Résumé : Offshore marine renewable energy installations (MREI) introduce structure into the marine environment and can locally exclude destructive, bottom tra
Résumé : The wind power industry has experienced rapid growth over the past few decades, but the operation and maintenance costs have become huge challenges to achieve better economic returns and enhance the market competitiveness. In this paper, an opportunistic maintenance strategy for wind turbines considering stochastic weather conditions and spare parts management is proposed. The Markov chain model is adopted to generate wind speed time series and obtain the maintenance wait time owing to weather restrictions. The opportunistic maintenance threshold is a dynamic value related to the wind speed to reduce power generation losses. Moreover, the (s, S) inventory policy, with the reorder stock level s and maximum stock level S , is employed. Numerical examples are used to illustrate the economic advantages of the proposed strategy. Compared with a static opportunistic maintenance strategy and a strategy not considering opportunistic maintenance, the life cycle operation and maintenance cost for the proposed dynamic opportunistic maintenance strategy shows a decline of 10.927% and 18.304%, respectively. The optimal maintenance and inventory strategy is obtained with the decision variables of opportunistic maintenance reliability threshold and reorder stock level, and the effects of various applied parameters are described.
Résumé : Offshore wind turbines and their foundations experience loading from varying directions, yet understanding of the effect of changes in the direction of applied cyclic loading on foundation response remains limited. This study investigates the behaviour of a suction caisson foundation in sand over clay under various types of multidirectional cyclic loading. The findings are significant: although the caisson rotation (or tilt) is affected by changes in load direction, the caisson rotation is less than that in a unidirectional test with the same cyclic load magnitude and symmetry, meaning that a unidirectional test may serve as a conservative estimate of caisson rotation for multidirectional loading. This contrasts with previous findings for monopiles in sand, where prediction of the accumulated displacement based on unidirectional cyclic loading was substantially un-conservative for multidirectional loading. Changes in unloading stiffness due to changes in load direction are slight, varying by an amount that is no greater than the change measured over the course of a unidirectional test. Foundation stiffness and ultimate capacity following multidirectional cyclic loading are largely unaffected, unlike unidirectional cyclic loading, where consolidation of the clay layer improves both the stiffness and capacity.
Résumé : The Ocean has provided a new way in the quest for renewable energy. One potential source of energy is the tidal current. The objective of this paper is to carry out a review of systems for the recovery of tidal energy and its conversion into electricity which represents one of the most interesting renewable energy resources precisely Marines Current Turbine MCT. In the first part of this work, a comprehensive description of marine current is performed, in which the physics of tide, the marine current prediction and the tidal Current Kinetic energy extraction models are given. In the second part, a detailed assessment of various state of art MCT systems (horizontal axis, vertical axis, and oscillating Hydroplane Systems), along with their classification and qualitative comparison, is presented. In the last part of this work, an outline of direct-drive electrical generator topologies is sketched in order to identify suitable generator concepts for direct-drive MCT. The comparison of different generator systems in literature is discussed with the criteria based on the energy yield, cost, weight and maintenance problem.
Résumé : The current study systematically analyzes the impact of solidity (σ) and number of blades (n) on the aerodynamic performance of 2-, 3- and 4-bladed Darrieus H-type vertical axis wind turbines (VAWTs). Solidity varies within the wide range of 0.09–0.36. A large number of operational parameters, i.e., tip speed ratio (λ), Reynolds number (Re), turbulence intensity and reduced frequency (K) are investigated to provide a deeper insight into the impact of σ and n on the dynamic loads on blades, the turbine performance and the wake. High-fidelity unsteady Reynolds-averaged Navier-Stokes (URANS) simulations, extensively validated with experiments, are employed. The results show that the turbine optimal tip speed ratio (λopt) is invariant to a newly-introduced parameter ‘σλ3’, regardless of the turbine geometrical and operational characteristics. In addition, a new correlation is derived to estimate λopt as a function of σ, which can also be employed to predict the optimal σ for a turbine with a given λ. It is also found that: (i) for constant-speed urban VAWTs, which due to the low mean wind speed in the urban environment, frequently operate at moderate to high λ, a relatively-low σ is optimal; (ii) an optimal VAWT is a moderately-high-solidity variable-speed rotor maintaining a relatively-low λ, where due to the large blade chord length the resulting Re and K are favorably high; (iii) within the turbine optimal operational range, turbine power coefficient (CP) is almost independent of n. The present findings support the optimal aerodynamic design of small-to large-scale VAWTs.
Résumé : Early in an offshore wind farm development, the project developer needs to determine which type of offshore wind foundations are suitable to its site. At that stage, only a limited amount of site-specific data is available. However this conceptual study is critical to estimate a preliminary cost target and assess the techno-economic viability of an offshore wind farm at that location.In this context, INNOSEA has developed a user-friendly preliminary design tool for foundations (monopile, jacket and gravity-based foundation) named PREDIN. This numerical software tool is able to perform semi-automatically: the conceptual design, the planning of the installation phase, the cost estimate of fabrication, transport and installation of foundations and substations for sound decision-making. The software features a lean graphical user interface which provides an integrated vision: from foundation design to planning and key cost drivers. PREDIN is adapted for uninitiated users, by providing guidelines and standards values, and for specialist users by enabling a total control of the process.The foundation design methodology is based on a two-step approach: General conception, mainly based on verification of the dynamics of the structure; Local sizing: PREDIN interfaces with a standard structural software from the offshore industry: ANSYS Structural. This two-step approach therefore makes it possible to be able to rapidly iterate on the foundation design.The transport and installation module methodology relies on 4 different functions: Weather Data extraction, Marine Spread selection, Operabilities and T&I planning.The cost estimate methodology is based on a Monte Carlo probabilistic approach, integrating the projects uncertainties in order to generate the probability distribution of the final cost.This study highlights the capabilities of PREDIN software to efficiently deliver a preliminary design and EPCI cost of offshore wind foundations for project developers, relying on extensive metocean, turbine, foundation and cost databases.
Résumé : The global development of the offshore renewable energy sector has been driven by extensive investment and research in the utilization of offshore renewable energies, mainly at the regional level. However, for mid to long-term marine energy development planning, a comprehensive assessment of the global potential for the exploitation of the main offshore resources is required. This work developed and implemented an innovative methodological approach to identify potential zones for wind and wave energy exploitation at the global level, using long-term data series with fine spatial and temporal resolution. The proposed methodology was based on a five-step approach comprised of: (i) a resource assessment, to identify the zones with favorable conditions for energy exploitation; (ii) a structural survivability assessment, to identify feasible areas which would likely ensure the integrity and durability of the wind and wave devices; (iii) a logistics assessment, to evaluate the possibility of carrying out installation, operations, and maintenance activities; (iv) an assessment of the distance to consumer centers, to estimate the feasibility of transmission to the main urban areas; and (v) an estimate of the extractable power of the identified potential zones. For wind power, the United Kingdom (with 1470 TWh/month using a 10-MW turbine) and the United States (1079 TWh/month) were the countries with the highest estimated energy output of the identified potential zones. For wave energy, Brazil and New Zealand presented good opportunities for the development of the wave energy industry, with an estimated extractable power of 372 TWh/month and 286 TWh/month, respectively. The unique preliminary global analysis presented in this work provides guidelines to assist in the development of wave and offshore wind industries, in addition to supporting the management of marine spaces. Moreover, the methodologies can be replicated for other marine activities.
Résumé : An experimental marine current power station has been deployed in So¨derfors, Sweden. It comprises a vertical axis turbine directly connected to a permanent magnet synchronous generator rated at 7.5 kW. The generator is controlled by a Back-To-Back 2L-3L Cascaded H-Bridge full scale bi-directional Power Converter located on shore. This paper presents the ﬁrst test results of the power converter, including grid connection. The startup of the turbine, power extraction and initial active power injection to the grid, at 50 % of rated power, operated as predicted by laboratory experiments and simulations. After 40 seconds of grid connection the safety system disconnect the grid converter due to high currents injected to the grid. The problem is mostly likely associated with the current controller in the dq0 frame. Further tuning of the PI regulators and the potential addition of an anti-windup could mitigate the control issue.
Résumé : This paper addresses a fundamental study of a floating type shrouded wind turbine on the design, mathematical model and motion analysis. Several novel concepts are introduced to the system for cost reduction: a revolute hinge is applied between the tower and the nacelle to maintain the orientation of the nacelle even in a large tower inclination, a swashplate mechanism with cyclic control is employed for blade pitch regulation to improve the system controllability, a novel mooring system with a slewing bearing is utilized to build the passive yawing system, and an advanced spar-type floater is used to obtain high restoring performance with a short spar. Firstly, the design aspects of the main components of the system are given. Then, the numerical model including the structural model, hydrodynamic/aerodynamic model, and the control system is presented. The static and dynamic responses under both the operational situation and survival conditions are finally studied. The paper illustrates the probability of the shrouded wind turbine on floating offshore application, and can provide critical information for the optimization design in next stage.
Résumé : This paper presents the development of an open-source object-oriented program, named OpenMOOR, for static and dynamic analyses of mooring systems in ocean renewable energy applications, including offshore wind turbines and wave energy devices. The program is developed for cross-platform applications. It can be used as a standalone software or a dynamic linking library for developing coupled models of the moored structures/devices. A finite difference model of mooring cables is adopted for solving the motion of a single cable which can deal with the hydrodynamic effect, cable bending/torsional stiffness and nonlinear strain-tension relationship. Parallel computing is implemented for efficient analysis of a mooring system consisting of multiple cables, as common in the practice. OpenMOOR has then applied to analyse a single mooring cable under forced harmonic motions at the top end. The cable responses are found to agree well with the experimental data in the literature, which validates OpenMOOR.
Résumé : Offshore wind farm operations and maintenance costs currently total 6 m€/year, or 25–28% of total costs. For wave and tidal energy converters, this cost is projected to be twice that of offshore wind, but has high levels of uncertainty. As the wave and tidal energy industries mature, decreasing O&M costs through reliability-based design optimization is critical to increasing feasibility and competitiveness with other energy technologies. In this paper, we will synthesize existing information on reliability-based optimization in systems analogous to offshore renewable energy systems. We will conclude by highlighting opportunities for future work in this field.
Résumé : Cost of energy is one of the main reasons why wind power generation hasn’t been able to compete with fossil fuels. However, in the past decade wind energy field has made quite a big leap in making this way of energy generation cheaper and more competitive. As a result, the price of onshore wind energy has already reached the price of fossil fuel power generation. The progress has been made with offshore wind turbine technology as well, however ever increasing energy demand has forced industry to push the limits even further. Attempts are being made to build wind farms further offshore where wind resource is much higher and where more space is available. This on the other side requires new technological development and finding new ways to decrease the cost of energy.<br/>This thesis is a part of a larger project (DOT - Delft Offshore Turbine) which represents one such attempt to make the offshore wind energy much more competitive by combining wind turbine and hydraulic turbine technology. DOT company works on the development of the fluid power transmission in offshore wind turbines, using seawater as medium. The idea is that every wind turbine drives a hydraulic pump. Each turbine thus creates a flow of water under high pressure which is converted to electricity using a Pelton turbine generator. The main objective of this thesis is to identify and try to overcome challenges in design of Pelton turbines for high water pressures, variable flow rates and<br/>seawater conditions. In order to accomplish this objective, theoretical, experimental and numerical approach was used.<br/>Theoretical approach was used to develop a tool for initial Pelton turbine design. Small program was developed in Python programming language which enabled faster and easier turbine dimensioning for any operating conditions based on standard Pelton turbine design procedure. Next, test rig was designed and built as part of the experimental investigation. Test was divided in two phases. Phase I was meant to show the influence of the flow rate, pressure and pressure fluctuations on the development and quality of the water jet. Pressure is measured at the inlet of the injector and flow visualization of the jet was conducted with the high speed camera. Experimental set-up for Phase<br/>II was concluded while performing experimentation has been left out for a future research project. As last step, CFD simulation of the designed model was conducted using Ansys CFX commercial solver and results were presented and discussed.<br/>Although, all three approaches are conducted independently each of them contributed to answering the research questions and giving a better insight in problem definition. Furthermore it helped identifying the differences between the standard Pelton turbine design and the DOT concept. The research brings<br/>us one step closer to making DOT concept a viable sustainable energy solution for the future.
