Raw Seawater Research Articles

Development and characterization of an asymmetrical flat microfiltration membrane based on natural phengite clay: Application as a pretreatment for raw seawater reverse osmosis desalination

The work focuses on developing a new asymmetric flat microfiltration membrane using an inexpensive geological material, natural Moroccan phengite clay. The optimal porous ceramic support was prepared by applying the paste casting method and sintering at a low temperature of 1050 °C for 2 h. Secondly, the microfiltration layer was developed by the spin coating method. The layer was then dried and sintered at 850 °C/2h. SEM analysis revealed that the morphological structure of the layer is homogeneous and free from cracks. Furthermore, the microfiltration layer has an average pore size of 1.23 μm, a thickness ranging from 30.3 μm to 31.3 μm, a water permeability of 258.1 L/h.m2.bar, and good chemical stability against corrosion. The performance of the manufactured membrane was evaluated by filtering raw seawater (RSW1 and RSW2) as a potential application for seawater pretreatment before desalination by reverse osmosis. The prepared membrane significantly reduced turbidity concentrations by 98.7 % for RSW1 and 96.8 % for RSW2. The fouling and antifouling mechanisms were also examined. Finally, the preparation cost of the phengite membrane was estimated to be 125 $/m2.

Myxospore density of Kudoa inornata varies significantly within symmetrical white muscle tissue replicates of its fish host, the spotted seatrout, Cynoscion nebulosus

The spotted seatrout, Cynoscion nebulosus, is a popular game fish in the southeastern USA. It is estimated that nearly 90% of the adult population in South Carolina estuaries are infected in their skeletal muscle by the myxosporean, Kudoa inornata. However, little is known about this parasite’s biology, including the distribution and densities of myxospores within tissues of infected fish, which we expect affect the physiology of their hosts. In order to correlate densities with physiological parameters in future studies, we quantified the myxospores density in muscle and characterized the variation among individual fish. Naïve juvenile seatrout was experimentally infected via presumed K. inornata actinospores exposure to raw seawater. A plug of muscle was extracted from two bilaterally symmetrical regions in the epaxial fillet from fresh and frozen carcasses. Variation in density data was calculated both within and among individuals. Within individuals, density counts were compared between left- and right-side biopsies. There was no significant difference between fresh and frozen plugs, and variation among individuals accounted for the greatest proportion of variation at 68.8%, while variation within individuals was substantial at 25.6%. Simulation and correlation tests confirmed that bilaterally symmetrical replicates varied significantly within individuals. When sampled from areas surrounding the initial biopsies, myxospore density estimates were more similar than between sides. Our findings have important implications for sampling design, particularly for studies investigating physiological parameters at the cellular or molecular level in association with parasite infection.

Isochrysis Crisis

Isochrysis galbana, a brown algae, was trialed to grow at the CFK aquaculture lab but failed until we tried comparing different tank salts to create a wellbalanced base. Our objective was to demonstrate and compare the different saltwater mixes that can be used in cultivating brown algae. Isochrysis galbana and other green algae that are grown at the CFK lab play a very important part in the aquaculture system. Algae is used as a good source of food and nutrients for many primary producers. Algae are one of the most important animals on earth. They create most of the oxygen that we breathe, and they filter every part of the water around the world. Brown algae is known around Florida because of certain species, like sargassum. We are currently having an issue with sargassum, so learning about different brown algae species can benefit everyone around the world. If Isochrysis sp. is kept at a stable salinity of 35ppt then it will easily and successfully grow. The samples were grown according to the standard measures but with different salt bases one was raw salt water, live aquaria and REEF salt. The raw seawater sample grew over a 1–2-day period with salinity that usually stayed around 40. The samples mixed into each artificial reef salt took about a week or more to grow color and cultivate the algae.

