Method and kit for antimicrobial treatment of fuel containers using interfacially trapped particles

Abstract

A method and kit for inhibiting microbial proliferation in a fuel container are disclosed. The method involves introducing antimicrobial particles designed to be trapped at the fuel-water interface by interfacial tension, thereby concentrating antimicrobial agents at a primary site of microbial growth. These particles release antimicrobial ions into the water phase, creating a growth inhibition zone that can extend into the sludge zone. A kit is also provided, including at least two separate containers of particles being a denser type that settles and remains at the tank bottom and a lighter type that settles but is subsequently lifted to the interface upon water accumulation.

Description

[0001]Method and Kit for Antimicrobial Treatment of Fuel Containers Using Interfacially Trapped Particles FIELD OF THE INVENTION Embodiments of the present invention pertain to the prevention of microbial contamination in crude oil and fuel storage tanks. BACKGROUND OF THE INVENTION Water, a common contaminant in hydrocarbon fuels, provides a fertile ground for microbial growth. This is particularly problematic at the fuel-water interface and within the sludge or sediment layers that accumulate at the bottom of storage tanks. Microorganisms thrive in these environments, and their metabolic byproducts can degrade the physical and chemical properties of fuels and oils. Since it is practically impossible to maintain sterile conditions in fuel tanks, microbial contamination remains a persistent concern. This contamination leads to a cascade of problems: ● Fuel degradation: The quality of the fuel itself is compromised. ● Biofouling: Biomass accumulates, clogging and damaging fuel systems. ● Microbiologically Influenced Corrosion (MIC): Microbes, especially sulfate-reducing bacteria (SRB), accelerate corrosion of tank infrastructure. These issues have serious environmental and economic consequences. From an environmental standpoint, leaks caused by corroded infrastructure can lead to soil and groundwater pollution, requiring costly and extensive cleanup efforts. Economically, MIC poses a significant financial burden. In the United States alone, the annual costs related to MIC in crude oil and fuel production, transport, and storage are estimated to be in the hundreds of millions of dollars, not including the additional losses from spills or environmental remediation. The problem is expected to become even more pronounced with the increasing use of biofuels, such as biodiesel. While biofuels are similar to petroleum-based fuels in their combustion properties, they contain components that make them more water-soluble and more easily broken down by microorganisms. These characteristics heighten the risk of biofouling and biodeterioration. Current methods to combat microbial contamination in fuels are not fully effective or economically viable. While various physical, mechanical, and chemical strategies have been proposed, the most effective approach to date involves using biocidal additives that suppress microbial activity. Biocides with a partition coefficient between 0.5 and 0.8 are often recommended because this range ensures a balanced distribution between the aqueous and fuel phases. However, this method has a significant drawback: the amount of biocide needed is proportional to the total volume of fuel, making the treatment prohibitively expensive for many applications. The present invention addresses this limitation by offering a novel, localized approach to controlling microbial growth. Instead of distributing an antimicrobial agent throughout the entire volume of fuel, the present invention targets areas most susceptible to contamination: the oil / fuel-water interface and the sludge zone. Unlike the three-dimensional volume of the fuel, these regions are predominantly two-dimensional, with the interface's size correlating to the tank’s cross-sectional area, which is largely independent of the fuel volume. By localizing the antimicrobial agent to these specific, high-risk areas, the required amount is dramatically reduced. Furthermore, our approach uses antimicrobial particles that retain their activity over time, and because the interface is relatively undisturbed during tank refills, reapplication may not be necessary. This targeted method significantly reduces the amount of antimicrobial agent required, lowers costs, and simplifies regulatory compliance. SUMMARY OF THE INVENTION The present invention relates to methods and a kit for inhibiting microbial proliferation in a fuel container. The method comprises introducing antimicrobial particles into the container, where the particles are configured to be trapped at the fuel-water interface due to forces of interfacial tension. This trapping action concentrates the particles at the interface, which is a primary location for microbial growth. In certain embodiments, the antimicrobial particles are microparticles ranging from 10 μm to 100 μm in size, or composite particles with a radius between 0.1 mm and 10 mm. The particles can be made from a variety of materials, including silver, silver oxide, zinc oxide, and other metal oxides, and may be used in combinations to achieve a synergistic antimicrobial effect. The particles are configured to release antimicrobial ions, such as silver (Ag+), when in contact with the water phase, thereby creating a growth inhibition zone (GIZ) that can extend into the sludge zone at the tank's bottom. The invention also provides a kit for a fuel system, comprising at least two separate containers of antimicrobial particles. In one embodiment, the kit contains two types of beads: a denser type that settles to and remains at the tank bottom, and a lighter type that settles to the bottom but is subsequently lifted to the fuel-water interface upon water accumulation. This sequential delivery method ensures a multi-layered protection strategy within the fuel tank. The particles may also be of a uniform size to promote the formation of a stable, close- packed monolayer at the interface, enhancing the physical barrier against microbial growth. BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS The present invention will be better understood with reference to the following drawings: FIG.1 is a flowchart of a typical fuel distribution system. FIG.2A is a schematic illustration of a fuel tank, and highlights fuel tank components and the locations most susceptible to microbial proliferation. FIG.2B is a schematic illustration of a level of biomass and oxygen concentration in a microbially contaminated fuel tank, representative of the fuel tank of FIG.2A. FIG.3A schematically illustrates an overview of typical actions which are taken for mitigating fuel microbial contamination. For each action the number of $ signs symbolizes the magnitude of the associated cost. FIG.3B is a schematic illustration of a fuel microbial mitigation approach of the current invention compared to a conventional approach of employing biocides. FIG.3C is a schematic illustration of an embodiment of the present invention, including a suspension of antimicrobial particles selected and treated in a manner that, after dispensing the suspension, the antimicrobial particles travel to a fuel-water interface and / or sludge zone and spontaneously stay there. FIG.4 schematically illustrates a fuel-water interface laden with trapped microparticles. FIG.5 is a schematic illustration of an idealized particle trapped at a fuel-water interface. θ is a contact angle and indicates relative wettability of the particle by the fuel and water phases. R is a radius of the particle and h is a distance of its center of mass from the interface. Fgis a difference between weight and buoyancy force. TW, TFand TW-Frespectively represent interfacial tensions of water, fuel, and water-fuel which act along a fuel-water-particle contact line, L. A resultant tension force is T. FIG.6A is a table providing characteristic attributes of AgNbO3and Ag2O particles used to perform tests. FIG.6B illustrates the size distribution of Ag2O particles used to be encapsulated in the resins. FIG.7 is a table that presents labels and parameters of the tests performed to observe the influence of particle suspension liquid on the formation of particle laden fuel-water interface. FIG.8 is a photograph of a glass tube (left), containing separated water and fuel columns with particle laden interface, corresponding to Test B2 (using Ag2O particles from Bin1 size). The photograph on the right presents an Erlenmeyer Flask ), containing separated water and fuel columns with 2mm size acrylic beads trapped at the fuel-water interface. FIG.9A is a schematic illustration of transporting particles from particle suspension through a fuel phase to a fuel-water interface. FIG.9B is a schematic illustration of transporting particles from particle suspension through a water phase to a fuel-water interface. FIG.9C FIG.9C is a schematic illustration of transporting particles from particle suspension through a feeder nozzle to a fuel-water interface. FIG.10 is a schematic illustration of the break-up of a particle suspension drop over time (t1-t4) as the drop falls through the fuel phase, if dispensed as according to FIG.9A. FIG.11 is a schematic illustration of AgNbO3particle distribution across the fuel-water interface (1) prior to agitation, (2) during agitation, and (3) post-agitation. Prior to agitation, the particle distribution is characterized as typically heterogeneous, accumulating towards the edges of the interface, along the walls of the container. A brief agitation causes the particles to move towards the center of the interface, but no particle enters either the fuel or water columns. FIG.12 is a schematic illustration of the fuel-water interface (1) prior to addition of a water droplet, (2) during addition of the water droplet, and (3) post-addition of the water droplet. As seen in (2), the water droplet falls through the fuel until reaching the fuel-water interface. Upon contact with water, the droplet spreads. A droplet without particles does not substantially disturb the original distribution of the particles at the fuel-water interface. FIG.13 is a table that illustrates settling time (ts) for particles with diameter (d) needs to fall a distance of 1 meter (m) inside diesel fuel according to Sock’s law. FIG.14 is a photograph of tubes containing jet fuel and water phases in which Cladiosporium resinae cells have been added. One of the tubes is supplied with antimicrobial microparticles at the interface. The zoomed photo of the negative control tube is shown on the right side to better illustrate the growth of fungal cells. FIG.15 illustrates the amount of Ag2O, used as microparticles or encapsulated in acrylic beads with 2% w / w mass ratio, needed to cover an interface with a particle monolayer. FIG.16 is a graphical illustration of the cumulative percentage of silver content of epoxy discs, having 1% weight per weight (w / w) of encapsulated Ag2O microparticles, released into water. Also included is a graphical illustration of cumulative ion release from suspended Ag2O microparticles to water. FIG.17 is a photograph of agar plates on which “dense type” epoxy resin disks with different amounts of Ag2O microparticles had been placed after inoculating with Pseudomonas aeruginosa cells. A top row of agar plates provides a view immediately after removing the disks following 24 hours of incubation, and a bottom row of agar plates show 24 hours after removal of the disks and incubation at 35 degrees Celsius (oC). The dashed circles indicate approximate boundaries of the disks. FIG.18A is a photograph of agar plates on which “light type” epoxy resin disks with different amounts of Ag2O microparticles had been placed after inoculating with Pseudomonas aeruginosa cells. The photos were taken 24 hours after removal of the disks and incubation at 35 degrees Celsius (oC). The dashed white circles indicate approximate boundaries of the disks. FIG.18B is a photograph of agar plates on which “light type” epoxy resin disks with different amounts of ZnO microparticles had been placed after inoculating with Pseudomonas aeruginosa cells. The photos were taken 24 hours after removal of the disks and incubation at 35 degrees Celsius (oC). FIG.19 Illustrates the post-incubation picture of the Muller Hinton agar plates, streaked with a cell suspension of Pseudomonas aeruginosa, on which three differently treated epoxy discs (dry, soaked in water, soaked in sea water were placed. The dashed white circles indicate approximate boundaries of the zones of inhibition. FIG.20 is a schematic illustration of sequentially transporting two types of particles from their respective containers through a fuel column to the bottom of a fuel tank. DETAILED DESCRIPTION OF THE INVENTION Various embodiments and aspects of the disclosure will be described with reference to details discussed below. The following description and the associated drawings are illustrative of the disclosure and are not to be construed as limiting the disclosure. Many specific details are described to provide a thorough understanding of various embodiments of the present disclosure. However, in certain instances, well-known or conventional details are not described to provide a concise discussion of the embodiments of the present disclosure. DEFINITIONS As used herein, the following terms have the meanings set forth below: ● Fuel refers to a material used to generate heat or power through combustion. Unless otherwise specified, this term refers to liquid-state fuels. ● Biofuel is a fuel derived directly from living matter. An example is biodiesel, which is composed of mono-alkyl esters of long-chain fatty acids from various feedstocks, such as recycled cooking oil, soybean oil, and animal fats. Biodiesel conforms to the ASTM D6751 specification for use in diesel engines. Biodiesel blends, denoted as "BXX," contain a specified percentage of biodiesel, with "XX" representing the volume percentage (e.g., B20 is 20% biodiesel and 80% petroleum diesel). ● Jet fuel refers to a class of fuels with carbon chain lengths typically ranging from C10 to C16 and a boiling range between 130°C and 300°C. Common grades include Jet A, Jet A-1, Jet B, and TS-1 for commercial use, and JP-4, JP-5, and JP-8 for military applications. ● Petroleum diesel is a middle distillate stream from refineries that is less volatile than gasoline and is used to power diesel engines. ● Free water in fuel refers to water that is not dissolved or suspended within the fuel and has separated, typically settling at the bottom of a storage tank. ● Interface is the general term for the boundary region separating two distinct phases of matter (e.g., fuel and water). The term surface typically refers to the boundary between a condensed phase and a gas. ● Oil / fuel sludge, or simply sludge, is the solid or semi-solid waste that accumulates as a layer at the bottom of an oil or fuel tank. ● Agglomerates are weakly bound collections of particles. In contrast, aggregates are more tightly bound assemblies that are difficult to break down into primary particles using mechanical forces. ● Dispersion is the process of distributing solid particles uniformly throughout a liquid medium. ● Colloid refers to a stable dispersion of small particles, typically ranging in size from 1 nanometer to 10 micrometers, throughout a liquid. ● Epoxy resin is a type of thermosetting polymer formed by mixing a resin with a curing agent, also known as a hardener. ● Dispersant, or dispersing agent, is a substance, often a surfactant, added to a suspension of solid particles in a liquid to prevent settling or clumping and promote uniform