Conidia Bioscience Ltd

FAQs

FAQs
FAQs about the diesel bug in diesel fuel, the jet fuel fungus in aviation fuel and Fuelstat® tests.

 
Diesel Bug & Jet Fuel Fungus Contamination


Why is there a problem with diesel bug microbes?

Micro-organisms are present wherever sources of food and water exist together. In a fuel system fuel provides the food source, whilst water comes from the fuel itself as well as from external sources like atmospheric humidity, cooling systems and the moisture attractant, (hygroscopic) nature of biofuel.
 

Why should I worry about having the diesel bug in my fuel system?

Water is heavier than fuel and so is found at the bottom of tanks &stores. Microbes tend to live at the water fuel interface, living in the water and feeding off the fuel. They also seek out low flow areas of fuel system and are known to over time to actively create these conditions by ‘digging in’ to structure of tanks and lines, resulting in corrosion and pitting. Heavy contamination can block filters and stop engines too.
 

Why is the diesel bug problem getting worse now?

Governments worldwide are taking measures to reduce emissions and eke out dwindling fossil fuel stocks. There is also an imperative to reduce the economic risk of and politically unacceptable dependence on fossils fuels and their suppliers. The emissions drive has led to sulphur, seen as the main culprit in the emissions issue, being targeted for reduction. Adding biofuels to fossil fuels is seen as the best current solution to eking out fuel stocks and spreading risk.
 

FAQ's

FAQs
FAQs about the diesel bug in diesel fuel, the jet fuel fungus in aviation fuel and Fuelstat® tests.

 

Tell me more about Sulphur

Sulphur is a lubricant and so cutting its levels increases fuel system wear and reduces efficiency. Older engines in particular suffer from its reduction. Sulphur also is a bacteria-stat. This means that it interferes with the lifecycle of bugs and slows down their ability to colonise the fuel system.
 

Tell me more about Biofuels

Biofuel is a non-fossil fuel derived from organic sources, from purpose grown and professionally processed crops like jatropha to highly variable waste by-products like spent chip shop oil. It is almost impossible to remove biofuels completely from the supply pipelines, so they are present, albeit in very small quantities, in all fuels. The moisture attractant nature of biofuels is believed to be a major factor in increasing the incidence of microbial contamination in blended fuels. The seals and gaskets in older engines can deteriorate in the face of higher water content fuels.
 

What’s happening with legislation in this area?

In Europe, the EU is driving these changes through a continuous stream of fuel directives. Road transport has been at the vanguard of these changes, mainly through the various Fuel Quality Directives. Non Road Mobile Machinery (NRMM) including marine fuels, mining equipment and construction plant, stored fuel plus fuel used for heating and ventilation and generators has been second on the hit list. These trends are worldwide. All parties to the Kyoto agreement are moving in the same direction.
 

What’s the Solution to the diesel bug?

The solution involves a multi-stage process. The first stage is to establish if there is a diesel bug problem and if so how severe it is. Then the next step is to select and apply appropriate remedial treatments. Finally, in order to prevent further diesel bug problems, fuel users need to design and rigorously implement a fuel hygiene regime appropriate to the individual risk of the system at any point in time. Testing is the only reliable way to establish the diesel bug microbe status of the fuel system.
 

Tell me more about testing

Tests are available based on various technologies with their respective pros and cons. These technologies include the laboratory only IP385 which is the gold standard, colony forming unit, counts, ATP (Adenosine triphosphate) and pregnancy style immune- assay based.
 

Tell me more about remedial treatments

Treatments include fuel additives, biocides and mechanical methods
 

Tell me more about fuel additives

Fuel additives are designed to remove water and slow down the growth of microbes. They are often a cocktail of ingredients aiming to offer a spectrum of benefits like increased lubricity or fuel efficiency. These liquids act through biological and/or chemical activity. They frequently include enzymes.
 

Tell me more about Biocides

Biocides are toxic chemicals which kill diesel bug microbes, when administered under the correct conditions. These conditions include a full fuel tank, the right dosage and appropriate treatment intervals. Careful personal protection and disposal precautions are essential. Under dosing and frequent use, can result in the development of resistance, that is the diesel bug becomes immune to the product.
 

