Résumé : The future growth of maritime activities may be limited due to competition for space as coastal areas become overcrowded. This has led to interest in promoting more efficient and sustainable use of the sea and its resources through the sharing of space. The MARIBE (MARine Investment for the Blue Economy) project investigated the potential of combining marine renewable energy technologies with other emerging industries. The project assessed potential combinations, and identified challenges including the perception of risk due to the combination of new technologies. This work documents the methodology used to assign the risks to various potential combination projects within the blue economy, and applies it to one of the MARIBE case studies: combining wave energy with aquaculture. A standardised methodology of risk assessment was developed comprising three core elements of the risk management process: risk identification, risk analysis and risk mitigation. This method could be applied to each potential project combination, allowing results to be directly comparable, and allowing all stakeholders to have a full understanding of the risks identified. By using a standardised methodology, critical risks could be identified and mitigated, allowing informed decisions to be made on the most suitable combination projects to pursue. The methodology can be applied to other combination projects within these sectors.
Résumé : Field measurements of the flow in the benthic boundary layer (BBL) of a tidal channel are presented which compare data collected in the wake of a marine renewable energy installation (MREI) with control data representative of the natural conditions. The results show significant flow modification in the wake of the MREI including a reduction in mean velocity, enhanced turbulence, and the breakdown of the natural structure and dynamics of the BBL. This study provides new information relevant to the environmental impact assessment of MREIs and to the design and consenting of marine renewable energy projects.
Résumé : The structural design of marine tidal turbine blades is governed by the hydrodynamic shape of the aerofoil, extreme loadings and composite material mechanical properties. The design of the aerofoil, chord and twist distribution along the blade is generated to optimise turbine performance over its life time. Structural design gives the optimal layout of composite laminae such that ultimate strength and buckling resistance requirements are satisfied. Most structural design approaches consider only extreme static loads, with a lack of dynamic load-based fatigue design for tidal blades. Approaches for tidal turbine blade design based on dry and immersed composite material fatigue life are studied.
Résumé : Numerical modelling of wave energy converters (WECs) is currently an area of interest within the marine renewable energy industry, due to its ability to streamline design processes and accelerate scientific understanding. The presented project investigates the capacity of linear potential flow theory to accurately model wave excitation of a 2D WEC buoy-section, identifying wave conditions under which computational fluid dynamics (CFD) become a more appropriate strategy.
OpenFOAM® v1612+ is utilised to simulate fully non-linear, viscous wave-structure interactions for comparison with linear theory and experimental results. Regular waves are generated to study both fixed and floating body cases.
Linear forces are compared with those computed during fixed body CFD simulations, the validity of which is investigated using wave flume experiments carried out in NTNU s Ladertanken wave flume facility. Experimental and numerical results show reasonable agreement. 1st harmonic CFD forces compare well with linear forces in cases where overtopping is not observed. 2nd harmonic loads are shown to have significant contributions to total forces.
Floating body CFD simulations are carried out allowing heave response displacements to be obtained for comparison with linear theory predictions. For the tested cases, responses are dominated by 1st harmonics, making comparison with linear theory particularly interesting. Good agreement is seen between linear theory and CFD for wave frequencies far from the natural frequency in heave, however divergence is seen for steep waves close to resonance where overtopping is extensive.
Résumé : The present paper compares in economic terms, four technological alternatives to use offshore renewable energies: floating offshore wind energy technology, floating offshore wave energy systems, floating offshore co-located systems and floating offshore hybrid systems. These alternatives are compared considering different locations and sizes of the farms. Studies such as this can be useful for planning strategies and decision-making, particularly to investors that have to decide if and how to develop and deploy particular technologies in deep waters. The results indicate that the best alternative considering the life-cycle cost and LCOE is the floating offshore wind energy technology. Floating offshore co-located systems have the second best result, being a better alternative than floating offshore wave energy devices or floating offshore hybrid systems.
Résumé : A new type of the installation equipment for offshore wind turbine is proposed. Its three dimensional model and mechanism are designed. The kinematical analysis and dynamic analysis are conducted. Finally, according to the fuzzy theory, the method of calculating fuzzy reliability of kinematical accuracy of mechanism of the installation equipment is given out.
Résumé : The Actuator Disk concept is suitable to simulate the flow interactions between tidal turbines. As the computational expense of AD simulations is too large for applications at regional scale, the “bed friction” method is generally preferred. It consists in applying an enhanced drag over the tidal farm area. The main drawback is that the flow around each turbine is not resolved and that the flow interactions between the turbines’ wakes are neglected. The extent to which this simplification affects the accuracy of the large scale flow is not well understood. Here, we propose a methodology for representing large arrays of tidal turbines in Shallow Water Equations solvers. It consists in representing individual turbines as small areas where a sink momentum term is applied. The sink term is calculated from the vertical integration of the force exerted on an AD. After validating the model, we apply the methodology to simulate the effect of 45 turbines placed in the Alderney Race. The results are compared to the results obtained with the “bed friction” method. The two approaches give similar results because the hydrodynamics conditions of the Alderney Race favor the mixing of the wakes which prevents the flow interactions between the turbines.
Résumé : Along with global warming threat, importance of renewable energy development is on the rise for global sustainable development. To amplify productivity of ocean renewable energy, a multi-unit floating offshore wind turbine platform (MUFOWT)
Résumé : During power generation, the rotor of wind turbine needs to be aligned with the incoming wind for optimal energy production. On state-of-the-art upwind wind turbines, this step is usually achieved through the yaw control system in the nacel
Résumé : Extensive marine growth on man-made structures in the ocean is commonplace, yet there has been limited discussion about the potential implications of marine growth for the wave and tidal energy industry. In response, the Environmental Interactions of Marine Renewables (EIMR) Biofouling Expert Workshop was convened. Discussions involved participants from the marine renewable energy (MRE) industry, anti-fouling industry, academic institutions and regulatory bodies. The workshop aimed to consider both the benefits and negative effects of biofouling from engineering and ecological perspectives. In order to form an agenda for future research in the area of biofouling and the marine renewable energy industry, 119 topics were generated, categorised and prioritised. Identified areas for future focus fell within four overarching categories: operation and maintenance; structured design and engineering; ecology; and knowledge exchange. It is clear that understanding and minimising biofouling impacts on MRE infrastructure will be vital to the successful development of a reliable and cost effective MRE industry.
Résumé : As advanced natural gas power generation systems evolve, the thrust for increased efficiencies and reduced emissions results in increasingly harsh conditions inside the turbine environment. These high temperatures, pressures, and corrosive atmospheres result in accelerated rates of degradation, leading to failure of turbine materials and components. Wolfspeed, A Cree Company, Siemens Energy and Siemens Corporate Technology, in collaboration with the DoE's National Energy Technology Laboratory (NETL), are developing a reliable and long-term monitoring capability in the turbine hot gas path in the form of novel ceramic based thermocouples and wide band gap instrumentation electronics that will contribute to the overall reliability of gas turbines. When equipped with better monitoring and controls, power plants can operate with increased fuel-burning efficiency, improved process dynamics and gas concentrations, and increased overall longevity of the power plant components. This will result in increased turbine availability and a reduction in outages and maintenance costs. The technology being developed in this program is based upon advanced techniques and innovations in nearly every aspect of high temperature electronics, including materials, subcomponents, semiconductors, electronic packaging, and system integration. The environment in which this wireless system must operate has continuous g-loads on the order of 16,000g, and temperatures exceeding 400 °C. This paper will specifically discuss the background and motivation for the high temperature instrumentation system, and will explain the high-level electrical system, the construction of the instrumentation package, the techniques utilized for integration onto rotating components, as well as the wireless power and data transmission systems. In addition to the electrical and mechanical design, this paper will also discuss results from laboratory bench testing as well as heated spin rig testing. Finally, this paper will highlight the future direction of the instrumentation system evolution, with a final objective of insertion into Siemens natural gas turbine power plants.
Résumé : The probabilistic distribution analysis of the mooring line tension for the floating offshore wind turbine is performed in this paper. The OC3-Hywind-Spar with 5 MW baseline wind turbine presented by American National Renewable Energy Labor
Résumé : Despite the large number of wave energy converter concepts proposed over the past three decades, only a few field measurement datasets are available in the public domain. The sparse nature of device performance and reliability data coupled with a general lack of design convergence means that technological and economic progress within the sector is fragmented. Fundamental to ensuring device efficiency and survivability is the acquisition of long-term, open sea, device and mooring system response data, combined with comprehensive numerical modelling. With mooring systems representing approximately 10% of marine renewable energy device CAPEX, the evolution of shared mooring systems and the use of novel materials with load reduction capabilities represent clear strategies to achieve more favourable project finances. This paper will report on design of the mooring load monitoring system as well as preliminary analysis of several load cases identified from field data recorded during the winter of the first deployment. Comparisons are made to numerical simulations of the device and mooring system subjected to representative environmental conditions. The measured mooring line tensions also provide operational design criteria (i.e. load capacity and durability requirements) for two elastomeric tethers which will replace the polyester ropes currently used in the seaward catenary lines.
Résumé : The extraction of tidal energy is one of the most promising Marine Renewable Energies (MRE) and is nowadays in a preindustrial phase. The Alderney Race (France) capitalizes a resource estimated between 5 and 14 TWh/year. This great tidal resource attracts tidal energy developers. Harnessing the high potential of the Alderney Race requires deploying numerous turbines in arrays.
Résumé : Interest in Marine Renewable Energies (MREs) is growing worldwide because they are seen as a potential resource to harness for the production of electric power. Furthermore, they could contribute to the reduction of the emission of greenhouse gases. Almost two-third of the Earth is covered by oceans, so that a huge amount of energy could be produced. Among the different types of MRE (i.e. thermal energy, chemical energy, biological energy, wave and tidal energy) tidal current energy seems to be the most attractive. Firstly, contrarily to wind energy, it is highly predictable. Secondly, the tidal resource is generally characterized by a low variation in direction. Finally, tidal energy has a high potential that could allow increasing the energy mix in Europe. France has the second production potential of electrical energy from MREs, behind the UK. In fact, French production potential is estimated between 5 and 14 TWh/year. The Alderney Race (Raz Blanchard in French), situated between the Alderney Island and La Hague Cape (France), capitalizes about half of the national resource (Bahaj and Myers, 2004, Myers and Bahaj, 2005). The French premier announced in that the Government will support two projects consisting in the installation of two little pilot tidal turbines farms in the Alderney Race. These projects will represent a decisive step towards setting up pre-commercial and commercial operations in tidal energy. Two of the main issues for the commercial development of tidal farms is the optimization of the turbines layout for maximizing the producible energy and the energy management for optimizing the energy production. These aspects depend on the wake effect and on the control of the electrical conversion chain. One of the factor that influences the producible energy of a park is its layout. In fact, optimized positions of turbines allows reducing the so called wake effect, which is a natural phenomenon consisting on increased values of turbulence and a reduced flow velocity behind a tidal turbine (Stallard et al., 2015). Nowadays, the wake effect is analyzed mainly with numerical methods that are highly precise but computationally expensive (Funke et al., 2014). After that the producible energy has been achieved, the electrical production has to be improved. This aim can be carried out through the correct modeling of the electrical components (Zhou et al., 2015). One time the electrical chain has been implemented, the control system can be tested to allow the system working at optimal operation points. The objectives of this dissertation are the development of an optimization tool to maximize the producible energy of a tidal farm and the improvement of the control of the electrical chain. To this scope, in Chapter I the state of art about the analysis of tidal farms is presented. In Chapter II, an analytical model of the wake effect in a park is developed and validated. Moreover, a parametric study of the tidal farm layout is applied to the Alderney Race. In Chapter III, different types of optimization algorithms are compared to solve the tidal farm layout optimization problem. The optimization tool (in which the analytical wake model is employed) is presented and tested in one site in the Alderney Race. Finally, in Chapter IV all the components of the electrical conversion chain are modelled. Furthermore, different strategies to maximize the electrical production of the tidal farm are compared. A complete electrical model including all the components and the control are implemented to test the dynamic behavior of a hypothetical tidal farm subject to the changes in tidal speed in a site in the Alderney Race and to grid disturbances (for example, voltage dips)
Résumé : ABSTRACT To develop renewable energy, the offshore wind energy technology has become an attractive research field. Considering the coupling effect of the platform motions and aerodynamic loads, how to accurately simulate the aero-hydrodynamics of fl
Résumé : Two common offshore wind turbine structures, the monopile type and the jacket type, subjected to ocean wave load were analyzed using finite element simulations. The FEM models were built in ABAQUS, and applied the load combinations consisti
Résumé : This paper presents the detailed modeling and the Energetic Macroscopic Graphical Representation of the Marine Current Turbine (MCT) System. The studied marine current turbine system consists of 1.5 MW Fixed Pitch Tidal Turbine, Permanent Magnet Synchronous Generator; AC-DC fully controlled machine side converter, DC link, DC-AC fully controlled grid side converter, connection cables, transformer, and the central grid. The control of each converter is designed based on defining the tuning chain as a part of the system energetic macroscopic representation. The machine side converter control depends on the torque control maximum power point tracking and the generator loss minimization (Output Maximization) techniques to enhance the overall efficiency when the system runs under the rated marine current speed. The control mode is changed to the rated power limiting mode when the system runs above the base speed. The grid side converter is controlled to stabilize the DC link voltage within a certain range beside the reactive power control. The proposed control strategies are evaluated based on the model results by using the real data of The Alderney Race (Raz Blanchard in French) marine site.