separation. ● Biofilms are aggregates of microorganisms embedded in a self-produced matrix of extracellular polymeric substances (EPS) that adhere to each other and / or a surface. ● Biomass refers to biological material, excluding fossil fuels, that is or was a living organism or a component or product of a living organism. ● Biodeterioration is the loss of commercial value or performance characteristics of a product (e.g., fuel) or material (e.g., a fuel system) due to biological processes. This term is distinct from bioremediation, which refers to desired microbial degradation used for environmental cleanup (e.g., after spills). ● Biocide is a substance toxic to living organisms. Microbicides kill both bacteria and fungi. Bactericides kill bacteria, while fungicides kill fungi. Biocides are also referred to as antimicrobials. ● Antimicrobial particle refers to a particle that kills or inhibits the proliferation of at least one class of microbial cells. This action may occur through the release of antimicrobial compounds or direct interaction upon contact with the microbial cell. ● Microparticles are particles with a size between 0.1 and 100 micrometers (µm). Nanoparticles are defined as particles between 1 and 100 nanometers (nm). Beads are generally larger particles, defined herein as having a size greater than 100 µm. ● Minimum Inhibitory Concentration is the lowest concentration of an antimicrobial that prevents visible microbial growth after a specified incubation period in a liquid medium. Analogously, Surface Minimum Inhibitory Concentration (sMIC) is the lowest surface concentration of a particulate antimicrobial that prevents visible microbial growth on a solid growth medium. The embodiments of the present disclosure relate to preventing microbial contaminants in oil / fuel tanks. In what follows, unless it is explicitly specified, the subject matter is described in reference to fuels, including biofuels, with the understanding that all the disclosed methods are equally applicable in the case of crude oil. The presence of water is the primary catalyst for microbial contamination in fuel storage tanks, leading to significant environmental and economic damage. Industry data highlights the severity of this issue: an estimated 10-14% of oil and gas is lost due to microbial activity, and microbiologically induced corrosion (MIC) accounts for over 20% of global corrosion costs, which were estimated at $2.5 trillion in 2013. The context for the present disclosure requires an understanding of how free water originates and propagates throughout the fuel distribution system. As illustrated in the flowchart of a typical fuel distribution system 100, shown in FIG.1, water is introduced at various stages. While high temperatures within refinery distillation towers 110 prevent water condensation, newly refined fuel cools in refinery product tanks 120, causing dissolved water to precipitate. Additionally, tank vents can draw in atmospheric moisture or allow rainwater to enter. During subsequent transport stages, including by tanker or pipeline 130, and in later storage and distribution facilities 140, 150, and 160, additional water can be introduced through rain ingress or gas exchange with humid air. Beyond environmental exposure, water can be introduced intentionally or incidentally. For example, inadequate cargo compartment stripping or the use of water as a false bottom to facilitate complete cargo discharge can introduce substantial quantities of water. Some tank farms even use a layer of water at the bottom to reduce the risk of groundwater contamination from fuel leaks. In summary, although fuel may be "dry" upon leaving the refinery, it can collect free water during transportation and storage through several mechanisms: 1. Rainwater Ingress: Rain can seep in through faulty seals on floating-roof tanks or open hatches. 2. Poor Maintenance: Inadequate procedures after tank cleaning can leave residual water. 3. Condensation: In vented, fixed-roof tanks, moist air can cool, causing water to condense on the tank walls. 4. Temperature Changes: A drop in temperature causes dissolved water in the fuel to precipitate. 5. Microbial Byproducts: Microbes themselves can produce water as a metabolic byproduct. While fuel-handling operators strive to minimize water-fuel contact due to the risk of microbial growth, it is impossible to completely exclude water from these systems. At a minimum, water from condensation accumulates at the bottom of the tank. In tanks with slow turnover rates, this water column can constitute a few percent of the tank volume. A particularly challenging scenario is naval applications where saltwater ballasting is common. As fuel is consumed, seawater is pumped into the tank to maintain buoyancy, and in some vessels, water can occupy over 80% of the tank volume, leading to prolonged intimate contact between fuel and seawater. Water can be present in fuel in three forms: dissolved, suspended as an emulsion, or as free water. Dissolved water is considered a fuel constituent, with its solubility depending on the fuel's chemical composition. For example, aromatic hydrocarbons can dissolve up to five times more water than straight-chain hydrocarbons. Kerosene fuels are particularly susceptible to microbial attack because they have a high capacity to absorb dissolved water and release it as free water when temperatures drop. Biofuels, such as biodiesel, are more hygroscopic and water-soluble than conventional fuels, which increases their capacity to absorb and retain water. The ability of a fuel to hold water in solution is highly temperature dependent. As temperature, pressure, and humidity increase, so does water solubility. For instance, the dissolved water content in jet fuel increases from 45 milligram per liter (mg / L) to 92 mg / L as its temperature rises from 1°C to 34°C. Consequently, a drop in temperature increases the availability of free water, often resulting in a visible fuel-water haze. Suspended water appears as a cloudy emulsion, which, over time, coalesces and settles to the bottom as free water. The settling rate is governed by Stoke's Law, which states that larger droplets settle faster. This process of fuel-water shedding is particularly pronounced in areas with significant diurnal temperature variation. The settled water accumulates at the bottom of any storage vessel, forming a distinct fuel- water interface 215 at the boundary between the fuel 210 and the free water 220, as depicted in the schematic of a typical fuel tank in FIG.2. The interface rim 216 indicates where this boundary meets the tank wall. Additionally, particulate matter, such as sand, rust, and microbial debris, settles into a sludge zone 225 at the bottom of the tank. The composition of this sludge is heterogeneous and can include products of tank corrosion and microbial growth. The fuel-water interface 215 is the most vulnerable site for microbial contamination. While some research suggests this interface is a molecularly sharp boundary, other theories propose it is a dynamic, three-phase region where a mixture of fuel and water forms a middle layer. Regardless of its exact structure, this interface is the primary location where microbes thrive and cause damage. The high temperatures used in refining processes typically sterilize crude oil and other feedstocks. However, as fuel moves through the distribution chain—including refinery tankage 120, transport systems 130, terminal storage 140, and end-user tanks 180—more favorable conditions arise for microbial contamination. Refinery tanks are the first stage where significant contamination can occur. As fuel is withdrawn, the resulting vacuum pulls in air, which can carry pollen, dust, and other particles containing microbes through the tank vents. Once inside, these microorganisms may adhere to overhead surfaces or settle at the fuel-water interface, a boundary that is either pre- existing or forms from condensation. Because microorganisms require water for growth, their proliferation is restricted to the water phase of fuel systems. However, the most significant microbial activity occurs at the fuel- water interface 215 and especially at the interface rim 216, as shown in FIG.2B, where all essential physiological requirements for growth—including oxygen, carbon, and water—are readily available. Hydrocarbons serve as a carbon source for a wide variety of microorganisms. These microbes can metabolize straight-chain aliphatic hydrocarbons as well as lower-molecular- weight cyclic and aromatic molecules in the fuel to generate energy. Inorganic nutrients essential for growth, such as nitrogen, sulfur, and phosphorus, are typically available in tank sediment, water, and dust. Trace elements are also required and can sometimes be provided by fuel additives. Complex microbial communities form at the interface, consisting of hydrocarbon-oxidizing microorganisms and bacteria that utilize the metabolic byproducts of the former. Oxygen is a key requirement for aerobic microorganisms. The solubility of oxygen is significantly higher in most hydrocarbon mixtures than in water. This leads to a concentration of aerobic and facultative aerobic species in the biofilm at the oil-water interface. As these microbes consume oxygen and nutrients, they create increasingly anaerobic conditions deeper within the tank. This makes the sludge zone 225 a perfect environment for anaerobic species, particularly sulfate-reducing bacteria (SRB). SRBs are commonly associated with the microbial corrosion of carbon steel due to their production of hydrogen sulfide (H2S). The shift in the microbial community structure from aerobic to anaerobic further exacerbates this corrosive process. This qualitative understanding of biomass and oxygen distribution (schematically shown in FIG.2B) indicates that any effective solution to fuel contamination must target two key areas: the fuel-water interface 215, (including its rim 216,) and the sludge zone 225. Over 200 species of microorganisms, including 30 families of bacteria, yeasts, and fungi, are known to utilize hydrocarbons as their sole source of carbon and energy. The most common culprits in fuel contamination are bacteria like Pseudomonas aeruginosa and fungi like Cladosporium resinae (also known as "kerosene fungus"). When introduced to a surface, microorganisms proliferate into complex communities known as biofilms. The formation of biofilms at the fuel-water interface differs from that on solid surfaces. Studies using the bacterial adhesion to hydrocarbons (BATH) test suggest that the hydrophobicity of bacteria is a crucial factor in their ability to adhere and form biofilms at this interface. For example, hydrophobic species like P. aeruginosa readily form biofilms, while species with negligible hydrophobicity, such as S. aureus, do not. However, the methods disclosed herein are effective against any microbial species at the interface, regardless of the adhesion mechanism. The destructive effects of microbial processes on materials can be categorized into three main types: biofouling, biodeterioration, and microbiologically influenced corrosion (MIC). ● Biofouling refers to the accumulation of microorganisms on surfaces. In fuel systems, this can lead to clogged filters, restricted fuel flow, and malfunctioning equipment like valves and pumps. Common symptoms include rapid filter clogging, slime buildup, and inaccurate fuel gauges caused by hydrated microbial slime. These risks are heightened with the use of biofuels due to their more biologically reactive nature. ● Biodeterioration is the process by which microorganisms degrade the fuel itself, compromising its quality and damaging the fuel system. Jet fuels and other middle distillates are particularly susceptible because they contain a high proportion of low- molecular-weight hydrocarbons (C10 to C16), which microbes prefer to break down. ● Microbiologically Influenced Corrosion (MIC) occurs when microbes accelerate the electrochemical or chemical deterioration of materials. Biofilms are central to MIC, as the co-metabolism of different species within the community initiates and exacerbates corrosive reactions. Biofilms create chemical and electrical gradients, but more importantly, they are metabolically active and can create an anoxic environment where SRB and other anaerobes thrive. MIC is a major problem in fuel storage tanks, and the highest levels of corrosion are typically found at the fuel-water interface rim 216 and in the sludge zone 225. Completely preventing microbial contamination of fuels is impractical. Traditional measures for reducing the impact of microbial contamination of fuels fall into three broad categories: good housekeeping, physical decontamination and chemical methods. The physical decontamination and biofouling suppression methods include, regular and careful cleaning of tanks from sediments, effective filtration of fuel, excluding superficial microbial contamination, and more frequent water removal. In addition, ultra-violet and electromagnetic fuel irradiation, heating, and ultrasonic processing have also been suggested in prior art as plausible contamination mitigation methods. An overview of the current fuel contamination mitigation approach is presented in FIG.3A. As it is indicated, careful removal of the water in the bottom of storage systems is a primary way for preventing crude oil and its products from microbial contamination. In many cases, this is easier said than done, because typical tank, sump and drain configurations make it impossible to remove water thoroughly. Another impediment for water removal as a mitigation strategy is environmental safety concerns when biocides are used. Those biocides with broad spectrum activities, such as those approved for use in fuels, could be toxic if released into surrounding ecosystems or waterways at sufficient concentrations. Because of this, any bottom water removed from tanks treated with biocides must be collected and treated or disposed of in accordance with federal, state and local regulations. This can significantly increase operating costs. During the last two decades, first the aviation industry and later fuel suppliers and some militaries have used simple on-site microbiological tests to monitor fuel and fuel systems and use the results to take remedial actions before operational problems occur. Testing and monitoring fuel tanks represent a recurring cost. If the tank monitoring indicates heavy microbial contamination, the fuel is generally required to be disposed of due to its unsuitability for use, costing more than 5 US$ per gallon for disposal, not including the cost of replacement fuel. Traditional tank cleaning methods have historically incompletely sterilized a tank after cleaning, and as a result the remaining microbial biofilms will generally re-contaminate the tank within 12-18 months. If the contamination level is not high, the fuel may be subjected to a polishing process that removes microbial growth and the environment they live in and reduces the recurrence rate of microbial growth to almost zero. The major deficiency of physical methods for cleaning tanks is their short-lasting impact, i.e., reinfection is a possibility after treatment. Therefore, chemical protection of fuels, i.e. use of various chemical compounds and / or biocides, which operate for long periods of time, appear to be a more effective strategy to combat biodeterioration. Various fuel additives and corrosion suppressors with antistatic and anti-icing additives are used to improve aviation fuel quality. These additives usually possess biocidal (biostatic) properties as well. Nevertheless, once significant microbial contamination is present, the primary processes for removing accumulated biomass and for eradicating