Changes in microbial community structure related to biodegradation of eelgrass (Zostera marina)

Seagrass meadows produce organic carbon and deposit it on the seabed through the decaying process. Microbial activity is closely related to the process of eelgrass death and collapse. We investigated the microbial community structure of eelgrass during the eelgrass decomposition process by using a microcosm containing raw seawater and excised eelgrass leaves collected from a Zostera marina bed in Futtsu, Chiba Prefecture, Japan. The fast-growing microbes (i.e., Alphaproteobacteria, Gammaproteobacteria, and Flavobacteriia) rapidly adhered to the eelgrass leaf surface and proliferated in the first two weeks but gradually decreased the relative abundance as the months moved on. On the other hand, the slow-growing microbes (i.e., Cytophagia, Anaerolineae, Thaumarchaeota, and Actinobacteria) became predominant over the eelgrass surface late in the culture experiment (120, 180 days). The fast-growing groups of Gammaproteobacteria and Flavobacteriia appear to be closely related to the initial decomposition of eelgrass, especially the rapid decomposition of leaf-derived biopolymers. Changes in nitrogen content due to the bacterial rapid consumption of readily degradable organic carbon induced changes in the community structure at the early stage of eelgrass decomposition. In addition, shifts in the C/N ratio were driven by microbial community changes during later decomposition phases.

Non-target screening and prioritization of organic contaminants in seawater desalination and their ecological risk assessment

The impact of desalination brine on the marine environment is a global concern. Regarding this, salinity is generally accepted as the major environmental factor in desalination concentrate. However, recent studies have shown that the influence of organic contaminants in brine cannot be ignored. Therefore, a non-targeted screening method based on comprehensive two-dimensional gas chromatography-quadrupole mass spectrometry (GC × GC-qMS) was developed for identifying organic contaminants in the desalination brine. A total of 404 compounds were tentatively identified from four seawater desalination plants (three reverse osmosis plants and one multiple effect distillation plant) in China. The identified compounds were prioritized based on their persistence, bioaccumulation, ecotoxicity, usage, and detection frequency. Twenty-one (21) compounds (seven phthalates, ten pesticides, four trihalomethanes) were then selected for further quantitative analysis and ecological risk assessment, including compounds from the priority list along with substances from the same chemical classes. Ecologically risky substances in brine include diisobutylphthalate and bis(2-Ethylhexyl) phthalate, atrazine and acetochlor, and bromoform. Most of the contaminants come from raw seawater, and no high risk contaminants introduced by the desalination process have been found except for disinfection by-products. In brine discharge management, people believed that all pollution in raw seawater was concentrated by desalination process. This study shows that not all pollutants are concentrated during the desalination process. In this study, the total concentration of pesticide in the brine increased by 58.42%. The concentration of ∑PAEs decreased by 13.65% in reverse osmosis desalination plants and increased by 10.96% in the multi-effect distillation plant. The concentration of trihalomethane increased significantly in the desalination concentrate. The change in the concentration of pollutants in the desalination concentrate was related to the pretreatment method and the chemical characteristics of the contaminants. The method and results given in this study hinted a new idea to identify and control the environmental impact factors of brine.

Evaluating mechanism of banana pseudo-stem retting using seawater: A cost-effective surface pre-treatment approach

Retting has been employed to extract natural fibers from agricultural wastes as a biological and cost-effective approach for centuries. With its global abundance, banana pseudo-stem is a promising agro-waste for lignocellulosic fiber extraction. In this study, fibers were extracted from the pseudo-stems after being pre-treated under four conditions using seawater at room temperature for up to 35 d Bacterial isolation from the fresh seawater sample and screening for ligninolytic ability were conducted. Bacterial load as well as laccase and manganese peroxidase enzyme activity profile assay during the retting duration were analyzed. Fourier transform infrared (FT-IR) and X-day diffraction (XRD) analyses were also examined for both pre-treated and untreated extracted fibers. The results shows that six out of the eight bacterial isolates had the ability to degrade lignin. The treatments (Raw stem + Raw seawater) and (Autoclaved stem + Raw seawater) recorded the highest viable bacterial load of 9.24 × 102 and 4.46 × 102 CFU, respectively, on the 14th day of the retting process. Additionally, the highest laccase and manganese peroxidase enzymes activity was recorded for (Raw stem + Raw seawater) and (Autoclaved stem + Raw seawater) treatments in the second to the third week. The FT-IR spectra of the pre-treated fibers revealed relative reductions in peaks attributed to polysaccharides and other amorphous substances for all retting conditions. The XRD diffractogram revealed that the crystallinity index (CI) of pre-treated fibers increased in all seawater retting treatment conditions. However, the CI for fibers pre-treated under enzymatic conditions were enhanced even after five weeks. Sequence analysis for selected bacterial isolates showed homology to sequences of Bacillus velezensis, Shewanella sp. L8–5, and Citrobacter amalonaticus and Bacillus subtilis j8 strain. From these findings, it was suggested that physical, biological, and chemical actions were collectively involved in the seawater retting process of banana pseudo-stems.

