient conditions. Our strategy lowers electrocatalyst d-band position to weaken H adsorption and concurrently creates electron deficient sites to kinetically drive NRR by promoting catalyst-N 2 interaction. The ZIF coating on electrocatalyst doubles as a hydrophobic layer to suppress HER, further improves FE by >44-fold compared to without ZIF (~1%). Experimental and in-silico studies reveal PtAu-N ZIF interaction is key to enable strong N 2 adsorption over H atom. Our electrocatalytic design is universal and can be extended across metal electrocatalysts for diverse applications in NRR and air-to-fuel conversion.
    • Mapping the condition of macadamia tree crops using multi-spectral UAV and WorldView-3 imagery

      Johansen, Kasper; Duan, Qibin; Tu, Yu-Hsuan; Searle, Chris; Tu, Yu Hsuan; Phinn, Stuart; Robson, Andrew; McCabe, Matthew (ISPRS Journal of Photogrammetry and Remote Sensing, Elsevier BV, 2020-05-20) [Article]
      Australia is one of the world’s largest producers of macadamia nuts. As macadamia trees can take up to 15 years to mature and produce maximum yield, it is important to optimize tree condition. Field based assessment of macadamia tree condition is time-consuming and often inconsistent. Using remotely sensed imagery may allow for faster, more extensive, and more consistent assessment of macadamia tree condition. To identify individual macadamia tree crowns, high spatial resolution imagery is required. Hence, the objective of this work was to develop and test an approach to map the condition of individual macadamia tree crowns using both multispectral Unmanned Aerial Vehicle (UAV) and WorldView-3 imagery for different macadamia varieties and three different sites located near Bundaberg, Australia. A random forest classifier, based on all available spectral bands and selected vegetation indices was used to predict five condition categories, ranging from excellent (category 1) to poor (category 5). Various combinations of the developed models were tested between the three sites and over time. The results showed that the multi-spectral WorldView-3 imagery produced the lowest out of bag (OOB) classification errors in most cases. However, for both the UAV and the WorldView-3 imagery, more than 98.5% of predicted macadamia condition categories were either correctly mapped or offset by a single category out of the five condition categories (excellent, good, moderate, fair and poor) for trees of the same variety and at one point in time. Multi-temporally, the WorldView-3 imagery performed better than the UAV data for predicting the condition of the same macadamia tree variety. Applying a model from one site to another site with the same macadamia tree variety produced OOB classification between 31.20 and 42.74%, but with > 98.63% of trees predicted within a single condition category. Importantly, models trained based on one type of macadamia tree variety could not be successfully applied to a site with another variety. The developed classification models may be used as a decision and management support tool for the macadamia industry to inform management practices and improve on-demand irrigation, fertilization, and pest inspection at the individual tree level.
    • A comparison between chemical cleaning efficiency in lab-scale and full-scale reverse osmosis membranes: Role of extracellular polymeric substances (EPS)

