It’s now clear that no good fuel management program is complete without a robust testing element. Fuel testing gives you the benefit of a clearly defined problem instead of forcing you to rely on guess work. This is especially true for the issue of microbial contamination in stored fuel and storage tanks. It’s not somebody else’s problem, it’s everyone’s problem - both in the sense that virtually all storage tanks have microbial contamination and that a much larger chunk of fuel problems are related to microbial activity than one might think.
Lucky for today’s businesses and fuel managers, there are great options available for testing microbial content in samples. Each has advantages and disadvantages relative to the others. The key is (from a best practice standpoint) to use the one(s) that best fit your test plan and your needs.
ATP testing is really the best option for monitoring the condition of your fuel and fuel system when it comes to microbial presence. A fuel microbiologist might call that “condition monitoring”. More specifically, ATP testing with the ASTM designation D7687 (also called the ATP By Filtration method) provides reliable and accurate results in minutes that are highly useful because they are qualitative in nature – they can be translated into an estimation of the microbial counts in your sample.
What is ATP testing all about? Essentially, it’s a process that detects the amount of ATP (the molecule adenosine triphosphate) present in a sample. What does this have to do with microbial contamination? ATP is a molecule present in every living cell (because it’s essential to energy transport). That means if you have microbes like bacteria, yeasts and molds, present in a fuel sample, you’ve got ATP present in that fuel sample. And if you isolate that ATP and measure it, you can get an accurate sense of how badly that fuel or system is infected. The D7687 ATP By Filtration method was created to help you do that.
Besides the D7687 ATP By Filtration test method, you might have seen another kind of ATP test which has the ASTM number D7463 – what some call the “ATP pen test” or some similar name. The “pen tests” really predated the filtration method in the marketplace. They’re around for a while and then the ATP By Filtration tests come along, such that some start calling the pens “first generation ATP” while the filtration ATP tests are “second generation ATP”. Strictly speaking, because of all the work that went into developing the Filtration method, a more accurate name for ATP By Filtration could be "12th generation ATP". But we admit that doesn't quite have the same ring.
If you were to try and boil down the real advantage, the biggest improvement that ATP By Filtration made, it would be in the area of interference-free testing. Simply put, the ATP By Filtration method gives more accurate results by providing a way in its test method to separate out the things that otherwise would muddy your reading and make them less accurate.
Speaking of accurate results, another feature of ATP By Filtration tests are their ability to let you filter and assess larger sample sizes. The larger your sample size, the more accurate your results (with respect to how close your measured results are to the actual microbial count in your tested sample). A typical filtered sample size might be 20 mL, but you could do 50 or 100 mL or more, if you felt the need. This is an especially large difference from the older culture tests which based results on samples that were only fractions of a milliliter. Accuracy of results is of paramount importance.
These factors help make ATP By Filtration tests a great improvement upon an already-revolutionary way to assess microbial content. This kind of knowledge is an indispensable tool if you’re aiming to make the best decisions possible.
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This post was published on July 9, 2019 and was updated on March 1, 2023.