In a fuel supply system with a fuel supply pipe for pumping fuel from a fuel tank via a fuel supply pipe to a fuel injection device of an internal combustion engine, wherein a fuel filter including a water separator is arranged in the fuel supply pipe for removing water collected in the water separator and injecting it into an exhaust gas system, a fuel/water discharge arrangement is provided which includes a main pipe connected to the fuel filter, a branch pipe connected to a water collection region of the fuel filter and a mixing device arranged in the main pipe for mixing water to a fuel flow in the main pipe for injection into the exhaust gas system.