Filtration Issues

Filter water separators (EI 1581) are extensively used in the supply and distribution of aviation fuel to remove particulates and water.  However, in less utilised Filter Water Separator (FWS) units, microbes may grow in any residual water on the outer sock of coalescer elements, resulting in the formation of brown spots of microbial growth, known as “leopard spotting.”  This microbial growth occurring downstream of the coalescer can contaminate otherwise clean fuel passing through the filter. Additionally, if there is heavy microbial growth on the filter’s surface it can produce biosurfactants that hinder the coalescer’s effectiveness in removing water from fuel, thereby disarming the coalescer.

Different types of filters used in the aviation fuel supply chain, such as Filter Monitors (formerly EI 1583, now withdrawn but still employed in certain airports), dirt defence filters (EI 1599), and microfilters (EI 1590), could potentially experience clogging due to particles of microbial biomass suspended in the fuel.

Similarly, Water Barrier Filters (EI 1588) are known to trap microbial contaminants that may be present in the fuel. Although microbial growth typically occurs predominantly in tank bottoms at the fuel-water interface or as a slimy film on tank surfaces, turbulence within a contaminated tank can disperse biomass particles into the fuel. In severe instances, this dispersion can lead to unacceptable differential pressure (DP) as filters become clogged.

A significant development in the industry is the decision to withdraw Filter Monitors from use in the aviation fuel supply chain. Various alternative technologies have been suggested as replacements, including Filter Water Separators or Water Barrier Filters, coupled with enhanced particulate monitoring. The long-term consequences of this change on the prevalence of microbial growth and contamination have yet to be fully determined, and a heightened level of vigilance and monitoring may be advisable.

How ECHA can help with Microbial contamination issues in filters 

• Perform thorough analysis on samples of fuel and filters collected from your facility at our UK laboratory to assess the level of microbiological contamination.
• We offer on-site microbial Test Kits, including the MicrobMonitor®2, an industry-standard test recognised globally (IP 613/ASTM D7978). This test can be easily conducted on-site or in the laboratory by non-microbiologists to detect microbiological contamination. By testing filter drains and fuel both upstream and downstream of filters, we can determine potential contamination. The test can also assess filter surfaces when utilised with our swabs.
• ECHA can conduct comprehensive site surveys of tanks, fuel systems, and filters at your facility if there are concerns regarding microbiological contamination.
• We provide expert advice on remediation, control, monitoring strategies, and best practices. Discover more about our Consultancy Services.
• Additionally, we offer tailored training courses on microbiological contamination of jet fuel within the supply chain.