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Significance and Use
5.1 Biodeteriogenic microbes infecting fuel systems typically are most abundant within slime accumulations on system surfaces or at the fuel-water interface (Guide D6469). However, it is often impractical to obtain samples from these locations within fuel systems. Although the numbers of viable bacteria and fungi recovered from fuel-phase samples are likely to be several orders of magnitude smaller than those found in water-phase samples, fuel-phase organisms are often the most readily available indicators of fuel and fuel system microbial contamination.
5.2 Growth Medium Selectivity—Guide E1326 discusses the limitations of growth medium selection. Any medium selected will favor colony formation by some species and suppress colony formation by others. As noted in 6.3, physical, chemical and physiological variables can affect viable cell enumeration test results. Test Method D7463 provides a non-culture means of quantifying microbial biomass in fuels and fuel associated water.
5.3 Since a wide range of sample sizes, or dilutions thereof, can be analyzed by the membrane filter technique (Test Methods D5259 and F1094), the test sensitivity can be adjusted for the population density expected in the sample.
1.1 This practice covers a membrane filter (MF) procedure for the detection and enumeration of Heterotrophic bacteria (HPC) and fungi in liquid fuels with kinematic viscosities ≤24 mm2 · s-1 at ambient temperature.
1.2 This quantitative practice is drawn largely from IP Method 385 and Test Method D5259.
1.4 The ability of individual microbes to form colonies on specific growth media depends on the taxonomy and physiological state of the microbes to be enumerated, the chemistry of the growth medium, and incubation conditions. Consequently, test results should not be interpreted as absolute values. Rather they should be used as part of a diagnostic or condition monitoring effort that includes other test parameters, in accordance with Guide D6469.
1.5 This practice offers alternative options for delivering fuel sample microbes to the filter membrane, volumes or dilutions filtered, growth media used to cultivate fuel-borne microbes, and incubation temperatures. This flexibility is offered to facilitate diagnostic efforts. When this practice is used as part of a condition monitoring program, a single procedure should be used consistently.
2. Referenced Documents (purchase separately) The documents listed below are referenced within the subject standard but are not provided as part of the standard.
D1129 Terminology Relating to Water
D1193 Specification for Reagent Water
D4175 Terminology Relating to Petroleum, Petroleum Products, and Lubricants
D5259 Test Method for Isolation and Enumeration of Enterococci from Water by the Membrane Filter Procedure
D6426 Test Method for Determining Filterability of Middle Distillate Fuel Oils
D6469 Guide for Microbial Contamination in Fuels and Fuel Systems
D7463 Test Method for Adenosine Triphosphate (ATP) Content of Microorganisms in Fuel, Fuel/Water Mixtures and Fuel Associated Water
D7464 Practice for Manual Sampling of Liquid Fuels, Associated Materials and Fuel System Components for Microbiological Testing
E1326 Guide for Evaluating Nonconventional Microbiological Tests Used for Enumerating Bacteria
F1094 Test Methods for Microbiological Monitoring of Water Used for Processing Electron and Microelectronic Devices by Direct Pressure Tap Sampling Valve and by the Presterilized Plastic Bag Method
Energy Institute StandardsIP385 Viable aerobic microbial content of fuels and fuel components boiling below 90C--Filtration and culture method
ICS Number Code 75.160.20 (Liquid fuels)
UNSPSC Code 15101500(Petroleum and distillates)