•There is a lack of information on the use of ultrasonication at large scales/the field.•The efficiency of ultrasonication for algal removal in field is still debatable.•Attenuation of ultrasonic ...intensity needs to be considered in field applications.•Further field data is required for the upscaling of ultrasonication devices.
Algal blooms are a naturally occurring phenomenon which can occur in both freshwater and saltwater. However, due to excess nutrient loading in water bodies (e.g. agricultural runoff and industrial activities), harmful algal blooms (HABs) have become an increasing issue globally, and can even cause health effects in humans due to the release of cyanotoxins. Among currently available treatment methods, sonication has received increasing attention for algal control because of its low impact on ecosystems and the environment. The effects of ultrasound on algal cells are well understood and operating parameter such as frequency, intensity, and duration of exposure has been well studied. However, most studies have been limited to laboratory data interpretation due to complicated environmental conditions in the field. Only a few field and pilot tests in small reservoirs were reported and the applicability of ultrasound for HABs prevention and control is still under question. There is a lack of information on the upscaling of ultrasonication devices for HAB control on larger water bodies, considering field influencing factors such as rainfall, light intensity/duration, temperature, water flow, nutrients loading, and turbidity. In this review article, we address the challenges and field considerations of ultrasonic applications for controlling algal blooms. An extensive literature survey, from the fundamentals of ultrasound techniques to recent ultrasound laboratory and field studies, has been thoroughly conducted and summarized to identify future technical expectations for field applications. Case studies investigating spatial distribution of frequency and pressure during sonication are highlighted with future implications.
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•A facile additive free electroplating method was applied to obtain a nanostructured cobalt film.•Cobalt nanoflake/particles were obtained with a sacrificial ZnO nanoflake ...template.•Limit of detection of phosphate measurements was improved with the nanostructured sensor.•A dominant charge transfer mechanism was proposed to explain the transformation of sensor performance.
In this work, a novel method using hydrothermal grown ZnO nanoflakes as a template for nanostructured metal film electroplating was proposed. Compared with the commonly used anodic aluminum oxide (AAO) template, the in-situ grown ZnO nanoflake template can be applied for large area electroplating with a relatively simple process. This method was applied for nanostructured cobalt electrode electroplating. The fabricated electrode was then tested for in situ phosphate detection in aqueous environments. The results showed that the ZnO nanoflake template successfully incorporated nanostructure into a cobalt film, and compared with a planar cobalt film, the sensor’s limit of detection (LOD) was improved by an order of magnitude.
Ultrafiltration (UF) is a low-pressure membrane that yields higher permeate flux and saves significant operating costs compared to high-pressure membranes; however, studies addressing the combined ...improvement of anti-organic and biofouling properties of UF membranes are lacking. This study investigated the fouling resistance and antimicrobial property of a UF membrane via silver phosphate nanoparticle (AgPNP) embedded polyelectrolyte (PE) functionalization. Negatively charged polyacrylic acid (PAA) and positively charged polyallylamine hydrochloride (PAH) were deposited on the membrane using a fluidic layer-by-layer assembly technique. AgPNPs were immobilized within the crosslinked "bilayers" (BL) of PAH/PAA. The effectiveness of AgPNP immobilization was confirmed by microprofile measurements on membrane surfaces using a solid contact Ag micro-ion-selective electrode. Upon stable and uniform BL formation on the membrane surface, the permeate flux was governed by a combined effect of PAH/PAA-derived hydrophilicity and surface/pore coverage by the BLs "tightening" of the membrane. When fouled by a model organic foulant (humic acid), the functionalized membrane exhibited a lower flux decline and a greater flux recovery due to the electrostatic repulsion imparted by PAA when compared to the unmodified membrane. The functionalization rendered antimicrobial property, as indicated by fewer attachments of bacteria that initiate the formation of biofilms leading to biofouling.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
•Salt concentration had more of an effect than salt type on algal metabolisms.•Salinity stress reduced the growth of Chlorella vulgaris.•Salinity stress increased total lipid content and saturated ...portions of fatty acids.•Algae settling was improved by 33–83% with increased NaCl concentrations.