Résumé : This report addresses a number of key issues in the physical and numerical testing of marine renewable energy systems, including wave energy devices, current turbines, and offshore wind turbines. The report starts with an overview of the types of devices considered, and introduces some key studies in marine renewable energy research. The development of new ITTC guidelines for testing these devices is placed in the context of guidelines developed or under development by other international bodies as well as via research projects. Sites developed around the world for full-scale testing of Marine Renewable Energy Devices are discussed. Some particular challenges are introduced in the experimental and numerical modelling and testing of these devices, including the simulation of Power-Take-Off systems (PTOs) for physical models of all devices, approaches for numerical modelling of devices, and the correct modelling of wind load on offshore wind turbines. Finally issues related to the uncertainty in performance prediction from test results are discussed. Definition of the stages of a device test program – Technology Readiness Level (TRL) definition <li> Summary of testing requirements / challenges for device type (ocean v tidal current, rotating v non-rotating, shallow v deep deployment, rigid mounting v flexible mooring) and device development stage; <li> Coupling between model scale, choice of facility, device type, and experiment stage. <li> Identification of common error sources associated with small to field-scale testing with guidelines on impact on test success, interpretation of test results and how to quantify and report measurement error.</ul>
Résumé : The effect of modified flow on epifaunal boulder reef communities adjacent to the SeaGen, the world's first grid-compliant tidal stream turbine, were assessed. The wake of the SeaGen was modelled and the outputs were used in conjunction with positional and substrate descriptor variables, to relate variation in epifaunal community structure to the modified physical environment. An Artificial Neural Network (ANN) and Generalised Linear Model (GLM) were used to make predictions on the distribution of Ecological Status (ES) of epifaunal communities in relation to the turbulent wake of the SeaGen. ES was assigned using the High Energy Hard Substrate (HEHS) index. ES was largely High throughout the survey area and it was not possible to make predictions on the spatial distribution of ES using an ANN or GLM. Spatial pattern in epifaunal community structure was detected when the study area was partitioned into three treatment areas: area D1; within one rotor diameter (16 m) of the centre of SeaGen, area D2; between one and three rotor diameters, and area D3; outside of three rotor diameters. Area D1 was found to be significantly more variable in terms of epifaunal community structure, bare rock distributions and ES than areas D2 and D3.
Résumé : This paper investigates numerically and experimentally the behaviour of a Tension Leg Platform (TLP) floating wind turbine, under regular waves. The physical model tests have been performed at the Danish Hydraulic Institute (DHI) offshore wave basin. The general aim of this work is to form an accurate set of data, basically consisting in incident waves, 3D wave oscillation and mooring loads that may be used as a possible term of reference for numerical models. The paper provides a thorough description of the geometrical and dynamic characteristics of the floating body, and the results in terms of the incident waves interpreted on the basis of an array of resistive wave gauges, the displacements as observed by a tracking camera system (surge, sway, heave and roll, pitch, yaw), and the loads measured by a load cell located at the fairlead of the anchoring lines, simulating in the physical model scale the tendons characteristics in full scale. Experimental results are given in graphical form for the case of regular wave conditions. Corresponding numerical results that have been obtained using home developed software for the hydrodynamic- and the static- and dynamic-analysis of the mooring lines (HAMVAB  and STATMOOR , respectively) compare well with the experimental data. STATMOOR  is capable to handle the static analysis of extensible mooring lines made of several segments each of them with different geometrical properties and with attached submerged buoys along them.
Résumé : The present paper studies the control of monopile offshore wind turbines subjected to multi-hazards consisting of wind, wave and earthquake. A Semi-active tuned mass damper (STMD) with tunable natural frequency and damping ratio is introduced to control the dynamic response. A new fully coupled analytical model of the monopile offshore wind turbine with an STMD is established. The aerodynamic, hydrodynamic and seismic loading models are derived. Soil effects and damage are considered. The National Renewable Energy Lab monopile 5 MW baseline wind turbine model is employed to examine the performance of the STMD. A passive tuned mass damper (TMD) is utilized for comparison. Through numerical simulation, it is found that before damage occurs, the wind and wave induced response is more dominant than the earthquake induced response. With damage presence in the tower and the foundation, the nacelle and the tower response is increased dramatically and the natural frequency is decreased considerably. As a result, the passive TMD with fixed parameters becomes off-tuned and loses its effectiveness. In comparison, the STMD retuned in real-time demonstrates consistent effectiveness in controlling the dynamic response of the monopile offshore wind turbines under multi-hazards and damage with a smaller stroke.
Résumé : This paper investigates the motivations for energy storage solutions for offshore Wave Energy Converters (WEC) and tidal energy prototypes. It examines the power and energy storage solutions on offer for developers to aid them during the design stage. Energy storage solutions examined include lead acid batteries, lithium ion batteries, supercapacitors, lithium ion capacitors and diesel for diesel generators. A focus is placed on key installation, operation and maintenance requirements associated with the apparent suitable technologies which are often overlooked. A case study examining a tidal developer's energy storage needs is then presented.
Résumé : Marine Renewable Energy (MRE) devices require mooring and foundation systems that are suitable in terms of device operation, are robust and also cost effective. In the initial stages of mooring and foundation development a large number of possible configuration permutations exist. Filtering of unsuitable designs is possible using information specific to the deployment site (i.e. bathymetry, environmental conditions) and device (i.e. mooring and/or foundation system role and cable connection requirements). The identification of a final solution requires detailed analysis, which includes load cases based on extreme environmental statistics following certification guidance processes. Static and/or quasi-static modelling of the mooring and/or foundation system serves as an intermediate design filtering stage enabling dynamic time-domain analysis to be focused on a small number of potential configurations.
Mooring and foundation design is therefore reliant on logical decision making throughout this stage-gate process. The open-source DTOcean (Optimal Design Tools for Ocean Energy Arrays) Tool includes a Mooring and Foundation (MF) module, which automates the configuration selection process for fixed and floating wave and tidal energy devices. As far as the authors are aware this is one of the first tools to be developed for the purpose of identifying potential solutions during the initial stages of MRE design. Whilst the MF module does not replace a full design assessment, it provides in addition to suitable configuration solutions, assessments in terms of reliability, economics and environmental impact. This paper provides insight into the solution identification approach used by the module and features the verification of both the mooring system calculations and the foundation design using commercial software. Several case studies are investigated; a floating wave energy converter and several anchoring systems. It is demonstrated that the MF module is able to provide device and/or site developers with rapid mooring and foundation design solutions to appropriate design criteria.
Résumé : A new semi type floating offshore wind turbine platform called Y-Wind is developed to support a 5MW wind turbine, considering various design aspects from engineering through to installation, which can reduce the CAPEX. The platform is designed to achieve the integration of the tower and rotor to the platform at quayside in a US shipyard. Also a proper lightship draft is considered in the early platform design phase to enable wet-tow from the yard to the installation site with no dedicated extra equipment, as the majority of shipyards in US east and west coasts may not be able to accommodate floating wind platforms with deep lightship draft. The Y-Wind platform with damping plates consists of four columns having the same diameter. No deck structures and braces are used. Center column supports a 5MW wind turbine and three other offset columns connected to the center column by respective pontoon are optimally placed such that the hydrostatic stability and minimal static heeling angle by wind turbine peak thrust are ensured. The platform is moored with three catenary lines with a sufficient length to avoid the uplift at the anchor. Time domain coupled simulations under typical US offshore metocean conditions are conducted to assess the platform dynamic responses including motions, accelerations, and mooring tensions for the design load cases of the power production, 50-yr extreme and 500-yr survival conditions in accordance with ABS floating offshore wind turbine guide. The present design is checked against the ABS design criteria and confirmed to comply with the design requirements. Also significant reductions of motions are observed due to the damping plates, which also results in reducing the mooring line tensions. Preliminary global structural analysis was performed to assess the stress ratios of the primary structures.
Résumé : Scaling and biofouling are two major problems in the operation of reverse osmosis (RO) membranes. A variety of control measures are employed in practice, including the use of pulsed electromagnetic fields (EMF), which can avoid the use of chemical anti-fouling agents (e.g. halogen-based biocides) that may be toxic to humans or the environment. This is a fairly recent and controversial technology and, from the available documentation and literature, it is clear that the scientific basis for its purported effectiveness is not yet firmly established, although some studies suggest that beneficial effects could be possible. In particular, the various conditions under which EMF technologies are likely to be effective for real world applications have not been scientifically established. This review collates the relevant literature on the problem of scaling and biofouling in RO membranes and heat exchangersystems (e.g. cooling towers), with a particular focus on the application of pulsed EMF technologies, including the broad documentation, relevant scientific studies, proposed mechanisms of action and further research directions. This review demonstrates that a lot more systematic scientific research is needed in order to validate the application and commercialization of EMF technologies as a pretreatment to control fouling in RO membrane systems.
Résumé : The offshore wind power industry is the branch of electric energy production from renewable sources which is most intensively developed in EU countries. At present, there is a tendency to install larger-power wind turbines at larger distances from the seashore, on relatively deep waters. Consequently, technological solutions for new supporting structures intended for deeper water regions are undergoing rapid development now. Various design types are proposed and analysed, starting from gravitational supports (GBS), through monopiles and 3D frame structures (jackets, tripods), and ending with floating and submerged supports anchored to the seabed by flexible connectors, including TLP type solutions.
Résumé : Fluctuating loads on tidal turbines are important for fatigue analysis and there is limited information or simulation available for full-scale conditions. Here, CFD simulations have been performed for a geometry-resolved full-scale tidal-stream turbine and compared with experimental data from a 1 MW machine deployed at the EMEC test site. Initially, Reynolds-averaged Navier-Stokes (RANS) and large-eddy simulations (LES) were performed using an inflow mean velocity profile representative of the site but low inflow turbulence. Mean blade pressures were similar for the two types of turbulence closure and yielded mean power coefficients comparable with measurements. Then, to simulate the effect of turbulence on loads, LES with synthetic turbulence prescribed at inlet was employed. For these simulations, inflow profiles of mean velocity, Reynolds stresses and length scales were determined from a precursor channel-flow simulation, with additional factoring of stresses and length scales to match hub-height conditions measured on site. Fluctuations in thrust, power and blade bending moment arise cyclically from onset mean velocity shear and the blocking effect of the support tower and over continuous spectral ranges from blade-generated turbulence, approach-flow turbulence and waves. LES simulations with realistic inflow turbulence satisfactorily reproduced the relative spectral distribution of blade bending moments in low-wave conditions.
Résumé : The potential of generating electricity from marine tidal currents is enormous. Tidal energy is a renewable source that has an additional value in a future energy market with regard to other renewable energy sources thanks to its high predictability. Moreover, tidal energy technologies are characterized by CO2 emission-free power, thus enabling energy security and contributing to economic growth and job creation in coastal and remote areas. Substantial progress is currently being made by the European Union as regards the reduction of greenhouse gas emissions, renewable energy and energy efficiency, in order to fulfil the target of an installed capacity of 3.6 GW of ocean energy by 2020, and to achieve a future installed capacity of 188 GW of ocean energy in 2050. This paper presents a comprehensive review of the current status of tidal energy conversion technologies and describes the costs incurred in the development of tidal energy projects so as to study their economic viability. The study also identifies the principal current risks and the role of each of the stakeholders involved in the successful development of tidal energy projects. Finally, future challenges in tidal technologies that will influence the increase in their current potential are briefly presented along with the current developments of our research group in the field of tidal energy converters design.
Résumé : Environmental effects have an important influence on Offshore Wind Turbine (OWT) power generation efficiency and the structural stability of such turbines. In this study, we use an in-house Boundary Element (BEM)—panMARE code—to simulate the unsteady flow behavior of a full OWT with various combinations of aerodynamic and hydrodynamic loads in the time domain. This code is implemented to simulate potential flows for different applications and is based on a three-dimensional first-order panel method. Three different OWT configurations consisting of a generic 5 MW NREL rotor with three different types of foundations (Monopile, Tripod, and Jacket) are investigated. These three configurations are analyzed using the RANSE solver which is carried out using ANSYS CFX for validating the corresponding results. The simulations are performed under the same environmental atmospheric wind shear and rotor angular velocity, and the wave properties are wave height of 4 m and wave period of 7.16 s. In the present work, wave environmental effects were investigated firstly for the two solvers, and good agreement is achieved. Moreover, pressure distribution in each OWT case is presented, including detailed information about local flow fields. The time history of the forces at inflow direction and its moments around the mudline at each OWT part are presented in a dimensionless form with respect to the mean value of the last three loads and the moment amplitudes obtained from the BEM code, where the contribution of rotor force is lower in the tripod case and higher in the jacket case and the calculated hydrodynamic load that effect on jacket foundation type is lower than other two cases.
Résumé : The extraction of marine energy , through either tidal or wave array operation, will clearly influence the hydrodynamics of a region. Although the influence on tidal currents and wave properties is likely to be very small for most extraction scenarios, the influence on bed shear stress is likely to be greater, because bed shear stress is quadratically related to tidal currents and wave orbital velocities. Further, the transport of sediments is a function of tidal current and wave orbital velocity cubed. Therefore, even small modifications to the flow field through tidal or wave array operation could lead to significant impacts on regional sediment dynamics. In this chapter, after providing an introduction to sediment dynamics in the marine environment, we explore the impact of tidal energy devices/arrays on regional sediment dynamics, with a particular emphasis on offshore sand banks —important sedimentary systems that protect our coastlines from the full impact of storm waves. Next, we discuss how generating electricity from waves could influence nearshore sediment processes, such as beach erosion or replenishment, over a range of timescales. To assess the magnitude of impacts on sedimentary systems, it is essential to consider the scale of the impact in relation to the range of natural variability. We suggest ways in which impacts can be assessed using numerical models, tuned by in situ measurements, that quantify variability over a range of timescales from individual storm events and lunar cycles to seasonal and interannual periods. We also discuss the sedimentary processes associated with tidal lagoons , such as scour and sediment drift outside a lagoon and sediment accretion inside a lagoon.
