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Increasing bio-content in fuels exacerbating microbial contamination

Microbial contamination can be a serious issue for users of middle distillate fuels, jet fuels, and diesel fuels. Fuels and fuel systems are vulnerable to biodeterioration, with biofilm communities a primary cause of degradation. When fuel leaves the sterile environment of a refinery it becomes susceptible to contamination, with water typically the root of all evil. Water ingress can occur due to condensation or fuels may collect water or particulates during transportation, before it hits the storage tank. In hot and humid regions such as in Asia Pacific, microbial troubles can quickly compound.

F+L Magazine spoke with David Armitage, global business development manager for Conidia Bioscience Ltd, based in Surrey, England, on the latest advances in testing for microbial contamination in fuels. Conidia Bioscience has been involved in the development, manufacture, and supply of fuel tests into the aviation, marine, and land diesel sectors for more than 20 years. The company produces FUELSTAT, a rapid on-site testing kit to detect microbes that thrive and can damage fuels. Armitage joined Conidia in 2014 and is focused on growing the non-aviation fuel supply chain.

Microbial contamination can result in blocked filters, contaminated water scavenge systems, fuel probe malfunctions and blocked injectors. Severe operational issues can force assets out of service.   Microbially influenced corrosion is also a credible long-term threat to metal structures that are used for fuel storage. Perhaps the most noteworthy consideration is the impact on the safety of fuel systems and the persons that rely on it.

The Conidia representative noted an increasing use of biofuels. A shift to higher levels of bio content has the potential to exacerbate microbial issues, and bio content is certainly speeding up the microbial process, says Armitage. Biodiesel is not such an issue at this point. It is the introduction of ethanol, which has a high water content, that is creating a different set of organisms, he says.   

Some changes in the diesel environment are also prone to contamination, however. Armitage highlighted the reduction of sulphur in marine fuels following the introduction of IMO 2020, and higher levels of fatty acid methyl ester (FAME) in fuels, particularly diesel fuel. FAME is typically a feedstock for microorganisms and the reduction of sulphur in fuels may make microbial contamination more frequent in the future, he says.

Dual-fuel vessels running on marine gasoil (MGO) also pose a risk, says Armitage. Fuel sources can be left in the belly of a vessel for prolonged periods while ships are in open waters, potentially only employed when a vessel arrives in an environmentally controlled area. We do not want organisms to grow during a voyage and cause a problem when they switch over the fuel, says Armitage.

A broad range of tests are available for fuel contamination. Some can be performed quickly on site, whereas others require more elaborate testing in a laboratory environment.  Regular testing is critical to detect contamination at its earliest point to enable corrective action – including removing water microbes, cleaning surfaces and microbiocide treatments. 

Armitage emphasised the importance of speed in any testing regime. Within 24 hours of sample testing, organisms can change and adapt to their environment or perish —potentially providing a different result. In the marine industry, vessels can be navigating international waters for long amounts of time with only short periods in transit. Testing while on board, or quickly during transit is essential, says Armitage.

One of the outcomes of the Covid-19 pandemic has been a greater need for people to get a much faster result from testing, says Armitage. Modern test methods enable greater speed and efficiency of microbial fuel testing, he says.

Conidia is one of several companies operating in the area of microbial fuel testing. The organisation recently launched an upgraded digital verification tool FUELSTAT® Result for iOS and Android. The new mobile application allows operators to complete compliance testing on-site without paper and without the need to register, representing a significant productivity improvement, he says. The app works in conjunction with the FUELSTAT immunoassay antibody fuel tests which are compliant to ASTM B8070.

FUELSTAT is based on lateral flow technology and provides results that are categorical, with a high range and low range for bacteria, fungi and a specific fungus — hormoconis resinae. The panel will let users know if the tested specimen has negligible, moderate or suffers from heavy microbial contamination. The FUELSTAT app is not to be used as a scientific piece of equipment so it's not meant to be used as the empirical results, says Armitage, comparing it to reading a human pregnancy test. 

Differentiating between positive and negative results can be tricky with the naked eye. The app is designed to eliminate that subjectivity.  Upgraded technology includes trend analysis, to enable organisations to track the trend of a particular asset over a period of time.

While Conidia is singing the praises of its FUELSTAT testing and mobile app, there are several other testing programs that include more cost effective dip slide technology, though it requires an incubation period, to ATP testing. All the testing options play a valid role in fuel system microbial contamination testing corrective action, says Armitage. Though, more traditional methods can take several days and require technical people with suitable expertise, he says.  

A competing technology, LuminUltra’s latest ATP test technology uses a mobile phone app and cloud technology to capture ATP test data. ATP stands for adenosine triphosphate, a molecule found only in and around living cells, and as such,  gives a direct measure of biological concentration and health. A key difference from the FUELSTAT app is that the luminometer yields qualitative data, while FUELSTAT only provides categorical data . ATP is quantified by measuring light produced through a reaction with the naturally occurring firefly enzyme luciferase using a luminometer. 

In microbial testing, there is a general trend towards molecular microbiology methods where non-technical personnel can obtain genetic data in the fuel. The same quantitative polymerase chain reaction (qPCR) kit being used at airports and other public facilities to screen for the SARS-COV-2 virus contamination can be used to screen fuel samples for specific types of microbes.  The only difference is in the detection cartridges used. ASTM has a Standard Practice in the works for the quantitative polymerase chain reaction which has been balloted once and will be ready for re-ballot in July. 

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