Biofouling Removal Research Articles

Structural Design and Horizontal Wave Force Estimation of a Wall-Climbing Robot for the Underwater Cleaning of Jackets

Currently, divers face significant safety risks when cleaning marine organisms from the steel structures of offshore underwater platform jackets. Consequently, utilizing robots instead of divers to carry out underwater biofouling removal operations will be an important development direction for the underwater maintenance of offshore platforms in the future. In this study, a wall-climbing robot was designed to clean marine organisms from the underwater surface of a platform jacket leg. The overall structure of the underwater cleaning wall-climbing robot is introduced, including the cleaning actuator and the variable curvature-adapted connecting rod mechanism. The corresponding relationship between the variable curvature-adapted connecting rod mechanism and the jacket leg is analyzed in detail. The variable curvature-adapted connecting rod mechanism was optimized using a genetic algorithm to ensure that the underwater cleaning wall-climbing robot can adapt to a minimum diameter of 1 m for the jacket leg. By drawing on Airy wave theory and random wave theory, the Airy wave parameters for waves were analyzed under different sea conditions, considering practical application scenarios. By using Fluent software 2022, a 2D numerical wave tank was constructed to simulate waves under various sea conditions, and the wave surface shapes for different sea states were determined. By building on the Morison equation, a method for calculating the horizontal wave forces on the underwater cleaning wall-climbing robot using the equivalent area and equivalent volume is proposed. By using the two aforementioned methods, the horizontal wave forces on the underwater cleaning wall-climbing robot under specific sea states were determined. The horizontal wave forces of the underwater cleaning wall-climbing robot under different sea conditions were analyzed and simulated in a 3D numerical wave tank. By comparing the theoretical analysis results with the numerical simulation results, where the maximum difference at the extreme points is approximately 11%, the feasibility of the proposed horizontal wave force estimation method was verified.

Evaluation of Influencing Factors in Cleaning Performance for Bio-Fouling Removal Based on High-Pressure Water Jets

Evaluation of Influencing Factors in Cleaning Performance for Bio-Fouling Removal Based on High-Pressure Water Jets

Photoacoustic imaging-based in situ biofouling monitoring in underwater optical windows—A novel approach

The accuracy of optical instruments is inevitably affected by marine biofouling as their optical windows become obscured in seawater. The continuous removal of biofouling imposes a substantial energy burden on the offshore instruments. Therefore, monitoring biofouling and selecting an appropriate time for biofouling removal is essential. However, an efficient in situ monitoring strategy for biofouling in underwater optical windows is currently lacking. To address these challenges, we conducted exploratory research on a new technology based on photoacoustic imaging for the in situ monitoring of marine biofouling in optical windows. First, poly methyl methacrylate coupons were hung and immersed in the coastal waters of Qingdao for varying durations during the sea trials. Evident photoacoustic signals from the biofouling attached to the surfaces of the coupons were collected by means of photoacoustic experimental platform. Two-dimensional photoacoustic images were reconstructed using photoacoustic microscopy. On comparing the optical and photoacoustic images of biofouling, photoacoustic images can more effectively reflect the degree of biological fouling. Finally, the optical and photoacoustic images of coupons subjected to ultrasonic treatment were compared and analyzed to further review the feasibility of fouling monitoring based on photoacoustic technology. These findings provide new insights into in situ detection of marine biofouling.

Experimental insights on biofouling growth in marine renewable structures.

Marine biofouling is a threat to industries working in the marine environment, representing significant costs associated with equipment impairment and loss of performance. In the Marine Renewable Energy (MRE) and other maritime sectors which operate at sea for long periods, an important aspect of biofouling is related to the type and frequency of inspections and biofouling removal procedures. This study investigated important parameters of macrofouling ( e.g. composition, including the presence of non-indigenous species, thickness, and weight) from communities growing on samples that emulate tubular components of marine renewable devices. The trials were performed during short periods of submersion (one to eight weeks) in the seasons when the colonisation process should be most intensive (spring, summer, and autumn). Furthermore, the frictional resistance forces generated during the scraping of biofouling from those components were investigated. Overall, results provide insights on the growth rates and removal requirements of biofouling in marine components. The results show that, while biofouling growth in early colonization stages might not present great detrimental effects to wave energy components, the consequent marine corrosion (fostered by biofouling) and the settlement of non-indigenous species (NIS) should be factors of concern. Performing biofouling-related maintenance activities after the peak of maximum growth and reproduction (during the warmer seasons in temperate to cold environments) is suggested to reduce the number and frequency of activities. NIS can be detected at very early stages in the colonization process, highlighting the importance of biofouling monitoring and the implementation of biosecurity risk assessment plans early in the operational stage of MRE projects.