Microalgae can offer several benefits for wastewater treatment with their ability to produce large amounts of lipids for biofuel production and the high economic value of harvested biomass for biogas and fertilizer. This study found that salt concentration (∼45gL−1) had more of an effect than salt type on metabolisms of Chlorella vulgaris for wastewater treatment and biofuel production. Salinity stress decreased the algal growth rate in wastewater by 0.003day−1permScm−1 and slightly reduced nutrient removal rates. However, salinity stress was shown to increase total lipid content from 11.5% to 16.1% while also increasing the saturated portions of fatty acids in C. vulgaris. In addition, salinity increased the algal settling rate from 0.06 to 0.11mday−1 which could potentially reduce the cost of harvesting for algal biofuel production. Overall, C. vulgaris makes a suitable candidate for high salinity wastewater cultivation and biofuel production.
Literature on bilgewater focuses on empirically determined treatment methods and lacks specific information on emulsion characteristics. Therefore, this review discusses potential emulsion ...stabilization mechanisms that occur in bilgewater and evaluates common approaches to study their behavior. Current knowledge on emulsion formation, stabilization, and destabilization is outlined to provide researchers and bilgewater treatment operators with the knowledge needed to determine emulsion prevention and treatment strategies. Furthermore, a broad assessment of bilgewater emulsion characterization techniques, from general water quality analysis to advanced droplet stability characterization methods are discussed in detail. Lastly, a survey of typical bilgewater characteristics and information on standard synthetic bilgewater mixtures used in the testing of oil pollution abatement equipment are presented. Overall, the goal of this article is to provide a better understanding of physical and thermodynamic properties of emulsions to help improve bilgewater treatment and management.
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•Bilgewater characteristics can influence emulsion formation and stability.•Emulsion characterization methods were reviewed for bilgewater applications.•Bilgewater characteristics are highly variable based on daily shipboard operations.•Emulsion characterization can assist to develop effective emulsion treatment.
Chemically stabilized emulsions are difficult to break because of micelle stability. Many physical and chemical processes have been used for emulsion breaking/separation; however, most operational ...parameters are based on empirical data and bulk analysis. A multiscale understanding of emulsions is required before these processes can advance further. This study utilized needle-type microsensors and confocal laser scanning microscopy (CLSM) for characterizing simulated bilge water emulsions with different types of surfactants (Triton X-100 and sodium dodecyl sulfate SDS) under various NaCl concentrations at microscale. Using microsensors, a diffusion process was clearly visualized across the oil/water interface which appears to be related to emulsion formation kinetics and mass transfer. While emulsion stability decreased with NaCl concentrations, SDS (anionic surfactant) is more likely to form emulsion as salinity increases, requiring more salinity to coalesce SDS emulsions than Triton X-100 (nonionic surfactant) emulsions. Triton X-100 emulsions showed the potential to exhibit particle stabilized emulsions with NaCl concentration below 10–2.5 M. The research demonstrated that the use of nonionic surfactant allows better oil-in-water separation than anionic surfactant. Significant pH changes of emulsions from unknown additives have implications when operating pH-sensitive emulsion breaking/separation processes (e.g., electrocoagulation).
Oxygen (O2) is a strong inhibitor of hydrogenase (HydA) activity and expression and altering the sulfur (S) oxidizing transitions in photosystem II (PSII) often allows algal photohydrogen production; ...however, this may not be practical in a wastewater environment. To counteract natural mechanisms of oxygen evolution in PSII, we utilized acetic acid and butyric acid, which are main volatile fatty acids (VFAs) found in anaerobic bacterial digestion in wastewater treatment, as oxygen regulators for photosynthetic biohydrogen production using Chlorella vulgaris. It was found that a VFA-containing synthetic wastewater promotes oxygen depletion in a photobioreactor (PBR), producing maximum hydrogen yield of 65.4 ± 0.3 μmoL H2 L−1 mM−1 acetate without artificial sulfur or chloride deprivation. Butyric acids showed no significant effect on oxygen depletion and biohydrogen production in the PBR. The measurements of both relative expression level of mRNA and specific activities of reactivate HydA revealed that repetitive algal H2 photo-evolution was possible by HydA synthesis in C. vulgaris followed by complete oxygen depletion controlled by acetic acid levels in the PBR. This emerging understanding of the role of VFAs on oxygen regulation in PSII in natural environments is expected to lead algal-driven bioenergy production technologies to the next level.
