There are enough patches in the recording with the hum and without the voice to use a noise removal tool -- Audacity has one built in and the LADSPA plugins provide this kind of thing. I'd be shocked if the likes of Protools, Logic etc didn't have such a thing. As the comment mentions below, the noise is sampled and then its audio spectrum removed from the FFT of the sound.
For future, you may actually find it quicker to resolve the cause of the hum (which is probably due to an earth inconsistency with the recording equipment, although it sounds to me more like a cable that's been unplugged so maybe a channel open which shouldn't have been, or you're not using a balanced cable run in which case you can forget about getting a decent signal) and then re-record, depending on how much time things take.