Résumé : The tremendous wind-wave excitations bring about structural vibrations, which would have adverse influences on the power generation efficiency of the spar floating offshore wind turbine (FOWT). Therefore, two tuned mass dampers (TMDs) are installed in the platform and nacelle of the spar FOWT to control the vibration responses of the structure. The aero-hydro-servo-structure-TMDs coupling kinetics model of 16-degree-of-freedom (DOF) is firstly established for the spar FOWT. The correctness of the coupled model is then verified through comparing with OC3 project of FAST developed by the National Renewable Energy Laboratory (NREL). Subsequently, the TMDs stiffness and damping coefficients are optimized in constraints of the TMDs mass and stroke. Furthermore, the vibration reduction effects of TMDs are studied in the free decay state and wind-wave load cases, respectively. The simulation results demonstrate that the platform TMD can effectively reduce the platform pitch (PFPI) movement and low frequency vibration of the tower top fore-aft (TTFA) deflection, while the nacelle TMD is effective for the high frequency vibration of the TTFA deflection. Thus, the TMDs can control the structural vibration responses of spar FOWTs.
Résumé : The purpose of this chapter is to provide an assessment of the resource potential for ocean thermal energy conversion (OTEC) in the Mexican Pacific Ocean (MPO). Research methodology adopted in this study is a combination of geographic information system (GIS), to identify the most promising site in the MPO for OTEC deployment. Site selection criteria rely on conditions such as distance to cold water pumping, bathymetry, thermal difference (not less than 20°C), and social and environmental aspects. Finally we concluded that sites located in the states of Guerrero and Oaxaca have the highest potential of the entire MPO, although there are other areas in the states of Baja California Sur, Nayarit, or Michoacan that might have some interest for OTEC technology.
Résumé : The search for potential investors in the conversion of ocean thermal energy to power or hydrogen, and its spinoff projects in Malaysia and the region, continues. In the meantime, several pre-feasibility studies have been completed for selected sites, including that of Pulau Layang-Layang and Pulau Kalumpang (Sabah, Malaysia); Timor-Leste, and off Pulau Weh (Aceh, Indonesia). Various research projects have been completed such as the conversion of solar-thermal to the chilled-water system; the cooling of tropical soils for the culture of temperate crops; the design of offshore structure off the continental slope; hydrogen fuel production and distribution, deep seawater properties to reduce obesity, cholesterol and blood pressure; and the legal-institutional framework for the development of ocean thermal energy conversion. UTM Ocean Thermal Energy Centre (UTM OTEC) has entered into the Collaborative Research Agreement with the Institute of Ocean Energy of Saga University (Japan) to undertake joint research for the development of an experimental rig that introduces a hybrid system with stainless steel heat exchanger. Other aspects of this joint research would include a new design for 3 kW turbine, the introduction of nano-working fluids, the eDNA of intake waters, and improved productivity in the culture of high-value marine produce and products.
Résumé : Hu, J.; Li, Z., and Zhang, Y., 2020. Numerical study on initial laying process of submarine cables for wave energy booster station in real sea states. In: Zheng, C.W.; Wang, Q.; Zhan, C., and Yang, S.B. (eds.), Air-Sea Interaction and Coastal Environments of the Maritime and Polar Silk Roads. Journal of Coastal Research, Special Issue No. 99, pp. 60-66. Coconut Creek (Florida), ISSN 0749-0208.Based on real sea conditions of the national wave energy demonstration site in Wanshan sea area of Zhuhai City, China, some numerical experiments are carried out to simulate the submarine cables initial laying process of the Wave Energy Booster Station in this demonstration site. The numerical model is established with the Orcaflex software employed. The motion response of laying ship and the hydrodynamic characteristics of submarine cables are simulated here under three sea conditions, i.e. usual waves, waves with current combined and possible extreme waves. Research results show that the tension and curvature of the cable are large under the condition for wave direction perpendicular to the ship axial direction, which is a relatively bad sea condition. The current also has some influences on the submarine cable laying, and the maximum effective tension of cable produced by the combined wave-current action is 1.35 times that of cable with the wave action alone. When extreme waves appear, pitch, heave and heave acceleration of the laying ship and tension of the cable ends increases obviously. And the variation of effective tension at both cable ends can reach 1.67 times that of cable ends under usual random waves. The numerical model and research results in this paper can provide some guidance for the research and construction of the cable laying of booster stations for marine renewable energy power plants in real sea conditions.
Résumé : Simulations are conducted in time domain to investigate the dynamic response of a Spar-type floating offshore wind turbine under the freak wave scenarios. Towards this end, a coupled aero-hydro-mooring in-house numerical code is adopted to perform the simulations. The methodology includes a blade-element-momentum model for simulating the aerodynamic loads, a nonlinear model for simulating the hydrodynamic loads, a nonlinear restoring model of Spar buoy and a nonlinear algorithm for simulating the mooring cables. The OC3 Hywind Spar-type FOWT is adopted as an example to study the dynamic response under the freak wave conditions, meanwhile the time series of freak waves are generated using the random frequency components selection phase modulation method. The motion of platform, the tension applied on the mooring lines and the power generation performance are documented in several cases. According to the simulations, it is indicated that when a freak wave acts on the FOWT, the transient motion of the FOWT is induced in all DOFs, as well as the produced power decreases rapidly. Furthermore, the impact of freak wave parameters on the motion of FOWT is discussed.
Résumé : In the last decade, several countries started work on the development of Floating Vertical Axis Wind Turbines, which have significant advantages over Floating Horizontal Axis Wind Turbines. In the present work, we expose a brief history of the use of this type of wind turbines, and we contribute to understanding the existing technologies and we also propose a new design of Floating H-Darrieus Vertical Axis Wind Turbine with three stage rotors. This design solves the problem of starting a large turbine and facilitates maintenance by adopting three mechanisms Bearing Swivel Rollers at each stage. We use the Double Multiple StreamTube method for aerodynamic simulations. The numerical results of the aerodynamic performance analysis show that variable radius rotors maximize the power generated.
Résumé : Tidal current turbine is one of the innovative and emerging technologies of marine renewable energies because it offers constant and predictable energy source that can be very beneficial, especially for commercial scale production of electrical power. Hydrofoils (HF) are essential elements of tidal current turbine (TCT) and should be properly designed as they play a vital role in improving the turbine output and providing adequate resistance to the blade structure. In connection with the hydrofoil designs, it is noteworthy that the primary objectives in their designs are to increase the coefficient of lift and to reduce the coefficients of drag and pitching moment, thus delaying the cavitation phenomenon. In this paper, the technology developments of the hydrofoil designs used in the horizontal axis TCT industry are reviewed, including the hydrodynamics design and the mechanical structure design. Besides, an up-to-date review and the newest achievements of marine TCT technologies with their developing histories are further explored. Included are also reviews on the numerical models used to assess the performance of TCT and optimization methods applied to design the hydrofoils. This in turn significantly contributes to a better knowledge on the recent designs of TCT hydrofoils for the researchers working in the marine turbine energy domain. Such information could also have important implications in the design of more sophisticated hydrofoils for the exploitation in diverse tidal current energy technologies for reaching a sustainable future.
Résumé : Tidal energy has clear potential in producing large amounts of energy as the world’s capacity exceeds 120 GW. Despite being one of the oldest renewable energy sources exploited by man, the technology is still in its pre-commercialisation stage and so lags behind other renewable sources such as wind and geothermal energy in terms of development and energy produced. One of the emerging energy extraction technologies in the tidal energy field is the Horizontal Axis Hydrokinetic Turbine (HAHT) which harness tidal stream energy the same way Horizontal Axis Wind Turbine (HAWT) extract energy from the wind. While HAHT has been the topic of many researches over the past decade, design of hydrofoils plays a vital role in increasing the structural strength of the blade and maximizing the output of the marine current turbines. In this context, a numerical investigation is conducted in this research in which new hydrofoil for marine current turbines underwater conditions was designed and evaluated. The turbine blade is designed using XFLR5 code and QBlade which is a Blade-Element Momentum solver with a blade design feature. Then, the hydrodynamic performance of hydrofoil was tested using Computational Fluid Dynamics (CFD) consisting of lift and drag coefficients, and velocities distribution. The results showed that the new design of the hydrofoil of marine current turbine blade maintained a CPower value of 50% more from normal range at the TSR 5 to 9 and 51% more at TSR = 6,5 in the performance curve.
Résumé : This work examines the steady-state potential and feasibility of Yaw and Induction-based Turbine Repositioning (YITuR), which is a wind farm control concept that passively repositions floating offshore wind turbines using existing turbine control degrees of freedom. To this end, the Floating Offshore Wind Farm Simulator (FOWFSim) is developed to model steady-state wind farm power production while considering floating platform relocation. Optimization studies are carried out with different floating wind farm design parameters and configurations. The objective is to determine sets of optimal wind turbine operating parameters that relocate floating turbines such that wind farm efficiency is maximized. Results show that the potential of YITuR is starkly limited by wind farm design parameters. In particular, anchors should be placed adequately far from floating platform neutral positions, mooring lines should be sufficiently long, and only specific mooring system orientations permit substantial gains in wind farm efficiency. With specific combinations of these parameters, simulation results show that the efficiency of a 7 × 7 floating offshore wind farm may be raised by 42.7% when implementing YITuR in comparison to greedy operation.
Résumé : Abstract Objectives/Scope The goal of this work was to develop a consistent and semi-automated seafloor survey method for generating high-resolution, benthic habitat maps for environmental assessments and monitoring of marine renewable energy sites.
Résumé : In order to meet the growing demand for energy and also to fight against global warming, Renewable Marine Energies (RME) appeared as a great opportunity for a real ecological and industrial choice. Tidal current turbines are used to extract this energy and installed on the seabed at locations where the nozzle can be prone to the accidental impact and critical loads. The principal objective of this research is to investigate the effects of environmental exposure on the mechanical properties of composite tidal current turbine, the most advanced features currently available in finite element (FE) Abaqus/Explicit have been employed to simulate the behavior of the composite nozzle under static and dynamic loading conditions. To investigate this situation, a parametric analysis is conducted which deals with the effect of velocity and geometry of the impactor. The mechanical behavior has been analyzed as both kinematic effect due to deflection of the composite structure and dynamic effect caused by the interaction between the impactor and the hydrodynamic and hydrostatic pressures over the loading. The stress and the deformation distribution are presented. On the other hand, damage modeling was formulated based on Hashin criteria for intra-laminar damage. This has been accomplished by forming a user-created routine (VUMAT) and executing it in the Abaqus software.
