Nissan Repair: fuel pump noise humming, rear seat area, contaminated fuel

Question
I had to drain my tank after putting contaminated fuel in,after cleaning the tank etc sbd putting new fuel in I have noticed a constant humming noise coming from the rear seat area of the car the pump was fine before the mishap what can it be please

Answer
Patrick,

The fuel pump is exposed to the contaminated petrol and this can damage the bearings.  Also, if the filter was not changed or the new filter has absorbed water or other contaminates the pump might be pushing against a filter that is plugging.