Résumé : This book identifies the challenges, solutions, and opportunities offered by smart energy grids (SEGs) with regard to the storage and regulation of diversified energy sources such as photovoltaic, wind, and ocean energy. It provides a detailed analysis of the stability and availability of renewable sources, and assesses relevant socioeconomic structures.The book also presents case studies to maximize readers’ understanding of energy grid management and optimization. Moreover, it offers guidelines on the design, implementation, and maintenance of the (SEG) for island countries.
Résumé : When conducting tidal energy resource characterization and assessment, it is important to capture the strong variations of tidal currents in time and space. Field measurements can quantify many of these variations, which have both deterministic and stochastic components. The deterministic components occur on timescales of hours to years. As such, they are repeatable and well-suited to harmonic analyses associated with astronomical tidal forcing. The stochastic components are well-suited to statistical descriptions of fluid turbulence , from the short scales (milliseconds and millimeters), where dissipation occurs, to the long scales (seconds and meters), where large eddies occur. While the resolution of deterministic components may be adequate for characterizing annual energy production, both components need to be quantified to determine design loads on tidal energy conversion devices. In addition to the direct utility of field measurements to characterize and assess the tidal energy resource, field measurements are also essential to validate computational models used to assess the resource over large spatial domains.
Résumé : A Virtual Blade Model is coupled with a CFD model to simulate impacts from a Horizontal Axis Tidal Turbine under combined surface waves and a steady current. A two-equation model is used to represent the turbulence generation and dissipation due to turbine rotation and background wave-current flows. The model is validated against experimental measurements, showing good agreement in both surface elevation and fluid hydrodynamics. It is then scaled up to investigate a steady current with large stream-wise surface waves in the presence of a turbine. A strong interaction is found between surface wave-induced flows and that around the turbine, which clearly impacts on both hydrodynamics within the wake and wave propagation, and produces large fluctuations in power production. Model results show that the wave-period-averaged velocities are similar to those in the steady-current-only condition. However, the wave enhances the turbulence immediately behind the turbine and reduces the length of the flow transition. The wave height reduces by about 10% and the wavelength extends by 12% when propagating over the turbine region in comparison with the no-turbine condition. The wave shape also becomes asymmetric. Compared with the current-alone situation, the model results suggest that the power production is similar. However, wave oscillation produces noticeably larger fluctuations.
Résumé : Abstract This paper will report on the status of the US power industry today and how close some Marine Energy Converters (MECs) options are to becoming commercially viable in the near future. The paper provides an overview of the rules and regulatio
Résumé : Abstract Marine energies (including wind turbine, tidal current and wave energy) are now recognized not only as high potential energy sources, but also as a significant and maturing energy market. Nevertheless, renewable marine energies are highly i
Résumé : The estimation of the cost of energy of offshore wind farms has a high uncertainty, which is partly due to the lacking accuracy of information on wind conditions and wake losses inside of the farm. Wake models that aim on reducing the uncertainty by modeling the wake interaction of turbines for various wind conditions need to be validated with measurement data before they can be considered as a reliable estimator. A methodology is shown to create realistic transient wind conditions in a Large-Eddy-Simulation of a marine boundary layer interacting with an offshore wind turbine for a direct comparison of modeled with measured flow data. A mesoscale simulation is used for determining the boundary conditions of the model. The simulations of the ambient wind conditions and the wake simulation generally show a good agreement with measurements from a met mast and lidar measurements, respectively. Advanced metrics to describe the wake shape and development are derived from simulations and measurements but a quantitative comparison is difficult due to the scarcity and the low sampling rate of the available measurement data. The methodology presents a possibility to compare flow measurements with simulations. Due to the implementation of changing wind conditions in the LES it could be also beneficial for case studies of wind turbine and wind farm control.
Résumé : Optimization of the life-cycle costs and reliability of offshore wind turbines (OWTs) is an area of immense interest due to the widespread increase in wind power generation across the world. Most of the existing studies have used structural reliability and the Bayesian pre-posterior analysis for optimization. This paper proposes an extension to the previous approaches in a framework for probabilistic optimization of the total life-cycle costs and reliability of OWTs by combining the elements of structural reliability/risk analysis (SRA), the Bayesian pre-posterior analysis with optimization through a genetic algorithm (GA). The SRA techniques are adopted to compute the probabilities of damage occurrence and failure associated with the deterioration model. The probabilities are used in the decision tree and are updated using the Bayesian analysis. The output of this framework would determine the optimal structural health monitoring and maintenance schedules to be implemented during the life span of OWTs while maintaining a trade-off between the life-cycle costs and risk of the structural failure. Numerical illustrations with a generic deterioration model for one monitoring exercise in the life cycle of a system are demonstrated. Two case scenarios, namely to build initially an expensive and robust or a cheaper but more quickly deteriorating structures and to adopt expensive monitoring system, are presented to aid in the decision-making process.
Résumé : Field measurement of turbulence in strong tidal currents is difficult and expensive, but the tidal energy industry needs to accurately quantify turbulence for adequate resource characterisation and device design. Models that can predict such turbulence could reduce measurement costs. We compare a Regional Ocean Modelling System (ROMS) simulation with acoustic Doppler current profiler (ADCP) measurements from a highly-energetic tidal site. This comparison shows the extent to which turbulence can be quantified by ROMS, using the conventional k − ε turbulence closure model. Both model and observations covered the same time period, encompassing two spring-neap cycles. Turbulent kinetic energy (TKE) density was calculated from measurements using the variance method; turbulent dissipation, ε, was calculated using the structure function method. Measurements show that wave action dominates turbulent fluctuations in the upper half of the water column; comparing results for deeper water, however, shows very strong agreement. A best fit between ROMS and ADCP results for mean velocity yields R 2 = 0.98 ; for TKE, R 2 is 0.84 when strongly wave-dominated times are excluded. Dissipation agrees less well: although time series of ε are well-correlated at similar depths, ROMS estimates a greater magnitude of dissipation than is measured, by a factor of up to 4.8.
Résumé : This article addresses the joining of 5 mm thick plates of marine grade, super-austenitic (AISI 904L) and super-duplex stainless steels (UNS S32750) by pulsed current gas tungsten arc welding using duplex and austenitic stainless steel fillers. Microstructure studies revealed the segregation of Mo-rich phases in the fusion zone while employing ERNiCrMo-10. Grain coarsening was observed at the heat affected zone (HAZ) of super-duplex stainless steel in both the cases. The study attested that all the tensile failures experienced in the parent metal, AISI 904L for both the weldments. Charpy V-notch impact studies demonstrated that the weldments employing ER2553 were experienced better impact toughness than ERNiCrMo-10 weldments. Further potentiodynamic polarization test in 3.5% NaCl environment was conducted on the coupons of the weldments. The coupons of the weldments were then tested for accelerated corrosion in salt fog chamber for 300 h in 3.5% NaCl environment. This accelerated corrosion test concludes that the parent metal AISI 904L experienced better corrosion resistance than the fusion zones. The investigation also deals with biocorrosion studies of the dissimilar welds of super-austenitic and super-duplex stainless steels. Microbial consortium comprising of six bacterial isolates of which four were Pseudomonas strains P. aeruginosa strain MB1, P. aeruginosa strain MB2, P. fluorescens and P. flavescens, two belonged to Bacillus strains, B. subtilis and B. cereus, for the first time. The bacterial isolates were inoculated in the medium with the presence of the metal coupons. The results were obtained after 15 and 30 days interval and compared with the control to determine the rate of biocorrosion which confirms that there is an accelerated deterioration of the metal coupons by the microbial strains.
Résumé : In this work, corrosion of an X52 pipeline steel was investigated in a field-collected soil containing sulfate-reducing bacteria (SRB) by weight-loss testing, bio-testing, electrochemical measurements and surface analysis techniques. The SRB can grow well in the soil and attach to the steel surface, leading to microbiologically influenced corrosion (MIC) of the steel. The SRB are able to accelerate corrosion of the steel remarkably. Compared to the corrosion rate of 0.0473mm/y in SRB-absent soil, the corrosion rate of the steel is up to 0.282mm/y when SRB are contained in the soil. An increase of the water content in the soil favors the growth of SRB, increasing the thickness of the biofilm formed on the steel surface and accelerating the steel MIC. At individual water contents, the presence of CO2 in the soil accelerates the steel MIC induced by SRB, which is associated with the increasing amount of SRB cells in CO2-containing soil. The SRB also result in localized corrosion of the steel. This is associated with the unique soil corrosion environment, where the sessile SRB cells and corrosion products do not move freely. The porous structure of the surface film contributes to the initiation of localized corrosion.
Résumé : This study introduces a novel approach intertwining analytics of spatial microbial distribution with chemical, mineralogical and (micro)structural related aspects in corroded concrete sewer environments. Samples containing up to 4 cm thick corrosion layers were collected from concrete manholes and analysed using hydro-geochemical, microbiological, biochemical and mineralogical methods. Opposed to the current opinion DNA and RNA indicating microbial activity were found throughout the entire deterioration layer down to the corrosion front. Elemental distributions of corresponding areas revealed a dynamic pH- and diffusion-controlled system in which a distinct succession of elemental accumulations was unequivocally correlated with responding pH levels, associated dissolution and precipitation of solids, as well as with the spatially resolved presence of microbes. Microbial activity further coincided with massive iron deposition zones, within the inner anoxic to anaerobic corrosion layers. As a possible microbial catalyst for iron oxidation and in-situ acid production in this zone, we propose Acidithiobacillus ferrooxidans which were isolated from the deteriorated concrete. Based on the data we propose a new model in which biogenic induced in-situ acid production is a decisive factor, steering high concrete corrosion rates of > 1 cm yr− 1.
Résumé : The effect of thiosulphate reducing bacteria (TRB) on the corrosion of carbon steel covered by a complex oilfield deposit has been assessed in CO2-containing seawater at 55° C. TRB were found to significantly accelerate localized corrosion at deposited steels. This effect of TRB on under-deposit corrosion (UDC) was related to metabolic production of corrosive compounds, such as sulphide and acidic species, through biodegradation of organic matter and thiosulfate reduction in the deposit. TRB were also found to promote accumulation of hydrocarbons and metals in the deposit. Results highlight that microbial-deposit interactions are a noteworthy process in corrosion of oilfield facilities.
Résumé : Microbiologically influenced corrosion (MIC) is prevalent in the oil and gas industry. Problematic biofilms cause MIC and reservoir souring. A high biocide concentration is usually required to mitigate biofilms compared with planktonic cells. This causes economic and environmental concerns. A biocide enhancer can make a biocide more effective using the same or lower biocide dosage. In this work, an equimolar mixture of 100 ppm (w/w) of four D-amino acids (D-methionine, D-tyrosine, D-tryptophan, and D-leucine) labeled as D-mix enhanced 100 ppm tetrakis (hydroxymethyl) phosphonium sulfate (THPS) against a field biofilm consortium on C1018 carbon steel coupons. In order to test chemical compatibilities, D-amino acids were added together with THPS and enhanced oil recovery chemicals (a polymer, a surfactant, a corrosion inhibitor, and a scale inhibitor) to treat the mature biofilm consortium. After a 7-day biofilm removal test in 125 ml anaerobic vials, the cocktail of 100 ppm THPS +100 ppm D-mix achieved extra logs of reduction in sessile cell counts compared with the 100 ppm THPS alone treatment. The combination also achieved lower weight loss and smaller maximum pit depths. Electrochemical tests corroborated the weight loss and pitting data.
Résumé : Biofilms of sulfate-reducing bacteria (SRB) are often the major cause of microbiologically influenced corrosion. The representative SRB Desulfovibrio vulgaris has previously been shown to have a biofilm that consists primarily of protein. In this study, by utilizing lectin staining, we identified that the biofilm of D. vulgaris also consists of the matrix components mannose, fucose, and N-acetylgalactosamine (GalNAc), with mannose predominating. Based on these results, we found that the addition of mannose and the non-metabolizable mannose analog 2-deoxy-D-glucose inhibits the biofilm formation of D. vulgaris as well as that of D. desulfuricans; both compounds also dispersed the SRB biofilms. In addition, the enzyme N-acetylgalactosaminidase, which degrades GalNAc, was effective in dispersing D. vulgaris biofilms. Therefore, by determining composition of the SRB biofilm, effective biofilm control methods may be devised. This article is protected by copyright. All rights reserved.
Résumé : At geothermal plants, process failures often occur due to corrosion and scaling processes. Especially after heat extraction, sulfate reducing bacteria contribute to corrosion processes by producing reduced sulfur compounds. In biofilms containing scales such as iron sulfides, corrosion processes are enhanced. In a mobile bypass system located at the geothermal plant in Neubrandenburg (North German Basin), the influence of biofilm formation on corrosion and scaling was investigated. Short-term heat shocks were successfully tested in the bypass system in order to reduce biofilm formation and thus to diminish corrosion and scaling processes.