Résumé : Biofouling is the unwanted attachment of organisms and microorganisms to a submerged surface. It is a natural phenomenon that results in negative impacts on man-made industries such as the marine industry, food industry, water treatment among others. Studies have shown that the application of surface topography with varied geometries and sizes have the potential to prevent biofouling. This research aims to assess microtopographies of varied geometries and shape in relation to biofouling control. The size and dimensions of the topographies were kept the same at 150 µm. This research is computational where simulations of flow in three-dimensional (3D) models were performed with ANSYS Fluent, a Computational Fluid Dynamics (CFD) software. With the aid of CFD, simulations of fluid flow in 3D models that consist of surface topographies with varied geometries and defined boundary conditions were conducted. The topographies investigated include pillars, octagonals, cross shaped grooves and square grooves. Hydrodynamic variations of interest that were analysed upon completion of the simulations include wall shear stress and velocity. Analysis of simulations show that the presence of topographies disrupt uniform flow and creates hydrodynamic fluctuations that discourage biofouling settlement. Simulations indicate that the pillars topography would likely have the best antifouling potential because it is the least likely to result in the formation of many vortices and also because shear stresses at the peaks of this topography are the highest among the four investigated topographies.
Résumé : The growing awareness of climate change and the recognised need to secure energy production has been a driving force behind the expansion of the offshore wind industry across the world. Benefits from offshore wind farms (OWFs) may extend further than low CO2 energy production. Wind turbine substructures introduce hard surfaces that are rapidly colonised by epibenthic marine organisms, altering biomass and biodiversity within the local ecosystem. Biodiversity plays a critical role in supporting ecosystem processes and functions that maintain ecosystem services. As offshore wind development continues to grow and modify marine habitats, changes in biodiversity could affect the provision of ecosystem services. In this context, this review sets out to capture the current understanding of epibenthic biodiversity change following the installation of OWFs and attempt to link these changes in biodiversity with marine ecosystem services through the associated processes and functions.
Résumé : Monopiles are the most common type of foundation used for bottom-fixed offshore wind turbines. This investigation concerns the influence of uncertainty related to soil–structure interaction models used to represent monopile–soil systems. The system response is studied for a severe sea state. Three wave-load cases are considered: (i) irregular waves assuming linearity; (ii) highly nonlinear waves that are merged into the irregular wave train; (iii) slamming loads that are included for the nonlinear waves. The extreme response and Fourier amplitude spectra for external moments and mudline bending moments are compared for these load cases where a simpler static pile-cap stiffness and a lumped-parameter model (LPM) are both considered. The fundamental frequency response of the system is well represented by the static pile-cap stiffness model; however, the influence of higher modes (i.e., the second and third modes with frequencies of about 1 Hz and 2 Hz, respectively) is significantly overestimated with the static model compared to the LPM. In the analyzed case, the differences in the higher modes are especially pronounced when slamming loads are not present.
Résumé : The stability of scour protections is, potentially, an important issue during the design of fixed foundations for offshore wind turbines. One of the failure mechanisms observed at placed scour protection around offshore foundations is suction of sediment through the scour protection and subsequent sinking of the scour protection. Incipient motion of sediment and the initiation of suction underneath scour protections around piles in the marine environment were studied under waves, current and combined waves and current conditions. The motion of a thin layer of sediment underneath the scour protection was studied through the glass bottom of the test flume, which provided a clear view of the initiation of the motion of the sediment. The results show that the mobility depends on the Keulegan–Carpenter ( K C ) number for the pile, the ratio between waves and current flow and the ratio between the thickness of the scour protection and the base sediment. The critical mobility number is smaller for the wave-dominated situation compared to current-dominated conditions, which again are smaller than for combined waves and current conditions. Consequently, larger K C -numbers cause larger critical mobility numbers than smaller K C -numbers. Design diagrams are presented for the threshold of incipient motion of sediment underneath a scour protection in waves, current and combined waves and current.
Résumé : This paper considers two methods for determining the local wave particle kinematics and hydrodynamic forces on an idealised wind turbine monopile in the southern North Sea using sea state data at Teesside Offshore Wind farm. An assessment of local flow hydrodynamics is important with regard to safe access of personnel from a crew transfer vessel to a monopile. The hydrodynamic behaviour is calculated using an analytical solution from linear diffraction theory and numerical predictions using OpenFOAM, with both slip and no-slip cylinder boundary conditions. Provided the underlying sea state is unidirectional, it is found that close agreement is obtained between analytical and numerical spectra derived from the time series of local free surface elevation, water particle velocity components, and in-line wave force loading on the monopile. Less satisfactory agreement is achieved with sea states possessing a bimodal spectrum, which suggests that bimodal spectra may not be unidirectional.
Résumé : The fundamental roadblock toward commercial-scale wave power operations is cost. The main objective of this work was to address the cost challenge facing wave energy commercialization through cost-sharing with pile breakwaters to be built for shore protection. This was achieved in this study through a dual-functional wave-power plant for generation of wave-power electricity and protection against coastal erosion for sustainable coastal development. The dual-functional wave-power plant was formed by integrating oscillating-water-column (OWC) devices into a pile breakwater, with each pile being an OWC-pile equipped with a power take-off device. The power extraction efficiency and hydrodynamic characteristics of the dual-functional wave-power plant were measured in a wave flume under various wave conditions. An orifice was used at the top of the pneumatic chamber of each OWC-pile to simulate the power take-off device. To evaluate the performance of the power plant in wave power extraction and shore protection, the surface elevation and pressure inside the OWC chamber, as well as the scattered waves, were measured. It was found that comparing to a standalone OWC-pile device with an identical design and geometric characteristics, an OWC-pile in the dual-functional wave-power plant could achieve significantly larger power-extraction efficiency. Comparing to a pile breakwater with the same dimensions, the wave transmission and reflection of the dual-functional wave-power plant were both weaker, especially the wave reflection, which is beneficial for structure safety and shore protection. Based on the Froude’s law of similarity and an estimation of the effect of air compressibility at full scale, an evaluation of the performance of a dual-functional wave-power plant at full scale was also provided. The findings of this work promote close collaboration between wave-energy utilization community and the shore-protection community for commercial-scale deployment of wave energy converters and contribute to making wave energy economically competitive.
Résumé : In this thesis, a novel smart inspection-ROV is described. The research addresses the need for a highly-capable ROV with abilities to carry out close-quarters inspections of marine renewable energy installations in their inherently challenging environments where strong waves, current and wind are the norm. The use of such an ROV can aid towards the reduction of levelised costs for generating electricity of these MRE devices through maintenance operations and support. The design, fabrication and integration of the inspection-class ROV (I-ROV) are detailed. To ensure that the ROV can operate within the challenging conditions associated with MRE sites it has been designed to be reconfigurable, with options to use different types of thrusters in different configurations. For robust control, the ROV combines a state-of-the-art navigational sensor suite with the enhanced OceanRINGS+ control system. The ROV has also been designed to incorporate fault-tolerant control through the use of active or passive thruster fault detection (FDI) subsystems. The development of all the subsystems within the ROV is documented along with the testing and validation of the full ROV in virtual (simulated) and real-world environments. The agile hardware-in-the-loop (HIL) development and testing of the thruster FDI subsystems are described, with results issued. The thesis concludes with a summary of the work conducted for the research and provides suggestions for future work.
Résumé : Power estimation is the most important task in the performance assessment of wave energy converters (WEC). Depending on the type of WEC, power take-off (PTO) system, and available instrumentation, different approaches are usually applied to assess power from experimental tests. Since neither for tests execution nor for the analyses exist standard methodologies, the estimated power can significantly differ among the approaches, thus, introducing inaccuracies in the assessment of the WEC’s performance. This study analyzed an extensive set of experimental results of a WEC and applied different power estimation approaches to compare and validate the obtained results. The strengths and weaknesses of those methodologies were analyzed and discussed. The major outcomes were: (a) PTO damping characterization based on bench tests can lead to unrealistic values of the WEC’s absorbed power; (b) the hybrid (experimental plus numerical) approach provide more reliable results than the traditional ones; (c) the kinetic energy harvester approach underestimates power but can be useful for preliminary qualitative performance assessments; (d) the new proposed gross efficiency index allows the definition of upper boundaries for wave power conversion as well as the identification of the wave conditions for which WEC performance can be improved.
Résumé : ABSTRACT Measurements at Offshore Wind Turbine (OWT) substructures show that typical loading patterns include overloads, underloads, and shifts in mean stress cycles, due to the everchanging wind direction. These events follow each other in time and
Résumé : The support structure for offshore wind turbines (OWTs) plays significant roles in maintaining the structural stability and reducing the initial cost. An innovative hybrid monopile foundation for OWTs is proposed. The concept has a wider adaptability by using established knowledge to solve for new problems. A series of centrifuge tests is performed to investigate the behavior of this hybrid foundation system in extreme and service conditions. OWTs with the original monopile foundation as well as the wheel-only foundations are tested for comparisons, and two clay profiles are considered. The test results show that the hybrid monopile foundation provides larger ultimate bearing capacities compared to the traditional foundations. Two analytical methods are proposed to estimate the ultimate bearing capacity of this innovative design, and the results are calibrated by the centrifuge tests. In service conditions, the hybrid monopile foundation shows stronger cyclic resistances. Influence factors of the cyclic responses are summarized. An analytical solution is put forward to estimate the accumulated lateral displacement of the hybrid monopile foundation. A degradation factor is suggested based on the results of the centrifuge tests. The study aims to enrich the understanding of the innovative foundation concept and to provide design references for practical applications.
Résumé : ABSTRACT Cyclic loading could lead to progressive degradation of soil in terms of plastic strain accumulation, pore pressure build up and changes in soil strength and stiffness. The present paper outlines an explicit method to predict the accumulate
Résumé : This study aims to reveal the dynamic response and power output characteristics of a floating tidal turbine with prescribed motions in six degrees of freedom. Floater motions were calculated in the time domain based on linear potential theory. Both wave-induced inflow fields and floater motions are considered in a modified blade element momentum theory model for rotor load simulation. Generator power production and loads on a reference tidal turbine system were investigated. The torque and thrust response spectra are found to be dominated by floater-motion-induced contributions, and two response peaks can be clearly identified. A cancellation effect occurs between direct wave effects and floater-motion-induced loads, and horizontal and vertical rotor positions can significantly affect the dynamic responses of the blade loads; the rotor should be placed close to the floater centre to avoid large floater-motion-induced velocity on the blade section. Sensitivity studies are carried out with varying significant wave heights and peak periods. These results may contribute to a general understanding of floater-induced dynamic loads on floating tidal turbines in a random sea.
Résumé : The exploitation of oceans is currently recognized as an abundant, geographically diverse and renewable source of energy which still remains largely untapped. Marine currents are, together with waves, one of the most promising sources of ocean energy thanks to their enormous potential for electricity production and their high predictability. Owing to the fact that the marine current harnessing industry has only just begun to demonstrate full-scale devices and device arrays, most of the research papers related to marine current harnessing technologies have been focused on improving their technical aspects. However, there is limited information as regards other aspects, such as those of an economic nature, that should be studied in detail in order not to compromise the future of these technologies. The objective of this research is to address this gap by providing an economic-financial methodology that will help quantify the profitability and feasibility of these renewable energy projects. The methodology developed considers the following aspects: (i) a definition of the fundamental variables of the economic model. (ii) a definition of its financing structure on the basis of the industry's common stockholder equity that partners must provide and the estimation of bank financing needs; (iii) a definition of the main components required to obtain the forecast balance, the forecast income statement and the forecast sources and application of funds for the entire service life of the project; (iv) a determination of the cost-benefit analysis, carried out using the information provided in the cash-flows of the project and the forecast sources and application of funds; (v) an analysis of the most important economic-financial ratios of the model and; (vi) the realization of a sensitivity analysis, with the aim of detecting business risks when fundamental variables of the model, such as investment, the annual energy production, the price of energy or the percentage of loan requested, among others, oscillate. The proposed model has been applied to a case study, after which it was found to provide a good profitability for the project and the stakeholders. The results also indicate that the variables that most affect the profitability of the project are the interest rate, the price of energy and the annual energy produced.
Résumé : This paper describes the state-of-the art in the area of underwater robot manipulator systems. A brief introduction is given on the use of manipulators in various offshore industries for different subsea intervention applications. It provides a comprehensive summary of existing commercial and prototype underwater manipulators, covering relevant aspects such as design features, their capabilities and merits, and provides a detailed comparison. This is followed by a thorough analysis of advantages and disadvantages of both electrically and hydraulically actuated manipulators. Furthermore, a detailed description of commercially available underwater manipulator control systems is presented in order to provide a realistic picture of the existing technology and its limitation. In addition, an extensive bibliography covering research results in the field of control algorithms is presented, including low level motion control, high level kinematic control and motion planning schemes along with the implementation issues.
Résumé : The new type of foundation which comprises a monopile and a friction wheel is an innovative solution for offshore structures subjected to large lateral loading and has not been extensively investigated. In this paper, two types of friction wheels, namely the solid wheel and gravel wheel, are integrated to a monopile respectively to perform as hybrid foundations. The hybrid foundations are examined under lateral loading via centrifuge tests and three-dimensional finite-element (FE) analysis. The results show that the introduction of the wheel significantly enhances the lateral bearing capacity and stiffness of the monopile. By means of FE analysis, the load transfer mechanism and interaction between the foundations and soils are illustrated to study how the solid wheel and gravel wheel contribute to the performance of the foundation system. Finally, parametric studies about the geometry of the foundations and loading conditions are carried out, which can be used as references for the preliminary design of the monopile-friction wheel foundation.