Tell me more about fuel polishing

Fuel Polishing encompasses a variety of mechanical means of reducing the contaminant levels within the fuel. Cost and effectiveness vary. Methods include filtering, magnets, lasers, catalytic converters. Most are administered as a one off intervention. There are also some in line systems which can be retro-fitted to certain classes of fuel system.
 

How do I manage the risk involved in diesel bug contaminated fuel

Risk is influenced by; Fuel specification, the sulphur and biofuel content and the amount of water, both free and entrained. Condensation potential, cleanliness and integrity of the fuel system infrastructure. Appropriateness of fuel hygiene regime and its implementation. Environmental conditions especially temperature & humidity. Standard of fuel supplier quality control processes.
 

What’s the next step?

In the early stages of responding to either the threat or the reality of a microbially contaminated fuel system, most users need a quick diagnosis before deciding on their next action.
 

What’s the quickest and easiest diesel bug test?

The Conidia Biocience immuno-assay test is ideal in these circumstances. It is a fast accurate on-site test which needs no special skill or equipment and zero capital investment. It is colloquially known as the 10 minute test. Alternative tests require hundreds of pounds worth of investment and or special skills plus up to 4 days elapsed time for the results to develop. Some do not adequately distinguish between the types of organism and their levels and therefore the true nature of the problem. A comparative table can be found below.
 

How do I get access to experts to resolve any problem?

If you have a problem and don’t have internal engineering resources, then your regular maintenance supplier should be able to quote for designing and implementing a solution. A specialist tank cleaning and maintenance organisation is another alternative. Fuel consultants, fuel, fuel treatment, fuel testing and redial equipment suppliers and trade organisations all have useful resources on offer. Links to most of these organisations can be found on the Conidia website, www.conidia.com.
 

Help me compare tests for ongoing use

Test Technology Colony Forming Units Immuno-assay ATP
Test Microbe Monitor 2 IP385 Easicult Combi Fuelstat® HY-LITE
Supplier ECHA Approved Laboratories   Conidia Bioscience Merck
Measurement Criteria Quantitative assessment of CFU Quantitative assessment of CFU Semi-quantitative assessment of CFU Accurate levels of contamination of Hres, Yarrowia Lipolytica & Pseudomonas Aeruginata Quantitative assessment of ATP
Measurement Method Count number of colonies or compare to chart Count number of colonies Compare to chart to assess number of colonies Visual assessment of lines on pregnancy test style paddle Numerical reading from HY-LITE instrument
Detects with Water Sample yes yes yes yes yes
Detects with Fuel Sample yes yes no yes yes
Time from Test to Result 1 to 6 days (depending on level of contamination and use of an incubator) 3-5 days 2-5 days 10 minutes Up to 10minutes
Suitable for On Site use yes no yes yes yes
Shelf life 1 year ambient 2 years refrigerated not applicable 9 months ambient 18 months ambient 1 year refrigerated
Skill Level medium high low low medium
Equipment Required Clean bottle gloves and preferably incubator Fully equipped & certified laboratory Clean bottle & gloves Clean bottle & gloves Hy-lite Instrument
Investment required medium high low low medium
Disposal Arrangements in disinfectant not applicable in disinfectant none none
Microbes Detected Bacteria yes yes yes yes yes
SRB’s   Only with modified protocol     yes
Yeasts yes yes yes yes yes
Moulds yes yes yes yes yes
H.res yes yes yes yes yes
Mould mycellium yes yes yes yes yes
Mould spores yes yes yes yes yes
Biocide Treatment Validation Capability yes yes Yes but underestimates Yes though may show positive for up to 3 days Yes special protocol needed in some cases
 

Fuelstat® Test Kits


No lines have appeared at all, why?

This usually means that the blue liquid has not been allowed to settle fully in the Sample Extraction Buffer bottle so that neat fuel has been added to the test well. As the test fails-safe, no lines will be seen. However, the test cannot be reused and a new foil pack must be opened.

 

Are the control lines supposed to be brighter than the test lines?

Yes, the control line shows that the kit has operated properly and should be very distinct. The test line is a response to the level of contamination in the fuel and is usually less bright.

 

Fuelstat® jet fuel fungus & diesel bug tests

Frequently asked questions about Fuelstat® tests.
 