Résumé : In this work the poly(3,4-ethylenedioxythiophene) (PEDOT) was evaluated to mitigate biocorrosion of conventional stainless steel (SS), grade AISI 304, under exposure to natural seawater. PEDOT was obtained electrochemically onto the steel and coated coupons were immersed in flow-through exposure rig fed with fresh seawater. Corrosion performance of the coupons SS and SS/PEDOT was characterised using electrochemical analysis of open circuit potentials and polarization curves measured on samples retrieved after 7, 35 and 210 days of exposure. For the same retrieval times, the evolution of the biofilm was inspected by scanning electron microscopy (SEM), and microbiological analysis by denaturing gradient gel electrophoresis (DGGE) and fluorescence microscopy. Results indicate that PEDOT delays the growth of the biofilm on the modified steel surface by at least 35 days, producing a less variable bacterial community over time as compared to the uncoated steel surface. In addition, PEDOT retains electrochemical stability throughout the exposure, which is mainly attributed to the intrinsic properties of the conducting polymer.
Résumé : Corrosion is the result of damage to material degradation through a chemical or electrochemical reaction spontaneously and causes a decrease in the quality of the material. One of the causes of corrosion is the presence of bacteria on the material. The danger posed by corrosion is fatality, especially on offshore platforms, namely cessation of production at offshore rigs. This study is an experiment using material carbon steel API 5L Grade B and ASTM A53 commonly used as a base for the manufacture of subsea pipelines. Material to be heat-treated before immersion for corrosion test in artificial seawater (salinity 35‰), which have been added with bacteria and without bacteria. The method used in measuring the rate of corrosion steel data is the weight loss. The highest corrosion rate of the original material ASTM A53 and API 5L with the addition of T. ferrooxidans bacteria are, respectively, 3.63 mpy and 3.50 mpy. While the lowest corrosion rate of ASTM A53 and API 5L both with heat treatment but without adding bacteria are 2.33 mpy and 2.01 mpy. This indicates that the steel API 5L have high levels of corrosion resistance, better than ASTM A53 in the marine environment with bacteria or without bacteria.
Résumé : Microorganisms are the main engines of elemental cycling in this planet and therefore have a profound impact on both organic and mineral substrates. As such, past and present human-made structures and cultural heritage can be negatively affected by microbial activity. Processes such as bioweathering (rocks and minerals), biodeterioration (organic substrates) or biocorrosion (metals) participate to the degradation or structural damage of construction and heritage materials. This structural damage can cause major economic losses (e.g. replacement of cast-iron pipes in water distribution networks), and in the case of heritage materials, the entire loss of invaluable objects or monuments. Even though one can regard the influence of microbial activity on construction and heritage materials as negative, remarkably, the same metabolic pathways involved in degradation can be exploited to increase the stability of these materials.
Résumé : Biological corrosion is caused by presence of microbes in environment. Escherichia coli causes serious biofouling in various environments and its pronounced influence on marine biofouling that causing serious problems such as accelerated corrosion. E. coli shares similar properties with most marine bacteria and it was extensively studied for marine environment. The aims of this research was to determine the corrosion rate on Aluminium 6063 by E. coli in deep seawater (salinity of 33‰), medium seawater (salinity of 35‰), shallow seawater (salinity of 37‰). Based on results, bio-corrosion rate on Al 6063 were higher than control. The bio-corrosion rate Al 6063 at day 28 in salinity of 37‰ was 1.1233 mm/year, meanwhile the corrosion rate for control was 0.7225 mm/year. Visual observation showed that corrosion occured on surface on specimen. Macrostructure observation showed that white spots occured on surface of specimen with E. coli was higher than specimen in control (without E. coli, only saline water) It was indicating that presence of E. coli caused increasing of corrosion rate on Al 6063.
Résumé : Testing conditions have been shown to influence the outcomes of microbiologically influenced corrosion (MIC) studies. Despite this there are only limited reports comparing the performance of different metal types in MIC studies using exactly the same test conditions. This makes it difficult to predict the relative performance of different materials in applications in which MIC may occur. In the present work, the microbiologically influenced corrosion of a range of ferrous and non-ferrous alloys have been studied under identical test conditions. Metal coupons were exposed to a relatively common MIC test arrangement consisting of the sulphate-reducing bacterium, Desulfovibrio desulfuricans, in modified Baar's medium for a period of 90 days under anaerobic conditions. The results showed accelerated corrosion of carbon steel and copper-nickel alloys in the biotic test condition (i.e. with bacteria) compared to abiotic test conditions. No evidence of corrosion, however, was observed on any of the stainless steels, Inconel or titanium alloys in either of the abiotic or biotic test conditions studied.
Résumé : Different electrochemical techniques and surface analysis methods were used to continuously monitor the corrosion of 2205 duplex stainless steel (DSS) in P. aeruginosa inoculated medium. It was found that linear polarization resistance and electrochemical impedance spectroscopy, significantly inhibited the attachment and growth of the biofilm, due to an internal electric field, leading to lower corrosion rates. In comparison, electrochemical noise as a passive electrochemical measurement technique did not adversely impact the biofilm, and the corrosion rate and the largest pit depth distribution from electrochemical noise were the closest to those from weight-loss data, making it a more suitable technique to monitor MIC by fragile biofilms.
Résumé : We have created inorganic-organic hybrid composites and antibiocorrosive coatings based on an epoxy modified with silicon-containing polyepoxies and bioactive coordination compounds. The scratch resistance was determined using a conical diamond indenter with linearly increased load. Repetitive scratching along the same groove (sliding wear determination) was also performed. Whether in single or in repetitive scratching, for most hybrids the residual depth is shallower than for the pure epoxy. Dynamic friction was determined on a pin-on-disk tribometer using steel pins. Lower friction is accompanied by higher scratch resistance. Surface morphology seen in scanning electron microscopy (SEM) shows that increasing modifier content causes more ductile behavior with less crack nucleation; no debris formation is observed. The composites were also characterized by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Isothermal aging and water absorption ability (WH2O) of the hybrids were determined. The hybrids are optically transparent, visually homogeneous, with smooth surfaces.
Résumé : Coiled tubing corrosion was investigated for 16 field water samples (S5 to S20) from a Canadian shale gas field. Weight loss corrosion rates of carbon steel beads incubated with these field water samples averaged 0.2 mm/yr, but injection water sample S19 had 1.25±0.07 mm/yr. S19 had a most probable number of zero acid-producing bacteria and incubation of S19 with carbon steel beads or coupons did not lead to big changes in microbial community composition. In contrast other field water samples had most probable numbers of APB of 102/mL to 107/mL and incubation of these field water samples with carbon steel beads or coupons often gave large changes in microbial community composition. HPLC analysis indicated that all field water samples had elevated concentrations of bromide (average 1.6 mM), which may be derived from bronopol, which was used as a biocide. S19 had the highest bromide concentration (4.2 mM) and was the only water sample with a high concentration of active bronopol (13.8 mM, 2760 ppm). Corrosion rates increased linearly with bronopol concentration, as determined by weight loss of carbon steel beads, for experiments with S19, with filtered S19 and with bronopol dissolved in defined medium. This indicated that the high corrosion rate found for S19 was due to its high bronopol concentration. The corrosion rate of coiled tubing coupons also increased linearly with bronopol concentration as determined by electrochemical methods. Profilometry measurements also showed formation of multiple pits on the surface of coiled tubing coupon with an average pit depth of 60 μm after 1 week of incubation with 1 mM bronopol. At the recommended dosage of 100 ppm the corrosiveness of bronopol towards carbon steel beads was modest (0.011 mm/yr). Higher concentrations, resulting if biocide is added repeatedly as commonly done in shale gas operations, are more corrosive and should be avoided. Overdosing may be avoided by assaying the presence of residual biocide by HPLC, rather than by assaying the presence of residual surviving bacteria.
Résumé : Extensive marine growth on man-made structures in the ocean is commonplace, yet there has been limited discussion about the potential implications of marine growth for the wave and tidal energy industry. In response, the Environmental Interactions of Marine Renewables (EIMR) Biofouling Expert Workshop was convened. Discussions involved participants from the marine renewable energy (MRE) industry, anti-fouling industry, academic institutions and regulatory bodies. The workshop aimed to consider both the benefits and negative effects of biofouling from engineering and ecological perspectives. In order to form an agenda for future research in the area of biofouling and the marine renewable energy industry, 119 topics were generated, categorised and prioritised. Identified areas for future focus fell within four overarching categories: operation and maintenance; structured design and engineering; ecology; and knowledge exchange. It is clear that understanding and minimising biofouling impacts on MRE infrastructure will be vital to the successful development of a reliable and cost effective MRE industry.
Résumé : An austenitic antibacterial stainless steel formulation provides a high strength, highly corrosion resistant, antimicrobial product at a relatively low cost wherein antimicrobial performance is dramatic and greater mechanical properties and corrosion resistance are achieved as well. The alloy may comprise key constituents of Fe, Cr, Ni, and C plus a mischmetal having Ce and La components.
Résumé : The current state of understanding of CO2 corrosion as related to internal corrosion of oil and gas pipelines made from mild steel is reviewed. The review covers the effects of basic physicochemical phenomena underlying CO2 corrosion, such as surface electrochemistry, homogenous aqueous chemistry, mass transfer, and formation of protective corrosion product layers. It then addresses some of the main “complicating factors,” such as multiphase flow, additional aqueous species, hydrocarbon composition, inhibition, and localized corrosion. Additional challenges seen in the field are presented at the end.
Résumé : This paper systematically summarizes the formation and evolution of the iron oxidizing bacteria (IOB) related biofilm and the relevant mechanism, and then introduces the metabolic process of IOB and the corrosion process induced by IOB with emphasis on the role in the corrosion process of their metabolite of extracellular polymeric substance (EPS). The paper also reviews the research progress of synergic corrosion induced by typical aerobic IOB and anaerobic sulfate reducting bacteria (SRB). In addition, the paper further summarizes corrosion prevention methods applied in oilfields and the corresponding research progress, which may provide reference for the corrosion control for oilfield.
Résumé : X80 pipeline steel is inevitably corroded by sulphate-reducing bacteria (SRB) in soil. Corrosion-induced damage to the pipeline steel could result in serious consequences. Studies have shown the critical role of interfacial film in SRB-induced corrosion. However, the specific effect of interfacial film was not examined. The effect of film on the corrosion of X80 steel in neutral soil environment was determined using scanning electron microscopy, energy-dispersive spectroscopy, and electrochemical impedance spectroscopy. The structure and electrochemical characteristics of the surface film of X80 steel were examined in the presence of SRB in Shenyang soil. The results showed that, at the beginning of immersion (14 h), the steel surface mainly adsorbed the SRB biofilm, and the biofilm slowed down the corrosion reaction. A small amount of the biofilm and corrosion product film was observed on the electrode surface after immersion for 14–48 h. The corrosion product film destroyed the protection of the biofilm, increasing corrosion. After immersion for 48 h, the corrosion product contents and polarisation resistance increased. After immersion for 240 h, a dense corrosion product film formed on the sample surface, showing the least corrosion. The protective effect of corrosion products on X80 steel was much greater than that of the biofilm.
Résumé : Water treatment plants (WTP) are vital in the food, pharmaceutical and chemical process industries. This investigation describes the dense microbial fouling by microbes and organic compounds in a WTP of a heavy water producing industrial unit. On-site observations showed severe algal and bacterial growth in the various units of the WTP which are open to the atmosphere and very dense fungal fouling in the closed vacuum degasser unit. Digital and microscopic images showed that the microbial fouling problem was primarily due to a fungus. Microbiological analysis showed a count of ~10(5) cfu mL(-1) in various sections of the WTP. On the contrary, slime/biofilm scrapings had very high bacterial populations (>10(9) cfu cm(-2)). High organic carbon values in the system (5.0 to 19.5 ppm) had supported the growth of the fouling fungus in various sections of the WTP along with bacteria. Chlorination was found to be inadequate in controlling the biofouling problem. Consequently chlorine dioxide was tested and found to be a better biocide in controlling the bacterial population. A 2.0% Sodium-2-pyridinethiol-1-oxide solution had completely inhibited the fouling fungus. The paper discusses the importance of fungal adaptation in an industrial unit and highlights the biodeterioration of various sections of the WTP unit.
Résumé : Electrochemical and immersion tests were conducted to characterize the bio-corrosion resistance of as-extruded Mg–Ca binary alloys with submicron grain size. The microstructures were further characterized by optical microscopy (OM), scanning electronic microscopy and transmission electron microscope (TEM). The grain size was estimated from OM and TEM images. Three samples and at least 20 images were used to evaluate the average grain size. Macro-textures of the as-extruded samples were measured via X-ray diffraction. The Mg–2Ca alloy extruded at 300 °C (2Ca-300) exhibits the lowest current density of 1.683 mA·cm−2 and corrosion rate of 22.14 g·m−2·day−1 in simulated body fluid, which is comparable with that of pure Mg. The Ca addition can reduce grain size of as-extruded Mg alloy and decrease the corrosion rate. The formed Mg2Ca phases would accelerate the local galvanic corrosion and protect the α-Mg matrix simultaneously due to the lower electrode potential. The lower defect density, finer grain size and weaker basal texture intensity contribute to the excellent bi-corrosion resistance of the 2Ca-300 alloy.
Résumé : According to data gathered in the last Metal Foundry Industrial Production Survey , approximately 46% of the industrial production of ferrous alloys is gray-iron. In this context the study of the atmospheric corrosion resistance of gray-iron becomes interesting to asset its useful life when subject to weathering conditions. The studies of gray-iron atmospheric corrosion behavior are scarce due to the fact that it takes long periods of time for its real-time characterization.