Résumé : The efflux velocity is the basis for the prediction of turbine wake. A novel energy coefficient is defined to propose a new theoretical equation to predict the efflux velocity of tidal current turbine in this paper. Several CFD cases with different tip speed ratio and solidity is conducted using the DES-SA model. In order to overcome the limitations of the axial momentum theory, the effects of tip speed ratio and solidity on the efflux velocity are studied and the energy coefficients with different tip speed ratio and solidity are determined using the proposed equation based on the CFD results. Several semi-empirical efflux velocity equations are finally proposed by fitting the equation of the energy coefficient with tip speed ratio. The application of these equations in the prediction of wake flow and the power calculation of tidal turbine are also introduced in this paper.
Résumé : Preventive maintenance of wind turbine can effectively improve the reliability of wind turbine. This paper firstly set single component reliability of wind turbine as constraint condition, single component minimum unit time maintenance cost as objective function to obtain optimal maintenance cycle and maintenance times. On this basis, repairing component which meet certain conditions, then build opportunistic maintenance model of wind turbine. Lastly, set the minimum total cost under opportunistic maintenance as objective function, the wind turbine availability as constraint condition, then solve this model to obtain optimal threshold of opportunistic maintenance and minimum total maintenance cost using genetic algorithm. The example analysis shows that the model can effectively save the total maintenance cost. This study has some reference significance for the maintenance department to make the maintenance plan.
Résumé : Tidal energy exploitation is at an early deployment stage and costs need to be reduced to improve the long term economic viability of the sector. High costs of tidal turbines are, in part, the result of load uncertainties, which lead to the use of high factors of safety in the design to ensure survival. One of the most important causes of uncertainty is hydrodynamic loadings. To date, most of the scaled model experiments with horizontal axis turbines investigating this issue have been carried out with collinear wave and current directions. To the authors’ knowledge, the work presented herein is the first experimental investigation of a horizontal axis turbine model subjected to combined oblique waves and current. Turbine performance and loading are measured for a 1:15 scale model tested in the FloWave circular, combined wave and current basin at the University of Edinburgh (UK). Three different flow directions were tested and each of them were also combined with regular waves in three different directions non-collinear with the flow. Fifteen physical quantities were measured including flow velocity, rotor and foundation loads and turbine speed. Characterisation of loads and turbine performance in those oblique current and wave conditions are presented. Waves affect means and standard deviation of rotor power and thrust, but off-axis waves are associated with lower thrust loads than head-on waves. Compared to current only, rotor torque and thrust standard deviations are higher in the presence of waves and almost twice as high when the wave crest is parallel to the rotor plan.
Résumé : AbstractIn recent decades, the globally demand for renewable energy has continued to enhance, even with contrary economic conditions such as trade disputes, world economic recessions and falls in gas and oil prices. The potential of producing electric power from marine renewable energy is massive. Marine waves are being very familiar as a renewable resource to be exploited for the sustainable generation of electrical power. The expectable resource features style ocean waves and tides chiefly attractive for power generation and beneficial when comparing to other sources of renewable energies. The proposed review will specifically highlight the main wave energy conversion projects around the world. The wave and tidal energy is having more and more support and interest as an auspicious renewable resource to replace part of the energy supply, although it is still immature compared to other renewable technologies. This work presents a complete analysis of the wave energy technology, starting with the characterization of this global resource in which the most suitable places to be exploited are displayed. The given paper discusses a complete review of wave and tidal energy technologies.Keywords: tidal, Marine, wave energy, tidal energyCite this ArticleRashmi Singh. Recent Trends in Wave and Tidal Current Energy: A Review. Journal of Offshore Structure and Technology. 2018; 5(1): 30–33p.
Résumé : Fatigue is a common issue in steel structures such as wind turbine towers, which is caused by cyclic wind and wave excitations. Therefore, estimation of the remaining fatigue life of the structural and foundation system is of concern. For this purpose, continuous monitoring of the structure is necessary to obtain strain data at fatigue critical points. Since installing and maintaining strain sensors in critical underwater location is difficult, strain data is often available only from a few sensors at accessible locations. Using these sparse sensors, the strain time histories at fatigue critical points can be estimated using estimation techniques. These techniques can identify the structural system using limited measured response data and a system model. In this paper, we implement a model updating approach followed by modal expansion to estimate the strain time history at critical points in a numerical case study representing an offshore wind turbine tower. The acceleration response of the structure is simulated using a finite element model and polluted with Gaussian white noise to represent measurements. The measurements are then used for model updating and strain estimation. The accuracy of the methods and their robustness to the measurement noise and model uncertainty are investigated. The estimated strain response time histories can later be used as input to an appropriate fatigue damage model to estimate the current state of fatigue damage in the system.
Résumé : Loin du monde du silence, le milieu marin doit se concevoir comme un environnement sonore. L’océan est porteur de bruits d’origine physique (vagues, pluie, glace, séismes) et biologiques (chant des baleines, clics des dauphins, claquements de crevettes ou d’oursins). Ce paysage acoustique est essentiel pour la faune marine. Il participe, entre autres, à l’orientation des larves, à la communication des animaux entre eux, à la détection de prédateurs. Toutefois, depuis un peu plus d’un siècle, les activités humaines modifient grandement ce paysage acoustique. Les bruits d’origine anthropique proviennent des navires, des installations posées en mer, des sonars et plus récemment de l’utilisation des énergies marines renouvelables. La faune marine perçoit-elle ces nouveaux sons ? La question de l’impact des sons anthropiques sur la faune marine se révèle un enjeu écologique et économique majeur pour les années à venir. Les auteurs montrent la diversitéde leurs effets sur la faune grâce à une approche multidisciplinaire associant la physique, la réglementation, la biologie et l’étude d’impact ; une place particulière est donnée aux premiers retours d’expérience de production d’énergies marines renouvelables (EMR) en Europe. Cet ouvrage se veut un premier état des lieux d’un champ de recherche qui ne fait que commencer.
Résumé : The aim of this study is to present, compare and improve the options of power
transmission for tidal current arrays. The potential to generate low or zero carbon
power from the world’s tides is increasing as technology moves forward. The
technically available tidal current energy resource, the resource that can be captured
using existing technology, in the United Kingdom can supply a significant amount of
the UK electricity demand. Even though tidal current devices have similarities to
offshore wind turbines in many aspects, a number of characteristics differentiate the
approach needed regarding power transmission and drive-train design. Some of these
characteristics are: predictable direction and speed of the tidal current, predetermined
available area in a tidal channel, less swept area due higher density of water,
continuous underwater operation and smaller distances to shore.
This thesis is based on the hypothesis that tidal current energy can be harnessed using
today’s technology in an efficient manner. Technology progression never stops and as
new materials and methods become available the cost of utilising tidal current energy
will drop in the years to come. However, the research question that has to be asked is
whether using today’s technology tidal arrays can be an alternative source of electrical
In order to respond to this research question electromechanical models of tidal current
devices have been developed in detail, from resource to the grid connection, using
mathematical linear and non-linear programming in MATLAB/Simulink. The tidal
models developed include the tidal resource, the tidal turbine with pitch control, geared
induction and synchronous generators, the power electronics with the generator
controller, the grid side controller, the cables for power transmission, the filters and
the grid connection. All the modelling aspects of this study are presented in Chapter
3. Single tidal current devices were compared using different generator technologies,
squirrel cage induction generator or permanent magnet synchronous generator, and
different location of the power converters, in the nacelle near the generator or many
kilometres apart from the generator. Regarding the generator technology, results
showed that even though differences are minor, the permanent magnet synchronous
generators are more efficient. Regarding the location of the power converters results
showed that positioning the power converters in the nacelle always yields fewer
electrical losses but component accessibility is minimised due to the underwater
operation of the tidal current device.
A key focus aspect of the study is the power transmission option with onshore
converters which is presented in detail. Using this concept it is possible to generate
electricity from tidal current devices but at the same time keep the highest possible
system reliability despite the continuous underwater operation. This concept has been
used in the first demonstration tidal current arrays developed by Andritz Hydro
Hammerfest. What is more, data provided by Andritz Hydro Hammerfest were utilised
in order to validate the simulation models. In this study a step forward is taken
regarding the concept of keeping the converter dry and controlling the tidal current
generator from afar. An algorithm is developed to design power harmonic filters for
systems that use long distance controls. Power harmonic filters allow the long distance
control system to operate reliably under all conditions but generate significant
electrical losses. The power harmonic filter design algorithm presented in this thesis
estimates the exact filter parameters so that the filter ensures maximum system
reliability and generate minimum possible losses. In addition tidal array topologies
using this concept are developed.
The final part of this thesis compares a number of different tidal array topologies based
on resource to grid efficiency and component accessibility for maintenance. Results
showed that when tidal current devices are clustered per four turbines on offshore
platforms it is efficient to use as many clusters as possible connected to a single cable
whose both ends are connected to the grid. Locating the power converters in the nacelle
yields fewer electrical losses compared to locating the power converters on the
offshore platform. However, the difference is minimised because the distance between
the tidal current device and the offshore platform is the least possible. Having the
power converters on an offshore platform is beneficial in terms of accessibility for
maintenance and operation because they are not underwater. The results and the
methodology from this thesis can be extended to other offshore renewable energy
systems such as the wind and wave. In addition, this study can be used as a stepping
stone for decision making by tidal current developers.
Résumé : The present invention relates to a method of correcting rotor imbalance and a wind turbine thereof. The correction method comprises measuring the vibrations within at least one time window and determining an imbalance factor and an imbalance phase. The values of the parameters in the equation for calculating the correction action are then updated based on the imbalance factor and an imbalance phase. A correction angle for each of the wind turbine blades is calculated using these adjusted parameters. The correction angle is used to aerodynamically balance the rotor, and a model may be used to determine the initial values of the parameters. Another imbalance factor and imbalance phase is determined based on another set of measurements. This imbalance factor is then used to calculate a mass moment for correcting the mass imbalance in the wind turbine blades. The weight and location of a balancing mass is finally calculated based on this mass moment and installed in the respective wind turbine blades.
Résumé : This paper describes the setup and some results of an accelerated life testing study of a tidal turbine blade attachment, which involved high-cycle fatigue testing of a tidal turbine subsystem at the Large Structure Laboratory of the National University of Ireland Galway (NUI Galway). Tidal turbines are in an early stage of development, which implies that there is no standard design and many different approaches are emerging in the market. The subsystem described in this paper is a 3/8 scaled down part of a 10-blade hubless turbine, developed by OpenHydro, a company specialising in the design, manufacture, installation, and maintenance of marine turbines generating renewable energy from tidal streams. The subsystem consists of a blade and a sector of the rotating ring. The sample was installed on an existing 10 m × 6 m × 6 m reconfigurable test frame and was loaded with a servo-hydraulic actuator controlled by an advanced software system, which allowed for an accurate sinusoidal load-controlled high-cycle fatigue test. The sample was loaded at four different levels to accumulate damage representative of a typical tidal turbine deployment life. The main objective of the test was to analyse the structural behaviour of the attachment system solution (blade-rotating ring) under fatigue load, particularly the internal structural welds, and to validate previously developed numerical models. To address all the requirements and to obtain valuable data, a large experimental test was set up. A total of 110 channels in a multi-channel data acquisition system were used to simultaneously acquire strain, displacement, and load data. Accurate measurements of temporal deformations and movement in a 3D field at the rear side of the ring were also acquired using a Digital Image Correlation system. The mechanism of failure was expected to be fatigue crack propagation at locations pre-determined in a structural analysis of the system.
Résumé : Corrosion degradation was observed in a nuclear power plant spent fuel cooling system. A systematic and comprehensive investigation program was developed to reveal the root cause of the degradation. Series of corrosion tests, mechanical, microstructural and microbiological investigations were carried out. Also, simulations of the operating conditions and welding parameters were performed. Based on the results, the major contributors to the degradation process were identified and a possible degradation mechanism was proposed.
Résumé : Steel corrosion is a global problem in marine engineering. Numerous inhibitory treatments have been applied to mitigate the degradation of metallic materials; however, they typically have a high cost and are not environmental-friendly. Here we present a novel and “green” approach for the protection of steel by a marine bacterium Pseudoalteromonas lipolytica. This approach protects steel from corrosion in seawater via the formation of a biofilm followed by the formation of an organic-inorganic hybrid film. The hybrid film is composed of multiple layers of calcite and bacterial extracellular polymeric substances, exhibiting high and stable barrier protection efficiency and further providing in situ self-healing activity. The process involving the key transition from biofilm to biomineralized film is essential for its lasting anti-corrosion activity, which overcomes the instability of biofilm protection on corrosion. Therefore, this study introduces a new perspective and an option for anticorrosion control in marine environments.