Résumé : Abstract Fatigue is one of the key design considerations for moorings, risers, and umbilicals in offshore floating systems. Due to differences in materials, components, configurations, and functionality, these slender structures have distinct driver
Résumé : The technology of multi-turbine platform design is currently in development which can accommodate multiple turbines on a single platform that results in a reduction of installation and mooring costs. This paper presents a method to analyze the effects of the wake between the wind turbines on a multi-turbine platform and use it to find a suitable distance for spacing the wind turbines on the platform. Jensen wake model, Larsen wake model, and CFD simulations are used for calculating the wake effects. The actuator disk theory is used for modeling the rotor. The RANS equations with the 𝒌−𝝎 SST turbulence model are used for CFD calculations. Based on the results of wake effects the spacing requirements for the wind turbines are calculated and the design of the platform is carried out. Hydrostatic analysis of the modeled platform is done to study the floating stability behavior of the platform. The first order hydrodynamics and wave loadings on the platform are calculated in the frequency domain using the potential flow linear diffraction model. The hydrodynamic analysis is carried out on the platform to predict the wave-body interaction between the platform and the waves.
Résumé : This paper proposes designs for blades and a water velocity amplification device for the development of a 5-kW duct-type floating tidal current turbine. In addition, it verifies the power performance by a CFD simulation. A BEM theory-based algorithm is used for iterative design and analysis to delay the onset of the chronic problem of cavitation in tidal current turbine blades. The HEEDS optimization software connected to CAE tools is applied to optimize the design of the duct shape, thereby improving the efficiency of the tidal current turbine. The performance of the designed turbine is verified using the CFD software STAR CCM+. A wave model is established to reflect the pressure variation in shallow water when analyzing the cavitation and power performance. The power and efficiency at the rated water velocity are 5 kW and 44 %, respectively. The results indicate that power can be stably controlled due to stalling under the high-flow-velocity condition.
Résumé : The structural response of the main components of offshore wind turbines (OWTs) is considerably sensitive to amplification as their excitation frequencies approach the natural frequency of the structure. Furthermore, uncertainties present in the loading conditions, soil and structural properties highly influence the dynamic response of the OWT. In most cases, the cost of the structure reaches around 30% of the entire OWT because conservative design approaches are employed to ensure its reliability. As a result, this study aims to address the following research question: can the structural reliability of OWT under fatigue loading conditions be predicted more consistently? The specific aims are to (1) establish the design parameters that most impact the fatigue life, (2) determine the probability distributions of the design parameters, and (3) predict the structural reliability. An analytical model to determine the fatigue life of the structure under 15 different loading conditions and two different locations were developed. Global sensitivity analysis was used to establish the more important design parameters. Also, a systematic uncertainty quantification (UQ) scheme was employed to model the uncertainties of model input parameters based on their available information. Finally, the framework used reliability analysis to consistently determine the system probability of failure of the structure based on the fatigue limit state design criterion. The results show high sensitivity for parameters usually considered as deterministic values in design standards. Additionally, it is shown that applying systematic UQ produces a better approximation of the fatigue life under uncertainty and more accurate estimations of the structural reliability. Consequently, more reliable and robust structural designs may be achieved without the need for overestimating the offshore wind turbine response.
Résumé : It is known that surface waves have significant influence on the hydrodynamic performance of ocean current turbines which locate near the water surface. In order to quantitatively analyze the wave influence and reveal the interaction mechanism between the wave and the turbine flow, this paper proposes a three-dimensional transient computational fluid dynamics (CFD) model which can accurately predict the hydrodynamic performance of ocean current turbines under current-wave interaction flow conditions. The influences of two key wave parameters, the wave height and the submerged depth of the turbine, on the hydrodynamic forces and flow structures of a three-bladed horizontal axis ocean current turbine are discussed in depth. It is found that the both the average value and the oscillation amplitude of the torque on the turbine increase with the increased wave height, but decrease with the increase of the submerged depth. It is also found that in the cases of shallow submerged depth, the wake structures of the turbine are affected by the surface wave.
Résumé : Accurate estimation of extreme wind and wave conditions is critical for ocean engineering activities and applications. Various renewable energy offshore structures, particularly floating wind turbines are designed to sustain extreme wind and wave induced loads. Statistics of wind speeds and wave heights is the key input for structural safety and reliability study. Consequently, development of novel robust methods, able to predict extreme wind-wave conditions is essential. This paper discusses criteria for selecting design point by applying recently developed method for estimating extreme wave statistics, based on the hourly wave height and wind speed maxima at the location of interest. Wave and wind data, analyzed in this paper, was obtained from the hindcast model applied to the SEM-REV offshore sea location, near the coast of France, during years 2001–2010. The ECMWF (European Centre for Medium range Weather Forecasting) framework along with the atmospheric model SKIRON were employed to generate accurate hindcast wind-wave hourly data at the location of interest. Note that the SEM-REV site was built within the framework of the CPER (Contrat de Projet Etat-Région) 2007–2013 for the Pays de la Loire region, therefore it is important to note that 2001–2010 data studied in this paper was obtained by hindcast into the time period before SEM-REV began operations. Structural design values are often based on univariate statistical analysis, while actually multivariate statistics is more appropriate for modelling the whole structure. The bivariate analysis of extremes is often poorly understood and generally not adequately considered in most practical measurements/situations, therefore it is important to utilize recently developed bivariate average conditional exceedance rate (ACER2D) method. This paper studies extreme wind speeds and wave heights, that are simultaneously obtained at the same location. Due to less than full correlation between wind speed and wave height, application of the multivariate, or bivariate in the simplest case, extreme value theory is of practical importance. This paper focuses on application of the bivariate ACER2D method for prediction of bivariate extreme value statistics. Finally, this paper suggests how the design point should be chosed based on bivariate analysis. The latter is of particular engineering importance as it presents first application of bivariate wind-wave statistics to a raw SEM-REV site data.
Résumé : Over the last decade, research on technologies to exploit tidal current kinetic energy for renewable electricity generation has had a significant growth. However, as to date, there is not a consensus worldwide on standard Power Take-Off (PTO) systems, due to the current immaturity of tidal energy converter technologies. In most cases, mechanical/electrical power conversion follows well-proven technologies derived by the mature wind-energy sector. However, the peculiarities of tidal energy resource impose ad hoc technology solutions. In this paper, different generator topologies and recent developments for marine tidal energy systems are reviewed and compared. The aim is to provide an overall perspective and identify areas for further development. Among considered technologies, the direct-drive permanent magnet synchronous generator by the full-rated frequency converter (FFC) represents an appealing solution, for reduced system complexity and maintenance requirements and possibility to develop smart Maximum Power Point Tracking (MPPT) strategies.
Résumé : The purpose of this paper is to explore and define an adequate numerical setting for the computation of aerodynamic performances of wind turbines of various shapes and sizes, which offers the possibility of choosing a suitable approach of minimal complexity for the future research. Here, mechanical power, thrust, power coefficient, thrust coefficient, pressure coefficient, pressure distribution along the blade, relative velocity contoure at different wind speeds and streamlines were considered by two different methods: the blade element momentum (BEM) and computational fluid dynamics (CFD), within which three different turbulence models were analyzed. The estimation of the mentioned aerodynamic performances was carried out on two different wind turbine blades. The obtained solutions were compared with the experimental and nominal (up-scaled) values, available in the literature. Although the flow was considered as steady, a satisfactory correlation between numerical and experimental results was achieved. The comparison between results also showed, the significance of selection, regarding the complexity and geometry of the analyzed wind turbine blade, the most appropriate numerical approach for computation of aerodynamic performances.
Résumé : Floating structures have become the most feasible solution for supporting wind turbines when offshore wind project move to deeper water. In this paper, a hydrodynamic analysis of three different semisubmersible floating offshore wind turbines is carried out including second-order hydrodynamic effects. The three examined platforms are V-shaped semisubmersible, Braceless semisubmersible and OC4-DeepCwind semisubmersible and are used to support the NREL 5 MW reference wind turbine. The main objective of the present study is to investigate and compare the hydrodynamic response of the three different semisubmersible floaters in two water depths (100 m, and 200 m) under different load conditions. The effects of second-order wave loads on the platform motions and mooring tension are discussed and compared by using different methods including Newman's approximation and the full QTF (Quadratic transfer function) method. The drag effect on the structure motion response is also discussed in this paper. The comparison presented is based on statistical values and response spectra of floating platform motions as well as mooring tensions. The results show that the dynamic response of semisubmersible FOWTs (floating offshore wind turbines) is overestimated when ignoring the Morison drag effect on the columns of the semisubmersible FOWT. The second-order difference wave loads can excite the resonance of motion especially for the platform-pitch motion, which could cause structural failures. The full QTF method should be used to calculate the second-order wave force to better simulate the realistic dynamic response of semisubmersible FOWTs.
Résumé : The underwater sound emitted during the operation of the Atlantis AR1500 turbine, a 1.5 MW three bladed horizontal axis tidal-stream turbine, was measured in the Pentland Firth, Scotland. Most sound was concentrated in the lower frequencies, ranging from 50 to 1000 Hz. Within 20 m of the turbine, third-octave band sound pressure levels were elevated by up to 40 dB relative to ambient conditions. In comparison, ambient noise at these frequencies fluctuated by about 5–10 dB between different tidal states. At the maximum recording distance of 2300 m from the turbine, median sound pressure levels when the turbine was operational were still over 5 dB higher than ambient noise levels alone. A higher frequency, tonal signal was observed at 20 000 Hz. This signal component appears at a constant level whenever the turbine is operational and did not change with turbine rotation rate. It is most likely produced by the turbine's generator. This study highlights the importance of empirical measurements of turbine underwater sound. It illustrates the utility and challenges of using drifting hydrophone systems to spatially map operational turbine signal levels with reduced flow noise artefacts when recording in high flow environments.