In order to validate an accelerated atmospheric corrosion test, a gray cast iron  and a carbon steel  were subjected to a 40 days accelerated testing, that includes wetting in a saline fog chamber, washing and drying , measuring the corroded thickness at each exposure time. These results were then compared with those obtained by Southwell et al  after 16 years of exposure in a marine environment (Panamá Canal). The result analysis reveals that both materials show a bimodal behavior, in accordance with those results reported by Melchers et al [6, 7, 8]. This behavior is characterized by an inflection point in the kinetic curve of corrosion, meanly related to the presence of bacteria in the interphase metal-corrosion products. The fact that the kinetic curve of corroded thickness shows an inflection point, allows the validation of the proposed methodology as a path to evaluate the atmospheric corrosion resistance in a short time test
Résumé : Influence of Bis[triethoxysilyl]ethane (BTSE) silane coating on the corrosion resistance of a mild steel in an aerobic chloride medium and an anaerobic microbial medium containing sulphate reducing bacteria (SRB) was analysed using a comprehensive electrochemical and chemical analyses. The Silane coating acted as a physical barrier and significantly improved the corrosion resistance of mild steel in an aerobic chloride medium. However, the improvement was limited in the anaerobic microbial medium. Surface morphology examination and chemical analysis using Fourier transformed infrared spectroscopy confirm the formation of a dense biofilm on BTSE-coated surface after pre-exposure to biotic media, which can be attributed to the absence of any antimicrobial functional group in this silane. This study is first of its kind to indicate the limitations of established coating systems in retarding microbial corrosion and emphasizes the importance of the modification of current coating systems with anti-microbial functional groups to impede the formation of biofilms and effectively hinder microbial corrosion.
Résumé : This paper reviews the types of bacteria used in concrete and the ways it can be applied as a healing agents. This paper also gives a brief description of the various properties of concrete which vary with the addition of bacteria. Micro-cracks are inherently present in concrete. This causes degradation of concrete leading to ingress of deleterious substances into concrete, resulting in deterioration of structures. Due to this concrete needs to be rehabilitated. To surmount these situations self-healing techniques are adopted. By the addition of urease engendering bacteria along with calcium source results in calcite precipitation in concrete. Bio-mineralization techniques give promising results in sealing the micro-cracks in concrete. The freshly composed micro-cracks can be sealed up by perpetual hydration process in concrete. The ureolytic bacteria which include Bacillus Pasteurii, Bacillus Subtilis which can engender urea are integrated along with the calcium source to seal the freshly composed micro cracks by CaCO3 precipitation. For the amelioration of pore structure in concrete, the bacterial concentrations were optimized for better results. The literature shows that Encapsulation method will give better results than direct application method and also shows that the use of bacteria can increase the strength and durability properties of concrete.
Résumé : This study hypothesised that there may be induction of pitting corrosion or microbially-induced corrosion on stainless steel (SS) dairy-processing surfaces by biofilms of common milk sporeformers such as Bacillus sporothermodurans and Geobacillus stearothermophilus. Scanning electron microscopy (SEM) and micrographs generated from energy-dispersive spectroscopy were used to observe pitting corrosion and to find the elemental composition and distribution on the control and pitted surfaces. From SEM images and energy-dispersive spectroscopy micrographs, it was observed that pitting corrosion on SS could be induced by biofilms of both B. sporothermodurans and G. stearothermophilus.
Résumé : There is no coating technology currently available to prevent the notorious biofilm formation issue. Here, a potential solution to fully address this tough issue is reported by developing a super-antifouling coating. The use of zwitterionic hydrogel (a double-sided tape) and commercial superglue is combined and a durable and ultrarobust antifouling zwitterionic (DURA-Z) coating is created that can be easily and universally applied on common substrates. Commercial superglue mostly for binding hydrophobic materials is used to strongly immobilize the superhydrophilic DURA-Z coating through interpenetration. DURA-Z coating effectively solves several key challenges preventing the current antifouling coatings from practical use, including difficult fabrication, low efficacy, poor toughness, and durability. The fabricated DURA-Z coating retains antifouling property after 90 d of immersion in water, 50 d of buffer shearing, and 30 d of water flushing, and after repeated knife scratch and sandpaper abrasion under 570 kPa. The DURA-Z coating achieves a rarely reported long-term biofilm resistance to both Gram-positive and Gram-negative bacteria and fungi: it remains almost “zero” microbe adhesion after continuously challenged by more than 109 cells mL−1 culture medium for 30 d.
Résumé : Microbial communities of six samples from Escravos and Meren oil production facility in Nigeria were examined after biocide treatment using cultural and molecular approaches. Sulfate reducing bacteria (SRB) count and activity were the highest in skimmer pit samples (1N1) which was affiliated with Euryarchchaeota (44%) and Proteobacteria (39%). Treatment of Meren injection water (1N2) with biocides significantly reduced SRB population (102 cell/ml). Sample 1N3 (produced water discharge area) and 1N5 (treated produced water) were dominated by 70.79 and 52% Euryarchaeota, respectively. 1N4 (partially treated produced water) was dominated by Euryarchaeota (51.78%) and Proteobacteria (38%), while 1N6 (produced oil) was dominated by Proteobacteria (28%) and Euryarchaeota (62.6%). Metabolic activities in 1N1, 1N4 and 1N5 were dominated by sulfate reduction and methanogenesis; however, that of 1N2 was dominated only by sulfate reduction, while 1N3 and 1N6 were dominated by methanogenesis. Anaerobic incubation of 1N1 samples gave relatively higher corrosion rates (0.065 mm/year) while 1N2, 1N3 and 1N5 gave moderate corrosion rates (0.018 to 0.037 mm/year). This investigation in a Nigerian oil facility have substantially expanded our knowledge on the extent of microbial diversity in these fields after routine biocide treatment and have also shown the abundance and complexity of microbial communities in these fields that have potential to initiate souring and corrosion despite regular biocide treatment. Key words: Sulfate reduction, methanogenesis, corrosion, souring, microbial diversity
Résumé : The paper presents the results on biofilm formation induced by pure Desulfovibrio desulfuricans strains and its effect on corrosion behaviour of 2205 duplex stainless steel (DSS). Biofilm formation and damage process stimulated by D. desulfuricans strains are analysed with reference to their metabolic activity and to the surface characterisation of structure and configuration of the biofilm. Electrochemical techniques are applied to monitor bacterial attachment to the steel surface and to determine the influence of bacteria on the passivity and corrosion resistance of 2205 DSS. The obtained results prove that 2205 DSS is rapidly colonised by D. desulfuricans and that the biofilms formed affect its corrosion resistance. Bacterial activity leads to the more noble corrosion potential values and to the increased current densities on the potentiodynamic polarisation curves. SEM observations reveal micropits as well as signs of crevice attack on the steel surface.
Résumé : Microbiologically influenced corrosion (MIC) is the terminology applied where the actions of microorganisms influence the corrosion process. In literature, terms such as microbial corrosion, biocorrosion, microbially influenced/induced corrosion, and biodegradation are often applied.
MIC research in the oil and gas industry has seen a revolution over the past decade, with the introduction of molecular microbiological methods: (MMM) as well as new industry standards and procedures of sampling biofilm and corrosion products from the process system.
This review aims to capture the most important trends the oil and gas industry has seen regarding MIC research over the past decade.
The paper starts out with an overview of where in the process stream MIC occurs − from the oil reservoir to the consumer. Both biotic and abiotic corrosion mechanisms are explained in the context of managing MIC using a structured corrosion management (CM) approach.
The corrosion management approach employs the elements of a management system to ensure that essential corrosion control activities are carried out in an effective, sustainable, well-planned and properly executed manner. The 3-phase corrosion management approach covering of both biotic and abiotic internal corrosion mechanisms consists of 1) corrosion assessment, 2) corrosion mitigation and 3) corrosion monitoring. Each of the three phases are described in detail with links to recent field cases, methods, industry standards and sampling protocols.
In order to manage the corrosion threat, operators commonly use models to support decision making. The models use qualitative, semi-quantitative or quantitative measures to help assess the rate of degradation caused by MIC. The paper reviews four existing models for MIC Threat Assessment and describe a new model that links the threat of MIC in the oil processing system located on an offshore platform with a Risk Based Inspection (RBI) approach.
A recent field case highlights and explains the conflicting historic results obtained through serial dilution of culture media using the most probable number (MPN) method as compared to data obtained from corrosion monitoring and the quantitative polymerase chain reaction (qPCR) method. Results from qPCR application in the field case have changed the way MIC is monitored on the oil production facility in the North Sea.
A number of high quality resources have been published as technical conference papers, books, educational videos and peer-reviewed scientific papers, and thus we end the review with an updated list of state-of-the-art resources for anyone desiring to become more familiar with the topic of MIC in the upstream oil and gas sector.
Résumé : Microbiologically influenced corrosion (MIC) attacks various types of metals and alloys including copper and its alloys. Copper and its alloys are widely used for seawater piping system and heat exchangers because of its good resistance to corrosion combined with mechanical workability, excellent electrical and thermal conductivity, and ease in soldering and brazing. Despite the well-known toxicity of cuprous ions toward living organisms, the copper based alloys are not immune to microbial colonization and resulting MIC. Localised corrosion attack has been reported for copper alloys when used in contact with seawater. Both biotic and abiotic mechanisms have been used to explain the nature of corrosion attack on these alloys. This article reviews the different mechanisms proposed for MIC of copper alloys, the tolerance of different microorganisms towards coppers ions and its effect on subsequent microbial corrosion. In addition, the results of some of our recent experiments showing localised and/or inter-granular corrosion of copper-nickel alloys by sulphate reducing
Résumé : Smart coatings are innovative coatings that can react spontaneously, due to inbuilt stimuli-responsive mechanisms. The functionality obtained from these class of coatings at the metal-solution interface in aggressive environments has led to advances in anticorrosion studies and applications. This review emphasizes the effects of corrosion sensing, self-healing, anti-fouling, and self-cleaning coatings for corrosion inhibition of metallic materials. However, in keeping with the theme, novel coating designs with anticorrosive characteristics that outweigh the limitations in the use of conventional coatings have been discussed. Noting that the presence of high-quality nanoparticles in coating formulations has outweighed the effects of the microparticles. These have triggered unprecedented functionalities in the smart coatings. The smart coatings respond to single/multiple external stimuli such as light, dirt, pH changes, temperature, aggressive liquids, bio-foulant, impact, fatigue etc; and have demonstrated outstanding, barrier properties with scratch resistance, in-situ healing, superhydrophobicity, superoleophilicity, high optical transmission, thermal stability, and resistance to strong acids etc., resulting in extended service life of the coatings and the protected metallic materials. The utilization of smart coatings in complex, real-time conditions, effectively controls the triggers of metallic degradation, structural failures, and resource depletion.
Résumé : Electron transfer is a rate-limiting step in microbiologically influenced corrosion (MIC) caused by microbes that utilize extracellular electrons. Cross-cell wall electron transfer is necessary to transport the electrons released from extracellular iron oxidation into the cytoplasm of cells. Electron transfer mediators were found to accelerate the MIC caused by sulfate reducing bacteria. However, there is no publication in the literature showing the effect of electron transfer mediators on MIC caused by nitrate reducing bacteria (NRB). This work demonstrated that the corrosion of anaerobic Pseudomonas aeruginosa (PAO1) grown as a nitrate reducing bacterium biofilm on C1018 carbon steel was enhanced by two electron transfer mediators, riboflavin and flavin adenine dinucleotide (FAD) separately during a 7-day incubation period. The addition of either 10 ppm (w/w) (26.6 μM) riboflavin or 10 ppm (12.7 μM) FAD did not increase planktonic cell counts, but they increased the maximum pit depth on carbon steel coupons considerably from 17.5 μm to 24.4 μm and 25.0 μm, respectively. Riboflavin and FAD also increased the specific weight loss of carbon steel from 2.06 mg/cm2 to 2.34 mg/cm2 and 2.61 mg/cm2, respectively. Linear polarization resistance, electrochemical impedance spectroscopy and potentiodynamic polarization curves all corroborated the pitting and weight loss data.
Résumé : Buried steel infrastructure can be a source of iron ions for bacterial species, leading to microbiologically influence corrosion (MIC). Localised corrosion of pipelines due to MIC is one of the key failure mechanisms of buried steel pipelines. In order to better understand the mechanisms of localised corrosion in soil, semi-solid agar has been developed as an analogue for soil. Here, Pseudomonas fluorescens has been introduced to the system to understand how bacteria interact with steel. Through electrochemical testing including open circuit potentials, potentiodynamic scans, anodic potential holds and electrochemical impedance spectroscopy it has been shown that P. fluorescens increases the rate of corrosion. Time for oxide and biofilms to develop was shown to not impact on the rate of corrosion but did alter the consistency of biofilm present and the viability of P. fluorescens following electrochemical testing. The proposed mechanism for increased corrosion rates of carbon steel involves the interactions of pyoverdine with the steel, preventing the formation of a cohesive passive layer, after initial cell attachment, followed by the formation of a metal concentration gradient on the steel surface.
Résumé : Microbiologically influenced corrosion (MIC) is the primary mechanism causing failures of upstream oil pipelines. This work investigated the biofilm formation and MIC of an X70 pipeline steel in oilfield produced water containing sulfate reducing bacteria at various flow velocities. Results demonstrate that the fluid flow affects the biofilm formation, and thus MIC of the steel under biofilm. At low flow velocities such as 0.2 m/s, a layer of biofilm forms on the steel surface, and the steel suffers from MIC, especially pitting corrosion. With the increase of flow velocity to 1.0 m/s, the biofilm is not able to form. Thus, the steel MIC reduces with the increasing flow velocity of the fluid. Moreover, the corrosion products and biofilm are overlapped at the low flow velocity. At the high flow velocity, the surface layer formed on the steel is mainly corrosion products. Corrosion pits can be formed on the steel at the low flow velocity due to microbial attack.
