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Recent Submissions

  • Continuous extraction and concentration of secreted metabolites from engineered microbes using membrane technology

    Overmans, Sebastian; Ignacz, Gergo; Beke, Aron K.; Xu, Jiajie; Saikaly, Pascal; Szekely, Gyorgy; Lauersen, Kyle J. (Green Chemistry, Royal Society of Chemistry (RSC), 2022-05-18) [Article]
    Microalgal cultivation in photobioreactors and membrane separations are both considered sustainable processes. Here we explore their synergistic combination to extract and concentrate a heterologous sesquiterpenoid produced by engineered green algal cells. A hydrophobic hollow-fiber membrane contactor was used to allow interaction of culture broth and cells with a dodecane solvent phase to accumulate algal produced patchoulol. Subsequent continuous membrane extraction of patchoulol from dodecane enabled product concentration in a methanol stream as well as dodecane recovery for its reuse. A structure-based prediction using machine learning was used to model a process whereby 100% patchoulol recovery from dodecane could be achieved with solvent-resistant nanofiltration membranes. Solvent consumption, E-factor, and economic sustainability were assessed and compared with existing patchoulol production processes. Our extraction and product purification process offers six- and two-orders of magnitude lower solvent consumption compared to synthetic production and thermal-based separation, respectively. Our proposed methodology is transferable to other microbial systems for the isolation of high-value isoprenoid and hydrocarbon products.
  • High-rate microbial electrosynthesis using a zero-gap flow cell and vapor-fed anode design

    Baek, Gahyun; Rossi, Ruggero; Saikaly, Pascal; Logan, Bruce (Water Research, Elsevier BV, 2022-05-13) [Article]
    Microbial electrosynthesis (MES) cells use renewable energy to convert carbon dioxide into valuable chemical products such as methane and acetate, but chemical production rates are low and pH changes can adversely impact biocathodes. To overcome these limitations, an MES reactor was designed with a zero-gap electrode configuration with a cation exchange membrane (CEM) to achieve a low internal resistance, and a vapor-fed electrode to minimize pH changes. Liquid catholyte was pumped through a carbon felt cathode inoculated with anaerobic digester sludge, with humidified N2 gas flowing over the abiotic anode (Ti or C with a Pt catalyst) to drive water splitting. The ohmic resistance was 2.4 ± 0.5 mΩ m2, substantially lower than previous bioelectrochemical systems (20–25 mΩ•m2), and the catholyte pH remained near-neutral (6.6–7.2). The MES produced a high methane production rate of 2.9 ± 1.2 L/L-d (748 mmol/m2-d, 17.4 A/m2; Ti/Pt anode) at a relatively low applied voltage of 3.1 V. In addition, acetate was produced at a rate of 940 ± 250 mmol/m2-d with 180 ± 30 mmol/m2-d for propionate. The biocathode microbial community was dominated by the methanogens of the genus Methanobrevibacter, and the acetogen of the genus Clostridium sensu stricto 1. These results demonstrate the utility of this zero-gap cell and vapor-fed anode design for increasing rates of methane and chemical productions in MES.
  • CNT/polyimide fiber-based 3D photothermal aerogel for high-efficiency and long-lasting seawater desalination

    Ren, Yafeng; Lian, Ruhe; Liu, Zongxu; Zhang, Guoxian; Wang, Wenbin; Ding, Dongliang; Tian, Miao; Zhang, Qiuyu (Desalination, Elsevier BV, 2022-05-12) [Article]
    Solar steam regeneration is considered an efficient way to desalinate seawater and alleviate the global shortage of freshwater resources. However, the poor mechanical properties, low evaporation rates, and short service life of the currently reported materials can not meet the requirement of actual applications. Here, a composite aerogel with high porosity up to 97.8% was developed by physically cross-linking the electrospinning PI fibers as the backbone and carbon nanotubes as the photothermal component. This composite aerogel composite reached the maximum temperature within 20 s and showed a stable evaporation rate of 2.08 kg m−2 h−1 under 1 sun irradiation (1 kW m−2). In simulated seawater distillation experiments, the material achieved 99% removal efficiency for various concentrations of NaCl solution. The aerogel consisting of polyimide backbone exhibited excellent UV resistance, showing an insignificant change in morphology and evaporation rate under continuous irradiation for 1 h at 40 mW cm−2 under 365 nm UV light. This study provides a reliable solution for developing high-performance solar evaporators with high porosity and endurance.
  • Global collision-risk hotspots of marine traffic and the world’s largest fish, the whale shark

