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PANORAMA: 1997

How Ketchup Keeps Aircraft Flying
by Michael Boyd

A STUBBORNLY glutinous bottle of tomato ketchup inspired Ted Hill to an invention that has revolutionised the on-site counting of bacteria. It has become one of the biggest forces in the continuing struggle against the potentially lethal microbial contamination of aircraft fuel.

While shaking the bottle over his breakfast plate, Hill idly wondered if he could substitute the thixotropic gelling agent in the sauce for the traditional agar gel that has been used by researchers to grow microbial colonies for over 100 years.

The problem he wanted to overcome was that testing for infestation was a costly and time-consuming business because it needed a laboratory where heat could be applied to melt the agar before the introduction of the microbes.

He was right in his early morning ruminations. After exhaustive tests his company, Echa Microbiology Ltd of Cardiff, Wales, has come up with a new nutritive solution gelled with thixotropic and/or pseudo plastic agents in place of agar. It is called Echa Smartgel.

"An aqueous or non-aqueous sample can be dispersed in the gel by simply shaking it in the hand and then allowing the gel to reset as a flat horizontal layer," says Ted Hill. "During incubation, colonies develop comparable to their normal formation in traditional plates."

A sensitive redox indicator gives an early indication of colony growth and helps with counting the number of bacteria present. The accuracy is equal to that of a traditional agar plate count. Very large numbers of microbes produce a coloured formazan within a few hours - a real time test.

Until this inspired moment the traditional count technology had been confined to laboratories because the 1.5 per cent aqueous solution of agar used in petri dishes required a temperature of 85 degrees Celsius (C) to melt it and set again at 39 degrees C. Such temperatures precluded their use for on-site counting of bacteria in distillate fuels such as aviation kerosine or diesel derv.

There have been growing practical problems for the air transport industry associated with microbial contamination. During the last few years, changes in fuel composition and handling have resulted in some changes in the type of causative micro-organisms and to a large increase in their distribution and occurrence.

Filter blockage, coalescer malfunctions, injector fouling, accelerated corrosion, fuel gauge errors and water entrainment are but some of the more common consequences of contamination. The results, if unchecked, could be catastrophic for an aircraft and those onboard.

The blame for tolerating or even encouraging microbial proliferation has often been laid at the end-user and his fuel supplier; "poor housekeeping" is normally cited as the prime cause, particularly failure to remove free water. But the problem also occurs in storage and distribution systems.

Whole cargoes have been affected necessitating expensive and time-consuming procedures to decontaminate the fuel. These developments have highlighted the need for improved standards of fuel system management and contaminant detection. But now, with the production of the ketchup-inspired Echa Smartgel, checks can not only be done in situ but quickly and cheaply.

"Preliminary tests on water, milk and various emulsions suggest that the methodology will have wide applications both in the laboratory and on site," added Mr Hill. "It is also going to be a boon for small medical and cosmetic companies that do not have a microbiology laboratory, and has great export potential for testing drinking water in developing countries."

Already the new Smartgel is being field tested all over Europe by international oil companies and airlines.

Echa is not only involved in monitoring bacterial contamination but is also very much concerned with its elimination, not only from distillate fuels but in any bulk liquid storage.

  

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