Biofouling Mitigation Research Articles

Marine biofouling mitigation of PDMS-based network coating with cross-linked contact- and release-active organoalkoxysilane

Poly (dimethylsiloxane) (PDMS) elastomer is one of key polymer resins for fouling release (FR) coatings, but it shows extremely poor antifouling (AF) activity in seawater since bacteria and diatoms could readily attach to surface. Modifying PDMS-based coatings via incorporating antifouling additives is effective for enhancing overall FR and AF activity. In this work, we prepared a well-defined organoalkoxysilane coating additive with quaternary ammonium and benzoisothiazolinone pendent groups, and the synthesized copolymers were covalently conjugated onto PDMS network in a one-pot reaction. AF and FR activities of the modified PDMS coatings were studied against soft fouling microorganisms. When microorganisms come into contact the coating surface, contact-active action mode works, quaternary ammonium groups could cause bacteria cell membrane disruption and microalgae photosynthesize inhibition via positive charge. Unexpectedly, a surprisingly lasting antimicrobial efficiency could be still observed in the neighboring coating, even the top-surface was completely covered with bacteria biofilm. Chemically conjugated benzoisothiazolinone could be sustainably released via side-group hydrolysis, thus, repelling and preventing the planktonic foulings from approaching the coating surface via release-active action mode. The modified PDMS coating with dual antifouling action modes could inhibit the biofilm formation at solid-liquid-air three-phase contact line, and could find valuable applications in marine transportation, water treatment and other antifouling fields.

Environmental impact of different Mediterranean technological systems for European sea bass (Dicentrarchus labrax) and Gilthead sea bream (Sparus aurata) farming

As at a global level, the aquaculture sector is growing in Italy too and, among the various species, European sea bass and Gilthead sea bream are becoming increasingly important. As a consequence, the environmental implications are an emerging issue and in-depth studies on the topic of farm sustainability are needed. This study compared the environmental performance of four specialised Sea bass and Sea bream farms in Italy, characterized by different technological system, using the Life Cycle Assessment approach. 1 tonne of fish biomass harvested and 1 kg of fish protein were chosen as functional units. The 'from cradle to gate' perspective was applied to define the system boundaries. The results revealed that land-based farms had higher environmental impacts compared to coastal farm with a Climate change of 9660 and 7250 kg CO2 eq for the former and 2443 and 3308 for the latter. Despite the use of aquafeeds emerged as a significant contributor of environmental impacts across all farms (with a share of more than 80 % of the Climate change in the coastal farms), even energy and liquid oxygen consumption, particularly on land-based farms, played a crucial role (with impact shares of 25–40 % in climate change). A sensitivity analysis on energy sources revealed that the use of more renewable energy can reduce the Climate Change of land-based farms by an average of 5 %, while an all-biodiesel fleet has a beneficial effect on particulate matter (-7.5 %) and acidification (-6 %) on coastal farms. The study provided a comprehensive overview of the environmental impact of Italian ESB and GSB production. In addition, highlighted areas for further research, including biofouling mitigation, optimization of energy consumption, and exploration of alternative oxygenation methods in land-based farms.

Advanced Tertiary Wastewater Treatment for Enhanced Effluent Quality by Electrically Conducting Membranes Operated at Altered Potential for Simultaneous Mitigation of Scaling and Biofouling

Advanced Tertiary Wastewater Treatment for Enhanced Effluent Quality by Electrically Conducting Membranes Operated at Altered Potential for Simultaneous Mitigation of Scaling and Biofouling

Mitigation of biofouling in membrane bioreactors by quorum-quenching bacteria during the treatment of metal-containing wastewater.