Growth, productivity and nutrient removal rates of sea lettuce (Ulva lactuca) in a land-based IMTA system with white seabass (Atractoscion nobilis) in Southern California

Three consecutive 3-week trials were conducted to assess the growth, productivity, and nutrient removal rates of sea lettuce (Ulva lactuca) cultured in effluents from white seabass (Atractoscion nobilis) raceways. All U. lactuca cultivation trials were conducted in 175 L tanks with a surface area of 0.89 m2 run in triplicate, with water quality and growth measurements taken weekly. For the shading trial, U. lactuca was stocked at 0.56 kg/m2 with either 0%, 30%, or 60% shade and seawater supplied at 63 tank volumes per day (vol./day) water exchange (7.6 L/min) for each tank. The removal rate of total ammonia nitrogen (TAN) decreased with increasing shade levels, and the peak exceeded 80% removal at 0% shading. Growth rate and productivity of U. lactuca under 0% shading was 12.09 ± 3.13%/d and 13.28 ± 4.66 g DW/m2/d, which were both significantly higher than other shading levels. For the stocking density and water exchange rate trial, the stocking density of U. lactuca was 0.56 or 1.12 kg/m2, and seawater exchange rates were 4, 12, or 63 vol./day in a 2-factor design. In this trial, TAN removal rates were 100% across all treatment combinations. Growth rate of U. lactuca was highest (20.36 ± 2.36%/d) at 0.56 kg/m2 under the exchange rate of 63 vol./day, and the productivity reached up to 30.89 ± 6.53 g DW/m2/d, which was not different than that of U. lactuca stocked with 1.12 kg/m2 at the same exchange rate (p = 0.47). In a trial comparing sand-filtered seawater (RAW seawater) with seawater effluent from a raceway containing A. nobilis (FISH seawater), TAN removal rate by U. lactuca was consistently nearly 100% when supplied with FISH seawater with a TAN concentration ranging from 0.11 to 0.18 mg/L. Growth rate and productivity of U. lactuca supplied with FISH seawater were 21.36 ± 2.25%/d and 33.83 ± 7.29 g DW/m2/d, respectively, which was not different than that for U. lactuca supplied with RAW seawater. However, the protein content of U. lactuca cultured with FISH seawater was significantly higher and C/N ratio significantly lower than those cultured with RAW seawater (p < 0.01), which indicated that U. lactuca was in a nitrogen-limited situation when cultured with RAW seawater. In light of the better understanding of U. lactuca performance achieved in our study, the optimum U. lactuca and A. nobilis density combinations will be confirmed in future studies based on nitrogen balance to maximize the nutrient removal rates and diversity of seafood production.

Impact of magnesium on the flocculation, sedimentation and consolidation of clay-rich tailings in lime-treated seawater

The sustainability of the mining industry in times of climate change, especially in arid regions, rests on seawater. However, now more than ever, it is necessary to optimize processes regarding water consumption and increase recovery and recirculation, including water trapped in tailings dams. Seawater also offers challenges, for example, the condition in which it must be used. This study examines the effects of raw seawater (SW) and lime-treated seawater to reduce Mg content (TSW) under strong alkaline conditions (pH 11) on the flocculation, sedimentation, and consolidation of flocculated quartz-kaolin suspensions using a high molecular weight anionic polyacrylamide as a flocculant. The presence of magnesium precipitates in SW, mainly magnesium hydroxide, leads to sedimentation rates of flocculated quartz-kaolin suspensions considerably lower than in TSW because the aggregates in SW are smaller than in TSW, according to chord size analyses. The precipitates interfere in the flocculant-particle interaction, limiting the adsorption of the flocculant and its ability to form bridges of any kind, polymeric or salt, with the tailings particles. However, Mg precipitates act as short-range and limited extension binders compared to flocculants increasing the resistance of the aggregates much more in SW than in TSW in processes without and with flocculant, whether it is measured as yield stress, elastic moduli, or compressive yield stress. Thus, the new result is that Mg precipitates are responsible for most of the resistance to consolidation of quartz-kaolin suspensions and, therefore, should be avoided. Therefore, TSW should be the choice to facilitate water clarification in thickeners and water recovery from the consolidation of deformable tailings aggregates.