Résumé : The composition and distribution characteristics of bacterial communities in biofilms attached to hydraulic concrete structure (HCS) surfaces were investigated for the first time in four reservoirs in the middle and lower reaches of the Yangtze River Basin using 16S rRNA Miseq sequencing. High microbial diversity was found in HCS biofilms, and notable differences were observed in different types of HCS. Proteobacteria, Cyanobacteria and Chloroflexi were the predominant phyla, with respective relative abundances of 35.3%, 25.4% and 13.0%. The three most abundant genera were Leptolyngbya, Anaerolineaceae and Polynucleobacter. The phyla Beta-proteobacteria and Firmicutes and genus Lyngbya were predominant in CGP, whereas the phyla Cyanobacteria and Chloroflexi and genera Leptolyngbya, Anaerolinea and Polynucleobacter survived better in land walls and bank slopes. Dissolved oxygen, ammonia nitrogen and temperature were characterized as the main factors driving the bacterial community composition. The most abundant groups of metabolic functions were also identified as ammonia oxidizers, sulphate reducers, and dehalogenators. Additionally, functional groups related to biocorrosion were found to account for the largest proportion (14.0% of total sequences) in gate piers, followed by those in land walls (11.5%) and bank slopes (10.2%). Concrete gate piers were at the greatest risk of biocorrosion with the most abundant negative bacterial groups, especially for sulphate reducers. Thus, it should be paid high attention to the biocorrosion prevention of concrete gate piers. Overall, this study contributed to the optimization of microbial control and the improvement of the safety management for water conservation structures.
Résumé : In this study, a silver and hydroxyapatite (Ag/HA) composite coating was generated on an extruded Mg-2Zn-1Mn-0.5Ca magnesium alloy through a chemical conversion process. Scanning electron microscopy (SEM) observation showed that a gray conversion coating was formed with white snow-like and gray globular particles or crystals located randomly above the coating. X-ray diffraction (XRD) combined with X-ray photoelectron spectroscopy (XPS) analysis indicated that the conversion coating was mainly composed of Ca10(PO4)6(OH)2 with limited quantities of Ag/Ag2CO3, CaHPO4·2H2O and CaSiO3. The formation mechanism of the Ag/HA composite conversion coating is discussed in this work. The electrochemical polarization and EIS tests showed that the conversion coating markedly improved the bio-corrosion resistance of the Mg-2Zn-1Mn-0.5Ca alloy in Hank's solution. Adhesion test showed that the coating has a strong bonding strength. The bactericidal activity was assessed with the zone of inhibition method, and the composite coating on the Mg alloy substrates exhibits good antibacterial performance.
Résumé : Offshore oil-producing platforms are designed for efficient and cost-effective separation of oil from water. However, design features and operating practices may create conditions that promote the proliferation and spread of biocorrosive microorganisms. The microbial communities and their potential for metal corrosion were characterized for three oil production platforms that varied in their oil-water separation processes, fluid recycling practices, and history of microbially influenced corrosion (MIC). Microbial diversity was evaluated by 16S rRNA gene sequencing, and numbers of total bacteria, archaea, and sulfate-reducing bacteria (SRB) were estimated by qPCR. The rates of 35S sulfate reduction assay (SRA) were measured as a proxy for metal biocorrosion potential. A variety of microorganisms common to oil production facilities were found, but distinct communities were associated with the design of the platform and varied with different locations in the processing stream. Stagnant, lower temperature (<37 °C) sites in all platforms had more SRB and higher SRA compared to samples from sites with higher temperatures and flow rates. However, high (5 mmol L−1) levels of hydrogen sulfide and high numbers (107 mL−1) of SRB were found in only one platform. This platform alone contained large separation tanks with long retention times and recycled fluids from stagnant sites to the beginning of the oil separation train, thus promoting distribution of biocorrosive microorganisms. These findings tell us that tracking microbial sulfate-reducing activity and community composition on off-shore oil production platforms can be used to identify operational practices that inadvertently promote the proliferation, distribution, and activity of biocorrosive microorganisms.
Résumé : The concentration of sulphate present in wastewater can vary from 10 to 500 mg SO42−/L. During anaerobic conditions, sulphate is reduced to sulphide by sulphate-reducing bacteria (SRB). Sulphide generation is undesired in wastewater treatment plants (WWTPs). Previous research indicated that SRB are inhibited by the presence of electron acceptors (such as O2, NO3 and NO2). However, the contact times and concentrations used in those studies are by far higher than occur in WWTPs. Since sulphide can influence the biological nitrogen and phosphorus removal processes, this research aimed to understand how the different electron acceptors commonly present in biological nutrient removal (BNR) systems can affect the proliferation of SRB. For this purpose, a culture of SRB was enriched in a sequencing batch reactor (approx. 88% of the total bacteria population). Once enriched, the SRB were exposed for 2 h to typical concentrations of electron acceptors like those observed in BNR systems. Their activity was assessed using three different types of electron donors (acetate, propionate and lactate). Oxygen was the most inhibiting electron acceptor regardless the carbon source used. After exposure to oxygen and when feeding acetate, an inactivation time in the sulphate reduction activity was observed for 1.75 h. Once the sulphate reduction activity resumed, only 60% of the original activity was recovered. It is suggested that the proliferation of SRB is most likely to occur in BNR plants with an anaerobic fraction higher than 15% and operating at sludge retention times higher than 20 days (at a temperature of 20 °C). These results can be used to implement strategies to control the growth of sulphate reducers that might compete for organic carbon with phosphate-accumulating organisms.
Résumé : In 2013 the Hull Inspection Techniques and Strategies (HITS) paper SPE-13OE-P-409-SPE [ 1 ], introduced and outlined the HITS joint industry project (JIP) objectives. This paper summarises the JIP's progress and the success achieved to date. It
Résumé : When cleaning the hull of a ship, significant shear stresses are needed to remove established biofouling organisms. Given that there exists a link between the amount of time that fouling accumulates and the stress required to remove it, it is not surprising that more frequent grooming requires less shear stress. Yet, it is unclear if there is a minimum stress needed to prevent the growth of macrofouling in the limit of continuous grooming. This manuscript shows that single bubble stream aeration provides continuous grooming and prevents biofouling accumulation in regions where the average wall stress exceeds 0.01 Pa. This value was found by comparing observations of biofouling growth from field studies with complementary laboratory measurements that probe the associated flow fields. These results suggest that aeration and other continuous grooming systems must exceed a wall stress of 0.01 Pa to prevent macrofouling accumulation.
Résumé : In this article, experimental analysis is done on shell-and-tube heat exchanger of a marine vessel for removal of fouling using optimum surface-cleaning techniques. The main objective is to compare the performance of the heat exchanger before and after maintenance. Two identical deteriorated systems of heat exchangers are taken and real-time analysis is conducted. The log data are taken before and after undergoing maintenance for the two systems. Two different cleaning techniques are used, namely, chemical cleaning and mechanical cleaning. Detailed calculations are made for the shell-and-tube heat exchanger. From the obtained data, comparisons are made for different parameters on the tube side such as friction factor, heat transfer coefficient and pressure drop, as well as total heat transfer rate on the shell side. From the analysis and comparison, it was found that greater heat transfer takes place for the tubes cleaned using the chemical cleaning method than for tubes cleaned by the mechanical cleaning method. Pressure drop is found to be less for chemical cleaning method than mechanical cleaning method. This indicates that the fouling effect is reduced for tubes cleaned by the chemical cleaning method, and furthermore these tubes remain corrosion-resistant for longer periods of time.
Résumé : Better understanding of the mechanisms of antifouling compounds is recognized to be of high value in establishing sensitive biomarkers, allowing the targeted optimization of antifouling compounds and guaranteeing environmental safety. Despite vigorous efforts to find new antifouling compounds, information about the mechanisms of antifouling is still scarce. This review summarizes the progress into understanding the molecular mechanisms underlying antifouling activity since 2012. Non-toxic mechanisms aimed at specific targets, including inhibitors of transmembrane transport, quorum sensing inhibitors, neurotransmission blockers, adhesive production/release inhibitors and enzyme/protein inhibitors, are put forward for natural antifouling products or shelf-stable chemicals. Several molecular targets show good potential for use as biomarkers in future mechanistic screening, such as acetylcholine esterase for neurotransmission, phenoloxidase/tyrosinase for the formation of adhesive plaques, N-acyl homoserine lactone for quorum sensing and intracellular Ca2+ levels as second messenger. The studies on overall responses to challenges by antifoulants can be categorized as general targets, including protein expression/metabolic activity regulators, oxidative stress inducers, neurotransmission blockers, surface modifiers, biofilm inhibitors, adhesive production/release inhibitors and toxic killing. Given the current situation and the knowledge gaps regarding the development of alternative antifoulants, a basic workflow is proposed that covers the indispensable steps, including preliminary mechanism- or bioassay-guided screening, evaluation of environmental risks, field antifouling performance, clarification of antifouling mechanisms and the establishment of sensitive biomarkers, which are combined to construct a positive feedback loop.
Résumé : Six new compounds, omaezol, intricatriol, hachijojimallenes A and B, debromoaplysinal, and 11,12-dihydro-3-hydroxyretinol have been isolated from four collections of Laurencia sp. These structures were determined by MS and NMR analyses. Their antifouling activities were evaluated together with eight previously known compounds isolated from the same samples. In particular, omaezol and hachijojimallene A showed potent activities (EC50 = 0.15–0.23 µg/mL) against larvae of the barnacle Amphibalanus amphitrite.
Résumé : In this review, a comprehensive overview about the antifouling compounds from marine invertebrates is described. In total, more than 198 antifouling compounds have been obtained from marine invertebrates, specifically, sponges, gorgonian and soft corals.
Résumé : Marine macroalgae produce a wide variety of biologically-active metabolites that have been developed into commercial products, such as antibiotics, immunosuppressive, anti-inflammatory, cytotoxic agents, and cosmetic products. Many marine algae remain clean over longer periods of time, suggesting their strong antifouling potential. Isolation of biogenic compounds and the determination of their structure could provide leads for the development of environmentally-friendly antifouling paints. Isolated substances with potent antifouling activity belong to fatty acids, lipopeptides, amides, alkaloids, lactones, steroids, terpenoids, and pyrroles. It is unclear as yet to what extent symbiotic microorganisms are involved in the synthesis of these compounds. Algal secondary metabolites have the potential to be produced commercially using genetic and metabolic engineering techniques. This review provides an overview of publications from 2010 to February 2017 about antifouling activity of green, brown, and red algae. Some researchers were focusing on antifouling compounds of brown macroalgae, while metabolites of green algae received less attention. Several studies tested antifouling activity against bacteria, microalgae and invertebrates, but in only a few studies was the quorum sensing inhibitory activity of marine macroalgae tested. Rarely, antifouling compounds from macroalgae were isolated and tested in an ecologically-relevant way.
Résumé : An electrochemical anti-fouling method, based upon the generation of chlorine from seawater, was applied to a proprietary design of Lab on a Chip conductivity, temperature and dissolved oxygen sensor. The method was evaluated using PCR after a six-week field trial in which it significantly reduced the burden of bacterial biofouling.
Résumé : Superhydrophobic coatings have broad applications owing to their excellent water-resisting and self-cleaning properties. In this study, we have successfully fabricated coated meshes with robust and superhydrophobic surface (i.e., water-repellent magnesium stearate powders on substrates made of phenol-formaldehyde resin). These coated meshes showed superhydrophobicity with water contact angles exceeding 150° and excellent self-cleaning property both in air and oil circumstances. Additionally, the superhydrophobic surfaces also exhibited prominent mechanical stability, thermal stability, corrosion resistance, and oil/water separation properties (>92%). Therefore, it is believed that the facile fabrication presented in this study may provide a novel methodology and these robust and superhydrophobic coated meshes have potential applications in oil/water separation.
Résumé : Biofouling, the adsorption of organisms to a surface, is a major problem today in many areas of our lives. This includes: (i) health, as biofouling on medical device leads to hospital-acquired infections, (ii) water, since the accumulation of organisms on membranes and pipes in desalination systems harms the function of the system, and (iii) energy, due to the heavy load of the organic layer that accumulates on marine vessels and causes a larger consumption of fuel. This paper presents an effective electrochemical approach for generating antifouling and antimicrobial surfaces. Distinct from previously reported antifouling or antimicrobial electrochemical studies, we demonstrate the formation of a hydrogen gas bubble layer through the application of a low-voltage square-waveform pulses to the conductive surface. This electrochemically generated gas bubble layer serves as a separation barrier between the surroundings and the target surface where the adhesion of bacteria can be deterred. Our results indicate that this barrier could effectively reduce the adsorption of bacteria to the surface by 99.5%. We propose that the antimicrobial mechanism correlates with the fundamental of hydrogen evolution reaction (HER). HER leads to an arid environment that does not allow the existence of live bacteria. In addition, we show that this drought condition kills the preadhered bacteria on the surface due to water stress. This work serves as the basis for the exploration of future self-sustainable antifouling techniques such as incorporating it with photocatalytic and photoelectrochemical reactions.
