SEVERE STP corrosion internally on Diesel

Underground storage tank regulations, compliance issues and news from EPA OUST, ASTSWMO, CALCUPA and state regulatory agencies.
cbauden
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Re: SEVERE STP corrosion internally on Diesel

Post by cbauden » Tue Mar 07, 2017 10:51 am

Fatmonk,

We have not heard of anyone reporting sulfate reducing bacteria being identified in the bottom sludge recently, however it does happen from time to time. Have you been hearing reports? Please provide additional information if assistance is needed.

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Re: SEVERE STP corrosion internally on Diesel

Post by Fatmonk » Tue Mar 07, 2017 11:57 am

I have not - just speculating. I've been in discussions with several tank repair (tank liners) groups out here in California. The common comment regarding primary breakthrough is that it generally occurs along the bottom under the sludge. This tends to be anaerobic and sulfur reducing thrive in that environment. I know they are having the sulfur reducing issues in pipelines (Alaska, etc.). I've also heard of pH levels in USTs lower than you would find with acetic acid.

I'm not a biologist, so again, just speculation. I'm guessing or hoping Dr. Bugbuster and/or Zane have sampled the UST bottom goo. I'll review the EPA and Battelle reports later today. I probably should have started there but tossed it out to our board experts.

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Re: SEVERE STP corrosion internally on Diesel

Post by bugbuster » Tue Mar 07, 2017 3:23 pm

Hi, Fatmonk!

There's an old Talmudic saying: "The answers you get depend on the questions you ask."

Neither the 2012 study (sponsored by the clean fuels alliance), nor the 2016 US EPA study - both investigating ULSD system corrosion reported SRB detection.

In my own work (fuel system microbial audits) I detect SRB in approximately 10% of all bottom samples. I've completed surveys in which I do not detect SRB in any of my samples; and surveys in which I've recovered in >90% of my samples.

SRB are tricky to detect by culture methods. Even using genetic testing (PCR or Next Generation Sequencing - NGS) SRB can be present but go undetected. The appearance of the corrosion provides the primary clues. We also now know that bugs called Archaea - a branch of the tree of life that was first discovered in the 1980's - can infect fuel systems. In the oilfield community the term "sulfate reducing bacteria" has been replaced with "sulfate reducing protists" - SRP - to reflect the possibility that the sulfate reducing bugs present might be bacteria, archaea, or both. We do not have culture tests that will detect sulfate reducing archaea.

Bottom line: neither of the two recent studies to investigate ULSD system corrosion detected SRP. I still detect them when I run microbial audits. My audits are biased. Clients rarely ask for microbial audits when they don't have certain body parts in the vice... Consequently, the percentage of SRB/SRP hits I get is likely to be greater than in the total population of ULSD tanks. Again, I'll qualify this is a guess. If we assume that there are >100 000 ULSD UST in service, you'd need to sample from at least 10% (10 000 UST) to get a representative estimate of what the ULSD UST universe looks like. The 2012 study looked at samples from 7 UST. The 2016 study increased the number to 40. That's 0.4% of the minimum number of UST that would need to be examined in order to have a representative number of UST. More than a few industry stakeholders choose not to have microbiological testing done at their sites. The common thinking is that if they don't test, they would be telling the truth when they reported that they have seen no evidence of microbial contamination (SRB or otherwise) in their UST. SO not reported SRB/SRP is a far cry from no SRB/SRP.

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Re: SEVERE STP corrosion internally on Diesel

Post by Fatmonk » Wed Mar 08, 2017 10:16 am

Dr. BB, you are a wealth o' information - many thanks. I'm still trying to figure out the right questions.

There's an old Chinese saying: "He who asks a question is a fool for five minutes; he who does not ask a question remains a fool forever."
Thanks for mercifully ending my five minutes...for now.