Résumé : Repair and replacement of offshore wind turbine blades are necessary for current and future offshore wind turbines. To date, repair activities are often conducted using huge jack-up crane vessels and by applying a reverse installation procedure. Because of the high costs associated with installation and removal of offshore wind turbine components and the low profit margin of the offshore wind industry, alternative methods for installation and removal are needed. This paper introduces a novel concept for replacement or installation of offshore wind turbine blades. The concept involves a medium-sized jack-up crane vessel and a tower climbing mechanism. This mechanism provides a stable platform for clamping, lowering, and lifting of a blade. A case study of a 5-MW offshore wind turbine is shown, where common engineering practices were applied and numerical simulations of the marine operations were carried out using finite element and multibody simulation tools. Operational limits for wave and wind actions were established to demonstrate the technical feasibility of the proposed concept.
Résumé : Thermoelectric Generator (TEG) provides unique advantages as compared to other heat engines as it is capable to convert heat to electricity directly without having any moving parts. Furthermore, TEG is compact, simple and noiseless and requires very minimal maintenance. This paper presents an experimental and analytical study of a model consisting of a TEG located between a copper water cooling jacket and an aluminium block which acts as a heat spreader. The copper water cooling jacket was used in this study as water has higher thermal capacity than air. Besides, copper is one of highest thermal conductivity materials. TEG characterisation in term of electrical was investigated in this study. Based on the result, it shows a linear proportion relationship between open-circuit voltage and temperature difference across TEG. The result also clearly shows the power output of TEG increases as the temperature gradient across TEG increases. In addition, the impact of water flowrate on TEG power output was also studied. Based on the finding, there was an optimum water flowrate of 80 ml/s. Further increasing the water flowrate is not favourable as it will not increase power output and may lead to higher pumping power for water circulation. At this optimum water flowrate, the maximum power output obtained is equal to 530 mW when TEG hot-side temperature (Th) is 180 ℃.
Résumé : The dynamic behaviour of an undulating tidal energy converter under wave and current loadings is studied. Therefore, a small scale prototype of a damped pre-stressed undulating membrane is tested in a wave and current recirculatory tank. The membrane’s dynamic profile and hydrodynamic forces are measured synchronously with the surface elevation for both regular and irregular waves in current direction. Spectrum analysis reveals that the response to wave loading depends on the wave frequency and is reduced by damping-type power take-off. Coupling between the wave frequency and the main undulation frequency or its harmonics is also observed. An increase of 30% of the forces must be foreseen in case of wave condition in the tested range.
Résumé : The maintenance of Wind farms located in the off shores are highly challenging as the preservation and the operational availability are tedious. The insufficiency in the traditional system for monitoring the conditions of the wind turbines located in the off shores has made this topic an attractive area of research. The proposed method in the paper utilizes the multiple intelligent smart sensors to detect the impairments in the structure of the wind turbines. The sensors utilized in the proposed method estimates the damage index in the wind turbine by engaging the embedded software. The effectiveness of the proposed method was measured by applying it to the off shore wind turbines. The results obtained evinces the minimized cost and the down time in maintaining the off shore wind farms.
Résumé : During the single blade installation of offshore wind turbines, relative motion between the blade root and turbine hub can cause a delay in the progression of the installation. This contribution presents the results of a monitoring campaign conducted during the installation of an offshore wind park in the North Sea. The campaign covered different states of the turbines: without rotor blades, with rotor blades, without supplementary damping system and with an installed, tuned mass damper system. The objective of the campaign was to determine the dynamic behaviour of the turbines in correlation with wind and wave data and to determine modal parameters. Accordingly, the turbines have been instrumented with sensors to record accelerations at three different positions. The modal parameters were then obtained using SSI/FDD algorithms. Structural damping is additionally determined with an RDM algorithm, and the results are being compared. The analysis of the data will be presented, including the different stages of the structural damping and the corresponding changes in movement patterns. The results shall be used to verify the load models and the predicted response of the structure.
Résumé : Improving the efficiency and power output of hydrokinetic turbines is critical to making them a viable and cost-effective renewable energy solution. Diffusing shrouds have already been shown to improve the performance of horizontal axis, axial-flow turbines. It has been suggested that adding pre-swirl stators to the shroud could alter the inlet flow so as to maximize net tangential force on the turbine blades, thus increasing power output. There is a scarcity of published physical model test data from pre-swirl stator turbines. The present study explores this concept. Four different pre-swirl stator configurations were designed and tested on a shrouded 3-bladed turbine (26.54 cm diameter) in the 36.5 m towing tank at the United States Naval Academy. Three Reynolds numbers (6.07×104, 8.10×104, and 1.01×105 based on stator chord length), corresponding to flow speeds 0.91 m/s, 1.22 m/s, and 1.52 m/s respectively, were tested. At the lowest Reynolds number, all 4 stator configurations improved the maximum Cp by 5–23% compared to the turbine with shroud only. At the middle and highest Reynolds numbers, the stator effect was mostly neutral, with one configuration showing a negative effect at the highest Reynolds number (i.e., lowered the maximum Cp). These results indicate that pre-swirl stators have the potential to improve turbine performance, particularly at lower Reynolds numbers, where the flow is more laminar and the absolute velocities are lower (for a given blade dimension). Pre-swirl stators also appear to reduce the dependence of performance on Reynolds number, flattening the curve and allowing optimal performance over a wider range of operating conditions. Further analytical and computational studies are recommended to explore these findings further, and to develop broader guidance on when pre-swirl stators are advantageous.
Résumé : Typical industry models for Offshore Wind Turbines with fixed substructures are based on decoupled models between the wind turbine and the substructure. It is proved that the complete dynamic response of the structure can only be captured with coupled models. In this paper a fully-coupled model for Offshore Wind Turbines with jacket support is presented. The computational model allows to obtain an accurate response of the whole structure and the dynamic interaction between all the elements. It also allows to reproduce particular effects such as the aerodynamic damping without the need for artificial damping ratios which would be needed in decoupled models. Typical environmental offshore conditions are integrated in the model and the response of the structure is obtained by means of a non-linear time integration algorithm in order to include the effect of the continuous rotation of the blades. A cost-efficient approach for the determination of fatigue-damage in the joints of the jackets is proposed. It is based on short-time simulations which allow to accurately estimate the long-term damage in general. The estimation shows a good agreement when compared to the damage values obtained by performing the whole time-interval simulation.
Résumé : Pitting corrosion of aluminium alloy AA5005-H34 immersed in natural sea water for up to 2 years is presented, together with new interpretations of the development of the pitting process over extended exposure periods. Trenching initiated at surface-located Fe-rich intermetallic (IM) particles. It occurred more extensively in sea water compared to atmospheric exposures. With increasing exposures, the pitting morphologies became more complex. Three types, i.e. hemispherical pits (Type 1), crystallographic pits (Type 2) and characteristic ‘petal’-like pits (Type 3), were observed after 12 months. It is suggested that the formation of Type 2 and Type 3 pits occurs at an advanced corrosion stage, and are associated with large Fe-rich IM particles near the metal surface. The influence of marine growth on pitting was negligible.
Résumé : The corrosions caused by sulfate-reducing bacteria (SRB) are serious problems in petroleum exploitation and transportation, which can lead to safety problems, environmental pollutions, and economic losses. Here, a charge-reversal surfactant antibiotic material N-dodecyl-1-carboxylic acid-1-cyclohexenyl-2-carboxamide (C12N-DCA) is designed and synthesized. C12N-DCA is a negatively charged surfactant, which cannot be adsorbed by soil and rock in a large amount. Therefore, it can reach the “lesion location”, with enough concentration. After being hydrolyzed and charge reversed under the acceleration of H2S produced by SRB, C12N-DCA becomes a positively charged surfactant dodecane ammonium salt to kill SRB. Through a simulating experiment, it is found that C12N-DCA can reach the SRB inhibition ratio of almost 100%, and it can reduce iron corrosion by 88%. Such an antibiotic material or its homologs may be added to the chemical flooding fluids, killing SRB during petroleum exploitation and reducing the SRB-induced corrosion in the petroleum exploitation and transportation.
The sulfate-reducing bacteria and related corrosion can be inhibited by charge-reversal surfactant antibiotic material.
The sulfate-reducing bacteria and related corrosion can be inhibited by charge-reversal surfactant antibiotic material.
Résumé : This article presents a synthesis of recent studies focused on the corrosion product layers forming on carbon steel in natural seawater and the link between the composition of these layers and the corrosion mechanisms. Additional new experimental results are also presented to enlighten some important points. First, the composition and stratification of the layers produced by uniform corrosion are described. A focus is made on the mechanism of formation of the sulfate green rust because this compound is the first solid phase to precipitate from the dissolved species produced by the corrosion of the steel surface. Secondly, localized corrosion processes are discussed. In any case, they involve galvanic couplings between anodic and cathodic zones of the metal surface and are often associated with heterogeneous corrosion product layers. The variations of the composition of these layers with the anodic/cathodic character of the underlying metal surface, and in particular the changes in magnetite content, are thoroughly described and analyzed to enlighten the self-sustaining ability of the process. Finally, corrosion product layers formed on permanently immersed steel surfaces were exposed to air. Their drying and oxidation induced the formation of akaganeite, a common product of marine atmospheric corrosion that was, however, not detected on the steel surface after the permanent immersion period.
Résumé : In this work, corrosion of an abandoned X52 pipeline steel containing artificial pits with varied depths was investigated in a simulated soil solution containing sulfate-reducing bacteria (SRB). Bio-testing, electrochemical measurements and surface analysis techniques were used to study the SRB-induced corrosion outside and inside the pits. Results show that the SRB tend to accumulate on the specimen surface (i.e., outside the pits), rather than inside the pits, resulting in accelerated corrosion of the steel. As the depth of the pit increases, there are fewer SRB adherent to the steel of the pit wall. Thus, compared to the specimen surface, the pits experience a reduced MIC. A galvanic effect exists between the outside and inside the pits, with the former serving as the anode and the latter as the cathode, further enhancing the corrosion of the steel outside the pits.
