To Make a Diesel Biocide More Effective, Don't Forget These Tips

Microbes in fuel are a fact of life for people who store fuel for any amount of time. Today's ULSD fuels are more prone to contamination than fuels of the past, not just because of lower sulfur content, but as a result of their higher processing. It's not a stretch to say that, if left alone, virtually all stored diesel fuels will experience microbial contamination issues.

The only thing that will kill microbes in diesel fuel and keep them from spreading is a diesel fuel biocide (like Bellicide). But you can't just dump a biocide into a storage tank and then "set it and forget it".

Using a fuel biocide is not complicated, but there are some small important steps you should always remember to take to make sure that the biocide you use does everything you expect it to.

Fill the diesel tank after you've added the biocide

We understand that whether you can do this may depend on if you've got fuel delivery schedules to contend with. But the best practice is to add biocide to the fuel in the tank, then fill the tank up to capacity with more fuel. You will have to add enough initial biocide so that once you add more fuel to the tank, the total fuel volume you end up with has the recommended concentration of biocide.

For example, Bellicide recommends a concentration of 1 ounce per 40 gallons to shock and kill an existing microbial contamination. If you have 400 gallons of infected fuel in a tank that normally holds 4,000 gallons, you want to add enough Bellicide to shock treat all 4,000 gallons (which is 100 ounces, or about 3 quarts). Then, when you fill the tank up to 4,000 gallons, it helps to mix the biocide in. Also important, it ensures that biocide makes contact with all the tank surfaces up to the top. Bacteria and microbes can live on these surfaces very easily.

Consider a Biomass Dispersant Alongside Your Biocide

Microbial contaminations in fuel tanks usually come with biomass contamination as well. Microbes produce biomass (or "biofilms") that collect and stick to solid surfaces, providing both a home for the microbes and also protection for the microbes from chemicals like the biocide you're trying to use to kill them. Biomass also isn't just a nuisance, it can contribute materially to problems like accelerating tank corrosion damage. So any time it's in there, you want to try and get it out. The best practice is, to add a biomass dispersant chemical (like Bell Tank Treatment SDF) at the same time you're adding your biocide. The dispersant will work alongside the biocide to break up the biomass formations, allowing the biocide to penetrate and kill more microbes than using biocide alone.

Recirculate the fuel for 30-60 minutes Or more

How long for depends on the volume of fuel treated. Larger volumes should circulate longer. Circulation of the fuel is essential - no, critical - to the biocide working properly because it's the best way to make sure it's completely blended and completely reaching all the areas where bacteria are living. A diesel biocide won't work if it can't contact the bacteria. Just adding biocide on top of fuel without circulating is going to prove much less effective.

Let the diesel fuel settle before using

This lets the treated diesel settle in the tank and allows any already-dead microbe bodies to settle at the bottom. You may even want to drain the sump at this point to clear any of them out.

Replace filters for a few days after fuel treatment

This has nothing to do with biocide effectiveness but does matter in that the biocide is going to kill all the microbes in the fuel, and their dead bodies are going to plug the fuel filters. There's nothing you can do about it, and it's nobody's filter. It's just the way it is. Change the filters a little more often and you'll be good to go.

And don't forget...

If you're storing diesel fuel for a longer period, a fuel stabilizer is a good idea. You want to look for a fuel antioxidant that will interrupt the chemical reactions in the fuel that result from exposure to water and air. Not only that but remember that any microbes you killed will have been secreting acidic byproducts into the fuel that will accelerate its breakdown over time. Adding a fuel stabilizer like Dee-Zol Life along with the biocide will provide your best protection for the stored diesel fuel over time.

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