Quorum quenching (QQ) is an efficient way to mitigate membrane biofouling in a membrane bioreactor (MBR) during wastewater treatment. A QQ bacterium, Lysinibacillus sp. A4, was isolated and used to mitigate biofouling in an MBR during the treatment of wastewater containing metals. A QQ enzyme (named AilY) was cloned from A4 and identified as a metallo-β-lactamase-like lactonase. The QQ activity of A4 and that of Escherichia coli BL21 (DE3) overexpressing AilY could be promoted by Fe2+, Mn2+, and Zn2+ while remaining unaffected by other metals tested. The two bacteria effectively mitigated biofouling by reducing the transmembrane pressure from around 30 to 20kPa without negative influence on the COD, NH4+-N, or total phosphorus of the effluent. The relative abundance of Lysinibacillus sp. A4 increased greatly from 0.04 to 8.29% in the MBR with metal-containing wastewater, suggesting that Lysinibacillus sp. A4 could multiply quickly and adapt to this environment. Taken together, the findings suggested that A4 could tolerate metal to a certain degree, and this property could allow A4 to adapt well to metal-containing wastewater, making it a valuable strain for mitigating biofouling in MBR during the treatment of metal-containing wastewater.

Isolation and application of Bacillus thuringiensis LZX01: Efficient membrane biofouling mitigation function and anti-toxicity potential

Significant progress has been made in mitigating membrane biofouling by microbial quorum quenching (QQ). More efficient and survivable QQ strains need to be discovered. A new strain named Bacillus thuringiensis LZX01 was isolated in this study using a low carbon source concentration “starving” method from a membrane bioreactor (MBR). LZX01 secreted intracellular lactonase to enable QQ behavior and was capable of degrading 90 % of C8-HSL (200 ng/mL) within 30 min, which effectively delayed biofouling by inhibiting the growth of bacteria associated with biofouling and improving the hydrophilicity of bound extracellular polymeric substances. As a result, the membrane biofouling rate of MBR adding LZX01 was four times slower than that of the control MBR. Importantly, LZX01 maintains its QQ activity even in environments contaminated with typical toxic pollutants. Therefore, with high efficiency, toxicity resistance, and easy culture, LZX01 holds great potential and significant promise for biofouling control applications.

Inhibition of Quorum Sensing to Mitigate the Risks of Membrane Biofouling in Biological Wastewater Treatment

Membrane-based systems play a pivotal role in various applications, providing efficient separation, purification, and filtration processes across diverse industries such as water purification and desalination. However, this system faces major challenge of membrane biofouling impacting the efficiency and sustainability of such systems. Biofouling occurs when various microorganisms like bacteria, fungi, etc. adheres to the surface of membrane and form biofilm which results in reducing membrane permeability and increasing its operational cost. Various physical, chemical and biological strategies are known to prevent biofouling. Inhibition of quorum sensing is a recent trend based on the researches that shows quorum sensing as an integral part of biofilm formation. Bacteria’s uses cell to cell communication mechanisms known as Quorum sensing, plays an important role in formation of virulence factors, biofilm. It is regulated by quorum sensing signalling molecules known as autoinducers like Autoinducing peptides, acyl homoserine lactones, Autoinducer-2. Various strategies can be adopted to inhibit quorum sensing: inhibition of Autoinducer synthase which is responsible for synthesizing autoinducers; inhibition/degradation of autoinducers and interfering with signal receptors. This article provides deeper knowledge of Quorum sensing (QS), methods of QS inhibition: Quorum quenching which involves the enzymatic degradation of QS signaling molecules, and the use of Quorum sensing inhibitor compounds in preventing membrane biofouling are discussed in detail. This article delves into the potential of disrupting quorum sensing pathways to prevent or reduce biofilm formation, thereby enhancing the performance and longevity of membranes in wastewater treatment. The mitigation of biofouling can revolutionize membrane-based systems, ensuring their sustainability and efficacy in water treatment processes

Mitigation of transparent exopolymer particles-induced membrane biofouling by the coupling process of magnetic ion exchange resin/ultrafiltration

The significant effects of transparent exopolymer particles (TEP) on membrane fouling have attracted the attention of several researchers. Finding an effective method for controlling membrane biofouling caused by TEP is essential for the long-term stable operation of membrane systems. The results of this experimental study show that the coupling process of magnetic ion exchange resin (MIEX)/Ultrafiltration (UF) can significantly mitigate membrane biofouling induced by TEP. Compared with the UF process, the irreversible growth rate of TEP on the membrane in the MIEX/UF process decreased by 75.9%, and the synergistic irreversible accumulation rate of TEP and bacteria decreased by 81.2%. The irreversible adhesion of bacteria to the membrane was significantly reduced, effectively inhibiting the formation of the primary level of biofilm and the development of biofouling. Further analysis showed that the MIEX inhibited the conversion of TEP precursors to TEP, and the quaternary ammonium salt functional groups on the surface of the MIEX sterilized bacteria and inhibited their proliferation in water. More importantly, because the interfacial forces between TEP/bacteria and MIEX were much higher than those between them and the UF membrane, the deposition of MIEX on the membrane surface not only prevented TEP and bacteria from reaching the membrane surface, but also removed the deposited TEP and bacteria from the membrane surface by hydraulic backwashing.