    Womersley, Freya C.; Humphries, Nicolas E.; Queiroz, Nuno; Vedor, Marisa; da Costa, Ivo; Furtado, Miguel; Tyminski, John P.; Abrantes, Katya; Araujo, Gonzalo; Bach, Steffen S.; Barnett, Adam; Berumen, Michael L.; Bessudo Lion, Sandra; Braun, Camrin D.; Clingham, Elizabeth; Cochran, Jesse; de la Parra, Rafael; Diamant, Stella; Dove, Alistair D. M.; Dudgeon, Christine L.; Erdmann, Mark V.; Espinoza, Eduardo; Fitzpatrick, Richard; Cano, Jaime González; Green, Jonathan R.; Guzman, Hector M.; Hardenstine, Royale; Hasan, Abdi; Hazin, Fábio H. V.; Hearn, Alex R.; Hueter, Robert E.; Jaidah, Mohammed Y.; Labaja, Jessica; Ladino, Felipe; Macena, Bruno C. L.; Morris, John J.; Norman, Bradley M.; Peñaherrera-Palma, Cesar; Pierce, Simon J.; Quintero, Lina M.; Ramírez-Macías, Dení; Reynolds, Samantha D.; Richardson, Anthony J.; Robinson, David P.; Rohner, Christoph A.; Rowat, David R. L.; Sheaves, Marcus; Shivji, Mahmood S.; Sianipar, Abraham B.; Skomal, Gregory B.; Soler, German; Syakurachman, Ismail; Thorrold, Simon R.; Webb, D. Harry; Wetherbee, Bradley M.; White, Timothy D.; Clavelle, Tyler; Kroodsma, David A.; Thums, Michele; Ferreira, Luciana C.; Meekan, Mark; Arrowsmith, Lucy M.; Lester, Emily K.; Meyers, Megan M.; Peel, Lauren R.; Sequeira, Ana M. M.; Eguíluz, V. M.; Duarte, Carlos M.; Sims, David W. (Proceedings of the National Academy of Sciences, 2022-05-09) [Article]
    Marine traffic is increasing globally yet collisions with endangered megafauna such as whales, sea turtles, and planktivorous sharks go largely undetected or unreported. Collisions leading to mortality can have population-level consequences for endangered species. Hence, identifying simultaneous space use of megafauna and shipping throughout ranges may reveal as-yet-unknown spatial targets requiring conservation. However, global studies tracking megafauna and shipping occurrences are lacking. Here we combine satellite-tracked movements of the whale shark, Rhincodon typus, and vessel activity to show that 92% of sharks’ horizontal space use and nearly 50% of vertical space use overlap with persistent large vessel (>300 gross tons) traffic. Collision-risk estimates correlated with reported whale shark mortality from ship strikes, indicating higher mortality in areas with greatest overlap. Hotspots of potential collision risk were evident in all major oceans, predominantly from overlap with cargo and tanker vessels, and were concentrated in gulf regions, where dense traffic co-occurred with seasonal shark movements. Nearly a third of whale shark hotspots overlapped with the highest collision-risk areas, with the last known locations of tracked sharks coinciding with busier shipping routes more often than expected. Depth-recording tags provided evidence for sinking, likely dead, whale sharks, suggesting substantial “cryptic” lethal ship strikes are possible, which could explain why whale shark population declines continue despite international protection and low fishing-induced mortality. Mitigation measures to reduce ship-strike risk should be considered to conserve this species and other ocean giants that are likely experiencing similar impacts from growing global vessel traffic.
  • Effects of temperature and humidity ratio on the performance of desiccant dehumidification system under low-temperature regeneration

