Types of fuel contamination

There are many varying types of fuel contamination found in gas oil also know as red diesel. It only takes one type to cause a breakdown to your uninterrupted power system.

Water is the arguably the most damaging contaminate to find in your fuel tank as it causes many other contamination chain reactions, there are three types of water contamination each have varying degrees of damage to your engine:

Free water

contamination 1Free water forms on the tank bottom, initaly as small puddles which develop into large volumes of free flowing water. This type of water contamination is the most developed and generally occurs after the fuel has reached its maximum saturation point of up to 1500 ppm. With large volumes of free water microbial growth is rapid.

Potential risk: Very high, act immediately to recover fuel



Emulsified water

emulsified waterEmulsified water occurs when very small droplets of water are suspended in the fuel. Fuel will appear cloudy. Emulsified water can cause long term damage to engines and even prevent them from starting.

Potential risk: High, action should be taken to prevent further contamination




Dissolved water

dissolved waterDissolved water forms when emulsified water is chemical dissolved using a surfactant or biofuel which will atomise the water molecules into microscopic particles. The water contamination will remain within the fuel however microbial growth will find it harder to colonise and grow.

Potential risk: Medium, step up fuel sampling to every three months



Water contamination causes:

Microbial growth

The majority of microbial growth occurs when water is present, microbes can grow in emulsified and free water.

When the conditions are right microbial growth will occur at the fuel/ water interface, they feed from the hydrocarbons found in diesel and gain other nutrients from the water. A large layer of slime can form quickly and block filters. Complications with fuel stability and tank corrosion can also occur.

Sulphur is poisonous to the microbes that grow in fuel; since the removal of sulphur microbial contamination has been on the rise. Biofuel facilitates the acceleration of microbes as it degrades at a much faster rate than pure petroleum gas oil. 

Where do Microbes come from?

Fungi are natural soil inhabitants. Their spores, similar to seeds, easily become airborne and may contaminate all fuels. Spores by themselves cause no problems; however when they germinate and grow the problems develop. There are over a 100 different types of mould, yeast and bacterial strains found within diesel fuel.

Conditions promoting microbial growth?

Types of microbial contamination commonly found in fuel

Bacteria  are very resilient and are made up of single cells typically 1-10 microns in size. In the right conditions they can multiply in 10-20 minutes. There are typically 40 million bacterial cells per millilitre of contaminated diesel.

Fungi are the most common microbe found in fuel contamination. There are two types of fungi present in fuel moulds and yeasts. Both are multi-cellular plant like organisms which attach to tank walls. The structure of this microbe can also block filters.

All types of microbes produce polysaccharides to digest hydrocarbons and survive in fuel oil; our advanced enzyme fuel emulsifies the polysaccharide therefore preventing the growth of microbes.

For expert advice contact the WP Technical team 0800 980 6172

Monthly Feature

WPvan tanker

total fuel management

WP Fuel Solutions (WPFS) provide bespoke fuel management packages to prevent fuel contamination and degradation in long term storage. Our fuel management packages removes the risk involved in storing fuel and ensures your investment is kept in the most efficient and reliable condition possible, ready for when you need it most.

Find Out More