Surface modification of FeⅢ-juglone coating on nanofiltration membranes for efficient biofouling mitigation

Nanofiltration membranes have increasingly played a vital role in the purification of surface water and the recycling of wastewater. However, the problem of membrane biofouling, which leads to shortened service life and increased energy consumption, has hindered the widespread application of nanofiltration membranes. In this study, we developed functionalized nanofiltration membranes with anti-adhesive and anti-biofouling properties by coordinating FeIII and juglone onto commercial nanofiltration membranes in a facile and viable manner. Due to the hydrophilic nature of the FeⅢ-juglone coating as well as its ultra-thin thickness and minimal impact on the membrane pores, the permeance of the optimally modified membrane even increased slightly (14 %). The outstanding anti-adhesive property of the FeⅢ-juglone coating was demonstrated by a significant reduction in the adsorption of proteins and bacteria. Furthermore, the modified membranes exhibited lower flux decline amplitude and reduced biofilm deposition during dynamic fouling experiment, further supporting the outstanding anti-biofouling performance of the nanofiltration membrane after the modification with FeⅢ-juglone coating. This study presents a novel and feasible approach for simultaneously improving the water permeance, anti-adhesive property and anti-biofouling property of commercial nanofiltration membranes.

Biofouling mitigation of a membrane bioreactor for industrial wastewater treatment by quorum quenching

Quorum quenching (QQ) has been extensively studied in sewage treatment membrane bioreactors (MBRs) to alleviate biofouling, but its application in industrial-wastewater MBRs remains limited. This study confirmed the applicability of QQ in MBRs treating wastewater from the display manufacturing process. QQ alginate and QQ polyvinyl alcohol (PVA)/alginate beads, which entrapped Bacillus sp. SDC-U1, a QQ isolate from tetramethylammonium hydroxide (TMAH)-wastewater treatment sludge, were applied to a lab-scale MBR treating real wastewater containing TMAH, a developer used in the display manufacturing process. To immobilize pH-sensitive SDC-U1 on PVA/alginate beads, the first cross-linking solution's pH was adjusted to 5, followed by a 4 h incubation in Luria-Bertani broth to enhance the activity of SDC-U1. MBRs with QQ alginate and QQ PVA/alginate beads showed a 40 % and 365 % longer time to reach 30 kPa TMP, respectively, compared to MBRs without beads. QQ beads significantly reduced the concentration of various N-acyl homoserine lactones, which are signaling molecules involved in quorum sensing, in the MBR. The observation of biofilm on the membrane surface confirmed the biofouling mitigation by QQ application. This study demonstrates that biofouling can be effectively mitigated using appropriate QQ bacteria and their immobilization methods in industrial wastewater MBRs containing toxic substances like TMAH.

Biofouling mitigation and microbial community dynamics in the membrane bioreactor by the indigenous quorum quenching bacterium Delftia sp. JL5

The quorum quenching (QQ) strategy has attracted increasing attention in membrane bioreactor (MBR) fouling control. However, the applicable QQ strain remains limited. This study investigated the antibiofouling performance of a new indigenous QQ bacterium, Delftia sp. JL5 (JL5) in MBR. JL5 produces intracellular acylase that irreversibly degrades N-acylhomoserine lactones (AHL), inhibited biofilm formation of quorum-sensing bacteria from activated sludge. During 120 days of operation, immobilized JL5 substantially delayed MBR biofouling by 2.1 and 2.9 times, at a flux rate of 30 L/(m2·h) and 20 L/(m2·h), respectively. A slower flux rate was favorable for effective mitigation of JL5 biofouling. JL5 reduced the AHL and extracellular polymeric substances of biocake without affecting the efficiency of waste removal. The presence of JL5 significantly changed the microbial structure of the membrane biocake, but not the activated sludge. Collectively, high activity, durability, and acid tolerance credited JL5 as a promising strain for QQ-MBR.

