PTQ Q3 2026 Issue

Figure 5 Diesel aspect from bottom of tank before treatment

Figure 6 Diesel aspect from bottom of tank after treatment

of corrosion products, such as metal oxides and hydroxides, as well as particulate material associated with degradation of metallic surfaces in the storage system. In contrast, the treated sample (see Figure 7B ) shows a pronounced reduction in both the quantity and average size of solid particles, as well as fewer agglomerates. The micro- scopic field predominantly shows fine and dispersed parti - cles, indicating reduced generation and/or release of solids in the system. This reduction is consistent with the mitigation of corrosive processes and control of microbial activity, since high microbial loads and corrosive environments are directly associated with intensified microbiologically influenced cor - rosion and the release of corrosion products into the fuel. These results corroborate the other data obtained during monitoring, indicating that the treatment contributed to system stabilisation, a reduction in particulate load, and an improvement in stored diesel quality, as well as suggesting a positive effect on asset integrity preservation. Best practices Based on results obtained and on widely adopted techni- cal guidelines for fuel storage systems, effective microbial contamination control should be structured as a continuous programme integrating preventive actions, monitoring, and corrective interventions. Periodic drainage of free water accumulated at the bottom of tanks should be considered a priority measure, since the presence of water represents the primary factor for microbial

development. Periodic inspection of breather systems, seals, and transfer lines is also recommended to minimise the ingress of moisture and external contaminants. Periodic microbiological monitoring of diesel and, prefer- ably, of the fuel-associated aqueous phase is essential for early detection of microbial growth trends. Techniques such as plate counts, dip slides, adenosine triphosphate (ATP) testing, and targeted analyses for risk groups (such as SRB and acid-producing bacteria [APB]) allow classification of operational risk levels and timely implementation of correc- tive actions before severe impacts occur. Preventive application of biocides under maintenance regimes defined based on operational history and contam - ination risk represents an essential tool for microbial control. This strategy should be integrated with shock treatments whenever elevated contamination levels are identified, ensuring rapid reduction of microbial load and interruption of biodeterioration and MIC cycles. In addition, the adoption of housekeeping practices, such as scheduled tank cleaning, sludge removal, solids control, and review of fuel receipt and transfer procedures, con- tributes to reducing niches favourable to microbial growth. Systematic integration of physical, chemical, and monitoring actions forms the basis of a robust microbiological man- agement programme capable of preserving diesel quality, reducing operational risks, and extending asset service life. Conclusion The management of microbial contamination in diesel storage systems is a critical element for operational efficiency, supply reliability, and preservation of asset integrity in refineries. The Mataripe Refinery case study demonstrates that micro - biological contamination can affect fuel quality by increasing sludge formation, turbidity, corrosive processes, and the time required for batch certification. Although not an obvious hypothesis, microbiological contamination may also be an underlying cause of disturbances in diesel storage tanks. The implementation of an integrated strategy, combining free water removal, cleaning practices, and application of a broad-spectrum biocide with controlled release, resulted

Figure 7 Solids in untreated sample (A) and treated sample (B) evaluated by optical microscopy at 40 × magnification

PTQ Q3 2026