Question 61 QMED01 - Junior Engineer

The Correct Answer is C **Explanation for Option C (Moisture or water to be present):** Microbiological organisms (like bacteria, yeasts, and molds) require water to survive, metabolize, and reproduce. In fuel tanks (containing fuels like diesel or jet fuel), these organisms thrive in the interface layer—the boundary between the heavier water accumulation at the bottom of the tank and the fuel itself. Without free water or moisture present, the organisms cannot grow, as they cannot utilize the hydrocarbons in the fuel directly without an aqueous medium. **Why the other options are incorrect:** **A) vanadium to be present:** Vanadium is an element sometimes found in residual fuel oils, often associated with high-temperature corrosion in engines (hot corrosion), but it is not a requirement for standard microbiological growth (like "diesel bug") in a fuel tank. **B) low temperatures to exist:** While extremely high temperatures kill microorganisms, microbiological growth is often slowed or inhibited at very low temperatures (e.g., freezing). These organisms generally thrive best at moderate ambient temperatures, and low temperatures are typically detrimental to their rate of growth, not necessary for them to thrive. **D) electrolysis to be occurring:** Electrolysis is a chemical process driven by electric current, usually involving the breakdown of compounds. While corrosion processes can occur in fuel tanks, electrolysis itself is not a prerequisite or necessary condition for the presence and thriving of microbial life. Microbes depend on water, nutrients (from the fuel), and oxygen (or sometimes lack thereof) to grow.