Strategies to Mitigate Biofouling of Nanocomposite Polymer-Based Membranes in Contact with Blood.

An extracorporeal blood purification method called continuous renal replacement therapy uses a porous hollow-fiber polymeric membrane that is exposed to prolonged contact with blood. In that condition, like with any other submerged filtration membrane, the hemofilter loses its properties over time and use resulting in a rapid decline in flux. The most significant reason for this loss is the formation of a biofilm. Protein, blood cells and bacterial cells attach to the membrane surface in complex and fluctuating processes. Anticoagulation allows for longer patency of vascular access and a longer lifespan of the membrane. Other preventive measures include the modification of the membrane itself. In this article, we focused on the role of nanoadditives in the mitigation of biofouling. Nanoparticles such as graphene, carbon nanotubes, and silica effectively change surface properties towards more hydrophilic, affect pore size and distribution, decrease protein adsorption and damage bacteria cells. As a result, membranes modified with nanoparticles show better flow parameters, longer lifespan and increased hemocompatibility.

Marine fouling: Factors affecting biofouling and future perspectives

Biofouling of the hulls of ships and vessels, caused by the colonization of animals and plants, is an ongoing problem for the shipping industry. Biofouling evokes surface roughness, which results in higher fuel consumption, emissions, and operating costs. Mitigation of biofouling is a complex problem and the effectiveness of any given approach depends on many factors. Compared to complex anti-fouling technologies, the use of anti-fouling coatings presents the most viable solution, both in terms of cost and efficiency. Nevertheless, due to the modest performance of most modern antifouling hull coatings, frequent maintenance, and dry-docking intervals are still required. In addition, application costs are often not negligible. New antifouling technologies, such as low-drag antifouling paints with broad spectrum activity are urgently required in order to promote smoothness of the surface as well as provide adequate protection against biofilm formation. The development of innovative nanocomposite coating structures which combine low-drag film surfaces with antimicrobial components within water-soluble matrices may be a drastic solution to the above problem. Moreover, applying such structures directly on the hulls of ships and marine vessels without the use of primers is a long-awaited possibility, which could have a tremendous impact on reducing application costs.

Let's Talk about Slime; or Why Biofouling Needs More Attention in Sensor Science.

Although there is a growing demand for new sensors for environmental monitoring, biofouling continues to plague current sensors and sensing networks. As soon as a sensor is placed in water, the formation of a biofilm begins. Once a biofilm is established, reliable measurements are often no longer possible. Although current biofouling mitigation strategies can slow the biofouling process, a biofilm will eventually develop on or near the sensing surface. While antibiofouling strategies are being continuously developed, the complexity of the biofilm community structure and the surrounding environment means that there is unlikely to be a single solution that will minimize biofilms on all environmental sensors. Thus, antibiofouling research often focuses on optimizing a specific biofilm mitigation approach for a given sensor, application, and environmental condition. While this is practical from the standpoint of a sensor developer, it makes the comparison of different mitigation strategies difficult. In this Perspective, we discuss the application of different biofouling mitigation strategies to sensing and then explore the need for the sensor community to adopt standard protocols to increase the comparability of the biofouling mitigation approaches and help sensor developers identify the most appropriate strategy for their system.

Identification of a phosphotriesterase-like lactonase in Klebsiella sp. and enhancement of its biofouling mitigation potential by γ-caprolactone

The formation of biofilm can result in membrane biofouling during the operation of a membrane bioreactor (MBR). Biofilm formation is regulated by quorum sensing (QS), and the QS process can be disturbed by quorum quenching (QQ). QQ is considered a promising strategy to mitigate membrane biofouling, and the use of QQ bacteria that possess QQ enzymes has aroused much interest. In this study, we identified a QQ gene (designated as kplD6) from a Klebsiella sp. and expressed the enzyme (KplD6) in Escherichia coli. KplD6 was the first phosphotriesterase-like lactonase identified in Klebsiella, and E. coli expressing KplD6 could effectively mitigate biofouling in MBRs by reducing the transmembrane pressure (TMP) from 35 to 26 kPa. Interestingly, the TMP was further reduced to about 20 kPa in MBRs where γ-caprolactone was added, and γ-caprolactone also enhanced the expression of kplD6 in Klebsiella. Moreover, the addition of E. coli expressing KplD6 or γ-caprolactone to the MBRs had no negative impact on the removal of COD and NH4+-N from the effluent, while exerting only a little effect on the relative abundance of the dominant phyla in the MBR. These findings have shed further light on the application of QQ via Klebsiella sp. in the mitigation of biofouling in MBRs.