contaminant microbes is treatment with biocides. The performance criteria for biocides used in fuel systems are 1) broad-spectrum antimicrobial activity (bactericidal and fungicidal);, 2) chemical stability;, 3) no adverse effects on engine or fuel system components;, 4) low ash content;, 5) low environmental impact;, 6) cost effectiveness;, 7) “reasonable” fuel and water solubility;, and 8) “very high water / oil partition coefficient” Biocides are also known as microbicides or antimicrobial pesticides. In the U.S., the use of antimicrobial pesticides is regulated under the Federal Insecticide Fungicide and Rodenticide Act (FIFRA). In Canada, their use is regulated under The Pest Control Products Act (PCPA)., In the European Union (EU), they are regulated under the Biocidal Products Directive (BPD). Biocides are restricted in their designated end-uses. There are only two biocides that are approved for use in aviation fuel. Since fuel treatment represents a tiny fraction of the total industrial microbicides market and the regulatory pressure is very high, imminent development of new biocides are unlikely. However, there is a major drawback associated with using biocides for countering microbial contamination of fuels.: “The biocides are added to the whole volume of fuel to achieve concentrations of above 100 parts per million (ppm) for effective activity”. As previously discussed, though, microbial activity is not a concern through the entire fuel volume but is instead localized to the fuel-water interface 215, the rim 216, and the sludge zone 225. To address this issue present in the art, the present invention targets microbial cells at the fuel-water interface 215 and sludge zone 225, where the proliferation actually takes place. Therefore, the amount of required antimicrobial agent, tailored to provide localized antimicrobial activity, is substantially low, as schematically presented in FIG.3B. As it is shown, the present invention mitigates fuel microbial contamination through applying one or more antimicrobial agents at the fuel-water interface 215. This is achieved by transporting antimicrobial particles to the fuel-water interface, and distributing the antimicrobial particles over a two-dimensional surface, and restricting displacement of the antimicrobial particles to a direction perpendicular to the interfaces. In addition, according to some embodiments of the invention, the antimicrobial particles may be transported to the sludge zone. Accordingly, the basic elements of the invention are 1) suspending the antimicrobial particles, 2) transporting the antimicrobial particles to the fuel-water interface and / or sludge zone, and 3) selecting the chemical and physical properties of the antimicrobial particles to spontaneously stay in the target locations. These three elements are schematically presented in FIG.3C. Also presented in the FIG.3C is the habitability conditions of the fuel tank for different classes of microbial species prior to dispensing the antimicrobial particles. The approach of the present invention is associated with at least three advantages.: First, the required amount of antimicrobial particles scales with the area of the interface, rather than the fuel volume. Therefore, there is no extra cost beyond a threshold volume of the fuel at which the cost associated with the new approach equals the cost associated with the conventional approach. Second, some embodiments of the invention employ particles with long lasting activity, and fuel turnover does not require addition of new particles. This attribute results in a significant cost saving., Third, since merely a relatively small quantity of particles prevents microbial proliferation, the likely change in the composition of the fuel bulk by the antimicrobial particles is low. This is a bonus for lowering regulatory hurdles. In one embodiment, the prevention of microbial proliferation at the fuel–water interface 215 may be further understood with reference to the schematic representation of FIG.4. In the illustrated configuration, antimicrobial particles 300 are substantially immobilized at the fuel– water interface 215. As used herein, “substantially immobilized” refers to a condition in which the particles 300 do not undergo spontaneous displacement in a vertical direction, irrespective of whether their mass density is greater or lesser than the mass density of either the water phase or the fuel phase. Thus, the interfacial surface tension forces contribute significantly to the positional stability of the particles 300 at the interface. In certain embodiments, the particles 300 may be coated with a surfactant 305, configured to inhibit particle coagulation in response to mechanical perturbations on the interface. The two- dimensional concentration of particles 300 at a particle-laden, fuel-water interface 215 is maintained at a level sufficient to reduce the probability of microbial cell division by several orders of magnitude. It is not required that such growth inhibition occur uniformly at all locations along the interface, provided that the particle 300 population is sufficient to limit the expansion of microcolonies—defined herein as colonies having a characteristic size of less than approximately 100 μm—and to prevent the establishment of a biofilm. As stated above, a main element of the current invention is antimicrobial microparticles 300, which after being transported to the fuel-water interface by external forces, such as gravity, are trapped there by replacing part of the fuel interface and reducing interfacial free energy. The extent of this energy reduction depends on the interfacial tension between the fuel 210 and water 220 and attributes of the particle 300, including size and wetting properties. Three transport mechanisms that promote the approach of microparticles 300, having a mass density higher than the mass density of the fuel, from the bulk fuel to the fuel-water interface are (i) Brownian diffusion, (ii) gravitational force, and (iii) hydrodynamic guidance. In the dilute regime, where interactions between particles can be neglected, the terminal velocity of a spherical particle with diameter d and falling in a fluid is determined by Stokes' law: మ^^ = ௗ ^ఘುିఘಷ^^௧ ^଼ఎ (Eq. 1)^^ிare, respectively, the densities of the particles and the fuel, g is the and ^^ is the dynamic viscosity. The relative strength of gravity and diffusion is evaluated by means of the Peclet number, which compares the ratio ofconvective to diffusive transport, defined as^^ ௗ௩^ = ^ଶ^ (Eq. 2)D is the bulk diffusion coefficient of the particles. Pe assumes values about 0.1 for of 1 μm diameter suspended in water, whereas particles of 10 μm present a Pe number almost 4 orders of magnitude higher. Therefore, the increase of the particle size favors ballistic movement over diffusive transport. Nanoparticles are therefore more sensitive to thermal fluctuations than microparticles. The conditions required for the attachment of a colloidal particle to a fuel-water interface may be understood by referring to FIG.5, which presents the forces acting on the particle at a fuel-water interface. The contact angle θ is indicative of the relative wettability of the particle by the fuel and water and determines distance h by which the particle’s center is settled below the interface. The main forces are Fg(the difference between weight and buoyancy force), and the interfacial tensions TW, TFand TW-F(respectively, corresponding to water, fuel, and water-fuel interfaces) acting along the fuel-water-particle contact line, L. At equilibrium, Fgand resultant tension force, T, cancel each other. In other words, the trapping occurs when the gravitational forces are overcome by the action of the interfacial tension forces, the balance of which can be evaluated in terms of the Bond number: మ^^^^ = ௗ ^ఘುିఘಷ^^ఊೈିఊಷ (Eq. 3)When Bo≤ 1, the interfacial are dominant and the vertical confinement of the particle 300 to the fuel-water interface is resilient, i.e. stable against mechanical perturbations in the interface. The phenomenon described can be understood as a reduction in interfacial energy that occurs when a particle settles at the interface between two fluids. For a spherical particle initially submerged in one of the fluids, it will diffuse vertically until it reaches the interface. Once there, the particle begins to be wetted by both fluid phases. This process minimizes the unfavorable interaction between the two fluids (for example, fuel and water) by reducing their direct contact area. The resulting decrease in energy helps to stabilize the interface. To effectively prevent microbial growth, a significant portion of the interface—over 10% of its total area— must be covered by particles 300. At this higher concentration, it becomes crucial to consider the interactions between the particles 300 themselves. These inter- particle interactions can negatively impact the particles' 300 ability to mitigate microbial contamination if they lead to coagulation of particles and leaving some areas in the interface devoid of particles and vulnerable to microbial growth. Therefore, the interactions between particles 300 should not be overlooked. There are two types of attractive inter-particle forces. First, there are short-ranged dispersion Van der Waals (VDW) forces, extending over a range of tens of nanometers for micrometer- sized colloids. Second, there are attractive capillary forces resulting from the distortions imposed on the interface by the particles 300 whose role is significant for particles with size over 5-10 μm. Repulsive forces include Coulomb interactions and steric repulsions. The electrostatic interactions emerge from the combination of the repulsive screened coulombic repulsion, which operates at short distances (also found in bulk suspensions), and a long-range attractive dipole-dipole interaction because of the particle 300 trapping at the fuel-water interface and the great difference between dielectric constants of water and the fuel. The screened Coulomb potential acts at short distances and is important in preventing particle 300 coagulation. In contrast, at distances much larger than Debye screening length, the dipolar interaction is the main component of the electrostatic contribution. The steric interactions emerge from the presence of additives to the particle 300 dispersions which form a capping layer on the particle surface. The presence of the capping layer leads to osmotic pressure as particles 300 approach each other. This creates an unfavorable entropic contribution associated with the compression of the capping layer, resulting in a repulsive contribution to the energetic balance of the system. The preceding discussion about particles 300 getting trapped at water-fuel interfaces implicitly assumed that the particles had been in one of the fluids for a long time, allowing them to be thoroughly wetted before moving to the fuel-water interface 215. In reality, this is rarely the case. Antimicrobial articles are often provided to an end user as a suspension, and the liquid medium used for this suspension is crucial for how the particles 300 behave after being dispensed. We observed this experimentally with AgNbO₃ and Ag₂O microparticles, noting how the suspension liquid influenced whether the particles 300 settled at the water- fuel interface 215 or sank to the sludge zone 225. This insight was used to select the appropriate suspension liquid to guide the particles 300 to their desired location. The specific characteristics of these microparticles are presented in FIG.6A. The experiments on the settling dynamics of AgNbO3and Ag2O particles were performed as the following according to the methods of Example 2. The labels and parameters of 6 tests are presented in FIG.7. The results are as the following: Test A1 (AgNbO3: water as the suspension liquid): The 100 microliter (μL) suspension drop, including the particles, which was gently added to the top of the fuel column, fell through the fuel column in the test tube. The droplets did not disintegrate at the fuel−water interfaces and kept moving down to the bottom of the water column. We conclude that selecting water as suspension liquid is appropriate for transporting AgNbO3microparticles to the sludge zone. Test B1 (Ag2O: water as the suspension liquid): The experiment was performed for the microparticles belonging to each of the six size bins (specified in Example 1B). In all cases, the particles’ transport dynamic was qualitatively similar to the results of Test A1: The dispensed droplets rapidly fell through the fuel column in the test tube. They did not disintegrate at the fuel−water interfaces and kept moving down to the bottom of the water column without being trapped at the fuel-water interface. We conclude that selecting water as suspension liquid is appropriate for transporting Ag2O microparticles to the sludge zone, without significantly losing them along the way either in fuel or water phases or being trapped at the fuel-water interface. Test A2 (AgNbO3: Jet fuel as the suspension liquid): The 100 μL suspension drop, including the particles, which was gently added to the top of the fuel column, slowly fell through the fuel column in the test tube and after fragmenting remained there. A microparticle laden interface was formed. Checking over 10 days, no visible change in the distribution of the particles was noticed. Test B2 (Ag2O: Jet fuel as the suspension liquid): The experiment was performed for the microparticles belonging to each of the six size bins (specified in Example 1B). In all cases, the particles’ transport dynamic was qualitatively similar to the results of Test A2: The 100 μL suspension drop, including the particles, which was gently added to the top of the fuel column, rapidly (compared to the case of Test A2) fell through the fuel column in the test tube and after fragmenting remained there. A microparticle laden interface was formed. Checking over 10 days, no visible change in the distribution of the particles was noticed. An example photo of the tube is presented in FIG.8 (left photo). Test A3 (AgNbO3: Ethanol as the suspension liquid): Very similar to the case of Test A2. Noting that Ethanol is miscible in jet fuel, we take the similarity with Test A2, to conclude that other liquids miscible with the target fuel (Jet fuel in the present case) may be used as suitable suspension for the particles when the intention is to transport the particles to the fuel-water interface. Test B3 (Ag2O: Ethanol as the suspension liquid): The experiment was performed for the microparticles belonging to each of the six size bins (specified in Example 1B). In all cases, the particles’ transport dynamic was qualitatively similar to the results of Test A3. Therefore, other liquids miscible with the target fuel (Jet fuel in the present case) may be used as suitable suspension for Ag2O microparticles when the intention is to transport the particles to the fuel-water interface. The experiments on the settling dynamics were also performed for ZnO particles having a size in 0.2-20 μm as measured by laser diffractometry. The methodology was according to the methods of Example 2. The results are as the following: Test C1 (ZnO: Water as the suspension liquid): The experiment was performed for the polydisperse particles. The dispensed droplets rapidly fell through the fuel column in the test tube. They did not disintegrate at the fuel−water interfaces and kept moving down to the bottom of the water column without being trapped at the fuel-water interface. We conclude that selecting water as suspension liquid is appropriate for transporting ZnO microparticles to the sludge zone, without significantly losing them along the way either in fuel or water phases or being trapped at the