    Yu, Hao; Seo, Sang won; Mikšík, František; Thu, Kyaw; Miyazaki, Takahiko; Ng, Kim Choon (Journal of Thermal Analysis and Calorimetry, Springer Science and Business Media LLC, 2022-05-06) [Article]
    The desiccant dehumidification system can separate the latent heat and sensible heat in the air-conditioning system and achieve energy savings by removing latent heat. Industrial waste heat and renewable energy could be utilized in desiccant dehumidification systems, where the desorption process can be performed below 70 °C. The vapor pressure and temperature of the regenerating air dictate the desorption process corresponding to the isotherm properties. This study has focused on the effects of various temperatures and humidity ratios of regeneration air on the performance of a desiccant dehumidifier using a polymer as an adsorbent. Experiments were performed using the regeneration air with the humidity ratios of 0.005 kg kg−1, 0.010 kg kg−1, 0.015 kg kg−1, and 0.020 kg kg−1, while the air temperatures were varied from 40 °C to 70 °C. The evaluation of this study employs the adsorption/desorption amount, average moisture removal capacity, and latent energy ratio (LER) of the regeneration process as key performance indexes. At the regeneration temperature of 68 °C, the peak desorption amount at the humidity ratio of 0.005 kg kg−1 and 0.010 kg kg−1 both reached 0.011 kg kg−1. The results indicated that the higher desorption temperature led to a higher desorption amount. Besides, with the increased desorption temperature, the average moisture removal capacity increases. In contrast, the high humidity ratio of regeneration air resulted in a weak dehumidification ability. Lower regeneration temperature was difficult to apply to regenerate the polymer-based desiccant under a high-humidity-ratio atmosphere. To attain a high LER, a lower humidity ratio of dry air and regeneration temperature was preferred. The regeneration air with a humidity ratio of 0.020 kg kg−1 is not suitable to apply in the dehumidification system in the temperature range of 40–70 °C.
  • A sacrificial protective layer as fouling control strategy for nanofiltration in water treatment

    Li, Sihang; Meng, Huanna; Wang, Haihua; Vrouwenvelder, Johannes S.; Li, Zhenyu (Water Research, Elsevier BV, 2022-05-06) [Article]
    High-performance nanofiltration (NF) membrane with super antifouling capability as well as reusability is highly desired in water treatment. A new antifouling strategy by a coating-decoating-recoating cycle was investigated for effective removal of fouling and restoring the original membrane performance. The functional membrane surface was fabricated by in-situ coating a ‘green’ and biodegradable carboxymethyl chitosan (CMCS) layer as physical barrier. The CMCS layer can be decoated and re-coated by simple procedures. Results showed that (i) the CMCS layer enhanced surface hydrophilicity, surface smoothness and fouling resistance of NF membrane, (ii) both the unfouled and fouled CMCS layer were easily decoated by the strong acid solution, (iii) the CMCS layer was easily re-coated by facile recoating and (iv) the water flux recovery ratio of membrane with coating layer was maintained more than 88.8% during fouling testing by natural organic matter (NOM) after four sequential cycles of coating, decoating and recoating process. The re-coated membrane exhibited stable, improved membrane operational and antifouling performance. The coating-decoating-recoating approach is proven to be low-cost and eco-friendly strategy for NOM fouling control on NF membrane in water treatment applications.
  • Monitoring coastal water flow dynamics using sub-daily high-resolution SkySat satellite and UAV-based imagery

    Johansen, Kasper; Dunne, Aislinn; Tu, Yu-Hsuan; Jones, Burton; McCabe, Matthew (Water Research, Elsevier BV, 2022-05-05) [Article]
    Sub-daily tracking of dynamic features and events using high spatial resolution satellite imagery has only recently become possible, with advanced observational capabilities now available through tasking of satellite constellations. Here, we provide a first of its kind demonstration of using sub-daily 0.50 m resolution SkySat imagery to track coastal water flows, combining these data with object-based detection and a machine-learning approach to map the extent and concentration of two dye plumes. Coincident high-frequency unmanned aerial vehicle (UAV) imagery was also employed for quantitative modeling of dye concentration and evaluation of the sub-daily satellite-based dye tracking. Our results show that sub-daily SkySat imagery can track dye plume extent with low omission (8.73–16.05%) and commission errors (0.32–2.77%) and model dye concentration (coefficient of determination = 0.73; root mean square error = 28.68 ppb) with the assistance of high-frequency UAV data. The results also demonstrate the capabilities of using UAV imagery for scaling between field data and satellite imagery for tracking coastal water flow dynamics. This research has implications for monitoring of water flows and nutrient or pollution exchange, and it also demonstrates the capabilities of higher temporal resolution satellite data for delivering further insights into dynamic processes of coastal systems.
  • In situ conductive spacers for early pore wetting detection in membrane distillation