Recovery of Lithium from Simulated Nanofiltration-Treated Seawater Desalination Brine Using Solvent Extraction and Selective Precipitation

ABSTRACT The world's seas and oceans contain vast amounts of lithium, but the low concentration hereof renders solvent extraction impractical for its recovery. By contrast, seawater desalination brine, after treatment by nanofiltration, contains a roughly tenfold greater concentration of lithium than raw seawater. Hence, lithium can be effectively recovered from such streams using solvent extaction. Compared with other techniques to sequester lithium from dilute solutions, solvent extraction offers the advantages of simple operations, robust and well-established technology and high recovery yields. Thus, we propose a solvent-extraction based process to recover lithium from seawater desalination brine, treated by nanofiltration. The first step comprises the removal of magnesium and calcium using methyltrioctylammonium neodecanoate in p-cymene. This is followed by a lithium extraction step using the extractants Mextral 54–100 and Cyanex 923 in Shellsol D70 diluent. The lithium extract is then scrubbed with water and stripped with hydrochloric acid. Subsequently, residual alkaline earth metals are removed with sodium hydroxide in ethanol and finally lithium is precipitated using sodium carbonate. The solvent extraction, scrubbing and stripping steps were demonstrated on mini-pilot scale in continuous countercurrent mode (in mixer-settlers), while the precipitation steps were demonstrated in batch. The process was found to have an overall yield of 74%, affording a lithium carbonate product with a purity of 97 wt%.

Development of softening and ballasted flocculation as a pretreatment process for seawater desalination through a reverse osmosis membrane

Efficient desalination through a reverse osmosis (RO) membrane requires the prior removal of blockade-causing substances from raw seawater. To achieve ultrahigh-speed processing of a pretreatment process for seawater RO desalination, we combine traditional softening with ballasted flocculation (SBF) for Ca2+ and Mg2+ removal. An alkaline mixture of Ca(OH)2 and Na2CO3 was the most suitable softening agent for Ca2+ and Mg2+ removal with a reduced amount of generated sludge. This softening treatment simultaneously removed the suspended solids and bacteria from actual seawater. The settling velocity of the suspended solids generated via seawater softening was extremely low. Under the optimum conditions for desalinating actual seawater using an anionic polymer flocculant and microsand, the settling velocity exceeded 3.5 cm/s, 833 times higher than that of softening without ballasted flocculation. The amount of sludge after standing for 3 min was 76.5% lower in SBF than in conventional softening. The silt density index of the treated seawater met the water-supply standard of RO membranes (i.e., <3.0). Furthermore, the SBF-generated sludge exhibited considerably improved dewatering property than the sludge obtained via conventional softening. SBF can efficiently and quickly remove the causative substances of RO membrane fouling from seawater, thereby improving the treatability of generated sludge. SBF provides a new pretreatment process for seawater desalination using RO membranes.

Application of machine learning algorithms for prediction of ultraviolet absorption spectra of chromophoric dissolved organic matter (CDOM) in seawater