Antibiotic Effect of High-Power Blue Laser Radiation

The development of sustainable alternatives to chemical and mechanical biofilm removal for submerged technical devices used in freshwater and marine environments represents a major technical challenge. In this context, the antibiotic impact of blue light with its low absorption underwater provides a potentially useful alternative. However, former technical limitations led to hours of treatment. Here, we applied high-power blue laser irradiation (1500 W) with a wavelength of 448 nm to demonstrate its strong antibiotic and algicidal effect on different bacteria and algae in seconds. High-power blue light treatment (139 W/cm2) for only 8.9 s led to the efficient deactivation of all tested organisms. Analyses of the underlying biological mechanisms revealed the absorption of the blue light by endogenous chromophores (flavins, tetrapyrroles) with the generation of reactive oxygen species (ROS). In agreement, Escherichia coli transcriptome analyses demonstrated a stress response at the level of DNA damage repair, respiration, and protein biosynthesis. Spectroscopic measurements of the irradiated algae indicated the irreversible damage of chlorophyll by photooxidation with the formation of singlet oxygen. In conclusion, high-power blue laser radiation provides a strong sustainable tool for the removal of biofouling in a very short time for applications in aquatic systems.

Iron nanoparticle coating and plasma-activated water cleaning as a biofouling removal method for reverse osmosis membranes suitable for desalination

Desalination provides crucial freshwater, but biofouling on reverse osmosis (RO) membranes is a major challenge due to hard-to-remove biofilms. Conventional treatments are often ineffective, prompting a shift to coatings with nanoparticles like copper, silver, and iron to combat fouling. This study demonstrates a unique combination of coating RO membranes with iron nanoparticles (FeNPs) and treatment with plasma-activated water (PAW) for the removal of biofilm formation. Pure and unbound FeNPs showed no significant inhibition of Escherichia coli biofilms. However, the attachment of FeNPs to RO membranes led to a decrease in biofilm growth on the membrane, and an additional PAW treatment was shown to significantly inhibit mature biofilms. SEM imaging revealed a higher density and uniform distribution of FeNPs on the RO membranes after PAW treatment. Zeta potential measurements showed positively charged FeNPs in PAW, enhancing their attraction with the negative membrane surfaces. The coated membrane using PAW solution with FeNPs exhibited no degradation in terms of pure water flux, saline water flux, and salt rejection compared to the immersion process in DI with FeNPs.

Antibiofouling polyethersulfone ultrafiltration membranes functionalized with MoS2 nanosheets and self-cleaning with hydrogen peroxide

The development of biofouling mitigation and cleaning strategy is of paramount importance for ultrafiltration (UF) membrane biofouling. In this study, polyethersulfone (PES) UF membrane was functionalized, namely MoS2/PES composite membrane. The MoS2/PES composite membrane exhibited superior antifouling property as evidenced by antibacterial circle, static and dynamic biofouling experiments. The permeate fluxes of the pristine PES and MoS2/PES composite membrane respectively decreased by 76% and 31% at the end of 3-h filtration. After exposure of E. coli to MoS2, inhibited cell growth led to reduced membrane biofouling. The biofilm formation was retarded under the dynamic flow condition, which were further confirmed by Scanning Electron Microscopy (SEM) and Confocal Laser Scanning Microscopy (CLSM) observations. As for the enhanced biofouling removal by cleaning with H2O2, 62% of the flux recovery rate for the MoS2/PES composite membrane was much higher than the pristine PES membrane (24%). The peroxidase-like properties of MoS2 were responsible for the enhancement of the superior cleaning performance. The use of H2O2 to trigger the in-situ catalytic function of the MoS2 nano-enzyme generated more ROS and O2 for inducing bacterial cells death and facilitating detachment of biofilm. This work will be helpful to provide important insights into developing more effective strategies for biofouling control and cleaning using advanced nanomaterials in membrane-based water treatment processes.

