Here is the report’s explanation for using the flushing pump to supply fuel to the ship’s service diesel generators (DG)
According to the chief engineer and previous chief engineer, for at least 7 months leading up to the accident, the crew exclusively used the flushing pump to supply fuel to DG3 and DG4. The crew believed that the DG supply and booster pumps and the associated piping contained other fuel (VLSFO or HFO) that was not compliant with emissions regulations in certain geographic areas, and that the pumps and piping may have contained bacterial growth that could have contaminated the entire fuel system (a common occurrence with stagnant marine fuels). The crew explained that cleaning the system to use the supply and booster pumps would have taken several days, so they and the previous chief engineer chose to keep the DG fuel supply system configured to run DG3 and DG4 solely with the flushing pump.