    Alpatova, Alla; Qamar, Adnan; Alhaddad, Mohammed; Kerdi, Sarah; Soo Son, Hyuk; Amin, Najat A.; Ghaffour, NorEddine (Separation and Purification Technology, Elsevier BV, 2022-04-30) [Article]
    Membrane distillation (MD) suffers from pore wetting which deteriorates membrane separation properties and causes water protrusion to permeate side. The early detection of pore wetting is a challenge which needs to be addressed to achieve stable MD performance. In this study, electrically-conductive Pt-coated spacers placed inside the feed and coolant channels with a dual purpose of maximizing permeate flux and instantaneous wetting detection once first membrane pores are compromised are proposed. Upon wetting, permeate salt concentration increases thereby initiating redox reactions at two spacer electrodes under the applied electrical potential. As a result, electrical current is produced and measured. The competence of the proposed wetting detection method was explored in MD process in the presence of organic substances with high wetting propensity. An increase in generated electrical current upon wetting development and substantial signal amplification with the voltage increase was demonstrated. The new wetting detection method achieved a faster response comparing to conventional conductivity measurements. Moreover, this method allows to define the wetting onset which can serve as an indication of early membrane impairment. Different spacer geometries and observed no adverse effect of spacer coating on MD performance were further compared. Experimental and numerical simulations accentuated an importance of spacer design by providing specific permeate flux gain for a 1-helical spacer comparing to a spacer with a smooth cylindrical filament. This effect became more evident at higher feed water temperature, condition that favors greater temperature polarization.
  • Home sweet home: spatiotemporal distribution and site fidelity of the reef manta ray (Mobula alfredi) in Dungonab Bay, Sudan.

    Knochel, Anna; Hussey, Nigel E; Kessel, Steven T; Braun, Camrin D; Cochran, Jesse E M; Hill, Graham; Klaus, Rebecca; Checkchak, Tarik; Elamin El Hassen, Nasereldin M; Younnis, Mohammed; Berumen, Michael L. (Movement ecology, BioMed Central Ltd, 2022-04-28) [Article]
    Background: Reef manta ray (Mobula alfredi) populations along the Northeastern African coastline are poorly studied. Identifying critical habitats for this species is essential for future research and conservation efforts. Dungonab Bay and Mukkawar Island National Park (DMNP), a component of a UNESCO World Heritage Site in Sudan, hosts the largest known M. alfredi aggregation in the Red Sea. Methods: A total of 19 individuals were tagged using surgically implanted acoustic tags and tracked within DMNP on an array of 15 strategically placed acoustic receivers in addition to two offshore receivers. Two of these acoustically monitored M. alfredi were also equipped with satellite linked archival tags and one individual was fitted with a satellite transmitting tag. Together, these data are used to describe approximately two years of residency and seasonal shifts in habitat use. Results: Tagged individuals were detected within the array on 96% of monitored days and recorded an average residence index of 0.39 across all receivers. Detections were recorded throughout the year, though some individuals were absent from the receiver array for weeks or months at a time, and generalized additive mixed models showed a clear seasonal pattern in presence with the highest probabilities of detection occurring in boreal fall. The models indicated that M. alfredi presence was highly correlated with increasing chlorophyll-a levels and weakly correlated with the full moon. Modeled biological factors, including sex and wingspan, had no influence on animal presence. Despite the high residency suggested by acoustic telemetry, satellite tag data and offshore acoustic detections in Sanganeb Atoll and Suedi Pass recorded individuals moving up to 125 km from the Bay. However, all these individuals were subsequently detected in the Bay, suggesting a strong degree of site fidelity at this location. Conclusions: The current study adds to growing evidence that M. alfredi are highly resident and site-attached to coastal bays and lagoons but display seasonal shifts in habitat use that are likely driven by resource availability. This information can be used to assist in managing and supporting sustainable ecotourism within the DMNP, part of a recently designated UNESCO World Heritage Site.
  • Adsorption heat transformer cycle using multiple adsorbent plus water pairs for waste heat upgrade

