ASTM D7978-14
(Test Method)Standard Test Method for Determination of the Viable Aerobic Microbial Content of Fuels and Associated Water—Thixotropic Gel Culture Method
Standard Test Method for Determination of the Viable Aerobic Microbial Content of Fuels and Associated Water—Thixotropic Gel Culture Method
SIGNIFICANCE AND USE
5.1 This test method is intended to provide a tool for assessing whether fuel storage and distribution facilities or end user fuel tanks are subject to microbial growth and alert fuel suppliers or users to the potential for fuel quality or operational problems and/or the requirement for preventative or remedial measures.
5.2 This test method detects numbers of microbial colony forming units (CFU), the same detection parameter used in the laboratory standard procedures Practice D6974 and IP 385. However, whereas Practice D6974 and IP 385 provide separate assessment of numbers of viable aerobic bacteria CFU and numbers of viable fungal CFU, this test method provides a combined total count of viable aerobic bacteria and fungal CFU.
5.3 This test method is designed to detect a recognized group of microorganisms of significance in relation to contamination of distillate fuels, but it is recognized that microbiological culture techniques do not detect all microorganisms that can be present in a sample. Culturability is affected primarily by the ability of captured microbes to proliferate on the growth medium provided, under specific growth conditions. Consequently, a proportion of the active or inactive microbial population present in a sample can be viable but not detected by any one culture test.7 In this respect, the test is indicative of the extent of microbial contamination in a sample ,and it is assumed that when a fuel sample is significantly contaminated, some of the dominant microbial species present will be quantifiably detected, even if not all species present are culturable.
5.4 Many samples from fuel systems can be expected to contain a low level of “background” microbial contamination, which is not necessarily of operational significance. The minimum detection level of this test method is determined by the volume of specimen tested and is set such that microbial contamination will generally only be detected when it is at levels indicative of active ...
SCOPE
1.1 This test method describes a procedure that can be used in the field or in a laboratory to quantify culturable, viable aerobic microorganisms present as contaminants in liquid fuels, including those blended with synthesized hydrocarbons or biofuels, with kinematic viscosities (at 40 °C) of ≤24 mm2 s-1 and heavy and residual fuels with kinematic viscosities (at 40 °C) of ≤700 mm2 s-1 and in fuel-associated water.
1.1.1 This test method has been validated by an ILS for a range of middle distillate fuels meeting Specifications D975, D1655, ISO 8217 DMA, and NATO F-76.2
1.2 This test method quantitatively assesses culturable, viable aerobic microbial content present in the form of bacteria, fungi, and fungal spores. Results are expressed as the total number of microbial colony forming units (CFU)/L of fuel or total number of CFU/mL of associated water. The number of CFU should not be interpreted as absolute values but should be used as part of a diagnostic or condition monitoring effort; for example, these values can be used to assess contamination as absent, light, moderate, or heavy.
Note 1: This test method is technically equivalent to IP 613, although the two methods are not currently jointed.
1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
General Information
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Standards Content (Sample)
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Designation: D7978 − 14
Standard Test Method for
Determination of the Viable Aerobic Microbial Content of
Fuels and Associated Water—Thixotropic Gel Culture
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Method
This standard is issued under the fixed designation D7978; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 2. Referenced Documents
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2.1 ASTM Standards:
1.1 This test method describes a procedure that can be used
D975 Specification for Diesel Fuel Oils
in the field or in a laboratory to quantify culturable, viable
D1129 Terminology Relating to Water
aerobic microorganisms present as contaminants in liquid
D1655 Specification for Aviation Turbine Fuels
fuels, including those blended with synthesized hydrocarbons
2 D4175 Terminology Relating to Petroleum, Petroleum
or biofuels, with kinematic viscosities (at 40 °C) of ≤24 mm
-1 Products, and Lubricants
s and heavy and residual fuels with kinematic viscosities (at
D4176 Test Method for FreeWater and Particulate Contami-
2 -1
40 °C) of ≤700 mm s and in fuel-associated water.
nation in Distillate Fuels (Visual Inspection Procedures)
1.1.1 This test method has been validated by an ILS for a
D6469 GuideforMicrobialContaminationinFuelsandFuel
range of middle distillate fuels meeting Specifications D975,
Systems
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D1655, ISO 8217 DMA, and NATO F-76.
D6974 Practice for Enumeration of Viable Bacteria and
Fungi in Liquid Fuels—Filtration and Culture Procedures
1.2 This test method quantitatively assesses culturable,
D7464 Practice for Manual Sampling of Liquid Fuels, As-
viable aerobic microbial content present in the form of
sociated Materials and Fuel System Components for
bacteria, fungi, and fungal spores. Results are expressed as the
Microbiological Testing
total number of microbial colony forming units (CFU)/L of
D7847 GuideforInterlaboratoryStudiesforMicrobiological
fuel or total number of CFU/mL of associated water. The
Test Methods
number of CFU should not be interpreted as absolute values
E2756 Terminology Relating to Antimicrobial and Antiviral
but should be used as part of a diagnostic or condition
Agents
monitoring effort; for example, these values can be used to
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2.2 Energy Institute Standards:
assess contamination as absent, light, moderate, or heavy.
IP 385 Determination of the Viable Aerobic Microbial Con-
NOTE 1—This test method is technically equivalent to IP613, although
tent of Fuels and Fuel Components Boiling Below 390
the two methods are not currently jointed.
°C—Filtration and Culture Method
1.3 The values stated in SI units are to be regarded as
IP 613 Determination of the Viable Aerobic Microbial Con-
standard. No other units of measurement are included in this
tent of Fuels and Associated Water—Thixotropic Gel
standard.
Culture Method
Guidelines for the Investigation of the Microbial Content of
1.4 This standard does not purport to address all of the
Petroleum Fuels and for the Implementation ofAvoidance
safety concerns, if any, associated with its use. It is the
and Remedial Strategies, 2nd Edition, 2008, Energy
responsibility of the user of this standard to establish appro-
Institute, London, ISBN 978 0 85293 524 8
priate safety and health practices and determine the applica-
2.3 Other Standards:
bility of regulatory limitations prior to use.
ISO 8217 DMA Petroleum Products, Fuels (Class F), Speci-
fications of Marine Fuels, 4th Edition 2010, ISO Switzer-
land
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This test method is under the jurisdiction of ASTM Committee D02 on
Petroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility of
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Subcommittee D02.14 on Stability and Cleanliness of Liquid Fuels. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved Dec. 15, 2014. Published February 2015. DOI: contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
10.1520/D7978-14. Standards volume information, refer to the standard’s Document Summary page on
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Defense Standard 91-4, Fuel, Naval, Distillate (NATO Code: F-76, Joint the ASTM website.
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Service designation DIESO F-76), Issue 9, 3 May 2013, UK Defense Standardiza- Available from Energy Institute, 61 New Cavendish St., London, WIG 7AR,
tion U.K., http://www.energyinst.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
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D7978 − 14
IATA Guidance Material on Microbiological Contamination 4.4 The bottle is incubated in the dark in this position for
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in Aircraft Fuel Tanks, 4th Edition, December 2011 four days.The gel contains components that sustain
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