Résumé : In this work, microbiologically influenced corrosion (MIC) of an X52 pipeline steel in thin layers of simulated soil solution in the presence of sulfate-reducing bacteria (SRB) under a disbonded polyethylene coating was investigated. The steel MIC depends heavily on the thickness of the solution layer. In the present testing system, there exists a critical solution layer thickness, i.e., 150 μm, where a maximum corrosion rate is reached. Pipeline corrosion in thin layers of solution containing SRB trapped under disbonded coating is resulted from the synergism of MIC and the film formation on the steel surface.
Résumé : Purpose
The purpose of this study is to investigate microbial influenced corrosion of steel because of iron oxidizing bacteria (IOB).
Carbon steel was selected for this study. Winogradsky media was used for isolation of IOB and as test solution for corrosion measurements. Electrochemical tests and immersion test were conducted to estimate the corrosion rate and extent of pitting. The corroded surface was analysed by SEM and corrosion products formed over the metal surface were identified by XRD and Fourier transformed infrared. Biofilm formed over the corroded metal was analysed by UV-visible spectroscopy for its extracellular polymeric substances (EPS) constituents.
Presence of IOB in Winogradsky medium enhances corrosion. Uniform and localized corrosion increases with increased bacterial concentration and EPS constituents of the biofilm. Iron sulphite formation as one of the corrosion products has been suggested to be responsible for increased corrosion attack in the inoculated media in comparison to control media where corrosion product observed is iron hydrogen phosphate which is protective in nature.
This work correlates increased corrosion of steel in the presence of bacteria with the nature of corrosion products formed over it in case of IOB. Formation of corrosion products is governed by various electrochemical reactions; hence, inhibition of such reactions may lead to reduce or stop the formation of such products which enhances corrosion and thereby may reduce the extent of microbial induced corrosion
Résumé : At present, most Microbiologically Influenced Corrosion (MIC) models used in the petroleum industry are risk based, and predict the likelihood of MIC. It is imperative that the industry adopts mechanistic models to accurately quantify MIC in pipes/facilities. This paper summarizes the findings of a literature review of mechanistic MIC models available in the public domain. The results indicated that most of the models reviewed consider Sulphate Reducing Bacteria (SRB) as the main players in MIC, and very few models consider biofilm formation and transport phenomena. Furthermore, no models were found to accurately correlate sessile and planktonic bacteria.
Résumé : The influence of aerobic halophilic archaea Natronorubrum tibetense on the corrosion of Q235 carbon steel was investigated. In immersion tests, more serious corrosion was observed in the N. tibetense-inoculated medium than in the sterile medium. Compared with the uniform corrosion morphologies in the sterile medium, severe localized corrosion occurred in the inoculated medium. After 14 days of immersion, the presence of N. tibetense caused a weight loss of 0.051 g/cm2 of the steel, which was about two times larger than that in sterile medium (0.026 g/cm2). The starved N. tibetense exhibited more aggressive MIC against the steel when organic sources were deficient.
Résumé : The large number of metallic systems developed for last few decades against both general uniform corrosion and localized corrosion. Among all microbiological induced corrosion (MIC) is attractive, multidisciplinary and complex in nature. Many chemical processing industries utilizes fresh water for fire service to nullify major/minor fire. One such fire water service line pipe attacked by micro-organisms leads to leakage which is industrially important from safety point of view. Also large numbers of leakage reported in similar fire water service of nearby food processing plant, paper & pulp plant, steel plant, electricity board etc...In present investigation one such industrial fire water service line failure analysis of carbon steel line pipe was analyzed to determine the cause of failure. The water sample subjected to various chemical and bacterial analyses. Turbidity, pH, calcium hardness, free chlorine, oxidation reduction potential, fungi, yeasts, sulphide reducing bacteria (SRB) and total bacteria (TB) were measured on water sample analysis. The corrosion rate was measured on steel samples and corrosion coupon measurements were installed in fire water for validating non flow assisted localized corrosion. The sulphide reducing bacteria (SRB) presents in fire water causes a localized micro biological corrosion attack of line pipe.
Résumé : This review evaluates the analytical methods used for detecting microbiologically influenced corrosion (MIC), which is an aggressive microbiota-facilitated degradation of engineering materials, and discusses their advantages and limitations. The challenges presented by the lack of a comprehensive mechanistic understanding on MIC detection, which include the need to use a combined array of morphological, chemical, electrochemical and biological characterization for MIC detection, are thoroughly discussed using multiple case studies from the literature. The paradigm shifts and research necessary for the early and real-time monitoring of MIC are presented.
Résumé : The influence of sulfate-reducing bacteria (SRB) on the corrosion of L245NS carbon steel was investigated in a medium containing H2S by various surface characterizations and electrochemical measurements. The addition of H2S will totally inhibit the planktonic SRB in the medium. However, the sessile SRB in the corrosion crust can survive under the protection of the biofilm. Pitting corrosion is found under the corrosion crust, which is caused by the sessile SRB. The pitting corrosion rate is 1.1 mm/a. Additionally, the corrosion rate increases with the corrosion time. The SRB influenced corrosion mechanism of the steel is discussed.
Résumé : One of the cause of corrosion is the attachment of bacteria or commonly called as bio-corrosion or Microbial Influenced Corrosion (MIC). This aim of the research was to determine effect of heat treatment process on the bio-corrosion rate of API 5L steel. The treatments were namely, without heat treatment as a control, and with the heat treatment (austempering process). The austenizing process was conducted before the austempering process. All specimens without and with the heat treatment were be used on bio-corrosion test. The bio-corrosion testing was conducted with immersion corrosion test method with artificial seawater salinity of 35‰. Three of species bacteria were be used, Escherichia coli, Pseudomonas fluorescens, and Thiobacillus ferrooxidans. The result showed the corrosion rate on API 5L steel without bacteria was 2.7558 mpy, but it reached 3.4273, 3.6062 and 3.7699 mpy after addition with E. coli, P. fluorescens, and T. ferrooxidans, respectively. It was indicating that bacteria can accelerate the corrosion rate. The highest bio-corrosion rate due to T. ferrooxidans without heat treatment process was 3.7699 mpy. Meanwhile, the bio-corrosion rate due to T. ferrooxidans with austempering process was 3.5046 mpy. It was indicating that heat treatment can decrease the bio-corrosion rate.
Résumé : Cu corrosion by Desulfovibrio vulgaris, an example of sulfate reducing bacteria (SRB), was investigated. D. vulgaris was first pre-grown in full-strength ATCC 1249 medium with coupons for three days. Then, the medium was switched to fresh media with decreased levels of carbon source. Unlike microbiologically influenced corrosion (MIC) of carbon steel by D. vulgaris, carbon starvation reduced Cu corrosion during the additional seven days of incubation. Experimental data and a thermodynamic analysis indicated that Cu MIC by SRB was caused by secreted sulfide rather than by electron harvesting for energy production, unlikely in the carbon steel MIC by SRB.
Résumé : Herein, a schematic model was established to assess the combined effect of deposited CaCO3 and thermophilic sulfate-reducing bacteria (SRB), at high CO2 and low O2 dissolution levels on the corrosion behavior and growth of corrosion scale on X65 pipeline carbon steel. Field emission scanning electron microscopy, energy-dispersive spectrometry, X-ray diffraction, confocal laser scanning microscopy, open circuit potential, and electrochemical impedance spectroscopy were used to characterize the corrosion pattern of water injection pipe. The results showed that a synergistic effect exists between CaCO3 and thermophilic SRB, both uniform and localized corrosion of CaCO3-coated X65 steel were promoted when inoculated with SRB. The corrosion process was comprised of three stages depending on the metabolism of SRB.
Résumé : Here, a heterogeneous Bacillus cereus (B. cereus) biofilm on the surface of 316 L stainless steel (SS) was observed. With electrochemical measurement and surface analysis, it was found that B. cereus biofilm could inhibit SS pitting corrosion, attributing to the blocking effect of bacterial biofilm on extracellular electron transfer (EET). Differential pulse voltammetry (DPV) and cyclic voltammetry (CV) results also showed that B. cereus biofilm clearly impeded the EET. The proposed mechanism for the decreased corrosion rates of SS involves the interactions of extracellular polymeric substance (EPS) with SS and biofilm formation blocking electron transfer, preventing the passive layer from destroying. After biofilm formation following initial attachment of cells and EPS, electron transfer between SS and the cathodic depolarizer (oxygen) was hindered.
Résumé : Mature sulfate reducing archaeon (Archaeoglobus fulgidus) biofilm at 80 °C was found more corrosive against C1018 carbon steel under organic carbon starvation. After 3-day pre-growth in enriched artificial seawater medium (EASW), C1018 coupons with biofilms were placed in fresh EASW with reduced carbon source levels for an additional 7 days of incubation. Coupon weight losses were 0.9 mg/cm2, 2.0 mg/cm2 and 1.4 mg/cm2 for this subsequent 7-day starvation period, corresponding to 0%, 90% and 100% carbon source reductions, respectively. Electrochemical tests corroborated the weight loss data, providing evidence for the utilization of elemental iron as electron donor through extracellular electron transfer.
Résumé : This chapter focuses on the various approaches to combat biofouling/biocorrosion. First, we present the vastness of the problem, along with known mechanisms of biofouling. This is followed by numerous molecular approaches (such as a surface assembled monolayer) to affect a biocidal substrate surface. Various measurement techniques, such as fluorescence labeling followed by microscopy AFM, XPS, SEM, etc.), along with standard electrochemical corrosion rate techniques to monitor surface microbiological fouling and its control are discussed with multiple case studies.
Résumé : Microbiologically influenced corrosion (MIC) is a big threat to the strength and safety of many metallic materials used in different environments throughout the world. The metabolites and bioactivity of the microorganisms cause severe deterioration on the metals. In this study, MIC of pure Ti was studied in the presence of a highly corrosive aerobic marine bacterium Pseudomonas aeruginosa. The results obtained from electrochemical test showed that Ti was corrosion resistant in the abiotic culture medium after 14 d, while the increased corrosion current density (icorr) obtained from polarization curves and the decreased charge transfer resistance (Rct) from electrochemical impedance spectroscopy (EIS) indicated the accelerated corrosion of Ti caused by Pseudomonas aeruginosa biofilm. For further confirmation of the above results, the surface of Ti was investigated using scanning electron microscopy (SEM), confocal laser scanning microscopy (CLSM) and X-ray photoelectron spectroscopy (XPS). According to the XPS results, TiO2 was formed in both abiotic and biotic conditions, while unstable oxide Ti2O3 was detected in the presence of Pseudomonas aeruginosa, leading to the defects in the passive film and localized corrosion. Pitting corrosion was investigated with the help of CLSM, and the largest pit depth found on Ti surface immersed in Pseudomonas aeruginosa was 1.2 μm. Ti was not immune to MIC caused by Pseudomonas aeruginosa.
Résumé : Microbiologically influenced corrosion (MIC) is a major concern in a wide range of industries, with claims that it contributes 20% of the total annual corrosion cost. The focus of this present work is to review critically the most recent proposals for MIC mechanisms, with particular emphasis on whether or not these make sense in terms of their electrochemistry. It is determined that, despite the long history of investigating MIC, we are still a long way from really understanding its fundamental mechanisms, especially in relation to non-sulphate reducing bacterial (SRB) anaerobes. Nevertheless, we do know that both the cathodic polarization theory and direct electron transfer from the metal into the cell are incorrect. Electrically conducting pili also do not appear to play a role in direct electron transfer, although these could still play a role in aiding the mass transport of redox mediators. However, it is not clear if the microorganisms are just altering the local chemistry or if they are participating directly in the electrochemical corrosion process, albeit via the generation of redox mediators. The review finishes with suggestions on what needs to be done to further our understanding of MIC.