Résumé : Antifouling and drag reduction is an important part of ship tribology. During the process of fouling, bacterial biofilms formation is the first step. Algae, barnacles and shells and other large bio fouling organisms attach on the hull becau
Résumé : Aluminum and its alloys are widely used in almost all industries and for marine and medical applications. However, their surfaces are easily colonized by bacteria that form biofilms and corroded by chemical reactions. We report here a simple method to fabricate polyaniline/chitosan/zinc stearate superhydrophobic coatings on aluminum with a micro–nanosurface structure by polymerization of aniline and deposition of chitosan and zinc stearate coating. The fabricated coatings have been characterized by ATR-IR, XRD, FE-SEM, and EDX. The superhydrophobic surface shows the highest water-repellent property with contact angle of 150.7°, which is responsible for antiadhesion of bacteria, antiicing property, and excellent corrosion resistance of aluminum. The corrosion behavior of the coating in the 3.5% NaCl solution was investigated by EIS and potentiodynamic polarization. The efficacies of the different coatings against bacteria that are commonly encountered in marine (Desulfovibrio desulfuricans) and medical applications (Staphylococcus aureus and Escherichia coli) are demonstrated.Graphical AbstractOpen image in new window
Résumé : Aims: To develop a method to screen antifouling agents against marine bacterial adhesion as a sensitive, rapid, quantitative microplate fluorescent test. Methods and Results: Our experimental method is based on a natural biofilm formed by mono-incubation of the marine bacterium Pseudoalteromonas sp. D41 in sterile natural sea water in a 96 wells polystyrene microplate. The 4'6-diamidino-2-phenylindole (DAPI) dye was used to quantify adhered bacteria in each well. Total measured fluorescence in wells was correlated with the amount of bacteria showing a detection limit of one bacterium per 5 µm2 and quantifying 2 x 107 to 2 x 108 bacteria adhered per cm2. The antifouling properties of three commercial surface active agents and chlorine were tested by this method in prevention of adhesion and also in detachment of already adhered bacteria. The marine bacterial adhesion inhibition rate depending on agent concentration showed a sigmoid shape like dose-response curve. Conclusions: This test is well adapted for a rapid and quantitative first screening of antifouling agents directly in seawater in the early steps of marine biofilm formation. Significance and impact of the study: In contrast with usual screenings of antifouling products which detect a bactericidal activity, this test is more appropriate to screen antifouling agents for bacterial adhesion removal or bacterial adhesion inhibition activities. This screening test focuses on antifouling properties of products, especially the first steps of marine biofilm formation.
Résumé : As part of ongoing commitments to produce electricity from renewable energy sources in Scotland, Orkney waters have been targeted for potential large-scale deployment of wave and tidal energy converting devices. Orkney has a well-developed infrastructure supporting the marine energy industry; recently enhanced by the construction of additional piers. A major concern to marine industries is biofouling on submerged structures, including energy converters and measurement instrumentation. In this study, the marine energy infrastructure and instrumentation were surveyed to characterise the biofouling. Fouling communities varied between deployment habitats; key species were identified allowing recommendations for scheduling device maintenance and preventing spread of invasive organisms. A method to measure the impact of biofouling on hydrodynamic response is described and applied to data from a wave-monitoring buoy deployed at a test site in Orkney. The results are discussed in relation to the accuracy of the measurement resources for power generation. Further applications are suggested for future testing in other scenarios, including tidal energy.
Résumé : Background
The past years have witnessed a growing number of researches in biofilm forming communities due to their environmental and maritime industrial implications. To gain a better understanding of the early bacterial biofilm community, microfiber nets were used as artificial substrates and incubated for a period of 24 h in Mauritian coastal waters. Next-generation sequencing technologies were employed as a tool for identification of early bacterial communities. Different genes associated with quorum sensing and cell motility were further investigated.
Proteobacteria were identified as the predominant bacterial microorganisms in the biofilm within the 24 h incubation, of which members affiliated to Gammaproteobacteria, Alphaproteobacteria and Betaproteobacteria were among the most abundant classes. The biofilm community patterns were also driven by phyla such as Firmicutes, Bacteroidetes, Chloroflexi, Actinobacteria and Verrucomicrobia. The functional analysis based on KEGG classification indicated high activities in carbohydrate, lipid and amino acids metabolism. Different genes encoding for luxI, lasI, agrC, flhA, cheA and cheB showed the involvement of microbial members in quorum sensing and cell motility.
This study provides both an insight on the early bacterial biofilm forming community and the genes involved in quorum sensing and bacterial cell motility.
Résumé : Dibromohemibastadin-1 (DBHB) is an already known potent inhibitor of blue mussel phenoloxidase (which is a key enzyme involved in bioadhesion). Within this study, the potentiality of DBHB against microfouling has been investigated. The activity of DBHB was evaluated on key strains of bacteria and microalgae involved in marine biofilm formation and bioassays assessing impact on growth, adhesion and biofilm formation were used. To assess the efficiency of DBHB when included in a matrix, DBHB varnish was prepared and the anti-microfouling activity of coatings was assessed. Both in vitro and in situ immersions were carried out. Confocal Laser Scanning Microscopy (CLSM) was principally used to determine the biovolume and average thickness of biofilms developed on the coatings. Results showed an evident efficiency of DBHB as compound and varnish to reduce the biofilm development. The mode of action seems to be based principally on a perturbation of biofilm formation rather than on a biocidal activity in the tested conditions.
Résumé : Progress in materials science is associated with the development of nanomaterials in terms of energy-saving, environmentally friendly, and low-cost methods. Since the use of tributyltin compounds in antifouling coatings was banned in 2003, the search for ecofriendly alternatives has been promoted. Foul-release (FR) nanocoatings have been extensively investigated because of their non-stick, ecological, and economic advantages. Such nanocomposite systems are dynamic non-stick surfaces that deter any fouling attachment through physical anti-adhesion terminology. Instead of biocidal solutions, several functional FR nanocomposite coatings have been developed to counter biofouling and biocorrosion with ecological and ecofriendly effects. Selected inorganic nanofillers have been incorporated because of their enhanced interaction at the filler‐polymer interface for nanocomposites. Metallic nanoparticles and their oxides have also been widely explored because of their unique morphological characteristics and size-dependent, self-cleaning properties. In modeling a novel series of FR nanocoatings, two modes of prevention are combined: chemical inertness and physical microfouling repulsion for maritime navigation applications. Long-term durability and self-cleaning performance are among the advantages of developing effective, stable, and ecofriendly modeling alternatives. This review provides a holistic overview of nano-FR research achievements and describes recent advancements in non-stick marine nanocoatings for ship hulls. This review highlights the key issues of nanocomposite structures and their features in improving the biological activity and surface self-cleaning performance of ship hulls. This review may also open new horizons toward futuristic developments in FR nanocomposites for maritime navigations.
Résumé : Marine biofouling is one of the most challenging problems today. Silicone polymer based coatings with low surface energy and elastic modulus can effectively inhibit or release biofouling. However, their non-repairable property and poor antifouling ability on static conditions limit their applications. Here, we report a self-repairing coating consisting of poly(dimethylsiloxane) based polyurea (PDMS-PUa) and a small amount of organic antifoulant (4,5-dichloro-2-n-octyl-4-isothiazolin-3-one) (DCOIT). The coating can completely recover itself from damaging in mechanical properties either in air or artificial seawater at room temperature. Such recovery can be accelerated at a higher temperature. Moreover, the release rate of DCOIT is almost constant and can be regulated by its concentration. The six-month marine field tests demonstrate that the system has a good antifouling/fouling release performance even on static conditions.
Résumé : In this work, 37 bacterial strains isolated from biofouling of marine organisms and from the Museum of Heterotrophic Bacteria of the National Scientific Center of Marine Biology were studied. The strains were identified based on their phenotypic characteristics and on the fatty acid composition of their cell wall lipids. Members of the genus Pseudoalteromonas prevailed both in associated microflora of two dinoflagellate clones and in the biofilms from marine hydrobionts. Associated microflora included also members of the CFB cluster, Bacillus, Sulfitobacter, Acinetobacter, Shewanella, and Psychrobacter. A considerable portion of strains (48.6%) exhibited antimicrobial activity. Antifouling activity against algal spores was studied using single-species bacterial biofilms and the spores of Ulva lactuca и Undaria pinnatifida, the algae most common in the Sea of Japan. Strong inhibitory effect on attachment of Ulva and Undaria spores was observed for 75 and 51% of the strains, respectively. Attached spores were, however, less sensitive to the inhibitory action of biofilms. Species specificity of algal response to bacteria was shown, with a strain having different effect on the spores of different algal species. Biotechnologically promising strains were determined, which exhibited high activity against the spores of macroalgae and could probably be used as producers of antifouling substances and as components of antifouling coatings. No relation was found between antifouling activity of bacteria and the source of their isolation. Our results indicate wide occurrence of bacteria with antifouling activity among associated microflora of marine hydrobionts and demonstrate the extent of complexity and diversity of relations between bacterial biofilms and algal spores.
Résumé : Boundary structure is an important factor for significantly influencing the settlement of microalgae. In order to investigate the effect of boundary structure on the antifouling performances of biomimetic textured coatings, three different boundary structures were fabricated via biomimetic replication method and evaluated by recording the settlement amount of fouling microalgae including Nitzschia closterium f. minutissima, Phaeodactylum tricornutum and Chlorella. The results showed that imbricate boundary structure was more positive for antifouling, but depressed boundary structure and raised boundary structure played a negative role for antifouling. Especially, the depressed boundary structure displayed the worst antifouling performance which attributed to providing shelters for microalgae. The antifouling mechanism of microalgae settled on the biomimetic textured coatings with different boundary structures was revealed deeply.
Résumé : Wave energy devices are novel structures in the marine environment and, as such, provide a unique habitat for biofouling organisms. In this study, destructive scrape samples and photoquadrats were used to characterise the temperate epibenthic community present on prototypes of the Pelamis wave energy converter. The biofouling observed was extensive and diverse with 115 taxa recorded including four non-native species. Vertical zonation was identified on the sides of the device, with an algae-dominated shallow subtidal area and a deeper area characterised by a high proportion of suspension-feeding invertebrates. Differences in species composition and biomass were also observed between devices, along the length of the device and between sampling dates. This research provides an insight into the variation of biofouling assemblages on a wave energy device as well as the potential technical and ecological implications associated with biofouling on marine renewable energy structures.
Résumé : The current study reports the first comprehensive evaluation of a class of allelopathic terrestrial natural products as antifoulants in a marine setting. To investigate the antifouling potential of the natural dihydrostilbene scaffold, a library of 22 synthetic dihydrostilbenes with varying substitution patterns, many of which occur naturally in terrestrial plants, were prepared and assessed for their antifouling capacity. The compounds were evaluated in an extensive screen against 16 fouling marine organisms. The dihydrostilbene scaffold was shown to possess powerful general antifouling effects against both marine microfoulers and macrofoulers with inhibitory activities at low concentrations. The species of microalgae examined displayed a particular sensitivity toward the evaluated compounds at low ng/mL concentrations. It was shown that several of the natural and synthetic compounds exerted their repelling activities via nontoxic and reversible mechanisms. The activities of the most active compounds such as 3,5-dimethoxybibenzyl (5), 3,4-dimethoxybibenzyl (9), and 3-hydroxy-3′,4,5′-trimethoxybibenzyl (20) were comparable to the commercial antifouling booster biocide Sea-nine, which was employed as a positive control. The investigation of terrestrial allelopathic natural products to counter marine fouling represents a novel strategy for the design of “green” antifouling technologies, and these compounds offer a potential alternative to traditional biocidal antifoulants.
Résumé : Aquaculture is a billion dollar industry and biofouling of aquaculture installations has heavy economic penalties. The natural antifouling (AF) defence mechanism of some seaweed that inhibits biofouling by production of reactive oxygen species (ROS) inspired us to mimic this process by fabricating ZnO photocatalytic nanocoating. AF activity of fishing nets modified with ZnO nanocoating was compared with uncoated nets (control) and nets painted with copper-based AF paint. One month experiment in tropical waters showed that nanocoatings reduce abundances of microfouling organisms by 3-fold compared to the control and had higher antifouling performance over AF paint. Metagenomic analysis of prokaryotic and eukaryotic fouling organisms using next generation sequencing platform proved that nanocoatings compared to AF paint were not selectively enriching communities with the resistant and pathogenic species. The proposed bio-inspired nanocoating is an important contribution towards environmentally friendly AF technologies for aquaculture.
Résumé : Marine biofouling causes huge economic losses and serious problems to maritime industries. Consequently, there is a great demand for environmentally friendly antibiofouling technology. In the present study, we developed novel antifouling coatings by incorporating butenolide derived from marine bacteria into biodegradable poly(ε-caprolactone) based polyurethane. Measurements of mass loss indicated that the polymer was degraded in seawater and that the degradation rate increased in the presence of marine organisms or enzymes. Moreover, measured release rates indicated that butenolide could be released from the biodegradable polymer for at least 3 months and the release rate depended on both the concentration of butenolide and the temperature. Incorporating a naturally occurring resin (rosin) into the biodegradable polymer increased the self-renewal rate and improved the later release rate of butenolide. The field test indicated that the system had excellent antifouling properties.
Résumé : This article reports a review of microbiological corrosion. It addresses the general perspectives of the various bacteria involved in the biocorrosion, and these include sulphate-reducing bacteria, slime-forming bacteria, iron-oxidizing bacteria and sulphur bacteria. The review also reported on biofilms and effects, various sulphate-reducing bacteria mechanisms, the biodeterioration control methods, environment, fouling and the impact of microbiological corrosion. Microbial corrosion, as it affects stainless steel, mildsteel, aluminium alloy, the AL6XN (N083677) super austenitic stainless steel, and manufacturing and transportation, were reviewed
Résumé : Antifouling paints were applied on a wide range of the under seawater structures in order to protect them from the growth of fouling organisms. The performance investigation of two commercial anticorrosion and antifouling paints was conducted in Muara Baru port, Jakarta. The specimens were coated by anticorrosion and/or antifouling paint. Blank specimen (without exposed) were also prepared as a control. On the other hand, bare mild steel was prepared for measure the corrosion rate through weight loss method. The test panels containing specimens were exposed up to 3 months for immersion depths of 0, 1, 2, 3 meters from sea level. Sea water parameters such as temperature, pH, salinity, conductivity and dissolved oxygen (DO) were also measured. The evaluation of coating performance was carried out such as thickness, glossy, hardness and adhesion strength. The results showed that both surfaces of anticorrosion paint and bare mild steel specimen covered by fouling organisms, whereas no fouling took place on the surface of antifouling paint. The corrosion rate of bare mild steel in the depths of 0, 1, 2, 3 meters were 12.5; 11.6; 8.3; 10.4 mpy, respectively.