    Saren, Sagar; Mitra, Sourav; Miyazaki, Takahiko; Ng, Kim Choon; Thu, Kyaw (JOURNAL OF THERMAL ANALYSIS AND CALORIMETRY, 2022-04-28) [Article]
    Adsorption heat transformers (AHTs) are considered as promising systems for upgrading waste heat to a higher temperature. The cycle operates among three temperature reservoirs: (i) heat sink at the low temperature (TL), (ii) heat source at the medium temperature (TM), and (iii) heat supply at the high temperature (TH). In the present study, the performance the AHT cycle was analyzed for possible applications in the waste heat upgrade and thermal desalination. An equilibrium model was developed using adsorption characteristics and isotherm data. Five types of commercially available silica gels and three types of zeolites were investigated as adsorbents. Nonlinear optimization technique was utilized for the determination of the intermediate pressure and uptake for preheating and precooling phase of the AHT cycle. The performance parameters in terms of useful heat ratio and condensation heat ratio were determined and compared for the reservoir temperatures at 30 °C (TL)—60 °C (TM)—80 °C (TH). Parametric evaluation of the performance parameters was carried out based on the variation in gross temperature lift, as well as the heat exchanger mass ratio. It was found out that reduction in the gross temperature lift had a positive impact on the useful heat ratio and a negative influence on the condensation heat ratio of the AHT cycle. Significant variations in the maximum adsorption capacity and slope of the isosteric heat of adsorption across various adsorption pairs containing zeolites were observed. As a result, AQSOA-Z01 zeolite exhibited the highest heat exchange values of the AHT cycle in the range of ~ 320–370 kJ per kg of adsorbent. On the contrary, type AQSOA-Z02 zeolite displayed the lowest corresponding values in the range of ~ 60–90 kJ kg-1 of adsorbent. On the other hand, variation across the different silica gel adsorbents was comparatively smaller because of similar isotherm and isosteric heat of adsorption characteristics. This study will assist the research on the theoretical development of the AHT cycle via material selection and system design optimization.
  • Control strategies against algal fouling in membrane processes applied for microalgae biomass harvesting

    Malaguti, Marco; Novoa, Andres F.; Ricceri, Francesco; Giagnorio, Mattia; Vrouwenvelder, Johannes S.; Tiraferri, Alberto; Fortunato, Luca (Journal of Water Process Engineering, Elsevier BV, 2022-04-22) [Article]
    Microalgae biomass is increasingly applied in a variety of high-end applications, such as biofuel production, CO2 fixation, food, and cosmetics. As the demand for microalgae increases, improvements in biomass harvesting techniques are required since dewatering represents a significant fraction of the total algae production cost. While membrane technology is growing as a means to achieve effective biomass harvesting, fouling from microalgae suspensions is a major drawback, since these streams are rich in organic compounds, nutrients, and biological materials. The aim of this paper is to present the state-of-the-art of the control strategies to manage algal fouling. The control strategies are divided into: (i) mitigation strategies, including pre-treatment options, modified membrane surfaces, and hydrodynamic approaches; and (ii) adaptation strategies, which include physical, mechanical, and chemical cleaning. Fouling mitigation strategies are implemented in membrane separation processes seeking to maintain high productivity without compromising biomass quality, while minimizing the energy cost related to fouling control. Adaptation techniques include optimization of the cleaning time and effective removal of the irreversible foulants. Further, minimization in the use of chemicals and of the backflush permeate must be achieved to ensure an efficient performance in chemical cleaning and backwash approaches, respectively. Finally, the article discusses future research perspectives in membrane-based microalgae harvesting with a focus on zero liquid discharge and effective fouling control strategies within the water-energy nexus.
  • Why did only one genus of insects, Halobates, take to the high seas?