Regulating Biomolecular Surface Interactions Using Tunable Acoustic Streaming.

Diffusion limitations and nonspecific surface absorption are great challenges for developing micro-/nanoscale affinity biosensors. There are very limited approaches that can solve these issues at the same time. Here, an acoustic streaming approach enabled by a gigahertz (GHz) resonator is presented to promote mass transfer of analytes through the jet mode and biofouling removal through the shear mode, which can be switched by tuning the deviation angle, α, between the resonator and the sensor. Simulations show that the jet mode (α ≤ 0) drives the analytes in the fluid toward the sensing surface, overcomes the diffusion limitation, and enhances the binding; while the shear mode (0 < α < π/4) provides a scouring action to remove the biofouling from the sensor. Experimental studies were performed by integrating this GHz resonator with optoelectronic sensing systems, where a 34-fold enhancement for the initial binding rate was obtained. Featuring high efficiency, controllability, and versatility, we believe that this GHz acoustic streaming approach holds promise for many kinds of biosensing systems as well as lab-on-chip systems.

Aquaculture net cleaning with cavitation improves biofouling removal

The attachment of a large number of biofouling organisms on net cages has a very negative impact on the safety of cage structure and aquaculture organisms. This paper presents a new type of marine aquaculture net-cleaning system (ANCS) that adopts the power of continuous cavitating jets to remove biofouling in underwater environments. The cavitation characteristics of the nozzle, which is the key component of the ANCS, were analyzed under different conditions in a submerged cage environment, and the system's cleaning rate with different inlet pressures (P) and nozzle diameters (d) was obtained. Under the same input flow rate and increasing nozzle aperture (from 0.6 to 1.0 mm), the gas phase volume fraction of the nozzle showed a rising trend (the maximum value reached 37.5% for the 1.0 mm nozzle) and jet velocity at 40 mm away from the nozzle was reduced by 85.6%–97.0%. Net-cleaning tests showed that, with an inlet pressure of 16.42 MPa and nozzle diameter of 0.8 mm, the ANCS achieved the highest rate of biofouling removal (79.8%) and the lowest specific energy consumption of removing unit mass fouling (5.13kw). The shellfish fouling organisms mainly fell off and their shells broke under the impact of the cavitating jet produced. After the cleaning experiment, most of the residues consisted in the soft byssus plaques of shellfish, which strongly adhered to the net. The soil on the net surface was completely removed, revealing the original color of the aquaculture cage net.

Incipient Biofouling Detection via Fiber Optical Sensing and Image Analysis in Reverse Osmosis Processes.

Reverse osmosis (RO) is a widely used membrane technology for producing process water or tap water that is receiving increased attention due to water scarcity caused by climate change. A significant challenge in any membrane filtration is the presence of deposits on the membrane surfaces, which negatively affect filtration performance. Biofouling, the formation of biological deposits, poses a significant challenge in RO processes. Early detection and removal of biofouling are essential for effective sanitation and prevention of biological growth in RO-spiral wound modules. This study introduces two methods for the early detection of biofouling, capable of identifying initial stages of biological growth and biofouling in the spacer-filled feed channel. One method utilizes polymer optical fibre sensors that can be easily integrated into standard spiral wound modules. Additionally, image analysis was used to monitor and analyze biofouling in laboratory experiments, providing a complementary approach. To validate the effectiveness of the developed sensing approaches, accelerated biofouling experiments were conducted using a membrane flat module, and the results were compared with common online and offline detection methods. The reported approaches enable the detection of biofouling before known online parameters become indicative, effectively providing an online detection with sensitivities otherwise only achieved through offline characterization methods.

