Despite their history of successful use as fuel system disinfectants and fuel preservatives, antimicrobial pesticide use faces increasing restrictions due to both regulatory control and public concerns. A variety of non-chemical treatments have been used with varying degrees of success to disinfect non-fuel fluids and to at least partially inhibit biofilm development on infrastructure surfaces. Promoters of one technology have claimed successful fuel disinfection and fuel-tank fouling prevention. This paper will review a range of non-chemical treatment technologies and will present the results of preliminary evaluations of several technologies that were tested on Jet A fuels that had been challenged with either Pseudomonas aeruginosa or Hormoconis resinae. Data are presented on treatment impact on adenosine triphosphate (ATP) concentration, culturability and live/dead direct counts in Jet A-1 and on glass microcosm surfaces.
This work was supported by USAF SBIR Research Grant FA8656-10-M-2034.
Uncontrolled microbial contamination in fuels can cause both fuel and equipment biodeterioration. Common symptoms of fuel biodeterioration include but are not limited to increased corrosivity, decreased oxidative stability and decreased energy value 1. Although filter clogging is the most commonly reported fuel system biodeterioration symptom, microbially influenced corrosion (MIC) and biofilm interference with fuel gauge sensors are also common problems 2, 3. Currently, microbial contamination is controlled by treating fuel systems with additives - microbicides. All microbicides are classified as hazardous chemicals. Consequently, personnel handling these products must receive specialized chemical handling training and wear special, personal protective equipment 4. Although there are numerous microbicides approved in the U.S. under the Federal Insecticide, Rodenticide and Fungicide Act (FIFRA) 5, only two products have been approved by the aviation industry for use in aircraft 6. One of these products (Biobor JF®; a 95% active blend of 2,2'-(1-methyltrimethylenedioxy) bis-(40methyl-1,3,2-Dioxaborinanes) + 2,2'-oxybis(4,4,6-trimethyl-1,2,3-Dioxaborinanes) ) is known to hydrolyze on contact with water, rendering the microbicide biologically inactive. The other (Kathon® FP1.5; a 1.5% active blend of 5-chloro-2-methyl-4-isothiazolin-3-one + 2-methyl-4-isothiazolin-3-one) is a known skin sensitizer. Given the hazards associated with the handling of microbicidal chemicals, current military regulations prohibit the use of microbicides in U.S. Air Force (USAF) aircraft. Although IATA recommends microbicide use as needed and permits the use of microbicide-treated fuel 6, commercial airlines typically drain treated fuel and replace it with microbicide-free fuel. The IATA-recommended soaking period (12h to 72h, depending on contamination severity and microbicide) is designed to kill-off biofilm microbial communities. During this period, aircraft are grounded. Non-chemical technologies, capable of inhibiting biofilm development and reducing toxic-chemical exposure would bring significant benefits to the aviation and other sectors for which fuel-quality stewardship is important.
This paper reports the results of a preliminary evaluation project in which the performance of four different non-chemical, antimicrobial technologies was tested.
Dr. Frederick Passman, PhD is a Certified Metalworking Fluids Specialist with over 35 years experience in Environmental & Industrial Microbiology. His company, Biodeterioration Control Associates, Inc. (BCA) provides clients with unparalleled expertise in Microbial Contamination Control.
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