But the test line is very faint, does that mean that it is positive?

No, if you can see a test line, even a faint one, that has a definite colour (i.e. is not a shadow) then the test is negative. This is due to the fact that the line does start to fade when the contamination level is near to the action levels, and then disappears when it exceeds the limit. So, if you can see a line then the level is below the cut-off point, so the test is negative.

 

Do I need to incubate the sample or the test paddle?

No, unlike other traditional growth methods used by our competitors, no incubation is needed for the Fuelstat™ resinae test.

 

Do I need to use sterile equipment to take the sample?

No, because the Fuelstat™ resinae test only detects H. resinae that has been growing in fuel, it does not matter what other organisms get into the sample. Using clean equipment is good practice, though.

 

Are there any restrictions on disposal of the test?

No, the paddle and the sample bottle can be disposed of with normal refuse. Any fuel used in the sample extraction bottle should be disposed of with the remainder of the sample taken from the aircraft tank.

 

Why have you set time limits for reading the test results?

The test should be read between 10 and 30 minutes after placing the four drops into the sample wells. The 10 minute limit is required because that is the time that the test needs to operate fully. We then guarantee the results for a further 20 minutes. In fact, nine times out of ten the result displayed will stay visible for a couple of days. However, in certain conditions of heat and humidity, and under certain bright light conditions, the picture may fade away. That is why we ask you to read it in that 20 minute period.

 

Other kits say that all organisms should be counted and not just H. resinae, is this true?

H. resinae is by far the most serious organism in aviation fuel in aircraft and short-term storage. In other fuels and longer-term reserve stores, where organisms have longer to develop, a much wider range of organisms come into play. This is why Fuelstat™ resinae has been specifically designed for aviation systems. Other organisms may be present but will not be causing the same amount of damage as H. resinae. Organisms never occur in isolation and where significant numbers are present, we find that H. resinae will be there as the most significant organism.

 

Can Fuelstat® resinae be used to show whether biocide treatment has been successful?

Fuelstat® resinae measures a change in the fungus that only occurs when it is grown in aviation fuel. If the fuel is successfully treated with a biocide, this will begin to diminish straight after the treatment. To ensure that the treatment has been successful, a further test is required within 7 days of the treatment, but after at least 5 flights. If levels have not reduced to negligible then the biocide has not been totally successful. A further biocide treatment is then required, using a full fuel load and the maximum soak time. H. resinae is more resistant to biocides than bacteria so other kits that only monitor bacterial growth within the shorter incubation periods will not indicate whether the H. resinae has been dealt with. H. resinae requires an absolute minimum of 4 days to begin to grow.

We use a dip slide. They are very cheap and are just as good, why should we pay extra for your test?

Dip slides are not designed for use with fuels. They will give incorrect, non-reproducible, counts and, of most concern, they will usually under-represent the problem. The manufacturers themselves do not recommend them for this purpose and are concerned with their use in fuel.

 

What do the Low and High levels mean in terms of colony forming units (CFU)?

Fuelstat™ resinae does not measure CFUs and the results cannot be directly correlated. The measurement of CFU for filamentous fungi is very inaccurate. CFUs have come to be accepted only because nothing better was available. The problem arises because of their structure; a mass of intertwined fibres, bearing long chains of spores. Each CFU may originate from a single spore, a clump of spores or a piece of fragmented hyphae (the "rooting" system). Any correlation to the actual biomass is, therefore, tentative. Fuelstat™ resinae overcomes this problem by measuring a change in all parts of the fungus which occurs when it grows on fuel. This also correlates directly with the fungal biomass present. This changed material is also released into the fuel and the water phase where the amount can be measured in micrograms (µg).

The tests are set to the following levels:

Fuel Samples:
Negligible: up to 150 µg/l
Low Positive: 150 - 750 µg/l
High Positive: over 750 µg/l

Water Samples:
Negligible: up to 33 µg/ml
Low Positive: 33 - 166 µg/ml
High Positive: over 166 µg/ml

These levels have been established after laboratory calibration studies, and comparative studies on over 400 field samples.

 

What happens if the device gets wet?

If the device is soaked either by water or fuel it will fail-safe. I.E. the control lines will not appear.