Net cleaning impacts Atlantic salmon gill health through microbiome dysbiosis

IntroductionNet biofouling has a significant impact for the global salmon industry in the seawater grow-out stage in terms of its management. Current mitigation strategies occur primarily through the regular removal of biofouling using in situ cleaning. While in situ net cleaning is effective there is uncertainty as to whether the equipment or dispersed material has an impact upon the fish in the cages. Through direct contact with the environment, the significant surface area of the gill including its microbiome is directly exposed to the acute environmental changes generated by net cleaning. This study aimed to provide a detailed understanding of the impact of in situ net cleaning on Atlantic salmon (Salmo salar) and rainbow trout (Oncorhynchus mykiss) gill health.MethodsThree field trials were conducted on commercial fish farms in western Norway. Fouling organisms on net pens and flushed particles during in situ cleaning were identified and screened for major fish pathogens. Hydrographic profile measurements were performed to measure the impact on water quality. Gill samples were examined for histopathological changes, immune gene expression, and the prevalence of major pathogens. 16S rRNA amplicon sequencing was employed to explore the impact of net cleaning on gill microbiome.Results and discussionData obtained from these trials identified a diversity of fouling species including hydroids, algae, skeleton shrimps, and filter feeders on net pens, a direct impact on measured water quality indicators, a moderate change in gill inflammatory and antigen presentation activity at the level of mRNA, and a large significant change in gill microbiome. Observed changes in gill microbial community involved a decrease in bacterial richness coupled to an increase in identified bacterial genera related to negative health consequences. Parallel analyses for pathogens load in biofouling organisms and flushed particles highlighted the presence of several fish bacteria and parasites. However, minor changes were detected in salmon gill pathogen diversity and loading. Our results suggest that biofouling organisms may act as transient reservoirs for some fish pathogens but not viruses and that gill microbial dysbiosis could be related to the host stress response during and post net cleaning.

Assessing the Effects of Physical Barriers and Hypoxia on Red Drum Movement Patterns to Develop More Effective Management Strategies

Human modification of coastal ecosystems often creates barriers to fish movement. Passive acoustic telemetry was used to quantify movement patterns and habitat use of red drums (Sciaenops ocellatus) within and around a complex of coastal impoundments, and explored how the presence of artificial structures (i.e., bollards and culverts) and a hypoxia-related mortality event impacted fish movement. Results indicated bollards impede the movement of individuals with head widths greater than the mean distance between bollards (~16.0 cm). Red drum home range area and daily distance traveled were related to water dissolved oxygen concentrations; as oxygen levels decreased, fish habitat use area decreased initially. However, continued exposure to hypoxic conditions increased fish cumulative daily distance traveled. When exposed to anoxic waters, fish daily distance traveled and rate of movement were greatly reduced. These findings suggest prolonged exposure to low dissolved oxygen in combination with artificial structures can reduce movement of red drum, increase risk of mortality, and decrease habitat connectivity. Constructing and maintaining (sediment and biofouling removal) larger culvert openings and/or using wider bollard spacing would improve water circulation in impoundments, increase habitat connectivity, and facilitate movement of large sportfish inhabiting Florida’s coastal waters.

Biofouling Removal Using a Novel Electronic System for Driving an Array of High Power Marinised Transducers

This paper explains producing a novel ultrasonic system to remove/prevent biofouling growth from wind turbines’ access ladders by means of producing local ultrasound cavitation. Using bespoke hardware, an array of high-power ultrasound transducers (HPUTS) and optimally synthesized signal types to remove/prevent biofouling growth from the ladder without violating the standard noise level in the sea is explained. This is a non-toxic and non-invasive solution to detach biofouling and prevent biofilm initiation on offshore structures. It is shown that the marinisation of the HPUT slightly shifts the main resonance frequency from 28.1 to 27.5 kHz. The vibration output from the HPUTs with different mounting systems showed that the transducer with the horn could vibrate the plate at 20 cm from the excitation point, with 300 pm, six times higher than the vibration output from the marinised HPUT. A transducer array and attachment are proposed to make the ultrasound noise below the standard underwater noise limits. The produced sound pressure level (SPL) and sound equivalent level (SEL) from the proposed ultrasonic system was measured. It was specified that the SPL came below 120 dB at 25 m from the excitation point and the SEL value below the 173 dB limit. Finally, the effectiveness of the marinised HPUTS on biofouling removal has been demonstrated with an in-situ measurement, and it was indicated that local biofouling removal could be achieved.