Résumé : This work aims to investigate the corrosion effect of different seawaters surrounding Peninsular Malaysia on the carbon steel of the petroleum/natural gas pipeline. The Tafel extrapolation technique has been applied to evaluate the corrosion rate of the pipeline steel and different locations of natural seawaters have been used as the electrolyte solution. In this experiment, carbon steel pipeline, API-5L-X42 was utilized as the sample and the seawaters were taken from several locations in Peninsular Malaysia, specifically at the South China Sea (Terengganu, Kelantan, Pahang) and the Strait of Melaka (Melaka, Johor, Negeri Sembilan). The corrosion rate calculation and the type of corrosion attack also have been discussed on the basis of the morphology and the metal contents of the seawaters. It was found that the corrosion rate of the carbon steel is relatively higher in the Strait of Melaka seawaters than that of the South China Sea seawaters. The corrosion rate results varied from 0.01 to 0.024 mm/year. Immersion test were carried out to examine the corrosion product formed on the surface of the pipe and from the result, localized corrosion (pitting) and uniform corrosion occurred at the specimen’s surface severely for both seawater electrolytes. In summary, South China Sea is more favorable environment for the application of this type of pipeline steel compared to that of Strait of Melaka.
Résumé : Methods of employing corrosion inhibitors with oxidizing and/or non-oxidizing biocides, such as peroxycarboxylic acids, to provide corrosion protected compositions are disclosed. Various corrosion inhibitors further provide biocidal efficacy in addition to the corrosion protection providing further benefits for application of use. Methods of employing corrosion protected biocide compositions, such as peroxycarboxylic acid compositions, for corrosion protection are particularly well suited for treating fluids intended to flow through pipes, namely in the energy industry, water and paper industries, etc. Methods providing suitable corrosion protection in comparison to untreated systems and corrosion protected systems using conventional corrosion inhibitors, such as quaternary amines and imidazolines commonly used in the industry, are disclosed.
Résumé : The bio-competitive exclusion (BCX) method is a practical, environment-friendly, and low-cost method of controlling sulfate-reducing bacteria (SRB) and focuses on research and preliminary applications. In this study, a nitrate-reducing bacteria (NRB) were screened and selected from oil-producing water and identified as heterotrophic Pseudomonas sp. through 16S rDNA. The NRB activation and the SRB inhibition systems were studied via the addition of the bio-activators NO3− and NO2−. In addition, the synergistic inhibitory effect of NRB and molybdate on SRB was studied. Results showed that the inhibitory effect of NO2− was better than that of NO3−. At NO3− to NO2− ratio of 1:4, the inhibitory effect was optimum. The addition of 5% activated NRB and a small amount of molybdic acid salt played a synergistic effect. The optimal inhibition system contained the following: 5% NRB, NO3−/NO2− of 1:4, and the amount of molybdate was 1/5 that of NO3−. In this inhibition system, S2− can maintain an extremely low content, and SRB activity was well inhibited. Static corrosion simulation experiments showed that SRB was the main cause of corrosion. The effects of biological inhibitors, fungicides, and corrosion inhibitors on the corrosion inhibition were investigated. Results showed that the corrosion rate of biological inhibitors was the lowest, and the best effect of corrosion inhibition was achieved. The surface morphology of the corroded steel sheet was analyzed via scanning electron microscope. In addition, the surface corrosion of the steel sheet was low, and no pitting was observed.
Résumé : <section class="abstract"><h2 class="abstractTitle text-title my-1" id="d802e2">Abstract</h2><p>Buried pipelines are essential for the delivery of potable water around the world. A key cause of leaks and bursts in these pipelines, particularly those fabricated from carbon steel, is the accelerated localized corrosion due to the influence of microbes in soil. Here, studies conducted on soil corrosion of pipelines' external surface both in the field and the laboratory are reviewed with a focus on scientific approaches, particularly the techniques used to determine the action and contribution of microbiologically influenced corrosion (MIC). The review encompasses water pipeline studies, as well as oil and gas pipeline studies with similar corrosion mechanisms but significantly higher risks of failure. Significant insight into how MIC progresses in soil has been obtained. However, several limitations to the current breadth of studies are raised. Suggestions based on techniques from other fields of work are made for future research, including the need for a more systematic methodology for such studies.</p></section>
Résumé : The central concept of microbiologically influenced corrosion is ‘biofilm’. However, it is neither a 100% biological fabric nor a film. While biofilms though mechanisms such as establishment of differential aeration cells can accelerate corrosion, under certain circumstances such as thickening may also decelerate corrosion. In this article, these mechanisms will be discussed. Along with that, this author also introduces a new term that can replace the term ‘biofilm’. This new term, ‘temenos’, has been proposed to indicate that when a biofilm forms, electrochemical conditions under the biofilm and those of the bulk will be highly different from each other.
Résumé : This paper presents the long-term effect of sulfate-reducing bacteria (SRB) on the corrosion of buried cast iron pipes in soil and culture medium which has no previous research in literature. The comprehensive experimental design for investigating the external corrosion of buried pipes in soil and culture medium is developed in the current research. Coated specimens except their one side simulating the exterior surface of buried pipes are exposed to the SRB for 365 days in both the media. From the test results of corrosion rates and maximum pit depth, significant microbiologically influenced corrosion (MIC) of cast iron in the soil is observed as compared to the culture medium. The test results suggest that the testing of specimens in simulated soil solutions or culture medium instead of natural soil may lead to underestimated corrosion measurements for the buried pipe. The findings of this paper have practical applications for the prediction of failure of buried cast iron pipelines.
Résumé : In the oil and gas industry, microbiologically influenced corrosion (MIC) is a major threat to hydrotest, a procedure which is required to certify whether a pipeline can be commissioned. Seawater is frequently used as a hydrotest fluid. In this biofilm prevention lab study, an oilfield biofilm consortium was grown in an enriched artificial seawater anaerobically at 37 °C for 60 days. The combination of 100 ppm (w/w) 2,2-dibromo-3-nitrilopropionamide (DBNPA) + 100 nM (180 ppb) Peptide A (a biofilm dispersal agent) led to extra SRB (sulfate reducing bacteria), APB (acid producing bacteria) and GHB (general heterotrophic bacteria) sessile cell count reductions of 0.9-log, 0.8-log and 0.6-log, respectively, compared with the outcome obtained by using 100 ppm DBNPA only. The Peptide A enhancement also led to extra reductions of 44% in weight loss, 40% in maximum pit depth, and 54% in corrosion current density.
Résumé : To obtain information on the mechanism of microbiologically influenced corrosion (MIC) under anaerobic conditions, metabolic processes and microbial community dynamics were analysed for MIC of carbon steel with lake-mud microbial consortium as inoculum. During one month of MIC experiment, the microbial consortium corroded carbon steel with sulphate reduction, methane and acetate production. The bacterial and archaeal community structure in the suspension culture and the crust formed on carbon steel were compared using high-throughput Illumina MiSeq sequencing and quantitative polymerase chain reaction. The data indicated that sulphate-reducing bacterium (Desulfovibrio genus), amino acid-degrading bacterium (Aminobacterium genus) and a hydrogenotrophic methanogen Methanofollis among Archaea increased in the crust. These microbes were estimated to collaboratively induced corrosion of carbon steel under anaerobic condition.
Résumé : A low pH Brine that flows through carbon steel pipe to the reinjection well will expose a rapid rate of pipe corrosion. Moreover, underground installation of pipe will multiply this corrosion effect and lead in environment pollution and financial losses. This issue could be reduced by applying novel method of corrosion prevention named Geothermal-powered Impressed Current Cathodic Protection (GICCP). This system utilizes a geothermal power source from heat of geothermal pipeline and converts to electric power by using thermoelectric device. Then the electric power is used in GICCP to develop a high potential difference between the surface of pipe to be protected and an anode. It is expected that the implementation of GICCP could inhibit the corrosion rate, extend the remaining life of pipeline, and reduce downtime period as well as the possibility of financial losses in geothermal industry.
Résumé : In order to evaluate the corrosive action of microorganisms on 316L metal exposed directly to a marine environment, a system was designed to immerse coupons in seawater. After periods of 30, 60 and 90 days, the coupons were recovered, the corrosion rates evaluated and the biofilm samples on their surface were analyzed by 16S rRNA gene sequencing. The results of the corrosion rate showed an acceleration over the entire experimental period. Alpha diversity measurements showed higher rates after 60 days of the experiment, while abundance measurements showed higher rates after 90 days of exposure to the marine environment. The beta-diversity results showed a clear separation between the three conditions and proximity in the indices between replicates of the same experimental condition. The results of 16S rRNA gene sequencing showed that after 30 days of exposure to seawater, there was massive representativeness of the pioneer bacteria, Gamma and Alphaproteobacteria, with emphasis on the genera Alcanivorax, Oceanospirillum and Shewanella. At the 60-day analysis, the Gammaproteobacteria class remained dominant, followed by Alphaproteobacteria and Flavobacteria, and the main representatives were Flexibacter and Pseudoalteromonas. In the last analysis, after 90 days, a change in the described bacterial community profile was observed. The Gammaproteobacteria class was still the largest in diversity and OTUs. The most predominant genera in number of OTUs were Alteromonas, Bacteriovorax and, Nautella. Our results describe a change in the microbial community over coupons directly exposed to the marine environment, suggesting a redirection to the formation of a mature biofilm. The conditions created by the biofilm structure suggest said condition favor biocorrosion on the analyzed coupons.
Résumé : Microbiologically influenced corrosion (MIC) and CO2 corrosion are the common types of corrosion in shale gas fields. In this study, the effect of quaternized polyacrylamide inhibitor on MIC was studied in the produced water from a shale gas field using a circulating loop system with CO2. The result shows that polyacrylamide can inhibit CO2 corrosion. However, in the presence of microorganisms, polyacrylamide failed to inhibit MIC. Microorganisms formed biofilm on the coupon surface. Pitting nucleated underneath the biofilm and developed into cavity-type due to the local acidification. According to crystal structure and chemical composition of matters in the biofilm, the mechanism of microbial acidification leading to pitting corrosion was proposed. The prevention and control strategy for MIC in CO2 environment was discussed.
Résumé : The influence of crude oil and chemical dispersant was evaluated over planktonic bacteria and biofilms grown on API 5L steel surfaces in microcosm systems. Three conditions were simulated, an untreated marine environment and a marine environment with the presence of crude oil and a containing crude oil and chemical dispersant. The results of coupon corrosion rates indicated that in the oil microcosm, there was a high corrosion rate when compared with the other two systems. Analysis of bacterial communities by 16S rRNA gene sequencing described a clear difference between the different treatments. In plankton communities, the Bacilli and Gammaproteobacteria classes were the most present in numbers of operational taxonomic unit (OTUs). The Vibrionales, Oceanospirillales, and Alteromonadales orders were predominant in the treatment with crude oil, whereas in the microcosm containing oil and chemical dispersant, mainly members of Bacillales order were detected. In the communities analyzed from biofilms attached to the coupons, the most preponderant class was Alphaproteobacteria, followed by Gammaproteobacteria. In the control microcosm, there was a prevalence of the orders Rhodobacterales, Aeromonadales, and Alteromonadales, whereas in the dispersed oil and oil systems, the members of the order Rhodobacterales were present in a larger number of OTUs. These results demonstrate how the presence of a chemical dispersant and oil influence the corrosion rate and bacterial community structures present in the water column and biofilms grown on API 5L steel surfaces in a marine environment.