Résumé : Microbiology Australia, bringing Microbiologists together
Résumé : The worst nightmare of the oil and gas industry which must not be taken lightly is the issue of corrosion which affects the pipes used for transportation of oil and gas. Corrosion problems need to be properly understood in order to prescribe the necessary kind of treatment that will ensure a long life span for the
pipeline. This paper gives a comprehensive review of corrosion problems in API 5L steel pipeline and the ways to mitigate the corrosion problems. Proper control and prevention of corrosion in API 5L steel would ensure long life span of the pipe, uninterrupted flow of products, reduction in shutdown time and generate more revenue for the industry. Oil and gas materials last longer when both inhibitors and protective coatings are used together or when protective
coating is used together with cathodic protection
Résumé : Iron (Fe)- and manganese (Mn)-oxidizing bacteria are often cited individually and collectively as putative microorganisms for microbiologically influenced corrosion (MIC). The two groups of microorganisms have in common the ability to attach to surfaces and produce macroscopic accumulations (deposits) of metal oxides/hydroxides/oxyhydroxides that can influence corrosion of some metals and alloys in some environments. In all cases, once initiated, the corrosion is independent of the activities of the colonizing species. Despite the phylogentic diversity of Fe-oxidizing bacteria the following sections will deal with corrosion mechanisms attributed to neutrophilic, lithotrophic, microerophilic Fe-oxidizing bacteria (FeOB). The mineralogy of biologically oxidized Fe is consistent over a wide range of environments. All FeOB produce dense deposits that can cause corrosion of low alloy stainless steels directly, i.e., under deposit corrosion. Association of MnOB and other microorganisms may stabilize the under deposit corrosion on low alloy stainless steels. The influence of FeOB on the corrosion of carbon steel may be related to deposition of metal ions, causing galvanic corrosion or association with other corrosion-causing microorganisms. All MnOB produce manganese oxides that are strong naturally-occurring oxidizing agents that can cause ennoblement of low alloy stainless steels and increase corrosion currents on carbon steel in fresh water. Corrosion associated with manganese deposits depends on the relationship between the mineral deposit and the substratum.
Résumé : Concrete structures develop biofilms when exposed to various environments. At a certain stage, the microbial films destroy the concrete structures leading to significant deterioration. Culture-dependent techniques give an incomplete picture of the microbial communities on the concrete surface. Culture independent techniques or molecular biological tools pave a new way to analyze microbial communities involved in concrete biodeterioration. This study highlights the need to ‘build’ a database, for Microbiologically Influenced Concrete Corrosion (MICC) involving microbial groups that are being identified using culture dependent and independent techniques. The role of molecular tools such as 16S rRNA sequencing, denaturing gradient gel electrophoresis (DGGE), Fluorescent in situ hybridization (FISH), Real time Polymerase Chain Reaction (RT-PCR), microarray analysis, 2-Dimensional gel electrophoresis (2-DE) in analyzing microbial communities on the concrete structures have been reviewed in this paper.
Résumé : The corrosion mechanism of a 2205 duplex stainless steel (DSS) in Pseudomonas aeruginosa inoculated medium was investigated using the information of electrochemical current noise (ECN) transients derived from Hilbert spectra and surface analysis. The pit depths from confocal laser scanning microscopy (CLSM) were analyzed stochastically. Results showed that metastable pitting and stable pitting occurred simultaneously, and they were controlled by different mechanisms in the presence of P. aeruginosa. Metastable pitting occurred in the region uncovered by P. aeruginosa unlike stable pitting. P. aeruginosa likely dissolved the passive film and produced soluble CrO3, leading to stable pitting.
Résumé : To explore how a succession of bacteria grown on steel coupons in a marine environment can influence their corrosion process, we designed a microcosm in laboratory to evaluate corrosion kinetics and microbial diversity over 30 days. The results described a clear influence of corrosion by a succession of different bacterial groups. During the initial period, 2–7 days, a sharp increase in the rate of corrosion was detected accompanied by the presence of Alteromonadaceae, Vibrionaceae, Oceanospirillaceae, Rhodobacteraceae, Rhodospirillaceae and Flavobacteriaceae bacteria families. After 15 days, representatives of families Piscirickettsiaceae and Pseudomonadaceae were also described, accompanied by a continuous corrosion process over the coupons. After 30 days, there was a sudden change in the profile of the bacteria present on the steel coupons, with a prevalence of Halomonadaceae family species, and establishment and continuity of the corrosion process by the biofilm grown on the coupons. The results describe differences in microbial diversity over the time, highlighting certain bacterial lithotrophic species that persisted for most of the experiment, through a complex association between bacteria and metal surfaces, which can be a new starting point for development and maintenance of a favorable microenvironment to accelerate corrosion processes.
Résumé : Influence of the surface characteristics of three stainless steels (SS304, 316L and 317) and presence of scale inhibitors on adhesion kinetics of sulfate reducing bacteria (SRB) in circulating cooling water, were investigated by evaluating surface free energy, adhesion kinetic constants in a parallel plate flow chamber. Results show that the surface free energy values of SS317, SS316L and SS304 are −31.69, −24.18 and −13.92 mJ m−2, respectively. SS317 surface had higher surface hydrophobicity than SS316L and SS304. In the process of bacteria cells adhesion onto SS surfaces, electrostatic interaction for SS is slightly more than hydrophobic interaction. The number of adhering bacteria and the adhesion kinetic constants are different on the three types of stainless steel. The adhesion kinetic constants for SS317 and 316L are greater than that for SS304, which are 0.0354, 0.0282 and 0.0190 min-1, respectively. Scale inhibitors of hydrosy ethyl fork phosphonic acid (HEDP) and phosphono butane-1, 2, 4-tricarboxylic acid (PBTCA) have a certain influence on the initial adhesion of bacteria cell and adhesion kinetics constants are reduced in the presence of HEDP and PBTCA.
Résumé : Microbiologically influenced corrosion is a serious type of corrosion as approximately 20% of the total economic losses. Sulfate reducing bacteria and Iron oxidizing bacteria are one of the typical representatives of the anaerobic and aerobic bacteria, which are ubiquitous in natural environments and corrode steel structures. Cathodic polarization has been recognized as an effective method for preventing steels from microbial corrosion. Although cathodic polarization method has been widely studied, the specific properties of cathodic current that influences the bacterial removal and inactivation remained largely unclear. This review is to show the main effects of Sulfate reducing bacteria and Iron oxidizing bacteria on metal decay as well as the inhibition mechanism of cathodic polarization in the study of bio-corrosion.
Résumé : ABSTRACT Sampling of pigging debris was performed from three multiphase pipelines that previously were exposed to microbiologically influenced corrosion (MIC) due to high abundances of sulfate-reducing prokaryotes (SRP) and methanogens. Sampling was
Résumé : ABSTRACT Microbiologically Influenced Corrosion (MIC) is a complex form of materials degradation caused by the biological activity of microorganisms such as bacteria, archaea and fungi. It is typically characterized by the presence of microbiologica
Résumé : ABSTRACT There is a wide range of opinions about the proper method of corrosion control, including the need for cathodic protection, tight bonded coating and polyethylene encasement for ductile iron pipe. While polyethylene encasements are commonly
Résumé : ABSTRACT API-RP38 culture medium was used to culture sulfate SRB isolated from an oilfield wastewater sample. SRB test bottle method was used to verify bacterial activity, and SEM was employed for identifying the microbial morphology. Corrosion beha
Résumé : This work aimed to identify microbial colonization and biocorrosion in welded seam areas of API 5 L X65 carbon steel, since microorganisms are ubiquitous and there is a lack of information on their biological and electrochemical interactions with these structures. In the present study, polished and unpolished welded coupons prepared by shielded metal arc welding were assayed to identify the effect of surface roughness and local changes in the metal microstructure on microbial colonization. Experiments were performed in glass cell vessels with fresh and sterile seawater to establish the presence or absence of microorganisms. For comparison, nonwelded coupons were simultaneously tested as a control. On the 15th day, both polished and unpolished welded coupons and the nonwelded coupons immersed in fresh seawater showed microbial colonization, though the corrosion products were more abundant for the welded coupons. Nevertheless, unpolished welded coupons showed a higher predominance of pitting around the beads than polished coupons. These results suggest that filler material creates conditions more favorable for biofilm development, thus intensifying the localized corrosion on the welds. It can be concluded that adhesion and subsequent biocorrosion are directly influenced by surface roughness, whereas microstructural modifications due to welding interfere little with microbial adhesion, regardless of the greater pit depths compared to those of nonwelded coupons. Additionally, although open circuit potential measurements indicated that metal surfaces are protected when coated with biofilms, pitting corrosion was more pronounced in welded coupons immersed in fresh seawater than in those immersed in seawater without microorganisms. Therefore, the use of open circuit analysis alone is not recommended for biocorrosion monitoring of welded coupons.
Résumé : Around the world, there are thousands of metal structures completely or partially buried in the soil. The main concern in their design is corrosion. Corrosion is a mechanism that degrades materials and causes structural failures in infrastructures, which can lead to severe effects on the environment and have direct impact on the population health. In addition, corrosion is extremely complex in the underground environment due to the variability of the local conditions. The problem is that there are many methods to its evaluation but none have been clearly established. In order to ensure the useful life of such structures, engineers usually consider an excess thickness that increases the economic cost of manufacturing and does not satisfy the principles of efficiency in the use of resources. In this paper, an extended revision of the existing methods to evaluate corrosion is carried out to optimize the design of buried steel structures according to their service life. Thus, they are classified into two categories depending on the information they provide: qualitative and quantitative methods. As a result, it is concluded that the most exhaustive methodologies for estimating soil corrosion are quantitative methods fed by non-electrochemical data based on experimental studies that measure the mass loss of structures.
Résumé : Abstract Management of bacteria remains a concern for most Operators and the ability for micro-organisms to generate hydrogen sulphide (H 2 S) that results in reservoir souring and microbiologically influenced corrosion is well documented. This pape
Résumé : Abstract The pipelines and vast infrastructure required for the production and transport of oil and gas are largely constructed of carbon steel. This material is highly susceptible to damage and failure as a result of direct or indirect Microbially
Résumé : There have been revealed and summarized the regulari-
ties in biocorrosion of steel 17G1S-U, which is traditionally
used for manufacturing oil and gas mains. The basic regulari-
ties of biocorrosion processes in the 17G1S-U pipe steel under
the influence of SRB Desulfovibrio Sp. strains Kyiv-10 was ob -
tained by weight-loss testing and surface analysis techniques.
Effective inhibitors are proposed, which allow protecting ste-
el 17G1S-U against the development of anaerobic corrosion
under the influence of sulfate-reducing bacteria (SRB). The
effectiveness of inhibitors is estimated by the degree of their
protective effect. The porous structure of the surface film con - tributes to the initiation of localized corrosion. Damage analy-
sis of the specimen surface corroded under different test condi-
tions was performed.
Résumé : Buildings and structures reliability is a key question in human life and activities. Corrosion processes affect reliability of all water supply and distribution systems in buildings and structures.This research provides results of the tests for corrosion rate and for the time of steel water-pipes inhibition of corrosion in Samara. A gravimetric method was used to determine corrosion rate. The test subjects were surface (the Volga river) and underground (water treatment facilities of 113 km, Kuibyshev district) water supply sources. These tests proved that river water was highly aggressive in respect to other materials. Here the corrosion rate reached 0.1665 g/(m 2 /h) during in the 5 th month of exposure, and the specimens were damaged by pitting corrosion (within 1 month) and by cankers (within 5 months). The value of the corrosion rate in underground source water was within the range of 0.01-0.06 g/(m 2 /h), and the specimens were not subjected to any significant corrosion damage. The time of experience was not enough for complete inhibition of corrosion. The authors studied a sample with 50-year operational lifetime and proved that all corrosion processes affecting this sample had stopped, this sample material integrity had been pre-served which meant that steel pipes complete inhibition of corrosion was possible. The experiments also showed that the inner surface of the pipe was later filled with corrosion deposits. The thickness of corrosion deposits in the tray zone reached up to 7 mm.
Résumé : Sulfate reducing bacteria (SRB) was successfully isolated from Estuary Dam in Suwung Denpasar, Indonesia. This estuary catches highly polluted water from Badung River which runs across and hence carries pollution due to waste disposal from Denpasar City. SRB was studied in detail for their ability to reduce sulfate to sulfide with organic material as an oxidizing agent. SRB exploration of the estuary ecosystem of the contaminated dam was accomplished through isolation, selection and characterization of the isolates obtained. The result of this study found superior SRB named DPS 1711, DPS 1705 and DPS 1703. The bacteria have the ability to grow at pH 3, room temperature and uses compost as organic substrate. This ability is an important factor for the application of isolates in the treatment of acid mine waste. Isolates have optimum optical density under the pH range of 4 to 7 and the best at pH 5 have a growth rate profile at a temperature range of 25 to 40°C. The isolates observed were Gram-negative stem, motile bacteria which only grow in anaerobic condition. Physiological-biochemical characterization showed the three isolates, namely DPS 1703, DPS 1705 and DPS 1711 were SRB groups identified as Desulfotomaculum orientis.
Key words: Sulfate reducing bacteria, polluted waters, estuary dam ecosystem.