The ultraviolet absorption spectra of chromophoric dissolved organic matter (CDOM) can be used to trace its sources and to explore the dynamic of the CDOM pool. In previous studies, only the spectra above 240 nm can be used directly to characterize the CDOM in seawater, due to the overlapping of CDOM absorption spectra below 240 nm with inorganic chemicals such as NO3−, NO2−, Cl- and Br-. In this study, three different machine learning models, back propagation neural network (BPNN), random forest (RF) and extreme gradient boosting (XGBoost), were built to predict the CDOM ultraviolet absorption spectra between 215 and 350 nm after being trained with the raw absorption spectra of seawater. The optimal input wavelength range of the raw seawater spectra is 250-350 nm, and the optimal model parameters of machine learning algorithms were determined by using five-fold cross validation. The results show that the three models can well predict the CDOM absorption spectra. Comparatively, the XGBoost model gave the best prediction results. The reasons might be related to the fact that the XGBoost algorithm focuses on the residuals generated by the last iteration, which can reduce both variance and bias, especially for datasets with small sample sizes. Based on the predicted spectra by XGBoost algorithm, we calculated the spectra slopes of short wavelengths between 215 and 240 nm (S215-240) and between 215 and 275 nm (S215-275). The results show that the S215-240 and S215-275 are ~2 times the widely used spectra slopes between 275 and 295 nm (S275-295) obtained by traditional method based on the raw spectra. Moreover, the S215-240 and S215-275 are more relavant with salinity for marine CDOM than S275-295, suggesting spectra slopes of shorter wavelengths might be the better proxies for marine CDOM than that of longer wavelengths.

Study on the Possibility of Raw Seawater into Drinking Water&amp;lt;br/&amp;gt;—A Religious Water Literacy

Study on the Possibility of Raw Seawater into Drinking Water&amp;lt;br/&amp;gt;—A Religious Water Literacy

Novel multistage flash reversal Concept: Modelling and analysis

In this study, a rigorous modeling and simulation of a novel multi-stage flash (MSF) configuration consisting of reversing the brine circulation, termed MSF reversal (MSF-RV), is developed. Its performance is theoretically investigated and compared with conventional MSF Once Through (MSF-OT) with and without brine mixing. The MSF-RV concept is suitable for treating geothermal streams and can be driven by low grade thermal energy such as solar and geothermal energy and waste heat for direct seawater desalination. Hence, two options of MSF-RV are proposed, i) driven by a direct hot stream (MSF-RVc), and ii) powered by external heat to treat raw seawater (MSF-RVh). The analysis showed that the temperature distribution throughout the stages plays a significant role in the thermal efficiency and heat transfer area requirements for both configurations. Hence, careful selection of the design parameters is necessary to achieve the best performance. For the same recovery ratio, the MSF-RVc was found superior to MSF-OT in terms of gain output ratio (GOR) and specific energy consumption (SEC) by 52% and 60%, respectively. However, the specific area (sA) requirement of MSF-RVc is higher than that of MSF-OT by 50%. Brine mixing by recycling the rejected brine enhances the recovery ratio, GOR, and SEC for both structures. Conversely, the sA requirement increases with brine mixing but marginally for MSF-RV and remarkably for MSF-OT. Moreover, the design parameters of MSF-RVc such as the coolant inlet temperature, the temperature drop on the coolant side, and the coolant to brine ratio affect the overall performance. However, a trade-off between the thermal efficiency (GOR, SEC) and surface area requirement is still observed.

Evaluation of low energy consumption control for seawater desalination on Penghu Island

In fact, current water supplies due to natural constraints or lack of infrastructure (or both) cannot be provided in a sustainable manner for all increasing and competing uses (e.g. residential, industrial, agricultural). While promoting Penghu's low-carbon islands, in a water-scarce environment, it is the motivation of this research to take into account the development of water resources and lower energy consumption costs. The seawater desalination plant water production technology is improved, the cost of water production is reduced. This research uses a genetic algorithm (GA) to optimize the recovery rate to solve the minimum Specific energy consumption (SEC) value, and then, according to the required water production, the optimal flow rate of raw seawater of the high-pressure pump is obtained, so as to minimize the energy consumption of the reverse osmosis (RO) system. The energy recovery device has a great effect on reducing the energy consumption of the RO system, and it can be seen from the results that the higher efficiency does greatly reduce the energy consumption of the SEC and water production under the different energy recovery device efficiency. Calculated using genetic algorithms, and the SEC is 3.275 and the recovery rate is 45.1%, and the water production energy consumption is 2.35 kWh/m3. Scheme B changed the efficiency of the energy recovery unit to 97.22%, resulting in a SEC of 1.819 and a recovery rate of 25.3%, and a water production energy consumption of 1.31 kWh/m3. Finally, challenges and research gaps are also proposed.