Résumé : Compositions and methods are provided for use in controlling souring and corrosion causing prokaryotes, such as SRP, by treating oil and gas field environments or treatment fluids with a newly identified bacterial strain ATCC Accession No. PTA-124262 as a self-propagating whole cell that produces an anti-SRP bacteriocin in situ. In another aspect, the methods use one or more toxic peptides or proteins isolated therefrom in methods to control unwanted prokaryotic growth in these environments.
Résumé : Provided are methods for diagnosing, monitoring and mitigating microbiologically influenced corrosion (MIC). The methods employ steps to determine the nature and concentration of biological signatures, formed through metabolism of microorganisms, and correlating the biological signatures with MIC. Based on such analyses, appropriate MIC mitigation strategies may be implemented so as to efficiently target MIC at sites of interest. The methods advantageously allow selection of appropriate MIC mitigation treatments that correspond to the level of severity of the MIC and based on historical data correlating particular biological signatures with particular MIC risk.
Résumé : The movement towards the commercialization of biodegradable Fe has been hampered by the perceived slow degradation rate of the metal in physiological environments. The introduction of Fe-Mn alloys offers promise due to its significantly improved biocorrosion rates, excellent biocompatibility, and non-magnetic properties. However, the issue of slow corrosion rates persists in this alloy and its future hinges on addressing this issue. This short review report presents the current approaches to address this problem, the challenges concerning Fe-Mn corrosion, and some future techniques that may improve the degradation rate of Fe-Mn alloys.
Résumé : In the present work, we studied the stress-assisted microbiologically influenced corrosion mechanism of 2205 duplex steel caused by sulfate-reducing bacteria (SRB) in simulated seawater environment. The results suggested that SRB have a significant influence on the pitting behavior of 2205 DSS, and stress promotes the MIC behavior. The mechanism proposes that the ferrite phases and high-residual stress regions manifest as the preferential anodic electron donor for SRB respiration due to the galvanic effect caused by the composing duplex phases, high-stress regions and low-stress regions; this outcome leads to the preferential dissolution of ferrite phases and high-stress regions.
Résumé : In this work, corrosion of an X52 pipeline steel was investigated in a simulated soil solution containing Pseudomonas aeruginosa (PAO1), Desulfovibrio desulfuricans (sulfate-reducing bacteria, SRB) or both, where the corrosion rates of the steel are 0.035, 0.076 and 0.060 mm/y, respectively. There is no corrosion enhancement between PAO1 and SRB when they coexist. The presence of PAO1 facilitates the SRB cells to be surrounded by corrosion products, and cannot contribute to corrosion at the identical level to the SRB that are bare to the environment. The three microorganism scenarios cause localized corrosion on the steel.
Résumé : Stainless steels are widely used in various industries due to their desirable combination of mechanical properties and corrosion resistance. However, corrosion of stainless steels was reported seriously on the weld seam areas, and it is not exceptive for microbiologically influenced corrosion (MIC). In the present study, MIC resistance of two austenitic stainless steels (A1, A2 for short) and a duplex stainless steel (D1 for short) with weld seams were comparatively studied by measurement of average and maximum pit depths and electrochemical tests. Experimental results showed that the pit depth on the weld seam was much deeper than that on the base metal for all the stainless steels. The variations of linear polarization resistance (RLPR) values on base metal and weld seam showed that weld seam could promote MIC. Thus the study indicated that the weld seam accelerated the MIC. In addition, A1 steel with higher Cu content showed the best MIC resistance, followed by A2 steel with lower Cu content, and D1 steel without Cu addition exhibited the worst resistance to MIC, indicating that Cu addition in stainless steels is speculated to be beneficial to the MIC resistance. The mechanisms of Cu improving the MIC resistance in the stainless steels were discussed.
Résumé : Microbiologically influenced corrosion (MIC) is capable on weakening the metal’s strength, eventually leads to pipeline leakage, environmental hazard and financial loss. Sulfate reducing bacteria (SRB) is the principal causative organism responsible for external corrosion on steel structures. To date, considerable works have been conducted in Malaysia on the mechanisms of SRB upon MIC on the marine environment instead of underground. Moreover, commercial bacteria strain represents local strain in terms of performance and behavior upon corrosion of steel structure is yet to be proven. Thus, this paper aims to investigate the influence of environmental parameters towards MIC in corroding pipeline. Two types of SRB strain were used designated as SRB ATCC 7757 (commercial) and SRB Sg. Ular (local strain) isolated from Malaysian soil. The behavior of both strains was critically compared by calculating the rate of corrosion upon carbon steel coupons in stipulated environmental parameters. Four influential parameters i.e. pH, temperature, salinity concentration and iron concentration were considered. Collected data presented and analyzed using graphical and statistical analysis, respectively. The results showed the difference of corrosivity between two SRB strains in terms of corrosion behavior upon the X-70 steel coupon. SRB Sg. Ular able to cause severe effects upon steel structure as compared to SRB ATCC 7757 due to its aggressiveness shown by the recorded metal loss data. Thus, future works related to MIC for local environment in particular, should not compromise with the type of SRB strains considered due to differences of performance of the microorganisms onto tested environment and materials.
Résumé : In this work, we investigated microbiologically influenced corrosion (MIC) of X80 pipeline steel caused by nitrate-reducing bacteria Brevibacterium frigoritolerans (B. frigoritolerans) in an artificial Beijing soil using electrochemical measurements and surface analyses under aerobic conditions. The B. frigoritolerans was isolated from the surrounding soil of the X80 pipeline steel specimen in Beijing using culturing and molecular biology techniques. Confocal laser scanning microscopy images showed that the largest pit depth after 14 days due to B. frigoritolerans was approximately 7.16 μm. Electrochemical tests showed that the B. frigoritolerans could change the stability of the corrosion products on the 7th day. Inhomogeneous biofilm and the conductivity of Fe2O3 accelerated the corrosion process. The presence of NH4+ on the surface of the X80 pipeline steel revealed that the B. frigoritolerans acted as a biological cathode to promote the cathodic reaction.
Résumé : The corrosion behavior of X80 steel in Dagang soil simulated solution was verified by potentiostatic immersion test and AC impedance test, and the corrosion morphology of metal surface under different applied potential in bacterial solution and sterile solution was observed by scanning electron microscope (SEM).The results showed that the existence of sulfate reducing bacteria (SRB) can increase the corrosion trend of metals. In the simulated solution, the corrosion of samples became more and more serious with the increase of soaking days. With the negative shift of applied potential, the electrochemical corrosion rate of X80 pipeline steel was lower than that under self-corrosion potential.
Résumé : A conduit or pipeline system configured to use a liquid containing fluid, such as water, which typically accumulates in low flow pipelines causing corrosion and accumulation of sediments, to remove sediments and prevent corrosion. The liquid-containing fluid can be introduced into gas lines to remove solids, for example, black powder.
Résumé : Pseudomonas balearica strain EC28 is an iron-oxidizing bacterium isolated from corroded steel at a floating production storage and offloading facility in Australia. Here, we report its complete genome sequence, which comprises 4,642,566 bp with a GC content of 64.43%. The genome harbors 4,164 predicted protein-encoding genes.
Résumé : Microbial influenced corrosion (MIC) is one of the major concerns in industries due to huge economic losses. Sulfate-reducing bacteria (SRB) are well studied and highly corrosive in nature. However, the MIC mechanism, especially by iron-oxidizing bacteria (IOB) is not yet elucidated. In this context, this study presented the co-relation of extra polymeric substances (EPS) exuded by IOB strains as a key mechanism for MIC of mild steel. Herein, the corrosion behavior of mild steel influenced by EPS of two IOB strains; DASEWM1 and DASEWM2 isolated from river water was investigated. Comparative studies using surface analysis, electrochemical tests and immersion tests in nutrient broth media revealed a higher degree of corrosion in inoculated media (strain DASEWM1 < DASEWM2) than control media. These results were also supported by EIS and FESEM of corroded steel surfaces. Moreover, electrochemical and EPS constituent’s analysis, the correlation between the corrosion rate to the EPS constituents were also studied.
Résumé : Biofouling is an undesirable process in which biological molecules and organisms adhere to a surface. This process causes severe negative effects in various fields including healthcare, water distillation, and marine transportation. Therefore, its prevention is highly explored. Here, the prevention of biofouling by thin films, based on different sol–gel precursors, was studied. Specifically, films were formed by methyltrimethoxysilane (MTMOS), phenyltrimethoxysilane (PTMOS), 3,3,3-trifluropropyltrimethoxysilane (FTMOS), or 3-aminopropyltrimethoxysilane (APTMS) using spin-coating on glass. We found that hydrophobicity alone showed a moderate effect on the number of adsorbed bacteria onto the surface. The APTMS film showed, as expected, antibacterial properties and its combination with FTMOS led to a significant prevention of protein and bacterial adsorption. These results emphasize that a dual effect of antifouling and antibacterial properties, is preferred in the prevention of biomass on surfaces.