Résumé : This study addresses the potential usage of various herbaceous plants extract including betel leave extract (BLE), green tea (GTE), turmeric (TE), belalai gajah (BGE), garlic extracts (GE), and manjakani extracts (ME) as future biocides of SRB that are natural and nontoxic. Study revealed that retardation of growth was obtained after addition of 5mL of natural biocides to 100 mL of the culture. Reduced biomass growth was observed with most of the tested biocides, dictated by lower biomass contents accepts for ginger and garlic. The planktonic growth was successively suppressed with addition of GTE, TE, and BGE, where the biomass production was decreased by more than 80.0% compared to the control experiments. GRE increased the growth of planktonic bacteria while the GE induced the formation of biofilms, showed by increase in biomass productions with over 23.4% and 77.46% enhancements, respectively. These results suggest that turmeric, green tea, and belalai gajah plants extracts are highly potential biocidal agents for mitigating SRB, thus controlling the effect of MIC on metal surfaces. However, the chemical stability, potential toxicity, and consistent performance of the extracts need further investigation for optimization of its use on a real field scale.
Résumé : The interplay of Fe(II) oxidation and Fe(III) bio-reduction occurs widely in both natural and engineered redox-dynamic systems. This study aimed to unravel the impact of Fe(II) oxidation by O2 in the presence of iron-reducing bacteria on subsequent Fe(III) bio-reduction. Mixed solutions of Fe2+ (0.1–0.5 mM) and Shewanella oneidensis strain MR-1 (MR-1, 2.0 × 107 CFU/mL) at neutral pH were first exposed to laboratory air for Fe(II) oxidation and bacterial inactivation, and then the resultant Fe(III) suspensions were switched to anoxic conditions for bio-reduction by the surviving bacteria. In the oxidation step, the coexisting MR-1 was inactivated by 0.8–1.71 orders of magnitude within 60 min. In the subsequent bio-reduction step, the resultant Fe(III) was bio-reduced by the surviving MR-1. Bio-reduction of the resultant Fe(III) by the surviving MR-1 was 1.8–2.5 times faster than that of the Fe(III) that was produced from Fe2+ oxidation without MR-1 by fresh MR-1 cells at 2.0 × 107 CFU/mL. Although MR-1 inactivation during Fe(II) oxidation may inhibit Fe(III) bio-reduction, the increase in bio-availability of the resultant Fe(III) and the residual reactivity of dead cells led to net enhancement of bio-reduction under the tested conditions. Lepidocrocite was the sole Fe(III) mineral that was produced from Fe2+ oxidation without MR-1, while 19% ferrihydrite was produced from Fe2+ oxidation in the presence of MR-1. The formation of low-crystallinity ferrihydrite accounts for the increase in bio-availability of the Fe(III) minerals. The findings of this study highlight an important but overlooked impact underlying the interplay of Fe(II) oxidation and Fe(III) bio-reduction.
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Résumé : Biofouling on surfaces of various materials has aroused considerable attentions in biomedical and marine industry. Surface grafting based on covalent surface-initiated polymerization offers a popular route to address this problem by providing diverse robust polymer coatings capable of preventing the biofouling under complex environments. However, the existing methods to synthesize polymer coatings are complicated and rigorous, or require special catalysts, greatly limiting their practical applications. In this work, we report a radical cation-based surface-initiated polymerization protocol to graft the surafce of darkened rubber of trans-polyisoprene (TPI) with thermo-responsive smart polymer, poly(N-isopropylacrylamide) (PNIPAM) via a simple iodine doping process. A series of characterizations were performed to provide adequate evdiences to confirm the successful grafting. Combining thermal sensitivity of PNIPAM with the photothermal conversion ability of the darkened rubber, effecient bacterial killing and antifouling as a result of temperature-controlled iodine release and switchable amphiphilicity of PNIPAM are successfully achieved.
Résumé : The mitigation of biofouling has received significant research attention, with particular focus on non-toxic and sustainable strategies. Here, we investigated quorum sensing inhibitor (QSI) bacteria as a means of controlling biofouling in a laboratory-scale system. Approximately, 200 strains were isolated from coral (Pocillopora damicornis) and screened for their ability to inhibit quorum sensing (QS). Approximately, 15% of the isolates exhibited QSI activity, and a typical coral symbiotic bacterium, H12-Vibrio alginolyticus, was selected in order for us to investigate quorum sensing inhibitory activity further. Confocal microscopy revealed that V. alginolyticus extract inhibited biofilm formation from Pseudomonas aeruginosa PAO1. In addition, the secondary metabolites of V. alginolyticus inhibited PAO1 virulence phenotypes by downregulating motility ability, elastase activity and rhamnolipid production. NMR and MS spectrometry suggested that the potential bioactive compound involved was rhodamine isothiocyanate. Quantitative real-time PCR indicated that the bacterial extract induced a significant downregulation of QS regulatory genes (lasB, lasI, lasR, rhlI, rhlR) and virulence-related genes (pqsA, pqsR). The possible mechanism underlying
Résumé : Marine growth is a combination of biological species that accumulate on surfaces and structures in subsea environments. This may have several negative implications including structural damage, accelerated corrosion and increased hydrodynamic drag. In this project, the use of certain coatings is investigated as a method of preventing or removing marine growth on subsea equipment and structures. From field deployments lasting approximately 3 months at the Royal Freshwater Bay Yacht Club (RFBYC) and Nedlands Yacht Club (NYC) in the Swan River, it has been established that some tested coatings are able to outperform non-coated control segments in terms of lower marine growth accumulation at the field sites considered. However, no coating was able to completely repel 100% of marine growth.
Résumé : The effects of ZnO nanorod (NR) filler distribution and the nano-structured surface on the superhydrophobicity and fouling-release (FR) of silicone nanocoatings were investigated. Incorporation of 0.5 wt% ZnO NR fillers resulted in increasing the non-wettability characteristics and surface roughness and reducing the surface free energy were observed. Thus, an outstanding superhydrophobic nanocomposite coating model was fabricated with stable surface properties, surface innerness toward fouling adhesion, economic savings and prolonging longevity for marine applications. A polydimethylsiloxane/ZnO NR composite was prepared via in-situ technique. ZnO NRs were 30–40 nm wide and 0.5–1 µm long single-crystals with wurtzite structure grown in (0001) direction. Studying the influences of incorporation of different nanofiller concentrations on the surface and FR features was inevitable to achieve surface roughness with minimized free energy. Surface features were considered via water contact angles (WCAs), free energy calculations and atomic force microscopy. Mechanical characteristics were evaluated as a durability factor. Chosen micro-organisms were employed to investigate the nanocomposites' FR and biological characteristics. A tough field trial was performed on the nanocomposites which were immersed (for 6 months) in marine water of a tropical region. The most favorable FR properties with maximum WCA (158°) and minimum free energy (11.25 mN/m) were shown for 0.5 wt% NRs as an excellent distributed surface.
Résumé : Environmental concerns have been changing the way of looking for solutions to problems. The hydrosphere, together with its biosphere, has been feeling the impact of many pollutants, used for instance in the marine industry for economic reasons or lack of knowledge of their effects. In particular biocides, applied as coatings in paints, are released into the waters becoming toxic and persistent extending their action to an area far beyond the initial coated surface they should protect. In order to minimize these side effects, two biocides, Irgarol (I) and Econea (E), were covalently attached to polyurethane (PU) and foul-release silicone based (PDMS) marine paints through an isocyanate linker. Their antifouling bioactivity was better in PDMS coatings, both for single (Econea) and combined biocides (E/I ratio = 1.5) with contents lower than 0.6 wt%. The treated samples remained almost clean after more than one year immersion in the Portuguese shore of the Atlantic Ocean, and after about 24 weeks under the tropical conditions of Singapore (Fouling rate < 1%). Complementary biofilm adhesion susceptibility tests against Pseudoalteromonas tunicata D2 showed adhesion reduction higher than 90% for PU formulations containing single biocides and close to 100% for PDMS with combined biocides. The eco-toxicity assessment evidenced a low environmental impact, in accordance with the European standards. In addition, shipping field trial tests showed the best antifouling performance for the Econea-based PDMS formulations (E = 0.6 wt%), which remained clean for about nine months in open seawaters, proving the efficacy of this non-release strategy, when applied under dynamic conditions.
Résumé : Biofouling on artificial and biotic solid substrata was studied in several locations in the Baltic Sea brackish water (Gulf of Gdansk) during a three-year period with contact angle wettability, confocal microscopy and photoacoustic spectroscopy techniques. As a reference, the trophic state of water body was determined from chemical analyses according to the following parameters: pH, dissolved O2, phosphate, nitrite, nitrate, ammonium etc. concentrations and further correlated to the determined biofilm characterizing parameters by means of Spearman’s rank correlation procedure. Biofilm adhesive surface properties (surface free energy, work of adhesion etc.) were obtained with the contact angle hysteresis (CAH) approach using an automatic captive bubble solid surface wettability sensor assigned for in-situ, on-line and quasi-continuous measurements of permanently submerged samples (Pogorzelski et al., 2013, Pogorzelski and Szczepańska, 2014). Structural and morphological biofilm features (biovolume, substratum coverage, area to volume ratio, spatial spreading, mean thickness and roughness) were determined from confocal reflection microscopy (COCRM) data. Photosynthetic properties (photosynthetic energy storage (ES), photoacoustic amplitude and phase spectra) of biofilm communities exhibited a seasonal variability as indicated by a novel closed-cell type photoacoustic spectroscopy (PAS) system. That allowed mathematical modeling of a marine biofilm under steady state, in particular the specific growth rates μi, and the conditioning or induction times λi to be derived from simultaneous multitechnique signals. A set of the established biofilm structural and physical parameters could be modern water body trophic state indexes.
Résumé : Bioinspired superhydrophobic and oil-infused surfaces have been recognized as interesting and promising materials for a wide range of applications correlated with water environment, such as corrosion and biofouling inhibition. Which material is the better choice still waits to reveal. In this study, taking stainless steel as the substrate, superhydrophobic and oil-infused surface based on Cu(OH)2 matrix with prickly chestnut husk morphology is respectively obtained via successive steps. During the preparation of superhydrophobic surface, firstly, discrete Cu particles are electrodeposited onto stainless steel. After that, oxidation of the as-deposited Cu particles leads to the prickly Cu(OH)2 following a dissolution-crystallization mechanism. Under a mild condition, dodecanethiol vapor modifies prickly matrix to achieve superhydrophobicity by anchoring the long-chain organic moiety onto Cu(OH)2 surface. Since superhydrophobic matrix is intrinsically superoleophilic, oil-infused surface is finally constructed onto stainless steel. Taking typical marine fouling organisms including sulfate-reducing bacteria (SRB) and diatoms as the representatives, oil-infused surface can steadily prevent the biofouling on stainless steel, showing the better performance than superhydrophobic surface for biofouling inhibition. Using epoxy resin as the artificial fouling agent, the pulling force to remove the glued solid on oil infused surface is much lower than that on bare stainless steel, illustrating oil layer acting as the separation cushion between fouling agent and underneath substrate.
Résumé : Biofilm represents a non-uniform distribution of flexible microorganisms over a surface with variable density and height, it can be modified and displaced due to the flow. Therefore, the modelling of the flow and the assessment of resistance for surfaces covered with biofilm are problematic. Presently, there is no generally accepted method for the evaluation of the effects of a given biofilm on the resistance. Within this paper, roughness function models for surfaces covered with diatomaceous biofilm are established utilizing the experimental data presented in the literature. These roughness function models are then implemented within the wall function of the commercial software package STAR-CCM+. Numerical simulations of the rough plates in the turbulent channel flow are performed and the results are verified and validated against the experimentally obtained results presented in the literature. Utilizing the roughness length scale, proposed in the literature, and the proposed roughness function models, the effects of the biofilm on the resistance of any arbitrary body can be assessed using only roughness measurements. Finally, the increase in the frictional resistance and effective power due to the presence of the biofilm is determined using the validated roughness function models.
Résumé : The settlement and growth of marine organism increased sharply with the ships in a static environment, although the release rate of antibacterial agent decreased smoothly. Besides of a rapid release rate of the antibacterial agents, a destruction of films by sand and rocks restricted the long-term antibacterial efficiency of antifouling films on voyage. In this work, intelligent bacterial-triggered multilayer films are prepared via adding pH responsive nanocapsules to control releasing of antifouling agents during bacterial growth. Chitosan (CS) has a capability to change the swelling of capsules by amino protonation and deprotonation upon the change of the environmental pH. It is combined with capsaicin (CAP) to form nanocapsules for accomplishing a pH responsive behavior. The intelligent CAP@CS nanocapsules are added in polydopamine/sodium alginate (PDA/Alg)m PEM multilayer films to enable the (PDA/Alg-CAP@CS-n)m films with a pH-triggered antifouling agents (CAP) releasing performance. The results demonstrate that there are outstanding pH-triggered activities for the (PDA/Alg-CAP@CS-8)20 multilayer films. The released CAP concentration decreased by nearly 42% from pH 4 to pH 8.5. The bacteriostatic percentages of (PDA/Alg-CAP@CS-n)m against S. aureus and P. aeruginosa are 79% and 74%, respectively, after 60 days of immersion in pH 8.5 PBS buffer solutions. The amino deprotonation of CS in alkaline condition prevents the CAP release, resulting in an extended antibacterial performance. The electrostatic interaction between Alg and PDA in solutions leads to (PDA/Alg-CAP@CS-n)m films to exhibit the self-healing behaviors since the ions penetrate and free chins transfer in artificial seawater solutions after mechanical scratching.