fuel-water interface. Test C2 (ZnO: Jet fuel as the suspension liquid): The experiment was performed for the polydisperse particles. The 100 μL suspension drop, including the particles, which was gently added to the top of the fuel column, fell through the fuel column in the test tube and after fragmentation remained there. A microparticle laden interface was formed. Checking over 10 days, no visible change in the distribution of the particles was noticed. A suspension liquid for transporting particles 300 to a fuel-water interface 215 is selected based on its miscibility with a target fuel. The suspension liquid is miscible with the target fuel and has a density lower than that of water. In one embodiment, the suspension liquid is identical to the target fuel. In a further embodiment, the suspension liquid is selected to facilitate an increased rate of particle 300 transport to the fuel-water interface 215. This embodiment utilizes a suspension liquid that is miscible with the target fuel and has a density greater than the target fuel and less than that of water, i.e. a density between water and the target fuel. The particle 300 suspension, intended for fuel-water interface, can be dispensed into the fuel-water system of the tank in different ways. Three non-limiting approaches are presented in FIGS.9A-9C. In one embodiment, illustrated in FIG.9A and referred to as a "through-fuel" mode, a sprayer 250 is configured to introduce the particle 300 suspension onto a top surface 205 of a fuel column 210. The drops of the antimicrobial suspension 255 subsequently travel downward through the fuel column 210 toward the fuel-water interface 215. This travel is governed by a combination of the drops' initial momentum imparted by the sprayer and the force of gravity. As the drops descend, they deform and fragment, as depicted schematically in FIG.10 for the case of a particular suspension drop 260, resulting in a plurality of smaller fragments. The specific distance from the top of the fuel column at which this fragmentation occurs is a function of the suspension drop size, suspension viscosity, particle 300 concentration, and initial momentum of the drops. The distribution of antimicrobial particles 300 at the fuel-water interface 215 is consequently dependent on the distance traveled before fragmentation. In another embodiment shown in FIG.9B, referred to as the "through-water " mode, the sprayer 250 introduces the particle 300 suspension directly into a water column. The suspension drops 255 then travel to the target interface via a combination of their initial momentum and buoyancy or gravitational forces. When the “through-water” mode is employed for particle 300 transportation to fuel-water interface, the suspension liquid could be selected as a nonpolar liquid with a density less than 1 such that the suspension drops generated after spraying are allowed to travel upward via the buoyancy force. In yet another embodiment shown in FIG.9C, a "through-nozzle" mode is provided. A particle suspension container (270) is operably connected to a fuel feeder nozzle. This configuration permits the particle suspension 255 to be mixed with fuel at a predetermined ratio during the process of filling a tank. A particle-laden interface is formed by transporting particles 300 to the fuel-water interface 215, using a selected suspension liquid and dispensing method as described herein. The antimicrobial particles 300 are distributed across the interface, creating a layer. The morphology of this layer, including the variation in particle 300 surface density, is dependent on the specific details of the dispensing approach and the type of optional coatings 305 on the antimicrobial particles 300 (305 in FIG.3). The dispensing approach is preferably engineered to achieve a substantially uniform particle 300 distribution across the interface 215. A particle-laden, fuel-water interface 215, formed after transporting the particles 300 to the interface, demonstrates resilience against mechanical perturbations. Experiments conducted with microparticles such as Ag2O and AgNbO3, (having the attributes shown in FIG.6A,) as described in Example 3A, confirm this resilience. As depicted in FIG.11, prior to agitation (1), the particles 300 at the interface 215 exhibit a heterogeneous distribution, with a tendency to accumulate at the edges of the container due to the influence of the container wall. Following a brief mechanical agitation (2), the particles 300 move toward the center of the interface 215 but are observed to remain at the interface (3), rather than dispersing into the fuel 210 or water columns 220. This characteristic indicates that the particle-laden interface 215 is robust and capable of withstanding mechanical shocks, such as those that may occur during vehicle movement or fuel transfer operations. A particle-laden, fuel-water interface 215 also exhibits resilience against the introduction of water from the fuel phase, which may occur as a result of events such as water ingress into the tanks. This characteristic was demonstrated in an experiment conducted according to the method of Example 3B. As schematically shown in FIG.12, a fuel tank 200 with the particle-laden, fuel-water interface 215 is provided (1). A water drop falling through the fuel phase toward the interface is halted upon contact with the particle-laden interface (2). The drop then slowly spreads and merges with the bulk water below. Notably, the distribution of particles 300 at the point of impact is not significantly perturbed (3), confirming the interface's ability to resist disruption from intruding water. Appropriate antimicrobial particles 300 are the basic requirement for any embodiment of the present invention. The disclosed methods utilizes antimicrobial particles 300 that are effective against a broad spectrum of microbial species, including bacteria and fungi, both of which are known to cause contamination in fuel and oil. Many antimicrobial particles, typically in sub-micron range, have been investigated in the prior art for diverse applications. A non-exclusive list includes the particles synthesized using the following compounds, alone or in combination: silver, silver oxide, AgNbO3, zeolite-supported silver, silver-doped metal oxides, zinc oxide, titanium oxide, copper oxide, and magnesium oxide. All these particles owe their antimicrobial activity to the presence of transition metals. In prior art, two types of mechanisms of action have been proposed for the antimicrobial particles containing transition metals: 1) contact kill mechanism, and 2) activity through release of metallic ions. For instance Cu2O particles have been reported to kill by contact. As another example, the antimicrobial activity of AgNbO3has been hypothesized to be dominated by contact killing. In contrast, the antimicrobial activity of Ag2O particles is dominated by Ag+release. Another example is silver doped faujasite- type zeolite particles, for which silver cations are trapped into the nanopores through exchange with sodium. The process of exchange of sodium for silver is reversible and the particle releases silver ions if it is put in a solution where the cations concentration is lower than that of the initial solution. Employing particles 300 with antimicrobial activity through the release of metallic ions has two major advantages: A first advantage is that the ions, being much smaller than the particles 300, can penetrate into pre-existing biofilms. This penetration allows for the effective elimination of microorganisms residing within the biofilm structure, which would otherwise be shielded from direct particle 300 contact. Accordingly, larger antimicrobial particles 300 can be utilized without the risk of leaving the pre-existing biofilms to survive. A second advantage is that the continuous release of ions creates a growth inhibition zone (GIZ) in the vicinity of the particles 300. Within the GIZ, the concentration of the released ions is sufficient to inhibit or eliminate microbial growth. In one non-limiting description, the extent of the GIZ can be qualitatively estimated by considering a water column having a height of approximately 2.5 cm, wherein ions are released from silver oxide (Ag2O) particles having the characteristics listed in FIG.6A. The particles, when placed at the fuel-water interface, function as an approximately constant source of ions. For the sake of mathematical simplicity, the sludge zone at the bottom of the tank may be considered as an ion sink. These assumptions enable the use of known solutions of the diffusion equation to model the distribution of ions and provide a qualitative picture of the GIZ's extent. According to the published literature, the diffusion constant of silver ions in water is 3.5×10−5centimeters squared per second (cm2 / s). This means that, after one hour, most ions released from the particles will travel no more than 5 mm and it will take about 24 hours for the ions to reach the sludge zone. At this point, the system starts to reach a steady state. Once steady state is reached, the ion concentration at a distance of 5 mm from the interface is within 30% of the concentration at the interface itself. Thus, to ensure the inhibition of microbial growth within 5 mm of the interface, the particle concentration needs to be at least 3 times higher than the “Surface Minimum Inhibitory Concentration (sMIC)” for common microbes encountered in the contaminated fuel tanks. This guarantees that the ion concentration throughout this 5 mm zone is sufficient to stop microbial growth. As a result, GIZ is at least 5 mm wide. When the thickness of the water column 220 in a fuel tank 200 is only a few centimeters, the concentration of particles 300 at the fuel-water interface 215 can be selected sufficiently high to make both the interface and the sludge zone antimicrobial. If the particle 300 concentration at the interface is at least three times the sMIC, the ions released will be able to reach the sludge zone in sufficient quantity to inhibit microbial growth there. This means adding separate antimicrobial particles 300 destined to the sludge zone may not be needed as the microbial contamination there is prevented by the antimicrobial particle layer at the fuel-water interface. The prior art contains limited reports on the antimicrobial activity of microparticles, particularly in comparison to vast studies on antimicrobial nanoparticles. One of the co- inventors of the this disclosure have has investigated the antimicrobial efficacy of silver oxide (Ag2O) microparticles and much smaller silver niobate (AgNbO3) nanoparticle aggregates, the latter of which are considered microparticles according to the definition of this invention. The results of this investigation, detailed in US patent application publication no. US2022 / 0279792, indicate that particle size may not be a significant impediment to antimicrobial activity when the primary mechanism involves the release of antimicrobial ions (the case of Ag2O microparticles of FIG.6A). Accordingly, in all embodiments of the present invention, microparticles 300—defined as particles with a size ranging from 0.1 to 100 μm—can be utilized, provided that their number concentration is selected to ensure sufficient antimicrobial efficacy across the fuel-water interface. This approach leverages the beneficial attributes of microparticles 300, which may include lower production costs, more efficient transport to the target interface, and reduced agglomeration compared to nanoparticles. Studies on the growth dynamics of a typical strain of E. coli on a gel surface laden with AgNbO3microparticles have shown that a surface coverage of at least 15% with said microparticles is required to achieve effective inhibition of this typical microbial species on the surface. Accordingly, to achieve a GIZ extending about one centimeter into the water phase from the fuel-water interface, a higher surface coverage of 45% over the area of said interface is required. This represents a concentration approximately three times that needed for protecting only the fuel-water interface. Thus, in one embodiment of the present invention, a higher surface concentration of microparticles 300 may be necessary to extend the antimicrobial effect into an adjacent liquid phase, such as water. In one embodiment, intended to achieve a GIZ extending at least 0.5 centimeters into the water phase from the fuel-water interface, a surface coverage of 45% over the area of fuel-water interface is required. In another embodiment, the amount of microparticles intended for a given interface is selected to correspond to a full coverage to mitigate the possibility of microparticle aggregation and leaving some areas of the interface unprotected. In the context of the present invention, the performance of the microparticles 300 is also characterized by their sedimentation properties in various liquids. The primary governing parameter in this regard is the terminal velocity vt, as defined by Equation 1. This characteristic may impose limitations on the minimum particle 300 size, depending on the chosen delivery method for the antimicrobial particles and the desired maximum settling time. As an example, consider a scenario where a dilute suspension of sufficiently small particles is introduced at the top of a fuel column of height h. The average settling time ts, for a particle with diameter d to reach the fuel-water interface is given by the following approximate relationship:^^ ^଼ఎ^ = ℎ / ^^ ^௧ = ௗమ^ఘುିఘಷ^^ (Eq. 4)size in practical situations, the settling times were 4 some particles 300 with different mass densities and diameters settling through a 1-meter fuel column with a viscosity of 3 mPa·s (representative of diesel fuel). The results are depicted in FIG.13. If a maximum settling time of less than one day is desired, the listed AgNbO3microparticles will not be suitable. In contrast, Ag2O particles with diameters greater than 10 μm will provide satisfactory performance in terms of settling time. One aspect of the present invention is the ability to overcome the limitations of particle 300 sedimentation through the use of active dispensation methods. By employing such methods, the lower size limit for the microparticles 300 can be significantly reduced without compromising performance. In one embodiment, the microparticles 300 are carried for a substantial portion of their path within a drop of the liquid suspension which has been sprayed into the fuel column. This configuration allows the particles 300 to benefit from the momentum of the liquid drop, which further facilitates their rapid and efficient transport to the fuel-water interface, thereby mitigating the effects of slow terminal velocity. A core premise of the present invention is that a particle 300 with known antimicrobial activity, established through standard susceptibility tests, retains its efficacy after being suspended in a nonpolar liquid, traversing through a fuel column, and settling at a fuel-water interface. A main concern is that a fuel barrier could form around the particle's 300 surface, thereby shielding microbial cells from its antimicrobial action. This concern was experimentally ruled out by a procedure consistent with the method described in Example 4B, employing AgNbO3and Ag2O particles whose attributes are shown in FIG.6A. The target microorganism for this investigation was Pseudomonas aeruginosa ATCC 27853. In all cases 400 mg of microparticle was added to the interface, which had an area of about 5 cm2. This amount is selected such that theoretically a close-pack monolayer of microparticles is formed in the case of Ag2O microparticles. Evidently, the layer will be more than the one layer for the case of AgNbO3, as the microparticles have much smaller