Surface Zwitterionization via Grafting of Epoxylated Sulfobetaine Copolymers onto PVDF Membranes for Improved Permeability and Biofouling Mitigation

Grafting of zwitterionic moieties has been shown to overcome the decrease in permeability after membrane modification. Herein, we report the grafting of epoxylated sulfobetaine (poly(glycidyl methacrylate-co-sulfobetaine methacrylate or poly(GMA-co-SBMA)) zwitterionic copolymers onto polyvinylidene fluoride (PVDF) surfaces to obtain superhydrophilic and superoleophobic membranes. The three-dimensionally modified membranes simultaneously exhibit excellent fouling resistance and hemocompatibility with improved water permeability during protein filtration. The zwitterionic moiety in the bulk membrane promotes the formation of a hydration layer, resulting in a dramatic reduction in hydrophobic interactions between the membrane and proteins or bacteria. Zwitterionic polymers establish a relatively electrically neutral surface through the presence of positive and negative charge groups on their pendant, leading to a reduction of adhesion between charged protein molecules and membranes. The modified PVDF surface exhibits very high hemocompatibility for human erythrocytes, platelets, and leukocytes. In the static fouling test, this biofouling hardly adhered to the membrane surface. The developed membrane has 3 times higher water permeability than the unmodified commercial membrane. It also showed a significant improvement in antifouling performance during dynamic fouling testing. Furthermore, flux regeneration of the modified membranes is easier to achieve by simple water recirculation compared to pristine PVDF membranes. Therefore, this study provides a promising way to develop antifouling membrane surface modification, which can be potentially used for bioseparation applications.

Reducing biofouling on optical oxygen sensors; a simple modification enabling sensor cleaning via water splitting.

Biofouling is a major challenge in environmental sensing. Current mitigation strategies are often expensive, energy consuming or require toxic chemicals. In this contribution electrochemical biofouling control is evaluated as an alternative approach to reduce biofouling on an optical O2 sensor (optode). By using the outer stainless-steel sleeve of the optode as an electrode, water splitting increases the local pH and forms H2 bubbles close to the optode surface. As seen in a biofouling assay, the combination of those processes leads to biofilm removal when compared to a non-modified optode. The findings suggest that electrochemical biofouling control can be an attractive, low-cost alternative to current biofouling mitigation strategies and that this approach may not be limited to O2 optodes.

Quorum Quenching-Mediated Biofilm Mitigation on Functionalized Ultrafiltration Membranes via Atom Transfer Radical Polymerization

Quorum sensing (QS) critically affects biofilm formation during membrane filtration, which can be manipulated for membrane biofouling mitigation. This study demonstrates a quorum quenching strategy for combating membrane biofouling by functionalizing poly(vinylidene fluoride) (PVDF) membranes via atom transfer radical polymerization of a QS inhibitor, vanillin. Poly(vanillin) brushes are successfully grafted on the membrane surface, which is verified by extensive membrane characterization. The effective biofilm inhibition ability and mitigation mechanism of poly(vanillin) brushes are evaluated by analyzing the QS-related gene expression and acyl-homoserine lactone (AHL) signal molecule concentrations. We show that poly(vanillin) brushes can inhibit the bacterial QS system and decrease the AHL concentration to mitigate membrane biofouling. In dynamic filtration experiments, the vanillin-grafted PVDF membrane exhibits a 50% increase in stable flux compared to that of the pristine PVDF membrane. Our results provide an alternate strategy for mitigating membrane biofouling by regulating the bacterial QS system via inhibitor-functionalized membranes.

