Question

How do you separate water and glycerin ?

Answer 1

Traditionally, the easiest ways to separate water from low-level contaminants are (a) reverse osmosis, and (b) multi-effect distillation.

EXPLANATION

Reverse osmosis requires a semi-permeable membrane and a fairly high pressure pump. Otherwise, it is quite simple. Multi-effect distillation/evaporation requires a purpose-built machine which is a series of heat exchangers and evaporation chambers driven by a pump. Neither of these processes works well as a consumer product for the application you appear to have in mind.That is, in both cases you need an industrial or at least equipment-friendly setting. The armed services of many countries use the RO process (actually both processes, but most recently favor the RO process) for water purification quite routinely.