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Re: SEVERE STP corrosion internally on Diesel

Post by ZMiller » Wed Mar 08, 2017 12:14 pm

"It may be best to remain silent and be thought a fool than to speak and remove all doubt"


Abraham Lincoln
When you are dead it's likely you won't know it. It could be difficult for others. It's the same if you are stupid.
"Tact is the ability to tell someone to go to Hell in a way that they will begin looking forward to the trip"


ZMiller
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Re: SEVERE STP corrosion internally on Diesel

Post by ZMiller » Wed Mar 08, 2017 12:20 pm

"A wise man learns more from a fool's question than a fool learns from a wise answer"
When you are dead it's likely you won't know it. It could be difficult for others. It's the same if you are stupid.
"Tact is the ability to tell someone to go to Hell in a way that they will begin looking forward to the trip"

eLabs

Re: SEVERE STP corrosion internally on Diesel

Post by eLabs » Wed Apr 12, 2017 12:04 am

My crew and I do internal lining. We find pitting in the bottoms of the tanks and the strangest shapes. It is my understanding that the feces from the microbes that cause the corrosion in the wet portion of the tanks, and the leftover ethanol vapor from previous loads that cause the tank top corrosion.

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Re: SEVERE STP corrosion internally on Diesel

Post by bugbuster » Thu Apr 13, 2017 5:06 pm

Hi, eLabs:
"It is my understanding that the feces from the microbes that cause the corrosion in the wet portion of the tanks, and the leftover ethanol vapor from previous loads that cause the tank top corrosion."

It's quite possible that ethanol vapor trapped in the STP spill containment well oxidizes chemically to acetic acid, which proceeds to corrode the exposed fittings (turbine distribution manifold, couplings, etc.). Other processes might contribute to this corrosion too (for example: water vapor in the well).

I can see how, in an attempt to keep the language simple, someone might say: "the feces from the microbes that cause the corrosion in the wet portion of the tanks", but in this case, the attempt to simplify language is very misleading. Microbes tend to live within complex communities that are surrounded by slime. We (microbiologists) call these biofilms or biofilm communities. Traces of water <1 mL in volume can support a health biofilm community. Understanding this is critical for several reasons:
1. The physical presence of biofilm on a tank surface, primes electron flow (current) between the covered and exposed areas of that surface. This electron flow causes Galvanic corrosion.
2. The microbes within the biofilm are quite remarkable. In many respects they are like the cells in our bodies. Just like eye cells, heart cells, etc., genetically identical microbes look and act differently, depending on where they are within the biofilm. Some use oxygen, others don't. Some attack fuel directly and produce wastes that other use as food. Genetically identical cells behaving like different types of microbes makes things complicated. Now think about how much more complicated biofilm communities - with 5, 10 or 100 different types of microbes - are. If it doesn't make your head spin, it should.
3. Not all of the chemicals that microbes produce and excrete are wastes. Some act like detergents - dispersing water into fuel; making the fuel more available as food. Large molecules (polymers) form the biofilm structure. Many of the microbes produce acids. We call these weak acids. When salts are present, the weak acids react with them to product strong acids (for example a weak acid + sodium or calcium chloride will react to from a weak base + hydrochloric acid; hydrochloric acid is a strong acid).

This all might seem complicated, but it's really still an over simplification. I offer this as a superficial explanation of why the image of microbe feces is so far off the mark.

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Re: SEVERE STP corrosion internally on Diesel

Post by ZMiller » Thu Apr 13, 2017 7:07 pm

Are we saying that we should keep water out of the tank and thus prevent the "Cauldron Effect" ?
When you are dead it's likely you won't know it. It could be difficult for others. It's the same if you are stupid.
"Tact is the ability to tell someone to go to Hell in a way that they will begin looking forward to the trip"

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Re: SEVERE STP corrosion internally on Diesel

Post by Fatmonk » Tue Jul 25, 2017 11:31 am

We're seeing a tank repair/lining almost weekly now. API 1631 (2001) and NLPA 631 (1991) were both written based on single wall - external corrosion. STI has the newest (2015) and addresses DW tanks but only condemns a tank for deflection. The general standard has been if the tank has 75% of it's existing steel, it's good. Is anyone seeing states using different standards out there?

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