    Cheng, Lanna; Mishra, Himanshu (PLOS Biology, Public Library of Science (PLoS), 2022-04-13) [Article]
    Oceans cover more than 70% of the Earth’s surface and house a dizzying array of organisms. Mammals, birds, and all manner of fish can be commonly sighted at sea, but insects, the world’s most common animals, seem to be completely absent. Appearances can deceive, however, as 5 species of the ocean skater Halobates live exclusively at the ocean surface. Discovered 200 years ago, these peppercorn-sized insects remain rather mysterious. How do they cope with life at the ocean surface, and why are they the only genus of insects to have taken to the high seas?
  • Solar thermal energy conversion and utilization—New research horizon

    Wang, Peng; Zhu, Jia (EcoMat, Wiley, 2022-04-12) [Article]
  • Innovative Solid Desiccant Dehumidification Using Distributed Microwaves

    Ybyraiymkul, Doskhan; Chen, Qian; Burhan, Muhammad; Shahzad, Muhammad Wakil; Akhtar, Faheem; Kumja, M; AlRowais, Raid; Ng, Kim Choon (SSRN Preprint Server, 2022-04-06) [Preprint]
    Dehumidification is one of the key challenges facing the air conditioning (AC) industry in the treatment of moist air. Over many decades, the dual role of heat exchangers of AC chillers for the sensible and latent cooling of space has hindered the thermal-lift reduction in the refrigeration cycle, due to the requirements of water vapor removal at dew-point and heat rejection to the ambient air. These practical constraints of AC chillers have resulted in the leveling of energy efficiency of mechanical vapor compressors (MVC) for many decades. One promising approach to energy efficiency improvement is the decoupling of dehumidification from sensible processes so that innovative but separate processes can be applied. In this paper, an advanced microwave dehumidification method is investigated in the laboratory, where the microwave (2.45 GHz) energy can be irradiated onto the dipole structure of water vapor molecules, desorbing rapidly from the pores of adsorbent. Results show a significant improvement in performance for microwave dehumidification, up to 4-fold, as compared to data available in the literature.
  • Direct imaging of polymer filaments pulled from rebounding drops

    Yang, Zi Qiang; Zhang, Peng; Shi, Meng; Julaih, Ali Al; Mishra, Himanshu; Fabrizio, Enzo Di; Thoroddsen, Sigurdur T (arXiv, 2022-04-04) [Preprint]
    Polymer filaments form the foundation of biology from cell scaffolding to DNA. Their study and fabrication play an important role in a wide range of processes from tissue engineering to molecular machines. We present a simple method to deposit stretched polymer fibers between micro-pillars. This occurs when a polymeric drop impacts on and rebounds from an inclined superhydrophobic substrate. It wets the top of the pillars and pulls out liquid filaments which are stretched and can attach to adjacent pillars leaving minuscule threads, with the solvent evaporating to leave the exposed polymers. We use high-speed video at the microscale to characterize the most robust filament-forming configurations, by varying the impact velocity, substrate structure and inclination angle, as well as the PEO-polymer concentration. Impacts onto plant leaves or randomized nano-structured surface leads to the formation of a branched structure, through filament mergers at the free surface of the drop. SEM shows the deposition of filament bundles which are thinner than those formed by evaporation or rolling drops. Raman spectroscopy identifies mode B stretched DNA filaments from aqueous-solution droplets.
  • Enzymatic bioprospection of cultured bacterial diversity of Al-Wahbah crater, Saudi Arabia

