What kind of fuel microbes are out there?
The two types that can form in fuel are bacteria and fungi
What can they do to the fuel?
Microbes excrete waste products which will begin the biodeteriotion process of the fuel. Chemically
changing the fuel over time.
What are the primary factors affecting microbial growth?
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Air (oxygen availability)
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Water
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Temperature
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pH
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Nutrient Availability
Each of these factors are described in detail:
Air:
As a rule of thumb if you're storing fuel, fill the tank up completely. The less air in the tank, the better.
Facultative anaerobes scavenge oxygen and create anonix conditions, favorable for obligate anaerobes, within biofilms,
sludges, sediments, and other niches where fuel and water can stagnate within fuel systems.
Water:
Colonization and growth can occur wherever the relative humidity is sufficiently high. Fuels containing
as much as .1% water generally meet quality criteria such as those specified in ASTM fuel standards. A fuels
ability to hold water decreases with decreasing temperature, free water availability typically increases
as fuels cool. A tank with no measurable water may still have sufficient water to accommodate
considerable biomass.
Temperature:
Fuel and fuel system biodeterioration has been reported in fuel systems ranging from the equator to the
highest latitudes where tankage has been installed. Life at low temperatures takes place
at a slower pace than life at high temperatures. Therefore, biodeterioration takes place
faster at higher temperatures.
pH:
A pH level of the fuel will favor certain microbes at certain levels. Microbes can also increase
or decrease of the pH depending on what kind of microbe they are. A certain pH will not limit
the microbial biodeterioration process.
Nutrient Availability:
Biodeterioration is less likely to occur in fuel systems from which mature
biofilms are absent.
Operational Factors:
System Configuration:
The zone of the tank where water, sludge and sediment accumulate are mainly the area where
microbes call home. Although this zone may only contain 5% of the tank volume, it is the main area
biodeterioration zone. When sampling for microbes, it is essential to sample this portion of the tank.
Turnover Rates:
Most high turnover retail outlets show little evidence of biofilm accumulation on the upper two-thirds
of the interior surface of the storage tank. If the bottom third of the tank is not routinely turned over
or cleaned, biofilms are able to develop.
Housekeeping:
A routine tank dry application can go a long way in preventing microbial growth. With routine tank drying and high turnover
your tank should be in good shape. A monthly sampling program is also a good idea to determine if you do have a problem.
Our
bacteria/mold test kits are an effective and affordable to make sure you do not have a problem.
Information on this page is from the ASTM book: Fuel and Fuel System Microbology: fundamentals, diagnosis, and contamination control
ISBN: 0-8031-3357-X