sizes. Test 1 was conducted in accordance with Version A of Example 4B, utilizing AgNbO3particles. After a period of 24 hours, the water column of the control tube (Tube 1) exhibited visible turbidity, indicating significant bacterial proliferation. Conversely, the water column of the corresponding test tube (Tube 2) showed no visible signs of microbial growth. However, subsequent subculturing of an aliquot from the TSB column of Tube 2 indicated the presence of viable bacterial cells. Moreover, after an additional 24 hours of incubation, the water column in Tube 2 also became turbid. This experimental result demonstrates that the majority of the inoculated bacterial cells were retained at the fuel-water interface. We speculate that the said retention at the interface is due to high adhesion capacity of P. aeruginosa to hydrocarbons. The proliferation of these cells, which were already situated at the interface, was effectively inhibited by the antimicrobial particles that had been subsequently introduced and similarly trapped at the fuel-water interface. The limited number of bacteria that were able to pass into the bulk TSB medium proliferated due to the availability of nutrients and the short range nature of the antimicrobial activity AgNbO3particles, which are known to inhibit growth through contact. The overall observations above confirm the effectiveness of the antimicrobial effects of the particles 300, even after they have undergone wetting by the fuel and are situated in partial contact with the fuel at the fuel-water interface. The results of Test 2 indicate that even the minimal number of bacterial cells that successfully pass through the fuel-water interface are inhibited. This outcome is attributed to the mechanism of action of the Ag2O particles, which release Ag+ions through a slow corrosion process. These ions diffuse into the bulk liquid phase and provide antimicrobial activity remotely, in contrast to AgNbO3particles, which have been hypothesized to exert their antimicrobial activity through contact. Test 3 was performed in accordance with Version B of Example 4B, utilizing AgNbO3particles. After an initial 24-hour incubation period, the control tube (Tube 1) exhibited turbidity in its water column, whereas the water column in the test tube (Tube 2) remained clear. Following an additional 48 hours of incubation, the water column in Tube 2 was still transparent, with no signs of microbial growth. Test 4 was performed in accordance with Version B of Example 4B, utilizing Ag2O particles. After a 24-hour incubation period, the water column in the control tube (Tube 1) was turbid, while the water column in the test tube (Tube 2) showed no turbidity. After an additional 48 hours, the water column in Tube 2 also remained clear. The combined results of Test 3 and Test 4 indicate that any microbial cells that manage to pass through the particle-laden fuel-water interface are effectively inhibited. This effect may be attributed to an antimicrobial impact sustained during their temporary residence at the interface 215. As a more likely scenario, the growth inhibition of microbes passing through particle laden interfaces is caused by a small number of particles that are carried with the cells as they pass into the bulk liquid. The antimicrobial activity of the microparticle laden interfaces were also performed for microbial species isolated from an actual contaminated tank. A sample of contaminated fuel was obtained from a company, engaged in servicing petroleum and fluid handling equipment in the Midwest. Microbiological techniques were used to culture and isolate microorganisms from the sample. Bacterial species Pseudomonas aeruginosa and the kerosene fungus (Cladiosporium resinae) were successfully purified from the sample. Test 5 was performed for Pseudomonas aeruginosa isolated from contaminated fuel in accordance with Version A of Example 4B and utilized Ag2O microparticles. After 24 hours, the water column in the control tube (Tube 1) exhibited turbidity, indicative of robust bacterial growth. Conversely, the water column in the corresponding test tube (Tube 2) showed no visible signs of growth. Subsequent subculturing of an aliquot from the TSB column of Tube 2 also revealed no presence of viable bacterial cells. Test 6 was performed for Cladiosporium resinae in accordance with Version A of Example 4B and utilized Ag2O microparticles. After 5 days of incubation at room temperature, the test sample containing the Ag₂O microparticles remained clear. In contrast, the control sample exhibited initial fungal growth, observed as a faint, whitish turbidity. After 10 days of incubation at room temperature, the test sample remained clear, indicating a sustained absence of fungal growth. The control sample, however, showed significant fungal proliferation, characterized by robust growth at both the bottom and the surface interface of the test tube, as depicted in FIG.14. Test 7 was performed following the procedure outlined in Example 4B, Version A, to evaluate the fungicidal efficacy of the trapped zinc oxide (ZnO) microparticles against Cladosporium resinae. The ZnO microparticles, as measured by laser diffractometry, had a size distribution in the range of 0.2-20 μm. The results were consistent with those observed in Example 6. Specifically, after 10 days of incubation at room temperature, the test sample containing the ZnO microparticles remained clear, demonstrating the sustained inhibition of C. resinae growth at the fuel-water interface. In order to ensure complete coverage of the fuel-water interface and to prevent microbial contamination, the quantity of microparticles employed should be sufficient to form at least a single, continuous layer at the interface. This provides a safeguard against potential coagulation or flocculation of the microparticles, which can lead to the formation of larger aggregates. Such aggregation may result in unprotected areas or "patches" at the interface, thereby compromising the intended antimicrobial barrier. A similar criterion is applied when the microparticles are intended to protect the sludge zone. A primary criterion for selecting the composition of the suspension liquid is to ensure the long-term stability of the chosen antimicrobial particles. To illustrate this, consider the use of Ag2O microparticles in an aqueous-based suspension liquid. This selection is made to ensure the particles will settle through a fuel column and reach the bottom of the tank without being trapped at fuel-water interface. It is known that silver oxide undergoes a dissolution reaction in an aqueous medium as follows: ½ Ag2O (s) + H+(aq) ←→ Ag+(aq) + ½ H2O(l) This reaction has an equilibrium constant of logK=6.30, which can lead to an equilibrium concentration for Ag+in the order of 1mol / L at a circumneutral pH. Under these conditions, Ag2O is generally not stable; as observed in FIG.16, a typical Ag2O microparticle can lose approximately 10% of its mass after one month of storage at circumneutral pH. However, published literature indicates that at a pH of approximately 10, the solubility of Ag2O is reduced by a factor of about 1000. It is a well-established principle, as described by the Noyes-Whitney equation, that very low dissolution rates are correlated with low solubilities, and vice versa. Therefore, increasing the pH of the aqueous suspension liquid ensures the stability of the particles against dissolution over a long storage period prior to use. To form an antimicrobial microparticle-laden interface, the microparticles 300 suspended in an appropriate suspension liquid 255, are dispensed into the fuel column 200 by the user. The design of both the bottle and its contents is governed by the performance criteria, which mandate that the microparticles remain uncoagulated during storage and transportation. In a preferred embodiment, the user is not required to perform any preparation beyond shaking the bottle prior to use. To satisfy this requirement, a stable suspension 255 is prepared from a dry powder through a multi-step process. In a general approach, particle 300 agglomerates are first broken apart by the application of shear stress forces. Subsequently, the particles 300 are dispersed and stabilized by either electrostatic repulsive forces or the excluded volume effect, both of which are influenced by the presence of stabilizing additives. Well-dispersed particles in a liquid phase can be achieved by considering particle size, chemistry, and liquid viscosity, as well as by adding surface-active compounds. Published research has shown that increasing particle size enhances colloidal stability and provides greater resistance to aggregation. Conversely, particle size is inversely proportional to aggregation tendency at the nanoscale. Nanoparticles in a solution often form a relatively unstable colloidal system because they tend to aggregate to reduce their high surface energy. Therefore, in one embodiment of the present disclosure, the microparticle 300 size is selected to be greater than 10 μm to reduce the incidence of microparticle aggregation. Selecting a larger size for the microparticles 300 may not, by itself, provide sufficient stability against aggregation in the suspension. As such, stability may be further improved by preventing agglomeration through surface functionalization and manipulation of surface charge, or by attaching macromolecules or polymers to the particle 300 surfaces. Additionally, the stability of the microparticle suspension may be improved by adding dispersants, which work to lower the attractive interactions between the particles 300. In one embodiment, the upper limit for the diameter of the microparticles 300 is determined by cost considerations. For example, the amount of silver oxide (Ag2O) needed to cover an interface with a monolayer of particles was calculated as a function of the microparticle diameter, with the results shown in FIG.15. As indicated by the "microparticle" curve in FIG. 15, a particle diameter of 100 µm requires approximately 374 g of Ag2O to achieve full coverage of a 1 m2area. This significant material requirement diminishes the cost- effectiveness of using these interfacially trapped antimicrobial particles for fuel contamination mitigation when compared to existing methods. In contrast, an alternative embodiment of the present invention, depicted as a "bead" in FIG.15, which will be described below, can achieve full interface coverage using approximately 30 times less Ag2O. This reduction in material cost also allows for the implementation of a "close-packed coverage" configuration. The close-packed arrangement minimizes intra-particle gaps, which enhances the resilience of the layer and improves the inhibition of microbial growth at the interface. This configuration is particularly advantageous as it optimizes both material usage and antimicrobial efficacy. In an embodiment of the present invention, the upper size limit for the antimicrobial particles is extended from the micrometer regime (e.g., less than 100 µm) to approximately 10 mm. This is achieved by encapsulating a silver compound within a host matrix material. The host matrix material may be a porous host, such as a polymer, ceramic, a metal-organic framework (MOF), or a zeolite. In an alternative embodiment, microparticles that release silver ions (Ag+), such as Ag2O microparticles, are incorporated within a porous shell, forming a core-shell composition. In a preferred embodiment, Ag2O microparticles are encapsulated within a polymer matrix, such as an acrylic. In all of these cases, the resulting composite material is formed into beads. These beads are referred to as "antimicrobial beads" to distinguish them from "antimicrobial microparticles." It is understood, however, that the term "antimicrobial particle," schematically represented by element 300 in FIG.4, applies to both antimicrobial microparticles and antimicrobial beads. Moreover, it is understood that the name “bead” doesn’t necessarily imply a substantially spherical shape. The antimicrobial beads possess a substantially reduced mass density compared to the antimicrobial microparticles, allowing for a significant increase in particle size while maintaining a manageable Ag2O mass. The substantial increase in particle size, from the micrometer regime to millimeter range, which facilitates easier handling and deployment of the antimicrobial material, is made possible by the significantly lower density of the selected composite matrix. To demonstrate the positive impact of reduced mass density, two exemplary cases are considered: Ag2O having a density of approximately 7.1 g / cm3and composite beads, formed by encapsulating approximately 1% w / w of small (~10 µm) Ag2O particles within a polymer matrix and having a final bulk density of 1.2 g / cm3. Using the Bond number (Bo) of Equation 3, the behavior of particles in both cases was analyzed at a diesel-water interface, assuming that the interface tension at the interface is similar in both cases. The difference in density, Δρ, in the numerator of the equation is approximately 18 times greater for the Ag2O microparticles compared to the composite beads. This translates to a reduction of the Bond number by a factor of approximately 18 for the composite beads. This reduced Bo allows for the use of a composite particle with a diameter approximately 4.2 times (the square root of 18) larger than a solid Ag2O microparticle while maintaining a stable interfacial position, as dictated by a safe value of Bo. This allows for the use of significantly larger, more easily handled composite particles without compromising their ability to remain interfacially trapped. It should also be noted that the reduction in density is not the only means of increasing the size of antimicrobial particles. In one embodiment this may be achieved by forming the beads into more optimal shapes dictated by a combination of empirical and theoretical approaches. In another embodiment, the upper limit for the size of antimicrobial particles arefurther increased by reducing the quantity (^^^ − ^^ி) at the denominator of Equation 4. Thisis achieved by modifying surface properties of the particles. To illustrate the stable interfacial trapping of relatively large composite particles (beads), an experiment was conducted. Acrylic beads with a diameter of 2 mm and a mass density of 1.2 g / cm3were introduced into the fuel phase of a test tube, similar to the one depicted in FIG. 8. It was observed that the beads spontaneously migrated to and were effectively trapped at the diesel-water interface, demonstrating their capability for resilient trapping. The characteristic porous nature of the antimicrobial beads ensures the gradual release of the primary biocide agent, the silver ion, upon contact with an aqueous phase. The controlled release of Ag+is a beneficial aspect of using these beads, as it can be regulated by selecting appropriate synthesis parameters for the host matrix material. In one embodiment, intended for fabrication of antimicrobial beads, Ag2O microparticles are dry-mixed with a zeolite powder and a polymer resin acting as a binder. The resulting mixture is then atomized to produce antimicrobial composite beads with a desired size distribution. In an alternative embodiment, Ag2O microparticles are dispersed within a polymer solution. This solution is then subjected to a pulverization process to obtain composite beads having a desired size distribution. During atomization or pulverization, a gas, such as air or argon, may be co-injected with the mixture or solution into a nozzle. This process allows for the formation of antimicrobial composite beads with a predetermined size and a desired density. The key aspects of using antimicrobial beads (typically with sizes