Résumé : Establishment of protected areas to maintain biodiversity requires identification, prioritization and management of stressors that may undermine conservation goals. Nonindigenous species and climate change are critical ecosystem stressors that need greater attention in the context of spatial planning and management of protected areas. Risk of invasion into protected areas needs to be quantified under current and projected climate conditions in conjunction with prioritization of key vectors and vulnerable areas to enable development of effective management strategies. We assessed the likelihood of invasion across networks of marine protected areas (MPAs) to determine how invaded MPAs may compromise MPA networks by sharing nonindigenous species. We evaluated invasion risk in 83 MPAs along Canada's Pacific coast for eight nonindigenous species based on environmental suitability under current and future (average conditions from 2041 to 2070) climate conditions and association with shipping and boating pathways. We applied species distribution models and network analysis of vessel tracking data for 805 vessels in 2016 that connected MPAs. The probability of occurrence within MPAs and the proportion of MPA area that is suitable to the modelled species significantly increased under future climate conditions, with six species reaching over 90% predicted occurrence across MPAs and over 70% of suitable area within MPAs. Vessel traffic created four network clusters of 61 highly connected MPAs that spanned the coastline. Occupancy of over 90% of the MPAs within the clusters was predicted for most species. Synthesis and applications. Our results indicate a high likelihood of marine protected area (MPA) network invasion based on current and future environmental conditions and vectors of spread, and the potential for extensive nonindigenous species distributions within MPAs. Our approach highlights how interacting stressors can exacerbate MPA susceptibility to nonindigenous species, adding further challenges for protected area management. Management planning that invests in understanding connectivity and vector processes (human behaviours) is more likely to derive effective policies to stem the flow of nonindigenous species under both current and future conditions. In particular, biosecurity measures including vessel biofouling regulations and MPA- and MPA network-specific plans for prevention, monitoring and mitigation of nonindigenous species are needed.
Résumé : Ultraviolet light (UV) is currently under investigation as an environmentally friendly alternative for antifouling prevention in the marine environment. A novel apparatus based on a Nautilus shell was designed, to test UV exposure on multiple surfaces with varying distances from a lamp source. Several proof of concept tests were conducted in-situ to determine if the Nautilus design would indeed be an effective method for studying UV in the marine environment. Specifically, the in-situ tests studied the effect of UVC (λ = 254 nm) exposure (continuous and one minute per day) on biofouling settlement at distances ranging from 25 mm to 275 mm. Continuous UV exposure resulted in minimal (≤5% total coverage) settlement, which consisted of biofilms. UV exposure of one minute per day had a greater biofouling settlement with trends observed in the community composition related to distance from the lamp. The coverage of soft fouling organisms decreased with increased distance from the lamp; meanwhile, hard fouling abundance increased with increasing distance. In order to investigate how UV impacts already established fouling, continuous exposure was then applied to a fully developed biofouling community. This resulted in a decrease in total fouling coverage across all distances and live barnacles were only present on surfaces at distances ≥200 mm from the lamp. Overall, the Nautilus design presented a viable option for studying UV in the marine environment and allowing for the identification of UV tolerances within fouling communities.
Résumé : Biofouling reduces the overall hydrodynamic performance of a ship and increases fuel consumption. Four different fouling resistant coatings were experimentally investigated to study their surface roughness properties, during two years of exposure at sea water. An open source RANS solver, OpenFOAM, with integrated rough wall function model, was verified and validated for frictional and total resistance prediction for smooth (no coating) surface conditions. Next, the solver was validated against available CFD and Empirical results for ship frictional resistance prediction with different levels of slime and fouling. Finally, frictional and total resistance was predicted for a ship hull surface with the experimentally studied coatings. The experimental outputs were used to model surface roughness properties of the ship hull, and predict the resistance performance of the ship after one and two years of exposure at sea, with the studied hull coatings. The study reveals that the determination of frictional resistance alone is not enough to understand the required change in propulsion power requirement due to fouling, total drag resistant prediction is also important. It also shows that coatings with initial low roughness may not retain the low resistance property over a long period of exposure to the sea, comparing to other coatings. Overall, the study concludes that CFD can prove to be a very effective tool to study the effect of biofouling on hull properties.
Résumé : Oil fields harbour a wide variety of microorganisms with different metabolic capabilities. To examine the microbial ecology of petroleum reservoirs, a molecular-based approach was used to assess the composition of bacterial communities in produced water (PW) of Diyarbakır oil fields in Turkey. Denaturing gradient gel electrophoresis (DGGE) of PCR-amplified 16S rRNA gene fragments was performed to characterise the bacterial community structure of PW samples and to identify predominant community members after sequencing of separated DGGE bands. The majority of bacterial sequences retrieved from DGGE analysis of PW samples belonged to unclassified bacteria (50%). Among the classified bacteria, Proteobacteria (29.2%), Firmicutes (8.3%), Bacteroidetes (8.3%) and Actinobacteria (4.2%) groups were identified. Pseudomonas was the dominant genus detected in the PW samples. The results of this research provide for, the first time, insight into the complexity of microbial communities in the Diyarbakır oil reservoirs and their dominant constituents.
Résumé : One of the current challenges in maritime antifouling is the development of new nanostructured coatings which can replace the old protection coatings based on tributyltin biocides prohibited by EU and US legislation as ecologically dangerous. In our study, antibacterial/antifouling polymer coatings containing innovative dual functionalized nanocapsules demonstrate high antifouling activity in various tests. Capsules are MCM-48 SiO2 nanoparticles loaded with eco-friendly 4,5-dichloro-2-octyl-4-isothiazolin-3-one (DCOIT) antifouling agent and decorated with dimethyloctadecyl [3-(trimethoxysilyl) propyl] ammonium chloride or dimethyltetradecyl [3-(triethoxysilyl) propyl] ammonium chloride (quaternary ammonium salts, QASs) also possessing antifouling activity. Cross section images of the coatings demonstrated the absence of the capsule aggregates in the coatings with slight increase of the surface roughness. The formulated coatings revealed excellent antibacterial performance against E. coli and Staphylococcus aureus according to ISO 22196:2011 protocol. This antifouling activity was also confirmed by immersion of the coated polyvinyl chloride (PVC) panels at a depth of 8–9 m in the sea (Eilat, Israel). Biofouling coverage of 6.9% was observed for nanocapsules-loaded coatings (5 wt % concentration of nanocapsules) compared to the 49% of the coverage for nonmodified coating after 6 months of immersion. The nanocapsules-loaded coatings with dual antifouling functionality demonstrated antifouling activity even after complete release of encapsulated DCOIT because of chemically attached QAS groups on the nanoparticles surface. Moreover, active antifouling materials presented in nanocapsules do not demonstrate any toxicity to the brine shrimps Artemia salina, which are widely used in the food industry.
Résumé : While nature has optimized its antifouling strategies over millions of years, synthetic antifouling coatings have not yet reached technological maturity. For an antifouling coating to become technically feasible, it should fulfill many requirements: high effectiveness, long-term stability, durability, ecofriendliness, large-scale applicability, and more. It is therefore not surprising that the search for the perfect antifouling coating has been going on for decades. With the discovery of metal-based antifouling paints in the 1970s, fouling was thought to be a problem of the past, yet its untargeted toxicity led to serious ecological concern, and its use became prohibited. As a response, research shifted focus toward a biocompatible alternative: polymer-based antifouling coatings. This has resulted in numerous advanced and innovative antifouling strategies, including fouling-resistant, fouling-release, and fouling-degrading coatings. Here, these novel and exciting discoveries are highlighted while simultaneously assessing their antifouling performance and practical feasibility.
Résumé : Although quite some self-healing coatings have been reported to date, underwater healable coatings were involved very limited. Here, we report a novel underwater healable superoleophobic coating through depositing functional SiO2@PDA@Ag particles on the TPA/EVA-70% film. The obtained coating not only possess excellent underwater superoleophobic and antifouling properties, but also quick healable performance by remote NIR irradiation. Thus, it may provide stable and long-lasting underwater antifouling properties against marine growth and oil contamination.
Résumé : Biofouling accumulation on ships’ submerged surfaces typically occurs during stationary periods that render surfaces more susceptible to colonization than when underway. As a result, stationary periods longer than typical port residence times (hours to days), often referred to as lay-ups, can have deleterious effects on hull maintenance strategies, which aim to minimize biofouling impacts on ship operations and the likelihood of invasive species transfers. This experimental study tested the effects of different lay-up durations on the magnitude of biofouling, before and after exposure to flow, using fouling panels with three coating treatments (antifouling, foul-release, and controls), at two sites, and a portable field flume to simulate voyage sheer forces. Control panels subjected to extended stationary durations (28-, 45- and 60-days) had significantly higher biofouling cover and there was a 13- to 25-fold difference in biofouling accumulation between 10-days and 28-days of static immersion. Prior to flume exposure, the antifouling coating prevented biofouling accumulation almost entirely at one site and kept it below 20% at the other. Foul-release coatings also proved effective, especially after flume exposure, which reduced biofouling at one site from >52% to <6% cover (on average). The experimental approach was beneficial for co-locating panel deployments and flume processing using a consistent (standardized) flow regime on large panels across sites of differing conditions and biofouling assemblages. While lay-ups of commercial vessels are relatively common, inevitable, and unavoidable, it is important to develop a better understanding of the magnitude of their effects on biofouling of ships’ submerged surfaces and to develop workable post-lay-up approaches to manage and respond to elevated biofouling accumulation that may result.
Résumé : Due to the current dependence on biocidal antifouling coatings for biofouling control, there is a continuing international challenge to develop more environmentally acceptable antifouling systems. Fluctuating the pH values on paint surfaces is one of these approaches. We developed an antifouling test device to investigate algal biofilms on conductive paints by using a flume with electrochemically working test panels and subsequent confocal laser scanning microscopy (CLSM) of biofilms. By employing a pole reversal of direct current, fluctuating pH values on the paint surface were generated. As a consequence of the resulting pH stress, colonization of the paint surface by diatoms decreased substantially. The density of biofilm algae decreased with increasing pH fluctuations. However, breaks between electrochemical treatments should not exceed one hour. Overall, we established an experimental setup for testing the antifouling capabilities of electrodes based on conductive paints, which could be used for further development of these varnishes.
