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Fuel Microbiology
Two major groups of microorganisms contaminate fuel systems: bacteria and fungi which can further by divided into yeasts and moulds.
The microbial growth lives in water and feeds off the hydrocarbons in fuel. As water collects inside the fuel tank the possible risk of microbial growth starts to increase dramatically. Microorganisms tend to grow at the fuel/water interface in the fuel tanks. However growth can also take place in other areas such as on the surfaces of the fuel tank and pipelines.
Impact of Microbial Contamination:
- Biodegradation of fuel
- Microbially induced corrosion of tanks/pipe work
- Biofilm formation
- Production of corrosive acids
- Transfer-line flow restrictions
- Filter plugging
- Engine wear
- Corrosive deposits on engine parts (injectors, cylinder linings etc.)
- Reduced heat of combustion
- Fuel property changes: colour, pour point, cloud point, and thermal stability
- Loss of additive performance
- Sludge formation
As bacteria and fungi reproduce they form biomass which accumulates at the fuel: water interface, on tank surfaces and on filters. As biomass increases and as metabolic waste and dead cells accumulate they settle out as sludge which accumulates on tank bottoms. The important issue here is the accumulation of a mass, beneath which microbially induced corrosion and acid accumulation occurs. If sufficient sludge builds up, sludge particles will be drawn out with the diesel fuel. As a result filter and injector orifices may be clogged. More often, filter and line plugging result from biofilm formation on transfer wall lines and filter surfaces. The first symptom of this is reduced filter life. Occasionally, catastrophic failures, like engine shut down due to fuel starvation, provide convincing evidence of the importance of contamination control. A further aspect of the filter-plugging problem is that the biofilm is often nearly transparent, consequently it generally goes unnoticed.
How Can SGS Help
SGS can provide analysis to determine the viable aerobic bacteria of fuel and fuel components by IP 385, enumerate the most probable number of sulphate-reducing bacteria and fungal fragment content by IP 472. We can also provide guidance on sampling procedures and often carry out sampling ourselves.
Bugbusters Test Kits
Within our microbiological service, we can also provide field-use test kits called Bugbusters to allow continual monitoring for microbial growth.
Bug busters test kits serve as an early warning to detect poor quality fuel deliveries or fuel deterioration during storage. The kits are simple to use and no microbial training is required for use or interpretation of the results. Colour changes in four detection vials indicate the presence and severity of the contamination of four microbial types. The kits are designed to detect the onset of contamination but will also indicate where advanced contamination has occurred. Full instructions are included with each kit.
Water Analysis
Drinking water is heavily governed by regulatory authorities such as the European Union and World Health Organisation. Drinking water should be fit for purpose and free from any bacteria that may adversely affect public health. Due to this, limits have been placed by these agencies to ensure wholesomeness.
Coliform bacteria are widely regarded as the most reliable indicator of potable water quality. Coliform bacteria are found in the human and animal intestine but may be of environmental origin. Consequently, they serve as indicators of potential faecal pollution. Escherichia coli is only found in human and animal intestines and best for its presence in water are necessary to confirm that pollution is of human or animal origin.
Enterococci are more resistant to environmental stress and chlorination and as a result, survive longer. Enterococci normally inhabit the intestine of man and animals, and can provide an indication of past pollution.
What Can SGS Do?
SGS can provide analysis to ensure that drinking water is fit for purpose by analyzing for Total Viable Aerobic Bacteria, Coliforms, Escherichia coli and Enterococcus spp. by National Standard Methods W4, W18 and W3 respectively.
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