•Oxygen is a strong inhibitor of hydrogenase (HydA) activity in algal metabolism.•VFA from wastewater can control oxygen deprivation for microalgal hydrogen production.•Repetitive algal H2 photo-evolution was feasible by HydA synthesis in C. vulgaris.•VFA-rich wastewater is a good candidate for biophotolysis.
This study presents in situ detection of Zn
2+
using a novel two-step square-wave anodic stripping voltammetry (SWASV)-based needle-type microsensor for citrus plant applications. A double-barrel ...bismuth/platinum (Bi/Pt) microelectrode was fabricated with a solid metal tip (~110 urn), which was durable enough to penetrate the thick skin of the citrus leaves and sensitive enough to detect ppb changes in Zn
2+
concentration using SWASV. The microelectrode tip size was also determined to reduce mass transport limitation and improve limit of detection. Overall, the developed Bi/Pt microelectrode successfully measured Zn
2+
concentrations within the vascular bundle of citrus plants.
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•An aquaporin-based forward osmosis membrane was evaluated for algae dewatering.•NH4Cl showed the highest flux improvement with the lowest reverse salt flux.•NaCl and natural seawater ...showed well-defined draw solution performance.•No significant flux drop was observed for 81% algae dewatering.
Low energy requirement in algae harvesting is necessary for sustainable biofuel production. Forward osmosis (FO) can provide a potential alternative for low energy consumption by using osmotic pressure between the draw solution (DS) and feed solution (FS). In this study, an aquaporin-based polyethersulfone (PES) membrane was evaluated for algal dewatering using FO. Three different types of DS (NaCl, KCl and NH4Cl), different cross flow velocities (CFVs), and configuration variations were compared to determine the FO performance to dewater Chlorella vulgaris. For short-term operation (500 min), the average water fluxes were 5.6, 4.8, and 4.3 L m−2 h−1 for NaCl, KCl, and NH4Cl, respectively and all DSs showed increased fluxes with increased CFVs. In particular, this study found that NH4Cl is the best candidate among the three tested DSs for improved water flux and low reverse salt flux for the aquaporin-based PES FO membrane. Natural seawater was also tested and revealed well-defined DS performance compatible with NaCl. For a longer duration experiment, 81% of algae dewatering was achieved with a 29% flux drop which may be attributed to the increasing FS concentration, concentration polarization and the loosely attached algal biofilm on the membrane surface. Overall, this study demonstrates a new iteration of the aquaporin-based PES membrane for algal dewatering in FO application.
Abstract
Two-dimensional molybdenum disulfide (2D MoS
2
) presents extraordinary optical, electrical, and chemical properties which are highly tunable by engineering the orientation of constituent 2D ...layers. 2D MoS
2
films with vertically-aligned layers exhibit numerous 2D edge sites which are predicted to offer superior chemical reactivity owing to their enriched dangling bonds. This enhanced chemical reactivity coupled with their tunable band gap energy can render the vertical 2D MoS
2
unique opportunities for environmental applications that go beyond the conventional applications of horizontal 2D MoS
2
in electronics/opto-electronics. Herein, we report that MoS
2
films with vertically-aligned 2D layers exhibit excellent visible light responsive photocatalytic activities for efficiently degrading organic compounds in contaminated water such as harmful algal blooms. We demonstrate the visible light-driven rapid degradation of microcystin-LR, one of the most toxic compounds produced by the algal blooms, and reveal that the degradation efficiency can be significantly improved by incorporating noble metals. This study suggests a high promise of these emerging 2D materials for water treatment, significantly broadening their versatility for a wide range of energy and environmental applications.
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