Highly-efficient cathodic lysis of biofilm on conductive carbon nanotube membranes

Biofouling is a major problem observed with membrane-based water treatment systems. In this work, cathodic lysis of bacteria and biofilms on carbon nanotube (CNT) membrane was investigated as a novel mechanism for biofouling reduction. Considering the biofilm growth cycle, electrolysis of sessile bacteria and established bacterial biofilms were separately investigated. The results showed that cathodic electrolysis at 3.0 V for 3 h effectively eliminated 99.23% of the sessile bacteria on the CNT membrane. An extended treatment of mature biofilm for 21 h led to 93.92% reduction in viable bacterial density and 98.6% decrease in biofilm coverage. Besides, analyses of the membrane permeate revealed that the biofilm lysis released cell contents into the CNT matrix, which were subsequently removed by electrolysis. As a result, the normalized transmembrane pressure for the fouled membrane decreased from 4.23 to 2.06 after 21 h of electrolysis. Moreover, the cathodic lysis of bacteria and biofilm by the low-voltage electric field was mainly ascribed to the electro-generated H2O2 and the associated bio-electrochemical effects. This work provided a facile approach for in-situ mitigation of biofouling caused by chlorine-resistant bacteria, which was conducive to energy-efficient operation of membrane-based water treatment facilities.

Biofilm-responsive encapsulated-phage coating for autonomous biofouling mitigation in water storage systems

Biofilms in water storage systems may harbor pathogens that threaten public health. Chemical disinfectants are marginally effective in eradicating biofilms due to limited penetration, and often generate harmful disinfection byproducts. To enhance biofouling mitigation in household water storage tanks, we encapsulated bacteriophages (phages) in chitosan crosslinked with tri-polyphosphate and 3-glycidoxypropyltrimethoxysilane. Phages served as self-propagating green biocides that exclusively infect bacteria. This pH-responsive encapsulation (244 ± 11 nm) enabled autonomous release of phages in response to acidic pH associated with biofilms (corroborated by confocal microscopy with pH-indicator dye SNARF-4F), but otherwise remained stable in pH-neutral tap water for one month. Encapsulated phages instantly bind to plasma-treated plastic and fiberglass surfaces, providing a facile coating method that protects surfaces highly vulnerable to biofouling. Biofilm formation assays were conducted in tap water amended with 200 mg/L glucose to accelerate growth and attachment of Pseudomonas aeruginosa, an opportunistic pathogen commonly associated with biofilms in drinking water distribution and storage systems. Biofilms formation on plastic surfaces coated with encapsulated phages decreased to only 6.7 ± 0.2% (on a biomass basis) relative to the uncoated controls. Likewise, biofilm surface area coverage (4.8 ± 0.2 log CFU/mm2) and live/dead fluorescence ratio (1.80) were also lower than the controls (6.6 ± 0.2 log CFU/mm2 and live/dead ratio of 11.05). Overall, this study offers proof-of-concept of a chemical-free, easily implementable approach to control problematic biofilm-dwelling bacteria and highlights benefits of this bottom-up biofouling control approach that obviates the challenge of poor biofilm penetration by biocides.

Low-biofouling anaerobic electro-conductive membrane bioreactor: The role of pH changes in bacterial inactivation and biofouling mitigation

Membrane biofouling presents a great challenge to the adoption of anaerobic membrane bioreactors (AnMBRs) for wastewater treatment. A promising method for mitigating biofouling is applying an external charge to carbon-based electroconductive membranes (ECMs). This research investigated biofouling mitigation in an AnMBR mimicking system equipped with an ECM (EC-AnMBR), where the ECM serves as a cathode and a platinum plate as the counter electrode. A cation exchange membrane separated the anode and cathode to decouple the reactions on each electrode. Bacterial inactivation was estimated under varying cathodic potentials (0 to −2.5 V vs. Ag/AgCl), and reactive oxygen species formation and changes in pH were monitored. Bacterial inactivation was also evaluated in solutions with pH values similar to those recorded in the applied potentials experiments. Biofouling formation under the different applied potentials was then assessed during 48 h of filtration, and the biofilm formed on the ECM after 48 h was analyzed. Our results show that the EC-AnMBR had very low biofouling, attributed to bacterial inactivation and biofilm mitigation from extreme local pH conditions developed by hydrogen evolution at the cathode. This work addresses biofouling mechanisms on externally charged ECMs, which could be potentially applicable to AnMBRs for advanced wastewater treatment.