Either particles from the ring are falling down onto Enceladus, or Enceladus is supplying the ring with particles. Though a definite answer is not known, evidence point to Enceladus as the source for the ring particles. The E ring is being disrupted by the solar wind and is losing particles. It must therefore, be getting replenished from somewhere. Secondly, there are not many craters on the surface of Enceladus, and that suggests that something covers the craters up soon after impact.
Volcanoes are the most likely culprit.
Voyager spacecraft images of Enceladus show what look like lava flows, except that in this moon's case, it would be icy water flows. No geysers or active volcanos have been found, but they are probably the only answer that makes sense to the question of Enceladus' surface and the E ring particles. Just why Enceladus would be geologically active is another mystery. Jupiter causes such activity on its moons, but Saturn exerts only one forth the tidal stress on its moons. Enceladus is not big enough to have internal heat or pressures create volcanos, and the moons around it should not have any gravitational effect either.