    Romanenko, Andrii (2022-04) [Thesis]
    Advisor: Rosado, Alexandre S.
    Committee members: Saikaly, Pascal; Saad, Maged
    The push for greener chemistry and less impactful production in the industrial processes requires enzymes that can withstand under hostile industrial conditions, e.g. high temperatures, pH and pressure. A great and unveiled source of (novel) enzymes are the extreme environments and the extremophilic microbes living and thriving in these environments. Due to the metabolic adaptations, extremophiles can be a valuable reservoir of extremozymes that can be a more stable alternative to mesophilic catalysts. Al Wahbah crater is one of the scenic landscapes of Saudi Arabian volcanic sites. The microbial community flourishing in its extreme conditions is underexplored, and its potential application in biotechnology (e.g., enzymes) remain hidden. In this way, the main objective of this work was to identify bacterial strains from the crater that are capable of producing important hydrolysing enzymes and to investigate their genomes. In this study, soil samples were collected and analysed for elemental composition and further used for the isolation of culturable microbes. Soil samples were very saline with sodium concentrations of 23-59 g/Kg and slightly alkaline. The majority of the bacteria were identified under mesophilic temperatures and from the clay sample using R2A culture medium. The bacterial fraction was morphologically and molecularly identified using 16S sequencing, and explored for the production of hydrolysing enzymes using selective media. The dominance of Firmicutes was observed in the strains, with Bacillus the most common genus.. The five bacterial strains producing enzymes in the highest quantities were sent for the whole genome sequencing with the following bioinformatics analysis. They were identified as Bacillus spizizenii, B. cereus, B. vallismortis, and B. haynesii. Apart from different families of enzymes annotated in the respective genomes, such as Glycoside Hydrolases, Glycosyl Transferases, Polysaccharide Lyases, a great number of secondary metabolites with antimicrobial and antifungal properties were predicted. The result of the study revealed the great metabolic potential of the selected bacterial strains, generated data for further studies and was just a first step in the exploration of genomic features and biotechnological potential of those bacteria.
  • Long-Term Fouling Control Strategies in Gravity-Driven Membrane Bioreactors (Gd-Mbrs): Impact on Process Performance and Membrane Fouling Properties

    Ranieri, Luigi; Vrouwenvelder, Johannes S.; Fortunato, Luca (SSRN Electronic Journal, Elsevier BV, 2022-04-01) [Preprint]
    This study aims to assess the effects of periodic physical cleanings operations in Gravity-Driven Membrane Bioreactor (GD-MBR) treating primary wastewater. The impact of each cleaning strategy on the reactor performance (permeate flux and water quality), biomass morphology, and fouling composition were evaluated. The application of air scouring coupled with intermittent filtration resulted in the highest permeate flux (4 LMH) compared to only intermittent filtration (i.e., relaxation) (1 LMH) and air scouring under continuous filtration (2.5 LMH). Air scouring coupled with relaxation led to a thin (~50 µm) but with more porous fouling layer and low hydraulic resistance, presenting the lowest concentration of extracellular polymeric substance (EPS) in the biomass. Air scouring under continuous filtration led to a thin (~50 µm), dense, compact, and less porous fouling layer with the highest specific hydraulic resistance. The employment of only relaxation led to the highest fouling deposition (~280 µm) on the membrane surface. The highest TN removal (~62%) was achieved in the reactor with only relaxation (no aeration) due to the anoxic condition in the filtration tank, while the highest COD removal (~ 60%) was achieved with air scouring under continuous filtration due to the longer aeration time and the denser fouling layer. The presented results highlighted the versatility of the GD-MBR, where the choice of the appropriate operation relies on the eventual discharge or reuse of the treated effluent.
  • Monitoring and characterization of biofouling development in a membrane fouling simulator (MFS) fed with natural seawater

    Franco Clavijo, Natalia (2022-04) [Thesis]
    Advisor: Vrouwenvelder, Johannes S.
    Committee members: Blankert, Bastiaan; Witkamp, Geert Jan
    Reverse osmosis (RO) desalination plants enable the production of high-quality freshwater from seawater, explaining the increasing global use of this technology. However, a major operational challenge for RO is biofouling, caused by excessive biomass accumulation. Membrane fouling simulators (MFSs), downsized membrane systems, were demonstrated to be suitable for biofouling studies using tap water. There is a need to investigate biofouling using natural seawater. The seawater MFS studies involved (i) an exploratory study to evaluate the MFS setup, (ii) long-term operation without feed water nutrient dosage, (iii) impact of nutrient concentration, and (iv) a comparison of biofouling development with freshwater. MFSs were operated parallel at constant feed flow (0.2 m/s), with feed spacer and RO membrane, at varying biodegradable organic nutrient concentrations (0, 50, and 200 µg C/L). The relative pressure drop (RPD) was monitored over time, and biofilm development was characterized through the MFS window applying optical coherence tomography (OCT). Results demonstrated for seawater that (i) the developed setup had a reliable operation and provided reproducible data, (ii) biofouling development presented a minimal effect when nutrient concentration was quadrupled, (iii) there was no correlation between the nutrient concentration and growth rate for seawater experiments, suggesting biofilm development under conditions close to the maximum growth rate. Compared to tap water at the same nutrient concentrations, seawater showed much faster biofilm development, pressure drop increase, and strongly different biofilm morphology. This research provides new insights, new research directions and underlines the importance of doing MFS research with natural seawater.
  • Using Unmanned Aerial Vehicles and Carbon Assimilation Rate Measurements to Estimate Carbon Capture for Red Sea Mangroves

