TERM-MICROBIAL-CONTAMINATION
Microbial Contamination
Water & Fuel
Also: biological contamination · fuel bugs · microbiological growth · bacterial contamination · fungal contamination
Canonical Definition
The colonisation of diesel fuel, biodiesel blends, and fuel system components by bacteria, fungi, and yeasts at the water-fuel interface. Microbial organisms metabolise hydrocarbons as a carbon source while using free water as a growth medium. They generate acidic metabolic waste products (pH 3–5 at colony sites) that corrode metal tanks and components, produce biomass and biofilm that block fuel filters, and generate hydrogen sulfide that corrodes fuel system materials. ULSD (Ultra Low Sulfur Diesel) fuels are more susceptible than high-sulfur fuels because sulfur compounds previously acted as natural biocides.
Engineering Context
Microbial contamination is a primary fuel system issue in marine, generator, and bulk storage applications where fuel sits for extended periods with free water present. Free water must be removed below 200 ppm to inhibit growth. Biocide treatment (BIOGUARD, Grotamar 82, etc.) treats existing contamination but does not replace water removal. Contaminated fuel systems require complete system drain, tank cleaning, and filter replacement.
Applicable Standards
Related Technologies
Protection Systems
Knowledge Center Articles
KC-00 Governance Metadata
| Permanent ID | TERM-MICROBIAL-CONTAMINATION |
| Category | Water & Fuel |
| Status | Published |
| Version | 1.0 |
| Last Reviewed | 2026-07-05 |