Résumé : <p>The clogging of drippers due to the development of biofilms reduces the benefits and is an obstacle to the implementation of drip irrigation technology. The geometry of the dripper channel has an impact on the flow behaviours and head loss. The objective of this study was to analyse the influence of hydrodynamic parameters of three types of drippers (flow rates of 1, 2 and 4 l.h-1) fed by reclaimed wastewater on biofilm development kinetics and on the bacterial community. Using optical coherence tomography, we demonstrated that the inlet of the drippers (mainly the first baffle) and vortex zones are the most sensitive area for biofouling. Drippers with the lowest flow rate (1 l.h-1) and the smallest channel section were the favourable areas to biofouling. The low inlet velocity (0.34 m.s-1) in this type of dripper compared to 2 l.h-1 (0.61 25 m.s-1) and 4 l.h-1 (0.78 m.s-1) drippers can favour the deposition and development of biofilms. In addition, the water velocity influenced the structure of the bacterial communities in the biofilm. Low velocity (0.34 m.s-1) favoured the presence of Hydrogenophaga and Pseudoxanthomonas genera at the early stage of biofilm formation and filamentous bacteria belonging to Chloroflexi phylum at the end. So, maintaining a high flow rate and using drippers with a large flow cross-section is an effective way to control the development of biofilms by limiting the presence of filamentous bacteria.</p>
Résumé : In this manuscript, a series of amine tagged short cyclic molecules (cyclopropylamine, cyclobutylamine, cyclopentylamine and cyclohexylamine) were thermally grafted onto p-type silicon (111) hydride surfaces via nucleophilic addition. The chemistries of these grafting were verified via XPS, AFM and sessile droplet measurements. Confocal microscopy and cell viability assay was performed on these surfaces incubated for 24 hours with triple negative breast cancer cells (MDA-MB 231), gastric adenocarcinoma cells (AGS) endometrial adenocarcinoma (Hec1A). All cell types had shown a significant reduction when incubated on these ring-strain cyclic monolayer surfaces than compared to standard controls. The expression level of focal adhesion proteins (vinculin, paxilin, talin and zyxin) were subsequently quantified for all three cell types via qPCR analysis. Cells incubate on these surface grafting were observed to have reduced levels of adhesion protein expression than compared to positive controls (collagen coating and APTES). A potential application of these anti-adhesive surfaces is the maintenance of the chondrocyte phenotype during in-vitro cell expansion. Articular chondrocytes cultured for 6 days on ring strained cyclopropane-modified surfaces was able to proliferate but had maintained a spheroid/aggregated phenotype with higher COL2A1 and ACAN gene expression. Herein, these findings had help promote grafting of cyclic monolayers as an viable alternative for producing antifouling surfaces.
Résumé : Biofouling is the colonization of underwater surfaces by microorganisms, plants, algae or animals and can be divided into soft and hard fouling. Soft fouling is consisted of algae, slime and grasses and typically has a lower impact on the performance of the ship than hard fouling, which has a calcareous structure. Furthermore, hard fouling can be extremely detrimental to the performance of machinery and coating systems. Within this paper, the effect of hard fouling on the ship resistance is assessed utilizing Computational Fluid Dynamics (CFD). The roughness function model for the hard fouling is implemented within the wall function of the CFD software. Afterwards, numerical simulations of fouled flat plates are performed, and the obtained results are verified and validated with the experimental results published in the literature. Once validated, numerical simulations with implemented roughness function model and roughness length scale, proposed in the literature, can be used for the determination of the effect of hard fouling on the resistance of any arbitrary body. Lastly, the effects of hard fouling on the resistance characteristics of two merchant ships at full-scale are determined utilizing the validated CFD model. Benefits of the proposed method for the determination of the effect of hard fouling on the ship resistance are highlighted and discussed.
Résumé : The negative effect of biofouling on ship resistance has been investigated since the early days of naval architecture. However, for more precise prediction of fuel consumption of ships, understanding the effect of biofouling on ship propulsion performance is also important. In this study, computational fluid dynamics (CFD) simulations for the full-scale performance of KP505 propeller in open water, including the presence of marine biofouling, were conducted. To predict the effect of barnacle fouling on the propeller performance, experimentally obtained roughness functions of barnacle fouling were used in the wall-function of the CFD software. The roughness effect of barnacles of varying sizes and coverages on the propeller open water performance was predicted for advance coefficients ranging from 0.2 to 0.8. From the simulations, drastic effects of barnacle fouling on the propeller open water performance were found. The result suggests that the thrust coefficient decreases while the torque coefficient increases with increasing level of surface fouling, which leads to a reduction of the open water efficiency of the propeller. Using the obtained result, the penalty of propeller fouling on the required shaft power was predicted. Finally, further investigations were made into the roughness effect on the flow characteristics around the propeller and the results were in correspondence with the findings on the propeller open water performance.
Résumé : The development of environmentally friendly alternatives is a crucial issue, since the prohibition of tributyltin (TBT)-based antifouling coatings. In this work, a series of fluorinated diols modified polythiourethane (HO-FPTU-x) have been synthesized via a simple and convenient polymerization reaction with HDI, PETMP and various of 2,3,5,6-tetrafluoro-1,4-benzenedimethanol (HOCH2-FB-Al) at the room temperature, and their antifouling properties are explored as well. The laboratory assays and marine field tests (6 months) show that the HO-FPTU-7.5 (with 7.5 wt% HOCH2-FB-Al) coating has shown excellent antifouling/fouling release properties. The side chains of the HO-FPTU polymers simultaneously contain hydrophobic and hydrophilic groups, which construct an “ambiguous’’ surface after immersing into water. The marine organisms may be “confused’’ by the “ambiguous’’ surface and be removed easily during settlement and adhesion. This work provides a facile strategy for designing environment friendly marine antifouling coatings.
Résumé : Biofouling is a major problem facing the marine industry. Since toxic antifouling coatings were banned globally due to their negative impacts on the marine environment, the development of environmental-friendly and efficient antifouling coatings has been identified as a pressing need. As an alternative, the antifouling coatings inspired by corals have attracted a great deal of attention over these years. within the marine environment, corals have evolved an excellent antifouling capability. There are five major antifouling strategies applied by corals, including natural antifoulants, foul release effect, sloughing effect, soft tentacles, and fluorescence effect. In this paper, a brief review is conducted to introduce the antifouling coatings inspired by the five strategies. Moreover, a discussion is conducted about the existing problems with the five strategies and the direction of their further development is indicated.
Résumé : Zinc oxide with the morphology of nanopillar is promising marine antifouling materials as they can kill adhered bacteria and fungi. The zinc oxide with the morphology of nanopillar has shown super-antibacterial properties on galvanized steel, which makes ZnO/Zn nanopillar films promising in marine antifouling and antimicrobial corrosion. Thus, an efficient approach to coat ZnO/Zn nanopillar films on steel is of great significance. The electrodeposition method is a universal method for both ZnO crystals and galvanized coatings, and it can control the morphologies and structures of the resultant films. Therefore, in this study, capsaicin was added into an alkaline electrolyte to induce the formation of ZnO nanopillars. Due to capsaicin addition to the electrolyte, ZnO/Zn nanopillar films were obtained in a single cathodic electrodeposition. The added capsaicin in the electrolyte was absorbed on the electrodepositing surface by the functional –NH– groups in amide bond. The Zn(OH)42− diffusion was promoted by negatively shifted electrodepositing potential. The scanning electron microscopy (SEM) and X-ray diffraction (XRD) results illustrate that regular ZnO nanopillars were obtained when the capsaicin concentration was 0.6 g L−1 in the electrolyte. The resultant ZnO/Zn nanopillar films showed high antibacterial properties in Escherichia coli suspended solutions and relatively low living bacterial coverage, indicating promising application in marine antifouling. Electrochemical evaluation revealed that the obtained capsaicin-induced ZnO/Zn nanopillar films exhibited significantly enhanced corrosion resistance in a sulfate-reducing bacteria (SRB) medium. Moreover, the results illustrate that adding 0.6 g L−1 concentration of capsaicin in the electrolyte yielded the best films, which featured the lowest bacterial coverage and highest corrosion resistance.
Résumé : Nanosecond pulsed laser texturing has been performed on stainless steel with the objective of developing surface treatments to reduce bacterial adhesion on mechanical components in food handling machinery. The adhesion of Escherichia coli (E. coli) on four distinct textures has been investigated with standardised protocols for measurement of antibacterial performance. Surface morphology has been studied in detail for each texture to ascertain the presence of hierarchical structures and determine the role of topography in reducing bacterial adhesion. Despite the absence of sub-micrometric features comparable with bacterial size, this work highlights the crucial role that nanosecond pulsed laser irradiation plays in promoting a thin layer of iron oxide that reduces E. coli adhesion through local repulsive electrostatic interactions.
Résumé : The present invention provides a marine cable device configured for preventing or reducing biofouling along its exterior surface, which during use is at least temporarily exposed to water. The marine cable device according to the present invention comprises at least one light source configured to generate an anti-fouling light and at least one optical medium configured to receive at least part of the anti-fouling light. The optical medium comprises at least one emission surface configured to provide at least part of said anti-fouling light on at least part of said exterior surface.
Résumé : Formation of biofilms is one of the most serious problems affecting the integrity of marine structures both onshore and offshore. These biofilms are the key reasons for fouling of marine structures. Biofilm and biofouling cause severe economic loss to the marine industry. It has been estimated that around 10% of fuel is additionally spent when the hull of ship is affected by fouling. However, the prevention and control treatments for biofilms and biofouling of marine structures often involve toxic materials which pose severe threat to the marine environment and are strictly regulated by international maritime conventions. In this context, biomaterials for the treatment of biofilms, fouling, and corrosion of marine structures assume much significance. In recent years, due to the technological advancements, various nanomaterials and nanostructures have revolutionized many of the biological applications including antibiofilm, antifouling, and anticorrosive applications in marine environment. Many of the biomaterials such as furanones and some polypeptides are found to have antibiofilm, antifouling, and anticorrosive potentials. Many of the nanomaterials such as metal (titanium, silver, zinc, copper, etc.) nanoparticles, nanocomposites, bioinspired nanomaterials, and metallic nanotubes were found to exhibit antifouling and anticorrosive applications in marine environment. Both biomaterials and nanomaterials have been used in the control and prevention of biofilms, biofouling, and corrosion in marine structures. In recent years, the biomaterials and nanomaterials were also characterized to have the ability to inhibit bacterial quorum sensing and thereby control biofilm formation, biofouling, and corrosion in marine structures. This chapter would provide an overview of the biomaterials from diverse sources and various category of nanomaterials for their use in antibiofilm, antifouling, and anticorrosion treatments with special reference to marine applications.
Résumé : Carbon nanotubes (CNTs) are versatile nanomaterials with outstanding properties that can be used in different fields. This chapter reviews the use of single- and multi-walled CNTs in the development of antimicrobial and antifouling surfaces. The performance of CNT-containing surfaces seems to depend on a multiplicity of factors that can be conjugated in order to improve their activity. A substantially higher body of knowledge has accumulated regarding the use of multi-walled CNTs and their composites and exciting developments in CNT modification and combination with different molecules are being reported. Although some of the available results are promising, contradictory findings suggest that further investigation is needed to validate the antimicrobial and antifouling activities of developed surfaces in a wider range of conditions. The existing evidence seems to indicate that CNTs and their composites will remain a promising strategy to delay bacterial adhesion and reduce biofilm formation in very different environments.