Résumé : Biofouling as a global problem has made detrimental impact on many fields, especially for marine industry. Polydimethylsiloxane-based coatings are environment-friendly and exhibiting good fouling release performance in the marine coating application. However, their intrinsic low surface energy and high hydrophobic character lead to poor fouling resistance property and weak adhesion to substrate. In this work, we firstly fabricate self-adhesive PDMS-based amphiphilic cross-linked coatings with good anti-biofouling performance via synthesizing dopamine methacrylamide which then copolymerized with mercaptopropyl methylsiloxane- dimethysiloxane, poly (ethylene glycol) diacrylate under UV photo-cross-linking. The coating exhibits devisable heterogeneous nanoscale mosaic chemical surfaces caused by micro phase segregation, effectively resistance to nonspecific protein adsorption and marine fouling organism (P. tricornutum) attachment which are mainly ascribed to the unique surface topography and chemical heterogeneity. Moreover, the resulting coatings exhibit significantly improved adhesion to substrates, due to complex interfacial catechol chemistry reaction. This simple design provides a novel methodology for preparing an efficient and eco-friendly anti-biofouling PDMS-based amphiphilic coating.
Résumé : ABSTRACT The attachment of marine fouling organisms is harmful to any marine structure such as ship hulls, fishing nets, jetties and platforms. Marine antifouling coating is still the widely commercial used solution for marine antifouling in shippin
Résumé : Abstract. The introduction of artificial hard substrates in an area dominated by a sandy seabed increases habitat available to epifouling organisms. To investi
Résumé : In order to prevent the formation of a biofilm on the surface of materials in an aqueous environment various strategies could be developed. Notably following an electrochemical route it is possible to apply a potential which could lead to (i) oxidation of halide anions leading to the formation of biocidal molecules, (ii) O2 reduction leading to H2O2, (iii) water reduction leading to H2 bubbles or (iv) a low-intensity electric potential. Moreover an electrochemical method could be used to nano or microstructure the material surface or to deposit on the material a coating which would avoid protein adsorption or microorganism attachment and therefore the formation of a biofilm, this coating could be of an inorganic or an organic film.
Résumé : Biofilms and biofouling as important ecological phenomena have important implications affecting the development of invertebrates on surfaces in aquatic ecosystems, with economic impacts in several industries. Microbial biofilms on the surfaces of materials also affect the properties, longevity, and performance. The process of fouling and its prevention has been a major scientific challenge for many decades. Biofilms and fouling on surfaces affects the integrity of the substrutam materials from metals to inorganic and composites. Biodegradation and biodeterioration of materials are discussed here with information on relevant testing techniques tailored to material types. Biodeterioration by microorganisms is also discussed and prevention strategies offered to allow effective management of selective environmental conditions to ensure material integrity.
Résumé : Marine biotechnology is an emerging field in Brazil and includes the exploration of marine microbial products, aquaculture, omics, isolation of biologically active compounds, identification of biosynthetic gene clusters from symbiotic microorganisms, investigation of invertebrate diseases caused by potentially pathogenic marine microbes, and development of antifouling compounds. Furthermore, the field also encompasses description of new biological niches, current threats, preservation strategies as well as its biotechnological potential. Finally, it is important to depict some of the major approaches and tools being employed to such end. To address the challenges of marine biotechnology, the Brazilian government, through the Ministry of Science, Technology, Innovation, and Communication, has established the National Research Network in Marine Biotechnology (BiotecMar) (www.biotecmar.sage.coppe.ufrj.br). Its main objective is to harness marine biodiversity and develop the marine bioeconomy through innovative research.
Résumé : Habitat destruction is one of the main causes of the decline of biodiversity and of fishery resources in the marine environment. An artificial reef (AR) could be a tool for protecting or restoring these habitats and their declining biodiversity, and also help to enhance sustainable fisheries. The goal is to design non-polluting structures that best mimic the complexity of natural habitats in order to improve their service to the community. To date, the assessment of reef performance has been mostly focused on fish assemblages and species of ecological and/or socio-economic interest, and has disregarded the biofilm communities that determine the first level of an AR’s trophic network. In this work, we used biofilm formation to compare the quality of substrates used as building parts for an AR, in order to optimize an eco-friendly material that will be used to design a new generation of ARs produced by giant 3D printers. The structure of the photosynthetic communities has been identified using pigment biomarkers and their production of exudates has been analysed. These polymeric substances were quantified in terms of total sugar and protein concentrations. They were further analysed in terms of amino acid content. We found no significant differences between the micro-algae communities developed on the different substrates. These photosynthetic communities were mainly composed of diatoms, prasinophytes, haptophytes, and dinoflagellates. However, we showed that the material for ARs is crucial for biofilm development, especially with regard to its secretions of sugar. The choice of an appropriate substrate for AR construction is thus of particular importance since biofilm secretions determine the organic substrate on which sessile macro-organisms will settle.
Résumé : In this study, the antifouling (AF) performance of different carbon nanotubes (CNTs)-modified polydimethylsiloxane (PDMS) nanocomposites (PCs) was examined directly in the natural seawater, and further analyzed using the Multidimensional Scale Analyses (MDS) method. The early-adherent bacterial communities in the natural biofilms adhering to different PC surfaces were investigated using the single-stranded conformation polymorphism (SSCP) technique. The PCs demonstrated differences and reinforced AF properties in the field, and they were prone to clustering according to the discrepancies within different CNT fillers. Furthermore, most PC surfaces only demonstrated weak modulating effects on the biological colonization and successional process of the early bacterial communities in natural biofilms, indicating that the presence of the early colonized prokaryotic microbes would be one of the primary causes of colonization and deterioration of the PCs. C6 coating seems to be promising for marine AF applications, since it has a strong perturbation effect on pioneer prokaryotic colonization.
Résumé : Marine biofouling is an increasing problem from both economic and environmental points of view in terms of increased resistance, increased fuel consumption, increased GHG emissions and transportation of harmful non-indigenous species. Marine coatings are prevalently used to mitigate biofouling and smooth the surfaces of hulls. This paper aims at introducing new horizons and novel approaches in marine antifouling coatings. Firstly, marine biofouling and fouling prevention methods are briefly introduced. Afterwards, latest research in coating/fouling hydrodynamics is presented. Biomimetic approach to antifouling technology, bio-inspired antifouling strategies and the challenges in designing bio-inspired antifouling coatings are then discussed in detail. It is believed that, the on-going research in marine coatings will lead to an effective mitigation of marine biofouling while maintaining the harmony between man-made structures and marine life.
Résumé : The manufacture and preliminary testing of a drag-reducing riblet texture with fouling-control properties is presented. The commercial fouling-release product Intersleek® 1100SR was modified to manufacture riblet-textured coatings with an embossing technology. Hydrodynamic drag measurements in a Taylor–Couette set-up showed that the modified Intersleek® riblets reduced drag by up to 6% compared to a smooth surface. Barnacle settlement assays demonstrated that the riblets did not substantially reduce the ability of Intersleek® 1100SR to prevent fouling by cyprids of Balanus amphitrite. Diatom adhesion tests revealed significantly higher diatom attachment on the riblet surface compared to smooth Intersleek® 1100SR. However, after exposure to flow, the final cell density was similar to the smooth surface. Statically immersed panels in natural seawater showed an increase of biofilm cover due to the riblets. However, the release of semi-natural biofilms grown in a multi-species biofilm culturing reactor was largely unaffected by the presence of a riblet texture.
Résumé : A hydrosound marine anti-fouling system with a microcontroller monitoring and modifying, as desired, hydrosound pulse rate, output frequencies and volume level. This allows hydrosound pulse rate, output frequency and volume to be adjusted to levels determined to be effective with local marine growth. By adding a sensor to monitor hydrosound pulse rate, output frequencies and volume, an automatic testing process can be instituted at timed intervals and monitored by the microcontroller to confirm the hydrosound marine anti-fouling system is fully functioning.
Résumé : Interfacial water structure on a polymer surface in water (or surface hydration) is related to the antifouling activity of the polymer. Zwitterionic polymer materials exhibit excellent antifouling activity due to their strong surface hydration. It was proposed to replace zwitterionic polymers using mixed charged polymers because it is much easier to prepare mixed charged polymer samples with much lower costs. In this study, using sum frequency generation (SFG) vibrational spectroscopy, we investigated interfacial water structures on mixed charged polymer surfaces in water, and how such structures change while exposing to salt solutions and protein solutions. The 1:1 mixed charged polymer exhibits excellent antifouling property while other mixed charged polymers with different ratios of the positive/negative charges do not. It was found that on the 1:1 mixed charged polymer surface, SFG water signal is dominated by the contribution of the strongly hydrogen bonded water molecules, indicating strong hydration of the polymer surface. The responses of the 1:1 mixed charged polymer surface to salt solutions are similar to those of zwitterionic polymers. Interestingly, exposure to high concentrations of salt solutions leads to stronger hydration of the 1:1 mixed charged polymer surface after replacing the salt solution with water. Protein molecules do not substantially perturb the interfacial water structure on the 1:1 mixed charged polymer surface and do not adsorb to the surface, showing that this mixed charged polymer is an excellent antifouling material.
Résumé : An antifouling coating composition contains a silyl ester (co)polymer and medetomidine and is used to prevent the fouling of substrates by aquatic organisms and which can form antifouling coating films exhibiting outstanding antifouling properties over a long period and also has good storage stability. The antifouling coating composition includes a silyl ester (co)polymer (A) and medetomidine (B), the silyl ester (co)polymer (A) including structural units derived from a monomer (a) represented by the general formula (I): R1—CH═C(CH3)—COO—(SiR2R3O)n—SiR4R5R6, and structural units derived from an unsaturated monomer (b) copolymerizable with the monomer (a).
Résumé : One of the most important research areas in the marine industry is to investigate new and effective anti-biofouling technologies. In this study, high voltage pulse electric field (HPEF) mediated by carbon fiber (CF) composite coating was utilized to prevent the fouling of bacteria, microalgae and barnacle larvae in seawater. The plate count, 2, 3, 5-triphenyl-tetrazolium chloride (TTC) reduction assay and neutral red (NR) staining and larval motility detection showed that the inactivation rates were at the highest levels, which reached 99.1%, 99.9%, 99.7%, 98.7% and 85% respectively for Pseudomonas sp., Vibrio sp., iron bacteria, Navicula sp. and the second stage nauplii of Balanus reticulatus, under the HPEF with 19 kV pulse amplitude, 23.15 kHz frequency and 0.5 duty cycle. The field-emission scanning electron microscopy (FE-SEM) of Navicula sp. revealed that the HPEF brought about the cell lysis and the cell organic matter release on the coating, which could be the mechanism of the inactivation by the HPEF. Additionally, the FE-SEM and Raman spectroscopy indicated that the HPEF hardly damaged the coating.
Résumé : There is an important need for the development of new “environmentally-friendly” antifouling molecules to replace toxic chemicals actually used to fight against marine biofouling. Marine biomass is a promising source of non-toxic antifouling products such as natural antimicrobial peptides produced by marine organisms. The aim of this study was to demonstrate the efficiency of antimicrobial peptides extracted from snow crab (SCAMPs) to reduce the formation of marine biofilms on immerged mild steel surfaces. Five antimicrobial peptides were found in the snow crab hydrolysate fraction used in this study. SCAMPs were demonstrated to interact with natural organic matter (NOM) during the formation of the conditioning film and to limit the marine biofilm development in terms of viability and bacterial structure. Natural SCAMPs could be considered as a potential alternative and non-toxic product to reduce biofouling, and as a consequence microbial induced corrosion on immerged surfaces.