Miniature sono-electrochemical platform enabling effective and gentle electrode biofouling removal for continuous sweat measurements

• Sono-electrochemical lab-on-a-chip device with gigahertz bulk acoustic resonator. • Acoustic actuation in-situ releasing fouled electrode′s electrochemical activity. • Non-invasiveness to intrinsic film electrode and the decorated nanoparticles. • Continuous and repeatedly electrochemical measurements to human sweat. Developing miniature smart electrochemical sweat sensors to perform continuous and noninvasive health diagnosis at molecule level is in the spotlight. Sensor's biofoulings hinder the targets' approaching, decreasing the detection sensitivity over time and further limiting the accurate analysis. Effective cleaning to remove biofoulings on electrochemical sensors is a main challenge and needs to overcome urgently for such purpose. We propose a miniature sono-electrochemical platform utilizing submillimeter gigahertz acoustic resonator to effectively clean away the biofoulings and release sensors inherent electrochemical activities. Resonator induced super strong fluid streaming can completely and repeatedly remove sweat biofoulings from gold electrode surface, leading to 100% recovery of sensor’s activities for continuous reliable measurements. Compared with common sensor renewal strategies, such as acidic or basic solution cleaning, mechanical polishing, traditional low frequency ultrasound treatment, this electrode surface renewal technique is stable, mathematically predictable, effective and gentle so that it does not cause any destructions to inherent electrode surface, and therefore the sensed electrochemical signals on raw and cleaned electrodes are comparable and improvable with no unexpectable deviation. Together with submillimeter size of the resonator, it shows potential to be integrated within wearable electroanalytical microfluidics for developing smart device to carry out continuous health diagnosis.

Rheological characterisation of alginate-like exopolymer gels crosslinked with calcium

Bacterial alginate-like exopolymers (ALE) gels have been used in this work as a model for the extracellular polymeric matrix of biofilms. Aim was to relate the mechanical properties and strength of this matrix that make biofilms as persistent to cleaning as they are, to the complex cohesive molecular interactions involved. Mechanical properties of the gels as a function of CaCO3 concentration were investigated using dynamic and static rheology. Gels with relatively low CaCO3 concentrations, between 100 μmol and 300 μmol per g ALE, were found to exhibit similar viscoelastic behaviour as real biofilms, with elastic moduli between 50 Pa and 100 Pa and dissipation factors between 0.2 and 0.3. Increasing CaCO3 concentrations resulted in an increase of the elastic modulus up to 250 Pa, accompanied by an increase in brittleness. At a CaCO3 concentration of 1250 μmol per g ALE this trend stopped, probably due to disturbance of the continuous ALE network by precipitation of salts. Therefore, overdosing of Ca salts can be an adequate approach for the removal of biofouling. All gels exhibited permanent strain hardening under medium strain, and their mechanical properties showed dependency on their strain history. Even after application of an oscillatory strain with 200% amplitude that caused the gel structure to collapse, the gels recovered 65 to 90% of their original shear modulus, for the major part within the first 20 s. Recovery was slightly less for gels with high CaCO3 concentration. In creep tests fitted with a Burgers model with multiple Kelvin elements at least three different interactions in the ALE gels could be distinguished with characteristic retardation times in the range of 10, 100 and 1000 s. Further identification of the mechanisms underlying the gel mechanics will allow the development of targeted strategies to undermine the mechanical strength of biofouling and aid the cleaning process.

Fouling Release Coatings Based on Acrylate-MQ Silicone Copolymers Incorporated with Non-Reactive Phenylmethylsilicone Oil.