      Jafari, M.; D'haese, A.; Zlopasa, J.; Cornelissen, E. R.; Vrouwenvelder, Johannes S.; Verbeken, K.; Verliefde, A.; van Loosdrecht, M. C.M.; Picioreanu, C. (Journal of Membrane Science, Elsevier BV, 2020-05-04) [Article]
      Chemical cleaning is vital for the optimal operation of membrane systems. Membrane chemical cleaning protocols are often developed in the laboratory flow cells (e.g., Membrane Fouling Simulator (MFS)) using synthetic feed water (nutrient excess) and short experimental time of typically days. However, full-scale Reverse Osmosis (RO) membranes are usually fed with nutrient limited feed water (due to extensive pre-treatment) and operated for a long-time of typically years. These operational differences lead to significant differences in the efficiency of chemical Cleaning-In-Place (CIP) carried out on laboratory-scale and on full-scale RO systems. Therefore, we investigated the suitability of lab-scale CIP results for full-scale applications. A lab-scale flow cell (i.e., MFSs) and two full-scale RO modules were analysed to compare CIP efficiency in terms of water flux recovery and biofouling properties (biomass content, Extracellular Polymeric Substances (EPS) composition and EPS adherence) under typical lab-scale and full-scale conditions. We observed a significant difference between the CIP efficiency in lab-scale (~50%) and full-scale (9–20%) RO membranes. Typical biomass analysis such as Total Organic Carbon (TOC) and Adenosine triphosphate (ATP) measurements did not indicate any correlation to the observed trend in the CIP efficiency in the lab-scale and full-scale RO membranes. However, the biofilms formed in the lab-scale contains different EPS than the biofilms in the full-scale RO modules. The biofilms in the lab-scale MFS have polysaccharide-rich EPS (Protein/Polysaccharide ratio = 0.5) as opposed to biofilm developed in full-scale modules which contain protein-rich EPS (Protein/Polysaccharide ratio = 2.2). Moreover, EPS analysis indicates the EPS extracted from full-scale biofilms have a higher affinity and rigidity to the membrane surface compared to EPS from lab-scale biofilm. Thus, we propose that CIP protocols should be optimized in long-term experiments using the realistic feed water.
    • Biomimetic Coating-free Superomniphobicity.

      Das, Ratul; Ahmad, Zain; Nauruzbayeva, Jamilya; Mishra, Himanshu (Scientific reports, Springer Science and Business Media LLC, 2020-05-15) [Article]
      Superomniphobic surfaces, which repel droplets of  polar and apolar liquids, are used for reducing frictional drag, packaging electronics and foods, and separation processes, among other applications. These surfaces exploit perfluorocarbons that are expensive, vulnurable to physical damage, and have a long persistence in the environment. Thus, new approaches for achieving superomniphobicity from common materials are desirable. In this context, microtextures comprising "mushroom-shaped" doubly reentrant pillars (DRPs) have been shown to repel drops of polar and apolar liquids in air irrespective of the surface make-up. However, it was recently demonstrated that DRPs get instantaneously infiltrated by the same liquids on submersion because while they can robustly prevent liquid imbibition from the top, they are vulnerable to lateral imbibition. Here, we remedy this weakness through bio-inspiration derived from cuticles of Dicyrtomina ornata, soil-dwelling bugs, that contain cuboidal secondary granules with mushroom-shaped caps on each face. Towards a proof-of-concept demonstration, we created a perimeter of biomimicking pillars around arrays of DRPs using a two-photon polymerization technique; another variation of this design with a short wall passing below the side caps was investigated. The resulting gas-entrapping microtextured surfaces (GEMS) robustly entrap air on submersion in wetting liquids, while also exhibiting superomniphobicity in air. To our knowledge, this is the first-ever microtexture that confers upon intrinsically wetting materials the ability to simultaneously exhibit superomniphobicity in air and robust entrapment of air on submersion. These findings should advance the rational design of coating-free surfaces that exhibit ultra-repellence (or superomniphobicity) towards liquids.
    • Minimum Net Driving Temperature Concept for Membrane Distillation

      Blankert, Bastiaan; Vrouwenvelder, Johannes S.; Witkamp, Geert Jan; Ghaffour, NorEddine (Membranes, MDPI AG, 2020-05-14) [Article]
      <jats:p>In this study, we analyzed the heat requirement of membrane distillation (MD) to investigate the trade-off between the evaporation efficiency and driving force efficiency in a single effect MD system. We found that there exists a non-zero net driving temperature difference that maximizes efficiency. This is the minimum net driving temperature difference necessary for a rational operational strategy because below the minimum net driving temperature, both the productivity and efficiency can be increased by increasing the temperature difference. The minimum net driving temperature has a similar magnitude to the boiling point elevation (~0.5 °C for seawater), and depends on the properties of the membrane and the heat exchanger. The minimum net driving temperature difference concept can be used to understand the occurrence of optimal values of other parameters, such as flux, membrane thickness, and membrane length, if these parameters are varied in a way that consequently varies the net driving temperature difference.</jats:p>