Efficiency of a triangular solar still integrated with external PVC pipe solar heater and internal separated condenser

Modern designs of solar still desalination technology are reported to tackle the cost and energy issues. However, the low productivity of this technology is the main challenge that inhibits its commercialization uses. In this study, a triangular solar still (TrSS) integrated with an external PVC pipe solar heater and an internal separated condenser is designed for the first time to enhance water desalination under Malaysian climate conditions. The daily water production of active still was 24% higher than that of passive one. The temperatures of water and ambient air, relative humidity inside the still and the intensity of solar radiation affect the daily distillate output of both stills. Besides, a few strong relationships were developed between the intensity of solar radiation and water productivity, between the daily average ambient temperature and water productivity, and between the daily average water temperature and water productivity. The desalinated water cost per liter is estimated and is reasonable. Finally, the water quality tests of raw seawater and product water were performed and analyzed. A significant improvement in the desalinated water quality is realized when compared with raw seawater quality. The product water was considered as safe drinkable water while comparing its quality with the World Health Organization (WHO) standards.

Effects of the soaking-related parameters in a combined freezing-based seawater desalination process.

A combined freezing, soaking, and centrifugal desalination (FSCD) process was employed to desalt seawater taken from Bohai Bay. The seawater was frozen into two kinds of sea water ice having different texture and size using either commercial refrigerator or experimental setup. For both kinds of ice samples, the influences of soaking-related parameters on the desalination effect were studied. For most ice samples treated with FSCD process, the salt removal efficiencies are higher than 90%. The purity of ice product increases as increasing soaking time and at higher initial soaking liquid temperature, while the ice yield rate decreases. At the same ice yield rate, the salt removal efficiency for ice flakes is higher than that for crushed ice samples, whereas when the raw seawater of 27°C is used as soaking liquid, FSCD process is not feasible due to too lower ice yield rate.

Single-atom tungsten engineering of MOFs with biomimetic antibiofilm activity toward robust uranium extraction from seawater

Selective uranium extraction from seawater is challenging because of ubiquitous marine biofouling and poor reusability of adsorbents. A reusable atomic-scale tungsten nanozyme integrating uranium capture capacity and intrinsic haloperoxidase-like activity is constructed, resulting in strong antibiofouling ability and superb reusability for uranium extraction after consecutive multiple regeneration cycles in bio-aggressive seawater. • Atomically dispersed tungsten is anchored in metal organic frameworks (W-UiO). • The presence of atomic-scale tungsten endows W-UiO with haloperoxidase-mimicking activity. • W-UiO nanozyme exerts strong antibacterial activity and inhibition effect against marine microbial colonization. • Such nanozyme exhibits excellent reusability for uranium extraction from seawater. Uranium is the essential element for nuclear power industry. Selective uranium extraction from seawater is very attractive, but challenging because ubiquitous marine biofouling seriously impairs the uranium extraction capacity and reusability of absorbents in bio-aggressive seawater. Herein, we construct a reusable nanozyme for uranium recovery from seawater based on atomically dispersed tungsten anchored on metal organic frameworks (W-UiO). We illustrate that W-UiO nanozyme mimics naturally occurring vanadium haloperoxidase that catalytically converting halides to biocidal hypobromous acid, inducing strong antibiofouling activity against marine microbial colonization. As demonstrated, W-UiO nanozyme shows superb reusability in raw seawater simultaneously, preserving a 78.0% of its initial uranium capture capacity (6.8 times higher than its pristine counterpart) after five consecutive adsorption-desorption cycles. This study is anticipated to spur rationally realizing robust absorbents by mimicking the natural enzymes for practical application in uranium recovery from seawater.

Molecular identification and antibiotic resistance patterns of diverse bacteria associated with shrimp PL nurseries of Bangladesh: suspecting Acinetobacter venetianus as future threat.