Résumé : Abstract The development of biofouling on surfaces in the marine environment impacts operations and efficiency. A management plan is presented to enable an estimation of the risk posed by biofouling and a strategy to accommodate and control the problem.
Résumé : Rosin-based antifouling paint with the incorporation of butenolide, a promising antifoulant, possesses the potential to deter the settlement of marine organisms on submerged surfaces. With the purpose to extend the antifouling duration, this research investigated the respective contribution of paint ingredients, including butenolide concentrations (5%, 10% and 15%), pigment choices (TiO2, Fe2O3, Cu2O and ZnO) and binder compositions (acrylic copolymer to rosin at 1: 2.5, 1.5: 2 and 2.5: 1), to the field antifouling performance of butenolide. A raft trial was carried out at Yung Shue O, Hong Kong after the application of antifouling paints on PVC panels. Biofouling dynamics on panel surfaces, such as coverage percentage and biomass accumulation, were monitored until submersion for 6 months to allow for the assessment of antifouling efficiency. Field results showed that butenolide incorporation generally inhibited the settlement of fouling species on the coated panels as demonstrated by the decreased surface coverage and biomass weight. Coatings with 1: 2.5 paints containing 10% butenolide exhibited the best antifouling performance with only 34% of the surface covered by fouling organisms, which mainly consisted of algae and slime. The smallest biomass increase of the fouling community was also observed for 1: 2.5 coatings. An increased proportion of rosin in binder compositions yielded better antifouling performance following the order of 1: 2.5 > 1.5: 2 > 2.5: 1. Laboratory experiments were also conducted to examine the behavior of paint coatings in stirring artificial seawater. Butenolide addition decreased the film hardness and inhibited water uptake, but resulted in weight loss of paint coatings. Along with the gradual release of butenolide, the hardness of paint films increased gradually. Overall, a service life of 6 months, while eliminating the use of heavy metals, highlights the effectiveness of butenolide-incorporated paint formulation, especially 1: 2.5 paint, as an environmentally benign and fouling-resistant candidate for future antifouling application.
Résumé : This study presents an analysis of a wave energy converter (WEC) system consisting of a buoy, a mooring system, and a power cable connected to a hub. The investigated WEC system is currently under full-scale testing near Runde in Norway. The purpose of the study was to investigate the characteristics of the entire system, primarily with regard to energy performance and the fatigue life of the mooring lines and power cable, considering the effects of marine biofouling and its growth on the system’s components. By means of parametric study, the energy performance and fatigue life of the mooring lines and power cable were investigated considering two mooring configurations, three biofouling conditions, four sea states in a scatter diagram, and three wave and current directions. Hydrodynamic and structural response simulations were conducted in a coupled response analysis using the DNV-GL software SESAM. Energy performance analyses and stress-based rainflow counting fatigue calculations were performed separately using an in-house code. The results show that, for a WEC system which has been deployed for 25 years, biofouling can reduce the total power absorption by up to 10% and decrease the fatigue life of the mooring lines by approximately 20%.
Résumé : SeaNine 211, with 4,5-dichloro-2-n-octyl-4-isothiazolin-3-one (DCOIT) being the biocidal ingredient, is a widely-used antifouling agent to deter the undesirable biofouling phenomenon. It is commercially promoted as an environmentally acceptable antifoulant mainly due to its claimed rapid degradation in marine environment. However, increasing researches document varying degradative kinetics in different environments, proving that SeaNine 211 is actually not degraded equally fast around the world (half-life between < 1 day and 13.1 days). Large-scale application of SeaNine 211 in antifouling coatings has also caused global contamination of marine environment in various compartments. For example, accumulation of SeaNine 211 is detected as high as 3700 ng/L in Spanish seawater and 281 ng/g dry weight in Korean sediment. Considering that SeaNine 211 is highly toxic against non-target marine organisms, environmental risk assessment finds that most marine organisms are endangered by SeaNine 211 in worst-case scenario. Its endocrine disrupting and reproductive impairing effects at environmentally worst-case concentrations further constitute a long-term threat to the maintenance of population stability. Therefore, in the light of the varying degradability, environmental pollution and high toxicity, especially the endocrine disruption, SeaNine 211 as an antifouling agent is likely to cause non-negligible damages to the marine ecosystem. There is an urgency to perform a systematic ecological risk assessment of SeaNine 211 to prevent the potential impacts on the health of marine environment. A regular monitoring also becomes necessary to place the usage of antifouling biocides under control.
Résumé : The aim of this study was to investigate, at a laboratory scale, the potentialities of an ultrasound-based treatment initially designed to eliminate fouling, as a ballast water treatment system. Therefore, early life stages of three different zooplanktonic species (Amphibalanus amphitrite, Brachionus plicatilis and Artemia salina) were exposed to ultrasound waves (20–22 kHz). The experimental set up included static assays with variations of time exposure (30 s, 60 s and 30 s on/60 s off/30 s on), material of tanks (stainless steel, galvanized steel and plastic) and position of the ultrasound source. Results showed that the treatment efficacy increased from 30 to 60 s and no differences were registered between 60 s-continuous exposure and pulse exposure. The highest efficacy was observed in Experiment I (metal-to-metal contact assay) with a mortality value of 93–95% for B. plicatilis and A. salina. It consisted of organisms located inside stainless steel tubes that were located in direct contact with the ultrasound source and treated for 60 s. Further, we found that, generally, A. amphitrite and B. plicatilis were the most resistant species to the ultrasound treatment whereas A. salina was the most sensitive. We further discuss that US may unlikely be used for commercial vessels, but may be used to treat ballast water in smaller ballast tanks as on board of mega yachts.
Résumé : Thus far, biofouling on material surfaces has been investigated from various viewpoints, and concrete methods for its evaluation have been proposed. Biofilms, which are formed by bacterial activities, are essential components of biofouling. They play an important role in the occurrence of biofouling on the materials of structures, which leads to serious economic loss. Therefore, the establishment of countermeasures for biofilm formation and its control are needed urgently. In addition, appropriate evaluation techniques to measure biofilm formation are required. Thus far, we have used scientific evaluation devices and techniques such as an optical microscope and Raman spectroscopy to evaluate biofouling/biofilms. In this study, we used the silane coating of dispersed silver and copper nanopowder rather than that of dispersed organometals. Specimens were immersed into a laboratory biofilm reactor. Then, the biofouling behavior on the sheets was investigated using an optical microscope, Raman spectroscopy, a focused ion beam system (FIB), and scanning electron microscopy (SEM). The optical-microscope observations showed many deposits on the specimens without any metallic dispersions. Although the amount of deposits on the specimens decreased with copper dispersions, many deposits were still observed on them with silver dispersion. These deposits were not confirmed by Raman spectroscopy because of the surface plasmon resonance of silver. Next, we observed and analyzed the specimens using the FIB system (combination of FIB–SEM and EDX) instead of Raman spectroscopy. The SEM image showed that the deposition had formed pores and irregularities on the specimens. FIB–SEM confirmed the existence of deposition on coating layers and revealed that it originated from biooraganisms. Based on these experiments, we could conclude that the structure of antifouling coating could be observed and analyzed using a combination of FIB–SEM and EDX even when other analysis methods are not useful because of various reasons.
Résumé : Surface colonization in seawater first corresponds to the selection of specific microbial biofilm communities. By coupling flow cytometry, microscopy and high throughput sequencing (HTS, 454 pyrosequencing) with artificial surfaces and environmental analyses, we intend to identify the contribution of biofilm community drivers at two contrasted French sites, one temperate and eutrophic (Lorient, Atlantic coast) and the other at a mesotrophic but highly contaminated bay (Toulon, North-Western Mediterranean Sea). Microbial communities were shaped by high temperatures, salinity and lead at Toulon by but nutrients and DOC at Lorient. Coatings including pyrithione exhibited a significant decrease of their microbial densities except for nanoeukaryotes. Clustering of communities was mainly based on the surface type and secondly the site, whereas seasons appeared of less importance. The in-depth HTS revealed that γ- and α-proteobacteria, but also Bacteroidetes, dominated highly diversified bacterial communities with a relative low β-diversity. Sensitivity to biocides released by the tested antifouling coatings could be noticed at different taxonomic levels: the percentage of Bacteroidetes overall decreased with the presence of pyrithione, whereas the α/γ-proteobacteria ratio decreased at Toulon when increased at Lorient. Small diatom cells (Amphora and Navicula spp.) dominated on all surfaces, whereas site-specific sub-dominant taxa appeared clearly more sensitive to biocides. This overall approach exhibited the critical significance of surface characteristics in biofilm community shaping.
Résumé : This paper presents a novel assay that allows a quick and robust assessment of the effects of biocides on the initial settling and establishment of marine photoautotrophic biofilms. The assay integrates the response of the multitude of indigenous fouling organisms, which overcomes a major limitation of existing assays which are largely limited to testing only lab-cultivatable species. The assay was evaluated using eight antifouling biocides, for which full concentration-response curves are presented. The efficacy ranking, based on EC 98 values from most to least efficacious compound is: copper pyrithione >TPBP >DCOIT >tolylfluanid>zinc pyrithione >medetomidine >copper (Cu 2+ ), while the ecotoxicological ranking (based on E C10 values) is irgarol, copper pyrithione >zinc pyrithione >TPBP >tolylfluanid >DCOIT >copper (Cu 2+ ) > medetomidine. The algaecide irgarol did not cause full inhibition. Instead the inhibition leveled out at 95% effect at 30 nmol l -1 , a concentration that was clearly lower than for any other of the tested biocides.
Résumé : Superrepellency is an extreme situation where liquids stay at the tops of rough surfaces, in the so-called Cassie state. Owing to the dramatic reduction of solid/liquid contact, such states lead to many applications, such as antifouling, droplet manipulation, hydrodynamic slip, and self-cleaning. However, superrepellency is often destroyed by impalement transitions triggered by environmental disturbances whereas inverse transitions are not observed without energy input. Here we show through controlled experiments the existence of a "monostable" region in the phase space of surface chemistry and roughness, where transitions from Cassie to (impaled) Wenzel states become spontaneously reversible. We establish the condition for observing monostability, which might guide further design and engineering of robust superrepellent materials.
Résumé : A straightforward mussel-inspired approach was proposed to construct chitosan-polyurethane coatings and load Ag nanoparticles (AgNPs) to endow polyethersulfone (PES) membranes with dual-antibacterial and antifouling properties. The macromolecule O-carboxymethyl chitosan (CMC) was directly reacted with catechol in the absence of carbodiimide chemistry to form the coating and load AgNPs via in situ reduction; while lysine (Lys) was used as a representative small molecule for comparison. Then, PEG-based polyurethane (PU) was used for constructing Lys-Ag-PU and CMC-Ag-PU composite coatings, which substantially improved the protein antifouling property of the membranes. Furthermore, the CMC-Ag-PU coating exhibited superior broad-spectrum antibacterial property towards E. coli and S. aureus than Lys-Ag-PU coating. Meanwhile, the CMC-Ag-PU coating showed sustained antifouling property against bacteria and could reload AgNPs to be regenerated as antibacterial and antifouling coating. This approach is believed to have potential to fabricate reusable antifouling and antibacterial coatings on materials surfaces for aquatic industries.
Résumé : Biofilm is a biological complex caused by bacteria settlement to the substrates, their subsequent reproduction and secretion. This phenomena reduce heat transfer efficiency and cause significant losses in treated sewage heat recovering systems. This paper describes a physical approach to inhibit the bacteria settlement and biofilm formation by Bacillus subtilis, which is the dominant genera in the treated sewage. Here, the micro-patterned surfaces with different characteristics (stripe and cube) and dimensions (1 μm to 100 μm) were fabricated as surfaces of interest. Model sewage was prepared and a rotating coupon device was used to form the biofilms. Precision balance, scanning electron microscope (SEM) and confocal laser scanning microscope (CLSM) were employed to investigate the inhibitory effects and the mechanisms of the biofilm-surface interactions. The results have shown that surfaces with small pattern sizes (1 μm and 2 μm) all reduced biofilm formation significantly. Interestingly, the CLSM image...
Résumé : Amphiphiles (i.e. amphiphilic molecules such as surfactants, block copolymers and similar compounds) are used in small amounts to modify the surface properties of polymeric materials. In silicone fouling-release coatings, PEG-based amphiphiles are added to provide biofouling-resistance. The success of this approach relies on the ability of the amphiphiles to diffuse through the coating film and cover the surface of the coating.
A novel method for the measurement of diffusion coefficients of PEG-based amphiphiles of different chemistries in PDMS-based coatings is presented here. The diffusion coefficient of the amphiphiles shows a weak dependency on their molecular weight, although this dependency is much less pronounced than for other rubbery polymeric materials. The biofouling-resistance properties in fouling-release coatings were also studied for these amphiphiles. It was found that the diffusion coefficient does not have any influence on the biofouling-resistance results for the studied compounds. Instead, the chemistry of the hydrophobic block of the amphiphiles is much more significant, with PEG-PDMS block copolymers showing the best properties among the studied compounds.