    Lara, Mariana Elias (2022-04) [Thesis]
    Advisor: McCabe, Matthew
    Committee members: Johansen, Kasper; Daffonchio, Daniele
    To meet ambitious net-zero greenhouse gas emission targets by 2050, large-scale CO₂ reduction and removal are required. Nature-based solutions have been proposed as a potential aid to this process. Mangrove ecosystems, as well as their conservation and restoration, have the potential to make significant contributions in Saudi Arabia and other coastal regions. While field measurements of carbon assimilation rate and leaf area index (LAI) in mangroves provide important insights into carbon fluxes, they are time-consuming, labor-intensive, and limited when covering large areas. To address this issue, multispectral images captured by unmanned aerial vehicles (UAV) are used to generate spectral vegetation indices, which can then be used to build regression models for estimating mangrove LAI and carbon capture capabilities. The carbon assimilation rate measurements in the field for studying both diurnal and sub-seasonal fluxes revealed that Avicennia marina has a high carbon assimilation rate peak in the morning, which decreases thereafter, and a smaller peak in the afternoon. Furthermore, comparing all the studied sites, the KAM site (June) had the highest morning overall carbon assimilation rate values, ranging from 15- 20 μmol CO₂ m⁻² s⁻¹, followed by Island (October) ranging from 10- 17 μmol CO₂ m⁻² s⁻¹, and finally Rheem (February) ranging from 5- 15 μmol CO₂ m⁻² s⁻¹. Moreover, the acquired multispectral images were used to generate spectral vegetation indices, which were then used as input to build a random forest algorithm for estimating the LAI of mangroves. Following an evaluation of each mangrove site, the Rheem site dataset yielded the best Random forest algorithm (R²= 0.88 and RMSE= 0.39), so this model was used to create high resolution spatially distributed LAI-based maps for all of the mangrove sites studied. Knowing the carbon uptake per leaf area as well as the total leaf area (based on UAV-derived LAI estimates) within a mangrove site enabled us to create carbon capture maps (kg C yr⁻¹ per pixel) for all of the sites studied. To enable a more complete carbon accounting of mangrove ecosystems, future research should explore remote sensing approaches for inferring carbon assimilation in both belowground biomass and soils.
  • CubeSat constellations provide enhanced crop phenology and digital agricultural insights using daily leaf area index retrievals

    Johansen, Kasper; Ziliani, Matteo G.; Houborg, Rasmus; Franz, Trenton E.; McCabe, Matthew (Springer Science and Business Media LLC, 2022-03-28) [Article]
    Satellite remote sensing has great potential to deliver on the promise of a data-driven agricultural revolution, with emerging space-based platforms providing spatiotemporal insights into precision-level attributes such as crop water use, vegetation health and condition and crop response to management practices. Using a harmonized collection of high-resolution Planet CubeSat, Sentinel-2, Landsat-8 and additional coarser resolution imagery from MODIS and VIIRS, we exploit a multi-satellite data fusion and machine learning approach to deliver a radiometrically calibrated and gap-filled time-series of daily leaf area index (LAI) at an unprecedented spatial resolution of 3 m. The insights available from such high-resolution CubeSat-based LAI data are demonstrated through tracking the growth cycle of a maize crop and identifying observable within-field spatial and temporal variations across key phenological stages. Daily LAI retrievals peaked at the tasseling stage, demonstrating their value for fertilizer and irrigation scheduling. An evaluation of satellite-based retrievals against field-measured LAI data collected from both rain-fed and irrigated fields shows high correlation and captures the spatiotemporal development of intra- and inter-field variations. Novel agricultural insights related to individual vegetative and reproductive growth stages were obtained, showcasing the capacity for new high-resolution CubeSat platforms to deliver actionable intelligence for precision agricultural and related applications.

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