Résumé : Abstract Corrosion and biofouling control is an important consideration for offshore oil structures. Corrosion rates for steel exposed to seawater immersion and brine air can easily exceed 10 mils per year if left unprotected in the splash zone, whi
Résumé : There is a need for the development of antifouling materials to resist adsorption of biomacromolecules. Here we describe the preparation of a novel zwitterionic block copolymer with the potential to prevent or delay the formation of microbial biofilms. The block copolymer comprised a zwitterionic (hydrophilic) section of alternating glutamic acid (negatively charged) and lysine (positively charged) units and a hydrophobic polystyrene section. Cryo-TEM and dynamic-light-scattering (DLS) results showed that, on average, the block copolymer self-assembled into 7-nm-diameter micelles in aqueous solutions (0 to 100 mM NaCl, pH 6). Quartz crystal microbalance with dissipation monitoring (QCM-D), atomic force microscopy (AFM), and contact angle measurements demonstrated that the block copolymer self-assembled into a brush-like monolayer on polystyrene surfaces. The brush-like monolayer produced from a 100 mg/L block copolymer solution exhibited an average distance, d, of approximately 4–8 nm between each block copolymer molecule (center to center). Once the brush-like monolayer self-assembled, it reduced EPS adsorption onto the polystyrene surface by ∼70% (mass), reduced the rate of bacterial attachment by >80%, and inhibited the development of thick biofilms. QCM-D results revealed that the EPS molecules penetrate between the chains of the brush and adsorb onto the polystyrene surface. Additionally, AFM analyses showed that the brush-like monolayer prevents the adhesion of large (>d) hydrophilic colloids onto the surface via hydration repulsion; however, molecules or colloids small enough to fit between the brush polymers (
Résumé : Biofouling causes huge economic loss and generates serious ecological issues worldwide. Marine coatings incorporated with antifouling (AF) compounds are the most common practices to prevent biofouling. With a ban of organotins and an increase in the restrictions regarding the use of other AF alternatives, exploring effective and environmentally friendly AF compounds has become an urgent demand for marine coating industries. Marine microorganisms, which have the largest biodiversity, represent a rich and important source of bioactive compounds and have many medical and industrial applications. This review summarizes 89 natural products from marine microorganisms and 13 of their synthetic analogs with AF EC50 values ≤ 25 μg/mL from 1995 (the first report about marine microorganism-derived AF compounds) to April 2017. Some compounds with the EC50 values < 5 μg/mL and LC50/EC50 ratios > 50 are highlighted as potential AF compounds, and the preliminary analysis of structure-relationship (SAR) of these compounds is also discussed briefly. In the last part, current challenges and future research perspectives are proposed based on opinions from many previous reviews. To provide clear guidance for the readers, the AF compounds from microorganisms and their synthetic analogs in this review are categorized into ten types, including fatty acids, lactones, terpenes, steroids, benzenoids, phenyl ethers, polyketides, alkaloids, nucleosides and peptides. In addition to the major AF compounds which targets macro-foulers, this review also includes compounds with antibiofilm activity since micro-foulers also contribute significantly to the biofouling communities.
Résumé : The bacterial and eukaryotic communities forming biofilms on six different antifouling coatings, three biocidal and three fouling-release, on boards statically submerged in a marine environment were studied using next-generation sequencing. Sequenced amplicons of bacterial 16S ribosomal DNA and eukaryotic ribosomal DNA internal transcribed spacer were assigned taxonomy by comparison to reference databases and relative abundances were calculated. Differences in species composition, bacterial and eukaryotic, and relative abundance were observed between the biofilms on the various coatings; the main difference was between coating type, biocidal compared to fouling-release. Species composition and relative abundance also changed through time. Thus, it was possible to group replicate samples by coating and time point, indicating that there are fundamental and reproducible differences in biofilms assemblages. The routine use of next-generation sequencing to assess biofilm formation will allow evaluation of the efficacy of various commercial coatings and the identification of targets for novel formulations.
Résumé : An experimental study was carried out by a dynamic fouling monitor system to investigate the fouling process in convective heat transfer by ultrasonic treatment. During the experiment, the cooling water in heat exchanger was used as working fluid with the inlet temperature of 22.5 °C and 44 °C and the initial hardness of 300 mg/L and 500 mg/L, respectively. For all cases the inlet temperature of hot water was kept at 70°C, and the flowrates of cooling water and hot water were set at 0.77 m3/h and 0.81 m3/h, respectively. In this experimental setup, a double-tube heat exchanger was served as a test section of heat transfer, in which hot water flows inside the inner copper tube and cooling water flows in the annular gap between the two tubes, thus forming a counter-flow situation. Further, an ultrasonic device was installed for water treatment with a frequency of 20.7 kHz and power ranging from 0 to 75 W. The results showed that the fouling resistance for hard water increased evidently with increasing of water temperature and hardness. With the ultrasonic treatment, the fouling resistance decreased remarkably compared with the untreated case, and the asymptotic fouling resistance decreased monotonously with increasing of the ultrasonic power. Subsequently, the crystal morphology of calcium carbonate was observed in microscopic view and the transform of crystal from the vaterite to aragonite and calcite was analyzed based on the theory of the formation energy. It was confirmed that the ultrasonic treatment may have significant effect on the crystal shape, and more aragonites appeared with increasing powers of ultrasound.
Résumé : The invention provided herein presents a novel family of antifouling agents based on hydroxylated and fluorinated compounds.
Résumé : Membrane fouling, which arises from the nonspecific interaction between the membrane surface and foulants, significantly impedes the efficient application of membrane technology. Antifouling and antimicrobial materials are important classes of functional materials for the surface modification of reverse osmosis and nanofiltration membranes. Applications of various organic and inorganic materials having different characteristics such as size, surface charge, hydrophilicity, functionality and biocidal activity, provide protective/sacrificial layers to the membrane surface against different foulants and microorganisms. This review summarizes the properties and applications of organic and inorganic materials, antifouling mechanisms, and surface modification of pre-formed membranes. Materials such as zwitterionic polymers, neutral polymers, polyelectrolytes, amphiphilic polymers, quaternary ammonium polymers, biopolymers, hydrophilic polymers, polydopamine, inorganic salts, and nanomaterials have shown great potential in reducing foulant adhesion and/or proliferative microbial growth on membrane surfaces.
Résumé : The present invention is directed to bioactive microcapsules and to the process for their production. More in particular, the present invention relates to the production of bioactive microcapsules, or porous microspheres by a water-in-oil (W/O) microemulsion method combined with interfacial polymerization, involving the full or partial covalent immobilization of biocides and/or modified biocides within the microcapsules shell, or porous microspheres. In addition, the present invention further relates to the use of said bioactive microcapsules/microspheres for controlled release of biocides in antifouling application and their incorporation in matrices such as marine coatings.
Résumé : Abstract This chapter contains sections titled: Introduction Antifouling Options Problem Statement Coatings with Special Wettability and Performance Against Biofouling General Discussion Summary
Résumé : Persistent protein resistance is critical for marine antibiofouling. We have prepared copolymer of 2-methylene-1,3-dioxepane (MDO), tertiary carboxybetaine ester (TCB), and 7-methacryloyloxy-4-methylcoumarin (MAMC) via radical ring-opening polymerization, where MDO, TCB, and MAMC make the polymer degradable, protein resistible, and photo-cross-linkable, respectively. Our study shows that the polymer can well adhere to the substrate with controlled degradation and water adsorption rate in artificial seawater (ASW). Particularly, the polymer film can generate zwitterions via surface hydrolysis in ASW. Quartz crystal microbalance with dissipation measurements reveal that such hydrolysis-induced zwitterionic surface can effectively resist nonspecific protein adsorption. Moreover, the surface can inhibit the adhesion of marine bacteria Pseudomonas sp. and Vibrio alginolyticus as well as clinical bacterium Escherichia coli.
Résumé : Hydrophilic coatings have recently emerged as a new approach to avoid the adhesion of (bio)organisms on surfaces immersed in water. In these coatings the hydrophilic character is crucial for the anti-fouling (AF) performance. However, this property can be rapidly lost due to the inevitable damages which occur at the surface, reducing the long-term effectiveness of the AF functionality. We report hydrophilic polycarbonate-mPEG polyurethane coatings with tunable hydrophilic properties as well as an excellent and long-term stability in water. The coatings exhibit low protein adhesion values and are able to self-replenish their hydrophilicity after damage, due to the existence of a reservoir of hydrophilic dangling chains incorporated in the bulk. The combination of low Tg and sufficient mobility of the mPEG dangling chains (enabled by chains with higher molecular weight) proved to be crucial to ensure autonomous surface hydrophilicity recovery when the coatings were immersed in water. This coatings and design approach offer new possibilities towards high performance AF coatings with an extended service life-time which can be used in several major applications areas, such as marine and biomedical coatings, with major economic and environmental benefits.
Résumé : Stainless steel (SS) have been widely used in marine structures and food industry due to its high corrosion resistance and excellent mechanical strength. Marine structures such as ships, ocean engineering and offshore rigs, are easily attacked by crude oil generated by oil spills and SS vessels applied in food industry are fouled by the organic matters in the fluid. Here, fish-scale-like SS surfaces with superhydrophilic and underwater superoleophobic property, including 316 L SS mesh and 304 SS plate, are designed by a facile chemical-based oxidation method. The obtained SS surfaces show excellent underwater anti-crude-oil-fouling property and thermal stability. Furthermore, the obtained 316 L SS mesh can effectively separate crude oil/water mixture solely driven by gravity. Significantly, the as-prepared SS surfaces possess robust antifouling and self-cleaning property during multiple cycles with the aid of Fenton-like catalytic reaction between Fe (III) and H2O2 or calcination at high temperature. Therefore, the fish-scale-like SS surfaces show great potential in a wide range of fields, such as marine antifouling, oil-water separation and food industry.
Résumé : The significance of wettability between solid and liquid substances in different fields encourages scientists to develop accurate models to estimate the resultant apparent contact angles. Surface free energy (SFE), which is principally defined for ideal (flat) surfaces, is not applicable to predict the wettability of real (rough) surfaces. This paper introduces a new parameter, namely normalized surface free energy (NSFE) as a combination of SFE and roughness, to predict the contact angle of liquids on non-ideal low-energy surfaces. The remarkable consistency of the predicted and measured contact angles of liquids on some rough surfaces also confirm the validity of the approach.
Résumé : This study evaluates anti-biofilm activity of four extracts from marine fungi; Penicillium citrinum PR1T4, Sarocladium strictum PP2L4, Aspergillus sydowii PR3T13, and Aspergillus spp. PR5T4 against Staphylococcus aureus, Listeria monocytogenes (ATCC 19115), Escherichia coli, and Salmonella typhi (ATCC 14028). The ability of bacterial cells to adhere, detach, and form biofilm on stainless steel surface were examined and ethyl acetate extract of the fungal culture (15 mg/ml) were tested for anti-biofilm activity for 3, 6, 9, 12, and 15 days. E. coli showed the highest ability to adhere (>8 log CFU/cm2) and lowest detachment (<4 log CFU/cm2) after 24, 48, and 72 hr. Extract PP2L4 had the highest anti-biofilm activity against S. typhi (1.70 ± 0.04 log CFU/cm2). Fungal extracts, bacteria, and incubation period were significant factors and their interactions were significant. The results showed that marine fungal extracts are important natural sources for anti-biofilm agents that have high potential as food-contact surface sanitizers.
Biofilm removal from food contact surfaces has been one of the greatest challenges for food industry. There have been efforts to explore natural agents with anti-biofilm properties. This study showed that marine-derived fungal extracts significantly reduced the number of attached cell on stainless steel discs and, therefore, is potential candidates for anti-biofilm agents. Special attention would be given to the fungal isolate (S. strictum PP2L4) that presented a promising activity against the gram-negative S. typhi. As the active fungal extracts were unable to completely remove the adhered bacterial cells, optimization is recommended to increase probability of isolating active compounds capable for complete biofilm removal. The active compounds could be used in sanitizer formulation and applied on various food-contact surfaces (e.g., stainless steel and plastic) at food related industries such as in institutional food service kitchens as well as home kitchens.
Résumé : Basing on the previous syntheses of ester compounds containing gramine functional groups, the researchers synthesized two novel acylamino compounds containing gramine groups and the structures of target compound were established using 1HNMR, 13CNMR, IR spectra, and elemental analysis. The antibacterial activity of the synthesized compounds against Escherichia coli and Staphylococcus aureus, as well as their antifouling activity were studied. The results showed that these compounds possessed high antibacterial activity and a minimal inhibitory concentration value of 0.03 mg/mL against bacteria. Moreover, their antifouling properties are superior to cuprous oxide and chlorothalonil, which are widely used as antifoulants. Furthermore, quantitative structure activity relationship studies with antibacterial activity of the nine gramine compounds were established. These provide theoretical and technical bases for preparing environment-friendly antifouling coatings with the compounds as antifouling agents.
Résumé : Anti-biofouling technology is based on specifically designed materials and coatings. This is an enduring goal in the maritime industries, such as shipping, offshore oil exploration, and aquaculture. Recently, research of the relationship between wettability and antifouling effectiveness has attracted considerable attention, due to the anti-biofouling properties of the lotus leaf and shark skin. In this study, super-hydrophobic surfaces (SHSs) with controllable periodic structures were fabricated on AISI304 stainless steel by a picosecond laser, and their anti-biofouling performance were investigated by seawater immersion for five weeks in summertime. The results showed that the specimens with SHS demonstrate significant anti-biofouling effect as compared with the bare stainless steel plate. We observed that nearly 50% decrease of the average microbe attachment area ratio (Avg. MAAR) could be obtained. The micro-groove SHS with more abundant hierarchical micro-nano structures showed better anti-biofouling performance than the micro-pit SHS.