I had a period of time where I was doing a lot of university work, working part-time about 2 8-hour shifts a week, and was in the committee of a society. I will say it is possible, and although I did feel overwhelmed at times (although I am a very anxious, neurotic person so this probably would have happened anyway), it was managable, and I was still getting 8 hours sleep each night. However I wouldn't recommend joining more than one society if you're going for this, or maybe two societies that don't require a lot of commitment, as personally I felt one was my limit along with a job!