in the range of 100μm to 10mm) to mitigate fuel microbial contamination are illustrated below, with reference to the non-limiting example of a composite material consisting of Ag2O microparticles encapsulated in epoxy resin. It is understood that epoxy resin is selected as an example for illustration purposes and the intended scope includes any contact leaching biocidal matrix. Encapsulation substantially reduces the rate of silver ion release from Ag2O microparticles, thereby prolonging the antimicrobial efficacy of the antimicrobial beads for periods exceeding five years. To demonstrate this, epoxy discs were prepared according to the method of Example 5 and contained 1% w / w of Ag2O microparticles, and their silver release was measured from both free and encapsulated particles (in the form of a solid disc) following the methods of Example 6. The accumulated silver release data is presented in FIG.16. As shown, encapsulation reduced the silver release rate by approximately 10-fold. It is understood that this measurement represents an average over the entire thickness of the disc, and that the release rate from microparticles closer to the surface may have been reduced by a smaller factor. We prepared “dense type” epoxy resin disks with embedded Ag2O microparticles at different concentrations according to the method of Example 5. The antimicrobial activity of freshly prepared “dense type” disks were measured against Pseudomonas aeruginosa following the method of Example 7A for different levels of Ag2O content within the epoxy resin. The results, which are presented in FIG.16, indicate that the antimicrobial activity is acceptable even at a concentration as low as 0.5% w / w. It is observed that the inhibition zone does not extend significantly beyond the disk at this low concentration. However, this does not imply that this level represents the lower limit of the disc's efficacy in impeding microbial growth. The discs used in this particular experiment were "dry," meaning they were being used for the first time. As it is demonstrated later, long-term contact with water improves the antimicrobial activity of the coating over time. “Light type” epoxy resin disks embedded with either Ag2O or ZnO microparticles were prepared according to the method of Example 5. The antimicrobial activity of these disks was subsequently assessed using the protocol of Example 7B. The results for the disks embedded with Ag2O microparticles are presented in FIG.18A. These disks exhibited a higher level of antimicrobial activity compared to the "dense type" disks, as evidenced by the larger zones of inhibition observed for the same mass loading of Ag2O microparticles. Specifically, the antimicrobial activity of the light-type disks at a given microparticle content was found to be comparable to that of dense-type disks containing a two-fold higher microparticle content. It is believed that this enhanced activity is due to the more porous nature of the light-type disk matrix, which facilitates a higher rate of microparticle dissolution and subsequent leaching of silver ions. The results for the disks embedded with ZnO microparticles are presented in FIG.18B. These discs demonstrated no significant antimicrobial activity, as indicated by the absence of a measurable zone of inhibition. Furthermore, after the removal of the discs, the level of microbial growth in the zones directly beneath them was similar to that observed in the negative control discs. This finding is notable when considered in light of a previous observation where ZnO microparticles, when trapped at a fuel-water interface, completely inhibited the growth of the more resilient Cladiosporium resinae cells. This suggests that the environment and configuration of the particles play a critical role in their antimicrobial efficacy. We assessed the impact of a saline environment on the antimicrobial efficacy of the disks, following the methodology described in Example 7B. This evaluation may be important in some cases due to the potential for silver ions (Ag+), which leach through the porous coating, to react with chloride ions (Cl−) in the environment. Such a reaction could result in the precipitation of silver chloride (AgCl) within the matrix pores, potentially blocking them and inhibiting further biocide release. The results of this analysis, presented in FIG.19, indicate no significant adverse effect from the presence of salt on the antimicrobial activity of the disks. The antimicrobial disks (or other shapes) of types discussed above may be used as starting material for preparing antimicrobial beads. The disks are crushed into beads with mm-range sizes, using a bead mill or similar device to grind them down to the desired size. Epoxy resins, in which Ag2O particles are encapsulated, can be formed into mm-sized beads using various techniques, including molding with silicone molds, or by encapsulating droplets of epoxy in a liquid medium like oil. These methods allow for the creation of beads with consistent sizes and shapes. In one encapsulation preparation of antimicrobial epoxy resin beads are created through encapsulation in oil, often involving a process where a mixture of epoxy resin, comprising Ag2O microparticles, and a blowing agent (like ammonium bicarbonate) is dispersed in heated oil. This results in the formation of porous epoxy beads. The specific properties of the resulting beads, such as size and porosity, can be influenced by factors like the concentration of the blowing agent and the ratio of epoxy to hardener. Typically, the preparation parameters of the beads intended for the sludge zone are selected such that the porosity is high for more efficient release of ions. In contrast, the beads intended for the fuel- water interface are preferred to have less surface porosity. A notable advantage of the antimicrobial beads, as compared to antimicrobial microparticles, is their ability to form a close-packed particle monolayer across the fuel-water interface at a more tolerable cost. The mechanical integrity and stiffness of the monolayer can be significantly improved by using beads of a uniform size and by appropriately selecting their surface properties, such as a balanced hydrophobicity. The particle shape also influences stability at the interface by affecting adsorption energy, interfacial packing. Anisotropic (non- spherical) particles, such as those with a rod-shaped morphology, may achieve more stable packing at lower particle coverage compared to spherical particles. A further advantage of the antimicrobial beads, as compared to antimicrobial microparticles, is their recoverability from the water, sludge, or fuel residues removed from the bottom of a fuel container. The recovered beads may be cleaned and subsequently re-used. This recoverability attribute is significant as it substantially mitigates the potential hazard posed by the beads discarded to the environment. Unlike conventional fuel biocides, which are often classified as pesticides and require extensive environmental impact studies for regulatory approval, the easy separability and the reusability of the present invention's beads eliminate their potential environmental risk. A close-packed bead layer forms a dense, almost solid-like structure that creates a physical barrier separating the continuous water and oil phases. This physical separation may further contribute to limiting the proliferation of microbial cells at the interface. An additional advantage of the antimicrobial beads is their capacity to provide a fuel tank with long-term contamination prevention, even when no free water phase is present at the time of tank filling. In one embodiment, the beads are fabricated with a density that is less than the density of water but falls within the upper range of fuel densities. This upper range corresponds to the density of biodiesel, which typically ranges from 860 to 900 kg / m3at 15°C (59°F). A container for the beads (270 in FIG.9C) is operably connected to a fuel feeder nozzle. As fuel is introduced into the tank, the beads are distributed throughout the fuel column due to turbulence. Over time, these beads gradually settle to the tank bottom due to gravitational forces. If a water phase subsequently forms within the tank, the release of antimicrobial ions into this water pocket begins. As the volume of the water phase increases and the water pockets coalesce, a continuous fuel-water interface laden with antimicrobial beads is formed. Further increases in the water volume cause the bead layer to lift, and the protection against microbial growth at the interface continues. In another embodiment of the present invention, two distinct types of antimicrobial beads are utilized. The first type of bead, labeled as non-floating beads and designated as 301 in FIG. 20, is an antimicrobial bead with a combination of density, diameter, physical shape, and surface properties such that after settling through a fuel column to the bottom of a tank, it is not lifted by the subsequent accumulation of water. To achieve this, the density of bead 301 is selected to be greater than the density of water. The second type of bead, labeled as floating beads, and designated as 302 in FIG.20, is an antimicrobial bead with a combination of density, diameter, physical shape, and surface properties such that after settling through a fuel column to the tank bottom, it is subsequently lifted to and becomes trapped at the fuel-water interface upon water accumulation. In one embodiment, the density of bead 302 is selected to be less than the density of water and less than the density of biodiesel, which typically does not exceed 900 kg / m3at 15°C (59°F). In an embodiment of the present invention, the two aforementioned types of antimicrobial beads are delivered to the bottom of a fuel tank using a "through-nozzle" method, as shown in FIG.19. Two separate bead containers, 271 and 272, are used to hold bead types 301 and 302, respectively. Both containers are operably connected to a fuel feeder nozzle. During the process of tank filling, a predetermined quantity of beads 301 is first introduced into the fuel flow and mixed with the fuel. After this quantity is dispensed, the container 271 is disconnected, and a predetermined quantity of beads 302 is subsequently introduced into the fuel flow and mixed with the fuel. In a properly designed operation, the beads 301 will settle first to the tank bottom, forming a substantially uniform, closed-packed layer. The beads 302 will then settle atop the first bead layer. This layered arrangement ensures that the beads with the desired density and size for interfacial trapping (302) are positioned optimally to lift to the fuel-water interface upon water accumulation, while the non-floating beads 301 remain at the tank bottom. The beads 301 and 302, when contained within their respective containers 271 and 272 in a dry state, are susceptible to the generation of static electrical charge. Such charge can be created by contact, friction, or separation of materials, a phenomenon known as triboelectrification. This electrostatic buildup can lead to undesirable effects, including clumping of the beads, contamination, or safety risks. According to an embodiment of the invention, this problem is substantially reduced or eliminated by storing the beads in a liquid medium that is electrically conductive. The liquid acts as a pathway for static charges to dissipate effectively from the surface of the beads. In a preferred embodiment, water is employed as the liquid medium within containers 271 and 272 for the purpose of controlling and reducing static charge on the beads. In one embodiment, a method for inhibiting microbial proliferation in a fuel container 200 having a fuel phase 210, a water phase 220, and a fuel-water interface 215 is provided. The method includes introducing antimicrobial particles 300 into the container 200, wherein said particles are trapped at fuel-water interface due to the forces of interfacial tension. In one embodiment of the invention, the method further includes introducing antimicrobial particles 300 into the sludge zone 225 of the tank container 200 and inhibiting the microbial growth therein. In one embodiment of the invention, the antimicrobial particles 300 are configured to release ions to inhibit microbial growth in a liquid medium. In one embodiment, the method involves introducing a sufficient concentration of antimicrobial particles 300 to the fuel-water interface 215. The particles 300 are configured to release antimicrobial ions that diffuse from the interface 215 into the aqueous column 220 and create a growth inhibition zone (GIZ) in the vicinity of the particles. In one embodiment, the concentration of the antimicrobial particles 300 is such that the GIZ extends downwards into the sludge zone at the bottom of the fuel tank. In one embodiment, the antimicrobial particles 300 comprise microparticles selected from the group consisting of: silver, silver oxide (Ag2O), AgNbO3, AgTaO3, zeolite-supported silver, silver-doped metal oxides, zinc oxide, titanium oxide, copper oxide, and magnesium oxide. In another embodiment, the antimicrobial particles may be a combination of two or more different types of antimicrobial microparticles 300. Such combinations are selected to exhibit a synergistic antimicrobial effect, which is advantageous for broadening the spectrum of antimicrobial activity and for reducing the development of antimicrobial resistance. In one embodiment, the microparticles 300 transported to the fuel-water interface have a surface coverage of at least 15% of the total surface area. In another embodiment, the microparticles 300 transported to the fuel-water interface have a surface coverage of at least 45% of the total surface area. In one embodiment, the microparticles 300 transported to the fuel-water interface have a full surface coverage, corresponding to a substantially closed pack distribution. In one embodiment, the antimicrobial particles 300 are of a composite type, having a radius in the range of 0.1 mm to 10 mm. In another embodiment, the antimicrobial particles 300 are of a composite type, having a radius in the range of 0.5 mm to 5 mm. In one embodiment, the antimicrobial particles 300 are of a composite type, having a density greater than 1.0 g / cm3. In another embodiment, the antimicrobial particles 300 are of a composite type, having a density greater than 0.9 g / cm3. In one embodiment, the composite antimicrobial particles 300 have a polymer matrix with encapsulated Ag2O microparticles in a concentration range of 0.5% to 5% w / w. In one embodiment, the composition matrix of the composite particles are selected from material such as specific diesel-resistant epoxy formulations and acrylic, so that the beads keep their integrity and the antimicrobial ions are released only upon contact with the water phase to provide sustained, long-lasting nature of the contamination prevention provided by the particles. In one embodiment, the quantity of microparticles 300 transported to the fuel-water interface is sufficient to form at least a monolayer. In one embodiment, the quantity of microparticles 300 transported to the sludge zone is sufficient to form at least a monolayer. An embodiment of the present invention provides a method for inhibiting microbial proliferation in a fuel container having a fuel phase, a water phase, a fuel-water interface, and a sludge zone. The method utilizes a first antimicrobial particle suspension 255 having a water-based suspension liquid and a second antimicrobial particle suspension 255 having an organic suspension liquid miscible with the fuel. The method includes transporting particles 300 to a sludge zone, including dispensing the first particle suspension 255 onto the fuel phase 