Fuel Contamination - The Problem

Diesel Bug explained

Microbial contamination of fuels, can cause severe fouling and damage to machinery and corrosion /deteriation of fuel tanks. Contamination in fuels is generally caused by poor housekeeping in the storage and supply chain. Add a humid warm enviorment and According to a fact sheet from Lloyds Register of Shipping:

There are three defined kinds of microbes: Bacteria, Moulds & Fungi,and Yeasts.
To survive and grow, bacteria need water and a food source, both of which can usually be found in the interface between water and diesel in tanks at temperatures between 15°C and 40°C.

Bacteria exist in two distinct groups: aerobic, which use oxygen to oxidize their nutrients, and anaerobic, which cannot tolerate oxygen. Of the latter type, one strain, called sulphate reducing bacteria (SRB) is particularly virulent, producing highly corrosive sulphides as a result of chemical reaction.

Moulds (small fungi) form a thin visible layer of filaments which intertwine and grow into large mats doubling in size every two hours if enough nutrients are available.

Yeasts/Fungi utilise the hydrocarbons in fuels and oils to produce organic acids which then corrode surfaces and can produce large amounts of biomass.

Fuels

Microbial contamination of fuels is usually limited to Diesel Fuels, Aviation Fuel and Kerosines, as microbes do not survive in the high temperatures needed to handle heavy fuels.