Shrimp aquaculture has been accomplished with breeding and nursing of shrimp in an artificial environment to fulfill the increasing demand of shrimp consumption worldwide. However, the microbial diseases appear as a serious problem in this industry. The study was designed to identify the diverse bacteria from shrimp PL (post-larvae) nurseries and to profile antibiotic resistance patterns. The rearing water (raw seawater, treated and outlet water) and shrimp PL were collected from eight nurseries of south-west Bangladesh. Using selective agar plates, thirty representative isolates were selected for 16S rRNA gene sequencing, antibiotic susceptibility test and MAR index calculation. Representative isolates were identified as Aeromonas caviae, Pseudomonas monteilii, Shewanella algae, Vibrio alginolyticus, V. brasiliensis, V. natriegens, V. parahaemolyticus, V. shilonii, V. xuii, Zobellella denitrificans which are Gram-negative, and Bacillus licheniformis and B. pumilus which are Gram-positive. Notably, six strains identified as Acinetobacter venetianus might be a concern of risk for shrimp industry. The antibiotic resistance pattern reveals that the strain YWO8-97 (identified as P. monteilii) was resistant to all twelve antibiotics. Ceftazidime was the most powerful antibiotic since most of the studied strains were sensitive against it. The six strains of A. venetianus showed multiple antibiotic resistance patterns. MAR index were ranged from 0.08 to 1.0, and values of 26 isolates were more than 0.2 which means prior high exposure to the antibiotics. From the present study, it can be concluded that shrimp PL nurseries in southern part of Bangladesh are getting contaminated with antibiotic resistant pathogenic bacteria.

Self-powered antifouling UVC pipeline sterilizer driven by the discharge stimuli based on the modified freestanding rotary triboelectric nanogenerator

Microbial fouling and the resulting corrosion in marine environment cause severe economic and safety problems. It is urgent to develop feasible and efficient methods for controlling marine microbial fouling. In this study, the self-powered antifouling ultraviolet C (UVC) pipeline sterilizer was developed based on modified freestanding rotary triboelectric nanogenerator (MFR-TENG) with the function of discharge stimuli. Taking the advantage of breakdown discharge stimuli, the output voltage of the MFR-TENG is up to 6.9 kV, which is about 3-fold higher than the case in the absence of discharge stimuli (2.4 kV). This MFR-TENG provides sufficient energy for mercury vapor to generate ultraviolet radiation. The sterilization experiments demonstrate the self-powered antifouling UVC pipeline sterilizer exhibits superior antimicrobial ability against typical corrosive bacteria, including Halomonas titanicae, Pseudomonas aeruginosa, and miscellaneous bacteria cultured in raw seawater. Further investigation on morphological change of bacterium demonstrates the UVC radiation excited by discharge stimuli cause significant damage to the bacterial membrane. As a result, the antibacterial rate of the self-powered antifouling UVC pipeline sterilizer (75%) is higher as compared with that without discharge phenomenon (44%) after 10 min of sterilization. This study offers an eco-friendly and efficient strategy for preventing marine microbial fouling.

Reducing Magnesium within Seawater Used in Mineral Processing to Improve Water Recovery and Rheological Properties When Dewatering Clay-Based Tailings.

In areas where access to water for mineral processing is limited, the direct use of seawater in processing has been considered as an alternative to the expense of its desalination. However, efficient flotation of copper sulfides from non-valuable phases is best achieved at a pH > 10.5, and raising the pH of seawater leads to magnesium precipitates that adversely affect subsequent tailings dewatering. Seawater pre-treatment with lime can precipitate the majority of magnesium present, with these solids then being removed by filtration. To understand how such treatment may aid tailings dewatering, treated seawater (TSw) was mixed with raw seawater (Rsw) at different ratios, analyzing the impact on the flocculated settling rate, aggregate size as measured by focused beam reflectance measurement (FBRM), and vane yield stress for two synthetic clay-based tailings. A higher proportion of Tsw (10 mg/L Mg2+) led to larger aggregates and higher settling rates at a fixed dosage, with FBRM suggesting that higher calcium concentrations in Tsw may also favor fines coagulation. The yield stress of concentrated suspensions formed after flocculation decreased with higher proportions of Tsw, a consequence of lower flocculant demand and the reduced presence of precipitates; while the latter is a minor phase by mass, their high impact on rheology reflects a small particle size. Reducing magnesium concentrations in seawater in advance of use in processing offers advantages in the water return from thickening and subsequent underflow transport. However, this may not require complete removal, with blending Tsw and Rsw an option to obtain acceptable industrial performance.