210, wherein the water-wetted particles 300 are carried down by the suspension drops through the fuel phase and the fuel-water interface 215 to reach the bottom of the container, thereby inhibiting microbial growth in the sludge zone; and transporting particles 300 to the fuel-water interface 215, including dispensing the second particle suspension 255 onto the fuel column 210, wherein the particles settle to the fuel-water interface 215 and form a substantially trapped particle layer that inhibits microbial proliferation at the interface. In another embodiment, a kit for providing antimicrobial treatment to a fuel system is disclosed. The kit includes at least two separate containers, each containing a suspension 255 of antimicrobial particles 300. The first container provides a particle suspension 255 where the suspension liquid is an organic liquid, preferably a liquid that is miscible with the target fuel. This organic liquid suspension 255 may also contain additives, which may differ from those in the water-based suspension, to support the stability and performance of the product. The second container holds a particle suspension 255 where the suspension liquid is a water-based formulation. This water-based suspension 255 may further include additives selected to enhance the stability and performance of the product. In one embodiment, the water-based suspension liquid has a pH value greater than 8, in order to minimize the dissolution of silver ions prior to use. In one embodiment, the antimicrobial particles 300 are characterized by a density that is less than 1000 kg / m³, yet within the upper range of fuel densities, such as the density of biodiesel (approximately 860 to 900 kg / m³ at 15°C). A container for the particles is operably connected to a fuel feeder nozzle, allowing the particles to be distributed throughout the fuel column as the tank is filled. These particles will then gradually settle to the bottom of the tank. The combination of the properties of the beads, including density, diameter, physical shape, and surface properties, are selected such that the presence of a subsequent water phase will cause the particles to be lifted to the fuel-water interface, where they will form a protective layer. Another embodiment utilizes two distinct types of antimicrobial particles. The first type of particle, referred to as a non-floating particle, is designed with a density greater than water. This ensures that after the particle settles to the tank bottom, it remains there, even with the accumulation of a water phase. The second type of particle, a floating particle, has a density less than water but greater than the density of the target fuel. The properties of these beads, including a combination of density, diameter, physical shape, and surface properties, are selected such that upon the accumulation of water at the bottom of the container the beads are lifted to the fuel-water interface. One embodiment describes a method for delivering the two types of particles from the embodiment above to a fuel tank. A "through-nozzle" method is employed, where two separate particle containers are operably connected to a fuel feeder nozzle. A predetermined quantity of the non-floating particles is first introduced into the fuel flow, followed by a predetermined quantity of the floating particles. In one embodiment, the particles are of a uniform size to promote the formation of a close- packed, single-layer particle array at the fuel-water interface. This uniform packing enhances the mechanical integrity and stiffness of the interfacial layer, thereby improving its stability. Another embodiment involves the use of particles with balanced hydrophobicity to improve the mechanical integrity and stiffness of the bead monolayer at the fuel-water interface. The selection of appropriate surface properties prevents bead coagulation and ensures a continuous, protective layer. One embodiment utilizes anisotropic (non-spherical) particles, such as those with a rod- shaped morphology. The use of such particles is designed to achieve more stable packing and a more robust antimicrobial barrier at lower particle coverage compared to spherical particles. EXAMPLES The following examples are presented to enable those skilled in the art to understand and to practice embodiments of the present disclosure. They should not be considered as a limitation on the scope of the disclosure, but merely as being illustrative and representative thereof. Example1A: Preparation of AgNbO3microparticles AgNbO3 particles were synthesized using the Activated Reactive Synthesis (ARS) method as described in the published literature (Talebpour et al, Nondegradable Antimicrobial Silver-Based Perovskite. ACS Sustainable Chem. Eng 2022, 10 (15), 4922-4928). Briefly, the method consists of the mixing of Ag2O (Sigma-Aldrich Corp) and Nb2O5 (InframatⓇ Advanced Materials LLC) in a 1 g to 1.147 gram (g) weight ratio respectively; The mixture is calcined so that the raw material undergoes the reaction necessary to form AgNbO3. The post-synthesis treatment included subjecting the as-calcined powder to successive steps of high and low energy ball milling, yielding nanostructured AgNbO3particles. The particles had a specific surface area of 7.9 meter squared per gram (m2 / g) and the average particle size was 438 nm. The silver release rate of the particles was recorded to be less than 1% of its total mass after 35 days of storing in water. Example1B: Preparation of Ag2O microparticles An aliquot of the silver oxide particle stock, obtained from Sigma Aldrich, was sequentially sieved with mesh sizes in ascending order. The particles passing the mesh were collected and used for different tests. The particle size bins, based on sieve mesh size were the following: Bin1: < 20 µm, Bin2: [20 µm, 25 µm], Bin3: [25 µm, 38 µm], Bin4: [38 µm, 53 µm], Bin5: [53 µm, 75 µm], and Bin6: >75 µm. The size distribution is presented in FIG.6B. The silver release rate of the particle stock (before sieving) was measured according to the method of Example 6. It was observed that the silver release rate was less than 10% of its total mass after 35 days of storing in water. However, the rate substantially decreased afterward such that after two years of staying inside water the particles were still in particulate form and had not yet dissolved. Example2: The Influence of Suspension Liquid on Particle Placement in a Fuel- Water System This example is intended to demonstrate that creating a resilient particle-laden fuel-water interface depends on the nature of the liquid the particles are suspended in. The test is performed by following these steps: 1. Weigh 1 mg of the target particle and add it to 1 milliliter (mL) of the target suspension liquid. 2. Vortex the suspension for 1 minute, 3. Take a 30 mL glass tube. 4. Add 5 mL of water to the tube to represent the water phase. 5. Add 10 mL of jet fuel over the water column from step 4 to represent fuel phase, 6. Gently, add 100 μL of particle suspensions into the upper part of the fuel column and qualitatively observe the dynamics of the particles. Example 3A: Testing the stability of particle laden fuel-water interface against mechanical turbulences This example is intended to illustrate that the particle laden fuel-water interface is resilient against mechanical turbulences of the liquid columns. The test is performed through the following steps: 1. Weigh 1 mg of the target particle and add it to 1 mL of fuel 2. Vortex the suspension to obtain particle stock 3. Take a 500 mL glass beaker 4. Add 150 mL of water to the beaker 5. Add 150 mL of jet fuel on top of the water column in the beaker. 6. Gently, add 200 microliters (μL) of particle stock into the top part of the fuel column and wait until the particles settle down to the interface. 7. Hold the beaker and move it 5 times along a horizontal circular path (approximate frequency of 0.5 Hertz (Hz)) 8. Record the observation Example 3B: Testing the stability of particle laden fuel-water interface against rupture by the water drop ingress from fuel column This example is intended to illustrate that the particle laden fuel-water interface is resilient against perturbations caused by the ingress of water drops from the fuel column. The test is performed through the following steps: 1. Weigh 1 mg of the target particle and add it to 1 mL of fuel 2. Vortex the suspension to obtain particle stock 3. Take a 500 mL glass beaker 4. Add 150 mL of water to the beaker 5. Add 150 mL of jet fuel on top of the water column in the beaker. 6. Gently, add 200 μL of particle stock into the top part of the fuel column and wait until the particles settle down to the interface. 7. Dispense a 200 μL drop of water into the fuel column. 8. Record the observation Example 4A: Measuring the antimicrobial activity of AgNbO3 and Ag2O by broth microdilution method This example is intended to assess the antimicrobial of antimicrobial particles used to prevent proliferation of microbial cells at fuel-water interface and / or sludge zone. The method employs broth microdilution antimicrobial susceptibility test (AST), which involves growing bacterial cells inside a series of wells on a microwell plate containing growth media. Each well was supplied with different concentrations of the antimicrobial agent, differing by a factor of two from one well to the next. A known number of bacterial cells in the range of 105CFU (CFU = colony forming unit, meaning a cell that is viable and can divide) was dispensed into each well. After overnight incubation, the wells were inspected for signs of growth by visual inspection or turbidimetry. Thus, the minimum concentration required to inhibit growth was determined and reported as minimum inhibitory concentration (MIC) value. Example 4B: Illustrating the antimicrobial activity of particle laden interface This example is intended to illustrate that the antimicrobial particle laden fuel-water interface prevents proliferation of microbial cells. The test procedure was done through the following steps, in two versions: In “Version A” the microbial cells are at fuel-water interface before the inclusion of antimicrobial particles. In “Version B” the microbial cells enter a fuel-water interface already laden with antimicrobial particles. Version A: 1. Prepare microbial suspension: 1 / 100 dilution of 0.5 McFarland turbidity. 2. Weigh 1 mg of the target particle and add it to 1 mL of fuel 3. Vortex the suspension to obtain particle stock 4. Take two sterile 30 mL glass tubes, having a cross section of 4.9 cm2, and label them as 1 (control), and 2. 5. Add 10 mL of jet fuel in each tube 6. Add each of the inoculated 9.5 mL of water and 0.5 mL of TSB media to the top of the fuel columns in their corresponding tubes. 7. Add 50 μL of microbial cell stock to fuel columns of each tube. 8. Gently add 100 μL of 4 g / mL particle stock to tube 2. 9. Close the tubes by their lids and incubate at 35oC overnight. Version B: the procedure is similar to Version A, except Steps 6 and 7 are exchanged, meaning that particles are added before adding microbial cells Example 5: Preparation of epoxy resin with embedded antimicrobial microparticles This example presents the steps for encapsulating Ag2O or ZnO microparticles in the body of an epoxy polymer. Two versions of the polymer were prepared. Version 1 is a “dense type” polymer, and version 2 is a “light type” polymer. For both cases, raw materials are provided in two components: a first component (A) is a liquid epoxy resin, and a second component (B) is an aqueous composition based on a water-thinnable epoxy hardener. The main difference between the two versions is that for the dense type polymer the components A and B are mixed in 2:1 volume-to-volume (v / v) ratio, in contrast to the 1:1 v / v ratio for the case of the light type Silver oxide or ZnO microparticle stock, obtained from Sigma Aldrich, was added to part A of the epoxy with a predetermined w / w ratio and the mixture was mixed well with shaking. Then the corresponding volume of part B was added and mixed. The mixture was poured into silicone molds to make discs with 13 mm diameter and 3 mm depth. The disks were removed from the mold 48 hours after they were hardened. Example 6: Measuring the release of silver ions from free and encapsulated silver oxide microparticles This example is intended to measure the silver ion release from free and encapsulated Ag2O microparticles placed in water. 500 mg of Ag2O stock was added to 1L of water in the beaker. The beaker was covered to prevent evaporation or effects of light. At time points (2, 7, 14, 21, 28, 35) days, two 10 mL replicate samples were taken from the beaker and 20 mL of water was added to the beaker to compensate for the removed volume. The collected samples were analyzed for silver ion concentration by Avio 200 ICP-OES (PerkinElmer). Each sample measurement was performed in three replicates and averaged. The test for measuring ion release rate from encapsulated Ag2O microparticles is performed through the following steps: 1) Prepare dense disks with 1% w / w Ag2O microparticle content, 2) Place each disk in a 15 mL tube containing 10 mL of water and store the tube at room temperature 3) At a selected time interval, remove a 1mL aliquot from the tube for determining silver ion content by atomic absorption mass spectrometer, 4) Add 1 mL of water to the tube to replace the removed 1mL aliquot and store the tube in room temperature, and 5) Repeat steps 3 and 4 in series of future selected time intervals Example 7A: Measuring the antimicrobial activity of resin disks with embedded antimicrobial microparticle This example is intended to verify if an antimicrobial particle embedded resin prevents proliferation of microbial cells at the proximity of its surface. The test procedure was done through the following steps. Bacteria: Pseudomonas aeruginosa ATCC 27853 Cell suspension: 0.5 McFarland in saline Media: Muller Hinton Each plate was inoculated with P. aeruginosa cell suspension using a swab dipped into cell suspension. Each plate was streaked twice; First time in horizontal direction and the second time in vertical direction. As soon as plates were dried (cell suspension liquid was absorbed), three discs (replica) were placed on the plate. After overnight incubation at 35oC, a photo was taken from each plate to indicate if there was an inhibition zone around discs. Then discs were removed gently, and the plate was incubated another day to see if any growth happened under the area where the discs were located. Example 7B: Assessing the impact of salt to the antimicrobial activity of microparticle embedded resin disks To assess the effect of a saline environment on the antimicrobial efficacy of microparticle- embedded epoxy discs, the following protocol was used. Three light-curable resin discs, each containing 0.5% (w / w) Ag2O microparticles, were fabricated according to the method described in Example 5. These discs were then subjected to three distinct storage conditions for one week: 1. Disk 1: Stored at ambient conditions. 2. Disk 2: Immersed in deionized water. 3. Disk 3: Immersed in saline water (deionized water containing 3% sea salt). After one week, the discs were removed from their respective solutions, briefly rinsed with deionized water, and gently blotted to remove excess surface liquid. The discs were then allowed to air-dry at room temperature. Subsequently, each of the three discs was carefully placed on the surface of a Mueller-Hinton agar plate. The plate had been previously inoculated with a suspension of Pseudomonas aeruginosa cells, prepared to a 0.5 McFarland standard. The plates were then incubated overnight at 35°C. Following incubation, the plates were photographed to document the zone of inhibition.