Résumé : The ability to produce fresh potable water is an ever-growing challenge, especially with an increase in drought conditions worldwide. Due to its capacity to treat different types of water, reverse osmosis (RO) technology is an increasingly popular solution to the water shortage problem. The major restriction associated with the treatment of water by RO technology is the fouling of the RO membrane, in particular through biofouling. Membrane fouling is a multifaceted problem that causes an increase in operating pressure, frequent cleaning and limited membrane lifespan. The current paper summarizes the impact of biofouling of RO membranes used in seawater desalination plants. Following a brief introduction, the elements that contribute to biofouling are discussed: biofilm formation, role of extracellular polymeric substances (EPS), marine environment, developmental phases of biofouling. Following this, is a section on the implications of membrane biofouling especially permeate flux and salt rejection. The final section focuses on the new phenomenon of compression and hydraulic resistance of biofilms. Lastly, considerations on future research requirements on biofouling and its control in seawater reverse osmosis (SWRO) membrane systems are presented at the end of the article.
Résumé : Hydrogels, as a representative of soft and biocompatible material, have been widely used in biosensors, biomedical devices, soft robotics, and the marine industry. However, the ir-recoverability of hydrogels after dehydration, which will cause the loss of original mechanical, optical and wetting properties, has severely restricted their practical applications. At present, this critical challenge of maintaining hydrogels’ accurate character has caused less attention. To address this, here we report a hydrogel based on synergistic effects to achieve both the well-regulated rehydration and deswelling properties. The hydrogel after dehydration can quickly restore its’ original state both on the macro and micro scale. In addition, the hydrogel has excellent mechanical stability after several dehydration-rehydration cycles. All of these properties offer a possibility of water condition endurance and increase the service life. The robust property is attributed to the hydrophilic-hydrophobic and ionic interactions induced by the synergy of hydrophilic/oleophilic hetero-networks. Moreover, zwitterionic segments as hydrophilic network play a vital role to fabricate anti-biofouling hydrogels. The durable and reusable hydrogel may have promising applications for biomedical materials, flexible devices and the marine industry.
Résumé : The undesirable colonization of anthropogenic surfaces by organisms in the marine environment is stated as marine biofouling. The biofouling of marine systems is a global concern, with economic impact estimated at billions of dollars. The widely used antifouling biocides including tributyltin tin (TBT) have been previously assimilated into marine paints. Although it has remarkable antifouling performance, it is toxic to the marine environment. Therefore, it is essential to develop ecofriendly antifouling compounds. In the recent times, the physical, chemical, and mechanical properties of nanomaterials have considerably improved the potential applications ranging from environment and energy to healthcare compared with those of bulk materials. Marine antifouling coating is the most effective way for avoiding marine organism attachment till date. However, the cost associated with the commercial antifouling agents and their maintenance is quite high. Therefore, it is indispensable to develop ecofriendly antifouling compounds. This chapter discusses ecofriendly method to produce biopolymer and nanomaterials conglomerating the antimicrobial property of nanoparticles and the unique structure of the biopolymer PHB against marine biofouling.
Résumé : A green approach based on plasma enhanced chemical vapour deposition (PECVD) method was adopted in this work to modify surface properties of thin film composite (TFC) membranes for improved antifouling resistance during desalination process. Two types of hydrophilic monomers, i.e., acrylic acid (AA) and 2-hydroxyethyl methacrylate (HEMA) was respectively deposited onto the surface of commercial TFC membranes (XLE and NF270) and the effect of plasma deposition time (15 s, 1 min and 5 min) on the membrane physiochemical properties was investigated using different analytical instruments. The deposition of AA and HEMA was able to improve the membrane hydrophilicity owing to the presence of hydroxyl and carboxyl functional groups. However, prolonged plasma polymerization period was not encouraged as it led to the formation of thicker skin layer that significantly reduced water permeability. With 15-s plasma deposition time, AA and HEMA-modified XLE and NF270 membranes could achieve higher NaCl and Na2SO4 rejections as well as demonstrate 100% flux recovery rate. The improved antifouling resistance of modified TFC membranes is mainly due to the improved surface hydrophilicity coupled with greater surface charge properties. This work demonstrated a rapid solvent-free surface modification method that can be employed to enhance TFC membrane properties for desalination process.
Résumé : Biofouling is a worldwide problem from healthcare to the marine exploration. Aggressive biofouling, wear, and corrosion lead to severe deterioration in function and durability. Here, micro and nano-structured hierarchical diamond films, mimicking morphology of plant leaves were developed to simultaneously achieve superhydrophobicity, antibacterial efficacy and marine antibiofouling, combined with mechanical and chemical robustness. These coatings were designed and successfully constructed on various commercial substrates, such as titanium alloys, silicon, and quartz glass via a chemical vapor deposition process. The unique surface structure of diamond films reduced bacteria attachment by 90-99%. In the marine environment, these biomimetic diamond films significantly reduced more than 95% adhesion of green algae. The structured diamond films remained mechanical robustness, superhydrophobicity and antibacterial efficacy under high abrasion and corrosive conditions, exhibiting at least 20 times enhanced wear resistance than the bare commercial substrates even after long-term immersion in seawater.
Résumé : The rapid degradation of marine infrastructure at the low tide level due to accelerated low water corrosion (ALWC) is a problem encountered worldwide. Despite this, there is limited understanding of the microbial communities involved in this process. We obtained samples of the orange-coloured tubercles commonly associated with ALWC from two different types of steel sheet piling, located adjacent to each other but with different levels of localised corrosion, at a seaside harbour. The microbial communities from the outer and inner layers of the orange tubercles, and from adjacent seawater, were studied by pure culture isolation and metabarcoding of the 16S rRNA genes. A collection of 119 bacterial isolates was obtained from one orange tubercle sample, using a range of media in anaerobic and aerobic conditions. The metabarcoding results showed that sulfur and iron oxidisers were more abundant on the outer section of the orange tubercles compared to the inner layers, where Deltaproteobacteria (which includes many sulfate reducers) were more abundant. The microbial communities varied significantly between the inner and outer layers of the orange tubercles and also with the seawater, but overall did not differ significantly between the two steel sheet types. Hence we saw similar microbial communities in orange tubercles present, but different levels of localised corrosion, for two different types of co-located steel sheet piling. Metallurgical analysis found differences in composition, grain size, ferrite-pearlite ratio and the extent of inclusions present between the two steel types investigated.
IMPORTANCE The presence of orange tubercles on marine steel pilings is often used as an indication that accelerated low water corrosion is taking place. We studied the microbial communities in attached orange tubercles on two closely located sheet pilings that were of different steel types. The attached orange tubercles were visually similar, but the extent of underlying corrosion on the different steel surfaces were substantially different. No clear difference was found between the microbial communities present on the two different types of sheet piling. However, there were clear differences in the microbial communities in the corrosion layers of tubercles, which were also different to the microbes present in adjacent seawater. The overall results suggest that the presence of orange tubercles, a single measurement of water quality, or the detection of certain general types of microbes (e.g. sulfate reducing bacteria) should not be taken alone as definitive indications of accelerated corrosion.
Résumé : Biofouling accumulation on synthetic underwater surfaces presents serious economic problem for the marine industry. When a substrate-bonded dielectric elastomer (DE) is subjected to high voltage, deformations in form of creases can be formed at the surface of the DE. This deformation, has been already demonstrated for the prevention and detachment of biofouling from the surface of DEs. In this work, we add sensing capability to the anti-biofouling effect of active DE surfaces. A device consisting of a metallic plate, a Kapton sheet, and a thin silicone membrane is immersed in conductive solution, which acts as one electrode, with the metal plate being the second electrode. Two different conductive solutions were used 3.5 wt% NaCl and 20 wt% NaCl. The surface deformation of the silicone as a function of applied voltage is monitored under microscope in order to verify electrical measurements. Breakdown measurements of the dielectric material in different conductive solutions are also performed. Because the membrane is made from incompressible elastomer and bonded to a rigid substrate, voltages below the creasing threshold create no deformation in the membrane, and therefore no change in capacitance. Above the voltage threshold, creasing instabilities appear at the surface of the silicone, thus increasing the capacitance of the device. Therefore, the capacitance of the sensor is measured as a function of applied voltage, and the voltage at which the capacitance increases is the threshold voltage at which creases occur. Creases are identified when using both 3.5 wt% NaCl and 20 wt% NaCl as top electrode. Theoretical values of creasing voltage deviate from the experimental measurements. Type of conductive solution is shown to have no significant influence on a breakdown voltage.
Résumé : Green Adhesives: Preparation, Properties and Applications deals with the fabrication methods, characterization, and applications of green adhesives. It also includes the collective properties of waterborne, bio, and wound-healing green adhesives. Exclusive attention is devoted to discussing the applications of green adhesives in biomedical coatings, food, and industrial applications.
Résumé : Since the inhibition of organotin as antifouling additives in 2003, many scientists direct their efforts to develop novel environment-friendly marine antifouling additives. This work declares and evaluates the antifouling activity of Nano chitosan capped ZnO nanoparticles against primary biofilm and biofouling. Chitosan nanoparticles were prepared from the shrimp shell obtained, which will be environmentally friendly and will have no adverse effects on the environment's antialgal, antimicrobial and antifungal characteristics. Using co-precipitation method, the present study manages synthesis and characterization of Nano chitosan capped ZnO nanoparticles (NCCZO NPs) and was identified by FTIR, XRD, HRTEM, SEM, EDX, and UV-VIS. NCCZO NPs have been mixed in the prepared formula of inert marine paint. The formulated paints were then brushed twice on PVC panels, hung in a steel frame and immersed in the Mediterranean Sea Eastern Harbor of Alexandria, followed by visual examination and photographic recordings. The findings revealed once 64 days of immersion that (NCCZO NPs) are resistant to tubeworms and barnacles formation due to their functional groups. This inhibition activity was linked to the significant functional groups (hydroxyl and amine) of the NCCZO NPs. The strong antifouling activity makes them promising candidates for new antifouling additives.