Copolymers containing MQ silicone and acrylate were synthesized by controlling the additive amount of compositions. Subsequently, fouling release coatings based on the copolymer with the incorporation of non-reactive phenylmethylsilicone oil were prepared. The surface properties of the coating (CAMQ40) were consistent with that of the polydimethylsiloxane (PDMS) elastomer, which ensured good hydrophobicity. Moreover, the seawater volume swelling rate of all prepared coatings was less than 5%, especially for CAMQ40 with only 1.37%. Copolymers enhanced the mechanical properties of the coatings, while the enhancement was proportional to the molar content of structural units from acrylate in the copolymer. More importantly, the adhesion performance between the prepared coatings and substrates indicated that pull-off strength values were more than 1.6 MPa, meaning a high adhesion strength. The phenylmethylsilicone oil leaching observation determined that the oil leaching efficiency increased with the increase in the structural unit’s molar content from MQ silicone in the copolymer, which was mainly owing to the decrease in compatibility between oil and the cured coating, as well as the decrease in mechanical properties. High oil leaching efficiency could make up for the decrease in the biofouling removal rate due to the enhancement of the elastic modulus. For CAMQ40, it had an excellent antifouling performance at 30 days of exposure time with more than 92% of biofouling removal rate, which was confirmed by biofilm adhesion assay.

A methodology for removing biofouling of the hull based on ultrasonic guided waves

Marine biofouling is considered as the undesired growth and accumulation of biological organisms on the surface of materials submerged in seawater. Marine biofouling could increase the resistance and fuel consumption of ships. In this paper, a novel method for removing biofouling on ship hull based on cavitation effect and ultrasonic guided waves (UGWs) is proposed, which is eco-friendly and could remove biofouling online. The simulation model is established by finite element method to study the sound pressure distribution on the steel plat. The biofouling removal experiment is designed, which reveals that it is feasible to remove biofouling efficiently with UGWs.

Solvent-Based Elimination of Organic Matter from Marine-Collected Plastics

The physical-chemical characterization of plastic litter from the marine environment requires the prior removal of the biofouling attached to their surface without causing any degradation in the polymer. The absence of a standardized protocol for digesting biofouling and organic matter of both macro and microplastic samples extracted from seawater has been the main motivation for this research work, which aims to evaluate the effectiveness of different solvents (hydrogen peroxide, ethanol, a commercial enzymatic detergent, and potassium hydroxide) for the digestion of organic matter and biofouling in different samples recovered from the Spanish Atlantic and Mediterranean coast. Moreover, the potential effect of those solvents on the physical-chemical structure of polymers, four virgin plastic reference materials (low-density polyethylene, polyamide, poly(ethylene terephthalate) and polystyrene) without any type of prior degradation has been characterized in terms of Fourier transform infrared spectroscopy (FTIR) and optical microscopy. Results indicate that the hydrogen peroxide at 15% concentration applied for one week at 40 °C is the most effective solvent for organic matter and biofouling removal, without causing any apparent damage on the structure of plastic samples analyzed.

Mitigating non-indigenous species movements: effects of pressure-washing intensity and duration on the removal of biofouling and mobile invertebrates from cultured Pacific oysters (Crassostrea gigas (Thunberg, 1793))

Mitigating non-indigenous species movements: effects of pressure-washing intensity and duration on the removal of biofouling and mobile invertebrates from cultured Pacific oysters (Crassostrea gigas (Thunberg, 1793))

Underwater shear-based grooming of marine biofouling using a non-contact Bernoulli pad device

The biofouling removal ability of a shear-based device was tested on two submerged surface types, Garolite G-10 and Intersleek 1100SR. Each surface was groomed at four frequencies along with a control group. The seven-week grooming study was conducted in Narragansett Bay, Rhode Island. The Bernoulli pad device uses confined radial outflow to generate both surface-normal forces to grip the submerged surface and shear stress to groom the surface without contact. An image-processing algorithm was developed and used to assess the effectiveness of the various grooming protocols, along with direct measurements of chlorophyll a per surface area. The image-processing data showed that the grooming resulted in ∼50% cleanliness on the Garolite at the end of the study whereas the Intersleek was continuously restored to nearly its initial clean state. Chlorophyll a data supported these overall conclusions. These results indicate that surface cleanliness can be maintained effectively on Intersleek using frequent shear-based grooming.