Claims

1. CLAIMS 1. A method for inhibiting microbial proliferation in a fuel container having a fuel phase, a water phase, and a fuel-water interface, the method comprising: introducing antimicrobial particles into the fuel container, wherein said particles are trapped at the fuel-water interface due to interfacial tension.

2. The method of claim 1, wherein the fuel container further comprises a sludge zone at a bottom of the fuel container, and the antimicrobial particles are introduced into the sludge zone to inhibit microbial growth therein.

3. The method of claim 1, wherein the antimicrobial particles are configured to release antimicrobial ions or compounds while in contact with the water phase.

4. The method of claim 3, wherein the antimicrobial particles are configured to release antimicrobial ions that diffuse from the fuel-water interface into the water phase to create a growth inhibition zone in a vicinity of the antimicrobial particles.

5. The method of claim 4, wherein a concentration of the antimicrobial particles at the fuel-water interface is sufficient for the growth inhibition zone to extend downwards into a sludge zone.

6. The method of claim 1, wherein the antimicrobial particles have a size between 10 micrometer (µm) to 100 µm and are selected from the group consisting of silver, silver oxide, AgNbO3, AgTaO3, zeolite-supported silver, silver-doped metal oxides, zinc oxide, titanium oxide, copper oxide, and magnesium oxide.

7. The method of claim 6, wherein the antimicrobial particles comprise a combination of two or more different types of antimicrobial microparticles.

8. The method of claim 7, wherein the combination of antimicrobial microparticles provides a synergistic antimicrobial effect.

9. The method of claim 1, wherein the antimicrobial particles are of a composite type.

10. The method of claim 9, wherein the composite antimicrobial particles have a radius in the range of 0.1 millimeters (mm) to 10 mm.

11. The method of claim 9, wherein the composite antimicrobial particles have a radius in the range of 0.5 millimeters (mm) to 5 mm.

12. The method of claim 9, wherein the composite antimicrobial particles have a density greater than 1.0 g / cm3.

13. The method of claim 9, wherein the composite antimicrobial particles have a density greater than 0.9 g / cm3.

14. The method of claim 9, wherein the composite antimicrobial particles have a polymer matrix with encapsulated Ag2O microparticles in a concentration range of 0.5% to 5% weight per weight (w / w).

15. The method of claim 1, wherein the antimicrobial particles are delivered to the fuel- water interface by dispensing a particle suspension having an organic suspension liquid that is miscible with the fuel phase.

16. A kit for providing antimicrobial treatment to a fuel system, comprising: at least two separate containers, each container containing antimicrobial particles.

17. The kit of claim 16, wherein the antimicrobial particles of a first container have a density greater than the density of water.

18. The kit of claim 16, wherein the antimicrobial particles of a second container have a density less than the density of water and greater than the density of the fuel phase.

19. The kit of claim 16, wherein a first container of the at least two separate containers provides antimicrobial particles configured to be introduced into a fuel container first, and a second container of the at least two separate containers provides antimicrobial particles configured to be introduced into the fuel container after the particles from the first container.

20. The kit of claim 16, wherein the antimicrobial particles in at least one of the containers are of a uniform size to promote the formation of a close-packed monolayer at the fuel-water interface.

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