Filters are used throughout the aviation fuel supply chain and on aircraft to ensure the fuel which reaches the aircraft engine is clean and dry.  Filter water separators (EI 1581) are widely used in the supply and distribution of aviation fuel to remove both particulates and water. In under-utilised FWS units, microbes may proliferate in any water which remains on the outer sock of coalescer elements resulting in the formation of brown spots of microbial growth, often referred to as “leopard spotting”. Because this microbial growth develops on the downstream side of the coalescer, it can then contaminate clean fuel passing through the filter. Further, if heavy microbial growth develops on the surface of the filter, the biosurfactants produced by the microbes can inhibit the ability of the coalescer to remove water from fuel and thus disarm the coalescer.

Other types of filter used in the aviation fuel supply chain, such as Filter Monitors (EI 1583 now withdrawn although still used in some airports), dirt defence filters (EI 1599) and microfilters (EI 1590) may theoretically be prone to clogging by particles of microbial biomass suspended in fuel.  Likewise Water Barrier Filters (EI 1588) are reported to retain microbial contaminants that may be in fuel.  Although microbial growth tends to be most predominant in tank bottoms at the interface between fuel and any water or as a slimy film of growth on tank surfaces, turbulence in a contaminated tank can disperse particles of biomass into the fuel.  In severe cases this can result in unacceptable differential pressure (DP) as filters become clogged. A major industry development is the decision to withdraw Filter Monitors from use in the aviation fuel supply chain.  A number of alternative technologies have been proposed as replacement, including Filter Water Separators or Water barrier filters, combined with enhanced particulate monitoring.  The long-term implications of this change on the incidence of microbial growth and contamination has yet to be fully established, and some degree of increased diligence and monitoring may be warranted.

ECHA has up-to-date expertise in the latest developments in filtration and associated microbial issues and can;

• Conduct analysis of samples of fuel and filters from your facility in our laboratory to assess the extent of microbiological contamination. Learn more about our lab analysis service here.
• Provide on-site microbial Test Kits. ECHA’s MicrobMonitor2 is a globally recognised industry standard test (IP 613/ASTM D7978) which can be used on-site or in the laboratory by non-microbiologists for the detection of microbiological contamination. Testing filter drains and fuel upstream and downstream of filters can help establish whether they are contaminated. The test can also be used to test filter surfaces when used with our swabs.  Learn more about the test here.
• Conduct surveys of tanks, fuel systems and filters at your facility if you have a concern about microbiological contamination. Learn more about our Site Surveys here.
• Provide advice on remediation, control, monitoring strategies and best practice. Learn more about our Consultancy Services here.
• Offer comprehensive, tailored training courses on microbiological contamination of jet fuel in the supply chain. Learn more about our Training Courses here.